JP2009180884A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which achieves higher speed, detects the position of an endless belt member in a main scanning direction with a simple structure, and surely controls it, and prevents image distortion or color slippage. <P>SOLUTION: The image forming apparatus includes: a belt position detection means for detecting the position of the endless belt member in the main scanning direction by sequentially detecting the position in the main scanning direction of a plurality of detection marks which are formed on the endless belt member; a displacement detection means in belt main scanning direction for sequentially detecting displacement in the main scanning direction of the detection marks on the endless belt member due to belt conveyance of prescribed intervals; a belt position adjusting means for adjusting the position in the main scanning direction of the endless belt member on the basis of information of the position in the main scanning direction which is detected by the belt position detection means; and a latent image forming position correction means for correcting a latent image forming position in the main scanning direction on an image carrier on the basis of the information of the displacement in the main scanning direction which is detected by the belt displacement detection means. The displacement detection means in the belt main scanning direction is arranged within a plane transferring a visible image on the image carrier among the belt plane sections among a plurality of conveying rollers. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus such as a copying machine, a facsimile machine, a printer, etc., which develops a latent image formed on an image carrier to make a visible image and a plurality of visible images The present invention relates to an image forming apparatus that obtains a plurality of color images by superimposing images.

  2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, an image forming apparatus using an endless belt as an intermediate transfer member that is a transfer medium or a recording sheet that is a transfer medium is known. The endless belt is stretched around a plurality of rollers and driven to circulate. At this time, a meandering phenomenon in which the belt position moves in a direction (main scanning direction) orthogonal to the belt conveying direction (sub-scanning direction) may occur. is there. When this meandering phenomenon occurs, the image forming position on the transfer medium such as the intermediate transfer member or the recording paper is displaced, and this causes image distortion. Also, in a color image forming apparatus that forms black, yellow, magenta, and cyan single color images and superimposes them on a transfer medium to obtain a color image, the image formation position shifts between the color toner images. Appears as a gap. All of these lead to degradation of image quality, and it is necessary to take some measures for belt meandering in order to obtain a high-quality image.

  Therefore, various methods have been proposed in order to deal with such problems, and one of them is a method in which a guide member is provided near the endless belt. However, the force in the main scanning direction generated in the endless belt is regulated by bringing a shift guide member provided on the belt surface into contact with the end surface of the belt conveying roller, and the meandering of the endless belt is suppressed. Belt meandering due to the main guide in the main scanning direction of the shift guide member and the wobbling of the end face of the conveying roller cannot be suppressed, and there is a drawback in that image distortion and color misregistration occur due to positional deviation in the main scanning direction.

  On the other hand, in Patent Document 1, in a method in which the meandering of the belt is regulated by a side guide member provided on the belt, in order to remove the influence of the shake of the end face of the transport roller, the phase is opposite to that of the end face of the transport roller. In addition, an image forming apparatus for controlling the position of a latent image formed on an image carrier has been proposed.

  Further, in Patent Document 2, in a system in which the meandering of the belt is regulated by a side guide member provided on the belt, the latent image formed on the image carrier is measured based on the meandering component for one period of the belt measured in advance. An image forming apparatus that controls the position has been proposed.

  Further, as a method other than providing a guide member near the endless belt, in Patent Document 3, a slit parallel to the transport direction is printed in advance on the end of the endless belt in the main scanning direction, and the meandering displacement is detected by a sensor that detects the slit position. An image forming apparatus that detects and controls the position of a latent image formed on an image carrier has been proposed.

Further, in Patent Document 4, the belt is reciprocated in the main scanning direction by releasing the parallel relationship of the conveying rollers of the endless belt, the position detecting means for the endless belt member, and the reciprocating speed storage means for the endless belt. And an image forming apparatus that controls the position of the latent image formed on the image carrier in accordance with the moving speed stored in accordance with the reciprocating direction of the belt.
JP 2005-84063 A JP 2005-148127 A JP 2004-226660 A JP 2003-162196 A

  However, in Patent Document 1, the belt meandering component due to the contact with the end face of the belt conveying roller can be suppressed, but the belt meandering due to the shake of the shift guide member cannot be suppressed, and the image distortion due to the displacement in the main scanning direction, Color shift occurs. Further, in Patent Document 2, since the meandering component for one belt cycle including the belt transport roller end surface touch and the main scanning direction deflection of the shift guide member is measured in advance, the belt caused by the deflection of both the roller end surface and the guide member. Although meandering can be suppressed, it is necessary to frequently measure meandering components in order to cope with deformation over time of endless belts and offset guide members, and deformation due to environmental changes such as temperature and humidity. Since the operation is frequently interrupted, this greatly hinders the speeding up of image output. There is also a problem that it is difficult to cope with dynamic deformation due to the influence of vibration or the like. In addition, in the method of suppressing the belt meandering by providing a side guide member on the endless belt, when the belt is driven at a high speed, a large external force is applied to the side guide member, and the belt and the side guide member are buckled or damaged. It is easy to invite and it is difficult to speed up image output.

  On the other hand, by detecting the detection mark formed on the endless belt with a sensor without providing a guide member near the endless belt, the meandering of the endless belt is detected, and the latent image forming position on the image carrier is controlled. The method for suppressing the influence of the belt meandering has the following problems. In Patent Document 3, the belt is detected by detecting a slit parallel to the conveyance direction of the intermediate transfer body printed in advance on the main scanning end on the transfer surface, which is a non-image forming area of the endless belt-shaped intermediate transfer body, with a reflective sensor. The amount of meandering is detected. Further, in Patent Document 4, a marker on a line having a width extending over the entire circumference is provided on an endless belt, and a marker detection unit having a linear CCD is disposed along the direction across the endless belt. The belt position in the meandering direction is detected. In these methods, it is impossible to form detection marks such as slits and signs formed on the belt over the entire circumference of the endless belt completely in parallel with the conveyance direction, and detection mark formation errors exist reliably. . Further, the detection mark formed on the belt is also deformed due to deformation of the belt with time or deformation accompanying environmental changes such as temperature and humidity. Therefore, in Patent Documents 3 and 4, since the detection mark is detected one-dimensionally by a reflective sensor or a line-shaped CCD, when detecting the belt meandering amount per unit time, it is detected at a reference time. The sensor mark position that is detected after a unit time from the sensor mark position is actually a position that is separated by the distance that the belt is transported within the unit time. The detection mark formation error at this distance and the influence of deformation are the results of belt meandering detection. Even if no meandering occurs, the latent image formation position on the image carrier is controlled in accordance with the detection mark formation error and deformation. There is a problem that image distortion and color misregistration occur due to.

  In addition, detection marks such as slits and signs formed on the belt can be formed over the entire circumference of the endless belt completely in parallel with the circumferential direction. Even if there is no deformation due to environmental changes, the belt detection mark that passes through a portion corresponding to a detector such as a reflective sensor or a line CCD can be detected by the methods of Patent Document 3 and Patent Document 4. It is impossible to detect the behavior of each part in the belt that is displaced in the main scanning direction when each part in the belt moves in the transport direction.

  Here, a behavior analysis result of a belt that is stretched around a plurality of rollers and driven to circulate is shown. FIG. 16 shows an analysis target model in which another driven roller rotary shaft is inclined outwardly from the belt conveying surface with respect to a reference driving roller rotary shaft in a belt stretched around three rollers. FIG. In the model, the position in the main scanning direction of the belt center line conveyed near the measurement point A in space is shown in FIG. It can be seen that as the belt is transported, the position of the belt center line transported in the vicinity of the measurement point A in space moves at a constant speed in the main scanning direction. On the other hand, the measurement point B on the belt is largely displaced in the main scanning direction in the range where it is in contact with the inclined driven roller, and is in the range where it is in contact with the other non-inclined driving roller and driven roller. It can also be seen that the sheet is conveyed while being always displaced in the main scanning direction even in a range where it does not contact any roller.

  Based on the above analysis results, when the behavior of the entire belt moving in the main scanning direction from the reference position in space is measured, such as the behavior of the belt center line at the measurement point A in space, and the behavior of the measurement point B on the belt. Thus, it can be seen that the results obtained are different from the case where the behavior of each part on the belt moving in the main scanning direction with conveyance is measured. This is a state in which the belt deviation caused by the installation error of each roller that stretches the belt is adjusted so that the entire belt does not move in the main scanning direction by changing the inclination of one roller. Each part on the belt moves in various ways in the main scanning direction as it is conveyed, indicating that it has only returned to the same main scanning direction position after one rotation.

  What can be detected by the configurations of Patent Literature 3 and Patent Literature 4 is the same behavior as the measurement result at the spatial measurement point A in the above analysis result, and the amount by which the entire belt moves in the main scanning direction with conveyance. Therefore, it is possible to detect the belt deviation allowable range in Patent Document 4.

  However, as described in Patent Document 3, in order to correct the image forming position on the image carrier in order to prevent the color misregistration of the image superimposed on the intermediate transfer belt, the intermediate transfer belt is in contact with the image carrier contact surface. It is necessary to detect what behavior is being conveyed in the main scanning direction within the main scanning direction. For this purpose, it is necessary to detect the same behavior as the measurement result at the measurement point B in the above analysis result. It becomes.

  The present invention is for solving these problems, and it is not necessary to interrupt the image forming operation for correcting the shift and meandering without using a configuration that hinders high-speed driving of the belt such as a shift guide member. The image output can be greatly speeded up, and the position of the endless belt member in the main scanning direction can be accurately detected and controlled with a simple configuration, and the endless belt member can be accurately displaced in the main scanning direction. By detecting and reliably correcting the image forming position on the image carrier, it is possible to prevent image distortion and color misregistration due to misregistration in the main scanning direction. It aims to be realized.

  In order to solve the above problems, an image forming apparatus according to the present invention visualizes a latent image forming unit that forms a latent image on an image carrier and the latent image formed on the latent image forming unit. A developing unit; an intermediate transfer member that primarily transfers a visible image formed on the image bearing member; and a recording material conveying unit that conveys a recording material that secondarily transfers the transfer image on the intermediate transfer member. The transfer body includes a plurality of conveyance rollers disposed substantially in parallel with each other at a predetermined distance, and an endless belt member that is supported by the conveyance rollers and carries the transfer image. A visible image formed on the body is sequentially superimposed on the intermediate transfer body to form a multicolor image. The image forming apparatus according to the present invention includes a belt position detecting unit that sequentially detects main scanning direction positions of a plurality of detection marks formed on the endless belt member, and detects the main scanning direction position of the endless belt member; A belt main scanning direction displacement detecting means for sequentially detecting displacement in the main scanning direction accompanying belt conveyance at a predetermined interval of detection marks on the belt member, and an endless belt based on information on the position in the main scanning direction detected by the belt position detecting means. A belt position adjusting means for adjusting the position of the member in the main scanning direction, and a latent image forming position for correcting the latent image forming position in the main scanning direction on the image carrier based on information on the displacement in the main scanning direction detected by the belt displacement detecting means. The belt main scanning direction displacement detecting means is arranged in a plane where a visible image on the image carrier is transferred among belt flat portions between a plurality of conveying rollers. Is the fact is characterized in. Therefore, it is not necessary to use a configuration that obstructs high-speed belt driving such as a shift guide member, and it is not necessary to interrupt the image forming operation for correction of shift and meandering, so that the image output speed can be greatly increased. In addition, the position and displacement of the endless belt in the main scanning direction can be accurately detected with a simple configuration, and the belt position is reliably controlled based on the detected position information, and the image forming position of the image carrier based on the detected displacement information Since the image distortion and the color misregistration due to the positional deviation in the main scanning direction can be prevented by reliably correcting the image quality, an image forming apparatus capable of greatly improving the output image quality can be realized.

  The image forming apparatus of the present invention also includes a latent image forming unit that forms a latent image on the image carrier, a developing unit that visualizes the latent image formed on the latent image forming unit, and an image carrier. A recording material conveying means for conveying a recording material for transferring a visible image formed thereon, and the recording material conveying means includes a plurality of conveying rollers disposed substantially parallel to each other at a predetermined distance. And an endless belt member that is carried around and conveyed by the respective conveying rollers, and sequentially overlays the visible image formed on the image carrier on the recording material on the recording material conveying means so as to obtain a multi-color image. Form. The image forming apparatus according to the present invention includes a belt position detecting unit that sequentially detects main scanning direction positions of a plurality of detection marks formed on the endless belt member, and detects the main scanning direction position of the endless belt member; A belt main scanning direction displacement detecting means for sequentially detecting displacement in the main scanning direction accompanying belt conveyance at a predetermined interval of detection marks on the belt member, and an endless belt based on information on the position in the main scanning direction detected by the belt position detecting means. A belt position adjusting means for adjusting the position of the member in the main scanning direction, and a latent image forming position for correcting the latent image forming position in the main scanning direction on the image carrier based on information on the displacement in the main scanning direction detected by the belt displacement detecting means. The belt main scanning direction displacement detecting means is arranged in a plane where a visible image on the image carrier is transferred among belt flat portions between a plurality of conveying rollers. Is the fact is characterized in. Therefore, it is not necessary to use a configuration that obstructs high-speed belt driving such as a shift guide member, and it is not necessary to interrupt the image forming operation for correction of shift and meandering, so that the image output speed can be greatly increased. In addition, the position and displacement of the endless belt in the main scanning direction can be accurately detected with a simple configuration, and the belt position is reliably controlled based on the detected position information, and the image forming position of the image carrier based on the detected displacement information Since the image distortion and the color misregistration due to the positional deviation in the main scanning direction can be prevented by reliably correcting the image quality, an image forming apparatus capable of greatly improving the output image quality can be realized.

  Further, the belt main scanning direction displacement detecting means is in the vicinity of an intermediate position in the belt conveying direction within a range in which the plurality of arranged image carriers are in contact with the belt in a plane for transferring a visible image on the image carrier. Placed in. Therefore, since the information on the displacement in the main scanning direction can be accurately detected, the image forming position of the image carrier can be reliably corrected, and image distortion and color misregistration due to displacement in the main scanning direction can be prevented. .

  Further, the belt main scanning direction displacement detecting means is a position in the belt conveyance direction at a position where each image carrier adjacent to the belt conveyance direction abuts the endless belt member in a plane for transferring a visible image on the image carrier. Arranged in the vicinity of the intermediate position. Therefore, since the information on the displacement in the main scanning direction can be detected more accurately, the image forming position of the image carrier can be surely corrected, and image distortion and color misregistration due to displacement in the main scanning direction can be prevented. it can.

  Further, the belt main scanning direction displacement detecting means is composed of sensors provided at at least two positions in the belt conveying direction capable of detecting the positions in the main scanning direction of a plurality of detection marks formed on the endless belt member. Each detection mark in the plurality of detection marks on the belt member is detected by a sensor, and the amount of movement in the main scanning direction due to conveyance between the two belt conveyance direction detection positions is sequentially detected to detect the belt displacement information and endlessly The position information of the belt main scanning direction is detected by sequentially detecting the position of each detection mark on the belt member in the main scanning direction for each rotation of the belt. Therefore, since it is possible to accurately detect displacement information and position information in the main scanning direction with a simple configuration, it is possible to reliably control the belt position and to reliably correct the image forming position of the image carrier. Further, it is possible to prevent image distortion and color misregistration due to positional deviation in the main scanning direction.

  The sensor is a one-dimensional sensor, and the detection mark formation interval in the main scanning direction is smaller than the detection position interval in the belt conveyance direction of two adjacent one-dimensional sensors. Therefore, since it is possible to accurately detect information on displacement in the main scanning direction over the entire endless belt cycle with a simple configuration, the belt position can be reliably controlled and the image forming position of the image carrier can be reliably corrected. Thus, image distortion and color misregistration due to misalignment in the main scanning direction can be prevented.

  Further, the sensor is a two-dimensional area sensor, and the formation interval of detection marks in the main scanning direction is smaller than the main scanning direction detection range of the two-dimensional area sensor. Therefore, since it is possible to accurately detect information on displacement in the main scanning direction over the entire endless belt cycle with a simple configuration, the belt position can be reliably controlled and the image forming position of the image carrier can be reliably corrected. Thus, image distortion and color misregistration due to misalignment in the main scanning direction can be prevented.

  In addition, since the detection mark has at least two intersecting sides, it is possible to detect the displacement information in the main scanning direction over the entire endless belt in a simple configuration with a simple configuration. As a result, the image forming position of the image carrier can be reliably corrected, and image distortion and color misregistration due to misregistration in the main scanning direction can be prevented.

  Further, a sub-scanning direction conveyance speed calculating means is provided for sequentially measuring a conveyance time between two belt main scanning direction detection positions where the sensor detects the detection mark and calculating a conveyance speed in the sub-scanning direction of the endless belt member. Have. Accordingly, since it is possible to accurately detect the displacement and position information of the endless belt in the main scanning direction with a simple configuration, it is also possible to accurately detect the sub-scanning direction speed information of the endless belt member. By controlling the image forming position of the image bearing member with certainty, it is possible not only to prevent image distortion and color misregistration due to misregistration in the main scanning direction, but also to achieve a predetermined belt sub-scanning direction speed. By performing the above, color misregistration due to position misalignment in the sub-scanning direction can be reliably prevented.

  Further, the detection marks are formed on the endless belt member at regular intervals, and the sub-scanning direction conveyance speed calculation means for calculating the conveyance speed in the sub-scanning direction of the endless belt member by counting the detection marks detected by the sensor at a certain time. Have Therefore, the information on the displacement in the main scanning direction of the endless belt and the position information can be accurately detected with a simple configuration, and the speed information on the sub scanning direction of the endless belt can be detected more accurately. By controlling the image forming position of the image bearing member with certainty, it is possible not only to prevent image distortion and color misregistration due to misregistration in the main scanning direction, but also to achieve a predetermined belt sub-scanning direction speed. By performing the above, color misregistration due to misregistration in the sub-scanning direction can be prevented more reliably.

  Further, the detection marks are formed on the endless belt member at regular intervals, and the phase difference of the detection cycle at the main scanning detection position obtained by the two sensors detecting the same detection mark is detected to detect the detection mark. It has expansion / contraction detection means for detecting the expansion / contraction value in the scanning direction. Therefore, with a simple configuration, it is possible to accurately detect the displacement and position information of the endless belt in the main scanning direction, and it is possible to accurately detect the expansion and contraction of the endless belt in the sub-scanning direction. In addition to preventing image distortion and color misregistration due to misregistration in the main scanning direction by controlling the image forming position of the image bearing member reliably, the speed in the belt sub-scanning direction is determined based on endless belt elongation information. By performing the control, it is possible to more reliably prevent color misregistration due to misregistration in the sub-scanning direction.

  A sub-scanning direction conveyance speed correction unit that corrects the sub-scanning direction conveyance speed calculated by the sub-scanning direction conveyance speed calculation unit based on the sub-scanning direction expansion / contraction value of the endless belt member detected by the expansion / contraction detection unit; Have. Therefore, it is possible to accurately detect the displacement and position information of the endless belt in the main scanning direction with a simple configuration, and more accurately detect the speed information in the sub-scanning direction of the endless belt based on the elongation information of the endless belt. Therefore, the belt position is reliably controlled and the image forming position of the image carrier is surely corrected to prevent image distortion and color misregistration due to misalignment in the main scanning direction. By performing the control so that the speed in the sub-scanning direction is reached, it is possible to prevent the color shift due to the positional shift in the sub-scanning direction more reliably.

  Further, the belt position detecting means and the belt main scanning direction displacement detecting means are constituted by an area sensor that can detect the detection mark on the endless belt member as an image, and perform image processing on the image of the detection mark detected by the area sensor. Belt position information and belt main scanning direction displacement information are detected. Therefore, it is not necessary to use a configuration that obstructs high-speed belt driving such as a shift guide member, and it is not necessary to interrupt the image forming operation for correction of shift and meandering, so that the image output speed can be greatly increased. In addition, the position and displacement of the endless belt in the main scanning direction can be accurately detected with a simple configuration, and the belt position is reliably controlled based on the detected position information, and the image forming position of the image carrier based on the detected displacement information Since the image distortion and the color misregistration due to the positional deviation in the main scanning direction can be prevented by reliably correcting the image quality, an image forming apparatus capable of greatly improving the output image quality can be realized.

  In addition, the sum of the belt conveyance direction formation interval and the belt conveyance direction formation width of the detection mark is smaller than the detection range of the area sensor, and the area sensor sequentially images at a constant timing when two detection marks are positioned within the detection range of the area sensor. The obtained image is subjected to image processing on two consecutive images and sequentially compared to detect displacement in the belt main scanning direction. Therefore, since it is possible to accurately detect information on displacement in the main scanning direction over the entire endless belt cycle with a simple configuration, the belt position can be reliably controlled and the image forming position of the image carrier can be reliably corrected. Thus, image distortion and color misregistration due to misalignment in the main scanning direction can be prevented.

  Further, based on the images of the two detection marks acquired by the area sensor, the position of the center of gravity of the detection mark within the detection range of the area sensor is derived to detect the position of the endless belt member in the main scanning direction, and within the detection range of the area sensor. A change in the center of gravity of the detection mark is derived to detect displacement in the belt main scanning direction. Therefore, since it is possible to accurately detect the displacement and position information of the endless belt in the main scanning direction with a simple configuration, the belt position can be reliably controlled and the image forming position of the image carrier can be reliably corrected. Thus, image distortion and color misregistration due to misalignment in the main scanning direction can be reliably prevented.

  In addition, the detection mark image acquired by the area sensor is compared with the detection mark image registered in advance, and the position of the detection mark in the detection range of the area sensor is derived to detect the position of the endless belt member in the main scanning direction. The belt main scanning direction displacement is detected by deriving a change in the position of the detection mark within the detection range of the sensor. Accordingly, since the information on the displacement in the main scanning direction and the position information of the endless belt can be detected more accurately with a simple configuration, the belt position is reliably controlled and the image forming position of the image carrier is reliably corrected. Therefore, image distortion and color misregistration due to misalignment in the main scanning direction can be prevented more reliably.

  Furthermore, the detection mark image acquired by the area sensor is extracted to detect the position of the endless belt member in the main scanning direction, the extracted detection mark image is registered, and the detection mark image acquired sequentially is registered and extracted first. The detected detection mark image is compared with the detection mark image acquired and extracted later, and the change in the position of the detection mark within the detection range of the area sensor is sequentially derived to detect the displacement in the belt main scanning direction. Accordingly, since the information on the displacement in the main scanning direction and the position information of the endless belt can be detected more accurately with a simple configuration, the belt position is reliably controlled and the image forming position of the image carrier is reliably corrected. Thus, image distortion and color misregistration due to misregistration in the main scanning direction can be prevented more reliably.

  The image forming apparatus of the present invention also includes a latent image forming unit that forms a latent image on the image carrier, a developing unit that visualizes the latent image formed on the latent image forming unit, and an image carrier. An intermediate transfer member that primarily transfers a visible image formed thereon; and a recording material conveying unit that conveys a recording material that secondarily transfers the transfer image on the intermediate transfer member. And a plurality of conveying rollers arranged substantially parallel to each other with a gap therebetween, and an endless belt member that is stretched over each of the conveying rollers and carries and conveys the transfer image, and is formed on the image carrier. The images are sequentially stacked on the intermediate transfer member to form a multicolor image. The image forming apparatus of the present invention sequentially detects the position of the edge portion in the main scanning direction at the end of the endless belt member in the main scanning direction, and detects the position of the endless belt member in the main scanning direction. Main scanning direction displacement detecting means for sequentially detecting displacement in the main scanning direction accompanying belt conveyance at predetermined intervals of the edge portion, and main scanning of the endless belt member based on information on the position in the main scanning direction detected by the belt position detecting means. Belt position adjusting means for adjusting the direction position, and latent image forming position correcting means for correcting the main scanning direction latent image forming position on the image carrier based on information on the main scanning direction displacement detected by the belt displacement detecting means. The belt main scanning direction displacement detecting means is arranged in a plane for transferring the visible image on the image carrier among the belt plane portions between the plurality of conveying rollers. Accordingly, since the information on the displacement in the main scanning direction and the position information of the endless belt can be accurately detected with a simple and low-cost configuration, the belt position can be reliably controlled and the image forming position of the image carrier can be reliably detected. Correction can be performed, and image distortion and color misregistration due to misregistration in the main scanning direction can be prevented.

  Furthermore, an image forming apparatus of the present invention includes a latent image forming unit that forms a latent image on an image carrier, a developing unit that visualizes the latent image formed on the latent image forming unit, and an image carrier. A recording material conveying means for conveying a recording material for transferring a visible image formed thereon, and the recording material conveying means includes a plurality of conveying rollers disposed substantially parallel to each other at a predetermined distance. And an endless belt member that is carried around and conveyed by the respective conveying rollers, and sequentially overlays the visible image formed on the image carrier on the recording material on the recording material conveying means so as to obtain a multi-color image. Form. The image forming apparatus of the present invention sequentially detects the position of the edge portion in the main scanning direction at the end of the endless belt member in the main scanning direction, and detects the position of the endless belt member in the main scanning direction. Main scanning direction displacement detecting means for sequentially detecting displacement in the main scanning direction accompanying belt conveyance at predetermined intervals of the edge portion, and main scanning of the endless belt member based on information on the position in the main scanning direction detected by the belt position detecting means. Belt position adjusting means for adjusting the direction position, and latent image forming position correcting means for correcting the main scanning direction latent image forming position on the image carrier based on information on the main scanning direction displacement detected by the belt displacement detecting means. The belt main scanning direction displacement detecting means is arranged in a plane for transferring the visible image on the image carrier among the belt plane portions between the plurality of conveying rollers. Accordingly, since the information on the displacement in the main scanning direction and the position information of the endless belt can be accurately detected with a simple and low-cost configuration, the belt position can be reliably controlled and the image forming position of the image carrier can be reliably detected. Correction can be performed, and image distortion and color misregistration due to misregistration in the main scanning direction can be prevented.

  The image forming apparatus of the present invention also includes a latent image forming unit that forms a latent image on the image carrier, a developing unit that visualizes the latent image formed on the latent image forming unit, and an image carrier. An intermediate transfer member that primarily transfers a visible image formed thereon; and a recording material conveying unit that conveys a recording material that secondarily transfers the transfer image on the intermediate transfer member. And a plurality of conveying rollers arranged substantially parallel to each other with a gap therebetween, and an endless belt member that is stretched over each of the conveying rollers and carries and conveys the transfer image, and is formed on the image carrier. The images are sequentially stacked on the intermediate transfer member to form a multicolor image. The image forming apparatus of the present invention sequentially detects the position of the endless belt member in the main scanning direction of the density unevenness in the main scanning direction, detects the position of the endless belt member in the main scanning direction, The main scanning direction displacement detecting means for sequentially detecting the main scanning direction displacement accompanying the belt conveyance at a predetermined interval, and the main scanning direction position of the endless belt member based on the main scanning direction position information detected by the belt position detecting means. Belt position adjusting means for adjusting, and latent image forming position correcting means for correcting the main scanning direction latent image forming position on the image carrier based on the information on the main scanning direction displacement detected by the belt displacement detecting means, The belt main scanning direction displacement detecting means is arranged in a plane for transferring a visible image on the image carrier among the belt plane portions between the plurality of conveying rollers. Accordingly, since the information on the displacement in the main scanning direction and the position information of the endless belt can be accurately detected with a simple and low-cost configuration, the belt position can be reliably controlled and the image forming position of the image carrier can be reliably detected. Correction can be performed, and image distortion and color misregistration due to misregistration in the main scanning direction can be prevented.

  Furthermore, an image forming apparatus of the present invention includes a latent image forming unit that forms a latent image on an image carrier, a developing unit that visualizes the latent image formed on the latent image forming unit, and an image carrier. A recording material conveying means for conveying a recording material for transferring a visible image formed thereon, and the recording material conveying means includes a plurality of conveying rollers disposed substantially parallel to each other at a predetermined distance. And an endless belt member that is carried around and conveyed by the respective conveying rollers, and sequentially overlays the visible image formed on the image carrier on the recording material on the recording material conveying means so as to obtain a multi-color image. Form. The image forming apparatus of the present invention sequentially detects the position of the endless belt member in the main scanning direction of the density unevenness in the main scanning direction, detects the position of the endless belt member in the main scanning direction, The main scanning direction displacement detecting means for sequentially detecting the main scanning direction displacement accompanying the belt conveyance at a predetermined interval, and the main scanning direction position of the endless belt member based on the main scanning direction position information detected by the belt position detecting means. Belt position adjusting means for adjusting, and latent image forming position correcting means for correcting the main scanning direction latent image forming position on the image carrier based on the information on the main scanning direction displacement detected by the belt displacement detecting means, The belt main scanning direction displacement detecting means is arranged in a plane for transferring a visible image on the image carrier among the belt plane portions between the plurality of conveying rollers. Accordingly, since the information on the displacement in the main scanning direction and the position information of the endless belt can be accurately detected with a simple and low-cost configuration, the belt position can be reliably controlled and the image forming position of the image carrier can be reliably detected. Correction can be performed, and image distortion and color misregistration due to misregistration in the main scanning direction can be prevented.

  According to the image forming apparatus of the present invention, it is not necessary to use a configuration that hinders belt high-speed driving such as a shift guide member, and it is not necessary to interrupt the image forming operation for correction of shift and meandering. In addition to the simple configuration, the position of the endless belt in the main scanning direction can be accurately detected and reliably controlled, and the endless belt can be accurately detected in the main scanning direction. By reliably correcting the image forming position, it is possible to prevent image distortion and color misregistration due to misregistration in the main scanning direction, so that it is possible to realize an image forming apparatus capable of significantly improving the output image quality.

  FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus to which the present invention is applied. The image forming apparatus shown in FIG. 1 uses four photosensitive drums provided with developing devices in parallel, and forms a full-color image on an intermediate transfer member. In this image forming apparatus 100, during image formation, four image carriers (hereinafter referred to as photosensitive drums) 101, 102, 103, and 104 are rotationally driven in an arrow direction (counterclockwise direction), and the surface thereof is charged by a charger 111. , 112, 113, 114 are uniformly charged, and then exposure is performed according to the input image information by the exposure devices 121, 122, 123, 124 to form an electrostatic latent image. Then, the yellow developing unit 131, the magenta developing unit 132, the cyan developing unit 133, and the black developing unit 134 cause the toner to adhere to the electrostatic latent image on the photosensitive drum 101 and develop it as a yellow toner image, and the photosensitive drum 102. Toner is attached to the upper electrostatic latent image and developed as a magenta toner image. Toner is attached to the electrostatic latent image on the photosensitive drum 103 and developed as a cyan toner image. Toner is attached to the latent image and developed as a black toner image. The yellow toner image, the magenta toner image, the cyan toner image, and the black toner image are primarily transferred onto the intermediate transfer belt 200 that contacts the photosensitive drums 101, 102, 103, and 104 and rotates in the direction of the arrow. Is done. Then, four color toner images are superimposed on the intermediate transfer belt 200. These four color toner images are secondarily transferred to the recording material P conveyed from a paper feed cassette (not shown), whereby a full color image can be obtained.

  FIG. 2 is a perspective view showing the configuration of the belt displacement detecting means in the image forming apparatus of the present invention. As shown in the figure, a plurality of detection marks 201 are formed in advance on the surface of the intermediate transfer belt 200 over the entire circumference in the conveyance direction. Belt displacement detection means 202 is disposed at a position facing the detection mark 201, and is configured to be able to detect the position of the detection mark 201 in the main scanning direction at at least two locations in the belt conveyance direction. By sequentially detecting the position of each detection mark 201 in the main scanning direction for each rotation of the belt, the belt displacement detection means 202 such as the amount of displacement in the belt main scanning direction of the formation position of each detection mark 201 from the start of belt conveyance. It is possible to detect absolute displacement detection information in the belt main scanning direction. Therefore, the average moving speed of the belt in the main scanning direction during one rotation of the belt at the position where each detection mark 201 is formed can also be obtained. Further, each detection mark 201 detects the displacement in the belt main scanning direction during the conveyance between the detection positions of the two belt displacement detection means 202 in the belt conveyance direction, thereby detecting each of the detection marks 201 in the belt displacement detection means. Information such as the belt displacement amount during the time conveyed between the detection positions 202 and the average moving speed of the belt in the main scanning direction during conveyance between the detection positions can be detected, and by accumulating this information, belt displacement detection means The belt main scanning direction relative displacement information at 202 can be detected.

  FIG. 3 is a perspective view showing the configuration of the belt position adjusting means in the image forming apparatus of the present invention. In the figure, the same reference numerals as those in FIG. As shown in the figure, the intermediate transfer belt 200 is stretched by a plurality of substantially parallel rollers, and is driven in the belt conveying direction by one drive roller 203 among them. While the driving roller 203 and the driven rollers 204 and 205 are fixed at predetermined positions, both ends of the rotation shaft of the tension roller 206 are urged in the direction of the arrow, and the intermediate transfer belt 200 is stretched with a substantially constant tension. Yes. The correction roller 207 corrects the belt transfer direction movement such as deviation and meandering generated in the intermediate transfer belt 200. One end of the rotation shaft of the correction roller 207 can be swung in a direction perpendicular to the roller rotation axis by a pivot bearing or the like. The other end is supported by an actuator 208, which is a belt position adjusting means, so as to be reciprocally movable in the direction of the arrow. Based on the belt main scanning direction absolute displacement detection information generated from the belt main scanning direction absolute displacement detection information from the belt displacement detection means 202, the actuator 208 is driven and the correction roller 207 is swung in a direction to return the generated belt displacement to the base. By continuously performing this operation, the belt slippage and meandering are controlled within a certain range, and the belt slippage and meandering can be suppressed without providing a slip guide member or the like.

  FIG. 4 is a block diagram showing the configuration of the latent image forming position correcting means in the image forming apparatus of the present invention. In the figure, the image signal transferred from the printer driver unit 301 is input to the image signal generation unit 303 that constitutes the image writing control unit 302. Engine control information from the engine control unit 304 is also input to the image writing control unit 302. The image signal generation unit 303 performs image processing on the input image signal by processing according to engine control information. At this time, since the image signal generation unit 303 actually develops the image on the photographic paper, it is processed with a pixel clock signal (wclk) that defines the minimum pixel used for image formation. The pixel clock signal is generated by a pixel clock generation unit 305 by a clock signal (wclk) having a predetermined frequency based on information from the engine control unit 304 such as resolution, photosensitive drum linear speed, and the like. Input to the circuit unit 306. The actual image signal subjected to the image processing by the image signal generation unit 303 is input to the writing position control unit 307. In addition, the writing position control unit 307 is generated based on the synchronization detection signal (DETP) from the synchronization detection unit 309 of the laser writing control unit 308 and the belt main scanning direction relative displacement information from the belt displacement detection unit 202 on the intermediate transfer belt. The belt main scanning direction relative displacement signal (Δa) and the engine control information from the engine control unit 304 are input. The synchronization detection signal (DETP) is a signal for keeping the writing start position in the main scanning direction constant when the laser beam is exposed on the photosensitive drum 310. This signal is an output signal from the synchronization detection plate arranged outside the scanning area on the photosensitive drum 310 of the laser beam reflected and deflected by the polygon mirror 311 of the laser writing control unit 308. A light receiving element such as a photodiode is cast as a synchronization detection sensor, and the synchronization detection unit 309 photoelectrically converts the incident laser beam and outputs a synchronization detection signal (DETP). The belt main scanning direction relative displacement signal (Δa) is a signal indicating the amount of meander during conveyance of the intermediate transfer belt, and cannot be completely suppressed even during belt meandering control by the belt position adjusting means. This is a signal obtained by detecting displacement in the main scanning direction of the detection mark on the transfer belt 200 by the belt displacement detecting means 202. In the writing position control unit 307, the real image signal from the image signal generation unit 303 is combined with the synchronization detection signal (DETP) at a predetermined timing, and a signal for driving the semiconductor laser as the light source is generated. At this time, the start timing of writing the actual image signal from the synchronization detection signal is controlled in accordance with the belt main scanning direction relative displacement signal (Δa). The wobble correction clock signal (dclk) obtained by multiplying the pixel clock signal (wclk) generated by the pixel clock generation unit 305 is input to the writing position control unit 307. This meandering correction clock signal (dclk) is a signal having a frequency higher than that of the pixel clock signal obtained by multiplying the pixel clock signal (wclk) that defines the minimum pixel capable of forming an image. The meandering correction clock signal (dclk) is a clock signal having a frequency corresponding to the detection resolution of the transfer slit position sensor, and one clock of the meandering correction clock signal (dclk) corresponds to one resolution of the belt displacement detection means 202. ing. The belt displacement detection means 202 detects the belt main scanning direction relative displacement signal (Δa), and the writing position control unit 307 receives the synchronization detection signal (DETP) and the belt main scanning direction relative displacement signal (Δa). Assuming that A (= N × wclk) from the synchronization detection signal when the belt main scanning direction relative displacement signal (Δa) is 0 to the start position of the actual image signal in the main scanning direction, Δa> 0 is detected. Changes the delay time from the synchronization detection signal to the actual image writing timing to A + Δa × dclk, and delays the actual image writing start position with respect to the case where there is no meandering conveyance. On the other hand, when Δa <0, the delay time is set to A−Δa × dclk, and the actual image writing start timing is relatively accelerated. The laser driving signal synthesized by the writing position control unit 307 is input to the laser driving unit 312. The semiconductor laser mounted on the laser driver 312 is repeatedly driven to turn on / off by turning on / off the laser drive signal. The laser beam emitted by driving the semiconductor laser is incident on the laser writing device 308, passes through and reflects a plurality of lenses, mirrors, etc., and travels in the optical path. It is rotationally deflected by a polygon mirror 311 disposed in the middle of the optical path, and a laser beam is exposed on the photosensitive drum 310 in the main scanning direction. The process from this exposure until an output image is obtained is as described above.

  In the above configuration, the belt displacement detection means 202 can detect a displacement in the belt conveyance direction caused by conveyance of a predetermined distance by each of a plurality of detection marks formed on the surface of the intermediate transfer belt 200 over the entire circumference in the belt conveyance direction. It is configured. For this reason, in Patent Document 3 and Patent Document 4 described above, the detection accuracy of the detection mark and the deformation are not affected by the belt displacement detection result, and the belt conveyance direction displacement can be detected accurately. Based on the belt main scanning direction absolute displacement signal obtained from the belt conveying direction displacement generated with respect to the belt position in the belt conveying direction at the time of starting the belt conveyance, the detection position of each belt is detected based on the belt main scanning direction absolute displacement signal. The position in the belt conveyance direction is controlled by the adjusting means, and the meandering component in the belt rotation conveyance that cannot be controlled is obtained by accumulating the belt main scanning direction displacement information generated by the movement of each detection mark by the specified distance. By controlling the latent image formation position on the image carrier based on the belt main scanning direction relative displacement signal, image distortion and color misregistration due to misregistration in the sub-scanning direction, which is the belt conveying direction, can be prevented, and the output image can be greatly increased. High image quality can be achieved.

  In the above-described configuration, the belt displacement detecting means is arranged in a plane for transferring the visible image on the image carrier among the plurality of belt flat portions between the conveying rollers. Here, in the main scanning direction displacement behavior of the measurement point on the belt shown in FIG. 18 described above, the main scanning direction behavior of the measurement point in the belt plane portion between the conveying rollers is not a straight line but a gentle curved locus. You can see that For this reason, in order to detect the average value of the displacement in the main scanning direction of the measurement points in the entire flat surface portion where the visible image on the image carrier is transferred, the belt conveyance in the range where the image carrier abuts the belt. By disposing the belt displacement detecting means in the vicinity of the intermediate position in the direction, it is possible to detect the displacement in the belt main scanning direction with higher accuracy. In addition, by disposing belt displacement detection means in the vicinity of each intermediate position in the belt conveyance direction at a position where each image carrier adjacent to the belt conveyance direction abuts on the belt, the belt main scanning direction can be made with higher accuracy. Can be detected with higher accuracy.

  FIG. 5 is a plan view showing another configuration of the belt displacement detecting means in the image forming apparatus of the present invention. In the figure, a plurality of line-shaped detection marks 201 are formed on the intermediate transfer belt 200 over the entire circumference in the belt conveyance direction. At a position facing the detection mark 201, a line CCD or the like and two one-dimensional line sensors 209 and 210 that can detect the position of the detection mark 201 in the belt main scanning direction are provided side by side in the belt conveyance direction. The two one-dimensional sensors 209 and 210 are set so that outputs from the respective one-dimensional sensors become equal when one detection mark 201 is conveyed without being displaced in the belt main scanning direction. With the start of conveyance of the intermediate transfer belt 200, the sensor output when each detection mark 201 faces the upstream one-dimensional sensor 209 or the downstream one-dimensional sensor 210, and the upstream side again every rotation of the belt. By comparing the sensor output when facing the one-dimensional sensor 209 or the downstream one-dimensional sensor 210, it is possible to detect the displacement in the belt main scanning direction in which each detection mark 201 has moved after the start of belt conveyance. Although this information cannot detect the detailed belt behavior such as the belt meandering state in one rotation of the belt, the absolute belt main scanning direction position of the belt can be detected, and when used for belt main scanning direction position adjustment, The belt position can be accurately defined in the belt conveyance direction.

  Further, as the intermediate transfer belt 200 is conveyed, one of the plurality of detection marks 201 is used as a reference mark, and the sensor output when the reference mark faces the upstream one-dimensional sensor 209 and the downstream 1 By comparing the sensor output when facing the dimension sensor 210, it is possible to detect the displacement in the belt main scanning direction that occurs during the time when one reference mark is conveyed between the two sensors. By sequentially detecting the displacement in the belt main scanning direction of each detection mark 201, it is possible to detect the displacement information in the belt main scanning direction of the conveyance time between the sensors. By sequentially accumulating this information, the intermediate transfer belt 200 Relative belt main scanning direction displacement information is obtained. Since this information accumulates detection errors sequentially, there is a problem that the belt position moves in the belt main scanning direction due to this accumulated error when used for belt main scanning direction position adjustment. Since it is possible to detect the movement of the belt in the main scanning direction at shorter intervals than the absolute position information, it is possible to detect the meandering state of the belt within one rotation of the belt, and from the absolute position information as in the latent image formation position correction. This is useful when the relative position information between the color latent image formation timings is important. Here, by setting the formation interval D1 of each detection mark 201 in the belt conveyance direction to be equal to or less than the arrangement interval D2 of the two sensors in the belt conveyance direction, it is possible to detect the relative displacement in the belt main scanning direction in the entire belt one cycle.

  FIG. 6 is a plan view showing another configuration of the belt displacement detecting means in the image forming apparatus of the present invention. In the figure, a plurality of rectangular detection marks 201 are formed on the intermediate transfer belt 200 over the entire circumference in the transport direction. A two-dimensional area sensor 211 such as an area CCD that can detect the position of the detection mark 201 in the belt conveyance direction and the position in the sub-scanning direction that is orthogonal to the belt conveyance direction is arranged at a position facing the detection mark 201. It is installed. The two-dimensional area sensor 211 is set so that the displacement detection output of the detection mark in the main scanning direction in the sensor detection area becomes zero when one reference mark is conveyed without being displaced in the main scanning direction. Here, the sensor output when each detection mark 201 faces the two-dimensional area sensor 211 with the start of belt conveyance is compared with the sensor output when the detection mark 201 faces the two-dimensional area sensor 211 again every belt rotation conveyance. Thus, it is possible to detect the displacement in the main scanning direction in which each detection mark 201 has moved after the start of belt conveyance.

  Further, when the intermediate transfer belt 200 is conveyed, the belt main scanning direction displacement detection output from when one of the plurality of detection marks 201 enters the detection area of the two-dimensional area sensor 211 to when the detection mark 201 moves out of the detection area. Due to this change, it is possible to detect the displacement in the belt main scanning direction that occurred at the time when one reference mark was conveyed in the sensor detection area. By sequentially detecting the displacement in the belt main scanning direction of each detection mark 201, it is possible to detect the belt main scanning direction displacement information of the conveyance time between the sensors, and by sequentially accumulating this information, Displacement detection information is obtained. Here, by setting the formation interval of each detection mark 201 in the belt conveyance direction to be equal to or less than the detection area range Dw in the belt conveyance direction of the two-dimensional area sensor 211, it is possible to detect the relative displacement in the belt main scanning direction over the entire belt period. Become.

  Here, in order to accurately detect the displacement in the belt main scanning direction by the two-dimensional area sensor 211, it is necessary to accurately define which portion of the detection mark 201 the belt main scanning direction displacement is detected in the belt conveyance direction. . In the rectangular detection mark 201, the belt conveyance direction detection position can be accurately defined on the side 201a parallel to the belt conveyance direction at a point intersecting the side 201b or 201c parallel to the main scanning direction. Thus, it is desirable to use a detection mark having at least two intersecting sides for detecting the displacement in the belt main scanning direction by the two-dimensional CCD.

  Further, as shown in FIG. 7, the endless belt member is often processed by cutting both ends in the width direction of the belt member in manufacturing, and in this case, the cut surface of the belt has minute irregularities. For this reason, it is possible to detect the displacement in the main scanning direction by detecting the displacement of the minute unevenness by the two-dimensional area sensor 211, and it is not necessary to form a detection mark on the belt. Cost can be reduced.

  Further, as shown in FIG. 8, the endless belt member has uneven surface concentration due to non-uniform material in manufacturing. For this reason, it is possible to detect the displacement in the main scanning direction by detecting the minute displacement of the surface density unevenness by the two-dimensional area sensor 211, and it is not necessary to form a detection mark on the belt. The cost can be reduced.

  In FIG. 5, from the time when one of the plurality of detection marks 201 faces the upstream one-dimensional sensor 209 and the time facing the downstream one-dimensional sensor 210 along with the conveyance of the intermediate transfer belt 200, 1 It is possible to detect the time during which one reference mark is transported between two one-dimensional sensors. Since the two one-dimensional sensor intervals D2 are constant, the conveyance speed in the conveyance direction of the belt can be detected from the conveyance time between the sensors and the sensor interval. By controlling the rotation motor of the belt drive roller using this speed signal, compared to the case of controlling the rotation based on the speed signal of the encoder of the rotation motor and the encoder provided on the roller that stretches the intermediate transfer belt, Since the conveyance speed on the intermediate transfer belt can be directly detected and controlled, it is possible to control the belt conveyance speed with high accuracy without being affected by variations in the drive system, roller eccentricity, belt thickness variation, and the like.

  Further, by forming a plurality of detection marks 201 formed on the intermediate transfer belt 200 at regular intervals in the belt conveyance direction, the upstream one-dimensional sensor 209 or the downstream one-dimensional sensor 210 detects the detection marks 201 at a certain time. By counting the number of detection marks, the conveyance speed of the belt in the sub-scanning direction can be similarly detected. In this case, the belt sub-scanning can be performed more accurately without being affected by the setting error or fluctuation of the interval between the two one-dimensional sensors. The direction conveyance speed can be detected.

  In FIG. 5, when the belt expands or contracts in the sub-scanning direction due to environmental fluctuations such as temperature and humidity, or belt creep characteristics due to belt tension, the interval between the belt detection marks formed at a certain interval varies. Therefore, there is a problem that an error occurs in the detected belt sub-scanning direction conveyance speed. On the other hand, as shown in FIG. 9, when the belt expands and contracts, the phase difference of the information detection cycle on the endless belt at the two belt conveyance direction detection positions changes. By detecting this, it is possible to detect the expansion and contraction of the endless belt member in the sub-scanning direction, and by correcting the detected belt sub-scanning direction conveyance speed in accordance with the detected sub-scanning direction expansion and contraction, the belt sub-scanning direction It is possible to detect the conveyance speed in the belt sub-scanning direction more accurately without being affected by expansion and contraction.

  Also, as shown in FIG. 10, the sum of the formation interval D1 in the belt conveyance direction and the belt conveyance direction formation width D3 of each detection mark 201 is less than the detection area range Dw in the belt conveyance direction of the sensor. Sensor images are sequentially acquired at a fixed timing at which two detection marks are located in the detection area, and the upstream detection mark position in the previous image and the downstream detection mark position in the rear image between the two consecutive sensor images. By sequentially comparing by image processing, it is possible to detect the relative displacement in the belt main scanning direction over the entire belt period.

  Further, as one of image processing techniques for detecting a specific image position in the sensor detection area, there is a particle analysis technique for a binary image. In this method, an image is divided into a particle region and a background region, and the number of particle regions, the size and position of particles, and the like are detected.

  As shown in FIG. 11A, by performing particle analysis on the detected binary image in a state where the two detection marks 201 are located in the area sensor detection area of the two-dimensional area sensor 211, the area sensor detection area The gravity center positions of the two detection marks in the main scanning direction and the sub scanning direction can be derived. Here, by deriving and comparing the position of the center of gravity in the main scanning direction of each detection mark 201 for each rotation of the belt, it is possible to detect the position in the main scanning direction in which each detection mark has moved every rotation of the belt after the start of belt conveyance. Become. In addition, in FIGS. 11A and 11B, which are area sensor detection images while one detection mark 201 moves in the area sensor detection region, the barycentric positions in the main scanning direction and the sub scanning direction are derived. By comparing, the displacement in the main scanning direction and the sub-scanning direction between the sensor detection timings of one detection mark 201 can be detected. By sequentially detecting the displacement in the main scanning direction of each detection mark image, it is possible to detect the displacement information in the belt main scanning direction between the detection timings of the sensor detection areas. Thus, displacement information in the main scanning direction can be obtained. When the edge position of the detection mark 201 is detected by the two-dimensional area sensor 211, the detection edge position is detected when the binarization condition of the image changes due to a change in exposure sensitivity due to the influence of external light, a change in environmental conditions, a change in sensor sensitivity due to a change over time, However, when the detection mark position is detected from the position of the center of gravity of the image, as shown in FIGS. 12A and 12B, it is affected by the change of the binarization condition of the two-dimensional area sensor 211. Since it is difficult, detection accuracy can be improved.

  As one of image processing techniques for detecting a specific image position in the sensor detection area of the two-dimensional area sensor 211, there is a pattern matching technique. In this method, a pattern image registered in advance and a detected image are compared, and the number, position, and the like of the pattern image included in the detected image are detected. As shown in FIG. 13A, a detection mark image (FIG. 13) registered in advance as a pattern image with respect to a detection image in a state where two detection marks 201 are located in the area sensor detection region of the two-dimensional area sensor 211. By performing the pattern matching analysis with (b)), the positions of the two detection marks in the area sensor detection region in the main scanning direction and the sub scanning direction can be derived. Here, by deriving and comparing the position of each detection mark in the main scanning direction for each rotation of the belt, it is possible to detect the position in the main scanning direction in which each detection mark has moved for each rotation of the belt after the start of belt conveyance. In addition, the positions in the main scanning direction and the sub-scanning direction are derived in FIGS. 13A and 13C showing the area sensor detection image while one detection mark 201 moves in the area sensor detection region. By comparing, it becomes possible to detect the displacement in the main scanning direction and the sub scanning direction between the sensor detection timings of one detection mark 201. By sequentially detecting the displacement in the main scanning direction of each detection mark image, it is possible to detect the displacement information in the belt main scanning direction between the detection timings of the sensor detection areas. Thus, displacement information in the main scanning direction can be obtained.

  Furthermore, when the center of gravity of the detection mark 201 is detected by the two-dimensional area sensor 211, there is a problem that the detection center of gravity changes when the image shape changes due to dust, dust, noise, or the like. In the case of detection, as shown in FIGS. 14A and 14B, it is difficult to be affected by the change in the image shape, so that the detection accuracy can be further improved.

  As another method of pattern matching technology, there is a method of updating a registered pattern image as needed. In this method, a part of the acquired image is registered as a pattern image at any time, the registered pattern image is compared with the next acquired detection image, and the position change of the pattern image included in the detection image is detected. As shown in FIG. 15A, the detection mark image (FIG. 15B) is extracted from the detection image in a state where the two detection marks 201 are positioned in the two-dimensional area sensor detection region, and the pattern image is displayed. The main detection mark moved in the two-dimensional area sensor detection region is registered, and pattern matching analysis is performed between the acquired image and the detection mark image registered as a pattern image (FIG. 15B). A change in position in the scanning direction and the sub-scanning direction can be derived. Here, each detection mark image of the two-dimensional area sensor detection image is extracted, registered, and compared for each rotation of the belt, and the position of the main scanning direction is derived for each rotation of the belt. It is possible to detect the position in the main scanning direction that has moved for each rotation of the belt. 15A and 15C of the area sensor detection image while one detection mark 201 moves in the two-dimensional area sensor detection region, the detection mark image (a) on the upstream side of FIG. (B) in FIG. 15 is extracted and a pattern image is registered, and the next acquired image is a detection mark on the downstream side in FIG. 15C, and a detection mark image registered as a pattern image ((b) in FIG. 15). ), The positional change in the main scanning direction and the sub-scanning direction of the detection mark moved in the two-dimensional area sensor detection region can be derived. By sequentially detecting the displacement in the main scanning direction of each detection mark image, it is possible to detect the displacement information in the belt main scanning direction between the detection timings of the sensor detection areas. Thus, displacement information in the main scanning direction can be obtained.

  Here, by detecting the detection mark position by pattern matching with the registered pattern image updated at any time, it is more difficult to be affected by the change in the image shape, so that the detection accuracy can be greatly improved.

  In the present embodiment, the transfer medium is illustrated and described as an intermediate transfer body, but the transfer medium may be a recording sheet attached to a sheet conveying belt. In this case, the belt displacement detecting means and the belt position adjusting means are provided on the paper transport belt.

  Further, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications and substitutions are possible as long as the description is within the scope of the claims.

1 is a schematic diagram illustrating a configuration of an image forming apparatus to which the present invention is applied. FIG. 3 is a perspective view illustrating a configuration of a belt displacement detection unit in the image forming apparatus of the present invention. FIG. 3 is a perspective view illustrating a configuration of a belt position adjusting unit in the image forming apparatus of the present invention. FIG. 3 is a block diagram illustrating a configuration of a latent image formation position correcting unit in the image forming apparatus of the present invention. FIG. 6 is a plan view showing another configuration of a belt displacement detection unit in the image forming apparatus of the present invention. FIG. 6 is a plan view showing another configuration of the belt displacement detection means in the image forming apparatus of the present invention. FIG. 6 is a plan view showing another configuration of the belt displacement detection means in the image forming apparatus of the present invention. FIG. 6 is a plan view showing another configuration of the belt displacement detection means in the image forming apparatus of the present invention. It is a time chart which shows the signal output of each one-dimensional sensor of a belt displacement detection means. FIG. 6 is a plan view showing another configuration of the belt displacement detection means in the image forming apparatus of the present invention. It is a figure which shows the detection image of a detection mark. It is a figure which shows the mode of matching of the detection image of the detection mark of normal detection conditions, and the detection mark image at the time of condition change. It is a figure which shows the detection image of a detection mark. It is a figure which shows the mode of matching of the detection image of a detection mark, and the registration detection mark image. It is a figure which shows the detection image of a detection mark. It is a figure which shows the analysis object model of the belt stretched around three rollers. It is a figure which shows the main scanning direction position change of the belt centerline conveyed in the vicinity of the measurement point A of FIG. It is a figure which shows the main scanning direction position change accompanying the belt conveyance of the measurement point B of FIG.

Explanation of symbols

200; intermediate transfer belt, 201; detection mark,
202; belt displacement detection means, 209, 210; one-dimensional sensor;
211; Two-dimensional area sensor.

Claims (21)

A latent image forming unit that forms a latent image on the image carrier, a developing unit that visualizes the latent image formed on the latent image forming unit, and a visible image formed on the image carrier are primary An intermediate transfer body to be transferred; and a recording material transport means for transporting a recording material for secondary transfer of the transfer image on the intermediate transfer body. The intermediate transfer bodies are substantially parallel to each other at a predetermined distance. A plurality of transport rollers disposed, and an endless belt member that is supported by the transport rollers and carries the transfer image, and the visible image formed on the image carrier is transferred to the intermediate transfer member. In an image forming apparatus that forms a multi-color image by sequentially superposing on
Belt position detecting means for sequentially detecting positions in a main scanning direction of a plurality of detection marks formed on the endless belt member, and detecting positions in the main scanning direction of the endless belt member;
Belt main scanning direction displacement detecting means for sequentially detecting main scanning direction displacement associated with belt conveyance at a predetermined interval of detection marks on the endless belt member;
Belt position adjusting means for adjusting the main scanning direction position of the endless belt member based on information on the main scanning direction position detected by the belt position detecting means;
Latent image forming position correcting means for correcting a main scanning direction latent image forming position on the image carrier based on information on displacement in the main scanning direction detected by the belt displacement detecting means;
The belt main scanning direction displacement detecting means is arranged in a plane for transferring a visible image on the image carrier among belt flat portions between a plurality of conveying rollers. A latent image forming unit that forms a latent image on the image carrier, a developing unit that visualizes the latent image formed on the latent image forming unit, and a visible image formed on the image carrier are transferred. A recording material conveying means for conveying the recording material to be conveyed, and the recording material conveying means is spanned between each of the conveying rollers and a plurality of conveying rollers arranged substantially parallel to each other at a predetermined distance. An endless belt member that carries and conveys the transferred image, and forms a multi-color image by sequentially superimposing the visible image formed on the image carrier on the recording material on the recording material conveying means. In the device
Belt position detecting means for sequentially detecting positions in a main scanning direction of a plurality of detection marks formed on the endless belt member, and detecting positions in the main scanning direction of the endless belt member;
Belt main scanning direction displacement detecting means for sequentially detecting main scanning direction displacement associated with belt conveyance at a predetermined interval of detection marks on the endless belt member;
Belt position adjusting means for adjusting the main scanning direction position of the endless belt member based on information on the main scanning direction position detected by the belt position detecting means;
Latent image forming position correcting means for correcting a main scanning direction latent image forming position on the image carrier based on information on displacement in the main scanning direction detected by the belt displacement detecting means;
The belt main scanning direction displacement detecting means is arranged in a plane for transferring a visible image on the image carrier among belt flat portions between a plurality of conveying rollers.   The belt main scanning direction displacement detecting means is an intermediate position in the belt conveying direction within a range in which the plurality of arranged image carriers are in contact with the belt in a plane for transferring a visible image on the image carrier. The image forming apparatus according to claim 1, wherein the image forming apparatus is disposed in the vicinity.   The belt main scanning direction displacement detecting means is configured to convey the belt at a position where each of the image carriers adjacent in the belt conveyance direction contacts the endless belt member in a plane on which a visible image on the image carrier is transferred. The image forming apparatus according to claim 1, wherein the image forming apparatus is disposed near an intermediate position in the direction.   The belt main scanning direction displacement detecting means is composed of sensors provided in at least two positions in the belt conveying direction, which can detect the main scanning direction positions of a plurality of detection marks formed on the endless belt member, The detection marks in the plurality of detection marks on the endless belt member are detected by the sensor, and the belt displacement information is detected by sequentially detecting the movement amount in the main scanning direction due to the conveyance between the two belt conveyance direction detection positions. The belt main scanning direction position information is detected by sequentially detecting the main scanning direction position of each detection mark on the endless belt member for each rotation of the belt for one rotation. Image forming apparatus.   6. The sensor according to claim 5, wherein the sensor is a one-dimensional sensor, and a formation interval of the detection marks in the main scanning direction is smaller than a detection position interval in the belt conveyance direction of the two adjacent one-dimensional sensors. Image forming apparatus.   The image forming apparatus according to claim 5, wherein the sensor is a two-dimensional area sensor, and a formation interval of the detection marks in the main scanning direction is smaller than a main scanning direction detection range of the two-dimensional area sensor.   The image forming apparatus according to claim 1, wherein the detection mark has at least two intersecting sides.   Sub-scanning direction conveyance speed calculating means for sequentially measuring the time during which the sensor is conveyed between the two belt main scanning direction detection positions for detecting the detection mark and calculating the conveyance speed in the sub-scanning direction of the endless belt member. The image forming apparatus according to claim 1, further comprising:   The detection marks are formed on the endless belt member at regular intervals, and the detection marks detected by the sensor at a predetermined time are counted to calculate the conveyance speed of the endless belt member in the sub scanning direction. The image forming apparatus according to claim 1, further comprising a speed calculating unit.   The detection marks are formed on the endless belt member at regular intervals, and the endless belt is detected by detecting a phase difference of detection periods at main scanning detection positions obtained by two sensors detecting the same detection mark. The image forming apparatus according to claim 1, further comprising an expansion / contraction detection unit configured to detect an expansion / contraction value of the member in the sub-scanning direction.   A sub-scanning direction conveyance speed correction unit that corrects the sub-scanning direction conveyance speed calculated by the sub-scanning direction conveyance speed calculation unit based on a sub-scanning direction expansion / contraction value of the endless belt member detected by the expansion / contraction detection unit. The image forming apparatus according to claim 10, wherein the image forming apparatus includes:   The belt position detection means and the belt main scanning direction displacement detection means are configured by an area sensor capable of detecting the detection mark on the endless belt member as an image, and an image is displayed on the image of the detection mark detected by the area sensor. The image forming apparatus according to claim 1, wherein processing is performed to detect belt position information and belt main scanning direction displacement information.   The sum of the belt conveyance direction formation interval and the belt conveyance direction formation width of the detection mark is smaller than the detection range of the area sensor, and the area sensor is at a fixed timing when the two detection marks are positioned within the detection range of the area sensor. The image forming apparatus according to claim 13, wherein images are sequentially acquired, image processing is performed on two successive images, and the belt main scanning direction displacement is detected by sequentially comparing the images.   Based on the images of the two detection marks acquired by the area sensor, the position of the center of gravity of the detection mark within the detection range of the area sensor is derived to detect the main scanning direction position of the endless belt member, and the area sensor The image forming apparatus according to claim 13, wherein a displacement of the center of gravity of the detection mark within a detection range is derived to detect the displacement in the belt main scanning direction.   The image of the detection mark acquired by the area sensor is compared with the image of the detection mark registered in advance, and the position of the detection mark in the detection range of the area sensor is derived to determine the position of the endless belt member in the main scanning direction. The image forming apparatus according to claim 13, wherein the image forming apparatus detects, and detects a displacement in the belt main scanning direction by deriving a change in a position of the detection mark within a detection range of the area sensor.   The detection mark image acquired by the area sensor is extracted to detect the position of the endless belt member in the main scanning direction, the extracted detection mark image is registered, and the detection mark image sequentially acquired first. By comparing the image of the detection mark extracted and registered with the image of the detection mark acquired and extracted later, a change in the position of the detection mark within the detection range of the area sensor is sequentially derived, and the belt The image forming apparatus according to claim 13, wherein a displacement in the main scanning direction is detected. A latent image forming unit that forms a latent image on the image carrier, a developing unit that visualizes the latent image formed on the latent image forming unit, and a visible image formed on the image carrier are primary An intermediate transfer body to be transferred; and a recording material transport means for transporting a recording material for secondary transfer of the transfer image on the intermediate transfer body. The intermediate transfer bodies are substantially parallel to each other at a predetermined distance. A plurality of transport rollers disposed, and an endless belt member that is supported by the transport rollers and carries the transfer image, and the visible image formed on the image carrier is transferred to the intermediate transfer member. In an image forming apparatus that forms a multi-color image by sequentially superposing on
Belt position detecting means for sequentially detecting a position in the main scanning direction of an edge portion at an end of the endless belt member in the main scanning direction, and detecting a position in the main scanning direction of the endless belt member;
Belt main scanning direction displacement detecting means for sequentially detecting displacement in the main scanning direction accompanying belt conveyance at a predetermined interval of the edge portion;
Belt position adjusting means for adjusting the main scanning direction position of the endless belt member based on information on the main scanning direction position detected by the belt position detecting means;
Latent image forming position correcting means for correcting a main scanning direction latent image forming position on the image carrier based on information on displacement in the main scanning direction detected by the belt displacement detecting means;
The belt main scanning direction displacement detecting means is arranged in a plane for transferring a visible image on the image carrier among belt flat portions between a plurality of conveying rollers. A latent image forming unit that forms a latent image on the image carrier, a developing unit that visualizes the latent image formed on the latent image forming unit, and a visible image formed on the image carrier are transferred. A recording material conveying means for conveying the recording material to be conveyed, and the recording material conveying means is spanned between each of the conveying rollers and a plurality of conveying rollers arranged substantially parallel to each other at a predetermined distance. An endless belt member that carries and conveys the transferred image, and forms a multi-color image by sequentially superimposing the visible image formed on the image carrier on the recording material on the recording material conveying means. In the device
Belt position detecting means for sequentially detecting a position in the main scanning direction of an edge portion at an end of the endless belt member in the main scanning direction, and detecting a position in the main scanning direction of the endless belt member;
Belt main scanning direction displacement detecting means for sequentially detecting displacement in the main scanning direction accompanying belt conveyance at a predetermined interval of the edge portion;
Belt position adjusting means for adjusting the main scanning direction position of the endless belt member based on information on the main scanning direction position detected by the belt position detecting means;
Latent image forming position correcting means for correcting a main scanning direction latent image forming position on the image carrier based on information on displacement in the main scanning direction detected by the belt displacement detecting means;
The belt main scanning direction displacement detecting means is arranged in a plane for transferring a visible image on the image carrier among belt flat portions between a plurality of conveying rollers. A latent image forming unit that forms a latent image on the image carrier, a developing unit that visualizes the latent image formed on the latent image forming unit, and a visible image formed on the image carrier are primary An intermediate transfer body to be transferred; and a recording material transport means for transporting a recording material for secondary transfer of the transfer image on the intermediate transfer body. The intermediate transfer bodies are substantially parallel to each other at a predetermined distance. A plurality of transport rollers disposed, and an endless belt member that is supported by the transport rollers and carries the transfer image, and the visible image formed on the image carrier is transferred to the intermediate transfer member. In an image forming apparatus that forms a multi-color image by sequentially superposing on
Belt position detection means for sequentially detecting a position in the main scanning direction of density unevenness in the main scanning direction of the endless belt member, and detecting a position in the main scanning direction of the endless belt member;
Belt main scanning direction displacement detecting means for sequentially detecting displacement in the main scanning direction accompanying belt conveyance at a predetermined interval of density unevenness;
Belt position adjusting means for adjusting the main scanning direction position of the endless belt member based on information on the main scanning direction position detected by the belt position detecting means;
Latent image forming position correcting means for correcting a main scanning direction latent image forming position on the image carrier based on information on displacement in the main scanning direction detected by the belt displacement detecting means;
The belt main scanning direction displacement detecting means is arranged in a plane for transferring a visible image on the image carrier among belt flat portions between a plurality of conveying rollers. A latent image forming unit that forms a latent image on the image carrier, a developing unit that visualizes the latent image formed on the latent image forming unit, and a visible image formed on the image carrier are transferred. A recording material conveying means for conveying the recording material to be conveyed, and the recording material conveying means is spanned between each of the conveying rollers and a plurality of conveying rollers arranged substantially parallel to each other at a predetermined distance. An endless belt member that carries and conveys the transferred image, and forms a multi-color image by sequentially superimposing the visible image formed on the image carrier on the recording material on the recording material conveying means. In the device
Belt position detection means for sequentially detecting a position in the main scanning direction of density unevenness in the main scanning direction of the endless belt member, and detecting a position in the main scanning direction of the endless belt member;
Belt main scanning direction displacement detecting means for sequentially detecting displacement in the main scanning direction accompanying belt conveyance at a predetermined interval of density unevenness;
Belt position adjusting means for adjusting the main scanning direction position of the endless belt member based on information on the main scanning direction position detected by the belt position detecting means;
Latent image forming position correcting means for correcting a main scanning direction latent image forming position on the image carrier based on information on displacement in the main scanning direction detected by the belt displacement detecting means;
The belt main scanning direction displacement detecting means is arranged in a plane for transferring a visible image on the image carrier among belt flat portions between a plurality of conveying rollers.

Images