JP2004101694A - Color image forming apparatus, its control method and control program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color image forming apparatus and so on by which a color image formation can be formed without needing a reference position detection when forming the color image by superimposing images of a plurality of colors, and color misregistration can also be corrected. <P>SOLUTION: The color image forming apparatus includes: a light beam generating means which generates light beams corresponding to images; a rotary polygon mirror which scans a specific surface of photoreceptor with the light beam; and an image carrier on which the images on the photoreceptor are transferred and images of the plurality of colors are superimposed one on another. The color image forming apparatus performs color image formation by rotating the rotary polygon mirror and the image carrier. The apparatus performs in advance a calculating process for obtaining a time difference by which the rotation period of the image carrier and time needed for scanning with the light beam do not match in integral ratio. When a color image is formed, the rotation of the rotary polygon mirror or image carrier is controlled based upon the calculation result of the calculation process. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a color image forming apparatus such as a color laser beam printer that forms a color image by superimposing images of a plurality of colors.
[0002]
[Prior art]
In a general color laser printer, a color image is formed by superimposing images of a plurality of colors. In order to superimpose colors of one pixel or less by aligning image forming positions of main scanning and sub-scanning, in the related art, driving of an image carrier (a drum or a belt serving as an intermediate transfer member) and driving of a polygon motor are performed. The technique of synchronizing the rotation of the motor is used.
[0003]
A reference position signal indicating a reference position is generated in these image carriers, and in order to adjust the image forming position of each color based on the timing, control of the rotation phase of the image carrier or control of the rotation phase of the polygon motor is performed. Means for keeping the time from the reference position to the start of writing constant for each color is used.
[0004]
For example, in a color printer provided with one photosensitive drum and performing image superposition of four colors by rotating the image carrier four times, a reference position signal indicating a reference position of the image carrier of the first color is generated, The rotation phase control of the polygon motors of the second and subsequent colors is performed with reference to (for example, see Patent Document 1). When superimposing images of four colors, polygon rotation phase control of a total of four times for each color or polygon rotation phase control of a total of three times for the second and subsequent colors is performed.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 9-292852
[Problems to be solved by the invention]
However, the conventional image alignment using the reference position signal has the following problems.
[0007]
In color image formation, the image carrier rotates several times for color. However, even when the image carrier forms an image smaller than the entire length, after the final color has been written, the image carrier for the next first color is formed. The next image formation cannot be started until the reference position comes. For example, in an image forming apparatus capable of performing color printing of A3 size in four colors, in the case of performing color printing of one business card size, even if the image formation of the business card image of the fourth color is completed, the business card from the subsequent A3 width is used. The next image cannot be formed until the image carrier rotates over the width.
[0008]
Further, similarly, when a color image is formed after a monochrome image that does not follow the reference position is formed, even if the image formation of the monochrome image is completed, the next position until the reference position for the next first color comes. Cannot be formed.
[0009]
In the conventional method in which image alignment is performed by changing the rotation drive of the image carrier, when the drive of the image carrier is changed, charging of the photoconductor, electrostatic development, image transfer, cleaning of the image carrier, and the like are performed. In this case, the processing is simultaneously performed on the image carrier separately, and the transfer position is shifted particularly in the transfer of the previous image. Therefore, the next image formation cannot be started until the rotation drive of the image carrier is changed within the range not affected by these other processes or the other processes are completed.
[0010]
The present invention has been made in view of the above-described conventional problems, and in the case of forming a color image by superimposing images of a plurality of colors, it is possible to form an image without waiting for reference position detection and to perform color misregistration correction. It is an object to provide a forming apparatus and the like.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, in the color image forming apparatus of the present invention, a light beam generating means for generating a light beam according to an image, a rotating polygon mirror for scanning the light beam on a predetermined photosensitive member, An image carrier for transferring an image on a photoreceptor and superimposing images of a plurality of colors; and a color image forming apparatus for forming a color image by rotating the rotating polygon mirror and the image carrier. Calculating means for determining a time difference in which the rotation period of the carrier and the scanning time of the light beam do not match at an integer ratio; and at the time of forming a color image, the rotating polygon mirror or the image carrier based on a calculation result of the calculating means. And control means for controlling the rotational drive of the motor.
[0012]
According to the control method of the color image forming apparatus of the present invention, a light beam generating means for generating a light beam corresponding to an image, a rotary polygon mirror for scanning the light beam on a predetermined photosensitive member, and an image on the photosensitive member And a control method for a color image forming apparatus for forming a color image by rotating the rotating polygon mirror and the image carrier, the image carrier comprising: The rotation cycle of the light beam scanning time and the scanning time of the light beam do not match at an integer ratio, a calculation process is previously performed, and at the time of forming a color image, based on the calculation result of the calculation process, the rotating polygon mirror or the rotation polygon mirror is used. It is characterized in that the rotation driving of the image carrier is controlled.
[0013]
According to the control program of the present invention, a light beam generating means for generating a light beam corresponding to an image, a rotary polygon mirror for scanning the light beam on a predetermined photosensitive member, and a plurality of images for transferring the image on the photosensitive member An image carrier for superimposing color images, and a computer-readable code for executing a method of controlling a color image forming apparatus for forming a color image by rotating the rotating polygon mirror and the image carrier. A control program, wherein a calculation step for determining a time difference in which the rotation period of the image carrier and the scanning time of the light beam do not match at an integer ratio, and at the time of forming a color image, based on a calculation result of the calculation step, And a control step of controlling a rotation drive of the rotating polygon mirror or the image carrier.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0015]
<Main Configuration of Color Image Forming Apparatus>
FIG. 1 is a block diagram showing a configuration of a main part of a color image forming apparatus according to an embodiment of the present invention, and shows only a part particularly related to the present invention. FIG. 2 is a cross-sectional view showing the overall structure of a color laser beam printer applied as the color image forming apparatus of the present embodiment.
[0016]
First, in FIG. 2, a color laser beam printer applied to the present embodiment includes a laser driver 1002 that drives a laser beam L emitted from a laser generator 201 on and off according to image data supplied from a printer controller 1001. The laser beam L emitted from the laser generator 201 is swung in the main scanning direction by a polygon mirror (rotating polygon mirror) 202. The laser beam L oscillated in the main scanning direction is guided back to the photosensitive drum 210 via a reflection mirror, and exposes the photosensitive drum 210 in the main scanning direction.
[0017]
At this time, an electrostatic latent image is formed on the photosensitive drum 210 previously uniformly charged by a primary charger (not shown) by scanning exposure with a laser beam L. The toner is visualized by the supplied toner. The toner image on the photosensitive drum 210 is supplied by an intermediate transfer unit such as an intermediate transfer belt 220 or the like in a sub-scanning direction by a paper supply processing mechanism (a paper cassette 1008, a paper supply roller 1009, and conveyance rollers 1010 and 1011). The image is transferred to the recording paper. Here, the intermediate transfer belt 220 is illustrated by three points supported by rollers in FIG. 2, but is illustrated by a cylinder in FIG. 1 to show the concept.
[0018]
The image forming process is performed for each color, and a color image is formed by, for example, superimposing four colors.
[0019]
<Main Configuration of this Embodiment>
In FIG. 1, reference numeral 201 denotes a laser generation unit including a semiconductor laser or the like that generates a laser beam L modulated by an image signal, and 202 scans the laser beam L generated by the laser generation unit 201 on the photosensitive drum 210. This is a polygon mirror (rotating polygon mirror). Reference numeral 203 denotes a polygon motor that rotationally drives the polygon mirror 202.
[0020]
A laser scanning start detection sensor (BD sensor) 204 detects the start of scanning of the photosensitive drum 210 with the laser beam L. A rotation speed control unit 205 controls the rotation speed of the polygon motor 203 by taking in the output of the BD sensor 204.
[0021]
Reference numeral 206 denotes a phase rotation amount holding memory, which holds the phase rotation amount (remaining time to be described later) of the polygon motor 203. An image writing timing unit 207 controls the timing at which image formation is started based on the output of the BD sensor 204. Reference numeral 210 denotes a photosensitive drum on which an electrostatic latent image is formed by scanning exposure with the laser beam L.
[0022]
Reference numeral 221 denotes a position mark attached to the intermediate transfer belt 220, 222 denotes a position mark reading sensor for reading the position mark 221, and 230 denotes a signal for inputting a signal from the reading sensor 222 and measuring the interval. An interval measuring unit is used to measure the rotation time of the intermediate transfer belt 220, and the measurement result is stored in the measurement result holding memory 232.
[0023]
Reference numeral 231 denotes a CPU that controls the operation of the entire apparatus. Each of the above-described electric blocks, that is, the signal interval measurement unit 230, the measurement result holding memory 232, the image writing timing unit 207, the rotation speed control unit 205, and the phase rotation amount The memory 206 is connected to the CPU 231 via the communication line 233, and the apparatus operates as a system in conjunction with the instruction of the CPU 231.
[0024]
<Color misregistration correction sequence>
FIG. 3 is a flowchart illustrating a color misregistration correction sequence in the color image forming apparatus of the present embodiment. In this example, a description is given on the assumption that a color image is formed by superimposing four colors. The following control method can be realized by storing a program according to the flowchart of FIG. 3 in a storage device in the controller 1001 and executing the program by the CPU 231.
[0025]
First, the rotation time of the intermediate transfer belt 220 is measured (Step S11). The CPU 231 instructs the signal interval measuring section 230 to prepare for reading (reset). Next, the intermediate transfer belt 220 is driven at a constant speed, and the position mark reading sensor 222 detects the position mark 221 on the intermediate transfer belt 220 twice. The signal interval measuring section 230 measures this detection interval with an accuracy of about several [μsec], and holds the measurement result in the measurement result holding memory 232. Here, it is assumed that the measurement time is 1 [sec].
[0026]
Then, the CPU 231 obtains a remainder by dividing the measurement time by the rotation time of one surface of the polygon motor 203 (step S12). Here, assuming that the polygon motor 203 rotates at a speed of 600 [μsec] / plane,
1 [sec] / 600 [μsec] = 1666.66 ...
1 [sec] -1666 * 600 [μsec] = 400 [μsec]
The number of polygon surfaces in one round of the intermediate transfer belt 220 is 1666 or more to less than 1667, and the remaining time is 400 [μsec]. The CPU 231 writes this calculation result in the measurement result holding memory 232 and the phase rotation amount holding memory 206, respectively. That is, a time difference (the remaining time) in which the rotation time of the intermediate transfer belt 220 and the light beam scanning time do not match at an integer ratio is held in advance.
[0027]
As described above, the preparations before the color image forming operation are made in advance, and the image forming apparatus is in a standby state, and then the image is formed (step S15) in accordance with the image forming instruction from the user (step S14).
[0028]
During image formation, the laser generation unit 201, polygon motor 203, photosensitive drum 210, intermediate transfer belt 220, and the like are driven by instructions from the CPU 231. At this time, the rotation speed control unit 205 normally controls the polygon motor 203 to rotate at a constant speed of 600 [μsec] / plane. In accordance with an instruction from the CPU 231, the image writing timing section 207 counts the number of signals from the BD sensor 204, and synchronizes with the signal from the BD sensor 204 to control the image forming position of main scanning / sub-scanning at a predetermined timing. To start image formation for the first color (steps S16 and S17).
[0029]
When the image formation for the first color is completed (steps S18 and S19), the CPU 231 instructs the phase change of the polygon motor 203 via the communication line 233 at a predetermined timing (step S20). Upon receiving the instruction, the rotation speed control unit 205 controls the rotation speed of the polygon motor 203 so that the phase is delayed by the remaining time 400 [μsec] held in the phase rotation time holding memory 206.
[0030]
Since it takes about 100 msec from the start to the end of the phase control, the instruction from the CPU 231 is issued 100 msec or more before the second color image formation starts.
[0031]
That is, one round of the intermediate transfer belt 220 is (1666 lines + 0.66...), And the remaining amount is corrected by changing the phase of the polygon motor 203.
[0032]
In response to an instruction from the CPU 231, the image writing timing unit 207 counts the number of signals from the BD sensor 204 (step S21), and the counted number exceeds 1666 times stored in the measurement result holding memory 232 to 1667 times. At this time, the image formation is started with the 1667th time as the first time of the second color (step S17 and thereafter).
[0033]
When the image formation of the second and third colors is completed, the CPU 231 instructs the phase change of the polygon motor 203 via the communication line 233 at a predetermined timing. The operation at this time is the same as that when shifting from the first color to the second color.
[0034]
When the image formation for the fourth color is completed, the image in which the four colors are superimposed is transferred from the intermediate transfer member to a desired image carrier (not shown) such as paper, and the image on the intermediate transfer member is transferred to the next area. Is started.
[0035]
As described above, before the start of the second, third, and fourth colors, the phase change control of the polygon motor 203 is performed, and image formation control without color shift of one pixel in the sub-scanning direction is performed.
[0036]
As described above, in the present embodiment, the time difference (the remaining time) in which the rotation time of the image carrier (such as the intermediate transfer belt 220) and the light beam scanning time do not match at an integer ratio is held in advance and started at an arbitrary timing. In the color image forming performed, the phase of the rotating polygon mirror or the rotating body of the image carrier is controlled by the time difference during the image forming process of each color, so that the image is formed in accordance with the reference position of the image carrier. In contrast to the technique, since image formation is started at an arbitrary position of the image carrier, image formation can be performed without waiting for reference position detection, and throughput can be increased. Further, the phase control of the rotating polygon mirror or the image carrier is performed to minimize the color misregistration, thereby improving the image quality.
[0037]
<Modification>
The present invention is not limited to the illustrated embodiment, and various modifications are possible. For example, there are the following modifications.
[0038]
(1) In the above embodiment, an example in which the rotation phase of the rotary polygon mirror is delayed corresponding to the remaining time has been described. However, the phase is rounded up to increase the phase by an amount of phase change of 600-400 = 200 [μsec]. The same can be achieved by increasing the BD count number of one round of the image carrier to 1667.
[0039]
(2) In the above-described embodiment, the orbiting time of the image carrier is measured and calculated. However, as long as the time is measured or calculated prior to image formation, a fixed value adjusted in advance at a factory or the like may be used. It may be a time measurement during the previous image formation in the image forming apparatus, or may be a means for calculating from a result of averaging the measurement results.
[0040]
(3) In the above-described embodiment, the phase change control of the rotary polygon mirror is performed with respect to the retained extra time. However, the same color shift control can be performed by means for changing the rotation phase of the image carrier. . Image positioning is performed by changing the rotational drive of the image carrier to accelerate or decelerate so that the phase advances for a remaining time of 400 [μsec].
[0041]
In addition, the present invention is not limited to the apparatus of the above-described embodiment, and may be applied to a system including a plurality of devices or an apparatus including a single device. A storage medium storing software program codes for realizing the functions of the above-described embodiments is supplied to a system or apparatus, and a computer (or CPU or MPU) of the system or apparatus reads and executes the program code stored in the storage medium. It goes without saying that it will be completed by doing so.
[0042]
In this case, the program code itself read from the storage medium realizes the function of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. As a storage medium for supplying the program code, for example, a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape, nonvolatile memory card, or ROM is used. Can be. When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also an OS or the like running on the computer performs actual processing based on the instruction of the program code. It goes without saying that a case where some or all of the functions are performed and the functions of the above-described embodiments are realized by the processing is also included.
[0043]
Further, after the program code read from the storage medium is written to a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the expansion is performed based on the instruction of the next program code. It goes without saying that a CPU or the like provided in an expansion board or an expansion unit performs processing and performs a part or all of actual processing, and the processing realizes the functions of the above-described embodiments.
[0044]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to form an image at an arbitrary timing without waiting for the reference position detection, and it is possible to increase the throughput. Further, the phase control of the rotating polygon mirror or the image carrier is performed to minimize the color misregistration, thereby improving the image quality.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a main configuration of a color image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view illustrating the overall structure of a color laser beam printer applied as the color image forming apparatus of the embodiment.
FIG. 3 is a flowchart illustrating a color misregistration correction sequence in the color image forming apparatus according to the embodiment.
[Explanation of symbols]
201 Laser generator 202 Polygon mirror 203 Polygon motor 204 Laser scanning start detection sensor (BD sensor)
205 Rotation speed control unit 206 Phase rotation amount holding memory 207 Image writing timing unit 210 Photosensitive drum 220 Intermediate transfer belt 221 Position mark 222 on intermediate transfer belt Position mark reading sensor 230 Signal interval measuring unit 232 Measurement result holding memory 231 CPU
233 communication line

Claims (11)

A light beam generating means for generating a light beam corresponding to an image, a rotating polygon mirror for scanning the light beam on a predetermined photoconductor, and an image for transferring an image on the photoconductor and superimposing images of a plurality of colors. A color image forming apparatus having a carrier, and forming a color image by rotating the rotating polygon mirror and the image carrier.
Calculating means for determining a time difference in which the rotation period of the image carrier and the scanning time of the light beam do not match at an integer ratio;
A color image forming apparatus, comprising: a control unit that controls the rotation of the rotary polygon mirror or the image carrier based on a calculation result of the calculation unit when forming a color image. The arithmetic unit may divide the rotation period of the image carrier by the unit of the sub-scanning time for a predetermined sub-scanning time that is an integral multiple of the surface period of the rotary polygon mirror to obtain the time difference corresponding to the remainder. The color image forming apparatus according to claim 1, wherein: 2. The image processing apparatus according to claim 1, further comprising: a measuring unit configured to measure a rotation cycle of the image carrier, wherein the calculation unit uses a measurement value measured by the measurement unit as the rotation cycle of the image carrier. Color image forming device. The measuring means,
4. The color image according to claim 3, further comprising: a position signal generation unit that outputs a rotation position signal indicating a rotation position of the image carrier; and a rotation cycle measurement unit that measures an interval between the rotation position signals. Forming equipment. Holding means for holding the calculation result of the calculation means before forming a color image,
5. The image forming apparatus according to claim 1, wherein the control unit controls the rotation of the rotary polygon mirror or the image carrier based on the calculation result held in the holding unit when forming a color image. Color image forming device. A light beam generating means for generating a light beam corresponding to an image, a rotating polygon mirror for scanning the light beam on a predetermined photoconductor, and an image for transferring an image on the photoconductor and superimposing images of a plurality of colors. A control method of a color image forming apparatus having a carrier, and forming a color image by rotating the rotating polygon mirror and the image carrier.
A calculation process for calculating a time difference in which the rotation period of the image carrier and the scanning time of the light beam do not match at an integer ratio is performed in advance,
A method for controlling a color image forming apparatus, comprising: controlling a rotation drive of the rotary polygon mirror or the image carrier based on a calculation result of the calculation step when forming a color image. The calculation step may include, for a predetermined sub-scanning time that is an integral multiple of the surface cycle of the rotary polygon mirror, dividing the rotation cycle of the image carrier by the sub-scanning time unit to obtain the time difference corresponding to the remainder. The control method for a color image forming apparatus according to claim 6, wherein: 7. A measurement process for measuring a rotation cycle of the image carrier, wherein the calculation process uses a measured value measured in the measurement process as a rotation cycle of the image carrier. 8. The method for controlling a color image forming apparatus according to claim 7. 9. The control method for a color image forming apparatus according to claim 8, wherein in the measuring step, an interval of a rotation position signal indicating a rotation position of the image carrier is measured. Holding the calculation result of the calculation step in a holding unit before forming a color image;
10. The color image forming apparatus according to claim 6, wherein a rotation driving of the rotary polygon mirror or the image carrier is controlled based on the calculation result held in the holding unit when forming a color image. Control method. A light beam generating means for generating a light beam corresponding to an image, a rotating polygon mirror for scanning the light beam on a predetermined photoconductor, and an image for transferring an image on the photoconductor and superimposing images of a plurality of colors. A computer readable control program for carrying out a control method of a color image forming apparatus for forming a color image by rotating the rotating polygon mirror and the image carrier, comprising a carrier.
A calculating step of determining a time difference in which the rotation period of the image carrier and the scanning time of the light beam do not match at an integer ratio;
A control step of controlling a rotation drive of the rotary polygon mirror or the image carrier based on a calculation result of the calculation step at the time of forming a color image.

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