JP4386168B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile using an electrophotographic method, and more particularly to an image forming apparatus provided with an intermediate transfer member.

  In the image forming apparatus, the toner image primarily transferred from a latent image carrier such as a photosensitive member to an intermediate transfer member such as an intermediate transfer belt is secondarily transferred onto a recording medium such as transfer paper. Then, after the secondary transfer, the transfer residual toner remaining on the intermediate transfer member is removed from the intermediate transfer member by a cleaning means such as a cleaning blade that contacts the surface of the intermediate transfer member and scrapes the transfer residual toner. ing.

  In this image forming apparatus, when the cleaning blade is separated from the surface of the intermediate transfer member, a streak-like cleaning mark (hereinafter referred to as a separation line) is generated. As a result, the separation line is transferred to the intermediate transfer in the next image forming process. There arises a problem that the toner image is primarily transferred onto the body. Therefore, conventionally, the separation timing of the cleaning unit is controlled on the basis of the toner image primarily transferred onto the intermediate transfer member so that the separation line of the cleaning unit does not enter the image area.

However, even if the above-mentioned separation line is formed in the non-image area, the following problem occurs. This will be described with reference to FIG. In the figure, 3 is an image carrier, 6a is a developing roller, 10 is a driving roller, 11 is a driven roller, 12 is an intermediate transfer member, 13 is a primary transfer roller, and 15 is a secondary transfer roller. As shown in FIG. 4A, the separation stripe formed in the non-image area is formed on the side of the secondary transfer roller 15 when the secondary transfer roller 15 contacts the intermediate transfer body 12 immediately before the secondary transfer. The two-roller stains 24 become attached. Then, when the secondary transfer to the recording medium S is completed and the secondary transfer roller 15 is separated from the intermediate transfer body 12, as shown in FIG. Will adhere (see Patent Document 1).
JP 2002-82533 A

  FIG. 2 is a diagram illustrating a state in which the two-roller roller smear line 24 passes through the primary transfer position T1. FIG. (A) shows a state in which the adhesion position C1 of the 2-roller roller streak 24 of the intermediate transfer body 12 advances to the primary transfer position T1, and FIG. FIG. 8C shows a state where the position reaches the position T1, and FIG. 8C shows a state where the two-roller roller smear line 24 passes through the primary transfer position T1 and the electrostatic latent image formed on the image carrier 3 is developed by the developing roller 6a. Is shown.

  By the way, when the inventor conducted various experiments, it was found that the following problems occur. That is, when the latent image writing operation is performed on the image carrier 3 when the two-roller roller smear 24 is at the primary transfer position T1 as shown in FIG. It was found that density unevenness and color misregistration due to speed unevenness of the carrier 3, so-called banding occurred. This is because if there is a two-roller smear line (toner) between the intermediate transfer member 12 and the image carrier 3, the frictional force between them decreases, and as a result, the image carrier slips and speed fluctuation occurs. It is caused by that.

FIG. 3 is a diagram showing experimental data obtained by measuring the speed fluctuation of the image carrier. In this experiment, the peripheral speed of the intermediate transfer member is set 0.7% faster than the peripheral speed of the image carrier, and Bk (black), C (cyan), M (magenta), and Y (yellow) are set on the intermediate transfer member. The toner images are transferred in this order. In FIG. 2, the vertical axis represents speed unevenness, the horizontal axis represents time,
(Rotation speed of the intermediate transfer member−Rotation speed of the image carrier) / Rotation speed of the image carrier × 100 Therefore, the plus of the unevenness of the speed is slower than the intermediate transfer member, and the minus of the unevenness of the speed is It shows that the image carrier is faster than the intermediate transfer member. Here, the first large speed irregularity appears because of the disturbance of the signal that hits the belt joint of the encoder that detects the rotation, and it is ignored because it does not indicate the disturbance of the rotation directly.

  According to this, it can be seen that when the two-roller roller smear of the intermediate transfer member comes to the primary transfer position, remarkable speed unevenness occurs as shown by the arrows in FIG.

  This phenomenon is particularly remarkable when there is a speed difference between the rotation of the image carrier 3 and the intermediate transfer member 12. Hereinafter, a case where the intermediate transfer member 12 has a higher peripheral speed than the image carrier 3 will be described. Generally, a frictional force and an electrostatic attraction force act between the image carrier 3 and the intermediate transfer member 12, and the image carrier 3 is driven to be pulled by the intermediate transfer member 12 by these two forces. However, if the secondary transfer roller smear line (toner) is locally present in the primary transfer region, the frictional force of that portion rapidly decreases, and the force with which the intermediate transfer member 12 pulls the image carrier 3 decreases. As a result, the speed of the image carrier 3 is instantaneously decreased. When a latent image is written on the image carrier 3 at this time, the writing position is shifted, and the above banding occurs.

  The speed fluctuation of the image carrier 3 is further promoted by the cleaning means for the image carrier 3. Hereinafter, a case where a cleaning blade is used as the cleaning means will be described. The cleaning blade uses a stick-slip phenomenon to remove toner. Accordingly, stress is always applied to the tip of the cleaning blade, and when the speed of the image carrier 3 is decreased for a moment, the stress at the tip of the blade is released, thereby further promoting the speed fluctuation.

  Further, at the primary transfer position T1, the electrostatic attraction force acts between the image carrier 3 and the intermediate transfer member 12 as described above, and the speed variation also depends on this force. That is, even if the frictional force due to the separating muscle is reduced, if the electrostatic attraction force is large, the influence of the change can be reduced. Conversely, if the electrostatic attraction force is weak, the speed fluctuation becomes large.

  In short, the above banding problem occurs when toner is present at the primary transfer position between the image carrier 3 and the intermediate transfer body 12 in the non-image area on the intermediate transfer body 12. Even when the roller contacts the intermediate transfer body 12, the two-roller roller streaks adhere.

  Further, the above banding problem occurs even if toner streaks adhere to the area of the image carrier 3 corresponding to the non-image area on the intermediate transfer body 12. FIG. 4 is a diagram for explaining this. As shown in FIG. 4A, in the rotary developing device, when the developing roller 6a of each color comes into contact with the image carrier 3, the contact stripe 25 adheres to the image carrier 3 due to the impact, and FIG. As shown in the drawing, the contact stripe 25 reaches the primary transfer position T1, and a part of the contact stripe 25 is transferred to the non-image area of the intermediate transfer body 12 as shown in FIG. The electrostatic latent image that has passed and formed on the image carrier 3 is developed by the developing roller 6a.

  Also in this case, when the latent image writing operation is performed on the image carrier 3 when the contact position B1 of the contact stripe 25 is at the primary transfer position T1 as shown in FIG. It was found that fluctuations occurred and density unevenness and color misregistration due to speed unevenness of the image carrier 3, so-called banding occurred.

  FIG. 5 is a diagram showing experimental data obtained by measuring the speed variation of the image carrier. According to this, it can be seen that when the abutment stripe of the image carrier 3 comes to the primary transfer position, remarkable speed unevenness occurs as shown by the arrows.

  The present invention solves the above-mentioned conventional problems, even if toner streaks adhere to a non-image area on the intermediate transfer member or an image carrier corresponding to the non-image region and the speed of the image carrier changes. An object of the present invention is to provide an image forming apparatus capable of preventing the occurrence of banding without being affected by the influence.

Therefore, the image forming apparatus of the present invention includes a latent image forming unit that forms an electrostatic latent image on an image carrier, a developing unit that develops the electrostatic latent image into a toner image, and the toner image as an intermediate transfer member. a primary transfer unit that transfers the provided intermediate transfer member secondary transfer means for the transferred toner image onto a recording medium, and the image bearing member corresponding non-image area or that on the intermediate transfer body In the image forming apparatus having a member that performs separation and contact operations with the intermediate transfer member or the image carrier or a member that performs drive and stop operations in the region, any one of the separation, contact, drive, and stop forming measures image the consisting intermediate transfer body traveling direction upstream side of the non-image areas on the surface image including the position of the intermediate transfer member corresponding to the intermediate transfer member or the image bearing member performs an operation, the measures image after starting passing through the transfer position Characterized by starting the latent image formed by said latent image forming means so as not to overlap with the measures image.
Further, the member that performs the separation and contact operation is a member selected from any one or more of a secondary transfer roller , a developing roller, an image carrier cleaning unit, and a contact charging unit .
Further, in the transfer position, wherein the circumferential speed of the intermediate transfer member and the image bearing member is different.
Further, the image carrier and the intermediate transfer member, characterized in that it is driven through a gear train from each one of the drive motor.
more than

  According to the present invention, it is possible to reduce the fluctuation in the speed of the image carrier caused by the toner streaks adhering to the non-image area on the intermediate transfer body or the area of the image carrier corresponding thereto, and to prevent the occurrence of banding. Can do.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 6 is a diagram showing an embodiment of an image forming apparatus according to the present invention. In the figure, 1 is an image forming apparatus, 2 is a main body case, 3 is an image carrier such as a photoconductor, 4 is a charging device, 5 Is an exposure device (latent image forming means), 6 is a rotary developing device (developing means), 7 is a photoreceptor cleaner, 12 is an intermediate transfer member comprising an intermediate transfer belt, 13 is a primary transfer roller (transfer means), 15 Is a secondary transfer roller, 16 is a power supply device, 17 is a paper feed tray, 20 is a fixing device, and 21 is a paper discharge tray.

  As shown in FIG. 6, the image forming apparatus 1 according to the present embodiment includes a paper discharge tray 21 formed on the upper portion of the main body case 2 and a front cover 2 a that is openably and detachably inserted on the front surface. In the main body case 2, a rotary developing device 6 having a plurality of developing cartridges, an image carrier 3 on which an electrostatic latent image is formed and developed to form a toner image, and a toner image on the image carrier 3 are displayed. An intermediate transfer unit to be transferred, a control unit for controlling each drive motor and bias, a power supply device 16, a paper feed tray 17 for storing a recording medium, a fixing device 20 for fixing a toner image on the recording medium, and the like are provided. Yes. A paper transport unit 19 for transporting the recording medium from the paper feed tray 17 to the fixing device 20 through the secondary transfer roller 15 is disposed in the front cover 2a. Each unit and device is configured to be detachable from the main body, and can be removed and repaired or replaced integrally during maintenance or the like.

  The photoreceptor 3 as an image carrier has a thin cylindrical conductive substrate and a photosensitive layer formed on the surface thereof. On the outer periphery of the photoconductor 3, a charging device 4 for uniformly charging the photoconductor 3 along the rotation direction, an exposure device 5 for forming an electrostatic latent image on the photoconductor 3, an electrostatic latent A developing device 6 for developing an image, an intermediate transfer belt 12 for transferring a toner image on the photoconductor 3, a photoconductor cleaner 7 for cleaning the surface of the photoconductor 3 after the primary transfer, and the like are provided. Yes.

  The intermediate transfer unit is composed of a driving roller 10 and a driven roller 11 and an endless intermediate transfer belt 12. The intermediate transfer unit is wound around both rollers 10 and 11 and is driven in the direction of the arrow in the drawing to transfer the toner image on the photoreceptor 3. An intermediate transfer belt 12, a primary transfer roller 13 that is disposed on the back surface of the intermediate transfer belt 12 so as to face the photoreceptor 3 and primarily transfers the toner image on the photoreceptor 3 to the intermediate transfer belt 12, and intermediate transfer A transfer belt cleaning unit 14 that removes residual toner on the belt 12 and a drive roller 10 are arranged to face the four-color full-color toner image formed on the intermediate transfer belt 12 as a recording medium (paper or the like). ) And a secondary transfer roller 15 for secondary transfer.

  A power supply device 16 is disposed below the exposure device 5, and a paper feed cassette 17 is disposed at the bottom of the main body case 2. A recording medium in the paper feed cassette 17 is a pickup roller 18, a sheet material conveyance path. 19, the secondary transfer roller 15, and the fixing device 20 are conveyed to the paper discharge tray 21. The paper feed cassette 17 is attached to the front of the apparatus by a handle 17b so that it can be pulled out, and an auxiliary cassette 17a is attached so that it can be pulled out so as to protrude toward the rear of the apparatus so as to cope with a large paper size. Yes.

  In the image forming apparatus 1 configured as described above, when an image forming signal is input to the exposure device 5, the photoconductor 3, the developing roller 6 a of the rotary developing device 6, and the intermediate transfer are performed in accordance with the drive motor and bias control by the control unit. The belt 12 is rotationally driven, and first, the outer peripheral surface of the photoreceptor 3 is uniformly charged by the charging device 4. Thereafter, the exposure device 5 selectively exposes the surface of the photoreceptor 3 in accordance with the image information to form an electrostatic latent image. At this time, the developing device 6 rotates so that the developing roller 6 a of the developing cartridge comes into contact with the photoreceptor 3. As a result, a toner image of an electrostatic latent image is formed on the photoreceptor 3. The toner image formed on the photoreceptor 3 is transferred onto the intermediate transfer belt 12 by the primary transfer roller 13 to which a primary transfer voltage having a polarity opposite to the toner charging polarity is applied, and remains on the photoreceptor 3. The remaining toner is removed by the photoreceptor cleaner 7.

  In the full-color image forming apparatus, development cartridges 6Y, 6M, 6C, and 6K for yellow Y, magenta M, cyan C, and black K are detachably mounted on the rotary developing device 6. In the image forming operation, the exposure device 5 selectively exposes the surface of the photoreceptor 3 in accordance with image information of the first color, for example, yellow Y, to form a yellow Y electrostatic latent image. At this time, the rotary developing device 6 rotates so that the developing roller 6a of the yellow Y developing cartridge 6Y contacts the photoconductor 3, and a yellow Y electrostatic latent image toner image is formed on the photoconductor 3. Subsequently, the toner image is transferred onto the intermediate transfer belt 12 by the primary transfer roller 13 to which a primary transfer voltage having a polarity opposite to the charging polarity of the toner is applied.

  During this time, the transfer belt cleaning means 14 and the secondary transfer roller 15 are separated from the intermediate transfer belt 12. A four-color full-color image is obtained by repeating this series of processes corresponding to the second color, the third color, and the fourth color of the image formation signal, thereby obtaining yellow Y, Magenta M, cyan C, and black K toner images are sequentially superimposed and transferred from the photoreceptor 3 onto the intermediate transfer belt 12. Note that the order of yellow Y, magenta M, cyan C, and black K is arbitrary.

  The recording medium on the paper feed tray 17 is conveyed from the pickup roller 18 to the secondary transfer roller 15 through the registration roller and the sheet material conveyance path 19 at the timing when the superimposed image of each color toner image reaches the secondary transfer roller 15. The secondary transfer roller 15 is pressed against the intermediate transfer belt 12 and a secondary transfer voltage is applied to transfer the toner image on the intermediate transfer belt 12 onto the recording medium. The recording medium onto which the toner image has been transferred in this manner is conveyed to the fixing device 20, and the toner image on the recording medium is heated and pressed by the fixing device 20 to be fixed. The toner remaining on the intermediate transfer belt 12 is removed by the cleaning unit 14.

  In the case of double-sided printing, the recording medium exiting the fixing device 20 is switched back so that its trailing edge is the leading edge, and is supplied again to the secondary transfer roller 15 via the double-sided printing conveyance path 22. The full-color toner image on the intermediate transfer belt 12 is transferred onto the recording medium, is heated and pressed again by the fixing device 20, and is discharged onto the paper discharge tray 21.

  In the rotary developing device 6 according to the present embodiment, the four developing cartridges 6Y, 6M, 6C, and 6K are detachably mounted as described above to form a four-color full-color image forming apparatus. As the forming apparatus, only the black K developing cartridge 6K is mounted and mounted, and the developing cartridge 6K waits at the standby position (home position), and the black K developing cartridge 6K rotates from the standby position during image formation. The electrostatic latent image on the photoreceptor 3 may be developed into a toner image at the development position. This makes it possible to use the developing device 6 with the same design specifications for full color and mono color, and maintenance management and design compared to designing an image forming apparatus dedicated to full color and mono color by sharing full color and mono color. Manufacturing costs can be greatly reduced.

  Next, a mechanism related to the speed unevenness of the image carrier will be described. FIG. 7 is a diagram for explaining a drive system for the image carrier 3 and the intermediate transfer member 12 of FIG. A drive gear 3a is connected to one end of the image carrier 3, and the drive gear 3a is connected to an output gear 23a of the drive motor 23 via transmission gears 3b and 3c. A driving gear 10a is connected to one end of the driving roller 10 that drives the intermediate transfer body 12, and is connected to an output gear 23a of the driving motor 23 through a transmission gear 10b.

  Thus, since the image carrier 3 and the intermediate transfer member 12 are each driven by the single drive motor 23 through the gear train, there is a minute gap in the meshing portion of the gear, and the primary transfer portion. When the frictional force between the image carrier 3 and the intermediate transfer member 12 is changed, the gear meshing portion is shaken, and the peripheral speed of the image carrier 3 or the intermediate transfer member 12 is changed. Speed unevenness will occur.

  8 to 12 are diagrams for explaining an embodiment of the present invention. FIG. 8 is a diagram showing an outline of an operation sequence of the color image forming apparatus. FIG. 9 is a diagram for explaining the operation of FIG. 10 is a diagram showing the positional relationship between the two-roller streaks and the countermeasure image, FIG. 11 is a diagram showing measurement data, and FIG. 12 is a diagram showing a modification of FIG.

  FIG. 8 shows the vsync signal, the image signal, the color switching operation of the developing device, the developing operation, the primary transfer position, and the secondary transfer roller operation. This operation sequence will be described with reference to FIGS. The surface of the image carrier 3 is uniformly charged by the charging device 4 and the image signal is turned on in synchronization with the vsync signal. First, an electrostatic latent image 26 ′ as a countermeasure image is formed on the surface of the image carrier 3. Is done. Next, the surface of the image carrier 3 is selectively exposed according to the first color image information to form an electrostatic latent image. At this time, the developing device 6 rotates so that the first color developing roller 6a contacts the image carrier 3, and a countermeasure image and a first color toner image are formed on the image carrier 3, and then 1 The countermeasure image 26 and the first color toner image are transferred onto the intermediate transfer body 12 by the primary transfer roller 13 to which the next transfer voltage is applied.

  During this time, the transfer belt cleaning unit 14 and the secondary transfer roller 15 are separated from the intermediate transfer body 12. In a four-color full-color image, this series of processing is repeatedly executed corresponding to the second color, the third color, and the fourth color of the image formation signal, so that a toner image corresponding to the content of each image formation signal is obtained. From the image carrier 3, the images are sequentially superimposed and transferred onto the intermediate transfer body 12. The recording medium S is conveyed to the secondary transfer roller 15 at a timing when the superimposed image of each color toner image reaches the secondary transfer roller 15, and the secondary transfer roller 15 is pressed against the intermediate transfer belt 12 and 2. The next transfer voltage is applied, and the toner image on the intermediate transfer body 12 is transferred onto the recording medium S.

  Next, the toner remaining on the intermediate transfer belt 12 is removed by the cleaning unit 14. The cleaning unit 14 is in contact with the intermediate transfer body 12 after the trailing edge of the third color image has passed the cleaning blade position, and the leading edge of the first color image of the (second) image formed in the next step. Is separated from the intermediate transfer body 12 before reaching the cleaning blade position. By the separation contact of the cleaning unit 14, the toner image on which the fourth color is superimposed is transferred to the recording medium S, and the toner remaining on the intermediate transfer body 12 is removed by the cleaning unit 14.

  When the secondary transfer is completed, the secondary transfer roller 15 is separated from the intermediate transfer body 12, and the secondary transfer roller streak 24 adheres to the intermediate transfer body 12 at this time. In this embodiment, as shown in FIG. Further, in the non-image area (area where the transfer image is not formed) G of the intermediate transfer body 12, the surface image is located upstream of the separation position C 1 on the intermediate transfer body 12 by the secondary transfer roller 15 in the traveling direction of the intermediate transfer body 12. The countermeasure image 26 is formed. After the countermeasure image 26 starts to pass the primary transfer position T1, the image signal is turned on after a predetermined time t to start image writing and form an electrostatic latent image. Yes. Accordingly, since the countermeasure image 26 passes before the secondary transfer roller streak 24 reaches the primary transfer position T1, it is possible to reduce rapid fluctuations in the frictional force between the image carrier 3 and the intermediate transfer body 12. Further, the speed unevenness of the image carrier 3 can be reduced.

FIG. 11 is a diagram showing experimental data obtained by measuring the speed variation of the image carrier. In this experiment, the peripheral speed of the intermediate transfer member is set 0.7% faster than the peripheral speed of the image carrier, and Bk (black), C (cyan), M (magenta), and Y (yellow) are set on the intermediate transfer member. The toner images are transferred in this order. In FIG. 11, the vertical axis represents speed unevenness, the horizontal axis represents time,
(Rotation speed of the intermediate transfer member−Rotation speed of the image carrier) / Rotation speed of the image carrier × 100 Therefore, the plus of the unevenness of the speed is slower than the intermediate transfer member, and the minus of the unevenness of the speed is It shows that the image carrier is faster than the intermediate transfer member. Here, the first large speed irregularity appears because of the disturbance of the signal that hits the belt joint of the encoder that detects the rotation, and it is ignored because it does not indicate the disturbance of the rotation directly.

  According to this, it can be seen that when the two-roller roller smear of the intermediate transfer member comes to the primary transfer position, the speed unevenness is reduced as shown by the arrows in FIG.

  FIG. 12 is a diagram for explaining a modification of the embodiment of FIG. 10, and is a diagram showing a positional relationship between the secondary transfer roller stripes and the countermeasure image. In this embodiment, the countermeasure image 26 is formed so as to include the secondary transfer roller stripes 24, and control is performed so that an electrostatic latent image is formed by writing an image while the countermeasure image 26 passes through the primary transfer position T1. is doing. In the present embodiment, it is possible to further reduce the rapid fluctuation of the frictional force between the image carrier 3 and the intermediate transfer member 12, and to reduce the speed unevenness of the image carrier 3.

  13 to 17 show another embodiment of the present invention, FIG. 13 is a diagram showing an outline of an operation sequence of the color image forming apparatus, FIG. 14 is a diagram for explaining the operation of FIG. 13, and FIG. FIG. 16 is a diagram showing the positional relationship between the two-roller streaks and the countermeasure image, FIG. 16 is a diagram showing measurement data, and FIG. 17 is a diagram showing a modification of FIG.

  FIG. 13 shows a vsync signal, an image signal, a developing contact operation, and a primary transfer position. This operation sequence will be described with reference to FIGS. The surface of the image carrier 3 is uniformly charged by the charging device 4 and the image signal is turned on in synchronization with the vsync signal. First, the electrostatic latent image 26 ′ of the countermeasure image 26 is formed on the surface of the image carrier 3. It is formed. Next, the surface of the image carrier 3 is selectively exposed according to the first color image information to form an electrostatic latent image. At this time, the developing device 6 rotates so that the first color developing roller 6a contacts the image carrier 3, and the countermeasure image 26 and the first color toner image are formed on the image carrier 3, and subsequently. The countermeasure image 26 and the first color toner image are transferred onto the intermediate transfer body 12 by the primary transfer roller 13 to which the primary transfer voltage is applied.

  During this time, the transfer belt cleaning unit 14 and the secondary transfer roller 15 are separated from the intermediate transfer body 12. In a four-color full-color image, this series of processing is repeatedly executed corresponding to the second color, the third color, and the fourth color of the image formation signal, so that a toner image corresponding to the content of each image formation signal is obtained. From the image carrier 3, the images are sequentially superimposed and transferred onto the intermediate transfer body 12. The recording medium is conveyed to the secondary transfer roller 15 at a timing when the superimposed images of the respective color toner images reach the secondary transfer roller 15, and the secondary transfer roller 15 is pressed against the intermediate transfer belt 12 and the secondary transfer roller 15. A transfer voltage is applied, and the toner image on the intermediate transfer body 12 is transferred onto the recording medium.

  Next, the toner remaining on the intermediate transfer belt 12 is removed by the cleaning unit 14. The cleaning unit 14 comes into contact with the intermediate transfer body 12 after the rear end of the third color image has passed the cleaning blade position, and corresponds to the first color of the (second) image formed in the next step. Is separated from the intermediate transfer body 12 before reaching the cleaning blade position. By the separation and contact of the cleaning unit 14, the toner image on which the fourth color is superimposed is transferred to the recording medium, and the toner remaining on the intermediate transfer body 12 is removed by the cleaning unit 14.

  At the time of contact (contact) of the developing roller with the image carrier 3, as shown in FIG. 14, development contact stripes 25 are generated on the image carrier 3, but in this embodiment, as shown in FIG. 15. In the non-image area (area where the transfer image is not formed) G of the intermediate transfer body 12, the countermeasure image 26 composed of a surface image is located upstream of the development contact position B 1 on the image carrier 3 in the traveling direction of the intermediate transfer body 12. After the countermeasure image 26 starts to pass through the primary transfer position T1, the image signal is turned on after a predetermined time t, and image writing is started to form an electrostatic latent image. Accordingly, since the countermeasure image 26 passes before the development contact stripe 25 reaches the primary transfer position T1, there is no sudden change in the frictional force between the image carrier 3 and the intermediate transfer member 12, and the image carrier 3 is not affected. Speed unevenness can be reduced.

  FIG. 16 is a diagram showing experimental data obtained by measuring the speed fluctuation of the image carrier. In this experiment, the peripheral speed of the intermediate transfer member is set 0.7% faster than the peripheral speed of the image carrier, and the toner image is transferred to the intermediate transfer member. According to FIG. 16, it can be seen that when the development contact stripe passes the primary transfer position, the speed unevenness does not occur at the position indicated by the arrow.

  FIG. 17 is a diagram for explaining another embodiment of the present invention and is a diagram showing a positional relationship between the development contact stripe 25 and the countermeasure image. In the present embodiment, the countermeasure image 27 is formed so as to include the development contact stripe 25, and the countermeasure image 26 is controlled to start image writing after the passage of the primary transfer position T1 and form an electrostatic latent image. ing. In this embodiment, the frictional force between the image carrier 3 and the intermediate transfer member 12 is not rapidly changed, and the speed unevenness of the image carrier 3 can be further reduced.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, in the above-described embodiment, the example of the separation of the secondary transfer roller or the contact of the developing roller has been described. However, toner streaks also occur due to the contact of the secondary transfer roller or the separation of the developing roller. You may apply. Further, the adhesion of the toner streaks to the image carrier also occurs when the image carrier cleaning means comes in contact with and separates from the contact charging means such as a charging brush. Is possible. In short, in an image forming apparatus having a member that performs separation and contact operations or a member that performs drive and stop operations in a non-image region on the intermediate transfer member or a region of an image carrier corresponding thereto, the separation, contact, A countermeasure image is formed upstream of the position on the intermediate transfer member where the driving or stopping operation is performed, and the intermediate image starts to pass through the transfer position. It is characterized by starting image formation.

  In the above embodiment, the electrostatic latent image is formed on the image carrier by the exposure device. However, the electrostatic latent image may be formed by a charging / writing device. It is defined as an image forming means. Although the intermediate transfer belt has been described in the above embodiment, it can be applied to an intermediate transfer drum, and in the present invention, these are defined as intermediate transfer members.

It is a figure which shows the process by which the 2 rolling-roller stain | fouling streaks adhere to an intermediate transfer body. It is a figure which shows the state in which 2 rolling-roller stain | pollution | contamination stripe | line passes a transfer position. It is a figure which shows the experimental data which measured the speed fluctuation | variation of the image carrier by the 2 rolling-roller stain | pollution | contamination streak. FIG. 6 is a diagram for explaining a process in which toner streaks adhere to an image carrier. It is a figure which shows the experimental data which measured the speed fluctuation | variation of the image carrier by a development contact stripe | line | muscle. 1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 5 is a diagram for explaining a drive system for the image carrier and the intermediate transfer member in FIG. 4. FIG. 2 is a diagram for explaining an embodiment of the present invention, and is a diagram showing an outline of an operation sequence of a color image forming apparatus. It is a figure for demonstrating the operation | movement of FIG. It is a figure which shows the positional relationship of a 2 rolling-roller line | wire and a countermeasure image. It is a figure which shows the measurement data of embodiment of FIG. It is a figure which shows the modification of FIG. It is a figure which shows the operation | movement sequence of other embodiment of this invention. It is a figure for demonstrating the operation | movement of FIG. It is a figure which shows the positional relationship of a development contact line and a countermeasure image. It is a figure which shows the measurement data of embodiment of FIG. It is a figure which shows the modification of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 ... Image carrier, 5 ... Latent image formation means, 6a ... Developing means, 12 ... Intermediate transfer body 13 ... Primary transfer roller (primary transfer means)
15 ... secondary transfer roller (secondary transfer means)
23 ... Drive motor, 3a-3c, 10a-10b ... Gear train 26 ... Countermeasure image C1 ... Separated position, B1 ... Contact position, T1 ... Primary transfer position (transfer position)

Claims (4)

A latent image forming means for forming an electrostatic latent image on the image carrier;
Developing means for developing the electrostatic latent image into a toner image;
Primary transfer means for transferring the toner image to an intermediate transfer member;
Secondary transfer means for transferring the toner image transferred to the intermediate transfer member to a recording medium;
With
In the intermediate non-image area of the transfer body or the image bearing member corresponding thereto region, the intermediate transfer body or spaced apart from the image bearing member, member or drive to perform the contact operation, an image having a member for stopping operation In the forming device,
The separation, abutting, driving the intermediate transfer body traveling direction upstream side of the non, including a position on the intermediate transfer member corresponding to the intermediate transfer member or the image bearing member performs one of operations of the stop Form a countermeasure image consisting of surface images in the image area ,
Image forming apparatus, characterized in that the countermeasure image starts a latent image formed by said latent image forming means so as not to overlap after starting passing through the transfer position, and the measures image. 2. The member that performs the separation and contact operation is a member selected from one or more of a secondary transfer roller , a developing roller, an image carrier cleaning unit, and a contact charging unit. Image forming apparatus. In the transfer position, the image forming apparatus according to claim 1 or 2 peripheral speed of said image bearing member and the intermediate transfer member are different from each other. It said image bearing member and the intermediate transfer member, the image forming apparatus according to claim 3, wherein the respectively driven from one drive motor through a gear train.

Images