Drive transmission device, drive device, and image forming apparatus

Abstract

The present invention provides a drive transmission device, a drive device, and an image forming apparatus. The drive transmission device has a housing portion, a fixing pin, and a support portion. The housing portion houses a gear and is formed with a through hole corresponding to the gear. The fixing pin rotatably supports the gear. The support portion fixes the fixing pin in a state where a tip portion of the fixing pin is inserted into the through hole. A hole-side chamfered portion obtained by removing a sharp edge is formed at an opening edge portion outside the through hole. A shaft-side chamfered portion obtained by removing a sharp edge is formed at the tip portion of the fixing pin. In a state where the fixing pin is inserted into the through hole, a lubricant is interposed between a contact portion between the fixing pin and the through hole. A hole-side boundary portion, which is a boundary between an inner peripheral surface of the through hole and the hole-side chamfered portion, contacts an outer peripheral surface of the fixing pin, and a shaft-side boundary portion, which is a boundary between the outer peripheral surface of the fixing pin and the shaft-side chamfered portion, faces the hole-side chamfered portion with a gap therebetween. Accordingly, generation of chemical cracks can be suppressed.

Description

Technical Field

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

[0002] The prior art discloses a drive unit in which a fixing pin is provided between a pair of support portions, and an idle gear is rotatably supported by the fixing pin. A D-notch portion is formed at one end of the fixing pin, and the D-notch portion is non-rotatably fixed to one of the support portions. The other end of the fixing pin is fitted into a hole opened in the other support portion.

[0003] When assembling a drive unit as described above, generally, a lubricant such as grease is applied to the contact portion between the fixing pin and the hole of the support portion. Due to differences in the type of lubricant and the raw materials of the support portion, etc., deterioration sometimes occurs at the attachment portion of the lubricant. On the other hand, when using the drive unit, since the fixing pin and the support portion continuously bear loads such as vibrations generated by the rotation of the idle gear, the deformation of the fixing pin and the support portion increases over time (creep deformation). When creep deformation occurs at a portion deteriorated due to the attachment of the lubricant, there is a concern that cracks (chemical cracks) may occur at that portion. Summary of the Invention

[0004] In view of the above circumstances, the present invention provides a drive transmission device, a drive device, and an image forming device capable of suppressing the occurrence of chemical cracks.

[0005] The drive transmission device of the present invention has a housing portion, a fixing pin, and a support portion. The housing portion houses a gear and is formed with a through hole corresponding to the gear. The fixing pin rotatably supports the gear. The support portion fixes the fixing pin in a state where the tip portion of the fixing pin is inserted into the through hole. A hole-side chamfered portion obtained by removing the sharp edge is formed on the opening edge portion outside the through hole. An axis-side chamfered portion obtained by removing the sharp edge is formed on the tip portion of the fixing pin. In a state where the fixing pin is inserted into the through hole, a lubricant is interposed between the contact portion between the fixing pin and the through hole. The hole-side boundary portion, which is the boundary between the inner peripheral surface of the through hole and the hole-side chamfered portion, contacts the outer peripheral surface of the fixing pin, and the axis-side boundary portion, which is the boundary between the outer peripheral surface of the fixing pin and the axis-side chamfered portion, faces the hole-side chamfered portion with a gap therebetween.

[0006] The drive device of the present invention has a drive source and the drive transmission device described above, wherein the drive source drives a drive object; and the drive transmission device transmits the driving force of the drive source to the drive object.

[0007] The image forming apparatus of the present invention has the above-described driving device. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a front view showing a general structure inside the image forming apparatus according to an embodiment of the present invention.

[0009] Figure 2 is a perspective view showing the driving device according to an embodiment of the present invention.

[0010] Figure 3 is an exploded perspective view showing the driving device according to an embodiment of the present invention.

[0011] Figure 4 is a perspective view showing the first cover portion and the like of the drive transmission device according to an embodiment of the present invention.

[0012] Figure 5 is a perspective view showing the second cover portion and the like of the drive transmission device according to an embodiment of the present invention.

[0013] Figure 6 is a perspective view showing the driving device according to an embodiment of the present invention.

[0014] Figure 7 is Figure 6 a cross-sectional view taken along VII-VII. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described with reference to the accompanying Figure 1 drawings. In addition, Fr, Rr, L, R, U, and D shown in the drawings represent front, rear, left, right, up, and down. Although terms indicating directions and positions are used in this specification, these terms are used for convenience of explanation and do not limit the technical scope of the present invention.

[0016] Refer to Figure 1 to describe the image forming apparatus 1 according to the embodiment. Figure 1 is a front view showing a general structure inside the image forming apparatus 1.

[0017] The image forming apparatus 1 is a printer that transfers a toner image formed by an electrophotographic method onto a sheet of paper (not shown) to form an image. As Figure 1As shown, the image forming apparatus 1 has a device main body 2 having an outer appearance in a substantially rectangular parallelepiped shape. A paper feed cassette 3 for accommodating paper is provided at the lower part of the device main body 2 in a detachable manner, for example. A paper discharge tray 4 is provided on the upper surface of the device main body 2. A toner container 5 for accommodating replenishing toner (developer) is detachably mounted above the inside of the device main body 2. In addition, paper, which is an example of a medium, is not limited to paper quality and may be a resin sheet or the like.

[0018] A conveyance path 6 that becomes a path for conveying paper and a reverse conveyance path 7 are formed inside the device main body 2. The conveyance path 6 is formed in a substantially S shape spanning from the front lower part to the rear upper part of the device main body 2 and is a path for conveying paper from the paper feed cassette 3 to the paper discharge tray 4. The reverse conveyance path 7 branches downward on the downstream side of the conveyance path 6 and extends forward, and merges on the upstream side of the conveyance path 6. The reverse conveyance path 7 is a path for conveying paper after flipping it and then conveying it to an image forming device 11 (described later). In addition, in this specification, the terms "upstream" and "downstream" refer to "upstream" and "downstream" in the conveyance direction of paper (medium).

[0019] The image forming apparatus 1 has a paper feed device 10, an image forming device 11, a fixing device 12, and a conveyance device 13. The paper feed device 10 is provided at the upstream end of the conveyance path 6, the image forming device 11 is provided at the middle part of the conveyance path 6, and the fixing device 12 is provided on the downstream side of the conveyance path 6. The conveyance device 13 is provided at appropriate positions on the conveyance path 6 and the reverse conveyance path 7.

[0020] <Paper Feed Device>

[0021] The paper feed device 10 has a pick up roller 10A and a paper feed roller pair 10B. The pick up roller 10A takes out the uppermost paper from the stack of papers accommodated in the paper feed cassette 3. The paper feed roller pair 10B separates the papers taken out by the pick up roller 10A one by one and conveys them to the downstream side.

[0022] <Image Forming Device>

[0023] The image forming device 11 has 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 substantially cylindrical shape that is long in the left-right direction and is driven by a motor (not shown) to rotate about its axis. The charging device 15, the developing device 16, and the transfer roller 17 are sequentially arranged around the photosensitive drum 14 in accordance with the image forming process. The transfer roller 17 contacts the photosensitive drum 14 from below to form a transfer nip portion. The optical scanning device 18 is provided at a position above the photosensitive drum 14 and emits scanning light to the surface of the photosensitive drum 14.

[0024] <Fixing Device>

[0025] 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 into a substantially cylindrical shape that is long in the left-right direction, and are supported by a housing (not shown) in a rotatable manner. A heater (not shown) for heating the fixing belt 12A is provided inside the fixing belt 12A. The pressure roller 12B pushes against the fixing belt 12A from the lower side to form a fixing nip. The pressure roller 12B is driven by a motor (not shown) to rotate around an axis, and the fixing belt 12A rotates following the pressure roller 12B.

[0026] <Conveying device>

[0027] The conveying device 13 includes: a delivery roller 20A; a registration roller pair 20B; a conveying roller pair 20C; a paper discharge roller pair 20D; two double-sided conveying roller pairs 20E; and a driving device 21 (see Figure 2 The delivery roller 20A, the registration roller pair 20B, the conveying roller pair 20C and the paper discharge roller pair 20D are arranged on the upstream side of the conveying path 6, and the two double-sided conveying roller pairs 20E are arranged on the reverse conveying path 7. The driving device 21 drives the above-mentioned delivery roller 20A and the like to rotate.

[0028] The delivery roller 20A is arranged on the downstream side of the paper feed roller pair 10B, and conveys the paper passing through the paper feed roller pair 10B. The registration roller pair 20B is arranged between the delivery roller 20A and the transfer roller 17, and temporarily blocks the conveyed paper to correct the inclination of the paper (skew correction). The conveying roller pair 20C is arranged at a position downstream of the fixing device 12, and conveys the paper passing through the fixing nip. The paper discharge roller pair 20D is arranged at the downstream end of the conveying path 6, and discharges the paper passing through the conveying roller pair 20C to the paper discharge tray 4. In addition, the paper discharge roller pair 20D switches back the paper with an image formed on the surface, and delivers it to the reversing conveying path 7. The two double-sided conveying roller pairs 20E convey the paper delivered by the paper discharge roller pair 20D. In addition, the reversing conveying path 7 merges with the conveying path 6 between the delivery roller 20A and the registration roller pair 20B.

[0029] The driving device 21 is supported by an internal frame (not shown) of the device body 2, and drives the delivery roller 20A, one or both rollers of each roller pair 20B to 20E, etc. to rotate around the axis. In addition, the driving device 21 drives the developing roller 20F built into the developing device 16 to rotate around the axis. In addition, the delivery roller 20A, each roller pair 20B to 20E, and the developing roller 20F are examples of drive objects, and components other than these can also be driven by the driving device 21. In addition, in the following description, for convenience, the delivery roller 20A, each roller pair 20B to 20E, and the developing roller 20F are collectively referred to as "drive object rollers 20".

[0030] [Image formation process]

[0031] Here, the operation of the image forming apparatus 1 will be described. A control unit (not shown) performs image forming processing (control) as follows based on image data input from an external terminal.

[0032] The charging device 15 charges the surface of the photosensitive drum 14. The optical scanning device 18 exposes the photosensitive drum 14, and an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 14. The developing device 16 uses the toner supplied from the toner container 5 to develop the electrostatic latent image on the photosensitive drum 14 into a toner image.

[0033] The paper feeding device 10 separates the sheets in the paper supply cassette 3 one by one and sends them out to the conveyance path 6. The registration roller pair 20B sends the skewed-corrected paper to the transfer nip portion at a prescribed time. The transfer roller 17 transfers the toner image on the photosensitive drum 14 to the surface of the paper passing through the transfer nip portion. The fixing device 12 passes the paper between the fixing belt 12A that rotates about an axis and the pressure roller 12B (fixing nip portion), thereby thermally fixing the toner image on the paper. In the case of single-sided printing, the paper discharge roller pair 20D discharges the paper with the toner image fixed thereon to the paper discharge tray 4.

[0034] In the case of double-sided printing, the paper discharge roller pair 20D turns the paper back and sends it out to the reverse conveyance path 7. Two double-sided conveyance roller pairs 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, an image is also formed on the back surface of the paper in the same steps as in the above single-sided printing, and the paper with double-sided printing is discharged to the paper discharge tray 4.

[0035] [Drive device]

[0036] Next, with reference to Figures 2 to 6 , the drive device 21 will be described in detail. Figure 2 FIG. is a perspective view showing the drive device 21. Figure 3 FIG. is an exploded perspective view showing the drive device 21. Figure 4 FIG. is a perspective view showing the first cover portion 30 and the like of the drive transmission device 23. Figure 5 FIG. is a perspective view showing the second cover portion 40 and the like of the drive transmission device 23. Figure 6 FIG. is a perspective view showing the drive device 21 (left side).

[0037] As shown in Figure 2 and Figure 3 , the drive device 21 includes a drive motor 22 and a drive transmission device 23.

[0038] [Drive motor]

[0039] The drive motor 22, as an example of a drive source, is, for example, a stepper motor capable of positioning control. The drive motor 22 generates a driving force for driving the driven roller 20.

[0040] <Drive transmission device>

[0041] 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 has a housing portion 24 and a support portion 25.

[0042] (Housing portion)

[0043] The housing portion 24 is a housing for housing a plurality of gears 27, a plurality of clutches 28, etc. As Figure 3 shown, a gear train is formed by meshing adjacent gears 27 with each other. One gear 27 meshes with a drive gear (not shown) fixed to the drive shaft 26 of the drive motor 22 and transmits the rotational force to other gears 27. Each clutch 28 has: a gear portion (not shown) that meshes with any one of the plurality of gears 27; and a clutch shaft (not shown) that transmits the driving force to any one of the plurality of driven rollers 20. Each clutch 28 is controlled by a control unit and has a function of switching to an engaged state or a disengaged state, where the engaged state is a state in which the rotational driving force received from the gear 27 is transmitted to the clutch shaft, and the disengaged state is a state in which the transmission of the rotational driving force to the clutch shaft is blocked. In addition, the detailed description of the meshing relationship of each gear 27 and the detailed description of the connection relationship between each clutch 28 and each driven roller 20 are omitted.

[0044] The housing portion 24 is formed of, for example, a synthetic resin (polycarbonate resin, acrylonitrile-butadiene-styrene synthetic resin, etc.) into a substantially rectangular parallelepiped that is thin in the left-right direction (see Figure 2 ). The housing portion 24 has a first cover portion 30 and a second cover portion 40, where the first cover portion 30 forms the right side of the housing portion 24, and the second cover portion 40 forms the left side of the housing portion 24. The first cover portion 30 and the second cover portion 40 face each other across the space for housing the gear train.

[0045] (First cover portion)

[0046] As Figure 3 and Figure 4 shown, the first cover portion 30 is formed in a tray shape with the substantially left side face open. A plurality of engagement holes 34 are opened in the outer peripheral portion of the first cover portion 30 (see Figure 4 ). In addition, only a part of the plurality of engagement holes 34 is shown in Figure 4 .

[0047] The first cover portion 30 is formed with a first opening 31, a plurality of first through holes 32, and a plurality of clutch receiving 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 later) that rotatably supports 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 to be larger than the outer diameter of the fixing pin 53, and the fixing pin 53 penetrates through the first through hole 32 with a gap. Each clutch receiving portion 33 is a recess for fitting the clutch 28.

[0048] (The second cover portion)

[0049] As Figure 3 , Figure 5 and Figure 6 shown, the second cover portion 40 is formed in a tray shape with its substantially right side open. A plurality of engaging portions 44 are formed on the outer peripheral portion of the second cover portion 40 so as to protrude to the right (refer to Figure 5 ). By engaging each engaging portion 44 with the engaging hole 34 of the first cover portion 30, the first cover portion 30 and the second cover portion 40 are joined together to form a space for housing the gear train.

[0050] As Figure 5 and Figure 6 shown, the second cover portion 40 is formed with a second opening 41, a plurality of second through holes 42, and a plurality of gear receiving portions 43. The second opening 41 is a bearing for rotatably supporting the drive shaft 26 of the drive motor 22. The plurality of second through holes 42 are holes formed corresponding to the plurality of gears 27. The tip portion of the fixing pin 53 passing through the first through hole 32 is inserted into each of the second through holes 42. The diameter (inner diameter) of the second through hole 42 is set to be slightly larger than the outer diameter of the fixing pin 53, and the tip portion of the fixing pin 53 is fitted into the first through hole 32 in a substantially gapless state. Each gear receiving portion 43 is a recess for rotatably supporting the clutch shaft of the clutch 28 and for housing the gear portion of the clutch 28. In addition, in Figure 6 , a part of the plurality of second through holes 42 is blocked by an external gear.

[0051] (Support portion)

[0052] As Figure 3As shown, the support portion 25 is made of metal (such as iron, stainless steel, or aluminum alloy) and is formed in a flat plate shape. A support opening 51 through which the drive shaft 26 of the drive motor 22 passes is open on the support portion 25. The drive shaft 26 is inserted into the support opening 51 from the right to the left, and the drive motor 22 is screwed to the right surface of the support portion 25. In addition, a plurality of clearance through holes 52 through which screws (not shown) pass are open on the support portion 25, and on the first cover portion 30, a plurality of threaded holes 35 are formed at positions corresponding to the plurality of clearance through holes 52 (see Figure 4 ).

[0053] (Fixed pin)

[0054] As Figure 3 shown, on the support portion 25, a plurality of fixing pins 53 are fixed at positions corresponding to the plurality of gears 27 (the first through hole 32 and the second through hole 42). Each fixing pin 53 is made of metal (such as iron, stainless steel, or aluminum alloy) and is formed in a substantially cylindrical shape, and is fixed to the left surface of the support portion 25 by riveting. Each fixing pin 53 extends from the left surface of the support portion 25 to the right. Each fixing pin 53 supports the gear 27 in a rotatable manner in a state where it passes through the housing portion 24 and its tip portion is inserted into each second through hole 42. In addition, the fixing method of the fixing pin 53 fixed to the support portion 25 may also be screw fixing, welding, etc.

[0055] Here, the case of assembling the drive device 21 will be briefly described. The support portion 25 for fixing the drive motor 22 is disposed on the right side of the housing portion 24, and the drive shaft 26 passes through the first opening 31 of the first cover portion 30 from the right to the left (see Figure 4 ) and is inserted into the second opening 41 of the second cover portion 40 (see Figure 6 ). In addition, each fixing pin 53 is inserted into the first through hole 32 of the first cover portion 30 from the right to the left (see Figure 4 ) and passes through the axial center portion of the gear 27, and is inserted into the second through hole 42 of the second cover portion 40 (see Figure 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. And by screwing the screws passing through the respective clearance through holes 52 of the support portion 25 with the threaded holes 35 of the first cover portion 30, the support portion 25 is fixed to the first cover portion 30. In addition, the support portion 25 may be fixed to the device main body 2 (not shown) instead of being fixed to the housing portion 24.

[0056] Next, the operation of the drive device 21 will be briefly described. The drive motor 22 is driven while being controlled by the control unit. The rotational driving force of the drive motor 22 is transmitted to the driven roller 20 via a plurality of gears 27 (gear train). Each clutch 28 is controlled by the control unit to switch to the engaged state or the disengaged state, whereby only the selected driven roller 20 can be rotated (or stopped).

[0057] In addition, when assembling the drive device 21 (or the drive transmission device 23), a lubricant (for example, a lubricating oil mainly composed of polyalphaolefin) is applied to the tip of each fixing pin 53 so that the plurality of fixing pins 53 can be smoothly fitted into the plurality of second through holes 42. Therefore, in a state where the fixing pin 53 is inserted into the second through hole 42, the lubricant is interposed on the contact portion P between the fixing pin 53 and the inner peripheral surface 47 of the second through hole 42. Generally, compared with metals, synthetic resins are more likely to deteriorate due to the adhesion of lubricants. Therefore, in the second cover portion 40 made of synthetic resin, the inner peripheral surface 47 of the second through hole 42, which may be a lubricant adhesion site, may deteriorate.

[0058] On the other hand, when the drive device 21 is operating (in use), since each fixing pin 53 and the housing portion 24 continuously bear loads such as vibrations generated by the rotation of the drive motor 22 and each gear 27, over time, a phenomenon of increased deformation (creep deformation) of the fixing pin 53 and the housing portion 24 occurs. Assuming that creep deformation occurs at a portion (the inner peripheral surface 47 of the second through hole 42) deteriorated due to the adhesion of the lubricant, there is a concern that cracks (chemical cracks) may occur at this portion. Therefore, the drive device 21 (drive transmission device 23) according to the present embodiment has a structure for suppressing chemical cracks in each second through hole 42 and each fixing pin 53. In addition, in the following description, for convenience, one fixing pin 53 and one second through hole 42 are taken as an example for description.

[0059] Next, with reference to Figure 7 , a structure for suppressing the occurrence of chemical cracks will be described. Figure 7 is Figure 6 a cross-sectional view (and a partial enlarged view thereof) taken along VII-VII of

[0060] <The opening edge portion of the second through hole>

[0061] The opening edge of the second through-hole 42 is formed in a conical shape that expands toward both sides in the left-right direction. Specifically, a guiding chamfered portion 45 is formed on the opening edge of the second through-hole 42 that is on the inner side (the space side for housing the gear train) of the second cover portion 40, and the guiding chamfered portion 45 is obtained by cutting off the sharp edge into a straight line. That is, the guiding chamfered portion 45 is a so-called C chamfer (C angle). A hole-side chamfered portion 46 is formed on the opening edge of the second through-hole 42 that is on the outer side of the second cover portion 40, and the hole-side chamfered portion 46 is obtained by cutting off the sharp edge into an arc shape. That is, the hole-side chamfered portion 46 is a so-called R chamfer (R angle). An inner peripheral surface 47 is formed between the guiding chamfered portion 45 and the hole-side chamfered portion 46, and the inner peripheral surface 47 has substantially the same inner diameter throughout the left-right direction.

[0062] <The tip of the fixing pin>

[0063] The tip of the fixing pin 53 is formed in a conical shape that tapers as it approaches the tip (left side). Specifically, a shaft-side chamfered portion 56 is formed on the tip of the fixing pin 53, and the shaft-side chamfered portion 56 is obtained by cutting off the sharp edge into a straight line. That is, the shaft-side chamfered portion 56 is a so-called C chamfer (C angle). The outer peripheral surface 57 of the fixing pin 53 except for the shaft-side chamfered portion 56 has substantially the same outer diameter throughout the left-right direction.

[0064] When inserting the tip of the fixing pin 53 into the second through-hole 42, in the case where the axis of the fixing pin 53 is slightly deviated from the axis of the second through-hole 42, a part of the shaft-side chamfered portion 56 of the fixing pin 53 contacts a part of the guiding chamfered portion 45 of the second through-hole 42. The tip of the fixing pin 53 (shaft-side chamfered portion 56) also smoothly slides on the guiding chamfered portion 45 toward the axis of the second through-hole 42 under the action of the applied lubricant. Accordingly, the axes of the fixing pin 53 and the second through-hole 42 are made substantially coincident, and then the tip of the fixing pin 53 is inserted into the second through-hole 42 (fitting is performed).

[0065] In the state where the tip of the fixing pin 53 is inserted into (fitted into) the second through-hole 42, the lubricant is interposed 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 top surface of the fixing pin 53 penetrates the second through-hole 42 and protrudes slightly outward from the outer surface of the second cover portion 40.

[0066] The hole-side boundary portion 48, which is the boundary between the inner peripheral surface 47 of the second through-hole 42 and the hole-side chamfered portion 46, contacts the outer peripheral surface 57 of the fixing pin 53. That is, in Figure 7 the straight portion of the fixing pin 53 contacts the inner peripheral surface 47 of the second through-hole 42 and the hole-side boundary portion 48. In addition, the "contact" here means that in addition to direct contact, it also includes the case of contact via the lubricant.

[0067] The axial-side boundary portion 58, which is the boundary between the outer peripheral surface 57 of the fixing pin 53 and the axial-side chamfered portion 56, faces the hole-side chamfered portion 46 with a gap M1 therebetween. That is, the axial-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.

[0068] The interval M2 between the hole-side boundary portion 48 and the axial-side boundary portion 58 is set to be more than half and less than or equal to the radius (the radius of the R chamfer) of the hole-side chamfered portion 46. In the present embodiment, as an example, the radius of the hole-side chamfered portion 46 is 0.5 mm, and the interval M2 between the hole-side boundary portion 48 and the axial-side boundary portion 58 is set to 0.3 mm. In addition, the upper limit of the radius of the hole-side chamfered portion 46 can be less than the wall thickness of the second cover portion 40 other than the guiding chamfered portion 45.

[0069] In the drive device 21 (drive transmission device 23) according to the present embodiment described above, the structure is configured such that the hole-side boundary portion 48 contacts the outer peripheral surface 57 of the fixing pin 53, and the axial-side boundary portion 58 does not contact the hole-side chamfered portion 46. According to this structure, since only the outer peripheral surface 57 of the fixing pin 53 is in surface contact with the inner peripheral surface 47 of the second through hole 42, the fixing pin 53 can be reliably held by the inner peripheral surface 47 of the second through hole 42. In addition, even if creep deformation occurs in the fixing pin 53 and the housing portion 24 (the second cover portion 40), the axial-side boundary portion 58 of the fixing pin 53 does not interfere with the inner peripheral surface 47 of the second through hole 42 or the hole-side chamfered portion 46. Accordingly, it is possible to prevent local stress concentration from occurring at the contact portion P between the tip of the fixing pin 53 provided with a lubricant and the inner peripheral surface 47 of the second through hole 42, and thus, chemical cracks at the contact portion P can be suppressed.

[0070] In addition, in the drive device 21 (drive transmission device 23) according to the present embodiment, in a state where the fixing pin 53 is inserted into the second through hole 42, the hole-side boundary portion 48 is provided at a position that is inward by a predetermined interval M2 from the axial-side boundary portion 58. Accordingly, interference between the axial-side boundary portion 58 and the hole-side chamfered portion 46 can be appropriately prevented, and thus, chemical cracks at the contact portion P between the fixing pin 53 and the second through hole 42 can be effectively prevented.

[0071] In addition, in the drive device 21 (drive transmission device 23) according to the present embodiment, the chamfered portion 46 on the hole side is an R chamfer, and the chamfered portion 56 on the shaft side is a C chamfer. However, the present invention is not limited thereto. At least one of the chamfered portion 46 on the hole side and the chamfered portion 56 on the shaft side may be cut into an arc shape. For example, both the chamfered portion 46 on the hole side and the chamfered portion 56 on the shaft side may be R chamfers (not shown). Alternatively, both the chamfered portion 46 on the hole side and the chamfered portion 56 on the shaft side may be C chamfers (not shown). For example, when the hole-side boundary portion 48 is a C chamfer, the interval M2 between the hole-side boundary portion 48 and the shaft-side boundary portion 58 may be set within a range of not less than half and not more than the distance from the outer surface of the second cover portion 40 to the hole-side boundary portion 48 (not shown). Additionally, for example, by making the chamfered portion 56 on the shaft side an R chamfer, when the fixing pin 53 is inserted into the first through hole 32 and the second through hole 42, even if the tip of the fixing pin 53 interferes with the edges of the first through hole 32 and the second through hole 42, it is possible to suppress the tip of the fixing pin 53 from being crushed or the like. Also, the guiding chamfered portion 45 is a C chamfer, but it may be an R chamfer or the chamfer may be omitted (not shown). Furthermore, the angle of the C chamfer can be set to any angle.

[0072] In addition, in the drive device 21 (drive transmission device 23) according to the present embodiment, a plurality of gears 27, a plurality of clutches 28, a plurality of fixing pins 53, etc. are provided, but the present invention is not limited thereto, and at least one gear 27 or the like may be provided. Additionally, if the clutch 28 is not required, it may also be omitted (not shown).

[0073] In addition, in the drive device 21 (drive transmission device 23) according to the present embodiment, the housing portion 24 is composed of a first cover portion 30 and a second cover portion 40 that can be divided in the left-right direction. However, the present invention is not limited thereto. For example, the housing portion 24 may be a structure that can be divided in the up-down direction, or may be an integrally formed structure (not shown). Additionally, for example, the housing portion 24 may also be a structure that can be divided into three or more parts (not shown).

[0074] In addition, the image forming apparatus 1 according to the present embodiment is a monochrome printer, but the present invention is not limited thereto. For example, the present invention may also be applied to a color printer, a copying machine, a facsimile machine, or a multifunction machine, etc.

[0075] Furthermore, the description of the above embodiment represents one mode of the drive transmission device, the drive device, and the image forming apparatus according to the present invention. The technical scope of the present invention is not limited to the above embodiment. The present invention can be variously changed, replaced, and deformed within the scope of its technical idea. The scope of protection claimed by the present invention includes all embodiments that can be included within the scope of its technical idea.

Claims

1. A drive transmission device, characterized in that, it has a receiving portion, a fixing pin and a supporting portion, wherein, the receiving portion receives a gear and is formed with a through hole corresponding to the gear, the fixing pin rotatably supports the gear, the supporting portion fixes the fixing pin in a state where the tip end portion of the fixing pin is inserted into the through hole, a hole side chamfered portion obtained by removing the sharp corners is formed on the opening edge portion outside the through hole, a shaft side chamfered portion obtained by removing the sharp corners is formed on the tip end portion of the fixing pin, in a state where the fixing pin is inserted into the through hole, a lubricant is interposed between the contact portions of the fixing pin and the through hole, the boundary between the inner peripheral surface of the through hole and the hole side chamfered portion, i.e., the hole side boundary portion, contacts the outer peripheral surface of the fixing pin via the lubricant, and the boundary between the outer peripheral surface of the fixing pin and the shaft side chamfered portion, i.e., the shaft side boundary portion, faces the hole side chamfered portion with a gap therebetween.

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

3. The drive transmission device according to claim 1, characterized in that, the hole side chamfered portion is cut into an arc shape, in a state where the fixing pin is inserted into the through hole, the interval between the hole side boundary portion and the shaft side boundary portion is set within a range of more than half of the radius of the hole side chamfered portion and less than or equal to the radius.

4. The drive transmission device according to claim 1, characterized in that, the fixing pin is made of metal and the receiving portion is made of resin.

5. The drive transmission device according to claim 1, characterized in that, a guiding chamfered portion obtained by removing the sharp corners is formed on the opening edge portion inside the through hole.

6. A drive device, characterized in that, it has a drive source and the drive transmission device according to claim 1, wherein the drive source is used to drive a drive object; the drive transmission device transmits the driving force of the drive source to the drive object.

7. An image forming device, characterized in that, it has the drive device according to claim 6.

Images