JP2015069094A - Fixing device and fixing belt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device and a fixing belt that enable suppression of lubricant agents lubricating between inner surfaces of fixing belts and nip members from being leaked from ends of fixing belts in a width direction.SOLUTION: According to the fixing device, a pressure roller 150 rotates with a fixing belt 110 sandwiched between a nip plate 130 and the pressure roller, so that the fixing belt 110 of which an inner surface is in contact with the nip plate 130 via a lubricant agent smoothly rotates, subjecting to a lubrication action of the lubricant agent. In this case, in a width direction of the fixing belt 110, surface roughness Ra2 of an inner surface of a second part 110B located in the vicinity of both ends is larger than surface roughness Ra1 of an inner surface of a first part 110A located in an intermediate part, thus, the lubricant agent has difficulty flowing at the second part 110B located in the vicinity of both ends of the fixing belt 110. As a result, a leakage of the lubricant agent from ends in the width direction of the fixing belt 110 is suppressed and the fixing belt 110 stably rotates in an excellent lubricating state.

Description

  The present invention relates to a fixing device and a fixing belt used in an electrophotographic image forming apparatus.

  In general, an electrophotographic image forming apparatus such as a laser printer or a digital copying machine includes a fixing device that thermally fixes a developer image formed on a recording sheet. As this type of fixing device, for example, Patent Document 1 discloses a flexible endless fixing film that can rotate in the circumferential direction, a heating body that contacts the inner surface of the fixing film via a lubricant, and a heating body. And a pressure roller that rotates while forming a fixing nip portion by sandwiching a fixing film therebetween.

  In this fixing device, a sheet on which a developer image is formed is sandwiched between a pressure roller and an endless fixing film and conveyed, so that heat is applied to the sheet from the heating body via the fixing film, The formed developer image is heat-fixed.

JP-A-3-210588

  By the way, in the fixing device described in Patent Document 1, the lubricant that lubricates between the inner surface of the fixing film as the fixing belt and the heating body as the nip member leaks from the end in the width direction of the fixing film. Sometimes. In this case, it is difficult to stably rotate the fixing film in a good lubricating state, and as a result, there is a problem that unevenness occurs in the thermal fixing of the developer image formed on the sheet.

  SUMMARY OF THE INVENTION Accordingly, the present invention provides a fixing device and a fixing belt that can prevent the lubricant that lubricates between the inner surface of the fixing belt and the nip member from leaking from the end in the width direction of the fixing belt. Let it be an issue.

  The fixing device according to the present invention for solving the above-described problems includes an endless fixing belt, a heating element disposed inside the fixing belt, and a nip member that contacts the inner surface of the fixing belt via a lubricant. And a backup member that forms a nip portion with the fixing belt by sandwiching the fixing belt with the nip member. The inner surface of the fixing belt has a first portion located at an intermediate portion in the width direction of the fixing belt and a second portion located on the outer side in the width direction than the first portion. The surface roughness Ra2 of the second part is larger than the surface roughness Ra1 of the first part.

  In this fixing device, when the backup member rotates with the fixing belt interposed between the fixing member and the nip member, the fixing belt whose inner surface comes into contact with the nip member through the lubricant receives the lubricating action of the lubricant and rotates smoothly. To do.

  At this time, in the width direction of the fixing belt, the surface roughness Ra2 of the inner surface of the second portion located on the outer side in the width direction than the first portion is smaller than the surface roughness Ra1 of the inner surface of the first portion located in the intermediate portion. Therefore, the lubricant that lubricates between the inner surface of the fixing belt and the nip member is less likely to flow in the second portion of the fixing belt. As a result, the lubricant is prevented from leaking from the end in the width direction of the fixing belt, and the fixing belt rotates stably in a good lubricating state.

  In this fixing device, both ends of the backup member are preferably arranged at positions corresponding to the second portion in the width direction of the fixing belt. In this case, since both ends of the backup member are pressed against the second portion having a large surface roughness on the inner surface of the fixing belt, leakage of the lubricant from the end portion in the width direction of the fixing belt is more effectively suppressed. .

  Further, it is preferable that both ends of the nip member are disposed outside the both ends of the fixing belt in the width direction of the fixing belt. In this case, since the nip member can easily sandwich the second portion having a large surface roughness on the inner surface of the fixing belt with the backup member, the lubricant leaks from the end portion in the width direction of the fixing belt. Is suppressed more effectively.

  Furthermore, it is preferable that both ends of the printing area are arranged on the inner side of the position corresponding to the second portion in the width direction of the fixing belt. In this case, the inner surface of the fixing belt facing the print area is the first portion having a smaller surface roughness than the second portion, and therefore does not adversely affect printing on the paper.

  Here, on the inner surface of the fixing belt, third portions positioned at both ends in the width direction of the fixing belt can be provided outside the second portion in the width direction. The surface roughness Ra3 of the third portion is preferably smaller than the surface roughness Ra2 of the second portion, and can be made equal to, for example, the surface roughness Ra1 of the first portion.

  In this case, at both ends in the width direction of the fixing belt, the decrease in rigidity is suppressed by the amount that the surface roughness Ra3 of the third portion is smaller than the surface roughness Ra2 of the second portion, and the both ends of the fixing belt in the width direction are suppressed. Rigidity is ensured. When the surface roughness Ra3 of the third portion is equal to the surface roughness Ra1 of the first portion, only the surface roughening process corresponding to the surface roughness Ra2 of the second portion is performed on the inner surface of the fixing belt. That's it.

  In addition, the fixing device may include a regulating member that contacts an end portion in the width direction of the fixing belt and regulates movement of the fixing belt in the width direction. In this case, if the rigidity of both end portions in the width direction of the fixing belt is ensured, the regulating member can reliably regulate the movement of the fixing belt in the width direction.

  On the other hand, the fixing belt according to the present invention is a fixing belt whose inner surface is in contact with the nip member via a lubricant, and the inner surface of the fixing belt includes a first portion located at an intermediate portion in the width direction of the fixing belt; And a second portion located on the outer side in the width direction than the first portion. The surface roughness Ra2 of the second part is larger than the surface roughness Ra1 of the first part.

  According to the fixing device of the present invention, the lubricant that lubricates between the inner surface of the fixing belt and the nip member does not easily flow in both sides where the surface roughness of the inner surface is large in the width direction of the fixing belt. The agent can be prevented from leaking from the end portion in the width direction of the fixing belt. As a result, the fixing belt can be stably rotated in a good lubrication state.

1 is a side sectional view showing a schematic configuration of a laser printer including a fixing device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a schematic configuration of the fixing device illustrated in FIG. 1. FIG. 3 is an exploded perspective view showing components of the fixing device shown in FIG. 2 in an exploded manner. FIG. 4 is a perspective view showing an assembled state of a frame member that supports the end portion of the stay shown in FIG. 3 and a regulating member that regulates movement of the fixing belt in the width direction. 2 is a longitudinal sectional view showing a detailed configuration of a fixing belt. FIG.

  Hereinafter, embodiments of a fixing device and a fixing belt according to the present invention will be described in detail with reference to the drawings as appropriate. The fixing device of one embodiment is embodied as a fixing device 100 of a laser printer 1 as shown in FIG. First, the configuration of the laser printer 1 will be schematically described with reference to FIG. 1, and then the configuration of the fixing device 100 will be described in detail with reference to FIGS. 2 to 5.

  Here, in the description with reference to FIG. 1, the description is based on the direction based on the user who uses the laser printer 1. That is, the description will be made assuming that the right direction is “rear”, the left direction is “front”, the up and down direction is “up and down”, the front direction is “right”, and the back direction is “left”.

<Schematic configuration of laser printer>
As shown in FIG. 1, the laser printer 1 includes a main body housing 2 in which a paper sheet 3 as an example of a recording sheet is fed, an exposure device 4, and a toner image (developer) on the paper P. And a fixing device 100 for thermally fixing the toner image on the paper P.

  The paper feed unit 3 is provided at a lower portion in the main body housing 2 and mainly includes a paper feed tray 31, a paper pressing plate 32, and a paper feed mechanism 33. The paper P accommodated in the paper feed tray 31 is moved upward by the paper pressing plate 32 and supplied toward the process cartridge 5 (between the photosensitive drum 61 and the transfer roller 63) by the paper feed mechanism 33.

  The exposure apparatus 4 is disposed in the upper part of the main body housing 2 and includes a laser light emitting unit (not shown), a polygon mirror, a lens, a reflecting mirror, and the like that are not shown. In this exposure device 4, the surface of the photosensitive drum 61 is exposed by scanning the surface of the photosensitive drum 61 at high speed with laser light (see the chain line) based on the image data emitted from the laser light emitting unit.

  The process cartridge 5 is disposed below the exposure apparatus 4 and is detachably mounted on the main body housing 2 through an opening formed when the front cover 21 provided on the main body housing 2 is opened. Yes. The process cartridge 5 includes a drum unit 6 and a developing unit 7.

  The drum unit 6 mainly includes a photosensitive drum 61, a charger 62, and a transfer roller 63. The developing unit 7 is configured to be detachably attached to the drum unit 6, and includes a developing roller 71, a supply roller 72, a layer thickness regulating blade 73, and a toner that contains toner (developer). The housing part 74 is mainly provided.

  In the process cartridge 5, the surface of the photosensitive drum 61 is uniformly charged by the charger 62 and then exposed by high-speed scanning of the laser light from the exposure device 4, whereby an image is formed on the photosensitive drum 61. An electrostatic latent image based on the data is formed. Further, the toner in the toner container 74 is supplied to the developing roller 71 via the supply roller 72 and enters between the developing roller 71 and the layer thickness regulating blade 73 to form a thin layer of a certain thickness on the developing roller 71. It is carried on.

  The toner carried on the developing roller 71 is supplied from the developing roller 71 to the electrostatic latent image formed on the photosensitive drum 61. As a result, the electrostatic latent image is visualized and a toner image is formed on the photosensitive drum 61. Thereafter, the paper P is conveyed between the photosensitive drum 61 and the transfer roller 63, whereby the toner image on the photosensitive drum 61 is transferred onto the paper P.

  The fixing device 100 is provided behind the process cartridge 5. The toner image (toner) transferred onto the paper P is thermally fixed onto the paper P by passing through the fixing device 100. The paper P on which the toner image is thermally fixed is discharged onto the paper discharge tray 22 by the transport rollers 23 and 24.

<Detailed configuration of fixing device>
2, the fixing device 100 includes an endless fixing belt 110, a halogen lamp 120 as an example of a heating element, a nip plate 130 as an example of a nip member, a reflection plate 140, A pressure roller 150 as an example of a backup member and a stay 160 are provided.

  The halogen lamp 120, the nip plate 130, the reflecting plate 140, and the stay 160 are members that are arranged in parallel to each other as shown in FIG. 3 and extend in the left-right direction. As shown in FIG. Is arranged.

  The halogen lamp 120 is a heating element that heats the toner image on the paper P by generating radiant heat and heating the nip plate 130 and the fixing belt 110. The halogen lamp 120 is a straight tubular lamp disposed substantially parallel to the virtual rotation axis X1 of the fixing belt 110, and is disposed at a predetermined interval from the inner surface on the upper side of the nip plate 130.

  The nip plate 130 is a long plate member that receives radiant heat from the halogen lamp 120, and heats the toner image on the paper P through the fixing belt 110 by the received radiant heat. The nip plate 130 is made of an aluminum plate having a high thermal conductivity or the like, and is formed in a shallow tray shape having a flat U-shaped cross section perpendicular to the longitudinal direction. The nip plate 130 has a main body 131 along the conveyance direction of the paper P and a side wall 132 bent so as to rise upward from the side edge of the main body 131 in a cross section orthogonal to the longitudinal direction. doing.

  The lower outer surface 131A of the main body 131 of the nip plate 130 is in contact with the inner surface of the fixing belt 110 via a lubricant. The lubricant preferably has a viscosity sufficient to be retained on the inner surface of the fixing belt 110, and is preferably a grease exhibiting a solid or semi-solid property at room temperature, particularly a heat-resistant grease.

  The reflection plate 140 has a reflection portion 141 formed in an inverted U-shaped cross-sectional shape surrounding the halogen lamp 120. Flange portions 142, 142 that overlap the inner surface of the main body 131 of the nip plate 130 are bent at both side edges orthogonal to the longitudinal direction of the reflecting portion 141. The reflection part 141 of the reflection plate 140 reflects the radiant heat from the halogen lamp 120 to the inside, and efficiently heats the upper surface of the main body 131 of the nip plate 130.

  The stay 160 is a member that secures the rigidity of the nip plate 130 by supporting both side portions 131 </ b> B positioned at both ends in the front-rear direction of the main body portion 131 of the nip plate 130 via the flange portions 142 of the reflection plate 140. The stay 160 has an inverted U-shaped cross-sectional shape along the outer surface shape of the reflecting portion 141 of the reflecting plate 140 and is disposed so as to cover the reflecting plate 140. Such a stay 160 has a relatively large rigidity, for example, is formed by bending a steel plate or the like into a substantially U shape in cross section.

  As shown in FIGS. 2 and 3, a total of four abutting bosses 168 projecting inward are provided on the inner surfaces of both ends in the longitudinal direction of the side walls 161, 162 of the stay 160. The abutting boss 168 abuts against the outer surface of the side wall of the reflecting plate 140, thereby suppressing vibration and displacement of the side wall portion of the reflecting plate 140.

  As shown in FIG. 3, the nip plate 130 includes an insertion portion 133 that extends in a flat plate shape from one end portion in the longitudinal direction of the main body portion 131, and an engagement portion 134 that is formed at the other end portion in the longitudinal direction. Yes. The engaging portion 134 is formed to be bent in a U shape, and engaging holes 134B and 134B are formed in the front and rear standing portions 134A and 134A protruding upward.

  Further, a total of four flange-shaped locking portions 143 are formed at both ends in the longitudinal direction of the reflecting plate 140 (only three are shown). Each locking portion 143 is located above the flange portion 142. A plurality of contact portions 163 formed in a substantially comb-like shape are provided at the lower ends of the side walls 161 and 162 along the longitudinal direction of the stay 160.

  Further, a substantially L-shaped locking portion 165 is provided at the left end of the side walls 161 and 162 of the stay 160 so as to extend downward in FIG. 3 and further to the right. Further, at the right end of the stay 160, a holding portion 167 is provided that is bent in a substantially U shape in a side view and extends rightward from the upper wall 166 of the stay 160. Engagement bosses 167B (only one is shown) projecting inward are provided on the inner surfaces of the side wall portions 167A of the holding portion 167.

  When the reflecting plate 140 and the nip plate 130 are assembled to the stay 160, first, the reflecting plate 140 is attached to the stay 160 so as to be fitted. Since the abutting boss 168 is provided on the inner surfaces of the side walls 161 and 162 of the stay 160, the abutting boss 168 abuts against the side wall portion of the reflecting plate 140, so that the reflecting plate 140 is temporarily held by the stay 160. The

  Thereafter, the insertion portion 133 of the nip plate 130 is inserted between the locking portions 165 of the stay 160 to engage the main body portion 131 with the locking portion 165, and then the engaging hole of the engaging portion 134 of the nip plate 130. 134B and the engaging boss 167B of the holding portion 167 of the stay 160 are engaged.

  Accordingly, the insertion portion 133 is supported by the locking portion 165 of the stay 160 and the engaging portion 134 is held by the holding portion 167 of the stay 160 so that the nip plate 130 is held by the stay 160. The reflecting plate 140 is held by the stay 160 in a state where the flange portion 142 is sandwiched between the nip plate 130 and the stay 160.

  Here, around the stay 160 in which the reflector plate 140 is sandwiched between the halogen lamp 120 and the nip plate 130, the fixing belt 110 is externally mounted as shown in FIG. And the edge part of this stay 160 is supported by the frame member 170 shown in FIG.

  In the frame member 170, a frame portion 171 and an inner surface guide portion 173 that guides the inner surface of the end portion in the width direction of the fixing belt 110 shown in FIG. 4 are integrally formed of synthetic resin.

  Between the frame portion 171 and the inner surface guide portion 173 of the frame member 170, the fixing belt 110 moves in the width direction by contacting the end portion in the width direction that is the direction of the virtual rotation axis X 1 of the fixing belt 110. A regulating member 180 for regulating is assembled.

<Configuration of pressure roller>
On the other hand, as shown in FIGS. 2 and 5, the pressure roller 150 is disposed outside the fixing belt 110 below the nip plate 130. The pressure roller 150 has an outer peripheral surface covered with an elastically deformable rubber layer, and the fixing belt 110 is sandwiched between the main body 131 of the nip plate 130 while the rubber layer is elastically deformed. A nip portion N is formed between the belt 110 and the belt 110.

  The pressure roller 150 receives a driving force from a driving motor (not shown) provided in the main body casing 40 shown in FIG. 1, so that a rotation axis substantially parallel to the virtual rotation axis X1 of the fixing belt 110 is obtained. It is configured to rotate around X2.

  Such a pressure roller 150 rotates around the rotation axis X2, thereby causing the fixing belt 110 to be driven to rotate around the virtual rotation axis X1 in the circumferential direction by a frictional force with the fixing belt 110 (or paper P). Then, the sheet P is conveyed through the nip portion N between the pressure roller 150 and the heated fixing belt 110, whereby the toner image transferred onto the sheet P is thermally fixed.

<Detailed configuration of fixing belt>
Here, the fixing belt 110 is made of a material having heat resistance and flexibility, for example, a SUS film or a synthetic resin film such as PI. If the thickness of the fixing belt 110 is too thin, the shape is liable to collapse due to a decrease in rigidity. If the thickness is too thick, the flexibility is lowered and the heating becomes difficult. Therefore, the thickness of the fixing belt 110 is, for example, in the range of 30 to 50 μm.

  As shown in FIG. 5, the inner surface of the fixing belt 110 includes a first portion 110 </ b> A that is located at an intermediate portion in the width direction of the fixing belt 110, and an outer side in the width direction of the fixing belt 110, i. Second portions 110B and 110B located in the vicinity of both ends of the fixing belt 110 and third portions 110C and 110C located at both ends in the width direction of the fixing belt 110.

  Here, the printing area of the maximum width paper P conveyed to the nip N between the pressure roller 150 and the fixing belt 110, that is, the printing area of the maximum width paper P that can be fixed by the fixing device 100 is denoted by W. In this case, the width A1 of the first portion 110A of the fixing belt 110 is set to be larger than the width of the print area W.

  The second portions 110B and 110B of the fixing belt 110 are adjacent to both sides of the first portion 110A, and have a width that reaches from both ends of the first portion 110A to positions outside the both ends of the pressure roller 150. The third portions 110C and 110C are adjacent to the outside of the second portions 110B and 110B, and constitute both ends of the fixing belt 110 in the width direction.

  Here, the surface roughness Ra2 of the second portions 110B and 110B is set to be larger than the surface roughness Ra1 of the first portion 110A. Further, the surface roughness Ra3 of the third portions 110C and 110C is smaller than the surface roughness Ra2 of the second portions 110B and 110B, and more specifically, is set to be approximately the same as the surface roughness Ra1 of the first portion 110A. . In addition, surface roughness Ra1-Ra3 is arithmetic mean roughness.

  Specifically, the surface roughness Ra1 of the first portion 110A and the surface roughness Ra3 of the third portions 110C and 110C are the surface roughness of the raw tube itself of the film constituting the fixing belt 110. It is about 4 to 0.8. Further, the surface roughness Ra2 of the second portion is the surface roughness after the surface of the raw tube of the film is roughened by physical or chemical means, for example, about 0.8 to 2.0 It is.

  Here, a specific example of the surface roughening process of the raw tube constituting the fixing belt 110 will be described. When the raw tube is made of a metal belt such as SUS, a spinning mold that is roughened in advance on a portion corresponding to the second portion is used as a spinning mold that is used at the time of molding. Similarly, when the raw tube is made of a resin belt such as PI, an injection mold in which the portion corresponding to the second portion is roughened in advance is used as the injection mold used for the molding. As an example of performing surface roughening after completion of the raw tube rather than at the time of forming the raw tube, an example in which the surface of the raw tube is roughened using a drill with sandpaper can be given.

  Here, the pressure roller 150 is disposed so that the positions of both ends in the axial direction overlap with the second portion 110 </ b> B in the width direction of the fixing belt 110. Further, the nip plate 130 is disposed at both ends in the longitudinal direction outside the both ends in the width direction of the fixing belt 110.

  The print area W of the maximum width paper P that can be fixed by the fixing device 100 is arranged so as to overlap with the first portion 110 </ b> A in the width direction of the fixing belt 110. In other words, both ends of the print area W are disposed on the inner side of the positions corresponding to the second portions 110 </ b> B and 110 </ b> B in the width direction of the fixing belt 110.

  In the fixing device 100 of the present embodiment configured as described above, the pressure roller 150 shown in FIG. 2 rotates with the fixing belt 110 sandwiched between the nip plate 130 and the main body of the nip plate 130. The fixing belt 110 whose inner surface is in contact with the lower outer surface of the portion 131 via grease as a lubricant is smoothly rotated in the circumferential direction under the lubricating action of the lubricant.

  At that time, in the width direction of the fixing belt 110, the surface roughness Ra2 of the second portion 110B located in the vicinity of both end portions is larger than the surface roughness Ra1 of the first portion 110A located in the intermediate portion, so that as a lubricant. The grease is less likely to flow in the second portion 110 </ b> B located in the vicinity of both ends of the fixing belt 110. As a result, the lubricant is prevented from leaking from both ends of the fixing belt 110 in the width direction, and the fixing belt 110 rotates stably in a good lubricating state.

  At that time, the fixing belt 110 rotates while the inner surface of the end portion in the width direction is guided by the inner surface guide portion 173 shown in FIG. The fixing belt 110 is restricted from moving in the width direction by the end in the width direction coming into contact with the restriction surface 180 </ b> A of the restriction member 180.

  Here, the inner surfaces of both ends of the fixing belt 110 are configured as a third portion 110C having a surface roughness Ra3 that is smaller than the surface roughness Ra2 of the second portion and substantially the same as the surface roughness Ra1 of the first portion 110A. Therefore, the lowering of the rigidity of the both ends in the width direction of the fixing belt 110 is suppressed as much as the surface roughness Ra3 of the third portion 110C is small, and the fixing belt 110 secures the rigidity of the both ends in the width direction. Has been. As a result, the end portion of the fixing belt 110 in the width direction is not inadvertently damaged even if it contacts the regulating surface 180A of the regulating member 180.

  That is, according to the fixing device 100 of the present embodiment, the grease as a lubricant that lubricates between the inner surface of the fixing belt 110 and the lower outer surface 131A of the main body 131 of the nip plate 130 is the width of the fixing belt 110. Since the second portion 110B located in the vicinity of both end portions in the direction hardly flows, the leakage of the lubricant from both end portions in the width direction of the fixing belt 110 can be suppressed, and the fixing belt 110 can be in a good lubricating state. Can be rotated stably. In addition, it is possible to prevent the end portion of the fixing belt 110 in the width direction from coming into contact with the regulating surface 180A of the regulating member 180 and being inadvertently damaged.

  In addition, when the surface roughness Ra3 of the third portions 110C and 110C of the fixing belt 110 is equal to the surface roughness Ra1 of the first portion 110A, the surface roughness corresponding to the surface roughness Ra2 of the second portions 110B and 110B. Since only the inner surface of the fixing belt needs to be processed, the fixing belt 110 can be easily processed.

  Although one embodiment of the fixing device according to the present invention has been described above, the fixing device of the present invention is not limited to one embodiment, and the structure thereof can be changed as appropriate. For example, the third portions 110C and 110C shown in FIG. 5 may be omitted, and the widths of the second portions 110B and 110B may be extended to both ends of the fixing belt 110 instead.

  Further, the surface roughness Ra3 of the third portions 110C and 110C only needs to be smaller than the surface roughness Ra2 of the second portions 110B and 110B, and may be larger than the surface roughness Ra1 of the first portion 110A.

  Furthermore, the fixing belt 110 having a single layer structure shown in FIG. 2 may have a multilayer structure including a base layer, a rubber layer covering the outer surface of the base layer, and a fluororesin layer covering the outer surface of the rubber layer. Further, the fixing belt 110 may be a seamless belt or a jointed belt.

  Note that the halogen lamp 120 as the heating element may be a ceramic heater.

DESCRIPTION OF SYMBOLS 1 Laser printer 100 Fixing apparatus 110 Fixing belt 110A 1st part 110B 2nd part 110C 3rd part 120 Halogen lamp (heating element)
130 Nip plate (nip member)
140 Reflector 150 Pressure roller (backup member)
160 Stay 180 Regulating member W Print area

Claims (8)

An endless fixing belt,
A heating element disposed inside the fixing belt;
A nip member that contacts the inner surface of the fixing belt via a lubricant;
A fixing device including a backup member that forms a nip portion with the fixing belt by sandwiching the fixing belt with the nip member;
The inner surface of the fixing belt has a first portion located at an intermediate portion in the width direction of the fixing belt, and a second portion located on the outer side in the width direction than the first portion,
The fixing device according to claim 1, wherein a surface roughness Ra2 of the second portion is larger than a surface roughness Ra1 of the first portion.   The fixing device according to claim 1, wherein both ends of the backup member are disposed at positions corresponding to the second portion of the fixing belt in the width direction of the fixing belt.   3. The fixing device according to claim 1, wherein both ends of the nip member are arranged outside both ends of the fixing belt in a width direction of the fixing belt.   The both ends of the printing area in the width direction of the fixing belt are arranged inside a position corresponding to the second portion of the fixing belt. The fixing device described.   The inner surface of the fixing belt has third portions positioned at both ends in the width direction of the fixing belt on the outer side in the width direction than the second portion, and the surface roughness Ra3 of the third portion is the first portion. The fixing device according to claim 1, wherein the fixing device is smaller than the surface roughness Ra <b> 2 of the two portions.   The fixing device according to claim 1, wherein a surface roughness Ra3 of the third portion is equal to a surface roughness Ra1 of the first portion.   The fixing device according to claim 5, further comprising a regulating member that contacts an end of the fixing belt in the width direction and regulates movement of the fixing belt in the width direction. A fixing belt whose inner surface is in contact with a nip member via a lubricant;
The inner surface of the fixing belt has a first portion located at an intermediate portion in the width direction of the fixing belt, and a second portion located on the outer side in the width direction than the first portion,
The fixing belt according to claim 1, wherein a surface roughness Ra2 of the second portion is larger than a surface roughness Ra1 of the first portion.

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