JP5959895B2 - Image forming apparatus - Google Patents

Description

  An image forming apparatus that periodically changes the writing of the electrostatic image on the image carrier so as to cancel out the periodic displacement of the adjustment toner image in the main scanning direction, and more specifically, the adjustment toner image is placed on the belt member. It is related with the control which removes the error resulting from the support rotary body of the belt member at the time of detecting by (3).

  The electrostatic image formed on the image carrier is developed into a toner image, the toner image is transferred to a recording material using a belt member (intermediate transfer belt or recording material conveying belt), and the recording material on which the toner image is transferred is obtained. 2. Description of the Related Art Image forming apparatuses that heat and press to fix an image on a recording material are widely used. In the image forming apparatus, when the rotation axis of the image carrier is decentered or inclined, an electrostatic image is formed on the image carrier with a periodic positional shift in the main scanning direction, and the rotation cycle of the image carrier is changed. A toner image whose position varies in the main scanning direction is formed. For this reason, a linear adjustment toner image that is continuous in the sub-scanning direction is formed and detected on the image carrier using the image sensor, and the main scanning direction with respect to the image carrier is set so as to cancel periodic position fluctuations. Control for periodically changing the writing start position of the electrostatic image has been put into practical use.

  However, with the recent miniaturization of image forming apparatuses, the image carrier is also miniaturized, and a large image sensor cannot be disposed around the image carrier. Further, when a plurality of image carriers are arranged along the belt member, if an image sensor is provided for each image carrier, the component cost of the image sensor increases. Therefore, an adjustment toner image for adjusting the position of the electrostatic image of the image in the main scanning direction is transferred from a plurality of image carriers to a common belt member, and each adjustment toner image is acquired by one image sensor. The technique of the adjustment mode which detects this is proposed (Patent Document 1).

  In the adjustment mode, the position information in the main scanning direction of the adjustment toner image acquired by the image sensor is accumulated corresponding to the plurality of phase positions of the image carrier, and electrostatic images at the plurality of phase positions of the image carrier are obtained. The formation position in the main scanning direction and the formation magnification in the main scanning direction are adjusted. Only one amplitude component of the rotation period of the image carrier is extracted by a kind of filter calculation processing that integrates corresponding to a plurality of phase positions of the image carrier, and a correction amount corresponding to the plurality of phase positions of the image carrier Create a conversion table that determines.

JP-A-10-153896

  When the imaging sensor is arranged close to the support rotating body of the belt member, the adjustment toner is caused by a periodic positional deviation in the main scanning direction of the belt member due to the inclination or shakiness of the central axis of the support rotating body. It is detected by the image sensor due to the misalignment of the image. When the electrostatic image forming position is adjusted including periodic positional fluctuations in the main scanning direction of the belt member, the positional deviation of the toner image in the main scanning direction due to the eccentricity or inclination of the central axis of the image carrier is reduced. Since it cannot be canceled out sufficiently, position variations in the main scanning direction remain in the formed image.

  In particular, when the circumference of the image carrier is equal to the circumference of the support rotator, the periodic displacement in the main scanning direction caused by the image carrier and the periodic displacement in the main scanning direction caused by the support rotator And overlap exactly periodically. In this case, no matter how many times the integration is performed corresponding to a plurality of phase positions of the image carrier, periodic position fluctuations in the main scanning direction caused by the image carrier cannot be separated, and an electrostatic image of the image is formed. The correction amount for adjusting the position in the main scanning direction cannot be obtained accurately.

  Even if the circumferences of the image carrier and the support rotator are not the same, the closer to an integral multiple, the greater the number of integration iterations required to separate them, and the longer the adjustment mode control time. End up.

  As will be described later, as the value obtained by dividing the distance from the transfer position of the toner image to the detection position by the circumference of the support rotator approaches 0.5, the periodic position in the main scanning direction caused by the support rotator There is also a problem that the influence of the deviation on the correction amount becomes large.

  The present invention reduces the amount of correction of periodic position fluctuations in the main scanning direction of an image formed on an image carrier without being affected by periodic position fluctuations caused by the support member of the belt member. An object of the present invention is to provide an image forming apparatus that can be accurately obtained by the above method.

The image forming apparatus of the present invention, developing the image bearing member, a writable electrostatic image forming means to a predetermined position of the electrostatic image for adjustment main scanning direction of the image bearing member, said adjusting electrostatic image And a belt member arranged so that the adjusted toner image can be transferred from the image carrier. Main scanning of the adjustment toner image on the belt member transferred from the image carrier a first detecting means for detecting the direction position, and a second detecting means for detecting a main scanning direction position location of the belt member, the adjustment toner image at each position in the sub-scanning direction of the image bearing member is a plurality of times The adjustment electrostatic image is drawn so as to be formed, and each of the adjustment toner images formed at the respective positions and detected by the first detection unit is calculated based on a variation amount with respect to a reference position in the main scanning direction . Toner image for adjustment formed at the position The exception of the amount of fluctuation in the main scanning direction of said belt member at the time it was transferred to the belt member, so as to cancel those integrated over the number of times the adjustment toner image is formed for each location, the image bearing Control means capable of executing an adjustment mode for adjusting at least one of the formation position and the formation magnification of the electrostatic image corresponding to the output image at each position in the sub-scanning direction of the body.

  In the image forming apparatus of the present invention, the main position of the adjustment toner image detected by using the first detection unit is extracted by independently extracting periodic position fluctuations caused by the support rotating body using the second detection unit. Remove from initial position information. For this reason, it is possible to obtain the correction amount of the periodic position fluctuation caused by the image carrier in a state where the periodic position fluctuation caused by the support rotating body is excluded.

  Therefore, the correction amount of the periodic position fluctuation in the main scanning direction of the image formed on the image carrier can be reduced with a small number of integrations without being affected by the periodic position fluctuation caused by the support rotating body of the belt member. It can be determined accurately.

1 is an explanatory diagram of a configuration of an image forming apparatus. It is explanatory drawing of a structure of an image formation part. FIG. 6 is an explanatory diagram of an adjustment toner image. This is a position variation in the main scanning direction of the adjustment toner image detected by the image sensor. 2 is a block diagram of a control system of the image forming apparatus. FIG. FIG. 7 is an explanatory diagram of an adjustment toner image transferred to an intermediate transfer belt. It is a flowchart of sampling control of the toner image for adjustment. 10 is a flowchart of sampling control of a shift position of an intermediate transfer belt. It is explanatory drawing of the sampling data of the toner image for adjustment. It is explanatory drawing of the correction timing of a write start position. FIG. 10 is an explanatory diagram of a partial configuration of an image forming apparatus according to a fifth embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention replaces part or all of the configuration of the embodiment as long as the positional information of the adjustment toner image on the belt member is integrated by subtracting the amount of positional deviation of the belt member in the main scanning direction. Other embodiments replaced with a typical configuration can also be implemented.

  Therefore, the belt member is not limited to the intermediate transfer belt that is in contact with the photosensitive member, but may be a recording material conveying belt that sucks and conveys the recording material to transfer the toner image from the photosensitive member. As long as the belt member is used, the image forming apparatus can be used in full color / monochrome, 1 drum type / tandem type, recording material conveyance system / intermediate transfer system, image carrier type, charging system, exposure system, transfer system, and fixing system. It can be done regardless. In the present embodiment, only main parts related to toner image formation / transfer will be described. However, the present invention includes a printer, various printing machines, a copier, a fax machine, a composite machine, in addition to necessary equipment, equipment, and a housing structure. It can be implemented in various applications such as a machine.

<Image forming apparatus>
FIG. 1 is an explanatory diagram of the configuration of the image forming apparatus. FIG. 2 is an explanatory diagram of the configuration of the image forming unit.

  As shown in FIG. 1, the image forming apparatus 100 is a tandem intermediate transfer type full-color printer in which image forming units PY, PM, PC, and PK are arranged along an intermediate transfer belt 9. In the image forming unit PY, a yellow toner image is formed on the photosensitive drum 1Y and transferred to the intermediate transfer belt 9. In the image forming unit PM, a magenta toner image is formed on the photosensitive drum 1M and transferred to the intermediate transfer belt 9. In the image forming units PC and PK, cyan toner images and black toner images are formed on the photosensitive drums 1 </ b> C and 1 </ b> K and transferred to the intermediate transfer belt 9. The belt cleaning device 18 rubs the intermediate transfer belt 9 with a cleaning blade to collect the transfer residual toner attached to the intermediate transfer belt 9.

  The four-color toner images transferred to the intermediate transfer belt 9 are conveyed to the secondary transfer portion T2 and are collectively secondary transferred to the recording material P. The separation roller 15 separates the recording material P drawn from the recording material cassette 20 by the pickup roller 14 one by one and sends it to the registration roller 16. The registration roller 16 sends the recording material P to the secondary transfer portion T2 in time with the toner image on the intermediate transfer belt 9. The opposing roller 10 is connected to the ground potential, and the power source D2 applies a positive DC voltage to the secondary transfer roller 11 to transfer the toner image on the intermediate transfer belt 9 to the recording material P. The recording material P on which the four-color toner images are secondarily transferred is heated and pressurized by the fixing device 17 to fix the toner images on the surface, and then is discharged out of the machine body.

  The image forming units PY, PM, PC, and PK are configured substantially the same except that the color of toner used in the developing devices 4Y, 4M, 4C, and 4K is different from yellow, magenta, cyan, and black. Hereinafter, the image forming unit PY will be described with reference to FIG. 2, and redundant description of the other image forming units PM, PC, and PK will be omitted.

  As shown in FIG. 2, the image forming unit PY surrounds the photosensitive drum 1Y and includes a corona charger 2Y, an exposure device 3Y, a developing device 4Y, a primary transfer roller 5Y, and a drum cleaning device 6Y. The photosensitive drum 1Y has a photosensitive layer formed on the outer peripheral surface of an aluminum cylinder, and rotates in the direction of arrow A at a predetermined process speed. The charging device 2Y applies a negative voltage from the power source D3 and irradiates the surface of the photosensitive drum 1Y with charged particles, thereby charging the surface of the photosensitive drum 1Y to a uniform negative polarity potential VD.

  The exposure apparatus 3Y scans the scanning line image data obtained by developing the yellow separated color image with a rotating mirror, and writes an electrostatic image of the image on the surface of the charged photosensitive drum 1Y. The resolution of the electrostatic image of the image is 600 dpi (dots / inch).

  The developing device 4Y stirs the developer in which the carrier is mixed with the toner to charge the toner to the negative polarity and the carrier to the positive polarity. The charged developer is carried on the developing sleeve 4s rotating around the fixed magnetic pole 4j in the counter direction with the photosensitive drum 1Y, and rubs against the photosensitive drum 1Y. The power source D4 applies an oscillating voltage obtained by superimposing an AC voltage to a negative DC voltage to the developing sleeve 4s, and attaches toner to the electrostatic image of the photosensitive drum 1Y that has a relatively positive polarity relative to the developing sleeve 4s. The electrostatic image is reversely developed.

  The primary transfer roller 5Y presses the intermediate transfer belt 9 to form a primary transfer portion TY between the photosensitive drum 1Y and the intermediate transfer belt 9. The power source DY applies a positive DC voltage to the primary transfer roller 5Y to primarily transfer the negatively charged toner image on the photosensitive drum 1Y to the intermediate transfer belt 9 passing through the primary transfer portion TY.

  The secondary transfer roller 11 contacts the intermediate transfer belt 9 supported by the counter roller 10 to form a secondary transfer portion T2. The drum cleaning device 6Y collects the transfer residual toner attached to the surface of the photosensitive drum 1Y that has passed through the primary transfer portion TY by sliding the cleaning blade against the photosensitive drum 1Y.

<Color shift of each color image>
Since the image forming apparatus 100 forms a full-color image by superimposing different color toner images, the toner images of each color are accurately superimposed on the intermediate transfer belt 9 in order to obtain a high-quality image without color misregistration. It is necessary to match.

  However, the color of each color image is controlled by the eccentricity of the photosensitive drum 1Y, the inclination of the central axis, the eccentricity of the driving roller 13 of the intermediate transfer belt 9, the inclination of the central axis, the profile of the end face of the intermediate transfer belt 9, and the deviation control of the steering roller. Deviation may occur.

  The color misregistration of each color image is caused by the main scanning direction color misregistration in the width direction of the intermediate transfer belt 9 and the sub-scanning color misregistration in the intermediate transfer belt 9 in the transport direction. It is roughly divided into Then, the color shift in the main scanning direction and the color shift in the sub-scanning direction each include a periodic positional fluctuation (AC component) and a certain level of positional shift (DC component).

  For a certain level of misalignment (DC component), registration marks are formed on the photosensitive drums 1Y, 1M, 1C, and 1K, transferred to the intermediate transfer belt 9, and the misregistration amount is measured using the image sensors IS1 and IS2. Measured. Regarding the color misregistration in the main scanning direction, the writing start position of the electrostatic image in the main scanning direction on the photosensitive drums 1Y, 1M, 1C, and 1K is adjusted so as to cancel the actually measured misregistration amount. Regarding the color misregistration in the sub-scanning direction, the writing start position of the electrostatic image in the sub-scanning direction with respect to the photosensitive drums 1Y, 1M, 1C, and 1K is adjusted so as to cancel the actually measured misregistration amount.

  By reducing a certain level of positional deviation (DC component) in both the main scanning direction and the sub-scanning direction, the image forming apparatus 100 greatly improves the image quality of the output image. However, in order to output a higher quality image, it is necessary to reduce periodic position fluctuation (AC component) in both the main scanning direction and the sub-scanning direction.

  Periodic position fluctuations (AC components) in the sub-scanning direction can be considerably removed by making the intervals between the photosensitive drums 1Y, 1M, 1C, and 1K equal to the circumferential length of the driving roller 13. This is because the fluctuation pattern of the conveyance speed of the intermediate transfer belt 9 due to the fluctuation of the rotation speed of the driving roller 13 is equally reproduced for the transfer of the toner image from the photosensitive drums 1Y, 1M, 1C, and 1K.

  However, the periodic position fluctuation (AC component) in the main scanning direction of the toner images formed on the photosensitive drums 1Y, 1M, 1C, and 1K is accurate in the adjustment toner image transferred to the intermediate transfer belt 9. The amount is difficult to detect. This is because it is difficult to separate the noise component accompanying the positional fluctuation of the intermediate transfer belt 9 in the main scanning direction.

  Therefore, in the image forming apparatus 100, color misregistration detection is performed on the photosensitive drums 1Y, 1M, 1C, and 1K in order to reduce periodic color misregistration in the main scanning direction due to periodic position fluctuations (AC components) in the main scanning direction. An adjustment toner image is formed. As described in Patent Document 1, if the photosensitive drum 1Y is decentered, the distance between the exposure scanning unit (polyhedral mirror) and the surface of the photosensitive drum 1Y varies, so that an adjustment toner image drawn on the photosensitive drum 1Y. Distortion in the main scanning direction occurs. As shown in FIG. 1, the adjustment toner image is detected on the intermediate transfer belt 9 by using image sensors IS1 and IS2. Periodic fluctuations in the rotation cycle of the photosensitive drum are extracted from position fluctuations in the main scanning direction obtained by the image sensors IS1 and IS2, and fed back to writing start timing control of the exposure apparatuses 3Y, 3M, 3C, and 3K.

  The adjustment toner image is formed over a plurality of rotations of the photosensitive drum, and the position in the main scanning direction is repeatedly sampled at a timing for each predetermined phase position of the photosensitive drum. Then, the frequency components other than the rotation period of the photosensitive drum are removed by adding the positions in the main scanning direction at each sample timing over a plurality of rotations. As a result, the amplitude and phase of the fluctuation in the main scanning direction of the exposure start position in the rotation cycle of the photosensitive drum are detected.

  As shown in FIG. 1, the image sensors IS1 and IS2 are installed facing the intermediate transfer belt 9 on the downstream side of the image forming units PY, PM, PC, and PK. The image sensors IS1 and IS2 read adjustment toner images for color misregistration correction formed on the intermediate transfer belt 9 through exposure, development, and primary transfer processes. The encoders EY, EM, EC, and EK detect the rotational phase positions of the photosensitive drums 1Y, 1M, 1C, and 1K, respectively.

<Influence of fluctuation in the main scanning direction of the intermediate transfer belt>
FIG. 3 is an explanatory diagram of an adjustment toner image. FIG. 4 shows the position variation of the adjustment toner image detected by the image sensor in the main scanning direction.

  As shown in FIG. 3 (a), even when an electrostatic image of the adjustment toner image of the straight original image is printed, it has an AC component in the main scanning direction as shown in FIG. 3 (b). A distorted electrostatic image is formed on the photosensitive drum 1Y. When the distorted electrostatic image drawn on the photosensitive drum 1Y is developed into a toner image and transferred to the intermediate transfer belt 9, a distorted adjustment toner image is formed on the intermediate transfer belt 9. If there is a fluctuation in the main scanning direction in the rotation of the intermediate transfer belt 9, the intermediate transfer belt 9 changes in a state where the deviation of the intermediate transfer belt 9 is superimposed on the fluctuation in the main scanning direction of the adjustment toner image caused by the eccentricity of the photosensitive drum 1Y. An adjustment toner image distorted on the transfer belt 9 is formed.

  As indicated by a thick line in FIG. 4, the adjustment toner images detected by the image sensors IS1 and IS2 fluctuate in the main scanning direction during a time corresponding to two rotations of the photosensitive drum 1Y. At this time, the movement of the adjustment toner image in the main scanning direction is a combination of the fluctuation pattern indicated by the broken line due to the eccentricity of the central axis of the photosensitive drum 1Y and the deviation fluctuation pattern of the intermediate transfer belt 9. The fluctuation pattern indicated by the broken line is a fluctuation caused by the photosensitive drum 1Y, such as eccentric rotation, razor rotation, and rattling of the photosensitive drum 1Y. The dotted line fluctuation pattern includes a cycle component (thin line) of one cycle of the intermediate transfer belt 9 and a component of one cycle of the driving roller 13 that drives the rotation of the intermediate transfer belt 9. In the shift variation pattern of the intermediate transfer belt 9, a short cycle component corresponding to the rotation cycle of the drive roller 13 is added to a long cycle component (thin line) corresponding to the rotation cycle of the intermediate transfer belt 9.

  In such a case, even if the total fluctuation indicated by the thick line is added at each phase position of the photosensitive drum, the fluctuation amount in the main scanning direction at each phase position of the photosensitive drum indicated by the broken line cannot be extracted. Since the fluctuation in the main scanning direction of the intermediate transfer belt 9 indicated by the dotted line is superimposed, the exposure start timing is set at a position deviating from the exposure start timing that can cancel the fluctuation amount of the broken line. Even if the adjustment toner image is sampled by the image sensors IS1 and IS2 at the timing corresponding to the phase position every 1/10 rotation of the photosensitive drum, and the 10 rotations of the photosensitive drum are added, the main image of the intermediate transfer belt 9 is added. Variations in the scanning direction cannot be removed sufficiently.

  In particular, when the circumferential length (diameter) of the photosensitive drum is close to a natural number multiple of the circumferential length (diameter) of the driving roller, the frequency of fluctuation in the main scanning direction caused by the photosensitive drum and the driving roller 13 of the intermediate transfer belt 9 are caused. The frequency of fluctuation in the main scanning direction is close. In this case, with the method of Patent Document 1, it is difficult to separate and extract fluctuations caused by the photosensitive drum, and a large error occurs in the set exposure start timing, so that it is not possible to correct image misregistration.

  Therefore, in the following embodiments, the deviation variation of the intermediate transfer belt 9 is independently extracted by the deviation sensor YS, and is subtracted from the fluctuation amount in the main scanning direction of the adjustment toner image detected by the image sensors IS1 and IS2. A fluctuation pattern in the main scanning direction of the rotation cycle of the photosensitive drum is extracted in a state where the fluctuation amount in the main scanning direction on the intermediate transfer belt 9 side caused by the drive roller 13 or the like is first subtracted.

  For this reason, even if the shift of the intermediate transfer belt 9 includes a frequency component close to the rotation cycle of the photosensitive drum, the fluctuation in the main scanning direction caused by the photosensitive drum can be accurately extracted. Further, since it is not necessary to separate the shift of the intermediate transfer belt 9, it is possible to reduce the number of repetitions to be added, reduce the amount of toner used, and shorten the time required for the adjustment mode.

  In the following embodiment, only the control related to the image forming unit PY will be described, but the control of the first embodiment is similarly executed for the image forming units PM, PC, and PK.

<Example 1>
FIG. 5 is a block diagram of a control system of the image forming apparatus. FIG. 6 is an explanatory diagram of the adjustment toner image transferred to the intermediate transfer belt. FIG. 7 is a flowchart of the sampling control of the adjustment toner image. FIG. 8 is a flowchart of the sampling control of the shift position of the intermediate transfer belt. FIG. 9 is an explanatory diagram of an adjustment toner image.

  As shown in FIG. 1, in Example 1, when the diameter of the photosensitive drum 1Y is D, the diameter of the driving roller 13 is d, and a specific natural number is n, “0.8 <D / (n × d ) <1.2 ”is established. For this reason, it is difficult to remove the rotation period component of the driving roller 13 from the fluctuation of the adjustment toner image in the main scanning direction.

  The exposure apparatus 3Y, which is an example of an electrostatic image forming unit, can write an adjustment electrostatic image for adjusting the position of the electrostatic image of the image in the main scanning direction at a predetermined position in the main scanning direction of the photosensitive drum 1Y. is there.

  The intermediate transfer belt 9, which is an example of a belt member, is arranged so that an adjustment toner image obtained by developing the adjustment electrostatic image can be transferred from the photosensitive drum 1Y.

  Image sensors IS1 and IS2, which are examples of first detection means, are driving that is an example of a support rotating body that stretches the intermediate transfer belt 9 with the adjustment toner image on the intermediate transfer belt 9 transferred from the photosensitive drum 1Y. Detection is performed at a position close to the roller 13. The image sensors IS1 and IS2 output position information of the adjustment toner image in the main scanning direction.

  A shift sensor YS, which is an example of a second detection unit, detects the intermediate transfer belt 9 at a position close to the drive roller 13 and outputs position information of the intermediate transfer belt 9 in the main scanning direction.

  The control unit 101, which is an example of a control unit, can execute an adjustment mode that adjusts at least one of the formation position in the main scanning direction and the formation magnification in the main scanning direction of the electrostatic image of the image at a plurality of phase positions on the photosensitive drum 1Y. It is. In the adjustment mode, the difference amount between the main scanning direction position information of the toner image for adjustment and the main scanning direction position information of the intermediate transfer belt 9 is integrated in correspondence with a plurality of phase positions of the photosensitive drum 1Y, thereby performing photosensitive. The fluctuation of the rotation cycle of the drum 1Y is extracted. Then, based on the integration result at each position in the sub-scanning direction, exposure position or exposure magnification correction data is acquired.

  Prior to the adjustment mode, the control unit 101 accumulates the main scanning direction position information of the intermediate transfer belt 9 in correspondence with a plurality of phase positions of the intermediate transfer belt 9, and positions the intermediate transfer belt 9 in the main scanning direction. Obtain correction data for information. The control unit 101 obtains a difference amount using the main scanning direction position information of the intermediate transfer belt 9 corrected using the correction data.

  The intermediate transfer belt 9 is supported around a tension roller 12, a counter roller 10, and a driving roller 13, and is driven by the driving roller 13 to rotate in the arrow B direction. Positioning of the intermediate transfer belt 9 in the lateral direction is performed by engaging ribs formed on the belt edge of the intermediate transfer belt 9 with the end surfaces of the drive roller 13 and the like.

  The deviation sensor YS is a sensor that detects deviation fluctuation of the intermediate transfer belt 9. The shift sensor YS is disposed close to the inner edge of the intermediate transfer belt 9, reads the position of the edge of the intermediate transfer belt 9 with a linear CCD sensor, and outputs an electrical signal of position information of the intermediate transfer belt 9 in the main scanning direction. Output.

  As shown in FIG. 5, the control unit 101 controls the operation of the present invention. The writing control unit 102 controls the exposure start position of laser exposure by controlling the exposure apparatus (laser unit) 3Y. The image storage unit 103 stores the image data of the adjustment toner image read by the image sensors IS1 and IS2. The shift storage unit 104 stores the shift amount of the intermediate transfer belt detected by the shift sensor YS. The sampling control unit 105 generates timings for detecting adjustment toner images by the image sensors IS1 and IS2, and timings for correction writing to the photosensitive drum 1Y. The sampling control unit 105 receives the phase signal (Z phase and A or B phase) of the encoder EY, and sends a timing signal to the image storage unit 103, the shift storage unit 104, and the write control unit 102.

  As shown in FIG. 6A, when the photosensitive drum 1Y is not decentered or inclined, and the intermediate transfer belt 9 does not fluctuate, a linear adjustment toner image is observed on the intermediate transfer belt 9. As shown in FIG. 6B, when the photosensitive drum 1Y is decentered or inclined, or when the intermediate transfer belt 9 is fluctuating, a curved adjustment toner image is observed on the intermediate transfer belt 9. The

  As shown in FIG. 7 with reference to FIG. 5, after acquiring the edge profile of the intermediate transfer belt 9 using the shift sensor YS, the control unit 101 samples the yellow adjustment toner image by the image sensors IS1 and IS2. To do. The edge profile is correction data for removing an error component of the rotation cycle of the intermediate transfer belt 9 included in the output of the deviation sensor YS.

  When the image generation unit PY starts writing the electrostatic image of the adjustment toner image, the control unit 101 issues a command to the sampling control unit 105 and waits until the encoder EY of the photosensitive drum 1Y detects the Z phase (s1). No). The Z phase is a reference pulse that is output once for one rotation of the photosensitive drum 1Y.

  When the control unit 101 finds the Z phase (Yes in s1), it waits for a delay time until the adjustment toner images reach the image sensors IS1 and IS2 (s2). The delay time TD is the sum of the rotation time Tx of the photosensitive drum 1Y from the electrostatic image writing position of the photosensitive drum 1Y to the primary transfer portion and the rotation time Ty of the intermediate transfer belt 9 from the primary transfer portion to the image sensors IS1 and IS2. is there.

  Here, when the process speed is 300 mm / sec and the diameter of the photosensitive drum 1Y is 80 mm, the rotation time Tx of the photosensitive drum 1Y is 0.42 seconds corresponding to about a half circumference of the photosensitive drum 1Y. The distance between the photosensitive drums 1Y, 1M, 1C, and 1K is 250 mm, and the distance from the primary transfer portion of the photosensitive drum 1K to the image sensors IS1 and IS2 is also 250 mm. At this time, the distance from the primary transfer portion of the photosensitive drum 1Y to the image sensors IS1 and IS2 is 1000 mm in total. The rotation time Ty of the intermediate transfer belt 9 is about 3.33 seconds when 1000 mm is divided by a process speed of 300 mm. Therefore, the delay time TD is 0.42 seconds + 3.33 seconds = 3.75 seconds in total.

  When the delay time TD elapses, the control unit 101 generates a sampling timing signal for one rotation of the photosensitive drum 1Y because the adjustment toner image reaches the image sensors IS1 and IS2 (s3).

  Here, the frequency of fluctuation in the main scanning direction caused by the photosensitive drum 1Y may be about 1 Hz and its multiplied wave, which can be detected up to several Hz, by dividing the circumference of the photosensitive drum 1Y by the process speed. Assuming a sine wave, it is sufficient to sample several tens of samples in one cycle. Therefore, here, one cycle is sampled by dividing it into 36 intervals every 10 degrees. Further, assuming that the number of repetitions n of one set of sampling of the rotation cycle of the photosensitive drum 1Y is 10, the fluctuation in the main scanning direction is repeatedly sampled over 10 rotations of the photosensitive drum 1Y.

  When generating the sampling signal for one rotation of the photosensitive drum 1Y (s3), the control unit 101 checks whether n rotations, that is, 10 rotations (s4). If it has not reached 10 laps (No in s4), the control unit 101 continues sampling (s3). When 10 laps are reached (Yes in s4), sampling is terminated. The image storage unit 103 receives the sampling signal, samples and stores the detected image data of the image sensors IS1 and IS2.

  Note that in the image forming units PM, PC, and PK other than the yellow image forming unit PY, the sampling time is generated in the same manner as the image forming unit PY by changing the delay time TD depending on the distance, and the image sensors IS1, The detected image data of IS2 is sampled.

  As shown in FIG. 8 with reference to FIG. 5, the control unit 101 detects the shift of the intermediate transfer belt 9 at the phase position corresponding to each sampling position of the yellow adjustment toner image. To sample. When the image generation unit PY starts writing the electrostatic image of the adjustment toner image, the control unit 101 issues a command to the sampling control unit 105 and waits until the encoder EY of the photosensitive drum 1Y detects the Z phase (s11). No).

  When the control unit 101 finds the Z phase (Yes in s11), it waits for a delay time of the rotation time Tx of the photosensitive drum 1Y from the electrostatic image writing position of the photosensitive drum 1Y to the primary transfer unit (s12). As described above, the rotation time Tx of the photosensitive drum 1Y is 0.42 seconds corresponding to about a half circumference of the photosensitive drum 1Y.

  When the delay time TD elapses, the control unit 101 generates a sampling timing signal for one rotation of the photosensitive drum 1Y because the adjustment toner image reaches the primary transfer unit (s13).

  Sampling is performed at an interval of 36 degrees, which is the same interval as that of the image sensors IS1 and IS2, for easy calculation later. The number of repetitions n of sampling in one cycle is also 10 rounds together with the detection by the image sensors IS1 and IS2.

  When generating the sampling signal for one rotation of the photosensitive drum 1Y (s13), the control unit 101 checks whether or not n rotations, that is, 10 rotations (s14). If it has not reached 10 laps (No in s14), the control unit 101 continues sampling (s13). When 10 laps are reached (Yes in s14), the sampling is finished. The shift storage unit 104 receives the sampling signal, samples and stores the shift detection data detected by the shift sensor YS.

  As shown in FIG. 9, the adjustment toner image shown in FIG. 6B is sampled by the image sensor IS1 (IS2). After the Z phase is recognized by the encoder EY and after a delay time TD, the image data of the image sensor IS1 (IS2) is sampled by the sampling signal from the first round to the tenth week of the photosensitive drum 1Y. Further, the data of the shift variation amount sampled using the shift sensor YS is also acquired in the same manner as in FIG. 9 although the delay time is different.

  Note that the fluctuation amount in FIG. 9 is a plot of the fluctuation amount of the adjustment toner image with respect to the reference position in the main scanning direction, and is not sampled imaging data itself.

  After the end of these samplings, the drawing position analysis unit 106 adds the data obtained by subtracting the deviation amount of the intermediate transfer belt 9 from the fluctuation amount of the adjustment toner image for each same writing position of the photosensitive drum 1Y, and takes the average. Thus, components that are not synchronized with the photosensitive drum 1Y are canceled. Thereby, only the fluctuation in the main scanning direction due to the photosensitive drum 1Y (broken line in FIG. 4) is extracted. Based on the analysis result of the drawing position analysis unit 106, the control unit 101 electrostatically charges the exposure device 3Y at each phase position of the photosensitive drum 1Y so as to cancel out only the fluctuation in the main scanning direction caused by the photosensitive drum 1Y. The image writing start position is corrected in the main scanning direction.

  The drawing position analysis unit 106 extracts the amount of fluctuation in the main scanning direction caused by the photosensitive drum 1Y from the stored image data of the adjustment toner image and the deviation detection data of the intermediate transfer belt. As described above, since sampling is performed with an appropriate delay time, the stored data is synchronized with the Z phase of the photosensitive drum 1Y. Therefore, if the sampled data is converted into the fluctuation amount from the reference position in the main scanning direction, and the deviation amount obtained by converting the deviation detection data is subtracted from the fluctuation amount in the main scanning direction obtained by converting the image data, the intermediate transfer belt. The 9 fluctuation component is offset.

  The edge profile of the intermediate transfer belt 9 described above is the rotation cycle of the intermediate transfer belt 9 obtained by averaging the output of the shift sensor YS a plurality of times at each position of the intermediate transfer belt 9 without forming an adjustment toner image. It is a fluctuation amount. The output of the shift sensor YS when sampling the adjustment toner image is used by subtracting the edge profile of the intermediate transfer belt 9.

  In Example 1, the adjustment toner image is transferred to the intermediate transfer belt 9 and read by the image sensors IS1 and IS2. When the fluctuation component in the main scanning direction due to the photosensitive drum 1Y is extracted from the read information, the shift amount information of the intermediate transfer belt 9 is subtracted from the fluctuation information in the main scanning direction read from the adjustment toner image. . The read value of the deviation sensor YS of the intermediate transfer belt 9 is subtracted from the fluctuation value obtained by reading the adjustment toner image.

  According to the adjustment mode of the first embodiment, even when the frequency of fluctuation caused by the photosensitive drum 1Y is close to the frequency of fluctuation caused by the driving roller 13 that is a disturbance, the read data of the adjustment toner image is transferred to the photosensitive drum 1Y. It is not difficult to extract the fluctuation component in the main scanning direction.

  According to the adjustment mode of the first embodiment, when the fluctuation due to the photosensitive drum is extracted, the shift fluctuation component is subtracted, so that the fluctuation amount can be accurately extracted even by sampling with a small number of rotations. By shortening the sampling time, toner consumption can be reduced and the execution time of the adjustment mode is shortened.

  In the description, the sampling interval is divided into 36. However, this timing is not limited to this as long as the delay time TD from the Z phase is secured, and it is only necessary to perform sampling at a constant time interval. The position correction in the main scanning direction in the scanning line writing may be a table method or a method of calculating each time as a function as in the second embodiment.

<Example 2>
In the second embodiment, the operation of the drawing position analysis unit 106 in the first embodiment is executed using mathematical expressions. Although there are two image sensors IS1 and IS2, the processing is the same, so only the processing of the image sensor IS1 will be described.

36 × 10 values obtained by converting the image data of the toner image for adjustment stored in the image storage unit 103 into the amount of variation from the reference position are determined as follows.
ID1, ID2, ... IDn ... ID360 (1)

36 × 10 values obtained by converting the shift detection data of the intermediate transfer belt 9 stored in the shift storage unit 104 into the shift amount from the reference position are determined as follows.
YD1, YD2, ... YDn ... YD360 (2)

Here, since the reading position is a distance L from the photosensitive drum, the intermediate transfer belt moves in the main scanning direction during that time. Therefore, if the acquired shift position data is added with the phase difference of the reading position shifted, the amount of fluctuation from the writing position is corrected. Since one round is 36 data, the number j of phase difference data is expressed by the following equation, where int () is a function indicating an integer part in parentheses.
j = int (L / πd × 36)

Assuming that the amount of deviation from the reference position obtained by correcting equation (2) from the amount of variation from the reference position of equation (1) is YDCn, the amount of deviation YDCn is a function “mod (n + j, 360) ”is expressed by the following equation.
YDCn = YDn-YD.mod (m + j, 360)

Equation (3) may be calculated using YDCn obtained as described above instead of YDn. The drawing position analysis unit 106 subtracts the shift amount YDCn from the reference position in order at n = 1 to 360, and executes the following calculation.
FDn = IDn-YDCn (3)

  The FDn in the expression (3) is a fluctuation amount in the main scanning direction due to the photosensitive drum from which the close component is removed.

  When the calculation of the expression (3) is completed, the drawing position analysis unit 106 cancels out disturbance components other than the photosensitive drum 1Y by adding 10 rotations for each same phase position of the photosensitive drum 1Y and taking an average. That is, 360 pieces of data are added every other 36 and divided by 10.

  M in the formula (4) is a number from 1 to 36 obtained by dividing one round into 36. FDA1 to FDA36 calculated in this way represent the fluctuation amount in the main scanning direction caused by the photosensitive drum.

As shown in FIG. 6B, the adjustment toner image for color misregistration detection is in the vicinity of both ends of the photosensitive drum 1Y, and the image sensors IS1 and IS2 are provided on both sides of the intermediate transfer belt 9 in the width direction. ing. Therefore, the shift amount of each color can be obtained from the fluctuation amount in the main scanning direction obtained from the image sensors IS1 and IS2. The drawing position analysis unit 106 obtains the following shift amount and transmits it to the control unit 101.
Yellow FDAY1m, FDAY2m
Magenta FDAM1m, FDAM2m
Cyan FDAC1m, FDAC2m
Black FDAK1m, FDAK2m

Here, if the image sensor IS1 side is the laser scanning start side, the value of FDAY1m can be used as it is with the sign inverted for correction of the writing position. The correction value of the exposure apparatus (laser unit) 3Y, that is, the correction amount of the writing position is expressed by the following equation.
Yellow -FDAY1m
Magenta-FDAM1m (5)
Cyan -FDAC 1m
Black -FDAK1m

Further, since FDAY2m-FDY1m represents the fluctuation of the scanning line length for drawing an electrostatic image, if the reference value of the length between both ends of the scanning line is L, the following expression is contracted (enlarged) in the scanning line direction. Represents the rate.
MYm = (FDAY2m−FDY1m + L) / L (6)

Therefore, the correction value for contraction (enlargement) in the scanning line direction is the reciprocal of MYm.
1 / MYm = L / (FDAY2m−FDY1m + L) (7)

  The control unit 101 transmits correction values (6) and (7) to the writing control unit 102 prior to the start of image formation. The writing control unit 102 corrects the writing position and magnification of laser drawing with the transmitted correction values (6) and (7), and controls the position and length of the laser drawing scanning line in the main scanning direction.

  As shown in FIG. 10, switching of 36 correction values per rotation in the writing control unit 102 is performed according to a signal from the sampling control unit 105. The Z phase is a reference signal for the phase of the photosensitive drum 1Y, and the correction value described above is taken in synchronization with the Z phase, and one round is divided into 36 so that it can be switched at the same interval as when the sampling is performed. That's fine. When the Z phase is recognized, the first correction value is selected, the correction values are switched to the 36th in order, and the 36th returns to the first.

  In the second embodiment, the same operation is performed on the photosensitive drums 1M, 1C, and 1K of the other image forming units PM, PC, and PK, thereby correcting fluctuations in the main scanning direction of the image caused by the photosensitive drums. The color shift of each color is reduced.

  In the second embodiment, the sampling time interval of the image data of the adjustment toner image and the correction value switching time interval at the time of image formation are the same. May be set.

<Example 3>
As shown in FIG. 1, in the third embodiment, the support rotating body adjacent to the image sensors IS1 and IS2 is a steering roller that tilts and controls the intermediate transfer belt 9 to be shifted. The deviation sensor YS also serves as a sensor for detecting the deviation amount of the intermediate transfer belt 9 used for deviation control of the intermediate transfer belt 9.

  In the third embodiment, the driving roller 13 in the first embodiment is a steering roller (13) that rotates following the rotation of the intermediate transfer belt 9. In the first and second embodiments, the shift sensor YS is a dedicated sensor for executing the adjustment mode, but in the third embodiment, the shift of the intermediate transfer belt 9 fed back to the amount of tilt of the steering roller (13). It also serves as a steering sensor that detects the amount. A belt shift control unit (not shown) changes the tilt amount of the steering roller in real time so as to cancel the shift amount of the intermediate transfer belt 9 detected by the shift sensor YS so that the fluctuation of the shift of the intermediate transfer belt 9 does not increase. Is controlling.

  In the third embodiment, since the deviation variation in the main scanning direction of the intermediate transfer belt 9 is measured using the existing deviation sensor YS, it is not necessary to provide a dedicated deviation sensor YS.

<Example 4>
In Examples 1 and 2, a linear adjustment toner image was formed so as to go around a predetermined position of the photosensitive drum 1Y in the main scanning direction. However, the adjustment toner image is not limited to a linear one. For example, a toner image for adjustment having a broken line shape that covers a phase position necessary for measurement may be employed.

  Alternatively, a V-shaped intermittent adjustment toner image opened in the main scanning direction may be employed. The V-shaped intermittent adjustment toner image opened in the main scanning direction is widely used as a registration mark for measuring a certain amount of positional deviation (DC component) of the toner images of the two image forming units. . In the case of a V-shaped pattern adjustment toner image used as a registration mark, an ordinary reflective optical sensor can also measure the positional deviation between the main scanning direction and the sub-scanning direction.

<Example 5>
FIG. 11 is an explanatory diagram of a partial configuration of the image forming apparatus according to the fifth embodiment. As shown in FIG. 11, a plurality of photosensitive drums 1 </ b> Y, 1 </ b> M, 1 </ b> C, and 1 </ b> K, which are examples of image carriers, are arranged in the rotation direction of the intermediate transfer belt 9 with an interval equal to the circumferential length of the driving roller 13. . When the diameter of the driving roller 13 is d and the distance from the adjustment toner image transfer position to the detection position of the image sensors IS1 and IS2 is L, “0.4 <L / (π × d) <0.6. It is. That is, it is a range in which fluctuation in the sub-scanning direction of the intermediate transfer belt 9 becomes an error in the reverse phase, which can be regarded as substantially 0.5.

  As shown in FIG. 1, in the image forming apparatus 100 according to the first embodiment, the photosensitive drums 1Y, 1M, 1C, and 1K are spaced by an interval equal to an integral multiple of the circumferential length of the driving roller 13 and the rotational direction of the intermediate transfer belt 9. Is arranged in multiple. Specifically, when the diameter of the driving roller 13 is d, the intervals between the image forming portions PY, PM, PC, and PK are set to be equal to πd. Toner images from the photosensitive drums 1Y, 1M, 1C, and 1K in the state where the color shifts in the main scanning direction and the sub-scanning direction of the intermediate transfer belt 9 due to the eccentricity and inclination of the driving roller 13 repeated for each circumferential length of the driving roller 13 are equal. This is because primary transfer is performed.

A distance L along the intermediate transfer belt 9 from the primary transfer portion of the photosensitive drum 1K to the image sensors IS1 and IS2 is set as follows. An adjustment toner image that has passed through the photosensitive drum 1K is imaged in the state where the color shift in the main scanning direction and the sub-scanning direction of the intermediate transfer belt 9 due to the eccentricity and inclination of the driving roller 13 repeated for each circumferential length of the driving roller 13 is equal. This is because they are detected by the sensors IS1 and IS2.
L = πd

However, as shown in FIG. 11, in the image forming apparatus of Example 5, in order to shorten the circumference of the intermediate transfer belt 9 and reduce the size, the primary transfer unit from the photosensitive drum 1K to the image sensors IS1 and IS2 is used. A distance L along the intermediate transfer belt 9 is set as follows.
L = πd / 2

  In this case, the adjustment that has passed through the photosensitive drum 1K in a state where the color shift in the main scanning direction and the sub-scanning direction of the intermediate transfer belt 9 due to the eccentricity or inclination of the driving roller 13 repeated every circumferential length of the driving roller 13 is just reversed. The toner image is detected by the image sensors IS1 and IS2. For this reason, distortion in the main scanning direction of the toner image caused by the intermediate transfer belt 9 is increased.

  Even in such a case, by executing the adjustment modes of the first and second embodiments, the writing start position of the electrostatic image can be adjusted so that the fluctuation in the main scanning direction of the intermediate transfer belt 9 is also removed. . As a result, as shown in (b) of FIG. 3, the distortion of the toner image of the image can be made inconspicuous as shown in (a) of FIG. It was.

1Y, 1M, 1C, 1K Photosensitive drums 3Y, 3M, 3C, 3K Exposure devices 4Y, 4M, 4C, 4K Developing devices 5Y, 5M, 5C, 5K Primary transfer roller 9 Intermediate transfer belt 10 Secondary transfer counter roller 11 2 Next transfer roller, 12 Tension roller 13 Drive roller 101 Control unit, 106 Drawing position analysis unit IS1, IS2 Image sensor YS Shift sensor, EY encoder

Claims (5)

An image carrier;
An electrostatic image forming means can be written into the electrostatic image for adjustment a predetermined position in the main scanning direction of the image bearing member,
An image forming apparatus comprising: a belt member arranged to transfer an adjustment toner image obtained by developing the adjustment electrostatic image from the image carrier;
First detection means for detecting a position in the main scanning direction of the adjustment toner image on the belt member transferred from the image carrier;
A second detecting means for detecting a main scanning direction position of the belt member,
The adjustment electrostatic image is drawn so that the adjustment toner image is formed a plurality of times at each position in the sub-scanning direction of the image carrier, and is formed at each position and detected by the first detection means. Further, the fluctuation in the main scanning direction of the belt member at the time when the adjustment toner image formed at each position is transferred to the belt member from the fluctuation amount of the adjustment toner image with respect to the reference position in the main scanning direction . The main image of the electrostatic image corresponding to the output image at each position in the sub-scanning direction of the image carrier so as to cancel out the amount accumulated over the number of times the adjustment toner image is formed at each position, except for the amount. An image forming apparatus comprising: a control unit capable of executing an adjustment mode for adjusting at least one of a forming position in a scanning direction and a forming magnification.   The image carrier is in the form of a drum;
  A support rotating body that supports and rotates the belt member;
  When the diameter of the image carrier is D and the diameter of the support rotating body is d, a relationship of 0.8 <D / (n × d) <1.2 holds for a certain natural number n. The image forming apparatus according to claim 1. 3. The image forming apparatus according to claim 2 , wherein a plurality of the image carriers are arranged in the rotation direction of the belt member with an interval equal to an integral multiple of the circumference of the support rotating body.   The support rotator is a steering roller that tilts and controls the belt member to be shifted,
  The image forming apparatus according to claim 2, wherein the second detection unit also serves as a sensor that detects a shift amount of the belt member used for the shift control of the belt member. Said control means, by bereaved the adjustment mode, the main scanning direction position location of the belt member, wherein each integrated to in correspondence to a plurality of phase position of the belt member in the main scanning direction position location of said belt member Get correction data,
Wherein, in the adjustment mode, it compares the amount of change with respect to the reference position in the main scanning direction of the adjusting toner image using the amount of variation in the main scanning direction of the belt member that has been corrected using the correction data The image forming apparatus according to claim 1 , wherein the image forming apparatus is an image forming apparatus.

Images