Sheet cutting apparatus and image forming apparatus

Abstract

The present invention provides a sheet cutting apparatus and an image forming apparatus that can suppress the rotation of the drive roller due to being pulled by the sheet during sheet cutting, thereby suppressing the problem of being unable to cut the sheet straight. [Solution] The sheet cutting device 2 comprises a first transport roller pair 70 that holds the sheet SH by stopping the drive roller 70A when the sheet SH is nipped, a cutter mechanism 4 having blades 411, 412 located upstream or downstream of the first transport roller pair 70 in the transport direction DT1, and the cutter mechanism 4 that cuts the sheet SH held by the first transport roller pair 70 with the blades 411, ..., a first motor M1, a first gear 75 fixed to the rotating shaft 73 and transmitting the driving force of the first motor M1 to the rotating shaft 73, and a brake mechanism 6 that contacts the side surface 75A of the first gear 75 when the sheet SH is cut by the blades 411, ... to suppress the rotation of the first gear 75.

Description

Technical Field

[0001] The present invention relates to a sheet cutting device and an image forming apparatus.

Background Art

[0002] Patent Document 1 discloses an example of a conventional sheet cutting device. This sheet cutting device includes a pair of conveyance rollers and a cutter.

[0003] As shown in FIGS. 4 to 6 thereof, the pair of conveyance rollers has a drive roller that conveys a fanfold continuous sheet in the conveyance direction, and a shaft that rotates integrally with the drive roller. The pair of conveyance rollers holds the fanfold continuous sheet by stopping the drive roller while nipping the fanfold continuous sheet.

[0004] Also, this sheet cutting device includes a rotation suppression unit. The rotation suppression unit has a stopper that is non-rotatably supported by a pressing member and is biased toward the end of the shaft by a leaf spring. The rotation suppression unit suppresses the rotation of the shaft by the stopper that abuts against the end of the shaft when cutting the fanfold continuous sheet with the cutter.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the conventional sheet cutting device described above, the diameter of the shaft is smaller than the diameter of the drive roller. As a result, the rotation suppression unit can only apply frictional force between the end of the shaft and the stopper at a position close to the rotation center of the drive roller. Therefore, this sheet cutting device has difficulty increasing the braking torque to suppress the rotation of the shaft. Consequently, this sheet cutting device may experience a problem where the drive roller is pulled and rotated by the fanfold continuous paper during cutting, making it impossible to cut the fanfold continuous paper straight.

[0007] The present invention has been made in view of the above-mentioned conventional circumstances, and aims to provide a sheet cutting apparatus and an image forming apparatus that can suppress the rotation of the drive roller due to being pulled by the sheet during sheet cutting, thereby suppressing the problem of being unable to cut the sheet straight. [Means for solving the problem]

[0008] The sheet cutting apparatus of the present invention comprises a first conveying roller pair having a drive roller for conveying a sheet in the conveying direction and a rotating shaft that rotates integrally with the drive roller, wherein the first conveying roller pair holds the sheet by stopping when the sheet is nipped, A cutter mechanism having a blade located upstream or downstream of the first transport roller pair in the transport direction, wherein the cutter mechanism cuts a sheet held by the first transport roller pair in a cutting direction perpendicular to the transport direction using the blade, A sheet cutting device equipped with, A first motor that generates driving force, A first gear fixed to the rotating shaft and transmitting the driving force of the first motor to the rotating shaft, A brake mechanism that contacts the side surface of the first gear to suppress the rotation of the first gear when the sheet is cut by the blade, It is characterized by having the following features.

[0009] In the sheet cutting apparatus of the present invention, the side surface of the first gear is larger than or equal to the circle that inscribes the bottom of the plurality of gear teeth formed on the outer circumference of the first gear. The diameter of the side surface of the first gear is larger than the diameter of the rotating shaft. Furthermore, the diameter of the side surface of the first gear is often larger than or equal to the diameter of the drive roller, and even if it is smaller than the diameter of the drive roller, it is close to the diameter of the drive roller.

[0010] This allows the braking mechanism to apply frictional force between the side of the first gear and the braking mechanism at a position far from the rotation center of the drive roller and the rotating shaft. As a result, this sheet cutting device can increase the braking torque required to suppress the rotation of the rotating shaft.

[0011] Therefore, the sheet cutting device of the present invention can suppress the rotation of the drive roller due to being pulled by the sheet during sheet cutting, and as a result, it can suppress the problem of being unable to cut the sheet straight. Furthermore, this sheet cutting device achieves a reduction in the number of parts by having the first gear combine the function of transmitting driving force to the rotating shaft and the function of receiving braking torque from the brake mechanism. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a perspective view of the image forming apparatus of Example 1. [Figure 2] Figure 2 is a schematic cross-sectional view of the image forming apparatus of Example 1. [Figure 3] Figure 3 is a partial top view mainly showing the cutter mechanism and joint cover. [Figure 4] Figure 4 is a schematic cross-sectional view of a magnified portion of the main part of Figure 2. [Figure 5] Figure 5 is a schematic partial side view of the image forming apparatus of Embodiment 1, showing the first motor, the drive force transmission mechanism, and the second motor. [Figure 6] Figure 6 is a front view showing the cutter mechanism, the second motor, the first drive train, and the second drive train. [Figure 7]FIG. 7 is a partial perspective view showing a pre-cut cover, a pre-cut guide, a first pair of conveying rollers, a cutter mechanism, a brake mechanism, and a second motor. [Figure 8] FIG. 8 is a partial perspective view mainly showing a second motor, a first drive train, a second drive train, a brake mechanism, a first gear, and a rotating shaft. [Figure 9] FIG. 9 is an exploded perspective view showing a drive roller, a rotating shaft, a first gear, a second gear, a cam, a cam follower, and a compression coil spring. [Figure 10] FIG. 10 is an exploded perspective view showing a drive roller, a rotating shaft, a first gear, a second gear, a cam, a cam follower, and a compression coil spring. [Figure 11] FIG. 11 is a partial schematic view showing a state in which the brake mechanism abuts against the side surface of the first gear to suppress the rotation of the first gear when the sheet is cut by the fixed blade and the moving blade. [Figure 12] FIG. 12 is a partial schematic view showing a state in which the cam at the initial position moves the cam follower to the separated position. [Figure 13] FIG. 13 is a partial schematic view showing a state in which the cam rotates from the initial position and moves the cam follower to the abutting position. [Figure 14] FIG. 14 is a partial schematic view showing a state in which the cam further rotates from the initial position and maintains the cam follower at the abutting position. [Figure 15] FIG. 15 is a partial schematic view showing a brake mechanism according to the sheet cutting apparatus of Example 2.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, Examples 1 and 2 embodying the present invention will be described with reference to the drawings.

[0014] (Example 1) As shown in FIG. 1, the image forming apparatus 1 of Example 1 is an example of a specific aspect of the image forming apparatus of the present invention. As shown in FIG. 2, the image forming apparatus 1 is a multifunction device including an image forming unit 3 that forms an image on a sheet SH by an electrophotographic method, a fixing device 7, and an image reading unit 35 that reads an image of a document.

[0015] The image forming apparatus 1 is equipped with the sheet cutting apparatus 2 of Example 1. The sheet cutting apparatus 2 is an example of a specific embodiment of the sheet cutting apparatus of the present invention. The image forming apparatus 1 will be described first, followed by the sheet cutting apparatus 2.

[0016] In Figure 1, the side with the operation panel 37 of the image forming apparatus 1 is the front. The left-right direction of the image forming apparatus 1 is perpendicular to the front-back direction and extends horizontally. The side that is to the left when facing the operation panel 37 is defined as the left. All directions shown in Figures 2 and onward correspond to the directions shown in Figure 1.

[0017] <Overall configuration of the image forming apparatus> As shown in Figures 1 and 2, the image forming apparatus 1 comprises a first housing 10, a joint cover 50, and a second housing 30.

[0018] The first housing 10 is roughly box-shaped. The second housing 30 is a flattened, roughly box-shaped body, with a significantly smaller vertical length than the first housing 10. The second housing 30 is located above the first housing 10. The joint cover 50 supports the second housing 30 from below, above the first housing 10.

[0019] As shown in Figure 2, the first housing 10 houses a sheet cassette 10C at its lower part. The sheet cassette 10C supports the sheets SH to be image-formed in a stacked state. The sheets SH are paper, OHP sheets, etc. Above the sheet cassette 10C, the first housing 10 houses the image forming unit 3 and the fuser 7.

[0020] As shown in Figures 1 and 2, the joint cover 50 has a discharge tray 9. The discharge tray 9 is located in the center of the upper surface of the first housing 10 in the left-right direction. The discharge tray 9 extends horizontally backward from the front end of the upper surface of the first housing 10, then bends and slopes downward backward.

[0021] The second housing 30 and the joint cover 50 have a discharge space AD1. The discharge space AD1 is partitioned between the first housing 10 and the second housing 30.

[0022] The discharge tray 9 defines the lower part of the discharge space AD1. The sheet SH, which has had an image formed after passing through the image forming unit 3 and the fuser 7, is discharged into the discharge space AD1. The discharge tray 9 supports the sheet SH that has been discharged into the discharge space AD1.

[0023] As shown in Figures 1 and 3, the joint cover 50 has support portions 57L and 57R. Support portion 57L is a portion of the joint cover 50 that is located to the left of the discharge tray 9 and protrudes upward. Support portion 57R is a portion of the joint cover 50 that is located to the right of the discharge tray 9 and protrudes upward.

[0024] The joint cover 50 has inner wall surfaces 58 and 59. Inner wall surface 58 is the right side of the support portion 57L. Inner wall surface 58 defines the left side of the discharge space AD1. Inner wall surface 59 is the left side of the support portion 57R. Inner wall surface 59 defines the right side of the discharge space AD1.

[0025] The support portions 57L and 57R of the joint cover 50 support the second housing 30 above the first housing 10 by their respective upper ends.

[0026] As shown in Figure 2, the second housing 30 houses the image reading unit 35. The image reading unit 35 is located above and away from the output tray 9. The image reading unit 35 has a well-known configuration, so its explanation will be brief, but it reads the image of a document placed on the upper surface of the second housing 30 using a reading sensor (not shown). The document is a book, a sheet, etc.

[0027] Furthermore, the second housing 30 includes a document cover 40 whose top surface can be opened and closed, and an automatic document transport mechanism 45 housed in the document cover 40.

[0028] As shown in Figure 1, the document cover 40 has a supply tray 41 and an output tray 42 located on its right side. The supply tray 41 is positioned above the output tray 42.

[0029] The automatic document transport mechanism 45 has a well-known configuration, so its explanation will be brief, but it transports a sheet-like document supported on the supply tray 41 to a position where it can be read by a reading sensor (not shown) of the image reading unit 35, and then discharges it into the output tray 42. The reading sensor (not shown) reads the image of the transported document.

[0030] The control panel 37 protrudes forward from a portion located to the left of the discharge space AD1 on the front end surface of the second housing 30. The control panel 37 is supported from below by the front end of the support portion 57L of the joint cover 50.

[0031] The control panel 37 has an operating surface that receives input from the user's finger, and a display unit such as an LCD located below the operating surface. The control panel 37 displays information indicating the operating status and settings of the image forming apparatus 1, and also provides notifications by displaying error messages, etc.

[0032] As shown in Figure 2, the image forming unit 3 includes a developing device 3A, a photoreceptor 5, and a scanner unit 8. The image forming apparatus 1 includes a feed roller 21, a separation roller 22, a separation pad 22A, a transport roller pair 23, a resist roller pair 24, and a post-fixing transport roller pair 25, all housed together in the first housing 10 along with the image forming unit 3 and the fuser 7.

[0033] The front of the first housing 10 is located a feed roller 21, a separation roller 22, a separation pad 22A, and a pair of transport rollers 23. The rear of the first housing 10 is located a pair of post-fixing transport rollers 25.

[0034] A transport path P1 is provided inside the first housing 10. The transport path P1 is a path that starts from the front end of the sheet cassette 10C, makes an upward U-turn, passes through the feed roller 21, separation roller 22, separation pad 22A and transport roller pair 23, then proceeds backward almost horizontally, passing through the resist roller pair 24, photoreceptor 5 and fuser 7, and finally reaches the transport roller pair 25 after fixing.

[0035] The feed roller 21 is located at the uppermost end of the transport path P1. The separation roller 22 and separation pad 22A are located downstream of the feed roller 21 in the transport path P1. The transport roller pair 23 is located downstream of the separation roller 22 and separation pad 22A in the transport path P1, and is situated in the middle of the upward U-turn portion of the transport path P1.

[0036] The resist roller pair 24 is located downstream of the transport roller pair 23 in the transport path P1, and upstream of the photoreceptor 5 in the transport path P1, and is positioned in the middle of the portion of the transport path P1 that moves substantially horizontally in the backward direction.

[0037] The feed roller 21 feeds the sheet SH supported by the sheet cassette 10C toward the photoreceptor 5. The separation roller 22 and separation pad 22A separate the sheets SH sent toward the transport path P1 by the feed roller 21 into individual sheets if there are multiple sheets. Then, the transport roller pair 23 and the resist roller pair 24 transport the sheets SH toward the photoreceptor 5.

[0038] The developing device 3A includes a toner storage chamber 3D for storing toner and a developing roller 3B from which toner is supplied from the toner storage chamber 3D. The photoreceptor 5 is located behind and below the developing roller 3B and is in contact with the developing roller 3B.

[0039] The photoreceptor 5 is a cylindrical rotating body with a rotation axis extending in the left-right direction. A positively charged photosensitive layer is formed on the surface of the photoreceptor 5, corresponding to a positively charged toner. In some cases, a negatively charged photosensitive layer may be formed on the surface of the photoreceptor 5; in this case, a negatively charged toner is used.

[0040] The photoreceptor 5 can contact the sheet SH from above as it is transported along the portion of the transport path P1 that moves approximately horizontally in the backward direction. Below the photoreceptor 5 is the transfer roller 5A. The transfer roller 5A faces the photoreceptor 5 from below, across the transport path P1.

[0041] The developing device 3A further includes a charger 3E. The charger 3E faces the photoreceptor 5 from the rear. The charger 3E is a well-known scorotron charger.

[0042] The scanner unit 8 is located above the developing device 3A and the photoreceptor 5. The scanner unit 8 has a well-known configuration including a laser light source, a polygon mirror, an fθ lens, and a reflector. The scanner unit 8 irradiates the surface of the photoreceptor 5 with a laser beam.

[0043] The surface of the photoreceptor 5 is uniformly positively charged by the charger 3E as it rotates, and then exposed by high-speed scanning of a laser beam irradiated from the scanner unit 8. As a result, an electrostatic latent image corresponding to the image to be formed on the sheet SH is formed on the surface of the photoreceptor 5.

[0044] Then, the developing roller 3B supplies toner to the photoreceptor 5 in response to the electrostatic latent image formed on the surface of the photoreceptor 5. As a result, a toner image is supported on the surface of the photoreceptor 5. The photoreceptor 5 then transfers this toner image to the upward-facing surface of the sheet SH as it passes through the nip position between the photoreceptor 5 and the transfer roller 5A.

[0045] The fuser unit 7 is located behind the photoreceptor unit 5 and in front of the post-fixing transport roller pair 25. The fuser unit 7 includes a heating element 7A located above the transport path P1, and a pressure roller 7B facing the heating element 7A from below, across the transport path P1.

[0046] The heating element 7A includes an endless belt, a guide member that supports the endless belt so that it can circulate from its inner circumference, and a heater that heats the endless belt from its inner circumference. The heating element 7A may also be composed of a heating roller having a heater such as a halogen heater, or it may be composed of a heater, a nip plate that receives radiant heat from the heater, and a heating belt that rotates around the nip plate.

[0047] The fuser unit 7 heats and pressurizes the sheet SH onto which the toner image has been transferred using the heating element 7A and the pressure roller 7B, thereby thermally fixing the toner image onto the sheet SH. After fixing, the transport roller pair 25 transports the sheet SH that has passed through the fuser unit 7 upwards and backwards.

[0048] The image forming apparatus 1 includes a control unit C1, a pre-cash register sheet sensor S1, a post-cash register sheet sensor S2, and a post-fixing sheet sensor S3.

[0049] The first enclosure 10 houses the control unit C1. The control unit C1 is an electronic circuit unit comprising a CPU (not shown), an interface circuit, and a memory unit. The control unit C1 performs overall control of each part of the image forming apparatus 1.

[0050] The control unit C1 is electrically connected to the pre-cash register seat sensor S1, the post-cash register seat sensor S2, and the post-fixing seat sensor S3.

[0051] The pre-register sheet sensor S1 is located directly in front of the register roller pair 24 in the transport path P1 and detects the passage of the sheet SH and transmits the information to the control unit C1. Based on the detection result of the pre-register sheet sensor S1, the control unit C1 performs control such as correcting the skew of the sheet SH as it approaches the register roller pair 24.

[0052] The post-register sheet sensor S2 is located immediately after the register roller pair 24 in the transport path P1 and detects the passage of the sheet SH and transmits the information to the control unit C1. Based on the detection result of the post-register sheet sensor S2, the control unit C1 controls the timing of the image forming operation by the image forming unit 3 and the fuser 7.

[0053] The post-fixed sheet sensor S3 is located between the fuser 7 and the post-fixed transport roller pair 25 in the transport path P1, and detects the passage of the sheet SH and transmits the information to the control unit C1. Based on the detection result of the post-fixed sheet sensor S3, the control unit C1 controls the timing of several operations performed from the time the sheet SH passes through the fuser 7 until it is discharged into the discharge tray 9.

[0054] As the pre-cash register sheet sensor S1, the post-cash register sheet sensor S2, and the post-fixing sheet sensor S3, sensors having actuators that oscillate when the sheet SH comes into contact with them, or light-reflecting sensors, etc., can be used.

[0055] The image forming apparatus 1 is equipped with a flapper 26. The flapper 26 is located above the post-fixing transport roller pair 25 and is connected to a solenoid (not shown). The control unit C1 controls the solenoid (not shown) to swing the flapper 26 between the position shown by the solid line in Figure 2 and the position shown by the dashed line in Figure 2.

[0056] The image forming apparatus 1 is equipped with a first discharge path PD1 and a second discharge path PD2. The upstream ends of the first discharge path PD1 and the second discharge path PD2 are connected to the downstream end of the transport path P1.

[0057] The first discharge route PD1 is the discharge route that is effective when the flapper 26 is in the position shown by the dashed line in Figure 2. The second discharge route PD2 is the discharge route that is effective when the flapper 26 is in the position shown by the solid line in Figure 2.

[0058] The first discharge path PD1 guides the sheet SH, which has passed through the image forming unit 3 and the fuser 7, along the flapper 26 located at the position shown by the dashed line in Figure 2, and discharges the sheet SH into the discharge space AD1 with the transport direction DT1 facing approximately horizontally forward.

[0059] The second discharge path PD2 guides the sheet SH, which has passed through the image forming unit 3 and the fuser 7, upward along the flapper 26 located at the position shown by the solid line in Figure 2. Above the flapper 26, the transport direction DT1 of the sheet SH is made approximately horizontal and forward, and guided to the cutter mechanism 4, which will be described later. The sheet SH that has passed through the cutter mechanism 4 is then discharged into the discharge space AD1. The second discharge path PD2 discharges the sheet SH into the discharge space AD1 at a position above the first discharge path PD1 and downstream of the first discharge path PD1 in the transport direction DT1.

[0060] Furthermore, the transport direction DT1 of the sheet SH when it passes through the image forming unit 3 is approximately horizontal and backward.

[0061] The image forming apparatus 1 includes a third transport roller pair 28 located at the downstream end of the first discharge path PD1. The third transport roller pair 28 is located above the upstream end 9U in the transport direction DT1 of the discharge tray 9. The third transport roller pair 28 has a drive roller 28A and a driven roller 28B. The driven roller 28B is located below the drive roller 28A and faces the drive roller 28A.

[0062] The third transport roller pair 28, driven by the drive roller 28A and driven roller 28B, transports the sheet SH along the first discharge path PD1. The third transport roller pair 28 discharges the sheet SH, which has passed through the image forming unit 3 and the fuser 7 but not through the cutter mechanism 4, to the discharge tray 9. The discharge tray 9 supports the sheet SH that is discharged without being cut.

[0063] The image forming apparatus 1 includes a pre-cutting cover 80 and a first transport roller pair 70 located in the second discharge path PD2. The pre-cutting cover 80 and the first transport roller pair 70 are positioned vertically above the flapper 26.

[0064] The first conveyor roller pair 70 has a drive roller 70A and a driven roller 70B. The pre-cutting cover 80 rotatably supports the drive roller 70A and the driven roller 70B. The driven roller 70B is located above the drive roller 70A and faces the drive roller 70A. The first conveyor roller pair 70, with the drive roller 70A and the driven roller 70B, conveys the sheet SH along the second discharge path PD2 in the conveying direction DT1.

[0065] As shown in Figures 2 and 4, the image forming apparatus 1 includes a pre-cutting guide 300, a cutter mechanism 4, a first guide 100, a second guide 200, a sheet sensor S4, and a second transport roller pair 29.

[0066] The pre-cutting guide 300, cutter mechanism 4, first guide 100, second guide 200, sheet sensor S4, and second transport roller pair 29 are positioned downstream of the first transport roller pair 70 in the transport direction DT1 in the second discharge path PD2, and are also positioned along the portion of the transport direction DT1 in the second discharge path PD2 that is substantially horizontal and forward.

[0067] As shown in Figure 2, the second transport roller pair 29 is located below the image reading unit 35 and above the third transport roller pair 28. The second transport roller pair 29 is located downstream in the transport direction DT1 from the upstream end 9U of the discharge tray 9.

[0068] As shown in Figure 4, the second transport roller pair 29 is located downstream of the first transport roller pair 70 in the transport direction DT1, and is located on the opposite side of the cutter mechanism 4 from the first transport roller pair 70. Specifically, the fixed blade 411 and the movable blade 412 of the cutter mechanism 4, which will be described later, are located downstream of the first transport roller pair 70 in the transport direction DT1, and upstream of the second transport roller pair 29 in the transport direction DT1.

[0069] The second conveyor roller pair 29 has a drive roller 29A and a driven roller 29B. The driven roller 29B is located below the drive roller 29A and faces the drive roller 29A.

[0070] As shown in Figure 2, the second transport roller pair 29, driven by the drive roller 29A and driven roller 29B, transports the sheet SH along the second discharge path PD2. The second transport roller pair 29 passes through the image forming unit 3 and the fuser 7, and the cutter mechanism 4 cuts the sheet SH (SH1) in half along the transport direction DT1, and discharges it to the discharge tray 9. The discharge tray 9 supports the sheet SH (SH1) that has been cut in half.

[0071] In other words, the discharge tray 9 supports the sheets SH discharged from the first discharge path PD1 and the second discharge path PD2. The third transport roller pair 28 and the second transport roller pair 29 have the same direction for discharging the sheets SH toward the discharge tray 9.

[0072] As shown in Figures 3 and 5, the image forming apparatus 1 is equipped with a first motor M1. The first motor M1 generates driving force to drive the drive roller 70A of the first transport roller pair 70, the drive roller 29A of the second transport roller pair 29, and the drive roller 28A of the third transport roller pair 28. In this embodiment, the first motor M1 is a stepping motor and is located within the support portion 57L of the joint cover 50.

[0073] As shown in Figure 5, the image forming apparatus 1 is equipped with a drive force transmission mechanism 500. While a detailed explanation is omitted, the drive force transmission mechanism 500 has a well-known configuration in which multiple transmission gears and clutches are combined. The drive force transmission mechanism 500 is also located within the support portion 57L of the joint cover 50.

[0074] When the sheet SH is discharged from the first discharge path PD1 without being cut, the drive force transmission mechanism 500 transmits the drive force generated by the first motor M1 to at least the drive roller 28A of the third transport roller pair 28.

[0075] When the sheet SH (SH1), which has been cut in half, is discharged from the second discharge path PD2, the drive force transmission mechanism 500 transmits the drive force generated by the first motor M1 to at least the drive roller 70A of the first transport roller pair 70 and the drive roller 29A of the second transport roller pair 29.

[0076] <Pre-cutting guide, cutter mechanism, first guide, second guide, sheet sensor, and second transport roller pair> As shown in Figures 3 and 4, the pre-cutting guide 300, the cutter mechanism 4, and the first guide 100 are fastened together to form a unit. The pre-cutting guide 300, the cutter mechanism 4, and the first guide 100 are assembled into the joint cover 50 in this unit state. The second guide 200 is assembled to the first guide 100. The joint cover 50 houses the pre-cutting guide 300, the cutter mechanism 4, the first guide 100, and the second guide 200.

[0077] As shown in Figure 4, the pre-cutting guide 300 is located upstream of the fixed blade 411 and movable blade 412 of the cutter mechanism 4, which will be described later, in the transport direction DT1.

[0078] The pre-cutting guide 300 has guide surfaces 301 and 302 that guide the sheet SH as it passes through the cutter mechanism 4. Guide surface 301 faces guide surface 302 from above. In this embodiment, the pre-cutting guide 300 is a resin molded product manufactured by injection molding of a thermoplastic resin or the like.

[0079] The sheet SH, which is conveyed toward the cutter mechanism 4 by the first conveyor roller pair 70, passes between the guide surface 301 and the guide surface 302 and reaches the cutter mechanism 4.

[0080] As shown in Figures 4 and 6, the cutter mechanism 4 includes a movable blade 412, a holder 460, a cutter carriage 420, a cutter frame 400, and a fixed blade 411. The fixed blade 411 and the movable blade 412 are examples of the "blade" of the present invention.

[0081] The movable blade 412 is a circular blade for cutting sheet SH. The holder 460 rotatably supports the movable blade 412. As shown in Figure 4, the cutter carriage 420 detachably holds the holder 460. In other words, the movable blade 412 is supported by the cutter carriage 420 with the holder 460 interposed between them.

[0082] As shown in Figures 3 and 6, the cutter frame 400 extends in the cutting direction DC1, which is perpendicular to the transport direction DT1, i.e., in the left-right direction.

[0083] As shown in Figure 6, a cutter frame opening 409 is formed in the cutter frame 400. The inner width of the cutter frame opening 409 is larger than the width of the sheet SH so that the sheet SH, which is guided by the guide surfaces 301 and 302 of the pre-cutting guide 300, can pass through.

[0084] The cutter frame 400 is made of metal, specifically manufactured by pressing, punching, bending, etc., a steel plate. As shown in Figure 4, the downstream side of the guide surface 301 in the transport direction DT1 enters the cutter frame opening 409.

[0085] As shown in Figures 4 and 6, the cutter frame 400 has a guide portion 402 above the cutter frame opening 409 and on the opposite side from the pre-cutting guide 300. The guide portion 402 guides the cutter carriage 420 in the cutting direction DC1 and restricts the cutter carriage 420 from coming off the guide portion 402.

[0086] In other words, the cutter frame 400 holds the cutter carriage 420 so that it can move in the cutting direction DC1. Therefore, the cutter mechanism 4 cuts the conveyed sheet SH in the cutting direction DC1.

[0087] In this embodiment, one cutting direction DC1 is to the left, and the other cutting direction DC1 is to the right.

[0088] As shown in Figures 3, 6, and 7, the image forming apparatus 1 is equipped with a second motor M2. The second motor M2 generates a driving force to reciprocate the cutter carriage 420 in the cutting direction DC1. The driving force generated by the second motor M2 is also used to reciprocate the cam follower 65 of the brake mechanism 6, which will be described later. The second motor M2 is fixed to the left end of the cutter frame 400, in a portion located above the cutter frame opening 409.

[0089] As shown in Figure 6, the cutter mechanism 4 has a timing belt 430. The timing belt 430 is wrapped around a drive pulley 431 and a plurality of driven pulleys 432, 433, and 434, surrounding the cutter frame opening 409. The drive pulley 431 and the plurality of driven pulleys 432, 433, and 434 are rotatably supported on the cutter frame 400.

[0090] The cutter carriage 420 is connected to the portion of the timing belt 430 that extends laterally above the cutter frame opening 409.

[0091] Figure 8 shows the cutter frame 400 and the pre-cutting guide 300 shown in Figure 7 removed. As shown in Figures 6 and 8, the cutter mechanism 4 has a first drive train 510. The first drive train 510 has a transmission gear 511 that meshes with the drive gear of the second motor M2, a transmission gear 515 that rotates integrally with the drive pulley 431, and a plurality of gears that transmit driving force from the transmission gear 511 to the transmission gear 515.

[0092] The first drive train 510 transmits the driving force of the second motor M2 to the timing belt 430, and then transmits it to the cutter carriage 420 via the timing belt 430. The cutter carriage 420 is able to move in the cutting direction DC1 together with the holder 460 and the movable blade 412 when the driving force of the second motor M2 is transmitted to it.

[0093] The control unit C1 controls the second motor M2 to rotate in the forward and reverse directions. The cutter carriage 420 is configured to move to one side of the cutting direction DC1, i.e., to the left, when the second motor M2 rotates in the forward direction, and to the other side of the cutting direction DC1, i.e., to the right, when the second motor M2 rotates in the reverse direction.

[0094] In Figure 6, the cutter carriage 420 (420A), shown by the dashed line, is in a standby position located on the right end of the cutter frame opening 409, where it does not interfere with the right edge of the sheet SH. The standby position (420A) of the cutter carriage 420 is a position where the moving blade 412 is away from the sheet SH in the other direction DC1 of the cutting direction, i.e., to the right.

[0095] In Figure 6, the cutter carriage 420 (420C), shown by a solid line, is located at the left end of the cutter frame opening 409 and is in a folded position that does not interfere with the left edge of the sheet SH. The folded position (420C) of the cutter carriage 420 is the position where the moving blade 412 moves away from the sheet SH in one direction DC1, i.e., to the left.

[0096] In other words, the cutter carriage 420 is movable in the cutting direction DC1 between the standby position, cutter carriage 420A, and the return position, cutter carriage 420C. Figure 3 shows the cutter carriage 420 (420A) in the standby position.

[0097] As shown in Figures 4 and 6, the fixed blade 411 extends in the cutting direction DC1 and is fastened to the cutter frame 400 below the lower edge of the cutter frame opening 409. The fixed blade 411 has a cross-sectional shape that extends upward from the fastened portion, then bends and extends downstream in the conveying direction DT1. The cutting edge of the fixed blade 411 extends linearly in the cutting direction DC1.

[0098] The movable blade 412 moves in the cutting direction DC1 while sliding against the cutting edge of the fixed blade 411. The cutter mechanism 4 cuts the sheet SH that has passed through the image forming unit 3 and the fuser 7 in the cutting direction DC1 using the fixed blade 411 and the movable blade 412. Since the fixed blade 411 is fixed to the cutter frame 400, the sheet SH is cut as the movable blade 412 moves.

[0099] As shown in Figure 4, the first guide 100 is located downstream in the transport direction DT1 from the fixed blade 411 and movable blade 412 of the cutter mechanism 4. The first guide 100 has a bottom wall 105 and a plurality of ribs 107 that are spaced apart from each other in the left-right direction. Each rib 107 protrudes upward from the upper surface of the bottom wall 105 and extends in the front-rear direction. In this embodiment, the first guide 100 is a resin molded product manufactured by injection molding of a thermoplastic resin or the like.

[0100] The first guide 100 has a first guide surface 101. The first guide surface 101 is formed by the tips of each rib 107. The first guide 100 guides the sheet SH being conveyed from the cutter mechanism 4 to the second conveyor roller pair 29 by the first guide surface 101.

[0101] The first guide 100 rotatably supports the driven roller 29B of the second conveyor roller pair 29. The driven roller 29B is rotatably supported on the downstream end side of the conveyor direction DT1 in the first guide 100.

[0102] The second guide 200 is located downstream of the fixed blade 411 and movable blade 412 of the cutter mechanism 4 in the transport direction DT1, and above the first guide 100. The second guide 200 has an upper wall 205 and a plurality of ribs 207 that are spaced apart from each other in the left-right direction. Each rib 207 protrudes downward from the lower surface of the upper wall 205 and extends in the front-rear direction. In this embodiment, the second guide 200 is a resin molded product manufactured by injection molding of a thermoplastic resin or the like.

[0103] The second guide 200 has a second guide surface 202. The second guide surface 202 is formed by the tips of each rib 207 and faces the first guide surface 101. The second guide 200 guides the sheet SH being conveyed from the cutter mechanism 4 to the second conveyor roller pair 29 by the second guide surface 202.

[0104] The second guide 200 rotatably supports the drive roller 29A of the second conveyor roller pair 29. The drive roller 29A is rotatably supported on the downstream end side of the conveying direction DT1 in the second guide 200 and faces the driven roller 29B.

[0105] The sheet sensor S4 is provided on the first guide 100. The sheet sensor S4 is located downstream of the fixed blade 411 and movable blade 412 of the cutter mechanism 4 in the transport direction DT1, and upstream of the second transport roller pair 29 in the transport direction DT1.

[0106] The sheet sensor S4 is an actuator that oscillates when the sheet SH comes into contact with it. The sheet sensor S4 detects the sheet SH as it passes through the cutter mechanism 4 and then through the first guide 100 and the second guide 200. The oscillation of the sheet sensor S4 is converted into an electrical signal by a photointerrupter (not shown) and transmitted to the control unit C1. Based on the detection result of the sheet sensor S4, the control unit C1 performs timing control, etc., when the cutter mechanism 4 cuts the sheet SH.

[0107] Specifically, the cutter carriage 420 is in a standby position (420A) until the sheet SH reaches the cutting position of the fixed blade 411 and the movable blade 412.

[0108] The control unit C1 determines the timing at which the point where half the length of the sheet SH reaches the cutting position of the fixed blade 411 and the movable blade 412, based on the elapsed time since the sheet sensor S4 detected the leading edge of the sheet SH passing through the cutter mechanism 4 and the conveying speed of the sheet SH. When that timing arrives, it controls the first motor M1 to stop the drive roller 70A of the first conveying roller pair 70 and the drive roller 29A of the second conveying roller pair 29.

[0109] The first transport roller pair 70 holds the sheet SH by stopping the drive roller 70A while the sheet SH is nipped. The second transport roller pair 29 holds the sheet SH by stopping the drive roller 29A while the sheet SH is nipped.

[0110] Then, the control unit C1 controls the second motor M2 to rotate in the forward direction, thereby moving the cutter carriage 420 from the standby position (420A) to the turning position (420C). As a result, the cutter mechanism 4 cuts the sheet SH held by the first transport roller pair 70 and the second transport roller pair 29 in the cutting direction DC1 with the fixed blade 411 and the movable blade 412, creating a sheet SH (SH1) that is half the length.

[0111] Subsequently, the control unit C1 controls the second motor M2 to reverse rotation, thereby returning the cutter carriage 420 from the folded position (420C) to the standby position (420A). Finally, the control unit C1 controls the first motor M1 to rotate the drive roller 70A of the first transport roller pair 70 and the drive roller 29A of the second transport roller pair 29, and discharges the sheet SH (SH1), which has been divided into two pieces by cutting, into the discharge tray 9.

[0112] <Configuration of the sheet cutting device> As shown in Figures 2, 7, and 8, the sheet cutting device 2 is equipped with the pre-cutting cover 80 and the first transport roller pair 70 described above.

[0113] As shown in Figure 2, the pre-cutting cover 80 is located furthest upstream in the transport direction DT1 among the multiple elements that make up the sheet cutting device 2. In other words, the fuser 7 is located upstream of the sheet cutting device 2 in the transport direction DT1.

[0114] As shown in Figures 9 and 10, the first conveyor roller pair 70 has a rotating shaft 73. The rotating shaft 73 is a round metal rod centered on a rotation axis X1 that extends in the left-right direction, and rotates together with the drive roller 70A. The diameter of the rotating shaft 73 is significantly smaller than the diameter of the drive roller 70A.

[0115] The right end of the rotating shaft 73 protrudes to the right of the right end of the drive roller 70A. The left end of the rotating shaft 73 protrudes to the left of the left end of the drive roller 70A. The left end of the rotating shaft 73 has a roughly "D" shaped cross-section, in which a portion of the cylindrical outer surface has been changed to a flat surface.

[0116] As shown in Figures 8 and 11, the left wall 80L of the uncut cover 80 supports the left end of the rotating shaft 73 so that it can rotate around the rotation axis X1, with a bearing 83 interposed therebetween. Although not shown in the figures, the right wall of the uncut cover 80 also supports the right end of the rotating shaft 73 so that it can rotate around the rotation axis X1, with a bearing interposed therebetween therebetween.

[0117] As shown in Figure 5, the sheet cutting device 2 includes the first motor M1 and the drive force transmission mechanism 500 described above. The drive force transmission mechanism 500 has a first gear 75. The first gear 75 is the most downstream of a plurality of transmission gears that transmit the driving force of the first motor M1 to the rotating shaft 73.

[0118] As shown in Figures 9 and 10, the first gear 75 integrally comprises multiple gear teeth 75G, a cylindrical portion 75C, and a disc portion 75D. In this embodiment, the first gear 75 is a resin molded product manufactured by injection molding of a thermoplastic resin or the like.

[0119] Each gear tooth 75G is arranged in the circumferential direction of the rotation axis X1. The cylindrical portion 75C is located to the right of each gear tooth 75G and has a cylindrical shape centered on the rotation axis X1. The diameter of the cylindrical portion 75C is smaller than the circle inscribed in the base of each gear tooth 75G. The disc portion 75D is located to the left of each gear tooth 75G and has a disc shape centered on the rotation axis X1. The diameter of the disc portion 75D is slightly larger than the outer diameter of the cutting edge of each gear tooth 75G.

[0120] As shown in Figures 9 to 11, the first gear 75 has a shaft hole 75H. The shaft hole 75H penetrates from the right side of the cylindrical portion 75C to the left side of the disc portion 75D, with the rotation axis X1 as the center. The shaft hole 75H is a round hole on the side of the cylindrical portion 75C, and has a roughly "D" shaped cross-section on the side of the disc portion 75D.

[0121] As shown in Figure 9, the leftward-facing side surface 75A of the first gear 75 is the left side surface of the disc portion 75D. The side surface 75A is larger than the circle that inscribes the bottom of each gear tooth 75G. The diameter of the side surface 75A is slightly larger than the outer diameter of the cutting edge of each gear tooth 75G. The diameter of the side surface 75A is significantly larger than the diameter of the rotating shaft 73. Also, the diameter of the side surface 75A is larger than the diameter of the drive roller 70A.

[0122] Two annular protrusions 75T are formed on the outer peripheral edge of side surface 75A. Each annular protrusion 75T is a rib that protrudes to the left, forming an annular shape with different diameters, centered on the rotation axis X1. Each annular protrusion 75T is positioned to overlap with each gear tooth 75G in the left-right direction.

[0123] As shown in Figure 11, the first gear 75 is fixed to the rotating shaft 73 by fitting the shaft hole 75H with the left end of the rotating shaft 73. The first gear 75 directly transmits the driving force of the first motor M1, which is transmitted by the driving force transmission mechanism 500, to the rotating shaft 73.

[0124] As shown in Figure 8, the rightward movement of the rotating shaft 73 and the first gear 75 is restricted by the right side of the cylindrical portion 75C coming into contact with the bearing 83.

[0125] As shown in Figures 2 and 4, the sheet cutting device 2 includes the pre-cutting guide 300, cutter mechanism 4, first guide 100, second guide 200, sheet sensor S4, and second transport roller pair 29. As shown in Figure 7, the sheet cutting device 2 includes the second motor M2 described above.

[0126] The pre-cutting guide 300 integrally includes a second drive row support 310 and a cam follower support 320. The second drive row support 310 and the cam follower support 320 are located to the left of the guide surfaces 301 and 302. Furthermore, the second drive row support 310 and the cam follower support 320 are located to the left of the left side wall 80L of the pre-cutting cover 80. In Figure 12, the cam follower support 320 is shown by a dashed line.

[0127] As shown in Figures 6 and 8, the cutter mechanism 4 has a second drive train 520. The second drive train 520 has a transmission gear 521 that meshes with the transmission gear 515 of the first drive train 510, a second gear 525 located furthest downstream in the second drive train 520, and a plurality of gears that transmit driving force from the transmission gear 521 to the transmission gear 525. The second drive train 520 is rotatably supported by the second drive train support 310 shown in Figure 7.

[0128] As shown in Figure 8, the rotation axis X525 of the second gear 525 extends in the front-rear direction at a position separated to the left from the side surface 75A of the first gear 75. As shown in Figure 11, the vertical position of the rotation axis X525 is the same as the vertical position of the rotation axis X1.

[0129] <Brake mechanism> As shown in Figures 8 to 11, the sheet cutting device 2 is equipped with a brake mechanism 6. The brake mechanism 6 includes a cam 61, a cam follower 65, and a compression coil spring 69. The compression coil spring 69 is an example of the "biasing member" of the present invention.

[0130] As shown in Figure 8, the cam 61 is formed on the rearward-facing side surface 525A of the second gear 525. The second drive train 520 branches off from the first drive train 510 and transmits the driving force of the second motor M2 to the second gear 525 and the cam 61. In this embodiment, the transmission gear 525 and the cam 61 are resin molded products manufactured by injection molding of thermoplastic resin or the like.

[0131] As shown in Figures 9 and 10, the cam 61 has a first arc portion 61A, a second arc portion 61B, and connecting portions 61C1 and 61C2 that extend along the outer peripheral edge of the side surface 525A.

[0132] The first arc portion 61A is a rib that forms an arc shape centered on the rotation axis X525 and protrudes rearward from the side surface 525A. The angle from one end to the other in the circumferential direction of the first arc portion 61A is approximately 280°.

[0133] The second arc portion 61B is located in the area where the first arc portion 61A is interrupted, and is closer to the rotation axis X525 than the first arc portion 61A. It is a rib that forms an arc shape centered on the rotation axis X525 and protrudes rearward from the side surface 525A.

[0134] The connecting portion 61C1 is a rib that protrudes rearward from the side surface 525A between one circumferential end of the first arc portion 61A and one circumferential end of the second arc portion 61B. The connecting portion 61C1 connects one circumferential end of the first arc portion 61A and one circumferential end of the second arc portion 61B by a gentle curve.

[0135] The connecting portion 61C2 is a rib that protrudes rearward from the side surface 525A between the other circumferential end of the first arc portion 61A and the other circumferential end of the second arc portion 61B. The connecting portion 61C2 connects the other circumferential end of the first arc portion 61A and the other circumferential end of the second arc portion 61B by a gentle curve.

[0136] As shown in Figure 11, the distance SD1 is the distance at which the cam 61 moves radially outward from the rotation axis X525. The distance SD1(SD1B) at which the second arc portion 61B moves radially outward from the rotation axis X525 is smaller than the distance SD1(SD1A) at which the first arc portion 61A moves radially outward from the rotation axis X525.

[0137] In other words, the distance SD1 that the cam 61 moves radially outward from the rotation axis X525 varies within the range of distance SD1(SD1B) to distance SD1(SD1A), depending on the first arc portion 61A, the second arc portion 61B, and the connecting portions 61C1 and 61C2.

[0138] As shown in Figures 9 and 10, the cam follower 65 has a contact surface 65A, an upper protrusion 65U, a lower protrusion 65D, a front protrusion 65F, and a spring receiving portion 65B.

[0139] As shown in Figure 10, the contact surface 65A is a right-facing flat surface extending in the front-rear and left-right directions. As shown in Figure 12, the contact surface 65A faces the side surface 75A of the first gear 75. The upper end of the contact surface 65A is located above each annular protrusion 75T. The lower end of the contact surface 65A is located below each annular protrusion 75T.

[0140] As shown in Figures 9 and 10, the cam follower 65 has an upper surface that connects to the upper edge of the contact surface 65A and extends to the left, a lower surface that connects to the lower edge of the contact surface 65A and extends to the left, and a front surface that connects to the front edge of the contact surface 65A and extends to the left.

[0141] The upper protrusion 65U is a plate-like piece that protrudes upward from the upper surface of the cam follower 65. The lower protrusion 65D is a plate-like piece that protrudes downward from the lower surface of the cam follower 65. The front protrusion 65F is a plate-like piece that protrudes forward from the front surface of the cam follower 65. A curved surface with a semicircular cross-section is formed at the right end of the front protrusion 65F.

[0142] As shown in Figures 7 and 11, the upper protrusion 65U, the lower protrusion 65D, and the front protrusion 65F are guided in the front-rear direction by a plurality of guide grooves formed in the cam follower support 320. As a result, the cam follower 65 is movable between the contact position shown in Figures 7, 8, 11, 13, and 14 and the separated position shown in Figure 12.

[0143] As shown in Figure 11, the contact position of the cam follower 65 is the position where the contact surface 65A contacts each annular protrusion 75T of the side surface 75A.

[0144] As shown in Figure 12, the separation position of the cam follower 65 is such that the contact surface 65A is separated to the left from each annular protrusion 75T of the side surface 75A.

[0145] As shown in Figures 11 to 14, the front protrusion 65F is guided in the front-rear direction at the same position as the rotation axes X1 and X525 in the vertical direction.

[0146] As shown in Figure 9, the spring support portion 65B is formed on the opposite side of the contact surface 65A on the cam follower 65 and is recessed to the right. As shown in Figure 8, the spring support portion 65B holds the right end of the compression coil spring 69. As shown in Figure 7, the left side wall of the cam follower support portion 320 holds the left end of the compression coil spring 69. The compression coil spring 69 biases the cam follower 65 to the right, i.e., toward the contact position.

[0147] When the cutter carriage 420 is in the standby position (420A), the rotational position of the cam 61 is in the initial position shown in Figure 12. In this state, one circumferential end of the second arc portion 61B is at the same position as the rotational axes X1 and X525 in the vertical direction. The cam follower 65, biased by the compression coil spring 69, is held in a separated position by the right end of the front convex portion 65F contacting one circumferential end of the second arc portion 61B from the left.

[0148] When cutting the sheet SH with the fixed blade 411 and the movable blade 412, the control unit C1 rotates the second motor M2 in the forward direction, moving the cutter carriage 420 from the standby position (420A) to one side of the cutting direction DC1, i.e., to the left.

[0149] At this point, before the moving blade 412 reaches the right edge of the sheet SH held by the first transport roller pair 70 and the second transport roller pair 29, the cam 61 rotates counterclockwise in the plane of the paper in Figure 13, so that the right end of the front convex portion 65F faces the first arc portion 61A with a gap between them. As a result, the cam follower 65, biased by the compression coil spring 69, moves to the contact position.

[0150] In this way, when the sheet SH is cut by the fixed blade 411 and the movable blade 412, the brake mechanism 6 suppresses the rotation of the first gear 75 by having the contact surface 65A of the cam follower 65 come into contact with each annular protrusion 75T of the side surface 75A just before the movable blade 412 reaches the right edge of the sheet SH.

[0151] Then, as the control unit C1 continues the forward rotation of the second motor M2, the fixed blade 411 and the movable blade 412 cut the sheet SH, and the cutter carriage 420 reaches the folding position (420C). During this time, the cam 61 rotates counterclockwise in the plane of Figure 14, and the right end of the front convex portion 65F remains in a state where it faces the first arc portion 61A with a gap between them, so that the cam follower 65 biased by the compression coil spring 69 is maintained in contact position.

[0152] The second gear 525 and the cam 61 rotate in the forward direction in less than one full turn from their initial position, specifically by about 270°, thereby moving the cam follower 65 from the separated position to the contact position.

[0153] In this way, the brake mechanism 6 suppresses the rotation of the first gear 75 by having the contact surface 65A of the cam follower 65 contact each annular protrusion 75T of the side surface 75A until the cutting of the sheet SH by the fixed blade 411 and the movable blade 412 is completed. As a result, the sheet cutting device 2 can suppress the rotation of the drive roller 70A by being pulled by the sheet while the sheet SH is being cut.

[0154] In particular, in the drive force transmission mechanism 500, there is backlash, or play between the tooth surfaces of the meshing gear teeth, between the first gear 75 and the transmission gear located upstream of the first gear 75 that meshes with the first gear. However, the braking mechanism 6 can reliably suppress the rotation of the first gear 75 by the amount of this play.

[0155] Subsequently, the control unit C1 reverses the rotation of the second motor M2, returning the cutter carriage 420 to the standby position (420A). At this time, the cam 61 rotates clockwise in the direction of the paper shown in Figure 14, passing through the rotation position shown in Figure 13, and returning to the initial position shown in Figure 12.

[0156] The second gear 525 and the cam 61 rotate in less than one revolution in the reverse direction, thereby moving the cam follower 65 from the contact position to the separated position.

[0157] The driving force of the second motor M2 is transmitted to the second gear 525 and cam 61, causing the second gear 525 and cam 61 to rotate in the forward and reverse directions. As the distance SD1, the radially outward separation of the cam 61 from the rotation axis X525, changes, the cam follower 65 moves between a contact position and a separation position.

[0158] As shown in Figure 6, the range in which the cutter carriage 420 moves in the cutting direction DC1 is defined as range A1. One end of range A1, side A1E, is the left end of range A1.

[0159] As shown in Figures 6 and 7, the second motor M2, the first drive train 510, the second drive train 520, the cam 61, the cam follower 65, and the first gear 75 are located on one end A1E side of the range A1 in which the cutter carriage 420 moves in the cutting direction DC1.

[0160] <Effects and Effects> In the sheet cutting device 2 of Embodiment 1, as shown in Figure 9, the side surface 75A of the first gear 75 is larger than the circle that inscribes the bottom of each gear tooth 75G of the first gear 75. The diameter of the side surface 75A is slightly larger than the outer diameter of the cutting edge of each gear tooth 75G. The diameter of the side surface 75A is significantly larger than the diameter of the rotating shaft 73. Also, the diameter of the side surface 75A is larger than the diameter of the drive roller 70A. Each annular protrusion 75T formed on the side surface 75A is positioned to overlap with each gear tooth 75G in the left-right direction.

[0161] As a result, as shown in Figure 8, the brake mechanism 6 can apply the frictional force between each annular protrusion 75T of the side surface 75A and the contact surface 65A of the cam follower 65 at a position far from the rotation center X1 of the drive roller 70A and the rotating shaft 73. Therefore, this sheet cutting device 2 can increase the braking torque for suppressing the rotation of the rotating shaft 73.

[0162] Therefore, the sheet cutting apparatus 2 of Example 1 can suppress the rotation of the drive roller 70A due to being pulled by the sheet during cutting of the sheet SH, and as a result, the problem of being unable to cut the sheet SH straight can be suppressed. The same applies to the image forming apparatus 1 of Example 1.

[0163] Furthermore, as shown in Figures 5 and 8, the sheet cutting device 2 combines the functions of the first gear 75, which transmits driving force to the rotating shaft 73, and the function of receiving braking torque from the brake mechanism 6, thereby reducing the number of parts.

[0164] Furthermore, in this sheet cutting device 2, as shown in Figures 12 to 14, the brake mechanism 6 has a cam follower 65 and a cam 61. The cam follower 65 is movable between a contact position in which the contact surface 65A contacts each annular protrusion 75T of the side surface 75A and a separation position in which the contact surface 65A is separated from each annular protrusion 75T of the side surface 75A. The cam 61 moves the cam follower 65 between the contact position and the separation position when the driving force of the second motor M2 is transmitted. With this configuration, the brake mechanism 6 can eliminate the frictional force acting between each annular protrusion 75T of the side surface 75A and the contact surface 65A of the cam follower 65 by moving the cam follower 65 to the separation position when the sheet SH is being conveyed by the drive roller 70A. As a result, the brake mechanism 6 does not hinder the conveyance of the sheet SH by the drive roller 70A.

[0165] Furthermore, in this sheet cutting device 2, as shown in Figure 6, the cutter mechanism 4 has a cutter carriage 420 that can move in the cutting direction DC1 when the driving force of the second motor M2 is transmitted. The cutter carriage 420 supports the movable blade 412 with the holder 460 interposed therebetween. With this configuration, the second motor M2 serves to drive both the cam 61 and the cutter carriage 420, thus enabling miniaturization and a reduction in the number of parts.

[0166] Furthermore, in this sheet cutting device 2, the cutter mechanism 4 includes a first drive train 510 that transmits the driving force of the second motor M2 to the cutter carriage 420, and a second drive train 520 that branches off from the first drive train 510 and transmits the driving force of the second motor M2 to the cam 61. As shown in Figure 8, the cam 61 is formed on the side surface 525A of the second gear 525 of the second drive train 520. As shown in Figure 11, the cam 61 moves the front convex portion 65F that slides against the cam 61 in the front-rear direction as the distance SD1 that moves radially outward from the rotation axis X525 changes, causing the cam follower 65 to move between a contact position and a separation position. This configuration simplifies the brake mechanism 6.

[0167] Furthermore, in this sheet cutting device 2, as shown in Figure 6, the cutter carriage 420 is configured to move to one side of the cutting direction DC1, i.e., to the left, by the forward rotation of the second motor M2, and to the other side of the cutting direction DC1, i.e., to the right, by the reverse rotation of the second motor M2. As shown in Figures 12 to 14, the second gear 525 and the cam 61 rotate in less than one revolution in both forward and reverse rotation, thereby moving the cam follower 65 between a contact position and a separation position. This configuration simplifies the brake mechanism 6.

[0168] Furthermore, in this sheet cutting device 2, as shown in Figures 6 and 7, the second motor M2, the first drive row 510, the second drive row 520, the cam 61, the cam follower 65, and the first gear 75 are located on one end A1E side of the range A1 in which the cutter carriage 420 moves in the cutting direction DC1. This configuration allows for easy arrangement of the second motor M2, the first drive row 510, the second drive row 520, the cam 61, the cam follower 65, and the first gear 75.

[0169] Furthermore, in this sheet cutting device 2, as shown in Figure 8, the brake mechanism 6 has a compression coil spring 69 that biases the cam follower 65 toward the contact position. With this configuration, the frictional force acting between each annular protrusion 75T on the side surface 75A and the contact surface 65A of the cam follower 65 can be easily adjusted by the biasing force of the compression coil spring 69. In addition, with this configuration, the cam follower 65 that slides against the cam 61 can move smoothly between the contact position and the separation position.

[0170] Furthermore, in this sheet cutting device 2, as shown in Figure 4, the fixed blade 411 and the movable blade 412 are located downstream of the first conveyor roller pair 70 in the conveying direction DT1, and upstream of the second conveyor roller pair 29 in the conveying direction DT1. The cutter mechanism 4 cuts the sheet SH held by the first conveyor roller pair 70 and the second conveyor roller pair 29 in the cutting direction DC1 using the fixed blade 411 and the movable blade 412. With this configuration, the cutter mechanism 4 can stably cut the sheet SH held by the first conveyor roller pair 70 and the second conveyor roller pair 29. At this time, the sheet SH being cut tries to pull and rotate the drive roller 70A of the first conveyor roller pair 70, but the brake mechanism 6 can suppress the rotation of the drive roller 70A, and as a result, the problem of not being able to cut the sheet SH straight can be reliably suppressed.

[0171] (Example 2) As shown in Figure 15, the sheet cutting device of Example 2 employs a brake mechanism 6A instead of the brake mechanism 6 of the sheet cutting device 2 of Example 1, and eliminates the second drive row 520 from the cutter mechanism 4.

[0172] The other components of Example 2 are the same as those of Example 1. Therefore, components identical to those of Example 1 are denoted by the same reference numerals, and their descriptions are omitted or simplified.

[0173] The brake mechanism 6A includes a compression coil spring 69A and a spring retaining portion 330. The compression coil spring 69A is an example of the "biasing member" of the present invention.

[0174] The spring retaining portion 330 has a left wall 331 and connecting walls 332 and 333.

[0175] The left wall 331 faces the side 75A of the first gear 75 from the left. The connecting wall 332 connects the upper end of the left wall 331 to the left side wall 80L of the pre-cut cover 80. The connecting wall 333 connects the lower end of the left wall 331 to the left side wall 80L of the pre-cut cover 80.

[0176] The left wall 331 holds the left end of the compression coil spring 69A above the rotation axis X1. The compression coil spring 69A, in a state of compression deformation and storing restoring force, has its right end in contact with each annular protrusion 75T of the side surface 75A.

[0177] The braking mechanism 6A constantly suppresses the rotation of the first gear 75 by having the right end of the compression coil spring 69A contact each annular protrusion 75T of the side surface 75A, including when the sheet SH is being cut by the fixed blade 411 and the movable blade 412.

[0178] The brake mechanism 6A can apply the frictional force between each annular protrusion 75T of the side surface 75A and the right end of the compression coil spring 69A at a position far from the rotation center X1 of the drive roller 70A and the rotating shaft 73. Therefore, this sheet cutting device can increase the braking torque for suppressing the rotation of the rotating shaft 73.

[0179] Therefore, the sheet cutting device of Example 2, like the sheet cutting device of Example 1, can suppress the rotation of the drive roller 70A due to being pulled by the sheet during cutting of the sheet SH, and as a result, can suppress the problem of being unable to cut the sheet SH straight.

[0180] Although the present invention has been described above in reference to Examples 1 and 2, it goes without saying that the present invention is not limited to Examples 1 and 2, and can be applied with appropriate modifications without departing from its spirit.

[0181] In Examples 1 and 2, the sheet cutting apparatus of the present invention was implemented by applying it to an image forming apparatus 1 equipped with an image forming function and an image reading function. However, the present invention is not limited to this configuration. For example, the configuration of the present invention may be applied to an image forming apparatus equipped only with an image forming function.

[0182] In Examples 1 and 2, the fixed blade 411 and the movable blade 412 are located downstream of the first conveyor roller pair 70 in the conveying direction DT1, but the present invention is not limited to this configuration. For example, the present invention also includes a configuration in which the second conveyor roller pair 29 according to Example 1 is replaced with the first conveyor roller pair of the present invention, a first gear is fixed to the rotation axis of the drive roller 29A, and a brake mechanism contacts the side surface of the first gear to suppress the rotation of the first gear when the sheet is cut by the blade.

[0183] In Example 1, the cam 61 rotates, but the present invention is not limited to this configuration. For example, the cam may reciprocate.

[0184] In Example 1, the cam follower 65 moves linearly, but the present invention is not limited to this configuration. For example, the cam follower may swing.

[0185] In Examples 1 and 2, the sheet cutting device 1 is equipped with a first motor M1 and a second motor M2, but the present invention is not limited to this configuration. For example, a configuration in which one motor serves as both the first motor and the second motor is also included in the present invention.

[0186] In Examples 1 and 2, the cutter mechanism 4 has a fixed blade 411 and a movable blade 412, but the present invention is not limited to this configuration. For example, the cutter mechanism may have only a movable blade.

[0187] In Examples 1 and 2, the side surface 75A of the first gear 75 is the left side surface of the disc portion 75D, but the present invention is not limited to this configuration. For example, a configuration in which the disc portion 75D is removed from the first gear 75 and the circular left side surface inscribed in the bottom of each gear tooth 75G is the "side surface of the first gear" according to the present invention is also included in the present invention. [Explanation of Symbols]

[0188] 2…Sheet cutting device, 1…Image forming apparatus SH...sheet, DT1...conveying direction, 70A...drive roller 73... Rotating shaft, 70... First conveyor roller pair 411, 412... Blades (411... Fixed blade, 412... Moving blade) 4...Cutter mechanism, DC1...Cutting direction M1...First motor, 75...First gear 75A...Side of the first gear, 6, 6A...Brake mechanism M2...Second motor, 65...Cam follower 61...Cam, 420...Cutter carriage 510...First drive train, 520...Second drive train 525...Second gear, 525A...Side view of the second gear X525... Rotation axis of the second gear SD1... The distance radially outward from the rotation axis of the second gear. A1... The range in which the cutter carriage moves in the cutting direction A1E... One end of the range in which the cutter carriage moves in the cutting direction. 69, 69A... Biasing member (compression coil spring), 29... Second conveyor roller pair 7...Fuser, 3...Image forming unit

Claims

1. A first conveyor roller pair having a drive roller for conveying a sheet in the conveying direction and a rotating shaft that rotates integrally with the drive roller, wherein the first conveyor roller pair holds the sheet by stopping when the sheet is nipped, A cutter mechanism having a blade located upstream or downstream of the first transport roller pair in the transport direction, wherein the cutter mechanism cuts a sheet held by the first transport roller pair in a cutting direction perpendicular to the transport direction using the blade, A sheet cutting device equipped with, A first motor that generates driving force, A first gear fixed to the rotating shaft and transmitting the driving force of the first motor to the rotating shaft, A brake mechanism that contacts the side surface of the first gear to suppress the rotation of the first gear when the sheet is cut by the blade, A sheet cutting device characterized by having the following features.

2. Equipped with a second motor that generates driving force, The sheet cutting device according to claim 1, wherein the brake mechanism includes a cam follower that is movable between a contact position in contact with the side surface of the first gear and a separation position away from the side surface, and a cam that moves the cam follower between the contact position and the separation position when the driving force of the second motor is transmitted.

3. The cutter mechanism has a cutter carriage that is movable in the cutting direction when the driving force of the second motor is transmitted to it. The sheet cutting device according to claim 2, wherein the blade is a movable blade supported by the cutter carriage.

4. The cutter mechanism includes a first drive train that transmits the driving force of the second motor to the cutter carriage, and a second drive train that branches off from the first drive train and transmits the driving force of the second motor to the cam. The sheet cutting apparatus according to claim 3, wherein the cam is formed on the side surface of the second gear of the second drive row, and the cam follower that slides against the cam is moved between the contact position and the separation position by changing the distance that separates the cam radially outward from the rotation axis of the second gear.

5. The cutter carriage is configured to move in one direction of cutting by the forward rotation of the second motor and to move in the other direction of cutting by the reverse rotation of the second motor. The sheet cutting device according to claim 4, wherein the second gear and the cam rotate in less than one revolution in the forward rotation and the reverse rotation, thereby moving the cam follower between the contact position and the separation position.

6. The sheet cutting apparatus according to claim 4 or 5, wherein the second motor, the first drive train, the second drive train, the cam, the cam follower, and the first gear are located on one end of the range in which the cutter carriage moves in the cutting direction.

7. The sheet cutting device according to any one of claims 2 to 4, wherein the brake mechanism has a biasing member that biases the cam follower toward the contact position.

8. A second pair of conveying rollers is located downstream of the first pair of conveying rollers in the conveying direction and conveys the sheet in the conveying direction, and the second pair of conveying rollers holds the sheet by stopping in a nip position, The blade is located downstream of the first conveyor roller pair in the conveying direction and upstream of the second conveyor roller pair in the conveying direction. The sheet cutting device according to any one of claims 1 to 4, wherein the cutter mechanism cuts the sheet held by the first transport roller pair and the second transport roller pair in the cutting direction with the blade.

9. The sheet cutting device according to any one of claims 1 to 4, A fuser located upstream of the sheet cutting device in the conveying direction, An image forming unit located upstream of the fuser in the transport direction, Equipped with, The image forming unit forms a toner image on the sheet. The aforementioned fuser is an image forming apparatus characterized by fixing the formed toner image onto a sheet.

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