Reading device and image forming system

Abstract

To provide new forms of a reading device that can achieve highly accurate image reading and an image forming system.SOLUTION: A reading device is provided with: a transmission member that is arranged between a first roller pair and a second roller pair in a sheet conveyance direction and on a first side in a height direction with respect to a nip line that passes through a nip part of the first roller pair and extends in the sheet conveyance direction; reading means that reads image information on a sheet conveyed from the first roller pair toward the second roller pair; and an opposing member that is provided on a second side in the height direction with respect to the transmission member, forms a gap with the transmission member through which the sheet passes, and is opposite to the reading means with the transmission member therebetween. When seen in a sheet width direction, a surface of the transmission member on the second side in the height direction is inclined to the second side in the height direction toward the downstream in the sheet conveyance direction. An angle of inclination of the surface with respect to the nip line is 1° or more and 30° or less.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a reading device and an image forming system. [Background technology]

[0002] In an image forming apparatus, it is required to adjust the image quality (hereinafter referred to as image quality) of the image forming apparatus with high accuracy. Elements of image quality include color reproducibility, color stability, and front-back registration accuracy. Image quality adjustment has been performed using offline measuring devices or manual adjustment and eye adjustment by skilled workers. However, in order to adjust with high accuracy, repetitive work is required, and even in one operation, multiple samples are measured and the values ​​are averaged, making image quality adjustment a cumbersome task. Therefore, a so-called in-line reading device may be used, which allows automatic image quality adjustment by receiving a sheet (recording medium) on which an image is formed by an image forming apparatus and reading the image information of the sheet while conveying it. Patent Document 1 describes that the position of an image formed on a sheet by an image forming apparatus is corrected by reading the position of an identification mark (register mark) from both sides of the paper received from the image forming apparatus.

[0003] However, in a reading device, if the height of the sheet relative to the reading unit (the position of the sheet surface in the depth of field direction) fluctuates, the accuracy of the read image may decrease. In the above document, the introduction angle at which the first conveying roller introduces the sheet toward the reading position of the reading unit and the discharge angle at which the second conveying roller discharges the sheet from the reading position are inclined with respect to the surface of the opposing member facing the reading unit. With this configuration, the sheet is conveyed while being bent between the first and second conveying rollers and brought into contact with the surface of the opposing member, thereby suppressing fluctuations in the height of the sheet relative to the reading unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-184863 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the configuration of the above document, the sheet is actively brought into contact with the opposing member to stabilize the height relative to the reading unit, and the sheet comes into contact with the opposing member with a relatively high contact pressure. However, when the conveyed sheet comes into contact with the opposing member with high contact pressure, sheet powder (so-called paper powder) is generated and accumulates, which may reduce the image reading accuracy or leave friction marks on the image on the sheet.

[0006] The present disclosure provides a new form of a reading device and an image forming system capable of achieving highly accurate image reading. [Means for solving the problem]

[0007] One aspect of the present disclosure is a reading device that reads image information of a sheet on which an image is formed by an image forming device, the reading device including: a first roller pair that receives the sheet from the image forming device and conveys the sheet in a sheet conveying direction; a second roller pair that is disposed downstream of the first roller pair in the sheet conveying direction and conveys the sheet, the second roller pair being disposed so as to overlap a nip line that passes through a nip portion of the first roller pair and extends in the sheet conveying direction when viewed in a sheet width direction perpendicular to the sheet conveying direction; and a second roller pair that is disposed between the first roller pair and the second roller pair in the sheet conveying direction and is aligned with respect to the nip line in the sheet conveying direction and the sheet conveying direction. a transparent member that transmits light and is disposed on a first side in a height direction perpendicular to a sheet width direction; a reading means that reads image information of the sheet transported from the first roller pair to the second roller pair through the transparent member; and an opposing member that is provided on a second side opposite to the first side in the height direction with respect to the transparent member, forming a gap between the transparent member and the sheet through which the sheet passes, and opposing the reading means through the transparent member, wherein when viewed in the sheet width direction, a surface of the second side of the transparent member in the height direction is inclined toward the second side in the height direction toward downstream in the sheet transport direction, When viewed in the sheet width direction, a downstream end of the surface in the sheet conveying direction is located on the first side in the height direction with respect to the nip line. The reading device is characterized in that Another aspect of the present disclosure is a reading device that reads image information of a sheet on which an image is formed by an image forming device, the reading device including: a first roller pair that receives the sheet from the image forming device and conveys the sheet in a sheet conveying direction; a second roller pair that is disposed downstream of the first roller pair in the sheet conveying direction and conveys the sheet, the second roller pair being disposed so as to overlap a nip line that passes through a nip portion of the first roller pair and extends in the sheet conveying direction when viewed in a sheet width direction perpendicular to the sheet conveying direction; a transparent member that transmits light and is disposed between the first roller pair and the second roller pair in the sheet conveying direction and on a first side in a height direction perpendicular to the sheet conveying direction and the sheet width direction with respect to the nip line; a reading unit that reads image information of the sheet conveyed from the first roller pair to the second roller pair through the transparent member; and an opposing member that is provided on a second side opposite to the first side in the height direction with respect to the transparent member, forming a gap between the transparent member and the second roller pair in the height direction through which the sheet passes, and opposing the reading unit through the transparent member; when viewed in the sheet width direction, a surface of the second side in the height direction of the transparent member is inclined toward the second side in the height direction downstream in the sheet transport direction, and when viewed in the sheet width direction with the nip line as a first nip line, a downstream end of the surface in the sheet transport direction is located on the first side in the height direction with respect to a second nip line that passes through a nip portion of the second roller pair and extends in the sheet transport direction. Another aspect of the present disclosure is a reading device that reads image information of a sheet on which an image is formed by an image forming device, the reading device including: a first roller pair that receives the sheet from the image forming device and conveys the sheet in a sheet conveying direction; a second roller pair that is disposed downstream of the first roller pair in the sheet conveying direction and conveys the sheet, the second roller pair being disposed so as to overlap a nip line that passes through a nip portion of the first roller pair and extends in the sheet conveying direction when viewed in a sheet width direction perpendicular to the sheet conveying direction; a transparent member that transmits light and is disposed between the first roller pair and the second roller pair in the sheet conveying direction and on a first side of the nip line in a height direction perpendicular to the sheet conveying direction and the sheet width direction; The reading device comprises a reading means for reading through the transparent member, an opposing member that is provided on a second side of the transparent member opposite the first side in the height direction, forming a gap between the transparent member and the opposing member through which the sheet passes, and that faces the reading means through the transparent member, and a transport guide that is provided between the first roller pair and the transparent member in the sheet transport direction and on the first side in the height direction relative to the nip line, and that guides the sheet, wherein, when viewed in the sheet width direction, a surface of the second side of the transparent member in the height direction is inclined toward the second side in the height direction toward downstream in the sheet transport direction, and when viewed in the sheet width direction, the transport guide does not protrude toward the second side in the height direction relative to the nip line. Effect of the Invention

[0008] According to the present disclosure, highly accurate image reading can be achieved. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of an image forming system according to an embodiment of the present disclosure. [Diagram 2] FIG. 4 is a schematic diagram of an adjustment unit according to the embodiment. [Diagram 3] FIG. 2 is a schematic diagram of an image reading unit according to the embodiment. [Figure 4]5A and 5B are diagrams for explaining a shading operation according to the embodiment. [Diagram 5] 3A to 3C are cross-sectional views of a first reading unit according to the embodiment. [Figure 6] 3A to 3D are cross-sectional views of a first reading unit according to the embodiment. [Figure 7] 1 is a block diagram showing a configuration of an image forming system according to an embodiment. [Figure 8] 11A and 11B are images showing a display screen of a user interface according to an embodiment. [Figure 9] 3A and 3B are diagrams showing a measurement test pattern according to the embodiment. [Figure 10] 4 is a flowchart showing a control method of the image forming system according to the embodiment. [Figure 11] 6A and 6B are diagrams for explaining the operation of a normal job according to the embodiment. [Figure 12] 6A and 6B are diagrams for explaining the operation of an image position adjustment job according to the embodiment. [Figure 13] 1A to 1C are diagrams showing the configuration of a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.

[0011] 1 is a schematic diagram showing an image forming system 100S according to an embodiment. The image forming system 100S includes an image forming apparatus 100, an adjustment unit 400, and a finisher 600. The adjustment unit 400 is an example of a reading device that reads image information of a sheet, and the finisher 600 is an example of a sheet processing device that processes the sheet.

[0012] The housing 101 (also called the device body) of the image forming apparatus 100 is equipped with an image forming engine 102 as an image forming means, and a main controller that controls the operation of the image forming system 100S including the image forming apparatus 100. The image forming engine 102 of this embodiment includes an optical processing mechanism and a fixing processing mechanism that form an image on a recording material by an electrophotographic process, and a feeding processing mechanism and a conveying processing mechanism that feed and convey a sheet 110 used as a recording material. The image forming apparatus 100 is also equipped with a control board that includes an engine control unit 312 (FIG. 7) that controls the processing by each of these mechanisms (e.g., feeding processing), and a printer controller 103 (FIG. 7) that controls the entire image forming system 100S. The engine control unit 312 controls the operation of a conveying roller drive motor 311 and guide members (131, 132) that switch the conveying path based on detection signals from sensors (137, 153, 163) described later that are provided on the sheet conveying path in the image forming apparatus 100. As the recording material, a variety of sheet materials with different materials, thicknesses, sizes, shapes, etc. can be used, such as paper such as plain paper or cardboard, paper with a surface treatment such as coated paper or embossed paper, plastic film, or cloth.

[0013] The optical processing mechanism includes stations 120, 121, 122, and 123 that form toner images of each color of yellow, magenta, cyan, and black, and an intermediate transfer belt 106. In each of the stations 120 to 123, a primary charger 111 charges the surface of a photosensitive drum 105, which is a drum-shaped image carrier (also called an electrophotographic photosensitive member). The laser scanner unit 107 performs exposure processing of the photosensitive drum 105 based on a command signal that is generated based on image data and transmitted to the laser scanner unit 107. The laser scanner unit 107 has a laser driver that turns on and off a laser beam emitted from a semiconductor laser (not shown), and guides the laser beam from the semiconductor laser to the photosensitive drum 105 via a reflecting mirror 109 while distributing it in the main scanning direction by a rotating polygon mirror. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 105.

[0014] The developing unit 112 contains a developer containing toner therein, and supplies charged toner particles to the photosensitive drum 105. The toner particles adhere to the drum surface in accordance with the surface potential distribution, so that the electrostatic latent image carried on the photosensitive drum 105 is developed (i.e., visualized) as a toner image. The toner image carried on the photosensitive drum 105 is transferred (i.e., primary transfer) to the intermediate transfer belt 106 by a primary transfer roller to which a voltage of a polarity opposite to the normal charging polarity of the toner is applied. When a color image is formed, the toner images formed by the four stations 120 to 123 are multiple-transferred so as to be superimposed on each other on the intermediate transfer belt 106, so that a full-color toner image is formed on the belt.

[0015] Meanwhile, the feeding process mechanism feeds sheets 110 one by one from a storage 113 inserted retractably into a housing 101 of the image forming apparatus 100 toward a transfer roller 114. A toner image carried on an intermediate transfer belt 106, which is an intermediate transfer body, is transferred (i.e., secondary transfer) onto the sheet 110 by the transfer roller 114.

[0016] Around the intermediate transfer belt 106, there are arranged a start position detection sensor 115 for determining a print start position when forming an image, a feed timing sensor 116 for timing the feeding of the sheet 110, and a density sensor 117. The density sensor 117 measures the density of a patch image carried on the intermediate transfer belt 106. The main controller adjusts the operating conditions of the optical processing mechanism (for example, the setting of the charging target potential of the primary charger 111 and the bias voltage of the developer 112) based on the detection result of the density sensor 117.

[0017] The fixing mechanism of this embodiment is composed of a first fixing device 150 and a second fixing device 160. The first fixing device 150 includes a fixing roller 151 for applying heat to the sheet 110, a pressure belt 152 for pressing the sheet 110 against the fixing roller 151, and a first post-fixing sensor 153 for detecting the completion of the fixing process by the first fixing device 150. Each roller including the fixing roller 151 is a hollow roller and has a heater inside. The first fixing device 150 applies heat and pressure to the toner image on the sheet while conveying the sheet 110 by nipping it between the fixing roller 151 and the pressure belt 152, which are a pair of rotating bodies. This melts the toner particles, which then stick to each other, and the image is fixed to the sheet 110.

[0018] The second fixing device 160 is disposed downstream of the first fixing device 150 in the conveying path of the sheet 110. The second fixing device 160 has a function of increasing the glossiness of the image fixed by the first fixing device 150 and ensuring fixability of the image to the sheet 110. Like the first fixing device 150, the second fixing device 160 has a fixing roller 161 and a pressure roller 162 as a pair of rotating bodies that heat and pressurize the sheet 110 while conveying it, and a second post-fixing sensor 163 that detects the completion of the fixing process by the second fixing device 160.

[0019] Depending on the type of sheet 110, there may be cases where it is not necessary to pass the sheet 110 through the second fixing device 160. In such cases, the image forming apparatus 100 has a bypass conveying path 130 for discharging the sheet 110 without passing through the second fixing device 160 in order to reduce energy consumption. The sheet 110 sent out from the first fixing device 150 is guided by a first switching flap 131 to either the second fixing device 160 or the bypass conveying path 130.

[0020] The sheet 110 that has passed through the second fixing device 160 or the bypass conveying path 130 is guided by the second switching flap 132 to either the discharge conveying path 139 or the reverse conveying path 135. The position of the sheet 110 that has been conveyed to the reverse conveying path 135 is detected by the reverse sensor 137, and the leading end and trailing end in the sheet conveying direction are swapped by the switchback operation performed by the reverse unit 136. In the case of double-sided printing, the sheet 110 with an image formed on its first side is transported again toward the transfer roller 114 via the re-conveying path 138 with its leading and trailing ends swapped by the reverse unit 136, and an image is formed on its second side. The sheet 110 with the image formation completed in single-sided printing or the sheet 110 with the image formation completed in double-sided printing is discharged to the outside of the image forming apparatus 100 via the discharge conveying path 139. In addition, a switching flap 134 capable of guiding the sheet 110 switched back by the reversing unit 136 toward the discharge conveying path 139 is provided between the reversing conveying path 135 and the discharge conveying path 139. By providing the switching flap 134, it becomes possible to select the front or back of the sheet 110 when it is discharged from the image forming apparatus 100.

[0021] An original reading device 190 is installed on the top of the image forming apparatus 100. The original reading device 190 includes a main body portion fixed to a housing 101 of the image forming apparatus 100, and an automatic document feeder (hereinafter referred to as ADF). The ADF includes a feed tray on which original sheets are placed, and a discharge tray onto which the original sheets from which image information has been read are discharged. The original sheets set on the feed tray are fed and transported one by one by a feeding unit. During this time, the original sheets are optically scanned by an image sensor to read the image information of the sheets. The original sheets from which image information has been read are discharged onto the discharge tray by a pair of discharge rollers.

[0022] The image forming apparatus 100 is provided with an operation unit 180 that serves as a user interface for the image forming system 100S (see also FIG. 1). The operation unit 180 has a display as a display means for displaying information to the user. The operation unit 180 also has physical keys such as a numeric keypad and a print execution button, and a touch panel function of the display, as input means by which the user can input commands and data to the image forming system 100S. By operating the operation unit 180, the user can input information indicating sheet attributes such as the name, basis weight, and whether or not the sheet has been surface-treated of a sheet set in a certain storage 113 to the main controller. The input sheet attributes are registered in a paper library 900 stored in the memory 304.

[0023] 1, an intermediate transfer type color image forming apparatus has been described, but a direct transfer type image forming engine that transfers a toner image formed on an image carrier to a sheet without using an intermediate transfer body may be installed. Also, the image forming means is not limited to the electrophotographic type, and may be, for example, an inkjet type printing unit or an offset printing mechanism.

[0024] (Adjustment unit) Next, a description will be given of the adjustment unit 400. The adjustment unit 400 functions as an image reading device that reads image information in an image reading section 500 from a sheet on which an image has been formed by the image forming apparatus 100. The adjustment unit 400 of this embodiment is used to adjust the execution conditions of an image forming operation performed by the image forming apparatus 100, as will be described later.

[0025] 1, the adjustment unit 400 is installed between the image forming apparatus 100 and the finisher 600 in the horizontal direction H (left-right direction in the figure). That is, in this embodiment, the upstream device of the adjustment unit 400 is the image forming apparatus 100, and the downstream device of the adjustment unit 400 is the finisher 600. The finisher 600 has a processing section that performs processing such as binding processing or saddle processing on sheets, and discharges the processed sheet stack (or the sheets received from the upstream device when no processing is required) as a deliverable of the image forming system 100S.

[0026] The devices connected upstream and downstream of the adjustment unit 400 vary depending on the configuration of the image forming system 100S. For example, the adjustment unit 400 is not necessarily directly connected to the image forming apparatus 100, and an intermediate unit may be disposed between the image forming apparatus 100 and the adjustment unit 400, and the adjustment unit 400 may receive the sheet through the intermediate unit. An example of the intermediate unit is a device that performs a coating process to attach a transparent toner to the image surface of the image-formed sheet to give it gloss. In addition, a sheet processing device other than the finisher 600 may be connected downstream of the adjustment unit 400. Examples of such sheet processing devices include an inserter that inserts a sheet to be a cover into a sheet stack, a trimmer that cuts and aligns the ends of a bound sheet stack, and a stacker that can be moved by a cart while storing a large amount of products. In addition, the adjustment unit 400 may be configured to include a discharge tray that discharges sheets as products of the image forming system 100S (a configuration in which the finisher 600 is omitted from FIG. 1).

[0027] 2, the adjustment unit 400 includes an image reading unit 500, and a through path 431 and a discharge path 432 that configure a sheet transport path within the adjustment unit. In addition, a discharge tray 430 and an extension tray 423 that can be pulled out from the discharge tray 430 are provided on the upper part of the housing of the adjustment unit 400.

[0028] The through path 431 is a transport path that receives a sheet discharged from the image forming apparatus 100 and transports the sheet toward the finisher 600, and extends substantially in the horizontal direction H. An inlet roller pair 401 and an outlet roller pair 406 are arranged on the through path 431. In other words, the through path 431 extends along a straight line in the horizontal direction H when the image forming system 100S is viewed from the front side. The through path 431 extends from an opening (receiving port) provided on a side surface 400R on one side (the image forming apparatus 100 side) of the adjustment unit 400 in the horizontal direction H to an opening (discharge port) provided on a side surface 400L on the other side (the finisher 600 side).

[0029] The image reading unit 500 is disposed between the pair of entrance rollers 401 and the pair of exit rollers 406 in the through path 431. The image reading unit 500 reads image information of a sheet conveyed from the pair of entrance rollers 401 toward the pair of exit rollers 406. A detailed configuration of the image reading unit 500 will be described later.

[0030] The discharge path 432 branches off from the through path 431 and extends upward. In the discharge path 432, a first conveying roller pair 415, a second conveying roller pair 416, a third conveying roller pair 417, and a discharge roller pair 418 are arranged in this order from upstream to downstream in the sheet conveying direction of the discharge path 432. At the branch point between the discharge path 432 and the through path 431, a switching flap 422 is arranged as a guide member capable of switching the sheet conveying path between the through path 431 and the discharge path 432. The switching flap 422 is arranged downstream of the image reading unit 500 and upstream of the exit roller pair 406 in the sheet conveying direction of the through path 431. Note that the conveying path configuration of the adjustment unit 400 shown in the figure is an example, and for example, a conveying path that branches off from the through path 431 and then merges with the through path 431 may be provided to arrange the image reading unit 500.

[0031] The switching flap 422 can perform control such that, for example, a sheet on which a normal image is formed is conveyed to a downstream device via a pair of exit rollers, and a sheet on which an image for adjusting the execution conditions of an image forming operation is formed is discharged to a discharge tray 430 via a discharge path. In other words, by switching a sheet (user job sheet) as a product desired by a user and a sheet (adjustment sheet) created for adjusting the execution conditions of an image forming operation to a different tray, it is possible to prevent an adjustment sheet from being placed between user job sheets. A user job is also called a normal job. Since an adjustment sheet is basically unnecessary for a user, the above switching operation can prevent the user from having to go through the trouble of removing an adjustment sheet that has been placed between user job sheets (normal job sheets).

[0032] (Image reading section) The image reading unit 500 will be described. FIG. 3 is a schematic diagram of the image reading unit 500 seen in the sheet width direction. The image reading unit 500 includes a first reading unit 51 that reads image information from a first surface of the sheet (the lower surface of the sheet in the through path 431) and a second reading unit 52 that reads image information from a second surface of the sheet (the upper surface of the sheet in the through path 431) opposite to the first surface of the sheet. The image reading unit 500 also has a first roller pair 501, a second roller pair 502, and a third roller pair 503 as conveying means for conveying the sheet through the first reading unit 51 and the second reading unit 52. With respect to the sheet conveying direction D1 in the through path 431, the first reading unit 51 is provided between the first roller pair 501 and the second roller pair 502, and the second reading unit 52 is provided between the second roller pair 502 and the third roller pair 503.

[0033] In this embodiment, the sheet conveying direction D1 refers to the direction from the nip portion 1n of the first roller pair 501 toward the nip portion 2n of the second roller pair 502. The sheet width direction is the width direction of the sheet held by the first roller pair 501, and is a direction perpendicular to the sheet conveying direction D1, and is also the rotation axis direction of the first roller pair 501 and the main scanning direction of the first reading unit 51 and the second reading unit 52. The height direction D2 is a direction perpendicular to the sheet conveying direction D1 and the sheet width direction. In this embodiment, when the adjustment unit 400 is installed on a horizontal plane, the height direction D2 coincides with the vertical direction (gravity direction).

[0034] In this embodiment, the path from the nip portion 1n of the first roller pair 501 through the nip portion 2n of the second roller pair 502 to the nip portion 3n of the third roller pair 503 is a linear conveying path (straight path) along the nip line N1 of the first roller pair 501. In other words, when viewed in the sheet width direction, the second roller pair 502 overlaps with the nip line N1 of the first roller pair 501, and the third roller pair 502 overlaps with the nip line N1 of the first roller pair 501. 3 This line also overlaps with the nip line N1 of the first roller pair 501. The nip line N1 is an imaginary straight line that passes through a nip portion 1n where the two rollers 501a, 501b constituting the first roller pair 501 are in contact with each other, and extends in a direction perpendicular to a line segment connecting the rotation axes 1A, 1B of the rollers 501a, 501b (i.e., the sheet conveying direction D1).

[0035] Preferably, the nip line N1 of the first roller pair 501 passes between the rotation axes 2A, 2B of the two rollers 502a, 502b constituting the second roller pair 502 and between the rotation axes 3A, 3B of the two rollers 503a, 503b constituting the third roller pair 503. More preferably, the nip line N1 of the first roller pair 501 passes through the nip portions 2n, 3n of the second roller pair 502 and the third roller pair 503 (the nip lines of each roller pair are substantially aligned), excluding manufacturing tolerances. By adopting a straight path in the image reading unit 500, it is possible to obtain advantages such as being able to easily accommodate an increase in the sheet conveying speed (improved throughput) and being less likely to generate paper dust or scratches on the image by reducing the contact pressure between the sheet and the conveying guide.

[0036] Each of the first reading section 51 and the second reading section 52 of the image reading unit 500 includes sensors C1 and C2 as reading means, opposing rollers 511 and 521 as opposing members, and glass 512 and 522 as transparent members. The opposing rollers 511 and 521 also function as a sheet biasing member, a sheet pressing member, a sheet guide, or a backing member. The sensor C1, the opposing roller 511, and the glass 512 of the first reading section 51 are the first reading means, the first opposing member, and the first transparent member of this embodiment. The sensor C2, the opposing roller 521, and the glass 522 of the second reading section 52 are the second reading means, the second opposing member, and the second transparent member of this embodiment.

[0037] In the first reading unit 51, a gap 1g, which is a clearance (space) through which a sheet to be read passes, is formed between a glass 512 and an opposing roller 511 that face each other in the height direction D2. The sensor C1 faces the opposing roller 511 with the glass 512 and the gap 1g sandwiched between them. In other words, the sensor C1 and the glass 512 are located on one side (first side, lower side in this embodiment) of the gap 1g in the height direction D2, and the opposing roller 511 is located on the opposite side (second side, upper side in this embodiment) of the gap 1g in the height direction D2.

[0038] The second reading unit 52 has the same configuration as the first reading unit 51, except that the positional relationship in the height direction D2 is reversed. That is, a gap 2g is formed between the glass 522 and the opposing roller 521, which face each other in the height direction D2. The sensor C2 faces the opposing roller 521 with the glass 522 and the gap 2g sandwiched between them. That is, the sensor C2 and the glass 522 are located on the other side (second side, the upper side in this embodiment) of the gap 2g in the height direction D2, and the opposing roller 521 is located on one side (first side, one side in this embodiment) of the gap 2g in the height direction D2.

[0039] The glass 512, 522 is a light-transmitting member, and glass is used from the viewpoints of transparency, strength, light resistance, etc. The degree of freedom of the shape of glass is relatively low, and in many cases, a roughly rectangular parallelepiped member cut from a flat glass plate is used. Reference plates 515, 525 are attached to the glass 512, 522 as reference parts used for shading correction described later.

[0040] Sensor C1 reads image information on the first side of the sheet by optically scanning the first side of the sheet passing through gap 1g via glass 512 and converting it into an electronic signal. Sensor C2 reads image information on the second side of the sheet by optically scanning the second side of the sheet passing through gap 2g via glass 522 and converting it into an electronic signal. The image information from sensors C1 and C2 is used to detect the position of a patch image in a test pattern relative to the edge of the sheet, for example, in image position adjustment described below.

[0041] The sensors C1 and C2 are CIS type image sensors. As shown in FIG. 4(a), the sensor C1 includes an irradiation unit C1a, a condenser lens C1b, and a light receiving element C1c. The irradiation unit C1a irradiates light toward the gap 1g. The irradiation unit 701a includes an LED as a light source installed on a substrate, and a light guide extending in the sheet width direction from a position facing the LED and irradiating the light from the LED to substantially the entire gap 1g in the sheet width direction. The condenser lens C1b condenses the reflected light from the sheet passing through the gap 1g, and forms an image on the light receiving surface of the light receiving element C1c. The condenser lens C1b is a lens array in which cylindrical equal-magnification lenses are arranged in the sheet width direction in correspondence with each of the light receiving elements C1c. The light receiving element C1c is a CMOS sensor arranged in the sheet width direction on the substrate. Although FIG. 4(a) shows the sensor C1 of the first reading unit 51, the sensor C2 of the second reading unit 52 also has substantially the same configuration as the sensor C1.

[0042] As shown in Fig. 3, the opposing rollers 511 and 521 are rollers that can rotate around a rotation axis extending in the sheet width direction. The opposing roller 511 faces the sensor C1 through the glass 512 in a direction intersecting the sheet conveying direction D1 and the sheet width direction (particularly, the depth of field direction Df1 of the sensor C1) at the reading position of the sensor C1. Similarly, the opposing roller 521 faces the sensor C2 through the glass 522 in a direction intersecting the sheet conveying direction D1 and the sheet width direction (particularly, the depth of field direction Df2 of the sensor C2) at the reading position of the sensor C2. The depth of field directions Df1 and Df2 represent directions along the representative optical path of light taken in by the sensors C1 and C2 from the reading target, and are the optical axis directions of the condenser lens C1b when a CIS is used as the sensors C1 and C2.

[0043] The width of the gaps 1g, 2g in the depth of field directions Df1, Df2 is regulated by the opposing rollers 511, 521, so that the position of the sheet passing through the reading position in the depth of field directions Df1, Df2 is regulated. That is, the opposing rollers 511, 521 urge the sheet toward the glass 512, 522 at the reading positions of the sensors C1, C2. As a result, at the reading positions of the sensors C1, C2, the sheet passes through the focal positions (or a position sufficiently close to the focal positions) where the sensors C1, C2 are focused, and the sensors C1, C2 can read the image with high accuracy. For example, the positions of the edges of the sheet and the patches can be determined with high accuracy from the image information acquired by the sensors C1, C2. As a result, the image forming system 100S can perform image position adjustment and color adjustment with high accuracy based on the image information read by the image reading unit 500.

[0044] Each of the opposing rollers 511, 521 is driven by a motor (not shown) in a rotation direction in which the roller surface moves in the sheet conveying direction D1 at the gaps 1g, 2g. A part of the opposing roller 511 on the glass 512 side (lower side in the figure) protrudes (penetrates) into the glass 512 side beyond the nip line N1. Similarly, a part of the opposing roller 521 on the glass 522 side (upper side in the figure) protrudes (penetrates) into the glass 522 side beyond the nip line N1. This arrangement brings the sheet closer to the focal position of the sensors C1, C2. The opposing rollers 511, 521 are members that become the background when the sensors C1, C2 read the image information of the sheet, and their outer circumferential surfaces are, for example, black so that the edge detection of the sheet in the image processing can be easily performed.

[0045] Between the first roller pair 501 and the glass 512 in the sheet conveying direction D1 and below the nip line N1 in the height direction D2, a glass upstream guide 513 is provided as a conveying guide for guiding the lower surface of the sheet. Between the first roller pair 501 and the counter roller 511 in the sheet conveying direction D1 and above the nip line N1 in the height direction D2, a roller upstream guide 514 is provided for guiding the upper surface of the sheet. In addition, between the second roller pair 502 and the glass 522 in the sheet conveying direction D1 and above the nip line N1 in the height direction D2, a glass upstream guide 523 is provided for guiding the upper surface of the sheet. Between the second roller pair 502 and the counter roller 521 in the sheet conveying direction D1 and below the nip line N1 in the height direction D2, roller upstream guides 524a and 524b are provided for guiding the lower surface of the sheet.

[0046] The roller upstream guides 514, 524a, and 524b function as guides to guide the leading edge of the sheet toward the gaps 1g and 2g between the opposing rollers 511 and 521 and the glass 512 and 522. This can prevent poor conveyance caused by the leading edge of the sheet contacting the cylindrical opposing rollers 511 and 521 at a large contact angle. The downstream end of the roller upstream guide 514 in the sheet conveying direction D1 is located at a higher position in the height direction D2 than at least the end of the opposing roller 511 on the glass 512 side. The downstream end of the roller upstream guide 514 may be configured to slightly protrude downward in the height direction D2 with respect to the nip line N1, or may be configured to be located above the nip line N1. Similarly, the downstream end of the roller upstream guide 524b in the sheet conveying direction D1 is located at a lower position in the height direction D2 than at least the end of the opposing roller 521 on the glass 522 side. The downstream end of the roller upstream guide 524b may be configured to protrude slightly upward in the height direction D2 relative to the nip line N1, or may be configured to be located below the nip line N1.

[0047] In the illustrated example, the roller upstream guide 514 of the first reading unit 51 is configured from one member, but may be configured from a plurality of members, like the roller upstream guides 524a and 524b of the second reading unit 52. In the illustrated example, the roller upstream guides 524a and 524b of the second reading unit 52 are divided into a member (524a) facing the glass upstream guide 523 and a member (524b) facing the glass 522. However, the roller upstream guides 524a and 524b may be configured from a single member, like the roller upstream guide 514 of the first reading unit 51.

[0048] The shading correction operation of the sensor C1 will be described with reference to Figs. 4(a) and 4(b). When performing shading correction, the sensor C1 moves from a position (first position) for reading the image information of the sheet shown in Fig. 4(a) to a position (second position) shown in Fig. 4(b), that is, a position facing the lower surface of the reference plate 515. The lower surface of the reference plate 515 is white, which is the reference color, and the whiteness of the lower surface is controlled. The sensor C1 can adjust the amount of light to an optimal level by irradiating light onto the lower surface of the reference plate 515 and measuring the brightness of the reflected light. For example, if the brightness of the reflected light relative to the reference color is too high, the amount of light is reduced, and if the brightness is too low, the amount of light is increased. This shading correction allows the amount of light to be adjusted to an optimal level, and the color on the sheet can be detected with high accuracy. Similarly, the shading correction of the sensor C2 is performed by sliding the sensor C2 to a position facing the upper surface of the reference plate 525, irradiating light onto the upper surface of the reference plate 525, and adjusting the amount of light according to the brightness of the reflected light.

[0049] (tilted glass arrangement) Next, the arrangement of the first reading unit 51 as viewed in the sheet width direction (main scanning direction) will be described. Before describing a detailed arrangement example of this embodiment, the arrangement of a comparative example and conveyance failures that occur in the comparative example will be described with reference to Figs. 13(a-c). As described above, in a reading device that reads image information on a sheet, it is desirable to stabilize the height of the sheet (sheet position in the depth of field direction) relative to the reading unit (sensor) in order to improve the reading accuracy of the image. However, if the sheet is actively brought into contact with the opposing member as in the above-mentioned document, the contact pressure between the sheet and the opposing member increases, which may cause paper dust to be generated, the reading accuracy to be reduced due to accumulation, and friction marks to remain on the image on the sheet.

[0050] As a method for avoiding the problems of paper dust and friction marks, it is possible to adopt a straight path in which the roller pairs 601, 602 upstream and downstream of the reading unit are arranged on a common nip line Na, and to arrange the glass 702 parallel to the nip line Na, as shown in Fig. 13(a). Here, if the surface of the glass 702 facing the opposing roller 703 is away from the nip line Na as shown in Fig. 13(a), the fluctuation (flutter) of the sheet position in the height direction D2, which is the direction of the depth of field, becomes large. If the sheet position deviates from the focal position, the accuracy of image reading decreases, and the accuracy of image quality adjustment using the adjustment unit 400 also decreases.

[0051] For example, when adjusting color using a sensor such as a CIS or CCD, light is irradiated onto a patch on a sheet to be measured, the luminance is calculated from the amount of reflected light, and the luminance is converted into density to measure the density of the patch. If the patch is measured at a position where the sheet is out of focus in the depth of field direction, the detected luminance changes, leading to a decrease in color detection accuracy. A similar decrease in detection accuracy can also occur when a spectrophotometric unit is used as a reading means. In image position adjustment (front-back registration adjustment), if an identification mark (a mark such as a patch or a register mark described later) is read out of focus, a deviation occurs between the position of the identification mark detected from the read image information and the actual sheet position. That is, in both color adjustment and image position adjustment, it is important to read image information when the measurement target surface of the sheet is in focus. In particular, when using a CIS type sensor, which is cheaper and smaller than the CCD type but has a shallow depth of field, it is desirable to maintain the sheet in a position sufficiently close to the focus position.

[0052] 13B, it is possible to increase the intrusion amount (protrusion amount) of the opposing roller 703 into the nip line Na and reduce the gap width between the opposing roller 703 and the glass 702. However, there is a concern that a large intrusion amount of the opposing roller 703 may cause a large contact angle between the leading edge of the sheet (the downstream end in the sheet conveying direction D1) and the opposing roller 703, resulting in poor conveyance. In addition, if the intrusion amount of the upstream roller guide 705 that guides the sheet toward the opposing roller 703 is increased in accordance with the opposing roller 703 having a large intrusion amount, the contact pressure between the sheet and the upstream roller guide 705 will also increase, resulting in concerns about the generation and accumulation of paper dust and image damage.

[0053] As yet another comparative example, it is also possible to bring the glass 702 closer to the nip line Na as shown in Fig. 13(c). However, if the glass 702 is brought closer to the nip line Na while remaining parallel to the nip line Na, there is a concern that the leading edge of the sheet may get caught on the upstream end of the glass 702, so the upstream glass guide 704 is made to protrude toward the nip line Na from the glass 702. In other words, the upstream glass guide 704 is made to be closer to the nip line Na in the height direction D2 than the glass 702, or is made to protrude upward in the figure beyond the nip line Na. In this case, the contact pressure between the sheet and the upstream glass guide 704 becomes large, and there is a concern that paper dust may be generated, accumulated, or images may be damaged.

[0054] Therefore, there is a need for another configuration capable of improving the image reading accuracy, and in particular, it is desirable to prevent sheet conveyance failure and reduce the contact pressure between the sheet and the conveyance guide.

[0055] Next, the arrangement of the image reading unit 500 according to this embodiment will be described with reference to Figs. 5(a-c) and 6(a-d). Figs. 5(a-c) and 6(a-d) each show a cross section of the first reading unit 51 perpendicular to the sheet width direction.

[0056] 5(a), the sheet conveying path in the first reading unit 51 is substantially linear, and the glass 512 is inclined with respect to the nip line N1. That is, the upper surface 512a, which is the surface on the upper side (opposing roller 511 side, second side in this embodiment) in the height direction D2 of the glass 512, is inclined toward the upper side (second side) in the height direction D2 toward the downstream of the sheet conveying direction D1. It is preferable to incline the sensor C1 in accordance with the glass 512 and arrange the sensor C1 so that the depth of field direction Df1 is perpendicular to the glass 512.

[0057] More specifically, the upper surface portion 513a, which is the uppermost portion of the upstream glass guide 513, is separated (retracted) by a distance L1 from the nip line N1 of the first roller pair 501 downward in the height direction D2. Here, if the distance L1 is set to a value close to 0, the upper surface portion 513a of the upstream glass guide 513 may protrude upward beyond the nip line N1 in an actual device due to mechanical positional variations. In that case, the upper surface portion 513a, which has a short distance Ls1 to the first roller pair 501, will intrude into the nip line N1, and the sheet sent out from the nip portion 1n of the first roller pair 501 will come into strong contact with the upper surface portion 513a of the upstream glass guide 513. As a result, there is a concern that friction marks will remain on the image on the sheet due to friction with the upper surface portion 513a. Therefore, the distance L1 is set to, for example, 1 mm or more so as to absorb the mechanical positional variations described above. On the other hand, if the distance L1 is increased, the inclination of the glass 512 becomes unnecessarily large, so the distance L1 is set to, for example, 2 mm or less.

[0058] Next, the step between the upstream glass guide 513 and the upstream end 512b of the upper surface 512a of the glass 512 in the sheet conveying direction D1 will be described with reference to Fig. 5(b). In a configuration in which the upstream glass guide 513 is provided between the first roller pair 501 and the glass 512, a conveying failure may occur in which the leading edge of the sheet enters the gap between the upstream glass guide 513 and the glass 512 and gets caught on the upstream end surface of the glass 512. In particular, when the leading edge of the sheet is curved (curled) downward, the leading edge of the sheet is likely to get caught.

[0059] Therefore, in order to smoothly transfer the leading edge of the sheet from the upstream glass guide 513 to the glass 512, the upstream end 512b of the glass 512 is located on the lower side (first side) in the height direction D2 compared to at least the upper surface part 513a of the upstream glass guide 513. In other words, a step is provided between the upstream glass guide 513 and the glass 512 such that the glass 512 is retracted (separated) from the nip line N1 compared to the upstream glass guide 513.

[0060] The height L2 of the step, which is the distance in the height direction D2 between the upper surface 513a of the glass upstream guide 513 and the upstream end 512b of the glass 512, is set to, for example, 3 mm or more in consideration of sheets that tend to curl, such as thin paper. In the illustrated configuration example, the reference plate 515 is attached to an area of ​​the upper surface 512a of the glass 512 that includes the upstream end 512b, so that the height L2 of the step is more accurately measured based on the position of the upper surface of the reference plate 515 at the position of the upstream end 512b. By providing a step at such height L2, it is possible to reduce the possibility of poor conveyance of a sheet Sc with a curled leading end as shown in FIG. 5(c).

[0061] Next, the positional relationship between the opposing roller 511 and the glass 512 will be described with reference to FIG. 6(a). The gap width L3, which is the minimum width of the gap 1g between the opposing roller 511 and the glass 512 in the depth of field direction Df1, is set to, for example, about 1 mm. The gap width L3 is preferably a size that allows any type of sheet delivered from the image forming apparatus 100 to the adjustment unit 400 to pass through, regardless of the gap width variation in the actual device. In other words, it is preferable to satisfy the relationship L3>((variation of gap width in the actual device)+(maximum expected sheet thickness)). Also, in terms of reading accuracy, it is preferable to set L3 to a small value within the range in which the above relationship is established.

[0062] In the configuration example shown in FIG. 6(a), a part of the opposing roller 511 (end 511a on the glass 512 side) is disposed so as to protrude downward (toward the glass 512) beyond the nip line N1, thereby maintaining the gap width L3 at about 1 mm. In such a configuration in which a part of the opposing roller 511 enters the nip line N1, the sheet sent along the nip line N1 by the first roller pair 501 comes into contact with the surface of the opposing roller 511. However, the distance Ls2 in the sheet conveying direction D1 from the nip portion 1n of the first roller pair 501 to the rotation axis of the opposing roller 511 is sufficiently larger (for example, 10 times or more) than the protrusion amount of the opposing roller 511 relative to the nip line N1. Therefore, as shown in FIG. 6(b), the sheet S is conveyed in a gently curved state (with a small curvature) while in contact with the opposing roller 511 between the nip portions 1n and 2b of the first roller pair 501 and the second roller pair 502. As a result, the contact pressure of the sheet with the opposing roller 511 is unlikely to become large.

[0063] The arrangement and dimensions of the members in this embodiment will be further described with reference to FIG. 6(c). As described above, the upstream glass guide 513 is spaced (retracted) downward from the nip line N1 by a distance L1, and the upstream end 512b of the upper surface 512a of the glass 512 is spaced (retracted) downward from the upper surface portion 513a of the upstream glass guide 513 by a step height L2. On the other hand, the downstream end 512c of the upper surface 512a of the glass 512 is located above the upstream end 512b in the height direction D2 and below the nip portion 2n of the second roller pair 502 in the height direction D2. The distance in the height direction D2 from the nip portion 2n to the downstream end 512c of the glass 512 (the distance from the nip line N2 of the second roller pair 502 to the downstream end 512c) is set to L4. The distance L4 is set to, for example, 1 mm or more so that the sheet can be conveyed without strongly contacting the downstream end 512c regardless of the positional variation of the downstream end 512c in the actual device or the thickness of the sheet. In other words, the distance L4 is set to be approximately the same as the distance L1 from the nip line N1 to the upper surface 513a of the glass upstream guide 513 and the gap width L3 between the opposing roller 511 and the glass 512.

[0064] The roller pitch Lp, which is the distance from the nip portion 1n of the first roller pair 501 to the nip portion 2n of the second roller pair 502, is set to about 140 mm to 175 mm according to the minimum value of the sheet size (sheet length in the sheet conveying direction) supported by the adjustment unit 400. For example, to support a postcard size with a sheet length of 148 mm, the roller pitch Lp is set to less than 148 mm (specifically, about 140 mm). Also, to support a B5 size with a sheet length of 182 mm, the roller pitch Lp is set to less than 182 mm (specifically, about 175 mm).

[0065] Furthermore, the radius of each roller of the first roller pair 501 and the second roller pair 502 is, for example, about 10 mm, and the width of the glass upstream guide 513 in the sheet conveying direction D1 is, for example, about 20 mm. In this case, the width Lg of the glass 512 in the sheet conveying direction D1 is appropriately 100 mm to 135 mm. When the roller pitch Lp corresponds to the postcard size, the width Lg is 100 mm (= 140 - (10 + 20 + 10)), and when the roller pitch Lp corresponds to the B5 size, the width Lg is 135 mm (= 175 - (10 + 20 + 10)).

[0066] A preferred range of the inclination angle θ of the upper surface 512a of the glass 512 (the angle between the nip line N1 and the upper surface 512a when viewed from the sheet width direction) will be described. Within the appropriate range from the above-mentioned viewpoints, θ has a small value when the width Lg of the glass 512 is 135 mm and the height L2 of the step between the glass upstream guide 513 and the glass 512 is 3 mm. However, L1=L4. In this case, the inclination angle θ is about 1.3° from arctan(3 / 135). When the roller pitch Lp corresponds to the postcard size, Lg is 100 mm, so the inclination angle θ in this case is about 1.7° from arctan(3 / 100).

[0067] That is, for example, the inclination angle θ of the upper surface 512a of the glass 512 is preferably 1° or more, more preferably 1.5° or more, and even more preferably 2° or more. If θ is set to 1.5° or more or 2° or more, the positional variation (angle variation) of the glass 512 in the actual device is absorbed, and the actual inclination angle is expected to be 1.3° or more or 1.7° or more.

[0068] On the other hand, if the inclination angle θ of the upper surface 512a of the glass 512 is too large, the contact angle when the leading edge of the sheet contacts the upper surface 512a is large, which may cause a transport failure such as the leading edge of the sheet curling. In particular, transport failure is likely to occur when the leading edge of the sheet is curved (curled) downward. Therefore, considering that the expected degree of curl is an angle of 15° at the leading edge of the sheet with respect to the nip line N1 and the contact angle between the leading edge of the sheet and the upper surface 512a of the glass 512 is kept to 45° or less, the inclination angle θ should be set to 30° or less.

[0069] Moreover, to more reliably prevent the occurrence of transport defects, it is preferable that the inclination angle θ is small. Within the appropriate range from the above-mentioned viewpoints, θ becomes large when the width Lg of the glass 512 is 50 mm and the height L2 of the step between the glass upstream guide 513 and the glass 512 is 10 mm. In this case, the inclination angle θ is approximately 11.3° from arctan(10 / 50). Therefore, it is more preferable that the inclination angle θ is 12° or less.

[0070] The width Lg of the glass 512 is set to 50 mm or more so that the sensor C1 can be covered and the sheet can be conveyed while stabilizing its posture between the opposing roller 511. If the height L2 of the step is too large, the inclination angle θ becomes unnecessarily large without any particular improvement in the effect of preventing the leading edge of the sheet from getting caught, so the height is set to 10 mm or less.

[0071] As described above, the inclination angle θ of the upper surface 512a of the glass 512 with respect to the nip line N1 is preferably, for example, from 1° to 30°, and more preferably from 1.5° to 12°. However, depending on the specific configuration of the image reading unit 500, it is also possible to set the inclination angle θ outside this range.

[0072] In some cases, a tapered shape is provided at one or both ends in the sheet conveying direction D1 of the upper surface 512a of the glass 512 in order to prevent the sheet from getting caught or to reduce the contact pressure. In such cases, the inclination angle θ refers to the inclination angle of a flat area including a portion facing the opposing roller 511 at the reading position of the sensor C1.

[0073] Incidentally, in FIG. 6(c), the distance L4 in the height direction D2 from the nip portion 2n of the second roller pair 502 to the downstream end 512c of the glass 512 has been described. However, as shown in FIG. 6(d), the downstream end 512c is also located below the nip portion 1n of the first roller pair 501. In other words, the downstream end 512c of the glass 512 is separated (retracted) to the lower side (first side) in the height direction D2 from both the nip lines N1 and N2 of the first roller pair 501 and the second roller pair 502. The distance in the height direction D2 from the nip line N1 of the first roller pair 501 to the downstream end 512c of the glass 512 is defined as L5. In the illustrated configuration example, the nip portion 2n of the second roller pair 502 is located on the nip line N1 of the first roller pair 501, so L4=L5. When the nip portion 2n is not on the nip line N1 (the nip lines of the first roller pair 501 and the second roller pair 502 do not coincide), L4≠L5. When the nip portion 2n is lower than the nip portion 1n in the height direction D2 (lower side in the figure), L5>L4, and vice versa. <L5となる。

[0074] That is, when viewed in the sheet width direction, the upper surface 512a of the glass 512 does not intersect with the nip line N1 of the first roller pair 501. In this manner, by configuring the upper surface 512a of the glass 512 not to be positioned at the destination where the sheet is sent out from the first roller pair 501, it is possible to reduce the generation of paper dust and friction marks caused by the sheet coming into strong contact with the glass 512.

[0075] The above has explained the arrangement and dimensions of the members in first reading unit 51, but second reading unit 52 is basically configured in the same way as first reading unit 51, except that the positional relationship in height direction D2 is reversed. Note that in first reading unit 51, the arrangement based on nip line N1 of first roller pair 501 is based on the nip line of second roller pair 502, but if the two nip lines can be considered to be aligned, nip line N1 may also be based on the nip line.

[0076] The main arrangement of the second reading unit 52 will be described. An upper surface 522a, which is the surface on the lower side (opposing roller 521 side, first side in this embodiment) in the height direction D2 of the glass 522, is inclined toward the lower side (first side) in the height direction D2 toward the downstream of the sheet conveying direction D1. It is preferable to incline the sensor C2 in accordance with the glass 522 and arrange it so that the depth of field direction Df2 is perpendicular to the glass 522.

[0077] The bottom surface portion, which is the lowest part of the upstream glass guide 523, is spaced (retracted) by a distance L1 upward from the nip line of the second roller pair 502 in the height direction D2. The distance L1 is, for example, 1 mm or more and 2 mm or less. The upstream end of the glass 522 is located at least higher (on the second side) in the height direction D2 than the bottom surface portion of the upstream glass guide 523. In other words, a step is provided between the upstream glass guide 523 and the glass 522 such that the glass 522 is retracted (separated) from the nip line compared to the upstream glass guide 523. The height L2 of the step is set, for example, to 3 mm or more and 10 mm or less.

[0078] The gap width L3 of the gap 2g between the opposing roller 521 and the glass 522 is set to, for example, about 1 mm. The gap width L3 is maintained at about 1 mm by disposing the opposing roller 521 so that a part of it (the end on the glass 522 side) protrudes upward (toward the glass 522) beyond the nip line.

[0079] The downstream end of the lower surface of the glass 522 is located lower in the height direction D2 than the upstream end and higher in the height direction D2 than the nip portion 3n of the third roller pair 503. A distance L4 in the height direction D2 from the nip portion 3n to the downstream end of the glass 522 is set to, for example, 1 mm or more.

[0080] The roller pitch Lp, which is the distance from the nip portion 2n of the second roller pair 502 to the nip portion 3n of the third roller pair 503, is set to about 140 mm to 175 mm according to the minimum sheet size that the adjustment unit 400 can accommodate. The width Lg of the glass 522 in the sheet conveying direction D1 is appropriately set to 100 mm to 135 mm.

[0081] For example, the inclination angle θ of the lower surface of the glass 522 is preferably 1° or more, more preferably 1.5° or more, and even more preferably 2° or more. If θ is set to 1.5° or more or 2° or more, the position variation (angle variation) of the glass 522 in the actual device is absorbed, and the actual inclination angle is expected to be 1.3° or more or 1.7° or more. On the other hand, the inclination angle θ is preferably 30° or less, and in order to more reliably prevent the occurrence of conveyance defects, it is preferable that the inclination angle θ is small. For example, it is more preferable that the inclination angle θ is 12° or less. In other words, the inclination angle θ of the lower surface of the glass 522 with respect to the nip line is preferably, for example, 1° or more and 30° or less, and more preferably 1.5° or more and 12° or less. However, it is also possible to set the inclination angle θ outside this range depending on the specific configuration of the image reading unit 500.

[0082] (Image position adjustment) The image forming system 100S of this embodiment can adjust the execution conditions of the image forming operation performed by the image forming apparatus 100 based on information acquired using the image reading unit 500. As an example, an operation of adjusting the position (registration) of images on both sides of a sheet will be described.

[0083] 7 is a block diagram showing the system configuration of the image forming system 100S with respect to image position adjustment. The control unit 251 of the adjustment unit 400 is communicably connected to the printer controller 103 via the communication unit 450. The control unit 251 sends commands to one or more conveying motors M1 that drive the conveying roller pairs in the adjustment unit 400 and opposing roller drive motors M2 and M3 that drive the opposing rollers 511 and 521, respectively, to control the driving of each motor. The control unit 251 also sends commands to a flap moving motor M4 that moves the switching flap 422 and a sensor moving motor M5 that moves the sensors C1 and C2 to perform shading correction, to control the driving of each motor.

[0084] Furthermore, the control unit 251 detects the position of the sheet based on detection signals from sheet sensors S1 and S2 that detect the sheet, and sends commands such as to start reading image information to sensors C1 and C2, which are image sensors. The sheet sensor S1 is a sensor that detects the sheet upstream of the reading position of sensor C1 in the sheet conveying direction, and the sheet sensor S2 is a sensor that detects the sheet downstream of the reading position of sensor C1 and upstream of the reading position of sensor C2. The image processing unit 330 processes the image information read by sensors C1 and C2, and obtains information (such as data indicating the amount of correction of the image position) to be sent to the printer controller 103.

[0085] FIG. 8(a) is an example of a screen displayed on the operation unit 180, which is a paper library screen 1001 showing a list of information for each sheet used as a recording material (paper library 900 in FIG. 8). When the user touches the "image position adjustment" button 1002 in FIG. 8(a) with one of the columns showing the information for each sheet selected, a selection screen for a correction method in image position adjustment shown in FIG. 8(b) is displayed. When the user further operates the "read and adjust test page" button 1105, the printer controller 103 accepts a request to automatically adjust the image position for the selected sheet. In this case, the printer controller 103 causes the engine control unit 312 to start outputting measurement test patterns 802 and 803 for image position adjustment shown in FIG. 9(a and b) on both sides of the selected sheet. The measurement test patterns 802 and 803 are arranged with rectangular patch images 820 as identification markers at the four corners of the sheet.

[0086] When the measurement test patterns 802, 803 are formed on both sides of the sheet, the sheet is handed over from the image forming apparatus 100 to the adjustment unit 400. In the image reading section 500 of the adjustment unit 400, while the sheet is transported by a first roller pair 501, a second roller pair 502, and a third roller pair 503, the image information of the first and second sides is read in parallel by sensors C1, C2.

[0087] The image processing unit 330 (FIG. 7) of the adjustment unit 400 obtains information to be sent to the printer controller 103 based on the image information read by the sensors C1 and C2. That is, the line images read by the sensors C1 and C2 are joined in the sub-scanning direction (sheet conveying direction) to synthesize two-dimensional image data, and the edge of the sheet and the patch image 820 in the image data are detected. Then, based on the coordinates of the patch image 820 and the coordinates of the corners of the sheet, the sheet dimensions ((A) and (B) in FIG. 8(a) and (b)) and the distance from the patch image 820 to the edge of the sheet ((C) to (I)) are detected. In FIG. 8(a and b), the coordinates of the corners of the sheet are represented by (Xm1, Ym1) and (Xm2, Ym2) for m=0, 1, 2, 3, and the coordinates of the patch image 820 are represented by (Xm1, Ym1) and (Xm2, Ym2) for m=4, 5, 6, 7. In addition, the coordinate axes are represented as an X-axis in the main scanning direction of the image reading unit 500 and a Y-axis in the sub-scanning direction (sheet conveying direction).

[0088] Image processing unit 330 detects image distortion and image misalignment with respect to the sheet based on the values ​​of (A) to (I), and calculates geometric adjustment values ​​as parameters for correcting them. Examples of geometric adjustment parameters are a lead position that defines the start position of an image in the sub-scanning direction (sheet transport direction), a side position that defines the start position of an image in the main scanning direction (sheet width direction), and a magnification ratio for enlarging or reducing an image. Other examples of geometric adjustment parameters are squareness that transforms an image to match the non-squareness of a sheet (degree of distortion of a parallelogram or trapezoid with respect to an ideal rectangle), and an amount of rotation of an image.

[0089] The geometric adjustment values ​​calculated by the image processing unit 330 are stored in the paper library 900 in the image forming apparatus 100 via the communication unit 450. When the printer controller 103 executes an image forming operation according to a user job, it reads the geometric adjustment values ​​corresponding to the sheet to be used in the current image forming operation from the paper library 900 and causes the image shape correcting unit 320 to execute shape correction based on the geometric adjustment values. Then, the engine control unit 312 executes the image forming operation based on the image data after the shape correction, making it possible to output an image in which the positional deviation and distortion of the image have been corrected.

[0090] Here, the case where image position adjustment is performed based on an explicit instruction from the user has been described. However, image position adjustment using measurement test patterns 802, 803 may be performed autonomously, for example, when the printer controller 103 determines that calibration is necessary. For example, when a user job is input, image position adjustment may be automatically started as a process before outputting a deliverable, or image position adjustment may be automatically inserted at a predetermined timing during execution of the user job.

[0091] The geometric adjustment value is an example of the setting of the execution condition of the image forming operation performed by the image forming apparatus 100, and color adjustment may be performed using the adjustment unit 400, for example. As an example, when the printer controller 103 accepts a request for color adjustment by operating the operation unit 180, the printer controller 103 causes the image forming apparatus 100 to output a test chart in which color patches are arranged in a predetermined pattern. The adjustment unit 400 reads the density of each patch using the image reading unit 500, and feeds back a density correction value to the image forming apparatus 100 based on the read density value. The setting of the execution condition of the image forming operation that is changed in the case of color adjustment is, for example, a gamma value of a lookup table that indicates the relationship between image data and the exposure amount of the laser scanner unit 107. As with the image position adjustment, the color adjustment may be performed autonomously, for example, at a timing when the printer controller 103 determines that calibration is necessary.

[0092] (Flow of Control) Next, the control flow of image position adjustment performed using the above-mentioned image forming apparatus 100 and adjustment unit 400 will be described along the flowchart of Fig. 10 with reference to the block diagram of Fig. 7, Figs. 11(a, b), and 12(a, b). Each step of this flowchart is realized by the printer controller 103 reading and executing a program from a storage device, and sending instructions to the engine control unit 312 and the control unit 251 of the adjustment unit 400 (Fig. 7) as necessary.

[0093] When a user inputs an instruction to execute an image forming operation (user job) requesting output of a product (S01: Y), the image forming apparatus 100 and the adjustment unit 400 are made to wait at a home position (HP). At this time, the switching flap 422 of the adjustment unit 400 waits at an upward position (position in FIG. 11(a)) to guide the sheet S to the through path 431 (S02). After that, the image forming apparatus 100 forms an image on the sheet S (S03), and the sheet S is conveyed to the adjustment unit 400 as shown in FIG. 11(a) (S04). Then, the sheet S is conveyed along the through path 431 by the roller pairs (401, 501, 502, 503, 406) of the through path 431, and the sheet S is delivered to the finisher 600, which is a downstream device, as shown in FIG. 11(b), and is stacked on the tray of the finisher 600 (S05). When the above process is repeated up to the final sheet of the job (S06), the job is completed.

[0094] On the other hand, when a job for adjusting an image position is input by pressing the button 1105 in FIG. 9B (S01:N), the image forming apparatus 100 and the adjustment unit 400 are made to wait at the home position (HP). At this time, the switching flap 422 of the adjustment unit 400 waits at a downward position (position in FIG. 12A) to guide the sheet S to the discharge path 432 (S10). In addition, in preparation for reading image information, the amount of light is optimized by a shading correction operation of the sensors C1 and C2 (S10). Thereafter, measurement test patterns 802 and 803 (FIGS. 8A and 8B) are formed on the sheet S (S11), and the sheet S is conveyed to the adjustment unit 400 (S12).

[0095] As shown in FIG. 12(a), the sheet S conveyed to the adjustment unit 400 passes through the image reading section 500, whereby image information on the first and second sides of the sheet S is read, and the positional deviation of the patch image 820 relative to the sheet and the shape of the sheet S are measured (S13). At this time, the sensor C1 starts reading when a predetermined time has elapsed since the leading edge of the sheet S passed the sheet sensor S1. Also, the sensor C2 starts reading when a predetermined time has elapsed since the leading edge of the sheet S passed the sheet sensor S2. Based on the read image information, the image processing section 330 calculates a geometric adjustment value, which is notified to the image forming apparatus 100 through the communication section 250 and stored in the paper library 900, thereby completing the image position adjustment (S14). Then, as shown in FIG. 12(b), the sheet S is conveyed to the discharge path 432 by the switching flap 422 and discharged to the discharge tray 430 (S15). When the above process is repeatedly executed up to the final sheet of the job (S06), the job is completed.

[0096] In this embodiment, the automatic adjustment operation using the adjustment unit 400 has been described using image position adjustment (front-back registration) as an example, but the same operation is basically performed in the case of color adjustment. In this case, the image for measurement is changed from the position detection patterns (802, 803) as shown in Figure 9 (a, b) to a color adjustment chart in which patch images with gradation are arranged.

[0097] (Other embodiments) In the above embodiment, a configuration in which a CIS is used as the reading means has been described, but the reading means may be a CCD image sensor including a reduction optical system including multiple mirrors and a charge-coupled device as a light receiving element. Also, the reading means may be a spectrophotometer including a diffraction grating that separates the reflected light from the sheet into wavelengths and a light receiving element that measures the light intensity of each wavelength. Furthermore, the image information read by the reading means may be used for purposes other than adjusting the execution conditions of the image forming operation, and for example, the read image information may be compared with the image data used in the image formation to perform inspection (management of image quality and detection of image defects).

[0098] In the above embodiment, the opposing rollers 511 and 521 are exemplified as the opposing members, but the opposing members may be, for example, plate-shaped guide members. Such guide members may be biased toward the glass sheets 512 and 522 by spring members.

[0099] In the above embodiment, the reading device connected to the image forming apparatus has been described, but the present technology may be applied to a reading device arranged in a common housing with the image forming apparatus. That is, the image forming system may be a unit in which a part having an image forming function and a part having a reading function are integrated into one device. For example, the reversing unit 136 in FIG. 1 may be provided with a reading unit 200 similar to the first reading unit 51 in the above embodiment. The present technology may be applied not only to a reading device that reads a sheet on which an image is formed by an image forming apparatus, but also to a document reading device that reads image information from a document. [Explanation of symbols]

[0100] 100...image forming apparatus / 100S...image forming system / 400...reading device / 501...first roller pair / 502...second roller pair / 503...third roller pair / 511...opposing member, first opposing member (opposing roller) / 512...transparent member, first transparent member (glass) / 513...transport guide (upstream glass guide) / 521...opposing member, second opposing member (opposing roller) / 522...transparent member, second transparent member (glass) / C1...reading means, first reading means (sensor) / C2...reading means, second reading means (sensor) / D1...sheet transport direction / D2...height direction / N1...straight line (nip line)

Claims

1. A reading device that reads image information on a sheet on which an image is formed by an image forming apparatus, a first roller pair that receives the sheet from the image forming apparatus and conveys the sheet in a sheet conveying direction; a second roller pair disposed downstream of the first roller pair in the sheet conveying direction and conveying the sheet, the second roller pair disposed so as to overlap a nip line passing through a nip portion of the first roller pair and extending in the sheet conveying direction when viewed in a sheet width direction perpendicular to the sheet conveying direction; a light-transmitting member that is disposed between the first roller pair and the second roller pair in the sheet conveying direction and on a first side of the nip line in a height direction perpendicular to the sheet conveying direction and the sheet width direction; and a reading unit that reads image information of the sheet conveyed from the first roller pair toward the second roller pair through the transparent member; an opposing member that is provided on a second side of the transparent member opposite to the first side in the height direction, the opposing member forming a gap between the transparent member and the opposing member through which the sheet passes, and opposing the reading means via the transparent member; Equipped with When viewed in the sheet width direction, a surface of the second side in the height direction of the transparent member is inclined toward the second side in the height direction downstream in the sheet conveying direction, When viewed in the sheet width direction, a downstream end of the surface in the sheet conveying direction is located on the first side in the height direction with respect to the nip line. A reading device comprising:

2. A reading device for reading image information on a sheet on which an image is formed by an image forming apparatus, comprising: a first roller pair that receives the sheet from the image forming apparatus and conveys the sheet in a sheet conveying direction; a second roller pair disposed downstream of the first roller pair in the sheet conveying direction and conveying the sheet, the second roller pair disposed so as to overlap a nip line passing through a nip portion of the first roller pair and extending in the sheet conveying direction when viewed in a sheet width direction perpendicular to the sheet conveying direction; a light-transmitting member that is disposed between the first roller pair and the second roller pair in the sheet conveying direction and on a first side of the nip line in a height direction perpendicular to the sheet conveying direction and the sheet width direction; and a reading unit that reads image information of the sheet conveyed from the first roller pair toward the second roller pair through the transparent member; an opposing member that is provided on a second side of the transparent member opposite to the first side in the height direction, the opposing member forming a gap between the transparent member and the opposing member through which the sheet passes, and opposing the reading means via the transparent member; Equipped with When viewed in the sheet width direction, a surface of the second side in the height direction of the transparent member is inclined toward the second side in the height direction downstream in the sheet conveying direction, The nip line is a first nip line, When viewed in the sheet width direction, a downstream end of the surface in the sheet conveying direction is located on the first side in the height direction with respect to a second nip line that passes through a nip portion of the second roller pair and extends in the sheet conveying direction. A reading device comprising:

3. A reading device for reading image information on a sheet on which an image is formed by an image forming apparatus, comprising: a first roller pair that receives the sheet from the image forming apparatus and conveys the sheet in a sheet conveying direction; a second roller pair disposed downstream of the first roller pair in the sheet conveying direction and conveying the sheet, the second roller pair disposed so as to overlap a nip line passing through a nip portion of the first roller pair and extending in the sheet conveying direction when viewed in a sheet width direction perpendicular to the sheet conveying direction; a light-transmitting member that is disposed between the first roller pair and the second roller pair in the sheet conveying direction and on a first side of the nip line in a height direction perpendicular to the sheet conveying direction and the sheet width direction; and a reading unit that reads image information of the sheet conveyed from the first roller pair toward the second roller pair through the transparent member; an opposing member that is provided on a second side of the transparent member opposite to the first side in the height direction, the opposing member forming a gap between the transparent member and the opposing member through which the sheet passes, and opposing the reading means via the transparent member; a conveyance guide provided between the first roller pair and the transparent member in the sheet conveyance direction and on the first side in the height direction with respect to the nip line, the conveyance guide guiding the sheet; Equipped with When viewed in the sheet width direction, a surface of the second side in the height direction of the transparent member is inclined toward the second side in the height direction downstream in the sheet conveying direction, When viewed in the sheet width direction, the conveying guide does not protrude toward the second side in the height direction with respect to the nip line. A reading device comprising:

4. an upstream end of the surface of the transparent member in the sheet conveying direction is located on the first side relative to a portion of the conveying guide closest to the second side in the height direction; 4. The reading device according to claim 3,

5. an upstream end of the surface in the sheet conveying direction is located on the first side within a range of 3 mm to 10 mm from a portion of the conveying guide closest to the second side in the height direction; a downstream end of the surface in the sheet conveying direction is located on the second side in the height direction from the upstream end and on the first side with respect to the nip line; 4. The reading device according to claim 3,

6. The inclination angle of the surface with respect to the nip line is greater than or equal to 1° and less than or equal to 30°.

6. The reading device according to claim 1, wherein the reading device is a reading device for reading a document.

7. The inclination angle of the surface with respect to the nip line is greater than or equal to 1.5° and less than or equal to 12°.

7. The reading device according to claim 6,

8. a portion of the opposing member protruding from the second side in the height direction to the first side with respect to the nip line, the gap between the opposing member and the transparent member is located on the first side in the height direction with respect to the nip line; 8. The reading device according to claim 1, wherein the reading device is a reading device for reading a document.

9. The opposing member is a roller that rotates around an axis extending in the sheet width direction.

9. The reading device according to claim 1, wherein the reading device is a reading device for reading a document.

10. a reference portion for performing shading correction of the reading means, the reference portion being provided on the surface of the transparent member at a position different from the opposing member in the sheet conveying direction; the reading means is movable between a first position for reading image information from the sheet conveyed through the gap and a second position for reading the reference portion in order to perform the shading correction.

10. The reading device according to claim 1, wherein the reading device is a reading device for reading a document.

11. the transparent member, the reading means, and the opposing member are a first transparent member, a first reading means, and a first opposing member, respectively; a third roller pair disposed downstream of the second roller pair in the sheet conveying direction and configured to convey the sheet, the third roller pair overlapping the nip line that passes through the nip portion of the first roller pair and extends in the sheet conveying direction when viewed in the sheet width direction; a second transparent member that is disposed between the second roller pair and the third roller pair in the sheet conveying direction and on the second side in the height direction with respect to the nip line, and that transmits light; a second reading means for reading image information of the sheet conveyed from the second roller pair toward the third roller pair through the second transparent member; a second opposing member that is provided on the first side in the height direction with respect to the second transparent member, that forms a gap between the second transparent member and the second opposing member through which the sheet passes, and that faces the second reading means via the second transparent member; Further comprising: When viewed in the sheet width direction, a surface of the second transparent member on the first side in the height direction is inclined toward the first side in the height direction downstream in the sheet conveying direction, an inclination angle of the first side surface of the second transparent member with respect to the nip line in the height direction is greater than or equal to 1° and less than or equal to 30°; 11. A reading device according to any one of claims 1 to 10.

12. an image forming apparatus for forming an image on a sheet; A reading device according to claim 1 , which reads image information on a sheet on which an image is formed by the image forming device; An image forming system comprising:

Images