JP2004302308A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve speed at which prints are produced, without causing color shift in a four-cycle system full-color printer using an intermediate transfer belt. <P>SOLUTION: With a secondary transfer roller and a cleaning blade separated, a resist mark line is formed on the intermediate transfer belt and that is detected (S11). Next, while the secondary transfer roller and the cleaning blade are sequentially firmly pressed to the intermediate transfer belt or separated, a resist mark line is formed and that is detected (S12, S13). From the detection results, data about an amount of variation in the running speed of the intermediate transfer belt, which occurs due to the operation of firmly pressing the secondary transfer roller and the cleaning blade or separating them, is calculated (S14). Thus, a correction table about thinning and idling of scanning lines to be executed in actual image writing is created (S15). With reference to the correction table, correction of writing of corresponding specific color images on photoreceptor drums is controlled . <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus and an image forming method in which a toner image is temporarily transferred onto an intermediate transfer body such as an intermediate transfer belt, and is secondarily transferred to another transfer material to form an image.
[0002]
[Prior art]
Generally, in a color image forming apparatus, a document image is subjected to color separation to generate image data of each developing color of yellow (Y), magenta (M), cyan (C), and black (K), and A color image is formed by forming a toner image of each color on a photosensitive drum and superimposing and transferring these on a recording sheet.
[0003]
Among these, in a four-cycle type color image forming apparatus using an intermediate transfer belt, first, for example, a Y toner image is formed on the surface of one photosensitive drum, and the intermediate transfer is rotated. The toner image is transferred to a predetermined position on the belt, and subsequently, an M toner image is formed on the surface of the photoreceptor drum, and a corresponding pixel is superimposed on the Y toner image of the intermediate transfer belt that has been looped around. Then, the toner images of C and K are similarly successively superimposed and transferred to form a color image on the intermediate transfer belt (hereinafter, in this specification, each development color is formed on the intermediate transfer belt). The operation of forming the toner image is hereinafter referred to as “image formation”.)
[0004]
The color image formed on the intermediate transfer belt is further secondary-transferred to a transfer material such as a recording sheet, and then heat-fixed, thereby forming a color image on the transfer material.
In such an intermediate transfer type color image forming apparatus, the secondary transfer roller and the cleaning blade cannot always be kept in pressure contact with the intermediate transfer belt, and the toner images of four colors are multiplexed on the intermediate transfer belt. After the transfer, the secondary transfer roller is pressed against the surface of the intermediate transfer belt to secondarily transfer the color image to a recording sheet passing between the secondary transfer roller and the intermediate transfer belt. After the residual toner is removed by pressing against the belt surface, the next color image is formed.
[0005]
However, in order to improve the printing speed (the number of prints per unit time; usually indicated by the number of prints per minute), for example, when the previous color image is secondarily transferred, another position of the intermediate transfer belt is used. It is necessary to form a toner image of the first development color Y of the next color image on the intermediate transfer belt. At this time, the timing of the pressing or separating operation of the transfer roller and the cleaning blade is determined by the image formation of the next toner image. This will coincide with the operation timing.
[0006]
Normally, the drive mechanism of the intermediate transfer belt is controlled so that the intermediate transfer belt runs at a constant speed. However, the responsiveness of the constant speed control is limited, and the transfer roller and the cleaning blade described above are not controlled. An increase in the load when pressed against the transfer belt inevitably reduces the running speed for a moment, and conversely, when the members are separated from each other, the load is reduced, and the speed of the intermediate transfer belt increases for a moment.
[0007]
Therefore, there is a slight difference in the formation position of the toner image of the next development color on the intermediate transfer belt, which causes a color shift and deteriorates the color image.
In order to solve this problem, for example, Japanese Patent Application Laid-Open No. H11-163873 discloses that an image of each color is formed at a predetermined same timing after detecting a mark formed on an intermediate transfer belt in a color image forming apparatus of an intermediate transfer system. After the cleaning blade is separated from the intermediate transfer belt, when the mark is detected for the first time, an image of the first development color in the next image is formed.
[0008]
According to this, it can be said that there is no operation in which the cleaning blade presses and separates from the intermediate transfer belt during the formation of each developing color of the next color image, so that no color shift occurs.
[0009]
[Patent Document 1]
JP-A-9-146438
[0010]
[Problems to be solved by the invention]
However, according to the configuration described in Patent Document 1, at least while the cleaning blade is in contact with the intermediate transfer belt for cleaning, the image forming operation of the next image cannot be performed.
In addition, as described above, the speed of the intermediate intermediate transfer belt also fluctuates during the pressing and separating operations of the secondary transfer roller. In addition, the image forming operation of the next image is prohibited, and the overall printing speed is greatly reduced.
[0011]
This problem can occur not only when a color image is formed but also when a monochrome image is continuously formed as long as the cleaning blade and the transfer roller are pressed against and separated from the intermediate transfer belt.
The present invention has been made in view of the above problems, and has an image forming apparatus having a configuration in which a toner image is once formed on an intermediate transfer member such as an intermediate transfer belt, and is transferred to another transfer material. An object of the present invention is to provide an image forming apparatus and an image forming method in which the deterioration of an image is small without lowering the speed of image forming processing for a plurality of sheets.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention provides an image forming apparatus that primarily transfers a toner image formed by an image forming unit to a surface of an intermediate transfer member, and secondarily transfers the toner image to a transfer material to form an image. A secondary transfer means for causing a transfer material to abut on the surface of the intermediate transfer member by a transfer roller and secondary-transferring a toner image to the transfer material; and a cleaning device for pressing a cleaning member against the surface of the intermediate transfer member for cleaning. Means for acquiring information indicating the amount of change in the traveling speed of the surface of the intermediate transfer member when the cleaning member and / or the transfer roller is pressed against and / or separated from the surface of the intermediate transfer member; And a correction control means for correcting and controlling the image forming means based on the obtained information so as to eliminate the deterioration of the image caused by the fluctuation of the running speed.
[0013]
Also, the present invention provides a pattern forming means for forming a regular resist pattern on the surface of the intermediate transfer body along the running direction, a pattern detecting means for detecting the resist pattern, and a resist pattern formed by the pattern forming means. Control means for controlling the cleaning means and / or the secondary transfer means so that the cleaning member and / or the transfer roller is pressed against and / or separated from the surface of the intermediate transfer body during the formation; Is formed without involving the pressing and separating operations of the detection result of the resist pattern when the cleaning member and / or the transfer roller is pressed and / or separated from the surface of the intermediate transfer body by the pattern detecting means. Based on the detected result of the resist pattern, a change in the traveling speed of the surface of the intermediate transfer member is indicated. And acquiring the information.
[0014]
Note that the “pattern forming unit” may be a separate unit independent of the image forming unit, or the image forming unit may also be used as the pattern forming unit.
Further, in the invention, it is preferable that the control unit presses and / or separates the cleaning member and / or the secondary transfer roller from the surface of the intermediate transfer member at the same timing as the operation of the cleaning unit and / or the secondary transfer roller which occurs in actual image formation by the image forming unit. The cleaning unit and / or the secondary transfer unit is controlled so that the cleaning unit and / or the secondary transfer roller is pressed and / or separated during the formation of the resist pattern.
[0015]
Still further, according to the present invention, the image forming means forms a color image on an intermediate transfer member by multiplex-transferring the toner images of each developing color, and comprises a photosensitive drum, Exposing means for exposing and scanning the surface of the photosensitive drum to form an electrostatic latent image based on image data, and developing means for developing the electrostatic latent image with a toner of a corresponding developing color; The control unit may adjust the color misregistration of the image of the specific development color by at least one of exposure / writing timing adjustment, scanning line thinning, scanning line blanking, scanning line twice, or image correction. It is characterized in that correction control for correction is executed.
[0016]
Here, “thinning of scanning lines” refers to skipping a specific scanning line and performing exposure scanning of image data of the next scanning line, and “blank hitting of a scanning line” refers to a specific scanning line. Means that another scanning line composed of white pixels is inserted before exposure scanning. Further, "double scanning of a scanning line" means that a specific scanning line is repeatedly exposed and scanned twice. Further, “image correction” is a concept including a change in the position of a pixel on an image memory, addition or deletion of a scan line, and the like.
[0017]
Further, according to the present invention, the toner image formed by the image forming means is primarily transferred onto the surface of the intermediate transfer body, and this is secondarily transferred to a transfer material by a transfer roller to form an image. A method for preventing image deterioration in an image forming apparatus having a configuration in which a cleaning member is pressed against a body surface to perform cleaning, wherein the cleaning member and / or the transfer roller is pressed against and / or separated from the surface of an intermediate transfer body. An acquisition step of acquiring information relating to a change in the traveling speed of the surface of the intermediate transfer member; and, based on the acquired information, performing a correction control of the image forming means so as to eliminate the occurrence of image degradation caused by the change in the traveling speed. And a correction step.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described with reference to an intermediate transfer type full-color laser printer (hereinafter, simply referred to as “printer”).
(1) Overall configuration of printer
FIG. 1 is a schematic diagram illustrating the overall configuration of the printer 1.
[0019]
As shown in FIG. 1, the printer 1 includes a photosensitive drum 2, a developing device 4, an intermediate transfer belt 6, a cleaner 8 for cleaning residual toner and the like on the intermediate transfer belt 6, a fixing device 9, an exposure unit 11, and the like. Is a digital printer that forms a full-color image by a well-known electrophotographic method, including an image forming unit 10 having a sheet feeding unit 20 and a sheet feeding cassette 21 for accommodating the recording sheets S and the like.
[0020]
The printer 1 is connected to an external computer or the like (not shown) via a network such as a LAN (Local Area Network). When the control unit 100 receives print data of a color image from the external computer, necessary processing is performed. To generate image data of yellow (Y), magenta (M), cyan (C), and black (K) development colors.
[0021]
The image data of each of these developing colors is converted into a drive signal of the semiconductor laser of the exposure unit 11 and output to the semiconductor laser, whereby a laser beam (broken line in the figure) is emitted toward the photosensitive drum 2.
The laser beam is exposed and scanned in the main scanning direction (perpendicular direction in FIG. 1) on the surface of the photosensitive drum 2 which is cleaned by the cleaning blade 5, is uniformly charged by the charging charger 3 and rotates in the A direction, and An electrostatic latent image of a corresponding developing color is formed on the photosensitive drum 2.
[0022]
The developing device 4 has four developing units 40Y to 40K containing developers containing toners of respective colors of Y, M, C, and K mounted on the developing rack 15 at regular intervals of 90 degrees in the circumferential direction. In addition, the developing rack 15 can be rotated in the direction of arrow B in FIG. Then, the developing device 4 is rotated by a developing motor (not shown), and is controlled so that the developing rollers 41Y to 41K of the developing units 40Y to 40K corresponding to the next developing colors are located at the developing positions facing the photosensitive drum 2. The rotation of the electrostatic latent image on the photosensitive drum 2 is controlled by the rotation of the unit 100, and the development is performed.
[0023]
The intermediate transfer belt 6 is endless and is stretched by a primary transfer roller 61, a driving roller 62, and driven rollers 63 and 64, and runs in the direction of arrow E by the rotational driving force of the driving roller 62. Here, during the primary transfer, a voltage having a polarity opposite to the charging polarity of the toner is applied to the primary transfer roller 61. The drive roller 62 is grounded.
[0024]
The toner image formed on the photosensitive drum 2 is transferred onto the intermediate transfer belt 6 at the primary transfer position D by an electric field generated between the primary transfer roller 61 and the photosensitive drum 2 (primary transfer). Is done. At this time, the image forming operation on the photosensitive drum 2 is executed at a timing such that the toner images of each color are transferred to the same position on the intermediate transfer belt 6 in the order of Y, M, C, and K. Thus, the toner images of each color are sequentially superimposed on the intermediate transfer belt 6 to form a full-color toner image.
[0025]
The secondary transfer unit 7 includes a secondary transfer roller 71, a holding member 72 that rotatably supports the secondary transfer roller 71, and a transfer solenoid 73 that moves the holding member in the direction of the arrow in the drawing.
When a full-color toner image is formed on the intermediate transfer belt 6 as described above, the secondary transfer roller 71 is pressed against the drive roller 62 to apply a charge having a polarity opposite to the charge polarity of the toner. Due to the electric field generated between the secondary transfer roller 71 and the opposing drive roller 62 at the secondary transfer position F, a full-color toner image is formed on the recording sheet S fed from the paper supply cassette 21. Transcribed.
[0026]
The recording sheet S stored in the paper feed cassette 21 is fed to the timing roller 23 by the rotation of the paper feed roller 22, and synchronized with the operation of forming a full-color toner image on the intermediate transfer belt 6, To the transfer position F.
The recording sheet S on which the full-color toner image has been transferred is conveyed to the fixing device 9, where it is heated and pressed to melt and fix the toner on the surface of the recording sheet S, and then discharged to the discharge tray 13 by the discharge roller 12. You.
[0027]
The cleaner 8 as a cleaning unit for the intermediate transfer belt 6 supports a holding member 83 for holding a cleaning blade 81 at a tip thereof in a swingable manner by a support shaft 82, and a lower end of the holding member 83 is controlled by a cleaner solenoid 84. By moving the cleaning blade 81 in the direction of the arrow in the drawing, the pressing and separating operations of the cleaning blade 81 against the surface of the intermediate transfer belt 6 can be executed.
[0028]
Reference numerals 65 and 66 denote mark detection sensors, each of which is a reflective photoelectric sensor having a light emitting element and a light receiving element. The former is used to detect registration marks 200 (see FIG. 6) formed on the intermediate transfer belt 6 to obtain color shift correction data, and the latter is used to determine the timing of image formation. It is used to detect a reference mark 201 (see FIG. 6) provided on the belt 6 in advance. Details will be described later.
(2) Configuration of control unit 100
FIG. 2 is a block diagram showing a configuration of the control unit 100.
[0029]
As shown in FIG. 1, the control unit 100 includes a CPU 101, an interface (I / F) unit 102, an image processing unit 103, an image memory 104, an LD driving unit 105, a ROM 106, and a RAM 107.
The I / F unit 102 is a communication interface (LAN card, LAN board, etc.) for connecting to a LAN.
[0030]
The image processing unit 103 adds a known color correction process, an MTF correction process, and the like to the RGB image data received from an external device received via the I / F unit 102 to generate image data of a developed color YMCK. I do. The generated image data of each color is temporarily stored in the image memory 104, read out by the CPU 101 when image formation is performed, and transmitted to the LD driving unit 105.
[0031]
The LD drive unit 105 has a line memory therein, sequentially holds image data one scan line at a time, converts the image data into a drive pulse for driving the semiconductor laser of the exposure unit 11, and sends the drive pulse to the exposure unit 11.
As a result, exposure scanning of the photosensitive drum 2 based on the image data is performed, and an electrostatic latent image of each developing color is sequentially formed on the photosensitive drum 2.
[0032]
The CPU 101 reads out necessary programs from the ROM 106 and operates the photosensitive drum 2, the intermediate transfer belt 6, the secondary transfer unit 7, the cleaner 8, and the like of the image forming unit 10, and operates the paper feed roller 22 of the paper feed unit 10. The operation is generally controlled to smoothly execute an image forming operation and the like. It also has a timer function, a counter function, and the like, which are used when executing the control program.
[0033]
In addition, it executes a process of acquiring data relating to a change in the traveling speed of the intermediate transfer belt 6 due to the contact / separation operation of the transfer roller 71 and the cleaning blade 81, and a correction control associated therewith. Details will be described later.
The ROM 106 stores various programs for an image forming operation, color shift correction control, and the like. Further, a threshold necessary for each control described later, image data of a registration mark for detecting the amount of displacement, and the like are stored. The RAM 107 provides a work area for the CPU 101.
[0034]
(3) Transfer timing of images of each developed color
FIG. 3 is a timing chart showing the time relationship between the transfer of the image of each developing color onto the intermediate transfer belt 6 and the pressing and separating of the secondary transfer roller and the cleaning blade.
In the second stage transfer timing, for example, “Y1” indicates the transfer timing of the first Y color development.
[0035]
The intermediate transfer belt 6 is provided with a reference mark 201 (see FIG. 6). The reference mark 201 is detected by the mark detection sensor 66 and is transferred onto the intermediate transfer belt 6 after a predetermined time t1 has elapsed. The timing of the exposure scanning by the laser beam is determined for each color image, and when there is no fluctuation in the traveling speed of the intermediate transfer belt 6, the four color images in the order of Y, M, C, and K are the same on the intermediate transfer belt 6. Control is performed so that multiple transfer is performed at the position.
[0036]
In the present embodiment, when transferring the first Y toner image (hereinafter, simply referred to as “Y1 image” for other colors and the second and subsequent sheets) to the intermediate transfer belt 6, The secondary transfer roller 71 and the cleaning blade 81 are separated from the intermediate transfer belt 6, and the length of the toner image in the running direction of the intermediate transfer belt 6 is about 5 minutes of the total length of the intermediate transfer belt 6. When the front end of the toner image reaches the position of the cleaner 8, the length of the rear end of the toner image is still being transferred at the primary transfer position D. I do.
[0037]
As shown in FIG. 3, in the formation of the first color image, following the transfer of the Y1, M1, and C1 images, the primary transfer of the K1 image starts t1 seconds after the reference mark is detected for the fourth time. Since the leading end of the full-color toner image reaches the secondary transfer position on the way, the secondary transfer roller 71 is pressed in advance accordingly (after t2 seconds from the start of the transfer of the K1 image), and the secondary transfer roller 71 Transcription is made.
[0038]
Then, immediately before the transfer of the K image is completed, the cleaning blade 81 is pressed against the intermediate transfer belt 6 (t4 seconds after the start of the transfer of the K1 image), and the surface of the intermediate transfer belt 6 after the secondary transfer is cleaned.
Therefore, the pressing operation of the secondary transfer roller 71 and the cleaning blade 81 occurs during the transfer of the K1 image, thereby causing two speed fluctuations (deceleration).
[0039]
On the other hand, during the transfer of the next Y2 image, the secondary transfer roller 71 is separated before the leading end of the transfer toner image reaches the secondary transfer position F (after t3 seconds from the start of the transfer of the Y2 image). Since the cleaning blade 81 is separated (after t5 seconds from the start of the transfer of the Y2 image), this causes two speed fluctuations (acceleration).
FIG. 4 is a graph showing the relationship between the speed fluctuation of the intermediate transfer belt 6 and the amount of color shift at this time.
[0040]
First, during the transfer of the M and C images, there is no pressure contact / separation between the secondary transfer roller 71 and the cleaning blade 81 on the intermediate transfer belt 6, so that the speed of the intermediate transfer belt does not fluctuate. No displacement occurs between the images (between M and C).
However, as described above, during the transfer of the Y image (however, the second and subsequent Y images), (1) the speed of the intermediate transfer belt 6 is momentarily increased due to the separation of the secondary transfer roller 71. Is transferred to a position slightly behind the same scan line in the M image (about 25 μm in this example), and (2) due to the separation of the cleaning blade 81, Thereafter, the position of the scanning line of the Y image moves after the transfer position of the corresponding scanning line of the M image (about 50 μm in this example). As a result, the transfer position of the scan line of the Y image after the separation of the cleaning blade 81 in (2) is shifted by about 100 μm in total behind the scan line of the same number of the M image, and the color shift becomes remarkable.
[0041]
On the other hand, during the transfer of the K image, (3) the traveling speed of the intermediate transfer belt 6 is momentarily reduced due to the pressure contact of the secondary transfer roller 71, and the transfer position of the scanning line of the K image thereafter becomes the M image. And the transfer position of the Y image scan line is shifted forward by about 70 μm due to the pressure contact of the cleaning blade 81, so that the K image is shifted. Looking at the scan line after the cleaning blade 81 is pressed against the scan blade 81, a position shift occurs about 170 μm in total ahead of the scan line of the same number of the M image.
[0042]
Further, the maximum shift amount of the transfer position between the Y image and the K image is 100 μm + 170 μm = 270 μm. If the pixel density (dpi) in the sub-scanning direction (the running direction of the intermediate transfer belt 6) of the image formation of this printer is 600 dpi, the distance between the pixels is about 42.3 μm, so that 270 μm / 42. 3 μm ≒ 6.38, and when the transfer position is shifted by as much as 6 pixels, the color shift is extremely remarkable and the image is significantly deteriorated.
[0043]
Therefore, in the present invention, when forming the K image and the second and subsequent Y images, correction control is performed to eliminate color misregistration. More specifically, when the secondary transfer roller 71 and the cleaning blade 81 are separated from each other in the formation of the Y image, the scanning lines at the corresponding timing are thinned out, and the writing position of the subsequent operation line is shifted backward. On the other hand, when the secondary transfer roller 71 and the cleaning blade 81 are pressed against each other during K image formation, a blank scan line is inserted and the transfer position of the subsequent scan line does not shift forward. Control.
[0044]
(4) Color shift correction control
Hereinafter, the color misregistration correction control performed by the control unit 100 will be described in detail.
(4-1) Correction data acquisition processing
First, a correction data acquisition process is performed. This processing detects how much displacement between the scanning lines occurs due to a change in the traveling speed of the intermediate transfer belt 6 due to the pressing and separating operations of the secondary transfer roller 71 and the cleaning blade 81, and thereby, the correction data is obtained. Is a process for obtaining
[0045]
Specifically, as shown in the flowchart of FIG. 5, first, a plurality of registration marks 200 as shown in FIG. 6 are transferred to the intermediate transfer belt 6 with the secondary transfer roller 71 and the cleaning blade 81 being separated from the intermediate transfer belt 6. It is formed along the running direction of the belt 6, and is detected by the mark detection sensor 65 (step S11).
Each registration mark 200 is formed so as to be parallel to the main scanning direction (the direction orthogonal to the scanning direction of the intermediate transfer belt 6) and at equal intervals with the adjacent registration marks 200.
[0046]
In FIG. 6, each registration mark 200 is slightly exaggerated and drawn thick for easy understanding, but actually, as shown in the detection waveform of FIG. It is about one-half the thickness. Further, the interval between the registration marks is appropriately determined based on the length of time during which the speed changes due to the pressing and separating operations of the secondary transfer roller 71 and the cleaning blade 81. In the present embodiment, the formation interval of the registration marks 200 is set so that the influence of the fluctuation of the distance between the registration marks caused by one speed fluctuation is limited to the fluctuation between a pair of registration marks.
[0047]
The color of the toner used here is not particularly limited. However, considering that it is relatively inexpensive and easy to detect, it is desirable to form the toner with the K toner rather than the Y, M, and C color toners.
FIG. 7A is a diagram showing a detection result of the registration mark 200 by the mark detection sensor 65. The distance between the adjacent registration marks 200 can be easily obtained by multiplying the difference between the detection times by a specified traveling speed of the intermediate transfer belt 6 (a constant speed that is controlled).
[0048]
Since the sensor surface of the mark detection sensor 65 and the registration mark 200 have a width, the shape of the detection signal of one registration mark 200 becomes a mountain shape as shown in FIG. In order to specify the detection position of the registration mark 200, in this embodiment, the peak position of each detection signal is set as the detection position of each registration mark 200. Alternatively, the position of the center of gravity of the area of the detection waveform of the chevron may be determined and used as the detection position.
[0049]
After a series of plural registration marks 200 (hereinafter, referred to as “registration mark array”) formed as described above are detected by the mark detection sensor 65, the cleaning blade 81 is pressed against the intermediate transfer belt 6 to press the intermediate transfer belt 6. 6 is rotated once to prepare for the next registration mark row.
Next, a process of forming and detecting the registration mark 200 involving the pressing operation of the secondary transfer roller 71 and the cleaning blade 81 is performed (step S12).
[0050]
Specifically, the formation of the registration mark 200 is started in a state where the secondary transfer roller 71 and the cleaning blade 81 are separated from the intermediate transfer belt 6, and immediately after forming the h1st registration mark 200, the secondary transfer roller 71 is formed. Is pressed against the intermediate transfer belt 6, and the cleaning blade 81 is pressed against immediately after the formation of the h2th registration mark 200. Then, the formed registration mark row is detected by the mark detection sensor 65, and thereafter, is cleaned by the cleaner 8.
[0051]
FIG. 7B shows the detection result of the registration mark row at this time.
P and Q in FIG. 3 indicate positions where the traveling speed of the intermediate transfer belt 6 is momentarily reduced due to the pressure contact of the secondary transfer roller 71 and the cleaning blade 81, respectively. As shown in the drawing, the distances b1 and b2 between the registration marks 200 at these positions are equal to the corresponding distances a1 and a2 in FIG. 7A (a1 = a2 because there is no speed fluctuation in step S11). Is also getting smaller.
[0052]
Next, a process of forming and detecting a registration mark 200 involving an operation of separating the secondary transfer roller 71 and the cleaning blade 81 is performed (step S13).
Specifically, the formation of the registration mark 200 is started in a state where the secondary transfer roller 71 and the cleaning blade 81 are pressed against the intermediate transfer belt 6, and immediately after the h1st registration mark 200 is formed, the secondary transfer roller 71 is formed. Is separated from the intermediate transfer belt 6, and the cleaning blade 81 is further separated immediately after the formation of the h2th registration mark 200. Then, the formed registration mark row is detected by the mark detection sensor 65, and thereafter, is cleaned by the cleaner 8.
[0053]
FIG. 7C shows the detection result of the registration mark row at this time.
In the drawing, R and S indicate positions at which the traveling speed of the intermediate transfer belt 6 is momentarily increased by the separation of the secondary transfer roller 71 and the cleaning blade 81, respectively. As shown in the figure, the distances c1 and c2 between the registration marks 200 at these positions are wider than the corresponding distances a1 and a2 in FIG. 7A.
[0054]
After that, the process proceeds to step S14 to execute a calculation process of the correction data.
Specifically, the values of a1, b1, b2, c1, and c2 are obtained from the detection time of the corresponding registration mark 200 and the specified traveling speed of the intermediate transfer belt 6.
For example, the value of b1 is (T2−T1) v from FIG. 7 (where T1 and T2 are the detection times of the two registration marks 200 at the position of R, and v is the control of the intermediate transfer belt 6). Power speed (cm / s) which is stored in the ROM 107).
[0055]
Then, as a1-b1 = Δ1, a1-b2 = Δ2, a1-c1 = Δ3, and a1-c2 = Δ4, values from Δ1 to Δ4 are obtained as correction data. Note that these correction data are caused by fluctuations in the traveling speed of the intermediate transfer belt 6, and correspond to “information indicating the amount of fluctuation in the traveling speed on the surface of the intermediate transfer member” in claim 1. The image forming unit 10, the mark detection sensor 65, and the control unit 100 that controls them and executes the flowchart of FIG. 5 correspond to “acquiring means” in claim 1.
[0056]
Next, based on the correction data, a correction table to be referred to when actually performing the correction control of the image forming operation is created and stored in the RAM 107 (step S15).
FIGS. 8A and 8B show examples of correction tables when forming a Y image and when forming a K image, respectively.
When the Y image is created, the running speed of the intermediate transfer belt 6 is increased, so that the interval between the scanning lines at that portion is widened, and the subsequent scanning lines are located behind the scanning lines of the M and C images. Deviate. In order to correct this, a scan line thinning process is executed. As a result, the subsequent drawing order of the scanning lines is advanced by the thinned scanning lines (that is, their transfer positions are moved forward), and the positional deviation can be eliminated to some extent.
[0057]
Specifically, assuming that Δ1 and Δ2 are 25 μm and 50 μm, respectively, as in the example of FIG. 4 and the dpi in the sub-scanning direction of the printer is 600 dpi, the pitch between the scanning lines when there is no change is 42. Since it is 3 μm, the number of necessary thinning-outs may be one by one as shown in FIG. Here, the necessity of the thinning and the number thereof are determined based on whether or not the positional deviation amount between the scanning lines is smaller than a case where the thinning is not performed as a result of the thinning processing.
[0058]
For example, Δ1 indicates that there is a position shift of 25 μm. Here, if one scan line is thinned out, the position shift amount of the subsequent scan lines is 25 μm−42.3 μm = −17.3 μm. And its absolute value becomes smaller than before correction. If the amount of positional deviation is less than half the pixel pitch, the color deviation is considered to be almost invisible to the human eye, so such correction is sufficient. Similarly, thinning one scanning line is sufficient for correction of Δ2 (= 50 μm).
[0059]
The numbers n1 and n2 of the scanning lines to be thinned are the numbers of the scanning lines written on the photosensitive drum 2 immediately after the end of the pressing operation of the secondary transfer roller 71 and the cleaning blade 81, respectively. As shown in the timing chart of FIG. 3, the relationship between the timing of pressing the secondary transfer roller 71 and the cleaning blade 81 and the timing of transferring the Y image is known in advance. The time until the cleaning blade 81 is pressed is known, and the drawing time for one scan line is also determined. Therefore, the values of the scan line numbers n1 and n2 can be determined from these relationships.
[0060]
On the other hand, during the image formation of the K image, the pressing operation of the secondary transfer roller 71 and the cleaning blade 81 is performed, so that the running speed of the intermediate transfer belt 6 decreases during each operation, and the scanning line at that portion is reduced. The pitch becomes smaller, and the transfer position of the operation line thereafter is shifted forward compared to the corresponding scan line of the M image.
For this purpose, in the present embodiment, a process of interrupting the drawing of the scanning line composed of white pixels between the original scanning lines (hereinafter, referred to as “blank hit”) is executed.
[0061]
Assuming that the values of the correction data Δ3 and Δ4 are 100 μm and 70 μm, respectively, following the example of FIG. 4, two scan lines are respectively used for the same reason as in the case of correction of the Y image in order to correct the K image. It is necessary to make an empty shot (FIG. 8B).
The positions of the scanning lines to be subjected to idle printing are the scanning line numbers m1 and m2 immediately after the completion of the pressing of the secondary transfer roller 71 and the cleaning blade 81. These scanning line numbers are also the same as those in the case of FIG. Similarly, it can be easily obtained from the timing chart of FIG. 4 and the drawing time of one scanning line.
[0062]
Thus, the correction data acquisition processing ends. This process may be executed, for example, every time the power is turned on to the printer, or may be executed periodically at a time when the printing operation is not executed more frequently. Alternatively, in the case where materials such as the secondary transfer roller 71, the cleaning blade 81, and the intermediate transfer belt 6 that have little change with time are used, the processing may be performed only at the time of assembling the printer. When the correction data acquisition process is not performed frequently, it is desirable that the correction table be stored in a nonvolatile memory such as an EEPROM.
[0063]
By adjusting the timing of pressing and separating the secondary transfer roller 71 and the cleaning blade 81 to the timing of pressing and separating them at the time of actual image formation, the positional deviation occurring at the time of actual image formation is further improved. Correction data reflecting the amount can be obtained.
Specifically, for example, the first registration mark 200 is drawn after t1 after detecting the reference mark 201, and then, after t2, the secondary transfer roller 71 is pressed against the intermediate transfer belt 6 (see FIG. 3).
[0064]
This is because accurate correction data including other causes of positional deviation that can occur during actual image formation can be obtained, so that more accurate color deviation correction can be performed.
(4-2) Operation of image forming process
FIG. 9 is a flowchart showing a control operation relating to an image forming process of the respective colors on the intermediate transfer belt 6, among the print processes performed by the control unit 100, and is executed, for example, every time a print job is received from an external terminal. Things.
[0065]
First, it is determined whether or not the image data to be printed is the first sheet (step S21). If the image data is the first sheet, the traveling speed of the intermediate transfer belt 6 during image formation of the Y image is determined. Since the fluctuation factor does not occur, the normal Y image forming process of step S23 is executed.
If the image forming process is the image forming process for the second and subsequent image data, it is necessary to perform misregistration correction control in the creation of the Y image. .
[0066]
In the image forming process in the present embodiment, the exposure unit 11 reads image data from the image memory 104 one scan line at a time, writes an electrostatic latent image on the photosensitive drum 2 based on the image data, 10 includes a process of developing with the above-described toner and performing primary transfer on the intermediate transfer belt 6. However, since the correction control is performed for writing to the photosensitive drum 2, only the control content will be described with reference to the flowchart of FIG. I do.
[0067]
FIG. 10 is a flowchart showing the contents of the Y image writing correction control. As shown in the flowchart, when the reference mark 201 on the intermediate transfer belt 6 is detected by the mark detection sensor 66, the internal timer of the CPU 101 is started (step S31: Y, step S32), and the measured time t Is determined to be (t1-α) (step S33).
[0068]
Here, t1 is the time from the detection of the reference mark 201 as described with reference to FIG. 3 to the start of the primary transfer on the intermediate transfer belt 6, and α is the time of the photosensitive drum 2. This is the time required for the position scanned and exposed by the exposure unit 11 to reach the primary transfer position D due to the rotation of the photosensitive drum 2.
If it is determined in step S33 that time t = t1-α, the writing process by the exposure unit 11 is started (step S34). At this time, first, “i” indicating the scan line number of the image data is set to 1. Next, it is determined whether the scan line number i is n1 or n2 (steps S36 and S37). The meaning of n1 and n2 has been described with reference to the correction table in FIG.
[0069]
In the present embodiment, as can be seen from the timing chart of FIG. 3, since the secondary transfer roller 71 and the cleaning blade 81 are pressed in the middle of the Y image transfer process, both n1 and n2 are used. Not "1".
Since i has just been set to “1”, it is determined “No” in both steps S36 and S37, and writing of the i-th (ie, first) scanning line to the photosensitive drum 2 is executed in step S38. Is done.
[0070]
Thereafter, it is determined whether or not i = N (step S39). Here, "N" is the total number of scanning lines for one page of the Y image. Since the information of the image size for one page is usually added to the header of the received print data, the value of N is determined by the information. Can be obtained. Alternatively, the number of scanning lines of one page of image data expanded in the image memory 104 may be counted in advance.
[0071]
If “No” is determined in step S39, the value of i is incremented by “1” (step S40), and the process returns to step S36 to determine whether or not “i = n1”. For example, step S38 is skipped, and the scan line of the number is not written (scan line thinning processing).
If it is determined in step S36 that "i = n1" is not satisfied, the process proceeds to step S37, and it is determined whether or not "i = n2". If so, step S38 is skipped and the corresponding scan line is skipped. The thinning process is executed, and if not “i = n2”, the writing of the i-th scan line is executed in step S38.
[0072]
The processing from step S36 to step S40 is repeated until it is determined that “i = N” in step S39. When “i = N”, the writing control of the Y image is terminated, and the process returns to the upper routine. .
Next, the image forming process of the M image in step S24 of FIG. 9 and the image forming process of the C image in step S25 are respectively performed without correction control, and the image forming process of the K image (with correction control) is performed in step S26. .
[0073]
FIG. 11 is a flowchart showing the contents of the write correction control in the image forming process (with correction control) of the K image.
In this process, control is performed to perform the blanking process twice before writing the m1th and m2th scan lines in accordance with the correction table of FIG. 8B.
When the reference mark 201 on the intermediate transfer belt 6 is detected by the mark detection sensor 66, an internal timer of the CPU 101 is started (step S51: Y, step S52), and the time t reaches (t1-α). It is determined whether or not time t = t1−α, and a writing process by exposure scanning is started (step S53: Y, step S54).
[0074]
Here, the scanning line number i is set to "1", and the flags F1 and F2 are reset to "0" (step S55). Then, it is determined whether or not the scanning line number i is m1 or m2 (step S55). S56, S57). In the present embodiment, as can be seen from the timing chart of FIG. 3, since the secondary transfer roller 71 and the cleaning blade 81 are pressed against each other during the formation of the K image, both m1 and m2 are “1”. is not.
[0075]
Since i has just been set to "1", it is determined No in both steps S56 and S57, and writing of the i-th (= 1) scanning line to the photosensitive drum 2 is executed in step S58.
Thereafter, it is determined whether or not i = N (step S67). "N" is the total number of scanning lines for one page of the K image, which is the same as in the case of the Y image.
[0076]
If No is determined in step S67, the value of i is incremented by “1” (step S68), and the process returns to step S56 to determine whether or not “i = m1”. The process proceeds to step S59 to determine whether or not the flag F1 is "0". If "0", idle printing is performed for two scan lines (step S60), and the flag F1 is set to 1 and i is set. Is decremented by "1" (steps S61 and S62), and the process proceeds to step S67.
[0077]
If i is not equal to N, "1" is incremented by 1 in step S68. However, since it is decremented in step S62, it is determined in step S56 that the scan line number m1 is the same as the previous scan line number. The process proceeds to step S59, but since the flag F1 has already been changed to "1" in step S61, the result is "No" in step S59, and the scan line number is written in step S58.
[0078]
After that, through steps S67 and S68, No is determined in step S56, and if "Yes" is determined in step S57, the process proceeds to step S63, and if the value of the flag F2 is 0, two times Is executed (step S64), the value of F2 is set to 1 and i is decremented (steps S65 and S66). The processes in steps S57 and S63 to S66 are the same as the above-described processes in steps S56 and S59 to step S62 except that m1 is changed to m2 and the flag F1 is changed to F2, and thus will not be described in detail.
[0079]
Even if the flow circulates and “Yes” is determined again in step S57, “No” is determined in step S63, so that the m2th scan line is written.
As described above, the blanking for two scan lines is inserted before the writing of the m2th scan line, and the misalignment of the K image is eliminated.
[0080]
Upon completion of the K image forming process, the process returns to the flowchart of FIG. 9, and in step S27, it is determined whether or not printing of all sheets has been completed. If not, processing of steps S22 to S26 is performed until the printing is completed. repeat.
In this example, the control unit 100 that controls the exposure unit 11 to execute the position shift correction based on the flowcharts shown in FIGS. 10 and 11 corresponds to the “correction control unit” in claim 1. I do.
[0081]
<Modification>
It is needless to say that the technical scope of the present invention is not limited to the above embodiment, and for example, the following modified examples can be considered.
(1) In the above-described embodiment, as the control of the positional deviation correction, the deviation of the writing position of the scanning line is corrected by thinning out the scanning line or performing the blanking. However, the pressure contact between the secondary transfer roller 71 and the cleaning blade 81 is performed. Depending on the timing of the separating operation and the timing of image formation, in addition to or instead of thinning / blanket printing, the timing of writing the image of the developed color in which the displacement has occurred (the value of time t1 in the above example) May be changed. Instead of the blank shot, a so-called double shot process in which the same scanning line is continuously exposed and scanned twice may be performed.
[0082]
(2) Although the thinning and the blanking are rather read control of the memory in the exposure unit 11, the image data in the image memory may be corrected in advance (image correction). Specifically, in the case of the thinning process, the pixels of the scan line to be thinned are erased, and the pixels of the subsequent scan lines are reduced by the number of the thinned scan lines and stored in the image memory 104. However, in the case of blank shot, a scan line consisting of only white pixels may be inserted at the position where blank shot is to be performed and stored in the image memory 104.
[0083]
Then, by reading and forming an image sequentially from the first scanning line at the time of exposure scanning, a full-color image corrected for color shift can be obtained.
(3) When the image to be printed is not a full-color image but a monochrome image, the problem of color misregistration does not occur, but the speed of the intermediate transfer belt 6 due to the pressing and separating operations of the secondary transfer roller 71 and the cleaning blade 81. Since there is no change in the density of the scanning lines (uneven pitch) due to the fluctuation, a stripe-like pattern may be generated in the main scanning direction and the image quality may be degraded.
[0084]
As a correction in this case, a screen process as an image process may be executed in addition to the above-described scan line thinning process, a blank shot process, and the like.
This is, for example, a method of printing only specific pixels by applying a screen to a 40 × 40 pixel block as a unit, and it is possible to make pitch unevenness inconspicuous depending on the screen pattern. is there.
[0085]
FIGS. 12A to 12D show examples of the pattern of this screen, and image processing is performed so that only the hatched pixels are printed for each 40 × 40 pixel block. .
The pattern 301 has the least pitch unevenness, and the pattern 302, 303, and 304 have more pitch unevenness toward the right. Therefore, in order to make the pitch unevenness of the monochrome image less noticeable, the screen processing may be performed with the pattern 301 or the pattern 302.
[0086]
Specifically, for example, information on the pattern 301 or 302 is stored in the ROM 106, and the CPU 101 reads out the information on the pattern, sends it to the image processing unit 103, and prints based on the pattern information. After screen processing is performed on all pixels of the page, the image data is stored in the image memory 104, and an image is formed by the image forming unit 10 based on the processed image data.
[0087]
(4) In the above embodiment, the laser beam is deflected by the polygon mirror as the exposure unit 11 of the photosensitive drum, but an LED array may be used.
In the case of the exposure using the LED array, the position shift can be corrected by correcting the drive timing for each scanning line to correct the color shift, and the position shift can be corrected with higher accuracy.
[0088]
(5) In the above embodiment, the registration mark 200 parallel to the main scanning direction is formed along the traveling direction on the intermediate transfer belt 6 in order to obtain data on the amount of variation in the traveling speed of the intermediate transfer belt 6. However, the shape of the registration mark 200 is not limited to this, and any shape may be used as long as a certain regular pattern is formed along the running direction of the intermediate transfer belt 6 and the speed fluctuation of the intermediate transfer belt 6 can be reflected.
[0089]
In addition, instead of a method of forming a registration mark row by repeating a registration mark having a simple shape, for example, if a highly sensitive mark detection sensor 65 is used, the density is set along the running direction of the intermediate transfer belt 6. A belt-like pattern that changes regularly may be used. However, in this case, the detected amount of change in the density of the band-shaped mark and the amount of change in the distance in the belt running direction need to be associated in advance with a table or the like.
[0090]
Further, the registration mark row may be formed in advance on the surface of the intermediate transfer belt 6 by printing or the like. In this case, while the registration mark row is being detected by the mark detection sensor 65, the pressing and separating operations of the secondary transfer roller 71 and the cleaning blade 81 are performed, and the traveling speed of the intermediate transfer belt 6 at that time is performed. Will be obtained. In this case, when the speed decreases, the interval between mark detections becomes longer, and when the speed increases, the interval between mark detections becomes narrower, which is opposite to the detection result shown in FIG. 7 of the above embodiment.
[0091]
(6) In the above embodiment, the toner image of the registration mark 200 is also formed by using a normal image forming means. However, it is technically possible to separately provide an image forming means dedicated to creating the registration mark 200. is there.
(7) In the above embodiment, the intermediate transfer belt is used as the intermediate transfer member, but an intermediate transfer drum or the like may be used. Further, the mark detection sensor 65 may also serve as the mark detection sensor 66.
[0092]
(8) In the above embodiment, the cleaner section 8 includes the cleaning blade 81 as a cleaning member, but may be a cleaning roller in some cases.
Further, in all of the pressure contact / separation operations of the secondary transfer roller 71 and the cleaning blade 81, the positional deviation due to the speed fluctuation is corrected. However, in some cases, some of the operations, particularly one The correction may be made only in response to an operation with a large number position shift amount. This is because even in this case, the image quality is improved as compared with the related art.
[0093]
(9) In the above embodiment, a full-color laser printer has been described as an embodiment of the present invention. However, the present invention is not particularly limited to a full-color laser printer. The present invention can be generally applied to an image forming apparatus having an operation of pressing and separating at least one of the transfer roller 71 and the cleaning blade 81 from the intermediate transfer member.
[0094]
Therefore, the present invention is also applied to a copier equipped with an image reading device. However, in the case of the mirror scanning method of the image reading device, when the scanner that has read the document quickly returns to the home position, vibration occurs in the entire device. Thus, the running speed of the intermediate transfer belt 6 may fluctuate even if it is very small.
Therefore, data relating to the amount of change in the traveling speed of the intermediate transfer belt 6 due to the return of the scanner may be acquired in advance in the same manner as described above, and correction control of the positional deviation may be performed based on this data.
[0095]
However, in this case, there is a certain relationship between the timing of the returning operation of the scanner and the timing of the image forming operation of each color, and it is necessary to be able to predict in advance the image and the position of the scanning line that need correction.
(10) The present invention can be understood as a program for causing a computer in an image forming apparatus to execute the method for preventing image deterioration according to claim 5, and furthermore, the program for preventing image deterioration is executed by a computer. , For example, a recording medium readable by, for example, a flexible disk, hard disk, CD-ROM, MO, DVD, DVD-ROM, DVD-RAM, semiconductor memory, or the like.
[0096]
【The invention's effect】
As described above, according to the image forming apparatus and the image forming method of the present invention, the running of the cleaning member and / or the transfer roller on the surface of the intermediate transfer member when the cleaning member and / or the transfer roller are pressed against and / or separated from the surface of the intermediate transfer member. Since information indicating the amount of change in the speed is acquired in advance, and based on the acquired information, the image forming unit is corrected and controlled so as to eliminate the deterioration of the image caused by the change in the traveling speed. Since the next image is continuously formed on the intermediate transfer member for the purpose of improving the image forming processing speed, the press-contact / separation operation of the secondary transfer roller and / or the cleaning member is performed during the formation of the next image. Even if this is done, image degradation can be prevented by correcting and controlling this. Thus, the image forming speed of a plurality of sheets can be improved while maintaining the image quality.
[0097]
Also, the present invention provides a pattern forming means for forming a regular resist pattern on the surface of the intermediate transfer body along the running direction, a pattern detecting means for detecting the resist pattern, and a resist pattern formed by the pattern forming means. Control means for controlling the cleaning means and / or the secondary transfer means so that the cleaning member and / or the transfer roller is pressed against and / or separated from the surface of the intermediate transfer body during the formation; Detection result of the resist pattern when the cleaning member and / or the transfer roller is pressed against and / or separated from the surface of the intermediate transfer body by the pattern detection unit, and the resist pattern formed without the pressing and separating operations Based on the detection result, information indicating a change in the traveling speed of the surface of the intermediate transfer body is obtained. Since the way, thereby making it possible to obtain accurately the information indicative of the variation of the running speed of the intermediate transfer member surface.
[0098]
Further, in the invention, it is preferable that the control unit presses and / or separates the cleaning member and / or the secondary transfer roller from the surface of the intermediate transfer member at the same timing as the operation of the cleaning unit and / or the secondary transfer roller which occurs in actual image formation by the image forming unit. Since the cleaning unit and / or the secondary transfer unit is controlled so that the cleaning unit and / or the secondary transfer roller is pressed and / or separated during the formation of the resist pattern, an actual image forming operation is performed. It is possible to accurately obtain information indicating the fluctuation of the running speed of the surface of the intermediate transfer member that sometimes occurs.
[0099]
Still further, according to the present invention, the image forming means forms a color image on an intermediate transfer member by multiplex-transferring the toner images of each developing color, and comprises a photosensitive drum, An exposure unit that forms an electrostatic latent image by exposing and scanning the surface of the photoconductor drum based on image data, and a developing unit that develops the electrostatic latent image with toner of a corresponding development color, By performing at least one method of adjusting the exposure / writing timing, thinning out the scanning lines, hitting the scanning lines twice, hitting the scanning lines twice, or performing image correction on the image formation of an image of a specific development color, It is possible to accurately correct a color shift caused by a change in the traveling speed of the transfer member surface.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing the configuration of an intermediate transfer type digital full-color printer according to the present invention.
FIG. 2 is a block diagram illustrating a configuration of a control unit of the printer.
FIG. 3 is a flowchart showing the relationship between the transfer timing of each developing color and the timing between pressing and separating of a secondary transfer roller and a cleaning blade.
FIG. 4 is a graph showing a magnitude of a positional shift amount generated between images of respective developing colors due to the pressing and separating operations of a secondary transfer roller and a cleaning blade.
FIG. 5 is a flowchart illustrating a control operation of a correction data acquisition process executed by a control unit of the printer.
FIG. 6 is a perspective view of an intermediate transfer belt and a peripheral portion thereof showing a registration mark row formed on a secondary transfer roller.
FIGS. 7A and 7B show a normal state, FIG. 7B shows a state in which a secondary transfer roller and a cleaning blade are pressed, and FIG. 7C shows a state in which a secondary transfer roller and a cleaning blade are separated. FIG. 4 is a detection waveform diagram for a formed registration mark row.
8A is a diagram illustrating an example of a correction table when forming a Y image, and FIG. 8B is a diagram illustrating an example of a correction table when forming a K image.
FIG. 9 is a flowchart illustrating a control operation of an image forming process performed by a control unit of the printer.
FIG. 10 is a flowchart illustrating correction control for writing a Y image on a photosensitive drum.
FIG. 11 is a flowchart illustrating correction control for writing a K image on a photosensitive drum.
FIGS. 12A to 12D are diagrams illustrating examples of screen patterns in screen processing, respectively.
[Explanation of symbols]
1 Printer
2 Photoconductor drum
4 Developing unit
6 Intermediate transfer belt
7 Secondary transfer unit
8 Cleaner part
11 Exposure unit
65, 66 Mark detection sensor
71 Secondary transfer roller
73 Transfer Roller Solenoid
81 Cleaning blade
84 Cleaner Solenoid
100 control unit
101 CPU
102 Interface section
103 Image processing unit
104 Image memory
105 LD driver
200 Registration mark
201 fiducial mark

Claims (5)

An image forming apparatus for primary-transferring a toner image formed by an image forming unit onto a surface of an intermediate transfer body and secondary-transferring the toner image to a transfer material to form an image,
Secondary transfer means for causing the transfer material to abut on the surface of the intermediate transfer member by the transfer roller, and secondary transferring the toner image to the transfer material;
Cleaning means for pressing the cleaning member against the surface of the intermediate transfer member to clean the cleaning member;
Acquiring means for acquiring information indicating an amount of change in a traveling speed of the surface of the intermediate transfer member when the cleaning member and / or the transfer roller is pressed against and / or separated from the surface of the intermediate transfer member;
An image forming apparatus, comprising: a correction control unit configured to perform correction control on the image forming unit based on the acquired information so as to eliminate deterioration of an image due to a change in the traveling speed. On the surface of the intermediate transfer body, a pattern forming means for forming a regular resist pattern along the running direction,
The cleaning unit and / or the transfer unit may be configured such that the cleaning member and / or the transfer roller is pressed against and / or separated from the surface of the intermediate transfer body during the formation of the resist pattern by the pattern detecting unit and the pattern forming unit. Control means for controlling the secondary transfer means,
The acquisition unit may include a detection result of the resist pattern when the cleaning member and / or the transfer roller is pressed against and / or separated from the surface of the intermediate transfer body, and a resist formed without the pressing and separating operations. 2. The image forming apparatus according to claim 1, wherein information indicating a change in a traveling speed of the surface of the intermediate transfer body is acquired based on a pattern detection result. The control unit is configured to press the cleaning member and / or the secondary transfer roller against the surface of the intermediate transfer body and / or separate the cleaning member and / or the secondary transfer roller from the surface of the intermediate transfer member during the actual image formation by the image forming unit during the formation of the resist pattern. The image forming apparatus according to claim 2, wherein the cleaning unit and / or the secondary transfer unit is controlled to perform a pressing and / or a separating operation of the cleaning unit and / or the secondary transfer roller. The image forming means is to form a color image on the intermediate transfer member by multiple transfer of the toner image of each developing color,
A photosensitive drum, exposure means for exposing and scanning the surface of the photosensitive drum based on image data of each developing color to form an electrostatic latent image, and developing the electrostatic latent image with a toner of a corresponding developing color And developing means for performing
The correction control unit is configured to adjust a color of an image of a specific development color by at least one of exposure / writing timing adjustment, scan line thinning, blank hit of a scan line, double hit of a scan line, or image correction. The image forming apparatus according to claim 1, wherein a correction control for correcting a shift is performed. The toner image formed by the image forming means is primary-transferred onto the surface of the intermediate transfer member, and this is secondarily transferred to a transfer material by a transfer roller to form an image. A method for preventing image degradation in an image forming apparatus having a configuration for cleaning by pressing, comprising:
An acquisition step of acquiring information relating to a change in the traveling speed of the surface of the intermediate transfer member when the cleaning member and / or the transfer roller is pressed against and / or separated from the surface of the intermediate transfer member;
A correction step of correcting and controlling the image forming means so as to eliminate the occurrence of image deterioration due to the fluctuation of the traveling speed based on the acquired information. .

Images