IMAGE FORMING APPARATUS

An image forming apparatus includes a conveyance unit that conveys a recording medium in contact with one surface of the recording medium along a conveyance path; a first image forming group that is provided on the other surface side of the recording medium in the conveyance path, and includes plural image forming sections that form a toner image; a second image forming group that is provided on a downstream side in a conveyance direction of the first image forming group on the other surface side of the recording medium in the conveyance path, and includes plural image forming sections that form a toner image; a first intermediate transfer body that is provided on the downstream side in the conveyance direction of the first image forming group, and to which the toner image formed by the plural image forming sections of the first image forming group is primarily transferred; a second intermediate transfer body that is provided on an upstream side in the conveyance direction of the second image forming group, and to which the toner image formed by the plural image forming sections of the second image forming group is primarily transferred; a first transfer unit that secondarily transfers the toner image from the first intermediate transfer body to the other surface of the recording medium conveyed by the conveyance unit; and a second transfer unit that secondarily transfers the toner image from the second intermediate transfer body to the other surface of the recording medium conveyed by the conveyance unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2022-052244 filed Mar. 28, 2022.

BACKGROUND

(i) Technical Field

(ii) Related Art

JP1999-44973A discloses a technique relating to an image forming apparatus such as an electrophotographic copying machine and a printer, and particularly relating to an improvement of a double-sided image forming apparatus capable of forming a double-sided image. In this related art, an air conveyance unit that is disposed on at least one surface side of a recording material conveyance path between a most downstream transfer unit and a fixing unit, a recording material detecting unit which detects information on a recording material to be conveyed, and an air flow rate control unit that controls the air flow rate of the air conveyance unit, based on the detection result from the recording material detecting unit are provided. Further, one or a plurality of rows of star wheels are provided on at least one surface side of a recording material conveyance path so as to be rotatable with respect to the recording material conveyance direction. Further, a temporary fixing unit capable of temporarily fixing an unfixed image on at least one surface side of the recording material is provided, and the temporarily fixed recording material is guided to a fixing unit by a recording material guide member.

JP2009-3236A discloses an image forming apparatus, particularly a technique relating to an image forming apparatus capable of forming a developer image based on image information. In the related art, provided is a color printer capable of forming a developer image based on image information, which includes a main body having a plurality of first image forming units, a first transfer belt, and an elastic roller. The first image forming unit is a unit capable of forming an image of each color based on image information. The images formed by the first image forming unit are transferred to the first transfer belt. The intermediate transfer roller has at least a surface formed of an elastic member, and an image is transferred from the first transfer belt and the transferred image is transferred to paper. The main body can accommodate the first image forming units, the first transfer belt, and an intermediate transfer roller inside, and has a shutter portion that is disposed in the vicinity of the intermediate transfer roller and can be opened and closed.

JP2014-13388A discloses a technique relating to a color image duplication system in which a developed image is transferred from an image forming member to a receiving material via at least one intermediate transfer member. In this related art, a toner, and first and second toner image acquisition devices each having a toner are provided, the first toner image acquisition device transfers the toner to the second toner image acquisition device, and the second toner image acquisition device transfers the toner to the receiving material.

SUMMARY

In an image forming apparatus that secondarily transfers and superimposes toner images in sequence to a recording medium conveyed from a plurality of intermediate transfer bodies to which the toner images are primarily transferred, there is a risk that the recording medium tends to move away from the conveyance path, in a case where a space between the secondary transfer units arranged in the conveyance direction is wide.

Aspects of non-limiting embodiments of the present disclosure relate to an image forming apparatus that narrows a space between secondary transfer units arranged in the conveyance direction, as compared with the case where an image forming section is located between intermediate transfer bodies in the conveyance direction of the recording medium by a conveyance unit.

According to an aspect of the present disclosure, there is provided an image forming apparatus including: a conveyance unit that conveys a recording medium in contact with one surface of the recording medium along a conveyance path; a first image forming group that is provided on the other surface side of the recording medium in the conveyance path, and includes a plurality of image forming sections that form a toner image; a second image forming group that is provided on a downstream side in a conveyance direction of the first image forming group on the other surface side of the recording medium in the conveyance path, and includes a plurality of image forming sections that form a toner image; a first intermediate transfer body that is provided on the downstream side in the conveyance direction of the first image forming group, and to which the toner image formed by the plurality of image forming sections of the first image forming group is primarily transferred; a second intermediate transfer body that is provided on an upstream side in the conveyance direction of the second image forming group, and to which the toner image formed by the plurality of image forming sections of the second image forming group is primarily transferred; a first transfer unit that secondarily transfers the toner image from the first intermediate transfer body to the other surface of the recording medium conveyed by the conveyance unit; and a second transfer unit that secondarily transfers the toner image from the second intermediate transfer body to the other surface of the recording medium conveyed by the conveyance unit.

DETAILED DESCRIPTION

First Exemplary Embodiment

An image forming apparatus according to a first exemplary embodiment of the present invention will be described.

The width direction of the image forming apparatus10shown inFIG.1is an X direction, the height direction is a Y direction, and the depth direction is a Z direction, which are indicated by arrows X, Y, and Z, respectively. In a case where it is necessary to distinguish one side and the other side of the X direction, the Y direction, and the Z direction, with respect to the image forming apparatus10shown inFIG.1, the right side is described as the +X side, the left side is described as the −X side, and the upper side is described as the +Y side, the lower side is described as −Y side, the front side is described as +Z side, and the rear side is described as −Z side. Further, the case of viewing from the depth direction (Z direction) is referred to as a side view.

Further, in the present exemplary embodiment, the recording paper P is adopted as an example of the recording medium, the upstream side in the conveyance direction in which the recording paper P is conveyed is defined as the “upstream side in the conveyance direction”, and the downstream side in the conveyance direction is “downstream side in the conveyance direction”. The image forming apparatus10in the present exemplary embodiment is a so-called single-pass type, and printing is performed by the recording paper P passing through the front of the image forming unit30and the image forming unit50, which will be described later.

Overall Configuration

First, the overall configuration of the image forming apparatus will be described.

As shown inFIG.1, the image forming apparatus10includes an accommodating unit12that accommodates recording paper P (see alsoFIG.3) as an example of a recording medium, a conveyance unit11that conveys the recording paper P along a conveyance path19, and an image forming unit30and an image forming unit50that form a toner image to be transferred to the recording paper P. The “conveyance direction” is the direction in which the recording paper P is conveyed along the conveyance path19.

The accommodating unit12can be pulled out from the image forming apparatus main body10A, which is the apparatus main body of the image forming apparatus10, and accommodates the recording paper P.

The conveyance unit11includes a feed roll13, a conveyance roll14, a resist roll pair15, a conveyor belt device20, a fixing device18, a discharge roll17, and the like, in order from the upstream side in the conveyance direction.

The feed roll13sends out the recording paper P accommodated in the accommodating unit12to the conveyance path19configuring the conveyance unit11. The conveyance roll14conveys the recording paper P along the conveyance path19.

The resist roll pair15conveys the recording paper P conveyed by the conveyance roll14to a secondary transfer position TJ2on the upstream side, which will be described later. The resist roll pair15sandwiches the recording paper P between the resist roll15A and the pinch roll15B, and conveys the recording paper P to the downstream side in the conveyance direction.

The conveyor belt device20conveys the recording paper P to the downstream side in the conveyance direction along the conveyance path19while transferring the toner image formed by the image forming units30and50to the recording paper P. The details of the conveyor belt device20will be described later.

The fixing device18has a fixing roll pair16, and in a case where the recording paper P on which the toner image is transferred passes through the fixing roll pair16, the fixing device18heats and pressurizes the recording paper P to fix the toner image on the recording paper P.

The discharge roll17discharges the recording paper P on which the toner image is fixed by the fixing device18, to the discharge unit9.

The image forming unit30and the image forming unit50are disposed side by side in the vertical direction. In the present exemplary embodiment, the image forming unit50is disposed above the image forming unit30. From another point of view, the image forming unit50is disposed on the downstream side in the conveyance direction of the image forming unit30.

As shown inFIGS.2and3, the image forming unit30includes a plurality of (four in the present exemplary embodiment) image forming sections32, and a first endless intermediate transfer belt40. The four image forming sections32are designated as a first image forming group31. The toner images formed by the four image forming sections32are transferred to the first intermediate transfer belt40as an example of the first intermediate transfer body, and the first intermediate transfer belt40is mounted to be rotatable counterclockwise with a front view ofFIG.2.

The image forming section32includes an image forming section32W that forms a white toner image of white color, an image forming section32M that forms a magenta toner image of magenta color, an image forming section32C that forms a cyan toner image of cyan color, and an image forming section32Y that forms a yellow toner image of yellow color. The four image forming sections32are disposed in the order of the image forming section32Y, the image forming section32M, the image forming section32C, and the image forming section32W in order from the upstream side in the rotation direction (the side closer to the support roll44described later) in which the first intermediate transfer belt40rotates. In a case where it is not necessary to distinguish between Y, M, C, and W, Y, M, C, and W are omitted.

Further, in the following, the upstream side in the rotation direction of the first intermediate transfer belt40is referred to as “the rotation direction upstream side”, and the downstream side in the rotation direction is referred to as “the rotation direction downstream side”. That is, in the image forming section32, the image forming section32W is disposed on the most rotation direction downstream side.

As shown inFIG.2, the image forming section32includes a photoconductor33, a photoconductor charging member34that charges the peripheral surface of the photoconductor33, an exposure device35that irradiates the charged photoconductor33with exposure light, and a developing device36that develops an electrostatic latent image formed by the irradiation of the exposure light to be visualized as a toner image.

Developing rolls39Y,39M,39C, and39W are provided in the developing device36, respectively, and are applied with a developing bias by the power supply device99(seeFIG.5), respectively.

Further, primary transfer rolls37Y,37M,37C, and37W for transferring the toner image formed by the image forming section32to the first intermediate transfer belt40are disposed at positions facing each photoconductor33with the first intermediate transfer belt40interposed therebetween. The first intermediate transfer belt40is wound around a support roll44that supports the first intermediate transfer belt40and a backup roll42that is disposed on the first transfer unit74on the upstream side, which will be described later. The primary transfer unit70includes a photoconductor33, a primary transfer roll37, and a first intermediate transfer belt40. Further, the primary transfer positions TY1, TM1, TC1, and TW1are set between the photoconductors33Y,33M,33C, and33W and the first intermediate transfer belt40, respectively.

The image forming unit50has the same configuration as the above-described image forming unit30except that colors for forming an image are different.

As shown inFIGS.2and3, the image forming unit50includes a plurality of (four in the present exemplary embodiment) image forming sections52, and a second intermediate transfer belt60. The four image forming sections52are designated as a second image forming group51. The toner images formed by the four image forming sections52are transferred to the second intermediate transfer belt60as an example of the second intermediate transfer body, and the second intermediate transfer belt60is mounted to be rotatable counterclockwise with a front view ofFIG.2.

The image forming section52has the same configuration as the image forming section32of the image forming unit30except that colors for forming an image are different. Further, the second intermediate transfer belt60and the primary transfer roll57described later have the same configuration as the first intermediate transfer belt40and the primary transfer roll37of the image forming unit30. Further, the other constituent members configuring the image forming unit50are the same as in the image forming unit30.

As shown inFIG.2, the image forming section52includes an image forming section52K that forms a black toner image of black color, an image forming section52G that forms a gold toner image of gold color, an image forming section52S that forms a silver toner image of silver color, and an image forming section52T that forms a transparent toner image. In a case where it is not necessary to distinguish between T, S, G, and K, T, S, G, and K are omitted.

The four image forming sections52are disposed in the order of the image forming section52T, the image forming section52S, the image forming section52G, and the image forming section52K in order from the rotation direction upstream side (the side closer to the support roll64described later). That is, in the image forming section52, the image forming section52K is disposed on the most rotation direction downstream side, the image forming section52G and the image forming section52S are disposed on the rotation direction upstream side with respect to the image forming section52K, and the image forming section52T is disposed on the most rotation direction upstream side.

The image forming section52includes a photoconductor53, a photoconductor charging member54, an exposure device55, and a developing device56.

Developing rolls59T,59S,59G, and59K are provided in the developing device56, respectively, and are applied with a developing bias by the power supply device99(seeFIG.4), respectively.

Further, the primary transfer rolls57T,57S,57G, and57K are disposed at positions facing respective photoconductors53with the second intermediate transfer belt60interposed therebetween. The second intermediate transfer belt60is wound around a support roll64and a backup roll62disposed on a second transfer unit76on the downstream side, which will be described later. The primary transfer unit72includes the photoconductor53, the primary transfer roll57, and the second intermediate transfer belt60. Further, the primary transfer positions TT1, TS1, TG1, and TK1are set between the photoconductors53T,53S,53G, and53K and the second intermediate transfer belt60, respectively.

The developing device36of the image forming section32of each color of the image forming unit30and the developing device56of the image forming section52of each color of the image forming unit50are connected to a plurality of toner cartridges (not shown) in which a toner corresponding to each color is accommodated via a supply path. The toner accommodated in each toner cartridge is appropriately supplied to the developing devices36and56of each color via the supply path by operating a supply device (not shown) provided in the supply path.

Conveyor Belt Device

Next, the details of the conveyor belt device20will be described.

As shown inFIGS.2and3, the conveyor belt device20includes an endless conveyor belt21, a tension roll22that supports and stretches the conveyor belt21, a drive roll23that rotates the conveyor belt21, and secondary transfer rolls24and25disposed at positions facing the backup rolls42and62with the first intermediate transfer belt40and the second intermediate transfer belt60interposed therebetween.

The conveyor belt21as an example of the conveyance unit is stretched by the tension roll22and the drive roll23provided at intervals in the conveyance direction of the recording paper P (seeFIG.3), in the vertical direction (Y direction) in the present exemplary embodiment. The drive roll23is rotated by a drive mechanism (not shown), so that the endless conveyor belt21is rotated. The tension roll22is driven to rotate with the rotation of the conveyor belt21.

The conveyance direction of the recording paper P to be conveyed by the conveyor belt device20in the present exemplary embodiment is the Y direction.

The secondary transfer roll24sandwiches the recording paper P (seeFIGS.1and4) and the conveyor belt21between the backup roll42and the secondary transfer roll24, and transfers the toner image formed on the first intermediate transfer belt40of the image forming unit30to the surface PA (seeFIG.3) of the recording paper P conveyed by the conveyor belt21. Similarly, the secondary transfer roll25sandwiches the recording paper P and the conveyor belt21between the backup roll62and the secondary transfer roll25, and transfers the toner image formed on the second intermediate transfer belt60of the image forming unit50to the surface PA (seeFIG.3) of the recording paper P.

As shown inFIG.3, the side of the recording paper P on which the toner image is transferred is referred to as a surface PA, and the side in contact with the conveyor belt21is referred to as a surface PB.

As shown inFIGS.2and3, the first transfer unit74includes the backup roll42, the secondary transfer roll24, and the first intermediate transfer belt40. The second transfer unit76includes the backup roll62, the secondary transfer roll25, and the second intermediate transfer belt60.

The secondary transfer rolls24and25are driven to rotate with the rotation of the conveyor belt21. Further, a transfer bias is applied to the secondary transfer rolls24and25by the power supply device99(seeFIG.4), respectively.

The secondary transfer position TJ2is defined between the first intermediate transfer belt40of the image forming unit30and the conveyor belt21, and the secondary transfer position TK2is defined between the second intermediate transfer belt60of the image forming unit50and the conveyor belt21. The secondary transfer position TK2is the most downstream secondary transfer position.

Further, the conveyor belt device20includes a belt cleaning device (not shown) that cleans the conveyor belt21. The belt cleaning device (not shown) performs cleaning on the rotation direction upstream side of the most downstream secondary transfer position TK2and on the rotation direction downstream side of the most upstream secondary transfer position TJ2.

Main part Configuration

Next, the configuration of the main part of the present exemplary embodiment will be described, although the description will be partially repeated.

As shown inFIGS.2and3, in the present exemplary embodiment, the second image forming group51composed of the plurality of image forming sections52of the image forming unit50is disposed on the downstream side in the conveyance direction of the first image forming group31composed of the plurality of image forming sections32of the image forming unit30. The first intermediate transfer belt40is provided on the downstream side in the conveyance direction of the first image forming group31. Further, the second intermediate transfer belt60is provided on the upstream side in the conveyance direction of the second image forming group51. From another point of view, the first intermediate transfer belt40and the second intermediate transfer belt60are arranged in the conveyance direction between the first image forming group31and the second image forming group51arranged in the conveyance direction. The first intermediate transfer belt40and the second intermediate transfer belt60are independently provided and are not shared.

The conveyor belt21is wound around the tension roll22and the drive roll23, and is stretched in the conveyance direction. Further, the distance L1between the first transfer unit74and the second transfer unit76in the conveyor belt21is set to an integral multiple (the same magnification in the present exemplary embodiment) of the peripheral surface length L2of the peripheral surface23A of the drive roll23. That is, it is set that L1=L2.

In a case where L1is in the range of ±0.3% with respect to L2, L1=L2. In a case where L1is in the range of ±0.3% with respect to an integral multiple of L2, L1is an integral multiple of L2.

The first intermediate transfer belt40is stretched with the direction intersecting the conveyance path19(see alsoFIG.1) (the X direction in the present exemplary embodiment) as the longitudinal direction. The plurality of image forming sections32configuring the first image forming group31are arranged in the longitudinal direction on the upstream side in the conveyance direction of the first intermediate transfer belt40. The second intermediate transfer belt60is stretched with the direction intersecting the conveyance path19(see alsoFIG.1) (the X direction in the present exemplary embodiment) as the longitudinal direction. That is, the plurality of image forming sections52configuring the second image forming group51are arranged in the longitudinal direction on the downstream side in the conveyance direction of the second intermediate transfer belt60.

From another point of view, the first intermediate transfer belt40and the second intermediate transfer belt60are provided with the direction intersecting the conveyance path19(the X direction in the present exemplary embodiment) as the longitudinal direction, and are arranged in parallel or substantially parallel to the Y direction, in a side view viewed from the Z direction which is the rotation axis direction of the first intermediate transfer belt40and the second intermediate transfer belt60.

As shown inFIG.3, the image forming unit30has a first cleaning blade110as an example of a first cleaning member that cleans the first intermediate transfer belt40. The first cleaning blade110is provided at a position to clean a part of the first intermediate transfer belt40that is wound around the support roll44, which is the folded end portion in the longitudinal direction after the secondary transfer.

Further, the image forming unit50has a second cleaning blade120as an example of a second cleaning member that cleans the second intermediate transfer belt60. The second cleaning blade120is provided at a position to clean between the second transfer unit76and the image forming section52K of the second image forming group51after the secondary transfer of the second intermediate transfer belt60.

From another point of view, the first cleaning blade110and the second cleaning blade120are not provided between the first intermediate transfer belt40and the second intermediate transfer belt60.

Further, as shown inFIGS.2and3, the electric substrate100provided with the control device80, the power supply device99(seeFIG.4), which will be described later, and the like is provided on the upstream side in the conveyance direction of the first image forming group31(in the present exemplary embodiment, at the lower end portion of the image forming apparatus10).

As described above, between the first intermediate transfer belt40and the second intermediate transfer belt60, the first image forming group31, the second image forming group51, the first cleaning blade110, the second cleaning blade120, an electric substrate100, or the like are not provided. Therefore, the distance between the first transfer unit74and the second transfer unit76arranged in the conveyance direction is narrow.

Control Device

Next, the control device80that controls the operation of the image forming apparatus10will be described with reference toFIG.6.

As shown inFIG.6, an image forming unit30, an image forming unit50, a communication unit90, a non-volatile memory92, a power supply device99, or the like are electrically connected to the control device80.

The control device80is connected to a Central Processing Unit (CPU)81, a Read Only Memory (ROM)82, a Random Access Memory (RAM)83, and an input/output interface (I/O)84via a bus.

Here, the ROM82stores an image formation control program (not shown) to be executed by the CPU81. Then, the CPU81reads the image formation control program (not shown) from the ROM82and expands the image formation control program into the RAM83to execute a printing process by the image formation control program (not shown).

Further, the image forming unit30, the image forming unit50, the communication unit90, and the non-volatile memory92are connected to the I/O84. The communication unit90is an interface for mutual data communication between a terminal device such as a personal computer (not shown) and an image forming apparatus10. The non-volatile memory92stores information necessary for the image forming apparatus10to execute the image forming operation.

The control device80performs various controls for forming a toner image on the first intermediate transfer belt40(seeFIG.2and the like) by the image forming section32(seeFIG.2and the like) of each color of the image forming unit30. Similarly, various controls are performed for forming a toner image on the second intermediate transfer belt60(seeFIG.2and the like) by the image forming section52(seeFIG.2and the like) of each color of the image forming unit50.

Further, the control device80controls the developing bias to be applied to the developing rolls39Y,39M,39C,39W,59T,59S,59G, and59K (seeFIG.2or the like) of the developing devices36and56by the power supply device99. Further, the control device80controls the transfer bias to be applied to the secondary transfer rolls24and25(seeFIG.2or the like) by the power supply device99.

Image Formation Process

Next, the outline of the image formation process in the image forming apparatus10will be described.

First, the control device80controls each image forming section32such that a toner image is formed on the first intermediate transfer belt40of the image forming unit30. Similarly, each image forming section52is controlled such that a toner image is formed on the second intermediate transfer belt60of the image forming unit50.

Specifically, the control device80applies a voltage to the photoconductor charging members34,54, and charges the peripheral surfaces of the photoconductors33and53so as to have a predetermined potential, by using the photoconductor charging members34and54to which the voltage is applied. Subsequently, the control device80irradiates the peripheral surfaces of the photoconductors33and53charged by the photoconductor charging members34and54with exposure light by the exposure devices35and55to form an electrostatic latent image, based on the image data acquired via the communication unit90. Thus, an electrostatic latent image corresponding to the image data is formed on the peripheral surfaces of the photoconductors33and53.

Next, the control device80develops the electrostatic latent image formed by the exposure devices35and55by the developing devices36and56and visualizes the electrostatic latent image as a toner image. Further, the control device80superimposes and transfers the toner image formed on the peripheral surfaces of the photoconductors33and53of each color on the first intermediate transfer belt40and the second intermediate transfer belt60, by the primary transfer rolls37and57.

In this way, in the image forming unit30, for example, a toner image on which yellow (Y), magenta (M), cyan (C), and white (W) toners are superimposed is formed on the first intermediate transfer belt40. Similarly, in the image forming unit50, for example, a toner image in which black (K), gold (G), silver (S), and transparent (T) toners are superimposed is formed on the second intermediate transfer belt60.

Here, the recording paper P sent out from the accommodating unit12to the conveyance path19by the feed roll13is sent out to the secondary transfer position TJ2on the upstream side in the conveyance direction, after the convey timing is adjusted by the resist roll pair15based on the control of the control device80. At the secondary transfer position TJ2, the recording paper P is conveyed between the backup roll42and the secondary transfer roll24, so that the toner image on the outer peripheral surface of the first intermediate transfer belt40is transferred to the recording paper P. Then, the recording paper P on which the toner image is transferred is conveyed to the conveyance direction downstream side and reaches the secondary transfer position TK2on the conveyance direction downstream side.

At this time, the control device80adjusts the timing to start image formation such that the toner image formed on the second intermediate transfer belt60of the image forming unit50is superimposed and transferred on the toner image on the recording paper P that have been conveyed from the conveyance direction upstream side.

The recording paper P, on which the toner images of each color formed by the image forming unit30and the image forming unit50are superimposed and transferred, is fixed by the fixing roll pair16of the fixing device18, and then is discharged to the discharge unit9provided on the upper part of the image forming apparatus main body10A, by the discharge roll17.

Action

Next, the action of the present exemplary embodiment will be described.

The second image forming group51composed of the plurality of image forming sections52of the image forming unit50is disposed on the downstream side in the conveyance direction of the first image forming group31composed of the plurality of image forming sections32of the image forming unit30. The first intermediate transfer belt40is provided on the downstream side in the conveyance direction of the first image forming group31. The second intermediate transfer belt60is provided on the upstream side in the conveyance direction of the second image forming group51. That is, the first image forming group31and the second image forming group51are not provided between the first intermediate transfer belt40and the second intermediate transfer belt60. Therefore, compared with the case where the image forming sections32and52are located between the first intermediate transfer belt40and the second intermediate transfer belt60arranged in the conveyance direction, the space between the first transfer unit74and the second transfer unit76in the conveyance path19may be narrowed.

In this way, by narrowing the space between the first transfer units74and the second transfer unit76arranged in the conveyance direction, the separation of the recording paper P conveyed between the first transfer units74and the second transfer unit76from the conveyance path19is prevented. Therefore, the misalignment of the superposition of the toner images in the second transfer unit76due to the separation of the recording paper P conveyed between the first transfer unit74and the second transfer unit76arranged in the conveyance direction from the conveyance path19is prevented.

Further, the conveyor belt21is wound around the tension roll22and the drive roll23, and is stretched in the conveyance direction. Further, the distance L1between the first transfer unit74and the second transfer unit76in the conveyor belt21is set to an integral multiple (the same magnification (L1=L2) in the present exemplary embodiment) of the peripheral surface length L2of the peripheral surface23A of the drive roll23.

Therefore, the influence of rotation unevenness of the drive roll23is small, as compared with the case where the distance L1between the first transfer unit74and the second transfer unit76in the conveyor belt21is a non-integral multiple of the peripheral surface length L2of the peripheral surface23A of the drive roll23. Specifically, in a case of an integral multiple, the influence of the rotation unevenness in the first transfer unit74is canceled by the second transfer unit76, so that the influence of the rotation unevenness of the drive roll23is reduced.

Further, since the distance L1between the first transfer unit74and the second transfer unit76in the conveyor belt21is equal to the peripheral surface length L2of the peripheral surface23A of the drive roll23, a space between the first transfer unit74and the second transfer unit76becomes narrower, as compared with a case where the distance L1is equal to or more than twice the peripheral surface length L2.

Further, the first intermediate transfer belt40is stretched with the direction intersecting the conveyance path19(the X direction in the present exemplary embodiment) as the longitudinal direction. Therefore, the space between the first transfer unit74and the second transfer unit76in the conveyance path19can be narrowed, as compared with the case where the first intermediate transfer body is a drum instead of a belt.

Further, the second intermediate transfer belt60is stretched with the direction intersecting the conveyance path19(the X direction in the present exemplary embodiment) as the longitudinal direction. Therefore, the space between the first transfer unit74and the second transfer unit76in the conveyance path19can be narrowed, as compared with the case where the second intermediate transfer body is a drum instead of a belt.

Further, the first cleaning blade110is provided at a position to clean a part of the first intermediate transfer belt40that is wound around the support roll44, which is the folded end portion in the longitudinal direction after the secondary transfer. Therefore, as compared with the case where the first cleaning blade110is located between the first intermediate transfer belt40and the second intermediate transfer belt60, the distance between the first intermediate transfer belt40and the second intermediate transfer belt60can be narrowed, so that the space between the first transfer unit74and the second transfer unit76in the conveyance path19may be narrowed.

Further, the second cleaning blade120is provided between the second transfer unit76and the image forming section52K of the second image forming group51after the secondary transfer of the second intermediate transfer belt60. As compared with the case where the second cleaning blade120is located between the first intermediate transfer belt40and the second intermediate transfer belt60, the distance between the first intermediate transfer belt40and the second intermediate transfer belt60can be narrowed, so that the space between the first transfer unit74and the second transfer unit76in the conveyance path19may be narrowed.

Further, the electric substrate100provided with the control device80, the power supply device99, and the like is provided on the upstream side in the conveyance direction of the first image forming group31(in the present exemplary embodiment, at the lower end portion of the image forming apparatus10). Therefore, as compared with the case where the electric substrate100is located between the first intermediate transfer belt40and the second intermediate transfer belt60, the distance between the first intermediate transfer belt40and the second intermediate transfer belt60can be narrowed, so that the space between the first transfer unit74and the second transfer unit76in the conveyance path19may be narrowed.

Second Exemplary Embodiment

Next, an image forming apparatus according to a second exemplary embodiment of the present invention will be described. The first exemplary embodiment has the same configuration except that the distance between the first transfer unit74and the second transfer unit76is different. Therefore, other explanations will be omitted or simplified.

Main Part Configuration

The main part configuration of the present exemplary embodiment will be described.

The width of the minimum recording paper PS in the image forming apparatus200of the present exemplary embodiment shown inFIG.4in the conveyance direction is defined as the minimum width LS. In the present exemplary embodiment, the minimum width LS is for the lateral feed of the A5-size recording paper PS. That is, in the present exemplary embodiment, the minimum width LS is for the short side width of A5 size.

The distance L3between the first transfer unit74and the second transfer unit76is less than the minimum width LS. The distance L1is the distance between the axes of the secondary transfer rolls24and25.

Action

Next, the action of the present exemplary embodiment will be described.

Since the distance L3between the first transfer unit74and the second transfer unit76is less than the minimum width LS, in a case where the recording paper PS having the minimum width LS is conveyed, the recording paper PS rests on both the first transfer unit74and the second transfer unit76.

Therefore, the separation of the recording paper PS from the conveyance path19is prevented, as compared with the case where the distance L3between the first transfer unit74and the second transfer unit76is larger than the minimum width LS.

REFERENCE EXAMPLE

The image forming apparatus of a reference example will be described.

Configuration

First, the configuration of the reference example will be described.

An image forming apparatus910of a reference example shown inFIG.5includes an image forming unit30that forms a toner image to be transferred to the recording paper P, an image forming section900, and the like. Since the image forming unit30, the other control device80, the conveyor belt device20, and the like are the same as in the first exemplary embodiment and the second exemplary embodiment described above, the description thereof will be omitted.

The image forming section900is disposed at the same place as the image forming unit50(seeFIGS.3and4) in the first exemplary embodiment and the second exemplary embodiment. The image forming section900includes a photoconductor908, a photoconductor charging member906, an exposure device904, and a developing device902. The developing device902has a developing roll901to which a developing bias is applied. In addition, the image forming section900of the present exemplary embodiment forms a black (K) toner image.

The first intermediate transfer belt40is provided on the downstream side in the conveyance direction of the first image forming group31. Further, the distance L4between the first transfer unit74and the second transfer unit76in the conveyor belt21is equal to the peripheral surface length L2of the peripheral surface23A of the drive roll23(L4=L2), or is less than the minimum width LS.

Image Formation Process

Next, the outline of the image formation process in the image forming apparatus910will be described.

First, the control device80controls each image forming section32such that a toner image is formed on the first intermediate transfer belt40of the image forming unit30. Similarly, control is performed such that the toner image is formed on the photoconductor908of the image forming section900.

Next, a specific image formation process will be described. Since the formation of the toner image on the first intermediate transfer belt40of the image forming unit30is the same as in the first exemplary embodiment and the second exemplary embodiment described above, the description will be omitted.

The control device80applies a voltage to the photoconductor charging member906, and charges the peripheral surfaces of the photoconductor908so as to have a predetermined potential, by using the photoconductor charging member906to which the voltage is applied. Subsequently, the control device80irradiates the peripheral surfaces of the photoconductor908charged by the photoconductor charging member906with exposure light by the exposure device904to form an electrostatic latent image, based on the image data acquired via the communication unit90. Thus, an electrostatic latent image corresponding to the image data is formed on the peripheral surfaces of the photoconductor908.

Next, the control device80develops the electrostatic latent image formed by the exposure device904by the developing device902and visualizes the electrostatic latent image as a toner image.

In this way, in the image forming unit30, for example, a toner image on which yellow (Y), magenta (M), cyan (C), and white (W) toners are superimposed is formed on the first intermediate transfer belt40. Similarly, the toner image of black (K) is formed on the photoconductor908of the image forming section900.

Here, the recording paper P sent out from the accommodating unit12to the conveyance path19by the feed roll13is sent out to the secondary transfer position TJ2on the upstream side in the conveyance direction, after the convey timing is adjusted by the resist roll pair15based on the control of the control device80. At the secondary transfer position TJ2, the recording paper P is conveyed between the backup roll42and the secondary transfer roll24, so that the toner image on the outer peripheral surface of the first intermediate transfer belt40is transferred to the recording paper P. Then, the recording paper P on which the toner image is transferred is conveyed to the conveyance direction downstream side and reaches the secondary transfer position TK2on the conveyance direction downstream side.

At this time, the control device80adjusts the timing to start image formation such that the toner image formed on the photoconductor908of the image forming section900is superimposed and transferred on the toner image on the recording paper P that have been conveyed from the conveyance direction upstream side.

The recording paper P, on which the toner images of each color formed by the image forming unit30and the image forming section900are superimposed and transferred, is fixed by the fixing roll pair16of the fixing device18, and then is discharged to the discharge unit9provided on the upper part of the image forming apparatus main body10A, by the discharge roll17.

Action

The first intermediate transfer belt40is provided on the downstream side in the conveyance direction of the first image forming group31, and the first image forming group31is not provided between the first intermediate transfer belt40and the photoconductor908. Therefore, compared with the case where the first image forming group31is located on the downstream side in the conveyance direction of the first intermediate transfer belt40, the space between the first transfer unit74and the second transfer unit76in the conveyance path19may be narrowed.

Then, by narrowing the space between the first transfer units74and the second transfer unit76arranged in the conveyance direction, the separation of the recording paper P conveyed between the first transfer units74and the second transfer unit76from the conveyance path19is prevented. Therefore, the misalignment of the superposition of the toner images in the second transfer unit76due to the separation of the recording paper P conveyed between the first transfer unit74and the second transfer unit76arranged in the conveyance direction from the conveyance path19is prevented.

In a case where the distance L4between the first transfer unit74and the second transfer unit76in the conveyor belt21is equal to the peripheral surface length L2of the peripheral surface23A of the drive roll23(L4=L2), the influence of rotation unevenness of the drive roll23is smaller, and a space between the first transfer unit74and the second transfer unit76may be narrowed, as compared with the case where the distance L4is a non-integral multiple of the peripheral surface length L2of the peripheral surface23A of the drive roll23.

Further, in a case where the distance L4between the first transfer unit74and the second transfer unit76is less than the minimum width LS, the separation of the recording paper PS from the conveyance path19is prevented, as compared with the case where the distance L4is larger than the minimum width LS.

Others

The present invention is not limited to the above exemplary embodiments.

For example, in the above exemplary embodiments, in the first exemplary embodiment, the distance L1between the first transfer unit74and the second transfer unit76in the conveyor belt21is equal to the peripheral surface length L2of the peripheral surface23A of the drive roll23(L1=L2), but the distance L2may be an integral multiple of 2 or more. Even in a case where L1is an integral multiple of 2 or more of L2, the influence of rotation unevenness of the drive roll23is small, which is preferable. However, the present invention is not limited to the case where L1is an integral multiple of L2.

Further, for example, in the above exemplary embodiments, in the second exemplary embodiment, the distance L3between the first transfer unit74and the second transfer unit76in the conveyor belt21is less than the minimum width LS, but may be equal to or less than the minimum width LS. Even in a case where L3is the same as LS, the separation of the recording paper PS from the conveyance path19is prevented. However, the present invention is not limited to the case where L3is equal to or less than LS.

Further, for example, the distance between the first transfer unit74and the second transfer unit76in the conveyor belt21may be equal to the peripheral surface length of the peripheral surface23A of the drive roll23and less than the minimum width LS.

Further, for example, in the above exemplary embodiments, the first cleaning blade110is provided in a position to clean a part of the first intermediate transfer belt40that is wound around the support roll44, which is the folded end portion in the longitudinal direction after the secondary transfer, but the present invention is not limited thereto. The first cleaning blade110may clean a space between a part of the first intermediate transfer belt40that is wound around the support roll44, which is the folded end portion in the longitudinal direction after the secondary transfer and the image forming section32Y of the first image forming group31.

Further, for example, in the above exemplary embodiments, the first intermediate transfer belt40is cleaned by the first cleaning blade110, but the present invention is not limited thereto. For example, the first intermediate transfer belt40may be cleaned with a brush.

Further, for example, in the above exemplary embodiments, the second intermediate transfer belt60is cleaned by the second cleaning blade120, but the present invention is not limited thereto. For example, the second intermediate transfer belt60may be cleaned with a brush.

Further, for example, in the above exemplary embodiments, the image forming units30and50have four image forming sections32and52, respectively, but the present invention is not limited thereto. The image forming unit may have two or more image forming sections.

Further, for example, in the above exemplary embodiments, the image forming apparatus10includes two image forming units, that is, the image forming unit30and the image forming unit50, but the present invention is not limited thereto. The image forming apparatus may include three or more image forming units.

Further, in the above exemplary embodiments, the electric substrate100is on the upstream side in the conveyance direction of the first image forming group31, but the present invention is not limited thereto. The electric substrate100may be provided on the downstream side in the conveyance direction of the second image forming group51.

Further, for example, in the above exemplary embodiments, the recording medium is the recording paper P such as plain paper, but the present invention is not limited thereto. The recording medium may be a sheet-like member such as an OHP.

Further, for example, in the above exemplary embodiments, the conveyance unit that conveys a recording medium in contact with one surface of the recording medium is the conveyor belt21, but the conveyance unit is not limited thereto. The conveyance unit may be, for example, a drum other than the belt.

Further, for example, in the above exemplary embodiments, the first intermediate transfer body and the second intermediate transfer body on which the toner image is primarily transferred are the first intermediate transfer belt40and the second intermediate transfer belt60, but the present invention is not limited thereto. The first intermediate transfer body and the second intermediate transfer body may be, for example, a drum other than the belt.

Further, the configuration of the image forming apparatus is not limited to the configuration of the above exemplary embodiments, and various configurations can be used. Further, the present invention can be implemented in various ways without departing from the concept of the present invention.