JP2002162805A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimally corrects positional deviation according to a condition of the device. SOLUTION: The image forming device has a correction means that reads resist correction patterns formed by image forming sections and transferred on a moving body and that corrects positional deviation between images, formed by the image forming sections, in the scanning direction and sub-scanning direction based on the result of the reading of the patterns. Based on the result of the reading of an n-number of the resist correction patterns formed by the corresponding image forming sections, the correction means corrects positional deviation in the main scanning direction. Also, based on the result of the reading of an m (m>n) number of the resist correction patterns formed by the corresponding image forming sections, the correction means corrects positional deviation in the sub-scanning direction.

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 apparatus for forming an image by a plurality of image forming units.

[0002]

2. Description of the Related Art Conventionally, a photosensitive drum is irradiated with laser beam light modulated according to recorded information or light from a light emitting element such as an LED, and an electrostatic latent image on a photosensitive member is developed by an electrophotographic process. A plurality of recording devices for transferring images to transfer paper or an intermediate transfer belt by means of a transfer material transport belt, and while transferring the transfer paper to each of the recording devices sequentially, multiple transfer of each image on the transfer paper or an intermediate transfer belt There has been proposed an image forming apparatus capable of forming a color image by a method such as multiple transfer of each image and then collective transfer to transfer paper.

In this type of image forming apparatus, the photosensitive drum is formed on each photosensitive drum due to a mechanical mounting error between the photosensitive drums, an optical path length error of each laser beam, an optical path change, and a warpage due to an ambient temperature of the LED. The registration of each of the color images does not match on the transfer material to be finally multiply transferred. For this reason, conventionally, a pattern image for registration correction formed on a transfer belt from each photosensitive drum is read by a CCD sensor or the like, a registration shift on the photosensitive drum corresponding to each color is detected, and an image to be recorded is detected. The signal is subjected to electrical correction and / or a folding mirror provided in the laser beam optical path is driven to correct the optical path length or the optical path change.

[0004]

However, in the above-described image forming apparatus, there is a problem that a detection time and a correction time required for registration correction are required. Further, conventionally, since a pattern image for registration correction is formed on a transfer belt from each photosensitive drum, there is a problem that toner is consumed.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to carry out an optimum positional deviation correction according to the state of the apparatus.

[0006]

In order to solve the above-mentioned problems, the present invention provides a plurality of image forming units each having an image carrier, and an image formed by the plurality of image forming units is transferred at a transfer position. A moving body that moves to transfer, a reading unit that is formed by the plurality of image forming units and reads a plurality of registration correction patterns transferred on the moving body, and the plurality of the plurality of registration correction patterns based on a reading result of the reading unit; Correction means for correcting positional deviation in the main scanning direction and the sub-scanning direction between images formed by the image forming unit, wherein the correcting means comprises the n image forming units formed by the plurality of image forming units, respectively. The misregistration in the main scanning direction is corrected based on the reading result of the registration correction pattern, and m (m It has a configuration to correct the positional deviation of the sub-scanning direction on the basis of the registration correction pattern reading result of n).

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments shown in the drawings.

FIG. 1 is a sectional view of an essential part of an image forming apparatus embodying the present invention. The image forming apparatus of the present embodiment is described as an electrophotographic type, and furthermore, a color image output apparatus employing a plurality of image forming units in which the present invention is considered to be particularly effective, and employing an intermediate transfer method. Go.

The image output unit 1P is roughly divided into an image forming unit 1P.
0 (four stations a, b, c, and d are arranged side by side and have the same configuration), a paper supply unit 20, an intermediate transfer unit 30, a fixing unit 40, and a control unit (not shown). Is done.

Further, each unit will be described in detail. The image forming unit 10 has the following configuration. Photosensitive drums 11a and 11b as image carriers;
11c and 11d are pivotally supported at their centers, and are driven to rotate in the direction of the arrow. The primary chargers 12a, 12b, 12 face the outer peripheral surfaces of the photosensitive drums 11a to 11d in the rotational direction thereof.
c, 12d, optical systems 13a, 13b, 13c, 13d,
The folding mirrors 16a, 16b, 16c, 16d and the developing devices 14a, 14b, 14c, 14d are arranged. In the primary chargers 12a to 12d, the photosensitive drum 11
A charge of a uniform charge amount is given to the surfaces a to 11d. Next, light beams such as a laser beam modulated in accordance with a recording image signal are reflected by the optical systems 13a to 13d through the return mirrors 16a to 16d to form the photosensitive drums 11a to 11d.
Exposure above forms an electrostatic latent image thereon. Further, the electrostatic latent images are developed by developing devices 14a to 14d each storing a developer of four colors such as yellow (Y), cyan (C), maze (M), and black (Bk) (hereinafter referred to as toner). Visualize the image. On the downstream side of the image transfer areas Ta, Tb, Tc, and Td for transferring the visualized visible image to the intermediate transfer member, the photosensitive drums 11a to 11d are not transferred to the transfer material by the cleaning devices 15a, 15b, 15c, and 15d. The surface of the drum is cleaned by scraping off the toner remaining on 11d. According to the process described above, the image forming units 10a to 10d sequentially form Y, M, C, and Bk images, respectively.

The paper feed unit 20 includes cassettes 21 a and 21 b for storing the recording material P and a manual feed tray 2.
7. Pickup rollers 22a, 22 for feeding out recording materials P one by one from a cassette or a manual feed tray.
b and 26, a pair of paper feed rollers 23 and a paper feed guide 24 for transporting the recording material P sent from each pickup roller to the registration roller, and the secondary transfer of the recording material P in accordance with the image forming timing of the image forming unit. Transfer area Te
And registration rollers 25a and 25b for sending out the paper.

The intermediate transfer unit 30 will be described in detail. The intermediate transfer belt 31 includes a driving roller 32 that transmits drive to the intermediate transfer belt 31, a driven roller 33 that is driven by the rotation of the intermediate transfer belt 31, and a secondary transfer facing roller that faces the secondary transfer area Te with the belt therebetween. 34. Among these, a primary transfer plane A is formed between the driving roller 32 and the driven roller 33. The drive roller 32 has a surface of a metal roller coated with rubber (urethane or chloroprene) having a thickness of several mm to prevent slippage with the belt. The drive roller 32 is driven to rotate by a pulse motor (not shown). In primary transfer areas Ta to Td where the respective photosensitive drums 11a to 11d and the intermediate transfer belt 31 face each other, a primary transfer charger 35a is provided behind the intermediate transfer belt 31.
To 35d are arranged. A secondary transfer roller 36 is arranged to face the secondary transfer opposing roller 34, and forms a secondary transfer area Te by nip with the intermediate transfer belt 31. The secondary transfer roller 36 is pressed with an appropriate pressure on the intermediate transfer member. On the intermediate transfer belt, a cleaning blade 5 for cleaning the image forming surface of the intermediate transfer belt 31 is provided downstream of the secondary transfer area Te.
1 and a waste toner box 52 for storing waste toner.

The fixing unit 40 includes a fixing roller 41a having a heat source such as a halogen heater therein, a pressure roller 41b pressed against the roller (the roller may also have a heat source), and a nip portion of the roller pair. A guide 43 for guiding the transfer material P to the outside, an inner discharge roller 44 and an outer discharge roller 45 for further guiding the transfer material P discharged from the roller pair to the outside of the apparatus.

The control unit comprises a control board 50 for controlling the operation of the mechanism in each unit, a motor drive board (not shown), and the like.

Next, description will be made in accordance with the operation of the apparatus.

When an image forming operation start signal is issued from an operation unit (not shown) or an external host device, first, the transfer material P is sent out one by one from the cassette 21a by the pickup roller 22a. Then, the transfer material P is guided between the paper feed guides 24 by the paper feed roller pair 23 and is conveyed to the registration rollers 25a and 25b. At that time, the registration roller is stopped, and the leading end of the paper strikes the nip. Thereafter, the registration roller starts rotating at the timing when the image forming unit starts forming an image. During this rotation time, the transfer material P and the toner image primarily transferred from the image forming unit onto the intermediate transfer belt are in the secondary transfer area Te.
The timings are set so as to exactly match in.

On the other hand, in the image forming section, when an image forming operation start signal is issued, the toner image formed on the photosensitive drum 11d, which is the most upstream in the rotation direction of the intermediate transfer belt 31, by the above-described process is changed to a high voltage. Is primary-transferred to the intermediate transfer belt 31 in the primary transfer area Td by the primary transfer charger 35d to which. The primary-transferred toner image is transported to the next primary transfer area Tc. In this case, the image formation is performed with a delay of the time during which the toner image is conveyed between the respective image forming units, and the next toner image is transferred with the registration on the previous image. Hereinafter, the same steps are repeated, and the toner images of four colors are primarily transferred on the intermediate transfer belt 31 after all.

Thereafter, when the recording material P enters the secondary transfer area Te and comes into contact with the intermediate transfer belt 31, a high voltage is applied to the secondary transfer roller 36 in synchronization with the passage timing of the recording material P. Then, the four color toner images formed on the intermediate transfer belt by the above-described process are transferred onto the surface of the recording material P. Thereafter, the recording material P is accurately guided to the fixing roller nip by the conveyance guide 43. Then, the toner image is fixed on the paper surface by the heat of the roller pair 41A and 41B and the pressure of the nip. Thereafter, the paper is conveyed by the inner and outer paper discharge rollers 44 and 45, and the paper is discharged outside the apparatus.

FIG. 2 shows a characteristic portion of this embodiment.
And 3 will be described below.

FIG. 2 is a schematic diagram of the vicinity of a pattern image detecting means (including a CCD sensor) 60 for detecting a pattern image for registration correction of the image forming apparatus of FIG.

The intermediate transfer belt 31 is made of rubber as a raw material.
-An elastic body such as an elastomer is used, and the circumferential young
Rate is 1 × 10⁷ Pa or more. Of the intermediate transfer belt 31
Thickness ensures thickness accuracy and strength, and flexible rotation drive
0.3 mm to 3 mm is desirable from the viewpoint of realizing
No. Further, the intermediate transfer belt 31 is made of metal powder (carbon
Etc.) to obtain a desired resistance value (volume resistance).
1 × 10 ¹¹Ωcm or less is preferred)
Have been. Also, it turns in the direction of arrow B, and
The drive roller 32 is wound around the drive roller 32 to transmit the drive.
Have been.

On the other hand, the pattern image detecting section 60 is located between the photosensitive drum 11a, which is the most downstream in the belt advancing direction, and the drive roller 32 among the plurality of photosensitive drums,
At a position Sa on the intermediate transfer belt 31, a pattern image for registration correction formed on the intermediate transfer belt 31 by each of the image forming units 10a to 10d is read. Further, as shown in FIG. 3 (a top view of the main part of FIG. 2), they are arranged at both ends of the intermediate transfer belt 31.

Then, the registration controller 8
0 controls each of the image forming units 10a to 10d, forms a pattern image for registration correction on the intermediate transfer belt at a predetermined timing as described later, and outputs the result of reading of each registration correction pattern image by the pattern image detection unit 60. Accordingly, a registration shift on the photosensitive drum corresponding to each color is detected, an image signal to be recorded is electrically corrected, and / or a folding mirror 16a provided in a laser beam optical path is driven. , The correction of the optical path length change or the optical path change. Known methods can be used for the specific method of obtaining the position shift amount and the correction method.
0005.

At this time, according to the present embodiment, the registration correction pattern image formed on the intermediate transfer belt 31 by the plurality of photosensitive drums including the photosensitive drum 11a is moved to the area C by the rotation of the intermediate transfer belt 31. Since the pattern image detecting means 60 reads the registration correction mark image at the position Sa before entering and scattered due to expansion and contraction of the surface of the intermediate transfer belt 31 and deteriorating the image quality, the registration correction pattern image An erroneous detection due to image deterioration can be prevented, and accurate registration correction can be realized.

Next, a description will be specifically given of the misregistration correction operation in the present embodiment.

In the image forming apparatus according to the present embodiment, there are mainly four types of shifts: a shift in the main scanning direction, a shift in the sub-scanning direction, a magnification shift, and a tilt shift.

In the present embodiment, in the ordinary positional deviation correction processing, of these positional deviations, the deviation in the sub-scanning direction and the inclination deviation are determined for the transfer belt 30 for each color.
A registration correction pattern is formed over one rotation of the belt 30, and the position of each registration correction pattern based on the result of reading the registration correction pattern for one rotation of the belt 30 is averaged to obtain the registration pattern position of each color. On the basis of the position of the pattern, the positional deviation amount of each color in the sub-scanning direction and the inclination with respect to a predetermined reference color, for example, Bk is obtained.

As for the shift in the main scanning direction and the shift in magnification, a predetermined number (n) of resist correction patterns are formed for each color. Then, based on the reading result of the n resist correction patterns of each color, the position of each resist correction pattern is detected, and the position of each resist correction pattern is determined by averaging the positions of each resist correction pattern. Then, a predetermined reference color, for example, Bk
, The amount of displacement in the main scanning direction and the magnification of each color with respect to.

The above correction processing is called a first correction mode.

In this embodiment, a plurality of recording materials P
Also, in the continuous forming mode in which the image formation is performed by supplying the image data, the registration correction process is performed during the image formation. In this case, a registration correction pattern must be formed between images transferred onto the recording paper P on the transfer belt 30. For this reason, in the present embodiment, in the continuous forming mode, each of the registration correction patterns obtained by reading a predetermined number (one) of registration correction patterns for each color in each of the main scanning direction, the sub-scanning direction, the magnification, and the inclination. The amount of misregistration between the colors is obtained by averaging the pattern positions.

The above correction processing is called a second correction mode.

Hereinafter, the position shift correction processing of this embodiment will be described with reference to the flowchart of FIG. The processing in FIG. 4 is controlled entirely by the registration controller 80 in FIG.

In FIG. 4, first, when the power is turned on, an initialization process accompanying the power on is performed (S401). Then, the controller 80 controls the image forming units 10a to 10a to perform the position shift correction processing in the above-described first correction mode.
0d is controlled to execute the displacement correction processing in the first correction mode, and the internal counter is reset (S402).

Thereafter, the count value of the internal counter is confirmed, and it is determined whether a predetermined time has elapsed. Here, if the predetermined time has elapsed, the flow returns to S402, and the positional deviation correction processing in the first mode is performed again.

When the predetermined time has not elapsed and the continuous recording is instructed (S404), the controller 80 controls each of the image forming units 10a to 10d to transfer the image transferred to the continuously supplied recording material. A registration correction pattern is formed in the meantime, and a position shift correction process is performed in the second correction mode (S405). This is repeated until printing is completed (S40).
6).

As described above, according to the present embodiment, in the ordinary positional deviation correction processing, the sub-scanning direction and the inclination deviation are corrected based on the detection result of the registration correction pattern for one week of the belt. During continuous printing, position shift correction is performed based on the reading result of a predetermined number of registration correction patterns, so that position shift correction can be performed in a shorter time, and the standby time during continuous image formation can be shortened. Can be.

Further, in the present embodiment, in the ordinary positional deviation correction processing, the inclination deviation in the sub-scanning direction is corrected based on the result of reading the registration correction pattern for one week of the belt.

In the image forming apparatus of the present embodiment, in general, the moving speed of the transfer belt 30 is uneven due to the uneven thickness of the driving roller 32 and the transfer belt 30. For this reason, in the present embodiment, the influence of the positional deviation due to such speed unevenness is avoided by using the result of reading the registration correction pattern for one week of the belt for the sub-scanning direction and the inclination deviation.

Since the speed deviation hardly affects the main scanning direction and the magnification deviation, the amount of calculation is reduced by detecting the positional deviation amount using the reading result of a predetermined number of registration correction patterns. Less.

In this embodiment, the image forming apparatus using the intermediate transfer belt has been described. Alternatively, for example, a recording material may be directly placed on a transport belt and transported to transfer images of each color. The configuration may be as follows.

Further, in this embodiment, the image forming apparatus using laser beams has been described. However, the present invention can be applied to an apparatus in which image forming is performed by a plurality of image forming units. .

[0042]

As described above, according to the present invention,
Optimal displacement correction can be performed according to the state of the apparatus.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus to which the present invention is applied.

FIG. 2 is a diagram showing a configuration of a main part near a reading unit in the apparatus of FIG.

FIG. 3 is a view showing a state of a resist correction pattern formed by the apparatus of FIG. 1;

FIG. 4 is a flowchart for explaining the operation of a position shift correction process by the apparatus of FIG. 1;

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) G06T 7/60 150 G03G 21/00 372 F term (reference) 2C362 BA52 BA68 BA71 BB37 BB40 BB46 BB47 CA22 CA23 CA39 CB80 2H027 DA23 DE02 DE07 DE10 EB04 EC03 EC06 EC07 ED04 EF02 EF09 FA02 FA35 FB06 ZA07 2H030 AA01 AB02 AD12 AD17 BB02 BB16 BB42 BB63 5L096 BA07 CA14 FA32 FA69

Claims (9)

[Claims] 1. A plurality of image forming units each having an image carrier, a moving body that moves to transfer images formed by the plurality of image forming units at respective transfer positions, and the plurality of image forming units Reading means for reading a plurality of registration correction patterns formed on the moving body and transferred onto the moving body; and a main scanning direction between images formed by the plurality of image forming units based on a reading result of the reading means. Correction means for correcting a position shift in the sub-scanning direction, wherein the correction means is configured to adjust the position in the main scanning direction based on a result of reading the n registration correction patterns formed by the plurality of image forming units. A result of reading the registration correction pattern of m (m> n) formed by the plurality of image forming units while correcting the displacement. Image forming apparatus and correcting the positional deviation of the sub-scanning direction based. 2. The image forming apparatus according to claim 1, wherein said n is a predetermined number. 3. The moving object is an endless moving object, wherein the m
2. The image forming apparatus according to claim 1, wherein the number corresponds to the number of the registration correction patterns that can be formed in one round of the endless moving body. 4. The correction means detects a position of each resist correction pattern in accordance with a result of reading the n resist correction patterns, and based on an average of the positions of the n resist correction patterns, detects the plurality of images. 2. The image forming apparatus according to claim 1, wherein an amount of displacement in the main scanning direction between images formed by the forming unit is detected. 5. The correction means detects a position of each resist correction pattern in accordance with a result of reading the m number of resist correction patterns, and detects the plurality of images based on an average of the positions of the m number of resist correction patterns. 2. The image forming apparatus according to claim 1, wherein an amount of positional shift between images formed by the forming unit in the sub-scanning direction is detected. 6. The correction means further corrects a magnification shift based on a reading result of the n registration correction patterns formed by the plurality of image forming units, respectively, and controls the plurality of image forming units. 2. The image forming apparatus according to claim 1, wherein a tilt shift is corrected based on a reading result of the m registration correction patterns formed respectively. 7. A plurality of image forming units each having an image carrier, a moving body that moves to transfer images formed by the plurality of image forming units at respective transfer positions, and the plurality of image forming units Reading means for reading a plurality of registration correction patterns formed on the moving body and transferred onto the moving body; and a main scanning direction between images formed by the plurality of image forming units based on a reading result of the reading means. Correction means for correcting a position shift in the sub-scanning direction, wherein the correction means is configured to adjust the position in the main scanning direction based on a result of reading the n registration correction patterns formed by the plurality of image forming units. A result of reading the registration correction pattern of m (m> n) formed by the plurality of image forming units while correcting the displacement. First to correct the positional deviation of the sub-scanning direction based
And a second correction mode for correcting the positional deviation in the main scanning direction and the sub-scanning direction based on the result of reading one registration correction pattern formed by each of the plurality of image forming units. An image forming apparatus comprising: 8. A continuous image forming mode in which a plurality of recording materials are continuously supplied and an image is formed, and the correction unit corrects a position shift in the second correction mode. Item 8. The image forming apparatus according to Item 7. 9. The image forming apparatus according to claim 7, wherein the correction unit executes the position shift correction processing in the first correction mode in response to power-on of the apparatus.