JP2019124737A - Fixing device and image forming apparatus - Google Patents

Abstract

To provide a fixing device capable of highly accurately detecting the rotation of a fixing belt.SOLUTION: A fixing device 8A includes a pressure rotary body 10, an endless fixing belt 21, a pad member 22, and a reflection type photoelectric sensor 30 as a rotation detection part. The pressure rotary body 10 is rotationally driven in such a state that it presses the fixing belt 21 toward the pad member 22, to driven-rotate the fixing belt 21. The reflection type photoelectric sensor 30 is arranged so as to face the outer peripheral surface of the fixing belt 21 and an area to be detected having a part whose reflectivity is different in a circumferential direction is provided in the fixing belt 21 of a part facing the reflection type photoelectric sensor 30. A first guide part 26 coming into contact with the inner peripheral surface of the fixing belt 21 is provided in a position facing the reflection type photoelectric sensor 30 across the area to be detected. The fixing belt 21 of the part corresponding to the area to be detected slides on the surface of the first guide part 26, when the fixing belt is driven-rotated.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a fixing device for fixing a toner image formed on a recording material such as paper to the recording material, and forms an image using an electrophotographic method regardless of the type such as color / monochrome. The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile having the fixing device in an image forming unit.

  In an electrophotographic image forming apparatus, a fixing device of a heat fixing method is generally provided. The fixing device of the heat fixing type has a pressure rotating body and a heating rotating body, and the recording material on which the toner image is formed is sandwiched between the pressure rotating body and the heating rotating body, whereby the toner image is formed on the recording material. Heat fixing.

  For example, in JP 2005-173180 A (Patent Document 1), JP 2008-225066 A (Patent Document 2), JP A 2015-102660 (Patent Document 3), etc., a pressure rotating body is added A fixing device using a pressure roller and using an endless fixing belt as a heating roller is disclosed.

  In the fixing devices disclosed in these patent documents 1 to 3, pressure rollers are disposed so as to be capable of being in pressure contact with the outer peripheral surface of the fixing belt, and the recording material is conveyed between the pressure rollers and the fixing belt. A nip portion is formed. As a result, heat and pressure are applied to the toner image formed on the recording material at the nip portion, whereby the toner image is fixed to the recording material.

  In this type of fixing device, a pad member is usually disposed to face the inner peripheral surface of the fixing belt in a portion pressed against the pressure roller, and the fixing belt is directed to the pad member by the pressure roller. In many cases, when the pressure roller is rotationally driven in a pressed state, the fixing belt is rotated in accordance with the rotation of the pressure roller.

  In this case, the fixing belt may slip if the frictional force between the pad member and the fixing belt is increased for some reason. When the fixing belt slips, a conveyance failure of the recording material may occur, and the recording material may be clogged, wrinkles may occur in the recording material, or the recording material may be locally overheated. This may lead to problems such as uneven fixing.

  Therefore, generally, in this type of fixing device, a rotation detection unit that detects the rotation of the fixing belt is separately provided, and the operation or pressure of a heating source that heats the fixing belt based on the detection result of the rotation detection unit. The operation of the drive source for rotationally driving the roller is controlled.

  For example, in the fixing devices disclosed in Patent Documents 1 to 3 described above, by providing a mark portion at a predetermined position on the outer peripheral surface of the fixing belt, a detection area having portions having different reflectances in the circumferential direction on the fixing belt. Is provided, and a reflection type photoelectric sensor as a rotation detection unit is installed to face the detected area. Thus, the rotation of the fixing belt can be detected based on the photocurrent output from the reflection type photoelectric sensor, and the operation of the heating source and the driving source can be controlled based on the detection result.

JP, 2005-173180, A JP 2008-225066 A JP, 2015-102660, A

  However, as described above, when the fixing belt is configured to be driven to rotate as the pressure roller rotates, there is a problem that a considerable degree of rattling occurs in the fixing belt in a portion excluding the nip portion. Due to the occurrence of this flapping, the fixing belt is displaced in the thickness direction, and accordingly, the distance between the detection area and the reflection type photoelectric sensor is also changed.

  The fluctuation of the distance between the detection area and the reflection type photoelectric sensor may become an obstacle in accurately detecting the rotation of the fixing belt, and therefore, if no measures are taken, the fixing belt It is feared that the accuracy of the detection of rotation may be reduced.

  Therefore, the present invention has been made in view of the above-described problems, and an object of the present invention is to provide a fixing device capable of detecting the rotation of the fixing belt with high accuracy, and an image forming apparatus provided with the same.

  A fixing device according to the present invention fixes a toner image formed on a recording material to a recording material, and comprises an endless fixing belt, a pad member, a pressure roller, and a first support member. , A heating source, and a rotation detection unit. The pad member is disposed to face the inner circumferential surface of the fixing belt, and the pressure roller is disposed to face the outer circumferential surface of the fixing belt. The pressure roller is driven to rotate by being rotationally driven in a state in which the fixing belt is pressed toward the pad member, and the recording material is rotated between the fixing belt and the outer peripheral surface of the fixing belt. Form a nip to be transported. The first support member supports the pad member, and the heat source is disposed to face the inner peripheral surface of the fixing belt. The rotation detection unit detects the rotation of the fixing belt, and includes a reflection type photoelectric sensor disposed to face the outer peripheral surface of the fixing belt. A portion to be detected having a portion having a different reflectance in the circumferential direction is provided on the fixing belt at a portion facing the reflection type photoelectric sensor at the time of the driven rotation of the fixing belt. A first guide portion that contacts the inner peripheral surface of the fixing belt is provided at a position facing the reflective photoelectric sensor with the detection area interposed therebetween. In the fixing device according to the present invention, the fixing belt of a portion corresponding to the detection area is configured to slide on the surface of the first guide when the fixing belt is driven to rotate. ing.

  In the fixing device according to the present invention, it is preferable that a surface of a portion of the first guide portion in contact with the inner peripheral surface of the fixing belt has an uneven shape.

  In the fixing device according to the present invention, it is preferable that a surface of a portion of the first guide portion in contact with the inner peripheral surface of the fixing belt is made of fluorocarbon resin.

  In the fixing device according to the present invention, the coefficient of friction between the first guide portion and the fixing belt is preferably the same as the coefficient of friction between the pad member and the fixing belt.

  In the fixing device according to the present invention, a pair of second guide portions respectively contacting the inner peripheral surface of the fixing belt are provided at positions opposite to the pair of end portions in the width direction of the fixing belt. May be In that case, it is preferable that the detection area be provided at a portion inside the fixing belt in the width direction than a portion of the fixing belt that contacts each of the pair of second guides. .

  In the fixing device according to the present invention, it is preferable that each of the pair of second guide portions have a ridge portion facing an end surface located in the width direction of the fixing belt.

  In the fixing device according to the present invention, the first guide portion and the second guide portion may be configured as separate members, and in that case, the first guide portion may be the first member. It is preferable to be fixed to 1 support member.

  In the fixing device according to the present invention, the first guide portion and one of the pair of second guide portions may be constituted by a single member, in which case, It is preferable that the first guide portion is extended inward in the width direction of the fixing belt from the one of the pair of second guide portions.

  The fixing device according to the present invention may further include a second support member for supporting the reflective photoelectric sensor, in which case one of the second guide portions is the second support member. Preferably, the first guide portion is held by the second support member via the one of the second guide portions.

  In the fixing device according to the present invention, when the reflection type photoelectric sensor and the first guide portion are viewed along the width direction of the fixing belt, the light emitting device is not on the track of the fixing belt. It is preferable that the region excluding the portion corresponding to the nip portion be disposed in a region closer to the inlet side of the nip portion than the outlet side of the nip portion.

  In the fixing device according to the present invention, it is preferable that the reflection type photoelectric sensor and the first guide portion are disposed vertically lower than the heating source.

  In the fixing device according to the present invention, it is preferable that the reflection type photoelectric sensor and the first guide portion be blocked by the first support member with the heat source.

  An image forming apparatus according to the present invention comprises the above-described fixing device according to the present invention for image formation.

  According to the present invention, it is possible to provide a fixing device capable of detecting the rotation of the fixing belt with high accuracy, and an image forming apparatus provided with the same.

FIG. 1 is a schematic view of an image forming apparatus according to Embodiment 1; FIG. 2 is a schematic cross-sectional view of a central portion in the width direction of the fixing device according to Embodiment 1. It is a schematic cross section along the III-III line shown in FIG. It is a schematic cross section along the IV-IV line shown in FIG. It is a schematic cross section along the V-V line shown in FIG. It is a schematic diagram which shows the output waveform of the reflection type photoelectric sensor shown to FIG. 3 and FIG. FIG. 6 is a schematic cross-sectional view of a fixing device according to Embodiment 2. It is a schematic perspective view of the guide member shown in FIG. FIG. 10 is a schematic cross-sectional view of a fixing device according to Embodiment 3.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the embodiment described below, a so-called tandem-type color printer adopting an electrophotographic method and a fixing device provided therein will be described as an image forming apparatus and a fixing device to which the present invention is applied. . In the embodiments described below, the same or common parts are denoted by the same reference numerals in the drawings, and the description thereof will not be repeated.

Embodiment 1
FIG. 1 is a schematic view of an image forming apparatus according to the first embodiment. First, a schematic configuration and an operation of an image forming apparatus 1 according to the present embodiment will be described with reference to FIG.

  As shown in FIG. 1, the image forming apparatus 1 mainly includes an apparatus main body 2 and a sheet feeding unit 9. The apparatus main body 2 includes an image forming unit 2A which is a portion for forming an image on a sheet as a recording material, and a sheet feeding portion 2B which is a portion for supplying the sheet to the image forming portion 2A. The sheet feeding unit 9 stores sheets to be supplied to the image forming unit 2A, and is detachably provided in the sheet feeding unit 2B.

  Inside the image forming apparatus 1, a plurality of rollers 3 are installed, whereby a conveyance path 4 along which a sheet is conveyed along a predetermined direction straddles the image forming unit 2A and the sheet feeding unit 2B described above. It is built. Further, as shown in the drawing, a manual feed tray 9a for feeding sheets to the image forming unit 2A may be separately provided in the apparatus main body 2.

  The image forming unit 2A includes, for example, an image forming unit 5 capable of forming toner images of respective colors of yellow (Y), magenta (M), cyan (C) and black (K), and photosensitivity included in the image forming unit 5 An exposure unit 6 for exposing the body, an intermediate transfer belt 7a suspended by the image forming unit 5, a transfer unit 7 provided on the transport path 4 and on the runway of the intermediate transfer belt 7a, and transfer A fixing device 8A according to the present embodiment, which will be described later, is provided mainly on the conveyance path 4 at a portion downstream of the unit 7.

  The image forming unit 5 receives the exposure from the exposure unit 6 and receives a toner image of each color of yellow (Y), magenta (M), cyan (C) and black (K) or a toner image consisting only of black (K). And transfer it to the intermediate transfer belt 7a (so-called primary transfer). As a result, a color toner image or a monochrome toner image is formed on the intermediate transfer belt 7a.

  The intermediate transfer belt 7a transfers the color toner image or monochrome toner image formed on the surface thereof to the transfer unit 7, and is pressure-contacted in the transfer unit 7 with the sheet conveyed from the sheet feeding unit 2B to the transfer unit 7. Ru. As a result, the color toner image or the monochrome toner image formed on the surface of the intermediate transfer belt 7a is transferred onto the sheet (so-called secondary transfer).

  Thereafter, the sheet on which the color toner image or the monochrome toner image is transferred is pressurized and heated by the fixing device 8A. As a result, a color image or a monochrome image is formed on the sheet, and the sheet on which the color image or the monochrome image is formed is then discharged from the apparatus main body 2.

  FIG. 2 is a schematic cross-sectional view of the central portion in the width direction of the fixing device according to the present embodiment, and FIG. 3 is a schematic cross-sectional view along the line III-III shown in FIG. . 4 and 5 are schematic cross-sectional views taken along line IV-IV and V-V shown in FIG. 3 of the fixing device, respectively. Next, the configuration and operation of the fixing device 8A according to the present embodiment will be described with reference to FIGS. 2 to 5.

  Here, FIGS. 4 and 5 each show a cross section obtained by cutting the fixing device 8A at a predetermined position in the width direction of the fixing device 8A along the direction orthogonal to the width direction, as in FIG. The cross section shown in FIG. 4 is a cross section of the fixing device 8A in a portion including the second contact surface 27a provided in the second guide portion 27 described later, and FIG. 5 is provided in the first guide portion 26 described later. 8 is a cross section of the fixing device 8A in a portion including the first contact surface 26b. The cross section shown in FIG. 2 corresponds to the cross section of the fixing device 8A in the portion along the line II-II shown in FIG.

  As shown in FIGS. 2 to 5, the fixing device 8A includes a pressure roller 10 as a pressure rotating body, a fixing belt unit 20A including a fixing belt 21 as a heating rotating body, and a reflection type as a rotation detection unit. The photoelectric sensor 30 and various guides 41 to 43 for transporting a sheet are mainly provided.

  The pressure roller 10 is constituted of, for example, a metal core metal 11 made of an aluminum alloy or the like, and a rubber elastic layer 12 provided so as to cover the core metal 11 made of, for example, silicone rubber. The pressure roller 10 may further have a release layer made of, for example, a fluorine-based resin provided to cover the elastic layer 12.

  The axial length of the pressure roller 10 is, for example, 340 mm, and the diameter of the pressure roller 10 is, for example, 30 mm. When the pressure roller 10 has the above-described release layer, for example, the diameter of the core metal 11 is 25 mm, the thickness of the elastic layer 12 is 2.5 mm, and the thickness of the release layer is 30 μm. It is assumed.

  The pressure roller 10 is disposed to face the outer peripheral surface of the fixing belt 21, and both axial end portions thereof are rotatably supported by a support portion (not shown). The pressure roller 10 is rotatably driven by a drive source such as a motor (not shown). The pressure roller 10 is configured to be resiliently biased toward the fixing belt unit 20A by a biasing member (not shown).

  The fixing belt unit 20A includes the pad member 22, the first support member 23, the high reflectance member 24, the heating source 25, the first guide portion 26, and the pair of second guides in addition to the fixing belt 21 described above. It has the part 27 mainly.

  Fixing belt 21 is endless and is formed of, for example, a plurality of layers in consideration of heat resistance, strength, surface smoothness and the like. Specifically, fixing belt 21 includes a base material layer made of, for example, polyimide, a rubber elastic layer made of, for example, silicone rubber, and a release layer made of, for example, fluorocarbon resin. The plurality of layers are positioned from the inside to the outside of the fixing belt 21 in the order of the base material layer, the elastic layer, and the releasing layer.

  The length in the width direction of fixing belt 21 is, for example, 330 mm, and the diameter (that is, the outer peripheral length) of fixing belt 21 is, for example, 30 mm. The thickness of the base material layer is, for example, 70 μm, the thickness of the elastic layer is, for example, 200 μm, and the thickness of the release layer is, for example, 30 μm.

  The pad member 22 is an elongated member extending along the width direction of the fixing belt 21 (that is, the axial direction of the pressure roller 10), and is disposed in the space inside the fixing belt 21. ing. The pad member 22 has a substantially flat shape. Further, in order to improve the slidability of the fixing belt 21, the surface of the pad member 22 is preferably configured by a low friction portion 22 a as illustrated. The pad member 22 is made of, for example, a liquid crystal polymer, and the low friction portion 22a is formed of, for example, a sheet-like member made of a fluorocarbon resin.

  The length in the width direction of the pad member 22 is, for example, 350 mm, and the thickness of the pad member 22 is, for example, 2.1 mm at the central portion in the width direction, and 2 mm at both ends in the width direction. Here, the reason why the thickness of the pad member 22 is different in the width direction is that the deformation of the pad member 22 due to the pressing of the pressure roller 10 is taken into consideration.

  The thickness of the low friction portion 22a is, for example, 200 μm, and the surface on the fixing belt 21 side has a coefficient of friction with the fixing belt 21 of, for example, 0 in order to maintain good slidability of the fixing belt 21. Preferably, it is configured to be less than .18. The surface of the low friction portion 22 a on the fixing belt 21 side may be provided with minute irregularities for reducing the frictional resistance. By thus maintaining good slidability between the pad member 22 and the fixing belt 21, it is possible to suppress the occurrence of micro-vibrations, so-called chatter, in the fixing belt 21 and the pad member 22.

  The first support member 23 is a long member extending along the width direction of the fixing belt 21, and most of the first supporting member 23 is disposed in the space inside the fixing belt 21. The first support member 23 is for supporting the pad member 22 and has an L-shaped cross section including a flat base 23 a and a flat standing wall 23 b disposed in the space inside the fixing belt 21. have. The pad member 22 is fixed to the base 23 a of the first support member 23. The first support member 23 is made of, for example, a metal member such as an electrogalvanized steel plate (SECC).

  The high reflectance member 24 is a member having a surface whose reflectance is higher than the surface of the first support member 23, and is formed of, for example, a reflective plate made of aluminum. The high reflectance member 24 is a portion of the light (infrared radiation) emitted from the heating source 25 that is the light traveling toward the first support member 23 located on the opposite side to the first support member 23 side. It is a member for reflecting toward the fixing belt 21. The high reflectance member 24 is fixed to the first support member 23 so as to cover the surface of the base 23 a and the standing wall portion 23 b of the first support member 23 on the heating source 25 side. By providing the high reflectance member 24, the fixing belt 21 can be heated more efficiently.

  The length in the width direction of the first support member 23 is, for example, 360 mm, and the thickness of the first support member 23 is, for example, 2 mm. Further, the length in the width direction of high reflectance member 24 is, for example, 355 mm, and the thickness of high reflectance member 24 is, for example, 0.5 mm.

  The heating source 25 includes a long heater 25A and a short heater 25B, which are a pair of rod-like heaters extending along a direction parallel to the width direction of the fixing belt 21, and is disposed in the space inside the fixing belt 21. There is. The heating source 25 is for heating the fixing belt 21 and both axial ends thereof are held by holding portions 25a (see FIG. 3). Each of the long heater 25A and the short heater 25B is, for example, a halogen heater.

  The long heater 25A has a heat generating portion in a region corresponding to substantially the entire area in the width direction of the fixing belt 21. When the heat generating portion generates heat, the fixing belt 21 is mainly heated by the radiant heat. The axial length of the heat generating portion corresponds to the width of the sheet having the largest width among the sheets of various sizes supplied to the image forming apparatus 1. The axial length of the heat generating portion of the long heater 25A corresponds to the width of the sheet passing region R1 (see FIG. 3).

  The short heater 25B has a heat generating portion HG (see FIG. 3) only in a region corresponding to the central portion in the width direction of the fixing belt 21. When the heat generating portion HG generates heat, the fixing belt mainly uses the radiant heat. 21 is to heat. The axial length of the heat generating portion HG corresponds to the width of the sheet having the smallest width among the sheets of various sizes supplied to the image forming apparatus 1.

  The axial length of the heat generating portion of the long heater 25A is, for example, 320 mm, and the axial length of the heat generating portion HG of the short heater 25B is, for example, 160 mm. The wattage of long heater 25A is, for example, 1200 W, and the wattage of short heater 25B is, for example, 650 W.

  The first guide portion 26 is provided corresponding to a detection area R2 (see FIG. 3) of the fixing belt 21 described later (see FIG. 3), and is disposed in the space inside the fixing belt 21. The first guide portion 26 is for stably moving the fixing belt 21 of the corresponding portion without fluttering by contacting the inner peripheral surface of the fixing belt 21 of the portion corresponding to the detection region R2. Although there are, the details will be described later.

  The pair of second guide portions 27 is provided at positions corresponding to both end portions of the fixing belt 21 in the width direction, and a part of the second guide portions 27 is disposed in the space inside the fixing belt 21. Each of the pair of second guide portions 27 has a substantially C shape in cross section, and the fixing belt 21 is slidably suspended at a predetermined position on the outer peripheral surface thereof. The pair of second guide portions 27 is for guiding the movement of the fixing belt 21, and the details thereof will be described later.

  The reflective photoelectric sensor 30 is disposed to face the outer peripheral surface of the fixing belt 21. More specifically, the reflective photoelectric sensor 30 is disposed at a position corresponding to a detection area R2 (see FIG. 3) of the fixing belt 21 described later. ing. The reflection type photoelectric sensor 30 includes, for example, a light projector including an LED (light-emitting diode) and the like, and a light receiver including, for example, a PD (photodiode) and the like. The reflected light of the light emitted from the light projector is used as a light receiver. It is configured to be able to receive light. Although the presence or absence of the rotation of the fixing belt 21 is detected by the photocurrent output from the reflection type photoelectric sensor 30, the details will be described later.

  In the fixing device 8A according to the present embodiment, as described above, the pressure roller 10 is configured to be elastically biased toward the fixing belt unit 20A by a biasing member (not shown). Here, as shown in FIGS. 2, 4 and 5, in a state where the pressure roller 10 is elastically urged toward the fixing belt unit 20A by an urging member (not shown), the fixing belt 21 is a pad It will be pressed towards the member 22.

  Referring to FIGS. 2, 4 and 5, in a state where fixing belt 21 is pressed toward pad member 22, arrow A shown in the figure by driving source such as the above-mentioned motor, which pressure roller 10 does not illustrate. By being rotationally driven in the direction, the fixing belt 21 is driven to rotate in the direction of arrow B shown in the drawing so as to slide on the pad member 22.

  As a result, between the pressure roller 10 and the outer peripheral surface of the fixing belt 21, a nip portion N (see FIG. 2) in which the sheet is conveyed is formed. In other words, the pressure roller 10 and the fixing belt unit 20A are disposed so as to sandwich the conveyance path 4 such that the nip portion N formed between them is positioned on the conveyance path 4 of the sheet. It is done.

  Here, if the elastic layer 12 is exposed without providing the above-described release layer at both end portions in the axial direction which is a portion excluding the above-described sheet passing region R1 of the pressure roller 10, It becomes possible to increase the frictional resistance with the fixing belt 21 in the part, and the fixing belt 21 can be rotated more efficiently.

  In the state where the fixing belt 21 is pressed toward the pad member 22, the direction in which the pressure roller 10 and the fixing belt unit 20A are aligned is the pressing direction DR1 in which the fixing belt 21 is pressed toward the pad member 22. The direction orthogonal to the pressing direction DR1 and orthogonal to the axial direction of the pressure roller 10 (that is, the width direction of the fixing belt 21) corresponds to the sheet conveying direction DR2.

  Here, in the fixing device 8A according to the present embodiment, the pressure roller 10 and the fixing belt unit 20A are disposed to face each other in the substantially horizontal direction. As a result, the above-described transport direction DR2 is disposed along the substantially vertical direction. Further, the transport path 4 of the portion included in the fixing device 8A is configured such that the sheet is transported from the vertically lower side to the vertically upper side. As a result, the inlet of the nip portion N is provided at the vertically lower position, and the outlet of the nip portion N is provided at the vertically upper position.

  In a strict sense, the transport path 4 is formed only at a position corresponding to the above-described sheet passing area R1 between the pressure roller 10 and the outer peripheral surface of the fixing belt 21. Here, in order to facilitate understanding, the transport path 4 is schematically illustrated also in FIGS. 4 and 5 showing a cross section at a position not corresponding to the sheet passing region R1.

  The position on the transport path 4 on the upstream side of the nip portion N along the transport direction DR2 of the sheet (that is, the position on the lower side in FIGS. 2, 4 and 5) on the inlet side A guide 41 is provided. The inlet guide 41 is a guide for ensuring that the sheet fed on the conveyance path 4 is fed to the nip portion N.

  Further, at a position on the conveyance path 4 and at a position downstream of the nip portion N along the sheet conveyance direction DR2 (that is, the position on the upper side in FIGS. 2, 4 and 5), A separation guide 42 and an outlet side guide 43 are provided. The separation guide 42 is a guide for separating the sheet in a state of being in close contact with the fixing belt 21 when discharged from the nip portion N, and the exit side guide 43 is fixed by the separation guide 42 It is a guide for reliably returning the sheet separated from the belt 21 onto the conveyance path 4.

  As described above with reference to FIGS. 3 and 4, the second guide portions 27 are located at positions facing the pair of end portions in the width direction of the fixing belt 21. Each of the pair of second guide portions 27 is made of, for example, a resin-made member, and is preferably made of liquid crystal polymer. Each of the pair of second guide portions 27 is fixed, for example, by a screw 51 or the like to a chassis 50 which constitutes a fixing device 8A provided inside the image forming apparatus 1.

  Each of the pair of second guide portions 27 has a substantially C shape in cross section, and a curved plate-like portion whose axial direction is the width direction of the fixing belt 21 and a portion of the curved plate-like portion. And a collar portion provided radially outward from a predetermined position in the axial direction.

  The outer peripheral surface of the curved plate-like portion of each of the pair of second guides 27 functions as a second contact surface 27 a that contacts the inner peripheral surface of the fixing belt 21, and each of the pair of second guides 27 Of the buttocks included, the inner surface along the width direction of the fixing belt 21 functions as a restricting surface 27 b that faces the end surface of the fixing belt 21.

  That is, the second contact surface 27 a is in contact with the inner peripheral surface of a portion corresponding to the end of the fixing belt 21 in the width direction, whereby the fixing belt 21 is not rotated during the driven rotation of the fixing belt 21. 2) It slides on the contact surface 27a. Therefore, at the time of driven rotation of the fixing belt 21, both ends of the fixing belt 21 are guided by the second contact surfaces 27 a provided in each of the pair of second guides 27, and the fixing belt 21 is It becomes possible to make the driven rotation stably.

  Further, the regulating surface 27b is positioned to face the end face of the fixing belt 21, whereby it is possible to regulate that the fixing belt 21 moves along the width direction at the time of the following rotation of the fixing belt 21. become. Therefore, at the time of driven rotation of the fixing belt 21, the positional deviation in the width direction of the fixing belt 21 can be suppressed by the restriction surfaces 27 b provided on each of the pair of second guides 27. As a result, the fixing belt 21 can It becomes possible to make the driven rotation stably.

  The surface on the fixing belt 21 side of the second guide portion 27 is configured such that the coefficient of friction with the fixing belt 21 is, for example, less than 0.18, in order to keep the slidability of the fixing belt 21 good. Is preferred. The surface of the second guide portion 27 on the fixing belt 21 side may be provided with minute asperities for reducing frictional resistance. As described above, by maintaining good slidability between the second guide portion 27 and the fixing belt 21, it is possible to suppress the generation of micro-vibrations, so-called chatter, in the fixing belt 21 and the second guide portion 27. it can.

  Here, by providing the pair of second guide portions 27 as described above, the fixing belt 21 rotates more stably as described above, but in the fixing belt 21 of the portion excluding the nip portion N. It is impossible to completely prevent the occurrence of the rattling. Therefore, the fixing belt 21 has a considerable degree of flapping during the following rotation.

  The occurrence of the flapping of the fixing belt 21 is mainly caused by an imbalance in the width direction of the fixing belt 21 due to the force applied from the pressure roller 10 to the fixing belt 21 during the following rotation of the fixing belt 21. This is caused by the local deformation of the fixing belt 21 locally. Further, when the positional deviation occurs along the width direction as a whole in the fixing belt 21 (that is, when the fixing belt 21 is meandered), the end face of the fixing belt 21 is the restricting surface of the second guide portion 27. 27b, and as a result of the occurrence of bending deformation in the vicinity of the end of the fixing belt 21, fluttering of the fixing belt 21 also occurs.

  When this flapping of the fixing belt 21 occurs in a portion including the detection region R2, a change occurs in the distance between the fixing belt 21 and the reflective photoelectric sensor 30 in a portion corresponding to the detection region R2. become. Although the variation of the distance between the fixing belt 21 and the reflective photoelectric sensor 30 in the portion corresponding to the detection area R2 depends on the degree of the variation, it is generally in order to accurately detect the rotation of the fixing belt 21. It becomes an obstacle of

  Therefore, in the fixing device 8A according to the present embodiment, by providing the above-described first guide portion 26, flapping of the fixing belt 21 in a portion corresponding to the detection region R2 is suppressed, and thereby the reflection type photoelectric sensor It is possible to suppress the decrease in the detection accuracy of the rotation of the fixing belt 21 due to V.30. Hereinafter, this point will be described in detail.

  Referring to FIGS. 3 and 5, at a predetermined position in the width direction of fixing belt 21, there is provided a detection region R2 having portions having different reflectances in the circumferential direction. More specifically, in the detection region R2, the reflectances of the portion having a relatively high reflectance of the surface located on the outer peripheral surface side of the fixing belt 21 and the reflectance of the surface located on the outer peripheral surface side of the fixing belt 21 are relative. And lower portions, and these portions are configured to be alternately positioned in the circumferential direction.

  Various methods can be applied as a method of making the reflectance of the surface of fixing belt 21 different for each part, but in the present embodiment, it is possible to use a predetermined part of the surface layer of fixing belt 21 (i.e. release layer). This is realized by forming the mark portion 21a by irradiating a laser beam such as an ultraviolet laser. When the method is adopted, the reflectance of the mark portion 21a is lower than the reflectance of the portion where the mark portion 21a is not formed.

  As a method other than the method of irradiating a laser beam, for example, a method of affixing a sealing member such as aluminum foil to a predetermined portion of a fixing belt, a method of plating a predetermined portion of a fixing belt, a predetermined portion of a fixing belt Alternatively, a method of forming the mark portion by an ink jet or a stamp, a method of providing a concave portion, a convex portion, a hole portion or the like at a predetermined portion of the fixing belt can be applied.

  Here, in the present embodiment, the detection area R2 is provided in a portion of the fixing belt 21 which does not overlap the sheet passing area R1. This is because, with this configuration, it is possible to suppress the contamination of the detection area R2 due to the adhesion of paper dust, the adhesion of toner, etc., as compared to the case where the detection area R2 is provided in the sheet passing area R1.

  Further, in the present embodiment, the detection region R2 is a portion other than the portion of the fixing belt 21 suspended by the pair of second guides 27 (that is, the second guide portion 27 of the fixing belt 21). Of the fixing belt 21 in the width direction of the fixing belt 21 rather than the portions in contact with the respective. With this configuration, the detection region R2 is provided apart from the end portion of the fixing belt 21 that is more susceptible to fluttering, so that the rotation of the fixing belt 21 can be detected more stably.

  Although the shape, size, number, formation position, etc. of the mark portion 21a can be changed variously, in the present embodiment, the mark portion 21a is formed into a rectangular shape in plan view, and the mark portion 21a along the width direction of the fixing belt 21. The size of the mark 21a is 12 mm, and the size of the mark 21a along the circumferential direction of the fixing belt 21 is 10 mm. The number of mark portions 21a is four in total, and these four mark portions 21a are arranged at equal intervals along the circumferential direction of the fixing belt 21. Each of the four mark portions 21 a is formed at a position 5 mm away from one end of the fixing belt 21 in the width direction.

  The reflective photoelectric sensor 30 is disposed to face a portion of the outer peripheral surface of the fixing belt 21 that corresponds to the detection region R2. The reflection type photoelectric sensor 30 is supported immovably by a chassis or the like (not shown).

  Although various sensors can be used as the reflection type photoelectric sensor 30, in the present embodiment, a sensor having a detection distance of 2 mm to 45 mm and a heat resistance temperature of 85 ° C. is used. The beam diameter on the detection area R2 of the reflective photoelectric sensor 30 is set to, for example, 8 mm or more.

  The first guide portion 26 described above is disposed in the space inside the fixing belt 21 and is fixed to the standing wall portion 23 b of the first support member 23 supporting the pad member 22 by, for example, a screw or the like. More specifically, the first guide portion 26 is positioned to face the reflective photoelectric sensor 30 with the portion corresponding to the detection area R2 of the fixing belt 21 interposed therebetween. The first guide portion 26 is made of, for example, a resin-made member, and is preferably made of a liquid crystal polymer in consideration of heat insulation. The first guide portion 26 may be configured by a metal member.

  Further, in order to improve the slidability of the fixing belt 21, the surface of the first guide portion 26 is preferably configured by a low friction portion 26 a as illustrated. The low friction portion 26a is formed of, for example, a sheet-like member made of fluorine resin.

  A portion of the first guide portion 26 that faces the fixing belt 21 (that is, a portion of the surface of the low friction portion 26 a that faces the fixing belt 21) is a first contact surface that contacts the inner circumferential surface of the fixing belt 21. It functions as 26b. That is, the first contact surface 26b is in contact with the inner peripheral surface of the fixing belt 21 in a portion corresponding to the detection region R2, whereby the fixing belt 21 is not moved to the first position during the driven rotation of the fixing belt 21. It slides on the contact surface 26b.

  Therefore, when the fixing belt 21 is driven to rotate, the fixing belt 21 in a portion corresponding to the detection area R2 is guided by the first contact surface 26b provided in the first guide portion 26, and the detection area is detected. It is possible to more stably rotate the fixing belt 21 in a portion corresponding to R2 more stably.

  Here, the size in the width direction of the first guide portion 26 is not particularly limited, but is preferably about the same as the size in the width direction of the detection area R2, and more preferably in the detection area R2. It is larger than the size in the width direction. The thickness of the low friction portion 26a is, for example, 200 μm, and the surface on the fixing belt 21 side has a coefficient of friction with the fixing belt 21 of, for example, 0 in order to maintain good slidability of the fixing belt 21. Preferably, it is configured to be less than .18. The surface of the low friction portion 26 a on the fixing belt 21 side may be provided with minute irregularities for reducing the frictional resistance. As described above, by maintaining good slidability between the first guide portion 26 and the fixing belt 21, it is possible to suppress the generation of micro-vibrations, so-called chatter, in the fixing belt 21 and the first guide portion 26. it can.

  As described above, in the fixing device 8A according to the present embodiment, the fixing belt 21 in a portion corresponding to the detection area R2 slides on the first guide portion 26 during the driven rotation of the fixing belt 21. Thus, the rattling of the fixing belt 21 in the portion corresponding to the detection area R2 can be effectively suppressed. Therefore, the occurrence of fluctuations in the distance between the fixing belt 21 and the reflective photoelectric sensor 30 in the portion corresponding to the detection region R2 can be significantly suppressed, and as a result, the rotation of the fixing belt 21 is detected with high accuracy. It will be possible.

  FIG. 6 is a schematic view showing an output waveform of the reflection type photoelectric sensor shown in FIG. 3 and FIG. In the fixing device 8A according to the present embodiment, the photocurrent output from the reflective photoelectric sensor 30 is input to a control unit (not shown), and the magnitude of the photocurrent is obtained and obtained over time in the control unit. The presence or absence of the rotation of the fixing belt 21 is detected based on the amplitude of the photocurrent.

  That is, as shown in FIG. 6, when the fixing belt 21 is stopped, the magnitude of the photocurrent is maintained at a certain level without changing with time. On the other hand, when the fixing belt 21 rotates, the magnitude of the photocurrent changes with time, and in the state where the mark portion 21 a of the fixing belt 21 faces the reflective photoelectric sensor 30, the magnitude of the obtained photocurrent The size of the obtained photoelectric current becomes large in the state where the portion (ie, the non-mark portion) where the mark portion 21a of the fixing belt 21 is not formed is opposed to the reflection type photoelectric sensor 30. Therefore, the magnitude of the photocurrent fluctuates with a predetermined amplitude as shown, and the control unit (not shown) compares the magnitude of the amplitude with a predetermined threshold value to rotate the fixing belt 21. The presence or absence will be detected.

  Here, as described above, when the distance between the fixing belt 21 and the reflective photoelectric sensor 30 in the portion corresponding to the detection region R2 changes, the amplitude of the photocurrent is smaller than expected. (Ie, the difference between the photocurrent output from the reflective photoelectric sensor 30 in the state where the mark portions 21a face each other) and the photocurrent output from the reflective photoelectric sensor 30 in the state where the non-mark portions face each other is assumed. And the accuracy of detection of the rotation of the fixing belt 21 is lowered. However, in the fixing device 8A according to the present embodiment, the distance between the fixing belt 21 and the reflective photoelectric sensor 30 in the portion corresponding to the detection region R2 fluctuates due to the presence of the first guide portion 26 described above. Is less likely to occur, so that the rotation of the fixing belt 21 can be detected with higher accuracy.

  As described above, by using the fixing device 8A according to the present embodiment and the image forming apparatus 1 including the same, the rotation of the fixing belt 21 can be detected with high accuracy. The control unit described above appropriately controls the operation of the heating source 25 and the operation of the driving source (not shown) for driving the pressure roller 10 described above, so that the sheet as the recording material is clogged, or the sheet as the recording material is It is possible to significantly suppress the occurrence of defects such as the occurrence of wrinkles or the occurrence of uneven fixing due to local overheating of the sheet as the recording material.

  Here, as shown in FIG. 3 and FIG. 5, in the present embodiment, when the reflective photoelectric sensor 30 and the first guide portion 26 are viewed along the width direction of the fixing belt 21, the fixing belt 21 is fixed. It is an area | region except the part corresponding to the nip part N among on the track | orbit of, and is arrange | positioned in the area | region near the entrance side of the nip part N rather than the exit side of the nip part N. With this configuration, the rotation of the fixing belt 21 can be detected more accurately than in the case where the reflective photoelectric sensor 30 and the first guide portion 26 are disposed in the area on the exit side of the nip portion N described above. it can.

  This is because the strong pressing force acts on the fixing belt 21 at the nip portion N where the pressure roller 10 is in pressure contact when the fixing belt 21 is driven to rotate. This is because large flaps are easily generated in the fixing belt 21, whereas large flaps are not easily generated in the fixing belt 21 in the area on the entrance side of the nip portion N. Therefore, by configuring as described above, the distance between the fixing belt 21 and the reflective photoelectric sensor 30 in the portion corresponding to the detection region R2 hardly changes, and as a result, the rotation of the fixing belt 21 becomes high. It becomes possible to detect with accuracy.

  Here, as described above, the reason why it is difficult for the fixing belt 21 to generate large flapping in the area on the inlet side of the nip N is the distance from the nip N to the area toward the downstream of the rotation of the fixing belt 21 In the region, the fixing belt 21 is guided by the pair of second guides 27.

  Further, in the present embodiment, the reflective photoelectric sensor 30 and the first guide portion 26 are disposed vertically lower than the heating source 25. With this configuration, the reflection type photoelectric sensor 30 and the first guide portion 26 are less susceptible to the heat generated by the heating source 25. Also in this sense, the fixing of the portion corresponding to the detection region R2 The variation in the distance between the belt 21 and the reflective photoelectric sensor 30 is less likely to occur, and as a result, the rotation of the fixing belt 21 can be detected with high accuracy.

  Furthermore, in the present embodiment, the reflective photoelectric sensor 30 and the first guide portion 26 are blocked by the first support member 23 with the heating source 25. Also in this configuration, the reflection type photoelectric sensor 30 and the first guide portion 26 are less susceptible to the heat generated by the heating source 25. Also in this sense, the portion corresponding to the detection region R2 As a result, the distance between the fixing belt 21 and the reflective photoelectric sensor 30 hardly changes, and as a result, the rotation of the fixing belt 21 can be detected with high accuracy.

  Note that, under the influence of the heat described above, the reflective photoelectric sensor 30 and the first guide portion 26 are excessively heated and expand, and as a result, the fixing belt 21 of the portion corresponding to the detection region R2 and the reflective photoelectric Unintended fluctuation in the distance to the sensor 30, error in detection of rotation due to output fluctuation of the photocurrent due to the temperature characteristic of the reflection type photoelectric sensor 30, It includes the fact that the guide portion 26 is melted by heat.

  Here, it is preferable that the coefficient of friction between the first guide portion 26 and the fixing belt 21 be configured to be the same as the coefficient of friction between the pad member 22 and the fixing belt 21. With this configuration, no difference occurs between the slidability between the first guide portion 26 and the fixing belt 21 and the slidability between the pad member 22 and the fixing belt 21. It will rotate more smoothly.

  Furthermore, the coefficient of friction between the second guide portion 27 and the fixing belt 21 is preferably configured to be the same as the coefficient of friction between the pad member 22 and the fixing belt 21. With this configuration, no difference occurs between the slidability between the second guide portion 27 and the fixing belt 21 and the slidability between the pad member 22 and the fixing belt 21. It will rotate more smoothly.

Second Embodiment
FIG. 7 is a schematic cross-sectional view of a fixing device according to Embodiment 2, and FIG. 8 is a schematic perspective view of a guide member shown in FIG. Hereinafter, the fixing device 8B according to the present embodiment will be described with reference to FIGS. 7 and 8. Fixing device 8B in the present embodiment is incorporated in image forming apparatus 1 in the first embodiment described above, instead of fixing device 8A in the first embodiment described above.

  As shown in FIG. 7, the fixing device 8B according to the present embodiment is different from the fixing device 8A according to the first embodiment described above only in that the fixing belt unit 20B has a different configuration. doing. More specifically, in the fixing device 8A according to the first embodiment described above, one and the other of the first guide portion 26 and the pair of second guide portions 27 are formed of separate members. On the other hand, in the fixing device 8B according to the present embodiment, among these, the first guide portion 26 and one of the pair of second guide portions 27 are configured by the guide member 28 formed of a single member.

  Specifically, as shown in FIGS. 7 and 8, the guide member 28 is located at the end of the fixing belt 21 in the width direction near the detection area R2 provided on the fixing belt 21. It is provided at a corresponding position, and a part thereof is disposed in the space inside the fixing belt 21.

  In particular, as shown in FIG. 8, the guide member 28 has a substantially C shape in cross section, and has a curved plate-like portion whose axial direction is the width direction of the fixing belt 21 and the curved plate A ridge portion erected radially outward from a predetermined position in the axial direction of the portion, and a tongue-shaped portion locally extended inwardly in the width direction of the fixing belt 21 from the curved plate portion And the site of Among them, the tongue-like portion corresponds to the first guide portion 26, and the curved portion and the heel portion correspond to the second guide portion 27.

  The outer peripheral surface of the tongue-shaped portion of the guide member 28 functions as a first contact surface 26 b that contacts the inner peripheral surface of the fixing belt 21. The outer peripheral surface of the curved plate-like portion of the guide member 28 functions as a second contact surface 27 a that abuts on the inner peripheral surface of the fixing belt 21, and the fixing belt 21 of the ridge portion of the guide member 28 The inner surface along the width direction of the belt functions as a restricting surface 27 b opposed to the end surface of the fixing belt 21.

  As shown in FIG. 7, the guide member 28 is fixed, for example, by a screw 51 or the like to a chassis 50 which constitutes a fixing device 8 B provided inside the image forming apparatus 1. More specifically, when the second guide portion 27 of the guide members 28 is fixed to the chassis 50 by the screws 51, the first guide portion 26 of the guide members 28 is the second guide portion 27. It is held by the chassis 50. Here, the chassis 50 constitutes a part of a second support member for supporting the reflective photoelectric sensor 30, whereby positioning of the reflective photoelectric sensor 30 and the first guide portion 26 is performed. Become.

  Also in this configuration, when the fixing belt 21 is driven to rotate, the fixing belt 21 in a portion corresponding to the detection area R2 slides on the first contact surface 26b of the guide member 28. The distance between the fixing belt 21 and the reflective photoelectric sensor 30 in the portion corresponding to the detection region R2 hardly changes. Therefore, the same effect as the effect described in the first embodiment described above can be obtained, and the rotation of the fixing belt 21 can be detected more accurately.

  Here, when the configuration as in the present embodiment is adopted, not only the number of parts can be reduced but also the workability at the time of assembling thereof is significantly greater than in the above-described first embodiment. It is possible to improve and reduce the manufacturing cost. In particular, when the configuration is adopted as in the first embodiment described above and the circumferential length of the fixing belt 21 is relatively small, the pad member 22 assembled in advance, the first support member 23, the high reflectance When the fixing belt 21 is extrapolated to the subassembly composed of the member 24 and the heating source 25 etc., it is assumed that the first guide portion 26 becomes an obstacle for the extrapolation of the fixing belt 21, possibly damaging the fixing belt 21. When the configuration as in this embodiment is adopted, the fixing belt 21 is extrapolated to the above-described subassembly, and then the guide member 28 is inserted into the fixing belt 21. Since the first guide portion 26 can be installed, the occurrence of the above problem can be avoided.

Third Embodiment
FIG. 9 is a schematic cross-sectional view of a fixing device according to the third embodiment. The fixing device 8C according to the present embodiment will be described below with reference to FIG. Fixing device 8C in the present embodiment is incorporated in image forming apparatus 1 in the first embodiment described above, instead of fixing device 8A in the first embodiment described above.

  As shown in FIG. 9, in the present embodiment, the conveyance path 4 of the portion provided in the fixing device 8C extends along the substantially horizontal direction, and along with this, the pressure roller 10 and the fixing are fixed. The belt unit 20C is disposed to face in the substantially vertical direction. That is, the pressing direction DR1 which is a direction in which the fixing belt 21 is pressed toward the pad member 22 coincides with the substantially vertical direction, and the conveying direction DR2 which is a direction in which the sheet is conveyed is substantially horizontal. It agrees.

  Along with this, although the reflective photoelectric sensor 30 and the first guide portion 26 are positioned vertically above the transport path 4, the width direction of the fixing belt 21 is the same as in the first embodiment described above. In the track of the fixing belt 21 except for the portion corresponding to the nip N and in the area closer to the entrance of the nip N than the exit of the nip N It is arranged.

  Here, in the present embodiment, although the reflection type photoelectric sensor 30 and the first guide portion 26 are disposed at substantially the same height as the heating source 25 in the vertical direction, 1 is interrupted by the support member 23; Therefore, the reflection type photoelectric sensor 30 and the first guide portion 26 are configured to be less susceptible to the heat generated by the heating source 25.

  Also in this configuration, when the fixing belt 21 is driven to rotate, the fixing belt 21 in a portion corresponding to the detection area R2 slides on the first contact surface 26b of the guide member 28. The distance between the fixing belt 21 and the reflective photoelectric sensor 30 in the portion corresponding to the detection region R2 hardly changes. Therefore, the same effect as the effect described in the first embodiment described above can be obtained, and the rotation of the fixing belt 21 can be detected more accurately.

(Other modes)
Although the first to third embodiments of the present invention have been described by exemplifying the case where the present invention is applied to a fixing device and an image forming apparatus provided with a halogen heater as a heating source, the heating source is not limited thereto. Naturally, the present invention can be applied to a fixing device and an image forming apparatus provided with an IH (electromagnetic induction heating) type heating source, a heating source comprising a resistance heating element, etc. It is.

  In the first to third embodiments of the present invention described above, the first guide portion in contact with the fixing belt in the portion corresponding to the detection area, and the first guide portion with the fixing belt interposed therebetween. When the reflection type photoelectric sensor is viewed along the width direction of the fixing belt, it is an area excluding the portion corresponding to the nip portion on the trajectory of the fixing belt and from the exit side of the nip portion Also in the case where the first guide portion and the reflection type photoelectric sensor are susceptible to the influence of the heat generated by the heat source, the case where the first guide portion and the reflection type photoelectric sensor are significantly affected If it is possible, or if the degree of the influence can be reduced by means of a separate device, etc., these first guide portion and reflective photoelectric sensor should be provided in the area near the exit side of the above-mentioned nip portion. It may be. Further, as described above, even in the case where the first guide portion and the reflective photoelectric sensor are provided in the area close to the entrance side of the above-described nip portion, the specific position can be appropriately changed. The position may be closer to the inlet side of the nip than the position shown, or may be farther from the inlet side of the nip than the position shown.

  In the first to third embodiments of the present invention described above, the first guide portion or the guide member is fixed to the first support member or the second support member by a screw or the like. These fixing methods are not limited to this, For example, various fixing methods, such as fixation by a to-be-locked part and the latching claw engaged with this, fixation by an adhesive agent, etc., are applicable.

  Furthermore, the characteristic configurations shown in the above-described first to third embodiments of the present invention can be combined with each other without departing from the spirit of the present invention.

  As described above, the above-described embodiment disclosed this time is illustrative in all points and not restrictive. The technical scope of the present invention is defined by the scope of the claims, and includes all the modifications within the meaning and scope equivalent to the description of the scope of the claims.

  Reference Signs List 1 image forming apparatus, 2 apparatus main body, 2A image forming section, 2B sheet feeding section, 3 rollers, 4 conveyance path, 5 image forming unit, 6 exposure unit, 7 transfer section, 7a intermediate transfer belt, 8A-8C fixing device, 9 sheet feeding unit, 9a manual feed tray, 10 pressing roller, 11 core metal, 12 elastic layer, 20A to 20C fixing belt unit, 21 fixing belt, 21a mark portion, 22 pad member, 22a low friction portion, 23 first support Member 23a base 23b vertical wall 24 high reflectance member 25 heat source 25A long heater 25B short heater 25a holding portion 26 first guide portion 26a low friction portion 26b first contact surface 27 Second guide portion, 27a Second contact surface, 27b Regulating surface, 28 Guide member, 30 Reflective photoelectric sensor, 41 Entrance Side guide, 42 separating guide, 43 outlet side guide, 50 chassis, 51 screw, DR1 pressing direction, DR2 conveying direction, HG heating part, N nip part, R1 sheet passing area, R2 detected area.

Claims (13)

A fixing device for fixing a toner image formed on a recording material to the recording material, comprising:
Endless fixing belt,
A pad member disposed to face the inner circumferential surface of the fixing belt;
The fixing belt is disposed so as to face the outer peripheral surface of the fixing belt, and is rotationally driven in a state where the fixing belt is pressed toward the pad member, whereby the fixing belt is driven to rotate and the outer peripheral surface of the fixing belt A pressure roller that forms a nip portion through which the recording material is conveyed between
A first support member for supporting the pad member;
A heating source disposed to face the inner circumferential surface of the fixing belt;
A rotation detection unit that detects the rotation of the fixing belt;
The rotation detection unit includes a reflective photoelectric sensor disposed to face the outer peripheral surface of the fixing belt.
In the fixing belt of a portion facing the reflection type photoelectric sensor at the time of the driven rotation of the fixing belt, a detection area having a portion having a different reflectance in the circumferential direction is provided.
A first guide portion contacting the inner peripheral surface of the fixing belt is provided at a position facing the reflective photoelectric sensor with the detection area interposed therebetween.
The fixing device is configured such that the fixing belt of a portion corresponding to the detection area slides on the surface of the first guide portion during driven rotation of the fixing belt.   The fixing device according to claim 1, wherein a surface of a portion of the first guide portion in contact with the inner peripheral surface of the fixing belt has a concavo-convex shape.   The fixing device according to claim 1, wherein a surface of a portion of the first guide portion in contact with the inner peripheral surface of the fixing belt is made of a fluorocarbon resin.   The fixing device according to any one of claims 1 to 3, wherein a coefficient of friction between the first guide portion and the fixing belt is the same as a coefficient of friction between the pad member and the fixing belt. A pair of second guide portions are provided at positions facing the pair of end portions in the width direction of the fixing belt, the second guide portions being in contact with the inner peripheral surface of the fixing belt,
5. The image forming apparatus according to claim 1, wherein the detection target area is provided at a portion inside the fixing belt in the width direction than a portion in contact with each of the pair of second guides of the fixing belt. Fixing device described in.   6. The fixing device according to claim 5, wherein each of the pair of second guide portions has a hook portion facing an end surface located in the width direction of the fixing belt. The first guide portion and the second guide portion are configured by separate members,
The fixing device according to claim 5, wherein the first guide portion is fixed to the first support member. The first guide portion and one of the pair of second guide portions are constituted by a single member;
The fixing device according to claim 5, wherein the first guide portion is extended inward in the width direction of the fixing belt from the one of the pair of second guide portions. It further comprises a second support member for supporting the reflective photoelectric sensor,
By fixing one of the second guide portions to the second support member, the first guide portion is held by the second support member via the one of the second guide portions. The fixing device according to claim 8.   The reflection type photoelectric sensor and the first guide portion are areas other than the portion corresponding to the nip portion on the path of the fixing belt when viewed along the width direction of the fixing belt. The fixing device according to any one of claims 1 to 9, wherein the fixing device is disposed in a region closer to the inlet side of the nip portion than the outlet side of the nip portion.   The fixing device according to any one of claims 1 to 10, wherein the reflection type photoelectric sensor and the first guide portion are disposed vertically lower than the heating source.   The fixing device according to any one of claims 1 to 11, wherein the reflective photoelectric sensor and the first guide portion are interrupted by the first support member with the heat source.   An image forming apparatus comprising the fixing device according to any one of claims 1 to 12 for image formation.

Images