Fixing device and image forming apparatus equipped with said fixing device

Abstract

To provide a fixing device including a fixing rotor heated by a heating unit, a pressure rotor pressed against the fixing rotor, a first bearing for rotatably supporting the shank of the fixing rotor, a second bearing for rotatably supporting the shank of the pressure rotor, and an annular heat insulating member interposed between the first bearing and the shank of the fixing rotor and / or between the second bearing and the shank of the pressure rotor, in which the occurrence of an abnormal sound due to friction between end faces of the heat insulating member facing each other across a slit.SOLUTION: A heat insulating member 40 includes a slit 40c in at least one circumferential point that divides the heat insulating member 40 in the circumferential direction. On one end face 40d, out of circumferential end faces 40d, 40e of the slit 40c, is formed a protrusion 40f that protrudes toward the other end face 40e.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a fixing device and an image forming apparatus equipped with the fixing device. [Background technology]

[0002] Conventionally, there has been known a fixing device that includes a fixing roller heated by a heating unit and a pressure roller pressed against the fixing roller, and fixes a toner image onto a sheet by passing the sheet through a nip formed between the two rollers. In this fixing device, an annular heat insulating member may be disposed between the shaft of the fixing roller and a bearing that supports the shaft (see, for example, Patent Document 1).

[0003] In this heat insulating member, a slit is formed at one location in the circumferential direction of the heat insulating member in order to prevent rattling of the fixing roller caused by thermal expansion and contraction. The heat insulating member is divided in the circumferential direction at the slit.

[0004] In addition, in Patent Document 1, a heat insulating member is provided between the shaft portion and the bearing of the fixing roller, but a heat insulating member may also be provided between the shaft portion and the bearing of the pressure roller. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2001-56020 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the conventional fixing device shown in Patent Document 1, there is a problem in that the two opposing end faces of the heat insulating member sandwiching the slit therebetween rub against each other when the fixing roller rotates, generating abnormal noise. In particular, when the temperature of the fixing roller is relatively low, that is, when the amount of thermal expansion of the fixing roller is relatively small, the gap between the slits in the heat insulating member is narrow, so that the two end faces of the slits are likely to rub against each other, and the above-mentioned problem becomes particularly noticeable.

[0007] The present invention has been made in consideration of the above points, and its purpose is to prevent the generation of abnormal noise caused by the friction between both end faces of an insulating member that face each other across a slit. [Means for solving the problem]

[0008] The fixing device of the present invention is a fixing device comprising a fixing rotor heated by a heating section, a pressure applying rotor pressed against the fixing rotor, a first bearing rotatably supporting the shaft portion of the fixing rotor, a second bearing rotatably supporting the shaft portion of the pressure applying rotor, and an annular insulating member interposed at least between the first bearing and the shaft portion of the fixing rotor and at least one between the second bearing and the shaft portion of the pressure applying rotor, wherein the insulating member has a slit at least at one location in the circumferential direction that divides the insulating member in the circumferential direction, and one of the circumferentially opposing end faces of the slit has a protrusion formed on it that protrudes toward the other end face. Effect of the Invention

[0009] According to the present invention, it is possible to prevent the generation of abnormal noise caused by friction between both end faces of a heat insulating member that face each other across a slit. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of an image forming apparatus according to the present embodiment. [Diagram 2] FIG. 2 is a perspective view showing the fixing roller and a sheet metal frame that supports the fixing roller. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a perspective view showing a state in which a heat insulating member is attached to one end of the fixing roller. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiment.

[0012] First Embodiment <Image forming device> FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus 1 according to the present embodiment.

[0013] 1, the image forming apparatus 1 includes a box-shaped image forming apparatus main body 2, a cassette paper feed section 4, an image forming section 5, a fixing device 6, and a paper discharge section 10. The image forming apparatus 1 is configured to form a toner image on a paper based on image data transmitted from a terminal (not shown) or the like while transporting the paper along a transport path within the image forming apparatus main body 2.

[0014] The cassette paper feed unit 4 is provided at the bottom of the image forming apparatus main body 2. The cassette paper feed unit 4 includes a paper feed cassette 11 that stores a plurality of sheets of paper stacked on top of each other, and a pick roller 12 that picks up the sheets of paper in the paper feed cassette 11 one by one.

[0015] The image forming unit 5 is provided above the cassette paper supply unit 4 in the image forming apparatus main body 2. The image forming unit 5 includes a photosensitive drum 16 which is an image carrier rotatably provided in the image forming apparatus main body 2, a charging roller 17 arranged around the photosensitive drum 16, a developing unit 18, a transfer roller 19, a cleaning unit 20, and an optical scanning device 30 arranged on the side of the photosensitive drum 16. Thus, the image forming unit 5 forms an image on the paper supplied from the cassette paper supply unit 4.

[0016] The conveying path is provided with a pair of registration rollers 15 that temporarily hold the paper fed from the paper feed cassette 11 and then supply it to the image forming unit 5 at a predetermined timing.

[0017] The fixing device 6 is disposed above the image forming section 5. The fixing device 6 includes a fixing roller 22 and a pressure roller 23 which rotate while being pressed against each other. The fixing device 6 is configured to fix the toner image transferred to the paper by the image forming section 5 to the paper. The fixing roller 22 is an example of a fixing rotator, and the pressure roller 23 is an example of a pressure rotator.

[0018] The paper discharge section 10 is provided diagonally above the fixing device 6. The paper discharge section 10 includes a paper discharge tray 3, a paper discharge roller 24 for transporting the paper to the paper discharge tray 3, and a transport guide rib 25 for guiding the paper to the paper discharge roller 24. The paper discharge tray 3 is formed in a concave shape on the upper part of the image forming apparatus main body 2.

[0019] When the image forming apparatus 1 receives image data, in the image forming unit 5, the photosensitive drum 16 is rotationally driven, and the charging roller 17 charges the surface of the photosensitive drum 16.

[0020] Then, based on the image data, a laser beam is emitted from the optical scanning device 30 to the photosensitive drum 16. An electrostatic latent image is formed on the surface of the photosensitive drum 16 by irradiating the surface with the laser beam. Meanwhile, toner is supplied from a toner container 21 to the developing unit 18. The electrostatic latent image formed on the photosensitive drum 16 is developed by the developing unit 18 into a visible toner image.

[0021] Thereafter, the paper passes between the transfer roller 19 and the photosensitive drum 16. At that time, the toner image on the photosensitive drum 16 is transferred to the paper by the transfer bias transferred to the transfer roller 19. The paper onto which the toner image has been transferred is heated and pressed by the fixing roller 22 and pressure roller 23 in the fixing device 6. As a result, the toner image is fixed to the paper.

[0022] <Fixing device> The fixing device 6 includes a fixing roller 22, a pressure roller 23, and a housing . The housing 26 has a generally rectangular parallelepiped shape that is long in the front-rear direction, and the fixing roller 22 and the pressure roller 23 are housed within the housing 26 in a state in which they extend in the front-rear direction.

[0023] As shown in Fig. 2, fixing roller 22 is rotatably supported by a pair of sheet metal frames 27 provided in housing 26 via bearings 28 (an example of a first bearing). Although pressure roller 23 (shown only in Fig. 1) is omitted in Fig. 2, pressure roller 23 is actually disposed diagonally above and to the right of fixing roller 22.

[0024] As shown in Fig. 3, the fixing roller 22 has a cylindrical core 22c, a release layer (not shown) provided on the outer circumferential surface of the core 22c via an adhesive layer, and a shaft portion 22a protruding from both axial end surfaces of the cylindrical core 22c. A halogen heater 29 (an example of a heating unit) is accommodated inside the fixing roller 22. The halogen heater 29 radiates radiant heat to the inner circumferential surface of the fixing roller 22 to heat the fixing roller 22. The shaft portion 22a of the fixing roller 22 is rotatably supported by a bearing 28 attached to a sheet metal frame 27. In this example, the bearing 28 is a rolling bearing, and is fixed by being pressed into a mounting hole 27a formed in the sheet metal frame 27.

[0025] A heat insulating member 40 is interposed between the shaft portion 22a of the fixing roller 22 and the bearing 28. The fixing roller 22 is driven by a motor (not shown) to rotate in a counterclockwise direction in Figs. 1 and 2. The pressure roller 23 has a rotating shaft 23a, an elastic layer provided on the outer peripheral surface of the rotating shaft 23a, and a release layer provided on the outer peripheral surface of the elastic layer via an adhesive layer. The pressure roller 23 is supported by a bearing (not shown) and is pressed against the fixing roller 22 by a biasing mechanism. Thus, a nip portion through which paper passes is formed between the pressure roller 23 and the fixing roller 22.

[0026] [Insulation material composition] 4, the heat insulating member 40 is made of, for example, PPS (polyphenylene sulfide) or PEEK (polyether ether ketone). The heat insulating member 40 has a cylindrical main body tube portion 40a fitted onto the shaft portion 22a of the fixing roller 22, and a flange portion 40b protruding radially outward from one end of the main body tube portion 40a in the axial direction.

[0027] 3, flange portion 40b of heat insulating member 40 abuts against the end face of bearing 28, thereby restricting inward movement in the axial direction of fixing roller 22. A ring groove 22b in which a C-ring 13 is fitted is formed in shaft portion 22a of fixing roller 22, and C-ring 13 restricts outward movement of heat insulating member 40 in the axial direction.

[0028] A slit 40c extending in the axial direction of the cylinder is formed in the main body cylinder portion 40a of the heat insulating member 40. The heat insulating member 40 is divided at the slit 40c. A protrusion 40f is formed on one end face 40d (in this example, the end face 40d on the downstream side in the rotation direction of the fixing roller 22) of both end faces 40d, 40e facing each other in the slit 40c.

[0029] The protrusion 40f protrudes from one end face 40d toward the other end face 40e. In this example, the protrusion 40f is semicircular when viewed from the radial direction of the fixing roller 22. The protrusion 40f is formed in the center of the roller axial direction (axial direction of the fixing roller 22) on one end face 40d. The top surface of the protrusion side of the protrusion 40f abuts against the other end face 40e of the slit 40c in a room temperature state before the halogen heater 29 is activated.

[0030] [Effects] As described above, in this embodiment, the insulating member 40 has a slit 40c at least at one location in the circumferential direction that divides the insulating member 40 in the circumferential direction, and one of the end faces 40d, 40e that face each other in the circumferential direction in the slit 40c has a protrusion 40f formed on one of the end faces 40d, 40e that protrude toward the other end face 40e.

[0031] According to this configuration, by forming the slit 40c, it is possible to suppress rattling of the shaft portion 22a of the fixing roller 22 caused by thermal expansion and thermal contraction. In addition, since the protrusion 40f is formed on one end face 40d of the slit 40c, it is possible to minimize the area where both end faces 40d, 40e facing each other across the slit 40c rub against each other while the fixing roller 22 is rotating, and to suppress the generation of abnormal noise caused by the rubbing of both end faces 40d, 40e.

[0032] In this embodiment, the protrusion 40f is formed so as to come into line contact with the other end surface 40d of the slit 40c.

[0033] According to this configuration, the contact area between the protrusion 40f and the other end surface 40e of the slit 40c can be reduced as much as possible, and the generation of the abnormal noise can be suppressed more reliably.

[0034] Specifically, the protrusion 40f is formed into a cylindrical surface so as to be in line contact with the other end surface 40e of the slit 40c.

[0035] This configuration makes it possible to prevent the projection 40f from hitting the edge of the other end surface 40e of the slit 40c, thereby suppressing the generation of abnormal noise.

[0036] The protrusion 40f is formed at the center of the fixing roller 22 in the axial direction on one end surface 40d of the slit 40c.

[0037] According to this configuration, by disposing the protrusion 40f at the center of the slit 40c in the roller axial direction, the shape of the slit 40c can be always maintained as a rectangle extending in the roller axial direction. Therefore, for example, it is possible to prevent edge contact between one end face 40d and the other end face 40e caused by the slit 40c deforming into a V-shape.

[0038] Moreover, the image forming apparatus 1 of this embodiment includes the fixing device 6.

[0039] This makes it possible to prevent the generation of abnormal noise caused by friction between both end faces 40d, 40e of the slit 40c in the heat insulating member 40 after the image forming apparatus 1 is operated, particularly before the temperature of the fixing roller 22 is sufficiently increased. This makes it possible to prevent the user from mistaking the abnormal noise caused by friction of the heat insulating member 40 for a malfunction.

[0040] Other Embodiments In the above embodiment, the heat insulating member 40 is provided between the fixing roller 22 and its bearing 28, but the present invention is not limited to this. It is sufficient that the heat insulating member 40 is provided at least one of between the fixing roller 22 and its bearing 28 and between the pressure roller 23 and its bearing (corresponding to the second bearing). Also, in the above embodiment, there is one slit 40c, but there may be multiple slits. In this case, the heat insulating member 40 is divided into multiple pieces, and the present invention can be applied to such a configuration.

[0041] In the above embodiment, the protrusion 40f formed on one end face 40d of the slit 40c in the heat insulating member 40 is formed so as to be in line contact with the other end face 40e, but this is not limited thereto. The protrusion 40f may be formed so as to be in point contact with the other end face 40e. In this case, it is preferable that the tip face of the protrusion 40f is formed in a spherical shape. This makes it possible to reduce the contact area between the protrusion 40f and the other end face 40e as much as possible, thereby reducing abnormal noise.

[0042] In the above embodiment, the end face (one end face 40d) of the slit 40c on which the protrusion 40f is formed is located downstream in the rotation direction of the fixing roller 22 relative to the other end face 40e, but this is not limited to this and may be located upstream in the rotation direction of the fixing roller 22. [Industrial Applicability]

[0043] As described above, the present invention is useful for a fixing device and an image forming apparatus including the fixing device, and is particularly useful when applied to an image forming apparatus such as a printer, a facsimile, or a multifunction peripheral (MFP). [Explanation of symbols]

[0044] 1. Image forming device 6 Fixing device 22 Fixing roller (fixing rotor) 23 Pressure roller (pressure rotating body) 22a Shaft 28 Bearings 40 Insulation materials 40c slit 40d End face (one end face) 40e End face (other end face) 40f protrusion 50 Insulation materials

Claims

1. A fixing device including a fixing rotor heated by a heating section, a pressure rotor pressed against the fixing rotor, a first bearing rotatably supporting a shaft portion of the fixing rotor, a second bearing rotatably supporting a shaft portion of the pressure rotor, and an annular heat insulating member interposed at least one between the first bearing and the shaft portion of the fixing rotor and between the second bearing and the shaft portion of the pressure rotor, The heat insulating member has a slit at least at one location in a circumferential direction to divide the heat insulating member in a circumferential direction, a protrusion is formed in a center portion in an axial direction of the fixing rotor of one of both end faces of the slit that are opposed to each other in a circumferential direction, the protrusion protruding toward the other end face, the other end surface of the slit contacts the protrusion and does not contact the one end surface of the slit excluding the protrusion.

2. 2. The fixing device according to claim 1, The protrusion is formed so as to be in line contact with the other end surface of the slit.

3. 3. The fixing device according to claim 2, The protrusion has a tip surface formed in a cylindrical shape so as to be in line contact with the other end surface of the slit.

4. 2. The fixing device according to claim 1, The protrusion is formed so as to make point contact with the other end surface of the slit.

5. 5. The fixing device according to claim 4, The protrusion has a tip surface formed in a spherical shape so as to make point contact with the other end surface of the slit.

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

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