JP2019191332A - Fixing device and image forming apparatus - Google Patents

Abstract

To provide a fixing device having a configuration capable of easily securing a desired nip pressure distribution in a nip part and to provide an image forming apparatus.SOLUTION: The fixing device for fixing a toner image formed on a recording medium, while conveying the recording medium from an upstream side to a downstream side includes a pressure mechanism 60 for pressurizing a pressure roller 58 toward the side of a pressure pad 52. On the side facing the pressure roller 58 of the pressure pad 52, a recess area 52a which is recessed in a direction away from the oppositely arranged pressure roller 58 and a downstream side projection area 52c which bulges in a direction projecting with respect to the pressure roller 58 and is located on the downstream side of the recess area 52a are provided. The pressure mechanism 60 pressurizes the pressure roller 58 toward the side of the pressure pad 52 in a vertical direction with respect to the tangent of the recess area 52a.SELECTED DRAWING: Figure 3

Description

  The fixing device and the image forming apparatus of the present invention relate to a fixing device and an image forming apparatus that form an image by electrophotography. Regardless of color or monochrome, the image forming apparatus includes a digital copying machine, a FAX, an electrophotographic apparatus such as a printer, a recording apparatus, a display apparatus, and the like.

  In the fixing device disclosed in Japanese Patent Application Laid-Open No. 2017-72711 (Patent Document 1), a so-called pad pressure fixing system is employed. The outer shape of the pad is characterized in that a concave surface portion curved along the outer peripheral surface of the pressure roller is provided on the downstream side of the nip, and the curvature radius of the concave surface is larger than the curvature radius of the pressure roller. It is described that this structure widens the contact surface between the curved surface and the pressure roller, secures the nip width, and can solve the problems of the energy saving performance of the fixing device, the increase of the rotational torque of the belt, and the rotation failure. Yes.

  In the fixing device disclosed in Japanese Patent Laid-Open No. 2012-108189 (Patent Document 2), a technique for applying a load perpendicularly to the thickness direction of the reinforcing member from the pressure roller to a flat pad is disclosed. .

JP 2017-72711 A JP 2012-108189 A

  In the technique disclosed in Patent Document 1, the pad surface has a nip along the conveyance direction of the recording medium in order to obtain a desired nip pressure for functions such as fixing and separation. The part is provided with a concave surface, and a convex arc is provided on the upstream side of the inlet of the nip part.

  In order to secure a desired nip pressure distribution in the nip portion, it is necessary to design in consideration of pad manufacturing tolerances, support member manufacturing tolerances, mounting tolerances, and the like. Therefore, members such as pads are required to have high-precision design, production, quality control, and the like. As a specific pad outer shape, the recording medium is provided with a plane along the conveyance direction and a concave surface with a radius of curvature larger than the radius of the pressure roller on the downstream side of the nip portion. It has not been. In the technique disclosed in Patent Document 2, as described above, a load is applied in a direction straight to the pad.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device and an image forming apparatus having a configuration capable of easily ensuring a desired nip pressure distribution in a nip portion.

  The fixing device is a fixing device that fixes a toner image formed on the recording medium while conveying the recording medium from the upstream side to the downstream side, and is an endless fixing unit configured to be rotatable. A belt, a pressure pad disposed on the inner peripheral side of the fixing belt, a pressure roller that forms a fixing nip portion by facing the pressure pad and facing the outer peripheral surface of the fixing belt, A heating roller that supplies heat to the toner image, and a pressure mechanism that pressurizes the pressure roller toward the pressure pad, and on the side of the pressure pad that faces the pressure roller, A recessed area that is recessed in a direction away from the pressure roller that is disposed oppositely, and a downstream raised area that swells in a direction that protrudes with respect to the pressure roller and is located downstream of the recessed area. Vignetting, the pressure mechanism, the pressure roller in the direction perpendicular to the tangent of the recessed regions pressurized toward the pressure pad side.

  In another form, the pressurizing mechanism applies the pressurizing roller in a direction perpendicular to a tangent line of the concave region passing through a transition point where the concave region and the downstream convex region join. Pressurize toward the pressure pad.

  In another embodiment, the pressurizing mechanism pressurizes the pressurizing roller toward the pressurizing pad in a direction perpendicular to a tangent line passing through the center position of the concave region.

  In another form, the curvature radius of the said recessed area | region of the said pressure pad is provided larger than the curvature radius of the outer peripheral surface of the said pressure roller.

  In another form, the said pressure pad contains the circular-arc-shaped upstream convex area | region which becomes convex facing the outer peripheral side of the said pressure roller in the upstream of the said recessed area.

  In another embodiment, the pressure mechanism includes a biasing member that presses the pressure roller toward the pressure pad, and the biasing member is a spring.

  In another embodiment, the heating roller includes a heating source, and the heating source is a halogen heater.

  In another embodiment, a sliding member is provided between the pressure pad and the fixing belt.

  In another embodiment, a support member is disposed on the opposite side of the pressure roller across the pressure pad, the support member is U-shaped, and the rising portion on the downstream side of the support member is upstream. It is longer than the side.

  In this image forming apparatus, the image forming apparatus includes a fixing device that fixes the toner image formed on the recording medium while conveying the recording medium from the upstream side to the downstream side, and the fixing device includes: The fixing device according to any one of the above.

  According to the fixing device and the image forming apparatus, it is an object to provide a fixing device and an image forming apparatus having a configuration capable of easily ensuring a desired nip pressure distribution in the nip portion.

1 is a schematic diagram of an image forming apparatus according to Embodiment 1. FIG. 1 is a schematic sectional view of a fixing device according to a first embodiment. 3 is a schematic diagram illustrating a schematic configuration of a pressurizing mechanism according to Embodiment 1. FIG. 6 is a diagram illustrating a schematic configuration of a pressurizing mechanism according to a second embodiment. FIG. It is the schematic which shows only the relationship between the press pad of Embodiment 3, and a press roller.

  Hereinafter, a fixing device and an image forming apparatus according to an embodiment will be described with reference to the drawings. In the embodiments described below, when referring to the number, amount, and the like, the scope of the present invention is not necessarily limited to the number, amount, and the like unless otherwise specified. The same parts and corresponding parts are denoted by the same reference numerals, and redundant description may not be repeated. In the drawings, there are portions that are not illustrated in accordance with the ratios of actual dimensions, but are illustrated with the ratios changed so that the structures are clear in order to facilitate understanding of the structures.

(Embodiment 1: Image forming apparatus)
The image forming apparatus 100 will be described with reference to FIG. FIG. 1 is a diagram illustrating an example of the internal structure of the image forming apparatus 100.

  FIG. 1 shows an image forming apparatus 100 as a color printer. Hereinafter, the image forming apparatus 100 as a color printer will be described, but the image forming apparatus 100 is not limited to a color printer. For example, the image forming apparatus 100 may be a monochrome printer, a fax machine, or a multifunction printer (MFP: Multi-Functional Peripheral) of a monochrome printer, a color printer, and a fax machine.

  The image forming apparatus 100 includes image forming units 1Y, 1M, 1C, and 1K, an intermediate transfer belt 30, a primary transfer roller 31, a secondary transfer roller 33, a cassette 37, a driven roller 38, and a drive roller 39. A timing roller 40, a fixing device 50, a housing 80, and a control device 101. The image forming apparatus 100 includes a display device 150 and displays the state of the image forming apparatus 100. By using a touch-type display for the display device 150, the operation setting of the image forming apparatus 100 can be performed.

  The housing 80 defines an outer shell of the image forming apparatus 100. The housing 80 includes an image forming unit 1Y, 1M, 1C, 1K, an intermediate transfer belt 30, a primary transfer roller 31, a secondary transfer roller 33, a cassette 37, a driven roller 38, and a driving roller. 39, the timing roller 40, the fixing device 50, and the control device 101 are accommodated.

  The image forming units 1Y, 1M, 1C, and 1K, the intermediate transfer belt 30, the primary transfer roller 31, the secondary transfer roller 33, the cassette 37, the driven roller 38, the drive roller 39, and the timing roller 40 An image forming unit is configured. The image forming unit forms a toner image on a sheet S as a recording medium conveyed along a conveyance path 41 described later.

  The image forming units 1Y, 1M, 1C, and 1K are arranged in order along the intermediate transfer belt 30. The image forming unit 1Y receives the supply of toner from the toner bottle 15Y and forms a yellow (Y) toner image. The image forming unit 1M receives the supply of toner from the toner bottle 15M and forms a magenta (M) toner image. The image forming unit 1C receives toner from the toner bottle 15C and forms a cyan (C) toner image. The image forming unit 1K receives the supply of toner from the toner bottle 15K and forms a black (BK) toner image.

  The image forming units 1Y, 1M, 1C, and 1K are arranged along the intermediate transfer belt 30 in the order of the rotation direction of the intermediate transfer belt 30, respectively. Each of the image forming units 1Y, 1M, 1C, and 1K includes a photoconductor 10, a charging device 11, an exposure device 12, a developing device 13, and a cleaning device 17.

  The charging device 11 uniformly charges the surface of the photoconductor 10. The exposure device 12 irradiates the photoconductor 10 with laser light in accordance with a control signal from the control device 101, and exposes the surface of the photoconductor 10 according to the input image pattern. Thereby, an electrostatic latent image corresponding to the input image is formed on the photoreceptor 10.

  The developing device 13 applies a developing bias to the developing roller 14 while rotating the developing roller 14, and causes the toner to adhere to the surface of the developing roller 14. As a result, the toner is transferred from the developing roller 14 to the photoreceptor 10, and a toner image corresponding to the electrostatic latent image is developed on the surface of the photoreceptor 10.

  The photoconductor 10 and the intermediate transfer belt 30 are in contact with each other at a portion where the primary transfer roller 31 is provided. The primary transfer roller 31 has a roller shape and is configured to be rotatable. By applying a transfer voltage having a polarity opposite to that of the toner image to the primary transfer roller 31, the toner image is transferred from the photoreceptor 10 to the intermediate transfer belt 30. A yellow (Y) toner image, a magenta (M) toner image, a cyan (C) toner image, and a black (BK) toner image are sequentially superimposed and transferred from the photoreceptor 10 to the intermediate transfer belt 30. As a result, a color toner image is formed on the intermediate transfer belt 30.

  The intermediate transfer belt 30 is stretched around a driven roller 38 and a driving roller 39. The drive roller 39 is rotationally driven by, for example, a motor (not shown). The intermediate transfer belt 30 and the driven roller 38 rotate in conjunction with the driving roller 39. As a result, the toner image on the intermediate transfer belt 30 is conveyed to the secondary transfer roller 33.

  The cleaning device 17 is in pressure contact with the photoreceptor 10. The cleaning device 17 collects the toner remaining on the surface of the photoreceptor 10 after the transfer of the toner image.

  A sheet S is set in the cassette 37. The sheets S are sent one by one from the cassette 37 to the secondary transfer roller 33 along the transport path 41 by the timing roller 40. The secondary transfer roller 33 has a roller shape and is configured to be rotatable. The secondary transfer roller 33 applies a transfer voltage having a polarity opposite to that of the toner image to the sheet S being conveyed. As a result, the toner image is attracted from the intermediate transfer belt 30 to the secondary transfer roller 33, and the toner image on the intermediate transfer belt 30 is transferred.

  The conveyance timing of the sheet S to the secondary transfer roller 33 is adjusted by the timing roller 40 in accordance with the position of the toner image on the intermediate transfer belt 30. The toner image on the intermediate transfer belt 30 is transferred to an appropriate position on the paper S by the timing roller 40.

  The fixing device 50 pressurizes and heats the paper S passing through the fixing device 50. As a result, the toner image is fixed on the paper S. As described above, the fixing device 50 fixes the toner image on the sheet S conveyed along the conveyance path 41. The sheet S on which the toner image is fixed is discharged to the tray 48.

  Although the image forming apparatus 100 adopting the tandem method as the printing method has been described above, the printing method of the image forming device 100 is not limited to the tandem method. The arrangement of the components in the image forming apparatus 100 can be changed as appropriate according to the employed printing method. As a printing method of the image forming apparatus 100, a rotary method or a direct transfer method may be employed.

  In the case of the rotary system, the image forming apparatus 100 includes a single photoconductor 10 and a plurality of developing devices 13 configured to be coaxially rotatable. At the time of printing, the image forming apparatus 100 sequentially guides the developing devices 13 to the photoreceptor 10 and develops toner images of the respective colors. In the case of the direct transfer method, the image forming apparatus 100 directly transfers the toner image formed on the photoreceptor 10 onto the paper S.

  A waste toner recovery container 200 that stores waste toner and / or waste developer is provided on one end side in the direction in which the rotation shaft of the photoconductor 10 extends. In the present embodiment, a common waste toner collecting container 200 is provided for the image forming units 1Y, 1M, 1C, and 1K. A corresponding waste toner collection container may be provided in each of the image forming units 1Y, 1M, 1C, and 1K.

(Fixing device 50)
A schematic configuration of the fixing device 50 will be described with reference to FIG. FIG. 2 is a schematic sectional view of the fixing device 50.

  The fixing device 50 includes an endless fixing belt 51 configured to be rotatable, a pressure roller 58, a pressure pad 52 as a pressure member, a sliding member 53, a support member 54, and a lubricant application. And a heating roller 57 that stretches the fixing belt 51 together with the pressure roller 58.

  The arrows shown in FIG. 2 indicate the transport direction DR1 and the thickness direction DR2. The transport direction DR1 is the transport direction of the paper S, and is the upward direction in FIG. The thickness direction DR2 is the thickness direction of the paper S, and is the left-right direction in FIG.

(Fixing belt 51)
The outer diameter of the fixing belt 51 is arbitrary, but is, for example, 10 [mm] to 100 [mm]. The fixing belt 51 has a base layer, an elastic layer, and a release layer. The base layer is made of, for example, polyimide (PI), SUS, Ni, or the like. The thickness of the base layer is, for example, 5 [μm] to 80 [μm].

  The elastic layer is preferably made of a material having high heat resistance such as silicone rubber and fluorine rubber. The thickness of the elastic layer is, for example, 10 [μm] to 300 [μm]. The release layer preferably has a configuration imparting release properties such as a fluorine tube and a fluorine-based coating. The release layer is, for example, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) tube. The thickness of the release layer is, for example, 5 [μm] to 100 [μm].

(Pressure pad 52)
The pressure pad 52 is disposed on the inner peripheral side of the fixing belt 51. The pressure pad 52 is fixed by a support member 54 and slides with the inner peripheral surface of the fixing belt 51. The pressure pad 52 is made of, for example, a resin such as polyphenylene sulfide, polyimide, or a liquid crystal polymer, a metal such as aluminum or iron, a ceramic, or the like, and has an arbitrary shape. A two-part configuration with a support member 54 made of silicone rubber, fluororubber, or the like may be used.

(Supporting member 54)
The support member 54 is disposed on the opposite side of the pressure roller 58 with the pressure pad 52 interposed therebetween. The support member 54 has a U-shape, and the rising portion on the downstream side of the support member 54 is longer than the upstream side, and receives a greater pressure on the downstream side than the upstream side of the fixing nip portion N. When the downstream side strength of the support member 54 is increased, a gentle pressure can be applied to the fixing nip portion N. The support member 54 is fixed to a frame (not shown) at both ends in the axial direction (perpendicular to the paper surface), and a desired nip pressure distribution is ensured by pressing the pressure member with a surface parallel to the axial direction. Is possible.

(Pressure roller 58 / Pressure pad 52)
The pressure roller 58 is rotated at a predetermined rotation speed, for example, 415 [mm / s] by a drive device (not shown) such as a motor (direction A in FIG. 2). The fixing belt 51 rotates following the rotation of the pressure roller 58 (direction B in FIG. 2).

  The outer diameter of the pressure roller 58 is, for example, 50 [mm]. The pressure roller 58 has an iron cored bar, an elastic layer, and a release layer. The thickness of the core metal is, for example, 40 [mm]. The thickness of the elastic layer is, for example, 5 [mm]. The release layer is, for example, a PFA tube. The thickness of the release layer is, for example, 20 [μm].

  The pressure roller 58 presses the pressure pad 52 via the fixing belt 51. The pressure roller 58 faces the pressure pad 52 and faces the outer peripheral surface of the fixing belt 51 to form the fixing nip portion N. The fixing nip N is an area formed when the pressure roller 58 presses the pressure pad 52.

(Sliding member 53)
The sliding member 53 is disposed between the pressure pad 52 and the inner peripheral surface of the fixing belt 51. The sliding member 53 reduces the frictional force generated between the pressure pad 52 and the inner peripheral surface of the fixing belt 51. Thereby, stable rotation of the fixing belt 51 is obtained. The sliding member 53 is fixed by being wound around the pressure pad 52.

  The sliding member 53 generally has a configuration in which a glass cloth is used as a base material and a sliding surface is covered with a fluorine-based resin. However, a woven fabric of fluorine fibers, a fluorine resin sheet, a glass coat, or the like is used. As the sliding member 53, a glass cloth fluororesin-impregnated type may be used. For example, the sliding member 53 is preferably made of a material having high wear resistance and heat resistance, such as a fluororesin fabric (MS fabric) manufactured by Chuko Kasei Kogyo Co., Ltd. and a cross-linked fluororesin FEX manufactured by Sumitomo Electric Fine Polymer.

(Support member 54 / lubricant application part 55)
The lubricant application unit 55 is disposed on the downstream side in the rotation direction of the fixing belt 51 with respect to the pressure pad 52. The lubricant application part 55 is fixed by a support member 54. The lubricant application unit 55 is disposed on the inner peripheral side of the fixing belt 51 and supports the fixing belt 51.

  The lubricant application unit 55 applies a lubricant to the inner peripheral surface of the fixing belt 51. The lubricant may be silicon oil or fluorine grease. In the case of silicone oil, KF96-300CS manufactured by Shin-Etsu Silicone, and in the case of fluorine grease, G8005 manufactured by Toray Dow Corning is preferable. The lubricant is provided between the inner peripheral surface of the fixing belt 51 and the sliding member 53. When the sliding member 53 is not provided, the lubricant is provided between the inner peripheral surface of the fixing belt 51 and the pressure pad 52.

  The lubricant application part 55 holds felt (not shown). The felt is in contact with the inner peripheral surface of the fixing belt 51. The felt is impregnated with a lubricant. Thereby, the lubricant application unit 55 can apply the lubricant uniformly to the inner peripheral surface of the fixing belt 51.

(Heating roller 57)
The heating roller 57 is disposed on the inner peripheral side of the fixing belt 51. The heating roller 57 has a heating source 56. The heating roller 57 is made of a metal cylinder such as aluminum or SUS. The outer diameter is arbitrary, but 10 [mm] to 100 [mm] is desirable, and the thickness is desirably 0.1 [mm] to 5 [mm]. When a halogen heater is used as the heating source 56, it is desirable to make the inner surface black. In order to prevent damage to the outer surface due to foreign matter or the like, the outer surface may be coated with polytetrafluoroethylene (PTFE). The thickness of the coating layer is, for example, 40 [μm].

  The output of the heating source 56 (halogen heater or the like) is, for example, 1000 [W]. The temperature control temperature is, for example, 170 [° C.]. The heating source 56 heats the fixing belt 51 via the heating roller 57. In the embodiment, the heating source 56 supplies heat to the toner image T via the fixing belt 51. The heating roller 57, the pressure pad 52, and the lubricant application unit 55 stretch the fixing belt 51.

  In addition to the halogen heater, the heating source 56 includes a heating roller 57 and a fixing belt 51 that are heated by IH, a heating roller 57 and a fixing belt 51 that are resistance heating elements, and a heating method.

  In the fixing device 50 configured as described above, the magnitude of the load at the fixing nip portion N is, for example, 700 [N] or more and 1000 [N] or less. The width (nip width) of the fixing nip portion N in the transport direction DR1 is, for example, 18 [mm]. The length of the fixing nip portion N in the width direction DR3 is, for example, 320 [mm].

  A toner image T is formed on the paper S. The length of the sheet S in the thickness direction DR2 is, for example, 140 [μm]. The sheet S is transported in the transport direction DR1 by a roller (not shown), and enters the fixing nip portion N together with the toner image T. In the fixing nip portion N, the toner image T on the paper S is heated and pressurized and fixed on the paper S.

(Pressure mechanism 60)
With reference to FIG. 3, the pressure mechanism 60 to the pressure roller 58 will be described. FIG. 3 is a schematic diagram illustrating a schematic configuration of the pressurizing mechanism 60 according to the first embodiment. In FIG. 3, the description of the fixing belt 51 is omitted for convenience of explanation.

  On the side facing the pressure roller 58 of the pressure pad 52, a recessed area 52 a that is recessed in a direction away from the pressure roller 58 disposed opposite to the pressure roller 58, and an upstream side that swells in a direction protruding from the pressure roller 58. A convex region 52b and a downstream convex region 52c are provided. The upstream convex region 52b is located on the most upstream side in the transport direction of the paper S, then the concave region 52a, and the downstream convex region 52c is located on the most downstream side in the transport direction of the paper S.

  The concave region 52a is curved in a concave shape with a constant radius of curvature, and the upstream convex region 52b and the downstream convex region 52c also protrude in a convex shape with a constant radius of curvature. The point where the upstream convex region 52b and the concave region 52a join constitutes the inflection point A1, and the point where the concave region 52a and the downstream convex region 52c join constitutes the inflection point A2. The inflection point A2 located on the downstream side bites into the pressure roller 58 more than the inflection point A1.

  The pressure roller 58 is provided with a pressure mechanism 60 that pressurizes the pressure roller 58 toward the pressure pad 52. This pressurizing mechanism 60 has a pressurizing lever 61 provided at one end so as to be rotatable at a fulcrum B. The pressure lever 61 is connected to, for example, a rotation shaft of the pressure roller 58, and moves the pressure roller 58 toward the pressure pad 52 as the pressure lever 61 moves.

  A coil spring 62 as an urging member is connected to the other end of the pressure lever 61. The direction in which the force of the coil spring 62 connected to the other end of the pressure lever 61 is applied (direction X2 in the figure) is a direction of approximately 90 degrees with respect to the pressure lever 61, and the pressure pad 52 is provided. Force is applied in the direction of being pulled to the side. The coil spring 62 may be restricted in the moving direction (X2 direction in the drawing) by adopting a configuration in which the coil spring 62 is moved along a groove provided in a frame (not shown).

  At the inflection point A1, the position of the fulcrum B is selected so that a load is applied in a direction perpendicular to the tangent L1 to the recessed area 52a passing through the inflection point A1 (X1 direction in the figure).

  As described above, the inflection point A1 is a position where the pressure at the fixing nip portion N is highest (position where the peak pressure is generated). For this point, a load is applied to the tangent L1 in the vertical direction. As a result, a load is applied in the vertical direction with respect to the thickness direction of the paper S, so that the dispersion of the load due to the pressurization can be avoided.

  As a result, it is possible to avoid the application of a large load in anticipation of the dispersion of the load, and it is possible to design and manufacture the pressure pad 52 with gentle pressure. Since the pressurizing mechanism 60 for the pressurizing roller 58 is not a complicated device configuration, its manufacture and quality control can be easily performed.

  By controlling an appropriate load, it is possible to prevent occurrence of a peak pressure that is too high and to suppress stress applied to the fixing belt 51. Further, it is possible to suppress the increase in the rotational torque of the fixing belt 51, the wear of the fixing belt 51, and the occurrence of image defects resulting therefrom.

(Embodiment 2: Pressurizing mechanism 60A)
With reference to FIG. 4, the structure of 60 A of pressurization mechanisms in Embodiment 2 is demonstrated. FIG. 4 is a diagram illustrating a schematic configuration of a pressurizing mechanism 60A according to the second embodiment. In FIG. 4, the description of the fixing belt 51 is omitted for convenience of explanation. In the second embodiment, the basic configurations of the image forming apparatus 100 and the fixing device 50 shown in the first embodiment are the same, and therefore, repeated description is not repeated here.

  The structure of the pressurizing mechanism 60A is basically the same as that of the pressurizing mechanism 60 shown in the first embodiment. The pressure pad 52 is the same as that in the first embodiment. The difference is that the positions of the fulcrum B and the fulcrum C are selected so that a load is applied in a direction perpendicular to the tangent line L1 passing through the center position A3 of the recessed area 52a (X1 direction in the drawing).

  By pressing the pressure roller 58 against the center position of the recessed area 52a, the amount of biting into the pressure pad 52 by the pressure roller 58 can be evenly distributed toward both sides with the center position A3 as the center. . Thereby, the load can be made uniform by pressurization.

  As a result, it is possible to avoid the application of a large load in anticipation of non-uniform loads, and it is possible to design and manufacture the pressure pad 52 with gentle pressure. Since the pressurizing mechanism 60 for the pressurizing roller 58 is not a complicated device configuration, its manufacture and quality control can be easily performed.

(Embodiment 3: Pressure pad 52)
The shape of the pressure pad 52 will be described with reference to FIG. FIG. 5 is a schematic diagram showing only the relationship between the pressure pad 52 and the pressure roller 58. As the shape of the pressure pad 52, the pressing surface that presses the pressure pad 52 against the pressure roller 58 has a recessed area 52 a that is curved along the outer peripheral side of the pressure roller 58 in the transport direction of the paper S. Is provided. Since the radius of curvature of the recessed area 52a is larger than the radius of curvature of the outer peripheral surface of the pressure roller 58, the nip width of the fixing nip portion N can be sufficiently secured. For example, in the case of the present embodiment, the radius R1 of the recessed area 52a may be provided larger than the radius R3 of the pressure roller 58.

  Further, on the upstream side of the entrance of the fixing nip portion N in the conveyance direction (DR1) of the sheet S, the pressure pad 52 has an arcuate upstream side that protrudes opposite to the outer peripheral side of the pressure roller 58. A convex region 52b is provided. Thereby, a sufficient space is secured between the pressure pad 52 and the pressure roller 58 at the entrance of the fixing nip portion N, and the sheet S can be reliably introduced into the fixing nip portion N.

  As described above, according to the fixing device and the image forming apparatus in the present embodiment, the pressure pad 52 can be designed and manufactured with gentle pressure. Since the pressurizing mechanism 60 for the pressurizing roller 58 is not a complicated device configuration, its manufacture and quality control can be easily performed.

  According to the conventional fixing device and the image forming apparatus, when it is intended to secure a desired pressure in the fixing nip portion N, the manufacturing tolerance of the pressure pad 52, the manufacturing tolerance of the support member 54, the mounting tolerance, and the like are considered. Therefore, high-precision design, production, quality control, etc. are required. On the other hand, according to the fixing device and the image forming apparatus in the present embodiment, it is possible to provide a fixing device and an image forming apparatus that can ensure a wide operation window.

  Although the embodiments of the present invention have been described above, the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, and includes meanings equivalent to the terms of the claims and all modifications within the scope.

  1C, 1K, 1M, 1Y Image forming unit, 10 photoconductor, 11 charging device, 12 exposure device, 13 developing device, 14 developing roller, 15C, 15K, 15M, 15Y toner bottle, 17 cleaning device, 30 intermediate transfer belt, 31 Primary transfer roller, 33 Secondary transfer roller, 37 Cassette, 38 Driven roller, 39 Drive roller, 40 Timing roller, 41 Transport path, 48 Tray, 50 Fixing device, 51 Fixing belt, 52 Pressure pad, 52a Recessed area, 52b Upstream convex region, 52c Downstream convex region, 53 Sliding member, 54 Support member, 55 Lubricant application unit, 56 Heat source, 57 Heating roller, 58 Pressure roller, 60, 60A Pressure mechanism, 61 Pressure lever, 62 coil spring, 80 housing, 100 image formation Location, 101 control unit, 150 display unit, 200 waste toner collecting container.

Claims (10)

A fixing device that fixes a toner image formed on the recording medium while conveying the recording medium from the upstream side to the downstream side,
An endless fixing belt configured to be rotatable;
A pressure pad disposed on the inner peripheral side of the fixing belt;
A pressure roller that forms a fixing nip portion by facing the pressure pad and facing the outer peripheral surface of the fixing belt;
A heating roller for supplying heat to the toner image;
A pressure mechanism that pressurizes the pressure roller toward the pressure pad;
With
On the side of the pressure pad facing the pressure roller,
A recessed area that is recessed in a direction away from the pressure roller disposed oppositely;
Bulges in a direction protruding with respect to the pressure roller, and is provided with a downstream convex region located downstream from the concave region,
The fixing device, wherein the pressure mechanism presses the pressure roller toward the pressure pad in a direction perpendicular to a tangent line of the recessed area.   The pressure mechanism directs the pressure roller toward the pressure pad in a direction perpendicular to a tangent line of the concave area passing through a transition point where the concave area and the downstream convex area are joined. The fixing device according to claim 1, wherein pressure is applied.   The fixing device according to claim 1, wherein the pressure mechanism presses the pressure roller toward the pressure pad in a direction perpendicular to a tangent passing through a center position of the recessed area.   4. The fixing device according to claim 1, wherein a radius of curvature of the recessed area of the pressure pad is larger than a radius of curvature of an outer peripheral surface of the pressure roller.   5. The pressure pad according to claim 1, wherein the pressure pad includes an arcuate upstream convex region that is convex facing the outer peripheral side of the pressure roller on the upstream side of the concave region. The fixing device according to Item.   6. The pressure mechanism according to claim 1, wherein the pressure mechanism includes a biasing member that pressurizes the pressure roller toward the pressure pad, and the biasing member is a spring. Fixing device.   The fixing device according to claim 1, wherein the heating roller includes a heating source, and the heating source is a halogen heater.   The fixing device according to claim 1, wherein a sliding member is provided between the pressure pad and the fixing belt.   A support member is disposed on the opposite side of the pressure roller across the pressure pad, the support member is U-shaped, and the rising portion on the downstream side of the support member is provided longer than the upstream side. The fixing device according to claim 1, wherein the fixing device is a fixing device. An image forming apparatus including a fixing device that fixes a toner image formed on the recording medium while conveying the recording medium from the upstream side to the downstream side,
10. The image forming apparatus according to claim 1, wherein the fixing device is a fixing device according to claim 1.

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