Fixing device and image forming apparatus

Abstract

The present application provides a fixing device and an image forming apparatus, which can prevent as much as possible the lubricant from leaking out of the belt in a pad fixing method. In the fixing section, the stationary pad (32) disposed on the inner side of the endless belt in the pad fixing method has a pressed portion (322) pressed by the press roller disposed on the outer side of the belt across the belt, and an upstream side guide (321) extending from the pressed portion (322) to the upstream side of the belt in the belt circumferential direction (arrow B), convex portions (324, 325) protruding toward the belt are provided at both end portions of the upstream side guide (321) in the belt width direction (arrow G), and the convex portions (324, 325) are shaped such that the length (W) in the belt circumferential direction gradually decreases from the end portions toward the central portion in the belt width direction.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a fixing device that fixes unfixing images on a sheet and an image forming apparatus. BACKGROUND

[0002] In an image forming apparatus such as a printer, there is an image forming apparatus provided with a fixing device of a pad fixing method that presses a fixing pad as a non-rotating body disposed on the inner peripheral side of a belt that is circularly traveling, using a pressure roller disposed on the outer peripheral side of the belt, across the belt, forms a fixing nip between the belt and the pressure roller, and fixes unfixing images on a sheet by passing the sheet through the fixing nip (for example, Patent Literatures 1 and 2).

[0003] In such a pad fixing method, since the pressing force generated between the pressure roller and the fixing pad across the belt is large, the frictional resistance between the belt and the fixing pad also becomes large, and the wear of the inner peripheral surface of the belt easily progresses. Therefore, in the past, a lubricant has been applied to the inner peripheral surface of the belt to reduce the frictional resistance between the belt and the fixing pad.

[0004] However, since the pressure of the fixing nip is quite high, the lubricant applied to the inner peripheral surface of the belt easily separates into a lubricant that can enter between the belt and the fixing pad and a lubricant that cannot enter and flows to the end portion side in the width direction of the belt (corresponding to the axial direction of the pressure roller) when passing through the fixing nip. The lubricant that flows to the end portion side eventually leaks out to the outside of the belt from the width direction end edge of the belt. In accordance with the amount of the lubricant that leaks out from the width direction end edge of the belt, the amount of the lubricant on the inner peripheral surface of the belt decreases, and the smaller the amount of the lubricant on the inner peripheral surface of the belt, the greater the frictional resistance between the belt and the fixing pad. Due to this increase in the frictional resistance, it is possible to cause the progress of the wear of the belt to accelerate, or to cause an obstacle to the smooth rotation of the belt and the pressure roller due to the rise in the torque for driving the belt, thereby causing poor conveyance of the sheet.

[0005] In Patent Literature 1, a structure is disclosed in which the end portion of the belt in the belt circumferential direction on the upstream side of the roller nip forming member (fixing pad) is formed into a comb-tooth shape over the entire region from one end to the other end in the width direction of the belt, and it is described that by causing the lubricant to enter the recessed portions (grooves) of the comb-tooth shape, it is possible to prevent leakage to the outside from the width direction edge of the belt.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT LITERATURE

[0008] Patent Literature 1: Japanese Patent Application Laid-Open No. 2017-90885

[0009] Patent Literature 2: Japanese Patent Application Laid-Open No. 2006-38990 SUMMARY

[0010] PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] In the above structure, although it is possible to accumulate the lubricant in the comb-tooth-shaped recesses formed in the nip-forming member, in a state where the lubricant is accumulated in the recesses to a certain extent, in a case where new lubricant to be applied to the inner peripheral surface of the belt in conjunction with the endless traveling of the belt attempts to enter the recesses, it is easy to cause a situation where the new lubricant does not completely enter the recesses and overflows. If the overflowed lubricant flows to the adjacent recesses in the belt width direction, the recesses overflow, and the lubricant continues to flow to the adjacent recesses, the lubricant gradually flows to the end portion side in the belt width direction, and as a result, it is possible to cause a situation where the lubricant leaks out to the outside from the belt edge end in the belt width direction.

[0012] The present disclosure was completed in view of the above problems, and aims to provide a fixing device and an image forming apparatus which can prevent the lubricant from leaking out to the outside as much as possible in a pad fixing method.

[0013] Means for solving the problem

[0014] To achieve the above object, the fixing device of the present disclosure forms a fixing nip by pressing the belt on which the lubricant is applied to the inner peripheral surface with a press roller disposed on the outer peripheral side of the endless belt, makes the sheet pass through the fixing nip, and fixes the unfixed image on the sheet, and is characterized by comprising: a non-rotating body pad having a pressed portion pressed by the press roller on the inner peripheral side of the belt with the belt interposed therebetween, and a guide provided at a position on the upstream side of the pressed portion in the belt circumferential direction to guide the belt toward the fixing nip; and a pressure applying portion applying a pressure that gradually decreases from the end portion side toward the center side in the belt width direction between the end portion of the belt and the guide at a position immediately adjacent to the fixing nip on the upstream side in the belt circumferential direction.

[0015] In addition, it can also be that the guide has a convex surface portion protruding toward the inner peripheral surface of the belt at a position corresponding to the end portion of the belt, and the pressure applying portion is the convex surface portion, and the convex surface portion is formed in a tapered shape in which the length of the convex surface portion in the belt circumferential direction gradually decreases from the end portion side toward the center side in the belt width direction, so as to apply the gradually decreasing pressure.

[0016] In addition, it can also be that the guide has a convex surface portion protruding toward the inner peripheral surface of the belt at a position corresponding to the end portion of the belt, and the pressure applying portion is the convex surface portion, and the convex surface portion is formed in a tapered shape in which the length of the convex surface portion in the belt circumferential direction gradually decreases from the end portion side toward the center side in the belt width direction, so as to apply the gradually decreasing pressure.

[0017] Further, it can be that the end portion of the convex surface portion on the central side in the belt width direction extends to a position closer to the axial center of the press roller than the axial end portion of the press roller in the belt width direction.

[0018] Further, it can be that the tapered shape is formed by a first side parallel to the belt width direction and a second side inclined with respect to the first side at a position upstream in the belt surrounding direction from the first side.

[0019] Further, it can be that the end portion of the convex surface portion on the central side in the belt width direction extends to a position closer to the axial center of the press roller than the axial end portion of the press roller in the belt width direction.

[0020] Further, it can be that the pressure applying portion is a press roller of a circular truncated cone shape that presses the end portion of the belt from the outer peripheral side of the belt against the guide at the immediately adjacent position, the press roller being disposed in a posture with an end portion of a large diameter directed toward the end portion side in the belt width direction and an end portion of a small diameter directed toward the central side in the belt width direction.

[0021] Further, it can be that the axial end portion of the press roller is closer to the central side in the belt width direction of the belt than the end edge of the belt in the belt width direction.

[0022] Further, it can be that the entire region of the belt from one end to the other end in the belt width direction is in contact with the guide at the immediately adjacent position.

[0023] Further, it can be that a low-friction sheet is provided between the belt and the pad.

[0024] Here, it can be that the entire region of the belt from one end to the other end in the belt width direction is in contact with the guide via the low-friction sheet at the immediately adjacent position.

[0025] Further, it can be that a lubricant supply member that supplies a lubricant to the inner peripheral surface of the belt is provided.

[0026] Further, the pressure applied by the pressure applying portion can be in a range of 1 to 200 kPa, and further, the height of the convex surface portion can be in a range of 0.1 to 0.5 mm.

[0027] An image forming apparatus of the present disclosure includes a fixing portion that fixes an unfixed image formed on a recording sheet being conveyed, the image forming apparatus being characterized by including the fixing device described above as the fixing portion.

[0028] Effects of the Invention

[0029] According to the above structure, when the lubricant applied to the inner circumferential surface of the belt along with the circumferential travel of the belt reaches the guide, the pressure generated between the belt and the guide is high near the end edge of the belt in the belt width direction, and therefore, even if the lubricant is intended to flow into the space between the belt and the guide, only a small amount of the lubricant enters, and the remaining portion easily flows into the central portion where the pressure is lower than the end edge of the belt. That is, by applying the pressure as described above, the lubricant near the end edge of the belt easily flows toward the center, and the lubricant can be prevented from leaking out from the end edge of the belt. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a schematic view showing the overall structure of the printer.

[0031] Figure 2 is a cross-sectional view showing the schematic structure of the fixing portion of the printer.

[0032] Figure 3 is a schematic exploded perspective view of the support member, the fixing pad, the guide member, the sliding member, and the lubricant supply member in the fixing portion.

[0033] Figure 4 is a schematic view showing the structure of the fixing pad.

[0034] Figure 5 is a schematic perspective view of the fixing pad as viewed from the direction indicated by an arrow E of Figure 4 .

[0035] Figure 6 is a schematic plan view as viewed from above the belt, the fixing pad, and the pressure roller.

[0036] Figure 7 is a schematic side view as viewed from the belt and the fixing pad in a state where the pressure roller is viewed in the direction of an arrow Xa of Figure 2 .

[0037] Figure 8 is a schematic view showing the magnitude relationship of the pressure generated between the belt and the fixing pad at three positions different in the belt width direction in the embodiment.

[0038] Figure 9 is a graph showing a graph of the pressure distribution between the upstream-side guide and the belt.

[0039] Figure 10 is a schematic view showing the magnitude relationship of the pressure generated between the belt and the fixing pad at three positions different in the belt width direction in the comparative example.

[0040] Figure 11 (a) is a schematic view for explaining how the lubricant flows along with the circumferential travel of the belt in the embodiment, and (b) is a schematic view for explaining the flow of the lubricant in the comparative example.

[0041] Figure 12 Fig. 1 is a view showing the structure of a convex portion of a modification example.

[0042] Figure 13 Figs. (a) and (b) are views showing the structure of another convex portion of a modification example.

[0043] Figure 14 Fig. 1 is a view showing the structure of a convex portion of a modification example.

[0044] Figure 15 Figs. (a) and (b) are views showing the structure of a pressure applying portion of a modification example.

[0045] BRIEF DESCRIPTION OF THE DRAWINGS

[0046] 1 printer

[0047] 3 fixing nip

[0048] 30 fixing portion

[0049] 31 belt

[0050] 32 stationary pad

[0051] 34 support member

[0052] 35 heating roller

[0053] 36 heater

[0054] 37 slide member

[0055] 38 lubricant supply member

[0056] 39 pressure roller

[0057] 111, 112 conical press roller (pressure applying portion)

[0058] 241 first edge

[0059] 242 second edge

[0060] 243 base end of the convex portion on the belt width direction end portion side

[0061] 244, 254 front end of the convex portion on the belt width direction central side

[0062] 311 inner peripheral surface of the belt

[0063] 320 guide surface

[0064] 318 one end (end edge) of the belt in the belt width direction

[0065] 319 the other end (end edge) of the belt in the belt width direction

[0066] 321 upstream side guide of the fixing pad

[0067] 324, 325, 424, 524 convex portion (pressure application portion) in the upstream side guide

[0068] 326 region other than the convex portion in the guide surface of the upstream side guide

[0069] 333 position immediately adjacent to the fixing nip

[0070] 398, 399 end edge in the belt width direction of the nip formation region (axial end portion of the pressure roller)

[0071] B belt circumferential direction

[0072] G belt width direction

[0073] J lubricant

[0074] P pressure between the belt and the upstream side guide

[0075] S recording sheet

[0076] W length (width) of the convex portion in the belt circumferential direction DETAILED DESCRIPTION

[0077] Hereinafter, with regard to the fixing device and the image forming apparatus of the embodiment of the present disclosure, a serial type color printer (hereinafter, simply referred to as "printer") is exemplified, and the description is made with reference to the accompanying drawings.

[0078] (1) Overall structure of the printer Figure 1 is a schematic cross-sectional view showing the overall structure of the printer 1.

[0079] As shown in the drawing, the printer 1 is provided with an image forming section 10, a paper feeding section 20, and a fixing section 30.

[0080] The image forming section 10 is provided with image forming units 11Y, 11M, 11C, 11K corresponding to each color of Y (yellow), M (magenta), C (cyan), and K (black), and an intermediate transfer belt 13.

[0081] The image forming unit 11K is provided with a photosensitive drum 12, a charging section 16, an exposure section 17, a developing section 18, and a cleaner 19 arranged along the circumferential direction of the photosensitive drum 12.

[0082] The exposure section 17 is provided with a light emitting element such as a laser diode and a lens, and performs exposure scanning on the photosensitive drum 12 by modulating laser light according to a drive signal from a control section not shown.

[0083] The photosensitive drum 12 is rotationally driven by a drive source not shown, and after the surface is cleaned of residual toner by the cleaner 19 before receiving the exposure described above, is uniformly charged by the charging section 16. If exposure based on the laser described above is received in this uniformly charged state, an electrostatic latent image is formed on the surface of the photosensitive drum 12.

[0084] The electrostatic latent image formed on the photosensitive drum 12 is developed by the developing section 18, and thereby a toner image of K color is formed on the surface of the photosensitive drum 12. This toner of K color is once transferred from the photosensitive drum 12 to the intermediate transfer belt 13 by the primary transfer roller 14 disposed on the side opposite the photosensitive drum 12 via the intermediate transfer belt 13 that travels in a loop.

[0085] The image forming units 11Y, 11M, 11C are also of the same structure as the image forming unit 11K, and for each image forming unit, a toner image of the corresponding color (Y, M, or C color) is formed on the photosensitive drum 12 and is once transferred to the intermediate transfer belt 13 by the primary transfer roller 14.

[0086] The image forming operations in the respective image forming units 11Y to 11K are executed at timings staggered in a manner that the toner images are once transferred to the same position on the intermediate transfer belt 13. Thereby, a color toner image of Y to K colors is formed on the intermediate transfer belt 13.

[0087] The paper feed section 20 is provided with a paper feed cassette 21 that houses the recording sheet S, a draw-out roller 22, a conveyance roller 23, and a timing roller 24.

[0088] The draw-out roller 22 contacts the uppermost recording sheet S of the paper feed cassette 21 and draws it out toward the conveyance path 25. The conveyance roller 23 conveys the recording sheet S drawn out by the draw-out roller 22 toward the timing roller 24. The timing roller 24 feeds the recording sheet S to the downstream side at a timing designated from a control section not shown.

[0089] The color toner image that is once transferred to the intermediate transfer belt 13 in the image forming section 10 is moved to the secondary transfer position 15a that is the contact position of the intermediate transfer belt 13 and the secondary transfer roller 15 by the loop travel of the intermediate transfer belt 13.

[0090] The recording sheet S is conveyed on the conveyance path 25 from the timing roller 24 of the paper feed section 20 in correspondence with the timing of movement of the toner image on the loop-traveling intermediate transfer belt 13, and when the recording sheet S passes through the secondary transfer position 15a, the color toner image on the intermediate transfer belt 13 is secondary transferred to the recording sheet S by the secondary transfer roller 15. The recording sheet S that has passed through the secondary transfer position 15a is conveyed to the fixing section 30.

[0091] The fixing section 30 passes the recording sheet S conveyed from the secondary transfer roller 15 in the direction indicated by the arrow D (sheet conveying direction) through the fixing nip 3, and fixes the color toner image (unfixed image) on the recording sheet S to the recording sheet S by heating and pressing.

[0092] The recording sheet S that has passed through the fixing section 30 is discharged to the outside of the apparatus by the discharge roller 26, and is housed in the paper discharge tray 27.

[0093] (2) Structure of fixing section Figure 2 is a schematic cross-sectional view that shows the structure of the fixing section 30. Here, in the drawing, the X-axis direction, the Y-axis direction indicate the left-right direction, the up-down direction when the printer 1 is viewed from the front side, and the Z-axis direction is a direction orthogonal to both the X-axis and the Y-axis, and corresponds to the depth direction of the printer 1. The drawing is a cross-sectional view in the case where the fixing section 30 is cut with an X-Y plane orthogonal to the Z-axis.

[0094] As shown in the drawing, the fixing section 30 is provided with: an endless belt 31; a stationary pad 32 that contacts the inner circumferential surface 311 of the belt 31 via a sliding member 37; a guide member 33 that contacts the inner circumferential surface 311 of the belt 31 after the belt 31 has just passed through the fixing nip 3, and guides the belt 31; a support member 34 that supports the stationary pad 32 and the guide member 33; a heating roller 35 that heats the belt 31; a heater 36 that imparts heat to the heating roller 35; a lubricant supply member 38 that applies a lubricant to the inner circumferential surface 311 of the belt 31; and a pressure roller 39 that presses the outer circumferential surface 312 of the belt 31.

[0095] The belt 31 is wound around the stationary pad 32, the heating roller 35, and the guide member 33, and the heating roller 35 is urged in a direction away from the stationary pad 32 by an elastic member such as a spring, not shown, so that a tension acts.

[0096] The belt 31 is made by sequentially laminating an elastic layer made of a material such as silicone rubber or fluorine rubber that has high heat resistance, and a fluorine tube and a fluorine coating layer that impart mold releasability, on a base layer made of polyimide, SUS (stainless steel), Ni (nickel) electroforming, or the like. The outer diameter of the belt 31 is arbitrary, but is preferably in the range of 10 to 100 mm. The thickness of the base layer is preferably in the range of, for example, 5 to 100 μm, the thickness of the elastic layer is preferably in the range of, for example, 10 to 300 μm, and the thickness of the mold releasable layer is preferably in the range of, for example, 5 to 100 μm. The inner diameter of the belt 31 is the same size at any position in the Z-axis direction (belt width direction).

[0097] The pressurizing roller 39 is formed by sequentially stacking an elastic layer 39b made of a material having high heat resistance such as silicone rubber or fluorine rubber, and a release layer 39c made of a fluorine tube or a fluorine coating layer, on a solid core shaft 39a made of aluminum, iron or the like. The outer diameter of the pressurizing roller 39 is arbitrary, but is preferably in the range of 20 to 100 mm. The core shaft 39a may, for example, also be a pipe-shaped core shaft having a thickness in the range of 0.1 to 10 mm, or a core shaft having a non-circular cross-sectional shape such as a three-arrow shape. In addition, the thickness of the elastic layer 39b is preferably in the range of 1 to 20 mm, for example, and the thickness of the release layer 39c is preferably in the range of 5 to 100 μm, for example.

[0098] The axis 395 of the rotation shaft of the pressurizing roller 39 is parallel to the Z-axis, and the axial both end portions of the pressurizing roller 39 are rotatably supported by a fixed frame (not shown: hereinafter referred to as "frame") constituting a frame of the fixing section 30, and the outer peripheral surface 391 of the pressurizing roller 39 is pressed against the belt 31 by the force of an elastic member (not shown) such as a spring.

[0099] The pressurizing roller 39 is rotationally driven in the direction indicated by the arrow A at a predetermined rotational speed by the rotational driving force of the fixing conveyance motor 40. The belt 31 is driven to rotate (travel) in the direction indicated by the arrow B (belt winding direction) by the rotation of the pressurizing roller 39.

[0100] The fixing pad 32 and the guide member 33 are arranged in the belt winding direction, are non-rotating bodies that do not rotate together with the winding belt 31, and have a slightly longer length in the Z-axis direction than the length in the Z-axis direction (belt width) of the belt 31.

[0101] The fixing pad 32 is arranged on the inner peripheral side of the belt 31 at a position on the side opposite to the pressurizing roller 39 located on the outer side of the belt 31 with the belt 31 interposed therebetween, and the upstream side guide 321, the pressed portion 322, and the downstream side guide 323 are arranged adjacent to each other in the belt winding direction in this order.

[0102] The upstream side guide 321 is arranged at a position on the upstream side in the belt winding direction from the pressed portion 322, and guides the belt portion 315 in the belt 31 on the upstream side in the belt winding direction from the fixing nip 3 and before entering the fixing nip 3 to the fixing nip 3. The upstream side guide 321 is arranged at a position on the upstream side in the belt winding direction from the fixing nip 3, and does not contribute to the formation of the fixing nip 3.

[0103] Here, the fixing pad 32 is a single molded product, and the upstream side guide 321 is arranged extending from the pressed portion 322 to the upstream side in the belt winding direction, but if possible, a fixing pad 32 in which the upstream side guide 321 and the pressed portion 322 are formed by different members can also be used.

[0104] In the upstream-side guide 321, pressure-applying portions 324, 325 that apply pressure that gradually decreases as it moves from the end edge of the width direction of the belt 31 (corresponding to the Z-axis direction) toward the center are provided between the belt 31 and the pressure-applying portions 324, 325 Figure 5 ). The pressure-applying portions 324, 325 will be described later. Hereinafter, the width direction of the belt 31 will be referred to as the belt width direction.

[0105] The pressed portion 322 receives the pressing force from the pressure roller 39 via the sliding member 37 present between the inner peripheral surface 311 of the belt 31. The pressure roller 39 located on the outer peripheral side of the belt 31 presses the pressed portion 322 of the fixing pad 32 located on the inner peripheral side of the belt 31 via the belt 31, whereby the outer peripheral surface 391 of the pressure roller 39 is pressure-bonded to the outer peripheral surface 312 of the belt 31, and a fixing nip 3 is formed between the belt 31 and the pressure roller 39. The upstream end in the belt-encircling direction of the fixing nip 3 is 3b, and the downstream end in the belt-encircling direction is 3c.

[0106] The downstream-side guide 323 guides the belt portion 317 of the belt 31 that has just passed through the fixing nip 3 to the guide member 33 on the downstream side in the belt-encircling direction thereof.

[0107] The fixing pad 32 uses, for example, a resin such as polyphenylene sulfide, polyimide, liquid crystal polymer, or the like, and a material having excellent heat resistance is preferred. In addition, it can also be composed of a metal such as aluminum, iron, or the like, or a ceramic, and a material in which these are compounded with silicone rubber, fluororubber, or the like can also be used.

[0108] The guide member 33 is located on the downstream side in the belt-encircling direction of the fixing pad 32 and on the upstream side in the belt-encircling direction of the heating roller 35, is disposed at a position closer to the fixing pad 32 than the heating roller 35, that is, at a position in the vicinity of the fixing pad 32, via the space 45, and guides the belt portion 317 of the belt 31 guided by the downstream-side guide 323 further to the downstream side in the belt-encircling direction. Note that the guide member 33 is present at a position deviated from the fixing nip 3 in the belt-encircling direction and does not contribute to the formation of the fixing nip 3. The material of the guide member 33 can be the same as or different from that of the fixing pad 32.

[0109] The support member 34 is a member made of a metal such as aluminum, iron, SUS, or the like, and has a cross-sectional shape of a Japanese character "コ" (Hiragana "ko"). The fixing pad 32, the guide member 33, and the sliding member 37 are fixed and supported by the support member 34.

[0110] Figure 3 is an exploded perspective view of the support member 34, the fixing pad 32, the guide member 33, the sliding member 37, and the lubricant supply member 38, and the belt 31 is not shown.

[0111] As shown in the figure, the support member 34 is long in the Z-axis direction, and both end portions in the length direction thereof are fixedly supported to the frame, and has a central portion 341 in the up-down direction, an upper horizontal portion 342 extending to the left direction from the upper end of the central portion 341, and a lower horizontal portion 343 extending to the left direction from the lower end of the central portion 341.

[0112] The fixing pad 32 is fixedly supported to the right side surface 345 of the central portion 341 of the support member 34 through the sliding member 37 by adhesion or the like, and the guide member 33 is fixedly supported to the upper surface 346 of the upper horizontal portion 342 of the support member 34 by adhesion or the like.

[0113] The lubricant supply member 38 is long in the Z-axis direction, and is embedded in a groove portion 339 provided to the belt guide surface 335 of the guide member 33 in the Z-axis direction, and has a length substantially the same as the belt width of the belt 31. The lubricant supply member 38 contains a lubricant J, and an upper surface 381 thereof is in contact with the inner peripheral surface 311 of the belt 31 to apply the lubricant J to the inner peripheral surface 311 of the belt 31. In addition, the lubricant supply member 38 also has a function of collecting and holding the lubricant J applied to the inner peripheral surface 311 of the belt 31 from the belt 31 running around, and reapplying the held lubricant J to the inner peripheral surface 311 of the belt 31.

[0114] The lubricant supply member 38 uses a material suitable for holding the lubricant J, such as a fibrous material such as aramid fiber, fluorine fiber, or a porous material such as silicon sponge. Here, a material capable of elastic deformation is used, but is not limited thereto. As the lubricant J, a lubricant of a silicon or fluorine type having high heat resistance is preferable, but other materials such as fluorine grease can also be used. By using a lubricant having high viscosity and containing a solid component, the lubricant is easily left between the belt 31 and the sliding member 37 at the fixing nip 3, and wear can be suppressed for a longer period of time.

[0115] The sliding member 37 is a low-friction sheet, and here, is wound around the fixing pad 32 in a manner of surrounding the periphery of the fixing pad 32 by about 1 turn, and for example, a sheet having a structure in which a sliding surface (outer surface) using glass cloth as a base material is covered with a fluorine resin is used.

[0116] A minute concavo-convex is formed on a surface 371 of the sliding member 37 on the belt 31 side, and by the concavo-convex, the contact area with the belt 31 is reduced, and the frictional force is reduced. The size of the concavo-convex is arbitrary, but from the viewpoint of the function of holding the lubricant J and image unevenness caused by the hardness of the concavo-convex, the surface roughness Ra of the surface 371 is preferably in the range of 1 to 50 μm, for example. The sliding member 37 is a member composed of a material capable of reducing the sliding resistance with the belt 31, and for example, a woven fabric of fluorine fiber, a fluorine resin sheet, or a glass coating can also be used.

[0117] By interposing the sliding member 37 between the belt 31 and the fixing pad 32 and supplying the lubricant J to the face 371 of the sliding member 37 via the belt 31 by the lubricant supplying member 38 applied to the inner peripheral face 311 of the belt 31, the sliding resistance when the belt 31 passes through the fixing nip 3 is reduced, the stability of the endless travel of the belt 31 is ensured for a long period, and the wear of the belt 31 is also reduced.

[0118] Returning to Figure 2 The heating roller 35 is composed of a cylindrical metal such as aluminum or SUS, the axis 359 of the rotating shaft thereof is parallel to the Z-axis direction, and the axial both end portions of the heating roller 35 are rotatably supported to the frame. The outer diameter of the heating roller 35 is arbitrary, but is preferably in the range of 10 to 100 mm, and the thickness is preferably in the range of 0.1 to 5 mm.

[0119] The heater 36 as a heat source is a halogen heater in a long strip along the axial direction of the heating roller 35, is inserted into the inner space of the cylindrical heating roller 35, and imparts heat generated by the power supply from a not-shown power source to the heating roller 35. In order to efficiently perform heat transfer from the halogen heater to the heating roller 35, the inner peripheral face of the heating roller 35 is preferably black.

[0120] Note that the method of heating the belt 31 by the heat of the halogen heater is not limited. For example, the heater 36 can be an infrared heater, an electric heater, or the like. Also, any structure in which the belt 31 is heated can be used, for example, a resistance heating method in which the belt 31 is formed of a resistance heating body that generates heat by the power supply can be used. In this structure, the energization of the resistance heating body becomes the heating of the belt 31. Also, a so-called induction heating (IH) method in which the belt 31 is heated by electromagnetic induction can be used.

[0121] In the above structure, when the pressure roller 39 is rotationally driven in the arrow A direction, the belt 31 is driven to travel in the arrow B direction by the rotational driving force. This travel direction becomes the belt winding direction. When the heater 36 is energized in the rotational driving of the pressure roller 39, the heat emitted from the heater 36 is transferred from the heating roller 35 to the belt 31, and reaches the fixing nip 3 by the endless travel of the belt 31. Thus, the heat of the heater 36 is supplied to the fixing nip 3.

[0122] In the present embodiment, although not shown, a sensor that detects the surface temperature of the belt 31 and transmits the detection result to a not-shown control section is provided in the fixing section 30. The control section performs temperature adjustment control that switches the lighting and the extinguishing of the heater 36 based on the detected temperature of the sensor, so that the temperature of the fixing nip 3 is maintained at a fixing temperature (for example, 170°C) required for fixing.

[0123] By this temperature adjustment control, the temperature of the fixing nip 3 is stabilized at the fixing temperature, and when the recording sheet S conveyed in the conveyance path 25 passes through the fixing nip 3, the unfixed image on the recording sheet S is heated and fused and is pressed to be fixed on the recording sheet S.

[0124] (3) Structure of the fixing pad Figure 4 is a schematic view showing the structure of the fixing pad 32, Figure 5 is a schematic perspective view when the upstream side guide 321 of the fixing pad 32 is viewed from the direction indicated by the arrow E of Figure 4 , and Figure 6 is a schematic plan view when the belt 31, the fixing pad 32, and the pressure roller 39 are viewed from above, and the illustration of components other than the belt 31, the fixing pad 32, and the pressure roller 39 is omitted.

[0125] As shown in Figure 4 and Figure 5 , the upstream side guide 321 of the fixing pad 32 has a guide surface 320 that contacts the inner circumferential surface 311 of the belt 31 across the sliding member 37, and at the end portion on the downstream side in the belt winding direction (arrow B direction) and both end portions in the belt width direction (arrow G direction), convex surface portions (pressure application portions) 324, 325 that protrude by a prescribed amount H toward the inner circumferential surface 311 of the belt 31 are provided.

[0126] Here, the upstream side guide 321 and the pressed portion 322 for forming the fixing nip 3 are adjacent in the belt winding direction in this order, and therefore the positions of the convex surface portions 324, 325 provided to the upstream side guide 321 in the belt winding direction can be said to be positions of the region just before reaching the fixing nip 3 (reference numeral 333 of Figure 4 , Figure 7 ). Hereinafter, this position will be referred to as the immediately adjacent position of the fixing nip 3.

[0127] If a portion (dotted line) 326 that is sandwiched between the convex surface portions 324, 325 on both end sides in the belt width direction and is in the center in the belt width direction is taken as a central portion, the central portion 326 becomes a region other than the convex surface portions 324, 325 on the guide surface 320 of the upstream side guide 321, and becomes a concave relationship with respect to the convex surface portions 324, 325.

[0128] Therefore, the guide surface 320 of the convex portions 324 and 325 is said to be higher (in the thickness direction) than the guide surface 320 of the central portion 326 by a predetermined amount H in the direction approaching the inner peripheral surface 311 of the belt 31. The predetermined amount H is a value in the range of 0.1 to 0.5 mm. The wall thickness of the convex portions 324 and 325 is thicker than that of the central portion 326, so that the height of the convex portions 324 and 325 is higher than that of the central portion 326 by the predetermined amount H. It should be noted that, depending on the device structure, there may be cases where the predetermined amount H is set to a value within a different range than described above.

[0129] like Figure 5 As shown, the convex portion 324 is a right-angled triangle when viewed from above, having a side 241 (first side) parallel to the width direction of the belt, a hypotenuse 242 (second side), and a side 243 along the belt wrapping direction. The angle between side 241 and side 243 is 90°, and the angle θ between side 241 and hypotenuse 242 is 30°.

[0130] The convex portion 324 is formed with its edge 243 facing the end side in the width direction and its vertex 244, at a 30° angle, facing the center side in the width direction. That is, the edge 243 becomes the outermost end in the width direction (the base end of the end side in the width direction), and the vertex 244 becomes the side furthest from the end in the width direction, i.e., the end side of the center side in the width direction. The edge 243 is referred to as the base end of the convex portion 324 in the width direction, and the vertex 244 is referred to as the front end of the convex portion 324 in the width direction.

[0131] The length (width) W of the convex portion 324 in the band circumferential direction is equivalent to the interval between the side 241 and the inclined side 242, and becomes a tapered shape that gradually decreases from the base end 243 in the band width direction, which is the end side in the band width direction, toward the front end 244 in the band width direction, which is the central part side in the band width direction.

[0132] The convex portion 325 has essentially the same shape and height as the convex portion 324, and is a right-angled triangle when viewed from above, such as... Figure 5 As shown, the tapered shape is formed by the length W of the tape in the wrapping direction gradually decreasing from the base end 253 in the tape width direction toward the front end 254 in the tape width direction.

[0133] The positional relationship of the convex portions 324 and 325, the belt 31, and the pressure roller 39 in the belt width direction is as follows: Figure 6 As shown. That is, on one end side in the belt width direction (the left end side of the figure), the belt width direction base end 243 of the convex part 324, the belt width direction end (end edge) 318 of the belt 31, the axial end 398 of the pressure roller 39, and the belt width direction front end 244 of the convex part 324 are arranged in this order in the direction from one end in the belt width direction toward the center (arrow Z direction).

[0134] Similarly, on the other end side in the belt width direction (the right end side in the figure), the base end 253 in the belt width direction of the convex surface portion 325, the other end (edge) 319 in the belt width direction of the belt 31, the other end portion 399 in the axial direction of the pressure roller 39, and the front end 254 in the belt width direction of the convex surface portion 325 are arranged in this order in the direction from the other end in the belt width direction toward the center (the opposite direction of the arrow Z).

[0135] Here, the region 3d where the pressure roller 39 contacts the belt 31 represents the nip forming region of the fixing nip 3, and the end portions 398 and 399 in the axial direction of the pressure roller 39 are equal to the edges in the belt width direction of the nip forming region 3d.

[0136] According to Figure 6 , the base ends 243 and 253 in the belt width direction of the convex surface portions 324 and 325 protrude outward from the belt 31 in the belt width direction.

[0137] In addition, the front end 244 in the belt width direction of the convex surface portion 324 extends to a position closer to the center in the nip forming region 3d (the axial center of the pressure roller 39) than one edge (one end portion of the pressure roller 39) 398 in the belt width direction of the nip forming region 3d.

[0138] Similarly, the front end 254 in the belt width direction of the convex surface portion 325 extends to a position closer to the center in the nip forming region 3d (the axial center of the pressure roller 39) than the other edge (the other end portion of the pressure roller 39) 399 in the belt width direction of the nip forming region 3d.

[0139] Figure 7 is a schematic side view when observing the belt 31 and the fixing pad 32 in a state where the pressure roller 39 is viewed in perspective from the arrow Xa direction. The rectangular region shown by the solid line 3d represents the nip forming region. Figure 2 As shown in

[0140] , when the belt width direction length of the nip forming region 3d is set as L1, the belt width direction length of the belt 31 is set as L2, and the belt width direction length of the fixing pad 32 is set as L3, there is a size relationship of L1 < L2 < L3. The belt width direction length L1 of the nip forming region 3d is equal to the axial length of the pressure roller 39. Figure 7 The size relationship of the pressures generated between the belt 31 and the fixing pad 32 at three different positions α, β, and γ in the belt width direction is shown in the schematic diagram of

[0141] In Figure 8 when the pressure roller 39 presses the fixing pad 32 with the standard pressure during printing隔着 the belt 31. This pressure is the value obtained by dividing the pressing force acting in the direction perpendicular to the inner peripheral surface 311 of the belt 31 by the unit area.

[0142] Here, the position a is a position outside the nip formation region 3d in the tape width direction.

[0143] The position β is a position within the region between the one end 398 of the nip formation region 3d and the tape width direction front end 244 of the convex portion 324, or a position within the region between the other end 399 of the nip formation region 3d and the tape width direction front end 254 of the convex portion 325, in the nip formation region 3d in the tape width direction.

[0144] The position γ is a position within the nip formation region 3d in the tape width direction that is more central than the tape width direction front ends 244, 254 of the convex portions 324, 325.

[0145] As shown in FIG. 6, at the position a, the pressure P between the tape 31 and the upstream side guide 321 is Pa, and the pressure P between the pressed portion 322 and the tape 31 is Pe. Figure 8

[0146] The position a is offset from the nip formation region 3d, and therefore the pressures Pa, Pe are not pressing forces generated by the press rollers 39, but are generated by the tension acting on the tape 31 stretched by the stationary pad 32, the heating roller 35, and the guide member 33.

[0147] As described above, the inner diameter of the tape 31 is the same at any position in the tape width direction. Therefore, if the portion in which the convex portions 324, 325 are provided on the upstream side guide 321 (tape width direction end portion: position a) is compared with the portion in which the convex portions 324, 325 are not provided (tape width direction central portion: position γ), the force with which the convex portions 324, 325 press the tape 31 from the inner peripheral surface side to the outer peripheral surface side increases by an amount corresponding to the thickness of the convex portions 324, 325 at the end portion in which the convex portions 324, 325 are provided, as compared with the central portion in which the convex portions 324, 325 are not provided. In correspondence with the amount of increase in this pressing force, the tension acting on the tape 31 as a reaction to this increases as compared with the central portion in which the convex portions 324, 325 are not provided, and in correspondence with the amount of increase in this tension, the pressure P appears as the magnitude Pa.

[0148] The pressed portion 322 is a concave curved surface, and is different from the guide 321, which is a convex curved surface, in that the pressed portion 322 is not provided with the convex portions 324, 325. Therefore, the pressure Pe is much smaller than the pressure Pa of the guide 321.

[0149] ​At the position β, the pressure P is Pb (< Pa), and the pressure P between the presser 322 and the belt 31 is Pc (> Pb). Since the position β is within the nip formation region 3d, the pressure Pc (nip pressure) becomes considerably large due to the pressing force of the pressure roller 39. In this drawing, the size Pc of the pressure P is shown as about twice the size of Pb for the sake of easy illustration, but in reality, it is about 10 times or more. Note that if the nip pressure is excessively high, the lubricant J sometimes cannot reach between the belt 31 and the fixing pad 32 at all, and therefore, the nip pressure appropriate for fixing is set in advance within a range in which the required amount of lubricant J can reach between the belt 31 and the fixing pad 32 through experiments or the like.

[0150] On the other hand, the pressure Pb at the position β is smaller than the pressure Pa at the position α. This is because the length Wb of the convex portions 324, 325 in the belt-circulating direction at the position β is shorter than the length Wa of the convex portions 324, 325 in the belt-circulating direction at the position α. That is, at the position β as well as at the position α, the pressing force of the pressure roller 39 does not act in the immediate vicinity of the fixing nip 3, and therefore, the size of the tension acting on the belt 31 has an influence on the size of the pressure Pb. The thickness of the convex portions 324, 325 is the same at any position in the belt width direction as described above, but the shorter the length W in the belt-circulating direction, the shorter the length of the region in the belt-circulating direction in which the belt 31 is pressed from the inner peripheral surface side to the outer peripheral surface side, and accordingly, the force with which the convex portions 324, 325 press the belt 31 from the inner peripheral surface side to the outer peripheral surface side decreases. In correspondence with the amount of decrease in the pressing force, the tension acting on the belt 31 decreases, and in correspondence with the amount of decrease in the tension, the pressure Pb at the position β is smaller than the pressure Pa at the position α.

[0151] Although the pressure P is not shown between the position α and the position β, as shown in Figure 7 , the convex portions 324, 325 are in the shape of a right triangle in plan view, and the convex portions 324, 325 are formed in a shape in which the length W in the belt-circulating direction of the convex portions 324, 325 gradually decreases as it goes from the end portion side toward the central side in the belt width direction. Due to this gradual decrease in the length W of the convex portions 324, 325, the pressure P between the upstream-side guide 321 and the belt 31 becomes a pressure distribution that gradually decreases as it goes from the end edge of the belt 31 in the belt width direction toward the center (from the end portion side toward the central side in the belt width direction), as shown by the solid line graph of Figure 9 . This pressure distribution is equivalent to having a relationship in which, in the region in which the belt 31 is pressed by the convex portions 324, 325, the pressure P is higher at the end portion side (outer side) than at the central side (inner side) at any position in the belt width direction, regardless of which two points are compared.

[0152] The magnitude of the pressure P is preferably, for example, in the range of 1 to 200 kPa. If the pressure P is less than 1 kPa, the contact state of the belt 31 with the upstream-side guide 321 easily becomes unstable, and if a portion with a strong pressing force and a portion with a weak pressing force are formed between one end and the other end in the belt width direction, it is possible that temperature unevenness in the belt width direction occurs, resulting in unevenness of the image after fixing. On the other hand, if the pressure P exceeds 200 kPa, the pressure becomes excessively high, the lubricant J has difficulty in entering between the belt 31 and the upstream-side guide 321, and the wear of the belt 31 and the sliding member 37 is promoted, and it is possible that the durability is reduced. Note that depending on the device structure, there can be cases where the magnitude of the pressure P is set to a value in a range different from the above.

[0153] Returning to Figure 8 At the position γ (central portion in the belt width direction), the pressure P between the upstream-side guide 321 and the belt 31 is Pd (< Pb), and the pressure P between the pressed portion 322 and the belt 31 is Pc. The position γ is also within the nip formation region 3d as with the position β, and thus the pressure Pc of the pressed portion 322 becomes the same magnitude of the nip pressure Pc as at the position β.

[0154] The pressure Pd between the belt 31 and the upstream-side guide 321 is relatively small. This is because the position γ is within a region of the central portion where the convex portions 324, 325 are not provided, and thus the tension acting on the belt 31 is lower than in regions of the ends where the convex portions 324, 325 are provided.

[0155] In the guide surface 320 of the upstream-side guide 321, the pressure P in a region of the central portion (region where the convex portions 324, 325 are not provided: Figure 5 of the 326) between the convex portions 324, 325 is substantially the same magnitude as Pd (> 0) at any position in the belt width direction.

[0156] That is, at the position immediately adjacent to the fixing nip 3, a predetermined pressing force is acting between the guide surface 320 of the upstream-side guide 321 and the belt 31 at any position in the entire region of the belt 31 from one end to the other end in the belt width direction due to the tension of the belt 31. By the action of this pressing force, at the position immediately adjacent to the fixing nip 3, the entire region of the belt 31 from one end 318 to the other end 319 in the belt width direction is in a state of being in contact with the upstream-side guide 321 with the sliding member 37 interposed therebetween.

[0157] Thus, for example, in a structure in which portions in contact with the inner peripheral surface 311 of the belt 31 and portions not in contact with it, such as a comb-shaped guide, alternate, it is possible to prevent temperature unevenness in the belt width direction caused by heat dissipation of the belt 31 at the contact portions and non-dissipation of heat of the belt 31 at the non-contact portions. It should be noted that the magnitude relationship between the pressure Pe and the pressure Pd is arbitrary, but there may be cases where Pe < Pd or cases where they are approximately the same.

[0158] Here, in the case where a structure without the convex portions 324 and 325 is set as a structure corresponding to the prior art (comparative example), Figure 10 In the schematic diagram, the magnitudes of the pressure P at positions α, β, and γ are shown. The upstream guide 921 without the convex portions 324 and 325 is denoted by 921, and the pressed portion 922 and the downstream guide 923 correspond to components substantially the same as the above-mentioned pressed portion 322 and downstream guide 323.

[0159] As Figure 10 shown, in the comparative example, the magnitudes of the pressure P of the pressed portion 922 and the downstream guide 923 are substantially the same as Figure 8 shown. On the other hand, in the upstream guide 921, since it does not have the convex portions 324 and 325, the pressure P with respect to the belt 31 becomes the same magnitude Pd regardless of which position among α, β, and γ. The same applies to positions other than α and β, and in the entire region from one end to the other end in the belt width direction, it is substantially constant at Pd ( Figure 9 the wavy line graph).

[0160] In Figure 7 and Figure 8 shown structure (embodiment) having a pressure distribution in which the pressure gradually decreases from the edge of the belt width direction of the belt 31 toward the center and Figure 10 shown structure (comparative example) having a pressure distribution in which the pressure is constant in the belt width direction, which corresponds to the prior art, Figure 11 (a) and (b) are used to explain how the lubricant J flows as the belt 31 travels around.

[0161] Here, Figure 11 (a) of the embodiment is a schematic side view when observing the fixed pad 32 from the perspective of the arrow Xa direction of Figure 2 the pressing roller 39, the belt 31, and the sliding member 37, and schematically shows a case where the lubricant J coated on the inner peripheral surface 311 of the belt 31 enters between the upstream guide 321 of the fixed pad 32 and the belt 31 as the belt 31 travels around. In this figure, the direction from bottom to top corresponds to the belt winding direction.

[0162] As shown in the example, at a position 328 in the direction of the width of the belt, when the lubricant J reaches the convex portion 324 of the upstream-side guide 321, a part Ja of the lubricant J directly passes between the convex portion 324 and the belt 31 in the direction of the belt winding (from the lower to the upper direction) to enter the nip formation region 3d, but the remaining part Jb travels in a direction slightly inclined toward the center of the width of the belt with respect to the direction of the belt winding, passes between the convex portion 324 and the belt 31, and enters the nip formation region 3d at a position 329 closer to the center of the width of the belt than the position 328.

[0163] This is because, as described above Figure 9 The pressure distribution shown in the drawing, in which the pressure P between the belt 31 and the convex portion 324 gradually decreases as from the end edge 318 in the direction of the width of the belt toward the center, at the position 329 where the pressure is low, the lubricant J present at the end in the direction of the width of the belt is transported to a position closer to the center in the direction of the width of the belt to enter the nip formation region 3d. Note that, with respect to the convex portion 325, although the flow of the lubricant J is not shown, the lubricant J is transported from the end edge 319 in the direction of the width of the belt toward a position closer to the center, as with the convex portion 324. Also, with respect to the lubricant J present at the center in the direction of the width of the belt, this is not shown, but this lubricant J directly enters the nip formation region 3d. Figure 9 The pressure distribution shown in the drawing, in which the pressure P between the belt 31 and the convex portion 324 gradually decreases as from the end edge 318 in the direction of the width of the belt toward the center, at the position 329 where the pressure is low, the lubricant J present at the end in the direction of the width of the belt is transported to a position closer to the center in the direction of the width of the belt to enter the nip formation region 3d. Note that, with respect to the convex portion 325, although the flow of the lubricant J is not shown, the lubricant J is transported from the end edge 319 in the direction of the width of the belt toward a position closer to the center, as with the convex portion 324. Also, with respect to the lubricant J present at the center in the direction of the width of the belt, this is not shown, but this lubricant J directly enters the nip formation region 3d.

[0164] In contrast, in the comparative example, in which the convex portions 324, 325 are not provided to the upstream-side guide 921, at the position immediately adjacent to the fixing nip 3, the pressure P between the belt 31 and the upstream-side guide 921 is the same size throughout the region from one end to the other end in the direction of the width of the belt.

[0165] Therefore, a part Jc of the lubricant J present at the end in the direction of the width of the belt, which reaches the nip formation region 3d of high pressure, cannot escape from the nip formation region 3d in the direction toward the end edge of the width of the belt (the left direction in the drawing), and eventually leaks out from the end edge of the belt 31 to the outside of the belt 31.

[0166] In the example, by the convex portions 324, 325 provided at both end portions in the direction of the width of the belt of the upstream-side guide 321 at the position immediately adjacent to the fixing nip 3, the lubricant J present at the end in the direction of the width of the belt passes through the nip formation region 3d after being transported to a position closer to the center in the direction of the width of the belt, and therefore, it is possible to prevent the lubricant J present at the end in the direction of the width of the belt from leaking out to the outside of the belt 31 as in the comparative example.

[0167] Lubricant J will not leak out of belt 31, thus the amount of lubricant J on the inner circumferential surface 311 of belt 31 can be stably maintained, preventing an increase in the frictional resistance between belt 31 and the fixing pad 32 that clamps the sliding component 37. By preventing this increase in frictional resistance, the accelerated wear of belt 31 and the increase in the torque driving belt 31 can be prevented, the smooth rotation of belt 31 and pressure roller 39 can be maintained for a long time, and the reduction in the transportability of recording film S can be prevented.

[0168] Furthermore, since the convex portions 324 and 325 are provided only at both ends in the belt width direction, the sliding resistance with the inner circumferential surface 311 of the belt 31 can be suppressed, and the lubricant J can be returned from the ends in the belt width direction to the center. Moreover, the length J of the convex portions 324 and 325 in the belt wrapping direction gradually decreases from the end edge of the belt 31 in the belt width direction toward the center. As a result, the area of ​​contact between the convex portions 324 and 325 and the inner circumferential surface 311 of the belt 31 decreases toward the center in the belt width direction, thereby suppressing the sliding resistance with the inner circumferential surface 311 of the belt 31.

[0169] <Variation Example>

[0170] The present disclosure has been described above based on the embodiments, but the present disclosure is not limited to the above embodiments, and the following variations are possible.

[0171] (1) In the above embodiment, the angle θ of the front end 244 of the convex portions 324 and 325 in the width direction is set to 30°, but it is not limited to this. Any angle that can form the pressure distribution required to return the lubricant J from the end in the width direction to the center is acceptable. If the angle θ is too large, the area of ​​the convex portions 324 and 325 will increase, and the sliding resistance with the belt 31 will increase. Conversely, if the angle θ is too small, it will be difficult to ensure the pressure distribution. From the viewpoints of both ensuring the sliding resistance of the belt 31 and ensuring the pressure distribution, an appropriate range of angles is determined in advance through experiments, etc.

[0172] (2) In the above embodiment, the top view of the convex parts 324 and 325 of the upstream guide 321 is set as a right-angled triangle, but it is not limited to this. It is acceptable as long as the shape can form the above pressure distribution.

[0173] For example, you can also set Figure 12 The convex portion 424 is shown in the top view. The convex portion 424 is formed into a conical shape by forming an arc (solid line) that connects the front end 444 in the width direction of the belt to the upstream end 445 in the circumferential direction of the belt.

[0174] Even such an arc-shaped end edge 442 can be applied as long as the above-described pressure distribution can be formed. Also, as shown by a dotted line, the end edge 442 can be formed into an arc shape that protrudes in a direction opposite to the direction in which the belt 31 is wound.

[0175] Also, it can be configured so that Figure 13 the convex portion 524 of the structure shown in (a) and (b). Figure 13 (a) is a schematic view when viewing the convex portion 524 from above, Figure 13 (b) is a view showing Figure 13 the Q-Q cross section of (a). As shown in (a), the convex portion 524 is rectangular when viewed from above, and as shown in (b), the convex portion 524 has a shape in which the height I in the thickness direction (the direction approaching the belt 31) gradually decreases as it goes from the base end 545 in the belt width direction (the direction of the arrow G) toward the belt width direction front end 544. This decrease in the height I forms the above-described pressure distribution. In the above description, only the convex portion on one end side in the belt width direction is shown, but the convex portion on the other end side in the belt width direction can also be configured to have the same shape. Figure 13 Figure 13 (3) In the above-described embodiment, a structure example in which the belt width direction front ends 244, 254 of the convex portions 324, 325 of the upstream side guide 321 are located at positions in the belt width direction that are more central than one end (end edge) 398, the other end (end edge) 399 of the nip formation region 3d, as shown in (a), has been described, but it is not limited thereto.

[0176] (3) In the above-described embodiment, a structure example in which the belt width direction front ends 244, 254 of the convex portions 324, 325 of the upstream side guide 321 are located at positions in the belt width direction that are more central than one end (end edge) 398, the other end (end edge) 399 of the nip formation region 3d, as shown in (a), has been described, but it is not limited thereto. Figure 7

[0177] For example, as shown in (a), a structure in which the belt width direction front ends 244, 254 of the convex portions 324, 325 are located at positions that are closer to the end edges 318, 319 of the belt 31 in the belt width direction than the end edges 398, 399 of the nip formation region 3d, i.e., a structure in which the belt width direction front ends 244, 254 do not extend to positions in the belt width direction of the end edges 398, 399 of the nip formation region 3d, can also be employed. If the pressure of the end portion of the belt 31 in the belt width direction at the position immediately adjacent to the fixing nip 3 becomes the above-described pressure distribution, the leakage of the lubricant J from the end edge of the belt 31 can be prevented. Figure 14 (4) In the above-described embodiment, a structure example in which the convex portions 324, 325 that are pressure application portions for forming the above-described pressure distribution are provided at the belt width direction both end portions of the upstream side guide 321 of the fixing pad 32 has been described, but it is not limited thereto.

[0178] In a structure in which the convex portions 324, 325 are not provided to the fixing pad 32, for example, a structure in which a convex portion 524 having

[0179] Figure 15 ​​​(a) The pressure-applying portion 100 of the conical frustum-shaped press rollers 111, 112 is provided on the outer circumferential side of the belt 31.

[0180] Figure 15 (a) is a schematic plan view when the belt 31, the fixing pad 32, the pressure roller 39, and the pressure-applying portion 100 are viewed from above in this modification.

[0181] As shown in the figure, the pressure-applying portion 100 has: the conical frustum-shaped press rollers 111, 112; and the rotation shafts 113, 114 that support the press rollers 111, 112 so as to be rotatable about axes that pass through the center of the conical frustum.

[0182] The conical frustum-shaped press rollers 111, 112 press the end portions of the belt 31 in the belt width direction to the upstream side guide 321 of the fixing pad 32 through the belt 31 in the vicinity of the fixing nip 3, and are disposed in the belt width direction at positions closer to the end edges 318, 319 of the belt 31 than the axial end portions 398, 399 of the pressure roller 39 and slightly upstream of the pressure roller 39 in the belt circumferential direction (upstream in the sheet conveyance direction). By this disposition, the end portions of the pressure roller 39 and a part of the end portions of the press rollers 111 (or 112) become in an overlapping state when viewed from the axial direction of the pressure roller 39.

[0183] The rotation shaft 113 is parallel to the belt width direction, and the press roller 111 is rotatably fitted to the front end side 115 thereof, and the base end side 116 is fixed to the frame. The rotation shaft 114 is also parallel to the belt width direction like the rotation shaft 113, and the press roller 112 is rotatably fitted to the front end side 115 thereof, and the base end side 116 is fixed to the frame.

[0184] Figure 15 (b) is an enlarged view of the press roller 111, and is in a conical frustum shape in which the diameter Da of the end portion 118 on one side is larger than the diameter Db of the end portion 119 on the other side. The press roller 112 on the other side is also in a conical frustum shape in which the diameter Da of the end portion 118 is larger than the diameter Db of the end portion 119. The press rollers 111, 112 are fitted to the rotation shafts 113, 114 in a posture in which the large-diameter end portion 118 faces the end portion side in the belt width direction, and the small-diameter end portion 119 faces the central side in the belt width direction.

[0185] By making the press rollers 111, 112 conical frustum-shaped, the pressure in the belt width direction of the pressure of the press rollers 111, 112 when pressing the upstream side guide 321 of the fixing pad 32 through the belt 31 becomes the pressure distribution shown by the solid line of the above Figure 7 Thus, like the embodiment, it is possible to prevent the lubricant J from leaking out from the end edge of the belt 31.

[0186] (5) In the above-described embodiments, the convex portions 324, 325 are provided at the end portions in either one of the belt width directions, but are not limited thereto. For example, a structure in which the convex portions are provided only at either one of the end portions in the belt width directions can be employed. Specifically, a structure in which the belt 31 gradually approaches either one of the end portions in the belt width directions in the circumferential direction of travel.

[0187] In this structure, the lubricant J applied to the inner circumferential surface of the belt 31 also easily flows in the same direction as the direction in which the belt 31 approaches in the vicinity of the fixing nip 3, and the lubricant J easily leaks from the belt 31. On the other hand, in the direction opposite to the direction in which the belt 31 approaches, the lubricant J hardly leaks from the belt 31.

[0188] Therefore, by providing the convex portions only at the end portions in the direction in which the belt 31 approaches, it is also possible to prevent the lubricant J from leaking from the belt 31.

[0189] (6) In the above-described embodiments, a structure example in which the heating roller 35 and the guide member 33 are used as the stretching member that stretches the belt 31 together with the fixing pad 32 is described, but is not limited thereto. For example, there is a structure in which the guide member 33 is not provided, and in this structure example, the heating roller 35 becomes the stretching member. In addition, in the electromagnetic induction method or the resistance heating method, in a structure in which the heater 36 is not provided, a structure in which another driven roller is provided instead of the heating roller 35 as the stretching member can be employed. In addition, in the structure example of the modification shown in (a), a structure in which the member that stretches the belt 31 is not provided can be employed as long as the belt 31 is a self-shape-maintaining belt that is able to maintain a substantially cylindrical elastic shape by itself. In addition, in the case where the self-shape-maintaining belt is used in the above-described embodiments, in the case where the same pressure distribution as described above can be formed even if the stretching member is not provided, a structure in which the stretching member is not provided can be employed in the embodiments. Figure 15 (a) In the structure example of the modification shown in (a), a structure in which the member that stretches the belt 31 is not provided can be employed as long as the belt 31 is a self-shape-maintaining belt that is able to maintain a substantially cylindrical elastic shape by itself. In addition, in the case where the self-shape-maintaining belt is used in the above-described embodiments, in the case where the same pressure distribution as described above can be formed even if the stretching member is not provided, a structure in which the stretching member is not provided can be employed in the embodiments.

[0190] (7) In the above-described embodiments, a structure example in which the lubricant supply member 38 that applies the lubricant J is provided at the inner circumferential surface 311 of the belt 31 is described, but is not limited thereto, and for example, a structure in which the lubricant supply member 38 is not provided can be employed. In this structure, the inner circumferential surface 311 of the belt 31 is applied with the lubricant J by the worker at the manufacturing stage of the fixing portion 30, at the time of maintenance, or the like.

[0191] In addition, a structure example in which the sliding member 37 is provided is described, but is not limited thereto, and a structure in which the sliding member 37 is not provided can be employed as long as the stable circumferential travel of the belt 31 can be maintained. In this structure, the entire region in the belt width direction from the one end 318 to the other end 319 of the belt 31 directly contacts the upstream guide 321 of the fixing pad 32 in the vicinity of the fixing nip 3.

[0192] (8) In the above-described embodiment, the structure in which the fixing pad 32 is fixedly supported by the support member 34 and the pressure roller 39 presses the fixing pad 32 through the belt 31 is adopted, but is not limited thereto. The fixing pad 32 can be a non-rotating body that does not rotate in conjunction with the circumferential travel of the belt 31, and for example, can be a structure in which the fixing pad 32 presses the pressure roller 39 through the belt 31 by the force of a force applying member such as a spring. In any case, since the pressing force acts between the pressure roller 39 and the fixing pad 32, the structure in which the pressure roller 39 presses the fixing pad 32 is included.

[0193] (9) In the above-described embodiment, an example in which the image forming apparatus of the present disclosure is applied to a color printer of a tandem type is described, but is not limited thereto. It can be applied to a fixing apparatus having a belt in a ring shape and an image forming apparatus provided with the fixing apparatus. As the image forming apparatus, it can be applied to an apparatus capable of performing color image formation, an apparatus capable of performing monochrome image formation only, and is not limited to a printer, and for example, can be applied to an image forming apparatus such as a copier, a facsimile apparatus, an MFP (Multiple Function Peripheral), and the like.

[0194] The size, shape, material, number, and each numerical value of each component described above are an example, and the size, shape, material, number, and each numerical value of each component are determined in advance in accordance with the structure of the apparatus.

[0195] In addition, the contents of the above-described embodiment and the above-described modified example can be combined as much as possible, respectively. In a range in which the effects of the present disclosure can be obtained, each part of the fixing portion and the like can be applied by replacing the mechanism, each component, and the like with other mechanisms, other components, and the like.

[0196] Industrial Applicability

[0197] The present disclosure can be widely applied to a fixing apparatus having a belt in a ring shape.

Claims

1. A fixing device comprising: a pressure roller disposed on the outer periphery of an annular belt pressing the belt, the inner periphery of which is coated with lubricant, to form a fixing roller gap; a film passing through the fixing roller gap to fix an unfixed image on the film; the fixing device being characterized in that it comprises: A non-rotating pad having a pressed portion and a guide, the pressed portion being pressed by a pressure roller across the belt on the inner circumferential side of the belt, the guide being positioned upstream of the pressed portion in the belt circumferential direction to guide the belt toward the fixing roller gap; and The pressure application section is located immediately upstream of the fixing roller gap in the belt wrapping direction, and applies pressure that gradually decreases from the end of the belt in the belt width direction toward the guide member. The guide has a convex portion that rises toward the inner circumferential surface of the belt at a position corresponding to the end of the belt. The pressure-applying part is the convex part. The convex portion is formed as a tapered shape in which the length of the convex portion in the belt wrapping direction gradually decreases from the end side in the belt width direction toward the central side, so as to apply the gradually decreasing pressure, and is not provided in the pressed portion located downstream of the guide in the belt wrapping direction.

2. The fixing device as claimed in claim 1, characterized in that, The tapered shape is formed by a first side parallel to the width direction of the belt and a second side inclined relative to the first side at a position upstream of the belt wrapping direction.

3. The fixing device as described in claim 1 or 2, characterized in that, The height of the convex portion is within the range of 0.1 to 0.5 mm.

4. A fixing device comprising: a pressure roller disposed on the outer periphery of an annular belt pressing the belt, the inner periphery of which is coated with lubricant, to form a fixing roller gap; a film passing through the fixing roller gap to fix an unfixed image on the film; the fixing device being characterized in that it comprises: A non-rotating pad having a pressed portion and a guide, the pressed portion being pressed by a pressure roller across the belt on the inner circumferential side of the belt, the guide being positioned upstream of the pressed portion in the belt circumferential direction to guide the belt toward the fixing roller gap; and The pressure application section is located immediately upstream of the fixing roller gap in the belt wrapping direction, and applies pressure that gradually decreases from the end of the belt in the belt width direction toward the guide member. The guide has a convex portion that rises toward the inner circumferential surface of the belt at a position corresponding to the end of the belt. The pressure-applying part is the convex part. The convex portion is formed such that its height gradually decreases from the end side toward the center side in the width direction of the belt, so as to apply the gradually decreasing pressure, and is not provided in the pressed portion located downstream of the guide in the belt wrapping direction.

5. The fixing device as described in claim 1 or 4, characterized in that, The end of the convex portion extends to the central side in the width direction, closer to the axial center of the pressure roller than the axial end of the pressure roller in the width direction.

6. The fixing device as described in claim 1 or 4, characterized in that, The base end of the convex portion protrudes outward in the width direction of the belt.

7. A fixing device comprising: a pressure roller disposed on the outer periphery of an annular belt pressing the belt, the inner periphery of which is coated with lubricant, to form a fixing roller gap; a film passing through the fixing roller gap to fix an unfixed image on the film; the fixing device being characterized in that it comprises: A non-rotating pad having a pressed portion and a guide, the pressed portion being pressed by a pressure roller across the belt on the inner circumferential side of the belt, the guide being positioned upstream of the pressed portion in the belt circumferential direction to guide the belt toward the fixing roller gap; and The pressure application section is located immediately upstream of the fixing roller gap in the belt wrapping direction, and applies pressure that gradually decreases from the end of the belt in the belt width direction toward the guide member. The pressure application section is a truncated cone-shaped pressing roller that presses the end of the belt against the guide from the outer periphery of the belt at the adjacent position. On the outer side of the belt, in the belt width direction, at the side where the pressure applying roller is located closer to the end of the belt and in the belt wrapping direction, the pressing roller is configured with its major diameter end facing the end side in the belt width direction and its minor diameter end facing the center side in the belt width direction.

8. The fixing device as described in any one of claims 1, 4, and 7, characterized in that, The axial end of the pressure roller is closer to the center of the belt width direction than the end edge of the belt width direction.

9. The fixing device as described in any one of claims 1, 4, and 7, characterized in that, The entire area of ​​the belt from one end to the other in the width direction is in contact with the guide at the adjacent position.

10. The fixing device as described in any one of claims 1, 4, and 7, characterized in that, The fixing device includes a low-friction pad located between the belt and the pad.

11. The fixing apparatus as claimed in claim 10, characterized in that, The belt contacts the guide across the low-friction pad at the adjacent position, covering the entire area from one end to the other in the belt width direction.

12. The fixing device as described in any one of claims 1, 4, and 7, characterized in that, The fixing device includes a lubricant supply component that supplies lubricant to the inner circumferential surface of the belt.

13. The fixing device as described in any one of claims 1, 4, and 7, characterized in that, The pressure applied by the pressure application unit is within the range of 1 to 200 kPa.

14. An image forming apparatus comprising a fixing unit that fixes an unfixed image formed on a transported recording film, characterized in that... The fixing unit includes the fixing device according to any one of claims 1 to 13.

Images