JP2003177587A - Color image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color image forming device that makes it possible to perform an alignment-pattern detection process in a short time by performing a pattern formation process one time even when a density change occurs. <P>SOLUTION: The color image forming device has a detection-pattern forming means which forms on a carrying body a misalignment detection pattern used for detecting misalignment of each color of overlaid images. The device also has a misalignment-detection-pattern detecting means which detects a misalignment detection pattern, and a misalignment correction means which corrects the misalignment of the overlaid images based upon the result of the detection of the misalignment detection pattern. The device further has a misalignment correction execution means that forms a misalignment detection pattern between recording media when prints are consecutively formed, and a density-detection-pattern forming means which forms on the carrying body a density detection pattern used for detecting the density of the overlaid images. The density detection pattern formed by the density-detection-pattern forming means is detected by the alignment-detection pattern detecting means. Based upon the result of the detection, an alignment detection reference value for detecting the alignment detection pattern is adjusted. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus, and more particularly to a color image forming apparatus that forms a color image using an electrophotographic process.

[0002]

2. Description of the Related Art In a conventional color image forming apparatus, a tandem image is obtained in which images formed by an electrophotographic process are sequentially superimposed and transferred onto a single recording medium conveyed by a recording paper conveying belt to obtain a color image. There is something called a method. In this conventional color image forming apparatus, due to a change in environment due to temperature and humidity fluctuations, a change over time, and the like, the density of the misregistration detection mark decreases and uneven density occurs, so that a misregistration detection mark of a correct shape is not formed. In some cases, accurate mark detection could not be performed, and color misregistration could not be corrected normally. In order to solve such a problem, Japanese Unexamined Patent Publication No. 10-260567 (hereinafter referred to as a conventional example) discloses that if an alignment mark cannot be detected due to a density variation during alignment adjustment, the image forming condition is changed and By creating the alignment mark, keeping the detection signal level of the alignment mark constant, calculating the density data, and changing the bias value for creating the image when the density data is out of the proper range, A method has been proposed in which the deviation pattern detection value is maintained at a certain value or more.

[0003]

However, according to the method of the above-mentioned conventional example, when the pattern density variation occurs, it is necessary to execute the positional deviation pattern creating processing a plurality of times, and the positional deviation correction processing takes time. There was a problem that it would take.

The present invention is intended to solve this problem, and by detecting the density detection pattern and changing the reference value for detecting the misregistration pattern based on the detection result, the density fluctuation can be achieved. An object of the present invention is to provide a color image forming apparatus capable of executing a pattern detection process for alignment in a short time by a single pattern formation process even in the case of occurrence of.

[0005]

In order to solve the above problems, the color image forming apparatus of the present invention forms a misregistration detection pattern for detecting misregistration of each color of a superposed image on a carrier. Misregistration detection pattern forming means, misregistration detection pattern detection means for detecting misregistration detection patterns, and misregistration correction means for correcting misregistration of superimposed images based on detection results of misregistration detection patterns. When a plurality of sheets are continuously printed, a misregistration detection pattern is formed between recording media, misregistration correction execution means for performing misregistration correction, and a density detection pattern for detecting the density of a superimposed image are formed on a carrier. And a density detecting pattern forming unit. Then, the density detecting pattern formed by the density detecting pattern forming means is detected by the position detecting pattern detecting means, and the position detecting reference value for detecting the position detecting pattern is adjusted based on the detection result. To do. Therefore, it is necessary to perform the alignment process a plurality of times even when the density change occurs by detecting the density detection pattern and changing the reference value for detecting the displacement pattern based on the detection result. Instead, the pattern detection process for alignment can be executed by one pattern formation process, and the processing time can be shortened.

Further, a non-volatile memory for storing the reference value for detecting the positional deviation is provided, and the reference value for detecting the positional deviation adjusted by the detection result of the density detection pattern is stored in the non-volatile memory at any time. This makes it possible to obtain the optimum reference value.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The color image forming apparatus of the present invention is
The density detecting pattern formed by the density detecting pattern forming means is detected by the positional deviation detecting pattern detecting means, and the positional deviation detecting reference value for detecting the positional deviation detecting pattern is adjusted based on the detection result.

[0008]

FIG. 1 is a schematic view showing the arrangement of a color image forming apparatus according to an embodiment of the present invention. It should be noted that Y, M, C, and K after the reference symbols in the figure correspond to yellow, magenta, cyan, and black, respectively. In the figure, four image forming units 1 each forming a different color
Y, 1M, 1C and 1K are linearly arranged along the recording paper conveyance belt 8. In addition, each image forming unit 1Y, 1
M, 1C and 1K are photoconductor drums 2Y, 2M, 2C and 2K which function as image forming media, and the photoconductor drum 2
Charging device 3 arranged around Y, 2M, 2C and 2K
Y, 3M, 3C, 3K, exposure apparatus 4Y, 4M, 4C, 4
K, developing devices 5Y, 5M, 5C, 5K, and cleaning devices 6Y, 6M, 6C, 6K.

Next, a series of image forming operations of the color image forming apparatus of FIG. 1 will be described. First, the two rollers 9
The recording paper conveyance belt 8 suspended between the rollers is rotationally driven in the direction of arrow A by a roller 9, one of which is a driving roller. Then, after the surfaces of the photoconductor drums 2Y, 2M, 2C, 2K are uniformly charged by the charging devices 3Y, 3M, 3C, 3K, images to be output by the exposure devices 4Y, 4M, 4C, 4K are formed. The pattern is exposed in a corresponding pattern to form an electrostatic latent image on the surface of each photoconductor drum 2Y, 2M, 2C, 2K. The electrostatic latent images formed on the photoconductor drums 2Y, 2M, 2C, 2K are transferred to the developing devices 5Y, 5M, 5C,
The toner image of each color is formed by developing at 5K. Then, the recording paper 10 is sent out from the paper feed tray 11, and the recording paper conveying belt 8 is used to form the image forming units 1Y, 1M, 1C, and
1K sequentially, transfer positions 7Y, 7M, 7C, 7K
Then, the toner images of the respective colors formed on the respective photoconductor drums 2Y, 2M, 2C and 2K are sequentially transferred to the same position on the recording paper 10 and superposed on each other to obtain one color image. Four
The recording paper 10 on which the color toner images have been transferred is peeled off from the recording paper conveyance belt 8 and fixed by the fixing device 12. After the transfer of the toner images of the respective colors formed on the photoconductor drums 2Y, 2M, 2C and 2K, the photoconductor drums 2Y and 2Y are transferred.
The toner remaining on the surfaces of M, 2C and 2K is removed by the cleaning devices 6Y, 6M, 6C and 6K to prepare for the next image forming cycle.

FIG. 2 is a block diagram showing a schematic structure of a part of the color image forming apparatus of this embodiment. In FIG.
The same reference numerals as in FIG. The arrow B in the drawing indicates the main scanning direction, which is a direction orthogonal to the moving direction of the recording paper conveyance belt 8. Further, an arrow C indicates a sub-scanning direction which is a direction parallel to the moving direction of the recording paper conveyance belt 8. In the figure, the misregistration detection marks 201 and 202 and the density detection marks 31 and 32 transferred onto the recording paper conveyance belt 8 are detection devices 14 and 15 having a light reflection type sensor including a light emitting portion and a light receiving portion. The analog signal detected by the A / D converter 16 is converted into a digital signal to be acquired as a voltage value. The alignment controller 17 calculates the positions of the misregistration detection marks 201 and 202 from the acquired voltage value, and based on the data stored in the RAM 19 according to the calculation method stored in the ROM 18, the skew misregistration amount and the main scanning registration misalignment. Amount, main scanning magnification shift amount, sub-scanning resist shift amount, and correction amount,
The setting values of the control signals such as the write clock and the write timing are transmitted to the system controller 18. The system controller 18 changes the respective timings to the transmitted set values to execute the alignment of the respective colors. Here, FIG. 3A shows a characteristic diagram of output values of the detection devices 14 and 15. In FIG. 3A, the position of 5 V is the output value of only the conveyor belt, and the detection devices 14, 15
When the toner mark passes through, the output level changes to around 0V. When the output levels of the detection devices 14 and 15 are such that the output level equal to or lower than the reference voltage X [V] continues for n points or more continuously, it is determined that the misregistration detection marks 201 and 202 have passed and the mark position detection is started. Although the detection devices 14 and 15 use reflection type sensors,
A transmissive sensor may be used.

Next, the misregistration correction operation in the color image forming apparatus of this embodiment will be described with reference to FIG. 4 showing the operation flow. First, the misregistration detection mark 20
Before forming 1,202, the density detection marks 31, 3 are formed.
2 is formed (step S101), the reference voltage Xm [V] is read from the non-volatile memory, and the density signal mark signal output value D [V] is acquired (steps S102, S10).
3). The difference between the output value D [V] and the reference voltage Xm [V] is calculated. If the difference is S [V] or more, the reference voltage X
The detection of the misregistration detection mark is started using [V] as it is as the detection reference voltage (step S104; YES, step S105). On the other hand, the output value D [V] and the reference voltage X
When the difference from m [V] is smaller than S [V], the output value D
The value at which the difference from [V] is S [V] is the new reference voltage Xs.
[V] is calculated (step S104; NO, step S
106), the reference voltage Xm [V] is changed to the new reference voltage Xs [V]
The detection of the misregistration detection mark is started by replacing it with (steps S107 and S105).

It is needless to say that the present invention is not limited to the above embodiments, and various modifications and substitutions can be made within the scope of the claims.

[0013]

As described above, in the color image forming apparatus of the present invention, the positional deviation detecting pattern forming means for forming the positional deviation detecting pattern for detecting the positional deviation of each color of the superimposed image on the conveyance body. And a positional deviation detection pattern detecting means for detecting the positional deviation detection pattern, a positional deviation correction means for correcting the positional deviation of the superimposed image based on the detection result of the positional deviation detection pattern, and a recording during continuous printing of a plurality of sheets. A misregistration correction execution unit that forms a misregistration detection pattern between media and executes misregistration correction, and a density detection pattern forming unit that forms a density detection pattern that detects the density of a superposed image on a conveyance body. Have and.
Then, the density detecting pattern formed by the density detecting pattern forming means is detected by the position detecting pattern detecting means, and the position detecting reference value for detecting the position detecting pattern is adjusted based on the detection result. To do.
Therefore, it is necessary to perform the alignment process a plurality of times even when the density change occurs by detecting the density detection pattern and changing the reference value for detecting the displacement pattern based on the detection result. Instead, the pattern detection process for alignment can be executed by one pattern formation process, and the processing time can be shortened.

Further, a non-volatile memory for storing the positional deviation detection reference value is provided, and the positional deviation detection reference value adjusted by the detection result of the density detection pattern is stored in the non-volatile memory at any time. This makes it possible to obtain the optimum reference value.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a color image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a schematic configuration of a part of a color image forming apparatus of this embodiment.

FIG. 3 is a characteristic diagram showing changes in the output value of the detection device according to the present embodiment.

FIG. 4 is a flowchart showing a positional deviation correction operation in the color image forming apparatus of this embodiment.

[Explanation of symbols]

14, 15; detection device, 16; A / D converter, 17; alignment controller, 18; ROM, 19; RAM,
20; system controller, 21; print number counter, 31, 32; density detection mark, 201, 202;
Misalignment detection mark.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C362 BA52 BA66 BA67 BA69 BA71                       BB28 BB30 BB32 BB34 BB46                       CA18 CA22 CA23 CA24 CA39                 2H027 DA09 DA21 EB06 EC03 EC09                       EE02 EE08 EF09                 2H030 AA01 AB02 AD05 AD16 BB02                       BB23                 5C074 AA10 BB02 BB26 DD01 DD15                       DD16 DD24 DD28 EE04 EE11                       FF15

Claims (2)

[Claims] 1. A color image is formed on a recording medium by sequentially superimposing and transferring images formed by image forming units arranged along the conveying body onto a recording medium conveyed by the conveying body. In a color image forming apparatus for obtaining an image, a positional deviation detecting pattern forming unit for forming a positional deviation detecting pattern for detecting positional deviation of each color of a superimposed image on the conveyance body, and detecting the positional deviation detecting pattern. Position deviation detection pattern detection means, position deviation correction means for correcting the position deviation of the superimposed image based on the detection result of the position deviation detection pattern, and the position deviation detection between the recording media during continuous printing of a plurality of sheets. Misregistration correction execution means for forming a pattern for position misalignment correction and density detection pattern for detecting the density of the superimposed image. And a density detection pattern forming means formed on the carrier, wherein the density detection pattern formed by the density detection pattern forming means is detected by the positional deviation detection pattern detecting means, and the detection result is obtained. The color image forming apparatus is characterized in that the reference value for detecting the positional deviation for detecting the positional deviation detecting pattern is adjusted by. 2. The color image according to claim 1, further comprising a non-volatile memory for storing the reference value for detecting the positional deviation, and storing the reference value for detecting the positional deviation adjusted by a detection result of the density detection pattern. Forming equipment.