JP2000310898A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an image of high image quality where the deterioration of image quality due to deviation in picture elements caused by periodical unevenness of drive can be kept down to a minimum by having the periodical unevenness in the drive itself decreased by facilitating the adjustment of a relative angle for attachment of photoreceptors drums for each color and a driving gear in the rotational direction. SOLUTION: In the image forming device, an image station P to form an image on each photoreceptor drum 222 (222a to 222d), a sensor S (S1-S4) where one photoreceptor drum 222 is deemed to be a standard photoreceptor drum and detecting a stopping position for rotation of at least one photoreceptor drum that is other than the standard photoreceptor drum, a driving motor M enabling independent rotational drive of at least one photoreceptor drum among the photoreceptor drums other than the standard photoreceptor drum with respect to the standard photoreceptor drum and a control part CON controlling the driving motor M based on a value by which a relative relationship of position of the standard photoreceptor drum and at least one image carrier that is other than the standard photoreceptor drum is showed an the value that is also dividing one circumference of at least one photoreceptor drum into n (n>1) and a detected signal from the sensor S, are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image transfer apparatus in which a transfer material is supported and conveyed by a transfer conveyance belt which comes into contact with a surface of a transfer portion of a rotating image carrier (photosensitive drum) in a predetermined positional relationship. The present invention relates to an image forming apparatus that transfers and reproduces a toner image formed on a carrier on a transfer material.

[0002]

2. Description of the Related Art Conventionally, there is a color image forming apparatus which transfers a color image as YMCK image data to a recording unit and sequentially superimposes and reproduces a color image while reproducing each color image. In such a color image forming apparatus, there is a problem that a color image cannot be faithfully reproduced unless images of respective colors are accurately superimposed, and how to solve this problem is a major issue in technical development. Had become.

In an image forming apparatus having an infinite number of components, there is a small variation in the component accuracy of each component, and the variation varies in each image forming device due to the assembling accuracy when assembling these components. appear. Therefore, conventionally, a pattern adjustment of each color is performed by trially forming a pattern image of each color, and confirming a positional relationship between the pattern images of each color, and performing an image forming position adjustment for each image forming unit of each color. Registered Patent No. 2642351).

However, even if the above-described registration adjustment is performed, the color shift due to the shift of the image writing start position can be corrected, but the periodic drive of a drive system such as a drive gear for driving the photosensitive drum is performed. It was not possible to correct a color shift caused by irregular speed fluctuations on the photosensitive drum caused by unevenness. That is, in such an image forming apparatus,
Conventionally, periodic drive unevenness in each recording unit has been a problem, and the periodic drive unevenness occurs in each print unit, so that images recorded with color materials of each color are sequentially superimposed on each other. When reproducing as an image,
There was a problem that color shift occurred and a faithful color image could not be reproduced.

(Prior Art 1) Therefore, in a conventional color image forming apparatus, when an image formed on a photosensitive drum in each recording section is transferred in a transfer section,
In order that the condition of the drive unevenness that occurs periodically becomes the same,
It has been considered that the relationship between the distance (time) from the image writing position to the transfer position to the transfer position and the drive fluctuation period of the drive mechanism is N times as large as the relationship (Japanese Patent Publication No. Hei 7-31446). Gazette, Japanese Patent Publication No. 8-14731, etc.).

FIG. 17 shows a configuration around a transfer belt which conveys each image forming section and a transfer material for transferring an image formed by each image forming section in a conventional color image forming apparatus employing the above-mentioned method. Is shown. In FIG. 17, photosensitive drums 322a, 322b, 322c, and 322d constituting black, cyan, magenta, and yellow recording units in order from the left. The images of the respective colors formed on the photosensitive drums 322 are transferred onto the transfer material supported and conveyed by the transfer / transport belt 316 as the transfer / conveyance belt 316 moves.
Are transferred in superimposed order from black at a transfer portion A adjacent to the transfer portion. Here, the rotation of each photoconductor drum 322 is started at the same time.
2 is mounted so that its rotational drive unevenness has the same phase.

As a specific example, each photosensitive drum 322
Are mounted such that all the reference (for example, a key-shaped hole ha as shown in the figure) indicating the period of the drive unevenness are aligned in the same direction. This allows
At the same time, the photosensitive drums 322 always rotate with the same drive unevenness. Therefore, each distance L ′ between the transfer portions A-A of each photoconductor drum 322 is represented by (L ′ = Nπd ‥‥) where d is the diameter of the photoconductor drum 322.
(N is an integer), so that in the transfer process of the image at each transfer portion A of the four photosensitive drums 322 arranged in parallel, the drive unevenness period is always the same on the transfer material. Thus, the images formed by the color materials of the respective colors are sequentially superimposed, and as a result, it is possible to eliminate the color shift caused by the driving unevenness.

(Prior Art 2) Japanese Patent Application Laid-Open No. 5-197244 is a conventional technique for preventing color misregistration due to driving unevenness of another color image forming apparatus. This technique is a color image forming apparatus having black, cyan, magenta, and yellow color recording units, but can perform monochrome image formation using only the black recording unit. Therefore, in the photoconductor driving unit of each color recording unit, the driving force is transmitted from a single drum driving motor to cyan, magenta, and yellow via a single driving clutch, and only black is different from the above driving clutch. The driving force is transmitted through the recording medium, so that only the black recording unit can operate.

However, since the drive system is made independent only for black, it is necessary to synchronize the rotating positions of the photosensitive drums of black and the other three colors. Therefore, the rotation position of the black photoconductor drum and the rotation position of one of the cyan, magenta, and yellow photoconductor drums are detected from the light shielding members on each drum pulley, and whether the detection signals are synchronized or not. Is determined and the operation control of the two drive clutches is performed so that the determination results are synchronized, so that drive unevenness with respect to the rotational positions of the photosensitive drums of black and the other three colors can be prevented.

[0010]

However, in the configuration of the prior art 1, the distance relationship between the recording units A-A arranged in parallel must be arranged in accordance with the periodic drive fluctuation. If the distance between the recording units A-A is determined in accordance with the periodic drive fluctuation, a distance corresponding to the peripheral length of the photosensitive drum is necessarily required even if the integer N is set to 1. As a result, the size of the image forming apparatus itself increases, and it is not possible to reduce the size as desired by the user. In particular, as described above, the photosensitive drum is Y
(Yellow), M (magenta), C (cyan), and B
This is a serious problem in an image forming apparatus provided with four colors of k (black).

[0011] In addition, these drive unevenness adjustments can only be performed by a person who is skilled while actually taking images.

For this reason, in the image forming apparatuses according to the prior art 1 and the prior art 2, at the time of production, the relative mounting angles of the photosensitive drums and the driving gears of the respective colors in the rotation direction are adjusted. It is assumed that no adjustment is necessary.

However, in a recent color image forming apparatus,
The image forming apparatus includes a monochrome mode in which an image is formed using a black-only recording unit as in the related art 2, a mono-color mode in which an image is formed using a single-color recording unit among cyan, magenta, and yellow. Methods are diversifying. For this reason, after the image forming apparatus is once set at the user's hand, there is a time-dependent change for each photosensitive drum in the above-described monochrome mode or mono-color mode, or a scratch on the one-color photosensitive drum by mistake at the time of clearing a jam. When a situation such as attachment occurs, it is necessary to replace each photosensitive drum of each color. However, an apparatus such as the above-mentioned prior art 1 and prior art 2 which can only adjust the angle at the time of production has a problem that maintenance such as individual replacement of the photosensitive drum of each color is very difficult.

(Prior Art 3) Japanese Patent Laid-Open No. 9-304
Japanese Patent Application Publication No. 992 discloses a technique of forming a test image using a test chart, reading a correction value for drive unevenness of each color image forming unit from a pattern appearing there, and adjusting the read value. . This adjustment method is used to prevent periodic drive unevenness due to vibration of the photosensitive drum.
This is to optimize the relative video output start timing of the print head of each color so that unevenness is hardly noticeable.

According to this technique, maintenance such as individual replacement of the photosensitive drum of each color becomes possible. However, since the relative angle between the photoconductor drum and the drive gear already set is not changed, the periodic drive unevenness itself does not change. That is, even if the periodic driving unevenness can be made inconspicuous, there remains a problem that it cannot be reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has reduced periodic drive unevenness itself and minimized image quality deterioration due to pixel shift caused by periodic drive unevenness. It is an object of the present invention to provide an image forming apparatus capable of easily adjusting a relative mounting angle of a photosensitive drum or a driving gear of each color in a rotation direction so that a high-quality image can be formed.

[0017]

The present invention has the following configuration to achieve the above object. The invention of claim 1 is
A plurality of rotatable image carriers, an image forming means for forming an image on the image carriers, and one of the plurality of image carriers as a reference image carrier, other than the reference image carrier Detecting means for detecting the rotation stop position of at least one image carrier, and driving means for enabling at least one image carrier other than the reference image carrier to be rotatable independently of the reference image carrier. And a value indicating the relative positional relationship of at least one image carrier other than the reference image carrier with respect to the reference image carrier. One round of at least one image carrier is divided into n (n> 1) An image forming apparatus comprising: a control unit that controls a driving unit based on a value to be performed and a detection signal of a detection unit.

According to a second aspect of the present invention, the control means switches the value indicating the relative positional relationship from the first value to the n-th value,
The image forming apparatus according to claim 1, wherein the driving unit is controlled so that the image is formed by the image forming unit.

According to a third aspect of the present invention, the control means controls the driving means so that the image forming means forms an image by changing the number of divisions n of n divisions (n> 1). 2. The image forming apparatus according to item 2.

According to a fourth aspect of the present invention, a plurality of rotatable image carriers, image forming means for forming an image on the image carriers, and one of the plurality of image carriers are used as a reference image. Detecting means for detecting the rotational position of each of at least two image carriers other than the reference image carrier, and at least two image carriers other than the reference image carrier being independent of the reference image carrier; Image forming based on a detection signal of a detecting unit and a value indicating a relative positional relationship between at least two image carriers other than the reference image carrier with respect to the reference image carrier. Control means for controlling the driving means so as to form an image by means,
The control unit controls the respective values indicating the relative positional relationship of at least two image carriers other than the reference image carrier with the same value.

According to a fifth aspect of the present invention, the control means causes the image forming means to form an image on at least two image carriers other than the reference image carrier on the transfer material. An image forming apparatus according to any one of the preceding claims.

According to a sixth aspect of the present invention, there is provided the image forming apparatus according to the fifth aspect, further comprising a display unit for displaying a set value of each of the plurality of image carriers in a list.

According to the first aspect of the present invention, one of the plurality of image carriers is used when initial setting of the image forming apparatus or when image unevenness occurs in the sub-operation direction in a copy result. Is used as a reference image carrier, and the rotation stop position of the other image carriers is detected by the detecting means, and the detection result and a value indicating a relative positional relationship with respect to the reference image carrier (one rotation of the image carrier is divided into n parts) The control unit drives and stops the driving units of the image carriers other than the reference image carrier based on (value of (n> 1)), thereby forming the relative rotational phase relationship of each image carrier. It becomes possible.

Therefore, the value indicating the relative positional relationship is changed,
The adjustment makes it possible to easily perform the adjustment for preventing the periodic drive unevenness even if the image carriers of each color are replaced after the image forming apparatus is installed at the user's site.

Further, by reducing the periodic driving unevenness itself, it is possible to provide a high quality image in which the deterioration of the image quality due to the pixel shift caused by the periodic driving unevenness is suppressed as much as possible.

Further, since the relative positions of the image carriers and the driving means of the respective colors in the rotational direction can be adjusted with an easily recognizable adjustment value, the adjustment can be performed by a simple operation.
A user-friendly image forming apparatus can be provided.

According to the second aspect of the present invention, n kinds of test images can be output at once without outputting a test image corresponding to a value indicating one positional relationship. The troublesome operation of inputting a value indicating a and outputting a test image can be eliminated.

Since n kinds of test images can be output collectively over the entire circumference of the image carrier, one test image of one circumference of the image carrier can be output.
It is possible to easily know which rotational position value is the value that minimizes the periodic drive unevenness with / n accuracy.

According to the third aspect of the present invention, when a test image is output with a small number of divisions n, the number of test images can be reduced, so that the most periodic drive unevenness in one rotation of the image carrier can be reduced. The vicinity of the rotation position of the adjustment value to be performed can be quickly checked. Further, when a test image is output with a large number of divisions n, the number of divisions n can be checked more accurately around the rotational position than when a test image is output with a small number of divisions.

According to the fourth aspect of the present invention, the values indicating the relative positions of at least two image carriers other than the reference image carrier with respect to the reference image carrier are set to the same value, so that the respective positions are set. The trouble of inputting the value indicating the relationship one by one can be saved, and efficient operation can be performed.

According to the fifth aspect of the present invention, it is possible to perform test printing at the same rotation stop position of the rotation stop position of another image carrier with respect to the reference image carrier, and to perform periodic driving unevenness of each image carrier. It is not necessary to uselessly use the image forming and transfer sheet to check the state at each rotation stop position. Further, since the image of the periodic drive unevenness of each image carrier can be formed on one transfer sheet, the adjustment can be made easier.

According to the sixth aspect of the present invention, the periodic drive unevenness state of each image carrier is formed as an image on one transfer sheet and output, so that a display screen or the like adjusted for each image carrier can be displayed. Switching is not only annoying, but also susceptible to input errors. However, by displaying the list at the same time, the input operation of the operator can be made less likely to be erroneous.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described below with reference to FIGS. FIG. 1 is a schematic front sectional view showing a configuration of a digital color copying machine 1 which is an image forming apparatus according to an embodiment of the present invention. A document table 111 and an operation panel (not shown) are provided on the upper surface of the copying machine main body 1, and an image reading section 110 and an image forming section 210 are provided inside the copying machine main body 1. On the upper surface of the platen 111, the platen 1
11 is supported so as to be openable and closable with respect to the platen 111.
A two-sided automatic document feeder (RADF; Reversing Automatic)
c Document Feeder) 112 is mounted.

The double-sided automatic document feeder 112 first conveys the document so that one side of the document faces the image reading unit 110 at a predetermined position on the document table 111, and the image reading on this one side is completed. Later, when the other surface is at a predetermined position on the
The document is inverted and conveyed toward the document table 111 so as to face the document table 111. Then, after the two-sided image reading for one document is completed, the double-sided automatic document feeder 112 discharges this document and performs a double-sided conveyance operation for the next document. The above-described operation of conveying the document and reversing the front and back is controlled in relation to the operation of the entire copying machine 1.

The image reading section 110 is disposed below the document table 111 for reading an image of the document conveyed onto the document table 111 by the automatic duplex document feeder 112. The image reading unit 110 includes the platen 1
Document scanning body 11 reciprocating in parallel along the lower surface of 11
3, 114, an optical lens 115, and a CCD line sensor 116 as a photoelectric conversion element.

The original scanning members 113 and 114 are composed of a first scanning unit 113 and a second scanning unit 114. The first scanning unit 114 has an exposure lamp for exposing the surface of the document image and a first mirror for deflecting a reflected light image from the document in a predetermined direction. It reciprocates in parallel at a predetermined scanning speed while maintaining the distance. The second scanning unit 114 has second and third mirrors for further deflecting the reflected light image from the document deflected by the first mirror of the first scanning unit 113 in a predetermined direction. It reciprocates in parallel with one scanning unit 113 while maintaining a constant speed relationship.

The optical lens 115 reduces the reflected light image from the document deflected by the third mirror of the second scanning unit, and forms the reduced light image at a predetermined position on the CCD line sensor 116. It is.

The CCD line sensor 116 photoelectrically converts the formed light image sequentially and outputs it as an electric signal. The CCD line sensor 116 reads a black-and-white image or a color image, and outputs R (red), G (green), B
(Blue), which is a three-line color CCD capable of outputting line data that is color-separated into the respective color components of (blue). This C
The document image information converted into an electric signal by the CD line sensor 116 is further transferred to an image processing unit (not shown) and subjected to predetermined image data processing.

Next, the configuration of the image forming unit 210 and the configuration of each unit related to the image forming unit 210 will be described.
Below the image forming unit 210, paper (for example, a recording medium such as paper or OHP paper) P stored and stored in the paper tray TR is separated one by one and supplied to the image forming unit 210. A paper mechanism 211 is provided. Then, the sheets P separated and supplied one by one are conveyed to the image forming unit 210 at a controlled timing by a pair of registration rollers 212 disposed in front of the image forming unit 210.
Further, the sheet P on which an image is formed on one side is transferred to the image forming unit 2 in synchronization with the image forming of the image forming unit 210.
10 and re-conveyed.

Below the image forming section 210, a transfer and transport belt mechanism 213 is disposed. The transfer / transport belt mechanism 213 is provided between the drive roller 214 and the driven roller 215 to extend substantially in parallel with the transfer / transport belt 21.
6, the paper P is electrostatically attracted and transported. Further, a pattern image detection unit 300 that detects a test pattern formed on the transfer / transport belt 216 is provided near the lower side of the rotation orbit of the transfer / transport belt 216.

Further, on the downstream side of the transfer transport belt mechanism 213 in the paper transport path, close to the drive roller 214,
A fixing device 217 for fixing the toner image transferred and formed on the sheet P to the sheet P is provided. The sheet P that has passed through the nip between the pair of fixing rollers of the fixing device 217 passes through a conveyance direction switching gate 218 and is discharged by a discharge roller 219 onto a discharge tray 220 attached to the outer wall of the copying machine main body 1. Is discharged.

The switching gate 218 is connected to the sheet P after fixing.
Is selectively switched between a path for discharging the sheet P to the copying machine main body 1 and a path for re-supplying the sheet P toward the image forming unit 210. The sheet P whose transport direction has been switched again toward the image forming unit 210 by the switching gate 218 is turned upside down via the switchback transport path 221, and then the image forming unit 210 is turned over.
Is supplied again.

Above the transfer belt 216 in the image forming section 210, a first image forming station Pa, a second image forming station Pb, and a third image forming station are disposed adjacent to the transfer belt 216. P
c, and a fourth image forming station Pd are provided in order from the upstream side of the paper transport path.

The transfer conveyance belt 216 is driven by the driving roller 21.
4, the sheet P is frictionally driven in the direction indicated by the arrow Z in FIG. 1, grips the sheet P fed through the sheet feeding mechanism 211 as described above, and transfers the sheet P to the image forming station Pa.
To Pd. Each image station Pa-P
d has substantially the same configuration. Each of the image stations Pa, Pb, Pc, and Pd has a photosensitive drum 222a, 222b, which is rotationally driven in the direction of arrow F shown in FIG.
222c and 222d (which may be abbreviated as the photosensitive drum 222), respectively.

Around the photosensitive drums 222a to 222d, chargers 223a, 223b, 223c, 22 for uniformly charging the photosensitive drums 222a to 222d, respectively.
3d and developing devices 224a and 224 for developing electrostatic latent images formed on the photosensitive drums 222a to 222d, respectively.
4b, 224c, 224d and transfer dischargers 225a, 225b, 225c, 225d for transferring the developed toner images on the photosensitive drums 222a to 222d to the paper P.
Cleaning devices 226a, 226b, and 2 for removing toner remaining on photoconductor drums 222a to 222d.
26e and 226d are photosensitive drums 222a to 222d
Are sequentially arranged along the rotation direction.

Each of the photosensitive drums 222a to 222d
Above the laser beam scanner unit 227
a, 227b, 227c, and 227d are provided, respectively. Each laser beam scanner unit 227a-
Reference numeral 227d denotes a semiconductor laser device (not shown) for emitting dot light modulated according to image data, a polygon mirror (deflecting device) 240 for deflecting a laser beam from the semiconductor laser device in the main scanning direction, and a polygon. It is composed of an fθ lens 241 and mirrors 242 and 243 for imaging the laser beam deflected by the mirror 240 on the surfaces of the photosensitive drums 222a to 222d.

The laser beam scanner 227a receives a pixel signal corresponding to a black component image of a color original image, the laser beam scanner 227b receives a pixel signal corresponding to a cyan component image of a color original image, and the laser beam scanner 227c. The pixel signal corresponding to the magenta color component image of the color original image is output to the laser beam scanner 2
A pixel signal corresponding to the yellow component image of the color document image is input to 27d.

As a result, an electrostatic latent image corresponding to the color-converted document image information is formed on each of the photosensitive drums 222a to 222d. The developing device 227a receives the black toner, the developing device 227b receives the cyan toner, the developing device 227c receives the magenta toner, and the developing device 227c.
27d contains yellow toner, respectively, and the electrostatic latent images on the photosensitive drums 222a to 222d are:
The image is developed with the toner of each color. As a result, the document image information color-converted by the image forming unit 210 is reproduced as a toner image of each color.

A paper-suction (brush) charger 228 is provided between the first image forming station Pa and the paper feeding mechanism 211. And the sheet feeding mechanism 211
The sheet P supplied from the first image forming station Pa is securely sucked onto the transfer / conveying belt 216.
To the fourth image forming station Pd without shifting.

On the other hand, a static eliminator (not shown) is provided almost directly above the drive roller 214 between the fourth image station Pd and the fixing device 217. An AC current is applied to the static eliminator to separate the paper P electrostatically attracted to the conveyor belt 216 from the transfer conveyor belt 216.

In the digital color copying machine having the above configuration, cut sheet-shaped paper is used as the paper P. The sheet P is sent out from the sheet cassette and fed to the sheet feeding mechanism 2.
When the paper P is fed into the guide of the paper feed conveyance path 11, the leading end of the paper P is detected by a sensor (not shown),
It is temporarily stopped by the pair of registration rollers 212 based on a detection signal output from this sensor. The paper P is transferred to the transfer conveyor belt 2 rotating in the direction of arrow Z in FIG.
16 is sent. At this time, since the transfer conveyor belt 216 has been given a predetermined charge by the attraction charger 228 as described above, the paper P is transferred to each image station Pa.
ＰPd is stably conveyed and supplied.

In each of the image stations Pa to Pd, a toner image of each color is formed, and is superposed on the support surface of the paper P conveyed by being electrostatically attracted and conveyed by the transfer conveyance belt 216. Fourth image station Pd
Is completed, the paper P is sequentially transferred from the leading end portion thereof to the transfer conveyance belt 216 by the discharger for static elimination.
It is peeled off from above and guided to the fixing device 217. Finally, the paper P on which the toner image has been fixed is discharged onto a paper discharge tray 220 from a paper discharge port (not shown). In the above description, the laser beam scanner unit 2
Optical writing to the photoreceptor is performed by exposing the laser beam by scanning with the laser beams 27a to 227d.

Note that a writing optical system (LED head) including a light emitting diode array and an imaging lens array may be used instead of the laser beam scanner unit.
The LED head is smaller in size than the laser beam scanner unit, and has no moving parts and is silent.
Therefore, it can be suitably used in an image forming apparatus such as a tandem type digital color copying machine which requires a plurality of optical writing units.

Next, the rotation phase control of each photosensitive drum, which is a feature of the present embodiment, will be described. In the digital color copying machine of the present embodiment, as shown in FIG. 2, unlike the conventional image forming apparatus shown in FIG. 17, the four photosensitive drums 222a to 222d of the image forming stations Pa to Pd are provided. In addition, the photosensitive drums are rotationally driven in a state where the phases of the rotational drive unevenness (common to each photosensitive drum if the phases match) are shifted by a predetermined amount. More specifically, the photosensitive drums start rotating at the same time and stop rotating at the same time. Therefore, the stop positions (rotation start positions) are shifted and stopped.

In FIG. 2, similarly to FIG. 17, the phase shift in each photosensitive drum is changed by a key-shaped hole (or convex portion) ha of a drive gear attached to a shaft of the photosensitive drum.
Is shown as a reference. Now, the black photosensitive drum 222a
, The cyan photosensitive drum 222 next to it
The phase of b is advanced by about 60 degrees. Similarly, the phase of the magenta photosensitive drum 222c is advanced by 120 degrees, and the phase of the yellow photosensitive drum 222d is advanced by 180 degrees.

As described above, by shifting the phase of the drive unevenness in each photosensitive drum, the distance between the transfer units A-A corresponding to the respective image forming stations Pa to Pd is reduced by the amount of the phase shift. , The drive unevenness between the photosensitive drums can be the same for the transfer material passing through the transfer section A.

As described above, if the diameter of the photosensitive drum is d by advancing the period of the drive unevenness between the adjacent photosensitive drums by 60 degrees, L corresponding to the distance between the transfer portions A-A.
Is L = circumference πd of the photosensitive drum × ((360−60)
Degrees / 360 degrees).

Although the distance between the transfer portions A-A is set based on the phase shift in each photosensitive drum for the sake of convenience, the distance between the transfer portions A-A is actually set. L may be determined, and the phase shift of each photoconductor drum may be set based on L. For example, using a photosensitive drum having a drum diameter of 40 mm, the distance L between the transfer portions A-A is set to 10
In the case of 5 mm, the stop position between the adjacent photosensitive drums is set so as to shift the phase of each drive unevenness by about 60 degrees as described above.

The manner in which the images of the respective photosensitive drums are superposed without any color shift due to driving unevenness will be described with reference to FIG. Now, it is assumed that four photosensitive drums are rotating in a state as shown in FIG. The image written at the timing of (1) at the position of “G” of the black photosensitive drum 222a (the reference of drive unevenness is indicated by line a for clarity) is the timing of (4) (the timing of the photosensitive drum 222a). 1
After the time required for 80 ° rotation has elapsed),
6 and is superimposed on the image on the cyan photosensitive drum 222b at the timing of (9). Here, an image has already been formed on the cyan photosensitive drum 222b by the laser beam at the timing (6). FIG. 3 (a)
9 shows the position of the line a of the cyan photosensitive drum 222b at the timings (1) to (6). As is clear from the figure, the line a at the timing (9) is located at the same position as the black photosensitive drum 222a at the timing (4). Therefore, the driving unevenness of the superimposed images becomes the same, and there is no color shift due to the influence of the driving unevenness.

Similarly, the magenta photosensitive drum 222c
Is superimposed on the image formed at the timing (14). Here, the magenta photosensitive drum 222c has
An image has already been formed at the timing of (11). FIG.
(B) shows the position of the line a of the magenta photosensitive drum 222c at the timings (1) to (11). As is clear from the figure, the line a at the timing of (11) is
(1) It is at the same position as the black and cyan photosensitive drums at the timings of (6). Therefore, the superimposed images have the same driving unevenness, and there is no color shift due to the influence of the driving unevenness.

Similarly, the yellow photosensitive drum 222d
Is superimposed on the image formed at the timing (19). Therefore, the yellow photosensitive drum 222d has
An image has already been formed at the timing of (16). FIG.
(C) shows the position of the line a of the yellow photosensitive drum 222d at the timings (1) to (16). As is clear from the figure, the line a at the timing of (16) is
It is located at the same position as the black and cyan photosensitive drums at the timings (1), (6) and (11). Therefore, the superimposed images have the same driving unevenness, and there is no color shift due to the influence of the driving unevenness. Such four photosensitive drums 222
The rotational drivings a to d are controlled by the control unit CON shown in FIG. 4 on the basis of the reference marks Q that can specify the driving unevenness of each photosensitive drum.

Hereinafter, the rotational drive control of the photosensitive drum will be described with reference to FIGS. As described above, the photosensitive drum 2 in the digital color copying machine of the present embodiment
Drive gears G1 to G4 for transmitting rotational driving force to 22a to 22d
Since a key-shaped mark (convex portion) ha is provided in the hole, a rectangular reference mark Q is provided in accordance with the key-shaped convex portion as shown in FIG. S1 to S4
To read each. Of course, it is not limited to this.

Each of the sensors S1 to S4 is mounted at the same position from each transfer portion A. The sensor output is
The control unit CON is sent to the control unit CON, and based on this, the control unit CON controls each of the motors M that independently rotates and drives each of the photosensitive drums.

The control unit CON includes the optical sensors S1 to S4
Based on the detection result from, the respective photosensitive drums 222 are reliably stopped at the respective stop positions, and the rotations are simultaneously started at the start of copying.

FIG. 5 is a timing chart showing the outputs of the sensors S1 to S4 when the photosensitive drum 222 is stopped. The reference mark Q is detected and turned on sequentially from the sensor S4 of the photosensitive drum 222d located on the downstream side, and the sensor Sl of the photosensitive drum 222a located on the most upstream side is turned on last. After this last sensor Sl is turned on,
The time required for the reference mark Q shown in FIG. 4 to reach the transfer portion A (here, the time required to rotate about 90 degrees) is a margin time and a margin angle.
After the allowance time has elapsed, the photosensitive drum 222a is stopped. Then, in the photosensitive drums 222b to 222d other than the reference photosensitive drum 222a, the respective sensors S2 to S4
The correction amount is detected based on the detection result of (i) and the detection result of the sensor S1, and the correction amount is added to the margin time, and then stopped when that time has elapsed.

For example, when the photosensitive drum 222b for cyan is considered, there is a shift of 60 degrees between the photosensitive drum 222b and the reference photosensitive drum 222a. Therefore, when the sensor S1 is turned on and the sensor S2
The correction amount of the photosensitive drum 222b is calculated from the timing of N. Here, if the interval is 61 degrees and is advanced by 1 degree, it is necessary to return it once. Therefore, the correction amount is set to −1, and this is added to 90 degrees of the extra time, and the extra time is 89. As a degree, after the sensor S1 is turned ON, a margin time of 89 degrees elapses, and then the operation is stopped.

If the above-mentioned margin time is not set, if the correction amount is positive, the photosensitive drum 222b may be further rotated and stopped by that much.
In the case of minus, since the stop position has already been passed, it is necessary to make another rotation to stop at the correct position.
Although the surface or the surface of the photoconductor drum may be damaged by contact, the above-described configuration can stop the recording in a state where an ideal image can be recorded in a short time while suppressing damage and the like. Recording can be done smoothly.

A stepping motor is most suitable as a motor for individually driving the photosensitive drums. In other words, the pulse motor generates a holding torque by energizing and energizing it, so that it can be easily locked without rotating at a certain position, and the rotation movement of the photosensitive drum that does not perform image formation due to external force can be prevented. In addition, the pulse motor can perform high-precision rotation in an open loop in accordance with a set drive pulse signal, and can easily position the set rotation position. Therefore, the photosensitive drum that is not used can be securely locked, and the photosensitive drum used for image formation can be accurately and easily positioned so that the rotational phase with the unused photosensitive drum is in a predetermined phase state. Can be. In addition, by using a pulse motor, a high-precision rotation operation can be realized in an open loop while the rotation phases of the photosensitive drums are in a predetermined state when all the photosensitive drums operate.

Even if the dimension between the transfer portions A-A is set with high accuracy, if the mounting position of the photosensitive drum shifts and there is an error of only 100 μm in the dimension, 600 dpi (one dot of one dot) (Diameter: about 43μm)
In such an image forming apparatus for high-density recording, a large color shift appears. Therefore, it is preferable that a means for adjusting the stop position of each photoconductor drum be provided separately irrespective of the drive unevenness of the photoconductor drum. Similarly, an error is likely to occur in the mounting position of the above-described sensors S1 to S4. Therefore, it is desirable that the configuration be such that such an error can be corrected.

Specifically, the above-mentioned margin time (margin angle)
Can be adjusted for each photosensitive drum.
That is, in the above description, the spare time is set to 90 degrees for all four photosensitive drums.
It is only necessary to correct each of them in advance in accordance with the dimensional error between the transfer units and to add (subtract) the correction amount at the time of stopping to the corrected margin time.

The above is a description of the drive control method for stopping the rotation by stopping the rotation by rotating the stop position by a predetermined amount when the rotation is stopped while the phase of the rotational drive unevenness in each photosensitive drum is shifted by a predetermined amount. is there.

Next, a description will be given of a method of ascertaining the rotational drive unevenness of each photosensitive drum 222, and adjusting and setting the stop position according to the degree of the rotational drive unevenness.

<Drum Position Adjustment Data Input Screen> FIG. 6 shows an example of a display screen DP used by the operator to adjust the rotational drive unevenness of the photosensitive drum 222 and for setting and inputting the drum position. I have. FIG. 6 shows a display example using a liquid crystal display screen (LCD) of a touch panel type.
A display screen DP for setting and inputting a drum position by a screen switching operation is displayed from an image forming display screen (not shown) used for performing normal copying.

In FIG. 6, reference numerals 301 indicate the print mode setting values of the sample for image confirmation, and 302 indicates the photosensitive drum for black toner, which is arranged from top to bottom substantially toward the center of the display screen DP. , The stop value of the photosensitive drum stop position counter for magenta toner with respect to the black drum, and the stop value of the yellow toner photosensitive drum with respect to the black drum. Displays the set value of the position counter. In the following, the photosensitive drum for black toner is referred to as “black drum”, the photosensitive drum for cyan toner is referred to as “cyan drum”, the photosensitive drum for magenta toner is referred to as “magenta drum”, and the photosensitive drum for yellow toner. May be abbreviated as “yellow drum”.

The stop position counter values 302 to 304
Is a count value assigned to each angle when one rotation of each photosensitive drum is divided by a predetermined angle. For example,
When one rotation of the photosensitive drum (360 °) is divided into 12 parts, the number corresponding to 0 ° is [1], the number corresponding to 30 ° is [2], and so on, corresponding to 330 °. Set the number as [12].

A display screen area 305 arranged on the left side of the display screen DP displays the mode number 301 and the set values selected by the set values 302 to 304, and is displayed by pressing the arrow key 306. Mode number 30
The display is sequentially switched to 1 and setting value displays 302 to 304.

In the display screen area 305, there are provided a display unit 305a for displaying a mode number 301, a display unit 305b for displaying setting data or input data, and a display unit 305c for displaying an input range of setting data. .

The mode number 301 and the set value displays 302 to 304 are sequentially switched in black and white in reverse by pressing an arrow key 306 arranged vertically on the right side of the display screen DP. Interlock. The set value is read out to a storage medium (not shown) by an input operation of the arrow key 306 or the [OK] key 307 provided on the near side (lower side), and is stored in a changeable manner.

By pressing the [EXECUTE] key 308 provided on the front side of the operation of the display screen DP, a sample print operation for image confirmation to be described later is executed in the print mode displayed in the setting item of the mode number 301. I do.

After the operator has finished adjusting the rotational drive unevenness of the photosensitive drum 222, the user presses the "CLOSE" key arranged at the upper right of the display screen DP to perform normal copying. (Not shown).

<Drum Position Adjustment Data Input Screen Operation Procedure> Next, the drum position setting input display screen DP shown in FIG.
A simulation of the drum position setting will be described.

In STEP 1, the mode is switched from the normal mode to the test mode by a combination of key input means such as ten keys operated for setting image forming conditions in a normal image forming mode (not shown), or by a specific key input.

In STEP 2, the display screen DP shown in FIG.
Then, the mode is switched by the mode switching to prepare for the photosensitive drum position setting input.

In STEP 3, it is determined whether or not a setting input screen cancel key (not shown) has been input.
The process proceeds to EP7 to end the simulation of the photosensitive drum position setting, and proceeds to STEP4 if the release key is not input.

In STEP 4, [EXECUT] in FIG.
E] It is determined whether or not there is an input of the key 308, and if there is no input, the process proceeds to STEP5, and if there is an input, STEP6.
To enter a test print mode for each photosensitive drum.

In STEP 5, the [OK] key 30 in FIG.
It is determined whether or not there is an input of the key 7 or the arrow key 306. If the condition is set by the key input, the process proceeds to STEP9, and if there is no key input, the process returns to STEP3.

In STEP 6, the mode number 301 shown in FIG.
Is set to "1" or "2", the process proceeds to STEP 10 (FIG. 8) to confirm and set the rotational phase relationship of each photosensitive drum, otherwise, at the set rotation stop position. ST to perform test printing of photoconductor drum
The process proceeds to EP19 (FIG. 9B).

In STEP 7, a test mode end process is performed, and the flow advances to STEP 8 to switch the display screen from the test mode to the normal mode.

Step 9 shown in FIG. 9A is a step of setting and storing a correction angle recognized by the operator based on a test printing step (STEP 10 to STEP 18) described later. That is, if the display of the display screen area 305 in FIG. 6 is the setting value display 302 to 304, the setting data (FIG. 6, the display unit 30)
5b) is stored in a memory (storage medium) not shown, and ST
Return to EP3 (FIG. 7).

STEP 10 to STEP 18 shown in FIG.
Is a test printing process performed to grasp the state of deviation of the rotational phase of each of the cyan drum, magenta drum, and yellow drum with reference to the black drum.

In STEP 10, [EXECUT] in FIG.
[E] key 308 is displayed in reverse black and white to indicate that test printing is being executed, and the flow proceeds to STEP 11.

In STEP 11, the positions of the reference marks Q provided on the driving gears G1 to G4 rotating in synchronization with the respective photosensitive drums are stopped under the control of the control unit CON in accordance with the sensors S1 to S4 in FIG. Then, in order to adjust the rotational drive unevenness in the positional relationship between the photosensitive drums, ST
Proceed to EP12.

In STEP 12, a test pattern (described later in detail) for a specific pattern, which will be described later, for confirming drive unevenness at each photosensitive drum position (a phase shift in the rotational direction between the respective drums) is performed, and the process proceeds to STEP 13.

In STEP 13, it is determined whether or not a setting release key (not shown) has been input. If the setting release key has been input, the process returns to STEP 7 to end the test mode. The process proceeds to STEP 14 to execute test printing.

In STEP 14, the set value 301 in FIG.
Is "1", and the stop positions of the cyan drum, magenta drum, and yellow drum are shifted by 30 ° with respect to the black drum rotation stop position (based on the reference mark Q). When a total of 12 test prints have been completed, the operation proceeds to STEP 18, otherwise, the operation proceeds to STEP 15.

In STEP 15, the set value 301 in FIG.
Is "2", and while the rotation stop positions of the cyan drum, magenta drum, and yellow drum are shifted by 90 degrees with respect to the black drum position, a total of four test prints are completed. STEP18
Otherwise, to STEP16.

In STEP 16, the rotation stop positions of the cyan drum, magenta drum, and yellow drum with respect to the black drum position are set to [30 × (n-1) sheets] ° in accordance with the set value 301 of FIG. Or [90x
(N-1) sheets] ° (details will be described later), and the process proceeds to STEP 17 to perform test printing again.

In STEP 17, at the rotation stop positions of the photosensitive drums of the respective colors changed in the settings in STEP 16 described above,
In order to confirm the phase shift in the rotation direction between the drums, a specific pattern described later is printed again (details will be described later). After the end, the process returns to STEP13.

In STEP 18, when the predetermined number of test prints have been completed in the setting of the set value 301 in FIG. 6, the [EXECUTE] key 308 in FIG. Is displayed, and said STEP 3 (FIG. 7)
Return to

On the basis of the results output in STEP 10 to STEP 17, the operator determines the amount of deviation of the rotational phase of each of the cyan, magenta and yellow drums by pressing the [OK] key 307 or the arrow key 30 in FIG.
6 are set respectively. The key-inputted setting data is stored in a memory (not shown) in STEP 9 (FIG. 9).

STEP 19 to STEP shown in FIG.
In step 22, a confirmatory test print is performed in a state where the rotation of the cyan drum, magenta drum, and yellow drum is stopped with reference to the black drum stored in the memory in step 9 described above.

In STEP 19, as in STEP 10, the [EXECUTE] key 308 is displayed in black and white inverted.
A message that test printing is being executed is displayed, and the flow advances to STEP20.

In STEP 20, the rotation stop position angles of the cyan drum, magenta drum, and yellow drum are set as follows.
In order to confirm the phase shift again according to the positional relationship set in the set value displays 302 to 304 in FIG.
Proceed to EP21.

In STEP 21, a specific pattern described later is printed (details will be described later) to confirm the rotation stop positions of the cyan drum, magenta drum, and yellow drum with respect to the black drum. After printing, STEP2
Proceed to 2.

In STEP 22, the black-and-white inverted display of the [EXECUTE] key 308, which was black-and-white inverted in STEP 19, is returned to its original state, indicating that test printing has been completed, and the flow returns to STEP 3 (FIG. 7).

By repeating the above-described drum position setting simulation operation, the rotation stop position (color shift adjustment) between the photosensitive drums of each color can be adjusted.

In the above simulation, STEP 14
As shown in STEP 16, test images of all the drums other than the reference drum can be output collectively at intervals of 30 degrees and / or at intervals of 90 degrees, so that the positional relationship of each drum is set for each angle. The inconvenience of inputting the drum or the like and outputting the test image and the input error of the person who makes the adjustment can be avoided, and the efficiency of the adjustment work can be improved and anyone can easily adjust the drum rotation stop position.

In the present embodiment, the above two types of angles (30
(Degree and 90 degrees), but the set angle and the type of the set angle are not limited. For example, when the set angle is increased (the number of divisions is small), a small number of test images can be output, so that it is possible to quickly check the vicinity of the rotational position of the adjustment value that reduces the most periodic drive unevenness in one rotation of each drum. Conversely, when the set angle is reduced (the number of divisions is large), it is possible to check with higher accuracy than when a test image is output with a small number of divisions. For example, first, 3 in FIG.
When the setting value of 01 is set to [1] and the number of divisions is adjusted to 90 degrees with n = 4, and the adjustment value is not known in the printing result, the setting value of 301 is set to [2] and the number of divisions is set. To n
By adjusting with an accuracy of 30 degrees when = 12, the adjustment value can be almost surely understood. Therefore, various adjustments can be made by the combination of the division numbers.

<Drum Phase Confirmation Pattern> Next, the test printing of the specific pattern will be described in detail. In the test printing according to the present embodiment, a test print is output so that an operator can easily visually recognize a synthesis shift of pixels between images generated on each photoconductor due to driving unevenness of each photoconductor drum. As a preferable example of the test print (test print), when a color image is synthesized, each image generated by a photosensitive drum of three colors of yellow, cyan, and magenta and generated by a black photosensitive drum as a reference A case will be described in which it is easy to determine the combination unevenness with the image to be processed. This test print (test print) may output pattern data stored in a memory provided inside or outside the image forming apparatus, or may generate a circuit for generating internal or external pattern data. Or output from software.

FIGS. 10 (a) and 10 (b) are explanatory diagrams of a sample in a good state without rotation unevenness of an ideal photosensitive drum as an example of a test print (test print) according to the present invention. In this good case, the general band-like pattern of each color appears almost linearly in the sub-scanning direction. On the other hand, FIGS. 11A and 11B are explanatory diagrams showing an unfavorable state in which rotational unevenness has occurred in the cyan and yellow photosensitive drums to be compared with the reference black drum. . In this case, cyan and yellow belt-like patterns appear wavy in the sub-scanning direction.

In FIGS. 10A and 11A, on the test paper, a drum phase confirmation pattern printing area S1 of yellow, cyan, and magenta is provided in the main scanning direction. In each print area in the print area S1, a yellow band pattern Pyl as a yellow print sample, a cyan band pattern Pcl as a cyan print sample, and a magenta band pattern Pm1 as a magenta print sample are printed.

Each color printing sample in each printing area is
Drum rotation unevenness for each color and black is generated for each color by a drum phase confirmation pattern generation method described later. For example, in the case of a yellow pattern, this drum phase confirmation pattern generation method includes a composite pattern of a diagonal pattern formed in yellow and a lattice pattern formed in black.

The drum phase confirmation pattern will be described at the pixel level with reference to FIG. First, FIG. 12A shows a hatched pattern YP formed in yellow. This oblique line pattern YP is output with a width of 4 pixels in the sub-scanning direction and shifted by one pixel in the sub-scanning direction every 16 pixels in the main scanning direction.

Next, FIG. 12B shows a lattice pattern BP formed in black. This lattice pattern BP
Outputs a straight line having a width of 4 pixels every 8 pixels in the sub-scanning direction,
This is a pattern in which a straight line having a width of 4 pixels is output every 16 pixels in the main scanning direction. With this lattice pattern BP, (4 × 1
2) A white pixel window WW of the pixel is generated.

Then, when the oblique line pattern YP formed in yellow in FIG. 12A and the lattice pattern BP formed in black in FIG. 11B are combined, FIG.
The synthesis process will be described in detail below.

<Principle of Combination Unevenness Appearing in Drum Phase Confirmation Pattern> Both patterns YP in the case where the black image and the yellow image shown in FIG.
The state of the composite image of P and BP will be described. Here, white pixel windows WW of (4 × 12) pixels generated by the black grid pattern BP are represented by W (1,1), W (1,2) to W (3,3).
3), W (1, 1), W in the first column in the main scanning direction
In the white pixel windows of (1, 2) and W (1, 3), the yellow diagonal line pattern completely overlaps the black lattice pattern in the sub-scanning direction, so that the yellow image cannot be seen.

Then, W (2, 2) in the second column in the main scanning direction
In the white pixel windows of 1), W (2,2) and W (2,3), the yellow oblique line pattern YP is shifted by one pixel from the black lattice pattern BP in the sub-scanning direction, so that the yellow pixel of one pixel width is used. Can be seen.

Similarly, W (3,3) in the third column in the main scanning direction
In the white pixel windows of 1), W (3,2) and W (3,3), the yellow diagonal line pattern YP is displaced from the black lattice pattern BP by two pixels in the sub-scanning direction, so that a yellow pixel having a width of two pixels is used. Can be seen.

Although not shown in FIG. 12C, in the white pixel window WW in the fourth column in the main scanning direction, the yellow diagonal line pattern YP is shifted by three pixels from the black pattern BP in the sub-scanning direction, so that the width is three pixels. Yellow pixels are visible.

In the white pixel window WW in the fifth column in the main scanning direction, since the yellow oblique line pattern YP is shifted by four pixels from the black lattice pattern BP in the sub-scanning direction, all the white pixel windows WW are yellow pixels.

In the white pixel window WW in the sixth column in the main scanning direction, the yellow diagonal line pattern YP is shifted by 5 pixels in the sub-scanning direction from the black lattice pattern BP, but one of the yellow diagonal line patterns YP on the most downstream side in the sub-scanning direction. The pixel overlaps the black lattice pattern BP, and a yellow pixel having a width of 3 pixels can be seen in the white pixel window WW.

In the white pixel window WW of the seventh column in the main scanning direction, the yellow diagonal line pattern YP is shifted by 6 pixels in the sub-scanning direction from the black lattice pattern BP, and two pixels of the yellow diagonal line pattern YP which is the most downstream in the sub-scanning direction. Overlaps the black lattice pattern BP, and yellow pixels having a width of two pixels can be seen in the white pixel window WW.

In the white pixel window WW of the eighth column in the main scanning direction, the yellow diagonal line pattern YP is shifted by 7 pixels in the sub-scanning direction from the black lattice pattern BP, and the three pixels of the yellow diagonal line pattern YP which is the most downstream in the sub-scanning direction. Overlaps with the black lattice pattern BP, and yellow pixels of one pixel width can be seen in the white pixel window WW.

In the white pixel window WW of the ninth column in the main scanning direction, the yellow oblique line pattern YP is shifted by 8 pixels in the sub-scanning direction from the black lattice pattern BP. Yellow diagonal line pattern YP
Completely overlaps the black lattice pattern BP, so that the yellow pixels become invisible.

Thereafter, the white pixel window WW in the tenth column in the main scanning direction is WW3, as in the second column.
It becomes the same as the column, and yellow pixels can be seen in the same pattern in a period of 8 columns.

When the test print is viewed, the yellow color appears darker on the test print by the number of yellow pixels visible in the white pixel window WW. Then
A yellow linear strip pattern Pyl is generated in the sub-scanning direction as shown in FIG. Thus, as long as the image generated on the black photoconductor drum transferred to the test paper and the image generated on the yellow photoconductor drum are ideally synchronized and synthesized on the test paper , The yellow band pattern Pyl is linear.

Next, the state of the composite image of the pattern when the above-described black image and yellow image are not synchronized will be described. In general, in this pattern, when a pixel to be synthesized is shifted, the yellow band-shaped pattern Pyl changes its shape from a straight line in accordance with the manner of occurrence of the shift. This phenomenon occurs due to the appearance of yellow pixels in each column of the white pixel window WW in the main scanning direction.

When viewed in the first column of the white pixel window WW in the main scanning direction, the image generated on the black photosensitive drum is not expanded and contracted in the sub-scanning direction and the image generated on the yellow photosensitive drum is not generated. In a portion where the portion where the obtained image is not expanded and contracted is combined with the black diagonal pattern in the sub-scanning direction in the white pixel window WW. However, other than the synthesized portion of the portions that have not been expanded or contracted, a pixel shift occurs due to the difference in the length of the black and yellow images described above, and the yellow pixel appears in the white pixel window WW in the sub-scanning direction. As a result, the pixels are seen by the amount of the shift.

Similarly, also in the second column in the main scanning direction,
The same phenomenon occurs, and when viewed in the sub-scanning direction, a portion where the image generated on the black photoconductor drum is not expanded and contracted and a portion where the image generated on the yellow photoconductor drum is not expanded and contracted. In the white pixel window WW of the synthesized portion, the yellow diagonal line pattern YP is shifted by one pixel from the black lattice pattern BP in the sub-scanning direction, so that a yellow pixel of one pixel width can be seen. Except for the portion where the portions that have not been expanded and contracted are combined, as in the first row in the main scanning direction, the white pixel window WW displays a portion in which only pixels shifted by yellow in the sub-scanning direction are visible. In the scanning direction, a portion where the yellow oblique line pattern YP completely overlaps the black lattice pattern BP occurs.

The same applies to the third and subsequent columns. The method of shifting the pixels in the sub-scanning direction in each column in the main scanning direction is as follows.
It follows how the length of the black image and the yellow image in the sub-scanning direction changes. Therefore, on the test print sample, the yellow band pattern P
yl changes in the main scanning direction in proportion to the pixel shift in the sub-scanning direction. Therefore, if the change in the length of the black image and the yellow image is periodic, the yellow band pattern Pyl also has a periodic wave shape, and if there is a steep change, the yellow band pattern Pyl is formed. The amount of change in Pyl also becomes steep.

Next, how to change the length of the black image and the yellow image in the sub-scanning direction will be described. The reason why the change in the length is not synchronized is due to the above-described periodic drive unevenness. The causes of the drive unevenness include eccentricity of the photosensitive drum, drive unevenness of the drive system, and parts. Various factors such as accuracy and mounting accuracy can be considered. In any case, as long as the same component is used for the rotational drive of the black and yellow photoconductor drums, it is due to the tendency of eccentricity and cylindricality of the photoconductor drum and the drive components. Driving unevenness occurs.

Therefore, as a typical example of the cause of the periodic drive unevenness that is most likely to occur, pixel displacement due to drive unevenness in a case where the photosensitive drum is eccentric is described in the embodiment of the present invention. The following describes how much a pattern can be expressed by increasing specific numerical values. In this embodiment, in particular,
An example in which both the black and yellow photosensitive drums are eccentric as shown in FIG.

When the eccentricity is the cause, the latent image generated by the laser exposure device is formed on the photosensitive drum at the same timing, but the eccentricity causes the peripheral surface of the photosensitive drum rotating at a constant angular velocity to rotate. The moving amount is not uniform, and fluctuates in a cycle of one rotation of the photoconductor. For this reason, development occurs in which the image extends in the sub-scanning direction in the cycle of one rotation of the photosensitive drum and contracts.

First, the radius is R [mm] and the eccentricity is a [m
m], the amount of movement of the peripheral surface due to eccentricity when the single photosensitive drum rotates at a constant angular velocity will be obtained. If the angle with respect to the eccentric direction is α [rad] and the angle from the original center O1 of the photosensitive drum is θ [rad], then R sin α = rsin θ R cos α = r cos θ−a. Expressed as a function of angle θ,
The following equation (1) is obtained.

[0135]

(Equation 1)

Now, at the angle θ [rad], the radius r
(Θ) [mm] has a relation of dL = r (θ) · dθ with respect to the length dL [mm] of the minute arc formed by the minute angle dθ [rad], so that the arc at the angle θ [rad] The length L (θ) [mm] is represented by the following equation (2), which is the amount of movement of the eccentric peripheral surface.

[0137]

(Equation 2)

Next, this equation will be approximated. Here, the arc length for n pixels in the sub-scanning direction is Ln [mm], and 1
When an angle θp [rad] corresponding to a pixel is set to a small angle, it is expressed by the following approximate expression (3).

[0139]

(Equation 3)

Further, the arc length L (θ) [mm] with respect to an arbitrary angle θ [rad] is expressed by the following approximate expression (4) assuming that the angle θ is composed of n pixels. .

[0141]

(Equation 4)

When the resolution in the sub-scanning direction of this image forming apparatus is A [dpi], the length py [mm] of one pixel in the sub-scanning direction is py = 25.4 / A [mm]. is there.

If the radius of the photosensitive drum of this image forming apparatus is R [mm], the number of pixels in the sub-scanning direction per one rotation of the photosensitive drum is N = 2πR / py [pixe].
l], and the angle θp [rad] corresponding to one pixel is θp = 2π / N = py / R = 25.4 / AR [rad].

Here, referring to FIG. 14, when the black photosensitive drum is Dk and the yellow photosensitive drum is Dy, the pixel shift amount will be calculated. The radius of both photosensitive drums is R [mm], and the amount of eccentricity is a [mm]. The phase angle β [rad] is an angle formed by a line segment connecting the center Ok of the black photosensitive drum and the eccentric center O and a line segment connecting the center Oy of the yellow photosensitive drum and the eccentric center O.
And Here, the eccentric center O and the laser exposure device L
The state where the center Ok of the black photosensitive drum Dk is on a line segment connecting the irradiation point of the black photosensitive drum Dk with the black photosensitive drum Dk is clockwise. It rotates at an angular velocity.

In the state shown in FIG. 13, the black photosensitive drum Dk and the yellow photosensitive drum Dy rotate clockwise at an angle θ.
[Rad] shows a rotated state. At this time, the length Lk of the arc of the black photosensitive drum Dk subjected to laser exposure
(Θ) [mm] is given by equation (5).

[0146]

(Equation 5)

The length Ly (θ) [mm] of the arc on which the yellow photosensitive drum Dy has been exposed to the laser is given by the following equation (6).

[0148]

(Equation 6)

However, the number of pixels in the sub-scanning direction of both photosensitive drums is the same. That is, at the angle θ [rad], the arc length Lk (θ) of the black photosensitive drum Dk
[Mm] and the length Ly of the arc of the yellow photosensitive drum Dy
This means that the pixels of the yellow photosensitive drum Dy are shifted from the pixels of the black photosensitive drum Dk by a difference ΔL (θ) [mm] from (θ) [mm]. Assuming that the number of pixels is （Np (θ) [pixel], it can be expressed by the following equation (7).

[0150]

(Equation 7)

Here, specifically, the resolution in the sub-scanning direction is A
= 600 [dpi], the radius R of the photosensitive drum = 20 [m]
m], eccentricity is a = 0.1 [mm], phase angle β = 30
When [deg] = π / 6 [rad], the length py of one pixel in the sub-scanning direction is py = 0.0423 [mm], and the angle θp of one pixel is 0.002117 [rad]. , The number of pixels that deviate from the above equation △ Np (θ) [pixel
l] is obtained as shown in FIG. That is, when the test pattern according to the present embodiment is used under the above conditions, as shown in FIG. 15, at a location corresponding to about 195 [degrees] and about 1600 [pixels] in the sub-scanning direction, (−2.
4) It can be seen that a pixel shift occurs. Main scanning direction 1
1600/8 = 200 in the sub-scanning direction of the white pixel window of the column
It shows that 2.4 pixels of yellow pixels can be seen around the [unit].

Further, with respect to the angle θ [deg] at which the photosensitive drum advances as shown in FIG. 15, the number of pixels that are shifted ΔNp (θ) [p
pixel] changes smoothly with one cycle of the photosensitive drum as a cycle. Each time the pixel is shifted by one column in the main scanning direction, the pixel is shifted by one pixel in the sub-scanning direction, so that the number of yellow pixels seen in the white pixel window WW increases by one pixel per column in the main scanning direction. Then, if a shift of 5 pixels occurs, it is reduced to 3 pixels.

For example, in the first column in the main scanning direction, in a portion where one yellow pixel is seen in the white pixel window WW in the sub-scanning direction, the white pixel window W in the second column in the main scanning direction is displayed.
Two yellow pixels are seen in W. Similarly, three pixels appear in the third column in the main scanning direction, four pixels in the fourth column, three pixels in the fifth column, two pixels in the sixth column, one pixel in the sixth column, and a seventh pixel.
Not visible in the column, one pixel in the eighth column, 2 in the ninth column
It looks like a pixel. The same applies hereinafter.

The result of the test pattern for each column in the main scanning direction under the above conditions is that the test pattern is placed in the white pixel window WW in the sub-scanning direction in each column in the main scanning direction in accordance with the periodic fluctuation of the pixel shift amount. FIG. 16 shows the number of yellow pixels that can be seen.
become that way. Here, the number of three or more yellow pixels that can be seen in the white pixel window is indicated by a circle.

Thereafter, as the position shifts by one column, the shift method shifts one by one. Then, as described above, the yellow color looks as dark as the number of yellow pixels visible in the white pixel window WW, so that the yellow band pattern Pyl appears wavy on the test print.

If the phase angle β is 180 ° [degree] at the maximum and becomes larger, the yellow band-shaped pattern Pyl further undulates accordingly. Also,
If it exceeds 180 [degree], the waving of the yellow band-shaped pattern Pyl becomes smaller accordingly.
Of course, if it is 360 [degrees], the yellow band-shaped pattern Pyl does not undulate.

The change of the test print due to the eccentricity between the black photosensitive drum and the yellow photosensitive drum has been described above. Basically, this print pattern is used to detect a slight image shift in the sub-scanning direction in the main scanning direction. Since it can be expressed as a change in an image, for example, if it is due to the eccentricity of the drive gear of the photosensitive drum, the pattern appears as a band of one cycle of the drive gear.

Further, the present invention is not limited to the deviation of the composite image due to the cylindricality of the photosensitive drum itself, the eccentricity and the cylindricity of the driving gear, etc.
Even with a photoreceptor belt, the deviation of the composite image due to the eccentricity or cylindricality of the rollers supporting the belt can be easily visually recognized. Of course, the reference photosensitive drum or belt may be anything, and the photosensitive drum or belt to be compared may be any other than the reference drum or belt.

The phase confirmation pattern is not limited to the above-mentioned pattern. As a first pattern corresponding to the above-described black grid pattern BP, n pixels (n> 0) of reference colors and m pixels (m
> 0) As a pattern to be output periodically and a second pattern corresponding to the above-mentioned yellow oblique line pattern YP, n pixels in the sub-scanning direction and n pixels in the sub-scanning direction and m pixels other than the comparatively symmetric color in the sub-scanning direction And the second pattern has q pixels (| q |) in the sub-scanning direction every p pixels (p> 0) in the main scanning direction.
> 0), and may be any pattern obtained by combining the first pattern and the second pattern. Further, the second pattern corresponding to the above-mentioned yellow oblique line pattern YP may output m pixels in the sub-scanning direction and n pixels in the sub-scanning direction except for the pixels in the sub-scanning direction.

For example, the reference color is cyan, the comparative symmetric color is magenta, the first pattern is a pattern that outputs 10 yellow pixels and 20 black pixels in the sub-scanning direction, and the second pattern is a second pattern. Outputs 20 magenta pixels and 10 yellow pixels in the sub-scanning direction, and shifts the second pattern by two pixels in the sub-scanning direction every 20 pixels in the main scanning direction. Is a combined pattern. At this time, the white pixel window WW corresponds to the first pattern of ten yellow pixels, and this corresponds to the second pattern of magenta 20 pixels.
A red pixel obtained by synthesizing the pixel or the ten yellow pixels is seen against the black background from the ten yellow pixels of the first pattern. For this reason, a yellow band pattern extending in the sub-scanning direction is generated in the test print, and the determination can be made based on the shape of the band pattern.

As described above, according to the print pattern shown in the present embodiment, a slight image shift in the sub-scanning direction can be expressed as a change in the image in the main scanning direction. The test print result of (a) is 1
When it is determined that the test sample is the second test sample in the two test samples, only the magenta band pattern Pml is not wavy, and the phase angle of the second sample is the stop position counter value of the magenta drum. Can be visually recognized by the operator. Therefore, the set value of the stop position counter of the magenta drum with respect to the black drum is 3
The value to be set to 03 is input as “2” and stored in a memory (not shown) in STEP 9 (FIG. 9).

On the other hand, for cyan and yellow, FIG.
Among the eleven sheets output in the same process as the sample 1 (a), sample prints in which the cyan and yellow belt-shaped patterns Pcl and Pyl are not wavy are found, and the stop position counters for cyan and yellow are set, respectively. Value 30
By inputting and storing appropriate values in the fields 4 and 302, the respective photosensitive drums can be set at positions where slight image shift in the sub-scanning direction is prevented.

Under the control of the control unit CON, the set value 3 stored in the memory with reference to the sensors S1 to S4.
Test printing (STEP 21) using each photoconductor drum for which the rotation stop position is set to 02 to 304 (STEP 20)
In this case, a test pattern printing result as shown in FIG. 10 is obtained.

According to the present embodiment described above, a slight image shift in the sub-scanning direction of each photosensitive drum caused by various factors can be expressed as an amount of change in the image in the main scanning direction. At the same time as grasping the deviation, the amount of the deviation can be properly grasped and adjusted.For example, when starting the use of a new image forming apparatus or when adjusting the deviation after maintenance, special tools and techniques are used as in the past. Easy to adjust without the need.

[0165]

As described above, according to the first aspect of the present invention, when a copy result using the image forming apparatus has image unevenness in the sub-operation direction or when an initial image unevenness occurrence test is performed, a plurality of images can be obtained. Of the image carriers, one image carrier is used as a reference image carrier, and the rotation stop positions of the other image carriers are detected by a detection unit, and the detection result and a relative positional relationship with respect to the reference image carrier are shown. The control unit drives and stops the driving units of the image carriers other than the reference image carrier based on the value (the value that divides one circumference of the image carrier into n (n> 1)). Can be formed.

Thus, the value indicating the relative positional relationship is changed,
By performing the adjustment, it is possible to easily perform the periodic drive unevenness prevention even if the image carriers of the respective colors are replaced after the image forming apparatus is installed before the user (user).

Further, by reducing the periodic driving unevenness itself, it is possible to provide a high-quality image in which the deterioration of the image quality due to the pixel shift due to the periodic driving unevenness is suppressed as much as possible.

Also, since the relative positions of the image carriers and the driving means of the respective colors in the rotating direction can be adjusted with easily recognizable adjustment values, the adjustment can be performed by a simple operation and a user-friendly image forming apparatus is provided. it can.

According to the second aspect of the present invention, since n kinds of test images can be output at once without outputting a test image corresponding to one value indicating the positional relationship, the positional relationship of the image carrier can be repeated n times. The troublesome operation of inputting a value indicating a and outputting a test image can be eliminated.

[0170] Since n kinds of test images can be output collectively over the entire circumference of the image carrier, one test image of one circumference of the image carrier can be output.
It is possible to easily know which rotational position value is the value that minimizes the periodic drive unevenness with / n accuracy.

According to the third aspect of the present invention, when a test image is output with a small number of divisions n, the number of test images can be reduced, so that the most periodic drive unevenness in one rotation of the image carrier can be reduced. The vicinity of the rotation position of the adjustment value to be performed can be quickly checked. Further, when a test image is output with a large number of divisions n, the number of divisions n can be checked more accurately around the rotational position than when a test image is output with a small number of divisions.

According to the fourth aspect of the present invention, the values indicating the relative positional relationships of at least two image carriers other than the reference image carrier with respect to the reference image carrier are set to be the same value, so that each position is obtained. The trouble of inputting the value indicating the relationship one by one can be saved, and efficient operation can be performed.

According to the fifth aspect of the present invention, it is possible to form an image such as a test print at the same image transfer position with respect to the reference image carrier at the same rotational position of each image carrier. It is not necessary to use unnecessary image forming and transfer sheets to check the state of typical drive unevenness at each rotational position. Further, since the image of the periodic drive unevenness of each image carrier can be formed on one transfer sheet, the adjustment can be made easier.

According to the sixth aspect of the present invention, since the periodic drive unevenness state of each image carrier is formed on one transfer sheet and output, a display screen or the like adjusted for each image carrier is provided. Switching is not only annoying, but also susceptible to input errors. However, by displaying the list at the same time, the input operation of the operator can be made less likely to be erroneous.

[Brief description of the drawings]

FIG. 1 is an operational explanatory diagram showing a side cross section of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an operational explanatory diagram of a plurality of photosensitive drums arranged in parallel according to an embodiment of the present invention in a phase matching state;

FIG. 3 is an operational explanatory diagram illustrating an overlapping state of images on a plurality of photosensitive drums according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram of phase control of a plurality of arranged photosensitive drums according to the embodiment of the present invention.

FIG. 5 is a time chart according to the embodiment of the present invention, in which the photosensitive drums are stopped while detecting the deviation angles of the plurality of photosensitive drums.

FIG. 6 is an explanatory diagram of a stop position setting input display screen of each photosensitive drum according to the embodiment of the present invention.

FIG. 7 is a flowchart showing a part of an operation procedure of a stop position setting input display screen of each photosensitive drum according to the embodiment of the present invention.

FIG. 8 is a flowchart showing a part of an operation procedure of a stop position setting input display screen of each photosensitive drum according to the embodiment of the present invention.

FIG. 9 is a flowchart illustrating a part of an operation procedure of a stop position setting input display screen of each photosensitive drum according to the embodiment of the present invention.

FIGS. 10A and 10B are an explanatory view and a partially enlarged view of a printing example of a pattern for confirming the position of each photosensitive drum according to the embodiment of the present invention; FIGS.

FIGS. 11A and 11B are an explanatory diagram of an example of printing a position confirmation pattern of each photosensitive drum according to the embodiment of the present invention and a partially enlarged view of FIG.

FIG. 12 is an operational explanatory view of the partially enlarged view of FIG. 10 (b).

FIG. 13 is an explanatory diagram of the eccentricity of the photosensitive drum.

FIG. 14 is a diagram illustrating the principle of eccentricity and color shift of the photosensitive drum.

FIG. 15 is an explanatory diagram showing a shift of a pixel in a sub-scanning direction of a test pattern according to an embodiment of the present invention, as a relationship between the number of pixels and an angle.

FIG. 16 is an explanatory diagram two-dimensionally showing a shift amount of an image in a main scanning direction of a test pattern according to the embodiment of the present invention.

FIG. 17 is an operational explanatory view of a conventional phase matching state of a plurality of photosensitive drums arranged in parallel.

[Explanation of symbols]

 Reference Signs List 1 image forming apparatus 216 transfer belt 222a to 222d photoconductor drum Pa to Pd image station M motor Q reference mark CON control unit G1 to G4 drive gear S1 to S4 sensor DP display screen S1 pattern printing area Pml magenta strip pattern Pcl cyan strip pattern Pyl Yellow strip pattern YP Slant pattern BP Lattice pattern WW White pixel window

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H030 AA01 AA06 AB02 AD16 BB02 BB23 BB44 BB71 2H071 BA05 BA16 BA29 CA02 CA09 DA09 DA15 DA26 DA32 EA18

Claims (6)

[Claims] A plurality of rotatable image carriers; an image forming means for forming an image on the image carriers; one image carrier of the plurality of image carriers as a reference image carrier; Detecting means for detecting a rotation stop position of at least one image carrier other than the reference image carrier; and at least one image carrier other than the reference image carrier,
A driving unit that can be independently driven to rotate with respect to the reference image carrier; and a value indicating a relative positional relationship of at least one image carrier other than the reference image carrier with respect to the reference image carrier. Wherein one circumference of the at least one image carrier is divided into n parts (n
> 1) An image forming apparatus comprising: a control unit that controls the driving unit based on a value to be performed and a detection signal of the detection unit. 2. The image processing apparatus according to claim 1, wherein the control unit controls the driving unit to switch the value indicating the relative positional relationship from a first value to an n-th value to form an image by the image forming unit. Item 2. The image forming apparatus according to Item 1. 3. The method according to claim 2, wherein the control unit is configured to perform the n division (n> 1).
The image forming apparatus according to claim 2, wherein the driving unit is controlled so that the image forming unit forms an image by changing a division number n of the image forming unit. 4. A plurality of rotatable image carriers, image forming means for forming an image on the image carriers, one of the plurality of image carriers as a reference image carrier, Detecting means for detecting a rotational position of each of at least two image carriers other than the reference image carrier, at least two image carriers other than the reference image carrier,
A driving unit that can be independently driven with respect to the reference image carrier; and a value indicating a relative positional relationship of at least two image carriers other than the reference image carrier with respect to the reference image carrier. Control means for controlling the driving means so that an image is formed by the image forming means, based on the detection signal of the detection means, wherein the control means comprises at least two components other than the reference image carrier. An image forming apparatus, wherein each value indicating a relative positional relationship of an image carrier is controlled by the same value. 5. The image forming apparatus according to claim 4, wherein said control means causes the image forming means to form an image on at least two image carriers other than the reference image carrier on a transfer material. Image forming device. 6. A display unit for displaying a set value of each of the plurality of image carriers in a list.
An image forming apparatus according to claim 1.