Fixing device and image forming apparatus

Abstract

To prevent a support member from closing inward during assembly of a holding member and the support member.SOLUTION: A fixing device 9 has a belt member 20, a heating member 22 that heats the belt member 20, a holding member 23 that holds the heating member 22, a support member 32 that supports an end of the belt member 20, and an opposing member 21 that is in contact with an outer peripheral surface of the belt member 20 to form a nip part N. When assembling the support member 32 and the holding member 23, the support member 32 is partially spread by the holding member 23.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] As shown in Figures 4-6 of Patent Document 1, a fixing device is known in which a heating device having flanges as support members at both ends in the longitudinal direction is fitted into a frame in the short direction of the heater and inserted in the thickness direction of the heater.

[0003] The flange is made of resin and has a roughly U-shape when viewed in the axial direction of the belt (Fig. 12(a)). Therefore, as shown in Fig. 12(b), the tip of the U-shape may close due to shrinkage, pressure, thermal deformation, etc. during flange molding.

[0004] As shown in Figure 13(a), in this type of fixing device, the heater is positioned on the heater holder, the heater holder is positioned on the stay, the stay is positioned on the flange, and the flange is positioned on the frame. Therefore, if the flange deforms, the heater position will shift from the target position (Figure 13(b)). If the heater position shifts, the heat from the heater will not be transferred effectively to the fixing belt, which may result in fixing failure. In addition, the heater may overheat partially, causing cracking due to thermal stress.

[0005] In addition to the flange tilting, the belt sliding section is deformed to close as shown in Figure 14, which causes the belt to flutter when driven, making the belt's running performance unstable and increasing the risk of the belt being damaged.

[0006] As shown in Fig. 15, in order to prevent the U-shaped portion of the flange from closing inward, it is known to provide a bridging portion that prevents the U-shaped portion from closing inward (Patent Document 2). In this case, the bridging portion provided on the flange makes the flange have a roughly square shape when viewed in the axial direction of the belt.

[0007] However, a flange having such a bridging portion has the following disadvantages. (1) The formation of the bridge portion limits the assembly direction of the parts. (2) The amount of resin used to make the flange increases, raising material costs and part costs. (3) The opening of the U-shaped part of the belt sliding part where the fixing belt slides is located, and the fixing belt and the heater that contacts the fixing belt are located in the opening. Therefore, even if the bridge part were located in another part of the flange, the belt sliding part would be slightly deformed and close inward. Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, an object of the present invention is to prevent the support member from closing inward when assembling the holding member and the support member, and to prevent the support member from being deformed by heat after assembly. [Means for solving the problem]

[0009] This problem is solved by a fixing device having a belt member, an opposing member that contacts the outer peripheral surface of the belt member to form a nip portion, a heating member that heats the belt member, a holding member that holds the heating member, and a support member that supports an end of the belt member, wherein when the support member and the holding member are assembled, the support member is partially spread by the holding member. [Effects of the Invention]

[0010] This prevents the support member from closing inward when assembling the holding member and the support member, and prevents the support member from being deformed by heat after assembly. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram illustrating the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2]FIG. 2 is a cross-sectional view of the fixing device according to the embodiment. [Figure 3] 3 is a schematic view of a portion of a flange according to an embodiment of the present invention. FIG. [Figure 4] 3 is a schematic view of a portion of a flange according to an embodiment of the present invention. FIG. [Figure 5] FIG. 10 is a schematic cross-sectional view showing a fixing device according to another embodiment. [Figure 6] FIG. 10 is a schematic view of a flange portion of a fixing device according to another embodiment. [Figure 7] FIG. 10 is a schematic view of a flange portion of a fixing device according to another embodiment. [Figure 8] FIG. 10 is a schematic view of a flange portion of a fixing device according to another embodiment. [Figure 9] FIG. 1 is a schematic diagram illustrating a conventional fixing device. [Figure 10] FIG. 10 is a schematic perspective view showing a conventional fixing device. [Figure 11] FIG. 1 is a schematic diagram showing a conventional sliding bearing. [Figure 12] FIG. 2 is a schematic view showing a flange viewed in the axial direction of the belt. [Figure 13] FIG. 2 is a schematic diagram illustrating a pressure roller, a heater, a heater holder, a stay, a flange, a frame, and the like of the fixing device. [Figure 14] 10 is a schematic diagram showing deformation of the belt sliding portion of the flange due to the presence of an opening. FIG. [Figure 15] 10 is a schematic diagram showing a bridging portion that prevents the U-shaped portion of the flange from closing inward. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described below with reference to the accompanying drawings. In each drawing for explaining the present invention, components such as members and components having the same function or shape are designated by the same reference numerals as far as they can be distinguished, and descriptions thereof will be omitted once they have been described.

[0013] 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus may be a printer, a copier, a facsimile, or a combination machine of these.

[0014] The image forming apparatus 100 shown in FIG. 1 includes four imaging units 1Y, 1M, 1C, and 1Bk that form an image. Each imaging unit 1Y, 1M, 1C, and 1Bk is detachably attached to the image forming apparatus main body and has the same configuration except that it contains a different color developer—yellow, magenta, cyan, or black—that corresponds to the color separation components of a color image. Specifically, each imaging unit 1Y, 1M, 1C, and 1Bk includes a drum-shaped photoconductor 2 as an image carrier, a charging device 3 that charges the surface of the photoconductor 2, a developing device 4 that supplies toner as a developer to the surface of the photoconductor 2 to form a toner image, and a cleaning device 5 that cleans the surface of the photoconductor 2.

[0015] The image forming apparatus 100 also includes an exposure device 6 that exposes the surface of each photosensitive element 2 to light to form an electrostatic latent image, a paper feed device 7 that supplies paper P as a recording medium, a transfer device 8 that transfers the toner image formed on each photosensitive element 2 to the paper P, a fixing device 9 that fixes the toner image transferred to the paper P, and a paper discharge device 10 that discharges the paper P outside the apparatus.

[0016] The transfer device 8 has an endless intermediate transfer belt 11 as an intermediate transfer body stretched by a plurality of rollers, four primary transfer rollers 12 as primary transfer members that transfer the toner images on the photosensitive members 2 onto the intermediate transfer belt 11, and a secondary transfer roller 13 as a secondary transfer member that transfers the toner images transferred onto the intermediate transfer belt 11 onto paper P. Each of the primary transfer rollers 12 contacts the photosensitive members 2 via the intermediate transfer belt 11. This brings the intermediate transfer belt 11 and each photosensitive member 2 into contact with each other, forming a primary transfer nip between them. Meanwhile, the secondary transfer roller 13 contacts one of the rollers that stretch the intermediate transfer belt 11 via the intermediate transfer belt 11. This causes the secondary transfer roller 13 to contact the photosensitive members 2. A secondary transfer nip is formed between the intermediate transfer belt 11 and the roller 11 .

[0017] Also, a paper transport path 14 is formed inside the image forming apparatus 100, along which paper P sent out from the paper feeder 7 is transported. A pair of timing rollers 15 is provided on the paper transport path 14 midway from the paper feeder 7 to the secondary transfer nip (secondary transfer roller 13).

[0018] Next, the printing operation of the image forming apparatus will be described with reference to FIG.

[0019] When a command to start a printing operation is issued, in each of the imaging units 1Y, 1M, 1C, and 1Bk, the photoconductor 2 is rotated clockwise in FIG. 1, and the surface of the photoconductor 2 is charged to a uniform high potential by the charging device 3. Next, the exposure device 6 exposes the surface of each photoconductor 2 based on the image information of the original document read by the original document reader or the print information instructed to be printed from a terminal, thereby reducing the potential of the exposed area and forming an electrostatic latent image. Then, toner is supplied from the developing device 4 to this electrostatic latent image, and a toner image is formed on each photoconductor 2.

[0020] When the toner images formed on each photoconductor 2 reach the primary transfer nip (position of primary transfer roller 12) as each photoconductor 2 rotates, they are transferred sequentially onto the intermediate transfer belt 11, which rotates counterclockwise in FIG. 1, so as to overlap one another. The toner images transferred onto the intermediate transfer belt 11 are then transported to the secondary transfer nip (position of secondary transfer roller 13) as the intermediate transfer belt 11 rotates, and are transferred to the transported paper P at the secondary transfer nip. This paper P is supplied from the paper feeder 7. The paper P supplied from the paper feeder 7 is temporarily stopped by timing roller 15, and then transported to the secondary transfer nip in time with the toner image on the intermediate transfer belt 11 reaching the secondary transfer nip. In this way, a full-color toner image is carried on the paper P. After the toner image is transferred, any toner remaining on each photoconductor 2 is removed by the cleaning devices 5.

[0021] The paper P onto which the toner image has been transferred is transported to a fixing device 9, which fixes the toner image onto the paper P. The paper P is then discharged outside the apparatus by a paper discharge device 10, completing the series of printing operations.

[0022] Next, the configuration of the fixing device 9 will be described.

[0023] 2, the fixing device 9 according to this embodiment includes a fixing belt 20, which is an endless belt member serving as a fixing member, a pressure roller 21 serving as an opposing member that contacts the outer peripheral surface of the fixing belt 20 to form a nip portion N, and a heating device 19 that heats the fixing belt 20. The heating device 19 also includes a planar heater 22 serving as a heating member, a heater holder 23 serving as a holding member that holds the heater 22, and a stay 24 serving as a reinforcing member that reinforces the heater holder 23 in the longitudinal direction.

[0024] The fixing belt 20 has a cylindrical substrate made of polyimide (PI) with an outer diameter of 25 mm and a thickness of 40 to 120 μm. A release layer made of a fluorine-based resin such as PFA or PTFE and having a thickness of 5 to 50 μm is formed on the outermost surface of the fixing belt 20 to enhance durability and ensure releasability. A 50 to 500 μm elastic layer made of rubber or the like may be provided between the substrate and the release layer. The substrate of the fixing belt 20 is not limited to polyimide, and may be a heat-resistant resin such as PEEK or a metal substrate such as nickel (Ni) or SUS. The inner peripheral surface of the fixing belt 20 may be coated with a sliding layer made of polyimide, PTFE, or the like.

[0025] The pressure roller 21 has an outer diameter of, for example, 25 mm and is composed of a solid iron core 21a, an elastic layer 21b formed on the surface of the core 21a, and a release layer 21c formed on the outside of the elastic layer 21b. The elastic layer 21b is made of silicone rubber and has a thickness of, for example, 3.5 mm. To improve the release properties of the surface of the elastic layer 21b, it is desirable to form the release layer 21c, which is a fluororesin layer having a thickness of, for example, about 40 μm.

[0026] The heater 22 is provided longitudinally across the width of the fixing belt 20 and is disposed so as to contact the inner circumferential surface of the fixing belt 20. The heater 22 may be in non-contact with the fixing belt 20 or indirect contact with the fixing belt 20 via a low-friction sheet or the like; however, direct contact of the heater 22 with the fixing belt 20 improves the efficiency of heat transfer to the fixing belt 20. The heater 22 may also be in contact with the outer circumferential surface of the fixing belt 20; however, since there is a risk of deterioration in fixing quality if the outer circumferential surface of the fixing belt 20 is damaged by contact with the heater 22, it is preferable that the heater 22 be in contact with the inner circumferential surface of the fixing belt 20. The heater 22 is composed of a base layer 50, a first insulating layer 51, a conductor layer 52 having a heat generating portion 60, a second insulating layer 53, and a third insulating layer 54, which are sequentially stacked on the nip portion N side of the base layer 50.

[0027] The heater holder 23 and the stay 24 are disposed on the inner circumferential side of the fixing belt 20. The stay 24 is made of a metal channel material, and both ends thereof are supported by both side walls of the fixing device 9. The stay 24 supports the surface of the heater holder 23 opposite to the heater 22 side, so that the heater 22 and the heater holder 23 are maintained without being significantly deflected by the pressure force of the pressure roller 21, and a nip N is formed between the fixing belt 20 and the pressure roller 21.

[0028] The heater holder 23 is desirably made of a heat-resistant material because it is prone to becoming hot due to the heat from the heater 22. For example, if the heater holder 23 is made of a heat-resistant resin with low thermal conductivity, such as LCP or PEEK, heat transfer from the heater 22 to the heater holder 23 is suppressed, and the fixing belt 20 can be heated efficiently.

[0029] The pressure roller 21 and the fixing belt 20 are pressed against each other by a spring that serves as a biasing member. This forms a nip N between the fixing belt 20 and the pressure roller 21. The pressure roller 21 also functions as a drive roller that is driven to rotate by a driving force transmitted from a driving unit provided in the image forming apparatus main body. Meanwhile, the fixing belt 20 is configured to rotate in response to the rotation of the pressure roller 21. During rotation, the fixing belt 20 slides against the heater 22. To improve the sliding properties of the fixing belt 20, a lubricant such as oil or grease may be interposed between the heater 22 and the fixing belt 20.

[0030] When the printing operation is started, pressure roller 21 is driven to rotate, and fixing belt 20 starts to rotate in response. Furthermore, power is supplied to heater 22, thereby heating fixing belt 20. Then, when the temperature of fixing belt 20 reaches a predetermined target temperature (fixing temperature), as shown in FIG. 2, paper P carrying an unfixed toner image is transported between fixing belt 20 and pressure roller 21 (nip portion N), whereby the unfixed toner image is heated and pressurized and fixed to paper P.

[0031] 3 and 4 are schematic diagrams of a portion of a flange according to an embodiment of the present invention. The fixing device according to this embodiment includes flanges 32 adjacent to both ends of the fixing belt 20 in the rotational axis direction. The rotational axis direction of the fixing belt 20 is the same as the longitudinal direction of at least one of the stay 24, the heater 22, and the heater holder 23. As shown in FIG. 3 , the flange 32 functions as a support member that supports one end of the stay 24, the heater 22, and the heater holder 23 in the rotational axis direction. The flanges 32 are fitted into both ends of the assembly of the heater holder 23 and the stay 24 to hold both ends of the stay 24, the heater 22, and the heater holder 23 in the rotational axis direction. The flanges 32 are inserted into loops at both ends of the fixing belt in the rotational axis direction and contact the inner circumferential surfaces on both sides to guide the rotation of the fixing belt 20. When the fixing belt 20 moves in the rotational axis direction, the end of the fixing belt 20 comes into contact with one of the flanges 32, preventing the fixing belt 20 from moving in the rotational axis direction. In other words, the flanges 32 function as belt holding members. The flanges 32 are inserted into openings provided in both side plates of the fixing device, slide along the edges of the openings, and are set in the both side plates.

[0032] The flange 32 does not have a bridging portion, and therefore has a substantially U-shape when viewed in the axial direction of the belt. In this embodiment, when the flange 32 is assembled to the heater holder 23, the U-shaped flange 32 is partially expanded by the heater holder 23. In other words, the shape of the flange 32 is determined by the heater holder 23. Therefore, the heater holder 23 acts as a stopper, and the flange 32 does not close inward when the heater holder 23 and the flange 32 are assembled, specifically, it is possible to prevent deformation of the flange 32 when pressure is applied or thermal deformation.

[0033] As shown in Fig. 3, the flange 32 has a belt sliding portion 32a on which the inner peripheral surface of the end of the fixing belt slides. Fig. 4(a) is a schematic side view of the flange 32 of Fig. 3 before assembly, as seen in the direction of the rotation axis. Fig. 4(b) is a schematic side view of the heater holder 23 of Fig. 3, as seen in the direction of the rotation axis. The belt sliding portion 32a of the flange 32 has an opening and a protrusion 32c at the end of the opening. The heater holder 23 has protrusions 23c at both ends in the short-side direction. As shown in FIG. 3, the end of the opening of the belt sliding portion 32a extends in the direction of the rotation axis, and the protrusion 32c is located on at least a portion of the end of the opening. The protrusion 23c of the heater holder 23 is arranged so that at least a portion of the protrusion 23c overlaps with at least a portion of the protrusion 32c after the flange 32 is assembled to the heater holder 23. The protrusion 23c is the longest portion of the heater holder 23 in the short-side direction and forms a portion having a length A. The protrusion 32c is the narrowest portion of the opening of the belt sliding portion 32a and forms a portion having a length B. The heater holder 23 and the flange 32 are designed so that the length A is longer than the length B. Therefore, when heater holder 23 is attached to flange 32, heater holder 23 elastically deforms belt sliding portion 32a of flange 32, slightly widening belt sliding portion 32a. As a result, heater holder 23 supports the edge of the opening of belt sliding portion 32a, preventing belt sliding portion 32a from deforming and closing due to pressure or heat.

[0034] Also, AB is 0.1 mm or less because if the AB value becomes too large, it becomes difficult to assemble the parts, and stress is applied to the parts during assembly, which can cause breakage.

[0035] Referring to FIG. 3, when assembling heater holder 23 and flange 32, the gap between the heater holder and flange (i.e., distance AB) changes depending on the insertion position of the components. Specifically, the widest part of heater holder 23 (the part that constitutes distance A) has a tapered shape, and the narrowest part of the opening of the belt holding portion of flange 32 (the part that constitutes distance B) also has a tapered shape to fit into this. Therefore, when flange 32 is inserted into heater holder 23 from the right side to the left side in the figure, the two are initially not fixed and are loosely engaged, but when inserted to the insertion end, flange 32 widens and they are tightly fixed to each other. In this way, the opening shape of belt sliding portion 32a of flange 32 is fixed.

[0036] In other words, in the fixing device according to this embodiment, protrusion 23c, which has length A and is the longest portion of heater holder 23 in the short direction, has a tapered shape that tapers toward the longitudinal direction of heater holder 23. Similarly, protrusion 32c, which has length B and is the narrowest portion of the opening of belt sliding portion 32a, also has a tapered shape that tapers toward the longitudinal direction of heater holder 23. As a result, as described above, when flange 32 is inserted into heater holder 23 from the right side to the left side in the figure, the two are initially loosely engaged and not fixed, but when inserted to the insertion end, flange 32 widens and they are tightly fixed to each other. In this way, the opening shape of belt sliding portion 32a of flange 32 is fixed.

[0037] FIG. 5 is a schematic cross-sectional view showing a fixing device according to another embodiment. In the fixing device according to this embodiment, protrusion 23c, which has length A and is the longest portion of heater holder 23 in the lateral direction, has a tapered shape that tapers in a direction perpendicular to the longitudinal and lateral directions of heater holder 23. Similarly, protrusion 32c, which has length B and is the narrowest portion of the opening of belt sliding portion 32a, also has a tapered shape that tapers in a direction perpendicular to the vertical and lateral directions of heater holder 23. Specifically, flange 32 has protrusion 32c that is inclined in a direction intersecting the longitudinal and lateral directions of heater holder 23, and heater holder 23 has protrusion 23c that engages with protrusion 32c and is inclined in a direction intersecting the longitudinal direction. When viewed in the axial direction of the belt, the height of protrusion 32c of flange 32 gradually increases toward stay 24 that supports heater holder 23, while the height of protrusion 23c of heater holder 23 gradually decreases toward stay 24 that supports heater holder 23. According to this embodiment, unlike the embodiment of FIG. 3, the heater holder 23 can be assembled by inserting it into the opening of the flange 32 from right to left in the figure, that is, in a direction intersecting the longitudinal direction of the heater holder 23.

[0038] 3 and 5, protrusion 23c, which determines distance A at the widest point of heater holder 23, and protrusion 32c, which determines distance B at the narrowest point of the opening of flange 32, have a tapered shape, which makes it easy to assemble heater holder 23 and flange 32.

[0039] FIG. 6 is a schematic view of a flange portion of a fixing device according to another embodiment. The frame 35 fits into the flange 32 axially outward of the belt sliding portion 32a of the flange 32. In the area where the belt sliding portion 32a of the flange 32 and the heater holder 23 overlap, the widest part of the heater holder 23 and the narrowest part of the opening of the flange 32 axially extend not only to the belt sliding portion 32a of the flange 32 but also to the position where the frame 35 fits into the flange 32 (the range indicated by X in the figure). As explained in relation to FIG. 13 , if the flange is pressed against the pressure roller in a deformed state, the entire device, including the stay, heater holder, and heater, will tilt. To prevent this, it is desirable that the widest part of the heater holder 23 and the narrowest part of the opening of the flange 32 extend to the position of the frame 35.

[0040] FIG. 7 is a schematic view of a flange portion of a fixing device according to another embodiment. At the connection point between the frame 35 and the flange 32, a bridging portion 32b is provided on the flange 32. The widest point of the heater holder 23 and the narrowest part of the opening of the flange 32 are located in range Y in FIG. 7 along the belt sliding portion 32a. The structure of this embodiment is such that the widest part of the heater holder 23 and the narrowest part of the opening of the flange 32 are provided from the belt sliding portion 32a to the connection point between the frame 35 and the flange 32, thereby improving the ease of assembly of the heater holder 23 and the flange 32.

[0041] FIG. 8 is a schematic view of a flange portion of a fixing device according to another embodiment. According to this embodiment, in the direction of the rotation axis of the fixing belt 20, a gap G1 between the short-side end of the heater holder 23 and the short-side end of the heater 22 at the position where the belt sliding portion 32a is present is larger than a gap G2 at other positions, i.e., at positions where the belt sliding portion 32a is not present. Since the heater holder 23 and the flange 32 are assembled so that the flange 32 expands, the heater holder 23 may be slightly deformed as a result. To prevent deformation of the heater holder 23 from affecting the heater 22, a gap larger than the aforementioned gap G2 is formed at the widest point of the heater holder 23 that engages with the narrowest part of the opening of the flange 32.

[0042] 9 to 11 are schematic diagrams showing conventional fixing devices. In the fixing device 9, a ball bearing 28 is used as a bearing for the pressure roller 21. As shown in Figures 9 and 10, when ball bearing 28 and a conventional bridging portion 32b are used, bridging portion 32b and ball bearing 28 may come into contact with each other depending on the size of ball bearing 28. In this case, from the viewpoint of component layout as well, it is preferable to provide belt sliding portion 32a where the widest portion of heater holder 23 and the narrowest portion of the opening of flange 32 are located.

[0043] As shown in Figure 11, conventionally, when a ball bearing is not used, a U-shaped plain bearing 29 is used, and bridging portion 32b is located at the opening of plain bearing 29, so plain bearing 29 and bridging portion 32b do not come into contact. However, when plain bearing 29 is changed to ball bearing 28, there is a possibility that bridging portion 32b will come into contact with ball bearing 28, as described above. However, according to the embodiment in Figure 3, for example, bridging portion 32b is not formed, so ball bearing 28 can be used as a bearing for pressure roller 21.

[0044] As described above, according to the present invention, the dimension of the overlapping portion of the heater holder 23 and flange 32 is reduced, and the flange 32 has a portion that is narrower than the heater holder 23. In other words, there is a portion where "distance A at the widest point of the heater holder 23" is greater than "distance B at the narrowest point of the opening of the belt holding portion of the flange 32." This prevents the heater holder 23 from closing the flange 32 inward.

[0045] For example, aspects of the present invention are as follows. (Aspect 1) A belt member; a heating member that heats the belt member; a holding member for holding the heating member; a support member for supporting an end of the belt member; an opposing member that contacts the outer peripheral surface of the belt member to form a nip portion, The fixing device, wherein when the support member and the holding member are assembled, the support member is partially expanded by the holding member. (Aspect 2) The fixing device described in aspect 1 is characterized in that, in an unloaded state before assembly, in the portion where the belt sliding portion of the support member and the holding member overlap as viewed in the axial direction of the belt member, the distance A of the widest point of the holding member is greater than the distance B of the narrowest part of the opening of the belt holding portion of the support member. (Aspect 3) 3. The fixing device according to claim 2, wherein AB is 0.1 mm or less. (Aspect 4) A fixing device according to any one of aspects 1 to 3, characterized in that when the holding member and the support member are assembled, the gap between the widest point of the holding member and the narrowest part of the opening of the belt holding portion of the support member changes depending on the insertion position of the members. (Aspect 5) A fixing device according to aspect 4, wherein the distance between the widest point of the holding member and the narrowest point of the opening of the belt holding portion of the support member varies along the longitudinal direction of the holding member. (Aspect 6) 5. The fixing device according to claim 4, wherein the distance between the widest point of the holding member and the narrowest point of the opening of the belt holding portion of the support member varies along the vertical direction of the holding member. (Aspect 7) The fixing device according to any one of aspects 2 to 6, wherein the protrusion that determines the distance A at the widest point of the holding member and the protrusion that determines the distance B at the narrowest point of the opening of the support member have a tapered shape. (Aspect 8) A fixing device according to any one of aspects 1 to 7, characterized in that, at the portion where the belt sliding portion of the support member and the holding member overlap, the widest point of the holding member and the narrowest portion of the opening of the support member extend axially not only from the belt sliding portion of the support member but also to the connection point between the frame and the support member. (Aspect 9) Aspect 9. The fixing device according to aspect 8, wherein a bridging portion is provided on the support member at the connection portion between the frame and the support member. (Aspect 10) The fixing device according to any one of aspects 1 to 9, wherein, in the axial direction of the fixing device, a gap between the holding member and the heating member at a position where a belt sliding portion exists is larger than a gap between the holding member and the heating member at a position where the belt sliding portion does not exist. (Aspect 11) 11. The fixing device according to any one of aspects 1 to 10, wherein the bearing of the opposing member is a ball bearing. (Aspect 12) An image forming apparatus having the fixing device according to any one of aspects 1 to 11. [Explanation of symbols]

[0046] 9 Fixing device 20 Fixing belt (belt member) 21 Pressure roller (opposing member) 22 heater (heating element) 23 Heater holder (holding member) 23c Protrusion 32 Flange (support member) 32a Belt sliding part 32b Bridging section 32c protrusion 35 frames A. Distance B distance N Nip section [Prior art documents] [Patent documents]

[0047] [Patent Document 1] Japanese Patent Publication No. 2020-052347 [Patent Document 2] Patent No. 5924915

Claims

1. A belt member; a heating member that heats the belt member; a holding member for holding the heating member; a support member for supporting an end of the belt member; an opposing member that contacts the outer peripheral surface of the belt member to form a nip portion, The fixing device, wherein when the support member and the holding member are assembled, the support member is partially expanded by the holding member.

2. 2. The fixing device according to claim 1, wherein, in an unloaded state before assembly, in the portion where the belt sliding portion of the support member and the holding member overlap as viewed in the axial direction of the belt member, a distance A at the widest point of the holding member is greater than a distance B at the narrowest point of the opening of the belt holding portion of the support member.

3. 3. The fixing device according to claim 2, wherein A-B is 0.1 mm or less.

4. 2. The fixing device according to claim 1, wherein when the holding member and the support member are assembled, the gap between the widest point of the holding member and the narrowest part of the opening of the belt holding portion of the support member changes depending on the insertion position of the members.

5. 5. The fixing device according to claim 4, wherein the distance between the widest point of the holding member and the narrowest point of the opening of the belt holding portion of the support member varies along the longitudinal direction of the holding member.

6. 5. The fixing device according to claim 4, wherein the distance between the widest point of the holding member and the narrowest point of the opening of the belt holding portion of the support member varies along the vertical direction of the holding member.

7. 3. The fixing device according to claim 2, wherein the protrusion that determines the distance A at the widest point of the holding member and the protrusion that determines the distance B at the narrowest point of the opening of the support member have a tapered shape.

8. The fixing device according to claim 1, characterized in that, at the portion where the belt sliding portion of the support member and the holding member overlap, the widest point of the holding member and the narrowest portion of the opening of the support member extend axially not only to the belt sliding portion of the support member but also to the connection point between the frame and the support member.

9. 9. The fixing device according to claim 8, wherein a bridge portion is provided on the support member at the connection portion between the frame and the support member.

10. 2. The fixing device according to claim 1, wherein, in the axial direction of the fixing device, a gap between the holding member and the heating member at a position where the belt sliding portion exists is larger than a gap between the holding member and the heating member at a position where the belt sliding portion does not exist.

11. 2. The fixing device according to claim 1, wherein the bearing of the opposing member is a ball bearing.

12. An image forming apparatus comprising the fixing device according to any one of claims 1 to 11.

Images