JP2008139441A - Color image forming apparatus and driving method for color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color image forming apparatus forming an image of high quality, by correcting density and color shift with higher accuracy. <P>SOLUTION: When forming color shift correction patterns and density correction patches on an intermediate transfer belt 8, the color image forming apparatus reduce the speed of the intermediate transfer belt 8 and the speeds of image carriers 2a, 2b, 2c, and 2d to a first speed. When a detection means 9a, detects the color shift correction patterns the apparatus 1 drives the intermediate transfer belt 8 at the first speed. When the detecting means 9a, detects the density correction patches the apparatus drives the intermediate transfer belt at a second speed lower than the first speed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a color image forming apparatus such as a printer or a copying machine, and a driving method of the color image forming apparatus.

  In color image forming apparatuses, electrophotographic recording methods are roughly classified into a one-drum type method and a tandem type method.

  In the one-drum type system, developing devices of a plurality of colors are arranged around one image carrier, toner is attached to the image carrier by each developing device, and the toner image is formed on an intermediate transfer belt as an intermediate transfer member. The synthesized toner image is formed, and the synthesized toner image is transferred to a recording medium to record a color image.

  On the other hand, in the tandem type system, a single color developing device is arranged on each of a plurality of image carriers, and a single color toner image is formed on each image carrier, and these single color toner images are transferred to a transfer material such as an intermediate transfer belt. Are sequentially transferred to record a composite color image.

  Comparing the 1-drum system and the tandem system, the 1-drum system requires only one image carrier, so that the image forming unit can be made smaller and less expensive than the tandem system. However, since a color image is formed by repeating image formation a plurality of times using one image carrier, it is not suitable for speeding up image formation.

  On the other hand, the tandem type is inferior to the one-drum type in terms of downsizing and cost, but is suitable for high speed because it can form images while performing almost parallel processing independently for each color. Therefore, in color image forming apparatuses, attention has been paid to a tandem type system that can obtain a monochrome-like speed from the viewpoint of image forming speed.

  By the way, in an image forming apparatus, a density correction patch or a color misregistration correction pattern (hereinafter referred to as a color misregistration pattern) is formed on an image carrier or an intermediate transfer belt, and the detection information of the patch or pattern is used as a basis. In addition, correction of density and color misregistration is performed.

In order to increase the accuracy of patch and pattern detection, for example, when detecting a density correction patch formed on the image carrier with respect to density correction, the driving speed of the image carrier is set at the time of normal image formation. A slower technology has been proposed (see, for example, Patent Document 1).
JP 2003-021939 A

  In order to perform density correction and color misregistration correction with high accuracy, it is necessary to increase detection accuracy and form correction patches and patterns with high accuracy. Also, when performing color misregistration correction, it is necessary to form a set of color misregistration patterns of different colors with different specific densities and detect the positional relationship of each color. It is necessary to keep driving. On the other hand, when performing density correction, detection is performed by forming a specific density patch or multiple patches of different densities, but this affects the overall image quality. It is necessary to raise. In particular, when performing color misregistration correction and density correction continuously, it is indispensable to improve both the accuracy of detection and to optimize the correction processing time.

  In Patent Document 1, since the driving speed of the image carrier when detecting the density correction patch is slower than that during normal image formation, it is possible to improve the detection accuracy of the density correction patch.

  However, there is no mention of speed control when forming a density correction patch, and there is no disclosure of the technical significance for improving the accuracy and optimization of both density correction and color misregistration correction. .

  Accordingly, the present invention provides a color image forming apparatus capable of realizing high-quality image formation by improving both accuracy and optimization of both density correction and color misregistration correction, and a driving method of the color image forming apparatus. The purpose is to provide.

  In order to achieve the above object, a color image forming apparatus according to claim 1 is formed on a plurality of image forming stations, a plurality of image forming stations for forming images of different colors on the plurality of image bearing members. An intermediate transfer member that transfers the transferred image at a transfer position, and a prescribed speed when forming the image, a first speed that is slower than the prescribed speed, or a second speed that is slower than the first speed, An image formed by the drive means for driving the plurality of image carriers and the intermediate transfer member and the plurality of image stations, and the image transferred onto the intermediate transfer member is a color misregistration correction pattern and a density correction patch. And detecting means for detecting the color misregistration correction pattern and the density correction patch, and when the detection means detects the color misregistration correction pattern, the driving means is configured to detect the intermediate transfer. When the body is driven at the first speed and the density correction patch is detected by the detection means, the drive means drives the intermediate transfer body at the second speed.

  6. The color image forming apparatus driving method according to claim 5, wherein a plurality of image forming stations for forming images of different colors on a plurality of image carriers, and a position at which images formed on the plurality of image carriers are transferred. The intermediate transfer member to be transferred at the intermediate transfer member, the plurality of image carriers and the driving means for driving the intermediate transfer member, and the plurality of image stations, and the image transferred onto the intermediate transfer member is color-shifted. A detection method for detecting the color misregistration correction pattern and the density correction patch with a correction pattern and a density correction patch, and a driving method of a color image forming apparatus, wherein the driving means When the color misregistration correction pattern is detected by a detection unit, the intermediate transfer member is driven at a first speed that is slower than a prescribed speed for forming the image, and the density correction is performed by the detection unit. When detecting use patches, it drives the intermediate transfer member at a slower second rate than the first speed, characterized in that.

  According to the present invention, when density correction and color misregistration correction are continuously performed, the driving speed of the intermediate transfer body on which the color misregistration pattern is formed is slowed down in order to detect the color misregistration pattern. On the other hand, when detecting the density correction patch, the driving speed is made slower than the above-described driving speed. Further, when forming a color misregistration pattern and a density correction patch, the image carrier and the intermediate transfer member are set to drive speeds for detecting the above color misregistration pattern. As a result, the color deviation correction pattern and density can be detected without adding a new mechanism, parts, or control because the drive speed is changed from that state only when the accuracy is increased when the formation is detected with the changed drive speed. The detection accuracy of both correction patches can be increased. Further, optimization of color misregistration correction and density correction can be achieved, and high-quality image formation can be realized.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic sectional view for explaining a color image forming apparatus as an example of an embodiment of the present invention, FIG. 2 is a control block diagram of the color image forming apparatus as an example of an embodiment of the present invention, and FIG. These are explanatory drawings for explaining an optical sensor. FIG. 4 is an explanatory diagram for explaining a color misregistration correction pattern, FIG. 5 is a circuit diagram for explaining a light receiving circuit of an optical sensor, and FIG. 6 is a diagram showing a detection level at the time of detecting a color misregistration correction pattern. FIG. 7 is a graph showing the correlation between belt speed and belt flutter. FIG. 8 is a diagram showing belt output fluctuations and color deviation correction pattern fluctuations, FIG. 9 is a flowchart for explaining an example of the operation of density correction control, and FIG. 10 is a chart for performing color deviation correction and density correction. It is a graph which shows the correlation with the flapping of a belt, and a driving speed. FIG. 11 is a flowchart for explaining an example of the operation of the color misregistration correction control, and FIG. 12 is a flowchart for explaining an example of the operation when the color misregistration correction control and the density correction control are continuously performed. .

  As shown in FIG. 1, a color image forming apparatus as an example of an embodiment of the present invention forms a yellow image image forming station (hereinafter referred to as an image forming unit) 1Y and a magenta image. An image forming unit 1M that forms a cyan image, and an image forming unit 1Bk that forms a black image. These image forming units 1Y, 1M, 1C, and 1Bk are arranged in a line at substantially equal intervals to form a tandem type.

  Below the image forming units 1Y, 1M, 1C, and 1Bk, sheet feeding units 17 and 20 are disposed, and a conveyance path 18 for the recording medium P is disposed between the sheet feeding units 17 and 20 and the fixing unit 16. Has been.

  In each of the image forming units 1Y, 1M, 1C, and 1Bk, drum-type electrophotographic photosensitive members (hereinafter referred to as photosensitive drums) 2a, 2b, 2c, and 2d are installed as image carriers. Around each photosensitive drum 2a, 2b, 2c, 2d, there are primary chargers 3a, 3b, 3c, 3d, developing devices (developing means) 4a, 4b, 4c, 4d, transfer rollers 5a, 5b, 5c, 5d, Drum cleaner devices 6a, 6b, 6c and 6d are respectively arranged. A laser exposure device 7 is installed below the photosensitive drums 2a, 2b, 2c and 2d.

  Each of the photosensitive drums 2a, 2b, 2c, and 2d is a negatively charged OPC photosensitive member having a photoconductive layer on an aluminum drum base, and is driven in a clockwise direction in FIG. 1 by a driving device (not shown). Driven at process speed.

  The primary chargers 3a, 3b, 3c, and 3d uniformly charge the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d to a predetermined negative potential by a charging bias applied from a charging bias power source (not shown).

  The laser exposure device 7 includes laser light emitting means for emitting light corresponding to a time-series electric digital pixel signal of given image information, a polygon lens, a reflection mirror, and the like, and exposes the photosensitive drums 2a, 2b, 2c, and 2d. An electrostatic latent image of each color corresponding to image information is formed on the surface of the photosensitive drums 2a, 2b, 2c, and 2d charged by the primary chargers 3a, 3b, 3c, and 3d.

  The developing devices 4a, 4b, 4c, and 4d store yellow toner, cyan toner, magenta toner, and black toner, respectively, and apply toner of each color to the electrostatic latent images formed on the photosensitive drums 2a, 2b, 2c, and 2d. It is attached and developed (visualized) as a toner image.

  The transfer rollers 5a, 5b, 5c, and 5d are disposed so as to be in contact with the photosensitive drums 2a, 2b, 2c, and 2d via the intermediate transfer belt 8 in the primary transfer regions 32a, 32b, 32c, and 32d, and the photosensitive drum 2a. , 2b, 2c, and 2d are sequentially transferred onto the intermediate transfer belt 8.

  The drum cleaners 6a, 6b, 6c, and 6d are provided with a cleaning blade and the like, and the residual toner at the time of primary transfer on the photosensitive drums 2a, 2b, 2c, and 2d is scraped off from the photosensitive drums 2a, 2b, 2c, and 2d. Clean the surface.

  The intermediate transfer belt 8 is disposed on the upper surface side of the photosensitive drums 2 a, 2 b, 2 c, 2 d and is stretched between the secondary transfer counter roller (support roller) 10 and the tension roller 11. The secondary transfer counter roller 10 is disposed in the secondary transfer region 34 so as to be in contact with the secondary transfer roller 12 via the intermediate transfer belt 8.

  The image transferred to the intermediate transfer belt is conveyed from the paper feeding unit 17 and transferred onto the recording medium P in the secondary transfer area 34. A belt cleaning device (not shown) for removing and collecting the transfer residual toner remaining on the surface of the intermediate transfer belt 8 is installed outside the intermediate transfer belt 8 and in the vicinity of the tension roller 11.

  The paper feed unit includes a pickup roller (not shown) for feeding recording media P one by one from the paper feed cassette 17 or the manual feed tray 20. The recording medium P sent out from the pickup roller is a resist that sends out the recording medium P to the secondary transfer area in accordance with the image forming timing of the image forming units 1Y, 1M, 1C, and 1Bk via the paper feeding roller and the paper feeding guide 18. It is conveyed to the roller 19.

  The fixing unit 16 includes a fixing roller 16a having a heat source such as a ceramic heater substrate therein, and a pressure roller 16b (the pressure roller 16b may be provided with a heat source in some cases). Before and after the fixing unit 16 in the transport direction, a guide (not shown) for guiding the recording medium P to the nip portion 31 of the roller pair 16a, 16b and the recording medium P discharged from the roller pair 16a, 16b are fed. A paper discharge roller 21 is disposed to guide the outside of the apparatus.

  An optical sensor (detection means) that detects a color misregistration correction pattern and a density correction patch formed on the intermediate transfer belt 8 at a position spaced apart from the secondary transfer counter roller 10 of the intermediate transfer belt 8 by a predetermined distance. 9a is arranged.

  Referring to FIG. 3, the optical sensor 9 a includes an LED 61 a that is a light emitting element and a phototransistor 61 b that is a light receiving element, and is provided at two predetermined distances in a direction orthogonal to the conveyance direction of the intermediate transfer belt 8. Has been placed.

  The intermediate transfer belt 8 is made of a material that is larger than the reflectance of the color misregistration correction pattern and the density correction patch for the light (for example, infrared light) irradiated by the LED 61a of the optical sensor 9a. Due to this difference in reflectance, it is possible to detect a color misregistration correction pattern and a density correction patch.

  Next, a control system of a color image forming apparatus which is an example of an embodiment of the present invention will be described with reference to FIG.

  A color image forming apparatus as an example of an embodiment of the present invention includes a controller unit 150 and an image processing unit 300 as shown in FIG.

  The controller unit 150 includes a CPU 201, a bused diver / address decoder 202, a ROM 203, a RAM 204, a serial IC 220, an I / O port 206, a PWM 215, a motor driver 85, an image modulation unit 84, a pattern width storage unit 69, and a light receiving circuit 70.

  The CPU 201 is a central processing unit that controls the entire image processing apparatus. The CPU 201 sequentially reads a program from a ROM that is a read-only memory storing a control procedure (control program) of the apparatus main body, and executes predetermined processing.

  The address bus and data bus of the CPU 201 are connected to each load via a bus driver / address decoder circuit 202. The RAM 204 is a main storage device used as input data storage, a working storage area, and the like.

  The I / O port 206 detects the operation panel 151, the clutches 208, the solenoids 209, and the recording medium P to be conveyed, in which the operator inputs a key and displays the state of the apparatus using a liquid crystal display or LED. Connected to each load of the apparatus, such as the paper detection sensors 210.

  In addition, the I / O port 206 includes an output signal from the toner sensor 211 and the optical sensor 9a that detects the amount of toner in the developing devices 4a, 4b, 4c, and 4d, a home position of each load, an open / closed state of the door, and the like. A signal from the switches 212 for detection is input.

  Further, the I / O port 206 is connected to the photosensitive drums 2a, 2b, 2c, 2d, the intermediate transfer belt 8, the paper feed system, the transport system, and motors 207 for driving the optical system. In particular, photosensitive drums 2 a, 2 b, 2 c, 2 d, which will be described later, and motors 207 of the intermediate transfer belt 8 are driven independently, and the speed is controlled via a motor driver 85 in accordance with instructions (settings) from the CPU 201.

  The driven speed is any one of a speed (specified speed) V1 for forming a normal image, a first speed V2 that is slower than the specified speed V1, or a second speed V2 that is slower than the first speed V1. .

The high voltage control unit 213 is connected to the primary chargers 3a, 3b, 3 in accordance with instructions from the CPU 201.
c, 3d, the developing devices 4a, 4b, 4c, 4d, the transfer rollers 5a, 5b, 5c, 5d, the secondary transfer roller 12, and the like.

  The image processing unit 300 performs image processing based on the image signal output from the personal computer 106 or the like, and outputs the processed image data to the laser exposure device 7 via the PWM 215. The laser beam output from the laser exposure device 7 exposes the photosensitive drums 2a, 2b, 2c, and 2d. Further, the beam detection sensor 214 detects laser light in the non-image area where the light emission state at the time of exposure is, and the detection signal is output to the I / O port 206.

  The light receiving circuit 70 outputs an output signal when the reflected light of the light emitted from the LED 61a of the optical sensor 9a toward the color misregistration correction pattern or density correction patch on the intermediate transfer belt 8 is received by the phototransistor 61b. Convert to

  Specifically, as shown in FIG. 5, when a portion other than the color misregistration correction pattern and the density correction patch of the intermediate transfer belt 8 is detected by the optical sensor 9a, the amount of reflected light increases. For this reason, a large amount of photocurrent flows through the phototransistor 61 b, undergoes current / voltage conversion by the resistor 62, and is amplified by the resistors 63, 64, 65 and the operational amplifier 66.

  On the other hand, when a color misregistration correction pattern or a density correction patch is detected by the optical sensor 9a, the amount of reflected light is reduced. Therefore, a small photocurrent flows through the phototransistor 61b as compared with the portion of the intermediate transfer belt 8, and similarly, current / voltage conversion is performed by the resistor 62 and amplified by the resistors 63, 64, 65 and the operational amplifier 66.

  FIG. 6 shows a state in which the optical sensor 9a detects reflected light in the order of a part of the intermediate transfer belt 8 → a color misregistration correction pattern of a specific density or a density correction patch of a specific density → a part of the intermediate transfer belt 8. When the density correction patch is formed from a plurality of different densities, the detection level corresponds to the plurality of densities.

  In FIG. 6, a threshold level Vt is set between the belt detection level Va when the intermediate transfer belt 8 is detected by the optical sensor 9a and the pattern detection level Vb when the color misregistration correction pattern or density correction patch is detected.

  This threshold level Vt is set by the variable resistor 67 shown in FIG. The comparator 68 compares the voltage value output from the operational amplifier 66 after the photocurrent flowing through the phototransistor 61 b is current / voltage converted and the voltage value of the threshold level Vt set by the variable resistor 67. As a result, the pattern detection output 28 shown in FIG. 6 can be created.

  Then, based on the pattern detection output 28 sequentially detected, for example, a registration shift is detected from the width and interval of the color shift correction pattern, and electrical correction is performed on the image signal to be recorded. Further, the optical path length change or the optical path change correction is performed by driving a folding mirror provided in the laser beam optical path.

  Next, a method for calculating the number of additional pixels for correcting the overall magnification difference will be described with reference to FIG.

  In the present embodiment, a set of color misregistration correction patterns 82a to 82h made of a “V-shaped” pattern is formed a plurality of times on the intermediate transfer belt 8 as shown in FIG. 4 using four lasers. Thereafter, the widths 82a to 82h of the plurality of color misregistration correction patterns formed on the intermediate transfer belt 8 are detected using the optical sensor 9a, converted into an electrical signal by the light receiving circuit 70, and the pattern width storage unit (register ) 69.

  Then, the CPU 201 calculates an image magnification difference by averaging the plurality of pattern width data stored in the pattern width storage unit 69. For example, when the value of (82a-82e) is compared with the value of (82b-82f), the larger the width, the wider the output image.

  In this case, since magenta (M) is larger, the width of the output image of yellow (Y) is widened to match the width of the output image of M, or the width of the output image of Y is reduced by reducing the width of the output image of M. To match. Alternatively, the magnification difference is corrected by controlling to widen or shrink the output image to fit the size stored in advance in the ROM 203.

  However, the actual pattern detection output 28 is not smooth as shown in FIG. 6 due to uneven driving of the intermediate transfer belt 8 and fluttering, and output unevenness occurs as shown in FIG. 7B. In order to perform highly accurate color misregistration correction and density correction, it is necessary to suppress such output unevenness as much as possible. Therefore, in the present embodiment, the following is performed in order to suppress this output unevenness.

  First, control when forming a color misregistration correction pattern or a color misregistration correction pattern and a density correction patch will be described.

  When the intermediate transfer belt 8 is used as in the present embodiment, the transfer rollers 5a, 5b, 5c, and 5d are pressed against the intermediate transfer belt 8 by springs and are rotated around, so that the photosensitive drums 2a, 2b, There is a factor that the transfer positions from 2c and 2d are slightly shifted.

  Further, the secondary transfer roller 12 also rotates along with the intermediate transfer belt 8 along the intermediate transfer belt 8, and a cleaning blade (not shown) is pressed to clean the belt surface. For this reason, a force opposite to the conveying direction is applied to the intermediate transfer belt 8, and the belt expands and contracts. In particular, the greater the belt drive speed, the greater the effect, which also causes color misregistration.

  Therefore, in this embodiment, in order to eliminate the influence of such a transfer position shift and the expansion / contraction of the intermediate transfer belt 8, when forming the color shift correction pattern and the density correction patch, the intermediate transfer belt 8 and the photosensitive belt are exposed. The driving speeds of the drums 2a, 2b, 2c, and 2d are changed from the specified speed V1 to the first speed V2, and are slowed down. By doing so, an image can be formed with high accuracy.

  For example, when the speed of the intermediate transfer belt 8 at the time of density correction patch formation is halved, the rotation speed of the motor for driving the intermediate transfer belt is halved and the rotation speed of the motor for driving the photosensitive drum is 1 / mu. This can be achieved by setting the rotation speed of the polygon motor for driving the polygon mirror to ½. Alternatively, the rotation speed of the polygon motor is normal, and can be realized by performing image formation with a polygon mirror by skipping one surface. Also, when forming a color misregistration correction pattern, it can be realized with the same control, but when using the same surface as when forming an image at a constant speed, the rotation speed of the polygon motor is constant. A finer pattern can be formed.

  Next, control when detecting the pattern formed as described above will be described.

  In this embodiment, since the diameter of the roller 10 that drives the intermediate transfer belt 8 is small, if the optical sensor 9a is arranged toward the center of the driving roller 10, light is blocked by the R (curved surface) portion of the roller 10. There is a risk of it. In this case, there is a method of adjustment, but adjustment costs are incurred.

  Therefore, in order to reduce the adjustment cost, the optical sensor 9a is disposed at a position slightly shifted from the center of the driving roller 10 to eliminate the influence of the R portion of the roller 10.

  However, if the optical sensor 9a is arranged so as to be shifted from the center of the roller 10 in this way, it is affected by the flapping of the intermediate transfer belt 8, and the output waveform of the sensor becomes as shown in FIG. 7B.

  In this embodiment, in order to reduce the influence of the flapping of the intermediate transfer belt 8, the drive speed of the intermediate transfer belt 8 is changed from the specified speed V1 to the first speed V2 as shown in FIG. And is late. As shown in FIGS. 7A and 7B, the influence of the flapping of the intermediate transfer belt 8 on the output of the optical sensor 9a is reduced by reducing the driving speed of the intermediate transfer belt 8, and the color The shift correction pattern and the density correction patch can be read with high accuracy.

  In this way, by suppressing the fluttering of the intermediate transfer belt 8, fluctuations in the detection level of reflected light from the intermediate transfer belt 8 can be suppressed as shown in FIG. As a result, fluctuations in the read value of the density correction patch can be suppressed, and the pattern width when the color misregistration correction pattern is read can also be read accurately.

  Also, when detecting the color misregistration correction pattern and counting the pattern width, the sampling speed is substantially shortened because the drive speed is reduced even if the detection clock is left as it is. Can be raised.

  However, it is necessary to continue driving the intermediate transfer belt 8 in order to detect the pattern width when reading the color misregistration correction pattern, but it is not always necessary to continue driving when detecting the density correction patch.

  Therefore, in this embodiment, as shown in FIG. 10, the photosensitive drums 2a, 2b, 2c, and 2d are formed when the color misregistration correction pattern is formed and read, and when the density correction patch is formed and read, respectively. Optimization is achieved by changing the speed of the intermediate transfer belt 8.

  Specifically, when only density correction is performed, referring to FIG. 10, when the density correction patch is formed, the driving speeds of the intermediate transfer belt 8 and the photosensitive drums 2a, 2b, 2c, and 2d are set from the specified speed V1. Decelerate to a low first speed V2. When the density correction patch is detected, the driving speed of the intermediate transfer belt 8 is reduced to the second speed V3 that is lower than the first speed V2 or stopped, and then returned to the specified speed V1 after the detection.

  When only the color misregistration correction is performed, the driving speeds of the intermediate transfer belt 8 and the photosensitive drums 2a, 2b, 2c, and 2d are defined with reference to FIG. Decelerate to a first speed V2 lower than the speed V1. After the detection is completed, the speed is returned to the specified speed V1.

  Further, when the color misregistration correction and the density correction are continuously performed, the driving speeds of the intermediate transfer belt 8 and the photosensitive drums 2a, 2b, 2c, and 2d are reduced to the first speed V2 that is lower than the specified speed V1. First, a color misregistration correction pattern is formed, and then a density correction patch is formed.

  Then, after detecting the color misregistration correction pattern at the first speed V2, the driving speed of the photosensitive drums 2a, 2b, 2c, 2d and the intermediate transfer belt 8 or only the intermediate transfer belt 8 is set to the first speed. Decelerate or stop at a second speed V3 that is slower than V2, detect the density correction patch, and then return to the specified speed V1.

  Next, an example of the density correction control operation will be described with reference to FIG.

  When the density correction control sequence is started, the LED 61a of the optical sensor 9a is turned on in step S1. In step S2, driving of the intermediate transfer belt 8 and the photosensitive drums 2a, 2b, 2c, and 2d is started at a first speed V2 that is slower than the specified speed V1. In step S3, the density correction patch is transferred and formed on the intermediate transfer belt 8.

  Next, in step S4, the driving speeds of the photosensitive drums 2a, 2b, 2c, 2d and the intermediate transfer belt 8 are further decelerated to a second speed V3 that is slower than the first speed V2, or stopped. In step S5, a density correction patch is detected. The second speed V3 may be set when the density correction patch has a plurality of different densities or specific densities, and the stop may be set when the density correction patch has a specific density.

  After the detection of the density correction patch in step S5, the LED 61a of the optical sensor 9a is turned off in step S6. In step S7, before entering the normal sequence, various correction amounts such as a toner replenishment amount and a transfer current are set, and the density correction control sequence ends.

  Next, an example of the operation of color misregistration correction control will be described with reference to FIG.

  When the color misregistration correction control sequence is started, the LED 61a of the optical sensor 9a is turned on in step S11. In step S12, driving of the intermediate transfer belt 8 and the photosensitive drums 2a, 2b, 2c, and 2d is started at a first speed V2 that is slower than the specified speed V1. In step S13, a color misregistration correction pattern is transferred and formed on the intermediate transfer belt 8.

  Next, in step S14, the driving speeds of the photosensitive drums 2a, 2b, 2c, 2d and the intermediate transfer belt 8 are maintained at the first speed V2. In step S15, a color misregistration correction pattern is detected.

  After the detection of the color misregistration correction pattern in step S15, the LED 61a of the optical sensor 9a is turned off in step S16. In step S17, before entering the normal sequence, various correction amounts such as a writing position are set, and the color misregistration correction control sequence ends.

  Next, an example of an operation when the color misregistration correction control and the density correction control are continuously performed will be described with reference to FIG.

  When the correction control sequence is started, the LED 61a of the optical sensor 9a is turned on in step S21. In step S22, driving of the intermediate transfer belt 8 and the photosensitive drums 2a, 2b, 2c, and 2d is started at a first speed V2 that is slower than the specified speed V1. In step S23, the color misregistration correction pattern and the density correction patch are formed in this order.

  Next, in step S24, the driving speeds of the photosensitive drums 2a, 2b, 2c, 2d and the intermediate transfer belt 8 are maintained at the first speed V2, and in step S25, a color misregistration correction pattern is detected.

  Next, in step S26, the driving speeds of the photosensitive drums 2a, 2b, 2c, 2d and the intermediate transfer belt 8 are further decelerated to a second speed V3 that is slower than the first speed V2, or stopped. In step S27, a density correction patch is detected.

  After the detection of the density correction patch in step S27, the LED 61a of the optical sensor 9a is turned off in step S28. In step S29, before entering the normal sequence, various correction amounts such as a writing position, a toner replenishment amount, and a transfer current are set, and the correction control sequence ends.

  As described above, in this embodiment, when the color misregistration correction pattern and the density correction patch are formed on the intermediate transfer belt 8 by transfer, the intermediate transfer belt 8 and the photosensitive drums 2a, 2b, 2c. , 2d is decelerated from the specified speed V1 to the first speed V2. When the color misregistration correction pattern is detected by the optical sensor 9a, the photosensitive drums 2a, 2b, 2c, 2d and the intermediate transfer belt 8 are driven at the first speed V2. When the density correction patch is detected by the optical sensor 9a, the photosensitive drums 2a, 2b, 2c, 2d and the intermediate transfer belt 8 are set to a second speed that is lower than the first speed V2 or zero (stopped). Drive at speed V3.

  Thereby, the influence of the flapping of the intermediate transfer belt 8 on the output of the optical sensor 9a can be reduced, and the color misregistration correction pattern and the density correction patch can be formed with high accuracy. The detection accuracy of the correction patch can be increased. As a result, high accuracy and optimization of color misregistration correction and density correction can be achieved, and high-quality image formation can be realized.

  In addition, this invention is not limited to what was illustrated to the embodiment, In the range which does not deviate from the summary of this invention, it can change suitably.

  For example, in the case where the drive speeds of the photosensitive drums 2a, 2b, 2c, and 2d and the intermediate transfer belt 8 described above are reduced, both have been described as being decelerated. By providing a contact / separation mechanism to the control member and controlling the solenoids 209 to separate them, only the intermediate transfer belt 8 can be decelerated and stopped.

  In the above embodiment, the toner images on the photosensitive drum are sequentially transferred onto the intermediate transfer belt. However, when the toner images on the photosensitive drum are sequentially transferred onto the recording medium conveyed by the conveying belt. The present invention can also be applied.

  In this case, when the toner image on the photosensitive drum has a color misregistration correction pattern, control is performed so that the toner image is transferred from the photosensitive drum to the conveyance belt, and color misregistration correction is performed by the first optical sensor provided on the conveyance belt. Detect patterns. When the toner image on the photosensitive drum is a density correction patch, control is performed so that the toner image is not transferred from the photosensitive drum to the conveyance belt, and is detected by a second optical sensor provided near the photosensitive drum. The transfer formation from the photosensitive drum to the conveyance belt may be controlled by using the same contact / separation mechanism for the photosensitive drum and the conveyance belt, independently driving the photosensitive drum and the conveyance belt at a speed, and controlling the transfer voltage.

  When the color misregistration correction pattern and the density correction patch are successively formed and detected, first, the driving speed of the photosensitive drum and the conveyance belt is reduced to the first speed, and the color misregistration correction pattern is generated. Form and detect. Subsequently, the photosensitive drum and the conveyor belt are detached, and at least the photosensitive drum drive speed is reduced to the second speed described above, and a density correction patch is formed and detected. Alternatively, the photosensitive drum and the conveyor belt are detached, and the driving speed of the photosensitive drum is maintained at the first speed to form the density correction patch, and then decelerated to the second speed and detected.

1 is a schematic cross-sectional view for explaining a color image forming apparatus which is an example of an embodiment of the present invention. 1 is a control block diagram of a color image forming apparatus which is an example of an embodiment of the present invention. It is explanatory drawing for demonstrating an optical sensor. It is explanatory drawing for demonstrating the color misregistration correction pattern. It is a circuit diagram for demonstrating the light-receiving circuit of an optical sensor. It is a figure which shows the detection level at the time of the detection of the pattern for color misregistration correction. It is a graph which shows the correlation with belt speed and the flapping of a belt. It is a figure which shows the output fluctuation of a belt, and the pattern fluctuation for color misregistration correction. It is a flowchart for demonstrating an example of operation | movement of density correction control. FIG. 6 is a graph showing a correlation between belt flapping and driving speed when color misregistration correction and density correction are performed. It is a flowchart for demonstrating an example of operation | movement of color misregistration correction control. FIG. 6 is a flowchart for explaining an example of an operation when color misregistration correction control and density correction control are continuously performed.

Explanation of symbols

1Y, 1M, 1C, 1Bk Image forming unit (image forming station)
2a, 2b, 2c, 2d Photosensitive drum (image carrier)
3a, 3b, 3c, 3d Primary chargers 4a, 4b, 4c, 4d Developing devices 5a, 5b, 5c, 5d Transfer rollers 6a, 6b, 6c, 6d Drum cleaner device 7 Exposure device 8 Intermediate transfer belt (intermediate transfer member)
9a Optical sensor (detection means)
10 Secondary transfer counter roller (support roller)
11 Tension roller 12 Secondary transfer roller 16 Fixing unit 16a Fixing roller 16b Heating roller 17 Paper feed cassette 18 Transport path 21 Paper discharge roller

Claims (8)

A plurality of image forming stations for forming images of different colors on a plurality of image carriers;
An intermediate transfer member for transferring an image formed on the plurality of image carriers at a transfer position;
The plurality of image bearing members and the intermediate transfer member are driven at any one of a prescribed speed when forming the image, a first speed slower than the prescribed speed, or a second speed slower than the first speed. Driving means for
Detection that an image formed by the plurality of image stations and transferred onto the intermediate transfer body is a color misregistration correction pattern and a density correction patch, and detects the color misregistration correction pattern and the density correction patch. Means and
When the color shift correction pattern is detected by the detection unit, the drive unit drives the intermediate transfer body at the first speed, and when the detection unit detects the density correction patch, the drive unit Driving the intermediate transfer member at the second speed;
A color image forming apparatus. When the image forming station forms the color misregistration correction pattern and the density correction patch on the intermediate transfer member, the driving unit moves the intermediate transfer member and the image carrier at the first speed. Drive,
The color image forming apparatus according to claim 1. The intermediate transfer member is composed of an intermediate transfer belt,
The color image forming apparatus according to claim 1, wherein the detection unit is disposed at a position separated from a support roller of the intermediate transfer belt. When the color misregistration correction pattern and the density correction patch are successively formed and detected,
After forming the color misregistration correction pattern, forming the density correction patch,
Detecting the density correction patch after detecting the color misregistration correction pattern;
The color image forming apparatus according to claim 1, wherein the color image forming apparatus is a color image forming apparatus. A plurality of image forming stations for forming images of different colors on a plurality of image carriers;
An intermediate transfer member for transferring an image formed on the plurality of image carriers at a transfer position;
Drive means for driving the plurality of image carriers and the intermediate transfer member;
Detection that an image formed by the plurality of image stations and transferred onto the intermediate transfer body is a color misregistration correction pattern and a density correction patch, and detects the color misregistration correction pattern and the density correction patch. And a color image forming apparatus driving method comprising:
When the detection unit detects the color misregistration correction pattern, the driving unit drives the intermediate transfer member at a first speed slower than a prescribed speed when forming the image, and the detection unit performs the density correction. When detecting a patch, the intermediate transfer member is driven at a second speed slower than the first speed;
A method for driving a color image forming apparatus. When the image forming station forms the color misregistration correction pattern and the density correction patch on the intermediate transfer member, the driving unit moves the intermediate transfer member and the image carrier at the first speed. Drive,
6. A method for driving a color image forming apparatus according to claim 5, wherein: The intermediate transfer member is composed of an intermediate transfer belt,
The detecting means is disposed at a position spaced apart from a support roller of the intermediate transfer belt;
The method for driving a color image forming apparatus according to claim 5 or 6, wherein: When the color misregistration correction pattern and the density correction patch are successively formed and detected,
After forming the color misregistration correction pattern, forming the density correction patch,
Detecting the density correction patch after detecting the color misregistration correction pattern;
The method for driving a color image forming apparatus according to any one of claims 5 to 7.

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