Fixing device and image forming apparatus

Abstract

To provide a fixing device capable of reducing frictional resistance between a sliding member coming into contact with a fixing belt rotating in a fixing nip part and the fixing belt on the downstream side of the fixing nip part.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 has a sheet shape, 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 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 has a projection 841 formed on the opposite side to the fixing nip N. The sliding member 85 includes coupling holes 851 which are formed at both end portions in the rotation direction Dc of the fixing belt 81 and into which the protruding portions 841 are inserted, and a facing hole 852 which is formed on the downstream side of the fixing nip portion N in the rotation direction Dc of the fixing belt 81 and faces the inner peripheral surface of the fixing belt 81.SELECTED DRAWING: Figure 5

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, a fixed member, and a sheet-like member. The fixed member is disposed on the inner circumferential side (inside in the radial direction) of the fixing belt and forms a nip by being pressed against the pressure roller via the fixing belt. The sheet-like member is disposed so as to cover the periphery of the fixed member and is disposed opposite the pressure roller with the fixing belt sandwiched therebetween. The sheet-like member reduces the sliding resistance between the fixed member and the fixing belt. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-180569 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-described conventional technology, the sheet-like member (sliding member) is provided to cover the periphery of the fixed member by overlapping and fitting holes formed on both the upstream and downstream sides of the sheet-like member in the conveying direction with protrusions on the fixed member. When the fixing belt rotates, the sheet-like member is pulled toward the downstream side of the fixing nip, which can deform the holes. Furthermore, the sheet-like member stretches toward the downstream side of the fixing nip, increasing the contact area with the inner circumferential surface of the fixing belt. This increases frictional resistance between the sheet-like member and the fixing belt, raising concerns about damage to the sliding sheet and malfunction of the fixing belt.

[0006] 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 reduce the frictional resistance between a sliding member that contacts a rotating fixing belt in a fixing nip portion and the fixing belt downstream of the fixing nip portion. [Means for solving the problem]

[0007] 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 sheet-shaped and disposed adjacent to the radially inner side of the fixing belt, with the inner circumferential surface of the rotating fixing belt slidingly contacting 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 pressure member. The nip forming member has a protrusion formed on the opposite side of the fixing nip portion. The sliding member has connecting holes formed at both ends of the fixing belt in the rotation direction, into which the protrusions are inserted, and opposing holes formed downstream of the fixing nip portion in the rotation direction of the fixing belt, facing the inner surface of the fixing belt. [Effects of the Invention]

[0008] According to the configuration of the present invention, when the sliding member is stretched by being pulled toward the downstream side of the fixing nip as the fixing belt rotates, the opposing hole is positioned downstream of the fixing nip. This prevents an increase in the contact area between the sliding member and the fixing belt downstream of the fixing nip. In other words, it is possible to reduce the frictional resistance between the sliding member and the fixing belt downstream of the fixing nip, preventing damage to the sliding member and malfunction of the fixing belt. [Brief explanation of the drawings]

[0009] [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] 3 is a top view of a nip forming member of the fixing device of FIG. 2. FIG. [Figure 4] 3 is a plan view of a sliding member (in a flat state) of the fixing device of FIG. 2. FIG. [Figure 5] 3 is a partially enlarged cross-sectional front view of the fixing device of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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).

[0025] Next, the configuration of the fixing device 8 of this embodiment will be described in detail. Figure 2 is a cross-sectional front view of the fixing device 8 of the image forming apparatus 1 of Figure 1.

[0026] 2, for ease of explanation, a configuration is depicted in which the fixing belt 81 is disposed above the fixing nip portion N and the pressure roller (pressure member) 82 is disposed below the fixing nip portion N. In FIG. 2, the right side is the upstream side (transfer section 7 side) in the sheet conveyance direction relative to the fixing device 8, and the left side is the downstream side (sheet discharge section 9 side) in the sheet conveyance direction relative to the fixing device 8. For ease of explanation, the upper and lower sides in FIG. 2 may be described as the upper and lower sides of the fixing device 8.

[0027] As shown in FIG. 2, 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.

[0028] 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 configured in 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). The fixing belt 81 is rotatable along the conveyance direction of the sheet S, which is a recording medium.

[0029] 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 a metal film such as nickel having a thickness of 30 μm to 50 μm, or a polyimide film having a thickness of 50 μm to 100 μm and containing metal powder such as copper, silver, or aluminum. The elastic layer is made of silicone rubber having a thickness of 100 μm to 500 μm. The release layer is made of a fluorine-based resin such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) having a thickness of 30 μm to 50 μm. The fixing belt 81 is heated by a heating unit 83.

[0030] 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).

[0031] 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.

[0032] 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 counterclockwise 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 clockwise 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] Heating unit 83 heats fixing belt 81 by electromagnetic induction. More specifically, heating unit 83 heats fixing belt 81 by inductively heating the heat-generating layer of fixing belt 81. Heating unit 83 may be configured by a halogen heater that is disposed close to the inner circumferential surface of fixing belt 81 in fixing nip N and extends over the entire area in the rotational axis direction of fixing belt 81.

[0037] 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.

[0038] 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.

[0039] 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-like member with a thickness of about 0.5 mm. The sliding member 85 aims to reduce the sliding load between the inner circumferential surface of the fixing belt 81 and the nip forming member 84.

[0040] 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 cylindrical member, and supports the nip forming member 84 between itself and the inner surface of the fixing belt 81.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] Next, the detailed configuration of the fixing device 8 will be described in detail. Fig. 3 is a top view of the nip forming member 84 of the fixing device 8 of Fig. 2. Fig. 4 is a plan view of the sliding member 85 (in a flat state) of the fixing device 8 of Fig. 2. Fig. 5 is a partially enlarged cross-sectional front view of the fixing device 8 of Fig. 2. Note that Fig. 5 depicts the initial state (dashed line) and the deformed state (solid line) of the sliding member 85 on the downstream side of the fixing nip portion N with respect to the rotation direction Dc of the fixing belt 81.

[0045] 3, 4, and 5, the direction indicated by the arrow Dw in the drawings is the rotation axis direction (sheet width direction) of the fixing belt 81, and the direction indicated by the arrow Dc is the rotation direction (sheet conveyance direction) of the fixing belt. The rotation axis direction (sheet width direction) Dw of the fixing belt 81 and the rotation direction (sheet conveyance direction) Dc of the fixing belt 81 are perpendicular to each other.

[0046] 2 and 3, the nip forming member 84 has a protrusion 841. The protrusion 841 is formed on the side of the nip forming member 84 opposite to the fixing nip portion N. In other words, the protrusion 841 is formed on the surface of the nip forming member 84 that faces the support member 86.

[0047] A plurality of protrusions 841 are formed on the surface facing the support member 86 and are arranged side by side in the rotational direction Dc and rotational axis direction Dw of the fixing belt 81. In this embodiment, the nip forming member 84 has twelve protrusions 841, as shown in FIG. 3 . More specifically, of the twelve protrusions 841, six are arranged side by side in the rotational axis direction Dw of the fixing belt 81, and six are arranged side by side in two rows in the rotational direction Dc of the fixing belt 81. The protrusions 841 have an oval shape (elliptical shape) in a plan view that extends in the rotational axis direction Dw of the fixing belt 81, and protrude toward the support member 86.

[0048] The support member 86 has connection holes 861 formed on the surface facing the nip forming member 84. The connection holes 861 face the protrusions 841 of the nip forming member 84 in the radial direction of the fixing belt 81. Twelve connection holes 861, the same number as the twelve protrusions 841, are formed on the surface facing the nip forming member 84. The connection holes 861 have a shape, size, and arrangement (positional relationship) that allows the protrusions 841 to be inserted therein. The support member 86 supports the nip forming member 84 by inserting the protrusions 841 into the respective connection holes 861.

[0049] 2 and 4, sliding member 85 has a connecting hole 851 and an opposing hole 852. Note that Fig. 4 illustrates a state in which sheet-like sliding member 85 is laid out flat. In the flat state, sliding member 85 has a rectangular shape in a plan view that extends in the rotation direction Dc and the rotation axis direction Dw of fixing belt 81.

[0050] The connecting holes 851 are formed at both ends of the sheet-like sliding member 85 in the rotation direction Dc of the fixing belt 81. As shown in FIG. 4, twelve connecting holes 851 are provided in each region of both ends of the sliding member 85 in the rotation direction Dc of the fixing belt 81, the same number as the twelve protrusions 841. The twelve connecting holes 851 are arranged side by side in the rotation direction Dc and the rotation axis direction Dw of the fixing belt 81. Like the protrusions 841, the connecting holes 851 have an oval shape (elliptical shape) in a plan view extending in the rotation axis direction Dw of the fixing belt 81. The connecting holes 851 have a shape, size, and arrangement (positional relationship) that allow the protrusions 841 to be inserted therein. The connecting holes 851 penetrate the sheet-like sliding member 85 in the thickness direction.

[0051] Sheet-like sliding member 85 has a generally cylindrical shape extending in the rotational axis direction Dw of fixing belt 81, and is wound around nip forming member 84 to cover the periphery (see FIGS. 2 and 5). At this time, sheet-like sliding member 85 is wound around nip forming member 84 with one end side and the other end side in the rotational direction Dc of fixing belt 81 overlapping in the opposing region between support member 86 and nip forming member 84.

[0052] When the sliding member 85 is wound around the nip forming member 84, the twelve connecting holes 851 formed on each end of the sliding member 85 in the rotation direction Dc of the fixing belt 81 overlap (see FIG. 5). The protrusions 841 are inserted into the connecting holes 851. More specifically, for each of the twelve protrusions 841, the protrusion 841 is inserted into the connecting hole 851 on one end side of the sliding member 85 in the rotation direction Dc of the fixing belt 81 and the connecting hole 851 on the other end side in succession.

[0053] The opposing holes 852 are formed in the sheet-like sliding member 85 on the downstream side of the fixing nip portion N with respect to the rotation direction Dc of the fixing belt 81. In this embodiment, six opposing holes 852 are provided and arranged side by side in the rotation axis direction Dw of the fixing belt 81. Like the connecting holes 851, the opposing holes 852 have an oval shape (elliptical shape) in a plan view that extends in the rotation axis direction Dw of the fixing belt 81. They penetrate the sheet-like sliding member 85 in the thickness direction.

[0054] The opposing hole 852 faces the inner circumferential surface of the fixing belt 81 on the downstream side of the fixing nip portion N of the sliding member 85 with respect to the rotation direction Dc of the fixing belt 81.

[0055] 5, when the sliding member 85 is pulled toward the downstream side of the fixing nip N and stretched as the fixing belt 81 rotates, the opposing hole 852 is positioned downstream of the fixing nip N. This makes it possible to prevent an increase in the contact area between the sliding member 85 and the fixing belt 81 downstream of the fixing nip N. In other words, it is possible to reduce the frictional resistance between the sliding member 85 and the fixing belt 81 downstream of the fixing nip N, thereby preventing damage to the sliding member 85, malfunction of the fixing belt 81, etc.

[0056] Further, the opposing holes 852 are disposed downstream of the connecting holes 851 with respect to the rotation direction Dc of the fixing belt 81. Specifically, as shown in Fig. 4, the six opposing holes 852 arranged side by side in the rotation axis direction Dw of the fixing belt 81 are disposed downstream of the rotation direction Dc with respect to the six connecting holes 851 arranged side by side in the same direction, without any difference in position in the rotation axis direction (sheet width direction) Dw.

[0057] According to the above configuration, the opposing hole 852 is located downstream of the connecting hole 851, which is at risk of deformation due to the sliding member 85 being pulled toward the downstream side of the fixing nip N when the fixing belt 81 rotates. In other words, the opposing hole 852 is located at a position where the sliding member 85 is likely to stretch toward the downstream side of the fixing nip N, which can enhance the effect of suppressing an increase in the contact area between the sliding member 85 and the fixing belt 81.

[0058] Furthermore, sliding member 85 is made of a fiber material. Specifically, sliding member 85 is, for example, a heat-resistant fiber made of a fluorine-based resin such as PTFE (polytetrafluoroethylene). Furthermore, if the sliding surface of sliding member 85 that comes into contact with fixing belt 81 is made of a fluorine-based resin, sliding member 85 may have PPS (polyphenylene sulfide) fiber or the like woven therein for reinforcement.

[0059] A fibrous member is effective in reducing the sliding load between the inner circumferential surface of fixing belt 81 and nip forming member 84, but on the other hand, it may be easily deformed as fixing belt 81 rotates. Therefore, according to the above configuration, sliding member 85 is made of a fibrous member, and even if sliding member 85 is pulled downstream as fixing belt 81 rotates and stretched, it is possible to suppress an increase in the contact area between sliding member 85 and fixing belt 81.

[0060] Furthermore, the area around the connecting hole 851 of the sliding member 85 is easily pulled toward the downstream side of the fixing nip N due to the influence of factors such as the fibers of the sliding member 85 being broken by providing the connecting hole 851 and the connecting hole 851 itself being easily deformed. As a result, the area of ​​the sliding member 85 downstream of the connecting hole 851 is more likely to stretch than other areas.

[0061] Therefore, in order to prevent an increase in the contact area between the sliding member 85 and the fixing belt 81 on the downstream side of the fixing nip N, it is preferable that the opposing hole 852 has a width equal to or greater than the width (length in the rotational axis direction Dw) of the connecting hole 851 in the rotational axis direction Dw of the fixing belt 81. The upper limit of the width of the opposing hole 852 is the length that prevents the opposing hole 852 from connecting with another opposing hole 852 adjacent to it in the rotational axis direction Dw.

[0062] According to the above configuration, it is possible to reduce the area where sliding member 85 faces the inner circumferential surface of fixing belt 81 on the downstream side of fixing nip portion N. In other words, it is possible to enhance the effect of suppressing an increase in the contact area between sliding member 85 and fixing belt 81 on the downstream side of fixing nip portion N.

[0063] 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.

[0064] 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]

[0065] The present invention can be used in fixing devices and image forming apparatuses. [Explanation of symbols]

[0066] 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 Protrusion 851 coupling hole 852 Opposite holes 861 Connection hole Dc Rotation direction Dw Rotation axis direction 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 sheet-like 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 nip forming member has a protrusion formed on the opposite side of the fixing nip portion, The sliding member is coupling holes formed at both ends of the fixing belt in the rotation direction, into which the protrusions are inserted; a facing hole formed downstream of the fixing nip portion with respect to the rotation direction of the fixing belt and facing an inner circumferential surface of the fixing belt; A fixing device comprising:

2. The fixing device according to claim 1 , wherein the counter hole is disposed downstream of the connecting hole in the rotation direction of the fixing belt.

3. 2. The fixing device according to claim 1, wherein the sliding member is made of a fibrous material.

4. 2. The fixing device according to claim 1, wherein the opposing hole has a width equal to or greater than the width of the connecting hole in the direction of the rotation axis of the fixing belt.

5. an image forming unit that forms a toner image on the recording medium; a fixing device according to any one of claims 1 to 4, 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