JP2009063768A - Image forming apparatus and control method for image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus suppressing an image defect caused for prevention of transfer scattering. <P>SOLUTION: The image forming apparatus includes: a plurality of photoreceptor drums 40, 50, 60 and 70 on the surfaces of which a developer image is formed; an intermediate transfer belt 8 to which a plurality of developer images formed on the surfaces of the plurality of image carriers are transferred to be superposed each other; primary transfer rollers 14, 15, 16 and 17 provided opposite to the plurality of photoreceptor drums respectively across the intermediate transfer belt 8; roller members 34, 35, 36 and 37 provided so as to abut on the intermediate transfer belt near the upstream side of at least one primary transfer roller out of the primary transfer rollers, and arranging the intermediate transfer belt along the surfaces of the photoreceptor drums; and a control part 30 controlling the rotation of the roller member and the photoreceptor drum so as to provide a speed difference between the circumferential speed of the roller member and that of the photoreceptor drum arranged near the downstream side of the roller member. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile.

  In recent years, full-color copying machines as well as monochrome copying machines are often used as image forming apparatuses. As such a full-color copying machine, a tandem color copying machine in which a photosensitive drum is provided for each color toner is often used because of its high printing speed.

  In such a tandem type color copying machine, a toner image formed on a photosensitive drum for each color is temporarily transferred onto an intermediate transfer belt and superimposed, and then transferred onto a recording medium such as paper. Is done. The secondary transferred toner image is fixed on a sheet and discharged from the copying machine.

  Here, a toner and a reverse bias are applied to a primary transfer roller disposed opposite to the photosensitive drum with the intermediate transfer belt interposed therebetween, and primary transfer is performed by pressing by the primary transfer roller. However, when the toner image on the photosensitive drum approaches the vicinity of the nip portion, discharge may occur and so-called “transfer scattering” may occur.

  In order to prevent this “transfer scattering”, an image forming apparatus having a belt lifting roller in the vicinity of the upstream side of the nip portion is disclosed (for example, see Patent Document 1).

FIG. 5 is a view showing the vicinity of one photosensitive drum and the nip portion 204 of the intermediate transfer belt 202 in the tandem type image forming apparatus disclosed in Patent Document 1. As shown in FIG. 5, an intermediate transfer belt 202 is passed through a nip portion 204 formed by the photosensitive drum 200 and the primary transfer roller 201, and the intermediate transfer belt 202 is lifted by a roller 203 on the upstream side of the nip portion 204. Is lifted to the photosensitive drum 200 side. In this way, by reducing the gap on the upstream side of the nip portion 204, “transfer scattering” is suppressed.
Japanese Patent Laid-Open No. 2001-75370

  However, since the intermediate transfer belt 202 is disposed so as to be pressed against the photosensitive drum 200, the adhesion of the intermediate transfer belt 202 to the photosensitive drum 200 becomes greater, and the aggregated toner adheres to the drum surface. In some cases, image defects such as missing characters may occur.

  An object of the present invention is to provide an image forming apparatus and a method for controlling the image forming apparatus that can suppress the adverse effects caused by preventing transfer scattering in consideration of the problems of the conventional image forming apparatus. And

In order to achieve the above object, the first present invention provides:
A plurality of image carriers on which developer images are formed; and
An intermediate transfer body on which a plurality of developer images formed for each image carrier are transferred and superimposed;
A transfer member provided to face each of the plurality of image carriers with the intermediate transfer member interposed therebetween;
Of each nip portion formed by the image carrier and the intermediate transfer member, it is provided in contact with the intermediate transfer member in the vicinity of the upstream side of at least one of the nip portions, and in the vicinity of the upstream side of the nip portion. A roller member for narrowing an interval between the image carrier and the intermediate transfer member;
The rotation of the roller member and the image carrier is controlled so as to provide a speed difference between the circumferential speed of the roller member and the circumferential speed of the image carrier disposed near the downstream side of the roller member. And an image forming apparatus.

The second aspect of the present invention is
A plurality of the roller members are provided,
The control unit is the image forming apparatus according to the first aspect of the present invention, which controls the plurality of roller members so that their peripheral speeds are the same.

The third aspect of the present invention
One image carrier on which a plurality of developer images are sequentially formed on the surface;
An intermediate transfer body on which the plurality of developer images are transferred and superimposed;
A transfer member provided so as to face the image carrier with the intermediate transfer member interposed therebetween;
Provided in contact with the intermediate transfer body in the vicinity of the upstream side of the nip portion formed by the image carrier and the intermediate transfer body, and the image carrier and the intermediate transfer body in the vicinity of the upstream side of the nip portion. A roller member for narrowing the gap between,
The rotation of the roller member and the image carrier is controlled so as to provide a speed difference between the circumferential speed of the roller member and the circumferential speed of the image carrier disposed near the downstream side of the roller member. And an image forming apparatus.

The fourth aspect of the present invention is
The controller is
Controlling rotation of the roller member and the image carrier so that a circumferential speed of the roller member is faster than a circumferential speed of the image carrier disposed in the vicinity of the downstream side of the roller member; The image forming apparatus according to any one of items 1 to 3.

The fifth aspect of the present invention is
The plurality of developer images are images of black, yellow, cyan, and magenta toners,
The intermediate transfer body is the image forming apparatus according to any one of the first to third aspects of the present invention, which is a belt-like member wound around the transfer member and the roller member.

The sixth aspect of the present invention
A plurality of image carriers on which developer images are formed, an intermediate transfer member on which a plurality of developer images formed for each of the image carriers are transferred and superimposed, and the intermediate transfer member interposed therebetween Near the upstream side of at least one of the transfer members provided to face each of a plurality of image carriers and at least one nip formed by the image carrier and the intermediate transfer member And a roller member for reducing the distance between the image carrier and the intermediate transfer member in the vicinity of the upstream side of the nip portion. And
The rotation of the roller member and the image carrier is controlled so as to provide a speed difference between the circumferential speed of the roller member and the circumferential speed of the image carrier disposed near the downstream side of the roller member. And a control method for controlling the image forming apparatus.

The seventh aspect of the present invention
One image carrier on which a plurality of developer images are sequentially formed on the surface, an intermediate transfer member on which the plurality of developer images are transferred and overlaid, and facing the image carrier across the intermediate transfer member A transfer member provided in contact with the intermediate transfer member in the vicinity of the upstream side of each nip formed by the image carrier and the intermediate transfer member, and upstream of the nip. A control method for an image forming apparatus, comprising a roller member for narrowing a gap between the image carrier and the intermediate transfer member in the vicinity,
The rotation of the roller member and the image carrier is controlled so as to provide a speed difference between the circumferential speed of the roller member and the circumferential speed of the image carrier disposed near the downstream side of the roller member. And a control step for controlling the image forming apparatus.

Further, the eighth aspect of the present invention is
The control step includes
The step of controlling the rotation of the roller member and the image carrier so that the circumferential speed of the roller member is faster than the circumferential speed of the image carrier disposed in the vicinity of the downstream side of the roller member. 6 is a control method for an image forming apparatus according to the sixth or seventh aspect of the present invention.

  According to the present invention, it is possible to provide an image forming apparatus and an image forming apparatus control method capable of suppressing adverse effects caused by preventing transfer scattering.

  A copier as an example of an image forming apparatus according to the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a front sectional view of a copying machine according to an embodiment of the present invention. As shown in FIG. 1, the copying machine 1 according to the first embodiment includes a plurality of paper feed cassettes 2 for storing paper on which images are formed on the bottom. In addition, the copying machine 1 includes a document reading unit 3 that reads an image of a document by using an exposure lamp, a lens, a mirror, and the like.

  The copying machine 1 according to the present embodiment is a color copying machine using a tandem method, and includes a black image forming unit 4, a yellow image forming unit 5, a cyan image forming unit 6, and a magenta arranged in order in the horizontal direction. An image forming unit 7 is provided. An intermediate transfer belt 8 for superimposing images formed by these image forming units is disposed. Further, a secondary transfer unit 9 that transfers the toner image superimposed on the intermediate transfer belt 8 to a sheet and a fixing unit 10 that fixes the transferred toner image to the sheet are provided.

  In addition, a registration roller 25 is provided on the upstream side of the secondary transfer unit 9 in the paper conveyance direction (see arrow E). The registration roller 25 is provided between the secondary transfer unit 9 and the fixing unit 10 for conveying the paper. A conveyor belt 26 is provided. Further, a discharge roller pair 12 for discharging the paper that has passed through the fixing unit 10 to the outside of the copying machine 1 is provided on the side surface, and a discharge tray 13 on which the paper discharged by the discharge roller pair 12 is placed is provided. Is provided. In FIG. 1, the sheet conveyance direction is indicated by an arrow E.

  Next, the configuration of the image forming unit and the intermediate transfer belt 8 will be described.

  FIG. 2 is an enlarged configuration diagram in the vicinity of the intermediate transfer belt 8. In FIG. 2, the thickness of the intermediate transfer belt 8 is shown thicker than usual for easy understanding. As shown in FIGS. 1 and 2, the black image forming unit 4 includes a photosensitive drum 40 made of amorphous silicon, a charger 41, a developing unit 42, a cleaning unit 43, a static eliminator 44, and the like. A laser scanner unit (hereinafter referred to as LSU) 46 that forms an electrostatic latent image by optically scanning the surface of the photosensitive drum 40 charged by the charger 41 of the black image forming unit 4 is a photosensitive drum. 40 is provided above. Similarly, the other image forming units 5, 6, 7 also have photosensitive drums 50, 60, 70, chargers 51, 61, 71, developing units 52, 62, 72, cleaning units 53, 63, 73, static eliminators. 54, 64, 74 and LSUs 56, 66, 76 and the like.

  Further, primary transfer rollers 14, 15, 16, and 17 are disposed so as to face the photosensitive drums 40, 50, 60, and 70 with the intermediate transfer belt 8 interposed therebetween, and the primary transfer rollers 14, 15, 16 are arranged. , 17 are pressed against the photosensitive drums 40, 50, 60, 70 facing each other with the intermediate transfer belt 8 sandwiched between them by a spring member 31. The developing units 42, 52, 62, and 72 are provided with developing rollers 45 and 55 that are disposed in contact with the photosensitive drums to supply toner to the surfaces of the photosensitive drums 40, 50, 60, and 70, respectively. , 65, 75 are provided. In FIG. 2, only the photosensitive drum, the charger, and the developing roller are shown.

  Further, the intermediate transfer belt 8 is provided with a layer of an elastic member such as rubber on a resin belt in order to achieve both running performance and high image quality. As shown in FIG. 2, the secondary transfer unit 9 has a secondary transfer roller 92, and the secondary transfer roller 92 forms a black image based on the rotation direction of the intermediate transfer belt 8 (see arrow A). They are disposed downstream of the unit 4 and upstream of the magenta image forming unit 7 and outside the intermediate transfer belt 8.

  A driven roller 21 is provided inside the intermediate transfer belt 8 so as to face the secondary transfer roller 92. Further, a driven roller 22 is provided inside the intermediate transfer belt 8 in the vicinity of the upstream side of the magenta image forming unit 7. A driving roller 24 for driving the intermediate transfer belt 8 is provided on the downstream side of the black image forming unit 4 and inside the intermediate transfer belt 8 on the upstream side of the driven roller 21. Further, as shown in FIG. 1, a cleaning device 11 for removing residual toner on the surface of the intermediate transfer belt 8 is disposed upstream of the driven roller 22 and downstream of the driven roller 21.

  Further, as shown in FIG. 2, the intermediate transfer belt 8 is formed by the intermediate transfer belt 8 and the photosensitive drums 40, 50, 60, and 70, and is located in the vicinity of the upstream side of the nip portions 84, 85, 86, and 87. On the inside, roller members 34, 35, 36, and 37 are arranged. The intermediate transfer belt 8 is lifted by these roller members 34, 35, 36, 37, and the intermediate transfer belt 8 upstream of the nip portions 84, 85, 86, 87 and the photosensitive drums 40, 50, 60, 70. The gap is narrowed and transfer scattering is suppressed.

  The roller members 34, 35, 36, and 37 have driving means, and the peripheral speed is controlled by the control unit 30 together with the photosensitive drums 40, 50, 60, and 70 and the driving roller 24.

  An example of the image carrier of the present invention corresponds to the photosensitive drums 40, 50, 60, and 70 of the present embodiment, and an example of the intermediate transfer member of the present invention is the intermediate transfer belt 8 of the present embodiment. It corresponds to. An example of the transfer member of the present invention corresponds to the primary transfer rollers 14, 15, 16, and 17 of the present embodiment.

  Next, a method for controlling the copier according to the present embodiment will be described, and an example of a method for controlling the image forming method according to the present invention will also be described.

  A photoconductor uniformly charged by a charger in the magenta image forming unit 7, the cyan image forming unit 6, the yellow image forming unit 5 and the black image forming unit 4 based on the image data read by the document reading unit 3. An electrostatic latent image is formed by the LSUs 46, 56, 66, and 76 on the surfaces of the drums 40, 50, 60, and 70, and a toner image visualized by the developing units 42, 52, 62, and 72 is formed (see FIG. 1). ). At this time, the toner on the photosensitive drums 40, 50, 60, and 70 is positively charged, and due to the negative voltage applied to the primary transfer rollers 14, 15, 16, and 17, and the pressing force of the primary transfer roller, The toner images are superimposed on the intermediate transfer belt 8 in the order of magenta, cyan, yellow, and black.

  At this time, the peripheral speeds of the roller members 34, 35, 36, and 37 and the peripheral speed of the driving roller 24 are the same, and the control is performed so that the peripheral speeds of the photosensitive drums 40, 50, 60, and 70 are slightly higher. Done. This control corresponds to an example of a control step of the present invention. Here, the peripheral speeds of the roller member, the driving roller, and the photosensitive drum are speeds on the respective roller surfaces.

  The toner remaining on the photosensitive drum by the primary transfer is removed by the cleaning units 43, 53, 63, and 73, and the surface of the photosensitive drum is charged by the static eliminators 44, 54, 64, and 74.

  At the same time, paper is fed from the paper feed cassette 2, the paper is temporarily stopped by the registration roller 25, and sent to the secondary transfer unit 9 in accordance with the movement timing of the area on the intermediate transfer belt 8 where the toner image is formed. It is.

  The toner image superimposed on the intermediate transfer belt 8 is transferred onto the sheet by the secondary transfer roller 92, and the sheet is conveyed to the fixing unit 10 by the conveyance belt 26. Then, the sheet on which the toner image is fixed by the fixing unit 10 is discharged onto the discharge tray 13 through the discharge roller pair 12 (see FIG. 1).

  When printing of the read image data is completed, the operations of the photosensitive drum, the intermediate transfer belt 8, the secondary transfer roller 92, and the like are stopped, and the image forming operation is completed.

  In the copying machine of the present embodiment, the circumferential speed of the roller members 34, 35, 36, and 37 is controlled to be higher than the circumferential speed of the photosensitive drums 40, 50, 60, and 70. By controlling, a speed difference is generated between the photosensitive drums 40, 50, 60, 70 and the intermediate transfer belt 8 in the nip portions 84, 85, 86, 87. Due to this speed difference, the adhesion between the photosensitive drums 40, 50, 60, and 70 and the intermediate transfer belt 8 can be reduced, so that it is possible to suppress the occurrence of image defects such as missing characters.

  Examples will be described below.

  In the above embodiment, the photosensitive drums 40, 50, 60, and 70 have a diameter of 30 mm, and the length of the intermediate transfer belt 8 between the photosensitive drums is set to 100 mm. The roller members 34, 35, 36, and 37 are metal rollers, and are set to φ10 mm.

  FIG. 3 is a partially enlarged view of FIG. As shown in FIG. 3, the position of the intermediate transfer belt 8 on the upper surface side in the center of the contact portion with the roller member 35 is J, and the center position of the nip portion 85 between the intermediate transfer belt 8 and the photosensitive drum 50 is K. And Further, the position of the upper surface side of the center of the contact portion of the intermediate transfer belt 8 with the roller member 34 is L, and the center position of the nip portion 84 between the intermediate transfer belt 8 and the photosensitive drum 40 is M. The length between JK and LM is set to 25 mm, and the length between KL is set to 75 mm. The contact position Ha between the roller member 35 and the intermediate transfer belt 8 is set to be 2 mm higher than the contact position Hb between the primary transfer roller 15 and the intermediate transfer belt 8. The other photosensitive drums and roller members are arranged in the same manner.

  When image formation is performed in the copying machine having such a configuration, the peripheral speed of the roller members 34, 35, 36, and 37 and the peripheral speed of the drive roller 24 are set to 250 mm / sec, and the photosensitive drums 40, 50, 60, The peripheral speed of 70 is set to 251 mm / sec.

  Here, assuming that the linear velocity of the intermediate transfer belt 8 near the upstream of the nip portion formed by the primary transfer roller and the photosensitive drum follows the roller member, the linear velocity is 0.4% faster than the peripheral velocity of the photosensitive drum, The intermediate transfer belt between the roller member and the photosensitive drum is loosened by 0.4% compared to the case where the roller member is not driven. As a result, in order to prevent transfer scattering, the adhesion between the intermediate transfer belt 8 and the photosensitive drum caused by the provision of the roller member can be reduced, and the occurrence of image defects such as missing characters is suppressed. I can do it.

  In the above embodiment, the difference in the peripheral speed between the photosensitive drum and the roller member is 1 mm / sec, but it goes without saying that the value is not limited to this value. However, when the peripheral speed difference is increased to 1% or more, slip occurs between the roller members 34, 35, 36, and 37 and the back surface of the intermediate transfer belt 8, and the back surface of the intermediate transfer belt 8 is damaged. Or the intermediate transfer belt 8 is too slack in the upstream of the nip portion, and the speed of the intermediate transfer belt 8 becomes unstable, causing color misregistration. Therefore, even if the peripheral speed difference between the photosensitive drum and the roller member is excessively large, an image defect occurs. Therefore, it is necessary to control the peripheral speed difference to be less than 1%.

  Further, in the above-described embodiments and examples, the roller member and the photosensitive drum are arranged so that the circumferential speed of the roller member is faster than the circumferential speed of the photosensitive drum arranged in the vicinity of the downstream side of the roller member. Although the peripheral speed is set, the peripheral speed of the roller members 34, 35, 36, and 37 is higher than the peripheral speed of the photosensitive drums 40, 50, 60, and 70 disposed in the vicinity of the downstream side of the roller member. You may set so that it may become late. In short, if a speed difference is provided between the peripheral speed of the roller member and the peripheral speed of the photosensitive drum arranged in the vicinity of the downstream side of the roller member, the difference in speed between the intermediate transfer belt and the photosensitive drum at the nip portion. And the adhesion between the intermediate transfer belt and the photosensitive drum can be reduced, so that it is possible to suppress the occurrence of image defects such as missing characters.

  In this embodiment, the peripheral speed of the drive roller 24 for driving the intermediate transfer belt 8 is 251 mm / sec, which is faster than the peripheral speed of the photosensitive drum 250 mm / sec. And it can be slow. The photosensitive member is not limited to the peripheral speed of the driving roller 24 that drives the intermediate transfer belt 8, but if there is a speed difference between the peripheral speed of the photosensitive drum and the peripheral speed of the roller member provided in the vicinity of the upstream side. Since a speed difference is generated between the drum and the intermediate transfer belt, it is possible to suppress the occurrence of image defects such as missing characters.

  In this embodiment, the roller members 34, 35, 36, and 37 are disposed so as to lift the intermediate transfer belt 8. However, the roller members 34, 35, 36, and 37 are appropriately changed depending on the arrangement of the photosensitive drum and the intermediate transfer belt. In short, it is only necessary to determine the position of the roller member so as to narrow the gap between the photosensitive drum and the intermediate transfer belt in the vicinity of the upstream side of the nip portion.

  In the present embodiment, the photosensitive drums 40, 50, 60, 70, the roller members 34, 35, 36, 37, and the drive roller 24 are controlled by one control unit. The rotation may be controlled by the unit.

  Further, the roller members 34, 35, 36, and 37 may be controlled separately so that each peripheral speed can be individually changed. In this case, if there is a speed difference between the roller members 34, 35, 36, 37 or between the photosensitive drums 40, 50, 60, 70 in the apparatus due to an assembly error at the time of manufacture, the speed difference It is possible to adjust so as to cancel.

  In this embodiment, the roller members 34, 35, 36, and 37 are controlled at the same peripheral speed, but may be controlled at different peripheral speeds. For example, in the case where there is a toner that is less likely to cause character dropout compared to other types of toner, the circumference of a set of a photosensitive drum on which the toner is used and a roller member disposed in the vicinity of the photosensitive drum is used. The speed difference may be set to be smaller than the peripheral speed difference in the set of other roller members and the photosensitive drum. For the toner that is liable to cause the character missing, the photosensitive drum using the toner is used. And the difference in the peripheral speeds in the set of roller members may be set larger than the difference in the peripheral speed in the other sets. As described above, the speed of the roller member may be set individually for each of the image forming units 4, 5, 6, and 7 during maintenance and manufacturing.

  In this embodiment, roller members are provided in the vicinity of all the upstream sides of the four nip portions 84, 85, 86, 87 formed by the four photosensitive drums and the intermediate transfer belt 8. For example, in the case where there is a nip portion where transfer scattering is difficult to occur due to a low charge amount of toner used, a roller member need not be provided upstream of the nip portion.

  In the above embodiment, the tandem type image forming apparatus has been described. However, the present invention can also be applied to a one-drum type image forming apparatus. FIG. 4 is a partial configuration diagram of a one-drum type image forming apparatus. The image forming apparatus illustrated in FIG. 4 includes a single photosensitive drum 100 and a developing device 101 that supplies four types of toners of black, yellow, cyan, and magenta to the photosensitive drum 100 for each color. The developing device 101 includes a black developing device 101K, a yellow developing device 101Y, a cyan developing device 101C, and a magenta developing device 101M. By rotating, each developing device is placed at a developing position facing the photosensitive drum 100. By moving sequentially, toner images of opposite colors are formed on the surface of the photosensitive drum 100.

  Further, an intermediate transfer belt 102 is provided for superimposing developer images for respective colors. Inside the intermediate transfer belt 102, a primary transfer roller 103 is provided at a position facing the photosensitive drum 100. In addition, a driving roller 104, a driven roller 105, and a roller member 106 are also provided. The driven roller 105 is disposed at a position facing the secondary transfer roller 107 for secondary transfer of the toner image on the intermediate transfer belt 8 to the sheet, and the drive roller 104 is rotated in the rotational direction of the intermediate transfer belt 102 ( With reference to the arrow H), it is provided downstream of the primary transfer roller 103 and upstream of the driven roller 105. The paper transport direction is indicated by an arrow I.

  A roller member 106 is disposed in the vicinity of the upstream side of the nip portion 108 formed between the photosensitive drum 100 and the intermediate transfer belt 8. Similar to the roller members 34, 35, 36, and 37, the roller member 106 is provided to narrow the interval between the photosensitive drum 100 and the intermediate transfer belt 102 in the vicinity of the upstream side of the nip portion 108.

  In the image forming apparatus shown in FIG. 4, a toner image of one color is formed on the surface of the photosensitive drum 100, and after the toner image is primarily transferred to the intermediate transfer belt 102, the toner image of the other color is transferred to the photosensitive member. The toner image is formed on the surface of the drum 100 and is primarily transferred onto the previously transferred toner image. In this manner, toner images are sequentially formed on the photosensitive drum 100 and are primarily transferred onto the intermediate transfer belt 102 so as to be primary transferred, whereby a color toner image is formed on the intermediate transfer belt 102 and the secondary transfer roller 107. Is transferred to a recording medium such as paper.

  Here, in performing the primary transfer, by controlling the rotation of the roller member 106 so that the peripheral speed of the roller member 106 is faster or slower than the peripheral speed of the photosensitive drum 100, the photosensitive drum is similar to the above. Since a speed difference can be provided between the intermediate transfer belt 100 and the intermediate transfer belt 102, it is possible to suppress the occurrence of image defects such as voids caused by providing the roller member 106 to prevent toner scattering.

  INDUSTRIAL APPLICABILITY The image forming apparatus and the image forming apparatus control method according to the present invention have an effect capable of suppressing adverse effects caused by preventing transfer scattering, and are useful as printers, copiers, facsimiles, and the like.

1 is a front configuration diagram schematically showing a copying machine according to a first embodiment of the present invention. 1 is a configuration diagram schematically showing the vicinity of an intermediate transfer belt 8 of a copying machine according to a first embodiment of the present invention. Partial enlarged schematic view of FIG. 1 is a front configuration diagram schematically showing an image forming apparatus according to a modification of the first embodiment of the present invention. Partial enlarged view of a conventional image forming apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 4 Black image formation part 5 Yellow image formation part 6 Cyan image formation part 7 Magenta image formation part 8 Intermediate transfer belt 9 Secondary transfer part 10 Fixing part 11 Cleaning device 12 Discharge roller pair 13 Discharge trays 14, 15, 16, 17 Primary Transfer roller 21, 22 Driven roller 24 Drive roller 25 Registration roller 26 Conveyor belt 34, 35, 36, 37 Roller member 40, 50, 60, 70 Photosensitive drum 41, 51, 61, 71 Charger 42, 52, 62, 72 Developing unit 43, 53, 63, 73 Cleaning unit 44, 54, 64, 74 Static eliminator 45, 55, 65, 75 Developing roller 46, 56, 66, 76 LSU

Claims (8)

A plurality of image carriers on which developer images are formed; and
An intermediate transfer body on which a plurality of developer images formed for each image carrier are transferred and superimposed;
A transfer member provided to face each of the plurality of image carriers with the intermediate transfer member interposed therebetween;
Of each nip portion formed by the image carrier and the intermediate transfer member, it is provided in contact with the intermediate transfer member in the vicinity of the upstream side of at least one of the nip portions, and in the vicinity of the upstream side of the nip portion. A roller member for narrowing an interval between the image carrier and the intermediate transfer member;
The rotation of the roller member and the image carrier is controlled so as to provide a speed difference between the circumferential speed of the roller member and the circumferential speed of the image carrier disposed near the downstream side of the roller member. And an image forming apparatus. A plurality of the roller members are provided,
The image forming apparatus according to claim 1, wherein the control unit controls the plurality of roller members so that peripheral speeds thereof are the same. One image carrier on which a plurality of developer images are sequentially formed on the surface;
An intermediate transfer body on which the plurality of developer images are transferred and superimposed;
A transfer member provided so as to face the image carrier with the intermediate transfer member interposed therebetween;
Provided in contact with the intermediate transfer body in the vicinity of the upstream side of the nip portion formed by the image carrier and the intermediate transfer body, and the image carrier and the intermediate transfer body in the vicinity of the upstream side of the nip portion. A roller member for narrowing the gap between,
The rotation of the roller member and the image carrier is controlled so as to provide a speed difference between the circumferential speed of the roller member and the circumferential speed of the image carrier disposed near the downstream side of the roller member. And an image forming apparatus. The controller is
The rotation of the roller member and the image carrier is controlled so that the circumferential speed of the roller member is faster than the circumferential speed of the image carrier arranged near the downstream side of the roller member. The image forming apparatus according to any one of 1 to 3. The plurality of developer images are images of black, yellow, cyan, and magenta toners,
The image forming apparatus according to claim 1, wherein the intermediate transfer member is a belt-like member wound around the transfer member and the roller member. A plurality of image carriers on which developer images are formed, an intermediate transfer member on which a plurality of developer images formed for each of the image carriers are transferred and superimposed, and the intermediate transfer member interposed therebetween Near the upstream side of at least one of the transfer members provided to face each of a plurality of image carriers and at least one nip formed by the image carrier and the intermediate transfer member And a roller member for reducing the distance between the image carrier and the intermediate transfer member in the vicinity of the upstream side of the nip portion. And
The rotation of the roller member and the image carrier is controlled so as to provide a speed difference between the circumferential speed of the roller member and the circumferential speed of the image carrier disposed near the downstream side of the roller member. A control method for an image forming apparatus, comprising a control step. One image carrier on which a plurality of developer images are sequentially formed on the surface, an intermediate transfer member on which the plurality of developer images are transferred and overlaid, and facing the image carrier across the intermediate transfer member A transfer member provided in contact with the intermediate transfer member in the vicinity of the upstream side of each nip formed by the image carrier and the intermediate transfer member, and upstream of the nip. A control method for an image forming apparatus, comprising a roller member for narrowing a gap between the image carrier and the intermediate transfer member in the vicinity,
The rotation of the roller member and the image carrier is controlled so as to provide a speed difference between the circumferential speed of the roller member and the circumferential speed of the image carrier disposed near the downstream side of the roller member. And a control step for controlling the image forming apparatus. The control step includes
The step of controlling the rotation of the roller member and the image carrier so that the circumferential speed of the roller member is faster than the circumferential speed of the image carrier disposed in the vicinity of the downstream side of the roller member. A method for controlling an image forming apparatus according to claim 6 or 7.

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