JP2008024483A - Sheet carrying device, automatic document carrying device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet carrying device, an automatic document carrying device and an image forming device capable of inexpensively and accurately correcting a skew. <P>SOLUTION: This image forming device 100 has a plurality of carrier roller pairs 81 and 82, skew quantity detecting sensors 52A and 52B, a driving motor 74, and a position control motor 66. The carrier roller pairs 81 and 82 are arranged in a plurality of positions in a direction orthogonal to the paper carrying direction X. Among two trollers in respective positions of bringing peripheral surfaces which are pressure contact with each other, at least one roller can be freely moved in the rotary shaft direction. The skew quantity detecting sensors 52A and 52B detect skew quantities of paper. The driving motor 74 rotates one roller among the two rollers. The position control motor 66 moves one roller among the two rollers in the rotary shaft direction Y according to the skew quantity. Among the plurality of carrier roller pairs 81 and 82, at least one roller 71 of the two rollers in at least one carrier roller pair 81 is different in outer diameter by a position in the rotary shaft direction Y. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sheet conveying apparatus, an automatic document conveying apparatus, and an image forming apparatus provided with a plurality of conveying roller pairs arranged at a plurality of positions in a direction orthogonal to a sheet conveying direction.

  A sheet conveying apparatus having a plurality of conveying roller pairs arranged at a plurality of positions in a direction orthogonal to the sheet conveying direction is generally used. In such a sheet conveying apparatus, the sheet may be skewed with respect to the conveying direction at the time of feeding the sheet to the conveying path or in the middle of conveying on the conveying path. When the sheet is skewed, the sheet may be damaged or clogged in the conveyance path, or the processing on the sheet after conveyance may be hindered.

For this reason, a conventional sheet conveying apparatus includes a plurality of motors that individually drive a plurality of pairs of conveying rollers in a direction orthogonal to the sheet conveying direction, and controls the rotational speed of each motor. There is one that adjusts the rotational speed of each pair of conveying rollers to correct sheet skew (see, for example, Patent Document 1).
JP-A-6-191684

  However, in the conventional sheet conveying apparatus, it is necessary to control the rotational speeds of a plurality of motors with high accuracy. For this reason, the apparatus for controlling the rotational speed of the motor is complicated, and the cost is increased.

  An object of the present invention is to provide a sheet conveying apparatus, an automatic document conveying apparatus, and an image forming apparatus capable of accurately correcting skew feeding at low cost.

  (1) A sheet conveying apparatus of the present invention includes a plurality of conveying roller pairs, a detecting device, a first drive source, and a second drive source. The pair of conveyance rollers includes two rollers whose circumferential surfaces are pressed against each other, and is disposed at each of a plurality of positions in a direction orthogonal to the sheet conveyance direction. In at least one of the plurality of transport roller pairs, the first roller that is at least one of the two rollers is movable in the rotation axis direction. The detection device detects the skew amount of the sheet in the vicinity of the pair of conveyance rollers. The first drive source rotates one of the two rollers. The second drive source moves the first roller in the direction of the rotation axis in accordance with the skew amount detected by the detection device. In at least one of the plurality of transport roller pairs, at least one of the two rollers has a different outer diameter depending on the position in the rotation axis direction.

  In this configuration, a pair of conveyance rollers is disposed at each of a plurality of positions in a direction orthogonal to the sheet conveyance direction. One of the two rollers whose circumferential surfaces are pressed against each other is rotated by the first drive source. In at least one of the plurality of conveyance roller pairs, at least one of the two rollers has an outer diameter that varies depending on the position in the rotation axis direction. For this reason, the peripheral speed of the roller whose outer diameter varies depending on the position in the rotation axis direction varies depending on the position in the rotation axis direction. Accordingly, the first roller, which is one of the two rollers constituting the pair of conveying rollers, is moved in the direction of the rotation axis within a range where the peripheral surfaces are in pressure contact with each other, thereby conveying the first roller. The sheet conveyance speed by the pair changes. The first roller is moved in the rotation axis direction in accordance with the skew amount of the sheet, and the sheet conveyance speed is changed between the conveyance roller pairs at a plurality of positions in the direction orthogonal to the sheet conveyance direction. Lines are corrected correctly. For this reason, it is not necessary to provide a plurality of drive sources for separately driving each of the conveyance roller pairs arranged at a plurality of positions in a direction orthogonal to the sheet conveyance direction.

  (2) In the sheet conveying apparatus according to the present invention, the shape in the cross section including the rotation axis of the peripheral surface of the roller having a different outer diameter depending on the position in the rotation axis direction is an arc shape in which the central portion in the rotation axis direction is convex. It can be.

  If the cross-sectional shape including the rotation axis of the roller having a different outer diameter depending on the position in the rotation axis direction is a quadrangle, the corner may come into contact with the peripheral surface of the other roller that is in pressure contact. In this case, there is a risk that the corners may be damaged, such as scraping off. However, in this configuration, the cross-sectional shape including the rotation axis of the peripheral surface of the roller having a different outer diameter depending on the position in the rotation axis direction is an arc shape having a convex central portion in the rotation axis direction. Damage to a roller having a different outer diameter depending on the position is suppressed.

  (3) In the sheet conveying apparatus according to the present invention, a registration roller that corrects the skew of the sheet when the leading end of the sheet abuts on the downstream side of the conveying roller pair in the conveying direction may be disposed.

  In this configuration, as the first opportunity, the skew of the sheet is corrected by moving one of the two rollers constituting the conveying roller pair in the rotation axis direction, and further, as the second opportunity, the sheet The skew of the sheet is also corrected by the end of the sheet being abutted against the registration roller.

  (4) In the sheet conveying apparatus of the present invention, the amount of movement of the first roller in the rotational axis direction by the second drive source is the skew amount and the distance along the conveying path from the conveying roller pair to the registration roller. It can be set based on.

  In this configuration, the amount of movement of the first roller in the rotational axis direction is set so that the detected skew amount of the sheet is corrected between the pair of conveying rollers and the registration rollers. For this reason, when the leading edge of the sheet is abutted against the registration roller, the correction of the skew of the sheet by moving the first roller in the rotation axis direction is completed.

  (5) The first roller of the sheet conveying apparatus of the present invention can be a driven roller that rotates with the rotation of the rollers whose circumferential surfaces are pressed against each other.

  In this configuration, since the driven roller is movable in the direction of the rotation axis, there is no drive source as compared with the case where the drive roller is moved in the direction of the rotation axis, so a mechanism for moving in the direction of the rotation axis is simplified. Become.

  According to the present invention, the following effects can be obtained.

  (1) The skew of the sheet can be accurately corrected by moving one of the two rollers constituting the pair of conveying rollers in the rotation axis direction according to the skew of the sheet. For this reason, it is not necessary to control the rotational speeds of a plurality of drive sources with high accuracy. Therefore, it is possible to correct the skew of the paper accurately at low cost.

  (2) The cross-sectional shape including the rotation axis of the peripheral surface of the roller whose outer diameter varies depending on the position in the rotation axis direction is formed into an arc shape with a convex central portion in the rotation axis direction. Damage to rollers having different diameters can be suppressed.

  (3) By providing two sheet skew feeding correction means and having two sheet skew feeding correction opportunities, the sheet skew feeding can be corrected more accurately.

  (4) When the leading edge of the sheet is abutted against the registration roller, the correction of the skew of the sheet by moving the first roller in the rotation axis direction is completed. The skew correction can be performed more accurately.

  (5) By making the driven roller movable in the direction of the rotation axis, since there is no drive source, the mechanism for moving in the direction of the rotation axis can be simplified.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a schematic front sectional view showing the configuration of an image forming apparatus 100 to which a sheet conveying apparatus according to an embodiment of the present invention is applied. The image forming apparatus 100 includes an image reading unit 200, an image recording unit 300, and a paper feed unit 400.

  The image reading unit 200 includes an automatic document feeder (ADF) 201, a first document table 202, a second document table 203, a first mirror base 204, a second mirror base 205, a lens 206, and a solid-state imaging device ( A CCD (Charge Coupled Device) 207 is provided.

  In the ADF 201, a document transport path 213 is formed from the document tray 211 to the discharge tray 212 via the second document table 203. The ADF 201 conveys documents one by one in the document conveyance path 213. The ADF 201 is rotatable about the back side so that the top surface of the first document table 202 can be opened and closed. By rotating the ADF 201 so that the front side moves upward, the upper surface of the first document table 202 is exposed, so that the document can be placed on the first document table 202 by manual operation.

  Both the first platen 202 and the second platen 203 are made of hard glass plates.

  The first mirror base 204 and the second mirror base 205 are movable in the horizontal direction below the first document table 202 and the second document table 203. The moving speed of the second mirror base 205 is ½ of the moving speed of the first mirror base 204. The first mirror base 204 is equipped with a light source and a first mirror. The second mirror base 205 is equipped with a second mirror and a third mirror.

  When reading an image of a document conveyed by the ADF 201, the first mirror base 204 is stopped below the second document table 203. The light from the light source is emitted toward the image surface of the document passing over the second document table 203, and the reflected light on the image surface of the document is reflected toward the second mirror base 205 by the first mirror.

  When reading an image of a document placed on the first document table 202, the first mirror base 204 and the second mirror base 205 move horizontally below the first document table 202. The light from the light source is emitted toward the image surface of the document placed on the first document table 202, and the reflected light on the image surface of the document is reflected toward the second mirror base 205 by the first mirror.

  Regardless of whether or not the ADF 201 is used, the reflected light on the image surface of the document is incident on the CCD 207 via the lens 206 by the second mirror and the third mirror with a constant optical path length.

  The CCD 207 outputs an electrical signal corresponding to the amount of reflected light on the image surface of the document. This electrical signal is input to the image recording unit 300 as image data (image information).

  The image recording unit 300 includes a photosensitive drum 31, a charger 32, an exposure device 33, a developing device 34, a transfer belt 35, a cleaner 36, and a fixing device 37 that constitute the image forming unit 30.

  The photosensitive drum 31 has a photosensitive layer formed on the surface thereof, and rotates in the direction of the arrow. The charger 32 uniformly charges the surface of the photosensitive drum 31 to a predetermined potential. As the charger 32, either a non-contact method using a charger or a contact method using a roller or a brush may be used.

  The exposure device 33 irradiates the surface of the photosensitive drum 31 with light based on the image data. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 31 by the photoconductive action in the photosensitive layer. The exposure device 33 scans the laser beam modulated based on the image data in the axial direction of the photosensitive drum 31 through a polygon mirror. Alternatively, an exposure apparatus in which light emitting elements such as EL and LEDs are arranged in an array can be used.

  The developing device 34 supplies toner to the surface of the photosensitive drum 31 and visualizes the electrostatic latent image into a toner image.

The transfer belt 35 is looped between a plurality of rollers below the photosensitive drum 31, and has a resistance value of about 1 × 10 ⁹ to 1 × 10 ¹³ Ω · cm. A transfer roller 35A that presses against the photosensitive drum 31 with the transfer belt 35 interposed therebetween is provided inside the loop-shaped movement path of the transfer belt 35. A predetermined transfer voltage is applied to the transfer roller 35 </ b> A, and a toner image carried by the photosensitive drum 31 is transferred onto a sheet passing between the transfer belt 35 and the photosensitive drum 31.

  The cleaner 36 removes residual toner from the surface of the photosensitive drum 31 after the transfer of the toner image to the paper.

  The fixing device 37 includes a heating roller 37A and a pressure roller 37B. The heating roller 37A is heated by an internal heater to a temperature at which the toner can be melted. The pressure roller 37B is in pressure contact with the heating roller 37A with a predetermined pressure. The fixing device 37 firmly fixes the toner image to the paper by heating and pressurizing the paper passing between the heating roller 37A and the pressure roller 37B. The paper that has passed through the fixing device 37 is discharged to a paper discharge tray 38 mounted on one side surface of the image forming apparatus 100.

  The paper feed unit 400 includes paper feed cassettes 401, 402, 403, 404 and a manual feed tray 405. Each of the paper feed cassettes 401, 402, 403, 404 stores a plurality of sheets of the same size. On the manual feed tray 405, paper of a size or quality that is not frequently used is placed.

  The paper feed unit 400 feeds paper one by one from one of the paper feed cassettes 401, 402, 403, 404 or the manual feed tray 405. The sheet fed from the sheet feeding unit 400 is formed into an image by a pair of conveyance rollers 81 and 82 (the conveyance roller pair 82 is not shown in FIG. 1) via the sheet conveyance path 10 and the sheet conveyance path 11. It is conveyed to the unit 30.

  A registration roller 51 is disposed downstream of the conveyance roller pair 81 and 82 in the sheet conveyance direction. The sheet conveyed by the conveyance roller pair 81 and 82 is abutted against the registration roller 51 with the registration roller 51 stopped. The rotation shaft of the registration roller 51 is arranged in a direction orthogonal to the paper transport direction. The leading edge of the sheet is abutted against the resist roller 51 in a stopped state, and the skew is corrected when the sheet is skewed.

  The registration roller 51 starts to rotate at the timing when the leading edge of the paper is aligned with the leading edge of the toner image formed on the surface of the photosensitive drum 31, and supplies the paper between the photosensitive drum 31 and the transfer belt 35. The toner image is transferred and fixed on the paper as described above, and the paper is discharged to the paper discharge tray 38.

  A large-capacity paper feed cassette (hereinafter referred to as LCC: Large Capacity Cassette) can be disposed on the side of the image forming apparatus 100 and below the manual feed tray 405. A large amount of paper is stored in the LCC. The paper fed from the LCC is transported to the image forming unit 30 via the paper transport path 16.

  FIG. 2 is a schematic front sectional view showing the configuration of the ADF 201. The ADF 201 includes a document tray 211, a pickup roller 214, a paper feed roller 215 and a separation roller 216, a driving roller 217 and a pressing roller 218, a registration roller 219, and a paper discharge roller 220.

  A document bundle is placed on the document tray 211. The pickup roller 214 sends the document from the document bundle to the document conveyance path 213. The paper feed roller 215 and the separation roller 216 convey the document sent to the document conveyance path 213 to the downstream side of the document conveyance path 213 while separating the documents one by one.

  The driving roller 217 and the pressing roller 218 convey the document along the document conveyance path 213. The pressing roller 218 is a driven roller that presses the document against the driving roller 217. The registration roller 219 is disposed on the downstream side of the driving roller 217 and the pressing roller 218 in the document conveyance direction. The registration roller 219 sends the document so that the document passes on the second document table 203 at a predetermined timing. The rotation axis of the registration roller 219 is arranged in a direction orthogonal to the document conveyance direction. The paper discharge roller 220 discharges the document whose image has been read to the discharge tray 212.

  The document tray 211 can move in the vertical direction, and when a bundle of documents is placed, a sensor (not shown) detects it. When a print request is made by the user, the document tray 211 moves upward, and the document located at the top of the document bundle is sent out to the document conveyance path 213 by the pickup roller 214.

  When the originals are sent to the original conveyance path 213 in the overlapped state, the double feeding state is canceled by the separation roller 30 and conveyed one by one by the paper feed roller 215 to the downstream side of the original conveyance path 213.

  The document is further conveyed by the driving roller 217 and the pressing roller 218, and is abutted against the registration roller 219 in a state where the leading end is stopped. Thereby, when the document is skewed, the skew of the document is corrected. As described above, the registration roller 219 starts to rotate at a timing when the document is sent onto the second document table 203 at a predetermined timing. The document sent out by the registration roller 219 is discharged to the discharge tray 212 by the discharge roller 220 after the image is read.

  FIG. 3 is a block diagram illustrating a partial configuration of the image forming apparatus 100. FIG. 4 is an explanatory diagram in plan view showing the driven roller 61 and the skew amount detection sensor 52. FIG. 5 is an explanatory view showing a mechanism for moving the driven roller 61 in the rotation axis direction Y. FIG. 6A to 6C are explanatory views showing the configuration of the conical roller 71. FIG.

  In this embodiment, two pairs of conveyance rollers 81 and 82 are arranged in a rotation axis direction Y that is a direction orthogonal to the conveyance direction X. The conveyance roller pair 81 includes a conical roller 71 and a driven roller 61. The conveyance roller pair 82 includes a cylindrical roller 73 and a driven roller 62. The conical roller 71 and the driven roller 61 are disposed so as to face each other so that their peripheral surfaces are in pressure contact with each other. The cylindrical roller 73 and the driven roller 62 are arranged to face each other so as to press the peripheral surfaces of each other. The driven roller 61 corresponds to the first roller of this invention.

  The driven roller 61 is disposed so as to face the conical roller 71 and conveys the paper while sandwiching the paper between the conical roller 71. The distance from the conveyance roller pair 81 along the paper conveyance path 11 to the registration roller 51 is set to a distance L. The paper transport path 11 corresponds to the transport path of the present invention. The paper is an example of the sheet of the present invention.

  The driven roller 61 and the driven roller 62 rotate around the rotation shaft 63. The rotation shaft 63 is arranged in a direction orthogonal to the paper transport direction X. The image forming apparatus 100 further includes an elastic member (not shown), and the rotation shaft 63 is applied with a force in a direction approaching the conical roller 71 and the cylindrical roller 73 by the elastic member. The driven roller 61 and the driven roller 62 rotate freely with respect to the rotation shaft 63. The shapes of the peripheral surfaces of the driven roller 61 and the driven roller 62 in the cross section including the rotation shaft 63 are formed in an arc shape in which the central portion in the rotation axis direction Y is convex. The shape in the cross section containing the rotating shaft 63 of the surrounding surface of each of the driven roller 61 and the driven roller 62 is formed in an ellipse, for example. The dimension in the rotation axis direction Y of the driven roller 61 and the driven roller 62 is, for example, 5 mm.

  As shown in FIG. 5, both end portions of the rotating shaft 63 are rotatably supported by bearing members 64 and 65. The driven rollers 61 and 62 are movable together with the rotation shaft 63 in a rotation axis direction Y orthogonal to the paper transport direction X. A position control motor 66 is connected to the rotating shaft 63 via a connecting lever 67. One end of the connecting lever 67 is fixed to the bearing member 64, and the other end of the connecting lever 67 is connected to the position control motor 66 by a worm gear. As the position control motor 66 rotates, the rotational force of the position control motor 66 is converted into the rotation axis direction Y by the worm gear, and the rotation shaft 63 moves in the rotation axis direction Y. As the position control motor 66, for example, a stepping motor is used. The position control motor 66 corresponds to the second drive source of the present invention.

  Since no drive source is connected to the driven rollers 61 and 62, a mechanism for moving in the rotational axis direction Y can be easily configured.

  The rotation of the position control motor 66 is controlled by a CPU 54 that is a control unit via a driver 67. A memory 55 is connected to the CPU 54.

  Skew amount detection sensors 52A and 52B are disposed in the vicinity of the transport roller pair 81 and 82 along the paper transport path 11 and upstream of the transport roller pair 81 and 82 in the paper transport direction X. The skew amount detection sensors 52A and 52B correspond to the detection device of the present invention. As the skew amount detection sensors 52A and 52B, for example, an optical sensor including a light emitting unit and a light receiving unit is used.

  The skew amount detection sensor 52A is disposed upstream of the transport roller pair 81 along the paper transport direction X, and the skew amount detection sensor 52B is disposed upstream of the transport roller 82 along the paper transport direction X. ing. The skew amount detection sensors 52A and 52B are arranged in a direction orthogonal to the paper transport direction X so that the distances from the transport roller pair 81 and the transport roller pair 82 are equal.

  The skew amount detection sensors 52 </ b> A and 52 </ b> B detect the skew amount S of the sheet based on the amount of deviation of the timing for detecting the leading edge of the sheet, and output it to the CPU 54.

  As shown in FIGS. 6A to 6C, the conical roller 71 has a truncated cone shape, and the dimension in the rotation axis direction Y is, for example, 30 mm. The conical roller 71 is formed so that the outer diameter is larger on the upstream side in one direction P along the rotation axis direction Y and the outer diameter is smaller on the downstream side.

  Three positions A, B, and C are set on the driven roller 61 in order from the upstream side in the direction P along the rotation axis direction Y. For example, the position B is the central portion of the driven roller 61 in the rotation axis direction Y. As an example, the outer diameter of the conical roller 71 at the position A is 21 mm, the outer diameter of the conical roller 71 at the position B is 20 mm, and the outer diameter of the conical roller 71 at the position C is 19 mm. For example, the distance between the position A and the position B is 10 mm, and the distance between the position B and the position C is 10 mm.

  The conical roller 71 rotates around the shaft 72. In addition to the conical roller 71, a cylindrical roller 73 is attached to the shaft 72. The interval between the conical roller 71 and the cylindrical roller 73 is, for example, 80 mm. The outer diameter of the cylindrical roller 73 is the same at any position in the rotation axis direction Y, and is 20 mm, for example. The dimension of the cylindrical roller 73 in the rotation axis direction Y is, for example, 30 mm. The shaft 72 is rotated by a drive motor 74. The drive motor 74 corresponds to the first drive source of the present invention. The conical roller 71 and the cylindrical roller 73 are rotated by a single drive motor 74.

  The conical roller 71 is disposed so that the peripheral surface is in pressure contact with the peripheral surface of the driven roller 61. The driven roller 61 is in pressure contact with the conical roller 71 at the position B as a reference position. The driven roller 61 is movable in the rotational axis direction Y so as to come into pressure contact with the conical roller 71 between position A and position C.

  The cylindrical roller 73 is arranged so that the circumferential surface is in pressure contact with the circumferential surface of the transport roller 62. When the driven roller 61 is disposed at the reference position, the outer diameter of the conical roller 71 at the position B where the driven roller 61 is pressed and the outer diameter of the cylindrical roller 73 pressed against the driven roller 62 are equal. The sheet conveyance speed by the pair 81 and the sheet conveyance speed by the conveyance roller pair 82 are the same.

  When the driven roller 61 is in pressure contact with the conical roller 71 at the position A, the outer diameter of the position A of the conical roller 71 is the largest as compared with the other positions B and C, so that the sheet conveying speed by the conveying roller pair 81 is the highest. Become. When the driven roller 61 comes into contact with the position C, the outer diameter of the position C of the conical roller 71 is the smallest compared to the other positions A and B, so the sheet conveyance speed by the conveyance roller 81 is the lowest. On the other hand, since the outer diameter of the cylindrical roller 73 is constant regardless of the position in the rotation axis direction Y, the sheet conveyance speed by the conveyance roller pair 82 is constant regardless of the position in the rotation axis direction Y.

  As described above, the shapes of the peripheral surfaces of the driven roller 61 and the driven roller 62 in the cross section including the rotation shaft 63 are arc shapes in which the central portion in the rotation axis direction Y is convex. For this reason, when the peripheral surface of the driven roller 61 and the peripheral surface of the conical roller 71 are pressed against each other, a part of the driven roller 61 is not scraped off, and damage to the driven roller 61 can be suppressed. The peripheral surface of the driven roller 61 can be accurately pressed against a predetermined position on the peripheral surface of the conical roller 71.

  FIG. 7 is a flowchart showing a part of the processing procedure of the CPU 54. The CPU 54 feeds paper from the paper feed unit 400 and transports it through the paper transport path 11 (S1). The CPU 54 detects the skew amount S of the sheet by the skew amount detection sensors 52A and 52B (S2), and temporarily stops the conveyance of the sheet in the vicinity of the upstream side of the pair of conveyance rollers 81 and 82 in the sheet conveyance direction X ( S3).

  Next, the CPU 54 determines the reference position (driven) of the driven roller 61 based on the skew amount S detected in S2 and the distance L along the paper transport path 11 from the transport roller pair 81, 82 to the registration roller 51. A movement amount D (mm) in the rotation axis direction Y from the position where the roller 61 contacts the position B) is calculated (S4). The CPU 54 calculates the movement amount D as follows.

  Here, the relationship between the peripheral speed VB of the conical roller 71 at the position B, the peripheral speed VA of the conical roller 71 at the position A, and the peripheral speed VC of the conical roller 71 at the position C is as follows. It becomes like this.

VA / VB = 21π / 20π = 105%
VC / VB = 19π / 20π = 95%
As described above, in this embodiment, the intervals between the position A, the position B, and the position C are 10 mm. For this reason, the conveyance speed of the sheet by the conveyance roller pair 81 changes by 0.5% per 1 mm of the movement amount of the driven roller 61 in the rotation axis direction Y. Specifically, when the driven roller 61 is moved by 1 mm in the direction Q opposite to the direction P, the sheet conveyance speed by the conveyance roller 81 is increased by 0.5%, and when the driven roller 61 is moved by 1 mm in the direction P, the conveyance roller The sheet conveyance speed by the pair 81 is reduced by 0.5%.

  Therefore, the movement amount D is calculated by the following formula based on the skew amount S and the distance L.

D = S ÷ L × 100 ÷ 0.5
That is, the CPU 54 first calculates the ratio (%) of the skew amount S to the distance L by calculating S ÷ L × 100. Here, when the driven roller 61 is at the reference position, the left and right sides (both ends in the rotation axis direction Y) of the sheet are conveyed at the same speed, and when the sheet is not skewed, the left and right ends of the sheet are the registration rollers 51. Arrive at the same time. From this, the ratio obtained by S ÷ L × 100 means what percentage of the conveyance speed of one of the left and right sides of the sheet can be increased to correct the skew. Accordingly, by further dividing this by 0.5 (%), the amount of movement D (mm) of the driven roller 61 in the rotational axis direction Y is calculated.

  When the left side (conveying roller pair 81 side) of the paper advances from the right side (conveying roller pair 82 side), the CPU 54 moves the driven roller 61 in the direction P by the movement amount D, and the left side of the paper is delayed from the right side. If so, the driven roller 61 is moved in the direction Q by the movement amount D (S5). Thus, the skew of the sheet is corrected in the sheet conveyance path 11 from the conveyance roller pair 81, 82 to the registration roller 51. When the leading edge of the sheet is abutted against the registration roller 51, correction of the skew of the sheet by moving the driven roller 61 in the rotation axis direction Y is completed. Is corrected more accurately. The movement of the driven roller 61 in the direction P or the direction Q in S5 is preferably performed before the leading edge of the sheet reaches the driven roller 61.

  There is no need to provide a plurality of drive sources for separately driving the conveyance roller pair 81 and the conveyance roller pair 82 arranged at a plurality of positions in the rotation axis direction Y, and the driven roller 61 is rotated according to the skew amount of the paper. Since the skew of the sheet can be corrected by moving in the axial direction Y, it is not necessary to control the rotational speeds of the plurality of drive sources with high accuracy. Therefore, it is possible to correct the skew of the paper accurately at low cost.

  The CPU 54 resumes the conveyance of the sheet (S6), and further corrects the skew of the sheet by abutting the leading end of the sheet against the registration roller 51 (S7). By including two types of paper skew correction means including correction of paper skew by moving the driven roller 61 in the rotation axis direction Y and correction of paper skew by the registration roller 51, In addition, since the skew correction opportunity of the paper is provided twice, the skew of the paper is corrected more accurately.

  The CPU 54 sends the sheet whose skew has been accurately corrected to the image forming unit 30, transfers the image to the sheet (S8), and fixes the image to the sheet (S9). The CPU 54 returns the driven roller 61 to the reference position and prepares for the next sheet conveyance (S10).

  The conical roller 71 is not limited to a frustoconical shape, and has at least part of an inclined portion having an outer diameter that varies depending on the position in the rotation axis direction Y, and the peripheral surface of the inclined portion is the peripheral surface of the first conveying roller 61. The structure which contacts with may be sufficient.

  8A to 8C are explanatory diagrams illustrating a partial configuration of an image forming apparatus 100A to which a sheet conveying apparatus according to another embodiment is applied. The image forming apparatus 100 </ b> A according to this embodiment is configured in the same manner as the above-described image forming apparatus 100 except that a second conical roller 75 is disposed instead of the cylindrical roller 73. In this embodiment, a conical roller 71 is used as the second conical roller 75 and is arranged in a direction symmetrical to the conical roller 71 with respect to a plane orthogonal to the shaft 72. That is, the second conical roller 75 is arranged so that the outer diameter is smaller toward the upstream side in the direction P and the outer diameter is larger toward the downstream side.

  As shown in FIG. 8A, when the driven roller 61 contacts the position A of the conical roller 71, the driven roller 62 contacts the position C ′ of the second conical roller 75. As shown in FIG. 8B, when the driven roller 61 comes into contact with the position B of the conical roller 71, the driven roller 62 comes into contact with the position B ′ of the second conical roller 75. As shown in FIG. 8C, when the driven roller 61 contacts the position C of the conical roller 71, the driven roller 62 contacts the position A ′ of the second conical roller 75.

  As the driven rollers 61 and 62 move in the direction P, the rotation speed of the conveyance roller pair 81 decreases and the rotation speed of the conveyance roller pair 82 increases. On the other hand, as the driven rollers 61 and 62 move in the direction Q, the rotation speed of the conveyance roller pair 81 increases and the rotation speed of the conveyance roller pair 82 decreases.

  In the image forming apparatus 100A, the skew of the sheet is corrected by controlling the rotational speeds of both the transport roller pair 81 and the transport roller pair 82. For this reason, even when the moving distance of the driven rollers 61 and 62 in the rotation axis direction Y is reduced, the skew of the sheet can be accurately corrected. Accordingly, it is possible to reduce the size of the image forming apparatus 100A.

  Instead of the driven rollers 61 and 62, the conical rollers 71 and 75 can be configured to be movable in the rotation axis direction Y.

  The sheet conveying apparatus of the present invention can also be applied to the document conveying path 213 of the ADF 201 that conveys the document toward the second document table 203. In this case, the document conveying path 213 corresponds to the conveying path of the present invention, the driving roller 217 and the pressing roller 218 correspond to the conveying roller pair of the present invention, and the document is an example of the sheet of the present invention. For example, although the pressing roller 218 is movable in the rotation axis direction Y, the conveyance roller 217 can be moved in the rotation axis direction Y.

  Finally, the description of the above-described embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

1 is a schematic front sectional view showing a configuration of an image forming apparatus to which a sheet conveying apparatus according to an embodiment of the present invention is applied. It is the schematic of the front cross section which shows the structure of ADF. 1 is a block diagram illustrating a partial configuration of an image forming apparatus. It is explanatory drawing of planar view which shows a driven roller and a skew feeding amount detection sensor. It is explanatory drawing which shows the moving mechanism to the rotating shaft direction of a driven roller. It is explanatory drawing which shows the structure of a conical roller. It is a flowchart which shows a part of processing procedure of CPU. FIG. 10 is an explanatory diagram illustrating a partial configuration of an image forming apparatus to which a sheet conveying device according to another embodiment is applied.

Explanation of symbols

11 Paper transport path (transport path)
30 Image forming section 51 Registration roller 52A, 52B Skew amount detection sensor (detection device)
61, 62 Followed roller 66 Position control motor (second drive source)
71 Conical roller 74 Drive motor (first drive source)
81, 82 Conveying roller pair 100, 100A Image forming apparatus 200 Image reading unit 213 Document conveying path (conveying path)
218 Pressure roller 300 Image recording unit 400 Paper feed unit

Claims (7)

In the sheet conveying apparatus provided with each of a plurality of positions in a direction perpendicular to the sheet conveying direction, a pair of conveying rollers composed of two rollers whose circumferential surfaces are pressed against each other,
In at least one of the plurality of transport roller pairs, a first roller that is at least one of the two rollers is movable in a rotation axis direction;
A detection device for detecting the amount of skew of the sheet in the vicinity of the pair of conveyance rollers;
A first drive source for rotating one of the two rollers;
A second drive source that moves the first roller in the direction of the rotation axis in accordance with the amount of skew detected by the detection device;
The sheet conveying apparatus according to claim 1, wherein in at least one of the plurality of conveying roller pairs, at least one of the two rollers has a different outer diameter depending on a position in a rotation axis direction.   The shape in a cross section including the rotation axis of the peripheral surface of the roller, the outer diameter of which varies depending on the position in the rotation axis direction, is an arc shape in which a central portion in the rotation axis direction is convex. The sheet conveying apparatus according to the description.   3. The sheet conveyance according to claim 1, wherein a registration roller that corrects skew of the sheet by a leading edge of the sheet hitting is disposed downstream of the conveyance roller pair in the conveyance direction. apparatus.   The amount of movement of the first roller in the rotation axis direction by the second drive source is set based on the skew amount and the distance along the conveyance path from the conveyance roller pair to the registration roller. The sheet conveying apparatus according to claim 3.   5. The sheet conveying apparatus according to claim 1, wherein the first roller is a driven roller that rotates in accordance with rotation of rollers whose circumferential surfaces are pressed against each other. 6.   6. An automatic document conveying device comprising the sheet conveying device according to claim 1, and conveying a document whose image is to be read as a sheet. An image forming unit that forms an image on a sheet based on image information;
An image forming apparatus comprising: the sheet conveying apparatus according to claim 1.

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