JPH08286459A - Multicolor image forming device - Google Patents

Abstract

PURPOSE: To shorten a waiting time during a normal operation, while providing an image reduced in a color slurring. CONSTITUTION: This multicolor image forming device is provided with ROSs 4 for forming different color images by superimposing, a CCD 11 detecting a test pattern for detecting a skewing quantity between the ROSs 4 and the slurring quantity of color except skew and a registration controller. This registration controller compares the skewing quantity detected by a skewing quantity detecting means 22 with a first specific quantity by a first comparing means 23 and controls the ROS 4 so as to correct the color slurring except the skew, based on the slurring quantity of the color except the skew, when the skewing quantity is smaller than the first specific one. On the other hand, when the skewing quantity is not smaller than the first specific one, a skew correction with respect to the ROS 4 is executed with the skewing quantity and the ROS 4 is controlled to execute a color slurring correction except the skew, based on the slurring quantity of the color except the skew detect by the detecting means 22, after the skew correction is completed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiple image forming apparatus used in a copying machine, a printer, a facsimile, etc., and more particularly to a multiple image forming apparatus using a registration control system.

[0002]

2. Description of the Related Art Conventionally, a so-called tandem type color image forming apparatus is known as a multiple image forming apparatus for forming a color image. In this apparatus, for example, four image forming means are arranged for each color of black (K), yellow (Y), magenta (M), and cyan (C) along one transfer belt. The image forming unit includes a ROS (Raster Output Scanne) on the photosensitive drum.
r: raster output scanning device) to form a single color image, and these four images are transferred onto one transfer belt in an overlapping manner to form one color image. In this type of multiple image forming apparatus, since images of respective colors are transferred to the same position of the transfer belt so as to form one color image, it is necessary to accurately superpose the images of the respective colors.

For this reason, a registration control (registration control) system for measuring and correcting a so-called misregistration, which is a misregistration between colors to be superimposed at the same position on the transfer belt, is provided in this type of multiple image forming apparatus. Has been adopted. The registration shift is roughly classified into so-called skew shift and color shift other than the skew shift, and the color shift other than the skew shift includes a shift in the main scanning direction, a shift in the sub-scanning direction, and a shift in magnification. Among these misregistrations, the skew misalignment does not fluctuate to a level that causes a serious problem due to heat change, vibration, etc. during the image forming operation in a normal use state. On the other hand, deviations in the main scanning direction other than skew deviations are said to fluctuate due to thermal changes and vibrations during the image forming operation even in normal use.

Specifically, in the registration control system, first, a test pattern for measuring the registration shift amount is transferred at a constant interval on the transfer belt by the image forming means for each color, and the transferred test pattern is transferred. A CCD (Charged Co
The amount of misregistration is detected by executing a test pattern sampling cycle that is measured by an up-loaded device (charge coupled device). Since this pattern sampling cycle usually involves the operation of driving the ROS and the transfer belt, it takes a relatively long time such as ten and several seconds. Next, from the detected registration shift amount,
The skew correction amount is calculated as appropriate, and the correction amount in the main scanning direction, the correction amount in the sub-scanning direction, and the correction amount for magnification are calculated appropriately. When performing skew correction, mechanical adjustment is added to the optical system of the ROS using the calculated skew correction amount. On the other hand, when the color misregistration other than the skew misregistration is corrected, the calculated color misregistration correction amount other than the skew is used to electrically adjust the electrical circuit of the ROS and the signal system to the ROS. Here, especially when skew correction is performed, all color shifts other than the skew shift generally change. Therefore, after the skew correction, the registration control cycle for the color shift other than the skew shift including the pattern sampling cycle should be executed again. Is required.

As described above, firstly, skew correction is not required to be performed during normal operation unlike color misregistration correction other than skew. Secondly, skew correction is performed in a pattern sampling cycle. Since it is necessary to execute the above two times before and after the skew correction, the registration control including the skew correction cycle (skew correction cycle) is executed only in the service mode performed by the service person for maintenance. That is, in the service mode, since the pattern sampling cycle is re-executed to correct the color misregistration other than the skew after the skew is corrected, it takes time to execute the registration control. On the other hand, in the customer mode, which is the normal operation mode,
A registration control cycle (a registration control without skew) including only a cycle for correcting a color misregistration other than the skew misregistration is executed without including the skew correction cycle. That is, in the customer mode, since it is only necessary to execute the pattern sampling cycle once for the color misregistration correction other than the skew, it does not take much time to execute the registration control.

According to this registration control system, it is possible to mainly correct the DC (steady) component of the registration deviation depending on the mechanical accuracy of the image forming means, the pitch between the photosensitive drums, the exposure point and the like. . Furthermore, JP-A-6-
According to the registration control system disclosed in Japanese Patent No. 253151 or the like, a coarse registration deviation amount measurement pattern and a fine registration deviation amount measurement pattern are formed, so that mainly the photosensitive drum, various rollers and gears, transfer Highly accurate DC without being affected by the DC component error caused by the AC (periodic fluctuation) component of the registration shift depending on the rotation cycle of the belt or the like.
The component can be corrected.

[0007]

Generally, in a multiple image forming apparatus, an image forming operation including a registration control operation is provided especially in a normal operation mode (customer mode) while providing a high quality image with little color misregistration. It is generally desired that the work be done quickly.

However, according to the conventional registration control system described above, the skew is not offset during normal use, and skew correction is not performed during normal operation. When the installation surface changes, a mechanical shock is applied to the main body of the apparatus, or mechanical parts inside the apparatus are tampered with, the skew may shift to a level that causes a serious problem. In this case, a high quality image cannot be expected until the service person performs skew correction next time. Also,
Even if the service person performs maintenance, there is a possibility that the skew deviation slightly exceeding the allowable amount is visually overlooked. In addition, defects in units of micron meters resulting from the use of non-standard parts and defects due to aging may not be detected during maintenance.

On the other hand, in the conventional registration control system described above, if the registration control cycle including the skew correction cycle is performed in the customer mode as in the service mode, pattern sampling is performed before and after the skew correction as described above. Since the cycle needs to be executed twice, the user may have to wait a very long time during the image forming work.

Therefore, it is an object of the present invention to provide a multiple image forming apparatus which provides a high quality image with less color misregistration and has less waiting time during normal operation.

[0011]

In order to solve the above problems, a multiple image forming apparatus of the first invention of the present application has a plurality of image forming means for forming images of different colors and a skew between the image forming means. A detection unit that detects a color shift amount other than the shift amount and the skew, and if the skew shift amount is smaller than a first threshold value, the color shift correction other than the skew is performed based on the color shift amount other than the skew. If the skew deviation amount is not smaller than the first threshold value, the skew deviation correction is executed based on the skew deviation amount and the skew deviation is controlled. After the correction is completed, pattern sampling is performed again, and the color misregistration correction other than the skew is performed based on the color misregistration amount other than the skew detected by the detection unit. Characterized in that a control means for controlling the serial image forming means.

The multiplex image forming apparatus of the second invention of the present application is the first
In the multiple image forming apparatus of the invention, further comprising a skew storage unit for storing the skew deviation amount detected by the detection unit, the detection by the detection unit, the control by the control unit and the storage by the skew storage unit, When a predetermined color misregistration correction start condition is satisfied, the process is performed in one operation cycle, and the control means sets n
The skew deviation amount detected by the detection means in the (n: natural number) th operation cycle is smaller than the first threshold value and smaller than the second threshold value less than the first threshold value. Is larger, the skew storage means stores the n values before performing the pattern sampling for color misregistration correction other than the skew misregistration in the (n + 1) th operation cycle.
The image forming unit is controlled so as to execute the skew deviation correction based on the skew deviation amount stored during the operation cycle of the first time.

The multiple image forming apparatus of the third invention of the present application is the first
The multiple image forming apparatus of the present invention further comprises: a calculating unit that calculates a skew correction amount from the skew deviation amount detected by the detecting unit; and a skew storage unit that stores the calculated skew correction amount. The detection by the detection unit, the control by the control unit, the calculation by the calculation unit, and the storage by the skew storage unit are performed in one operation cycle when a predetermined color misregistration correction start condition is satisfied. The control means is configured such that the skew deviation amount detected by the detection means in the nth (n: natural number) operation cycle is smaller than the first threshold value and less than the first threshold value. If it is larger than the threshold value of, before performing pattern sampling for color misregistration correction other than skew misregistration in the (n + 1) th operation cycle, Serial based on the skew storage unit skew correction amount stored in the n-th operation cycle, and controlling said image forming means to perform said skew correction.

The multiplex image forming apparatus of the fourth invention of the present application is the second invention.
Alternatively, the multiple image forming apparatus according to the third aspect of the present invention further includes flag storage means for storing a flag signal when the skew deviation amount detected by the detection means is larger than the second threshold value, and the control is performed. In the (n + 1) th operation cycle, the means detects the skew detected by the detection means in the nth operation cycle based on the flag signal stored in the flag storage means during the nth operation cycle. It is characterized in that it is determined whether or not the amount of deviation is smaller than the first threshold and larger than the second threshold.

The multiple image forming apparatus of the fifth invention of the present application is the fourth invention.
In the multiple image forming apparatus of the invention, the skew storage means and the flag storage means are each formed of a non-volatile memory.

[0016]

According to the multiple image forming apparatus of the first invention of the present application, the plurality of image forming means form images of different colors in an overlapping manner. When performing the color misregistration correction between the image forming units, the detecting unit detects the skew misalignment amount between the image forming units and the color misregistration amount other than the skew. Here, under the control of the control unit, the image forming unit corrects the color misregistration other than the skew based on the color misregistration amount other than the skew when the detected skew misregistration amount is smaller than the first threshold value. To execute. On the other hand, when the detected skew shift amount is not smaller than the first threshold value, the skew shift correction is performed based on the skew shift amount, and the pattern sampling is performed again after the skew shift correction is completed. The color misregistration correction other than the skew is executed based on the color misregistration amount other than the skew detected by the detection means. Therefore, if a value corresponding to a skew deviation amount that is so large that skew correction is immediately required is set as the first threshold value, and the detected skew deviation amount is smaller than the first threshold value, In this case, it is assumed that the skew correction is unnecessary, and the color misregistration correction other than the direct skew is executed without executing the skew correction. As a result, only one time is required to detect the color misregistration amount even though the skew misregistration amount is monitored. If the skew shift amount is not smaller than the first threshold value, it is determined that the skew correction is necessary, and after the skew shift correction is executed based on the skew shift amount, pattern sampling is performed again to detect the skew shift amount. Since the color misregistration correction other than the skew is executed based on the color misregistration amount other than the skew detected by the means, the skew correction is automatically performed appropriately even in the normal operation mode (customer mode).

When the skew correction is performed, a relatively long time (for example, ten and several seconds) required for the detecting means to detect the amount of color misregistration between the image forming means is required twice.
According to the present invention, the situation in which the time for detecting the color misregistration amount twice is required can be suppressed to the minimum necessary. In particular, the skew misalignment hardly changes due to heat change, vibration, etc. during normal image forming operation, and if the skew misalignment occurs even several times a day or a week, the skew correction up to maintenance by a service person is required. Considering that not performing the correction is extremely inconvenient from the viewpoint of maintaining high image quality, the configuration of the first invention for performing the skew correction to the minimum and surely is extremely practical and rational.

According to the multiplex image forming apparatus of the second aspect of the present invention, the skew storage means stores the skew deviation amount detected by the detection means. The detection by the detection unit, the control by the control unit, and the storage by the skew storage unit are performed in one operation cycle when a predetermined color misregistration correction start condition is satisfied. Here, under the control of the control means, when the skew deviation amount detected by the detection means in the nth operation cycle is smaller than the first threshold value and larger than the second threshold value, The image forming means, before performing the pattern sampling for color misregistration correction other than the skew deviation in the (n + 1) th operation cycle, the skew deviation amount stored in the skew storage means during the nth operation cycle. Skew skew correction is performed based on

Therefore, as the second threshold value, a value corresponding to the minimum skew deviation amount at which meaningful skew correction can be performed in consideration of the skew correction resolution of the multiplex image forming apparatus is set. If so, the skew deviation can be further reduced by the (n + 1) th operation cycle. Here, even when performing a relatively small amount of skew correction that is not indispensable as described above, color misregistration correction other than skew is necessary after the skew correction, and thus the color misregistration amount must be detected again. Since the amount of color misregistration detected in one operation cycle is used as it is for skew correction in the next operation cycle, it is sufficient to detect the amount of color misregistration once in each cycle.

As a result, even when compared with the conventional registration control in the customer mode in which skew deviation correction is not executed,
The time required for the cash register is not too long.
This means that if the skew correction is performed as in the case of the conventional service mode, the operation of detecting the color misregistration amount before and after the skew correction is performed twice in each cycle (for example,
This is a great advantage when compared to the need for a relatively long time such as ten and a few seconds twice.

As described above, when the skew correction is necessary, the skew correction is executed immediately after confirming the skew deviation even if the user waits, and the skew deviation is improved even if the skew correction is not necessary. When there is room, the second invention is configured so that the skew correction is executed at the time when the image forming operation is continued for a while and the next cycle is executed without waiting the user unnecessarily. Is extremely practical and rational, especially in view of the characteristic that the skew shift hardly changes due to heat change, vibration, etc. during a normal image forming operation.

According to the multiplex image forming apparatus of the third invention, in the first invention, the calculating means calculates the skew correction amount from the skew deviation amount detected by the detecting means. Here, in the second invention, the skew storage means stores the skew deviation amount, whereas in the third invention, the skew storage means stores the calculated skew correction amount. The detection by the detection unit, the control by the control unit, the calculation by the calculation unit, and the storage by the skew storage unit are performed in one operation cycle when a predetermined color misregistration correction start condition is satisfied. Here, under the control of the control means, when the skew deviation amount detected by the detection means in the nth operation cycle is smaller than the first threshold value and larger than the second threshold value, , The image forming means is n + 1
Before performing pattern sampling for color misregistration correction other than skew misregistration in the operation cycle of the first time, skew misalignment correction is performed based on the skew correction amount stored in the skew storage means during the nth operation cycle. To execute.

Therefore, as in the case of the second aspect of the invention, the skew deviation is further reduced and the skew correction amount calculated in a certain operation cycle is used for skew correction in the next operation cycle. It is sufficient to detect the amount of color misregistration once. Moreover, when the skew correction is performed in the next operation cycle, the skew correction amount is already calculated, so that the skew correction can be performed more quickly than the second invention.

According to the multiple image forming apparatus of the fourth invention, in the second or third invention, the flag storage means flags if the skew deviation amount detected by the detection means is larger than the second threshold value. Memorize the signal. Then n + 1
In the operation cycle of the first time, the control means, based on the flag signal stored in the operation cycle of the nth time in the flag storage means, the skew deviation amount detected by the detection means in the operation cycle of the nth time is first. It is determined whether or not it is smaller than the threshold value of 1 and larger than the second threshold value. As described above, by using the flag signal as information indicating that the skew correction should be executed in the next operation cycle, the control by the control means can be performed with a relatively simple configuration.

According to the multiple image forming apparatus of the fifth aspect of the invention, in the fourth aspect of the invention, the skew storage means and the flag storage means, which are nonvolatile memories, respectively store the skew deviation amount and the flag signal in the n-th operation cycle. . Therefore, even at the time of start-up after the power supply of the multiple image forming apparatus is once turned off or in the subsequent operation cycle,
Skew correction can be appropriately performed using the skew shift amount detected in the previous operation cycle. At this time, it is sufficient to detect the color misregistration amount once in each operation cycle.

As described above, according to the present invention, it is possible to obtain a high-quality image with less color deviation by constantly monitoring the skew deviation amount that is not always corrected during normal operation, and at the same time, for normal operation. The waiting time inside can be reduced.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described with reference to the drawings. FIG. 1 shows the configuration of the essential parts of a tandem color image forming apparatus according to the first embodiment of the present invention.

In FIG. 1, the color image forming apparatus 1 is
It is configured to be able to form a multiple image of four colors of K (black), Y (yellow), M (magenta), and C (cyan), and IPS (Image Processing Sy).
and a ROS-I / F (ROS-InterFac) for K, Y, M, and C colors, respectively.
e: ROS-interface) 3k, 3y, 3m and 3
c and ROS 4k, 4y for K, Y, M and C colors, respectively
4m and 4c, image forming devices 5k, 5y, 5m and 5c for K, Y, M and C colors respectively, a transfer belt 6, a motor 7, a paper suction roller 8 and a belt cleaner 10. It is configured.

Here, the IPS 2 is configured to supply write image data for each K, Y, M and C color of one color image data to the ROS-I / Fs 3k, 3y, 3m and 3c. There is. ROS-I / F 3k, 3
y, 3m, and 3c are image data from the IPS2 and test pattern data for a registration control, which will be described later, respectively, and ROS4.
k, 4y, 4m and 4c. ROS 4k, 4y, 4 as an example of image forming means
m and 4c are image forming devices 5k, 5y, and
By scanning the photosensitive drums of 5 m and 5 c, respectively, a raster image corresponding to the write signal supplied from the ROS-I / F 3 k, 3 y, 3 m, and 3 c is formed.
It is configured to write on the k, 5y, 5m, and 5c drums, respectively. Imaging devices 5k, 5y, 5m and 5c
Includes a photoconductor drum, a charger, a developing device, and the like, and a raster-shaped electrostatic latent image is sequentially written by writing light, and a toner image is formed on the drum by further development.

The image forming devices 5k, 5y, 5m and 5c form toner images corresponding to image data on the recording paper 100 supplied by the paper suction roller 8 on the transfer belt 6 driven by the motor 7. Transfer it while synchronizing
Each toner image corresponding to the test pattern data for registration control is directly transferred onto the transfer belt 6. The belt cleaner 10 is configured to remove the test pattern directly transferred to the transfer belt 6 from the transfer belt 6.

In FIG. 1, the color image forming apparatus 1 further includes a CCD 11 and a registration controller 12.
And skew correction devices 13k and 13 for K, Y, M and C colors respectively built in the ROSs 4k, 4y and 4m.
y, 13m and 13c.

The CCD 11 is an image forming device 5 for the transfer belt 6.
Downstream of k, 5y, 5m and 5c and belt cleaner 1
The test pattern which is arranged on the upstream side of 0 and is formed on the transfer belt 6 is measured.

The registration controller 12 is
For example, test pattern data consisting of K, Y, M, and C as shown in FIG. 2 is generated, and test pattern data for each K, Y, M, and C color is generated by ROS-I / F 3k, 3 and 3.
Set to y, 3m and 3c. ROS 4k, 4y, 4m
And 4c are each K, Y, corresponding to the set pattern.
The write test pattern data for each of M and C is received at a predetermined timing, and the test light is written on the drums of the image forming devices 5k, 5y, 5m, and 5c by the write light instead of the image data from the IPS2. The raster images corresponding to the data are written respectively. At this time, the recording sheet 1
By not supplying 00, the test pattern is directly transferred onto the transfer belt 6 by the image forming devices 5k, 5y, 5m and 5c.

Further, the registration controller 1
Reference numeral 2 is configured to sample the skew shift amount and the color shift amount other than the skew shift in the main scanning direction, the sub scanning direction, and the magnification shift amount from the test pattern measured by the CCD 11. There is. Then, after determining whether or not the sampled skew deviation amount is smaller than a predetermined threshold value, a registration control cycle including skew deviation correction is performed or skew deviation is performed depending on the judgment result, as described later. It is configured to perform a registration control cycle without correction.

The skew correction device 13 is adapted to the image forming devices 5k, 5y, 5m and 5 according to the correction amount thus calculated.
Color misregistration correction is performed by adjusting the optical system of c.

Registration controller 1 of FIG.
FIG. 3 shows the configuration of the main part 2 of the second embodiment together with the CCD 11 and the skew correction device 13.

In FIG. 3, the registration control system 12a includes a state detecting means 21, a skew amount detecting means 22, a first comparing means 23, a second comparing means 24, a flag storing means 25, a skew amount storing means 26 and The skew correction amount calculation means 27 is provided.

The state detection device 21 detects a predetermined color misregistration correction start state and gives an instruction to start the registration control cycle. The predetermined color misregistration correction start state includes, for example, clearing a paper jam, turning on the power, a high temperature state seen during continuous operation, and setting a transfer module.

The skew amount detecting means 22 samples the skew shift amount from the test pattern measured by the CCD 11.

The first comparing means 23 compares the first predetermined amount as the first threshold value with the sampled skew deviation amount. As the first predetermined amount, a value corresponding to a large amount of skew deviation is set in advance so that skew correction is required immediately. More specifically, if the skew displacement amount is set to a value corresponding to the displacement amount indicating that the skew displacement amount is approaching the limit of the allowable range of the registration control system, the first predetermined amount is set to the skew before the allowable range is exceeded. Since correction is executed, it is preferable from the viewpoint of maintaining high image quality. However, in order to reduce the number of times of skew correction that requires test pattern sampling twice in one registration control cycle and reduce the waiting time during operation, the first predetermined amount is skew shift. The value is preferably set to a value corresponding to the deviation amount indicating that the amount slightly exceeds the limit of the allowable range of the registration control system.

The second comparing means 24 compares the second threshold value with the sampled skew shift amount. Second
The threshold value of is set in advance to a value corresponding to the minimum skew shift amount that allows meaningful skew correction in consideration of the skew correction resolution of the color image forming apparatus 1. More specifically, if a value corresponding to one step of the skew correction resolution is set, the skew correction can be improved as long as there is room for improving the skew deviation. However, if there is a skew deviation in the practical range, it does not matter, but in order to prevent the skew correction from being executed too often, it is sufficient to set the value corresponding to a plurality of steps of the skew correction resolution. .

The flag storage means 25 includes the second comparison means 2
If the compared skew deviation amount is larger than the second threshold value according to 4, the flag is set to 1 and stored as a flag signal. If the flag is not large, the flag is set to 0. This flag is information indicating whether or not skew correction is included in the next registration control cycle.

The skew amount storage means 26 stores the skew deviation amount sampled by the skew amount detection means 22.
In particular, the skew amount storage means 26 is the flag storage means 25.
Together with non-volatile RAM (Random Access)
It is preferable to configure each from a non-volatile memory such as Memory). In this case, even when the color image forming apparatus 1 is powered off once and then started up or in the subsequent registration control cycle, the skew deviation amount detected in the previous registration control cycle is used to appropriately perform skew correction. can do.

Further, when the skew amount storage means 26 is composed of a non-volatile memory, the color shift amount including the skew shift amount and the color shift correction amount including the skew correction amount are provided only when the sample state is good. It may be overwritten and stored. Here, whether or not the sample state is good can be determined from the image width of the sampled pattern, the contrast, the background level, and the like.
In this case, as the reference correction value for the next registration control cycle,
If the stored color shift amount is adopted, a stable correction state can be secured regardless of temperature changes and changes in installation environment due to seasonal changes, etc., and high correction accuracy can be ensured even after correction immediately after power is turned on. This is extremely advantageous as compared with the conventional technique that uses a uniform reference correction value regardless of the seasons. Furthermore, even when an abnormality that is impossible due to some reason for the sampling of the test pattern is used, the stored latest correction amount or the like can be used to minimize the deterioration of image quality.

The skew correction amount calculation means 27 calculates the skew correction amount from the skew shift amount stored in the skew amount storage means 26 before executing the skew shift correction.

Registration controller 12a
Has a function of correcting color misregistration other than skew (not shown), and more specifically, the misregistration amount in the main scanning direction, which is the color misregistration amount other than the skew deviation from the test pattern measured by the CCD 11, the sub-scanning direction. A color shift amount detecting means for sampling the shift amount in the direction and a shift amount for the magnification respectively, and a calculating means for calculating a color shift correction amount other than the skew from the color shift amounts other than the sampled skews are provided.

As a result, in the skew correction device 13, when the state detection means 21 detects the color misregistration correction start condition, as described later in detail, the skew amount detected by the output of the first comparison means 23 is the first. Is larger than the predetermined amount, or if there is a flag signal previously stored in the flag storage means 25, the skew correction amount calculation means 26 calculates the skew correction amount from the skew deviation amount stored in the skew amount storage means 26. Then, based on this calculation result, ROS4
The skew correction for will be executed.

Next, regarding the operation of the color image forming apparatus 1 of the present embodiment, (1) normal color image forming operation, (2)
The following description will be divided into three cases, that is, a registration control operation without skew correction and (3) a registration control operation with skew correction.

(1) Normal Color Image Forming Operation In the normal color image forming operation, the IPS 2 causes each color K, Y, M and C for one color image data.
The image data for writing for each is ROS-I / F3k, 3
ROS 4k, 4y, 4m via y, 3m and 3c respectively
And 4c. ROS 4k, 4y, 4m and 4c
By the writing light, image forming devices 5k, 5y, 5m and 5
By scanning the drums of c respectively, the corresponding raster images are respectively written. Image forming devices 5k, 5y, 5m and 5
c develops the raster-shaped electrostatic latent image written on the drum to form a toner image. The transfer belt 6 is driven in the forward direction by a motor 7, and the paper suction roller 8 supplies the recording paper 100 onto the transfer belt 6. The image forming devices 5k, 5y, 5m, and 5c transfer the respective toner images onto the recording paper 100 on the transfer belt 6 in synchronization with each other to synthesize a color image. The color image formed on the recording paper 100 is discharged from the color image forming apparatus after being subjected to heat fixing processing and the like.

(2) Registration Compensation Operation Without Skew Correction When the state detecting means 21 detects a predetermined color misregistration correction start condition, the registration controller 12 causes, for example, K, Y, M as shown in FIG. And C to generate a test pattern for automatic registration shift correction, and write image data for each of K, Y, M and C colors corresponding to this test pattern to ROS-I / F 3k, 3y, 3m and 3c.
To ROS 4k, 4y, 4m, and 4c, respectively. In response to this, ROS 4k, 4y, 4m and 4c
Raster images corresponding to this test pattern are written on the drums of the image forming devices 5k, 5y, 5m, and 5c by writing light. At this time, by not supplying the recording paper 100, the image forming devices 5k and 5k are directly attached onto the transfer belt 6.
The test pattern is transferred by y, 5m, and 5c.
When the CCD 11 measures the test pattern on the transfer belt 6, the registration controller 12 detects the color misregistration amount other than the skew based on the measurement result, but also detects the skew misregistration amount at the same time. In the case of this (2), since the skew deviation amount is smaller than the first predetermined amount and the flag is not set in the flag storage means 25, the skew correction is not performed. A color misregistration correction amount other than the skew is calculated based on the detected color misregistration amount other than the skew. Registration controller 12
Makes electrical adjustments to the electrical circuit of ROS 4 and the signal system to ROS 4 based on the result of this calculation. For example, R
Adjust the write timing of OS4. By the above registration control operation, color misregistration other than skew is corrected.

(3) Registration Control Operation for Skew Correction This case (3) is further understood when the flag is stored in the flag storage means 25 or when the flag is not set. (3-1) When the flag is not set in the flag storage means 25, the operation is the same as that of the above (2) until the registration controller 12 detects the color shift amount and the skew shift amount other than the skew. . In the case of (3-1), since the skew shift amount is larger than the first predetermined amount, the skew correction amount is calculated based on the detected skew shift amount. Based on this calculation result, the skew correction device 13 makes mechanical adjustments to the optical system of the ROS 4. For example, the angle of the mirror that constitutes the optical system of the ROS 4 is adjusted. After that, the registration controller 12 again generates a test pattern, and C
The CD 11 measures the test pattern on the transfer belt 6. A color misregistration correction amount other than the skew is calculated based on the color misregistration amount other than the skew detected from the test pattern, and based on the calculation result, the electrical circuit of the ROS 4 and the signal system to the ROS 4 are electrically adjusted. Add. By the above registration control operation, the skew shift and the color shift other than the skew are corrected. In this case, even when the registration controller 12 again generates a test pattern, the skew deviation amount is detected from the test pattern measured by the CCD 11 to prepare for the next registration control cycle. (3-2) When the flag is stored in the flag storage means 25, the skew correction amount calculation means 27 is based on the skew shift amount stored in the skew amount storage means 26, which is the previously detected skew shift amount. The skew correction amount is calculated by. Based on this calculation result, the skew correction device 13 makes mechanical adjustments to the optical system of the ROS 4. After this, the registration controller 12
A test pattern is generated, and the CCD 11 transfers the transfer belt 6
Measure the test pattern above. A color misregistration correction amount other than the skew is calculated based on the color misregistration amount other than the skew detected from the test pattern, and based on the calculation result, the electrical circuit of the ROS 4 and the signal system to the ROS 4 are electrically adjusted. Add. In this case, even when the registration controller 12 generates a test pattern, the skew deviation amount is detected from the test pattern measured by the CCD 11 to prepare for the next registration control cycle.

The operation of the first embodiment will be described with reference to the flowchart of FIG. In FIG. 7, first, it is determined by a flag of the flag storage means 25 whether or not there is a request for registration deviation correction (step S1). When it is determined that there is a request (step S1: NO), the skew correction amount is calculated from the skew deviation amount stored in the skew amount storage means 26 at the time of the previous registration control, and the skew correction is executed based on the calculation result. (S2). At this point, the skew shift detected at the previous registration control is eliminated. Then, in order to measure the amount of color misregistration other than the skew, sampling processing of the test pattern is performed (step S).
3). When it is determined in step S1 that there is no request (step S1: YES), the process directly proceeds to step S3 (step S3).

Next, each color shift amount including the skew shift amount is calculated (step S4), and it is determined whether the skew shift amount is zero, that is, smaller than the second predetermined amount (step S4). S5). If it is determined to be zero (step S5: YES), the color misregistration correction amount other than the skew is calculated (step S6), and the color misregistration correction amount other than the skew is set in each image forming unit (step S7).
The process ends.

When it is determined in step S5 that it is not zero (step S5: NO), the skew deviation correction amount is calculated from the skew deviation amount (step S8), and it is determined whether or not the skew deviation amount is allowable. (Step S
9). If it is determined to be acceptable (step S9: YE
S), the skew correction amount is stored (step S10),
At the beginning of the next cycle, a flag is set in the flag storage means 25 so as to request execution of skew correction at the beginning (step S11), and then the process proceeds to step S6.

If it is determined in step S9 that it is not acceptable (step S9: NO), skew correction is executed based on the skew correction amount obtained in this sample (step S12), and the test pattern sampling processing is performed. (Step S13), after the color shift amount other than the skew is calculated (Step S14), the above-mentioned Step S6 is performed.
Proceed to. The operation of the first embodiment is performed as described above.

Next, a tandem type color image forming apparatus according to the second embodiment of the present invention will be described. The second embodiment is different from the first embodiment only in the configuration of the registration controller, and the other configurations are the same, so the description thereof will be omitted. FIG. 4 shows the configuration of the registration controller of the second embodiment. In addition, in FIG.
The same components as those of the first embodiment shown in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 4, the registration controller 12b does not include the skew amount storage means 26 for storing the skew amount in the first embodiment shown in FIG. 3, and instead the calculation result of the skew correction amount calculation means 27 is obtained. Skew amount storage means 28 for storing the skew correction amount. That is, the second embodiment is configured to store the skew correction amount instead of the skew deviation amount of the first embodiment for the next registration control cycle.

In the operation of the second embodiment, the skew correction amount calculated in a certain registration control cycle is stored in the skew amount storage means 28, and in the next registration control cycle,
Skew correction is executed based on the stored skew correction amount. As a result, it is not necessary to perform the calculation immediately before executing the skew correction, which is advantageous in that the skew correction can be executed more quickly. Other operations are first
The description is omitted because it is the same as the embodiment.

Next, a tandem color image forming apparatus according to the third embodiment of the present invention will be described. The third embodiment is different from the first embodiment only in the configuration of the registration controller, and the other configurations are the same, so the description thereof will be omitted. FIG. 5 shows the configuration of the registration controller of the third embodiment. In addition, in FIG.
The same components as those of the first embodiment shown in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 5, the registration controller 12c is not provided with the skew amount storage means 26 for storing the skew amount in the first embodiment shown in FIG. That is, the third embodiment does not have a configuration for storing the skew deviation amount and the skew correction amount in preparation for the next registration control cycle as in the first and second embodiments, and when performing the skew correction, The skew correction is performed based on the skew correction amount obtained by executing the pattern sampling. In the third embodiment, the first predetermined amount used in the first comparing means 23 is set to a value corresponding to the limit of the allowable range of the registration control system. on the other hand,
The second predetermined amount used in the second comparison means 24 is set to a value corresponding to the shift amount indicating that the skew shift amount has approached the limit of the allowable range of the registration control system.

In the operation of the third embodiment, when the skew deviation amount exceeds the first predetermined amount, the skew correction is immediately executed within the registration control cycle. On the other hand, if the skew deviation amount does not exceed the first predetermined amount but exceeds the second predetermined amount, a flag is set in the flag storage means 25, and the skew correction is first executed in the next registration control cycle. . As a result, according to the present embodiment, since the skew correction is performed when the allowable range is about to be exceeded, it is possible to keep the skew deviation within the allowable range while reducing the number of time-consuming skew corrections.

The operation of the third embodiment will be described in detail with reference to the flow chart of FIG. In FIG. 8, first, the state detection means 21 determines whether or not the registration shift correction is necessary (step S21). Unless it is determined to be necessary (step S21: NO), normal operation is continued. If it is determined to be necessary (step S21: Y
ES), it is determined whether the flag of the flag storage unit 25 for the skew is 0 (step S22).
If the flag is not 0, that is, if the flag is 1 (step S22: NO), the skew correction cycle is executed (step S23), and subsequently the registration control cycle other than the skew correction is executed (step S24). If the flag is 0 in step 22, (step S22: YE
S), the registration control cycle other than the skew correction is executed as it is (step S24).

Next, it is judged whether or not the skew deviation amount detected in the registration control cycle other than the skew correction is smaller than the second predetermined amount (step S25). If it is smaller (step S25: YES), step S21
Return to If not smaller (step S25: NO), it is further determined whether or not the skew deviation amount detected in the registration control cycle other than the skew correction is smaller than the first predetermined amount (step S26). If it is smaller (step S26: YES), the flag storage means 2 is set to start from the skew correction cycle at the next registration control cycle.
1 is set to the flag of 5 (step S27), and step S
Return to 21. If not smaller (step S26: N
O), the process proceeds to step S23 described above.

Next explained is a tandem color image forming apparatus according to the fourth embodiment of the invention. The fourth embodiment is different from the first embodiment only in the configuration of the registration controller, and the other configurations are the same, so the description thereof will be omitted. FIG. 6 shows the configuration of the registration controller of the fourth embodiment. In addition, in FIG.
The same components as those of the first embodiment shown in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 6, the registration controller 12d does not have the skew amount storage means 26 for storing the skew amount in the first embodiment shown in FIG. 3, the second comparison means 24, and the flag storage means 25. That is, in the fourth embodiment, as in the first to third embodiments, in preparation for the next registration control cycle, the skew deviation amount and the skew correction amount are stored, and a flag for requesting execution of skew correction is set. When the skew correction is performed, the skew correction is always performed based on the skew correction amount obtained by first performing the pattern sampling. In the fourth embodiment, the skew correction is immediately executed selectively according to the comparison result of the first comparing means 23. As the first threshold value, a value corresponding to a large skew shift amount is set so that skew correction is required immediately.

In the operation of the fourth embodiment, when the detected skew deviation amount is smaller than the first threshold value, it is determined that the skew correction is unnecessary, and the skew correction is not executed, and the skew correction is directly performed. Color misregistration correction other than skew is executed. As a result, in this registration control cycle, only one time is required to detect the color misregistration amount. If the skew deviation amount is not smaller than the first threshold value, it is determined that the skew correction is necessary, and the skew deviation correction is immediately executed based on the detected skew deviation amount.

As a result, according to the present embodiment, the situation in which it is necessary to detect the color misregistration amount twice during one registration control cycle is suppressed to the minimum necessary.

In order to explain the effect of the first embodiment, FIG.
Further, FIG. 10 schematically shows each operation and each state with respect to time in the first embodiment and the comparative example.

As shown in FIG. 9, according to the first embodiment,
Even if the skew deviation within the allowable range occurs at time T1, if the registration control is performed twice after that, the flag is set by the first registration control, and the skew correction is performed by the second registration control. Therefore, at time T2. Skew deviation can be eliminated.

On the other hand, as shown in FIG. 10, according to the comparative example in which the skew deviation is not corrected in the normal operation,
A skew deviation within an allowable range occurs at time T1, and the skew deviation continues to exist unless maintenance is performed by a service person thereafter.

Further, in order to explain the effect of the third embodiment,
FIG. 11 schematically shows each operation and each state with respect to the time of the third embodiment.

As shown in FIG. 11, according to the third embodiment, even if a large skew deviation exceeding the allowable range occurs at time T3, the skew correction is also executed in the subsequent registration control cycle. The skew deviation can be eliminated at time T4. That is, such a large skew deviation can be automatically corrected even if maintenance by a service person is not performed.

The color image forming apparatus described above can be used in copying machines, printers, facsimiles and the like.
Further, in the above embodiment, 4 of K, Y, M and C are used.
Although the case of color has been described, the present invention is not limited to these four colors, and the present invention can be applied to an apparatus that forms multiple images by superposing arbitrary plural colors.

[0073]

According to the first aspect of the present invention, skew correction can be performed reliably and minimally, so that a high-quality image with less color misregistration can be realized while waiting time during normal operation by the registration control cycle. Can be reduced.

According to the second aspect of the present invention, since the color shift amount detected in a certain operation cycle is used as it is for skew correction in the next operation cycle, it is possible to detect the color shift amount once in each cycle. Therefore, the time required for the registration control does not have to be long, and it is possible to realize a high-quality image with less color shift and reduce the waiting time during the normal operation due to the registration control cycle.

According to the third invention of the present application, as in the case of the second invention, it is sufficient to detect the color misregistration amount once in each cycle while further reducing the skew misalignment. Moreover, when the skew correction is performed in the next operation cycle, the skew correction amount is already calculated, so that the skew correction can be performed more quickly than the second invention.

According to the fourth invention of the present application, by using the flag signal as information indicating that the skew correction should be executed in the next operation cycle, the control by the control means can be performed with a relatively simple structure. You can

According to the fifth aspect of the present invention, the skew deviation amount detected in the previous operation cycle is utilized even at the time of start-up after the power source of the multiple image forming apparatus is once turned off and the subsequent operation cycle. Therefore, skew correction can be appropriately performed. At this time, in each operation cycle,
It is sufficient to detect the amount of color misregistration once.

As a result, according to the present invention, the skew deviation amount, which is not always corrected during the normal operation, is constantly monitored, so that the skew correction is executed if necessary, so that the normal operation may be performed with the skew being deviated. Is reduced, skew correction is not performed if unnecessary, and the skew deviation amount obtained in a certain registration control cycle is used in the next registration control cycle. For this reason, the time during which the apparatus cannot be used can be reduced by the adjustment by the service person, and the increase in the time when the operation of the apparatus is stopped due to the execution of the register control can be minimized. Moreover, since skew correction is appropriately performed in the normal operation mode, the time and labor required for maintenance by the service person are reduced. Further, even if a component that does not meet the standard is erroneously used, it is possible to detect and correct even a defect in the unit of micrometer or a defect due to aging.

[Brief description of drawings]

FIG. 1 is a block diagram of a color image forming apparatus that is an embodiment of the present invention.

FIG. 2 is a plan view showing an example of a measurement pattern for registration control used in an example of the present invention.

FIG. 3 is a block diagram of a resist controller used in the first embodiment of the present invention.

FIG. 4 is a block diagram of a resist controller used in a second embodiment of the present invention.

FIG. 5 is a block diagram of a resist controller used in a third embodiment of the present invention.

FIG. 6 is a block diagram of a resist controller used in a fourth embodiment of the present invention.

FIG. 7 is a flowchart showing the operation of the first embodiment of the present invention.

FIG. 8 is a flowchart showing the operation of the third embodiment of the present invention.

FIG. 9 is a time chart showing the operation of the first embodiment of the present invention.

FIG. 10 is a time chart showing the operation of the comparative example.

FIG. 11 is a time chart showing the operation of the third embodiment of the present invention.

[Explanation of symbols]

1 ... Color image forming apparatus, 2 ... IPS, 3 ... ROS-I
/ F, 4 ... ROS, 5 ... Image forming device, 6 ... Transfer belt, 7
... motor, 8 ... paper suction roller, 10 ... belt cleaner, 11 ... CCD, 12 ... registration controller, 13 ... skew correction device, 21 ... state detection means,
22 ... Skew amount detecting means, 23 ... First comparing means, 2
4 ... Second comparing means, 25 ... Flag storing means, 26 ... Skew amount storing means, 27 ... Skew correction amount calculating means, 2
8 ... Skew correction amount storage means, 24 ... Second comparison means.

Claims (5)

[Claims] 1. A plurality of image forming means for forming images of different colors in an overlapping manner, a detecting means for detecting a skew shift amount between the image forming means and a color shift amount other than the skew, and the skew shift amount is When it is smaller than the threshold value of 1, the image forming unit is controlled so as to perform the color misregistration correction other than the skew based on the color misregistration amount other than the skew, and the skew misregistration amount is the first If it is not smaller than the threshold value, the skew shift correction is executed based on the skew shift amount and the color shift amount other than the skew detected again by the detecting means after the skew shift correction is finished. A multiple image forming apparatus comprising: a control unit that controls the image forming unit so as to perform color misregistration correction other than the skew. 2. A skew storage means for storing the skew shift amount detected by the detection means is further provided, and the detection by the detection means, the control by the control means, and the storage by the skew storage means have a predetermined color. When the deviation correction start condition is satisfied, the operation is performed in one operation cycle, and the control unit controls the skew deviation amount detected by the detection unit in the n (n: natural number) operation cycle. N + 1 if less than the first threshold and greater than a second threshold less than the first threshold
Before performing the pattern sampling for color misregistration correction other than the skew misregistration in the operation cycle of the first time, the skew misregistration is performed based on the skew misregistration amount stored in the skew memory during the operation cycle of the nth time. 2. The multiplex image forming apparatus according to claim 1, wherein the image forming unit is controlled so as to execute the shift correction. 3. The detecting means further comprises a calculating means for calculating a skew correction amount from the skew deviation amount detected by the detecting means, and a skew storing means for storing the calculated skew correction amount. The detection, the control by the control unit, the calculation by the calculation unit, and the storage by the skew storage unit are performed when a predetermined color misregistration correction start condition is satisfied.
It is performed in one operation cycle, and the control unit is configured such that the skew deviation amount detected by the detection unit in the n (n: natural number) operation cycle is smaller than the first threshold value. And greater than a second threshold less than the first threshold, n + 1
Before performing the pattern sampling for the color misregistration correction other than the skew misregistration in the operation cycle of the first time, the skew misregistration correction is performed based on the skew correction amount stored in the skew storage means during the nth operation cycle. 2. The multiplex image forming apparatus according to claim 1, wherein the image forming unit is controlled so as to execute. 4. The apparatus further comprises flag storage means for storing a flag signal when the skew deviation amount detected by the detection means is larger than the second threshold value, and the control means is the (n + 1) th time. In the above operation cycle, the skew deviation amount detected by the detecting means in the nth operation cycle is based on the flag signal stored in the flag storage means during the nth operation cycle, and Smaller than the threshold value of
4. The multiple image forming apparatus according to claim 2, wherein it is determined whether or not it is larger than the threshold value of. 5. The multiple image forming apparatus according to claim 4, wherein the skew storage means and the flag storage means each comprise a non-volatile memory.