JP2001215769A - Image forming device and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact image forming device and an image forming method by which a high-quality image is formed in high throughput. SOLUTION: A photoreceptor 21 and an intermediate transfer belt 41 rotating at fixed speed (1st driving speed) Vcons are temporarily accelerated/decelerated by ΔV during an accelerating/decelerating time ΔTUDV by the acceleration/ deceleration control of a DC motor and driven to be rotated at 2nd driving speed (=Vcons+ΔV). Thus, a latent image forming position is shifted and moved by a registration controlled variable in a subscanning direction from a reference latent image forming position (previously set latent image forming position). Thus, the transfer position of a toner image on the belt 41, which is primarily transferred, is also moved in the subscanning direction by the registration controlled variable, so that registration deviation is restrained and the high-quality image is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus and an image forming method for forming a color image by superimposing toners of a plurality of colors. A transfer step of transferring a toner image onto a transfer medium such as a transfer belt, an intermediate transfer drum, and a transfer sheet is performed for each toner color to form a color image on the transfer medium.

[0002]

2. Description of the Related Art An example of this type of image forming apparatus is shown in FIG. This image forming apparatus forms a full-color image by superimposing four color toners of yellow (Y), cyan (C), magenta (M), and black (K). When an image signal is given to a control unit (not shown), each part of the engine unit E is controlled in accordance with a command from the control unit to correspond to an image signal on a sheet member S such as a transfer sheet, a copy sheet or an OHP sheet. To form an image.

In the engine section E, a toner image can be formed on the photosensitive member 21 of the image carrier unit 2. That is, the image carrier unit 2 includes a photoconductor 21 rotatable in the direction of the arrow in FIG. 21, and further includes a charging roller 22 as a charging unit, a developing unit around the photoconductor 21 along the rotation direction. Developing units 23Y, 23C, 2
3M, 23K, and a photoreceptor cleaner blade 24 are disposed, respectively.

In this apparatus, the charging roller 22 is connected to the photosensitive member 2
After the outer peripheral surface of the photoreceptor 21 is uniformly charged by contacting the outer peripheral surface of the photoconductor 1, the laser light L is emitted from the exposure unit 3 toward the outer peripheral surface of the photoconductor 21. As shown in FIG. 1, the exposure unit 3 includes a light emitting element 31 such as a semiconductor laser that is modulated and driven in accordance with an image signal, and a laser beam L from the light emitting element 31 is rotated by a high-speed motor 32. Incident on a polygon mirror 33 to be formed. The laser light L reflected by the polygon mirror 33 is transmitted to the lens 34 and the mirror 3
5, the photosensitive drum 21 is scanned in the main scanning direction (a direction perpendicular to the plane of the drawing) to form an electrostatic latent image corresponding to an image signal. Reference numeral 36 denotes a horizontal synchronization reading sensor for obtaining a synchronization signal in the main scanning direction, that is, a horizontal synchronization signal HSYNC.

The electrostatic latent image formed in this way is
Is developed with toner. That is, in this embodiment, as the developing unit 23, a developing unit 23Y for yellow, a developing unit 23C for cyan, a developing unit 23M for magenta, and a developing unit 23K for black are arranged along the photoconductor 21 in this order. Have been. These developing units 23Y and 23
Each of C, 23M, and 23K is configured to be able to freely contact and separate from the photoconductor 21, and the four developing units 23Y, 23M, 23C, and 23 according to instructions from the control unit.
B selectively contacts the photoconductor 21 and applies a high voltage to apply a toner of a selected color to the surface of the photoconductor 21 to apply electrostatic latent on the photoconductor 21. Reveals an image.

[0006] The toner image developed by the developing unit 23 is transferred onto the intermediate transfer belt 41 of the transfer unit 4 in a primary transfer region R1 located between the black developing device 23K and the photosensitive member cleaner blade 24. Transcribed. A cleaner blade 24 for the photoconductor is disposed at a position in the circumferential direction (in the direction of the arrow in FIG. 21) from the primary transfer region R1, and remains on the outer peripheral surface of the photoconductor 21 after the primary transfer. Scrape off the toner.

Next, the configuration of the transfer unit 4 will be described. In this embodiment, the transfer unit 4 includes a roller 4
2 to 47; an intermediate transfer belt 41 stretched over the rollers 42 to 47; a secondary transfer roller 48 for secondary transferring the intermediate toner image transferred to the intermediate transfer belt 41 to the sheet member S; Photoconductor 21 and intermediate transfer belt 4
1 and a photoreceptor / belt drive unit (not shown) for rotating and driving the photoconductor 1 in synchronization. When the color image is to be transferred to the sheet member S, the color images are formed by superimposing the toner images of the respective colors formed on the photoreceptor 21 on the intermediate transfer belt 41. The sheet member S is taken out from the cassette 61, the manual feed tray 62 or an additional cassette (not shown) by the sheet feeding unit 63, and is conveyed to the secondary transfer area R2. Further, a full-color image is obtained by secondarily transferring the color image to the sheet member S.

After the secondary transfer, toner remaining on the outer peripheral surface of the intermediate transfer belt 41 is removed by a cleaner blade 491 provided on a belt cleaner 49. That is, the belt cleaner 49
Is disposed opposite to the roller 46 with the intermediate transfer belt 41 interposed therebetween. At an appropriate timing, the cleaner blade 491 comes into contact with the intermediate transfer belt 41 to scrape toner remaining on the outer peripheral surface thereof. Drop.

A sensor 40 for detecting a reference position of the intermediate transfer belt 41 is disposed near the roller 43, and a synchronization signal in a sub-scanning direction substantially orthogonal to the main scanning direction, that is, a vertical synchronization signal. It functions as a vertical synchronization reading sensor for obtaining VSYNC.

The sheet member S on which the toner image has been transferred by the transfer unit 4 as described above is secondarily transferred along a predetermined feeding path (two-dot chain line) by the feeding section 63 of the feeding / discharging unit 6. The toner image is conveyed to the fixing unit 5 disposed downstream of the region R2, and the conveyed toner image on the sheet member S is fixed on the sheet member S. Then, the sheet member S is further conveyed to the paper discharge section 64 along the paper supply path, and then discharged to the standard paper discharge tray.

[0011]

In the image forming apparatus constructed as described above, in order to superimpose a plurality of color toner images while registering each other, the vertical synchronizing reading sensor 40 outputs a vertical synchronizing read sensor 40. The synchronization signal VSYNC is used. That is, each time the vertical synchronization signal VSYNC is output, a toner image is formed on the photoconductor 21 at a predetermined timing, and then the toner image is formed on the intermediate transfer belt 41 that rotates at a constant transport speed in synchronization with the photoconductor 21. Is primarily transferred, and by controlling the registration in this way, toner images of a plurality of colors are accurately superimposed. Therefore, the intermediate transfer belt 41 needs to be rotated and conveyed at a constant speed in synchronization with the photosensitive member 21 during the period from the output of the vertical synchronization signal VSYNC to the completion of the primary transfer.

However, as described above, the secondary transfer roller 48 is attached to the intermediate transfer belt 41 at an appropriate timing.
And the cleaner blade 491 temporarily abuts. Therefore, the rotation of the intermediate transfer belt 41 is hindered by the contact, the intermediate transfer belt 41 is elastically extended, and a load is applied to a belt driving unit (not shown) that rotationally drives the intermediate transfer belt 41. As a result, the intermediate transfer belt 41 cannot be rotated and conveyed at a constant speed. If the secondary transfer roller 48 or the cleaner blade 491 comes into contact with the intermediate transfer belt 41 during the period from the output of the vertical synchronization signal VSYNC to the completion of the primary transfer, the toner image is Deviate from each other, that is, a registration shift occurs, which causes a deterioration in image quality.

Here, for example, from the output of the vertical synchronization signal VSYNC to the completion of the primary transfer, the secondary transfer roller 4
8 and the cleaner blade 491
The above-mentioned problem can be solved by setting an operation sequence so as not to come in contact with or to perform the secondary transfer process and the cleaning process after the primary transfer is completed. When the image forming process is performed in the above, the total processing time becomes longer, and the number of processed sheets per unit time, that is, the throughput is greatly reduced. In particular, in order to efficiently carry the toner image on the intermediate transfer belt 41, for example, when the maximum size toner image is set to be carried on almost the entirety of the intermediate transfer belt 41, the primary transfer is completed. In order to perform the secondary transfer process and the cleaning process later, the intermediate transfer belt 41 is idled at least once more than the four primary transfer processes, and the secondary transfer process and the belt cleaning are performed during the idle rotation process. It is necessary to perform processing and the like, and as a result, the throughput is greatly reduced.

If the entire circumference of the intermediate transfer belt 41 is set to be sufficiently longer than the maximum image size, idling of the intermediate transfer belt 41 can be avoided. In this case, the utilization efficiency of the intermediate transfer belt 41 is reduced. And the throughput decreases accordingly. Moreover, the intermediate transfer belt 4
The size of the device is increased by an amount corresponding to the length of 1.

The present invention has been made in view of the above problems, and has as its object to provide a compact image forming apparatus and an image forming method capable of forming a high-quality image with high throughput.

[0016]

According to the present invention, a transfer process of transferring a toner image formed on a photoreceptor to a transfer medium rotated in a sub-scanning direction is repeated for a plurality of different toner colors. The present invention relates to an image forming apparatus and an image forming method for forming a color image by superimposing toner images of toner colors.

In order to achieve the above object, an image forming apparatus according to one aspect of the present invention includes a driving unit that synchronously rotates a photosensitive member and a transfer medium in a sub-scanning direction, and a method that repeats transfer processing. A contact means for temporarily contacting the transfer medium, and registration control necessary to correct a relative registration deviation of the toner image on the transfer medium caused by the contact means coming into contact with the transfer medium. Control means for correcting the transfer start position of the toner image for each toner color based on the amount. The control unit is configured to control the driving unit to rotate the photoconductor and the transfer medium at first and second driving speeds different from each other, and
In the correction process, the photosensitive member and the transfer medium are temporarily accelerated and decelerated from the first drive speed to the second drive speed to shift the formation position of the toner image on the photosensitive member by the registration control amount in the sub-scanning direction. To correct the transfer start position of the toner image on the transfer medium in the sub-scanning direction.

In order to achieve the above object, the image forming method according to one aspect of the present invention provides a method for forming an image on a transfer medium caused by a temporary contact of a contact means with a transfer medium during repetition of a transfer process. Control amount setting step for obtaining a registration control amount necessary for correcting a relative registration shift of the toner image in the step (a), and temporarily accelerating and decelerating the photosensitive member and the transfer medium from the first drive speed to the second drive speed And correcting the toner image transfer position on the transfer medium in the sub-scanning direction by shifting the formation position of the toner image on the photosensitive member by the registration control amount in the sub-scanning direction. I have.

According to the invention having such a configuration, during the repetition of the transfer process, the contact and separation of the contact means with the transfer medium are performed. Therefore, after the primary transfer is completed, the secondary transfer process and the cleaning process are performed. Has higher processing efficiency and higher throughput as compared with the prior art that executes the above. Further, the transfer medium does not need to be set longer than necessary as in the related art, and the size of the apparatus can be reduced.

In this case, as described above, registration deviation occurs when the contact means comes into contact with the transfer medium. In the present invention, the registration deviation is corrected as follows. That is, a registration control amount required to correct such registration deviation is obtained, and the transfer start position of the toner image is corrected for each toner color based on the registration control amount. Therefore, a high quality color image can be obtained by suppressing the registration deviation.

Further, in the present invention, the transfer start position of the toner image is corrected by temporarily controlling the driving speed of the photosensitive member and the transfer medium. More specifically, at the time of the correction processing, the control means controls the driving means, and controls the acceleration and deceleration of the photosensitive member and the transfer medium from the first drive speed to the second drive speed temporarily to form a toner image on the photosensitive member. The formation position is shifted by a registration control amount in the sub-scanning direction.
By this shift movement, the transfer start position of the toner image on the transfer medium is corrected in the sub-scanning direction.

In order to achieve the above object, an image forming apparatus according to another aspect of the present invention includes a photosensitive member driving means for rotating a photosensitive member in a sub-scanning direction at a predetermined first drive speed;
Transfer medium driving means for rotating the transfer medium in the sub-scanning direction, contact means for temporarily contacting the transfer medium during repetition of the transfer process, and contact means for separating from and contacting the transfer medium Control means for correcting a transfer start position of a toner image for each toner color based on a registration control amount necessary for correcting a relative registration shift of a toner image on a transfer medium caused by the Can control the transfer medium driving means to rotate the transfer medium at first and second drive speeds different from each other, and temporarily move the transfer medium from the first drive speed to the second drive speed during the correction processing.
Acceleration / deceleration control is performed on the driving speed to correct the transfer start position of the toner image on the transfer medium in the sub-scanning direction.

Further, according to another aspect of the present invention, there is provided an image forming method, wherein a relative contact of a toner image on a transfer medium caused by a temporary contact of the contact means with the transfer medium during repetition of a transfer process is provided. A registration control amount setting step for obtaining a registration control amount necessary to correct a large registration deviation, and temporarily controlling acceleration and deceleration of the transfer medium from a first drive speed to a second drive speed to transfer the transfer medium to the photosensitive member. Is relatively shifted by a registration control amount in the sub-scanning direction to correct the transfer start position of the toner image on the transfer medium in the sub-scanning direction.

According to the invention having the above-described structure, similarly to the above-described invention, the separation / contact of the contact means with the transfer medium is performed during the repetition of the transfer processing, so that excellent processing efficiency, high throughput and apparatus size can be obtained. Can be reduced in size. Further, registration deviation caused by the contacting means contacting the transfer medium is suppressed by correcting the transfer start position of the toner image for each toner color, and as a result, a high-quality color image is obtained. However, in the present invention, only the drive speed of the transfer medium is subjected to acceleration / deceleration control in order to correct the transfer start position of the toner image, which is different from the above-described one mode in which the photosensitive member and the transfer medium are accelerated / decelerated. . More specifically, at the time of the correction processing, the control means controls the transfer medium driving means to temporarily move the transfer medium from the first driving speed to the second driving speed.
The drive speed is controlled to be accelerated / decelerated, and the transfer medium is shifted relative to the photoconductor by a registration control amount in the sub-scanning direction. By this shift movement, the transfer start position of the toner image on the transfer medium is corrected in the sub-scanning direction.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention utilizes the basic principle first discovered by the present inventor, and the following describes the basic principle of the present invention.
The present embodiment using the basic principle will be described in detail.

A. Basic Principle of the Invention Conventionally, when primary transfer processing is repeated and a contact means such as a secondary transfer roller or a cleaner blade is brought into contact with an intermediate transfer belt, registration deviation occurs and image quality deteriorates. The phenomenon itself was known. However, it has not been analyzed in detail what kind of technical matter it is based on, or the relationship between the separation / contact of the contact means and the amount of registration deviation. Therefore, FIG.
In order to improve the image quality by correcting the registration error based on the result of the detailed examination of the state of occurrence of the registration error when the first image forming apparatus is operated in the operation sequence shown in FIG. The resist control amount was determined.
Hereinafter, this will be described in detail with reference to FIGS.

FIG. 1 is a timing chart showing an example of an operation sequence in the image forming apparatus of FIG.
As shown in the figure, after the apparatus power is turned on or when the sleep mode of the image forming apparatus is released, the intermediate transfer belt 41 is rotated and conveyed, and the vertical synchronization reading sensor 40 is moved.
Outputs the vertical synchronization signal VSYNC intermittently. Then, the vertical synchronization signal VSYNC is output at timings VT1 to VT7,.
Each time is output, a yellow electrostatic latent image, a cyan electrostatic latent image, a magenta electrostatic latent image, and a black electrostatic latent image are formed on the photoreceptor 21 repeatedly in this order after a certain period of time. After the electrostatic latent image is formed, the developing units 23Y and 23
One of the developing devices M, 23C and 23B selectively comes into contact with the photoconductor 21 to make an electrostatic latent image on the photoconductor 21 visible,
The toner image is primarily transferred onto the intermediate transfer belt 41.
Accordingly, all the toner images of each color are formed at a predetermined position on the photoconductor 21, that is, a reference latent image forming position, and the intermediate transfer belt 41 that rotates in synchronization with the photoconductor 21 is formed.
Is primarily transferred at the same position (primary transfer processing for each toner color).

When the primary transfer process is repeated for four colors, the four color toner images are superimposed on the intermediate transfer belt 41 to form a color image. When a color image is obtained in this way, the secondary transfer roller 48 abuts on the intermediate transfer belt 41 with the sheet member S interposed therebetween, and secondary-transfers the color image onto the sheet member S. At the same time, the cleaner blade 491 is turned on according to the CB signal. The toner remaining in contact with the intermediate transfer belt 41 on the belt surface is removed. The sheet member S on which the color image is formed by repeating such an operation is sequentially discharged to the standard discharge tray.

This is the outline of the operation of the image forming apparatus in accordance with the operation sequence shown in FIG. 1. The relationship between such an operation and the amount of registration deviation in the sub-scanning direction is examined. Gave different results. Such a difference is caused by the difference in the operation sequence. Hereinafter, the operation sequence for forming the first sheet (hereinafter, referred to as “first print sequence”) and the image formation for the second and subsequent sheets will be described. The operation sequence (hereinafter, referred to as “second printing sequence”) will be described separately. Also, in this type of apparatus, since there is a third print sequence associated with the idling process, this will also be described.

A-1. First Printing Sequence First, when the apparatus power is turned on (or the sleep mode of the image forming apparatus is released), the intermediate transfer belt 41
Are rotated and conveyed, and the vertical synchronization signal VSYNC is sequentially output from the vertical synchronization reading sensor 40 at timings VT1 to VT3. The yellow toner image Y1 is transferred to the intermediate transfer belt 41 as described above corresponding to the first timing VT1. One on top
Next, the cyan toner image C1 is primary-transferred onto the intermediate transfer belt 41 so as to overlap the yellow toner image Y1 at the timing VT2, and the magenta toner image M1 is further converted into the yellow toner image Y1 at the timing VT3.
And an intermediate transfer belt 41 superimposed on the cyan toner image C1.
The primary transfer is performed thereon. During this time, the cleaning process and the secondary transfer process of the intermediate transfer belt 41 are not performed, and the abutting means (the secondary transfer roller 48 and the cleaner blade 49) are not used.
1) is separated from the intermediate transfer belt 41. Therefore, these three toner images Y1, C1, and M1 are all superimposed at the same position on the intermediate transfer belt 41, and are accurately registered in the sub-scanning direction. That is, FIG.
As shown in FIG. 3, these three toner images Y1, C1, M1
All of the transfer start positions coincide with the reference transfer start position, and their post-transfer end positions also coincide with the reference transfer post-end position. FIG. 1 (and FIG. 1 described later)
The dashed line in 1) indicates the primary transfer position where each toner image is transferred. In the actual primary transfer process, the toner images are sequentially superimposed at the dashed line portion. For convenience of explanation, the respective toner images are shown separated in the vertical direction.

Next, at timing VT4, the vertical synchronizing signal VS
When the YNC is output, as shown in FIG.
Thereafter, a VIDEO signal is supplied to the exposure unit 3 to form an electrostatic latent image corresponding to the black toner image K1 at a predetermined reference latent image forming position in the same manner as other toner colors. I do. Then, the primary transfer process is started from a point in time when a predetermined time T20 has elapsed from the output of the vertical synchronization signal VSYNC (timing VT4). At this point, the yellow toner image Y1 and the cyan toner image C
1 and the magenta toner image M1, the cleaner blade 491 is separated from the intermediate transfer belt 41, and as a result, as shown in FIG.
The transfer start position of No. 1 also coincides with the reference transfer start position similarly to the other toner images Y1, C1, M1. During the continuation of the separation, the conveyance speed V of the intermediate transfer belt 41 is constant, and the black toner image K1 is superposed while being accurately registered with the other toner images Y1, C1, and M1 that have already been primary-transferred. To go.

However, 1 of the black toner image K1
At a certain point when the second half of the next transfer is reached, that is, at the timing t
At 1, the CB signal for controlling the operation of the cleaner blade 491 rises from the L level to the H level, the cleaner blade 491 contacts the intermediate transfer belt 41, and the black toner image K1 is compared with the other toner images Y1, C1, and M1. In the sub-scanning direction. That is, the timing t
At 1, the cleaner blade 491 contacts the intermediate transfer belt 41, acts as a transport load for the intermediate transfer belt 41, and instantaneously extends the intermediate transfer belt 41 in the sub-scanning direction.
27 occurs. As a result, the resist displacement amount A in the (-) direction
A resist shift occurs only by 27.

Further, after the timing t1, the cleaner blade 491 is kept in contact with the intermediate transfer belt 41 to execute the cleaning process of the intermediate transfer belt 41 until the CB signal next rises again from the L level to the H level. However, the primary transfer processing of the black toner image K1 is continued in the contact state until timing t2. As a result, the registration deviation is further increased, and the final registration deviation amount of the black toner image K1 in the sub-scanning direction is A32 = A27 + A6, and as shown in FIG. It is shifted from the rear end position of the transfer by the shift amount A32 in the (-) direction. However, the symbol A6 corresponds to the belt elongation caused by the cleaner blade 491 continuing to contact the intermediate transfer belt 41 from the timing t1 to the timing t2 (that is, the time A7). Also, in the same figure (and a diagram showing the state of registration deviation described later), a thick solid line indicates the registration deviation of the toner image of the corresponding toner color, while a thick broken line indicates an aid for understanding the occurrence state of the registration deviation. Line.

As described above, for the first color image, as shown in FIG.
Only 1 deviates from the other toner images Y1, C1 and M1, and in particular, at the rear end of the color image, deviates by the registration deviation amount A32. More specifically, as shown in FIG. 3, for the first black toner image, the registration deviation in the sub-scanning direction during the primary transfer is (+) and (+) in the sub-scanning direction with the center of the swing width AC1 as the center. This occurs within the range of the amount of deviation (A32 / 2) in the (-) direction, respectively, and causes deterioration in image quality. Incidentally, before the cleaner blade 491 abuts, the secondary transfer roller 48 also abuts on the intermediate transfer belt 41 and a similar registration shift occurs. The corresponding registration shift amount is smaller than that of the cleaner blade 491. Here, in order to facilitate understanding of the basic principle of the present invention, the description will be made ignoring the registration deviation caused by the separation and contact of the secondary transfer roller 48 with the intermediate transfer belt 41.

A-2. Second printing sequence Such a registration error does not occur only on the first sheet, but also appears on the second color image. That is, in order to form the second yellow toner image Y2,
As shown in FIG. 4, at timing VT5, the vertical synchronizing signal VS
After a predetermined time T10 has elapsed from the output of YNC, a VIDEO signal for forming the yellow toner image Y2 is given to the exposure unit 3. Then, while an electrostatic latent image corresponding to the yellow toner image Y2 is formed on the photoreceptor 21, toner development is performed by the yellow developing unit 23Y.
Output of the vertical synchronization signal VSYNC (timing VT5)
After a lapse of a predetermined time T20 from the time t3
Then, the primary transfer process is started.

However, some time after the output timing VT5 of the vertical synchronizing signal VSYNC, the cleaner blade 491 comes into contact with the intermediate transfer belt 41 as described above, and the intermediate transfer belt 41 instantaneously expands in the sub-scanning direction. Moreover, the contact state is changed to C as described later.
Since the B signal continues until it rises to the H level, the elongation in the sub-scanning direction increases as time elapses. And
At the primary transfer start timing t3, the registration deviation amount A30 in the sub-scanning direction is A30 = A27 + A9. However, the symbol A9 corresponds to belt elongation caused by the cleaner blade 491 continuing to contact the intermediate transfer belt 41 from the timing t1 to the timing t3 (that is, the time A10).

When the intermediate transfer belt 41 has passed through the belt cleaner 49 for about one revolution, the entire belt is cleaned and the cleaning process is completed. At a timing t4, the CB signal rises again from the L level to the H level. The cleaner blade 491 is used for the intermediate transfer belt 41
Separate from. During the period from the start of the primary transfer (timing t3) to the separation of the cleaner blade 491 (timing t4), the cleaner blade 491 keeps contacting the intermediate transfer belt 41. During that time, the intermediate transfer belt 41 is moved to A12 (= t4−t3). Is extended by the extension amount A11 in the sub-scanning direction, and the registration deviation further increases, and the registration deviation amount immediately before the timing t4 becomes the deviation amount A35 in the (-) direction.

On the other hand, at this timing t4, the cleaner blade 491 separates from the intermediate transfer belt 41. Accordingly, the load applied to the intermediate transfer belt 41 is released contrary to the time of the contact.
Is reduced by the contraction amount A26, and the registration deviation amount in the sub-scanning direction is reduced by A26.

As described above, for the second color image, the transfer start position of the yellow toner image Y2 is greatly shifted from the reference transfer start position. In addition, as the primary transfer proceeds, the amount of deviation increases, and when the cleaner blade 491 separates at the timing t4 during the primary transfer, the amount of registration deviation decreases in reverse. That is, as shown in FIG. 4, with respect to the second yellow toner image Y2, the registration shift in the sub-scanning direction during the primary transfer is (+) and ( −) Occurs within the range of the deviation amount (A26 / 2) in each of the directions, resulting in a decrease in image quality.

The transfer start position of the cyan toner image C2, which is primarily transferred after the yellow toner image Y2, is shifted from the reference transfer start position under the influence of the separation and contact of the cleaner blade 491. This phenomenon will be described with reference to FIG.

In order to form the second cyan toner image C2, a VIDEO signal for forming the cyan toner image C2 is supplied to the exposure unit after a predetermined time T10 has elapsed from the output of the vertical synchronization signal VSYNC at timing VT6. 3
Given to. Then, while forming an electrostatic latent image corresponding to the cyan toner image C2 on the photoconductor 21, the toner is developed by the cyan developing unit 23C. Further, the primary transfer process is started at a time when a predetermined time T20 has elapsed from the output of the vertical synchronization signal VSYNC (timing VT6), that is, at timing t5.

Here, at the output timing VT6 of the vertical synchronization signal VSYNC, the cleaner blade 491 is in contact with the intermediate transfer belt 41 as described above, and the timing t4 (the CB signal rises again from the L level to the H level). This contact state is maintained until the time A14. Therefore, the intermediate transfer belt 41 extends by A13 between the timing VT6 and the timing t4.
On the other hand, when the cleaner blade 491 separates from the intermediate transfer belt 41 at the timing t4, the load applied to the intermediate transfer belt 41 is released and the Shrinks by A26. Thereafter, the separated state is maintained until the CB signal next rises from the L level to the H level again. As a result, at the start of the primary transfer of the cyan toner image C2 (timing t5), the registration deviation amount A34 in the sub-scanning direction is A34 = A26-A13.

As described above, the second cyan toner image C2
With respect to (3), the registration deviation in the sub-scanning direction during the primary transfer has an amplitude amount of 0 around the fluctuation center AC3, and the registration deviation amount does not change during the primary transfer process, but the deviation center AC3 does not change. The image itself is parallel-shifted by the shift amount A34 in the sub-scanning direction (+), which causes deterioration in image quality.

As described above, 1 of the cyan toner image C2
When the next transfer is completed, the toner image formation of the magenta toner image M2 and the primary transfer process are performed next. During the process, the cleaner blade 491 rotates the intermediate transfer belt 41.
In the same manner as the first sheet, there is no registration shift in the sub-scanning direction, and the shift amount is zero. Therefore, with respect to the magenta toner image M2, the registration deviation in the sub-scanning direction during the primary transfer is centered on the axis where the amount of registration deviation is zero (the one-dot chain line AC0 in FIGS. The amplitude is also zero. For this reason, in the image forming apparatus that forms an image in the operation sequence shown in FIG. 1, the magenta toner image is used as the reference toner image, and the transfer start position and the transfer end position thereof are referred to as “reference transfer start position” and “reference transfer position”, respectively. Transfer end position ".

When the primary transfer of the magenta toner image M2 is completed, the image formation of the third black toner image and the primary transfer process are performed. In this case, the primary transfer is performed in the same manner as the second sheet. On the way, the cleaner blade 491 abuts on the intermediate transfer belt 41 to extend the intermediate transfer belt 41 by A32, and a registration shift occurs in the (-) direction in the sub-scanning direction. Note that a profile (hereinafter, simply referred to as “profile”) indicating a change in the amount of registration deviation with respect to the operation sequence is the same as FIG.
The registration deviation in the sub-scanning direction during the next transfer occurs within the range of the deviation amount (A32 / 2) in each of the (+) and (-) directions in the sub-scanning direction with the center of the fluctuation width AC1 as the center. Has been reduced.

Further, following the third color image, 4
In the case of successively forming color images on the second and subsequent sheets, the same registration deviation as in the above-described second sheet occurs.

A-3. Third printing sequence Further, in this type of image forming apparatus, the intermediate transfer belt 4
1 may run idle. For example, if the interval between image data from an external device such as a host computer is longer than a certain value, the intermediate transfer belt 41 is idled.
At this time, the cleaner blade 491 is
1 is in a contact state. When a new image formation is started, the intermediate transfer belt 41 is driven to rotate to start image formation. However, when the first yellow toner image is primarily transferred, the second and subsequent sheets shown in FIG. The same registration deviation as in the case of the cyan toner image occurs.

That is, as shown in FIG. 6, when the image formation is restarted and the intermediate transfer belt 41 is driven to rotate, the vertical synchronizing signal VSYNC is output from the vertical synchronizing reading sensor 40 at the timing VT01, and the timing VT01 is obtained. After a predetermined time A14 after the cleaning blade 491 separates from the intermediate transfer belt 41, the primary transfer of the yellow toner image is started. For this reason, the transfer start position is shifted in the (+) direction by the shift amount A34 for the same reason as in the case of the cyan toner image C2 in the above “A-2. Second print sequence”. In other words, the registration deviation in the sub-scanning direction during the primary transfer has an amplitude of 0 centered on the center of the fluctuation width AC3. Although the registration deviation does not change during the primary transfer processing, the deviation of the deviation center AC4 itself does not change. Are shifted in parallel in the sub-scanning direction (+) by the shift amount A34, which causes deterioration in image quality.

Since the subsequent primary transfer of the cyan and magenta toner images is always performed with the cleaner blade 491 being separated from the intermediate transfer belt 41, no registration deviation occurs. 1 as in the case of the first and second print sequences.
During the next transfer, the cleaner blades 491 and 2
When the next transfer roller 48 comes into contact with the intermediate transfer belt 41, a registration shift of the shift amount A32 occurs in the (-) direction.

As described above, when the contacting means such as the cleaner blade 491 comes into contact with the intermediate transfer belt 41 while the primary transfer process is repeated, a predetermined registration deviation amount is set in accordance with the timing of the contact / separation. Occurs. This profile itself is determined by the device configuration and operating conditions.The profile itself does not change unless the device configuration or operation sequence is changed, but the transfer start position is moved in the sub-scanning direction according to the amount of registration deviation. By doing so, registration deviation from the reference toner image can be reduced to zero or suppressed. For example, as for the cyan toner image C2, as shown in FIG. 5, the transfer start position of the cyan toner image C2 has a shift amount A34 in the (+) direction with respect to the reference transfer start position. Is not seen, the transfer start position of the cyan toner image C2 is shifted from the reference transfer start position by the amount of registration deviation A34 (-).
By controlling so as to shift in the direction, the amount of registration deviation can be made zero.

Therefore, prior to the actual image forming process, the same analysis as described above is performed in advance from the apparatus configuration and operation sequence to derive the registration deviation amount, and it is necessary to reduce or eliminate the registration deviation amount. In the actual image forming process, the transfer start position is corrected in the sub-scanning direction based on the registration control amount (e.g., A34 in the case of cyan). By adjusting the center of fluctuations AC1 to AC4 of the toner colors (Y, C, K) other than magenta) to the center of fluctuation AC0 of the reference toner color, it is possible to suppress registration deviation and form a high-quality image. it can.

B. First Embodiment Image forming apparatuses according to the first embodiment and other embodiments use the above-described "basic principle of the invention", and have the same mechanical configuration as that of FIG. On the other hand, it has remarkable features not found in the prior art in its electrical configuration and image forming method. Therefore, in the following, the description of the mechanical configuration is omitted, and the electrical configuration and the image forming method will be mainly described in detail.

B-1. Electrical Configuration FIG. 7 is an electrical configuration diagram showing an embodiment of an image forming apparatus according to the present invention, and has a configuration common to all embodiments. In the image forming apparatus, when an image signal is given to the main controller 11 of the control unit 1 from an external device such as a host computer, the engine controller 12 responds to a command from the CPU 111 of the main controller 11 as shown in FIG. An image corresponding to the image signal is formed on the sheet member S by controlling the components of the engine unit E thus configured.

The engine controller 12 has a CPU 1
And a horizontal synchronization signal HSYNC from the horizontal synchronization reading sensor 36 as an input signal from the engine unit E.
Also, the vertical synchronization signal VSYNC is output from the vertical synchronization read sensor 40.
And a temperature sensor 51 provided in the fixing unit 5.
, Respectively.
In addition, based on these input signals and various information,
The CPU 121 supplies a photoconductor / belt drive control circuit 122 with a photoconductor / belt drive unit 41a that rotationally drives the photoconductor 21 and the intermediate transfer belt 41 in synchronization with each other. Belt drive control circuit 1
22 controls the photosensitive member / belt drive unit 41a using a DC motor as a drive source to control the rotational speed of the photosensitive member 21 and the transport speed V of the intermediate transfer belt 41 by acceleration / deceleration.
Further, the CPU 121 establishes and sets a registration control amount described later.
A storage process, a sequence flag update process, a registration control amount establishment process, and the like are executed.

The engine controller 12 has a dedicated control circuit for controlling the transfer unit 4, a transfer roller separation / contact control circuit 123 and a belt cleaner separation / contact control circuit in addition to the photoconductor / belt drive control circuit 122. 1
24 is further provided. The transfer roller separation / contact control circuit 123 controls the secondary transfer roller driving section 48a based on a command signal from the CPU 121 to perform the transfer at an appropriate timing.
The next transfer roller 48 is brought into contact with and separated from the intermediate transfer belt 41. On the other hand, the belt cleaner separation / contact control circuit 124 controls the belt cleaner drive unit 49a by giving the CB signal to the belt cleaner drive unit 49a based on the command signal from the CPU 121, and transfers the cleaner blade 491 to the intermediate transfer at an appropriate timing. The belt 41 is brought into contact with and separated from the belt 41.

Reference numeral 113 in the figure is an image memory provided in the main controller 11 for storing an image provided from an external device such as a host computer via the interface 112, and reference numeral 125 is an engine unit E. Is a RAM for temporarily storing control data for controlling the operation, calculation results in the CPU 121, and the like, and a reference numeral 126 is a ROM for storing a calculation program executed by the CPU 121 and the like.

B-2. Next, the operation of the image forming apparatus according to this embodiment will be described. FIG. 8 is a flowchart showing the operation of the image forming apparatus. In this image forming apparatus, when the apparatus power is turned on, prior to actual image forming processing, a registration control amount establishing step (step S1) is executed to automatically establish three types of registration control amounts and store the same. RAM as a part
125. In this embodiment, the following resist control amounts Ra, Rb, Rc, as three types of resist control amounts,
That is, Ra: as shown in FIGS. 2 and 3, the cleaner blade 491 abuts during the primary transfer process, and the registration deviation generated by completing the primary transfer process in the abutted state is corrected. For example, as shown in FIG. 4, the cleaner blade 491 abuts before the start of the primary transfer, the primary transfer process is continued in the abutted state, and the cleaner blade 49 during the process.
A registration control amount for correcting a registration deviation caused by the separation of R 1, Rc: for example, as shown in FIGS. 5 and 6, the cleaner blade 491 contacted before the start of the primary transfer is separated,
Thereafter, a registration control amount for correcting a registration deviation generated when performing the primary transfer process in the separated state is established. The details of the operation for automatically setting the three types of registration control amounts (step S1) will be described later.

Thus, the three types of resist control amounts Ra, R
When the establishment of b and Rc (step S1) is completed, the process waits for a print request from an external device such as a host computer (step S2). When there is a print request, it is determined whether the print mode is monochrome printing or color printing (step S3). If it is determined that the printing mode is monochrome printing, normal image forming processing is performed without registration control. Execute and return to step S2. On the other hand, if it is determined in step S3 that the printing is color printing, the three sequence flags F
A sequence flag corresponding to the printing sequence state is selectively set from 0, F1, and F2 (identification variable setting step: step S4). Here, three sequence flags F0, F1, and F2 are prepared. These are identification variables corresponding to the first to third print sequences, respectively. This is because it can be associated with the control amounts Ra, Rb, and Rc.

FIG. 9 is a flowchart showing the updated contents of the sequence flag of FIG. In this sequence flag updating process, it is determined whether or not the print content is the first color print (step S41). Then, when it is determined that it is the first sheet, that is, when it is detected that the first print sequence is executed, a sequence flag F0 is set (step S42). On the other hand, in step S41,
If it is determined that the image is the second or later, step S43
Then, it is determined whether or not the idling process is being performed.

In the case where the idling process is not performed, that is, in the case of continuous printing, since the second printing sequence is executed, the sequence flag F1 is set (step S4).
4). On the other hand, if the idling process is being performed, the third print sequence is executed, so the sequence flag F2
Is set (step S45).

As described above, the print sequence is detected by the sequence flag update process (step S4), and the corresponding sequence flag is set / updated. And the following associations are made.

<Sequence Flag F0: First Print Sequence> As shown in FIG. 9, the first print sequence is the first color print, that is, the first color print performed after the power is turned on or the sleep mode is canceled. This is for forming an image. As described above, when the power is turned on or the sleep mode is released, no toner remains on the intermediate transfer belt 41 and the primary transfer process can be executed as it is. ,
During the primary transfer of each of the cyan and magenta toner images, both the cleaner blade 491 and the secondary transfer roller 48 are separated from the intermediate transfer belt 41. When these primary transfers are performed, the registration error is reduced. Does not occur. In contrast,
During the primary transfer of the black toner image, the cleaner blade 491 and the secondary transfer roller 48 come into contact with the intermediate transfer belt 41, and a registration shift occurs.

Therefore, in the first print sequence, the flag F0 is set, and as shown in Table 1, the registration control amounts of the yellow toner image Y1, the cyan toner image C1, and the magenta toner image M1 correspond to the sequence flag F0. Is set to “0”, while the control amount Ra is set as the registration control amount of the black toner image K1.

[0064]

[Table 1]

<Sequence Flag F1: Second Print Sequence> The second print sequence is for the case where color printing of the second and subsequent sheets is continuously performed as shown in FIG.
In this manner, on the second and subsequent sheets, the transfer start position of the yellow toner image is shifted in the sub-scanning direction as described in detail with reference to FIG. 4, and the cleaner blade 491 is also provided during the primary transfer.
For example, the amount of registration deviation changes due to separation and contact with the intermediate transfer belt 41. During the primary transfer of the cyan toner image,
As described with reference to FIG. 5, the transfer start position is shifted in the sub-scanning direction. In addition, for the black toner image, 1
Similarly to the sheet, during the primary transfer, the cleaner blade 491 and the secondary transfer roller 48
1, a registration error occurs.

Therefore, in the second print sequence, the flag F1 is set, and as shown in Table 1, the control amount Rb is set as the registration control amount of the yellow toner image Y2 in accordance with the sequence flag F1, and the cyan toner is set. Image C2
The control amount Rc is set as the registration control amount of the magenta toner image M2, "0" is set as the registration control amount of the magenta toner image M2, and the control amount Ra is set as the registration control amount of the black toner image (K2).

<Sequence Flag F2: Third Print Sequence> The third print sequence is a color print for the second and subsequent sheets as shown in FIG. is there. As described above, when the next n-th image formation (n ≧ 2) is started in the case where the idling process exists, as described above, before the yellow toner image is primarily transferred, the cleaner blade 491 causes the intermediate transfer. The transfer start position is shifted from the belt 41 in the sub-scanning direction (FIG. 6). Then, the subsequent primary transfer of the cyan and magenta toner images is always performed with the cleaner blade 491 being separated from the intermediate transfer belt 41, so that no registration deviation occurs. As in the case of the second printing sequence, during the primary transfer, the cleaner blade 491 and the secondary transfer roller 48 come into contact with the intermediate transfer belt 41, and a registration shift occurs.

Therefore, in this printing sequence, the flag F2 is set, and as shown in Table 1, the control amount Rc is set as the registration control amount of the yellow toner image corresponding to the sequence flag F2, and the cyan toner image and the control amount are set. “0” is set as the registration control amount of the magenta toner image, and the control amount Ra is set as the registration control amount of the black toner image.

When the updating of the sequence flag corresponding to the printing sequence is completed as described above, a registration control amount corresponding to the sequence flag is set (registration control amount setting step: step S5), and then each toner image is set to 1 In performing the next transfer, the photosensitive member 21 is subjected to acceleration / deceleration control during a predetermined acceleration / deceleration possible period (to be described in detail later) to shift the latent image forming position with respect to the reference latent image forming position in the sub-scanning direction. Shift only. More specifically, the shift movement is performed as follows.

A temperature sensor known per se, in the vicinity of the photosensitive member 21 or the transfer unit 4, especially the primary transfer area R
Measure the temperature near 1. The acceleration / deceleration time corresponding to the registration control amount and the internal temperature of the apparatus is stored in the ROM 126.
And sets it as the acceleration / deceleration time ΔTUDV. In this embodiment, the temperature environment inside the device is divided into three stages of a low temperature environment, a normal temperature environment, and a high temperature environment based on the internal temperature of the device, and as shown in Table 2, the resist control amount in each temperature environment and The acceleration and deceleration time ΔTUDV of the DC motor, which is the drive source of the belt driving unit 41a, is associated and stored in advance in the ROM 126 as correction information.

[0071]

[Table 2]

The “set multiplier” in the table is a multiplier indicating the maximum acceleration / deceleration amount ΔV during the acceleration / deceleration time ΔTUDV, and a negative value is a constant speed (first drive speed) Vcons.
In FIG. 10, the rotating photoconductor 21 and the intermediate transfer belt 41 are decelerated, while the plus value means that the photoconductor 21 and the intermediate transfer belt 41 are accelerated. Here, except for the case where the registration control amount is 0, the absolute values of the set multipliers are all set to “31”, and the absolute value of the set multiplier is set to about 0.1 with respect to the speed Vcons. It accelerates and decelerates by a few percent. However, the value of the set multiplier is not limited to this, and is arbitrary. Further, the set multiplier may be set to a different value according to the resist control amount or the temperature environment.

When the acceleration / deceleration time ΔTUDV corresponding to the registration control amount is set as described above, as shown in FIG. During the possible period, the CPU 121 changes the clock signal supplied to the photoconductor / belt drive control circuit 122 to control the acceleration / deceleration of the DC motor serving as the drive source of the photoconductor / belt drive unit 41a (step S7). Here, the “acceleration / deceleration possible period” refers to a period during which the VIDEO signal is at the H level and the exposure processing is stopped. Only during the period when the exposure process is stopped, the photosensitive member 21
Is controlled at a constant first drive speed Vcons during the formation of the latent image, and the disturbance of the latent image can be prevented. In this acceleration / deceleration possible period, the primary transfer process of the immediately preceding toner image may be continued. In this embodiment, the intermediate transfer belt 41 is drive-controlled in synchronization with the photoconductor 21. Therefore, no disturbance occurs in the toner image primarily transferred in parallel with the acceleration / deceleration control of the photosensitive member 21 and the intermediate transfer belt 41.

By the acceleration / deceleration control of the DC motor, the photosensitive member 21 and the intermediate transfer belt 41 rotating at a constant speed (first driving speed) Vcons are temporarily accelerated / decelerated by ΔV only during the acceleration / deceleration time ΔTUDV. Second drive speed (= Vcons
+ ΔV). As a result, the latent image forming position shifts by a registration control amount in the sub-scanning direction with respect to the reference latent image forming position (a preset latent image forming position). The intermediate transfer belt 4 to which primary transfer is performed by this
The transfer position of the toner image on the reference numeral 1 also moves by the registration control amount in the sub-scanning direction.

For example, when printing the first color image, the sequence flag F0 corresponding to the first print sequence is set in step S4.
, “0” is set as the registration control amount of the yellow toner image Y1, the cyan toner image C1, and the magenta toner image M1, while the control amount Ra is set as the registration control amount of the black toner image K1. Therefore, the yellow toner image Y1, the cyan toner image C1, and the magenta toner image M1
As with the conventional example, the photoconductor 21 is kept at the first driving speed Vcons without changing the driving speed even during the transfer process.
And the intermediate transfer belt 41 is driven synchronously. for that reason,
The yellow toner image Y1, the cyan toner image C1, and the magenta toner image M1 are all formed at predetermined positions on the photoconductor 21, that is, at a reference latent image forming position, and the intermediate transfer belt 41 rotates in synchronization with the photoconductor 21. Also, primary transfer is performed at the same position. As a result, as shown in FIG.
The transfer start positions of these three toner images Y1, C1, and M1 all match the reference transfer start position, and their transfer rear end positions all match the reference transfer rear end position.

On the other hand, for the black toner image K1,
Since the control amount Ra is set as the registration control amount, as shown in FIG. 12, the acceleration / deceleration possible period T is determined based on the vertical synchronization signal VSYNC output at the timing VT4.
At timing t11 of 11, the photosensitive member 21 and the intermediate transfer belt 41 are moved from the first drive speed Vcons to the second drive speed (= Vco
(ns + ΔV). As a result, the latent image formation position of the black toner image is shifted by a control amount Ra (= A32 / 2) to the (+) side in the sub-scanning direction with respect to the reference latent image formation position.

The latent image formed on the photosensitive member 21 as described above is visualized by the developing device 23K, and the black toner image K1 is primarily transferred onto the intermediate transfer belt 41. As a result, as shown in FIG. 11, the transfer start position of the black toner image K1 is shifted from the reference transfer start position by the registration control amount Ra in the (+) direction.

Then, as shown in FIG. 12, the CB for controlling the operation of the cleaner blade 491 at the timing t1 when the primary transfer process proceeds and reaches the latter half thereof.
The signal rises from the L level to the H level, the cleaner blade 491 abuts on the intermediate transfer belt 41, and the black toner image K1 shifts in the sub-scanning direction with respect to the other toner images Y1, C1, and M1. Further, the contact state is continued until timing t2. As a result, the registration deviation further increases, but the registration deviation amount in the sub-scanning direction of the final black toner image K1 is shifted in the (-) direction (A32 / 2). That is, by moving the transfer start position of the black toner image K1 in the (+) direction with respect to the reference transfer start position by the registration control amount Ra, the center of the swing width AC1 for the black color is set for the magenta color which is the reference toner color. Of the swing center AC0 of
By doing so, the center of the deviation width of the registration shift in the sub-scanning direction for each toner color during the primary transfer process for all the toner colors coincides with each other.

As a result, in this embodiment, as shown in FIG. 11, the black toner image K1 is different from the other toner images Y1,
In the (+) direction on the transfer start side with respect to C1 and M1 (A32 /
2) and at the rear end side of the transfer, in the (-) direction by (A32 / 2), and the maximum deviation amount is half that in the case where no registration control is performed (FIGS. 2 and 3).

When the formation of the first color image is completed while suppressing the registration deviation based on the registration control amount in this way, it is determined in step S7 whether or not the printing has been completed, and it is determined that the printing has been completed. In this case, the process returns to step S2 and waits for the next print request. On the other hand, if it is determined that printing has not been completed, the process returns to step S3, and the same processing as described above is repeated. Therefore, as described above, when the second color image is formed following the formation of the first color image (second printing sequence), the process proceeds from step S3 to step S4, and the flag F1 is set as the sequence flag. After the setting, a high-quality image can be formed by suppressing the registration deviation as described below.

That is, in step S5, a registration control amount corresponding to the sequence flag F1 is set. That is, the control amount Rb is set as the registration control amount of the yellow toner image Y2, the control amount Rc is set as the registration control amount of the cyan toner image C2, and the magenta toner image M
In addition, “0” is set as the registration control amount of No. 2, and the control amount Ra is set as the registration control amount of the black toner image K2. Then, registration control is executed for each toner image.

First, for the yellow toner image Y2,
Since the control amount Rb is set as the registration control amount, as shown in FIG. 13, the acceleration / deceleration possible period T
At timing t11 of 11, the photoconductor 21 and the intermediate transfer belt 41 are temporarily accelerated / decelerated by ΔV for the acceleration / deceleration time ΔTUDV, and are rotationally driven at the second drive speed (= Vcons + ΔV) to perform the latent image of the yellow toner image. The forming position is shifted by a control amount Rb to the (+) side in the sub-scanning direction with respect to the reference latent image forming position. Then, this latent image is visualized by the developing device 23Y.

At timing t 1, the CB signal rises from L level to H level, and the separated cleaner blade 491 contacts the intermediate transfer belt 41. Thereafter, the transfer process of the yellow toner image Y2 is performed while the amount of registration shift changes according to the profile indicated by the thick solid line in FIG. The maximum deviation amount with respect to the toner image (magenta toner image M2) is greatly reduced as compared with the case where no registration control is performed (FIG. 4).

As described above, in this embodiment, the photosensitive member 2
The transfer start position of the second yellow toner image Y2 is adjusted by shifting the latent image formation position on the reference image 1 in the sub-scanning direction with respect to the reference latent image formation position by the registration control amount Rb. As a result, the center of the fluctuation width AC2 for the yellow color is matched with the center of the fluctuation width AC0 for the magenta color which is the reference toner color. Therefore, the amount of deviation from the reference toner image (magenta toner image M2) can be suppressed within the range of the fluctuation width (A26 / 2).

Following the yellow toner image Y2, the primary transfer processing of the cyan toner image C2 is performed, and the control amount Rc is set as the registration control amount of the cyan toner image C2. Therefore, as shown in FIG. 14, the driving speed of the photosensitive member 21 and the intermediate transfer belt 41 is temporarily reduced at the timing t11 of the acceleration / deceleration possible period T11 based on the vertical synchronization signal VSYNC output at the timing VT6. In the case of rotating and conveying at a constant speed (first driving speed) Vcons (in the case of a reference toner image, that is, a magenta toner image)
And the rotation amount of the photoconductor 21 and the intermediate transfer belt 41
Is reduced by the registration control amount Rc. As a result, the latent image forming position on the photoconductor 21 shifts by the registration control amount Rc in the sub-scanning direction with respect to the reference latent image forming position.

Then, the latent image formed on the photosensitive member 21 as described above is visualized by the developing device 23C, and the cyan toner image C2 is primarily transferred onto the intermediate transfer belt 41. Therefore, the amount of registration deviation (A26) due to the separation and contact of the cleaner blade 491 and the amount of shift Rc of the toner image C2 on the photoconductor 21 match, and the cyan toner image C2
Transfer start position coincides with the reference transfer start position.

The timing t before the primary transfer of the cyan toner image C2 to the intermediate transfer belt 41 is started.
4, the CB signal rises from the L level to the H level, and the cleaner blade 491 in contact with the intermediate transfer belt 4
Since it is separated from 1, no misregistration occurs during the primary transfer process. For this reason, the transfer end position of the cyan toner image C2 coincides with the transfer end position.

As described above, in this embodiment, the photosensitive member 21 and the intermediate transfer belt 4 are controlled based on the registration control amount Rc.
1 from the first drive speed Vcons to the second drive speed (= Vcons +
By temporarily performing acceleration / deceleration control to ΔV), the swing center AC3 for cyan is matched with the swing center AC0 for magenta, which is the reference toner color. Therefore, the amount of deviation from the reference toner image (magenta toner image M2) can be suppressed to zero.

The primary transfer process of the magenta toner image M2 is executed following the cyan toner image C2. In this transfer process, there is no separation / contact of the cleaner blade 491 and the secondary transfer roller 48, and the magenta toner image The transfer start position and the transfer end position of the image M2 coincide with the reference transfer start position and the transfer end position, respectively.

Thus, the three color toner images Y2, C2, M
When Step 2 is completed, next, primary transfer processing of the final toner color, that is, the black toner image K2 is executed. In this primary transfer process, the latent image formation position on the photoconductor 21 is set to the registration control amount R, as in the case of the first black toner image K1.
By shifting by b in the sub-scanning direction, the center of fluctuation AC1 for the black color coincides with the center of fluctuation AC0 for the reference toner color, magenta.

Therefore, the transfer is shifted by (A32 / 2) in the (+) direction on the transfer start side with respect to the reference toner image.
On the trailing end side of the transfer, there is a shift in the (-) direction by (A32 / 2), and the maximum shift amount is half that in the case where the resist control is not performed (FIGS. 2 and 3).

As described above, also for the second sheet, for all the toner colors, the center of the deviation width of the registration shift in the sub-scanning direction for each toner color during the transfer process coincides with each other. The transfer start position of the toner image is corrected by synchronously controlling the rotation speed of the photoconductor 21 and the conveyance speed of the intermediate transfer belt 41 based on the registration control amount corresponding to the registration control amount. As a result, the cyan toner image C2 can be completely registered with the magenta toner image M2 as the reference toner image, and the yellow toner image Y2 and the black toner image K2 cannot be completely registered with the reference toner image. Also minimizes the amount of misregistration,
High quality image formation is possible.

When the sequence flag F2 is set, the control amount Rc is set as the registration control amount of the yellow toner image Yn, and "0" is set as the registration control amount of the cyan toner image Cn and the magenta toner image Mn. Is set, and the control amount Ra is set as the registration control amount of the black toner image Kn. Then, registration control is executed for each toner image.

First, for the yellow toner image Yn,
Since the control amount Rc is set as the registration control amount, as shown in FIG. 15, the acceleration / deceleration possible period T is determined based on the vertical synchronization signal VSYNC output at the timing VT01.
At timing t11 of 11, the drive speed of the photoconductor 21 and the intermediate transfer belt 41 is temporarily reduced so that the photoconductor 21 is rotated and conveyed at a constant speed (first drive speed) Vcons (the reference toner image, that is, the magenta toner image). In this case, the amount of rotation of the photoconductor 21 and the amount of conveyance of the intermediate transfer belt 41 are reduced by the registration control amount Rc. As a result, the photoconductor 21
The above-described latent image formation position shifts by the registration control amount Rc in the sub-scanning direction with respect to the reference latent image formation position.

Then, the latent image formed on the photosensitive member 21 as described above is visualized by the developing device 23Y, and the yellow toner image Yn is primarily transferred onto the intermediate transfer belt 41. Therefore, the amount of registration deviation (A26) due to the separation and contact of the cleaner blade 491 and the shift amount Rc of the toner image Yn on the photoconductor 21 match, and the yellow toner image Yn
Transfer start position coincides with the reference transfer start position.

Further, at timing t4 before the primary transfer processing of the yellow toner image Yn to the intermediate transfer belt 41 is started, the CB signal rises from L level to H level,
Since the cleaner blade 491 that has come into contact with the intermediate transfer belt 41 is separated from the intermediate transfer belt 41, no registration deviation occurs during the primary transfer process. For this reason, the transfer end position of the yellow toner image Yn coincides with the transfer end position.

As described above, in this embodiment, the photosensitive member 21 and the intermediate transfer belt 4 are controlled based on the registration control amount Rc.
By controlling the acceleration / deceleration of 1, the swing center AC4 for the yellow color is matched with the swing center AC0 for the magenta color, which is the reference toner color. For this reason, the amount of deviation from the reference toner image (magenta toner image Mn) can be suppressed to zero.

Following the yellow toner image Yn, the primary transfer processes of the cyan toner image Cn and the magenta toner image Mn are sequentially performed. In these transfer processes, the separation of the cleaner blade 491 and the secondary transfer roller 48 is performed. There is no contact, the center of the fluctuation width for both toner colors coincides with each other, and the transfer start position and the transfer end position of both toner images Cn and Mn coincide with the reference transfer start position and the transfer end position, respectively. .

Thus, the three color toner images Yn, Cn, Mn
Is completed, next, primary transfer processing of the final toner color, that is, the black toner image Kn is executed. In this primary transfer process, the photosensitive member 21 and the intermediate transfer belt 41 are changed from the first drive speed Vcons to the second drive speed (= Vcons + ΔV) based on the registration control amount Rc, as in the case of the first and second print sequences. By temporarily controlling acceleration / deceleration,
The center of amplitude AC1 for the black color is matched with the center of amplitude AC0 for the reference toner color of magenta. Therefore, the reference toner image is shifted by (A32 / 2) in the (+) direction on the transfer start side and (A32 / 2) in the (-) direction on the rear end side of the transfer,
The maximum deviation amount is half of the case where the resist control is not performed (FIGS. 2 and 3).

As described above, also in the color printing after the idling process, for all the toner colors, each of the toner colors in the sub-scanning direction in the sub-scanning direction during the transfer process is aligned with each other so that the centers of the fluctuation widths of the registration deviations coincide with each other. The transfer start position of the toner image is corrected by controlling the acceleration and deceleration of the photoconductor 21 and the intermediate transfer belt 41 based on the registration control amount Rc for each toner color. As a result, the yellow toner image Y
n, the cyan toner image Cn and the magenta toner image (reference toner image) Mn can be completely registered, and the black toner image Kn can be completely registered with the reference toner image even if it cannot be completely registered. It can be minimized, and high quality image formation becomes possible.

B-3. Operation and Effect As described above, according to the first embodiment, the contact means (the secondary transfer roller 48 and the cleaner blade 49) with the intermediate transfer belt 41 as the transfer medium during the transfer process is repeated.
Since the separation / contact of 1) is performed, higher throughput and higher throughput can be obtained than in the related art in which the secondary transfer process and the cleaning process are performed after the primary transfer is completed. Further, as in the prior art, the intermediate transfer belt 41 is used.
Does not need to be set longer than necessary, and the device size can be reduced.

Of course, the contact means is the intermediate transfer belt 41
A registration deviation is generated by contact with the toner, but a registration control amount required to correct the registration deviation in accordance with the printing sequence state is obtained, and the transfer start position of the toner image for each toner color is determined based on the registration control amount. Is corrected, registration deviation can be minimized. More specifically, in this embodiment, for the black, yellow, and cyan colors, the center of deviation width AC1, AC2 (or AC4), and AC3 of the registration shift in the sub-scanning direction for each toner color during the primary transfer process is determined. By matching the center of the fluctuation width AC0 with respect to the magenta color as the reference toner color, registration deviation between all the toner colors is suppressed to a minimum, and a high-quality color image is obtained.

In the above-described embodiment, a so-called external clock for changing the clock signal supplied from the CPU 121 to the photoconductor / belt drive control circuit 122 to perform acceleration / deceleration control of the DC motor which is the drive source of the photoconductor / belt drive unit 41a. The DC motor is controlled by the method. Therefore, the DC motor can be controlled with excellent controllability. This is because, when the external clock method is adopted, the DC motor can be controlled with an arbitrary control waveform (acceleration / deceleration pattern) by changing the clock signal given from the CPU 121.

In the above embodiment, the registration control amount is associated with the acceleration / deceleration time ΔTUDV of the DC motor serving as the drive source of the photoreceptor / belt drive unit 41a, and these are stored as correction information in advance in a table as shown in Table 2. ROM1 in format
26. Therefore, the correction information in the table can be optimally set or changed at any time in accordance with the individual differences of the apparatuses, the installation environment, and the like, and the influence of the individual differences of the apparatuses can be reduced.

In this embodiment, since the registration control amount and the acceleration / deceleration time ΔTUDV of the DC motor are set for each temperature environment, even if the temperature inside the apparatus changes,
The acceleration / deceleration time ΔTUDV following the temperature change can be obtained, and a registration error can be suppressed and a high-quality image can be formed in any temperature environment. Here, only the temperature environment is considered, but other environmental factors, for example, humidity, are also taken into consideration, and the resist control amount and the acceleration / deceleration time ΔTUDV of the DC motor may be set for each environmental factor. Good.

In this embodiment, the following operation and effect can be obtained. In other words, as described above, the cleaner blade 491 abuts to generate a registration shift. In order to suppress the shift amount, for example, it is considered that the Young's modulus of the intermediate transfer belt 41 is increased to suppress elastic elongation at the time of the abutment. However, this limits the usable belt material and increases the cost. Further, it cannot be directly applied to a device that has already been designed and manufactured, and the device needs to be improved. On the other hand, according to the above-described embodiment, the registration deviation can be suppressed without depending on the device configuration, and the image quality can be improved.

Further, this type of image forming apparatus is not powered on all day, but is generally turned on when starting a day's work, and is turned off once the day's work is completed. It is a mode of use, and every time the device power is turned on,
The registration control amounts Ra, Rb, and Rc are automatically obtained by executing a registration control amount establishment process (step S1).
Even if the image forming apparatus is used for a long period of time, the registration deviation can be corrected with the latest and optimal registration control amounts Ra, Rb, Rc every day, and a stable high-quality color image can be obtained over a long period of time. . Hereinafter, the process of establishing the resist control amount will be described in detail.

B-4. FIG. 16 is a flowchart showing a process of automatically establishing a registration control amount. First, the following initial setting conditions are set in advance based on the apparatus configuration and operation sequence of the image forming apparatus according to the first embodiment, and are stored in the ROM 126. Then, as shown in FIG.
Based on the signal, (1) a cycle T1 in which the cleaner blade 491 and the secondary transfer roller 48 abut on the intermediate transfer belt 41, and (2) a cycle in which the cleaner blade 491 and the secondary transfer roller 48 keep abutting on the intermediate transfer belt 41. T2,
(3) Cleaner blade 491 and secondary transfer roller 48
Is separated from the intermediate transfer belt 41 by a period T3, and
(4) Cleaner blade 491 and secondary transfer roller 48
Is a registration control amount establishing job (step S1) in which the cycle T4 in which the
1) is repeated a predetermined number of times, for example, 20 times (step S)
12).

The initial conditions are: A2: process speed (peripheral speed of the intermediate transfer belt 41), A7: time from contact of the cleaner blade 491 to completion of the primary transfer of the black toner image (see FIGS. 3 and 12). A8: Time required for the intermediate transfer belt 41 to make one rotation A10: One of the yellow toner images from the contact of the cleaner blade
Time until the next transfer starts (see FIGS. 4 and 13), A12: Time from the transfer start position of the yellow toner image to separation of the cleaner blade (see FIGS. 4 and 13), A14: Time from the VSYNC signal to the separation of the cleaner blade Time (see FIGS. 5 and 14), A17: a time interval from the VSYNC signal to the cleaner blade contact in the cycle T1 (see FIG. 17), A18: a time interval from the VSYNC signal to the cleaner blade separation in the cycle T3 (FIG. 17) See)).

In this embodiment, the charging bias and the primary transfer bias are always set to ON while the registration control amount establishing job (step S11) is repeatedly executed. Although illustration is omitted in FIG. 21, a static elimination lamp is provided between the primary transfer region R1 and the photoreceptor cleaner blade 24, and this static elimination lamp is also set to be always ON. I have.
Further, while the secondary transfer roller 48 is in contact with the intermediate transfer belt 41, a secondary transfer bias is applied to obtain a registration control amount in a state close to actual printing.

As described above, when 20 actual measured values are obtained for each of the periods T1 to T4, the average value T1 is obtained.
(av) to T4 (av) are calculated (step S1)
3). Further, the registration control amounts Ra, Rb, and Rc are obtained by calculation based on the following equations, respectively (step S:
14). The reason will be described separately.

<Registration Control Amount Ra> As shown in FIG.
During the primary transfer, the contact of the cleaner blade 491 is started. For example, even when the primary transfer of the A3 size black toner image K1 is completed, the contact of the cleaner blade 491 is continued. Therefore, a registration shift amount A32 in the sub-scanning direction occurs. The resist displacement A32 is the sum of the two elongations A6 and A27. That is, A32 = A6 + A27.

Here, the contact elongation A6 is the contact elongation generated when the intermediate transfer belt 41 is rotated and conveyed while the cleaner blade 491 is in contact, and the elongation A27 is
This is the instantaneous elongation (elasticity + slippage) when the cleaner blade 491 contacts the intermediate transfer belt 41.

First, the elongation A6 will be examined. The periodic difference A1 is generated by the contact of the cleaner blade 491, and the periodic difference A1 can be obtained by the following equation: A1 = (T2 (av) -T4 (av)) × A2 × 1000 . Then, the black toner image K1
During the primary transfer, the cleaner blade 491 is in contact only for a predetermined time A7, so that the contact elongation A6 is A6 = A1 × A7 / A8.

On the other hand, the instantaneous elongation A27 can be obtained by comparing the periods T1 and T4. That is, the instantaneous elongation A27 can be obtained by the following equation: A27 = (T1 (av) -T4 (av)) * A2 * 1000-A15. However, as shown in FIG. 17, the elongation A15 does not increase during the period T1.
Numeral 1 is the elongation due to the contact for a predetermined time A17, and this elongation A15 can be obtained by A15 = A1 × (A8−A17) / A8.

Therefore, the registration deviation amount A32 can be obtained by A32 = A6 + A27, and by shifting the transfer start position in advance in the sub-scanning direction with respect to the reference transfer start position by half the value, the black toner image K1 can be obtained. Can be minimized. Therefore, in this embodiment, the resist control amount Ra is set to Ra = A32 / 2.

<Registry control amount Rb> As shown in FIG. 4, when the yellow toner image Y2 is primarily transferred to the intermediate transfer belt 41 following the primary transfer of the black toner image K1, the yellow is changed from the contact of the cleaner blade to the yellow toner image Y2. A elongates in the sub-scanning direction during the time A10 until the start of the primary transfer of the toner image.
30 (= A27 + A9) has occurred. Further, even after the primary transfer is started, the elongation A11 occurs because the cleaner blade 491 is in contact with the intermediate transfer belt 41.
Immediately before the completion of the next transfer, the cleaner blade 491 separates from the intermediate transfer belt 41, and contraction A26 occurs. Accordingly, as shown in the figure, when the contraction A26 is larger than the elongation A11, the resist control amount Rb is set to Rb = A35-A26 / 2 where A35 = A30 + A11, while the opposite case (A26 < In A11), the registration deviation of the yellow toner image can be minimized by setting the registration control amount Rb to Rb = A35-A11 / 2.

Here, the elongation at the start of the primary transfer A30
As described above, A30 = A27 + A9, where the elongation A9 is the elongation caused by the intermediate transfer belt 41 being rotated and conveyed only for the time A10 while the cleaner blade 491 is in contact with the following equation. A9 = A1 × A10 / A8

Further, the elongation A11 is an elongation caused by the cleaner blade 491 being in contact with the intermediate transfer belt 41 even after the primary transfer is started. Can be.

Further, the contraction A26 is caused by the cleaner blade 4
The reference numeral 91 indicates the separation from the intermediate transfer belt 41, which can be obtained by comparing the periods T3 and T4. That is, it can be obtained based on the following equation: A26 = A25− (T3 (av) −T4 (av)) × A2 × 1000. A25 in the formula is
As shown in FIG. 17, it is the elongation in the cycle T3, which can be obtained by the following equation: A25 = A1 × A18 / A8.

<Registry Control Amount Rc> As shown in FIG. 5, when the cyan toner image is primary-transferred onto the intermediate transfer belt 41 following the primary transfer of the yellow toner image, it becomes a reference for the primary transfer. When the VSYNC signal VT6 is output, the cleaner blade 491 is in contact with the intermediate transfer belt 41, and then remains in contact for a time A14 before the primary transfer of the cyan toner image is started. Since the intermediate transfer belt 41 is rotated and conveyed, elongation A13 occurs. That is, the elongation A13 is A13 = A1 × A14 / A8.

When the cleaner blade 491 separates from the intermediate transfer belt 41, the above-mentioned <registration control amount Rb
As described in the section, shrinkage A26 occurs. Therefore, at the start of the primary transfer of the cyan toner image, the amount of registration deviation A34 (= A13−A26) occurs, but no deviation occurs in the sub-scanning direction during the primary transfer. Therefore, in this embodiment, by shifting the transfer start position in the sub-scanning direction by this value (registration shift amount A34) in advance, the registration shift of the cyan toner image can be suppressed to zero.
c is set to Rc = A34.

As described above, in the process for establishing the registration control amount, the secondary transfer bias is applied while the secondary transfer roller 48 is in contact with the intermediate transfer belt 41. Is not an essential requirement for establishing the second transfer bias, a secondary transfer bias may not be applied, or a bias having a polarity opposite to that of the secondary transfer bias may be applied. In each case, the following effects are obtained. That is, when the secondary transfer bias is not applied, the process of establishing the resist control amount can be simplified. Also,
When a secondary transfer bias is applied, the secondary transfer roller 4
8, the load applied to the intermediate transfer belt 41 and the photoconductor / belt drive unit 41a approaches the actual printing state, and the registration control amount can be accurately obtained. Further, when a bias of the opposite polarity is applied, the toner adhered to the secondary transfer roller 48 is returned to the intermediate transfer belt 41 side to clean the secondary transfer roller 48, and the back transfer of the sheet member by the secondary transfer roller 48 is performed. And a good printing result can be obtained.

In the above-described registration control amount establishing process, the primary transfer bias is applied to the intermediate transfer belt 41 to obtain the registration control amount in a state close to actual printing.
The resist control amount can be accurately obtained.

Further, in the above-described registration control amount establishment processing, the registration control amount establishment job (step S11) is repeated 20 times (step S12) from the start of driving, and 20 measured values of the periods T1 to T4 are measured. The resist control amount is obtained based on these actually measured values. However, immediately after the start of driving, the intermediate transfer belt 41
May not be stable, and if the registration control amount is obtained based on the actually measured periods T1 to T4 in such a state, the accuracy of the registration control amount may be reduced. Therefore, in order to solve such a problem, the intermediate transfer belt 41 is rotated and conveyed a predetermined number of times from the start of driving, and after its operation is stabilized, each cycle T1 to T4
May be measured, and the resist control amount may be determined based on the measured values. In this way, the resist control amount can be determined with high accuracy.

C. Second Embodiment In the first embodiment, as shown in FIG. 10, the DC motor is accelerated / decelerated by a rectangular control waveform (acceleration / deceleration pattern), and the registration deviation is corrected by relatively simple acceleration / deceleration control. Can be obtained, for example, FIG.
As shown in FIG. 8, the DC motor may be subjected to acceleration / deceleration control using a trapezoidal or triangular control waveform (acceleration / deceleration pattern). More specifically, as shown in FIG. 19, the drive speed is slowed up (or slowed down) by a minute amount dV corresponding to one drive pulse, and when 31 drive pulses are received, the second drive speed ( = Vcons + ΔV), and after maintaining the same speed for a certain period of time, the driving speed is slowed down (or slowed up) by a small amount dV corresponding to one driving pulse to return to the first driving speed Vcons. The driving speed may be controlled. Further, as shown in FIG. 20, the driving speed is reduced by a very small amount dV corresponding to the two driving pulses.
By configuring so as to slow down or slow down only, the driving speed can be accelerated / decelerated more slowly than the acceleration / deceleration pattern in FIG.

As described above, according to the second embodiment, since the photosensitive member 21 and the intermediate transfer belt 41 are controlled to be accelerated / decelerated in the acceleration / deceleration patterns shown in FIGS. Can be driven with high accuracy and good controllability. As a result, the formation position of the toner image on the photoreceptor 21 can be accurately shifted in the sub-scanning direction, and the toner on the intermediate transfer belt 41 can be moved. The transfer start position of the image can be corrected more accurately.

A plurality of acceleration / deceleration patterns are prepared in advance, and the acceleration / deceleration control of the photosensitive member 21 and the intermediate transfer belt 41 is performed in a rectangular, trapezoidal or triangular acceleration / deceleration pattern according to the registration control amount. May be.

D. Others The present invention is not limited to the above-described embodiment, and various changes other than those described above can be made without departing from the gist of the present invention. For example, in the above-described embodiment, in order to adjust the transfer start position according to the registration control amount, the photosensitive member 21 and the intermediate transfer belt 41 are controlled at a variable speed in synchronization with each other, so that the latent image on the photosensitive member 21 is controlled. The forming position is shifted in the sub-scanning direction according to the registration control amount. Here, as a method of shifting the latent image forming position on the photoconductor 21, besides the photoconductor / belt drive control, it is also possible to control the exposure timing. Therefore, the photoconductor / belt drive control and the exposure timing control may be combined, which is effective when the registration control amount is relatively large.

This is because, for example, when transferring the yellow toner image Y2 and cyan toner image C2 in the second print sequence, and when transferring the yellow toner image Yn in the third print sequence, the registration control amount is relatively large. If the registration deviation is to be corrected only by the photoconductor / belt drive control, the acceleration / deceleration amount ΔV of the photoconductor 21 and the intermediate transfer belt 41 needs to be set large accordingly, and the accuracy of the photoconductor / belt drive control decreases. And the motor load increases. On the other hand, by shifting the latent image formation position by the exposure timing control, the shift movement amount of the latent image formation position by the photoconductor / belt drive control can be reduced. That is, the acceleration / deceleration amount ΔV of the photoconductor 21 and the intermediate transfer belt 41 can be reduced to a value that can be easily controlled, and controllability can be improved.

In the above embodiment, the photosensitive member 21 and the intermediate transfer belt 41 are driven and controlled by the same photosensitive member / belt driving section (driving means) 41a, so that both are driven in synchronization. A photoconductor drive unit for driving and controlling the photoconductor 21 and a belt drive unit for driving and controlling the intermediate transfer belt 41 are provided, and these photoconductor drive unit and belt drive unit constitute a “drive unit” according to the present invention. Then, the photoconductor 21 and the intermediate transfer belt 41 may be driven synchronously by this driving unit.

When the photoconductor drive unit and the belt drive unit are separately provided as described above, the photoconductor 21 is driven to rotate at a constant speed, and no toner image is formed on the intermediate transfer belt 41. During the period in which the region is located in the primary transfer region R1 (the period in which the primary transfer is not performed), the transfer start position may be adjusted by controlling only the intermediate transfer belt 41 at a variable speed based on the registration control amount. Good.

In the above-described embodiment, the sequence flags F0, F1, and F2 are set as identification variables in one-to-one correspondence with the three types of printing sequences. An identification variable may be used.

In the above embodiment, the print sequence is divided into three types, and the identification variables corresponding to the respective print sequences are set. However, the number of divisions of the print sequence is not limited to this. If the number of divisions is two or more, the same operation and effect as in the above-described embodiment, that is, it is not necessary to newly obtain the resist control amount every time the sequence changes, and excellent controllability can be obtained.

In the above embodiment, a DC motor is used as a drive source for driving the intermediate transfer belt 41 to rotate.
Registration control is performed by controlling the acceleration and deceleration of the DC motor based on the registration control amount, but instead of using a DC motor, a pulse motor such as a stepping motor is used, and registration control is performed by performing pulse drive control based on the registration control amount. It may be.

The image forming apparatus according to the above embodiment prints an image given from an external device such as a host computer via the interface 112 on sheet members such as copy paper, transfer paper, paper, and a transparent sheet for OHP. However, the present invention can be applied to an electrophotographic color image forming apparatus such as a copying machine or a facsimile apparatus, that is, an image forming apparatus that forms a color image by superimposing a plurality of color toners.

Further, in the above embodiment, the transfer step of transferring the toner image formed on the photoreceptor 21 onto the intermediate transfer belt 41 is executed for each toner color to form a color image on the intermediate transfer belt 41. However, the toner image is transferred to a transfer medium other than the intermediate transfer belt (a transfer drum, a transfer belt, a transfer sheet, an intermediate transfer drum, an intermediate transfer sheet, a reflective recording sheet, a transparent storage sheet, etc.), and a color image is formed. The present invention can also be applied to an image forming apparatus that forms the image.

[0138]

As described above, according to the present invention, the separation / contact of the contact means with the transfer medium is performed during the repetition of the transfer process, so that the secondary transfer is completed after the primary transfer is completed. Compared to the conventional technology that performed the transfer process and the cleaning process, it has excellent processing efficiency, can perform image formation with high throughput, and requires the transfer medium to be set longer than necessary as in the conventional technology. In addition, the size of the device can be reduced. In addition, registration deviation occurs when the contact means comes into contact with the transfer medium.A registration control amount required to correct the registration deviation is obtained, and a toner image is transferred for each toner color based on the registration control amount. Since the start position is corrected, registration deviation can be suppressed and a high-quality color image can be obtained. In addition, according to the present invention, the transfer start position of the toner image is corrected by temporarily controlling the transfer medium (and the photosensitive member) from the first drive speed to the second drive speed during the correction process. The registration error can be corrected with high accuracy, and as a result, a higher quality color image can be obtained.

[Brief description of the drawings]

FIG. 1 is a timing chart showing an example of operation timing in an image forming apparatus to which the present invention is applied.

FIG. 2 is a diagram schematically illustrating a registration state of each toner image when a primary transfer process is performed at the operation timing of FIG. 1 without performing registration control.

FIG. 3 is a diagram illustrating a registration deviation state when a black toner image is transferred without performing registration control.

FIG. 4 is a diagram illustrating a registration deviation state when a yellow toner image is transferred without performing registration control.

FIG. 5 is a diagram illustrating a registration deviation state when a cyan toner image is transferred without performing registration control.

FIG. 6 is a diagram illustrating a state of registration deviation when a yellow toner image is transferred without performing registration control.

FIG. 7 is an electrical configuration diagram showing an embodiment of the image forming apparatus according to the present invention.

FIG. 8 is a flowchart illustrating an operation of the image forming apparatus according to the first embodiment.

FIG. 9 is a flowchart showing the updated contents of the sequence flag in FIG. 8;

FIG. 10 is a diagram showing one mode of acceleration / deceleration control of the DC motor in the first embodiment.

11 is a diagram schematically illustrating a registration state of each toner image when a primary transfer process is performed at the operation timing of FIG. 1 while performing registration control.

12 is a diagram illustrating registration control contents when a black toner image is transferred in the image forming apparatus illustrated in FIG. 8;

13 is a diagram showing registration control contents when a yellow toner image is transferred in the image forming apparatus shown in FIG. 8;

14 is a diagram illustrating registration control contents when a cyan toner image is transferred in the image forming apparatus illustrated in FIG. 8;

15 is a diagram illustrating registration control when a yellow toner image is transferred in the image forming apparatus illustrated in FIG. 8;

FIG. 16 is a flowchart illustrating processing for automatically establishing a registration control amount.

FIG. 17 is a timing chart showing the contents of a registration control amount establishment job.

FIG. 18 is a diagram showing another mode of the acceleration / deceleration control of the DC motor in the first embodiment.

19 is a diagram showing an example of the acceleration / deceleration pattern in FIG.

20 is a diagram showing another example of the acceleration / deceleration pattern in FIG.

FIG. 21 is a diagram showing a configuration of an image forming apparatus as a background art of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 control unit (control means) 3 exposure unit (exposure means) 4 transfer unit 5 fixing unit (fixing means) 11 main controller 12 engine controller (control means) 21 photoconductor 23 developing section 23Y 23C, 23M, 23K Developing device 41 Intermediate transfer belt (transfer medium) 41a Photoconductor / belt drive unit (drive unit) 48 Secondary transfer roller (contact unit) 121 CPU (control unit) 122 photosensitive Body / belt drive control circuit (drive means) 123: transfer roller separation / contact control circuit 124: belt cleaner separation / contact control circuit 126: ROM (storage unit) 491: cleaner blade (contact means) C1, C2: cyan toner Image E: engine unit K1, K2: black toner image M1, M2: magenta toner image Ra, Rb, Rc: registration control amount T1 to T4: cycle Vcons: first drive speed Y1, Y2: yellow toner image

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 27, 2000 (2009.2)
7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

The electrostatic latent image formed in this way is
Is developed with toner. That is, in this embodiment, as the developing unit 23, a developing unit 23Y for yellow, a developing unit 23C for cyan, a developing unit 23M for magenta, and a developing unit 23K for black are arranged along the photoconductor 21 in this order. Have been. These developing units 23Y and 23
C, 23M, and 23K are configured to be freely movable toward and away from the photoreceptor 21, respectively, and in response to a command from the control unit, the four developing units 23Y , 23C, 23M, and 23.
One of the developing devices of K selectively contacts the photosensitive member 21, and a high voltage is applied to apply the toner of the selected color to the surface of the photosensitive member 21, and the electrostatic latent on the photosensitive member 21 is applied. Reveals an image.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

However, as described above, the secondary transfer roller 48 is attached to the intermediate transfer belt 41 at an appropriate timing.
And the cleaner blade 491 temporarily abuts. Therefore, the rotation of the intermediate transfer belt 41 is hindered by the contact, the intermediate transfer belt 41 is elastically extended, and a load is applied to a belt driving unit (not shown) that rotationally drives the intermediate transfer belt 41. As a result, the intermediate transfer belt 41 cannot be rotated and conveyed at a constant speed. As a result, the intermediate transfer belt 41
To the secondary transfer roller 48 or the cleaner blade 491
When the toner images come into contact with each other, the toner image
They are shifted from each other, that is, a registration error occurs.
In some cases, the image quality is degraded.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Deleted

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Deleted

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

The present invention has been made in view of the above problems, and has as its object to provide an image forming apparatus and an image forming method capable of forming a high-quality image .

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction contents]

In the invention configured as described above, during the repetition of the transfer processing, the contact and separation of the contact means with the transfer medium are executed . In this case, as described above, the abutting means is a transfer medium.
The contact with the resist causes a registration error.
Then, the registration deviation is corrected as follows. sand
In other words, it is necessary to correct such misregistration.
Calculate the resist control amount, and based on this resist control amount,
The transfer start position of the toner image is corrected for each toner color.
Therefore, high quality color image
An image is obtained.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Deleted

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0027

[Correction method] Change

[Correction contents]

FIG. 1 is a timing chart showing an example of an operation sequence in the image forming apparatus of FIG.
As shown in the figure, after the apparatus power is turned on or when the sleep mode of the image forming apparatus is released, the intermediate transfer belt 41 is rotated and conveyed, and the vertical synchronization reading sensor 40 is moved.
Outputs the vertical synchronization signal VSYNC intermittently. Then, the vertical synchronization signal VSYNC is output at timings VT1 to VT7,.
Each time is output, a yellow electrostatic latent image, a cyan electrostatic latent image, a magenta electrostatic latent image, and a black electrostatic latent image are formed on the photoreceptor 21 repeatedly in this order after a certain period of time. After the electrostatic latent image is formed, the developing devices 23Y and 23Y
One of the developing devices C, 23M, and 23K selectively comes into contact with the photoconductor 21 to make the electrostatic latent image on the photoconductor 21 visible,
The toner image is primarily transferred onto the intermediate transfer belt 41.
Accordingly, all the toner images of each color are formed at a predetermined position on the photoconductor 21, that is, a reference latent image forming position, and the intermediate transfer belt 41 that rotates in synchronization with the photoconductor 21 is formed.
Is primarily transferred at the same position (primary transfer processing for each toner color).

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0101

[Correction method] Change

[Correction contents]

B-3. Operation and Effect As described above, according to the first embodiment, the contact means (the secondary transfer roller 48 and the cleaner blade 49) with the intermediate transfer belt 41 as the transfer medium during the transfer process is repeated.
Since the separation / contact of 1) is performed, the contact means is an intermediate transfer.
Registration misalignment occurs due to contact with belt 41
Corrects registration errors according to the printing sequence status.
The required amount of resist control for
Transfer start position of toner image for each toner color based on control amount
Can minimize registration misalignment.
it can. More specifically, in this embodiment, the black
For primary, yellow and cyan colors during primary transfer
In the sub-scanning direction for each toner color in
Center of deviation width AC1, AC2 (or AC4) and
AC3 is the fluctuation of magenta color which is the reference toner color
By matching with the width center AC0, all toner colors
High quality color with minimum registration gap
An image is obtained.

[Procedure amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0102

[Correction method] Deleted

[Procedure amendment 11]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

[0138]

As described above, according to the present invention, during the repetition of the transfer processing , the contacting means is separated from and brought into contact with the transfer medium, so that the contacting means comes into contact with the transfer medium. As a result, registration deviation occurs . However, since the registration control amount required to correct the registration deviation is obtained, and the transfer start position of the toner image is corrected for each toner color based on the registration control amount, the registration deviation is suppressed to achieve high quality. A color image can be obtained. Moreover, according to the present invention, the transfer medium (and the photoconductor)
Since the transfer start position of the toner image is corrected by temporarily controlling the variable speed from the first drive speed to the second drive speed, the registration deviation can be corrected with high accuracy. A quality color image can be obtained.

Continued on the front page F term (reference) 2H027 DA11 DA14 DA16 EA18 EB04 EC20 ED02 ED24 EE01 EE03 EE04 EE07 EF09 ZA07 2H030 AA01 AD17 BB42 BB44 BB56 2H032 AA05 AA15 BA09 BA19 BA30 CA02 CA13 CA14

Claims (12)

[Claims] 1. A transfer process for transferring a toner image formed on a photoconductor to a transfer medium that is driven to rotate in a sub-scanning direction.
In an image forming apparatus that repeatedly forms a color image by superimposing toner images of respective toner colors on a plurality of different toner colors, a driving unit that synchronously rotates and drives the photoconductor and the transfer medium in a sub-scanning direction; An abutting unit that temporarily abuts on the transfer medium when the transfer process is repeated, and a toner image on the transfer medium generated by the abutting unit coming into contact with the transfer medium. Control means for correcting a transfer start position of a toner image for each toner color based on a registration control amount necessary for correcting a relative registration shift, wherein the control means controls the driving means to The photoconductor and the transfer medium can be driven to rotate at different first and second drive speeds. The transfer medium is controlled by temporarily accelerating and decelerating the recording medium from a first driving speed to a second driving speed and shifting a formation position of a toner image on the photoconductor by the registration control amount in the sub-scanning direction. An image forming apparatus, wherein the transfer start position of the toner image is corrected in the sub-scanning direction. 2. An exposure device for exposing and forming an electrostatic latent image corresponding to the toner image on the photosensitive member, wherein the control device is capable of accelerating and decelerating the latent image formation by the exposure device. 2. The image forming apparatus according to claim 1, wherein the photosensitive member and the transfer medium are temporarily accelerated and decelerated from a first drive speed to a second drive speed during a period. 3. 3. The driving unit has a DC motor as a driving source, and the control unit receives a clock signal from a clock signal generation unit that generates a clock signal for controlling the DC motor. 3. The image forming apparatus according to claim 1, further comprising: a drive control unit configured to drive and control the DC motor based on a clock signal to be supplied. 4. A transfer process for transferring a toner image formed on a photoconductor to a transfer medium that is driven to rotate in a sub-scanning direction.
An image forming apparatus for forming a color image by repeatedly superimposing toner images of respective toner colors on a plurality of different toner colors, wherein the photoconductor is driven to rotate at a predetermined first drive speed in a sub-scanning direction. A driving unit, a transfer medium driving unit that rotationally drives the transfer medium in the sub-scanning direction, a contact unit that temporarily contacts the transfer medium when the transfer process is repeated, and the contact unit. A transfer start position of the toner image is set for each toner color based on a registration control amount necessary to correct a relative registration shift of the toner image on the transfer medium caused by the means coming into contact with the transfer medium. A control unit for correcting the transfer medium, wherein the control unit controls the transfer medium driving unit to rotate the transfer medium at first and second driving speeds different from each other. During the correction process, the transfer medium is temporarily accelerated / decelerated from the first drive speed to a second drive speed to correct the transfer start position of the toner image on the transfer medium in the sub-scanning direction. An image forming apparatus comprising: 5. The transfer medium driving unit includes a DC motor as a driving source, the control unit includes a clock signal generation unit that generates a clock signal for controlling the DC motor, and a clock signal generation unit that generates the clock signal. The image forming apparatus according to claim 4, further comprising: a drive control unit configured to drive and control the DC motor based on a clock signal supplied from the unit. 6. An acceleration / deceleration pattern indicating a change in acceleration / deceleration of a drive speed of the transfer medium is a rectangular shape.
The image forming apparatus according to any one of the above. 7. The image forming apparatus according to claim 1, wherein the acceleration / deceleration pattern indicating the acceleration / deceleration change of the drive speed of the transfer medium has a triangular or trapezoidal shape. 8. The control unit includes a storage unit that stores a registration control amount and an acceleration / deceleration pattern in association with each other in advance,
8. The image forming apparatus according to claim 6, wherein when a registration control amount corresponding to each transfer process is obtained, an acceleration / deceleration pattern corresponding to the registration control amount is selected, and acceleration / deceleration control is performed based on the acceleration / deceleration pattern. 9. The image forming apparatus according to claim 8, wherein the storage unit stores a registration control amount and a deceleration pattern in association with each other for each apparatus environment. 10. The acceleration / deceleration time for accelerating / decelerating from a first driving speed to a second driving speed as a value indicating the acceleration / deceleration pattern is stored in the storage unit in association with a registration control amount. The image forming apparatus as described in the above. 11. A transfer process for transferring a toner image formed on a photoreceptor to a transfer medium that is rotationally driven in synchronization with the photoreceptor in a sub-scanning direction is repeated for a plurality of different toner colors. In the image forming method for forming a color image by superimposing color toner images, the toner on the transfer medium generated by the contact unit temporarily contacting the transfer medium when the transfer process is repeated A registration control amount establishing step for obtaining a registration control amount necessary for correcting a relative registration deviation of an image; and a control for temporarily accelerating and decelerating the photosensitive member and the transfer medium from a first drive speed to a second drive speed. Then, the formation position of the toner image on the photoconductor is shifted by the registration control amount in the sub-scanning direction, so that the transfer of the toner image on the transfer medium is started. Image forming method characterized by position and a correction step of correcting in the sub-scanning direction. 12. A transfer process for transferring a toner image formed on a photoconductor rotating at a predetermined first drive speed to a transfer medium rotated in a sub-scanning direction is repeated for a plurality of different toner colors. In an image forming method for forming a color image by superimposing toner images of respective toner colors, a contact unit temporarily abuts on the transfer medium when the transfer process is repeated. A registration control amount establishing step for obtaining a registration control amount necessary for correcting a relative registration deviation of the toner image of the above, and controlling the acceleration and deceleration of the transfer medium from a first driving speed to a second driving speed temporarily. The transfer start position of the toner image on the transfer medium by shifting the transfer medium relative to the photoconductor in the sub-scanning direction by the registration control amount. Image forming method characterized by comprising a correction step of correcting in the sub-scanning direction.