JP2017137172A - Sheet conveyance device and image forming apparatus and image reading apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet conveyance device capable of shortening a time period elapsed since a sheet passed in a small size and at a low cost until an abutment member returns to a standby state, and an image forming apparatus and an image reading apparatus.SOLUTION: An abutment section 200 constituting a sheet detection section 143 which detects a sheet conveyed by sheet conveyance means and passing through a sheet conveyance path R is supported by a support section 12 movably in a crossing direction in which an abutment section 201 projects into the sheet conveyance path R and a sheet conveyance direction while a roller 202 is rotatably provided at a leading end in the crossing direction of the abutment section 201 which abuts on the sheet when the abutment member 200 moves.SELECTED DRAWING: Figure 15

Description

  The present invention relates to a sheet conveying apparatus, an image forming apparatus, and an image reading apparatus, and more particularly to a configuration of a sheet detecting unit that detects passage of a sheet.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines, printers, and facsimiles are provided with a sheet conveying apparatus that conveys a sheet. The sheet conveying device conveys the sheet to the image forming unit to transfer the toner image formed on the photosensitive drum onto the sheet, conveys the toner image transferred sheet to the fixing unit, and then discharges the sheet. It is transported to the part. In recent years, image forming apparatuses have been required to further improve productivity, that is, to improve the number of images formed per unit time. For this reason, speeding up of the sheet conveyance speed and shortening of the interval from the trailing edge of the continuously conveyed sheet to the leading edge of the next sheet (hereinafter referred to as a sheet interval) are achieved. In addition, in an image reading apparatus that reads an image formed on a sheet (original) by an image reading unit, the space between the sheets is shortened.

  By the way, in the conventional sheet conveying apparatus, when the sheet is conveyed, the switching operation of various switching members, the switching operation of the rotation direction of the sheet conveying means, and the like are performed based on the detection of the leading edge of the sheet. In order to detect the leading edge of the sheet, a sheet detection unit that detects the leading edge of the sheet is provided in the sheet conveyance path.

  Here, the sheet detection unit includes a contact member that rotates in contact with the leading end of the sheet, and a detection sensor that detects the rotated contact member and inputs a detection signal to the control unit. . In this sheet detection unit, when the contact member pressed by the sheet moves (changes) from a non-detection position (non-detection state) to a detection position (detection state) that can be detected by the detection sensor, the detection is detected. The sensor inputs a detection signal to the control unit. When the detection signal is input, the control unit determines that the conveyed sheet has reached the sheet conveyance path. After that, when the sheet passes through the contact member and the pressing by the sheet is released and the contact member returns from the detection position to the original non-detection position, the detection signal is not input from the detection sensor, and the detection signal is input. When it disappears, the control unit determines that the sheet has passed through the sheet conveyance path.

  However, in the case of the sheet detection unit having such a configuration, a certain amount of time is required until the contact member returns from the detection position to the non-detection position. I can't. In view of this, conventionally, there has been disclosed a structure in which the rotation shaft of the contact member is inclined obliquely with respect to the sheet conveying direction when viewed from the normal direction of the sheet surface (see Patent Document 1).

  Then, by tilting the rotation axis of the contact member in this way, the amount of tilting of the sensor in the sheet conveyance direction when the sensor is turned on can be reduced, so that the contact member is moved from the detection position. Mechanical loss until returning to the non-detection position can be reduced. Further, there is disclosed a system in which the contact member is not reciprocated between the detection position and the non-detection position, but the system in which the contact member is rotated to return from the detection position to the non-detection position. (See Patent Document 2). The mechanical loss can be greatly reduced by rotating the contact member once every time one sheet passes.

JP 2008-1465 A JP 2012-144350 A

  In such a conventional sheet conveying apparatus, for example, when the rotation axis of the abutting member is inclined with respect to the sheet conveying direction when viewed from the normal direction of the sheet surface, the abutting member is in the non-detection position. It starts after the trailing edge of the sheet has passed. In other words, the contact member cannot start returning to the non-detection position until the trailing edge of the sheet passes. For this reason, even when the abutting member is tilted, it is not possible to cope with the further small paper. In the case where the contact member is rotated once every time a sheet passes, the number of parts is increased and a space for rotating the contact member in the sheet conveying direction is required. This increases the size and the cost.

  The present invention has been made in view of such a current situation, and is a small size, low cost sheet transporting device capable of shortening the time from when the sheet passes until the contact member returns to the standby state, and An object of the present invention is to provide an image forming apparatus and an image reading apparatus.

  The present invention provides a sheet conveying apparatus, comprising: a sheet conveying unit that conveys a sheet; and a detecting unit that detects a sheet conveyed by the sheet conveying unit and passing through a conveying path. The main body has an abutting portion that abuts against the sheet at one end thereof, the moving member that moves when the abutting portion abuts on the sheet, the moving member, and the transverse portion where the abutting portion crosses the conveyance path. A support portion that is movably supported in the cutting direction and the sheet conveying direction; an urging unit that urges the moving member in a direction opposite to the transverse direction and the sheet conveying direction; and a sensor that detects movement of the moving member. The contact portion has a friction reducing means at a tip that contacts the sheet.

  As in the present invention, when the moving member moves, by providing a friction reducing means at the tip of the abutting portion that contacts the sheet, the moving member returns to the standby state after the sheet passes at a small size and low cost. Can be shortened.

1 is an overall configuration diagram of an electrophotographic full-color laser printer that is an example of an image forming apparatus including a sheet conveying device according to a first reference example of the present invention. FIG. 2A and 2B are diagrams illustrating a configuration of a sheet detection unit provided in the sheet conveying apparatus, where FIG. 3A is a perspective view, and FIG. The disassembled enlarged view around the contact member of the sheet detection unit. FIG. 3A is a perspective view and a side view illustrating the sheet detection unit, in which FIG. 3A shows a state where the contact part is positioned at a standby position (first position), and FIG. (C) shows a state where the contact portion is located at the second position. FIG. 7 is a perspective view and a side view showing the sheet detection unit, where (a) shows a state in which the contact part is located at the third position, and (b) shows an operation in which the contact part returns from the third position to the standby position. Show. The figure explaining the tension | pulling spring provided in the said sheet | seat detection part. (A) is a figure explaining the inclination-angle of the rocking | fluctuation axis | shaft of the said contact member, (b) is a side view which shows the amount of movement locus | trajectory of a contact part. It is a side view which shows a photo sensor, (a) is the state where the contact part was located in the standby position, (b) is the state where the contact part is located in the second position, and (c) is the contact part. The state located in the 3rd position is shown. The disassembled enlarged view which shows the sheet | seat detection part in a modification. 9A and 9B are a perspective view and a side view illustrating a sheet detection unit according to a modified example, in which FIG. 9A illustrates a state where the contact portion is positioned at a standby position, and FIG. 9B illustrates a state where the leading end of the sheet contacts the contact portion. . It is the perspective view and side view which show a sheet | seat detection part, Comprising: (a) is the state in which the contact part was located in the 2nd position, (b) shows the state in which the contact part was located in the 3rd position. FIG. 9 is a perspective view illustrating a sheet detection unit provided in a sheet conveying apparatus according to a second reference example of the present invention. FIG. 3A is a perspective view and a side view illustrating a sheet detection unit, where FIG. 3A is a state where the contact portion is positioned at a standby position (first position), and FIG. A state, (c) shows a state in which the contact portion is located at the second position. FIG. 7 is a perspective view and a side view showing the sheet detection unit, where (a) shows a state in which the contact part is located at the third position, and (b) shows an operation in which the contact part returns from the third position to the standby position. Show. FIG. 3 is a perspective view showing a sheet detection unit provided in the sheet conveying apparatus according to the first embodiment of the present invention. The disassembled enlarged view of the contact part of the contact member of the said sheet | seat detection part. FIG. 4 is a side view showing the sheet detection unit, where (a) shows a state where the contact part is located at the first position, (b) shows a state where the leading end of the sheet comes into contact with the contact part, and (c) shows a state where The state where the contact portion is located at the second position, (d) is the state where the contact portion is located at the third position, and (e) is the operation where the contact portion returns from the third position to the standby position. . 4A is an enlarged view of a main part and FIG. 4B is a cross-sectional view of an abutting portion of an abutting member of a sheet detecting unit provided in a sheet conveying apparatus according to a second embodiment of the present invention. The figure explaining operation | movement of the roller provided in the said contact part. 4A and 4B are diagrams illustrating a configuration of a sheet detection unit provided in a sheet conveying apparatus according to a third embodiment of the present invention, where FIG. 5A is a one-way perspective view, and FIG. FIG. 3 is a side view illustrating an image reading apparatus including a sheet detection unit.

<First Reference Example>
Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is an overall configuration diagram of an electrophotographic full-color laser printer which is an example of an image forming apparatus including a sheet conveying apparatus according to a first reference example of the present invention. In FIG. 1, reference numeral 100 denotes a full-color laser printer, and 101 denotes a full-color laser printer main body (hereinafter referred to as a printer main body). A printer main body 101 that is an image forming apparatus main body includes an image forming unit 102 that forms an image on a sheet, a sheet feeding device 113 that feeds a sheet, and a sheet that transports a sheet fed from the sheet feeding device 113. A transport device 103 and the like are provided.

  The image forming unit 102 is detachably attached to the printer main body 101 and includes a process cartridge 7 (7a, 7b, 7c, 7d) that forms toner images of four colors of yellow, magenta, cyan, and black. . The process cartridge 7 includes a developing unit 4 (4a, 4b, 4c, 4d) and a toner unit 5 (5a, 5b, 5c, 5d). The developing unit 4 includes a photosensitive drum 1 (1a, 1b, 1c, 1d) which is an image carrier, a charging roller 2 (2a, 2b, 2c, 2d), and a drum cleaning blade 8 (8a, 8b, 8c, 8d) and the like. The developing unit 4 includes a developing roller 40 (40a, 40b, 40c, 40d) and a developer application roller 41 (41a, 41b, 41c, 41d).

  The image forming unit 102 is disposed above the process cartridge 7 and includes a scanner unit 3 that irradiates a laser beam based on image information and forms an electrostatic latent image on the photosensitive drum 1. In addition, the image forming unit 102 includes an intermediate transfer belt unit 112 that is disposed below the process cartridge 7 and includes an intermediate transfer belt 112e to which the toner images on the photosensitive drums are sequentially transferred.

  The intermediate transfer belt unit 112 includes primary transfer rollers 112a, 112b, 112c, and 112d disposed inside the intermediate transfer belt 112e, in addition to the intermediate transfer belt 112e that rotates counterclockwise as indicated by an arrow P. Yes. The intermediate transfer belt 112e is stretched around the drive roller 112f, the secondary transfer counter roller 112g, and the tension roller 112h, and is tensioned in the direction of arrow n by the tension roller 112h.

  Further, the primary transfer rollers 112a, 112b, 112c, and 112d are disposed to face the respective photosensitive drums 1, and a transfer bias is applied by a transfer bias applying device (not shown). By applying a primary transfer bias by the primary transfer rollers 112a, 112b, 112c, and 112d, each color toner image on the photosensitive drum is sequentially transferred to the intermediate transfer belt 112e, and a full color image is formed on the intermediate transfer belt. It is formed. The sheet feeding device 113 includes a sheet feeding cassette 111 that is detachably mounted on the printer main body 101, a sheet feeding roller 9 that feeds the sheet S stored in the sheet feeding cassette 111, and the like.

  In FIG. 1, reference numeral 117 denotes a registration roller pair, and 116, together with a secondary transfer counter roller 112g, a secondary transfer unit 115 that transfers a full-color toner image formed on the intermediate transfer belt 112e onto a sheet. Laura. A fixing unit 114 fixes the toner image by applying heat and pressure to the toner image transferred onto the sheet by the secondary transfer unit 115. The fixing unit 114 has a fixing roller pair 96 including a fixing roller 96a having a heater (not shown) therein and a pressure roller 96b that is in pressure contact with the fixing roller 96a.

  A sheet discharge unit 118 discharges the sheet on which the toner image is fixed in the fixing unit 114 to the discharge sheet stacking unit 121 on the upper surface of the printer main body. The sheet discharge unit 118 includes a discharge roller pair 120 capable of forward and reverse rotation, a switchback roller pair 120a, a reverse conveyance path R1, and the like. The sheet conveying apparatus 103 conveys the sheet S by rollers such as a registration roller pair 117, a secondary transfer roller 116, and a fixing roller pair 96, and includes a sheet detection unit 143 and the like described later. A control unit 119 controls an image forming operation and a sheet conveying operation.

  Next, an image forming operation of the full color laser printer 100 configured as described above will be described. When an image signal is input to the scanner unit 3 from a personal computer (not shown) or the like, a laser beam corresponding to the image signal is emitted from the scanner unit 3 onto the photosensitive drum. At this time, the surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by a charging roller 2 in advance, and an electrostatic latent image is formed on the surface by irradiating laser light from the scanner unit 3. The

  Thereafter, the electrostatic latent image is developed by the developing unit 4 to form four color toner images of yellow, magenta, cyan and black on the photosensitive drum of each process cartridge 7. Then, the four color toner images are sequentially transferred onto the intermediate transfer belt by the primary transfer bias applied to the primary transfer rollers 112a, 112b, 112c, and 112d, thereby forming a full color toner image on the intermediate transfer belt. . The toner remaining on the surface of the photosensitive drum after the toner image is transferred is removed by the drum cleaning blade 8.

  In parallel with this toner image forming operation, the sheet S accommodated in the sheet feeding cassette 111 is sent out by the sheet feeding roller 9 and then separated one by one by the separation roller pair 10. Then, it is conveyed to the registration roller pair 117. Next, the sheet S is conveyed to the secondary transfer unit 115 after the timing is adjusted by the registration roller pair 117. Then, a full-color toner image on the intermediate transfer belt is secondarily transferred onto the conveyed sheet S by applying a positive bias to the secondary transfer roller 116 in the secondary transfer unit 115.

  After the toner image is transferred, the sheet S is conveyed to the fixing unit 114 and heated and pressed by the fixing roller 96a and the pressure roller 96b to fix the toner image on the surface. Next, after the full-color toner image is fixed, the sheet S is discharged and stacked on the discharge sheet stacking unit 121 by a discharge roller pair 120 provided in the sheet discharge unit 118. When images are formed on both sides of the sheet, the sheet S is conveyed again to the registration roller pair 117 through the reverse conveyance path R1 by reversing the discharge roller pair 120 and the switchback roller pair 120a. Thereafter, the sheet S is conveyed to the secondary transfer unit 115 by the registration roller pair 117, and image formation is performed on the second surface. The sheet S on which the image is formed on the second surface in this way is fixed with the toner image when passing through the fixing unit 114, and is then stacked on the discharge sheet stacking unit 121 by the discharge roller pair 120.

  As shown in FIG. 1, a sheet detection unit 143 that is a detection unit that detects the sheet S that is nipped and conveyed by the pair of fixing rollers 96 is provided downstream of the fixing roller pair 96 that is a sheet conveyance unit. It has been. The sheet detection unit 143 is connected to the control unit 119, and the control unit 119 detects the sheet S that has passed through the fixing roller pair 96 based on a signal transmitted from the sheet detection unit 143. Based on the detection information received from the sheet detection unit 143, the control unit 119 performs conveyance control of the sheet S on the downstream side in the sheet conveyance direction of the fixing unit 114, notification of jamming (sheet jam), and the like.

  Here, as shown in FIGS. 2A and 2B, the sheet detection unit 143 includes a contact member (moving member) 11, a light emitting unit and a light receiving unit (not shown), and is in contact with each other. The photo sensor 30 (sensor) which detects the member 11 is provided. As shown in FIG. 2A, the contact member 11 has an arm 11b that is a main body disposed in parallel with the width direction W orthogonal to the sheet conveying direction, and a predetermined end with respect to the arm 11b at the tip of the arm 11b. And an abutting portion 11a that is inclined and provided at an angle θ1.

  In FIG. 2A, reference numerals 98 and 99 denote sheet guides, and the sheet S that has passed through the fixing roller pair 96 passes between the sheet guides 98 and 99. In addition, openings 98a and 99a are formed in the sheet guides 98 and 99, and the contact portion 11a of the contact member 11 is configured to be able to contact the sheet S passing between the sheet guides 98 and 99. It is inserted into the openings 98a and 99a. The contact member 11 is supported by a support portion 12 provided on the sheet guide 99 via a swing shaft 11c that is a shaft portion.

  Here, in this reference example, the swing shaft 11c of the contact member 11 provided on the arm 11b is a method of the sheet conveyance path R formed by the sheet guides 98 and 99 as shown in FIG. They are arranged with a predetermined inclination θ2 with respect to the line direction N. That is, the rocking shaft 11c of the contact member 11 is arranged in a direction that is not parallel to the width direction. In other words, the rocking shaft 11c is inclined so that the portion close to the conveyance path is on the downstream side in the sheet moving direction than the distant portion.

  And the contact member 11 moves centering on the rocking | fluctuation axis | shaft 11c which is a movement center (rocking center) arrange | positioned in such a state. Further, a light shielding portion 11d is provided at an end of the contact member 11 on the opposite side of the contact portion 11a with the rocking shaft 11c as a center, and the photosensor 30 is located at a position corresponding to the light shielding portion 11d. Is supported by the support portion 12.

  When the contact member 11 is in a non-detection state where the contact portion 11a is positioned at a standby position where the contact portion 11a can contact the sheet S, the contact portion 11a is pressed and swung by the conveyed sheet S. Then, the light shielding unit 11d shields the optical path between the light emitting unit and the light receiving unit of the photosensor 30. As a result, the photosensor 30 is turned off. That is, when the contact member 11 changes from the non-detection state to the detection state, the photosensor 30 is turned off.

  Further, when the sheet S passes and the pressing by the sheet S against the contact portion 11a is released, the contact member 11 in a detection state detected by the photosensor 30 returns to the original standby position. As a result, the light shielding portion 11d is retracted from the optical path between the light emitting portion and the light receiving portion of the photosensor 30, and the photosensor 30 is turned on. That is, when the contact member 11 changes from the detection state to the non-detection state, the photosensor 30 is turned on. Based on such OFF and ON of the photosensor 30, the control unit 119 determines the passage of the leading edge and the trailing edge of the sheet.

  In the present reference example, the sheet guides 98 and 99 have a linear guide shape, but even in a curved guide shape, the sheet detection unit 143 can detect the leading edge and the trailing edge of the sheet. Here, when the sheet conveyance path R is curved by the curved sheet guides 98 and 99, the normal direction N of the sheet conveyance path R is the sheet at the position of the contact portion 11 a of the contact member 11. Defined as a normal to the transport path R.

  As shown in FIG. 3, the support portion 12 that holds the swing shaft 11c includes a main body portion 12d and a support member 12a (first support portion) that supports the abutting member 11 together with the main body portion 12d via the swing shaft 11c. And. The support member 12a is formed with a round hole 12a1 into which one end portion of the swing shaft 11c is inserted, and the other end portion of the swing shaft 11c is slidable (sliding) in the main body portion 12d (second support portion). A slit-shaped sliding portion 12b is formed which is locked to (possible).

  Here, the swing shaft 11c is supported by the support portion 12 with a predetermined inclination θ2 with respect to the normal direction N of the sheet conveying path R as described above. Further, in the present reference example, the swing shaft 11c is supported by the support portion 12 with a predetermined inclination θ5 with respect to the sheet conveyance direction, and along the slit-shaped sliding portion 12b in the sheet conveyance direction. Is supported so as to be movable (slidably movable) along a plane orthogonal to.

  By supporting the swing shaft 11c in this manner, the contact member 11 can move (swing) in the X direction and the Y direction along the sliding portion 12b with the swing shaft 11c as a fulcrum. That is, in this reference example, the support member 12 supports the contact member 11 so as to be movable in two axial directions, ie, the X direction and the Y direction. Then, by allowing the contact member 11 to move in two axial directions, the contact portion 11a is independent of the sheet conveying direction T of the sheet S and the normal direction N of the sheet conveying path R shown in FIG. Movement is possible.

As shown in FIG. 3, hooks 11e and 12c are formed on the arm 11b and the main body 12d of the support 12, respectively, and the abutting member 11 is biased to the hooks 11e and 12c. A tension spring 13 as an urging means is hooked. The tension spring 13 is attached so as to have a predetermined angle θ _S with respect to the normal direction of the sheet conveying path R as shown in FIG. When the tension spring 13 is pulled, the contact member 11 is given a force to return to the standby position in the X direction and the Y direction with the swing shaft 11c as a fulcrum.

  Here, as shown in FIG. 2A, the sheet guide 99 is provided with an abutting rib 99 b against which the arm 11 b of the abutting member 11 abuts. When the contact member 11 biased by the spring force of the tension spring 13 swings about the swing shaft 11c and the arm 11b contacts the butting rib 99b, the contact member 11 is shown in FIG. ) And stops at a standby position (first position) that is a detected position. In this state, the abutting portion 11a enters the sheet conveying path so as to abut on the leading edge of the conveyed sheet. In this reference example, the photosensor 30 is arranged within the roller width of the fixing roller pair 96. However, the light shielding portion 11d is further extended in the direction E in FIG. It can also be arranged outside the 96 roller width.

  By the way, in this reference example, when the contact member 11 is supported by the support portion 12, the arm 11b is parallel to the width direction orthogonal to the sheet conveying direction. Usually, in order to reduce the mechanical loss, it is necessary to reduce the swing angle of the abutting member 11. For this purpose, it is necessary to increase the arm length in the conventional sensor, and a large motion locus area in the apparatus cross-sectional direction is required. Necessary. However, in this reference example, since the arm 11b extends in parallel to the width direction, the motion trajectory required by the sheet detection unit 143 in the apparatus cross-sectional direction can be kept small regardless of the length of the arm length. Therefore, the sheet detection unit 143 of this reference example can be mounted even in a full-color laser printer (image forming apparatus) that is becoming smaller and faster. The angle of the arm 11b does not need to be parallel to the width direction, and the angle of the arm 11b can be adjusted, and may be inclined within a predetermined range with respect to the width direction according to the device configuration.

  Next, the operation of the sheet detection unit 143 of the present reference example will be described with reference to FIGS. 4A to 5B. 4A to 4C, a perspective view of the sheet detection unit 143 viewed from the same direction as that in FIG. 2A and a fixing roller pair 96 in the same direction as that in FIG. 2B. The sectional view (DD sectional view) seen from the axial direction is shown as a set.

  When the sheet S is conveyed in the sheet conveyance path provided between the sheet guides 98 and 99, the contact of the contact member 11 in which the leading end of the sheet S (the downstream end in the sheet conveyance direction) protrudes into the sheet conveyance path. Abutting on the part 11a, the abutting part 11a is pushed up. At this time, as shown in FIG. 4A, the leading edge of the sheet hits the contact portion 11a at a right angle. Here, as shown in FIG. 2A, the contact portion 11a of the contact member 11 is inclined at a predetermined angle θ1 with respect to the extending direction of the arm 11b. Further, the contact portion 11 a of the contact member 11 can be independently moved (swinged) along a surface parallel to the sheet transport direction T and a surface parallel to the normal direction N of the sheet transport path R. .

  Accordingly, when the sheet S comes into contact with the contact portion 11a at a contact angle of 90 °, a force is applied to the contact portion 11a by the sheet S along the sheet conveyance direction. In other words, a force in a direction perpendicular to the sheet conveying direction is applied to the contact member 11. Thereby, the contact member 11 starts swinging in the X direction shown in FIG. As shown in FIG. 4A, the tension spring 13 is locked at an angle θs with respect to the normal direction N of the sheet conveying path R. When the abutting member 11 is in the standby position, the swinging shaft 11c of the abutting member 11 shown in FIG. 3 is held by the tension spring 13 in a state of being brought close to the one end 12b1 side of the sliding portion 12b. The In this state, when the leading end of the sheet hits the contact portion 11a and is pressed by the sheet S, the contact member 11 is centered on the swing shaft 11c held at a position that becomes the first movement center (swing center). As shown in FIG. 4B, swinging is started in the arrow G direction. Note that the first movement center extends in a direction not parallel to the sheet width direction and intersects a virtual plane parallel to the surface of the conveyed sheet.

  When the sheet S is further conveyed, the contact member 11 continues to swing in the arrow G direction around the swing shaft 11c. In this reference example, as shown in FIG. 2B, the swing shaft 11c is inclined at an angle θ2 with respect to the normal direction N of the sheet conveying path R. Further, as shown in FIG. 3, the swing shaft 11c is inclined within the range indicated by the arrow Y along the sliding portion 12b. For this reason, the swing trajectory of the contact member 11 is a trajectory in a direction in which the contact portion 11a is retracted from the sheet conveyance path R. Further, as shown in FIG. 2A described above, the contact portion 11a of the contact member 11 is inclined by θ1 with respect to the arm 11b. The angle θ3 changes from 90 degrees to an acute angle.

  Thereafter, when the sheet S is further conveyed, the leading edge of the sheet S passes through the abutting portion 11a of the abutting member 11 as shown in FIG. When passing through the portion 11a, the pressing by the sheet S is released. As a result, the abutting member 11 is swung in the direction I in FIG. 5A while the tip of the abutting portion 11 a is in contact with the sheet S by the tension spring 13, and the abutting provided on the sheet guide 99. It strikes against the abutment rib 99b and stops. In addition, the position of the contact part 11a in FIG.4 (c) is made into the 2nd position. That is, the contact portion 11a moves from the first position to the second position where contact with the front end of the sheet is released by the pressing force received from the front end of the sheet.

  As described above, when the sheet S passes through the contact portion 11a of the contact member 11, the contact member 11 contacts the abutment rib 99b and moves to the side of the standby position. That is, in the present reference example, the contact member 11 is returned to the vicinity of the standby position before the trailing edge of the sheet passes, in other words, during sheet conveyance.

  When the contact member 11 swings while the tip of the contact portion 11a is in contact with the sheet S, the contact member 11 resists the urging force of the tension spring 13 with the round hole 12a1 as a fulcrum. It swings (moves) in the Y1 direction along the slit-shaped sliding portion 12b of the support portion 12. As a result, the swing shaft 11c moves to a position that becomes the second movement center (swing center) when the contact member 11 swings while the tip of the contact portion 11a is in contact with the sheet S. To do. The second movement center extends in a direction not parallel to the sheet width direction and intersects a virtual plane parallel to the surface of the conveyed sheet. After that, until the trailing end of the sheet S (upstream end in the sheet conveying direction) passes, the contact portion 11a of the contact member 11 presses the sheet S at a contact angle of 90 °. The position where the abutting portion 11a in FIG. 5A stops is defined as a third position. That is, the third position is a position where the contact portion 11a has moved in a direction opposite to the sheet moving direction (conveyance direction) than the second position.

  As a result, when the rear end of the sheet S passes thereafter, the contact member 11 swings in the J direction as shown in FIG. 11a returns to the standby position (first position) for entering the sheet conveyance path R.

  As described above, in the present reference example, the abutting member 11 is made to wait at the third position near the standby position (first position) in the sheet conveyance direction T during the conveyance of one sheet. As a result, immediately after the trailing edge of the sheet passes, it returns to the standby position (first position) only by moving in the normal direction N (J direction) of the sheet conveying path R, and preparation for receiving the subsequent sheet S1 is completed. . In this configuration, the mechanical loss until the preparation for receiving the succeeding sheet S1 is completed, as shown in FIG. 5B, the thickness D1 of the contact member 11 in the sheet conveyance direction and the contact portion 11a are J Only the distance D2 corresponding to the time required to detect the gap between the paper is detected. As a result, the mechanical loss can be greatly reduced. Further, regarding the number of parts, in this reference example, only the parts of the contact member 11 and the tension spring 13 are used, and the configuration is simple and the cost is not increased.

In this reference example, a single tension spring 13 applies a force in two directions (the sheet conveyance direction T and the normal direction N of the sheet conveyance path R). Therefore, as shown in FIG. 6, the tension angle of the tension spring 13 is θs, the spring force is f, the dynamic friction coefficient between the sheet S and the contact portion 11a is μ ₁ , and the dynamic friction coefficient between the arm 11b and the abutment rib 99b is μ. Assuming ₂ , θs needs to be set so that the following relationship is established.

That is, it is necessary to set the following relationship as the relationship between the forces acting in the sheet conveyance direction T.
fsin θs> fμ ₁ cos θs

That is, in the sheet conveyance direction T, the force that the contact member 11 returns to the upstream side in the sheet conveyance direction is represented by the restoring force fsinθs by the tension spring 13, and the friction between the sheet S and the contact portion 11a on the downstream side in the sheet conveyance direction. The force needs to be greater than fμ ₁ cos θs.

Further, it is necessary to set so that the following relationship is established as the relationship between the forces acting in the normal direction N of the sheet conveyance path R.
f cos θs> f μ ₂ sin θs

That is, in the normal direction N of the sheet conveyance path R, the force of the contact member 11 returning to the direction N of the sheet conveyance path R is indicated by the restoring force fcos θs by the tension spring 13. The return force fcos θs needs to be larger than the frictional force fμ ₂ sin θs generated between the contact member 11 and the abutment rib 99b.

From the above two relational expressions, the installation angle θs of the spring needs to be set so as to satisfy the following relational expression.
μ1 <tan θs <1 / μ2

  For example, if μ1 is 0.4 and μ2 is 0.3, the spring installation angle θs is 22 ° <θs <73 °. In this case, it is calculated that the sliding frictional force of the swing shaft 11c and the weight of the contact member 11 are so small as to be negligible with respect to the above force. Further, in this reference example, since the linear sheet conveyance path is assumed, the relational expression of the above force is obtained. However, when the sheet conveyance path is curved, the relationship of the force due to the curve is taken into consideration. It is necessary to set θs by calculation.

  Next, the inclination angle θ2 of the swing shaft 11c of the contact member 11 in this reference example will be described. As shown in FIG. 2B, the swing shaft 11c is inclined with respect to the normal direction N of the sheet conveying path R by an angle θ2. The inclination angle θ2 is intended to ensure operational stability by moving the contact portion 11a of the contact member 11 in the direction of retreating from the sheet conveyance path R by swinging the contact member 11. Therefore, it is necessary to set an appropriate angle.

  For example, when the inclination angle θ2 of the swing shaft 11c is close to 0 °, the G direction shown in FIG. 4B is also close to 0 °. In this case, the angle by which the abutting portion 11a of the abutting member 11 swings until it moves to a position that does not interfere with the conveyance of the sheet S becomes large, and the amount of movement locus M shown in FIG. On the other hand, when the tilt angle θ2 of the swing shaft is close to 90 °, the contact portion 11a of the contact member 11 moves to a position that does not interfere with the conveyance of the sheet S even with a small swing angle, so that the motion trajectory amount M becomes small. . However, in this case, when the contact portion 11a is pressed by the sheet S, the component force acting in the G direction (swinging direction) shown in FIG. Power increases. As a result, it is conceivable that a dent is generated at the front end of the sheet S or the contact member 11 is damaged.

Next, the inclination angle θ2 component force component F _G of the operation path weight M of the pivot shaft 11c of the contact member 11 in the present embodiment the direction of rotation are compatible, FIGS. 7 (a) and 7 (b) Will be described. The vertical axis on the left side of FIG. 7A indicates the movement trajectory amount M in the sheet conveyance direction of the contact member 11 of this reference example, and the vertical axis on the right side indicates that the contact portion 11a of the contact member 11 is a sheet. A component component FG in the _G direction acting when pressed is shown. The horizontal axis in FIG. 7A indicates the inclination angle θ2 with respect to the normal direction N of the swing shaft 11c of the contact member 11 of this reference example.

7 (b) is a diagram showing the motion track amount M, the relationship between the force component force component F _G of the pivot shaft 11c direction. The protruding amount of the contact portion 11a sheet conveying path of the contact member 11 D3, when the inclination angle of the pivot shaft 11c and .theta.2, component force component F _G to motion track amount M and the pivot shaft 11c direction It is shown in the following relationship.
Motion trajectory amount M = D3 / tan θ2
Component component F _G = cos θ2 in the direction of the swing axis 11c

Then, D3 and 2 mm, a plot of the component force component F _G to motion track amount M and the pivot shaft 11c direction at each angle of inclination is shown in FIG 7 (a). The movement trajectory amount M is a downward convex function, and particularly increases rapidly in a region where the tilt angle θ2 is small (for example, 20 ° or less), and almost zero in a region where the tilt angle is large (for example, 80 ° or more). Become. On the other hand, the component force component FG in the direction of the swing shaft 11c also decreases as the tilt angle θ2 of the swing shaft increases. It has become.

In this reference example, the contact member 11 has a component component in order to make the sensor operate smoothly without causing damage to the front end of the sheet while keeping the movement trajectory amount M as small as possible so that the contact member 11 can be accommodated in an apparatus body that is becoming smaller. there is a need to be as large as possible the F _G. From this point of view, in (a) of FIG. 7, the difference between the operating locus amount M component force component F _G is the largest angular range, is ensured further component force component F _G is more than 50% 30 ° to 50 It is preferable that “°” be a recommended range of the inclination angle θ2 of the swing shaft 11c of the contact member 11. Incidentally, the component force component F _G shown in FIG. 7 (a), on drawing a graph with the motion track quantity M, the more the frictional force between the contact portion 11a of the sheet S tip and the contact member 11 is negligible Calculated as small.

  Next, a method for detecting the contact member 11 in this reference example will be described. FIG. 8A shows a state where the optical axis of the photosensor 30 is shielded by the light shielding portion 11 d of the contact member 11. Thereafter, when the contact member 11 is pushed up by the conveyed sheet S, as shown in FIG. 8B, the light shielding part 11d moves in the arrow P direction, which is the lower right direction, and the light shielding part 11d is a photosensor. Retreat from 30 optical axis regions 30a. As a result, the photosensor 30 switches from the light shielding state to the transmission state, and the control unit 119 detects the passage of the sheet based on a change in the signal from the photosensor 30.

  Thereafter, when the leading edge of the sheet passes and the contact member 11 swings in the I direction as shown in FIG. 5A, the light shielding portion 11d is in the upward direction as shown in FIG. 8C. It moves in the direction of arrow Q, moves to the side of the photosensor 30, and keeps that position until the sheet S passes. Even in this state, since the light shielding portion 11d is in a position retracted with respect to the optical axis region 30a, the photosensor 30 outputs a transmission signal, and the control portion 119 maintains a state where the sheet is detected. .

  When the rear end of the sheet passes through the contact member 11, the contact member 11 swings about the swing shaft 11c and returns to the position shown in FIG. Further, by the swinging of the contact member 11, the light shielding portion 11d moves in the arrow K direction on the left side in the horizontal direction shown in FIG. 8A to shield the optical axis region 30a of the photosensor 30, and the control portion 119. Detects the passage of the sheet. In this way, the light shielding unit 11d detects the leading edge and the trailing edge of the sheet S by moving back and forth from the two directions (P direction and K direction) to the optical axis region 30a and switching to light shielding / transmission. doing. In other words, the signal of the photosensor 30 when the contact portion 11a is in the first position is different from the signal of the photosensor 30 when the contact portion 11a is in the second position and the third position. .

  As described above, in this reference example, when the contact portion 11a is pressed by the conveyed sheet, the contact member 11 is moved along the sheet conveyance direction and the normal direction of the sheet conveyance direction. It changes to the detection state. When the pressing by the sheet is released, the contact member 11 is moved in the direction opposite to the sheet conveying direction along the sheet surface and returned to the vicinity of the standby position. When the sheet passes, the contact member 11 is returned to the standby position where the contact portion 11a comes into contact with the conveyed sheet. In this way, when the pressing by the sheet is released, the contact member 11 is returned to the vicinity of the standby position, so that the contact member 11 returns to the non-detection position after the sheet passes at a small size and low cost. Can be shortened.

<Modification>
In this reference example, the sliding portion 12b has a slit shape, but the sliding portion 12b may have a shape other than the slit shape as shown in FIG. Hereinafter, a configuration in which the sliding portion 12b is not slit-shaped will be described as a modified example with reference to FIGS. 9 to 11B. 10A to 11B, a modified sheet detection unit 143A is seen from a perspective view and a cross-sectional view (DD cross-sectional view and E-D view) seen from the axial direction of the fixing roller pair 96. E cross-sectional view).

  FIG. 10A shows a state in which the contact member 11 is in the standby position (first position). When the sheet S comes into contact with the contact portion 11a, first, the contact member 11 is arranged such that the swing shaft 11c, one end of which is loosely fitted in the round hole 12a1, is separated from the sliding portion 12b in the Z direction shown in FIG. Swing. That is, the contact member 11 swings from the standby position in the direction of arrow V as shown in FIG. Thereafter, the swinging shaft 11c is tilted with respect to the round hole 12a1, so that the gap between the swinging shaft 11c and the round hole 12a1 is clogged, and after the swinging shaft 11c is locked by the side wall of the round hole 12a1, 9 starts to swing clockwise in the X direction and moves in the Y direction.

  As a result, the contact member 11 swings in the direction of the arrow G ′ as shown in FIG. Then, when the leading edge of the sheet passes through the contact portion 11a, the pressing by the sheet S is released. The abutting member 11 is swung in the direction I in FIG. 11B while the tip of the abutting portion 11 a is in contact with the sheet S by the tension spring 13, and abutment rib 99 b provided on the sheet guide 99. It stops at and stops. At this time, the abutting member 11 swings in the direction opposite to the Z direction shown in FIG. 9 so that the swing shaft 11c contacts the sliding portion 12b, and Y shown in FIG. 9 along the sliding portion 12b. Swings in the opposite direction. Thereafter, the movement when the rear end of the sheet S passes is the same as in the above-described embodiment. In addition, the contact part 11a is located in the 2nd position in Fig.11 (a), and is located in the 3rd position in FIG.11 (b).

<Second Reference Example>
Next, a second reference example of the present invention will be described. FIG. 12 is a diagram illustrating a configuration of a sheet detection unit 142B (detection unit) provided in the sheet conveying apparatus according to this reference example. In FIG. 12, the same reference numerals as those in FIG. 2A described above indicate the same or corresponding parts.

  In FIG. 12, reference numeral 60 denotes an abutting member, and this abutting member 60 is composed of two parts: an abutting portion 60a that constitutes an abutting portion that abuts against the sheet, and an arm member 60b that is a main body portion. Has been. The arm member 60b swings along the plane parallel to the sheet conveyance path R to the support portion 12 with a swing shaft 60c that is a first axis parallel to the normal direction N of the sheet conveyance path R as a fulcrum. It is supported movably. The contact portion 60a is supported on the arm member 60b by a rotation shaft 60d, which is a second axis parallel to the sheet conveyance direction T, so as to be rotatable along a plane orthogonal to the sheet conveyance path R. Yes.

  Here, the rocking shaft 60c and the rotating shaft 60d are in a positional relationship orthogonal to each other when viewed from the axial direction of the fixing roller pair 96. With such a positional relationship, the rocking shaft 60c and the rotating shaft 60d are The pivoting and swinging operations can be performed independently. In this reference example, the swing shaft 60c is parallel to the normal direction N of the sheet transport path R, and the rotation shaft 60d is parallel to the sheet transport direction T. However, the present invention is not limited to this. The angular relationship between the shaft 60c and the rotation shaft 60d may be determined according to the device configuration.

  The abutting portion 60a is always urged in the Y direction by the torsion spring 61 with respect to the arm member 60b, and is positioned by hitting a stopper (not shown) provided on the arm member 60b. Further, the arm member 60 b is always urged in the Z direction by the tension spring 62, and is positioned by abutting against a rib 80 a erected on the seat guide 80.

  In FIG. 12, 60a1 is a contact surface that comes into contact with the sheet S in the locus where the contact portion 60a swings, and this contact surface 60a1 is formed in the width direction as shown in FIG. It is inclined by θ4 with respect to W. Reference numeral 60e denotes a light shielding part provided on the bottom surface of the contact part 60a. Reference numerals 80 and 81 denote sheet guides, and the sheet that has passed the fixing roller pair passes between the sheet guides 80 and 81. Note that openings 80c and 81c are formed in the sheet guides 80 and 81, and the contact portion 60a is in the openings 80c and 81c so as to contact the sheet S passing between the sheet guides 80 and 81. Has been inserted.

  Further, a support plate 80b is erected on the sheet guide 80, and the photosensor 31 is attached to the support plate 80b. When the light path between the light emitting portion and the light receiving portion of the photosensor 31 is shielded by the light shielding portion 60e provided on the bottom surface of the contact portion 60a, the signal from the photosensor 31 changes from ON to OFF. Thus, the control unit 119 detects the passage of the sheet S.

  Next, the operation of the sheet detection unit 143B of this reference example will be described with reference to FIGS. 13 (a) to 13 (c). 13A to 13C are a perspective view of the sheet detection unit 143B viewed from the same direction as FIG. 12 and a cross-sectional view of the fixing roller pair 96 viewed from the axial direction (HH cross-sectional view). ) Is shown as a set. Until the sheet is conveyed and comes into contact, the contact portion 60a waits for the sheet S in a state of protruding into the sheet conveyance path R at a right angle to the sheet conveyance direction T as shown in FIG. Yes. At this time, the contact portion 60a is located at the standby position (first position).

  When the sheet S is conveyed, as shown in FIG. 13B, the leading end of the sheet comes into contact with the contact portion 60a, and the contact portion 60a is pressed in the downstream direction in the sheet conveyance direction by the conveyance force F1 of the sheet S. To do. Thereby, the contact portion 60a and the arm member 60b are integrated, that is, the contact member 60 is downstream of the sheet conveying direction along the plane parallel to the −Z direction, ie, the sheet conveying direction, around the swing shaft 60c. Swing to the side.

  Here, as described above, the contact surface 60a1 in contact with the sheet S is inclined with respect to the width direction W in the locus where the contact portion 60a swings. Since the contact surface 60a1 has an inclination angle (for example, the angle θ4) in this way, the leading edge of the sheet is increased with an increase in the swing angle in the −Z direction around the swing shaft 60c of the contact member 60. Presses the contact surface 60a1. As a result, as shown in FIG. 13B, a component force P2 is generated that rotates the contact portion 60a in the −Y direction, that is, the direction orthogonal to the sheet conveying direction, with the rotation shaft 60d as a fulcrum.

  Then, when the sheet S is further conveyed, the contact force 60a is rotated in the −Y direction with the rotation shaft 60d as a fulcrum as shown in FIG. Evacuate from. At this time, the contact portion 60a is located at the second position. Then, when the leading edge of the sheet S passes, the contact member 60 rotates in the Z direction by the spring force of the tension spring 62 as shown in FIG. Stop at the direction. That is, also in this reference example, the contact member 60 is returned to the vicinity of the standby position before the trailing edge of the sheet passes, in other words, during sheet conveyance. At this time, since the sheet S is being conveyed, the contact portion 60a rotates by a predetermined angle with respect to the arm member 60b, and waits in a state where the sheet S being conveyed is pressed by the spring force of the torsion spring 61. To do. At this time, the contact portion 60a is located at the third position.

  Next, when the sheet S is conveyed and the trailing end of the sheet S passes through the contact member 60, only the contact portion 60a rotates in the Y direction about the rotation shaft 60d by the spring force of the torsion spring 61. Return to the standby position shown in FIG. At this time, as in the first reference example described above, the mechanical loss is only the distance of the plate thickness of the contact member 60 and the time required for the contact portion 60a to detect the paper interval, thereby greatly reducing the paper interval. Is possible.

  Next, a method for detecting the contact member 60 will be described. When the contact member 60 is located at the standby position, the optical axis 31a of the photosensor 31 is shielded by the light shielding portion 60e of the contact portion 60a, as shown in FIG. At this time, the contact portion 60a extends in a direction perpendicular to the sheet S, and the force received by the contact portion 60a when the leading end of the sheet S contacts is the same direction as the sheet conveying direction.

  Next, as shown in FIG. 13 (b), when the contact portion 60a is pressed and pushed up by the leading edge of the sheet, the light shielding portion 60e is retracted from the optical axis 31a of the photosensor 31, thereby turning on the photosensor 31. Thus, the control unit 119 detects the passage of the sheet. When the sheet is being conveyed, as shown in FIG. 13C, the light-shielding portion 60e operates at a position largely retracted from the optical axis 31a of the photosensor 31, and the photosensor 31 The state of detecting passing (ON state) is maintained.

  During sheet conveyance after the leading edge of the sheet has passed, as shown in FIG. 14A, the contact member 60 returns to the same level as the standby position in the sheet conveyance direction, and waits at a position retracted from the sheet conveyance path. doing. Even in this state, since the light shielding unit 60e is retracted from the optical axis 31a of the photosensor 31, the sheet detection state of the photosensor 31 is maintained. That is, the contact member 60 of this reference example detects the leading edge and the trailing edge of the sheet in two directions because the direction of passing through the optical axis of the photosensor 31 differs between the leading edge detection and the trailing edge detection. Immediately after the trailing edge of the sheet S passes, the light shielding part 60e again shields the optical axis 31a of the photosensor 31 by returning the contact part 60a to the standby position as shown in FIG. As a result, the photo sensor 31 is turned OFF, and the control unit 119 detects that the sheet has passed.

  As described above, in this reference example, when the contact portion 60a is pressed by the conveyed sheet, the contact portion 60a is moved along a plane orthogonal to the sheet conveyance direction. Further, when the pressing by the sheet is released, the contact portion 60a is moved in the direction opposite to the sheet conveying direction along the sheet surface, and when the sheet passes, the contact portion 60a is returned to a position where it comes into contact with the conveyed sheet. I am doing so.

  That is, when the contact portion 60a is pressed by the conveyed sheet, the contact member 60 moves along the sheet conveyance direction while moving the contact portion 60a in a direction along a plane orthogonal to the sheet conveyance direction. I try to let them. Further, when the pressing by the sheet is released, the contact member 60 moves in the direction opposite to the sheet conveying direction along the sheet surface, and when the sheet passes, the position where the contact portion 60a contacts the conveyed sheet. Return to the standby position. Thereby, the same effects as those of the first reference example described above can be obtained.

<First Embodiment>
Next, a first embodiment of the present invention will be described. FIG. 15 is a diagram illustrating a configuration of a sheet detection device provided in the sheet conveyance device according to the present embodiment. In FIG. 15, components similar to those in Reference Example 1 and Reference Example 2 have the same reference numerals or the same member names even if the reference numerals are different, and a description thereof is omitted.

  As shown in FIG. 15, the contact member 200 according to the present embodiment is composed of two parts, an arm 200 a and a contact portion 201 provided at the tip of the arm 200 a so as to be able to protrude into the sheet conveyance path R. . The arm 200a is supported by the support portion 12 so as to be swingable around a swing shaft 200b movable in two axial directions as in the first reference example described above. Further, the contact member 200 is urged by the tension spring 13 and is positioned at the first position as in the first reference example described above until the sheet is conveyed. A light shielding part 200c is provided on the opposite side of the arm 200a with respect to the rocking shaft 200b, and is supported by the support part 12 provided on the sheet guide 99 at a position corresponding to the light shielding part 200c. A photosensor 30 serving as a detection unit that detects a moving state is provided.

  Here, in the present embodiment, a roller 202 that is a cylindrical rotating body that comes into contact with the conveyed sheet is pivotally supported at the front end in the transverse direction where the contact portion 201 crosses the sheet conveying path R. As shown in FIG. 16, the roller 202 as the friction reducing means includes a sheet contact portion 202a that comes into contact with the conveyed sheet, and shaft holes 202b formed on both side surfaces in the axial direction. Further, a roller rotation shaft 201e is formed at the tip of the contact portion 201 so as to be opposed to the roller 202. The roller 202 is brought into contact with the contact portion 201 by engaging the roller rotation shaft 201e with the shaft hole 202b of the roller 202. It is supported rotatably.

  In addition, the roller 202 is provided to be inclined at the tip of the contact portion 201 at an angle that is parallel to the sheet surface when the contact member 200 moves from the second position to the third position. Accordingly, when the contact member 200 moves from the second position to the third position, the roller 202 is driven to rotate when the sheet contact portion 202a comes into contact with the conveyed sheet. In the present embodiment, the sheet contact portion 202a has a circumferential surface, the shaft hole 202b has a circular shape, and the roller rotation shaft 201e has a cylindrical shape. Any shape that rotates smoothly with respect to the sheet may be used.

  Next, operation | movement of the contact member 200 of this Embodiment is demonstrated using FIG. 17A to 17E are cross-sectional views of the fixing roller pair 96 viewed from the axial direction, and show the movement of the contact member 200 accompanying the conveyance of the sheet. First, in FIG. 17A, the contact member 200 stands by at the first position. Next, in FIG. 17B, the leading edge of the conveyed sheet S comes into contact with the contact portion 201, and the contact member 200 starts swinging in the direction of arrow G. Further, in FIG. 17C, the contact member 200 continues to swing in the direction of the arrow G by the leading edge of the conveyed sheet S and moves to the second position retracted from the sheet conveying path R.

  In FIG. 17D, the contact member 200 swings in the I direction in a state where the roller 202 is in sliding contact with the sheet S, and abuts against the abutment rib 99 b provided on the sheet guide 99. Move to the third position to stop. Finally, in FIG. 17E, the contact member 200 returns to the first position immediately after the trailing edge of the sheet S passes.

In the state of FIG. 17D, that is, when the contact member 200 moves from the second position to the third position, the roller 202 is driven and rotated by the conveyed sheet S. Here, in the above description of the first reference example, the following relational expression is defined as a force relationship acting in the sheet conveying direction T as shown in FIG.
fsin θs> fμ ₁ cos θs

That is, in order to realize a stable operation of the contact member 200, it is necessary to keep μ ₁ that is a dynamic friction coefficient between the sheet and the contact member 200 small for various types of sheets having different surface properties. Therefore, in the present embodiment, the roller 202 is driven and rotated by the conveyed sheet, whereby the magnitude of the frictional force between the sheet and the contact member 200 when the contact member 200 is in sliding contact with the sheet is set. I try to reduce it. Further, by reducing the friction between the shaft hole 202b of the roller 202 and the roller rotation shaft 201e, a stable operation of the abutting member 200 is realized regardless of variations in sheet posture due to sheet rigidity or curl. ing.

  In the present embodiment, the contact member 200 is formed of synthetic resin because of its complicated shape. The roller 202 is made of polyacetal so that the dynamic friction coefficient between the shaft hole 202b of the roller 202 and the roller rotation shaft 201e provided on the contact member 200 is smaller than the dynamic friction coefficient between the sheet and the contact member 200. It is formed using a material having a low coefficient of friction.

  Further, as described above, the roller 202 is provided in an inclined state at the tip of the contact portion 201 so as to be parallel to the sheet surface when the contact member 200 moves from the second position to the third position. It has been. Accordingly, in the state shown in FIG. 17D, the roller 202 comes into line contact with the conveyed sheet S perpendicularly to the sheet conveying direction, so that it can be efficiently rotated. In addition, since the roller 202 is in line contact with the sheet, the dynamic friction coefficient between the shaft hole 202b of the roller 202 and the roller rotation shaft 201e can be reduced. Wear of the contact member 200 can be reduced.

  As described above, in the present embodiment, when the contact member 200 moves, the roller 202 is rotatably provided at the tip of the contact portion 201 of the contact member 200 that is in sliding contact with the sheet surface. The frictional force between the contact portion 201 and the contact portion 201 can be reduced. As a result, the contact member 200 can be smoothly moved to the third position, so that the contact member 200 can be moved to the third position before the sheet passes. As a result, the time from when the sheet passes through the small size and low cost until the contact member 200 returns to the standby state can be shortened, and the detection accuracy of the sheet detection unit 143 can be increased.

<Second Embodiment>
Next, a second embodiment of the present invention will be described. FIG. 18A is an enlarged view of a main part of a contact member provided in the sheet detection device of the sheet conveying apparatus according to the present embodiment. As shown in FIG. 18A, a roller 302 is rotatably supported at the tip of the contact portion 301 of the contact member 300 of the present embodiment.

  A roller rotating shaft 301 b that is a shaft that supports the roller 302 is provided at the tip of the contact portion 301. In addition, the roller 302 is formed with a sheet contact portion 302a that comes into contact with the conveyed sheet and an insertion hole 302b through which the roller rotation shaft 301b is inserted. Here, the inner wall surface of the insertion hole 302b is formed with a tapered surface 302b1 that is inclined so that the diameter of the insertion hole 302b increases from the center to the end in the axial direction as shown in FIG. 18B.

  Accordingly, when the contact member 300 moves from the second position to the third position, the roller 302 that rotates while contacting the sheet is parallel to the sheet with the center in the axial direction of the roller rotation shaft 301b as a fulcrum. The direction can be changed. Then, by changing the direction so as to be parallel to the sheet, the rotation efficiency of the sheet S and the roller 302 can be increased regardless of the position of the contact member 300 with respect to the sheet, and the roller 302 can be smoothly rotated. Can be made.

  FIG. 19 shows that the roller 302 is oriented by the conveyed sheet S when moving from the second position to the third position as shown in FIG. 17C described in the first embodiment. FIG. 10 is a cross-sectional view of the contact member 300 when viewed from the sheet guide 98 when changed. When the contact member 300 moves from the second position to the third position, the orbit at the tip of the contact portion 301 becomes an arc instead of a straight line, and is not parallel to the sheet conveyance direction. When the tip of the contact portion 301 moves in such a path, a force in a direction to change the direction of the roller 302 to a direction perpendicular to the sheet conveyance direction is generated in the roller 302 due to friction with the sheet.

  When such a force is generated, since the tapered surface 302b1 is formed on the inner wall surface of the insertion hole 302b as described above, the roller 302 is centered in the axial direction of the roller rotation shaft 301b indicated by the alternate long and short dash line. To the direction perpendicular to the sheet conveying direction. As a result, the roller 302 rotates about an axis indicated by a two-dot chain line different from the roller rotation shaft 301b, and the roller 302 is also in the state of FIG. 17D of the first embodiment described above. Follows the sheet surface.

  Thus, in this embodiment, when the roller 302 abuts on the sheet, the roller 302 becomes perpendicular to the sheet conveying direction. Thereby, the rotational efficiency of a sheet | seat and the roller 302 can be improved, and the stable operation | movement of the contact member 300 is realizable also in a state like FIG. As a result, the same effects as those of the first embodiment described above can be obtained.

  Further, in such a configuration, even in the state of FIG. 17D of the first embodiment described above, the rotation axis of the roller 302 follows the sheet surface. A stable operation of the contact member 300 can be realized regardless of variations. In this embodiment, the tapered surface 302b1 is formed on the inner wall surface of the insertion hole 302b. However, the roller rotation shaft 301b is inclined so that the diameter of the roller rotation shaft 301b decreases from the center to the end in the axial direction. Even if the tapered surface is formed, the same effect can be obtained.

<Third Embodiment>
Next, a third embodiment of the present invention will be described. FIG. 20 is a diagram illustrating a configuration of a sheet detection device provided in the sheet conveying device according to the present embodiment.

  As shown in FIG. 20, the contact member 400 according to the present embodiment includes two parts, an arm 401 and a contact portion 401 a provided at the tip of the arm 401. The arm 401 is swingably supported by the support portion 12 around a swing shaft 401b that can swing in two different axial directions as in the first reference example described above. Further, as in the first reference example described above, the contact member 400 is urged by the tension spring 13 and is positioned at the first position until the sheet is conveyed. A light shielding portion 401c is provided on the opposite side of the arm 401 with respect to the swing shaft 401b, and is supported by the support portion 12 provided on the sheet guide 99 at a position corresponding to the light shielding portion 401c. A photosensor 30 serving as a detection unit that detects a moving state is provided.

  In the present embodiment, a cap 402 as an example of a fitting member that is a friction reducing means that comes into contact with the conveyed sheet is attached to the tip of the contact portion 401a. In addition, since the contact part 401a is complicated shape, it is shape | molded with the synthetic resin. And the stainless steel with the smooth surface rolled as the cap 402 is used so that the dynamic friction coefficient of a sheet | seat and the cap 402 may become smaller than the dynamic friction coefficient of a sheet | seat and the contact part 401a.

  As described above, in the present embodiment, by providing the cap 402 at the tip of the contact portion 201 of the contact member 200, the frictional force between the sheet and the contact portion 201 can be reduced. As a result, the contact member 200 can be smoothly moved to the third position, so that a decrease in detection accuracy of the sheet detection unit 143 can be prevented. Instead of the cap 402, a metal wire or fluorocarbon resin with a smooth surface may be placed on the contact portion 401a.

  In the first, second, and third embodiments described so far, the full-color laser printer shown in FIG. 1 is exemplified as the image forming apparatus including the sheet detection unit. However, the present invention is not limited to this. It is not something. For example, the present invention can be applied to the image reading apparatus 500 shown in FIG. 21 that reads an image recorded on the sheet S.

  In FIG. 21, the feeding roller 222 feeds the document D set on the document tray 221. The fed document D is transported by document transport rollers 223, 224, 225, and 226 in the document transport path. A reading sensor 229 serving as an image reading unit reads the document D being conveyed by the document conveying rollers 223, 224, 225, and 226, and the read document D is transferred from the document discharge roller 227 onto the document discharge tray 228. Discharge. A sheet detection unit 230 having the same configuration as that of the first to third embodiments is provided in the document conveyance path through which the document D is conveyed, detects the document D, and reads the reading sensor 229 according to the detection timing of the document D. Starts reading the document D.

  Further, the contact member of the sheet detection unit that detects the leading edge and the trailing edge of the sheet has been described so far, but the configuration of the present invention is not necessarily limited to sheet detection. For example, the present invention may be applied to an abutting member used for a skew correction unit that corrects skew during sheet conveyance, a full load detection unit that detects a full load state of stacked sheets on a paper discharge tray, and the like.

DESCRIPTION OF SYMBOLS 11 ... Contact member (moving member), 11a ... Contact part, 11b ... Arm (main-body part), 11c ... Swing axis, 12 ... Support part, 13 ... Tension spring (biasing means), 30 ... Photosensor ( Sensor), 60 ... Abutting member (moving member), 60a ... Abutting portion, 60a1 ... Abutting surface, 60b ... Arm member (main body portion), 60c ... Oscillating shaft, 60d ... Rotating shaft, 61 ... Torsion spring (Biasing means), 62 ... tension spring (biasing means), 96 ... pair of fixing rollers (sheet conveying means), 98, 99 ... sheet guide, 100 ... full color laser printer, 102 ... image forming unit, 103 ... sheet conveying Device 143 sheet detecting section (detection means) 200 contact member (moving member) 200a arm (main body) 201 contact section 200b swinging shaft 202 roller (rotating body) 202b ... shaft hole, 201e ... Rotating shaft 300 ... Contact member (moving member) 301 ... Contact portion 301b ... Roller rotating shaft 302 ... Roller (rotating body) 302b ... Insertion hole 302b1 ... Tapered surface 400 ... Contact member ( (Moving member), 401 ... arm (main body), 401a ... contact portion, 402 ... cap (fitting member), 500 ... image reading device, R ... sheet conveying path, S ... sheet

Claims (11)

Sheet conveying means for conveying the sheet;
Detecting means for detecting a sheet conveyed by the sheet conveying means and passing through a conveyance path,
The detection means includes
A main body and a moving member that has an abutting portion that abuts against the sheet at one end of the main body, and moves when the abutting portion abuts on the sheet;
A support portion that supports the moving member so that the contact portion can move in a transverse direction and a sheet conveyance direction in which the conveyance section crosses the conveyance path;
An urging means for urging the moving member in a direction opposite to the transverse direction and the sheet conveying direction;
A sensor for detecting the movement of the moving member,
The sheet conveying apparatus according to claim 1, wherein the abutting portion has a friction reducing means at a tip abutting on the sheet. The moving member has a first position at which the abutting portion protrudes into the conveying path, and is detected by the sensor, and the abutting portion is downstream of the first position in the sheet conveying direction and the conveying path. The second position moved to a position where the pressing by the sheet is released and the contact portion can move to the third position moved to the upstream side in the sheet conveying direction from the second position,
When the abutting portion is pressed by the sheet passing through the conveyance path, the sheet is moved from the first position to the second position against the urging force of the urging unit, and then the urging unit is urged. The leading edge of the abutting portion is moved from the second position to the third position while sliding the tip of the abutting portion against the surface of the sheet by the force, and the sheet passes and the abutting of the abutting portion with the sheet is released. 2. The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is configured to move from the third position to the first position by an urging force of the urging means.   3. The sheet conveyance according to claim 2, wherein the friction reducing unit is a rotating body that contacts and rotates with the sheet when the moving member moves from the second position to the third position. apparatus.   The sheet conveying apparatus according to claim 3, wherein the rotating body is a cylindrical member that is rotatably supported at a tip of the contact portion.   The rotating body is provided at the tip of the contact portion at an angle that is parallel to the sheet surface when the moving member moves from the second position to the third position. The sheet conveying apparatus according to claim 4. The rotating body has a shaft hole;
The contact portion has a shaft through which the shaft hole of the rotating body is inserted,
The rotating body changes its direction so as to be parallel to the sheet surface with the axial center of the shaft as a fulcrum when the moving member moves from the second position to the third position. The sheet conveying apparatus according to claim 4 or 5.   The sheet conveying apparatus according to claim 6, wherein a tapered surface is formed on an inner wall surface of the shaft hole so as to increase in diameter from the center to the end in the axial direction.   The sheet conveying apparatus according to claim 2, wherein the friction reducing unit is a fitted member formed of a material having a lower friction coefficient than the material of the moving member. The main body has an axial direction inclined with respect to a normal direction of a sheet surface conveyed along the conveyance path, and is further downstream in a moving direction of the sheet than a portion far from the conveyance path A shaft portion that is inclined as shown in FIG.
The sheet conveyance according to any one of claims 1 to 8, wherein the support unit supports the moving member so as to be movable in the transverse direction and the sheet conveyance direction with the shaft portion as a fulcrum. apparatus.   An image forming apparatus comprising: an image forming unit; and the sheet conveying device according to claim 1 that conveys a sheet to the image forming unit.   An image reading apparatus comprising: an image reading unit; and the sheet conveying device according to claim 1 for conveying a sheet to the image reading unit.

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