JP2004177507A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which an accurate correction process can be performed by carrying out misalignment correction processing only once. <P>SOLUTION: The image forming apparatus is provided with: a pattern forming means for forming on a carrier a plurality of sets of misalignment detection patterns for detecting misalignment of each color of a superposed image; a pattern detecting means for differentiating the misalignment detection pattern by comparing detected image data with a reference value which is set beforehand; a correcting means for correcting the misalignment of the image for each color on the basis of the detection result which is detected by the pattern detecting means; a write finish detecting means for detecting the finish of write of the image; and a control means to make the pattern forming means produce the misalignment detecting pattern when the write finish is detected by the write finish detecting means. Judgment of whether the condition for preparing the misalignment detecting pattern is to be calculated is made on the basis of the detection result of the pattern detecting means. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a color image forming apparatus which performs full-color, preferably tandem, full-color image forming means.
[0002]
[Prior art]
As this kind of technology, for example, the invention disclosed in Japanese Patent Application Laid-Open No. 10-260567 is known.
[0003]
In the above-mentioned publication, a change in temperature, humidity, etc., an environmental change, a change over time, or the like, a decrease in density or density unevenness of the misregistration detection mark occurs, and a misregistration detection mark having a correct shape is not formed. To solve the problem that accurate mark detection cannot be performed and color misregistration correction cannot be performed normally, the density data of the misregistration detection mark is calculated, and an image is created when the density data is out of the appropriate range. For maintaining the detected value of the displacement pattern at a certain value or more by changing a bias value for the shift.
[0004]
[Patent Document 1]
JP-A-10-260567 [0005]
[Problems to be solved by the invention]
However, according to this method, when a pattern density fluctuation occurs, the misregistration pattern creation processing must be executed a plurality of times, and there is a problem that the misregistration correction processing takes time.
[0006]
The present invention has been made in view of such a situation of the related art, and an object of the present invention is to provide a color image forming apparatus capable of performing an accurate correction process only by performing a displacement correction process once. .
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the first means is a method for obtaining a color image by sequentially superimposing and transferring images formed by a plurality of image forming units provided along a carrier onto a recording medium. In the image forming apparatus, a pattern forming unit that forms a plurality of sets of misregistration detection patterns for detecting misregistration of each color of the superimposed image on the carrier is compared with the detected image data with a preset reference value. Pattern detecting means for discriminating the pattern for detecting the positional deviation, correcting means for correcting the positional deviation of the image of each color based on the detection result detected by the pattern detecting means, and writing end detection for detecting the end of image writing Means for causing the pattern forming means to create a misregistration detection pattern when the writing end detecting means detects the end of writing. And a control means, said control means may determine whether to calculate a generation condition of the positional deviation detecting pattern based on a detection result of the pattern detection means.
[0008]
The second means is the first means, wherein the control means, when calculating the creation condition, creates a misregistration detection pattern based on the calculated creation condition after the calculation, and The means corrects the positional deviation of each color image based on the generated positional deviation detecting pattern.
[0009]
The third unit is a color image forming apparatus that obtains a color image by sequentially transferring images formed by a plurality of image forming units installed along a transport body onto a recording medium in a superimposed manner. Pattern forming means for forming a plurality of sets of misregistration detection patterns for detecting misregistration of each color of an image on the carrier, and comparing the detected image data with a preset reference value to obtain the misregistration detection pattern Pattern detecting means for discriminating image, correcting means for correcting the positional deviation of the image of each color based on the detection result detected by the pattern detecting means, writing end detecting means for detecting the end of image writing, and writing end detecting Control means for causing the pattern forming means to create a misregistration detection pattern when the means detects the end of writing. Unit may determine whether to calculate the reference value again based on a detection result of the pattern detection means.
[0010]
A fourth means is the third means, wherein in the third means, if the control means calculates the reference value again, after the calculation, the pattern detection means sets the pattern for detecting the displacement based on the calculated reference value. Is distinguished.
[0011]
The fifth means is the first or third means, further comprising means for adjusting toner density, and determining whether or not to perform toner density adjustment based on a detection result detected by the pattern detecting means. Features.
[0012]
A sixth means is the fifth means, wherein the means for adjusting the density is configured to correct the displacement by the correcting means based on a detection result detected by the pattern detecting means when the toner density is adjusted. It is characterized in that the toner density adjustment is performed immediately before execution.
[0013]
The seventh means is the first or third means, further comprising a temperature detecting means for detecting a temperature in the apparatus, and a counting means for counting the number of image formed sheets, wherein the temperature detecting means and the counting means When the condition for executing the position shift correction set based on the output is satisfied, the correcting means executes a position shift correction process of the image.
[0014]
Eighth means is the first, third, and fourth means, wherein the reference value is set to a level sufficient to discriminate a detection value from the detection pattern from another detection value. Features.
[0015]
In the first and second means, a misregistration detection pattern is created immediately after printing is performed immediately before execution of misregistration correction, pattern detection is performed, and a charging bias, a developing bias, a transfer bias, and a transfer bias are determined in accordance with the detected output value. By changing the image forming parameters such as the bias and the writing light amount and creating the pattern for detecting the displacement, accurate correction can be performed without repeating the displacement correction processing a plurality of times.
[0016]
In the third and fourth means, a misregistration detection pattern is created immediately after printing is performed immediately before execution of misregistration correction, pattern detection is performed, and the misregistration detection pattern is generated in accordance with the detected output value. By changing the reference value (threshold) of the pattern detection voltage for detecting the position shift of the detection unit, it is possible to perform the accurate correction without repeating the position shift correction processing a plurality of times.
[0017]
In the fifth and sixth means, a misregistration detection pattern is created immediately after printing is performed immediately before execution of misregistration correction, pattern detection is performed, and density adjustment processing is performed in accordance with the detected output value. By making the determination, unnecessary density adjustment processing is not performed, so that productivity can be improved. Further, when the density is unstable, by performing the density adjustment immediately before the position shift correction processing, it is possible to accurately execute the position shift pattern detection.
[0018]
In the seventh means, when a predetermined position shift correction execution condition set based on the outputs from the temperature detecting means and the counting means is satisfied, the image position shift correction processing is executed in an execution difference sequence. No correction is performed under any conditions, and no useless correction is performed.
[0019]
In the eighth means, the detection value from the detection pattern can be reliably discriminated from the other detection values, so that there is no risk of erroneous detection, and reliable correction can be guaranteed.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0021]
FIG. 1 is a diagram showing a schematic configuration of a tandem type color image forming apparatus according to an embodiment of the present invention. In FIG. 1, the color image forming apparatus includes four image forming units 1Y, 1M, 1C, and 1K provided for each color of yellow (Y), magenta (M), cyan (C), and black (K). Y, M, C, and K attached after the reference numerals respectively correspond to the components of the respective colors. Hereinafter, the description will be made by omitting the reference numerals indicating the colors.) The colors are arranged in order of the colors from the upstream side in the rotation direction along a belt 8 (hereinafter, a conveyance belt).
[0022]
Each image forming section 1 includes a photosensitive drum 2 functioning as an image forming medium, a charging unit 3, an exposure unit 4, a developing unit 5, a cleaning unit 6, and a charging unit 3, which are arranged around the photosensitive drum. It consists of a static elimination unit. The transport belt 8 is rotationally driven in the direction of arrow A by a roller 9 having one drive roller.
[0023]
After the surface of the photosensitive drum 2 is uniformly charged by the charging device 3, the surface of the photosensitive drum 2 is exposed by a pattern corresponding to an image to be output by the exposure device 4, and an electrostatic latent image is formed on the surface of the photosensitive drum 2. You. The electrostatic latent image formed on each photosensitive drum 2 is developed by the developing device 5 to form a toner image of each color as a visible image.
[0024]
A recording paper 10 as a recording medium is sent out from a paper feed tray 11, sequentially passes through image forming units 1 Y, 1 M, 1 C, and 1 K by a conveyor belt 8 and is formed on each photosensitive drum 2 at each transfer position 7. The toner images of the respective colors are sequentially transferred to the same position on the recording paper 10 by the transfer roller 13 and are superimposed, whereby one color image is obtained on the transfer paper 10. The recording paper 10 onto which the four color toner images have been transferred is peeled off from the transport (transfer) belt 8, fixed by a fixing device 12, and discharged from a paper discharge roller 12.
[0025]
The toner remaining on the surface of the photosensitive drum 2 after the transfer of the toner image of each color formed on each photosensitive drum 2 is removed by the cleaning unit 6 to prepare for the next image forming cycle.
[0026]
FIG. 2 is a perspective view showing the conveyor belt 8 and the photosensitive drums 2Y, 2M, 2C, 2K of the color image forming apparatus of FIG. Arrow B indicates the main scanning direction in a direction orthogonal to the moving direction of the conveyor belt 8, and arrow C indicates the sub-scanning direction in a direction parallel to the moving direction of the conveyor belt 8.
[0027]
FIG. 3 is a perspective view showing a relationship between misregistration detection marks 201 and 203 transferred on the conveyor belt 8 and detectors 14 and 15 for detecting the marks 201 and 203. FIG. FIG. 3 is a block diagram schematically illustrating a control circuit of a control device that performs write alignment based on an analog signal detected from the control signal 15;
[0028]
In this device, as shown in FIG. 3, the displacement detection marks 201 and 203 are detected by detection devices 14 and 15 each composed of a light reflection type sensor having a light emitting portion and a light receiving portion, and the detected analog signal is converted into an analog signal. The signal is converted into a digital signal by the D converter 41 and input as a voltage value to the positioning controller 45 in the subsequent stage.
[0029]
The alignment controller 45 calculates the positions of the positional deviation detection marks 201 and 203 from the voltage value acquired by the A / D converter 41, and calculates the skew deviation amount, the main scanning registration deviation amount, the main scanning magnification deviation amount, and the sub-scanning amount. The register shift amount and the correction amount are calculated, and set values of control signals such as a write clock and a write timing are transmitted to the system controller 46. Then, the system controller 46 changes the timing to each of the transmitted set values to execute the alignment of each color. The ROM 43 stores a program to be executed by the alignment controller 45 and the system controller 46. The alignment controller 45 and the system controller 46 execute the program while using the RAM 44 as a work area. Further, a printing number counter 47 is connected to the positioning controller 45 and the system controller 46, and a temperature sensor 48 for detecting the temperature in the apparatus is connected to the positioning controller 45.
[0030]
FIG. 5 is a plan view showing details of the misregistration detection marks 201 and 203 formed on the transport belt 8 according to the embodiment of the present invention. As shown in FIG. 5, the misregistration detection patterns constituting the misregistration detection marks 201 and 203 are formed in one line on the front side (operation side) and the back side (rear side) of the apparatus, and these patterns can be detected. The first and second detection devices 14 and 15 are arranged at positions. The misregistration detection patterns are black (k), yellow (y), cyan (c), magenta (m) from the upstream side in the rotation direction on the front side (shown as f on the front side) and on the back side (shown as r on the rear side). m) are formed in parallel in the order of 4 (Akf, Ayf, Acf, Amf), and incline at an angle of 45 ° to form 4 lines (Bkf, Byf, Bcf, Bmf) in the above order. Eight sets of Mtf1 to Mtf8 and eight sets of Mtr1 to Mtr8 are formed. This image forming pattern is stored in the ROM 43, forms an image on the recording paper 10 for each predetermined number of formed images at a timing at which no image is formed, and executes the positional deviation correction control described later. The four patterns Msf and Msr in the main scanning direction x formed on the downstream side of the first patterns Mtf1 and Mtr1 in the transfer belt transport direction are patterns that trigger the start of pattern detection. After that, the displacement correction control is started. In FIG. 5, d represents the interval between the four parallel patterns (Akf, Ayf, Acf, Amf) and the four patterns (Bkf, Byf, Bcf, Bmf) inclined at 45 °. A space in the direction parallel to the transfer direction of the transfer belt 8 is shown, c is a space between the parallel pattern and a 45 ° oblique pattern, and A is a direction in the direction parallel to the paper conveyance direction of the 45 ° oblique pattern length. The components are shown.
[0031]
The first and second detection devices 14 and 15 optically detect the reflected light of the position shift detection marks (position shift detection patterns) 201 and 203 formed as described above and the background portion of the conveyor belt 8. , And A / D converter 41, and then compare the two. FIG. 6A is a diagram showing output waveforms of the output value from the transport belt and the output values from the positional deviation detection marks 201 and 203. The position of 5 V is an output value from the background of the conveyor belt 8, and when the displacement detection marks 201 and 203 are detected, the output value changes from 5 V to around 0 V.
[0032]
When the output drops from 5 V to 0 V in this way, it is determined that the start trigger patterns Msf and Msr of the misregistration detection marks 201 and 203 have passed through the first and second detection devices 14 and 15 and the mark position is determined. Start detection control.
[0033]
When printing is started, the alignment controller 45 monitors the count value P pages of the print sheet number counter 47 and the output value T degrees of the temperature sensor 48, and when a predetermined misregistration correction execution condition is satisfied, Issues a position shift correction execution request to the system controller 46.
[0034]
As shown in the flowchart of FIG. 8, the system controller 46 interrupts the printing process when the positional deviation correction can be executed (step 101), or interrupts (or finalizes) the last sheet (step 102). When writing a page, the writing of each station of Y, M, C, and K is monitored, and as shown in FIG. 7, the misregistration detection patterns 71f and 71r are shifted from the writing end position of each station to a position of X [mm]. One set is created (step 103-step 111), and a registration execution permission and a density pattern creation end notification are issued to the positioning controller 45.
[0035]
In the controller 45, the detection devices 14 and 15 detect one set of misregistration detection patterns created after the end of the data writing process, and compare the detected output value D [V] with the reference value S [V] (step S15). 112) If it is determined that the density is sufficient, the position adjustment processing is executed without changing the image forming conditions (step 113). If it is determined that the density is not sufficient, the image forming conditions including the charging bias, the developing bias, the transfer bias, and the exposure power for forming the positional deviation detecting patterns 71f and 71r are calculated (step 114). Then, the positioning process is executed based on the calculation result (step 113).
[0036]
Further, as shown in the flowchart of FIG. 9, after the processing from step 101 to step 111 is performed in the same manner as in the flowchart of FIG. 8, the alignment controller 45 determines one set of the positional deviation detection pattern created after the end of the data writing processing. The detection devices 14 and 15 detect and compare the detected output value D [V] with the reference value S [V] (step 112). If it is determined that the displacement threshold pattern cannot be detected with the current threshold, the threshold is determined. A new calculation can be performed (step 115), and processing can be performed to execute the alignment processing using this threshold (step 113).
[0037]
Further, as shown in the flowchart of FIG. 10, after performing the same processing from step 101 to step 111 as in the flowchart of FIG. 8, the alignment controller 45 outputs one set of the positional deviation detection pattern created after the end of the data writing processing. The output values D [V] detected by the detection devices 14 and 15 are compared with a reference value S [V] (step 112). If the density is determined to be insufficient, the density correction processing is performed. After the density adjustment is completed (step 116), a position shift correction process is executed (step 113).
[0038]
As a result of detecting such position shift detection marks 201 and 203, when a position shift of the optical writing position for each color is detected, the front and rear side detection marks 201 and 203 are detected, and the front side detection mark 201 is respectively detected. The writing position is corrected until the positional deviation of the detection mark on the rear side disappears. For the correction process of the writing position, a known correction process as disclosed in the above-mentioned known example is applied.
[0039]
The correction processing of the writing position in which the position shift detection marks 201 and 203 are written is performed every time a predetermined number of images have been formed. Therefore, the number of image formation sheets is counted by the number-of-prints counter 47, and the system controller 46 determines that the number of image formation sheets has exceeded the preset number of sheets, and after the job being executed at that time ends, the alignment controller Then, a position shift pattern detection process is executed for the position 45, and the writing position is corrected according to the amount of shift.
[0040]
In this embodiment, a reflection type optical sensor is used as the first and second detection devices 14 and 15. However, if the transfer belt is a light transmission type, a light transmission type optical sensor is used. You can also.
[0041]
As described above, according to the present embodiment, even when the density of the misregistration detection pattern fluctuates and the detection level from the pattern decreases and it becomes difficult to discriminate the detection pattern from noise, the reference for discrimination is used. By changing the value, it is only necessary to read the next detection pattern and execute the misregistration pattern detection process, so that the misregistration mark can be detected without executing the misalignment process a plurality of times, and the processing time is reduced. Can be shortened.
[0042]
In addition, by using a reference voltage suitable for the environment of the machine (image forming apparatus), it is possible to reduce the recalculation processing of the reference voltage and to shorten the processing time.
[0043]
【The invention's effect】
As described above, according to the present invention, it is possible to prevent the detection of the misregistration pattern during the alignment processing without performing the density adjustment processing after the printing, and to improve the productivity.
[0044]
Further, according to the present invention, since the density adjustment is performed only when necessary before the alignment processing, an unnecessary density adjustment processing can be deleted, thereby improving the productivity.
[0045]
Furthermore, since the position adjustment processing is executed after the density adjustment processing when necessary, the pattern detection during the position adjustment processing does not fail.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a schematic configuration of a tandem type color image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a perspective view showing a conveyance belt and a photosensitive drum for each color of the color image forming apparatus of FIG. 1;
FIG. 3 is a perspective view illustrating a relationship between a misregistration detection mark transferred onto a conveyance belt and a detection device that detects the mark.
FIG. 4 is a block diagram schematically illustrating a control circuit of a control device that performs write alignment based on an analog signal detected from a detection device of the tandem-type color image forming apparatus according to the embodiment of the present invention.
FIG. 5 is a plan view showing details of a misregistration detection mark formed on the transport belt according to the embodiment of the present invention.
FIG. 6 is a measurement diagram showing a relationship between a detection level of a detection unit and a width of a detected pattern.
FIG. 7 is a diagram showing a state in which one set of positional deviation detection patterns is created at a position of X [mm] from a write end position of each station.
FIG. 8 is a flowchart illustrating a processing procedure for detecting a misregistration pattern, in particular, a processing procedure including a misregistration pattern image forming condition calculation process according to the embodiment of the present invention.
FIG. 9 is a flowchart illustrating a processing procedure for detecting a misregistration pattern, particularly a processing procedure including a misregistration pattern detection threshold calculation process according to the embodiment of the present invention.
FIG. 10 is a flowchart showing a processing procedure for detecting a misregistration pattern, particularly a processing procedure including a temperature adjustment processing in the embodiment of the present invention.
[Explanation of symbols]
8 Conveyor belts 14, 15 Detector 41 A / D converter 45 Alignment controller 46 System controller 47 Number of printed sheets counter 48 Non-volatile memory (EPROM)
201, 203 Position shift detection mark

Claims (8)

In a color image forming apparatus that obtains a color image by sequentially transferring images formed by the image forming units that are provided along the transporting body on a recording medium in an overlapping manner,
Pattern forming means for forming a plurality of sets of misregistration detection patterns for detecting misregistration of each color of the superimposed image on the carrier,
Pattern detection means for comparing the detected image data with a preset reference value to discriminate the misregistration detection pattern,
Correction means for correcting the displacement of the image of each color based on the detection result detected by the pattern detection means,
Writing end detecting means for detecting the end of image writing;
Control means for causing the pattern forming means to create a misregistration detection pattern when the writing end detection means detects the end of writing,
With
The color image forming apparatus according to claim 1, wherein the control unit determines whether to calculate a condition for generating the position shift detection pattern based on a detection result of the pattern detection unit. The control means, when calculating the creation condition, creates a displacement detection pattern based on the calculated creation condition after the calculation,
2. The color image forming apparatus according to claim 1, wherein the correction unit corrects the positional deviation of each color image based on the generated positional deviation detecting pattern. In a color image forming apparatus that obtains a color image by sequentially transferring images formed by the image forming units that are provided along the transporting body on a recording medium in an overlapping manner,
Pattern forming means for forming a plurality of sets of misregistration detection patterns for detecting misregistration of each color of the superimposed image on the carrier,
Pattern detection means for comparing the detected image data with a preset reference value to discriminate the misregistration detection pattern,
Correction means for correcting the displacement of the image of each color based on the detection result detected by the pattern detection means,
Writing end detecting means for detecting the end of image writing;
Control means for causing the pattern forming means to create a misregistration detection pattern when the writing end detection means detects the end of writing,
With
The color image forming apparatus according to claim 1, wherein the control unit determines whether to calculate the reference value again based on a detection result of the pattern detection unit. 4. The method according to claim 3, wherein when the control unit calculates the reference value again, after the calculation, the pattern detection unit discriminates the pattern for detecting the positional deviation based on the calculated reference value. Color image forming apparatus. 4. The color image forming apparatus according to claim 1, further comprising: means for adjusting toner density, wherein it is determined whether or not to adjust toner density based on a detection result detected by the pattern detecting means. The means for performing the density adjustment, when adjusting the toner density, performs the toner density adjustment immediately before execution of the positional deviation correction by the correction means based on the detection result detected by the pattern detection means. The color image forming apparatus according to claim 5, wherein Temperature detection means for detecting the temperature inside the device,
Counting means for counting the number of formed images,
Further comprising
2. The image forming apparatus according to claim 1, wherein when a condition for executing a positional deviation correction set based on outputs from the temperature detecting unit and the counting unit is satisfied, the correcting unit executes an image positional deviation correcting process. Or a color image forming apparatus according to 3. 5. The method according to claim 1, wherein the reference value is set to a level sufficient to discriminate a detection value from the detection pattern from other detection values. Color image forming device.

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