JP2009149407A - Sheet feeder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet feeder which protects sheets from damage or from going disorder on a sheet stack tray by being mixed up among other sheets on the sheet stack tray when doubly fed sheets are returned in the opposite direction to the sheet transfer direction. <P>SOLUTION: The sheet feeder comprises separating/feeding means 104, 105 for feeding sheets loaded on the sheet stack tray 101 one by one separately to the feeding path, a double feed detection means 107 disposed on the downstream side of the separating/feeding means 104, 105 and for detecting double feed of the sheets fed to the feeding path, a reverse transfer means 108 for reversely transferring the passing sheets from the transfer direction to the opposite direction when the double feed sheets detection means 107 detects the multi-ply transfer, a sheet condition detection means 201 for detecting the condition of sheets being transferred/or reversely transferred, and a control means determining whether the reverse sheet transfer by the reverse transfer means 108 should be stopped or not, based on the result of detection by the sheet condition detection means 201. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sheet feeding apparatus used in an image forming apparatus and an image reading apparatus such as a copying machine, a printer, a facsimile machine, and a scanner.

  In recent years, image forming apparatuses such as copiers, printers, facsimiles, and the like can form high-quality images when images are formed on thick paper coated on the surface, so sheets with various surface coatings and sheets with various thicknesses can be obtained. It is required to form an image corresponding to the above.

  Similarly, the image reading apparatus is required to stably feed and convey various sheets with such diversification of sheets.

  However, in a sheet that is likely to generate static electricity or a surface-treated sheet, a phenomenon (multiple feeding) in which a plurality of documents are simultaneously fed to the conveyance path may occur.

  If a plurality of multi-feed sheets continue to be conveyed as they are, the image forming apparatus causes, for example, a fixing defect such as toner, resulting in problems such as in-machine contamination, and the image reading apparatus cannot read necessary information. Such a problem occurs.

  Therefore, in the image forming apparatus and the image reading apparatus, a double feed detecting unit is arranged to detect the double feeding of the sheet as described above, and the feeding of the sheet is stopped when the double feeding of the sheet is detected. Some of them are

  FIG. 8 shows a scanner provided with a conventional sheet feeding device in which double feed detecting means is arranged.

  The sheet feeding apparatus shown in FIG. 8 includes a pickup roller 102 that abuts against the upper surface of a bundle of documents (sheets) stacked on the sheet feed tray 101 and feeds the documents in the transport direction.

  The document 100a sent out by the pickup roller 102 is separated one by one by the feeding roller 104 and the separation roller 105 and fed to the conveyance path.

  Between the feed roller 104 and separation roller 105 and the registration roller pair 115, a double feed detecting means 107 for detecting double feed of the original is disposed.

  In the conventional sheet feeding apparatus, when the double feed detection unit 107 detects double feed of a document, generally, the document fed by the pickup roller 102 is separated and fed one by one by the feed roller 104 and the separation roller 105. Stop operation and issue a warning of double feed. The operator re-feeds the document that has been double-feeded based on this warning or the like to prevent image loss.

  However, if double feeding of originals occurs in the image reading process, paper feeding stops, and the operator needs to remove the double fed originals or check whether the originals being read remain in the device. There is.

  Also, since the operation of the scanner is temporarily stopped every time a document is double-fed, a reduction in operating rate is unavoidable, so that work efficiency is greatly reduced when processing a large amount of documents.

  In order to eliminate such inconvenience, when a double feed of a document is detected, the document feed operation is once stopped, the double fed document 100a is automatically returned to the paper feed tray 101 side, and a separate feed operation is performed again. There has been proposed a scanner that performs a return operation to perform (Patent Document 1).

In such a scanner, after detecting the double feed of the document, the feed roller 104 is rotated in a direction opposite to the document feed direction, and the separation roller 105 is rotated in the document separation direction to perform double feed. Documents can be returned to the paper feed tray 101 side.
JP 2001-158538 A

  By the way, a business image reader may handle sheets such as bills, checks, and contracts. Further, the sheets that are separated and fed by such an image reading apparatus are often stapled sheets or very thin originals.

  In this case, in the scanner disclosed in the above-mentioned Patent Document 1, if a sheet bound with staples or a sheet that is largely skewed and jammed in the conveyance path is returned to the paper feed tray 101 side when double feeding is detected, the sheet is There is a problem of damage.

  Further, when returning the double-fed sheets to the paper feed tray 101 side, the sheets are skewed, or the sheets bound with staples jump up and are jammed around the paper feed tray 101, and the sheets are damaged. is there.

  Further, when the double-fed sheets return to the paper feed tray 101 side, the sheets are pushed away from other sheets stacked on the paper feed tray 101 and enter between the stacked sheets. There is a problem that the stacking order of the sheets stacked on the sheet is disturbed.

  In view of this, the present invention provides a method for returning a plurality of double-fed sheets in the direction opposite to the feeding direction. An object of the present invention is to provide a sheet feeding apparatus capable of preventing the stacking order from being disturbed.

  In order to achieve the above object, a sheet feeding apparatus according to claim 1 is configured to separate a stacking unit on which a plurality of sheets are stacked and a sheet stacked on the stacking unit one by one and feed the sheet to the conveyance path. Separating feeding means for feeding, double feeding detecting means arranged downstream of the separating feeding means for detecting double feeding of sheets fed to the conveying path, and double feeding of sheets by the double feeding detecting means When the sheet is detected, reverse conveying means for performing reverse conveyance to return the sheet being fed in the direction opposite to the feeding direction, and at least one of the state of the fed sheet and the state of the reversely fed sheet And a control unit for determining whether to stop the reverse conveyance of the sheet by the reverse conveyance unit based on a detection result of the sheet state detection unit. .

  According to a second aspect of the present invention, the sheet feeding apparatus according to the first aspect is characterized in that the sheet state detecting means detects the jumping of the sheet.

  According to a third aspect of the present invention, the sheet feeding apparatus according to the first aspect is characterized in that the sheet state detecting means detects the skew of the sheet.

  According to a fourth aspect of the present invention, there is provided the sheet feeding apparatus according to the first aspect, wherein the sheet state detection unit detects a jam of the sheet in the conveyance path.

  According to a fifth aspect of the present invention, the sheet feeding apparatus according to the first aspect is characterized in that the sheet state detection unit detects a feeding operation of the uppermost sheet stacked on the stacking table.

  According to the present invention, when a plurality of multi-feed sheets are returned in the direction opposite to the feeding direction, the sheets are damaged, or are interleaved between other sheets stacked on the stacking table and stacked on the stacking table. It is possible to prevent the sheet stacking order from being disturbed.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a sectional view for explaining a sheet feeding apparatus according to a first embodiment of the present invention, and FIG. 2 is a sectional view for explaining a scanner including the sheet feeding apparatus of FIG.

  As shown in FIGS. 1 and 2, the sheet feeding apparatus according to the present embodiment includes a sheet feeding tray (stacking table) 101, a pickup roller 102, a feeding roller 104, a separation roller 105, a double feed detection unit 107, and a return. A roller 108 is provided. Here, in the present embodiment, the feeding roller 107 and the separation roller 105 constitute the separation feeding unit of the present invention.

  The pickup roller 102 abuts on the upper surface of the original (sheet) bundle 100 stacked on the paper feed tray 101 and sends out the original 100 a in the transport direction. The pickup roller 102 is rotatably supported by a swing arm 103, and the swing arm 103 is swingably supported by a support shaft 103a.

  The document 100a sent out by the pickup roller 102 is separated one by one by the feeding roller 104 and the separation roller 105 and fed to the conveyance path. Above and below the conveyance path, a conveyance guide 113 is provided that guides the document along the conveyance path while regulating the posture of the document conveyed on the conveyance path.

  Between the feed roller 104 and separation roller 105 and the registration roller pair 115, a double feed detecting means 107 for detecting double feed of the original is disposed.

  As the double feed detection means 107, an optical double feed detection sensor such as a transmission type optical sensor for detecting double feed based on a change in the amount of light transmitted between a single document and a plurality of documents is known. In addition, the double feed detecting means 107 is provided with an ultrasonic transmitter and a receiver with the document conveyance path in between, and the attenuation of the ultrasonic wave when the original is being fed is used as a reference. In addition, there is known an ultrasonic double feed detection sensor that determines double feed when an attenuation greater than this is detected.

  A registration sensor 106 is disposed between the feeding roller 104 and the separation roller 105 and the double feed detection unit 107. Based on the detection result of the original by the registration sensor 106, a control unit (not shown) detects the next original. The paper feed timing is determined.

  A pair of return rollers (reverse conveying means) 108 that are rotationally driven in at least the opposite direction to the document feeding direction are disposed at substantially symmetrical positions on both ends in the axial direction of the feeding roller 104. .

  As shown in FIG. 1, the pair of return rollers 108 are arranged such that the axis thereof overlaps with the feed roller 104 when viewed in the position substantially equal to the axis of the feed roller 104, that is, in the axial direction. Note that the pair of return rollers 108 may be disposed on the upstream side of the conveyance path with respect to the axis of the feed roller 104.

  The pair of return rollers 108 is rotatably supported by the arm 109 via a support shaft 109a, and the arm 109 is a position where the return roller 108 contacts the document according to the state of the fed document. And a retreat position.

  A driving pulley 110a driven by driving means (not shown) is attached to the arm 109, and the rotational driving force of the driving pulley 110a is transmitted to the driven pulley 110c attached to the return roller 108 via the timing belt 110b. The As a result, the return roller 108 is rotationally driven in a direction opposite to the document feeding direction.

  The arm 109 has a position where the return roller 108 comes into contact with the document by the cam action of the rotation lever 111 in a state where the return roller 108 is urged by the tension coil spring 112 in a direction to contact the document with a constant load. It swings to a position where it is retracted from the document.

  That is, the arm 109 is displaced to a position for retracting the return roller 108 from the fed document by cam-engaging with the rotation lever 111 when the document is normally separated and fed.

  In this state, when the rotation lever 111 rotates and the cam engagement with the arm 109 is released, the arm 109 is fixed to the document fed with the return roller 108 by the urging force of the tension coil spring 112. It swings to the position where it makes pressing contact with the load. Note that the rotation control of the rotation lever 111 and the drive means of the drive pulley 110a are controlled by a control means (not shown).

  A return driven roller 114 is disposed at a position facing the return roller 108 across the conveyance path. The return driven roller 114 is rotatably supported by the conveyance guide 113.

  On the downstream side of the registration roller pair 115, an image reading unit 116 for reading an image of a document conveyed on the conveyance path by photoelectric conversion and taking it as image data is disposed. The document whose image has been read by the image reading unit 116 is discharged to the paper discharge tray 119 via the conveyance roller pair 117 and the paper discharge roller pair 118.

  Next, a series of operation examples of the scanner configured as described above will be described. A series of operations of the scanner described here is performed by loading a control program stored in a storage unit (not shown) (ROM, hard disk, etc.) into a RAM (not shown), and then by a control unit (CPU, etc.) not shown. Executed.

  First, when an image reading command is input from an external device such as a PC (not shown), the control means controls the drive mechanism (not shown) of the swing arm 103 and the pickup roller 102 to move the pickup roller 102 in FIG. Move in the direction of arrow a and rotate. As a result, the pickup roller 102 comes into contact with the upper surface of the original bundle 100 loaded on the paper feed tray 101, and the operation of feeding out the original is started.

  The documents sent out by the pickup roller 102 are separated one by one by a feeding roller 104 and a separation roller 105 driven by the control of the control means, and fed to the conveyance path.

  Here, the drive shaft of the feed roller 104 and the feed roller 104 are connected via a one-way clutch (not shown). When the conveyance speed of the document conveyed by the registration roller pair 115 becomes faster than the document feeding speed by the feeding roller 104, the feeding roller 104 is rotated with the conveyed document.

  The separation roller 105 is driven in a direction opposite to the document feeding direction via a torque limiter (not shown). When a torque exceeding the torque that can be transmitted by the torque limiter is applied, the separation roller 105 moves in the document feeding direction. Take around.

  In this state, the control means controls the rotation position of the rotation lever 111 so that the rotation lever 111 is cam-engaged with the arm 109, and the outer periphery of the return roller 108 is located on the upper side as shown in FIG. Is retracted to a position substantially on the same plane as the transport guide 113.

  Here, when the return roller 108 is retracted to a position above the conveyance guide 113, the document may be caught in a hole at a position corresponding to the return roller 108 of the conveyance guide 113, so the return roller 108 is retracted. It is necessary to cover the hole later with another member. In this case, the number of parts increases, the structure becomes complicated, and the cost increases.

  On the other hand, the return roller 108 is generally made of a material having a high coefficient of friction such as rubber in order to secure the conveying force of the document. If the document comes into contact with the retracted position, a large load is applied to the document. Or a paper jam.

  For this reason, when a normal document feeding operation is performed, the return roller 108 is retracted to the position of the conveyance guide 113 and rotated in the same direction and at the same peripheral speed as the feeding roller 104 to convey the document. It is preferable to have a guiding function.

  Next, when the original document separated and fed to the conveyance path is conveyed to the registration sensor 106, the control unit controls the drive mechanism based on the original detection signal from the registration sensor 106 to move the pickup roller 102 to the original document. The swing arm 103 is moved so as to be retracted. As a result, the delivery of the next document is stopped.

  Next, the control means determines whether or not the document is being double fed based on the detection signal from the double feed detection means 107. If it is determined that the document is not double-fed, the control unit continues to transport the document, and after the document reaches the registration roller pair 115, the control unit transports the document to the image reading unit 116 at a constant speed. Then, the image reading unit 116 reads the image of the document.

  The document that has passed through the image reading unit 116 is discharged to the discharge tray 119 by the conveyance roller pair 117 and the discharge roller pair 118. By performing the above operation for each original document, all images of the original document loaded on the paper feed tray 101 are read by the image reading unit 116.

  On the other hand, when the control unit determines that the document is being double-fed based on the detection signal from the double-feed detection unit 107, the control unit performs the separation / feed operation of the document by the feed roller 104 and the separation roller 105. The drive system of each roller 104, 105 is controlled so as to stop once.

  At this time, the multiple fed originals are stopped on the conveyance path, and the originals fed to the conveyance path before that are read by the image reading unit 116 in the same manner as described above, and then the conveyance roller pair The paper is discharged to a paper discharge tray 119 via 117 and a paper discharge roller pair 118.

  Next, the control means controls the rotation position of the rotation lever 111 so that the cam engagement between the rotation lever 111 and the arm 109 is released. As a result, the arm 109 is rotated counterclockwise in FIG. 1 by the urging force of the tension coil spring 112, and a plurality of documents fed by the return roller 108 are sandwiched between the return driven roller 114. Thus, the original is pressed against the original with a constant load.

  Then, the control unit controls the drive system of the feed roller 104, the separation roller 105, and the return roller 108 so as to return the multiple fed documents to the paper feed tray 101 side (in the direction of arrow D in FIG. 3). Then, the rollers 104, 105, 108 are rotated in the direction opposite to the document feeding direction. As a result, it is possible to obtain a sufficient conveying force for returning the multiple fed documents to the paper feed tray 101 side.

  At this time, the multiple fed originals pass through the double feed detecting means 107 or the registration sensor 106, and are then conveyed and stopped for a predetermined time or a predetermined rotation amount of the drive motor of the return roller 108, for example.

  Regardless of whether or not the document double feed is detected, the control means rotates the return roller 108 in the direction opposite to the document feeding direction, and the arm 109 rotates the return roller 108. You may make it contact or retract.

  After returning the multiple fed documents to the paper feed tray 101 side, the control means controls the rotation position of the rotation lever 111 so that the rotation lever 111 is cam-engaged with the arm 109. As a result, the outer peripheral portion of the return roller 108 is retracted to a position substantially on the same plane as the upper conveyance guide 113.

  Then, the control unit drives the pickup roller 102, the feed roller 104, the separation roller 105, and the like so that the original returned to the paper feed tray 101 side is separated and fed again to the conveyance path in the same manner as described above. Control the system.

  Here, in the present embodiment, bounce detection sensors (sheet state detection means) 201 for detecting the state of the document being fed to the conveyance path are disposed on both sides of the pickup roller 102 in the width direction of the document.

  Based on the detection result of the bounce detection sensor 201, the control unit determines whether or not there is a possibility of causing damage to the original when returning the multiple fed originals in the direction opposite to the feeding direction. To do. As the bounce detection sensor 201, for example, a bounce detection sensor disclosed in Japanese Patent Application Laid-Open No. 2004-182449 can be used.

  In addition to the bounce detection sensor 201, the sheet state detection means includes, for example, a sensor that detects skew of the original, a sensor that detects the movement of the original onto the conveyance guide, a sensor that detects the paper type, and the vicinity of the registration sensor. The sensor which detects the paper jam in can be illustrated.

  By the way, when a plurality of documents are sequentially separated and fed, if a document bundled with staples is mixed, a feeding roller 104 that rotates in the feeding direction and a rotation drive in the direction opposite to the feeding direction are driven. The action of the separating roller 105 causes the document to jump up.

  If the document continues to be fed in a state where the jump has occurred, the document is jammed in the conveyance path, and the document is damaged. For this reason, the control unit controls the drive system of each of the rollers 104 and 105 so as to stop the rotation of the feeding roller 104 and the separation roller 105 when the jumping detection sensor 201 detects the jumping of the document. Stop feeding the original.

  In this embodiment, when the control unit determines that the document is double-fed based on the signal from the double-feed detection unit 107, as described above, a plurality of double-fed documents are fed into the paper feed tray 101. The drive system of the separation roller 105 and the return roller 108 is controlled so as to return to the side. That is, the separation roller 105 and the return roller 108 are rotationally driven in the direction opposite to the document feeding direction.

  At this time, if the jump of the document is detected by the signal from the bounce detection sensor 201, the control unit is likely to damage the document if the document is returned to the paper feed tray 101 side. The conveyance to the tray 101 side is interrupted.

  That is, the control unit controls the drive system of each of the rollers 105 and 108 so as to stop the rotation of the separation roller 105 and the return roller 108.

  On the other hand, the double feed detecting means 107 is arranged as upstream as possible in the document feeding direction so as to detect double feeding of documents as quickly as possible. For this reason, when the double feed of the original is detected, the jump-up detection sensor 201 may not be able to detect the jump-up of the original even if the original is stapled.

  In this case, in this embodiment, the control unit determines that the document is double-fed based on a signal from the double-feed detection unit 107, and as described above, a plurality of double-fed documents are fed to the paper feed tray 101 side. Will be returned to.

  Assuming that the stapled position is the upper left of the document when viewed from the conveyance direction, it is highly possible that the stapled portion of the document has passed the feeding roller 104 when the document double feed is detected.

  In this state, when reverse conveyance is performed to return the document to the paper feed tray 101 side, the vicinity of the staple fixing portion of the document is clogged between the feeding roller 104 and the separation roller 105, and the right side portion of the document that is not stapled Only the sheet feed tray 101 is returned.

  As a result, the original is stopped on the left side due to clogging, and only the right side is returned to the paper feed tray 101 side, causing a jump. If the reverse conveyance of returning the document to the paper feed tray 101 side is continued in a state in which the document jumps up, the document may be damaged.

  Further, even when the document does not jump up, the document conveyed in the reverse direction to the sheet feed tray 101 enters the bundle of documents loaded on the sheet feed tray 101 or pushes out another document to stack the document. May be disturbed.

  4 and 5 are explanatory diagrams for explaining a phenomenon in which the stacking order of the documents stacked on the sheet feeding tray 101 is disturbed.

  In FIG. 4, when the multi-feed original 100 a is reversely conveyed after the trailing edge of the multi-feed original 100 a is sent to the downstream side of the front end of the original bundle 100, a part of the original bundle 100 is pushed up, and the original bundle 100. There is a case to get in between.

  As shown in FIG. 5, the bounce detection sensor 201 is disposed as close as possible to the end of the paper feed tray 101 on the paper feed port side, that is, as close as possible to the front end of the document bundle 100. The light emitted from the light emitting unit 201 a of the bounce detection sensor 201 is irradiated in the direction indicated by the arrow E, and is received by the light receiving unit 201 b of the bounce detection sensor 201.

  Here, when an operation is performed in which the double-fed original 100a that is reversely conveyed to the paper feed tray 101 presses the leading end of the original bundle 100 and enters between the original bundles 100, a part of the originals in the original bundle 100 is directed upward. The light emitted from the light emitting unit 201a is blocked. Accordingly, since the output signal of the light receiving unit 201b changes, the state in which the document stacking order is disturbed can be detected by using the jump detection sensor 201.

  Therefore, in the present embodiment, the control unit monitors the output signal of the jump detection sensor 201 not only during the document separation and feeding operation but also during the reverse conveyance of returning the multi-fed document to the paper feed tray 101 side.

  When the control unit detects the jumping of the document or the disturbance of the stacking order of the documents by the signal from the jump detection sensor 201 during the reverse conveyance to return the document to the sheet feeding tray 101 side, the control unit detects the document on the sheet feeding tray 101 side. Reverse transport to return to is interrupted. Alternatively, when the reverse conveyance of the original is to be started, the reverse conveyance is not started when the jumping of the original is detected.

  That is, the control unit controls the drive systems of the rollers 104, 105, and 108 so as to stop the rotation of the feeding roller 104, the separation roller 105, and the return roller.

  Here, the document damage in the image reading apparatus has been described. However, in the image forming apparatus or the like, for example, the transfer drum may be damaged due to the reverse conveyance of the jammed sheet. It goes without saying that it is not limited to only.

  On the other hand, if no jumping of the document is detected during reverse conveyance to return the document to the paper feed tray 101 side, the control means returns the double-fed document to the paper feed tray 101 side, and then the rotation lever 111 The rotational position of the rotary lever 111 is controlled so that the arm 109 is cam-engaged.

  As a result, the outer peripheral portion of the return roller 108 is retracted to a position substantially on the same plane as the upper conveyance guide 113. Further, the control means controls the drive system of the swing arm 103 so that the swing arm 103 rotates to a position where the pickup roller 104 contacts the document.

  Since the document is returned by a predetermined time or a predetermined rotation amount of the motor after passing through the double feed detecting means 107 or the registration sensor 106, as shown in FIG. 3, a nip where the feeding roller 104 and the separation roller 105 are almost in contact with each other is returned. It is returned until the tip comes out.

  Subsequently, the control means again picks up the roller 102, the feeding roller 104, and the separation roller so that the original returned to the paper feed tray 101 side is again separated and fed one by one to the conveyance path in the same manner as described above. The drive system such as 105 is controlled.

  Note that the separate separation and feeding operation of the double-fed original is automatically performed, but the image reading unit 116 reads the original image in a state where the original is conveyed backward to the paper feed tray 101 side. You may make it cancel. In that case, the operator performs an operation of confirming the document conveyed backward to the paper feed tray 101 side and instructing rereading or the like.

  As described above, in the present embodiment, the output signal of the jump detection sensor 201 is monitored even during reverse conveyance to return the double-fed original to the paper feed tray 101 side, and the jump of the original and the disorder of the stacking order of the originals are monitored. Is detected, the reverse conveyance for returning the original to the paper feed tray 101 is interrupted.

  As a result, when returning the double-fed original to the paper feed tray 101 side, the original is damaged, or the original loaded on the paper feed tray 101 is stacked between the other originals loaded on the paper feed tray 101. It is possible to prevent the order from being disturbed.

(Second Embodiment)
Next, a sheet feeding apparatus according to the second embodiment of the present invention will be described with reference to FIG.

  In the first embodiment, the jump detection sensor 201 is used to detect the disorder of the document stacking order. In the present embodiment, the uppermost surface of the document bundle 100 stacked on the paper feed tray 101 is used. The movement of the original document is monitored to detect the disorder of the original stacking order.

  That is, in this embodiment, as shown in FIG. 6, the document feed detection is performed so that the document bundle 100 stacked on the sheet feeding tray 101 is in contact with the uppermost document of the document bundle 100 at the leading end side in the conveyance direction. A roller (sheet state detection means) 204 is disposed.

  The document feed detection roller 204 is a driven roller that is rotated by following a document that is moved by a document feeding operation or a returning operation.

  For example, an encoder (not shown) is connected to the document feed detection roller 204. Therefore, the control unit can detect the moving direction and the moving amount of the document based on the output of the encoder.

  Normally, when the reverse conveyance of the original to the paper feed tray 101 is normally performed, the original feed detection roller 204 that contacts the original returned to the paper feed tray 101 rotates in the return direction.

  However, if the double-fed original 100a is returned so as to enter between the original bundles 100 and the stacking order of the originals is disturbed, the original feed detection roller 204 is in contact with the uppermost original of the original bundle 100, so Does not rotate.

  Therefore, the control unit can detect the disorder of the document stacking order by monitoring the output signal of the encoder. The processing of the control means after detecting the disorder of the document stacking order is the same as described above.

  As a means for detecting the document feeding operation, in addition to the document feeding detection roller 204, for example, a two-dimensional image sensor or the like is used to analyze the image of the uppermost document, surface unevenness, etc. The document feeding operation can be detected. Other configurations and operational effects are the same as those of the first embodiment.

(Third embodiment)
Next, with reference to FIG. 7, a sheet feeding apparatus according to a third embodiment of the present invention will be described.

  FIG. 7 is a diagram illustrating a state where the document 100a being fed is skewed. If the document is skewed, the corners of the document may exceed the installation position of the document guide member 202. In this case, when reverse feeding is performed to return the double-fed document to the paper feed tray 101 side, the document is The document may break into the guide member 202 or the like and the document may be damaged.

  As an example of a method for detecting the skew state of such a document, a line image sensor 203 serving as a skew detection unit is disposed so as to straddle two document guide members 202, and a side portion of the document in the width direction is arranged. There is a way to detect.

  For example, when the line image sensor 203 detects that the document exceeds the installation position of the document guide member 202, the control unit can determine that the document is skewed. It is also possible to detect the position of the side in the width direction of the document by the line image sensor 203 a plurality of times at predetermined time intervals, and the control means calculates the skew amount of the document based on this information.

  When it is determined by these methods that the skew of the document exceeds a certain limit that is expected to cause jamming or breakage of the document, the control means interrupts the reverse conveyance of the document or the document The same control as described above is performed so as not to start the reverse conveyance. As a result, it is possible to prevent the document from being damaged. Other configurations and operational effects are the same as those of the first embodiment.

(Fourth embodiment)
Next, referring to FIG. 3, a sheet feeding apparatus according to a fourth embodiment of the present invention will be described.

  This embodiment is an example in which a registration sensor 106 is used as a sheet state detection unit. In a normal document separation and feeding operation, the time required to reach the double feed detecting means 107 after passing through the registration sensor 106 is obtained by actual measurement or calculation. Accordingly, this time is stored in advance in the storage means (not shown) as the document double feed detection time in advance or every time it is actually measured.

  On the other hand, when reverse feeding is performed to return the double-fed original to the paper feed tray 101 side, the double-feed detection unit 107 stops detecting the double-feed if the original is not clogged. When a time approximately equal to the time elapses, the output of the registration sensor 106 should be turned off.

  If the output of the registration sensor 106 does not turn off even after the double feed detection time has elapsed, the control unit determines that a document jam or the like has occurred during the reverse conveyance of the original, and interrupts the reverse conveyance of the original. The same control as described above is performed. When the document feeding speed and the reverse conveyance speed are different, the control means may calculate the ratio to the double feed detection time and make a determination.

  In this embodiment, the case where the registration sensor 106 is used as the sheet state detection unit is illustrated, but a sensor other than the registration sensor may be used, or a sensor prepared separately may be used. Further, although the document transport time in the feeding direction is used as the double feed detection time, it may be set to a time corresponding to the length of the maximum transportable document according to the specifications of the device.

  If the double feed detection unit 107 can detect a single original document as well as a double-fed document, either detection time may be used, but the latter makes it possible to make the above determination more accurately. Therefore, it is preferable. Other configurations and operational effects are the same as those of the first embodiment.

  In addition, this invention is not limited to what was illustrated by said each embodiment, In the range which does not deviate from the summary of this invention, it can change suitably.

FIG. 3 is a cross-sectional view for explaining the sheet feeding apparatus according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view for explaining a scanner including the sheet feeding device in FIG. 1. FIG. 6 is a cross-sectional view for explaining a state in which a plurality of documents that are double-fed are returned to the paper feed tray. FIG. 10 is a side view for explaining a phenomenon in which the stacking order of documents stacked on a sheet feeding tray is disturbed. FIG. 10 is a plan view for explaining a phenomenon in which the stacking order of documents stacked on a sheet feeding tray is disturbed. It is explanatory drawing for demonstrating the sheet feeding apparatus which is the 2nd Embodiment of this invention. FIG. 10 is an explanatory diagram for describing a sheet feeding device according to a third embodiment of the present invention. It is sectional drawing for demonstrating the conventional sheet feeding apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Document bundle 100a Document 101 Feed tray 102 Pickup roller 103 Swing arm 104 Feed roller 105 Separation roller 106 Registration sensor 107 Double feed detection means 108 Return roller 109 Arm 111 Rotating lever 112 Pulling coil spring 114 Return driven roller 201 Bounce detection Sensor 201a Light emitting unit 201b Light receiving unit 202 Document guide member 203 Line image sensor 204 Document feed detection roller

Claims (5)

A loading table for loading a plurality of sheets;
Separation feeding means for separating the sheets stacked on the loading table one by one and feeding them to the conveyance path;
A multi-feed detection unit that is arranged on the downstream side of the separation feeding unit and detects a multi-feed of the sheet fed to the conveyance path;
Reverse conveying means for performing reverse conveyance to return the sheet being fed in a direction opposite to the feeding direction when double feeding of the sheet is detected by the double feeding detecting means;
Sheet state detection means for detecting at least one of the state of a fed sheet and the state of a reversely conveyed sheet;
And a control unit that determines whether or not to stop the reverse conveyance of the sheet by the reverse conveyance unit based on a detection result of the sheet state detection unit. The sheet state detecting means detects the sheet jumping;
The sheet feeding apparatus according to claim 1. The sheet state detection means detects skew of the sheet;
The sheet feeding apparatus according to claim 1. The sheet state detecting means detects a jam of the sheet in the conveyance path;
The sheet feeding apparatus according to claim 1. The sheet state detecting means detects a feeding operation of the uppermost sheet stacked on the stacking table;
The sheet feeding apparatus according to claim 1.

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