JP2005350155A - Sheet transporting device and image forming device - Google Patents

Sheet transporting device and image forming device Download PDF

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Publication number
JP2005350155A
JP2005350155A JP2004169506A JP2004169506A JP2005350155A JP 2005350155 A JP2005350155 A JP 2005350155A JP 2004169506 A JP2004169506 A JP 2004169506A JP 2004169506 A JP2004169506 A JP 2004169506A JP 2005350155 A JP2005350155 A JP 2005350155A
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Japan
Prior art keywords
sensor
paper
sheet
edge
direction
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JP2004169506A
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Japanese (ja)
Inventor
Satoshi Harada
Eiji Inoue
Shoichi Maeda
Koichi Sato
Kiyoshi Watanabe
英治 井上
浩一 佐藤
祥一 前田
智 原田
潔 渡邊
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Fuji Xerox Co Ltd
富士ゼロックス株式会社
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Priority to JP2004169506A priority Critical patent/JP2005350155A/en
Publication of JP2005350155A publication Critical patent/JP2005350155A/en
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Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that many sensors must be installed in order to sense accurately the skew amount of a paper sheet being transported. <P>SOLUTION: A sheet transporting device is equipped with a transporting means to transport sheets using the center position Pc as reference, a register sensor 23 to sense passage of each sheet, and an edge sensor 24 to sense the side edge of the sheet, wherein the register sensor 23 is installed in a position perpendicularly intersecting the sheet transporting direction and between the specified position Ps where the side edge of a sheet 40 in the smallest size will pass and the center position Pc, while the edge sensor 24 is installed on the side opposite the register sensor 23, and the sensing of the side edge is executed by moving the edge sensor 24 in the direction of going apart from the edge sensor 23 after the edge sensor 24 has sensed passage of the leading edge of the sheet in the standby position set previously according to the sheet size, and also the skew amount of the sheet is sensed on the basis of the timing at which the edge sensor 24 has sensed passage of the leading edge of the sheet and the timing at which the register sensor 23 has sensed passage of the leading edge of the sheet. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly, to a sheet conveying device used in the image forming apparatus.

  2. Description of the Related Art Image forming apparatuses such as copiers, printers, and facsimiles incorporate a paper conveyance device that conveys paper along a predetermined conveyance path. A plurality of transport rollers are disposed on the transport path of the paper transport device. Each transport roller is rotationally driven using a motor or the like as a drive source, and the paper is transported according to the rotation of the transport roller.

  In an image forming apparatus provided with such a sheet conveying device, skew (skew) may occur during conveyance of the sheet. If the skewed sheet is sent to the image transfer unit as it is, The image is transferred in a tilted state. Therefore, the skew of the paper is corrected before the paper is sent to the image transfer unit.

  In general, since the paper is fed to the image transfer unit by the registration roll, the skew correction of the paper needs to be executed before (upstream) the registration roll. Therefore, conventionally, the skew of the sheet is corrected by abutting the leading end of the sheet against the resist roll and bending it in a loop shape. At that time, in order to more appropriately correct the skew of the paper, the amount of skew indicating the degree of the paper skew is detected before the leading edge of the paper is brought into contact with the registration roll, and the leading edge of the paper is detected by the registration roll. It is desirable to control the amount of paper fed (the size of the loop) after being abutted against the head according to the previously detected skew amount.

  When detecting the skew amount of a sheet with a sensor, at least two sensors are arranged on the same straight line orthogonal to the sheet conveyance direction, and the respective sheets are detected on the basis of a deviation in timing at which the sensor detects passage of the leading edge of the sheet. A technique for obtaining the skew amount is known (see, for example, Patent Document 1). In order to detect the skew amount of the paper with high accuracy, a sensor is arranged in the direction orthogonal to the paper transport direction as much as possible (in the vicinity) of both side edges of the paper, thereby the distance between the two sensors. It is effective to secure a long period of time.

  However, the position where the paper passes in the side direction differs depending on the size of the paper that is actually conveyed. For example, if A4 size paper is transported with the short side facing in the transport direction, the paper size (paper width) in the side direction will be 210 mm, but if B5 size paper is transported with the short side facing in the transport direction, side When the paper size in the direction is 182 mm and the B4 size paper is transported with the short side facing the transport direction, the paper size in the side direction is 257 mm.

  Therefore, in order to accurately detect the skew amount of the paper, as described in Patent Document 1 below, a number of sensors are arranged on the same straight line according to various paper sizes, and among them, Therefore, it is necessary to detect the passage of the leading edge of the sheet by using two sensors arranged at positions that match the size of the sheet that is actually conveyed.

JP-A-5-338859

  However, in the technique described in Patent Document 1, the number of sensors for detecting the skew amount of the sheet increases, which increases the cost of the apparatus.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a sheet conveying apparatus capable of accurately detecting a sheet skew amount with a smaller number of sensors than the conventional one, An image forming apparatus is provided.

  A sheet conveying apparatus according to the present invention detects a passage of a sheet conveyed by the conveying unit, and a conveying unit that conveys the sheet based on a center position through which the center portion of the sheet passes in a direction orthogonal to the sheet conveying direction A path sensor that is disposed upstream or downstream in the transport direction with respect to the path sensor, detects an edge sensor of the sheet transported by the transport unit, and moves the edge sensor in a direction orthogonal to the transport direction. Sensor moving means and control means for controlling the movement operation of the edge sensor by driving the sensor moving means, and the side edge portion of the minimum size paper passes in the direction orthogonal to the transport direction. A path sensor is arranged between the predetermined position and the center position, and the edge is placed on the opposite side of the path sensor across the center position. The sensor is arranged, and the control means moves the edge sensor away from the path sensor after the edge sensor detects passage of the leading edge of the paper at a standby position set in advance according to the size of the paper conveyed by the conveyance means. Thus, the side edge detection operation is performed, and the skew amount of the paper is detected based on the timing when the edge sensor detects the passage of the leading edge of the paper and the timing when the path sensor detects the passage of the leading edge of the paper. Further, an image forming apparatus according to the present invention includes the paper transport device having the above-described configuration.

  In the paper conveying apparatus and the image forming apparatus according to the present invention, the skew amount of the paper using the path sensor that detects the passage of the paper and the edge sensor that detects the side edge of the paper on the upstream side or the downstream side of the path sensor. When this skew amount is detected, a long sensor distance is ensured between the path sensor and the edge sensor by moving the edge sensor to a standby position corresponding to the size of the paper that is actually conveyed. Is done.

  According to the present invention, it is possible to accurately detect the skew amount of the paper by using both the path sensor and the edge sensor without separately providing a sensor for detecting the skew amount. Therefore, it is possible to accurately detect the skew amount of the paper with a smaller number of sensors than in the past. As a result, it is possible to reduce the cost of the apparatus while maintaining high detection accuracy of the skew amount.

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

  FIG. 1 is a schematic diagram showing a configuration example of an image forming apparatus to which the present invention is applied. The illustrated image forming apparatus has a sheet conveying device. This sheet conveying apparatus is incorporated in the apparatus main body 1 of the image forming apparatus. That is, a plurality of (four in the illustrated example) sheet storage cassettes 2... Having a multistage structure are incorporated in the apparatus main body 1 with casters. Each of the paper storage cassettes 2,... Stores paper in a stacked state, and is detachably incorporated in the apparatus main body 1. These paper storage cassettes 2,... Have basically the same configuration, although the size of the entire cassette differs depending on the size and type of paper to be stored.

  Further, in the vicinity of the sheet storage cassette 2, a call roll 3, a separation roll 4, and a delivery roll 5 are arranged as paper feed rolls. The calling roll 3 calls a sheet from the sheet storage cassette 2 by rotating in contact with the uppermost surface of the sheet stored in the sheet storage cassette 2. The separation roll 4 separates and feeds the sheets called up by the calling roll 3 one by one. The delivery roll 5 sends out the paper separated by the separation roll 4 toward the transport path. These three paper feed rolls 3, 4, and 5 are provided in a 1: 1 correspondence with the paper storage cassette 2.

  In addition, a plurality of transport rolls 6 are provided at predetermined intervals in a transport path that is a destination of the paper fed from each paper storage cassette 2, and the paper is downstream of the transport path by the rotation of the transport rolls 6. It is transported to the side. A transport roll 7 is disposed at a paper transport destination of the transport roll 6. The paper fed from each paper storage cassette 2 is sent to a common transport roll 7 by the rotation of the transport roll 6. The transport roll 7 transports the paper transported by the transport roll 6 toward the registration roll 8.

  The registration roll 8 feeds a sheet on which an image is to be formed toward an image transfer unit (to be described later) and aligns the sheet at the time of feeding. The registration of the sheet by the registration roll 8 involves correcting the skew by abutting the leading edge of the sheet against the registration roll 8, or adjusting the sheet conveyance start timing (rotation start timing of the registration roll 8) after the skew correction. Is done. A transport roll (hereinafter referred to as a “pre-registration roll”) 7 is disposed immediately before (on the upstream side) the registration roll 8.

  In addition, a bulging portion 9 is formed in the conveyance path between the pre-registration roll 7 and the registration roll 8. The bulging portion 9 is for bending the paper in a loop shape by feeding by the pre-registration roll 7 when correcting the skew of the paper by abutting against the registration roll 8. By forming this loop, the leading edge of the paper is uniformly abutted against the resist roll 8.

  A photosensitive drum 10 and a vacuum transport unit 11 are disposed at the paper destination of the registration roll 8. The photosensitive drum 10 is rotationally driven in the counterclockwise direction in the figure. Around the photosensitive drum 10, as a means for forming an image (toner image) to be transferred onto a sheet, for example, a charger (not shown) for uniformly charging the surface of the photosensitive drum 10, and this An image writing device (laser ROS; Laser Raster Output Scanner) 12 for writing an electrostatic latent image on the surface of the photosensitive drum 10 charged by the charger, and a photosensitive member on which the electrostatic latent image is written by the image writing device 12. A developing device (not shown) for supplying toner to the surface of the drum 10, a transfer roll 13 for transferring a toner image developed by the developing device to a sheet, and the surface of the photosensitive drum 10 without being transferred to the sheet A cleaner (not shown) for removing unnecessary toner remaining on the surface and a static eliminator (not shown) for discharging the surface of the photosensitive drum 10 are sequentially arranged in accordance with the rotation direction of the photosensitive drum 10. It has been.

  The image writing device 12 writes an image by scanning a laser beam on the surface of the photosensitive drum 10. The image writing device 12 includes, for example, a laser element (semiconductor laser or the like) serving as a laser beam generation source, and a polygon mirror (rotating polygon mirror) that scans in a line while reflecting the laser beam generated from the laser element. And an imaging optical system that narrows the beam diameter of the laser beam reflected by the polygon mirror. The image writing operation by the image writing device 12 is performed by exposing the surface of the photosensitive drum 10 charged to a predetermined potential by irradiation with a laser beam and blinking (modulating) the laser beam in accordance with an image signal. Done.

  The vacuum transport unit 11 includes an endless transport belt 11A and two rolls 11B that support the transport belt 11A. In the vacuum transport unit 11, the sheet fed by the registration roll 8 is placed on the transport belt 11A, and the back surface of the sheet (the surface opposite to the surface on which the image is transferred) is vacuumed on the transport belt 11A. The sheet is transported in accordance with the travel of the transport belt 11A accompanying the rotational driving of the belt support roll 11B while being adsorbed by the belt. Further, the transfer roll 13 is disposed at a position facing the photosensitive drum 10 via the conveyance belt 11 </ b> A of the vacuum conveyance unit 11. Therefore, the sheet conveyed by the vacuum conveying unit 11 passes through the opposite portion of the photosensitive drum 10 and the transfer roll 13 during the conveyance, and the image is transferred from the photosensitive drum 10 to the sheet at the opposite portion. Therefore, the facing portion between the photosensitive drum 10 and the transfer roll 13 corresponds to the image transfer portion.

  A fixing roll 14 is disposed at a sheet destination by the vacuum conveyance unit 11, and conveyance rolls 15 </ b> A and 15 </ b> B are sequentially disposed at a predetermined interval on the downstream side of the fixing roll 14. Further, the conveyance path is branched into two on the downstream side of the conveyance roll 15B, and a gate member (not shown) is provided at the branched portion. The gate member switches the traveling direction of the paper at a branching portion of the transport path. A discharge roll 16 is disposed at the end of one transport path serving as the switching destination, and the transport roll 17 is disposed in the middle of the other transport path. Is arranged. The discharge roll 16 discharges the paper toward the discharge tray 21. The conveyance roll 17 conveys the sheet toward the reverse roll 18.

  The reversing roll 18 is provided so as to be capable of rotating in both directions. The reversing roll 18 performs a so-called switchback method in which the sheet is drawn in by rotating in one direction and the sheet is fed out by rotating in the other direction. It will be reversed. In the paper feeding direction by the reversing roll 18, a conveyance path leading to the discharge roll 16 and a conveyance path leading to the pre-registration roll 7 are formed. A transport roll 19 is disposed on the transport path leading to the discharge roll 16, and a plurality of transport rolls 20 are disposed on the transport path leading to the pre-registration roll 7 at a predetermined interval. The transport roll 19 transports the paper sent out by the reversing roll 18 to the discharge roll 16, and the transport roll 20 transports the paper sent out by the reverse roll 18 to the pre-registration roll 7.

  In addition, various sensors necessary for controlling the sheet conveying operation and the image forming operation are arranged at appropriate positions (positions indicated by triangles in the drawing) of the sheet feeding portion and the conveying path. . Among these, between the pre-registration roll 7 and the registration roll 8, two path sensors 22 and 23 are arranged at different positions in the transport direction, and an edge sensor 24 and a home sensor 25 are arranged in the vicinity of the path sensor 22. ing. The upstream path sensor 22 is disposed in the vicinity (downstream side) of the pre-registration roll 7, and the downstream path sensor 23 is disposed in the vicinity (upstream side) of the registration roll 8.

  The path sensors 22 and 23 are composed of, for example, a reflection type photosensor in which a light emitting element and a light receiving element are arranged on the same sensor surface, and a sheet exists at a position facing the sensor surface in the vicinity (hereinafter referred to as a sensor detection position). When it does, it becomes an on state, and when it does not exist, it becomes an off state. Therefore, when the leading edge of the paper passes through the sensor detection position of the path sensors 22 and 23, the state is switched from the OFF state to the ON state, and thereafter when the trailing edge of the paper passes the sensor detection position of the path sensors 22 and 23. Switch from state to off state. Therefore, it is possible to detect the passage of the leading edge and the trailing edge of the paper based on the on / off state of each of the path sensors 22 and 23. In the following description, the path sensor 22 near the pre-registration roll 7 is referred to as a pre-registration sensor 22, and the path sensor 23 near the registration roll 8 is referred to as a registration sensor 23.

  The edge sensor 24 and the home sensor 25 are included in the sensor moving mechanism 26 as shown in FIG. The sensor moving mechanism 26 moves the edge sensor 24 in the side direction in order to detect the position of the side edge of the paper in a direction (side direction) orthogonal to the paper transport direction. In addition to the edge sensor 24 and the home sensor 25, the sensor moving mechanism 26 moves a sensor moving motor 27 serving as a driving source for moving the edge sensor 24 and the edge sensor 24 in a direction orthogonal to the paper transport direction. The guide mechanism 28 is configured to guide and support it as much as possible, and a power transmission mechanism 29 that transmits the driving force of the sensor moving motor 27 to the guide mechanism 28.

  The edge sensor 24 is composed of a reflection type photosensor in which a light emitting element and a light receiving element are arranged on the same sensor surface in the same manner as the path sensors 22 and 23, for example, and is turned on when a sheet is present at the sensor detection position. When it does not exist, it is turned off. Accordingly, when the edge sensor 24 is moved in the side direction so as to cross the side edge of the sheet, the edge sensor 24 is switched from the off state to the on state, or from the on state to the off state during the movement. Therefore, it is possible to detect the side edge of the sheet based on the on / off state of the edge sensor 24.

  The home sensor 25 is composed of, for example, a transmission type photosensor in which a light emitting element and a light receiving element are arranged to face each other, and the optical path between the elements is not blocked (the light emitted by the light emitting element is received by the light receiving element). Is in the on state, and in the state in which the optical path is blocked (the light emitted by the light emitting element is not received by the light receiving element), it is in the off state. The home sensor 25 is a sensor for defining the home position of the edge sensor 24 when the edge sensor 24 is moved in the side direction.

  The sensor moving motor 27 is configured by using, for example, a pulse motor that can easily control the rotation direction and the rotation amount.

  The guide mechanism 28 is configured using a sensor support bracket 30, a pair of guide shafts 31, and a moving member 32. The sensor support bracket 30 is obtained, for example, by bending a rectangular thin metal plate. One end of the sensor support bracket 30 is inclined obliquely, and the edge sensor 24 is fixed to the inclined portion by screwing, bonding, or the like. The other end of the sensor support bracket 30 is bent at a substantially right angle.

  The pair of guide shafts 31 are round shafts each having a circular cross section, and are arranged in parallel to each other in a direction orthogonal to the paper transport direction. Further, both end portions of each guide shaft 31 are fixed to shaft support portions 33A and 33B integrally formed on the plate-like base member 33 in a fitted state.

  The moving member 32 is substantially U-shaped in a plan view, and is guided and supported by the pair of guide shafts 31 so that the opposing portions are fitted to the pair of guide shafts 31 slidably. ing. Further, the lower end portion of the moving member 32 is attached to the sensor support bracket 30 in a fixed state. Therefore, when the moving member 32 moves along the pair of guide shafts 31, the sensor support bracket 30 also moves together with the moving member 32.

  The power transmission mechanism 29 is configured using two large and small pulleys 34 and 35 and an endless belt 36. The pulley 34 on the large diameter side is fitted and fixed to the rotating shaft (drive shaft) of the sensor moving motor 27 attached to the base member 33. The small-diameter pulley 35 is rotatably mounted on the base member 33 at a position away from the large-diameter pulley 34 by a predetermined distance. The belt 36 is stretched around the two pools 34 and 35 in a loop shape. Further, a part of the belt 36 is fixed to the other end portion (a portion bent substantially at a right angle) of the above-described sensor support bracket 30 by screwing, bonding or the like. Further, a detection piece 37 is fixedly attached to the sensor support bracket 30. The detection piece 37 is arranged so as to shield the optical path of the home sensor 25 at one moving terminal when the sensor support bracket 30 is moved integrally with the moving member 32.

  In the sensor moving mechanism 26 configured as described above, when the pulley 34 on the large diameter side is rotated by driving the sensor moving motor 27, the belt 36 travels using the pulley 34 as a driving pulley, and the belt 36 travels with a small diameter. The side (driven side) pulley 35 rotates. When the belt 36 travels, the sensor support bracket 30 and the moving member 32 move accordingly. At this time, since the moving member 32 moves along the pair of guide shafts 31, the moving direction of the sensor support bracket 30 is guided by the pair of guide shafts 31. Therefore, by arranging the pair of guide shafts 31 in a direction orthogonal to the paper transport direction, the edge sensor 24 on the sensor support bracket 32 can be moved in a direction (side direction) orthogonal to the paper transport direction. . Further, by reversing the rotation direction of the sensor moving motor 27 (forward rotation, reverse rotation), the edge sensor 24 can be moved (reciprocated) in one direction and the other direction in a direction orthogonal to the paper transport direction. it can.

  FIG. 3 is a block diagram showing the configuration of the control system of the image forming apparatus according to the embodiment of the present invention. In the figure, a main control unit 38 controls the overall processing operation of the image forming apparatus. Various sensors including the pre-registration sensor 22, the registration sensor 23, the edge sensor 24, and the home sensor 25 are electrically connected to the main control unit 38 so that signals output from the respective sensors are taken into the main control unit 38. It has become. The main control unit 38 is connected to a sensor moving motor 27 and a writing control circuit 39. The sensor moving motor 27 is rotationally driven in accordance with a driving pulse supplied from the main control unit 38. The writing control circuit 39 controls an image (electrostatic latent image) writing operation by the image writing device 12 in accordance with the paper positional deviation information supplied from the main control unit 38.

  FIG. 4 is a diagram illustrating a sensor arrangement state on the sheet conveyance path between the pre-registration roll and the registration roll. In the figure, between the pre-registration roll 7 and the registration roll 8, a center position (center registration position) through which the center portion of the sheet (the center of the sheet width) passes in a direction (left and right direction in the figure) perpendicular to the sheet conveyance direction. ) The paper is transported based on Pc. A pre-registration sensor 22, an edge sensor 24, and a registration sensor 23 are arranged in this order from the pre-registration roll 7 toward the registration roll 8 in the sheet conveyance direction (the vertical direction in the figure). Among these, the edge sensor 24 is provided so as to be movable in the left-right direction in the figure by the sensor moving mechanism 26, and the pre-registration sensor 22 and the registration sensor 23 are provided in a fixed state. Further, in the direction orthogonal to the sheet conveyance direction, the pre-registration sensor 22 and the registration sensor 23 are disposed at substantially the same position, and the edge sensor 24 is disposed on the opposite side of the sensors 22 and 23 with the center position Pc interposed therebetween. That is, the pre-registration sensor 22 and the registration sensor 23 are arranged on the right side in the figure with the center position Pc as a boundary, and the edge sensor 24 is arranged on the left side in the figure with the center position Pc as a boundary.

  More specifically, in the direction orthogonal to the sheet conveyance direction, the pre-registration sensor 22 and the registration sensor 23 have the smallest sheet size (sheet width) in the side direction among the various sheet sizes actually handled. It is disposed between a predetermined position Ps through which one side edge portion 40A of the paper 40 passes and the center position Pc, and more preferably is disposed in the vicinity of the predetermined position Ps. The vicinity of the predetermined position Ps refers to a position that is perpendicular to the paper transport direction and is closer to the predetermined position Ps than the intermediate point between the predetermined position Ps and the center position Pc. The position closest to the predetermined position Ps within a range where the passage of 40 can be detected. The predetermined position Ps is set to a position where the side edge portion 40A of the paper 40 passes when the paper 40 of the minimum size is transported to the left side of the drawing with the maximum allowable amount in the side direction when the paper 40 of the minimum size is conveyed. Is done. Therefore, even if the minimum size sheet 40 is laterally shifted by the maximum allowable amount during actual sheet conveyance, the leading end portion 40B of the sheet 40 always passes through the sensor detection positions of the pre-registration sensor 22 and the registration sensor 23. Further, even when the paper 41 larger than the minimum size is conveyed, the leading end of the paper 41 always passes through the sensor detection positions of the pre-registration sensor 22 and the registration sensor 23.

  The operation of the image forming apparatus based on the control process of the main control unit 38 will be described below. First, the user inputs desired image forming conditions (for example, image forming density and number of copies, designation of duplex printing, etc.) using an operation panel (not shown) of the image forming apparatus, and then a start button in the operation panel. push. Thereby, one job is started. At this time, the paper feed rolls 3, 4, and 5 corresponding to the paper storage cassette 2 that stores the paper designated by the user's input operation using the operation panel or the paper selected by the automatic selection function are rotated. Thus, the sheets stored in the sheet storage cassette 2 are separated one by one in order from the top and sent out onto the conveyance path. In this case, it is assumed that the sheet is conveyed by the sensor reference method on the sheet conveyance path.

  The paper thus sent out from the paper storage cassette 2 to the transport path is transported downstream by the rotation of the transport roll 6 and is fed into the pre-registration roll 7. Next, the sheet is fed into the registration roll 8 according to the rotation of the pre-registration roll 7. The rotation of the registration roll 8 is stopped before the paper is fed by the pre-registration roll 7. Therefore, the leading edge of the sheet fed by the pre-registration roll 7 is abutted against the nip portion of the registration roll 8 in the rotation stopped state. Further, by feeding an appropriate amount of paper by the pre-registration roll 7 in this abutting state, the paper is bent in a loop shape at the bulging portion 9 in front of the registration roll 8, that is, the paper skew is corrected. In this state, the paper is temporarily stopped.

  Thereafter, the rotation of the resist roll 8 is started in accordance with the timing at which the electrostatic latent image written on the surface of the photosensitive drum 10 by the image writing device 2 is developed into a toner image and sent to the image transfer unit. As a result, the paper whose skew has been corrected as described above is sent to the image transfer unit according to the rotation of the registration roll 8. In the image transfer section, the sheet fed by the registration roll 8 is placed on the transport belt 11A of the vacuum transport section 11, and the image transfer section (transferred to the photosensitive drum 10 and the photosensitive drum 10) by the travel of the transport belt 11A. It moves so as to pass through a portion facing the roll 13). At this time, the toner image arrives at the image transfer portion in accordance with the timing when the leading edge of the paper reaches the image transfer portion, and the transfer roll 13 imparts a charge having a polarity opposite to that of the toner, whereby the surface of the photosensitive drum 10 is The toner image is transferred to the first side of the paper.

  Thereafter, the sheet is sent to the fixing roll 14 by the vacuum conveyance unit 11, and the image is fixed on the first surface of the sheet by a pressurizing action and a heating action applied between the rolls. Next, the sheet fed from the fixing roll 14 is conveyed by the conveyance rolls 15A and 15B. At this time, if the sheet is not designated for duplex printing, the sheet is fed to the discharge roll 16 according to the rotation of the transport rolls 15A and 15B, and the sheet is discharged to the discharge tray 21 by the rotation of the discharge roll 16.

  On the other hand, if the paper is designated for double-sided printing, the paper is fed to the transport roll 17 according to the rotation of the transport rolls 15A and 15B, and the paper is fed to the reversing roll 18 according to the rotation of the transport roll 17. Send it in. Then, the reversing roll 18 sequentially performs the paper drawing operation and the feeding operation, thereby feeding the paper to the transport roll 20 in a state where the paper is reversed. Next, after the paper is sent again to the pre-registration roll 7 according to the rotation of the plurality of transport rolls 20, the toner is applied to the second surface of the paper in the same procedure as when forming (printing) an image on the first surface of the paper. The image is transferred and the toner image is fixed on the second side of the paper. As a result, images are formed (printed) on both sides of the paper.

  The paper on which double-sided printing is performed in this way is sent again to the transport roll 17 according to the rotation of the transport rolls 15A and 15B, and is sent to the reverse roll 18 via the transport roll 17. The reversing roll 18 feeds and feeds the paper, and the paper is fed into the transport roll 19 in a state where the paper is turned upside down. The paper is discharged to the discharge tray 21 by the rotation of the transport roll 19 and the rotation of the discharge roll 16. The

  When the image forming apparatus is operated as described above, the main control unit 38 executes processing for aligning the position of the paper and the image (hereinafter also referred to as “registration processing”) according to the flowchart of FIG. . FIG. 6 is a schematic diagram showing a series of procedures when the edge sensor is moved in order to detect the side edge of the paper in the registration process. As a method of taking the conveyance reference in the side direction, a center reference method (center registration method) using the position where the center portion of the paper passes as a conveyance reference, and a side reference using the position where the side edge portion of the paper passes as a conveyance reference. There is a method (side registration method), but in the present embodiment, it is assumed that the sheet is conveyed by the sensor reference method.

  First, when the conveyance of the sheet is started, the sensor moving motor 27 is driven to start moving the edge sensor 24 toward the home position (step S1). When the sheet is conveyed by the center reference method, the home position is the timing when the detection piece 27 that moves together (integrally) with the edge sensor 24 blocks the optical path of the home sensor 25 (when the home sensor 25 is turned on). It is a position uniquely identified based on this. On the other hand, the position of the edge sensor 24 before the start of movement (hereinafter referred to as “initial position”) is determined by the edge sensor 24 after the detection operation of the side edge position of the paper in the previous image forming job. This is the stop position. In the direction orthogonal to the paper transport direction, the home position is the same regardless of the paper size, but the initial position is a position that depends on the previously processed paper size. Therefore, the distance from the initial position to the home position differs depending on the previously processed paper size (paper width).

  Next, it is confirmed whether or not the home sensor 25 is turned on (step S2). When the home sensor 25 is turned on, the sensor moving motor 27 is driven by a certain number of pulses from the home sensor 25 and then the edge sensor 24 is turned on. The movement is stopped (step S3). The sensor stop position at this time becomes the home position of the edge sensor 24. Next, the sensor moving motor 27 is driven to move the edge sensor 24 from the home position to the standby position (step S4). The processing so far is performed before the paper reaches the pre-registration roll 7.

  The standby position is a position where the edge sensor 24 is kept waiting until the paper is conveyed to a position where the edge sensor 24 can detect the side edge of the paper. The standby position of the edge sensor 24 is set on the opposite side of the predetermined position Ps across the center position Pc and slightly closer to the center position Pc (for example, about 5 mm) than the position where the other side edge portion of the paper passes. Is. Therefore, when transporting the minimum size paper 40, the standby position is set closer to the center position Ps than the position through which the other side edge portion 40C of the paper 40 passes.

  Further, the number of drive pulses supplied to the sensor moving motor 27 when the edge sensor 24 is moved from the home position to the standby position is set in advance for each paper size (paper width). Therefore, the standby position of the edge sensor 24 differs depending on the paper size. That is, as shown in FIG. 7A, when transporting the minimum-size paper 40, the standby is closer to the center position Pc than the position where the side edge portion 40C of the paper 40 passes in the left portion of the center position Pc. When the position P1 is set and the sheet 41 larger than the minimum size is conveyed as shown in FIG. 7B, the position on the left side of the center position Pc is larger than the position where the side edge portion 41A of the sheet 41 passes. A standby position P2 is set closer to the center position Pc.

  Subsequently, it is confirmed whether or not the pre-registration sensor 22 is turned on (step S5), and the leading edge of the sheet sent out by the pre-registration roll 7 passes through the sensor detection position of the pre-registration sensor 22, whereby the pre-registration sensor 22 is turned off. When switching from ON to ON, it is subsequently checked whether or not the edge sensor 24 is ON (step S6). Then, when the leading edge of the sheet sent out by the pre-registration roll 7 passes the sensor detection position of the edge sensor 24, and when the edge sensor 24 is switched from the off state to the on state, time measurement by a timer is started at that time. After (step S7), the side edge detection operation using the edge sensor 24 is started (step S8).

  In the side edge detection operation, a drive pulse is supplied to the sensor movement motor 27 to move the edge sensor 24 from the standby position to the end position, and the drive pulse supplied to the sensor movement motor 27 during the movement is detected. This is done by counting the number in real time. The end point position of the edge sensor 24 in the edge detection operation is set on the opposite side to the standby position with the position where the side edge portion of the sheet to be detected passes in the direction orthogonal to the sheet transport direction. Accordingly, when the minimum size paper 40 is conveyed as shown in FIG. 8A, the edge sensor 24 is moved in the direction of the arrow (from the standby position P1 set according to the size of the paper 40 toward the end point Pe). When the paper 41 larger than the minimum size is transported as shown in FIG. 8B, it is moved from the standby position P2 set according to the size of the paper 41. The edge sensor 24 is moved in the direction of the arrow (the direction away from the sensors 22 and 23) toward the end point position Pe. At this time, the sensor movement distance from the standby position to the end point position is set to a constant distance (for example, 10 mm) regardless of the paper size. Further, when the edge sensor 24 is moved from the standby position to the end point position, the edge sensor 24 crosses the side edge portion of the sheet during the movement, and at that moment, the edge sensor 24 switches from the on state to the off state.

  Therefore, the main control unit 38 checks whether or not the edge sensor 24 is turned off (step S9), and when the edge sensor 24 is switched from the on state to the off state, the side edge detection using the edge sensor 24 is performed. Based on the result, the amount of misalignment of the paper in the direction orthogonal to the paper transport direction is calculated (step S10). In calculating the sheet position deviation amount, when the edge sensor 24 is moved from the standby position toward the end point position as described above, this movement is started (the drive of the sensor moving motor 27 is started). The count value of the drive pulse supplied to the sensor moving motor 27 until the edge sensor 24 is turned off is acquired as the detection result of the side edge. This pulse count value becomes smaller as the sheet position approaches the standby position (home position) of the edge sensor 24 in the direction orthogonal to the sheet conveyance direction. Therefore, the main control unit 38 compares the pulse count value (hereinafter referred to as detection value) obtained by actually performing the side edge detection operation with a preset reference pulse count value (hereinafter referred to as reference value), Based on the comparison result, the amount of sheet misalignment is obtained.

  Specifically, for example, a difference between the reference value and the detected value (a value obtained by subtracting the detected value from the reference value) is obtained, and if this difference is within the detection error range (almost zero), the sheet in the side direction is detected. The amount of displacement is zero. Further, when the difference between the reference value and the detection value exceeds the detection error range, the paper position deviation amount is obtained from the magnitude of the difference, and the difference (paper position deviation amount) is a positive value or a negative value. The direction of misalignment of the paper is recognized depending on whether it is a value. The amount of misalignment of the paper can be obtained by multiplying the difference between the reference value and the detected value by the sensor movement amount per pulse. In addition, if the difference between the reference value and the detected value is a positive value, it is recognized that the paper is shifted to the standby position side, and if the value is negative, the paper is on the opposite side of the standby position. It can be recognized that it is shifted.

  Next, the image writing position in the main scanning direction is corrected based on the previously calculated sheet position deviation amount (step S11). The image writing position is corrected when the image writing device 12 writes an electrostatic latent image on the surface of the photosensitive drum 10. The electrostatic latent image writing operation (scanning operation) by the image writing device 12 is performed in the main scanning direction along the axial direction of the photosensitive drum 10, and in the sub-scanning direction (drum rotating direction) orthogonal thereto, the photosensitive drum. The electrostatic latent image writing position by the image writing device 12 is moved according to the rotation of 10. As a result, electrostatic latent images are sequentially written on the surface of the photosensitive drum 10 line by line by the image writing device 12. When writing an image on each line, the image writing start timing in the main scanning direction is controlled according to the output of a synchronization signal (hereinafter referred to as “writing start signal”) instructing the image writing start.

  Therefore, when controlling the writing position of the electrostatic latent image in the main scanning direction by the image writing device 12, the output timing of the writing start signal is changed according to the detected paper position deviation amount as described above. Such control of the writing position is performed by the writing control circuit 40 according to the data of the paper position deviation amount given from the main control unit 38. As an example, the writing control circuit 40 outputs a writing start signal at a preset reference timing if the amount of paper misregistration calculated by the main control unit 38 is zero. In addition, if the paper misregistration amount is a positive value, a writing start signal is output at a timing earlier than the reference timing by a time corresponding to the paper misregistration amount, and if the paper misregistration amount is a negative value, A writing start signal is output at a timing later than the reference timing by a time corresponding to the amount of paper position deviation. As a result, if the paper position is deviated in the side direction, the image writing position in the main scanning direction is corrected accordingly.

  Subsequently, it is confirmed whether or not the registration sensor 23 has been turned on (step S12), and the leading edge of the sheet fed by the pre-registration roll 7 passes the sensor detection position of the registration sensor 23, whereby the registration sensor 23 is turned off. When switching from ON to ON, after reading the measured value of the timer at the switching timing (step S13), the skew amount of the paper is detected (step S14). The amount of skew of the paper is measured by the timer read in step S13, that is, the timing when the edge sensor 24 is turned on in step S6 (the timing when the edge sensor 24 detects the passage of the leading edge of the paper) and the step S12. It is calculated based on the difference in timing when the registration sensor 23 is turned on (timing when the registration sensor 23 detects passage of the leading edge of the paper).

  More specifically, assuming that the paper transport speed by the pre-registration roll 7 is constant, the elapsed time (timer measurement) from when the edge sensor 24 detects the passage of the leading edge of the paper until the registration sensor 23 detects the passage of the leading edge of the paper. (Value) varies depending on the skew amount of the paper. Specifically, the elapsed time when the paper is conveyed without skew as shown in FIG. 9A is “T1”, and the paper is on one side (clock shown in FIG. 9B). The elapsed time when the paper is skewed in the rotation direction) is “T2”, and the paper is skewed and conveyed in the other side (counterclockwise direction in the figure) as shown in FIG. 9C. Assuming that the elapsed time is “T3”, the relationship of T3 <T1 <T2 holds between these elapsed times. That is, the elapsed time T2 is longer than the elapsed time T1, and the elapsed time T3 is shorter than the elapsed time T1. 9B is proportional to the time difference between the elapsed times T1 and T2, and the paper skew amount shown in FIG. 9C is proportional to the time difference between the elapsed times T1 and T3. .

  Therefore, the main control unit 38 sets the elapsed time T1 when the sheet is conveyed without skew as shown in FIG. 9A as the reference time Tref in advance from, for example, design data and experimental data. The reference time Tref depends on the distance (interval) between the sensors 22 and 23 in the paper transport direction and the paper transport speed by the pre-registration roll 7. Then, if the elapsed time from when the edge sensor 24 actually detects the passage of the leading edge of the paper until the registration sensor 23 detects the passage of the leading edge of the paper is measured with a timer, the timer measurement value Td and the reference time Tref are calculated. The difference is obtained as a paper skew amount.

  Next, the amount of paper fed by the pre-registration roll 7 is controlled in accordance with the previously detected paper skew amount (step S15), so that the leading edge of the paper abuts against the registration roll 8 in a loop shape. Bend. In this case, even if the paper skew amount detected in step S14 is the same, if the paper size (paper width) in the side direction is different, the paper feed amount is also variably controlled accordingly. The reason is as follows.

  That is, when the paper size is small in the direction (side direction) orthogonal to the paper conveyance direction, the distance between the sensors between the edge sensor 24 and the registration sensor 23 is set accordingly, and when the paper size is large, Accordingly, the inter-sensor distance between the edge sensor 24 and the registration sensor 23 is set large. In such a case, even if the skew amount of the sheet detected in step S14 (in other words, the timer measurement value read in step S13) is the same, the distance between the sensor between the edge sensor 24 and the registration sensor 23 is set to be large. The degree of skew (paper inclination angle) is smaller than when the value is set to be small. For this reason, if the skew amount of the paper detected in step S14 is the same, the amount of paper fed by the pre-registration roll 7 increases as the paper size in the side direction recognized based on the input information on the operation panel during paper transport increases. Control so as to decrease (so that the size of the loop becomes smaller).

  Thereafter, it is determined whether or not there is a sheet to be processed next (hereinafter, the next sheet) (step S16). If it is determined that there is no next sheet, a series of processing is terminated at that time. If it is determined that there is a next sheet, the process returns to step S4, where the sensor moving motor 27 is driven to move the edge sensor 24 to the standby position again. Thereby, the process after step S4 is implemented also with respect to the following paper. Further, when one job is finished and then a new job is started, the same registration process as described above is performed.

  As described above, in the present exemplary embodiment, the sheet skew is detected by using the registration sensor 23 that detects the passage of the sheet before the registration roll 8 and the edge sensor 24 that detects the side edge of the sheet on the upstream side of the registration sensor 23. In addition to detecting the amount of skew, the edge sensor 24 is moved to a standby position corresponding to the size of the sheet that is actually conveyed when the skew amount is detected. A distance can be secured. Therefore, it is possible to accurately detect the skew amount of the paper by using both the registration sensor 23 and the edge sensor 24 without providing a sensor for detecting the skew amount. Therefore, it is possible to accurately detect the skew amount of the sheet with a smaller number of sensors than in the past.

  In the above embodiment, the registration sensor 23 and the edge sensor 24 are used to detect the skew amount of the paper. However, the present invention is not limited to this, and the pre-registration sensor 22 and the edge sensor 24 are used to detect the paper skew. It is also possible to detect the amount of skew.

  In the above-described embodiment, the paper feed amount (paper loop size) at the time of skew correction is controlled based on the paper skew amount detected by using the registration sensor 23 and the edge sensor 24. For example, when the skew amount of the sheet actually detected is compared with a preset allowable amount (correctable limit amount) and the skew amount exceeds the allowable amount in the comparison result, the operation panel or the like A warning display or the like may be displayed on the user interface unit.

1 is a schematic diagram illustrating a configuration example of an image forming apparatus to which the present invention is applied. It is a perspective view which shows the structure of a sensor moving mechanism. FIG. 2 is a block diagram showing a configuration of a control system of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is a diagram illustrating an arrangement state of sensors on a paper conveyance path. 6 is a flowchart illustrating a processing procedure for aligning a sheet and an image. FIG. 6 is a schematic diagram illustrating a series of procedures when an edge sensor is moved to detect a side edge of a sheet. FIG. 6 is a diagram illustrating an example of setting a standby position corresponding to a paper size. It is a figure which shows the movement operation | movement of the edge sensor at the time of side edge detection. FIG. 6 is a diagram for explaining a relationship between a skew state of a sheet and a timer measurement value.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 7 ... Conveyance roll (pre-registration roll), 8 ... Registration roll, 10 ... Photosensitive drum, 12 ... Image writing device, 13 ... Transfer roll, 22 ... Pre-registration sensor (pass sensor), 23 ... Registration sensor (pass sensor), 24 ... Edge sensor , 25 ... Home sensor, 26 ... Sensor moving mechanism, 27 ... Sensor moving motor, 38 ... Main control unit, 39 ... Writing control circuit, 40, 41 ... Paper, Pc ... Center position, P1, P2 ... Standby position

Claims (5)

  1. Transport means for transporting the paper based on the center position through which the center portion of the paper passes in a direction orthogonal to the paper transport direction;
    A path sensor for detecting the passage of the paper conveyed by the conveying means;
    An edge sensor that is disposed on the upstream side or the downstream side in the transport direction from the path sensor and detects a side edge of the paper transported by the transport unit;
    Sensor moving means for moving the edge sensor in a direction orthogonal to the transport direction;
    A sheet conveying apparatus comprising: a control unit that drives the sensor moving unit to control a moving operation of the edge sensor;
    In the direction orthogonal to the transport direction, the path sensor is disposed between a predetermined position through which a side edge portion of a minimum size sheet passes and the center position, and the path sensor is disposed on the opposite side of the path sensor across the center position. Place the edge sensor,
    The control means moves the edge sensor away from the path sensor after the edge sensor detects passage of the leading edge of the paper at a preset standby position according to the size of the paper conveyed by the conveying means. The side edge detection operation is executed, and the skew amount of the paper is detected based on the timing when the edge sensor detects the passage of the leading edge of the paper and the timing when the path sensor detects the passage of the leading edge of the paper. Characteristic paper transport device.
  2. The sheet conveying apparatus according to claim 1, wherein the path sensor is arranged in the vicinity of the predetermined position in a direction orthogonal to the conveying direction.
  3. The control means is based on the detected skew amount of the paper when correcting the skew by feeding the paper by a predetermined amount with the leading end of the paper conveyed by the conveying means being in contact with the registration roll. The sheet conveying apparatus according to claim 1, wherein the sheet feeding amount during skew correction is controlled.
  4. An image forming apparatus comprising the sheet conveying device according to claim 1.
  5. The image forming apparatus according to claim 4, wherein the control unit corrects an image writing position in a main scanning direction based on a detection result of the side edge by the edge sensor.
JP2004169506A 2004-06-08 2004-06-08 Sheet transporting device and image forming device Pending JP2005350155A (en)

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010047408A (en) * 2008-08-25 2010-03-04 Sharp Corp Sheet conveyance device and image forming device with the same
US7900913B2 (en) 2008-03-18 2011-03-08 Kabushiki Kaisha Toshiba Image forming apparatus and method for controlling the same
US7942408B2 (en) 2007-09-11 2011-05-17 Kabushiki Kaisha Toshiba Image forming apparatus and method for transporting sheet thereof
JP2012076903A (en) * 2010-10-05 2012-04-19 Seiko Epson Corp Skew detection method, skew detection device and printer having the same
JP2013140212A (en) * 2011-12-28 2013-07-18 Kyocera Document Solutions Inc Document conveyance device and image forming apparatus
JP2015151233A (en) * 2014-02-14 2015-08-24 セイコーエプソン株式会社 Liquid discharge device, and method for delivering medium
JP2016175718A (en) * 2015-03-19 2016-10-06 株式会社沖データ Medium conveyance device and image formation apparatus

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7942408B2 (en) 2007-09-11 2011-05-17 Kabushiki Kaisha Toshiba Image forming apparatus and method for transporting sheet thereof
US7900913B2 (en) 2008-03-18 2011-03-08 Kabushiki Kaisha Toshiba Image forming apparatus and method for controlling the same
JP2010047408A (en) * 2008-08-25 2010-03-04 Sharp Corp Sheet conveyance device and image forming device with the same
JP4550134B2 (en) * 2008-08-25 2010-09-22 シャープ株式会社 Sheet conveying apparatus and image forming apparatus having the same
JP2012076903A (en) * 2010-10-05 2012-04-19 Seiko Epson Corp Skew detection method, skew detection device and printer having the same
JP2013140212A (en) * 2011-12-28 2013-07-18 Kyocera Document Solutions Inc Document conveyance device and image forming apparatus
JP2015151233A (en) * 2014-02-14 2015-08-24 セイコーエプソン株式会社 Liquid discharge device, and method for delivering medium
JP2016175718A (en) * 2015-03-19 2016-10-06 株式会社沖データ Medium conveyance device and image formation apparatus

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