JP2020052326A - Fixation device and image forming apparatus - Google Patents

Abstract

To provide a fixation device that prevent fatigue breaking of a sheet-metal member constituting a nip formation member without increasing a thickness of the sheet-metal member, and can achieve both of long-service life and a fast temperature rise.SOLUTION: A fixation device of the present invention comprises: a rotatable fixation member; a rotatable pressurization member that is arranged while facing the fixation member; a nip formation member that is provided on the inner side of the fixation member, and forms a fixation nip part between the pressure member and the nip formation member via the fixation member; and a contact/separation mechanism that brings the fixation member into contact with the pressurization member or that separates the fixation member from the pressurization member, and pressurizes or depressurizes the fixation nip part. The nip formation member has a sheet-metal member provided in a surface facing the inner surface of the fixation member, and when the fixation nip part is depressurized, a center part in a longer direction of the sheet-metal member is configured to support the sheet-metal member so as to protrude on a side of the pressurization member. The sheet-metal member has a coating applied to a surface in slide-contact with at least the inner side of the fixation member. A rolling direction of the sheet-metal member is orthogonal or inclined at a prescribed angle with respect to a conveyance direction of a recording material in the fixation nip part.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a fixing device and an image forming device.

  2. Description of the Related Art As a fixing device used in an electrophotographic image forming apparatus, a fixing film method in which heating rises quickly is widely used. This is a configuration in which a pressure roller is brought into contact with a nip forming member via a thin fixing film to form a fixing nip portion. The sliding fixing film has a lubricant interposed between the inner surface and the nip forming member surface. The nip forming member is used as a sliding member obtained by coating a sheet metal.

  For example, Patent Document 1 discloses a configuration in which a sheet metal member having a coating layer is used as a nip forming member, and in order to improve the slidability between the fixing belt (tubular member) and the nip forming member, the rolling direction (roll) A fixing device is disclosed in which the eye is arranged along the direction of conveyance of the recording material.

  In a configuration in which a fixing belt (fixing film) and a sheet metal member are in contact with each other via a coating layer (coating) as in Patent Literature 1, heat of the fixing belt is easily diffused to the sheet metal member. If the heat of the fixing belt moves to the sheet metal member, there is a problem that the rise of the fixing belt temperature is delayed.

  Therefore, a configuration is often used in which the thickness of the sheet metal member is made as small as possible to reduce the heat capacity, thereby making it difficult to remove the heat of the fixing belt.

  By the way, in the fixing device, in order to prevent deformation of the pressure roller and remove jammed paper, a configuration is used in which the fixing belt is separated from / contact with the pressure roller so that the fixing nip can be depressurized / pressed. However, when the depressurization / pressurization of the fixing nip portion is repeated, the sheet metal member of the nip forming member is repeatedly subjected to bending stress, and may be broken by fatigue. Further, if cracks or plastic deformation occur and the nip forming member (sheet metal member) does not function properly, it needs to be replaced. These problems are more likely to occur when the thickness of the sheet metal member is reduced to reduce the heat capacity, because the strength is reduced.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device that can prevent fatigue fracture without increasing the thickness of a sheet metal member constituting a nip forming member, and can achieve both long life and fast temperature rise.

  The object is to provide a rotatable fixing member, a rotatable pressing member disposed to face the fixing member, and a rotatable pressing member provided between the fixing member and the pressing member via the fixing member. A nip forming member that forms a fixing nip portion therebetween; and a contact / separation mechanism that contacts or separates the fixing member and the pressing member and presses or depressurizes the fixing nip portion. In the fixing device for fixing, the nip forming member is provided with a sheet metal member on a surface facing the inner surface of the fixing member, and when the fixing nip portion is depressurized, the central portion in the longitudinal direction of the sheet metal member is pressed. The sheet metal member is supported so as to protrude toward the pressure member side, and the sheet metal member is coated at least on a surface that slides inside the fixing member, and the rolling direction of the sheet metal member is the fixing nip. Note in the department With respect to the transport direction of the timber, or it is perpendicular, or are solved by a fixing device, characterized in that inclined at a predetermined angle.

  In the fixing device of the present invention, the rolling direction of the sheet metal member constituting the nip forming member is orthogonal to the conveying direction of the recording material in the fixing nip portion or is inclined at a predetermined angle. Therefore, the strength against bending stress can be increased without increasing the thickness of the sheet metal member. Therefore, fatigue fracture can be prevented, and both long life and fast temperature rise can be achieved.

FIG. 1 is a schematic diagram illustrating an image forming apparatus according to an embodiment of the present disclosure. FIG. 1 is a schematic cross-sectional configuration diagram of a fixing device according to an embodiment of the present disclosure. It is a schematic diagram which shows the shape of the longitudinal direction of a nip formation member. It is a schematic diagram which shows the relationship of the roll direction of a heat transfer auxiliary member with respect to the conveyance direction of a recording material, (a) is parallel to the conveyance direction of a recording material, (b) is orthogonal to the conveyance direction of a recording material. In the case (c), the recording material is inclined with respect to the conveying direction of the recording material.

  Hereinafter, the configuration of an image forming apparatus according to an embodiment of the present invention will be described with reference to FIG. The image forming apparatus 100 shown in FIG. 1 is a tandem type color printer in which image forming units for forming a plurality of color images are juxtaposed along a belt extending direction. However, the present invention is not limited to this method, and can be applied not only to printers but also to copiers and facsimile machines.

  The image forming apparatus 100 includes photoconductor drums 20Y, 20C, 20M, and 20Bk as image carriers capable of forming images as images corresponding to colors separated into yellow, cyan, magenta, and black, respectively. The tandem structure is adopted.

  In the image forming apparatus 100, a visible image formed on each of the photosensitive drums 20Y, 20C, 20M, and 20Bk is an intermediate transfer member (hereinafter, referred to as an endless belt) that is an endless belt that can move in the direction of arrow A1 while facing each of the photosensitive drums. , A transfer belt). The images of the respective colors are superimposedly transferred by performing the primary transfer process, and thereafter, the images are collectively transferred by performing the secondary transfer process on a recording material S using a recording sheet or the like.

  Around the photosensitive drums 20, devices for performing image forming processing in accordance with the rotation of the photosensitive drums 20 are arranged. Explaining the photosensitive drum 20Bk for forming a black image as a representative, a charging device 30Bk for performing an image forming process, a developing device 40Bk, a primary transfer roller 12Bk, and a cleaning device 50Bk are arranged along the rotation direction of the photosensitive drum 20Bk. Have been. The optical writing device 8 is used for writing using the writing light Lb performed after the photosensitive drum 20 is charged.

  In the superimposition transfer onto the transfer belt 11, the visible images formed on the photosensitive drums 20Y, 20C, 20M, and 20Bk are transferred to the same position on the transfer belt 11 while the transfer belt 11 moves in the A1 direction. Is done. For this reason, the transfer is performed on the upstream side in the A1 direction by applying a voltage by the primary transfer rollers 12Y, 12C, 12M, and 12Bk disposed opposite to the photosensitive drums 20Y, 20C, 20M, and 20Bk with the transfer belt 11 interposed therebetween. The timing is shifted from to the downstream side.

  The photoconductor drums 20Y, 20C, 20M, and 20Bk are arranged in this order from the upstream side in the A1 direction. The photosensitive drums 20Y, 20C, 20M, and 20Bk are provided in image stations for forming yellow, cyan, magenta, and black images, respectively.

  The image forming apparatus 100 includes four image stations that perform image forming processing for each color, and is disposed above each photosensitive drum 20 so as to face each other, and includes a transfer belt 11 and primary transfer rollers 12Y, 12C, 12M, and 12Bk. And a transfer belt unit 10 having the same. Further, a secondary transfer roller 5, which is a transfer roller serving as a transfer member that is disposed to face the transfer belt 11 and follows the transfer belt 11 and rotates therewith, and a transfer belt 11 that is provided to face the transfer belt 11. And a belt cleaning device 13 for cleaning the upper side. Furthermore, an optical writing device 8 is provided below and opposed to the four image stations.

  The optical writing device 8 is equipped with a semiconductor laser as a light source, a coupling lens, an fθ lens, a toroidal lens, a folding mirror, a rotating polygon mirror as a polarizing means, and the like. The optical writing device 8 emits writing light Lb corresponding to each color to each of the photosensitive drums 20Y, 20C, 20M, and 20Bk, and forms an electrostatic latent image on the photosensitive drums 20Y, 20C, 20M, and 20Bk. It is configured as follows. In FIG. 1, for convenience, reference numerals are given only to image stations for black images, but the same applies to other image stations.

  The image forming apparatus 100 is provided with a sheet feeding device 61 as a sheet feeding cassette loaded with a recording material S conveyed between the photosensitive drums 20Y, 20C, 20M, and 20Bk and the transfer belt 11. I have. Further, the recording material S conveyed from the sheet feeding device 61 is directed to a transfer portion between each photosensitive drum 20 and the transfer belt 11 at a predetermined timing corresponding to a timing of forming a toner image by an image station. A registration roller pair 4 is provided. Further, a sensor (not shown) for detecting that the leading end of the recording material S has reached the registration roller pair 4 is provided.

  The image forming apparatus 100 includes a fixing device 200 as a fixing unit of a roller fixing type for fixing the toner image on the recording material S on which the toner image is transferred, and a recording device S on which the toner image is fixed. 100 is provided with a paper discharge roller 7 for discharging to the outside of the main body. At the upper part of the main body of the image forming apparatus 100, there is provided a paper discharge tray 17 on which the recording material S discharged from the main body of the image forming apparatus 100 by the paper discharge rollers 7 is stacked. On the lower side of the discharge tray 17, there are provided toner bottles 9Y, 9C, 9M, 9Bk filled with toners of yellow, cyan, magenta, and black, respectively.

  The transfer belt unit 10 includes, in addition to the transfer belt 11, the primary transfer rollers 12Y, 12C, 12M, and 12Bk, a drive roller 72 around which the transfer belt 11 is wound and a driven roller 73.

  The driven roller 73 also has a function as a tension urging unit for the transfer belt 11. For this purpose, the driven roller 73 is provided with an urging unit using a spring or the like. Such a transfer belt unit 10, the primary transfer rollers 12Y, 12C, 12M, and 12Bk, the secondary transfer roller 5, and the belt cleaning device 13 constitute a transfer device 71.

  The sheet feeding device 61 is provided at a lower portion of the main body of the image forming apparatus 100, and has the feeding roller 3 as a sheet feeding roller that contacts the upper surface of the uppermost recording material S. By rotating the feed roller 3 counterclockwise in the figure, the uppermost recording material S is fed toward the registration roller pair 4.

  Although not shown in detail, the belt cleaning device 13 provided in the transfer device 71 has a cleaning brush and a cleaning blade arranged so as to face and contact the transfer belt 11. The belt cleaning device 13 cleans the transfer belt 11 by scraping off and removing foreign matters such as residual toner on the transfer belt 11 with a cleaning brush and a cleaning blade.

  The belt cleaning device 13 also has a discharging unit (not shown) for carrying out and discarding the residual toner removed from the transfer belt 11.

  FIG. 2 is a schematic cross-sectional configuration diagram of a fixing device according to an embodiment of the present invention. As shown in FIG. 2, the fixing device 200 includes a fixing belt 201 as a rotatable fixing member, and a pressing roller 203 as a rotatable pressing member that is disposed to face the fixing belt 201. Further, the fixing belt 201 is directly heated by radiant heat from the inner peripheral side by halogen heaters 202A and 202B as a plurality of heat sources.

  To detect the temperature of the fixing belt 201, temperature sensors 230A and 230B are attached, and the temperature of the fixing belt 201 is detected in a non-contact manner. The control unit of the fixing device 200 controls the lighting rates of the halogen heaters 202A and 202B based on the detected temperature, and controls the temperature of the fixing belt 201 to a desired temperature.

  The fixing belt 201 is configured by a metal belt such as nickel or SUS, or an endless belt or film using a resin material such as polyimide. The surface layer of the belt has a release layer such as a PFA or PTFE layer, and has a release property so that toner does not adhere. An elastic layer formed of a silicone rubber layer or the like may be provided between the base material of the belt and the PFA or PTFE layer.

  If there is no silicone rubber layer, the heat capacity will be small and the fixability will be improved.However, when the unfixed image is crushed and fixed, the minute irregularities on the belt surface will be transferred to the image, and the solid part of the image will have a scumming appearance. There is a possibility that gloss unevenness (yuzu skin image) remains. In order to improve this, it is sufficient to provide a silicone rubber layer of 100 (μm) or more. Due to the deformation of the silicone rubber layer, minute unevenness is absorbed, so that it is possible to improve the skin image of Yuzu.

  The pressing roller 203 has a configuration in which an elastic rubber layer 204 is provided on a cored bar 205 and a release layer (PFA or PTFE layer) is provided on the surface of the elastic rubber layer 204 to obtain releasability. The pressing roller 203 is rotated by a driving force transmitted from a driving source such as a motor provided in the image forming apparatus 100 via a gear. Further, the pressure roller 203 is pressed against the fixing belt 201 by a spring or the like, and has a predetermined nip width when the elastic rubber layer 204 is crushed and deformed.

  The pressure roller 203 may be a hollow roller, or may have a heating source such as a halogen heater inside the pressure roller 203. The elastic rubber layer 204 may be solid rubber, but if there is no heater inside the pressure roller 203, sponge rubber may be used. Sponge rubber is more preferable because the heat insulating property is enhanced and the heat of the fixing belt 201 is hardly deprived.

  Inside the fixing belt 201, a nip forming member 206 arranged to face the pressure roller 203 and a heat transfer assisting member 216 covering a surface of the nip forming member 206 facing the inner surface of the fixing belt 201 are provided. ing. Further, a stay member 207 for holding the nip forming member 206 against the pressing force from the pressing roller 203 is also provided.

  The nip forming member 206 forms a fixing nip portion N with the pressure roller 203 via the fixing belt 201 and slides indirectly on the inner surface of the fixing belt 201 via the heat transfer assisting member 216.

  An end heater 226 as an end heat source different from a main heat source (fixing heat source) is integrally attached to both ends in the longitudinal direction of the nip forming member 206. As the end heater 226, a contact heat transfer type heat source which is a resistance heating element such as a ceramic sweater is generally used.

  The heat transfer assisting member 216 prevents the heat of the end heater 226 from staying locally, and positively transfers the heat in the longitudinal direction to reduce the temperature non-uniformity in the longitudinal direction. For this reason, the heat transfer assisting member 216 is desirably a material capable of transferring heat in a short time, and is desirably a member having high thermal conductivity, such as copper, aluminum, or silver. Considering cost, availability, thermal conductivity characteristics, and workability comprehensively, it is most preferable to use aluminum or copper.

  In the present embodiment, the surface of the heat transfer assisting member 216 facing the inner surface of the fixing belt 201 is a surface that directly contacts the fixing belt 201 and is a nip forming surface. The surface of the heat transfer assisting member 216, that is, the surface in contact with the inner surface of the fixing belt 201, is provided with a sliding coating that is low in friction and hard to wear. As the sliding coating, a material such as fluorine coating having low friction or DLC having high wear resistance is used.

  In FIG. 2, the shape of the heat transfer assisting member 216 is flat, but it may be concave or another shape. When the recording material S has a concave shape, the discharge direction of the leading end of the recording material S is closer to the pressure roller 203, and the separability is improved, so that the occurrence of jam is suppressed.

  The stay member 207 is a support member for supporting the nip forming member 206 and the fixing nip portion N. The stay member 207 can obtain a uniform nip width in the axial direction in order to prevent the nip forming member 206 from receiving the pressure from the pressure roller 203. The stay member 207 is held and fixed to the side plate at both ends and positioned.

  The stay member 207 has upright portions 207a and 207b in which the opposite side to the fixing nip portion N side is upright, and halogen heaters 202A and 202B as fixing heat sources are arranged between the upright portions 207a and 207b. . Therefore, the fixing belt 201 is directly heated by the radiant heat from the inner surface side by the halogen heaters 202A and 202B.

  In addition, a reflection member 209 is provided between the halogen heater 202 and the stay member 207 to suppress wasteful energy consumption due to heating of the stay member 207 by radiant heat from the halogen heater 202 or the like. Here, instead of providing the reflecting member 209, the same effect can be obtained by performing heat insulation or mirror finishing on the surface of the stay member 207.

  In the present embodiment, as shown in FIG. 2, a reflection member 209 is provided between the halogen heaters 202A and 202B. By preventing each heater from heating the other glass tube, the fixing belt 201 can be efficiently heated.

  The fixing device 200 of the present embodiment includes a contact / separation mechanism 65 that contacts or separates the fixing belt 201 and the pressure roller 203 and presses or depresses the fixing nip N. The contact / separation mechanism 65 includes a pressure arm 67 that rotates around a rotation shaft 66, a cam 68 that moves the pressure arm 67 in the direction of arrow B1, and the like. When the fixing belt 201 and the pressure roller 203 approach each other by the contact / separation mechanism 65, a fixing nip portion N is formed at the pressure contact portion between the two, and when the two are separated from each other, the fixing nip portion N is eliminated.

  If the pressure roller 203 is pressed against the fixing belt 201 for a long time, the elastic rubber layer 204 is deformed and rigid, and there is a possibility that abnormal noise or glossy stripes may be generated at the next printing. For this reason, after a predetermined time (for example, one minute) has elapsed after the fixing is performed, the contact / separation mechanism 65 is operated to release the pressure of the fixing nip N. Accordingly, the pressure roller 203 is not deformed or has a small deformation amount, and the elastic rubber layer 204 is prevented from being deformed.

  Further, even when a paper jam or the like occurs, the user can easily remove the jammed paper by operating the contact / separation mechanism 65 and depressurizing the fixing nip portion N.

  In the fixing device 200 of this embodiment, the fixing belt 201 is rotated by the pressure roller 203. Specifically, the pressure roller 203 is rotated by a driving source, and the driving force is transmitted to the belt at the fixing nip N, whereby the fixing belt 201 is rotated. The fixing belt 201 rotates while being sandwiched between the fixing nip portions N, and is guided by flanges (not shown) at both ends other than the fixing nip portion N and travels. The toner image on the recording material S is heated and pressed at the fixing nip N and fixed.

  With the above configuration, an inexpensive fixing device that can be warmed up quickly can be realized.

  FIG. 3 is a schematic diagram illustrating a shape of the nip forming member in the longitudinal direction. For convenience of explanation, the nip forming member 206 is shown separated from the stay member 207. Actually, the configuration is such that it is in contact with and held by the stay member 207.

  As shown in FIG. 3, the nip forming member 206 receives a pressing force from the pressing roller 203 via the heat transfer assisting member 216 and is pressed against the stay member 207. The stay member 207 is supported by the side plate 210 at both ends, and is bent by the pressing force from the pressing roller 203. The amount of deflection becomes maximum (the amount of deflection L2) at the center in the longitudinal direction.

  When the stay member 207 bends, the nip forming member 206 (the heat transfer assisting member 216) also bends in a direction away from the pressing roller 203, with the central portion in the longitudinal direction being the maximum. Therefore, the contact surface between the fixing nip N and the pressure roller 203 is reduced.

  In order to offset this decrease in the contact surface, the nip forming member 206 of the present embodiment has a convex shape in which the center in the longitudinal direction protrudes toward the pressure roller 203 side. Further, the amount of protrusion of the nip forming member 206 is the maximum (the amount of protrusion L1) at the center in the longitudinal direction.

  In FIG. 3, the central portion in the longitudinal direction of the nip forming member 206 has a convex shape protruding toward the stay member 207. Actually, the nip forming member 206 has a convex shape protruding toward the pressure roller 203.

  Here, it is desirable that the projection amount L1 is smaller than the deflection amount L2 of the stay member 207 (L1 <L2). This is because the fixing nip pressure is larger at both ends in the longitudinal direction than at the center in the longitudinal direction of the fixing nip portion N. Fixing wrinkles and the like are less likely to occur, and there is an effect that the transportability of the recording material is stabilized.

  As described above, the nip forming member 206 and the heat transfer assisting member 216 attached to the nip forming member 206 are elastically deformed into a concave shape toward the pressure roller 203 at the center in the longitudinal direction during printing (fixing). .

  On the other hand, when the pressure roller 203 retreats from the nip and the fixing nip portion N releases the pressure, the deflection L2 'of the stay member 207 becomes smaller than the deflection L2 (L2' <L2). Since the amount of deflection L2 ′ is smaller than the amount of projection L1 (L2 ′ <L1), the nip forming member 206 and the heat transfer assisting member 216 are elastically deformed such that the central portion in the longitudinal direction is convex toward the pressure roller 203. Will do.

  That is, when the fixing nip portion N is pressurized or depressurized, the heat transfer assisting member 216 receives bending stresses in opposite directions, and is deformed into a concave shape (when pressurized) or a convex shape (when depressurized). Will be.

  Subsequently, a characteristic configuration of the present invention will be described.

  Generally, a thin metal plate can be mass-produced by rolling using a roll, and the mechanical properties can be improved. The heat transfer assisting member 216, which is a thin sheet metal member, is also manufactured by rolling processing.

  FIGS. 4A and 4B are schematic diagrams showing the relationship between the rolling direction of the heat transfer assisting member and the conveying direction of the recording material, where FIG. 4A is parallel to the conveying direction of the recording material, and FIG. In the case of being orthogonal, (c) is a case where the recording medium is inclined with respect to the conveying direction of the recording material.

  The heat transfer assisting member 216 has a concave shape toward the pressure roller 203 when the pressure roller 203 is pressed, and has a convex shape toward the pressure roller 203 when the pressure roller 203 is depressurized. Therefore, it receives positive and negative repeated bending stress.

  In general, in bending parallel to the rolling direction (the rolling direction is parallel to the bending line), cracks tend to occur in the bent portion. The heat transfer assisting member 216a shown in FIG. 4A has a possibility that fatigue fracture occurs quickly due to repeated bending, and abnormalities such as surface cracks may occur.

  Therefore, in the present embodiment, as shown in FIG. 4B, the heat transfer auxiliary member 216b is formed so that the rolling direction is orthogonal to the transport direction. In this case, since the bending direction is perpendicular to the rolling direction, the strength is highest, and fatigue fracture due to repeated bending can be prevented.

  Further, as shown in FIG. 4C, the rolling direction of the heat transfer assisting member 216c may be a direction inclined with respect to the transport direction (a relationship in which the bending line and the rolling direction intersect at a predetermined angle). Here, since the direction of the bending stress acting on the heat transfer assisting member 216c, which is a sheet metal member, is determined, the rolling direction of the sheet metal member is not less than 45 degrees and not more than 90 degrees (= direction orthogonal) to the transport direction. It is desirable to do.

  In this case, the strength becomes an intermediate value between FIGS. 4A and 4B, and depending on the magnitude of the bending stress generated during pressurization and depressurization, fatigue failure can be prevented until the unit life of the fixing device. .

  As described above, the fixing device of the present embodiment is configured such that the rolling direction of the heat transfer assisting member 216 as a sheet metal member is orthogonal or inclined at a predetermined angle with respect to the conveying direction of the recording material in the fixing nip portion. Features. Thereby, the strength against bending stress can be increased, and therefore, fatigue fracture can be prevented.

  In addition, the fixing device is required to reduce the warm-up time, that is, to quickly bring the fixing belt 201 to a desired temperature. Therefore, the heat transfer assisting member 216 is desirably a member (thin plate) having a low heat capacity.

  The present inventors formed the heat transfer assisting member 216c from aluminum sheet metal (plate thickness 0.4 to 0.6 mm) and mounted it on a fixing device. As a result, the amount of heat that escaped from the fixing belt 201 to the heat transfer assisting member 216c was reduced. The warm-up time was reduced. Further, even with this fixing device, it was possible to prevent fatigue destruction until the unit life of the fixing device.

  From this, it can be said that the fixing device of the present embodiment can prevent fatigue destruction and achieve both long life and fast temperature rise.

  In addition, it was confirmed that even when brass (C2801P) or a steel material such as a cold-rolled forged steel plate (SPCC) or a stainless steel plate (SUS) was used as another material, it was similarly effective.

  By the way, when the rolling direction is inclined (orthogonal) to the conveying direction as in the heat transfer assisting members 216b and 216c, the rolling roll becomes the frictional resistance of the fixing belt and the sliding resistance increases. Can be considered. On the other hand, by making the surface of the coating sufficiently random as compared to the rolling roll, the influence on the sliding resistance can be eliminated.

  The present invention has been described in detail with reference to the embodiments. This embodiment is merely an example, and various changes can be made without departing from the scope of the invention.

  For example, the fixing device according to the present invention is not limited to the color laser printer shown in FIG. 1, but can be mounted on a monochrome image forming device, other printers, copiers, facsimile machines, or a multifunction peripheral thereof. This makes it possible to provide an image forming apparatus that is excellent in energy saving.

Reference Signs List 3 feed roller 4 registration roller pair 5 secondary transfer roller 7 discharge roller 8 optical writing device 9Y, 9M, 9C, 9Bk toner bottle 10 transfer belt unit 11 transfer belt 12Y, 12M, 12C, 12Bk primary transfer roller 13 belt Cleaning device 17 Discharge tray 20Y, 20M, 20C, 20Bk Photoconductor drum 30Y, 30M, 30C, 30Bk Charging device 40Y, 40M, 40C, 40Bk Developing device 50Y, 50M, 50C, 50Bk Cleaning device 61 Sheet feeding device 65 contact Separation mechanism 66 Rotary shaft 67 Pressure arm 68 Cam 71 Transfer device 72 Drive roller 73 Follower roller 100 Image forming device 200 Fixing device 201 Fixing belt 202A, 202B Halogen heater 203 Pressure roller 204 Elastic rubber layer 205 core 206 Nip forming member 207 Stay member 207a, 207b Standing portion 209 Reflecting member 210 Side plate 216, 216a, 216b, 216c Heat transfer assist member 226 End heater 230A, 230B Temperature sensor L1 Projection amount L2, L2 'Deflection amount Lb Write light N Fixing nip S Recording material t Coating thickness

Patent No. 5895417

Claims (5)

A rotatable fixing member,
A pressure member disposed rotatably facing the fixing member,
A nip forming member that is provided inside the fixing member and forms a fixing nip portion between the fixing member and the pressure member;
A contact / separation mechanism that abuts or separates the fixing member and the pressure member, and pressurizes or depressurizes the fixing nip portion;
In a fixing device for fixing an image on a recording material,
In the nip forming member, a sheet metal member is provided on a surface facing an inner surface of the fixing member, and when the fixing nip portion is depressurized, a longitudinal central portion of the sheet metal member protrudes toward the pressing member. Supporting the sheet metal member, and coating the sheet metal member at least on a surface that slides inside the fixing member, and conveying the recording material in the fixing nip portion in a rolling direction of the sheet metal member. A fixing device characterized by being orthogonal to the direction or inclined at a predetermined angle.   The fixing device according to claim 1, wherein a rolling direction of the sheet metal member is inclined at an angle of 45 degrees or more and 90 degrees or less with respect to a conveyance direction of the recording material in the fixing nip portion.   The fixing device according to claim 1, wherein the sheet metal member is formed of a material having a high thermal conductivity such as aluminum or copper.   4. The fixing device according to claim 1, wherein the contact / separation mechanism reduces a pressing force between the nip forming member and the pressing member when a predetermined time has elapsed after the fixing is performed, as compared with a time when the fixing is performed. The fixing device according to claim 1.   An image forming apparatus comprising the fixing device according to claim 1.

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