Image reading device and image forming system

Abstract

To provide an image reader allowing for improving the accuracy of image reading.SOLUTION: An image reader comprises a first rotating-body pair 401 that nips / carries a sheet, a second rotating-body pair 402 that nips / carries the sheet downstream of the first rotating-body pair 401, and reading means 701 that reads image information of the sheet carried by the second rotating-body pair 402. A second nip portion N2 of the second rotating-body pair 402 comprises first and second nip regions N2a, N2b to nip the sheet and a recess region N2c lying between the first nip region N2a and the second nip region N2b. The first rotating-body pair 401 forms a first nip portion N1 so as to nip the sheet in a region overlapping with the recess region N2c in a rotary axis C1 direction and delivers the sheet to the second nip portion N2 in a state nipped / carried by the first nip portion N1.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to an image reading device for reading an image on a sheet and an image forming system. [Background technology]

[0002] Conventionally, an image forming system has been disclosed that includes an image forming device that forms an image on a sheet and an image reading device that reads the image formed on the sheet by the image forming device using an image scanner (see Patent Document 1). This image forming system compares the image data (image information) read by the image reading device with the image data used when the image forming device forms the image, and performs front / back position adjustment, density adjustment, color adjustment, etc. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-166916 Summary of the Invention [Problem to be solved by the invention]

[0004] Such an image forming system can be configured to perform the processes from image formation to sheet reading in a continuous manner. However, the image reading device used in such an image forming system must have pairs of conveying rollers and a reading sensor arranged along the conveying path, making it difficult to reduce the size of the device.

[0005] Therefore, the present invention provides: The device has been made smaller The object is to provide an image reading device and an image forming system. [Means for solving the problem]

[0006] One aspect of the present invention is an image reading device that reads image information of a sheet discharged from an image forming device that forms an image on the sheet, the image reading device comprising: a plurality of roller pairs to which drive is transmitted and which nip and transport the sheet discharged from the image forming device; a reading unit that reads image information of the sheet transported by the plurality of roller pairs; and a detection sensor that detects the sheet upstream of the reading unit in the sheet transport direction, wherein a first roller pair that is closest to the reading unit on the upstream side of the reading unit in the sheet transport direction among the plurality of roller pairs comprises a first nip region and a second nip region that nip the sheet, and a recessed region that does not nip the sheet between the first nip region and the second nip region, and the detection sensor is disposed so that at least a portion of the detection sensor is within the recessed region when viewed from a rotation axis direction perpendicular to the sheet transport direction. The image reading device is characterized in that the first roller pair is composed of a first rotating body including a rotating portion extending continuously in the direction of the rotation axis between the first nip area and the second nip area, a first rotating portion that forms the first nip area between itself and the first rotating body, a second rotating portion that forms the second nip area between itself and the first rotating body, and a second rotating body having the recessed area formed between the first rotating portion and the second rotating portion, and the first rotating body is arranged below the second rotating body. [Effects of the Invention]

[0007] According to the present invention, Miniaturizing image reading devices and image forming systems This becomes possible. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of an image forming system according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing a control configuration of the image forming system. [Figure 3] Schematic diagram of the adjustment unit. [Figure 4] Schematic diagram of the front and back register section. [Figure 5] 1A is an image showing a display screen of a sheet library, and FIG. 1B is an image showing a selection screen for a correction method for geometric adjustment values. [Figure 6] FIG. 1A is a diagram showing a test pattern for front-to-back registration formed on the front side, and FIG. 1B is a diagram showing a test pattern for front-to-back registration formed on the back side. [Figure 7] 10 is a flowchart showing an example of control of the image forming system. [Figure 8] 1A and 1B are schematic diagrams for explaining a sheet conveying operation in a normal job, in which (a) and (b) show different states. [Figure 9] 1A to 1C are schematic diagrams for explaining a sheet conveying operation in a front-to-back registration job, each showing a different state. [Figure 10] FIG. [Figure 11] FIG. [Figure 12] (a) A view in the sheet conveying direction showing a sheet in a bent state being conveyed by an upstream conveying roller pair, and (b) A view in the sheet conveying direction showing a sheet in a state in which the bend is suppressed being conveyed by an upstream conveying roller pair. [Figure 13] FIG. 10 is a plan view showing a front and back register unit according to a second embodiment. [Figure 14] FIG. 11 is a plan view showing a front and back register unit according to a third embodiment. [Figure 15] FIG. 10 is a plan view showing a front and back register unit according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an image reading device and an image forming device according to each embodiment will be described with reference to the drawings. The dimensions, materials, shapes, relative positions, etc. of the components described in the following embodiments are not intended to limit the scope of application of the present technology to only those unless otherwise specified.

[0010] First Embodiment [Image formation system overview] FIG. 1 is a schematic diagram showing an image forming system 100S according to this embodiment. The image forming system 100S includes an image forming apparatus 100, an adjustment unit 400, and a finisher 600. In this embodiment, the image forming apparatus will be described taking the image forming apparatus 100, which is an electrophotographic laser beam printer, as an example, but is not limited thereto, and the image forming apparatus may also be an inkjet printer or a dye-sublimation printer. The adjustment unit 400 is the image reading device of this embodiment.

[0011] The housing 101 of the image forming apparatus 100 is equipped with an image forming engine 102 and a control board storage section (not shown) that houses a printer controller 103 (see FIG. 2) that controls the operation of the image forming system 100S. The image forming engine 102 as an image forming section includes an optical processing mechanism 10 and a fixing processing mechanism 20 that form an image on a recording material by an image formation process, and a feeding processing mechanism 30 and a conveying processing mechanism 40 that feed and convey a rectangular sheet 1 used as the recording material. The recording material can be paper such as plain paper or cardboard, paper with a surface treatment such as coated paper or embossed paper, plastic film, cloth, or other sheets.

[0012] The optical processing mechanism 10 includes stations 120, 121, 122, and 123 that form toner images of yellow, magenta, cyan, and black, and an intermediate transfer belt 106. In each of the stations 120-123, a primary charger 111 charges the surface of a photosensitive drum 105, a drum-shaped photosensitive member. A laser scanner unit 107 exposes the photosensitive drum 105 based on command signals generated based on image data and transmitted to the laser scanner unit 107. The laser scanner unit 107 includes a laser driver that turns on and off a laser beam emitted from a semiconductor laser (not shown). The laser scanner unit 107 distributes the laser beam from the semiconductor laser in the main scanning direction (the width direction of the sheet) using a rotating polygonal mirror and guides it to the photosensitive drum 105 via a reflecting mirror 109. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 105.

[0013] The developing unit 112 contains a developer containing toner 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, thereby visualizing the electrostatic latent image carried on the photosensitive drum 105 as a toner image. The toner image carried on the photosensitive drum 105 is transferred (primary transfer) to the intermediate transfer belt 106, to which a voltage of the opposite polarity to the normal charging polarity of the toner is applied. When forming a color image, the toner images formed by the four stations 120 to 123 are transferred in multiple layers onto the intermediate transfer belt 106 so that they overlap each other, forming a full-color toner image on the belt.

[0014] Meanwhile, the feeding processing mechanism 30 feeds the sheets 1 one by one from a sheet storage 113 inserted retractably into the 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 (secondary transfer) onto the sheet 1 by the transfer roller 114.

[0015] Around the intermediate transfer belt 106, there are arranged an image formation start position detection sensor 115 for determining the print start position when forming an image, a feed timing sensor 116 for timing the feeding of the sheet 1, and a density sensor 117. The density sensor 117 measures the density of a test patch image carried on the intermediate transfer belt 106. The printer controller 103 adjusts the operating conditions of the optical processing mechanism 10 (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.

[0016] The fixing process mechanism 20 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 1, a pressure belt 152 for pressing the sheet 1 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. The fixing roller 151 is a hollow roller and has an internal heater. The first fixing device 150 applies heat and pressure to the toner image on the sheet while nipping and transporting the sheet 1 between the fixing roller 151 and the pressure belt 152, which are a pair of rotating bodies. This melts the toner particles and then fixes them, thereby fixing the image on the sheet 1.

[0017] The second fixing device 160 is disposed downstream of the first fixing device 150 in the conveyance path of the sheet 1. The second fixing device 160 has the function of increasing the glossiness of the image fixed by the first fixing device 150 and ensuring fixation of the image to the sheet 1. Similar to 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 1 while conveying it, and a second post-fixing sensor 163 that detects the completion of the fixing process by the second fixing device 160.

[0018] Depending on the type of sheet 1, there may be cases where it is not necessary to pass the sheet 1 through the second fixing device 160. In such cases, the image forming apparatus 100 has a bypass conveying path 130 for discharging the sheet 1 without passing through the second fixing device 160 in order to reduce energy consumption. The sheet 1 sent out from the first fixing device 150 is guided by a first switching flapper 131 to either the second fixing device 160 or the bypass conveying path 130.

[0019] The sheet 1 that has passed through the second fixing device 160 or the bypass conveying path 130 is guided by the second switching flapper 132 to either the discharge conveying path 139 or the reverse conveying path 135. The position of the sheet 1 that has been conveyed into the reverse conveying path 135 is detected by the reverse sensor 137, and the downstream end (leading end) and upstream end (trailing end) in the sub-scanning direction (the direction in which the sheet is conveyed) are swapped by a switchback operation performed by the reversing unit 136. In the case of double-sided printing, the sheet 1 with an image formed on its front side is transported again toward the transfer roller 114 via the re-conveying path 138, with its leading and trailing ends swapped by the reversing unit 136, and an image is formed on the back side opposite to the front side.

[0020] The sheet 1 on which image formation for single-sided printing has been completed, or the sheet 1 on which image formation for the back side has been completed in double-sided printing, is discharged to the outside of the image forming apparatus 100 by discharge rollers 139a (discharge section) provided on the discharge conveyance path 139. Note that a switching flapper 134 is provided between the reversing conveyance path 135 and the discharge conveyance path 139, which can guide the sheet 1 switched back by the reversing section 136 toward the discharge conveyance path 139, and is configured so that the front or back of the sheet 1 when discharged from the image forming apparatus can be selected. Note that an image reading device 190 that reads image information from a document is provided above the image forming apparatus 100.

[0021] 2, image forming apparatus 100 includes printer controller 103 as control means for overall control of the operation of image forming system 100S (see FIG. 1), and engine control unit 312 for controlling image forming engine 102 (see FIG. 1). Printer controller 103 is a control board on which at least one processor (hereinafter referred to as CPU) 301, memory 302, and external interface (hereinafter referred to as I / F) 303 are mounted. Memory 302 includes a transient storage medium and a non-transient storage medium, and serves as a storage location for programs and data, as well as a workspace for CPU 301 to execute programs.

[0022] The engine control unit 312 causes the image forming engine 102 to perform the image forming process described above to form an image on a sheet, based on command signals from the printer controller 103, etc. For example, the engine control unit 312 controls the operations of a conveying motor 311 that drives rollers that convey a sheet, a first switching flapper 131, and a second switching flapper 132, based on detection signals from the first post-fixing sensor 153, the second post-fixing sensor 163, and the reversal sensor 137.

[0023] 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 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 input means, such as physical keys such as a numeric keypad and a print execution button, and a touch panel function of the display, that allow the user to 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 surface treatment is performed, of a sheet set in a certain sheet storage cabinet 113 (see FIG. 1), to the printer controller 103. The input sheet attributes are registered in a sheet library 900 stored in memory 302.

[0024] The printer controller 103 is connected to an external wired or wireless communication network via an external interface (I / F) 303, and is capable of communicating with an external computer (not shown). The printer controller 103 is also connected to the control circuits of devices (in this embodiment, the adjustment unit 400 and the finisher 600) that are connected to the image forming apparatus 100 and that constitute the image forming system 100S. The printer controller 103 communicates with these devices to coordinate the operations of the image forming apparatus 100 and each device. The control configuration of the adjustment unit 400 will be described later.

[0025] [General configuration of the adjustment unit] Next, a schematic configuration of adjustment unit 400, which is an image reading device according to the present embodiment shown in FIG. 1 and reads image information from a sheet discharged from image forming apparatus 100, will be described. Generally, image forming apparatuses that use a printing method for forming an image on a cut sheet, such as an electrophotographic method or an inkjet method, form an image on the sheet based on one side of a rectangular sheet. Therefore, the positional accuracy between the outline of the sheet and the image formed on the sheet, and the relative positional accuracy between the image on the front side and the image on the back side of the sheet, or the so-called front-to-back register accuracy, depend on the cutting accuracy of the sheet (length, width, perpendicularity, and parallelism).

[0026] When the image forming apparatus 100 forms an image on a sheet, the image forming system 100S of this embodiment adjusts the relative positions of the images on the front and back sides of the sheet (front-to-back registration) by adjusting the position of the image relative to the outline (outer shape) of the sheet, the magnification of the image, etc. Specifically, when performing front-to-back registration, the image forming system 100S first forms a test pattern 820 (see FIG. 6(a)) on the front and back sides of the sheet using the image forming apparatus 100. For example, the test pattern 820 includes a plurality of rectangular images (patch images) formed near the outer edge of the sheet.

[0027] Thereafter, adjustment unit 400 reads test pattern 820 on the sheet and transmits (feeds back) information based on the reading results to image forming apparatus 100. Image forming apparatus 100 performs front-to-back registration based on the information received from adjustment unit 400. By performing such front-to-back registration, image forming system 100S of the present embodiment can improve the accuracy of front-to-back registration even when there is variation in the cutting of the sheet.

[0028] In image forming system 100S of this embodiment, adjustment unit 400 is installed between image forming apparatus 100 and finisher 600 in the horizontal direction (left-right direction in FIG. 1, Y direction). That is, in this embodiment, the upstream device of adjustment unit 400 is image forming apparatus 100, and the downstream device of adjustment unit 400 is finisher 600. Finisher 600 has a processing section 601 that performs processes such as cutting margins of sheets, binding, and saddle processing, and discharges the processed sheets or sheet bundle (or sheets received from the upstream device if no processing is required) as a deliverable product of image forming system 100S.

[0029] The upstream and downstream devices of the adjustment unit 400 vary depending on the configuration of the image forming system 100S. For example, the adjustment unit 400 does not necessarily need to be directly connected to the image forming apparatus 100. An intermediate unit may be disposed between the image forming apparatus 100 and the adjustment unit 400, and the adjustment unit 400 may receive sheets from the intermediate unit. An example of the intermediate unit is a device that performs a coating process to apply a transparent toner to the image surface of an image-formed sheet to impart gloss. Also, 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 serve as a cover into a sheet stack, and a stacker that can be moved by a cart while holding a large number of finished products.

[0030] 3, adjustment unit 400 includes an inlet 441 that receives sheets discharged from image forming apparatus 100 into adjustment unit 400, and a first discharge port (discharge port) 442 that discharges the sheets toward finisher 600 (see FIG. 1). Adjustment unit 400 also includes a through path 430 that is formed to linearly connect inlet 441 and first discharge port 442 along a substantially horizontal direction (Y direction), and a discharge path 432 that branches off from the middle of through path 430 and is formed facing upward. Adjustment unit 400 also includes a second discharge port 443 that discharges sheets received from inlet 441 to the outside of the apparatus via discharge path 432, and a discharge tray 423 that is provided at the top of adjustment unit 400 and on which sheets discharged from second discharge port 443 are stacked. The through path 430 is a first sheet transport path (sheet transport path) in this embodiment, the discharge path 432 is a second sheet transport path in this embodiment, and the discharge tray 423 is a sheet stacking means in this embodiment.

[0031] On the through path 430, there is provided an inlet conveyance roller pair 401 that is arranged facing the receiving port 441 and conveys the sheet received from the receiving port 441 toward the inside of the adjustment unit 400. Also on the through path 430, there is provided an outlet conveyance roller pair 405 that is arranged facing the first discharge port 442 and conveys the sheet from the first discharge port 442 toward the finisher 600. Also on the through path 430, there is provided a front-to-back registration unit 700 that reads the sheet while conveying it, downstream of the inlet conveyance roller pair 401 and upstream of the outlet conveyance roller pair 405 in the sheet conveyance direction Y2 by the inlet conveyance roller pair 401.

[0032] The inlet conveying roller pair 401, which serves as a first pair of rotating bodies (first conveying means), includes a drive roller 401a and a driven roller 401b, which are rotating bodies disposed opposite each other. For example, the inlet conveying roller pair 401 is configured with the drive roller 401a, which is one of the pair of rotating bodies, and the driven roller 401b, which is the other of the pair of rotating bodies. The drive roller 401a is driven by a conveying motor 452 (see FIG. 2), which serves as a driving means, and is supported to rotate about a rotation axis C1 (see FIG. 10), which is disposed along the main scanning direction (X direction). In this embodiment, the main scanning direction is substantially horizontal. The drive roller 401a is disposed above the through path 430 in the sheet thickness direction (the vertical direction in FIG. 3).

[0033] The driven roller 401b is supported so as to be rotatable about a rotation axis parallel to the rotation axis C1 of the drive roller 401a, and is disposed below the through-path 430 in the sheet thickness direction. An entrance nip N1 is formed between the drive roller 401a and the driven roller 401b as a first nip that holds the sheet.

[0034] The inlet conveying roller pair 401 conveys a sheet discharged from the image forming apparatus 100 in a conveying direction Y2 along the through path 430 toward the front and back register section 700 while nipping the sheet at an inlet nip N1 between the rotating drive roller 401a and driven roller 401b. The conveying direction Y2 as the sheet conveying direction is a direction (sub-scanning direction) toward the left along the through path 430 and is perpendicular to the main scanning direction (direction of the rotation axis C1). At this time, the inlet conveying roller pair 401 absorbs the difference in sheet conveying speed between the image forming apparatus 100 and the adjustment unit 400, enabling the sheet to be conveyed at a conveying speed suitable for sheet reading in the front and back register section 700. As a result, the adjustment unit 400 of this embodiment improves the reading accuracy when the sheet is read by the front and back register section 700.

[0035] The pair of exit conveying rollers 405 includes a drive roller 405a that rotates facing each other, and a driven roller 405b that faces the drive roller 405a. The drive roller 405a is driven by a conveying motor 452, and an exit nip portion N5 that holds the sheet between the drive roller 405a and the driven roller 405b. The pair of exit conveying rollers 405 conveys the sheet that has been read by the front and back register unit 700 toward the finisher 600 while holding it in the exit nip portion N5.

[0036] At a branching point 431 between the discharge path 432 and the through path 430, there is disposed a switching flapper 422, which is a guide member that can switch the conveyance path of a sheet conveyed along the upstream portion of the through path 430, between the downstream portion of the through path 430 and the discharge path 432. Furthermore, in the discharge path 432, conveyance roller pairs 415, 416, 417, and 418 for conveying the sheet are disposed at a plurality of positions along the sheet conveyance direction in the discharge path 432. These conveyance roller pairs 415 to 418 convey the sheet along the discharge path 432 toward the second discharge outlet 443.

[0037] As shown in FIG. 4, the front and back registration unit 700 includes a contact image sensor (hereinafter, CIS) 701 (front CIS) and a CIS 702 (rear CIS) disposed downstream of the CIS 701 in the conveying direction Y2. The CIS 701 reads the outline of a sheet conveyed along the through path 430 and an image formed on the sheet from the bottom surface (front surface, first surface) of the sheet at a first reading position P1. Specifically, the first reading position P1 is the optical axis position of an optical system (lens array 7c in this embodiment) that guides reflected light from the bottom surface of the sheet to the imaging element of the CIS 701. Note that in this embodiment, reading the outline of a sheet and an image formed on a sheet is also referred to as sheet reading.

[0038] Furthermore, the CIS 702 reads the sheet conveyed along the through path 430 from its upper surface (rear surface, second surface) at a second reading position P2. Specifically, the second reading position P2 is the optical axis position of an optical system (lens array 7c in this embodiment) for guiding reflected light from the upper surface of the sheet to the imaging element of the CIS 702. The CIS 701 is a first reading means (reading means) in this embodiment that reads image information on the first surface of the sheet, and the CIS 702 is a second reading means in this embodiment that reads image information on the second surface opposite to the first surface of the sheet.

[0039] In this embodiment, by using a CIS to read the sheet, it is possible to read the sheet while conveying it without moving the sensor, thereby shortening the time required to read the sheet. Also, by using an image sensor with a life-size optical system, it is possible to make the device more compact than a sensor with a reduction optical system (such as a CCD).

[0040] Although the CISs 701 and 702 are located in different positions, they share a common configuration. Specifically, the CISs 701 and 702 each include an LED array 7a as a light source, a sensor array 7b consisting of an imaging device such as a CMOS, and a lens array 7c that focuses light reflected from the conveyed sheet onto the sensor array 7b. The lens array 7c is made up of multiple gradient index lenses that form an equal-magnification optical system. The LED array 7a, sensor array 7b, and lens array 7c are arranged in the main scanning direction (the width direction of the sheet) across the entire range in which the CISs 701 and 702 can read image information.

[0041] The front and back registration unit 700 further has a transparent guide 703 and a black guide 705 that guide the conveyed sheet at the first reading position P1. The transparent guide 703 is disposed below the through path 430 and above the CIS 701 in the thickness direction of the sheet (the up-and-down direction in FIG. 4), and the black guide 705 is disposed above the through path 430 in the thickness direction of the sheet.

[0042] Furthermore, the front and back registration unit 700 has a transparent guide 704 and a black guide 706 that guide the conveyed sheet at the second reading position P2. The transparent guide 703 is disposed above the through path 430 in the thickness direction of the sheet and below the CIS 701, and the black guide 706 is disposed below the through path 430 in the thickness direction of the sheet.

[0043] The transparent guides 703 and 704 are made of a transparent material that transmits light reflected from the sheet. The black guides 705 and 706 are components that form the background when the CISs 701 and 702 scan the sheet, and are low-brightness, for example, black, components that provide a clear contrast with the sheet. The black guides 705 and 706 are arranged opposite the transparent guides 703 and 704, respectively, with a predetermined gap therebetween that allows the sheet to pass through.

[0044] The transparent guide 703 and the black guide 705 regulate the position of the sheet in the focal depth direction (sheet thickness direction) at the reading position P1, and the transparent guide 704 and the black guide 706 regulate the position of the sheet in the focal depth direction at the reading position P2. Note that instead of a configuration in which the transparent guides 703 and 704 are provided separately from the CISs 701 and 702, the transparent guides may be integrated with the CISs as part of a housing that houses the sensor arrays.

[0045] The front and back registration section 700 also has an upstream conveying roller pair 402, an intermediate conveying roller pair 403, and a downstream conveying roller pair 404 for conveying the sheet in the conveying direction Y2 along the through path 430. The upstream conveying roller pair 402, which serves as a second rotating body pair (second conveying means), is disposed downstream of the inlet conveying roller pair 401 and upstream of the transparent guide 703 and the black guide 705 in the conveying direction Y2. The upstream conveying roller pair 402 is disposed adjacent to the inlet conveying roller pair 401, the transparent guide 703, and the black guide 705.

[0046] The upstream conveying roller pair 402 has a drive roller 402a as a third rotating means and a driven roller 402b as a fourth rotating means, which are arranged opposite each other and rotate. For example, the upstream conveying roller pair 402 is composed of the drive roller 402a, which is one of a pair of rotating bodies, and the driven roller 402b, which is the other of the pair of rotating bodies. The drive roller 402a, which is a second rotating body, is driven by a conveying motor 452 and is supported to rotate about a rotation axis C2 (see FIG. 10) arranged along the main scanning direction.

[0047] The driven roller 402b, which serves as a first rotating body, is supported so as to be rotatable about a rotation axis extending along the main scanning direction. The drive roller 402a is disposed above the through path 430 in the thickness direction of the sheet, and the driven roller 402b is disposed below the through path 430 in the thickness direction of the sheet. In other words, as viewed from the main scanning direction, the drive roller 402a is disposed above a nip line Na, which is a common tangent to the drive roller 402a and the driven roller 402b, and the driven roller 402b is disposed below the nip line Na. An upstream nip portion N2, which serves as a second nip portion that holds the sheet, is formed between the drive roller 402a and the driven roller 402b.

[0048] A distance L1 in the conveying direction Y2 between the inlet nip portion N1 of the inlet conveying roller pair 401 and the upstream nip portion N2 of the upstream conveying roller pair 402 is smaller than the length in the sub-scanning direction of a sheet of the smallest size that can be conveyed by the adjustment unit 400 (image forming apparatus 100). Therefore, the inlet conveying roller pair 401 is configured to deliver the sheet to the upstream nip portion N2 of the upstream conveying roller pair 402 while the sheet is being nipped and conveyed at the inlet nip portion N1. Furthermore, a distance L4 (see FIG. 11) between one end N2a1 and the other end N2b2 in the main scanning direction of the upstream nip portion N2 is larger than the length in the main scanning direction of a sheet of the largest size that can be conveyed by the adjustment unit 400 (image forming apparatus 100) (hereinafter also referred to as the maximum sheet width). The upstream conveying roller pair 402 conveys the sheet conveyed by the inlet conveying roller pair 401 toward the reading position P1.

[0049] The intermediate conveying roller pair 403 is disposed downstream of the transparent guide 703 and the black guide 705 and upstream of the transparent guide 704 and the black guide 706 in the conveying direction Y2. The intermediate conveying roller pair 403 is disposed adjacent to the transparent guide 703 and the black guide 705, and is also disposed adjacent to the transparent guide 704 and the black guide 706.

[0050] The intermediate conveying roller pair 403 has a drive roller 403a and a driven roller 403b that are disposed opposite each other and rotate. The drive roller 403a is driven by a conveying motor 452 and is supported so as to rotate about a rotation axis that is disposed along the main scanning direction. The driven roller 403b is supported so as to be rotatable about a rotation axis that is disposed along the main scanning direction. An intermediate nip portion N3 that holds the sheet is formed between the drive roller 403a and the driven roller 403b.

[0051] A distance L2 in the conveying direction Y2 between the upstream nip portion N2 of the upstream conveying roller pair 402 and the intermediate nip portion N3 of the intermediate conveying roller pair 403 is smaller than the length in the sub-scanning direction of the smallest size sheet that can be conveyed by the adjustment unit 400 (image forming apparatus 100). The intermediate conveying roller pair 403 conveys the sheet toward the reading position P2 while nipping the sheet together with the upstream nip portion N2 of the upstream conveying roller pair 402 at the intermediate nip portion N3.

[0052] The downstream conveying roller pair 404 is disposed downstream of the transparent guide 704 and the black guide 706 in the conveying direction Y2, and upstream of a branch point 431 between the through path 430 and the discharge path 432. The downstream conveying roller pair 404 has a drive roller 404a and a driven roller 404b that are disposed opposite each other and rotate. The drive roller 404a is driven by a conveying motor 452 and is supported so as to rotate about a rotation axis that is disposed along the main scanning direction. A downstream nip portion N4 that sandwiches the sheet is formed between the drive roller 404a and the driven roller 404b.

[0053] In the conveying direction Y2, a distance L3 between the intermediate nip portion N3 of the intermediate conveying roller pair 403 and the downstream nip portion N4 of the downstream conveying roller pair 404 is approximately the same length as a distance L2 between the upstream nip portion N2 and the intermediate nip portion N3. The downstream conveying roller pair 404 conveys the sheet toward a branching portion 431 between the through path 430 and the discharge path 432 while nipping the sheet together with the intermediate nip portion N3 of the intermediate conveying roller pair 403 at the downstream nip portion N4.

[0054] The front and back registration unit 700 further includes a sheet detection sensor S700 as a detection unit for detecting the downstream end (leading edge) of the sheet conveyed by the upstream conveying roller pair 402. The sheet detection sensor S700 is disposed downstream of the upstream nip portion N2 of the upstream conveying roller pair 402 and upstream of the reading position P1 in the conveying direction Y2. The sheet detection sensor S700 outputs a detection signal when the downstream end of the sheet conveyed by the upstream conveying roller pair 402 reaches a detection position P3 between the upstream nip portion N2 and the reading position P1. The timing for starting sheet reading by the CISs 701 and 702 is determined based on the detection signal output by the sheet detection sensor S700.

[0055] The sheet reaches the front and back registration section 700 and is conveyed by the upstream conveying roller pair 402. While being conveyed, the bottom surface of the sheet is scanned and read by the CIS 701 at a first reading position P1, and the sheet is further conveyed by the intermediate conveying roller pair 403. While being conveyed by the intermediate conveying roller pair 403, the top surface of the sheet is scanned and read by the CIS 702 at a second reading position P2, and the sheet is further conveyed by the downstream conveying roller pair 404.

[0056] [Reading the sheet and providing feedback on the results] Next, sheet reading by the front and back registration unit 700 and feedback of the reading results will be described with reference to Figures 1, 2, and 5 to 7. The sheet library 900 (see Figure 2) held in the memory 302 by the printer controller 103 is data that stores a list of sheets that can be used as recording materials by the image forming apparatus 100, in association with attribute information such as lengths in the sub-scanning and main-scanning directions and basis weights. The sheet library 900 includes geometric adjustment values ​​that are used when performing an image formation process on each sheet. The geometric adjustment values ​​are parameters for correcting the position of an image on a sheet, the magnification of an image, and so forth, when performing an image formation process.

[0057] As shown in Fig. 5(a), the contents of the sheet library 900 can be confirmed by displaying a library display screen 1001 on the operation unit 180 (see Fig. 1). Furthermore, when a "Print Position Adjustment" button 1002 on the library display screen 1001 is operated, a selection screen 1003 for selecting a correction method for geometric adjustment values, as shown in Fig. 5(b), is displayed. If the user selects the "Manual Adjustment" option 1004, the user can directly specify the geometric adjustment value by inputting a numerical value using the numeric keypad 181 (see Fig. 1) or the like provided on the operation unit 180.

[0058] On the other hand, if the user selects option 1005 for "Read test page and adjust," image forming system 100S (see FIG. 1) executes front-to-back registration processing to perform front-to-back registration based on the results of reading the sheet. In the front-to-back registration processing, image forming apparatus 100 forms test pattern 820 (see FIGS. 6(a) and 6(b)) for front-to-back registration on the sheet. Also, in the front-to-back registration processing, front-to-back registration section 700 (see FIG. 1) of adjustment unit 400 reads the sheet conveyed from image forming apparatus 100 and feeds back the reading result to image forming apparatus 100. Image forming apparatus 100 adjusts (corrects) the geometric adjustment values ​​based on the feedback from adjustment unit 400.

[0059] Specifically, when front-to-back registration processing is initiated, the image forming apparatus 100 according to this embodiment first feeds a sheet 1 from the sheet storage 113 that stores sheets designated as targets for front-to-back registration processing. Then, the image forming apparatus 100 uses the image forming engine 102 to form a test pattern 820 (see FIGS. 6A and 6B ) on both sides of the sheet 1, with rectangular patch images arranged near the four corners of the sheet surface. After forming the test pattern 820, the image forming apparatus 100 ejects the sheet 1 toward the adjustment unit 400. Note that the test pattern is not limited to being composed of multiple rectangular patch images, but may also be composed of multiple square patch images. Furthermore, the test pattern may be composed of so-called registration marks, which are markers for cutting positions or folding positions, or may be composed of images of other shapes, or a combination of these. Furthermore, the color and density of the test pattern are not limited to being uniform, but may include patch images of multiple colors and densities.

[0060] Upon receiving sheet 1 from image forming apparatus 100, adjustment unit 400 reads the front and back sides of sheet 1 as line images using CISs 701 and 702 (see FIG. 4) while conveying sheet 1 using each conveyance roller pair. Then, image processing unit 460 (see FIG. 2) of adjustment unit 400 joins the read line images in the sub-scanning direction (the conveyance direction of sheet 1), thereby synthesizing image data of the front and back sides of sheet 1, including test pattern 820. In this way, adjustment unit 400 reads image information of test pattern 820 when reading the sheet conveyed by CISs 701 and 702.

[0061] The image processing unit 460 (see FIG. 2) of the adjustment unit 400 identifies the contours of the sheet 1, the contours of the patch images formed on the sheet, and the positional relationship between them. Specifically, from the combined image data, the corner coordinates and the coordinates of each patch image of the test pattern 820 are identified for the front and back surfaces of the sheet 1. As shown in FIGS. 6(a) and 6(b), the corner coordinates of the sheet 1 represent the positions {(X01, Y01) to (X31, Y31), (X02, Y02) to (X32, Y32)} of the four corners of the sheet 1 when the X axis is the main scanning direction and the Y axis is the sub-scanning direction. Furthermore, the coordinates of the test pattern 820 represent the positions {(X41, Y41) to (X71, Y71), (X42, Y42) to (X72, Y72)} of specific portions of the patch images in the same coordinate system as the corner coordinates.

[0062] The corner coordinates of the sheet 1 can be used to geometrically calculate the length of the sheet in the main scanning direction (short side length) (A), the length of the sheet in the sub-scanning direction (long side length) (B), the squareness of the corner, etc., and therefore the corner coordinates can be said to contain information about the contour (outer shape) of the sheet 1. Furthermore, the corner coordinates and the coordinates of the test pattern 820 can be used to geometrically calculate the positional deviation and distortion of the image relative to the contour of the sheet, and therefore the corner coordinates and the coordinates of the test pattern 820 can be said to contain information about the position and distortion of the image relative to the sheet.

[0063] The image processing unit 460 further determines (calculates) geometric adjustment values ​​for this sheet 1 using the corner coordinates of the sheet 1 and the coordinates of the test pattern 820. For example, the image processing unit 460 determines the lead position, side position, main scanning magnification, and sub-scanning magnification as geometric adjustment values. The lead position is a parameter that defines the image position in the sub-scanning direction relative to the sheet 1. The side position is a parameter that defines the image position in the main scanning direction relative to the sheet 1. The main scanning magnification is a parameter that defines the magnification for enlarging or reducing the image data in the main scanning direction. Furthermore, the sub-scanning magnification is a parameter that defines the magnification for enlarging or reducing the image data in the sub-scanning direction. The geometric adjustment values ​​are determined so that, when the image shape is corrected, the distance from the test pattern 820 to the edge of the sheet ((C) to (J) in FIGS. 6(a) and 6(b)) becomes equal to a preset value.

[0064] Although the four parameters of lead position, side position, main scanning magnification, and sub-scanning magnification are listed here as geometric adjustment values, other parameters may be calculated by the image processing unit 460. Examples of other parameters include a parameter for correcting the squareness of an image, a parameter for correcting trapezoidal shape of an image, and a parameter for specifying the rotation angle of an image relative to the sheet.

[0065] The geometric adjustment values ​​determined by the image processing unit 460 are sent to the printer controller 103 of the image forming apparatus 100 via the communication unit 450 and registered in the sheet library 900. When the image forming apparatus 100 executes an image formation job, the image shape correction unit 320 references the sheet library 900 to acquire sheet information 910, 911, 912, ... (see FIG. 5) and geometric adjustment values ​​of the sheets designated as recording materials. The image shape correction unit 320 then corrects the image data based on the acquired geometric adjustment values ​​of the sheets. By correcting the image data of the front and back sides of the sheet, front and back registration of the sheet is performed.

[0066] Here, the case where the test pattern 820 for front-to-back registration is formed based on an explicit instruction from the user and the adjustment unit 400 acquires the geometric adjustment values ​​has been described, but this is not limiting. For example, when an image formation job is submitted, as a preparatory operation before the job is executed, the test pattern 820 may be formed on the same sheet as specified in the job to acquire the geometric adjustment values. Furthermore, during the execution of an image formation job requiring a large number of deliverables, a job for forming the test pattern 820 may be automatically inserted to perform correction (calibration) every time a certain number of deliverables are output. Furthermore, the purpose of the adjustment unit 400 reading the sheet is not limited to acquiring the geometric adjustment values ​​and correcting the misalignment or distortion of the image relative to the sheet. For example, the adjustment unit may read the sheets on which the images of the deliverables are continuously conveyed (reading the image information from the sheets) to monitor whether the misalignment or distortion of the image relative to the sheet is within a predetermined value.

[0067] [Control method] In the image forming system 100S configured as above, a control method for conveying and reading a sheet by the adjustment unit 400 will be described with reference to FIGS. 2, 7 and 8. FIG.

[0068] In the following description, among image forming jobs, a job that requests output of a product and in which the adjustment unit 400 does not read a sheet is referred to as a "normal job." Furthermore, among image forming jobs, a job in which the adjustment unit 400 reads a sheet using the CIS 701, 702 (see FIG. 4) to perform front-to-back registration is referred to as a "front-to-back registration job." Note that a normal job is submitted to the printer controller 103 when it is input from an external computer via the external I / F 303 (see FIG. 2), or when a user commands the start of a copying operation via the operation unit 180. Furthermore, as described above, a front-to-back registration job may be executed by an explicit command from the user, or may be executed spontaneously by the image forming system 100S.

[0069] At the start of an image formation job (S1), the printer controller 103 determines whether the job is a normal job or a front-to-back registration job (S2). If it is a normal job (S2: Y), the image forming apparatus 100 and the adjustment unit 400 cause members involved in sheet transport (e.g., flappers) to wait at default positions (home positions). For example, the adjustment unit 400 positions the switching flapper 422 at a position for guiding the sheet along the through path 430 (see FIG. 8(a)) to the first discharge outlet 442 (S4). That is, as shown in FIG. 8(a), the switching flapper 421 is held in the upper position.

[0070] Image forming apparatus 100 forms an image on sheet 1 according to image data requested to be output by the image formation job (S5), and adjustment unit 400 receives sheet 1 with the image formed thereon (S6). Then, as shown in FIGS. 8(a) and 8(b), adjustment unit 400 passes sheet 1 in order via each conveyance roller pair and causes it to pass through through path 430. Then, adjustment unit 400 discharges sheet 1 from first discharge port 442 to finisher 600 (see FIG. 1) via exit conveyance roller pair 405 (S7). Upon receiving sheet 1, finisher 600 processes sheet 1 in processing unit 601 and stacks the processed sheet on stacking tray 602 as a product.

[0071] In the case of a front-to-back registration job (S3:N), the adjustment unit 400 positions the switching flapper 421 at a position for guiding the sheet to the discharge path 432 (see FIG. 9(a)) (S10). That is, as shown in FIG. 9(a), the switching flapper 422 is held in the lower position.

[0072] Image forming apparatus 100 forms test patterns 820 (see FIGS. 6A and 6B) for front-to-back registration on both sides of a sheet (S11), and adjustment unit 400 receives the sheet on which test patterns 820 have been formed (S12). Adjustment unit 400 reads sheet 1 using CISs 701 and 702 when sheet 1, which has been conveyed into through path 430, passes through reading positions P1 and P2 (see FIG. 4) of CISs 701 and 702 (S13, FIGS. 9A and 9B). Note that before test pattern 820 on the sheet reaches reading position P1 of CIS 701, control unit 451 of adjustment unit 400 may reduce the conveying speed of sheet 1 to a conveying speed suitable for reading by CISs 701 and 702.

[0073] The image data read by the CISs 701 and 702 is processed by the image processing unit 460, and geometric adjustment values ​​are calculated. The calculated geometric adjustment values ​​are sent to the image forming apparatus 100 via the communication unit 450 and stored in the sheet library 900 (S14).

[0074] When sheet 1 that has passed through reading positions P1 and P2 reaches branch section 431 where through path 430 branches into discharge path 432, adjustment unit 400 conveys sheet 1, guided by switching flapper 422, along discharge path 432 toward second discharge outlet 443. Adjustment unit 400 discharges sheet 1 conveyed along discharge path 432 from second discharge outlet 443 to discharge tray 423 (S15). In this way, adjustment unit 400 of the present embodiment is capable of discharging sheets, the images of which have been read by front-to-back registration section 700, to discharge tray 423 instead of finisher 600. This makes it possible to prevent sheets for front-to-back registration from being mixed in with the deliverables, even when, for example, sheets for front-to-back registration separate from sheets serving as deliverables are inserted during the execution of an image formation job that requires a large number of deliverables.

[0075] The above process is repeated for each sheet of the number of sheets specified in the job, and after the process for the final sheet is completed (S8: Y), the job ends (S9). Note that in the control example shown in FIG. 7, the job type is determined for each sheet during the processing of the same job. However, the type may be determined at the start of the job and the same process as for the previous sheet may be applied without determination during the job. Also, in the control example shown in FIG. 7, in a job that performs front-to-back registration, the sheet is read and then discharged to the discharge tray 423. However, this is not limited to this. The image forming system may be capable of executing control to discharge the sheet to the finisher after reading the sheet in a job that performs front-to-back registration. For example, the image forming apparatus may form an image of the deliverable and a test pattern to be placed in the margin on the sheet, and the adjustment unit may read the sheet and then discharge it to the finisher, and the finisher may trim the margin of the sheet together with the test pattern.

[0076] [Details of the front and back register and the entrance conveyor roller pair] Next, the front and back registration unit 700 and the pair of inlet conveying rollers 401 will be described in detail. Generally, the above-mentioned sheet cutting accuracy (cutting accuracy of a sheet before image formation) is affected by the material of the sheet, the ambient environment (temperature, humidity), etc., and therefore varies depending on the sheet cutting lot. In order to obtain highly accurate reading results in an image reading device such as the adjustment unit 400, it is desirable to read multiple sheets for each sheet cutting lot and perform front and back registration based on the averaged reading results.

[0077] A possible configuration for improving the efficiency of such front-to-back registration work is a configuration in which the processes from image formation to sheet reading are performed continuously, as in image forming system 100S of this embodiment. However, in order to read the sheet in accordance with the high sheet conveyance speed of the image formation process, it is important to ensure a sufficient amount of light during reading. However, ensuring a sufficient amount of light tends to require a large light source and a CIS that includes the light source, making it difficult to miniaturize the device.

[0078] Furthermore, since conveying a sheet on which an image has been formed along a conveying path with a large curvature may cause the sheet to warp, it is desirable that the sheet after image formation be conveyed along a straight conveying path. However, in an image reading device capable of reading a sheet conveyed along a straight conveying path, it is necessary to arrange each conveying roller pair and a reading sensor along this straight conveying path, making it more difficult to reduce the size of the device.

[0079] To solve this problem, the front and back registration unit 700 of this embodiment aims to reduce the size of the device by suitably arranging the sheet detection sensor S700 and the upstream conveying roller pair 402. The specific configuration of the front and back registration unit 700 that aims to reduce the size of the device will be described below.

[0080] 10 and 11, the drive roller 402a of the upstream conveying roller pair 402 of this embodiment has a drive shaft 402a3 that is rotationally driven by a conveying motor 452, and a first rotating portion 402a1 and a second rotating portion 402a2 that are supported by the drive shaft 402a3. The drive shaft 402a3 is formed along the main scanning direction, and positions the first rotating portion 402a1 as the first rotating portion and the second rotating portion 402a2 as the second rotating portion in the rotation direction of the drive shaft 402a3. The drive shaft 402a3, the first rotating portion 402a1, and the second rotating portion 402a2 rotate integrally about a rotation axis C2.

[0081] The first rotating portion 402a1 and the second rotating portion 402a2 are formed in cylindrical shapes with the same diameter and approximately the same length along the main scanning direction, and the second rotating portion 402a2 is disposed on one side of the first rotating portion 402a1 in the main scanning direction (the X1 direction side shown in FIG. 10). Meanwhile, the driven roller 402b of the upstream conveying roller pair 402 has a driven shaft 402b2 extending in the main scanning direction and a rotating portion 402b1 rotatably supported on the driven shaft 402b2. The rotating portion 402b1 is integrally formed in a cylindrical shape of the same diameter from one end to the other end of the nip portion (upstream nip portion N2) in the main scanning direction. In other words, the rotating portion 402b1 extends continuously in the direction of the rotation axis C1 between the first upstream nip region N2a and the second upstream nip region N2b, and the driven roller 402b is a so-called through roller.

[0082] A first upstream nip region N2a that holds a sheet is formed between the first rotating portion 402a1 and the driven roller 402b, and a second upstream nip region N2b that holds a sheet is formed between the second rotating portion 402a2 and the driven roller 402b. In other words, the upstream nip portion N2 formed between the drive roller 402a and the driven roller 402b has the first upstream nip region N2a as the first nip region that holds a sheet, and the second upstream nip region N2b as the second nip region.

[0083] The second rotating portion 402a2 is disposed with a gap in the main scanning direction relative to the first rotating portion 402a1. As a result, a recessed portion 402a4 is formed between the first rotating portion 402a1 and the second rotating portion 402a2. The recessed portion 402a4 has a smaller radial dimension (radius) about the rotation axis C2 than the first rotating portion 402a1 and the second rotating portion 402a2. In other words, the upstream nip portion N2 has a recessed portion N2c between the first upstream nip region N2a and the second upstream nip region N2b, where the drive roller 402a is recessed from the outer surface (cylindrical surface) toward the rotation axis and does not clamp the sheet. In addition, since the first rotating portion 402a1 and the second rotating portion 402a2 have approximately the same length in the main scanning direction, the recessed portion 402a4 (recessed portion N2c) is formed in a central portion 402a5 in the main scanning direction of the drive roller 402a.

[0084] The above-described sheet detection sensor S700 is disposed so that a portion thereof fits into the recess 402a4 of the drive roller 402a. In other words, the sheet detection sensor S700 is disposed so that a portion thereof overlaps with the recess 402a4 of the drive roller 402a in the direction of the rotation axis C1 when viewed from the main scanning direction (see FIG. 4). In other words, the sheet detection sensor S700 is disposed between the first rotating portion 402a1 and the second rotating portion 402a2 in the direction of the rotation axis C1 when viewed from the main scanning direction, so that a portion thereof overlaps with the first rotating portion 402a1 and the second rotating portion 402a2.

[0085] As a result, in the adjustment unit 400 of this embodiment, the sheet detection sensor S700 can be disposed closer to the rotation axis C2 of the drive roller 402a than when the drive roller of the upstream conveying roller pair is a through roller, thereby enabling the device to be made more compact. This also makes it possible to shorten the distance L2 in the conveying direction Y2 between the upstream nip portion N2 of the upstream conveying roller pair 402 and the intermediate nip portion N3 of the intermediate conveying roller pair 403, making it possible to convey sheets of various sizes, including smaller sizes.

[0086] In this embodiment, the drive roller 402a of the upstream conveying roller pair 402 has a drive shaft 402a3, a first rotating portion 402a1, and a second rotating portion 402a2, and a recess 402a4 is formed between the first rotating portion 402a1 and the second rotating portion 402a2, but is not limited to this. It is sufficient that at least one of the drive roller 402a and the driven roller 402b of the upstream conveying roller pair 402 has a recess. For example, the drive roller 402a may have a drive shaft and a rotating portion supported by the drive shaft, and the rotating portion may have a recess in a portion (e.g., a central portion) in the main scanning direction that is smaller in radial dimension than other portions.

[0087] Alternatively, the driven roller 402b may have a recess, and the sheet detection sensor S700 may be disposed so as to fit into the recess of the driven roller 402b, or the driven roller 402b may be disposed higher than the drive roller 402a. Alternatively, both the drive roller 402a and the driven roller 402b may have recesses. It is sufficient that at least a portion of the sheet detection sensor S700 overlaps with the recess formed in the drive roller 402a or the driven roller 402b when viewed from the direction of the rotation axis. In other words, it is sufficient that at least a portion of the sheet detection sensor S700 is disposed so as to fit into the recess. For example, the sheet detection sensor S700 and the recess may partially overlap, or a portion of the recess may overlap the entire sheet detection sensor S700.

[0088] Incidentally, in the nip portion of a roller pair having a roller with a recess formed therein, such as the drive roller 402a in this embodiment, a recessed region is formed at a position corresponding to the recess where the sheet is not clamped. As shown in FIG. 12(a), a sheet conveyed by such a roller pair may have a portion (in this embodiment, the central portion in the width direction of the sheet) enter the recess, causing wrinkles or warping (waviness) in the width direction. In particular, when conveying a sheet with low rigidity, such as thin paper, the sheet is likely to wrinkle or warp. Furthermore, when reading a sheet conveyed in a warped state, it is difficult to obtain sufficient reading accuracy.

[0089] For this reason, the adjustment unit 400 of this embodiment provides a suitable configuration for the inlet conveying roller pair 401, thereby suppressing wrinkling and bending of the sheet at the recessed portion 402a4 of the upstream conveying roller pair 402. Hereinafter, the specific configuration of the inlet conveying roller pair 401 will be described with reference to FIGS.

[0090] As shown in FIGS. 10, 11, and 12(b), the drive rollers 401a of the inlet conveying roller pair 401 of this embodiment are arranged with gaps in the main scanning direction, and each has multiple rotating portions that form part of the inlet nip N1 with the driven roller 401b. Specifically, the drive roller 401a has a drive shaft 401a4 that is driven and rotated by a conveying motor 452, and a first inlet rotating portion 401a1, a second inlet rotating portion 401a2, and a third inlet rotating portion 401a3 that are supported by the drive shaft 401a4. The drive shaft 401a4 is formed along the main scanning direction and positions the first inlet rotating portion 401a1 to the third inlet rotating portion 401a3 in the rotation direction of the drive shaft 401a4. The drive shaft 401a4 and the first inlet rotating portion 401a1 to the third inlet rotating portion 401a3 rotate integrally about a rotation axis C1.

[0091] The first to third inlet rotation portions 401a1 to 401a3 are cylindrical and have the same diameter and approximately the same length along the main scanning direction, and are arranged with gaps between them in the main scanning direction. Specifically, the second inlet rotation portion 401a2 is arranged on one side of the first inlet rotation portion 401a1 in the main scanning direction (X1 direction side), and the third inlet rotation portion 401a3 is arranged on one side of the second inlet rotation portion 401a2 in the main scanning direction (X1 direction side). The lengths of the first to third rotation portions along the main scanning direction may be different from one another.

[0092] Furthermore, driven roller 401b has multiple rotating parts that are arranged with gaps between them in the main scanning direction. Specifically, driven roller 401b has a driven shaft 401c that extends in the main scanning direction, and a first driven rotating part 401b1, a second driven rotating part 401b2, and a third driven rotating part 401b3 that are rotatably supported on driven shaft 401c.

[0093] A first inlet nip area N1a that holds a sheet is formed between the first inlet rotating portion 401a1 and the first driven rotating portion 401b1. A second inlet nip area N1b that holds a sheet is formed between the second inlet rotating portion 401a2 and the second driven rotating portion 401b2. A third inlet nip area N1c that holds a sheet is formed between the third inlet rotating portion 401a3 and the third driven rotating portion 401b3. In other words, the inlet nip area N1 formed between the drive roller 401a and the driven roller 401b has a first inlet nip area N1a, a second inlet nip area N1b, and a third inlet nip area N1c that hold a sheet.

[0094] 12B, the second inlet nip region N1b, which is located between the first inlet nip region N1a and the third inlet nip region N1c, is positioned so as to partially overlap with the central portion 402d of the upstream conveyance roller pair 402 in the main scanning direction, as viewed in the conveyance direction Y2. In other words, the second inlet rotation portion 401a2 is positioned so as to partially overlap with the recessed portion 402a4 of the upstream conveyance roller pair 402 in the direction of the rotation axis C1, as viewed in the conveyance direction Y2. In other words, the inlet conveyance roller pair 401 forms the inlet nip portion N1 so as to sandwich the sheet in a region 401a5 that overlaps with the recessed portion region N2c of the upstream nip portion N2 in the direction of the rotation axis C1, as viewed from a direction perpendicular to the main scanning direction. The pair of entrance conveying rollers 401 sandwiches and conveys the sheet at the entrance nip portion N1, thereby delivering the sheet to the upstream nip portion N2 in a state in which bending of the sheet at an area 401a5 overlapping with the recessed area N2c is suppressed.

[0095] As a result, even when the upstream conveying roller pair 402 has the recessed portion 402a4, the adjustment unit 400 of this embodiment can suppress wrinkles and warping of the conveyed sheet and improve the sheet reading accuracy by the front and back register unit 700. Note that the inlet conveying roller pair 401 may have an inlet nip portion N1 formed therebetween so as to hold the sheet in a region that overlaps with a part of the recessed portion region N2c in the direction of the rotation axis C1 when viewed from a direction perpendicular to the main scanning direction.

[0096] Furthermore, the distance L5 between one end N1a1 and the other end N1c2 of the inlet nip portion N1 in the main scanning direction is greater than the length L6 of the recessed portion 402a4 (recessed portion area N2c) in the main scanning direction. That is, the distance between one end N1a1 of the first inlet nip area N1a in the main scanning direction and the other end N1c2 of the third inlet nip area N1c in the main scanning direction is greater than the distance between the other end N2a2 of the first upstream nip area N2a and one end N2b1 of the second upstream nip area N2b. As a result, the inlet conveyance roller pair 401 clamps the sheet over a wider area than the recessed portion area N2c where the upstream conveyance roller pair 402 does not clamp the sheet, thereby effectively suppressing sheet deflection at the recessed portion 402a4 and improving sheet reading accuracy.

[0097] Furthermore, the distance L5 between one end N1a1 and the other end N1c2 of the entrance nip N1 in the main scanning direction is smaller than the maximum sheet width. Therefore, the distance L5 is smaller than the distance L4 between one end N2a1 and the other end N2b2 of the upstream nip N2 in the main scanning direction. This allows the components of the drive roller 401a and the driven roller 401b to be made smaller and costs reduced compared to when the lengths of the drive roller and driven roller of the entrance conveying roller pair in the main scanning direction are greater than the maximum sheet width.

[0098] As described above, the driven roller 402b of the upstream conveying roller pair 402 is disposed below the drive roller 402a and serves as a through roller. This allows the upstream conveying roller pair 402 to support the center of the sheet in the width direction, preventing the sheet from bending downward due to gravity in the recessed region N2c, thereby improving sheet reading accuracy. In the present embodiment, the driven roller 402b of the upstream conveying roller pair 402, disposed below the drive roller 402a, serves as a through roller. However, this is not limiting. Of the pair of rotating bodies constituting the upstream conveying roller pair 402, it is sufficient that the lower rotating body can support the sheet in at least a portion of the recessed region formed by the recess of the upper rotating body. For example, the driven roller 402b may have multiple rotating parts disposed with gaps between them in the main scanning direction, and one of these rotating parts may support the sheet in the recessed region.

[0099] As described above, according to this embodiment, the inlet conveying roller pair 401 forms the inlet nip portion N1 so as to sandwich the sheet in the region 401a5 that overlaps with the recessed region N2c of the upstream nip portion N2 in the direction of the rotation axis C1 when viewed from a direction perpendicular to the main scanning direction. The inlet conveying roller pair 401 delivers the sheet to the upstream nip portion N2 of the upstream conveying roller pair 402 while the sheet is sandwiched and conveyed in the inlet nip portion N1. This suppresses wrinkles and warping at the recessed portion 402a4 of the conveyed sheet, thereby improving the reading accuracy when reading the sheet contour and the image formed on the sheet. Furthermore, improving the image reading accuracy improves the image quality when forming an image on a sheet in the image forming apparatus 100.

[0100] Furthermore, since reading accuracy can be improved even when the drive roller 402a has the recess 402a4, the sheet detection sensor S700 can be positioned to overlap the recess 402a4 in the direction of the rotation axis C1 as viewed from the main scanning direction, thereby enabling the device to be miniaturized. This also allows a larger light source with a greater light output to be installed, thereby improving the image reading speed. Furthermore, miniaturization makes it easier to form the through-path 430, which reads images, in a straight line. Forming the through-path 430 in a straight line reduces the likelihood of sheet curling even when the sheet, which is the output, is discharged to the finisher after being read, thereby improving the quality of the output. Furthermore, forming the through-path 430 in a straight line reduces the time required for reading and sheet transport, thereby improving work efficiency. Furthermore, miniaturization makes it possible to transport sheets of various sizes, including smaller sheets.

[0101] Note that a sheet transport path (path) being linear does not necessarily mean that the sheet transport path is formed along a completely straight line. The sheet transport path extending from the receiving inlet to the discharge outlet and including the reading device may be formed along a generally straight line. For example, the sheet transport path may be formed so that, when viewed from the direction of the rotation axis, its distance from a predetermined imaginary line is within a range equal to or less than the diameter (preferably equal to or less than the radius) of one of the rotating bodies (rollers). Furthermore, for example, the sheet transport path may be formed so that, when viewed from the direction of the rotation axis, the change in the direction in which the sheet is transported from the receiving inlet to the discharge outlet is limited to a maximum of 30°. In this way, by slightly curving the sheet transport path to a degree that does not cause the sheet to warp, it is possible to suppress changes in the distance between the reading device at the reading position and the sheet being transported.

[0102] Furthermore, in the present embodiment, the image reading device has been described as an adjustment unit 400 that reads the test pattern 820 for front-to-back registration and the outline of the sheet, but is not limited thereto. The image reading device may be any device that includes a reading unit that reads image information on a nipped and conveyed sheet, and does not necessarily have to read the outline of the sheet or perform front-to-back registration. For example, the image reading device may include a color sensor as a reading unit that reads color information (density information) of a test pattern (image) formed on a sheet to perform color adjustment, density adjustment, etc. Furthermore, the image reading device may be an image reading device that is intended to read general images, documents, etc. and convert the contents into electronic data.

[0103] In the present embodiment, the entrance conveying roller pair 401, the upstream conveying roller pair 402, the intermediate conveying roller pair 403, the downstream conveying roller pair 404, and the exit conveying roller pair 405 are all driven by the conveying motor 452, but this is not limiting. The image reading device may be provided with a plurality of conveying motors that can independently drive the roller pairs described above as driving means for the roller pairs.

[0104] <Second embodiment> The second embodiment differs from the first embodiment in the configuration of the inlet conveying roller pair, and a description of the same configuration as in the first embodiment will be omitted. In the first embodiment, the drive roller 401a of the inlet conveying roller pair 401 has three rotating parts that are arranged with a gap between them in the main scanning direction and form the inlet nip portion N1 with the driven roller 401b. However, this is not limited to this. The inlet conveying roller pair only needs to form a nip portion so as to sandwich a sheet in an area that overlaps with the recessed area N2c of the upstream nip portion N2 of the upstream conveying roller pair 402 in the direction of the rotation axis C1 when viewed from a direction perpendicular to the rotation axis. For example, like the inlet conveying roller pair 406 serving as the first rotating body pair in the second embodiment shown in FIG. 13, the drive roller 406a serving as a rotating body may have seven rotating parts 406a1 to 406a7, or may have any other number of rotating parts.

[0105] The driven roller that forms a nip with the drive roller 406a may have the same number of rotating parts as the drive roller 406a, or a different number of rotating parts, or may be a through roller. It is desirable that the number of rotating parts of the drive roller and driven roller of the inlet transport roller pair be an odd number to prevent uneven conveyance force being applied to the sheet in the main scanning direction. The inlet transport roller pair may be configured so that the length of the nip formed between the drive roller and the driven roller in the main scanning direction is greater than the maximum sheet width. When configured in this way, the inlet transport roller pair can apply a uniform conveyance force in the main scanning direction regardless of the size of the sheet being transported, thereby improving the straightness of the sheet being transported.

[0106] <Third embodiment> The third embodiment differs from the first embodiment in the configuration of the inlet conveying roller pair, and a description of the same configuration as the first embodiment will be omitted. In the first embodiment, the inlet conveying roller pair 401 has a drive roller 401a with three rotating parts, and the length of the inlet nip portion N1 in the main scanning direction is shorter than the maximum sheet width. However, this is not limited to this. For example, as in the inlet conveying roller pair 407 serving as the first rotating body pair in the third embodiment shown in FIG. 14, the rotating part 407a1 of the drive roller 407a as a rotating body and the driven roller may be a through roller. That is, the drive roller 407a of the inlet conveying roller pair 407 may be integrally formed as a cylinder of the same diameter from one end to the other in the rotational axis direction of the inlet nip portion N1, and may have a rotating part 407a1 that forms a nip portion with the driven roller. Furthermore, the driven roller of the inlet conveying roller pair 407 may be a through roller or may have multiple rotating parts.

[0107] <Fourth embodiment> The fourth embodiment differs from the first embodiment in the configuration of the inlet conveying roller pair, and the same configuration as the first embodiment will not be described. In the first embodiment, the drive roller 401a of the inlet conveying roller pair 401 has three rotating parts that are arranged with gaps in the main scanning direction and form the inlet nip N1 with the driven roller 401b. However, this is not limited to this. For example, as in the inlet conveying roller pair 408 serving as the first rotating body pair in the fourth embodiment shown in FIG. 15, the drive roller 408a and the driven roller as rotating bodies may be configured with a single rotating part that forms the inlet nip N1 that is shorter than the maximum sheet width. That is, the inlet nip N1 may have a rotating part 408a1 that is integrally formed in a cylindrical shape of the same diameter from one end to the other end in the main scanning direction of the inlet nip N1 that is shorter than the maximum sheet width. [Explanation of symbols]

[0108] 1...sheet / 100...image forming apparatus / 100S...image forming system / 102...image forming section (image forming engine) / 400...image reading device (adjustment unit) / 401...first rotating body pair (entrance conveying roller pair) / 401a...rotating body (drive roller) / 401a1...rotating section (first entrance rotating section) / 401a2...rotating section (second entrance rotating section) / 401a3...rotating section (third entrance rotating section) / 401a5...area / 401b...rotating body (driven roller) / 402...second rotating body Pair (upstream conveying roller pair) / 402a... second rotating body (driving roller) / 402a1... first rotating portion / 402a2... second rotating portion / 402a4... recess / 402b... first rotating body (driven roller) / 402b1... rotating portion / 406... first rotating body pair (inlet conveying roller pair) / 406a... rotating body (driving roller) / 406a1... rotating portion / 406a2... rotating portion / 406a3... rotating portion / 406a4... rotating portion / 406a5... rotating portion / 406a6... rotating portion / 406a7... rotating portion / 07...first rotating body pair (entrance conveying roller pair) / 407a...rotating body (drive roller) / 407a1...rotating unit / 408...first rotating body pair (entrance conveying roller pair) / 408a...rotating body (drive roller) / 408a1...rotating unit / 423...sheet stacking means (discharge tray) / 430...first sheet conveying path (through path) / 432...second sheet conveying path (discharge path) / 441...receiving port / 442...first discharge outlet (discharge outlet) / 443...second discharge outlet / 701...first reading means (CIS) / 702...second reading means (CIS) / C1...rotation axis / L1...distance / L4...distance / L5...distance / L6...length / N1...first nip portion (entrance nip portion) / N1a1...one end / N1c2...other end / N2...second nip portion (upstream nip portion) / N2a...first nip area (first upstream nip area) / N2a1...one end / N2b...second nip area (second upstream nip area) / N2b2...other end / N2c...recessed area / S700...detection means (sheet detection sensor) / Y2...conveyance direction

Claims

1. An image reading device that reads image information on a sheet discharged from an image forming device that forms an image on the sheet, a plurality of roller pairs to which a driving force is transmitted and which sandwich and transport a sheet discharged from the image forming apparatus; a reading unit for reading image information on the sheet conveyed by the plurality of roller pairs; a detection sensor that detects the sheet upstream of the reading means in the sheet conveying direction, a first roller pair, which is closest to the reading means on the upstream side of the reading means in the sheet conveying direction among the plurality of roller pairs, includes a first nip region and a second nip region that sandwich the sheet, and a recessed region between the first nip region and the second nip region that does not sandwich the sheet; the detection sensor is disposed so that at least a portion thereof is within the recessed area when viewed from a rotation axis direction perpendicular to the sheet conveying direction, The first roller pair is a first rotating body including a rotating portion that extends continuously in the rotation axis direction across the first nip region and the second nip region; a second rotating body having a first rotating portion that forms the first nip region between itself and the first rotating body, a second rotating portion that forms the second nip region between itself and the first rotating body, and the recessed region that is formed between the first rotating portion and the second rotating portion, The first rotating body is disposed below the second rotating body. An image reading device characterized by:

2. a distance between one end and the other end of a nip portion formed by the first roller pair in the direction of the rotation axis is greater than a length in the direction of the rotation axis of a sheet of a maximum size that can be conveyed by the image reading device; 2. The image reading device according to claim 1, wherein:

3. the recessed region is formed in a central portion of the first roller pair in the rotation axis direction, 3. The image reading device according to claim 1, wherein the image reading device is a scanning device.

4. the reading means reads image information on the surface of the sheet facing the first rotating body; 4. The image reading device according to claim 1, wherein the image reading device is a scanning device.

5. the reading unit is a first reading unit that reads image information on a first surface of the sheet conveyed by the plurality of roller pairs, a second reading unit configured to read image information on a second surface of the sheet conveyed by the plurality of roller pairs, the second surface being opposite to the first surface; 5. The image reading device according to claim 1, wherein the image reading device is a scanning device.

6. a receiving port for receiving a sheet from the image forming apparatus; the plurality of roller pairs includes a second roller pair that is closest to the receiving opening in the sheet conveying direction; the first roller pair is a roller pair among the plurality of roller pairs that is disposed adjacent to the second roller pair in the sheet conveying direction; 6. The image reading device according to claim 1, wherein the image reading device is a scanning device.

7. the reading unit controls timing for starting reading of image information on the sheet based on the detection of the sheet by the detection sensor; 7. The image reading device according to claim 1, wherein the image reading device is a scanning device.

8. the image forming apparatus having an image forming unit that forms an image on a sheet; and the image reading device according to any one of claims 1 to 7, which reads image information on a sheet discharged from the image forming device. An image forming system comprising:

9. the image forming apparatus corrects the position of the image relative to the sheet when forming the image on the sheet based on the image information read by the image reading apparatus; 9. The image forming system according to claim 8, wherein:

Images