JP2015206889A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that can reduce a rotational load at the initial operation to reduce friction and wear on the surface of a bearing, and an image forming apparatus.SOLUTION: A fixing device 19 includes a heat roller 41 and slide bearings 80. The heat roller 41 rotates by receiving a rotational driving force. The slide bearings 80 include journals 62 formed respectively on both ends in the axial direction D1 of the heat roller 41 to rotatably support the heat roller 41. The slide bearings 80 each have a plurality of projection parts 85 formed on a bearing surface 81 that is in slide contact with the surface of the journal 62.

Description

  The present invention relates to a fixing device and an image forming apparatus including a roller member that is rotated by receiving a rotational driving force, and particularly relates to a rotation support mechanism for the roller member.

  An electrophotographic image forming apparatus includes a fixing device that fixes a toner image transferred to a sheet member such as a printing sheet on the sheet member. The fixing device includes a heat roller and a pressure roller, and these rollers are rotatably supported while being pressed against each other. When the sheet member is passed between the heat roller and the pressure roller, heat is transmitted from the heat roller at that time, whereby the toner image is melted and the image is fixed on the sheet member.

  Conventionally, as a configuration for rotatably supporting the heat roller, a support mechanism for supporting both ends of the heat roller by sliding bearings is known (see Patent Document 1). In this support mechanism, the bearing surface is inclined with respect to the axial center of the heat roller, whereby the scraps generated by sliding contact with both ends of the heat roller can be discharged. Further, in order to reduce the friction and wear of the bearing surface, a support mechanism is known in which the bearing surface of the sliding bearing is not mirror-finished and has a concavo-convex shape having no directivity (see Patent Document 2).

JP 2011-21637 A Japanese Patent Application Laid-Open No. 7-190065

  In the above-described support mechanism in which irregularities are provided on the bearing surface, wear powder is generated between the bearing surface and the support surface of the roller until the convex portion of the bearing surface wears during initial operation and the slidability is stabilized. This wear powder increases the rotational load (rotational torque) of the rotating shaft during the initial operation. If the bearing surface is inclined in order to discharge such wear powder, the friction and wear of the bearing surface cannot be sufficiently reduced.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to fix a fixing device and an image forming apparatus capable of reducing a rotational load during initial operation and reducing friction and wear of a bearing surface. Is to provide.

  A fixing device according to one aspect of the present invention includes a first roller and a sliding bearing. The first roller receives a rotational driving force and rotates. The sliding bearing includes a sliding portion formed at each of both axial ends of the first roller and rotatably supports the first roller. The sliding bearing has one or a plurality of convex portions on an inner peripheral surface of the sliding bearing that is in sliding contact with the surface of the sliding portion.

  An image forming apparatus according to another aspect of the present invention includes the fixing device and an image forming unit. The image forming unit forms a toner image fixed by the fixing device on a predetermined sheet member.

  According to the present invention, it is possible to reduce the rotational load during the initial operation of the roller, and it is possible to reduce the friction and wear of the dynamic bearing surface that is the sliding contact surface between the sliding bearing and the roller.

FIG. 1 is a diagram illustrating an internal configuration of an image forming apparatus including a fixing device according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration of the fixing device illustrated in FIG. 1. FIG. 3 is a diagram illustrating an example of a sliding bearing provided in the fixing device of FIG. FIG. 4 is a view showing another example of the sliding bearing provided in the fixing device of FIG. FIG. 5 is a diagram illustrating another example of the sliding bearing provided in the fixing device of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment described below is merely an example embodying the present invention, and the embodiment of the present invention can be changed as appropriate without departing from the scope of the present invention.

[Image forming apparatus 10]
FIG. 1 is a diagram illustrating a configuration of an image forming apparatus 10 according to an embodiment of the present invention. The image forming apparatus 10 is a printer that prints an image on a sheet member such as printing paper based on input image data. Note that the image forming apparatus 10 is not limited to a printer having only a printing function. For example, the present invention can be applied to a printer, a facsimile machine, a copier, or a multifunction machine having these functions. In the following description, the vertical direction 6 is defined with reference to the state in which the image forming apparatus 10 is installed (the state shown in FIG. 1), and the right side in FIG. 1 is the front side (front side). 7 is defined, and the horizontal direction 8 is defined when the image forming apparatus 10 is viewed from the front.

  As shown in FIG. 2, the image forming apparatus 10 mainly includes an electrophotographic image forming unit 18, a fixing device 19, a paper feeding unit 15, a paper unit 21, and the image forming apparatus 10. And a control unit (not shown) for controlling. The image forming apparatus 10 is provided on a casing 14 constituting an outer frame cover and an inner frame of the image forming apparatus 10.

  The paper feeding unit 15 is provided at the lowermost part of the image forming apparatus 10. The paper feed unit 15 includes a paper feed tray 50, a pickup roller 51, and a paper feed roller 52. When an instruction to start the sheet member feeding operation is input to the image forming apparatus 10, the pickup roller 51 and the paper feed roller 52 are driven to rotate by a transport motor (not shown), and the paper feed tray 50 A sheet member is fed.

  The image forming unit 18 transfers the toner image to the sheet member using a printing material such as toner. Specifically, the image forming unit 18 includes a photosensitive drum 31, a charging unit 32, a developing unit 33, a transfer unit 35, a cleaning unit 36, and an LSU (Laser Scanning Unit) 34. When the image forming operation is started, the charging unit 32 charges the surface of the photosensitive drum 31 to a uniform potential. Further, the laser beam is scanned from the LSU 34 to the photosensitive drum 31 according to the image data. Thereby, an electrostatic latent image is formed on the photosensitive drum 31. Thereafter, toner is attached to the electrostatic latent image by the developing unit 33, and the toner image is developed on the photosensitive drum 31. The toner image is transferred by the transfer unit 35 to the sheet member fed from the paper feed tray 50. The sheet member to which the toner image has been transferred is sent out to a conveyance path 27 provided between the image forming unit 18 and the fixing device 19 and is arranged downstream of the image forming unit 18 in the conveyance direction (that is, the rear side). Then, it is conveyed to the fixed fixing device 19.

  The fixing device 19 fixes the toner image transferred to the sheet member to the sheet member by heat and pressure. The fixing device 19 includes a heat roller 41 (an example of a first roller), a pressure roller 42 (an example of a second roller), and a heating unit 43. The heat roller 41 is heated to a high temperature by a heating unit 43 such as a heater during a fixing operation. When the sheet member passes through the fixing device 19, the toner is heated and melted by the heat roller 41 of the fixing device 19 and pressed by the pressure roller 42. As a result, the toner image is fixed on the sheet member, and an image is formed on the sheet member. The sheet member on which the image is fixed by the fixing device 19 is conveyed upward from the fixing device 19 and then discharged from the paper discharge port 22 to the paper discharge unit 21 by the paper discharge roller pair 23.

  Hereinafter, the support mechanism of the fixing device 19 will be described with reference to FIGS.

  As shown in FIG. 2, the heat roller 41 is a roller member formed in a long shape in the axial direction D1. The heat roller 41 is rotatably supported inside the fixing device 19. The heat roller 41 is connected to a motor that is driven and controlled by a control unit (not shown). The heat roller 41 is rotated in the clockwise direction in FIG. 1 by transmitting the rotational driving force when the motor is rotationally driven.

  The heat roller 41 has a roller body 61 formed in a cylindrical shape. The roller surface of the roller body 61 is a part that is in contact with the developing surface (the surface on which the toner image is attached) of the sheet member during fixing. The roller body 61 is made of a material having high thermal conductivity, and is made of a metal such as aluminum, for example. The surface of the roller body 61 is coated with a fluororesin layer in order to improve toner separation. The fluororesin layer is coated on the entire outer peripheral surface including journals (shaft necks) 62 (62A, 62B) of the heat roller 41 described later.

  The fixing device 19 includes two sliding bearings 80 (80A, 80B) for supporting the journals 62 at both ends of the roller body 61. The slide bearing 80 includes the journal 62 and supports the heat roller 41 so as to be rotatable. The sliding bearing 80 is integrally formed of a synthetic resin (engineering plastic or the like) that has high heat resistance and excellent wear resistance. As a material of the sliding bearing 80, for example, polyphenylene sulfide (PPS), polyether safphone (PES), or the like is applicable. At both ends of the roller main body 61, journals 62 (an example of a sliding portion) serving as a rotation shaft at the time of rotation are provided. The journal 62 is an end portion of the roller body 61 in the axial direction D1. The sliding bearing 80 supports the journal 62 rotatably.

  Specifically, a frame (not shown) for supporting the heat roller 41 is provided above the heat roller 41. The flange 82 of the sliding bearing 80 is provided with a fixing portion 83 that is engaged with and fixed to the frame. The fixing portion 83 is engaged with the frame so as to be suspended, and the sliding bearing 80 is fixed to the frame. Then, the journal 62 of the heat roller 41 is inserted into the sliding bearing 80 so that the bearing surface 81 (see FIG. 3) which is the inner peripheral surface of the sliding bearing 80 and the journal 62 are slidably in contact with each other. Thereby, the heat roller 41 is supported so as to slide with respect to the bearing surface 81.

  In the present embodiment, the journal 62A on the sliding bearing 80A side passes through the sliding bearing 80A in the axial direction D1, and a gear 67 is fixed to the end portion thereof. The rotational driving force from the motor is transmitted to the gear 67.

  The heat roller 41 has a heating unit 43. The heating unit 43 is provided inside the roller body 61. The heating unit 43 is composed of, for example, a halogen lamp. The heating unit 43 extends in the axial direction inside the roller body 61, and the roller body 61 is heated by the heating unit 43 in the entire axial direction from the inside.

  The pressure roller 42 is a roller member formed in a long shape in the axial direction D1. The pressure roller 42 is disposed to face the heat roller 41 and is provided in parallel to the heat roller 41. In the present embodiment, the pressure roller 42 is disposed below the heat roller 41. The pressure roller 42 is supported inside the fixing device 19 so as to be rotatable in a state where it is pressed against the surface of the heat roller 41 with a predetermined pressure.

  The pressure roller 42 has a rotation shaft 69 at the center. Side frames 71 of the fixing device 16 are provided outside both ends of the rotation shaft 69. The side frame 71 is formed with a support groove (not shown) which is formed long in the vertical direction and is open on the upper side and closed on the lower side. A bearing bracket 75 is supported in the support groove so as to be movable in the vertical direction. A rotation shaft 69 of the pressure roller 42 is rotatably supported by the bearing bracket 75. Thereby, the pressure roller 42 can be rotated.

  The rotating shaft 69 of the pressure roller 42 is provided with a cylindrical elastic portion 68 such as elastic silicon or porous rubber. In the support groove, an elastic member 76 is provided between the bearing bracket 75 and the bottom of the support groove. The elastic member 76 is a coil spring in a compressed state, and biases the bearing bracket 75 in a direction (upward) away from the bottom of the support groove. For this reason, the elastic part 68 of the pressure roller 42 is pressed against the heat roller 41. In this way, the elastic portion 68 is pressed against the heat roller 41 by the elastic member 76, so that the elastic portion 68 is elastically deformed and dented in a curved shape between the heat roller 41 and the pressure roller 42. 64 is formed. Further, the pressure roller 42 is rotated in the counterclockwise rotation direction in FIG. 2 following the rotation of the heat roller 41 due to the contact friction at the nip portion 64.

  By the way, in the configuration in which the bearing surface 81 of the sliding bearing 80 and the journal 62 are slidably supported, when the image forming apparatus 10 is operated for the first time and the heat roller 41 is rotated, the bearing surface 81 is worn and slid. Wear powder is generated from the bearing surface 81 until the mobility is stabilized. In particular, as described above, when the fluororesin layer is coated on the roller body 61, the fluororesin layer is worn to become wear powder. This wear powder increases the rotational load (rotational torque) of the journal 62 during the initial operation of the heat roller 41. In order to discharge such wear powder from the bearing surface 81, a convex portion 85 described later is provided on the bearing surface 81 in the present embodiment.

  Hereinafter, the convex portion 85 of the sliding bearing 80A will be described. 3A is a perspective view showing a sliding bearing 80A corresponding to one journal 62A of the roller body 61, and FIG. 3B partially shows a bearing surface 81 of the sliding bearing 80A. It is a schematic diagram. In addition, about the other sliding bearing 80B, since the convex-shaped part 85 same as 80 A of sliding bearings is formed, description of the sliding bearing 80B is abbreviate | omitted.

  As shown in FIG. 3, a plurality of convex portions 85 are provided on the bearing surface 81 of the sliding bearing 80 </ b> A. The convex portion 85 is a chevron rib extending in the same direction as the axial direction D1 of the heat roller 41. The convex portion 85 is integrally formed when the sliding bearing 80 </ b> A is molded, and a plurality of convex portions 85 are formed along the circumferential direction D <b> 2 of the bearing surface 81.

  The convex part 85 protrudes perpendicularly from the bearing surface 81, and its protruding end is formed in an arc shape. The convex portion 85 extends in the axial direction on the bearing surface 81. The protruding height of the convex portion 85 is about 0.5 mm to 1.0 mm from the bearing surface 81. In the present embodiment, as a preferred size, the protruding height of the convex portion 85 is set to 0.5 mm.

  On the bearing surface 81, a plurality of convex portions 85 are arranged at equal intervals along the circumferential direction D2. Specifically, the interval between the plurality of convex portions 85 is about 0.5 mm to 1.0 mm. In this embodiment, as a preferable size, the interval (pitch) between the convex portions 85 is set to 0.5 mm. Further, the width of the convex portion 85 in the circumferential direction D <b> 1 is slightly smaller than the width of the valley portion 86 between the adjacent convex portions 85. Of course, the width of the convex portion 85 and the width of the valley portion 86 may be the same size.

  Since such a convex portion 85 is formed on the bearing surface 81, when the journal 62 is inserted into the sliding bearing 80, the journal 62 and the apex of the convex portion 85 come into point contact. When a rotational driving force is transmitted to the heat roller 41 in this state, the heat roller 41 rotates while the journal 62 is in sliding contact with the convex portion 85. At this time, since the top of the convex portion 85 comes into contact with and slidably contacts the journal 62, the convex portion 85 wears out early, and as a result, the rotational load (rotational torque) during the initial operation of the heat roller 41. Can be reduced early. Further, due to the sliding contact between the journal 62 and the convex portion 85, the fluororesin layer of the convex portion 85 is abraded or the resin material of the convex portion 85 is abraded to generate wear powder. The wear powder does not stay at the contact portion between the convex portion 85 and the journal 62 but is drawn from the convex portion 85 to the valley portion 86. And the abrasion powder of the trough part 86 moves to the axial direction D1 gradually, and is discharged | emitted outside the sliding bearing 80 (dotted line arrow direction of FIG. 3 (B)). Thus, since the wear powder is discharged to the outside, the friction of the bearing surface 81 can be reduced, and excessive wear of the bearing surface 81 due to the wear powder can be prevented.

  In the above-described embodiment, the configuration in which the convex portions 85 are arranged on the bearing surface 81 at equal intervals along the circumferential direction D2 is illustrated, but the present invention is not limited to this. For example, in the configuration in which the pressure roller 42 is in pressure contact with the heat roller 41, the pressing force from the journal 62 received by the surface on the nip portion 64 side on the bearing surface 81 of the sliding bearing 80 is weak, and the surface on the opposite side to the nip portion 64. The pressing force received is stronger than that on the nip portion 64 side. For this reason, the convex part 85 may be densely provided on the opposite side of the bearing surface 81 from the nip part 64 side. In this case, the wear on the surface opposite to the nip portion 64 side does not progress more than the other portions, and the entire area of the bearing surface 81 is evenly worn. As a result, eccentricity of the heat roller 41 due to uneven wear is prevented.

  In addition, although embodiment mentioned above demonstrated the example in which the convex-shaped part 85 extended in the axial direction D1 was provided in the bearing surface 81, this invention is not limited to this. For example, a convex portion 85 </ b> A as shown in FIG. 4 may be formed on the bearing surface 81. 4A is a perspective view showing a sliding bearing 80A corresponding to one journal 62A of the roller body 61, and FIG. 4B partially shows a bearing surface 81 of the sliding bearing 80A. It is a schematic diagram. The convex portion 85 </ b> A shown in FIG. 4 is a spiral chevron rib centered on the central axis of the heat roller 41, and is formed along the circumferential direction D <b> 2 of the bearing surface 81.

  The convex portion 85A is formed by threading the inner peripheral surface of the sliding bearing 80A. Accordingly, the convex portion 85A is formed in a spiral shape in a direction away from the journal 62A to the outside in the axial direction D1 of the heat roller 41. In this case, the convex portion 85A is a single chevron rib continuous in the circumferential direction D2. In other words, in the screw hole formed on the inner peripheral surface of the sliding bearing 80A, the thread portion corresponds to the convex portion 85A. The protruding height of the convex portion 85A is approximately 0.5 mm to 1.0 mm from the bearing surface 81. Moreover, the space | interval (screw thread pitch) of the axial direction D1 of 85 A of convex-shaped parts is about 0.5 mm-1.0 mm.

  Further, the convex portion 85 </ b> A extends spirally in a direction away from the journal 62 </ b> A to the outside of the axial direction D <b> 1 of the heat roller 41 when the rotation direction of the heat roller 41 is used as a reference. Specifically, as shown in FIG. 4A, when the heat roller 41 is rotated in the rotation direction D3 indicated by the arrow, the outer side of the axial direction D1 with respect to the bearing surface 81 (indicated by the arrow D4). The convex portion 85A is formed by machining a screw hole in the same direction as the rotation direction D3.

  By forming such a convex portion 85A on the bearing surface 81, in addition to the effect produced by the convex portion 85 described above, not only the wear powder is collected in the valley portion 86A adjacent to the convex portion 85A. The wear powder in the valley portion 86A is pushed outward in the axial direction D1 (in the direction of the dotted line arrow in FIG. 4B) by the rotation of the heat roller 41, and the wear powder is suitably discharged to the outside.

  Moreover, it may replace with the above-mentioned convex-shaped part 85, and the convex-shaped part 85B as shown in FIG. 5 (A) may be formed in the bearing surface 81. FIG. Here, FIG. 5A is a schematic view partially showing the bearing surface 81 of the sliding bearing 80A.

  The convex portion 85 </ b> B shown in FIG. 5A is a helical chevron rib centered on the central axis of the heat roller 41, and is formed along the circumferential direction D <b> 2 of the bearing surface 81. The convex portion 85B is a spiral chevron rib inclined at a predetermined angle (for example, 45 degrees) with respect to the axial direction D1, and a plurality of chevron ribs are formed side by side in the circumferential direction D2. The convex portion 85B is inclined in a direction away from the journal 62A to the outside of the axial direction D1 of the heat roller 41 when the rotation direction of the heat roller 41 is used as a reference. Specifically, when the heat roller 41 is rotated, it is inclined in the same direction as the rotation direction of the heat roller 41 in the direction toward the outside of the axial direction D1 with respect to the bearing surface 81.

  By forming such a convex portion 85B on the bearing surface 81, in addition to the effect produced by the convex portion 85 described above, the wear powder collected in the valley portion 86B adjacent to the convex portion 85B is heated. The roller 41 is pushed to the outside in the axial direction D1 (in the direction indicated by the dotted line in FIG. 5A), and the wear powder is suitably discharged to the outside.

  Further, instead of the above-described convex portion 85, a convex portion 85C as shown in FIG. 5B may be formed on the bearing surface 81. Here, FIG. 5B is a schematic view partially showing the bearing surface 81 of the sliding bearing 80A.

  The convex portion 85C shown in FIG. 5B is an annular chevron rib extending in the circumferential direction D2 of the bearing surface 81 of the sliding bearing 80A, and the plurality of annular chevron ribs are in the same direction as the axial direction D1. Is formed. A groove-shaped valley portion 86C (an example of a groove portion) is formed between adjacent convex portions 85C and 85C. Each of the convex portions 85C is formed with a communication path 87 that communicates between two valley portions 86C adjacent to both sides in the axial direction D1. In the present embodiment, the communication passage 87 is formed vertically downward in the sliding bearing 80A.

  By forming such a convex portion 85C on the bearing surface 81, in addition to the effect produced by the convex portion 85 described above, the wear powder collected in the valley portion 86C adjacent to the convex portion 85C is connected. It is preferably discharged outside the sliding bearing 80 through the passage 87 (in the direction of the dotted arrow in FIG. 5B).

  In the above-described embodiment, the fixing device 19 is illustrated as an example of the present invention. However, the present invention can be understood as an image forming apparatus 10 including the fixing device 19.

10: image forming device 18: image forming unit 19: fixing device 41: heat roller 42: pressure roller 62: journal 64: nip 80: sliding bearing 85: convex 86: valley

Claims (8)

A first roller that is rotated by receiving a rotational driving force;
A sliding bearing that includes a sliding portion formed at each of both axial ends of the first roller and rotatably supports the first roller;
The sliding bearing includes a fixing device having one or a plurality of convex portions on an inner peripheral surface of the sliding bearing that is in sliding contact with a surface of the sliding portion.   The fixing device according to claim 1, wherein the convex portion is a rib extending in the same direction as the axial direction of the first roller, and a plurality of the convex portions are formed along the circumferential direction of the inner peripheral surface of the sliding bearing.   The said convex-shaped part is a helical rib centering on the central axis of the said 1st roller, One or more are formed along the circumferential direction of the internal peripheral surface of the said sliding bearing. Fixing device.   The said convex part is spirally extended in the direction which leaves | separates to the outer side of the axial direction of a said 1st roller from the said sliding part, when the rotation direction of a said 1st roller is made into the reference | standard. Fixing device.   2. The fixing device according to claim 1, wherein the convex portion is an annular rib extending in a circumferential direction of an inner circumferential surface of the sliding bearing, and a plurality of the convex portions are formed in the same direction as the axial direction of the first roller. .   The fixing device according to claim 5, wherein the convex portion has a communication path communicating between two groove portions adjacent to both sides in the axial direction. A second roller disposed opposite the first roller and pressed against the roller surface of the first roller to form a nip portion;
The fixing device according to claim 1, wherein the convex portion is densely provided on an inner peripheral surface of the sliding bearing on a side opposite to the nip portion with respect to the nip portion side. A fixing device according to any one of claims 1 to 7,
An image forming apparatus comprising: an image forming unit that forms a toner image fixed by the fixing device on a predetermined sheet member.

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