Fixing device

Abstract

To provide a fixing device capable of inhibiting, with a simple configuration, the curling up of a sliding sheet that slides along a fixing belt.SOLUTION: A sliding sheet 41 is mounted to a stay 36 by a fixing mechanism 42. The fixing mechanism 42 includes a plate-like member 42a and screws 42b. The sliding sheet 41 is placed between the plate-like member 42a and a stay 36, and the plate-like member 42a is attached to the stay 36 with the screws 42b, so that the sliding sheet 41 is fixed between the plate-like member 42a and the stay 36. For this purpose, the plate-like member 42a is arranged to allow the sliding sheet 41 to be put between the plate-like member and the stay 36, across the entire longitudinal length of the sliding sheet 41 including both ends. The plate-like member 42a is attached to the stay 36 with each of both ends of the plate-like member positioned between the respective end of the sliding sheet 41 and of the fixing belt 33, ensuring that both ends of the sliding sheet are put between the stay 36 and the plate-like member 42a.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] Image forming apparatuses are equipped with a fixing device that applies heat and pressure to a recording material on which an unfixed toner image has been formed, thereby fixing the toner image to the recording material. Conventionally, fixing devices have been used that include an endless fixing belt, a pressure member disposed inside the fixing belt, and a roller (pressure roller) that contacts the fixing belt. In this fixing device, the pressure member presses the fixing belt against the roller, and the recording material is sandwiched and conveyed in a heated and pressurized state through the fixing nip formed between the fixing belt and the roller. This fixes the toner image to the recording material.

[0003] In the fixing device described above, if the friction between the fixing belt and the pressure member is large, the rotation of the fixing belt may be hindered. This may cause the toner image fixed on the recording material to become distorted or wrinkles to form on the recording material. To prevent this, a sliding sheet containing a lubricant is placed between the fixing belt and the pressure member to reduce the friction between the pressure member and the fixing belt (Patent Document 1, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-109878 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-125889 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the sliding sheet is turned up due to friction with the fixing belt, the turned-up sliding sheet may rub against the fixing belt, hindering the rotation of the fixing belt or reducing the durability of the fixing belt and the sliding sheet. In the device described in Patent Document 1, the sliding sheet's ends (longitudinal ends; the same applies hereinafter) are not fixed and are free ends, which makes the sliding sheet prone to turning up from the end side. On the other hand, in the device described in Patent Document 2, the sliding sheet is wrapped around a pressing member and fixed, including the end, by a fixing member secured with screws. However, with this configuration, it is difficult to properly wrap the sliding sheet around the pressing member, and properly wrapping and fixing the sliding sheet is time-consuming. Therefore, a fixing device that can simply prevent the sliding sheet from turning up when the sliding sheet is disposed between the fixing belt and the pressing member has been desired, but such a device has not yet been proposed.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to provide a fixing device that can suppress curling of a sliding sheet that slides against a fixing belt with a simple configuration. [Means for solving the problem]

[0007] A fixing device according to one embodiment of the present invention is a fixing device that fixes an unfixed toner image formed on a recording material to the recording material, and is characterized in that it comprises an endless belt, a heating section that heats the belt, a pressure rotor that forms a fixing nip between the belt and the heating section to sandwich and transport the recording material and that rotates the belt, a pad that presses the belt toward the pressure rotor, and a sliding sheet that is arranged inside the belt and is pressed by the pad to slide against the belt, the sliding sheet having a first surface on one side in its thickness direction and a second surface on the other side in the thickness direction that is located opposite the first surface and in contact with the belt, and a contact member made of metal that contacts the second surface of the sliding sheet, the sliding sheet being arranged so as not to extend outside the contact member in the longitudinal direction of the belt, and the length of the sliding sheet in the longitudinal direction is shorter than the length of the contact member. [Effects of the Invention]

[0008] According to the present invention, it is possible to suppress curling of the sliding sheet that slides on the belt with a simple configuration. [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. [Figure 3] FIG. [Figure 4] FIG. 2 is a cross-sectional view illustrating a fixing belt assembly. [Figure 5] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Image forming equipment] The fixing device of this embodiment will be described below. First, an image forming apparatus suitable for using the fixing device of this embodiment will be described with reference to Fig. 1. The image forming apparatus 100 shown in Fig. 1 is an intermediate transfer tandem type color image forming apparatus in which image forming units PY, PM, PC, and PK for four colors (yellow, cyan, magenta, and black) are arranged opposite an intermediate transfer belt 8 within the apparatus main body.

[0011] The recording material conveyance process of the image forming apparatus 100 will be described. The recording materials S are stored in a stacked form in a cassette 62 and are fed one by one to a conveyance path 64 by a paper feed roller 63 in accordance with the image formation timing. Alternatively, recording materials S stacked on a manual feed tray (not shown) may be fed one by one to the conveyance path 64. The recording material S is conveyed to a registration roller 65 arranged midway along the conveyance path 64, where it is subjected to skew correction and timing correction before being sent to a secondary transfer portion T2. ​​The secondary transfer portion T2 is a transfer nip formed by an opposing inner secondary transfer roller 66 and outer secondary transfer roller 67. At the secondary transfer portion T2, a secondary transfer voltage is applied to the inner secondary transfer roller 66, thereby secondarily transferring the toner image from the intermediate transfer belt 8 to the recording material S.

[0012] The process of forming an image sent to the secondary transfer station T2 at the same timing as the process of conveying the recording material S to the secondary transfer station T2 described above will now be described. First, the image forming stations PY to PK will be described. However, the image forming stations PY to PK are configured almost identically except that the toner colors used in the developing devices 4Y, 4M, 4C, and 4K are different: yellow, magenta, cyan, and black. Therefore, the following description will be given using the yellow image forming station PY as a representative example, and descriptions of the other image forming stations PM, PC, and PK will be omitted.

[0013] The image forming unit PY is mainly composed of a photosensitive drum 1Y, a charging device 2Y, a developing device 4Y, and a photosensitive drum cleaner 6Y. The surface of the rotationally driven photosensitive drum 1Y is uniformly charged in advance by the charging device 2Y, and then an electrostatic latent image is formed on the surface by an exposure device 3 driven based on image information signals. The electrostatic latent image formed on the photosensitive drum 1Y is then visualized through toner development by the developing device 4Y. Thereafter, a predetermined pressure and primary transfer bias are applied by a primary transfer roller 5Y, which is disposed opposite the image forming unit PY across the intermediate transfer belt 8, and the toner image formed on the photosensitive drum 1Y is primarily transferred onto the intermediate transfer belt 8. Any residual toner remaining on the photosensitive drum 1Y after the primary transfer is removed by a photosensitive drum cleaner 6Y (e.g., a cleaning blade) to prepare the photosensitive drum for the next image formation process.

[0014] The intermediate transfer belt 8 is tensioned by a tension roller 10, a secondary transfer inner roller 66, and driven rollers 7a and 7b, and is driven to move in the direction of arrow R2 in the figure. In this embodiment, the secondary transfer inner roller 66 also serves as a drive roller that drives the intermediate transfer belt 8. The image formation process for each color performed by the image forming units PY to PK described above is performed at a timing to sequentially superimpose the toner image of the color upstream in the movement direction that has been primarily transferred onto the intermediate transfer belt 8. As a result, a full-color toner image is finally formed on the intermediate transfer belt 8 and transported to the secondary transfer unit T2. Note that any residual toner remaining after passing through the secondary transfer unit T2 is removed from the intermediate transfer belt 8 by a transfer cleaner device 11.

[0015] Through the conveying process and image creation process described above, the timing of the recording material S and the full-color toner image are synchronized at the secondary transfer portion T2, and the toner image is secondarily transferred from the intermediate transfer belt 8 to the recording material S. The recording material S is then conveyed to the fixing device 30, where it is pressurized and heated, melting and fixing the toner image on the recording material S. In the case of single-sided printing, the recording material S with the fixed toner image is discharged onto the discharge tray 601 by the forward-rotating discharge rollers 69. On the other hand, in the case of double-sided printing, the recording material S is conveyed by the forward-rotating discharge rollers 69 until the trailing edge of the recording material S passes through the switching member 602, and then the discharge rollers 69 are switched to reverse rotation, swapping the leading and trailing edges, and conveying the recording material to the double-sided conveying path 603. The recording material S is then sent back to the conveying path 64 by the re-feed rollers 604. The subsequent conveying and the image creation process for the second side are the same as those described above, and therefore will not be described here.

[0016] [Fixing device] Next, the fixing device 30 of this embodiment will be described with reference to FIGS. 2 to 5. As shown in FIG. 2, the fixing device 30 of this embodiment includes a fixing belt assembly 31 and a pressure roller 32. The pressure roller 32, which serves as a driving rotor, is rotatably mounted on the device body by having its rotation shaft 32a supported by bearing members 39 provided on side plates 38L and 38R of the device body. The pressure roller 32 is disposed parallel to the fixing belt assembly 31 and is adapted to abut against the fixing belt 33 of the fixing belt assembly 31 and apply pressure to the fixing belt 33. The pressure roller 32 may be, for example, a pressure roller having an elastic layer of silicone rubber or the like on the outer periphery of a metal rotation shaft 32a (core metal), or a pressure roller having a fluororesin layer of PTFE, PFA, FEP or the like on the outer periphery of the elastic layer.

[0017] [Fuser Belt Assembly] The fixing belt assembly 31 is mounted on side plates 38L and 38R of the device body so as to be movable toward the pressure roller 32. As shown in FIGS. 2 and 3, the fixing belt assembly 31 includes a cylindrical (endless) and flexible fixing belt 33 and end holders 37 that hold both ends of the fixing belt 33 in the longitudinal direction (the direction of the axis of rotation of the fixing belt 33). The fixing belt 33 may be, for example, a resin belt having a conductive layer with high thermal conductivity and low heat capacity, or a composite layer structure belt having a metal belt as a base layer and an elastic layer, a release layer, etc. on the outer periphery. Note that the fixing belt 33 referred to in this specification also includes a thin film-like belt.

[0018] In this embodiment, end holders 37 are fitted to both ends of the fixing belt 33. When the fixing belt 33 deviates in the longitudinal direction, the end holders 37, which function as regulating members, receive the longitudinal ends of the fixing belt 33 and regulate the longitudinal movement of the fixing belt 33. In other words, when the fixing belt 33 deviates in the longitudinal direction while being rotated by the pressure roller 32, one longitudinal end of the fixing belt 33 abuts against the end holder 37, thereby regulating further deviation. That is, the pressure roller 32 and the fixing belt 33 may be positioned slightly out of parallel alignment due to an installation error of the pressure roller 32 or the fixing belt assembly 31. In this case, the fixing belt 33 may deviate in the longitudinal direction while being rotated by the rotating pressure roller 32. Therefore, the end holders 37 are fitted to the fixing belt 33 to prevent the fixing belt 33 from deviating in the longitudinal direction due to the pressure roller 32.

[0019] 3, the longitudinal position of end holder 37 is determined by flat surface 37a of end holder 37 abutting against annular protrusion 36b formed on stay 36. End holder 37 is arranged so that it will not move in the longitudinal direction even if it abuts against fixing belt 33 at that position.

[0020] In this embodiment, the end holder 37 restricts longitudinal movement of the fixing belt 33 and is configured to rotate along with the fixing belt 33. To enable the end holder 37 to rotate along with the fixing belt 33, the end holder 37 has a fitting portion 37b that fits with the fixing belt 33 and protrudes toward the center in the longitudinal direction. Being configured so that the end holder 37 can rotate along with the fixing belt 33 reduces friction caused by sliding between the fixing belt 33 and the end holder 37. The end holder 37 may be used as a detection target for detecting the rotation speed of the fixing belt 33. For example, it is preferable to detect the rotation speed of the end holder 37 using an optical sensor (not shown) or the like, and to consider the detected rotation speed of the end holder 37 as the rotation speed of the fixing belt 33.

[0021] In this embodiment, the stay 36 (specifically, its arm 36a) is biased toward the pressure roller 32 with a predetermined biasing force F by a biasing mechanism (not shown), such as a spring. This causes the fixing belt 33 and the pressure roller 32 to be pressed against each other with a desired pressure. By bringing the fixing belt 33 and the pressure roller 32 into pressure contact, a fixing nip N is formed in which the recording material S passes under pressure between the fixing belt 33 and the pressure roller 32 and heats and fixes the toner image. In this embodiment, a pad 34 (see FIG. 4) supported by the stay 36 presses the fixing belt 33 toward the pressure roller 32 from the inside, thereby more reliably forming the fixing nip N. The biasing mechanism (not shown) that biases the stay 36 may have a release function that releases the bias toward the pressure roller 32, allowing a user to remove the recording material S remaining in the fixing nip N by releasing the bias when clearing a jam, for example.

[0022] As shown in FIG. 2, a drive gear G is provided on the rotation shaft 32a of the pressure roller 32. The rotational force of a motor (see FIG. 4: M1) is transmitted to the drive gear G via a power transmission mechanism (not shown), causing the pressure roller 32 to rotate. A fixing nip N is formed between the fixing belt 33 and the pressure roller 32, and the rotational force of the pressure roller 32 is transmitted to the fixing belt 33 by frictional force generated at the fixing nip N. In this manner, the fixing belt 33 is driven to rotate by the pressure roller 32 (a so-called pressure roller drive system). The recording material S is sandwiched and conveyed between the rotating pressure roller 32 and the fixing belt 33. In this embodiment, regardless of the usable length of the recording material S in the width direction (longitudinal direction of the fixing belt 33), the recording material S is conveyed in accordance with center-reference conveyance, in which the center of the width direction of the recording material S passes through a center paper-passing reference line P (virtual line) of the fixing belt 33. The fixing belt assembly 31 is configured to be substantially symmetrical in the longitudinal direction with respect to the central paper passing reference line P described above.

[0023] 4, the fixing belt assembly 31 includes a pad 34, a stay 36, a belt guide 40, a sliding sheet 41, and a fixing mechanism 42 on the inside of the endless fixing belt 33. The fixing belt 33 is rotatably fitted around the heat-resistant, rigid belt guide 40. The belt guide 40 is a plate-like member extending in the longitudinal direction of the fixing belt 33, and is formed in an arc shape so that its outer surface forms a sliding surface with the fixing belt 33. In other words, the outer circumferential surface of the belt guide 40 contacts the inner circumferential surface of the fixing belt 33, allowing the belt guide 40 and the fixing belt 33 to slide against each other. The belt guide 40 is formed by pressing a metal plate such as an aluminum plate, and functions as a rotation guide for the fixing belt 33 together with a pad 34 (described later).

[0024] The belt guide 40 is fixed to a stay 36. The stay 36 is a rigid member that extends in the longitudinal direction along the fixing belt 33. Arms 36a are formed at both ends of the stay 36, and the end holders 37 are rotatably attached to the arms 36a (see FIG. 3).

[0025] The stay 36 has a main body 361, an upstream fixing portion 362 and a downstream fixing portion 363 extending from the main body 361 toward the opposite side of the pressure roller 32, and has a generally U-shaped cross section with an opening on the belt guide 40 side. The main body 361 is provided on the opposite side of the opening of the stay 36 (i.e., the pressure roller 32 side) and supports the pad 34. The pad 34 is, for example, a molded product made of heat-resistant resin extending in the longitudinal direction and pressed against the fixing belt 33 with a sliding sheet 41 sandwiched therebetween. In this manner, the fixing belt 33 can rotate while sliding its inner circumferential surface against the sliding sheet 41 on the fixing nip N side and against the belt guide 40 on the opening side of the stay 36. In this embodiment, the pad 34 has a longitudinal length substantially equal to the longitudinal length of the pressure roller 32 main body excluding the rotation shaft 32a (see FIG. 2).

[0026] The sliding sheet 41 is formed into a sheet having a thickness of 40 μm to 300 μm using thread-like fiber members made of, for example, glass or resin as warp and weft. For the sliding sheet 41, it is preferable to use a fiber member coated with a low-friction resin (for example, a fluororesin such as PTFE or PFA) or a fiber member made of a low-friction resin, as this improves the slidability of the surface.

[0027] [Temperature sensor and induction heating device] The fixing device 30 also has a temperature sensor TH1 for detecting the temperature of the fixing belt 33 and an induction heating device 300 for induction heating the fixing belt 33. The temperature sensor TH1 is, for example, a thermistor, and is disposed near the longitudinal center of the fixing belt 33 so as to be in contact with the inner circumferential surface of the fixing belt 33. The temperature detected by the temperature sensor TH1 is transmitted to a control unit (not shown) having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc. The control unit controls the induction heating device 300 based on the temperature detected by the temperature sensor TH1 so as to maintain the temperature of the fixing belt 33 at a target temperature (e.g., 180°C).

[0028] The induction heating device 300 serving as a heating means is disposed on the belt guide 40 side of the fixing belt assembly 31 with a predetermined gap between it and the outer peripheral surface of the fixing belt 33. The induction heating device 300 includes an excitation coil 301, an outer magnetic core 302, and a coil holding member 303. The excitation coil 301 is a coil extending in the longitudinal direction and wound with an electric wire such as a Litz wire, and is curved to fit the outer peripheral surface of the fixing belt 33. An AC current having a frequency of, for example, 20 to 60 kHz is applied to the excitation coil 301 by a power supply unit (excitation circuit, etc.) not shown. The frequency of this AC current is changed by a control unit. When the AC current is applied to the excitation coil 301, it generates an AC magnetic field (magnetic flux). When the AC magnetic field is generated by the excitation coil 301, the fixing belt 33 is induction-heated. In order to efficiently inductively heat the fixing belt 33, the outer magnetic core 302 is made of a material with high magnetic permeability, such as ferrite, that can shield AC magnetic fields. The outer magnetic core 302 is disposed so as to cover the exciting coil 301, thereby suppressing leakage of the AC magnetic field. The exciting coil 301 and the outer magnetic core 302 are supported by a coil holding member 303 made of an electrically insulating resin.

[0029] In the fixing device 30, the recording material S on which an unfixed toner image t is formed is conveyed to the fixing nip N while the temperature of the fixing belt 33 is maintained at a desired target temperature. The recording material S is conveyed with the side on which the unfixed toner image t is formed facing the fixing belt 33. The recording material S is conveyed between the fixing belt 33 and the pressure roller 32, which are both rotating, and passes through the fixing nip N. Then, while the recording material S is being pressed by the fixing belt 33 and the pressure roller 32, the toner image t is fixed to the recording material S by being heated by the fixing belt 33.

[0030] The sliding sheet 41 described above remains between the pressing surface of the pad 34 and the fixing belt 33 and slides against the fixing belt 33, thereby reducing the frictional force that may occur between the sliding sheet 41 and the fixing belt 33 compared to when the pad 34 and the fixing belt 33 slide directly against each other. However, frictional force inevitably occurs between the sliding sheet 41 and the fixing belt 33 due to the pressure from the pad 34, and this frictional force may pull the sliding sheet 41 in the rotational direction of the fixing belt 33. Here, within the fixing nip N region, the fixing belt 33 and the sliding sheet 41 are sandwiched relatively tightly between the pad 34 and the pressure roller 32, so the fixing belt 33 and the sliding sheet 41 are maintained in close contact with each other so as to follow the shape of the pad 34. Therefore, the sliding sheet 41 is less likely to turn up within the fixing nip N.

[0031] In contrast, outside the fixing nip N, the fixing belt 33 and the sliding sheet 41 are not sandwiched between the pad 34 and the pressure roller 32, and therefore the sliding sheet 41 is more likely to be pulled toward the longitudinal end farther from the fixing nip N. In particular, when the end of the sliding sheet 41 is not fixed and is a free end, the end side is more likely to deform when pulled than the fixing nip N, making the behavior of the sliding sheet 41 unstable, and thus the end side of the sliding sheet 41 is more likely to curl up. This is because the tension (pulling tension) of the sliding sheet 41 cannot be maintained uniformly, which disrupts the balance with the frictional force generated by sliding with the fixing belt 33.

[0032] Also, when the end holder 37 is externally fitted to the fixing belt 33, curling is more likely to occur on the end side of the sliding sheet 41. That is, when the end holder 37 is externally fitted to the fixing belt 33, the fixing belt 33 is deformed so as to be constricted in the inner diameter direction by the end holder 37. In that case, since the sliding sheet 41 that receives pressure from the fixing belt 33 constricted in the inner diameter direction is also pushed in the inner diameter direction, depending on variations (such as eccentricity) in the shape and rotational behavior of the fixing belt 33 and the sliding sheet 41, curling is likely to occur on the end side of the sliding sheet 41. When curling occurs on the sliding sheet 41, the frictional force increases due to one-sided contact, hindering the movement of the fixing belt 33, or the curled sliding sheet 41 is卷入 the fixing nip N, which may reduce the durability of the sliding sheet 41 and the fixing belt 33.

[0033] Therefore, in this embodiment, in view of the above points, the sliding sheet 41 is fixed to the stay 36 in order to uniformly maintain the tension of the sliding sheet 41 in the rotational direction of the fixing belt 33 over the entire longitudinal direction. In addition to that, the sliding sheet 41 is attached such that both ends thereof are sandwiched between the stay 36 by the fixing mechanism 42. Hereinafter, the fixing mode of the sliding sheet 41 to the stay 36 in this embodiment will be described using FIGS. 4 and 5. In FIG. 5, the longitudinal length of the sliding sheet 41 is indicated as "L1", the longitudinal length of the fixing mechanism 42 (specifically, the plate-like member 42a) is indicated as "L2", and the longitudinal length of the fixing belt 33 is indicated as "L3". In the case of this embodiment, the sliding sheet 41, the fixing mechanism 42, and the fixing belt 33 are each formed with a longitudinal length longer than the fixing nip N (N < L1 < L2 < L3) and are relatively arranged so as to include the fixing nip N in the longitudinal direction.

[0034] 4, sliding sheet 41 is held by stay 36. Specifically, with respect to the rotation direction of fixing belt 33, sliding sheet 41 is fixed at its upstream end 41a to upstream fixed portion 362 of stay 36 by fixing mechanism 42, and at its downstream end 41b to downstream fixed portion 363 of stay 36 by fixing mechanism 42. In this way, by fixing upstream end 41a and downstream end 41b of sliding sheet 41 to stay 36 by fixing mechanism 42, sliding sheet 41 can be fixed with uniform tension in the rotation direction of fixing belt 33 with a simple configuration.

[0035] The sliding sheet 41 is attached to the stay 36 by a fixing mechanism 42 because its low rigidity means that it is prone to longitudinal movement and displacement due to friction with the fixing belt 33. As shown in FIG. 5 , the fixing mechanism 42 includes, for example, a long plate-like member 42a extending in the longitudinal direction and screws 42b. The sliding sheet 41 is disposed between the plate-like member 42a and the stay 36, and the plate-like member 42a is attached to the stay 36 by the screws 42b, so that the sliding sheet 41 is sandwiched and fixed between the plate-like member 42a and the stay 36. In this embodiment, the plate-like member 42a is attached to the stay 36 by a plurality of screws 42b at multiple points in the longitudinal direction.

[0036] 5, the sliding sheet 41 is attached to the stay 36 by the fixing mechanism 42. That is, the plate-shaped member 42a of the fixing mechanism 42 is disposed so that the sliding sheet 41 is sandwiched between the stay 36 and the plate-shaped member 42a over the entire longitudinal length, including both end portions. As described above, the longitudinal length (L2) of the plate-shaped member 42a is longer than the longitudinal length (L1) of the sliding sheet 41 and shorter than the longitudinal length (L3) of the fixing belt 33. The plate-shaped member 42a is attached to the stay 36 with both end portions positioned between the end of the sliding sheet 41 and the end of the fixing belt 33, respectively, so that both end portions of the sliding sheet 41 are sandwiched between the stay 36 and the plate-shaped member 42a.

[0037] As described above, in this embodiment, a simple configuration can be used to maintain uniform tension on the sliding sheet 41 throughout its entire length, including both longitudinal ends, regardless of the rotation of the fixing belt 33. That is, by fixing the upstream end 41a and downstream end 41b of the sliding sheet 41 to the stay 36, the sliding sheet 41 is pulled uniformly throughout its entire length due to friction with the fixing belt 33, making it difficult for a difference in tension to occur between the area inside the fixing nip N and outside the fixing nip N. Furthermore, by fixing the sliding sheet 41, including both ends, to the stay 36, it is easy to maintain uniform tension on the sliding sheet 41 throughout its entire length. This stabilizes the behavior of the sliding sheet 41, thereby making it less likely for the sliding sheet 41 to curl up. Even when the end holders 37 are fitted around the fixing belt 33, it is possible to prevent the sliding sheet 41 from curling up from its end. Also, it is advantageous that the sliding sheet 41 can be properly attached to the pad 34 simply by attaching the sliding sheet 41 to the stay 36.

[0038] <Other embodiments> The fixing mechanism 42 may be only the screw 42b, in which case the sliding sheet 41 is fixed by being sandwiched between the screw 42b and the stay 36. Also, a plurality of plate-like members 42a may be arranged at intervals, and in this specification, these are all referred to as the long plate-like member 42a. It is sufficient that the sliding sheet 41 is fixed so that at least both longitudinal ends thereof are sandwiched between the stay 36.

[0039] In the above-described embodiment, the sliding sheet 41 is fixed to the upstream-side fixing portion 362 and the downstream-side fixing portion 363 of the stay 36. However, this is not limiting. For example, the sliding sheet 41 may be fixed to the main body portion 361 as long as the tension of the sliding sheet 41 can be maintained uniform. However, from the viewpoint of adjusting the surface pressure of the pad 34 using a biasing mechanism (not shown) so that the fixing belt 33 and the pressure roller 32 are pressed against each other with a desired pressure, it is preferable to fix the sliding sheet 41 to the upstream-side fixing portion 362 and the downstream-side fixing portion 363 rather than to the main body portion 361. Furthermore, fixing the sliding sheet 41 to the upstream-side fixing portion 362 and the downstream-side fixing portion 363 makes it easier to attach the sliding sheet 41 to the stay 36. To achieve this, the upstream-side fixing portion 362 and the downstream-side fixing portion 363 of the stay 36 are preferably spaced apart from each other in a direction intersecting the longitudinal direction by a distance wider than the fixing nip N (see FIG. 4 ).

[0040] In the above-described embodiment, the induction heating device 300 employs an induction heating method to heat the fixing belt 33, but the present invention is not limited to this. For example, a heat source such as a halogen heater, a ceramic heater, or an infrared lamp may be provided on the inside or outside of the fixing belt 33 to heat the fixing belt 33. Alternatively, a heat source for heating the pressure roller 32 may be provided instead of the fixing belt 33. [Explanation of symbols]

[0041] 30... fixing device, 32... driving rotor (pressure roller), 33... belt (fixing belt), 34... pad, 36... stay, 37... regulating member (end holder), 37b... fitting portion, 41... sliding sheet, 42... fixing mechanism, 42a... plate-shaped member, 42b... screw, 300... heating means (induction heating device), N... fixing nip

Claims

[Claim 1] A fixing device that fixes an unfixed toner image formed on a recording material to the recording material, An endless belt; a heating unit that heats the belt; a pressure rotating member that forms a fixing nip portion between the belt and the pressure rotating member and that rotates the belt; a pad that presses the belt toward the pressure rotor; a sliding sheet disposed inside the belt and pressed by the pad to slide relative to the belt, the sliding sheet having a first surface on one side in a thickness direction of the sliding sheet and a second surface on the other side in the thickness direction, the second surface being located opposite to the first surface and in contact with the belt; a contact member made of metal that contacts the second surface of the sliding sheet, the sliding sheet is disposed so as not to protrude outward from the contact member in the longitudinal direction of the belt, and the length of the sliding sheet in the longitudinal direction is shorter than the length of the contact member; A fixing device characterized by:

Images