Image heating apparatus having a separation plate to separate a sheet from an endless belt

An image heating apparatus includes an endless belt in contact with a toner image on a recording material, a separation member that separates the recording material from the endless belt, a regulation member that regulates a longitudinal position of the endless belt, and an interlocking mechanism. The interlocking mechanism interlocks a movement of an end portion of the separation member on the same side as a first edge of the endless belt with movement of the regulation member. The interlocking mechanism performs interlocking so that, when the regulation member moves toward an upstream in a conveyance direction, the end portion of the separation member moves toward the upstream in the conveyance direction.

BACKGROUND OF THE INVENTION

Field of the Invention

The present disclosure relates to an image heating apparatus for heating an image formed on a recording material.

Description of the Related Art

Conventionally, an image forming apparatus such as an electrophotographic apparatus and an electrostatic recording apparatus forms a toner image on a sheet and then heats and pressurizes the image to fix it. In recent years, from a viewpoint of energy-saving promotion, a fixing apparatus (image heating apparatus) using a film heating method for heating an image via a fixing belt (hereinafter referred to as a fixing film or a film) having a low thermal capacity has been in practical use. The film heating method is known to provide a high heat transfer efficiency and a short apparatus activation time.

In the film heating method, a film is known to laterally deviate in a longitudinal direction of the film during rotation of the film. To regulate the longitudinal position of the film, a regulation member is often disposed at the position facing an edge face of the film. This regulation member has a portion facing the inner circumferential surface of the film, and a function of stabilizing a rotational orbit of the film.

If the film rotates in a state where the edge face of the film abuts on the regulation member, sliding between the edge face of the film and the regulation member may possibly cause wear of the film accompanied by durability degradation. Japanese Patent Application Laid-Open No. 2015-28527 discusses a configuration including a mechanism for moving the position of the film by moving a portion facing the inner circumferential surface of the film to an upstream side in a recording material conveyance direction when the film laterally deviates. In the configuration discussed in Japanese Patent Application Laid-Open No. 2015-28527, when the film laterally deviates, the film position is moved to the upstream side in the recording material conveyance direction to reduce the force with which the film abuts on a regulation member.

On the other hand, generally, a fixing apparatus using a film heating method may be provided with a separation plate (separation member) to separate a recording material with an image fixed thereon from the surface of the film. The separation plate is disposed separately from the film surface across a minute gap.

In the configuration discussed in Japanese Patent Application Laid-Open No. 2015-28527, as the film is moved to the upstream side of the film in the recording material conveyance direction, the gap between the film and a separation guide increases, possibly resulting in a separation failure of the recording material.

SUMMARY OF THE INVENTION

The present disclosure is directed to work towards preventing an occurrence of a separation failure in an image heating apparatus having a mechanism for moving a film (a belt) to an upstream side in a recording material conveyance direction when the film (the belt) laterally deviates.

According to an aspect of the present invention, an image heating apparatus includes an endless belt configured to heat a toner image on a recording material while being in contact with the toner image on the recording material at a nip portion, a rotary member configured to form the nip portion in collaboration with the endless belt, and rotate the endless belt, a separation member configured to face an outer circumferential surface of the endless belt across a gap, and separate a leading edge of the recording material passing through the nip portion from the endless belt, a regulation member having a regulating surface disposed to be able to abut on an edge face of a first edge of the endless belt in a longitudinal direction of the endless belt and configured to regulate a longitudinal position of the endless belt, and a facing surface disposed to face an inner circumferential surface of the first edge of the endless belt, a guide portion configured to guide the regulation member so that the regulation member moves toward an upstream in a conveyance direction of a recording material in response to a movement of the endless belt in a direction from a side of a second edge as another edge of the endless belt to a side of the first edge of the endless belt in the longitudinal direction and a movement of the regulating surface in a direction from the side of the second edge to the side of the first edge by the edge face of the first edge of the endless belt, wherein, with the movement of the regulation member toward the upstream in the conveyance direction, the facing surface moves the first edge of the endless belt toward the upstream in the conveyance direction, and an interlocking mechanism configured to interlock a movement of an end portion of the separation member on the same side as the first edge of the endless belt with the movement of the regulation member, wherein the interlocking mechanism performs interlocking so that, when the regulation member moves toward the upstream in the conveyance direction, the end portion of the separation member moves toward the upstream in the conveyance direction.

DESCRIPTION OF THE EMBODIMENTS

An embodiment will be described in detail below with reference to the accompanying drawings. Components described in the embodiment are to be considered as illustrative and not restrictive of the scope of the present disclosure.

[Configuration of Image Forming Apparatus]

FIG. 1illustrates an example of an image forming apparatus.FIG. 1is a cross-sectional view illustrating an electrophotographic color printer as an example of an image forming apparatus when viewed from the front.

Although, in a present first embodiment, an image forming apparatus1having image forming units employing a full color intermediate transfer method will be described below, the image forming apparatus1is not limited thereto. For example, the image forming apparatus1may be an apparatus employing a direct transfer method for directly transferring an image from a photosensitive drum11to a recording material P without using an intermediate transfer belt31(described below), or an apparatus for forming a monochromatic toner image (for example, a monochrome apparatus). The image forming apparatus1may also be a copying machine, a printer, a facsimile machine, or a multifunction peripheral having a plurality of functions of these apparatuses.

The recording material P is a medium on which a toner image is formed by the image forming apparatus1. Examples of the recording material P include plain paper, thick paper, and an overhead projector sheet. For convenience, the recording material (sheet) P will be described below using paper-related terms such as sheet supply, paper feed, paper discharge, a sheet supply portion, and a non-sheet supply portion, the recording material P is not limited to paper.

The image forming apparatus1illustrated inFIG. 1includes image forming units10corresponding to the Y (yellow), M (magenta), C (cyan), and Bk (black) colors. More specifically, each of the image forming units10includes a photosensitive drum11as an image bearing member for bearing an electrostatic latent image on its surface, a charging device12, a laser scanner13, a developing device14, a primary transfer blade17, and a cleaner15for each of the Y, M, C, and K colors. The image forming units10form Y, M, C, and K toner images on the intermediate transfer belt31in a superimposed way.

An electrophotographic process of each image forming unit10for each color will be described below. The photosensitive drum (photosensitive member)11is pre-charged by the charging device (charging unit)12. Then, when the photosensitive drum11is exposed to light corresponding to image data from the laser scanner (exposure unit)13, an electrostatic latent image is formed on the photosensitive drum11. The developing device14develops the electrostatic latent image on the photosensitive drum11with toner (developer). The toner image formed on the photosensitive drum11by the developing device14is primarily transferred onto the intermediate transfer belt31by the primary transfer blade (primary transfer unit)17. After primary transfer, residual toner on the photosensitive drum11is removed by the cleaner (cleaning apparatus)15.

Meanwhile, the recording material P is sent from a sheet cassette20ain the first stage, a sheet cassette20bin the second stage, or a multi-feed tray25to a registration roller pair23.

The registration roller pair23once catches the recording material P and corrects skew of the recording material P. The registration roller pair23sends the recording material P to a secondary transfer nip portion in synchronization with the toner image on the intermediate transfer belt31. The secondary transfer nip portion is formed by a secondary transfer roller (secondary transfer unit)35and a backup roller34via the intermediate transfer belt31. The toner image on the intermediate transfer belt is transferred onto the recording material P by the secondary transfer roller35.

Then, the recording material P is conveyed to a fixing apparatus (image heating apparatus)40. The fixing apparatus40applies heat and pressure to the recording material P at a fixing nip portion N to fix the toner image onto the recording material P.

When forming a toner image only on one surface of the recording material P and when a toner image has been formed on a second surface in double-sided printing for forming toner images on both surfaces of the recording material P, the recording material P with toner images fixed thereon is discharged out of the image forming apparatus1. More specifically, the recording material P with toner images fixed thereon is discharged to a discharge tray64disposed on a lateral face out of the image forming apparatus1via a discharge roller63through switching by a switching flapper61. The recording material P with toner images fixed thereon may be discharged to a discharge tray65disposed on an upper face of the image forming apparatus1.

The recording material P with a toner image fixed on a first surface in double-sided printing is upwardly guided by the switching flapper61. When the trailing edge of the recording material P reaches an inverse point V, the recording material P is conveyed in a switchback way through a conveyance path73and front/back surface inversion is completed. The portion composed of the switching flapper61and the conveyance path73is an example of an inversion unit. Then, the recording material P is conveyed along the conveyance way70, undergoes toner image forming on the second surface through a process similar to the toner image forming on the first surface, and is discharged to the discharge tray64or65.

A configuration of the fixing apparatus40will be described in detail below with reference toFIGS. 2 and 3.

FIG. 2illustrates an example of a fixing apparatus when viewed from a downstream side in a recording material conveyance direction.FIG. 2illustrates a state of the fixing apparatus40in a longitudinal direction, where an F side is a front side of the image forming apparatus1and an R side is a back side of the image forming apparatus1.

FIG. 3is a cross-sectional view illustrating an example of the fixing apparatus40when viewed from the R side illustrated inFIG. 2. An arrow S illustrated inFIG. 3indicates a recording material P conveyance direction in the fixing apparatus40.

As illustrated inFIG. 2, in the fixing apparatus40, one edge (first edge) of a film101in a longitudinal direction is positioned on the F side of the fixing apparatus40, and the other edge (second edge) of the film101in the longitudinal direction is positioned on the R side of the fixing apparatus40.

The fixing apparatus40is a film heating type heating apparatus. The fixing apparatus40further includes a roller106as a rotary member, a ceramic heater100as a heating member, and the film (a belt)101, which is cylindrical, as a fixing member (a fixing belt). The fixing apparatus40further includes a regulation member104at both ends of the film101. The fixing apparatus40further includes, inside the film101, a pad member103for forming a nip portion N with the roller106across the film101, and a stay102for ensuring the strength of the pad member103. The fixing apparatus40further includes a pressurization unit (for example, pressurizing spring) for applying pressure to the nip portion N. The pressurization unit is disposed at both ends of the fixing apparatus40, respectively, in the longitudinal direction. When the pressurization units apply pressure to holding members111disposed at both ends in the longitudinal direction, the holding members111, the stay102, and the pad member103are urged toward the roller106. The fixing apparatus40further includes a separation member107.

The roller106is composed of a core metal106a, an elastic layer106b, and a releasable layer in this order from an innermost side. The elastic layer106bcan be selectively made of a heat-resistant elastic material such as silicone rubber, fluorocarbon rubber, and fluororesin. For example, the releasable layer can be selectively made of a material having favorable mold-releasability and resistance to heat, such as fluororesin, silicone resin, fluorosilicone rubber, fluoro rubber, silicone rubber, perfluoro alkoxy alkane (PFA), polytetrafluoroethylene (PTFE), and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Bearing members (not illustrated) made of heat-resistant resin such as polyetheretherketone (PEEK), polyphenylene sulfide (PPS), and a liquid crystal polymer are attached at both ends of the core metal106ain the longitudinal direction of the core metal106a. The roller106is rotatably held with respect to side plates105of the fixing apparatus40.

The roller106is connected to a motor (drive unit) via a gear108attached to an end of the roller106in the longitudinal direction, to be driven to rotate by the motor.

The film101is driven to rotate by the roller106.

The ceramic heater100(hereinafter referred to as the heater100) as a heating member for heating the film101is composed of an elongated sheet-like ceramic substrate extending along the longitudinal direction of the film101, and a heating register layer disposed on the substrate. When the heating register layer is supplied with electricity, the temperature of the heating register layer rises with steep rising characteristics. The heater100is a low thermal capacity heater. The heater100is supported by being fit into a fitting groove103aformed on the surface of the pad member103on the side of the roller106. The fitting groove103ais formed along the longitudinal direction of the film101.

When the film101is heated by the heater100, the film101heats the recording material P at the nip portion N. The film101is a cylindrical heat-resistant film and is also a flexible seamless film (an endless belt). The film101is composed of a base layer (for example, 0.04 mm thick) made of a metal such as stainless steel (SUS) and nickel, an elastic layer (for example, silicone rubber layer), and a releasable layer (for example, PFA resin tube) in this order from an innermost side.

The inner surface of the film101is not provided with a stretching roller, and the film101is not stretched.

The film101is respectively fit into an outside of the regulation members104at both ends in the longitudinal direction.

Each of the regulation members104is provided with an inner surface facing portion (facing surface)104afacing an inner surface of the film101, and an edge face regulation portion (regulating surface) (stopper portion)104bfor regulating a longitudinal position of the film101in a state where the regulation member104is fit into the inner side of the film101. The inner surface facing portion104ahas a facing surface which faces the inner surface of the film101to guide a rotational orbit of the film101. The edge face regulation portion104bhas a surface to be in contact with an edge face of the film101(when the film101moves in a thrust direction) to regulate the movement of the film101in the longitudinal direction.

The regulation member104is fit into the side plate105of the fixing apparatus40. At each of both ends of the film101, the regulation member104is engaged with an end of the assembly of the pad member103and the stay102.

The pad member103comes in pressure contact with the roller106via the film101to form the nip portion N. The pad member103is a heat-resistant heat-insulation material made of phenol resin, polyimide resin, polyamide resin, polyamide imide resin, PEEK resin, poly ether sulfone (PES) resin, PPS resin, PFA resin, PTFE resin, and liquid crystal plastic (LCP) resin.

The stay102is pressed onto the back surface of the pad member103made of resin to provide the pad member103with the longitudinal strength.

The separation member107is a separation plate for separating the recording material P having passed through the nip portion N from the surface of the film101. The separation member107is disposed at a position away from the outer circumferential surface of the film101by a predetermined distance. The material of the separation member107may be an alloy material of polybutylene terephthalate (PBT) and acrylonitrile-butadiene-styrene (ABS) resin, resin such as PPS and LCP, or a metal such as SUS formed in the shape of a plate, with the surface coated with fluorine.

Lateral deviation of the film101will be described below. There are some cases where the film101laterally deviates to one side of the film in the longitudinal direction during film rotation.

Examples of such cases include a case where an assembly tolerance causes a relative alignment deviation between the roller106and the film101. More specifically, when attaching the regulation member104to the side plate105, a tolerance in dimensions related to positioning may cause a deviation between the positions of the regulation members104on the F and the R sides in the recording material P conveyance direction. In this case, since the film101forms an intersecting angle with the roller106, the film101is applied with a force in the longitudinal direction as the film rotates, laterally deviating in the longitudinal direction. In this case, the film101laterally deviates toward the regulation member104disposed more on the downstream side in the recording material P conveyance direction S with respect to the rotational axis of the roller106out of the regulation members104on the F and the R sides. More specifically, when the regulation member104on the F side is disposed more on the downstream side than the regulation member104on the R side in the recording material P conveyance direction S, the film101laterally deviates in the direction from the regulation member104on the R side to the regulation member104on the F side.

There are some cases where a lateral deviation is caused by factors other than a tolerance in assembly. Examples of such cases include a case where a deviation of the passage position of the recording material P in the longitudinal direction of the roller106causes a deviation in the temperature distribution in the longitudinal direction of the roller106. Examples of such cases further include a case where a difference between pressurizing forces applied by the pressurization units disposed at both ends (R and F sides) in the longitudinal direction causes a deviation of the pressurizing force distribution in the longitudinal direction of the roller106. In these cases, if a longitudinal deviation occurs in deformation of the roller106due to outer diameter thermal expansion or pressurization, a longitudinal deviation also arises in the rotational speed of the film101being driven by the roller106, possibly resulting in a lateral deviation of the film101. For example, when the rotational speed on the F side becomes higher than the rotational speed on the R side, the film101moves to the F side (for example, the direction of an arrow B illustrated inFIG. 4A) which is rotating at higher rotational speed.

When the film101laterally deviates toward the F side, an edge face101aof the film101on the F side contacts the edge face regulation portion104bof the regulation member104on the F side. If the film101rotates with the edge face101aand the edge face regulation portion104bin contact with each other, the edge of the film101may be possibly worn by a sliding motion between the edge face101aof the film101and the edge face regulation portion104b. In particular, if the edge face101aof the film101strongly abuts on the edge face regulation portion104b, the load on the film101due to the sliding motion increases, possibly resulting in durability degradation.

According to the present embodiment, the fixing apparatus40is provided, on the F side, with a displacement mechanism109for moving the position of the edge of the film101on the F side to an upstream side in the recording material P conveyance direction S when the film101laterally deviates to the F side. The displacement mechanism109moves the edge of the film101to the upstream side in the recording material P conveyance direction S to reduce the force with which the edge face101aof the film101abuts on the edge face regulation portion104b.

Also when the film101laterally deviates toward the R side, the load on the film101due to the sliding increases in a similar way to the lateral deviation to the F side, possibly resulting in durability degradation. For this reason, the fixing apparatus40according to the present embodiment is provided, also on the R side, with the displacement mechanism109for moving the position of the edge of the film101on the R side to the upstream side in the recording material P conveyance direction S when the film101laterally deviates to the R side.

A configuration of the displacement mechanism109will be described in detail below with reference toFIGS. 4A and 4B.

FIGS. 4A and 4Billustrate an example of a configuration of the displacement mechanism109.FIGS. 4A and 4Bare cross-sectional views taken along the dotted line A-A illustrated inFIG. 3, i.e.,FIGS. 4A and 4Billustrate the fixing apparatus40viewed from the side of the roller106.

The displacement mechanism109is disposed at both ends of the film101in the longitudinal direction. The displacement mechanisms109on the R and the F sides have approximately symmetrical shapes and functions with respect to the dotted line X as a conveyance reference for the recording material P illustrated inFIG. 2. Therefore, the following describes the displacement mechanism109on the F side with reference toFIGS. 4A and 4B, and descriptions of the displacement mechanism109on the R side (opposite side) will be omitted.

The displacement mechanism109includes the regulation member104, a movable member110, a holding member111for holding the movable member110, and a compression spring (urging member)112for urging the movable member110.

The holding member111is fit into (and fixed to) the side plate105of the fixing apparatus40. Therefore, the position of the holding member111in the longitudinal direction of the fixing apparatus40and in the recording material P conveyance direction is fixed.

The movable member110is a part which movably engages with the holding member111. The movable member110is provided with the above-described regulation member104. More specifically, the movable member110has the edge face regulation portion104bfacing the edge face101aof the film101. As the film101laterally deviates in the direction of the arrow B illustrated inFIG. 4A, a gap Δ between the edge face101aof the film101on the F side and the edge face regulation portion104bdecreases, and eventually the edge face101aof the film101abuts on the edge face regulation portion104b.

On the movable member110, the regulation member104has the inner surface facing portion104afacing the inner surface of the film101at the edge of the film101. The inner surface facing portion104aguides an inner surface101bof the film101during rotation.

The movable member110has a convex portion110aextending in the longitudinal direction of the film101. The convex portion110ahas a tip portion110pand an obtuse angle portion110ewith an angle α.

The holding member (guide member)111has a concave portion (guide portion)111ain the longitudinal direction of the film101. The concave portion111ahas an acute angle portion111pat the concave111aand an obtuse angle portion111ewith the angle α. As described below, the holding member111functions as a moving portion for moving the movable member110to the upstream side in the recording material P conveyance direction.

As illustrated inFIGS. 4A and 4B, the convex portion110aof the movable member110is set in the concave portion111aof the holding member111. The compression spring112is disposed between the movable member110and the holding member111. The compression spring112urges the convex portion110aso that the tip portion110pof the convex portion110aof the movable member110moves away from the acute angle portion111pof the concave portion111aof the holding member111. When the movable member110is applied with a force in a direction of an arrow M1exceeding the urging force by the compression spring112, the movable member110slides in a direction of an arrow M2along with the concave portion111aof the holding member111.

[Operations of Displacement Mechanism Accompanying Lateral Deviation]

Operations of the displacement mechanism109will be described below. A case where the film101laterally deviates in the direction from the R side to the F side (the direction of the arrow B) will be described below with reference toFIGS. 4A and 4B.

FIG. 4Aillustrates the displacement mechanism109in a state where the edge face101aof the film101is not in contact with the edge face regulation portion104b. When the edge face101aof the film101is not in contact with the edge face regulation portion104b, the obtuse angle portion110eof the convex portion110aof the movable member110urged by the compression spring112is at the position closest to the obtuse angle portion111eof the concave portion111aof the holding member111.

FIG. 4Billustrates a state where the movable member110is applied with a force in the direction of the arrow M1and slides in the direction of the arrow M2along with the concave portion111aof the holding member111. The gap Δ between the edge face101aof the film101and the edge face regulation portion104bbecomes zero, achieving a contact state.

When the film101laterally deviates toward the regulation member104on the F side (in the direction of the arrow B illustrated inFIG. 4A), the edge face101aof the film101contacts the edge face regulation portion104b. Since the regulation member104and the movable member110are integrally formed, the movable member110moves together with the regulation member104. In a state where the edge face101aof the film101contacts the edge face regulation portion104b, when the film101further laterally deviates in the direction of the arrow B, the film101provides a force for pressing the edge face regulation portion104b. If this pressing force exceeds the urging force by the compression spring112, the film101presses the movable member110together with the regulation member104in the direction of the arrow M1. Accordingly, the convex portion110aof the movable member110moves along with the concave portion111aof the holding member111, and the movable member110moves in the direction of the arrow M2. As a result, the movable member110moves to the upstream side in the recording material P conveyance direction S compared to the state illustratedFIG. 4A.

The inner surface101bof the film101is in contact with the inner surface facing portion104aof the movable member110. Therefore, when the movable member110moves to the upstream side in the recording material P conveyance direction S, the inner surface facing portion104apresses the inner surface101bof the film101. As a result, the edge of the film101on the side of the direction in which the film101has laterally moved (the F side illustrated inFIGS. 4A and 4B) moves to the upstream side in the recording material P conveyance direction S.

On the other hand, the edge face regulation portion104bof the regulation member104on the R side (opposite side) of the film101in the longitudinal direction is disposed at a position where the edge face regulation portion104bis not pressed by the edge face of the film101on the R side when the film101laterally deviates in the direction of the arrow B. Therefore, when the film101laterally deviates in the direction of the arrow B, the movable member110on the R side does not move to the upstream side in the recording material P conveyance direction S. Thus, a rotation center line101cof the film101and a rotational axis106cof the roller106form an angle θ1. When the film101is rotated by the roller106in the state illustrated inFIG. 4B, the film101is applied with a force for moving in the direction away from the movable member110on the F side (in the direction opposite to the direction of the arrow B illustrated inFIG. 4A). More specifically, the force applied to the edge face101aof the film101is restricted. This works towards reducing wear of the film101.

The separation member107will be described in detail below with reference toFIGS. 3, 4A, 4B, and 5.FIG. 5illustrates an example of a supporting portion of the separation member107when viewed from the R side illustrated inFIG. 2.

The separation member107is a separation plate for separating the recording material P having passed through the nip portion N from the film101to prevent the recording material P having passed through the nip portion N from winding around the film101.

The recording material P is nipped and conveyed by the film101and the roller106at the nip portion N. When a toner image t on the recording material P is applied with heat and pressure at the nip portion N, the toner image t is fixed onto the recording material P. Then, the recording material P is conveyed by the rotation of the film101from the nip portion N to the downstream side in the conveyance direction. The recording material P is likely to stick to the surface of the film101by the toner image t melted at the nip portion N. If the portion on the recording material P for bearing the toner image t sticks to the surface of the film101, the recording material P will be conveyed along the circumferential surface of the film101to the downstream side of the nip portion N in the conveyance direction. More specifically, the recording material P may possibly wind around the film101.

The separation member107is disposed on the downstream side of the nip portion N in the recording material P conveyance direction. In consideration of a rotation locus of the film101, the separation member107is disposed between the surface of the film101(outer circumferential surface) and a tip portion107aof the separation member107across a predetermined gap to prevent the surface of the film101from being damaged by contact. Since there is a marginal area where the toner image t is not borne at a leading edge of the recording material P, the leading edge of the recording material P having passed through the nip portion N can abut on the separation member107without sticking to the surface of the film101. The recording material P having abutted on the separation member107is guided by the separation member107to be separated from the surface of the film101. More specifically, the separation member107separates from the film101the leading edge of the recording material P currently passing through the nip portion N.

According to the present embodiment, both ends of the separation member107in the longitudinal direction are supported by separation member supporting portions110bdisposed on the movable members110. More specifically, the end of the separation member107on the R side is supported by the separation member supporting portion110bof the movable member110disposed on the R side, and the end of the separation member107on the F side is supported by the separation member supporting portion110bof the movable member110disposed on the F side.

As illustrated inFIG. 5, for example, the separation member supporting portion110bincludes a groove portion110cformed on the movable member110and a leaf spring member (urging member)113. The width of the groove portion110cis formed to be slightly larger than the plate thickness of the separation member107. The separation member107is fit into (and engaged with) the groove portion110cwhile the separation member107is being slid in the direction in which the tip portion107aof the separation member107moves toward a back end110dof the groove portion110c.

In a state where the separation member107is engaged with the groove portion110c, the separation member107is urged toward the back end110dof the groove portion110cby the leaf spring member113, and therefore the tip portion107aof the separation member107constantly abuts on the back end110dof the groove portion110cwith respect to the movable member110. This prevents the separation member107from being dropped off from the groove portion110c, and at the same time determines a position at the tip portion107aof the separation member107relative to the movable member110. More specifically, as illustrated inFIG. 5, the leaf spring member113urges the separation member107toward the upstream side in the recording material P conveyance direction to achieve a predetermined relative position between the separation member107and the movable member110.

To follow the movement of the movable member110, the separation member107is supported by the separation member supporting portion110bso as to be slidable relative to the separation member supporting portion110bin the longitudinal direction of the separation member107. Even if the separation member107slides following the movement of the movable member110(to be described below), the separation member107does not drop off from the separation member supporting portion110b.

The separation member107is supported by the separation member supporting portion110bdisposed on the movable member110in order to prevent a separation failure from occurring when the film101is moved by the displacement mechanism109.

As described above, in the fixing apparatus40according to the present embodiment, the position of the film101may be moved to the upstream side in the recording material P conveyance direction S by the displacement mechanism109. If the separation member107does not move while the film101is moving, the gap between the separation member107and the film101will increase. As a result, the recording material P passes through between the separation member107and the film101, making it impossible to separate the recording material P.

According to the present embodiment, therefore, the end of the separation member107on the F side is supported by the separation member supporting portion110bdisposed on the movable member110on the F side. Thus, the movable member110on the F side is moved to the upstream side in the conveyance direction S by the displacement mechanism109on the F side, and at the same time, the end of the separation member107on the F side also moves to the upstream side in the conveyance direction S.

This operation also applies to the R side. More specifically, the end of the separation member107on the R side is supported by the separation member supporting portion110bdisposed on the movable member110on the R side. Thus, the movable member110on the R side is moved to the upstream side in the conveyance direction S by the displacement mechanism109on the R side, and at the same time, the end of the separation member107on the R side also moves to the upstream side in the conveyance direction S.

In this way, the gap between the film101and the separation member107increases to prevent a separation failure from occurring.

The above-described operation will be described in more detail below with reference toFIGS. 4A and 4B.

For example, a case where the movable member110in an initial state is as illustrated inFIG. 4Awill be described below. More specifically, in the initial state, the rotation center line101cof the film101is approximately in parallel with the longitudinal direction perpendicularly intersecting with the recording material P conveyance direction S, and the separation member107is disposed so that the tip portion107athereof becomes in parallel with the rotation center line101c. Suppose that the displacement mechanism109is not subjected to a one-sided moving force (a force in a direction in which the edge face101aof the film101presses the edge face regulation portion104b) from the film101. At this timing, a predetermined gap D1is formed between the tip portion107aof the separation member107and the surface of the film101. According to the present embodiment, for example, the gap D1is set to 0.5 mm.

Then, the film101laterally deviates in the direction of the arrow B illustrated inFIG. 4A, and the displacement mechanism109on the F side is applied with a one-sided moving force of the film101. Then, the movable member110moves from the initial position to the upstream side in the recording material P conveyance direction S, as illustrates inFIG. 4B. At this timing, the angle θ1formed between the rotation center line101cof the film101and a rotational axis106cof the roller106increases with the movement of the movable member110.

Since the separation member107is supported by the separation member supporting portion110bwhich integrally moves with the movable member110, the separation member107also moves to the upstream side in the recording material P conveyance direction S together with the movable member110.

An angle θ2formed between the tip portion107aof the separation member107and a direction parallel to the rotational axis106cof the roller106also increases with the movement of the movable member110. The angles θ1and θ2are approximately the same regardless of the amount of movement of the movable member110.

As a result, the tip portion107aof the separation member107maintains approximately in parallel with the rotation center line101c. At this timing, the gap D2formed between the tip portion107aof the separation member107and the surface of the film101is approximately the same as the gap D1. More specifically, the separation member supporting portion110bmakes the movement of the separation member107follow up the movement of the movable member110to maintain a predetermined gap between the tip portion107aof the separation member107and the surface of the film101.

As described above, also when the film101moves to the upstream side in the recording material P conveyance direction S by an operation of the displacement mechanism109, the separation member107also moves to the upstream side in the conveyance direction S together with the movable member110. This works towards preventing the increase in gap between the film101and the tip portion107aof the separation member107. Therefore, a separation failure can be prevented from occurring by the movement of the film101by the displacement mechanism109. More specifically, in an image heating apparatus having a mechanism for moving a film to the upstream side in the recording material conveyance direction when the film laterally deviates, a separation failure can be prevented from occurring.

A configuration according to a second embodiment will be described below with reference toFIGS. 6A, 6B, and 7.FIGS. 6A and 6Billustrate an example of a configuration of the displacement mechanism109.FIG. 7illustrates an example of a supporting portion of the separation member107.

The separation member supporting portion (interlocking mechanism)110binterlocks the movement of the separation member107with the movement of the movable member110to maintain a predetermined gap between the tip portion107aof the separation member107and the surface of the film101. The present embodiment is characterized in that the separation member supporting portion110bis rotatably engaged with the separation member107. Other configurations are similar to those according to the first embodiment and descriptions thereof will be omitted.

With the separation member supporting portion110b, a pin-shaped protrusion114is formed in a direction perpendicular to the movable surface of the separation member107(more specifically, in a direction perpendicular to the plane formed by the moving directions M1and M2of the movable member110). The protrusion114may be formed integrally with or separately from the movable member110. The protrusion114is, for example, 1.5 mm in diameter and 3 mm in length. Although the separation member supporting portion110bon the F side is illustrated inFIGS. 6A and 6B, the descriptions thereof also apply to the separation member supporting portion110bon the R side.

On the other hand, an oblong hole portion107bfor engaging with the protrusion114is formed at the end of the separation member107in the longitudinal direction of the separation member107. The hole portion107bis, for example, 1.5 mm in width (a size in the widthwise direction of the separation member107) and 5 mm in length (a size in the lengthwise direction of the separation member107). The shape of the hole portion107bto be engaged with the protrusion114is not limited to an oblong hole and may be a square hole or a round hole.

The width of the hole portion107bis at least in size which fits the protrusion114. The length of the hole portion107bis made larger than the protrusion114so that the protrusion114is slidable in the longitudinal direction of the separation member107. When the movable member110moves in the moving directions M1and M2, the separation member107also rotates and slidably moves in the plane in the moving directions M1and M2. More specifically, the separation member supporting portion110binterlocks the movement of the separation member107with the movement of the movable member110.

The above-described shapes of the separation member supporting portion110band the separation member107for engagement may be exchanged. More specifically, if an oblong hole is formed as the separation member supporting portion110band the protrusion114is formed on the separation member107, similar effects to the above-described ones can be acquired. Even in this case, the separation member supporting portion110bmay be an oblong hole, a square hole, or a round hole.

Also in the fixing apparatus40according to the second embodiment, the above-described configuration allows obtaining similar actions and effects to the fixing apparatus40according to the first embodiment. More specifically, it is possible to prevent a separation failure from occurring in an image heating apparatus having a mechanism for moving a film to the upstream side in the recording material conveyance direction when the film laterally deviates.

This application claims the benefit of Japanese Patent Application No. 2016-206241, filed Oct. 20, 2016, which is hereby incorporated by reference herein in its entirety.