JP2001235921A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of improving the accuracy of image alignment. SOLUTION: A reading means 60A reads toner images for adjusting image alignment successively transferred to an intermediate transfer body 31 after they are respectively formed on image carriers 11a, 11b, 11c and 11d provided in plural image forming parts 10a, 10b, 10c and 10d, while a control means controls the plural image forming parts 10a, 10b, 10c and 10d based on a read signal from the reading means 60A so that the forming positions of the toner images for adjusting transferred to the transfer body 31 may be aligned, and also controls so that the moving speed of the transfer body 31 at the time of reading the toner image for adjusting may be lower than the speed at the time of transferring the toner image to a sheet P.

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 more particularly to an image forming apparatus having a plurality of image forming units and forming an image by superimposing toner images formed by the image forming units.

[0002]

2. Description of the Related Art Conventionally, in a color image forming apparatus which is an example of an image forming apparatus employing an electrostatic recording system, an electrophotographic recording system, or the like, a toner image formed by a plurality of image forming units is temporarily transferred to an intermediate transfer member. There are those using an intermediate transfer method in which images are sequentially superimposed on each other and then collectively transferred to a sheet, and those in which toner images formed by a plurality of image forming units are sequentially transferred to a sheet.

FIG. 5 is a diagram showing a configuration of a conventional image forming apparatus using an intermediate transfer system. The image forming apparatus 1 is roughly divided into four types for forming yellow, cyan, magenta, and black images. Stations 10 (10a, 10b, 10c, 10) which are image forming units arranged side by side
d), a sheet feeding unit 20, an intermediate transfer unit 30 as a transfer unit including an intermediate transfer belt 31 as an intermediate transfer body,
The image output unit 1P includes a fixing unit 40 and a control unit 80.

Here, the station 10 (10a, 10a
b, 10c, 10d) are photosensitive drums 11 (11a, 11b, 11) as image carriers which are driven to rotate in the direction of the arrow.
c, 11d) and the photosensitive drums 11a to 11d.
d, a primary charger 12 (12a, 12b, 12c, 12d), an optical system 13 (13a, 13b, 13c, 13d), and a developing device 14 (14a, 14b) arranged in the rotation direction in that order. , 14c, 14d) and a cleaning device 15 (15a, 15b, 15c, 15d).

[0005] Such stations 10a-
In 10d, at the time of image formation, first, the primary chargers 12a to 12d apply a uniform amount of charge to the surfaces of the photosensitive drums 11a to 11d, and then, in response to a recording image signal from the image reading unit 1R. By exposing the photosensitive drums 11a to 11d with, for example, a laser beam irradiated by the optical systems 13a to 13d,
An electrostatic latent image is formed on a to d.

Next, the electrostatic latent images are visualized by the developing devices 14a to 14d containing developers (toners) of four colors of yellow, cyan, magenta, and black, respectively. The toner image, which is an image, is primarily transferred to the intermediate transfer belt 31 in each of the image transfer areas Ta, Tb, Tc, and Td where the respective photosensitive drums 11a to 11d and the intermediate transfer belt 31 face each other.

After that, the toner remaining on the photosensitive drum 11 without being transferred to the intermediate transfer belt 31 is scraped off by the cleaning devices 15a to 15d. The image forming and the intermediate transfer belt 3 by each of the stations 10a to 10d are performed by the processes described above.
The primary transfer of the toner image with respect to 1 is sequentially performed.

On the other hand, the paper feeding unit 20 includes cassettes 21 a and 21 b for storing the transfer material P,
7. Cassette 21a, 21b or manual feed tray 27
Rollers 22a, 22b, 26 for feeding out the transfer material P stored in the intermediate transfer belt 3 one by one.
Registration rollers 25a and 25b for sending out the transfer material P to the secondary transfer area Te in accordance with the timing of the primary transfer of the toner image to
The paper feed roller pair 23 and the paper feed guide 24 for transporting the transfer material P sent out from the transfer rollers P, a, 22b, 26 to the registration rollers 25a, 25b are provided.

The intermediate transfer unit 30 applies an appropriate tension to the intermediate transfer belt 31 by urging the intermediate transfer belt 31, a driving roller 32 for transmitting the drive to the intermediate transfer belt 31, and a spring (not shown). The secondary transfer area Te with the tension roller 33 and the intermediate transfer belt 31 interposed therebetween.
, And a driven roller 34 that faces the driven roller 34.

These rollers 32, 33, 34
The intermediate transfer belt 31 is wound around, and a primary transfer plane A is interposed between a driving roller 32 and a tension roller 33.
Is formed. The driving roller 32
Is rotatably driven by a pulse motor (not shown), and is configured to prevent slippage with the intermediate transfer belt 31 by coating rubber (urethane or chloroprene) with a thickness of several mm on the surface of a metal roller. .

Further, the intermediate transfer unit 30 includes a primary transfer blade 35 (35a, 35b, 35b) disposed behind the intermediate transfer belt 31 in the primary transfer areas Ta to Td.
35c, 35d), and a secondary transfer roller 36 that is arranged to face the driven roller 34 and forms a secondary transfer area Te by nip with the intermediate transfer belt 31. The secondary transfer roller 36 is pressed against the intermediate transfer belt 31 with an appropriate pressure.

Further, the intermediate transfer unit 30
Includes a cleaning device 50 that is disposed downstream of the secondary transfer area Te and cleans the image forming surface of the intermediate transfer belt 31. The cleaning device 50
Is a cleaner blade 5 made of a material such as polyurethane rubber.
1 and a waste toner box 52 for storing waste toner.

On the other hand, the fixing unit 40 is provided with a fixing roller pair including a fixing roller 41a having a heat source such as a halogen heater therein and a pressure roller 41b pressed against the fixing roller 41a, and a nip portion between the fixing roller pair 41a and 41b. Guide 43 for guiding transfer material P, fixing roller pair 41a, 41
b, an inner discharge roller 44, an outer discharge roller 45, and the like for guiding the transfer material P discharged from the outside of the apparatus.

The control unit 80 includes a control board 81 on which a control device (not shown) for controlling the operation of the mechanism in each unit is mounted, and a motor drive board (not shown).

Next, an image forming operation of the image forming apparatus 1 configured as described above will be described.

When an image forming operation start signal is issued, first, the transfer materials P are sent out one by one from the cassettes 21a, 21b or the manual feed tray 27 by the pickup rollers 22a, 22b, 26. The paper is guided between paper feed guides 24 by a pair of paper rollers 23 and is conveyed to registration rollers 25a and 25b. At this time, the registration rollers 25a and 25b are stopped, so that the leading end of the transfer material abuts the nip of the registration rollers 25a and 25b.

Thereafter, the registration rollers 25a and 25b start rotating at the timing when the stations 10a to 10d start image formation. The rotation start timing is a timing at which the transfer material P and the toner image formed on the intermediate transfer belt after being formed by the stations 10a to 10d exactly coincide with each other in the secondary transfer area Te.

On the other hand, in each of the stations 10a to 10d, when an image forming operation start signal is issued, a toner image is sequentially formed on each of the photosensitive drums 11a to 11d by the above-described process. The toner image formed on the photosensitive drum 11d which is the most upstream in the rotation direction of 31 is primarily transferred to the intermediate transfer belt 31 in the primary transfer area Td by the primary transfer blade 35d to which a high voltage is applied.

Thereafter, the primary-transferred toner image is transported together with the intermediate transfer belt 31 to the next primary transfer area Tc. The next primary transfer area T
In (c), the image formation is performed with a delay of the time during which the toner image is transported between the respective stations, so that the next toner image is transferred with the registration on the previously transferred toner image. become. Thereafter, the same process is repeated, and as a result, the four color toner images are primarily transferred onto the intermediate transfer belt 31.

Next, after the four color toner images are primarily transferred onto the intermediate transfer belt 31, the transfer material P enters the secondary transfer area Te and comes into contact with the intermediate transfer belt 31, so that the transfer is performed. A high voltage is applied to the secondary transfer roller 36 in accordance with the passage timing of the material P, whereby the four color toner images formed on the intermediate transfer belt are transferred to the surface of the transfer material P.

Next, the transfer material P on which the toner image has been transferred is transported by a conveyance guide 43 to a pair of fixing rollers 41a and 41a.
After being accurately guided to the nip portion of b, the roller pair 41
a, 41b, the toner image is fixed to the surface by the pressure of the nip, and thereafter, the inner and outer discharge rollers 44, 4 are fixed.
5, and the transfer material P is discharged onto a tray 48 mounted outside the machine.

When a monochromatic image is to be obtained, the intermediate transfer belt 3 is controlled by a specific station, for example, a station 10a located at the most downstream in the traveling direction of the intermediate transfer belt 31.
First, a single-color visible image is primarily transferred onto the transfer material 1 and a single-color image is formed on the transfer material P through a process similar to that for forming a full-color image.

[0023]

However, in such a conventional image forming apparatus, when a full-color image is obtained, the toner images formed by the plurality of stations 10a to 10d are overlapped. It is necessary to make an adjustment to superimpose the image on the image.

For this reason, conventionally, when the power supply of the image forming apparatus 1 is turned on, when the jam processing is restarted, or when the power supply
When a predetermined time elapses after N, the control device mounted on the control board 81 controls each of the stations 10a to 10d, forms a predetermined registration pattern on the photosensitive drums 11a to 11d, and intermediates this registration pattern. The image is transferred onto the transfer belt 31.

The transferred registration pattern on the intermediate transfer body is read by a registration sensor 60 provided downstream of the photosensitive drum 11d, which is the most downstream in the traveling direction of the intermediate transfer belt 31, as shown in FIG. By feeding back the read signal from 60,
Timing of image writing of main scanning and sub-scanning, change of magnification due to temperature change of stations 10a to 10d,
The automatic registration is performed in which the registration pattern is adjusted by correcting the deviation of the image inclination due to the unit assembly accuracy.

However, at the time of such image registration, for example, the influence of the light quantity of the light emitting diode illuminating the registration pattern for reading the registration pattern, the influence of the fluttering of the intermediate transfer belt 31, and the like, the registration pattern of the registration sensor 60 is changed. Reading accuracy may decrease.
When the accuracy of reading the registration pattern is reduced, the accuracy of image alignment is reduced, and the image quality is reduced.

Accordingly, the present invention has been made in view of such a situation, and an object of the present invention is to provide an image forming apparatus capable of improving the accuracy of image alignment.

[0028]

According to the present invention, a plurality of image forming units and toner images formed on image carriers provided in the plurality of image forming units are sequentially superimposed and primary-transferred. An image forming apparatus comprising: a transfer unit having an intermediate transfer body that collectively transfers a toner image to a sheet in a batch manner. Reading means for reading a toner image for adjustment, and controlling the plurality of image forming units based on a read signal from the reading means so as to match the formation positions of the toner images for adjustment transferred to the intermediate transfer member. And control means for controlling the moving speed of the intermediate transfer body, wherein the control means controls the moving speed of the intermediate transfer body when reading the toner image for adjustment to the sheet. It is characterized in that the controls to slower than the speed at the time of transferring the toner image.

Further, according to the present invention, the control means controls the moving speed of the intermediate transfer body when reading the toner image for adjustment so as to be the slowest of the settable moving speeds. It is a feature.

Further, the present invention has a plurality of image forming units and a transport unit for sequentially transporting a sheet to a position where a toner image formed on each of the image carriers provided in the plurality of image forming units is transferred. And a reading unit for reading a toner image for image alignment adjustment sequentially formed on the image carrier after being formed on the image carrier, and a reading signal from the reading unit. Control means for controlling the plurality of image forming units to match the formation positions of the respective toner images for adjustment transferred to the carrier, and controlling the moving speed of the carrier, The control means controls the moving speed of the carrier when reading the toner image for adjustment to be lower than the speed when transferring the toner image to the sheet. Is shall.

Further, according to the present invention, the control means controls the moving speed of the intermediate transfer member when reading the toner image for adjustment to be the slowest speed among the settable moving speeds. It is a feature.

Further, as in the present invention, the toner image for adjusting the image alignment, which is formed on the image carriers provided in the plurality of image forming portions and then sequentially transferred to the intermediate transfer member, is read by the reading means. The control unit controls the plurality of image forming units based on a read signal from the reading unit so as to match the formation positions of the respective adjustment toner images transferred to the intermediate transfer member, and controls the adjustment toner images. The moving speed of the intermediate transfer member when reading is controlled to be lower than the speed when transferring the toner image to the sheet.

[0033]

Embodiments of the present invention will be described below.

FIG. 1 is a diagram showing a configuration of an image forming apparatus according to a first embodiment of the present invention. In FIG. 1, the same reference numerals as those in FIG. 5 denote the same or corresponding parts.

In FIG. 1, reference numeral 1A denotes an image forming apparatus main body (hereinafter, referred to as an apparatus main body), and 80A denotes a control unit. This control unit 80A is a formed image (full-color image, single-color image) or a sheet to be used. A transfer material P
A control device (not shown) for controlling the process speed depending on the type (OHP, thick paper, thin paper) or the like is provided.

In the present embodiment, the control device sets the process speed faster than in the normal full-color mode because there is a margin in the fixability of the toner image in the single-color image mode or the thin paper mode. For disadvantageous thick paper and OHP, the process speed is set to be low so as to increase the fixing property.

Reference numeral 60A denotes a registration sensor such as a CCD serving as a reading means, and two registration sensors 60A are arranged in parallel in a direction orthogonal to the transfer material P transport direction as shown in FIG. In the auto registration mode (image adjustment mode), each of the stations 10a to 10a
d of the intermediate transfer belt 3 by the photosensitive drums 11a to 11d.
After reading a registration pattern, which is a toner image for image alignment adjustment and formed at predetermined intervals on FIG. 1 and shown in FIG. 1, this read signal is input to the control device. A light emitting diode (not shown) is provided around the registration sensor 60A so as to illuminate the registration pattern.

The control device operates the registration sensor 60
The position of the registration pattern is detected based on the read signal from A, and the read signal is fed back to perform the registration correction so as to adjust the timing of writing the image, the magnification, the inclination of the image, and the like.

In FIG. 1, reference numeral 82 denotes an apparatus main body 1A.
Operation panel provided on the upper surface of the image forming apparatus 1
By operating a predetermined switch provided on the operation panel 82 when the power is turned on, when a restart is performed after a jam is cleared, or when a predetermined time elapses after the power is turned on, the automatic registration mode is set. It is to be set.

When the automatic registration mode is set as described above, the control device controls the rotation speed of the drive roller 32 by controlling, for example, a pulse motor (not shown), and controls the movement speed of the intermediate transfer belt 31 to the normal speed. Is set to be slower than the full color image. In the present embodiment, the control device sets the moving speed of the intermediate transfer belt 31 in the automatic registration mode to the slowest of the settable moving speeds.

By lowering the moving speed of the intermediate transfer belt 31, that is, by lowering the process speed, the reading time of the registration sensor 60A in the sub-scanning direction becomes longer, and image registration in the auto registration mode is performed. Accuracy can be increased.

Next, the image registration in the automatic registration mode will be described with reference to FIG.

When performing image matching, the control device first determines the interval L1 between the two registration patterns S1 formed by the reference station, for example, the black station 10a, and the next station (yellow, magenta, cyan) 10b to 10b. The interval L2 between the two registration patterns S2 formed by 10d is detected based on the read signals from the two registration sensors 60A.

Next, the control device operates the registration sensor 60A.
Register patterns S1 and S based on the read signal from
The intervals L1 and L2 are compared, and the next stations 10b to 10d are controlled so that L1 = L2, and the magnification of the image is adjusted. Note that the reference station 10a is positioned with respect to the apparatus main body 1A by adjusting the inclination, the one-side magnification, and the like.

Next, the image writing position (main scanning writing,
In order to perform left correction, the writing position is moved so that △ 1 (= L1−L2) becomes 0. Thereafter, the registration pattern S2 whose magnification and image writing have been corrected is transferred to the intermediate transfer belt 31.

Next, in order to correct the inclination of the image, the difference between left and right △ 1, △ 2 in the transport direction (main scanning direction) of the two registration patterns S1, S2 is matched, and the reference station 1
Match the registration pattern S1 of 0a. Finally, # 1 is added to stations 10a to 10
Adjust to the interval of d or adjust so as to be a predetermined distance.

Then, such a cash register pattern is again
The image is transferred to the intermediate transfer belt 31 and read by the registration sensor 60. If the registration is not correct, this routine is repeated several times to increase the accuracy of image alignment.

When performing such inclination correction and image leading edge alignment, the process speed (movement speed of the intermediate transfer belt 31) is reduced as described above. Thus, the resolution of the registration sensor 60A on the sub-scanning side can be improved. That is, by reducing the process speed to 1 / n compared to the normal process speed,
The reading with respect to the time on the sub-scanning side becomes n times, whereby the registration sensor 60A has n times resolution performance.

When an image is actually formed after such inclination correction and image tip alignment, the image formation is performed n times the time of the data read by the registration sensor 60A. Also, when the line width in the sub-scanning direction is converted by returning the process speed to the standard, the line width becomes the same as the line becomes thinner, and the edge determination of the line becomes reliable.

Further, by slowing down the moving speed of the intermediate transfer belt 31, the light of the light emitting diode for causing the registration sensor 60A to detect the registration pattern becomes less affected by the gloss of the intermediate transfer belt 31 and the like. Since the fluttering is reduced, the light quantity can be reduced.

As described above, when the image is aligned, the moving speed of the intermediate transfer belt 31 is set to be lower than the speed at which the image is transferred onto the transfer material P.
The accuracy of reading the registration pattern by 0A can be improved, and the image quality of the image formed on the transfer material P can be improved.

In the above description, an image forming apparatus using the intermediate transfer belt 31 has been described. However, the present invention is not limited to this. For example, an image is directly formed on a sheet without using the intermediate transfer belt 31. The present invention can also be applied to an image forming apparatus having a configuration for transferring. Next, such an image forming apparatus according to the second embodiment of the present invention will be described.

FIG. 4 is a diagram showing a configuration of the image forming apparatus according to the present embodiment. In the figure, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts.

In FIG. 7, reference numeral 70 denotes a transfer material P which is conveyed to stations 10a to 10d,
The transfer unit is a transfer unit that transfers the visible image visualized by Od to the transfer material P.
Reference numeral 0 denotes a transfer belt 71 which is a conveyance body, a drive roller 72 for transmitting drive to the transfer belt 71, a tension roller 73 for applying an appropriate tension to the transfer belt 71 by urging of a spring (not shown), and a driven roller 74.

The rollers 72, 73, 74
The transfer belt 71 is wound. The drive roller 72 is driven to rotate by a pulse motor (not shown), and is coated with rubber (urethane or chloroprene) having a thickness of several mm on the surface of the metal roller so as to prevent slippage with the transfer belt 71. It is configured.

The transfer unit 70 includes transfer blades 75a to 75d arranged behind the transfer belt 71 in transfer areas Ta to Td where the photosensitive drums 11a to 11d and the transfer belt 71 face each other.

Next, an image forming operation of the image forming apparatus 1 configured as described above will be described.

When the image forming operation start signal is issued, first, the transfer materials P are fed out one by one from the cassettes 21a, 21b or the manual feed tray 27 by the pickup rollers 22a, 22b, 26, and the transfer materials P are fed. The paper is guided between paper feed guides 24 by a pair of paper rollers 23 and is conveyed to registration rollers 25a and 25b. At this time, the registration rollers 25a and 25b are stopped, so that the leading end of the transfer material abuts the nip of the registration rollers 25a and 25b.

Thereafter, the registration rollers 25a and 25b start rotating at the timing when the stations 10a to 10d start forming images. The rotation start time is determined by the transfer material P and the station 1
This is a timing at which the toner images formed by Oa to 10d exactly coincide with each other in the transfer areas Ta to Td.

On the other hand, in the stations 10a to 10d,
When the image forming operation start signal is issued, the toner image formed on the photosensitive drum 11d at the most upstream in the rotation direction of the transfer belt 71 by the above-described process is transferred to the transfer area by the transfer blade 75d to which a high voltage is applied. T
At d, the image is transferred onto the transfer material P conveyed by the transfer belt 71.

The transfer material P on which the toner image has been transferred in this manner is transferred by the transfer belt 71 to the next transfer area Tc.
Transported to In the next transfer area Tc, image formation is performed with a delay of the time for transporting the toner image between the stations, so that the next toner image is transferred with the registration on the previous image. Will be done. Thereafter, the same process is repeated, and as a result, the toner images of four colors are transferred onto the transfer material P.

Next, after the four color toner images are transferred in this manner, the transfer material P is transferred to the fixing roller pair 41a, 41b.
Roller pairs 41a and 41b
The toner image is fixed on the surface by the heat and the pressure of the nip. Thereafter, the toner image is conveyed by the inner and outer discharge rollers 44 and 45 and discharged onto the discharge tray 48.

When a single-color image is to be obtained, a single-color visible image is transferred onto the transfer material P by a specific station, for example, the station 10a located at the most downstream position in the traveling direction of the transfer belt 71, thereby forming a full-color image. A monochrome image is formed on the transfer material P through the same process as in the case.

On the other hand, in the figure, reference numeral 80B denotes a control unit, which depends on the formed image (full-color image, single-color image), the type of the transfer material P to be used (OHP, thick paper, thin paper), and the like. A control device (not shown) for controlling the process speed is provided.

In the present embodiment, the control device sets the process speed faster than in the normal full-color mode because there is a margin in the fixing property of the toner image in the single-color image mode or the thin paper mode, so that the fixing property is improved. For disadvantageous thick paper and OHP, the process speed is set to be low so as to increase the fixing property.

Reference numeral 60B denotes a registration sensor such as a CCD, which is a reading means. The registration sensor 60B is the same as the registration sensor 60A of the first embodiment described above, and has a transfer material P.
Are arranged in parallel with each other in a direction orthogonal to the transport direction of each station.
After reading the automatic registration pattern formed on the transfer belt 71 by a to d, the read signal is input to the control device.

The control device operates the registration sensor 60
In addition to detecting the position of the auto-registration pattern based on the read signal from B,
The readout signal is fed back so as to adjust the inclination of the image and the like, and registration correction is performed.

When the automatic registration mode is set, the control device controls, for example, a pulse motor (not shown) to reduce the rotation speed of the drive roller 72 and to transfer the transfer belt 7.
1 is set to be slower than a normal full-color image. In the present embodiment, the control device sets the moving speed of the transfer belt 71 in the automatic registration mode to the slowest of the settable moving speeds.

By lowering the moving speed of the transfer belt 71, that is, by lowering the process speed, the reading time of the registration sensor 60B in the sub-scanning direction becomes longer, and the accuracy of image alignment in the automatic registration mode is improved. Can be raised.

Next, the image registration in the automatic registration will be described.

When performing image alignment, the control device firstly forms an interval L1 (see FIG. 3) between two registration patterns S1 formed by a reference station, for example, a black station 10a, and a next station 10b to 10d. The interval L2 (see FIG. 3) between the two registered patterns S2 is detected by the register sensor 60B.

Next, the controller 80B determines two intervals L1, L2 based on the read signal from the registration sensor 60B.
And the next station 1 is set so that L1 = L2.
0b to 10d are controlled to adjust the magnification of the image.

Next, to set the image writing position,
The writing position is moved so that (see FIG. 3) becomes zero. Thereafter, the image of the registration pattern S2 whose magnification and image writing have been corrected is transferred to the transfer belt 71 at the next stations 10b to 10d.

Next, in order to correct the inclination of the image, the difference △ 1, △ 2 (see FIG. 3) in the transport direction (main scanning direction) of the two registration patterns S1, S2 is matched, and a reference station is set. Match the registration pattern S1 of 10a. Finally, in order to adjust the position of the leading edge of the image, # 1 is adjusted to the interval between the stations 10a to 10d, or is adjusted to a predetermined distance.

When performing such tilt correction and image tip alignment, the process speed (movement speed of the transfer belt 71) is reduced as described above. Thus, the resolution of the registration sensor 60B on the sub-scanning side can be improved. That is, by reducing the process speed to 1 / n compared to the normal process speed, reading with respect to the time on the sub-scanning side becomes n times, whereby the registration sensor 60B has n times resolution performance.

As described above, when adjusting the image, the moving speed of the transfer belt 71 is set to be lower than the speed at which the image is transferred to the transfer material P.
, The reading accuracy of the registration pattern can be improved, and the image quality of the image formed on the transfer material P can be improved.

[0077]

As described above, according to the present invention, the moving speed of the intermediate transfer member or the conveying member at the time of image alignment is made slower than the speed at which the toner image is transferred onto the sheet, and By extending the reading time, the accuracy of image alignment can be improved. Further, this can improve the image quality.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a registration pattern and a registration sensor formed on an intermediate transfer belt of the image forming apparatus.

FIG. 3 is a diagram illustrating image matching in the image forming apparatus.

FIG. 4 is a diagram illustrating a configuration of an image forming apparatus according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating a configuration of an image forming apparatus using a conventional intermediate transfer method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image forming apparatus 10 station 11 photosensitive drum 30 intermediate transfer unit 31 intermediate transfer belt 32 drive roller 60A, 60B registration sensor 70 transfer unit 71 transfer belt 72 drive roller 80A, 80B control unit P transfer material S1, S2 registration pattern

Claims (4)

[Claims] 1. A method according to claim 1, wherein a plurality of image forming units and toner images formed on image carriers provided in the plurality of image forming units are sequentially superimposed and primary-transferred, and then the toner images are collectively formed on a sheet. An image forming apparatus provided with a transfer unit having an intermediate transfer body for secondary transfer, wherein reading is performed to read toner images for image alignment adjustment formed on the image carrier and sequentially transferred to the intermediate transfer body. Means, based on a read signal from the reading means, controlling the plurality of image forming units to match the formation position of each adjustment toner image transferred to the intermediate transfer body, and Control means for controlling a movement speed, wherein the control means determines a movement speed of the intermediate transfer body when reading the toner image for adjustment, and a transfer speed when transferring the toner image onto the sheet. Image forming apparatus and controls to slower than speed. 2. The method according to claim 1, wherein the control unit controls the moving speed of the intermediate transfer body when reading the toner image for adjustment to be the slowest of the settable moving speeds. The image forming apparatus according to claim 1. 3. A transfer unit having a plurality of image forming units and a transfer unit for sequentially transferring sheets to positions where toner images respectively formed on image carriers provided on the plurality of image forming units are transferred. A reading unit that reads toner images for image alignment adjustment sequentially formed on the image carrier after being formed on the image carrier, based on a read signal from the reading unit, Control means for controlling the plurality of image forming units so as to match the formation positions of the respective toner images for adjustment transferred to the carrier, and controlling a moving speed of the carrier, and Controlling the moving speed of the carrier when reading the toner image for adjustment to be lower than the speed at which the toner image is transferred onto the sheet. Apparatus. 4. The apparatus according to claim 1, wherein the control unit controls the moving speed of the intermediate transfer body when reading the toner image for adjustment to be the slowest of the settable moving speeds. The image forming apparatus according to claim 3.