Image reading device and image forming system

Abstract

To guarantee gaps between a light transmission member and a plurality of rollers.SOLUTION: An image reading device 700 comprises: a conveyance path 231 on which a sheet P is conveyed in a conveyance direction CD; a light transmission member 704 that is arranged to form part of the conveyance path; a plurality of reading means 702, 703 that read the sheet conveyed on the conveyance path in the conveyance direction through the light transmission member; a plurality of rollers 706, 707 that are arranged opposite to the plurality of reading means; a plurality of abutting members 708, 709 that are provided on both ends of the plurality of rollers and in contact with the light transmission member to guarantee gaps between the light transmission member and the plurality of rollers; urging means 753 that urges the plurality of abutting members against the light transmission member; and holding means 752 that integrally holds the plurality of rollers. The holding means is elastically deformed by the urging force of the urging means so as to bring the plurality of abutting members into contact with the light transmission member.SELECTED DRAWING: Figure 11

Description

[Technical field]

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

[0002] An image forming apparatus that forms an image on cut-sheet paper (hereinafter referred to as a sheet) provides high-precision printing position stability by aligning (registration) the sheet. Usually, registration is performed using one side of a rectangular sheet as a reference, so the accuracy variation of each sheet depends on the cutting accuracy of the sheet. The cutting accuracy of a sheet includes perpendicularity and parallelism in addition to length. The registration accuracy is greatly affected by the difference in the cutting lot of the sheet and the surrounding environment. For this reason, the front and back registration accuracy of the sheet is also affected by the shape of the sheet, just like the color reproducibility. Therefore, in order to provide a front and back printing accuracy equivalent to offset printing with a cut-sheet printing machine, it is necessary to adjust the front and back misalignment by adjusting the printing position, magnification, and distortion every time the cutting lot of the sheet or the setting environment changes (front and back registration).

[0003] For an image forming apparatus that forms images on various sheets, front and back registration is one of the items that require adjustment time, depending on the material of the sheet. This is because, in order for the front and back registration section to perform front and back registration with high accuracy, it is necessary to measure and average multiple sheets in order to average out the sheet variations. In order to shorten the time required for front and back registration adjustment, there is a demand for an image forming apparatus that can perform front and back registration continuously from image formation to sheet discharge and automatically adjust according to the type of sheet.

[0004] For example, there is known an image reading device that reads the image of a sheet by an image sensor while conveying the sheet in order to check the front and back of the sheet. Patent Document 1 discloses an image forming apparatus provided with an image reading device that reads the image of a sheet while conveying the sheet by using a plurality of image sensors arranged in a staggered pattern to widen the readable width in the main scanning direction. In addition, generally, a reference white board is read by the image sensor to perform shading correction in order to correct unevenness in the amount of light of the light source of the image sensor and unevenness in the sensitivity of the light receiving unit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4571027 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in order to suppress the fluttering of the sheet transported on a light-transmitting member such as transparent glass and to properly read the sheet, a plurality of backing rollers are arranged at positions facing a plurality of reading means such as an image sensor. The sheet is read by the plurality of reading means while being transported through the gap between the light-transmitting member and the plurality of backing rollers. Therefore, it is important that the gap between the light-transmitting member and the plurality of backing rollers is uniform. However, since the device is provided with a plurality of reading means, the area of ​​the light-transmitting member is large, and it is difficult to ensure the planarity of the light-transmitting member. If the light-transmitting member is not flat, the gap between the light-transmitting member and the plurality of backing rollers will not be uniform. For example, if the gap is too large, the fluttering of the transported sheet will increase and the resolution of the read image will decrease. If the gap is too small, the image on the transported sheet may be scratched.

[0007] Therefore, the present invention provides an image reading device that can ensure gaps between a light transmitting member and a plurality of rollers even if the surface of the light transmitting member has low flatness. [Means for solving the problem]

[0008] An image reading device according to an embodiment of the present invention comprises: a conveying path along which the sheet is conveyed in a conveying direction; a light transmitting member arranged to form a part of the transport path; a first reading means for reading an image on a first surface of the sheet conveyed on the conveying path in the conveying direction through the light transmitting member; a second reading means arranged at a position different from that of the first reading means in the conveying direction, and configured to read an image on the first surface of the sheet together with the first reading means through the light transmitting member; A first roller disposed opposite the first reading means; A second roller disposed opposite the second reading means; The first roller and the second roller Both Hold One retention Materials and, a plurality of first abutment members provided on both end sides of the first roller in a width direction perpendicular to the conveying direction, the abutment members contacting the light transmitting member to form a gap between the light transmitting member and the first roller; a plurality of second abutment members provided on both end sides of the second roller in the width direction and abutting against the light transmitting member to form a gap between the light transmitting member and the second roller; The above One retention Materials a biasing means for biasing the light transmitting member against the light transmitting member; The present invention is characterized by comprising: Effect of the Invention

[0009] According to the present invention, even if the surface of the light transmitting member has low flatness, the gaps between the light transmitting member and the plurality of rollers can be ensured. [Brief description of the drawings]

[0010] [Figure 1]FIG. [Diagram 2] FIG. 2 is a block diagram of an image forming apparatus and an adjustment unit. [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] FIG. [Figure 7] 11 is a cross-sectional view of the front surface reading unit when the CIS is moved to a shading correction position. [Figure 8] FIG. 3 is a perspective view of the CIS as seen from the reading glass side. [Figure 9] FIG. [Figure 10] FIG. [Figure 11] 4 is a cross-sectional view of a backing roller portion in contact with the reading glass. FIG. [Figure 12] FIG. 4 is a cross-sectional view of a backing roller portion spaced apart from the reading glass. [Figure 13] 4 is a cross-sectional view of a backing roller portion that follows a dent in the reading glass. [Figure 14] FIG. [Figure 15] A diagram showing the Sheets library. [Figure 16] FIG. 4 is a diagram showing a sheet library editing screen displayed on the operation unit. [Figure 17] 4A and 4B are diagrams showing patch images formed on a sheet. [Figure 18] 11 is a flow chart of a control operation for conveying a sheet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (Image forming system) FIG. 1 is a partial cross-sectional view of an image forming system 100. The image forming system 100 includes an image forming apparatus 101, an operation unit (user interface) 180, an adjustment unit (automatic adjustment device) 200, and a post-processing device (finisher) 600. The image forming apparatus 101 forms an image on a recording medium (hereinafter referred to as a sheet) P. The operation unit 180 is operated by a user to set image formation conditions, and also displays the state of the image forming apparatus 101. The adjustment unit 200 performs front-back registration to adjust the positional deviation between an image formed on the front side of the sheet P by the image forming apparatus 101 and an image formed on the back side. The post-processing device 600 discharges the sheet P on which the image has been formed to a discharge tray 601, and performs post-processing such as stapling, punching, and sorting.

[0012] (Image forming device) The image forming apparatus 101 is an electrophotographic laser beam printer. The image forming apparatus 101 forms an image on a sheet using an electrophotographic image forming process. In addition to a laser beam printer, the image forming apparatus 101 may be, for example, an electrophotographic copying machine (e.g., a digital copying machine), a color LED printer, an MFP (multifunction machine), a facsimile machine, or a printing machine. The image forming apparatus 101 is not limited to a color image forming apparatus that forms a color image, but may also be a monochrome image forming apparatus that forms a monochrome image. The image forming apparatus 101 is not limited to an electrophotographic image forming apparatus, but may also be an inkjet printer, a dye-sublimation printer, or a thermal printer using a thermal drying method.

[0013] The image forming apparatus 101 will be described with reference to Fig. 1 and Fig. 2. Fig. 2 is a block diagram of the image forming apparatus 101 and the adjustment unit 200. The image forming apparatus 101 has a printer controller 103, an engine control unit 312, and an engine unit 140. The printer controller 103 has a sheet library 900 and an image shape correction unit 320. The printer controller 103 is electrically connected to the operation unit 180, the engine control unit 312, and a communication unit 250 of the adjustment unit 200.

[0014] The engine control unit 312 is electrically connected to the conveying roller drive motor 311 and the flapper drive unit 141. The flapper drive unit 141 drives the flappers 131, 132, 133, and 134. The engine control unit 312 is further electrically connected to the first post-fixing sensor 153, the second post-fixing sensor 163, the inversion sensor 137, and the engine unit 140. The engine control unit 312 controls the engine unit 140 to execute the image forming process (including the sheet feeding process). The engine unit 140 has a yellow image forming unit 120, a magenta image forming unit 121, a cyan image forming unit 122, and a black image forming unit 123. The engine unit 140 further has a feed cassette 113, an intermediate transfer body 106, a secondary transfer roller 114, a first fixing unit 150, and a second fixing unit 160.

[0015] The yellow image forming unit 120 forms a yellow (Y) toner image. The magenta image forming unit 121 forms a magenta (M) toner image. The cyan image forming unit 122 forms a cyan (C) toner image. The black image forming unit 123 forms a black (K) toner image. The yellow image forming unit 120, the magenta image forming unit 121, the cyan image forming unit 122, and the black image forming unit 123 have almost the same structure except for the color of the toner, so the yellow image forming unit 120 will be described below.

[0016] The yellow image forming unit 120 has a rotating photosensitive drum 105. Around the photosensitive drum 105, a charger 111, a laser scanner 107, a developing unit 112, and a primary transfer roller 118 are arranged. The charger 111 uniformly charges the surface of the photosensitive drum 105. The laser scanner 107 has a laser driver (not shown) that turns on / off a laser beam emitted from a semiconductor laser 108 according to image data supplied from the printer controller 103. The laser beam emitted from the semiconductor laser 108 is deflected in the main scanning direction by a rotating polygon mirror (not shown). The laser beam deflected in the main scanning direction is guided to the surface of the photosensitive drum 105 by a reflecting mirror 109, and exposes the uniformly charged surface of the photosensitive drum 105 in the main scanning direction. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 105 according to the image data.

[0017] The developing device 112 develops the electrostatic latent image on the surface of the photosensitive drum 105 with yellow (Y) toner to form a yellow (Y) toner image. A voltage of the opposite polarity to that of the toner image is applied to the primary transfer roller 118, which transfers the yellow (Y) toner image on the surface of the photosensitive drum 105 onto the intermediate transfer body 106. Similarly, a magenta (M) toner image, a cyan (C) toner image, and a black (K) toner image formed by a magenta image forming unit 121, a cyan image forming unit 122, and a black image forming unit 123 are sequentially transferred onto the intermediate transfer body 106. The yellow (Y), magenta (M), cyan (C), and black (K) toner images are transferred onto the intermediate transfer body 106 in a superimposed manner to form a full-color toner image.

[0018] Meanwhile, the sheets P stored in the feeding cassette 113 are conveyed one by one to the secondary transfer roller 114. The secondary transfer roller 114 presses the sheet P against the intermediate transfer body 106 and simultaneously applies a bias of the opposite polarity to the toner. The secondary transfer roller 114 transfers the toner image on the intermediate transfer body 106 to the sheet P. The photosensitive drum 105 and the developing device 112 are detachable. A feeding timing sensor 116 for timing the feeding of the sheet P is disposed in the sheet conveying path in front of the secondary transfer roller 114. In addition, an image formation start position detection sensor 115 for determining the print start position when forming an image and a density sensor 117 for measuring the density of a patch image during density control are disposed around the intermediate transfer body 106. When performing density control, the density sensor 117 measures the density of each patch image.

[0019] The image forming apparatus 101 has a first fixing device 150 and a second fixing device 160 that heat and pressurize the toner image transferred to the sheet P to fix the toner image to the sheet P. The first fixing device 150 includes a fixing roller 151 having an internal heater, a pressure belt 152 that presses the sheet P against the fixing roller 151, and a first post-fixing sensor 153 that detects the completion of fixing. The fixing roller 151 and the pressure belt 152 hold the sheet P between them and heat and pressurize it to fix the toner image to the sheet P, while conveying the sheet P. The second fixing device 160 is disposed downstream of the first fixing device 150 in the conveying direction of the sheet P. The second fixing device 160 is provided to increase the gloss of the image fixed to the sheet P by the first fixing device 150 and ensure fixability. The second fixing device 160 includes a fixing roller 161, a pressure roller 162, and a second post-fixing sensor 163.

[0020] Depending on the type of sheet P, it is not necessary to use the second fixing device 160. The flapper 131 switches the destination of the sheet P to the conveying path 130. In this case, the sheet P is conveyed to the conveying path 130 without passing through the second fixing device 160 for the purpose of reducing energy consumption. The flapper 132 switches the destination of the sheet P to the conveying path 135 and the discharge path 139. For example, in the face-up discharge mode, the flapper 132 switches the destination of the sheet P to the discharge path 139 in order to convey the sheet P having an image formed on its first side to the discharge path 139. For example, in the face-down discharge mode, the flapper 132 switches the destination of the sheet P to the conveying path 135 in order to convey the sheet P having an image formed on its first side to the conveying path 135. When the rear end of the sheet P passes through the flapper 134, the conveying direction of the sheet P is reversed, and the destination of the sheet P is switched to the discharge path 139 by the flapper 134.

[0021] For example, in the double-sided printing mode, in order to print the adjustment chart on the second side of the sheet P after the adjustment chart (measurement test pattern) is printed on the first side of the sheet P, the flapper 132 switches the conveyance destination of the sheet P to the conveyance path 135. The sheet P conveyed to the conveyance path 135 is conveyed to the inversion section 136. After the rear end of the sheet P conveyed to the inversion section 136 is detected by the inversion sensor 137, the conveyance direction of the sheet P is reversed. The flapper 133 switches the conveyance destination of the sheet P to the conveyance path 138. This inverts the front and back of the sheet P. The sheet P is conveyed from the conveyance path 138 to the secondary transfer nip between the intermediate transfer body 106 and the secondary transfer roller 114. The adjustment chart is transferred to the second side of the sheet at the secondary transfer nip. The sheet P with the adjustment charts printed on both sides is conveyed from the discharge path 139 to the adjustment unit 200.

[0022] (Adjustment unit) The adjustment unit 200 is disposed downstream of the image forming apparatus 101 in the conveying direction of the sheet P. FIG. 3 is a cross-sectional view of the adjustment unit 200. The adjustment unit 200 has a through path 230, a measurement path (conveyance path) 231 bypassed to the lower side, and a discharge path 232 for discharging the sheet from the through path 230 or the measurement path 231 to a post-processing apparatus 600 disposed downstream of the adjustment unit 200. The measurement path 231 is provided with a front-back registration unit (image reading device) 700 as a measurement unit that performs front-back registration by reading adjustment charts formed on both sides of the sheet P. The adjustment unit 200 has a flapper 221 that switches the conveying destination of the sheet P between the through path 230 and the measurement path 231.

[0023] When front and back registration is not performed by the front and back registration section 700, the flapper 221 waits in a downward position to switch the destination of the sheet P to the through path 230. The adjustment unit 200 receives the sheet P from the image forming apparatus 101, and conveys the sheet P to the through path 230 by the first conveyance roller 201. The sheet P is conveyed from the through path 230 to the discharge path 232 by the second conveyance roller 202 and the third conveyance roller 203. The sheet P is discharged to the post-processing device 600 by the fourth conveyance roller 204.

[0024] On the other hand, when front and back registration is performed by the front and back registration section 700, the flapper 221 waits in an upward position to switch the conveyance destination of the sheet P to the measurement path 231. The adjustment unit 200 receives the sheet P from the image forming apparatus 101, and conveys the sheet P to the measurement path 231 by the first conveyance roller 201. The sheet P is conveyed to the front and back registration section 700 by conveyance roller pairs 205, 206, 207, 208, 209, and 210. The front and back registration section 700 reads the adjustment charts formed on both sides of the sheet P while conveying the sheet P by the conveyance roller pairs 211, 212, and 213. The sheet P is conveyed to the discharge path 232 by the conveyance roller pair 214, and discharged to the post-processing device 600 by the fourth conveyance roller 204.

[0025] As shown in FIG. 2, the adjustment unit 200 has a communication unit 250, an image processing unit 260, and a control unit (control means) 251. The communication unit 250 is electrically connected to the image processing unit 260 and the control unit 251. The communication unit 250 is electrically connected to the printer controller 103 of the image forming apparatus 101. The adjustment unit 200 further has a conveying motor 252, a conveying path sensor 253, a flapper switching motor 240, a backing motor 834, a shading motor 810, a photosensor 816, an image sensor 702, and an image sensor 703. The conveying motor 252, the conveying path sensor 253, the flapper switching motor 240, the backing motor 834, the shading motor 810, the photosensor 816, the image sensor 702, and the image sensor 703 are electrically connected to the control unit 251. The image processing unit 260 is electrically connected to the image sensor 702 and the image sensor 703.

[0026] (Front and back registration section) The structure of the front and back registration unit 700 will be described with reference to FIG. 4. FIG. 4 is a diagram showing the front and back registration unit 700. The front and back registration unit 700 measures the shape of the sheet P and the shape and positional relationship of the image pattern formed on the sheet P. To obtain highly accurate measurement results, it is necessary to average out the shape variations and print position variations for each sheet P, so multiple sheets P are measured. In order to shorten the adjustment time for measuring multiple sheets P, the front and back registration unit 700 measures the sheet P while transporting it. In addition, since it is desirable for the size of the front and back registration unit 700 to be small, the front and back registration unit 700 uses contact image sensors (hereinafter referred to as CIS) 702 and 703 (FIG. 5) as image sensors.

[0027] The front and back registration unit 700 includes a front reading unit 911 that reads the front side of the sheet P, and a back reading unit 912 that reads the back side of the sheet P. The front and back registration unit 700 reads the adjustment charts formed on the front and back sides of the sheet P almost simultaneously. The front reading unit 911 and the back reading unit 912 are disposed on opposite sides of the measurement path 231. The front reading unit 911 includes a front reading box 901, a reading glass (glass plate) 704 as a transparent member (light-transmitting member), and a plurality of backing rollers (a plurality of rollers) 706 and 707. The back reading unit 912 includes a back reading box 902, a reading glass 704, and backing rollers 706 and 707. The reading glass 704 forms a part of the measurement path 231. The front reading box 901 is disposed on one side of the measurement path 231. The back side reading box 902 is disposed on the other side of the measurement path 231. The front side reading box 901 and the back side reading box 902 continuously read the front and back sides of the sheet P transported in the transport direction CD. The front side reading box 901 and the back side reading box 902 are each provided with a plurality of CISs 702 and 703 as reading means. The front side reading box 901 and the back side reading box 902 are each disposed facing the measurement path 231 via the reading glass 704. The backing rollers 706 and 707 are disposed on the opposite side of the measurement path 231 facing the reading glass 704.

[0028] The conveying roller pairs (conveying means) 211, 212, and 213 convey the sheet P in the conveying direction CD at a stable conveying speed. The conveying roller pairs 211, 212, and 213 are driven by a conveying motor (driving means) 252. The reading glass 704 functions as a guide member that guides the movement of the sheet P to stabilize the position of the sheet P in the focal depth direction of the CISs 702, 703 of the front side reading box 901 and the CISs 702, 703 of the back side reading box 902. The backing rollers 706 and 707 are black to clarify the contrast between the front sides of the backing rollers 706 and 707 and the edge of the sheet P. The backing rollers 706 and 707 are driven by a backing motor 834.

[0029] (Reading unit) The front side reading unit 911 and the back side reading unit 912 have almost the same structure except that their orientations with respect to the measurement path 231 are opposite. Therefore, the front side reading unit 911 will be described below, and the description of the back side reading unit 912 will be omitted. FIGS. 5 and 6 are cross-sectional views of the front side reading unit 911. A state in which the sheet P is transported to the front side reading unit 911 will be described with reference to FIGS. 5 and 6. The CIS 702 is disposed facing the backing roller 706 across the reading glass 704. The CIS 703 is disposed facing the backing roller 707 across the reading glass 704. The CIS 702 and 703 are carried by a carriage (carrier) 835. The CIS 702 and 703 can be moved by the carriage 835 in the sub-scanning direction Y along the transport direction CD.

[0030] The sheet P is conveyed in the conveying direction CD to the upper surface of a transparent reading glass 704 by a conveying roller pair 211. A plurality of reference white plates (a plurality of reference members) 831 and 832 are arranged on a surface (first surface) of the reading glass 704 on the side of the measurement path (conveying path) 231. A sheet guide member 830 is arranged on the reference white plates 831 and 832. The sheet P is conveyed on the sheet guide member 830, passes through the gap between the CIS 702 and the backing roller 706 and the gap between the CIS 703 and the backing roller 707, and is conveyed by the downstream conveying roller pair 212 as shown in FIG. 6.

[0031] The CISs 702 and 703 each irradiate light toward the sheet P using a light-emitting unit 805 having a light source, and collect reflected light from the sheet P on a linear light-receiving unit (light-receiving sensor surface) 806 using a rod lens array or the like. The reflected light received by the CISs 702 and 703 is photoelectrically converted and output as an output signal to the image processing unit 260. The image processing unit 260 generates image data based on the output signals of the CISs 702 and 703. The CISs 702 and 703 positioned at the reading position RP read an image of the sheet P conveyed at a constant speed on the reading glass 704 using a sheet flow reading method. The image processing unit 260 generates a surface measurement pattern image 822 of the sheet P, which will be described later, based on the output signals of the CISs 702 and 703.

[0032] The backing rollers 706 and 707 are driven by a backing motor 834 so as to rotate in the direction of the arrows in Figures 5 and 6 at a peripheral speed substantially equal to the conveying speed (reading speed) of the sheet P. The backing rollers 706 and 707 are set with a gap δ between the backing rollers 706 and 707 and the reading glass 704 so as to reduce the turbulence (wobbling) of the sheet P conveyed to the reading positions RP of the CISs 702 and 703. Abutment rollers (gap guarantee members) 708 and 709 are disposed at both ends of the backing rollers 706 and 707 in the axial direction as abutment members that abut against the reading glass 704 to guarantee the gap δ between the backing rollers 706 and 707 and the reading glass 704. The gap δ between the backing rollers 706 and 707 and the reading glass 704 is obtained by adding a margin (extra gap) to the thickness of the sheet P being conveyed. The gap δ is set so that the surface (read surface) of the sheet P falls within the readable range of the CISs 702 and 703 even if the sheet P moves wildly.

[0033] (Shading correction) Shading correction will be described with reference to Figures 7 and 8. Figure 7 is a cross-sectional view of the front side reading unit 911 in a state in which the CISs 702 and 703 have been moved to the shading correction position SH. Figure 8 is a perspective view of the CISs 702 and 703 as viewed from the side of the reading glass 704. To perform shading correction, the CISs 702 and 703 are moved in the sub-scanning direction Y by the carriage 835 from a downstream reading position RP (Figure 6) in the conveying direction CD of the sheet P to an upstream shading correction position SH (Figure 7).

[0034] The CIS 702 and 703 cannot perform uniform image reading due to unevenness in the amount of light of the light emitting unit 805 and unevenness in the sensitivity of the light receiving unit 806. Therefore, in order to enable uniform image reading, shading correction is performed. In shading correction, the CIS 702 and 703 read the reference white plates 831 and 832 from the surface (second surface) opposite to the surface (first surface) of the reading glass 704 on the side of the measurement path (conveying path) 231. The color of the reading surfaces of the reference white plates 831 and 832 is managed over the entire surface. The CIS 702 and 703 output output signals (image data) as the reading results to the image processing unit 260. The image processing unit 260 generates a correction value for correcting the image data when the sheet P is read based on the output signals of the CIS 702 and 703 when the reference white plates 831 and 832 are read. The control unit 251 corrects the amount of light emitted by the light-emitting unit 805 that irradiates the sheet P based on the correction value, and corrects the amplification factor (gain) that amplifies the output signal of the light-receiving unit 806 when reading the sheet P based on the correction value. In this way, by adjusting the amount of light emitted by the light-emitting unit 805 and / or the amplification factor (gain) of the light-receiving unit 806 based on the reading results of the reference white plates 831 and 832, the CISs 702 and 703 can uniformly read the sheet P.

[0035] In this embodiment, the shading correction position SH (FIG. 7) is disposed upstream of the reading position RP (FIG. 6) in the transport direction CD of the sheet P. Therefore, the reference white plates 831 and 832 are disposed upstream of the reading position RP in the transport direction CD of the sheet P. The accuracy of shading correction is improved if the reference white plates 831 and 832 are as high as possible in the focal depth direction of the CISs 702 and 703 as the sheet P transported on the measurement path 231. Therefore, in this embodiment, the reference white plates 831 and 832 are disposed on the surface (upper surface) of the reading glass 704 on the measurement path 231 side.

[0036] If the reference white plates 831 and 832 are arranged on the upper surface of the reading glass 704 downstream of the reading position RP (FIG. 6) in the conveying direction CD of the sheet P, the leading edge of the sheet P that has passed the reading position RP will be caught by the reference white plates 831 and 832, causing a jam. If the reference white plates 831 and 832 are arranged on the lower surface (back side) of the reading glass 704 to prevent the occurrence of a jam, the accuracy of the shading correction will decrease. This is because the accuracy of the shading correction is increased by arranging the reference white plates 831 and 832 at the same height as the flowing sheet in the focal depth direction of the CISs 702 and 703. Therefore, in this embodiment, as described above, the reference white plates 831 and 832 are arranged on the surface (upper surface) of the reading glass 704 on the measurement path 231 side, upstream of the reading position RP (FIG. 6) in the conveying direction CD of the sheet P.

[0037] The reference white plates 831 and 832 may be formed on the surface (upper surface) of the reading glass 704 on the side of the measurement path 231 by printing or painting. Alternatively, the reference white plates 831 and 832 may be attached to the surface (upper surface) of the reading glass 704 on the side of the measurement path 231 by adhesive or double-sided tape. The reference white plates 831 and 832 are provided so that the reference white surface, the color of which is controlled all over, is located on the front side of the reading glass 704. The reference white plates 831 and 832 are expensive, and are handled with care to avoid scratches, dust, and the like.

[0038] As shown in FIG. 8, the CISs 702 and 703 are arranged (staggered) in a shifted manner in the main scanning direction X (width direction) and the sub-scanning direction Y (conveying direction CD). By arranging the two CISs 702 and 703 in a shifted manner in the main scanning direction X so as to overlap partially, it is possible to read a reading area wider than the reading area that can be read by one CIS 702. In this embodiment, by arranging the two CISs 702 and 703 in a shifted manner in the main scanning direction X so as to overlap partially, it is possible to read a reading area wider than the width of the sheet P in the main scanning direction X. The CISs 702 and 703 read the image of the sheet P as well as the black areas of the backing rollers 706 and 707, which are the background, and the contrast between the edge of the sheet P and the black areas is increased, so that the edge of the sheet P can be detected. This improves the accuracy of front-back registration.

[0039] Similarly to the CIS 702 and 703, the reference white plates 831 and 832 are also arranged (staggered) in a shifted manner in the main scanning direction X and the sub-scanning direction Y, as shown in FIG. 8. This reduces the area of ​​the reference white plates 831 and 832, thereby reducing costs. Furthermore, a sheet guide member (guide sheet) 830 is arranged to cover the reference white plates 831 and 830. The sheet guide member 830 is bonded to the reference white plates 831 and 832, covering the entire surfaces of the reference white plates 831 and 832, so that the leading edge of the sheet P being conveyed is not caught by the reference white plates 831 and 832. The reference white plates 831 and 832 arranged in a staggered manner are arranged on the upper surface of the reading glass 704 on the upstream side in the conveying direction CD, and are covered by the sheet guide member 830, so that the reference white plates 831 and 832 are not soiled, and sheet conveyance is improved.

[0040] The sheet guide member 830 may be attached to the reading glass 704 so as to smoothly connect to a conveying guide member 833 that forms part of the measurement path 231 between the conveying roller pair 211 arranged upstream of the reading glass 704 and the reading glass 704. In order to prevent the surface of the sheet guide member 830 from becoming wavy, wrinkled or uneven, underlay sheets 860 and 861 are provided in areas where the reference white plates 831 and 832 are not present, thereby improving the smoothness of the surface of the sheet guide member 830. Since the sheet guide member 830 is rubbed by the sheet P being conveyed, it is made of a conductive member, for example, a stainless steel sheet, and is earthed (grounded) in order to suppress frictional static electricity. By making the sheet guide member 830 conductive, it is possible to reduce adhesion of paper powder and dirt from the sheet P to the sheet guide member 830.

[0041] (Shading drive unit) The shading drive unit 840 will be described with reference to Figures 9 and 10. Figure 9 is a perspective view of the shading drive unit 840. Figure 10 is a side view of the shading drive unit 840. The shading drive unit 840 has a shading motor 810, a motor gear 811, a gear pulley 812, a timing belt 813, an idler pulley 814, and a slide guide shaft 815. The shading drive unit 840 further has a photosensor 816, a sensor flag 817, a belt holder 818, and a carriage 835.

[0042] The carriage 835 holds the CIS 702 and 703. The slide guide shaft 815 extends in the sub-scanning direction Y parallel to the conveying direction CD of the sheet P. The slide guide shaft 815 supports the carriage 835 so as to be slidable in the sub-scanning direction Y. The carriage 835 is provided with a belt holding portion 818. The belt holding portion 818 holds a part of the timing belt 813 and is fixed to the timing belt 813. The timing belt 813 is wound around the pulley of the gear pulley 812 and the idler pulley 814. The idler pulley 814 stretches the timing belt 813. The gear of the gear pulley 812 meshes with a motor gear 811 of a shading motor 810, which is a driving source. The driving force of the shading motor 810 is transmitted to the timing belt 813 via the motor gear 811 and the gear pulley 812.

[0043] As the shading motor 810 rotates, the carriage 835 is moved in the sub-scanning direction Y via the timing belt 813. The carriage 835 is provided with a sensor flag 817. A photosensor 816 detects the transmission and blocking of light by the sensor flag 817 accompanying the movement of the carriage 835. The home position and stop position of the carriage 835 are controlled based on the detection timing of the sensor flag 817 by the photosensor 816. By controlling the shading motor 810 based on the detection result of the photosensor 816, the CISs 702 and 703 can be driven to reciprocate between the reading position RP and the shading correction position SH.

[0044] (Backing roller configuration) The backing roller unit 701 arranged to face the front side reading box 901 will be described with reference to Figs. 11 to 14. Fig. 11 is a cross-sectional view of the backing roller unit 701 in contact with the reading glass 704. Fig. 12 is a cross-sectional view of the backing roller unit 701 separated from the reading glass 704. Fig. 13 is a cross-sectional view of the backing roller unit 701 following the recessed portion 770 of the reading glass 704. Fig. 14 is a perspective view of the backing roller unit 701.

[0045] As shown in Fig. 11, a plurality of backing rollers 706 and 707 are disposed facing a plurality of CISs 702 and 703, respectively. Abutting rollers 709 having a radius larger than that of the backing roller 706 by the amount of the gap between the backing roller 706 and the reading glass 704 are disposed at both ends of the backing roller 706. The abutting rollers 709 come into contact with the reading glass 704, thereby ensuring a predetermined amount (predetermined distance) of gap δ between the backing roller 706 and the reading glass 704. Abutting rollers 708 having a radius larger than that of the backing roller 707 by the amount of the gap between the backing roller 707 and the reading glass 704 are disposed at both ends of the backing roller 707. The abutting rollers 708 come into contact with the reading glass 704, thereby ensuring a predetermined amount of gap δ between the backing roller 707 and the reading glass 704.

[0046] The backing roller unit 701 has a holding frame (holding means) 752. The backing rollers 706 and 707 and the abutting rollers 708 and 709 are axially supported by one holding frame 752. By integrally holding the backing rollers 706 and 707 and the abutting rollers 708 and 709 by one holding frame 752, the positional accuracy of the backing rollers 706 and 707 in the conveying direction CD is more assured. The backing rollers 706 and 707 are disposed directly above the CISs 702 and 703, respectively, and are close to each other. This makes it possible to suppress, with a simple configuration, the disturbance of the sheet P conveyed over the CISs 702 and 703.

[0047] Four step shafts (shaft members) 754 are protruding from the holding frame 752. The step shafts 754 are provided so as to protrude from the holding frame 752 to the side opposite to the side where the backing rollers 706 and 707 of the holding frame 752 are held. Two step shafts 754 are provided at one end of the holding frame 752 in the longitudinal direction (main scanning direction X). The other two step shafts 754 are provided at the other end of the holding frame 752 in the longitudinal direction. The step shafts 754 have a small diameter portion 755 on the tip side. The small diameter portion 755 is inserted into a hole of a bearing 751 provided in a frame (holding member) 750 of the backing roller portion 701. The bearing 751 is fixed to the frame 750. A stopper flange 756 is provided at the tip of the small diameter portion 755 as a stopper member (stopper). The stepped shaft 754 is inserted into a compression spring (biasing means) 753 serving as an elastic member. One end of the compression spring 753 abuts against the holding frame 752. The other end of the compression spring 753 abuts against a bearing 751 of the frame 750. The compression spring 753 biases the holding frame 752 in a direction away from the frame 750. The stopper flange 756 restricts the movement of the stepped shaft 754 so that the biasing force of the compression spring 753 does not cause the stepped shaft 754 to come off the bearing 751. The frame 750 holds the holding frame 752 via the stepped shaft 754.

[0048] A frame 750 of the backing roller portion 701 is rotatably held by a hinge mechanism (not shown) on the housing (main body) 270 (FIG. 3) of the adjustment unit 200. The hinge mechanism (not shown) allows the backing roller portion 701 to move between a contact position AP (FIG. 11) where the abutment rollers 708 and 709 contact the reading glass 704 and a separation position SP (FIG. 12) where the abutment rollers 708 and 709 are separated from the reading glass 704.

[0049] As shown in FIG. 11, when the backing roller portion 701 is in the abutment position AP, the abutment rollers 708 and 709 are urged against the reading glass 704 by the urging force of the compression spring 753. The holding frame 752 is a structure configured to pivotally support the abutment rollers 708 and 709, and is formed to be elastically deformable by the urging force of the compression spring 753. The elastic deformation of the holding frame 752 causes the abutment rollers 708 and 709 to abut against the surface of the reading glass 704, and to be able to follow the shape of the surface of the reading glass 704. The two backing rollers 706 and 707 each have the abutment rollers 708 and 709 disposed at both ends, so that a total of four abutment portions abut against the surface of the reading glass 704. The small diameter portion 755 of the step shaft 754 provided on the holding frame 752 is held by a bearing 751 provided on the frame 750 so as to be slidable in the axial direction of the step shaft 754. The elastic deformation of the holding frame 752 and the sliding movement of the small diameter portion 755 relative to the bearing 751 allow the abutment rollers 708 and 709 to land reliably at four points on the surface of the reading glass 704 .

[0050] The backing roller unit 701 can be opened and closed freely relative to the front side reading box 901 by a hinge mechanism (not shown). When a sheet P jams at the reading position above the CISs 702 and 703 or when the reading glass 704 is to be cleaned, the backing roller unit 701 opens the reading glass 704 as shown in Fig. 12 to ensure space for jamming and cleaning. When the backing roller unit 701 is released from the front side reading box 901, the stopper flange 756 comes into contact with the bearing 751 to prevent the holding frame 752 from jumping out of the frame 750. The backing rollers 706 and 707 are prevented from falling from the backing roller unit 701 by the stopper flange 756.

[0051] The surface of the reading glass 704 shown in Figs. 11 and 12 is flat. However, there are cases where the surface of the reading glass 704 is not flat. When multiple CISs 702 and 703 and multiple reference white plates 831 and 832 are arranged in the width direction (conveying direction CD) of the reading glass 704 as in this embodiment, it is necessary to ensure a movement space for the CISs 702 and 703 for shading correction. For this reason, since the length in the width direction of the reading glass 704 is long, the reading glass 704 may be deformed due to its own weight or the method of holding the reading glass 704, resulting in a dent 770 of about several tens of micrometers. According to the backing roller unit 701 of this embodiment, the abutting roller 709 can abut against the surface of the dent 770 as shown in Fig. 13. 13, and the small diameter portion 755 of the stepped shaft 754 slides relative to the bearing 751, so that the abutting roller 709 reliably abuts against the recessed portion 770 of the reading glass 704. This ensures a predetermined gap δ between the backing roller 706 and the reading glass 704. Because the predetermined gap δ is ensured, even if the sheet P transported between the backing roller 706 and the reading glass 704 moves wildly, the sheet P is maintained within the readable range of the CISs 702 and 703. Therefore, the images read by the CISs 702 and 703 are not disturbed.

[0052] (Front and back registration feedback configuration) Measurement by the front and back registration unit 700 and feedback destination of the measurement result will be described. FIG. 15 is a diagram showing a sheet library 900. As shown in FIG. 15, a first geometric adjustment value 921 for the front side and a second geometric adjustment value 922 for the back side are set corresponding to a sheet type 910. FIG. 16 is a diagram showing a sheet library editing screen 1001 displayed on the operation unit 180. A user can select and set the sheet type 910 from the sheet library editing screen 1001. When the image forming apparatus 101 receives a request from the print position adjustment 1002 in the sheet library editing screen 1001 shown in FIG. 16 by the user operating the operation unit 180, the image forming apparatus 101 forms a patch image 820 (FIG. 17) as an adjustment chart on the sheet P.

[0053] 17 is a diagram showing a patch image 820 formed on a sheet P. The front and back registration section 700 reads the front side of the sheet P on which the patch image 820 as an adjustment chart is formed by the CISs 702 and 703 of the front side reading box 901 while conveying the sheet P by the conveying roller pairs 211, 212, and 213. The front side of the sheet P is continuously read by the CISs 702 and 703, and the read line images are joined together to synthesize image data, and measurement is performed from the synthesized image. Similarly, the CISs 702 and 703 of the back side reading box 902 read the back side of the sheet P conveyed by the conveying roller pairs 211, 212, and 213.

[0054] 17(a) is a diagram showing a surface measurement pattern image 822 obtained by reading the surface of a sheet P on which a patch image 820 is formed, by the CISs 702 and 703 of a surface reading box 901. The four patch images 820 are formed in the four corner areas of the surface measurement pattern image 822. The surface measurement pattern image 822 includes a leading edge 822a and a trailing edge 822b in the conveying direction CD of the sheet P, and a left edge 822c and a right edge 822d along the conveying direction CD. The conveying direction CD of the sheet P is defined as the sub-scanning direction Y, and the direction perpendicular to the sub-scanning direction Y is defined as the main scanning direction X.

[0055] The image processing unit 260 obtains the sheet P detection coordinates (X 01 ,Y 01 ), (X 11 ,Y 11 ), (X 21 ,Y 21 ) and (X 31 ,Y 31 The image processing unit 260 calculates the detection coordinates (X 41 ,Y 41 ), (X 51 ,Y 51 ), (X 61 ,Y 61 ) and (X 71 ,Y 71The image processor 260 calculates the detection coordinates (X 01 ,Y 01 )~(X 71 ,Y 71 ), the amount of distortion of the image on the front side and the amount of misalignment between the sheet P and the image are measured. Based on the amount of distortion and the amount of misalignment of the image on the front side, the image processing unit 260 calculates first geometric adjustment values ​​921 (FIG. 15) that can instruct the image shape correction unit 320 to correct the shape. The first geometric adjustment values ​​921 include the lead position, side position, main scanning magnification, sub scanning magnification, perpendicularity, and rotation amount.

[0056] 17(b) is a diagram showing a back surface measurement pattern image 823 obtained by reading the back surface of a sheet P on which a patch image 820 is formed by the CISs 702 and 703 of a back surface reading box 902. The four patch images 820 are formed in the four corner areas of the back surface measurement pattern image 823. The back surface measurement pattern image 823 includes a leading edge 823a and a trailing edge 823b in the conveying direction CD of the sheet P, and a left edge 823c and a right edge 823d along the conveying direction CD.

[0057] The image processing unit 260 detects the detection coordinates (X 02 ,Y 02 ), (X 12 ,Y 12 ), (X 22 ,Y 22 ) and (X 32 ,Y 32 The image processing unit 260 calculates the detection coordinates (X 42 ,Y 42 ), (X 52 ,Y 52 ), (X 62 ,Y 62 ) and (X 72 ,Y 72 The image processor 260 calculates the detection coordinates (X 02 ,Y 02 )~(X 72 ,Y 72), the amount of distortion of the image on the back side and the amount of misalignment between the sheet P and the image are measured. Based on the amount of distortion and the amount of misalignment of the image on the back side, the image processing unit 260 calculates second geometric adjustment values ​​922 (FIG. 15) that can instruct the image shape correction unit 320 to correct the shape. The second geometric adjustment values ​​922 include the lead position, the side position, the main scanning magnification, the sub-scanning magnification, the perpendicularity, and the amount of rotation.

[0058] The first geometric adjustment value 921 and the second geometric adjustment value 922 calculated by the image processing unit 260 are transmitted to the sheet library 900 in the image forming apparatus 101 through the communication unit 250. The first geometric adjustment value 921 and the second geometric adjustment value 922 are stored in the sheet library 900 as front and back parameters. In this manner, the setting values ​​are stored in the sheet library 900 for each sheet type 910. By reading out the setting values ​​from the sheet library 900 according to the sheet type 910 on which the print job is executed and correcting the image position and image distortion, it is possible to output a print image in which the front and back printing positions are corrected with high accuracy. Here, the front surface measurement pattern image 822 and the back surface measurement pattern image 823 exemplified in this description may be measured before the execution of the print job, or may be automatically measured at a predetermined timing as calibration during the execution of the print job.

[0059] (Control Action) Hereinafter, the control operation of conveying the sheet P in the image forming apparatus 101 and the adjustment unit 200 will be described with reference to FIG. 18. FIG. 18 is a flow chart of the control operation of conveying the sheet P. The control unit 251 executes the control operation according to a program stored in an internal memory (not shown). When a job is input by a user from the operation unit 180, the control unit 251 starts the control operation. The control unit 251 judges whether the job is a normal print job or not (S1101). If the job is a normal print job (YES in S1101), the control unit 251 makes each member of the image forming apparatus 101 and the adjustment unit 200 wait at the home position (HP) (S1102). At this time, in order to guide the sheet P to the through path 230 in the adjustment unit 200, the control unit 251 makes the flapper 221 wait in the downward direction (through path position) (S1102).

[0060] The image forming apparatus 101 forms an image on the sheet P (S1103). The adjustment unit 200 receives the sheet P on which the image has been formed from the image forming apparatus 101 (S1104). The control unit 251 controls the conveying motor 252 to discharge the sheet P to the post-processing apparatus 600 through the through path 230 and the discharge path 232 by the first conveying roller 201, the second conveying roller 202, the third conveying roller 203, and the fourth conveying roller 204 (S1105). The control unit 251 determines whether the sheet P is the last sheet (S1106). If the sheet P is not the last sheet (NO in S1106), the control unit 251 returns the process to S1101. If the sheet P is the last sheet (YES in S1106), the control unit 251 ends the control operation.

[0061] On the other hand, when the user selects the sheet type 910 from the sheet library 900 by the operation unit 180 and selects the print position adjustment 1002, a front and back registration job is submitted. If the job is a front and back registration job (NO in S1101), the control unit 251 causes each member of the image forming apparatus 101 and the adjustment unit 200 to wait at the home position (HP) (S1107). At this time, in order to guide the sheet P to the measurement path 231 in the adjustment unit 200, the control unit 251 causes the flapper 221 to wait in the upward direction (measurement path position) (S1107).

[0062] The image forming apparatus 101 forms patch images 820 as adjustment charts on both sides of the sheet P (S1108). The control unit 251 moves the CISs 702 and 703 to the shading correction position SH before reading both sides of the sheet P, and executes shading correction (S1109). The control unit 251 moves the CISs 702 and 703 to the reading position RP (S1110). The adjustment unit 200 receives the sheet P on which the patch images 820 have been formed (S1111). The sheet P transported to the adjustment unit 200 is transported to the measurement path 231 by the flapper 221 (S1112). The sheet P is transported to the front and back registration unit 700 by the transport roller pairs 205, 206, 207, 208, 209, and 210.

[0063] The control unit 251 reads the patch images 820 formed on both sides of the sheet P and the sheet P by the CISs 702 and 703 of the front side reading box 901 and the back side reading box 902, respectively (S1113). The image processing unit 260 obtains a front side measurement pattern image 822 and a back side measurement pattern image 823 from the reading results of the CISs 702 and 703. The front and back registration unit 700 performs high-definition line image synthesis, and measures the printing position deviation of the patch image 820 on the sheet P and the shape of the sheet P. The image processing unit 260 calculates a first geometric adjustment value 921 and a second geometric adjustment value 922 from the front side measurement pattern image 822 and the back side measurement pattern image 823. The image processing unit 260 saves the first geometric adjustment value 921 and the second geometric adjustment value 922 in the sheet library 900 of the image forming apparatus 101 through the communication unit 250 (S1114). This completes the print position adjustment for front and back registration.

[0064] The sheet P that has passed through the front and back registration section 700 is conveyed to the through path 230 by the conveyance roller pair 214 (S1115). Thereafter, the sheet P is conveyed to the discharge path 232 by the third conveyance roller 203, and is discharged to the post-processing device 600 by the fourth conveyance roller 204 (S1105). The control section 251 determines whether the sheet P is the last sheet (S1106), and if the sheet P is the last sheet (YES in S1106), the control section 251 ends the control operation.

[0065] According to this embodiment, even if the surface of the reading glass 704 has low flatness, the gap δ between the reading glass 704 and the plurality of backing rollers 706 and 707 can be guaranteed. [Explanation of symbols]

[0066] 231... Measurement path 700 Front and back registration section 702, 703...CIS 704 Reading glass 706, 707 Backing roller 708, 709: Stop roller 752···Holding frame 753 Compression spring P···Sheet CD...Transport direction

Claims

1. a conveying path along which the sheet is conveyed in a conveying direction; a light transmitting member arranged to form a part of the transport path; a first reading unit configured to read an image on a first surface of the sheet conveyed along the conveying path in the conveying direction through the light transmitting member; a second reading means arranged at a position different from that of the first reading means in the conveying direction, and configured to read an image on the first surface of the sheet together with the first reading means through the light transmitting member; a first roller disposed opposite the first reading means; A second roller disposed opposite the second reading means; a holding member that holds both the first roller and the second roller; a plurality of first abutment members provided on both end sides of the first roller in a width direction perpendicular to the conveying direction, the abutment members contacting the light transmitting member to form a gap between the light transmitting member and the first roller; a plurality of second abutment members provided on both end sides of the second roller in the width direction and abutting against the light transmitting member to form a gap between the light transmitting member and the second roller; a biasing means for biasing the one holding member against the light transmitting member; An image reading device comprising:

2. a frame for holding the holding member, 2. The image reading apparatus according to claim 1, wherein the biasing means is disposed between the holding member and the frame.

3. The holding member has a shaft portion at each end in the width direction, 3. The image reading device according to claim 2, wherein the shaft portion is inserted into a hole provided in the frame.

4. 4. The image reading apparatus according to claim 1, wherein the biasing means is a compression spring.

5. a plurality of reference members disposed on a surface of the light transmitting member on the side of the transport path; 5. The image reading device according to claim 1, wherein the reference members are disposed upstream of a reading position where the first reading unit and the second reading unit read the sheet in the transport direction.

6. 6. The image reading device according to claim 5, wherein the first reading means and the second reading means are movable between a position facing the first roller and the second roller and a position facing the plurality of reference members.

7. 7. The image reading device according to claim 5, wherein each of the plurality of reference members is a reference white plate.

8. 8. The image reading device according to claim 1, wherein the surfaces of the first roller and the second roller are black.

9. 9. The image reading apparatus according to claim 1, wherein the holding member is elastically deformed by the biasing force of the biasing means.

10. the second reading means is disposed at a position shifted from the first reading means in the width direction, 10. The image reading device according to claim 1, wherein the first reading unit and the second reading unit are arranged to partially overlap each other when viewed in the transport direction.

11. 11. The image reading device according to claim 1, wherein the first roller and the second roller are movable between an abutment position where the plurality of first abutment members and the plurality of second abutment members abut against the light-transmitting member and a spaced position where the plurality of first abutment members and the plurality of second abutment members are spaced from the light-transmitting member.

12. a light transmitting member separate from the light transmitting member, the light transmitting member being disposed so as to form a part of the transport path; a third reading means for reading, through the other light transmitting member, an image on a second surface of the sheet conveyed along the conveying path in the conveying direction, the second surface being opposite to the first surface of the sheet; a fourth reading means arranged at a position different from that of the third reading means in the conveying direction, and reading an image on the second surface of the sheet together with the third reading means through the separate light transmitting member; a third roller disposed opposite the third reading means; a fourth roller disposed opposite the fourth reading means; 12. The image reading device according to claim 1, further comprising:

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

Images