JP2593665Y2 - Heat roller power supply structure - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat roller for use in a fixing device provided for fixing a toner image transferred on a recording paper in an electrostatic recording system device such as a copying machine, a facsimile, a printer and the like. More specifically, the present invention relates to a heat roller with a modified power supply method.

[0002]

2. Description of the Related Art In an electrostatic recording system such as a copying machine, a facsimile, a printer, or the like, a toner image transferred from a photosensitive drum of a developing device onto a recording paper is formed by wrapping toner particles on fibers of the recording paper. It is necessary to fix the recording paper by heat. As shown in FIG. 11, the fixing device includes a heat roller A having a heat source and a pressing roller B having a surface coated with a heat-resistant resin.
The toner is fixed by passing the recording paper C on which the toner image has been transferred between the pressing roller B and the pressing roller B.

The most common type of heat roller is an indirect heating type in which a heat source such as an infrared lamp or a halogen lamp is provided at an axial position of a metal pipe having good heat conduction, but this indirect heating type is expensive. In addition to the need for a thin tubular lamp, a thick metal pipe with a smooth surface with high precision is also required as a metal pipe, which is extremely expensive, and requires a long time to raise the temperature due to indirect heating. There's a problem. In order to solve such a problem, a direct heating type has recently become widespread instead of an indirect heating type.

In the direct heating type, a cylindrical body (hereinafter referred to as a "cerapipe") entirely formed of conductive ceramics is rotatably supported by rolling bearings (bearings). Are known to transmit and supply electric power. In the heat roller having such a structure, the point is how to devise the power supply method and the driving force transmission method.

There are various power supply methods.
For example, in the method of supplying power to both ends of the ceramic pipe via the rolling bearing as described above, electricity is performed through steel balls interposed between an outer ring and an inner ring constituting the rolling bearing. Since the contact with the inner ring is not always perfect, there has been a problem of poor contact, and sparks have also been generated.

[0006] In order to solve such a problem, the present inventors have proposed:
In Japanese Utility Model Application No. 3-26704, a new power supply method was proposed. In this method, as shown in FIG. 12, a soft conductive metal b
Is coated by means such as vapor deposition, plating, or coating, and a conductive terminal c made of a metal material that elastically expands and contracts in the radial direction is closely fitted in the hollow portion.

[0007]

According to this method, the contact between the conductive terminal and the conductivity of the inner surface of the end portion of the ceramic pipe is extremely good, and the occurrence of poor contact can be extremely reduced. In some cases, the pressure applied by the member is insufficient, and in particular, the elastic restoring force of the elastic expansion / contraction member decreases during a long-term use process. It is expected that sparks will occur between the contact points with the coating. In particular, when the conductive film is an aluminum vapor-deposited film or the like, there is a concern that the vapor-deposited film evaporates due to sparks and becomes unable to conduct. When such a situation occurs, there is no other way but to replace the conductive terminal.

Further, since the power supply structure only serves to supply power to the ceramic pipe, a mechanism for rotating the ceramic pipe is separately required. As this rotation drive mechanism,
For example, there is one proposed by the present inventor in the application. As shown in FIG. 13, a shaft portion d having a smaller diameter than the main body portion is formed at both ends of the ceramic pipe a, and a fitting portion e having an irregular cross section represented by a D-cut is formed on one shaft portion. By connecting a coupling body or an annular gear having an inner surface shape or an outer surface shape corresponding to the fitting portion to the fitting portion e,
This is for transmitting a rotational force to the ceramic pipe a.

However, according to this method, it is necessary to provide a deformed fitting portion with the main body at the end of the sera pipe, so that there is a problem that the number of processing steps is large and the cost is high.
In addition, it is difficult to form a fitting portion having an irregular cross-section by cutting or grinding when the ceramic pipe is thin in such a method, and even if the processing can be performed, cracking or chipping occurs during processing or use. May occur.

The present invention has been made in view of such a situation, and maintains a good contact state by maintaining a sufficient pressing force for a long period of time, and can appropriately increase the pressure when the pressing force decreases. The present invention proposes an expanding / contracting member that can always secure an appropriate pressing force. Further, by using this expanding / contracting member, it is possible to completely eliminate the occurrence of poor contact,
It is an object of the present invention to propose a power supply structure capable of maintaining a good power supply state for a long time. Also, by ensuring the pressure contact state of the expanding / contracting member against the inner surface of the end of the sera pipe, the expanding / contracting member can also be used as a member for holding the rotation driving mechanism of the sera pipe, and the sera pipe is provided with an irregular cross section. In other words, the present invention proposes a power supply structure that enables the rotational driving of the ceramic pipe while basically maintaining the external shape of the ceramic pipe formed by extrusion molding.

[0011]

Means for Solving the Problems In order to solve the above problems, the present inventors have made intensive studies and as a result, they can forcibly expand and contract by rotating the screw, and appropriately adjust the width of expansion and contraction according to the amount of rotation of the screw. It is possible to solve the above-mentioned problem by preparing a forcible expansion / contraction member that can be inserted, inserting the forcible expansion / contraction member into the inner surface of the end of the ceramic pipe, and forcibly pressing the conductive coating portion on the inner surface of the end from the inner surface. The idea was completed to complete the present invention.

The power supply structure of the heat roller of the present invention based on such an idea is rotatably supported, and means for depositing, plating, or coating a soft conductive metal on a part or all of the inner surfaces of the hollow portions at both ends. An electrically conductive ceramic pipe covered by the above, and a shaft rod is laid across the opposing portions of a deformable frame made of a metal plate, and one contact portion of the frame and the shaft is connected to the shaft. While restricting movement in the longitudinal direction, the other contact part is screwed into the threaded part of the shaft,
A forced expansion / contraction member configured to rotate the shaft rod to expand and contract the distance between the opposing portions of the frame through which the shaft rod penetrates, thereby causing the other portion to expand and contract in the opposite direction. With the shaft inserted into the hollow part at the end of the ceramic pipe, the shaft is rotated to expand and deform the frame body radially outward, and the frame body is pressed against the metal coating on the inner peripheral surface of the conductive ceramic pipe. It is characterized in that power is supplied through the shaft of the forcible expansion / contraction member in contact therewith.

From the viewpoint of further improving the adhesion to the conductive film, it is preferable to use an elastically deformable frame as the frame of the forcibly expanding and contracting member.

[0014] Further, a flange having a partially formed engaging portion is provided at an end portion of the shaft of the forcibly expanding / contracting member, and this engaging portion is engaged with a proper position of an annular gear externally fitted on the outer periphery of the end of the ceramic pipe. Let me
By prohibiting the relative rotation of the annular gear with respect to the sera pipe and indirectly fixing the annular gear and the sera pipe via a forced expansion / contraction member, the shape of the sera pipe obtained by extrusion molding without providing a deformed cross section at the end of the sera pipe. The rotational driving force can be transmitted to the ceramic pipe while basically maintaining it.

The outer surface of the frame and the metal coating on the inner surface of the end of the ceramic pipe may be in point contact or line contact. However, from the viewpoint of reliably transmitting the rotational driving force acting on the annular gear by the ceramic pipe, the outer surface of the frame is It is preferable to make surface contact with the metal coating.

The method of externally supplying power to the shaft rod is arbitrary. For example, a cylindrical head projecting outward from the end face of the ceramic pipe is provided at one end of the shaft rod penetrating the frame. If a configuration is used in which the cylindrical head is used as a conductive terminal for contacting the power supply brush, power supply becomes easy.

[0017]

In order to assemble the heat roller having such a configuration, the forcible expansion / contraction members are inserted into the hollow portions at both ends of the ceramic pipe having the conductive coating formed on the inner surfaces of both ends, and then the shaft is rotated to move the frame body to the first position. It is expanded radially outward in the hollow portion, and its outer surface is adjusted so as to come into contact with the conductive coating on the inner surface of the end portion of the ceramic pipe with an appropriate pressing force. Next, after the forcibly expanding / contracting member rotatably supports the cera pipe attached to both ends via bearings, a mechanism for rotationally driving the cera pipe is related to the cera pipe, and further, with respect to the shaft of the forcibly expanding / contracting member. Attach members and supply wires to supply external power. In some cases, the order of insertion of the forcibly expanding / contracting member into the hollow portion of the end of the sera pipe, support of the sera pipe by bearings, and association of the rotary drive mechanism may be reversed.

In the assembled heat roller, since the outer surface of the frame of the forcibly expanding and contracting member is in contact with the conductive coating on the inner surface of the end portion of the ceramic pipe in a pressurized state, the electric power supplied from the shaft of the forcibly expanding and contracting member is not contacted. It can be performed reliably without causing defects or the like. Further, when the pressing force is reduced during a long-term use process, the contact state of the frame with the conductive coating can be adjusted by rotating the shaft rod.

When an elastically deformable frame is used as the frame of the forced expansion member, after the outer surface of the frame of the forced expansion member comes into contact with the surface of the ceramic pipe, the shaft is rotated to further apply the inner peripheral surface of the end of the ceramic pipe. When pressed, the frame body is elastically deformed, and the contact with the conductive film becomes closer.

When the engaging portion of the flange provided at the shaft end of the forcibly expanding / contracting member is engaged with the annular gear, the ceramic pipe and the annular gear are connected via the forcibly expanding / contracting member. The rotational force applied to the ring gear is transmitted to the sera pipe. In this case, the shape of the end of the sera pipe to which the annular gear is fitted may be the same outer diameter as the other part of the sera pipe,
There is no need for a specially shaped cross-section for fitting.

Further, when the outer surface of the frame and the conductive film are brought into surface contact with each other, since they are in contact over a wide range, electrical conduction is ensured, and at the same time, rotational driving force can be transmitted reliably.

When a substantially cylindrical conductive terminal is extended at one end of the shaft rod, power can be supplied to the ceramic pipe by receiving the conductive terminal with a power supply brush.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. FIG. 1 is an explanatory view of an essential part end face showing a typical embodiment of the present invention, and FIG. 2 is a side view of the embodiment. The heat roller of the present invention includes a conductive ceramic pipe 2 (hereinafter, referred to as a “sera pipe 2”) rotatably supported at appropriate positions on both sides in a longitudinal direction by a side frame or the like via a bearing 1, and a hollow end portion of the “sera pipe 2”. Forced expansion / contraction member 3 inserted
An annular gear 4 as a rotation transmission mechanism is attached to one end of the ceramic pipe 2. In general, a rolling bearing is used as the bearing 1, but a sliding bearing using an oil-impregnated resin or the like may be used. Although the figure shows only one end of the ceramic pipe 2, the forced expansion / contraction member 3 is inserted on the opposite side (not shown). still,
The forced expansion / contraction member 3 is provided at only one end, and the other end can use another expansion / contraction member that has already been proposed by the present inventor.

The ceramic pipe 2 has the same outer diameter over the entire length, and basically maintains the shape produced by extrusion. In a predetermined range excluding both end portions of the outer surface of the ceramic pipe 2, in order to improve the heat fixing effect by improving the adhesiveness to the recording paper, the adhesiveness of tetratetrafluoroethylene and silicon rubber is excellent and the thermal conductivity is also good. Heat resistant resin 5 is coated. In the figure, reference numeral 6 denotes a boundary between the coated portion and the non-coated portion of the heat resistant resin 5, and a portion inside the boundary 6 is a paper passage area, that is, an effective use range. The heat resistant resin 5 may not be covered. A part or all of the inner surfaces of the hollow portions at both ends of the ceramic pipe 2 is coated with a soft conductive metal by means such as vapor deposition, plating, or coating to form a conductive film 7.
Is formed, and this portion is used as a contact portion with the forced expansion / contraction member 3. In the illustrated example, the conductive coating 7 is formed on the enlarged diameter step 8 formed on the inner peripheral surface of the end of the ceramic pipe 2. However, the diameter of the conductive film 7 is the same as that of the other parts without forming the enlarged diameter step 8. A conductive coating 7 may be formed on the inner surface of the end.

As shown in FIG. 3, the forcibly expanding / contracting member 3 fixes an elastically deformable frame 9 formed by bending a metal plate into a substantially hexagonal shape in a front view to a disc-shaped flange 10, and the frame 9 It has a schematic configuration in which a shaft rod 11 is provided horizontally between opposed portions. In the illustrated example, a normal bolt having a threaded portion formed on the entire length is used as the shaft 11, but a shaft having a threaded portion only at a necessary portion may be used. Frame 9 and Tsuba 1
A head 12 is formed at one end of the shaft 11 that penetrates through 0 to restrict the movement of the shaft 11 to the left in the drawing.
The other end of the shaft 11 is connected to a nut 13 fixed to the frame 9.
The screw part is screwed. With such a configuration,
In the section between the head 12 and the nut 13, the expansion of the frame 9 that is to be expanded in the axial direction of the shaft 11 is restricted. By rotating the shaft 11, the frame 9 is expanded and contracted in the axial direction of the shaft, and at the same time, the other part of the frame 9 is forcibly expanded in the radial direction of the shaft 11, that is, in the vertical direction in the figure. It is configured so that it can be opened.

As shown in FIGS. 1 and 2, the annular gear 4
A gear body 4b having teeth 4a formed on the outer periphery thereof; and a cylindrical portion 4c for stably supporting the gear body 4b at the end of the ceramic pipe.
It is composed of An annular body having engagement recesses 15, 15 is formed on the end side of the annular gear 4, and engagement protrusions 14, 14 formed on the outer periphery of the flange 10 are fitted into the engagement recesses 15, 15. By matching, the rotation of the annular gear 4 with respect to the ceramic pipe 2 is prohibited, and the annular gear 4 is indirectly fixed to the ceramic pipe 2 via the forced expansion / contraction member 3.
The annular gear 4 is formed by injection molding using so-called engineering plastics.
Polyimide and polyacetal are suitable.

FIG. 4 shows the procedure for assembling each component. First, the annular gear 4 is externally fitted to one end of the ceramic pipe 2, and then the forced expansion / contraction member 3 is inserted into the hollow at the end of the ceramic pipe 2. The insertion of the forcibly expanding / contracting member 3 is performed by engaging the engagement protrusions 14 formed on the outer periphery of the flange 10 with the engagement recesses 15 formed on the annular gear 4. Subsequently, the shaft rod 11 of the forcibly expanding / contracting member 3 is rotated by using a jig such as a screwdriver, and the frame 9 is expanded in the diameter direction in the hollow portion of the ceramic pipe 2 as shown in FIG. This expansion is performed at the corner 9a of the frame 9.
Is carried out after contact with the conductive coating 7, and the frame 9 contacts the conductive coating 7 in a pressurized state while being elastically deformed, so that the corner 9 a of the frame enters into the conductive coating 7 partially. Do until. Then, if this pressing force becomes an appropriate magnitude, the frame 9
Stop expansion.

After that, a member for supplying electric power is attached to the shaft rod 11, electric wiring is performed, and a rotational driving force transmission mechanism is linked to the annular gear 4 to complete the assembly. The sera pipe 2 is rotatably supported on the side frame via the bearing 1. Whether the rotation support work of the sera pipe 2 by the bearing 1 is performed before or after the annular gear 4 and the forced expansion / contraction member 3 are mounted. Is appropriately selected.

The heat roller assembled in this manner supplies the electric power supplied from the shaft rod head 12 to both ends of the ceramic pipe 2 via the frame 9 and the conductive coating 7.
Since the frame 9 is in contact with the conductive coating 7 in a pressurized state while being elastically deformed, the electrical contact between the frame 9 and the conductive coating 7 is ensured. Further, the insertion of the forcible expansion / contraction member 3 into the end of the ceramic pipe 2 is easy because the frame 9 is contracted. Since the adjustment of the applied pressure after the interpolation can be easily performed by rotating the shaft rod 11, when the applied pressure is reduced during a long-term use, the applied pressure can be adjusted appropriately. Further, since the frame body 9 is elastically deformed, there is no possibility that an excessive pressing force which leads to breakage of the cera pipe 2 or the like is applied.

Further, in this embodiment, the annular gear 4 engages with the forcibly expanding / contracting member 3 inserted into the inner surface of the end of the cera pipe 2 so as to be able to rotate integrally with the cera pipe 2 and is transmitted to the annular gear 4. The rotational force is indirectly transmitted to the ceramic pipe 2 via the forced expansion / contraction member 3. The frame 9 is made of a conductive film 7
, The connection between the forced expansion / contraction member 3 and the ceramic pipe 2 is strong, and the rotational force applied to the annular gear 4 is reliably transmitted to the ceramic pipe 2.

Further, since the annular gear 4 is indirectly integrated with the sera pipe 2 by an engagement relationship with the forcible expansion / contraction member 3, it is necessary to provide a fitting portion such as a D-cut on the outer peripheral surface of the sera pipe 2. In addition, it is possible to basically maintain the shape of the cera pipe manufactured by extrusion.
Therefore, the number of processing steps for the ceramic pipe 2 can be reduced, which can contribute to cost reduction. In addition, D
Since there is no need to provide a cut or the like, there is no occurrence of cracking or chipping due to processing, and application to a thin-walled ceramic pipe 2 is also possible.

As the forced expansion / contraction member 3, other forms can be adopted. For example, as shown in FIG. 5, a frame body 16 having flat surfaces 16a, 16a formed in contact with the conductive film 7 is used. The surface 16a may be brought into surface contact with the conductive film 7, or a ring-shaped frame 17 may be used as shown in FIG. In particular, when the frame 16 having the flat surface 16a is used, the contact area between the frame 9 and the conductive film 7 increases, which is advantageous in transmitting the rotational driving force.

As shown in FIG. 7, as the forcible expansion / contraction member 3, a member using a shaft 18 having a columnar head 18a can be adopted. In this case, electric power can be supplied to the ceramic pipe 2 by directly supporting the cylindrical head 18a with the power supply brush 19 as shown in FIG. As a form of the power supply brush 19, FIG.
As shown in FIG. 9B, the power supply brushes 19a, 19a are opposed to each other so as to sandwich the side surface of the cylindrical head 18a from both sides, or as shown in FIG.
It is considered that the power supply brush 19b is arranged so as to elastically press the power supply brush 8a from the side. Of course, it is also optional to associate other old electric means with the cylindrical head 18a.

What has been described above uses the forcible expansion / contraction member 3 having the flange 10, and the engaging projections 14,
The figure assumes that the annular gear 4 is indirectly coupled to the ceramic pipe 2 via the forcible expansion / contraction member 3 by engaging the engaging recesses 14 with the engagement recesses 15 of the annular gear 4. As shown in FIG. 10, a fitting portion 20 having an irregular cross-sectional shape such as a D-cut is formed at the end of the ceramic pipe 2 as in the prior art, and an annular gear 21 is fitted into the fitting portion 20 to transmit a rotational driving force. You can also. In this case, as shown in the figure, it is not necessary to provide the engagement convex portion of the forcibly expanding / contracting member 3,
Needless to say, the work is easier when the collar is present in order to position the forced expansion / contraction member 3 in the hollow at the end of the ceramic pipe 2 in a predetermined posture.

[0035]

According to the heat roller of the present invention, since the outer surface of the frame of the forced expansion / contraction member is in contact with the conductive coating on the inner surface of the end of the ceramic pipe in a pressurized state, the electric power supplied from the shaft of the forced expansion / contraction member. Is reliably supplied to the ceramic pipe without causing a contact failure or the like. Further, when the pressing force is reduced in the course of use for a long period of time, the contact state of the frame with the conductive coating can be adjusted by rotating the shaft rod, and a good conduction state is always maintained. Further, since the forcible expansion / contraction member can be inserted into the hollow portion of the cera-pipe end in a contracted state, and can be expanded by operating the shaft rod after the insertion, the setting of the forcible expansion / contraction member into the hollow portion of the cera-pipe end is required. Easy.

When an elastically deformable frame is used as the frame of the forcibly expanding / contracting member, the frame is appropriately elastically deformed and comes into pressure contact with the conductive film. The contact state is more reliable. Further, since the pressing force is moderately relieved by the elastic deformation of the frame body, no excessive pressing force which may cause breakage of the ceramic pipe does not act.

In the case where the engagement portion of the flange provided at the end of the shaft of the forcible expansion / contraction member is engaged with the annular gear to transmit the rotational force applied to the annular gear to the ceramic pipe,
The end of the ceramic pipe to which the annular gear is externally fitted does not need to have an irregular cross-sectional shape, and a ceramic pipe having the same outer diameter over the entire length can be used. Therefore, the number of processing steps for the ceramic pipe can be reduced, which can contribute to cost reduction. Further, since there is no need to provide an irregular cross-sectional shape portion, there is no occurrence of cracks or chipping due to processing, and application to a thin-walled ceramic pipe is also possible.

When the outer surface of the frame is brought into surface contact with the conductive film, the two are in contact over a wide range, so that electrical conduction is ensured and rotation driving force can be transmitted reliably.

When a substantially cylindrical conductive terminal is extended at one end of the shaft rod, power can be supplied to the ceramic pipe by receiving the conductive terminal with a power supply brush.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of a main part showing a typical embodiment of a heat roller of the present invention.

FIG. 2 is a right side view of the embodiment.

FIG. 3 shows a forcible expansion / contraction member, (a) is a front view, (b)
Is the left side view

FIG. 4 is an explanatory view showing an example of an assembling procedure of the embodiment.

FIG. 5 is a front view showing another embodiment of the forced expansion member.

FIG. 6 is a front view showing another embodiment of the forced expansion member.

FIG. 7 is a front view showing another embodiment of the forcibly expanding and contracting member when a cylindrical head is provided on a shaft of the forcibly expanding and contracting member.

FIG. 8 is an explanatory cross-sectional view of a main part in a case where a cylindrical head provided on a shaft rod of a forced expansion / contraction member is supported by a power supply brush.

FIG. 9A is an explanatory view showing a case where a cylindrical head is supported by a power supply brush arranged oppositely, and FIG. 9B is an explanatory view showing a case where one power supply brush is elastically pressed against the cylindrical head. Figure

FIG. 10 is another embodiment of the heat roller of the present invention, and is an explanatory view of an end face of a main part when a deformed cross section is provided at an end of a ceramic pipe.

FIG. 11 is an explanatory diagram illustrating a schematic configuration of a fixing device.

FIG. 12 is an explanatory diagram showing a power supply structure already proposed by the present inventors.

FIG. 13 is a perspective view showing a ceramic pipe having a D-cut portion formed at an end portion.

[Explanation of symbols]

 Reference Signs List A Heat roller B Pressing roller C Recording paper 1 Bearing 2 Ceramics pipe 3 Forced expansion / contraction member 4 Annular gear 4a Teeth 4b Gear body 4c Tube 5 Heat resistant resin 6 Boundary part 7 Conductive coating 8 Large diameter step 9 Frame 10 Flange 11 Shaft rod 12 Head 13 Nut 14 Engagement convex part 15 Engagement concave part 16 Frame 16a Flat surface 17 Frame 18 Shaft rod 18a Cylindrical head 19, 19a, 19b Power supply brush 20 Fitting part 21 Ring gear

Claims (5)

(57) [Scope of request for utility model registration] 1. A conductive ceramic pipe rotatably supported, wherein a part or all of the inner surface of a hollow portion at both ends is coated with a soft conductive metal by means of vapor deposition, plating, coating, or the like; An annular gear externally provided on a pipe and having a tooth portion formed on an outer peripheral surface thereof, and a shaft rod is laid across the opposing portions of a deformable frame made of a metal plate. While restricting the movement of one contact part in the longitudinal direction of the shaft rod, the other contact part is screwed into the screw part of the shaft rod, and the shaft rod is rotated to rotate the shaft part between the opposed parts of the frame. A forced expanding / contracting member configured to expand / contract the other part in the opposite direction when the distance is expanded / contracted, and the shaft rod is inserted in a state where the forced expanding / contracting member is inserted into the hollow end portion of the conductive ceramic pipe. Rotate to expand and deform the frame radially outward in the hollow part, A power supply structure for a heat roller, wherein the frame body is pressed against the metal coating on the inner peripheral surface of the conductive ceramic pipe to supply power via the shaft of the forced expansion / contraction member. 2. The power supply structure for a heat roller according to claim 1, wherein the frame of the forced expansion / contraction member is elastically deformable. 3. A flange portion partially formed with an engagement portion is provided at an end of a shaft of a forcibly expanding / contracting member, and the engagement portion is provided at an appropriate position of an annular gear externally fitted on an outer periphery of an end portion of a conductive ceramic pipe. 3. The heat roller according to claim 1 or 2, wherein the relative rotation of the annular gear with respect to the conductive ceramics pipe is prohibited, and the annular gear and the conductive ceramics pipe are indirectly fixed via a forced expansion / contraction member. Power supply structure. 4. The power supply structure for a heat roller according to claim 1, wherein the outer surface of the frame of the forced expansion member is brought into surface contact with the metal coating on the inner peripheral surface of the conductive ceramic pipe. 5. A cylindrical head protruding outward from an end surface of a conductive ceramic pipe is extended at one end of a shaft penetrating the frame, and the cylindrical head is used as a conductive terminal for contacting a power supply brush. The power supply structure for a heat roller according to claim 1, 2, 3, or 4.