Image formation device

Abstract

To provide an image formation device in which a position of a sheet cut by a cutter mechanism can be accurately determined if there is no controlled adjustments of the cut position of the sheet.SOLUTION: An image formation device 1 includes an image formation unit 3, a fixation unit 7, a cutter mechanism 4 having a moving knife 412 and a cutter frame 400, a sheet guide 100 provided in an upstream or a downstream with respect to the cutter mechanism 4 in a conveyance direction DT1, the sheet guide guiding a sheet SH passing through the cutter mechanism 4; and a sheet sensor S4 provided in the sheet guide 100, the sheet sensor detecting the sheet SH passing through the cutter mechanism 4. The sheet guide 100 is positioned in the cutter frame 400.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] An example of a conventional image forming apparatus is disclosed in Patent Document 1. This image forming apparatus includes an image forming unit, a fixing device, a cutting device, an entrance sensor, and an exit sensor.

[0003] The cutting device has a cutter mechanism consisting of a first cutting section and the like, and cuts the sheet that has passed through the fixing device with the cutter mechanism. The entrance sensor and the exit sensor are located upstream and downstream of the cutter mechanism in the conveying direction, respectively, and detect the sheet that passes through the cutter mechanism. The detection results of the entrance sensor and the exit sensor are used to accurately determine the position where the cutter mechanism cuts the sheet.

[0004] Patent Document 2 discloses a cutter mechanism having a moving blade and a cutter frame made up of two guide plates. The cutter frame movably holds the moving blade. The cutter mechanism cuts a sheet by moving the moving blade. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2023-19469 A [Patent Document 2] JP 2011-235428 A Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, in the above-mentioned conventional image forming apparatus, when the cutter mechanism has a moving blade and a cutter frame as in Patent Document 2, the load acting on the cutter frame during cutting tends to be large. For this reason, the cutter frame is often made of a highly rigid material, such as metal.

[0007] In addition, the image forming apparatus generally includes a sheet guide that is provided upstream or downstream of the cutter mechanism in the conveying direction and guides the sheet passing through the cutter mechanism. The sheet guide has a large area and needs to be wear-resistant, so it is often made of a material with lower rigidity than the material that constitutes the cutter frame, such as resin.

[0008] In most cases, the cutter frame and the sheet guide are separately assembled to the image forming apparatus.

[0009] Furthermore, when this image forming apparatus is provided with a sheet sensor that detects a sheet passing through the cutter mechanism, such as the entrance sensor and exit sensor in Patent Document 1, the sheet sensor is often provided in the sheet guide. Therefore, if the relative position of the sheet guide with respect to the cutter mechanism is shifted, the position at which the sheet sensor detects the sheet may shift from the designed position with respect to the cutter mechanism, and even if the sheet is transported by a preset transport amount to the cutting position of the sheet, the cutter mechanism may not be able to cut the sheet at the target cutting position.

[0010] Therefore, it is conceivable to carry out printing with cutting several times before shipping the image forming apparatus, measure the deviation of the position where the sheet sensor detects the sheet, and perform adjustment to control and match the necessary transport amount from the detection of the sheet to the position where the sheet is to be cut. However, in this case, if the cutter mechanism is replaced due to deterioration over time after installation, it will be necessary to carry out adjustment again, which will take time for repairs.

[0011] The present invention has been made in consideration of the above-mentioned conventional situation, and aims to provide an image forming apparatus that can accurately determine the position at which a cutter mechanism cuts a sheet without having to make controlled adjustments to the sheet cutting position. [Means for solving the problem]

[0012] The image forming apparatus of the present invention includes an image forming unit that forms an image by transferring a toner image onto a sheet transported in a transport direction; a fixing unit that fixes the toner image onto the sheet that has passed through the image forming unit; a cutter mechanism including a moving blade that cuts the sheet that has passed through the fixing unit and a cutter frame that movably holds the moving blade; a sheet guide provided upstream or downstream of the cutter mechanism in the conveying direction and configured to guide a sheet passing through the cutter mechanism; a sheet sensor provided in the sheet guide to detect a sheet passing through the cutter mechanism; Equipped with The sheet guide is characterized in that it is positioned on the cutter frame.

[0013] In the image forming apparatus of the present invention, the sheet sensor is provided in the sheet guide, which is often made of a material having a lower rigidity than the material that constitutes the cutter frame, and the sheet guide is positioned relative to the cutter frame.

[0014] Therefore, compared to a case where the cutter frame and the sheet guide provided with the sheet sensor are separately assembled to the image forming apparatus, it is possible to suppress deviation of the relative position of the sheet guide with respect to the cutter mechanism. As a result, in this image forming apparatus, the position where the sheet sensor detects the sheet is less likely to deviate from the designed position with respect to the cutter mechanism, and when the sheet is transported by a predetermined transport amount to the cutting position of the sheet, a malfunction in which the cutter mechanism is unable to cut the sheet at the target cutting position is less likely to occur.

[0015] As a result, with this image forming device, there is no need to perform printing with cutting several times before the product is shipped, measure the deviation in the position where the sheet sensor detects the sheet, and perform adjustments to control the required transport amount from when the sheet is detected to the position where the sheet is to be cut. In addition, there is no need to perform adjustments even if the cutter mechanism is replaced due to deterioration over time after installation.

[0016] Therefore, the image forming apparatus of the present invention can accurately determine the position at which the cutter mechanism cuts the sheet without controlling and adjusting the cutting position of the sheet. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view of an image forming apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view of the image forming apparatus of the embodiment, showing a state in which the second guide is in the first guide position, the pre-cutting cover is in the first cover position, and the exterior cover is closed. [Diagram 3] FIG. 3 is a schematic cross-sectional view similar to FIG. 2, illustrating a state in which the second guide is in the second guide position, the pre-cutting cover is in the second cover position, and the exterior cover is open. [Figure 4] FIG. 4 is an enlarged partial perspective view of a main part of FIG. [Diagram 5] FIG. 5 is a perspective view showing a unit including the cutter mechanism, the first guide and the pre-cutting guide. [Figure 6] FIG. 6 is a schematic enlarged partial cross-sectional view of a main part of FIG. [Figure 7] FIG. 7 is a perspective view showing a unit including the cutter mechanism, the first guide and the pre-cutting guide. [Figure 8] FIG. 8 is an exploded perspective view of the cutter mechanism, the first guide, and the pre-cutting guide. [Figure 9] FIG. 9 is a front view showing a unit including the cutter mechanism, the first guide and the pre-cutting guide. [Figure 10] FIG. 10 is a front view showing the cutter mechanism. [Figure 11] FIG. 11 is a partial top view showing a unit of the cutter mechanism, the first guide and the pre-cutting guide, and a joint cover. [Figure 12] FIG. 12 is a partial top view illustrating the folding back position of the moving blade of the cutter mechanism. [Figure 13] FIG. 13 is a partial schematic cross-sectional view similar to FIG. 6, relating to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0019] (Example) As shown in Fig. 1, an image forming apparatus 1 of the embodiment 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 machine including an image forming unit 3 and a fixing unit 7 that form an image on a sheet SH by an electrophotographic method, and an image reading unit 35 that reads an image of a document.

[0020] In Fig. 1, the side of the operation panel 37 of the image forming apparatus 1 is the front. The left-right direction of the image forming apparatus 1 is a direction that is perpendicular to the front-rear direction and extends horizontally. The side that is to the left when facing the operation panel 37 is the left side. The directions shown in Fig. 2 and subsequent figures are all displayed in accordance with the directions shown in Fig. 1.

[0021] <Overall composition> As shown in FIGS. 1 and 2, the image forming apparatus 1 includes a first housing 10, a second housing 30, and a joint cover 50. The first housing 10 includes a first fixing member 12 and a second fixing member 13. The first fixing member 12 is a fixing member for fixing the first fixing member 12.

[0022] The first housing 10 is a generally box-shaped body. The second housing 30 is a generally box-shaped body with a flat shape whose vertical length is significantly smaller than that of the first housing 10. The second housing 30 is spaced upward from the first housing 10. The joint cover 50 supports the second housing 30 from below above the first housing 10.

[0023] As shown in Fig. 2, the first housing 10 accommodates a sheet cassette 10C in its lower portion. The sheet cassette 10C supports sheets SH on which images are to be formed in a stacked state. The sheets SH are paper, overhead projector sheets, etc. The first housing 10 accommodates an image forming unit 3 and a fixing unit 7 above the sheet cassette 10C.

[0024] As shown in FIGS. 2 and 3, the first housing 10 has a maintenance opening 19 and an exterior cover 90.

[0025] The maintenance opening 19 is a large, generally rectangular opening that exposes a portion of the rear surface of the first housing 10 that is located above the rear end of the sheet cassette 10C.

[0026] 2, the exterior cover 90 closes the maintenance opening 19 in an upright state, and constitutes part of the exterior surface of the rear of the first housing 10. As shown in Fig. 3, the exterior cover 90 opens the maintenance opening 19 by rotating its lower end portion as a rotation axis and moving its upper end portion rearward and downward.

[0027] 2 and 4, the joint cover 50 has a discharge tray 9. The discharge tray 9 is located in the center in the left-right direction on the top surface of the first housing 10. The discharge tray 9 extends horizontally rearward from the front end side of the top surface of the first housing 10, and then bends and slopes downward rearward.

[0028] The discharge tray 9 defines the lower side of a discharge space AD1 defined between the first housing 10 and the second housing 30. A sheet SH on which an image has been formed after passing through the image forming unit 3 and the fixing unit 7 is discharged to the discharge space AD1. The discharge tray 9 supports the sheet SH discharged to the discharge space AD1.

[0029] As shown in FIG. 4, the joint cover 50 has inner wall surfaces 58 and 59 .

[0030] The inner wall surface 58 is the right side surface of a portion of the joint cover 50 that is located to the left of the discharge tray 9 and protrudes upward. The inner wall surface 58 defines the left side of the discharge space AD1.

[0031] 2 and 4, the inner wall surface 59 is the left side surface of a portion of the joint cover 50 that is located to the right of the discharge tray 9 and protrudes upward. The inner wall surface 59 defines the right side of the discharge space AD1.

[0032] 2, the second housing 30 houses the image reading unit 35. The image reading unit 35 is located at a position spaced above the discharge tray 9. The image reading unit 35 has a well-known configuration and will not be described briefly, but reads an image of a document placed on the upper surface of the second housing 30 by a reading sensor (not shown). The document is a book, a sheet, or the like.

[0033] The second housing 30 also has 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.

[0034] 1, the document cover 40 has a supply tray 41 and a discharge tray 42 located on the right side thereof. The supply tray 41 is spaced above the discharge tray 42.

[0035] The automatic document feed mechanism 45 is a well-known configuration and will not be described here, but it feeds the 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 the document onto the discharge tray 42. The reading sensor (not shown) reads the image of the document being fed.

[0036] The operation 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 operation panel 37 is supported from below by the front end of a portion of the joint cover 50 that is located to the left of the discharge tray 9 and protrudes upward.

[0037] The operation panel 37 has an operation surface that receives operation input by a user's finger, and a display unit such as an LCD located below the operation surface. The operation panel 37 displays information indicating the operating state and settings of the image forming apparatus 1, and notifies the user by displaying error messages, etc.

[0038] As shown in FIG. 2, in the image forming apparatus 1, the image forming section 3 includes a developing device 3A, a photoconductor 5, and a scanner section 8.

[0039] The image forming apparatus 1 includes a first feed roller 21, a first separation roller 22, a separation pad 22A, a conveying roller pair 23, a registration roller pair 24 and a post-fixing conveying roller pair 25 housed in a first housing 10 together with the image forming section 3 and the fixing unit 7.

[0040] A first feeding roller 21, a first separation roller 22, a separation pad 22A, and a transport roller pair 23 are located in the front portion of the first housing 10. A post-fixing transport roller pair 25 is located in the rear portion of the first housing 10.

[0041] 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 a U-turn upward, passes through a first feeding roller 21, a first separation roller 22, a separation pad 22A, and a transport roller pair 23, and then proceeds approximately horizontally backward, passes through a registration roller pair 24, a photoconductor 5, and a fixing device 7, and reaches a post-fixing transport roller pair 25.

[0042] The first feeding roller 21 is located at the most upstream end of the conveying path P1. The first separation roller 22 and the separation pad 22A are located downstream of the conveying path P1 from the first feeding roller 21. The conveying roller pair 23 is located downstream of the first separation roller 22 and the separation pad 22A from the conveying path P1, midway through the portion of the conveying path P1 that makes an upward U-turn.

[0043] The registration roller pair 24 is located downstream of the transport roller pair 23 on the transport path P1 and upstream of the photoconductor 5 on the transport path P1, midway along the portion of the transport path P1 that advances substantially horizontally backward.

[0044] The first feeding roller 21 feeds the sheet SH supported by the sheet cassette 10C toward the photoconductor 5. If there are multiple sheets SH sent to the conveying path P1 by the first feeding roller 21, the first separation roller 22 and the separation pad 22A separate the sheets SH one by one. Then, the conveying roller pair 23 and the registration roller pair 24 convey the sheet SH to the photoconductor 5.

[0045] The developing device 3A has a toner storage chamber 3D that stores toner, and a developing roller 3B to which toner is supplied from the toner storage chamber 3D. The photoconductor 5 is located behind and below the developing roller 3B, and is in contact with the developing roller 3B.

[0046] The photoreceptor 5 is a cylindrical rotating body centered on a rotation axis extending in the left-right direction. A positively charged photosensitive layer is formed on the surface of the photoreceptor 5 in correspondence with the positively charged toner. Note that a negatively charged photosensitive layer may also be formed on the surface of the photoreceptor 5, in which case a negatively charged toner is used.

[0047] The photoreceptor 5 can come into contact with the sheet SH transported along a portion of the transport path P1 that moves rearward and approximately horizontally from above. A transfer roller 5A is located below the photoreceptor 5. The transfer roller 5A faces the photoreceptor 5 from below, with the transport path P1 in between.

[0048] The developing device 3A further includes a charger 3E. The charger 3E faces the rear of the photoconductor 5. The charger 3E is a well-known Scorotron charger.

[0049] The scanner unit 8 is located above the developing device 3A and the photoconductor 5. The scanner unit 8 has a laser light source, a polygon mirror, an fθ lens, a reflecting mirror, and the like, which are well-known components. The scanner unit 8 irradiates the surface of the photoconductor 5 with a laser beam.

[0050] The surface of the photoreceptor 5 is uniformly positively charged by the charger 3E as it rotates, and then exposed to high-speed scanning of a laser beam emitted 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.

[0051] Then, the developing roller 3B supplies toner to the photoreceptor 5 in accordance with the electrostatic latent image formed on the surface of the photoreceptor 5. As a result, a toner image is carried on the surface of the photoreceptor 5. The photoreceptor 5 transfers the toner image to the upward surface of the sheet SH that passes through the nip position between the photoreceptor 5 and the transfer roller 5A.

[0052] The fixing unit 7 is located behind the photoconductor 5 and in front of the post-fixing transport roller pair 25. The fixing unit 7 has a heating member 7A located above the transport path P1, and a pressure roller 7B facing the heating member 7A from below with the transport path P1 in between.

[0053] The heating member 7A includes an endless belt, a guide member that supports the endless belt from its inner periphery so as to be circulable, and a heater that heats the endless belt from its inner periphery. The heating member 7A and the pressure roller 7B nip the sheet SH at the fixing nip portion 7N.

[0054] The fixing unit 7 heats and presses the sheet SH onto which the toner image has been transferred, by using a heating member 7A and a pressure roller 7B, thereby thermally fixing the toner image onto the sheet SH. A post-fixing transport roller pair 25 transports the sheet SH that has passed through the fixing unit 7 upward and backward.

[0055] The image forming apparatus 1 includes a control unit C1, a pre-registration sheet sensor S1, a post-registration sheet sensor S2, and a post-fixing sheet sensor S3.

[0056] The first housing 10 houses a control unit C1. The control unit C1 is an electronic circuit unit including a CPU, an interface circuit, and a storage unit (not shown). The control unit C1 performs overall control over each unit of the image forming apparatus 1.

[0057] The control unit C1 is electrically connected to the pre-registration sheet sensor S1, the post-registration sheet sensor S2, and the post-fixing sheet sensor S3.

[0058] The pre-registration sheet sensor S1 is located immediately before the pair of registration rollers 24 on the transport path P1, detects the passage of the sheet SH, and transmits the detection result to the control unit C1. The control unit C1 performs control to correct the skew of the sheet SH that reaches the pair of registration rollers 24 based on the detection result of the pre-registration sheet sensor S1.

[0059] The post-registration sheet sensor S2 is located immediately behind the pair of registration rollers 24 on the transport path P1, and detects the passage of the sheet SH and transmits the detection result to the control unit C1. The control unit C1 controls the timing of the image forming operation by the image forming unit 3 and the fixing unit 7 based on the detection result of the post-registration sheet sensor S2.

[0060] The post-fixing sheet sensor S3 is located between the fixing unit 7 and the post-fixing conveying roller pair 25 on the conveying path P1, detects the passage of the sheet SH, and transmits the detection result to the control unit C1. The control unit C1 controls the timing of a plurality of operations performed until the sheet SH that has passed through the fixing unit 7 is discharged to the discharge tray 9, based on the detection result of the post-fixing sheet sensor S3.

[0061] As the pre-registration sheet sensor S1, the post-registration sheet sensor S2, and the post-fixing sheet sensor S3, a sensor having an actuator that swings when the sheet SH comes into contact with it, a light reflection type sensor, or the like can be used.

[0062] The image forming apparatus 1 includes a flapper 26. The flapper 26 is located above the post-fixing conveying 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 FIG. 2 and the position shown by the two-dot chain line in FIG. 2.

[0063] The image forming apparatus 1 includes 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.

[0064] The first discharge path PD1 is an effective discharge path when the flapper 26 is in the position shown by the solid line in Fig. 2. The second discharge path PD2 is an effective discharge path when the flapper 26 is in the position shown by the two-dot chain line in Fig. 2.

[0065] The first discharge path PD1 advances upward between the flapper 26, which is positioned as shown by the solid line in FIG. 2, and the outer cover 90, and discharges the sheet SH that has passed through the fixing device 7 into the discharge space AD1 by making the conveying direction DT1 of the sheet SH face forward and substantially horizontal above the flapper 26.

[0066] 2, the sheet SH is guided in a conveying direction DT1 of the sheet SH toward a substantially horizontal forward direction, and the sheet SH that has passed through the fixing unit 7 is discharged to the discharge space AD1. The second discharge path PD2 discharges the sheet SH to the discharge space AD1 at a position lower than the first discharge path PD1 and upstream of the first discharge path PD1 in the conveying direction DT1.

[0067] The image forming apparatus 1 includes a pre-cutting cover 80, a first conveying roller 71, and a second conveying roller 72, which are arranged at a portion of the first discharge path PD1 where the conveying direction DT1 changes from upward to forward.

[0068] 2, 5 and 6, the image forming apparatus 1 includes a pre-cutting guide 300 arranged along a portion of the first discharge path PD1 in which the conveying direction DT1 faces substantially horizontally forward, a cutter mechanism 4, a first guide 100, a second guide 200, a sheet sensor S4, and a first discharge roller pair 29. The first guide 100 is an example of the "sheet guide" of the present invention.

[0069] As shown in FIG. 2, the image forming apparatus 1 includes a second discharge roller pair 28 disposed at the most downstream end of the second discharge path PD2.

[0070] The second discharge roller pair 28 is located above an upstream end 9U in the transport direction DT1 of the discharge tray 9. The second discharge roller pair 28 discharges the sheet SH that passes through the fixing unit 7 and is transported without passing through the cutter mechanism 4 onto the discharge tray 9.

[0071] 2 and 4, the first discharge roller pair 29 is located below the image reading unit 35 and above the second discharge roller pair 28. The first discharge roller pair 29 is located downstream of the second discharge roller pair 28 in the transport direction DT1. The first discharge roller pair 29 is located above the middle part in the front-to-rear direction of the downwardly inclined portion of the discharge tray 9. The first discharge roller pair 29 is located downstream of the cutter mechanism 4 in the transport direction DT1. The first discharge roller pair 29 discharges the sheet SH (SH1) that has passed through the fixing unit 7 and has been cut in half in length by the cutter mechanism 4 to the discharge tray 9.

[0072] <Pre-cutting cover, first conveyor roller and second conveyor roller> 2 and 3, the pre-cutting cover 80 is located at the lower end of the pre-cutting cover 80 and is rotatable around a cover axis X80 parallel to the left-right direction. The cross section of the pre-cutting cover 80 shown in Figs. 2 and 3 shows the center in the left-right direction of the pre-cutting cover 80. Although not shown, the lower end of the pre-cutting cover 80 is located outside the sheet SH transported along the first discharge path PD1 in the left-right direction and extends to the cover axis X80.

[0073] The pre-cutting cover 80 supports the first conveyor roller 71 and the second conveyor roller 72. The second conveyor roller 72 is located below the first conveyor roller 71 and faces the first conveyor roller 71.

[0074] The pre-cutting cover 80 can be moved between a first cover position shown in FIG. 2 and a second cover position shown in FIG. 3 by rotating about a cover axis X80 with the exterior cover 90 open.

[0075] 2, when the pre-cutting cover 80 is in the first cover position, it guides the sheet SH that has passed through the fixing unit 7 and is transported along the first discharge path PD1 toward the cutter mechanism 4. In this state, the first transport roller 71 and the second transport roller 72 are located upstream of the cutter mechanism 4 in the transport direction DT1. The first transport roller 71 and the second transport roller 72 transport the sheet SH that has passed through the fixing unit 7 toward the cutter mechanism 4.

[0076] 3, the pre-cutting cover 80 moves away from the cutter mechanism 4 upstream in the conveying direction DT1 by rotating to the second cover position with the exterior cover 90 open to open the maintenance opening 19. In this state, the first conveying roller 71 and the second conveying roller 72 also move rearward and downward away from the cutter mechanism 4. This causes the maintenance opening 19 to expose the pre-cutting cover 80 at the second cover position to the outside of the first housing 10. As a result, the user can remove the sheet SH that is jammed around the exterior cover 90 and the pre-cutting cover 80 in the first discharge path PD1.

[0077] In addition, in a state in which the exterior cover 90 is opened to expose the maintenance opening 19 and in a state in which the pre-cutting cover 80 is in the first cover position, the user can carry out the operation of removing the sheet SH that is clogged in the second discharge path PD2.

[0078] <Pre-cutting guide, cutter mechanism, first guide, second guide, sheet sensor, and first discharge roller pair> 5 to 10, the pre-cutting guide 300, the cutter mechanism 4, and the first guide 100 are fastened together to form a unit. As shown in Fig. 2 and Fig. 11, the pre-cutting guide 300, the cutter mechanism 4, and the first guide 100 are assembled to the joint cover 50 as a unit and fixed to the joint cover 50. During maintenance work, etc., the pre-cutting guide 300, the cutter mechanism 4, and the first guide 100 are removed from the joint cover 50 as a unit.

[0079] As shown in Fig. 2, the pre-cutting guide 300 is provided downstream in the conveying direction DT1 of the pre-cutting cover 80 at the first cover position. As shown in Fig. 6, the pre-cutting guide 300 is provided upstream in the conveying direction DT1 of the cutter mechanism 4. As shown in Fig. 5 and Fig. 8, the pre-cutting guide 300 is a resin molded product manufactured by injection molding of thermoplastic resin or the like.

[0080] 6 and 9, the pre-cutting guide 300 has guide surfaces 301 and 302 that guide the sheet SH passing through the cutter mechanism 4. The guide surface 301 faces the guide surface 302 from above. The guide surface 301 is formed by the lower ends of a plurality of ribs that are arranged apart from each other in the left-right direction.

[0081] As shown in FIG. 6, the sheet SH conveyed by the first conveying roller 71 and the second conveying roller 72 toward the cutter mechanism 4 passes between a guide surface 301 and a guide surface 302 and reaches the cutter mechanism 4. As shown in FIG.

[0082] The cutter mechanism 4 has a cutter carriage 420 shown in Figures 5 to 8 and 10 to 12, a cutter frame 400 shown in Figures 5 to 11, a moving blade 412 shown in Figures 6 and 10, and a fixed blade 411 shown in Figures 6, 8 and 10.

[0083] As shown in FIG. 6, the cutter carriage 420 rotatably holds a circular moving blade 412 .

[0084] 6, 8, and 10, the cutter frame 400 is made of metal, and is specifically manufactured by pressing, punching, bending, etc., a steel plate. A cutter frame opening 409 is formed in the cutter frame 400. The cutter frame opening 409 has an inner width in the left-right direction larger than the width of the sheet SH so that the sheet SH guided by the guide surfaces 301 and 302 of the pre-cutting guide 300 can pass through the cutter frame opening 409. As shown in FIG. 6, the downstream side of the guide surface 301 in the conveying direction DT1 enters the cutter frame opening 409.

[0085] 6, 8, and 10, the cutter frame 400 has a guide portion 402 above the cutter frame opening 409 and on the opposite side to the pre-cutting guide 300. The guide portion 402 guides the cutter carriage 420 in a cutting direction DC1 perpendicular to the conveying direction DT1, i.e., in the left-right direction, and regulates the cutter carriage 420 so as not to come off the guide portion 402. In other words, the cutter frame 400 holds the cutter carriage 420 movably in the cutting direction DC1.

[0086] As shown in FIG. 11, the cutter frame 400 extends in a direction perpendicular to the transport direction DT1, that is, in the left-right direction, when assembled to the image forming apparatus 1.

[0087] 5, the cutter frame 400 has a first motor M1 and a timing belt 430. The first motor M1 is located on the left end side of the cutter frame 400 and above the cutter frame opening 409.

[0088] 10, the first motor M1 is located above the cutter frame opening 409 when viewed along the conveying direction DT1, and the first motor M1 entirely overlaps with the cutter frame opening 409 in the cutting direction DC1. With this configuration, it is possible to more reliably prevent the image forming apparatus 1 from becoming larger in the cutting direction DC1, compared to a case in which the first motor M1 entirely does not overlap with the cutter frame opening 409 in the cutting direction DC1 when viewed along the conveying direction DT1.

[0089] The cutter mechanism 4 includes a drive pulley 431 , a plurality of driven pulleys 432 , 433 , 434 , a belt tensioner 435 , and a tension spring 436 .

[0090] The longitudinal direction of the cutter frame opening 409 is the same as the cutting direction DC1, i.e., the left-right direction. The drive pulley 431 is located at one end of the longitudinal direction of the cutter frame opening 409, i.e., to the left of the left end, and is rotatably supported by the cutter frame 400. The driven pulley 432 is located on the left end side of the cutter frame opening 409, below the cutter frame opening 409, and is rotatably supported by the cutter frame 400.

[0091] The driven pulley 433 is housed in an upper portion of the belt tensioner 435. In this state, the driven pulley 433 is located at the other end in the longitudinal direction of the cutter frame opening 409, i.e., to the right of the right end, and is rotatably supported by the cutter frame 400. The belt tensioner 435 is capable of swinging coaxially with the driven pulley 433. This makes it possible to achieve space saving compared to a case in which the swing shaft of the belt tensioner 435 is not coaxial with the driven pulley 433.

[0092] The driven pulley 434 is housed in a lower portion of the belt tensioner 435. The lower end of the belt tensioner 435 protrudes downward further than the driven pulley 434. The tension spring 436 is a metallic compression coil spring. One end of the tension spring 436 is engaged with a right lower corner of the cutter frame 400. The other end of the tension spring 436 is engaged with the lower end of the belt tensioner 435.

[0093] Timing belt 430 is wound around driving pulley 431 and driven pulleys 432, 433, and 434, and surrounds cutter frame opening 409. Belt tensioner 435 is biased by tension spring 436 to swing, and driven pulley 434 moves to the right, thereby applying tension to timing belt 430. As a result, even if timing belt 430 that is easily affected by heat from fixing and the like is used, the compression coil spring made of a metal with high heat resistance can stably apply appropriate tension to timing belt 430.

[0094] As shown in FIG. 5, the cutter carriage 420 is connected to a portion of the timing belt 430 that extends in the left-right direction above the cutter frame opening 409 .

[0095] The first motor M1 drives the drive pulley 431 via a gear train to rotate it in the forward and reverse directions, whereby the cutter carriage 420 and the moving blade 412 move in the cutting direction DC1.

[0096] 5, the cutter carriage 420 (420A) is shown in a standby position at the right end of the cutter frame opening 409 where it does not interfere with the right edge of the sheet SH. The cutter carriage 420 (420B) is shown in a state in the middle of moving in the cutting direction DC1. The cutter carriage 420 (420C) is shown in a folded-back position at the left end of the cutter frame opening 409 where it does not interfere with the left edge of the sheet SH.

[0097] The cutter carriage 420 (420A) shown in Figures 7, 10, and 11 is in a standby position. The cutter carriage 420 (420B) shown in Figure 7 is in the middle of moving in the cutting direction DC1. The cutter carriage 420 (420C) shown in Figures 7, 8, 10, and 12 is in a return position.

[0098] 6 and 8, the fixed blade 411 is fastened to the cutter frame 400 below the lower edge of the cutter frame opening 409. The fixed blade 411 extends upward and then bends to extend downstream in the conveying direction DT1. The cutting edge of the fixed blade 411 extends linearly in the cutting direction DC1.

[0099] When moving in the cutting direction DC1, the moving blade 412 comes into sliding contact with the cutting edge of the fixed blade 411. The cutter mechanism 4 cuts the sheet SH that has passed through the fixing device 7 by the fixed blade 411 and the moving blade 412 in the cutting direction DC1.

[0100] 5 to 8, the first guide 100 is provided downstream in the conveying direction DT1 from the cutter mechanism 4. The first guide 100 has a bottom wall 105 and a plurality of ribs 107. The first guide 100 is a resin molded product manufactured by injection molding of a thermoplastic resin or the like.

[0101] The bottom wall 105 is curved and extends in the front-rear direction and 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. Each rib 107 is spaced apart from each other in the left-right direction.

[0102] The first guide 100 has a first guide surface 101. The first guide surface 101 is formed by the tips of the front ribs 107. The first guide 100 guides the sheet SH, which is transported from the cutter mechanism 4 to the first discharge roller pair 29, by the first guide surface 101.

[0103] The first discharge roller pair 29 includes a first discharge roller 29A which is a driven roller, and a second discharge roller 29B which is a drive roller.

[0104] The first guide 100 rotatably supports the first discharge roller 29A. The first discharge roller 29A is rotatably supported on the downstream end 100D side of the first guide 100 in the transport direction DT1.

[0105] A pressure spring (not shown) is positioned between the first guide 100 and the first discharge roller 29A. When the first discharge roller 29A and the second discharge roller 29B are in a nip state, the pressure spring (not shown) applies a pressure force to the first discharge roller 29A to ensure a nip pressure.

[0106] 5 and 8, the first guide 100 has a left wall 106L and a right wall 106R. The left wall 106L is connected to the left end of the bottom wall 105, extends upward, and also extends in the front-to-rear direction. The right wall 106R is connected to the right end of the bottom wall 105, extends upward, and also extends in the front-to-rear direction.

[0107] As shown in Fig. 8, a shaft hole 102H is formed at a rear and lower position of the left wall 106L so as to penetrate therethrough in the left-right direction. A shaft hole 102H is also formed at a rear and lower position of the right wall 106R so as to penetrate therethrough in the left-right direction. The shaft hole 102H is a circular hole centered on a rotation axis X200 extending in the left-right direction.

[0108] 4 and 6, the second guide 200 has an upper wall 205. The upper wall 205 is bent so that the front portion is one step higher than the rear portion, and extends in the front-rear direction and also in the left-right direction. The second guide 200 is a resin molded product manufactured by injection molding of a thermoplastic resin or the like.

[0109] The second guide 200 has a pair of rotation shafts (not shown) provided to the left of the left end of the upper wall 205 and to the right of the right end of the upper wall 205. The pair of rotation shafts (not shown) are inserted into shaft holes 102H in the left wall 106L and right wall 106R of the first guide 100, so that the second guide 200 can rotate about a rotation axis X200. The joint cover 50 to which the first guide 100 is fixed supports the second guide 200 to be rotatable about the rotation axis X200.

[0110] As shown in FIG. 6, the rotation axis X200 is located on the upstream end 200U side of the second guide 200 in the conveying direction DT1.

[0111] The second discharge roller 29B is rotatably supported by the second guide 200. The second discharge roller 29B is rotatably supported on the downstream end 200D side of the second guide 200 in the transport direction DT1.

[0112] The second guide 200 is movable between a first guide position where the first discharge roller 29A and the second discharge roller 29B are in a nipped state, as shown in Figures 2 and 6, and a second guide position where the first discharge roller 29A and the second discharge roller 29B are in a separated state, as shown in Figure 3.

[0113] The position of the second discharge roller 29B when the second guide 200 is in the second guide position is spaced above the discharge tray 9 further than the position of the second discharge roller 29B when the second guide 200 is in the first guide position.

[0114] 6, the second guide 200 has a plurality of ribs 207. Each rib 207 protrudes downward from the lower surface of the upper wall 205 and extends in the front-rear direction. Each rib 207 is separated from each other in the left-right direction.

[0115] The second guide 200 has a second guide surface 202. The second guide surface 202 is formed by the tip of each front rib 207. The second guide surface 202 faces the first guide surface 101 when the second guide 200 is in the first guide position. The rotation axis X200 is located between the first guide surface 101 and the second guide surface 202 when the second guide 200 is in the first guide position.

[0116] When the second guide 200 is in the first guide position, the upstream side 202U of the second guide surface 202 in the conveying direction DT1 is inclined away from the first guide surface 101 toward the upstream end 200U of the second guide 200, relative to the downstream side 202D of the second guide surface 202 in the conveying direction DT1.

[0117] The second guide 200 guides the sheet SH, which is transported from the cutter mechanism 4 to the first discharge roller pair 29, by the second guide surface 202.

[0118] 5 and 6, the sheet sensor S4 is provided on the first guide 100. The sheet sensor S4 is located between the cutter frame 400 and the first discharge roller pair 29 in the conveying direction DT1.

[0119] 6, the distance in the conveying direction DT1 between the sheet sensor S4 and the cutting position of the fixed blade 411 and the movable blade 412 in the cutter mechanism 4 is defined as LA2. The distance in the conveying direction DT1 between the sheet sensor S4 and the first discharge roller pair 29 is defined as LA1. The distance LA2 is shorter than the distance LA1.

[0120] The sheet sensor S4 is an actuator that swings when the sheet SH comes into contact with it, and detects the sheet SH passing through the cutter mechanism 4. The swing of the sheet sensor S4 is converted into an electric signal by a photointerrupter (not shown) and transmitted to the control unit C1. The control unit C1 controls the timing when the cutter mechanism 4 cuts the sheet SH based on the detection result of the sheet sensor S4.

[0121] Specifically, the control unit C1 determines the timing when the portion of the sheet SH that is half the length of the sheet SH reaches the cutting position of the fixed blade 411 and the moving 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, and when that timing arrives, stops the first conveying roller 71, the second conveying roller 72, and the first discharge roller pair 29 that nip the sheet SH. Then, the control unit C1 controls the first motor M1 to move the moving blade 412 in the cutting direction DC1. As a result, the cutter mechanism 4 cuts the sheet SH to half its length. Thereafter, the control unit C1 rotates the first conveying roller 71, the second conveying roller 72, and the first discharge roller pair 29, and discharges the sheet SH (SH1) that has been cut into two pieces to the discharge tray 9.

[0122] 3, when a sheet SH becomes jammed around the cutter mechanism 4, the user moves the second guide 200 from the first guide position to the second guide position. This separates the first discharge roller 29A and the second discharge roller 29B, allowing the user to easily grab and pull out the jammed sheet SH. As a result, the image forming apparatus 1 can easily remove the jammed sheet SH around the cutter mechanism 4.

[0123] <Positioning and fastening of pre-cutting guide, cutter mechanism and first guide> In order to prevent the position at which the sheet sensor S4 provided on the first guide 100 detects the sheet SH from shifting relative to the cutter mechanism 4, the image forming apparatus 1 fastens and positions the pre-cutting guide 300, the cutter mechanism 4 and the first guide 100 as a unit in the following manner.

[0124] As shown in FIG. 8, the first guide 100 has four fastening bosses 181, 182, 183, and 184, and two first positioning portions 191 and 192.

[0125] Each of the fastening bosses 181, 182, 183, and 184 is a cylinder that protrudes toward the upstream in the conveying direction DT1. A screw hole that is recessed from the center of the tip surface toward the downstream in the conveying direction DT1 is formed in each of the fastening bosses 181, 182, 183, and 184. The tip of the fastening boss 184 is tapered in diameter in two stages.

[0126] The fastening boss 181 is located to the left of the upper end side of the left wall 106L of the first guide part 100. The fastening boss 182 is located on the left end side of the upstream end 100U of the first guide part 100 in the conveying direction DT1. The fastening boss 183 is located on the right end side of the upstream end 100U of the first guide part 100. The fastening boss 184 is located between the fastening boss 182 and the fastening boss 183 at the upstream end 100U of the first guide part 100.

[0127] Each of the first positioning portions 191 and 192 is a convex portion made up of a cylinder that protrudes upstream in the transport direction DT1 and a truncated cone that is connected to the tip of the cylinder and protrudes upstream in the transport direction DT1.

[0128] The first positioning portion 191 is located to the right of the fastening boss 182 at the upstream end 100U of the first guide portion 100. The second positioning portion 192 is located to the left of the fastening boss 183 at the upstream end 100U of the first guide portion 100.

[0129] The cutter frame 400 of the cutter mechanism 4 has four insertion holes 481, 482, 483, and 484, two screw holes 485 and 486, and two second positioning portions 491 and 492.

[0130] The insertion hole 481 is located to the left of the first motor M1 on the cutter frame 400, and is positioned to align with the fastening boss 181. The insertion holes 482, 483, 484 are located below the cutter frame opening 409 on the cutter frame 400.

[0131] The insertion hole 482 is located at one end side in the longitudinal direction of the cutter frame opening 409 in the cutter frame 400 , that is, at the left end side, and at a position aligned with the fastening boss 182 .

[0132] The insertion hole 483 is located at the other end side in the longitudinal direction of the cutter frame opening 409 in the cutter frame 400 , that is, at the right end side, and at a position aligned with the fastening boss 183 .

[0133] The insertion hole 484 is located between the insertion holes 482 and 483 in the cutter frame 400, and is aligned with the fastening boss 184. The inner diameter of the insertion hole 484 is set to a size that allows the first reduced diameter portion at the tip of the fastening boss 184 to pass through.

[0134] The screw hole 485 is located to the right of the right end of the cutter frame opening 409 in the cutter frame 400. The screw hole 486 is located above the middle part of the cutter frame opening 409 in the left-right direction in the cutter frame 400.

[0135] Each of the second positioning portions 491 and 492 is located below the cutter frame opening 409 in the cutter frame 400 .

[0136] The second positioning portion 491 is located on the left end side of the cutter frame opening 409 and is in a position aligned with the first positioning portion 191. The second positioning portion 491 is a circular through hole into which the first positioning portion 191 fits.

[0137] The second positioning portion 492 is located at a position on the right end side of the cutter frame opening 409 and aligned with the first positioning portion 192. The second positioning portion 492 is an oval through-hole that is long in the left-right direction and fits with the first positioning portion 192.

[0138] The pre-cutting guide 300 has six insertion holes 381, 382, ​​383, 384, 385, and 386, and two third positioning portions 391 and 392.

[0139] The insertion hole 381 is located on the upper end side of the left end portion of the pre-cutting guide 300 and is positioned to align with the insertion hole 481 and the fastening boss 181. The insertion hole 382 is located on the lower end edge side of the pre-cutting guide 300 and is positioned to align with the insertion hole 482 and the fastening boss 182. The insertion hole 383 is located on the lower end edge side of the pre-cutting guide 300 and is positioned to align with the insertion hole 483 and the fastening boss 183. The insertion hole 384 is located on the lower end edge side of the pre-cutting guide 300 and is positioned to align with the insertion hole 484 and the fastening boss 184.

[0140] The insertion hole 385 is located at the right end side of the pre-cutting guide 300, at a position that aligns with the screw hole 485. The insertion hole 386 is located at the center in the left-right direction of the upper part of the pre-cutting guide 300, at a position that aligns with the screw hole 486.

[0141] As shown in FIGS. 8 and 9, the third positioning portions 391 and 392 are located below the guide surface 302 of the pre-cutting guide 300.

[0142] The third positioning portion 391 is located at a position that aligns with the first positioning portion 191 and the second positioning portion 491. The third positioning portion 391 is a circular through hole into which the first positioning portion 191 fits.

[0143] The third positioning portion 392 is located at a position that aligns with the first positioning portion 192 and the second positioning portion 492. The third positioning portion 392 is an oval through hole that is long in the left-right direction and into which the first positioning portion 192 fits.

[0144] The first positioning portions 191, 192 are fitted one-to-one with the second positioning portions 491, 492. The first positioning portions 191, 192 pass through the second positioning portions 491, 492 and are fitted one-to-one with the third positioning portions 391, 392.

[0145] The first guide 100 is positioned on the cutter frame 400 by fitting the first positioning portions 191, 192 with the second positioning portions 491, 492. The pre-cutting guide 300 is positioned on the first guide 100 and the cutter frame 400 by fitting the first positioning portions 191, 192 with the third positioning portions 391, 392.

[0146] The pre-cutting guide 300, the cutter frame 400 and the first guide 100 are fastened together by the screws 501 to 504.

[0147] Specifically, the screw 501 is inserted through the insertion holes 381 and 481 and screwed into the screw hole of the fastening boss 181. The screw 502 is inserted through the insertion holes 382 and 482 and screwed into the screw hole of the fastening boss 182. At this time, the tip surface of the fastening boss 182 is in close contact with the cutter frame 400. The screw 503 is inserted through the insertion holes 383 and 483 and screwed into the screw hole of the fastening boss 183. At this time, the tip surface of the fastening boss 183 is in close contact with the cutter frame 400. The screw 504 is inserted through the insertion holes 384 and 484 and screwed into the screw hole of the fastening boss 184. At this time, the tip surface of the fastening boss 184 has a shaft shape that reduces in diameter in two stages as shown in FIG. 8, so that it does not come into close contact with the cutter frame 400 but comes into close contact with the pre-cutting guide 300.

[0148] As shown in FIGS. 8 and 9, the pre-cutting guide 300 and the cutter frame 400 are fastened together by screws 505, 506.

[0149] Specifically, the screw 505 is inserted into the insertion hole 385 and screwed into the screw hole 485. The screw 506 is inserted into the insertion hole 386 and screwed into the screw hole 486.

[0150] In this manner, the first guide 100 and the pre-cutting guide 300 are fixed by fastening with the cutter frame 400 sandwiched between them.

[0151] <Positioning and fastening of the pre-cutting guide, cutter mechanism and first guide unit to the joint cover> As shown in FIG. 11, the unit of the pre-cutting guide 300, the cutter mechanism 4 and the first guide 100 is positioned by four positioning bosses 50M1 to 50M4 formed on the joint cover 50, and then fastened with screws at five fastening points 50N1 to 50N5.

[0152] The two positioning bosses 50M1, 50M2 position the pre-cutting guide 300 relative to the joint cover 50. The other two positioning bosses 50M3, 50M4 position the first guide 100 relative to the joint cover 50.

[0153] The two fastening points 50N1 and 50N2 fasten the pre-cut guide 300 to the joint cover 50. The other three fastening points 50N3 to 50N5 fasten the first guide 100 to the joint cover 50.

[0154] <How to determine the turnaround position and waiting position> 5, the first motor M1 is a stepping motor having an encoder M1E. A restricting protrusion 420T is formed on the left side surface of the cutter carriage 420 so as to protrude leftward by a short distance.

[0155] When the image forming apparatus 1 is powered on, the control unit C1 performs an initial operation to position the cutter carriage 420 at the standby position (420A) as follows.

[0156] The control unit C1 actuates the first motor M1 to rotate the drive pulley 431 in the forward direction, whereby the cutter carriage 420 moves leftward, that is, in a direction approaching the turning back position (420C).

[0157] As shown in FIG. 12, there is a regulating wall 120T on the left end side of the first guide 100. When the encoder M1E detects that the first motor M1 has stopped rotating, the control unit C1 determines that the regulating protrusion 420T of the cutter carriage 420 has come into contact with the regulating wall 120T and the cutter carriage 420 has reached the turn-back position (420C), and stops the first motor M1. As a result, the cutter carriage 420 is positioned at the turn-back position (420C). By using the regulating wall 120T, there is no need to provide a dedicated stopper for positioning the cutter carriage 420 at the turn-back position (420C).

[0158] Next, the control unit C1 operates the first motor M1 to rotate the drive pulley 431 in the reverse direction. This causes the cutter carriage 420 to move rightward, that is, in the direction approaching the standby position (420A). Then, when the amount of rotation detected by the encoder M1E reaches a value indicating that the cutter carriage 420 has reached the standby position (420A), the control unit C1 determines that the cutter carriage 420 has reached the standby position (420A) and stops the first motor M1. As a result, the cutter carriage 420 is accurately positioned at the standby position (420A).

[0159] 10 is a sensor capable of detecting whether or not the moving blade 412 is attached to the cutter carriage 420 when the cutter carriage 420 is in the standby position. The sensor S6 goes into a state where it outputs a presence signal of the moving blade 412 when the actuator is pressed by the moving blade 412 held by the cutter carriage 420, and goes into a state where it outputs an absence signal in any other case. The control unit C1 can detect the presence or absence of the moving blade 412 by checking the state of the sensor S6 at an appropriate timing.

[0160] <Action and effect> 8, in the image forming apparatus 1 of the embodiment, the sheet sensor S4 is provided on the first guide 100 made of a material constituting the cutter frame 400, that is, a material having a lower rigidity than metal, that is, a resin. The first guide 100 is positioned on the cutter frame 400.

[0161] Therefore, compared to a case in which the cutter frame 400 and the first guide 100 provided with the sheet sensor S4 are separately assembled to the image forming apparatus 1, it is possible to suppress deviation of the relative position of the first guide 100 with respect to the cutter mechanism 4. As a result, in this image forming apparatus 1, the position at which the sheet sensor S4 detects the sheet SH is less likely to deviate from the designed position with respect to the cutter mechanism 4, and a malfunction in which the cutter mechanism 4 is unable to cut the sheet SH at the target cutting position is less likely to occur when the sheet SH is transported by a transport amount to a preset cutting position of the sheet SH.

[0162] As a result, this image forming apparatus 1 does not need to perform printing with cutting several times before shipping, measure the deviation in the position where the sheet sensor S4 detects the sheet SH, and perform adjustments to control the required transport amount from when the sheet SH is detected to the position where the sheet SH is to be cut. In addition, there is no need to perform adjustments even if the cutter mechanism 4 is replaced due to deterioration over time after installation.

[0163] Therefore, the image forming apparatus 1 of the embodiment can accurately determine the position where the cutter mechanism 4 cuts the sheet SH without controlling and adjusting the cutting position of the sheet SH.

[0164] Furthermore, in this image forming apparatus 1, the first guide 100 is positioned on the cutter frame 400 by fitting the first positioning portions 191, 192 and the second positioning portions 491, 492 together. With this configuration, the first guide 100 is directly positioned on the cutter frame 400, so it is possible to highly reliably prevent the relative position of the first guide 100 with respect to the cutter mechanism 4 from shifting. As a result, in this image forming apparatus 1, the position at which the sheet sensor S4 detects the sheet SH is even less likely to shift with respect to the cutter mechanism 4, and the position at which the cutter mechanism 4 cuts the sheet SH can be determined with even greater accuracy.

[0165] Furthermore, in this image forming apparatus 1, the second positioning portion 491 is located on the left end side of the cutter frame opening 409, and the second positioning portion 492 is located on the right end side of the cutter frame opening 409, and each of the first positioning portions 191, 192 fits one-to-one with each of the second positioning portions 491, 492. With this configuration, the first guide 100 is directly positioned on the cutter frame 400 at two points, and the two points are largely separated in the longitudinal direction (left-right direction), so that it is possible to more reliably prevent the position of the first guide 100 relative to the cutter mechanism 4 from shifting.

[0166] In the image forming apparatus 1, the second positioning portions 491, 492 are through holes, and the first positioning portions 191, 192 are protrusions. With this configuration, the second positioning portions 491, 492 and the first positioning portions 191, 192 can be simplified.

[0167] 6, in this image forming apparatus 1, the first guide 100 provided downstream of the cutter mechanism 4 in the conveying direction DT1 corresponds to the "sheet guide" of the present invention. The movement distance of the sheet SH from when the sheet sensor S4 provided downstream of the cutter mechanism 4 in the conveying direction DT1 detects the leading edge of the sheet SH to when the cutter mechanism 4 starts cutting the sheet SH and the variation therein are smaller than the movement distance of the sheet SH from when the sheet sensor S4 provided upstream of the cutter mechanism 4 in the conveying direction DT1 detects the leading edge of the sheet SH to when the cutter mechanism 4 starts cutting the sheet SH and the variation therein. This allows the image forming apparatus 1 to more accurately determine the position at which the cutter mechanism 4 cuts the sheet SH.

[0168] 8, the pre-cutting guide 300 has two third positioning portions 391, 392, and the pre-cutting guide 300 is positioned with respect to the first guide 100 and the cutter frame 400 by fitting the first positioning portions 191, 192 with the third positioning portions 391, 392. With this configuration, the pre-cutting guide 300 is positioned together with the cutter frame 400 by the same first positioning portions 191, 192 of the first guide 100. As a result, the image forming apparatus 1 can accurately determine the relative positions of the first guide 100 and the pre-cutting guide 300 with respect to the cutter mechanism 4.

[0169] 11, in the image forming apparatus 1, the cutter frame 400 extends in a direction perpendicular to the transport direction DT1, i.e., in the left-right direction, when assembled to the image forming apparatus 1. As shown in FIG. 8, the first positioning parts 191, 192 protrude upstream in the transport direction DT1 and penetrate the second positioning parts 491, 492 to engage with the third positioning parts 391, 392. With this configuration, the relative positions of the first guide 100 and the pre-cutting guide 300 with respect to the cutter mechanism 4 can be determined with high accuracy.

[0170] In addition, in this image forming apparatus 1, the first guide 100 and the pre-cutting guide 300 are fixed by fastening with the cutter frame 400 sandwiched between them. With this configuration, the first guide 100, the cutter frame 400, and the pre-cutting guide 300 that are fastened together can be easily handled as a unit.

[0171] 5 and 11, in this image forming apparatus 1, the first guide 100, the cutter frame 400, and the pre-cutting guide 300 are attached to and detached from the image forming apparatus 1 while being fastened to one another. With this configuration, the first guide 100, the cutter frame 400, and the pre-cutting guide 300 can be easily attached to and detached from the image forming apparatus 1 as a unit, and there is no need to adjust each member separately.

[0172] 6, in the image forming apparatus 1, the sheet sensor S4 is located between the cutter frame 400 and the first discharge roller pair 29 in the conveying direction DT1. With this configuration, the sheet sensor S4 can detect the leading edge of the sheet SH in a stable state by the posture of the sheet SH passing through the cutter mechanism 4 being aligned with the first guide 100.

[0173] Furthermore, in this image forming apparatus 1, a distance LA2 between the sheet sensor S4 and the cutting positions of the fixed blade 411 and the movable blade 412 in the cutter mechanism 4 in the transport direction DT1 is shorter than a distance LA1 between the sheet sensor S4 and the first discharge roller pair 29 in the transport direction DT1. With this configuration, the sheet sensor S4 is disposed close to the cutter mechanism 4. Therefore, this image forming apparatus 1 can speed up the timing for detecting a jam of the sheet SH around the cutter mechanism 4, and as a result, the range of the jam of the sheet SH can be narrowed.

[0174] (Modification) In the embodiment, the distance LA2 is shorter than the distance LA1, but as in a modified example shown in FIG. 13, the distance LA2 may be longer than the distance LA1.

[0175] In the image forming apparatus of the modified example, the sheet sensor S4 is disposed away from the cutter mechanism 4. Therefore, this image forming apparatus can reduce the movement distance and the variation thereof of the sheet SH from when the leading edge of the sheet SH passing through the cutter mechanism 4 is detected until the cutter mechanism 4 starts cutting the sheet SH, and can more accurately determine the position at which the cutter mechanism 4 cuts the sheet SH.

[0176] Although the present invention has been described above with reference to the embodiments, it goes without saying that the present invention is not limited to the above embodiments and can be modified as appropriate without departing from the spirit of the present invention.

[0177] In the embodiment, the image forming apparatus of the present invention is embodied as the image forming apparatus 1 which is a multifunction machine equipped with an image reading device on the upper side, but 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 that is not a multifunction machine.

[0178] In the embodiment, the sheet guide is the first guide 100 provided downstream of the cutter mechanism 4 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 sheet guide is changed to a pre-cutting guide 300 provided upstream of the cutter mechanism 4 in the conveying direction DT1 and the sheet sensor S4 is provided in the pre-cutting guide 300.

[0179] In the embodiment, each of the second positioning portions 491, 492 is a through hole, but the present invention is not limited to this configuration. For example, the second positioning portions may be recesses. [Explanation of symbols]

[0180] 1...Image forming device DT1: Transport direction SH…Sheet 3...Image forming section 7. Fixing unit 412...moving blade 400…Cutter frame 4…Cutter mechanism 100…Sheet guide (first guide) S4…Seat sensor 191, 192...First positioning part 491, 492...Second positioning part 409…Cutter frame opening 300…Pre-cut guide 391, 392...Third positioning part 29...First discharge roller pair LA2: Distance between the sheet sensor and the cutter mechanism in the conveying direction LA1: Distance between the sheet sensor and the first discharge roller pair in the conveying direction

Claims

1. an image forming unit that transfers a toner image onto a sheet transported in a transport direction to form an image; a fixing unit that fixes the toner image onto the sheet that has passed through the image forming unit; a cutter mechanism including a moving blade that cuts the sheet that has passed through the fixing unit and a cutter frame that movably holds the moving blade; a sheet guide provided upstream or downstream of the cutter mechanism in the conveying direction and configured to guide a sheet passing through the cutter mechanism; a sheet sensor provided in the sheet guide to detect a sheet passing through the cutter mechanism; Equipped with The image forming apparatus according to claim 1, wherein the sheet guide is positioned on the cutter frame.

2. The sheet guide has a first positioning portion, The cutter frame has a second positioning portion, 2. The image forming apparatus according to claim 1, wherein the sheet guide is positioned on the cutter frame by the first positioning portion and the second positioning portion being fitted together.

3. the cutter frame has a plurality of the second positioning portions and a cutter frame opening through which a sheet passes, One of the second positioning portions is located on one end side of the cutter frame opening in the longitudinal direction, The other of the second positioning portions is located on the other end side of the cutter frame opening in the longitudinal direction, 3. The image forming apparatus according to claim 2, wherein the sheet guide has a plurality of the first positioning portions which are fitted one-to-one with the second positioning portions.

4. Each of the second positioning portions is a recess or a through hole, 4. The image forming apparatus according to claim 3, wherein each of the first positioning portions is a protrusion.

5. 5. The image forming apparatus according to claim 2, wherein the sheet guide is a first guide provided downstream of the cutter mechanism in the transport direction.

6. a pre-cutting guide provided upstream of the cutter mechanism in the transport direction and configured to guide the sheet passing through the cutter mechanism; The pre-cutting guide has a third positioning portion, 6. The image forming apparatus according to claim 5, wherein the pre-cutting guide is positioned relative to the first guide and the cutter frame by the first positioning portion and the third positioning portion being fitted together.

7. the cutter frame extends in a direction perpendicular to the conveying direction when assembled to the image forming apparatus, 7. The image forming apparatus according to claim 6, wherein the first positioning portion protrudes toward the upstream side in the transport direction, penetrates the second positioning portion, and fits into the third positioning portion.

8. 8. The image forming apparatus according to claim 7, wherein the first guide and the pre-cutting guide are fixed to each other by fastening while sandwiching the cutter frame therebetween.

9. 9. The image forming apparatus according to claim 8, wherein the first guide, the cutter frame and the pre-cutting guide are attached to and detached from the image forming apparatus in a state where they are fastened to one another.

10. a first discharge roller pair located downstream of the cutter mechanism in the transport direction and configured to discharge the sheet that has passed through the cutter mechanism; 6. The image forming apparatus according to claim 5, wherein the sheet sensor is located between the cutter frame and the first pair of discharge rollers in the transport direction.

11. 11. The image forming apparatus according to claim 10, wherein a distance between the sheet sensor and the cutter mechanism in the transport direction is shorter than a distance between the sheet sensor and the first discharge roller pair in the transport direction.

12. 11. The image forming apparatus according to claim 10, wherein a distance between the sheet sensor and the cutter mechanism in the transport direction is longer than a distance between the sheet sensor and the first discharge roller pair in the transport direction.

Images