Fixing device and image forming apparatus

Abstract

To provide a fixing device capable of firmly fixing a sliding member coming into contact with a fixing belt rotating in a fixing nip part with a simple configuration.SOLUTION: The fixing device 8 includes a fixing belt 81, a sliding member 85, a nip forming member 84, and a pressure roller 82. The sliding member 85 is disposed adjacent to the inner side of the fixing belt 81 in the radial direction, and the inner peripheral surface of the rotating fixing belt 81 comes into contact with the sliding member 85 while sliding. The nip forming member 84 is disposed radially inside the fixing belt 81 with the sliding member 85 interposed between the nip forming member 84 and the inner peripheral surface of the fixing belt 81. The nip forming member 84 includes an uneven portion 841 formed on a contact surface with the sliding member 85.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a fixing device and an image forming apparatus. [Background technology]

[0002] In electrophotographic image forming devices such as copiers and printers, a fixing device employing a thermal fixing method is widely used to fix an unfixed toner image formed on a sheet-like recording medium to the recording medium. The recording medium is heated and pressurized by passing through a fixing nip formed by contact between a heating member and a pressure member, thereby fixing the unfixed toner image.

[0003] For example, a conventional fixing device disclosed in Patent Document 1 includes a fixing belt, a pressure roller, and a nip forming member. The nip forming member is disposed on the inner circumferential side (inside in the radial direction) of the fixing belt and contacts the inner circumferential surface of the fixing belt by receiving pressure from the pressure roller, thereby forming a nip. The nip forming member includes a sliding sheet interposed between a base member and the fixing belt. This reduces sliding friction between the fixing belt and the nip forming member when the fixing belt rotates. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-92569 Summary of the Invention [Problem to be solved by the invention]

[0005] The sliding sheet (sliding member) is positioned opposite the pressure roller across the fixing belt, and must be fixed in place at the nip because it comes into sliding contact with the inner surface of the rotating fixing belt. If the sliding sheet is not fixed properly, there is a risk that a portion of the sliding sheet will be displaced (moved) as the fixing belt rotates. This raises concerns that the sliding sheet may be damaged or the fixing belt may not rotate properly.

[0006] In the above-mentioned conventional technology, both ends of the sliding sheet in the recording medium transport direction are fixed to the stays using screws. However, this conventional technology requires processes such as drilling screw holes in the sliding sheet and fastening with screws, which increases the number of steps and reduces workability.

[0007] The present invention has been made in consideration of the above points, and aims to provide a fixing device and an image forming apparatus that can fix a sliding member that contacts a fixing belt rotating in a fixing nip portion with a simple configuration. [Means for solving the problem]

[0008] To solve the above problems, the fixing device of the present invention includes a fixing belt, a sliding member, a nip forming member, a support member, and a pressure member. A recording medium is inserted into the fixing nip portion and heated and pressurized to fix a toner image formed on the recording medium to the recording medium. The fixing belt is endless, heated by a heating unit, and rotates along the recording medium conveyance direction. The sliding member is disposed adjacent to the radially inner side of the fixing belt, and the inner circumferential surface of the rotating fixing belt slides against the sliding member. The nip forming member is disposed radially inner of the fixing belt, sandwiching the sliding member between the sliding member and the inner circumferential surface of the fixing belt. The support member is disposed radially inner of the fixing belt and supports the nip forming member. The pressure member contacts the nip forming member with a predetermined pressure, sandwiching the sliding member and the fixing belt, to form a fixing nip portion between the fixing belt and the nip forming member. The nip forming member has an uneven portion formed on the contact surface with the sliding member. [Effects of the Invention]

[0009] According to the configuration of the present invention, it is possible to increase the frictional resistance between the sliding member and the nip forming member, thereby suppressing the relative displacement of the sliding member with respect to the nip forming member. That is, it is possible to fix the sliding member in the fixing nip portion. This makes it possible to suppress the displacement (movement) of the sliding member as the fixing belt rotates. Therefore, it is possible to prevent the occurrence of problems such as damage to the sliding member and poor rotation of the fixing belt. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional front view of an image forming apparatus according to an embodiment of the present invention; [Figure 2] 2 is a cross-sectional front view of a fixing device of the image forming apparatus of FIG. 1. [Figure 3] 2 is a side view of the end surface of a cutting portion of the fixing device of the image forming apparatus of FIG. 1. [Figure 4] FIG. 3 is a partial enlarged view of the fixing device in FIG. 2. [Figure 5] FIG. 10 is a cross-sectional front view of a fixing device according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to the following.

[0012] 1 is a schematic cross-sectional front view of an image forming apparatus 1 according to an embodiment. An example of the image forming apparatus 1 according to this embodiment is a tandem color printer that transfers a toner image onto a sheet (recording medium) S using an intermediate transfer belt 71. The image forming apparatus 1 may be a so-called multifunction peripheral that has functions such as printing, scanning (image reading), and facsimile transmission.

[0013] As shown in FIG. 1, the image forming apparatus 1 includes a sheet supply unit 3, a sheet conveying unit 4, an exposure unit 5, an image forming unit 6, a transfer unit 7, a fixing device 8, a sheet discharge unit 9, and a control unit 10, which are provided in a main body 2 of the apparatus.

[0014] The sheet supply unit 3 is located at the bottom of the device body 2. The sheet supply unit 3 stores multiple sheets (recording media) S before printing, and separates and sends out the sheets S one by one during printing. The sheet conveying unit 4 extends in the vertical direction along the side wall of the device body 2. The sheet conveying unit 4 conveys the sheet S sent out from the sheet supply unit 3 to the secondary transfer unit 73 and the fixing device 8, and then discharges the sheet S after fixing from the sheet discharge port 4a to the sheet discharge unit 9.

[0015] The exposure unit 5 is disposed above the sheet supply unit 3. The exposure unit 5 irradiates the image forming unit 6 with laser light controlled based on image data.

[0016] The image forming units 6 are disposed above the exposure unit 5 and below the intermediate transfer belt 71. The image forming units 6 include an image forming unit 6Y for yellow, an image forming unit 6C for cyan, an image forming unit 6M for magenta, and an image forming unit 6B for black. These four image forming units 6 have the same basic configuration. Therefore, in the following description, the identification symbols "Y," "C," "M," and "B" representing each color may be omitted unless otherwise specified.

[0017] The image forming unit 6 includes a photosensitive drum that is supported so as to be rotatable in a predetermined direction (clockwise in FIG. 1). The image forming unit 6 also includes a charging unit, a developing unit, and a drum cleaning unit that are arranged around the photosensitive drum along the direction of rotation of the photosensitive drum. A primary transfer unit 72 is arranged between the developing unit and the drum cleaning unit.

[0018] The photosensitive drum has a photosensitive layer formed on its outer circumferential surface. The charging unit charges the outer circumferential surface of the photosensitive drum to a predetermined surface potential. The exposure unit 5 exposes the outer circumferential surface of the photosensitive drum, which has been charged by the charging unit, to light, forming an electrostatic latent image of the original image on the outer circumferential surface of the photosensitive drum, with the charge attenuated. The development unit supplies toner to the electrostatic latent image on the outer circumferential surface of the photosensitive drum, developing it to form a toner image. Each of the four image forming units 6 forms a toner image of a different color. After the toner image is primarily transferred to the outer circumferential surface of the intermediate transfer belt 71, the drum cleaning unit removes and cleans any toner remaining on the outer circumferential surface of the photosensitive drum. In this way, the image forming unit 6 forms an image (toner image) that is later transferred to the sheet S.

[0019] The transfer unit 7 includes an intermediate transfer belt 71, primary transfer units 72Y, 72C, 72M, and 72B, a secondary transfer unit 73, and a belt cleaning unit 74. The intermediate transfer belt 71 is disposed above the four image forming units 6. The intermediate transfer belt 71 is supported so as to be rotatable in a predetermined direction (counterclockwise in FIG. 1), and is an endless intermediate transfer body onto which the toner images formed by each of the four image forming units 6 are sequentially superimposed and primarily transferred. The four image forming units 6 are disposed in a so-called tandem arrangement, lined up in a row from the upstream side to the downstream side in the rotation direction of the intermediate transfer belt 71.

[0020] Primary transfer units 72Y, 72C, 72M, and 72B are disposed above image forming units 6Y, 6C, 6M, and 6B of the respective colors, with intermediate transfer belt 71 sandwiched therebetween. Secondary transfer unit 73 is disposed upstream of fixing device 8 in the sheet conveying direction of sheet conveying unit 4, and downstream of four image forming units 6Y, 6C, 6M, and 6B in the rotation direction of intermediate transfer belt 71. Belt cleaning unit 74 is disposed downstream of secondary transfer unit 73 in the rotation direction of intermediate transfer belt 71.

[0021] The primary transfer unit 72 transfers the toner image formed on the outer circumferential surface of the photosensitive drum onto the intermediate transfer belt 71. In other words, the toner image is primarily transferred onto the outer circumferential surface of the intermediate transfer belt 71 at the primary transfer units 72Y, 72C, 72M, and 72B for each color. Then, as the intermediate transfer belt 71 rotates, the toner images of the four image forming units 6 are successively superimposed and transferred onto the intermediate transfer belt 71 at a predetermined timing, thereby forming a color toner image on the outer circumferential surface of the intermediate transfer belt 71 in which toner images of four colors, yellow, cyan, magenta, and black, are superimposed.

[0022] The color toner image on the outer surface of the intermediate transfer belt 71 is transferred to the sheet S, which is fed synchronously by the sheet conveying unit 4, at a secondary transfer nip formed in the secondary transfer unit 73. The belt cleaning unit 74 cleans the outer surface of the intermediate transfer belt 71 by removing toner and other adhering matter remaining on the outer surface of the intermediate transfer belt 71 after the secondary transfer. In this way, the transfer unit 7 transfers (records) the toner image formed on the outer surface of the photosensitive drum onto the sheet S.

[0023] The fixing device 8 is disposed above the secondary transfer section 73. The fixing device 8 fixes the toner image to the sheet S by applying heat and pressure to the sheet S onto which the toner image has been transferred.

[0024] The sheet discharge section 9 is disposed above the transfer section 7. The sheet S on which the toner image has been fixed and printing has been completed is transported to the sheet discharge section 9. The sheet discharge section 9 takes out the printed sheet (printed material) from above.

[0025] The control unit 10 includes a CPU, an image processing unit, a memory unit, and other electronic circuits and electronic components (all not shown). The CPU controls the operation of each component provided in the image forming apparatus 1 based on control programs and data stored in the memory unit to perform processing related to the functions of the image forming apparatus 1. The sheet supply unit 3, the sheet conveying unit 4, the exposure unit 5, the image forming unit 6, the transfer unit 7, and the fixing unit 8 each receive individual commands from the control unit 10 and work together to print on the sheet S. The memory unit is configured by a combination of a non-volatile storage device (not shown) such as a program ROM (Read Only Memory) or a data ROM, and a volatile storage device (not shown) such as a RAM (Random Access Memory).

[0026] Next, the configuration of the fixing device 8 of the embodiment will be described in detail. Fig. 2 is a cross-sectional front view of the fixing device 8 of the image forming apparatus 1 of Fig. 1. Fig. 3 is a side view of a cut end surface of the fixing device 8 of the image forming apparatus 1 of Fig. 1.

[0027] 2 and 3, for convenience of explanation, a configuration is depicted in which fixing belt 81 is disposed above fixing nip portion N and pressure roller (pressure member) 82 is disposed below. In FIG. 2, the left side is the upstream side (transfer section 7 side) in the sheet conveyance direction relative to fixing device 8, and the right side is the downstream side (sheet discharge section 9 side) in the sheet conveyance direction relative to fixing device 8. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 3, and FIG. 3 is a cross-sectional end view taken along line III-III in FIG. 2.

[0028] As shown in FIGS. 2 and 3, the fixing device 8 includes a fixing belt 81, a pressure roller 82, a heating section 83, a nip forming member 84, a sliding member 85, a support member 86, and a belt guide 87.

[0029] The fixing belt 81 is supported on the housing of the fixing device 8 so as to be rotatable about a horizontal axis. The fixing belt 81 is endless and has a cylindrical shape with an outer diameter of, for example, 20 mm to 50 mm, and is longer than the pressure roller 82 in the direction of the rotation axis (the sheet width direction perpendicular to the sheet conveyance direction, the depth direction of the paper in FIG. 2, and the left-right lateral direction in FIG. 3). The fixing belt 81 is rotatable along the conveyance direction of the sheet S, which is a recording medium.

[0030] The fixing belt 81 has a laminated structure in which an elastic layer and a release layer are provided on the outer periphery of a heat-generating layer, which is a base layer. The heat-generating layer is made of, for example, a 30-50 μm thick metal film such as nickel, or a 50-100 μm thick polyimide film containing metal powder such as copper, silver, or aluminum. The elastic layer is made of, for example, a 100-500 μm thick silicone rubber. The release layer is made of, for example, a 30-50 μm thick fluorine-based resin such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer). The fixing belt 81 is heated by a heating unit 83.

[0031] The pressure roller 82 is supported rotatably about a horizontal axis on the housing of the fixing device 8. The pressure roller 82 has a cylindrical shape and is shorter than the fixing belt 81 in the direction of the rotation axis (the sheet width direction, the depth direction of the paper in FIG. 2, and the left-right lateral direction in FIG. 3).

[0032] A predetermined pressure is applied to the pressure roller 82 by a pressure mechanism (not shown) toward the fixing belt 81. As a result, the pressure roller 82 comes into contact with the outer peripheral surface of the fixing belt 81. In other words, the pressure roller 82 comes into contact with the nip forming member 84 at a predetermined pressure, sandwiching the sliding member 85 and the fixing belt 81 therebetween. A fixing nip N is formed between the pressure roller 82 and the fixing belt 81.

[0033] The pressure roller 82 is connected to a drive source (not shown) including, for example, a motor, and receives power from the motor to rotate clockwise in FIG. 2. The pressure roller 82 comes into contact with the outer peripheral surface of the fixing belt 81 and applies a rotational driving force to the fixing belt 81. The fixing belt 81 rotates counterclockwise in FIG. 2 in accordance with the rotation of the pressure roller 82. The operation of the fixing belt 81 is controlled by the control unit 10.

[0034] The pressure roller 82 has a laminated structure with an elastic layer and a release layer provided on the outer periphery of a core metal. The core metal is made of metal such as iron or aluminum, for example, with a diameter of 20 mm to 25 mm. The elastic layer is made of silicone rubber, for example, with a thickness of 3 mm to 8 mm, and has an outer diameter of 30 mm to 35 mm. The release layer is made of fluororesin such as PFA, for example, with a thickness of approximately 10 μm to 50 μm.

[0035] The heating unit 83 is disposed opposite the outer peripheral surface of the fixing belt 81 across a predetermined gap in an area opposite the side where the pressure roller 82 is disposed with respect to the fixing belt 81. The heating unit 83 extends along the rotation axis direction of the fixing belt 81 (sheet width direction) longer than the fixing belt 81 and the belt guide 87.

[0036] The heating unit 83 includes an exciting coil 831, and a holding member, a core, etc. (not shown). The exciting coil 831 and the core are held in predetermined positions relative to the fixing belt 81 by the holding member. The exciting coil 831 is made of a Litz wire made by bundling multiple conductive wires, and is wound so as to extend along the rotation axis direction (sheet width direction) of the fixing belt 81. The exciting coil 831 is formed in an arc shape along the outer peripheral surface of the fixing belt 81 in the circumferential direction of the fixing belt 81.

[0037] Heating unit 83 uses electromagnetic induction to heat fixing belt 81. More specifically, heating unit 83 heats fixing belt 81 by causing a heat generating layer of fixing belt 81 to generate heat through induction heating.

[0038] Nip forming member 84 is disposed radially inside fixing belt 81, with sliding member 85 sandwiched between nip forming member 84 and the inner circumferential surface of fixing belt 81. Nip forming member 84 is disposed opposite pressure roller 82, with sliding member 85 and fixing belt 81 between them. Nip forming member 84 comes into contact with the inner circumferential surface of fixing belt 81 via sliding member 85, and forms a fixing nip N between fixing belt 81 and pressure roller 82.

[0039] Nip forming member 84 has a generally rectangular parallelepiped shape that extends along the rotation axis direction (sheet width direction) of fixing belt 81, with approximately the same length as fixing belt 81. Nip forming member 84 has a base material made of a metal such as aluminum, or a heat-resistant resin such as a liquid crystal polymer. Nip forming member 84 may have an elastic layer made of, for example, elastomer, silicone rubber, or the like on the side of the base material facing fixing belt 81.

[0040] The sliding member 85 is disposed adjacent to the radially inner side of the fixing belt 81 in the fixing nip portion N. The sliding member 85 is sandwiched between the inner circumferential surface of the fixing belt 81 and the nip forming member 84. The sliding member 85 comes into sliding contact with the inner circumferential surface of the rotating fixing belt 81. The sliding member 85 is a sheet material made of a fluorine-based resin such as PFA. The thickness of the sliding member 85 is, for example, approximately 200 μm to 400 μm. The sliding member 85 reduces the sliding load between the inner circumferential surface of the fixing belt 81 and the nip forming member 84.

[0041] The support member 86 is disposed radially inward of the fixing belt 81. The support member 86 extends along the rotation axis direction (sheet width direction) of the fixing belt 81, longer than the fixing belt 81. The support member 86 is held by side plates (not shown) provided on both outer sides of the rotation axis direction of the fixing belt 81, and ensures strength that allows pressure to be applied between the support member 86 and the pressure roller 82. The support member 86 is formed, for example, of a rectangular column shape, and supports the nip forming member 84 between itself and the inner surface of the fixing belt 81.

[0042] The belt guide 87 is disposed radially inward of the fixing belt 81, facing the heating unit 83 across the fixing belt 81. The belt guide 87 contacts the inner peripheral surface of the fixing belt 81 except for the fixing nip portion N, and supports the fixing belt 81 from the radially inner side. The belt guide 87 is made of a metal plate that extends along the rotation axis direction of the fixing belt 81 (sheet width direction) for approximately the same length as the fixing belt 81.

[0043] Belt guide 87 is made of an elastic magnetic metal such as SUS430 with a thickness of 0.1 mm to 0.5 mm. Belt guide 87 stabilizes the rotational orbit of fixing belt 81 and heats fixing belt 81 by absorbing the magnetic field that penetrates fixing belt 81, thereby increasing the efficiency of heating fixing belt 81.

[0044] With the above configuration, the fixing device 8 inserts the sheet S into the fixing nip portion N between the fixing belt 81 and the pressure roller 82, and fixes the toner image formed on the sheet S to the sheet S by applying heat and pressure.

[0045] Next, a detailed description will be given of the detailed configuration of the fixing device 8. Fig. 4 is a partially enlarged view of the fixing device 8 in Fig. 2. Fig. 4 is a partially enlarged view of the area circled A in Fig. 2.

[0046] Nip forming member 84 has uneven portion 841. Uneven portion 841 is the surface of nip forming member 84 that faces sliding member 85, and is formed on the surface of nip forming member 84 that contacts sliding member 85. Uneven portion 841 is an area where convex portions that face sliding member 85 and concave portions that face sliding member 85 repeatedly expand in the radial direction of fixing belt 81.

[0047] According to the above configuration, it is possible to increase the frictional resistance between the sliding member 85 and the nip forming member 84, and to suppress the relative displacement of the sliding member 85 with respect to the nip forming member 84. In other words, it is possible to fix the sliding member 85 in the fixing nip portion N. This makes it possible to suppress the sliding member 85 from being displaced (moved) in accordance with the rotation of the fixing belt 81. Therefore, it is possible to prevent the occurrence of problems such as damage to the sliding member 85 and poor rotation of the fixing belt 81.

[0048] In order to reduce the sliding load, a lubricant may be applied between the inner circumferential surface of fixing belt 81 and sliding member 85. In this case, there is a concern that the lubricant may find its way between sliding member 85 and nip forming member 84, reducing the frictional resistance between sliding member 85 and nip forming member 84. However, as in the present embodiment, by forming uneven portion 841 on nip forming member 84, the lubricant can be moved to the recesses of uneven portion 841, allowing nip forming member 84 to contact sliding member 85 at the protrusions of uneven portion 841 without the lubricant passing through. This makes it possible to prevent a reduction in the frictional resistance between sliding member 85 and nip forming member 84.

[0049] Furthermore, it is preferable that uneven portion 841 is formed over the entire contact area with sliding member 85 on the contact surface of nip forming member 84 with sliding member 85. This configuration makes it difficult for sliding member 85 to displace (move), thereby improving the effect of suppressing relative displacement of sliding member 85 with respect to nip forming member 84. This makes it possible to enhance the effect of suppressing displacement (movement) of sliding member 85 as fixing belt 81 rotates.

[0050] If the maximum height roughness Rz (JIS B 0601:2001) of the uneven portion 841 exceeds the radial thickness of the sliding member 85, the pressure between the pressure roller 82 and the fixing belt 81 in the fixing nip N may become too high, which may adversely affect the image (toner image) on the sheet S. Furthermore, if the pressure at the protruding portions of the uneven portion 841 becomes too high, there is a concern that the fixing belt 81 may be scratched and damaged.

[0051] Therefore, it is preferable that the maximum height roughness Rz (JIS B 0601:2001) of the uneven portion 841 is equal to or less than the radial thickness of the sliding member 85. This configuration increases the frictional resistance between the sliding member 85 and the nip forming member 84. This enhances the effect of suppressing the relative displacement of the sliding member 85 with respect to the nip forming member 84. In other words, it is possible to fix the sliding member 85 in the fixing nip N.

[0052] Furthermore, the unevenness of the uneven portion 841 should have a height difference (roughness) necessary to fix the sliding member 85 in the fixing nip portion N. If the height difference (roughness) of the uneven portion 841 is less than a predetermined value, there is a risk that the sliding member 85 cannot be fixed in the fixing nip portion N.

[0053] Therefore, it is preferable that the maximum height roughness Rz (JIS B 0601:2001) of the uneven portion 841 is 20 μm or more. This configuration increases the frictional resistance between the sliding member 85 and the nip forming member 84. This increases the effect of suppressing the relative displacement of the sliding member 85 with respect to the nip forming member 84. In other words, it is possible to fix the sliding member 85 in the fixing nip N.

[0054] Next, a description will be given of the configuration of the fixing device 8 of the modified example. Fig. 5 is a cross-sectional front view of the fixing device 8 of the modified example.

[0055] The sliding member 85 of the fixing device 8 of the modified example has a fixed portion 851. The fixed portion 851 is disposed upstream of the fixing nip portion N in the rotation direction (counterclockwise in FIG. 5) of the fixing belt 81. The fixed portion 851 is adjacent to the support member 86. The fixed portion 851 is fixed to the support member 86 using a fastening member (not shown) such as a screw. In other words, the sliding member 85 is fixed to the support member 86 upstream of the fixing nip portion N in the rotation direction of the fixing belt 81.

[0056] According to the above configuration, by fixing the sliding member 85 to the support member 86, it is possible to suppress the relative displacement of the sliding member 85 with respect to the nip forming member 84. In other words, it is possible to fix the sliding member 85 in the fixing nip portion N. This makes it possible to suppress the sliding member 85 from being displaced (moved) in accordance with the rotation of the fixing belt 81. Therefore, it is possible to prevent the occurrence of problems such as damage to the sliding member 85 and poor rotation of the fixing belt 81.

[0057] Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these, and various modifications can be made without departing from the spirit of the invention.

[0058] For example, in the above embodiment, the image forming apparatus 1 is a so-called tandem type image forming apparatus for color printing that forms images of multiple colors by sequentially overlapping them, but the image forming apparatus is not limited to this type. The image forming apparatus may be a non-tandem type image forming apparatus for color printing or a monochrome image forming apparatus. [Industrial Applicability]

[0059] The present invention can be used in fixing devices and image forming apparatuses. [Explanation of symbols]

[0060] 1. Image forming device 2. Device body 8 Fixing device 81 Fixing belt 82 Pressure roller (pressure member) 83 Heating section 84 Nip forming member 85 Sliding member 86 Support member 87 Belt guide 841 Uneven part 851 Fixed part N Fixing nip S seat

Claims

1. an endless fixing belt that is heated by a heating unit and rotates in the recording medium conveyance direction; a sliding member disposed adjacent to the inner side of the fixing belt in the radial direction, with which the inner circumferential surface of the rotating fixing belt comes into sliding contact; a nip forming member disposed radially inside the fixing belt, with the sliding member sandwiched between the nip forming member and an inner circumferential surface of the fixing belt; a support member disposed radially inside the fixing belt and supporting the nip forming member; a pressure member that contacts the nip forming member with a predetermined pressure across the sliding member and the fixing belt to form a fixing nip portion between the pressing member and the fixing belt; a fixing device for fixing a toner image formed on a recording medium to the recording medium by inserting the recording medium into the fixing nip portion and applying heat and pressure to the recording medium, The fixing device is characterized in that the nip forming member has an uneven portion formed on a surface that comes into contact with the sliding member.

2. 2. The fixing device according to claim 1, wherein the maximum height roughness Rz of the uneven portion is equal to or less than the thickness of the sliding member in the radial direction.

3. 2. The fixing device according to claim 1, wherein the maximum height roughness Rz of the uneven portion is 20 [mu]m or more.

4. 2. The fixing device according to claim 1, wherein the uneven portion is formed over the entire contact area with the sliding member.

5. 2. The fixing device according to claim 1, wherein the sliding member is fixed to the support member on the upstream side of the fixing nip portion in the rotation direction of the fixing belt.

6. an image forming unit that forms a toner image on the recording medium; a fixing device according to any one of claims 1 to 5, which heats and pressurizes the recording medium on which the toner image has been formed by the image forming unit to fix the toner image to the recording medium; An image forming apparatus comprising:

Images