JP2013120305A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: Conventionally, in order to configure two registration mark detection sensors on the left and right, it is necessary to prepare a plurality of projection LED driving circuits, input waveform shaping circuits, pulse width measurement circuits, etc. in addition to the registration mark detection sensors. The pulse width measurement circuit is expensive because it uses the unique function of the central processing unit, which is one of the causes of cost increase.
According to the present invention, a plurality of outputs of a registration mark detection sensor for detecting a registration pattern formed on a belt are combined into one signal by calculation, and a circuit is shared, thereby reducing color at low cost. It is possible to provide an image forming apparatus capable of obtaining a high-quality color image without deviation.
[Selection] Figure 1

Description

  The present invention relates to an image forming apparatus including a plurality of image carriers and capable of forming a toner image formed on each image carrier on a recording medium.

  Conventionally, as a color image forming apparatus, an electrostatic latent image is formed by irradiating a photosensitive drum, which is a photosensitive medium, with a laser beam by an electrophotographic process, and a plurality of image forming units for developing the electrostatic latent image are provided. Then, a color image is obtained by superimposing and transferring images of a plurality of colors onto an intermediate transfer member that is an image carrier, and recording paper that is also an image carrier is sequentially conveyed to the image forming unit of the intermediate transfer member by a transfer belt. An apparatus for transferring a color image onto a recording paper to obtain a color image formed product is known. There is also an image forming apparatus of a type that has a structure very similar to this, and that directly transfers an image from a photosensitive drum to a recording sheet conveyed by a transfer belt for conveying the recording sheet, that is, a belt-shaped conveying unit.

  When this type of image forming apparatus is used, an electrostatic latent image is formed on each photosensitive drum and transferred to a recording sheet on an intermediate transfer member or transfer belt. On the transfer body or recording paper, an image with a color shift and a color shift is formed as the degree further progresses. These phenomena significantly degrade the image quality.

  Therefore, conventionally, a registration mark, which is a pattern image for registration correction formed on each intermediate transfer member or transfer belt from each photosensitive drum, is read by a registration mark detection sensor, which is a pattern image detection means such as an optical sensor, and each color is read. The registration deviation on the photosensitive drum corresponding to is detected, the image signal to be recorded is electrically corrected, and the reflection mirror provided in the laser beam optical path is driven to correct the optical path length change. It is carried out.

  As a registration correction method, the color shift is calculated by measuring the time when each color pattern is detected by the optical sensor with reference to a certain color pattern and calculating how far the measured time is from the theoretical value. A method for determining the amount is common (see, for example, Patent Document 1).

  Various resist patterns are considered. Registered at both ends in the width direction (hereinafter referred to as the main scanning direction) perpendicular to the moving direction (hereinafter referred to as the sub-scanning direction) of the conveyance belt and intermediate transfer belt (hereinafter simply referred to as the belt when there is no misunderstanding). A configuration in which a pattern is formed and the pattern is read by two registration mark detection sensors is often used.

JP 2002-174992 JP

  However, in order to configure the two registration mark detection sensors on the left and right, it is necessary to prepare a plurality of projection LED drive circuits, input waveform shaping circuits, pulse width measurement circuits, etc. in addition to the registration mark detection sensors. The pulse width measurement circuit is expensive because it uses the unique function of the central processing unit, which is one of the causes of cost increase.

  Accordingly, an object of the present invention is to combine a plurality of outputs of a registration mark detection sensor that detects a registration pattern formed on a belt into one signal by calculation and to share a circuit, thereby reducing color misregistration at a low cost. It is an object to provide an image forming apparatus capable of obtaining a high-quality color image.

  In order to achieve the above object, in the present invention, an image forming apparatus is configured as follows.

  1) A toner image carrier having a plurality of image carriers on which toner images are formed for each toner color, and comprising an intermediate transfer member or a transfer material carrier onto which a plurality of toner images on the image carrier are transferred. A plurality of toners independently at both ends in a direction perpendicular to the conveying direction of the toner image carrier, and an image forming unit that performs latent image formation, development on the plurality of image carriers, and transfer to the toner image carrier; A means for forming a positional deviation pattern using a plurality of detection sensors for detecting the positional deviation pattern, and a central processing unit for calculating a deviation amount of the detection pattern with respect to a reference pattern from the output of the detection sensor, Computation means for inputting the outputs of the plurality of detection sensors to the central processing unit as one computation result.

  As described above, according to the present invention, a plurality of outputs of the registration mark detection sensor that detects the registration pattern formed on the belt is combined into one signal by calculation, and the circuit is shared, thereby reducing the cost. Thus, it is possible to provide an image forming apparatus capable of obtaining a high-quality color image without color misregistration.

Block diagram of the present invention Diagram for explaining the first embodiment Cross-sectional view of main parts of color image forming apparatus of the present invention Explanation of cash register sensor Output characteristics of registration sensor Explanatory drawing of positional relationship between registration sensor and registration pattern Explanatory diagram of how to calculate the registration error Explanation of cash register pattern detection method LED drive circuit explanatory diagram Explanatory drawing of calculation means The figure explaining operation of the LED drive circuit Flowchart explaining the first embodiment Diagram for explaining the second embodiment Flowchart explaining the second embodiment Flowchart explaining the third embodiment

[Example 1]
Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 3 is a cross-sectional view of the main part of a color image forming apparatus to which the present invention is applied.

  In this color image forming apparatus, in order to increase the speed of color image output, a plurality of photoconductors are stacked and a toner image is sequentially transferred in multiple layers (generally called a 4-drum tandem system).

  As shown in FIG. 3, this image forming apparatus has a plurality of image forming units Y114, M116, C115, and K116 (in order, a yellow unit, a magenta unit, a cyan unit, and a black unit), and passes through each image forming unit. A conveyor belt 105 is provided. In each of the image forming units Y114, M116, C115, and K116, cylindrical photosensitive members (photosensitive drums) 106, 107, 108, and 109 as electrostatic latent image carriers are rotatably supported. Reference numerals 118, 119, 120, and 121 denote laser exposure apparatuses that expose the photosensitive drums 106, 107, 108, and 109, respectively.

  The conveyor belt 105 is driven by the driving roller 104.

  Images manifested on each photosensitive drum are sequentially transferred onto a transfer material P by transfer rollers 110, 111, 112, and 113 to form a full-color image.

  The operation of the image forming apparatus configured as described above will be described using the image forming unit Y114 as an example.

  The photosensitive drum 106 has a light semiconductive layer on the surface of a conductive substrate such as aluminum, and rotates in the direction of arrow a. Then, after the surface is uniformly negatively charged by the primary charger 141, exposure is performed by the laser exposure device 118, and an electrostatic latent image corresponding to the original is formed. The developing device 151 performs development using negatively charged toner, and forms a toner image corresponding to the electrostatic latent image on the surface of the photosensitive drum 106. The toner image formed on the surface of the photosensitive drum 106 is transferred to the transfer material P by the transfer roller 110.

  The above operation is performed in each image forming unit with a predetermined timing, and the toner image formed on each photosensitive drum is transferred onto the transfer material P.

  The transfer material P onto which the toner image has been transferred is supplied to the fixing device 122, and is fixed by being heated and pressurized to obtain a full color image.

  Further, two optical sensors (hereinafter referred to as registration sensors) 127 for detecting registration are arranged on the left and right (main scanning direction) facing the conveyance belt 105.

  Next, the configuration and characteristics of the registration sensor 127 will be described.

  As shown in FIG. 4, the registration sensor 127 includes a light emitting element 401 such as an LED and a light receiving element 402 such as a photodiode, and irradiates the registration pattern 403 on the conveyor belt 105 with infrared light from the light emitting element 401. The position of the registration pattern 403 is detected by measuring the regularly reflected light from the light receiving element 402. A curve A in FIG. 5 represents the output characteristics of the registration sensor 127, and the sensor output (the amount of light received by the photodiode 402) decreases as the amount of applied toner increases. This is because when the amount of toner on the transport belt increases, the irradiation light is diffused by the toner, and at the same time, the surface of the transport belt that is the base is hidden and the regular reflection light from the transport belt decreases.

  In order to obtain the same detection performance between the left and right registration sensors, it is necessary to align the light emission amounts of the left and right registration sensors, that is, to set the drive currents individually.

  The LED driving circuit 160 can change the light emission amount of the LED by changing the driving current for the LED. For example, a PWM waveform is input from the drive signal output circuit 167, and the LED light emission amount is made variable according to the duty ratio. As shown in FIG. 9, the drive circuit 160 changes the LED drive current after integrating the input PWM signal. Integrate the input signal using R601 and C601. R602 determines the LED drive current. Usually, the LED has a ratio of the amount of emitted light to the input current, that is, an individual difference in so-called luminous efficiency. In order to obtain the same amount of emitted light with a plurality of LEDs, it is necessary to individually set the drive current. The LED light is reflected by the conveyor belt 105. The reflected light is received by the left and right registration sensors 127 and separately input to the A / D conversion circuit 165 for the right registration sensor and the A / D conversion circuit 166 for the left registration sensor. The central processing unit sets the drive signal output circuit (167, 168) so that the outputs of the two A / D conversion circuits (165, 166) are equal.

  As shown in FIG. 1, by providing the left and right registration sensors individually with the LED drive circuit 160, it is possible to align the light emission amounts of the left and right registration sensors, and the same detection performance can be obtained with the left and right registration sensors.

  The main configuration of the color image forming apparatus used in the present invention has been described above.

  Next, a registration deviation amount detection method will be described.

  FIG. 6 is an explanatory diagram of the positional relationship between the registration sensor and the registration pattern in the present embodiment. Two registration sensors 127 are arranged in the main scanning direction so that the registration patterns formed on the left and right on the conveyor belt 105 can be detected.

  The registration pattern R-c is a registration pattern for detecting a coarse adjustment amount of registration in the sub-scanning direction, and is sequentially formed with yellow, magenta, cyan, and black toners. The hatched registration patterns R-f1, R-f2 and L-f1, L-f2 are registration patterns for detecting fine adjustment amounts of registration in the main scanning direction and registration in the sub-scanning direction. , Magenta, yellow, cyan, yellow, black, and yellow toner.

  A method of calculating the registration error using the registration pattern will be described in detail with reference to FIG.

First, the coarse registration detection in the sub-scanning direction will be described. In FIG. 7 (1), R-cY represents an actually formed registration pattern for detecting sub-registration in the sub-scanning direction, and R-cY 'represents a registration pattern formed when the registration error is zero. Represents. Here, assuming that the timing at which the right registration sensor detects the registration pattern R-cY is T _R-cY , and the timing at which the ideal registration pattern is to be detected is T _R-cY ′, the sub-scanning direction of the Y registration pattern in the right registration sensor The registration deviation PD _RCY can be calculated by the following equation.

PD _RCY = (T _R-cY -T _{R-cY '} ) × ps (ps is the moving speed of the belt) ...... (Equation 1)
By the same method, the registration deviations PD _RCM, PD _RCC, PD _{RCK of the} right registration sensor in the M, C, and K sub-scanning directions and the registration deviation PD _{LCY in} the Y, M, C, and K sub-scanning directions of the left registration sensor PD _LCM, PD _LCC, PD _LCK can be detected.

Next, detection of fine registration in the main scanning direction and the sub-scanning direction will be described. In FIG. 7 (2), R-f1Y1, R-f1Y2, R-f2Y1, R-f2Y1, represent the yellow registration detection patterns actually formed, and R-f1Y1, R-f1Y2 , Represents a magenta registration detection registration pattern. The registration pattern for fine adjustment detection in the main scanning direction and the sub-scanning direction is an oblique line pattern composed of lines with an angle of 45 degrees, and the passage timings of these patterns are _designated as TR _-f1Y1 , TR _-f1Y2 , TR _-f2Y1 , _{respectively.} , T _R-f2Y1 , T _R-f1M1 , T _R-f2M1 , the registration shift SD _{RY in} the main scanning direction of the Y registration pattern in the right registration sensor can be calculated by the following equation.

SD _RY = {(T _R-f1M1 -T _R-f1Y1 )-(T _R-f1Y2 -T _R-f1M1 )-(T _R-f2M1 -T _R-f2Y1 ) + (T _R-f2Y1 -T _R-f2M1 )} / 4 × ps
...... (Formula 2)
Similarly, the fine adjustment registration deviation PD _RYf in the sub-scanning direction can be calculated by the following equation.

PD _RYf = {(T _R-f1M1 -T _R-f1Y1 )-(T _R-f1Y2 -T _R-f1M1 ) + (T _R-f2M1 -T _R-f2Y1 )-(T _R-f2Y1 -T _R-f2M1 )} / 4 × ps
...... (Formula 3)
Next, a method for detecting the time when the registration pattern has passed through the registration sensor will be described with reference to FIG.

  FIG. 8A shows the sensor output when the registration pattern passes through the registration sensor. When the registration sensor detects a pattern other than the registration pattern (belt base), the amount of specular reflection light incident on the light receiving member is large, so the sensor output is large and the sensor output is constant. When the registration pattern passes through the registration sensor unit, the amount of specularly reflected light incident on the light receiving member by the toner decreases, and the sensor output decreases. Thereafter, the sensor output A is output as a digital signal B through a comparison circuit (not shown). In the figure, a dotted line C represents a threshold value of the comparison circuit, and an output signal B from the comparison circuit is turned on when the threshold value C is equal to or less. Then, the center T of the ON signal portion is set as a registration pattern detection timing.

  The above is the method of detecting the registration deviation amount in the image forming apparatus.

  In the registration correction, the color misregistration is corrected by adjusting the Y, M, C, and K image signal transmission timings according to the detected value of the registration misregistration amount.

  In this example, only the effect on the registration error in the vertical direction (sub-scanning direction) and the registration error in the main scanning direction has been described, but the main scanning magnification difference, the inclination deviation in the main scanning direction (SKEW), etc. Similar effects can be obtained.

  Next, a calculation means for inputting the outputs of a plurality of registration sensors as one calculation result to the central processing unit, which is a feature of the present invention, will be described with reference to FIG.

  Usually, when performing registration detection, a total of two registration sensors are arranged, one at each end of the belt. This is to detect not only the color shift between the image forming units but also the main scanning magnification shift and the tilt shift in the main scanning direction within one image forming unit.

  In the present invention, the logical product of the right registration sensor output 201 and the left registration sensor output 202 is calculated by the arithmetic means 161. FIG. 10 shows a circuit example of the calculation means 161. The right registration sensor output 201 is input to the comparator 701, and binarization is performed. Similarly, the left registration sensor output 202 is input to the comparator 702, and binarization is performed. When an open collector output comparator is used for the comparators 701 and 702, the logical product of two register sensor outputs can be obtained by connecting the respective outputs.

  The calculation result 203 is input to the pulse width measurement circuit 164. Here, logical operation using a comparator is used as the arithmetic means, but other arithmetic means such as an adder circuit may be used.

  Here, left and right registration detection registration patterns are formed at positions separated in the belt conveyance direction. Therefore, the left registration sensor and the right registration sensor do not detect a registration pattern at the same time. Therefore, the central processing unit 162 can obtain the arrival time T of all the registration patterns at the registration sensor by inputting the obtained calculation result 203 to the pulse width measurement circuit. Thereafter, various registration deviations can be calculated based on the above-described calculation formula.

  In FIG. 2, a right coarse adjustment pattern 204 indicates a coarse adjustment pattern formed for the right registration sensor. Similarly, the coarse adjustment pattern formed for the left registration sensor is the left coarse adjustment pattern 205, the fine adjustment pattern formed for the right registration sensor is the right fine adjustment pattern 206, and the fine adjustment pattern formed for the left registration sensor is The left fine adjustment pattern 207 is assumed. The image forming apparatus according to the present exemplary embodiment forms the adjustment patterns 204 to 207 at positions separated in the belt conveyance direction.

  FIG. 12 shows a flowchart for explaining the operation of the central processing unit 162 of this embodiment.

  First, the LED light amount is adjusted before forming the registration pattern (901). The conveyance belt on which the toner image is not formed is illuminated with an LED as an illumination means, and the amount of reflected light is detected by a registration sensor. The LED drive circuit is adjusted by the drive signal output circuit so that the amount of reflected light is constant.

  Next, a registration pattern is created on the conveyor belt 105 (902 to 905). The photosensitive drum 106 in the image forming unit 114 is exposed by a laser exposure device 118, and a latent image of a Y registration pattern is created on the photosensitive drum. The latent image on the photosensitive drum is developed by the developing device 151 and then transferred onto the conveying belt 105. Similarly, M, C, and K registration patterns are respectively created by the image forming units 115 to 117, and sequentially transferred onto the conveying belt 105. As shown in FIG. 2 by combining the registration patterns formed with Y, M, C, and K toners, the right coarse adjustment registration pattern 204 is created (902), the left coarse adjustment registration pattern 205 is created (903), The right fine adjustment registration pattern 206 creation (904) and the left fine adjustment registration pattern 207 creation (905) are sequentially performed.

Next, the time T at which the registration pattern arrives at the registration sensor is sequentially detected (906 to 909). Arrival times T _R-cY , T _R-cM , T _R-cC , T _R-cK , T _L-cY , T _L-cM , T _L-cC , T _L-cK and left and right coarse adjustment register patterns After _detecting the arrival time of the fine adjustment registration pattern, for example, TR _-f1Y1 , TR _-f1Y2 , TR _-f2Y1 , TR _-f2Y1 , TR _-f1M1 , TR _-f2M1 , (Equation 1), (Equation 1) 2) By using (Equation 3), the coarse registration error amount PD _ncm in the sub-scanning direction, the registration error amount SD _nm in the main scanning direction, and the fine adjustment registration error PD _{rmf in the} sub-scanning direction (n = R, L / m = Y, M, C, K) is calculated (910).

  As shown in FIG. 16, the LED drive circuit 160 can be configured by only one for the LEDs of the left and right registration sensors. When the right registration sensor detects the registration pattern, the left and right registration sensor LEDs are simultaneously driven so that the amount of light is appropriate for the LED of the right registration sensor. Similarly, when the left registration sensor detects a registration pattern, the left and right registration sensor LEDs are simultaneously driven so that the amount of light is appropriate for the LED of the left registration sensor. As shown in FIG. 11, the right sensor setting value 802 is set in the drive signal output circuit 167 at the timing when the right coarse adjustment pattern 204 reaches the right registration sensor. Similarly, a left sensor setting value 803 is set for the left coarse adjustment pattern 205, a right sensor setting value 802 is set for the right fine adjustment pattern 206, and a left sensor setting value 803 is set for the left fine adjustment pattern 205. In this way, by forming the position shift patterns for the left and right sensors at positions separated in the transport direction of the transport belt, it is possible to have only one LED drive circuit 160.

  As described so far, by inputting the outputs of a plurality of registration sensors as a single calculation result to the central processing unit, it is possible to obtain a high-quality color image without color misregistration at low cost. Can be provided.

[Example 2]
Since the basic configuration of the second embodiment is the same as that of the first embodiment except that the registration pattern for coarse registration detection in the sub-scanning direction is formed at the same position in the transport direction, detailed description thereof is omitted.

As shown in FIG. 13, in this embodiment, the registration pattern for coarse registration detection in the sub-scanning direction is formed at the same position in the transport direction. Therefore, this registration pattern is formed so as to reach the left and right registration sensors almost simultaneously. Actually, since it is affected by the deviation of the inclination in the main scanning direction, a slight deviation occurs in the left and right arrival times. In the present invention, since the logical product of the outputs of the left and right registration sensors is input to the central processing unit 162, the approximate center value of the deviation between the left and right sensors is determined as the measurement value of the registration pattern. Here the sub-scanning direction misregistration amount PD _CY of Y registration pattern of lateral registration sensor is expressed by the following equation.

PD _CY = (T _cY -T _{cY '} ) × ps (ps is the moving speed of the belt) (Equation 4)
Similarly, registration deviation amounts PD _CM, PD _{CC, and} PD _CK in the sub-scanning direction of M, C, and K can be obtained.

  FIG. 14 shows a flowchart for explaining the operation of the central processing unit 162 of this embodiment.

  First, the LED light amount is adjusted before forming the registration pattern (1101). The conveyance belt on which the toner image is not formed is illuminated with an LED as an illumination means, and the amount of reflected light is detected by a registration sensor. The LED drive circuit is adjusted by the drive signal output circuit so that the amount of reflected light is constant.

Next, a registration pattern is created on the conveyor belt 105 (1102 to 1105). The photosensitive drum 106 in the image forming unit 114 is exposed by a laser exposure device 118, and a latent image of a Y registration pattern is created on the photosensitive drum. The latent image on the photosensitive drum is developed by the developing device 151 and then transferred onto the conveying belt 105. Similarly, M, C, and K registration patterns are respectively created by the image forming units 115 to 117, and sequentially transferred onto the conveyance belt 105. By combining registration patterns formed with Y, M, C, and K toners, coarse adjustment registration pattern creation (1102), right fine adjustment registration pattern creation (1103), left fine adjustment registration pattern creation (1104) ) In order.
Next, the time T at which the registration pattern arrives at the registration sensor is sequentially detected (1105 to 1107). Arrival time T _cY of coarse registration _{pattern, T cM, T cC, T} cK and fine arrival of adjustment registration pattern time e.g. _{T R-f1Y1, T R-} f1Y2, T R-f2Y1, T R-f2Y1, T after detecting the _{R-f1M1, T R-f2M1} , ( equation 2), (equation 3), (equation 4) sub-scan direction of the coarse misregistration amount PD _cm using, in the main scanning direction misregistration amount SD _nm , a fine registration displacement PD _rmf (n = R, L / m = Y, M, C, K) in the sub-scanning direction is calculated (1108).

  Here, the registration deviation amount in the sub-scanning direction detected with the registration pattern for coarse registration registration detection in the sub-scanning direction is for coarse adjustment. Therefore, the method according to this embodiment that measures the right and left deviation amounts simultaneously is sufficient. Accuracy can be obtained.

  Compared to the first embodiment, in this embodiment, it is not necessary to prepare the registration pattern for detecting the coarse adjustment registration in the sub-scanning direction separately, so that the time required for registration detection can be shortened.

  As described above, according to this embodiment, the registration detection pattern for coarse registration detection in the sub-scanning direction is formed at the same position in the transport direction, so that an image with a short registration detection time can be obtained even at a low cost. A forming apparatus can be provided.

[Example 3]
Since the basic configuration of the third embodiment is the same as that of the first embodiment except that the registration pattern for registration detection in the main scanning direction is formed based on the result of detection of the coarse adjustment registration in the sub-scanning direction, a detailed description will be given. Omitted.

  In the present invention, the registration patterns for the left and right registration sensors are formed at positions separated from each other in the transport direction. Therefore, the registration detection time becomes longer than in the conventional example in which each is formed at the same position in the transport direction. In order to minimize the detection time, it is desirable to form the registration patterns for the left and right registration sensors as close as possible to the conveyance direction. However, when the registration pattern is formed, it is not possible to know how much registration deviation exists in the main scanning direction and the sub-scanning direction.

  Therefore, in this embodiment, the fine adjustment resist pattern is formed after correcting the shift in the sub-scanning direction based on the detection result of the coarse adjustment resist pattern. For this reason, the distance between the registration patterns for the left and right registration sensors can be brought close to the maximum registration deviation amount assumed in the main scanning direction.

  FIG. 15 shows a flowchart for explaining the operation of the central processing unit 162 of this embodiment.

  First, the LED light amount is adjusted before forming a registration pattern (1201). The conveyance belt on which the toner image is not formed is illuminated with an LED as an illumination means, and the amount of reflected light is detected by a registration sensor. The LED drive circuit is adjusted by the drive signal output circuit so that the amount of reflected light is constant.

  Next, a registration pattern is created on the conveyor belt 105 (1202 to 1203). The photosensitive drum 106 in the image forming unit 114 is exposed by a laser exposure device 118, and a latent image of a Y registration pattern is created on the photosensitive drum. The latent image on the photosensitive drum is developed by the developing device 151 and then transferred onto the conveying belt 105. Similarly, M, C, and K registration patterns are respectively created by the image forming units 115 to 117, and sequentially transferred onto the conveying belt 105. By combining registration patterns formed with Y, M, C, and K toners, right rough adjustment pattern creation (1202) and left rough adjustment pattern creation (1203) are sequentially performed.

  Next, the time T at which the registration pattern arrives at the registration sensor is sequentially detected (1204 to 1205).

After detecting the arrival times T _cY, T _cM , T _cC , T _cK of the coarse adjustment registration pattern, the provisional sub-scanning direction color misregistration correction amount PD _cm (m = Y, M, C, K) is calculated (1206).

  Next, after correcting the amount of deviation in the sub-scanning direction using the provisional color misregistration correction amount, the right fine adjustment registration pattern creation (1207) and the left fine adjustment registration pattern creation (1208) are performed in the same manner as the coarse adjustment pattern. I do.

Next, the time when the fine adjustment pattern arrives at the registration sensor, for example, TR _-f1Y1 , TR _-f1Y2 , TR _-f2Y1 , TR _-f2Y1 , TR _-f1M1 , TR _-f2M1, is sequentially detected (1209 to 1210). After detecting the arrival times of all fine adjustment patterns, the registration deviation amount SD _{nm in} the final main scanning direction and the fine registration registration deviation PD _rmf (n in the final sub-scanning direction are calculated using (Expression 2) and (Expression 3). = R, L / m = Y, M, C, K) is calculated as the color misregistration correction amount of this image forming apparatus (1211).

  As described above, according to the present embodiment, the registration pattern for main scanning direction registration detection is formed on the basis of the result of sub-scanning direction coarse registration detection. An image forming apparatus with a short detection time can be provided.

101: Image forming apparatus
102: Paper cassette
103: Pickup roller
104: Conveyor belt drive roller
105: Conveyor belt
106-109: Photosensitive drum
110 to 113: Transfer roller
114-117: Image forming unit
118-121: Laser exposure equipment
122: Fixer
123: Output tray
124: Discharge sensor
127: Registration sensor
128: Regirolla
129 to 130: Conveying roller
141: Charger
151: Developer
160: LED drive circuit
161: Calculation means
162: Central processing unit
164: Pulse width measurement circuit
165: A / D conversion circuit for right registration sensor
166: A / D conversion circuit for left registration sensor
167,168: Drive signal output circuit
201: Left sensor output
202: Right sensor output
203: Calculation result
204: Rough adjustment pattern
205: Left coarse adjustment pattern
206: Right fine adjustment pattern
207: Left fine adjustment pattern
401: Light emitting element
402: Light receiving element
403: Cash register pattern
701,702: Comparator
801: Drive circuit output
802: Setting value for right sensor
803: Left sensor set value
901-910: In-flowchart processing
1001: Left sensor output
1002: Right sensor output
1003: Calculation result
1101 to 1107: Flowchart processing
1201 to 1210: Processing in flowchart

Claims (6)

A plurality of image carriers;
A transfer body onto which an image formed on the image carrier is transferred;
A plurality of illumination means for irradiating light to a plurality of pattern images formed by the plurality of image carriers and transferred to the transfer body;
A plurality of sensors for detecting reflected light from a plurality of misregistration pattern images transferred to the transfer body;
Control means for calculating a shift amount of a pattern image with respect to a reference pattern image in the plurality of misalignment pattern images from output signals from the plurality of sensors;
Signal calculation means for outputting output signals output from each of the plurality of sensors to the control means at different timings;
An image forming apparatus, comprising: a drive signal output unit that outputs a drive signal from the control unit to each of the plurality of illumination units at different timings. The misregistration pattern is
A first misalignment pattern formed on the right side in the main scanning direction on the image carrier;
A second misalignment pattern formed on the left side in the main scanning direction on the image carrier,
The image forming apparatus according to claim 1, wherein the first misregistration pattern and the second misregistration pattern are formed at positions separated in a conveyance direction of the image carrier. From the calculation result input to the central processing unit, calculate the deviation amount of the detection pattern with respect to the reference pattern in the positional deviation pattern on one side, and then calculate the deviation amount of the detection pattern with respect to the reference pattern in the positional deviation pattern on the opposite side. The image forming apparatus according to claim 2. Illuminating means for illuminating the misregistration pattern; and the sensor for reading light emitted from the illuminating means and reflected by the misregistration pattern;
Drive signal output means for driving the illumination means, and adjustment means for adjusting the drive signal output means so that the amount of light detected by the sensor is constant,
The image forming apparatus according to claim 2, wherein the plurality of illumination units are driven by the same drive signal output circuit by adjusting the plurality of illumination units at different timings. The misregistration pattern is
A first coarse adjustment misalignment pattern formed on the right side in the main scanning direction on the image carrier;
A first fine adjustment misalignment pattern formed on the right side in the main scanning direction on the image carrier;
A second coarse adjustment misalignment pattern formed on the left side in the main scanning direction on the image carrier;
The second fine adjustment position shift pattern formed on the left side in the main scanning direction on the image carrier,
The image forming apparatus according to claim 1, wherein the first coarse adjustment position deviation pattern and the second coarse adjustment position deviation pattern are formed at the same position in the conveyance direction of the image carrier. The misregistration pattern is
A first coarse adjustment misalignment pattern formed on the right side in the main scanning direction on the image carrier;
A first fine adjustment misalignment pattern formed on the right side in the main scanning direction on the image carrier;
A second coarse adjustment misalignment pattern formed on the left side in the main scanning direction on the image carrier;
The second fine adjustment position shift pattern formed on the left side in the main scanning direction on the image carrier,
An approximate deviation amount of the detection pattern with respect to the reference pattern is calculated by the central processing unit using the first and second coarse adjustment position deviation patterns, and the first and second fine adjustments are performed according to the obtained approximate deviation amount. The image forming apparatus according to claim 1, wherein an image forming position of the position misalignment pattern for use is corrected.