Skew correction device, sheet transport device, automatic document transport device, and image forming apparatus

Abstract

The present invention provides a skew correction device, a sheet transport device, an automatic document transport device, and an image forming apparatus that can suppress wrinkles and folds in the sheet. [Solution] The skew correction mechanism 50, which is a skew correction device, comprises gate members 151A and 151B that are rotatably supported, and a restricting member that has a contact portion 152A that the leading edge of the original document (sheet) contacts and restricts the rotation of the gate members 151A and 151B. The gate members 151A and 151B are provided one on one side and one on the other side in the original document width direction, with the contact portion 152A in between. In addition, the distance X1 between the two gate members is shorter than the minimum width size W1 of the sheet that the ADF (Automatic Document Feeder) can transport.

Description

Technical Field

[0001] The present invention relates to a skew correction device, a sheet conveyance device, an automatic document conveyance device, and an image forming device.

Background Art

[0002] Conventionally, there is known a skew correction device including an abutting portion against which the leading end in the sheet conveyance direction abuts, the abutting portion having a gate member movable between an abutting position and a retracted position retracted from the abutting position, and a restricting member for restricting the movement of the abutting portion from the abutting position to the retracted position. The restricting member is located upstream of the abutting portion in the conveyance direction, has a contact portion that contacts the central portion in the width direction of the leading end of the sheet, and is configured such that when the leading end of the sheet pushes the contact portion in the conveyance direction, the restriction on the movement of the abutting portion is released.

[0003] Patent Document 1 describes, as the above skew correction device, one in which a plurality of gate members are provided with a predetermined interval on each of one side and the other side in the sheet width direction with the contact portion interposed therebetween. Each gate member is a plate-like member, and each gate member is rotatably supported such that the abutting surface as the abutting portion against which the leading end of the sheet abuts moves in the conveyance direction together with the sheet.

[0004] The restricting member has a rotation axis extending in the width direction of the sheet, and the contact portion extends from the center in the width direction of the rotation axis toward the sheet conveyance path. The rotation axis of the restricting member is located upstream of each gate member in the conveyance direction, and the rotation axis has a restricting portion for restricting the rotation of the gate member facing the end portion on the opposite side to the portion where the leading end of the sheet abuts the gate member from the upstream side in the conveyance direction.

[0005] When the sheet skews and enters the skew correction device, the leading end of the sheet's widthwise edge abuts against the abutment surface of the gate member. At this time, the gate member's rotation is restricted by the regulating member. Therefore, the sheet rotates using the widthwise edge of the sheet that is abutting against the abutment surface as a pivot point, and the skew is corrected. As the skew is corrected, the widthwise center of the sheet's edge abuts against the contact point, pushing the contact point in the transport direction. This causes the regulating member to rotate around its pivot point, moving the regulating member to a position where it does not face the gate member, and the restriction on the gate member's rotation is released. Once the restriction on the gate member's rotation is released, the force pushing the abutment surface of the sheet's edge causes the gate member to rotate. As a result, the abutment surface moves with the sheet in the transport direction, moving from the abutment position to the retracted position, and the skew-corrected sheet moves downstream in the transport direction.

[0006] Patent Document 1 describes that by providing multiple gate members at predetermined intervals on one side and the other side in the sheet width direction, flanking the contact portion, skew correction can be performed by the inner gate members even when a narrow sheet is being transported, thereby enabling the sheet to be transported appropriately. [Overview of the project] [Problems that the invention aims to solve]

[0007] However, depending on the width of the sheet, the widthwise edge of the leading edge of the sheet may get caught between the gate members. When the sheet attempts to rotate due to the conveying force of the upstream conveyor roller pair while the widthwise edge of the leading edge of the sheet is caught between the gate members, the widthwise edge of the leading edge of the document between the gate members may get caught on the outer gate member. As a result, folds or wrinkles may occur on the leading edge side. [Means for solving the problem]

[0008] To solve the above-mentioned problems, the present invention provides a skew correction device comprising: a gate member configured to be movable between a stop position in which the leading edge of a sheet in the conveying direction abuts and a retracted position where the gate member is retracted from the stop position; and a restricting member located upstream of the gate member in the conveying direction and having a contact portion that abuts the center of the leading edge of the sheet in the width direction, the restricting member moving from a restricting position that restricts the movement of the gate member from the stop position to the retracted position to a release position that releases the restriction on the movement of the gate member when the leading edge of the sheet pushes the contact portion in the conveying direction, wherein one gate member is provided on one side and the other side in the sheet width direction, flanking the contact portion, and the distance between the two gate members is shorter than the minimum width of a sheet that can be conveyed by a sheet conveying device on which the skew correction device is mounted. [Effects of the Invention]

[0009] According to the present invention, it is possible to suppress wrinkles, folds, and other damage that may occur in the sheet. [Brief explanation of the drawing]

[0010] [Figure 1] An explanatory diagram showing the schematic configuration of a copier in an embodiment. [Figure 2] An explanatory diagram showing the schematic configuration of an automatic document feeder (ADF). [Figure 3] A forward perspective view of the same ADF. [Figure 4] Rearward perspective view of the ADF. [Figure 5] A block diagram showing the configuration of the control unit for the ADF. [Figure 6] A block diagram showing the essential electrical circuit components of the second image reading unit in the ADF. [Figure 7] A diagram illustrating the arrangement of the skew correction mechanism in the ADF. [Figure 8] A perspective view showing a conventional skew correction mechanism. [Figure 9] This diagram illustrates the skew correction in the conventional skew correction mechanism. [Figure 10]A diagram illustrating the challenges of the conventional configuration. [Figure 11] A diagram illustrating another problem with the conventional configuration. [Figure 12] A plan view showing the relationship between the skew correction mechanism of this embodiment and the original document of the minimum width size. [Figure 13] A plan view showing the relationship between the skew correction mechanism of this embodiment and the original document of the maximum width size. [Figure 14] This figure illustrates the skew correction mechanism of this embodiment. [Modes for carrying out the invention]

[0011] One embodiment of the present invention will be described below with reference to the drawings. Figure 1 is an explanatory diagram showing the schematic configuration of the copier 1 as an image forming apparatus in this embodiment. This copier 1 comprises an automatic document feeder (ADF) 100, a document feeding unit 2, and an image forming unit 3.

[0012] The feeding unit 2 includes feeding cassettes 21 and 22 for storing transfer paper (sheets) of different sizes, and a feeding means 23 consisting of various rollers for transporting the transfer paper stored in the feeding cassettes 21 and 22 to the image forming unit 3.

[0013] The image forming unit 3 comprises an exposure device 31, four photoreceptor drums 32 for each of the four colors, a developing device 33, a transfer belt 34, and a fixing device 35. Based on the image data of the original document read by the image reading unit located inside the ADF 100, the image forming unit 3 uses the exposure device 31 to expose each photoreceptor drum 32 and form latent images of each color on each photoreceptor drum 32. Then, the developing device 33 for each color supplies toner of each color to each photoreceptor drum 32, developing the latent images on each photoreceptor drum 32 to form toner images. After that, the image forming unit 3 uses the transfer belt 34 to transfer the toner images of each photoreceptor drum 32 to the recording paper supplied from the feeding unit 2, and then the fixing device 35 melts the toner of the toner images transferred to the recording paper to fix the color image to the recording paper.

[0014] FIG. 2 is an explanatory diagram showing a schematic configuration of an automatic document feeder (ADF) 100 having functions as an image reading device. FIG. 3 is a front perspective view of the ADF 100. FIG. 4 is a rear perspective view of the ADF 100.

[0015] As shown in FIG. 1, the ADF 100 is provided on the upper part of the copying machine 1. The ADF 100 includes a document set portion A, a separation and feeding portion B as a feeding portion, a registration portion C, a turning portion D, a first reading and conveying portion E, a second reading and conveying portion F, a paper discharge portion G, and a stack portion H. In the document set portion A, a stack of documents is set. In the separation and feeding portion B, documents are separated one by one from the set stack of documents and fed. In the registration portion C, the fed documents are brought into primary contact alignment and the aligned documents are drawn out and conveyed. In the turning portion D, the conveyed documents are turned and conveyed with the document surface facing the reading side (downward in the figure) by the first image reading unit 131. In the first reading and conveying portion E, the surface image of the document is read by the first image reading unit 131 from below the contact glass 4. In the second reading and conveying portion F, the back surface image of the document after the surface image has been read is read by the second image reading unit 132. In the paper discharge portion G, the document for which the front and back images have been read is discharged outside the machine, and in the stack portion H, the discharged documents are stacked and held.

[0016] In the document set portion A, a single sheet document to be read or a stack of two or more documents (hereinafter collectively referred to as a "stack of documents") is set. The stack of documents is set on a document table 120 as a sheet placement portion including a movable table 121.

[0017] In the present embodiment, a contact glass 4 made of a translucent member is provided on the upper surface of the main body of the copying machine 1, and the ADF 100 is provided adjacent to the contact glass. The ADF 100 is rotatable (openable and closable) to open and close the contact glass 4 via hinge members 110R and 110L.

[0018] The ADF100 supports both sheet-through scanning (automatic transport mode) and fixed-document scanning (pressure plate mode). In the sheet-through scanning method, with the first image reading unit 131 fixed, the document to be scanned is transported at a predetermined speed while the image is read by either the first image reading unit 131 or the second image reading unit 132 or both. In the fixed-document scanning method, the document to be scanned is placed on the contact glass 4, and the first image reading unit 131 is moved along the contact glass 4 while the image is read.

[0019] The copier 1 of this embodiment has an operation unit 5 (see Figure 5) as an operation receiving means for receiving user input. The operation unit 5 is configured to allow arbitrary setting of operating modes, such as the automatic document feeder (ADF) mode in which the original document is read using the original document fixed reading method described above, and the pressure plate mode in which the original document is read using the sheet-through reading method described above.

[0020] Figure 5 is a block diagram showing the configuration of the control unit of the ADF100. As shown in Figure 5, the ADF100 is also equipped with various motors 101 to 107 as drive sources for driving the document feeding operation (document transport operation) in each mechanism A to H, as well as a control unit 150 that controls various operations including the operation of the various motors 101 to 107.

[0021] The control unit 150 supplies power to each component installed in the ADF 100 and performs control of each component installed in the ADF 100 based on control signals transmitted from the main unit control unit 6 located in the main unit of the copier 1.

[0022] When reading a document image using the fixed document reading method, the document is placed on the contact glass 4 and the ADF 100 is closed. The bottom of the ADF 100 is provided with a pressure plate for pressing the document against the contact glass 4 when reading a document using the fixed document reading method. When the ADF 100 is closed and a document reading instruction is given to the operation unit 5, the first image reading unit 131 reads the document while moving in the left-right direction in Figure 1. In the fixed document reading method, for example, for each A4-size document read, a gate signal is sent from the control unit 150 to the first image reading unit 131, and reading control is performed.

[0023] When scanning a document image using the sheet-through scanning method, the stack of documents is placed on the document table 120 (sheet placement section), which includes the movable table 121, with the document surface (first side) facing upwards. Furthermore, the width direction of the stack of documents (the direction perpendicular to the document transport direction) is restricted by the side fence 122, which acts as a sheet restricting member, and the side fence 122 is positioned (aligned) according to the width of the stack of documents. The fact that the stack of documents has been set (set state) is detected by the document set sensor 115 provided on the movable table 121 and transmitted to the main unit control unit 6 via the interface (I / F).

[0024] The movable table (bottom plate) 121 is supported so that its rear end (rear in the document feeding direction) is rotatable around a pivot shaft 121a. The movable table 121 is configured to be able to move up and down by rotating around the pivot shaft 121a using a bottom plate lifting motor 105, thereby allowing the front end of the movable table 121 (forward in the document feeding direction) to move up and down.

[0025] Before the documents are placed on the document table 120, the movable table 121 of the document table 120 is in the lowered home position (shown by the dashed line in Figure 2). With the movable table 121 in the home position, the user places the stack of documents on the document table 120. At this time, the top surface of the stack of documents on the movable table 121 in the home position is separated from the pickup roller 141.

[0026] When the document setting sensor 115 detects that a document has been placed, the control unit 150 rotates the bottom plate lifting motor 105 forward. As a result, the movable table 121 rises so that the top surface of the document stack on the movable table 121 comes into contact with the pickup roller 141, which acts as a document feeder. When the movable table 121 rises and the top surface of the document stack on the movable table 121 pushes up the pickup roller 141, this is detected by the table lifting sensor 118. Upon receiving this detection signal, the control unit 150 stops the drive of the bottom plate lifting motor 105, so that the movable table 121 stops in the correct position.

[0027] In other words, the table rise sensor 118 is a sensor that detects when the movable table 121 has reached the correct position and maintains the top surface of the document stack at the correct feeding height. Specifically, when the table rise sensor 118 turns ON, the rise of the movable table 121 is stopped. Then, as the top surface of the document stack is lowered by repeating document feeding, the table rise sensor 118 turns OFF, and the movable table 121 is raised again. When the table rise sensor 118 turns ON again, the rise of the movable table 121 is stopped. By repeatedly performing this control operation, the top surface of the document stack (height of the top document) is maintained within a height range suitable for document feeding.

[0028] When the entire stack of documents placed on the document table 120 has been fed, the document set sensor 115 turns OFF. When the document set sensor 115 turns OFF, the control unit 150 reverses the bottom plate lifting motor 105 to lower the movable table 121 to the home position so that the next stack of documents can be placed on the document table 120. In this embodiment, a bottom plate home position sensor 117 is provided to detect when the movable table 121 is in the home position, and the control unit 150 can confirm whether the movable table 121 is in the home position.

[0029] When a document scanning instruction (feed start instruction) is given to the operation unit 5, the main unit control unit 6 sends a document feed transmission signal (feed start signal) to the control unit 150 via the interface. This starts the feeding operation, and with the top surface of the stack of documents on the movable table 121 maintained at the appropriate feeding height, the pickup roller 141 is rotated by the forward rotation of the feed motor 102, and several documents (ideally one) are picked up from the document table 120. The direction of rotation at this time is to transport the topmost document forward in the feeding direction. The separation mechanism 142 consists of a feed belt 142A and a reverse roller 142B opposite to it. The feed belt 142A is rotated in the feeding direction by the forward rotation of the feed motor 102. The reverse roller 142B is rotated in the opposite direction to the feeding direction by the forward rotation of the feed motor 102.

[0030] The original document, separated into a single sheet by the separation mechanism 142, is further transported by the feed belt 142A. After its leading edge is detected by the abutment sensor 111, it moves further and abuts against the stationary pull-out roller pair 143. Subsequently, the original document is transported a predetermined distance from the detection timing of the abutment sensor 111, so that its leading edge is pressed against the pull-out roller pair 143 with a predetermined amount of deflection. In this state, stopping the feed motor 102 stops the drive of the feed belt 142A that is transporting the original document.

[0031] When the leading edge of the document is detected by the stop sensor 111, the control unit 150 rotates the pickup motor 101, retracting the pickup roller 141 from the top surface of the document. Therefore, the document is transported solely by the transport force of the feed belt 142A of the separation mechanism 142. Through this operation, the leading edge of the document enters the nip portion of the pull-out roller pair 143, and the leading edge is aligned (skew correction). The pull-out roller pair 143 has a skew correction function and is a roller that transports the skew-corrected document to the intermediate roller 144 after separation, and is driven by the pull-out motor 106. The intermediate roller 144 is driven by the intermediate motor 107. When the pull-out roller pair 143 is driven, the intermediate roller 144 is driven, but the pickup roller 141 and feed belt 142A are not driven.

[0032] The length of the document in the transport direction is detected from the motor pulse by detecting the leading and trailing ends of the document with a stop sensor 111. The document is transported from the resist section C to the turn section D by driving the pull-out roller pair 143 and the intermediate roller 144. At this time, the transport speed in the resist section C is set to be faster than the transport speed in the first reading transport section E. This makes it possible to shorten the processing time for feeding the document to the first reading transport section E.

[0033] When the leading edge of the document is detected by the reading entrance sensor 112, the document transport speed is reduced to match the reading transport speed before the leading edge of the document enters the nip portion of the reading entrance roller pair 145. Simultaneously, the reading motor 103 is driven in the forward direction to drive the reading entrance roller pair 145, the first reading exit roller 146, and the second reading exit roller 147.

[0034] When the leading edge of the document is detected by the resist sensor 113, the control unit 150 pauses the document before it reaches the first reading transport unit E and transmits a pause signal to the main control unit 6 via the interface. Next, when the control unit 150 receives a reading start signal from the main control unit 6, it increases the transport speed so that the leading edge of the document, which was paused, reaches a predetermined transport speed by the time it reaches the first reading transport unit E. At the timing when the leading edge of the document, detected by the pulse count of the reading motor 103, reaches the first reading transport unit E, the control unit 150 transmits a gate signal to the first image reading unit 131 indicating the effective image area in the sub-scanning direction of the first surface. This gate signal is transmitted until the trailing edge of the document leaves the first reading transport unit E.

[0035] In the case of single-sided scanning, the document that has passed through the first reading and transport unit E is transported through the second reading and transport unit F to the paper output unit G. At this time, when the paper output sensor 114 detects the leading edge of the document, the control unit 150 drives the paper output motor 104 in the forward direction to rotate the paper output roller pair 148. The control unit 150 also counts the pulses of the paper output motor 104 after the leading edge of the document is detected by the paper output sensor 114. Then, just before the trailing edge of the document leaves the nip portion of the paper output roller pair 148, the control unit 150 reduces the drive speed of the paper output motor 104 to prevent the document from flying out onto the paper output tray 149 of the stacking unit H.

[0036] In the case of double-sided scanning, the control unit 150 detects the leading edge of the document that has passed through the first reading transport unit E using the paper discharge sensor 114, and then counts the pulses of the reading motor 103. Next, the control unit 150 transmits a gate signal to the second image reading unit 132 indicating the effective image area in the sub-scanning direction when the leading edge of the document reaches the second reading transport unit F. This gate signal is transmitted until the trailing edge of the document leaves the second reading transport unit F. After that, the document that has passed through the second reading transport unit F is transported to the paper discharge unit G.

[0037] Figure 6 is a block diagram showing the main parts of the electrical circuit of the second image reading unit 132. The second image reading unit 132 has a light source unit 200 consisting of an LED array, a fluorescent lamp, or a cold cathode tube. It also has a plurality of sensor chips 201 arranged in the main scanning direction (the direction corresponding to the document width direction), a plurality of operational amplifier circuits 202 individually connected to each sensor chip 201, and a plurality of A / D converters 203 individually connected to each operational amplifier circuit 202. Furthermore, it also has an image processing unit 204, a frame memory 205, an output control circuit 206, an I / F circuit 207, and so on.

[0038] The sensor chip 201 is equipped with a photoelectric conversion element and a focusing lens, which are referred to as a 1:1 close-contact image sensor. Prior to the document entering the reading position of the second image reading unit 132, the control unit 150 sends an ON signal to the light source unit 200. As a result, the light source unit 200 lights up and shines its light toward the document. The reflected light reflected from the document is focused by the focusing lenses of the multiple sensor chips 201 onto the photoelectric conversion elements and read as image information. The image information read by each sensor chip 201 is amplified by the op-amp circuit 202 and then converted into digital image information by the A / D converter 203. This digital image information is input to the image processing unit 204, where shading correction and other processes are performed, and then temporarily stored in the frame memory 205. After that, the output control circuit 206 converts it into a data format that can be accepted by the main unit control unit 6, and then outputs it to the main unit control unit 6 via the I / F circuit 207. The control unit 150 outputs timing signals to indicate when the leading edge of the document reaches the reading position by the second image reading unit 132 (image data from that point onward is treated as valid data), as well as signals for turning on the light source and power supply.

[0039] In this embodiment, as described above, after the leading edge of the document is brought into contact with the pull-out roller pair 143, the document is transported for a predetermined distance, and skew correction is performed so that the leading edge is pressed against the pull-out roller pair 143 with a predetermined amount of deflection. However, if the amount of skew is large, the pull-out roller pair 143 may not be able to completely correct the skew.

[0040] On the document table 120, side fences 122 are placed against both ends in the width direction of the set document stack to restrict its movement and prevent the document from skewing during feeding, thereby reducing the amount of skew of the document entering the pull-out roller pair 143. However, the pair of side fences 122 are manually slid to abut against the width direction ends of the set document stack. As a result, some users may stop the movement of the side fences 122 before they abut against the width direction ends of the document stack. In this case, a gap is created between the document stack and the side fences 122. If the document is transported in this state, the skew of the document may increase, and the amount of skew may exceed the amount of skew that can be corrected by the pull-out roller pair 143. Therefore, in this embodiment, as shown in Figure 7, a skew correction mechanism 50, which is a skew correction device, is provided between the separation mechanism 142 and the pull-out roller pair 143.

[0041] Note that in the separation mechanism 142 shown in Figure 7, the member that contacts the reverse roller 142B is the feed roller 142C. In the following explanation, we will describe the case where the member that contacts the reverse roller 142B is the feed roller 142C, but the member that contacts the reverse roller 142B may also be the feed belt 142A shown in Figure 2.

[0042] Figure 8 is a perspective view showing a conventional skew correction mechanism 50'. In Figure 8, arrow T indicates the transport direction of the original document P, and arrow W in the figure indicates the width direction. The skew correction mechanism 50' includes a regulating member 152 and a pair of gate members 151A and 151B. Each gate member 151A and 151B is a plate-shaped member and has support shafts 153A and 153B that are rotatably supported on the main body of the ADF 100. As the gate members 151A and 151B rotate around the support shafts 153A and 153B as pivot points, the abutting surface against which the leading edge of the sheet of the gate members 151A and 151B abuts moves between an abutting position and a retracted position that is moved away from the abutting position.

[0043] The regulating member 152 has a rotating shaft 152B that extends in the width direction and is rotatably supported on the main body of the ADF 100, and a contact portion 152A that contacts the center of the leading edge of the document P in the width direction W. The contact portion 152A extends from the center of the rotating shaft 152B in the width direction towards the document transport path. The contact portion 152A is located upstream in the transport direction T from each gate member 151A, 151B.

[0044] On both sides of the width direction W of the rotating shaft 152B, there are regulating parts 152C that extend in the transport direction T, facing the gate members 151A and 151B from the upstream side in the transport direction T, and restricting the rotation of the gate members 151A and 151B.

[0045] Figure 9 is a diagram illustrating the skew correction in the conventional skew correction mechanism 50' shown in Figure 8. As shown in the plan view of Figure 9(a), when the document P is transported skewed counterclockwise in the figure, the leading end of the document's front edge (the upper end in the plan view of Figure 9) comes into contact with the abutment surface of the gate member 151A. The transport force of the document then pushes the gate member 151A in the transport direction T. However, as shown in the cross-sectional view of Figure 9(a), the restricting portion 152C of the restricting member 152 faces the upper end of the gate member 151A, restricting the clockwise rotation of the gate member 151A in the figure. Therefore, the gate member 151A does not rotate due to the above pushing, and the transport of one end of the front edge of the document in the width direction is restricted by the gate member 151A. As a result, the document P is propelled by the transport force of the feed roller 142C, using the end of the front edge that is abutting the gate member 151A as a pivot point, and the skew is corrected as shown in the plan view of Figure 9(a).

[0046] When the document P rotates clockwise in the figure, the center of the leading edge of the document P comes into contact with the contact portion 152A of the restricting member 152, and the contact portion 152A is pushed in the transport direction by the transport force of the feed roller 142C. This pushing of the contact portion 152A causes the restricting member 152 to rotate clockwise in the cross-sectional view of Figure 9, with the rotation axis 152B as the pivot point. When the contact portion 152A moves by a distance S in the transport direction due to the leading edge of the sheet, as shown in Figure 9(b), the restricting portion 152C of the restricting member 152 no longer faces the gate members 151A and 151B, as shown in the cross-sectional view of Figure 9(b). As a result, the restriction on the rotation of the gate members 151A and 151B by the restricting member 152 is released.

[0047] When the restriction on the rotation of the gate members 151A and 151B by the restricting member 152 is released, the gate members 151A and 151B rotate clockwise in the cross-sectional view of Figure 9 due to the pushing of the leading edge of the document by the transport force of the feed roller 142C. As a result, the abutting surfaces of the gate members 151A and 151B move together with the document in the transport direction and move to the retracted position shown in Figure 9(c).

[0048] Even after the rotation restriction of gate members 151A and 151B is released, the restricting member 152 rotates as the document is pushed in, causing the contact portion 152A to move with the document in the transport direction, and the contact portion 152A also moves to the retracted position shown in Figure 9(c).

[0049] In the skew correction mechanism, the skew is not completely corrected, and some skew remains in the original document. However, the remaining skew is corrected by the skew correction performed by the pull-out roller pair 143. As described above, the original document flexes when the skew is corrected by the pull-out roller pair 143. When the original document flexes, the gate members 151A, 151B and the regulating member 152 rotate, causing the original document to flex properly and allowing the skew to be corrected properly by the pull-out roller pair 143.

[0050] When the trailing edge of the manuscript passes through the skew correction mechanism, the gate members 151A, 151B and the regulating member 152 rotate counterclockwise under their own weight in the cross-sectional view of Figure 9, resulting in the state shown in Figure 9(a).

[0051] In the configuration shown in Figure 8, if the document P is narrow, the document P may pass through the gate members, and the skew may not be corrected. Therefore, conventionally, in order to perform skew correction even for narrow documents P, two gate members were provided on one side in the width direction and the other side of the contact portion 152A, with a predetermined distance between them. This allowed narrow documents to abut against the inner gate member in the width direction and perform skew correction. However, this conventional configuration had the following problems.

[0052] Figure 10 illustrates the problems with the conventional configuration. As shown in Figure 10, depending on the width of the document, the widthwise end of the leading edge of a skewed document may get caught between gate member 151A-1 and gate member 151A-2. In this state, if the document P attempts to rotate clockwise in the figure due to the transport force of the feed roller 142C, the widthwise end of the leading edge of the document between gate member 151A-1 and gate member 151A-2 may get caught on the outer gate member 151A-1. As a result, folds or wrinkles may occur on the widthwise end of the leading edge.

[0053] Figure 11 illustrates another problem with the conventional configuration. As shown in Figure 11, conventionally, the distance from the outer end of the outer gate member 151A-1 located on one side in the width direction to the outer end of the outer gate member 151B-1 located on the other side in the width direction is shorter than the maximum width size of a document that the ADF 100 can transport. As a result, as shown in Figure 11, when a document of the maximum width size is skewed, the leading width end of the document's leading edge is located downstream of the gate member in the transport direction, and the part of the document inside the leading width end of the document's leading edge abuts against the gate member 151A-1. This results in a shorter distance between the center of the leading edge of the document P and the contact portion 152A compared to when the leading width end of the leading edge of the document P abuts against the gate member 151A-1. As a result, before the skew is sufficiently corrected, the center of the leading edge of the document P pushes against the contact portion 152A, releasing the restriction on the rotation of each gate member, and there is a risk that skew correction will not be possible until the desired state is achieved.

[0054] Figures 12 and 13 are plan views showing the skew correction mechanism 50 of this embodiment. The basic configuration of each gate member 151A, 151B and regulating member 152 of the skew correction mechanism 50 of this embodiment is the same as the configuration shown in Figure 8. That is, each gate member 151A, 151B is a plate-shaped member and has support shafts 151A1, 151B1 that are rotatably supported on the main body of the ADF 100. By rotating the gate members 151A, 151B with the support shafts 151A1, 151B1 as pivot points, the abutting surface of the gate members 151A, 151B that the leading edge of the document abuts against moves between the abutting position and a retracted position that is moved away from the abutting position.

[0055] The restricting member 152 has a rotating shaft 152B that extends in the width direction and is rotatably supported on the main body of the ADF 100, a contact portion 152A that contacts the center of the leading edge of the document P in the width direction W, and a restricting portion 152C that restricts the rotation of the gate members 151A and 151B. The contact portion 152A extends from the center of the rotating shaft 152B in the width direction towards the document transport path. The contact portion 152A is located upstream of each gate member 151A and 151B in the transport direction T. When the contact portion 152A is pushed in by the leading edge of the document, the restricting member 152 rotates, causing the restricting portion 152C to no longer face the gate members 151A and 151B, thereby releasing the restriction on the rotation of the gate members 151A and 151B.

[0056] In this embodiment, gate members 151A and 151B are provided one on each side in the sheet width direction, flanking the contact portion 152A. As shown in Figure 12, the distance X1 between the gate members is made shorter than the minimum document width W1 that the ADF 100 can transport. By making the distance X1 between the gate members shorter than the minimum document width W1 that the ADF 100 can transport, the widthwise edges of the document with the minimum width W1 can abut against the gate members 151A and 151B. This allows for good correction of the skew of the document with the minimum width W1.

[0057] Furthermore, as shown in Figure 13, the distance X2 from the outer end of one gate member 151A to the outer end of the other gate member 151B is made longer than the maximum document width W2 that the ADF 100 can transport. Specifically, the distance X2 from the outer end of one gate member 151A to the outer end of the other gate member 151B is made longer than the maximum separation distance between the pair of side fences 122, so that the gate members 151A and 151B are positioned wider than the side fences 122. This allows the widthwise ends of a document with a maximum width W2 to abut against the gate members 151A and 151B. Therefore, after the skew has been sufficiently corrected, the widthwise center of the leading edge of the document pushes against the contact portion 152A, releasing the restriction on the rotation of the gate members 151A and 151B, and the desired skew correction can be performed.

[0058] Figure 14 illustrates the skew correction mechanism of this embodiment. As shown in Figure 14(a), the user may stop the movement of the side fences 122 before they abut the widthwise ends of the document, resulting in a predetermined gap between the document and the side fences 122 (the document being set without being restricted by the side fences 122). If the document is fed in this state, the document may skew, as shown in Figure 14(b). When the document passes through the separation mechanism 142 in this skewed state, the leading end of the document's leading edge will abut against the gate member (gate member 151A in Figure 14).

[0059] In this embodiment, since the gate members 151A and 151B are provided one on one side and one on the other side in the width direction of the document, flanking the contact portion 152A, the leading end of the leading edge of the document P in the width direction will not get caught between the gate members. This prevents wrinkles, folds, and other damage from occurring on the width direction end of the leading edge of the document.

[0060] Furthermore, the inner ends of the gate members 151A and 151B in the width direction W are located further inward than the width direction end of the document with the smallest width, and the outer ends of the gate members 151A and 151B in the width direction W are located further outward than the width direction end of the document with the largest width. Therefore, regardless of the width of the document, the width direction end of the leading edge of a skewed document can abut against the gate members 151A and 151B. As a result, regardless of the width of the document, after the skew has been sufficiently corrected, the width direction center of the leading edge of the document P pushes against the contact portion 152A, releasing the restriction on the rotation of the gate members 151A and 151B, and allowing the desired skew correction to be performed.

[0061] After passing through the skew correction mechanism 50, the leading edge of the document P enters the nip portion of the pull-out roller pair 143, and the remaining skew is corrected by the skew correction mechanism 50. In this embodiment, the skew is corrected by the skew correction mechanism 50 before the document P enters the pull-out roller pair 143. This makes it possible to reduce the amount of skew of the document P entering the pull-out roller pair 143 to an amount that can be corrected by the pull-out roller pair 143. As a result, the skew of the document being transported from the pull-out roller pair 143 can be effectively suppressed.

[0062] In this embodiment, as in the conventional model, when the rear end of the document P passes through the skew correction mechanism 50, the gate members 151A and 151B rotate under their own weight and are positioned at the abutment position. The regulating member 152 also rotates under its own weight and is positioned at the regulating position that restricts the rotation of each gate member 151A and 151B. Alternatively, the gate members 151A and 151B may be configured to rotate from the retracted position to the abutment position using the biasing force of a biasing means such as a spring, or the regulating member may be configured to rotate from the released position to the regulating position using the biasing force of a biasing means.

[0063] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the spirit of the invention as described in the claims, unless otherwise specifically limited in the above description. The above describes an example of applying the skew correction mechanism of the present invention to the ADF100, but the skew correction mechanism of the present invention may also be applied to the transport device that transports the recording paper of the image forming unit 3. Specifically, the skew correction mechanism of the present invention is placed between the pair of register rollers that feed the recording paper from the feeding unit 2 to the secondary transfer unit, which secondarily transfers the toner image supported on the transfer belt 34 to the recording paper. This allows the skew of the recording paper in the transport path from the feeding unit 2 to the pair of register rollers to be corrected to some extent in advance by the skew correction mechanism of the present invention, and then the leading edge of the recording paper is brought against the pair of register rollers, and the remaining skew can be corrected by the skew correction mechanism. In this way, by correcting the skew with the skew correction mechanism of the present invention before the recording paper enters the pair of register rollers, the amount of skew of the recording paper entering the pair of register rollers can be reduced to an amount of skew that can be corrected by the pair of register rollers. As a result, the skew of the recording paper transported from the pair of register rollers can be effectively suppressed, and the toner image can be successfully secondarily transferred to the recording paper. In particular, it is preferable to provide the skew correction mechanism of the present invention in front of the register roller pair so that the skew of both the recording paper fed from the feeding unit 2 and the recording paper fed from the manual feed tray can be corrected.

[0064] Furthermore, the skew correction mechanism of the present invention may be applied in the transport section of a post-processing device that performs predetermined post-processing such as punching, stapling, and folding on recording paper discharged from an image forming apparatus such as a copier 1.

[0065] The above is just one example; each of the following embodiments produces its own unique effects. (Aspect 1) In a skew correction device such as a skew correction mechanism 50, the gate members 151A and 151B are provided one on each side of the sheet width direction, with the contact portion 152A in between, and the distance between the two gate members is shorter than the minimum width of a sheet that can be transported by a sheet transport device such as an ADF 100 on which the skew correction device is mounted. The gate members 151A and 151B are provided one on each side of the contact portion 152A in the sheet width direction, and the distance between the two gate members is shorter than the minimum width of a sheet that can be transported by a sheet transport device such as an ADF 100 on which the skew correction device is mounted. According to this, as described in the embodiment, even for sheets of the minimum width that can be transported by a sheet transport device equipped with a skew correction device, if skew occurs, the leading edge of the sheet will abut against one of the two gate members, and skew correction can be performed. Furthermore, only one gate member is provided on each side of the sheet width direction, flanking the contact portion. Therefore, the widthwise end of the skewed sheet does not get caught between the gate members. This allows the skewed sheet to rotate smoothly to correct the skew, and prevents wrinkles and folds from forming in the sheet.

[0066] (Aspect 2) In embodiment 1, the distance between the outer ends in the width direction of the two gate members is longer than the maximum width of a sheet that can be transported by the sheet transport device on which the skew correction device is installed. According to this, as described in the embodiment, the widthwise end of the leading edge of a skewed document, regardless of the width of the document, can be brought into contact with the gate members 151A and 151B. This makes it possible to correct the skew of any size or width of document as intended.

[0067] (Aspect 3) A sheet transport device equipped with a skew correction device, such as a skew correction mechanism, for correcting the skew of sheets fed from a sheet loading section, such as a document table 120 on which sheets of documents are loaded, is provided with a skew correction device according to embodiment 1 or 2. According to this, the skew of the sheets fed from the sheet stacking section, such as the document table 120, can be effectively corrected.

[0068] (Aspect 4) In embodiment 3, the skew correction device, such as the skew correction mechanism 50, is positioned in the sheet transport direction between the feed section, such as the separation feed section B that feeds sheets from the sheet stacking section, such as the document table 120, and the transport roller pair, such as the pull-out roller pair 143, which temporarily stops the transport of the sheet when the leading edge of the sheet hits it. According to this, as described in the embodiment, by correcting the skew of a sheet such as an original document with a skew correction device such as the skew correction mechanism 50, the amount of skew of the sheet entering the transport roller pair can be reduced to an amount of skew that can be corrected by stopping the transport of the sheet by bringing the leading edge of the sheet against the transport roller pair. As a result, the skew of the sheet being transported from the transport roller pair can be effectively suppressed.

[0069] (Appendix 5) In embodiment 3 or 4, the device has a pair of sheet restricting members, such as side fences 122, which are configured to be movable in the width direction and restrict the width direction position of sheets such as documents placed on a sheet stacking section such as a document table 120, The distance between the outer ends of the two gate members 151A and 151B in the width direction is longer than the distance between the pair of sheet regulating members when they are spaced apart. According to this, as described in the embodiment, the distance between the outer ends in the width direction of the gate members 151A and 151B can be made longer than the maximum width of a sheet that can be transported by a sheet transport device such as the ADF 100.

[0070] (Aspect 6) In an automatic document transport device such as an ADF100, which includes a document sheet transport unit for transporting document sheets and transports the document sheets to an image reading unit by the document sheet transport unit, a sheet transport device from any of embodiments 3 to 5 was used as the document sheet transport unit. According to this method, it is possible to suppress the reading of the original document image at an angle.

[0071] (Aspect 7) An image forming apparatus for forming an image on a sheet comprises at least one of the sheet transport device described in embodiments 3 to 5 and the automatic document transport device described in embodiment 6. According to this method, it is possible to suppress the formation of images on the sheet at an angle. [Explanation of Symbols]

[0072] 2: Feeding section 3: Image forming unit 4: Contact Glasses 5:Operation section 6: Main Unit Control 50: Skew correction mechanism 100 :ADF 121: Movable Table 121a: Rotary shaft 122: Side fence 141: Pickup Roller 142: Separation mechanism 142A: Feed belt 142B: Reverse Roller 142C: Feed roller 143: Pull-out roller vs. 151: Gate member 152: Regulating member 152A: Contact part 152B: Rotation axis 152C:Regulatory Department 153A: Support shaft A: Manuscript preparation section B: Separation feeding section C: Resist part D: Turn section E: First reading and transport unit F: Second reading and transport unit G: Paper output section H: Stack section P:Manuscript T: Conveying direction W: width direction W1: Minimum width W2: Maximum size width X1: Distance between gate members X2: Distance from the outer end of one gate member to the outer end of the other gate member. [Prior art documents] [Patent Documents]

[0073] [Patent Document 1] Patent No. 6999524

Claims

1. A gate member having a stopper portion against which the leading edge of the sheet in the conveying direction abuts, wherein the stopper portion is movable between the stopper position and a retracted position moved away from the stopper position, The abutment portion has a restricting member that restricts the movement of the abutment portion from the abutment position to the retracted position, In a skew correction device in which the restricting member is located upstream of the abutment portion in the conveying direction and has a contact portion that abuts the center of the sheet's leading edge in the width direction, and the restriction on the movement of the abutment portion is released when the leading edge of the sheet pushes the contact portion in the conveying direction, The gate members are provided one on each side in the sheet width direction, with the contact portion in between. A skew correction device characterized in that the distance between two gate members is shorter than the minimum width size of a sheet that can be transported by a sheet transport device equipped with the skew correction device.

2. In the skew correction device according to claim 1, A skew correction device characterized in that the distance between the outer ends in the width direction of the two gate members is longer than the maximum width of a sheet that can be conveyed by the sheet conveying device on which the skew correction device is installed.

3. In a sheet conveying device equipped with a skew correction device for correcting the skew of sheets fed from a sheet loading section where sheets are loaded, A sheet conveying device characterized by comprising the skew correction device described in claim 1 as the skew correction device.

4. In the sheet conveying device according to claim 3, The sheet conveying device is characterized in that the skew correction device is positioned in the conveying direction between the feeding unit that feeds sheets from the sheet loading unit and the pair of conveying rollers that temporarily halt the conveying of the sheets when the leading edge of the sheet hits the roller.

5. In the sheet conveying device according to claim 3, It has a pair of sheet regulating members that are configured to be movable in the width direction and that regulate the width direction position of the sheets placed on the sheet loading section, A sheet conveying device characterized in that the distance between the outer ends in the width direction of the two gate members is longer than the distance between a pair of sheet regulating members when they are spaced apart.

6. It is equipped with a document sheet transport unit that transports document sheets, In an automatic document transport device that transports a document sheet to an image reading unit using the document sheet transport unit, An automatic document transport device characterized in that the aforementioned document sheet transport unit uses the sheet transport device described in claim 3.

7. In an image forming apparatus that forms an image on a sheet, An image forming apparatus comprising at least one of the sheet transport device described in claim 3 and the automatic document transport device described in claim 6.

Images