Fixing device

Abstract

In a longitudinal end portion region of the sliding member, when a corner portion of the sliding portion and a locus of the fixing belt are close to each other and contact each other, the belt is broken.SOLUTION: A fixing device according to an embodiment of the present disclosure includes a belt (301), a rotating member (305), and a nip forming member, wherein the nip forming member includes a sliding member (304) that slides on the belt, and the sliding member includes a base and a sliding portion (304b) that has a plurality of protrusions protruding from the base and slides on an inner peripheral surface of the belt. In a longitudinal central portion of the sliding member, a first region (701) which is a surface on which the sliding portion is formed and a second region (703) which is the same surface as a substrate of the first region and on which the sliding portion is not formed are provided, and an upstream end of the first region at the first position with respect to the recording material feeding direction is positioned upstream of an upstream end of the second region at the second position with respect to the recording material feeding direction.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a fixing device. [Background technology]

[0002] The image forming apparatus is equipped with a fixing device that applies heat and pressure to a recording material on which a toner image has been formed, thereby fixing the toner image to the recording material. The fixing device has a rotating, endless fixing belt, a fixing pad that is non-rotatingly disposed on the inner periphery of the fixing belt, and a pressure roller that abuts the outer periphery of the fixing belt. In this fixing device, the fixing pad is pressed by the pressure roller to form a fixing nip. By nipping and conveying the recording material in the fixing nip, the toner carried on the recording material is fixed to the recording material by the heat and pressure.

[0003] If the friction between the fixing belt and the fixing pad is large, the rotation of the fixing belt is hindered. Therefore, in order to reduce the friction between the fixing belt and the fixing pad, a device has been proposed that includes a sliding member with multiple protrusions that slides against the fixing belt on the inner circumferential surface of the belt (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-125019 Summary of the Invention [Problem to be solved by the invention]

[0005] The fixing belt's trajectory around the fixing nip is formed along the fixing pad's upstream guide portion of the fixing nip, the sliding member, and the downstream guide portion of the fixing nip, and tension is applied to prevent slack. In a specific region at the end of the endless fixing belt in the direction of the belt's rotation axis, where the protrusions of the sliding member are not distributed, the fixing belt trajectory is closer to the corners of the sliding member than in the center. In this case, the corners of the sliding member may come into contact with the fixing belt in the specific region, potentially damaging the fixing belt.

[0006] SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a fixing device in which the corners of the fixing pad end portions are shaped to avoid contact with the fixing belt, thereby preventing damage to the fixing belt. [Means for solving the problem]

[0007] The fixing device according to an embodiment of the present invention comprises a rotatable endless belt (301), a rotating body (305) that contacts the outer peripheral surface of the fixing belt, and a nip forming member that is provided inside the belt with the rotating body and the belt sandwiched therebetween and that applies heat and pressure to fix the toner image to the recording material while nipping and conveying the recording material on which a toner image has been formed, and the nip forming member has a sliding member (304) that slides against the belt on a surface that contacts the inner peripheral surface of the belt, and the sliding member has a base and a plurality of protrusions protruding from the base. The recording material conveying device has a sliding portion (304b) that slides against the inner peripheral surface of the belt, and has a first region (701) at the longitudinal center of the sliding member, which is a surface on which the sliding portion is formed with a plurality of protrusions protruding from the base, and a second region (703) that is the same surface as the base of the first region, is a surface on the outside of the first region in the longitudinal direction, and is a surface on which the sliding portion is not formed, and is characterized in that the upstream end of the first region at a first position in the conveying direction of the recording material is located upstream of the upstream end of the second region at a second position in the conveying direction. [Effects of the Invention]

[0008] According to the present invention, by forming the sliding member in a shape that can prevent unnecessary contact between the corners of the sliding member and the fixing member, damage to the fixing member can be prevented and the life of the fixing member can be improved. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing an image forming apparatus suitable for using the fixing device of the present embodiment. [Figure 2] FIG. 2A is a schematic diagram showing a fixing device, and FIG. 2B is a cross-sectional view showing a fixing belt, a pressure roller, and a fixing pad unit. [Figure 3] FIG. 2A is a schematic diagram showing a sliding member, and FIG. 2B is a top view showing the sliding member. [Figure 4] FIG. 2 is a cross-sectional view showing the vicinity of a fixing nip portion of the embodiment. [Figure 5] 10 is a cross-sectional view showing the vicinity of the entrance of the fixing nip portion during attachment / detachment operations in a case where there is no step portion (conventional example). FIG. [Figure 6] 10 is a cross-sectional view showing the vicinity of the entrance of the fixing nip portion during attachment / detachment operations when a step portion is provided (this embodiment). FIG. [Figure 7] 1A is a diagram showing the longitudinal arrangement of a sliding member having a notch portion as viewed from below in the pressure direction of the fixing pad in this embodiment, and FIG. 1B is an enlarged view of a longitudinal end portion of the sliding member having a notch portion. [Figure 8] FIG. 3A is a partial perspective view showing the positional relationship and shape of a fixing pad and a sliding member having a cutout portion in the embodiment. [Figure 9] 6 is a graph showing the relationship between the proximity distance between the fixing member and the corner of the sliding member in the embodiment. [Figure 10] FIG. 10 is a diagram showing the results of a durability evaluation for confirming the effect of the present embodiment. [Figure 11] FIG. 10 is a partial perspective view for explaining a modified example of the embodiment in which both the upstream and downstream sides of the sliding member are provided with cutout portions. [Figure 12] 10 is a diagram showing an example in which a plurality of cutout lengths are provided in the cutout portion of the sliding member in a modified example of the embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Example> Hereinafter, embodiments of the present invention will be described. Although these examples are examples of the best mode for carrying out the present invention, the present invention is not limited to these examples.

[0011] <Image forming device> The image forming apparatus 1 is an electrophotographic full-color printer having four image forming units Pa, Pb, Pc, and Pd corresponding to the four colors of yellow, magenta, cyan, and black. In this embodiment, the image forming apparatus 1 is a tandem type 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 reading device 2 connected to a device main body 3 of the image forming apparatus 1 or from a host device such as a personal computer connected to the device main body 3 so as to be able to communicate with the device main body 3. Examples of the recording material include sheet materials such as paper, plastic film, and cloth.

[0012] As shown in FIG. 1, image forming apparatus 1 includes document reading device 2 and device main body 3. Document reading device 2 reads a document placed on document glass 21. Light emitted from light source 22 is reflected by the document and forms an image on CCD sensor 24 via optical components 23, such as lenses. When this optical unit is scanned in the direction indicated by the arrow under the control of a reader control unit, it reads the document line by line and converts it into an electrical signal data stream. The image signal obtained by CCD sensor 24 is sent to device main body 3, where it is processed by control unit 30 in accordance with the image forming units described below. Control unit 30 also receives external inputs as image signals from external host devices, such as a print server.

[0013] The apparatus main body 3 includes multiple image forming units Pa, Pb, Pc, and Pd, and each image forming unit forms an image based on the image signal. That is, the image signal is converted into a laser beam that is PWM (pulse width modulation) controlled by a control unit 30. A polygon scanner 31 serving as an exposure device scans the laser beam in accordance with the image signal. The laser beam is then irradiated onto photosensitive drums 200a to 200d serving as image carriers of each image forming unit Pa to Pd.

[0014] Image forming unit Pa forms a toner image of yellow (Y), image forming unit Pb forms a toner image of magenta (M), image forming unit Pc forms a toner image of cyan (C), and image forming unit Pd forms a toner image of black (Bk), respectively. Since these image forming units Pa to Pd have substantially the same configuration, the following description will be given taking image forming unit Pa, which forms a toner image of yellow (Y), as an example, and will not include a description of the other image forming units Pb to Pd. In image forming unit Pa, a toner image is formed on the surface of photosensitive drum 200a based on an image signal, as will be described below.

[0015] A charging roller 201a, which serves as a primary charger, charges the surface of the photosensitive drum 200a to a predetermined potential to prepare for the formation of an electrostatic latent image. A laser beam from a polygon scanner 31 forms an electrostatic latent image on the surface of the photosensitive drum 200a, which has been charged to a predetermined potential. A developing unit 202a develops the electrostatic latent image on the photosensitive drum 200a to form a toner image. A primary transfer roller 203a discharges electricity from the back surface of the intermediate transfer belt 204 and applies a primary transfer bias of opposite polarity to the toner, transferring the toner image on the photosensitive drum 200a onto the intermediate transfer belt 204. After transfer, the surface of the photosensitive drum 200a is cleaned by a cleaner 207a.

[0016] The toner image on intermediate transfer belt 204 is then transported to the next image forming station, where the toner images of each color formed at each image forming station are transferred in the order of Y, M, C, and Bk, forming a four-color image on the surface. The toner image that has passed through Bk image forming station Pd, which is located at the most downstream side in the rotation direction of intermediate transfer belt 204, is transported to a secondary transfer station made up of a pair of secondary transfer rollers 205 and 206. In the secondary transfer station, a secondary transfer electric field of opposite polarity to the toner image on intermediate transfer belt 204 is applied, thereby secondarily transferring the toner image from intermediate transfer belt 204 to the recording material.

[0017] Recording materials are stored in cassettes 11 and 12, and recording materials fed from cassettes 11 and 12 are transported to a registration unit 208, which is made up of, for example, a pair of registration rollers, and wait at the registration unit 208. Thereafter, 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 position of the paper, and the recording material is transported to the secondary transfer unit.

[0018] The recording material onto which the toner image has been transferred in the secondary transfer section is transported to a fixing device 8, where the toner image carried on the recording material is fixed to the recording material by heating and pressing. The recording material that has passed through the fixing device 8 is discharged onto a discharge tray 7. When forming images on both sides of the recording material, after the toner image has been transferred and fixed onto the first side (front side) of the recording material, the recording material is turned over via a reversing conveyance section 10, and the toner image is transferred and fixed onto the second side (rear side) of the recording material, and the recording material is then stacked on the discharge tray 7.

[0019] As described above, the control unit 30 controls the entire image forming apparatus 1. The control unit 30 can also perform various settings based on input from the operation unit 4 of the image forming apparatus 1. The control unit 30 has a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The CPU controls each unit by reading a program corresponding to a control procedure stored in the ROM. The RAM stores working data and input data, and the CPU performs control by referring to the data stored in the RAM based on the aforementioned programs.

[0020] <Fixing device> Next, the configuration of the fixing device 8 in this embodiment will be described with reference to FIGS. 2 to 4. In this embodiment, a fixing device of a belt heating type using an endless belt is adopted. As shown in FIG. 2, in the fixing device 8, the recording material is conveyed from right to left (in the direction of the arrow X). In this specification, the width direction (longitudinal direction) refers to the direction intersecting the conveyance direction (short direction) of the recording material in the fixing nip N, in other words, the direction of the rotation axis of the pressure roller 305 as a rotating body.

[0021] The fixing device 8 has a heating roller 307 as a rotating body, 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, and a fixing pad unit 300.

[0022] <Fixing belt> The fixing belt 301 is replaceably provided in the fixing pad unit 300. The fixing belt 301 has thermal conductivity, heat resistance, and the like, and is formed in a thin cylindrical shape. In this embodiment, as shown in FIG. 2, the fixing belt 301 has a three-layer structure including a base layer 301a on the inner periphery, an elastic layer 301b on the outer periphery of the base layer 301a, and a release layer 301c on the outer periphery of the elastic layer 301b. As an example, the base layer 301a is 80 μm thick and made of polyimide resin (PI). The elastic layer 301b is 300 μm thick and made of silicone rubber, and the release layer 301c is 30 μm thick and made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin). The outer diameter of the fixing belt 301 is set to, for example, 150 mm. The fixing belt 301 is stretched between the heating roller 307 and the fixing pad unit 300.

[0023] <Pressure roller> 2, pressure roller 305 is rotatably supported on a fixing frame (not shown) of fixing device 8, has a gear (not shown) fixed to one end in the width direction, and is connected to a drive source (not shown) such as a motor via the gear to be rotated. When pressure roller 305 rotates, frictional force generated in fixing nip portion N transmits the rotational force of pressure roller 305 to fixing belt 301. In this way, fixing belt 301 is rotated by pressure roller 305.

[0024] Pressure roller 305 has elastic layer 305b formed on the outer periphery of rotating shaft 305c, and release layer 305a formed on the outer periphery of elastic layer 305b. As an example, rotating shaft 305c is made of stainless steel (SUS) with a diameter of 72 mm, elastic layer 305b is made of conductive silicone rubber with a thickness of 8 mm, and release layer 305a is made of PFA with a thickness of 100 μm.

[0025] 2, the pressure roller 305 contacts the outer peripheral surface of the fixing belt 301 so as to sandwich the fixing belt 301 between itself and a sliding member 304 (described later), and forms a fixing nip N where the recording material is sandwiched and conveyed in the conveyance direction (direction of arrow X) to fix a toner image onto the recording material. To do this, the pressure roller 305 is pressed toward the fixing pad unit 300 via the fixing belt 301 by a drive source (not shown). In the case of this embodiment, the pressure roller 305 contacts the fixing belt 301 so that, for example, the pressure (NF) at the fixing nip N is "1600 N," and the length of the fixing nip N in the conveyance direction is "24.5 mm" and the length in the width direction is "326 mm."

[0026] Similarly, the pressure roller 305 can be moved by a drive source (not shown) to separate it from the fixing belt 301 and release the fixing nip portion N. When no recording material is passed through the fixing nip portion N, the pressure roller 305 is separated from the fixing belt 301 to prevent the temperature of the pressure roller 305 from rising.

[0027] <Heating roller> Next, the heating roller 307 will be described with reference to FIG.

[0028] Heating roller 307 is disposed on the inner circumferential side of fixing belt 301, and stretches fixing belt 301 together with fixing pad unit 300. Heating roller 307 is formed into a cylindrical shape from a metal such as aluminum or stainless steel, and has a halogen heater 306 disposed inside as a heat source for heating fixing belt 301. Heating roller 307 is heated to a predetermined temperature by halogen heater 306.

[0029] In this embodiment, the heating roller 307 is formed from an aluminum pipe, for example, 1 mm thick, from the viewpoint of thermal conductivity, and the surface is anodized. While a single halogen heater 306 is acceptable, it is preferable to have multiple heaters in order to facilitate temperature distribution control in the rotational axis direction (width direction) of the heating roller 307. The multiple halogen heaters 306 have different light distributions in the width direction, and the lighting ratio is controlled by the control unit 30 (see FIG. 1) according to the size of the recording material. In this embodiment, three halogen heaters 306 are provided. The heat source is not limited to a halogen heater, and other heaters, such as a carbon heater, may be used as long as they are capable of heating the heating roller 307.

[0030] In this embodiment, the heating roller 307 has a rotation center near one end or the center of the rotation axis (width direction) and oscillates to generate a tension difference between one side and the other side of the fixing belt 301 in the width direction, allowing the fixing belt 301 to move in the width direction. That is, depending on the outer diameter accuracy of the heating roller 307 that it stretches and the alignment accuracy between the fixing belt 301 and the fixing pad 303 (described later), the fixing belt 301 may shift to one end in the width direction during rotation (so-called belt shift). Therefore, the position of the fixing belt 301 in the rotation axis direction (shift position) is controlled by oscillating the heating roller 307 as steering control. The heating roller 307 is also biased by a spring supported by the frame (not shown) of the fixing device 8 and serves as a tension roller that applies a predetermined tension to the fixing belt 301. In this embodiment, the heating roller 307 oscillates to shift the belt and applies tension, but a configuration in which a separate roller having these functions is added may also be used.

[0031] <Fixing pad unit> Next, the fixing pad unit 300 will be described with reference to FIGS.

[0032] 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 circumferential side of the fixing belt 301. The fixing stay 302 is a rigid member made of, for example, metal that extends in the width direction along the fixing belt 301, and supports the fixing pad 303 on the pressure roller 305 side. In this embodiment, at least the fixing pad 303 and the sliding member 304 are collectively referred to as a nip forming member.

[0033] In this embodiment, a pressure roller 305 presses a fixing pad 303 supported by a fixing stay 302 from the outer periphery of the fixing belt 301. In this manner, a wide fixing nip N is formed between the pressure roller 305 and the fixing belt 103, ensuring a sufficient length in both the conveyance direction and the width direction of the belt. In addition, by supporting the resin fixing pad 303 on the metal fixing stay 302, which has a higher rigidity, deflection of the fixing pad 303 caused by pressure when applied is reduced, thereby achieving a uniform fixing nip width in the width direction.

[0034] <Fixing pad> Fixing pad 303, which serves as a holding member, is non-rotatably provided on the inner circumferential side of fixing belt 301, has fitting groove 303f (see FIG. 4) into which elongated sliding member 304 can be fitted, and holds sliding member 304 so as to contact the inner circumferential surface of fixing belt 301. Fixing pad 303 is a resin member that extends in the width direction, and the width direction length of fixing pad 303 is longer than the width direction length of the largest size recording material on which an image can be formed. Fixing pad 303 is made of a resin with good insulating properties and heat resistance, such as LCP (liquid crystal polymer resin). Fixing pad 303 is a molded product manufactured from this resin by injection molding using a mold.

[0035] 4, the fixing pad 303 has an upstream guide portion 303c that contacts the fixing belt 301 upstream of a bottom surface 303d of the fitting groove portion 303f in the conveyance direction, and a downstream guide portion 303b that contacts the fixing belt 301 downstream of the bottom surface 303d. The bottom surface 303d is the surface that contacts the side opposite the sliding surface (tip of the convex portion) 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 the fixing belt 301 away from the fixing nip portion N after passing through the fixing nip portion N. The upstream guide portion 303c and downstream guide portion 303b contact the fixing belt 301 across the entire paper passage area in the width direction, through which a recording material of the maximum size on which an image can be formed passes at the fixing nip portion N.

[0036] <Sliding member> If the frictional force between the fixing belt 301 and the fixing pad 303 is large, the rotation of the fixing belt 301 is hindered. Therefore, in this embodiment, as shown in FIG. 4, in order to reduce the frictional force between the fixing belt 301 and the fixing pad 303 in the fixing nip N where pressure is high, 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 sandwiched between them. Note that in this embodiment, the sliding member 304 is held by the fixing pad 303 so that its short side direction is the transport direction.

[0037] Sliding member 304 has heat resistance and strength, and has a sliding surface that contacts the inner circumferential surface of rotating fixing belt 301 and slides against fixing belt 301 while being held by fixing pad 303. By interposing sliding member 304 between fixing pad 303 and fixing belt 301, the frictional force between fixing pad 303 and fixing belt 301 is reduced, and fixing pad 303 does not interfere with the rotation of fixing belt 301. A lubricant may be applied to the inner circumferential surface of fixing belt 301 to allow fixing belt 301 to slide smoothly against sliding member 304. For example, silicone oil or the like is used as the lubricant.

[0038] As described above, in this embodiment, the frictional force with the fixing belt 301 is reduced by the sliding member 304. In this embodiment, the sliding member 304 has a convex portion formed on the sliding surface that slides against the fixing belt 301, as shown in FIG. 2.

[0039] The sliding member 304 is made of a metal such as stainless steel (SUS), copper, or aluminum. Since the sliding member 304 comes into contact with the heated fixing belt 301, it is desirable that the thermal capacity of the sliding member 304 be small. Therefore, in this embodiment, the sliding member 304 is made of stainless steel (SUS) with a thickness of 1 mm. Note that the sliding member 304 is not limited to metal, and may be made of engineering plastic such as polyimide resin (PI), polyether ether ketone resin (PEEK), or LCP (liquid crystal polymer resin).

[0040] As shown in FIGS. 3(a) and 3(b), the sliding member 304 has a plate-shaped base 304a and a plurality of protruding portions 304b that protrude from the base 304a and slide against the fixing belt 301. As shown in FIG. 3(a), the protruding portions 304b protrude from the surface of the base 304a. The protruding amount (height in the Z direction) of the protruding portions 304b from the surface of the base 304a is, for example, 250 μm. As shown in FIG. 3(b), the protruding portions 304b are arranged on the base 304a with substantially equal spacing between adjacent protruding portions 304b in the transport direction and with substantially equal spacing between adjacent protruding portions 304b in the width direction. The spacing (d) between adjacent protruding portions 304b is, for example, 1.4 mm in both the transport direction and the width direction.

[0041] Furthermore, a low-friction layer 304c is formed on the surface of the sliding member 304 using, for example, PTFE (polytetrafluoroethylene resin), PFA, or the like to reduce the frictional force with the fixing belt 301. In this embodiment, a 20 μm-thick PTFE is coated on the surfaces of the base 304a and the protrusions 304b.

[0042] 4, in this embodiment, a convex shape is formed on the surface of sliding member 304, and sliding member 304 slides against fixing belt 301 at the tip surface of convex portion 304b. This reduces the contact area between sliding member 304 and fixing belt 301, thereby reducing the frictional force with fixing belt 301. In addition, the surface of convex portion 304b is coated with low-friction layer 304c as described above, which also reduces the frictional force with fixing belt 301.

[0043] As described above, the fixing pad 303 holds the sliding member 304 so that the inner circumferential surface of the fixing belt 301 slides on the tip surface of the protrusion 304b. To achieve this, the fixing pad 303 is formed with a recessed fitting groove 303f on the side opposite to the side supported by the fixing stay 302, into which the sliding member 304 is fitted and held.

[0044] When forming the fixing nip N, as the pressure roller 305 rotates, the fixing belt 301 slides against the convex portion 304b of the sliding member 304, and the sliding member 304 receives a frictional force toward the downstream side in the recording material transport direction. At this time, the downstream abutment portion 304e on the base 304a of the sliding member 304 abuts against the downstream side surface 303e of the engagement groove portion 303f formed in the fixing pad 303. This determines the position of the sliding member 304 in the recording material transport direction relative to the fixing pad 303. The downstream side surface 303e of the fixing pad 303 is formed continuously with the downstream guide portion 303b across the arc-shaped corner portion 303k. This allows the fixing belt 301 to be continuously in contact with and guided by the sliding member 304 and the fixing pad 303.

[0045] The necessity of the upstream and downstream steps 304s' and 304e' formed on the fixing pad 303 will be explained with reference to FIGS.

[0046] 5 is a diagram showing a state where the nip N is normally formed (a so-called attached state) when the above-mentioned 304s' and 304e' are not provided, and a state where the pressure roller 305 is separated from the fixing belt 301 and releases the fixing nip N (a so-called detached state). In this embodiment, the relevant regions have a symmetrical structure upstream and downstream, so for simplicity, the diagram shows only 304s'.

[0047] In the detached state, it can be seen that the corners of sliding member 304 (areas surrounded by dashed lines in FIG. 5) come into contact with the path of fixing belt 301. In the detached state, sliding member 304 is held with a gap in the vertical direction relative to sliding member 304 to avoid expansion and deformation due to thermal expansion. Therefore, when fixing nip N is released, sliding member 304 maintains contact with fixing belt 301 and moves in a direction away from fixing pad 303. This brings the corners of sliding member 304 and the fixing belt into close proximity.

[0048] 6 is a similar diagram of the detached state, but shows the case where 304s' (304e') of this embodiment is provided, and it can be seen that an appropriate distance is maintained between the fixing belt 301 and the sliding member 304. Regarding the dimensions of 304s' (304e'), in this embodiment, a step portion of 400 μm in the pressure direction and 800 μm in the short direction is provided, and the shape is uniform along the length.

[0049] Therefore, it was shown that the provision of the upstream and downstream step portions 304e' and 304s' on the sliding member 304 prevents contact between the belt and the corners of the sliding member 304, thereby preventing damage.

[0050] The shape of the step is not limited to the above, and any structure can be used as long as it can maintain an appropriate distance between the fixing belt 301 and the corner of the sliding member 304.

[0051] <Shape of the longitudinal end region of the sliding member> Figure 7(a) is a diagram showing the longitudinal arrangement of the sliding member 304 from the bottom in the pressure direction. The region in Figure 7A-e is the region where the convex portions 304b are distributed. The region A-ne in Figure 7 is the region where the convex portions 304b are not distributed on the sliding member 304. In this embodiment, the width of the region A-e was set to 350 mm, and the width of the region A-ne was set to 15 mm.

[0052] The reason for setting the A-ne region is to prevent lubricant and wear powder carried by the inner surface of the fixing belt 301 from wrapping around the belt surface. If convex portions 304b are distributed in this region, when the lubricant reaches the convex portions, for example, two flow paths are formed: one that goes over the convex portions and another that bypasses the convex portions. The lubricant that flows into the bypass flow path accumulates on the convex portions 304b, and the lubricant remaining on the convex portions adheres to the end surfaces of the fixing belt 301 and wraps around to the surface. Even when the fixing belt 301 is subjected to deviation position control, both ends of the fixing belt 301 do not enter the An region, and both ends of the fixing belt 301 are always located in the A-ne region or at the end of the A-ne region.

[0053] Therefore, by providing the A-ne region where the convex portion 304b is not distributed, the structure is such that lubricant, wear powder, etc. do not accumulate at the position where it comes into contact with the end surface of the fixing belt 301, thereby preventing it from getting around to the belt surface.

[0054] In this embodiment, a notch 304x is formed upstream of the A-ne region in the sliding member 304. The reason for this shape is that the A-ne region eliminates the protrusion 304b that supports the fixing belt 301, which causes the path of the fixing belt 301 to approach the sliding member 304, preventing contact between the fixing belt 301 and the sliding member at the corners. The possibility of belt damage due to contact at the corners is more pronounced on the upstream side where the belt enters the nip than on the downstream side where the belt leaves the nip. Therefore, this embodiment will be described with an example in which a notch is provided at least on the upstream side. However, if belt damage due to contact at the corners is likely on the downstream side due to consideration of other components that form the nip, it may be provided only on the downstream side. In this embodiment, the notch 304x is cut out 14.5 mm from the longitudinal end of the sliding member 304 toward the center and 1.5 mm in the lateral direction, and the same shape is used on both longitudinal ends. In this embodiment, the cutout is 1.5 mm in the short direction, but it is sufficient if the cutout is 3% or more in the short direction of the sliding member 304. Here, the reason for 3% is that there is a 0.8 mm step in the short direction, and it is necessary to provide a cutout that is at least larger than the step. A cutout of 5-6% is more preferable.

[0055] FIG. 7(b) is an enlarged view of the end of the A-ne region of the sliding member 304. Region 701 is the surface of the sliding member 304 where the protrusion 304b serving as the sliding portion is formed on the base 304a. Region 702 is the surface where the step portion is provided. Region 703 is the surface including the longitudinal end of the sliding member 304 where the protrusion 304b is not formed. Region 703 is the same surface as the base and is continuous with region 701 where the protrusion 304b is formed. Although region 703 is described as being the same as the base, a slight difference in height is not a problem. It is sufficient that the region is continuous with region 701 and is a surface that has not been bent as shown in region 304l in FIG. 8. In FIG. 7, the shape of the notch is depicted as having the same length as the step portion in the short direction, but this is not limited thereto. The notch may be deeper in the short direction than the step portion, or may be shallower in the short direction than the step portion as long as the notch is 3% or more in the short direction of the sliding member 304. Here, the length (L1) in the conveying direction of the recording material at a position of the region 703 serving as the first region is shorter than the length (L2) in the conveying direction of the recording material at a position of the region 701 serving as the second region. Also, the upstream end in the conveying direction of the region 703 is located upstream in the conveying direction of the upstream end in the conveying direction of the region 701.

[0056] 8 is a partial perspective view illustrating the relationship between fixing pad 303 and sliding member 304. Fixing belt 301 (not shown) comes into contact with and slides on sliding member 304 within the range indicated by Ae in the figure. Outside the area where sliding member 304 slides against fixing belt 301, sliding member 304 is held by stepped fastening member 308 at slit portion 304j.

[0057] The sliding member 304 and the stepped fastening member 308 are held with gaps in the vertical direction of the fixing pad 303, the direction of the rotation axis (width direction), and the recording material conveyance direction. The slit portion 304j is formed by bending the sliding member 304 and has a step from the plate-shaped base 304a. The slit 304j is attached to the fixing stay 302 with an attachment portion 304k such as a screw. The bent portion is an outer region 304l, and the region 304l is formed closer to the center of rotation of the pressure roller than the plate-shaped base. The stepped slit portion 304j allows the stepped fastening member 308 to be attached at a lower height than the fixing belt 301, making it possible to assemble and remove the fixing belt 301 without removing the stepped fastening member 308.

[0058] Furthermore, as shown in region 304m, for example, the edge portion of the base body and the edge portion of the notch 304x may be chamfered or may have a curved shape.

[0059] <Examples and comparative examples to confirm the effect> FIG. 9 is a graph showing the relationship between the proximity distance d between the fixing belt 301 and the corner of the sliding member 304 with the notch 304x in the A-e and A-ne regions, and the distance d' between the fixing belt 301 and the corner of the sliding member 304 without the notch 304x. The cross-sectional view shown on the left of the figure is a cross-sectional view of the cross-sectional view shown in the upper right drawing. Note that d and d' were measured at multiple longitudinal positions of the corresponding locations from the front in the paper conveyance direction with the fixing belt 301 removed from the fixing device 8 using a Keyence LJ-V7000 series measuring instrument. Similar measurements were then performed with the fixing belt 301 attached, and the difference between the measurements was used to calculate the data.

[0060] This shows that the proximity distance d' is abruptly close in the A-ne region where the convex portions 304b at the longitudinal ends are not distributed, and that the edges of the corners of the sliding member 304 (points A and B on the graph) come into contact with the belt. On the other hand, in the case of the proximity distance d, an appropriate distance is maintained even in the A-ne region, and it was confirmed that there is a sufficient distance that prevents contact between the fixing belt 301 and the corners of the sliding member 304.

[0061] Next, the following durability test was carried out to verify the effect of the shape of the cutout portion 304x.

[0062] The lifespan of the fixing belt 301 was evaluated using a printer (product name: Canon Inc. imagePRESS V1000). The peripheral speed of the pressure roller 305 installed in the fixing device 8 was set to 450 mm / sec, and the temperature of the halogen heater 306 was set to 190°C. The following method was used to determine the lifespan: 10,000 sheets of paper with a print pattern were printed continuously, then the printer was stopped temporarily, the belt 301 was checked, and another 10,000 sheets were printed continuously. This procedure was repeated. The number of sheets passed until cracks appeared in the fixing belt was defined as the lifespan. The occurrence of edge belt damage was determined by visual inspection of the belt edge. The maximum number of sheets that could be printed was 1,000,000, and any value exceeding this was defined as achieving the target. The temperature and humidity conditions during measurement were 23°C and 30% humidity. A4-size paper was used for this study on the CS-680 (Canon Inc.).

[0063] FIG. 10 is a table showing the durability results. According to this, (i) the fixing device 8 equipped with the notched portion 304x exceeded 1000K, and no damage was observed in the fixing belt 301, achieving the target. (ii) In a test performed using a sliding member without the notched portion 304x, breakage of the base layer was confirmed at the end of the fixing belt 301 after 400,000 sheets. The breakage occurred at the longitudinal end of the fixing belt 301, and wear marks were confirmed on the sliding member 304 corresponding to the breakage position, which would have been caused by contact with the belt. Therefore, it is believed that the inner surface of the fixing belt 301 was subjected to intermittent friction due to contact at these locations, leading to wear and breakage of the belt base material.

[0064] As described above, as shown in this embodiment, by providing the notch 304x in the sliding member 304, it is possible to avoid contact between the fixing belt 301 and the corners of the sliding member 304, and by preventing damage to the fixing belt, it is possible to significantly improve the lifespan of the fixing belt 301.

[0065] In this embodiment, the distance between fixing belt 301 and the corner of sliding member 304 is closer in the detached state, but depending on the configuration, it is conceivable that the distance may be closer in the attached state. Even in that case, by providing notch 304x, it is possible to increase the distance between belt 301 and the corner of sliding member 304 and avoid contact.

[0066] In addition, in this embodiment, the case where the notch 304x is provided in the upstream portion has been described, but it is also possible to provide a notch in the downstream portion under the same conditions as in the upstream portion, as shown in Fig. 11, in which case it is possible to further improve the life of the fixing belt. With reference to Fig. 7(b), when a notch is also provided in the downstream portion, the downstream end in the transport direction at a position where the region 703 is located is located further upstream in the transport direction than the downstream end in the transport direction at a position where the region 701 is located.

[0067] In this embodiment, the notch 304x is formed in the A-ne region, but the notch may extend into the A-e region. In that case, however, since the corners of the sliding member 304 have the function of positioning by upstream and downstream abutment, as described above, a portion that is not the notch 304x is required at least somewhere in the longitudinal Ae region.

[0068] It is not necessary to limit the cutout amount of the cutout portion 304x to a constant amount, and as shown in FIG. 12, a plurality of cutout amounts may be provided along the length. [Explanation of symbols]

[0069] 8 Fixing device 301 Fixing belt 303 Holding member (fixing pad) 303b Downstream guide 303c Upstream guide 303e downstream side 303f Fitting groove 303k Corner on a circular arc 304 Sliding members 304a Base 304b Convex part 304c low friction layer 304e downstream side 304j Slit 304k mounting part 305 Pressure Roller 306 Halogen heater 307 Heating Roller 308 Stepped fastening members N Fixing nip

Claims

1. A fixing device, A rotatable endless belt; a rotating body that contacts the outer peripheral surface of the fixing belt; a nip forming member that is provided on the inner circumferential surface of the belt, sandwiching the rotating body and the belt, and that applies heat and pressure to a recording material on which a toner image has been formed while sandwiching and conveying the recording material, thereby forming a nip portion where the toner image is fixed to the recording material; the nip forming member has a sliding member on a surface that contacts the inner circumferential surface of the belt, the sliding member sliding against the belt, the sliding member has a base body and a sliding portion having a plurality of protrusions protruding from the base body and sliding against the inner peripheral surface of the belt; a first region in a longitudinal center portion of the sliding member, the first region being a surface on which the sliding portion having a plurality of protrusions protruding from the base body is formed; a second region that is the same surface as the base of the first region, is an outer surface of the first region in the longitudinal direction, and is a surface on which the sliding portion is not formed; and The upstream edge of the recording material at the first position in the first region is located upstream in the conveyance direction of the recording material from the upstream edge of the recording material at the second position in the second region. A fixing device characterized by:

2. A downstream end of the first region at the first position in the conveying direction of the recording material is located downstream of a downstream end of the second region at the second position in the conveying direction.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

3. The sliding portion is composed of a plurality of convex shapes.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

4. The sliding member has a step portion in a direction perpendicular to the conveying direction along the longitudinal direction of the upstream end portion in the conveying direction.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

5. The sliding member has a step portion in a direction perpendicular to the conveying direction along the longitudinal direction of the downstream end portion in the conveying direction.

5. The fixing device according to claim 1, wherein the fixing member is a fixing member.

6. The longitudinal end of the sliding member is curved.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

7. The rotor further includes an outer portion that is provided on the outer side of the second region in the longitudinal direction, and the outer portion is closer to the center of rotation of the rotor than the second region in a direction perpendicular to the same plane as the base body.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

8. At the outer portion, the sliding member is supported by another member that constitutes the nip forming member.

8. The fixing device according to claim 7,

9. A fixing device, A rotatable endless belt; a rotating body that contacts the outer peripheral surface of the fixing belt; a nip forming member that is provided on the inner circumferential surface of the belt, sandwiching the rotating body and the belt, and that applies heat and pressure to a recording material on which a toner image has been formed while sandwiching and conveying the recording material, thereby forming a nip portion where the toner image is fixed to the recording material; the nip forming member has a sliding member on a surface that contacts the inner circumferential surface of the belt, the sliding member sliding against the belt, the sliding member has a base body and a sliding portion having a plurality of protrusions protruding from the base body and sliding against the inner peripheral surface of the belt; a first region in a longitudinal center portion of the sliding member, the first region being a surface on which the sliding portion having a plurality of protrusions protruding from the base body is formed; a second region that is the same surface as the base of the first region, is an outer surface of the first region in the longitudinal direction, and is a surface on which the sliding portion is not formed; and The downstream end of the recording material at the first position in the first region is located downstream in the conveyance direction of the recording material from the downstream end of the recording material at the second position in the second region. A fixing device characterized by:

Images