Image reading device and image forming system

Abstract

To provide an image reading device that can improve the accuracy in reading images.SOLUTION: An image reading device reads image information on a sheet ejected from an image forming apparatus that forms an image on a sheet, and comprises: a first rotating body pair 402 that are provided upstream of a light-transmissive plate 703 in a sheet conveyance direction Y2 and convey a sheet toward a reading position P1; and a second rotating body pair 401 that are provided upstream of the first rotating body pair 402 in the sheet conveyance direction Y2 and convey the sheet toward the reading position P1. The first rotating body pair 402 and the second rotating body pair 401 are arranged such that when the leading end of the sheet enters between a guide member 405 and the light-transmissive plate 703, a nip part N2 and a nip part N1 of these first rotating body pair 402 and the second rotating body pair 401 sandwich the sheet.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an image forming system that reads an image on a sheet. Image reading device and

Background Art

[0002] Conventionally, an image forming system has been disclosed that includes an image forming apparatus that forms an image on a sheet and a reading apparatus that reads an image formed on the sheet by the image forming apparatus using a line sensor (see Patent Document 1). This image forming system reads an image including a bar code as an identification mark formed on both the front and back sides of the sheet while conveying the sheet, and performs correction processing of the image forming position in the image forming apparatus based on the reading result.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the image reading apparatus as described above, when the leading end of the sheet comes into contact with a sheet guiding member or the like of the sheet when reading the leading end of the sheet, and the sheet receives an external force in the direction opposite to the conveying direction, the conveying speed of the sheet changes, and it is difficult to obtain good reading accuracy.

[0005] Therefore, an object of the present invention is to provide an image forming system capable of improving the reading accuracy of an image. Image reading device and

Means for Solving the Problems

[0006] One aspect of the present invention is an image forming apparatus having an image forming unit that forms an image on a sheet, and an image reading apparatus that reads image information of the sheet discharged from the image forming apparatus. placed ​​​placed Present before A first pair of conveying rollers that receives a sheet from the image forming apparatus and conveys it in the sheet conveying direction, a first motor, and a first toothed belt that transmits the driving force from the first motor to the first pair of conveying rollers; A second pair of conveying rollers that is disposed adjacent to the downstream of the first pair of conveying rollers in the sheet conveying direction and conveys the sheet conveyed by the first pair of conveying rollers in the sheet conveying direction, a second motor, and a second toothed belt that transmits the driving force from the second motor to the second pair of conveying rollers; Reading means for reading image information on the first surface of the sheet at a reading position downstream of the second pair of conveying rollers in the sheet conveying direction, wherein the distance between the nip portion of the first pair of conveying rollers and the reading position in the sheet conveying direction is less than 210 mm yes, this And an image characterized by reading device Is. One aspect of the present invention is an image reading device that reads image information of a sheet discharged from an image forming device having an image forming unit that forms an image on the sheet, the image reading device receiving the sheet from the image forming device and conveying it in the sheet conveying direction, a first pair of conveying rollers, a first motor, a first toothed belt that transmits the driving force from the first motor to the first pair of conveying rollers, a second pair of conveying rollers that is disposed adjacent to the downstream of the first pair of conveying rollers in the sheet conveying direction and conveys the sheet conveyed by the first pair of conveying rollers in the sheet conveying direction, a second motor, a second toothed belt that transmits the driving force from the second motor to the second pair of conveying rollers, and reading means that reads the image information of the first surface of the sheet at a reading position downstream of the second pair of conveying rollers in the sheet conveying direction, wherein the distance between the nip portion of the second pair of conveying rollers and the reading position in the sheet conveying direction is larger than the distance between the nip portion of the first pair of conveying rollers and the nip portion of the second pair of conveying rollers. The image reading device is characterized by this.

Effect of the Invention

[0007] According to the present invention, it becomes possible to improve the reading accuracy of an image.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

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

[0010] [Schematic Configuration of Image Forming System] FIG. 1 is a schematic diagram showing an image forming system 100S according to the present embodiment. The image forming system 100S includes an image forming apparatus 100, an adjustment unit 400, and a finisher 600. In the present embodiment, as the image forming apparatus, the image forming apparatus 100, which is a laser beam printer using the electrophotographic method, will be described as an example, but the present invention is not limited thereto, and the image forming apparatus may be an inkjet printer or a sublimation printer. Further, the adjustment unit 400 is the image reading apparatus of the present 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) for housing 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 unit includes an optical processing mechanism 10 and a fixing processing mechanism 20 that form an image on a recording material by an image forming process, and a feeding processing mechanism 30 and a conveyance processing mechanism 40 that feed and convey a rectangular sheet 1 used as the recording material. As the recording material, paper such as plain paper and thick paper, paper with surface treatment such as coated paper and embossed paper, plastic film, cloth, etc. can be used.

[0012] The optical processing mechanism 10 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. At each of the stations 120 to 123, a primary charger 111 charges the surface of a photosensitive drum 105, which is a drum-shaped photosensitive member. The laser scanner unit 107 performs an exposure process on the photosensitive drum 105 based on a command signal generated based on image data and transmitted to the laser scanner unit 107. The laser scanner unit 107 has a laser driver that drives the laser light emitted from a semiconductor laser (not shown) to be turned on and off. The laser scanner unit 107 distributes the laser light from the semiconductor laser in the main scanning direction (the width direction of the sheet) by a rotating polygon mirror and guides it to the photosensitive drum 105 via a reflection mirror 109. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 105. In the present embodiment, the main scanning direction is a substantially horizontal direction (the depth direction in FIG. 1).

[0013] The developing device 112 houses a developer containing toner inside and supplies charged toner particles to the photosensitive drum 105. The electrostatic latent image carried on the photosensitive drum 105 is visualized as a toner image by the toner particles adhering to the drum surface according to the surface potential distribution. The toner image carried on the photosensitive drum 105 is transferred (primary transfer) to the intermediate transfer belt 106 to which a voltage of a polarity opposite 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 multi-transferred so as to overlap each other on the intermediate transfer belt 106, and a full-color toner image is formed on the intermediate transfer belt 106.

[0014] On the other hand, the sheet feeding processing mechanism 30 feeds the sheets 1 one by one from a sheet storage 113 that is inserted into the housing 101 of the image forming apparatus 100 so as to be pull-outable, toward a transfer roller 114. The toner image carried on the intermediate transfer belt 106, which is an intermediate transfer member, is transferred (secondary transfer) to the sheet 1 by the transfer roller 114.

[0015] Around the intermediate transfer belt 106, an image formation start position detection sensor 115 for determining the print start position when performing image formation, a feed timing sensor 116 for timing the feeding of the sheet 1, and a density sensor 117 are arranged. 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 charging target potential of the primary charger 111 and the setting of the bias voltage of the developing device 112) based on the detection result of the density sensor 117.

[0016] The fixing processing mechanism 20 of the present 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 a heater inside. The first fixing device 150 sandwiches and conveys the sheet 1 by the fixing roller 151 and the pressure belt 152 which are a pair of rotating bodies, and applies heat and pressure to the toner image on the sheet. As a result, the toner particles melt and then adhere, so that the image is fixed on the sheet 1.

[0017] The second fixing device 160 is arranged on the downstream side of the sheet 1 conveyance path from the first fixing device 150. The second fixing device 160 has a function of enhancing the glossiness of the image subjected to the fixing process by the first fixing device 150 or ensuring the fixability of the image on 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 which are a pair of rotating bodies for heating and pressurizing while conveying the sheet 1, and a second post-fixing sensor 163 for detecting the completion of the fixing process by the second fixing device 160.

[0018] Note that depending on the type of the sheet 1, it may not be necessary to pass through the second fixing device 160. In such a case, the image forming apparatus 100 has a bypass conveyance path 130 for discharging the sheet 1 without passing through the second fixing device 160 for the purpose of reducing energy consumption. The sheet 1 sent out from the first fixing device 150 is guided by the first switching flapper 131 to either the second fixing device 160 or the bypass conveyance path 130.

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

[0020] The sheet 1 for which the image formation for single-sided printing has been completed or the sheet 1 for which the image formation on the back surface in double-sided printing has been completed is discharged to the outside of the image forming apparatus 100 by the discharge roller 139a (discharge unit) provided in the discharge conveyance path 139. Note that between the reverse conveyance path 135 and the discharge conveyance path 139, a switching flapper 134 is provided that can guide the sheet 1 switched back by the reverse unit 136 toward the discharge conveyance path 139, and is configured to be able to select the front and back of the sheet 1 when discharging from the image forming apparatus. Note that an image reading device 190 for reading image information from the original is installed above the image forming apparatus 100.

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

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

[0023] The image forming apparatus 100 is provided with an operation unit 180 that serves as a user interface of the image forming system 100S (see FIG. 1). The operation unit 180 includes a display as display means for displaying information to the user. Further, the operation unit 180 includes input means such as physical keys such as numeric keys and a print execution button, and a touch panel function of the display, through 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 representing sheet attributes such as the name, basis weight, and presence or absence of surface treatment of the sheet set in a certain sheet storage bin 113 (see FIG. 1) to the printer controller 103. The input sheet attributes are registered in a sheet library 900 stored in the 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 can communicate with an external computer (not shown). Further, the printer controller 103 is connected to the image forming apparatus 100 and is also connected to the control circuits of apparatuses (in this embodiment, the adjustment unit 400 and the finisher 600) that constitute the image forming system 100S. The printer controller 103 communicates with these apparatuses to coordinate the operations of the image forming apparatus 100 and other apparatuses. Note that the control configuration of the adjustment unit 400 will be described later.

[0025] [Schematic Configuration of Adjustment Unit] Next, the schematic configuration of the adjustment unit 400, which is the image reading apparatus according to the present embodiment shown in FIG. 1 and reads the image information of the sheet discharged from the image forming apparatus 100, will be described. Generally, an image forming apparatus that forms an image on a cut sheet using a printing method such as an electrophotographic method or an inkjet method forms an image on the sheet with one side of the rectangular sheet as a reference. Therefore, the positional accuracy between the contour (outer edge) of the sheet and the image formed on the sheet, the relative positional accuracy between the image on the front surface and the image on the back surface of the sheet, that is, the so-called front-back registration accuracy is usually greatly affected by the cutting accuracy (length, width, squareness, parallelism) of the sheet.

[0026] In the image forming system 100S according to the present embodiment, when the image forming apparatus 100 forms an image on a sheet, the relative position of the image on the front surface and the image on the back surface of the sheet (front-back registration) is adjusted by adjusting the position, magnification, etc. of the image with respect to the contour of the sheet. Specifically, when performing front-back registration, the image forming system 100S first forms test patterns 820 (see FIGS. 8(a) and (b)) on the front and back surfaces of the sheet by 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] After that, the adjustment unit 400 reads the test pattern (image information) 820 of the sheet and the outline of the sheet, and transmits (feedback) the information based on the reading result to the image forming apparatus 100. The image forming apparatus 100 determines the front and back based on the information received from the adjustment unit 400. By performing such front and back determination, the image forming system 100S according to the present embodiment can improve the front and back determination accuracy even when there are variations in the cutting of the sheet.

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

[0029] Note that the upstream and downstream apparatuses of the adjustment unit 400 change 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 arranged between the image forming apparatus 100 and the adjustment unit 400, and the adjustment unit 400 may receive the sheet from the intermediate unit. Examples of the intermediate unit include an apparatus that performs a coating process of attaching a transparent toner to the image surface of the formed image sheet to give gloss. Also, a sheet processing apparatus other than the finisher 600 may be connected to the downstream side of the adjustment unit 400. Examples of such a sheet processing apparatus include an inserter that inserts a cover sheet into a sheet bundle, and a stacker that can be moved by a cart while accommodating a large number of products.

[0030] As shown in FIG. 3, the adjustment unit 400 includes an entrance 441 that receives the sheet discharged from the image forming apparatus 100 into the adjustment unit 400, and a first discharge port (discharge port) 442 that discharges the sheet toward the finisher 600 (see FIG. 1). Further, the adjustment unit 400 includes a through path 430 formed to connect the entrance 441 and the first discharge port 442 in a substantially straight line along a substantially horizontal direction (Y direction), and a discharge path 432 that branches from the middle of the through path 430 and is formed upward. The adjustment unit 400 also includes a second discharge port 443 that discharges the sheet received from the entrance 441 to the outside of the apparatus via the discharge path 432, and a discharge tray 423 provided at the upper part of the adjustment unit 400 on which the sheet discharged from the second discharge port 443 is stacked. The through path 430 is the first sheet conveyance path (sheet conveyance path) of the present embodiment, the discharge path 432 is the second sheet conveyance path of the present embodiment, and the discharge tray 423 is the sheet stacking means of the present embodiment.

[0031] In the through path 430, there are provided a front-back alignment unit 700 that reads the sheet while conveying the sheet received from the entrance 441, and an exit conveyance roller pair 406 that conveys the sheet from the first discharge port 442 toward the finisher 600. A plurality of roller pairs are arranged along the through path 430 in the front-back alignment unit 700, and the front-back alignment unit 700 conveys the sheet in the conveyance direction (sheet conveyance direction) Y2 toward the exit conveyance roller pair 406 while sandwiching the sheet by these plurality of roller pairs. The conveyance direction Y2 is the sub-scanning direction of the sheet on the through path 430 that goes leftward in FIG. 3 along the through path 430 and is orthogonal to the main scanning direction.

[0032] The exit conveyance roller pair 406 is configured by a pair of rollers (rotating bodies) that are arranged opposite to each other and rotated by a conveyance motor M406 (see FIG. 2). The exit conveyance roller pair 406 sandwiches the sheet read by the front-back alignment unit 700 and conveys it along the through path 430, and discharges it from the first discharge port 442 toward the finisher 600.

[0033] At the branch portion 431 from the through path 430 to the discharge path 432, a switching flapper 422, which is a guide member capable of switching the sheet conveyance path between the downstream portion of the through path 430 and the discharge path 432, is arranged. In the adjustment unit 400, a plurality of pairs of conveyance rollers 415, 416, 417, 418 for conveying the sheet are arranged at a plurality of positions along the discharge path 432. These pairs of conveyance rollers 415 to 418 convey the sheet along the discharge path 432 toward the second discharge port 443, and discharge the conveyed sheet from the second discharge port 443 to the discharge tray 423.

[0034] As shown in FIG. 4, the front-back alignment unit 700 includes a first reading unit 700A that reads the image information of the outline and the lower surface of the sheet, and a second reading unit 700B that is arranged downstream of the first reading unit 700A in the conveyance direction Y2 and reads the image information of the outline and the upper surface of the sheet. Note that the order of reading the image information of the sheet is not limited to this, and a reading unit that reads the image information of the lower surface of the sheet may be arranged downstream of the reading unit that reads the image information of the upper surface of the sheet.

[0035] The first reading unit 700A includes a first pair of conveyance rollers 401 as a second pair of rotators arranged facing the receiving port 441 (see FIG. 3), and a second pair of conveyance rollers 402 as a first pair of rotators arranged adjacent to the downstream of the first pair of conveyance rollers 401 in the conveyance direction Y2. Further, the first reading unit 700A includes a back surface CIS 701 as a first reading means arranged downstream of the second pair of conveyance rollers 402 in the conveyance direction Y2, a guide roller 705 as a first guide member, and a transparent guide 703 as a first light-transmitting plate.

[0036] The first pair of conveying rollers 401 rotates about a rotation axis (not shown) arranged along the main scanning direction (the width direction of the sheet, the X direction shown in FIG. 6), and has a pair of rollers (rotating bodies) arranged opposite to each other, forming a first nip portion N1 capable of sandwiching the sheet. The first pair of conveying rollers 401 is driven by a conveying motor M401 (see FIG. 6) as a motor, and conveys the sheet received from the receiving port 441 in the conveying direction Y2 toward the inside of the adjustment unit 400 while sandwiching the sheet at the first nip portion N1.

[0037] The second pair of conveying rollers 402 rotates about a rotation axis (not shown) arranged along the main scanning direction, and has a pair of rollers (rotating bodies) arranged opposite to each other, forming a second nip portion N2 capable of sandwiching the sheet. The second pair of conveying rollers 402 is driven by a conveying motor M402 (see FIG. 6) as a motor, and conveys the sheet conveyed by the first pair of conveying rollers 401 in the conveying direction Y2 while sandwiching the sheet at the second nip portion N2. Note that each of the first pair of conveying rollers 401 and the second pair of conveying rollers 402 may be composed of only a pair of rollers, or may be composed of a plurality of pairs of rollers (pairs of rotating bodies) arranged with a gap in the main scanning direction.

[0038] The back surface CIS 701 is a contact image sensor arranged on the lower surface (back surface, first surface) side of the sheet conveyed along the through path 430. The back surface CIS 701 includes an LED array 7a as a light source, a sensor array 7b composed of an imaging element such as a CMOS, and a lens array 7c that forms the reflected light from the conveyed sheet on the sensor array 7b. The lens array 7c is composed of a plurality of refractive index distribution type lenses that constitute an equal magnification optical system. These LED array 7a, sensor array 7b, and lens array 7c are arranged along the main scanning direction over the entire range in the main scanning direction where the back surface CIS 701 can read the sheet.

[0039] Configured in this way, the backside CIS 701 reads the outline and image information of the sheet conveyed along the through path 430 from the lower surface of the sheet at the first reading position P1. Specifically, the first reading position P1 is the optical axis position of the lens array 7c for guiding the reflected light of the LED array 7a from the lower surface of the sheet to the sensor array 7b of the backside CIS 701.

[0040] Generally, in order to perform highly accurate front-back alignment, it is necessary to read a plurality of sheets and perform front-back alignment based on the averaged results. In this embodiment, by using a contact image sensor, it is possible to read the sheet while conveying the sheet without moving the sensor, and even when reading a plurality of sheets, the time required for reading can be shortened. In addition, by using an image sensor with an equal magnification optical system, the size of the apparatus can be reduced compared to a sensor with a reduction optical system (such as a CCD).

[0041] The guide roller 705 is disposed above the through path 430 and is a rotating body rotatably supported about a rotation axis (not shown) disposed along the main scanning direction. The guide roller 705 abuts on the upper surface of the sheet conveyed along the through path 430 to guide the sheet. The guide roller 705 is disposed opposite to the backside CIS 701 with the transparent guide 703 interposed therebetween. In other words, the guide roller 705 is disposed on the opposite side of the backside CIS 701 with the transparent guide 703 interposed therebetween. Also, in other words, as shown in FIG. 4, when viewed from the direction (vertical direction) orthogonal to the surface of the sheet conveyed along the through path 430, the guide roller 705 is disposed so as to overlap with the first reading position P1 and the conveyance direction Y2. Further, since the guide roller 705 is disposed opposite to the backside CIS 701, it serves as a background when the backside CIS 701 reads the outline of the sheet. For this reason, the guide roller 705 is formed of a low-luminance color, such as black or gray rubber, so that the contrast with the sheet is clear, over the entire range where the backside CIS 701 can read the sheet along the main scanning direction.

[0042] Further, a part of this guide roller 705 is arranged to protrude toward the back surface CIS701 side (lower side, reading means side) beyond a nip line Np (common tangent line) in a second nip portion N2 of a pair of rollers constituting the second conveyance roller pair 402. Thereby, the sheet passing through the first reading position P1 is easily conveyed while contacting the guide roller 705, and the position of the sheet in the thickness direction at the first reading position P1, that is, the position in the depth of focus direction of the back surface CIS701 is stabilized, and the reading accuracy can be improved. Note that the guide roller 705 may be configured to be driven by a driving means (motor) (not shown) in order to reduce the frictional resistance with the sheet.

[0043] The transparent guide 703 is formed in a flat plate shape along the main scanning direction and the sub-scanning direction by a light-transmissive material, for example, transparent glass or the like, and transmits the light emitted from the back surface CIS701 and the reflected light from the lower surface of the sheet. The transparent guide 703 is arranged below the through path 430 between the back surface CIS701 and the guide roller 705. Further, in the conveyance direction Y2, the upstream end of the transparent guide 703 is located downstream of the second conveyance roller pair 402 and upstream of the guide roller 705. Configured in this way, the transparent guide 703 contacts the lower surface of the sheet conveyed along the through path 430 to guide the sheet.

[0044] The transparent guide 703 is arranged with respect to the guide roller 705 with a predetermined gap through which the conveyed sheet can pass. For example, the transparent guide 703 and the guide roller 705 are arranged in proximity such that the distance Lg between them (see FIG. 5) is not less than the thickness of the thickest sheet that the image forming apparatus 100 (adjustment unit 400) can convey and not more than three times the thickness of the thickest sheet. For example, when the thickest sheet is 0.35 mm, the distance Lg is not less than 0.35 mm and not more than 1.05 mm. Therefore, the sheet conveyed along the through path 430 has its position in the sheet thickness direction restricted without being nipped at the first reading position P1 between the transparent guide 703 and the guide roller 705. This suppresses the generation of abrasion powder due to friction between the sheet and the transparent guide 703 when the sheet is conveyed, and aims to protect the sheet and improve the reading accuracy. The sheet conveyed along the through path 430 is read on the back surface by the back surface CIS 701 while being conveyed in a state where its position in the sheet thickness direction is restricted.

[0045] Note that the front-back alignment unit 700 may be configured to be adjustable within a range where the distance Lg is not less than the thickness of the thickest sheet that the image forming apparatus 100 (adjustment unit 400) can convey and not more than three times the thickness of the thickest sheet. Also, the transparent guide 703 is not limited to being provided separately from the back surface CIS 701, and may be integrally formed with the housing of the back surface CIS, for example, as a part of the housing that houses the sensor array.

[0046] Also, the first reading unit 700A is arranged between the second conveyance roller pair 402 and the back surface CIS 701, and has a sheet detection sensor S701 for detecting the leading edge of the sheet conveyed along the through path 430. When the leading edge of the sheet reaches the optical axis position of the sheet detection sensor S701, a detection signal is output from the sheet detection sensor S701, and the start timing of reading the sheet by the back surface CIS 701 is determined.

[0047] The second reading unit 700B includes a third pair of conveying rollers 403 as a fourth pair of rotating bodies arranged downstream in the conveying direction Y2 of the first reading position P1, and a fourth pair of conveying rollers 404 as a third pair of rotating bodies arranged adjacent to the downstream in the conveying direction Y2 of the third pair of conveying rollers 403. Further, the second reading unit 700B includes a surface CIS 702 as a second reading means arranged downstream of the fourth pair of conveying rollers 402 in the conveying direction Y2, a guide roller 706 as a second guiding member, and a transparent guide 704 as a second light-transmitting plate. Further, the second reading unit 700B has a sheet detection sensor S702 arranged between the fourth pair of conveying rollers 404 and the surface CIS 702 for detecting the leading edge of the sheet conveyed along the through-path 430.

[0048] Each component of the second reading unit 700B corresponds to each component of the first reading unit 700A. Specifically, the third pair of conveying rollers 403 corresponds to the first pair of conveying rollers 401, the fourth pair of conveying rollers 404 corresponds to the second pair of conveying rollers 402, and the sheet detection sensor S702 corresponds to the sheet detection sensor S701. Further, the surface CIS 702 corresponds to the back surface CIS 701, the guide roller 706 corresponds to the guide roller 705, and the transparent guide 704 corresponds to the transparent guide 703. These corresponding components have the same functions and are arranged symmetrically up and down, and the description of the content of the second reading unit 700B common to the first reading unit 700A is omitted.

[0049] The third pair of conveying rollers 403 forms a third nip portion N3 capable of sandwiching the sheet, is driven by a conveying motor M403 (see FIG. 6) as a motor, and conveys the sheet conveyed from the first reading unit 700A in the conveying direction Y2. The fourth pair of conveying rollers 404 forms a fourth nip portion N4 capable of sandwiching the sheet, is driven by a conveying motor M404 (see FIG. 2) as a motor, and conveys the sheet conveyed by the third pair of conveying rollers 403 in the conveying direction Y2.

[0050] The surface CIS702 is disposed on the upper surface (front surface, second surface) side of the sheet conveyed along the through-path 430, and reads the outline and image information of the sheet conveyed along the through-path 430 from the upper surface of the sheet at the second reading position P2. The guide roller 706 is disposed below the through-path 430 and is arranged to protrude beyond the nip line (common tangent line) at the fourth nip portion N4 of the pair of rollers that partly constitutes the fourth conveying roller pair 404 toward the surface CIS702 side (upper side).

[0051] The sheet conveyed along the through-path 430 by the fourth conveying roller pair 404 is nipped at the second reading position P2 between the transparent guide 704 and the guide roller 706, and the position in the thickness direction of the sheet, i.e., the position in the depth of focus direction of the surface CIS702, is restricted without being nipped. The sheet conveyed along the through-path 430 is read on the surface by the surface CIS702 while being conveyed in a state where the position in the thickness direction of the sheet is restricted.

[0052] Downstream of the second reading unit 700B in the conveyance direction Y2, a fifth conveying roller pair 405 for conveying while sandwiching the sheet is provided. The sheets read by the first reading unit 700A and the second reading unit 700B are conveyed by the fifth conveying roller pair 405 toward the branching unit 431. In the present embodiment, the first conveying roller pair 401 to the fifth conveying roller pair 405 are arranged such that their nip lines coincide with each other, but the present invention is not limited thereto, and these nip lines may not coincide with each other and may be arranged to intersect or be parallel to each other. Further, the guide rollers 704 and 706 only need to be arranged such that at least a part thereof is disposed closer to the reading means for reading the sheet than the nip line of the immediately preceding conveying roller pair. For example, when the nip line of the first conveying roller pair and the nip line of the fourth conveying roller pair do not coincide with each other, the guide roller 706 only needs to be arranged such that at least a part thereof is disposed closer to the surface CIS702 than the nip line of the fourth conveying roller pair. Further, a rotating body or a guide member (not shown) for guiding the sheet may be provided in the sheet conveyance path from the second conveying roller pair 402 to the guide roller 705 and in the sheet conveyance path from the fourth conveying roller pair 404 to the guide roller 706.

[0053] [Details of the front and back alignment section] Next, the details of the front and back alignment section 700 will be described. In order to obtain good reading accuracy of the sheet in the front and back alignment section 700, it is desirable that the sheet passes through the first reading position P1 and the second reading position P2 at a predetermined constant conveyance speed. However, since the guide rollers 705 and 706 are arranged so as to overlap the nip line Np respectively, the leading edge of the sheet conveyed through the front and back alignment section 700 is likely to contact the guide rollers 705 and 706. When reading while conveying the sheet in the front and back alignment section 700, if the leading edge of the sheet contacts the guide rollers 705 and 706, the leading edge of the sheet instantaneously receives an external force in the direction opposite to the conveyance direction Y2. When the sheet receives such an external force, changes in the conveyance speed of the sheet and vibrations in the conveyance direction Y2 are likely to occur due to slippage between the roller pair holding the sheet and the sheet or out-of-tune of the motor driving the roller pair, making it difficult to obtain good reading accuracy of the sheet.

[0054] As shown in FIG. 5, in the first reading section 700A of the present embodiment, the back surface CIS 701 can read the leading edge of the sheet held between the first conveyance roller pair 401 and the second conveyance roller pair 402. That is, the back surface CIS 701, the first conveyance roller pair 401, and the second conveyance roller pair 402 are arranged such that the leading edge of the sheet reaches the first reading position P1 before the trailing edge of the sheet passes through the first nip portion N1. In other words, the back surface CIS 701, the first conveyance roller pair 401, and the second conveyance roller pair 402 are arranged such that when the leading edge of the sheet enters between the guide roller 705 and the transparent guide 703, each of the nip portions of these roller pairs holds the sheet. By being arranged in this way, for example, compared with the case of reading the leading edge of a sheet in a state where the trailing edge side of the sheet is held by only one roller pair, it becomes possible to firmly hold (clamp) the trailing edge side of the sheet by a plurality of roller pairs. As a result, it becomes possible to suppress changes in the conveyance speed of the sheet and vibrations in the conveyance direction Y2 when the leading edge of the sheet contacts the guide roller 705 or the like, and the reading accuracy of the sheet can be improved.

[0055] For example, the distance (L1 + L2) in the conveyance direction Y2 between the first nip portion N1 and the first reading position P1 is smaller than 210 mm, which is the length in the short side direction of the A4 size. As a result, when the leading edge of an A4-size sheet, which is a small size among sheet sizes with high market demand, is read by the backside CIS701, the trailing edge side of the sheet can be firmly held by a plurality of roller pairs.

[0056] Note that the distance (L1 + L2) in the conveyance direction Y2 between the first nip portion N1 and the first reading position P1 may be configured to be smaller than the length in the sub-scanning direction of the smallest-size sheet that the image forming apparatus 100 (adjustment unit 400) can convey. For example, the distance (L1 + L2) in the conveyance direction Y2 between the first nip portion N1 and the first reading position P1 may be configured to be smaller than the distance in the conveyance direction Y2 between the second nip portion N2 and the third nip portion N3.

[0057] Further, the first reading unit 700A is not limited to having only one backside CIS and one guide roller, respectively. The first reading unit 700A may have a plurality of backside CISs arranged at different positions in the main scanning direction or the sub-scanning direction, or may have a plurality of guide rollers arranged at different positions in the sub-scanning direction. In such a case, it is desirable that the distance in the sub-scanning direction (conveyance direction) between the first nip portion N1 and the reading position of the backside CIS arranged most upstream is smaller than 210 mm (or the length in the sub-scanning direction of the smallest-size sheet).

[0058] Also, in the first reading unit 700A of the present embodiment, the distance L2 in the conveyance direction Y2 between the second nip portion N2 and the first reading position P1 is larger than the distance L1 in the conveyance direction Y2 between the first nip portion N1 and the second nip portion N2. As a result, it becomes possible to reduce the stress applied to the sheet from the guide roller 705.

[0059] Also in the second reading unit 700B, the positional relationship in the conveyance direction Y2 of the third nip unit N3, the fourth nip unit N4, and the second reading position P2 is the same as the positional relationship in the conveyance direction Y2 of the first nip unit N1, the second nip unit N2, and the first reading position P1. Specifically, when the leading edge of the sheet enters between the guide roller 706 and the transparent guide 704, the surface CIS 702, the third conveyance roller pair 403, and the fourth conveyance roller pair 404 are arranged such that each of the nip portions of these roller pairs sandwiches the sheet. Thereby, the second reading unit 700B of the present embodiment can suppress changes in the conveyance speed of the sheet and vibrations in the conveyance direction Y2 when reading the sheet, and can improve the reading accuracy of the sheet.

[0060] As shown in FIG. 6, the front-back alignment unit 700 includes a driving device 400K as a driving means for driving each roller, having the above-described conveyance motors M401 to M406 and a toothed belt for transmitting the driving force of each conveyance motor M401 to M406 to each roller.

[0061] Specifically, the driving device 400K has a toothed belt 401b that connects the conveyance motor M401 and the first conveyance roller pair 401 and transmits the driving force of the conveyance motor M401 to the first conveyance roller pair 401. Further, the driving device 400K has a toothed belt 402b that connects the conveyance motor M402 and the second conveyance roller pair 402 and transmits the driving force of the conveyance motor M402 to the second conveyance roller pair 402. Further, the driving device 400K has a toothed belt 403b that connects the conveyance motor M403 and the third conveyance roller pair 403 and transmits the driving force of the conveyance motor M403 to the third conveyance roller pair 403. Further, the driving device 400K has a toothed belt (not shown) that connects the conveyance motor M404 and the fourth conveyance roller pair 404 and transmits the driving force of the conveyance motor M404 to the fourth conveyance roller pair 404.

[0062] Thereby, for example, the backlash between the motor and the roller can be reduced as compared with the case where the driving force of the motor is transmitted by gears or the like, and it becomes possible to suppress changes in the conveyance speed of the sheet and vibrations in the conveyance direction Y2.

[0063] Note that although the driving device 700K according to the present embodiment is configured to transmit the driving forces of the conveyance motors M401 to M404 to the rollers by toothed belts, it is not limited thereto. The driving device 700K may have at least one motor and one toothed belt that transmits the driving force of the motor to at least one pair of rollers capable of holding the rear end side of the sheet when the leading end of the sheet reaches the reading position. For example, the driving device 700K may drive a plurality of pairs of rollers with one motor, or may transmit the driving force of one motor to a plurality of pairs of rollers by one toothed belt. Further, for example, the driving device 400K may be configured to transmit the driving force of the motor to either the first conveyance roller pair 401 or the second conveyance roller pair 402 by gears or the like.

[0064] [Sheet Reading and Feedback of Reading Results] Next, with reference to FIGS. 1, 2, 7 to 11, the reading of the sheet by the front-back identification unit 700 and the feedback of the reading result will be described. The sheet library 900 (see FIG. 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 the length in the sub / main scanning direction and the basis weight. The sheet library 900 includes geometric adjustment values used when performing an image forming process on each sheet. The geometric adjustment value is a parameter for correcting the position, magnification, etc. of the image with respect to the contour of the sheet when performing the image forming process.

[0065] As shown in FIG. 7(a), the content of the sheet library 900 can be confirmed by causing the operation unit 180 (see FIG. 1) to display the library display screen 1001. Further, when the "print position adjustment" button 1002 on the library display screen 1001 is operated, a selection screen 1003 for the correction method of the geometric adjustment value shown in FIG. 7(b) is displayed. When the user selects the option 1004 of "manual adjustment", the user can directly specify the geometric adjustment value by inputting a numerical value using the numeric keypad 181 (see FIG. 1) provided in the operation unit 180 or the like.

[0066] On the other hand, when the user selects the option 1005 of "read the test page and adjust", the image forming system 100S (see FIG. 1) executes a front / back determination process for performing front / back determination based on the sheet reading result. In the front / back determination process, the image forming apparatus 100 forms a test pattern 820 (see FIG. 8) for front / back determination on the sheet. Further, in the front / back determination process, the front / back determination unit 700 (see FIG. 1) of the adjustment unit 400 reads the sheet conveyed from the image forming apparatus 100 and feeds back the reading result to the image forming apparatus 100. The image forming apparatus 100 performs adjustment (correction) of the geometric adjustment value based on the feedback from the adjustment unit 400.

[0067] Specifically, when the front-back alignment process is started, the image forming apparatus 100 first feeds the sheet 1 from the sheet storage bin 113 that stores the sheet designated as the target of the front-back alignment process. After that, the image forming apparatus 100 forms, by the image forming engine 102, a test pattern 820 (see FIG. 8) in which rectangular patch images are arranged near the four corners of the sheet surface, on both sides of the sheet. After forming the test pattern 820, the image forming apparatus 100 discharges the sheet toward the adjustment unit 400. Note that the test pattern is not limited to being composed of a plurality of rectangular patch images, and may be composed of a plurality of square patch images. Further, the test pattern may be composed of a so-called tombo mark which is a trimming position mark or a folding position mark, may be composed of images of other shapes, or may be a combination thereof. Also, the color and density of the test pattern are not limited to being uniform, and the test pattern may include patch images of a plurality of colors and a plurality of densities.

[0068] When receiving the sheet from the image forming apparatus 100, while conveying the received sheet 1 by each pair of conveyance rollers, the adjustment unit 400 reads the front and back surfaces of the sheet 1 as line images by the back surface CIS 701 and the front surface CIS 702 (see FIG. 4). Then, the image processing unit 460 (see FIG. 2) of the adjustment unit 400 stitches together the read line images in the sub-scanning direction (the conveyance direction of the sheet 1), so that the image data of the front and back surfaces of the sheet 1 including the test pattern 820 is synthesized. In this way, when reading the sheet conveyed by the back surface CIS 701 and the front surface CIS 702, the adjustment unit 400 reads the image information of the test pattern 820.

[0069] The image processing unit 460 of the adjustment unit 400 identifies the shape (outline) of the sheet, the shape of the patch images formed on the sheet, and their positional relationship. Specifically, from the synthesized image data, for the front and back surfaces of the sheet 1, the corner coordinates and the coordinates of each patch image of the test pattern 820 are identified. As shown in FIGS. 8(a) and 8(b), the corner coordinates of the sheet 1 represent the positions of the four corners of the sheet 1 {(X01, Y01) to (X31, Y31), (X02, Y02) to (X32, Y32)} when the X-axis is the main scanning direction and the Y-axis is the sub-scanning direction. Also, the coordinates of the test pattern 820 represent the positions of specific parts of the patch images {(X41, Y41) to (X71, Y71), (X42, Y42) to (X72, Y72)} in the same coordinate system as the corner coordinates.

[0070] From the corner coordinates of the sheet 1, since the length in the main scanning direction (short side length) (A), the length in the sub-scanning direction (long side length) (B), and the right angle of the corners of the sheet can be geometrically calculated, it can be said that the corner coordinates contain information regarding the shape (outline) of the sheet 1. Also, since the positional deviation and distortion of the image with respect to the outline of the sheet can be geometrically calculated from the corner coordinates and the coordinates of the test pattern 820, it can be said that the corner coordinates and the coordinates of the test pattern 820 contain information regarding the position and distortion of the image with respect to the sheet.

[0071] The image processing unit 460 further determines (calculates) the geometric adjustment values for the sheet 1 by using the corner coordinates of the sheet 1 and the coordinates of the test pattern 820. For example, the image processing unit 460 determines, as the geometric adjustment values, the lead position, the side position, the main scanning magnification, and the sub-scanning magnification. The lead position is a parameter that defines the image position in the sub-scanning direction with respect to the sheet 1. The side position is a parameter that defines the image position in the main scanning direction with respect 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. Also, 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 such that when the image shape is corrected, the distance from the test pattern 820 to the end of the sheet ((C) to (J) in FIGS. 8(a) and (b)) becomes equal to a preset value.

[0072] Here, four parameters, namely the lead position, the side position, the main scanning magnification, and the sub-scanning magnification, are listed as the geometric adjustment values. However, the image processing unit 460 may calculate other parameters. Examples of other parameters include a parameter for correcting the right-angledness of the image, a parameter for performing trapezoidal correction of the image, a parameter for defining the rotation angle of the image with respect to the sheet, and the like.

[0073] The geometric adjustment values determined by the image processing unit 460 are sent to the printer controller 103 of the image forming apparatus 100 through the communication unit 450 and registered in the sheet library 900. When the image forming apparatus 100 executes an image forming job, the image shape correction unit 320 refers to the sheet library 900 to acquire the sheet information 910, 911, 912,... of the sheet designated as the recording material and the geometric adjustment values (see FIG. 7(a)). Then, the image shape correction unit 320 corrects the image data based on the geometric adjustment values of the acquired sheet. By correcting the image data on the front and back surfaces of the sheet, the front and back identification of the sheet is performed.

[0074] Here, the case where the test pattern 820 for front / back determination is formed based on an explicit instruction from the user and the adjustment unit 400 acquires the geometric adjustment value has been described, but the present invention is not limited to this. For example, when an image formation job is input, as a preparatory operation before executing the job, the test pattern 820 may be formed on the same sheet as that specified in the job to acquire the geometric adjustment value. Further, during the execution of an image formation job that requires a large number of products, a job for forming the test pattern 820 may be automatically inserted each time a certain number of products are output to perform correction (calibration). Further, the purpose for which the adjustment unit 400 reads the sheet is not limited to acquiring the geometric adjustment value to correct the positional deviation and distortion of the image with respect to the sheet. For example, the adjustment unit may read (read image information from the sheet) the sheet on which the image of the continuously conveyed product is formed in order to monitor that the positional deviation and distortion of the image with respect to the sheet are within a predetermined value.

[0075] [Control Method] In the image forming system 100S configured as described above, a control method when the adjustment unit 400 conveys and reads the sheet will be described with reference to the flowchart of FIG. 9 while referring to the block diagram of FIG. 2.

[0076] In the following description, among the image formation jobs, a job that requests output of a product and for which the adjustment unit 400 does not read the sheet is referred to as a "normal job". Further, among the image formation jobs, a job for which the adjustment unit 400 reads the sheet by the back CIS 701 and the front CIS 702 (see FIG. 4) to perform front / back determination is referred to as a "front / back determination job". Note that the normal job is input to the printer controller 103 when it is input from an external computer via the external I / F 303 (see FIG. 2), or when the user instructs the start of a copying operation via the operation unit 180. Further, as described above, the front / back determination job may be executed by an explicit instruction from the user or may be spontaneously executed by the image forming system 100S.

[0077] At the start of an image forming job (S1), the printer controller 103 determines whether the job is a normal job or a front / back identification job (S2). In the case of a normal job (S2: Y), the image forming apparatus 100 and the adjustment unit 400 cause members involved in sheet conveyance (e.g., flappers, etc.) to standby at their 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. 10(a)) to the first discharge port 442 (S4). That is, as shown in FIG. 10(a), the switching flapper 421 is held at the upper position.

[0078] The image forming apparatus 100 forms an image on the sheet 1 according to the image data required to be output by the image forming job (S5), and the adjustment unit 400 receives the sheet 1 on which the image has been formed (S6). Then, as shown in FIGS. 10(a) and (b), the adjustment unit 400 sequentially transfers the sheet 1 by each pair of conveyance rollers, and passes it through the through path 430. Then, the adjustment unit 400 discharges the sheet 1 from the first discharge port 442 to the finisher 600 (see FIG. 1) by the exit conveyance roller pair 406 (S7). When the finisher 600 receives the sheet 1, it processes the sheet 1 with the processing unit 601 and stacks the processed sheet as a product on the stacking tray 602.

[0079] In the case of a front / back identification job (S2: N), the adjustment unit 400 positions the switching flapper 421 at a position for guiding the sheet to the discharge path 432 (see FIG. 11(a)) (S10). That is, as shown in FIG. 11(a), the switching flapper 422 is held at the lower position.

[0080] The image forming apparatus 100 forms a test pattern 820 (see FIG. 8) for front-back identification on a sheet (S11), and the adjustment unit 400 receives the sheet on which the test pattern 820 is formed (S12). When the adjustment unit 400 passes the sheet 1 carried into the through path 430 through the reading positions P1 and P2 (see FIG. 4) of the back surface CIS 701 and the front surface CIS 702, the CISs 701 and 702 read the sheet 1 (S13, FIGS. 11(a) and (b)). Before the test pattern 820 on the sheet reaches the first reading position P1 of the back surface CIS 701, the control unit 451 of the adjustment unit 400 may decelerate the conveyance speed of the sheet 1 to a conveyance speed suitable for reading by the CISs 701 and 702.

[0081] The image data read by the back surface CIS 701 and the front surface CIS 702 is processed by the image processing unit 460, and geometric adjustment values are calculated. The calculated geometric adjustment values are transmitted to the image forming apparatus 100 via the communication unit 450 and stored in the sheet library 900 (S14).

[0082] When the sheet 1 that has passed through the reading positions P1 and P2 reaches the branch portion 431 from the through path 430 to the discharge path 432, the adjustment unit 400 conveys the sheet 1 guided by the switching flapper 422 along the discharge path 432 toward the second discharge port 443. The adjustment unit 400 discharges the sheet 1 conveyed along the discharge path 432 from the second discharge port 443 to the discharge tray 423 (S15).

[0083] In order to determine the front and back based on the averaged geometric adjustment value, the above processing is repeatedly executed for each sheet of the number of sheets specified in the job. After the processing for the last sheet is completed (S8: Y), the job ends (S9). In the control example shown in FIG. 9, the type of job 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 processing as the previous sheet may be applied without determination during the processing of the job. Also, in the control example shown in FIG. 9, in the job for determining the front and back, the sheet is discharged to the discharge tray 423 after the sheet is read, but it is not limited to this. The image forming system may be capable of executing control to discharge the sheet to the finisher after the sheet is read in the job for determining the front and back. For example, the image forming apparatus may form the image of the product and the test pattern arranged in the margin on the sheet, the adjustment unit may discharge the sheet to the finisher after reading the sheet, and the finisher may cut the margin of the sheet together with the test pattern.

[0084] As described above, according to the present embodiment, the adjustment unit 400 can read the leading end of the sheet while the rear end side is held by a plurality of roller pairs. Thereby, it is possible to suppress the change in the conveyance speed of the sheet and the vibration in the conveyance direction Y2 when reading the sheet, and improve the reading accuracy of the sheet.

[0085] In addition, in the present embodiment, the test pattern 820 for performing front / back identification and the adjustment unit 400 for reading the shape of the sheet have been described as the image reading device, but the present invention is not limited thereto. The image reading device only needs to be equipped with a reading means for reading the image information of the sheet while being sandwiched and conveyed, and it does not necessarily need to read the contour of the sheet, nor does it necessarily need to be for performing front / back identification, nor does it necessarily need to be able to read the images on both sides of the sheet. For example, the image reading device may be equipped with a color sensor as a reading means for reading the color information (density information) of the test pattern (image) formed on the sheet in order to perform color adjustment, density adjustment, etc. Further, for example, the image reading device may be an image reading device for the purpose of reading general images, documents, etc. and converting the content into electronic data. Further, for example, the image reading device may be equipped with one of the first reading unit 700A and the second reading unit 700B and be able to read only the image on one side (the first side) of the sheet.

Explanation of Reference Numerals

[0086] 1…Sheet / 100…Image Forming Apparatus / 100S…Image Forming System / 400…Image Reading Device (Adjustment Unit) / 401…Second Rotating Body Pair (First Conveying Roller Pair) / 401b…Toothed Belt / 402…First Rotating Body Pair (Second Conveying Roller Pair) / 403…Fourth Rotating Body Pair (Third Conveying Roller Pair) / 404…Third Rotating Body Pair (Fourth Conveying Roller Pair) / 701…Reading Means (Back Surface CIS) / 702…Reading Means (Front Surface CIS) / 703…Light Transmitting Plate (Transparent Guide) / 704…Light Transmitting Plate (Transparent Guide) / 705…Guide Member (First Guide Roller) / 706…Guide Member (Second Guide Roller) / L1…Distance / L2…Distance / Lg…Distance / M401…Motor (Conveying Motor) / N1…Nip Portion (First Nip Portion) / N2…Nip Portion (Second Nip Portion) / N3…Nip Portion (Third Nip Portion) / N4…Nip Portion (Fourth Nip Portion 9 / Np…Common Tangent Line (Nip Line) / P1…Reading Position (First Reading Position) / P2…Reading Position (Second Reading Position) / Y2…Conveying Direction

Claims

1. An image reading apparatus that reads image information of a sheet discharged from an image forming apparatus having an image forming unit that forms an image on the sheet, comprising: a first pair of conveying rollers that receives the sheet from the image forming apparatus and conveys the sheet in the sheet conveying direction; a first motor; a first toothed belt that transmits the driving force from the first motor to the first pair of conveying rollers; a second pair of conveying rollers that is disposed adjacent to the downstream of the first pair of conveying rollers in the sheet conveying direction and conveys the sheet conveyed by the first pair of conveying rollers in the sheet conveying direction; a second motor; a second toothed belt that transmits the driving force from the second motor to the second pair of conveying rollers; reading means for reading image information on the first surface of the sheet at a reading position downstream of the second pair of conveying rollers in the sheet conveying direction; wherein a distance between a nip portion of the first pair of conveying rollers and the reading position in the sheet conveying direction is less than 210 mm; An image reading apparatus characterized by the above.

2. An image reading apparatus that reads image information of a sheet discharged from an image forming apparatus having an image forming unit that forms an image on the sheet, comprising: a first pair of conveying rollers that receives the sheet from the image forming apparatus and conveys the sheet in the sheet conveying direction; a first motor; a first toothed belt that transmits the driving force from the first motor to the first pair of conveying rollers; a second pair of conveying rollers that is disposed adjacent to the downstream of the first pair of conveying rollers in the sheet conveying direction and conveys the sheet conveyed by the first pair of conveying rollers in the sheet conveying direction; a second motor; a second toothed belt that transmits the driving force from the second motor to the second pair of conveying rollers; reading means for reading image information on the first surface of the sheet at a reading position downstream of the second pair of conveying rollers in the sheet conveying direction; wherein a distance between a nip portion of the second pair of conveying rollers and the reading position in the sheet conveying direction is greater than a distance between a nip portion of the first pair of conveying rollers and a nip portion of the second pair of conveying rollers; An image reading apparatus characterized by the above.

3. a light-transmitting plate through which light from the sheet conveyed by the first pair of conveying rollers and the second pair of conveying rollers passes to the reading means; a guide member that is disposed to face the reading means at the reading position and guides the sheet conveyed by the first pair of conveying rollers and the second pair of conveying rollers. The image reading apparatus according to claim 1 or 2, characterized in that...

4. When the leading edge of the sheet enters between the guide member and the light-transmitting plate, the first pair of conveying rollers and the second pair of conveying rollers are arranged such that each of the first pair of conveying rollers and the second pair of conveying rollers sandwiches the sheet. The image reading apparatus according to claim 3, characterized in that...

5. A part of the guide member is arranged on the side of the reading means with respect to the common tangent line at the nip portion of the second pair of conveying rollers. The image reading apparatus according to claim 3 or 4, characterized in that...

6. The guide member is a rotating body of black or gray. The image reading apparatus according to any one of claims 3 to 5, characterized in that...

7. The distance between the guide member and the light-transmitting plate is equal to or greater than the thickness of the thickest sheet that the image reading apparatus can convey and equal to or less than three times the thickness of the thickest sheet. The image reading apparatus according to any one of claims 3 to 6, characterized in that...

8. The reading means and the reading position are a first reading means and a first reading position, respectively. A second reading means for reading image information on a second surface of the sheet opposite to the first surface of the sheet at a second reading position. A third pair of conveying rollers provided downstream of the first reading position and upstream of the second reading position in the sheet conveying direction for conveying the sheet toward the second reading position. A fourth pair of conveying rollers provided downstream of the third pair of conveying rollers and upstream of the second reading position in the sheet conveying direction for conveying the sheet toward the second reading position. The image reading apparatus according to any one of claims 1 to 7, characterized in that...

9. The image forming apparatus for forming an image on a sheet. An image reading apparatus according to any one of claims 1 to 8, and... The image forming apparatus corrects the position of the image with respect to the sheet when forming an image on the sheet based on the image information read by the image reading apparatus. An image forming system, characterized in that...

Images