JPH1184809A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tandem engine type image forming device constituted so that the variance of the color image quality of a recording material is minimized. SOLUTION: This device is constituted so that plural image forming units 1(1a-1d, for example) are disposed along the moving path of an intermediate transfer body 2 or the recording material 3 in parallel. The respective units 1 are provided with image carriers 4 carrying the images of respective color components. Then, the images of the respective color components formed on the carriers 4 of the units 1 are transferred on the material 3 directly or through the transfer body 2. When the circumferential length of the carriers 4 of the units 1 are defined as S and the forming pitch of the images G is defined as P, the relation of P=n.S [(n) is an integer or 1/2 thereof] is satisfied. The image forming control system 5 of the respective units 1 is constituted so that the image forming start positions of the carriers 4 of the units 1 are always synchronized beyond the range of job.

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 such as an electrophotographic copying machine, and more particularly to a so-called image forming apparatus in which a plurality of image forming units are arranged in parallel along a moving path of an intermediate transfer member or a recording material. The present invention relates to an improvement in an image forming apparatus called a tandem engine type.

[0002]

2. Description of the Related Art Conventionally, as this type of image forming apparatus, for example, a plurality of image forming units (for example, adopting an electrophotographic system) are arranged in parallel with respect to an intermediate transfer belt extending in a horizontal direction, and each image forming unit is formed. A toner image of each color component is formed on an image carrier such as a photosensitive drum of the unit, and the toner images are sequentially transferred from the image forming units to the intermediate transfer belt. A so-called tandem engine type that performs batch transfer on paper is already known. It is also known that a transport belt for transporting paper is provided without using an intermediate transfer belt, and each color component toner image from each image forming unit is sequentially transferred to paper on the transport belt. ing.

[0003]

However, in this type of tandem engine type image forming apparatus, even if the latent image writing timing of each color component image is precisely aligned for each image forming unit, it is the same. In the case of forming a plurality of color images, there has been a technical problem that the color tone of the color image between the sheets tends to vary. Incidentally, such a technical problem is that a toner image of each color component is sequentially formed on a single image carrier, and is transferred to a sheet via an intermediate transfer member such as an intermediate transfer belt. This is not so noticeable in a so-called single-engine type image forming apparatus in which the image is directly transferred to a sheet held on a drum. SUMMARY An advantage of some aspects of the invention is to provide a tandem engine-type image forming apparatus that minimizes variation in color image quality of a recording material. .

[0004]

Means for Solving the Problems The present inventors have studied the above-mentioned technical problems and arrived at the following knowledge. That is, since each image carrier of each image forming unit includes a slight eccentricity error, when the image carrier makes one rotation, the outer surface of the image carrier mainly has a swell component for one cycle. I have. For this reason, for example, since the gap between the image carrier and the charger, the developing device fluctuates according to the undulation component, the surface of the image carrier is uniformly charged by the charger, or a constant value by the developing device. Even if the solid electrostatic latent image at the potential level is visualized, the charge distribution on the surface of the image carrier, and the density of the visualized solit image are not completely uniform. It was confirmed that it would have an effect. In such a state, in the conventional tandem engine type image forming apparatus, the image forming start position (image writing position) of each page with respect to each image carrier of each image forming unit (engine) is particularly synchronized. Therefore, the potential distribution and the degree of development on the surface of each image carrier vary from page to page, and the same color component toner image itself generated from each image forming unit varies. For this reason, when such color component toner images are transferred in a multiplex manner, variations in the respective color component toner images affect the multiplexing, and accordingly, it is considered that variations in the color tone of the color image on the paper tend to be remarkable. Can be That is, in a single engine type image forming apparatus, since there is only one image carrier, the variation in color tone for a color image is not so noticeable, but in a tandem engine type image forming apparatus, a plurality of image Since the individual variations of the body are not synchronized, the variation of the color tone with respect to the color image tends to be remarkable.

Therefore, the present inventors synchronize the image forming start positions of the respective pages with respect to the respective image carriers of the respective image forming units, and adjust the potential distribution and the development degree of the respective image carriers on each page. Invented the present invention. That is, according to the present invention, as shown in FIGS.
Alternatively, a plurality of image forming units 1 (for example, 1a to 1d) are arranged in parallel along the movement path of the recording material 3, and each image forming unit 1 includes an image carrier 4 that carries each color component image. The image carrier of each image forming unit 1 in an image forming apparatus that transfers each color component image formed on the image carrier 4 of each image forming unit 1 to the recording material 3 via the intermediate transfer body 2 or directly. 4 is S, and P is the image forming pitch of the image G (length of the image G + span between images (inter-image length)), and P = n · S (n: integer or 1 / integer) It is characterized by satisfying the relationship. In FIG. 1B, P1 (P) is the image carrier 4
The image forming pitch is one time of the circumference S of P.
Exemplifies an image forming pitch twice as long as the circumference of the image carrier 4.

In such technical means, the image forming control system 5 of each image forming unit 1 always synchronizes the image forming start position on the image carrier 4 between each image forming unit 1 across jobs. It is preferable that the The job referred to here is to create the same image on one or a plurality of recording materials 3 by one image forming start operation.
And one unit.

Although the synchronization timing by the image forming control system 5 may be appropriately selected, from the viewpoint of maintaining good color image quality on the recording material 4, the hue difference of the composite image is minimized. It is preferable to select as follows. In this case, the image forming control system 5 of each image forming unit 1
For example, a fluctuation component detecting unit that detects a fluctuation component caused by one rotation of the peripheral surface of the image carrier 4 of each image forming unit 1, and a composite image based on the fluctuation component detected by the fluctuation component detection unit. What is necessary is just to include image forming start position determining means for determining the image forming start position on each image carrier 4 so that the hue difference is minimized.

Here, as the fluctuation component detecting means, for example, the density of a solid image on the peripheral surface of each image carrier 4 is detected, or the uniform charging state of the peripheral surface of each image carrier 4 is detected. Alternatively, an appropriate selection may be made as long as it can detect a fluctuation component associated with one rotation of the peripheral surface of the image carrier 4 such as detecting a locus due to eccentricity of the peripheral surface of the image carrier 4. Further, as the image formation start position determining means,
Any method may be appropriately selected as long as it employs an algorithm that minimizes the hue difference of the composite image based on each variation component.
The reason for paying attention to the hue difference here is to ensure good color image quality by minimizing the hue difference with high visual sensitivity.

Next, the operation of the above technical means will be described. 1A and 1B, when the circumference of the image carrier 4 of each image forming unit 1 is S and the image forming pitch of the image G is P (for example, P1, P2), P = nS ( n: integer or 1 / integer). At this time, if the image forming control system 5 of each image forming unit 1 always synchronizes the image forming start position on the image carrier 4 between each image forming unit 1 beyond the time between jobs, for example, each image forming unit 1 Since the image formation starting position of each page with respect to each image carrier 4 is always constant, the potential distribution and the development degree of the surface of each image carrier 4 tend to be constant for each page, and accordingly, each image formation The same color component toner image generated from the unit 1 is constant without variation between pages. For this reason, even when such color component toner images are transferred multiple times, the color tone of the color image on the recording material 3 is constant without variation because the color component toner images do not vary between pages.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. First Embodiment FIG. 2 shows a first embodiment of a tandem engine type image forming apparatus to which the present invention is applied. In the figure, an image forming apparatus uses, for example, an electrophotographic method to form four color components (yellow (Y), magenta (M), cyan (C), and black (K)) images (toner images). Image forming units 20 (20Y to 20K), an intermediate transfer belt 30 for sequentially transferring (primary transfer) each color component image formed by each image forming unit 20, and transferring the image on the intermediate transfer belt 30. Paper (recording material) 1
A collective transfer device 50 for performing collective transfer (secondary transfer) at 00;
The image forming apparatus includes a belt cleaner 60 that removes residual toner on the intermediate transfer belt 30 and a fixing device 70 that fixes a batch-transferred image on the sheet 100.

In this embodiment, each of the image forming units 20 (20Y to 20K) has a photosensitive drum (image carrier) 21, and the image carrier 21 is provided around each image carrier 21. A charging device 22 such as a corotron to be charged; an exposure device 23 such as a laser scanning device in which an electrostatic latent image is written on the charged image carrier 21; an electrostatic latent image written on the image carrier 21 Device 2 in which is developed with each color component toner
4. The toner image on the image carrier 21 is transferred to the intermediate transfer belt 30.
A primary transfer device 25 such as a transfer roll to be transferred to the image carrier 21 and a cleaner 26 for removing residual toner on the image carrier 21 are provided. In particular, in the present embodiment, when the circumference of the image carrier 21 is S and the image forming pitch is P, the relationship of P = n · S (n: integer or 1 / integer) is satisfied. (See FIG. 9). Reference numeral 27 denotes a pre-transfer processing device such as a corotron that is processed before the primary transfer process, and reference numeral 28 denotes a pre-cleaning device such as a corotron that is processed before the cleaning process.

The intermediate transfer belt 30 is stretched over a plurality of (six in this embodiment) support rolls 31 to 36, and is arranged between the support rolls 31 and 32 in the direction in which the image carriers 21 are arranged. A linear portion 30a extending substantially linearly along the supporting portion, and the support roll 35 is most distant from the linear portion 30a on the lower side.
The support roll 33 is formed so that the angle between
Is arranged outside the straight line connecting the support rolls 32 and 34, and the support roll 36 is set so that the angle formed by the support rolls 35, 36 and 31 becomes an obtuse angle (approximately 180 degrees in the present embodiment). It is arranged slightly outside the straight line connecting the support rolls 35 and 31. In the present embodiment, the support roll 31 is used as a drive roll driven by a belt drive motor (not shown), the support rolls 32, 34, and 36 are used as driven rolls, and the support roll 33 is used. Is the intermediate transfer belt 30
Is used as a correction roll for regulating meandering in a direction substantially orthogonal to the moving direction of the steering roll (steering roll: provided to be tiltable around one axial end as a fulcrum).
5 is a batch transfer device (secondary transfer device) 50 as described later.
Used as a backup roll. and again,
In the present embodiment, the outer peripheral length L of the intermediate transfer belt 30 is
It is set to an integral multiple of the circumference S of the image carrier 21, for example, about 6 to 10 times (8 times in the present embodiment).

Further, in the present embodiment, the collective transfer device 50 is provided on the surface side of the intermediate transfer belt 30 so as to be retractable and is grounded, and is provided at a portion opposed to the transfer roll 51. Backup roll 52 (also used as support roll 35 in the present embodiment) and bias roll 53 which is arranged in contact with backup roll 52 and to which a predetermined DC bias is applied.
It is provided with. In the present embodiment, the paper 100 enters the transfer area (corresponding to the nip area between the transfer roll 51 and the backup roll 52) of the collective transfer device 50 through the chute 101. on the other hand,
A paper guide plate 102 is provided on the downstream side of the batch transfer device 50, and a paper 100 is provided on the downstream side of the paper guide plate 102.
For example, two transports 103 and 104 for transport are provided, and a fixing device 70 is provided behind the transport 104 on the subsequent stage.

In the present embodiment, the belt cleaner 60 is provided at a position corresponding to the drive roll 31 and the support roll 36 so as to be retractable, and the residual toner on the intermediate transfer belt 30 is removed by a blade 61, for example. It is designed to be removed. In this embodiment, the belt cleaner 60 is retracted to the retracted position during maintenance or the like.

Further, in the present embodiment, the intermediate transfer belt 30 located behind the last-stage image forming unit 20K is provided.
A plurality (four in this embodiment) of density detectors 80 (specifically, 80Y, 80M, 80C, 80
K: see FIG. 3) are arranged in parallel in the width direction of the intermediate transfer belt 30 (the direction orthogonal to the moving direction).

FIG. 3 is a block diagram showing an image forming control system used in the present embodiment. In FIG. 1, reference numeral 110 denotes an image forming timing control device that mainly controls timing when forming an image (including a sample image to be described later), and includes a microcomputer system such as a CPU, a ROM, a RAM, and an input / output interface. Be built. Reference numeral 111 denotes each image forming unit 20
(20Y to 20K) an image carrier driving device such as a servo motor for driving the image carrier 21; 112, a rotation position sensor (SN in the figure) for detecting a reference position of one rotation of each image carrier 21;
R). In FIG. 3, charging, exposure, development, primary transfer, secondary transfer, and fixing indicate the charging device 22, the exposure device 23, the developing device 24, the primary transfer device 25, the secondary transfer device 50, and the fixing device 70, respectively. . In the present embodiment, the image forming timing control device 110 captures signals from the density detector 80 (80Y to 80K), the rotation position sensor 112, and the like, and executes, for example, an image forming preparation mode shown in FIG. The image forming unit 20 controls the image forming start position of each image carrier 21 and thereafter executes a normal image forming mode.

Next, the operation of the image forming apparatus according to this embodiment will be described. In the image forming apparatus according to the present embodiment, the image forming preparation mode (FIG. 4) is executed before the image forming mode is executed. The image forming preparation mode is, for example, when the power of the image forming apparatus is turned on (at the start of a print cycle).
(ST in FIG. 4 (step)).
1), “Image preparation start signal” in ST1 of FIG. 4 indicates a power-on signal. Note that the execution timing of the image forming preparation mode is not limited to the above-described timing, and is performed when the power of the image forming apparatus is turned off (at the end of a print cycle) or at an appropriate timing during a print cycle (for example, a predetermined time). (For each number of prints) or at the time of initial installation of the image forming apparatus. At this time, the "image preparation start signal" in FIG. 4 is a power-off signal of the image forming apparatus, a signal indicating that the number of prints has reached a predetermined number, or an image preparation mode at the time of initial installation of the image forming apparatus. , Etc., indicating the start of the operation.

Now, when the power of the image forming apparatus is turned on, an image preparation start signal is generated, so that the image preparation mode is substantially started, and a sample image for one round of each image carrier 21 is formed. (ST2 in FIG. 4). In the present embodiment, the process of creating a sample image is performed, for example, as shown in FIG.
As shown in (b), each image carrier 2 is provided for each image carrier 21.
1 is uniformly charged (charged potential VH: FIG. 5).
(See FIG. 5 (b)), and then uniformly expose at least the peripheral surface of the image carrier 21 corresponding to each of the density detectors 80 in a strip shape (exposure portion potential VS: see FIG. 5 (b)). The belt-shaped toner images TY (TM, TC,
TK) is primarily transferred to the intermediate transfer belt 30. At this time, each sample image, that is, the belt-shaped toner image TY (T
M, TC, TK) is at least as large as the density detector 8
It is sufficient that the width ds of the detection surface 81 is zero, but in the present embodiment, from the viewpoint of maintaining good density detection accuracy by the density detector 80, the width ds is smaller than the width of the detection surface of the density detector 80. It is set large (see FIG. 6). In addition, the uniform exposure intensity may be appropriately set, but in the present embodiment, the toner consumption is suppressed as much as possible and the density detection accuracy is kept good (the output of the density detector is saturated in a high density region. , The state of density detection drops)
From the viewpoint, an exposure intensity lower than the maximum exposure intensity in the image forming mode is set.

Thereafter, the band-shaped toner images TY (TM, TC, TK), which are the respective sample images on the intermediate transfer belt 30, are converted into the respective density detectors 80 (80Y to 80K) as shown in FIG.
Sequentially passes through the locations corresponding to
Detects the density fluctuation of the sample image corresponding to one rotation of the image carrier 21. The detection signal from the density detector 80 is taken into the image forming timing control device 110 (FIG. 4).
In the middle ST3), the image forming timing control device 110 determines an image forming start position for each image carrier 21 based on each density variation pattern (ST4 in FIG. 4).

Here, the density detector 80 (80Y to 80Y)
The detection signal of each sample image from K) is, for example, as shown on the left side of FIG. 7, mainly for one cycle for one circumference of the image carrier 21 (S in FIG. 7 indicates the circumference of the image carrier 21). It shows a sinusoidal pattern that fluctuates by minutes. Note that FIG.
In the middle, D (D (Y) to D (K)) on the vertical axis indicates the density level of each detection signal. Such a one-period variation pattern occurs as analyzed in the section of the means for solving the problem,
Each of the image carriers 21 of each image forming unit 20 slightly includes an eccentric error, and when the image carrier 21 makes one rotation, the outer surface of the image carrier 21 mainly generates a swell component for one cycle. Accordingly, it is considered that, for example, the gap between the image carrier 21 and the charging device 22 and the developing device 24 fluctuates with the undulation component.

The image forming timing control device 11
A value of 0 checks, for example, the time difference in the change in the density pattern of the sample image of each color component with reference to the density pattern of the sample image of the Y color component (Y sample image). For example, assuming that the density pattern of each color sample image is as shown on the left side of FIG. 7, the M sample image fluctuates in phase with respect to the Y sample image by ΔtM, and the C sample image and the K sample image change. , And Y sample images, the phases advance and fluctuate by ΔtC and ΔtK, respectively. Therefore, the image forming timing control device 110 determines the time differences ΔtM (−), ΔtC (+), and ΔtK of the color sample images.
Understand (+). Thereafter, the image forming timing control device 110 determines the image forming start position (indicating an absolute position for starting image forming) on each image carrier 21 by the time difference ΔtM.
The position is determined to be shifted by (−), ΔtC (+), and ΔtK (+), and is stored in the memory (ST5 in FIG. 4).

Thereafter, the image forming timing control device 11
0 generates a desired speed control signal based on the stored image forming start position information, and transmits it to each image carrier driving device 111.
To control the speed of each image carrier 21,
1 to control the image forming start position. At this time, FIG.
So that the image forming start position A on each image carrier 21 (21Y, 21M, 21C, 21K) reaches the exposure point EP at the start of the exposure in the image forming mode so that the state changes from the upper state to the lower state. Then, the position of each image carrier 21 is controlled. As a result, for example, the density pattern of each sample image from the image forming start position on each image carrier 21 matches each cycle as shown in the right side of FIG.

Further, each sample image formed on the intermediate transfer belt 30 is cleaned by a belt cleaner 60. This ends a series of image preparation modes,
After that, it waits for the execution of the image forming mode.

Thereafter, when a print start switch (not shown) is turned on, an image forming mode is executed. Now, for example, when a plurality of continuous (multiple pages) color prints are to be made on JIS standard B5 size paper 100, as shown in FIG. 2, each color component toner image is formed by each image forming unit 20 (20Y to 20K). The toner images of the respective color components are sequentially multiplex-transferred onto the intermediate transfer belt 30, and the intermediate transfer belt 3
The multi-transferred image on the sheet No. 0 is transferred onto the sheet 100 at a time. At this time, the multiple transfer image G of each page on the intermediate transfer belt 30
For example, as shown in FIG. 9, the image forming pitch P1 is sequentially formed at the same dimensional interval as the circumference S of the image carrier 21.

Also, when a plurality of continuous (multiple pages) color prints are made on JIS A4 size paper 100, the multiple transfer image G of each page on the intermediate transfer belt 30 is
For example, as shown in FIG.
1 are formed sequentially at the same dimensional interval as the perimeter S. Furthermore, J
In a case where a plurality of continuous (multiple pages) color prints are performed on IS standard B4 size or A3 size paper 100, in this embodiment, the multiple transfer image G of each page on the intermediate transfer belt 30 is, for example, as shown in FIG. As shown in FIG.
Are sequentially formed at a dimensional interval, for example, twice the circumference S of the image carrier 21. In the present embodiment, the image forming pitches P1,
P2 is set to be one or two times the circumference S of the image carrier 21, but is not limited to this and is an integral multiple or (1
/ Integer) times.

In such an image forming process, each color component toner image is transferred to the image carrier 21 having the potential distribution shown in FIG.
Formed on top. That is, in the present embodiment, as shown in FIG. 8, all of the image forming start positions A on each image carrier 21 pass through the exposure point EP at the time of starting the exposure. The initial charge distribution (charge potentials V (Y) to V (K)) of the image carrier 21 from the image start position A changes at the same cycle as shown in FIG. At this time, the potential levels at the corresponding positions of the image carriers (Y image carrier to K image carrier) of each color component are denoted by hY, hM, hC, and hK, respectively. In this embodiment, assuming that hY, hM, hC, and hK have substantially the same value h, if the hue difference and lightness difference between the Y and M color components are approximated, the hue difference (YM ) Is | hY−hM | = 0, and the brightness difference (YM) is | h
Y + hM | = | 2h |. The same applies to hue differences and lightness differences between other color components.

As described above, in this embodiment, since the image forming start position of each page on each image carrier 21 is always constant, the potential distribution and the development degree on the surface of each image carrier 21 are different for each page. It becomes a certain tendency, and accordingly, each image forming unit 20
Are uniform without variation. For this reason, even when such color component toner images are transferred in a multiplex manner, the hue of the color images on the plurality of sheets of paper 100 is kept constant without variation because the color component toner images do not vary.

In particular, in the present embodiment, since the hue difference with high visual sensitivity is minimized, a very good color image can be obtained. Note that while the hue difference is minimized, the brightness difference is maximized, but the brightness difference itself has low visual sensitivity and thus does not significantly affect the change in the color tone of the color image.

Here, as a form of comparison, FIG.
As shown in the figure, assuming that the Y image carrier and the M image carrier are asynchronous and the phase is deviated by, for example, １ ／ period, the color between the Y color component and the M color component is assumed. When the phase difference and the brightness difference are approximated, the hue difference (YM) is | hY−hM | = | hY |, the brightness difference (YM)
Is expressed as being proportional to | hY + hM | = | hY |. Then, FIG.
For example, assuming that the Y image carrier and the M image carrier are asynchronous and the phase is further deviated by 周期 period, the color between the Y color component and the M color component as shown in FIG. When the phase difference and the brightness difference are approximated, the hue difference (YM) is | hY−hM | = 2 | hY |, the brightness difference (Y
M) is expressed as being proportional to | hY + hM | = 0. However, in FIG. 11B, it is approximately | hY | = | hM |. The same applies to hue differences and lightness differences between other color components. As described above, when the colors are asynchronous, the hue difference having high visual sensitivity changes for each page, and thus the color tone of the color image between the pages greatly changes.

Second Embodiment FIG. 12 is a block diagram showing an image forming control system used in the second embodiment. In this figure, the basic configuration of the image forming control system is substantially the same as that of the first embodiment, but is different from the first embodiment in that the density detecting cycle of the sample image by the density detector 80 is eliminated and the image forming preparation mode is set. Is simplified. That is, in the present embodiment, upon receiving the image formation preparation start signal, the image formation timing control device 110 determines the position on each image carrier 21 that reaches the exposure point at the start of exposure as the image formation start position. , And store this in a memory. Thereafter, in the image forming mode, the image forming start position on each image carrier 21 always passes through the exposure point at the start of exposure, and an electrostatic latent image is formed on each image carrier 21.

Also in this embodiment, as shown in FIG. 9, for example, as shown in FIG. 9, the multiple transfer image G of each page on the intermediate transfer belt 30 is such that the image forming pitches P1 and P2 are equal to one of the circumferential length S of the image carrier 21.
They are sequentially formed at double or double dimensional intervals. At this time, the initial potential distributions (charging potentials V (Y) to V (Y) to V (Y)) from the image formation start positions of the respective color components on the image carrier (Y image carrier to K image carrier) 21
(K)) shows, for example, as shown in FIG.
, The predetermined time differences (phase differences) ΔtM, ΔtC,
It fluctuates in the same cycle with ΔtK.

At this time, the potential levels at the corresponding positions of the image carriers of each color component (Y image carrier to K image carrier) are denoted by hY, hM, hC and hK, respectively. Now, when the hue difference and lightness difference between the Y color component and the M color component are approximated, the hue difference (YM) is | hY−hM |, and the lightness difference (YM) is | hY +
hM |. The same applies to hue differences and lightness differences between other color components. At this time, the hue differences (YM), (MC), (CK), and (YK) of the respective color components are different values, and are not minimized as in the first embodiment. Each hue difference of the toner image is always kept constant. Therefore, in the present embodiment, the same color component toner image generated from each image forming unit 20 is constant without variation. For this reason, even when such color component toner images are transferred in a multiplex manner, the hue of the color images on the plurality of sheets of paper 100 is kept constant without variation because the color component toner images do not vary.

[0033]

As described above, according to the present invention, in a so-called tandem engine type image forming apparatus,
Since the dimensional relationship between the circumference S of the image carrier and the image forming pitch P of the image is set so that P = n · S (n: integer or 1 / integer), the image forming control system of each image forming unit. Therefore, if the image forming start position on the image carrier between the image forming units is always synchronized beyond the job, the fluctuation component of the peripheral surface of the image carrier of each image forming unit may occur. The density difference and the color difference tendency of each color component image generated at the same time can be reproduced at the same position on the recording material. For this reason, even when a plurality of the same images are formed, it is possible to make the composite images of the respective color component images equal without dispersing the hue, and accordingly, the variation of the color image quality of each page is correspondingly increased. And the color image quality can always be kept good.

In particular, in the present invention, if the image forming control system of each image forming unit is devised and selected so as to minimize the hue difference of the composite image, the color image quality can be kept better.

[Brief description of the drawings]

FIG. 1A is an explanatory diagram illustrating a schematic configuration example of an image forming apparatus according to the present invention, and FIG. 1B is an explanatory diagram illustrating a relationship between a peripheral length of an image carrier and an image forming pitch.

FIG. 2 is an explanatory diagram illustrating an outline of the image forming apparatus according to the first embodiment;

FIG. 3 is a block diagram illustrating an overall configuration of an image forming control system used in the first embodiment.

FIG. 4 is a flowchart showing an image forming preparation mode of an image forming control system according to the first embodiment.

5A is a flowchart showing a subroutine for creating a sample image for one round of each image carrier in FIG. 4; FIG.
FIG. 4 is a schematic diagram showing a process of creating a sample image.

FIG. 6 is a schematic diagram illustrating a process of detecting the density of a sample image.

FIG. 7 is an explanatory diagram showing a detection result of a density variation of each color component sample image and an algorithm for determining an image forming start position of each image carrier performed based on each detection result.

FIG. 8 is a schematic diagram showing the contents of post-processing by an algorithm for determining an image forming start position of each image carrier.

FIG. 9 is an explanatory diagram showing image forming states in various image forming modes after completion of the image forming preparation mode.

FIG. 10 is an explanatory diagram showing image quality evaluation according to the first embodiment.

FIGS. 11A and 11B are explanatory diagrams illustrating image quality evaluation according to a comparative example. FIGS.

FIG. 12 is a block diagram illustrating an overall configuration of an image forming control system used in the second embodiment.

FIG. 13 is an explanatory diagram illustrating image quality evaluation according to the second embodiment.

[Explanation of symbols]

1 (1a to 1d): image forming unit, 2: intermediate transfer member, 3: recording material, 4: image carrier, 5: image forming control system, S:
Perimeter of image carrier 1, P (P1, P2) ... image forming pitch

Claims (3)

[Claims] A plurality of image forming units arranged in parallel along a moving path of an intermediate transfer body or a recording material, each image forming unit including an image carrier for carrying each color component image; In an image forming apparatus that transfers each color component image formed on the image carrier of each image forming unit to a recording material via an intermediate transfer body or directly, the peripheral length of the image carrier of each image forming unit is represented by S, P = n · S (n: integer or 1 /
(Integer). 2. The image forming apparatus according to claim 1, wherein the image forming control system of each image forming unit always synchronizes the image forming start position on the image carrier between the image forming units over the jobs. An image forming apparatus comprising: 3. The image forming apparatus according to claim 2, wherein the image forming control system of each image forming unit detects a fluctuation component associated with one rotation of the peripheral surface of the image carrier of each image forming unit. And image forming start position determining means for determining an image forming start position on each image carrier based on the fluctuation component detected by the fluctuation component detecting means so as to minimize the hue difference of the composite image. An image forming apparatus comprising: