JP2017199968A - Image reading device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of image defects due to attachment of foreign substances, and suppress a variation in sheet conveying speed.SOLUTION: An image reading device (103) comprises: first image reading means (151) that reads an image from a first surface of a sheet (D) through a first transparent part (152); and second image reading means (201) that reads an image from a second surface of the sheet through a second transparent part (202). A first guide part (402) facing the first transparent part when viewed from a sheet conveying direction in a reading part of the second image reading means is located on the opposite side of the second transparent part with respect to a second guide part (502) facing the second transparent part. A guide part (403) is provided on downstream of the first guide part for guiding the rear end of the sheet to move along the position of the second guide part.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image reading apparatus that reads image information from a sheet, and an image forming apparatus including the image reading apparatus.

  As an image reading apparatus used in an image forming apparatus such as a digital copying machine, an apparatus equipped with an automatic document feeder (hereinafter referred to as ADF) is widely known. This type of image reading apparatus reads image information from a document by a scanning device such as a CCD method or a CIS method while automatically feeding a document placed on a feeding tray toward an image reading unit by an ADF. . A transparent member such as glass covering the scanning device is disposed in the image reading unit, and the scanning device optically scans the document through the transparent member.

  Here, when foreign matter adheres to the surface of the transparent member that covers the scanning device, the scanning light is shielded by the foreign matter, so that linear image noise (hereinafter referred to as an image streak) appears in the read image information. Sometimes. Examples of such foreign matters include toner powder that has fallen from the original during document conveyance, paper dust generated from the document, and scraps (rubber debris) of a conveyance roller that conveys the document. Therefore, a configuration is known in which the transparent member is electrically grounded to reduce the electrostatic adsorption force acting between the foreign material and the transparent member, thereby preventing the foreign material from staying. The foreign matter having weakened the attractive force with respect to the transparent member is scraped off by the leading end portion of the document passing through the surface of the transparent member, and thus is removed from the transparent member as the document is conveyed by the ADF.

  On the other hand, in some image reading apparatuses, two scanning devices corresponding to the front surface and the back surface of a document are arranged, and image information is acquired from both surfaces of the document by one document transport by ADF. In Patent Document 1, in an image reading apparatus in which images can be read from both sides of a document by two optical modules (scanning devices), the document passing between the transparent members covering each optical module is directed to one transparent member. A configuration in which an elastic member for biasing is provided has been proposed. In this configuration, the position variation of the document in the optical axis direction of the optical module is restricted by pressing the document against one transparent member by the elastic member.

U.S. Pat. No. 8,830,537

  Here, in the configuration of Patent Document 1, since the document is conveyed on substantially the same plane, the document passes through the image reading unit without contacting the transparent member on the side opposite to the urging direction by the elastic member. Conceivable. Therefore, even if a foreign substance adheres to the transparent member, it cannot be removed by conveying the document, which may cause image streaks. Therefore, the scanning position of the image by each scanning device is arranged at a different position in the document conveyance direction, and the document conveyance path is curved between the upstream reading position and the downstream reading position, thereby leading the leading edge of the document. It is possible to consider a configuration in which is conveyed in contact with two transparent members in order.

  However, when the conveyance path of the original sheet is curved, the conveyance speed of the sheet may fluctuate, which may affect the reading of image information. That is, when a sheet bent along the curve of the conveyance path passes through the curved portion, the trailing edge jumps up due to the elasticity of the sheet, collides with a nearby member, and the conveyance resistance changes irregularly. The speed has fluctuated. When the sheet conveyance speed fluctuates, the read image information is distorted in the sub-scanning direction, which causes a decrease in fidelity to the original image.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image reading apparatus and an image forming apparatus provided with the image reading apparatus that can prevent the occurrence of an image defect due to adhesion of foreign matter and can suppress fluctuations in the sheet conveyance speed.

  An image reading apparatus according to an aspect of the present invention includes a first transparent unit, a first transparent unit that faces the first transparent unit with a sheet conveyance path interposed therebetween, and a first reading unit is formed between the first transparent unit and the first transparent unit. A first guide unit; a first image reading unit configured to read image information from the first surface of the sheet passing through the first reading unit through the first transparent unit; and a downstream of the first reading unit in the sheet conveying direction. A second guide part that forms a second reading part between the second transparent part, the second transparent part facing the second transparent part across the sheet conveyance path, and the second reading part. A second image reading means for reading image information from the second surface opposite to the first surface of the passing sheet through the second transparent portion; and a sheet disposed downstream of the second reading portion in the sheet conveying direction. Conveying means, and the first reading unit and the front in the sheet conveying direction Intermediate guide means for guiding the sheet to and from the second reading unit, and when viewed from the sheet conveyance direction in the second reading unit, the first guide unit is configured to move the second guide unit relative to the second guide unit. The intermediate guide means is located on the opposite side of the transparent portion, and the intermediate guide means guides the downstream end of the sheet in the sheet conveying direction toward the second transparent portion, and the upstream end of the sheet in the sheet conveying direction. And a second intermediate guide portion capable of guiding the second reading portion so as to move along the position of the second guide portion as viewed from the sheet conveying direction in the second reading portion.

  According to the present invention, it is possible to prevent the occurrence of an image defect due to the adhesion of foreign matter and to suppress fluctuations in the sheet conveyance speed.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present disclosure. FIG. 3 is a schematic diagram illustrating a configuration of an image reading apparatus. (A) is a schematic diagram which shows the structure of the double-sided reading part which concerns on this indication. FIG. 5B is a schematic diagram illustrating a trajectory drawn by the trailing edge of the sheet passing through the image reading unit. FIG. 6C is a schematic diagram illustrating a trajectory drawn by the rear end of the sheet in the comparative configuration. 6 is a graph showing a change in sheet conveyance speed at a second reading position.

  Hereinafter, an image reading apparatus and an image forming apparatus according to the present disclosure will be described with reference to the drawings. The image forming apparatus according to the present disclosure includes an image reading apparatus that reads image information from a document, such as a copying machine, a facsimile machine, a printer, and a multifunction machine, and can store, transfer, and print the image information. It is. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the following embodiments are not intended to limit the scope of application of the present technology only to those unless otherwise specified. .

[Image forming apparatus]
First, a schematic configuration of the image forming apparatus will be described with reference to FIG. As shown in FIG. 1, the image forming apparatus 101 includes an image forming apparatus main body 101 </ b> A and an image reading apparatus 103. The image reading apparatus 103 disposed above the image forming apparatus main body 101A includes an apparatus main body 30 and an ADF 1 as will be described in detail later, and reads image information by optically scanning the document D. The document D is a sheet such as a sheet of paper or an envelope, a plastic film such as an overhead projector sheet (OHT), or a cloth. Image information converted into an electronic signal by the image reading device 103 is transferred to the control unit 132 provided in the image forming apparatus main body 101A.

  The image forming apparatus main body 101A includes an image forming unit 133 that forms an image on a sheet P that is a recording medium, and a sheet feeding unit 34 that feeds the sheet P to the image forming unit 133. The sheet feeding unit 34 includes sheet storage units 137a, 137b, 137c, and 137d that can store sheets of different sizes. The sheets stored in each sheet storage unit are fed out by the pickup roller 32, separated one by one by the feed roller 33a and the retard roller 33b, and delivered to the corresponding conveyance roller pair 131. Then, the sheet P is conveyed to the registration roller pair 136 by sequentially transferring the conveyance roller pair 131 arranged along the sheet conveyance path. Note that the sheet P placed on the manual feed tray 137e by the user is fed into the image forming apparatus main body 101A by the feeding roller 138 and conveyed to the registration roller pair 136. The registration roller pair 136 corrects the skew by stopping the leading edge of the sheet P, and resumes the conveyance of the sheet P in accordance with the progress of the image forming operation that is a toner image forming process by the image forming unit 133.

  An image forming unit 133 as an image forming unit that forms an image on the sheet P is an electrophotographic image forming unit including a photosensitive drum 121 as a photosensitive member. The photosensitive drum 121 can be rotated along the conveyance direction of the sheet P. Around the photosensitive drum 121, a charger 118, an exposure device 123, a developing device 124, a transfer charger 125, a separation charger 126, and a cleaner 127. Is arranged. The charger 118 uniformly charges the surface of the photosensitive drum 121, and the exposure device 123 exposes the photosensitive drum 121 based on image information input from the image reading device 103 or the like to form an electrostatic latent image on the drum. To do.

  The developing device 124 contains a two-component developer containing toner and carrier, and develops the electrostatic latent image into a toner image by supplying charged toner to the photosensitive drum 121. The toner image carried on the photosensitive drum 121 is transferred to the sheet P conveyed from the registration roller pair 136 by a bias electric field formed by the transfer charger 125. The sheet P to which the toner image has been transferred is separated from the photosensitive drum 121 by the bias electric field formed by the separation charger, and is conveyed toward the fixing unit 129 by the pre-fixing conveyance unit 128. Note that deposits such as transfer residual toner remaining on the photosensitive drum 121 without being transferred to the sheet P are removed by the cleaner 127, and the photosensitive drum 121 prepares for the next image forming operation.

  The sheet P conveyed to the fixing unit 129 is heated while being sandwiched and pressed by a pair of rollers, and the image is fixed by melting and fixing the toner. When the image output is completed, the sheet P on which the fixed image is obtained is discharged to the discharge tray 130 protruding outward from the image forming apparatus main body 101A via the discharge roller pair 40. When an image is formed on the back side of the sheet P in duplex printing, the sheet P that has passed through the fixing unit 129 is switched between the front side and the back side by the reversing unit 139, and is conveyed to the registration roller pair 136 by the duplex conveyance unit 140. The Then, the sheet P on which the image is formed again by the image forming unit 133 is discharged to the discharge tray 130.

[Image reading device]
Next, the configuration of the image reading apparatus 103 will be described with reference to FIGS. 2 and 3A. As shown in FIG. 2, the image reading apparatus 103 includes an image reading apparatus main body (hereinafter simply referred to as “apparatus main body”) 30 and an ADF 1 serving as a document feeding unit. The image reading apparatus 103 includes a first reading unit 151 disposed in the apparatus main body 30 and a second reading unit 201 disposed in the ADF 1. Hereinafter, each element constituting the image reading apparatus 103 will be described.

  The first reading unit 151 is an example of a first image reading unit that reads image information from the first surface of the sheet. The second reading unit 201 is an example of a second image reading unit that reads an image on the second surface opposite to the first surface of the document D. In the present embodiment, the first surface is a lower surface of the document D in the duplex reading unit DR, and the second surface is an upper surface of the document D in the duplex reading unit DR. The first reading unit 151 and the second reading unit 201 constitute a double-sided reading unit DR that can simultaneously read both sides of the document D conveyed by the ADF 1. However, the double-sided reading unit DR does not always execute simultaneous reading of both sides, and can also read only one side.

  The first reading unit 151 and the second reading unit 201 include a contact image sensor (hereinafter referred to as a CIS) that is a scanning device of an equal magnification optical system. The first reading unit 151 and the second reading unit 201 include a light source composed of an LED array arranged in the main scanning direction orthogonal to the document conveying direction, and sensor elements arranged in the main scanning direction as well (whichever (Not shown). The reflected light emitted from the LED array and reflected by the document D is imaged on each sensor element via a lens and is photoelectrically converted by the sensor element.

  The apparatus main body 30 is fixed to the upper surface of the image forming apparatus main body 101A (see FIG. 1). As shown in FIG. 2, a flat bed type document table 31 is disposed on the upper surface of the apparatus main body 30. The first reading unit 151 is supported by a carriage (not shown) that can move in the left-right direction in the drawing. The first reading unit 151 extends from the predetermined position (shown position) in the double-sided reading unit DR along the document table 31. It can move over its entire length.

  The ADF 1 is rotatably supported by a hinge mechanism (not shown) disposed on the back side in the drawing, and can be opened and closed with respect to the apparatus main body 30 in the vertical direction. In addition to the second reading unit 201, the ADF 1 includes a document feeding tray 2, a document transport unit 11, and a document discharge unit 12. The document feeding tray 2 as a sheet support unit that supports the sheet supports the document D placed by the user. The document transport unit 11 has a document transport path T formed therein, and feeds the document D on the document feed tray 2 to the duplex reading unit DR via the document transport path T. The document discharge unit 3 is disposed below the document feed tray 2 and supports the document D that has passed through the duplex reading unit DR and is discharged from the document transport unit 11. The document feeding tray 2 and the document discharge unit 3 are disposed on the same side with respect to the document transport unit 11 and are in a position overlapping when viewed from above and below. The lower surface of the document discharge unit 3 is opposed to the document table 31 of the apparatus main body 30 in a state where the ADF 1 is closed, and serves as a document pressing unit 12 that presses the document placed on the document table 31.

  The document transport unit 11 will be described in detail. The document transport unit 11 includes a pickup roller 4, a feed roller 5, a retard roller 6, a registration roller pair 7, transport roller pairs 8 and 9, and a discharge roller pair 10. It has in this order along the direction (arrow). The pickup roller 4 as a feeding unit for feeding a sheet is movable in the vertical direction with respect to the upper surface of the document feeding tray 2 and starts feeding by contacting the document D on the tray. The feed roller 5 transports the document D received from the pickup roller 4 toward the downstream in the document transport direction. The retard roller 6 is pressed against the feed roller 5 and receives rotational driving in a direction opposite to the document conveyance direction via a torque limiter, and separates the document D conveyed by the feed roller 5 one by one.

  The registration roller pair 7 receives the downstream end (hereinafter referred to as the front end) of the document D conveyed by the feed roller 5 in a state where the rotation is stopped, and bends the document D to remove skew. Further, the registration roller pair 7 conveys the document D whose skew has been corrected through the bent portion of the document conveyance path T, and delivers it to the conveyance roller pair 8. The conveyance roller pair 8 conveys the document D to the lower right in the drawing, sends it to the double-sided reading unit DR, and delivers it to the conveyance roller pair 9 on the downstream side. At this time, the image of the document D is read by the first reading unit 151 and the second reading unit 201. The conveyance roller pair 9 conveys the document D that has passed through the double-sided reading unit DR in the upper right direction in the drawing and delivers it to the discharge roller pair 10. The discharge roller pair 10 discharges and stacks the document D from the document transport unit 11 to the document discharge unit 3.

  The image reading apparatus 103 configured as described above uses the document reading mode that scans the document image while feeding the document D by the ADF 1 and the fixed reading mode that scans the document placed on the document table 31. The image information is read from. The flow-reading mode is selected when the apparatus detects the document D placed on the document feeding tray 2 or when the user explicitly instructs the operation panel or the like of the image forming apparatus main body 101A. In this case, the ADF 1 feeds the document D one by one toward the double-sided reading unit DR in a state where the first reading unit 151 is at a predetermined position of the double-sided reading unit DR. Then, both of the first reading unit 151 and the second reading unit 201 perform scanning by irradiating the document D with scanning light in the case of simultaneous scanning on both sides, and one of these in the case of single-sided scanning. Image information converted into an electronic signal by the sensor element is transferred to the control unit 132 of the image forming apparatus main body 101A.

  On the other hand, the fixed reading mode is selected when the apparatus detects the document D placed on the document table 31 or when the user explicitly instructs the operation panel or the like of the image forming apparatus main body 101A. In this case, the first reading unit 151 scans the document D placed on the document table 31 by irradiating light while moving along the document table 31. The image information converted into an electronic signal by the sensor element of the first reading unit 151 is transferred to the control unit 132 of the image forming apparatus main body 101A.

[Detailed configuration of duplex scanning unit]
Next, a detailed configuration of the double-sided reading unit DR will be described. As shown in FIG. 3A, in addition to the first reading unit 151 and the second reading unit 201, the double-sided reading unit DR includes a first flow reading glass 152, a second flow reading glass 202, and a first horizontal guide 402. The second horizontal guide 502 is provided.

  The first flow reading glass 152 and the first horizontal guide 402 are arranged substantially horizontally, and face each other across the document conveyance path T at the first reading position R1, which is the optical axis position of the sensor element of the first reading unit 151. doing. The first flow reading glass 152 and the first horizontal guide 402 form a first reading portion P1 in which the first reading unit 151 reads image information from the first surface of the document D through the first flow reading glass 152.

  The second flow reading glass 202 and the second horizontal guide 502 are arranged substantially horizontally, and sandwich the document transport path T at the second reading position R2 that is the optical axis position of the sensor element of the second reading unit 201. Are facing each other. The second flow reading glass 202 and the second horizontal guide 502 form a second reading portion P2 in which the second reading unit 201 reads image information from the second surface of the document D through the second flow reading glass 202.

  The distance between the flow reading glass (152, 202) and the corresponding horizontal guide (402, 502) is set in consideration of the depth of field of the first reading unit 151 and the second reading unit 201. The depth of field of the first reading unit 151 and the second reading unit 201 that are CIS is typically about 0.3 to 0.4 mm. For this reason, it is preferable to set the distance in the vertical direction between the flow-reading glass and the horizontal guide to, for example, 0.6 mm.

  The first flow reading glass 152 and the second flow reading glass 202 are imparted with conductivity to the surface facing the document conveying path T by vapor deposition of indium tin oxide (ITO) or adhesion of a conductive transparent film. It has a conductive layer. The first flow reading glass 152 and the second flow reading 202 are configured to be electrically grounded at least when the ADF 1 is closed.

  The first horizontal guide 402 is a part of the upper conveyance guide 400 supported by the frame of the ADF 1 and is set to white for the background. Similarly, the second horizontal guide 502 is a part of the lower conveyance guide 500 supported by the frame of the ADF 1, and has a white background guide 2a fitted at a position facing the second reading unit P2. Yes. The background guide 2a and the surrounding horizontal guide 502 are configured to be flush with each other.

  The first flow reading glass 152 is an example of a first transparent portion, and the second flow reading glass 202 is an example of a second transparent portion. You may comprise these 1st and 2nd transparent parts with transparent materials, such as resin other than glass. The first horizontal guide 402 is an example of a first guide part that faces the first transparent part across the sheet conveyance path, and the second horizontal guide 502 is a second guide that faces the second transparent part across the sheet conveyance path. It is an example of a part.

  Here, the curved shape of the document conveyance path T and the self-cleaning of the first flow reading glass 152 and the second flow reading glass 202 will be described. As shown in FIG. 3A, the document conveyance directions in the first reading unit P1 and the second reading unit P2 are substantially parallel to each other (horizontal direction). The second reading unit P2 is disposed downstream of the first reading unit P1 and in the vertical direction above the first reading unit P1. That is, the first horizontal guide 402 is on the opposite side (lower side) to the second horizontal reading 502 with respect to the second horizontal guide 502 when viewed from the document conveyance direction (left and right direction in the drawing) in the second reading unit P2. positioned. In other words, the first horizontal guide 402 protrudes downward with respect to the tangent line Hc of the second horizontal guide 502 in the second reading unit P2. With such an arrangement, the document transport path T in the double-sided reading unit DR is formed in an S-shape that is gently curved.

  Between the first flow reading glass 152 and the second horizontal guide 502, an inclined guide 501 that is inclined upward toward the downstream in the document conveying direction is disposed. The inclined guide 501 is an example of a first intermediate guide portion that guides the front end of the document D toward the second flow reading glass 202. The inclined guide 501 constitutes an intermediate guide 450 as intermediate guide means for guiding a sheet between the first reading unit P1 and the second reading unit P2, together with a guide unit 403 as a second intermediate guide unit described later. The inclined guide 501 extends above the downstream end Q1 of the first horizontal guide 402, and is configured at an angle at which the extended line of the inclined surface intersects the second flow reading glass 202 upstream from the second reading position R2. .

  As shown in FIG. 2, the nip portion of the conveyance roller pair 8 located upstream of the double-sided reading unit DR is located slightly above the first reading unit P1, and conveys the document D to the lower right in the drawing. It is sent to the first reading unit P1. Upstream of the first reading unit P1, an upstream inclined guide 401 (see FIG. 3A) is provided as a part of the upper conveyance guide 400, and is inclined downward toward the downstream in the document conveyance direction. Is guided toward the first flow reading glass 152.

  Further, the nip portion of the conveying roller pair 9 positioned downstream of the duplex reading unit DR is positioned slightly above the second reading unit P2, and the document D that has passed through the second reading unit P2 is positioned at the upper right in the drawing. It is conveyed and delivered to the discharge roller pair 10. Downstream of the second reading unit P2, a downstream inclined guide 503 (see FIG. 3A) that is inclined upward toward the downstream in the document conveying direction is provided as a part of the lower conveying guide 500. The front end of D is guided toward the conveying roller pair 9.

  With such a configuration, the front end of the document D abuts against the first flow reading glass 152 and the second flow reading glass 202 in the process of transporting the document D along the document transport path T. It is removed (self-cleaning) by the document itself. However, the foreign matters are those that can cause linear image noise (image streaks) by blocking the scanning light from the first reading unit 151 and the second reading unit 201 such as paper dust adhered to the original. Point to. It is known that such foreign matter is likely to adhere to the glass surface when the surfaces of the first flow reading glass 152 and the second flow reading glass 202 rubbed by the original D are charged.

  Each process of self-cleaning will be described. When the document D transported by the transport roller pair 8 enters the double-sided reading unit DR, the front end of the document D is guided by the upstream inclined guide 401, and the first flow reading glass upstream of the first reading position R1. 152 abuts. As a result, the foreign matter adhering to the surface of the first flow reading glass 152 is scraped off and removed from the front end of the document D. Further, the front end of the document D that has passed through the first reading unit P1 is guided upward along the tilt guide 501 and abuts on the second flow reading glass 202 upstream of the second reading position R2. Thereby, the foreign matter adhering to the surface of the second flow reading glass 202 is scraped off and removed from the front end of the document D. The foreign matter scraped off by the document D is discharged out of the ADF 1 together with the document D by the transport roller pair 9 and the discharge roller pair 10.

  As described above, the front end of the document D transported along the document transport path T comes into contact with each of the first flow reading glass 152 and the second flow reading glass 202, thereby achieving self-cleaning of the double-sided reading unit DR. Is done.

  As long as the front end of the document D is in contact with the first flow reading glass 152 and the second flow reading glass 202, the shape of the document conveyance path T and the arrangement of the guide members are not limited to those described above. For example, the vertical positions of the first reading unit 151 and the second reading unit 201 with respect to the document transport path T are reversed, and the first reading unit 151 scans the upper surface of the document D and the second reading unit 201 scans the lower surface of the document D. It is good also as composition to do. In this case, instead of the inclined guide 501, an inclined guide that abuts on the upper surface of the document D is provided as a first intermediate guide, and the front end of the document D is guided downward to be brought into contact with the downstream reading glass. It is.

  Further, the document transport path T is not limited to the one curved in an S shape as in the present embodiment, and may be one curved in a V shape, for example. Specifically, in FIG. 3A, the first flow reading glass 152 and the first horizontal guide 402 are inclined with respect to the horizontal plane so that the document conveyance direction in the first reading unit P1 is on the upper right side in the drawing. It is possible. In this configuration, the front end of the document D can be brought into contact with the second flow reading glass 202 without providing an inclined guide inclined with respect to the first flow reading glass 152. In this case, a first intermediate guide in which the downstream portion (or a guide member flush with the first reading position R1) of the first flow reading glass 152 guides the front end of the sheet toward the second transparent portion. It corresponds to the part.

[Original transport speed]
Next, the influence of the deflection of the upstream end (hereinafter referred to as the rear end) in the document transport direction on the transport speed of the document D will be described. As described above, in the configuration in which the first horizontal guide 402 is positioned on the side opposite to the second flow reading glass 152 with respect to the tangent line Hc drawn from the second horizontal guide 502, the document D is conveyed in a bent state. The That is, the first horizontal guide 402 is in contact with the upper surface of the document D on the upstream side in the transport direction, and the second horizontal guide 502 is in contact with the lower surface of the document D on the downstream side, so that the document D is transported. (See FIG. 3 (a)). At this time, the document D is inclined with respect to the horizontal plane between the downstream end Q1 of the first horizontal guide 402 and the upstream end Q2 of the second horizontal guide 502, and is bent in an S shape as a whole. It has become.

  Here, when the trailing edge of the document D moves away from the downstream end Q1 of the horizontal guide 402, the trailing edge starts to move upward, and the elastic energy stored in the document D is released by bending. At this time, for example, as shown in a locus shown in FIG. 3C, in a configuration that allows the trailing edge of the document D to jump significantly (vibrates up and down), the document D is subjected to the second flow reading glass 202 and the tilt guide 501. There is a possibility that the conveyance resistance fluctuates by colliding with a nearby member. When the conveyance speed of the document D by the conveyance roller pair 9 changes due to the variation in conveyance resistance, the image information read by the second reading unit 201 is distorted in the sub-scanning direction.

  Therefore, as shown in FIG. 3B, in the present embodiment, the second intermediate guide capable of regulating the movement path of the trailing edge of the document D between the first reading unit P1 and the second reading unit P2. A guide portion 403 is arranged as a portion. The guide unit 403 is supported by the frame of the ADF 1 and can come into contact with the upper surface (second surface) of the document D transported through the document transport path T.

  The guide unit 403 is not limited to an independent member, and may be configured by projecting a part of a peripheral wall that surrounds and seals the second reading unit 201 together with the second flow reading glass 202. It may be configured to extend downstream. Further, as long as the locus can be regulated by contacting the upper surface of the document D, the document D is not limited to a plate-like member, and may be configured by a rib or the like. Hereinafter, the guide portion 403 refers to a contact surface of such a member with respect to the document D.

  The guide unit 403 includes an upstream portion 3a that is inclined upward toward the downstream side in the document conveyance direction and a downstream portion 3b that extends substantially in the horizontal direction. In other words, the upstream portion 3a is formed to be inclined with respect to the tangent line Hc of the second horizontal guide 502 so as to approach the second flow reading 202 from the first horizontal guide 402 toward the downstream in the document transport direction. . The downstream portion 3b is formed along the tangent line Hc of the second horizontal guide 502 across the upstream end G1 and the downstream end G2 in the document transport direction.

  The downstream portion 3b is disposed at a position closer to the tangent line Hc than at least the first horizontal guide 402, but is preferably disposed on substantially the same straight line as the tangent line Hc. “Substantially on the same straight line” means that the downstream end G2 of the downstream portion 3b in the document conveying direction is within a range of ± 1.5 mm with respect to the tangent line Hc, that is, the vertical distance is 1.5 mm or less. Shall point to.

  Under this configuration, the trailing end of the document D that has passed through the first reading unit P1 first moves along the upstream portion 3a of the guide unit 403 and reaches a position substantially equal to the second horizontal guide 502, and then Then, it moves in the horizontal direction along the downstream portion 3 b and is transferred to the second horizontal guide 502. For this reason, the trailing edge of the document D moves along the position of the second horizontal guide 502 viewed from the document conveying direction (left and right direction in the drawing) in the second reading unit P2, and the trailing edge of the document D is the first. It is possible to prevent the rear end from jumping up when separated from the horizontal guide 402. Then, by suppressing fluctuations in the conveyance speed of the document D, image information faithful to the document image can be acquired. That is, according to the present embodiment, in the configuration in which self-cleaning is achieved by the curvature of the document conveyance path T, fluctuations in the document conveyance speed can be suppressed and image reading accuracy can be improved.

[Verification of effect of this embodiment]
FIG. 4 shows a result of comparing changes in the document conveying speed between the image reading apparatus to which the present embodiment is applied and the comparative image reading apparatus. The horizontal axis represents time, and the vertical axis represents the document conveyance speed at each time point. The solid line is the one to which this embodiment is applied, and the broken line is the one to which the configuration for comparison is applied. However, the configuration for comparison is different from the present embodiment in that a part of the upstream portion 3a and the downstream portion 3b of the guide portion 403 are missing (see FIG. 3C). This is the same as this embodiment. Note that the conveyance speed of the document D can be calculated, for example, by preparing a test chart on which lines are printed at equal intervals in the sub-scanning direction and comparing the image information read from the test chart with the document image. .

  As shown in FIG. 4, in the comparative configuration (broken line), a large variation in the conveyance speed was observed as compared to the case where the present embodiment was applied (solid line). When the target value of the document conveyance speed (a preset value in the range of 280 to 400 (mm / sec)) is V0 (mm / sec), instantaneous conveyance at time S1 and time S2 of the comparative configuration is performed. The speeds were V0 + 60 and V0 + 50, respectively. This is because, as shown in FIG. 3C, a locus S that vibrates greatly after the trailing edge of the document D is separated from the first horizontal guide 402 is drawn. Times S1 and S2 correspond to the timing at which the trailing edge of the document D passes through the apex portion of the locus S, respectively.

  On the other hand, when this embodiment is applied, although a relatively small variation in the conveyance speed due to factors such as conveyance resistance by the second horizontal guide 502 and tolerance or eccentricity of the peripheral surfaces of the conveyance roller pair 9 is seen, the fluctuation range is It was almost constant. Therefore, it was confirmed that the variation in the conveyance speed can be sufficiently suppressed by the present embodiment.

[Other Embodiments]
In the above embodiment, the guide unit 403 is disposed as the second intermediate guide unit. However, the rear end of the sheet can be guided along the position of the second horizontal guide 502 viewed from the document conveyance direction in the second reading unit P2. For example, the configuration of the second intermediate guide portion is not limited to that described above. For example, the document D may be guided by a roller member instead of the plate-shaped or rib-shaped guide member. Further, the vibration of the document D may be absorbed by an elastic member such as a sponge.

  It is also conceivable that the document conveyance directions in the first reading unit P1 and the second reading unit P2 do not match, such as when the document conveyance path T in the double-sided reading unit DR is bent in a V shape. In such a case, the downstream part 3b of the guide part 403 shall be formed along the conveyance direction (tangential direction of the second guide part) in the second reading part P2. Accordingly, the trailing edge of the document D that has passed through the first reading unit P1 can be guided to the second reading unit P2 in the approach direction along the transport direction in the second reading unit P2, and the document D is transported by vibration. Speed fluctuation can be suppressed. Further, as long as at least the downstream portion of the guide portion 403 is formed along the document conveyance direction in the second reading portion P2, the entire guide portion may have a smoothly curved shape.

  In the present disclosure, the image reading apparatus 103 provided in the image forming apparatus 101 has been described. However, the present invention may be applied to an image reading apparatus that is used alone, such as a flatbed scanner including an ADF. In addition, the image forming apparatus main body is not limited to the electrophotographic system, and may include, for example, an inkjet image forming unit.

DESCRIPTION OF SYMBOLS 1 ... Original feeding part (ADF) / 2 ... Sheet support part (original feeding tray) / 3a ... Upstream part of second intermediate guide part / 3b ... Downstream part of second intermediate guide part / 4 ... Feeding means ( Pickup roller) / 9 ... Conveying means (conveying roller pair) / 30 ... Main body / 101 ... Image forming apparatus / 103 ... Image reading apparatus / 133 ... Image forming means / 151 ... First image reading means (first reading unit) / 152 ... 1st transparent part (first flow reading glass) / 201 ... 2nd image reading means (2nd reading unit) / 202 ... 2nd transparent part (2nd flow reading glass) / 402 ... 1st guide part ( First horizontal guide) / 403 ... second intermediate guide portion (guide portion) / 450 ... intermediate guide means (intermediate guide) / 501 ... first intermediate guide portion (inclined guide) / 502 ... second guide portion (second horizontal guide) Guide) / D ... Sheet (Original) / 2 ... second intermediate guide part of the downstream end / Hc ... tangential / P1 ... first reader / P2: second reading portion of the second guide portion

Claims (10)

A first transparent portion;
A first guide part that faces the first transparent part across a sheet conveyance path and forms a first reading part between the first transparent part;
First image reading means for reading image information from the first surface of the sheet passing through the first reading portion through the first transparent portion;
A second transparent portion disposed downstream of the first reading portion in the sheet conveying direction;
A second guide part that faces the second transparent part across a sheet conveyance path and forms a second reading part between the second transparent part;
Second image reading means for reading image information from the second surface opposite to the first surface of the sheet passing through the second reading portion through the second transparent portion;
A conveying unit disposed downstream of the second reading unit in the sheet conveying direction and conveying the sheet;
Intermediate guide means for guiding a sheet between the first reading unit and the second reading unit in the sheet conveying direction;
The first guide portion is located on the opposite side of the second transparent portion with respect to the second guide portion, as viewed from the sheet conveying direction in the second reading portion,
The intermediate guide means includes a first intermediate guide portion that guides the downstream end of the sheet in the sheet conveyance direction toward the second transparent portion, and an upstream end of the sheet in the sheet conveyance direction. A second intermediate guide portion that can be guided to move along the position of the second guide portion as viewed from the direction,
An image reading apparatus. The second intermediate guide portion can contact the second surface of the sheet conveyed through the sheet conveyance path,
A downstream portion of the second intermediate guide portion in the sheet conveyance direction is formed along a tangent line of the second guide portion in the second reading portion, and is disposed at a position closer to the tangent line than at least the first guide portion. ,
The image reading apparatus according to claim 1. A downstream end of the second intermediate guide portion in the sheet conveying direction is located at a distance of 1.5 mm or less with respect to the tangent line of the second guide portion;
The image reading apparatus according to claim 2. With respect to the tangent line of the second guide portion, the upstream portion of the second intermediate guide portion in the sheet conveyance direction approaches the second transparent portion from the first guide portion toward the downstream in the sheet conveyance direction. Inclined,
The image reading apparatus according to claim 2, wherein the image reading apparatus is an image reading apparatus. The first intermediate guide portion can be in contact with the first surface of the sheet conveyed through the sheet conveyance path.
The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus. The sheet conveyance direction in the first reading unit and the sheet conveyance direction in the first reading unit are substantially parallel,
The first intermediate guide part is formed to be inclined with respect to each of the first transparent part and the second guide part.
The image reading apparatus according to claim 5. The first image reading unit and the second image reading unit are contact image sensors;
The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus. Each of the first transparent part and the second transparent part is formed with a conductive layer having conductivity on a surface facing the sheet conveyance path, and is electrically grounded.
The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus. The device body;
A document support unit that includes a sheet support unit that supports the sheet, and a feeding unit that feeds the sheet supported by the sheet support unit to the first reading unit; With
The first image reading unit is disposed in the apparatus main body, and the second image reading unit is disposed in the document feeding unit;
The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus. An image reading apparatus according to any one of claims 1 to 9,
Image forming means for forming an image based on image information read by the image reading device;
An image forming apparatus.

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