JP2006267953A - Image forming apparatus and belt drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain the change of image quality between continuous pages when correcting meandering of a photoreceptor belt. <P>SOLUTION: When detecting the meandering of the photoreceptor belt, a remaining distance that the photoreceptor belt moves by the time a print job is finished is calculated. Then, correction amount per minimum unit time corresponding to the remaining moving distance of the photoreceptor belt is calculated, and the meandering of the photoreceptor belt is corrected according to the correction amount per minimum unit time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus for transferring an image carried on an image carrier belt to a recording medium, and a belt driving device for rotating an endless belt.

  In recent years, in electrophotographic color printers, in order to meet the demand for higher image quality, the toner particle size has become very small, about 6 μm, and the resolution has become very high, such as 1200 dpi or 2400 dpi, so a small amount of transfer Even if it is misaligned, the hue changes remarkably. For example, when four colors of toner are superimposed on a 42 μm dot at a resolution of 600 dpi, if a transfer deviation of half a dot (about 20 μm) occurs, a change in hue becomes remarkable, resulting in poor image quality. Therefore, the image carrier belt is detected by detecting the meandering (tilt with respect to the rotation direction) of the image carrier belt such as the photosensitive belt or the intermediate transfer belt, which is raised as a cause of transfer deviation, and tilting the driven roller. The color reproducibility is improved by rapidly correcting the meandering (see, for example, Patent Documents 1 to 3).

  However, in the so-called + N color image forming apparatus in which a plurality of colors are not superimposed on the same dot but each dot is formed with each color, the boundary between the colors is shifted due to the occurrence of transfer misregistration. Although the hue does not change, there is no need to perform the meandering correction of the image carrier belt rapidly, and conversely, the meandering correction of the image carrier belt was conducted rapidly. In such a case, the change in image quality between successive pages becomes significant. As a result, there arises a problem that the registration shift between the colors on the page where the transfer shift occurs in the continuous pages is easily recognized.

Further, in the conventional meandering correction mechanism for the image carrier belt, the sensor for detecting the meandering of the image carrier belt, the motor or solenoid for tilting the driven roller or moving the belt guide, and the meandering correction for the image carrier belt. There is a problem that an expensive system including a control circuit or the like for controlling is required, and the cost increases.
JP-A-6-115755 JP 2001-80782 A JP-A-4-272042

  The present invention has been made in consideration of the above facts, and suppresses a change in image quality between successive pages, which is caused by performing meandering correction of the image carrier belt. Further, the cost of a meandering correction mechanism for an endless belt such as an image carrier belt is reduced.

  The image forming apparatus according to claim 1 is an image carrier belt that rotates while carrying an image transferred to a recording medium, a detection unit that detects meandering of the image carrier belt, and a detection unit that detects the meandering belt. The correction means for correcting the meandering of the image carrier belt, and the correction so that the meandering of the image carrier belt detected by the detection means is corrected over time until the print job is completed. Control means for controlling the means.

  In the image forming apparatus of the first aspect, the image carrier belt carries an image and rotates to transfer the image to a recording medium. The meandering (inclination with respect to the rotation direction) of the image carrier belt is detected by the detecting means and corrected by the correcting means. As a result, image transfer deviation from the image carrier belt to the recording medium is suppressed.

  Here, when the meandering of the image carrier belt is detected by the detecting means, the correcting means is controlled by the control means, and the meandering of the image carrier belt is corrected over time until the print job is completed. That is, since the correction amount per unit time of transfer deviation is small, the change in image quality between successive pages is reduced, and it is difficult to visually recognize image quality defects in successive pages.

  The image forming apparatus according to claim 2, wherein the control unit detects the image carrier detected by the detecting unit during a print job of two or more colors. The correction means is controlled so that the meandering of the belt is corrected over time until the print job is completed.

  In the image forming apparatus according to claim 2, when the meandering of the image carrier belt is detected by the detection unit in a print job of two or more colors, the correction unit is controlled by the control unit, and the image carrier belt The meandering is corrected over time until the print job is completed. That is, since the meandering correction amount per unit time is reduced, the change in the registration deviation amount between the colors between successive pages is reduced. Therefore, it is difficult to visually recognize the registration shift between the colors in successive pages.

  In addition, since a change in image quality between successive pages is difficult to see in a monochrome print job, the image quality of each page is improved by rapidly correcting the meandering of the image carrier belt.

  The image forming apparatus according to claim 3 is the image forming apparatus according to claim 2, wherein the control unit performs a print job in which a range in which image regions of different colors are adjacent to each other is a predetermined range or more. The correction means is controlled so that the meandering of the image carrier belt detected by the detection means is corrected over time until the print job is completed.

  4. The image forming apparatus according to claim 3, wherein the meandering of the image carrier belt is detected by the detecting means during a print job in which the range in which image areas of two or more colors and different colors are adjacent to each other is a predetermined range or more. Then, the correction means is controlled by the control means, and the meandering of the image carrier belt is corrected over time until the print job is completed.

  Here, when there are many ranges in which image areas of different colors are adjacent to each other, a registration shift between the image areas of the respective colors becomes easy to be visually recognized, and accordingly, the image quality changes between successive pages. Is also easily visible. On the other hand, when there are few ranges in which image areas of different colors are adjacent to each other, it is difficult to see even if the registration between the image areas of different colors is misaligned, and it is also difficult to see changes in image quality between successive pages. .

  Therefore, in the present invention, when there are many ranges in which image areas of different colors are adjacent to each other, the image quality change between consecutive pages can be reduced by reducing the correction amount per unit time of the meandering of the image carrier belt. It is difficult to see. This makes it difficult to visually recognize image quality defects in successive pages.

  On the other hand, when the range in which the image areas of different colors are adjacent is small, the image quality of each page is improved by increasing the correction amount per unit time of the meandering of the image carrier belt.

  An image forming apparatus according to a fourth aspect is the image forming apparatus according to any one of the first to third aspects, wherein the control means performs the print job when the resolution is a predetermined value or more. The correction means is controlled so that the meandering of the image carrier belt detected by the detection means is corrected over time until the print job is completed.

  5. The image forming apparatus according to claim 4, wherein when the meandering of the image carrier belt is detected by the detection means during a print job having a resolution equal to or higher than a predetermined value, the correction means is controlled by the control means, and the image carrying The meandering of the body belt is corrected over time until the print job is completed.

  Here, when the resolution is high, transfer misalignment is easily recognized, and a change in image quality between successive pages is easily recognized. On the other hand, when the resolution is low, it is difficult to visually recognize the transfer deviation, and it is difficult to visually recognize the change in image quality between successive pages.

  Therefore, in the present invention, when the resolution is high, the amount of correction per unit time of the meandering of the image carrier belt is reduced, so that the change in image quality between successive pages is difficult to be visually recognized. This makes it difficult to visually recognize image quality defects in successive pages.

  On the other hand, when the resolution is low, the image quality of each page is improved by increasing the correction amount per unit time of meandering of the image carrier belt.

  An image forming apparatus according to a fifth aspect is the image forming apparatus according to any one of the first to fourth aspects, wherein the control means detects meandering of the image carrier belt by the detection means. The image carrier belt meandering detected by the detecting means is started when the distance that the image carrier belt moves from the start to the end of the print job is shorter than a predetermined distance. The correction means is controlled so as to be corrected over time.

  In the image forming apparatus according to claim 5, when the distance that the image carrier belt moves between the detection unit detecting the meandering of the image carrier belt and the end of the print job is shorter than a predetermined distance. The correction means is controlled by the control means, and the meandering of the image carrier belt is corrected over time until the next print job starts.

  That is, the image quality change between successive pages is suppressed by not completing the correction of the meandering of the image carrier belt in a short time after the meandering of the image carrier belt is detected.

  The belt drive device according to claim 6, wherein the drive roll and a belt drive device that rotates an endless belt stretched around a plurality of shafts arranged substantially parallel to the drive roll by a rotational force of the drive roll. And it has a supporting means which supports at least one shaft body of the above-mentioned plurality of shaft bodies so that it can tilt with a central portion in the axial direction as a fulcrum.

  In the belt drive device according to the sixth aspect, the endless belt is stretched between a drive roll and a plurality of shafts arranged substantially in parallel, and is rotated by the rotation of the drive roll. Here, at least one shaft body among the plurality of shaft bodies is supported by the support means so as to be tiltable with the central portion in the axial direction as a fulcrum.

  For this reason, the shaft supported by the support means is substantially parallel to the width direction of the endless belt when the endless belt rotates without meandering. When the tension on one end side in the width direction of the endless belt becomes stronger than the other end side due to the shape error of the drive roll and shaft, the influence of heat, etc., the endless belt is pulled to one end side in the width direction and Shift to the side. This causes endless belt meandering.

  Then, the shaft body supported by the support means is pulled and tilted from one end side in the width direction of the endless belt. In this state, since the tension on one end side in the width direction of the endless belt is weakened, the endless belt returns to the other end side in the width direction. The meandering of the endless belt is corrected when the tensions at one end and the other end in the width direction of the endless belt are balanced. Further, since the meandering of the image carrier belt is corrected and the tension of the endless belt applied to one end side and the other end side of the tilted shaft body is balanced, the shaft body is in its original position. Return to.

  In this way, the meandering of the endless belt is naturally corrected by allowing the shaft body around which the endless belt is wound to tilt about the axial center, so that the sensor detecting the meandering of the endless belt, The motor and solenoid for tilting the shaft body and the control circuit for controlling the meandering correction of the endless belt are not required, and the cost of the endless belt meandering correction function can be reduced.

  The belt drive device according to claim 7 is the belt drive device according to claim 6, wherein the support means supports the shaft body so as to be tiltable along a conveying surface of the endless belt. And

  In the belt driving device according to claim 7, the shaft body around which the endless belt is wound is supported by the support means so as to be tiltable along the conveying surface of the endless belt with the central portion in the axial direction as a fulcrum. ing.

  For this reason, since the posture in the width direction of the transport surface of the endless belt does not change even when the shaft body tilts, the parts and devices disposed around the transport surface of the endless belt, the transport surface of the endless belt, The positional relationship can be always kept constant.

  The belt drive device according to claim 8 is the belt drive device according to claim 6 or 7, wherein the support means is capable of adjusting a wrap angle between the shaft body and the endless belt. And

  In the belt drive device according to the eighth aspect, the wrap angle between the shaft body and the endless belt can be adjusted, and the frictional force between the shaft body and the endless belt can be adjusted. Thus, the amount of force that the shaft receives from the endless belt can be set arbitrarily, and the correction sensitivity of the meandering of the image carrier belt by the shaft can be set arbitrarily.

  The belt drive device according to claim 9 is the belt drive device according to any one of claims 6 to 8, wherein the support means includes a link mechanism that amplifies a range in which the shaft body tilts. It is characterized by that.

  In the belt drive device according to the ninth aspect, the range in which the shaft body is tilted by the meandering of the endless belt is amplified by the link mechanism. As a result, even when the endless belt meandering amount is small, it is possible to rapidly correct the endless belt meandering by largely tilting the shaft body.

  A belt drive device according to a tenth aspect is the belt drive device according to the ninth aspect, wherein the connection positions of a plurality of connection members constituting the link mechanism are adjustable.

  In the image forming apparatus according to the tenth aspect, the connecting positions of the plurality of connecting members constituting the link mechanism can be adjusted, and the movable range of the link mechanism can be adjusted. As a result, the degree of amplification by which the link mechanism amplifies the tilting range of the shaft body can be adjusted, and the correction sensitivity of the meandering of the endless belt can be adjusted.

  An image forming apparatus according to an eleventh aspect includes the belt driving device according to any one of the sixth to tenth aspects, wherein the endless belt is an image carrier belt that carries an image transferred to a recording medium. It is characterized by being.

  In the image forming apparatus according to claim 11, since the meandering of the image carrier belt is naturally corrected, the sensor for detecting the meandering of the image carrier belt and the shaft around which the image carrier belt is wound are tilted. Since a motor, a solenoid, and a control circuit for controlling meandering correction of the image carrier belt are not required, the cost of the image forming apparatus can be reduced.

  Since the present invention has the above-described configuration, it is possible to suppress a change in image quality between successive pages, which is generated by correcting the meandering of the image carrier belt. Further, the cost of a meandering correction mechanism for an endless belt such as an image carrier belt can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, the image forming apparatus 10 is a color laser printer using an electrophotographic method and performs so-called + N color printing in which N colors are added to black and no overcoating is performed. The image forming apparatus 10 is provided with a display unit 62 such as a liquid crystal display panel on the upper surface, and forms a desired image on a recording medium P and a paper feed cassette 20 loaded with preprinted paper P therein. An image forming unit 14 for fixing, a fixing device 12 for fixing an image formed on the recording medium P, a sheet conveying system including a conveying roll 18 for conveying the recording medium P, and the entire image forming apparatus 10 And a control unit 80 for controlling the operation.

  In this image forming apparatus 10, first, a toner image is formed on the photosensitive belt 16 by the image forming unit 14, and this toner image is transported from the paper feed cassette 20 to the transfer unit 22 by the transport roll 18. Is transcribed. Then, the recording medium P onto which the toner image has been transferred is pressurized and heated by the fixing device 12 on the downstream side in the transport direction of the transfer unit 22 to fix the toner image on the recording medium P, and is discharged to the stacker 26 by the paper discharge roll 24. The paper is ejected. When images are formed on both the front and back sides of the recording medium P, the conveyance path on the downstream side in the conveyance direction of the fixing device 12 is switched, and the recording medium P with the toner image fixed on the surface reverses the front and back sides. Is transported to the rear surface transport path 28. Then, the recording medium P with the front and back reversed is conveyed by the conveying belt 29 to the upstream side of the transfer unit 22 in the conveying direction, and again conveyed by the conveying roller 18 to the transfer unit 22, and a toner image is transferred from the photosensitive belt 16 to the back surface. Transcribed. Then, the recording medium P passes through the fixing device 12, the toner image is fixed on the back surface, and is discharged to the stacker 26 by the discharge roll 24.

  The image forming unit 14 includes a belt driving device 60. The belt driving device 60 includes a photosensitive belt 16 that is an endless belt, a driving roll 32 on which the photosensitive belt 16 is rotatably stretched, and a driven roll 34. The drive roll 32 is disposed along the conveyance path 30 extending in the up-down direction, the driven roll 34 is disposed in the horizontal direction of the drive roll 32, and the photosensitive belt 16 is stretched in the horizontal direction. ing.

  In the image forming unit 14, a plurality of print engines 36 for forming toner images of different colors such as red and black on the surface of the photoreceptor belt 16 are arranged along the lower flat surface 16B. Each print engine 36 includes a charger 37, an exposure head 38, and a developing device 39 that are sequentially arranged in the rotation direction of the photosensitive belt 16 (the direction of arrow A in the figure). The charger 37 uniformly charges the photosensitive belt 16 with a charging corotron, a charging roll, or the like. Further, the exposure head 38 exposes the charged surface of the photosensitive belt 16 with an LED array, an optical scanning device (Raster Optical Scanner), or the like to form an electrostatic latent image on the photosensitive belt 16 based on image data. . The developing device 39 contains a one-component developer made of toner or a two-component developer made of toner or carrier, and transports the developer to the developing roll 39A while stirring the developer in the developing device 39. The developing device 39 applies a developing bias to the developing roll 39A to move the toner from the developing roll 39A onto the electrostatic latent image on the photosensitive belt 16. As a result, the electrostatic latent image on the photoreceptor belt 16 is visualized with toner. Here, the toner of each color is not superimposed on the same dot, and each dot is formed with the toner of each color.

  A transfer corotron 42 is disposed facing the photoreceptor belt 16 with the conveyance path interposed therebetween. The transfer corotron 42 discharges toward the back surface of the recording medium P, gives the toner charge on the photosensitive belt 16 to the recording medium P in a non-contact manner and gives a charge having a polarity opposite to that of the toner. Transcript.

  Further, a cleaning mechanism 44 (cleaner blade is shown) such as a cleaner blade and a cleaner roll is disposed facing the upper flat surface 16A of the photosensitive belt 16. The cleaning mechanism 44 removes untransferred residual toner remaining on the photosensitive belt 16 without being transferred to the recording medium P by the transfer unit 22 from the photosensitive belt 16.

  The fixing device 12 disposed on the downstream side in the transport direction of the transfer unit 22 is pressed against the heat roll 46 between the heat roll 46 that rotates in contact with the transfer surface of the recording medium P and the recording medium P, A pressure roll 48 that rotates in contact with the back surface of the recording medium P is provided, and a fixing nip N is formed by the heat roll 46 and the pressure roll 48. A heater lamp 50 such as a halogen lamp is disposed inside the heat roll 46, and the surface of the heat roll 46 is heated. Therefore, when the recording medium P to which the toner image is transferred passes through the fixing nip N, the recording medium P is heated and pressurized, and the toner on the recording medium is melted and fixed to the recording medium P.

  Here, the fixing device 12 is provided with a release agent supply device 13. The release agent supply device 13 includes a donor roll 52 that is in contact with the surface of the heat roll 46, a tank 54 that stores a release agent such as silicon oil, a sponge and the like in the release roll in the donor roll 52 and the tank 54. And a metering roll 56 in contact with each other through the absorber.

  A metering blade (not shown) is in contact with the surface of the metering roll 56. The metalling blade contacts the surface of the metalling roll 56 with a predetermined pressure, and regulates (measures) the release agent on the surface of the metalling roll 56 to a predetermined thickness with micron order accuracy.

  A release agent having a predetermined thickness on the surface of the metalling roll 56 is conveyed to the surface of the heat roll 46 by the donor roll 52, and a layer of the release agent having a predetermined thickness is formed on the surface of the heat roll 46. Is formed. This improves the releasability of the toner on the recording medium P from the surface of the heat roll 46 in the fixing nip N, so that fixing failure and toner fixing offset can be prevented.

  Further, a purge tray 27 is disposed on the downstream side of the fixing device 12 in the conveyance direction, and some trouble occurs during the conveyance, and an appropriate printing process cannot be performed. Ejected and loaded.

  As shown in FIG. 2, the control unit 80 includes a display unit 62, an image forming unit 14, a fixing device 12, a belt driving device 60, and a conveyance system driving unit 78 that drives a paper conveyance system. It is connected. The control unit 80 sends control signals to these units to control the overall operation of the image forming apparatus 10.

  Here, the belt driving device 60 will be described.

  As shown in FIGS. 3 and 4, the belt driving device 60 includes a sensor 64 that detects the position of one end in the width direction of the photosensitive belt 16 and a driven roll 34 that is inclined with respect to the axial direction. 16 includes a meandering correction mechanism 66 that corrects 16 meanders (tilt with respect to the rotation direction) and a correction control unit 70 that controls the meandering correction mechanism 66.

  The sensor 64 includes a light emitting element array 64 </ b> A and a light receiving element array 64 </ b> B that are opposed to each other across one end in the width direction of the photosensitive belt 16, and an output of the light receiving element 64 </ b> B is connected to a meandering determination unit 88. The light emitting element array 64 and the light receiving element array 64B are arranged so as to protrude outward from one end portion in the width direction of the photosensitive belt 16, and the light receiving elements protruded outward from one end portion in the width direction of the conveying belt 16. Receives the light beam and outputs a voltage to the meandering determination unit 88. Then, the meandering determination unit 88 recognizes the traveling position of the photosensitive belt 16 from the boundary between the light receiving element that has received the light and the light receiving element that has not received the light, and compared with the reference position, the meandering of the photosensitive belt 16. Calculate the amount.

  The meandering correction mechanism 66 includes a pivot 72 that rotatably supports the other axial end of the rotating shaft 34A of the driven roll 34, and an arm 74 that is rotatably attached to one axial end of the rotating shaft 34A. . One end of the arm 74 in the longitudinal direction is rotatably attached to the rotating shaft 34 </ b> A, and the center in the longitudinal direction is rotatably supported by the support member 76 below the driven roll 34. Further, the meandering correction mechanism 66 includes an elastic member 82 that urges the arm 74 in the clockwise direction in FIG. 2, an eccentric cam 84 that faces the elastic member 82 across the arm 74, and the eccentric cam 84 on the rotation shaft 86A. And an attached motor 86.

  The elastic member 82 is a compression coil spring and is fitted between the support member 76 and the other longitudinal end portion of the arm 74, and presses the other longitudinal end portion of the arm 74 to the eccentric cam 84. That is, when the eccentric cam 84 is rotated by the motor 86, the arm 74 is displaced clockwise or counterclockwise, and the driven roll 34 is tilted with respect to the axial direction. As a result, the tension at both ends in the width direction of the transport belt 16 changes, and the transport belt 16 is moved in the width direction.

  Then, the meandering correction control unit 70 controls the motor 86 based on the meandering amount of the photosensitive belt 16 calculated by the meandering determination unit 88 and tilts the driven roll 34 with respect to the axial direction.

  As indicated by a solid line in FIG. 3, the longitudinal direction of the arm 74 is aligned with the vertical direction in a state where the surface of the eccentric cam 84 having the maximum rotation radius is in contact with the arm 74, and the driven roll 34 is the driving roll. 32 and approximately parallel. Then, the eccentric cam 84 rotates 180 ° from this state, and as shown by the chain line, the arm 74 is rotated clockwise in the figure in a state where the surface having the smallest rotation radius of the eccentric cam 84 is in contact with the arm 74. It rotates to the end of the movable range of the direction and tilts with respect to the vertical direction. As a result, the driven roll 34 tilts (for example, 10 °) to the end of the movable range on the drive roll 32 side.

  Here, a first embodiment of a meandering correction method for the photosensitive belt 16 by the meandering correction control unit 70 will be described with reference to the flowchart of FIG.

  First, when the power of the image forming apparatus 10 is turned on, a processing routine is started and the process proceeds to Step 100. In step 100, during the warm-up of the fixing device 12, the image quality adjustment mode is executed and the meandering correction mode of the photosensitive belt 16 is executed. In the meandering correction mode, the sensor 64 is operated to rotate the photosensitive belt 16 for a predetermined time, and the meandering amount of the photosensitive belt 16 is calculated by the meandering determination unit 88. Then, the meandering correction control unit 70 controls the motor 86 according to the meandering amount of the photosensitive belt 16 calculated by the meandering determination unit 88 to correct the meandering of the photosensitive belt 16.

  Next, in step 101, a ready signal is output from the control unit 80 to each drive unit, and the image forming apparatus 10 enters a ready state. Next, in step 102, it is determined whether or not the control unit 80 has received a print job. If the result is affirmative, the process proceeds to step 103. If the result is negative, the process proceeds to step 110. In step 103, the meandering correction control unit 70 calculates the moving distance of the photosensitive belt 16 from attributes such as the paper size, the number of prints, single-sided printing, and double-sided printing of the print job.

  Next, in step 104, a drive signal is output from the control unit 80 to each drive unit, print processing is executed, and the process proceeds to step 105. In step 105, the meandering determination unit 88 determines whether the amount of meandering of the photosensitive belt 16 is within ± 400 μm. If the determination is affirmative, the process proceeds to step 106 if the determination is negative. In step 109, the negative determination is repeated until the print job is completed. On the other hand, in step 106, it is determined whether the print job is a single color print job or a multi-color print job. If the print job is a single color, the flow proceeds to step 107, and if it is a multi-color print job, the flow proceeds to step 108.

  In step 107, the meandering correction control unit 70 drives the motor 86 to tilt the driven roll 34 from a position substantially parallel to the driving roll 32 to the end of the movable range, and rapidly corrects the meandering of the photosensitive belt 16. . When the meandering of the photosensitive belt 16 is corrected, the driven roll 34 is returned to the original position. As a result, the transfer deviation is rapidly corrected, and the image quality of each page is improved.

  On the other hand, in step 108, the meandering correction control unit 70 subtracts the moving distance up to the present time from the moving distance of the photosensitive belt 16 calculated in step 103 to calculate the moving distance until the print job is completed. A minimum correction amount per unit time that can correct the meandering amount of about 400 μm is calculated while the photosensitive belt 16 moves within the distance. Then, the meandering correction control unit 70 controls the rotation amount of the motor 86 according to the calculated correction amount per unit time so that the driven roll 34 is angled smaller than the step 107 (for example, 2 to 3 °). Tilt.

  As a result, the meandering of the photosensitive belt 16 is corrected over a period of time from when the meandering is detected until the print job is completed, and as shown in FIG. 6, a registration shift occurring between the colors is detected. It is gradually corrected from the last page to the last page. Therefore, since the change in registration between the colors between successive pages is suppressed, it is difficult to visually recognize the registration shift between the colors in successive pages.

  Then, the process proceeds to step 110 through step 109 described above, and it is determined whether or not the power of the image forming apparatus 10 is turned off. If the determination is negative, the process returns to step 102 and the processes of steps 102 to 110 are repeated. Then, the processing routine is terminated.

  Next, a second embodiment of the method for correcting the meandering of the photosensitive belt 16 by the meandering correction control unit 70 will be described with reference to the flowchart of FIG.

  First, when the power of the image forming apparatus 10 is turned on, a processing routine is started and the process proceeds to Step 200. In step 200, the image quality adjustment mode is executed during the warm-up of the fixing device 12, and the meandering correction mode of the photosensitive belt 16 is executed.

  Next, in step 201, a ready signal is output from the control unit 80 to each drive unit, and the entire image forming apparatus 10 is in a ready state. Next, in step 202, it is determined whether or not the control unit 80 has received a print job. If the result is affirmative, the process proceeds to step 203. If the result is negative, the process proceeds to step 212. In step 203, the meandering correction control unit 70 calculates the moving distance of the photosensitive belt 16 from the size of the image data of the print job and the number of prints.

  Next, in step 204, a drive signal is output from the control unit 80 to each drive unit, print processing is executed, and the process proceeds to step 205. In step 205, the meandering determination unit 88 determines whether or not the meandering amount of the photosensitive belt 16 is within ± 400 μm. If the result is affirmative, the process proceeds to step 206 if the result is negative. In step 211, the negative determination is repeated until the print job is completed. On the other hand, in step 206, it is determined whether the print job is a single color print job or a multi-color print job. If it is a single color print job, the flow proceeds to step 207. If it is a multi-color print job, the flow proceeds to step 208.

  In step 207, the meandering correction control unit 70 drives the motor 86 to tilt the driven roll 34 from a position substantially parallel to the driving roll 32 to the end of the movable range, and rapidly corrects the meandering of the photosensitive belt 16. . When the meandering of the photosensitive belt 16 is corrected, the driven roll 34 is returned to the original position. As a result, the transfer deviation is rapidly corrected, and the image quality of each page is improved.

  On the other hand, in step 208, it is determined whether or not the range in which image areas of different colors are adjacent to each other from the image data is equal to or less than a predetermined range (for example, 10% of the entire image data). Proceed to step 209. In step 209, it is determined whether or not the resolution is a predetermined value (for example, 1200 dpi) or less. If the determination is affirmative, the process proceeds to step 207. If the determination is negative, the process proceeds to step 210.

  In step 210, the moving distance until the end of the print job is calculated by subtracting the moving distance to the current time from the moving distance of the photosensitive belt 16 calculated in step 203. Then, the minimum correction amount per unit time that can correct the meandering amount of about 400 μm is calculated while the photosensitive belt 16 moves through the calculated distance. Then, the rotation amount of the motor 86 is controlled according to the calculated correction amount per unit time, and the driven roll 34 is tilted by an angle (for example, 2 to 3 °) smaller than that in Step 207.

  Here, when there are many ranges in which image areas of different colors are adjacent to each other, registration between the image areas of the respective colors becomes easy to be visually recognized, and accordingly, between the image areas of the respective colors between successive pages. The change in the registration is easily visually recognized. On the other hand, when there is a small range in which image areas of different colors are adjacent to each other, it is difficult to see even if the registration between the image areas of each color is misaligned, and registration between the image areas of each color between successive pages is difficult. The change in the adjustment is less visible.

  In addition, when the resolution is high, the registration between the image areas of each color is easily recognized, and the change in registration between the image areas of each color between successive pages is also easily recognized. On the other hand, when the resolution is low, it is difficult to visually recognize the registration between the image areas of each color, and it is also difficult to visually recognize the change in registration of the image areas of each color between successive pages.

  Therefore, in this embodiment, when there are many ranges in which image areas of different colors are adjacent to each other and the resolution is high, the correction amount per unit time of the meandering of the photosensitive belt 16 is minimized to make it continuous. Changes in registration between image areas of each color between pages are suppressed. This makes it difficult to visually recognize a registration error between image areas of each color in successive pages.

  On the other hand, when the range in which the image areas of different colors are adjacent is small and the resolution is low, the correction amount per unit time of the meandering of the photosensitive belt 16 is increased, so that the image area of each color on each page is increased. The registration between is improved.

  Then, the process proceeds to step 212 through step 211 described above, and it is determined whether or not the power of the image forming apparatus 10 is turned off. If the determination is negative, the process returns to step 202 and the processes of steps 202 to 212 are repeated. Then, the processing routine is terminated.

  Next, a third embodiment of a method for correcting the meandering of the photosensitive belt 16 by the meandering correction control unit 70 will be described with reference to the flowchart of FIG.

  First, when the power of the image forming apparatus 10 is turned on, a processing routine is started and the process proceeds to Step 300. In step 300, the image quality adjustment mode is executed during the warm-up of the fixing device 12, and the meandering correction mode of the photosensitive belt 16 is executed.

  Next, in step 301, a ready signal is output from the control unit 80 to each drive unit, and the entire image forming apparatus 10 is in a ready state. Next, in step 302, it is determined whether or not the control unit 80 has received a print job. If the result is affirmative, the process proceeds to step 303. If the result is negative, the process proceeds to step 313. In step 303, the meandering correction control unit 70 calculates the moving distance of the photosensitive belt 16 from the size of the image data of the print job and the number of prints.

  Next, in step 304, a drive signal is output from the control unit 80 to each drive unit, print processing is executed, and the process proceeds to step 305. In step 305, the meander determination unit 88 determines whether or not the meandering amount of the photosensitive belt 16 is within ± 400 μm. If the determination is affirmative, the process proceeds to step 306 if the determination is negative. In step 312, negative determination is repeated until the print job is completed. On the other hand, in step 306, it is determined whether the print job is a single color print job or a multi-color print job. If it is a single color print job, the flow proceeds to step 307, and if it is a multiple color print job, the flow proceeds to step 308.

  In step 307, the meandering correction control unit 70 drives the motor 86 to tilt the driven roll 34 from a position substantially parallel to the driving roll 32 to the end of the movable range, and rapidly corrects the meandering of the photosensitive belt 16. . When the meandering of the photosensitive belt 16 is corrected, the driven roll 34 is returned to the original position. As a result, the transfer deviation is rapidly corrected, and the image quality of each page is improved.

  In step 308, the meandering correction control unit 70 subtracts the moving distance up to the current time from the moving distance of the photosensitive belt 16 calculated in step 303 to calculate the remaining moving distance until the print job is completed. Then, it is determined whether or not the remaining moving distance is equal to or longer than a predetermined distance (for example, a distance corresponding to five turns of the photosensitive belt 16).

  In step 309, the meandering correction control unit 70 calculates a minimum correction amount per unit time that can correct the meandering amount of about 400 μm of the photosensitive belt 16 with the remaining moving distance. Then, the meandering correction control unit 70 controls the rotation amount of the motor 86 according to the calculated correction amount per unit time, and makes the driven roll 34 smaller than the step 307 (for example, 2 to 3 °). Tilt.

  As a result, the meandering of the photosensitive belt 16 is corrected over a period of time from the meandering detection to the end of the print job, and the registration shift generated between the colors is gradually corrected from the meandering detection to the last page. . Therefore, since the change in registration between the colors between successive pages is suppressed, it is difficult to visually recognize the registration shift between the colors in successive pages.

  On the other hand, in step 310, negative determination is repeated until the print job is completed. In step 311, like the step 307, the meandering correction control unit 70 rapidly corrects the meandering of the photosensitive belt 16. Then, the process proceeds to Step 313. In step 313, it is determined whether or not the power of the image forming apparatus 10 is turned off.

  As described above, in this embodiment, when the distance to which the photosensitive belt 16 moves after the meandering of the photosensitive belt 16 is detected until the print job is completed, the photosensitive belt 16 The meandering correction is not performed for the remaining time of the print job, but is performed between the end of the print job and the start of the next print job.

  In other words, the correction of the meandering of the photosensitive belt 16 is not completed in a short time after the meandering of the photosensitive belt 16 is detected, thereby suppressing a change in image quality between successive pages.

  Next, a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment, and description is abbreviate | omitted.

  As shown in FIG. 9, in the belt driving device 100, the photosensitive belt 16 is wound around a driving roll 32, a plurality of driven rolls 34, and a steering roll 90. The steering roll 90 is supported by a support mechanism 92 on the inner peripheral side of the photosensitive belt 16 and is in contact with the lower conveyance rear surface of the photosensitive belt 16.

  As shown in FIGS. 10 and 11, the support mechanism 92 includes a roll holder 96 that rotatably supports the steering roll 90 via a bearing 94, and a base frame fixed to a frame (not shown) of the image forming apparatus 10. 98 and a link mechanism 102 that connects the roll holder 96 to the base frame 98.

  The roll holder 96 is a sheet metal whose both ends in the longitudinal direction are bent in a U shape. The roll holder 96 extends in the axial direction on the upper side of the steering roll 90, and bearings 94 are attached to the both bent ends. The base frame 98 is configured by screwing two parts of the first frame 98A and the second frame 98B. The first frame 98A supports the roll holder 96 via the link mechanism 102, and the first frame 98A The two frames 98B are supported by the frame of the image forming apparatus 10.

  The first frame 98A is a plate material that extends in the axial direction of the steering roll 90, and is bent downward in a stepped manner at the center in the short-side direction. The second frame 98B is a plate material extending in the axial direction of the steering roll 90, and is bent upward in a step shape at the center in the short direction. One end side (the steering roll 90 side) of the first frame 98A in the short direction is superimposed on the roll holder 96, and the first arm 104, which is a component of the link mechanism 102, and the center in the longitudinal direction of the first frame 98A. The central portion of the roll holder 96 and the roll holder 96 are connected to each other via a pin 106 so as to be swingable.

  As a result, the roll holder 96 can be rotated with the central portion in the longitudinal direction as a fulcrum, and the steering roll 90 can be made with respect to the axial direction of the drive roll 32 and the driven roll 34 with the central portion in the axial direction as a fulcrum. It can be tilted. Note that all the pins 106 used for connecting the components of the link mechanism 102 are prevented from coming off by a C-ring 107.

  The other end side in the short direction of the first frame 98A is overlapped with one end side (the steering roll 90 side) in the short direction of the second frame 98A, and the overlapped surfaces are fastened by screws 108. Has been. Here, the screw 108 is screwed to both ends of the second frame 98B in the longitudinal direction, and long holes 110 extending in the short direction through which the screw 108 passes are formed at both ends of the first frame 98A in the longitudinal direction. ing.

  That is, as shown in FIG. 9, the positional relationship between the first frame 98A and the second frame 98B can be adjusted in the short direction of the first frame 98A and the second frame 98B (the arrow B direction in the figure). Yes. Here, since the overlapping surface of the first frame 98A and the second frame 98B is substantially parallel to the conveyance surface of the photosensitive belt 16, the position of the rotation axis of the steering roll 90 is the conveyance of the photosensitive belt 16. It can be adjusted along the surface. Thereby, the wrap angle β of the photosensitive belt 16 can be adjusted without displacing the conveying surface of the photosensitive belt 16 up and down.

  As shown in FIGS. 10 and 11, the link mechanism 102 is configured by connecting the first arm 104, the second arm 112, the third arm 114, and the fourth arm 116 described above. . The first arm 104 is pivotably connected at one end in the longitudinal direction to the center in the longitudinal direction of the roll holder 96 via a pin 106. The second arm 112 is a plate material extending in the longitudinal direction of the first frame 98A, and is supported on one end in the short direction of the first frame 98A so as to be slidable in the longitudinal direction of the first frame 98A. Further, the other end portion of the first arm 104 in the longitudinal direction is connected to the center portion of the second arm 112 in the longitudinal direction via a pin 106 so as to be swingable.

  Further, one end in the longitudinal direction of the third arm 114 and one end in the longitudinal direction of the fourth arm 116 are connected to the one end and the other end in the longitudinal direction of the second arm 112 so as to be swingable via the pin 106. Has been. The other end portion in the longitudinal direction of the third arm 114 and the other end portion in the longitudinal direction of the fourth arm 114 are slidably connected to one end portion and the other end portion in the longitudinal direction of the roll holder 96 through the pin 106, respectively. ing.

  Accordingly, as shown in FIG. 12, when the steering roll 90 is tilted clockwise (in the direction of arrow F in the figure) with the connection point (fulcrum A) between the first arm 104 and the first frame 98A as a fulcrum, the first The arm 104 rotates clockwise with the fulcrum A as a fulcrum, and the second arm 112 slides to the other end in the longitudinal direction (lower side in the figure). Then, the third arm 114 rotates clockwise with the connection point (fulcrum B) between the third arm 114 and the second arm 112 as a fulcrum, and the fourth arm 116 is rotated with the fourth arm 116 and the second arm 112. Rotate clockwise with the connecting point (fulcrum C) as a fulcrum.

  As a result, the roll holder 96 tilts with the central portion in the longitudinal direction as a fulcrum, and the steering roll 90 supported by the roll holder 96 tilts with the central portion in the axial direction as a fulcrum. As shown in FIG. 9, the angle α between the fulcrum A and the conveyance surface of the photosensitive belt 16 is substantially a right angle, and the steering roll 90 is displaced substantially parallel to the conveyance surface of the photosensitive belt 16. For this reason, the attitude of the conveyance surface of the photosensitive belt 16 in the width direction is not changed by tilting the steering roll 90.

  Here, as shown in FIG. 13, the distance r2 between the connecting point (fulcrum D) between the first arm 104 and the second arm 112 and the supporting point A is the connecting point (fulcrum) between the first arm 104 and the roll holder 96. E) is greater than the distance r1 between the fulcrum A. Therefore, the rotational force around the fulcrum A applied to the steering roll 90 is amplified by r2 / r1, and the range in which the steering roll 90 tilts is amplified by r2 / r1.

  Further, as shown in FIG. 10, the positions of the connection point D and the connection points B and C can be adjusted, and the amplification degree by which the link mechanism 102 amplifies the tilting range of the steering roll 90 can be adjusted. ing.

  Here, the operation of the steering roll 90 will be described with reference to FIG.

  As shown in FIG. 14A, first, the steering roll 90 is assembled in a state substantially parallel to the width direction of the photosensitive belt 16. Then, as shown in FIG. 14B, the tension on one end side in the width direction of the photosensitive belt 16 (upper side in the drawing) from the other end side due to the shape error of the driving roll 32 and the driven roll 34, the influence of heat, and the like. When the strength is increased, the photosensitive belt 16 is pulled toward one end in the width direction and shifted to one end in the width direction. As a result, meandering upward (in the direction of arrow A) in the figure occurs on the photosensitive belt 16.

  Then, one end side in the axial direction of the steering roll 90 is pulled from one end side in the width direction of the photosensitive belt 16 and tilts to the downstream side in the moving direction of the photosensitive belt 16. In this state, the tension on one end side in the width direction of the photoreceptor belt 16 is weakened, so that the photoreceptor belt 16 returns to the other end side in the width direction as shown in FIG. The meandering of the photosensitive belt 16 is corrected when the tensions at one end and the other end in the width direction of the photosensitive belt 16 are balanced. Since the meandering of the photosensitive belt 16 is corrected, the tension of the photosensitive belt 16 applied to one end and the other end in the width direction of the tilted steering roll 90 is balanced. Returns to its original position.

  In this manner, the meandering of the photosensitive belt 16 is naturally corrected by allowing the steering roll 90 around which the photosensitive belt 16 is wound to be tilted with the central portion in the axial direction as a fulcrum. Accordingly, a sensor for detecting the meandering of the photosensitive belt 16, a motor and a solenoid for tilting the steering roll 90, and a control circuit for controlling the meandering correction of the photosensitive belt 16 are not required. In addition, the cost of the image forming apparatus 10 can be reduced. The steering roll 90 may be replaced with a steering bar.

  Further, as shown in FIG. 9, since the steering roll 90 is tilted along the conveying surface of the photosensitive belt 16, the width of the conveying surface of the photosensitive belt 16 is also tilted when the steering roll 90 is tilted. The orientation of the direction does not change. Accordingly, the positional relationship between the print engine 36 disposed around the conveyance surface of the photosensitive belt 16 and the conveyance surface of the photosensitive belt 16 can be always kept constant.

  Further, since the wrap angle β between the steering roll 90 and the photosensitive belt 16 can be adjusted and the frictional force between the steering roll 90 and the photosensitive belt 16 can be adjusted, the amount of force that the steering roll 90 receives from the photosensitive belt 16 Can be arbitrarily set, and the correction sensitivity of the photosensitive belt 16 by the steering roll 90 can be arbitrarily set.

  Further, as shown in FIG. 13, the angle at which the steering roll 90 is inclined by the meandering of the photosensitive belt 16 is amplified by the link mechanism 102, so that the steering roll 90 can be moved even when the meandering amount of the photosensitive belt 16 is small. It is possible to rapidly correct the meandering of the photosensitive belt 16 by tilting it greatly.

  Furthermore, as shown in FIG. 10, at the position of the fulcrum D, which is the connection point between the first arm 104 and the second arm 112 constituting the link mechanism 102, and at the connection point between the second arm 112 and the third arm 114. The position of a certain fulcrum B and the position of a fulcrum C that is a connection point between the second arm 112 and the fourth arm 116 can be adjusted, and the movable range of the link mechanism 102 can be adjusted. As a result, the amplification degree by which the link mechanism 102 amplifies the tilt angle of the steering roll 90 can be adjusted, and the correction sensitivity of the meandering of the photosensitive belt 16 can be adjusted.

  In the first and second embodiments, the image forming apparatus of the present invention has been described by taking the image forming apparatus provided with the meandering correction mechanism for the photosensitive belt as an example. However, the image forming apparatus of the present invention is a transfer belt. The present invention can also be applied to other image forming apparatuses including a belt-shaped image carrier such as an image forming apparatus including a meandering correction mechanism.

  Further, the image forming apparatus of the present invention is not limited to an electrophotographic image forming apparatus, but can be applied to an ink jet image forming apparatus that performs offset printing using a transfer belt.

  Furthermore, in the second embodiment, the belt driving device of the present invention has been described by taking the belt driving device for driving the photosensitive belt in the image forming apparatus as an example. However, the belt driving device of the present invention is a sheet material conveying device. The present invention can also be applied to other belt driving devices that rotationally drive an endless belt.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to a first embodiment. 1 is a block diagram illustrating a configuration of an electric system of an image forming apparatus according to a first embodiment. 1 is a perspective view illustrating a belt driving device of an image forming apparatus according to a first embodiment. 1 is a cross-sectional view illustrating a belt driving device of an image forming apparatus according to a first embodiment. 3 is a flowchart for explaining a first example of a meandering correction method for a photosensitive belt of the image forming apparatus according to the first embodiment; FIG. 3 is a diagram illustrating a state in which a registration error between image areas of each color is corrected in the image forming apparatus according to the first embodiment. 6 is a flowchart for explaining a second example of the method for correcting the meandering of the photosensitive belt of the image forming apparatus according to the first embodiment. 12 is a flowchart for explaining a third example of the meandering correction method for the photosensitive belt of the image forming apparatus according to the first embodiment; It is sectional drawing which shows the belt drive device of 2nd Embodiment. It is a disassembled perspective view which shows the meandering correction mechanism of the belt drive device of 2nd Embodiment. It is a perspective view which shows the meandering correction mechanism of the belt drive device of 2nd Embodiment. It is a top view which shows the meandering correction mechanism of the belt drive device of 2nd Embodiment. It is a perspective view which expands and shows the meandering correction mechanism of the belt drive device of 2nd Embodiment. (A)-(C) are the operation | movement diagrams of the meandering correction mechanism of the belt drive device of 2nd Embodiment.

Explanation of symbols

10 Image forming device 16 Photosensitive belt (image carrier belt, endless belt)
32 Drive roll 34 Driven roll (shaft body)
60 belt drive device 64 sensor (meander detection means)
66 Meandering correction mechanism (correction means)
70 Meander correction control unit (control means)
88 Meandering determination unit (meandering detection means)
90 Steering roll (shaft)
92 Support mechanism (support means)
102 Link mechanism P Recording medium β Wrap angle

Claims (11)

An image carrier belt that carries and rotates an image transferred to a recording medium;
Detecting means for detecting meandering of the image carrier belt;
Correction means for correcting the meandering of the image carrier belt detected by the detection means;
Control means for controlling the correction means so that the meandering of the image carrier belt detected by the detection means is corrected over time until a print job is completed;
An image forming apparatus comprising:   The control means corrects the meandering of the image carrier belt detected by the detection means during a print job of two or more colors over time until the print job is completed. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled.   In the print job in which the range in which the image areas of different colors are adjacent to each other is a predetermined range or more, the control means causes the meandering of the image carrier belt detected by the detection means until the print job is completed. The image forming apparatus according to claim 2, wherein the correction unit is controlled so as to be corrected over time.   The control means corrects the meandering of the image carrier belt detected by the detection means over time until the print job is completed in a print job having a resolution equal to or higher than a predetermined value. 4. The image forming apparatus according to claim 1, wherein the correction unit is controlled.   The control means detects the detection means when the distance that the image carrier belt moves between the detection means detecting the meandering of the image carrier belt and the end of the print job is shorter than a predetermined distance. 5. The correction unit according to claim 1, wherein the correction unit is controlled so that the meandering of the image carrier belt detected by the correction is corrected over time until the next print job starts. The image forming apparatus according to claim 1. A belt driving device that rotates a driving roll and an endless belt stretched around a plurality of shafts arranged substantially parallel to the driving roll by a rotational force of the driving roll;
A belt drive device comprising: a support unit that supports at least one of the plurality of shaft bodies so as to be tiltable with a central portion in an axial direction as a fulcrum.   The belt driving device according to claim 6, wherein the supporting unit supports the shaft body so as to be tiltable along a conveying surface of the endless belt.   The belt driving device according to claim 6 or 7, wherein the support means is capable of adjusting a wrap angle between the shaft body and the endless belt.   The belt driving device according to any one of claims 6 to 8, wherein the support means includes a link mechanism that amplifies a range in which the shaft body tilts.   The belt drive device according to claim 9, wherein a connection position of a plurality of connection members constituting the link mechanism is adjustable. A belt drive device according to any one of claims 6 to 10, comprising:
An image forming apparatus, wherein the endless belt is an image carrier belt that carries an image transferred to a recording medium.

Images