JP2000147932A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance safety of a fixing device by preventing better the scattering of sparks, not only in a direction being away from a rotary shaft but also in the rotary shaft direction. SOLUTION: This device is equipped with a heating roller 310, where a heating resistor layer 314 is provided on the inner peripheral surface of a core bar through an insulating layer and an electrode member 39 for energizing in contact with the layer 314 is fixed at both ends, and a slide rubbing electrode which feeds power to the member 30. In this case, the device has a holding member (holder 43), integrally equipped with a protection part 43C for hermetically sealing the end side of the roller 310 from a bonding part M, where the member 39 and the layer 314 come in contact with each other, and a holding part 43E for holding the slide rubbing electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used for a copying machine, a printer, a facsimile, etc. of an electrostatic recording system for thermally fixing a toner image.

[0002]

2. Description of the Related Art As a heating roller used for a fixing device in an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile, etc., a metal pipe is provided with an insulating layer made of an organic resin such as polyimide on an outer peripheral surface or an inner peripheral surface thereof. There is known a heating roller having a structure in which a heating resistor layer is provided, a release layer is provided on the surface of the metal pipe, and an electrode member is joined to an end of the heating resistor layer. Since such a heating roller directly heats a metal pipe, it has advantages such as low heat loss, excellent temperature rise, and low power consumption.

However, during long periods of use while repeatedly generating and stopping heat generation, the insulating layer is damaged, the metal pipe is energized, and the damage is caused by the joint between the end and the electrode member. Progress gradually toward.
When the insulating layer is damaged at the joint between the metal pipe and the electrode member, there has been known a problem that the metal pipe and the electrode member are short-circuited, a large current flows, the metal is melted, and sparks are scattered.

Japanese Patent Application Laid-Open No. Hei 10-20693 discloses a fixing heating roller in which a heating resistor layer is provided on the surface of a metal pipe via an insulating layer, and electrode members are joined to both ends of the heating resistor layer. A fixing heating roller provided with a protective member so as to cover the outer periphery of the joint between the heating resistor layer and the electrode member has been proposed. Even if a spark occurs, the protective member prevents the scattering of the spark. It states that it is possible to prevent fire and electric leakage before the power fuse blows.

However, according to the technique described in Japanese Patent Application Laid-Open No. H10-20693, although the scattering of sparks in the direction away from the rotating shaft can be prevented, the scattering of sparks in the direction of the rotating shaft of the heating roller cannot be prevented. It is known to use a cover that covers the rotation axis direction.

[0006]

Even if a cover is separately provided for the protection member in the direction of the rotation axis, a gap is formed between the protection member and the cover, and sparks scatter from the gap. . Since both ends of the heating roller are portions where the electrode members, bearings and the like are densely packed, it is difficult to fill the gap. Then, there is a problem that a spark may jump out of the gap and ignite a combustible material such as recording paper.

SUMMARY OF THE INVENTION Accordingly, it is a first object of the present invention to prevent sparks not only in the direction away from the rotation axis but also in the direction of the rotation axis and to improve the safety of the fixing device.

In addition, there is a demand that the size of the heating roller should be reduced as much as possible by cutting off the portion exceeding the size of the recording paper as much as possible. However, if a new protective member is provided, a portion that comes into contact with the recording paper or a bearing is avoided, so that the structure of the heating roller increases in the direction of the rotating shaft, which complicates the structure and increases the size of the fixing device. There is a problem.

Accordingly, it is a second object of the present invention to prevent sparks from scattering in a direction away from the rotation axis and to avoid an increase in the size of the fixing device.

[0010]

SUMMARY OF THE INVENTION The object of the present invention is as set forth in claim 1.
Can be solved. That is, the fixing device according to claim 1, wherein a heating resistor layer is provided on the inner peripheral surface of the metal core via an insulating layer, and an electrode member that is in contact with the heating resistor layer and is energized at both ends is fixed. In a fixing device including a roller and a rubbing electrode for supplying power to the electrode member, a protection unit that seals an end side of the heating roller with respect to a joining portion where the electrode member and the heating resistor layer are in contact with each other. And a holding member integrally provided with a holding portion for holding the rubbing electrode.

According to the fixing device of the first aspect, the first object of the present invention can be achieved. That is, since the fixing device according to claim 1 includes the holding member in which the protection unit and the holding unit are integrated, the scattering of the spark not only in the direction away from the rotation axis but also in the rotation axis direction is better prevented. In addition, the safety of the fixing device can be improved.

The object of the present invention can be solved by the fixing device according to the third aspect. In other words, in the fixing device according to the third aspect, a heating resistor layer is provided on the inner peripheral surface of the metal core with an insulating layer interposed therebetween, and an electrode member that is in contact with the heating resistor layer and is energized at both ends is fixed. In a fixing device including a roller and a rubbing electrode for supplying power to the electrode member, a protection unit that seals an end side of the heating roller with respect to a joining portion where the electrode member and the heating resistor layer are in contact with each other. And a holding member having a bearing member integrally provided with a holding portion for holding the sliding electrode and a bearing portion for receiving the outer peripheral surface of the heating roller.

According to the fixing device of the third aspect, it is possible to achieve the second object in addition to the first object of the present invention. That is, since the fixing device according to claim 3 includes a bearing member integrally including the protection unit, the holding unit, and the bearing unit, sparks not only in the direction away from the rotating shaft but also in the rotating shaft direction. Scattering was also better prevented, and the safety of the fixing device was improved, and an increase in the size of the fixing device could be avoided.

The object of the present invention can be solved by a fixing device according to the present invention. That is, the fixing device according to claim 5, wherein a heating resistor layer is provided on the inner peripheral surface of the metal core with an insulating layer interposed therebetween, and an electrode member which is in contact with the heating resistor layer and is energized at both ends is fixed. In a fixing device having a roller, the fixing device includes a bearing member integrally provided with a protection portion corresponding to the electrode member and covering the outer peripheral surface of the heating roller, and a bearing portion sliding on the outer peripheral surface of the heating roller. And

According to the fixing device of the fifth aspect, the second object of the present invention can be achieved. That is, since the fixing device according to the fifth aspect has a bearing member integrally provided with the protection portion and the bearing portion, it is possible to prevent the scattering of sparks in a direction away from the rotating shaft and to reduce the size of the fixing device. The increase could be avoided.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a front sectional view for explaining an entire image forming apparatus provided with a fixing device of the present invention. An example of a copying machine will be described as an image forming apparatus.

Referring to FIG. 1, a copying machine 101 stores a recording paper P in a main body thereof and has a paper feed roller 1 having a double feed prevention mechanism.
At 06, the recording paper P used for the image forming operation is carried into the paper feeding unit 109 one by one. The paper feeding unit 109 is disposed immediately before the image forming unit 1 and includes a loop roller 110 and a registration roller 111.

On the other hand, in the image forming section 1, the photosensitive drum 2
Is rotated in the direction of arrow A, a uniform potential is applied by the charging electrode 3, and the scanner unit 112 acquires digital data corresponding to an original (not shown) on the original mounting glass 113 to perform image processing. The scanning exposure unit 114 irradiates the surface of the rotating photosensitive drum 2 based on the digital data subjected to the image processing, and forms an electrostatic latent image corresponding to the document. Next, the electrostatic latent image is visualized by the developing unit 5, and a toner image is developed on the surface of the photosensitive drum 2.

The registration roller 111 is driven in synchronization with the rotation of the photosensitive drum 2, and the recording paper P is sent to the transfer electrode 7. The toner image formed on the photosensitive drum 2 is transferred to the recording paper P sent to the transfer electrode 7, and thereafter, the recording paper P is separated from the photosensitive drum 2 by the separation electrode 8 and the separation claw 9. The transport unit 117 transports the sheet to the fixing unit 300 which is an example of the fixing device of the present invention. A cleaning unit 11 disposed on the downstream side in the rotation direction of the photosensitive drum 2 with respect to the separation claw 9 cleans the surface of the photosensitive drum 2 after the transfer to remove foreign matters, residual toner, and the like. When the residual toner is removed, the charging electrode 3 charges the surface of the photosensitive drum 2 again in preparation for the next image forming operation.

In the fixing unit 300, the recording paper P is heated and pressed to fix the toner image. The fixing unit 300 includes a heating roller 310 and the heating roller 31.
And a pressure roller 320 that is pressed against zero. The heating roller 310 is controlled so as to generate heat stably at a set temperature, and is controlled so as to convey the recording paper P at a predetermined speed while sandwiching the heating roller 310 with the pressure roller 320.
By appropriately selecting the conveyance speed of the recording paper P and the temperature of the heat generated by the heating roller 310, the toner image is satisfactorily heat-fixed to the recording paper P.

In the case of one-sided copying, the recording paper P on which the toner image has been fixed is nipped by transport rollers 119 and sent to a paper discharge tray 123. In the case of double-sided copying, the recording paper P on which the toner image has been fixed is sent to the stacker 120 via the escaping conveyance path 121 by the conveyance rollers 119 and temporarily evacuated. The recording paper P temporarily evacuated into the stacker 120 is sent out again, carried into the paper feeding unit 109 via the horizontal transport path 122, and the toner image is transferred and fixed again.

FIG. 2A is a front sectional view of the heating roller 310 and the pressure roller 320, and FIG.
10 is a side sectional view of FIG.

The heating roller 310 is a cylindrical base (core metal) 31 made of a conductive member made of a metal such as an aluminum alloy.
2, an insulating layer 313 is provided on the inner surface side, and a heating resistor layer 314 is provided on the inner surface side of the insulating layer 313. A disk-shaped electrode member 39 is inserted from both ends of the heating roller 310,
In the vicinity of both ends of the heating roller 310 in the roller axis direction, the heating roller 310 is fixed to and electrically connected to the heating resistor layer 314 with a conductive adhesive (not shown). The releasable layer 311 is a layer coated with a fluorine resin that covers the surface of the base 312, and makes it difficult for toner melted by heating to adhere to the heating roller 310.

The joining portion M is a portion where the electrode member 39 and the heating resistor layer 314 are joined to each other.
This corresponds to the range cut out between planes Y1 and Y2 perpendicular to the rotation axis of heating roller 310. However, the plane Y1 passes through the contact at the left end in the drawing with respect to the rotation axis direction between the electrode member 39 and the heating resistor layer 314, and the plane Y2 shows the rotation axis direction between the electrode member 39 and the heating resistor layer 314. Pass through the middle right contact. Then, a short circuit between the electrode member 39 and the base 312 is likely to occur at the joint M.

The insulating layer 313 is formed so as to cover the entire inner peripheral surface of the base 312. On the other hand, the heating resistor layer 314 is formed on the outer side of the heating roller 310 with respect to the electrode member 39 in the axial direction. Not provided.

In the present embodiment, the material of the base 312 is an aluminum alloy, the material of the insulating layer 313 is a heat-resistant insulating resin such as polyimide, and has a thickness of 30 to 60 μm.
The material of the material 14 is a low melting point glass containing a conductive filler, and the material of the release layer 311 is a resin having good releasability such as PFA (tetrafluoroethylene / perfluoroalkylvinyl ether copolymer), and tetrafluoroethylene. good.

The method of forming each of the releasable layer 311, the insulating layer 313, and the heat generating resistor layer 314 includes crushing, coating, coating, vapor deposition, bonding and the like. Here, “drowning” refers to a method in which an object is dropped into a tank containing a liquid material, and then the liquid material is applied to the surface of the object by lifting the object.

The pressure roller 320 has a silicon rubber layer 321 on the surface, and a release layer (not shown) on the surface of the silicon rubber layer 321 by the above-mentioned PFA tube using PFA.
Is provided. The silicone rubber layer 321 and the release layer are deformed following the surface shape of the heating roller 310 at the contact portion with the heating roller 310. When the recording paper P on which the toner image has been transferred passes between the contact portions, the heating roller 31
The toner is heated and melted by the heat generated by 0, and the toner image is thermally fixed on the recording paper P.

Next, a first example of the fixing unit 300 will be described with reference to a sectional view of an essential part showing one end of a heating roller 310 in FIG.

In FIG. 3, the outer peripheral portion of the power supply brush 42 slides on the first inner wall surface 43 A of the holder 43 and
Are guided so as to be movable in the axial direction. The holder 43 is fixed to the side plate 40B by screwing (not shown). Rear wall 43B of holder 43 and rear end 42 of power supply brush 42
A pressing spring 45 is interposed between B and B. The pressing spring 45 presses the power supply brush 42 to press the power supply brush 42 against the contact surface 39 </ b> A of the electrode member 39. In this crimped state, the contact surface portion 39A is rotatably slidably in contact with the distal end portion 42A of the power supply brush 42.

One end of a lead wire 46 is fixed to a part of the power supply brush 42. The other end of the lead wire 46 is connected to a power supply terminal 47. The power supply terminal 47 is connected to a power supply via wiring means (not shown).

The power supplied from the power supply is supplied to a power supply terminal 47.
And is conducted from the lead wire 46 to the power supply brush 42, and is conducted from the electrode member 39 in the heating and rotating heating roller 310 to the heating resistor layer 314. FIG. 3 shows the heating roller 3
Although only one end of 10 is shown, the other end (not shown) has the same configuration, and forms an electric path from the power supply terminal 47 (not shown) at the other end to a power supply (not shown). Heat is generated in the heating resistor layer 314 by energizing the electric circuit.

The holding section 43E is a part of the holder 43 and holds the power supply brush 42. The holding unit 43E is
Opening 310A of heating roller 310 (see FIG. 2B)
Is covered.

The outer peripheral surface of the heating roller 310 is
Is rotatably supported by a heat-insulating bearing member 51 fixed to the shaft. The metal E-ring 64 is fixed so as to tighten the outer peripheral surface of the heating roller 310 by its elastic force, and serves as a thrust bearing of the heating roller 310. The bearing member 51 is a sliding bearing having the heating roller 310 itself as a rotation axis, and slides on the surface of the heating roller 310.

The holder 43 integrally has a protection portion 43C. The protection portion 43C slidably contacts the outer peripheral surface of the heating roller 310 on the second inner wall surface 43D. The second inner wall surface 43D is in contact with the outer peripheral surface of the heating roller 310 inside the joint M. With the protection unit 43C and the holding unit 43E,
The heating roller 310 is hermetically sealed on the end side from the joining portion M. Here, it is assumed that the joining portion M is included on the end side.

As described above, the holder 43 is a holding member of the present invention and also serves as a protection portion of the present invention. If the base 312 and the electrode member 39 are short-circuited, sparks (first spark group) scattered from the outer peripheral surface of the heating roller 310 further away from the rotation axis and scatter in a direction substantially parallel to the rotation axis. Sparks (the second group of sparks) is a problem.

The holder 43 includes a protection section 43C and a holding section 43.
E, the heating roller 310 is located closer to the end than the joint M.
, The scattering of the first spark group and the scattering of the second spark group from the opening 310A (see FIG. 2B) can be prevented at the same time.

Incidentally, the protection portion 43C may be brought into contact so as to cover the outer peripheral surface of the heating roller 310 corresponding to the joining portion M.

Next, a second example of the fixing unit 300 will be described with reference to FIG.

In FIG. 4, the outer peripheral portion of the power supply brush 42 slides on the first inner wall surface 53 A of the holder 53 so that the heating roller 310
Are guided so as to be movable in the axial direction. The holder 53 is fixed to the side plate 40A by screwing (not shown). Rear wall 53B of holder 53 and rear end 42 of power supply brush 42
A pressing spring 45 is interposed between B and B. The pressing spring 45 presses the power supply brush 42 to press the power supply brush 42 against the contact surface 39 </ b> A of the electrode member 39. In this crimped state, the contact surface portion 39A is rotatably slidably in contact with the distal end portion 42A of the power supply brush 42.

One end of a lead wire 46 is fixed to a part of the power supply brush 42. The other end of the lead wire 46 is connected to a power supply terminal 47. The power supply terminal 47 is connected to a power supply via wiring means (not shown).

The power supplied from the power supply is supplied to the power supply terminal 47.
And is conducted from the lead wire 46 to the power supply brush 42, and is conducted from the electrode member 39 in the heating and rotating heating roller 310 to the heating resistor layer 314. FIG. 4 shows the heating roller 3
Although only one end of 10 is shown, the other end (not shown) has the same configuration, and forms an electric path from the power supply terminal 47 (not shown) at the other end to a power supply (not shown). Heat is generated in the heating resistor layer 314 by energizing the electric circuit.

The holder 53 is a holding member for holding the power supply brush 42, and has an opening 310A of the heating roller 310.
(See FIG. 2B). Further, the holder 53 is extended in both the rotation axis direction of the heating roller 310 than the joint M described with reference to FIG. 2 and integrally includes a protective portion 53C that covers the outer peripheral surface of the heating roller 310 corresponding to the joint M. Are prepared. The second inner wall surface 53D of the holder 53, which is a part of the protection portion 53C, is slidably in contact with the outer peripheral surface of the heating roller 310.

The outer peripheral surface of the heating roller 310 is
Are rotatably supported by a bearing portion 53E which forms a part of. The bearing 53E is a sliding bearing having the heating roller 310 itself as a rotation axis, and slides on the surface of the heating roller 310.

The second bearing 5 constituting a part of the holder 53
3F has some play between the heating roller 310 and the end of the heating roller 310 forming the opening 310A (see FIG. 2B), thereby preventing the heating roller 310 from being displaced in the rotation axis direction.

As described above, the holder 53 is the holding member of the present invention and also serves as the bearing portion of the present invention and the protection portion of the present invention. If the base 312 and the electrode member 39 are short-circuited, sparks (first spark group) scattered from the outer peripheral surface of the heating roller 310 further away from the rotation axis and scatter in a direction substantially parallel to the rotation axis. Sparks (the second group of sparks) is a problem. The protection unit 53C
Since it is slidably in contact with the outer peripheral surface of the heating roller 310 so as to cover all the joints M, it is possible to prevent the first group of sparks from scattering and prevent the opening 310A (see FIG. 2B). ), It is possible to prevent the aforementioned second spark group from scattering. Further, since it also serves as a bearing, it is possible to prevent the dimension of the fixing unit 300 of the heating roller 310 from increasing in the rotation axis direction.

The holder 53 also serves as the bearing 53E and the second bearing 53F, and serves as a radial bearing and a thrust bearing, respectively. As described above, the thrust bearing and the radial bearing may be formed as an integral structure, or one of the thrust bearing and the radial bearing may serve as the holding member and the protection portion.

Further, since the protective portion 53C is in contact with the outer peripheral surface of the heating roller 310 corresponding to the joint M, the rotating shaft of the heating roller 310 is stabilized.

Next, a third example of the fixing unit 300 will be described.
This will be described with reference to a cross-sectional view of a main part showing one end of the heating roller 310 in FIG.

In FIG. 5, the outer peripheral portion of the power supply brush 42 slides on the inner surface 63A of the holder 63 and is guided so as to be movable in the axial direction of the heating roller 310. The holder 63 includes a side plate 40B.
Are fixed by screws (not shown). The cover member 62 is positioned and fixed to the holder 63. Rear wall 63B of holder 63 and rear end 42B of power supply brush 42
, A pressing spring 45 is interposed. The pressing spring 45 presses the power supply brush 42 to press the power supply brush 42 against the contact surface 39 </ b> A of the electrode member 39. In this crimped state, the contact surface portion 39A is rotatably slidably in contact with the distal end portion 42A of the power supply brush 42.

One end of a lead wire 46 is fixed to a part of the power supply brush 42. The other end of the lead wire 46 is connected to a power supply terminal 47. The power supply terminal 47 is connected to a power supply via wiring means (not shown).

The power supplied from the power supply is supplied to the power supply terminal 47.
And is conducted from the lead wire 46 to the power supply brush 42, and is conducted from the electrode member 39 in the heating and rotating heating roller 310 to the heating resistor layer 314. FIG. 5 shows the heating roller 3
Although only one end of 10 is shown, the other end (not shown) has the same configuration, and forms an electric path from the power supply terminal 47 (not shown) at the other end to a power supply (not shown). Heat is generated in the heating resistor layer 314 by energizing the electric circuit.

The outer peripheral surface of the heating roller 310 is
Is rotatably supported by a heat-insulating bearing member 61 fixed by screws (not shown). The bearing member 61 is a sliding bearing having the heating roller 310 itself as a rotation axis, and slides on the surface of the heating roller 310 by its inner peripheral surface 61B.
The metal E-ring 64 is fixed so as to tighten the outer peripheral surface of the heating roller 310 by its elastic force, and serves as a thrust bearing of the heating roller 310. The bearing member 61 is extended in both directions of the rotation axis of the heating roller 310 beyond the joint M described with reference to FIG. 2, and integrally includes a protection portion 61A that covers the outer peripheral surface of the heating roller 310 corresponding to the joint M. In preparation. If the base 312 and the electrode member 39 are short-circuited, sparks that scatter from the outer peripheral surface of the heating roller 310 further away from the rotation axis pose a problem. Since the protection portion 61A is in contact with the outer peripheral surface of the heating roller 310 so as to completely cover the joining portion M, it is possible to prevent the above-mentioned problem of scattering of sparks. In addition, since the bearing member 61 also functions as the protection unit of the present invention, it is possible to prevent the size of the fixing unit 300 of the heating roller 310 from increasing in the rotation axis direction.

In each of the embodiments described above, the bearing member and the holder are made of polyamide (PA), polyimide (PI),
It is preferable to use a resin having good insulation properties and heat resistance, such as polyamide imide (PAI) and polyphenylsulfide (PPS), and having good slidability (slippery). Further, any material other than the above-mentioned resins may be used as long as the insulating property, heat resistance and slidability are good.

[0056]

According to the fixing device of the present invention, it is possible to prevent the spark from scattering not only in the direction away from the rotating shaft but also in the rotating shaft direction, and to enhance the safety of the fixing device. did it.

According to the fixing device of the third aspect, the safety of the fixing device can be improved by preventing the scattering of the spark not only in the direction away from the rotation axis but also in the direction of the rotation axis. Further, an increase in the size of the fixing device could be avoided.

According to the fixing device of the fifth aspect, it is possible to prevent the spark from scattering in the direction away from the rotating shaft, to enhance the safety of the fixing device, and to avoid an increase in the size of the fixing device. did it.

[Brief description of the drawings]

FIG. 1 is a front sectional view illustrating an entire image forming apparatus including a fixing device of the present invention.

FIG. 2 is a front sectional view of a heating roller 310 and a pressure roller 320 and a side sectional view of the heating roller 310.

FIG. 3 is a cross-sectional view of a main part illustrating a first example of a fixing unit 300.

FIG. 4 is a cross-sectional view of a main part illustrating a second example of the fixing unit 300.

FIG. 5 is a cross-sectional view of a main part illustrating a first example of the fixing unit 300.

[Explanation of symbols]

 300 Fixing unit 310 Heating roller 312 Base 313 Insulating layer 314 Heating resistor layer 320 Pressing roller 39 Electrode member 43C, 53C, 61A Protecting part 42 Power supply brush 43, 53, 63 Holder 43E Holding part 51, 61 Bearing member 53E Bearing part M joint

Claims (5)

[Claims] 1. A heating roller having a heating resistor layer provided on an inner peripheral surface of a metal core with an insulating layer interposed therebetween, and an electrode member which is in contact with the heating resistor layer and which is energized is fixed at both ends; In a fixing device provided with a rubbing electrode for supplying power, a protecting portion that seals an end side of the heating roller from a joining portion where the electrode member and the heating resistor layer are in contact with each other; A fixing device comprising a holding member integrally provided with a holding unit for holding. 2. The fixing device according to claim 1, wherein the protection portion contacts an outer peripheral surface of the heating roller corresponding to the bonding portion. 3. A heating roller in which a heating resistor layer is provided on an inner peripheral surface of a metal core via an insulating layer, and an electrode member which is in contact with the heating resistor layer and is energized is fixed at both ends, In a fixing device provided with a rubbing electrode for supplying power, a protecting portion that seals an end side of the heating roller from a joining portion where the electrode member and the heating resistor layer are in contact with each other; A fixing device comprising: a holding member having a bearing member integrally provided with a holding portion for holding and a bearing portion for receiving an outer peripheral surface of the heating roller. 4. The fixing device according to claim 3, wherein the protection portion contacts an outer peripheral surface of the heating roller corresponding to the bonding portion. 5. A fixing device comprising a heating roller having a heating resistor layer provided on an inner peripheral surface of a metal core with an insulating layer interposed therebetween, and an electrode member which is in contact with the heating resistor layer and is energized at both ends. And a bearing member integrally provided with a protection portion for covering an outer peripheral surface of the heating roller corresponding to the electrode member, and a bearing portion sliding on the outer peripheral surface of the heating roller.