JPH08286566A - Image forming device and image color slippage adjusting method thereof - Google Patents

Abstract

PURPOSE: To always obtain an excellent color image without deteriorating the forming efficiency thereof by correcting the slippage of the images of respective colors at a proper time as to an image forming device for obtaining one sheet of color image by successively superposing the images on a recording material which is carried. CONSTITUTION: A temperature sensor 41 is installed in the device. Based on the output of the sensor 41, it is judged by a color slippage adjustment control part 35 (color slippage adjusting means and adjusting time detection means) whether the color slippage must be adjusted or not. Then, when it is judged that the color slippage must be adjusted, it is adjusted. The fitting position of the sensor 41 is set on a frame supporting a photoreceptor 19 and on the back side of and near the device. Besides, it is set at the position nearer a fixing device 18 side a little than the middle point of plural arrayed image forming parts. The necessity of the adjustment of the color slippage is judged by selecting the various kinds of set up terms, for example, it is judged based on the change extent of temperature in the device. Thus, temperature information almost corresponding to the extent of the color slippage can be obtained and the timing that the color slippage must be adjusted can be properly detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus in which a plurality of image forming means are arranged along a transfer belt and a single color image formed by each of them is superposed to form one color image. In particular, the present invention relates to an image forming apparatus capable of correcting a deviation between superposed monochromatic images.

[0002]

2. Description of the Related Art In recent years, colorization of commercial documents has progressed, and image forming apparatuses such as copying machines, printers, and facsimiles have also been colorized. Color image forming apparatuses are generally
An electrophotographic color image forming apparatus forms an image of yellow toner, an image of magenta toner, an image of cyan toner, and an image of black toner, respectively. Then
These are overlaid to form a full-color image. As such a color image forming apparatus, one in which four photoconductors are arranged along the transfer belt and the toner images of the respective colors formed on the respective photoconductors are sequentially superposed and transferred onto the paper on the transfer belt (so-called There is a tandem type color image forming apparatus).

In such an image forming apparatus, the photoconductors on which the toner images of the respective colors are formed are separately provided, and the writing, development and transfer of the images are also carried out separately, so that the respective color images are exactly on the paper. The image writing timings must be set extremely accurately in accordance with the intervals between the transfer positions so that they overlap. In addition, if the fixing means of each device is loosened for maintenance or replacement of parts, the positional relationship between the color image forming means changes subtly, resulting in color misregistration. Further, the temperature inside the apparatus fluctuates due to the change of the outside air temperature and the heat of the fixing apparatus when continuously used, and the color shift occurs due to the expansion and contraction of the member. In an image forming apparatus in which an image is written by scanning a laser beam, such color misregistration includes deviation in the main scanning direction, deviation in the moving direction of the transfer belt, that is, deviation in the sub-scanning direction, expansion / contraction in the main scanning direction, or magnification Deviation and angular deviation in the main scanning direction. Of these, deviation in the sub-scanning direction is most likely to occur due to temperature changes, and correction is required.

The color misregistration is corrected, for example, by Japanese Patent Laid-Open No. 6-253.
As disclosed in Japanese Patent Publication No. 151, there is one in which a sample image for measuring color misregistration is transferred from an image forming unit for each color onto a transfer belt, and the sample image is detected by a CCD sensor or the like for correction. In this, an image of fine lines in the main scanning direction and the sub scanning direction is formed by the image forming means of each color as a sample image, and these are transferred at a predetermined interval. The color shift amount is detected by accurately measuring these intervals with a CCD sensor or the like and comparing them with a predetermined value. These color misregistrations are corrected by controlling the image writing timing of main scanning and sub scanning, phase correction of the polygon motor, control of scanning clock frequency, and the like.

[0005]

However, in order to accurately perform the color misregistration correction, it takes a considerable amount of time, for example, to form a sample image for one revolution of the transfer belt. Further, the above-described color misregistration correction must be performed before the image formation with the power of the apparatus turned on, and in order to always form an image with no color misregistration, it is necessary to continue. Even in the middle of forming an image, it is necessary to temporarily suspend the color misregistration correction. If such color misregistration correction is frequently performed, the image forming operation is stopped each time, and the efficiency is significantly deteriorated. Therefore, the color misregistration correction must be controlled so as to be executed only when the degree of color misregistration becomes large and the correction becomes necessary.

Regarding such a problem, Japanese Patent Laid-Open No. 1-14
The image forming apparatus described in Japanese Patent No. 2676 is equipped with a state change detecting means, and for example, the temperature inside the apparatus is measured, and the color misregistration correction is performed every time when the temperature changes to the extent that the color misregistration correction is considered necessary. I am going to do it. However,
In this image forming apparatus, the temperature is measured in the vicinity of the fixing device, and when the time when the color misregistration correction is necessary is determined based on the measurement result, the temperature misregistration is performed when the color misregistration is small and the correction is not yet necessary. The correction may not be executed even if the color shift occurs to the extent that the correction is necessary. This is because the temperature inside the device is significantly different depending on the position,
This changes with time because the gradient of the temperature change at that time and the functions of temperature and time are different depending on the position.

The present invention has been made in view of the above circumstances, and an object of the present invention is to perform color misregistration correction only when necessary so as to prevent a decrease in the efficiency of image formation and to prevent color misregistration. It is an object of the present invention to provide an image forming apparatus capable of obtaining a good color image free of color.

[0008]

According to a first aspect of the present invention, an image is formed by sequentially transferring images from a plurality of image forming means arranged at a predetermined interval onto a moving transfer body to form a composite image. In the forming apparatus, a temperature detecting means for detecting the temperature inside the image forming apparatus, and an adjustment timing detecting means for detecting a timing for adjusting the color misregistration between the images according to the temperature information based on the detection result of the temperature detecting means. Based on the result of the detection, the color misregistration is corrected or the necessity of the color misregistration correction is determined to perform the correction operation when the color misregistration correction is necessary, and when it is unnecessary, the correction is not performed and the normal cycle is performed. And a color misregistration adjusting means for returning to, wherein the temperature detecting means,
It is assumed that it is located in the vicinity of a support frame that contributes to support the plurality of image forming units.

According to a second aspect of the present invention, images are sequentially transferred from a plurality of image forming means arranged at predetermined intervals onto a moving transfer member to form a composite image, and the composite image is fixed. In an image forming apparatus in which the fixing to the image is performed by a heat fixing unit, the color misregistration adjustment between the images is performed according to the temperature detection unit that detects the temperature in the image forming apparatus and the temperature information based on the detection result of the temperature detection unit. Adjustment timing detection means for detecting the timing of performing the color shift, and based on the result of the detection, the color shift is corrected or the necessity of the color shift correction is determined to perform the correction operation when the color shift correction is necessary, The color detection device has a color misregistration adjusting unit that returns to the normal cycle without performing correction if unnecessary, and the temperature detecting unit has an image forming unit located on the most upstream side and an image forming unit located on the most downstream side in the transfer body moving direction. Intermediate point with means A remote said heat fixing means closer, assumed to be located at the midpoint closer than the downstream side end portion of the image forming means located downstream.

According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, four of the plurality of image forming units are arranged in parallel to the transfer body moving direction, and the temperature detection is performed. It is assumed that the means is located near the third image forming means in the transfer body moving direction.

According to a fourth aspect of the present invention, in an image forming apparatus for forming a composite image by sequentially transferring images from a plurality of image forming means arranged at predetermined intervals onto a moving transfer body, Temperature detection means for detecting the temperature inside the apparatus, adjustment timing detection means for detecting the timing for performing color misregistration adjustment between images according to the temperature information based on the detection result of the temperature detection means, and the detection result On the basis of the above, there is a color misregistration adjusting unit that corrects the color misregistration or judges the necessity of the color misregistration correction and executes the correction operation when the color misregistration correction is necessary. It is assumed that there is an air conditioning unit for discharging the air inside the image forming apparatus to the outside of the apparatus, and the temperature detecting unit is located closer to the inside air discharging unit than the outside air intake unit of the air conditioning unit.

According to a fifth aspect of the present invention, a composite image is formed by sequentially transferring images from a photosensitive drum provided on each of a plurality of image forming units arranged at a predetermined interval onto a moving transfer member. In the image forming apparatus that
Temperature detecting means for detecting the temperature in the image forming apparatus,
According to the temperature information based on the detection result of the temperature detecting means,
Adjustment time detection means for detecting the time when the color misregistration adjustment is performed between each image, and the case where the color misregistration correction is necessary by correcting the color misregistration or judging the necessity of the color misregistration correction based on the detection result. Has a color misregistration adjusting means for executing a correction operation, and the temperature detecting means is located on a line connecting the rotational axis positions of the respective photoconductor drums or in the vicinity thereof.

According to a sixth aspect of the present invention, there is provided an image forming apparatus for forming a composite image by sequentially transferring images from a plurality of image forming means arranged at a predetermined interval onto a moving transfer body. Temperature detection means for detecting the temperature inside the apparatus, adjustment timing detection means for detecting the timing for performing color misregistration adjustment between images according to the temperature information based on the detection result of the temperature detection means, and the detection result On the basis of the above, there is a color misregistration adjusting means for correcting the color misregistration or judging the necessity of the color misregistration correction and executing the correction operation when the color misregistration correction is necessary. It has a conversion means for converting the information into that of the optimum position, and operates the adjustment timing detection means in accordance with the converted information value.

According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the image forming apparatus has an outside air temperature detecting means for detecting an outside air temperature, and the converting means has a temperature detected by the outside air temperature detecting means. The conversion of the temperature information shall be performed by selecting and using a different conversion table according to the above.

The invention according to claim 8 is the invention according to claims 1 to 7.
In each of the image forming apparatuses, it is assumed that the temperature information based on the detection result of the temperature detecting unit is that the temperature inside the image forming apparatus has reached a predetermined temperature.

The invention according to claim 9 is the same as claims 1 to 7.
In each of the image forming apparatuses, it is assumed that the temperature information based on the detection result of the temperature detecting unit is that a predetermined temperature change occurs in the temperature inside the image forming apparatus.

According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the adjustment timing detecting means is activated when a predetermined temperature change occurs from a reference temperature in the image forming apparatus, and further, A new reference temperature is set, and the same operation is repeated based on the new reference temperature.

The invention described in claim 11 is the invention according to claim 10.
In the image forming apparatus described in the paragraph 1, the new reference temperature is set to a detection temperature when the color misregistration adjusting unit is operated.

The invention according to claim 12 is the same as claim 9.
In the image forming apparatus described in 10.11, the predetermined value of the predetermined temperature change is determined according to the adjustment result of the color shift adjusting unit.

The invention described in claim 13 is the same as claim 1.
In the image forming apparatus described in 0.11.12, it is assumed that the predetermined value of the predetermined temperature change is determined according to the reference temperature that is set.

The invention described in claim 14 is the same as claim 1.
In the image forming apparatus described in 0.11.12.13,
It is assumed that the color misregistration adjusting means is operated between the time when the power of the image forming apparatus is turned on and the first image formation is started, and the detected temperature immediately after that is set to the first reference temperature.

According to a fifteenth aspect of the present invention, an image color shift of an image forming apparatus for forming a composite image by sequentially transferring images from a plurality of image forming means arranged at predetermined intervals onto a moving transfer body. In the adjusting method, the temperature inside the image forming apparatus is detected, and when a predetermined temperature change from the reference temperature occurs in the detected temperature, a color shift between the images is detected, and a color difference is detected based on the detection result. After performing the shift adjustment, a new reference temperature is set, and the same operation is repeated based on the new reference temperature.

In the image forming apparatus according to claim 1,
The adjustment time detection means detects a time when the color misregistration adjustment is performed according to the temperature information, and outputs a signal for executing the color misregistration adjustment when the information that the color misregistration adjustment is determined to be necessary is detected. To do.

The color misregistration adjusting means includes any of the following three examples. In Example 1, a color misregistration correction is executed by forming a sample pattern for color misregistration measurement every time when performing color misregistration adjustment, measuring the amount of color misregistration. In Example 2, a check pattern for determining the necessity of color misregistration correction is created, an approximate value of the color misregistration amount is calculated from the result of reading the check pattern, and the necessity of color misregistration correction is determined from this approximate value. The color misregistration is corrected only when it is determined to be necessary. Example 3 creates and detects both a check pattern and a sample pattern, and only when it is determined from the detection result of the check pattern that color misregistration correction is necessary, an accurate value of the color misregistration amount is obtained from the sample pattern detection result. The calculation is performed to correct the color misregistration. The color shift adjusting means is not limited to the above three examples. Example 1 Sample pattern creation / detection → Correction execution Example 2 Check pattern creation / detection → → No correction required → No correction → Correction required → Sample pattern creation / detection → Correction execution Example 3 Check pattern / sample pattern creation / detection →
Approximate color shift amount is calculated → No correction required → No correction →
Correction required → Accurate value calculation / correction execution

According to the fifth aspect of the present invention, "near the line connecting the rotational axis positions of the respective photosensitive drums or on the extended line thereof".
The term "considers a line obtained by linking the positions of the photosensitive drums arranged along the transfer body on the vertical surface of the rotation axis and extending the line, and means the vicinity of the line or the extended line.

In the eleventh aspect, "when the color misregistration adjusting means is operating" includes the time during which the color misregistration adjusting means is operating and the time before and after that.

In the twelfth aspect of the present invention, "determining the predetermined value of the predetermined temperature change according to the adjustment result of the color misregistration adjusting means" means the color misregistration amount detected at the previous color misregistration adjustment or The predetermined value is determined so as to increase or decrease the temperature change amount until the next color misregistration adjustment is performed depending on conditions such as whether or not color misregistration correction has been performed, and includes the following operations. For example, if the color misregistration amount detected during the previous color misregistration adjustment is extremely small and the color misregistration correction is not executed, increase the predetermined value that is the temperature change amount until the next color misregistration adjustment is performed. A slight amount of color misregistration is recognized during color misregistration adjustment, but it is not enough to perform the correction, and when the color misregistration correction is not executed, reduce the predetermined value, In addition, the predetermined value may be increased.

In the image forming apparatus according to the fourteenth aspect, the operation of the color misregistration adjusting means may be performed at any time between the time when the image forming apparatus is turned on and the time when the first image formation is started. It is desirable to perform it immediately before the start of image formation.

[0029]

According to the image forming apparatus of the present invention, the image forming apparatus has a temperature detecting means for detecting the temperature in the image forming apparatus, and based on the temperature information obtained by the temperature detecting means, the time when the color misregistration adjustment is performed is performed. Since it is set, when color shift due to the influence of temperature occurs, the correction is appropriately performed. Further, when the influence of temperature such as temperature change is small, the color misregistration is less likely to occur, and at this time, the color misregistration is not frequently adjusted, and the efficiency of image formation is prevented from being deteriorated. Further, the color shift due to the influence of the temperature as described above is mostly caused by the expansion and contraction of the frame supporting the plurality of image forming means depending on the temperature, and the image forming apparatus according to the present invention includes the temperature detecting means. Is installed in the vicinity of the support frame, it is possible to obtain temperature information that accurately corresponds to the amount of color misregistration, and the time for performing color misregistration adjustment is set appropriately.

In the image forming apparatus according to the second aspect, the image forming means are sequentially arranged along the transfer body, the heat fixing means is provided on the downstream side thereof, and the temperature detecting means is arranged in the moving direction of the transfer body. It is closer to the heat fixing unit than the intermediate point between the image forming unit located at the most upstream and the image forming unit located at the most downstream, and closer to the intermediate point than the downstream end of the image forming unit located at the most downstream. Since it is located, temperature information corresponding to the occurrence of color misregistration is detected.

This is because of the following reasons.
The temperature in the image forming apparatus gradually rises due to the heat from the fixing means, but the temperature near the position near the fixing means rises rapidly and becomes high. The relationship between such temperature change and time has a distribution, for example, as shown in FIG. 8A, but the shape of the temperature rise curve and the value of rising temperature are different at each position. If this is set as the amount of change in temperature per unit time, as shown in FIG. 9, the amount of change in temperature is large at positions closer to the fixing means, which is the heat source, and the amount of change decreases with the passage of time at any position. Go on. The temperature saturation time becomes shorter at a position farther from the fixing unit. on the other hand,
The amount of color misregistration between the image forming units is almost proportional to the amount of change in the average temperature between the image forming units, and the image forming units are for black (K) and yellow (from the upstream side in the moving direction of the transfer member). Y), magenta (M), and cyan (C) are arranged, and if the fixing unit is located at the most downstream position, the amount of color misregistration between the image forming units changes with time as shown in FIG. 8B. To do. These color shifts occur between the two furthest positions, that is, between the image forming units for black and cyan (K-
(Between C and C), these become maximum, and these are between M and C, between Y and M, K
It is indicated by the sum of the color shift amounts between −Y. At this time, MC
The relationship between the amount of color misregistration between YY, Y-M, and K-Y and time substantially corresponds to the relationship between temperature change at these positions and time.
The relationship between these temperature changes and time differs depending on the respective positions, but if a certain appropriate position is selected, it will correspond to the relationship between the color shift amount between K and C and time. That is, when the temperature change at a certain appropriate position is multiplied by a certain constant, the color shift amount between K and C is obtained.

The above "some suitable position" can be considered as follows. The amount of color misregistration per unit time due to temperature change is large at a position near the heat source and small at a position distant from it, and decreases with time. The distribution of the color misregistration amount per unit time changes with the passage of time as shown in FIG. 10, but the position of the center of gravity of the color misregistration amount distribution slightly changes, and the color misregistration amount between the respective image forming units is changed. Can be represented by the position of the center of gravity. Therefore, the temperature information detected at this position substantially corresponds to the color shift amount between K and C in which the temperature information appears most significantly. In such a position, when there is a fixing unit serving as a heat source on the downstream side and the image forming units are arranged in a line on the upstream side, the image forming unit located at the most upstream side in the transfer body moving direction and the image forming unit located at the most upstream side. The position is closer to the heat fixing unit than the intermediate point with the image forming unit located downstream, and closer to the intermediate point than the downstream end of the image forming unit located most downstream. Therefore, with the above configuration, the temperature information is appropriately detected, and the time when the color misregistration adjustment is performed is appropriately detected.

In the image forming apparatus according to the third aspect, four image forming means are arranged, and the vicinity of the third image forming means is the "installation position of the temperature detecting means" according to the second aspect.
Would be equivalent to Therefore, the detection of the appropriate temperature information and the setting of the appropriate color misregistration adjustment timing are performed.

In the image forming apparatus according to the fourth aspect of the present invention, the air-conditioning means for taking in the outside air into the apparatus and discharging the air inside the apparatus is provided, but the temperature detecting means has the air inside the apparatus rather than the intake portion for the outside air. Since it is provided near the discharge part, the temperature inside the device can be accurately detected. That is, if the temperature detecting means is provided near the intake portion of the outside air, it is difficult to accurately detect the temperature inside the device due to the influence of the outside air temperature. It will be resolved.

In the image forming apparatus according to the fifth aspect, the temperature detecting means is installed near the line connecting the rotational axis positions of the photosensitive drum or in the vicinity thereof. In general, color shift due to temperature change is caused by expansion and contraction of the transfer position from the photoconductor to the transfer material, and the interval of the transfer position is that of the rotation shaft (support shaft) of the photoconductor. Therefore, by detecting the temperature information near the line connecting the rotating shafts of the photoconductor drums, the temperature information can be accurately associated with the color misregistration amount, and the timing for executing the color misregistration adjustment is appropriately set.

In the image forming apparatus according to the sixth aspect, even if the temperature detecting means cannot be installed at the most suitable position, the position where the temperature detecting means is actually provided and the most suitable position are provided. The correlation of the temperature information, such as the relationship with the temperature rise amount, is measured by an experiment or the like, and the actual detection value is converted into the temperature information of the optimum position by the conversion means. Therefore, even when the installation position of the temperature detecting means is not optimal, the timing for appropriately performing the color misregistration adjustment is set.

In the image forming apparatus according to the seventh aspect, when the position where the temperature detecting means is set is not the optimum position, a plurality of tables for converting the detected temperature information into the temperature information detected at the optimum position are provided. are doing. Therefore, even if the converted value differs depending on the detected temperature,
By selecting the conversion table according to the detected temperature, it is possible to accurately convert the temperature information obtained at the optimum position. Therefore, the color misregistration adjustment timing is set appropriately.

In the image forming apparatus according to the eighth aspect, the temperature detecting means detects the temperature in the image forming apparatus reaching a predetermined temperature and sets the timing of color misregistration adjustment based on the detected temperature. Since a temperature sensor can be used, accurate temperature information can be obtained with a simple device.

In the image forming apparatus according to the ninth aspect, it is necessary to perform the color misregistration adjustment because it detects that a predetermined temperature change has occurred in the apparatus and sets the color misregistration adjustment timing based on this. The color misregistration can be adjusted so that the color misregistration amount does not become excessively large.

In the image forming apparatus according to the tenth aspect, when a predetermined temperature change occurs from the reference temperature in the apparatus, the color misregistration is adjusted, and at this time, a new reference temperature is set and set. Since the next color misregistration correction is performed based on this, it is possible to speed up or delay the next color misregistration correction based on the environmental conditions when the color misregistration adjustment is performed. Become.

In the image forming apparatus according to the eleventh aspect, the temperature is detected when the color misregistration is adjusted, and the timing for performing the next color misregistration adjustment is set using this as a reference temperature. The time when the next color misregistration adjustment is performed can be appropriately set according to the temperature at that time.

In the image forming apparatus according to the twelfth aspect, since the predetermined value of the temperature change is determined according to the adjustment result of the color misregistration adjusting means, for example, the color misregistration amount is detected but the color misregistration is corrected. The time when the next color misregistration adjustment is performed can be set by discriminating whether the color misregistration is not performed or the color misregistration correction is performed, and an appropriate time can be set.

In the image forming apparatus according to the thirteenth aspect, the predetermined value of the temperature change is determined according to the set reference temperature, that is, the reference temperature appropriately set based on the temperature information obtained by the temperature detecting means. Therefore, the predetermined value can be appropriately set even when the degree of occurrence of color misregistration varies depending on the temperature difference. Therefore, the timing for performing the next color misregistration adjustment is appropriately set.

In the image forming apparatus according to the fourteenth aspect, since the color misregistration is adjusted between the time when the power is turned on and the first image formation is started, the color misregistration is appropriately adjusted for the first image formed. Will be things. Further, since the next color misregistration adjustment time is set with the detected temperature at this time as the reference temperature, the color misregistration adjustment will be performed at an appropriate time thereafter.

In the image color misregistration adjusting method according to the fifteenth aspect, the color misregistration is adjusted when a predetermined temperature change occurs in the apparatus, and a new reference temperature is set after the color misregistration adjustment. Since the time when the color misregistration adjustment is performed next is determined, the color misregistration adjustment can be performed at an appropriate time corresponding to the temperature at that time.

[0046]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an image forming apparatus which is an embodiment of the present invention. FIG. 2 is a block diagram showing a configuration for adjusting color misregistration in this image forming apparatus. This image forming apparatus includes a transfer belt 11 that conveys recording paper while electrostatically adhering it, and four image forming units 12 (image forming means) at positions facing the transfer belt. Each of these image forming units 12 has a drum-shaped photoconductor 19, and around each photoconductor 19, a charging device 13 that uniformly charges the surface of the photoconductor 19 and each photoconductor. An image writing device 14 that irradiates a laser beam onto a latent image to form a latent image, and a developing device 1 that visualizes a latent image formed on a photoconductor by attaching toner to the latent image.
5, a transfer device 16 for transferring the toner image formed on the photoconductor to the recording paper, and a cleaning device 17 for cleaning the toner remaining on the photoconductor after the toner image is transferred. Further, on the downstream side of the image forming unit 12 in the circumferential direction of the transfer belt 11, there is provided a fixing device 18 that heats and pressurizes the recording material on which the toner image is transferred to fuse the toner image. These transfer belts 11,
The image forming unit 12 and the fixing device 18 constitute a main part of an image forming section.

The image forming unit 12 forms toner images of different colors, and the transfer belt 11
The images forming images of black, yellow, magenta, and cyan are arranged from the upstream side in the moving direction of. The image writing device 14 includes a laser light generator that generates laser light based on an image signal, and a polygon mirror that reflects the laser light and scans the peripheral surface of the photoconductor in the axial direction. The scanning of the laser beam is repeated and the photosensitive member rotates, and the exposure scanning is sequentially performed in the sub-scanning direction to form a latent image corresponding to image information on the photosensitive member.

The transfer belt 11 is a sheet-shaped member supported by a support roller so as to be capable of endless movement.
This transfer belt is made of a transparent sheet, and a specific pattern image for image position detection formed on each photoconductor is directly transferred to the transfer belt.

Below the image forming unit 10, further,
A paper tray 21 for accommodating recording paper, a paper conveyance path 22 for conveying the recording paper from the paper tray 21 to a feeding position for the transfer belt 11, and a paper feed for supplying the recording material onto the transfer belt at a predetermined timing. A paper return path 24 for reversing the roller 23 and the recording material having an image formed on one surface thereof, and again conveying the image onto the transfer belt 11 so that the image is transferred to the other surface.
And have. The recording material is fed onto the transfer belt 11 at a predetermined timing by the paper feed roller 23,
It is designed to be carried at a fixed position on the peripheral surface of the transfer belt.

Further, the image reading device 32 is provided in the device.
Alternatively, an image processing unit 31 that performs processing such as digitization and gradation analysis of an image signal input from the external device 33, an image writing control unit 34 that controls writing of an image of each color based on the processed image signal, The color misregistration adjustment control unit 35 that outputs a color misregistration correction signal to the image writing device 14 and other devices in order to adjust the misregistration of the image formed by each image forming unit 12, and the operation of each device that performs image formation. A system controller 36 for controlling the temperature is provided, and a temperature sensor 41 for detecting the temperature inside the apparatus and a CCD sensor 42 for accurately detecting the position of the image on the transfer belt 11 are provided. The external device 33 that outputs an image signal is, for example, a personal computer, a workstation, or a device that converts sent image information.

The image processing section 31 performs digital processing of image signals, shading correction, gradation correction, chromaticity adjustment, and the like. Further, it includes a memory and stores an image signal forming a specific pattern image for image position detection. Based on the signal of this specific pattern image, the image writing device 14
A laser beam for forming a specific pattern image on the photoconductor 19 is output from the. The specific pattern image for detecting the image position is, as shown in FIG. 3, a pattern image 51 for detecting a deviation in the sub-scanning direction and a pattern image for detecting a deviation in the main scanning direction and an expansion or contraction of a range in the main scanning direction. 5
And 2. This specific pattern image is formed on both sides of the transfer belt 11 in the main scanning direction, and is formed for each color of black, yellow, magenta, and cyan.

The color misregistration adjustment control unit 35 determines whether or not the color misregistration adjustment is necessary based on the output from the temperature sensor 41, and when the color misregistration adjustment is determined to be necessary, the color misregistration adjustment control unit 35 is controlled. . The color misregistration adjustment may be performed by immediately performing color misregistration correction, or by determining an approximate value of color misregistration amount by detecting / calculating a pattern image and determining whether or not color misregistration correction is necessary. May be. Then, when the color misregistration correction is performed, the other three colors are changed from the position of the specific pattern image of another color with the black specific pattern image as a reference.
The amount of color image misregistration is precisely calculated, and a signal for correcting the color misregistration is output to the image writing controller 34, the image writing device 14 and the like based on the result of the calculation. Therefore,
The color misregistration adjustment control unit 35 has the functions of the adjustment timing detection unit and the color misregistration adjustment unit described in claim 1.

The correction of the color misregistration is performed as follows. The deviation due to the different angles in the main scanning direction is R
It is corrected by adjusting the angle of the mirror of the OS optical system. The scanning length in the main scanning direction, that is, the difference in magnification is corrected by controlling the frequency of the write clock. The deviation in the main scanning direction is corrected by controlling the writing timing and phase of the video clock. In addition, the deviation in the sub-scanning direction is due to line sync (Line Sy
It is corrected by adjusting the writing start timing of (nc) and controlling the phase of the polygon motor.

Further, the color misregistration adjustment control unit 35 includes a memory, and stores parameters for correcting the color misregistration with respect to the misregistration amount calculated from the image position of the specific pattern image. Then, in the image forming step, control is performed so that the laser beam is scanned in a corrected state based on the stored value.

When writing an image based on the image signal input from the image processing unit 31, the image writing control unit 34 determines the paper size, the image data amount, the writing start time, etc.
A signal for controlling the image writing operation is output. In addition, a part of the signal for correcting the color misregistration is also output from the image writing control unit 34. These signals, together with the signal and the image signal from the color misregistration adjustment control unit 35, the interface board (RO
It is input to the image writing device 14 via the S-I / F). Then, each color interface board (ROS-I
/ F) and the image writing device 14 to adjust the scanning timing, the clock frequency, and the skew (Ske).
w) Correction or the like is performed to correct the position where the toner image is transferred onto the recording material. That is, the first photoconductor 19K is applied to the recording material conveyed in the direction of arrow A in FIG.
From the second photoconductor 19Y, a yellow toner image from the second photoconductor 19Y, a magenta toner image from the third photoconductor 19M, and a fourth photoconductor 1
Image writing devices 14K, 14Y, 14M, 1 so that the cyan toner image is transferred from 9C in a superposed manner.
The operation of 4C is controlled.

The CCD sensor 42 is used for the transfer belt 11
The light emitted from the LED provided on the opposite side of the transparent transfer belt 11 is provided so as to face the light. The signal from the CCD sensor 42 is input to the color misregistration adjustment control unit 35, and the color misregistration amount is detected from the position of the specific pattern image.

The temperature sensor 41 is the image forming unit 12K located at the uppermost stream in the moving direction of the transfer belt 11.
And is provided closer to the fixing device 18 than the intermediate point between the image forming unit 12C located at the most downstream side and closer to the intermediate point than the image forming unit 12C located at the most downstream side, and near the support frame of the image forming unit. It is installed. This position is the third of the four image forming units 12 arranged in the order of black, yellow, magenta, and cyan from the upstream side along the transfer belt 11, that is, the vicinity of the image forming unit 12M that forms a magenta image. Also,
The vertical position is almost the same height as the support shaft of the photoconductor 19 provided in the image forming unit 12. Further, the support frame to which the temperature sensor 41 is attached is a support frame 61 at the rear of the image forming unit 12 as shown in FIG. 4, and an exhaust device at the rear of the outside air intake port 62 on the front side of the housing of the device. It is located on the downstream side of the airflow to 63.

In the image forming apparatus having the structure described above,
A color image is formed by the following steps. When the apparatus is activated, an image signal is input to the image processing unit 31 from the image reading apparatus 32 or the external apparatus 33, the transfer belt 11 and the photoconductor 19 are driven, and the charging device 1
The surface of the photoconductor 19 is uniformly charged by 3. Then, image light is emitted from the image writing device 14 based on the processed image signal, and a latent image is formed by a difference in electrostatic potential. Toner is selectively transferred to the latent image from the developing device 15 and is visualized as a toner image. This toner image is
It is transferred onto the recording paper supplied from the paper tray 21 onto the transfer belt 11. Such toner image formation / transfer is performed in each of the black, yellow, magenta, and cyan image forming units 12, and is transferred so as to be exactly overlapped on the recording paper. The recording sheet on which the toner image is transferred is sent to the fixing device 18, and is heated and pressed to fuse the toner image to the recording sheet. The recording paper on which the image has been fixed is discharged to a paper discharge tray (not shown) or, when images are to be formed on both sides, sent to the paper return path 24 and conveyed again onto the transfer belt 11. .

Next, an image color misregistration adjusting method according to claim 15 which is an operation for adjusting the misregistration of each color image in the image forming apparatus will be described. When the power of the image forming apparatus is turned on, the color misregistration adjustment is always performed before the first image is formed. At this time, the temperature detected by the temperature sensor 41 is stored in the memory and becomes the first reference temperature. After that, when the image forming operation is started and continuously performed, the operation of the color misregistration adjustment control unit 35 determines whether or not the color misregistration adjustment is necessary according to the flow shown in FIG. It is executed when it is judged necessary.

First, the temperature at the previous color misregistration adjustment, that is, the reference temperature is read from the memory (S1). Also,
The current temperature is detected by the temperature sensor 41 (S
2). The temperature at this time is reduced in error by performing the measurement a plurality of times (S3). These measured values of a plurality of times are averaged to calculate the current temperature (S4).
Further, the difference between the current temperature and the temperature at the previous color misregistration adjustment is calculated (S5). This temperature difference is compared with a predetermined value which is set in advance (S6), and when it is smaller than the predetermined value, the series of steps is ended. On the other hand, when the temperature difference is larger than the predetermined value, the specific pattern image is formed on the transfer belt 11 and the color misregistration adjustment is executed (S
7).

The contents of this color misregistration adjustment are as follows. First, an image signal of a specific pattern image is output from the image processing unit 31, and a latent image is formed and developed on the photoconductor 19 as with a normal image. The formed toner image is formed over the length of one round of the transfer belt and is directly transferred onto the transfer belt 11. This specific pattern image (sample pattern) is detected by the CCD sensor 42, and the color shift amount is calculated from the position of the image of each color. Then, a correction signal is output so as to correct the color shift amount, and the color shift correction is executed.

Further, as described above, the color misregistration adjustment is always performed until the color misregistration is corrected when it is determined from the amount of temperature change that the color misregistration adjustment is necessary. As described above, when it is determined that the color misregistration adjustment is necessary, a simple specific pattern image (check pattern), for example, a pattern image of about one rotation of the photosensitive drum is formed, and the approximate value of the color misregistration amount is calculated and actually It may be possible to determine again whether or not to perform color misregistration correction.

In the flow shown in FIG. 7A, when it is judged that the color shift adjustment is necessary, a simple check pattern image is formed (S21), and the approximate value of the color shift amount is calculated (S2).
2). It is judged from this rough value whether or not the color shift is actually required to be corrected (S23), and if necessary, a sample pattern image is formed (S24). This sample pattern image is
For example, the color shift amount can be accurately detected by forming the transfer belt 11 for one round in order to eliminate the influence of speed unevenness of the transfer belt 11. The color shift amount is calculated by detecting this sample pattern with the CCD sensor 42 (S25), and the actual color shift correction is executed (S26).

The flow shown in FIG. 7B forms both a simple check pattern image and a sample pattern image for precise color shift detection when it is determined that color shift adjustment is necessary ( S31), it is determined from the detection result (S32) of the check pattern image whether color shift correction is necessary (S33). Then, when it is determined that the color misregistration correction is necessary, a precise color misregistration amount is immediately calculated from the detection result of the sample pattern (S34), and the color misregistration correction is executed (S35).

After that, the current temperature is stored in the memory as a new reference temperature (S8), and the series of steps is completed. The process of detecting the temperature and determining whether color misregistration adjustment is necessary as shown in FIG. 5 is continuously performed while the power of the image forming apparatus is in the ON state, and is constant. Every time the time elapses, or every time a fixed number of images are formed.

In the above process, the color misregistration adjustment is executed when the temperature difference exceeds a preset predetermined value. However, as shown in FIG. 6, the color misregistration adjustment is executed. Each time (after the color misregistration adjustment is executed in the example shown in FIG. 7), the temperature change amount until the next color misregistration adjustment can be reset (S11). The temperature change amount set each time the color misregistration adjustment is performed may be determined according to the temperature when the color misregistration adjustment is performed, or may be determined according to the content of the color misregistration adjustment. It may be one.

In the case where the amount of temperature change until the next color misregistration adjustment is determined according to the content of the color misregistration adjustment,
For example, consider the following. -If the amount of color misregistration is large when the color misregistration is adjusted, set the temperature change amount until the next color misregistration adjustment to a small value. If the amount of color misregistration is small, the amount of temperature change until the next color misregistration adjustment is set to be large. When detecting the approximate value of the color misregistration amount from the check pattern and determining whether to actually perform the color misregistration correction as in the process shown in FIG. 7, the color misregistration amount is extremely small with the approximate value.
When correction is not performed, the amount of temperature change until the next color misregistration adjustment is set is set large. Further, when the color misregistration amount is slightly large, but is not so large as to perform the color misregistration correction, the temperature change amount until the next color misregistration adjustment is set to be small. Further, when the color misregistration amount reaches the amount to be subjected to color misregistration correction and the color misregistration correction is executed, the temperature change amount until the next color misregistration adjustment is set to be large.

In the embodiment described above, the temperature sensor 41 is used.
However, there are cases where the temperature sensor cannot be installed at the optimum position due to the requirements of the layout in the device. An image forming apparatus in which such a temperature sensor cannot be installed at an optimum position, which is an embodiment of the invention described in claim 6 or 7, will be described below. In this image forming apparatus, the temperature sensor is installed at a position slightly distant from the optimum position, but the other image forming units, the image processing unit, and the image writing control unit have the same configuration as in the above embodiment. Further, as shown in Table 1, for example, a table for converting the amount of temperature change detected by the temperature sensor into the amount of temperature change detected at an optimum position is provided in the color misregistration adjustment control unit of the image forming apparatus. A conversion table is stored, and the temperature change amount is converted using this table. This table is created in advance by experiments or the like.

[0069]

[Table 1]

In Table 1, the conversion value differs depending on each temperature band, and which conversion value to use is selected from the detected temperatures. When converting the temperature change amount in this table, when the temperature is 18 ° C. and the temperature change amount is detected as A ° C. by the temperature sensor, the temperature change amount X ° C. at the position considered to be optimum is calculated by the following formula. To be done. X (° C.) = A (° C.) × 2.8 According to the converted temperature change amount thus obtained, the timing for performing the color misregistration adjustment is set in the same manner as in the above embodiment, and the color misregistration adjustment is performed at an appropriate time. Be seen. Alternatively, these tables may be set for each outside temperature, and the table may be selected while monitoring the outside temperature to more accurately determine the color misregistration adjustment time.

[0071]

As described above, in the image forming apparatus or the image color misregistration adjusting method of the present invention, the temperature detecting means is installed at an appropriate position, and the color information is obtained based on the temperature information obtained by the temperature detecting means. Since the time when the misregistration is adjusted is determined, the color misregistration is adjusted at an appropriate time. Therefore,
By adjusting the color shift more than necessary, it is possible to avoid the deterioration of efficiency caused by suspending the image forming operation during that period, and the situation where the image forming operation is continued with the color shift occurring.
A good image can always be obtained efficiently. Also, if the temperature sensor cannot be installed at the position considered to be optimum, the detected value of the temperature sensor is converted into the value detected at the position considered to be optimum, so as in the above, an efficient and good image can be obtained. Obtainable.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus that is an embodiment of the present invention.

2 is a block diagram showing a configuration for adjusting color misregistration in the image forming apparatus of FIG.

3 is a diagram showing a specific pattern image for detecting a color shift amount used in the image forming apparatus of FIG.

FIG. 4 is a plan view showing a position where a temperature sensor of the image forming apparatus shown in FIG. 1 is provided.

FIG. 5 is a flow chart showing a process of determining the timing for performing color misregistration adjustment in the image forming apparatus shown in FIG.

FIG. 6 is a flowchart showing another example of the step of determining the timing for performing color misregistration adjustment in the image forming apparatus shown in FIG.

FIG. 7 is a flowchart showing steps of color misregistration adjustment in the image forming apparatus shown in FIG.

FIG. 8 is a relationship between the temperature inside the apparatus and the time and the relationship between the amount of color misregistration and the time of the image forming apparatus having four image forming units (K for black, Y for yellow, M for magenta, and C for cyan). FIG.

FIG. 9 is a diagram showing a relationship between a temperature change amount per unit time and time in each unit in the image forming apparatus having four image forming units.

FIG. 10 is a diagram showing a color shift occurrence amount per unit time between color images in an image forming apparatus having four image forming units.

[Explanation of symbols]

 10 image forming unit 11 transfer belt 12 image forming unit 13 charging device 14 image writing device 15 developing device 16 transfer device 17 cleaning device 18 fixing device 19 photoconductor 21 paper tray 22 paper transport path 23 paper feed roller 24 paper return path 31 image Processing unit 32 Image reading device 33 External device 34 Image writing control unit 35 Color shift adjustment control unit (adjustment timing detection means) 36 System control unit 41 Temperature sensor 42 CCD sensor 61 Support frame 62 Outside air intake port 63 Exhaust device

Claims (15)

[Claims] 1. An image forming apparatus for forming a composite image by sequentially transferring images from a plurality of image forming means arranged at a predetermined interval onto a moving transfer body to detect the temperature inside the image forming apparatus. According to the temperature detection means and the temperature information based on the detection result of the temperature detection means,
Adjustment time detection means for detecting the time when the color misregistration adjustment is performed between each image, and the case where the color misregistration correction is necessary by correcting the color misregistration or judging the necessity of the color misregistration correction based on the detection result. A color misregistration adjusting unit that performs a correction operation and returns to a normal cycle without performing a correction when unnecessary, and the temperature detecting unit is near a support frame that contributes to support the plurality of image forming units. The image forming apparatus is located at. 2. A plurality of image forming means arranged at a predetermined interval to successively transfer images onto a moving transfer body to form a composite image, and the composite image is fixed to a fixing object by heat fixing means. In the image forming apparatus, the temperature detecting means for detecting the temperature in the image forming apparatus, and the temperature information based on the detection result of the temperature detecting means,
Adjustment time detection means for detecting the time when the color misregistration adjustment is performed between each image, and the case where the color misregistration correction is necessary by correcting the color misregistration or judging the necessity of the color misregistration correction based on the detection result. Has a color misregistration adjusting means for performing a correction operation and returning to a normal cycle without making a correction if unnecessary, and the temperature detecting means with an image forming means located at the most upstream side in the transfer body moving direction. It is characterized in that it is located closer to the heat fixing means than an intermediate point with the image forming means located at the most downstream side, and closer to the intermediate point than a downstream side end portion of the image forming means located at the most downstream side. Image forming apparatus. 3. The four image forming means are arranged in parallel to the transfer body moving direction, and the temperature detecting means is located near the third image forming means from the transfer body moving direction. The image forming apparatus according to claim 2, wherein the image forming apparatus comprises: 4. An image forming apparatus for forming a composite image by sequentially transferring images from a plurality of image forming means arranged at a predetermined interval onto a moving transfer body to detect the temperature inside the image forming apparatus. According to the temperature detection means and the temperature information based on the detection result of the temperature detection means,
Adjustment time detection means for detecting the time when the color misregistration adjustment is performed between each image, and the case where the color misregistration correction is necessary by correcting the color misregistration or judging the necessity of the color misregistration correction based on the detection result. Has a color misregistration adjusting means for performing a correction operation, and has an air conditioning means for taking in outside air into the image forming apparatus and discharging the air inside the image forming apparatus to the outside of the apparatus. An image forming apparatus characterized in that the image forming apparatus is located closer to an in-apparatus air discharge section than an outside air intake section. 5. A photosensitive drum provided in each of a plurality of image forming means arranged at a predetermined interval,
In an image forming apparatus that sequentially forms images on a moving transfer body to form a composite image, a temperature detecting unit that detects a temperature inside the image forming apparatus and a temperature information based on a detection result of the temperature detecting unit is used. ,
Adjustment time detection means for detecting the time when the color misregistration adjustment is performed between each image, and the case where the color misregistration correction is necessary by correcting the color misregistration or judging the necessity of the color misregistration correction based on the detection result. And a color misregistration adjusting means for performing a correction operation, and the temperature detecting means is located on a line connecting the rotational axis positions of the respective photoconductor drums or in the vicinity of an extension thereof. Image forming apparatus. 6. An image forming apparatus for forming a composite image by sequentially transferring images from a plurality of image forming means arranged at a predetermined interval onto a moving transfer body to detect the temperature inside the image forming apparatus. According to the temperature detection means and the temperature information based on the detection result of the temperature detection means,
Adjustment time detection means for detecting the time when the color misregistration adjustment is performed between each image, and the case where the color misregistration correction is necessary by correcting the color misregistration or judging the necessity of the color misregistration correction based on the detection result. Has a color shift adjusting means for executing a correction operation, and a converting means for converting the temperature information into an optimum position according to the temperature zone of the detected temperature, and an adjusting timing detecting means according to the converted information value. An image forming apparatus characterized by operating the. 7. An outside air temperature detecting means for detecting the outside air temperature of the image forming apparatus, wherein the converting means selects and uses a different conversion table according to the detected temperature of the outside air temperature detecting means to convert the temperature information. The image forming apparatus according to claim 6, wherein: 8. The image formation according to claim 1, wherein the temperature information based on the detection result of the temperature detection means is that the temperature in the image forming apparatus has reached a predetermined temperature. apparatus. 9. The image according to claim 1, wherein the temperature information based on the detection result of the temperature detection means is that a predetermined temperature change has occurred in the temperature inside the image forming apparatus. Forming equipment. 10. The adjustment timing detection means operates when a predetermined temperature change occurs from a reference temperature in the image forming apparatus, sets a new reference temperature, and performs the same operation based on the new reference temperature. The image forming apparatus according to claim 9, which is repeated. 11. The image forming apparatus according to claim 10, wherein the new reference temperature is set to a detection temperature when the color misregistration adjusting unit is activated. 12. The image forming apparatus according to claim 9, wherein the predetermined value of the predetermined temperature change is determined according to the adjustment result of the color shift adjusting means. 13. The image forming apparatus according to claim 10.11.12, wherein a predetermined value of the predetermined temperature change is determined according to each of the set reference temperatures. 14. The color misregistration adjusting means is operated from the time the power of the image forming apparatus is turned on until the first image formation is started, and the detected temperature immediately after that is set to the first reference temperature. The image forming apparatus according to 11.12.13. 15. An image forming apparatus for forming a composite image by sequentially transferring an image onto a moving transfer member from a plurality of image forming means arranged at a predetermined interval, and detecting the temperature inside the image forming apparatus. However, when a predetermined temperature change from the reference temperature occurs in the detected temperature, a color shift between the images is detected, and after adjusting the color shift based on the detection result, a new reference temperature is set. An image color misregistration adjusting method for an image forming apparatus, comprising: setting and repeating the same operation based on a new reference temperature.