Fixing device and image forming apparatus

Abstract

To provide a fixing device capable of suppressing wear of a grounding member or the like and generation of abnormal noise at a contact part of the grounding member.SOLUTION: The fixing device includes a fixing belt configured to heat toner on a sheet while rotating around a shaft, a pressing roller configured to form a pressing area between the fixing belt and the pressing roller and to press the toner on the sheet passing through the pressing area while rotating around the shaft, a fixing frame configured to support both axial end portions of the fixing belt and the pressing roller, a roller bearing member including an inner ring configured to support a 21A portion of a core metal of the pressing roller and an outer ring fixed to the fixing frame in an electrically insulated state, and a grounding member configured to contact the outer ring and electrically ground the pressing roller via the roller bearing member.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a fixing device that fixes a toner image on a medium and an image forming apparatus. [Background technology]

[0002] A known fixing device includes a heating roller that heats a toner image transferred onto paper and a leaf spring member (earth member) that electrically grounds the heating roller (Patent Document 1). In this fixing device, multiple conductive ring-shaped members, each with a notch formed in part of its arc, are attached to the heating roller, aligned in the axial direction so that the positions of the notches are not in phase. The leaf spring member abuts against the outer peripheries of the multiple ring-shaped members, preventing the surface of the heating roller from being damaged by the leaf spring member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4538751 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the fixing device described above, multiple ring-shaped members rotate while in contact with the leaf spring member, which causes problems such as wear on the leaf spring member and the multiple ring-shaped members, and abnormal noises (friction noises) occurring at the contact points between the members.

[0005] In consideration of the above circumstances, the present invention provides a fixing device and an image forming apparatus that can suppress wear of the grounding member and the like and the generation of abnormal noise at the contact portion of the grounding member. [Means for solving the problem]

[0006] The fixing device of the present invention includes a fixing member that heats toner on a medium while rotating around its axis, a pressure member that forms a pressure area between the fixing member and the pressure member and pressurizes the toner on the medium that passes through the pressure area while rotating around its axis, a fixing frame that supports both axial ends of the fixing member and the pressure member, a rolling bearing member that includes an inner ring that supports the rotating shaft portion of either the fixing member or the pressure member so that it can rotate around its axis, and an outer ring that sandwiches a rolling element between the inner ring and the outer peripheral surface of the inner ring and is fixed to the fixing frame in an electrically insulated state, and an earth member that contacts the outer ring and electrically grounds either the fixing member or the pressure member via the rolling bearing member.

[0007] In this case, it is preferable that the bearing holder be made of an insulator, be fixed to the fixing frame while holding the rolling bearing member and the earthing member, and have a guide hole through which the earthing member can be inserted to contact the outer ring, and be further provided with an earth cover made of an insulator and fixed to the bearing holder so as to cover the earthing member that has contacted the outer ring through the guide hole.

[0008] In this case, the earth member may include a portion formed to be expandable and contractible in the axial direction, and may contact an outer edge of the outer ring in the axial direction.

[0009] In this case, the earthing member may include a first conductive member that contacts the outer ring, a second conductive member that contacts the fixing frame, and a resistance member that is provided between the first conductive member and the second conductive member and connected to the first conductive member and the second conductive member.

[0010] In this case, the first conductive member and the second conductive member may include a portion formed to be expandable and contractible in the axial direction, and the first conductive member may contact the outer edge of the outer ring in the axial direction.

[0011] An image forming apparatus according to the present invention includes the fixing device described above. [Effects of the Invention]

[0012] According to the present invention, it is possible to suppress wear of the grounding member and the like and the generation of abnormal noise at the contact portion of the grounding member. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram (side view) showing the internal structure of an image forming apparatus according to one embodiment of the present invention. [Figure 2] FIG. 1 is a perspective view showing a fixing device according to an embodiment of the present invention. [Figure 3] FIG. 2 is a perspective view showing a fixing belt and a pressure roller of a fixing device according to an embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. [Figure 5] FIG. 2 is a perspective view showing a grounding structure of a fixing device according to an embodiment of the present invention. [Figure 6] FIG. 2 is an exploded perspective view showing a grounding structure of a fixing device according to an embodiment of the present invention. [Figure 7] FIG. 2 is a side view showing a grounding structure of a fixing device according to an embodiment of the present invention. [Figure 8] FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In the drawings, Fr, Rr, L, R, U, and D indicate front, rear, left, right, top, and bottom. The front-to-back direction, left-to-right direction (axial direction), and top-to-bottom direction are perpendicular to one another. 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. Furthermore, the terms "upstream," "downstream," and similar terms refer to "upstream" and "downstream" in the transport direction of paper P (medium) and similar concepts. In each drawing, the dimensions and angles of components are not accurate and are shown schematically for the purpose of explanation.

[0015] An image forming apparatus 1 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic diagram (side view) showing the image forming apparatus 1.

[0016] The image forming apparatus 1 is an electrophotographic printer. The image forming apparatus 1 has an apparatus main body 2 that has a substantially rectangular parallelepiped appearance. A paper feed cassette 3 that stores, for example, paper P (medium) is detachably 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. Note that the paper P, which is an example of a medium, is not limited to being made of paper, and may be a resin sheet or the like.

[0017] The image forming apparatus 1 includes a paper feeder 5, an imaging device 6, and a fixing device 7. The paper feeder 5 is provided at the upstream end of a transport path 9A that extends from the paper feed cassette 3 to the paper output tray 4, and sends out paper P stored in the paper feed cassette 3 one sheet at a time to the transport path 9A. The imaging device 6 is provided in the middle of the transport path 9A, and forms a toner image on the transported paper P. The fixing device 7 is provided downstream of the transport path 9A, and thermally fixes the toner image to the paper P.

[0018] The conveying path 9A is provided with a pair of registration rollers 10A that temporarily block the conveyed paper P to correct (skew correct) the inclination of the paper P. Below the conveying path 9A, a reversing conveying path 9B is provided that branches off on the downstream side of the conveying path 9A and merges with the upstream side of the conveying path 9A. The reversing conveying path 9B is provided with a plurality of pairs of conveying rollers 10B that convey the paper P.

[0019] The image forming device 6 includes a toner container 11, a drum unit 12, and an optical scanning device 13. The toner container 11 is located at the upper front of the device main body 2 and contains, for example, black toner (developer). The drum unit 12 includes a photosensitive drum 14, a charging device 15, a developing device 16, and a transfer roller 17. The photosensitive drum 14 is formed in a substantially cylindrical shape and is driven to rotate about 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 13 is located above the photosensitive drum 14 and emits scanning light toward the surface of the photosensitive drum 14.

[0020] The image forming apparatus 1 is provided with a control device 8 that controls the entire apparatus. The control device 8 includes a processor and the like that reads and executes programs stored in memory to perform various processes. Note that the control device 8 is not limited to a processor and may be configured by a logic circuit (hardware) formed in an integrated circuit or the like.

[0021] [Image formation processing] The following describes the operation of the image forming apparatus 1. The control device 8, which controls the image forming apparatus 1, executes the image forming process as follows based on image data input from an external terminal.

[0022] The charging device 15 charges the surface of the photosensitive drum 14, and the optical scanning device 13 emits scanning light based on image data to form an electrostatic latent image on the photosensitive drum 14. The developing device 16 develops a toner image on the photosensitive drum 14 using toner supplied from the toner container 11. The paper feeder 5 feeds paper P one sheet at a time from the paper feed cassette 3 to the transport path 9A. The paper P is transported along the transport path 9A, skew-corrected by a pair of registration rollers 10A, and enters the transfer nip. The transfer roller 17 transfers the toner image on the photosensitive drum 14 to the surface of the paper P as it passes through the transfer nip. The fixing device 7 thermally fixes the toner image to the paper P. In the case of single-sided printing, the paper P that has passed through the fixing device 7 is discharged to the paper output tray 4.

[0023] In the case of double-sided printing, the paper P that has passed through the fixing device 7 switches back at the downstream end of the conveying path 9A and is sent to the reverse conveying path 9B. The paper P is conveyed by the conveying roller pair 10B, returned from the reverse conveying path 9B to the conveying path 9A again, and after skew correction by the registration roller pair 10A, is sent to the transfer nip. Thereafter, the toner image is transferred onto the paper P and thermally fixed, and the double-sided printed paper P is discharged onto the paper output tray 4.

[0024] [Fusing device] Next, the fixing device 7 will be described with reference to Figures 2 to 4. Figure 2 is a perspective view showing the fixing device 7. Figure 3 is a perspective view showing the fixing belt 20 and the pressure roller 21. Figure 4 is a cross-sectional view taken along line IV-IV in Figure 3.

[0025] The fixing device 7 includes a fixing belt 20, a pressure roller 21, a heater 22, and a fixing frame 23.

[0026] <Fixing belt> As shown in Figures 2 to 4, the fixing belt 20, which is an example of a fixing member, is an endless belt formed in a generally cylindrical shape that is long in the left-right direction (axial direction). The fixing belt 20 is made of a heat-resistant and flexible material (polymer resin, metal, or a combination of polymer resin and metal). A pair of holding members 24 (see Figure 3) is inserted into both ends of the fixing belt 20 in the left-right direction (axial direction). The pair of holding members 24 guide the fixing belt 20 to rotate around its axis while maintaining its generally cylindrical shape.

[0027] As shown in FIG. 4, a support member 25 and a heater holder 26 are provided in the space surrounded by the fixing belt 20. The support member 25 is formed of a metal (conductor) such as stainless steel in a generally rectangular cylindrical shape that is elongated in the left-right direction (axial direction), and is installed between a pair of holding members 24. The heater holder 26 is fixed to the lower part of the support member 25. The heater holder 26 is formed of, for example, a heat-resistant and abrasion-resistant synthetic resin in a generally semi-cylindrical shape that is elongated in the left-right direction. The heater holder 26 curves along the inner surface of the fixing belt 20 and is in contact with the lower side of the inner surface of the fixing belt 20 (the side of the pressure region N). The heater 22 is fitted into the lower part of the heater holder 26.

[0028] <Pressure roller> As shown in FIGS. 3 and 4, the pressure roller 21, which is an example of a pressure member, is formed in a generally cylindrical shape elongated in the left-right direction. The pressure roller 21 has a core 21A made of a metal (conductor) such as stainless steel or aluminum alloy, and an elastic layer 21B made of an elastic material such as silicone sponge and laminated on the outer surface of the core 21A (see FIG. 4). A drive motor M is connected to the left end of the core 21A, which is an example of a rotating shaft, via a gear train G (see FIG. 2). The pressure roller 21 is pressed against the fixing belt 20 by pressing mechanisms 27 (see FIG. 2) provided on both sides in the left-right direction. The pressure roller 21 contacts the fixing belt 20 from below, forming a pressure region N between the pressure roller 21 and the fixing belt 20. A toner image is fixed on the paper P as the paper P passes through the pressure region N. The pressure region N refers to the region extending from an upstream position where the pressure is 0 Pa, through a position where the pressure is applied, to a downstream position where the pressure returns to 0 Pa.

[0029] <Heater> The heater 22 has a substrate made of an insulating material such as ceramic and multiple heating resistors formed on the underside of the substrate using a metal material with high electrical resistance. The multiple heating resistors are electrically connected to a power source (not shown) via electrodes formed on the substrate. The heater 22 (substrate) extends in the left-right direction (axial direction) of the fixing belt 20 and is fitted under the heater holder 26 with the heating resistors facing downward (see FIG. 4). The heater 22 receives the fixing belt 20 pressed against the pressure roller 21, thereby forming a pressure zone N at the contact point between the fixing belt 20 and the pressure roller 21. The heater 22 (heating resistor) contacts the inner surface of the fixing belt 20 facing the pressure zone N and heats the fixing belt 20. The heating resistors are covered with a coating layer (not shown) to reduce friction between the heater 22 and the fixing belt 20. The fixing device 7 also has a temperature detector (not shown) that detects the temperature of the heater 22.

[0030] <Fixing frame> The fixing frame 23 forms the framework of the fixing device 7 and is fixed to the device body 2. The fixing frame 23 is made of a metal (conductor) such as stainless steel or aluminum alloy. As shown in FIG. 2, the fixing frame 23 has a pair of standing plates 23A spaced apart in the left-right direction and arranged in an upright position, and multiple connecting bars 23B installed between the pair of standing plates 23A. Each standing plate 23A has a cutout portion 23C (see FIG. 5, described later) extending from top to bottom, and the cutout portions 23C of the pair of standing plates 23A support both ends of the fixing belt 20 and the pressure roller 21 in the left-right direction (axial direction). More specifically, a holding member 24, a rolling bearing member 30, and the like (described later) are attached to each cutout portion 23C. The fixing belt 20 is supported by the fixing frame 23 via a pair of holding members 24 so as to be rotatable around its axis, and the pressure roller 21 is supported by the fixing frame 23 via a pair of rolling bearing members 30, etc. so as to be rotatable around its axis.

[0031] [Function of the fixing device] Here, we will explain the operation (fixing process) of the fixing device 7. The drive motor M, heater 22, temperature detection unit, etc. are electrically connected to the control device 8, power supply, etc., and the control device 8 appropriately controls the power supply, heater 22, etc.

[0032] The control device 8 controls the drive motor M to rotate the pressure roller 21 around its axis. The fixing belt 20 rotates following the rotation of the pressure roller 21 (see the arrow in FIG. 4). The control device 8 also receives a detection signal from the temperature detector and controls the heater 22 (or power supply) to maintain a preset target temperature. The heater 22 generates heat when energized, and heats the fixing belt 20 (pressure region N).

[0033] When the fixing belt 20 (heater 22) reaches the target temperature, the control device 8 starts the image formation process already described. The paper P onto which the toner image has been transferred enters the pressure area N. The fixing belt 20 heats the toner (toner image) on the paper P as it passes through the pressure area N while rotating around its axis. The pressure roller 21 pressurizes the toner on the paper P as it passes through the pressure area N while rotating around its axis. The toner image is then fixed to the paper P, forming a fixed image on the paper P. The paper P with the fixed image is then discharged to the paper output tray 4.

[0034] The fixing device 7 is provided with a grounding member 60 that electrically grounds (FG: frame ground) the pressure roller 21 (metal core 21A) to remove static electricity from the pressure roller 21 and to prevent malfunctions of the control device 8 and other devices (electrical circuits) due to noise. If the grounding member 60 were in direct contact with the metal core 21A of the pressure roller 21, the pressure roller 21 would rotate around its axis, causing the metal core 21A and the grounding member 60 to rub against each other, resulting in wear and noise (friction noise). If the wear between the two components progresses, they may not be properly grounded, making it impossible to remove static electricity from the pressure roller 21 or prevent malfunctions. Therefore, the fixing device 7 according to this embodiment is provided with a grounding structure to prevent wear of the grounding member 60 and noise generation at the contact points of the grounding member 60.

[0035] [Grounding structure] The grounding structure of the fixing device 7 according to this embodiment will be described with reference to Figs. 5 to 8. Fig. 5 is a perspective view showing the grounding structure of the fixing device 7. Fig. 6 is an exploded perspective view showing the grounding structure of the fixing device 7. Fig. 7 is a side view showing the grounding structure of the fixing device 7. Fig. 8 is a cross-sectional view taken along the line VIII-VIII in Fig. 7.

[0036] 5 and 6, the grounding structure has a rolling bearing member 30, a bearing holder 40, an earth member 60, and an earth cover 70. The rolling bearing member 30 and the bearing holder 40 are provided as a pair to support both the left and right ends of the core metal 21A of the pressure roller 21, and the earth member 60 and the earth cover 70 are provided only on the right side of the pressure roller 21 (core metal 21A). For ease of explanation, the present specification will focus on the right side of the pressure roller 21 (core metal 21A) on which the earth member 60 and the like are provided.

[0037] <Rolling bearing components> The rolling bearing member 30 is a so-called ball bearing made of, for example, high-carbon chromium bearing steel. As shown in FIGS. 7 and 8, the rolling bearing member 30 has an inner ring 31, an outer ring 32, and a plurality of rolling elements 33 (balls). The inner ring 31 is formed in an annular shape into which the core 21A of the pressure roller 21 can be inserted and supports the core 21A so that it can rotate about its axis. The outer ring 32 is formed in an annular shape with a larger diameter than the inner ring 31, and is provided coaxially with the inner ring 31, with a plurality of rolling elements 33 sandwiched between the outer ring 32 and the outer peripheral surface of the inner ring 31. Each of the plurality of rolling elements 33 is a sphere and is provided between the inner ring 31 and the outer ring 32 while being held in a cage (not shown).

[0038] <Bearing holder> The bearing holder 40 is formed (integrally molded) from an insulating material such as synthetic resin, etc. As shown in FIG.

[0039] (Bearing fitting part) The bearing fitting portion 41 is formed in a generally cylindrical shape with an open left surface (axial inner surface), and the rolling bearing member 30 (outer ring 32) is fitted into the bearing fitting portion 41 with almost no looseness. A shaft opening 43 is formed on the right surface (axial outer surface) of the bearing fitting portion 41, exposing the end of the core metal 21A that passes through the inner ring 31 of the rolling bearing member 30. A pair of front and rear positioning bosses 44 protrude from the right surface of the bearing fitting portion 41, sandwiching the shaft opening 43. A pair of mounting arms 45 are formed integrally with the bearing fitting portion 41. The pair of mounting arms 45 extend outward from both front and rear surfaces of the bearing fitting portion 41. The mounting arms 45 have through holes 80 opened in the mounting arms 45 for passing mounting screws 81 through.

[0040] (Earth support part) The earth support portion 42 is provided below the bearing fitting portion 41 and is formed integrally with the bearing fitting portion 41. A guide tube portion 46 protrudes to the right (outward in the axial direction) near the boundary between the earth support portion 42 and the bearing fitting portion 41. The guide tube portion 46 is formed in a cylindrical shape with a dome-shaped cross section, with a rectangular upper portion being semicircular. A guide hole 47 penetrates the guide tube portion 46 so as to face the right end (outer edge in the axial direction) of the outer ring 32 of the rolling bearing member 30 fitted into the bearing fitting portion 41 (see also Figure 8).

[0041] A first pair of support pieces 50 and a second pair of support pieces 51 are arranged side by side in the front-rear direction on the underside of the earth support portion 42 and protrude to the right (outward in the axial direction). The first and second pairs of support pieces 50, 51 are arranged facing each other with a gap in the front-rear direction. A pair of horizontal ribs 52 protrude to the right (outward in the axial direction) on both sides of the earth support portion 42 in the front-rear direction and between the guide tube portion 46 and the first and second pairs of support pieces 50, 51. A vertical rib 53 protrudes to the right (outward in the axial direction) on the underside of the earth support portion 42 to separate the first pair of support pieces 50 and the second pair of support pieces 51. A grounding piece 54 having a grounding hole 55 is integrally formed with the earth support portion 42 (see FIG. 7). The grounding piece 54 extends downward from the underside of the earth support portion 42 (see FIG. 7).

[0042] <Earthing material> 6, the grounding member 60 has a first conductive member 61, a second conductive member 62, and a resistance member 63. The first conductive member 61 and the second conductive member 62 include portions formed to be expandable and contractible in the left-right direction (axial direction). Specifically, the first conductive member 61 and the second conductive member 62 include compression coil springs formed of a metal wire (conductor) such as stainless steel.

[0043] (First conductive member) The first conductive member 61 has a first contact spring 64, a first support spring 65, and a first connecting portion 66, which are integrally formed. The first contact spring 64 and the first support spring 65 are compression coil springs that extend substantially parallel to each other in the left-right direction (axial direction). The first support spring 65 is disposed in front of and below the first contact spring 64 (see also FIG. 7). The first connecting portion 66 is bent in a substantially L-shape when viewed from the axial direction, and connects the right end (outer end in the axial direction) of the first contact spring 64 and the right end of the first support spring 65 (see also FIG. 7).

[0044] (Second conductive member) The second conductive member 62 has a second contact spring 67, a second support spring 68, and a second connecting portion 69, which are integrally formed. The second contact spring 67 and the second support spring 68 are compression coil springs that extend substantially parallel to each other in the left-right direction (axial direction). The second support spring 68 is disposed above the second contact spring 67. The second connecting portion 69 is formed linearly and connects the right end (outer end in the axial direction) of the second contact spring 67 to the right end of the second support spring 68 (see also FIG. 7). The tip side (left side) of the second contact spring 67 is formed with a smaller diameter than the right side.

[0045] (resistance member) The resistance member 63 is a resistor that limits the current flowing through the circuit and is formed in a generally plate-like shape that is long in the front-to-rear direction. A pair of resistance connection wires 63A is provided on the resistance member 63. The pair of resistance connection wires 63A extend downward from both the front and rear sides of the lower surface of the resistance member 63.

[0046] <Earth cover> The earth cover 70 is formed (integrally molded) from an insulating material such as synthetic resin, etc. As shown in FIGS.

[0047] (Press cover part) The pressing cover part 71 is formed in a box shape with an open left side so that it can cover the earth support part 42 (including the guide tube part 46) of the bearing holder 40. Four spring bosses (not shown) protrude from the inner surface of the pressing cover part 71 at positions corresponding to the guide tube part 46, the first support piece pair 50, the second support piece pair 51, and the earth hole 55. A through hole 80 is opened at the lower front corner of the mounting cover part 72, for passing a mounting screw 81 therethrough.

[0048] (Mounting cover part) The mounting cover portion 72 is formed in a generally flat plate shape extending upward from the upper left end of the pressing cover portion 71. The mounting cover portion 72 has a cover opening 73 that is aligned with the shaft opening 43 of the bearing fitting portion 41. The mounting cover portion 72 also has a pair of front and rear positioning holes 74 on either side of the cover opening 73. The front positioning hole 74 is a generally circular hole, while the rear positioning hole 74 is an elongated hole that is long in the front-to-rear direction. A cover arm 75 that extends rearward is formed integrally with the mounting cover portion 72. The cover arm 75 has a through hole 80 through which a mounting screw 81 is passed.

[0049] [Formation of grounding structure] The bearing holder 40 is fixed to the fixing frame 23 while holding the rolling bearing member 30. Specifically, the rolling bearing member 30 is fitted into the bearing fitting portion 41 of the bearing holder 40, and the end of the core metal 21A of the pressure roller 21 is fitted into the inner ring 31 of the rolling bearing member 30 (see FIGS. 7 and 8). The bearing holder 40 (bearing fitting portion 41) holding the rolling bearing member 30 is inserted from above into the notch portion 23C of the upright plate 23A of the fixing frame 23 (see FIG. 5).

[0050] Next, the earth member 60 is attached to the bearing holder 40. Specifically, the resistance member 63 is fitted and fixed in an area surrounded by the guide tube portion 46 of the earth support portion 42, the pair of horizontal ribs 52, and the vertical rib 53 (see FIGS. 7 and 8). The pair of resistance connection wires 63A are arranged between the first and second support piece pairs 50, 51 (see FIG. 7). Next, the first contact spring 64 of the first conductive member 61 is inserted into the guide hole 47 of the earth support portion 42, and the first support spring 65 is inserted between the first support piece pair 50 of the earth support portion 42 (see FIGS. 7 and 8). As a result, the first conductive member 61 is supported by the guide tube portion 46 and the first support piece pair 50. Further, the second contact spring 67 of the second conductive member 62 is inserted into the ground hole 55 of the earth support portion 42 (earth piece 54), and the second support spring 68 is inserted between the second support piece pair 51 of the earth support portion 42 (see FIG. 7). As a result, the second conductive member 62 is supported by the earth piece 54 and the second support piece pair 51.

[0051] In the above state, the first contact spring 64 contacts the outer ring 32 of the rolling bearing member 30 through the guide hole 47 (see FIGS. 7 and 8). Specifically, the tip of the first contact spring 64 passing through the guide hole 47 contacts (is connected to) the right end (outer edge in the axial direction) of the outer ring 32 (see FIG. 8). The tip of the second contact spring 67 contacts (is connected to) the upright plate 23A of the fixing frame 23 through the grounding hole 55. Meanwhile, the tip of the first support spring 65 and the tip of the second support spring 68 contact a pair of resistance connection wires 63A of the resistance member 63 (see FIG. 7). In this way, the resistance member 63 is provided between the first conductive member 61 and the second conductive member 62 and is connected to the first conductive member 61 and the second conductive member 62. The grounding member 60 electrically grounds the pressure roller 21 via the rolling bearing member 30.

[0052] Next, the earth cover 70 is fixed to the bearing holder 40 so as to cover the earth member 60. Specifically, the earth cover 70 is positioned so as to sandwich the earth member 60 between the bearing holder 40 and the earth cover 70. At this time, the pair of positioning bosses 44 formed on the bearing holder 40 are inserted into the pair of positioning holes 74 formed on the earth cover 70 (see FIG. 5), and the four spring bosses formed on the earth cover 70 are inserted into the first contact spring 64, the first support spring 65, the second contact spring 67, and the second support spring 68 supported by the bearing holder 40. In this state, the earth cover 70 is properly positioned with respect to the bearing holder 40, the cover opening 73 approximately aligns with the shaft opening 43, and the cover arm 75 overlaps the rear mounting arm 45 so that the through-holes 80 approximately align with each other.

[0053] Finally, three mounting screws 81 pass through the through holes 80 in the pair of mounting arms 45 (cover arms 75) and the through holes 80 in the front lower corners of the earth cover 70, and are screwed into female threaded holes (not shown) formed in the upright plate 23A (see FIG. 5). The mounting screw 81 at the rear upper part fastens the mounting arm 45 and the cover arm 75 together.

[0054] The above completes the grounding structure (see FIG. 5). The bearing holder 40 is fixed to the fixation frame 23 while holding the rolling bearing member 30 and the grounding member 60. The outer ring 32 of the rolling bearing member 30 is fixed to the fixation frame 23 via the bearing holder 40 in an electrically insulated state. The grounding cover 70 is fixed to the bearing holder 40 while compressing the first conductive member 61 and the second conductive member 62. The first contact spring 64 is pressed against the outer edge of the outer ring 32 of the rolling bearing member 30, and the second contact spring 67 is pressed against the upright plate 23A of the fixation frame 23. The first support spring 65 and the second support spring 68 are pressed against a pair of resistance connection wires 63A of the resistance member 63. As a result, the pressure roller 21 is grounded (frame grounded) to the fixation frame 23 via the rolling bearing member 30 and the grounding member 60.

[0055] In the fixing device 7 according to the present embodiment described above, the grounding member 60 is in contact with the outer ring 32 of the rolling bearing member 30, and the pressure roller 21 is electrically grounded via the rolling bearing member 30. With this configuration, the grounding member 60 is in contact with the outer ring 32 of the rolling bearing member 30, which is held immovably by the fixing frame 23, so that wear of the grounding member 60 and generation of abnormal noise at the contact portion of the grounding member 60 can be suppressed.

[0056] Furthermore, according to the fixing device 7 of this embodiment, the bearing holder 40 made of an insulator is fixed to the fixing frame 23 while holding the rolling bearing member 30, so that the rolling bearing member 30 can be held in an electrically insulated state by the fixing frame 23. Furthermore, the earth member 60 is fixed to the bearing holder 40 so as to cover the earth member 60 that is in contact with the outer ring 32 through the guide hole 47, so that the earth member 60 can be held in contact with the outer ring 32.

[0057] Incidentally, the pressure roller 21 expands in the axial direction when heated by the fixing belt 20 heated by the heater 22, and contracts in the axial direction when cooled while the image formation process (fixing process) is stopped. Accordingly, the rolling bearing member 30 may also move slightly in the axial direction. To address this phenomenon, the fixing device 7 according to this embodiment includes an earth member 60 (first conductive member 61, second conductive member 62) that includes a portion formed to be expandable and contractible in the axial direction, thereby absorbing the slight axial positional deviation of the rolling bearing member 30 that accompanies the expansion and contraction of the pressure roller 21. This allows the earth member 60 to continue to contact the outer edge of the outer ring 32 in the axial direction, thereby maintaining the pressure roller 21 in an appropriately grounded state.

[0058] If the heater 22 were to go out of control, an overcurrent may flow to the pressure roller 21 (core metal 21A). If this overcurrent reaches the fixing frame 23 through the rolling bearing member 30 and the earth member 60, the electric circuits and the like included in the image forming apparatus 1 may be damaged. To address this problem, in the fixing device 7 according to this embodiment, the first conductive member 61 is connected to the pressure roller 21 via the rolling bearing member 30, and the second conductive member 62 is connected to the first conductive member 61 via the resistance member 63, and is also connected to the fixing frame 23. This configuration improves the electrical resistance value from the pressure roller 21 through the rolling bearing member 30 and the ground member 60 to the fixing frame 23. This prevents overcurrent from being transmitted to the fixing frame 23, and prevents damage to electrical circuits and the like included in the image forming apparatus 1.

[0059] In the fixing device 7 according to the present embodiment, the grounding member 60 grounds the pressure roller 21 via the rolling bearing member 30, but the present invention is not limited to this. For example, if the fixing member is formed in a roller shape similar to the pressure roller 21, the grounding member 60 may ground the fixing member via the rolling bearing member 30 (not shown). Furthermore, although the grounding structure (grounding member 60, etc.) is provided on the right side of the fixing device 7, it may also be provided on the left side of the fixing device 7 (not shown).

[0060] In addition, in the fixing device 7 according to the present embodiment, the rolling bearing member 30 is a ball bearing including the spherical rolling elements 33, but the present invention is not limited to this. For example, the rolling bearing member 30 may be a cylindrical , a roller bearing including needle-shaped or conical rolling elements 33.

[0061] Furthermore, in the fixing device 7 according to the present embodiment, the bearing holder 40 is fixed to the fixing frame 23 while holding the rolling bearing member 30 and the earth member 60, but the present invention is not limited to this. For example, a holder that holds the rolling bearing member 30 and a holder that holds the earth member 60 may be provided separately (not shown).

[0062] Furthermore, in the fixing device 7 according to this embodiment, both the first and second conductive members 61, 62 of the grounding member 60 include compression coil springs as portions formed to be expandable and contractible in the axial direction, but the present invention is not limited to this. For example, at least one of the first conductive member 61 and the second conductive member 62 may be formed as a leaf spring or the like (not shown). Also, for example, the first conductive member 61 or the second conductive member 62 may be formed to be expandable and contractible in the axial direction (not shown). Furthermore, both the first and second conductive members 61, 62 may be formed as, for example, rod-shaped terminals or the like that are not expandable and contractible in the axial direction (not shown).

[0063] Furthermore, in the fixing device 7 according to the present embodiment, the grounding member 60 (first conductive member 61) is in contact with the outer edge in the axial direction of the outer ring 32 of the rolling bearing member 30, but this is not limiting and, for example, the grounding member 60 (second conductive member 62) may be in contact with the outer peripheral surface of the outer ring 32 (not shown). Furthermore, the grounding member 60 (second conductive member 62) is in contact with the upright plate 23A, but this is not limiting and, for example, the grounding member 60 may be in contact with the connecting bar 23B (not shown).

[0064] Furthermore, in the fixing device 7 according to this embodiment, the grounding member 60 includes the resistance member 63, but the present invention is not limited to this. For example, if sufficient electrical insulation is provided between the heater 22 and the pressure roller 21 (cored metal 21A), the resistance member 63 may be omitted (not shown). Furthermore, when the resistance member 63 is omitted, for example, the second conductive member 62 may be omitted, and the first conductive member 61 may be configured to contact the outer ring 32 of the rolling bearing member 30 and the fixing frame 23 (not shown).

[0065] Furthermore, in the fixing device 7 according to this embodiment, the pressure roller 21 is driven to rotate and the fixing belt 20 is rotated accordingly, but this is not limited to this, and the fixing belt 20 may be driven to rotate and the pressure roller 21 may be rotated accordingly.

[0066] Furthermore, in the description of the above embodiment, the present invention has been applied to a monochrome image forming device 1 as an example, but this is not limiting and the present invention may also be applied to, for example, a color printer, a copier, a facsimile, or a multifunction device.

[0067] The above-described embodiment shows one aspect of the fixing 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 without departing from the spirit of the technical concept, and the claims include all embodiments that may fall within the scope of the technical concept. [Explanation of symbols]

[0068] 1. Image forming device 7 Fixing device 20 Fixing belt (fixing member) 21 Pressure roller (pressure member) 21A Core (rotating shaft) 23 Fixing Frame 30 Rolling bearing components 31 Inner circle 32 outer ring 33 Rolling elements 40 Bearing holder 47 Guide hole 60 Earthing member 61 First conductive member 62 second conductive member 63 Resistance Members 70 Earth Cover N pressure area P Paper (media)

Claims

1. a fixing member that heats the toner on the medium while rotating around an axis; a pressure member that forms a pressure region between itself and the fixing member and that pressurizes the toner on the medium passing through the pressure region while rotating around its axis; a fixing frame supporting both axial end portions of the fixing member and the pressure member; a rolling bearing member including an inner ring that supports a rotation shaft portion of either the fixing member or the pressure member so as to be rotatable about an axis, and an outer ring that sandwiches rolling elements between the inner ring and an outer peripheral surface of the inner ring and is fixed to the fixing frame in an electrically insulated state; a grounding member that contacts the outer ring and electrically grounds either the fixing member or the pressure member via the rolling bearing member.

2. a bearing holder formed of an insulator, fixed to the fixing frame while holding the rolling bearing member and the earthing member, and having a guide hole into which the earthing member is inserted to contact the outer ring; 2. The fixing device according to claim 1, further comprising: an earth cover formed of an insulating material and fixed to the bearing holder so as to cover the earth member that contacts the outer ring through the guide hole.

3. 3. The fixing device according to claim 1, wherein the grounding member includes a portion formed to be expandable and contractible in the axial direction, and contacts an outer edge of the outer ring in the axial direction.

4. The earth member is a first conductive member in contact with the outer ring; a second conductive member in contact with the fixing frame; 3. The fixing device according to claim 1, further comprising a resistance member provided between the first conductive member and the second conductive member and connected to the first conductive member and the second conductive member.

5. the first conductive member and the second conductive member include portions formed to be expandable and contractible in the axial direction, The fixing device according to claim 4 , wherein the first conductive member contacts an outer edge of the outer ring in the axial direction.

6. 3. An image forming apparatus comprising the fixing device according to claim 1.

Images