JP2016072760A - Image reading device, and image forming apparatus including the image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, at a low cost, an image reading device that can execute shading correction even when stains adhere to a white reference member without being affected by the stains.SOLUTION: During a regular rotation operation of a conveyance drive roller 264a that is driven by a driving motor 335, that is, during conveyance of documents, a white reference member is connected to a cam-integrated gear 325 the drive of which is interrupted by a one-way clutch 329a; and during reverse rotation of the conveyance drive roller 264a, the white reference member connected to the cam-integrated gear is moved in the main scanning direction so as to collect shading data on a surface where stains do not adhere, and the white reference member can be retreated at a position separated from a conveyance surface during reading of documents, and thereby adhesion of stains on the white reference member can be prevented.SELECTED DRAWING: Figure 8

Description

  The present invention relates to an image reading apparatus and an image forming apparatus including the image reading apparatus.

  Conventionally, an image reading apparatus including a reading unit that optically reads an image of a document on a contact glass is known. The reading unit includes a light source that irradiates light toward the document, and a mirror that guides reflected light from the light source to light receiving elements arranged in a line. There are two methods for image reading by this image reading apparatus. The first method is a method of reading a document image while moving the reading unit in the sub-scanning direction, and the second method is to fix the reading unit and convey the document to be read by the document feeder. In this way, the original image is read. In the second method, a contact image sensor (image reading sensor) may be provided in the middle of the document conveyance path. According to this, in addition to reading the front image of the document by the reading unit, it is possible to read both sides of the document by reading the back image of the document by the contact image sensor.

  In the image reading apparatus, shading correction is performed using a white reference plate in order to correct variations in light receiving sensitivity between the light receiving elements provided in the reading unit. When the shading correction is performed, if the white reference plate is contaminated, the correction value at the contaminated portion becomes an abnormal value, so that the shading correction cannot be performed with high accuracy.

  Therefore, for example, Patent Document 1 discloses a method of moving the reading unit in the sub-scanning direction and acquiring correction data at a spot free from the white reference plate. However, the contact image sensor (image reading sensor) used in the second method is fixed in the middle of the document conveyance path. Therefore, as in Patent Document 1, the contact image sensor, which is a reading unit, cannot be moved to a clean spot on the white reference plate. On the other hand, for example, in the image forming apparatus shown in Patent Document 2, instead of the white reference plate, a roller member whose peripheral surface is coated in white is used, and the roller member is rotated so that dirt on the roller peripheral surface is obtained. The correction data is obtained at the places where there are no signs.

JP 2002-185725 A JP 2010-34932 A

  However, as shown in Patent Document 2, when a roller member is used as the white reference member, it is necessary to sufficiently increase the shape accuracy and rotation accuracy of the roller so that the shading correction accuracy does not vary. For this reason, compared with the case where a plate-shaped white reference member is used, there exists a problem that the processing cost of a roller (white reference member) and the cost of the bearing which supports a roller increase. In addition, since it is necessary to apply a white coating to the peripheral surface of the roller member, there is a problem that the cost is increased accordingly.

  The present invention has been made in view of the above points, and an object of the present invention is to perform image reading capable of executing shading correction with almost no influence even if dirt is attached to the white reference member. The object is to provide the device at a low cost.

  An image reading apparatus according to the present invention includes a main body case having a paper feed port and a paper discharge port arranged in the vertical direction, and a document that is provided in the main body case and is fed from the paper feed port. A document conveyance path that leads to the document sheet, a conveyance driving roller that extends in the main scanning direction and is driven by a drive motor to convey the document in the document conveyance path from the upstream side to the downstream side, and is provided in the middle of the document conveyance path An image reading sensor that optically reads an image of one side of the document passing through the document conveyance path, and the image reading sensor that is opposed to the image reading sensor with the document conveyance path interposed therebetween, and shading of the image reading sensor A white reference member functioning as a white reference at the time of correction.

  Further, a rotating cam member that rotates in conjunction with the rotation operation of the transport driving roller driven by the driving motor and moves the white reference member in the main scanning direction is further provided.

  According to this configuration, the white reference member can be moved in the main scanning direction by the rotating cam member in conjunction with the rotation operation of the transport driving roller. Therefore, even if dirt is adhered to the surface of the white reference member, for example, the image sensor can perform multiple image readings while moving the white reference member by a predetermined amount in the main scanning direction, thereby reducing the influence of the dirt. Shading correction can be executed with little reception. As a specific correction procedure, for example, it is possible to average the white reference data of a spot with a stain together with the white reference data of a spot with no stain, or to exclude the white reference data of a spot with a stain.

  In addition, according to the above configuration, since the configuration in which the white reference member is linearly moved in the main scanning direction is adopted, the shape accuracy and support accuracy of the white reference member are compared with the case where the white reference member is configured by a rotating roller member. The demand for is low. Therefore, it is possible to reduce the cost of the white reference member and reduce the cost of the entire apparatus.

  Provided in the power transmission path between the conveyance drive roller and the rotating cam member, and when the conveyance drive roller is rotating forward to convey the document from the upstream side to the downstream side, it idles and rotates from the conveyance drive roller. It is preferable to further include a one-way clutch that interrupts power transmission to the cam member and allows power transmission from the transport driving roller to the rotating cam member when the transport driving roller rotates in the reverse direction.

  According to this configuration, when the transport driving roller is rotating forward, the one-way clutch interrupts power transmission from the transport driving roller to the rotating cam member, so that the rotating cam member does not rotate. For this reason, the white reference member maintains a stationary state without moving in the main scanning direction. Therefore, it is possible to prevent the white reference member from moving unnecessarily in the main scanning direction during document conveyance by the conveyance drive roller, and it is possible to suppress conveyance failure such as a paper jam. On the other hand, when the transport roller is rotating in the reverse direction, power transmission from the transport drive roller to the rotating cam member is permitted by the one-way clutch, so that the rotating cam member rotates. As a result, since the white reference member is driven in the main scanning direction by the rotating cam member, shading correction can be executed without being affected by dirt adhering to the white reference member.

  In addition, since the rotary cam member is rotated using the drive motor that drives the transport drive roller, the parts can be shared and the cost of the entire apparatus can be reduced.

  The white reference member is preferably also used as a guide member for guiding a document passing through the document conveyance path.

  According to this configuration, since the white reference member is also used as a guide member for document guide, the cost of the entire apparatus can be reduced.

  The rotary cam member rotates in response to a rotational input from the drive motor and has a gear portion whose rotation axis extends in the main scanning direction, and extends from one side surface in the axial direction of the gear portion toward the one side. A cylindrical cam portion that rotates together with the gear portion, and the end surface on one side in the axial direction of the cylindrical cam portion is inclined toward one side in the axial direction or the other side in the circumferential direction. A drive shaft formed with a cam surface, having a contact portion that contacts the cam surface and connected to the white reference member so as to be movable in the main scanning direction, and the rotating cam member rotating once During this time, it is preferable to further include a biasing member that biases the drive shaft toward the cam surface so that the contact state between the contact portion of the drive shaft and the cam surface is maintained.

  According to this configuration, when the gear portion of the rotating cam member rotates in response to the rotation input from the drive motor, the cylindrical cam portion rotates integrally with the gear portion. Then, the drive shaft that contacts the cam surface formed on one side surface in the axial direction of the cylindrical cam portion moves in the main scanning direction according to the inclination of the cam surface. Since the drive shaft is constantly urged toward the cam surface by the urging member so that one end of the drive shaft comes into contact with the cam surface, the drive shaft returns to its original position when the cam member makes one revolution. Accordingly, the drive shaft reciprocates in the main scanning direction in conjunction with the rotation of the cam member, and accordingly, the white reference member reciprocates in the main scanning direction. By reciprocating the white reference member in this way, the number of times of image sampling by the image reading sensor at the time of shading correction can be increased by the number of reciprocations. Therefore, the shading correction accuracy can be improved.

  An image forming apparatus according to the present invention includes the image reading device and an image forming unit that forms an image on a sheet based on image data read by the image reading device.

  According to this configuration, as a result of improving the shading correction accuracy of the image reading sensor in the image reading apparatus, the density variation of the image formed on the paper by the image forming unit is suppressed, and as a result, the image formed on the paper Image quality can be improved.

  According to the present invention, it is possible to provide an image reading apparatus and an image forming apparatus that can execute shading correction with little influence even if dirt is attached to the white reference member.

FIG. 1 is a schematic cross-sectional view illustrating an image forming apparatus including an image reading apparatus according to an embodiment. FIG. 2 is a perspective view showing a document feeding device (a part of the image reading device). FIG. 3 is a schematic longitudinal sectional view showing the document feeder. FIG. 4 is a perspective view showing the internal structure of the document feeder. 5 is a cross-sectional view taken along line VV in FIG. FIG. 6 is an enlarged perspective view showing a connecting portion of the white reference member, the drive shaft, and the cam-integrated gear. FIG. 7 is a schematic side view seen from the left side of the image forming apparatus, showing a state in which the white reference member is assembled to the outer guide plate of the document conveyance path. FIG. 8 is an explanatory diagram for explaining a power transmission path to the cam-integrated gear for driving the white reference member.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiment.

<Embodiment>
FIG. 1 shows an image forming apparatus 1 including an image reading apparatus 200 according to this embodiment. The image forming apparatus 1 is a laser printer using an electrophotographic method. The image forming apparatus 1 includes an image forming apparatus main body 100, the image reading apparatus 200 attached to the upper part of the image forming apparatus main body 100, and a panel 290 that can be operated by a user. In the following description, the front side and the rear side mean the front side and the rear side (the front side and the back side in the direction perpendicular to the paper in FIG. 1), respectively, and the left side and the right side are the image forming apparatus 1. Means the left side and the right side when viewed from the front side.

  The image forming apparatus main body 100 has a box-shaped housing 60. An image reading device 200 is provided on the upper portion of the housing 60. In the housing 60, the paper feeding unit 10, the image forming unit 20, and the fixing unit 40 are accommodated. A plurality of transport roller pairs 11 to 13 that sandwich and transport the paper P are disposed in the paper transport path L from the paper supply unit 10 to the paper discharge tray unit 50. Further, a reverse conveyance path L ′ that branches from the downstream side of the sheet conveyance path L and joins the upstream side is provided. Conveying roller pairs 14 to 16 are arranged in the reverse conveying path L ′.

  The paper feeding unit 10 is disposed in the lower part of the housing 60. The paper feed unit 10 includes a paper feed cassette 10a in which sheet-like paper P is accommodated, and a pickup roller 10b for taking out the paper P in the paper feed cassette 10a and sending it out of the cassette. The paper P sent out of the cassette from the paper feed cassette 10 a is supplied to the image forming unit 20 through the transport roller pair 11.

  In the image forming unit 20, image forming units 20Bk, 20M, 20C, and 20Y that form toner images corresponding to the respective colors of black, magenta, cyan, and yellow are arranged in a line. Each of the image forming units 20Bk, 20M, 20C, and 20Y includes a photosensitive drum 21, a charging device 22, a developing device 23, and a cleaning device 24. Below the image forming units 20Bk, 20M, 20C, and 20Y, an exposure device 25 that irradiates the surface of each photosensitive drum 21 with laser light is disposed. An intermediate transfer unit 26 is disposed above the image forming units 20Bk, 20M, 20C, and 20Y. The intermediate transfer unit 26 is provided with an intermediate transfer belt 27 that travels in contact with each photosensitive drum 21. A primary transfer roller 28 is provided inside the intermediate transfer belt 27 so as to sandwich the intermediate transfer belt 27 with the photosensitive drum 21. A secondary transfer roller 29 is provided on the downstream side of the image forming unit 20Bk so as to be in contact with the surface of the intermediate transfer belt 27. Above the intermediate transfer unit 26, toner containers 30Bk, 30M, 30C, and 30Y are arranged. The toner containers 30Bk, 30M, 30C, and 30Y store toners of respective colors that are supplied to the developing devices 23 of the image forming units 20Bk, 20M, 20C, and 20Y.

  In the image forming unit 20, the exposure device 25 electrostatically irradiates the surface of each photosensitive drum 21 with laser light based on predetermined image data (original image data read by the image reading device 200 in this embodiment). A latent image is formed. The image forming unit 20 develops the formed electrostatic latent image with the developing device 23 to form a toner image of each color. Each color toner image formed on the surface of each photosensitive drum 21 is transferred onto the surface of the intermediate transfer belt 27 by the primary transfer roller 28 and superimposed. The toner image transferred onto the intermediate transfer belt 27 is transferred onto the paper P supplied from the paper supply unit 10 by the secondary transfer roller 29. The sheet P after the transfer is supplied to the fixing unit 40. The fixing unit 40 fixes the toner image on the paper P by pressing the paper P supplied from the image forming unit 20 between the fixing roller 40a and the pressure roller 40b. Then, the paper P on which the toner image is fixed by the fixing unit 40 is sent out to the downstream side by both rollers 40a and 40b. The paper P sent out from the fixing unit 40 is discharged to the paper discharge tray unit 50 through the conveyance roller pair 13. When toner images are formed on both sides of the paper P, the paper P is switched back by the transport roller pair 13 and transported to the reverse transport path L ′.

  The image reading apparatus 200 has a substantially rectangular parallelepiped case body 250, a document pressing cover 240, and a document feeding device 221. An upper surface of the case body 250 forms a document placement surface 250a on which a document is placed. A scanner unit 210 (see FIG. 3) is accommodated in the case body 250. The scanner unit 210 optically reads a document image placed on the document placement surface 250a and generates image data thereof. The scanner unit 210 includes, for example, a reflection mirror, a CCD sensor, and the like. The document pressing cover 240 covers the document placement surface 250a so that it can be opened and closed. The document pressing cover 240 is rotatably attached to the case body 250 via a hinge mechanism (not shown). The document feeder 221 is provided on the upper surface side of the document pressing cover 240.

  As shown in FIG. 2, the document feeder 221 has a main body case 222. The main body case 222 is provided at the left end portion on the upper surface side of the document pressing cover 240. The main body case 222 has a pair of side wall portions 222e facing each other in the front-rear direction and an upper cover 222k that can be opened and closed. The lower surface of the main body case 222 is constituted by the upper surface of the document pressing cover 240. The pair of side wall portions 222 e are fixed to the upper surface of the document pressing cover 240.

  FIG. 3 is a longitudinal sectional view of the document feeder 221. As shown in the figure, on the right side surface of the main body case 222, a paper feed port 222f and a paper discharge port 222g arranged in the vertical direction are formed. A paper feed tray 223 and a paper discharge tray 228 are provided on the right side of the paper feed port 222f and the paper discharge port 222g, respectively. A substantially U-shaped document transport path 225 is formed in the main body case 222 from the paper feed port 222f to the paper discharge port 222g. A feed roller 261, a paper feed roller 262, a transport roller pair 263, 264, 265 and a paper discharge roller pair 266 are provided in the main body case 222 in this order from the upstream side to the downstream side along the transport path 225. It has been. These rollers 261 and 262 and the conveying roller pairs 263 to 265 are arranged so as to extend in parallel to the main scanning direction (front-rear direction). An inner guide plate 270 and an outer guide plate 280 are provided in a portion between the pair of conveyance rollers 263 to 265 in the document conveyance path 225. The inner guide plate 270 and the outer guide plate 280 are disposed to face each other with the document conveyance path 225 interposed therebetween. The inner guide plate 270 forms the inner wall surface of the U-shaped document conveyance path 225, and the outer guide plate 280 forms the outer wall surface of the document conveyance path 225.

  The feed roller 261 and the paper feed roller 262 are connected via a bracket 231. During the paper feeding operation, the bracket portion 231 rotates around the support shaft 232 in the clockwise direction in the drawing, so that the feed roller 261 contacts the upper surface of the document. Note that reference numeral 205 in FIG. 3 denotes a stopper that regulates the leading end position of the document placed on the document feed tray 223. Each of the transport roller pairs 263 to 265 and the discharge roller pair 266 is composed of a driving roller positioned inside the document transport path 225 and a driven roller positioned outside the document transport path 225. Reference numeral 264 a in the figure is a driving roller (hereinafter referred to as a conveyance driving roller) of the conveying roller pair 264, and reference numeral 264 b is a driven roller of the conveying roller pair 264.

  When the paper feeding operation of the document feeder 221 is started, a normal document placed on the paper feed tray 223 is supplied to the document transport path 225 by the feed roller 261 and the paper feed roller 262, and then a pair of transport rollers. The paper is discharged to a paper discharge tray 228 by a pair of paper discharge rollers 265 via 263 to 265 (see thick arrows in FIG. 3). A first image reading position 226 and a second image reading position 227 are set in the middle of the document conveyance path 225. At the first image reading position 226, an image on the back side of the document is read by a contact image sensor 211. At the second image reading position 227, the scanner unit 210 reads an image on the surface of the document.

  The contact image sensor 211 is provided in the middle of the document conveyance path 225. Specifically, the contact image sensor 211 is accommodated in a U-shaped recess 271 formed on the inner guide plate 270 on the upstream side of the transport roller pair 264. The contact image sensor 211 is arranged with its image reading surface facing the document conveyance path 225. The contact image sensor 211 includes a light source that emits light toward a document passing through the document conveyance path 225, and a plurality of light receiving elements (not shown) arranged in the main scanning direction (a direction that matches the front-rear direction of the image forming apparatus). have. Each light receiving element receives reflected light from the document and outputs an image signal (voltage signal in the present embodiment) having a magnitude corresponding to the amount of light received. The image signal output from each light receiving element is transmitted to the controller 340 (see FIG. 8). The controller 340 generates image data on the back side of the document based on the image signal received from each light receiving element.

  A white reference member 300 is provided at a position facing the contact image sensor 211 across the document conveyance path 225. The white reference member 300 is used as a white reference when the shading correction of the contact image sensor 211 is performed. In the present embodiment, the white reference member 300 is also used as a guide member that guides a document passing through the document conveyance path 225. The contact image sensor 11 is electrically connected to the controller 340 (see FIG. 8). The controller 340 executes shading correction every time before execution of each print job in the image forming apparatus 1.

  As shown in FIGS. 4 and 5, the white reference member 300 (only the claw portion 303 of the white reference member 300 is visible in FIG. 4) is supported by the outer guide plate 280 of the document conveyance path 225. The white reference member 300 is made of, for example, a white resin material. As shown in FIGS. 6 and 7, the white reference member 300 has a white reference plate portion 301 having a rectangular plate shape extending in the front-rear direction (main scanning direction). A pair of support plate portions 302 (only the support plate portion 302 at the rear end portion is shown in FIGS. 5 to 7) are directed upward from the front end portion and the rear end portion of the white reference plate portion 301. It extends. The pair of support plate portions 302 are formed to face each other in the left-right direction. Claw portions 303 projecting outward from each other are formed at the upper ends of the pair of support plate portions 302. A U-shaped projecting portion 281 having a U-shaped cross section that projects outward from the document conveying path 225 is formed at a position of the outer guide plate 280 where the white reference member 300 is located. The U-shaped projecting portion 281 extends in the front-rear direction, and a pair of front end portions and rear end portions of the upper wall portion 282 of the U-shaped projecting portion 281 correspond to the pair of support plate portions 302, respectively. Through-holes 283 are formed. Each support plate portion 302 passes through each through hole 283. Then, the white reference member 300 (white reference plate portion 301) is supported by the upper wall portion 282 by the claw portion 303 at the upper end portion of each support plate portion 302 being hooked on the upper surface of the upper wall portion 282. Here, the through-hole 283 through which each support plate portion 302 passes is a rectangular long hole that is long in the front-rear direction. The length of the through hole 283 in the front-rear direction is longer than the length of each claw portion 303 in the front-rear direction. Accordingly, the white reference member 300 is slidable by a predetermined distance (3 mm in the present embodiment) in the front-rear direction while being supported by the upper wall portion 282.

  As shown in FIG. 7, a first compression coil spring 351 and a second compression coil spring 352 are provided between the white reference plate portion 301 and the outer guide plate 280 (specifically, the upper wall portion 282 of the U-shaped portion 281). Each is contained in a compressed state.

  The first compression coil spring 351 is accommodated in a state where its axis is directed in the vertical direction. The upper end portion of the first compression coil spring 351 is in contact with the lower surface of the support plate portion 302. The lower end portion of the first compression coil spring 351 is in contact with the upper surface of the white reference plate portion 301. Thus, the first compression coil spring 351 urges the white reference plate portion 301 (white reference member 300) downward with respect to the outer guide plate 280. Thereby, the vertical position of the white reference plate 301 can be stabilized and the shading correction accuracy can be improved. Further, even when an excessive upward load is applied to the white reference plate portion 301 during document conveyance, the white reference plate portion 301 is displaced upward so that conveyance failure such as a paper jam can be suppressed.

  The second compression coil spring 352 is accommodated in a state where the axis thereof faces the front-rear direction. The front end portion of the second compression coil spring 352 is in contact with a vertical plate portion 284 that hangs down from the outer guide plate 280. The rear end portion of the second compression coil spring 352 is in contact with the pressed plate portion 307 erected on the upper surface of the white reference plate portion 301. Thus, the second compression coil spring 352 biases the white reference member 300 to the rear side (the cam-integrated gear 325 side described later) with respect to the outer guide plate 280.

  As shown in FIGS. 6 and 7, the white reference member 300 is connected to a cam-integrated gear 325 as a rotating cam member via a drive shaft 315. A rectangular connecting plate portion 304 is erected on the rear end edge of the white reference plate portion 301. A protruding portion 305 that protrudes rearward is formed at the center in the width direction of the upper end portion of the connecting plate portion 304. The protrusion 305 is formed with an engagement hole 306 penetrating in the vertical direction. The drive shaft 315 extends in the front-rear direction, and an engagement claw portion 316 that engages with the engagement hole 306 is formed at a front end portion thereof. The drive shaft 315 passes through the side wall portion 222 e of the document feeder 221. A rear end portion of the drive shaft 315 is supported via a bearing member 320 with respect to a fixed metal plate 319 provided on the rear side of the side wall portion 222e. The bearing member 320 is supported so that the drive shaft 315 can rotate and move in the front-rear direction. A hook-shaped portion 317 that protrudes radially outward from the circumferential surface is formed at the intermediate portion in the front-rear direction of the drive shaft 315. A key-shaped protrusion 318 is formed on the rear side of the flange-shaped portion 317 on the peripheral surface of the drive shaft 315. The key-shaped protrusion 318 extends from the rear side surface of the flange-shaped portion 317 toward the rear side. The key-like protrusion 318 protrudes radially outward when viewed from the axial direction of the drive shaft 315. A cam-integrated gear 325 is rotatably supported at a position adjacent to the key-like protrusion 318 on the drive shaft 315. Drive systems such as a fixed metal plate 319 and a cam-integrated gear 325 that support the drive shaft 315 are covered with a drive case 222h (see FIG. 2).

  The cam-integrated gear 325 includes a disc-shaped gear portion 326, a cylindrical cam portion 327 that extends from the front side surface of the gear portion 326 toward the front side, and rotates integrally with the gear portion 326, and the gear portion 326. And a cylindrical boss portion 324 protruding rearward from the rear side surface. The front end surface of the cylindrical cam portion 327 forms a cam surface 327a that is inclined rearward toward one side in the circumferential direction (the direction of the arrow in FIG. 7). A rear end portion of a key-like protrusion (corresponding to a contact portion) 318 of the drive shaft 315 is always in contact with the cam surface 327a under the biasing force of the second compression coil spring 352. The second compression coil spring 352 moves the drive shaft 315 to the cam surface 327a side so that the contact state between the key-shaped protrusion 318 of the drive shaft 315 and the cam surface 327a is maintained during one rotation of the cam-integrated gear 325. It functions as an urging member for urging the The end surface of the cylindrical boss portion 324 of the cam-integrated gear 325 is in contact with the fixed metal plate 319 via the flange portion 321 of the bearing member 320. This prevents the cam-integrated gear 325 from moving rearward due to the urging force of the second compression coil spring 352.

  As shown in FIG. 8, the cam-integrated gear 325 is connected to the transport roller gear 330 via a first idle gear 328 and a second idle gear 329. The first idle gear 328 meshes with the gear portion 326 of the cam-integrated gear 325. The first idle gear 328 is coupled to the second idle gear 329 via a coupling shaft 331. The second idle gear 329 is integrated with the one-way clutch 329a. The second idle gear 329 meshes with the transport roller gear 330. The transport roller gear 330 is connected to a transport drive roller 264 a that is a drive roller of the transport roller pair 264 via a connecting shaft 332 so as to be integrally rotated. The transport roller gear 330 rotates in response to an input from the motor 335. In FIG. 8, for convenience of explanation, the gears 325 and 328 to 330 are arranged on a plane, but actually, the transport roller gear 330 in FIG. 8 is hidden behind the second idle gear 329. Absent.

  The one-way clutch 329a idles in a state where the motor 335 rotates forward and the conveyance driving roller 264a rotates so as to convey the document from the upstream side to the downstream side (the rotation state indicated by the solid line arrow in the drawing). Power transmission from the transport roller gear 330 to the cam-integrated gear 325 is interrupted. On the other hand, the one-way clutch 329a is camped from the transport roller gear 330 by coupling the second idle gear 329 and the connecting shaft 331 when the motor 335 is rotating in the reverse direction (the state indicated by the broken line arrow in the figure). Allow power transmission to the integrated gear 325.

  The motor 335 is controlled by a controller 340. The controller 340 includes a microcomputer having a CPU, a ROM, a RAM, and the like. When executing a print job, the controller 340 rotates the motor 335 in the forward direction and conveys the document from the upstream side to the downstream side. In the state where the motor 335 is rotating forward, the one-way clutch 329a rotates idly as described above, so that the power transmission path from the transport roller gear 330 to the cam-integrated gear 325 is blocked. Accordingly, since the cam-integrated gear 325 does not rotate, the white reference member 300 remains stationary. Thereby, it is possible to prevent the white reference member 300 from moving unnecessarily in the main scanning direction while the motor 335 is rotating in the forward direction, and thus it is possible to suppress document conveyance failure such as a paper jam.

  On the other hand, when executing the shading correction, the controller 340 reversely rotates the motor 335 by a predetermined amount (a rotation amount that causes the cam-integrated gear 325 to make one rotation). As a result, the one-way clutch 329a is coupled and power transmission from the transport roller gear 330 to the cam-integrated gear 325 is allowed. Then, the cam-integrated gear 325 makes one rotation, and the cam surface 327a reciprocates the drive shaft 315 in the front-rear direction while pressing the key-shaped protrusion 318 of the drive shaft 315. Along with this, the white reference member 300 reciprocates once in the front-rear direction. This movement amplitude is set to 3 mm, for example. In the present embodiment, the contact image sensor 211 performs an image reading operation for a preset number of times (for example, 256 times) while the white reference member 300 reciprocates once. The controller 340 acquires an electric signal (voltage value) output from each light receiving element every time the reading operation by the contact image sensor 211 is performed, and averages the acquired electric signal (voltage value) by the set number of times. This creates shading correction data. Therefore, even if dirt is attached to the surface of the white reference plate portion 301, the contact image sensor 211 reads white reference images at a plurality of places where dirt is not attached by reciprocating the white reference member 300. As a result, the shading correction data can be acquired with almost no influence of dirt. Instead of averaging the electrical signals output from the respective light receiving elements as described above, for example, shading correction data may be created by excluding an image of a spot with dirt.

  In this embodiment, an example in which the white reference member 300 is reciprocated once during shading correction has been described. However, the present invention is not limited to this, and the white reference member 300 may be reciprocated two or more times. By increasing the number of reciprocations of the white reference member 300, it is possible to increase the number of image reading samples by the contact image sensor 211 and improve the shading correction accuracy.

  In the present embodiment, since the configuration in which the white reference member 300 is linearly moved in the main scanning direction is adopted, the white reference member 300 is compared with the case where the white reference member 300 is configured by a rotating roller member. Low requirements for shape accuracy and support accuracy. Therefore, the component cost of the white reference member 300 can be reduced, and the cost of the entire apparatus can be reduced.

  In this embodiment, the cam-integrated gear 325 is rotated using the motor 335 that drives the transport driving roller 264a, so that the parts can be shared and the cost of the entire apparatus can be reduced. it can.

  In the present embodiment, the engagement claw 316 formed on the drive shaft 315 is engaged with the engagement hole 306 formed on the white reference member 300, so that the front end of the drive shaft 315 is simply moved. Compared with the case where the white reference member 300 is brought into contact, the followability of the drive shaft 315 with respect to the rotational operation of the cam-integrated gear 325 can be improved. Therefore, the speed profile of the white reference member 300 at the time of shading correction can be made into a smooth sine curve, so that the shading correction accuracy can be improved.

  In the present embodiment, the white reference member 300 is also used as a guide member for document guides, so that the cost of the entire apparatus can be reduced.

  Further, the image forming apparatus 1 according to the present embodiment improves the shading correction accuracy in the image reading apparatus 200. As a result, the image forming unit 20 suppresses the density variation of the image formed on the paper, and as a result, the image quality of the printed image. Can be improved.

<< Other embodiments >>
In the above-described embodiment, the example in which the electrophotographic method is adopted as the image forming method of the image forming apparatus 1 is described. However, the present invention is not limited to this, and for example, an ink jet method may be adopted.

  The front end face of the cylindrical cam portion 327 is inclined rearward toward one side in the circumferential direction (the direction of the arrow in FIG. 7). You may incline to the front side.

  As described above, the present invention is useful for an image reading apparatus and an image forming apparatus including the image reading apparatus.

1 Image forming apparatus 200 Image reading apparatus 211 Contact image sensor (image reading sensor)
222f Paper feed port 222g Paper output port 225 Document transport path 264a Transport drive roller 300 White reference member 315 Drive shaft 318 Key-shaped protrusion (contact portion)
325 Cam integrated gear (rotating cam member)
326 Gear portion 327 Cylindrical cam portion 327a Cam surface 330 Conveying roller gear 335 Motor (drive motor)
352 Second compression coil spring (biasing member)

Claims (5)

A main body case having a paper feed port and a paper discharge port arranged in the vertical direction; a document transport path provided in the main body case for guiding a document fed from the paper feed port to the paper discharge port; A conveyance driving roller that extends in the scanning direction and is driven by a drive motor to convey the document in the document conveyance path from the upstream side to the downstream side, and is provided in the middle of the document conveyance path and passes through the document conveyance path An image reading sensor that optically reads an image on one side of the original to be scanned, and a white sensor that is disposed opposite to the image reading sensor with the document conveyance path interposed therebetween, and that functions as a white reference for shading correction of the image reading sensor An image reading apparatus comprising a reference member,
An image reading apparatus further comprising a rotating cam member that rotates in conjunction with a rotation operation of the transport driving roller driven by the driving motor and moves the white reference member in a main scanning direction. The image reading apparatus according to claim 1.
Provided in the power transmission path between the conveyance drive roller and the rotating cam member, and when the conveyance drive roller is rotating forward to convey the document from the upstream side to the downstream side, it idles and rotates from the conveyance drive roller. An image reading apparatus further comprising a one-way clutch that interrupts power transmission to the cam member and allows power transmission from the transport driving roller to the rotating cam member when the transport driving roller rotates in the reverse direction. The image reading apparatus according to claim 1 or 2,
The image reading apparatus, wherein the white reference member is also used as a guide member for guiding a document passing through the document conveyance path. The image reading apparatus according to any one of claims 1 to 3,
The rotary cam member rotates in response to a rotational input from the drive motor and has a gear portion whose rotation axis extends in the main scanning direction, and extends from one side surface in the axial direction of the gear portion toward the one side. A cylindrical cam portion that rotates integrally with the gear portion;
A cam surface that is inclined toward one side or the other side in the axial direction toward one side in the circumferential direction is formed on one end face in the axial direction of the cylindrical cam portion,
A drive shaft having an abutting portion that abuts on the cam surface and connected to the white reference member and configured to be movable in the main scanning direction;
An urging member for urging the drive shaft toward the cam surface such that the contact state between the abutment portion of the drive shaft and the cam surface is maintained during one rotation of the rotating cam member; An image reading apparatus. An image reading apparatus according to any one of claims 1 to 4,
An image forming apparatus comprising: an image forming unit that forms an image on a sheet based on image data read by the image reading apparatus.

Images