JPH0944019A - Fixing heater, fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the wear of an annular electrode, to prolong the service life, and to easily set heating temperature. SOLUTION: This heater is equipped with a roller base substance 12 formed of a heat resistant electric insulating material in a tubular state or in a columnar state; a resistive heating element 13 formed at least on the outer surface of the base substance 12; a pair of annular electrodes 14a and 14b concentrically formed at least on the outer surface of the base substance 12 and electrically connected to the heating element 13; a pair of conductive receiving shafts 17a and 17b coaxially provided to protrude to the outside from a shaft center at both ends in the shaft direction of the base substance 12 and having smaller diameter than the base substance 12; and a connecting conductor electrically connecting the shafts 17a and 17b to the electrodes 14a and 14b at least at two spots in the circumferential direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller-type fixing heater suitable for use in small equipment such as office automation equipment, household electric equipment and precision manufacturing equipment, and a copying machine equipped with this fixing heater. The present invention relates to a fixing device used for fixing a toner such as a facsimile and an image forming apparatus using the fixing device.

[0002]

2. Description of the Related Art Generally, in an electronic copying machine, a copy sheet on which a toner image is formed is passed between a fixing heater and a pressure roller while directly or indirectly through a heat-resistant sheet while pressing the fixing sheet. It is equipped with a fixing device that heats, melts, and fixes the toner on the copy paper by the heating of.

As a conventional fixing device of this type, for example, a roller type fixing device configured as shown in FIGS. 13 and 14 has been put into practical use. This is elastically slidable on the pair of left and right annular electrodes 2a, 2b of the roller type fixing heater 1 on the curved tips of a pair of power feeding brushes 3a, 3b made of strip-shaped leaf springs made of phosphor bronze or the like. The resistance heating element 5 is energized and heated by being pressed against and feeding power to the annular electrodes 2a and 2b from the power feeding brushes 3a and 3b.

The fixing heater 1 has a resistance heating element 5 formed on at least the outer surface of the roller base 4 formed in a cylindrical shape from a heat-resistant electric insulating material such as ceramics, and both ends of the resistance heating element 5 in the axial direction. At the pair of annular electrodes 2
The a and 2b are integrally or integrally formed by, for example, pattern printing of an Ag-based good conductor paste, and are in contact with and electrically connected to the resistance heating element 5 over substantially the entire circumference.

A pressure roller (not shown) is lightly and elastically circumscribed to face the roller base 4 of the roller-type fixing heater 1, and the fixing heater 1 is rotated by the rotation of the pressure roller. At the same time, the copy sheet on which the toner image is formed, which is supplied between the rollers, is heated while being pinched to fix the toner image on the copy sheet P.

[0006]

However, in such a conventional roller-type fixing heater 1, the pair of annular electrodes 2 is used.
Since a and 2b are formed by pattern printing and firing of Ag-based good conductor paste, the power feeding brushes 3a and 3b
It is easily worn by sliding b and has a short life.

Further, since the feeding brushes 3a and 3b are slidably brought into contact with the outer peripheral surfaces of the respective annular electrodes 2a and 2b having the highest rotation speed, the abrasion of the respective annular electrodes 2a and 2b is further large and fast. . Therefore, there is a problem that the life is short.

Further, as shown by the broken line in FIG. 13, a pair of power feeding brushes 3 sliding on the pair of annular electrodes 2a, 2b.
Since both the sliding portions a and 3b are arranged substantially coaxially, current flows in the resistance heating element 5 in a concentrated manner at the portion indicated by the broken line in the figure.

For this reason, the amount of heat generated by the resistance heating element 5 in the vicinity of the broken line is larger than the others, so that temperature unevenness occurs in the circumferential direction, and it is not easy to set the heating temperature of the resistance heating element 5. There are challenges.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing heater, a fixing device and an image forming apparatus in which the annular electrode is less worn and has a long life, and the heating temperature of the resistance heating element can be easily set.

[0011]

According to a first aspect of the present invention, there is provided a base body formed of a heat-resistant electric insulating material in a cylindrical or columnar shape; a resistance heating element formed on at least an outer surface of the base body; A pair of annular electrodes concentrically formed on the outer surface and electrically connected to the resistance heating element;
A pair of electrically conductive shafts having a diameter smaller than that of the base body, which is provided coaxially outwardly in the axial direction from the axial center portions of both ends of the base body; and each shaft is provided on each annular electrode at at least two locations in the circumferential direction. And a connecting conductor for electrically connecting.

Therefore, according to the first aspect of the present invention, the power feeding body such as the power feeding brush is slidably brought into contact with the pair of conductive shafts so that the power feeding body can be rotated even when the cylindrical or columnar base body is rotated. Power is supplied to the pair of annular electrodes, and
It is possible to supply electricity to the resistance heating element from these electrodes to electrically heat the resistance heating element.

Since the pair of conductive shafts have a diameter smaller than that of the base body and are arranged at the shaft center portion of the base body having the slowest rotation speed, the power supply body slidably contacting the shafts slides. The speed of the department can be slowed down. For this reason, it is possible to reduce the wear of the power supply body and the conductive shaft, so that both of them can have a long life.

Further, since the positions at which the respective shafts are electrically connected to the respective annular electrodes via the connecting conductors are set at at least two positions in the circumferential direction, the electric current is locally concentrated on a part of the resistance heating element. It can be effectively prevented. Therefore, it is possible to effectively prevent the temperature unevenness from occurring in the circumferential direction of the resistance heating element, so that the heating temperature of the resistance heating element can be easily set.

According to a second aspect of the invention, in the fixing heater according to the first aspect, the conductive shaft is electrically connected to the entire circumference of each annular electrode by a connecting conductor.

Therefore, according to the second aspect of the present invention, the current supplied from each conductive shaft to each annular electrode can be made substantially uniform in the entire circumferential direction of each annular electrode. The temperature distribution in the circumferential direction can be made substantially uniform, and the heating temperature can be set more easily.

According to a third aspect of the present invention, a base body formed of a heat-resistant electric insulating material in a cylindrical or columnar shape; a resistance heating element formed on at least the outer surface of the base body; and concentric on at least the outer surface of the base body. A pair of annular electrodes that are electrically connected to the resistance heating element and are formed on the outer surface of each of the annular electrodes; and conductive caps that are closely fitted and electrically connected to the outer surfaces of the respective annular electrodes; A conductive shaft that is concentrically provided so as to project axially outward at the axial center of the end face;
Is provided.

Therefore, according to the third aspect of the present invention, each conductive shaft can be electrically connected to each annular electrode by simply fitting the cap having the protruding conductive shaft onto the annular electrode. Therefore, as compared with the case where the connection conductor is formed of a conductor foil or the like, the connection conductor can be formed easily, quickly and surely. Moreover, by simply fitting the cap onto each annular electrode, the shaft projecting from the cap can be electrically connected over substantially the entire circumference of each annular electrode.

According to a fourth aspect of the present invention, in the fixing heater according to the third aspect, each cap is made of a conductor having rigidity without an axis.

Therefore, according to the fourth aspect of the present invention, by feeding the feeding body such as the feeding brush elastically against the outer surface of each rigid cap, the feeding body feeds power to each annular electrode even during rotation, The resistance heating element can be electrically heated through this electrode.

Moreover, since the cap with which the power supply body is slidably contacted is made of a rigid conductor, it is possible to suppress wear and prolong the service life.

According to a fifth aspect of the present invention, in the fixing heater according to the first or second aspect, each shaft is fitted and fixed in a center hole of a heat-resistant electric insulator fitted and fixed in both ends of the opening of the tubular base body. ing.

Therefore, according to the fifth aspect of the present invention, the heat-resistant electric insulator is fitted and fixed in the opening end of the cylindrical substrate, and the conductive shaft is fitted and fixed in the center hole of the insulator. The connection conductor such as a conductor foil can be easily, quickly and surely formed on the insulator around the conductive axis.

A sixth aspect of the present invention is the fixing heater according to any one of the first to third aspects, or the fifth aspect; and a pair of power supply members that slidably contact the respective shafts of the fixing heater to supply electric power. It is equipped with.

According to a seventh aspect of the present invention, there is provided the fixing heater according to the fourth aspect, and a pair of power feeding members which slidably contact the central portions of the outer end surfaces of the respective caps of the fixing heater to feed power.

According to an eighth aspect of the present invention, in the fixing device of the sixth or seventh aspect, a conveying sheet that can travel in a direction intersecting the longitudinal direction of the fixing heater; and a fixing sheet that faces the fixing heater via the conveying sheet. A pressure roller which is arranged so as to press the fixing heater and causes heat from the fixing heater to act on the toner forming the image of the fixing target via the conveying sheet and conveys the fixing target. It has.

According to a ninth aspect of the present invention, the fixing device according to any one of the sixth to eighth aspects is provided; toner is attached to the electrostatic latent image formed on the medium to form a reverse image, and the reverse image is formed. And a means for forming a predetermined image by transferring the image onto a fixing target.

Therefore, according to the inventions of claims 6 to 9, since each of the above inventions is provided as appropriate, it has substantially the same operational effect.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
This will be described with reference to FIG. In addition, in FIGS.
The same or corresponding parts are designated by the same reference numerals.

FIG. 1 is a perspective view of a fixing heater according to a first embodiment of the present invention, and FIG. 2 is a sectional view taken along the line II--II of FIG. An insulating material such as alumina (Al ₂ O ₃ ) or mullite (3Al ₂ O ₃ .2SiO ₂ ) ceramics forms a roller body 12 in the form of a straight cylinder, for example, so that the roller base 12 can be rotatably supported. are doing.

The roller base 12 is, for example, silver / palladium (A
A film-shaped resistance heating element 13 mainly composed of a g.Pd) alloy, a nickel-tin (Ni.Sn) alloy, or the like is formed in an annular band shape by thick film printing or the like.

Further, the roller base 12 is formed on the outer peripheral surface at both ends in the axial direction thereof with an annular shape made of a good conductor film such as silver or silver-platinum (Ag.Pd) alloy, silver-palladium alloy (Ag.Pd). A pair of right and left strip-shaped electrodes 14a and 14b are formed by thick film printing.
Each of the inner end portions of the above partially overlaps with both end portions of the resistance heating element 12 in the vertical direction, for example, and is electrically connected to each other over the entire circumference to supply power to the resistance heating element 12. . The entire outer peripheral surface of the resistance heating element 12 is entirely covered with a glassy overcoat layer 15 to improve mechanical strength such as wear resistance and impact resistance, and to protect corrosion from sulfide and oxidation. , And is electrically insulated from the pressure roller and the like. However, the overcoat layer 15 may be omitted.

Then, on the outer peripheral surfaces of the pair of annular electrodes 14a and 14b at both axial ends of the roller base 12, a pair of left and right conductive cylindrical terminal caps 1 with a conductive lid are also shown in FIG.
6a and 16b are closely fitted and fixed concentrically, and the inner surface of each terminal cap 16a and 16b is fixed to the pair of electrodes 14.
It is electrically connected to a and 14b.

Each of the terminal caps 16a and 16b is made of, for example, a copper-based conductor or a conductor obtained by plating a copper-based conductor with silver, and has a diameter smaller than the outer diameter of the roller base 12 at the center of the outer end of the lid. In addition, short round rod-shaped power receiving shafts 17a and 17b having electrical conductivity and wear resistance are vertically provided integrally or integrally.

On the pair of power receiving shafts 17a and 17b of the fixing heater 11 constructed as described above, as shown in FIG. 4, a phosphor bronze plate or a conductive strip-shaped leaf spring material made of copper or copper plated with silver is used. The pair of power supply brushes 18a and 18b are elastically brought into contact with the outer surfaces of the curved tip end portions of the pair of power supply brushes 18a and 18b so as to be slidable, and electrically connected to form a fixing device 19.

A power supply circuit (not shown) is electrically connected to the pair of power supply brushes 18a and 18b, and the power supply brushes 18a and 18b are connected to the respective power receiving shafts 17a and 17b via terminals and terminal caps 16a and 16b. Electrodes 14a, 14
It is designed to supply power to b. In addition, each power receiving shaft 17
The free ends of a and 17b may be rotatably supported by an electrically insulating bearing (not shown).

Therefore, according to the embodiment of the present invention,
Even when the roller base 12 rotates, the pair of power feeding brushes 1
8a, 18b to a pair of power receiving shafts 17a, 17b, terminal caps 16a, 16b, and a pair of annular electrodes 14a, 14b.
It is possible to reliably supply power to the resistance heating element 13 via the to heat the resistance heating element 13.

Since the pair of power receiving shafts 17a and 17b have a diameter smaller than that of the roller base body 12 and are arranged at the shaft center portion of the roller base body 12 having the slowest rotation speed, the power receiving shafts 17a and 17b are Power supply brush 18 that slidably contacts
The speed of the sliding portions of a and 18b can be reduced. In addition, since the power receiving shafts 17a and 17b have wear resistance,
Since the abrasion between the power supply brushes 18a, 18b and the power receiving shafts 17a, 17b can be reduced, the life can be extended.

FIG. 5 is a perspective view of the fixing device 19 according to the second embodiment of the present invention, and FIG. 6 is a side view thereof. The fixing device 19A is a pair of terminal caps 1 of the fixing heater 11A.
Power receiving shafts 17a and 17b are removed from 6a and 16b to form closed flat surfaces 16a1 and 16b1 respectively, and a pair of power feeds made of a conductive strip-shaped leaf spring material such as phosphor bronze plate is provided on each of the end surfaces 16a1 and 16b1. Brush 18
It is characterized in that the arcuate curved end portions of a and 18b are directly and elastically pressed so as to supply required power to the terminal caps 16a and 16b while sliding the roller base body 12 while rotating.

Therefore, according to this second embodiment,
Since each of the power receiving shafts 17a and 17b shown in FIG. 4 and the like is simply deleted from each of the terminal caps 16a and 16b, the number of parts can be deleted without interfering with the effect similar to that of the first embodiment. , Each power receiving shaft 17a, 17b
The step of providing the terminal caps 16a and 16b on each terminal can be eliminated, and the cost can be reduced.

FIG. 7 is a perspective view of a fixing device 19B according to the third embodiment of the present invention. This fixing device 19B is shown in FIG.
It is characterized in that the pair of power feeding brushes 18a, 18b shown in (4) are replaced with the pair of power feeding pins 20, 21.

Each of the power supply pins 20 and 21 has a spring case 20a, 21a containing a coil spring (not shown).
Pins 20b, 21b having conductivity and wear resistance inside
The inner end of the pin 20b is housed so as to be able to reciprocate in the axial direction by the spring force of the coil spring, and the hemispherical tips 20c and 21c of the pins 20b and 21b are connected to the terminal caps 16a and 1a, respectively.
6b is always elastically pressed against the axial center portion of the outer end surface of 6b. A power supply circuit (not shown) is electrically connected to each of the power supply pins 20 and 21, and a required amount of power is supplied from the power supply circuit to the power supply pins 20 and 21.

Therefore, according to this embodiment as well, it is possible to obtain substantially the same effect as that of the first embodiment.

FIG. 8 is a perspective view of a fixing heater 11B according to a fourth embodiment of the present invention. The fixing heater 11B is at least a roller base 12B made of a heat-resistant electrically insulating material such as solid cylindrical ceramics. The resistance heating element 13B is formed on the outer surface, and the entire outer surface of the resistance heating element is covered with an electrically insulating overcoat layer 15B such as a glass film to electrically insulate the resistance heating element 13B. A pair of annular electrodes 14B on the roller bases 12B on both sides
a and 14Bb are arranged side by side in close contact with each other and electrically connected.

Further, each of the annular electrodes 14Ba, 14B
On the outer side of b, a pair of annular insulating portions 22 and 23 in which the outer peripheral surface and the outer end surface of the roller base body 12B are exposed in series are respectively formed.

The annular insulating portions 22 and 23 have their respective end faces 22.
circular holes 22b, 2 having a predetermined depth and a small diameter at the center of a, 23a
3b is bored, and small-diameter, electrically conductive power receiving shafts 24a, 24b are inserted into the circular holes 22b, 23b and fixed by an adhesive or the like.

As shown in FIG. 9A, a pair of two connecting conductors 25a, 25b, 2 made of a strip-shaped conductor foil or the like are formed on the end faces 22a, 23a of the annular insulating portion in the diameter direction thereof.
6a and 26b are attached to each of the power receiving shafts 24a, 24
They are electrically connected to b respectively.

Each connecting conductor 25a, 25b, 26a, 26
Each tip of b extends on the outer peripheral surface of each annular insulating portion 22 and 23, is connected to each side end surface of each annular electrode 14Ba, 14Bb, and is electrically connected.

Therefore, according to the fourth embodiment, the curved tips of the pair of power feeding brushes 18a and 18b shown in FIG. 4, for example, are slidably and elastically pressed onto the power receiving shafts 24a and 24b. As a result, even when the roller base body 12B is rotating, the power receiving brushes 24a, 24b and the connecting conductors 25a, 25b, 2 are connected from the power feeding brushes 18a, 18b.
6a, 26b through the respective electrodes 14Ba, 14
Power can be supplied to Bb or the resistance heating element 15B to generate heat.

Moreover, each connection conductor 25a, 25b, 26
Since the tips of a and 26b are electrically connected to the electrodes 14Ba and 14Bb at equal circumferential positions (180 ° equal positions), the concentration of the electric current supplied to the electrodes 14Ba and 14Bb is prevented. Can be even.

As a result, current concentration in the resistance heating element 15B can be effectively prevented and the current can be evenly distributed.
It is possible to effectively prevent the temperature unevenness from occurring in the resistance heating element 15B. Therefore, the temperature of the resistance heating element 15B can be easily set.

The above-mentioned connecting conductors 25a, 25b, 2
As shown in FIG. 9B, 6a and 26b may be formed in a cross shape so as to divide the circumferential direction of the annular insulating portion end faces 22a and 23a into four equal parts, and the number thereof is not limited. Further, the entire surface of each annular edge portion 22, 23, that is, the entire outer peripheral surface and the end surfaces 22a, 23a may be formed on the conductive surface by screen printing of a conductive paste or the like.

Further, as shown in FIG. 8C, insulating plugs 27 made of electrically insulating plastic or the like are inserted into both ends of the opening of the cylindrical roller base 12 and fixed by an adhesive or the like. The power receiving shafts 24a and 24b are inserted into the center hole 27a of the plug 27 and fixed by an adhesive or the like,
End surfaces 22a, 23a of the annular insulating portions 26a, 26b
You may comprise.

FIG. 10 shows the construction of an embodiment of an electronic copying machine 31 which is a kind of the image forming apparatus of the present invention. The copying machine 31 has a housing 32 in which copying paper P in a cassette 33 is placed. An image forming unit 34 that pulls in and forms a toner image corresponding to an image of an original (not shown) and a fixing device 35 that fixes the toner image on the copy paper P are built-in.

The fixing device 35 is constructed, for example, as shown in FIG. 11, and any one of the fixing heaters 11, 11A and 11B, for example, 11 is arranged in parallel so as to face the pressure roller 36. For example, as shown in FIG. 12, a pressure roller 36 and a pair of left and right supporting rollers 37a,
It may be rotatably held in the vertical direction by 37b,
The outer peripheral surface of the fixing heater 11 is elastically pressed against the silicone rubber layer 37 of the pressure roller 36.

The fixing heater 11 is a pair of power receiving shafts 1.
The resistance heating element 13 is heated by the pair of elastic power feeding brushes 18a, 18b made of a phosphor bronze plate or the like that slidably contacts the 7a, 17b to heat the overcoat layer 15. Therefore, the copying paper P on which the toner image T is formed is pinched between the outer surface of the surface glass coat layer 15 and the silicone rubber layer 37 of the pressure roller 36 and heated by the fixing heater 11, whereby the unfixed toner is unfixed. The image T can be melted and fixed on the copy paper P.

Further, since the fixing heater 11 has a long life and the temperature can be easily set, the fixing heater 35 and the electronic copying machine 31 also have a long life and the setting of the fixing temperature is easy.

[0058]

According to the first aspect of the present invention, a pair of conductive shafts are slidably brought into contact with a power feeding body such as a power feeding brush so that the pair of conductive shafts can be moved from the power feeding body even when the cylindrical or columnar substrate is rotated. The resistance heating element can be energized and heated via the annular electrode.

Since the pair of conductive shafts have a diameter smaller than that of the base body and are arranged at the shaft center portion of the base body having the slowest rotation speed, the power supply body slidably contacting the shafts slides. The speed of the department can be slowed down. For this reason, it is possible to reduce the wear of the power supply body and the conductive shaft, so that both of them can have a long life.

Further, since the positions where the respective shafts are electrically connected to the respective annular electrodes through the connecting conductors are set at least at two positions in the circumferential direction, it is possible to locally concentrate the energization on a part of the resistance heating element. It can be effectively prevented. For this reason, it is possible to effectively prevent the temperature unevenness from occurring in the circumferential direction of the resistance heating element, so that it is possible to easily set the heating temperature of the resistance heating element.

According to the second aspect of the present invention, the current supplied from each conductive shaft to each annular electrode can be made substantially uniform in the entire circumferential direction of each annular electrode. The temperature distribution can be made substantially uniform, and the heating temperature of the resistance heating element can be set more easily.

According to the third aspect of the present invention, each cap can be electrically connected to each annular electrode by simply fitting the cap having the protruding conductive shaft onto the annular electrode. As compared with the case where the conductor is formed of a conductor foil or the like, the conductor can be formed easily, quickly and surely. Moreover, by simply fitting the cap onto each annular electrode,
The shaft protruding from the cap can be electrically connected over substantially the entire circumference of each annular electrode.

According to the fourth aspect of the present invention, the power feeding body such as the power feeding brush is elastically pressed against the outer surface of each rigid cap, so that the resistance heating element can be applied to the resistance heating element through the respective annular electrodes even during rotation. It can be energized and heated.

Moreover, since the cap is slidably contacted with the power supply or is made of a rigid conductor, abrasion can be suppressed and the life can be extended.

According to the fifth aspect of the present invention, the heat resistant electrical insulator is fitted and fixed in the opening end of the cylindrical substrate, and the conductive shaft is fitted and fixed in the center hole of the insulator. A connection conductor such as a conductor foil can be easily, quickly and surely formed on the insulator around the property axis.

According to the inventions of claims 6 to 9, since the above inventions are provided as appropriate, they have substantially the same operational effects.

[Brief description of drawings]

FIG. 1 is a perspective view of a fixing heater according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a perspective view of a main part showing a state where a terminal cap is externally fitted to the roller base body shown in FIG.

FIG. 4 is a perspective view of a main part of a fixing device according to a second embodiment of the present invention.

FIG. 5 is a perspective view of a main part of a fixing device according to a third embodiment of the present invention.

6 is a side view of FIG.

FIG. 7 is a perspective view of a main part of a fixing device according to a fourth embodiment of the present invention.

FIG. 8 is a perspective view of a main part of a fixing device according to a fifth embodiment of the present invention.

9A is a side view of FIG. 8, FIG. 9B is a side view showing a modified example of the same embodiment, and FIG. 9C is a longitudinal sectional view of an essential part of another modified example.

FIG. 10 is an overall configuration diagram of an image forming apparatus according to a sixth embodiment of the present invention.

11 is an enlarged configuration diagram of a main part of the fixing device shown in FIG.

12 is a schematic configuration diagram of another example of the fixing device shown in FIG.

FIG. 13 is a perspective view of a part of a conventional fixing device.

FIG. 14 is a side view of the conventional fixing device shown in FIG.

[Explanation of symbols]

11, 11A, 11B Fixing heater 12 Roller base 13 Resistance heating element 14a, 14b, 14Ba, 14Bb A pair of annular electrodes 15 Glass coat layers 16a, 16b Terminal caps 17a, 17b, 24a, 24b Power receiving shaft (conductive shaft) 18a , 18b Power supply brush 19, 19A Fixing device 20, 21 A pair of power supply pins (power supply body) 22, 23 A pair of annular insulating parts 22a, 23a A pair of annular insulating part end faces 25a, 25b, 26a, 26b Connection conductor 31 Electronic type Copying machine (image forming apparatus) 32 Housing 33 Cassette 34 Image forming unit 35 Fixing device 36 Pressure roller 37 Silicone rubber layer P Copying paper T Toner image

Claims (9)

[Claims] 1. A substrate formed of a heat-resistant electric insulating material in a cylindrical or columnar shape; a resistance heating element formed on at least the outer surface of the substrate; and a resistance formed concentrically on at least the outer surface of the substrate. A pair of annular electrodes electrically connected to the heating element; and a pair of electrically conductive shafts having a diameter smaller than that of the base body and coaxially projecting axially outward from the axial center portions at both axial ends of the base body. And a connecting conductor that electrically connects each shaft to each annular electrode at least at two positions in the circumferential direction thereof; 2. The fixing heater according to claim 1, wherein a conductive shaft is electrically connected to the entire circumference of each annular electrode by a connecting conductor. 3. A base formed of a heat-resistant electric insulating material in a cylindrical or columnar shape; a resistance heating element formed on at least the outer surface of the base; and a resistance formed concentrically on at least the outer surface of the base. A pair of annular electrodes electrically connected to the heating element; a conductive cap tightly fitted and fixed to the outer surface of each annular electrode to be electrically connected; an axial center portion of the outer end surface of each cap And a conductive shaft that is concentrically provided so as to project outward in the axial direction. 4. The fixing heater according to claim 3, wherein each cap is made of a conductor having rigidity with an axis removed. 5. The fixing heater according to claim 1, wherein each shaft is fitted and fixed in a central hole of a heat-resistant electric insulator fitted and fixed in both end portions of the opening of the tubular substrate. Fixing heater. 6. A fixing heater according to claim 1, or a fixing heater according to claim 5; and a pair of power supply members that slidably contact the respective shafts of the fixing heater to supply power. A fixing device characterized by the above. 7. The fixing heater according to claim 4, further comprising: a pair of power supply members that slidably contact the central portions of the outer end surfaces of the caps of the fixing heater to supply power. apparatus. 8. The fixing device according to claim 6 or 7, wherein a conveying sheet that can travel in a direction intersecting the longitudinal direction of the fixing heater; and the fixing heater is pressed against the fixing heater via the conveying sheet. And a pressure roller that applies heat from the fixing heater to the toner forming the image of the fixing target through the conveyance sheet and that conveys the fixing target. Fixing device characterized by. 9. The fixing device according to claim 6, wherein toner is attached to the electrostatic latent image formed on the medium to form a reverse image, and the reverse image is transferred to a fixing target. And a means for forming a predetermined image.