Fixing device

Abstract

To provide a fixation device in which a sliding member is held in a stable state without generating a gap between the sliding member and a fitting groove part.SOLUTION: A sliding member 304 has a downstream side abutting part 310 which abuts on a downstream side surface 303e of a fitting groove part 303f on the downstream side relative to a downstream end 3042 of an opposite surface 304e. The downstream side abutting part 310 abuts on the downstream side surface 303e in such a state that the downstream end 3042 is located on the upstream side relative to a downstream side continuous part 303g. When the sliding member 304 moves to the downstream side following the rotation start of the fixation belt 301, the downstream side abutting part 310 abuts on the downstream side surface 303e before the downstream end 3042 contacts the downstream side continuous part 303g, and the sliding member 304 stops. Consequently, the sliding member 304 is held by a fixation pad 303 in such a state that the entire surface of the opposite surface 304e contacts a bottom surface 303h of the fitting groove part 303f and in such a state that a gap is not generated between the bottom surface 303h and the sliding member 304.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a fixing device suitable for use in an image forming apparatus using electrophotographic technology, such as a printer, a copier, a facsimile machine, or a multifunction peripheral.

Background Art

[0002] An image forming apparatus includes a fixing device that fixes a toner image onto a recording material by applying heat and pressure to the recording material on which the toner image is formed. The fixing device has a rotating endless fixing belt, a fixing pad disposed non-rotatably on the inner peripheral side of the fixing belt, and a pressure roller that abuts against the outer peripheral surface of the fixing belt. In this fixing device, the fixing belt is pressed by the fixing pad and the pressure roller to form a fixing nip portion between the fixing belt and the pressure roller. When the recording material is sandwiched and conveyed through the fixing nip portion, heat and pressure are applied, so that the toner image is fixed onto the recording material.

[0003] However, if the frictional force between the fixing belt and the fixing pad is large, the rotation of the fixing belt is hindered. Therefore, in order to reduce the frictional force between the fixing belt and the fixing pad, a device provided with a sliding member that slides on the fixing belt has been proposed (Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, the fixing pad has a concave fitting portion formed therein (hereinafter referred to as the fitting groove) for fitting the sliding member in order to hold the sliding member. The fixing pad is manufactured from resin by injection molding using a mold. When manufacturing the fixing pad by injection molding, in order to ensure release from the mold and prevent damage to the mold, the corners of the tips of the protrusions that form the fitting groove (the parts corresponding to the corners of the fitting groove) are rounded (so-called R processing) in the mold.

[0006] Due to the design of the mold, the corners of the fitting grooves of the fixing pad are formed in a curved shape (corner radius). Therefore, conventionally, when the sliding member was slid on the fixing belt, the corners of the sliding member would come into contact with the corners of the fitting grooves of the fixing pad, and the sliding member would move along the corners away from the bottom surface of the fitting grooves, resulting in a part of the sliding member being held without contact with the bottom surface. In other words, a gap was created between the bottom surface of the fitting grooves and the sliding member, and the sliding member was held in an unstable state by the fixing pad, which made it easy for uneven pressure to occur in the fixing nip, resulting in poor fixing of the toner image to the recording material, which is undesirable.

[0007] The present invention has been made in view of the above problems, and aims to provide a fixing device in which the sliding member is held in a stable state in contact with the bottom surface without creating a gap between the sliding member and the bottom surface of the fitting groove formed in the fixing pad, without creating a gap between the sliding member and the bottom surface of the fitting groove. [Means for solving the problem]

[0008] A fixing device according to one embodiment of the present invention is a fixing device for fixing a toner image formed on a recording material to the recording material, comprising: a rotating endless fixing belt; a sliding member having a sliding surface that slides on the fixing belt; a holding member provided non-rotatably on the inner circumference side of the fixing belt and having a fitting groove into which the sliding member can be fitted, and holding the sliding member so as to contact the inner circumference surface of the fixing belt; and an opposing member that abuts the outer circumference surface of the fixing belt so as to sandwich the fixing belt between itself and the sliding member, forming a fixing nip portion that grips and conveys the recording material in the conveying direction to fix the toner image to the recording material, wherein the holding member has a fitting groove opposite to the sliding surface of the sliding member Support A bottom surface, a downstream side surface formed in a direction intersecting the bottom surface downstream with respect to the conveying direction, and a continuous surface between the bottom surface and the downstream side surface. Forming a curved corner The sliding member has a downstream continuous section and ,before With respect to the transport direction, the downstream end of the opposite surface is located upstream of the downstream continuous section. Furthermore, while in contact with the bottom surface, It abuts against the downstream side surface downstream of the downstream end of the opposite surface. It is possible It is characterized by having a downstream abutment portion. Furthermore, a fixing device according to one embodiment of the present invention is a fixing device for fixing a toner image formed on a recording material to the recording material, comprising: a rotating endless fixing belt; a sliding member having a sliding surface that slides on the fixing belt; a holding member provided non-rotatably on the inner circumference side of the fixing belt and having a fitting groove that allows the sliding member to be fitted with a gap in the direction of transport of the recording material, and holding the sliding member so as to contact the inner circumference surface of the fixing belt; and an opposing member that abuts the outer circumference surface of the fixing belt so as to sandwich the fixing belt between itself and the sliding member, forming a fixing nip portion that grips and transports the recording material in the transport direction to fix a toner image to the recording material, wherein the holding member has the sliding surface in the fitting groove The sliding member has a bottom surface that supports the opposite surface of the sliding surface of the member, a downstream side surface formed in a direction that intersects the bottom surface downstream with respect to the transport direction, and a downstream continuous portion that extends toward the sliding member side from the position of the intersection of the line extending the bottom surface and the line extending the downstream side surface in a cross section perpendicular to the width direction of the recording material which is perpendicular to the transport direction, and forms a corner that is continuous with the bottom surface and the downstream side surface, wherein the sliding member has a downstream abutment portion that can abut the downstream side surface downstream of the downstream end of the opposite surface downstream of the downstream end of the opposite surface when the downstream end of the opposite surface is located upstream of the downstream continuous portion with respect to the transport direction and abuts against the bottom surface. Furthermore, a fixing device according to one embodiment of the present invention is a fixing device for fixing a toner image formed on a recording material to the recording material, comprising: a rotating endless fixing belt; a sliding member having a sliding surface that slides on the fixing belt; a holding member that is non-rotatably provided on the inner circumference side of the fixing belt and has a fitting groove that allows the sliding member to be fitted with a gap in the direction of transport of the recording material, and holds the sliding member so as to contact the inner circumference surface of the fixing belt; and an opposing member that abuts the outer circumference surface of the fixing belt so as to sandwich the fixing belt between itself and the sliding member, and forms a fixing nip portion that grips and transports the recording material in the transport direction to fix a toner image to the recording material, wherein the holding member has a bottom surface that supports the opposite surface of the sliding surface of the sliding member in the fitting groove, and the transport The sliding member has a downstream side surface formed in a direction intersecting the bottom surface on the downstream side with respect to the conveying direction, and a downstream continuous portion that extends toward the sliding member side from the position of the intersection of the line extending the bottom surface and the line extending the downstream side surface in a cross section perpendicular to the width direction of the recording material which is perpendicular to the conveying direction, and forms a corner continuous with the bottom surface and the downstream side surface, and the sliding member has a downstream abutment portion that abuts the downstream side surface downstream of the downstream end of the opposite surface with respect to the conveying direction, and the downstream abutment portion is characterized in that, when the sliding member is abutting the bottom surface and abutting the downstream side surface, one surface facing the downstream continuous portion can be separated from the downstream continuous portion to form a gap between it and the downstream continuous portion. Furthermore, a fixing device according to one embodiment of the present invention is a fixing device for fixing a toner image formed on a recording material to the recording material, comprising: a rotating endless fixing belt; a sliding member having a sliding surface that slides on the fixing belt; a holding member provided non-rotatably on the inner circumference side of the fixing belt and having a fitting groove that allows the sliding member to be fitted with a gap in the direction of transport of the recording material, and holding the sliding member so as to contact the inner circumference surface of the fixing belt; and an opposing member that abuts the outer circumference surface of the fixing belt so as to sandwich the fixing belt between itself and the sliding member, forming a fixing nip portion that grips and transports the recording material in the transport direction to fix a toner image to the recording material, wherein the holding member has a bottom surface that supports the opposite surface of the sliding surface of the sliding member in the fitting groove, and a bottom surface on the downstream side with respect to the transport direction The sliding member has a downstream side surface formed in an intersecting direction, and a downstream continuous portion that extends toward the sliding member beyond the position of the intersection of a line extending the bottom surface and a line extending the downstream side surface when viewed in the width direction of the recording material perpendicular to the transport direction, forming a corner continuous with the bottom surface and the downstream side surface. The sliding member has a flat opposite surface and a projection formed toward the downstream side surface downstream of the downstream end of the opposite surface with respect to the transport direction, and the projection is configured such that, when the sliding member is abutting against the bottom surface, it does not contact the holding member between the first boundary between the bottom surface and the downstream continuous portion and the second boundary between the downstream continuous portion and the downstream side surface, but can contact the downstream side surface on the sliding surface side of the second boundary. [Effects of the Invention]

[0009] According to the present invention, it is possible to hold the sliding member in a stable state in contact with the bottom surface without creating a gap between the sliding member and the bottom surface of the fitting groove formed in the holding member, without creating a gap between the sliding member and the bottom surface of the fitting groove formed in the holding member, using a simple configuration. [Brief explanation of the drawing]

[0010] [Figure 1] A schematic diagram showing a suitable image forming apparatus using the fixing device of this embodiment. [Figure 2] (a) A schematic diagram showing the fixing device, (b) A cross-sectional view showing the fixing belt, pressure roller, and fixing pad unit. [Figure 3](a) Schematic diagram showing the sliding member, (b) Plan view showing the sliding member. [Figure 4] A cross-sectional view showing the vicinity of the fixing nip. [Figure 5] A cross-sectional view showing the sliding member of this embodiment. [Figure 6] A cross-sectional view showing the sliding member of a comparative example. [Modes for carrying out the invention]

[0011] The fixing device of this embodiment will now be described. First, a schematic configuration of an image forming apparatus suitable for using the fixing device of this embodiment will be described with reference to Figure 1.

[0012] <Image forming apparatus> The image forming apparatus 1 is an electrophotographic full-color printer having four image forming units Pa, Pb, Pc, and Pd, corresponding to four colors: yellow, magenta, cyan, and black. This embodiment is a tandem-type image forming apparatus 1 in which the image forming units Pa, Pb, Pc, and Pd are arranged along the rotation direction of an intermediate transfer belt 204, which will be described later. The image forming apparatus 1 forms a toner image (image) on a recording material in response to an image signal from a document reader 2 connected to the main body 3 of the image forming apparatus 1 or from a host device such as a personal computer that is communicatively connected to the main body 3. Examples of recording materials include paper, plastic film, and sheet materials such as cloth.

[0013] As shown in FIG. 1, the image forming apparatus 1 includes a document reading apparatus 2 and an apparatus main body 3. The document reading apparatus 2 reads a document placed on the document table glass 21. The light irradiated from the light source 22 is reflected by the document and imaged on the CCD sensor 24 through an optical system member 23 such as a lens. When such an optical system unit is scanned in the direction of the arrow under the control of the reader control unit, the document is read line by line and converted into an electrical signal data series. The image signal obtained by the CCD sensor 24 is sent to the apparatus main body 3, and image processing is performed by the control unit 30 according to each image forming unit described later. Further, the control unit 30 also receives an external input from an external host device such as a print server as an image signal.

[0014] The apparatus main body 3 includes a plurality of image forming units Pa, Pb, Pc, Pd. In each image forming unit, image formation is performed based on the above-described image signal. That is, the image signal is converted into a laser beam PWM (pulse width modulation control) by the control unit 30. The polygon scanner 31 as an exposure device scans a laser beam according to the image signal. Then, the laser beam is irradiated onto the photosensitive drums 200a to 200d as image carriers of each image forming unit Pa to Pd.

[0015] Note that the image forming unit Pa forms a toner image of yellow (Y), the image forming unit Pb forms a toner image of magenta (M), the image forming unit Pc forms a toner image of cyan (C), and the image forming unit Pd forms a toner image of black (Bk). Since these image forming units Pa to Pd have substantially the same configuration, the image forming unit Pa that forms a toner image of yellow (Y) will be described as an example below, and the description of the other image forming units Pb to Pd will be omitted. In the image forming unit Pa, the photosensitive drum 200a has a toner image formed on its surface based on the image signal as described below. [[ID=⑨]] [[ID=⑩]]

[0016] [[ID=⑪]] The charging roller 201a as the primary charger charges the surface of the photosensitive drum 200a to a predetermined potential to prepare for forming an electrostatic latent image. An electrostatic latent image is formed on the surface of the photosensitive drum 200a charged to a predetermined potential by a laser beam from the polygon scanner 31. The developing device 202a develops the electrostatic latent image on the photosensitive drum 200a to form a toner image. The primary transfer roller 203a discharges from the back of the intermediate transfer belt 204 and applies a primary transfer bias of the opposite polarity to the toner, and transfers the toner image on the photosensitive drum 200a onto the intermediate transfer belt 204. After the transfer, the surface of the photosensitive drum 200a is cleaned by the cleaner 207a.

[0017] Also, the toner image on the intermediate transfer belt 204 is conveyed to the next image forming unit, and in the order of Y, M, C, Bk, the toner images of each color formed in each image forming unit are sequentially transferred, and a four-color image is formed on its surface. Then, the toner image that has passed through the Bk image forming unit Pd at the most downstream in the rotation direction of the intermediate transfer belt 204 is conveyed to the secondary transfer unit T2 composed of the secondary transfer roller pair 205 and 206. And in the secondary transfer unit T2, a secondary transfer electric field of the opposite polarity to the toner image on the intermediate transfer belt 204 is applied, and the toner image is secondarily transferred from the intermediate transfer belt 204 to the recording material.

[0018] The recording material is housed in the cassette 9, and the recording material fed from the cassette 9 is conveyed to the registration unit 208 composed of, for example, a pair of registration rollers and waits in the registration unit 208. Then, the timing of the registration unit 208 is controlled to align the position of the toner image on the intermediate transfer belt 204 with the paper, and the recording material is conveyed to the secondary transfer unit T2.

[0019] The recording material onto which the toner image has been transferred in the secondary transfer unit T2 is transported to the fuser unit 8, where it is heated and pressurized to fix the toner image onto the recording material. The recording material that has passed through the fuser unit 8 is discharged to the discharge tray 7. When image formation is performed on both sides of the recording material, once the transfer and fixing of the toner image to the first side (front) of the recording material is complete, the front and back sides of the recording material are reversed via the inversion transport unit 10, and the toner image is transferred and fixed to the second side (back) of the recording material, which is then loaded onto the discharge tray 7.

[0020] The control unit 30 controls the entire image forming apparatus 1 as described above. The control unit 30 can also perform various settings based on input from the operation unit 4 of the image forming apparatus 1. This control unit 30 includes a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). The CPU controls each part while reading programs corresponding to control procedures stored in the ROM. The RAM stores working data and input data, and the CPU controls the apparatus by referring to the data stored in the RAM based on the aforementioned programs.

[0021] <Fusing device> Next, the configuration of the fixing device 8 in this embodiment will be described with reference to Figures 2(a) to 4. In this embodiment, a belt heating type fixing device using an endless belt is employed. As shown in Figure 2(a), in the fixing device 8, the recording material is conveyed from right to left (arrow X direction). In this specification, the width direction (longitudinal direction) refers to the direction intersecting the conveying direction (short direction) of the recording material in the fixing nip section N, in other words, the direction of the rotation axis of the pressure roller 305.

[0022] The fixing device 8 includes an endless, rotatable fixing belt 301, a pressure roller 305 as an opposing member that contacts the fixing belt 301 and forms a fixing nip portion N together with the fixing belt 301, a heating roller 307, and a fixing pad unit 300.

[0023] <Fixing belt> The fixing belt 301 has thermal conductivity and heat resistance, and is formed in a thin-walled cylindrical shape. As shown in Figure 2(b), the fixing belt 301 has a three-layer structure with a base layer 301a on the inner circumference, an elastic layer 301b on the outer circumference of the base layer 301a, and a release layer 301c on the outer circumference of the elastic layer 301b. For example, the base layer 301a is made of polyimide resin (PI) with a thickness of "80 μm", the elastic layer 301b is made of silicone rubber with a thickness of "300 μm", and the release layer 301c is made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) with a thickness of "30 μm". The outer diameter of the fixing belt 301 is set to, for example, "150 mm". This fixing belt 301 is stretched by a heating roller 307 and a fixing pad unit 300.

[0024] <Pressure roller> The pressure roller 305 is rotatably supported on the fixing frame (not shown) of the fixing device 8, and a gear (not shown) is fixed to one end in the width direction. The gear is connected to a drive source (not shown) such as a motor, and the roller is rotationally driven. When the pressure roller 305 rotates, the rotational force of the pressure roller 305 is transmitted to the fixing belt 301 by the frictional force generated at the fixing nip portion N. In this way, the fixing belt 301 rotates in accordance with the pressure roller 305.

[0025] As shown in Figure 2(b), the pressure roller 305 has an elastic layer 305b formed on the outer circumference of the rotating shaft 305c, and a release layer 305a formed on the outer circumference of the elastic layer 305b. As an example, the rotating shaft 305c is made of stainless steel (SUS) with a diameter of 72 mm, the elastic layer 305b is made of conductive silicone rubber with a thickness of 8 mm, and the release layer 305a is made of PFA with a thickness of 100 μm.

[0026] As shown in Figure 2(a), the pressure roller 305 contacts the outer circumferential surface of the fixing belt 301 so as to sandwich the fixing belt 301 between itself and the sliding member 304 (described later), forming a fixing nip section N that grips and transports the recording material in the transport direction (arrow X direction) to fix the toner image onto the recording material. To do this, the pressure roller 305 is pressurized toward the fixing pad unit 300 via the fixing belt 301 by a drive source (not shown). In this embodiment, for example, the pressure roller 305 contacts the fixing belt 301 such that the pressure (NF) in the fixing nip section N is "1600N", the length of the fixing nip section N in the transport direction is "24.5mm", and the length in the width direction is "326mm".

[0027] <Heating roller> The heating roller 307 is positioned on the inner circumference of the fixing belt 301 and, together with the fixing pad unit 300, tensions the fixing belt 301. The heating roller 307 is formed in a cylindrical shape from a metal such as aluminum or stainless steel, and a halogen heater 306 is disposed inside it as a heat source for heating the fixing belt 301. The heating roller 307 is then heated to a predetermined temperature by the halogen heater 306.

[0028] In this embodiment, the heating roller 307 is formed from, for example, an aluminum pipe with a thickness of "1 mm" and its surface is anodized, from the viewpoint of thermal conductivity. While one halogen heater 306 may be used, it is desirable to have multiple halogen heaters to facilitate temperature distribution control in the direction of the heating roller 307's rotation axis (width direction). Multiple halogen heaters 306 have different light distributions in the width direction, and the lighting ratio is controlled by the control unit 30 (see Figure 1) according to the size of the recording material. In this embodiment, three halogen heaters 306 are arranged. Note that the heating source is not limited to halogen heaters; other heaters capable of heating the heating roller 307, such as carbon heaters, may also be used.

[0029] Furthermore, the heating roller 307 may have a pivot point at one end or near the center in the direction of the rotation axis (width direction) and swing to generate a tension difference between one side and the other side in the width direction of the fixing belt 301, thereby allowing the fixing belt 301 to move in the width direction. That is, depending on the outer diameter accuracy of the heating roller 307 on which it is tensioned and the alignment accuracy with the fixing pad 303 described later, the fixing belt 301 may shift towards one end in the width direction during rotation (so-called belt shift). For this reason, the position (shift position) of the fixing belt 301 in the direction of the rotation axis is controlled by swinging the heating roller 307. In addition, the heating roller 307 may be biased by a spring supported by the frame (not shown) of the fixing device 8 and may also serve as a tension roller that applies a predetermined tension to the fixing belt 301.

[0030] <Fuser pad unit> Next, the fixing pad unit 300 will be described. As shown in Figure 2(a), the fixing pad unit 300 has a fixing stay 302, a fixing pad 303, and a sliding member 304, which are arranged on the inner circumference side of the fixing belt 103. The fixing stay 302 is a rigid member, for example made of metal, that extends in the width direction along the fixing belt 301, and the fixing stay 302 supports the fixing pad 303 on the pressure roller 305 side.

[0031] In this embodiment, the fixing belt 301 is pressed from the inner circumference toward the pressure roller 305 by the fixing pad 303 supported by the fixing stay 302. This creates a fixing nip section N with a wide nip that ensures both the length in the conveying direction and the width direction between the pressure roller 305 and the fixing belt 103. Furthermore, by supporting the resin fixing pad 303 with a more rigid metal fixing stay 302, the deflection of the fixing pad 303 caused by the pressure when pressurized is reduced, and a uniform fixing nip width in the width direction is obtained.

[0032] <Overview of Fixing Pads> The fixing pad 303, acting as a holding member, is non-rotatably mounted on the inner circumference of the fixing belt 301 and has a fitting groove 303f (see Figure 4) into which the sliding member 304 can be fitted, and holds the sliding member 304 so as to contact the inner circumferential surface of the fixing belt 301. The fixing pad 303 is a resin member that extends in the width direction, and the width of the fixing pad 303 is longer than the width of the recording material of the maximum size in which an image can be formed. The fixing pad 303 is formed from a resin with good insulating and heat-resistant properties, such as LCP (liquid crystal polymer resin). The fixing pad 303 is a molded product manufactured by injection molding using a mold from these resins.

[0033] As shown in Figure 4, the fixing pad 303 has an upstream guide portion 303c that contacts and guides the fixing belt 301 upstream of the sliding member 304 with respect to the transport direction, and a downstream guide portion 303b that contacts and guides the fixing belt 301 downstream of the sliding member 304. The upstream guide portion 303c guides the fixing belt 301 toward the fixing nip portion N, and the downstream guide portion 303b guides the fixing belt 301 toward the fixing stay 302 so as to move it away from the fixing nip portion N after it has passed through the fixing nip portion N. With respect to the width direction, these upstream guide portion 303c and downstream guide portion 303b contact the fixing belt 301 over the entire area of ​​the paper transport region through which the largest size of recording material capable of image formation at the fixing nip portion N passes.

[0034] <Overview of sliding members> If the frictional force between the fixing belt 301 and the fixing pad 303 is large, the rotation of the fixing belt 301 will be hindered. Therefore, in this embodiment, as shown in Figure 2(a), in order to reduce the frictional force between the fixing belt 301 and the fixing pad 303 at the fixing nip portion N, the fixing pad 303 is provided with a sliding member 304 that slides against the fixing belt 301. The sliding member 304 is held by the fixing pad 303 and is positioned opposite the pressure roller 305 with the fixing belt 301 in between.

[0035] The sliding member 304 has heat resistance and strength, and while held by the fixing pad 303, it has a sliding surface that contacts the inner circumferential surface of the rotating fixing belt 301 and slides against the fixing belt 301. By interposing the sliding member 304 between the fixing pad 303 and the fixing belt 301, the frictional force between the fixing pad 303 and the fixing belt 301 is reduced, thereby preventing the fixing pad 303 from hindering the rotation of the fixing belt 301. The inner circumferential surface of the fixing belt 301 may be coated with a lubricant to allow the fixing belt 301 to slide smoothly against the sliding member 304. For example, silicone oil can be used as the lubricant.

[0036] As described above, in this embodiment, the sliding member 304 reduces the frictional force with the fixing belt 301. In the sliding member 304 of this embodiment, as shown in Figure 2(b), the sliding surface that slides against the fixing belt 301 is formed in an embossed (recessed) shape.

[0037] The sliding member 304 is formed from a metal such as stainless steel (SUS), copper, or aluminum. In this embodiment, the sliding member 304 is formed from stainless steel (SUS) with a thickness of 1 mm. The sliding member 304 is not limited to metal; it may also be formed from engineering plastics such as polyimide resin (PI), polyetheretherketone resin (PEEK), or LCP (liquid crystal polymer resin).

[0038] As shown in Figures 3(a) and 3(b), the sliding member 304 has a plate-shaped base 304a and a plurality of protrusions 304b that protrude from the base 304a and slide on the fixing belt 301. As shown in Figure 3(a), the protrusions 304b protrude from the surface of the base 304a. The amount of protrusion (height in the Z direction) of the protrusions 304b from the surface of the base 304a is, for example, "250 μm". Also, as shown in Figure 3(b), the protrusions 304b are arranged on the base 304a with approximately the same spacing between adjacent protrusions in the conveying direction and approximately the same spacing between adjacent protrusions in the width direction. The spacing (d) between adjacent protrusions 304b is, for example, "1.4 mm" in both the conveying direction and the width direction.

[0039] Furthermore, a low-friction layer 304c is formed on the surface of the sliding member 304 to reduce the frictional force with the fixing belt 301, using, for example, PTFE (polytetrafluoroethylene resin), PFA, etc. In this embodiment, PTFE with a thickness of "20 μm" is coated on the surface of the base body 304a and the protrusion 304b.

[0040] As shown in Figure 4, in this embodiment, the surface of the sliding member 304 is formed in an uneven manner, and the sliding member 304 slides against the fixing belt 301 at the tip of the protrusion 304b. This reduces the contact area between the sliding member 304 and the fixing belt 301, thereby reducing the frictional force with the fixing belt 301. Furthermore, as described above, the surface of the protrusion 304b is coated with a low-friction layer 304c, which also reduces the frictional force with the fixing belt 301.

[0041] As described above, the fixing pad 303 holds the sliding member 304 such that the inner circumferential surface of the fixing belt 301 slides against the tip surface of the protrusion 304b. To this end, the fixing pad 303 has a concave fitting groove 303f formed on the side opposite to the side supported by the fixing stay 302 for fitting and holding the sliding member 304. The fixing pad 303 is manufactured by injection molding using a mold with resin. When manufacturing the fixing pad 303 by injection molding, the corners of the tips of the protrusions formed for the fitting groove 303f are rounded in the mold to ensure release from the mold and prevent mold damage. Therefore, in the fixing pad 303, the corners of the fitting groove 303f (downstream continuous portion 303g) are formed in a curved shape (arc shape, corner R) (see Figures 5 and 6). Furthermore, the fitting groove 303f is formed to be longer than the length of the sliding member 304 in the transport direction, taking into consideration the ease of fitting the sliding member 304.

[0042] <Comparative Example> Incidentally, if the corner of the fitting groove 303f is formed in a curved shape as described above, there is a risk that the toner image may not adhere properly to the recording material. This point will be explained using the comparative example sliding member 3040 shown in Figure 6.

[0043] As shown in Figure 6, the fixing pad 303 has a flat bottom surface 303h, a flat downstream side surface 303e formed in a direction (arrow Z direction) that intersects the bottom surface 303h with respect to the transport direction (arrow X direction) downstream of the fitting groove portion 303f, and a downstream continuous portion 303g. The bottom surface 303h is the surface that contacts the opposite surface 304e of the sliding member 304, and the downstream continuous portion 303g is the portion corresponding to the curved corner described above, and is continuous with the bottom surface 303h and the downstream side surface 303e.

[0044] As shown in Figure 6, in the comparative example, the sliding member 3040 has a corner 3041 at the base 304a between the opposite surface 304e and the downstream end surface 304d that is approximately 90 degrees. In the comparative example, when the sliding member 3040 moves downstream as it slides on the fixing belt 301, the corner 3041 contacts the downstream continuous portion 303g upstream of the downstream side surface 303e. That is, in a configuration where the fixing nip portion N is formed by the fixing belt 301 and the pressure roller 305 to hold and transport the recording material (see Figure 2(a)), the sliding member 304 receives force from the pressure roller 305 via the fixing belt 301 in the direction of pressure (arrow Z direction). As a result, the sliding member 3040 held by the fixing pad 303 is pressed against the bottom surface 303h of the fitting groove portion 303f. As the fixing belt 301 begins to rotate, a frictional force is generated between the fixing belt 301 and the sliding member 304. As a result, the sliding member 304 is subjected to a force in the conveying direction (arrow X direction) and moves downstream, causing the corner portion 3041 of the fixing pad 303 to come into contact with the downstream continuous portion 303g.

[0045] As the corner portion 3041 moves while in contact with the downstream continuous portion 303g, the sliding member 3040 moves away from the bottom surface 303h along the downstream continuous portion 303g. In other words, as shown in the figure, the sliding member 3040 is held by the fixing pad 303 with a portion of its opposite surface 304e not in contact with the bottom surface 303h. This is an unstable state in which a gap is created between the bottom surface 303h of the fitting groove portion 303f and the sliding member 3040. In this case, it is not possible to obtain the desired nip pressure distribution in the fixing nip portion N, which makes it easy for uneven pressure to occur, and as a result there is a risk of poor fixing of the toner image to the recording material.

[0046] In view of the above points, this embodiment proposes a configuration in which the sliding member 304 is held stably by the fixing pad 303 even if the corner portion (downstream continuous portion 303g) of the fitting groove portion 303f is formed in a curved shape. This embodiment will be described below with reference to Figure 2(a) and Figure 5.

[0047] <Sliding member> As shown in Figure 5, the sliding member 304 of this embodiment has a downstream abutment portion 310 that abuts against the downstream side surface 303e of the fitting groove portion 303f downstream of the downstream end 3042 of the opposite surface 304e with respect to the transport direction (arrow X direction). The downstream abutment portion 310 abuts against the downstream side surface 303e when the downstream end 3042 of the opposite surface 304e is located upstream of the downstream continuity portion 303g, more specifically, when it is located upstream of the end of the corner R of the downstream continuity portion 303g (the boundary Q with the bottom surface 303h where the curvature of the corner ends). As a result, the sliding member 304 does not come into contact with the downstream continuity portion 303g, but instead contacts the downstream side surface 303e and the bottom surface 303h at a position outside the range of the downstream continuity portion 303g shown by the dotted line, and is held by the fixing pad 303.

[0048] In this embodiment, the downstream end face of the sliding member 304 is formed as an inclined surface 304d1 that slopes downstream from the opposite surface 304e towards the sliding surface (the tip surface of the protrusion 304b), thereby forming the downstream abutment portion 310. Compared with the sliding member 3040 of the comparative example described above (see Figure 6), in the base body 304a, the corner (downstream end 3042) between the opposite surface 304e and the downstream end face 304d is formed at an obtuse angle greater than 90 degrees. Thus, in this embodiment, the downstream tip of the inclined surface 304d1 of the sliding member 304 abuts against the downstream side surface 303e of the fixing pad 303. It is preferable that the downstream abutment portion 310 is formed over the entire paper-feeding area of ​​the fixing nip portion N in the width direction, as this makes it easier to obtain the desired fixing nip pressure.

[0049] As described above, in this embodiment, a downstream abutment portion 310 is formed on the sliding member 304. When the downstream abutment portion 310 is in contact with the downstream side surface 303e of the fixing pad 303, the sliding member 304 is held by the fixing pad 303 with the downstream end 3042 of the opposite surface 304e positioned upstream of the downstream continuity portion 303g. When the sliding member 304 moves downstream as the fixing belt 301 starts to rotate, the downstream abutment portion 310 abuts against the downstream side surface 303e before the downstream end 3042 of the opposite surface 304e contacts the downstream continuity portion 303g, and the sliding member 304 stops. That is, since the corner (downstream end 3042) does not move while in contact with the downstream continuity portion 303g, the sliding member 304 does not leave the bottom surface 303h. As a result, the sliding member 304 is held by the fixing pad 303 with the entire surface of its opposite side 304e in contact with the bottom surface 303h. This is a stable state in which there is no gap between the bottom surface 303h of the fitting groove 303f and the sliding member 304. Therefore, a desired nip pressure distribution can be obtained in the fixing nip section N, and uneven pressure is less likely to occur, which in turn suppresses poor fixing of the toner image to the recording material.

[0050] [Other embodiments] In the embodiment described above, an example was shown in which the downstream abutment portion 310 is formed by an inclined surface 304d1 on the downstream end face of the sliding member 304, but the embodiment is not limited to this. For example, a convex downstream abutment portion may be provided so as to protrude in the width direction from the downstream end face of the sliding member 304. In that case, the downstream abutment portion should abut against the downstream side surface 303e of the fixing pad 303 at a position further from the bottom surface 303h than the end of the corner R of the downstream continuous portion 303g (the boundary W with the downstream side surface 303e where the curvature of the corner ends, see Figure 5).

[0051] In the embodiment described above, an example was shown in which a downstream abutment portion 310 is formed on the downstream side in the conveying direction relative to the sliding member 304. However, a similar upstream abutment portion may be formed on the upstream side in the conveying direction. In that case, in the description of the downstream abutment portion 310 using Figure 5, "downstream" should be read as "upstream".

[0052] Furthermore, the above-described embodiment is not limited to a configuration in which the fixing belt 301 is heated, but can also be applied to a configuration in which a belt-shaped pressure belt is used instead of the pressure roller 305, and this pressure belt is heated by a heating heater or the like. [Explanation of symbols]

[0053] 8... Fixing device, 301... Fixing belt, 303... Holding member (fixing pad), 303e... Downstream side, 303f... Fitting groove, 303g... Downstream continuous section (corner), 303h... Bottom surface, 304... Sliding member, 304a... Base, 304b... Protrusion, 304c... Low friction layer, 304e... Opposite side, 305... Opposing member (pressure roller), 310... Downstream abutment section, N... Fixing nip section

Claims

1. A fixing device for fixing a toner image formed on a recording material to the recording material, A rotating, endless fixing belt, A sliding member having a sliding surface that slides on the aforementioned fixing belt, A retaining member is provided non-rotatably on the inner circumference side of the fixing belt, has a fitting groove into which the sliding member can be fitted, and holds the sliding member so as to contact the inner circumferential surface of the fixing belt, The system includes an opposing member that contacts the outer circumferential surface of the fixing belt so as to sandwich the fixing belt between itself and the sliding member, forming a fixing nip portion that grips and conveys the recording material in the conveying direction to fix a toner image onto the recording material, The retaining member has, in the fitting groove portion, a bottom surface that supports the opposite surface of the sliding surface of the sliding member, a downstream side surface formed in a direction that intersects the bottom surface downstream with respect to the conveying direction, and a downstream continuous portion that forms a curved corner portion continuous with the bottom surface and the downstream side surface. The sliding member has a downstream abutment portion that, with respect to the conveying direction, is positioned upstream of the downstream continuous portion and abuts against the bottom surface, and is capable of abutting against the downstream side surface downstream of the downstream end of the opposite surface. A fixing device characterized by the following features.

2. The downstream abutment portion has an inclined surface that slopes toward the sliding surface as it moves downstream from the downstream end of the opposite surface with respect to the conveying direction, The fixing device according to feature 1.

3. The sliding member has a base and a plurality of protrusions that protrude from the base and slide against the fixing belt, The fixing device according to claim 1 or 2.

4. The sliding member has a low-friction layer that reduces the frictional force between the plurality of protrusions and the fixing belt. The fixing device according to feature 3.

5. The retaining member is made of resin, The sliding member is made of metal. The fixing device according to any one of claims 1 to 4.

6. The retaining member has an upstream side surface formed in the fitting groove portion in a direction that intersects the bottom surface on the upstream side with respect to the transport direction, and an upstream continuous portion that forms a curved corner portion continuous with the bottom surface and the upstream side surface, When the sliding member is sliding on the fixing belt, with respect to the conveying direction, the upstream end of the opposite surface is located downstream of the upstream continuous portion, and the sliding member has an upstream abutment portion that abuts against the upstream side surface upstream of the upstream end of the opposite surface. The fixing device according to feature 1.

7. A fixing device for fixing a toner image formed on a recording material to a recording material, A rotating, endless fixing belt, A sliding member having a sliding surface that slides on the aforementioned fixing belt, A retaining member is provided non-rotatably on the inner circumference of the fixing belt, has a fitting groove into which the sliding member can be fitted with a gap in the direction of transport of the recording material, and holds the sliding member so as to contact the inner surface of the fixing belt, The system includes an opposing member that contacts the outer circumferential surface of the fixing belt so as to sandwich the fixing belt between itself and the sliding member, forming a fixing nip portion that grips and conveys the recording material in the conveying direction to fix a toner image onto the recording material, The retaining member has, in the fitting groove portion, a bottom surface that supports the opposite surface of the sliding surface of the sliding member, a downstream side surface formed in a direction that intersects the bottom surface downstream with respect to the transport direction, and a downstream continuous portion that extends toward the sliding member side from the position of the intersection of the line extending the bottom surface and the line extending the downstream side surface in a cross section perpendicular to the width direction of the recording material which is perpendicular to the transport direction, and forms a corner portion that is continuous with the bottom surface and the downstream side surface. The sliding member has a downstream abutment portion that, with respect to the conveying direction, is positioned upstream of the downstream continuous portion and abuts against the bottom surface, and is capable of abutting against the downstream side surface downstream of the downstream end of the opposite surface. A fixing device characterized by the following features.

8. A fixing device for fixing a toner image formed on a recording material to the recording material, A rotating, endless fixing belt, A sliding member having a sliding surface that slides on the aforementioned fixing belt, A retaining member is provided non-rotatably on the inner circumference of the fixing belt, has a fitting groove into which the sliding member can be fitted with a gap in the direction of transport of the recording material, and holds the sliding member so as to contact the inner surface of the fixing belt, The system includes an opposing member that contacts the outer circumferential surface of the fixing belt so as to sandwich the fixing belt between itself and the sliding member, forming a fixing nip portion that grips and conveys the recording material in the conveying direction to fix a toner image onto the recording material, The retaining member has, in the fitting groove portion, a bottom surface that supports the opposite surface of the sliding surface of the sliding member, a downstream side surface formed in a direction that intersects the bottom surface downstream with respect to the transport direction, and a downstream continuous portion that extends toward the sliding member side from the position of the intersection of the line extending the bottom surface and the line extending the downstream side surface in a cross section perpendicular to the width direction of the recording material which is perpendicular to the transport direction, and forms a corner portion that is continuous with the bottom surface and the downstream side surface. The sliding member has a downstream abutment portion that strikes the downstream side surface downstream of the downstream end of the opposite surface with respect to the conveying direction, The downstream abutment portion is such that, when the sliding member is abutting the bottom surface and abutting the downstream side surface, one surface facing the downstream continuous portion is spaced apart from the downstream continuous portion, forming a gap between it and the downstream continuous portion. A fixing device characterized by the following features.

9. A fixing device for fixing a toner image formed on a recording material to a recording material, A rotating, endless fixing belt, A sliding member having a sliding surface that slides on the aforementioned fixing belt, A retaining member is provided non-rotatably on the inner circumference of the fixing belt, has a fitting groove into which the sliding member can be fitted with a gap in the direction of transport of the recording material, and holds the sliding member so as to contact the inner surface of the fixing belt, The system includes an opposing member that contacts the outer circumferential surface of the fixing belt so as to sandwich the fixing belt between itself and the sliding member, forming a fixing nip portion that grips and conveys the recording material in the conveying direction to fix a toner image onto the recording material, The retaining member has, in the fitting groove portion, a bottom surface that supports the opposite surface of the sliding surface of the sliding member, a downstream side surface formed in a direction that intersects the bottom surface downstream with respect to the transport direction, and a downstream continuous portion that extends toward the sliding member from the position of the intersection of the line extending the bottom surface and the line extending the downstream side surface when viewed in the width direction of the recording material perpendicular to the transport direction, and forms a corner portion that is continuous with the bottom surface and the downstream side surface. The sliding member has a flat opposite surface and, with respect to the conveying direction, a protruding portion formed downstream of the downstream end of the opposite surface toward the downstream side surface. The protruding portion is configured such that, when the sliding member is abutting the bottom surface, it does not contact the holding member between the first boundary between the bottom surface and the downstream continuous portion and the second boundary between the downstream continuous portion and the downstream side surface, but can contact the downstream side surface on the sliding surface side of the second boundary. A fixing device characterized by the following features.

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