Drive transmission device, drive device, and image forming apparatus

Abstract

To provide a drive transmission device capable of suppressing the generation of chemical cracks.SOLUTION: A drive transmission device 23 is equipped with a storage portion 24 that is formed with a second through-hole 42 corresponding to a gear 27, and a supporting portion 25 to which a fixing pin 53 is fixed, which rotatably supports the gear 27 while a tip end portion is inserted in the second through-hole 42. At an opening edge portion of the second through-hole 42, a hole side chamfering portion 46 obtained by notching a ridge angle is formed. At a tip end portion of the fixing pin 53, a shaft side chamfering portion 56 obtained by notching a ridge angle is formed. While the fixing pin 53 is inserted in the second through-hole 42, a lubricant is interposed in a contacting portion P between the fixing pin 53 and the second through-hole 42. A hole side boundary portion 48 that is a boundary between an inner peripheral surface 47 of the second through-hole 42 and the hole side chamfering portion 46 contacts with an outer peripheral surface 57 of the fixing pin 53, and a shaft side boundary portion 58 that is a boundary between the outer peripheral surface 57 of the fixing pin 53 and the shaft side chamfering portion 56 opposes to the hole side chamfering portion 46 across a clearance M1.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a drive transmission device, a drive unit, and an image forming apparatus. [Background technology]

[0002] A drive unit is disclosed in Patent Document 1, in which a fixed pin is mounted on a pair of support members and an idle gear is rotatably supported on the fixed pin. One end of the fixed pin has a D-cut portion formed thereon, and the D-cut portion is fixed non-rotatably to one of the support members. The other end of the fixed pin is fitted into a hole opened in the other support plate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-261383 Summary of the Invention [Problem to be solved by the invention]

[0004] When assembling the drive unit described above, a lubricant such as grease is often applied to the contact points between the fixed pin and the hole in the support part. Depending on the type of lubricant and the material of the support part, the area where the lubricant is applied may deteriorate. On the other hand, when the drive unit is in use, the fixed pin and the support part are continuously subjected to loads such as vibrations caused by the rotation of the idle gear, which causes the distortion of the fixed pin and the support part to increase over time (creep deformation). If creep deformation occurs in areas deteriorated by the adhesion of lubricant, there is a concern that cracks (chemical cracks) will occur in those areas.

[0005] In consideration of the above circumstances, the present invention provides a drive transmission device, a drive unit, and an image forming apparatus that can suppress the occurrence of chemical cracks. [Means for solving the problem]

[0006] The drive transmission device of the present invention comprises an accommodating section that accommodates a gear and has a through hole formed corresponding to the gear, and a support section to which a fixing pin is fixed that passes through the accommodating section and rotatably supports the gear with its tip inserted into the through hole, wherein a hole side chamfer with a cut-out ridge is formed at the opening edge of the through hole, and a shaft side chamfer with a cut-out ridge is formed at the tip of the fixing pin, and when the fixing pin is inserted into the through hole, a lubricant is present at the contact point between the fixing pin and the through hole, and the hole side boundary, which is the boundary between the inner surface of the through hole and the hole side chamfer, is in contact with the outer surface of the fixing pin, and the shaft side boundary, which is the boundary between the outer surface of the fixing pin and the shaft side chamfer, faces the hole side chamfer across a gap.

[0007] In this case, at least one of the hole chamfered portion and the shaft chamfered portion may be cut out in an arc shape.

[0008] In this case, the hole side chamfer portion is cut out in an arc shape, and when the fixing pin is inserted into the through hole, the distance between the hole side boundary portion and the shaft side boundary portion may be set in a range of more than half the radius of the hole side chamfer portion and less than the radius.

[0009] A drive device of the present invention includes a drive source that drives a driven object, and any one of the drive transmission devices described above that transmits the drive force of the drive source to the driven object.

[0010] The image forming apparatus of the present invention includes the above-described drive device. [Effects of the Invention]

[0011] According to the present invention, it is possible to suppress the occurrence of chemical cracks in the drive transmission device. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a front view showing an outline of the interior of an image forming apparatus according to an embodiment of the present invention; [Figure 2]1 is a perspective view showing a drive device according to an embodiment of the present invention; [Figure 3] 1 is an exploded perspective view showing a drive device according to an embodiment of the present invention. [Figure 4] 2 is a perspective view showing a first cover portion and the like of the drive transmission device according to one embodiment of the present invention. FIG. [Figure 5] 4 is a perspective view showing a second cover portion and the like of the drive transmission device according to one embodiment of the present invention. FIG. [Figure 6] 1 is a perspective view showing a drive device according to an embodiment of the present invention; [Figure 7] FIG. 7 is a cross-sectional view taken along the line VII-VII in FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that Fr, Rr, L, R, U, and D shown in the drawings indicate front, rear, left, right, top, and bottom. Terms indicating directions and positions are used in this specification, but these terms are used for convenience of explanation and do not limit the technical scope of the present invention.

[0014] An image forming apparatus 1 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a front view showing an outline of the interior of the image forming apparatus 1.

[0015] The image forming apparatus 1 is a printer that forms an image by transferring a toner image formed by an electrophotographic method onto paper (not shown). As shown in FIG. 1, the image forming apparatus 1 includes an apparatus main body 2 having a substantially rectangular parallelepiped appearance. For example, a paper feed cassette 3 that stores paper is removably provided at the bottom of the apparatus main body 2. A paper output tray 4 is provided on the top surface of the apparatus main body 2. A toner container 5 that stores replenishment toner (developer) is removably attached to the upper interior of the apparatus main body 2. Note that the paper, which is an example of a medium, is not limited to paper, and may be a resin sheet or the like.

[0016] Inside the device main body 2, a transport path 6 and a reversing transport path 7 are formed as paths for transporting paper. The transport path 6 is formed in a roughly S-shape from the lower front to the upper rear of the device main body 2, and is a path for transporting paper from the paper feed cassette 3 to the paper output tray 4. The reversing transport path 7 branches downward on the downstream side of the transport path 6, extends forward, and merges with the upstream side of the transport path 6. The reversing transport path 7 is a path for reversing paper and transporting it again to the image forming device 11 (described later). In this specification, the terms "upstream" and "downstream" refer to "upstream" and "downstream" in the transport direction of the paper (medium).

[0017] The image forming apparatus 1 includes a paper feeder 10, an image forming device 11, a fixing device 12, and a conveying device 13. The paper feeder 10 is provided at the upstream end of the conveying path 6, the image forming device 11 is provided in the middle of the conveying path 6, and the fixing device 12 is provided on the downstream side of the conveying path 6. The conveying device 13 is provided at an appropriate position on the conveying path 6 and the reverse conveying path 7.

[0018] <Paper feeder> The paper feed device 10 has a pickup roller 10A and a pair of paper feed rollers 10B. The pickup roller 10A picks up the topmost paper from a stack of paper stored in the paper feed cassette 3. The pair of paper feed rollers 10B separates the paper picked up by the pickup roller 10A one by one and transports them downstream.

[0019] <Imaging device> The imaging device 11 includes a photosensitive drum 14, a charging device 15, a developing device 16, a transfer roller 17, and an optical scanning device 18. The photosensitive drum 14 is formed in a generally cylindrical shape that is long in the left-right direction, and is driven to rotate around its axis by a motor (not shown). The charging device 15, the developing device 16, and the transfer roller 17 are arranged around the photosensitive drum 14 in the order of the image formation process. The transfer roller 17 contacts the photosensitive drum 14 from below to form a transfer nip. The optical scanning device 18 is located above the photosensitive drum 14, and emits scanning light toward the surface of the photosensitive drum 14.

[0020] <Fixing device> The fixing device 12 includes a fixing belt 12A and a pressure roller 12B. The fixing belt 12A and the pressure roller 12B are formed in a generally cylindrical shape that is long in the left-right direction and are rotatably supported by a case (not shown). A heater (not shown) that heats the fixing belt 12A is provided inside the fixing belt 12A. The pressure roller 12B is pressed against the fixing belt 12A from below to form a fixing nip. The pressure roller 12B is driven to rotate around its axis by a motor (not shown), and the fixing belt 12A rotates following the rotation of the pressure roller 12B.

[0021] <Conveyor equipment> The conveying device 13 has a feed roller 20A, a pair of registration rollers 20B, a pair of conveying rollers 20C, a pair of paper discharge rollers 20D, two pairs of double-sided conveying rollers 20E, and a drive device 21 (see FIG. 2). The feed roller 20A, the pair of registration rollers 20B, the pair of conveying rollers 20C, and the pair of paper discharge rollers 20D are arranged upstream of the conveying path 6, and the two pairs of double-sided conveying rollers 20E are arranged in the reverse conveying path 7. The drive device 21 drives and rotates the feed roller 20A and the like.

[0022] The feed roller 20A is disposed downstream of the pair of feed rollers 10B and transports the paper that has passed through the pair of feed rollers 10B. The pair of registration rollers 20B is disposed between the feed roller 20A and the transfer roller 17 and temporarily blocks the transported paper to correct the paper's skew (skew correction). The pair of transport rollers 20C is disposed downstream of the fixing device 12 and transports the paper that has passed through the fixing nip. The pair of discharge rollers 20D is disposed at the downstream end of the transport path 6 and discharges the paper that has passed through the pair of transport rollers 20C toward the paper output tray 4. The pair of discharge rollers 20D also switchbacks the paper with an image formed on its front side and sends it toward the reverse transport path 7. Two pairs of double-sided transport rollers 20E transport the paper that has been sent out by the pair of discharge rollers 20D. The reverse transport path 7 merges with the transport path 6 between the feed roller 20A and the pair of registration rollers 20B.

[0023] The driving device 21 is supported by an internal frame (not shown) of the apparatus main body 2, and drives the feed roller 20A and one or both of the roller pairs 20B to 20E to rotate about their axes. The driving device 21 also drives the developing roller 20F built into the developing device 16 to rotate about its axis. Note that the feed roller 20A, each of the roller pairs 20B to 20E, and the developing roller 20F are examples of components to be driven, and other components may also be driven by the driving device 21. For convenience, in the following description, the feed roller 20A, each of the roller pairs 20B to 20E, and the developing roller 20F will be collectively referred to as the "driven rollers 20."

[0024] [Image formation processing] Here, we will explain the operation of the image forming apparatus 1. A control unit (not shown) executes image forming processing (control) as follows based on image data input from an external terminal.

[0025] The charging device 15 charges the surface of the photosensitive drum 14. The optical scanning device 18 exposes the photosensitive drum 14 to light and forms an electrostatic latent image corresponding to image data on the surface of the photosensitive drum 14. The developing device 16 uses toner supplied from the toner container 5 to develop the electrostatic latent image on the photosensitive drum 14 into a toner image.

[0026] The paper feed device 10 separates the paper sheets in the paper feed cassette 3 one by one and sends them to the conveying path 6. The pair of registration rollers 20B sends the skew-corrected paper sheets toward the transfer nip at a predetermined timing. The transfer roller 17 transfers the toner image on the photosensitive drum 14 onto the surface of the paper sheet as it passes through the transfer nip. The fixing device 12 thermally fixes the toner image onto the paper sheet by passing it through the fixing nip between the fixing belt 12A and pressure roller 12B, which rotate around an axis. In the case of single-sided printing, the pair of paper discharge rollers 20D discharges the paper sheet with the fixed toner image onto the paper discharge tray 4.

[0027] In the case of double-sided printing, the pair of paper discharge rollers 20D switches back the paper and sends it to the reverse conveyance path 7. The two pairs of double-sided conveyance rollers 20E convey the paper along the reverse conveyance path 7, and the paper re-enters the conveyance path 6 from the reverse conveyance path 7. Then, in the same procedure as in the case of single-sided printing described above, an image is formed on the back side of the paper, and the double-sided printed paper is discharged to the paper output tray 4.

[0028] [Drive unit] Next, the drive unit 21 will be described in detail with reference to Figures 2 to 6. Figure 2 is a perspective view showing the drive unit 21. Figure 3 is an exploded perspective view showing the drive unit 21. Figure 4 is a perspective view showing the first cover part 30 and the like of the drive transmission unit 23. Figure 5 is a perspective view showing the second cover part 40 and the like of the drive transmission unit 23. Figure 6 is a perspective view showing the drive unit 21 (left side).

[0029] As shown in FIGS. 2 and 3, the drive device 21 includes a drive motor 22 and a drive transmission device 23.

[0030] <Drive motor> The drive motor 22 is an example of a drive source, and is, for example, a stepping motor that can be controlled for positioning. The drive motor 22 generates a drive force for driving the driven roller 20.

[0031] <Drive transmission device> The drive transmission device 23 has a function of transmitting the driving force of the drive motor 22 to the driven roller 20. The drive transmission device 23 includes a housing portion 24 and a support portion 25.

[0032] (Storage section) The housing 24 is a case for housing multiple gears 27, multiple clutches 28, etc. As shown in FIG. 3 , adjacent gears 27 mesh with each other to form a gear train. One gear 27 meshes with a drive gear (not shown) fixed to the drive shaft 26 of the drive motor 22 and transmits rotational force to the other gears 27. Each clutch 28 has a gear portion (not shown) that meshes with one of the multiple gears 27 and a clutch shaft (not shown) that transmits driving force to one of the multiple driven rollers 20. Each clutch 28 is controlled by the control unit and has the function of switching between an ON state in which the rotational driving force received from the gear 27 is transmitted to the clutch shaft and an OFF state in which the transmission of the rotational driving force to the clutch shaft is interrupted. Note that detailed descriptions of the meshing relationship of each gear 27 and the connection relationship between each clutch 28 and each driven roller 20 are omitted.

[0033] The housing 24 is made of, for example, synthetic resin (such as polycarbonate resin or acrylonitrile-butadiene-styrene synthetic resin) and is formed in the shape of a roughly rectangular parallelepiped with a thin thickness in the left-right direction (see FIG. 2). The housing 24 has a first cover part 30 that forms the right side of the housing 24, and a second cover part 40 that forms the left side of the housing 24. The first cover part 30 and the second cover part 40 face each other with a space that houses the gear train between them.

[0034] (First cover part) 3 and 4, the first cover part 30 is formed in the shape of a tray with its left side open. A plurality of engagement holes 34 are formed on the outer periphery of the first cover part 30 (see FIG. 4). Note that only some of the engagement holes 34 are shown in FIG. 4.

[0035] The first cover portion 30 is formed with a first opening 31, a plurality of first through holes 32, and a plurality of clutch accommodating portions 33. The first opening 31 is a hole for inserting the drive shaft 26 of the drive motor 22. The plurality of first through holes 32 are circular holes formed corresponding to the plurality of gears 27. A fixing pin 53 (described below) for rotatably supporting the gear 27 is inserted into each of the first through holes 32. The diameter (inner diameter) of the first through hole 32 is set larger than the outer diameter of the fixing pin 53, and the fixing pin 53 passes through the first through hole 32 with play. Each clutch accommodating portion 33 is a recess for fitting a clutch 28.

[0036] (Second cover part) 3, 5, and 6, the second cover part 40 is formed in the shape of a tray with its right side open. A plurality of engagement parts 44 are formed on the outer periphery of the second cover part 40 so as to protrude to the right (see FIG. 5). Each engagement part 44 engages with an engagement hole 34 of the first cover part 30, thereby joining the first cover part 30 and the second cover part 40 and forming a space for accommodating the gear train.

[0037] As shown in FIGS. 5 and 6 , the second cover portion 40 is formed with a second opening 41, multiple second through holes 42, and multiple gear accommodating portions 43. The second opening 41 is a bearing for rotatably supporting the drive shaft 26 of the drive motor 22. The multiple second through holes 42 are holes formed corresponding to the multiple gears 27. The tip of a fixing pin 53 that passes through the first through hole 32 is inserted into each second through hole 42. The diameter (inner diameter) of the second through hole 42 is set slightly larger than the outer diameter of the fixing pin 53, and the tip of the fixing pin 53 fits into the first through hole 32 with almost no play. Each gear accommodating portion 43 rotatably supports the clutch shaft of the clutch 28 and is a recess for accommodating a gear portion of the clutch 28. Note that in FIG. 6 , some of the multiple second through holes 42 are hidden by the external gears.

[0038] (Support part) As shown in Fig. 3, the support part 25 is formed in a flat plate shape from, for example, metal (iron, stainless steel, aluminum alloy, or the like). The support part 25 has a support opening 51 through which the drive shaft 26 of the drive motor 22 passes. The drive shaft 26 is inserted into the support opening 51 from right to left, and the drive motor 22 is fixed to the right surface of the support part 25 with screws. The support part 25 also has a plurality of loose insertion holes 52 through which screws (not shown) pass, and the first cover part 30 has a plurality of screw holes 35 formed at positions corresponding to the plurality of loose insertion holes 52 (see Fig. 4).

[0039] (Fixed pin) As shown in FIG. 3 , a plurality of fixing pins 53 are fixed to the support portion 25 at positions corresponding to the plurality of gears 27 (first and second through holes 32, 42). Each fixing pin 53 is made of, for example, metal (iron, stainless steel, aluminum alloy, etc.) and formed into a generally cylindrical shape, and is fixed to the left surface of the support portion 25 by caulking. Each fixing pin 53 extends rightward from the left surface of the support portion 25. Each fixing pin 53 rotatably supports the gear 27 while passing through the housing portion 24 and with its tip inserted into the corresponding second through hole 42. The fixing pins 53 may be fixed to the support portion 25 by screwing, welding, or the like.

[0040] Here, a brief description will be given of the assembly of the drive unit 21. The support part 25 to which the drive motor 22 is fixed is disposed to the right of the housing part 24, and the drive shaft 26 passes from right to left through the first opening 31 of the first cover part 30 (see FIG. 4) and is inserted into the second opening 41 of the second cover part 40 (see FIG. 6). Furthermore, each fixing pin 53 is inserted from right to left into the first through-hole 32 of the first cover part 30 (see FIG. 4), passes through the axial center of the gear 27, and is inserted into the second through-hole 42 of the second cover part 40 (see FIG. 6). In this state, the drive gear of the drive motor 22 meshes with one gear 27, and each gear 27 is rotatably supported on the circumferential surface of the fixing pin 53. Then, the screws passing through the loose insertion holes 52 of the support part 25 are threaded into the screw holes 35 of the first cover part 30, thereby fixing the support part 25 to the first cover part 30. Note that the support part 25 may be fixed to the device body 2 instead of the accommodation part 24 (not shown).

[0041] Next, a brief description will be given of the operation of the drive device 21. The drive motor 22 is driven under the control of the control unit. The rotational drive force of the drive motor 22 is transmitted to the driven rollers 20 via multiple gears 27 (gear train). Each clutch 28 is controlled by the control unit and switched to an on or off state, so that only the selected driven roller 20 can be rotated (or stopped).

[0042] Incidentally, when assembling the drive unit 21 (or the drive transmission device 23), a lubricant (e.g., a lubricating oil mainly composed of poly-alpha-olefin) is applied to the tip of each of the fixing pins 53 to smoothly fit the fixing pins 53 into the second through holes 42. Therefore, when the fixing pins 53 are inserted into the second through holes 42, the lubricant is present at the contact portion P between the fixing pins 53 and (the inner circumferential surface 47 of) the second through holes 42. Generally, synthetic resins are more susceptible to deterioration due to the adhesion of lubricant than metals, and therefore, in the second cover part 40 made of synthetic resin, the inner circumferential surface 47 of the second through holes 42, where the lubricant is attached, may deteriorate.

[0043] On the other hand, during operation (use) of the drive device 21, each fixed pin 53 and the housing portion 24 are continuously subjected to loads such as vibrations caused by the rotation of the drive motor 22 and each gear 27, resulting in an increase in distortion of the fixed pins 53 and the housing portion 24 over time (creep deformation). If creep deformation occurs in a portion deteriorated by the adhesion of lubricant (the inner circumferential surface 47 of the second through hole 42), there is a concern that cracks (chemical cracks) may occur in that portion. Therefore, in the drive device 21 (drive transmission device 23) according to this embodiment, each second through hole 42 and each fixed pin 53 are provided with a structure for suppressing the occurrence of chemical cracks. Note that the following description will focus on one fixed pin 53 and one second through hole 42 for convenience.

[0044] A structure for suppressing the occurrence of chemical cracks will be described below with reference to Fig. 7. Fig. 7 is a cross-sectional view taken along line VII-VII in Fig. 6 (and a partially enlarged view thereof).

[0045] <Opening edge of second through hole> The opening edge of the second through hole 42 is tapered so as to widen toward both sides in the left-right direction. More specifically, a guide chamfer 45 is formed on the opening edge of the second through hole 42 on the inside of the second cover part 40 (the side of the space that houses the gear train), where a ridge is cut out in a straight line. In other words, the guide chamfer 45 is a so-called C-chamfer. The opening edge of the second through hole 42 on the outside of the second cover part 40 is formed on the hole side chamfer 46, where a ridge is cut out in an arc shape. In other words, the hole side chamfer 46 is a so-called R-chamfer. Between the guide chamfer 45 and the hole side chamfer 46, an inner circumferential surface 47 is formed, which has approximately the same inner diameter along the left-right direction.

[0046] <Tip of the fixing pin> The tip of the fixing pin 53 is tapered so that it becomes thinner toward the tip (left). More specifically, the tip of the fixing pin 53 is formed with a shaft side chamfer 56, in which an edge corner is linearly cut out. In other words, the shaft side chamfer 56 is a so-called C-chamfer. The outer peripheral surface 57 of the fixing pin 53, excluding the shaft side chamfer 56, has approximately the same outer diameter along the left-right direction.

[0047] When the tip of the fixing pin 53 is inserted into the second through hole 42, if the axis of the fixing pin 53 is slightly offset from the axis of the second through hole 42, part of the axial chamfer 56 of the fixing pin 53 will come into contact with part of the guide chamfer 45 of the second through hole 42. With the aid of the applied lubricant, the tip of the fixing pin 53 (guide chamfer 45) will smoothly slide on the guide chamfer 45 toward the axis of the second through hole 42. As a result, the axes of the fixing pin 53 and the second through hole 42 will approximately coincide, and the tip of the fixing pin 53 will be inserted into (fit with) the second through hole 42.

[0048] When the tip of the fixing pin 53 is inserted (fitted) into the second through-hole 42, a lubricant is present between the outer peripheral surface 57 of the fixing pin 53 and the inner peripheral surface 47 of the second through-hole 42 (contact portion P). The tip surface of the fixing pin 53 passes through the second through-hole 42 and protrudes slightly outward from the outer surface of the second cover part 40.

[0049] A hole-side boundary portion 48, which is the boundary between the inner circumferential surface 47 of the second through hole 42 and the hole side chamfered portion 46, is in contact with an outer circumferential surface 57 of the fixing pin 53. In other words, in Fig. 7, the inner circumferential surface 47 and the hole-side boundary portion 48 of the second through hole 42 are in contact with a straight portion of the fixing pin 53. Note that "contact" here means not only direct contact but also contact via a lubricant.

[0050] A shaft-side boundary portion 58, which is the boundary between the outer peripheral surface 57 of the fixing pin 53 and the shaft-side chamfered portion 56, faces the hole-side chamfered portion 46 across a gap M1. In other words, the shaft-side boundary portion 58 does not contact the inner peripheral surface 47 of the second through hole 42 or the hole-side chamfered portion 46.

[0051] The distance M2 between the hole-side boundary portion 48 and the shaft-side boundary portion 58 is set in the range of half the radius (radius of the R-chamfer) of the hole side chamfer portion 46 and less than this radius. In the present embodiment, as an example, the radius of the hole side chamfer portion 46 is 0.5 mm, and the distance M2 between the hole-side boundary portion 48 and the shaft-side boundary portion 58 is set to 0.3 mm. Note that the upper limit of the radius of the hole side chamfer portion 46 may be less than the thickness of the second cover portion 40 excluding the guide chamfer portion 45.

[0052] In the drive unit 21 (drive transmission device 23) according to the present embodiment described above, the hole-side boundary portion 48 contacts the outer peripheral surface 57 of the fixation pin 53, and the shaft-side boundary portion 58 does not contact the shaft-side chamfered portion 56. With this configuration, only the outer peripheral surface 57 of the fixation pin 53 comes into surface contact with the inner peripheral surface 47 of the second through hole 42, so the fixation pin 53 can be securely held by the inner peripheral surface 47 of the second through hole 42. Furthermore, even if the fixation pin 53 or the housing portion 24 (second cover portion 40) undergoes creep deformation, the shaft-side boundary portion 58 of the fixation pin 53 does not interfere with the inner peripheral surface 47 of the second through hole 42 or the hole-side chamfered portion 46. This prevents local stress concentration at the contact portion P between the tip end of the fixation pin 53 and the inner peripheral surface 47 of the second through hole 42, where lubricant is present, and thus chemical cracks at the contact portion P can be suppressed.

[0053] Furthermore, in the drive unit 21 (drive transmission device 23) according to this embodiment, when the fixing pin 53 is inserted into the second through hole 42, the hole-side boundary portion 48 is located at a position recessed by a predetermined distance M2 from the shaft-side boundary portion 58. This appropriately prevents interference between the shaft-side boundary portion 58 and the hole side chamfer portion 46, thereby effectively preventing chemical cracks at the contact portion P between the fixing pin 53 and the second through hole 42.

[0054] In the drive unit 21 (drive transmission device 23) according to this embodiment, the hole side chamfer 46 is an R-chamfer and the shaft side chamfer 56 is a C-chamfer, but the present invention is not limited to this. It is sufficient that at least one of the hole side chamfer 46 and the shaft side chamfer 56 is cut out in an arc shape. For example, both the hole side chamfer 46 and the shaft side chamfer 56 may be C-chamfered or R-chamfered (not shown). For example, if the hole side boundary portion 48 is a C-chamfer, the distance M2 between the hole side boundary portion 48 and the shaft side boundary portion 58 may be set in the range from half the distance from the outer surface of the second cover part 40 to this distance (not shown). Furthermore, for example, by making the shaft side chamfer 56 an R-chamfer, even if the tip of the fixing pin 53 interferes with the edges of the first and second through holes 32, 42 when the fixing pin 53 is inserted into the first and second through holes 32, 42, it is possible to prevent the tip of the fixing pin 53 from being crushed. Furthermore, although the guide chamfer 45 was a C-chamfer, it may be an R-chamfer or may be omitted (not shown). The angle of the C-chamfer can be set to any angle.

[0055] Furthermore, in the drive device 21 (drive transmission device 23) according to this embodiment, multiple gears 27, multiple clutches 28, multiple fixing pins 53, etc. are provided, but this is not limiting and it is sufficient to provide at least one gear 27, etc. Furthermore, if clutch 28 is unnecessary, it may be omitted (not shown).

[0056] Furthermore, in the drive unit 21 (drive transmission device 23) according to this embodiment, the housing portion 24 is configured with the first cover portion 30 and the second cover portion 40 that can be separated in the left-right direction, but the present invention is not limited to this. For example, the housing portion 24 may be configured to be separated in the up-down direction, or may be molded as a single unit (not shown). Furthermore, for example, the housing portion 24 may be configured to be separated into three or more parts (not shown).

[0057] Furthermore, the image forming apparatus 1 according to the present embodiment is a monochrome printer, but the present invention is not limited to this and may be applied to, for example, a color printer, a copying machine, a facsimile machine, a multifunction machine, or the like.

[0058] The above-described embodiment shows one aspect of the drive transmission device, drive device, and image forming apparatus according to the present invention, and the technical scope of the present invention is not limited to the above-described embodiment. The present invention may be variously changed, substituted, or modified within the scope of the technical concept, and the claims include all embodiments that may fall within the scope of the technical concept. [Explanation of symbols]

[0059] 1. Image forming device 20A Feeding roller (drive target) 20B Registration Roller Pair 20C Transport roller pair (drive target) 20D Paper ejection roller pair (drive target) 20E Double-sided transport roller pair (drive target) 20F Developing roller (drive target) 21 Drive unit 22 Drive motor (drive source) 23 Drive transmission device 24 Storage section 25 Support part 27 gears 42 Second through hole (through hole) 46 Hole side chamfer 47 Inner surface 48 Hole side boundary 53 Fixing pin 56 Shaft side chamfer 57 Outer surface 58 Axial side boundary M1 gap M2 spacing P contact part

Claims

1. a receiving portion that receives the gear and has a through hole formed therein corresponding to the gear; a support portion to which a fixing pin is fixed, the fixing pin passing through the accommodation portion and rotatably supporting the gear with a tip portion inserted into the through hole, A hole side chamfer is formed by cutting off an edge of the through hole, The tip of the fixing pin is formed with a chamfered shaft portion in which a corner is cut off, a hole-side boundary portion, which is the boundary between the inner peripheral surface of the through hole and the hole chamfered portion, contacts the outer peripheral surface of the fixation pin; and a shaft-side boundary portion, which is the boundary between the outer peripheral surface of the fixation pin and the shaft chamfered portion, faces the hole chamfered portion across a gap.

2. 2. The drive transmission device according to claim 1, wherein at least one of the hole chamfered portion and the shaft chamfered portion is cut out in an arc shape.

3. The hole chamfered portion is cut out in an arc shape, 3. The drive transmission device according to claim 1, wherein, when the fixing pin is inserted into the through hole, the distance between the hole-side boundary portion and the shaft-side boundary portion is set in a range of more than half the radius of the hole-side chamfer portion and less than the radius.

4. a drive source that drives the driven object; A drive unit comprising: a drive transmission device according to any one of claims 1 to 3, which transmits the drive force of the drive source to the driven object.

5. An image forming apparatus comprising the drive device according to claim 4.

Images