JP2020118785A - Image forming device - Google Patents

Abstract

To provide a fixing device using a fixing film of an endless belt as a fixing member which has a configuration that the fixing film is stretched over the entire length in a longitudinal direction by an internal regulation member placed inside the fixing film capable of providing proper separation performance while preventing the fixing film from being subjected to excessive stress.SOLUTION: An internal regulation member has a configuration that when unpressurized, it gradually retracts from the fixing film in a pressing direction as it approaches the center from the end in the longitudinal direction. With this, when a pressure is applied during fixing operation, it is possible to have a substantially flat shape in the pressing direction in the entire longitudinal direction, and thus, tension with which the internal regulation member stretches the fixing film can be approximately the same at any position in the longitudinal direction. It is possible to prevent occurrence of such events as the shortening of a life of the film, breakage, and a failure to obtain proper separation performance.SELECTED DRAWING: Figure 2

Description

The present invention relates to an electrophotographic image forming apparatus capable of forming an image on a recording material such as a copying machine or a printer adopting an electrophotographic method, or a facsimile, and more particularly to a pressure mechanism and a pressurizing mechanism using a pair of pressure contact members. The present invention relates to an image forming apparatus having a pressure releasing mechanism.

In an image forming apparatus, a recording material (transfer sheet, electrofax sheet, electrostatic recording paper, OHP sheet, printing paper, format paper) is formed by an appropriate image forming process means such as an electrophotographic process, an electrostatic recording process, a magnetic recording process. Image) is formed.

Specifically, an unfixed image (toner image) of image information formed and carried by a transfer method or a direct method is formed. Then, the unfixed image is fixed as a fixed image by the fixing device.

The mainstream of the fixing device is one that uses heat and pressure to perform fixing in a fixing nip portion formed by pressing a fixing member heated by a heat source and a pressure member.

Further, in a fixing device, an endless (cylindrical) fixing film is used as a fixing member, and a film fixing method of fixing an unfixed toner image on a recording material via the fixing film has been actively used. ing.

Compared with the roller fixing method, the film fixing method can form a wider nip without increasing the size of the apparatus. In addition, since the fixing film has a smaller heat capacity than the roller, the wait time is shortened and the apparatus is small. It is possible to increase speed and speed.

Further, in the fixing device, the medium adheres to the fixing member by the toner melted in the fixing nip portion, and therefore a means for peeling the medium after passing through the fixing nip portion is required.

At present, the medium is generally peeled off by bringing the conveyance guide as close as possible to the fixing member (hereinafter, the conveyance guide for peeling off the medium is referred to as a separation guide).

In recent years, various types of media have come to be used in image forming apparatuses, and, for example, there are many demands for using thin paper having a smaller basis weight than ever before.
Thin paper generally tends to have lower rigidity when the basis weight is smaller, and when trying to use thin paper with a smaller basis weight than before, it is now necessary to peel the media after passing through the fixing nip from the fixing member. It becomes more difficult than ever.

In addition, for example, when trying to use a medium such as a thin paper and a coated paper in which the gloss of the product is high, the tip of the medium separated from the fixing member using the separation guide is separated. Since the contact state with the fixing member is changed and the amount of heat applied is changed between the portion other than the leading edge that is subsequently conveyed, gloss unevenness called peeling unevenness may occur. ..

For these reasons, it is necessary to improve the separation performance when using thin paper having a smaller basis weight than before.

As an example of improving the separation performance, as disclosed in Japanese Patent Laid-Open Publication No. 2004-242, there is a structure in which the fixing film is guided from the inside, the rotation trajectory of the fixing film is regulated, and the separation guide is further brought closer.

Further, if the fixing film is configured to be guided from the inside only in a part of the longitudinal direction, a temperature difference occurs between the guided part and the other part, and uneven gloss occurs in the longitudinal direction. Therefore, in Patent Document 1, the fixing film is guided over the entire length, and the temperature difference in the length direction and the gloss unevenness in the length direction due to the temperature difference can be prevented.

JP, 2008-040363, A

However, depending on the medium, it is not enough to bring the separation guide close to each other, and it is necessary to increase the force for the medium to separate from the fixing member.

In order to achieve the above, for example, a fixing film is stretched by a member that guides the fixing film from inside (hereinafter, referred to as an internal restriction member) to restrict the rotational trajectory while deforming the rotation path, and an exit portion of the fixing nip portion is provided. It has been known that by rapidly bending the fixing film, it is possible to increase the force with which the medium tends to separate from the fixing film, and to efficiently separate the medium.

However, if a structure is adopted in which the fixing film is stretched over the entire length by an internal restriction member and tension is applied to change the trajectory of the fixing film, a difference occurs in the tension applied to the fixing film in the longitudinal direction. And the following problems may occur.

For example, if the tension of only a part of the fixing film becomes strong, the part of the fixing film where the tension is strong will be in a state where the fixing film is braked. There is a risk that the fixing film will be twisted, which may damage the fixing film. In particular, the influence is remarkable in a fixing device in which a fixing film is driven by a pressure roller.

Also, if the tension is weakened so that it does not become too strong, under some circumstances, the tension may become too weak, and there may be places where the fixing film cannot be stretched properly, and proper separation performance cannot be obtained in the longitudinal direction. There is a risk that some parts will be created.

Here, when a member inside the fixing film is pressed at both ends of the fixing film to form a fixing nip, a certain amount of bending is generated by the applied pressure.

In the configuration in which the fixing film is stretched by the internal restriction member in order to improve the separation performance, the internal restriction member arranged in the entire length of the fixing film also bends.

When the internal regulating member has a straight shape in the longitudinal direction, when the bending occurs, it causes a longitudinal difference in tension to the fixing film, which causes the fixing film to be damaged as described above and the longitudinal direction. There is a risk that some parts of the parts may not have proper separation performance, and that some parts may not be formed.

The present invention has been made in view of the above, in a fixing device using an endless fixing film, in order to improve the separation performance while preventing gloss unevenness in the longitudinal direction, the fixing film inside the entire length. Even with a structure in which the rotation path is regulated by being stretched by a regulation member, it is possible to stretch properly over the entire length while reducing the stress on the fixing film, so that even on thin paper, uneven gloss It is an object of the present invention to provide a fixing device capable of preventing the occurrence of image defects such as the above and preventing separation defects.

In order to achieve the above object, the fixing device according to the present invention,
A rotatable endless belt-shaped film member 100,
A pressure member 101 that is disposed to face the outer peripheral surface of the film member 100 and rotates to form a fixing nip portion N with the film member 100;
A heating source 102 disposed inside the film member 100 for heating the film member 100;
A pressure contact member 103 that is disposed inside the film member 100, supports the heating source 102, and sandwiches the film member 100 with the pressure member 101 to form a nip portion N;
A film support member 105 arranged at both ends of the film member 100 in the rotation axis direction for restricting rotation and position at both ends of the film member 100;
A stay 104 which receives a pressing force and pushes down the pressing member 103 toward the pressing member 101 to form a nip;
An internal restricting member 107 attached to the stay 104 and applying tension to the film member 100 from the inside in at least the entire region through which an image passes in the longitudinal direction;
In a fixing device including
The internal restriction member 107 is characterized in that, in the non-pressurized state, the central portion has a shape retracted from the film member 100 with respect to the end portion in the pressing direction.

According to the fixing device of the present invention, in the non-pressurized state, the internal restricting member has a curved shape that retracts in the direction opposite to the pressurizing direction from the end in the longitudinal direction toward the center. When the both end portions are pressed, the end portion and the central portion can have a substantially flat shape in the pressing direction, and the tension applied to the fixing film can be substantially the same in the longitudinal direction. As a result, it is possible to reduce the stress applied to the fixing film while maintaining proper separation performance.

Schematic cross-sectional view of the entire image forming apparatus Sectional drawing of the fixing device in this invention Diagram showing the inside of the pressure roller and the fixing film in the pressure state The figure which showed the inside of the fixing film in a non-pressurized state in 1st Example. Enlarged view of the internal control member enlarged in the bold line circle in FIG. The figure which showed the inside of the fixing film in a non-pressurized state in a 2nd Example. Enlarged view of the internal control member enlarged in the bold line square portion of FIG.

Hereinafter, specific examples (embodiments) of the embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following examples.

[Example 1]
FIG. 1 shows a tandem type digital color copying machine (hereinafter, simply referred to as a copying machine) as an image forming apparatus, and is a schematic cross-sectional view of a configuration along a conveyance direction of a sheet P.

The sheet P has a toner image formed thereon. Specific examples of the sheet P include plain paper, a resin sheet-like substitute for plain paper, thick paper, and an overhead projector.

The main configuration of the copying machine will be described below with reference to FIG.

The engine unit 600 of the copying machine includes the image forming units 10 of Y (yellow), M (magenta), C (cyan), and Bk (black). The photosensitive drums a to d included in the image forming units 1a to 1d are precharged by a charger, and then the laser scanner 6 forms a latent image of the original read image data from the image reading unit 601. The latent image becomes a toner image by the developing device. The toner images on the photosensitive drums a to d are sequentially transferred by the primary transfer rollers 2a to 2d to, for example, an intermediate transfer belt 2 which is an image carrier.

On the other hand, the sheets P are sent out one by one from the paper feed cassette 4, pass through the post-paper feed transport path 45, and are fed to the registration roller pair 9. The registration roller pair 9 temporarily receives the sheet P and straightens the sheet P when the sheet P is skewed. Then, the registration roller pair 9 sends the sheet P to the secondary transfer portion 3 between the intermediate transfer belt 2 and the secondary transfer roller 3a in synchronization with the toner image on the intermediate transfer belt 2.

The color toner image on the intermediate transfer belt is transferred to the sheet P by a transfer member such as the secondary transfer roller 3a. After that, the toner image on the sheet P passes through the pre-fixing conveyance path and is fixed on the sheet P by being heated and pressed by the fixing device 40.

When the toner image is formed on only one side of the sheet P, the sheet P is discharged to the sheet discharge tray 12 via the sheet discharge roller 11 by switching the switching flapper 46.

When a toner image is formed on both sides of the sheet P, the sheet P having the toner image fixed by the fixing device 40 is conveyed to the paper discharge roller 11, and when the rear end of the paper reaches the reversal point, the paper discharge roller 11 After being reversely rotated, it is switchback-transported, and after passing through the double-sided transport path 47, a toner image is formed on the other surface through the same process as the one-sided image formation, and the sheet is discharged to the discharge tray 12. The portion constituted by the switchback operation of the flapper 46 and the discharge roller 11 is an example of a reversing unit. In the present embodiment, the paper is discharged by the paper discharge roller 11, but in order to improve the productivity of printing, a reverse unit is provided, a plurality of paper discharge units are provided, and so on. You may flip in place.

Next, the configuration and mechanism of the fixing device 40 according to the present invention will be described with reference to FIGS. 2 to 5.

First, FIG. 2 shows a schematic cross-sectional view in this configuration.

The fixing device 40 includes a fixing film 100 in the shape of a thin hollow endless belt, a pressure roller 101 that is pressed against a pressing spring 113 and a pressing lever 112 to form a fixing nip portion N with the fixing film 100, and fixing. On the inner peripheral side of the film 100, there are a pressure contact member 103 and a heating member 102 that are in sliding contact with the fixing roller 100 while sandwiching the fixing film 100.
Further, a lubricant (not shown) is previously applied to the sliding surfaces of the fixing film 100 and the pressure contact member 103 for the purpose of reducing frictional force.

The fixing film 100 is sandwiched between the pressure contact member 103 and the pressure roller 101, and a predetermined pressure is applied.

The pressure roller 101 is rotationally driven by a fixing motor (not shown) and a fixing driving unit (not shown), and the fixing film 100 is driven to rotate accordingly. The heating member 102 includes a heating element (resistive heating element) as a heat source that generates heat when power is supplied, and the temperature of the heating member 102 is raised by the heat generated by the heating element. By passing the sheet P between the fixing film 100 and the pressure roller 101, thermal energy is applied to the sheet P from the heating member 102 via the fixing film 100 in the process of passing through the fixing nip portion N, and the sheet P The unfixed toner image T is fused and fixed. Then, after the sheet P passes through the fixing nip portion N, it is separated from the fixing film 100 and discharged.

The fixing film 100 is made of a heat resistant resin such as a polyimide film or PEEK film having a total thickness of 150 μm or less, or a metal such as SUS or Ni in order to reduce the heat capacity and improve the quick start property. An elastic layer made of a rubber material having a high thermal conductivity is formed on a resin layer provided with a conductive material so as to have a high thermal conductivity, and a release layer of a fluororesin is formed on the surface to form an endless shape with an inner diameter of 25 mm. Has been formed.

In this example, a polyimide having a thickness of 60 μm was used for the base layer, a silicone rubber having a thickness of 70 μm and a thermal conductivity of 1.0 W/m·K was used for the elastic layer, and a PFA tube having a thickness of 30 μm was used for the release layer. The PFA layer is preferably a sheet or a coat layer having high releasability, and for example, a fluororesin layer can be used. Further, a sheet-shaped member having high heat resistance represented by polyester, polyethylene terephthalate, polyimide amide or the like may be used as a base layer, a conductive layer may be formed on the base layer, and a surface release layer may be laminated on the conductive layer.

The pressure roller 101 has a cylindrical cored bar made of metal such as iron or aluminum as a core material, an elastic layer of a soft rubber material such as sponge or silicone rubber on the outer peripheral side of the cored bar, and a release layer on the surface layer. As a PFA layer.

In this embodiment, the surface of a cored bar made of iron, aluminum or the like is subjected to surface roughening treatment such as blasting, then washed, and then the cored bar is inserted into a cylinder and liquid silicone rubber is injected into the mold. Then heat cure. At this time, in order to form a resin tube layer such as a PFA tube on the surface layer of the pressure roller 101 as a release layer, a tube having a primer applied on its inner surface is inserted into the mold to heat-cure the rubber. At the same time, the tube and rubber layer are bonded. The pressure roller molded in this manner is subjected to a demolding treatment and then subjected to secondary vulcanization.

In this embodiment, the pressure roller 101 has a core metal diameter of 15 mm, the elastic layer has a wall thickness of 5 mm, the Asker hardness of 64° is silicone rubber, the release layer has a PFA tube thickness of 50 μm, and the outer diameter is about 25 mm. It was Laura.

The heating member 102 is a ceramic heater. This heating member 102 forms an exothermic body by printing a thick film of Ag/Pd paste on an AlN substrate having a good heat conduction in the form of an elongated thin plate and firing it. Then, a ceramic heater in which a glass coating layer having a thickness of about 50 to 60 μm is integrally provided as a sliding insulating member on the heating element is configured. In this embodiment, the heating resistance layer is formed on the AlN substrate having a thickness of 600 μm.

On the other hand, a thermistor (not shown) is arranged in contact with the heater 102 to monitor the temperature of the heater. The thermistor is pressed to the heater with a predetermined pressure by a pressing means such as a spring (not shown).

At both ends of the fixing film 100, film support members 105 are provided as restriction members for restricting the movement of the fixing film in the rotation axis direction and the circumferential shape.

The film supporting member 105 supports the stay 104 arranged inside the fixing film 100 and the pressure contact member 103 that presses and urges the fixing film 100 toward the pressure roller 101. The film support member 105 is made of a heat-resistant resin such as PPS, liquid crystal polymer, and phenol resin, and receives a pressure while supporting the edge surface of the fixing film 100.

The stay 104 is a member that receives a reaction force from the pressure roller 101, and is preferably made of a material that does not easily bend even when a high pressure is applied. In this embodiment, SUS304 is used.

The pressure contact member 103 is a nip forming member that fixedly supports the heating member 102. The pressure contact member 103 is a gutter type having a substantially semicircular cross section and is a heat insulating member such as a heat resistant resin having a longitudinal direction in the direction perpendicular to the cross section of the drawing. From the viewpoint of energy saving, it is desirable to use a material having a low heat conduction to the stay 104. For example, heat resistant glass or heat resistant resin such as liquid crystal polymer is used.

The lubricant (not shown) between the heating member 102 and the fixing film 100 is oil in this embodiment. As the oil, silicone oil or the like that can be used in a high temperature environment is preferable.

The fixing film 100 is loosely covered on the outside of the pressure contact member 103 and the heating member 102, and both ends thereof are supported by the film support member 105 so that the film support member 105 can move freely in the pressing direction. It is supported by a fixing frame 115 (not shown).

The pressure roller 101 is supported by a fixing frame 115 (not shown in FIG. 2) via pressure roller bearings 114 (not shown) provided at both ends.

The fixing film 100 is supported by a fixing frame 115 via a stay 104 and a film supporting member 105, and a pressing lever 112, which is also rotatably supported by the fixing frame 115, and a pressing roller 101 by a pressing spring 113. Is pressurized to. Specifically, the pressure lever pushes down the film support member 105, the film support member 105 pushes the stay 104, the stay 104 pushes the pressure contact member 103, and the fixing film 100 is sandwiched between the pressure contact member 103 and the pressure roller 101. By doing so, the fixing nip portion N is formed. In this embodiment, the applied pressure was 150 N on one end side and the total applied pressure was 300 N.

The internal restriction member 107 is a member that is fixed to the stay 104, stretches the fixing film 100 from the inside, and restricts the rotation trajectory of the fixing film 100 from the inside. From the viewpoint of energy saving, like the pressure contact member 103. It is desirable to use a material having a low heat conduction to the stay 104, for example, a heat resistant resin such as a liquid crystal polymer.

Next, in addition to FIG. 2, the internal regulating member 107 will be described in detail with reference to FIG. 3 showing a state of the inside of the fixing film 100 in a pressurized state as seen from the side.

The internal control member 107 is a member that stretches the fixing film 100 at least in the entire region where an image is formed on the medium (hereinafter referred to as an image region) in the longitudinal direction.

The contact length between the fixing film 100 and the internal regulating member 107 in the rotation direction of the fixing film 100 is set to be substantially the same at any position in the entire image area. It should be noted that, although strictly speaking, a minute gap may be generated between the two parts due to a very small recess of the fixing film 100 and the internal control member 107 or a variation in the size of the parts. Is considered to be in contact with a minute gap of the above level.

Thus, by setting the contact length of the fixing film 100 and the internal regulating member 107 to be the same at any position in the longitudinal direction, it is possible to prevent a temperature difference from occurring in the fixing film 100, It is possible to prevent uneven gloss in the longitudinal direction due to the temperature difference.

Further, the internal restricting member 107 restricts the rotation orbit of the fixing film 100 and applies tension to the fixing film 100 toward the upper left direction in FIG. 2, so that the S portion (hereinafter, referred to as the bent portion S) suddenly increases. I try to bend it. Normally, when a medium having unfixed toner on the fixing nip portion is passed, the fixing film 100 and the toner are stuck to each other due to the adhesive force of the toner melted in the fixing nip portion.

By forming the above-described bent portion S in the fixing film 100, when the medium passes through the bent portion S, the force of the medium to separate from the fixing film 100 becomes stronger, and the medium on which the toner is fixed becomes the fixing film. It becomes possible to peel efficiently from 100.

The height of the internal restriction member 107 in the pressing direction is preferably the same at any position in the longitudinal direction because the tension on the fixing film 100 is constant in the longitudinal direction.

However, when the height in the pressurizing direction is set to be the same at any position in the longitudinal direction in the non-pressurized state, the internal restricting member 107 is fixed to the stay 104, and therefore when the pressurizing is performed, Along with 104, bending occurs as the central portion projects with respect to the end portions.

In this embodiment, for example, when a stay 105 having a thickness of 2.2 mm is provided and a pressure force of 150 N (total 300 N) is applied to both ends, the stay 105 bends and the internal regulating member 107 also bends, In the direction opposite to the pressing direction, the center part is deformed so as to be 0.5 mm higher than the end part.

When the internal regulating member 107 is set so that the height in the pressing direction is constant at any position in the longitudinal direction in a non-pressurized state, the internal regulating member 107 may bend during an image forming operation. The central portion of the fixing film 100 is pushed down by 0.5 mm with respect to the end portions.

In such a case, when the fixing film 100 is set to have an appropriate rotation path at the end portion, the tension to the fixing film 100 becomes high at the center portion, and thus when the fixing film 100 travels. In addition, since the sliding resistance of the central portion is higher than that of the end portion, only the end portion advances, and the central portion is stopped, which causes the fixing film 100 to be twisted.

If the fixing film 100 is twisted, the fixing film 100 may be damaged depending on the situation.

Further, when the fixing film 100 is set such that the rotational trajectory of the fixing film 100 is appropriate in the central portion in the longitudinal direction, the internal regulating member 107 is retracted from the fixing film 100 at the longitudinal end portion, and the fixing film 100 is formed. The tension applied to it will be weaker than expected. As a result, the rotational trajectory of the fixing film 100 at the nip outlet cannot be sufficiently raised at the end in the longitudinal direction. If the rotation orbit of the fixing film 100 does not rise sufficiently at the end portion, proper separation performance cannot be obtained, and in some cases, the medium cannot be completely separated and is wound around the fixing film 100, or uneven gloss occurs. There is a fear.

Therefore, in the internal restriction member 107 in the present embodiment, in a non-pressurized state, as shown in FIGS. 4 and 5, in the direction opposite to the pressurizing direction F, the central portion is a substantially circular shape retracted from the end portion. It is set in an arc shape.

The shape of the internal regulation member 107 may be a curved shape that is set so as to cancel the flexure amount in accordance with the flexure amount distribution in the entire longitudinal direction of the internal regulation member 107 when pressurized.

Further, the difference Z in height between the longitudinal end portion and the central portion of the internal restriction member 107 in the direction opposite to the pressing direction F shown in FIG. 4 is an amount that absorbs the above-described bending during pressing. Desirably, in this embodiment, as an example, Z=0.5 mm is set in accordance with the bending amount of 0.5 mm described above.

With this setting, when pressure is applied at both ends to perform the fixing operation, the stay 104 and the internal regulating member 107 bend, and as a result, the internal regulating member 107 moves in the pressing direction F as shown in FIG. The height in the opposite direction can be made substantially the same at any position in the longitudinal direction.

Since the internal regulating member 107 is a member that applies tension to the fixing film 100 as described above, if the heights in the direction opposite to the pressing direction F are the same, fixing is performed at any position in the longitudinal direction. The tension applied to the film 100 can be the same.

With the above configuration, it is possible to set the tension applied to the fixing film 100 by the internal regulating member 107 during the fixing operation to be not excessive or insufficient, and prevent the fixing film 100 from being damaged and satisfy the proper separation performance. can do.

In addition, in the present exemplary embodiment, the configuration in which one internal regulating member 107 is arranged at the position on the upstream side in the rotation direction of the fixing film 100 with respect to the fixing nip portion N has been described. The present invention is not limited to this, and a configuration in which a plurality of internal regulating members 107 are arranged, such as one on the upstream side in the rotation direction of the fixing film 100 and one on the downstream side, as long as the function is satisfied, The internal regulating member 107 may be arranged so as to cover the entire opposite side of the fixing nip N.

[Example 2]
In this embodiment, as shown in FIGS. 6 and 7, in the non-pressurized state, in the non-pressurized state, the central portion in the longitudinal direction is stepwise with respect to the end in the direction opposite to the pressurizing direction F. It is a retracted shape.

It is desirable that the difference Z in height between the end portion and the central portion of the internal restriction member 107 in the direction opposite to the pressing direction F is an amount that absorbs the bending at the time of pressing, as in the first embodiment. In the example, as an example, Z=0.5 mm is set in accordance with the bending amount of 0.5 mm described above.

Although the height and width of the step are not uniquely limited, in this embodiment, the height of one step is 0.05 mm, and the height and width are set to be 21 divisions in the longitudinal direction.

When pressure is applied at both ends to perform the fixing operation, the stay 104 and the internal restricting member 107 are bent, and as a result, as shown in FIG. The same can also be applied to.

40 fixing device, 100 fixing film, 101 pressure roller,
105 film support member, 107 internal control member, 108 separation guide,
N nip part, S bent part

Claims (4)

A rotatable endless belt-shaped film member 100,
A pressure member 101 that is disposed to face the outer peripheral surface of the film member 100 and rotates to form a fixing nip portion N with the film member 100;
A heating source 102 disposed inside the film member 100 for heating the film member 100;
A pressure contact member 103 that is disposed inside the film member 100, supports the heating source 102, and sandwiches the film member 100 with the pressure member 101 to form a nip portion N;
A film support member 105 disposed at both ends of the film member 100 in the rotation axis direction for restricting rotation and position at both ends of the film member 100;
A stay 104 which receives a pressing force and pushes down the pressing member 103 toward the pressing member 101 to form a nip;
An internal restricting member 107 attached to the stay 104 and applying tension to the film member 100 from the inside in at least the entire region through which the image passes in the longitudinal direction;
In the fixing device including
The fixing device is characterized in that, in the non-pressurized state, the internal restricting member 107 has a shape in which the center portion is retracted from the film member 100 with respect to the end portion in the pressing direction. The internal control member 107 has an arc shape smoothly connected so that the internal control member 107 gradually retracts in a direction opposite to the pressurizing direction from the end in the longitudinal direction toward the center. The fixing device described. The internal restriction member 107 has a step-like shape that gradually retracts in a direction opposite to the pressing direction by a minute step shape as it approaches the central portion from the end portion in the longitudinal direction. The fixing device according to 1. The difference in height between the central portion and the end portion in the longitudinal direction in the direction opposite to the pressing direction of the internal restriction member 107 is such that the amount of bending of the internal restriction member 107 during pressurization is canceled out. The fixing device according to claim 2 or 3.