JP2016130173A - Sheet transport device - Google Patents

Abstract

An object of the present invention is to provide a sheet conveying device that is small in size, low cost, and can shorten the time from when a sheet passes until a contact member returns to a standby state. The image forming apparatus includes a pair of fixing rollers 96 (conveyance section) and a sheet detection section 143 (detection section) that detects conveyance of a sheet. The sheet detection section 143 includes an arm 11b (main body) and a contact section 11a (contact section) provided on the arm 11b so as to be able to come into contact with the sheet, and moves when the contact section 11a comes into contact with the sheet. a tension spring 13 (biasing member) that biases the contact portion 11a in a predetermined direction, and a photosensor 30 (that transmits a signal depending on the position of the contact member 11). sensor). The contact member 11 moves from the first position to the second position and then to the third position before the one sheet passes through the sheet detection unit 143. Configured to return to position. [Selection diagram] Figure 2

Description

  The present invention relates to a sheet conveying apparatus that conveys 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 unit, and the like are performed based on 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.

  Therefore, the present invention has been made in view of such a current situation, and is a small size, low cost sheet transporting apparatus that can shorten the time from when a sheet passes until the contact member returns to a standby state. The purpose is to provide.

  In the sheet conveying apparatus, the present invention includes a conveying unit that conveys a sheet, and a detecting unit that detects conveyance of the sheet, and the detecting unit is provided in the main body unit and the main body unit and can contact the sheet. A moving member that moves when the contact portion comes into contact with the sheet, a biasing member that biases the contact portion in a predetermined direction, and a position of the moving member A sensor for transmitting a signal, and the moving member has a second position and a third position from the first position until the one sheet passes through the detection section. After passing through the position, it is configured to return to the first position. The first position is a position where the contact portion protrudes into the sheet conveyance path, and the second position is the contact portion. But The third position is a position moved in the moving direction of the sheet and in a direction of retreating from the conveyance path from the first position, and the third position is a moving direction of the sheet than the second position of the contact portion. The sensor signal when the contact portion is in the first position and the sensor when the contact portion is in the second position and the third position. The contact portion starts contact with the leading edge of the sheet being conveyed by the conveying portion at the first position, and the first portion is pressed by the pressing force received from the leading edge of the sheet. The second position is moved by the urging force of the urging member from the position to the second position where the contact with the leading edge of the sheet is released. From the third position to the first position by the urging force of the urging member when the sheet passes through the detection unit and the contact with the sheet is released. It is characterized by moving.

  As in the present invention, when the pressing by the sheet is released, the contact member moves in the direction opposite to the sheet conveying direction along the sheet surface, so that the contact is made after the sheet passes at a small size and at a low cost. The time until the contact member returns to the standby state can be shortened.

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 device according to a first embodiment of the present invention. 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 showing a sheet detection unit in a modified example, in which FIG. 9A shows a state where the contact portion is positioned at the standby position, and FIG. . 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. The perspective view which shows the sheet | seat detection part provided in the sheet conveying apparatus which concerns on the 2nd Embodiment of this 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. 10 is a perspective view illustrating a sheet detection unit provided in a sheet conveying apparatus according to a third embodiment of the present invention. 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 stand-by position (1st position), (b) was the contact part located in the 2nd position. A state, (c) shows a state where the contact portion is located at the third position. FIG. 5A is a perspective view and a side view illustrating the sheet detection unit, in which FIG. 9A illustrates an operation in which the contact portion returns from the third position to the standby position, and FIG. 9B illustrates an operation in which the contact portion returns from the third position to the standby position. A state in which the subsequent sheet is in contact with the contact portion is shown. (C) shows a state where the contact portion is pushed up by the subsequent sheet. (A) is a side view showing a state in which a subsequent sheet comes into contact with the contact portion before the contact portion returns from the third position to the standby position, and (b) is a view in which the contact portion is pushed up by the subsequent sheet. The side view which shows the state which met, (c) is a side view explaining a mechanical loss. FIG. 10 is a perspective view showing a sheet detection unit provided in a sheet conveying apparatus according to a fourth embodiment of the present invention. 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 stand-by position (1st position), (b) was the contact part located in the 2nd position. Indicates the state. 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 side view illustrating an image reading apparatus including a sheet detection unit.

<First Embodiment>
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 embodiment 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 fixing roller pair 96 is provided downstream of the fixing roller pair 96 that is a conveyance unit in the sheet conveyance direction. ing. 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 (contact portion) 11a provided at an angle with 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 the present embodiment, as shown in FIG. 2B, the swing shaft 11c of the contact member 11 provided on the arm 11b is connected to the sheet conveyance path R formed by the sheet guides 98 and 99. They are arranged with a predetermined inclination θ2 with respect to the normal 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 swing 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 portion far away.

  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 embodiment, the sheet guides 98 and 99 have a linear guide shape. However, 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 unit 12 with a predetermined inclination θ2 with respect to the normal direction N of the sheet conveyance path R as described above. Further, in the present embodiment, the swing shaft 11c is supported by the support portion 12 with a predetermined inclination θ5 with respect to the sheet conveyance direction, and the sheet is conveyed along the slit-shaped sliding portion 12b. It is supported so as to be movable (slidable) along a plane orthogonal to the direction.

  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. In other words, in the present embodiment, the support member 12 supports the contact member 11 so as to be movable in the two axial directions of 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 that is an urging member is hooked. The tension spring 13 is attached so as to have a predetermined angle θ _S with respect to the normal direction N 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 the present embodiment, the photosensor 30 is disposed within the roller width of the fixing roller pair 96. However, the light-shielding portion 11d is further extended in the direction E of FIG. It can also be arranged outside the roller width of the pair 96.

  By the way, in this embodiment, 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 movement locus area in the apparatus cross-sectional direction. Is required. However, in the present embodiment, since the arm 11b extends in parallel to the width direction, the operation 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. . For this reason, the sheet detection unit 143 according to the present embodiment can be mounted on 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 according to the present embodiment will be described with reference to FIGS. 4 (a) to 5 (b). 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 the present embodiment, as shown in FIG. 2B described above, 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 embodiment, 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.

  Thus, in the present embodiment, the abutting member 11 is made to wait at the third position near the standby position (first position) in the sheet conveying 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 the present embodiment, 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 the present embodiment, a single tension spring 13 applies a force in two directions (the sheet conveying direction T and the normal direction N of the sheet conveying 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. In the present embodiment, 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 by the curve is taken into consideration. It is necessary to set θs by performing the above calculation.

  Next, the inclination angle θ2 of the swing shaft 11c of the contact member 11 in the present embodiment 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 rotational direction are compatible, FIGS. 7 (a) and 7 (b ). The vertical axis on the left side of FIG. 7A indicates the movement trajectory amount M in the sheet conveying direction of the contact member 11 of the present embodiment, and the vertical axis on the right side indicates that the contact portion 11a of the contact member 11 is the sheet. showing a component force component F _G to G direction acting when pressed by. The horizontal axis in FIG. 7A indicates the inclination angle θ2 of the swing shaft 11c of the contact member 11 of the present embodiment with respect to the normal direction N.

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 the present embodiment, the contact member 11 has a component force in order to operate the sensor smoothly without damaging the leading edge of the sheet while keeping the movement trajectory amount M as small as possible so that it can be accommodated in the apparatus body that is becoming smaller. it is necessary to as large as possible a component 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 the present embodiment 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 the retracted position with respect to the optical axis region 30a, the photosensor 30 outputs a transmission signal, and the control portion 119 maintains the state where the passage of the sheet is detected. ing.

  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 the present embodiment, when the contact portion 11a is pressed by the conveyed sheet, the contact member 11 is moved along the normal direction of the sheet conveyance direction and the sheet conveyance direction. However, the detection state is changed. 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 embodiment, the sliding portion 12b has a slit shape. However, as shown in FIG. 9, the sliding portion 12b may have a shape that does not have a slit shape and does not have one end 12b1. 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, the contact member 11 first swings from the standby position in the Z direction shown in FIG. 9 so that the shaft 11c is separated from the sliding portion 12b. That is, the contact member 11 swings in the arrow V direction as shown in FIG. After that, the shaft 11c is inclined with respect to the round hole 12a1, so that a gap between the shaft 11c and the round hole 12a1 is clogged. After the shaft 11c is locked by the side wall of the round hole 12a1, the X direction shown in FIG. Start swinging.

That is, 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 contact member 11 swings in the Z direction shown in FIG. 9 so that the shaft 11c contacts the sliding portion 12b, and swings in the Y direction shown in FIG. 9 along the sliding portion 12b. . 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 Embodiment>
Next, a second embodiment of the present invention will be described. FIG. 12 is a diagram illustrating the configuration of a sheet detection unit 142B (detection unit) provided in the sheet conveying apparatus according to the present embodiment. 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 embodiment, 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, and the swing shaft 60c is not limited thereto. The angular relationship between the moving shaft 60c and the rotating 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 the present embodiment 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 the present embodiment, 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 the 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 embodiment 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. It becomes 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 the present embodiment 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 the present embodiment, 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. As a result, the same effects as those of the first embodiment described above can be obtained.

<Third Embodiment>
Next, a third embodiment of the present invention will be described. FIG. 15 is a diagram illustrating a configuration of a sheet detection unit 143C (detection unit) provided in the sheet conveying apparatus according to the present embodiment. In FIG. 15, the same reference numerals as those in FIG. 2A described above indicate the same or corresponding parts.

In FIG. 15, reference numeral 70 denotes an abutting member, which is supported by a support portion 71 provided on the sheet guide 199 via a swing shaft 70c that is a shaft portion. A light shielding part 70d is provided at the end of the contact member 70, and the photosensor 32 is supported by the sheet guide 199 at a position corresponding to the light shielding part 70d.

  A method for detecting the contact member 70 in the present embodiment will be described with reference to FIGS. 16 (a) to 18 (c). 16A to 17C, the sheet detection unit 143C of the present embodiment is a perspective view and a cross-sectional view (FF cross-sectional view) viewed from the axial direction of the fixing roller pair 96. Is shown as a set. FIGS. 18A and 18B are cross-sectional views (DD cross-sectional views) seen from the axial direction of the fixing roller pair 96 in FIGS. 17B and 17C, respectively. In the present embodiment, unlike the first embodiment, the control unit 119 determines that a sheet is passing when the photosensor 32 is OFF, and that there is no sheet when the photosensor 32 is ON. .

  FIG. 16A shows a state (non-detection state) where the contact portion 70a is located at a standby position (first position) where the contact portion 70a contacts the sheet S. In this state, the light shielding unit 70d does not shield the photosensor 32. That is, the photo sensor 32 is ON, and the control unit 119 determines that there is no sheet.

  Thereafter, when the contact member 70 is pushed up by the conveyed sheet S, the light shielding portion 70d moves in the direction of arrow P shown in FIG. In this state, since the light shielding unit 70d is in a position retracted with respect to the optical axis region 32a, the photosensor 32 remains ON, and the control unit 119 has not yet detected the passage of the sheet. At this time, the contact portion 70a is located at the second position.

  Next, as shown in FIG. 16C, when the leading edge of the sheet S passes through the contact portion 70a of the contact member 70 and the contact member 70 moves to the side of the standby position, the light shielding portion 70d is moved to the arrow Q. It moves in the direction and enters the optical axis region 32 a of the photosensor 32. As a result, the photo sensor 32 is switched from ON to OFF, and the control unit 119 detects the passage of the leading edge of the sheet S based on a change in the signal from the photo sensor 32. At this time, the contact portion 70a is located at the third position.

  Subsequently, as shown in FIG. 17A, when the rear end of the sheet S passes through the contact member 70, the contact member 70 swings about the swing shaft 70c and returns to the standby position. Further, by the swinging of the contact member 70, the light shielding part 70 d moves in the direction of arrow K and retracts from the optical axis region 32 a of the photosensor 32. As a result, the photo sensor 32 is switched from OFF to ON, and the control unit 119 detects that the passage of the rear end of the sheet S is completed based on a change in the signal from the photo sensor 32.

  Here, as shown in FIGS. 17B and 18A, the trailing end of the sheet S passes through the contact member 70, and the subsequent sheet S1 contacts before the contact member 70 completely returns to the standby position. The state in contact with the member 70 will be described. The time from when the trailing edge of the sheet S passes through the contact member 70 until the subsequent sheet S1 contacts the contact member 70 is shorter than the time during which the light shielding unit 70d is retracted from the optical axis region 32a of the photosensor 32. Then, the photo sensor 32 is not switched from OFF to ON. Therefore, the control unit 119 does not detect that the passage of the rear end of the sheet S is completed at the timing of FIG.

  Thereafter, FIGS. 17C and 18B show a state in which the contact member 70 is pushed up by the subsequent sheet S1 conveyed. When the sheet S1 presses against the contact member 70 at a contact angle of 90 °, the sheet S1 tries to swing the contact member 70 in the direction of arrow G as shown in FIG. On the other hand, the tension spring 13 tries to swing the contact member 70 in the arrow J direction as shown in FIG. By the force applied from the sheet S1 and the tension spring 13 as described above, the contact member 70 is the direction of the resultant force of the force trying to move in the arrow G direction and the force trying to move in the arrow J direction, FIG. Swings in the direction of arrow L as shown in FIG. Accordingly, the light shielding part 70d moves in the direction of the arrow U as shown in FIG. 17C and retracts from the optical axis region 32a of the photosensor 32. As a result, the photo sensor 32 is switched from OFF to ON, and the control unit 119 detects that the passage of the rear end of the sheet S is completed based on a change in the signal from the photo sensor 32.

  As described above, in the present embodiment, after the trailing edge of the sheet S has passed, even when the contact portion 70a is pressed by the succeeding sheet S1 before returning to the standby position, the passage of the sheet S is terminated. It can be detected. In the first embodiment, the mechanical loss until the preparation for receiving the succeeding sheet S1 is completed after the trailing edge of the sheet S passes, as shown in FIG. 5B, the thickness D1 of the contact member 11, This is the sum of the distance D2 corresponding to the time required for detecting the sheet interval when the contact portion 11a moves in the J direction. As shown in FIG. 18C, the mechanical loss in the present embodiment is such that the thickness D1 of the contact member 70 in the sheet conveyance direction and the contact portion 70a move in the J direction, and the subsequent sheet S1 contacts. This is the sum of the distance D3 that moves to the position of pressing at a contact angle of 90 ° when the portion 70a is pressed.

  The thickness D1 secures a certain margin so that the output of the photosensor does not switch even when the sheet S is displaced in the normal direction N of the sheet conveyance path R in the state of FIG. It is necessary to keep. As shown in FIG. 18C, the distance D3 is a distance corresponding to the time required for the contact portion 70a to move in the J direction by the sum of the tip radius D4 of the contact portion 70a and the sheet thickness t. The distance D2 is shorter than the distance D2 shown in FIG. Therefore, in this embodiment, the mechanical loss can be reduced as compared with the first embodiment. In addition, although the contact member 70 of this embodiment was made into the form equivalent to 1st Embodiment, the form equivalent to 2nd Embodiment may be sufficient.

<Fourth embodiment>
By the way, the photo sensor used in the sheet conveying apparatus has a property of being weak against heat. When the temperature in the vicinity of the sheet guide becomes higher than the heat-resistant temperature of the photosensor due to heat generated from the fixing roller pair, the photosensor is mounted on the sheet as in the first to third embodiments described above. It cannot be arranged near the guide. FIG. 19 is a diagram illustrating the configuration of the sheet detection unit 143D provided in the sheet conveying apparatus according to the fourth embodiment of the present invention, which is a configuration that can achieve the effects of the present invention even in such a case. . In FIG. 19, the same reference numerals as those in FIG. 2A described above indicate the same or corresponding parts.

  In FIG. 19, reference numeral 280 denotes a side plate arranged perpendicular to the width direction W perpendicular to the sheet conveying direction, and rotatably supports the fixing roller 96a and the pressure roller 96b. The photo sensor 33 is disposed on the opposite side of the fixing roller pair 96 with the side plate 280 interposed therebetween, and is disposed in an environment that is protected from heat generated from the fixing roller pair 96 by the side plate 280 and has a heat resistance temperature or lower. The photosensor 33 is supported by a sensor support member 281 attached to the side plate 280.

  As described above, when the photosensor 33 is arranged on the side opposite to the fixing roller pair 96 with the side plate 280 interposed therebetween, the light shielding portion that can shield the photosensor is applied as in the first to third embodiments. If the contact member is integrated with the contact member, the contact member becomes longer in the width direction W. This is because the contact portion at one end of the contact member is disposed at the center of the roller width and the light shielding portion at the other end is disposed on the opposite side of the contact portion with the side plate 280 located outside the roller width. It is. Therefore, the movement locus of the contact member when detecting the sheet becomes large, and it becomes difficult to reduce the size of the printer body. Accordingly, the side plate 280 must be cut out in accordance with the movement of the contact member. As a result, the heat generated in the fixing nip is easily transferred to the photosensor side across the side plate, the temperature of the environment in the vicinity of the photosensor becomes high, and the heat resistance temperature of the photosensor 33 may be exceeded.

  Therefore, in the present embodiment, as shown in FIG. 19, the contact member 270 is divided into a swing member 271 and a light shielding member 272. The contact member 270 includes a contact portion 271a, an arm 271b, a swing shaft 271c, and a joint portion 271d, and the light blocking member 272 includes a light blocking portion 272a, a rotation shaft 272b, and a joint portion 272c.

  The swing member 271 includes an arm 271b disposed in parallel with the width direction W orthogonal to the sheet conveying direction, and a contact portion 271a provided at the tip of the arm 271b. The swing member 271 is supported by a support portion 273 provided on the sheet guide 299 via a swing shaft 271c that is a shaft portion.

  The light shielding member 272 includes a rotation shaft 272b extending in parallel with the width direction W orthogonal to the sheet conveyance direction, and a light shielding portion 272a provided at a position corresponding to the photosensor 33 at the tip of the rotation shaft 272b. Yes.

  The swing member 271 and the light shielding member 272 are in contact with each other through a joint 276 including joint portions 271d and 272c. A torsion spring 275 is attached to the light shielding member 272 and urges the light shielding member 272 toward the swinging member 271. Therefore, the light shielding member 272 follows the movement of the swinging member 271 and rotates around the rotation shaft 272b. That is, the movement of the swinging member 271 moving in the biaxial direction according to the conveyance of the sheet S is converted into a rotational movement of the light shielding member 272 around the rotation shaft 272b via the joint 276. Yes.

  A method for detecting the contact member 270 in the present embodiment will be described with reference to FIGS. 20 (a) to 21 (b). 20A to 21B, the sheet detection unit 143D of the present embodiment is shown in a perspective view and a sectional view (BB sectional view and CC sectional view) is shown as a set. In the present embodiment, as in the third embodiment, the control unit 119 determines that a sheet is passing when the photosensor 33 is OFF, and that there is no sheet when the photosensor 33 is ON. .

  FIG. 20A shows a state (non-detection state) where the contact portion 271a is located at a standby position where it comes into contact with the sheet S. In this state, the light shielding unit 272a does not shield the photosensor 33. That is, the photosensor 33 is ON, and the control unit 119 determines that there is no sheet.

  In this state, when the leading edge of the sheet hits the contact portion 271a and is pressed by the conveyed sheet S, as shown in FIG. 20B, the swinging member 271 has a first moving center (swinging center). It swings in the direction of arrow G about the swinging shaft 271c held at this position. By this swing, the joint portion 271d of the swing member 271 moves in the arrow G direction, but the light shielding member 272 does not rotate by the swing of the swing member 271 in the arrow G direction. This is because the contact surface of the joint portion 272c with the swinging member 271 is a surface parallel to the arrow G direction and the width direction W orthogonal to the sheet conveying direction, so the joint portion 271d of the swinging member 271 is a light shielding member. It is because it moves only on the joint part 272c of 272. Therefore, in this state, since the light shielding portion 272a is in a position retracted with respect to the optical axis region 33a, the photosensor 33 is ON, and the control portion 119 has not yet detected the passage of the sheet.

  And if the front-end | tip of the sheet | seat S passes the contact part 271a of the rocking | swiveling member 271, the press by the sheet | seat S to the contact part 271a will be cancelled | released. At this time, the contact portion 271a is located at the second position. Here, as shown in FIG. 19, the arm 271b and the support portion 273 are formed with hook shapes 271e and 273a, respectively, and the hook shapes 271e and 273a bias the swinging member 271. The tension spring 274 is hooked. Further, the sheet guide 299 is provided with an abutting rib 299b with which the arm 271b of the swing member 271 contacts.

  Thus, as shown in FIG. 21A, the swinging member 271 is moved in the direction of arrow I about the swinging shaft 271c while the tip of the contact portion 271a is in contact with the sheet S by the tension spring 274. Swing. Then, the swinging member 271 hits against the abutting rib 299b provided on the sheet guide 299 and stops. At this time, the contact portion 271a is located at the third position.

  Here, in the joint 276, the joint portion 271d of the swing member 271 tries to rotate in the direction of the arrow α about the rotation shaft 272b by pressing the joint portion 272c of the light shielding member 272 by the force received from the tension spring 274. . The force in the arrow α direction by the joint portion 271d is larger than the force by which the torsion spring 275 tries to rotate the light shielding member 272 in the −α direction. At this time, the light shielding portion 272a rotates in the α direction and enters the optical axis region 33a of the photosensor 33. As a result, the photosensor 33 is switched from ON to OFF, and the control unit 119 detects the passage of the sheet based on a change in the signal from the photosensor 33.

  Thereafter, when the rear end of the sheet S passes the swing member 271, the swing member 271 swings in the direction of arrow J about the swing shaft 271c by the tension spring 274 as shown in FIG. Then, the light shielding member 272 is rotated in the −α direction around the rotation shaft 272b by the torsion spring 275, and returns to the standby position. Further, by the rotation of the light shielding member 272, the light shielding portion 272a is also rotated in the -α direction, and is retracted from the optical axis region 33a of the photosensor 33. As a result, the photo sensor 33 is switched from OFF to ON, and the control unit 119 detects that the passage of the rear end of the sheet S is completed based on a change in the signal from the photo sensor 33.

  As described above, in the present embodiment, the photosensor 33 is disposed on the opposite side of the fixing roller pair 96 with the side plate 280 interposed therebetween, and the abutting member 270 is divided into the swing member 271 and the light shielding member 272. Turned into. As a result, the movement locus of the contact member 270 when detecting the sheet is only the movement locus of the swinging member 271 that is within the sheet width and the movement locus of the light shielding member 272 that is rotating. The movement trajectory is smaller than when the contact member is integral. This facilitates downsizing of the printer body. Further, since the rotation shaft 272b is parallel to the width direction W and is perpendicular to the side plate 280, it is sufficient to make a notch in the side plate 280 by making a hole penetrating the rotation shaft 272b.

  Therefore, unlike the case where the contact member has an integral shape, which requires a large notch in the side plate 280, the ambient temperature in the vicinity of the photosensor 33 can be easily made equal to or lower than the heat resistance temperature of the photosensor 33. As described above, this embodiment has the same effect as that of the above-described third embodiment even when the temperature in the vicinity of the sheet guide becomes higher than the heat-resistant temperature of the photosensor due to the heat generated from the fixing roller pair. Can play. Note that the technique of the present embodiment may be combined with the first to third embodiments.

  In the first to fourth 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. Absent. For example, the present invention can also be applied to an image reading apparatus 200 having an image reading unit shown in FIG. 22 that reads an image recorded on a sheet S.

  In FIG. 22, the document D set on the document tray 221 is fed by the feeding roller 222. 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 in the first to fourth 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 members 11, 60, 70, and 270 of the sheet detection unit that detects the leading edge and the trailing edge of the sheet have been described so far. However, 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.

11: Moving member (contact member) / 11a: Contact portion (contact portion) / 11b: Main body portion (arm) / 11c: Shaft portion (oscillating shaft) / 13: Biasing member (tensile spring) / 30: Sensor (photo sensor) / 96: Conveying section (fixing roller pair) / 143: Detection section (sheet detecting section) / R: Conveying path (sheet conveying path) / S: Sheet

Claims (4)

A transport unit for transporting the sheet;
A detection unit that detects conveyance of the sheet,
The detection unit includes a main body part and a contact part provided on the main body part so as to be able to contact the sheet, and a moving member that moves when the contact part comes into contact with the sheet; and the contact part. An urging member for urging in a predetermined direction; and a sensor for transmitting a signal according to the position of the moving member;
The moving member returns to the first position after the contact portion passes the second position and the third position from the first position until one sheet passes through the detection portion. Configured as
The first position is a position where the contact portion protrudes into the sheet conveyance path,
The second position is a position where the contact portion has moved in the direction of movement of the sheet and in the direction of retreating from the conveyance path from the first position.
The third position is a position where the contact portion has moved in a direction opposite to the moving direction of the sheet from the second position.
The sensor signal when the contact portion is in the first position is different from the sensor signal when the contact portion is in the second position and the third position,
The contact portion starts contact with the leading edge of the sheet conveyed by the conveying portion at the first position, and the leading edge of the sheet from the first position by a pressing force received from the leading edge of the sheet. To the second position where the contact is released, and from the second position to the third position by the urging force of the urging member, the sheet passes through the detection unit and the sheet When the contact is released, the biasing force of the biasing member moves from the third position to the first position.
A sheet conveying apparatus. The third position is the same position as the first position with respect to the movement direction of the sheet.
The sheet conveying apparatus according to claim 1. The contact portion reaches the first position from the third position only by movement in a direction orthogonal to the moving direction of the sheet.
The sheet conveying apparatus according to claim 1 or 2, wherein The main body portion of the moving member has a shaft portion whose axial direction is a direction inclined with respect to a normal direction of a surface of the sheet conveyed in the conveyance path,
The shaft portion is inclined so that a portion close to the conveyance path is on the downstream side in the moving direction of the sheet from a portion far away from the shaft.
The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is a sheet conveying apparatus.

Images