JP2000047448A - Multiple image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiple image forming device capable of precisely performing the correcting processing of convergence error. SOLUTION: This multiple image forming device is provided with an intermediate transfer body for successively superposing and transferring a monochromatic image formed on each photoreceptor thereon to form a composed image; a convergence error detecting means for detecting the slippage between each color toner image formed on the intermediate transfer body; a drive motor 3 for driving a rotating moving means 5 that is the intermediate transfer body through a drive transmitting means 4; a motor control means 2 for controlling the operation of the drive motor 2; a speed detecting means 6 for detecting the rotating speed of the rotating moving means 5 driven by the drive motor 3; and a control means 1 for preliminarily determining the stop moving distance of the rotating moving means 5 driven at a prescribed speed by the drive motor 3 at the time of stopping in interlocking with the rotation stop of the drive motor 3 from the speed detected by the speed detecting means 6, and stopping the rotation of the drive motor 3 on this side by the stop moving distance to stop the rotating moving means 5 in a desired position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiple image forming apparatus using an electrophotographic technique having a plurality of photoreceptors, and more particularly to a positioning control of a rotary moving means in the multiple image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus employing an electrophotographic technique, a photosensitive member as an image carrier is charged by a charger, and the photosensitive member is irradiated with light according to image information to form a latent image. Is formed, the latent image is developed by a developing device, and then transferred to a sheet material or the like to form an image.

On the other hand, with the colorization of images, a plurality of image forming stations for performing the above-described image forming processes are provided, and a cyan image, a magenta image, a yellow image,
And tandem color image formation in which each color image of a black image is preferably formed on each image carrier, and a full-color image is formed by superimposing and transferring each color image on a sheet material at a transfer position of each image carrier. Devices have also been proposed. Such a tandem type color image forming apparatus includes:
Since each image forming unit is provided for each color, it is advantageous for speeding up.

However, the tandem type color image forming apparatus (multiplex image forming apparatus) has a problem in how to properly perform registration (registration) of each image formed by different image forming units. Have.
This is because the shift of the image forming positions of the four colors transferred to the sheet material finally appears as a color shift or a change in color tone.

Therefore, a pattern (hereinafter referred to as a “registration pattern”) serving as a reference for color misregistration is drawn in advance, a registration pattern is detected by a plurality of sensors (color misregistration detection), and the amount of misregistration is determined from the result. The calculation is performed, and the position adjustment (color shift correction) of each image is performed according to the shift amount.

Hereinafter, the operation of the conventional multiple image forming apparatus and the color misregistration detecting operation will be described. Here, FIG. 8 is an explanatory diagram showing the configuration of a conventional multiplex image forming apparatus, FIG. 9 is a block diagram showing a control structure of a drive system in the multiplex image forming apparatus of FIG. 8, and FIG. 10 is a multiplex image forming apparatus of FIG. And FIG. 11 is an explanatory view showing a registration pattern on an intermediate transfer belt and an arrangement of the color misregistration detecting means in the multiplex image forming apparatus of FIG.

As shown in FIG. 8, the multiplex image forming apparatus of the present embodiment has four image forming stations Pa and P.
b, Pc, and Pd are arranged. Each of the image forming stations Pa, Pb, Pc, and Pd is a photosensitive drum (photosensitive member) 20a, 20b, 20c, or 2 serving as an image carrier.
0d.

The photosensitive drums 20a, 20b, 20c, 2
0d, each photosensitive drum 20a, 20b, 20
charging means 21a, 21b, 21c, 21d for uniformly charging the surfaces of c, 20d to a predetermined potential; and laser light corresponding to image data of a specific color on charged photosensitive drums 20a, 20b, 20c, 20d 22a, 22b, 22
Exposure unit 22, which is a scanning optical system that forms an electrostatic latent image by irradiating c and 22d, and photosensitive drums 20a, 20b, and 20
developing means 23a, 23b, 23c, and 23d for visualizing the electrostatic latent image formed on the photosensitive drum 20 and the photosensitive drum 20;
transfer devices (transfer means) 24a, 24b, 24c, 24 for transferring the toner images visualized on a, 20b, 20c, 20d to an endless intermediate transfer belt (intermediate transfer body) 26
d, cleaning means 25a, 25b, 2 for removing the residual toner remaining on the photosensitive drums 20a, 20b, 20c, 20d after transferring the toner image from the photosensitive drums 20a, 20b, 20c, 20d to the intermediate transfer belt 26.
5c and 25d are arranged respectively.

Here, the intermediate transfer belt 26 rotates in the direction of arrow A in the illustrated case. In the image forming stations Pa, Pb, Pc, and Pd, a black image, a cyan image, a magenta image, and a yellow image are formed, respectively. Then, the photosensitive drums 20a, 20
The monochrome images of the respective colors formed on b, 20c, and 20d are sequentially superimposed and transferred onto the intermediate transfer belt 26 to form a full-color image.

On the downstream side of the image forming stations Pa, Pb, Pc and Pd with respect to the rotation direction of the intermediate transfer belt 26, a color shift detecting means (hereinafter referred to as a color shift detecting means) for checking a shift between toner images formed by respective colors , "Sensor unit") 33. The sensor unit 33 will be described later.

At the lower part of the apparatus, there is provided a paper feed cassette 28 in which a sheet material 29 such as printing paper is stored.
Then, the sheet material 29 is sent out from the sheet feeding cassette 28 to the sheet conveying path one by one by the sheet feeding roller 27.

A sheet material transfer roller 30 which contacts the outer peripheral surface of the intermediate transfer belt 26 for a predetermined amount on the sheet transport path and transfers a color image formed on the intermediate transfer belt 26 to a sheet material 29, and a sheet material. A fixing device 31 having a heating roller 31a for fixing the color image transferred onto the sheet material 29 to the sheet material 29 by pressure and heat caused by the holding rotation of the roller is provided.

In the multiplex image forming apparatus having such a configuration, first, a latent image of a black component color of image information is formed on the photosensitive drum 20a by the charging unit 21a and the exposing unit 22 of the image forming station Pa. This latent image is visualized as a black toner image by a developing unit 23a having black toner, and is transferred as a black toner image onto the intermediate transfer belt 26 by a transfer unit 24a.

On the other hand, while the black toner image is being transferred to the intermediate transfer belt 26, the image forming station Pb
, A latent image of a cyan component color is formed.
At 3b, a cyan toner image by the cyan toner is visualized. Then, the cyan toner image is transferred by the transfer unit 24b of the image forming station Pb to the intermediate transfer belt 26 where the transfer of the black toner image has been completed at the previous image forming station Pa, and is superimposed on the black toner image.

Hereinafter, the magenta toner image and the yellow toner image are formed in the same manner, and when the superposition of the four color toner images on the intermediate transfer belt 26 is completed, the paper feed rollers 27 The toner images of four colors are collectively transferred by a sheet material transfer roller 30 onto a sheet material 29 fed from the printer. Then, the transferred toner image is heated and fixed on the sheet material 29 by the fixing device 12, and
A full color image is formed on the sheet material 29.

The photosensitive drums 20a, 20b, 20c, and 20d, to which the transfer has been completed, have their residual toner removed by the cleaning means 25a, 25b, 25c, and 25d, and are ready for the next image formation.

As shown in FIG. 9, the control of the drive system is performed by the motor control means 2 controlling the number of rotations of the drive motor 3 by the control signal of the control means 1 such as a CPU for controlling the operation of the whole apparatus. Will be Here, the drive transmission means 4
The driving force is transmitted from the rotation shaft of the drive motor 3 by a gear or the like to the rotation moving means 5, whereby the rotation of the photosensitive drums 20a, 20b, 20c, 20d, the intermediate transfer belt 26, and the heating roller 31a is performed. The moving means 5 is driven to rotate.

When a known stepping motor (not shown) is used as the drive motor 3, the motor control means 2 outputs a control signal having a frequency corresponding to the number of rotations to output the number of rotations of the drive motor 3. Control. When a DC motor (not shown) is used as the drive motor 3, the motor control means 2 controls the rotation speed of the drive motor 3 by, for example, a PLL control method. That is, the FG signal 32 that generates a frequency proportional to the rotation speed of the DC motor as the rotating drive motor 3 is detected, and the rotation speed control is performed so that the phase and the frequency match the reference clock frequency (not shown). Is what you do.

A color image is formed by the above-described configuration. When the power is turned on, each of the image forming stations Pa and
When replacing Pb, Pc, and Pd, a color shift occurs due to a positional shift of each of the image forming stations Pa, Pb, Pc, and Pd due to a change in the installation state of the multiple image forming apparatus or a temperature change in the apparatus, or a mounting shift of the scanning optical system. However, this appears as a position shift in the main scanning direction or a position shift in the sub-scanning direction.

Therefore, when the power is turned on, when each of the image forming stations Pa, Pb, Pc, and Pd is replaced, and every time the temperature inside the apparatus changes, the operation of detecting and correcting a color shift is performed.

Here, as shown in FIG. 10, a sensor unit 33 includes an image sensor (hereinafter referred to as “CCD”) 34, a light source 35 such as a lamp, and a light source 35 irradiating the intermediate transfer belt 26 from the light source 35. Reflected light to CCD34
And a selfoc lens array 36 for forming an image. Then, as shown in FIG.
Are arranged at positions where pixel rows of pixels 34a and 34b in the CCD are orthogonal to the rotation direction A of the intermediate transfer belt 26, and are installed at two positions near the scanning start position and near the scanning end position of the exposure means 22. .

The operation of detecting a color misregistration in the above-described configuration of the sensor unit 33 will be described.

In the same manner as the above-described printing operation, a registration pattern such as a predetermined straight line or graphic (for example, the scanning start of the exposure unit 22 formed on a line orthogonal to the rotation direction A of the intermediate transfer belt 26). A straight line including the position and a straight line including the scanning end position) 37, 38, 39, 40
Transferred as a toner image for each color at a predetermined interval,
The amount of misregistration (color misregistration) of each color is measured by the sensor units 33a and 33b. For example, in the sub-scanning direction (A in FIG. 11)
11), the registration patterns 37, 37 of the respective colors on the intermediate transfer belt 26, as shown in FIG.
38, 39, and 40 are CCDs 3 in the sensor unit 33a.
4a and a time difference (ΔT1 = T−T1, where T is a predetermined design value) between the time T1 passing through 4a and a predetermined design value, and the positional deviation of each color from the transport speed v (ΔY1 = ΔT1 · v).
Is calculated. The skew error (inclination in the main scanning direction) is caused by the fact that the registration patterns 37, 38, 39, 40 of the same color on the intermediate transfer belt 26 are detected by the CCDs 34a, 34b in the sensor units 33a, 33b.
Is calculated by calculating the skew error (ΔY2 = ΔT2 · v) of each color from the time difference (ΔT2) passing through the image and the transport speed v.

[0024]

However, in the prior art described above, since the drive motor 3 is only driven to rotate at the designated number of revolutions, the intermediate transfer belt 26 driven by the drive motor 3 is stopped at a predetermined stop position. Cannot perform positioning control such as stopping at a short time. For this reason,
Since the registration patterns 37, 38, 39, and 40 are read using the sensor units 33a and 33b for detection while rotating the intermediate transfer belt 26, a conveyance error of the intermediate transfer belt 26 (for example, the intermediate transfer belt 2
No. 6 jitter and errors such as slippage of the intermediate transfer belt 26), it is not possible to detect color misregistration with high accuracy. Has a problem of deteriorating.

Accordingly, an object of the present invention is to provide a multiplex image forming apparatus capable of accurately performing a color shift correction process.

[0026]

In order to solve this problem, a multiple image forming apparatus according to the present invention comprises a plurality of photoconductors provided corresponding to respective color toner images to be developed, and a plurality of photoconductors. A plurality of charging means for uniformly charging the surface of the photoconductor, and an exposure means for irradiating the charged photoconductor with laser light corresponding to image data of a specific color to form an electrostatic latent image. A plurality of developing means provided for each photoconductor to visualize an electrostatic latent image formed on the photoconductor, and a single-color image of each color provided on each photoconductor and formed on the photoconductor. A plurality of transfer means for sequentially transferring and superimposing the images on the intermediate transfer body to form a composite image, a color shift detection means for detecting a shift between the respective color toner images formed on the intermediate transfer body, and a drive transmission means. Drive mode to drive the intermediate transfer A motor control means for controlling the operation of the drive motor; a speed detection means for detecting a rotation speed of the intermediate transfer body driven by the drive motor; and an intermediate transfer body driven to rotate at a predetermined speed by the drive motor. The stop moving distance when stopping in conjunction with the rotation stop of the motor is previously obtained from the speed detected by the speed detecting means, and the rotation of the drive motor is stopped just before the stop moving distance to move the intermediate transfer body to a desired position. And a control means for stopping the operation.

This makes it possible to accurately stop the intermediate transfer member at a predetermined stop position and read the registration pattern transferred on the intermediate transfer member with high accuracy, thereby correcting color misregistration. Processing can be performed accurately, and high image quality can be obtained.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention provides a plurality of photoconductors provided corresponding to each color toner image to be developed, and a photoconductor provided for each photoconductor. A plurality of charging units for uniformly charging the photosensitive member, an exposure unit for irradiating a laser beam corresponding to image data of a specific color onto the charged photosensitive member to form an electrostatic latent image, And a plurality of developing means for visualizing the electrostatic latent image formed on the photoconductor, and a single color image of each color formed on the photoconductor is provided on each of the photoconductors sequentially on the intermediate transfer body. A plurality of transfer means for forming a composite image by superimposed transfer, a color shift detecting means for detecting a shift between toner images of respective colors formed on the intermediate transfer body, and driving of the intermediate transfer body via a drive transmitting means. Drive motor to be performed and operation control of the drive motor. Motor control means, speed detecting means for detecting the rotational speed of the intermediate transfer member driven by the drive motor, and the intermediate transfer member rotationally driven at a predetermined speed by the drive motor stops in conjunction with the rotation stop of the drive motor And a control means for stopping the rotation of the drive motor shortly by the stop movement distance and stopping the intermediate transfer member at a desired position. This is a multiplex image forming apparatus that can accurately stop the intermediate transfer member at a predetermined stop position and read the registration pattern transferred on the intermediate transfer member with high accuracy. This has the effect that the correction processing can be performed accurately.

According to a second aspect of the present invention, there is provided the multiplex image forming apparatus according to the first aspect, wherein the pixel rows of the color misregistration detecting means are arranged along the rotation direction of the intermediate transfer member. This has the effect that the color misregistration correction processing can be performed accurately.

According to a third aspect of the present invention, in the first or second aspect of the invention, the speed detecting means comprises: a rotation speed of a rotation shaft of a drive motor; This is a multiplex image forming apparatus that detects the number of rotations of a transfer body, and has an effect that color misregistration correction processing can be accurately performed.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

FIG. 1 is a block diagram showing a control structure of a drive system of a multiplex image forming apparatus according to an embodiment of the present invention.
Is a DC of the multiple image forming apparatus according to the embodiment of the present invention.
FIG. 3 is a schematic diagram illustrating a structure for detecting the number of rotations of a motor, FIG. 3 is a schematic diagram illustrating a structure for detecting the number of rotations of a rotation shaft of a drive transmission unit by a photo encoder of a multiplex image forming apparatus according to an embodiment of the present invention, and FIG. FIG. 5 is a schematic diagram showing a structure for detecting the number of rotations of a rotation moving unit by a photo encoder of the multiplex image forming apparatus according to one embodiment of the present invention, and FIG. 5 shows a multiplex image forming apparatus according to one embodiment of the present invention in which the drive motor is stopped. FIG. 6 is a time chart showing a home position detection signal and a speed detection signal when the rotary moving unit is stopped at a predetermined position in the multiplex image forming apparatus according to one embodiment of the present invention. FIG. 7 shows the arrangement of the registration pattern and the color misregistration detecting means on the intermediate transfer belt in the multiple image forming apparatus according to one embodiment of the present invention. It is an explanatory diagram showing. In the present embodiment, the overall configuration and operation of the multiplex image forming apparatus are substantially the same as those described with reference to FIG.
Here, description is omitted to avoid duplication.

As shown in FIG. 1, the drive system in the multiplex image forming apparatus of the present embodiment includes a control means 1 for performing arithmetic control of various printing timings in the apparatus, and a drive signal of the control means 1 for controlling the drive motor 3. Motor control means 2 for performing drive control; drive transmission means 4 for transmitting a rotational driving force generated on a rotating shaft (not shown) of drive motor 3 to rotational movement means 5; drive motor 3; drive transmission means 4; It comprises a speed detecting means 6 for detecting the rotational speed of the means 5 and a home position detecting means 7 for detecting a home position which is a reference of a position on the rotating surface of the rotating and moving means 5. The rotation moving means 5 is, for example, a photoconductor drum (photoconductor) shown in FIG.
20a to 20d, an intermediate transfer belt (intermediate transfer body) 26, and the like.

As shown in FIG. 2, the drive motor 3 (FIG. 1)
The rotor 9 is fixed to the rotating shaft 8 of the DC motor. Inside the peripheral wall 9a of the rotor 9, a permanent magnet 1
1 are attached at predetermined intervals. A coil 10 is provided on the rotating shaft 8 so as to be surrounded by the peripheral wall 9 a of the rotor 9. Therefore, when a current is applied to the coil 10 by the motor control means 2 (FIG. 1) to generate a magnetic field, the magnetic field acts on the permanent magnet 11 to apply a rotational driving force to the rotor 9.

The rotor 9 is provided with a magnetic sensor 12 such as a Hall element or a magnetic resistance. When the magnetic sensor 12 detects a change in the magnetic field of the permanent magnet 11 that rotates together with the rotor 9, an electric signal having a frequency proportional to the rotation speed is output to the rotating shaft 8.

As shown in FIG. 3, a drive transmitting means 4 (FIG. 1) such as a gear for transmitting the rotational driving force of the rotating shaft 8 (FIG. 2) of the driving motor 3 to the rotational moving means 5 (FIG. 1). A slit disk 14 having slits 15 formed at equal intervals is fixed coaxially to the transmission rotation shaft 13. Further, the light-emitting element 17 and the light-receiving element 1
A photo-interrupter 16 is provided so as to sandwich the slit 15 with 8.

The emitted light 19 output from the light emitting element 17 is cut off and transmitted by the slit 15 of the rotating slit disk 14, so that the light receiving element 18 emits the emitted light according to the rotation of the slit disk 14. 19 is intermittently received. ON / OFF from the light receiving element 18 in conjunction with this light reception
A signal is output. That is, the light receiving element 18 outputs a signal having a frequency proportional to the rotation speed of the transmission rotation shaft 13.

In FIG. 4, an intermediate transfer belt 2 which is one of the rotational moving means 5 driven to rotate by a drive motor 3 is shown.
Slits 15 are formed at equal intervals along one end in the width direction of No. 6. The photo-interrupter 16 is also provided on the intermediate transfer belt 26 such that the slit 15 is interposed between the light-emitting element 17 and the light-receiving element 18 that are arranged to face each other. Then, the emitted light 19 output from the light emitting element 17 is blocked and transmitted by the slit 15,
A signal having a frequency proportional to the rotation speed of the intermediate transfer belt 26 is output from the light receiving element 18.

The stop control of the rotation moving means 5 in the multiplex image forming apparatus of the present embodiment having the above configuration will be described.

Under the control of the control means 1 shown in FIG. 1, the motor control means 2 drives the drive motor 3 to rotate at a constant speed. As a result, the rotational driving force of the driving motor 3 is changed by the rotation moving means 5 by the drive transmitting means 4 such as gears (not shown).
(For example, the photosensitive drums 20a and 20
b, 20c, 20d, the intermediate transfer belt 26, the heating roller 31a, etc.), and the rotation moving means 5 rotates at a predetermined rotation speed.

At this time, the speed detecting means 6 detects the rotation speed of the drive motor 3, the rotation speed of the rotating shaft in the drive transmission means 4 or the rotation speed of the rotation moving means 5, and outputs the detection result to the control means 1. I do.

Here, when the rotational speed of the drive motor 3 is detected, if a DC motor is used as the drive motor, the output signal of the magnetic sensor 12 in FIG. 2 is used as the speed detection signal. When detecting the rotation speed of the drive transmission means 4, the output signal of the light receiving element 18 in FIG. 3 is used as the speed detection signal. And the rotation moving means 5
When the rotation speed of the intermediate transfer belt 26 is detected, the output signal of the light receiving element 18 in FIG. 4 is used as the speed detection signal. In any case, since a detection signal having a frequency proportional to the rotation speed is obtained, the rotation speed can be detected by calculation.

FIG. 5 is a timing chart of the speed detection signal until the rotation of the drive motor 3 stops and the rotation of the intermediate transfer belt 26 stops for the intermediate transfer belt 26 rotating at a predetermined rotation speed.

In FIG. 5, when the driving motor 3 rotated by the control means 1 and the motor control means 2 is stopped at the time point a, the intermediate transfer belt 26 is driven by the inertia of the rotating shaft 8 and the drive transmission means 4, or Due to the inertia of the intermediate transfer belt 26 itself, it does not stop immediately but continues to rotate for a while. That is, the rotation speed gradually decreases, and stops at the time point b, which is a predetermined time after the time point a. Since the rotation speed is proportional to the frequency, FIG. 5 shows a state where the frequency of the speed detection signal gradually decreases from the point a at which the drive motor 3 stops rotating and becomes zero when the point b stops.

Here, it is determined whether or not the intermediate transfer belt 26 has stopped at the point b by determining whether or not the rising edge of the next pulse is output within a predetermined time from the falling edge b 'of the previous pulse. Is determined. The stop moving distance of the intermediate transfer belt 26 at this time corresponds to the total number m of pulses between the points a and b in the speed detection signal. Therefore, the control means 1 determines the total number of pulses m
Is detected and stored as the stop moving distance of the intermediate transfer belt 26, for example, at the time of warm-up after the power of the multiplex image forming apparatus is turned on.

In order to detect color misregistration with high precision, a registration pattern is formed on the intermediate transfer belt 26, and the speed at which the registration pattern is stopped at the position of the color misregistration detecting means 33 (FIG. 8). FIG. 6 shows a timing chart of the detection signal.

In FIG. 6, the home position detection signal is a specific position on the intermediate transfer belt 26 (hereinafter, "home position").
That. ), The signal of the intermediate transfer belt 26
It is output once every rotation. Then, the control means 1 detects the moving distance of the intermediate transfer belt 26 based on the home position. The control means 1 forms a registration pattern on the rotating intermediate transfer belt 26 in order to detect a color shift, and detects a home position in order to stop the registration pattern at the position of the color shift detecting means 33. The intermediate transfer belt 26 is stopped at a point b which is advanced from the point c by a moving distance corresponding to the total pulse number n of the speed detection signal. For this purpose, the drive motor 3 is stopped at a point m pulses before the stop movement distance, that is, at a point (n−m) pulses after the point c where the home position is detected.

In this way, the registration pattern formed on the intermediate transfer belt 26 is stopped at the position of the color shift detecting means 33, and the color shift is detected.

Next, the operation of detecting a color shift will be described.
As shown in FIG. 8 already described, a sensor unit 33 for detecting a color shift is disposed downstream of each of the image forming stations Pa, Pb, Pc, and Pd, and this sensor unit 33 is configured as shown in FIG. An image sensor (hereinafter, referred to as "CCD") 34, a light source 35 such as a lamp, and a selfoc lens array 36 for forming reflected light on the CCD.

As shown in FIG. 7, the pixel rows of the pixels 34a and 34b in the CCD in the sensor unit 33 are arranged along the rotation direction A of the intermediate transfer belt 26, and the scanning of the exposure means 22 is started. It is installed at two places near the position and near the scan end position.

As a result, a registration pattern such as a predetermined straight line or figure (for example, a straight line formed on a line orthogonal to the rotation direction A of the intermediate transfer belt 26 and including the scanning start position of the exposure means 22) The straight lines 37, 38, 39, and 40 including the scanning end position are transferred as toner images for each color at predetermined intervals, and the transferred toner images are stopped at the reading positions of the pixels 34a and 34b in the CCD. Then, the amount of color shift of each color is measured.

For example, the amount of positional deviation in the sub-scanning direction (the direction A in FIG. 7) is determined by the distance between each color of the registration patterns 37, 38, 39, and 40 on the intermediate transfer belt 26 shown in FIG. It is detected from the deviation from the set value.
The skew error (inclination in the main scanning direction) is detected from the amount of displacement in the sub-scanning direction when the same color registration pattern on the intermediate transfer belt 26 is detected by the CCDs 34a and 34b in the sensor units 33a and 33b. .

With the above operation, the registration patterns 37, 37 formed on the intermediate transfer belt 26 are formed.
It is possible to accurately stop the color shifts 38, 39, and 40 at the position of the color shift detecting means 33 to detect the color shift, and to accurately execute the color shift correction processing based on the detection.

[0054]

As described above, according to the present invention, it is possible to accurately stop the intermediate transfer member at a predetermined stop position and read the registration pattern transferred on the intermediate transfer member with high accuracy. Therefore, an effective effect that the color shift correction processing can be performed accurately can be obtained.

As a result, an effective effect that high image quality can be obtained can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a control structure of a drive system of a multiplex image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a structure for detecting a rotation speed of a DC motor of the multiplex image forming apparatus according to the embodiment of the present invention;

FIG. 3 is a schematic diagram showing a structure for detecting a rotation speed of a rotation shaft of a drive transmission unit by a photo encoder of the multiplex image forming apparatus according to one embodiment of the present invention;

FIG. 4 is a schematic diagram showing a structure for detecting the number of rotations of a rotation moving unit by a photo encoder of the multiplex image forming apparatus according to one embodiment of the present invention;

FIG. 5 is a time chart showing a speed detection signal when the drive motor is stopped in the multiplex image forming apparatus according to the embodiment of the present invention;

FIG. 6 is a time chart showing a home position detection signal and a speed detection signal when the rotation moving unit is stopped at a predetermined position in the multiplex image forming apparatus according to one embodiment of the present invention;

FIG. 7 is an explanatory diagram showing an arrangement of a registration pattern on an intermediate transfer belt and a color misregistration detecting unit in the multiplex image forming apparatus according to one embodiment of the present invention;

FIG. 8 is an explanatory diagram showing a configuration of a conventional multiple image forming apparatus.

9 is a block diagram illustrating a control structure of a drive system in the multiplex image forming apparatus of FIG.

FIG. 10 is an explanatory diagram showing a configuration of a color misregistration detecting unit in the multiplex image forming apparatus of FIG.

FIG. 11 is an explanatory diagram showing an arrangement of a registration pattern on an intermediate transfer belt and a color misregistration detecting unit in the multiplex image forming apparatus of FIG. 8;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Control means 2 Motor control means 3 Drive motor 4 Drive transmission means 5 Rotation moving means (intermediate transfer body) 6 Speed detection means 20a, 20b, 20c, 20d Photoconductor drums (photoconductors) 21a, 21b, 21c, 21d Charging means 22 Exposure Means 23a, 23b, 23c, 23d Developing Means 24a, 24b, 24c, 24d Transfer Device (Transfer Means) 26 Intermediate Transfer Belt (Intermediate Transfer Body) 33 Color Shift Detection Means (Sensor Unit)

Claims (3)

[Claims] 1. A plurality of photoconductors provided corresponding to each color toner image to be developed, and a plurality of charging means provided for each of the photoconductors and for uniformly charging the surface of the photoconductor. Exposure means for irradiating the charged photoconductor with laser light corresponding to image data of a specific color to form an electrostatic latent image; provided for each of the photoconductors, formed on the photoconductor A plurality of developing means for visualizing the electrostatic latent image, provided for each of the photoconductors, and sequentially superimposing and synthesizing a single-color image of each color formed on the photoconductor on an intermediate transfer body. A plurality of transfer means for forming an image; a color shift detecting means for detecting a shift between respective color toner images formed on the intermediate transfer body; and a drive motor for driving the intermediate transfer body via a drive transmitting means. And the operation of the drive motor Motor control means for performing control; speed detecting means for detecting a rotation speed of the intermediate transfer member driven by the drive motor; and the drive motor for rotating the intermediate transfer member rotated at a predetermined speed by the drive motor. The stop moving distance when stopping in conjunction with the rotation stop is previously obtained from the speed detected by the speed detecting means, and the rotation of the drive motor is stopped just before the stop moving distance to stop the intermediate transfer body. A multiplex image forming apparatus, comprising: control means for stopping at a desired position. 2. The multiplex image forming apparatus according to claim 1, wherein the pixel rows of said color misregistration detecting means are arranged along a rotation direction of said intermediate transfer member. 3. The apparatus according to claim 1, wherein said speed detection means detects a rotation speed of a rotation shaft of said drive motor, a rotation speed of a rotation shaft of said drive transmission means, or a rotation speed of said intermediate transfer member. Or the multiplex image forming apparatus according to 2.