Fixing device

Abstract

To provide a fixation apparatus which can suppress the occurrence of a fixation failure in a recording material due a protrusion in such a configuration that the protrusion is formed in a sliding member.SOLUTION: A sliding member 304 includes a plurality of protrusions which protrude from a base body 304a and are slid on a fixation belt 301. The sliding member 304 has a first non-formation region 3041 and a second non-formation region 3042 in which the protrusions are not formed and which are not in contact with the fixation belt 301 within ranges (L1, L2) being equal to or greater than 0.5 mm and equal to or less than 2.0 mm from ends in a conveyance direction. A height of the protrusion can be correctly measured in such a state that the first non-formation region 3041 and the second non-formation region 3042 are clamped and warpage of the sliding member 304 is corrected. At this time, a scratch and a dent due to the clamp are not generated in the protrusion. Consequently, a fixation apparatus can suppress the occurrence of a fixation failure in a recording material due to the protrusions formed on the sliding member 304 without impairing the separability of the recording material passing through the fixation belt 301.SELECTED DRAWING: Figure 4

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 on 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 on 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, and a fixing nip portion is formed 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 on 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 in the fixing nip portion where the pressure is high, a device provided with a sliding member that slides on the fixing belt has been proposed (Patent Document 1). Recently, in order to reduce the frictional force between the fixing belt and the sliding member, a sliding member having a plurality of convex portions formed on its surface has been used.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, when using a sliding member with multiple protrusions formed on its surface, if the height of the protrusions is not approximately uniform, uneven pressure can occur at the fixing nip, potentially leading to poor fixing of the toner image to the recording material. Therefore, the sliding member is inspected by measuring the height of the protrusions (for example, non-contact inspection using laser scanning). However, if the sliding member is warped, the height of the protrusions cannot be measured correctly, so conventionally, the height of the protrusions has been measured with the warp corrected by clamping the sliding member. However, conventionally, the sliding member is clamped in the area including the protrusions, which can cause minute scratches or dents on the protrusions within the clamped area, potentially leading to poor fixing of the toner image to the recording material.

[0006] The present invention has been made in view of the above problems, and aims to provide a fixing device in which a protrusion is formed on the sliding member that slides against the fixing belt, and which can suppress the occurrence of fixing failures on the recording material caused by the protrusion. [Means for solving the problem]

[0007] 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 base body; a long sliding member having a plurality of protrusions protruding from the base body; a holding member non-rotatingly provided on the inner circumference side of the fixing belt and holding the sliding member such that the plurality of protrusions 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 sliding member is held by the holding member such that its short side is the conveying direction, and at both ends in the short side direction, there are non-formed regions in a range of 0.5 mm to 2.0 mm from each end in the short side direction where the protrusions are not formed and which do not contact the fixing belt Furthermore, the non-formed region is formed with a thickness of 30% to 70% of the thickness from the tip of the protrusion to the opposite surface of the substrate opposite to the surface on which the protrusion is formed. It is characterized by the following: 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 base body; a long sliding member having a plurality of protrusions protruding from the base body; a holding member provided non-rotatingly on the inner circumference side of the fixing belt and holding the sliding member such that the plurality of protrusions 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 a toner image to the recording material, wherein the sliding member is held by the holding member such that its short side is the conveying direction, and has non-formed regions at both ends in the short side direction, in a range of 0.5 mm to 2.0 mm from each end in the short side direction, where the protrusions are not formed and do not contact the fixing belt, and the sliding member has a low-friction layer that reduces the frictional force between the plurality of protrusions and the fixing belt. 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 base made of metal; a long sliding member having a plurality of protrusions made of metal protruding from the base; a non-rotating holding member provided on the inner circumference side of the fixing belt, which holds the sliding member such that the surface of the sliding member on the side where the plurality of protrusions are formed contacts the inner circumference surface of the fixing belt; and an opposing member that contacts 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 a toner image to the recording material, wherein the sliding member is held by the holding member such that its short side is the conveying direction, and has non-formed regions at both ends in the short side, in a range of 0.5 mm to 2.0 mm from each end in the short side, where the protrusions are not formed and do not contact the fixing belt. [Effects of the Invention]

[0008] According to the present invention, a configuration is achieved in which a protrusion is formed on the sliding member that slides against the fixing belt, and it is possible to suppress the occurrence of fixing failures on the recording material caused by the protrusion with a simple configuration. [Brief explanation of the drawing]

[0009] [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) A schematic diagram showing the sliding member of the first embodiment, (b) A top view showing the sliding member of the first embodiment. [Figure 4] A cross-sectional view showing the vicinity of the fixing nip. [Figure 5] A schematic diagram showing the clamping state of the sliding member, where (a) the sliding member of the comparative example is used, and (b) the sliding member of this embodiment is used. [Figure 6] A cross-sectional view showing the sliding member of the second embodiment. [Modes for carrying out the invention]

[0010] 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.

[0011] [First Embodiment] <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.

[0012] As shown in Figure 1, the image forming apparatus 1 comprises a document reader 2 and a main body 3. The document reader 2 reads a document placed on the document glass 21. Light emitted from the light source 22 is reflected by the document and formed on the CCD sensor 24 via optical system components 23 such as lenses. When this optical system unit is scanned in the direction of the arrow under the control of the reader control unit, it reads the document line by line and converts it into a sequence of electrical signal data. The image signal obtained by the CCD sensor 24 is sent to the main body 3, where the control unit 30 performs image processing according to each image forming unit described later. The control unit 30 also receives external input as an image signal from an external host device such as a print server.

[0013] The main unit 3 of the apparatus comprises multiple image forming units Pa, Pb, Pc, and Pd, and each image forming unit performs image formation based on the image signal described above. That is, the image signal is converted into a laser beam controlled by PWM (pulse width modulation) by the control unit 30. The polygon scanner 31, which acts as an exposure device, scans the laser beam according to the image signal. The laser beam is then irradiated onto the photosensitive drums 200a to 200d, which serve as image carriers for each of the image forming units Pa to Pd.

[0014] 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 an image signal as described below.

[0015] The charging roller 201a as a primary charger charges the surface of the photosensitive drum 200a to a predetermined potential to prepare for electrostatic latent image formation. 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 surface of the intermediate transfer belt 204 and applies a primary transfer bias of the opposite polarity to the toner, transferring the toner image on the photosensitive drum 200a onto the intermediate transfer belt 204. The photosensitive drum 200a after transfer is cleaned on its surface by the cleaner 207a.

[0016] 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 image forming unit Pd of Bk, which is 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.

[0017] The recording medium is housed in the cassette 9, and the recording medium 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. Thereafter, the timing of the registration unit 208 is controlled to align the positions of the toner image on the intermediate transfer belt 204 and the paper, and the recording medium is conveyed to the secondary transfer unit T2.

[0018] The recording medium onto which the toner image has been transferred in the secondary transfer unit T2 is conveyed to the fixing device 8, and in the fixing device 8, by being heated and pressurized, the toner image carried on the recording medium is fixed to the recording medium. The recording medium that has passed through the fixing device 8 is discharged onto the discharge tray 7. When forming an image on both sides of the recording medium, after the transfer and fixing of the toner image onto the first side (front surface) of the recording medium are completed, the recording medium is reversed through the reverse conveyance unit 10, and the transfer and fixing of the toner image onto the second side (back surface) of the recording medium are performed, and it is stacked on the discharge tray 7.

[0019] Note that the control unit 30 controls the entire image forming apparatus 1 as described above. Also, the control unit 30 can perform various settings based on the input from the operation unit 4 of the image forming apparatus 1. Such a control unit 30 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The CPU controls each unit while reading out a program corresponding to the control procedure stored in the ROM. Also, work data and input data are stored in the RAM, and the CPU controls by referring to the data stored in the RAM based on the aforementioned program and the like.

[0020] <Fixing 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.

[0021] 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.

[0022] <Fixing belt> The fixing belt 301 is replaceable and provided on the fixing pad unit 300. The fixing belt 301 has thermal conductivity and heat resistance, and is formed in a thin-walled cylindrical shape. In this embodiment, as shown in Figure 2(b), the fixing belt 301 has a three-layer structure in which a base layer 301a is formed on the inner circumference, an elastic layer 301b is formed on the outer circumference of the base layer 301a, and a release layer 301c is formed on the outer circumference of the elastic layer 301b. As an 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 tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin (PFA) 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.

[0023] <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.

[0024] 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.

[0025] 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".

[0026] <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.

[0027] 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.

[0028] 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.

[0029] <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.

[0030] 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.

[0031] <Fixing pad> 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 a long sliding member 304 can be fitted, and holds the sliding member 304 so as to contact the inner 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 made of 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.

[0032] As shown in Figure 4, the fixing pad 303 has, with respect to the transport direction, an upstream guide portion 303c that contacts the fixing belt 301 on the upstream side of the bottom surface 303h of the fitting groove portion 303f, and a downstream guide portion 303b that contacts the fixing belt 301 on the downstream side of the bottom surface 303h. The bottom surface 303h is the surface that contacts the opposite surface 304a2 of the sliding member 304, opposite to the sliding surface (the tip of the protrusion 304b). 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. These upstream guide sections 303c and downstream guide sections 303b are in contact with the fixing belt 301 over the entire paper-feed area through which the largest possible size of recording material capable of image formation in the fixing nip section N passes, in the width direction.

[0033] <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 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 in the fixing nip section N where the 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 in between. In this embodiment, the sliding member 304 is held by the fixing pad 303 such that its shorter side is in the conveying direction.

[0034] 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.

[0035] 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.

[0036] 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).

[0037] 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.

[0038] 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.

[0039] 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 with the tip surface 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.

[0040] 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 achieve this, 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 from resin by injection molding using a mold.

[0041] As mentioned earlier, if the heights of the multiple protrusions 304b on the sliding member 304 are not approximately uniform, uneven pressure will occur at the fixing nip portion N, causing poor fixing of the recording material. The difference in height of the protrusions 304b that causes poor fixing is, for example, about 20 μm to 50 μm. To prevent poor fixing of the recording material caused by the height of such protrusions 304b, the sliding member 304 is inspected by measuring the heights of the multiple protrusions 304b using a non-contact inspection device, such as a laser scan device. The non-contact inspection device measures the height of the protrusions 304b with a line-scan type sensor (called a scan sensor) using laser light and compares the measured value with a reference value specified in a pre-prepared protrusion shape profile. If the difference between the measured value and the reference value is within a predetermined range (for example, 15 μm or less), the sliding member 304 is judged to be a good product. Sliding members 304 that are not judged to be good products are not used.

[0042] Furthermore, when the sliding member 304 is formed from a base material such as stainless steel, warping may occur in the width direction (longitudinal direction) starting from the center due to the precision of the base material and residual stress during processing. The height difference due to warping between the width direction end and the center varies from one sliding member 304 to another, but is, for example, about "2 mm". If the sliding member 304 is warped, it is difficult to accurately measure the height of the protrusion 304b using the non-contact inspection device described above, so it is necessary to correct the warping of the sliding member 304 before measuring the height of the protrusion 304b. In order to correct the warping of the sliding member 304, the sliding member 304 is fixed (clamped) between a surface plate and a clamping member, as will be described later.

[0043] As shown in Figure 4, the sliding member 304 of this embodiment has a first non-formed region 3041 and a second non-formed region 3042 at both ends in the transport direction (short direction) where no protrusions 304b are formed. The first non-formed region 3041 is a flat region from the downstream end of the base body 304a to the downstreammost protrusion 304b1 formed among the multiple protrusions 304b, with respect to the transport direction. The second non-formed region 3042 is a flat region from the upstream end of the base body 304a to the upstreammost protrusion 304b2 formed among the multiple protrusions 304b, with respect to the transport direction. In this embodiment, when the sliding member 304 is held by the fixing pad 303, the first non-formed region 3041 and the second non-formed region 3042 are in contact with the bottom surface 303h of the fitting groove 303f of the fixing pad 303, similar to the base body 304a.

[0044] In this embodiment, the first non-formed region 3041 and the second non-formed region 3042 are clamped, allowing the height of the protrusion 304b to be measured with the curvature of the sliding member 304 corrected. The first non-formed region 3041 and the second non-formed region 3042 are formed to lengths (L1, L2) such that they can be clamped without interfering with the protrusion 304b in the transport direction. For example, the first non-formed region 3041 is formed to a length "L1" of "0.5 mm" or more in the short direction (transport direction) from one downstream end of the base body 304a. Similarly, the second non-formed region 3042 is formed to a length "L2" of "0.5 mm" or more in the short direction (transport direction) from the other upstream end of the base body 304a. This makes it possible to measure the height of the protrusion 304b with high accuracy with the curvature of the sliding member 304 corrected.

[0045] Furthermore, in order to securely clamp the sliding member 304 and correct its warping, it is preferable that the length of the first non-formed area 3041 and the second non-formed area 3042 in the transport direction be 1.0 mm or more. In addition, it is preferable that the first non-formed area 3041 and the second non-formed area 3042 be formed over the entire width (entire longitudinal) of the sliding member 304.

[0046] Figure 5(a) shows the clamping state when using the comparative example sliding member 404, and Figure 5(b) shows the clamping state when using the sliding member 304 of this embodiment. Generally, the warping of the sliding members (404, 304) is corrected when a portion of it is sandwiched between the clamp member 501 and the base plate 500, and pressed against the base plate 500 by the clamp member 501. If the thickness of the base body 304a is, for example, "1.0 mm", the clamping force (CF) by the clamp member 501 required to correct the warping of the sliding members (404, 304) is set to approximately "2 to 4 N".

[0047] As shown in Figure 5(a), the comparative sliding member 404 differs from the sliding member 304 of this embodiment in that it does not have flat areas that can be clamped by the clamping member 501, such as the first non-formed area 3041 and the second non-formed area 3042. In such a sliding member 404, an area including some of the multiple protrusions 304b is pressed against the surface plate 500 by the clamping member 501. For the protrusions 304b in the area pressed by the clamping member 501, it is difficult to measure the height with a scan sensor because the clamping member 501 gets in the way. In addition, the protrusions 304b pressed by the clamping member 501 may develop scratches or dents on the tip side, including the low friction layer 304c.

[0048] On the other hand, as shown in Figure 5(b), in the sliding member 304 of this embodiment, the first non-formed region 3041 and the second non-formed region 3042, where the protrusions 304b are not formed, are pressed against the surface plate 500 by the clamp member 501. The first non-formed region 3041 and the second non-formed region 3042 are flat regions where the protrusions 304b are not formed. Therefore, compared to the comparative example, the clamp member 501 does not get in the way, and the height of all the protrusions 304b on the sliding member 304 can be correctly measured by the scan sensor.

[0049] Furthermore, in the case of the sliding member 304 of this embodiment, as shown in Figure 4, the first non-formed area 3041 and the second non-formed area 3042 are formed outside the range of the fixing nip portion N so as not to come into contact with the fixing belt 301. Therefore, even if minute scratches or dents occur in the first non-formed area 3041 and the second non-formed area 3042 due to being pressed by the clamp member 501, it will not affect the fixing of the toner image to the recording material in any way.

[0050] As described above, from the viewpoint of ensuring secure clamping to the sliding member 304, the transport direction lengths (L1, L2) of the first non-forming region 3041 and the second non-forming region 3042 should be long, preferably 0.5 mm or more, and more preferably 1.0 mm or more. However, if the transport direction lengths (L1, L2) of the first non-forming region 3041 and the second non-forming region 3042 are longer than necessary, the transport direction length of the fixing nip section N (see Figure 2(a)) will be shortened, making it easier for uneven pressure to occur. To address this, it is conceivable to lengthen the sliding member 304 itself to secure the transport direction length of the fixing nip section N, but this is costly and difficult to adopt as it would enlarge the fixing device 8. Furthermore, depending on the transport direction lengths (L1, L2) of the first non-forming region 3041 and the second non-forming region 3042, the distance from the downstream end of the fixing nip section N to the upstream end of the separation plate (not shown) will be long. The separation plate is positioned downstream of the fixing device 8 to separate the recording material that has passed through the fixing nip section N from the fixing belt 301. However, this is undesirable because it makes it difficult to separate the recording material from the fixing belt 301.

[0051] In view of the above, in this embodiment, the transport direction length of the first non-formed region 3041 and the second non-formed region 3042 is set to "2.0 mm" or less. In summary, the transport direction length of the first non-formed region 3041 and the second non-formed region 3042 is "0.5 mm or more and 2.0 mm or less", preferably "1.0 mm or more and 1.5 mm or less".

[0052] Note that the transport-direction lengths of the first non-forming region 3041 and the second non-forming region 3042 do not have to be the same. The second non-forming region 3042 upstream of the fixing nip N has less influence on the separation of the recording material compared to the first non-forming region 3041 downstream of the fixing nip N. Therefore, it is preferable to make the transport-direction length of the second non-forming region 3042 longer than that of the first non-forming region 3041 (L2 > L1).

[0053] As described above, the sliding member 304 of this embodiment has a first non-formed region 3041 and a second non-formed region 3042 in the range of "0.5 mm to 2.0 mm" from each end in the conveying direction, where the protrusion 304b is not formed and does not come into contact with the fixing belt 301. By clamping the first non-formed region 3041 and the second non-formed region 3042, the height of the protrusion 304b can be measured correctly while the curvature of the sliding member 304 is corrected, and no scratches or dents are caused on the protrusion 304b by the clamp. As a result, it is possible to suppress the occurrence of fixing failures to the recording material caused by the protrusion 304b formed on the surface of the sliding member 304 without impairing the separation of the recording material that has passed through the fixing belt 301.

[0054] [Second Embodiment] Next, the sliding member of the second embodiment will be described with reference to Figures 2(a) and 4, and with reference to Figure 6. In the sliding member 304 of the first embodiment described above, as shown in Figure 4, with the sliding member 304 held by the fixing pad 303, the first non-formed region 3041 and the second non-formed region 3042 are formed such that they are at the same height as the height from the bottom surface 303h of the fitting groove portion 303f to the surface 304a1 of the base body 304a.

[0055] Incidentally, if the recording material comes into contact with the fixing belt 301 upstream or downstream of the fixing nip section N, fixing failure may occur. Even if the recording material becomes wavy or deformed, in order to prevent the recording material from coming into contact with the fixing belt 301, the fixing pad 303 should be able to guide the fixing belt 301 away from the pressure roller 305 upstream or downstream of the fixing nip section N. In other words, the upstream guide section 303c and the downstream guide section 303b of the fixing pad 303 are formed to move away from the pressure roller 305 upstream or downstream of the fixing nip section N. However, in such a case, the sliding member 304 of the first embodiment described above may have the upstream edge section or downstream edge section of the base body 304a come into contact with the fixing belt 301, which may accelerate the wear of the fixing belt 301 and lead to its replacement sooner.

[0056] Therefore, as shown in Figure 6, the first non-formed region 3041 and the second non-formed region 3042 are formed to be closer to the bottom surface 303h of the fitting groove 303f than to the surface 304a1 of the base body 304a on which the protrusion 304b is formed. However, if the thickness of the first non-formed region 3041 and the second non-formed region 3042 is made too thin, the rigidity will decrease, and there is a risk that the warping of the sliding member 304G cannot be corrected when clamped.

[0057] In this embodiment, the first non-formed region 3041 and the second non-formed region 3042 are formed with a thickness (H2) that is "30% or more and 70% or less" of the thickness (H1) from the tip of the protrusion 304b to the opposite surface 304a2 of the base 304aa opposite to the surface 304a1. For example, if the thickness (H1) from the tip of the protrusion 304b to the opposite surface 304a2 of the base 304a is "1.4 mm", then the thickness (H2) of the first non-formed region 3041 and the second non-formed region 3042 is "0.5 mm or more and 0.9 mm or less".

[0058] The thicknesses of the first non-formed region 3041 and the second non-formed region 3042 do not have to be the same. The second non-formed region 3042, located upstream of the fixing nip N, is less affected by the aforementioned warping and deformation of the recording material compared to the first non-formed region 3041, located downstream of the fixing nip N. Therefore, the thickness of the second non-formed region 3042 may be thicker than that of the first non-formed region 3041.

[0059] By doing so, even if the fixing pad 303 is formed so that the recording material does not come into contact with the fixing belt 301, it is possible to suppress the occurrence of poor fixing to the recording material caused by the protrusions 304b on the sliding member 304 without impairing the separability of the recording material.

[0060] [Other embodiments] 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]

[0061] 8... Fixing device, 301... Fixing belt, 303... Holding member (fixing pad), 303f... Fitting groove, 303h... Bottom surface, 304 (304G)... Sliding member, 304a... Base body, 304a2... Opposite surface, 304b... Protrusion, 304c... Low friction layer, 305... Opposing member (pressure roller), 3041... Non-formed area (first non-formed area), 3042... Non-formed area (second non-formed area), N... Fixing nip

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 base body, and an elongated sliding member having a plurality of protrusions projecting from the base body, A retaining member is provided non-rotatably on the inner circumference side of the fixing belt, and holds the sliding member such that the plurality of protrusions 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 sliding member is held by the holding member such that its shorter side is the conveying direction, and at both ends in the shorter side, there is a non-formed area in which the protrusion is not formed and does not come into contact with the fixing belt, within a range of 0.5 mm to 2.0 mm from each end in the shorter side. The non-formed region is formed with a thickness of 30% to 70% of the thickness from the tip of the protrusion to the opposite surface of the substrate opposite to the surface on which the protrusion is formed. A fixing device characterized by the following features.

2. 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 1.

3. A fixing device for fixing a toner image formed on a recording material to the recording material, A rotating, endless fixing belt, A base body, and an elongated sliding member having a plurality of protrusions projecting from the base body, A retaining member is provided non-rotatably on the inner circumference side of the fixing belt, and holds the sliding member such that the plurality of protrusions 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 sliding member is held by the holding member such that its shorter side is the conveying direction, and at both ends in the shorter side, there is a non-formed area in which the protrusion is not formed and does not come into contact with the fixing belt, within a range of 0.5 mm to 2.0 mm from each end in the shorter side. The sliding member has a low-friction layer that reduces the frictional force between the plurality of protrusions and the fixing belt. A fixing device characterized by the following features.

4. The base and the protrusion are made of metal. A fixing device according to any one of claims 1 to 3.

5. A fixing device for fixing a toner image formed on a recording material to a recording material, A rotating, endless fixing belt, A long sliding member having a base made of metal and a plurality of protrusions made of metal that protrude from the base, A retaining member is provided non-rotatably on the inner circumference side of the fixing belt, and holds the sliding member such that the surface of the sliding member on the side where the plurality of protrusions are formed contacts the inner circumference 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 sliding member is held by the holding member such that its shorter side is the conveying direction, and at both ends in the shorter side, there is a non-formed area in which the protrusion is not formed and does not come into contact with the fixing belt, within a range of 0.5 mm to 2.0 mm from each end in the shorter side. A fixing device characterized by the following features.

6. The non-formed region is formed over the entire longitudinal region of the sliding member, The fixing device according to any one of claims 1 to 5.

7. The retaining member has a fitting groove for fitting and holding the sliding member, The fixing device according to any one of claims 1 to 6.

8. The retaining member is made of resin, The fixing device according to any one of claims 1 to 7.

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