Fixing device and image forming apparatus

A fixing device includes: a fixing belt with no ends configured to stretch rotatably; a heating unit configured to heat the fixing belt; a fixing member disposed outside the fixing belt and configured to be in contact with the fixing belt by pressurizing; a pressing member disposed inside the fixing belt and configured to press the fixing member with the fixing belt involved; and a lubricant supply unit configured to supply a lubricant to the inner periphery of the fixing belt so as to supply the lubricant between the pressing member and the fixing belt, wherein the lubricant supply unit is disposed inside the fixing belt, configured to hold the lubricant, and includes a holding unit provided with a lubricant ejection port having a longitudinal shape and extending along a width direction of the fixing belt.

The entire disclosure of Japanese Patent Application No. 2016-122548 filed on Jun. 21, 2016 including description, claims, drawings, and abstract are incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a fixing device and an image forming apparatus.

Description of the Related Art

In recent years, what is called a belt-pad type image forming apparatus has been employed in the related art. In the belt-pad type image forming apparatus, a nip portion is formed by involving a fixing belt and bringing a pad (pressing member) disposed inside the fixing belt into contact with a pressurizing roller configured to pressurize.

In this fixing device, the fixing belt is driven to rotate with the pressurizing roller so as to fix unfixed toner on a sheet and convey the sheet to a sheet ejection tray. At that time, in order to smooth the rotation of the fixing belt, a lubricant is interposed between the inner periphery of the fixing belt and the pad so as to reduce sliding resistance.

However, compared to what is called a belt-roller type fixing device in which a roller instead of a pad is brought into contact with the inner periphery of a fixing belt, the belt-pad type fixing device has a disadvantageous short lifetime since the inner periphery of the fixing belt and the pad are slid, which exhausts the lubricant when being used for a long period.

Therefore, in the belt-pad type fixing device, it is necessary to prevent exhaustion of the lubricant in order to secure a long lifetime.

The following documents are examples of one disclosing a fixing device configured to supply a lubricant between a pad and the inner periphery of a fixing belt in order to prevent exhaustion of the lubricant: that is, JP 2014-174434 A, and JP 2013-68888 A.

In the fixing device disclosed in JP 2014-174434 A, a sheet-like sliding sheet containing a lubricant is mounted on a surface of a pressing member disposed in a fixing belt. The sliding sheet includes a fiber sheet and the like. This sliding sheet is provided with inclined creases for flowing the lubricant in one direction. Furthermore, a pipe that forms a circulation channel for circulating the lubricant is connected to one end and the other end of the sliding sheet. A container configured to accumulate the lubricant and provided outside the fixing device is connected to the pipe. The lubricant is pressed into the pipe from the container with a pump and is circulated within the circulation channel. The lubricant that has reached one end of the sliding sheet moves toward the other end of the sliding sheet along the creases and is introduced into the pipe connected to the other end.

In the fixing device disclosed in JP 2013-68888 A, a sliding sheet is interposed between a pressing member disposed in a fixing belt and the inner periphery of the fixing belt. The sliding sheet is conveyed in a reciprocating manner by a conveyance system. A moving direction of the sliding sheet differs between a driving mode and a cleaning mode. In the cleaning mode, a surface of the sliding sheet in a side close to the fixing belt is cleaned by a cleaning roller, and the cleaned surface is supplied with a lubricant by a lubricant supply roller. After the lubricant is supplied to the sliding sheet, the cleaning roller is separated from the sliding sheet, and the sliding sheet maintains in a standby condition until changing to the driving mode. In the driving mode, the sliding sheet moves toward a position between the pressing member and the fixing belt so that the lubricant is supplied between the fixing belt and the pressing member.

However, the fixing device disclosed in JP 2014-174434 A is configured to pour a lubricant with a pump, which may bring about pulsations in a circulation channel and uneven supply of the lubricant. Furthermore, such a fixing device requires a lubricant to fill inside a pipe so that an amount of the lubricant held in a container is increased. Still further, in a case of supplying semi-solid grease having high viscosity as a lubricant, a high pressure is required for moving the lubricant inside the thin pipe so that the pump grows in size. Therefore, the abovementioned fixing device is unsuitable when using a highly viscous lubricant.

In the fixing device disclosed in JP 2013-68888 A, a lubricant should be supplied to a sliding sheet over a range where the sliding sheet is to be conveyed, which increases an amount of the lubricant to be held by a lubricant supply roller. Furthermore, it is difficult for the sliding sheet to evenly hold the lubricant supplied over a wide range, which causes unevenness in an amount of the lubricant supplied between a pressing member and a fixing belt.

SUMMARY OF THE INVENTION

The present invention has been made in light of the abovementioned problems, and an object thereof is to provide a fixing device configured to moderate a lubricant to be supplied between a pressing member and a fixing belt while holding a small amount of a lubricant and to provide an image forming apparatus including the fixing device.

To achieve the abovementioned object, according to an aspect, a fixing device reflecting one aspect of the present invention comprises: a fixing belt with no ends configured to stretch rotatably; a heating unit configured to heat the fixing belt; a fixing member disposed outside the fixing belt and configured to be in contact with the fixing belt by pressurizing; a pressing member disposed inside the fixing belt and configured to press the fixing member with the fixing belt involved; and a lubricant supply unit configured to supply a lubricant to the inner periphery of the fixing belt so as to supply the lubricant between the pressing member and the fixing belt, wherein the lubricant supply unit is disposed inside the fixing belt, configured to hold the lubricant, and includes a holding unit provided with a lubricant ejection port having a longitudinal shape and extending along a width direction of the fixing belt.

According to the fixing device of the present invention, the holding unit is preferably provided to the fixing belt without being in contact with the fixing belt.

According to the fixing device of the present invention, in the width direction of the fixing belt, an amount of the lubricant to be ejected from a central part of the lubricant ejection port is preferably larger than an amount of the lubricant to be ejected from both ends of the lubricant ejection port.

According to the fixing device of the present invention, in the width direction of the fixing belt, an opening area in the central part of the lubricant ejection port is preferably larger than opening areas in both ends of the lubricant ejection port.

According to the fixing device of the present invention, in the width direction of the fixing belt, the lubricant ejection port preferably has an opening area equal from one end to the other end of the lubricant ejection port, and the lubricant is preferably held in the holding unit in such a manner that a height of the lubricant from an opening surface in a normal direction of the opening surface of the lubricant ejection port is set to be higher in the central part than in both ends of the lubricant in the width direction of the fixing belt.

According to the fixing device of the present invention, the lubricant supply unit is preferably stored inside the holding unit in a side opposite to a side where the lubricant ejection port is located with respect to the lubricant, and the lubricant supply unit is preferably configured to include a pushing member for pushing out the lubricant from the lubricant ejection port.

According to the fixing device of the present invention, the lubricant supply unit preferably includes an external force application system for applying an external force to the pushing member in order to press the pushing member toward the lubricant ejection port, and the external force application system is preferably stored inside the holding unit in a side opposite to a side where the lubricant is located with respect to the pushing member and is configured to include a biasing unit for biasing the pushing member toward the lubricant ejection port.

According to the fixing device of the present invention, the external force application system preferably further includes: a supporting unit movable with respect to the holding unit and configured to support the pushing member against the biasing force of the biasing unit; and an engagement unit configured to disengageably engage with the supporting unit and to immobilize the supporting unit while engaging with the supporting unit, and when the engagement unit is released from the supporting unit, the pushing member is preferably moved together with the supporting unit toward the lubricant ejection port by the biasing force of the biasing unit.

According to the fixing device of the present invention, the pushing member preferably has a first surface and a second surface opposing each other in a normal direction of an opening surface of the lubricant ejection port, and the pushing member is preferably disposed in a side close to the lubricant ejection port, being movable by pressure of gas supplied into the holding unit, the first surface is preferably disposed close to the lubricant ejection port, the second surface is preferably disposed far from the lubricant ejection port, and the holding unit preferably includes an introduction port into which gas is introduced and includes an accumulation chamber configured to communicate with the introduction port and to accumulate the gas introduced from the introduction port, and the accumulation chamber is preferably provided to a side opposite to a side where the lubricant is located with respect to the pushing member and has a bottom including the second surface.

According to the fixing device of the present invention, the lubricant supply unit preferably further includes a pipe for introducing gas to the introduction port, and the pipe preferably includes one end connected to the introduction port and the other end drawn out to the outside and connected to a source of gas supply.

According to the fixing device of the present invention, the first surface is preferably provided with an impregnated member impregnated with the lubricant, and the impregnated member preferably comes into contact with the inner periphery of the fixing belt after the pushing member moves toward the lubricant ejection port and pushes out the lubricant.

According to the fixing device of the present invention, the fixing device preferably further comprises a decompressing device configured to decompress the accumulation chamber.

According to the fixing device of the present invention, the accumulation chamber is preferably in a state of decompression before the lubricant is ejected from the lubricant ejection port.

According to the fixing device of the present invention, the pushing member preferably has a cylindrical shape.

According to the fixing device of the present invention, the pushing member preferably has flexibility.

According to the fixing device of the present invention, the holding unit is preferably disposed in an upstream side of the pressing member in a rotational direction of the fixing belt, and the rotation of the fixing belt preferably supplies, between the fixing belt and the pressing member, the lubricant ejected from the lubricant ejection port to the inner periphery of the fixing belt.

According to the fixing device of the present invention, the pressing member preferably includes at least one opening facing the inner periphery of the fixing belt; a channel section communicating with the opening; and an introducing portion for introducing gas into the channel section, and the gas introduced from the introducing portion preferably passes through the channel section and is sent out from the opening.

According to the fixing device of the present invention, the lubricant supply unit preferably has a rotary axis parallel to an extending direction in which the lubricant ejection port extends and includes a stirring member configured to stir the lubricant held inside the holding unit by rotating around the rotary axis.

To achieve the abovementioned object, according to an aspect, an image forming apparatus reflecting one aspect of the present invention comprises: an image forming section configured to form a toner image on a recording medium conveyed along a conveyance channel; and the fixing device described above configured to fix the toner image on the recording medium conveyed along the conveyance channel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples. In the following embodiment, note that the same or common parts are denoted by the same reference numerals in the drawings, and description thereof will not be repeated.

With reference toFIG. 1, hereinafter described is an image forming apparatus100with a fixing device50mounted thereon.FIG. 1is a view showing an example of an internal structure of the image forming apparatus100.

FIG. 1shows the image forming apparatus100serving as a color printer. Hereinafter described is the image forming apparatus100as a color printer, but the image forming apparatus100is not limited to a color printer. For example, the image forming apparatus100may be a monochrome printer, a facsimile machine, or a multi-function peripheral (MFP) of a monochrome printer, a color printer, and a facsimile machine.

The image forming apparatus100includes image forming units1Y,1M,1C, and1K, an intermediate transfer belt30, a primary transfer roller31, a secondary transfer roller33, a cassette37, a driven roller38, a driving roller39, a timing roller40, a fixing device50, a housing80, and a control device101.

The housing80defines an outer shell of the image forming apparatus100. The housing80contains the image forming units1Y,1M,1C, and1K, intermediate transfer belt30, primary transfer roller31, secondary transfer roller33, cassette37, driven roller38, driving roller39, timing roller40, fixing device50, and control device101.

The image forming units1Y,1M,1C, and1K, intermediate transfer belt30, primary transfer roller31, secondary transfer roller33, cassette37, driven roller38, driving roller39, and timing roller40compose an image forming section. The image forming section forms a toner image on a sheet S serving as a recording medium conveyed along a conveyance channel41to be described.

The image forming units1Y,1M,1C, and1K are arranged in order along the intermediate transfer belt30. Receiving toner from a toner bottle15Y, the image forming unit1Y forms a yellow (Y) toner image. Receiving toner from a toner bottle15M, the image forming unit1M forms a magenta (M) toner image. Receiving toner from a toner bottle15C, the image forming unit1C forms a cyan (C) toner image. Receiving toner from a toner bottle15K, the image forming unit1K forms a black (BK) toner image.

The image forming units1Y,1M,1C, and1K are disposed in order of a rotational direction of the intermediate transfer belt30along the intermediate transfer belt30. Each of the image forming units1Y,1M,1C, and1K includes a photo conductor10, a charging device11, an exposing device12, a developing device13, and a cleaning device17.

The charging device11uniformly charges a surface of the photo conductor10. The exposing device12irradiates the photo conductor10with laser light in accordance with a control signal from the control device101and exposes the surface of the photo conductor10in accordance with an input image pattern. Accordingly, an electrostatic latent image corresponding to the input image is formed on the photo conductor10.

The developing device13applies a developing bias to a developing roller14while rotating the developing roller14and attaches toner to the surface of the developing roller14. Accordingly, the toner is transferred from the developing roller14to the photo conductor10, and a toner image corresponding to the electrostatic latent image is developed on the surface of the photo conductor10.

The photo conductor10and intermediate transfer belt30are in contact with each other at a portion where the primary transfer roller31is provided. The primary transfer roller31has a roller shape and is rotatable. When a transfer voltage having a polarity opposite to that of the toner image is applied to the primary transfer roller31, the toner image is transferred from the photo conductor10to the intermediate transfer belt30. A yellow (Y) toner image, a magenta (M) toner image, a cyan (C) toner image, and a black (BK) toner image are sequentially superimposed and transferred from the photo conductor10to the intermediate transfer belt30. Accordingly, a color toner image is formed on the intermediate transfer belt30.

The intermediate transfer belt30is stretched by the driven roller38and driving roller39. The driving roller39is rotatively driven by, for example, a motor (not shown). The intermediate transfer belt30and driven roller38rotate in conjunction with the driving roller39. Accordingly, the toner image on the intermediate transfer belt30is conveyed to the secondary transfer roller33.

The cleaning device17is brought into contact with the photo conductor10by pressurizing. The cleaning device17collects remaining toner on the surface of the photo conductor10after transferring the toner image.

In the cassette37, a sheet S is set. The sheet S is sent one by one from the cassette37to the secondary transfer roller33by the timing roller40along the conveyance channel41. The secondary transfer roller33has a roller shape and is rotatable. The secondary transfer roller33applies a transfer voltage having a polarity opposite to that of the toner image to the sheet S being conveyed. Accordingly, the toner image is attracted from the intermediate transfer belt30to the secondary transfer roller33, and the toner image on the intermediate transfer belt30is transferred. The timing of conveying the sheet S to the secondary transfer roller33is adjusted by the timing roller40in accordance with a position of the toner image on the intermediate transfer belt30. The toner image on the intermediate transfer belt30is transferred by the timing roller40to an appropriate position on the sheet S.

The fixing device50pressurizes and heats the sheet S passing therethrough. Accordingly, the toner image is fixed on the sheet S. In this manner, the fixing device50fixes the toner image on the sheet S conveyed along the conveyance channel41. The sheet S on which the toner image is fixed is ejected to a tray48.

The abovementioned image forming apparatus100employs a tandem method as a printing process, but the printing process of the image forming apparatus100is not limited to the tandem method. Arrangement of each component in the image forming apparatus100can be appropriately changed in accordance with an employed printing process. Employable examples of the printing process of the image forming apparatus100include a rotary method and a direct transfer method. In a case of employing the rotary method, the image forming apparatus100is configured to include one photo conductor10and a plurality of coaxially rotatable developing devices13. At the time of printing, the image forming apparatus100sequentially guides each developing device13to the photo conductor10and develops a toner image of each color. In a case of employing the direct transfer method, the image forming apparatus100directly transfers a toner image formed on the photo conductor10onto a sheet S.

FIG. 2is a schematic view of the fixing device according to the first embodiment.FIG. 3is a partially enlarged view of the fixing device according to the first embodiment.FIG. 4is an enlarged view of a portion surrounded by the IV line shown inFIG. 3. The fixing device50according to the first embodiment will now be described with reference toFIGS. 2 to 4.

As shown inFIG. 2, the fixing device50includes a heating roller51, a pressing member52, a fixing belt53, an anchorage member54, a lubricant supply unit55, and a fixing roller56as a fixing member.

The heating roller51is disposed inside the fixing belt53. The heating roller51includes a heater H1, a cored bar, and a surface layer. The heating roller51is heated by the heater H1and transfers the heat received from the heater H1to the fixing belt53.

The cored bar is made of aluminum or iron and has a pipe shape. The cored bar has a thickness of, for example, 0.2 mm to 1 mm. The heater H1is disposed inside the cored bar. The surface layer of the heating roller51is formed on the outer periphery of the cored bar. The surface layer of the heating roller51is preferably coated with PTF having heat resistance and abrasion resistance.

The case where the fixing belt53is heated by the heater H1included in the heating roller51has been illustrated, but a heating process is not limited thereto. A fixing belt may be configured to contain a heat generating layer of non-magnetic metal by an IH fixing technique, and an IH coil for generating an alternating magnetic field may be sandwiched together with the fixing belt by two magnetic members disposed inside and outside the IH coil so that the fixing belt is heated by induction heating.

As shown inFIGS. 2 to 4, the pressing member52is disposed apart from the heating roller51. The pressing member52is disposed inside the fixing belt53. The pressing member52is provided so as to face the fixing roller56with the fixing belt53interposed therebetween. The pressing member52presses the fixing roller56, involving the fixing belt53. Accordingly, an elastic layer of the fixing roller56to be described is deformed, and a nip portion is formed between the fixing belt53and the fixing roller56.

The pressing member52includes a block portion521and a sliding sheet522. The block portion521extends in a direction parallel to an axial direction of the heating roller51. The block portion521is longer than a width of the sheet S in the axial direction of the heating roller51. The block portion521includes, for example, resin such as polyphenylene sulfide, polyimide, or liquid crystal polymer.

The sliding sheet522is provided on a surface521aof the block portion521positioned in the inner periphery of the fixing belt53. The sliding sheet522holds a lubricant60supplied between the pressing member52and the inner periphery of the fixing belt53. The sliding sheet522includes fluororesin such as polytetrafluoroethylene (PTFE) and perfluoroalkoxy (PFA) fluororesin.

The fixing belt53is stretched by the heating roller51and the pressing member52. The fixing belt53is an endless belt and is rotatable. The fixing belt53rotates so as to transmit heat received from the heating roller51to the nip portion, which is a contact portion between the fixing belt53and the fixing roller56. As the sheet S passes through the nip portion, the toner image is fused on the sheet S, and the toner image is fixed on the sheet S.

The fixing belt53includes, for example, a base layer and an elastic layer. The base layer of the fixing belt53includes a polyimide film. The base layer of the fixing belt53has an inner diameter of 50 mm, a width of 330 mm, and a thickness of 70 μm. The elastic layer of the fixing belt53includes silicone rubber. The elastic layer of the fixing belt53has a thickness of, for example, 100 μm to 200 μm. The surface of the fixing belt53may be coated with fluorine. The coating fluorine has a thickness of, for example, 30 μm.

The anchorage member54fixes the pressing member52and lubricant supply unit55. The anchorage member54includes a base portion541, a guiding portion542, and a mounting portion543. The base portion541has a mounting surface541aparallel to a back surface521bof the block portion521. The block portion521is fixed to the mounting surface541awith an adhesive or the like.

The guiding portion542is erected at one end of the base portion541. The guiding portion542extends so as to be apart from the block portion521. The guiding portion542contacts the inner periphery of the fixing belt53and guides the movement of the fixing belt53.

The mounting portion543is erected at the other end of the base portion541. The mounting portion543is provided so as to be apart from the block portion521, and a leading end of the mounting portion543is bent so as to approach the base portion541. A bending angle at the leading end of the mounting portion543is adjusted so that an opening surface of an ejection port551ato be described becomes parallel to the inner periphery of the fixing belt53with the lubricant supply unit55being mounted. The mounting portion543has a mounting surface543a. One side surface of the lubricant supply unit55is fixed to this mounting surface543awith an adhesive or the like.

The lubricant supply unit55is disposed inside the fixing belt53. The lubricant supply unit55is for supplying the lubricant60between the pressing member52and the fixing belt53by supplying the lubricant to the inner periphery of the fixing belt53.

More specifically, the lubricant supply unit55is for supplying the lubricant60to the inner periphery of the fixing belt53when the lubricant60which has been supplied in advance between the fixing belt53and the pressing member52deteriorates or decreases due to a long period of use of the image forming apparatus100.

The lubricant supply unit55includes a holding unit551and a pushing member553. The holding unit551holds the lubricant60. The holding unit551is fixed to the mounting surface543aof the mounting portion543so as not to be in contact with the inner periphery of the fixing belt53.

The holding unit551has a tubular shape, including the ejection port551aconfigured to open toward the inner periphery of the fixing belt53. The ejection port551ahas an elongated shape extending along a width direction of the fixing belt53. The ejection port551ahas an opening area equal from one to the other end of the ejection port551ain the width direction of the fixing belt53.

The holding unit551is provided with a storage space552for storing the pushing member553and the lubricant60. The holding unit551is disposed in an upstream side of the pressing member52in a rotational direction of the fixing belt53. Note that details of the lubricant supply unit55will be described later with reference toFIG. 5.

The fixing roller56is disposed outside the fixing belt53. The fixing roller56faces the pressing member52. The fixing roller56presses the pressing member52with the fixing belt53sandwiched therebetween. Accordingly, the fixing belt53is brought into contact with the fixing roller56by pressurizing.

The fixing roller56includes, for example, a cored bar and a surface layer. The cored bar is made of aluminum or iron and has a pipe shape. The surface layer is an elastic layer such as silicone rubber. The elastic layer has a thickness of about several millimeters.

FIG. 5is a cross sectional view of the lubricant supply unit included in the fixing device according to the first embodiment. The details of the lubricant supply unit will now be described with reference toFIG. 5.

As shown inFIG. 5, the lubricant supply unit55includes the holding unit551, the pushing member553, and an external force application system557. The holding unit551has a tubular shape having the ejection port551aas described above. The holding unit551extends in the width direction of the fixing belt53.

The storage space552is provided inside the holding unit551. An upper wall551cof the holding unit551that defines the storage space552is located at a height substantially equivalent from one end to the other end in a longitudinal direction.

The storage space552is provided in such a manner that a height along a direction perpendicular to the opening surface of the ejection port551adiffers between one end and the other end in the longitudinal direction. The height of the storage space552at the other end is larger than that of the storage space552at one end.

The lubricant60, the pushing member553, a spring554to be described, and a part of a supporting unit555are stored in the storage space552located at the other end. The lubricant60is stored in the storage space552so as to be adjacent to the ejection port551a.

The pushing member553is stored in the holding unit551in a side opposite to a side where the ejection port551ais located with respect to the lubricant60. Specifically, the pushing member553is stored inside the storage space552so as to be movable toward the ejection port551a. As moving toward the ejection port551a, the pushing member553pushes the lubricant60out from the ejection port551a.

The pushing member553has a cylindrical shape extending along the width direction of the fixing belt53. The pushing member553has a first surface553aand a second surface553bopposing each other in a normal direction of the opening surface of the ejection port551a. The first surface553ais disposed in the side close to the ejection port551aand the second surface553bis disposed in the side far from the ejection port551a.

As the pushing member553extending along the width direction of the fixing belt53pushes out the lubricant60, it is possible to push out the lubricant60overall so that the lubricant60can be uniformly extruded.

Note that the pushing member553is not limited to a cylindrical shape. As long as the pushing member553is configured to push out the lubricant60, the pushing member553may have a polygonal prism shape. When the pushing member553has a cylindrical shape, it is possible to prevent the pushing member553from being stuck with the inner periphery of the holding unit551and to smoothly move the pushing member553.

The pushing member553moves as it is pressed toward the ejection port551aby the external force application system557.

The external force application system557applies an external force to the pushing member553in order to press the pushing member553toward the ejection port551a. The external force application system557includes a plurality of springs554serving as biasing units, a plurality of supporting units555, and an engagement unit556.

The plurality of springs554are stored in the holding unit551in a side opposite to a side where the lubricant60is located with respect to the pushing member553. The plurality of springs554are fixed to the inner periphery of the upper wall551cof the holding unit551. The plurality of springs554biases the pushing member553toward the ejection port551a. The plurality of springs554are disposed at a predetermined pitch along the width direction of the fixing belt53, whereby an external force can be uniformly applied to the pushing member553. As an external force is applied to the pushing member553by the biasing units such as the springs554or the like, the pushing member553can be moved toward the ejection port551a.

The plurality of supporting units555are configured to be movable with respect to the holding unit551. The plurality of supporting units555are provided so as to penetrate the upper wall551cof the holding unit551. The plurality of supporting units555extend in the direction perpendicular to the opening surface of the ejection port551a. The plurality of supporting units555are disposed at a predetermined pitch along the width direction of the fixing belt53.

A root of each supporting unit555located in the storage space552is fixed to the pushing member553. An engaged portion555ato be engaged with the engagement unit556is provided to a leading end of each supporting unit555projecting outward from the upper wall551c. The engaged portion555aincludes, for example, a groove.

The engagement unit556has a substantially plate-like shape. The engagement unit556disengageably engages with the plurality of supporting units555. A part of the engagement unit556fits into the engaged portion555aof each supporting unit555, whereby the engagement unit556is engaged with each supporting unit555. The engagement unit556is configured to be slidable, for example, in a direction of the arrow AR1inFIG. 5. As the engagement unit556moves in the direction of the arrow AR1, the engagement between the engagement unit556and the supporting units555is released.

In a state before the lubricant60is ejected from the ejection port551a, the engagement unit556is engaged with the supporting units555so that the supporting units555support the pushing member553while counteracting biasing forces of the springs554. In this manner, as the supporting units555support the pushing member553while being engaged with the engagement unit556, it is possible to prevent the lubricant60from undesirably being in contact with the fixing belt53. Furthermore, the engagement between the engagement unit556and the supporting units555at a desirable timing brings about the supply of the lubricant60at a desirable timing.

Due to a long period of use of the image forming apparatus100, when the number of printed sheets reaches a predetermined number or when the lubricant60which has been supplied in advance between the fixing belt53and the pressing member52deteriorates or decreases and the load for driving the fixing belt53increases, the engagement unit556is slid as described above.

Accordingly, the engagement between the supporting units555and the engagement unit556is released, and the biasing forces of the springs554cause the pushing member553to move toward the ejection port551atogether with the supporting units555. Thus, the lubricant60is ejected from the ejection port551ato the inner periphery of the fixing belt53by the pushing member553.

The ejection port551ais configured to have the opening area equal from one end to the other end along the longitudinal direction, and the lubricant60is ejected from the ejection port551asubstantially uniformly along the width direction of the fixing belt53.

The lubricant60ejected from the ejection port551atoward the inner periphery of the fixing belt53is scraped off by the fixing belt53as the fixing belt53rotates. Therefore, even when employing a lubricant60having low surface tension, a small amount of the lubricant60held in the holding unit551can be efficiently ejected onto the inner periphery of the fixing belt53.

As the fixing belt53rotates, the lubricant60ejected onto the inner periphery of the fixing belt53is substantially uniformly supplied between the fixing belt53and the pressing member52along the width direction of the fixing belt53.

As described above, in the fixing device50according to the first embodiment, the lubricant supply unit55includes the holding unit551disposed inside the fixing belt53, holding the lubricant60, and provided with the ejection port551ahaving a longitudinal shape extending along the width of the fixing belt53. Therefore, it is possible to uniformly eject the lubricant60held in the holding unit551from the ejection port551aalong the width direction of the fixing belt53and to uniformly supply the lubricant60between the fixing belt53and the pressing member52along the width direction.

Accordingly, in the fixing device50according to the first embodiment and the image forming apparatus100including the same, it is possible to moderate the lubricant60to be supplied between the pressing member52and the fixing belt53, while holding a small amount of the lubricant60. Thus, a lifetime of the fixing device50can be prolonged.

In addition, the holding unit551is provided to the fixing belt53without being in contact so that it is possible to prevent the fixing belt53from being in contact with the holding unit551and to prevent a heat capacity of the fixing device50from growing large. Accordingly, it is possible to save energy and shorten a warm-up time.

Furthermore, as the lubricant supply unit55is disposed inside the fixing belt53and the lubricant60can be ejected to the inner periphery of the fixing belt53at a desired timing, it is possible to additionally supply the lubricant60between the fixing belt53and the pressing member52without disassembling the fixing device50. Thus, maintenance can be simplified.

FIG. 6is a cross sectional view of a lubricant supply unit according to a first modification. With reference toFIG. 6, a lubricant supply unit55A1according to the first modification will be described.

As shown inFIG. 6, compared to the lubricant supply unit55according to the first embodiment, the lubricant supply unit55A1according to the first modification is different in that, in a width direction of a fixing belt53, an amount of a lubricant60to be ejected from a central part of an ejection port551ais larger than that to be ejected from both ends of the ejection port551a.

Specifically, the lubricant supply unit55A1according to the first modification is different from the lubricant supply unit55according to the first embodiment in a configuration of a pushing member553A. Other configurations are substantially similar.

The pushing member553A is configured in such a manner that a first surface553alocated in a side close to the ejection port551agets farther from the ejection port551aas moving from both ends in a longitudinal direction along the width direction of the fixing belt53toward the central part.

Accordingly, in a state before the lubricant60is ejected from the ejection port551a, the lubricant60is held by the holding unit551in such a manner that a height of the lubricant60from an opening surface in a normal direction of the opening surface of the ejection port551ais larger in the central part than in both ends of the lubricant60in the width direction of the fixing belt53.

As described above, as the lubricant60is held in the holding unit551, the amount of the lubricant60to be ejected from the central part of the ejection port551acan be made larger than that to be ejected from both ends of the ejection port551a.

In a nip portion formed between the fixing belt53and a fixing roller56, due to a setting of pressure distribution, an amount of decrease in the lubricant60which has been supplied in advance between the fixing belt53and a pressing member52may differ in the width direction of the fixing belt53in accordance with a long period of use.

Therefore, by changing an amount of the lubricant60to be held for additional supply in accordance with the amount of decrease in the lubricant60, depending on the width direction of the fixing belt53, even a fixing device and an image forming apparatus including the lubricant supply unit55A1according to the first modification can moderate the lubricant60to be supplied between the pressing member52and the fixing belt53, while holding a small amount of the lubricant60. Accordingly, it is possible to prevent excessive supply of the lubricant60and to avoid such a problem that the lubricant60leaks from an end portion of the fixing belt53, which causes image abnormality.

In addition, since the lubricant60is not moved from the outside of the fixing belt53as in the prior document (JP 2014-174434 A), at the time of supplying the lubricant60and at the time of maintenance, not only a fixing device50but also the inside of an image forming apparatus100can be prevented from being contaminated.

Specifically, pressure tends to be high in the central part rather than in both ends in the width direction of the fixing belt53. In such a case, as the amount of the lubricant60to be held is distributed as described above, the abovementioned effects can be efficiently exerted.

FIG. 7is a view showing an ejection port of a lubricant supply unit according to a second modification. With reference toFIG. 7, a lubricant supply unit55A2according to the second modification will be described.

As shown inFIG. 7, compared to the lubricant supply unit55according to the first embodiment, the lubricant supply unit55A2according to the second modification is different in that, in a width direction of a fixing belt53, an amount of a lubricant60to be ejected from a central part of an ejection port551ais larger than that to be ejected from both ends of the ejection port551a.

Specifically, the lubricant supply unit55A2according to the second modification is different from the lubricant supply unit55according to the first embodiment in shape of the ejection port551a. Other configurations are substantially similar.

In the width direction of the fixing belt53, an opening area of the ejection port551ain the central part of the ejection port551ais larger than opening areas in both ends of the ejection port551a. More specifically, in the width direction of the fixing belt53, the opening area of the ejection port551aincreases as moving from both ends toward the central part.

Accordingly, by making the shape of the ejection port551aas described above, the amount of the lubricant60to be ejected from the central part of the ejection port551acan be made larger than that to be ejected from both ends of the ejection port551a.

As described above, even in a fixing device and an image forming apparatus including the lubricant supply unit55A2according to the second modification, it is possible to obtain effects substantially similar to those obtained in the fixing device and the image forming apparatus including the lubricant supply unit55A1according to the first modification.

FIG. 8is a schematic view of an image forming apparatus according to a second embodiment. With reference toFIG. 8, an image forming apparatus100B according to the second embodiment will be described.

As shown inFIG. 8, compared to the image forming apparatus100according to the first embodiment, the image forming apparatus100B according to the second embodiment is different in that the image forming apparatus100B includes a gas supply source71and in a configuration of a fixing device50B. Other configurations are substantially similar.

The gas supply source71is disposed outside a housing80. The gas supply source71is for supplying gas to a holding unit551B (seeFIG. 9) of a lubricant supply unit55B (seeFIG. 9) to be described. The gas supplied from the gas supply source71is preferably air, but is not particularly limited to air. The gas supply source71includes, for example, a cylinder or a compressor. In a case where the gas supply source71includes a cylinder, it is preferable that the gas supply source71is configured to be replaceable.

The fixing device50B is different from the fixing device50according to the first embodiment in a configuration of the lubricant supply unit55B.

FIG. 9is a cross sectional view of the lubricant supply unit included in the fixing device according to the second embodiment. With reference toFIG. 9, the lubricant supply unit55B according to the second embodiment will be described.

Compared to the lubricant supply unit55according to the first embodiment, the lubricant supply unit55B according to the second embodiment is different in that a pushing member553pushes an ejection port551aby pressure of the gas supplied into the holding unit551B.

As shown inFIG. 9, the lubricant supply unit55B includes the holding unit551B, the pushing member553, and a pipe57(seeFIG. 8).

The pipe57is for introducing gas from the gas supply source71to an introduction port551bof the holding unit551B to be described. One end of the pipe57is connected to the introduction port551bof the holding unit551B. The other end of the pipe57is drawn to the outside of the fixing device50B and further to the outside of the housing80of the image forming apparatus100B so as to be connected to the gas supply source71. The other end of the pipe57is detachably connected to the gas supply source71. Provision of the pipe57leads to wide variations of arrangement of the gas supply source71. Even when the gas supply source71is provided outside the housing80as described above, gas can be introduced into the introduction port551bof the holding unit551B through the pipe57.

The holding unit551B has a tubular shape, including the ejection port551aconfigured to open toward the inner periphery of a fixing belt53. The holding unit551B is provided with a storage space552for storing the pushing member553and a lubricant60.

In addition to the ejection port551a, the holding unit551B includes the introduction port551band an accumulation chamber559. The introduction port551bis provided to one end of the holding unit551B in a width direction of the fixing belt53.

The accumulation chamber559communicates with the introduction port551b. The accumulation chamber559accumulates the gas introduced into the introduction port551b. The accumulation chamber559is a part of the storage space552. The accumulation chamber559is located at a side opposite to a side where the lubricant60is located with respect to the pushing member553.

A bottom of the accumulation chamber559includes a second surface553bof the pushing member553positioned in a side far from the ejection port551a. Accordingly, when gas is introduced into the accumulation chamber559, substantially uniform pressure is applied to the second surface553bof the pushing member553so that the pushing member553moves toward the ejection port551a.

The ejection port551ais configured to have an opening area equal from one end to the other end along the longitudinal direction, and the lubricant60is ejected from the ejection port551asubstantially uniformly along the width direction of the fixing belt53.

As the fixing belt53rotates, the lubricant60ejected from the ejection port551aonto the inner periphery of the fixing belt53is substantially uniformly supplied between the fixing belt53and the pressing member52along the width direction of the fixing belt53.

As described above, even in the fixing device50B and the image forming apparatus100B according to the second embodiment, it is possible to obtain effects substantially similar to those obtained in the fixing device50and the image forming apparatus100according to the first embodiment.

Furthermore, as the pushing member553is configured to be movable toward the ejection port551aby the pressure of the gas supplied into the holding unit551, it is possible to omit the external force application system557as in the first embodiment. Therefore, the configuration of the lubricant supply unit55B can be simplified.

Note that the gas supply source71may be mounted on the image forming apparatus100B in advance or may be separately mounted by an operator at the time of maintenance and the like. As the gas supply source71is configured to be separately mountable, it is possible to downsize the image forming apparatus100B. As a serviceman, not a user, mounts the gas supply source71in after-sales maintenance, it is possible to improve the safety and prevent mistakes in operations.

In the second embodiment, such a case has been illustrated that the gas supply source71is provided outside the housing80of the image forming apparatus100B, but the present invention is not limited thereto. The gas supply source71may be provided inside the housing80of the image forming apparatus100B.

FIG. 10is a schematic view of an image forming apparatus according to a third embodiment. With reference toFIG. 10, an image forming apparatus100C according to the third embodiment will be described.

As shown inFIG. 10, compared to the image forming apparatus100B according to the second embodiment, the image forming apparatus100C according to the third embodiment is different in that a fixing device50C includes a decompressing device90and in a configuration of a lubricant supply unit55C (seeFIG. 11). Other configurations are substantially similar.

The decompressing device90is provided inside a housing80of the image forming apparatus100C. The decompressing device90is connected to an accumulation chamber559(seeFIG. 11) through a pipe58. The decompressing device90decompresses the accumulation chamber559.

Note that the decompressing device90may be provided outside the image forming apparatus100C. In a case where the decompressing device90is provided outside the image forming apparatus100C, the image forming apparatus100can be downsized. In addition, it is possible to reduce the number of assembling steps for mounting devices inside the image forming apparatus100C, which leads to cost reduction.

FIG. 11is a cross sectional view of the lubricant supply unit included in the fixing device according to the third embodiment. With reference toFIG. 11, the lubricant supply unit55C included in the fixing device50C according to the third embodiment will be described.

As shown inFIG. 11, compared to the lubricant supply unit55B according to the second embodiment, the lubricant supply unit55C according to the third embodiment is different in such respects that a pushing member553C has a different shape and an impregnated member558is provided.

The pushing member553C has a cuboid shape. The impregnated member558is provided to a first surface553aof the pushing member553C. The impregnated member558is in contact with a lubricant60. The impregnated member558is impregnated with the lubricant60. The impregnated member558includes a non-woven fabric and the like. The impregnated member558is configured to be in contact with the inner periphery of a fixing belt53in a state after the pushing member553C pushes out the lubricant60.

FIG. 12is a view showing a first state of the lubricant supply unit shown inFIG. 11.FIG. 13is a view showing a second state of the lubricant supply unit shown inFIG. 11.FIG. 14is a view showing a third state of the lubricant supply unit shown inFIG. 11. Operations of the lubricant supply unit55C will be described with reference toFIGS. 12 to 14.

As shown inFIG. 12, the first state of the lubricant supply unit55C represents a state before the lubricant supply unit55C supplies the lubricant60. In the first state of the lubricant supply unit55C, the accumulation chamber559is being decompressed, and a holding unit551stores the pushing member553C and holds the lubricant60. In this state, no gas is introduced inside the accumulation chamber559.

From this state, as gas is introduced into the accumulation chamber559, pressure of the gas moves the pushing member553C toward an ejection port551a. Accordingly, the lubricant60is pushed out from the ejection port551a.

As shown inFIG. 13, in the second state of the lubricant supply unit55C representing a state after the pushing member553C moving toward the ejection port551aand the pushing member553C pushing all the lubricant60out, the impregnated member558comes into contact with the inner periphery of the fixing belt53.

As the impregnated member558is configured to be in contact with the inner periphery of the fixing belt53, the lubricant60can be sufficiently supplied to the fixing belt53. Furthermore, as the fixing belt53is configured to rotate while the impregnated member558is in contact with the fixing belt53, it is possible to collect foreign materials adhered to the inner periphery of the fixing belt53.

After the impregnated member558is brought into contact with the inner periphery of the fixing belt53for a predetermined time, the decompressing device90decompresses the accumulation chamber559. Accordingly, the inside of the accumulation chamber559is under negative pressure, and the pushing member553C protruding outward from the ejection port551ais collected inside the holding unit551.

As shown inFIG. 14, in the third state of the lubricant supply unit55C, the pushing member553C is collected inside the holding unit551and held in the holding unit551so as not to protrude to the outside of the holding unit551.

As described above, even in the fixing device50C and the image forming apparatus100C according to the third embodiment, it is possible to obtain effects substantially similar to those obtained in the fixing device50B and the image forming apparatus100B according to the second embodiment.

In addition, by providing the impregnated member558and allowing it to come into contact with the inner periphery of the fixing belt53, it is possible to sufficiently push the lubricant60out to the fixing belt53as described above, and to collect the foreign materials adhered to the inner periphery of the fixing belt53.

Furthermore, by providing the decompressing device90and allowing it to decompress the inside of the accumulation chamber559, it is possible to collect the pushing member553into the holding unit551after pushing out the lubricant60. Accordingly, it is possible to prevent the foreign materials adhered to the impregnated member558from returning to the inner periphery of the fixing belt53. Therefore, it is possible to prevent unevenness in contact resistance between the fixing belt53and a fixing roller due to the foreign materials.

Still further, by not bringing the impregnated member558into contact with the fixing belt53, it is possible to prevent an increase in heat capacity of the fixing belt53and to restrain abrasion of the inner periphery of the fixing belt53.

Still further, even in a case where the inner periphery of the holding unit551is warped due to flexibility of the pushing member553C, the pushing member553C can move while deforming in accordance with the warpage of the inner periphery of the holding unit551. This makes it possible to prevent ejection defects.

FIG. 15is a schematic view of an image forming apparatus according to a fourth embodiment. With reference toFIG. 15, an image forming apparatus100D according to the fourth embodiment will be described.

As shown inFIG. 15, the image forming apparatus100D according to the fourth embodiment is different from the image forming apparatus100B according to the second embodiment in a configuration of a fixing device50D. Other configurations are substantially similar.

FIG. 16is a partial enlarged view of the fixing device according to the fourth embodiment. The fixing device50D according to the fourth embodiment will be described with reference toFIG. 16.

As shown inFIG. 16, the fixing device50D according to the fourth embodiment is different from the fixing device50B according to the second embodiment in a configuration of a pressing member52D, that of an anchorage member54D, and arrangement of a lubricant supply unit55D. Other configurations are substantially similar.

The pressing member52D includes a plurality of openings52afacing the inner periphery of a fixing belt53; a channel sections52bcommunicating with the openings52a; and a lubricant introducing portion52cfor supplying a lubricant60to the channel sections52b.

The plurality of openings52ais provided so as to penetrate a sliding sheet522. The lubricant60is supplied from the plurality of openings52ato the inner periphery of the fixing belt53. Each of the plurality of openings52aextends along a width direction of the fixing belt53. The plurality of openings52ais disposed side by side along a rotational direction of the fixing belt53. The number of the openings52ais not limited to a plural number, and may be a single number.

The channel sections52bare provided to a block portion521. The channel sections52bare provided so as to extend in a thickness direction of the block portion521. One end of each channel section52bis connected to the opening52a, and the other end of each channel section52bis connected to the lubricant introducing portion52c. The lubricant introducing portion52cis provided to a side opposite to a side where the fixing belt53is located. The lubricant introducing portion52cis opened toward a base portion541of the anchorage member54D.

A through hole541bis provided to the base portion541of the anchorage member54D. The through hole541bis provided so as to face the lubricant introducing portion52c.

The anchorage member54D is disposed in a side opposite to a side where the pressing member52D is positioned with respect to the base portion541. The anchorage member54D is fixed to a mounting portion543so that an ejection port551afaces the through hole541b.

As gas is introduced into an accumulation chamber559of the holding unit551, the pushing member553moves toward the ejection port551a, whereby the lubricant60is ejected from the ejection port551a. The lubricant60ejected from the ejection port551apasses through the through hole541bof the base portion541and is introduced into the lubricant introducing portion52cof the pressing member52D.

The lubricant60introduced into the lubricant introducing portion52cpasses through the channel sections52band is supplied from the plurality of openings52ato the inner periphery of the fixing belt53located between the pressing member52D and a fixing roller. Herein, each of the plurality of openings52ais configured to have an opening area equal from one end to the other end in the longitudinal direction, and the lubricant60is ejected from the plurality of openings52asubstantially uniformly along the width direction of the fixing belt53.

As described above, even in the fixing device50D and the image forming apparatus100D according to the fourth embodiment, it is possible to obtain effects substantially similar to those obtained in the fixing device50B and the image forming apparatus100B according to the second embodiment.

FIG. 17is a schematic view of an image forming apparatus according to a fifth embodiment. With reference toFIG. 15, an image forming apparatus100E according to the fifth embodiment will be described.

As shown inFIG. 17, compared to the image forming apparatus100B according to the second embodiment, the image forming apparatus100E according to the fifth embodiment is different in that a second gas supply source72is provided and in a configuration of a fixing device50E. Other configurations are substantially similar.

The gas supply source72is disposed outside a housing80. The gas supply source72is for introducing gas to a gas introducing portion52c1(seeFIG. 18) of a pressing member52E (seeFIG. 18) to be described.

The gas supplied from the gas supply source72is preferably air, but is not particularly limited to air. The gas supply source72includes, for example, a cylinder or a compressor. In a case where the gas supply source72includes a cylinder, it is preferable that the gas supply source72is configured to be replaceable.

FIG. 18is a partially enlarged view of the fixing device according to the fifth embodiment. With reference toFIG. 18, the fixing device50E according to the fifth embodiment will be described.

As shown inFIG. 18, compared to the fixing device50B according to the second embodiment, the fixing device50E according to the fifth embodiment is different in that a pipe59(seeFIG. 17) is provided and in a configuration of the pressing member52E. Other configurations are substantially similar.

The pipe59is for introducing gas from the gas supply source72to the gas introducing portion52c1of the pressing member52E. One end of the pipe59is connected to the gas introducing portion52c1. The other end of the pipe59is drawn to the outside of the fixing device50E and further to the outside of the housing80of the image forming apparatus100E so as to be connected to the gas supply source72.

The other end of the pipe59is detachably connected to the gas supply source72. Provision of the pipe59leads to wide variations of arrangement of the gas supply source72. Even when the gas supply source72is provided outside the housing80as described above, gas can be introduced into the gas introducing portion52c1through the pipe59.

The pressing member52E includes a plurality of openings52afacing the inner periphery of a fixing belt53; channel sections52bcommunicating with the openings52a; and a gas introducing portion52c1for supplying gas to the channel sections52b.

The plurality of openings52ais provided so as to penetrate a sliding sheet522. The lubricant60is supplied from the plurality of openings52ato the inner periphery of the fixing belt53. Each of the plurality of openings52aextends along a width direction of the fixing belt53. The plurality of openings52ais disposed side by side along a rotational direction of the fixing belt53. The number of the openings52ais not limited to a plural number, and may be a single number.

The channel sections52bare provided to a block portion521. The channel sections52bare provided so as to extend in a thickness direction of the block portion521. One end of each channel section52bis connected to the opening52aand the other end of each channel section52bis connected to the gas introducing portion52c1. The gas introducing portion52c1is provided to the block portion521positioned in a side close to the anchorage member54D.

In such a configuration, gas is introduced from the gas supply source72through the pipe59into the gas introducing portion52c1. The gas introduced into the gas introducing portion52c1passes through the channel sections52band is sent from the plurality of openings52atoward the inner periphery of the fixing belt53.

Accordingly, it is possible to remove foreign materials adhered to the inner periphery of the fixing belt53located between the pressing member52D and a fixing roller. As described above, before supplying the lubricant60by the lubricant supply unit55, the gas is delivered to the inner periphery of the fixing belt53so as to remove the foreign materials so that the lubricant60can be supplied more efficiently between the fixing belt53and the pressing member52E.

As described above, even in the fixing device50E and the image forming apparatus100E according to the fifth embodiment, it is possible to obtain effects substantially similar to those obtained in the fixing device50B and the image forming apparatus100B according to the second embodiment.

In addition, as the gas can be delivered to the inner periphery of the fixing belt53from the openings52aprovided to the pressing member52E, it is possible to remove the foreign materials adhered to the inner periphery of the fixing belt53as described above.

FIG. 19is a cross sectional view of a lubricant supply unit according to a third modification. With reference toFIG. 19, compared to the lubricant supply unit55according to the first embodiment, a lubricant supply unit55F according to the third modification is different in that a stirring member65is provided.

The stirring member65has a rotary axis parallel to an extending direction in which an ejection port551aextends. The stirring member65rotates around the rotary axis so as to stir a lubricant60held in a holding unit551. The stirring member65is driven by a driving source (not shown) disposed inside a housing of an image forming apparatus.

As holding the lubricant60inside the holding unit551over a long period of time, lubricant components may be separated within the lubricant60. Stirring the lubricant60with the stirring member65can make the components uniform.

Similar to the fixing device50and the image forming apparatus100according to the first embodiment, a fixing device and an image forming apparatus including the lubricant supply unit55F can also moderate a lubricant to be supplied between a pressing member and a fixing belt, while holding a small amount of the lubricant.

The characteristic configurations described in the first to fifth embodiments and the first to third modifications may be appropriately combined without departing from the gist of the present invention. For example, the lubricating member supply unit according to the first to third modifications may be used in the fixing device according to the first to fifth embodiments.

Although the embodiments and modifications of the present invention have been described and illustrated in detail, it is clearly understood that the same is by way of illustrated and example only and is not to be taken by way of limitation, the scope of the present invention being interpreted by terms of the appended claims. The scope of the present invention involves any meanings equivalent to the claims and all modifications within the scope of the claims.