JP7176424B2 - Sheet material reading device and image forming device - Google Patents

Description

The present invention relates to a sheet material reading device for reading a sheet material being conveyed and an image forming apparatus having the same.

A sheet material reading device that reads an image formed on a sheet material such as a document while conveying the sheet material, or an image forming apparatus that transfers an image read by such a sheet material reading device to copy paper or the like is widely used. in use. Conventionally, in this type of apparatus, the inclination angle (skew amount) of the sheet material at the upstream end of the sheet material in the movement direction or the downstream end of the document in the movement direction is detected, and skew is generated based on the detected skew amount. to form a corrected image.

For example, light is applied to the leading end of a document transported between a light source and a backing member, and the upstream end in the direction of movement is projected onto the backing member. edge) is detected. Then, there is known a technique for correcting the skew by rotating the read image of the document by the tilt angle (for example, Japanese Laid-Open Patent Publication No. 2002-100000).

In addition, for the purpose of detecting the shadow of the document with high accuracy, shadows (horizontal An image reading technique is also known in which an edge is detected and image processing is performed from the data of the shadow (for example, Patent Document 2, etc.).

However, if, for example, the edge of the sheet material is curled or folded, the lateral edge described above is not a projected straight edge of the actual sheet material. Therefore, in the conventional technique, there is a problem that the lateral edge of the shadow projected by the edge of the sheet material is not reliable as data for detecting the inclination angle of the sheet material.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a sheet material reading device capable of detecting the inclination angle of a sheet material with high precision, and an image forming apparatus equipped with such a sheet material reading device. for the purpose.

A sheet reading apparatus according to the present invention has been made to achieve the above objects, and includes a guide member that guides a sheet along a conveying path, and a shadow of the sheet that is guided by the guide. a background member to be projected; a reading unit for reading a shadow of a sheet material; and a transparent member between the background member and the reading unit and between the sheet material and the background member; a first transparent member extending to a reading position on a reading line of the reading unit extending in the main scanning direction; and a second transparent member on one end side in the extending direction of the first transparent member; wherein the distance between the sheet material side surface of the second transparent member and the background member is longer than the distance between the sheet material side surface of the first transparent member and the background member, and The reading unit reads the edge of the shadow of the end of the sheet material in the main scanning direction projected onto the background member through the second transparent member, and detects the tilt angle.

According to the present invention, the tilt angle of the sheet material can be detected with high precision.

1 is a perspective view showing the entire image forming apparatus according to an embodiment of the present invention, showing a state where the ADF is closed; FIG. 1 is a perspective view showing the entire image forming apparatus according to an embodiment of the present invention, showing a state where an ADF is opened; FIG. 1 is a front cross-sectional view schematically showing an internal configuration of an image forming apparatus according to one embodiment of the present invention; FIG. 1 is a front cross-sectional view showing the configuration of an ADF according to one embodiment of the present invention; FIG. 3 is a block diagram showing the control configuration of the ADF according to one embodiment of the present invention; FIG. FIG. 10 is a diagram for explaining the principle of projection of a shadow of a document sheet onto a conventional document reading guide; 2A and 2B are diagrams showing shadows of a document sheet projected onto a conventional document reading guide, in which (a) shows the case where the document sheet is not skewed, and (b) shows the case where the document sheet is skewed; there is FIG. 10 is a diagram showing a case where a shadow of a document sheet is not projected onto a conventional document reading guide; 1 is a front cross-sectional view showing a document reading guide, a transparent member, and an optical scanning unit according to one embodiment of the present invention; FIG. FIG. 10 is a cross-sectional view taken along the line XX of FIG. 9; FIG. 4 is a front cross-sectional view showing a state in which a document reading guide according to one embodiment of the present invention regulates a conveying position of a document sheet; FIG. 4 is a diagram showing a shadow of a document sheet projected onto a document reading guide according to one embodiment of the present invention; FIG. 4A is a diagram showing a state in which the image reading unit according to the embodiment of the present invention switches the reading position of the right side of the document sheet on the front side of the apparatus according to the width of the document sheet, and FIG. , (b) show the case where the width of the document sheet is small. FIG. 2 is a front cross-sectional view showing a document reading guide, a transparent member, and an optical scanning unit according to an embodiment of the present invention, showing a case where the transparent member is thinner than the depth of the concave portion of the document reading guide; FIG. 9 is a side view showing a document reading guide provided with a transparent member according to another embodiment of the present invention;

(embodiment)
An embodiment of the present invention will be described below with reference to the drawings.

1 and 2 show the overall appearance of an image forming apparatus 1 according to this embodiment, and FIG. 3 shows the internal structure of the image forming apparatus 1. As shown in FIG. The image forming apparatus 1 includes an apparatus main body 1M having a paper feeding device 2, an image forming section 3 and an image reading section 4, and an ADF (Auto Document Feeder) supported on the apparatus main body 1M so as to be openable and closable. 5 is a digital multi-function machine. FIG. 1 shows the ADF 5 closed, and FIG. 2 shows the ADF 5 open. The image reading unit 4 and the ADF 5 constitute an image reading device 6, and the image reading device 6 constitutes a sheet material reading device according to the present invention.

In FIGS. 1 to 3, an arrow T indicates the conveying direction of a document sheet S guided by a document reading guide 91, which will be described later. The document sheet S is a sheet material of the present invention, and is, for example, plain paper, gloss coated paper, Maccote paper, art coated paper, OHP sheet, embossed special paper, or other sheet material. The document sheet S is a rectangular sheet having vertical and horizontal directions with four right-angled corners. .

1 and 2, the arrow Q indicates the front side of the device in the front-rear direction perpendicular to the conveying direction of the document sheet S, and the arrow R indicates the rear side of the device in the front-rear direction. The front side of the device here corresponds to the front side of the present invention, and the back side of the device corresponds to the rear side of the present invention. The user of the image forming apparatus 1 is positioned on the front side (Q side) of the image forming apparatus 1, and performs various input and setting operations using the operation unit 108 provided on the upper front side of the apparatus main body 1M. ing. The direction in which the document sheet S is transported by the document reading guide 91 is from left to right as viewed from the user.

The ADF 5 is connected to the upper portion of the apparatus main body 1M via a pair of left and right hinge mechanisms 5h shown in FIG. 2 so as to be openable and closable. The hinge mechanism 5h is arranged on the back side, and the ADF 5 opens on the front side. As shown in FIG. 2, an elongated first contact glass 45 extending from the front side to the back side is provided on the upper left side of the image reading section 4 . A flat plate-shaped second contact glass 46 is provided on the right side of the first contact glass 45 in the upper portion of the image reading section 4 . The ADF 5 is pivotally operated between an open position exposing the contact glasses 45 and 46 and a closed position covering the contact glasses 45 and 46 .

Next, referring to FIG. 3, the configurations of the paper feeding device 2, the image forming section 3, the image reading section 4 and the ADF 5 will be described in detail.

The sheet feeding device 2 has a plurality of stages of sheet feeding cassettes 21A, 21B, and 21C each capable of storing cut sheets of transfer paper P in a stacked state. Each of the paper feed cassettes 21A, 21B, and 21C accommodates transfer paper P (for example, blank paper) of a sheet size preselected from a plurality of sheet sizes in the vertical or horizontal paper feed direction. ing.

The paper feeder 2 has paper feeders 22A, 22B, and 22C that sequentially pick up the transfer paper P stored in each of the paper feed cassettes 21A, 21B, and 21C from the uppermost layer side and separate and feed them. . The paper feeder 2 is further provided with various rollers 23 and the like, and these rollers 23 form a predetermined image of the transfer paper P fed from each of the paper feeders 22A, 22B, and 22C in the image forming section 3. A paper feeding path 24 is formed to convey the paper to the position.

The image forming unit 3 includes an exposure device 31, photosensitive drums 32K, 32Y, 32M, and 32C, and a developing device filled with black (K), yellow (Y), magenta (M), and cyan (C) toners. 33K, 33Y, 33M and 33C. The image forming section 3 also includes a primary transfer section 34 , a secondary transfer section 35 and a fixing section 36 .

The exposure device 31 is adapted to generate the laser light L for exposure of each color based on the image read by the image reading device 6, for example. Further, the exposure device 31 exposes the photosensitive drums 32K, 32Y, 32M and 32C of the respective colors with the laser light L to expose the surface layers of the respective photosensitive drums 32K, 32Y, 32M and 32C to the respective colors corresponding to the read image. It is adapted to form an electrostatic latent image.

Each of the developing devices 33K, 33Y, 33M, and 33C supplies a thin layer of toner to the corresponding photosensitive drums 32K, 32Y, 32M, and 32C so as to make the electrostatic latent image visible with the toner. It is designed to be developed.

The image forming section 3 primarily transfers the toner images developed on the photosensitive drums 32K, 32Y, 32M, and 32C to the primary transfer section 34, and the toner images are transferred to the secondary transfer section 35 adjacent to the primary transfer section 34. is secondarily transferred to the transfer paper P. Further, the image forming section 3 heats and pressurizes the toner image secondarily transferred to the transfer paper P to melt it by the fixing section 36, thereby fixing the color image on the transfer paper P and recording it.

The image forming section 3 has a conveying path 39A for conveying the transfer paper P supplied from the paper feeding device 2 through the paper feeding path 24 to the secondary transfer section 35 side. In the transport path 39A, first, the transport timing and transport speed of the transfer paper P are adjusted in the registration roller pair 37. As shown in FIG. Then, the transfer paper P passes through the secondary transfer section 35 and the fixing section 36 in synchronization with the belt speeds of the primary transfer section 34 and the secondary transfer section 35, and then is discharged onto the paper discharge tray 38. It's like

The image forming unit 3 has a manual feed path for feeding the transfer paper P placed on the manual feed tray 25 provided on the right side in FIG. It also has 39B.

Below the secondary transfer section 35 and the fixing section 36, a switchback conveying path 39C and a reverse conveying path 39D are provided, each comprising a plurality of conveying rollers, conveying guides, and the like.

In the case of forming images on both sides of the transfer paper P, the switchback transport path 39C allows the transfer paper P on which the image has been fixed on any one side to enter from one end, and then retreats (moves in the direction opposite to the entry direction). ), switchback transport is performed.

The reversing conveying path 39D turns over the transfer paper P that has been switchback conveyed by the switchback conveying path 39C, and feeds it to the registration roller pair 37 again.

The transfer paper P, which has undergone image fixing processing on one side thereof, is reversed in its advancing direction by the switchback conveying path 39C and the reversing conveying path 39D, is reversed, and enters the secondary transfer nip again. . After the transfer paper P is subjected to secondary transfer processing and fixing processing of the image on the other side, the transfer paper P is discharged onto the paper discharge tray 38 provided on the left side in FIG. .

The image reading unit 4 includes a first carriage 41 carrying a light source and a mirror member as a light emitting unit, a second carriage 42 carrying a mirror member, an imaging lens 43, an imaging unit 44 as a light receiving unit, and a second carriage 42 carrying a mirror member. 1 contact glass 45 . The image reading section 4 is provided on the device main body 1M side.

The image reading section 4 constitutes an optical scanning unit 40 for reading an image on one image surface (for example, the front image surface) of a document sheet S as a recording medium conveyed on the first contact glass 45 . The optical scanning unit 40 constitutes a reading section according to the invention.

The image reading unit 4 is provided with a second contact glass 46 on which the original sheet S is placed, and an abutment member 47a with which one side of the original sheet S is abutted to position the conveyance start position.

The first carriage 41 is provided below the first contact glass 45 and the second contact glass 46 so as to be movable in the left-right direction in FIG. 3 and position-controllable. Note that the first carriage 41 may be provided below the first contact glass 45 and another carriage may be newly provided movably below the second contact glass 46 .

The first carriage 41 reflects the illumination light from the light source with a mirror member and transmits it through the first contact glass 45 or the second contact glass 46 , so that the document sheet on the first contact glass 45 or the second contact glass 46 is reflected. S can be irradiated with light.

Reflected light reflected by the original sheet S passes through each mirror member mounted on the first carriage 41 and the second carriage 42 and is imaged by the image forming lens 43, and the image formed by the imaging unit 44 is imaged. It is ready to be read. The carriages 41 and 42, the imaging lens 43, and the imaging section 44 can be configured as an integrated carriage.

When reading the image of the document sheet S placed on the second contact glass 46, the image reading section 4 moves the first carriage 41 and the second carriage 42 at a speed ratio of, for example, 2:1 in FIG. 3 with the light source turned on. The image surface of the document sheet S on the second contact glass 46 is scanned while being moved rightward. The image reading section 4 reads the document image with the image capturing section 44 during this scanning, thereby exhibiting a fixed document reading function (a so-called flatbed scanner function).

When reading the image of the document sheet S on the first contact glass 45 , the image reading section 4 stops the first carriage 41 at a fixed position directly below the first contact glass 45 . Then, the image reading unit 4 reads the image of the first surface of the document sheet S (the surface of the document sheet S on the document table 51) during automatic document transport without moving the optical system including the light source, the reflecting mirror, and the like. A moving document reading function (so-called DF scanner function) can be exhibited.

The ADF 5 is configured as a sheet-through automatic document feeder. The ADF 5 includes a document table 51 serving as a document table, a document transport section 52 including various rollers and guide members, and a document discharge tray 53 for stacking the document sheets S after image reading. On the document table 51, one document sheet S in the form of a cut sheet or a document bundle of a plurality of document sheets S can be placed.

The document sheet S is positioned and placed on the document table 51 by always abutting the back side of the document sheet S against the same position regardless of the width of the document sheet. Therefore, the document sheet S sent onto the first contact glass 45 by the ADF 5 is such that the left side of the document sheet S in the conveyed state always passes through the far side.

After the image is read on the first contact glass 45 , the document sheet S is transported downstream by the document transport section 52 . A rear surface reading section 69 is provided downstream of the first contact glass 45 in the document conveying section 52 . The back surface reading unit 69 reads an image on the back surface of the original sheet S when the original sheet S passes through a reading position on a reading line 20 described later by the optical scanning unit 40 . The document sheet S that has passed through the back surface reading section 69 is discharged to the document discharge tray 53 by the discharge roller pair 67 .

FIG. 4 shows an ADF 5a that can replace the ADF 5 shown in FIG. Although the ADF 5a differs from the ADF 5 in the back side reading mechanism, the basic configuration is the same. Therefore, the same components as those of the ADF 5 are denoted by the same reference numerals. Hereinafter, the ADF 5a will be described in detail as an ADF according to one embodiment.

As shown in FIG. 4, the ADF 5a includes a document setting section A, a separation feeding section B, a registration section C, a turn section D, a reading/conveying section E, a discharge section F, and a stack section G as a plurality of functional sections. there is Among these functional units, the functions of the separating/feeding portion B, the registration portion C, the turning portion D, the reading/conveying portion E, and the discharging portion F are mainly realized by the document conveying portion 52 .

The document conveying portion 52 is covered with a paper feed cover portion 12 having a paper feed cover 55 that can be opened and closed at least above. Between the paper feed cover 55 and the document table 51, a paper feed port 55a for the document sheet S is formed, which opens to the right in FIG. The paper feed cover 55 covers the upper end of the document table 51 so that the front end of the document table 51 is positioned inside (on the left side in FIG. 4) of the paper feed port 55a.

The paper feed cover section 12 also has an opening/closing mechanism 13 for opening and closing the paper feed cover 55 and an open/close sensor 18 for detecting the open state and closed state of the paper feed cover 55 .

The opening/closing mechanism 13 is composed of a rotating shaft and a mechanism such as a bearing that supports the rotating shaft. It can be opened and closed. In the document conveying unit 52, when the document sheet S in the middle of conveyance is pushed into a component such as a roller and becomes jammed, the user can open the feed cover 55 and take out the jammed document sheet S. It has become.

The open/close sensor 18 is provided, for example, inside the paper feed cover section 12 and detects the open state and closed state of the paper feed cover 55 of the paper feed cover section 12 . The open/close sensor 18 may detect the open state and closed state of the paper feed cover 55. For example, when the paper feed cover 55 is opened, the shielding member retracts and light passes through to turn on. It consists of a well-known element consisting of a type photosensor. Alternatively, the open/close sensor 18 may be a microswitch that senses the operation of an actuator having a spring or hinge lever.

The document conveying portion 52 has a conveying path 56 for the document sheet S from the paper feed port 55 a to the paper discharge port 55 b above the document discharge tray 53 . The conveying path 56 is formed by ribs 55c formed on the paper feed cover 55, other guide members, and the like. The front-rear direction of the image forming apparatus 1 described above is the same direction as the direction perpendicular to the transport path 56 .

In the document conveying portion 52, a separation sensor 11, an abutment sensor 85, a document width sensor 86, a reading entrance sensor 87, a registration sensor 88, and a sheet ejection sensor 89 are arranged from the upstream side in the conveying direction of the document sheet S to the downstream side. arranged in order. These sensors 11 , 85 to 89 detect the position and shape of the original sheet S on the transport path 56 . In particular, the reading entrance sensor 87, the registration sensor 88, and the paper discharge sensor 89 are used for controlling the conveying distance and conveying speed of the document sheet S, jam detection, and the like. The document width sensor 86 constitutes width detection means according to the present invention.

In the document setting section A, a bundle of documents is set on a document table 51 in a state in which the leading edge of the document sheet S in the feeding direction is abutted against the document abutting claw 28 . When the document sheet S is a single-sided document, the document bundle is set on the document table 51 with the image-formed surface facing upward.

Separating and feeding unit B separates the uppermost sheet from a stack of original sheets S placed on original table 51 of original setting unit A one by one and feeds them to the entrance of conveying path 56 . It's becoming

The registration section C has a function of aligning the document sheets S successively fed from the separating and feeding section B to a required transport posture by primary abutment, and a function of pulling out and transporting the aligned document sheets S to the downstream side. have.

The turning section D has a function of reversing and conveying the document sheet S drawn out and conveyed by the registration section C such that the front and back surfaces of the document sheet S are reversed, and the surface of the document sheet S faces downward in FIG.

The reading/conveying section E conveys the document sheet S after being folded back from the turning section D at a predetermined speed in the sub-scanning direction of the optical scanning unit 40 while passing through the reading position on the first contact glass 45 . there is The sub-scanning direction of the optical scanning unit 40 is the same direction as the conveying direction of the document sheet S conveyed on the first contact glass 45 (the direction of the arrow T in FIGS. 1 to 3), and the document width of the document sheet S It is a direction orthogonal to the main scanning direction of the optical scanning unit 40, which is the direction.

The discharge section F discharges the original sheet S, which has been conveyed by the reading/conveying section E and whose original image has been read, to the stack section G side. Further, when the back side of the document sheet S needs to be read, the discharge section F reverses the document sheet S instead of discharging it to the stack section G side, and transports the document sheet S again through the transport path 56 . As a result, the reversed document sheet S passes through the reading/conveying unit E, and the back side is read, and both sides of the document sheet S are read.

The stack section G sequentially stacks the document sheets S sequentially discharged from the discharge section F onto a document discharge tray 53 arranged below the document set section A with the surface thereof facing downward. The document sheets S stacked in the stacking section G are arranged in the same page order as when they were placed in the document setting section A, and the stack as a whole is stacked with the document surfaces facing upside down.

The document setting section A, separation feeding section B, registration section C, turn section D, reading/conveying section E, discharge section F, and stacking section G are automatic document feeding sections shown in FIG. It is controlled by a controller section 100 for control.

The ADF 5 a separates the uppermost document sheet S one by one from the document stack of the document sheets S placed on the document table 51 , and transports the document sheet S to a predetermined transport path passing over the first contact glass 45 by the document transport section 52 . It is designed to be transported by Further, the ADF 5 a discharges the document sheet S to the document discharge tray 53 after reading the image of the document sheet S by the image reading section 4 when the document sheet S passes through the first contact glass 45 . ing.

The document table 51 on which the document sheet S is placed face up is arranged so that the document conveying unit 52 side is the leading edge side of the document sheet S, the leading edge side is downward and the trailing edge side is upward.

In addition, the ADF 5a has document length sensors 81A to 81C provided on the document table 51 along the feeding direction of the document sheet S at intervals. The document length sensors 81A to 81C are composed of, for example, known reflective photosensors, but are not limited to this, and may be microswitches or photosensors that sense the operation of actuators having springs or hinge levers. may

As shown in FIG. 4, the document length sensors 81A to 81C detect the document bundle in a state where the document bundle is set on the document table 51 with the leading end of the document bundle of the document sheet S abutting against the document abutment claw 28. is designed to detect the approximate length of The document abutting claw 28 adjusts the posture of the document stack set on the document table 51 .

In addition, the ADF 5a is placed above the front end of the document table 51, which is the upstream end on the paper feed port 55a side, with the document sheet S placed on the document table 51 as a reference, and the document sheet S placed on the document table 51 rotates the document set. It has a filler 57 .

Further, the ADF 5 a detects whether or not the document sheet S is set on the document table 51 by detecting the lowest portion of the movement locus of the leading end of the document set filler 57 near the bottom surface of the document table 51 near the leading end. It has a document set sensor 82 for detection. The document set sensor 82 detects the presence or absence of the document sheet S set on the document table 51 by detecting whether or not the document set filler 57 is rotated and removed from the document set sensor 82 . .

In addition, the ADF 5 a includes a plate-like pressing plate portion (not shown) arranged to face the second contact glass 46 . The pressure plate portion is configured to press the book or document to be read against the second contact glass 46 .

The document transport unit 52 includes a pickup roller 58 as a call roller arranged downstream of the document sheet S in the transport direction of the document sheet S from the paper feed port 55a, and an endless feeder arranged downstream of the pickup roller 58 and near the transport path 56. It has a paper belt 59 and a reverse roller 60 . The paper feed belt 59 is wound around a driving roller 71 and a driven roller 72 . The paper feed belt 59 and the reverse roller 60 are arranged to face each other with the transport path 56 interposed therebetween. The sheet feeding belt 59, the reverse roller 60, the driving roller 71 and the driven roller 72 constitute a separating feeding section B. As shown in FIG.

The pickup roller 58 moves up and down via a cam mechanism (not shown), and when it moves downward, it contacts the uppermost document sheet S among the document sheets S stacked on the document table 51 . At the contact position, the pickup roller 58 frictionally conveys several (ideally one) document sheets S from the uppermost side, picks them up, and sequentially conveys them to the separating and feeding section B. .

The paper feed belt 59 is rotationally driven to convey the original sheet S by a drive roller 71 driven by a paper feed motor 102 (see FIG. 5).

The reverse roller 60 is rotatable in a direction opposite to the feeding direction of the paper feed belt 59, separates the top document sheet S from the document sheets S below it, and feeds only the top document sheet S. Paper. Also, the reverse roller 60 incorporates a torque limiter. The reverse roller 60 is in pressure contact with the paper feed belt 59, and when it is in direct contact with the paper feed belt 59 or sandwiches one document sheet S between the paper feed belt 59 and the paper feed belt 59, the torque is The limiter is actuated, and the paper feed belt 59 rotates with it.

In the reverse roller 60, when a plurality of document sheets S enter between the reverse roller 60 and the paper feed belt 59, causing multiple feeding, the counterclockwise rotation force in FIG. lower than the force corresponding to the torque. As a result, the reverse roller 60 rotates clockwise in FIG. 4, which is the driving direction, to return the multi-fed document sheets S and prevent the multi-fed document sheets S from being multi-fed. .

The original document sheet S separated into one sheet by the action of the paper feed belt 59 and the reverse roller 60 is further fed by the paper feed belt 59, and the leading edge thereof is detected by the abutment sensor 85 downstream in the transport direction. It abuts against the rotating conveying roller pair 61 and stops. The abutment sensor 85 is arranged between the paper feed belt 59 and the conveying roller pair 61 and is configured to detect the leading edge and the trailing edge of the document sheet S. As shown in FIG.

The document transport unit 52 includes a transport roller pair 61 as pullout rollers that nip and transport the document sheet S so as to face each other across the transport path 56 , a transport roller pair 63 as reading entrance rollers, and a reading exit. and a conveying roller pair 65 as rollers. Each transport roller pair 61 , 63 , 65 transports the document sheet S to the document discharge tray 53 . The number and location of these transport roller pairs are appropriately set according to the path design of the transport path 56, the length of the minimum size of the document sheet S allowed by the ADF 5a in the document transport direction, and the like.

The document sheet S is fed with a sufficiently large distance from when it is detected by the abutment sensor 85 until it reaches the pair of conveying rollers 61, and is pressed against the pair of conveying rollers 61 with bending. The distance referred to here may be changed according to the paper quality of the document sheet S or the like. By stopping the paper feeding motor in this state, the driving of the paper feeding belt 59 is stopped.

At this time, the pickup roller 58 in contact with the upper surface of the document sheet S is retracted upward by the rotation of the pickup lifting motor 101 (see FIG. 5). By feeding the original sheet S by the conveying force of the paper feed belt 59 in this manner, the leading edge of the original sheet S enters the nip of the pair of conveying rollers 61, and the leading edge is aligned.

The conveying roller pair 61 is driven by a pullout motor 113 (see FIG. 5). The pull-out motor 113 feeds the original sheet S picked up by the pickup roller 58 by applying a conveying force due to the rotation of the conveying roller pair 61 .

The conveying roller pair 61 stops conveying when the leading edge of the document sheet S whose leading edge is detected by the abutment sensor 85 collides with the conveying roller pair 61, corrects the skew, and further conveys the skew-corrected document sheet S. It's becoming

A document width sensor 86 is arranged on the downstream side of the transport roller pair 61 in the document sheet S transport direction. The document width sensor 86 detects the size of the document sheet S transported by the transport roller pair 61 in the width direction perpendicular to the transport direction.

The document width sensor 86 includes, for example, a plurality of detection members arranged along the width direction of the document sheet S and configured to rotate when the document sheet S passes through, and detects the rotation state of these detection members. This sensor is capable of detecting the width of the document sheet S by detecting it with an optical element. The document width sensor 86 includes a plurality of light emitting elements arranged along the width direction of the document sheet S, and a light receiving element arranged opposite to the light emitting elements so as to form a pair with the transport path 56 interposed therebetween. can be anything. Further, the length of the document sheet S in the conveying direction can be detected, for example, from the detection of the leading edge and the trailing edge of the document sheet S by the abutment sensor 85 and the pulse count of the motor therebetween.

When the leading edge of the document sheet S is detected by the reading entrance sensor 87, the ADF 5a adjusts the transport speed of the document sheet S to a predetermined speed before the leading edge of the document sheet S enters the nip of the transport roller pair 63. to start decelerating. At the same time, the ADF 5a drives the reading motor 103 (see FIG. 5) to rotate forward to drive the conveying roller pair 63 and the conveying roller pair 65. As shown in FIG.

The transport roller pair 63 transports the document sheet S toward the document reading guide 91 . The conveying roller pair 65 conveys the document sheet S, which has passed between the document reading guide 91 and the first contact glass 45 of the image reading section 4 facing the document reading guide 91 and has been read, to the discharge section F side. . The document reading guide 91 guides the document sheet S passing through the first contact glass 45 of the image reading section 4 in the conveying direction. The document reading guide 91 that guides the upper surface of the document sheet S is a guide member according to the present invention. On the side facing the first contact glass 45 , a background member 200 a with a white surface is arranged above the reading line 20 read by the optical scanning unit 40 of the image reading section 4 . The background member 200a may be the same color as the document reading guide 91, the reading line 20 may be painted white, or a white sheet material may be used.

Further, the document conveying section 52 includes a paper discharge roller pair 67 , a branch claw 90 and a reversing roller pair 68 .

The paper discharge roller pair 67 discharges the document sheet S conveyed by the conveying roller pair 65 to the document discharge tray 53 when the reading of the front side of the document sheet S is completed and the reading of the back side is not performed. ing.

The pair of reversing rollers 68 reverses the document sheet S which has not been discharged to the document discharge tray 53 while being guided by the bifurcation claw 90 and conveyed when the reading of the front side of the document sheet S is finished and the back side of the document sheet S is to be read. It is designed to let The paper discharge roller pair 67 conveys the reversed document sheet S toward the conveying roller pair 61 .

FIG. 5 is a block diagram showing the control configuration of the ADF 5a. As shown in the figure, the image forming apparatus 1 includes a controller section 100 for controlling automatic document feeding, a main body control section 111 for controlling the main body of the apparatus, and an operation unit 108 attached to the main body control unit 111 .

The operation unit 108, which is also shown in FIGS. 1 and 2, has input/output units such as buttons and panels for starting operations and printing. Controller section 100 and main body control section 111 are connected via interface 107 . When the start button of the operation unit 108 is pressed and an input signal is received, the body control unit 111 transmits a document feed signal and a reading start signal to the controller unit 100 via the interface 107 .

The controller unit 100 includes a separation sensor 11, an opening/closing sensor 18, document length sensors 81A to 81C, a document setting sensor 82, a collision sensor 85, a document width sensor 86, a reading entrance sensor 87, a registration sensor 88, a paper ejection sensor 89, and A detection signal from the imaging unit 44 is captured. The imaging unit 44 constitutes a skew amount detection unit according to the present invention. Note that the skew amount detection unit may be in the ski controller unit 100 or the main body control unit 111 .

The controller unit 100 operates a pickup elevating motor 101 that raises and lowers the pickup roller 58 , a paper feed motor 102 that drives the paper feed belt 59 , and a reading motor 103 that drives the transport roller pairs 63 and 65 .

The controller unit 100 also includes a discharge motor 104 that drives the discharge roller pair 67, a pullout motor 113 that drives the transport roller pair 61, a pickup transport motor 115 that drives the pickup roller 58, and a reverse motor that drives the reverse roller 68. 105 is activated.

Based on the skew amount detected by the imaging unit 44, the controller unit 100 abuts the leading edge of the document sheet S fed to the conveying roller pair 61, and adjusts the skew, which is the inclination of the image read by the optical scanning unit 40. to correct. The imaging unit 44 detects a shadow projected on a document reading guide 91 (described later) based on the amount of reflected light detected by the optical scanning unit 40 at the detection position. A correction section according to the present invention is configured in the controller section 100 . Note that the correction unit may be in the body control unit 111 . The image forming section 3 forms a corrected image on the transfer paper P by using the correction values of the correcting section for the read image. Note that the controller unit 100, main body control unit 111, and skew amount detection unit are integrated circuits.

When the registration sensor 88 detects the leading edge of the document sheet S, the controller unit 100 transmits a conveyance stop signal to the main body control unit 111 via the interface 107 . Further, when the registration sensor 88 detects the leading edge of the document sheet S, the controller unit 100 decelerates the transport speed over a predetermined transport distance, and scans the document before the reading position on the reading line 20 by the optical scanning unit 40 . The sheet S is temporarily stopped. Hereinafter, the position of the leading edge of the document sheet S when the transport stop signal is transmitted is also referred to as a registration position.

Subsequently, when the controller unit 100 receives a reading start signal from the body control unit 111 , the document sheet S that has been temporarily stopped is conveyed by a predetermined amount until the leading edge of the document sheet S reaches the reading position on the reading line 20 . The speed is increased so that the material can be conveyed.

At the timing when the leading edge of the document sheet S reaches the reading position of the optical scanning unit 40, the controller unit 100 supplies the main body control unit 111 with a gate signal indicating the sub-scanning direction effective image area and the non-effective image area of the first surface. to start sending. Here, the non-effective image area is an area from the leading edge of the original sheet S to the beginning edge of the effective image area and from the trailing edge of the effective image area to the trailing edge of the original sheet S. FIG. The gate signal has ON/OFF, and the effective image area corresponds to ON and the ineffective image area corresponds to OFF. The gate signal is transmitted until the trailing edge of the document sheet S passes through the reading position on the reading line 20 by the optical scanning unit 40 . The timing at which the leading edge of the document sheet S reaches the reading position is detected by the pulse count of the reading motor 103 after the leading edge of the document sheet S is detected by the reading entrance sensor 87 .

The document sheet S that has passed through the reading/conveying section E is conveyed to the discharging section F. As shown in FIG. At this time, when the discharge sensor 89 detects the leading edge of the document sheet S, the controller unit 100 drives the discharge motor 104 forward to rotate the discharge roller pair 67 in the discharge direction. The controller unit 100 also calculates the timing at which the trailing edge of the document sheet S exits the nip of the sheet ejection roller pair 67 based on the ejection motor pulse count from the detection of the leading edge of the document sheet S by the ejection sensor 89 . Controller unit 100 reduces the driving speed of sheet discharge motor 104 based on the result of this calculation, and the document sheet is placed on document sheet discharge tray 53 at the timing just before the trailing edge of document sheet S exits the nip of sheet discharge roller pair 67 . control is performed so that the document sheet S ejected to .

The above is the overall configuration of the image forming apparatus 1 according to the present embodiment.

First, the shadow of the document sheet S will be described with reference to FIGS. 6 to 8. FIG.

Reference numeral 191 in FIG. 6 denotes a document reading guide provided in place of the document reading guide 91 according to the present embodiment. The document reading guide 191 has a guide surface 191A that faces the first contact glass 45 in close proximity and in parallel.

FIG. 6 shows a state in which the end of the document sheet S on the side of the leading edge of the sheet S is being transported in close proximity to the first contact glass 45 . Arrows L1 and L2 inclined upward from the first carriage 41 in FIG. An arrow L3 indicates the direction (light receiving line) of light reflected by the document reading guide 91. This light is received by the imaging section 44, which is a light receiving section, and is read by the aforementioned reading line 20 for reading the surface of the document sheet S. be.

When the document sheet S conveyed by the ADF 5 a reaches the first contact glass 45 , the light emitting line L 1 emitted from the light source in the first carriage 41 at a predetermined angle of inclination causes the guide surface 191 A of the document reading guide 191 to move. , the shadow W of the leading edge of the document sheet S is projected. Before the leading edge of the document sheet S reaches the reading position on the reading line 20, the shadow W is projected onto the document reading guide 191 from the diagonally lower left side in FIG. The shadow W is generated because the y-direction positions of the leading edge of the document sheet S and the document reading guide 91 are different, that is, there is a gap between the leading edge of the document sheet S and the document reading guide 191 .

FIG. 7 shows the shadow W of the document sheet S projected onto the document reading guide 191 when the document sheet S conveyed from above the document reading guide 191 is seen through. In the figure, S1, S2 and S3 denote the upper edge, left edge and right edge of the document sheet S, respectively. W1, W2, and W3 denote the horizontal edge of the upper side, the vertical edge of the left side, and the vertical edge of the right side, which are projection images of the upper side S1, the left side S2, and the right side S3 of the document sheet S in the shadow W, respectively.

Here, as shown in FIG. 7B, when the document sheet S is tilted with respect to the conveying direction, the extending direction of the lateral edge W1 of the shadow W and the arrow 40S of the optical scanning unit 40 indicate In comparison with the main scanning direction, the inclination angle of the document sheet S with respect to the conveying direction can be detected from the angle of the lateral edge W1 with respect to the main scanning direction.

The document sheet S shown in FIG. 6 is conveyed close to the first contact glass 45 because the leading end thereof is not curled. Therefore, the shadow W of the document sheet S is projected onto the document reading guide 91 as shown in FIG.

On the other hand, FIG. 8 shows a state in which the leading edge of the document sheet S is conveyed while being in contact with the document reading guide 191 . In this case, since there is no gap (distance in the y direction) between the leading edge of the document sheet S and the document reading guide 191, the shadow W of the document sheet S is not projected. When the leading edge of the document sheet S is close to the document reading guide 191 without contact, the width H of the shadow W shown in FIG. 7 becomes extremely small, making it difficult to detect the shadow W. FIG. Such a state in which the leading edge of the document sheet S contacts or approaches the document reading guide 191 can occur, for example, when the document sheet S is curled toward the document reading guide 191 . It can also occur with cardboard when the conveying guide is curved.

On the other hand, in the image reading device 6 of the image forming apparatus 1 according to the present embodiment, as shown in FIGS. 9 and 10, the surface of the document reading guide 91 facing the first contact glass 45 and the first contact A transparent member 200 for providing a gap between the document sheet S and the document reading guide 91 is provided between the surface of the glass 45 facing the document reading guide 91 . A background member 200a (200a1 and 200a2) with a white surface is provided on the surface of the transparent member 200 on the side of the document reading guide 91 on the reading line 20 read by the optical scanning unit 40 of the image reading section 4. FIG. The background member 200a may be the same color as the document reading guide 91, the reading line 20 may be painted white, or a white sheet material may be used. The background member 200 a of the transparent member 200 allows the shadow W to be reliably projected onto the document reading guide 91 . In this embodiment, the background member 200a made of a white sheet material is attached to the transparent member 200. However, if the distance between the surface of the transparent member 200 on the manuscript reading guide 91 side and the background member 200a is equal, There may be a gap between the transparent member 200 and the background member 200a.

The document reading guide 91 and the transparent member 200 according to this embodiment will be described below with reference to FIGS. 9 and 10. FIG.

The document reading guide 91 is an upper guide member that guides the inner circumference of the document sheet S conveyed along the conveying path 56 from the conveying upstream side through the conveying rollers 61 and 63 .

As shown in FIG. 9, the document reading guide 91 has guide surfaces 91A1 and 91A2 facing in parallel with the first contact glass 45, and is inclined upward from the guide surface 91A1 toward the upstream side (left side in FIG. 9). It has an inclined portion 91B1 and an inclined portion 91B2 that inclines obliquely upward from the guide surface 91A2 toward the downstream side (the right side in FIG. 9). Further, the document reading guide 91 has a region between the guide surface 91A1 and the guide surface 91A2 facing the first carriage 41, and a concave portion 94 is formed in this region.

A boundary portion between the guide surface 91A1 and the inclined portion 91B1 constitutes a regulating portion 91C that regulates the transport position of the document sheet S transported on the transport path 56. As shown in FIG. A boundary portion between the guide surface 91A2 and the inclined portion 91B2 constitutes a regulating portion 91D that regulates the transport position of the document sheet S transported on the transport path 56. As shown in FIG.

As shown in FIG. 11, when the transport path 56 of the document sheet S is a curved transport path and not a straight transport path, the transport position of the document sheet S is regulated in order to stabilize the read image on the reading line 20 . There is a need to.

In the case where the transparent member 200 whose surface on the side of the first contact glass 45 of the transparent member 200 serves as a guide is provided as in the present embodiment, the document sheet S is guided by the regulating portions 91C and 91D of the document reading guide 91. It is supposed to be regulated. In order to make such a structure, the guide surfaces 91A1 and 91A2 of the document reading guide 91 facing the optical scanning unit 40 are made substantially parallel to the first contact glass 45, and the recess 94 is formed between them. 200 was set.

The transparent member 200 according to the present embodiment includes a first transparent member 210 extending in the main scanning direction at a reading position on the reading line 20 extending in the main scanning direction, and and a second transparent member 220 having a thickness greater than that of the first transparent member 210, and a first background member 200a1 and a second background member 200a2 on the document reading guide 91 side. It has

As shown in FIG. 10, in this embodiment, the front end portion of the first transparent member 210 is arranged at a position through which the right side S3 of the largest document sheet S transported along the transport path 56 passes. Further, the back side of the second transparent member 220 is arranged at a position through which the left side S2 of the document sheet S conveyed on the conveying path 56 passes. Reference numeral 40A in FIG. 10 schematically indicates the direction of light (light emission line) from the optical scanning unit 40. As shown in FIG. The left side S2 and the right side S3 of the document sheet S are diffusely irradiated with light emitting lines in a direction perpendicular to the main scanning direction or at an angle to the direction perpendicular to the main scanning direction. Creates shadows with distinct edges that are illuminated at different illumination angles and distances. Also, the shadow of the background member is read with a reading line perpendicular to the background member. The right side S3 of the document sheet S is the front side (front side) edge, and the left side S2 is the back side (rear side) edge.

Each of the transparent members 210 and 220 is a rectangular parallelepiped transparent plate member made of a material such as glass or plastic and having the same width in the conveying direction. The transparent members 210 and 220 are provided in the concave portion 94 formed in the document reading guide 91 so that their longitudinal directions are parallel to the first contact glass 45 in the main scanning direction of the optical scanning unit 40 .

As shown in FIG. 10, the second transparent member 220 is shorter than the first transparent member 210, and the left side S2 of the document sheet S on the back side of the device while being guided by the document reading guide 91 is positioned at the second position. of the transparent member 220 in the longitudinal direction. Further, the first transparent member 210 is arranged so that the right side S3 of the document sheet S on the front side of the apparatus in the state of being guided by the document reading guide 91 passes through the longitudinal middle portion of the first transparent member 210 . It's becoming

In this embodiment, the first transparent member 210 and the second transparent member 220 are in contact with each other and arranged in a straight line in the main scanning direction, but there may be an ADF gap. The total length in the main scanning direction of the first transparent member 210 and the second transparent member 220 is longer than the length in the main scanning direction of the maximum passable size of the ADF 5a, and extends over the entire area in the main scanning direction. . In addition, the first transparent member 210 and the second transparent member 220 are aligned so that their lower surfaces facing the first contact glass 45 are flush with each other, and the upper surface of the second transparent member 220 is It protrudes toward the document reading guide 91 side. Furthermore, since the transparent members 210 and 220 are provided in the concave portion 94, the lower surfaces of the transparent members 210 and 220 are generally flush with the guide surfaces 91A1 and 91A2 of the document reading guide 91, and are not projected downward. It has become.

Each of the transparent members 210 and 220 is fixed to the document reading guide 91 by appropriate fixing means such as adhesion with an adhesive or fixing with an adhesive tape.

In this embodiment, the reading unit 4 reads the shadow W of the original sheet S projected onto the background member 200a2 through one of the first transparent member 210 and the second transparent member 220 through the transparent member 220. FIG. The shadow W is projected onto the flat surface of the background member 200a2 on the transparent member 220 side.

FIG. 9 shows a state in which the document sheet S is curled and is being conveyed while the leading edge on the conveying side is in contact with the transparent member 200 . With such a document sheet S, the leading edge of the document sheet S does not contact the document reading guide 191 unlike the configuration shown in FIG.

In this embodiment, as shown in FIG. 10, the background member 200a1 of the first transparent member 210 and the background member 200a2 of the second transparent member 220 are placed between the document sheet S and the document reading guide 91 by different distances from the document sheet S. exists in That is, the transparent members 210 and 220 secure the distance in the y direction between the document sheet S and the background member. Therefore, the shadow W of the document sheet S is projected with a width on the background member 200a2. In this embodiment, by comparing the extension direction of the edge of the shadow W read by the optical scanning unit 40 (the boundary between the shadow and the white background member 200a2) with the main scanning direction, the inclination of the document sheet S with respect to the transport direction is determined. Detect the angle and correct the skew of the image. The extending direction may be the boundary between the edge (generally white) of the document sheet and the shadow.

FIG. 12 shows a shadow W projected onto the background member through the first transparent member 210 and the second transparent member 220. As shown in FIG. As described above, the shadow W projected through the second transparent member 220 (the width of S2 and W2) is projected through the first transparent member 210 (S3 and W2). width of W3). This difference in width is due to the fact that the second transparent member 220 is thicker than the first transparent member 210 .

In the image forming apparatus 1 of the present embodiment, the following means are used to detect the angle of inclination of the document sheet S with respect to the conveying direction from the shadow W projected on the document reading guide 91 as shown in FIG. can be adopted.

(First detection method: detection of vertical edge on left side)
The first detection method reads the vertical edge on the left side (the edge where the edge of the document sheet S is projected in the main scanning direction). The optical scanning unit 40 reads the extending direction of the vertical edge W2 on the left side of the projected shadow W of the document sheet S through the second transparent member 220 . Then, the optical scanning unit 40 detects an angle .theta.5 between the vertical edge W2 on the left side with respect to the main scanning direction indicated by an arrow 40S in FIG. Then, the skew of the image is corrected by rotating the image by an inclination angle θ6 with respect to the conveying direction of the document sheet S. FIG. Note that the inclination angle of the document sheet S with respect to the main scanning direction may be detected from the calculated angle θ5.

When the leading edge of the document sheet S in the conveying direction is deformed by a disturbance factor such as curling or folding, the lateral edge W1 of the shadow W, which is the projected image of the leading edge of the document sheet S, may also be deformed. However, the inclination angle of the sheet material can be detected with high accuracy by the first detection method. That is, the vertical edge W2 on the left side of the shadow W is read without detecting the horizontal edge W1 on the upper side S1 including the deformation element. The vertical edge W2 on the left side is less susceptible to deformation such as curling in the main scanning direction, and the image of the left side S2 is accurately projected. Further, as shown in FIG. 12, in the case of the vertically long document sheet S, the vertical edge W2 on the left side is longer than the horizontal edge W1, so that the angle can be easily detected. can do.

(Second detection method: comparison of left and right vertical edges)
The second detection method reads the vertical edge W3 on the right side in addition to reading the vertical edge W2 on the left side. The position for reading the vertical edge W3 on the right side of the shadow W is switched according to the width of the document sheet S detected by the document width sensor 86, and the vertical edge W3 on the right side is read through the first transparent member 210. FIG. That is, both the left and right vertical edges W2 and W3 are read. FIG. 13 shows a state in which the reading position of the vertical edge W3 on the right side (front side) is switched for document sheets S with different widths. FIG. 13B shows the case of the original sheet S having a small width.

Then, the vertical edge W2 on the left side (rear side) of the shadow W of the document sheet S projected onto the document reading guide 91 and the vertical edge W3 on the right side are compared, and the one with the higher reliability as the tilt angle data is selected. The controller unit 100 selects a vertical edge (W2 or W3) and adopts the vertical edge as data for skew correction.

As an index of the reliability of the tilt angle data, there is an angle of intersection between each vertical edge W2, W3 of the shadow W and the main scanning direction 40S. That is, the closer these intersection angles are to the right angle, which is the intersection angle between the left side S2 and right side S3 of the document sheet S and the upper side S1, the higher the reliability.

Therefore, in this case, as shown in FIG. 12, the controller unit 100 determines an angle θ5 between the left vertical edge W2 and the main scanning direction 40S and an angle θ7 between the right vertical edge W3 and the main scanning direction 40S. By comparison, the vertical edge (W2 or W3) that indicates an angle close to a right angle is adopted as the data of the inclination angle of the sheet material S. FIG. Thus, by comparing the left and right vertical edges W2 and W3 and adopting the vertical edge with higher reliability as data of the tilt angle, the tilt angle of the document sheet S can be detected with high precision.

It is preferable that the thickness of the first transparent member 210 and the second transparent member 220 of the present embodiment be smaller than the depth dimension of the concave portion 94, as shown in FIG. With this configuration, the lower surfaces of the transparent members 210 and 220 facing the first contact glass 45 are located above the guide surfaces 91 A 1 and 91 A 2 of the document reading guide 91 . By providing the transparent members 210 and 220 inside the curved conveying path of the document reading guide 91 in this manner, the document sheet S is less likely to come into contact with the transparent member 200 . As a result, there is an advantage that the transparent member 200 is less likely to be scratched or stained.

Although the transparent members 210 and 220 constituting the transparent member 200 of this embodiment are configured as separate members, the transparent members 210 and 220 are integrally molded, and the transparent member 200 is formed to have a thickness may be configured as one member having different portions of Also, in this embodiment, the stationary optical scanning unit 40 is operated through the first contact glass 45 , but the movable optical scanning unit 40 may be operated through the second contact glass 46 .

Another embodiment will now be described with reference to FIG. As shown in FIG. 13, the image forming apparatus 1 of another embodiment does not have the first transparent member 210 at one end on the front side as in FIG. constitutes the transparent member 220 of . In particular, in the case of a movable optical scanning unit 40, a second transparent member 220 is provided on the back side along the moving direction of the optical scanning unit 40. As shown in FIG. Only the detection of the tilt angle of the document sheet S by the second transparent member 220 will be described below. In addition, in FIG. 15, the same reference numerals are assigned to the same components as in the above embodiment, and the description thereof will be omitted.

The second transparent member 220 is partially provided at a position on the reading line 20 of the optical scanning unit 40 at a predetermined position. side (right side in FIG. 15). The document sheet S conveyed on the reading line 20 passes under the second transparent member 220 at the leading edge on the left side S2 side, which is the back side. Therefore, the y-direction position (thickness direction) between the front end portion of the document sheet S and the background member attached to the second transparent member 220 can be provided, and the vertical edge can be reliably detected.

As described above, the image forming apparatus 1 having the image reading device 6 of the sheet material reading device according to the present embodiment includes the image forming section 3 that forms an image corrected by the controller section 100. Thus, the skew of the image formed on the transfer paper P can be corrected with high accuracy.

As described above, the image reading apparatus 6 according to the present embodiment includes the guide member 91 that guides the document sheet S along the transport path 56 and the background member 200a on which the shadow of the document sheet guided by the guide member 91 is projected. , an optical scanning unit 40 for reading the shadow of the original sheet, and a transparent member 200 between the background member and the reading section and between the original sheet and the background member, the transparent member extending in the main scanning direction. The first transparent member has a first transparent member 210 extending to a reading position on the reading line of the reading unit and a second transparent member 220 on one end side in the extending direction of the first transparent member. The distance between the document sheet side surface of the second transparent member and the background member is longer than the distance between the document sheet side surface of the second transparent member and the background member. It is configured to detect the tilt angle by reading the edge of the shadow at the end of the document sheet in the main scanning direction, and the tilt angle of the sheet material can be detected with high accuracy.

1 Image forming apparatus 3 Image forming unit 5a ADF
6 Image reader (sheet material reader)
20 reading line 40 optical scanning unit (reading section)
40S Main scanning direction 44 Imaging section (skew amount detection section)
56 transport path 86 document width sensor (width detection means)
91 document reading guide (guide member, background member)
94 recess 100 controller unit (correction unit)
200 transparent member 210 first transparent member 220 second transparent member S manuscript sheet (sheet material)
S1 Upper side of document sheet S2 Left side of document sheet (rear side)
S3 Right side of document sheet (front side)
T Transport direction W Shadow W1 Horizontal edge W2 Vertical edge on left side W3 Vertical edge on right side

Japanese Patent Application Laid-Open No. 2001-077986 JP 2013-078059 A

Claims (7)

a guide member for guiding a sheet material along a conveying path; a background member on which a shadow of the sheet material guided by the guide member is projected; a reading unit for reading the shadow of the sheet material; a transparent member between the part and between the sheet material and the background member;
The transparent member includes a first transparent member extending at a reading position on a reading line of the reading unit extending in the main scanning direction, and a second transparent member at one end side in the extending direction of the first transparent member. a member;
the distance between the sheet material side surface of the second transparent member and the background member is longer than the distance between the sheet material side surface of the first transparent member and the background member;
The sheet material reading device, wherein the reading unit reads an edge of a shadow of an end portion of the sheet material in a main scanning direction projected onto the background member through the second transparent member, and detects an inclination angle. . A direction orthogonal to the transport path is defined as a front-rear direction,
The first transparent member is disposed at a position through which a front edge in the front-rear direction of the sheet material conveyed on the conveying path passes,
The second transparent member is disposed at a position through which a rear edge of the sheet material conveyed in the conveying path passes in the front-rear direction,
3. The reading unit reads a rear vertical edge, which is a projected image of the rear edge in the shadow of the sheet material projected onto the background member, through the second transparent member. 2. The sheet material reading device according to 1. Width detection means for detecting a width of the sheet material along the main scanning direction,
According to the width of the sheet material detected by the width detection means, the reading unit detects a front longitudinal edge, which is a projected image of the front edge in the shadow of the sheet material projected onto the background member, as the 3. A sheet reading device according to claim 2, wherein the reading is through the first transparent member. The angle of intersection with the rear vertical edge and the angle of intersection with the vertical edge on the front side are compared, and the inclination angle of the vertical edge with respect to the main scanning direction that indicates an angle close to a right angle among these intersection angles. 4. The sheet material reading apparatus according to claim 3, wherein is adopted as the data of the inclination angle of the sheet material. 5. The sheet material reading device according to claim 1, wherein the first transparent member and the second transparent member are provided in recesses formed in the guide member. The reading unit is configured to read an image formed on the sheet material,
a skew amount detection unit that detects a skew amount of an image formed on the sheet material read by the reading unit based on the detected inclination angle of the sheet material;
6. The apparatus according to any one of claims 1 to 5, further comprising a correction unit that corrects skew of the image read by the reading unit based on the skew amount detected by the skew amount detection unit. sheet material reader. An image forming apparatus comprising: the sheet material reading device according to claim 6; and an image forming section that forms an image corrected by the correcting section .

Images