JP2011002532A - Image forming apparatus and image forming method - Google Patents

Abstract

An image is transferred to a predetermined position of a transfer material with high accuracy while suppressing occurrence of image transfer deviation with respect to the transfer material.
A secondary transfer nip 11a is formed by pressing an intermediate transfer belt 8 carrying a toner image, a recess 14 on a peripheral surface thereof, and a transfer material 20 being pressed against the intermediate transfer belt 8 to form a secondary transfer nip 11a. The secondary transfer roller 12 that transfers the toner image carried on the intermediate transfer belt 8 to the transfer material 20, the intermediate transfer belt position detector 28 that detects the position of the intermediate transfer belt 8, and the rotation of the secondary transfer roller 12. The image forming apparatus 1 includes an encoder 26 that detects a position.
[Selection] Figure 1

Description

  The present invention relates to an electrophotographic image forming apparatus and an image forming method for forming an image by transferring a toner image onto a transfer material such as transfer paper.

  Conventionally, in an electrophotographic image forming apparatus, many image forming apparatuses that transfer a toner image on a photoreceptor to an intermediate transfer belt and transfer the toner image transferred to the intermediate transfer belt onto a transfer material such as transfer paper have been developed. Has been. As a conventional image forming apparatus having an intermediate transfer belt, a mark is formed on the intermediate transfer belt, and an image is formed on the photoreceptor based on the movement (rotation) position of the intermediate transfer belt obtained by detecting the mark with a sensor. There has been proposed a color image forming apparatus that eliminates transfer deviation of each color by writing (see, for example, Patent Document 1).

Further, the belt mark formed on the photosensitive belt is detected, and each image of the first color and the reference mark are written on the photosensitive belt. Further, the reference mark is transferred to the intermediate transfer belt and transferred to the intermediate transfer belt. There has been proposed a multicolor image forming apparatus that eliminates the transfer deviation of each color by writing the second and subsequent color images on the photosensitive belt based on the reference mark (see, for example, Patent Document 2).
As described above, in the image forming apparatuses described in Patent Documents 1 and 2, the image is written based on the movement (rotation) position of the intermediate transfer belt, thereby eliminating the transfer deviation, that is, the toner image position deviation. .

  On the other hand, an image forming apparatus has been proposed in which a transfer material gripping member is disposed in a recess formed in the transfer drum, and the toner image is transferred to the transfer material in a state where the transfer material is gripped by the transfer material gripping member. (For example, refer to Patent Document 3).

JP-A-7-92763. JP-A-7-325455. JP-A-3-4241.

  However, in the image forming apparatuses described in Patent Documents 1 and 2, it is difficult to determine the position of the toner image due to expansion / contraction of the intermediate transfer belt, slippage of the intermediate transfer belt driving roller with respect to the intermediate transfer belt, and the like. For this reason, an image transfer deviation occurs with respect to the transfer material, and it is difficult to transfer the toner image to a predetermined position of the transfer material with high accuracy.

  Further, in the image forming apparatus described in Patent Document 3 described above, transfer cannot be performed in the concave portion formed on the transfer drum. For this reason, if the toner image on the photoconductor reaches the transfer nip position when the concave portion of the transfer drum reaches the transfer nip position, the transfer of the image with respect to the transfer material will occur. Similarly, the toner image is transferred to the transfer material. It is difficult to transfer to a predetermined position with high accuracy.

  The present invention has been made in view of such circumstances, and an object thereof is to suppress the occurrence of transfer deviation of an image with respect to a transfer material and to transfer the image to a predetermined position of the transfer material with high accuracy. An image forming apparatus and an image forming method are provided.

In order to solve the above-described problems, in the image forming apparatus and the image forming method according to the present invention, the position of the image carried on the image carrier belt and the position of the recess formed on the transfer roller are detected. Therefore, it is possible to transfer the image of the image carrier belt to a predetermined position of the transfer material with high accuracy even if the transfer roller has a recess due to the image position and the recess position.
In particular, it is possible to prevent the transfer material from being supplied to the recess of the transfer roller by controlling the feeding timing of the transfer material based on the position of the recess.

  Further, when controlling the supply of the transfer material based on the position of the recess of the transfer roller, if the position of the recess is deviated from the position of the image carrier belt set in a predetermined relationship, The timing of starting the supply of the transfer material based on the position of the recess is corrected and controlled. In that case, the feeding start timing of the transfer material is adjusted so as to suppress the transfer deviation of the image with respect to the transfer material, which is caused by the influence of the positional deviation. As a result, even if a position shift occurs in the detection position of the recess, the image transfer position with respect to the leading end position of the transfer material can be controlled with higher accuracy. As a result, the image on the image carrier belt can be transferred to a predetermined position of the transfer material with higher accuracy.

  Further, the image writing start timing of the image writing unit is controlled based on the position of the image carrier belt. As a result, the image is carried at a predetermined position of the image carrier belt. In addition, the predetermined position of the image carrier belt can be controlled based on the position of the concave portion of the transfer roller. As a result, it is possible to transfer the image carried on the predetermined position of the image carrier belt to the predetermined position of the transfer material with high accuracy.

  Furthermore, in controlling the timing of image writing start by the image writing unit based on the position of the image carrier belt, the position of the image carrier belt is set to a position of the concave portion of the transfer roller in which the position is set to a predetermined relationship. When there is a deviation, the positional deviation is corrected and the timing of image writing by the image writing unit based on the position of the image carrier belt is controlled and adjusted. In this case, the image writing start timing of the image writing unit is adjusted so that the transfer deviation of the image with respect to the transfer material caused by the influence of the positional deviation is suppressed. As a result, even if a position shift occurs at the detection position of the image carrier belt, the image transfer position relative to the leading end position of the transfer material can be controlled with higher accuracy. As a result, the image on the image carrier belt can be transferred to a predetermined position of the transfer material with higher accuracy.

1 is a diagram schematically and partially showing an example of an embodiment of an image forming apparatus according to the present invention. (A) is a figure explaining the drive of an intermediate transfer belt and a secondary transfer roller, (b) is the figure seen from the IIB direction in (a). (A) is a view showing an intermediate transfer belt position detection mark formed on the intermediate transfer belt, and (b) is a partially enlarged view of the intermediate transfer belt position detection mark. It is a block diagram of control of an intermediate transfer belt, a secondary transfer roller drive motor, and a gate roller drive motor. It is a figure explaining basic sequence control of feeding of a transfer material. It is a figure explaining sequence control which adjusts feeding timing of a transfer material by position shift of a crevice. FIG. 6 is a block diagram of control of an intermediate transfer belt / secondary transfer roller driving motor and an exposure unit. FIG. 10 is a diagram for explaining sequence control for correcting and adjusting the exposure start of the exposure unit based on the position shift of the intermediate transfer belt.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a diagram schematically and partially showing a part of an embodiment of an image forming apparatus according to the present invention.
In this example, the image forming apparatus 1 forms an image using a liquid developer containing solid toner and a carrier liquid. As shown in FIG. 1, the image forming apparatus 1 is a photosensitive that is a latent image carrier of yellow (Y), magenta (M), cyan (C), and black (K) arranged in tandem horizontally or substantially horizontally. The body 2Y, 2M, 2C, 2K is provided. Here, each photoreceptor 2Y, 2M,
In 2C and 2K, 2Y represents a yellow photoreceptor, 2M represents a magenta photoreceptor, 2C represents a cyan photoreceptor, and 2K represents a black photoreceptor. Similarly, the members of the respective colors are represented by adding Y, M, C, and K of the respective colors to the reference numerals of the members.

Charging units 3Y, 3M, 3C, and 3K are provided around the photoreceptors 2Y, 2M, 2C, and 2K, respectively. Further, exposure units 4Y, 4M, 4C, which are image writing units, are sequentially arranged from the respective charging units 3Y, 3M, 3C, 3K in the rotation direction α of the respective photoreceptors 2Y, 2M, 2C, 2K. 4K
The developing units 5Y, 5M, 5C, and 5K, the primary transfer units 6Y, 6M, 6C, and 6K, the neutralizing unit (not shown), and the photoconductor cleaning units 7Y, 7M, 7C, and 7K are disposed.

The image forming apparatus 1 also includes an endless intermediate transfer belt 8 that is an image carrier belt as well as a transfer belt. This intermediate transfer belt 8 is provided on each of the photoreceptors 2Y, 2M, 2C, 2K.
It is arranged above. The intermediate transfer belt 8 has primary transfer portions 6Y, 6M, 6C, 6
K is pressed against each of the photosensitive members 2Y, 2M, 2C, and 2K.

Although not shown, the intermediate transfer belt 8 includes a flexible base material such as a resin, an elastic layer such as a rubber layer formed on the surface of the base material, and a surface layer formed on the surface of the elastic layer. Is formed into a relatively soft elastic belt having a three-layer structure. Of course, the intermediate transfer belt 8 is not limited to this. The intermediate transfer belt 8 is stretched around an intermediate transfer belt driving roller 9 and an intermediate transfer belt tension roller 10 to which a driving force of a motor (not shown) is transmitted. As shown in FIG. 1, the intermediate transfer belt 8 is rotated in the rotation (movement) direction β in a tensioned state.
Note that the arrangement order of members such as photoconductors corresponding to the respective colors Y, M, C, and K is not limited to the example shown in FIG. 1 and can be arbitrarily set.

  On the intermediate transfer belt drive roller 9 side of the intermediate transfer belt 8, a secondary transfer unit 11 as a transfer device is provided. The secondary transfer unit 11 includes a secondary transfer roller 12 and a secondary transfer roller cleaning unit 13.

  The secondary transfer roller 12 has a concave portion 14 extending in the axial direction of the secondary transfer roller 12 on the outer peripheral surface thereof, and a rubber sheet wound around the outer peripheral surface of the arc portion of the base material 12 a excluding the concave portion 14. The sheet-like elastic member 12b is provided. In that case, although not shown, both end portions of the elastic member 12b are fixed to the side wall of the recess 14. A resistance layer is formed on the outer peripheral surface of the arc portion of the secondary transfer roller 12 by the elastic member 12b.

  Further, in the secondary transfer roller 12, the elastic member 12b is pressed against the intermediate transfer belt 8 by a biasing force of a biasing means such as a spring (not shown). As a result, a secondary transfer nip 11a is formed between the intermediate transfer belt 8 and the elastic member 12b of the secondary transfer roller 12 as shown in FIG. At this time, the intermediate transfer belt driving roller 9 functions as a backup roller against the pressing of the secondary transfer roller 12.

  Further, a transfer bias is applied to the secondary transfer roller 12. The secondary transfer roller 12 is transferred to the intermediate transfer belt 8 at the secondary transfer nip 11a by rotating in the rotation direction γ and applying a transfer bias when the intermediate transfer belt 8 moves in the movement direction β. The transferred toner image is transferred to a transfer material such as transfer paper.

  In the recess 14, a gripper 15 that is a transfer material gripping member, a gripper support portion 16 that is a transfer material gripping member receiving member on which the gripper 15 is seated, and a protruding claw 17 that is a transfer material peeling member are disposed. Although not shown, a predetermined number of grippers 15 are arranged along the axial direction of the secondary transfer roller 12, and each gripper 15 is configured in a comb-teeth shape. Further, the gripper support portions 16 are disposed corresponding to the grippers 15, and the protruding claws 17 are disposed between the comb teeth of the gripper 15 and outside the comb teeth positioned at both ends.

  The image forming apparatus 1 includes a gate roller 18 (corresponding to a transfer material feeding unit) that feeds a transfer material toward the secondary transfer nip 11a, and a transfer material supply guide 19 that guides the transfer material. When the toner image carried on the intermediate transfer belt 8 is secondarily transferred, the gate roller 18 supplies a transfer material to the secondary transfer nip 11a.

  Then, immediately before the concave portion 14 reaches the secondary transfer nip 11a, the gripper 15 rotates toward the gripper support portion 16 and is fed from the gate roller 18 to the leading end portion of the transfer material 20 fed in the feeding direction δ. 20a is gripped between the gripper support portion 16 and the gripper support portion 16. Further, after passing through the secondary transfer nip 11 a, the gripper 15 is rotated in a direction away from the gripper support portion 16 to release the grip of the leading end portion 20 a of the transfer material 20. Further, in parallel with the release of gripping of the transfer material by the gripper 15, the protruding claws 17 are protruded to the protruding position. As a result, the back surface of the front end portion of the transfer material 20 (the surface opposite to the transfer surface of the toner image of the transfer material) is protruded from each protrusion claw 17. In this way, the transfer material 20 is peeled off from the secondary transfer roller 12. Thereafter, each protruding claw 17 returns into the recess 14. The operations of the gripper 15 and the protrusion claw 17 are controlled by a gripper control cam and a protrusion claw control cam (not shown) as the secondary transfer roller 12 rotates.

  As shown in FIGS. 2A and 2B, the intermediate transfer belt driving roller 9 and the secondary transfer roller 12 are rotationally driven by the same intermediate transfer belt / secondary transfer roller driving motor 21. That is, the motor gear 22 and the intermediate transfer belt drive roller 9 are attached so that the driving force of the intermediate transfer belt / secondary transfer roller drive motor 21 can rotate integrally with the rotation shaft of the intermediate transfer belt / secondary transfer roller drive motor 21. Is transmitted to the intermediate transfer belt drive roller 9 via an intermediate transfer belt drive roller drive gear 23 attached to the rotary shaft 9a so as to be integrally rotatable. As a result, the intermediate transfer belt driving roller 9 rotates counterclockwise as indicated by an arrow in FIG. Further, the secondary transfer roller driving gear is attached so that the driving force of the intermediate transfer belt / secondary transfer roller driving motor 21 can rotate integrally with the motor gear 22, the intermediate gear 24, and the rotating shaft 12c of the secondary transfer roller 12. 25 to the secondary transfer roller 12. As a result, the secondary transfer roller 12 rotates clockwise as indicated by an arrow in FIG.

As shown in FIG. 1, on one end side of the secondary transfer roller 12, an encoder 26, which is a secondary transfer roller position detector (corresponding to a transfer roller position detection unit) that detects the rotational position of the secondary transfer roller 12, and A code wheel 27 is provided adjacent to the encoder 26. The code wheel 27 is composed of a disc having a slit (notch) 27 a and is provided on a rotation shaft (not shown) of the secondary transfer roller 12 so as to rotate integrally with the secondary transfer roller 12. Conventionally known encoders 26 and code wheels 27 can be used. The encoder 26 detects the rotational position of the slit 27 a of the code wheel 27 and outputs a secondary transfer roller position signal of the secondary transfer roller 12. That is, the rotational position of the secondary transfer roller 12 is detected. In this case, since the concave portion 14 is provided integrally with the secondary transfer roller 12, the rotational position of the secondary transfer roller 12 and the rotational position of the concave portion 14 do not change relatively, and both rotational positions are unambiguous. It is decided. Therefore, the secondary transfer roller position signal output from the encoder 26 is a recess position signal of the recess 14, and the encoder 26 and the code wheel 27 serve as a recess position detector that detects the rotational position of the recess 14.

  Further, an intermediate transfer belt position detector 28 (corresponding to a belt position detection unit) that detects the rotation (movement) position of the intermediate transfer belt 8 is disposed in the vicinity of the intermediate transfer belt tension roller 10. The intermediate transfer belt position detector 28 includes an optical sensor (not shown) such as a known light reflection type sensor or a light transmission type sensor, and one intermediate transfer belt 8 as shown in FIGS. 3 (a) and 3 (b). The intermediate transfer belt 8 is moved at an equal pitch in the moving direction β of the intermediate transfer belt 8 at an equal pitch or at a predetermined position on one side edge of the intermediate transfer belt 8. A predetermined number of intermediate transfer belt position detection marks 28a projecting in a direction orthogonal or substantially orthogonal. The intermediate transfer belt position detection mark 28a is moved to a region outside the image carrying region (primary transfer region) of the intermediate transfer belt 8 other than the example shown in FIGS. 3 (a) and 3 (b). If the position can be detected, the intermediate transfer belt position detection mark may be used. When the intermediate transfer belt 8 moves, the optical sensor detects these intermediate transfer belt position detection marks 28a, and the intermediate transfer belt position detector 28 performs intermediate transfer based on the intermediate transfer belt position detection marks detected by the optical sensor. An intermediate transfer belt position signal of the belt 8 is output. That is, the position of the intermediate transfer belt 8 is detected by the intermediate transfer belt position detector 28.

FIG. 4 is a block diagram of control of the intermediate transfer belt / secondary transfer roller driving motor and the gate roller driving motor.
As shown in FIG. 4, the intermediate transfer belt / secondary transfer roller drive motor 21 is controlled by an electronic control unit (control unit) 29 of the image forming apparatus 1. A gate roller driving motor 30 that drives the gate roller 18 is also controlled by the control unit 29. In that case, the control unit 29 drives and controls the gate roller drive motor 30 based on the secondary transfer roller position signal from the encoder 26 and the intermediate transfer belt position signal from the intermediate transfer belt position detector 28. This ensures that the transfer material 20 is positioned in the transfer image area other than the recess 14 of the secondary transfer roller 12. Accordingly, transfer defects caused by the transfer material 20 being positioned in the region of the recess 14 where transfer is not performed are prevented.

  Next, based on the rotation position of the intermediate transfer belt 8 and the rotation position of the concave portion 14 of the secondary transfer roller 12 in this embodiment, the sequence control of the rotation of the gate roller 18 will be described. In the image forming apparatus 1 of this example, the feeding timing of the transfer material 20 by the gate roller 18 is basically controlled based on the rotational position of the concave portion 14 of the secondary transfer roller 12.

FIG. 5 is a diagram showing a first embodiment which is basic sequence control of the feeding timing of the transfer material 20 in the image forming apparatus 1 of this example. The control unit 29 rotationally drives the intermediate transfer belt / secondary transfer roller drive motor 21 according to the image formation command signal. As shown in FIG. 5, when the first concave portion position signal (ON signal) is supplied from the encoder 26, the controller 29 determines that the concave portion 14 is secondary based on the concave portion position signal (ON signal). When the transfer roller 12 arrives just before it reaches the secondary transfer nip 11a in the rotational direction γ, the gate roller drive motor 30 receives the gate roller at the timing when the leading end 20a of the first transfer material 20 reaches the recess 14. A signal (ON signal) is output. Then, the gate roller drive motor 30 is driven to rotate. Accordingly, the gate roller 18 is rotated for feeding the first transfer material 20.

  Next, after the next second recess position signal (ON signal) is supplied from the encoder 26, the control unit 29 starts the rotation of the gate roller 18 after a predetermined time, that is, the rotation of the gate roller 18 is predetermined. When the rotation amount is reached, the output of the gate roller signal (ON signal) is stopped (gate roller signal: OFF). Then, the rotation of the gate roller 18 for feeding the first transfer material 20 stops. At this time, the first transfer material 20 is securely held by the gripper 15, guided to the outer peripheral surface of the transfer image area other than the concave portion of the secondary transfer roller 12, and conveyed toward the secondary transfer nip 11 a. After the second recess position signal (ON signal) is supplied, the gate roller 18 is rotated at the same timing as the first recess position signal (ON signal) described above, and the second transfer material 20 is transferred. Is sent. Further, when the third recess position signal (ON signal) is supplied from the encoder 26, the controller 29 controls the rotation of the gate roller 18 in the same manner as described above. When the next recess position signal (ON signal) from the encoder 26 is not supplied, the control unit 29 stops the rotation of the gate roller 18 after the previous rotation of the gate roller 18 reaches a predetermined rotation amount. At the same time, the rotation of the intermediate transfer belt / secondary transfer roller drive motor 21 is stopped after a predetermined time has elapsed since the rotation of the gate roller 18 was stopped. Thereby, the image forming operation of the image forming apparatus 1 is completed.

  During the transfer sequence control of the transfer material 20 in the first embodiment, the intermediate transfer belt position signal (ON signal) from the intermediate transfer belt position detector 28 is always in a constant relationship (fixed timing). For example, the concave portion position signal (ON signal) from the encoder 26 is supplied to the control unit 29 after a predetermined time has elapsed after the output of the intermediate transfer belt position signal (ON signal). Accordingly, a recess position signal (ON signal) based on the intermediate transfer belt position signal (ON signal) is supplied to the control unit 29. And the control part 29 outputs a gate roller signal (ON signal) to the gate roller drive motor 30 based on this recessed part position signal (ON signal). As a result, the gate roller 18 starts feeding the transfer material 20. Therefore, the image formable area of the transfer material 20 is surely positioned in the transfer image area other than the concave portion 14 of the secondary transfer roller 12, and the toner image primarily transferred to the intermediate transfer belt 8 is transferred at the time of secondary transfer. It is surely positioned in the image formable area. As a result, transfer defects caused by the transfer material 20 being positioned in the area of the recess 14 where transfer is not performed and the toner image of the intermediate transfer belt 8 being positioned outside the image formable area of the transfer material 20 are prevented. .

  In the image forming apparatus 1 of this example, the secondary transfer is performed in a state where the leading end portion 20 a of the transferred transfer material 20 is held by the gripper 15. Then, when the transfer material gripping portion by the gripper 15 passes through the secondary transfer nip 11a, the gripping of the transfer material 20 by the gripper 15 is released and the transfer material 20 comes to peel from the secondary transfer roller 12. At this time, it is protruded by the protruding claw 17 and is more reliably peeled off from the secondary transfer roller 12. Although not shown, the transfer material 20 peeled off from the secondary transfer roller 12 is transported to a fixing unit and the toner image of the transfer material is fixed, as in the conventional image forming apparatus, and then discharged to a waste transfer material tray.

According to the image forming apparatus 1 of the first embodiment, the position of the recess 14 formed in the secondary transfer roller 12 is controlled based on the movement (rotation) position of the intermediate transfer belt 8 and the controlled recess Based on the position 14, the timing for starting the supply of the transfer material 20 from the gate roller 18 is controlled. Therefore, the position of the transfer material 33 can be controlled with respect to the position of the recess 14, and when the recess 14 comes to the position of the secondary transfer nip 11 a, the transfer material 20 is positioned at the position of the secondary transfer nip 11 a, that is, the recess 14. Can be prevented from being fed to. Thereby, it is possible to suppress the occurrence of transfer deviation of the toner image with respect to the transfer material 20. As a result, the toner image transferred to the intermediate transfer belt 8 can be transferred to a predetermined position of the transfer material 20 with high accuracy.

  FIG. 6 is a sequence control of feeding the transfer material 20 by the gate roller 18 when the rotational position signal (ON signal) of the concave portion 14 of the secondary transfer roller 12 is shifted in the image forming apparatus 1 of this example. It is a figure which shows 2nd Example. In the second embodiment shown in FIG. 6, for example, the virtual peripheral length of the secondary transfer roller 12 (peripheral length of the secondary transfer roller 12 when the concave portion 14 is not provided) is 300 mm with respect to the intermediate transfer belt 8. In this example, the circumference is 600 mm, and the intermediate transfer belt position detection marks 28 a are formed on the intermediate transfer belt 8 at intervals of 300 mm. At this time, since the circumference of the intermediate transfer belt 8 is an integral multiple (2 times) of the virtual circumference of the secondary transfer roller 12, the intermediate transfer belt position signal is synchronized with the recess position signal. The circumference and the position where the intermediate transfer belt position detection mark 28a is disposed are the same as in the first embodiment.

  As shown in FIG. 6, in the sequence control for feeding the transfer material 20 of the second embodiment, the sequence control of the first embodiment is basically performed. By the way, the output timing of the concave position signal (ON signal) of the secondary transfer roller 12 from the encoder 26 is usually set due to a change in speed when the concave portion 14 of the secondary transfer roller 12 passes the position of the secondary transfer nip 11a. There may be a case where a deviation occurs with respect to the output timing. When a deviation occurs in the output timing of the recess position signal (ON signal) in this way, the gate roller signal (ON signal) is output at the output timing of the normal time (when no deviation occurs) in the first embodiment. Then, the transfer material 20 is not fed to the predetermined position of the secondary transfer roller 12, and the toner image on the intermediate transfer belt 8 is not transferred to the normal position of the transfer material 20.

  Therefore, in the second embodiment, the controller 29 detects the concave position signal (ON signal) from the encoder 26 and the intermediate transfer from the intermediate transfer belt position detector 28 during the execution of the sequence control of the first embodiment. The belt position signal (ON signal) is always compared. Then, the controller 29 does not supply the recess position signal (ON signal) to the intermediate transfer belt position signal (ON signal) in the above-described fixed relationship, and the time (output timing) is determined between the two signals. ) Is determined. For example, when the controller 29 determines that the timing of the recess position signal (ON signal) has shifted with respect to the timing of the intermediate transfer belt position signal (ON signal) when a certain number of transfer materials are fed, the shift is performed. Is used to control the output timing of the gate roller signal (ON signal).

For example, in FIG. 6, it is assumed that the recess position signal (ON signal) is output before the output of the intermediate transfer belt position signal (ON signal), and an output timing shift t ₁ occurs between the two signals in a certain relationship. At this time, since the output timing of the recess position signal (ON signal) is earlier than the output timing of the intermediate transfer belt position signal (ON signal), the transfer material is fed regardless of the intermediate transfer belt position signal (ON signal). When the next transfer is performed, the margin width of the leading end portion 20a of the transfer material 20 becomes large.

Therefore, when the deviation t ₁ is greater than or equal to the preset reference amount t ₀ , the control unit 29 determines that a deviation t ₁ greater than the reference amount t ₀ has occurred at the output timing of the recess position signal (ON signal). Judgment is made and the output timing of the gate roller signal (ON signal) is delayed. That is, the control unit 29 delays the output timing of the gate roller signal (ON signal) by time t ₂ from the output timing indicated by the two-dot chain line in FIG. 6 based on the recess position signal (ON signal) in the basic sequence control. The output timing is indicated by a solid line in FIG. In that case, the time t ₂ is set corresponding to t ₁ shift in shift t ₁ below along with greater than zero (0 <t ₂ ≦ t _1). In this way, the output timing of the gate roller signal (ON signal) is adjusted (corrected) based on the output timing deviation t ₁ of the recess position signal (ON signal), and the adjusted (corrected) gate roller signal (ON) Signal) output timing of the transfer material 20 of the transfer material 20 by the gate roller 18 is controlled. As a result, the image transfer position relative to the leading end position of the transfer material 20 can be controlled even if a deviation t ₁ greater than the reference amount t ₀ occurs in the output timing of the recess position signal (ON signal). As a result, the toner image on the intermediate transfer belt 8 is secondarily transferred with high accuracy by a predetermined position of the transfer material 20, and an increase in the margin width of the leading end 20a of the transfer material 20 is suppressed.

Further, it is assumed that the concave portion position signal (ON signal) is output later than a certain relationship from the output of the intermediate transfer belt position signal (ON signal), resulting in an output timing shift t ₁ ′ greater than the reference amount t ₀ . In this case, the control unit 29 controls the output timing of the gate roller signal (ON signal) to an output timing earlier than the normal output timing.
Other configurations of the second embodiment are the same as those of the first embodiment.

According to the second embodiment, when the supply of the transfer material 20 is controlled based on the rotation position of the recess 14, the position of the recess 14 is always compared with the movement (rotation) position of the intermediate transfer belt 8. When the position of the recess 14 is deviated from the movement (rotation) position of the intermediate transfer belt 8, the timing of starting the supply of the transfer material 20 with the position of the recess 14 as a reference is corrected by correcting the position shift. is doing. In that case, the feeding start timing of the gate roller 18 is adjusted (corrected) so that the transfer deviation of the toner image with respect to the transfer material, which is caused by the influence of the positional deviation, is suppressed. As a result, even if the position of the recess 14 is displaced, the image transfer position relative to the tip position of the transfer material 20 can be controlled with higher accuracy. As a result, the toner image transferred to the intermediate transfer belt 8 can be transferred to a predetermined position of the transfer material 20 with high accuracy.
Other functions and effects of the second embodiment are the same as those of the first embodiment.

Next, a third example which is another example of the embodiment of the image forming apparatus of the present invention will be described.
FIG. 7 is a block diagram of control of the intermediate transfer belt / secondary transfer roller drive motor and the exposure unit in the third embodiment.

In the image forming apparatus 1 of the third embodiment, the exposure start timing (image writing start timing) of the exposure units 4Y, 4M, 4C, and 4K is controlled based on the intermediate transfer belt position signal (ON signal). That is, as shown in FIG. 7, unlike the first and second embodiments, the control unit 29 of the third example is connected to the exposure units 4Y, 4M, 4C, 4K and not to the gate roller drive motor 30. .

FIG. 8 is a sequence control of image writing by the exposure units 4Y, 4M, 4C, and 4K when the position signal (ON signal) of the intermediate transfer belt 8 is shifted in the image forming apparatus 1 of this example. It is a figure which shows 3 Example. In the third embodiment shown in FIG. 8, for example, the secondary transfer roller 12 has a virtual peripheral length of 600 mm, and the intermediate transfer belt 8 has a peripheral length of 900 mm. This is an example when the position detection mark 28a is formed. In this example, the circumferential length of the intermediate transfer belt 8 is not an integral multiple of the virtual circumferential length of the secondary transfer roller 12, but the circumferential lengths of the both have the same common divisor, so the first and second implementations. As in the example, the intermediate transfer belt position signal is synchronized with the recess position signal.

As shown in FIG. 8, in the image forming apparatus 1 of the third embodiment, sequence control of the exposure start timing of the exposure units 4Y, 4M, 4C, and 4K is executed based on the intermediate transfer belt position signal. That is, the control unit 29 rotationally drives the intermediate transfer belt / secondary transfer roller drive motor 21 in accordance with the image formation command signal. As shown in FIG. 6, when the first intermediate transfer belt position signal (ON signal) is supplied from the intermediate transfer belt position detector 28, the controller 29 receives this intermediate transfer belt position signal (ON signal). The exposure units 4Y, 4Y, 4M, and 2K are each transferred to a predetermined position on the intermediate transfer belt 8 at the timing at which the toner images of the photoreceptors 2Y, 2M, 2C, 2K are primarily transferred.
Exposure start signals (ON signals) are output to 4M, 4C, and 4K, respectively. Then, each of the exposure units 4Y, 4M, 4C, and 4K starts exposure of the first photoconductors 2Y, 2M, 2C, and 2K in response to the exposure start signals (ON signals). 2M, 2C, and 2K are exposed for a predetermined time according to the latent images to be written. Then, for the second and subsequent exposures, the control unit 29 similarly outputs an exposure start signal (ON signal) based on predetermined (every other in the example shown in FIG. 8) intermediate transfer belt position signal (ON signal). .

In the sequence control of the exposure start in the third embodiment, it is always in a constant relation (constant timing) with respect to the concave position signal (ON signal) from the encoder 26, for example, after outputting the concave position signal (ON signal). After a certain period of time elapses, an intermediate transfer belt position signal (ON signal) from the intermediate transfer belt position detector 28 is supplied to the controller 29. Accordingly, the intermediate transfer belt position signal (ON signal) based on the recess position signal (ON signal) is supplied to the control unit 29. The control unit 29 outputs an exposure start signal (ON signal) to each of the exposure units 4Y, 4M, 4C, and 4K based on the intermediate transfer belt position signal (ON signal). As a result, each of the exposure units 4Y, 4M, 4C, and 4K starts exposure to the corresponding photoreceptors 2Y, 2M, 2C, and 2K, and a latent image is written on each of the photoreceptors 2Y, 2M, 2C, and 2K. It is. Therefore,
As a result, the toner image on the intermediate transfer belt 8 is surely positioned outside the region of the concave portion 14 of the secondary transfer roller 12 where the transfer is not performed. As a result, the toner image primary-transferred to the intermediate transfer belt 8 is reliably secondary-transferred to the transfer material 20, and transfer defects are prevented.

By the way, the output timing of the intermediate transfer belt position signal (ON signal) from the intermediate transfer belt position detector 28 is shifted due to expansion / contraction of the intermediate transfer belt 8 or slippage of the intermediate transfer belt 8 with respect to the intermediate transfer belt drive roller 9. It may occur. Therefore, in the third embodiment, during the execution of the exposure start sequence control, the control unit 29 determines the output timing of the intermediate transfer belt position signal (ON signal) and the output timing of the recess position signal (ON signal). Contrast always. Then, the control unit 29 does not supply the output timing of the intermediate transfer belt position signal (ON signal) with the above-described fixed relationship with respect to the output timing of the recess position signal (ON signal), and the output timing of both signals is constant. It is determined whether or not a deviation has occurred between the relationships. For example, if the timing of the intermediate transfer belt position signal (ON signal) is deviated from the timing of the recess position signal (ON signal) at a certain number of exposures, the control unit 29 sets each exposure unit based on this deviation. The output timing of each exposure start signal of 4Y, 4M, 4C, and 4K is controlled.

For example, in FIG. 8, it is assumed that the output of the intermediate transfer belt position signal (ON signal) is output before the recess position signal (ON signal), and an output timing shift t ₃ occurs between the two signals in a certain relationship. If the deviation t ₃ is greater than or equal to a preset reference amount t ₀ ′, the control unit 29 has caused a deviation t ₃ greater than the reference amount t ₀ ′ at the output timing of the intermediate transfer belt position signal (ON signal). And the output timing of the exposure start signal (ON signal) is delayed. That is, the control unit 29 sets the output timing of the exposure start signal (ON signal) in a two-dot chain line in FIG. 8 based on the intermediate transfer belt position signal (ON signal) in sequence control during normal time (when no deviation occurs). Control is performed to the output timing shown by the solid line in FIG. 8 delayed by time t ₄ from the output timing shown. In that case, the time t ₄ is set corresponding to t ₃ shift in shift t ₃ or less with greater than zero _{(0 <t 4 ≦ t 3} ). In this way, the output timing of each exposure start signal (ON signal) is adjusted based on the output timing deviation t ₃ of the intermediate transfer belt position signal (ON signal) (
Each exposure start is controlled at the output timing of the exposure start signal (ON signal) that has been corrected and adjusted (corrected).

Further, it is assumed that the intermediate transfer belt position signal (ON signal) is output later than a certain relationship from the output of the recess position signal (ON signal), and an output timing shift t ₃ ′ greater than the reference amount t ₀ ′ occurs. In this case, the control unit 29 controls the output timing of the exposure start signal (ON signal) to an output timing that is earlier than the normal output timing.

According to the image forming apparatus 1 of the third embodiment, the movement (rotation) position of the intermediate transfer belt 8 is controlled based on the position of the concave portion 14 formed in the secondary transfer roller 12, and the controlled intermediate Based on the position of the transfer belt 8, the exposure start timing of each of the exposure devices 4Y, 4M, 4C, and 4K is controlled. Accordingly, the exposure of the photosensitive members 2Y, 2M, 2C, and 2K by the exposure devices 4Y, 4M, 4C, and 4K is started (that is, the photosensitive members 2Y, 2M, and 2K are transferred to the intermediate transfer belt 8 at a predetermined position). 2C, 2K image writing start) timing can be controlled. Thereby, it is possible to suppress the occurrence of color misregistration of the toner images of the respective colors. Then, the position of the intermediate transfer belt 8 is controlled based on the rotational position of the concave portion 14 of the secondary transfer roller 12, so that the toner image transferred with the color shift suppressed to the intermediate transfer belt 8 is transferred to the transfer material 20. It becomes possible to transfer to a predetermined position with high accuracy.

Further, when the exposure start timing by the exposure devices 4Y, 4M, 4C, and 4K is controlled based on the position of the intermediate transfer belt 8, the moving position of the intermediate transfer belt 8 is always compared with the position of the recess 14. When the position of the intermediate transfer belt 8 is deviated from the position of the recess 14, the exposure start timing by each of the exposure devices 4Y, 4M, 4C, 4K with respect to the position of the intermediate transfer belt 8 is set to this position. Control is performed by correcting the deviation. In this case, the exposure start timing by each of the exposure devices 4Y, 4M, 4C, and 4K is adjusted so that the transfer deviation of the toner image with respect to the transfer material caused by the influence of the positional deviation is suppressed. As a result, even if the position of the intermediate transfer belt 8 is displaced, the image transfer position relative to the leading end position of the transfer material 20 can be controlled with higher accuracy. As a result, the toner image transferred to the intermediate transfer belt 8 can be transferred to a predetermined position of the transfer material 20 with high accuracy.
Other configurations and other functions and effects of the third embodiment are the same as those of the second embodiment.

  The image forming apparatus and the image forming method of the present invention are not limited to the examples of the above-described embodiments. For example, in the above-described example, the intermediate transfer belt 8 is used as the image carrier. However, an intermediate transfer drum can be used, and a photoconductor can be used as the image carrier. When a photoconductor is used as the image carrier, the toner image on the photoconductor is directly transferred to a transfer material. In each of the image forming apparatuses described above, the tandem type image forming apparatus is used. However, other types of image forming apparatuses or single color image forming apparatuses may be used. In short, the present invention can be modified in various ways within the scope of the matters described in the claims.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2Y, 2M, 2C, 2K ... Photoconductor, 5Y, 5M, 5C, 5K ... Developing part, 6Y, 6M, 6C, 6K ... Primary transfer part, 8 ... Intermediate transfer belt, 9 ... Belt drive Roller, 11 ...
Secondary transfer section, 11a ... secondary transfer nip, 12 ... secondary transfer roller, 14 ... concave, 18 ... gate roller, 20 ... transfer material, 21 ... intermediate transfer belt / secondary transfer roller drive motor, 26 ... encoder, DESCRIPTION OF SYMBOLS 27 ... Code wheel, 28 ... Intermediate transfer belt position detector, 28a ... Intermediate transfer belt position detection mark, 29 ... Electronic control part (control part), 30 ... Gate roller drive motor

Claims (7)

An image carrier belt carrying an image;
A transfer roller having a recess on the peripheral surface, forming a transfer nip by pressing a transfer material against the image carrier belt, and transferring the image carried on the image carrier belt to the transfer material at the transfer nip When,
A belt position detector for detecting the position of the image carrier belt;
A transfer roller position detector for detecting the rotation position of the transfer roller;
An image forming apparatus comprising: A transfer material feeding section for feeding the transfer material to the transfer nip;
A control unit that controls feeding of the transfer material of the transfer material feeding unit based on the rotational position of the transfer roller detected by the transfer roller position detection unit;
The image forming apparatus according to claim 1, comprising: The control unit is configured to control the transfer material feeding unit based on the rotation position of the transfer roller detected by the transfer roller position detection unit and the position of the image carrier belt detected by the belt position detection unit. The image forming apparatus according to claim 2, wherein the transfer material feeding timing is adjusted. An image writing unit for writing a latent image;
A latent image carrier on which a latent image is written by the image writing unit;
A developing unit for developing the latent image written on the latent image carrier;
A transfer unit that transfers the image developed by the developing unit to the image carrier belt;
A control unit for controlling image writing of the image writing unit based on the position of the image carrier belt detected by the belt position detection unit;
The image forming apparatus according to claim 1, comprising: The controller writes the image of the image writing unit based on the belt position of the image carrier detected by the belt position detector and the rotational position of the transfer roller detected by the transfer roller position detector. The image forming apparatus according to claim 4, wherein the timing is adjusted. Detecting the rotational position of the transfer roller that forms a transfer nip with the image carrier belt and has a recess,
Control based on the detected rotational position of the transfer roller to feed the transfer material to the transfer nip,
An image forming method, wherein the image carried on the image carrier belt is transferred to the fed transfer material. Detect the position of the image carrier belt that carries the image,
The image formation according to claim 6, wherein the timing for feeding the transfer material to the transfer nip is adjusted by control based on the detected position of the image carrier belt and the detected rotational position of the transfer roller. Method.

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