JP2008102164A - Image forming apparatus - Google Patents

Abstract

The object is to reduce the maximum load torque applied to a motor, to reduce the size and cost of the motor, and to extend the service life.
A monochrome mode includes a color mode in which an image is formed by using all Y, C, M, and Bk toner image forming units and a monochrome mode in which an image is formed by using only a Bk toner image forming unit. In this case, a contact / separation device 100 is provided to keep the primary transfer roller 12 carrying an image formed by the Y, C, M toner image forming means away from the intermediate transfer belt 11 at least until the primary transfer is completed. The contact / separation operation of the primary transfer roller 12 carrying the image formed by other toner image forming means and the intermediate transfer belt 11 is performed at a timing shifted for each toner color.
[Selection] Figure 3

Description

  The present invention relates to an image forming apparatus, and more particularly, a first mode in which an image is formed using all of a plurality of toner image forming units, and an image is formed using only at least one or more toner image forming units. The present invention relates to an image forming apparatus having a second mode for performing the above.

  In an image forming apparatus, demand for full-color output increases, and an output speed similar to monochrome is desired. Therefore, a tandem type color image forming apparatus has attracted attention. The tandem type electrophotographic apparatus includes a direct transfer system in which images on each photoconductor are sequentially transferred to a sheet conveyed by a sheet conveying belt by a transfer device, and an image on each photoconductor by a primary transfer device. There is an indirect transfer type in which images are sequentially transferred to an intermediate transfer member and then transferred onto a sheet by a secondary transfer device.

  As such an image forming apparatus, Patent Document 1 discloses a tandem type image forming apparatus. When an image read by a scanner is determined to be a single black color, a color photosensitive member other than black is separated from the intermediate transfer member. , A black monochromatic image is formed and primary transferred onto the intermediate transfer member, and the color photoconductor is brought into contact with the intermediate transfer member when the rear end of the black monochrome image is primary transferred onto the intermediate transfer belt. Has been.

In Patent Document 2, an intermediate transfer member to which a toner image developed on a photosensitive member is transferred while being rotated a plurality of times, and a sheet material is provided as an intermediate transfer member that is provided so as to be capable of being pressed and separated from the intermediate transfer member. In an image forming apparatus comprising a transfer roller for transferring a toner image on an intermediate transfer member to a sheet material while being pressed and conveyed to the shaft, a shaft provided rotatably, two cams provided on the shaft, and one end side thereof A push arm that abuts against the cam and has the other end abutting against a rotary bearing provided on one end of the transfer roller, and by shifting the phase of the two cams, the transfer roller becomes an intermediate transfer member. On the other hand, the timing of moving from the separated state to the contact state is described in which one end side in the longitudinal direction of the transfer roller contacts the intermediate transfer member before the other end side. This is the operation when the secondary transfer roller is brought into contact with each other in order at the end portions of the secondary transfer roller in the longitudinal direction so as to contact the intermediate transfer member from one side of the secondary transfer roller.
JP 2003-43770 A JP 2005-91725 A

  In recent years, image forming apparatuses are required to be reduced in size and energy saving, and the maximum load torque applied to the motor is reduced, and the motor is required to be reduced in size and price and extended in life.

  However, in Patent Document 1, the deterioration of both of the image carrier and the intermediate transfer member due to the contact between the image carrier and the intermediate transfer member in the intermediate transfer type tandem image forming apparatus is reduced, and the image carrier and the intermediate transfer member have a long life. In order to achieve this, the intermediate transfer and the image carrier are separated from each other.

  Further, the device described in Patent Document 2 does not mention the driving load and the load direction with respect to the operation, and is configured to operate in parallel with the longitudinal direction when the secondary transfer roller is separated.

  As described above, the techniques described in Patent Document 1 and Patent Document 2 reduce the maximum load torque applied to the motor, and no consideration is given to the reduction in size and price of the motor and the extension of the service life.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of reducing the maximum load torque applied to a motor and reducing the motor size and cost and extending the service life.

  According to a first aspect of the present invention, in the image forming apparatus, a plurality of image carriers, a plurality of toner image forming units that individually form toner images of a predetermined color on the plurality of image carriers, and the image carriers. A toner image on the plurality of image carriers, and sequentially transferring and superimposing the toner images on the plurality of image carriers onto the transfer material or a recording medium conveyed on the transfer material. An image forming apparatus for forming a combined toner image, the first mode for forming an image using all the toner image forming means, and at least one toner image forming means without using at least one toner image forming means A second mode in which an image is formed using the toner, and when forming an image in the second mode, an image formed by a toner image forming unit that is not used for image formation is supported at least until the transfer is completed. The image carrier In the image forming apparatus provided with the contact / separation device that is separated from the surface of the photoconductor, the contact / separation device contacts the transfer body with an image carrier that carries an image formed by a toner image forming unit that is not used for the image formation. In the image forming apparatus, the separation operation is performed at a timing shifted in each toner color.

  According to a second aspect of the present invention, in the image forming apparatus, a plurality of image carriers, a plurality of toner image forming means for individually forming toner images of predetermined colors on the plurality of image carriers, and the image carriers The toner images on the plurality of image carriers are sequentially transferred and superimposed on the transfer body or a recording medium conveyed on the transfer body at a contact position with the transfer body. An image forming apparatus for forming a combined toner image, the first mode for forming an image using all the toner image forming means, and at least one toner image forming means without using at least one toner image forming means And an image forming apparatus driven in a second mode in which image formation is performed using toner, and when forming an image in the second mode, toner that is not used for image formation until at least the primary transfer is completed Formed by image forming means In the image forming apparatus provided with the contact / separation device that separates the image carrier that carries the image from the surface of the transfer body, the contact / separation device is configured to form an image formed by a toner image forming unit that is not used for the image formation. The contacting / separating operation of the image carrier to be carried and the transfer member is performed at a timing shifted at each end in the longitudinal direction of the transfer roller disposed inside the transfer member so as to face the image carrier or the image carrier. An image forming apparatus.

  According to a third aspect of the present invention, in the image forming apparatus, a plurality of image carriers, a plurality of toner image forming units that individually form toner images of a predetermined color on the plurality of image carriers, and the image carriers. The toner images on the plurality of image carriers are sequentially transferred and superimposed on the transfer body or a recording medium conveyed on the transfer body at a contact position with the transfer body. An image forming apparatus for forming a combined toner image, the first mode for forming an image using all the toner image forming means, and at least one toner image forming means without using at least one toner image forming means A second mode in which an image is formed using the toner, and when forming an image in the second mode, an image formed by a toner image forming unit that is not used for image formation is supported at least until the transfer is completed. The image carrier In the image forming apparatus provided with the contact / separation device that is separated from the surface of the photoconductor, the contact / separation device contacts the transfer body with an image carrier that carries an image formed by a toner image forming unit that is not used for the image formation. The separation operation is performed at a timing shifted for each toner color, and at a timing shifted at each end in the longitudinal direction of the transfer roller disposed inside the transfer body or facing the image carrier. The image forming apparatus is characterized.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the first or third aspect, the contact / separation device separates the transfer roller that stretches the transfer member in order from the end of the transfer roller. It is characterized by that.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the contact / separation device operates to contact / separate a load direction for separating and holding the image carrier or the transfer roller. It is different from the load direction.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the contact / separation device is configured such that when the image carrier or the transfer roller moves vertically downward, all of the image carrier or the transfer device. The roller moves at the same timing.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the second or third aspect, the contact / separation device includes a rotation drive source, and when the image carrier or the transfer roller is returned to the contact position, it is opposite to the separation. The rotary drive source is driven in the direction.

  According to an eighth aspect of the present invention, in the image forming apparatus according to the second or third aspect, the driving of the transfer body is stopped during the contact / separation operation of the transfer roller.

  According to the image forming apparatus of the present invention, when the photosensitive member and the transfer belt are separated from each other and the driving of the photosensitive member is stopped, the contact / separation timing of the transfer roller is shifted. The load torque can be reduced, and the motor can be reduced in size and price and extended in life.

  Embodiments as the best mode for carrying out the present invention will be described below with reference to the drawings.

  Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram illustrating a configuration of an image forming apparatus according to an embodiment. This image forming apparatus is a tandem type color printer. As shown in FIG. 1, the color printer includes a transfer belt unit 10 having an intermediate transfer belt 11 and an image carrier corresponding to each color of yellow (Y), cyan (C), magenta (M), and black (Bk). The image stations having the photosensitive drums 20Y, 20C, 20M, and 20Bk are arranged, and around the photosensitive drums 20Y, 20C, 20M, and 20Bk, dedicated charging devices 30Y, 30C, 30M, and 30Bk are developed. Apparatuses 50Y, 50C, 50M, and 50Bk and cleaning apparatuses 40Y, 40C, 40M, and 40Bk are arranged.

  The toner bottle 9 for replenishing toner is filled with toners of yellow (Y), cyan (C), magenta (M), and black (Bk) from the left in the drawing. A predetermined replenishment amount is supplied to each color developing device 50Y, 50C, 50M, 50Bk.

  In this color printer, the transfer paper 2 as a recording medium is fed from the paper feed cassette 1 by the paper feed roller 3, and when the leading edge of the transfer paper 2 reaches the resist roller pair 4, it is detected by a sensor (not shown), and this detection signal The transfer paper 2 is conveyed to the nip portion between the secondary transfer roller 5 and the intermediate transfer belt 11 by the registration roller pair 4 while taking the timing.

  The photosensitive drums 20Y, 20C, 20M, and 20Bk, which are uniformly charged in advance by the charging devices 30Y, 30C, 30M, and 30Bk, are exposed and scanned with the laser beam by the optical writing device 8, and the photosensitive drums 20Y, 20C, and 20M. , 20Bk, an electrostatic latent image is created.

  The electrostatic latent images are developed by the developing devices 50Y, 50C, 50M, and 50Bk for the respective colors, and yellow, cyan, magenta, and black toner images are formed on the surfaces of the photosensitive drums 20Y, 20C, 20M, and 20Bk.

Next, a voltage is applied to the primary transfer rollers 12Y, 12C, 12M, and 12Bk, and the toner on the photosensitive drums 20Y, 20C, 20M, and 20Bk is sequentially transferred onto the intermediate transfer belt 11. At this time, the image forming operation for each color is executed while shifting the timing from the upstream side toward the downstream side so that the toner image is transferred to the same position on the intermediate transfer belt 11.

The image formed on the intermediate transfer belt 11 is conveyed to the position of the secondary transfer roller 5 and is secondarily transferred to the transfer paper 2. The transfer paper 2 on which the toner images of the respective colors are transferred is conveyed to the fixing device 6 and thermally fixed, and is discharged by the paper discharge roller 7.

  The residual toner on the photosensitive drums 20Y, 20C, 20M, and 20Bk is cleaned by the respective cleaning devices 40Y, 40C, 40M, and 40Bk, and then the charging devices 30Y and 30B in which the bias of the AC component is superimposed and applied to the direct current. 30C, 30M, and 30Bk are charged simultaneously with static elimination to prepare for the next image formation. The residual toner on the intermediate transfer belt 11 is cleaned by the intermediate transfer belt cleaning device 13 to prepare for the next image forming process.

  The developing device 50 includes a developing case 55 having an opening, a developing roller 51 disposed so as to face and face the surface of the photosensitive drum 20, a developing blade 52 that regulates the developer on the developing roller 51 to a certain height, The first conveying screw 53 and the second conveying screw 54 are arranged at positions facing the roller 51.

  The cleaning device 40 includes a cleaning case 43 having an opening, a cleaning blade 41 for cleaning residual toner on the photosensitive drum 20, and a waste toner screw 42 for transporting the cleaned waste toner to a waste toner bottle (not shown). Etc.

  The transfer belt unit 10 includes an intermediate transfer belt 11, a primary transfer roller 12 for transferring a toner image on the photosensitive drum 20 to the intermediate transfer belt 11, an intermediate transfer belt case 14 for holding these components, and the like. Has been.

  In the figure, reference numeral 30 indicates a charging roller as a charging device, 31 indicates a cleaning roller for the charging roller, and L indicates laser light from the optical writing device 8.

  Next, the fixing device 6 will be described. FIG. 2 is a schematic configuration diagram illustrating an example of a fixing device. The fixing device 6 includes a fixing belt 61 as a fixing member, a fixing roller 62, a heating roller 63, and a pressure roller 68 as a pressure member. The fixing belt 61 is an endless belt member and is wound around the heating roller 63 and the fixing roller 62. The heating roller 63 incorporates a heating means 64 such as a halogen lamp in a metal core, and the fixing belt 61 is heated from the inside via the heating roller 63 by this radiant heat. Here, the fixing roller 62 and the pressure roller 68 have a metal core and silicone rubber. The heating roller 63 is an aluminum or iron hollow roller, and the fixing belt 61 has a silicone rubber layer and a release layer on a polyimide or nickel base material.

  Further, a temperature sensor element 65 such as a thermistor is disposed on the heating roller 63 via a belt, and the heating means is controlled so as to reach the set temperature based on the temperature detection of the temperature sensor element 65. Further, the fixing roller 62 is pressed and contacted by an urging means such as a spring (not shown) through the fixing belt 61 to form a fixing nip portion through which the transfer paper 2 passes. The pressure roller 68 is rotationally driven by a driving unit (not shown), and the fixing roller 62 is rotated by the pressure roller 68. Further, the fixing device 6 is provided with a tension roller 66 that contacts the vicinity of the center portion of the fixing belt. The tension roller 66 pressurizes the fixing belt 61 inward by a spring 67, whereby a tension is applied to the fixing belt 61. In this embodiment, the driving means is provided on the pressure roller 68 side. However, the driving means may be provided on the fixing roller 62 and the pressure roller 68 may be driven to rotate. Further, a separation member 69 is provided on the downstream side of the fixing nip portion in the sheet conveyance direction, and prevents the transfer sheet 2 from being wound around the fixing belt 61. A guide member (not shown) is disposed at a position facing the separating member 69, and guides the paper after the fixing nip to the downstream side together with the separating member.

  In the image forming apparatus according to the present embodiment, the color mode, which is the first mode for forming an image using all the Y, C, M, and Bk toner image forming means, and the Bk toner without using any other toner image forming means. Image formation can be performed in a monochrome mode, which is a second mode in which image formation is performed using image forming means.

  In this example, when switching from the color mode to the monochrome mode, the contact / separation device 100 is operated so that only the primary transfer roller 12Bk contacts the transfer belt as the intermediate transfer member.

  The contact / separation device of the image forming apparatus according to the embodiment will be described. FIG. 3 is a perspective view showing the contact / separation apparatus according to the first embodiment, and FIG. 4 is a side view of the contact / separation apparatus shown in FIG.

  The contacting / separating device 100 according to this example includes an approaching / separating moving cam 101 that is driven to rotate about an approaching / separating moving cam shaft 103, and a push-up member that is linearly driven by the contact / separating moving cam 101 coming into contact with the end thereof 102.

As shown in FIGS. 3 and 4, the push-up member 102 includes four push-up portions 104Bk, 104M, 104C, and 104C linearly corresponding to the four primary transfer rollers 12Bk, 12M, 12C, and 12Y. It is configured. Further, the push-up portions 104Bk, 104M, 104C, and 104C form a slope portion s and flat portions 106Bk, 106M, 106C, and 106Y, respectively.

  The push-up member 102 is disposed near both ends of the primary transfer rollers 12Y, 12C, 12M, and 12Bk of the image forming apparatus, and the contact / separation moving cam shaft 103 is connected to a single contact / separation drive motor (not shown). ing.

  The interval P1 between the push-up portions 104Bk, 104M, 104C, and 104C of the push-up member 102 is formed to be larger than the interval P2 between the primary transfer rollers 12Bk, 12M, 12C, and 12Y. When driven linearly, the primary transfer roller 12Y, the primary transfer roller 12C, the primary transfer roller 12M, and the primary transfer roller 12Bk are pushed up in the order of the push-up portion 104Y, the push-up portion 104C, the push-up portion 104M, and the push-up portion 104Bk. .

  That is, when the contact / separation moving cam 101 rotates in the direction of the arrow in FIGS. 3 and 4, the push-up member 102 moves in the horizontal arrow direction, and the primary transfer rollers 12Y, 12C, 12M, and 12Bk are in the order described above. That is, it is pushed up by the slopes 105Bk, 105M, 105C, and 105Y from the downstream side with respect to the intermediate transfer belt running direction.

  In order to set the image-type sincerity device in the color mode to the monochrome mode using such a contact / separation device 100, the contact / separation moving cam 101 is rotated by driving a contact / separation drive motor (not shown). With the rotation of the contact / separation moving cam 101, the push-up member 102 moves in the direction of the arrow in FIG. 3, and the primary transfer roller 12Y is pushed up by the push-up portion 104Y, and then the primary transfer roller 12C is pushed up by the push-up portion 104C. The primary transfer roller 12M is pushed up by the portion 104M. Then, only the primary transfer roller 12Bk is brought into contact with the intermediate transfer belt 11. When all the primary transfer rollers 12Bk, 12M, 12C, and 12Y are separated from the intermediate transfer belt 11, the push-up member 102 is pushed out, and all the primary transfer rollers 12Bk, 12M, and 12C are pushed by the push-up portions 104Bk, 104M, 104C, and 104C. , 12Y may be pushed up.

  At this time, the primary transfer rollers pushed up by the push-up member 102 are shifted one by one, so that the load of the contact / separation drive motor that drives the contact / separation moving cam 101 pushes a plurality of primary transfer rollers at a time. It will be lighter than At this time, the load by the primary transfer rollers 12Y, 12C, 12M, and 12Bk in the separated holding state is perpendicular to the moving direction of the push-up member and does not work in the contact / separation operation direction.

  Therefore, according to the image forming apparatus of the present embodiment, the photosensitive drum and the intermediate transfer belt are separated from each other by moving the primary transfer roller that is pressed down from the inner side of the intermediate transfer belt and in contact with the photosensitive drum in a direction to escape from the photosensitive drum. Since the contact timing of the primary transfer roller is shifted when stopping photoconductor drive, the maximum load torque applied to the motor for contact / separation drive is reduced, and the motor is reduced in size, cost and life. Can be achieved.

  In this example, the shape of the push-up member 102 is as described above, but the shape of the push-up portion of the push-up member can be changed in order to realize the desired push-up state of the primary transfer roller.

  Next, another embodiment will be described. FIG. 5 is a perspective view showing a contact / separation device according to another embodiment, and FIG. 6 is a side view of the contact / separation device shown in FIG.

  The contact / separation device 200 according to this example includes a pair of contact / separation cams 204a and 204b, contact / separation cams 205a and 205b, and contact / separation cams in the vicinity of both ends of the primary transfer rollers 12Y, 12C, 12M, and 12Bk. 206a, b and contact cams 207a, b are arranged.

  The four pairs of contact / separation cams 204a, b, 205a, b, 206a, b, 207a, b can be plate cams having the same contour shape, and the primary transfer rollers that are in contact with each other by rotating. It has a contour that pushes up a certain amount, and then the primary transfer roller falls by its own weight. The shape of each contact / separation cam can be appropriately modified so that the primary transfer roller has a desired movement.

  Further, the respective contact / separation cams 207a, b, 206a, b, 206a, b, 207a, b are interlocked by a shaft and a gear (not shown) and are rotationally driven by one contact / separation drive motor. The contact / separation cam is rotated in the direction of the arrow in the drawing so that the primary transfer rollers 12Y, 12C, 12M, and 12Bk are sequentially pushed up in the vertical arrow direction to the separation holding state along the contour of the cam. Yes.

  Furthermore, the contact / separation cams arranged at both ends of the primary transfer rollers 12Y, 12C, 12M, and 12Bk are fixed with a predetermined phase difference and given the same rotation angle as shown in FIG. Sometimes, the timing at which the primary transfer rollers 12Y, 12C, 12M, and 12Bk start to be pushed up is shifted.

  For example, regarding the contact / separation cam 204a and the contact / separation cam 204b disposed on both sides of the primary transfer roller 12Bk, the contact / separation cam 204a pushes up the primary transfer roller 12Bk earlier than the contact / separation cam 204b, and then the contact / separation cam 204b The primary transfer roller 12Bk is pushed up.

  Further, the load caused by the primary transfer rollers 12Y, 12C, 12M, and 12Bk pushed up to the separated holding state by the contact / separation cam acts only on the rotation center direction load of the contact / separation cam, and does not work in the contact / separation operation direction.

  When the color mode is changed to the monochrome mode, the contact / separation cam rotation is stopped when the three primary transfer rollers 12Y, 12C, and 12M are pushed up to the separated holding state, and the monochrome mode is ready. When the primary transfer rollers 12Y, 12C, and 12M are returned from the separated holding state to the contact position in order to change from the monochrome mode to the color mode, the contact / separation cam is further rotated in the direction of the arrow in the drawing, and the maximum arc of the cam shape is formed. All the primary transfer rollers 12Y, 12C, 12M, and 12Bk are moved to the contact positions at the positions where they are interrupted.

  Note that the push-up timing of the primary transfer roller can be arbitrarily set by changing the outline of the contact / separation cam and the installation phase. That is, by making the shape of the contact / separation cam and the phase of the contact / separation cam predetermined, the push-up timing of the primary transfer roller is the push-up timing on each color of Y, M, C, Bk, and also on both sides of each color. Can be shifted.

  Further, in order to change the image forming apparatus from the monochrome mode to the color mode, a contact / separation drive motor (not shown) is rotated in the reverse direction so that the contact / separation cams 207a, b, 206a, b, 206a, The primary transfer rollers 12Y, 12C, 12M, and 12Bk can be sequentially moved in the direction opposite to the vertical arrow by rotating b, 207a, and b. In this case, the primary transfer rollers 12Y, 12C, 12M, and 12Bk are brought into contact with the surface of the photosensitive drums 20Y, 20C, 20M, and 20Bk in one direction in the longitudinal direction of the roller. From the end of the intermediate transfer belt 11 and from the primary transfer roller upstream of the running direction of the intermediate transfer belt 11.

  Therefore, according to the image forming apparatus of the present embodiment, the photosensitive drum and the intermediate transfer belt are separated from each other by moving the primary transfer roller that is pressed down from the inner side of the intermediate transfer belt and in contact with the photosensitive drum in a direction to escape from the photosensitive drum. Since the contact timing of the primary transfer roller is shifted when stopping photoconductor drive, the maximum load torque applied to the motor for contact / separation drive is reduced, and the motor is reduced in size, cost and life. Can be achieved.

  In the above embodiment, the image forming apparatus is described as a color printer having an intermediate transfer belt. However, the present invention is also applicable to a direct transfer type image forming apparatus. The image forming apparatus can also be a copying machine equipped with a document reading unit, a facsimile machine equipped with a communication device, or the like.

1 is a schematic configuration diagram illustrating a configuration of an image forming apparatus according to an embodiment. FIG. 2 is a schematic configuration diagram illustrating an example of a fixing device. 1 is a perspective view illustrating an approach / separation device of an image forming apparatus according to a first embodiment. It is a side view of the contacting / separating apparatus shown in FIG. It is a perspective view which shows the contact / separation apparatus of the image forming apparatus which concerns on a 2nd Example. FIG. 6 is a side view of the contacting / separating device shown in FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Paper feed cassette 2 Transfer paper 3 Paper feed roller 4 Registration roller pair 5 Secondary transfer roller 6 Fixing device 7 Paper discharge roller 8 Device 9 Toner bottle 10 Transfer belt unit 11 Intermediate transfer belt 12Y, 12C, 12M, 12Bk Primary transfer roller 13 Intermediate transfer belt cleaning device 14 Intermediate transfer belt case 20Y, 20C, 20M, 20Bk Photoconductor drum 30Y, 30C, 30M, 30Bk Charging device 40Y, 40C, 40M, 40Bk Cleaning device 41 Cleaning blade 42 Waste toner screw 43 Cleaning case 50Y , 50C, 50M, 50Bk Developing device 51 Developing roller 52 Developing blade 53 First conveying screw 54 Second conveying screw 55 Developing case 61 Fixing belt 62 Fixing roller 63 Heating roller 64 Heating means 65 Temperature sensor element Child 66 Tension roller 67 Spring 68 Pressure roller 69 Separating member 100 Contacting / separating device 101 Contacting / separating moving cam 102 Pushing member 103 Contacting / separating moving cam shaft 104Bk, 104M, 104C, 104C Push-up part 105Bk, 105M, 105C, 105Y Slope 106Bk, 106M, 106C, 106Y Flat part 200 Contact / separation device 204a, b Contact / separation cam 205a, b Contact / separation cam 206a, b Contact / separation cam 207a, b Contact / separation cam

Claims (8)

A plurality of image bearing members, a plurality of toner image forming means for individually forming toner images of a predetermined color on the plurality of image bearing members, and a transfer member that can come into contact with the image bearing member. An image forming apparatus for sequentially transferring toner images on the image bearing member onto the transfer member or a recording medium conveyed on the transfer member at a position in contact with the transfer member to form a superimposed toner image. ,
A first mode in which an image is formed using all the toner image forming means, and a second mode in which an image is formed without using at least one toner image forming means and using one or more toner image forming means. And when forming an image in the second mode, at least until the transfer is completed, an image carrier that carries an image formed by a toner image forming unit that is not used for image formation is separated from the surface of the transfer member. In an image forming apparatus provided with a contact / separation device to be placed,
The contact / separation device performs the contact / separation operation of an image carrier that carries an image formed by a toner image forming unit that is not used for image formation and a transfer member at a timing shifted in each toner color. Forming equipment. A plurality of image bearing members, a plurality of toner image forming means for individually forming toner images of a predetermined color on the plurality of image bearing members, and a transfer member that can come into contact with the image bearing member. An image forming apparatus for sequentially transferring toner images on the image bearing member onto the transfer member or a recording medium conveyed on the transfer member at a position in contact with the transfer member to form a superimposed toner image. ,
A first mode in which an image is formed using all the toner image forming means, and a second mode in which an image is formed without using at least one toner image forming means and using one or more toner image forming means. An image forming apparatus to be driven, which forms an image in the second mode, and carries an image formed by a toner image forming unit that is not used for image formation at least until the primary transfer is completed. In an image forming apparatus provided with a contact / separation device for separating the transfer member from the surface of the transfer member,
The contact / separation device performs the contact / separation operation between the image carrier that carries an image formed by a toner image forming unit that is not used for the image formation and the transfer member, on the inner side of the transfer member facing the image carrier or the image carrier. An image forming apparatus, wherein the image forming apparatus is performed at a timing shifted at each end in the longitudinal direction of the transfer roller disposed. A plurality of image bearing members, a plurality of toner image forming means for individually forming toner images of a predetermined color on the plurality of image bearing members, and a transfer member that can come into contact with the image bearing member. An image forming apparatus for sequentially transferring toner images on the image bearing member onto the transfer member or a recording medium conveyed on the transfer member at a position in contact with the transfer member to form a superimposed toner image. ,
A first mode in which an image is formed using all the toner image forming means, and a second mode in which an image is formed without using at least one toner image forming means and using one or more toner image forming means. And when forming an image in the second mode, at least until the transfer is completed, an image carrier that carries an image formed by a toner image forming unit that is not used for image formation is separated from the surface of the transfer member. In an image forming apparatus provided with a contact / separation device to be placed,
The contact / separation device performs the contact / separation operation of an image carrier that carries an image formed by a toner image forming unit that is not used for image formation and a transfer member at a timing shifted in each toner color, and the image carrier or An image forming apparatus, wherein the image forming apparatus is performed at a timing shifted at each end portion in the longitudinal direction of a transfer roller disposed inside the transfer member so as to face the image carrier.   The image forming apparatus according to claim 1, wherein the contact / separation device separates the transfer roller that stretches the transfer member in order from the end of the transfer roller.   4. The image according to claim 1, wherein the contact / separation device has a load direction for separating and holding the image carrier or the transfer roller different from an operation load direction for causing the contact / separation operation. Forming equipment.   4. The image forming apparatus according to claim 1, wherein when the image carrier or the transfer roller moves vertically downward, all of the image carrier or the transfer roller moves at the same timing.   4. The contact / separation device includes a rotation drive source, and drives the rotation drive source in a direction opposite to that when separating the image carrier or the transfer roller to return to the contact position. Image forming apparatus. 4. The image forming apparatus according to claim 2, wherein the driving of the transfer body is stopped during the contact / separation operation of the transfer roller.