Image forming apparatus and fixing device

An image forming apparatus has a conveying element for conveying a sheet, an image forming section for forming an image on the sheet with liquid developer, and a fixing device including a rubbing mechanism for rubbing the image on the sheet. A fixing device has a rubbing mechanism for rubbing an image which is formed with liquid developer.

BACKGROUND OF THE INVENTION

1. Field of the Invention. The present invention is related to an image forming apparatus for forming an image on a sheet and a fixing device for fixing the image onto the sheet.

2. Description of the Related Art. An image forming apparatus which uses liquid developer is known as a device for forming an image on a sheet. This type of image forming apparatuses typically has a fixing device configured to fix images onto sheets. The fixing device generates relatively high heat in order to melt toner components in the liquid developer transferred onto the sheet.

It is not necessary for a fixing device to generate heat if the fixing device uses liquid developer which has characteristics such that its components (carrier solution) permeate into a sheet and high-molecular compounds with dispersed pigment therein deposit on the surface of the sheet. However, the present inventors have discovered disadvantageous properties which are likely to cause peel-off of the image formed on the sheet by means of such liquid developer.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an image forming apparatus and fixing device which is less likely to allow the peel-off of images on a sheet.

An image forming apparatus according to one aspect of the present invention includes: a conveying element configured to convey a sheet; an image forming section configured to form the image on the sheet with liquid developer; and a fixing device configured to fix the image onto the sheet, wherein the fixing device includes a rubbing mechanism configured to rub the image on the sheet.

A fixing device according to another aspect of the present invention includes: a rubbing mechanism for rubbing an image which is formed with liquid developer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Various embodiments of image forming apparatuses and fixing devices are described hereinafter with reference to the accompanying drawings. It should be noted that directional terms such as “upper/above,” “lower/below,” “left” and “right” is merely used hereinafter to clarify the descriptions and not to limit methodologies of the image forming apparatus and the fixing device in any way.

FIGS. 1A to 1Cschematically show transfer processes for transferring an image obtained by means of liquid developer, respectively. The transfer processes are sequentially performed in the order ofFIGS. 1A to 1C. Transferring an image to a sheet and the image obtained after the transfer are described with reference toFIGS. 1A to 1C.

FIG. 1Ais a schematic cross-sectional view of a liquid layer L of liquid developer used for forming an image, which is transferred from an image carrier100to a sheet S. The image carrier100may be, for example, a transfer belt which is provided in an image forming apparatus (e.g., a printer, a copy machine, a facsimile device, or a combined machine with these functions) for forming an image by means of liquid developer. The image carrier100conveys the liquid layer L of the liquid developer for forming an image to a transfer position, where the image is transferred to the sheet S.

At the transfer position, the sheet S contacts the liquid layer L on the image carrier100. The liquid layer L of the liquid developer for forming the image includes carrier liquid C, colored particles P for coloring the image, and polymer compounds R dissolved or swollen in the carrier liquid C. The colored particles P, which are dispersed in the carrier liquid C, are electrostatically attracted to the sheet S. Consequently, the colored particles P adhere to the sheet S to form the image thereon. It should be noted that the attraction of the colored particles P to the sheet S is accomplished by, for example, an electric field, which traverses the sheet S. The methodologies relating to this attraction of the colored particles P to the sheet S is described in detail hereinafter in association with the image forming apparatus.

FIG. 1Bschematically shows the carrier liquid C permeating into the sheet S. The carrier liquid C with a relatively low kinetic viscosity permeates into the sheet S and forms a permeation layer PL in a surface layer of the sheet S. The polymer compounds R in the liquid layer L of the liquid developer becomes more concentrated as the carrier liquid C permeates into the sheet S.

As shown inFIG. 1C, when the carrier liquid C further permeates into the sheet S, the polymer compounds R of the liquid layer L deposit. As described above, the electrostatic adhesion of the colored particles P to the sheet S occurs prior to the deposition of the polymer compounds R. Thus, the polymer compounds R, which deposit on the surface of the sheet S, form a coating layer which is stacked on the layer of the color particles P forming the image on the sheet S.

FIGS. 2A and 2Bschematically show fixation processes performed after the transfer process.FIG. 2Aschematically shows the fixation process.FIG. 2Bis a schematic cross-sectional view of the sheet S obtained after the fixation process. Methodologies of the fixation process is described with reference toFIGS. 1A to 2B.

After the transfer process, the carrier liquid C substantially permeates into the sheet S, so that an image layer I with the polymer compounds R and the colored particles P is formed on the sheet S. In the transfer process, the image layer I is not applied with any physical force except for a pressure and electric field generated during transferring the liquid layer L (image) from the image carrier100to the sheet S. Therefore, before the fixation process, a physical bond between the image layer I and the sheet S is relatively weak, so that the image layer I may be peeled off as a result of a peel test using tape described hereinafter.

FIG. 2Ashows a rubbing plate200exemplified as the fixing device and/or the rubbing mechanism. The rubbing plate200has, for example, a substantially cuboid substrate210and a nonwoven fabric220which covers the surface of the substrate210. In the present embodiment, the layer of the nonwoven fabric220which forms the lower surface of the rubbing plate200and faces the image layer I is exemplified as the contact surface. In the present embodiment, a polypropylene nonwoven fabric is used as the nonwoven fabric220. Alternatively, a polytetrafluoroethylene (PTFE) nonwoven fabric with a dynamic friction coefficient of 0.10 (referred to as “PTFE felt A” hereinafter), a polytetrafluoroethylene (PTFE) nonwoven fabric with a dynamic friction coefficient of 0.13 (referred to as “PTFE felt B” hereinafter), polyester felt, polyethylene terephthalate felt (referred to as “PET felt” hereinafter), polyamide felt, or wool felt may be used as the nonwoven fabric220.

The rubbing plate200, which is placed on the image layer. I of the sheet S, is moved on the image layer I along the upper surface of the sheet S. As a result, some of the components of the image layer I (the colored particles P and/or the polymer compounds R) are wedged into the surface layer of the sheet S (anchor effect), as shown inFIG. 2B. Thus, the physical bond between the image layer I and the sheet S is strengthened.

As described above, the upper surface of the image layer I is covered with the polymer compounds R. Therefore, the colored particles P for coloring the image, which are covered with the coated layer of the polymer compounds R, are appropriately protected by a strong resin film which is formed by the rubbing operation of the rubbing plate200. Thus it becomes less likely that the rubbing operation of the rubbing plate200causes damages to the image.

FIG. 3is a graph schematically showing a relationship between a time period (rubbing time), during which the rubbing plate200slides on the image layer I, and fixation ratio of the image layer I. The relationship between the rubbing time and the fixation ratio is described with reference toFIGS. 2A to 3.

The rubbing time shown on the horizontal axis of the graph shown inFIG. 3indicates the time length during which a given region on the image layer I is in contact with the reciprocating rubbing plate200.

A fixation ratio FR shown on the vertical axis of the graph shown inFIG. 3is calculated by means of the following formula, where D0represents density of the image obtained before peeling a tape attached to the image layer I, and D1represents density of the image obtained after peeling the tape attached to the image layer I.
FR(%)=D1/D0×100  [Formula 1]

The tape used for evaluating the fixation ratio FR was Mending Tape produced by 3M. The Mending Tape was attached onto the image layer I by means of a dedicated tool. Therefore, attachment strengths between the image layer I in a test sample and the Mending Tape are kept substantially constant among data points shown in the graph ofFIG. 3. The Mending Tape was pressed to the image layer I of the test sample, and then was peeled off from the image layer I by means of a dedicated tool at a substantially constant peeling angle and substantially constant peeling speed.

The image density of the test sample was measured by SpectroEye, which is a spectrophotometer produced by Sakata Inx Eng. Co., Ltd.

As shown inFIG. 3, if the image layer I is rubbed for one second or longer, the image layer I may achieve a relatively high fixation ratio FR. Rubbing the image layer I for less than one second indicates a drastic increase in the fixation ratio FR of the image layer I. It should be noted that weight of the rubbing plate200is appropriately defined such that the surface of the image layer I is damaged.

FIG. 4is a graph schematically showing relationships of various nonwoven fabrics220to the fixation ratios FR. The relationship between each nonwoven fabric220and each fixation ratio FR is described with reference toFIGS. 2A to 4.

The horizontal axis ofFIG. 4represents types of nonwoven fabrics220. The PTFE felt A, PTFE felt B, polypropylene nonwoven fabric, polyester felt, PET felt, polyamide felt, and wool felt are used in this test.

The left vertical axis ofFIG. 4represents the abovementioned fixation ratios FR. The fixation ratios FR are expressed by bar graphs inFIG. 4. It should be noted that all types of the nonwoven fabrics220used in this test achieved relatively high fixation ratios FR in a longer rubbing time than one second. Therefore, the fixation ratios FR shown inFIG. 4are calculated on the basis of a rubbing time of 0.625 seconds in order to screen out relatively effective types of nonwoven fabrics220.

The right vertical axis ofFIG. 4represents dynamic friction coefficient of each nonwoven fabric220shown by a dot inFIG. 4. Lower dynamic friction coefficients are advantageous because of less impingement on conveyance of the sheet S and less damage to the image layer I.

As shown inFIG. 4, the PTFE felt A achieves the lowest dynamic friction coefficient and the highest fixation ratio FR. It is, therefore, clear that the PTFE felt A is the most advantageous among the tested nonwoven fabrics220. Any nonwoven fabric material, which is not shown inFIG. 4, may be used as the nonwoven fabric220. Preferably, a nonwoven fabric material with a dynamic friction coefficient of 0.50 or lower is used as the nonwoven fabric220. It is less likely that such a nonwoven fabric material with a dynamic friction coefficient of 0.50 or lower may impinge on the conveyance of the sheet S and damage to the image layer I.

FIG. 5is a schematic plan view of a fixing device configured to fix the image layer I to the sheet S by means of the aforementioned fixation methodologies, and a conveyor configured to convey the sheet S, which passes through the fixing device. The fixing device is described with reference toFIGS. 2A,2B and5.

A fixing device300comprises a rubbing roller310which comes in contact with the upper surface of the sheet S. The rubbing roller310includes a tubular contact cylinder311which contacts the upper surface of the sheet S and a shaft312which projects from each end surface of the contact cylinder311. One rotatable end of the shaft312is supported by a bearing stored in a housing320. A gear321is mounted on the other end of the shaft312. An image is formed on the upper surface of the sheet S ofFIG. 5by means of liquid developer. The contact cylinder311configured to rub the image on the upper surface of the sheet S is exemplified as the rubbing mechanism.

The fixing device300has a motor330coupled to the gear321. In the present embodiment, the motor330configured to rotate the contact cylinder311is exemplified as a drive mechanism.

The conveyor includes an upstream conveyor410before the upstream of the fixing device300and a downstream conveyor420after the downstream of the fixing device300. The upstream and downstream conveyors410,420are exemplified as conveying elements configured to convey the sheet S.FIG. 5shows a vector directed from the upstream conveyor410to the downstream conveyor420. The direction of the vector inFIG. 5is exemplified as the first direction D1indicating a conveying direction of the sheet S. The length of the vector inFIG. 5is exemplified as the first speed V1indicating a conveying speed for the sheet S. The upstream and downstream conveyors410,420both together convey the sheet S in the first direction D1at the first speed V1.

FIG. 6is a schematic side view of the fixing device300and the conveyors (the upstream and downstream conveyors410,420). The fixing device300and the conveyors (the upstream and downstream conveyors410,420) are described with reference toFIGS. 2A to 6.

The upstream conveyor410includes an upper roller411which contacts the upper surface of the sheet S, and a lower roller412which contacts the lower surface of the sheet S. The upper roller411includes a pair of journals413,414. The rotatable journal413is supported by a bearing stored in a housing415. A gear416is mounted on the journal414.

The upstream conveyor410comprises an upstream motor417. The upstream motor417is coupled to the gear416.

The upstream conveyor410comprises an upstream support mechanism430configured to elastically support the lower roller412. The lower roller412includes a journal418which is connected to the upstream support mechanism430.

The upstream support mechanism430comprises a bearing431which supports the rotatable journal418, and an elastic element432(e.g., a coil spring) which connects the bearing431with a supporting surface F supporting the upstream conveyor410, the downstream conveyor420and the fixing device300. The lower roller412pushed upward by the elastic element432works together with the upper roller411to hold the sheet S therebetween. As a result, the sheet S held between the upper and lower rollers411,412is conveyed to the fixing device300by drive of the upstream motor417.

The downstream conveyor420includes an upper roller421which contacts the upper surface of the sheet S, and a lower roller422which contacts the lower surface of the sheet S. The upper roller421includes a pair of journals423,424. The rotatable journal423is supported by a bearing stored in a housing425. A gear426is mounted on the journal424.

The downstream conveyor420comprises a downstream motor427. The downstream motor427is coupled to the gear426.

The downstream conveyor420comprises a downstream support mechanism440configured to elastically support the lower roller422. The lower roller422includes a journal428which is connected to the downstream support mechanism440.

The downstream support mechanism440comprises a bearing441which supports the rotatable journal428, and an elastic element442(e.g., a coil spring) which connects the bearing441with the supporting surface F supporting the upstream conveyor410, the downstream conveyor420and the fixing device300. The lower roller422pushed upward by the elastic element442works together with the upper roller421to hold the sheet S therebetween. As a result, the sheet S held between the upper and lower rollers421,422is pulled out from the fixing device300by drive of the downstream motor427.

As shown inFIG. 6, the contact cylinder311comprises a substantially cylindrical elastic layer313which surrounds the circumferential surface of the shaft312, and a nonwoven fabric layer314which covers the outer circumferential surface of the elastic layer313. The elastic layer313is formed by using, for example, sponge or other softer elastic material. The nonwoven fabric layer314is formed by using, for example, any of the nonwoven fabrics described in the context ofFIG. 4.

The fixing device300comprises a backup roller340disposed below the rubbing roller310. The backup roller340includes a substantially cylindrical support tube341formed by using sponge or other soft and elastic material, and a metallic shaft342inserted into the support tube341.

The fixing device300includes a press mechanism350configured to press the backup roller340to the rubbing roller310. The press mechanism350includes a bearing351which supports each of rotatable ends of the shaft342projecting from the end surface of the support tube341, and an elastic element352(e.g., a coil spring) which connects the bearing351with the supporting surface F supporting the upstream conveyor410, the downstream conveyor420and the fixing device300.

The elastic element352biases the backup roller340toward the rubbing roller310. As a result, the nonwoven fabric layer314and/or the elastic layer313is compressed and deformed to form a substantially flat upper nip surface N1along the upper surface of the sheet S passing through the fixing device300. The circumferential surface of the support tube341is compressed and deformed as well to form a substantially flat lower nip surface N2along the lower surface of the sheet S passing through the fixing device300. In the present embodiment, the upper nip surface N1which contacts the image (image layer I) formed on the upper surface of the sheet S is exemplified as the contact surface.

A vector shown above the upper nip surface N1inFIG. 6indicates a direction and speed of the movement of the upper nip surface N1. The motor330rotates the rubbing roller310such that the upper nip surface N1moves in the first direction D1. The rotating speed of the motor330is set such that the upper nip surface N1moves at a second speed V2, which is different from the first speed V1and defined by the upstream and downstream conveyors410,420. As a result, the image layer I formed on the sheet S is rubbed and fixed by the upper nip surface N1while the sheet S passes in between the upper and lower nip surfaces N1, N2according to the methodologies described in the context ofFIGS. 2A and 2B. The second speed V2shown inFIG. 6is greater than the first speed V1. Alternatively, the second speed V2may be lower than the first speed V1.

In the present embodiment, the difference between the first and second speeds V1, V2is defined by a relationship between the rotating speed of the motor330and the rotating speed of the upstream/downstream motors417,427, and/or a relationship between the diameter of the rubbing roller310and the diameters of the upper rollers411,421. In the present embodiment, the motors330,417,427are individually allocated to the fixing device300, the upstream conveyor410and the downstream conveyor420, respectively. Alternatively, the fixing device300, the upstream conveyor410and the downstream conveyor420may be driven by a common motor as a drive source. The difference between the first and second speeds V1, V2may be defined by a gear mechanism formed between the common motor and each of the fixing device300, the upstream conveyor410and the downstream conveyor420.

In the present embodiment, the single fixing device300is situated between the upstream and downstream conveyors410,420. Alternatively, several fixing devices300may be situated between the upstream and downstream conveyors410,420. The fixing devices300may contribute to an extension of the rubbing time described in the context ofFIG. 3.

FIG. 7schematically shows other operations performed by the fixing device300. The operations of the fixing device300are described with reference toFIGS. 5 to 7.

The motor330may rotate the rubbing roller310such that the upper nip surface N1moves in a second direction D2opposite to the first direction D1. As described above, the nonwoven fabric layer314with a relatively low dynamic friction coefficient allows a stable conveyance of the sheet S under the rotation of the rubbing roller310rotating in the opposite direction to the conveying direction of the sheet S.

<Application to Image Forming Apparatus>

FIG. 8is a schematic view of an image forming apparatus to which the methodologies of the fixation technology described in the context ofFIGS. 1A to 7are applied.FIG. 9is a schematic cross-sectional view of a color printer without circulation devices.FIG. 10is an enlarged cross-sectional view of one of image forming units. The image forming apparatus configured to form images is described with reference toFIGS. 1A to 1CandFIGS. 5 to 10. It should be noted that the image forming apparatus shown inFIGS. 8 to 10is a color printer. The image forming apparatus may be a copy machine, a facsimile device, a combined machine having these functions, or another device configured to form images on sheet S.

As shown inFIG. 8, the color printer1comprises an upper main portion1A configured to store various units and parts for forming images, and a lower main portion1B which is disposed under the upper main portion1A and stores circulation devices LY, LM, LC, LB (liquid mixture supply systems) for corresponding colors. A pipe and alike for connecting the upper and lower main portions1A,1B to each other is omitted herein. The circulation devices LY, LM, LC, LB circulate the liquid developer which is used in an image forming process executed by the upper main portion1A. Liquid developer circulation technologies used in a well-known image forming apparatus may be appropriately used in the configurations and methodologies of the circulation devices LY, LM, LC, LB.

As shown inFIG. 9, the upper main portion1A includes a tandem type image forming section2configured to form a toner image on the basis of image data, a sheet storage3configured to store sheets S, a secondary transfer portion4configured to transfer a toner image formed by the image forming section2onto the sheet S, a fixing portion5configured to fix the transferred toner image onto the sheet S, a discharge portion6used to discharge the sheet S on which the toner image is completely fixed, and a conveying portion7configured to convey the sheet S from the sheet storage3to the discharge portion6. In the present embodiment, the methodologies of the fixation technologies described in the context ofFIGS. 1A to 7are applied to the fixing portion5.

The image forming section2configured to form an image on a sheet S by using the liquid developer comprises an intermediate transfer belt21, a cleaning portion22configured to clean the intermediate transfer belt21, and the image forming units FY, FM, FC and FB corresponding to colors of yellow (Y), magenta (M), cyan (C), and black (Bk). In the present embodiment, the intermediate transfer belt21corresponds to the image carrier100described in the context ofFIGS. 1A to 1C.

The image forming section2comprises a drive roller41which drives the looped intermediate transfer belt21, and an idler49which is rotated by a traveling motion of the intermediate transfer belt21. The electrically-conductive intermediate transfer belt21is wrapped around the drive roller41and the idler49. The width of the intermediate transfer belt21is greater than the maximum width of the sheet S accepted by the color printer1. In the present embodiment, the drive roller41corresponds to the upper roller411of the upstream conveyor410described in the context ofFIGS. 5 to 7. An upward conveying direction of the sheet S defined by the drive roller41is exemplified as the first direction D1. The conveying speed of the sheet S defined by the drive roller41is exemplified as the first speed V1. In the following description, the side of the intermediate transfer belt21which faces the outside during a circulation drive motion is referred to as “outer surface” and the other side as “inner surface.”

The image forming units FY, FM, FC and FB are disposed side by side near the intermediate transfer belt21between the cleaning portion22of the intermediate transfer belt21and the secondary transfer portion4. Each of the image forming units FY, FM, FC and FB comprises a photoreceptor drum10, a charger11, an exposure device12, a developing device14, a primary transfer roller20, a cleaning device26, a neutralization device13, and a removing roller30. It should be noted that the closest image forming unit FB to the secondary transfer portion4among the image forming units FY, FM, FC, FB is not provided with the removing roller30, but the rest of its configurations is the same as those of the image forming units FY, FM and FC.

The circulation devices LY, LM, LC and LB correspond to the image forming units FY, FM, FC and FB, respectively. The circulation devices LY, LM, LC and LB supply and recover the liquid developer of the corresponding colors, respectively.

The circumferential surface of the tubular photoreceptor drum10is configured to carry a toner image with charged toner (charged to a positive polarity in the present embodiment). The photoreceptor drum10coming into contact with the intermediate transfer belt21rotates to follow the travelling direction of the intermediate transfer belt21. The charger11uniformly charges the surface of the photoreceptor drum10.

The exposure device12comprises, for example, an LED light source. The light source of the exposure device12emits light to the uniformly charged surface of the photoreceptor drum10, on the basis of the image data input from external equipment. As a result, an electrostatic latent image is formed on the surface of the photoreceptor drum10.

The liquid developing device14holding the liquid developer with the colored particles P, the carrier liquid C and the polymer compounds R faces the electrostatic latent image formed on the surface of the photoreceptor drum10, so that the colored particles P and the polymer compounds R adhere to the electrostatic latent image. As a result, the electrostatic latent image is developed into a colored image with the colored particles P.

As shown inFIG. 10, the developing device14includes a developer container140, a developing roller141, a feed roller142, a supporting roller143, a blade144which contacts the feed roller142, a blade145which cleans the developing roller141, a recovery device146which recovers the liquid developer, and a charger147which charges the developing roller141.

The liquid developer after adjusting concentrations of the colored particles P and the polymer compounds R in the carrier liquid C is fed from a feed nozzle278into the developer container140. It should be noted that the liquid developer is fed toward a nip portion between the feed and supporting rollers142,143. An excess of the liquid developer drops below the supporting roller143and accumulates on the bottom of the developer container140. The accumulated liquid developer is recovered through a pipe82by using the circulation devices LY, LM, LC LB.

The supporting roller143, which is disposed substantially in the middle of the developer container140, abuts the upper feed roller142to form the nip, portion therebetween. A groove for holding the liquid developer is formed on the circumferential surface of the feed roller142.

The liquid developer fed from the feed nozzle278is temporarily accumulated in the nip portion between the supporting and feed rollers143,142. The liquid developer held in the groove of the feed roller142at the nip portion is delivered to the upper developing roller141. The blade144which is brought into contact with the circumferential surface of the feed roller142regulates an amount of the liquid developer held in the groove of the feed roller142. The excessive liquid developer, which is scraped off by the blade144, is received by the bottom of the developer container140.

The developing roller141, which is disposed at an upper opening of the developer container140, contacts the feed roller142. The rotating directions of the developing and feed rollers141,142are defined such that the circumferential surface of the developing roller141moves in an opposite direction to the feed roller142at the nip portion, which is formed between the developing and feed rollers141,142. As a result, the liquid developer held on the circumferential surface of the feed roller142is delivered to the circumferential surface of the developing roller141. Because the layer thickness of the liquid developer on the feed roller142is appropriately regulated, the liquid developer on the surface of the developing roller141is adjusted to have a suitable thickness for forming images.

The surface of the developing roller141, which receives the liquid developer, moves above the charger147. The charger147provides charging potential having the same polarity as the charged polarity of the colored particles P. As a result, the colored particles P of the liquid developer carried on the developing roller141moves to the surface side of the developing roller141.

The surface of the developing roller141contacts the photoreceptor drum10after passing the charger147. The toner image based on the image data is formed on the surface of the photoreceptor drum10by a difference in potential between the electrostatic latent image on the surface of the photoreceptor drum10and a development bias applied to the developing roller141.

The circumferential surface of the developing roller141contacts the photoreceptor drum10and then with the blade145. The blade145removes the liquid developer on the surface of the developing roller141after the developing operation performed on the photoreceptor drum10.

The recovery device146recovers the liquid developer removed by the blade145, and then sends the liquid developer to a pipe81of each circulation devices LY, LM, LC, LB. The liquid developer flows downward along the surface of the blade145. If the liquid developer is highly viscous, the recovery device146may preferably have delivery rollers to assist in delivering the liquid developer.

The primary, transfer roller20works with the photoreceptor drum10to hold the intermediate transfer belt21therebetween. Voltage having an opposite polarity (negative polarity, in the present embodiment) to that of the colored particles P on the photoreceptor drum10is applied from a power source (not shown) to the primary transfer roller20. The primary transfer roller20applies, to the intermediate transfer belt21, the voltage with the opposite polarity to that of the toner. As a result, the colored particles P and the polymer compounds R are attracted to the outer surface of the electrically-conductive intermediate transfer belt21. Thus, the image formed on the surface of the photoreceptor drum10is transferred to the outer surface of the intermediate transfer belt21. The intermediate transfer belt21then carries and conveys the toner image to the sheet S.

The cleaning device26, which removes the liquid developer remaining on the photoreceptor drum10without being transferred from the photoreceptor drum10to the intermediate transfer belt21, comprises a developer conveying screw261and a cleaning blade262. An end of the planar cleaning blade262which extends toward the rotation axis of the photoreceptor drum10slides on the surface of the photoreceptor drum10. The cleaning blade262scrapes the liquid developer remaining on the photoreceptor drum as the rotation of the photoreceptor drum10. The scraped liquid developer is temporarily stored in the cleaning device26. The conveying screw261disposed in the cleaning device26conveys the residual developer to the outside.

In preparation for the image formation in the next cycle, the neutralization device13with a neutralization light source neutralize the surface of the photoreceptor drum10using the light from the light source, after the liquid developer is removed by the cleaning blade262.

The substantially tubular removing roller30contacts the intermediate transfer belt21. The removing roller30disposed between the image forming units FY, FM removes the carrier liquid C from the liquid developer transferred from the image forming unit FY to the intermediate transfer belt21. The removing roller30disposed between the image forming units FM, FC removes the carrier liquid C from the liquid developer transferred from the image forming unit FM to the intermediate transfer belt21. The removing roller30disposed between the image forming units FC, FB removes the carrier liquid C from the liquid developer transferred from the image forming unit FC to the intermediate transfer belt21. Because the image forming unit FB does not have the removing roller30as described above, the intermediate transfer belt21carries the liquid developer including the carrier liquid C, like the image carrier100shown inFIGS. 1A to 1C.

As shown inFIG. 9, the sheet storage3configured to store sheets S is disposed in a lower part of the upper main portion1A. The sheet storage3includes a feed cassette configured to store sheets S.

The secondary transfer portion4configured to transfer the image formed on the intermediate transfer belt21to the sheet S comprises a secondary transfer roller42, which faces the drive roller41for driving the intermediate transfer belt21. The secondary transfer roller42corresponds to the lower roller412of the upstream conveyor410described in the context ofFIGS. 5 to 7. The secondary transfer roller42generates an electric field between the secondary transfer roller42and the intermediate transfer belt21to attract the colored particles P to the sheet S, as described in the context ofFIGS. 1A to 1C.

The fixing portion5disposed above the secondary transfer portion4utilizes the methodologies of the fixation technologies described in the context ofFIGS. 1A to 7, to fix the toner image to the sheet S. Therefore, the fixing portion5comprises the rubbing roller310and the backup roller340which are described in the context ofFIGS. 5 to 7. As described above, the rubbing roller310rubs the image on the sheet S, so that the fixation process is appropriately performed. In addition, because the rubbing roller310is wide enough to rub the entire image, gloss of the image is evenly changed by the contact with the rubbing roller310. As a result, it is less likely that the gloss of the image is locally changed even if a user touches the image on the sheet S.

The sheet S onto which the toner image is fixed by the fixing portion5is discharged to the discharge portion6disposed in an upper part of the color printer1. The conveying portion7having several conveying roller pairs conveys the sheet S from the sheet storage3to the secondary transfer portion4, the fixing portion5, and the discharge portion6sequentially in this order.

The liquid developer includes the electrically insulating carrier liquid C and the colored particles P dispersed in the carrier liquid C. This liquid developer also contains the polymer compounds R. The liquid developer preferably has a viscosity of to 400 mPa·s at a measurement temperature of 25° C. The viscosity of the liquid developer (at the measurement temperature of 25° C.) is preferably 40 to 300 mPa·s, and more preferably 50 to 250 mPa·s.

The electrically insulating carrier liquid C which generally works as liquid carrier enhances electrical insulation of the liquid developer. For example, electrically insulating organic solvent having a volume resistivity of 1012Ω·cm or above at 25° C. (i.e., an electrical conductivity of 1.0 pS/cm or lower) is preferably used as the electrically insulating carrier liquid C. In addition, carrier liquid, which may further dissolve the polymer compounds R described hereinafter, is preferably used (the one with relatively high solubility for the polymer compounds R).

The viscosity and type of the carrier liquid C as well as the compounding amount therein are appropriately adjusted and selected in order to obtain the 30 to 400 mPa·s viscosity (at the measuring temperature of 25° C.) in the entire liquid developer. The viscosity of the liquid developer depends on a combination of the organic solvent used as the carrier liquid C and the organic polymer compounds R, which is described hereinafter. Therefore, the type and compounding amount of the organic solvent are appropriately determined in response to a desired viscosity of the liquid developer and the selected type of polymer compounds R.

Aliphatic hydrocarbons and vegetable oil, which are liquid at an ordinary temperature, are exemplified the electrically insulating organic solvent.

Liquid n-paraffinic hydrocarbons, iso-paraffinic hydrocarbons, halogenated aliphatic hydrocarbons, branched aliphatic hydrocarbons, and a mixture thereof are exemplified as the aliphatic hydrocarbons. For example, n-hexane, n-heptane, n-octane, nonane, decane, dodecane, hexadecane, heptadecane, cyclohexane, perchloroethylene, trichloroethane, and alike may be used as the aliphatic hydrocarbons. Nonvolatile organic solvent and organic solvent of relatively low volatility (with, for example, a boiling point of 200° C. or higher) are preferred from the perspective of environmental responsiveness (VOC measures). In addition, liquid paraffins which include a relatively large amount of aliphatic hydrocarbon with 16 or more carbon atoms may be preferably used.

Tall oil fatty acid (major components: oleic acid, linoleic acid), vegetable oil-based fatty acid ester, soybean oil, sunflower oil, castor oil, flaxseed oil, and tung oil are exemplified as the vegetable oil. The tall oil fatty acid and alike among them are preferably used.

In the present embodiment, any carrier liquid C may be used as long as it dissolves the polymer compounds R. In other words, the one with relatively high solubility for the polymer compounds R (the one which dissolves the polymer compounds R successfully) may be used alone as the carrier liquid C, or it may be combined with the one with relatively low solubility for the polymer compounds R (the one that poorly dissolves the polymer compounds R). It should be noted that the electrical conductivity of the entire carrier liquid C (the electrical conductivity of the liquid developer) is adjusted according to types of the carrier liquid C so that the electrical conductivity of the liquid developer does not becomes excessively high. For instance, vegetable oils such as tall oil fatty acids generally have higher electrical conductivities than the aliphatic hydrocarbons such as liquid paraffins. Therefore, if the aforementioned vegetable oils are included as the carrier liquid C in order to successfully dissolve the polymer compounds R in the carrier liquid C, the electrical conductivities should be carefully adjusted.

Carrier liquid C which has a greater amount of the aforementioned oil is more advantageous in terms of the solubility for the polymer compounds R whereas it may be disadvantageous in terms of the electrical conductivity. Carrier liquid C which has a less amount of the aforementioned oil is more advantageous in terms of the electrical conductivity whereas it may be disadvantageous in terms of the solubility for the polymer compounds R.

As described above, the content of the aforementioned oils in the entire carrier liquid C depends on the type and content of the polymer compounds R contained in the liquid developer, and is preferably, for example, 2 to 80 mass %, and more preferably 5 to 60 mass %. It becomes difficult to successfully dissolve the polymer compounds R in the carrier liquid C if the content of the oils is less than 2 mass %. The electrical conductivities of the entire carrier liquid C and the liquid developer become excessively high if the content of the oils exceeds 80 mass %. Excessively high electrical conductivity of the liquid developer leads to low image density.

In the present embodiment, the electrical conductivity of the liquid developer is preferably, for example, 200 pS/cm or lower. Therefore, the electrical conductivity of the entire carrier liquid C (the electrical conductivity of the liquid developer) is preferably adjusted to, for example, 200 pS/cm or lower by mixing a highly electrically resistant aliphatic hydrocarbon with resultant solution from dissolving the polymer compounds R in the oils such as tall oil fatty acids (often referred to as “resin solvent” hereinafter).

Pigment itself may be used as the colored particles P in the present embodiment. The liquid developer containing pigment may perform the non-thermal fixation process described in the context ofFIGS. 1A to 7. As a result, the pigment serving as the colored particles P are fixed onto a recording medium without consuming much thermal energy or optical energy.

For example, conventionally known organic pigment or inorganic pigment may be used as the pigments of the present embodiment without any limitation. Azine dyes such as carbon black, oil furnace black, channel black, lampblack, acetylene black, and aniline black, metal salt azo dyes, metallic oxides, and combined metal oxides are exemplified as black pigment. Cadmium yellow, mineral fast yellow, nickel titanium yellow, navels yellow, naphthol yellow S, hansa yellow G, hansa yellow 10G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, and tartrazine lake are exemplified as yellow pigment. Molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK are exemplified as orange pigment. Colcothar, cadmium red, permanent red 4R, lithol red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, and brilliant carmine 3B are exemplified as red pigment. Fast violet B and methyl violet lake are exemplified as purple pigment. C.I. Pigment Blue 15:3, cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, non-metal phthalocyanine blue, partial chloride of phthalocyanine blue, fast sky blue, and indanthrene blue BC are exemplified as blue pigment. Chrome green, chromium oxide, pigment green B, and malachite green lake are exemplified as green pigment.

The content of each pigment in the liquid developer is preferably 1 to 30 mass %, more preferably 3 mass % or more, and more preferably 5 mass % or more. The content of each pigment is also more preferably 20 mass % or less, and more preferably 10 mass % or less.

An average particle diameter of each pigment in the liquid developer, which is a volume basis median diameter (D50), is preferably 0.1 to 1.0 μm. The average particle diameter less than 0.1 μm leads to, for example, low image density. The average particle diameter above 1.0 μm leads to, for example, low fixation properties. The volume basis median diameter (D50) here generally denotes a particle diameter at the point where a cumulative curve based on the total volume 100% of one group of particles with a determined particle distribution attains 50%.

The liquid developer according to the present embodiment may contain dispersion stabilizer for facilitating and stabilizing dispersion of the particles in the liquid developer. Dispersion stabilizer “BYK-116” manufactured by BYK Co., Ltd., for example, may be suitably used as the dispersion stabilizer according to the present embodiment. In addition, “Solsperse 9000,” “Solsperse 11200,” “Solsperse 13940,” “Solsperse 16000,” “Solsperse 17000, and “Solsperse 18000” manufactured by The Lubrizol Corporation, and “Antaron™ V-216” and “Antaron™ V-220” manufactured by International Specialty Products, Inc. may be preferably used.

The content of the dispersion stabilizer in the liquid developer is approximately 1 to 10 mass %, and preferably approximately 2 to 6 mass %.

The polymer compounds R contained in the liquid developer according to the present embodiment are organic polymer compounds such as cyclic olefin copolymer, styrene elastomer, cellulose ether and polyvinyl butyral. A material which increases viscosity the liquid developer to prevent bleeding during the image formation may be selected as the organic polymer compounds with high solubility for the carrier liquid C. A cyclic olefin copolymer, styrene elastomer, cellulose ether, and polyvinyl butyral are exemplified as the organic polymer compounds. Preferably, styrene elastomer is used as the organic polymer compounds. A single type of organic polymer compound or several types of organic polymer compounds may be used as the polymer compounds R.

The liquid developer of the present embodiment contains the polymer compounds dissolved in the carrier liquid C. The organic polymer compounds dissolved in the carrier liquid C may be gel-like polymer compounds. Depending on the types and molecular weights of the organic polymer compounds, the organic polymer compounds are mutually entwined in the carrier liquid C and form gel. The gel-like organic polymer compounds have a relatively low fluidity. For example, if concentration of the organic polymer compounds is high or if affinity of the organic polymer compounds for the carrier liquid C is low or if the ambient temperature is low, the organic polymer compounds are likely to form gel. On the other hand, if the organic polymer compounds hardly entwine mutually in the carrier liquid C, solution with a relatively fluidity is obtained.

The content of the organic polymer compounds in the liquid developer is appropriately determined according to the type of the organic polymer compounds. The content of the organic polymer compounds is preferably, for example, 1 to 10 mass %.

If the content of the polymer compounds is less than 1 mass %, sufficient viscosity may not be obtained in the liquid developer, which may ineffectively prevent bleeding during the image formation. The content of the polymer compounds exceeding 10 mass % leads to formation of an excessively thick film of the organic polymer compounds on the surface of the sheet S, which significantly deteriorates drying characteristics of the film, increases the adherence (tackiness) of the film, and worsens scratch resistance of the image.

The organic polymer compounds which may be preferably used in the present embodiment are described hereinafter in more detail.

Cyclic olefin copolymer is amorphous, thermoplastic cyclic olefin resin which has a cyclic olefin skeleton in its main chain without environmental load substance and is excellent in transparency, lightweight properties, and low water absorption properties. The cyclic olefin copolymer of the present embodiment is an organic polymer compound with a main chain composed of a carbon-carbon bond, in which at least a part of the main chain has a cyclic hydrocarbon structure. The cyclic hydrocarbon structure is introduced by using, as a monomer, a compound having at least one olefinic double bond in the cyclic hydrocarbon structure (cyclic olefin), such as norbornene and tetracyclododecene.

Examples of the cyclic olefin copolymer that may be used in the present embodiment include (1) cyclic olefin-based addition (co) polymer or its hydrogenated product, (2) an addition copolymer of a cyclic olefin and an α-olefin, or its hydrogenated product, and (3) a cyclic olefin-based ring-opening (co) polymer or its hydrogenated product.

Specific examples of the cyclic olefin copolymer are as follows:

In the present embodiment, a method for polymerizing cyclic olefins, a method for polymerizing cyclic olefins with a-olefins, and a method for hydrogenating the resultant polymer are not particularly limited and may be carried out according to well-known methods.

In the present embodiment, the structure of the cyclic olefin copolymer is not particularly limited and may be linear, branched or crosslinked. In the present embodiment, the cyclic olefin copolymer is preferably linear.

In the present embodiment, a copolymer of norbornene and ethylene, or of tetracyclododecene and ethylene may be preferably used as the cyclic olefin copolymer, and the copolymer of norbornene and ethylene is more preferred. In this case, the content of norbornene in the copolymer is preferably 60 to 82 mass %, more preferably 60 to 79 mass %, yet more preferably 60 to 76 mass %, and most preferably 60 to 65 mass %. If the content of norbornene is less than 60 mass %, glass transition temperature of the cyclic olefin copolymer film may become excessively low, which may lead to a risk of lowering film formation properties of the cyclic olefin copolymer. If the content of norbornene exceeds 82 mass %, glass transition temperature of the cyclic olefin copolymer film may become excessively high, which may lead to a risk of lowering fixation properties of the pigments, that is, fixation properties of images by the film of the cyclic olefin copolymer. Or the solubility of the cyclic olefin copolymer for the carrier liquid C may also be reduced.

A conventionally known styrene elastomer may be used as the styrene elastomer available in the present embodiment. Specific examples thereof include a block copolymer composed of an aromatic vinyl compound and a conjugated diene compound or olefinic compound. Examples of the block copolymer include a block copolymer that has a structure expressed by Chemical Formula where A is a polymer block composed of an aromatic vinyl compound and B is a polymer block composed of an olefinic compound or a conjugated diene compound.

[C1]
[A-B]x-A  (Chemical Formula 1)(Where x represents an integer chosen such that the number molecular average weight ranges from 1,000 to 100,000.)

The polymer block A may be composed of one or two or more types of the aforementioned aromatic vinyl compounds. The one composed of styrene and/or α-methylstyrene among these aromatic vinyl compounds provides suitable properties for the liquid developer of the present embodiment.

Examples of the conjugated diene compound constituting the block copolymer include butadiene, isoprene, chloroprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadien, and 1,3-hexadien.

The polymer block B may be composed of one or two or more types of each of the olefinic compounds and the conjugated diene compounds. The one composed of butadiene and/or isoprene among these compounds provides suitable properties for the liquid developer of the present embodiment.

As the styrene elastomer which may be used in the present embodiment, it is preferred to use a styrene-butadiene elastomer (SBS) that has a structure in which the polymer block A and polymer block B are expressed by Chemical Formula 2.

(where R1, R2, R4, R5and R6each represent a hydrogen atom or methyl group; R3represents a hydrogen atom, a halogen atom, a phenyl group or a saturated alkyl group, a methoxy group or ethoxy group having 1 to 20 carbon atoms; and m, n each represent an integer chosen such that the content of the polymer block A ranges from 5 to 75 mass %.)

The styrene-butadiene elastomer has a number average molecular weight Mn in a range of, preferably, 1,000 to 100,000 (see Chemical Formula 1) and more preferably 2,000 to 50,000, in a molecular weight distribution measured by means of a GPC (gel permeation chromatography). A weight-average molecular weight Mw of the styrene-butadiene elastomer is in a range of, preferably, 5,000 to 1,000,000 and more preferably 10,000 to 500,000. In this case, at least one peak is present in the weight-average molecular weight Mw range of 2,000 to 200,000 and preferably in the weight-average molecular weight Mw range of 3,000 to 150,000.

In the styrene-butadiene elastomer, the value of ratio (weight-average molecular weight Mw/number average molecular weight Mn) is preferably equal to or lower than 3.0, and more preferably equal to or lower than 2.0.

The content of styrene in the styrene-butadiene elastomer (the content of the polymer block A) is in a range of, preferably, 5 to 75 mass % (see Chemical Formula 2) and more preferably 10 to 65 mass %. If the styrene content is less than 5 mass %, glass transition temperature of the styrene elastomer film becomes excessively low and deteriorates the film formation properties of the styrene elastomer. If the styrene content exceeds 75 mass %, a softening point of the styrene elastomer film becomes excessively high and worsens fixation properties of the pigments, that is, fixation properties of images by the styrene elastomer film.

In the present embodiment, a commercially available styrene elastomer may be used. For example, “Klayton” manufactured by Shell, “Asaprene™” T411, T413, T437, “Tufprene™” A, 315P, which are manufactured by Asahi Kasei Chemicals Corporation, and “JSR TR1086,” “JSR TR2000,” “JSR TR2250” and “JSR TR2827” manufactured by JSR Corporation, may be used as a styrene-conjugated diene block copolymer. “Septon” S1001, S2063, S4055, S8007, “Hybrar” 5127, 7311, which are manufactured by Kuraray Co., Ltd., “Dynaron” 6200P, 4600P, 1320P manufactured by JSR Corporation may be used as a hydrogenated product of the styrene-conjugated diene block copolymer. Also, “Index” manufactured by The Dow Chemical Company may be used as styrene-ethylene copolymer. As other styrene elastomers, “Aron AR” manufactured by Aronkasei Co., Ltd. and “Rabalon” manufactured by Mitsubishi Chemical Corporation may be used. These materials may be used alone or in combinations of two or more types thereof.

Cellulose ether is a polymer formed by substituting a hydroxyl group of a cellulose molecule with an alkoxy group. The substitution rate is preferably 45 to 49.5%. The alkyl moiety of the alkoxy group may be substituted with, for example, hydroxyl group or alike. A film formed by cellulose ether is excellent in toughness and thermal stability.

Examples of the cellulose ether which may be used in the present embodiment include: alkyl cellulose such as methylcellulose and ethylcellulose; hydroxyalkyl cellulose such as hydroxyethyl cellulose and hydroxypropyl cellulose; hydroxy alkyl alkyl cellulose such as hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl ethyl cellulose; carboxy alkyl cellulose such as carboxymethyl cellulose; and carboxy-alkyl hydroxy-alkyl cellulose such as carboxymethyl hydroxyethyl cellulose. These cellulose ethers may be used alone or in combinations of two or more thereof. Alkyl celluloses are preferred among these cellulose ethers. Ethyl celluloses are preferred among these alkyl celluloses.

In the present embodiment, a commercially available cellulose ether may be used. Examples of ethylcellulose include “Ethocel™ STD4,” “Ethocel™ STD7,” and “Ethocel™ STD10” manufactured by Nissin-Kasei Co., Ltd. These ethyl celluloses may be used alone or in combinations of two or more thereof, depending on the circumstances.

The polyvinyl butyral which may be used in the present embodiment (butyral resin: alkyl acetalized polyvinyl alcohol) is, as shown in Chemical Formula 3, a copolymer of a hydrophilic vinyl alcohol unit having a hydroxyl group, a hydrophobic vinyl acetal unit having a butyral group, and a vinyl acetate unit having an intermediate property between a vinyl alcohol unit and vinyl acetal unit and having an acetyl group. Polyvinyl butyral which has a degree of butyralization (the ratio between a hydrophilic moiety and a hydrophobic moiety) between 60 to 85 mol % is preferred in the liquid developer of the present embodiment in terms of its excellent film formation properties (film formation properties). The polyvinyl butyral has a vinyl acetal unit indicating the solubility of the polyvinyl butyral for nonpolar solvent and a vinyl alcohol unit for improving the bonding properties of the recording medium such as a paper sheet. Therefore, the polyvinyl butyral has high affinity with both the carrier liquid C and the recording medium.

The liquid developer according to the present embodiment may be produced by sufficiently dissolving or mixing/dispersing the carrier liquid C, pigments, polymer compounds and optionally the dispersion stabilizer for several minutes to over 10 hours, as appropriate, by using, for example, a ball mill, sand grinder, Dyno mill, rocking mill or alike (or a media distributed machine using zirconia beads and alike may be used).

Mixing/dispersing these components pulverize the pigments into fine pieces. The mixing/dispersion time and the rotating speed of the machine are adjusted so that the average particle diameter (D50) of the pigments in the liquid developer becomes, preferably, 0.1 to 1.0 μm as described above. If the dispersion time is excessively short or if the rotating speed is excessively low, the average particle diameter of the pigments (D50) exceeds 1.0 μm, and deteriorates the fixation properties as described above. If the dispersion time is excessively long or if the rotating speed is excessively high, the average particle diameter of the pigments (D50) becomes less than 0.1 μm, which in turn leads to poor developing properties and low image density.

In the present embodiment, the liquid developer may be produced by dissolving the polymer compounds in the carrier liquid C and then mixing/dispersing the pigments (along with the dispersion stabilizer, as appropriate). The liquid developer may also be produced by preparing solution obtained by dissolving the polymer compounds in the carrier liquid C and a pigment dispersion (obtained by mixing/dispersing the pigments in the carrier liquid C (along with the dispersion stabilizer, as appropriate)), and then mixing the resin solution with the pigment dispersion at an appropriate mixing ratio (mass ratio).

A particle size distribution needs to be measured in order to calculate the average particle diameter (D50) of the pigments. The particle size distribution of the pigments may be measured as follows.

A given amount of produced liquid developer or prepared pigment dispersion is sampled and diluted to 10 to 100 times of its volume with the same carrier liquid C as the one used in the liquid developer or the pigment dispersion. The particle size distribution of thus obtained liquid is measured on the basis of a flow system using a laser diffraction type particle size distribution measuring device “Mastersizer 2000” manufactured by Malvern Instruments Ltd.

The viscosity of the produced liquid developer may be measured at a measurement temperature of 25° C. by using a vibrational viscometer “Viscomate VM-10A-L” manufactured by CBC Co., Ltd.

Fixation methodologies according to the second embodiment are described hereinafter. The fixation methodologies of the second embodiment are associated with effects of a number of rubbing directions on the fixation ratios FR. It should be noted that the fixation methodologies described in the context of the first embodiment is preferably applied to the fixation methodologies of the second embodiment as well. Therefore, some descriptions overlapping with those of the first embodiment are omitted. Hereinafter, the same reference numerals are used for describing the same elements as those of the first embodiment. The descriptions in the context of the first embodiment are preferably incorporated into the elements which are not described hereinafter.

FIGS. 11A to 11Dare schematic views showing experimental methods, respectively, for investigating effects of a number of rubbing directions on the fixation ratios FR.FIGS. 11A to 11Ddepict experimental conditions according to the present embodiment.

In the present experiment, a sheet S having the image layer I formed thereon was prepared. The image layer I is rubbed by the rubbing plate200like the experiment described in the context of the first embodiment. The image layer I was rubbed under four conditions shown inFIGS. 11A to 11D. The other experimental conditions are the same as those described in the context of the first embodiment.

Under the first experimental condition (FIG. 11A), the image layer I was rubbed in a first experimental direction (from the right to the left). The rubbing was continued for 5 seconds. Meanwhile the image layer I was rubbed 80 times.

In the second experimental condition (FIG. 11B), the image layer I was rubbed in the first experimental direction and a second experimental direction (from the left to the right) opposite to the first experimental direction. The rubbing was continued for 5 seconds in total. The image layer I was rubbed 40 times in the first experimental direction and 40 times in the second experimental direction, respectively.

In the third experimental condition (FIG. 11C), the image layer I was rubbed in the first experimental direction, the second experimental direction and a third experimental direction (from the bottom to the top) perpendicular to the first and second experimental directions. The rubbing was continued for 5 seconds in total. Meanwhile the image layer I was rubbed 27 times in the first and second experimental directions, respectively, and 26 times in the third experimental direction.

In the fourth experimental condition (FIG. 11D), the image layer I was rubbed in the first experimental direction, the second experimental direction, the third experimental direction and a fourth experimental direction (from the top to the bottom) opposite to the third experimental direction. The rubbing was continued for 5 seconds in total. Meanwhile the image layer I was rubbed 20 times in the first to fourth directions, respectively.

FIG. 12is a graph showing fixation ratios FR obtained under the experimental conditions described in the context ofFIGS. 11A to 11D. The horizontal axis of the graph shown inFIG. 12represents the number of the rubbing directions described in the context ofFIGS. 11A to 11D. The vertical axis of the graph shown inFIG. 12represents the fixation ratios FR of the image layer I on the sheet S. The method for calculating the fixation ratios FR shown inFIG. 12is based on the calculation method described in the context of the first embodiment. The effects of the number of the rubbing directions on the fixation ratios FR are described with reference toFIGS. 11A to 12.

As shown inFIG. 12, the fixation ratio FR linearly went up as an increase in the number of rubbing directions. Under the first experimental condition described in the context ofFIG. 11A, the fixation ratio FR was 56%. Under the second experimental condition described in the context ofFIG. 11B, the fixation ratio FR was 73%. Under the third experimental condition described in the context ofFIG. 11C, the fixation ratio FR was 84%. Under the fourth experimental condition described in the context ofFIG. 11D, the fixation ratio FR was 94%.

It is clear from the graph shown inFIG. 12that the increase in the number of the rubbing directions causes a high fixation ratio FR in a relatively short period of time.

FIG. 13is a schematic plan view of a fixing device300A configured to perform the three-directional rubbing operations shown inFIG. 11C. The fixing device300A is described with reference toFIGS. 11A to 11Dand13.

The fixing device300A comprises the rubbing roller310described in the context of the first embodiment. The rubbing roller310includes the tubular contact cylinder311which contacts the image layer I, and the shaft312which supports the rotatable contact cylinder311. The shaft312includes a first end315and a second end316opposite to the first end315.

The fixing device300A has a gear321mounted on the second end316of the shaft312, and a motor330coupled to the gear321. The motor330rotates the shaft312by means of the gear321. As a result, the contact cylinder311is integrally rotated with the shaft312.

The fixing device300A has a pair of thrust bearings317configured to support the rotatable shaft312. The paired thrust bearings317are situated between the first end315of the shaft312and the contact cylinder311as well as between the gear321and the contact cylinder311. The thrust bearings317allow the shaft312not only to rotate but also to be displaced in an axial direction thereof.

The fixing device300A includes a cam gear318which contacts the first end315of the shaft312, and a motor319connected to the cam gear318. The cam gear318eccentrically situated with respect to the shaft312includes a circumferential surface361engaged with the motor319and a pressing surface362which contacts the first end315of the shaft312. The pressing surface362has a thickness that gradually increases toward the second end316of the shaft312. The vector shown inFIG. 13exemplifies the first direction D1indicating the conveying direction of the sheet S. The motor319eccentrically rotates the cam gear318with respect to the shaft312. As a result, the shaft312and the contact cylinder311are pressed and displaced in a first traverse direction T1perpendicular to the first direction D1. In the present embodiment, the cam gear318is exemplified as the cam element.

The fixing device300A has a coil spring363adjacent to the second end316of the shaft312. The coil spring363biases the gear321mounted on the second end316in a second traverse direction T2opposite to the first traverse direction T1. In the present embodiment, the motor319and the coil spring363which reciprocate the contact cylinder311in the first and second traverse directions T1, T2are exemplified as the drive mechanism.

FIG. 14shows a reciprocating movement of the rubbing roller310caused by the motor319. The upper drawing ofFIG. 14is a schematic plan view of the fixing device300A having the contact cylinder311near the cam gear318. The lower drawing ofFIG. 14is a schematic plan view of the fixing device300A having the contact cylinder311apart from the cam gear318. The fixing device300A is further described with reference toFIGS. 11A to 11D,13and14.

As described above, the cam gear318is eccentrically situated with respect to the shaft312. InFIG. 14, the eccentric amount between the cam gear318and the shaft312is expressed by an alphabet “e.” As shown in the upper drawing ofFIG. 14, when the first end315of the shaft312abuts a thin section of the cam gear318, the contact cylinder311approaches the cam gear318. As shown in the lower drawing ofFIG. 14, when the first end315of the shaft312abuts a thick section of the cam gear318, the contact cylinder311moves away from the cam gear318. InFIG. 14, the displacement amount of the contact cylinder311in the first or second traverse direction T1, T2is expressed by an alphabet As shown in the lower drawing ofFIG. 14, when the contact cylinder311moves away from the cam gear318, the coil spring363becomes compressed. Thereafter the first end315of the shaft312moves on the pressing surface362of the cam gear318, so that an abutting position between the first end315and the pressing surface362of the cam gear318moves to the thin section of the cam gear318, which in turn stretches the coil spring363. Thus, the coil spring363appropriately maintains the contact between the first end315of the shaft312and the cam gear318, which appropriately accomplishes the reciprocating movement of the contact cylinder311due to the rotation of the cam gear318by the motor319.

FIGS. 15A and 15Bare schematic side views of the fixing device300A and a conveyor which works with the fixing device300A to fix the image layer I on the sheet S.FIG. 15Aentirely shows the fixing device300A and the conveyor.FIG. 15Bis an enlarged view around the rubbing roller310. The fixing device300A is further described with reference toFIGS. 4,13,15A and15B.

The conveyor includes an upstream conveyor410A disposed before the fixing device300A, and a downstream conveyor420A disposed after the fixing device300A. The upstream and downstream conveyors410A,420A are exemplified as the conveying elements configured to convey the sheet S, like the first embodiment.

The conveyor comprises an intermediate conveyor450situated between the upstream and downstream conveyors410A,420A. In the present embodiment, in addition to the upstream and downstream conveyors410A,420A, the intermediate conveyor450is also exemplified as the conveying element.

As in the first embodiment, the upstream conveyor410A comprises the upper and lower rollers411,412. The upstream conveyor410A comprises an upper guide plate461configured to stably convey the sheet S to the intermediate conveyor450, and a lower guide plate462situated below the upper guide plate461. The sheet S conveyed by the upper and lower rollers411,412is guided by the upper and lower guide plates461,462and fed to the intermediate conveyor450.

Like the first embodiment, the downstream conveyor420A comprises the upper and lower rollers421,422. The downstream conveyor420A has an upper guide plate463configured to stably convey the sheet S from the intermediate conveyor450to a nip portion between the upper and lower rollers421,422, and a lower guide plate464situated below the upper guide plate463. The sheet S conveyed by the intermediate conveyor450is guided by the upper and lower guide plates463,464and fed to the nip portion between the upper and lower rollers421,422.

FIGS. 15A and 15Bschematically show the contact cylinder311and the shaft312of the rubbing roller310as the fixing device300A. Like the first embodiment, the contact cylinder311comprises the substantially cylindrical elastic layer313which surrounds the circumferential surface of the shaft312, and the nonwoven fabric layer314which covers the outer circumferential surface of the elastic layer313. The elastic layer313is formed by using, for example, sponge or other soft and elastic material. The nonwoven fabric layer314is formed by using, for example, any of the nonwoven fabrics described in the context ofFIG. 4.

The intermediate conveyor450includes a drive roller451, an idler452, and an endless belt453extending between the drive roller451and the idler452. The sheet S is sent from the upstream conveyor410A onto the endless belt453. The drive roller451revolves the endless belt453to convey the sheet S toward the downstream conveyor420A. The idler452is rotated in response to the revolution of the endless belt453. The directions of the vectors shown inFIGS. 15A and 15Bare exemplified as the first direction D1indicating the conveying direction of the sheet S, respectively. The lengths of the vectors shown inFIGS. 15A and 15Bare exemplified as the first speed V1indicating the conveying speed for the sheet S, respectively. In the present embodiment, the endless belt453is exemplified as the conveying belt.

The intermediate conveyor450has a backup roller340A and a cylinder device350A connected to the backup roller340A. The cylinder device350A causes the backup roller340A to separate from or approach the rubbing roller310. In the present embodiment, the cylinder device350A is exemplified as the separating/approaching mechanism. Alternatively, another mechanism configured to cause the backup roller340A to separate from or approach the rubbing roller310may be used as the separating/approaching mechanism

Like a commercially available cylinder device, the cylinder device350A comprises a shell353and a rod354which is stored in the shell353. The rod354includes a tip end configured to support the rotatable backup roller340A. The rod354is pushed from the shell353by, for example, working fluid (e.g., oil or air) which is fed into the shell353. As a result, the backup roller340A is displaced toward the rubbing roller310. The backup roller340A displaced toward the rubbing roller310pushes the endless belt453against the rubbing roller310. Thus, the circumferential surface of the rubbing roller310is deformed to form the upper nip surface N1along the upper surface of the sheet S passing through the fixing device300A, like the first embodiment. The outer surface of the endless belt453, which is deformed along the circumferential surface of the backup roller340A, forms the lower nip surface N2. In the present embodiment, the upper nip surface N1which contacts the image (image layer I) formed on the upper surface of the sheet S is exemplified as the contact surface.

The sheet S conveyed by the intermediate conveyor450passes between the endless belt453and the rubbing roller310. The motor330, which is described in the context ofFIG. 13, rotates the rubbing roller310such that the upper nip surface N1moves in the first direction D1at the second speed V2different from the first speed V1. In the present embodiment, the second speed V2is greater than the first speed V1. Alternatively, the second speed V2may be lower than the first speed V1.

As described in the context ofFIG. 13, the rotation of the cam gear318reciprocates the upper nip surface N1in the first and second traverse directions T1, T2. Furthermore, rubbing the image layer I in the first direction D1is accomplished by the speed difference of the upper nip surface N1of the sheet S in the first direction D1. In the present embodiment, the motor330moves the upper nip surface N1in the first direction D1. Alternatively, the motor330may move the upper nip surface N1in the second direction opposite to the first direction D1. In addition, the motor330and the gear321may be removed from the fixing device300A. In this case, rubbing the image layer I is accomplished by the reciprocating movement of the contact cylinder311in the first and second traverse directions T1, T2. It is preferred that the shaft312supports the rotatable contact cylinder311.

FIG. 16is a schematic side view of the fixing device300A and the conveyor after the sheet S passes through the intermediate conveyor450. The fixing device300A and the conveyor are further described with reference toFIGS. 15A to 16.

The upstream conveyor410A comprises a switch lever465. The switch lever465includes a turning shaft466adjacent to the lower roller412, and an arm467extending from the turning shaft466. The arm467turns between a reference position (seeFIG. 16) where the arm467traverses a conveyance path PS defined by the upper and lower guide plates461,462after the nip portion between the upper and lower rollers411,412, and an inclined position (seeFIG. 15A) where the arm467is inclined with respect to the reference position.

The arm467at the reference position is turned to the inclined position by the leading edge of the sheet S sent by the upper and lower rollers411,412. A biasing element (not shown), such as a twisted coil, is mounted on the turning shaft466. The biasing element biases the switch lever465to return the arm467to the reference position. Thus, once the conveyance of the sheet S from the upstream conveyor410A to the intermediate conveyor450completes, the arm467is returned to the reference position by the biasing element.

If the arm467reaches the inclined position, the switch lever465outputs a first trigger signal to a fluid controller (not shown) configured to control flow of the working fluid to the shell353of the cylinder device350A. Based on the first trigger signal, the fluid controller supplies the working fluid into the shell353to extend the rod354from the shell353. As a result, the backup roller340A approaches the rubbing roller310. If the arm467reaches the reference position, the switch lever465outputs a second trigger signal to the fluid controller. Based on the second trigger signal, the fluid controller discharges the working fluid from the shell353to retract the rod354in the shell353. As a result, the backup roller340A and the endless belt453separate from the rubbing roller310, as shown inFIG. 16. Therefore it is less likely that there are unnecessary rubbing operations between the endless belt453and the rubbing roller310.

The fixing device300A according to the second embodiment and the conveyor (the upstream, intermediate and downstream conveyor410A,450,420A), which is used for conveying the sheet S to the fixing device300A, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor described in the context of the first embodiment.

FIGS. 17 and 18are side views schematically showing a fixing device and a conveyor according to the third embodiment, respectively. Different features from those of the second embodiment are described hereinafter. Therefore, some descriptions overlapping with those of the second embodiment are omitted. Hereinafter, the same reference numerals are used for describing the same elements as those of the second embodiment. The descriptions associated with the second embodiment are preferably incorporated into the elements which are not described hereinafter. The fixing device and the conveyor according to the third embodiment are described with reference toFIGS. 3,17and18.

The conveyor includes the upstream conveyor410A situated before the fixing device300A, and the downstream conveyor420A situated after the fixing device300A. The upstream and downstream conveyors410A,420A are exemplified as the conveying elements configured to convey the sheet S, like the second embodiment.

The conveyor has an intermediate conveyor450B situated between the upstream and downstream conveyors410A,420A. In the present embodiment, in addition to the upstream and downstream conveyors410A,420A, the intermediate conveyor450B is also exemplified as the conveying element.

The intermediate conveyor450B includes the drive roller451, the idler452, and the endless belt453extending between the drive roller451and the idler452. The sheet S is sent from the upstream conveyor410A onto the endless belt453. The drive roller451revolves the endless belt453to convey the sheet S toward the downstream conveyor420A. The idler452is rotated in response to the revolution of the endless belt453.

The intermediate conveyor450B comprises an upstream backup roller343and a downstream backup roller344disposed between the drive roller451and the idler452. The intermediate conveyor450B further comprises a frame349configured to support the rotatable upstream and downstream backup rollers343,344. The frame349moves the endless belt453nearby the rubbing roller310or separates the endless belt453from the rubbing roller310by means of the same separating/approaching mechanism as that of the cylinder device350A described in the context of the second embodiment. Like the second embodiment, the switch lever465provided in the upstream conveyor410A controls the approaching and separating motions of the endless belt453with respect to the rubbing roller310. The rubbing roller310rubs the image layer I on the sheet S in three directions by means of the mechanism described in the context of the second embodiment. In the present embodiment, the upstream and downstream backup rollers343,344works like the backup roller340A described in the context of the second embodiment.

The intermediate conveyor450B comprises an upstream holding roller345and a downstream holding roller346situated after the rubbing roller310. The upstream holding roller345is disposed in correspondence with the upstream backup roller343. The downstream holding roller346is disposed in correspondence with the downstream backup roller344.

The upstream backup roller343pushes the endless belt453against the upstream holding roller345in response to the movement of the switch lever465to the inclined position. The downstream backup roller344pushes the endless belt453against the downstream holding roller346in response to the movement of the switch lever465to the inclined position. As a result, the endless belt453between the upstream backup roller343/upstream holding roller345and the downstream backup roller344/downstream holding roller346is pushed against the circumferential surface of the rubbing roller310. Thus, the rubbing roller310defines a travel path of the endless belt453curved toward the frame349. As a result, relatively long rubbing time between the rubbing roller310and the image layer I on the sheet S is ensured. This preferably contributes to higher fixation ratio FR, as described in the context ofFIG. 3.

While the rubbing roller310rubs the image layer I on the sheet S, the sheet S is appropriately held between the upstream backup roller343and the upstream holding roller345, as well as between the downstream backup roller344and the downstream holding roller346. As described in the context of the second embodiment, the rubbing roller310also reciprocally rubs the image layer I in the perpendicular direction to the conveying direction of the sheet S. It is likely that conveyance failures of the sheet S, which is caused by the reciprocal rubbing in the perpendicular direction to the conveying direction of the sheet S, are prevented by causing the upstream backup roller343, the upstream holding roller345, the downstream backup roller344and the downstream holding roller346to hold the sheet S.

In the present embodiment, the sheet S is held by the upstream backup roller343, the upstream holding roller345, the downstream backup roller344and the downstream holding roller346. Alternatively, the sheet S may be held only between the upstream backup roller343and the upstream holding roller345. Further alternatively, the sheet S may be held only between the downstream backup roller344and the downstream holding roller346.

FIGS. 19A and 19Bschematically show a rubbing roller according to the fourth embodiment.FIG. 19Ais a schematic cross-sectional view of the rubbing roller.FIG. 19Bis a schematic plan view of the rubbing roller. The rubbing roller according to the fourth embodiment is preferably applied in place of the rubbing roller310described in the context of the aforementioned embodiments.

In the present embodiment, a rubbing roller310C comprises a hard shaft312C (e.g., a metallic shaft) and a nonwoven fabric band314C spirally wrapped around the circumferential surface of the shaft312C. The nonwoven fabric band314C may be formed, for example, from any of the nonwoven fabrics described in the context ofFIG. 4.

In the present embodiment, a backup roller340C is formed from a softer elastic material than the shaft312C. If the backup roller340C is pressed to the shaft312C, the backup roller340C is elastically deformed to form an appropriate nip portion between the backup and rubbing rollers340C,310C. Rubbing on the sheet S which passes in between the backup and rubbing rollers340C,310C is performed on the basis of the fixation methodologies described in the context of the aforementioned embodiments. Thus, the image layer I is preferably fixed on the sheet S.

FIG. 20is a schematic view of a fixing device and a conveyor according to the fifth embodiment. The fixing device and the conveyor according to the fifth embodiment are described with reference toFIG. 20. Hereinafter, the same reference numerals are used for describing the same elements as those of the first embodiment. The descriptions associated with the first embodiment are preferably incorporated into the elements which are not described hereinafter.

A conveyor400configured to convey the sheet S with the image layer I thereon comprises a belt unit450D, an upstream guider460situated before the belt unit450D, and a downstream guider469situated after the belt unit450D. The sheet S is guided by the upstream guider460and sent to the belt unit450D. Thereafter, the sheet S is sent to the downstream guide469by the belt unit450D:

The belt unit450D comprises the drive roller451, the idler452, the endless belt453extending between the drive roller451and the idler452, and a tension roller454applying tension to the endless belt453. Rotation of the drive roller451causes the endless belt453to revolve around the drive roller451, the idler452and the tension roller454. As a result, the sheet S, which is sent from the upstream guider460to the outer surface455of the endless belt453, moves toward the downstream guider469in response to the revolution of the endless belt453. In the present embodiment, the belt unit450D is exemplified as the conveying element. The endless belt453is exemplified as the conveying belt.

The belt unit450D further comprises a charger456configured to charge the outer surface455of the endless belt453. The outer surface455of the endless belt453which is charged by the charger456causes the sheet S to electrostatically stick thereto. Therefore, the sheet S is stably conveyed by the endless belt453. In the present embodiment, the endless belt453is preferably formed from resin such as PVDF.

The endless belt453includes the inner surface457opposite to the outer surface455to which the sheet S sticks. The belt unit450D has a backup roller340D which abuts the inner surface457of the endless belt453. The backup roller340D includes the upstream and downstream backup rollers343,344. The downstream backup roller344is closer to the downstream guider469than the upstream backup roller343.

The fixing device300D comprises a rubbing roller310D configured to rub the image layer I on the sheet S. The rubbing roller310D includes an upstream rubbing roller323corresponding to the upstream backup roller343, and a downstream rubbing roller324corresponding to the downstream backup roller344. The downstream rubbing roller324rubs the image layer I after the upstream rubbing roller323. In the present embodiment, the rubbing roller310D is exemplified as the rubbing mechanism. The upstream and downstream rubbing rollers323,324are exemplified as an upstream rubbing mechanism and a downstream rubbing mechanism, respectively.

The fixing device300D comprises a housing329configured to partially store the upstream and downstream rubbing rollers323,324. The housing329opens toward the endless belt453. The upstream and downstream rubbing rollers323,324protrude from the opening of the housing329to abut the outer surface455of the endless belt453or the sheet S.

The fixing device300D comprises a presser355configured to press the rubbing roller310D against the sheet S. In the present embodiment, the presser355includes an upstream coil spring356configured to push the upstream rubbing roller323against the sheet S, and a downstream coil spring357configured to push the downstream rubbing roller324against the sheet S. Alternatively, the presser355may be a cylinder device configured to press the rubbing roller310D against the sheet S.

The upper end of the presser355is connected to a top plate325of the housing329. The lower end of the presser355is connected to, for example, a bearing (not shown) configured to support a rotatable shaft (not shown) of the rubbing roller310D.

FIG. 21is a schematic plan view of the fixing device300D. The fixing device300D is further described with reference toFIGS. 20 and 21.

The fixing device300D includes a drive mechanism331mounted on an outer surface of the housing329. The drive mechanism331includes an upstream gear332connected to a shaft326of the upstream rubbing roller323, a downstream gear333connected to a shaft327of the downstream rubbing roller324, an upstream motor334connected to the upstream gear332, and a downstream motor335connected to the downstream gear333. The upstream motor334rotates the upstream rubbing roller323on the image layer I. The downstream motor335rotates the downstream rubbing roller324on the image layer I. In the present embodiment, the upstream and downstream motors334,335are exemplified as the drive mechanisms, respectively.

The housing329and the drive mechanism331are configured to allow the rubbing roller310D to be displaced as the presser355expands or contracts. Thus, the rubbing roller310D is appropriately pressed against the image layer I on the sheet S.

FIG. 22is a schematic cross-sectional view of the rubbing roller310D. The rubbing roller310D is described with reference toFIGS. 4 and 22.

The rubbing roller310D comprises a metallic shaft312D, an elastic layer313D configured to cover the circumferential surface of the shaft312D, and a nonwoven fabric layer314D configured to cover the circumferential surface of the elastic layer313D. The nonwoven fabric layer314D of the upstream rubbing roller323is preferably formed from a material different from the nonwoven fabric layer314D of the downstream rubbing roller324. The upstream rubbing roller323may fix the image layer I to the sheet S at a different fixation ratio FR from that of the downstream rubbing roller324due to the difference between the materials of the nonwoven fabric layers314D, as described in the context ofFIG. 4. In the present embodiment, because the nonwoven fabric layer314D covers the elastic layer313D, the circumferential surface of the rubbing roller310D includes an elastic circumferential surface.

FIG. 23is a schematic cross-sectional view of the upstream and downstream rubbing rollers323,324which are pressed against the image layer I. The rubbing roller310D is further described with reference toFIGS. 1A to 1C,20,21and23.

The upstream coil spring356biases the upstream rubbing roller323downward with a force F1. The downstream coil spring357biases the downstream rubbing roller324downward with a force F2greater than the force F1. Therefore, the downstream rubbing roller324presses the image layer I with a greater force than the upstream rubbing roller323.

A flat upstream nip surface UN along the image layer I is formed on the circumferential surface of the upstream rubbing roller323pressed with the force F1. A flat downstream nip surface DN along the image layer I is formed on the circumferential surface of the downstream rubbing roller324pressed with the force F2.

In the present embodiment, the downstream rubbing roller324has the same structure as the upstream rubbing roller323. Therefore, the upstream nip surface UN of the upstream rubbing roller323, which is pressed by the smaller force F1than the force F2, is narrower than the downstream nip surface DN of the downstream rubbing roller324. Alternatively, the elastic layer313D of the downstream rubbing roller324may be less hard than the elastic layer313D of the upstream rubbing roller323. In this case, if the force F2is equal to or greater than the force F1, the area of the downstream nip surface DN is larger than the area of the upstream nip surface UN. Alternatively, the elastic layer313D of the downstream rubbing roller324may be harder than the elastic layer313D of the upstream rubbing roller323. In this case, if the force F2is greater than the force F1, it is less likely that an area between the upstream and downstream nip surfaces UN, DN changes. As a result, it is less likely that the rubbing times during which the upstream and downstream rubbing rollers323,324rub the image layer I changes, which result in facilitating parameter management on the fixation process.

As described above, the upper surface of the colored particles P in the image layer I is covered with the film formed from the polymer compounds R. The rubbing operation of the rubbing roller310D makes the covering film stronger, so that the image is appropriately protected. In other words, it becomes less likely that the image layer I which is protected by the film layer reinforced by the upstream rubbing roller323is damaged as the sheet S is conveyed toward the downstream. Therefore, the pressing force from the upstream rubbing roller323(i.e., the force F1) or the area of the upstream nip surface UN is preferably smaller than the pressing force from the downstream rubbing roller324(i.e., the force F2) or the area of the downstream nip surface DN. In the present embodiment, the surface pressure of the upstream nip surface UN is set at, for example, 0.02 g/cm2. The surface pressure of the downstream nip surface DN is set at, for example, 0.20 g/cm2.

As shown inFIG. 23, the endless belt453conveys the sheet S at the first speed V1. The upstream motor334rotates the shaft312D such that the upstream nip surface UN, which is exemplified as the contact surface, moves in the conveying direction of the sheet S at the second speed V2greater than the first speed V1. The downstream motor335rotates the shaft312D such that the downstream nip surface DN, which is exemplified as the contact surface, moves in the conveying direction of the sheet S at the second speed V2. As a result, the rubbing roller310D rotates with rubbing the image layer I. In the present embodiment, the first speed V1is set at, for example, 300.0 mm/sec. The second speed V2is set at, for example, 301.5 mm/sec or above.

FIGS. 24 and 25show another control method for controlling the rubbing roller310D by means of the upstream and downstream motors334,335(SeeFIG. 21). The rubbing roller310D is further described with reference toFIGS. 21,24and25.

If the movement speed of the upstream nip surface UN/downstream nip surface DN is different from the first speed V1, the upstream nip surface UN/downstream nip surface DN rubs the image layer I. Therefore, as shown inFIG. 24, the upstream motor334may rotate the shaft312D such that the upstream nip surface UN moves in the conveying direction of the sheet S at the second speed V2greater than the first speed V1. In addition, the downstream motor335may rotate the shaft312D such that the downstream nip surface UN moves in the conveying direction of the sheet S at a third speed V3greater than the second speed V2. In this case, the third speed V3may be set at, for example, 303.0 mm/sec, while the second speed V2is set at 301.5 mm/sec. The difference between the third and first speeds V3, V1is greater than the difference between the second and first speeds V2, V1. Thus, the image layer I is rubbed in response to a relatively small speed difference in the upstream. The image layer I is rubbed in response to a relatively large speed difference in the downstream. Thus, the image layer I is fixed at a relatively high fixation ratio FR without excessive damages.

As shown inFIG. 25, the upstream motor334may rotate the shaft312D such that the upstream nip surface UN moves in the conveying direction of the sheet S at the second speed V2lower than the first speed V1. The downstream motor335may rotate the shaft312D such that the downstream nip surface UN moves in the conveying direction of the sheet S at the third speed V3greater than the second speed V2.

Furthermore, the upstream motor334and the downstream motor335may rotate the rubbing roller310D to move the upstream and downstream nip surfaces UN, DN, respectively, in an opposite direction to the conveying direction of the sheet S.

The fixing device300D according to the fifth embodiment and the conveyor400which conveys the sheet S to the fixing device300D, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor that are described in the context of the first embodiment.

FIG. 26is a schematic view of a fixing device and a conveyor according to the sixth embodiment. Different features from those of the fifth embodiment are described hereinafter. Therefore, some descriptions overlapping with those of the fifth embodiment are omitted. Hereinafter, the same reference numerals are used for describing the same elements as those of the fifth embodiment. The descriptions associated with the fifth embodiment are preferably incorporated into the elements which are not described hereinafter. The fixing device and the conveyor according to the sixth embodiment are described with reference toFIG. 26.

A conveyor400E configured to convey the sheet S with the image layer I formed thereon has a belt unit450E, the upstream guider460situated before the belt unit450E, and the downstream guider469situated after the belt unit450E. The sheet S is guided by the upstream guider460and sent to the belt unit450E. Thereafter, the sheet S is sent to the downstream guide469by the belt unit450E.

The belt unit450E comprises the drive roller451, the idler452, an endless belt453E extending between the drive roller451and the idler452, and the tension roller454applying tension to the endless belt453E. Rotation of the drive roller451causes the endless belt453E to revolve around the drive roller451, the idler452and the tension roller454. As a result, the sheet. S, which is sent from the upstream guider460to the outer surface455of the endless belt453E, moves toward the downstream guider469in response to the revolution of the endless belt453E. In the present embodiment, the belt unit450E is exemplified as the conveying element. The endless belt453E is exemplified as the conveying belt.

The belt unit450E has a vacuum device456E. Several through-holes458are formed on the endless belt453E. While the sheet S is conveyed by the belt unit450E, the vacuum device456E suctions the sheet S on the endless belt453E through the through-holes458.

The endless belt453E includes the inner surface457opposite to the outer surface455to which the sheet S sticks. The belt unit450E has the backup roller340D which abuts the inner surface457of the endless belt453E. The backup roller340D includes the upstream and downstream backup rollers343,344. The downstream backup roller344is closer to the downstream guider469than the upstream backup roller343.

The fixing device300E has a rubbing roller310E configured to rub the image layer I on the sheet S. The rubbing roller310E comprises an upstream rubbing roller323E corresponding to the upstream backup roller343, and a downstream rubbing roller324E corresponding to the downstream backup roller344. The downstream rubbing roller324E rubs the image layer I after the upstream rubbing roller323E. In the present embodiment, the rubbing roller310E is exemplified as the rubbing mechanism. The upstream and downstream rubbing rollers323E,324E are exemplified as the upstream and downstream rubbing mechanisms, respectively.

The fixing device300E comprises the housing329configured to partially store the upstream and downstream rubbing rollers323E,324E. The housing329opens toward the endless belt453E. The upstream and downstream rubbing rollers323E,324E protrude from the opening of the housing329to abut the outer surface455of the endless belt453E or the sheet S.

Unlike the fifth embodiment, the upstream and downstream rubbing rollers323E,324E are fixedly mounted in the housing329. Therefore, the upstream and downstream rubbing rollers323E,324E may not separate from or approach the endless belt453E. It should be noted that the upstream and downstream rubbing rollers323E,324E are rotated by the same drive mechanism as that of the fifth embodiment.

FIG. 27is a schematic cross-sectional view of the upstream and downstream rubbing rollers323E,324E which rub the image layer I. The rubbing roller310E is further described with reference toFIGS. 26 and 27.

The rubbing roller310E comprises the metallic shaft312D, a base layer313E covering the circumferential surface of the shaft312D, and a brush layer314E configured by brush314eimplanted in the base layer313E. The brush314emay be formed from rayon (pile fineness: 300D/100F) or polyester (pile fineness 75D/12F). The rubbing roller310E includes a circumferential surface having the brush314edisposed thereon.

In the present embodiment, the brush314eis mounted on the shaft312D via the base layer313E. Alternatively, the brush314may be directly glued to the shaft312D with adhesive.

In the present embodiment, the brush314eof the upstream rubbing roller323E is the same as the brush314eof the downstream rubbing roller324E. The brush314eof the upstream rubbing roller323E significantly projects from the base layer313E, compared to the brush314eof the downstream rubbing roller324E. It should be noted that the diameter of the upstream rubbing roller323E is equal to the diameter of the downstream rubbing roller324E, and the degree of the projection of the brush314eis adjusted on the basis of the thickness of the base layer313E.

In the present embodiment, a degree of interference between the image layer I and the brush layer314E of the upstream rubbing roller323E is substantially equal to a degree of interference between the image layer I and the brush layer314E of the downstream rubbing roller324E. In addition, the upstream rubbing roller323E is rotated at a rotating speed substantially equal to the downstream rubbing roller324E.

As described above, the brush314eof the upstream rubbing roller323E significantly projects from the base layer313E, compared to the brush314eof the downstream rubbing roller324E. Therefore, a load applied to the image layer I by the brush314eof the upstream rubbing roller323E while the rubbing roller310E is rotated, becomes smaller than a load applied to the image layer I by the brush314eof the downstream rubbing roller324E. Hence, the image layer I is fixed at a relatively high fixation ratio FR without excessive damages.

It should be noted that there may be differences in bending strength, thickness and other characteristics between the upstream and downstream rubbing rollers323E,324E. The load applied to the image layer by the brush314eof the upstream rubbing roller323E may be smaller than the load applied to the image layer I by the brush314eof the downstream rubbing roller324E, in response to the differences in characteristics between, the upstream and downstream rubbing rollers323E,324E.

The fixing device300E according to the sixth embodiment and the conveyor400E which is used for conveying the sheet S to the fixing device300E, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor which are described in the context of the first embodiment.

FIG. 28is a schematic view of a fixing device and a conveyor according to the seventh embodiment. Different features from those of the fifth embodiment are described hereinafter. Therefore, some descriptions overlapping with those of the fifth embodiment are omitted. Hereinafter, the same reference numerals are used for describing the same elements as those of the fifth embodiment. The descriptions associated with the fifth embodiment are preferably incorporated into the elements which are not described hereinafter. The fixing device and the conveyor according to the seventh embodiment are described with reference toFIG. 28.

Like the fifth embodiment, the conveyor400configured to convey the sheet S having the image layer I thereon comprises the belt unit450D, the upstream guider460situated before the belt unit450D, and the downstream guider469situated after the belt unit450D. The sheet S is guided by the upstream guider460and sent to the belt unit450D. Thereafter, the sheet S is sent to the downstream guide469by the belt unit450D.

A fixing device300F comprises the rubbing roller310D configured to rub the image layer I on the sheet S. The rubbing roller310D comprises the upstream rubbing roller323corresponding to the upstream backup roller343, and the downstream rubbing roller324corresponding to the downstream backup roller344. The downstream rubbing roller324rubs the image layer I after the upstream rubbing roller323.

The fixing device300F comprises the housing329configured to partially store the upstream and downstream rubbing rollers323,324. The housing329opens toward the endless belt453. The upstream and downstream rubbing rollers323,324protrude from the opening of the housing329to abut the outer surface455of the endless belt453or the sheet S.

The fixing device300F comprises a cylinder mechanism370. The cylinder mechanism370causes the rubbing roller310D to separate from or approach the image layer I of the sheet S on the endless belt453. In the present embodiment, the cylinder mechanism370is exemplified as a separating/approaching mechanism. Alternatively, the separating/approaching mechanism may have another structure configured to cause the rubbing roller310D to separate from or approach the endless belt453. For instance, the rubbing roller310D may separate from or approach the endless belt453by means of a lever arm.

The cylinder mechanism370includes an upstream cylinder device371configured to cause the upstream rubbing roller323to separate from or approach the image layer I of the sheet S on the endless belt453, and a downstream cylinder device372configured to cause the downstream rubbing roller324to separate from or approach the image layer I of the sheet S on the endless belt453.

The cylinder mechanism370includes a shell353F configured to receive working fluid, and a rod354F stored the shell353F. The shell353F is mounted on the top plate325of the housing329. The rod354F of the upstream cylinder device371is mounted on the shaft326of the upstream rubbing roller323. The rod354F of the downstream cylinder device372is mounted on the shaft327of the downstream rubbing roller324.

The fixing device300F comprises a controller373configured to control the cylinder mechanism370. The controller373controls flow of the working fluid to the shell353F. If the working fluid flows to the shell353F under the control of the controller373, the rod354F extends from the shell353F and pushes the rubbing roller310D against the image layer I. If the working fluid flows out from the shell353F, the rod354F retracts in the shell353F, so that the rubbing roller310D separates from the image layer I.

The controller373controls the upstream and downstream cylinder devices371,372independently. Therefore, the controller373may push one of the upstream and downstream rubbing rollers323,324against the image layer I, and separate the other one from the image layer I. Alternatively, the controller373may push both the upstream and downstream rubbing rollers323,324against the image layer I. The controller373may separate both the upstream and downstream rubbing rollers323,324from the image layer I, as appropriate. For example, unless the sheet S is conveyed, the controller373may separate the upstream and downstream rubbing rollers323,324from the image layer I.

The rubbing roller310D may separate from or approach the image layer I in response to passage of the sheet S. Alternatively, the rubbing roller310D may determine to separate from or approach the image layer I depending on types of liquid developer or the sheet S, which is used for forming the image layer I. For instance, if an image layer I formed by means of liquid developer is likely to be damaged, position of the upstream and/or downstream rubbing rollers323,324may be controlled such that a degree of interference between the upstream rubbing roller323and the endless belt453becomes smaller than a degree of interference between the downstream rubbing roller324and the endless belt453.

The fixing device300F according to the seventh embodiment and the conveyor400which is used for conveying the sheet S to the fixing device300F, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor which are described in the context of the first embodiment.

FIG. 29is a schematic view of a fixing device and a conveyor according to the eighth embodiment. The fixing device and the conveyor according to the eighth embodiment are described with reference toFIG. 29. Hereinafter, the same reference numerals are used for describing the same elements as those of the aforementioned embodiments. The descriptions associated with the aforementioned embodiments are preferably incorporated into the elements which are not described hereinafter.

A conveyor400G configured to convey the sheet S having the image layer I formed thereon comprises a belt unit450G, the upstream guider460situated before the belt unit450G, and the downstream guider469situated after the belt unit450G. The sheet S is guided by the upstream guider460and sent to the belt unit450G. Thereafter, the sheet S is sent to the downstream guide469by the belt unit450G.

The belt unit450G comprises the drive roller451, the idler452, the endless belt453extending between the drive roller451and the idler452, and the tension roller454applying tension to the endless belt453. Rotation of the drive roller451causes the endless belt453to revolve around the drive roller451, the idler452and the tension roller454. The idler452and the tension roller454rotate in response to the revolution of the endless belt453. As a result, the sheet S, which is sent from the upstream guider460to the outer surface455of the endless belt453, moves toward the downstream guider469in response to the revolution of the endless belt453. The sheet S is conveyed from the upstream guider460to the downstream guider469at the first speed V1. In the present embodiment, the direction from the upstream guider460to the downstream guider469is referred to as “first direction D1”. The belt unit450G is exemplified as the conveying element. The endless belt453is exemplified as the conveying belt.

The belt unit450G further comprises the charger456configured to charge the outer surface455of the endless belt453. The outer surface455of the endless belt453, which is charged by the charger456, causes the sheet S to electrostatically stick thereto. Therefore, the sheet S is stably conveyed by the endless belt453. In the present embodiment, the endless belt453is preferably formed from resin such as PVDF.

The endless belt453includes the inner surface457opposite to the outer surface455to which the sheet S sticks. The belt unit450G comprises the backup roller340which abuts the inner surface457of the endless belt453.

The fixing device300G comprises a rubbing band310G configured to rub the image layer I on the sheet S. The rubbing band310G is prepared as a nonwoven fabric roll398wrapped around a substantially cylindrical core399. The rubbing band310G may be a nonwoven fabric band which is formed by using, for example, any of the nonwoven fabrics described in the context ofFIG. 4. In the present embodiment, the rubbing band310G is exemplified as the rubbing belt.

The fixing device300G has an unwinding spindle397installed with the nonwoven fabric roll398. The unwinding spindle397is inserted into the core399. The unwinding spindle397preferably includes a chuck mechanism (not shown) configured to hold the core399. The chuck mechanism stably holds the nonwoven fabric roll398on the unwinding spindle397. The rubbing band310G is unwound from the nonwoven fabric roll398on the reel spindle397. The unwinding spindle397rotates and unwinds the rubbing band310G from the nonwoven fabric roll398. In the present embodiment, the unwinding spindle397is exemplified as the unwinder.

The fixing device300G has a winding spindle396configured to rotate in cooperation with the unwinding spindle397. The winding spindle396is inserted into a substantially cylindrical core395. Like the unwinding spindle397, the winding spindle396comprises a chuck mechanism (not shown) configured to hold the core395. An end of the rubbing band310G, which is unwound by the unwinding spindle397, is connected to the outer circumferential surface of the core395. The rubbing band310G is wrapped around the core395as the winding spindle396rotates. Thus, the winding spindle396may wind the rubbing band310G. In the present embodiment, the winding spindle396is exemplified as the winder.

The fixing device300G has a press mechanism350G configured to press the rubbing band310G to the image layer I on the sheet S, the rubbing band310G extending between the unwinding and winding spindles397,396. The press mechanism350G comprises a press roller351G provided in correspondence with the backup roller340, and a coil spring352G configured to bias the press roller351G toward the rubbing band310G. In the present embodiment; the press mechanism350G is exemplified as the first press mechanism.

The rubbing band310G, which is unwound by the unwinding spindle397, passes between the press roller351G and the endless belt453, and is then wrapped around the winding spindle396. The coil spring352G configured to bias the press roller351G toward the endless belt453forms a nip portion N between the rubbing band310G and the endless belt453to hold the sheet S therebetween. When the sheet S passes through the nip portion N, the press roller351G presses the rubbing band310G to the image layer I. The coil spring352G further biases the press roller351G toward the image layer I. In the present embodiment, the press roller351G is exemplified as the press piece. The coil spring352G is exemplified as the biasing element.

The press roller351G comprises a rotating shaft312G and a bearing328configured to hold the rotating shaft312G. In the present embodiment, the press roller351G rotates around the rotating shaft312G as the rubbing band310G moves from the unwinding spindle397to the winding spindle396. Alternatively, a rod or other elements with a surface on which the rubbing band310G slides during the movement from the unwinding spindle397to the winding spindle396may be used as the press piece.

In the present embodiment, the coil spring352G connected to the bearing328is used as the biasing element. Alternatively, a cylinder device or other biasing mechanisms configured to bias the press piece toward the image layer I may be used as the biasing element.

In the present embodiment, the winding spindle396winds the rubbing band310G while the endless belt453conveys the sheet S. The rubbing band310G held between the press roller351G and the endless belt453moves in the first direction D1at the second speed V2lower than the first speed V1while the winding spindle396rotates. The difference between the conveying speed of the sheet S (the first speed V1) and the winding speed of the winding spindle396(the second speed V2) causes rubbing between the image layer I and the rubbing band310G. In the present embodiment, therefore, the winding spindle396, the unwinding spindle397and the press mechanism350G are exemplified as the sliding mechanisms.

The fixing device300G according to the eighth embodiment and the conveyor400G which is used for conveying the sheet S to the fixing device300G, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor which are described in the context of the first embodiment.

A fixing device according to the ninth embodiment is different from the fixing device300G according to the eighth embodiment, in terms of a separator configured to separate the press roller351G from the endless belt. The separator is described hereinafter. Some descriptions overlapping with those of the eighth embodiment are omitted for clarification. Hereinafter, the same reference numerals are used for describing the same elements as those of the eighth embodiment. The descriptions associated with the eighth embodiment are preferably incorporated into the elements which are not described hereinafter.

FIGS. 30A and 30Bare schematic views of a separator configured to separate the press roller351G from the endless belt.FIG. 30Ashows the press roller351G situated in a proximal position near the endless belt.FIG. 30Bshows the press roller351G situated in a separation position away from the endless belt. It should be noted that neitherFIGS. 30Anor30B shows the rubbing band in order to clarify the separator. The separator is described with reference toFIGS. 30A and 30B.

A press mechanism350H has a separator380configured to separate the press roller351G from the endless belt453E. The aforementioned coil spring352G includes a first end358connected to the bearing328which holds the rotating shaft312G of the press roller351G, and a second end359opposite to the first end358. The separator380has a rod arm381connected to the second end359. In the present embodiment, the press mechanism350H is exemplified as the first press mechanism.

The separator380comprises a turning shaft382configured to support the rotatable arm381. The arm381includes a base end383connected to the turning shaft382, and a tip end384opposite to the base end383. The base end383of the arm381is mounted on the turning shaft382via, for example, a twisted coil spring (not shown). The twisted coil spring biases the arm381downward. As a result, while the press roller351G is present in the proximal position, the coil spring352G is compressed to bias the press roller351G toward the image layer I on the sheet S.

The separator380comprises a rotating shaft385and an eccentric cam piece386integrally mounted on the rotating shaft385. The rotating shaft385is rotated by, for example, a solenoid switch (not shown) or other appropriate actuators. As a result, the eccentric cam piece386eccentrically rotates around the rotating shaft385to push the tip end384of the arm381upward. As a result, the press roller351G is moved to the separation position.

FIGS. 31A and 31Bare schematic views of the fixing device and the conveyor according to the ninth embodiment.FIG. 31Ashows the fixing device and the conveyor during a conveying time period in which the conveyor conveys the sheet S.FIG. 31Bshows the fixing device and the conveyor during a suspension time period in which the conveyor does not convey the sheet S. The fixing device and the conveyor according to the ninth embodiment are described with reference toFIGS. 30A to 31B.

A conveyor400H configured to convey the sheet S having the image layer I formed thereon comprises a belt unit450H, the upstream guider460situated before the belt unit450H, and the downstream guider469situated after the belt unit450H. Like the eighth embodiment, during the conveying time period, the sheet S is guided by the upstream guider460and sent to the belt unit450H. Thereafter, the sheet S is sent to the downstream guide469by the belt unit450H. On the other hand, during the suspension time period, the belt unit450H is stopped, and hence the sheet S is not sent to the conveyor400H.

The belt unit450H comprises the drive roller451, the idler452, the endless belt453E extending between the drive roller451and the idler452, and the tension roller454applying tension to the endless belt453E. Rotation of the drive roller451causes the endless belt453E to revolve around the drive roller451, the idler452and the tension roller454. The idler452and the tension roller454are rotated as the endless belt453E revolves. During the conveying time period, the sheet S, which is sent from the upstream guider460to the outer surface455of the endless belt453E, moves toward the downstream guider469in response to the revolution of the endless belt453E. The sheet S is conveyed from the upstream guider460to the downstream guider469at the first speed V1. In the present embodiment, the direction from the upstream guider460to the downstream guider469is referred to as “first direction D1”. The belt unit450H is exemplified as the conveying element. The endless belt453E is exemplified as the conveying belt.

The belt unit450H comprises the vacuum device456E which is disposed along the inner surface457opposite to the outer surface455of the endless belt453E configured to convey the sheet S, and the backup roller340. Several through-holes458are formed on the endless belt453E. During the conveying time period, the vacuum device456E suctions the sheet S through the through-holes458. As a result, the sheet S, which is conveyed by the traveling motion of the endless belt453E, sticks to the outer surface455of the endless belt453E.

Like the eighth embodiment, a fixing device300H comprises the rubbing band310G, the unwinding spindle397, and the winding spindle396. The fixing device300H also comprises the press mechanism350H described in the context ofFIGS. 30A and 30B. The arm381is partially shown as the separator380of the press mechanism350H.

The winding and unwinding spindles396,397are stopped during the conveying time period. The separator380keeps the press roller351G at the proximal position. Therefore, the rubbing band310G and the endless belt453E are held between the backup roller340and the press roller351G. The sheet S conveyed by the belt unit450H passes through the nip portion N between the rubbing band310G and the endless belt453E. Meanwhile, the image layer I on the sheet S is rubbed by the rubbing band310G.

If the belt unit450H is stopped thereafter, the separator380moves the press roller351G to the separation position, as described in the context ofFIGS. 30A and 30B. Meanwhile, the winding spindle396winds the rubbing band310G which sags as a result of the movement of the press roller351G to the separation position.

If the belt unit450H is activated again, the separator380moves the press roller351G to the proximal position. Meanwhile, the unwinding spindle397unwinds the rubbing band310G such that the tension added to the rubbing band310G becomes constant. Accordingly, when the belt unit450H is newly activated, a new section of the rubbing band310G rubs the image layer I. As a result, excessive abrasion or contamination of the rubbing band310G (e.g., contamination caused by paper dust, oil component, dust and alike on the sheet S). In addition, stopping the rubbing band310G during the conveying time period reduces frequency of replacing the rubbing band310G.

FIGS. 32A and 32Bshow other operations performed by the fixing device300H.FIG. 32Ashows the press roller351G at the proximal position.FIG. 32Bshows the press roller351G at the separation position. Other operations performed by the fixing device300H are described with reference toFIGS. 30A,30B,32A and32B. It should be noted thatFIGS. 32A and 32Bpartially show the arm381as the separator380of the press mechanism350H.

The conveyor400H conveys sheets S sequentially.FIGS. 32A and 32Bshow a sheet S1and a sheet S2conveyed after the sheet S1. In the present embodiment, the sheet S1is exemplified as the preceding sheet. The sheet S2is exemplified as the subsequent sheet.

As shown inFIG. 32A, when the sheet S1starts passing between the press and backup rollers351G,340, the separator380moves the press roller351G to the proximal position.

The separator380then keeps the press roller351G to the proximal position while the sheet S1passes between the press and backup rollers351G,340. Meanwhile, the rubbing band310G rubs the image layer I on the sheet S1. It should be noted that the winding and unwinding spindles396,397are stopped while the press roller351G exists in the proximal position.

As shown inFIG. 32B, after the sheet S1passes between the press and backup rollers351G,340, the separator380moves the press roller351G to the separation position. Meanwhile, the winding spindle396winds the rubbing band310G which sags as a result of the movement of the press roller351G to the separation position.

Thereafter, the separator380keeps the press roller351G in the separation position until the sheet S2starts passing between the press and backup rollers351G,340. When the sheet S starts passing between the press and backup rollers351G,340, the separator380moves the press roller351G to the proximal position again. While the press roller351G is moved to the proximal position, the unwinding spindle397unwinds the rubbing band310G such that the tension applied to the rubbing band310G becomes constant.

In the present embodiment, whenever the press roller351G separates from or approaches the endless belt453E, the rubbing band310G is wound by the winding spindle396and unwound by the unwinding spindle397. Alternatively, whenever a given number of the sheets S pass between the press and backup rollers351G,340, the rubbing band310G may be wound by the winding spindle396and unwound by the unwinding spindle310G. For instance, the rubbing band310G is wound by the winding spindle396and unwound by the unwinding spindle397, whenever 40 to 50 sheets S pass between the press and backup rollers351G,340, which result in less replacing frequency of the rubbing band310G.

The fixing device300H according to the ninth embodiment and the conveyor400H which is used for conveying the sheets S to the fixing device300H, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor which are described in the context of the first embodiment.

A fixing device according to the tenth embodiment is different from the fixing device300G according to the eighth embodiment, in terms of arrangement of the winding and unwinding spindles. The differences from the eighth embodiment are described hereinafter. Some descriptions overlapping with those of the eighth embodiment are omitted for clarification. Hereinafter, the same reference numerals are used for describing the same elements as those of the eighth embodiment. The descriptions associated with the eighth embodiment are preferably incorporated into the elements which are not described hereinafter.

FIG. 33is a schematic view of a fixing device and a conveyor according to the tenth embodiment. The fixing device and the conveyor according to the tenth embodiment are described with reference toFIG. 33.

FIG. 33shows the same conveyor400G as that of the eighth embodiment. A fixing device300I according to the present embodiment is adjacent to the conveyor400G, like the eighth embodiment.

The fixing device300I comprises an unwinding spindle397I and a winding spindle396I, in addition to the rubbing band310G and the press mechanism350G of the eighth embodiment. Unlike the eighth embodiment, the unwinding spindle397I is disposed near the downstream guider469of the conveyor400G. The winding spindle3961is disposed near the upstream guider460of the conveyor400G.

Like the eighth embodiment, the unwinding spindle397I is inserted into the core399of the nonwoven fabric roll398. The unwinding spindle397I preferably comprises a chuck mechanism (not shown) configured to hold the core399. The chuck mechanism stably holds the nonwoven fabric roll398on the unwinding spindle397I. The rubbing band310G is unwound from the nonwoven fabric roll398on the unwinding spindle397I. The unwinding spindle397I rotates and unwinds the rubbing band310G from the nonwoven fabric roll398. In the present embodiment, the unwinding spindle397I is exemplified as the unwinder.

The winding spindle396I rotates in cooperation with the unwinding spindle397I. The winding spindle396I is inserted into the substantially cylindrical core395. Like the unwinding spindle397I, the winding spindle396I comprises a chuck mechanism (not shown) configured to hold the core395. An end of the rubbing band310G which is unwound by the unwinding spindle397I is connected to the outer circumferential surface of the core395. The rubbing band310G is wrapped around the core395as the winding spindle396I rotates. Thus, the winding spindle396I may wind the rubbing band310G. In the present embodiment, the winding spindle396I is exemplified as the winder.

The rubbing band310G, which is unwound by the unwinding spindle397I, passes between the press roller351G and the endless belt453, and is then wrapped around the winding spindle396I. The coil spring352G configured to bias the press roller351G toward the endless belt453forms a nip portion N between the rubbing band310G and the endless belt453to hold the sheet S therebetween. When the sheet S passes through the nip portion N, the press roller351G presses the rubbing band310G to the image layer I. The coil spring352G biases the press roller351G toward the image layer I.

In the present embodiment, the winding spindle396I winds the rubbing band310G, while the endless belt453conveys the sheet S. The rubbing band310G held between the press roller351G and the endless belt453moves in the second direction D2, while the winding spindle396I rotates. The difference between the conveying direction of the sheet S (the first direction D1) and the winding direction of the winding spindle396I (the second direction D2) causes rubbing between the image layer I and the rubbing band310G. In the present embodiment, therefore, the winding spindle396I, the unwinding spindle397I and the press mechanism350G are exemplified as the sliding mechanism.

The fixing device300I according to the tenth embodiment and the conveyor400G which is used for conveying the sheet S to the fixing device300I, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor which are described in the context of the first embodiment.

FIG. 34is a schematic view of a fixing device and a conveyor according to the eleventh embodiment. Hereinafter, Differences from the eighth embodiment are described with reference toFIG. 34. It should be noted that some descriptions overlapping with those of the eighth embodiment are omitted for clarification. Hereinafter, the same reference numerals are used for describing the same elements as those of the eighth embodiment. The descriptions associated with the eighth embodiment are preferably incorporated into the elements which are not described hereinafter.

The conveyor400configured to convey the sheet S having the image layer I thereon comprises the belt unit450D, the upstream guider460situated before the belt unit450D, and the downstream guider469situated after the belt unit450D. The sheet S is guided by the upstream guider460and sent to the belt unit450D. Thereafter, the sheet S is sent to the downstream guide469by the belt unit450D.

The belt unit450D comprises the drive roller451, the idler452, the endless belt453extending between the drive roller451and the idler452, and the tension roller454applying tension to the endless belt453. Rotation of the drive roller451causes the endless belt453to revolve around the drive roller451, the idler452and the tension roller454. As a result, the sheet S, which is sent from the upstream guider460to the outer surface455of the endless belt453, moves toward the downstream guider469in response to the revolution of the endless belt453.

The belt unit450D comprises the charger456configured to charge the outer surface455of the endless belt453, like the eighth embodiment. The outer surface455of the endless belt453, which is charged by the charger456, causes the sheet S to electrostatically stick thereto.

The endless belt453includes the inner surface457opposite to the outer surface455to which the sheet S sticks. The belt unit450D comprises the backup roller340D which abuts the inner surface457of the endless belt453. In the present embodiment, the backup roller340D includes the upstream backup roller343disposed near the upstream guider460, and the downstream backup roller344disposed near the downstream guider469.

A fixing device300J comprises, like the eighth embodiment, the rubbing band310G configured to rub the image layer I on the sheet S, the unwinding spindle397configured to unwind the rubbing band310G from the nonwoven fabric roll398, and the winding spindle396configured to wind the rubbing band310G, which is unwound by the unwinding spindle397. The fixing device300J comprises a press mechanism350J configured to press the rubbing band310G to the image layer I. In the present embodiment, the press mechanism350J is exemplified as the first press mechanism.

The press mechanism350J includes an intermediate roller379situated between the unwinding and winding spindles397,396. The intermediate roller379defines a travel path of the rubbing band310G so that the rubbing band310G separates from the endless belt453. In the present embodiment, the intermediate roller379is exemplified as the intermediate piece.

The press mechanism350J includes an upstream press roller323J, which is provided in correspondence with the upstream backup roller343, and a downstream press roller324J, which is provided in correspondence with the downstream backup roller344. Before a sheet S passes between the intermediate roller379and the endless belt453, the upstream press roller323I presses the rubbing band310G to the image layer I. After the sheet S passes between the intermediate roller379and the endless belt453, the downstream press roller324I presses the rubbing band310G to the image layer I. In the present embodiment, the upstream press roller323J is exemplified as the upstream press piece. The downstream press roller324J is exemplified as the downstream press piece.

The upstream press roller323J comprises a rotating shaft326J and a bearing361J configured to hold the rotating shaft326J. In the present embodiment, the upstream press roller323J rotates around the rotating shaft326J as the rubbing band310G moves from the unwinding spindle397to the winding spindle396.

The upstream press roller324J comprises a rotating shaft327J and a bearing362J configured to hold the rotating shaft327J. In the present embodiment, the downstream press roller324J rotates around the rotating shaft327J as the rubbing band310G moves from the unwinding spindle397to the winding spindle396.

The press mechanism350J comprises a separator380J configured to separate the upstream and downstream press rollers323J,324J from the endless belt453.

The separator380J comprises an upstream cylinder device371J connected to the bearing361J of the upstream press roller323J. The upstream cylinder device371J comprises a shell374configured to receive working fluid, and a rod375which is stored in the shell374. A tip end of the rod375is connected to the bearing361J. In the present embodiment, the upstream cylinder device371J may be a commercially available cylinder device.

If the working fluid flows out of the shell374, the rod375retracts in the shell374. As a result, the upstream press roller323J connected to the rod375moves to a separation position where the upstream press roller323J is separated from the endless belt453.

If the working fluid flows into the shell374, the rod375extends from the shell374. Compressive elasticity of the working fluid in the shell374bias the upstream press roller323J toward the image layer I on the sheet S conveyed by the endless belt453. Therefore, the upstream cylinder device371J is also used as the biasing element.

The separator380J comprises a downstream cylinder device372J connected to the bearing362J of the downstream press roller324J. The downstream cylinder device372J comprises a shell376configured to receive the working fluid, and a rod377which is stored in the shell376. A tip end of the rod377is connected to the bearing362J. In the present embodiment, the downstream cylinder372J may be a commercially available cylinder device.

If the working fluid flows out of the shell376, the rod377retracts in the shell376. As a result, the downstream press roller324J connected to the rod377moves to a separation position where the downstream press roller324J is separated from the endless belt453.

If the working fluid flows into the shell376, the rod377extends from the shell376. Compressive elasticity of the working fluid in the shell376biases the downstream press roller324J toward the image layer I on the sheet S conveyed by the endless belt453. Therefore, the downstream cylinder device372J is also used as the biasing element.

The separator380J comprises a controller373J configured to control the upstream and downstream cylinder devices371J,372J. The controller373J independently controls the inflow and outflow of the working fluid to and from the shells374,376. Therefore, the upstream and downstream cylinder devices371J,372J are independently operated.

The controller373J may control the upstream and/or downstream cylinder devices371J,372J such that one of the upstream and downstream press rollers323J,324J is disposed in the separation position away from the endless belt453and that the other is disposed in the proximal position near the endless belt453. For instance, if the image layer I has a high print ratio, both the upstream and downstream press rollers323J,324J may be disposed in the proximal position. On the other hand, if the image layer I has a low print ratio, one of the upstream and downstream press rollers323J,324J may be disposed in the separation position.

Alternatively, the upstream and/or downstream cylinder devices371J,372J may be controlled such that the downstream press roller324I presses the rubbing band310G to the image layer I on the sheet S with a greater force than the upstream press roller323J. As a result, the rubbing band310G rubs the image layer I with a weak force in the upstream process where the image layer I is likely to be damaged, and then the rubbing band310G rubs the image layer with a strong force in the downstream process. Accordingly, less damage to the image layer I and high fixation ratio FR may be achieved.

The fixing device300J according to the eleventh embodiment and the conveyor400which is used for conveying the sheet S to the fixing device300J, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor which are described in the context of the first embodiment.

FIG. 35is a schematic side view showing a fixing device and a conveyor according to the twelfth embodiment.FIG. 36is a schematic plan view showing the fixing device and the conveyor according to the twelfth embodiment.FIG. 37is a schematic front view showing the fixing device and the conveyor according to the twelfth embodiment. The fixing device and the conveyor according to the twelfth embodiment are described with reference toFIGS. 4 and 35to37. Hereinafter, the same reference numerals are used for describing the same elements as those described in the aforementioned embodiments. The descriptions associated with the aforementioned embodiments are preferably incorporated into the elements which are not described hereinafter.

A conveyor400K configured to convey the sheet S having the image layer I formed thereon in the first direction D1comprises a substantially tubular backup roller910situated under the sheet S, and a substantially tubular nip roller920situated above the sheet S. The backup roller910is connected to a drive source such as a motor (not shown) and rotated to convey the sheet S in the first direction D1. The nip roller920contacts the circumferential surface911of the backup roller910, and works together with the backup roller910to form a nip portion for holding the sheet S therebetween. The nip roller920rotates in response to the rotation of the backup roller910and/or the conveyance of the sheet S. In the present embodiment, the backup roller910is exemplified as the conveying element. The nip roller920is exemplified as the nip element.

As shown inFIGS. 36 and 37, the backup roller910extends in a traverse direction T (a direction perpendicular to the conveying direction of the sheet S (the first direction D1)), and appropriately supports the sheet S during the conveyance thereof. The backup roller910comprises a substantially tubular trunk912, of which circumferential surface911is pressed to the nip roller920, and journals913which project from the end surfaces of the trunk912in the traverse direction T. One of the journals913is connected to the abovementioned drive source. The other rotatable journal913is supported, for example, by a bearing mounted to a wall of a housing (not shown) configured to store the conveyor400K.

The nip roller920comprises a rotating shaft921extending in the traverse direction T, and a substantially tubular rolling piece922mounted on the rotating shaft921. The rolling piece922includes a first rolling piece923and a second rolling piece924. The first and second rolling pieces923,924are aligned in the traverse direction T. The rolling piece922, which is pressed to the circumferential surface911of the backup roller910, rotates along with the rotating shaft921in response to the rotation of the backup roller910and/or the conveyance of the sheet S.

A fixing device300K comprises a nonwoven fabric band310K configured to rub the image layer I on the sheet S, an unwinding spindle397K around which the nonwoven fabric band310K is wrapped, and a winding spindle396K which winds the nonwoven fabric band310K. The nonwoven fabric band310K may be formed from any of the various nonwoven fabric materials described in the context ofFIG. 4. In the present embodiment, the nonwoven fabric band310K is exemplified as the rubbing belt. The unwinding spindle397K is exemplified as the unwinder. The winding spindle396K is exemplified as the winder.

As shown inFIG. 35, the nonwoven fabric band310K is unwound from a nonwoven fabric roll398K installed on the unwinding spindle397K. The nonwoven fabric roll398K includes the substantially cylindrical core399and the nonwoven fabric band310K wrapped around the core399. The unwinding spindle397K is inserted into the core399. The unwinding spindle397K may have, for example, a chuck mechanism (not shown) configured to hold the core399. The nonwoven fabric band310K is unwound from the nonwoven-fabric roll398K as the unwinding spindle397K rotates.

The winding spindle396K is inserted into the substantially cylindrical core395. The winding spindle396K may include, for example, a chuck mechanism (not shown) configured to hold the core395. The leading end of the nonwoven fabric band310K, which is unwound from the nonwoven fabric roll398K, is connected to the circumferential surface of the core395. The nonwoven fabric band310K is wrapped around the core395as the winding spindle396K rotates.

The nonwoven fabric band310K includes a central band394passing between the first and second rolling pieces923,924, a first edge band389adjacent to the first rolling piece923, and a second edge band388adjacent to the second rolling piece924. The first rolling piece923rolls between the first edge band389and the central band394. The second rolling piece924rolls between the second edge band388and the central band394.

As shown inFIG. 35, the fixing device300K comprises a pressing rod840which defines a travel path of the nonwoven fabric band310K such that the nonwoven fabric band310K contacts the image layer I on the sheet S between the unwinding and winding spindles397K,396K. A rubbing position, which is defined by the pressing rod840so that the nonwoven fabric band310K rubs the image layer I, and a nip portion defined between the nip and backup rollers920,910, are aligned in the traverse direction T. In the present embodiment, the pressing rod840is exemplified as the pressing member.

The pressing rod840includes a curved surface841, which is curved to project toward the backup roller910. The curved surface841defines a downwardly curved travel path of the nonwoven fabric band310K. The nonwoven fabric band310K rubs the image layer I on the sheet S between the curved surface841and the backup roller910.

As shown inFIGS. 36 and 37, the pressing rod840extends in the traverse direction T. The pressing rod840includes a central rod842configured to press the central band394against the image layer I, a first edge rod843configured to press the first edge band389against the image layer I, and a second edge rod844configured to press the second edge band388against the image layer I. The first edge rod843, the central rod842and the second edge rod844are aligned in the traverse direction T. The first edge rod843, the central rod842and the second edge rod844are situated between the rotating shaft921of the nip roller920and the backup roller910, respectively.

As shown inFIG. 35, the fixing device300K comprises a connector850configured to connect the pressing rod840with the rotating shaft921of the nip roller920. The connector850comprises a bearing block851configured to support the rotating shaft921of the nip roller920, a rod852stored in the bearing block851, and a connecting frame853which connects a housing (not shown) for storing the fixing device300K to the bearing block851.

As shown inFIGS. 36 and 37, the connectors850correspond to the first edge rod843, the central rod842, and the second edge rod844, respectively. The paired rods852and the bearing block851connected to each rod852are disposed on the first edge rod843. The tip ends of the rods852are connected to both ends of the upper surface of the first edge rod843, respectively. The paired rods852and the bearing block851connected to each rod852are disposed on the central rod842. The tip ends of the rods852are connected to both ends of the upper surface of the central rod842, respectively. The paired rods852and the bearing block851connected to each rod852are disposed on the second edge rod844. The tip ends of the rods852are connected to both ends of the upper surface of the second edge rod844, respectively.

As shown inFIG. 37, the connecting frame853of the connector850, which is provided in correspondence with the first edge rod843, comprises a connecting plate854connected to the upper surfaces of the paired bearing blocks851corresponding to the first edge rod843, and a connecting arm855configured to connect the connecting plate854with the abovementioned housing. The connecting frame853of the connector850, which is provided in correspondence with the central rod842, comprises a connecting plate854connected to the upper surfaces of the paired bearing blocks851corresponding to the central rod842, and a connecting arm855configured to connect the connecting plate854with the abovementioned housing. The connecting frame853of the connector850, which is provided in correspondence with the second edge rod844, comprises a connecting plate854connected to the upper surfaces of the paired bearing blocks851corresponding to the second edge rod844, and a connecting arm855configured to connect the connecting plate854with the abovementioned housing.

FIG. 38is a schematic cross-sectional view of the connector850. The connector850is described with reference toFIGS. 35 to 38.

Each bearing block851comprising an upper portion856into which the rotating shaft921of the nip roller920is inserted, and a hollow lower portion857. The connector850comprises a coil spring858buried in the lower portion857. The rod852is inserted into the lower portion857. The coil spring858biases the rod852and the pressing rod840downward (i.e., toward the backup roller910). As a result, the pressing rod840, which is biased toward the backup roller910, presses the nonwoven fabric band310K against the image layer I on the sheet S.

While the conveyor400K conveys the sheet S in the first direction D1, the winding spindle396K winds the nonwoven fabric band310K at a speed different from the conveying speed of the sheet S. The difference between the winding speed of the nonwoven fabric band310K and the conveying speed of the sheet S makes the image layer I on the sheet S appropriately rubbed. Alternatively, while the conveyor400K conveys the sheet S in the first direction D1, the winding spindle396K may be stopped. While the nonwoven fabric band310K pressed by the pressing rod840stops, the sheet S is conveyed by the backup roller910in the first direction D1, so that the image layer I is appropriately rubbed by the nonwoven fabric band310K. The unwinding and winding spindles397K,396K may be arranged such that the travelling direction of the nonwoven fabric band310K pressed by the pressing rod840becomes opposite to the conveying direction of the sheet S (i.e., the first direction D1). The image layer I is appropriately rubbed by the nonwoven fabric band310K due to the difference between the conveying direction of the sheet S and the travelling direction of the nonwoven fabric band310K.

FIG. 39is a schematic side view showing an improved fixing device and conveyor based on the methodologies described with respect toFIGS. 35 to 38.FIG. 40is a schematic plan view showing the improved fixing device and conveyor. The improved features are described with reference toFIGS. 4 and 38to40. Some descriptions overlapping with those associated withFIGS. 35 and 38are omitted for clarification. Hereinafter, the same reference numerals are used for describing the same elements as those described in the context ofFIGS. 35 to 38. The descriptions associated withFIGS. 35 to 38are preferably incorporated into the elements which are not described hereinafter.

In addition to the conveyor400K and the fixing device300K described above,FIGS. 39 and 40show an auxiliary conveyor600and an auxiliary fixing device500corresponding to the auxiliary conveyor600. The auxiliary conveyor600is situated before the conveyor400K. The auxiliary fixing device500is situated before the fixing device300K. After the auxiliary fixing device500rubs the image layer I on the sheet S, the fixing device300K rubs the image layer I.

Like the conveyor400K, the auxiliary conveyor600conveys the sheet S having the image layer I formed thereon, in the first direction D1. The auxiliary conveyor600has a substantially tubular backup roller610disposed under the sheet S, and a substantially tubular nip roller620disposed above the sheet S. The backup roller610is connected to a drive source such as a motor (not shown), and rotated to convey the sheet S in the first direction D1. The nip roller620is pressed to the circumferential surface611of the backup roller610, and works together with the backup roller610to form a nip portion for holding the sheet S therebetween. The nip roller620rotates in response to the rotation of the backup roller610and/or the conveyance of the sheet S. In the present embodiment, the backup roller610of the auxiliary conveyor600is exemplified as the conveying element, as well as the backup roller910of the conveyor400K. The nip roller620of the auxiliary conveyor600is exemplified as the nip element, as well as the nip roller920of the conveyor400K.

As shown inFIG. 40, the backup roller610of the auxiliary conveyor600(c.f.FIG. 39) has the same structure as the backup roller910of the conveyor400K. The nip roller620of the auxiliary conveyor600comprises a rotating shaft621extending in the traverse direction T, and a substantially tubular rolling piece622mounted on the rotating shaft621. The rolling piece622includes a third rolling piece623, a fourth rolling piece624, and a fifth rolling piece625. The third rolling piece623is situated in the upstream of the central band394of the fixing device300K. The fourth rolling piece624is situated in the upstream of the first edge band389. The fifth rolling piece625is situated in the upstream of the second edge band388. The third, fourth and fifth rolling pieces623,624,625are aligned in the traverse direction T. The rolling piece622, which is pressed to the circumferential surface611of the backup roller610, rotates along with the rotating shaft621in response to the rotation of the backup roller610and/or the conveyance of the sheet S.

The auxiliary fixing device500has a nonwoven fabric band510configured to rub the image layer I on the sheet S, an unwinding spindle520around which the nonwoven fabric band510is wrapped, and a winding spindle530configured to wind the nonwoven fabric band510. The nonwoven fabric band510may be formed from any of the various nonwoven fabric materials described in the context ofFIG. 4. In the present embodiment, the nonwoven fabric band510of the auxiliary fixing device500is exemplified as the rubbing belt, as well as the nonwoven fabric band310K of the fixing device300K. The unwinding spindle520of the auxiliary fixing device500is exemplified as the unwinder, as well as the unwinding spindle397K of the fixing device300K. The winding spindle530of the auxiliary fixing device500is exemplified as the winder, as well as the winding spindle396K of the fixing device300K.

As shown inFIG. 39, the nonwoven fabric band510is unwound from a nonwoven fabric roll511installed on the unwinding spindle520. The nonwoven fabric roll511includes a substantially cylindrical core512and the nonwoven fabric band510wrapped around the core512. The unwinding spindle520is inserted into the core512. The unwinding spindle520may include, for example, a chuck mechanism (not shown) configured to hold the core512. The nonwoven fabric band510is unwound from the nonwoven fabric roll511as the unwinding spindle520rotates.

The winding spindle530is inserted into a substantially cylindrical core513. The winding spindle530may include, for example, a chuck mechanism (not shown) configured to hold the core513. The leading end of the nonwoven fabric band510, which is unwound from the nonwoven fabric roll511, is connected to the circumferential surface of the core513. The nonwoven fabric band510is wrapped around the core513as the winding spindle530rotates.

As shown inFIG. 40, the nonwoven fabric band510includes a first auxiliary band515passing between the third and fourth rolling pieces623,624, and a second auxiliary band516passing between the third and fifth rolling pieces623,625. The first auxiliary band515rubs the image layer I in the upstream of the first rolling piece923. The second auxiliary band516rubs the image layer I in the upstream of the second rolling piece924.

As shown inFIG. 39, the auxiliary fixing device500comprises a pressing rod540which defines a travel path of the nonwoven fabric band510such that the nonwoven fabric band510contacts the image layer I on the sheet S between the unwinding and winding spindles520,530. A rubbing position, which is defined by the pressing rod540so that the nonwoven fabric band510rubs the image layer I, and a nip portion defined between the nip and backup rollers620,610are aligned in the traverse direction T. In the present embodiment, the pressing rod540of the auxiliary fixing device500is exemplified as the pressing member, as well as the pressing rod840of the fixing device300K.

The pressing rod540has a curved surface541, which is curved to project toward the backup roller610. The curved surface541defines a downwardly curved travel path of the nonwoven fabric band510. The nonwoven fabric band510rubs the image layer I on the sheet S between the curved surface541and the backup roller610.

As shown inFIG. 40, the pressing rod540extends in the traverse direction T. The pressing rod540includes a first auxiliary rod543configured to press the first auxiliary band515against the image layer I, and a second auxiliary rod544configured to press the second auxiliary band516against the image layer I. The first and second auxiliary rods543,544are aligned in the traverse direction T. The first and second auxiliary rods543,544are held between the rotating shaft621of the nip roller620and the backup roller610, respectively, by the connector850described in the context of withFIG. 38.

The central band394of the fixing device300K rubs a strip area A1extending in the first direction D1at substantially the center of the image layer I formed on the sheet S. The first edge band389of the fixing device300K rubs a strip area A2extending in the first direction D1along one edge of the image layer I. The second edge band388of the fixing device300K rubs a strip area A3extending along the other edge opposite to the one edge corresponding to the strip area A2.

The first auxiliary band515of the auxiliary fixing device500rubs a strip area B1between the strip areas A1, A2. The second auxiliary band516of the auxiliary fixing device500rubs a strip area B2between the strip areas A1, A3.

Because the third rolling piece623of the auxiliary conveyor600rolls on the strip area A1, the strip area A1is not rubbed by the nonwoven fabric band510of the auxiliary fixing device500. However, the strip area A1is appropriately rubbed by the central band394of the fixing device300K after the image layer I goes through the auxiliary fixing device500.

In cooperation with the backup roller610, the fourth rolling piece624of the auxiliary conveyor600holds a lateral edge SE1of the sheet S, which extends in the first direction D1. Therefore, the strip area A2nearby the lateral edge SE1of the sheet S is not rubbed by the nonwoven fabric band510of the auxiliary fixing device500. However, after the image layer I passes through the auxiliary fixing device500, the strip area A2is appropriately rubbed by the first edge band389of the fixing device300K.

In cooperation with the backup roller610, the fifth rolling piece625of the auxiliary conveyor600holds a lateral edge SE2opposite to the lateral edge SE1of the sheet S. Therefore, the strip area A3nearby the lateral edge SE2of the sheet S is not rubbed by the nonwoven fabric band510of the auxiliary fixing device500. However, after the image layer I passes through the auxiliary fixing device500, the strip area A3is appropriately rubbed by the second edge band388of the fixing device300K.

Because the first rolling piece923of the conveyor400K rolls on the strip area B1, the strip area B1is not rubbed by the nonwoven fabric band310K of the fixing device300K. However, before the image layer I reaches the fixing device300K, the strip area B1is appropriately rubbed by the first auxiliary band515of the auxiliary fixing device500.

Because the second rolling piece924of the conveyor400K rolls on the strip area B2, the strip area B2is not rubbed by the nonwoven fabric band310K of the fixing device300K. However, before the image layer I reaches the fixing device300K, the strip area B2is appropriately rubbed by the second auxiliary band516of the auxiliary fixing device500.

As described above, the entire image layer I is appropriately rubbed, because the fixing device300K rubs the strip areas A1, A2, A3, which are different from the strip areas B1, B2rubbed by the auxiliary fixing device500. It should be noted that the first auxiliary band515is arranged such that edges of the strip area B1preferably overlap with edges of the strip areas A1, A2. The second auxiliary band516is arranged such that edges of the strip area B2preferably overlap with edges of the strip areas A1and A3.

The fixing device300K, the auxiliary fixing device500, and the conveyor400K and the auxiliary conveyor600which are used for conveying the sheet S to the fixing device300K and the auxiliary fixing device500, respectively, according to the present embodiment, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor described in the context of the first embodiment.

FIG. 41is a schematic plan view showing a fixing device and a conveyor according to the thirteenth embodiment. The differences from the twelfth embodiment are described hereinafter with reference toFIGS. 38 and 41. Some descriptions overlapping with those of the twelfth embodiment are omitted for clarification. Hereinafter, the same reference numerals are used for describing the same elements as those of the twelfth embodiment. The descriptions associated with the twelfth embodiment are preferably incorporated into the elements which are not described hereinafter.

In addition to the conveyor400K, the auxiliary conveyor600and the auxiliary fixing device500, which are described in the context of the twelfth embodiment,FIG. 41shows a fixing device300L corresponding to the conveyor400K.

The fixing device300L has the nonwoven fabric band310K configured to rub the image layer I on the sheet S, the unwinding spindle397K around which the nonwoven fabric band310K is wrapped, and the winding spindle396K which winds the nonwoven fabric band310K.

The nonwoven fabric band310K includes the central band394passing between the first and second rolling pieces923,924, the first edge band389adjacent to the first rolling piece923, and the second edge band388adjacent to the second rolling piece924. The first rolling piece923rolls between the first edge band389and the central band394. The second rolling piece924rolls between the second edge band388and the central band394.

The fixing device300L comprises the pressing rod840, which defines a travel path of the nonwoven fabric band310K such that the nonwoven fabric band310K contacts the image layer I on the sheet S between the unwinding and winding spindles397K,396K.

The pressing rod840extends in the traverse direction T. The pressing rod840includes the central rod842configured to define a travel path in which the central band394is brought into contact with the image layer I on the sheet S, the first edge rod843configured to define a travel path in which the first edge band389is brought into contact with the image layer I on the sheet S, and the second edge rod844configured to define a travel path in which the second edge band388is brought into contact with the image layer I on the sheet S. The first edge rod843, the central rod842and the second edge rod844are aligned in the traverse direction T. The first edge rod843, the central rod842and the second edge rod844are arranged between the rotating shaft921of the nip roller920and the backup roller910, respectively.

The fixing device300L comprises three connectors850L connected to the first edge rod843, the central rod842, and the second edge rod844, respectively. The connector850L connects the pressing rod840(the first edge rod843, the central rod842, and the second edge rod844) and the rotating shaft921of the nip roller920to each other.

FIG. 42is a schematic cross-sectional view of one of the connectors850L. The connectors850L are described with reference toFIGS. 41 and 42.

Each connector850L has the paired rods852connected to the upper surface of the pressing rod840, and a bearing block851L connected to each rod852. Tip ends of the paired rods852are connected to both ends of the upper surface of the pressing rod840.

The connector850L comprises the connecting frame853connected to the paired bearing blocks851L. The connecting frame853comprises the connecting plate854connected to the upper end surfaces of the paired bearing blocks851, and the connecting arm855configured to connect the connecting plate854with a housing (not shown) for storing the fixing device300L.

Each bearing block851L comprises the upper portion856into which the rotating shaft921of the nip roller920is inserted, and the hollow lower portion857L. Each rod852is inserted into the lower portion857L. The rod852closes an opening formed in the lower end of the lower portion857L.

A through-hole891is formed on a circumferential wall of the lower portion857L of each bearing block851L. The connector850L comprises an activation unit892, which flows working fluid into and out of the lower portion857L of the bearing block851L via the through-hole891. If the activation unit892flows the working fluid into the lower portion857L, the pressing rod840is displaced downward and approaches the circumferential surface911of the backup roller910. If the activation unit892draws the working fluid from the lower portion857L, the pressing rod840is displaced upward and separates from the circumferential surface911of the backup roller910.

FIG. 43is a cross-sectional view schematically showing connections among the three connectors850L. The connectors850L are further described with reference toFIGS. 42 and 43.

The fixing device300L has a controller893, which independently control the activation units892for causing the central rod842to separate from or approach the circumferential surface911of the backup roller910, the activation unit892for causing the first edge rod843to separate from or approach the circumferential surface911of the backup roller910, and the activation unit892for causing the second edge rod844to separate from or approach the circumferential surface911of the backup roller910. Under the control of the controller893, the central rod842, the first edge rod843and the second edge rod844independently separate from or approach the circumferential surface911of the backup roller910.

FIG. 44is a schematic plan view showing the fixing device and the conveyor.FIGS. 45 and 46are cross-sectional views schematically showing the operations performed by the three connectors850L, respectively. The operations of the connectors850L are described with reference toFIGS. 41 and 44to46.

FIGS. 41,45show, as a sheet S, a first sheet SL that is relatively large in the traverse direction T.FIGS. 44,46show, as the sheet S, a second sheet SS that is relatively small in the traverse direction T.

As shown inFIGS. 41 and 45, the first sheet SL passes between the central band394and the backup roller910, between the first edge band389and the backup roller910, as well as between the second edge band388and the backup roller910. As shown inFIGS. 44 and 46, the second sheet SS passes between the central band394and the backup roller910, but not between the first edge band389and the backup roller910or between the second edge band388and the backup roller910.

As shown inFIG. 45, while the backup roller910conveys the first sheet SL, each of the three activation units892brings the central rod842, the first edge rod843and the second edge rod844close to the circumferential surface911of the backup roller910under the control of the controller893. As a result, the central band394, the first edge band389and the second edge band388may preferably rub the image layer I.

As shown inFIG. 46, while the backup roller910conveys the second sheet SS, the central activation unit892brings the central rod842close to the circumferential surface911of the backup roller910under the control of the controller893. The remaining activation units892separate the first and second edge rods843,844, respectively, from the circumferential surface911of the backup roller910under the control of the controller893. As a result, the central band394rubs the image layer I, but the first and second edge bands389,388are not rubbed by the circumferential surface911of the backup roller910to prevent unnecessary abrasion of the first and second edge bands389,388.

In a series of the aforementioned embodiments, the nonwoven fabric bands310K and510are used as the rubbing belts. Alternatively, a strip member configured to rub the image layer I may be used as the rubbing belt. For instance, a strip member having a brush implanted therein may be used as the rubbing belt.

The fixing device300L, the auxiliary fixing device500, and the conveyor400K and the auxiliary conveyor600, which are used for conveying the sheet S to the fixing device300L and the auxiliary fixing device500, respectively, according to the thirteenth embodiment, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor, which are described in the context of the first embodiment.

FIG. 47is a schematic view of a fixing device and a conveyor according to the fourteenth embodiment. The fixing device and the conveyor according to the fourteenth embodiment are described with reference toFIGS. 1A to 1CandFIGS. 4 and 47. Hereinafter, the same reference numerals are used for describing the same elements as those of the aforementioned embodiments. The descriptions associated with the aforementioned embodiments are preferably incorporated into the elements which are not described hereinafter.

The conveyor400G configured to convey the sheet S having the image layer I formed thereon comprises the belt unit450G, the upstream guider460situated before the belt unit450G, and the downstream guider469situated after the belt unit450G. The sheet S is guided by the upstream guider460and sent to the belt unit450G. Thereafter, the sheet S is sent to the downstream guide469by the belt unit450G.

The belt unit450G comprises the drive roller451, the idler452, the endless belt453extending between the drive roller451and the idler452, and the tension roller454applying tension to the endless belt453. Rotation of the drive roller451causes the endless belt453to revolve around the drive roller451, the idler452and the tension roller454. The idler452and the tension roller454rotate in response to the revolution of the endless belt453.

The endless belt453includes the outer surface455configured to receive the sheet S from the upstream guider460, and the inner surface457opposite to the outer surface455. The inner surface457abuts the drive roller451, the idler452, and the tension roller454. The sheet S, which is sent from the upstream guider460to the outer surface455of the endless belt453, moves toward the downstream guider469in response to the revolution of the endless belt453. The sheet S is conveyed from the upstream guider460to the downstream guider469at the first speed V1. In the following descriptions, the direction from the upstream guider460to the downstream guider469is referred to as “first direction D1”. In the present embodiment, the belt unit450G is exemplified as the conveying element. The endless belt453is exemplified as the conveying belt. The outer surface455of the endless belt453is exemplified as the conveying surface.

The belt unit450G further comprises the charger456configured to charge the outer surface455of the endless belt453. The outer surface455of the endless belt453, which is charged by the charger456, causes the sheet S to electrostatically stick thereto. Therefore, the sheet S is stably conveyed by the endless belt453. In the present embodiment, the endless belt453is preferably formed from resin such as PVDF.

The belt unit450G comprises the backup roller340, which abuts the inner surface457of the endless belt453. The backup roller340defines a travel path of the endless belt453, which is curved and protruded between the drive roller451and the idler452.

A fixing device300M has a nonwoven fabric band loop310M which rubs the image layer I on the sheet S, and a roller mechanism930which revolves the nonwoven fabric band loop310M. The nonwoven fabric band loop310M surrounds the roller mechanism930. The nonwoven fabric band loop310M may be formed from, for example, any of the nonwoven fabrics described in the context ofFIG. 4. In the present embodiment, the nonwoven fabric band loop310M is exemplified as the rubbing loop. The roller mechanism930, which is used as a drive mechanism for the nonwoven fabric band loop310M, is exemplified as the revolving mechanism.

The roller mechanism930has a drive roller917configured to revolve the nonwoven fabric band loop310M, a tension roller918configured to apply tension to the nonwoven fabric band loop310M, and a compression portion990configured to press the nonwoven fabric band loop310M to the image layer I on the sheet S. The compression portion990includes a first press roller993configured to push the nonwoven fabric band loop310M to the image layer I, and a second press roller994configured to push the nonwoven fabric band loop310M to the image layer I after the first press roller993. The compression portion990includes a first coil spring971connected to the first press roller993, and a second coil spring972connected to the second press roller994. In the present embodiment, the compression portion990is exemplified as the second press mechanism.

The first and second press rollers993,994define a travel path of the nonwoven fabric band loop310M along the outer surface455of the endless belt453. As described above, the backup roller340defines a travel path of the endless belt453protruding toward the roller mechanism930. The top of the travel path of the endless belt453, which is protruded by the backup roller340, enters in between the first and second press rollers993,994. Accordingly, the image layer I on the sheet S keeps in contact with the nonwoven fabric band loop310M for relatively long time.

The first coil spring971biases the first press roller993toward the endless belt453with a biasing force f1. The second coil spring972biases the second press roller994toward the endless belt453with a biasing force f2. The biasing force f2is preferably greater than the biasing force f1. As a result, the second press roller994presses the nonwoven fabric band loop310M to the image layer I with a stronger force than the first press roller993.

A layer of the polymer compounds R, which deposit on the surface of the image layer I, becomes hardened over time and increases scratching resistance. Therefore, rubbing the image layer I by means of the nonwoven fabric band loop310M under a relatively low pressing force in the upstream and scratching the image layer I by means of the nonwoven fabric band loop310M under a relatively high pressing force in the downstream may prevent damage to the image layer I and increase the fixation ratio FR of the image layer I to the sheet S.

The drive roller917revolves the nonwoven fabric band loop310M at the second speed V2. As a result of the rotation of the drive roller917, the nonwoven fabric band loop310M between the first and second press rollers993,994travels in the first direction D1at the second speed V2. In the present embodiment, the revolution speed of the nonwoven fabric band loop310M (the second speed V2) is greater than the conveying speed (the first speed V1) at which the sheet S is conveyed by the belt unit450G. The difference between the revolution speed of the nonwoven fabric band loop310M (the second speed V2) and the conveying speed of the sheet S (the first speed V1) makes the image layer I appropriately rubbed by the nonwoven fabric band loop310M. Alternatively, the drive roller917may revolve the nonwoven fabric band loop310M at a lower speed than the conveying speed of the sheet S (the first speed V1). The drive roller917may revolve the nonwoven fabric band loop310M such that the nonwoven fabric band loop310M between the first and second press rollers993,994travels in an opposite direction to the conveying direction (the first direction D1) of the sheet S.

The fixing device300M according to the fourteenth embodiment and the conveyor400G which is used for conveying the sheet S to the fixing device300M, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor which are described in the context of the first embodiment.

FIG. 48is a schematic view of a fixing device and a conveyor according to a fifteenth embodiment. The differences with the fourteenth embodiment are described hereinafter with reference toFIG. 48. Some descriptions overlapping with those of the fourteenth embodiment are omitted for clarification. Hereinafter, the same reference numerals are used for describing the same elements as those of the fourteenth embodiment. The descriptions associated with the fourteenth embodiment are preferably incorporated into the elements which are not described hereinafter.

The conveyor400H configured to convey the sheet S having the image layer I formed thereon comprises the belt unit450H, the upstream guider460situated before the belt unit450H, and the downstream guider469situated after the belt unit450H. The sheet S is guided by the upstream guider460and sent to the belt unit450H. Thereafter, the sheet S is sent to the downstream guide469by the belt unit450H.

The belt unit450H comprises the drive roller451, the idler452, the endless belt453E extending between the drive roller451and the idler452, and the tension roller454applying tension to the endless belt453E. Rotation of the drive roller451causes the endless belt453E to revolve around the drive roller451, the idler452and the tension roller454. The idler452and the tension roller454are rotated as the endless belt453E revolves.

The endless belt453E includes the outer surface455configured to receive the sheet S from the upstream guider460, and the inner surface457opposite to the outer surface455. The inner surface457abuts the drive roller451, the idler452, and the tension roller454. The sheet S, which is sent from the upstream guider460to the outer surface455of the endless belt453E, moves toward the downstream guider469in response to the revolution of the endless belt453E. The sheet S is conveyed from the upstream guider460to the downstream guider469at the first speed V1. In the present embodiment, the belt unit450H is exemplified as the conveying element. The endless belt453E is exemplified as the conveying belt. The outer surface455of the endless belt453E is exemplified as the conveying surface.

The belt unit450H comprises the vacuum device456E nearby the inner surface457opposite to the outer surface455of the endless belt453E, which is used as the conveying surface for conveying the sheet S. Several through-holes458are formed on the endless belt453E. The vacuum device456E suctions the sheet S on the outer surface455through the through-holes458. As a result, the sheet S is stably conveyed by the endless belt453E. In the present embodiment, the endless belt453E is preferably formed from resin such as urethane.

The belt unit450H comprises the backup roller340, which abuts the inner surface457of the endless belt453E. The backup roller340defines a travel path of the endless belt453E which is curved and protruded between the drive roller451and the idler452.

A fixing device300N includes a brush band loop310N configured to rub the image layer I on the sheet S, and a roller mechanism930N configured to revolve the brush band loop310N. The brush band loop310N includes a strip311N surrounding the roller mechanism930N, and a brush layer314N which includes multiple brushes314nimplanted in the strip311N. In the present embodiment, the brush band loop310N is exemplified as the rubbing loop.

The roller mechanism930N comprises the drive roller917configured to revolve the brush band loop310N, the tension roller918configured to apply tension to the brush band loop310N, and a compression portion990N configured to push the brush band loop310N to the image layer I on the sheet S. The compression portion990N comprises the first press roller993configured to push the brush band loop310N to the image layer I, and the second press roller994configured to push the brush band loop310N to the image layer I after the first press roller993.

The strip311N of the brush band loop310N includes an outer surface315N which holds the brushes314n, and an inner surface319N which contacts the drive roller917, the tension roller918, the first press roller993, and the second press roller994. The compression portion990N defines a rubbing path which extends along the first direction D1between the outer surfaces455,315N of the endless belt453E and the strip311N. The compression portion990N defines a distance between the outer surfaces455,315N of the endless belt453E and the strip311N in the rubbing path to be shorter than a length of each brush314n(the thickness of the brush layer314N). As a result, the brush layer314N appropriately rubs the image layer I on the sheet S traveling along the rubbing path. Preferably, the second press roller994sets the distance between the outer surfaces455,315N of the endless belt453E and the strip311N to be shorter than the distance defined by the first press roller993. As a result, the image layer I is rubbed more strongly as the sheet S is conveyed to the downstream.

As described above, the layer of the polymer compounds R, which deposit on the surface of the image layer I, becomes hardened over time and increases the scratching resistance. Therefore, rubbing the image layer I with the gradually increasing force may prevent damage to the image layer I and increase the fixation ratio FR of the image layer I to the sheet S.

The drive roller917revolves the brush band loop310N at the second speed V2. As a result of the rotation of the drive roller917, the brush band loop310N defining the rubbing path travels in the first direction D1at the second speed V2. In the present embodiment, the revolution speed of the brush band loop310N (the second speed V2) is greater than the conveying speed (the first speed V1) at which the sheet S is conveyed by the belt unit450H. The difference between the revolution speed of the brush band loop310N (the second speed V2) and the conveying speed of the sheet S (the first speed V1) makes the image layer I appropriately rubbed by the brush band loop310N. Alternatively, the drive roller917may revolve the brush band loop310N at a lower speed than the conveying speed of the sheet S (the first speed V1). The drive roller917may revolve the brush band loop310N such that the brush band loop310N defining the rubbing path travels in an opposite direction to the conveying direction of the sheet S (the first direction D1).

The fixing device300N according to the fifteenth embodiment and the conveyor400H which is used for conveying the sheet S to the fixing device300N, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor which are described in the context of the first embodiment.

A fixing device according to a sixteenth embodiment is different from the fixing device300M according to the fourteenth embodiment, in terms of a separating/approaching device configured to cause the compression portion990to separate from or approach the endless belt453. Some descriptions overlapping with those of the fourteenth embodiment are omitted for clarification. Hereinafter, the same reference numerals are used for describing the same elements as those of the fourteenth embodiment. The descriptions associated with the fourteenth embodiment are preferably incorporated into the elements which are not described hereinafter.

FIGS. 49A and 49Bare schematic views of a separating/approaching device configured to separate the compression portion990from the endless belt453.FIG. 49Ashows the compression portion990situated in a proximal position near the endless belt453.FIG. 49Bshows the first press roller993situated in a separation position away from the endless belt453, and the second press roller994situated in the proximal position. It should be noted that neitherFIGS. 49Anor49B shows the nonwoven fabric band loop in order to clarify the separating/approaching device.FIG. 50is a schematic view of the fixing device and a conveyor according to the sixteenth embodiment.

A fixing device300P adjacent to the conveyor400G configured to convey the sheet S includes the nonwoven fabric band loop310M which rubs the image layer I on the sheet S, and a roller mechanism930P configured to revolve the nonwoven fabric band loop310M. The roller mechanism930P is exemplified as the revolving mechanism.

The roller mechanism930P comprises the drive roller917configured to revolve the nonwoven fabric band loop310M, the tension roller918configured to apply tension to the nonwoven fabric band loop310M, and the compression portion990configured to press the nonwoven fabric band loop310M to the image layer I on the sheet S. The compression portion990includes the first press roller993configured to press the nonwoven fabric band loop310M to the image layer I, and the second press roller994configured to press the nonwoven fabric band loop310M to the image layer I after the first press roller993. The compression portion990includes the first coil spring971connected to the first press roller993, and the second coil spring972connected to the second press roller994.

The first press roller993includes a rotating shaft926and a bearing961configured to support the rotating shaft926. The second press roller994includes a rotating shaft927and a bearing962configured to support the rotating shaft927. The first coil spring971includes a first end956connected to the bearing961, and a second end957opposite to the first end956. The second coil spring972includes a first end958connected to the bearing962, and a second end959opposite to the first end958.

The roller mechanism930P comprises a separating/approaching device380P. The separating/approaching device380P includes a first separating/approaching device987configured to cause the first press roller993to separate from or approach the outer surface455of the endless belt453, and a second separating/approaching device988configured to cause the second press roller994to separate from or approach the outer surface455of the endless belt453.

The first separating/approaching device987comprises a rod arm981connected to the second end957of the first coil spring971, and a turning shaft982configured to support the rotatable arm981. The arm981includes a base end983connected to the turning shaft982, and a tip end984opposite to the base end983. The first coil spring971is connected to the tip end984of the arm981. The base end983of the arm981is mounted on the turning shaft982via, for example, a twisted coil spring (not shown). The twisted coil spring biases the tip end984of the arm981toward the outer surface455of the endless belt453. As a result, while the first press roller993exists in the proximal position, the compressed first coil spring971biases the first press roller993toward the image layer I on the sheet S.

The first separating/approaching device987comprises a rotating shaft985and an eccentric cam piece986integrally mounted on the rotating shaft985. The rotating shaft985is rotated by, for example, a first actuator989such as a solenoid switch (not shown). As a result, the eccentric cam piece986eccentrically rotates around the rotating shaft985to separate the tip end984of the arm981from the endless belt453. Consequently, the first press roller993is moved to the separation position.

The second separating/approaching device998comprises a rod arm991connected to the second end959of the second coil spring972, and a turning shaft992configured to support the rotatable arm991. The arm991includes a base end973connected to the turning shaft992, and a tip end974opposite to the base end973. The second coil spring972is connected to the tip end974of the arm991. The base end973of the arm991is mounted on the turning shaft992via, for example, a twisted coil spring (not shown). The twisted coil spring biases the tip end974of the arm991toward the outer surface455of the endless belt453. As a result, while the second press roller994exists in the proximal position, the compressed second coil spring972biases the second press roller994toward the image layer I on the sheet S.

The second separating/approaching device988comprises a rotating shaft975and an eccentric cam piece976integrally mounted on the rotating shaft975. The rotating shaft975is rotated by, for example, a second actuator979such as a solenoid switch (not shown). As a result, the eccentric cam piece976eccentrically rotates around the rotating shaft975to separate the tip end974of the arm991from the endless belt453. Consequently, the second press roller994is moved to the separation position.

The roller mechanism930P has a controller373P configured to independently control the first and second separating/approaching devices987,988. Under the control of the controller373P, the first and second separating/approaching devices987,988independently causes the first and second press rollers993,994to separate from or approach the outer surface455of the endless belt453. Therefore, a length of the rubbing path extending in the first direction D1is adjusted under the control of the controller373P.

The controller373P may cause the first or second press roller993,994to separate from or approach the outer surface455of the endless belt453, for example, in response to the print ratio of the image layer I. For instance, if the print ratio of the image layer I is relatively low, the controller373P may separate the first press roller993from the outer surface455of the endless belt453and keep the second press roller994at the proximal position. If the print ratio of the image layer I is relatively high, the controller373P may keep both the first and second press rollers993,994at the proximal position.

FIGS. 51A and 51Bschematically show the operations performed by the separating/approaching device380P.FIG. 51Aschematically shows the separating/approaching device380P which keeps the first and second press rollers993,994at the proximal position.FIG. 51Bschematically shows the separating/approaching device which displaces the first and second press rollers993,994to the separation position. The operations of the separating/approaching device380P are described with reference toFIGS. 50 to 51B.

The sheets S are sequentially sent from the upstream guider460to the belt unit450G. The sheets S, which electrostatically stick to the outer surface455of the endless belt453charged by the charger456, are sequentially conveyed toward the downstream guider469.

FIGS. 51A and 51Bshow the sheet S1and the sheet S2following the sheet S1, as the sheets S. Each sheet S includes a leading edge LE which first enters into the rubbing path and a trailing edge TE opposite to the leading edge LE. The leading edge LE of the sheet S2is away from the trailing edge TE of the preceding sheet S1. The conveyance of the sheets S shown inFIGS. 51A and 51Bis adopted in various image forming apparatuses such as copy machines, printers, facsimile devices, and combined machines.

As shown inFIGS. 51A and 51B, the sheets S1and S2are conveyed by the endless belt453in the first direction D1at the first speed V1. If the controller373P controls the first and second actuators989,979so that the first and second press rollers993,994approach the outer surface455of the endless belt453, the rubbing path extending in the first direction D1is defined between the nonwoven fabric band loop310M and the outer surface455of the endless belt453. While each sheet S passes through the rubbing path, the image layer I is rubbed by the nonwoven fabric band loop310M.

If the sheet S1passes through the rubbing path, the controller373P controls the first and second actuators989,979to displace the first and second press rollers993,994to the separation position away from the outer surface455of the endless belt453. Subsequently, immediately before the sheet S2passes between the first press roller993and the endless belt453, the controller373P controls the first and second actuators989,979so that the first and second press rollers993,994approach the outer surface455of the endless belt453. As a result, the rubbing path is defined. Therefore, it is less likely that the nonwoven fabric band loop310M and the endless belt453rub each other between the sheet S1and the sheet S2.

The fixing device300P according to the sixteenth embodiment and the conveyor400G which is used for conveying the sheet S to the fixing device300P, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor which are described in the context of the first embodiment.

FIG. 52is a schematic view of a fixing device and a conveyor according to the seventeenth embodiment. The differences from the fourteenth embodiment are described hereinafter with reference toFIGS. 1A to 1CandFIGS. 4 and 52. Some descriptions overlapping with those of the fourteenth embodiment are omitted for Clarification. Hereinafter, the same reference numerals are used for describing the same elements as those of the fourteenth embodiment. The descriptions associated with the fourteenth embodiment are preferably incorporated into the elements which are not described hereinafter.

The conveyor400configured to convey the sheet S having the image layer I formed thereon comprises the belt unit450D, the upstream guider460situated before the belt unit450D, and the downstream guider469situated after the belt unit450D. The sheet S is guided by the upstream guider460and sent to the belt unit450D. Thereafter, the sheet S is sent to the downstream guide469by the belt unit450D.

The belt unit450D comprises the drive roller451, the idler452, the endless belt453extending between the drive roller451and the idler452, and the tension roller454applying tension to the endless belt453. Rotation of the drive roller451causes the endless belt453to revolve around the drive roller451, the idler452and the tension roller454. The idler452and the tension roller454are rotated as the endless belt453revolves.

The endless belt453includes the outer surface455configured to receive the sheet S from the upstream guider460, and the inner surface457opposite to the outer surface455. The inner surface457abuts the drive roller451, the idler452, and the tension roller454. The sheet S, which is sent from the upstream guider460to the outer surface455of the endless belt453, moves toward the downstream guider469in response to the revolution of the endless belt453. The sheet S is conveyed from the upstream guider460to the downstream guider469at the first speed V1.

The belt unit450D further comprises the charger456configured to charge the outer surface455of the endless belt453. The sheet S electrostatically sticks to the outer surface455of the endless belt453charged by the charger456. Therefore, the sheet S is stably conveyed by the endless belt453.

The belt unit450D comprises the backup roller340D, which abuts the inner surface457of the endless belt453. The backup roller340D includes the upstream backup roller343nearby the idler452, and the downstream backup roller344near the drive roller451.

A fixing device300Q includes an upstream fixing device301corresponding to the upstream backup roller343, and a downstream fixing device302corresponding to the downstream backup roller344. The upstream fixing device301first rubs the image layer I on the sheet S, which has sent from the upstream guider460to the endless belt453. Subsequently, the downstream fixing device302rubs the image layer I. This increases the rubbing time for rubbing the image layer I.

The upstream fixing device301includes an upstream nonwoven fabric band loop1510configured to rub the image layer I on the sheet S, and an upstream roller mechanism1530configured to revolve the upstream nonwoven fabric band loop1510. The upstream nonwoven fabric band loop1510surrounds the upstream roller mechanism1530. The upstream nonwoven fabric band loop1510may be formed from any of the nonwoven fabrics described in the context ofFIG. 4.

The upstream roller mechanism1530comprises a drive roller1517configured to revolve the upstream nonwoven fabric band loop1510, a tension roller1518configured to apply tension to the upstream nonwoven fabric band loop1510, and an upstream compression portion1520configured to press the upstream nonwoven fabric band loop1510to the image layer I on the sheet S. The upstream compression portion1520comprises a first press roller1523configured to press the upstream nonwoven fabric band loop1510to the image layer I, and a second press roller1524configured to press the upstream nonwoven fabric band loop1510to the image layer I after the first press roller1523. The upstream compression portion1520comprises a first coil spring1571connected to the first press roller1523, and a second coil spring1572connected to the second press roller1524.

The first and second press rollers1523,1524define a travel path of the upstream nonwoven fabric band loop1510along the outer surface455of the endless belt453. The upstream backup roller343defines a travel path of the endless belt453protruding toward the upstream roller mechanism1530. The top of the travel path of the endless belt453, which is protruded by the upstream backup roller343, enters between the first and second press rollers1523,1524. Accordingly, the image layer I on the sheet S keeps in contact with the upstream nonwoven fabric band loop1510for relatively long time.

The downstream fixing device302includes a downstream nonwoven fabric band loop1610configured to rub the image layer I on the sheet S, and a downstream roller mechanism1630configured to revolve the downstream nonwoven fabric band loop1610. The downstream nonwoven fabric band loop1610surrounds the downstream roller mechanism1630. The downstream nonwoven fabric band loop1610may be formed from, for example, any of the nonwoven fabrics described in the context ofFIG. 4.

The downstream roller mechanism1630comprises a drive roller1617configured to revolve the downstream nonwoven fabric band loop1610, a tension roller1618configured to apply tension to the downstream nonwoven fabric band loop1610, and a downstream compression portion1620configured to press the downstream nonwoven fabric band loop1610to the image layer I on the sheet S. The downstream compression portion1620comprises a third press roller1623configured to press the downstream nonwoven fabric band loop1610to the image layer I, and a fourth press roller1624configured to press the downstream nonwoven fabric band loop1610to the image layer I after the third press roller1623. The downstream compression portion1620comprises a third coil spring1671connected to the third press roller1623, and a fourth coil spring1672connected to the fourth press roller1624.

The third and fourth press rollers1623,1624define a travel path of the downstream nonwoven fabric band loop1610along the outer surface455of the endless belt453. The downstream backup roller344defines a travel path of the endless belt453protruding toward the downstream roller mechanism1630. The top of the travel path of the endless belt453, which is protruded by the downstream backup roller344, enters between the third and fourth press rollers1623,1624. Accordingly, the image layer I on the sheet S keeps in contact with the downstream nonwoven fabric band loop1610for relatively long time.

The first coil spring1571biases the first press roller1523toward the endless belt453with the biasing force f1. The second coil spring1572biases the second press roller1524toward the endless belt453with the biasing force f2. The biasing force f2is preferably greater than the biasing force f1. As a result, the second press roller1524presses the upstream nonwoven fabric band loop1510to the image layer I with a stronger force than the first press roller1523.

The third coil spring1671biases the third press roller1623toward the endless belt453with a biasing force f3. The fourth coil spring1672biases the fourth press roller1624toward the endless belt453with a biasing force f4. The biasing force f4is preferably greater than the biasing force f3. As a result, the fourth press roller1624presses the downstream nonwoven fabric band loop1610to the image layer I with a stronger force than the third press roller1623.

A total force of the biasing forces f3, f4is preferably greater than a total force of the biasing forces f1, f2. The layer of the polymer compounds R, which deposit on the surface of the image layer I, becomes hardened over time and increases scratching resistance. Therefore, rubbing the image layer I by means of the upstream nonwoven fabric band loop1510under a relatively low pressing force in the upstream and rubbing the image layer I by means of the downstream nonwoven fabric band loop1610under a relatively high pressing force in the downstream may prevent damage to the image layer I and increase the fixation ratio FR of the image layer I to the sheet S.

The drive roller1517of the upstream roller mechanism1530revolves the upstream nonwoven fabric band loop1510at the second speed V2. As a result of the rotation of the drive roller1517, the upstream nonwoven fabric band loop1510between the first and second press rollers1523,1524travels in the first direction D1at the second speed V2. In the present embodiment, the revolution speed of the upstream nonwoven fabric band loop1510(the second speed V2) is greater than the conveying speed (the first speed V1) at which the sheet S is conveyed by the belt unit450D. The difference between the revolution speed of the upstream nonwoven fabric band loop1510(the second speed V2) and the conveying speed (the first speed V1) of the sheet S makes the image layer I appropriately rubbed by the upstream nonwoven fabric band loop1510.

The drive roller1617of the downstream roller mechanism1630revolves the downstream nonwoven fabric band loop1610at the third speed V3. As a result of the rotation of the drive roller1617, the downstream nonwoven fabric band loop1610between the third and fourth press rollers1623,1624travels in the first direction D1at the third speed V3. In the present embodiment, the revolution speed of the downstream nonwoven fabric band loop1610(the third speed V3) is greater than the revolution speed of the upstream nonwoven fabric band loop1510(the second speed V2). As a result, the image layer I is rubbed more by the downstream nonwoven fabric band loop1610than the upstream nonwoven fabric band loop1510.

The fixing device300Q according to the seventeenth embodiment and the conveyor400, which is used for conveying the sheet S to the fixing device300Q, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor which are described in the context of the first embodiment.

FIG. 53is a schematic view of a fixing device750and conveyor400G according to the eighteenth embodiment. The fixing device750and the conveyor400G according to the eighteenth embodiment are described with reference toFIG. 53. Hereinafter, the same reference numerals are used for describing the same elements as those of the aforementioned embodiments. The descriptions associated with the aforementioned embodiments are preferably incorporated into the elements which are not described hereinafter.

The sheet S having the image layer I formed thereon is conveyed to the fixing device750by the conveyor400G. The conveyor400G comprises the belt unit450G, the upstream guider460situated before the belt unit450G, and the downstream guider469situated after the belt unit450G. The sheet S is guided by the upstream guider460and sent to the belt unit450G. Thereafter, the sheet S is sent to the downstream guide469by the belt unit450G. In the present embodiment, the surface of the sheet S, on which the image layer I is formed, is exemplified as the formation surface.

The belt unit450G comprises the drive roller451, the idler452, the endless belt453extending between the drive roller451and the idler452, and the tension roller454applying tension to the endless belt453. Rotation of the drive roller451causes the endless belt453to revolve around the drive roller451, the idler452and the tension roller454. The idler452and the tension roller454rotate in response to the revolution of the endless belt453. As a result, the sheet S, which is sent from the upstream guider460to the endless belt453, moves toward the downstream guider469in response to the revolution of the endless belt453. The sheet S is conveyed from the upstream guider460to the downstream guider469at the first speed V1. Reference numeral D1represents the direction in which the sheet S is moved from the upstream guider460toward the downstream guider469by the belt unit450G. The belt unit450G is exemplified as the conveying element.

The belt unit450G further comprises the backup roller340arranged inside the endless belt453. The backup roller340abuts with the inner surface of the endless belt453at a position between the drive roller451and the idler452, which is situated on the opposite side to the tension roller454.

The fixing device750rubs and fixes the image layer I on the sheet S. The fixing device750includes a rubbing member751situated on the opposite side of the backup roller340so that the endless belt453intervenes between the rubbing member751and the backup roller340, and a drive source752configured to drive the rubbing member751.

The rubbing member751includes a supporting member753, a nonwoven fabric layer754, and a shaft755.

FIG. 54is a perspective view of the rubbing member751. The supporting member753is a cylindrical block member. The supporting member753includes a first supporting surface753a, which is an end surface facing the endless belt453, and a second supporting surface753b, which is an end surface opposite to the first supporting surface753ain the axial direction. The first and second supporting surfaces753a,753bare substantially circular.

The nonwoven fabric layer754rubs the image layer I on the sheet S. The nonwoven fabric layer754, which is made of a nonwoven fabric, is mounted on the entire first supporting surface753aand looks circular in a plane. Any of the nonwoven fabrics described in the context ofFIG. 4may be used as the nonwoven fabric. The dynamic friction coefficient of the nonwoven fabric is no more than 0.50. The backup roller340of the belt unit450G is arranged such that the surface pressure between the backup roller340and a layer surface754aof the nonwoven fabric layer754becomes, for example, 0.2 g/mm2. Therefore, the nonwoven fabric layer754keeps in surface contact with the endless belt453. The layer surface754aof the nonwoven fabric layer754, which contacts the endless belt453, forms a rubbing surface. The layer thickness of the nonwoven fabric layer754is appropriately set such that the nonwoven fabric layer754and the image layer I come into smooth contact with each other.

The nonwoven fabric layer754has a rubbing region CR in which the nonwoven fabric layer754rubs the image layer I while keeping in surface contact with the image layer I. The rubbing region CR is described with reference toFIGS. 53 to 55.FIG. 55is a plan view of the rubbing member751and the endless belt453. The shaft755is fixed to the second supporting surface753bof the supporting member753at a position where one end of the shaft755aligns with the central axis of the supporting member753. The drive source752is, for example, a motor, which is coupled to the other end of the shaft755and rotates the shaft755in the clockwise direction inFIG. 55. The nonwoven fabric layer754has a rotation center O, which conforms with the central axis of the supporting member753, and a rotation axis of the shaft755(a rotation axis extending in an intersecting direction with the surface of the sheet on which the image layer I is formed). When the shaft755rotates, the supporting member753rotates around the central axis. The nonwoven fabric layer754mounted on the first supporting surface753aof the supporting member753also rotates around the rotation center O while keeping in contact with the endless belt453. In the present embodiment, the layer surface754aof the nonwoven fabric layer754is exemplified as the rotation surface.

The rubbing region CR is a region which is set on the downstream side from the rotation center O of the nonwoven fabric layer754when viewed from the conveying direction (the first direction D1) of the sheet S, and looks a substantially semicircular shape in a plane. The nonwoven fabric layer754contacts the endless belt453to form a nip portion N with the endless belt only in the rubbing region CR. The entire rubbing region CR of the nonwoven fabric layer754comes into surface contact with the sheet S at the nip portion N. The position where the backup roller340abuts the endless belt453and the inclination angle of the shaft755with respect to the rubbing member751are appropriately adjusted such that the rubbing region CR becomes semicircular.

Therefore, when the sheet S is conveyed to the nip portion N, the nonwoven fabric layer754rotates around the rotation center O while keeping in surface contact with the sheet S in the rubbing region CR and rubs the image layer I.FIG. 55shows a state in which the leading end of the sheet S in the conveying direction (the first direction D1) is in surface contact with the rubbing region CR.

In the eighteenth embodiment, a linear speed in a tangential direction of the supporting member753rotated by the shaft755(that is a linear speed LV of the nonwoven fabric layer754) may be greater than the first speed V1of conveying the sheet S. In addition, the diameter of the supporting member753(that is the diameter D of the nonwoven fabric layer754) is greater than a sheet width W perpendicular to the conveying direction (the first direction D1) of the sheet S, so that the entire image layer I is rubbed.

According to the aforementioned fixing device750of the eighteenth embodiment, the rubbing region CR of the nonwoven fabric layer754, which rotates around the rotation center O, keeps in surface contact with the sheet S to rub the image layer I. In addition, the linear speed LV of the nonwoven fabric layer754may be greater than the first speed V1of conveying the sheet S. Thus, the time period in which the image layer I is rubbed by the nonwoven fabric layer754becomes long, compared to a configuration in which a roller rubs the image layer I while keeping in linear contact with the sheet S. Therefore, the components of the liquid developer, which forms the image layer I, are facilitated to enter into the surface layer of the sheet S, which results in shorter time period required for the fixation of the image layer I. Therefore it becomes less likely that the image layers I peels off because the image layer I is strongly fixed.

In the eighteenth embodiment, the nonwoven fabric layer754made of a nonwoven fabric is used as the rubbing surface. Therefore, it becomes easier for the nonwoven fabric layer754to bring into surface contact with the sheet S.

The nonwoven fabric, which forms the nonwoven fabric layer754, has a dynamic friction coefficient of 0.50 or lower, which is less likely to impinge on the conveyance of the sheet S and to cause a damaged image layer I under the rubbing operation.

It should be noted that the planar nonwoven fabric layer754described in the eighteenth embodiment is circular, but the planar nonwoven fabric layer754is not particularly limited thereto. The planar nonwoven fabric layer754may be, for example, a ring shape without a central portion where there is no rubbing region CR of the nonwoven fabric layer754.

The fixing device750according to the eighteenth embodiment and the conveyor400G which is used for conveying the sheet S to the fixing device750, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor which are described in the context of the first embodiment.

FIG. 56is a schematic view of a fixing device750R and conveyor400G according to the nineteenth embodiment. The sheet S having the image layer I formed thereon is conveyed to the fixing device750R by the conveyor400G. The configuration of the conveyor400G is described with reference toFIG. 53. The fixing device750R rubs and fixes the image layer I on the sheet S. The fixing device750R includes a rubbing member751R situated in an opposite side to the backup roller340so that the endless belt453intervenes between the rubbing member751R and the backup roller340, and the drive source752configured to drive the rubbing member751R.

The rubbing member751R includes the supporting member753(brush supporting member), a rubbing brush760, and the shaft755.

Like the supporting member753shown inFIGS. 53 and 54, the supporting member753is a cylindrical block member. The supporting member753includes the first supporting surface753awhich is an end surface facing the endless belt453and the second supporting surface753bwhich is an end surface opposite to the first supporting surface753ain the axial direction. The first and second supporting surfaces753a,753bare substantially circular.

The rubbing brush760rubs the image layer I on the sheet S. The entire first supporting surface753a(brush mounting surface) of the supporting member753is covered with the rubbing brush760. The rubbing brush760looks circular in a plane. The rubbing brush760has a brush surface760afacing the endless belt453, and a number of bristles761are implanted in the brush surface760a. The bristles761are implanted in the periphery of the brush surface760a. A piled woven fabric with electrically-conductive rayon or polyester is exemplified as a material of the bristles761. With the electrically-conductive rayon, the pile fineness thereof is 300D/100F. With the polyester, the pile fineness thereof is 75D/12F.

The tip ends of the bristles761of the rubbing brush760are pressed against the endless belt453to be bent. Therefore, the rubbing brush760is in surface contact with the endless belt453because of the bent bristles761. The bent tip ends of the bristles761form the rubbing surface. The bristles761of the rubbing brush760are pressed against the endless belt453such that the surface pressure applied to the endless belt453becomes, for example, 0.2 g/mm2. Not only the abovementioned pile fineness but also the density and length of the bristles761are appropriately set so as to achieve a given surface pressure.

The rubbing brush760has the rubbing region CR where the rubbing brush760rubs the image layer I while keeping in surface contact with the image layer I. The rubbing region CR is described with reference toFIGS. 56 to 58.FIG. 58is a plan view of the rubbing member751R and the endless belt453. Like the configuration described with reference toFIGS. 53 to 55, the shaft755is fixed to the second supporting surface753bof the supporting member753at a position where the shaft755aligns with the central axis of the supporting member753. The drive source752is, for example, a motor which is coupled to the shaft755and rotates the shaft755in the clockwise direction inFIG. 58. The rubbing brush760has a rotation center O which aligns with the central axis of the supporting member753and the rotation axis of the shaft755. When the shaft755rotates, the supporting member753rotates around the central axis. The rubbing brush760mounted on the first supporting surface753aof the supporting member753also rotates around the rotation center O. Meanwhile the bent bristles761are kept in contact with the endless belt453.

The rubbing region CR is a region which is set on the downstream side from the rotation center O of the rubbing brush760when viewed from the conveying direction (the first direction D1) of the sheet S, and looks a substantially semicircular shape in a plane. The bristles761of the rubbing brush760come into contact with the endless belt453to form the nip portion N with the endless belt453only in the rubbing region CR. The bristles761of the rubbing brush760in the entire rubbing region CR come into surface contact with the sheet S at the nip portion N.

Therefore, when the sheet S is conveyed to the nip portion N, the rubbing brush760rotates around the rotation center O. Meanwhile the bristles761are kept in surface contact with the sheet S and rub the image layer I.FIG. 58shows a state in which the leading edge of the sheet S in the conveying direction (the first direction D1) enters the rubbing region CR.

In the nineteenth embodiment, the linear speed in a tangential direction of the supporting member753rotated by the shaft755(that is a linear speed LV of the rubbing brush760) may be greater than the first speed V1of conveying the sheet S. In addition, the diameter of the supporting member753(that is the diameter D of the rubbing brush760) is greater than the sheet width W perpendicular to the conveying direction (the first direction D1) of the sheet S, so that the entire image layer I is rubbed.

In the nineteenth embodiment, the contact area of the contact surface between the bristles761of the rubbing brush760and the image layer I, which is the region area of the rubbing region CR where the bristles761of the rubbing brush760come into surface contact with the image layer I to rub the image layer I, may be switched between a first region area (first contact area) and a second region area (second contact area) larger than the first region area. The fixing device750R according to the nineteenth embodiment further includes a switching mechanism780configured to change the region area of the rubbing region CR, and a controller U configured to control the switching mechanism780.

The switching mechanism780is described with reference toFIGS. 56,59and60.FIG. 59shows a state in which the region area of the rubbing region CR is switched to the first region area, andFIG. 60shows a state in which the region area of the rubbing region CR is switched to the second region area. The drive source752of the fixing device750R is stored in a housing783. The shaft755of the rubbing member751R is coupled to the drive source752through a hole provided in the housing783. The housing783may be turn in a given range. By turning the housing783, the rubbing member751R is turned around drive source752.

The switching mechanism780includes, for example, a cam781and a biasing member782. The biasing member782, which is a spring member, for example, applies a basing force in a direction of an arrow B to the housing783in order to turn the housing783in a given direction (in the counterclockwise direction, inFIG. 56). The cam781abuts and turns the housing783in the clockwise direction inFIG. 56against the biasing force of the biasing member782.

In the nineteenth embodiment, an intersection angle α where a virtual line VL, which is an extension of the shaft755of the rubbing member751R, intersects with a virtual surface VS, which is an extension of the contact surface between the bristles761of the rubbing brush760and the image layer I, is switched between a first angle and a second angle greater than the first angle. Therefore the region area of the rubbing region CR is switched between the first and second region areas. An increase in the intersection angle α results in greater region area of the rubbing region CR. More specifically, if the intersection angle α is switched to the first angle, the region area of the rubbing region CR is switched to the first region area. If the intersection angle α is switched to the second angle, the region area of the rubbing region CR is switched to the second region area. For instance, the first and second angles are set at 60° and 90°, respectively.

The controller U controls the switching mechanism780to switch the region area of the rubbing region CR between the first and second region areas. Control operations performed by the controller U on the switching mechanism780are described hereinafter. If the controller U turns the cam781in the first direction to switch the region area of the rubbing region CR from the first region area shown inFIG. 59to the second region area, the biasing member782biases the housing783in the direction of the arrow B, and then the housing783is turned in the counterclockwise direction inFIG. 56. By turning the housing783in the counterclockwise direction, the rubbing member751R also turns around the drive source752in the counterclockwise direction. Meanwhile a turning range of the cam781and the rubbing member751R is set such that the intersection angle α becomes 90°. As a result, the region area of the rubbing region CR is switched to the second region area greater than the first region area.

On the other hand, if the controller U turns the cam781in the second direction opposite to the first direction to switch the region area of the rubbing region CR from the second region area to the first region area as shown inFIG. 60, the controller U turns the cam781in a second direction opposite to the first direction. As a result, the cam781turns against the biasing force of the biasing member782, so that the housing783is turned in the clockwise direction. In response to this turning of the housing783, the rubbing member751R also turns around the drive source752in the clockwise direction. Meanwhile the turning range of the cam781and the rubbing member751R is set such that the intersection angle α becomes 60°. As a result, the region area of the rubbing region CR is switched to the first region area smaller than the second region area.

If the sheets S include a thin sheet S with a first thickness (e.g., a normal A4-size thin sheet) and a thick sheet S with a second thickness thicker than the first thickness (e.g., a postcard or coated paper), the controller U controls the switching mechanism780to switch the region area of the rubbing region CR to the first region area (i.e., the intersection angle α is 60°) for the thin sheet S conveyed to the nip portion N. If the thick sheet S is conveyed to the nip portion P, the controller U controls the switching mechanism780to switch the region area of the rubbing region CR to the second region area (i.e., the intersection angle α is 90°). Because the second region area is greater than the first region area as described above, the time period during which the rubbing brush760rubs the image layer I in the rubbing region CR becomes longer. Thus, the controller U appropriately changes the rubbing time for rubbing the image layer I with the rubbing brush760in response to the thickness of sheets S (the type of the sheet S). In the present embodiment, the controller U and the switching mechanism780are exemplified as the adjustment mechanism.

According to the aforementioned fixing device750R of the nineteenth embodiment, the rubbing brush760rotates around the rotation center O while the bristles761in the rubbing region CR are kept in surface contact with the sheet S and rub the image layer I. In addition, the linear speed LV of the rubbing brush760may be greater than the first speed V1of conveying the sheet S. Thus, the time period in which the image layer I is rubbed by the bristles761of the rubbing brush760becomes long, compared to configurations which uses a roller for rubbing the image layer I while keeping in linear contact with the sheet S. Therefore, the components of the liquid developer which forms the image layer I are facilitated to enter into the surface layer of the sheet S, which shortens the time period during which the image layer I is fixed and preferably prevent the image layer I from peeling because of stronger fixation of the image layer I.

The fixing device750R according to the nineteenth embodiment uses the rubbing brush760with many bristles761to rub the image layer I. Appropriate adjustments of the bristles761such as material, pile fineness, density and length cause less impingement on the conveyance of the sheet S and less damage to the image even under the rubbing operation.

The controller U of the fixing device750R according to the nineteenth embodiment appropriately changes the rubbing time period for rubbing the image layer I in response to the thickness of sheets S, by switching the region area of the rubbing region CR between the first and second region areas in response to the thickness of the sheets S. Therefore, even if the sheets S are different in thickness, the components of the liquid developer for forming the image may be facilitated to permeate into the surface layer of the sheets S.

The rubbing brush760with the bristles761of the fixing device750R according to the nineteenth embodiment is used for rubbing the image layer I. Therefore, the intersection angle α may be switched between the first and second angles, so that the region area of the rubbing region CR may be easily switched between the first and second region areas.

The fixing device750R according to the nineteenth embodiment and the conveyor400G, which is used for conveying the sheet S to the fixing device750R, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor which are described in the context of the first embodiment.

Modifications from the nineteenth embodiment are described with reference toFIG. 61hereinafter.FIG. 61is a plan view of the rubbing member751R and the endless belt453. In the modifications from the nineteenth embodiment, two rubbing members, a first rubbing member1751and second rubbing member2751, are used. The first and second rubbing members1751,2751are situated side by side in a direction perpendicular to the conveying direction (the first direction D1) of the sheet S. In other words, a first rubbing surface (tip ends of first bristles1761) formed by a first rubbing brush1760of the first rubbing member1751and a second rubbing surface (tip ends of second bristles2761) formed by a second rubbing brush2760of the second rubbing member2751are situated side by side in the direction (a width direction W of the sheet S (a transverse direction T)) perpendicular to the conveying direction (the first direction D1) of the sheet S. Therefore, even if a color image layer I with an increased carrier liquid amount is fixed to the sheet S, the carrier liquid may be facilitated to enter the surface layer of the sheet S. In the present embodiment, the first rubbing brush1760is exemplified as the first brush. The second rubbing brush2760is exemplified as the second brush.

A first shaft1755of the first rubbing member1751is rotated by the drive source752in a first rotation direction R1(the clockwise direction inFIG. 61), and a second shaft2755of the second rubbing member2751is rotated by the drive source752in a second rotation direction R2(the counterclockwise direction inFIG. 61) opposite to the first rotation direction R1. Therefore, the first rubbing brush1760rubs the image layer I while rotating in the first rotation direction R1, and the second rubbing brush2760rubs the image layer I while rotating in the second rotation direction R2. The sheet S is consequently rubbed while being stretched to prevent wrinkles on the sheet S. In the present embodiment, the rubbing surface formed by the first rubbing brush1760is exemplified as the first rotation surface. The rubbing surface formed by the second rubbing brush2760is exemplified as the second rotation surface.

In the modifications of the nineteenth embodiment, the first and second rubbing members1751,2751are situated such that the first bristles1761of the first rubbing brush1760and the second bristles2761of the second rubbing brush2760come into contact with each other in the perpendicular direction to the conveying direction (the first direction D1) of the sheet S. Thus, a contact area OA where the first and second bristles1761,2761come into contact with each other is formed between the first and second rubbing members1751,2751. Therefore it is less likely that there are non-rubbing regions where the image layer I is not rubbed.

FIG. 61shows the configuration which uses two brushes, the first and second rubbing brushes1760,2760. However, in place of this configuration, two nonwoven fabric layers such as first and second nonwoven fabric layers may be situated side by side in the perpendicular direction to the conveying direction (the first direction D1) of the sheet S.

Modifications from the eighteenth embodiment are described with reference toFIG. 62hereinafter. The configuration according to the eighteenth embodiment described with reference toFIGS. 53 to 55has the nonwoven fabric layer754, which is partially brought into surface contact with the endless belt453. However, methodologies of the present invention is not limited to such a configuration, so that the entire nonwoven fabric layer754may be brought into contact with the endless belt453to rub the image layer I, as shown inFIG. 62. In this case, a support plate785configured to support the entire surface of the nonwoven fabric layer754is disposed on the opposite side of the nonwoven fabric layer754so that the endless belt453intervenes between the nonwoven fabric layer754and the support plate785. With the configuration shown inFIG. 62, the surface pressure applied to the endless belt453by the nonwoven fabric layer754is appropriately adjusted in order to prevent the image layer I from being excessively rubbed by the nonwoven fabric layer754. In the modifications shown inFIG. 62, the rubbing brush.760may be used in place of the nonwoven fabric layer754. In this case, the entire rubbing brush760is brought into contact with the endless belt453.

FIG. 63is a schematic view of a fixing device1050and the conveyor400G according to the twentieth embodiment.FIG. 64is a perspective view of the fixing device1050and the conveyor400G. Hereinafter, the same reference numerals are used for describing the same elements as those of the aforementioned embodiments. The descriptions associated with the aforementioned embodiments are preferably incorporated into the elements which are not described hereinafter.

The sheet S having the image layer I formed thereon is conveyed to the fixing device1050by the conveyor400G. The conveyor400G comprises the belt unit450G, the upstream guider460situated before the belt unit450G, and the downstream guider469situated after the belt unit450G. The sheet S is guided by the upstream guider460and sent to the belt unit450G. Thereafter, the sheet S is sent to the downstream guide469by the belt unit450G.

The belt unit450G comprises the drive roller451, the idler452, the endless belt453(conveying belt) extending between the drive roller451and the idler452, and the tension roller454applying tension to the endless belt453. Rotation of the drive roller451causes the endless belt453to revolve around the drive roller451, the idler452and the tension roller454. The idler452and the tension roller454rotate in response to the revolution of the endless belt453. As a result, the sheet S, which is sent from the upstream guider460to the endless belt453, moves toward the downstream guider469in response to the revolution of the endless belt453. The sheet S is conveyed from the upstream guider460to the downstream guider469. Reference numeral D1represents a direction in which the sheet S is moved from the upstream guider460toward the downstream guider469by the belt unit450G. The belt unit450G is exemplified as the conveying element.

The belt unit450G further comprises the backup roller340disposed inside the endless belt453. The backup roller340abuts the inner surface of the endless belt453to support the endless belt453between the drive roller451and the idler452, which is situated on the opposite side to the tension roller454.

The fixing device1050fixes the image layer I on the sheet S. The fixing device1050includes a rubbing member1051, a drive source1054, and a biasing member1055.

The rubbing member1051includes a supporting member1052and a nonwoven fabric layer1053. The supporting member1052is an elongated box, which is situated on the opposite side to the backup roller340, so that the endless belt453intervenes between the supporting member1052and the backup roller340. The supporting member1052extends in a width direction of the endless belt453and an axial direction of the backup roller340. The supporting member1052has a first supporting surface1052afacing the endless belt453and a second supporting surface1052bopposite to the first supporting surface1052a. The first supporting surface1052ais curved along the conveying direction of the sheet S. The second supporting surface1052bis substantially flat.

The nonwoven fabric layer1053rubs the image layer I on the sheet S. The nonwoven fabric layer1053is formed from a nonwoven fabric and entirely attached on the first supporting surface1052a. Therefore, the nonwoven fabric layer1053extends in the form of an arc along the conveying direction (the first direction D1) of the sheet S. Any of the nonwoven fabrics described in the context ofFIG. 4is used as the nonwoven fabric. The dynamic friction coefficient of the nonwoven fabric is 0.50 or lower. In the present embodiment, the surface of the nonwoven fabric layer1053rubbing the image layer I on the sheet S is exemplified as the contact surface.

The biasing member1055is, for example, a spring member mounted on the second supporting surface1052bof the supporting member1052. In the twentieth embodiment, the biasing member1055is mounted in each longitudinal end of the supporting member1052. The biasing member1055applies a biasing force F to the supporting member1052to allow the nonwoven fabric layer1053to keep in contact with the endless belt453. A nip portion N is formed between a layer surface1053aof the nonwoven fabric layer1053, which contacts the endless belt453, and the endless belt453. Therefore, the layer surface1053aof the nonwoven fabric layer1053forms a rubbing surface. The biasing member1055is set such that the nonwoven fabric layer1053is pressed against the endless belt453at a surface pressure of, for example, 0.2 g/mm2. The layer thickness of the nonwoven fabric layer1053is appropriately set such that the nonwoven fabric layer1053and the image layer I come into smooth contact with each other.

The drive source1054is held in an appropriate section (for example, a substantially intermediate portion of the supporting member1052in a longitudinal direction) inside the supporting member1052. The drive source1054stored in the supporting member1052vibrates the supporting member1052. A vibration motor is exemplified as the drive source1054.FIG. 65is a perspective view showing a schematic configuration of the vibration motor.

The vibration motor1054with an inner rotor structure comprises a main body1056, an output shaft1057, and an eccentric piece1058. The eccentric piece1058is, for example, a weight which is externally fitted to the outer shaft1057in order to disrupt a dynamic balance of the main body1056. Rotation of the main body1056causes vibration because the gravity center of the eccentric piece1058is not centered.

The vibration caused by the vibration motor1054vibrates the supporting member1052storing the vibration motor1054and the nonwoven fabric layer1053mounted on the first supporting surface1052aof the supporting member1052. The nonwoven fabric layer1053keeps the state where the nonwoven fabric layer1053is pressed against the endless belt453by the biasing member1055as described above. Therefore, when the sheet S is conveyed to the nip portion N, the nonwoven fabric layer1053utilizes the vibration to slide on the image layer I in multiple directions to rub the image layer I while keeping in contact with the image layer I without separating therefrom.

FIG. 66is a plan view of the endless belt453, on which the sheet S is placed, schematically showing the rubbing operation performed on the image layer I by the nonwoven fabric layer1053. It should be noted thatFIG. 66does not show the fixing device1050for clarification. The nonwoven fabric layer1053in the rubbing region CR shown by the dashed line inFIG. 66contacts the endless belt453, the sheet S and the image layer I. The rubbing region CR is situated on a line connecting a curvature center of the first supporting surface1052of the supporting member1052with the rotation center of the backup roller340, and extends in the sheet width direction W (a transverse direction T) perpendicular to the conveying direction (the first direction D1) of the sheet S. The rubbing region CR extends somewhat beyond the width of the sheet S. The nonwoven fabric layer1053rubs the image layer I while sliding on the image layer I in the rubbing region CR in multiple directions.

More specifically, when viewed from any rubbing section VP in the nonwoven fabric layer1053, the vibration of the nonwoven fabric layer1053reciprocates the rubbing section VP with a small amplitude in conveying direction (the first direction D1) of the sheet S, in the traverse direction T perpendicular to the conveying direction (the first direction D1) of the sheet S, or in an oblique direction K, which is oblique to the conveying direction (the first direction D1) or the traverse direction T. Because of the irregular rubbing operation performed on the rubbing section VP, the rubbing section VP slides irregularly on the image layer I in multiple directions including these directions D1, T, K with small amplitudes to rub the image layer I. As a result, the section of the image layer I into contact with the rubbing section VP is rubbed a number of times. It should be noted that the rubbing section VP does not necessarily reciprocate in these directions D1, T, K.

According to the aforementioned fixing device1050of the twentieth embodiment, the nonwoven fabric layer1053is vibrated by the vibration motor1054to rub the image layer I in multiple directions while keeping in contact with the image layer I. Therefore, the image layer I on the sheet S is rubbed a number of times by the nonwoven fabric layer1053. As a result, the components of the liquid developer forming the image layer I may be facilitated to enter the surface layer of the sheet S, which may reduce the time period during which the image layer I is fixed and preferably prevent the image layer I from peeling because of stronger fixation of the image layer I.

According to the fixing device1050of the twentieth embodiment, the vibration motor is used as the drive source1054. Therefore, the nonwoven fabric layer1053may vibrate with respect to the image layer I in multiple directions.

According to the fixing device1050of the twentieth embodiment, the nonwoven fabric layer1053is allowed to keep in contact with the image layer I by the biasing member1055. Accordingly, the vibration of the nonwoven fabric layer1053is easily transmitted the image layer I.

According to the fixing device1050of the twentieth embodiment, the backup roller340is disposed on the opposite side to the nonwoven fabric layer1053so that the endless belt453intervenes between the backup roller340and the nonwoven fabric layer1053. Therefore, the vibration of the nonwoven fabric layer1053is easily transmitted to the image.

According to the fixing device1050of the twentieth embodiment, the nonwoven fabric layer1053made of a nonwoven fabric is used as a rubbing member for the image layer I. The dynamic friction coefficient of the nonwoven fabric is 0.50 or lower, which result in less impingement on the conveyance of the sheet S as well as less damage to the image layer I under the rubbing operation.

The fixing device1050according to the twentieth embodiment and the conveyor400G, which is used for conveying the sheet S to the fixing device1050, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor which are described in the context of the first embodiment.

A fixing device3500according to the twenty-first embodiment is described with reference toFIG. 67hereinafter.FIG. 67is a schematic view of the fixing device3500and the conveyor400G according to the twenty-first embodiment. The sheet S having the image layer I formed thereon is conveyed to the fixing device3500by the conveyor400G. The configuration of the conveyor400G is described with reference toFIG. 63. The fixing device3500rubs and fixes the image layer I onto the sheet S. The fixing device3500includes a rubbing member3510, the drive source1054, and the biasing member1055.

The rubbing member3510has a supporting member3520and a nonwoven fabric layer3530. The supporting member3520is an elongated box which is situated on the opposite side to the backup roller340, so that the endless belt453intervenes between the supporting member3520and backup roller340. The supporting member3520extends in the width direction of the endless belt453and the axial direction of the backup roller340. The supporting member3520has a first supporting surface3520afacing the endless belt453and a second supporting surface3520bopposite to the first supporting surface3520a. The first supporting surface3520ahas a curved surface portion3520aa. The curved surface portion3520aais curved along the outer circumferential surface of the backup roller340. The second supporting surface3520bis substantially flat.

The nonwoven fabric layer3530rubs the image layer I on the sheet S. The nonwoven fabric layer3530is formed from a nonwoven fabric and entirely mounted on the first supporting surface3520a. Therefore, the nonwoven fabric layer3530has an arc section3530acorresponding to the curved surface portion3520aaof the first supporting surface3520a. Any of the nonwoven fabrics'described in the context ofFIG. 4is used as the nonwoven fabric. The dynamic friction coefficient of the nonwoven fabric is 0.50 or lower.

The biasing member1055is, for example, a spring member mounted on the second supporting surface3520bof the supporting member3520. In the twenty-first embodiment as well, although not shown, the biasing member1055is mounted in each longitudinal end of the supporting member3520. The biasing member1055applies a biasing force F to the supporting member3520to press the nonwoven fabric layer3530against the endless belt453to keep the surface contact between the entire arc section3530aof the nonwoven fabric layer3530and the endless belt453. A nip portion N is formed between the arc section3530aof the nonwoven fabric layer3530and the endless belt453. Therefore, the layer surface of the arc section3530aof the nonwoven fabric layer3530forms a rubbing surface. The biasing member1055is set such that the arc section3530aof the nonwoven fabric layer3530is pressed against the endless belt453at a surface pressure of, for example, 0.2 g/mm2. The layer thickness of the nonwoven fabric layer3530is appropriately set such that the nonwoven fabric layer3530and the image layer I come into smooth contact with each other.

The drive source1054is stored in the supporting member3520, and the same vibration motor as that of the twentieth embodiment is used. The vibration generated by the vibration motor1054vibrates the supporting member3520storing the vibration motor1054and the nonwoven fabric layer3530mounted on the first supporting surface3520aof the supporting member3520. The arc section3530aof the nonwoven fabric layer3530keeps its state where the arc section3530ais brought into surface contact with the endless belt453by the biasing member1055as described above. Therefore, when the sheet S is conveyed to the nip portion N, the arc section3530aof the nonwoven fabric layer3530utilizes the vibration to slide on the image layer I in multiple directions to rub the image layer I while keeping in surface contact with the image layer I without separating therefrom.

According to the fixing device3500of the twenty-first embodiment, the arc section3530aof the nonwoven fabric layer3530rubs the image layer I while keeping in surface contact with the image layer I. Therefore, the vibration of the arc section3530ais widely transmitted to the image layer I. A wide range of the image layer I on the sheet S is rubbed a number of times by the nonwoven fabric layer3530. Accordingly, the components of the liquid developer forming the image layer I may be facilitated to enter the surface layer of the sheet S, which may shorten the time period during which the image layer I is fixed and preferably prevent the image layer I from peeling because of stronger fixation of the image layer I.

According to the aforementioned fixing device3500of the twenty-first embodiment, the nonwoven fabric layer3530made of a nonwoven fabric is used as the rubbing surface. Thus, the nonwoven fabric layer3530may easily be brought into surface contact with the image layer I.

According to the fixing device3500of the twenty-first embodiment, the use of the nonwoven fabric with a low dynamic friction coefficient (0.5 or lower) is less likely to impinge on the conveyance of the sheet S and to damage the image layer I under the rubbing operation of the nonwoven fabric layer3530.

The fixing device3500according to the twenty-first embodiment and the conveyor400G, which is used for conveying the sheet S to the fixing device3500, are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor which are described in the context of the first embodiment.

A fixing device3600according to a twenty-second embodiment is described with reference toFIG. 68hereinafter.FIG. 68is a schematic view of the fixing device3600and the conveyor400G according to the twenty-second embodiment. In the twentieth and twenty-first embodiments, the nonwoven fabric layers1053and3530are used for rubbing the image layer I, but a rubbing brush1062may be used for rubbing the image layer I in the twenty-second embodiment as shown inFIG. 68. The fixing device3600shown inFIG. 68includes a rubbing member1060, the drive source1054, and the biasing member1055. The rubbing member1060includes a supporting member1061and the rubbing brush1062.

Like the twentieth and twenty-first embodiments, the supporting member1061is an elongated box which is situated on the opposite side to the backup roller340, so that the endless belt453intervenes between the supporting member1061and the backup roller340. The supporting member1061extends in the width direction of the endless belt453and the axial direction of the backup roller340. The supporting member1061includes a first supporting surface1061afacing the endless belt453and a second supporting surface1061bopposite to the first supporting surface1061a. The first and second supporting surface1061a,1061bare substantially flat.

The rubbing brush1062is mounted on the first supporting surface1061aof the supporting member1061. The rubbing brush1062includes a brush surface1062afacing the endless belt453. A number of bristles1063are implanted in the brush surface1062a. A range in which the bristles1063are implanted is appropriately set. InFIG. 68, the bristles1063are implanted only in a position on the brush surface1062awhich contacts the endless belt453. A piled woven fabric formed from electrically-conductive rayon or polyester is exemplified as a material of the bristles1063. With the electrically-conductive rayon, the pile fineness thereof is 300D/100F. With the polyester, the pile fineness thereof is 75D/12F.

The biasing member1055is mounted on the second supporting surface1061bof the supporting member1061. The biasing member1055applies a biasing force F to the supporting member1061and then to the rubbing brush1062, in order to press the bristles1063of the rubbing brush1062against the endless belt453. Accordingly, the tip ends of the bristles1063of the rubbing brush1062are pressed against the endless belt453to be bent. Therefore, the rubbing brush1062with the bent bristles1063is in surface contact with the endless belt453. The bent tip ends of the bristles1063form the rubbing surface. The bristles1063of the rubbing brush1062are pressed against the endless belt453such that the surface pressure applied to the endless belt453becomes, for example, 0.2 g/mm2. Not only the abovementioned pile fineness but also the density and length of the bristles1063are appropriately set so as to obtain a given surface pressure.

The drive source1054is stored in the supporting member1061, and the same vibration motor1054as those of the twentieth and twenty-first embodiments is used. The vibration generated by the vibration motor1054vibrates the supporting member1061storing the vibration motor1054and the rubbing brush1062mounted on the first supporting surface1061aof the supporting member1061. The tip ends of the bristles1063of the rubbing brush1062keep the state where the tip ends of the bristles1063are brought into surface contact with the endless belt453by the biasing member1055as described above. Therefore, when the sheet S is conveyed to the nip portion N, the bristles1063of the rubbing brush1062utilize the vibration to slide on the image layer I in multiple directions to rub the image layer I while keeping in surface contact with the image layer I without separating therefrom.

According to the fixing device3600of the twenty-second embodiment, the bristles1063of the rubbing brush1062slides on the image layer I while keeping surface contact therewith to rub the image layer I. Consequently, the image layer I on the sheet S is rubbed a number of times by the bristles1063of the rubbing brush1062. Therefore, the components of the liquid developer forming the image layer I may be facilitated to enter the surface layer of the sheet S, which may shorten the time period during which the image layer I is fixed and preferably prevent the image layer I from peeling because of stronger fixation of the image layer I.

Appropriate adjustments of the bristles1063such as material, fineness, density and length reduce impingement on the conveyance of the sheet S and damage to the image layer I under the rubbing operation of the rubbing brush1062.

The fixing device3600according to the twenty-second embodiment and the conveyor400G which is used for conveying the sheet S to the fixing device3600are preferably incorporated in the color printer1described in the context ofFIGS. 8 to 10, in place of the fixing device300and the conveyor described in the context of the first embodiment.

According to a series of the aforementioned embodiments, by moving the contact surface, which contacts an image, relative to the image on a sheet, the image is fixed onto the sheet. The movement of the contact surface relativd to the sheet may be accomplished not only by the mechanisms described in the context of these embodiments but also by other mechanisms. Therefore, the methodologies of these embodiments described above are not limited to the aforementioned structures in detail.

This application is based on Japanese Patent application Nos. 2010-177638, 2010-237186, 2010-237187, 2010-237188, 2010-237189, 2010-237190, 2010-237191, and 2010-237192 filed in Japan Patent Office on Aug. 6, 2010 and Oct. 22, 2010, the contents of which are hereby incorporated by reference.