Fixing apparatus and image forming apparatus

Abstract

This reduces damage to the ends of the anchoring belt, thereby increasing its durability. [Solution] The fixing device comprises an endless fixing belt, a heating unit for heating the fixing belt, a pressing rotating body for pressing the recording medium against the outer circumferential surface of the fixing belt, and a contact member disposed inside the fixing belt and in contact with the inner circumferential surface of the fixing belt. The contact member is disposed inside the fixing belt and in contact with the inner circumferential surface of the fixing belt, the length dimension of the contact portion of the contact member is set to be larger than the width dimension of the fixing belt, and the contact portion of the contact member has inclined surfaces on both ends that are inclined with respect to the width direction such that the contact pressure between the contact member and the inner circumferential surface of the fixing belt gradually decreases as it moves toward both ends of the fixing belt.

Description

Technical Field

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

Background Art

[0002] In general, in electrophotographic image forming apparatuses, a heat-fixing type fixing device that fixes a toner image (image) onto a recording medium such as paper by applying heat and pressure is widely used (see Patent Document 1 and the like). The fixing device of Patent Document 1 will be briefly described as follows.

[0003] The fixing device of Patent Document 1 includes an endless fixing belt capable of circulating, and a heating unit (referred to as a heat source in Patent Document 1) that heats the fixing belt. The fixing device of Patent Document 1 is provided with a pressure rotating body (referred to as a pressure member in Patent Document 1) that presses the recording medium against the outer peripheral surface side of the fixing belt, and the pressure rotating body is rotatably disposed at a position facing the outer peripheral surface of the fixing belt.

[0004] The fixing device of Patent Document 1 includes a heat equalizing member as a contact member that comes into contact with the inner peripheral surface of the fixing belt, and the heat equalizing member is disposed inside the fixing belt. In order to reduce the load on the inner peripheral surface of the fixing belt, the width of the contact portion of the heat equalizing member gradually decreases toward both end sides of the heat equalizing member.

Prior Art Literature

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0006] Incidentally, when the central part of a contact member such as a heat-distributing member flexes due to the tension of the stretched anchoring belt and / or the pressure applied by the pressurizing rotating body, the contact pressure between the contact member and the inner surface of the anchoring belt becomes locally higher at both ends of the anchoring belt. This accelerates wear at the ends of the inner surface of the anchoring belt, causing the ends of the anchoring belt to become thinner and reducing their strength. As a result, cracks and other damage are more likely to occur at the ends of the anchoring belt, making it difficult to improve the durability of the anchoring belt.

[0007] Furthermore, even when the width of the contact portion of a contact member, such as a heat-distributing member, is gradually reduced toward both ends of the contact member, as in the fixing device described in Patent Document 1, wear on the end side of the inner circumferential surface of the fixing belt cannot be sufficiently suppressed.

[0008] Therefore, the present invention aims to provide a fixing device and an image forming apparatus that can suppress damage to the end side of the fixing belt and improve the durability of the fixing belt. [Means for solving the problem]

[0009] One embodiment of the fixing device of the present invention is A circular, endless anchoring belt, A heating unit for heating the fixing belt, A pressing rotating body is rotatably positioned opposite the outer circumferential surface of the fixing belt and presses the recording medium toward the outer circumferential surface of the fixing belt, The fixing belt comprises a contact member positioned inside the fixing belt, extending in the width direction of the fixing belt, and contacting the inner circumferential surface of the fixing belt, The length dimension of the contact portion of the contact member is set to be greater than the width dimension of the fixing belt, and the contact portion of the contact member has inclined surfaces at both ends that are inclined with respect to the width direction such that the contact pressure with the inner circumferential surface of the fixing belt gradually decreases towards both ends of the fixing belt.

[0010] One aspect of the image forming apparatus of the present invention is: The system is equipped with the fixing device described above. [Effects of the Invention]

[0011] According to the present invention, damage to the end of the fixing belt can be suppressed, thereby increasing the durability of the fixing belt. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic front view of the image forming apparatus according to this embodiment. [Figure 2] Figure 2 is a schematic front view of the fixing device according to this embodiment. [Figure 3] Figure 3 is a schematic cross-sectional view of a fixing device according to the first aspect of this embodiment, and is a cross-sectional view along line II in Figure 2. [Figure 4] Figure 4 is a schematic cross-sectional view of a fixing device according to the first aspect of this embodiment, and is a cross-sectional view along the line II-II in Figure 2. [Figure 5] Figure 5 is a schematic cross-sectional view of a fixing device according to the first aspect of this embodiment, and is a cross-sectional view along the line III-III in Figure 2. [Figure 6] Figure 6 is a schematic cross-sectional view of a fixing device according to a second aspect of this embodiment, and is a cross-sectional view along line II in Figure 2. [Figure 7] Figure 7 is a schematic cross-sectional view of a fixing device according to a third aspect of this embodiment, and is a cross-sectional view along the line II-II in Figure 2. [Figure 8] Figure 8 is a schematic cross-sectional view of a fixing device according to a fourth aspect of this embodiment, and is a cross-sectional view along line II in Figure 2. [Modes for carrying out the invention]

[0013] Hereinafter, the present embodiment will be described with reference to the drawings. In the specification and claims of the present application, "in contact with the inner peripheral surface of the fixing belt" is intended to include not only direct contact with the inner peripheral surface of the fixing belt, but also indirect contact with the inner peripheral surface of the fixing belt via another member such as a sliding contact sheet. In the drawings, "front" refers to the front direction, "rear" refers to the rear direction, "left" refers to the left direction, "right" refers to the right direction, "upper" refers to the upward direction, and "lower" refers to the downward direction. "WD" refers to the width direction of the fixing belt, and "WDo" refers to the outer side in the width direction of the fixing belt.

[0014] The overall configuration of the image forming apparatus 10 according to the present embodiment will be described with reference to FIG. 1. FIG. 1 is a schematic front view of the image forming apparatus 10 according to the present embodiment.

[0015] As shown in FIG. 1, the image forming apparatus 10 according to the present embodiment is an apparatus that forms a toner image on a sheet S as a recording medium by an electrophotographic method. The image forming apparatus 10 includes a box-shaped apparatus main body 12, and the apparatus main body 12 constitutes a base frame of the image forming apparatus 10.

[0016] As shown in FIG. 1, an image forming unit 14 that forms an image by an electrophotographic method is provided inside the apparatus main body 12. The image forming unit 14 has four image forming units 16 (16Y, 16M, 16C, 16K) for forming toner images (electrostatic latent images) of respective colors of Y (yellow) component, M (magenta) component, C (cyan) component, and K (black) component based on image data. The four image forming units 16 (16Y, 16M, 16C, 16K) are arranged along the horizontal left-right direction. Each of the image forming units 16 (16Y, 16M, 16C, 16K) extends in the horizontal front-rear direction. The image forming units 16Y, 16M, 16C, and 16K for the Y component, M component, C component, and K component have the same configuration. For convenience of description, common constituent elements are denoted by the same reference numerals, and when distinguishing them from each other, the reference numerals are suffixed with Y, M, C, or K.

[0017] The image forming unit 16 includes a photoreceptor drum 18, and a charging section 20, a developing section 22, and a drum cleaning section 24 arranged around the photoreceptor drum. The image forming section 14 includes a scanning unit (exposure section) 26 that scans the surface of each photoreceptor drum 18 while exposing it, and the scanning unit 26 is disposed below the four image forming units 16 (16Y, 16M, 16C, 16K).

[0018] The photoreceptor drum 18 is an image carrier that carries a toner image (electrostatic latent image), and rotates at a constant peripheral speed by driving of a rotation motor (not shown). The charging section 20 uniformly charges the surface of the photoreceptor drum 18 to a negative polarity. The scanning unit 26 emits laser light as scanning light to scan and expose the surface of each photoreceptor drum 18 as the image carrier, thereby forming an electrostatic latent image on the surface of each photoreceptor drum 18. The light amount of the laser light emitted from the scanning unit 26 is modulated according to the image data of each color of YMCK.

[0019] The developing section 22 develops the electrostatic latent image of each color by a trickle developing system. The developing section 22 causes a two-component developer containing toner and carrier to adhere to the surface (outer peripheral surface) of the photoreceptor drum 18, thereby developing the electrostatic latent image of each color on the surface of the photoreceptor drum 18. The developing section 22 develops the electrostatic latent image of each color on the surface of the photoreceptor drum 18, so that a toner image is formed on the surface of the photoreceptor drum 18.

[0020] The drum cleaning section 24 removes and cleans residual toner remaining on the surface of the photoreceptor drum 18 after the transfer of the toner image. The drum cleaning section 24 includes a drum cleaning blade or the like that is in sliding contact with the surface of the photoreceptor drum 18.

[0021] As shown in FIG. 1, above the four image forming units 16Y, 16M, 16C, and 16K in the apparatus main body 12, a transfer section 28 for transferring a toner image onto a sheet S is provided. The transfer section 28 includes an endless intermediate transfer belt 30, a plurality of support rollers 32, a primary transfer roller 34, a secondary transfer roller 36, and a belt cleaning section 38.

[0022] The intermediate transfer belt 30 is an image carrier that holds the toner image and extends horizontally in the left-right direction. The intermediate transfer belt 30 is stretched over a plurality of support rollers 32 and rotates due to the rotation of the plurality of support rollers 32. One of the support rollers 32 is a drive roller that rotates by the drive of a rotary motor (not shown). The support rollers 32 other than the aforementioned support rollers 32 are driven rollers (free rollers) that rotate in accordance with the rotation of the drive rollers. Although only two support rollers 32 are shown in Figure 1, the number of support rollers 32 may be three or more.

[0023] The primary transfer roller 34 is positioned on the inner circumferential surface side of the intermediate transfer belt 30, facing the photoreceptor drums 18 for each color component. The primary transfer roller 34 works in cooperation with the photoreceptor drums 18 to grip the intermediate transfer belt 30. A primary transfer nip CN is formed between the outer circumferential surface of the primary transfer roller 34 and the outer circumferential surface of the photoreceptor drums 18 to transfer the toner image from the photoreceptor drums 18 to the intermediate transfer belt 30.

[0024] The secondary transfer roller 36 is positioned on the right side of the intermediate transfer belt 30 within the device body 12, facing a predetermined support roller 32 (the right support roller 32). The secondary transfer roller 36 works in cooperation with the predetermined support roller 32 to grip the intermediate transfer belt 30. A secondary transfer nip TN is formed between the outer circumferential surface of the secondary transfer roller 36 and the outer circumferential surface of the predetermined support roller 32 for transferring the toner image from the intermediate transfer belt 30 to the paper S.

[0025] As the intermediate transfer belt 30 passes through the primary transfer nip CN, the toner images of each color component from the photoreceptor drum 18 are sequentially superimposed onto the intermediate transfer belt 30 and primary transferred. Specifically, a primary transfer bias is applied to the primary transfer roller 34, and a charge with the opposite polarity to the toner is applied to the back side of the intermediate transfer belt 30 (the side that contacts the primary transfer roller 34), thereby electrostatically transferring the toner image to the intermediate transfer belt 30.

[0026] Subsequently, as the paper S passes through the secondary transfer nip TN, the toner image on the intermediate transfer belt 30 is secondary transferred to the paper S. Specifically, by applying a secondary transfer bias of the same polarity as the toner to a predetermined support roller 32 and applying a charge of the same polarity as the toner to the back side of the intermediate transfer belt 30, the toner image is electrostatically transferred to the paper S, and a toner image (image) can be formed on the paper S.

[0027] The belt cleaning unit 38 is located to the left of the intermediate transfer belt 30 within the main body 12 of the device, and cleans the surface of the intermediate transfer belt 30 by removing any remaining toner after the transfer of the toner image. The belt cleaning unit 38 has a cleaning blade that slides against the surface of the intermediate transfer belt 30.

[0028] As shown in Figure 1, a thermal fixing device 40 is provided above the secondary transfer nip TN within the main body 12 of the device, serving as a fixing unit for fixing the toner image (image) to the paper S. The fixing device 40 has a fixing nip FN for transporting the paper S while heating and pressurizing it. In the fixing nip FN, the paper S is transported while being heated and pressurized, allowing the unfixed toner image to be fixed to the paper S. The specific configuration of the fixing device 40 will be described later.

[0029] As shown in Figure 1, a paper feed cassette 42 is provided below the scanning unit 26 inside the main body 12 of the device, serving as a paper feed section for feeding paper S. The paper feed cassette 42 is capable of accommodating paper S. Furthermore, a paper output tray 44 is provided at the top of the main body 12 for ejecting the image-formed paper S. The paper output tray 44 accommodates the image-formed paper S.

[0030] As shown in Figure 1, the main body 12 of the device is provided with a transport path 46 for transporting paper S from the paper feed cassette 42 to the paper output tray 44 via the secondary transfer nip TN and the fuser nip FN. At the starting end of the transport path 46, there is a feed roller 48 that feeds paper S one sheet at a time from the paper feed cassette 42 into the transport path 46. Between the feed roller 48 and the secondary transfer nip TN in the middle of the transport path 46, there is a pair of registration rollers 50 that adjust the timing of feeding paper S to the secondary transfer nip TN. At the end of the transport path 46, there is a pair of paper output rollers 52 that outputs the image-formed paper S to the paper output tray 44.

[0031] The paper sheets S stored in the paper feed cassette 42 are fed one by one onto the transport path 46 by the feed roller 48 and transported toward the secondary transfer nip TN. At this time, the timing of feeding the paper sheets S toward the secondary transfer nip TN is adjusted by the registration roller pair 50. Then, at the secondary transfer nip TN, the toner image on the intermediate transfer belt 30 is transferred to the paper sheets S, and at the fuser nip FN, the toner image is fixed to the paper sheets S. After that, the image-formed paper sheets S are ejected into the output tray 44 by the output roller pair 52.

[0032] The specific configuration of the fixing device 40 according to this embodiment will be described with reference to Figures 1 to 8. Figure 2 is a schematic front view of the fixing device 40 according to this embodiment. Figures 3 to 5 are schematic cross-sectional views of the fixing device 40 according to the first embodiment of this embodiment. Figure 3 is a cross-sectional view along line II in Figure 2, Figure 4 is a cross-sectional view along line II-II in Figure 2, and Figure 5 is a cross-sectional view along line III-III in Figure 2. Figure 6 is a schematic cross-sectional view of the fixing device 40 according to the second embodiment of this embodiment, and is a cross-sectional view along line II in Figure 2. Figure 7 is a schematic cross-sectional view of the fixing device 40 according to the third embodiment of this embodiment, and is a cross-sectional view along line II-II in Figure 2. Figure 8 is a schematic cross-sectional view of the fixing device 40 according to the fourth embodiment of this embodiment, and is a cross-sectional view along line II in Figure 2.

[0033] As shown in Figures 1 and 2, the fixing device 40 includes a fixing frame 54 fixed to the upper side of the secondary transfer nip TN within the device body 12, and the fixing frame 54 is made of sheet metal. The fixing frame 54 constitutes the base frame of the fixing device 40.

[0034] As shown in Figures 2 and 3, the fixing device 40 is equipped with a circumferentially movable, endless fixing belt 56, the width direction of which is the front-to-back direction. The fixing belt 56 has a base layer, an elastic layer covering the base layer, and a release layer covering the elastic layer. The base layer of the fixing belt 56 is made of a metal such as nickel, stainless steel, or copper, or a resin such as polyimide, polyamide, or polyimidoamide. The elastic layer of the fixing belt 56 is made of a heat-resistant material such as silicone rubber or fluororubber. The release layer of the fixing belt 56 is made of a material with release properties such as fluororesin.

[0035] As shown in Figures 2 and 3, the fixing device 40 includes a cylindrical heating roller 58 positioned inside the fixing belt 56. The heating roller 58 extends in the front-rear direction, which is the width direction of the fixing belt 56, and both ends of the heating roller 58 are rotatably supported by the fixing frame 54. The heating roller 58 supports the fixing belt 56 from the inside and is configured to move relative to the fixing frame 54 in a direction toward and toward the fixing nip FN in order to apply tension to the fixing belt 56. The heating roller 58 is a contact member that contacts the inner circumferential surface of the fixing belt 56. In other words, the heating roller 58 has a contact portion that can contact the inner circumferential surface of the fixing belt 56. The heating roller 58 is made of a metal such as aluminum alloy or stainless steel.

[0036] As shown in Figures 2 and 3, the heating roller 58 has a heater 60 on its inside, which serves as a heating element for heating the fixing belt 56. For example, a halogen lamp is used as the heater 60. In addition, annular restricting members 62 are integrally provided at both ends of the heating roller 58 to restrict the movement of the fixing belt 56 in the width direction (front-back direction), and each restricting member 62 can slide against the end face of the fixing belt 56. Each restricting member 62 may be considered to constitute a part of the heating roller 58. For the sake of explanation, the heater 60 is not shown in Figure 3.

[0037] As shown in Figures 2 and 3, the fixing device 40 includes a pressure roller 64 as a pressing rotating body that presses the paper S against the outer circumferential surface of the fixing belt 56. The pressure roller 64 is rotatably positioned opposite the outer circumferential surface of the fixing belt 56. The pressure roller 64 applies pressure to the outer circumferential surface of the fixing belt 56 by the biasing force of a spring (not shown). The pressure roller 64 extends in the front-rear direction, and both ends of the pressure roller 64 are rotatably supported by the fixing frame 54. The pressure roller 64 is configured to move relative to the fixing frame 54 in a direction toward and toward the outer circumferential surface of the fixing belt 56.

[0038] The pressure roller 64 contacts the outer circumferential surface of the fixing belt 56. In other words, the pressure roller 64 has a contact portion that can contact the outer circumferential surface of the fixing belt 56. The length of the contact portion of the pressure roller 64 is set to be smaller than the width of the fixing belt 56. Both ends of the contact portion of the pressure roller 64 correspond to both ends of the fixing nip FN formation area.

[0039] The pressure roller 64 has a hollow cylindrical core, an elastic layer covering the outer surface of the core, and a release layer covering the outer surface of the elastic layer. The core of the pressure roller 64 is made of a metal such as aluminum alloy or steel. The elastic layer of the pressure roller 64 is made of an elastic material such as silicone rubber or fluororubber. The release layer of the pressure roller 64 is made of a material such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) or PTFE (polytetrafluoroethylene).

[0040] The pressure roller 64 is a driven rotating body that rotates by the drive of a rotary motor (not shown). As the pressure roller 64 rotates, the fixing belt 56 follows and rotates. As the fixing belt 56 rotates, the heating roller 58 follows and rotates. The heating roller 58 is a driven rotating body that rotates in accordance with the rotation of the fixing belt 56.

[0041] As shown in Figures 2 and 3, the fixing device 40 includes a transverse U-shaped support member 66 positioned inside the fixing belt 56. The support member 66 extends in the front-rear direction, and both ends of the support member 66 are integrally connected to the fixing frame 54. The support member 66 is made of a metal such as aluminum alloy or steel.

[0042] As shown in Figures 2 and 3, the fixing device 40 includes a pad portion 68 provided on the left side of the support member 66, and the pad portion 68 is positioned inside the fixing belt 56. The pad portion 68 extends in the front-rear direction and supports the fixing belt 56 from the inside. The pad portion 68 is a contact member that contacts the inner circumferential surface of the fixing belt 56. In other words, the pad portion 68 has a contact portion that can contact the inner circumferential surface of the fixing belt 56. The pad portion 68 forms a fixing nip FN with the pressure roller 64 via the fixing belt 56. The pad portion 68 is made of a heat-resistant resin such as polyphenylene sulfide, polyimide, or liquid crystal polymer.

[0043] The fixing device 40 includes a sliding contact sheet 70 that covers the entire surface of the pad portion 68 except for both end faces, and the sliding contact sheet 70 slides against the inner circumferential surface of the fixing belt 56. The sliding contact sheet 70 is positioned inside the fixing belt 56 and extends in the front-rear direction. The sliding contact sheet 70 is a contact member that contacts the inner circumferential surface of the fixing belt 56. In other words, the sliding contact sheet 70 has a contact portion that can contact the inner circumferential surface of the fixing belt 56.

[0044] The sliding contact sheet 70 has a base material made of glass fiber woven fabric and a coating layer formed on the surface of the base material and made of a fluororesin. The sliding contact sheet 70 does not need to cover the entire surface of the pad portion 68, as long as it is provided to cover the contact portion of the pad portion 68. The fixing device 40 may omit the sliding contact sheet 70 from its components.

[0045] As shown in Figures 2, 4, and 5, the fixing device 40 includes a guide member 72 provided on the upper surface of the support member 66. The guide member 72 is positioned downstream of the fixing nip FN on the inside of the fixing belt 56 in the circumferential direction. The guide member 72 extends in the front-rear direction and supports the fixing belt 56 from the inside. The guide member 72 tensions the fixing belt 56 in cooperation with the heating roller 58 and the pad portion 68. In other words, the fixing belt 56 is tensioned by the heating roller 58, the pad portion 68, and the guide member 72.

[0046] The guide member 72 is a contact member that contacts the inner circumferential surface of the fixing belt 56. In other words, the guide member 72 has a contact portion that can contact the inner circumferential surface of the fixing belt 56. A recess 72d extending in the front-rear direction is formed on the upper surface of the guide member 72. The guide member 72 is made of a heat-resistant resin such as polyphenylene sulfide, polyimide, or liquid crystal polymer. Note that the guide member 72 may be positioned upstream of the fixing nip FN in the circumferential direction of the fixing belt 56, rather than downstream.

[0047] As shown in Figures 2 and 4, an application member 74 for applying lubricant to the inner circumferential surface of the fixing belt 56 is attached to the bottom surface of the recess 72d, which is the adhesive surface of the guide member 72, using double-sided tape (not shown). The application member 74 is positioned downstream in the circumferential direction of the fixing belt 56 from the fixing nip FN on the inside of the fixing belt 56. The application member 74 is a contact member that contacts the inner circumferential surface of the fixing belt 56. In other words, the application member 74 has a contact portion that can contact the inner circumferential surface of the fixing belt 56.

[0048] The coating member 74 is made of a nonwoven fabric of a certain thickness. As a lubricant, for example, a lubricant such as grease is used. Note that the coating member 74 may be positioned upstream of the fixing nip FN in the circumferential direction of the fixing belt 56, rather than downstream.

[0049] As shown in Figure 3, in the fixing device 40 according to the first embodiment, the length dimension of the contact portion of the heating roller 58, which is a contact member, is set to be larger than the width dimension of the fixing belt 56. In addition, the contact portion of the heating roller 58 protrudes outward from both end faces of the fixing belt 56 in the width direction of the fixing belt 56.

[0050] As shown in Figure 3, in the fixing device 40 according to the first embodiment, the length dimension of the contact portion of the pad portion 68 as a contact member is set to be larger than the width dimension of the fixing belt 56. The contact portion of the pad portion 68 protrudes outward in the width direction of the fixing belt 56 from both end faces of the fixing belt 56. The contact portion of the pad portion 68 protrudes outward in the width direction of the fixing belt 56 from both ends of the fixing nip FN formation area.

[0051] The contact portion of the pad portion 68 has inclined surfaces 68g on both ends that are inclined with respect to the width direction of the fixing belt 56, such that the contact pressure with the inner circumferential surface of the fixing belt 56 gradually decreases as it moves toward both ends of the fixing belt 56. In other words, the contact portion of the pad portion 68 has inclined surfaces 68g on both ends that are inclined with respect to the width direction of the fixing belt 56, such that it gradually moves away from the inner circumferential surface of the fixing belt 56 as it moves toward both ends of the fixing belt 56. Each inclined surface 68g of the contact portion of the pad portion 68 protrudes outward in the width direction of the fixing belt 56 from the fixing nip FN formation region.

[0052] In the fixing device 40 according to the first embodiment, the length dimension of the contact portion of the sliding contact sheet 70 as a contact member is set to be larger than the width dimension of the fixing belt 56. The contact portion of the sliding contact sheet 70 protrudes outward in the width direction of the fixing belt 56 from both end faces of the fixing belt 56.

[0053] As shown in Figures 4 and 5, in the fixing device 40 according to the first embodiment, the length dimension of the contact portion of the guide member 72, which is a contact member, is set to be larger than the width dimension of the fixing belt 56. The contact portion of the guide member 72 protrudes outward from both end faces of the fixing belt 56 in the width direction of the fixing belt 56.

[0054] The contact portion of the guide member 72 has inclined surfaces 72g on both ends that are inclined with respect to the width direction of the fixing belt 56, such that the contact pressure with the inner circumferential surface of the fixing belt 56 gradually decreases as it moves toward both ends of the fixing belt 56. In other words, the contact portion of the guide member 72 has inclined surfaces 72g on both ends that are inclined with respect to the width direction of the fixing belt 56, such that it gradually moves away from the inner circumferential surface of the fixing belt 56 as it moves toward both ends of the fixing belt 56.

[0055] As shown in Figure 4, in the fixing device 40 according to the first embodiment, the length dimension of the contact portion of the coating member 74, which is a contact member, is set to be larger than the width dimension of the fixing belt 56. The contact portion of the coating member 74 protrudes outward in the width direction of the fixing belt 56 from both end faces of the fixing belt 56.

[0056] The contact portion of the coating member 74 has inclined surfaces 74g on both ends that are inclined with respect to the width direction of the fixing belt 56, such that the contact pressure with the inner circumferential surface of the fixing belt 56 gradually decreases as it moves toward both ends of the fixing belt 56. In other words, the contact portion of the coating member 74 has inclined surfaces 74g on both ends that are inclined with respect to the width direction of the fixing belt 56, such that it gradually moves away from the inner circumferential surface of the fixing belt 56 as it moves toward both ends of the fixing belt 56.

[0057] The bottom surface of the recess 72d of the guide member 72 has inclined surfaces 72dg on both ends that are inclined with respect to the width direction of the fixing belt 56, such that the contact pressure between the coating member 74 and the inner circumferential surface of the fixing belt 56 gradually decreases as it moves toward both ends of the fixing belt 56. In other words, the bottom surface of the recess 72d of the guide member 72 has inclined surfaces 72dg on both ends that are inclined with respect to the width direction of the fixing belt 56, such that they gradually move away from the inner circumferential surface of the fixing belt 56 as it moves toward both ends of the fixing belt 56.

[0058] As shown in Figures 2 and 6, in the fixing device 40 according to the second embodiment, the length dimension of the contact portion of the heating roller 58, which is a contact member, is set to be larger than the width dimension of the fixing belt 56. In addition, the contact portion of the heating roller 58 protrudes outward from both end faces of the fixing belt 56 in the width direction of the fixing belt 56.

[0059] The contact area of ​​the heating roller 58 has inclined surfaces 58g on both ends that are inclined with respect to the width direction of the fixing belt 56, such that the contact pressure with the inner circumferential surface of the fixing belt 56 gradually decreases as it moves toward both ends of the fixing belt 56. In other words, the contact area of ​​the heating roller 58 has inclined surfaces 58g on both ends that are inclined with respect to the width direction of the fixing belt 56, such that it gradually moves away from the inner circumferential surface of the fixing belt 56 as it moves toward both ends of the fixing belt 56.

[0060] The other components of the fixing device 40 according to the second embodiment are the same as those of the fixing device 40 according to the first embodiment. For the sake of clarity, the heater 60 is not shown in Figure 6.

[0061] As shown in Figures 2 and 7, in the fixing device 40 according to the third embodiment, the length dimension of the contact portion of the guide member 72 is set to be smaller than the width dimension of the fixing belt 56. In addition, the length dimension of the contact portion of the coating member 74, which is another contact member, is set to be smaller than the width dimension of the fixing belt 56. The entire area of ​​the contact portion of the coating member 74 is covered by the fixing belt 56.

[0062] The contact portion of the coating member 74 has inclined surfaces 74g on both ends that are inclined with respect to the width direction of the fixing belt 56, such that the contact pressure with the inner circumferential surface of the fixing belt 56 gradually decreases as it moves toward both ends of the fixing belt 56. In other words, the contact portion of the coating member 74 has inclined surfaces 74g on both ends that are inclined with respect to the width direction of the fixing belt 56, such that it gradually moves away from the inner circumferential surface of the fixing belt 56 as it moves toward both ends of the fixing belt 56.

[0063] The bottom surface of the recess 72d of the guide member 72 has inclined surfaces 72dg on both ends that are inclined with respect to the width direction of the fixing belt 56, such that the contact pressure between the coating member 74 and the inner circumferential surface of the fixing belt 56 gradually decreases as it moves toward both ends of the fixing belt 56. In other words, the bottom surface of the recess 72d of the guide member 72 has inclined surfaces 72dg on both ends that are inclined with respect to the width direction of the fixing belt 56, such that they gradually move away from the inner circumferential surface of the fixing belt 56 as it moves toward both ends of the fixing belt 56.

[0064] Furthermore, the other components of the fixing device 40 according to the third embodiment are the same as those of the fixing device 40 according to the first embodiment.

[0065] As shown in Figures 2 and 8, in the fixing device 40 according to the fourth embodiment, the length dimension of the contact portion of the pad portion 68 is set to be smaller than the width dimension of the fixing belt 56. The length dimension of the contact portion of the sliding contact sheet 70 as a contact member is set to be larger than the width dimension of the fixing belt 56.

[0066] The contact portion of the sliding contact sheet 70 has inclined surfaces 70g on both ends that are inclined with respect to the width direction of the fixing belt 56, such that the contact pressure with the inner circumferential surface of the fixing belt 56 gradually decreases as it moves toward both ends of the fixing belt 56. In other words, the contact portion of the sliding contact sheet 70 has inclined surfaces 70g on both ends that are inclined with respect to the width direction of the fixing belt 56, such that they gradually move away from the inner circumferential surface of the fixing belt 56 as it moves toward both ends of the fixing belt 56. Each inclined surface 70g of the contact portion of the sliding contact sheet 70 protrudes outward in the width direction of the fixing belt 56 from the fixing nip FN formation region.

[0067] The other components of the fixing device 40 according to the fourth embodiment are the same as those of the fixing device 40 according to the first embodiment. For the sake of explanation, the heater 60 is not shown in Figure 8.

[0068] According to the configuration of the fixing device 40 in the first aspect of this embodiment, as described above, the length dimension of the contact portion of the pad portion 68 as a contact member is set to be larger than the width dimension of the fixing belt 56. Therefore, it is possible to avoid scratching the inner circumferential surface of the fixing belt 56 by the edge portion at the end of the pad portion 68.

[0069] As mentioned above, the contact portion of the pad portion 68 has inclined surfaces 68g on both ends that are inclined with respect to the width direction of the fixing belt 56. Therefore, even if the central part of the pad portion 68 is deflected by the tension of the fixing belt 56 and / or the pressure applied by the pressure roller 64, it is possible to suppress the localized increase in contact pressure between the pad portion 68 and the inner circumferential surface of the fixing belt 56 at both ends of the fixing belt 56. This suppresses wear on the end sides of the inner circumferential surface of the fixing belt 56 and prevents a decrease in strength due to thinning of the end sides of the fixing belt 56.

[0070] Furthermore, according to the configuration of the fixing device 40 in the first aspect of this embodiment, as described above, the length dimension of the contact portion of the guide member 72 as a contact member is set to be larger than the width dimension of the fixing belt 56. Therefore, it is possible to avoid scratching the inner circumferential surface of the fixing belt 56 by the edge portion at the end of the guide member 72.

[0071] As mentioned above, the contact portion of the guide member 72 has inclined surfaces 72g on both ends that are inclined with respect to the width direction of the fixing belt 56. Therefore, even if the central part of the guide member 72 bends due to the tension of the fixing belt 56 and / or the pressure applied by the pressure roller 64, it is possible to suppress the localized increase in contact pressure between the guide member 72 and the inner circumferential surface of the fixing belt 56 at both ends of the fixing belt 56. This suppresses wear on the end side of the inner circumferential surface of the fixing belt 56 and prevents a decrease in strength due to thinning of the end side of the fixing belt 56.

[0072] Furthermore, according to the configuration of the fixing device 40 in the first aspect of this embodiment, as described above, the bottom surface of the recess 72d, which is the adhesive surface of the guide member 72, has inclined surfaces 72dg on both ends that are inclined with respect to the width direction of the fixing belt 56. Therefore, even if the central part of the guide member 72 bends due to the tension of the fixing belt 56 and / or the pressure applied by the pressure roller 64, it is possible to suppress the localized increase in contact pressure between the coating member 74 and the inner circumferential surface of the fixing belt 56 at both ends of the fixing belt 56. This suppresses wear on the end side of the inner circumferential surface of the fixing belt 56 and prevents a decrease in strength due to thinning of the end side of the fixing belt 56.

[0073] Therefore, according to the first embodiment of the fixing device 40, damage such as cracking at the end of the fixing belt 56 can be suppressed, thereby increasing the durability of the fixing belt 56. In particular, damage such as cracking at the end face of the fixing belt 56 due to sliding contact with the regulating member 62 can be suppressed.

[0074] Furthermore, according to the configuration of the fixing device 40 in the first aspect of this embodiment, as described above, each inclined surface 68g of the contact portion of the pad portion 68 protrudes outward in the width direction of the fixing belt 56 from the fixing nip FN formation region. Therefore, the paper S can be pressed with substantially uniform pressure along the width direction of the fixing belt 56 at the fixing nip FN.

[0075] Therefore, according to the fixing device 40 of the first aspect of this embodiment, density unevenness of the image formed on the paper S can be suppressed, thereby improving the image quality.

[0076] According to the configuration of the fixing device 40 in the second aspect of this embodiment, as described above, the contact portion of the heating roller 58 has inclined surfaces 58g on both ends that are inclined with respect to the width direction of the fixing belt 56. Therefore, even if the central part of the heating roller 58 bends due to the tension of the fixing belt 56, it is possible to suppress the localized increase in contact pressure between the heating roller 58 and the inner circumferential surface of the fixing belt 56 at both ends of the fixing belt 56. This suppresses wear on the end side of the inner circumferential surface of the fixing belt 56 and prevents a decrease in strength due to thinning of the end side of the fixing belt 56.

[0077] Therefore, according to the fixing device 40 of the second embodiment of this model, damage such as cracking at the end of the fixing belt 56 can be suppressed, thereby increasing the durability of the fixing belt 56. In particular, damage such as cracking at the end face of the fixing belt 56 due to sliding contact with the regulating member 62 can be suppressed.

[0078] According to the configuration of the fixing device 40 in the third aspect of this embodiment, as described above, the length dimension of the contact portion of the coating member 74, which is another contact member, is set to be smaller than the width dimension of the fixing belt 56. Also, as described above, the bottom surface of the recess 72d of the guide member 72 has inclined surfaces 72dg on both ends thereof that are inclined with respect to the width direction of the fixing belt 56. Therefore, bending of the fixing belt 56 can be suppressed on both ends of the contact portion of the coating member 74.

[0079] Therefore, according to the fixing device 40 of the embodiment 3, damage such as cracking of the fixing belt 56 can be suppressed, and the durability of the fixing belt 56 can be increased.

[0080] According to the configuration of the fixing device 40 in aspect 4 of this embodiment, as described above, the length dimension of the contact portion of the sliding contact sheet 70 as a contact member is set to be larger than the width dimension of the fixing belt 56. Therefore, it is possible to avoid scratching the inner circumferential surface of the fixing belt 56 by the edge portion of the sliding contact sheet 70.

[0081] Furthermore, as mentioned above, the contact portion of the sliding contact sheet 70 has inclined surfaces 70g on both ends that are inclined with respect to the width direction of the fixing belt 56. Therefore, even if the central part of the pad portion 68 is deflected by the tension of the fixing belt 56 and / or the pressure applied by the pressure roller 64, it is possible to suppress the localized increase in contact pressure between the sliding contact sheet 70 and the inner circumferential surface of the fixing belt 56 at both ends of the fixing belt 56. This suppresses wear on the end side of the inner circumferential surface of the fixing belt 56 and prevents a decrease in strength due to thinning of the end side of the fixing belt 56.

[0082] Therefore, according to the fixing device 40 of the fourth embodiment of this model, damage such as cracking at the end of the fixing belt 56 can be suppressed, thereby increasing the durability of the fixing belt 56.

[0083] Although this embodiment has been described in detail above, the present invention is not limited to the specific embodiments described above. Various modifications and changes are possible to the specific examples described in the above embodiments within the scope of the gist of the present invention as described in the claims. For example, instead of heating the fixing belt 56 with the heater 60 built into the heating roller 58, the fixing belt 56 may be heated directly from the inside. [Industrial applicability]

[0084] The present invention is useful as a fixing device and an image forming apparatus that can suppress damage to the end side of the fixing belt and improve the durability of the fixing belt. [Explanation of Symbols]

[0085] 10 Image forming apparatus 12 Main unit of the device 14 Image forming unit 16 Image-making units 16M Image Production Unit 16Y Image Production Unit 16C Image-making unit 16K Image Production Unit 18 Photoconductor drum 20 Charged parts 22. Developing Department 24 Drum Cleaning Section 26 Scanning unit (exposure section) 28 Transfer section 30 Intermediate transfer belt 32 Support rollers 34 Primary Transfer Roller 36 Secondary transfer roller 38 Belt Cleaning Section 40 Fixing device 42 Paper feed cassette 44 Paper output tray 46 Conveyor paths 48 rollers 50 Resist Roller 52 Paper output roller pair 54 Fixed Frame 56 Fixing belt 58. Heating roller (driven rotating body, contact member) 58g sloped surface 60 Heater (heating section) 62 Regulating members 64 Pressure roller (pressure rotating body) 66 Support Member 68 Pad portion (contact member) 68g inclined surface 70. Sliding contact sheet (contact member) 70g inclined surface 72 Guide member (contact member) 72g inclined surface 72d recess 72dg inclined plane 74 Coating member (contact member) CN primary transfer nip TN secondary transfer nip FN Fixing Nips S Paper (recording medium)

Claims

1. A circular, endless anchoring belt, A heating unit for heating the fixing belt, A pressing rotating body is rotatably positioned opposite the outer circumferential surface of the fixing belt and presses the recording medium toward the outer circumferential surface of the fixing belt, The fixing belt comprises a contact member positioned inside the fixing belt, extending in the width direction of the fixing belt, and contacting the inner circumferential surface of the fixing belt, The length dimension of the contact portion of the contact member is set to be greater than the width dimension of the fixing belt, and the contact portion of the contact member has inclined surfaces at both ends that are inclined with respect to the width direction such that the contact pressure with the inner circumferential surface of the fixing belt gradually decreases towards the ends of the fixing belt. Fixing device.

2. The contact member is a pad portion that forms a fixing nip with the pressurizing rotating body. The fixing device according to claim 1.

3. The system includes a sliding contact sheet that is provided so as to cover at least the contact portion of the pad and slides against the inner circumferential surface of the fixing belt, The fixing device according to claim 2.

4. The contact member is positioned downstream or upstream of the fixing belt in the circumferential direction from the fixing nip, and is an application member that applies lubricant to the inner circumferential surface of the fixing belt. The fixing device according to claim 1.

5. The fixing belt is equipped with a guide member positioned downstream or upstream of the fixing nip in the circumferential direction of the fixing belt, located inside the fixing belt. The coating member is attached to the adhesive surface of the guide member and is made of a nonwoven fabric of a certain thickness. The adhesive surface of the guide member has inclined surfaces on both ends that are inclined with respect to the width direction such that the contact pressure between the coating member and the inner circumferential surface of the fixing belt gradually decreases towards both ends of the fixing belt. The fixing device according to claim 4.

6. The contact member is positioned downstream or upstream of the fixing belt in the circumferential direction from the fixing nip, and is a guide member that supports the fixing belt from the inside. The fixing device according to claim 1.

7. The contact member is a driven rotating body that rotates in accordance with the circumference of the fixing belt. The fixing device according to claim 1.

8. The fixing belt is further provided with other contact members positioned downstream or upstream of the fixing nip on the inside of the fixing belt in the circumferential direction, and which contact the inner circumferential surface of the fixing belt. The length dimension of the contact portion of the other contact member is set to be smaller than the width dimension of the fixing belt. The fixing device according to claim 1.

9. The other contact member is an application member that applies lubricant to the inner circumferential surface of the fixing belt. The fixing device according to claim 8.

10. The fixing belt is equipped with a guide member positioned downstream or upstream of the fixing nip in the circumferential direction of the fixing belt, located inside the fixing belt. The coating member is attached to the adhesive surface of the guide member and is made of a nonwoven fabric of a certain thickness. The adhesive surface of the guide member has inclined surfaces on both ends that are inclined with respect to the width direction such that the contact pressure between the coating member and the inner circumferential surface of the fixing belt gradually decreases towards both ends of the fixing belt. The fixing device according to claim 9.

11. The pad portion is positioned inside the fixing belt, contacts the inner circumferential surface of the fixing belt, and forms a fixing nip with the pressurizing rotating body, The length dimension of the contact portion of the pad is set to be smaller than the width dimension of the fixing belt. The contact member is a sliding contact sheet provided so as to cover at least the contact portion of the pad and sliding against the inner circumferential surface of the fixing belt. The fixing device according to claim 1.

12. The inclined surface protrudes outward in the width direction from the fixing nip formation region. The fixing device according to claim 1.

13. The system includes a restricting member that is slidable against the end face of the fixing belt and restricts the movement of the fixing belt in the width direction. The fixing device according to claim 1.

14. A fixing device according to any one of claims 1 to 13, Image forming apparatus.

Images