JP2008076546A - Image forming apparatus and phase alignment control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration in a photoreceptor by simple rotation control in an image forming apparatus that has a means for detecting the angular velocity of a photoreceptor for each color so as to prevent displacement of an image writing position caused by an angular velocity difference and for adjusting the angular velocity (hereinafter referred to as phase alignment control), and in a phase alignment control method used by the image forming apparatus. <P>SOLUTION: The image forming apparatus includes a plurality of photoreceptors parallel to each other, and a control means that exerts phase alignment control for adjusting the angular velocity of the photoreceptor for each other so that an image forming position is not displaced by an angular velocity difference between the photoreceptors. The image forming apparatus forms images for respective colors on the corresponding photoreceptors and superposes the images, thereby forming a color image. When stopping each photoreceptor after the phase alignment control, the control means stops the photoreceptor at the position of timing TC with a prescribed quantity shifted to a predetermined stopping position (timing TB) after the phase alignment control. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having means for detecting the angular velocities of the photoconductors of the respective colors and matching the angular velocities (hereinafter referred to as phase matching control) so as not to cause an image writing position shift due to the angular velocity difference, and the image formation. The present invention relates to a phase matching control method implemented by an apparatus.

  In a so-called tandem type color image forming apparatus in which YMCK four-color photoconductor drums are arranged in parallel to form a full-color image, the angular velocity difference between the photoconductor drums is one of the causes of image positional deviation. For this reason, it is necessary to detect the angular velocity difference between the photosensitive drums and keep the photosensitive member moving distance between the developing unit and the transfer unit arranged around the photosensitive drums of the respective colors constant. As disclosed in Japanese Patent Laid-Open No. 2003-260, various techniques are known for phase matching control.

  Among these, in Patent Document 1, each color image that has been color-separated is formed on each of a plurality of photosensitive drums, visualized with color toners corresponding to each color separation, and then transferred onto a single sheet of transfer paper. In a color recording apparatus in which the visible images of the respective photosensitive drums are transferred one on top of the other, a driven rotating body that is rotated by one driving unit is fixed to each shaft of the photosensitive drum, and these driven rotations are performed. After forming the body into the same size and shape, the mark is attached at the same position, and when the driven rotor is assembled to the photosensitive drum shaft, the relative position of each driven rotor with respect to the drum axis is indicated by the mark. Is described based on the phase position corresponding to the speed fluctuation phase of each photosensitive drum.

Further, in Patent Document 2, even when a plurality of DC brushless motors are used as a drive source for a plurality of image carriers, in order to make it difficult for variations in rotational phase to occur in each image carrier during stop processing, Rotation speed at the time of image formation when a DC brushless motor is stopped in an image forming apparatus that rotates a plurality of image carriers independently using a plurality of DC brushless motors and performs color image formation by an electrophotographic process The DC brushless motor is rotationally driven for a predetermined time at a second rotational speed V2 that is slower than the first rotational speed V1, and then the stop process is performed, so that the phase shift between the individual DC brushless motors after the stop process It is described that the number is reduced.
Japanese Patent Publication No. 6-90561 JP 2005-266425 A

  In the known technique, in the sequence in which the driving of the photoconductor is stopped while the speed fluctuation is synchronized, each photoconductor drum executes a stop process at a phase angle calculated in advance. However, when stopping at the same angle based on the sensor, the photoreceptor stop position at the end of the print job is always the same position. For this reason, the charging, developing, and transfer bias applied to the photoconductor at the start of a print job are applied to the same surface of the photoconductor, which causes deterioration of the photoconductor.

  Therefore, the problem to be solved by the present invention is to prevent the photoreceptor deterioration by simple rotation control.

  In order to solve the above problems, the first means is a phase alignment in which a plurality of photoconductors are arranged side by side and the angular velocities of the photoconductors of the respective colors are adjusted so as not to cause an image forming position shift due to the angular velocity difference between the photoconductors. In the image forming apparatus that includes a control unit that performs control, forms an image of each color on each of the photoconductors, and forms a color image by superimposing these images, the control unit performs the photosensitivity after phase matching control. When the body is stopped, the body is stopped by shifting a predetermined amount with respect to the scheduled stop position after the phase matching control.

  The second means is characterized in that, in the first means, the position to be stopped by shifting the predetermined amount is set based on the positional relationship of the units around the photosensitive member.

  A third means is characterized in that, in the second means, the unit around the photosensitive member is at least one of a charging unit, a developing unit, and a transfer unit.

  The fourth means is characterized in that, in the first means, the stopping position is arbitrarily set.

  A fifth means is characterized in that, in any one of the first to third means, the predetermined amount is set from one of an angle, a distance, and a time.

  The sixth means is characterized in that in the first means, the control means performs the control to stop the shift at a predetermined timing.

  The seventh means is characterized in that, in the sixth means, the predetermined timing is determined by the number of stops or the number of image formation.

  The eighth means is characterized in that, in the sixth means, the predetermined timing is arbitrarily set.

  A ninth means includes a plurality of photoconductors arranged in parallel, forms an image for each color on each photoconductor, and superimposes these images to form a color image. In the phase matching control method for performing phase matching control for matching the angular velocities of the photoconductors of the respective colors so as not to cause image formation position shift due to the difference, when the photoconductor is stopped after the phase matching control, the schedule after the phase matching control It is characterized by stopping by shifting a predetermined amount with respect to the stop position.

  In the embodiments described later, the photosensitive member is denoted by reference numerals 3, 3Y, 3M, 3C, 3B, the control means is disposed in the main controller 200, and the units around the photosensitive member are disposed in the charging device 4, the developing device 6, and the transfer device 7. Each corresponds.

  According to the present invention, when stopping after phase matching control, the stop position is shifted, so that deterioration of the photoreceptor can be prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing an overall configuration of a tandem color image forming apparatus according to an embodiment of the present invention. In the image forming apparatus 100, the image forming unit 1A is located at the center in the vertical direction, the paper feeding unit 1B is provided below the image forming unit 1A, and the document placing table (contact glass) 1C1 is provided above the image forming unit 1A. A document scanning unit 1C is arranged. An intermediate transfer belt 102 having a horizontally extending surface is disposed in the image forming unit 1A, and a configuration for forming an image having a color complementary to the color separation color on the intermediate transfer belt 102. Is provided.

  The image forming unit 1A includes photoreceptors 3Y, 3M, 3C, and 3B that can carry images of toners of complementary colors such as yellow (Y), magenta (M), cyan (C), and black (B). (Here, Y, M, C, and B added after the reference number represent yellow, magenta, cyan, and black, respectively. In general, when indicating each part, the above-mentioned suffixes indicating colors are omitted.) Are juxtaposed along the extended surface of the intermediate transfer belt 102. Each of the photoreceptors 3Y, 3M, 3C, and 3B is composed of a drum that can rotate in the same direction (counterclockwise in FIG. 1). For example, around the photoreceptor 3Y, as shown in the drawing, a rotation process is performed. , A charging device 4Y that executes image forming processing, a writing unit 5Y, a developing device 6Y, a primary transfer device 7Y, and a cleaning device 8Y are arranged. Although reference numerals are omitted, a charging device, a writing device, a developing device, a primary transfer device, and a cleaning device are similarly arranged around the remaining photoconductors 3Y, 3M, and 3C. .

  The intermediate transfer belt 102 has a configuration that is wound around a plurality of rollers 2A to 2C and is movable in the same direction at positions facing the photoreceptors 3Y, 3M, 3C, and 3B. A roller 2C different from 2B faces the secondary transfer device 109 with the intermediate transfer belt 102 interposed therebetween. In FIG. 1, reference numeral 110 denotes a cleaning device for the intermediate transfer belt 102.

  The secondary transfer device 109 includes a transfer belt 9C that is wound around the charging drive roller 9A and the driven roller 9B and can move in the same direction as the intermediate transfer belt 102 at the secondary transfer position where the secondary transfer device 109 is located. Thus, by charging the transfer belt 9C with the charging drive roller 9A, it is possible to transfer a multicolor image superimposed on the intermediate transfer belt 102 or a single color image carried on the transfer paper.

  A sheet is fed from the sheet feeding unit 1B to the secondary transfer position. The paper feed unit 1B includes a plurality of paper feed cassettes 1B1, a plurality of transport rollers 1B2 arranged in a transport path for sheets fed from the paper feed cassette 1B1, and a registration roller 1B3 positioned in front of the secondary transfer position. ing.

  In the present embodiment, the sheet feeding unit 1B can feed a sheet of a type not stored in the sheet feeding cassette 1B1 toward the secondary transfer position in addition to the sheet conveyance path fed out from the sheet feeding tray 1B1. This configuration includes a manual feed tray 1A1 and a feeding roller 1A2 provided so that a part of the wall surface of the image forming unit 1A can be opened and closed. In the middle of the sheet conveyance path from the sheet feeding cassette 1B1 to the registration roller 1B3, the sheet conveyance path fed from the manual feed tray 1A1 joins, and the sheet fed from any conveyance path is registered by the registration roller 1B3. Timing is set.

  The writing device 105 controls the writing light according to image information obtained by scanning the document on the document table 1C1 included in the document scanning unit 1C or image information output from a computer (not shown), so that the photosensitive members 3Y, 3M, Writing light corresponding to image information is emitted to 3C and 3B to form an electrostatic latent image.

  The document scanning unit 1C is provided with a scanner 1C2 that exposes and scans the document on the document table 1C1, and an automatic document feeder 1C3 is disposed on the upper surface of the document table 1C1. The automatic document feeder 1C3 has a configuration capable of reversing the document fed on the document table 1C1, and can perform scanning on both sides of the document.

  The electrostatic latent image on the photosensitive member 3 formed by the writing device 105 is subjected to visible image processing by the developing devices of the photosensitive members 3Y, 3M, 3C, and 3B as in the developing device 6Y, and is primarily applied to the intermediate transfer belt 102. Transcribed. When the toner images for the respective colors are superimposed and transferred onto the intermediate transfer belt 102, the secondary transfer device 109 performs secondary transfer on the transfer paper at once. The unfixed image carried on the surface of the recording paper subjected to the secondary transfer is fixed by a fixing device 111 including a heating / pressure roller 121 and a fixing roller 122.

  The sheet passing through the fixing device 111 is switched in the conveying direction by a conveying path switching claw 12 disposed behind the fixing device 111, and includes a conveying path toward the paper discharge tray 13 and a reverse conveying path. The transport direction is selected for RP.

  In the image forming apparatus 100 having the above-described configuration, the photosensitive member uniformly charged on the basis of the image information transferred from the computer by exposing and scanning the document placed on the document table 1C1. An electrostatic latent image is formed on the bodies 3Y, 3M, 3C, and 3B. After the electrostatic latent image is visualized by the developing device 6, the toner image is primarily transferred to the intermediate transfer belt 102.

  The toner image transferred to the intermediate transfer belt 102 is transferred as it is to the sheet fed from the sheet feeding unit 1B in the case of a single color image, and the primary transfer is repeated in the case of a multicolor image. After being superposed, secondary transfer is performed on the sheet all at once. After the secondary transfer, the unfixed image is fixed by the fixing device 111, and then the sheet is reversed and fed again toward the registration roller 1B3. If a sorter is connected instead of discharging to the paper discharge tray 13, the paper is discharged to a tray in the sorter.

  FIG. 2 is a diagram showing an overall schematic configuration of the image forming apparatus according to the present embodiment. In FIG. 1, an image forming apparatus includes an operation unit 210, a printer control unit 220, a scanner / IPU (image processing unit) unit 230, an HDD (hard disk device) 240, and a page memory 250 with a main controller 200 as a center. The control unit 220 is connected to a sorter 260 and a bank (paper feeding device) 270 (1B), and the scanner (1C2) / IPU (image processing unit) unit 230 is connected to an ADF 280 (1C3). 2 shows an example in which a sorter 260 is connected instead of the paper discharge tray 13 of FIG.

  The main controller 200 sends the image data sent from the scanner / IPU unit 230 to the page memory 250 and holds it. If there is a request for image formation from the printer control unit 220, the requested image data is read from the page memory 250 and sent to the printer control unit 220. The HDD 240 temporarily stores image data when storing image data in the page memory 250 or reading image data from the page memory 250, or temporarily uses it when compressing / decompressing digital image data. The main controller 200 includes a CPU, a ROM, and a RAM, and the CPU executes control in the present embodiment while using the RAM as a work area based on a program stored in the ROM.

  The printer control unit 220 performs gamma conversion or the like for matching the digital image data sent from the main controller 200 to the characteristics unique to the image forming apparatus (printer), and based on the image processed image data, an LD (laser) Diode) is driven, and writing is performed on the charged photosensitive drums 3 by the writing device 105 to form an electrostatic latent image. Next, the electrostatic latent image is developed with toner by the developing device 6 to be visualized, and the visualized toner image is transferred to transfer paper fed from the bank 270. The toner image transferred onto the transfer paper is melted and fixed by the fixing device 111, and the transfer paper on which the toner image is formed is discharged from the image forming device 100 to the sorter unit 260.

  The operation unit 210 includes a print start key, a numeric keypad for determining the number of copies, an apparatus function setting key for setting functions provided in the digital image forming apparatus, a system function setting key for setting functions related to the image forming system, a set function, It has a liquid crystal touch panel that displays data.

  The ADF unit 280 feeds the set original on the contact glass at a predetermined timing, causes the scanner to read the original, and discharges the original after the reading at a predetermined timing.

  The scanner / IPU unit 230 irradiates the original set on the contact glass 1C1 with illumination light from an illumination lamp, forms an image of reflected light from the original on a CCD through a mirror group, a filter, and a lens, and performs photoelectric conversion. The signal is amplified and A / D converted to obtain digital image data. The scanner / IPU unit 230 includes image data patterned therein, and the internal pattern can be output by an instruction from the main controller (control unit) 200. The obtained digital image data is subjected to processing such as predetermined shading correction and gamma correction. Further, if there is a scaling process or a processing process designated by the operation unit 210 or the main controller 200, these processes are also performed, and the digital image data in the effective image area is sent to the main controller 200 at a predetermined timing. .

  The sorter unit 260 sorts the discharged transfer paper according to the mode set by the operation unit of the image forming apparatus and discharges it.

  The phase matching control will be described with reference to FIGS. FIG. 3 is a diagram showing an example of a phase reference position sensor attached around the photoconductor 3, FIG. 4 is a timing chart showing the relationship between the output timing of the transfer reference sensor SN and the drive timing of the photoconductor drive motor, and FIG. FIG. 6 is a diagram illustrating a driving state and phase control of a photoconductor during printing. The vertical axis represents motor rotation speed, and the horizontal axis represents time (T). In FIG. 3, the area divided into eight on the outer periphery of the photosensitive member 3 means a shifted area, and is shifted to positions 1, 2,...

The photosensitive member 3 is driven by a drive motor (not shown). As can be seen from FIG. 5, the photosensitive member 3 starts to be driven for printing operation at time T1, and the rotational speed of the photosensitive member 3 becomes constant at time T2. A printing operation (writing) is started. Printing is completed, and the process of stopping the photosensitive member 3 is started at time T3. Each photosensitive member 3 starts monitoring the input of the phase reference sensor SN and waits for the input of the phase alignment start reference. The time T4 is a time when the input of the phase reference sensor SN changes and the phase alignment starts, and thereafter, it becomes a waiting time for phase alignment. The waiting time is the time from time T4 to time T5,
Waiting time = T5-T4
It is represented by

  When waiting for the phase matching time is completed at time T5, the motor that drives the photosensitive member 3 performs a stop process to completely stop the motor. The time when the motor is completely stopped is T6. Phase alignment means that the angular velocities of the four photoconductors 3B, 3C, 3M, and 3Y are detected from the tandem system, and the angular velocities are adjusted, whereby the transfer positions of the sequentially transferred images on the transfer paper are determined. Match.

Referring to the timing chart of FIG. 4, a reference detection signal is input from the phase reference sensor SN, and the photosensitive member drive motor is driven at a certain angle using the input TA of the reference detection signal as a trigger, and then stopped. A certain angle driven for a period of time from timing TA to TB is the phase matching control section. FIG. 6 is a timing chart relating to motor driving when the shift angle (time) is taken into account. That is, the timing shown in the timing chart of FIG. 6 measures the time obtained by adding the shift angle (time) to the phase alignment time from the phase alignment reference detection TA, and stops the photoconductor drive motor at the timing end TC. . After stopping the drive motor, the shift angle is updated so that it will not stop at the same position when it is next stopped.

  The update of the shift angle, after stopping at the shift angle, becomes “the current shift angle + shift angle” as the next shift angle, and when it exceeds 360 °, the stop time is shortened by subtracting 360 °. .

  FIG. 7 is a diagram showing a relative relationship between the charging unit (charging device) 4, the developing unit (developing device) 6, the transfer unit (transfer device) 7, and the respective areas of the photoreceptor 3. Each time the stop position is stopped by the “current shift angle + shift angle”, the area number is shifted to the larger one. However, in this embodiment, since there are 8 divisions, the next to “8” returns to the previous and becomes “1”.

  The shift angle is variable and can be set by the user. Further, the shifting time (position) is preferably a time (position) at which the number of times of contact with units around the photosensitive member 3 is minimized. This time (position) can also be determined by the distance between the units around the photoreceptor 3 or the contact surface with the units. In this embodiment, the peripheral units of the photoreceptor 3 are the charging unit (charging device) 4, the developing unit (developing device) 6, and the transfer unit (transfer device) 7 shown in FIG.

  Further, this control need not be performed every time the photosensitive member 3 is stopped, but can be performed only when the number of stops and the number of printed sheets are equal to or greater than a specified value.

  In the tandem image forming apparatus as in the present embodiment, the photosensitive member 3 should be stopped in phase, but in the present embodiment, the stop position is positively shifted to move the photosensitive member 3 to the photosensitive member 3. Damage accumulation has been reduced. Since the slid amount (shift angle) is recognized by the main controller 200 of the image forming apparatus, image formation is performed in consideration of the positive shift amount executed in the present embodiment at the time of the next image formation. Therefore, the phase does not shift.

As described above, according to the present embodiment, when the photosensitive member 3 is stopped, the position is changed each time the photosensitive member 3 is stopped. The stop position is determined by the arrangement of the peripheral units of the photosensitive member 3, and the photosensitive member deterioration prevention control is executed. Since it is done at any time,
1) In addition to the phase matching control, the position where the photoconductor stops is shifted by the shift angle and stopped, so that the number of contacts with the peripheral unit at the same position is reduced. Thereby, the places where the charging bias and the developing bias are applied are dispersed, and the photoreceptor 3 can be prevented from being deteriorated.
2) Since the shift angle can be set arbitrarily, the stop time of the photoconductor drive motor can be adjusted, and the stop time can be shortened.
3) Since the stop time can be shortened, the shift control can be performed with little influence on the productivity.
There are effects such as.

1 is a diagram illustrating a schematic configuration of a tandem type color image forming apparatus according to an embodiment of the present invention. 1 is a block diagram illustrating an outline of an electrical configuration of a tandem type color image forming apparatus according to an embodiment of the present invention. It is a figure which shows an example of the phase reference position sensor attached around the photoconductor. 6 is a timing chart showing the relationship between the output timing of the reference detection signal of the phase reference sensor and the operation timing of the photosensitive member drive motor. FIG. 6 is a velocity diagram showing a driving state and phase control of a photoconductor during printing. It is a timing chart regarding a motor drive when the shift angle (time) is considered. It is a figure which shows the arrangement | positioning relationship between the phase reference position sensor attached around the photoconductor, and an image forming unit.

Explanation of symbols

3, 3Y, 3M, 3C, 3B photoconductor 4 charging device (unit))
5 Writing section 6 Developing device (unit)
7 Transfer device (unit)
DESCRIPTION OF SYMBOLS 100 Image forming apparatus 105 Writing apparatus 200 Main controller 210 Operation part 220 Printer control part 230 Scanner / IPU part 240 HDD
250 page memory 260 sorter 270 bank 280 ADF

Claims (9)

A plurality of photoconductors arranged side by side, and control means for performing phase matching control for adjusting the angular velocities of the photoconductors of the respective colors so as not to cause an image forming position shift due to an angular velocity difference between the photoconductors. In an image forming apparatus that forms an image for each color and forms a color image by superimposing these images,
The image forming apparatus, wherein when the photoconductor is stopped after phase alignment control, the control unit is shifted by a predetermined amount with respect to a scheduled stop position after the phase alignment control. The image forming apparatus according to claim 1.
The image forming apparatus according to claim 1, wherein the stop position is shifted by a predetermined amount based on a positional relationship between units around the photosensitive member. The image forming apparatus according to claim 2.
The image forming apparatus according to claim 1, wherein the unit around the photosensitive member is at least one of a charging unit, a developing unit, and a transfer unit. The image forming apparatus according to claim 1.
The image forming apparatus is characterized in that the stop position is arbitrarily set. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus, wherein the predetermined amount is set from one of an angle, a distance, and a time. The image forming apparatus according to claim 1.
The image forming apparatus, wherein the control means performs the control to stop the shift at a predetermined timing. The image forming apparatus according to claim 6.
2. The image forming apparatus according to claim 1, wherein the predetermined timing is determined by the number of stops or the number of image formation. The image forming apparatus according to claim 6.
The image forming apparatus, wherein the predetermined timing is arbitrarily set. When forming a color image by arranging a plurality of photoconductors in parallel and forming an image of each color on each photoconductor, and forming a color image by superimposing these images, an image formation position shift due to an angular velocity difference between the photoconductors In the phase matching control method for performing phase matching control for matching the angular velocities of the photoreceptors of the respective colors so as not to occur,
A phase alignment control method, wherein when stopping the photoconductor after phase alignment control, the photosensitive member is stopped by shifting a predetermined amount with respect to a scheduled stop position after the phase alignment control.

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