JP2017032853A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a sliding load on a fixing belt while suppressing deformation of the fixing belt.SOLUTION: A fixing device 18 of the present invention comprises: a fixing belt 22; a pressure member 23 that is in pressure contact with the fixing belt 22 to form a fixing nip N; a pressing member 26 that presses the fixing belt 22 toward a side of the pressure member 23; and a sheet member 27 including a main body part 71 that is interposed between the fixing belt 22 and pressing member 26, longitudinal covering parts 72 that extend from the main body part 71 to cover the end faces in the longitudinal direction of the pressing member 26, and longitudinal fixing parts 73 that extend from the longitudinal covering parts 72 to be fixed to the pressing member 26 or fixed to a member provided separately from the pressing member 26.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fixing device that fixes a toner image on a recording medium, and an image forming apparatus including the fixing device.

  2. Description of the Related Art Conventionally, electrophotographic image forming apparatuses such as copying machines and printers include a fixing device that fixes a toner image onto a recording medium such as paper.

  For example, a fixing belt, a pressing member that presses against the fixing belt to form a fixing nip, a pressing member that presses the fixing belt toward the pressing member, and a fixing belt and the pressing member are interposed. A fixing device including a sheet member is known (see Patent Document 1).

JP 2014-048487 A

  In the fixing device configured as described above, the temperature of the entire device rises when the toner image is fixed on the recording medium. Along with this, when the temperature of the sheet member rises, the sheet member may thermally contract. When the sheet member is thermally contracted in this way, the length in the longitudinal direction of the sheet member becomes shorter than the length in the longitudinal direction of the pressing member, and the longitudinal end portion of the fixing belt is in the longitudinal direction of the pressing member. There is a risk of sliding directly without using the sheet member. When such a situation occurs, the sliding load of the fixing belt increases, the fixing belt and the pressing member wear rapidly, and the product life of the fixing device is shortened.

  In order to avoid such a situation, a method in which the length of the sheet member in the longitudinal direction is made longer than the length of the pressing member in the longitudinal direction in advance (the sheet member is left in the longitudinal direction) can be considered. . However, when such a method is employed, there is a risk that the surplus portion of the sheet member contacts and deforms with another member, and the deformed portion presses the fixing belt, so that the fixing belt is deformed.

  Accordingly, an object of the present invention is to reduce the sliding load of the fixing belt while suppressing the deformation of the fixing belt in consideration of the above circumstances.

  The fixing device of the present invention includes a fixing belt, a pressing member that presses against the fixing belt to form a fixing nip, a pressing member that presses the fixing belt toward the pressing member, and the fixing belt. A main body part interposed between the pressing members, a long side covering part that extends from the main body part and covers an end surface in the longitudinal direction of the pressing member, and a long side covering part that extends from the long side covering part. A sheet member having a long-side fixing portion that is fixed or fixed to a member that is provided separately from the pressing member.

  By adopting such a configuration, it is possible to suppress thermal contraction in the longitudinal direction of the sheet member. Therefore, the length of the sheet member in the longitudinal direction is prevented from being shorter than the length of the pressing member in the longitudinal direction, and the end of the fixing belt in the longitudinal direction is set against the end of the pressing member in the longitudinal direction. It is possible to avoid the situation of sliding directly without being interposed. Accordingly, the sliding load of the fixing belt can be reduced, wear of the fixing belt and the pressing member can be suppressed, and the product life of the fixing device can be extended.

  Further, by adopting the above-described configuration, it is not necessary to leave the sheet member in the longitudinal direction, so that the remaining portion of the sheet member prevents the fixing belt from being deformed by pressing the fixing belt. be able to.

  The long side fixing portion may be fixed to a surface of the pressing member opposite to the fixing nip.

  By adopting such a configuration, it is possible to fix the long-side fixing portion using a simple configuration.

  The sheet member extends from the main body, covers an upstream surface of the pressing member in the recording medium conveyance direction, extends from the upstream covering, and the fixing nip of the pressing member. An upstream fixing portion fixed to the opposite surface, a downstream covering portion extending from the main body portion and covering a downstream surface of the pressing member in the recording medium conveyance direction, and the downstream covering portion And a downstream side fixing portion that is fixed to a surface of the pressing member opposite to the fixing nip, and has a fixing nip on the surface of the pressing member opposite to the fixing nip. The long side fixing portion, the upstream side fixing portion, and the downstream side fixing portion may be overlapped in order from the side.

  By adopting such a configuration, the pressing member can be wrapped from three directions by the sheet member, and the fixing strength of the sheet member and the pressing member can be increased. Further, by arranging the long side fixing portion closest to the fixing nip, it is possible to prevent the long side fixing portion from inadvertently dropping from the surface of the pressing member opposite to the fixing nip. Furthermore, by disposing the upstream fixing portion closer to the fixing nip than the downstream fixing portion, even if a larger load is applied to the upstream fixing portion than the downstream fixing portion during rotation of the fixing belt, the pressing member is fixed. It is possible to prevent the upstream side fixing portion from inadvertently dropping from the surface opposite to the nip.

  The fixing device may further include a support member that supports the pressing member, and the longitudinal side fixing portion may be fixed to the support member.

  By adopting such a configuration, it is possible to fix the long-side fixing portion using a simple configuration.

  The fixing device further includes a sandwiching member provided so as to sandwich between the support member and an upstream end portion to a downstream end portion of the longitudinal fixing portion in the conveyance direction of the recording medium. The side fixing portion may be fastened together with the holding member and fixed to the support member.

  By adopting such a configuration, the entire area of the long-side fixing portion in the recording medium conveyance direction can be sandwiched between the holding member and the support member in a balanced manner, and positional deviation of the long-side fixing portion can be suppressed. .

  The image forming apparatus of the present invention includes any one of the fixing devices described above.

  According to the present invention, it is possible to reduce the sliding load of the fixing belt while suppressing deformation of the fixing belt.

1 is a schematic diagram illustrating an outline of a printer according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a fixing device according to an embodiment of the present invention. FIG. 3 is a perspective view showing a front portion of the fixing device according to the embodiment of the present invention from slightly below the side. In the fixing device according to an embodiment of the present invention, it is a perspective view from the right slightly from directly above, showing a state in which a sheet member is wound around a pressing pad. It is VV sectional drawing of FIG. In the fixing device according to an embodiment of the present invention, it is a perspective view from the right slightly from right above, showing a state in the middle of winding a sheet member around a pressing pad. FIG. 9 is a perspective view showing a state in which only a longitudinal side fixing portion of a sheet member is fixed to a lower surface of a support member in a fixing device according to another different embodiment of the present invention. FIG. 9 is a perspective view showing a state in which a fixing member on a longitudinal side of a sheet member is fastened together with a clamping member and fixed to a lower surface of a support member in a fixing device according to another different embodiment of the present invention.

  First, the overall configuration of the printer 1 (image forming apparatus) will be described with reference to FIG. Hereinafter, the front side of the sheet in FIG. Arrows Fr, Rr, L, R, U, and Lo appropriately attached to the drawings indicate the front side, rear side, left side, right side, upper side, and lower side of the printer 1, respectively.

  The printer 1 includes a box-shaped printer main body 2, and a paper feed cassette 3 that stores paper (recording medium) is accommodated in a lower portion of the printer main body 2. A paper discharge tray is disposed on the upper surface of the printer main body 2. 4 is provided. An upper cover 5 is attached to the upper surface of the printer main body 2 so as to be openable and closable on the side of the paper discharge tray 4, and a toner container 6 is accommodated below the upper cover 5.

  An exposure unit 7 composed of a laser scanning unit (LSU) is disposed below the paper discharge tray 4 above the printer body 2, and an image forming unit 8 is provided below the exposure unit 7. Yes. The image forming unit 8 is rotatably provided with a photosensitive drum 10 as an image carrier. Around the photosensitive drum 10, a charger 11, a developing device 12, a transfer roller 13, and a cleaning device are provided. The apparatus 14 is disposed along the rotation direction of the photosensitive drum 10 (see arrow X in FIG. 1).

  A paper transport path 15 is provided inside the printer main body 2. A paper feed unit 16 is provided at the upstream end of the conveyance path 15, and a transfer unit 17 configured by the photosensitive drum 10 and the transfer roller 13 is provided at a middle portion of the conveyance path 15. Is provided with a fixing device 18, and a paper discharge unit 19 is provided at the downstream end of the conveyance path 15. A reverse path 20 for double-sided printing is formed below the transport path 15.

  Next, an image forming operation of the printer 1 having such a configuration will be described.

  When the printer 1 is turned on, various parameters are initialized, and initial setting such as temperature setting of the fixing device 18 is executed. Then, when image data is input from a computer or the like connected to the printer 1 and an instruction to start printing is given, an image forming operation is executed as follows.

  First, after the surface of the photosensitive drum 10 is charged by the charger 11, exposure corresponding to the image data is performed on the photosensitive drum 10 by laser light from the exposure device 7 (see the two-dot chain line P in FIG. 1). The electrostatic latent image is formed on the surface of the photosensitive drum 10. Next, the electrostatic latent image is developed by the developing device 12 into a toner image with toner.

  On the other hand, the sheet taken out from the sheet cassette 3 by the sheet feeding unit 16 is conveyed to the transfer unit 17 in synchronization with the above-described image forming operation, and the toner image on the photosensitive drum 10 is transferred to the sheet by the transfer unit 17. Is transcribed. The sheet on which the toner image has been transferred is conveyed downstream in the conveyance path 15 and enters the fixing device 18 where the toner image is fixed on the sheet. The paper on which the toner image is fixed is discharged from the paper discharge unit 19 to the paper discharge tray 4. The toner remaining on the photosensitive drum 10 is collected by the cleaning device 14.

  Next, the fixing device 18 will be described in detail with reference to FIGS. An arrow Y appropriately attached to each drawing indicates the sheet conveyance direction. An arrow I appropriately attached to each figure indicates an inner side in the front-rear direction, and an arrow O appropriately attached to each figure indicates an outer side in the front-rear direction.

  As shown in FIGS. 2 and 3, the fixing device 18 includes a box-shaped fixing frame 21 (not shown in FIG. 3), a fixing belt 22 accommodated in the upper part of the fixing frame 21, and a fixing frame 21. A pressure roller 23 (pressure member) housed in the lower portion and disposed on the lower side (outer diameter side) of the fixing belt 22 and a heater 24 (heat source) disposed in the upper portion of the inner diameter side space of the fixing belt 22. A reflecting member 25 disposed below the heater 24 in the space on the inner diameter side of the fixing belt 22, a pressing pad 26 (pressing member) disposed on the lower end portion of the space on the inner diameter side of the fixing belt 22, and pressing A sheet member 27 wound around the pad 26, a support member 28 disposed above the pressing pad 26 in the inner diameter side space of the fixing belt 22, and a cover portion provided between the fixing belt 22 and the heater 24. 29, the regulating member 30 to be attached to the front and rear end portions of the fixing belt 22 (in FIG. 2 not shown), and a.

  As shown in FIG. 2, the fixing frame 21 includes an upper frame portion 33 and a lower frame portion 34. The upper frame portion 33 is provided with a thermocut 35 (overheat prevention device) for preventing the fixing belt 22 from overheating.

  The fixing belt 22 has a substantially cylindrical shape that is long in the front-rear direction. The fixing belt 22 is provided to be rotatable around a rotation axis A extending in the front-rear direction. That is, in the present embodiment, the front-rear direction is the rotation axis direction of the fixing belt 22.

  The fixing belt 22 has flexibility and is endless in the circumferential direction. The fixing belt 22 includes, for example, a base material layer, an elastic layer provided around the base material layer, and a release layer that covers the elastic layer. The base material layer of the fixing belt 22 is formed of a metal such as SUS, for example. The base material layer of the fixing belt 22 may be formed of a resin such as PI (polyimide). The elastic layer of the fixing belt 22 is made of, for example, silicon rubber. The release layer of the fixing belt 22 is formed of, for example, a PFA tube.

  As shown in FIG. 3, the fixing belt 22 includes a passing region R1 and non-passing regions R2 provided on both front and rear sides of the passing region R1. The passing area R1 is an area through which a maximum size sheet (for example, A3 size sheet) passes, and the non-passing area R2 is an area through which the maximum size sheet does not pass.

  As shown in FIG. 2, the pressure roller 23 has a substantially cylindrical shape that is long in the front-rear direction. The pressure roller 23 is in pressure contact with the fixing belt 22, and a fixing nip N is formed between the fixing belt 22 and the pressure roller 23. The pressure roller 23 is connected to a drive source 50 configured by a motor or the like, and is configured to rotate the pressure roller 23 by the drive source 50.

  The pressure roller 23 includes, for example, a cylindrical core member 51, an elastic layer 52 provided around the core member 51, and a release layer (not shown) that covers the elastic layer 52. Yes. The core material 51 of the pressure roller 23 is made of metal such as iron, for example. The elastic layer 52 of the pressure roller 23 is made of, for example, silicon rubber. The release layer of the pressure roller 23 is formed by, for example, a PFA tube.

  The heater 24 is constituted by, for example, a halogen heater. The heater 24 has a long shape in the front-rear direction. The heater 24 is provided at a position biased to the upper side (side away from the pressure roller 23) with respect to the rotation axis A of the fixing belt 22.

  As shown in FIG. 3, the heater 24 includes a filament 54 (heat radiating portion), a housing portion 56 that houses the filament 54 together with a halogen gas, and sealing portions 57 that are provided on both front and rear sides of the housing portion 56. It is equipped with. The filament 54 is made of tungsten, for example, and has a coil shape. The filament 54 generates heat as the heater 24 is energized and emits radiant heat. The accommodating portion 56 is made of, for example, quartz glass. Each sealing portion 57 seals both front and rear end portions of the accommodating portion 56.

  As shown in FIG. 2, the reflecting member 25 has a substantially U-shaped cross section that is convex toward the upper side (side away from the pressure roller 23). The reflection member 25 has a long shape in the front-rear direction. The reflecting member 25 is made of a metal such as bright aluminum, for example. The reflection member 25 is disposed between the heater 24 and the support member 28.

  The reflection member 25 is bent downward from the reflection plate portion 59 provided along the paper conveyance direction and the left and right ends of the reflection plate portion 59 (upstream and downstream ends in the paper conveyance direction). The guide plate part 60 is provided. The upper surface of the reflection plate portion 59 faces the heater 24.

  As shown in FIGS. 2 and 3, the pressing pad 26 has a flat plate shape that is long in the front-rear direction. That is, in this embodiment, the front-rear direction is the longitudinal direction of the pressing pad 26. The pressing pad 26 is formed of a heat resistant resin such as LCP (liquid crystal polymer), for example. The lower surface (the surface on the fixing nip N side) of the pressing pad 26 is curved in an arc along the outer peripheral surface of the pressure roller 23. The lower surface of the pressing pad 26 presses the fixing belt 22 downward (pressure roller 23 side).

  As shown in FIG. 4, a plurality of sets (for example, 9 sets) of a pair of left and right support protrusions 66 are provided on the upper surface (the surface opposite to the fixing nip N) of the pressing pad 26 at intervals in the front-rear direction. Is provided. A plurality of (for example, seven) fixed protrusions 67 are provided at the center in the left-right direction on the upper surface of the pressing pad 26 at intervals in the front-rear direction. A plurality (for example, three) of protrusions 68 are provided at the formation interval of the fixed protrusions 67 at the center in the left-right direction on the upper surface of the pressing pad 26.

  The seat member 27 has a long shape in the front-rear direction. The sheet member 27 is made of, for example, a fluorine-based resin such as PTFE, and has a smaller friction coefficient and higher slidability than the pressing pad 26.

  As shown in FIGS. 3 to 5, the sheet member 27 includes a main body portion 71 interposed between an inner peripheral surface of the fixing belt 22 and a lower surface of the pressing pad 26, and an upper side from both front and rear end portions of the main body portion 71. Longitudinal covering portions 72 extending toward the side opposite to the fixing nip N and the upper end portions (end portions opposite to the fixing nip N) of the respective longitudinal side covering portions 72 toward the inner side in the front-rear direction. A longitudinal fixing portion 73 that extends, and an upstream covering portion 74 that extends from the right end portion (upstream end portion in the paper transport direction) of the main body portion 71 toward the upper side (opposite to the fixing nip N). (Not shown in FIG. 3) and upstream fixing extending from the upper end portion (the end portion opposite to the fixing nip N) of the upstream cover portion 74 toward the left side (downstream side in the paper transport direction). Portion 75 and the left end portion of the main body portion 71 (the downstream end portion in the paper transport direction) A downstream cover 76 that extends toward the upper side (opposite to the fixing nip N), and a right side (sheet transport direction) from the upper end (end opposite to the fixing nip N) of the downstream cover 76. And a downstream side fixing portion 77 extending toward the upstream side).

  6 indicates the boundary between the long side covering portion 72 and the long side fixing portion 73, and the two dot chain line R2 in FIG. 6 indicates the boundary between the upstream side covering portion 74 and the upstream fixing portion 75. The two-dot chain line R <b> 3 in FIG. 6 indicates the boundary between the downstream covering portion 76 and the downstream fixing portion 77.

  As shown in FIG. 3, each longitudinal side covering portion 72 of the sheet member 27 covers the front and rear end faces (end faces in the longitudinal direction) of the pressing pad 26 over the entire area. Each longitudinal side covering portion 72 is in contact with both front and rear end surfaces of the pressing pad 26. However, each long side coating | coated part 72 may be spaced apart from the front-and-rear both end surfaces of the press pad 26. FIG.

  Each longitudinal side fixing portion 73 of the sheet member 27 covers both front and rear end portions of the upper surface of the pressing pad 26. As shown in FIG. 6, each long-side fixing portion 73 is provided with a pair of left and right long-side first holes 79. A longitudinal second hole 80 is provided at the center in the left-right direction of each longitudinal fixing portion 73.

  As shown in FIG. 5, the upstream side covering portion 74 of the sheet member 27 covers the entire right side surface (the upstream surface in the paper transport direction) of the pressing pad 26. The upstream side covering portion 74 is in contact with the right side surface of the pressing pad 26. However, the upstream side covering portion 74 may be separated from the right side surface of the pressing pad 26.

  The upstream side fixing portion 75 of the sheet member 27 covers the entire upper surface of the pressing pad 26. As shown in FIG. 6, the upstream fixing portion 75 is provided with a plurality of sets (for example, 9 sets) of a pair of left and right upstream first holes 81. A plurality of (for example, seven) upstream second hole portions 82 are provided in the central portion in the left-right direction of the upstream fixing portion 75 at intervals in the front-rear direction. A plurality of (for example, three) upstream third hole portions 83 are provided at the formation interval of the upstream second hole portions 82 at the central portion in the left-right direction of the upstream fixing portion 75.

  As shown in FIG. 5, the downstream side covering portion 76 of the sheet member 27 covers the left side surface (the downstream side surface in the paper transport direction) of the pressing pad 26 over the entire area. The downstream side covering portion 76 is in contact with the left side surface of the pressing pad 26. However, the downstream coating portion 76 may be separated from the left side surface of the pressing pad 26.

  The downstream fixing portion 77 of the sheet member 27 covers the entire upper surface of the pressing pad 26. As shown in FIG. 6, the downstream fixing portion 77 is provided with a plurality of sets (for example, 9 sets) of a pair of left and right downstream first hole portions 84. A plurality of (for example, seven) downstream second hole portions 85 are provided in the central portion in the left-right direction of the downstream fixing portion 77 at intervals in the front-rear direction. A plurality of (for example, three) downstream third hole portions 86 are provided at the interval between the downstream second hole portions 85 at the central portion in the left-right direction of the downstream fixing portion 77.

  As shown in FIG. 2, the support member 28 has a substantially rectangular tube shape (a cross-sectional shape) that is long in the front-rear direction. The upper part of the support member 28 is inserted between the guide plate portions 60 of the reflection member 25. The support member 28 is formed by welding the first support plate 91 and the second support plate 92 in combination. The first support plate 91 and the second support plate 92 are formed of L-shaped sheet metal made of SECC (galvanized steel plate) or the like, and are provided separately from each other.

  The first support plate 91 of the support member 28 includes a first transport direction wall portion 93 extending along the paper transport direction, and a right end portion of the first transport direction wall portion 93 (an upstream end portion in the paper transport direction). And a first cross-direction wall portion 94 that is bent substantially at a right angle and extends toward the upper side (the side opposite to the fixing nip N) along a direction orthogonal (crossing) to the sheet conveyance direction. The upper end portions of the support protrusions 66 of the pressing pad 26 are in contact with the lower surface of the first transport direction wall portion 93. As a result, the pressing pad 26 is supported by the support member 28, and deformation of the pressing pad 26 is restricted. A plurality of (for example, three) through-holes 97 are provided at the center in the left-right direction of the first transport direction wall portion 93 at intervals in the front-rear direction. The part 68 has penetrated. Thereby, the pressing pad 26 is positioned with respect to the support member 28.

  The second support plate 92 of the support member 28 includes a second transport direction wall 95 extending along the paper transport direction, and a left end of the second transport direction wall 95 (an end on the downstream side in the paper transport direction). And a second cross-direction wall 96 extending downward (fixing nip N side) along a direction orthogonal (crossing) to the sheet conveyance direction. The right end portion of the second transport direction wall portion 95 is fixed to the upper end portion of the first cross direction wall portion 94 of the first support plate 91. The lower end portion of the second cross direction wall portion 96 is fixed to the left end portion of the first transport direction wall portion 93 of the first support plate 91.

  Each cover member 29 is formed of a metal such as SUS, for example. As shown in FIG. 3, each cover member 29 is provided so that the position in the front-rear direction overlaps with the non-passing region R <b> 2 of the fixing belt 22.

  As shown in FIGS. 2 and 3, each cover member 29 is bent from the bending portion 100 and both left and right end portions (both end portions in the paper conveyance direction) of the bending portion 100, and is orthogonal to the paper conveyance direction ( And a pair of attachment portions 101 extending toward the lower side (fixing nip N side) along the crossing direction.

  The curved portion 100 of each cover member 29 is curved in an arc shape along the inner peripheral surface of the fixing belt 22, and faces the inner peripheral surface of the fixing belt 22 with an interval. A plurality of (for example, three) slits 102 are provided in the inner portion in the front-rear direction of the bending portion 100 at intervals in the circumferential direction. Each slit 102 has a long hole shape extending in the front-rear direction.

  Each attachment portion 101 of each cover member 29 is provided in a flat plate shape. The portions on the outer side in the front-rear direction at the lower part of each attachment portion 101 are attached to the left and right side surfaces of the support member 28 via screws 103. A concave groove 104 is provided in the corner on the inner side in the front-rear direction of the lower portion of each attachment portion 101.

  A notch 105 is formed at the outer end in the front-rear direction of each cover member 29 across the bending portion 100 and each attachment portion 101. The cutout portion 105 is provided so that the sealing portion 57 of the heater 24 overlaps with the position in the front-rear direction. The front-rear inner end of the notch 105 coincides with the front-rear inner end of the sealing portion 57 in the front-rear direction. An end portion on the outer side in the front-rear direction of the notch 105 (corresponding to an end portion on the outer side in the front-rear direction of each cover member 29) is located on the inner side in the front-rear direction than the end portion on the outer side in the front-rear direction of the sealing portion Yes.

  As shown in FIG. 3, each regulating member 30 is disposed on the outer side in the front-rear direction than each cover member 29. Each regulating member 30 includes a regulating piece 108 and a ring piece 109 attached to the regulating piece 108.

  The restricting piece 108 of each restricting member 30 includes a base portion 110 and an insertion portion 111 that protrudes from the inner surface in the front-rear direction of the base portion 110. The restriction piece 108 is provided with a guide hole 112 penetrating the base portion 110 and the insertion portion 111 along the front-rear direction, and the heater 24 and the support member 28 penetrate the guide hole 112. The insertion portion 111 is curved along the outer periphery of the guide hole 112 and has an arc shape (downward C-shape). The insertion portions 111 are inserted at both front and rear end portions of the fixing belt 22. Thereby, the shape of the fixing belt 22 is regulated (deformation of the fixing belt 22 is suppressed).

  The ring piece 109 of each regulating member 30 has an annular shape. The ring piece 109 is attached to the outer periphery of the insertion portion 111 of the restriction piece 108. The ring piece 109 is disposed outside the front and rear ends of the fixing belt 22 in the front-rear direction, and regulates the meandering (movement outward in the front-rear direction) of the fixing belt 22.

  In the fixing device 18 configured as described above, when the toner image is fixed on the paper, the pressure roller 23 is rotated by the drive source 50 (see arrow B in FIG. 2). When the pressure roller 23 rotates in this manner, the fixing belt 22 that is in pressure contact with the pressure roller 23 is driven to rotate in the opposite direction to the pressure roller 23 (see arrow C in FIG. 2). When the fixing belt 22 rotates in this way, the fixing belt 22 slides with respect to the sheet member 27.

  Further, when the toner image is fixed on the paper, the heater 24 is energized. When the heater 24 is energized in this way, radiant heat is radiated from the filament 54 of the heater 24. A part of the radiant heat radiated from the filament 54 of the heater 24 is directly irradiated onto the inner peripheral surface of the fixing belt 22 and absorbed. Further, another part of the radiant heat radiated from the filament 54 of the heater 24 is reflected toward the inner peripheral surface of the fixing belt 22 by the upper surface of the reflecting plate portion 59 of the reflecting member 25, and the inner peripheral surface of the fixing belt 22. To be absorbed. Due to the above operation, the fixing belt 22 is heated by the heater 24. In this state, when the paper passes through the fixing nip N, the toner image is heated and melted, and the toner image is fixed on the paper.

  In the fixing device 18 configured as described above, when the sheet member 27 is wound around the pressing pad 26, first, the lower surface of the pressing pad 26 is overlapped with the upper surface of the main body 71 of the sheet member 27. The pressing pad 26 is placed on the sheet member 27.

  Next, as indicated by an arrow Z <b> 1 in FIG. 6, the long side covering portions 72 and the long side fixing portions 73 of the sheet member 27 are folded back in the front-rear direction. Then, the respective support protrusions 66 of the pressing pad 26 are passed through the respective first longitudinal holes 79 of the respective longitudinal fixing portions 73, and the pressing pad 26 is inserted into the longitudinal second hole 80 of each longitudinal fixing portion 73. The fixed protrusion 67 is penetrated. Thereby, each long side fixing | fixed part 73 is positioned on the upper surface of the press pad 26. FIG.

  Next, as shown by an arrow Z2 in FIG. 6, the upstream side covering portion 74 and the upstream side fixing portion 75 of the sheet member 27 are folded back to the left side (downstream side in the paper transport direction). The support protrusions 66 of the pressing pad 26 are passed through the upstream first hole portions 81 of the upstream fixing portion 75, and the pressing pad 26 is inserted into the upstream second hole portions 82 of the upstream fixing portion 75. The fixing protrusions 67 are penetrated, and the protrusions 68 of the pressing pad 26 are allowed to pass through the upstream third holes 83 of the upstream fixing part 75. As a result, the upstream side fixing portion 75 is positioned on the upper surface of the pressing pad 26.

  Next, as indicated by an arrow Z3 in FIG. 6, the downstream side covering portion 76 and the downstream side fixing portion 77 of the sheet member 27 are folded back to the right side (upstream side in the sheet conveyance direction). The support protrusions 66 of the pressing pad 26 are passed through the downstream first hole portions 84 of the downstream fixing portion 77, and the pressing pad 26 is inserted into the downstream second hole portions 85 of the downstream fixing portion 77. The fixing protrusions 67 are penetrated, and the respective protrusions 68 of the pressing pad 26 are penetrated into the respective downstream third holes 86 of the downstream fixing part 77. Thereby, the downstream side fixing portion 77 is positioned on the upper surface of the pressing pad 26.

  Through the above procedure, as shown in FIG. 5, on the upper surface of the pressing pad 26, the long side fixing portion 73, the upstream side fixing portion 75, and the downstream side are sequentially formed from the lower side (fixing nip N side). The side fixing part 77 is overlaid.

  Next, as shown in FIG. 4, the fixing member 115 is fastened to each fixing protrusion 67 of the pressing pad 26. Thereby, each long side fixing | fixed part 73 of the sheet | seat member 27, the upstream side fixing | fixed part 75, and the downstream side fixing | fixed part 77 are fixed to the upper surface of the press pad 26, and winding to the press pad 26 of the sheet member 27 is completed. As the fixing member 115, for example, a CS ring or a screw including an annular ring and a plurality of projecting pieces projecting inward from the ring can be used.

  As is apparent from the above description, in this embodiment, not only the right and left sides of the pressing pad 26 (both sides in the sheet conveyance direction), but also the front and rear ends (longitudinal ends) of the pressing pad 26. Also, the sheet member 27 is wound around.

  Incidentally, in the fixing device 18 configured as described above, the temperature of the entire device rises when the toner image is fixed on the paper. Along with this, when the temperature of the sheet member 27 rises, the sheet member 27 may thermally contract. When the sheet member 27 is thermally contracted in this way, the length in the front-rear direction of the sheet member 27 becomes shorter than the length in the front-rear direction of the pressing pad 26, so On the other hand, there is a risk of sliding directly without using the sheet member 27. When such a situation occurs, the sliding load of the fixing belt 22 increases, the fixing belt 22 and the pressing pad 26 are rapidly worn, and the product life of the fixing device 18 is shortened.

  In order to avoid such a situation, the length of the sheet member 27 in the front-rear direction is made longer than the length of the press pad 26 in the front-rear direction (the sheet member 27 is left in the front-rear direction). Can be considered. However, when such a method is adopted, the surplus portion of the sheet member 27 contacts and deforms with the restricting piece 108 of the restricting member 30, and the deformed portion pushes down the fixing belt 22 to deform the fixing belt 22. There is a fear.

  Therefore, the sheet member 27 of the present embodiment extends from the main body portion 71 and extends from the longitudinal side covering portion 72 covering the front and rear end faces of the pressing pad 26 and the longitudinal side covering portion 72 and is fixed to the pressing pad 26. A longitudinal side fixing portion 73. By adopting such a configuration, it is possible to suppress thermal contraction of the sheet member 27 in the front-rear direction. Therefore, the length of the sheet member 27 in the front-rear direction is suppressed from being shorter than the length of the press pad 26 in the front-rear direction, and the front and rear end portions of the fixing belt 22 are compared with the front and rear end portions of the press pad 26. It is possible to avoid the situation of sliding directly without going through. Accordingly, the sliding load of the fixing belt 22 can be reduced, wear of the fixing belt 22 and the pressing pad 26 can be suppressed, and the product life of the fixing device 18 can be extended.

  In addition, since the sheet member 27 does not need to be left in the front-rear direction by adopting the above-described configuration, the remaining portion of the sheet member 27 presses the fixing belt 22 and the fixing belt 22 is deformed. Can be suppressed. Along with this, it becomes possible to stabilize the rotation trajectory of the fixing belt 22 and to prevent the fixing belt 22 from cracking.

  Further, the longitudinal side fixing portion 73 of the sheet member 27 is fixed to the upper surface of the pressing pad 26. By adopting such a configuration, it is possible to fix the longitudinal side fixing portion 73 using a simple configuration.

  In addition, on the upper surface of the pressing pad 26, a long side fixing portion 73, an upstream side fixing portion 75, and a downstream side fixing portion 77 are superposed in order from the bottom side. By adopting such a configuration, it becomes possible to wrap the pressing pad 26 from three directions by the sheet member 27, and the fixing strength of the sheet member 27 and the pressing pad 26 can be increased. Moreover, it can suppress that the long side fixing | fixed part 73 falls carelessly from the upper surface of the press pad 26 by arrange | positioning the long side fixing | fixed part 73 to the lowest side. Further, by disposing the upstream side fixing portion 75 below the downstream side fixing portion 77, even if a larger load is applied to the upstream side fixing portion 75 than the downstream side fixing portion 77 when the fixing belt 22 rotates. It is possible to prevent the upstream fixing portion 75 from inadvertently dropping from the upper surface of the pressing pad 26.

  In the present embodiment, the case where the longitudinal side fixing portion 73 of the sheet member 27 is fixed to the upper surface of the pressing pad 26 has been described. On the other hand, in other different embodiments, as shown in FIGS. 7 and 8, the longitudinal side fixing portion 73 of the sheet member 27 may be fixed to the lower surface of the support member 28. By adopting such a configuration, it is possible to fix the longitudinal side fixing portion 73 using a simple configuration as in the present embodiment.

  When the long side fixing portion 73 of the sheet member 27 is fixed to the lower surface of the support member 28 as described above, the long side fixing portion 73 of the sheet member 27 is supported by a fastening member 118 such as a screw as shown in FIG. You may fix to the lower surface of the member 28 independently. By adopting such a configuration, the long side fixing portion 73 can be fixed to the lower surface of the support member 28 using a simple configuration.

  Further, as shown in FIG. 8, from the right end portion (upstream end portion in the paper transport direction) to the left end portion (downstream end portion in the paper transport direction) of the long side fixing portion 73 of the sheet member 27. May be provided between the lower surface of the support member 28, and the long side fixing portion 73 may be fastened together with the clamping member 117 by a fastening member 118 such as a screw to be fixed to the lower surface of the support member 28. . By adopting such a configuration, the entire region in the left-right direction of the long side fixing portion 73 can be sandwiched between the holding member 117 and the support member 28 in a balanced manner, and displacement of the long side fixing portion 73 can be suppressed. it can.

  Note that the upstream side fixing portion 75 and the downstream side fixing portion 77 of the sheet member 27 may also be fixed to the support member 28 by a fastening member 118 such as a screw as in the case of the long side fixing portion 73 ( 7), and may be fastened together with the clamping member 117 by a fastening member 118 such as a screw and fixed to the support member 28 (see FIG. 8).

  In another different embodiment, the longitudinal fixing part 73, the upstream fixing part 75, and the downstream fixing part 77 of the sheet member 27 may be fixed to members other than the pressing pad 26 and the support member 28.

  In the present embodiment, the case where the heater 24 is constituted by a halogen heater has been described. However, in another different embodiment, a ceramic heater or the like may be used as the heater 24.

  In this embodiment, the case where the configuration of the present invention is applied to the printer 1 has been described. However, in another different embodiment, the configuration of the present invention is applied to other image forming apparatuses such as a copying machine, a facsimile machine, and a multifunction machine. It is also possible.

1 Printer (image forming device)
18 Fixing Device 22 Fixing Belt 23 Pressure Roller (Pressure Member)
26 Pressing pad (pressing member)
27 Sheet member 28 Support member 71 Body portion 72 Long-side covering portion 73 Long-side fixing portion 74 Upstream-side covering portion 75 Upstream-side fixing portion 76 Downstream-side covering portion 77 Downstream-side fixing portion 117 Nipping member N Fixing nip

Claims (6)

A fixing belt,
A pressure member that presses against the fixing belt to form a fixing nip; and
A pressing member that presses the fixing belt toward the pressing member;
A main body portion interposed between the fixing belt and the pressing member, a long side covering portion that extends from the main body portion and covers an end surface in a longitudinal direction of the pressing member, and extends from the long side covering portion, A fixing device, comprising: a sheet member having a longitudinal side fixing portion fixed to the pressing member or fixed to a member provided separately from the pressing member.   The fixing device according to claim 1, wherein the long side fixing portion is fixed to a surface of the pressing member opposite to the fixing nip. The sheet member is
An upstream covering portion that extends from the main body and covers the upstream surface of the pressing member in the conveyance direction of the recording medium;
An upstream side fixing portion that extends from the upstream side covering portion and is fixed to a surface opposite to the fixing nip of the pressing member;
A downstream covering portion that extends from the main body and covers the downstream surface of the pressing member in the conveyance direction of the recording medium;
A downstream fixing portion that extends from the downstream coating portion and is fixed to a surface of the pressing member opposite to the fixing nip;
On the surface of the pressing member opposite to the fixing nip, the long side fixing portion, the upstream side fixing portion, and the downstream side fixing portion are superposed in order from the fixing nip side. The fixing device according to claim 2. A support member for supporting the pressing member;
The fixing device according to claim 1, wherein the long side fixing portion is fixed to the support member. A clamping member provided so as to sandwich between the support member and the upstream end of the longitudinal fixing portion in the recording medium conveyance direction to the downstream end;
The fixing device according to claim 4, wherein the long-side fixing portion is fastened together with the clamping member and fixed to the support member.   An image forming apparatus comprising the fixing device according to claim 1.

Images