JPH0711729B2 - Roller for heat fixing and fixing device having the same - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a heat fixing roller of a fixing device applied to a recording device such as an electrophotographic copying machine, a printing machine, a printer, or a facsimile machine.

The present invention relates to a heat fixing roller and a fixing device as heating means used for fixing an unfixed image.

(Prior Art) A heat-fixing roller that has been put into practical use has a temperature detector on its surface, and the temperature is controlled by switching a halogen heater provided in the center of the inside to a conducting or non-conducting state.

Since this temperature control is quite complicated, it has a Positive Temperature Co-efficient of res
It is proposed to use ceramics having istivity (hereinafter abbreviated as PTC) characteristics.

U.S. Pat. No. 4,266,155 shows a heat fixing roller using a semiconductor ceramic having PTC characteristics in a rod state. However, since this rod-shaped PTC ceramic is thick, it must be provided on the inner peripheral surface of the roller with a large distance. Therefore, in the roller disclosed in U.S. Pat. No. 4,266,155, the surface layer of the roller heated by the ceramics has an uneven temperature distribution, which causes fixing failure.

Further, since the PTC ceramic disclosed in this US patent is a rod-shaped ceramic after firing, there is a problem in providing an electrode for applying an applied voltage to the PTC ceramic. When heat is generated by passing an electric current from both ends of this rod shape, even if only the central part in the axial direction of the roller is deprived of heat by the paper and toner and the temperature drops, power is not supplied to that part and fixing is performed. It causes a defect. This is because the other parts of the roller have a predetermined temperature or higher, so that the PTC ceramics facing each other do not pass an electric current due to self-temperature control. On the contrary, when an electric current was applied by applying a voltage from the front surface and the back surface of the rod-shaped ceramics, the heat generation of the PTC ceramics was small, so that the fixing failure occurred when the fixing was continuously performed.

From these problems, an electrode capable of making the surface temperature of the heating and fixing roller uniform within a practical range is desired. Further, there is a demand for a heat fixing roller capable of performing stable fixing without causing fixing failure even on recording materials of various sizes.

In addition, the conventional PTC ceramics may have a poor heat conversion efficiency with respect to power supply, and this problem has not been clearly explained.

(Object of the Invention) In view of the above-mentioned problems, the present invention provides a heat fixing roller provided with an electrode capable of forming a uniform heating state in a heating layer having RTC characteristics that is not affected by recording materials of various sizes. The purpose is to provide.

The present invention aims to provide a fixing device having the heat fixing roller, and other objects will be described below.

(Structure of the Invention) The present invention is to solve the above-mentioned problems, and positive temperature coefficient of resistance (Positive Temperature Co-efficiency) is obtained by firing.
In a heat fixing roller having a heating element layer for obtaining an ent of resistivity) and an electrode pair fixed to the heating element layer, the heating element layer is provided on the entire cylindrical surface of the roller,
In the electrode pair, conductors forming one pole and conductors forming the other pole are alternately provided inside the cylindrical heating element layer, and the conductors are provided in the longitudinal direction of the heating element layer, and conductors of different polarities. A heating fixing roller and a fixing device having the heating fixing roller are characterized in that the surface temperature in the longitudinal direction of the roller is made uniform in the portion of the heating element layer between them.

(Explanation of Examples and Outline of the Invention) Examples and applications of the present invention which are suitable for each object of the present invention will be apparent from the description of FIG.

In FIG. 1, reference numeral 36 denotes a block of the image forming means,
It is shown that the built-in configuration includes various image forming means such as a general facsimile, a laser printer, and a printing machine.

For convenience, as an example of the image forming means 36, means A to H for forming a visible image by electrophotography are shown.

B shows a photosensitive drum having a photosensitive layer as an example of the image bearing member. The photosensitive drum B receives the copy signal, rotates in the direction of the arrow by the driving force of a driving source (not shown), and is precharged by a precharger (not shown). Next, the photosensitive drum B is charged by the primary charger E, and then subjected to secondary charge removal by the secondary charger H. On the other hand, at the same time, the original image is scanned by the optical device A including the optical member and the optical member moving means, and thus the image is exposed on the photosensitive drum B. Then, an electrostatic latent image is formed on the drum B by receiving the next whole surface exposure (not shown). This latent image is developed in the developing device C, becomes a visible image, rotates with the drum B, and reaches the transfer charger F.

On the other hand, recording materials S and S1 having different widths are sent one by one from the cassettes 30 and 31 by the conveying rollers 32 and 33, move along the guide member 34, and are timed by the registration roller G to receive the visible image. It is peeled off and conveyed close to the drum B. At this time, the recording material S, S1 is transferred by the transfer charger F.
Is charged from the back surface thereof in the opposite polarity to the visible image, whereby the visible image is transferred onto the recording material S, S1. After that, the surface of the photosensitive drum B is cleaned by the cleaning means D to prepare for the next copy.

On the other hand, the recording materials S and S1 that reliably carry the visible image T are separated from the photosensitive drum B and sent by the fixing device 37.

The heat fixing roller 1 has a configuration described later, and the pressure roller 2
The recording materials S and S1 are nipped and conveyed by and. At this time, the visible image thermoplastic powder developer (hereinafter referred to as toner) in contact with the fixing roller 1 is melted and pressed, and is heat-fixed on the recording material.

The pressure roller has a thick coating 43 of an elastic material such as silicone rubber on the circumference of a rigid metal roll 44, which has an offset preventing property. The fixing roller 1 and the pressure roller 2 are pressed against each other,
The elastic coating 43 elastically deforms to form a nip portion for fixing the recording materials S and S1. The rollers 1 and 2 are driven by a motor (not shown) on the main body side of the electrophotographic recording apparatus 3 to rotate the roller 1 in the direction of the arrow, and the roller 2 is driven to rotate by frictional force.
A web 51 for cleaning the surface of the fixing roller 1 is pressed against the peripheral surface of the fixing roller 1 by a pressing roller 38. After cleaning the surface of the fixing roller, the web wound around the shaft 40 moves to the shaft 39 which is rotated by the driving force and is wound around the shaft 39. More rollers 1,2,38 and shaft
The widths of 39 and 40 are not less than the widths of the recording materials S and S1, and are rotatably supported by the fuser box 52. 41 is in contact with the fixing roller,
A separation claw that separates the recording material from the roller surface, and 42 is a guide plate that is close to the pressure roller 2. 46 and 47 are separation claws 41
And a guide plate 42, which is a discharge roller for discharging the recording material conveyed to the tray 48.

The fixing device 37 can be attached to and detached from the device 3 by the outer arm 52 sliding on a rail fixed in the device.

The heat fixing roller 1 described above will be described in detail.

As shown in FIGS. 1 to 4, the roller 1 has a multi-layered structure. Reference numeral 50 is a hollow metallic cylindrical roller, which forms the base of the roller 1. Reference numeral 49 denotes an electric insulating layer provided on the metallic cylindrical roller 50, which electrically insulates the heating layer 4 of the upper PTC ceramic and the inner surface layer 7 of the PTC ceramic from the base of the roller 50. The insulating layer 49 is provided to increase the heat generation efficiency of the upper PTC ceramic.

The inner surface layer 7 is a cylindrical PTC ceramic layer as shown in FIG. 2, and has a joint portion 6 to form a cylindrical shape. The inner surface layer 7 has conductors 8A, 8 printed on the entire circumference of both ends.
There is B, which constitutes an electrode that receives the applied voltage from the device 3.

The heat generating layer 4 is a cylindrical PTC ceramic layer provided as an upper layer of the inner surface layer 7, and has a resistance lower than that of the ceramic of the inner surface layer 7. Inside the layer 4, conductors 5A and 5B are alternately printed at regular intervals. These conductors 5A and 5B form a linear pattern in the longitudinal direction over the entire length of the heat generating layer 4. The conductor 5B is between the two conductors 5A and the conductor 5A is between the two conductors 5B in the circumferential direction. Are provided so that they are adjacent to each other.

The distance between adjacent conductors 5A and 5B is constant, and conductor 5A
The distance between the comrades and the conductor 5B is also constant. As described above, it is preferable that the linear conductors 5A and 5B with constant intervals are provided at least in the region L which is equal to or larger than the pass band of the recording S and S1. The reason for this is that if the conductor spacing is constant, the PTC ceramics sandwiched between the conductors can generate uniform heat in the longitudinal direction of the roller.

The conductors 5A and 5B form electrodes respectively, but the gathering conductors 5A 'gather the conductors 5A and the gathering conductors 5B' gather the conductors 5B so that the conductors 5A and 5B have different polarities. These gathering conductors 5
A'and 5B 'are provided on the left and right of both ends of the heat generating layer 4 over the entire inner peripheral surface thereof (see FIG. 2). Only the gathering conductors 5A 'and 5B' are joined to the conductors 8A and 8B of the inner surface layer to form the power feeding mechanism of the roller 1.

The joint portion 6 of the heat generating layer 4 is opposed to the joint portion 6 of the inner surface layer 7 with a difference of 180 ° so as not to be at the same position with respect to the circumference. Not stacking the joint portions 6 has the effect of increasing the strength of the heat fixing roller. The heat-fixing roller has a surface release layer 9, such as PFA resin or FE, for preventing the toner from being fused to the image T on the surface of the heat-generating layer 4.
It has a layer composed of a polymeric material such as P resin or PTFE resin.

Reference numeral 35 is a voltage application device that applies a voltage between all the conductors 5A and 5B to flow a current, and has power supply brushes 35A and 35B (or power supply filaments 35A ′ and 35B ′ as shown in FIG. 3) to both electrodes. is doing. In FIG. 2, the bras 35A and 35B are in contact with the conductors 8A and 8B, respectively.

As described above, the width L _{0 of} the recording material S, the width L ₁ of the recording material S ₁ (L ₀ >
The roller surface corresponding to L ₁ ) is provided with the conductors 5A and 5B of electrodes different from each other in the circumferential direction in order, so that heat generation in the heat generating layer can be performed in the circumferential direction.
As a result, when the roller surface temperature in the area corresponding to the width of the recording material decreases, only the area in which the temperature has decreased is heated by the action of decreasing the resistance of the PTC ceramics in that area.
Therefore, unnecessary temperature rise on the roller surface is prevented,
The roller surface temperature distribution can be made uniform in the axial direction of the roller. Further, by making the distance between the conductors 5A and 5B substantially constant, preferable temperature uniformity is produced. Further, by arranging the conductors 5A and 5B alternately, uniform temperature distribution in the circumferential direction of the roller can be achieved.

Although the surface layer 9, the insulating layer 49, and the base roller 50 are not shown in FIG. 2 (however, the surface release layer 9 provided in the configuration of this figure is also an example of the roller configuration of the present invention). A longitudinal sectional view of the roller 1 can be understood from FIG.
In FIG. 3, the power supply filament 35 described in FIG. 2 is used.
Since A ′ and 35B ′ are used, a heat insulating and electrically insulating flange 52 is provided on one end surface of the roller, and the roller 1 is provided on the outer surface of the flange 52.
It has annular concentrating conductor rails 5A ", 5B" so as to draw a double concentric circle about the axis 54 of the. Rail 5A, ″, 5
All conductors 5A and 5B are electrically connected to B ″ respectively. Further, in FIG. 3, the shaft 54 is fixed to the substrate 56 of the apparatus, and the roller 1 is connected to the shaft 54. A bearing 53 is provided on the flange 52 to make it rotatable. The filaments 35A 'and 35B' are connected to the voltage applying device 35 and abutted against the rails 5A "and 5B" by a pressure spring 57, respectively. Since the width of the ends of filaments 35A 'and 35B' is smaller than the width of rails 5A "and 5B", they make stable contact with the rails. 55 is the shaft support that houses the filament and the pressure spring. Thus, it is fixed to the device via a minute gap with respect to the flange 52.

Conventionally, when an electrode is provided on the surface of a ceramic having PTC characteristics, the ceramic is locally heated to 500 ° C when setting the electrode.
As the temperature rises up to ~ 1000 ° C, cracking occurs in the ceramics. Conventionally, ceramics in the field of fixing have a binder mixed in powder, but they are so crumbly that they cannot maintain the shape, and they must be fired to obtain the shape. Therefore, the inventor of the present invention has thought that a conventional ceramic that can be easily changed in shape is required. In the conventional ceramics before firing, the amount of the binder was several% or less with respect to the powder raw material, and deformation was impossible.

Next, the manufacturing flow chart of FIG. 6 will be described with the explanation of FIG.

By firing, the solvent 1 and the dispersant 12 are added to the ceramic raw material 10 having a material structure having a Curie point, and a mixing / grinding step 13 is performed. The ceramic raw material 10 is an additive element (for example, La, Ce, Nb, Ta, Bi, Sb, W) for BaCO ₃ , TiO ₂ which is the raw material 10 of the BaTiO ₃ series ceramic having PTC characteristics.
And other oxides) to further increase the positive temperature coefficient of resistance (elements such as Mn, Fe, Cu and Cr) and to promote semiconductor formation and adjust the grain size (Al ₂ O ₃ , SiO ₂ , TiO ₂ ).

In this example, 16 parts of barium titanate is used to lead 9 parts of lead titanate.
The raw materials are mixed so as to have a composition ratio in which parts (or less) are added to obtain a heat generating layer having a Curie point of 100 ° C to 250 ° C. Here, trichlene, alcohol, ethyl acetate, toluene, acetone, MEK, water, etc. are used as the solvent 11, and fish oil, octylamine, glyceryl monooleate (Glyceryl monooleate), glyceryl trioleate (Glyceryl trioleate), etc. are used as the dispersant 12. To use.

Further, a plasticizer 15 and a binder 16 are added, and the mixture is sufficiently mixed, crushed 14 again, molded and dried 17 to produce a green sheet 18. Here, the green sheet contains 10 to 20% of the total amount of the binder and is flexible.
As this plasticizer 15, polyethylene glycol, DBP (dibutyl phthalate), DOP (dioctyl phthalate), SAI
B (isobutyral stearate), glycerin, etc. are used as the binder 16 for cellulose acetate, polyacrylate, PVA (polyvinyl alcohol), PVB (polyvinyl butyral), EVA (ethyl vinyl acetate), P
VA (polyvinyl acetate) or the like is used. In this manner, after producing a green sheet 18 having a thickness of 0.5 to 2 mm, a conductive paste for high temperature sintering, preferably a tungsten powder paste, is screen-printed on this sheet, and the conductors 5A, 5B, 5A ′ described above are used. , 5B 'are printed 19 in a tooth shape as shown. In the printed state, it has a sheet shape as shown by the broken line in FIG.
Far lower than high temperatures such as 500 ° C-1500 ° C. 2
It is heated below 00 ℃.

If the conductor is placed on the inner surface side of the green sheet on which the conductor is pattern-printed as described above, the heating layer 4 of FIG.
When the conductor is placed on the front surface side, the heating layer 4'in FIG. 4 is obtained. In any case, the sheet is formed into a cylindrical shape
Twenty.

Next, this sheet is formed into a cylindrical shape 20. Since this cylindrical molded product does not require a pressure applying means from the outside, a molded product which is not affected by residual stress, strain, etc. is formed in the molded product.

The binder 16 remaining inside the cylindrical molded product thus molded is removed by heating 21.

Following this heating, raise the temperature at 200-400 ° C per hour,
Sinter 22 for 22 hours in a reducing atmosphere at about 1300 to 1400 ° C.

Under this condition of high temperature and reducing atmosphere, the ceramic shrinks to obtain the PTC characteristic. Patterned conductor 5 at this time
Since A, 5B, 5A 'and 5B' are also exposed to high temperature at the same time, the conductor which was printed on the ceramic and was unstable was closely fixed to the ceramic during this firing. If this fired product is cooled at 100 ° C to 200 ° C per hour, a roller as shown in Fig. 4 is produced.

Since the inner surface layer 7 is provided in FIG. 1, this manufacturing method is supplemented. Similarly to the heat generating layer 4, the inner surface layer 7 is also made into a ceramic green sheet 18, and the conductors 8A and 8B as pattern electrodes are linearly printed 19 at both ends of one surface of the sheet. As described above, the heating layer 4 is prepared as a sheet in which the conductors 5A, 5B and the like are printed in advance, so that the conductors 8A, 8B of the sheet of the inner surface layer 7 are in contact with the conductors 5A ', 5B'. Overlap.
The superposed sheet pair is formed into a cylindrical shape 20 so that the sheets on which the conductors 8A and 8B are printed are inward and their seams do not overlap. After this, the above-mentioned heating 21,
Sinter 22. As a result, an integral roller shape of the heat generating layer 4 and the inner surface layer 7 is obtained.

Generally, ceramics shrink by firing, but due to partial unevenness of the shrinkage, cracks, qualitative unevenness, and dimensional unevenness occur. This partial shrinkage unevenness occurs due to uneven mixing of raw materials, residual stress and residual strain due to pressure during molding.

Conventionally, cracking and qualitative unevenness occurred during this firing, but in this method, there was no effect of external pressure during molding, and as a result, there was no residual stress or strain in the molded body. The roller can be produced without causing qualitative unevenness.

Thus, a PTC ceramic roller having PTC characteristics is manufactured. Since the electrodes of this roller are also baked at the same time as sintering, it is not necessary to attach the electrodes afterwards, so that it is possible to prevent the occurrence of cracks and dimensional deformation due to thermal shock during the attachment of the electrodes.

FIG. 2 is also a perspective view of another embodiment which can be used as the heat fixing roller of the present invention. In this case, in this case,
Wall thickness 0.5 mm to 4 mm (thickness obtained by bonding two sheets 4 and 7)
We can manufacture up to about 30φ. The size after firing is about
With a 10φ roller, the accuracy is about ± 0.3 to 0.5%.

In the example shown in Figs. 1 and 2, the electrodes (5A, 5A ', 5
B, 5B ') are not exposed, there is no unevenness of the electrode part, and there is no diffusion of heat into the air due to heat generation from the surface.

FIG. 5 shows the PTC characteristics of the roller 1 produced by this method. This figure shows the temperature change of the resistance according to this embodiment at 25 ° C.
It is standardized based on the resistance of. The data in FIG. 5 are obtained by substituting 25 wt% Pb for Ba atoms. In this case, as the substitution amount of Pb increases,
Since the non-uniformity at the time of firing due to the evaporation of Pb is likely to occur, the Pb substitution amount is preferably small.

By making the PTC ceramic in this way, not only can it be made with a thin roller, but also a roller with good dimensional accuracy and less distortion can be made by baking the electrodes at the same time. The surface of this PTC ceramic roller is coated with a fluorine resin, and a bearing is provided at the end as a toner image heating / melting member in electrophotography.
The temperature characteristics of the heating roller with a conventional halogen heater (25 ± 5μ thickness for both cylindrical SUS and surface PTFE coating)
It was measured in comparison with. The results are shown in Table 1.

As shown in Table 1, good rising characteristics and good temperature distribution were obtained.

In the conventional one in which the roller of good thermal conductor is simply heated by the rod-shaped PTC ceramics, the PTC ceramic itself can be heated to 180 ° C in 20 to 30 seconds, but in order to reach the fixing roller surface to 180 °, It took a second to 100 seconds and the temperature distribution on the surface was quite non-uniform, showing a large difference from the present invention.

As described above, the PTC ceramic raw material is formed into a sheet, the surface of which is electrode-printed, and then cylindrically formed and sintered.
By making a PTC ceramic roller, it becomes possible to 1. make a PTC roller without impairing dimensional accuracy and without causing cracking or qualitative unevenness.
It is possible to produce a PTC ceramic roller with good generation efficiency, 2. By forming the electrode at the same time as firing the ceramic roller, it is possible to prevent dimensional deformation and crack due to thermal shock at the time of electrode attachment, and to provide a low cost roller. 3. By using it as a heating roller in a fixing device for electrophotography, it is possible to provide a fusing device which has a good start-up characteristic and which can be quick-started in a short heating time until reaching a predetermined temperature.

Further, as described above, when the electrodes have different electrodes on the circumferential surface (either the inner surface or the outer surface) of the roller in order, a large amount of heat is generated. This is for each electrode conductor 5
If the distance d between A and 5B, the number of conductors n, the parallel length 1 of the conductors 5A and 5B, and the resistivity of the unit length are Os, the resistance of the layer is Therefore, in order to obtain the total heat generation amount at 1 KW, R = 10Ω when 1 = 300 mm and the applied voltage is 100 (V). That is, when obtaining the above-mentioned heat generation amount with the above-mentioned pattern electrode, Os is 10 Ω / mm.
Then, d and n so that d (mm) × n = 300 (mm)
Since it suffices to set, there is an advantage that the design can be facilitated and the practical range can be expanded. Conversely, if the unit resistance, the distance d, and the number of conductors n are changed, a larger amount of heat generation can be obtained. Therefore, when fixing an undetermined amount of toner image, a good fixing property can be expected.

Even if separate electrodes are provided on the surface and the inner surface of the heat generating layer 4 to generate heat, the resistance is (A is the inner diameter of the inner surface electrode, b is the outer diameter of the outer surface electrode, and ρ is the specific resistance per unit length).
If you try to get 1KW by multiplying (V), the resistance is l = 300
mm, ρ = 10Ω / mm and R = 10Ω, lnb / a = 200 → b /
Since a = e ²⁰⁰ , it is impossible to achieve. Again 10
Even if a voltage of (V) or 1 (V) is applied, ba / = e ² , b / a
= E ^0.02 ≈1.02, which is impossible or requires an extremely large transformer, which is a large demerit in practical use.

In the above embodiment, (d × n) is preferably 18 <(d × n) ≦ 42 based on the above formula. Also PTC
The ceramic resistance is preferably 6 Ω to 50 Ω, and preferably 14 Ω or less in consideration of the heat generation of 1.5 KW or less and the heat generation at the time of rising of 700 W or more.

As in the example shown in FIG. 1, the inner surface layer 7 and the heat generating layer 4 are both PTC.
When the heating layer is used, the resistance of the heating layer 4, which is the outer surface layer, is smaller than the resistance of the inner surface layer 7. This has the advantage of shortening the time required at the start-up and the effect of preventing heat reduction during continuous fixing. is there. Further, by having a plurality of PTC heating layers, there is an effect that the temperature distribution on the surface of the fixing roller can be made more uniform.

It is preferable to provide a releasable layer on the surface of the heat-fixing roller. Layers 49, 59 and 9 which are the other configurations in FIG. 1 may be provided by any method, and inner layers 49 and 50 may be formed. It may be an electrical insulating layer of ceramics which can obtain sufficient strength.

The heat-fixing roller in the present invention includes a fixing roller that contacts an unfixed toner image, a roller that nips and conveys a recording material with the fixing roller, a roller that heats the fixing roller, and the like.

Further, the present invention has a novel and sufficient effect not only in the heat fixing roller but also in the fixing device including the pressure roller used together with this roller.

The voltage applying means 35 may be a means for substantially flowing a current or the like, but may be an alternating current (including a voltage wave meter such as a sine wave, a rectangular wave, a pulse wave, a triangular wave) or a direct current. When an alternating current is applied, the conductor alternates between a positive electrode and a negative electrode, but the surface in the claims includes these.

Although the electrode pair is shown as being parallel to the axial direction of the roller, it may be spirally formed on the inner or outer peripheral surface of the roller or slightly inclined with respect to the axial direction of the roller. The spiral electrode pair preferably has a small gap in a direction substantially close to the circumferential direction.

(Effects of the Invention) Since the present invention has the electrodes as described above, it is possible to effectively use the PTC characteristics and obtain a fixing roller having the PTC characteristics with good heat generation efficiency, and fix an unfixed toner image. It can be expected that the fixing property will be good.

[Brief description of drawings]

FIG. 1 is an explanatory view of the overall structure of an embodiment of the present invention, FIG. 2 is a perspective view of the embodiment of the heat fixing roller of FIG. 1, and FIG.
FIG. 4 is a perspective view of an axial main part of the heat fixing roller shown in FIG. 4, FIG. 4 is a perspective view of another embodiment of the heat fixing roller, and FIG. 5 is a graph showing a resistance change curve of a heat generating layer of the heat fixing roller of the present invention. FIG. 6 is a flow chart for explaining the manufacturing process of the present invention. 1 is a heat fixing roller, 2 is a pressure roller, 4 is a heating layer (PT
C ceramics), 7 is the inner surface layer (PTC ceramics), 5A, 5B,
8A and 8B are conductors, 9 is a surface release layer, 35 is a voltage applying device, 49
Is an insulating layer and 50 is a metallic cylindrical roller.

Claims (4)

[Claims] 1. A positive resistance-temperature characteristic (Positive) due to firing.
A heat fixing roller having a heating element layer for obtaining a temperature co-efficient of resistivity and an electrode pair fixed to the heating element layer, wherein the heating element layer is provided on the entire cylindrical surface of the roller, The pair of conductors forming one pole and the conductor forming the other pole are alternately provided inside the cylindrical heating element layer, and the conductors are provided in the longitudinal direction of the heating element layer, and between the conductors of different polarities. A heating and fixing roller characterized in that a part of a heating element layer has a uniform surface temperature in the roller longitudinal direction. 2. The heat fixing roller according to claim 1, further comprising an insulating layer inside the heating element layer. 3. A positive resistance temperature characteristic (Positive) by firing.
In a fixing device for fixing an unfixed image on a recording material by a heat fixing roller having a heating element layer for obtaining a temperature co-efficient of resistivity, and an electrode pair fixed to the heating element layer, The layers are provided on the entire cylindrical surface of the roller, and the electrode pair has conductors having one pole and conductors having the other pole alternately provided inside the cylindrical heating element layer, and the conductors extend in the longitudinal direction of the heating element layer. A fixing device characterized in that the portion of the heating element layer provided between the conductors of different polarities is made uniform in the direction, and the surface temperature in the roller longitudinal direction is made uniform. 4. The fixing device according to claim 3, further comprising an insulating layer inside the heating element layer.