JP2009168868A - Belt traveling device and image forming apparatus including the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a belt traveling device and an image forming apparatus, detecting and correcting a deviation amount of a belt by a sensor having simple constitution. <P>SOLUTION: The end part of the belt 21 circulating at a fixed speed includes a detected corrugated area 71, a deviation amount in the width direction of an intermediate transfer belt 21 is calculated based on the length of time taken for detecting the wave of the detected area 71 by the sensor 52, and according to the deviation amount, an angle of inclination of an adjusting roller 62 is changed by a stepping motor 53 to correct the deviation of the intermediate transfer belt 21. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a belt traveling device for correcting and rotating an endless belt, and an image forming apparatus including the belt traveling device.

  2. Description of the Related Art Some image forming apparatuses use a wide endless belt that circulates as an image carrier and a pressing means for transferring and fixing. For example, in an image forming apparatus such as a tandem type color copying machine using an electrophotographic process, a photosensitive drum, a charging drum is charged for each of yellow (Y), magenta (M), cyan (C), and black (K) colors. An image forming unit comprising a scanning device, a scanning optical device, a developing device, etc. is prepared, arranged along an endless intermediate transfer belt, and images of each color Y, M, C, K are superimposed on the circulating intermediate transfer belt Together, a color image is formed.

  When such a meandering or deviation occurs in the belt, a color shift occurs and the image quality deteriorates. Therefore, in order to make the belt run stably, control is performed to detect and correct the deviation state of the belt with a sensor. For example, the deviation detection is performed by providing a sensor that reacts when the belt deviates from the center position to the right by a predetermined distance or more and a sensor that conveys when the belt deviates by a predetermined distance or more to the left. (See Patent Document 1).

  Also, the light receiving element and the light emitting part are arranged so that a part of the belt is inserted between them, and the range in which the belt shields a part of the light emitted from the light emitting element to the light receiving part is the offset amount There is also a sensor in which the output value of the light receiving unit is changed in accordance with the change (see, for example, Patent Document 2).

Japanese Patent Publication No. 63-64792 JP-A-9-48533

  When using a sensor that detects the presence or absence of a deviation, the amount of deviation cannot be recognized, so it is difficult to make the belt run stably by finely correcting the deviation.

  A sensor in which the amount of light received by the light receiving unit changes according to the amount of deviation of the belt can recognize the amount of deviation, but in order to realize such a sensor, a lens system for expanding the light receiving area is provided. Alternatively, as shown in FIG. 9A, a plurality of light receiving elements PS are arranged at intervals, and a light receiving element having a wide light receiving area such as the line image sensor 201 shown in FIG. 9B is used. In other words, there are problems such as an increase in component cost and difficulty in securing a component arrangement space.

  SUMMARY An advantage of some aspects of the invention is that it provides a belt traveling device capable of detecting and correcting a belt deviation amount with a sensor having a simple configuration, and an image forming apparatus including the belt traveling device. The purpose is that.

  The gist of the present invention for achieving the object lies in the inventions of the following items.

[1] A belt that is laid to form a circuit path;
A drive section for rotating the belt at a constant speed;
A sensor for detecting a detection area provided on the belt;
A calculation unit that calculates a deviation amount in the width direction of the belt based on a detection result of the sensor;
A moving part for moving the belt in the width direction;
A control unit configured to control the moving unit based on the amount of deviation calculated by the calculation unit to correct the deviation of the belt;
With
The detected area has a shape in which the length in the transport direction differs depending on the distance in the width direction from the reference position on the belt,
The belt travel device according to claim 1, wherein the calculation unit calculates the amount of deviation in the width direction of the belt based on a time when the sensor detects the detection area or a length of time when the detection area is not detected.

  According to the above invention, the detected area provided on the belt has a shape in which the length in the transport direction differs depending on the distance in the width direction from the reference position on the belt, so the sensor detects the detected area. The length of time changes according to the amount of deviation of the belt. Therefore, the control unit calculates and determines the amount of deviation from the length of time for which the sensor detects the detection area, and corrects the deviation of the belt based on the calculated amount of deviation.

[2] The belt traveling device according to [1], wherein a difference between a maximum distance and a minimum distance in the width direction from the reference position of the detection area is larger than a maximum allowable amount of the deviation amount.

  In the above invention, if the deviation amount is within the allowable range, the time detected by the sensor changes corresponding to the deviation amount. Therefore, the deviation amount is calculated from the time detected by the sensor at any position within the allowable range. Can be calculated.

[3] The belt traveling device according to [1] or [2], wherein the detected area is a portion where the end of the belt is corrugated.

  In the above invention, since the length in the transport direction changes on both the upward and downward inclination sides of the wave according to the distance from the reference position, the amount of time change with respect to the deviation amount can be increased. Therefore, it is possible to increase the detection accuracy of the deviation amount.

[4] The belt traveling device according to [3], wherein the waveform is a triangular wave.

  In the above invention, the relationship between the deviation amount and time becomes a linear function, and the calculation for calculation is simplified.

[5] In the above [3] or [4], the waveform is provided with N waves having the same shape with a period of 1 / N (N is an integer of 2 or more) of one rotation of the belt. The belt travel device described.

  In the above invention, the same detection result can be obtained regardless of which wave is detected by the sensor.

[6] The belt is provided with a rectangular region whose side in the transport direction is longer than the maximum length in the transport direction of the detected region, arranged in the transport direction with respect to the detected region,
The calculation unit obtains the belt rotation speed based on the length of the period in which the rectangular area is detected by the sensor, and the deviation amount based on the rotation speed and the time when the detection area is detected. The belt travel device according to any one of [1] to [4], wherein the belt travel device is calculated.

  In the above invention, the actual circumferential speed of the belt is obtained from the detection period of the rectangular area, and the deviation amount calculated from the time when the detected area is detected is corrected.

[7] The belt traveling device according to any one of [1] to [6] is provided, and the belt is a belt on which an image is formed or abutted against a transfer sheet on which the image is formed. An image forming apparatus.

  According to the belt traveling device and the image forming apparatus according to the present invention, the amount of deviation in the width direction of the belt is calculated based on the detection result of the sensor. Therefore, accurate deviation correction is performed using an inexpensive and simple sensor. Control can be performed.

    Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a cross-sectional configuration of an image forming apparatus 10 according to an embodiment of the present invention, and FIG. 2 shows an electrical schematic configuration of the image forming apparatus 10. The image forming apparatus 10 is an apparatus called a color digital copying machine, and includes a reading unit 12 including an automatic document feeder 11, a display operation unit 13, a printer unit 20, and a base unit 40. .

  The automatic document feeder 11 (see FIG. 1) has a function of feeding the originals 2 stacked on the original placement tray 11a one by one to the reading portion of the reading unit 12, and discharging the read originals to the discharge tray 11b. Fulfill.

  The reading unit 12 has a function of reading a document in color. The reading unit 12 includes an exposure scanning unit 15 including a light source and a mirror, a color line image sensor 16 that receives reflected light from the document and outputs an electrical signal corresponding to the light intensity, and reflection from the document. Various mirrors 17 and a condenser lens 18 for guiding light to the line image sensor 16 are provided.

  The printer unit 20 is a tandem type image forming apparatus, and includes an intermediate transfer belt 21 that is wider and endless than transfer paper, and a plurality of image forming units 30Y that form single-color images on the intermediate transfer belt 21, respectively. , 30M, 30C, and 30K, a paper feed unit 22 that feeds transfer paper, a transport unit 23 that transports the fed transfer paper, and a fixing device 24.

  The image forming unit 30Y forms a yellow (Y) image on the intermediate transfer belt 21, the image forming unit 30M forms a magenta (M) image on the intermediate transfer belt 21, and the image forming unit 30C uses cyan. (C) A color image is formed on the intermediate transfer belt 21, and the image forming unit 30 K forms a black (K) color image on the intermediate transfer belt 21.

  The image forming unit 30Y includes a photosensitive member 31Y as a cylindrical electrostatic latent image carrier on which an electrostatic latent image is formed, a charging device 32Y, a developing device 33Y, and a cleaning device 34Y disposed around the photosensitive member 31Y. Have In addition, a writing unit 35 </ b> Y including a laser diode that is turned on / off according to image data, a polygon mirror, various lenses, a mirror, and the like is provided.

  The photoreceptor 31Y is driven by a drive unit (not shown) and rotates in a certain direction (the direction of arrow A in the figure), and the charging device 32Y uniformly charges the photoreceptor 31Y. The writing unit 35Y functions to repeatedly scan the surface of the cylindrical photoreceptor 31Y with the laser light in the axial direction (main scanning direction) by reflecting the laser light emitted from the laser diode with a rotating polygon mirror. An electrostatic latent image is formed on the photoreceptor 31Y by scanning the uniformly charged surface of the photoreceptor 31Y with a laser beam that is turned on / off according to yellow image data.

  The developing device 33Y visualizes the electrostatic latent image on the photoreceptor 31Y with yellow toner. The toner image formed on the surface of the photoreceptor 31 </ b> Y is transferred to the intermediate transfer belt 21 at a location where it contacts the intermediate transfer belt 21. The cleaning device 34Y functions to remove and collect the toner remaining on the surface of the photoreceptor 31Y after the transfer by rubbing with a blade or the like.

  The image forming unit 30M, the image forming unit 30C, and the image forming unit 30K are different from the image forming unit 30Y except that the toner colors are different and the laser light is turned on / off with image data corresponding to each color. The configuration is the same, and a description thereof is omitted. In the figure, elements having the same configuration but having different colors are denoted by the same numerals and subscripts of “M”, “C”, and “K” instead of “Y”.

  The intermediate transfer belt 21 is wound around a plurality of rollers so as to form a circulation path, and rotates in the direction of arrow B in the drawing during image formation. In the process of turning, the images (toner images) of the respective colors (Y), (M), (C), and (K) are overlaid on the intermediate transfer belt 21 by the image forming units 30Y, 30M, 30C, and 30K. A color image is synthesized by being formed. This color image is transferred from the intermediate transfer belt 21 to the transfer paper by applying a high pressure to the secondary transfer roller 25 at the secondary transfer position D. A belt cleaning device 26 for removing the toner remaining on the intermediate transfer belt 21 after the transfer is installed downstream of the secondary transfer position D in the circumferential direction.

  The paper feed unit 22 has a plurality of paper feed cassettes 22a for storing transfer papers to be used for printing, and fulfills a function of feeding transfer sheets from the selected paper feed cassettes 22a one by one toward the transport unit 23. . The transport unit 23 passes the secondary transfer position D and the fixing device 24 through the secondary transfer position D and the fixing device 24 to discharge the transfer paper fed from the paper feed cassette 22a to the paper discharge tray outside the apparatus, and the fixing device 24. A reverse path 23b that reverses the front and back of the passed transfer paper and then merges again with the normal path 23a upstream of the secondary transfer position D is provided, which supports double-sided printing.

  The printer unit 20 primarily transfers each color image formed on the photoconductors 31Y, 31M, 31C, and 31K to the intermediate transfer belt 21 in accordance with the image data, and is formed on the intermediate transfer belt 21 in an overlapping manner. Is subjected to secondary transfer onto a transfer sheet by applying a high pressure to the secondary transfer roller 25, and the transfer sheet is fixed by a fixing device 24 and output.

  As shown in FIG. 2, the base unit 40 includes a control unit 41, an image processing unit 42, a nonvolatile memory 43, and a clock unit 44 connected to the control unit 41. The control unit 41 functions to control the overall operation of the image forming apparatus 10. The CPU (Central Processing Unit), a program executed by the CPU, a ROM (Read Only Memory) in which various fixed data are stored, and the CPU The main part is a RAM (Random Access Memory) or the like which is a work area when executing.

  The control unit 41 is further connected to a reading unit 12, a display operation unit 13, a printer unit 20, and the like. The display operation unit 13 has a function of receiving various operations and settings from the user and a function of displaying various operation screens, setting screens, guidance screens, and the like to the user. The display operation unit 13 includes, for example, a liquid crystal display having a touch panel for detecting a pressed position on the surface and other switches.

  The image processing unit 42 performs various types of image processing on the image data of each color input from the line image sensor 16 of the reading unit 12, compresses and temporarily stores the data, and then decompresses the obtained data (Y). , (M), (C), and (K) functions to output the image data of each color to the image forming units 30Y, 30M, 30C, and 30K of the printer unit 20, and the like. The non-volatile memory 43 is a memory that retains stored contents even when the power is turned off, and stores various setting values for offset correction.

  The control unit 41 further includes a belt drive motor 51 as a drive unit that circulates the intermediate transfer belt 21, a sensor 52 that detects a detection area 71 provided in the intermediate transfer belt 21, and the intermediate transfer belt 21 is moved in the width direction. A stepping motor 53 serving as a power source for the moving unit to be moved, a crimping / releasing unit 54 for switching between a state in which the intermediate transfer belt 21 is crimped to the photoreceptors 31Y, 31M, 31C, and 31K and a state in which the crimping is released and separated. It is connected. The crimping / releasing unit 54 performs crimping and releasing with the motor as power. The control unit 41 functions as a calculation unit that calculates the amount of displacement in the width direction of the intermediate transfer belt 21 based on the detection result of the sensor 52, and also corrects the meandering and displacement of the intermediate transfer belt 21. Further, the deviation of the intermediate transfer belt 21 is corrected (hereinafter also referred to as steering control) by controlling the operation of the stepping motor 53 of the moving unit based on the detection result of the sensor 52.

  In addition, the control unit 41 is connected to sensors, drive motors, and the like related to the paper feeding unit 22, the conveyance unit 23, the fixing device 24, and the like, and these are controlled by the control unit 41.

  FIG. 3 schematically shows the drive mechanism of the intermediate transfer belt 21. The intermediate transfer belt 21 is looped around a plurality of cylindrical rollers (see FIG. 1). Of the plurality of rollers, the driving roller 61 is rotationally driven by the belt driving motor 51, and the other rollers do not have a driving source.

  The moving unit that moves the intermediate transfer belt 21 in the width direction includes an adjustment roller 62 and a movable bearing unit 63. The adjustment roller 62 is mounted so that the inclination of the shaft can be changed around its one end 62a, and the other end 62b of the adjustment roller 62 is pivotally supported by a movable bearing portion 63 including a gear and a stepping motor 53. ing. By rotating the stepping motor 53 forward or backward, the angle of the shaft of the adjustment roller 62 can be adjusted in a range of ± predetermined with respect to a state parallel to the shaft of the drive roller 61.

  As shown in FIG. 3, one end of the intermediate transfer belt 21 is a detection area 71 (a shaded portion in FIG. 3) formed in a waveform, and the sensor 52 detects the detection area 71. Then, the control unit 41 calculates a deviation amount (position) in the width direction of the intermediate transfer belt 21 based on the length of time during which the sensor 52 detects the detection area 71.

  FIG. 4 shows an operation example of steering control for correcting the deviation of the intermediate transfer belt 21 based on the calculated deviation amount of the intermediate transfer belt 21 in the width direction. In FIG. 4, the waveform of the detection area 71 is omitted. In the steering control, when the intermediate transfer belt 21 is shifted in the width direction, the shift amount G with respect to the center position Cp is calculated based on the detection result of the sensor 52, and the intermediate transfer belt 21 is corrected in the direction in which the shift is corrected. Is a control in which the inclination of the adjustment roller 62 is changed by the stepping motor 53 so as to move.

  For example, in the example of FIG. 4, when the intermediate transfer belt 21 is displaced in the offset direction J (front side), the intermediate transfer belt 21 is adjusted so as to move in the belt movement direction K (back side) opposite to this. Control for changing the inclination of the roller 62 is performed. The inclination angle of the adjustment roller 62 with respect to the state parallel to the drive roller 61 is called a steering amount Q. In this way, by changing the inclination of the adjustment roller 62, a force in the F direction in the figure is applied to the intermediate transfer belt 21 to change the amount of deviation of the intermediate transfer belt 21.

  Here, a control table registered in advance in association with the amount of deviation of the belt and the steering amount for correcting the deviation of the amount of deviation is stored in the nonvolatile memory 43, and the control unit 41 includes the sensor 52. Steering control is performed in such a manner that a steering amount corresponding to the deviation amount calculated based on the detection result is obtained from the control table and the stepping motor 53 is driven.

  Such steering control is always performed during an image forming operation (during a printing operation). The overall operation sequence related to the rotation of the intermediate transfer belt 21 is as follows: (1) Start of rotation of the intermediate transfer belt 21, (2) Start of steering control, (3) Form a crimped state by the crimping / release part 54, (4) Necessary In this order, the number of images is formed, (5) release of pressure bonding, (6) stop rotation, and (7) stop steering control.

  As shown in FIG. 5A, the sensor 52 is a transmission type optical sensor composed of a light emitting element 52a and a light receiving element 52b facing each other, and the end of the intermediate transfer belt 21 is detected between them. It is attached so that the region 71 passes. The detection area 71 provided at the end of the intermediate transfer belt 21 has a triangular waveform (triangular wave) like a sawtooth, as shown in FIGS. 3 and 5B. Here, the wave is an isosceles triangle. A positive integer number of waves (triangular waves) having the same shape as the detection area 71 are provided at the end of the intermediate transfer belt 21. The number of waves may be at least one, but here, N waves having the same shape are provided in a cycle of N (N is an integer of 2 or more) of one turn of the intermediate transfer belt 21. Since a plurality of identical waveforms are continuously arranged over the entire circumference of the intermediate transfer belt 21, the same detection result can be obtained regardless of which wave is detected by the sensor 52, and management of detection timing becomes easy. .

  The detected area 71 has a shape in which the length L in the transport direction differs depending on the distance X in the width direction from the reference position E on the intermediate transfer belt 21, and the distance X and the length L are in a one-to-one relationship. It has become a relationship. In the example of FIG. 5B, the reference position E is the position of the most valley portion M <b> 1 of the wave in the detection area 71.

  During the steering control, the intermediate transfer belt 21 is driven by the belt drive motor 51 and moves in the transport direction B at a constant speed. Therefore, the length T of time during which the detected region 71 blocks the light traveling from the light emitting element 52a to the light receiving element 52b. Is proportional to the length L of the wave portion 71 in the conveyance direction at the position of the light receiving element 52b. Further, since the intermediate transfer belt 21 moves relative to the fixed sensor 52 in the width direction according to the amount of deviation, the distance X from the reference position E of the intermediate transfer belt 21 to the position of the light receiving element 52b is one piece. Changes according to the amount of shift Therefore, the deviation amount G can be calculated from the length T of time that the detection region 71 blocks the light from the light emitting element 52a to the light receiving element 52b.

  In the example of FIG. 5 (b), the time T when the intermediate transfer belt 21 is at a substantially allowable center position and the light receiving element 52b is at the position P2 is T2, from which the intermediate transfer belt 21 is shifted to the back side. When the light receiving element 52b reaches the position P1, the time T becomes T1, and conversely, when the intermediate transfer belt 21 is shifted to the front side from the center and the light receiving element 52b reaches the position P3, the time T is T3.

  For example, the inclination of the wave forming the isosceles triangle of the detection area 71 is 45 degrees, the conveyance speed is V, the wavelength of one wave of the detection area 71 is La, and the reference position E is the wave valley M1. Assuming that the position of the sensor 52b at the offset amount “0” is the position of the distance R from the reference position E to the wave top M2 side, L = La−2X, L = TV, and the offset amount G = X−. From R, the deviation amount G = (La−TV) ÷ 2−R (1) is calculated.

  The width of the detected area 71 (the difference between the maximum distance and the minimum distance from the reference position E = the amplitude of the wave = the distance in the width direction between the wave trough M1 and the wave top M2) is an intermediate transfer. The deviation amount G of the belt 21 is set to be larger than the maximum allowable amount (difference between the minimum value and the maximum value of the deviation amount). That is, when the offset amount G of the intermediate transfer belt 21 is within the allowable range, the light receiving element 52b of the sensor 52 is within the amplitude of the wave in the detection area 71. More specifically, even when the intermediate transfer belt 21 is located at the farthest rear side within the allowable range, the light receiving element 52b is located on the most valley portion M1 side from the wave top M2, and the intermediate transfer belt 21 is within the allowable range. The wave amplitude of the detection area 71 and the position of the sensor 52 are set so that the light receiving element 52b is located on the wave top M2 side of the wave trough M1 even when it is at the most offset position. Yes. Accordingly, the deviation amount G can be calculated from the time T detected by the sensor 52 within the allowable range.

  FIG. 6 shows the flow of a deviation amount detection process in which the control unit 41 calculates the deviation amount G from the detection result of the sensor 52. This process is repeatedly executed while the intermediate transfer belt 21 is driven by the belt drive motor 51 and is rotated or during steering control. The control unit 41 monitors whether there is a change in the detection state of the sensor 52 (step S101; No). If there is a change (step S101; Yes), the change is detected by the intermediate transfer belt 21 (the state where the light from the light emitting element 52a to the light receiving element 52b is blocked by the detection area 71: ON). Is detected (a state in which light from the light emitting element 52a to the light receiving element 52b is not shielded by the detection region 71; off) is determined (step S102). If the change is not from detection to no detection (step S102; No), the current time T0 is read from the clock unit 44, the time T0 is stored in the memory (step S103), and the process returns to step S101.

  In the case of a change from detection to non-detection (step S102; Yes), the current time Ta is read from the clock unit 44, and the time obtained by subtracting the stored time T0 from the current time Ta is the intermediate transfer belt. 21 is calculated as a time T during which 21 has been continuously detected (step S104), and a deviation amount G in the width direction of the intermediate transfer belt 21 is calculated from this time T (step S105), and this deviation amount G is transferred to the steering control. (Step S106), the process is terminated. The steering control is performed so that the shift of the intermediate transfer belt 21 is corrected based on the shift amount G delivered from the shift amount detection process.

  In this way, the waveform detection area 71 is provided at the end of the intermediate transfer belt 21, and the deviation amount G is obtained from the length T of time when the detection area 71 blocks the light of the sensor 52. The amount of deviation of the intermediate transfer belt 21 can be detected using a sensor 52 having a simple configuration that detects the presence or absence of the intermediate transfer belt 21 at one measurement point (light receiving element 52b). In comparison, the device configuration can be simplified and the cost can be reduced.

  Next, a case where the conveyance speed of the intermediate transfer belt 21 is actually measured and the calculated deviation amount is corrected will be described.

  As shown in FIG. 7, a rectangular region 81 having a side length Lb in the conveyance direction longer than the maximum length in the conveyance direction of one wave of the detection region 71 is formed at a predetermined position on the end of the intermediate transfer belt 21. They are arranged side by side in the transport direction with respect to the waves in the detection region 71. The length of time T12 for the sensor 52 to detect this rectangular area 81 is longer than the maximum time T13 for detecting the wave in the detected area 71, and because it is rectangular, it does not depend on the amount of deviation of the intermediate transfer belt 21.

  Therefore, it is determined that the rectangular region 81 has been detected when the sensor 52 detects that the maximum time T13 for detecting the wave in the detected region 71 has been exceeded. Then, a period T11 in which the intermediate transfer belt 21 makes one round is obtained by measuring a time from detection of the rectangular area 81 to detection of the rectangular area 81 next. Further, the conveyance speed V1 of the intermediate transfer belt 21 is obtained from the period T11, and the deviation amount G is calculated based on the time T obtained by measuring the wave in the detection area 71 with the conveyance speed V1. Accordingly, the amount of deviation can be calculated based on the actual conveyance speed V1 of the intermediate transfer belt 21, and an accurate amount of deviation can be obtained. For example, the conveyance speed V1 obtained by actual measurement may be used as V in Expression (1) as V in Expression (1).

  The embodiments of the present invention have been described with reference to the drawings. However, the specific configuration is not limited to the embodiments, and the present invention can be modified or added without departing from the scope of the present invention. included.

  For example, in the embodiment, the amount of deviation is calculated based on the time during which the wave portion of the detection area 71 is detected by the light receiving element 52b. However, as shown in FIG. 8, at the time Tf when no wave is detected. The deviation amount G may be calculated based on the above. In this case, when a plurality of waves are provided as the detected region 71, these waves may be provided at equal intervals. If the calculation formula is the same as the formula (1), the deviation G = TfV ÷ 2-R (2) formula.

  In addition, the wave shape of the detected region 71 is not limited to a triangular wave, and the length in the transport direction differs depending on the distance in the width direction from the reference position E. Any shape may be used as long as it has a one-to-one relationship, and for example, a sine wave, a trapezoid, or a triangle other than an isosceles triangle may be used. In order to increase the change in the length Y with respect to the change in the distance X, the wave shape is preferably inclined on both sides like an isosceles triangle rather than a right triangle. Further, in order to simplify the formula for calculating the deviation amount and to make the conversion accuracy into the deviation amount uniform, the wave preferably has a straight line with a hypotenuse like a triangular wave rather than a curve like a sine wave.

  In addition, the configuration of the moving unit that moves the intermediate transfer belt 21 in the width direction is not limited to that illustrated in the embodiment, and any configuration may be used as long as it has a similar function. In the embodiment, the case where the intermediate transfer belt 21 is a belt to be controlled has been described. However, other types of belts may be used as long as the belt is subjected to steering control for correcting meandering and deviation. Absent. For example, a belt that forms an image on the surface like the intermediate transfer belt 21 or a belt that is in contact with or pressed against the transfer paper in a part of the circulation path may be used.

  More specifically, when transferring the color image formed on the intermediate transfer belt 21 to the transfer paper, the endless belt (secondary transfer belt) that circulates the role of pressing the transfer paper from the back toward the intermediate transfer belt 21. ), The secondary transfer belt may be a control target. Further, in the process of fixing the toner image by pressurizing and heating the transfer paper, when the transfer paper is pressed with a rotating wide endless fixing belt, the fixing belt may be controlled.

  Further, the detection area may be formed by pasting the reflective material in the shape of a waveform or the like and pasting it on the back surface of the intermediate transfer belt 21. In this case, a reflective optical sensor that detects the presence or absence of reflection can be used as the sensor. In the case of a reflective material, the detection area does not need to be provided at the end of the intermediate transfer belt 21 and may be in the center or at an arbitrary position.

  The reference position E is not limited to the position exemplified in the embodiment, and may be an arbitrary position such as the center position in the width direction of the intermediate transfer belt 21 or the other end. In that case, an offset may be provided for the distance X in the equations (1) and (2).

  In the embodiment, the control unit 41 performs all other controls necessary for the image forming apparatus 10 in addition to the function of the calculation unit that calculates the deviation amount and the function of the control unit that performs steering control. Distributed control may be performed by the control unit. In addition, the image forming apparatus 10 is not limited to a multifunction machine, and may be an apparatus having a function of forming an image on transfer paper, such as a printer or a facsimile.

1 is an explanatory diagram illustrating a cross-sectional configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a block diagram showing a schematic electrical configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 4 is an explanatory diagram schematically showing a drive mechanism of an intermediate transfer belt. It is explanatory drawing which shows the example of a correction | amendment of a deviation correction (steering control). It is explanatory drawing which shows the relationship between deviation | shift amount and the time which the wave of a to-be-detected area interrupts | blocks the light of a sensor. It is a flowchart which shows the deviation amount detection process which a control part performs. FIG. 6 is an explanatory diagram illustrating an example of a shape of an end portion of an intermediate transfer belt provided with a rectangular region and an output waveform of a sensor. It is explanatory drawing which shows the example of a measurement in the case of calculating deviation | shift amount based on the time which is not detected. It is explanatory drawing which illustrated the case where the position of a belt is detected with a some sensor or a line image sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Document 10 ... Image forming apparatus 11 ... Automatic document feeder 11a ... Document loading tray 11b ... Paper discharge tray 12 ... Reading section 13 ... Display operation section 15 ... Exposure scanning section 16 ... Line image sensor 17 ... Mirror 18 ... Collection Optical lens 20 ... Printer unit 21 ... Intermediate transfer belt 22 ... Paper feeding unit 22a ... Paper feeding cassette 23 ... Conveying unit 23a ... Normal path 23b ... Reverse path 24 ... Fixing device 25 ... Secondary transfer roller 26 ... Belt cleaning device 30Y 30M, 30C, 30K ... Image forming portions 31Y, 31M, 31C, 31K ... Photoconductors 32Y, 32M, 32C, 32K ... Charging devices 33Y, 33M, 33C, 33K ... Developing devices 34Y, 34M, 34C, 34K ... Cleaning devices 35Y , 35M, 35C, 35K ... writing unit 40 ... base unit 41 ... control unit 4 Image processing unit 43 Non-volatile memory 44 Clock unit 51 Belt drive motor 52 Sensor 52a Light emitting element 52b Light receiving element 53 Stepping motor 54 Crimping / releasing unit 61 Driving roller 62 Adjusting roller 62a Adjusting roller One end (rotation center side)
62b ... The other end (displacement side) of the adjustment roller
63 ... Movable bearing portion 71 ... Detected area 81 ... Rectangular area A ... Rotation direction of photoconductor B ... Rotation direction of intermediate transfer belt (conveyance direction)
D: Secondary transfer position E: Reference position G: Misalignment amount J: Misalignment direction K: Belt movement direction L ... Length of wave portion in conveyance direction at distance X Lb: Length of side in conveyance direction of rectangular area M1 ... Wave trough M2 ... Wave top F ... Force applied to the transfer belt by changing the inclination of the adjustment roller Q ... Steering control correction amount

Claims (7)

A belt spanned to form a circuit path,
A drive section for rotating the belt at a constant speed;
A sensor for detecting a detection area provided on the belt;
A calculation unit that calculates a deviation amount in the width direction of the belt based on a detection result of the sensor;
A moving part for moving the belt in the width direction;
A control unit configured to control the moving unit based on the amount of deviation calculated by the calculation unit to correct the deviation of the belt;
With
The detected area has a shape in which the length in the transport direction differs depending on the distance in the width direction from the reference position on the belt,
The belt travel device according to claim 1, wherein the calculation unit calculates the amount of deviation in the width direction of the belt based on a time when the sensor detects the detection area or a length of time when the detection area is not detected. The belt travel device according to claim 1, wherein a difference between a maximum distance and a minimum distance in the width direction from the reference position of the detection area is larger than a maximum allowable amount of the deviation amount. The belt travel device according to claim 1, wherein the detected area is a portion where the end of the belt is corrugated. The belt traveling device according to claim 3, wherein the waveform is a triangular wave. 5. The belt traveling device according to claim 3, wherein the waveform is provided with N waves having the same shape in a period of 1 / N (N is an integer of 2 or more) of one circumference of the belt. . The belt is provided with a rectangular region whose side in the transport direction is longer than the maximum length in the transport direction of the detected region, aligned in the transport direction with respect to the detected region,
The calculation unit obtains the belt rotation speed based on the length of the period in which the rectangular area is detected by the sensor, and the deviation amount based on the rotation speed and the time when the detection area is detected. The belt travel device according to claim 1, wherein the belt travel device is calculated. The belt travel device according to claim 1 is provided, and the belt is a belt on which an image is formed or abutted against a transfer paper on which an image is formed. Image forming apparatus.

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