Sheet detection device and image forming apparatus

Abstract

To reduce operation sound in sheet detection.SOLUTION: A sheet detection device includes a rotating member that has a rotating shaft and is in a standby position when sheets are not transported, and rotates in a first direction from the standby position around the rotating shaft when it comes into contact with the transported sheets, a detecting part that detects the rotation of the rotating member, a support member that rotatably supports the rotating shaft, an energizing member that energizes the rotating member in a second direction opposite to the first direction, a restricting part that restricts the rotation of the rotating member in the second direction beyond the standby position after the sheets have passed the rotating member, the direction of a first force acting on the rotating shaft by the energizing member when the rotating member is in the standby position and the direction of a second force that the rotating member receives from the restricting part when the rotating member abuts on the restricting part and stops the rotation in the second direction are approximately the same direction.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a sheet detection device that detects a sheet, and an image forming apparatus that forms an image on a sheet. [Background technology]

[0002] Conventionally, in image forming devices such as copiers, printers, and facsimiles, a sheet detection device (medium detection device) is used to detect whether a sheet such as printing paper used as a recording medium has passed a predetermined position on a conveyance path and the timing of this passage. Based on the detection results of the sheet detection device, the image forming device monitors the sheet conveyance state within the device, detects conveyance delays, multiple feeds, jams, etc., and controls the image forming operation.

[0003] A known sheet detection device is one that combines a rotating member (also called a lever member or flag member) that rotates by contacting a sheet with an optical sensor such as a photointerrupter that detects the rotation of the rotating member. Patent Document 1 describes a medium detection device that has a sensor lever that rotates by contacting the leading edge of a recording medium being conveyed, and an optical sensor that switches between a light-transmitting state and a light-blocking state by the rotation of the sensor lever. According to the above document, a spring is provided that biases the sensor lever in a predetermined rotation direction, and after the recording medium has passed, the biasing force of the spring returns the sensor lever to a standby position, and the sensor lever is held in the standby position by abutting against a stopper. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-25568 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the structure described in the above document, the direction of the force that the spring exerts on the sensor lever is different from the direction of the force that the stopper exerts on the sensor lever when it returns to the standby position. This causes vibration due to play between the pivot shaft and the bearing of the sensor lever when the sensor lever returns to the standby position, which is one of the reasons why the operating noise of the sensor lever becomes louder.

[0006] SUMMARY OF THE PRESENT DISCLOSURE In view of the above, an object of the present invention is to provide a sheet detection device and an image forming apparatus capable of reducing the operating noise associated with sheet detection. [Means for solving the problem]

[0007] One aspect of the present invention is a sheet detection device comprising: a rotating member having a rotating shaft, which is in a standby position when a sheet is not being transported, and which rotates from the standby position in a first direction around the rotating shaft when it comes into contact with a transported sheet; a detection unit that detects the rotation of the rotating member; a support member that rotatably supports the rotating shaft; a biasing member that biases the rotating member in a second direction opposite to the first direction; and a regulating unit that regulates the rotating member from rotating in the second direction beyond the standby position after the sheet has passed through the rotating member, wherein the direction of a first force acting on the rotating shaft by the biasing member when the rotating member is in the standby position and the direction of a second force that the rotating member receives from the regulating unit when the rotating member abuts against the regulating unit and stops rotating in the second direction are approximately the same.

[0008] Another aspect of the present invention is a conveying device comprising: a rotating member having a rotation shaft, which is in a standby position when a sheet is not being conveyed, and which rotates from the standby position in a first direction about the rotation shaft when the rotating member abuts against a conveyed sheet; a detection unit that detects the rotation of the rotating member; a support member that rotatably supports the rotation shaft; a biasing member that biases the rotating member in a second direction opposite to the first direction; and a regulating unit that regulates the rotating member from rotating in the second direction beyond the standby position after the sheet has passed the rotating member; wherein, when viewed in the direction of the rotation axis of the rotating member, an angle between a direction of a first force acting on the rotating shaft by the biasing member when the rotating member is in the standby position and a direction of a second force that the rotating member receives from the regulating unit when the rotating member abuts against the regulating unit to stop rotating in the second direction is 20 degrees or less. the law of nature , the biasing member is a first biasing member, and the support member has a first bearing portion supporting one end of the rotation shaft in a rotation axis direction of the rotation member and a second bearing portion supporting the other end of the rotation shaft, the first biasing member is provided at the one end of the rotation shaft, the second biasing member is provided at the other end of the rotation shaft, the rotation member has a first abutment portion abutting against the seat and a second abutment portion abutting against the regulating portion, the first abutment portion and the second abutment portion are disposed on the same side as the first biasing member in the rotation axis direction of the rotation member, and the biasing force of the first biasing member is greater than the biasing force of the second biasing member; The sheet detection device is characterized in that Effect of the Invention

[0009] According to the present invention, it is possible to reduce the operation noise caused by sheet detection. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of a sheet feeding device according to a first embodiment. [Diagram 2] FIG. 2 is a schematic diagram illustrating a cross-sectional configuration of the sheet feeding device according to the first embodiment. [Diagram 3] FIG. 2 is a perspective view of a sheet sensor unit according to the first embodiment. [Figure 4] 5A and 5B are diagrams illustrating the operation of the sensor lever according to the first embodiment. [Diagram 5] 5A to 5C are diagrams illustrating the direction of a force acting on the sensor lever according to the first embodiment. [Figure 6] 11 is a graph showing the relationship between the angle between the direction of the force applied from the return spring and the direction of the force applied from the stopper during return, and the noise level of the sensor lever returning sound. [Figure 7] 5A to 5C are diagrams for explaining the direction of a force acting on a sensor lever according to a comparative example. [Figure 8] FIG. 11 is a perspective view of a sheet sensor unit according to a second embodiment. [Figure 9] 1 is a schematic diagram of an image forming apparatus according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings.

[0012] (Image forming device) 9 is a schematic diagram showing a cross-sectional configuration of an image forming apparatus 200 according to an embodiment of the present disclosure. The image forming apparatus 200 is an electrophotographic printer of an intermediate transfer type that forms (records) an image on a sheet S, which is a recording medium, based on image information input from an external device. As the recording medium, various sheets of different sizes and materials can be used, such as paper such as plain paper and thick paper, sheet materials with surface treatments such as plastic film, cloth, and coated paper, and sheet materials with special shapes such as envelopes and index paper.

[0013] The image forming apparatus 200 includes an image forming section 19, a fixing section 40, a cassette feeding section 10, a multipurpose feeding section (also called a manual feeding section) 100, and a discharge section 50. The image forming section 19 has a tandem type intermediate transfer system configuration including four process cartridges 20 for creating toner images of each color of yellow, magenta, cyan, and black, and an intermediate transfer unit 30. Each process cartridge 20 has a photosensitive drum 21 as an image carrier (electrophotographic photosensitive member), a charger 22, and a developing device 24, and an exposure unit 23 is disposed below the four process cartridges 20. When the image forming apparatus 200 performs an image forming operation, the photosensitive drum 21 rotates, and the charger 22 uniformly charges the surface of the photosensitive drum 21. The exposure unit 23 irradiates light modulated based on image information to expose the photosensitive drum 21, and writes an electrostatic latent image on the surface of the photosensitive drum 21. The developing unit 24 develops the electrostatic latent image carried on the photosensitive drum 21 into a toner image using a developer containing charged toner.

[0014] The intermediate transfer unit 30 has an intermediate transfer belt 31 as an intermediate transfer body. The toner images of each color formed on the photosensitive drum 21 in each process cartridge 20 are primarily transferred to the intermediate transfer belt 31 by the primary transfer roller 26 facing the photosensitive drum 21 with the intermediate transfer belt 31 sandwiched therebetween. At this time, the toner images of each color are multi-transferred so as to be superimposed on each other, thereby forming a full-color image on the surface of the intermediate transfer belt 31. The full-color image carried on the intermediate transfer belt 31 is conveyed toward a secondary transfer portion by the rotation of the intermediate transfer belt 31. The secondary transfer portion is a nip portion formed between a secondary transfer roller 33 in contact with the outer circumferential surface of the intermediate transfer belt 31 and an opposing roller 32 facing the secondary transfer roller 33 with the intermediate transfer belt 31 sandwiched therebetween.

[0015] In parallel with the above image formation process, sheets S are fed one by one from the cassette feeding unit 10 or the multipurpose feeding unit 100. A transport path a in Fig. 1 shows an example of a path along which the sheet S fed from the multipurpose feeding unit 100 undergoes image formation and is discharged.

[0016] The multipurpose feeding section 100 feeds the sheets S set on a tray 105 serving as a sheet supporting section one by one. That is, the sheet S is fed from the tray 105 by a pickup roller 101, and then separated into a single sheet by a feeding roller 102 and a separation roller 103. The sheet S passes through a sheet sensor section 120 and is conveyed further downstream. The configuration of the sheet sensor section 120 will be described in detail later. The sheet S is then conveyed to a registration roller pair 14 via a conveying roller pair 13.

[0017] The leading edge of the sheet S is abutted against the nip portion of the registration roller pair 14, which is in a stopped state. Then, the transport roller pair 13, which is further upstream, pushes the sheet S, causing a bend (hereinafter referred to as a loop) to form in the sheet S between the registration roller pair 14 and the transport roller pair 13. As the loop of the sheet S is formed, the skew of the sheet S is corrected so that the leading edge of the sheet S is aligned with the nip portion. Thereafter, the registration roller pair 14 transports the sheet S at a timing synchronized with the image formation process by the image forming unit 19.

[0018] An image formed on the intermediate transfer belt 31 in the image forming section 19 is secondarily transferred to the sheet S conveyed to the secondary transfer section by the pair of registration rollers 14 in the secondary transfer section. The sheet S that has passed through the secondary transfer section is conveyed to the fixing section 40. The fixing section 40 has a fixing roller 41, a pressure roller that is in pressure contact with the fixing roller 41, and a heating means (e.g., a halogen lamp) that heats the image on the sheet S through the fixing roller 41, and heats and pressurizes the image while conveying the sheet S. This melts the toner, which then becomes fixed, thereby obtaining an image fixed to the sheet S. The sheet S that has passed through the fixing section is conveyed to the discharge section 50, discharged from the device main body 201 by the pair of discharge rollers 15, and stacked on a stacking table 51 provided on the upper part of the device main body 201.

[0019] When a sheet is fed from the cassette feeding section 10, the sheets stored in the cassette 11 are fed one by one by the feeding roller 12, and are further conveyed by the conveying roller pair 13. After that, an image is formed on the sheet S in the same process as that on the sheet S fed from the multipurpose feeding section 100, and the sheet S is discharged from the apparatus body 201 and stacked on the stacking table 51.

[0020] 1 of the image forming apparatus 200 is configured as a cover unit 70 that can be opened and closed relative to the apparatus body 201. The cover unit 70 can be separated from the apparatus body 201 at a boundary 70b shown by a dotted line by an opening and closing structure such as a hinge. This opens at least a part of the conveying path that constitutes the conveying path a, making it easy to process a sheet that is jammed inside the image forming apparatus 200.

[0021] In the above description, the image forming unit 19 is an example of an image forming means, and a direct transfer type electrophotographic unit, or an inkjet type or offset printing type image forming unit may also be used.

[0022] (Sheet feeding device) As an example of a sheet feeding device to which the sheet sensor unit 120 according to this embodiment can be applied, the configuration of a multipurpose feeding unit 100 will be described with reference to Figs. 1 and 2. Fig. 1 is a perspective view of the multipurpose feeding unit 100, and Fig. 2 is a cross-sectional view taken along the cross section indicated by arrow A in Fig. 1. Fig. 1 is a perspective view of the multipurpose feeding unit 100 without the tray 105, as viewed from below (see arrow I in Fig. 2).

[0023] 1 and 2, the multipurpose feeding unit 100 includes a pickup roller 101, a feeding roller 102, a separation roller 103, a lifting plate 106, a roller holder 107, a torque limiter 104, a tray 105, and the like. The pickup roller 101 is rotatably supported by a roller shaft 101A held by the lifting plate 106. The lifting plate 106 can swing substantially vertically around a roller shaft 102A supporting the feeding roller 102, and is biased downward by a biasing force P of a pressure spring 113 supported by a frame 150. The lifting plate 106 is provided with a driving gear train 116, and the rotation input to the roller shaft 102A is transmitted to the pickup roller 101 via the driving gear train 116.

[0024] The separation roller 103 is supported by a roller shaft 103A fixed to a roller holder 107 via a torque limiter 104. The roller holder 107 is supported rotatably about a shaft 107a relative to the frame of the image forming apparatus, and is biased upward by a pressure spring 112. As a result, the separation roller 103 comes into contact with the feed roller 102 with a predetermined nip pressure, forming a nip portion (separation nip) between the feed roller 102 and the separation roller 103.

[0025] Hereinafter, the direction in which the sheet S is conveyed by the feed roller 102 is referred to as the conveying direction X. Moreover, the direction perpendicular to the conveying direction X (the directions of the rotation axes of the pickup roller 101, the feed roller 102, and the separation roller 103, which are parallel to each other) is referred to as the sheet width direction Y. Moreover, the direction perpendicular to the conveying direction and the sheet width direction (the direction perpendicular to the conveying path of the sheet S in the vicinity of the downstream side of the separation nip) is referred to as the perpendicular direction Z to the conveying path.

[0026] The roller shaft 102A of the feed roller 102 extends in the sheet width direction Y, and the feed roller 102 is attached to one end of the roller shaft 102A, and a feed gear 111 is attached to the other end of the roller shaft 102A (FIG. 1). The feed gear 111 is connected to a motor serving as a drive source provided inside the image forming apparatus, and rotates by the drive force transmitted from the motor.

[0027] The lift plate 106 also extends in the sheet width direction Y, and is provided with a pressed portion 106a pressed by the cam mechanism DT at an end portion opposite to the pickup roller 101 and the feed roller 102 in the sheet width direction Y. The cam mechanism DT includes a cam 108 and a cam drive gear 110 attached to a cam shaft 108A, and an arm 109 attached to an arm shaft 109A. The cam drive gear 110 meshes with the feed gear 111 and rotates integrally with the cam 108. The arm 109 periodically presses the pressed portion 106a of the lift plate 106 by the rotation of the cam 108, and swings the lift plate 106 upward against the biasing force of the pressure spring 113, thereby lifting the pickup roller 101. When the arm 109 is not pressing the pressed portion 106 a , the lift plate 106 is urged by the pressure spring 113 to take a position where the pickup roller 101 abuts against the uppermost sheet St on the tray 105 .

[0028] When a sheet feeding operation is performed, the feeding gear 111 rotates due to the driving force supplied from the motor. Then, due to the rotation of the roller shaft 102A, the pickup roller 101 and the feeding roller 102 start to rotate in a rotation direction (counterclockwise direction CC in FIG. 2) that feeds the sheet S in the feeding direction. Then, when the arm 109 is released from the pressed portion 106a due to the rotation of the cam 108, the lifting plate 106 is rotated by a moment MCC in the counterclockwise direction in the figure that acts on the lifting plate 106 due to the biasing force of the pressure spring 113. As a result, the pickup roller 101 abuts against the uppermost sheet St and feeds it toward the feeding roller 102.

[0029] The topmost sheet St is guided by a guide 105a provided at the downstream end of the tray 105 in the conveying direction X, and reaches the separation nip. At this time, when a plurality of sheets S enter the separation nip, the topmost sheet St is conveyed in the conveying direction X by the feed roller 102, while the other sheets are prevented from moving in the conveying direction X by the frictional force received from the separation roller 103. In other words, the torque value of the torque limiter 104 is set to a value capable of overcoming the frictional force between the overlapping sheets and restricting the rotation of the separation roller 103. On the other hand, when only the topmost sheet St enters the separation nip, the torque limiter 104 slips due to the force received from the topmost sheet St by the separation roller 103, and the separation roller 103 rotates following the feed roller 102. The topmost sheet St that has passed through the separation nip is further conveyed by a pair of conveying rollers 13 (FIG. 9) provided downstream in the conveying direction X.

[0030] After the leading edge of the uppermost sheet St (the downstream end in the conveying direction X) reaches the separation nip, the arm 109 presses the pressed portion 106a of the lift plate 106 again, causing the lift plate 106 to swing upward, and the pickup roller 101 moves away from the sheet S. This prevents the sheet S below the uppermost sheet St from being continuously sent out.

[0031] The above operation is repeated by the lifting and lowering operation of the lift plate 106 being repeated by the rotation of the feeding gear 111, and the sheets S set on the tray 105 are fed one by one while being separated.

[0032] The separation roller 103 is an example of a separation member for separating sheets, and a retard roller to which a driving force is input in a direction against the rotation of the feed roller 102 via a torque limiter may be used, or a pad-shaped friction member may be used. Also, the feeding means for feeding the sheets is not limited to the pickup roller 101 and the feed roller 102, and may be, for example, a belt that is rotated by suction of air to adsorb the sheets and transport them.

[0033] 2, a sheet sensor unit 120 is provided downstream of the separation nip in the conveying direction X as a detection mechanism for detecting a sheet fed from the multipurpose feeding unit 100. The sheet sensor unit 120 has a sensor lever that rotates when it comes into contact with a sheet passing through the conveying path, and is configured so that a detection signal changes depending on the position of the sensor lever. Therefore, based on the detection signal from the sheet sensor unit 120, the control unit of the image forming apparatus can determine whether the sheet has been normally fed from the multipurpose feeding unit 100, the timing when the leading and trailing ends of the sheet have passed, and the like, and appropriately control the operation of the image forming apparatus. A specific configuration example of the sheet sensor unit 120 will be described below. EXAMPLES

[0034] The sheet sensor unit 120 according to the first embodiment will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a perspective view showing the overall configuration of the sheet sensor unit 120. Fig. 4(a, b) are cross-sectional views of the sheet sensor unit 120 taken along a cross section perpendicular to the sheet width direction Y, showing the configuration in the vicinity of the sheet contact portion 122a and the return spring 124.

[0035] 3, the sheet sensor unit 120 includes a sensor 121, a sensor lever 122, a support member 123, a return spring 124, and a stopper 125. The sensor lever 122 is a rotating member in this embodiment, and the sensor 121 is a detection unit in this embodiment that detects the rotation of the rotating member. The stopper 125 is a restriction unit in this embodiment that restricts the position of the rotating member, and the return spring 124 is a biasing member in this embodiment that biases the rotating member.

[0036] In this embodiment, each member is supported by a support member 123 serving as a holder, and the sheet sensor section 120 is configured as a unit that can be collectively attached by fixing the support member 123 to a frame or the like of the image forming apparatus. However, the configuration is not limited to this unitized configuration, and the sensor lever 122 and the sensor 121 may be individually attached.

[0037] The sensor 121 is a photointerrupter (also called a photoelectric sensor or optical sensor) having a light-emitting portion 121a that emits light and a light-receiving portion 121b that faces the light-emitting portion 121a in the sheet width direction Y and receives the light from the light-emitting portion 121a. A signal (for example, a voltage) emitted by the light-receiving portion 121b changes depending on the amount of light incident on the light-receiving portion 121b.

[0038] The sensor lever 122 has a rotation shaft 122f extending in the sheet width direction Y, and a sheet contact portion 122a, a stopper contact portion 122b, and a sensor light shielding portion 122e, each of which protrudes from the rotation shaft 122f in a direction substantially perpendicular to the sheet width direction Y. One end portion 122c (one end portion) and the other end portion 122d (the other end portion) of the rotation shaft 122f are rotatably fitted to a bearing portion 123a (first bearing portion) and a bearing portion 123b (second bearing portion) of the support member 123, respectively. That is, the sensor lever 122 is supported by the support member 123 in a state in which it can rotate about the center of the rotation shaft 122f as the rotation axis. Moreover, the rotation axis direction of the sensor lever 122 in this embodiment is the same as the sheet width direction Y.

[0039] A small amount of play (e.g., a difference of 0.2 mm in diameter) is provided between the ends 122c, 122d of the rotating shaft 122f and the bearings 123a, 123b in consideration of component tolerances, environmental fluctuations, etc. This is to allow the sensor lever 122 to rotate smoothly without excessive frictional resistance being applied to the rotating shaft 122f from the bearings 123a, 123b even if there are component tolerances or environmental fluctuations (such as differences in thermal expansion due to temperature changes).

[0040] The sheet contact portion 122a extends from the pivot shaft 122f toward the conveying path of the sheet S. The conveying path is a space through which the sheet S sent out from the separation nip passes, and is formed by, for example, a plate-shaped conveying guide extending along the conveying direction X. As shown in FIG. 4(a), when the sheet S has not yet reached the sensor lever 122, the sheet contact portion 122a protrudes into the conveying path.

[0041] Hereinafter, the position of the sensor lever 122 when the sheet S is not in contact with the sensor lever 122 as shown in FIG. 4(a) is referred to as the "standby position" of the sensor lever 122. Also, the state of the sheet sensor unit 120 when the sensor lever 122 is in the standby position is referred to as the standby state (non-detection state). When the leading edge of the sheet S conveyed along the conveying path abuts against the sheet abutting portion 122a from the upstream side in the conveying direction X, the sensor lever 122 rotates from the standby position in the counterclockwise operating direction R1 (first direction) as shown in FIG. 4(b). This causes the sheet abutting portion 122a to move upward, allowing the sheet S to pass through.

[0042] The sensor light shielding portion 122e is disposed between the light-emitting portion 121a and the light-receiving portion 121b of the sensor 121 in the sheet width direction Y, and is formed to a size capable of shielding the optical axis connecting the light-emitting portion 121a and the light-receiving portion 121b as viewed in the sheet width direction Y. The sensor light shielding portion 122e in this embodiment is in a position that does not shield the sensor 121 when the sensor lever 122 is in the standby position, and is disposed so as to shield the sensor 121 when the sensor lever 122 rotates from the standby position in the operating direction R1 by a predetermined angle or more. As a result, the amount of light incident on the light-receiving portion 121b changes depending on the position of the sensor lever 122.

[0043] A state in which the signal of the light receiving unit 121b exceeds (or falls below) a predetermined threshold value due to the sensor lever 122 rotating in the operating direction R1 is regarded as an operating state (detection state) of the sheet sensor unit 120. Note that the sensor light shielding unit 122e may be configured to shield the sensor 121 when the sensor lever 122 is in the standby position, and not to shield the sensor 121 when the sensor lever 122 rotates from the standby position in the operating direction R1 by a predetermined angle or more.

[0044] 4(a), the sheet contact portion 122a has a length that penetrates into the guide surface 129 through an opening provided in the guide surface 129 of the conveying guide on the opposite side of the conveying path from the rotating shaft 122f. This allows the sheet conveyed on the conveying path to more reliably contact the sheet contact portion 122a.

[0045] The stopper contact portion 122b extends in a direction different from the direction in which the sheet contact portion 122a extends from the rotation shaft 122f. In this embodiment, the sheet contact portion 122a extends substantially downward from the rotation shaft 122f (toward the conveying path in the vertical direction Z), while the stopper contact portion 122b extends substantially upward from the rotation shaft 122f (away from the conveying path).

[0046] The return spring 124 is a torsion coil spring attached around the rotating shaft 122f. An arm 124a, which is one end of the return spring 124, is attached to a spring hook 123c provided on the support member 123 as shown in Fig. 3. An arm 124b, which is the other end of the return spring 124, is attached to a spring hook 122g provided on the sensor lever 122 as shown in Fig. 4(a).

[0047] The return spring 124 biases the sensor lever 122 in a return direction R2 (second direction) opposite to the operating direction R1, which is the rotation direction of the sensor lever 122 when the sensor lever 122 abuts against the sheet S. Specifically, with one arm 124a of the return spring 124 held by the support member 123, the other arm 124b presses the spring hook portion 122g of the sensor lever 122 to the right in FIG. 4(a). As a result, a force moment in the return direction R2 about the rotation shaft 122f acts on the sensor lever 122, with the spring hook portion 122g serving as the point of action of the force.

[0048] The stopper 125 is provided at a position facing the tip of the stopper abutment portion 122b in the circumferential direction centered on the rotation shaft 122f. In this embodiment, the stopper 125 is arranged to abut against the stopper abutment portion 122b from the downstream side in the conveying direction X when the sensor lever 122 is in the standby position. When the sensor lever 122 is in the standby position, the stopper 125 abuts against the stopper abutment portion 122b to restrict the rotation of the sensor lever 122 in the return direction R2, thereby holding the sensor lever 122 in the standby position against the biasing force of the return spring 124. The stopper 125 may be integrally formed as a part of the support member 123, or may be a member attached to the support member 123.

[0049] In addition, the sheet contact portion 122a and the stopper contact portion 122b of the sensor lever 122 are provided near one end 122c of the rotation shaft 122f in the sheet width direction Y, and the sensor light shielding portion 122e is provided near the other end 122d of the rotation shaft 122f (FIG. 3). In other words, the sheet contact portion 122a is provided near the center of the conveyance path in the sheet width direction Y, and the sensor light shielding portion 122e is disposed further outward in the sheet width direction Y. This allows the sheet to be brought into contact with the sensor lever 122 regardless of the size of the sheet conveyed on the conveyance path, and the sheet sensor portion 120 to detect the sheet. In addition, by moving the sensor 121 away from the sheet contact portion 122a, it is possible to reduce the possibility that foreign matter such as paper powder peeled off from the sheet will adhere to the sensor 121, and the wiring length of the sensor 121 can be shortened. However, the sheet contact portion 122a, the stopper contact portion 122b, and the sensor light shielding portion 122e may be arranged close to each other to make the length of the sensor lever 122 in the sheet width direction Y shorter.

[0050] (Direction of force acting on the sensor lever) The relationship between the direction of the force acting on the sensor lever 122 according to this embodiment and the operation sound will be described with reference to FIGS. 5(a) to 5(c).

[0051] 5(a) shows a state in which the sensor lever 122 is in the standby position. As described above, in the standby state, the sensor lever 122 is biased in the return direction R2 by the return spring 124, and the sensor lever 122 is held in the standby position by the abutment of the stopper 125 with the stopper abutment portion 122b.

[0052] Here, the arm 124b on the sensor lever side of the return spring 124 applies a force f1d in the direction approximately to the right in the figure to the spring hook portion 122g of the sensor lever 122. On the other hand, the arm 124a on the support member side of the return spring 124 applies a force f1c in the direction approximately to the right in the figure to the spring hook portion 123c (see also FIG. 3) of the support member 123. Therefore, the return spring 124 receives reaction forces f1a and f1b of the forces f1c and f1d from the support member 123 and the spring hook portions 123c and 122g of the sensor lever 122. Since the coil portion of the return spring 124 is attached to the rotation shaft 122f of the sensor lever 122, a force F1 equivalent to the resultant force of these reaction forces f1a and f1b acts on the rotation shaft 122f via the coil portion.

[0053] When a conveyed sheet abuts against the sensor lever 122 in the standby position, the sensor lever 122 rotates in the operating direction R1 (see FIG. 4(b)). At this time, the biasing force of the return spring 124 is charged up. Then, when the trailing end of the sheet leaves the sensor lever 122, the sensor lever 122, released from the sheet, rotates in the return direction R2 according to the biasing force of the return spring 124.

[0054] 5(b) shows the state at the moment when the sensor lever 122, rotating in the return direction R2, reaches the standby position (hereinafter referred to as "when the sensor lever returns"). The sensor lever 122 rotates vigorously due to the biasing force of the charged-up return spring 124, so when the stopper abutment portion 122b abuts against the stopper 125, the sensor lever 122 tries to move to the left in the figure. In other words, the entire sensor lever 122 tries to rotate in the direction in which the rotation shaft 122f moves in the direction of the force f2 that the stopper abutment portion 122b receives from the stopper 125, centered on the abutment position between the stopper abutment portion 122b and the stopper 125.

[0055] This can also be expressed as follows: When the sensor lever 122 receives force f2 from the stopper 125 and stops rotating, a moment M2 is generated around the contact position between the stopper contact portion 122b and the stopper 125 due to the inertia of the sensor lever 122. The force F2 represents the force F2 when it is considered that this moment M2 is generated by a virtual force F2 acting on the rotation shaft 122f.

[0056] 5(c) is a schematic diagram showing the bearing portion 123a of the support member 123 and the end portion 122c of the rotation shaft 122f of the sensor lever 122. As described above, in the standby state, the rotation shaft 122f is pressed against the bearing portion 123a by a force F1 (first force) equivalent to the resultant force of the reaction forces f1a, f1b that the return spring 124 receives from the spring hook portions 123c, 122g of the support member 123 and the sensor lever 122. On the other hand, when the sensor lever returns, the rotation shaft 122f is pressed against the bearing portion 123a by a force F2 (second force) equivalent to the force f2 that the sensor lever 122 receives from the stopper 125.

[0057] In this embodiment, the direction of the force F1 pressing the rotating shaft 122f against the bearing portion 123a in the standby state and the direction of the force F2 pressing the rotating shaft 122f against the bearing portion 123a when the sensor lever returns are set to be substantially the same. In other words, the return spring 124 is arranged so that the directions of the first force (F1) and the second force (F2) are substantially the same.

[0058] In this embodiment, when the angle between the forces F1 and F2 is α (degrees) when viewed in the sheet width direction Y (state of Figs. 5(a) to 5(c)), α is set to 1. As a result, the position of the rotation shaft 122f in the standby state shown by the solid line in Fig. 5(c) is approximately the same as the position of the rotation shaft 122f when the sensor lever returns (dashed line). In other words, the direction in which the rotation shaft 122f is pushed against the bearing portion 123a is approximately the same between the standby state and when the sensor lever returns, so that the variation in the axial position of the rotation shaft 122f is kept extremely small.

[0059] (Comparison with comparative examples) 7(a-c) is used as a comparative example for this embodiment. This comparative example has a common configuration with the first embodiment, except that the relationship between the directions of the forces F1 and F2 acting on the rotation shaft 122f of the sensor lever 122 in the standby state and when the sensor lever returns is different from that in the first embodiment, due to a different arrangement of the return spring 124.

[0060] As shown in Fig. 7(a), a torsion coil spring is also used as the return spring 224 in this comparative example. However, the arm 224b on the sensor lever side of the return spring 224 applies a force f1d' in the substantially downward direction in the figure to the spring hook 122g' of the sensor lever 122, thereby urging the sensor lever 122 in the return direction R2. The arm 224a on the support member side of the return spring 224 applies a force f1c' in the substantially leftward direction in the figure to the spring hook 123c' of the support member 123. Therefore, in the standby state, reaction forces f1a' and f1b' of the forces f1c' and f1d' act on the return spring 224, and a force F1' equivalent to the resultant force of the reaction forces f1a' and f1b' acts on the rotation shaft 122f. The direction of this force F1' faces downstream in the transport direction X, which is different from the direction of the force F1 in the first embodiment (FIGS. 5(a) and 5(c)).

[0061] On the other hand, as shown in FIG. 7(b), the positional relationship between the sensor lever 122 and the stopper 125 is the same as in the first embodiment, so in this comparative example, the direction of the force F2' pressing the pivot shaft 122f against the bearing portion 123a when the sensor lever returns is substantially the same as in the first embodiment.

[0062] As shown in Fig. 7(c), in this comparative example, the angle α between the force F1' pressing the rotating shaft 222c against the bearing portion 123a in the standby state and the force F2' pressing the rotating shaft 222c against the bearing portion 123a when the sensor lever returns is 150 degrees. In this case, the direction in which the rotating shaft 122f is moved against the bearing portion 123a is significantly different between the standby state and when the sensor lever returns, and the positional fluctuation of the rotating shaft 122f becomes large. As a result, the amplitude of the vibration of the sensor lever 122 caused by the play between the bearing portion 123a and the rotating shaft 122f becomes large, causing the operating sound of the sensor lever 122 to become louder.

[0063] 5(c), the direction in which the rotation shaft 122f is moved relative to the bearing portion 123a is substantially the same between the standby state and when the sensor lever returns as described above, so that the fluctuation in the axial position of the rotation shaft 122f is kept extremely small. As a result, the amplitude of the vibration when the sensor lever 122 returns to the standby position is reduced, and the operating noise of the sensor lever 122 can be suppressed.

[0064] 6 shows the relationship between the angle α between the forces F1 and F2 and the noise level. As can be seen from the graph, there is a correlation in which the larger the angle α, the higher the noise level. Therefore, if the angle α is set to a predetermined angle or less (for example, 20 degrees or less, more preferably 10 degrees or less), the operating sound of the sensor lever 122 can be effectively reduced. EXAMPLES

[0065] As the second embodiment, a configuration example in which a plurality of biasing members are arranged to bias the sensor lever 122 in the return direction R2 will be described. Fig. 8 is a perspective view (corresponding to Fig. 3) of the sheet sensor unit 120 according to this embodiment. Hereinafter, elements having substantially the same configurations and functions as those in the first embodiment will be denoted by the same reference numerals as those in the first embodiment, and descriptions thereof will be omitted.

[0066] As in the first embodiment, the rotation shaft 122f of the sensor lever 122 is a member extending in the sheet width direction Y, and the return spring 124 as a first biasing member is attached to one end 122c of the rotation shaft 122f. In this configuration, the sensor lever 122 may vibrate due to play between the end 122d opposite the return spring 124 and the bearing portion 123b of the support member 123. For example, if the torsional rigidity of the sensor lever 122 made of synthetic resin is not sufficiently high or if the rotation shaft 122f is very long, the biasing force of the return spring 124 may not be sufficiently transmitted to the end 122d opposite the rotation shaft 122f.

[0067] Therefore, in this embodiment, a return spring 126 is also attached to the opposite end 122d as a second biasing member. The return spring 126 is a torsion coil spring attached around the rotating shaft 122f, and one end (arm) is supported by the support member 123 and the other end (arm) is attached to the sensor lever 122, thereby biasing the sensor lever 122 in the return direction R2. By adding the return spring 126, the end 122d of the rotating shaft 122f is brought into contact with the bearing portion 123b, thereby further reducing the operating noise of the sensor lever 122.

[0068] In this embodiment, the additional return spring 126 is used as an auxiliary, and the biasing force of the return spring 126 (biasing force in the R2 direction) is set smaller than the biasing force of the return spring 124, specifically, set to 20 to 30% of the biasing force of the return spring 124. When there is a difference in the biasing forces of the return springs 124, 126, it is preferable to increase the biasing force of the return spring 124 on the same side as the sheet contact portion 122a (first contact portion) and the stopper contact portion 122b (second contact portion). This makes it possible to effectively reduce the operating sound of the sensor lever 122.

[0069] Also in this embodiment, the return springs 124 and 126 are arranged so that the direction of the force F1 pressing the rotating shaft 122f against the bearing portion 123a in the standby state and the direction of the force F2 pressing the rotating shaft 122f against the bearing portion 123a when the sensor lever returns are substantially the same. For example, it is preferable to set the angle α between the force of the added return spring 126 pressing the end portion 122d of the rotating shaft 122f against the bearing portion 123b in the standby state and the force F2 to 20 degrees.

[0070] (Other embodiments) In the above embodiment, a configuration example in which the sheet sensor unit 120 as a sheet detection device is arranged in the sheet feeding device has been described, but the sheet detection device according to the present disclosure may be applied to other parts where sheets are transported. For example, it may be used as a sheet detection device that detects a sheet discharged in a discharge unit that discharges a sheet from an image forming device. In addition, it may be used as a sheet detection device that detects a fed sheet in an image reading device equipped with an automatic document feeder that feeds sheets as documents, not limited to an image forming device. [Explanation of symbols]

[0071] 120...sheet detection device (sheet sensor portion) / 121...detection portion (sensor portion) / 122...rotating member (sensor lever) / 122f...rotating shaft / 123...support member / 124...urging member (return spring) / 125...regulating portion (stopper)

Claims

1. a rotating member having a rotation shaft, the rotating member being in a standby position when a sheet is not being conveyed, and being rotated in a first direction from the standby position about the rotation shaft when the rotating member is brought into contact with a conveyed sheet; A detection unit that detects the rotation of the rotating member; A support member that rotatably supports the rotation shaft; a biasing member that biases the rotating member in a second direction opposite to the first direction; a restricting portion that restricts the rotating member from rotating beyond the standby position in the second direction after the sheet has passed the rotating member; having a direction of a first force acting on the rotation shaft by the biasing member when the rotation member is in the standby position and a direction of a second force that the rotation member receives from the regulating portion when the rotation member abuts against the regulating portion to stop the rotation in the second direction are substantially the same direction. A sheet detection device comprising:

2. a rotating member having a rotation shaft, the rotating member being in a standby position when a sheet is not being conveyed, and being rotated in a first direction from the standby position about the rotation shaft when the rotating member is brought into contact with a conveyed sheet; A detection unit that detects the rotation of the rotating member; A support member that rotatably supports the rotation shaft; a biasing member that biases the rotating member in a second direction opposite to the first direction; a restricting portion that restricts the rotating member from rotating beyond the standby position in the second direction after the sheet has passed the rotating member; having when viewed in a direction of a rotation axis of the rotating member, an angle between a direction of a first force acting on the rotating shaft by the biasing member when the rotating member is in the standby position and a direction of a second force received by the rotating member from the regulating portion when the rotating member abuts against the regulating portion to stop the rotation in the second direction is 20 degrees or less, The biasing member is a first biasing member, and a second biasing member is further provided to bias the rotating member in the second direction, the support member has a first bearing portion that supports one end of the rotation shaft in a rotation axis direction of the rotation member, and a second bearing portion that supports the other end of the rotation shaft, the first biasing member is provided at the one end of the rotation shaft, the second biasing member is provided at the other end of the rotation shaft, the rotating member has a first contact portion that contacts the seat and a second contact portion that contacts the regulating portion, the first contact portion and the second contact portion being disposed on the same side as the first biasing member with respect to a rotation axis direction of the rotating member, The biasing force of the first biasing member is greater than the biasing force of the second biasing member. A sheet detection device comprising:

3. When viewed in the direction of the rotation axis of the rotating member, an angle between the direction of the first force and the direction of the second force is 10 degrees or less.

3. The sheet detecting device according to claim 2, wherein the sheet detecting device detects a position of the sheet.

4. The biasing member is a torsion coil spring attached around the rotating shaft, one end of which is attached to the support member and the other end of which is attached to the rotating member.

4. The sheet detecting device according to claim 1, wherein the sheet is conveyed by a conveying member.

5. when viewed in a direction of a rotation axis of the rotating member when the rotating member is in the standby position, the regulating portion and the other end of the torsion coil spring are provided on an opposite side of the rotation axis of the rotating member from a conveying path along which the sheet is conveyed, and the one end of the torsion coil spring is provided on the same side of the rotation axis of the rotating member as the conveying path, the other end of the torsion coil spring presses the rotating member downstream in a conveying direction of the sheet in the conveying path, The one end of the torsion coil spring presses the support member downstream in the conveying direction.

5. The sheet detecting device according to claim 4.

6. The detection unit is an optical sensor that is shielded from light by a light shielding unit provided on the rotating member.

6. The sheet detecting device according to claim 1, wherein the sheet is conveyed by a conveying member.

7. A sheet detection device according to any one of claims 1 to 6, an image forming means for forming an image on the sheet; An image forming apparatus comprising:

Images