JPH11296005A - Thermal fixing device - Google Patents

Abstract

(57) [Abstract] [Problem] While utilizing the energy saving and quick start property of a heat fixing device using a ceramic heater as a heat source,
Paper wrinkles due to overheating of the non-sheet passing portion due to variations in the transfer material size and damage to the periphery of the heater are prevented beforehand. SOLUTION: This is a heating and fixing device in which a heater substrate of a fixing unit is made of a high heat conductive ceramic such as an aluminum nitride ceramic, and a heat bypass including diamond having a high heat conductivity is arranged on at least one surface of the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating type toner image fixing device provided with a heater having an insulating ceramics substrate as a substrate and a heating portion provided thereon (hereinafter referred to as a ceramic heater in the present invention). .

[0002]

2. Description of the Related Art In an image fixing section (hereinafter simply referred to as a fixing section) of an image fixing apparatus such as a facsimile, a copying machine, a printer, etc., a toner image formed on a photosensitive drum is transferred onto a transfer material such as paper. After the fixing, the fixing unit heats and pressurizes the printing medium to print it on the transfer material. The fixing section has a heating roller provided with a ceramic heater and a pressure roller made of resin as main structural elements. In a fixing unit of a conventional fixing device, a heating roller is provided with a heat source such as a halogen lamp in a cylindrical metal roll, and heats the surface of the roll with radiant heat from the lamp.

In recent years, a heat source using a ceramic heater has been put to practical use. This type of fixing device is
For example, JP-A-63-313182, JP-A-1-263
679 and JP-A-2-157787. FIG. 1A schematically shows the structure of the fixing portion viewed from a cross section. In FIG. 1, reference numeral 2 denotes a resin support that forms the outer shape of the heating roller, 1 denotes a ceramic heater fixed to the support of the roller, and 3 denotes a fixing of the transfer material while rotating around the heater and the heating roller. Heat-resistant resin film to be fed into the part (hereinafter simply referred to as heat-resistant film), 4
Is a pressure roller, 5 is a transfer material fed between both rollers,
Reference numeral 10 denotes a toner image formed on the surface of the transfer material, which is exaggeratedly added. FIG. 1b is an enlarged view of the central part of a. In the figure, 11 is a substrate made of an insulating ceramic of a ceramic heater, 12 is a heat generating portion (hereinafter also referred to as a heat generating member) provided on the substrate, 14 is a heat-resistant film, and the surface of the heat generating portion is the same as the film. The insulating glass layer (hereinafter also simply referred to as a glass layer) that protects against direct sliding contact wear of the nip portion where the surface of the pressure roller is pressed against the heating roller side and the transfer material is sandwiched by being in close contact with the partner (W) (Hereinafter simply referred to as nip).

That is, while a transfer material is fed into a nip portion heated to a surface temperature sufficient to fix toner, a toner image is heated and pressed there to fix the toner image. As described above, the heat source is a ceramic heater, and the heater is arranged at a position close to the transfer material. In this method, the heat capacity of the heating element can be extremely reduced as compared with a conventional halogen lamp method in which the surface of a heating roller is heated from a heat source through a space. Therefore, power consumption can be reduced. In addition, since the heater and the fixing unit are close to each other, the temperature rises quickly, and there is no need to preheat the heat-generating unit to eliminate a waiting time unlike the conventional method, so that the so-called quick start property is excellent.

In recent years, demands for faster fixing operation, higher fixing quality, and more stable operation of the fixing device have been increasing daily in the market. Above all, the demand for high-speed fixing work is related to the fixing quality, which increases the heat cycle load on the ceramic heater and its peripheral parts. In the current fixing device, the substrate of the ceramic heater is made of alumina ceramics, and its normal fixing speed is 4 to 8 ppm (for example, 4 ppm).
Is an abbreviation of 4 Paper Per Minute, that is, a speed at which four A4-size transfer materials can be fed and fixed per minute.) There is a demand to further increase the speed to 12 ppm or more. In order to respond to this requirement while making use of the energy saving and quick start characteristics of the above-described method, it is necessary to reexamine the structure of the ceramic heater itself and the structure of the fixing unit around the ceramic heater itself. For example, current heaters that use alumina-based ceramics for substrates cannot follow the thermal conductivity and thermal shock resistance of the substrate, cannot withstand rapid temperature rise due to high speed, and cannot provide stable fixed images. Occurs. Therefore, it is necessary to review the substrate material. Even if the performance of such a substrate is reviewed, for example, if the thermal conductivity is increased, the amount of heat released to the surrounding area may be increased and energy saving may not be achieved, and it is necessary to review the heat insulation structure in the surrounding area is there. In order to meet the above-mentioned needs, the present inventors have proposed a structure of a fixing unit in which a ceramic having high thermal conductivity is used as a substrate and heat loss around the ceramic is reduced as described in Japanese Patent Application No. 8-285096. Have already proposed. As a result, with regard to the issues of rapid temperature rise and
It turns out that it can be overcome to some extent.

However, in a fixing operation in an office or the like, the size of the transfer material varies, so that
The following problems may occur. Usually, the size of the transfer material in the office is mainly A4, but in practice, for example, the size is large from A3 size to small postcard size.
According to the size, the length of the heat generating portion of the corresponding ceramic heater is also set to about 300 mm. Therefore, when fixing a transfer material of about A3 size corresponding to this, since the heat is almost uniformly removed by the transfer material, the heat uniformity of the nip portion is also kept almost constant. However, if a large number of transfer materials are continuously fixed to a fixing portion having the same length, for example, in a postcard size, a fixing portion in which the transfer material is not deprived of heat occurs, and the temperature is higher in that portion. A so-called abnormal heating section occurs. FIG. 2 illustrates this situation. FIG. 3 is a view of the fixing unit in FIG. 1 viewed from a direction in which the transfer material is fed. The parts indicated by the numbers 1 to 4 are the same as those in FIG. Reference numeral 5 denotes a transfer material having a small width such as a postcard or an envelope. The heat-resistant film 3 and the pressure roller 4 rotate synchronously in the direction of the arrow at the left end of the figure.
The transfer material 5 is sent from the near side to the far side.
The portion 6 divided by the dotted line is a portion through which the transfer material passes (hereinafter, referred to as a paper passing portion), and the portions 7 and 8 are portions through which the transfer material does not pass over the pressure roller (hereinafter, also referred to as a non-paper passing portion). . If the fixing of a large number of sheets is continued at the position of the sheet passing portion, the temperature of the non-sheet passing portion increases with time.

If such a situation continues, the surface of the rubber pressure roller at the corresponding position is deformed due to abnormal temperature rise of the non-paper passing portion, and the paper passing portion and the non-paper passing portion are deformed. The transfer speed of the transfer material changes, or the surface of the heater substrate corresponding to the non-sheet passing portion rises abnormally in temperature compared to the surface of the substrate corresponding to the sheet passing portion. Therefore, when the fixing operation of the transfer material having a large width is started again, wrinkles are generated near the edge of the transferred transfer material, or fixing failure due to the high-temperature offset phenomenon occurs. Further, the resin support to which the ceramic heater is fixed may be softened or partially melted. For this reason, Japanese Patent Application Laid-Open No. 6-149099 discloses a method in which a plurality of heat generating patterns are formed on a heater substrate and the length thereof is changed according to the width of the transfer material. Also, JP-A-8-3
Japanese Patent Laid-Open No. 05188 discloses a method of delaying the feeding of a transfer material having a small width when the transfer material is passed.

[0008]

However, according to the method described in Japanese Patent Application Laid-Open No. 6-149099, if the size variation of the transfer material to be fixed is to be increased, the length of the heater substrate in the width direction ( That is, the length in the depth direction of FIG. 2) must be increased. Therefore, the quick start performance, which is an advantage of the present method, is impaired. In addition, since the size of the substrate is increased, the substrate may not be able to withstand thermal shock due to rapid temperature rise and fall. Further, in the method described in JP-A-8-305188, it is inevitable that the fixing speed of the transfer material having a small size becomes slow and the work efficiency of the fixing decreases.

Therefore, the present inventors have already filed Japanese Patent Application No. 9-34.
No. 7760 and Japanese Patent Application No. 9-347761,
A heat fixing device incorporating a ceramic heater provided with a thermal bypass (commonly referred to as a heat spreader, which is also simply referred to as a bypass in the present invention) including a highly thermally conductive substance on the surface of a ceramic substrate has been proposed. . As a result, it was found that the above-described problems such as the generation of wrinkles of the large transfer material, the poor fixing due to the high-temperature offset phenomenon, and the softening of the resin support were considerably eliminated. In this application, as a high thermal conductive material constituting a thermal bypass (or a heat spreader), a metal containing copper / aluminum, molybdenum, tungsten as a main component, an alloy thereof, a high thermal conductive ceramic, and the like are exemplified. However, when a bypass is formed with a metal or an alloy thereof, the surface is liable to be oxidized by a rise in temperature when used for a long time, and it is necessary to cover the outermost surface with an oxidation-resistant layer.
Further, when a bypass is formed of ceramics having high thermal conductivity, for example, if ceramics having relatively high thermal conductivity is used for the heater substrate, a great effect of solving the above problem may not be expected. Therefore, in order to solve such various problems, it is necessary to arrange a bypass having higher thermal conductivity. An object of the present invention is to provide a bypass structure that can solve this problem while making use of the energy saving and quick start properties of the fixing system.

[0010]

In order to solve the above-mentioned problems, a heating and fixing apparatus provided by the present invention comprises a heater substrate of a fixing portion made of an electrically insulating ceramic and having a high heat conduction around a heating portion on the substrate. A thermal bypass including diamond, which is a conductive substance, is provided. That is, the heat fixing device of the present invention is provided on a heating roller, a ceramic heater provided with a heat generating portion on a substrate made of electrically insulating ceramics, a heat-resistant film that rotates in sliding contact with the ceramic heater, A pressure roller that slides and rotates while applying pressure, and is moved between the heat-resistant film and the pressure roller by pressing by the pressure roller and heating by the ceramic heater via the heat-resistant film. A heat fixing device for fixing a toner image formed on a surface of a transfer material to be formed, wherein a heat bypass including diamond which is a high thermal conductive material is provided on the surface of the ceramic heater.

Further, the heat fixing device of the present invention has a heater structure having the above-mentioned basic structure, in which a heat generating portion is formed on a substrate on a side opposite to a sliding contact surface between the heat-resistant film and the substrate (hereinafter also referred to as a rear type). ) Is also included.

According to one arrangement of the thermal bypass of the present invention, (1) there is an arrangement in which at least one surface of the ceramic substrate is disposed substantially over the entire surface. (2) Some of the ceramic substrates are arranged on at least one surface of the ceramic substrate, and are partially distributed in the same surface at positions substantially corresponding to the heat generating portions. Still further, (3) there is one provided on the surface of the substrate which is in sliding contact with the heat-resistant film. (4) As a preferable material of the electrically insulating ceramic substrate, there is one using aluminum nitride ceramics.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The abnormal temperature rise in the non-sheet passing portion, which is a problem in the present invention, is caused by the fact that the heat capacity of the ceramic substrate and its peripheral portion is small, and the heat supplied from the heater and accumulated in the non-sheet passing portion. It is caused by the inability to sufficiently inform the department. That is, the heat capacity of the substrate itself is small, and since the support and the pressure roller for fixing the heater are made of rubber or resin, heat transfer between the non-sheet passing portion and the sheet passing portion is not promoted. In order to solve this, in the present invention, a thermal bypass including diamond connecting them between the non-sheet passing portion and the sheet passing portion is provided on the ceramic substrate. The location where the bypass is formed is disposed so as to thermally connect corresponding portions of the ceramic substrate on which both the non-sheet passing portion and the sheet passing portion are formed. This makes it possible to increase the amount of heat transfer from the non-sheet passing portion to the sheet passing portion, thereby lowering the temperature of the non-sheet passing portion.

Hereinafter, the heat fixing device of the present invention will be described in detail. FIG. 3 schematically illustrates one basic structure of a ceramic heater used in the heat fixing device of the present invention. As shown in FIG. 1, a current is supplied to a resistance heating portion 12 provided on a substrate 11 made of electrically insulating ceramics from a current supply electrode 13 electrically connected to the resistance heating portion 12. In this case, the heater is fixed to the support with the heat generating portion forming surface facing the pressure roller side (this fixing method is also referred to as a front type). Therefore, in this case, a pressure from the pressure roller side is applied to the heat generating portion forming surface of the substrate, and the heat resistant film moves while sliding on the same surface. Therefore, the surface of the heat generating portion is covered with an insulating glass layer 14 in order to prevent the heat generating portion from being worn by sliding movement of the film. FIG. 3A is a view from the top of the heat generating portion, and actually, the heat generating portion 1 is shown.
2 is covered by the insulating glass layer 14. FIG.
B is its AA 'cross section.

In the fixing device of the present invention, the mounting direction of the ceramic heater to the support is generally the same as that shown in FIG.
Is set to the front type as described in. However, the direction can be reversed. In this case, the heat generating portion forming surface is on the opposite side to the pressure roller (that is, the above-mentioned back type). No sliding contact with heat-resistant film. Therefore, for example, the heating portion may not be covered with the insulating glass layer. 4A is a front type, and b is a back type. Note that the reference numerals in FIG.

According to the heat fixing apparatus of the present invention, in the above basic structure, a thermal bypass including diamond is thermally connected to the surface of the substrate made of electrically insulating ceramic by bonding or the like to the substrate surface. Thus, the heat radiation from the substrate can be made smooth, and the above-mentioned problem caused by abnormal heating of the non-sheet passing portion can be prevented even at the time of fixing after the continuous fixing operation in which the non-sheet passing portion is formed. Diamond is pure, has a thermal conductivity of 1000 W / m · K or more, and can be expected to have extremely excellent heat dissipation. Also in the thermal expansion coefficient is small as about 2.3 × 10 ^{over 6} / ° C., is excellent in its compatibility with the ceramic substrate. Regarding the composition of the material containing diamond constituting the thermal bypass and the structure and structure thereof, any material may be used as long as a heat radiation effect can be expected to the extent that the above-described abnormal overheating of the non-paper passing portion can be avoided. In order to ensure the heat dissipation of the bypass, the amount of pure diamond in the bypass is at least 50% by volume or more, preferably 70% by volume or more, and more preferably 100% by volume.
That is, a single phase is desirable. If the thermal conductivity can be enjoyed, minor components such as boron (B), phosphorus (P), and nitrogen (N) may be contained in a range of up to 1% by weight (hereinafter, in the present invention, such components are used). The diamond phase in the bypass containing the component is also called a diamond composition).

The texture or structure of the diamond or diamond composition being bypassed may be either (1) a single substance or (2) a composite with another substance. In the case of (1), it is usually formed in a film shape with various macro patterns. However, diamonds or diamond compositions are expensive, and it is economically desirable to minimize these amounts during bypass, as in (2). In the case of (2), usually a diamond or a diamond composition is used as a matrix, and another substance to be combined with the matrix is made to coexist in the gap. Other substances are preferably thermally conductive in order to sufficiently exhibit the function of the thermal bypass. When diamond or a diamond composition is distributed and compounded in the bypass, the individual distribution units may be in any shape such as particulate or fibrous, but the individual units are three-dimensionally connected to each other. Is desirable. In addition, the connecting portions may be connected by another substance, but in this case also, the other substance is preferably thermally conductive in order to sufficiently exhibit the function of the thermal bypass. The main component of the thermally conductive substance is aluminum nitride (AlN, the thermal conductivity is 150 W / m · K or more,
About thermal expansion coefficient of 4.2 × 10 ^{over 6} / ° C.), silicon nitride (Si ₃
N ₄ , thermal conductivity of 50 W / m · K or more, thermal expansion coefficient of 3.
0 × 10 ^{over 6} / ° C. approximately), boron nitride (BN, thermal conductivity 20
0 W / m · K or more, the thermal expansion coefficient of 3.5 × 10 ^-6 / ° C. approximately), silicon carbide (SiC, thermal conductivity of 200 W / m · K or more, the thermal expansion coefficient of 3.5 × 10 ^-6 / ° C), high thermal conductive ceramics, tungsten (W, thermal conductivity 170
W / m · K or so, the thermal expansion coefficient of about 4.3 × 10 ^{over 6} / ° C.),
Molybdenum (Mo, thermal conductivity of 140 W / m · K or so, the thermal expansion coefficient of about 4.9 × 10 ^{over 6} / ° C.), nickel (Ni, the thermal conductivity of 90W / m · K or so, the thermal expansion coefficient 13.3 × 1
0 ^{over 6} / ° C. approximately), a refractory metal or silver, etc. (Ag, thermal conductivity of 420 W / m · K or so, the thermal expansion coefficient of 19.7 ×
10 ^{@ 6} / ° C. approximately), platinum (Pt, thermal conductivity of 70 W / m · K
Extent, the thermal expansion coefficient of 8.9 × 10 ^{over 6} / ° C. C.), etc. of the precious metals and copper (Cu, the thermal conductivity of 400W / m · K or so, the thermal expansion coefficient of 17 × 10 ^{over 6} / ° C. approximately), etc. An alloy / composite of the above-mentioned metal and the above-mentioned metals, a product obtained by appropriately combining various materials such as the above-mentioned ceramics and metals, and a resin in which the various materials are dispersed are conceivable.

As a macro structure of the thermal bypass containing the diamond or the diamond composition of the present invention, the bypass main body may be made of the above-mentioned various materials having thermal conductivity, and a part thereof may be composed of the diamond or the diamond composition. This can reduce the amount of expensive diamond or diamond composition and reduce the cost of bypass. In this case, it is necessary to arrange a portion made of diamond or a diamond composition without fail in order to effectively utilize the heat radiation effect of the main body, especially at the contact portion with the ceramic substrate. Also, there are various possible arrangement patterns on the main body as viewed from the entire bypass, but it is necessary to consider the heat radiation direction and heat dissipation efficiency, and also to consider the thermal action on the surrounding parts enough to optimize it There is.

The connection method between the thermal bypass containing diamond of the present invention and the ceramic substrate may be any method as long as the above-mentioned object of the present invention can be achieved. Take the method. Here, the contact in the present invention refers to a state in which at least a part of the bypass is in contact with the surface of the substrate, and a close contact refers to a state in which at least a part of the bypass is easily peeled off on the surface of the substrate, The term "indicates a state in which at least a part of the bypass is fixed to the surface of the substrate to such an extent that the bypass is not easily removed chemically or physically. An intervening layer may be provided between the two layers for joining, but in this case, the same layer should not interfere with heat transfer.

[0020] When using a single of diamond or diamond composition, its thermal expansion coefficient of 2.3 × 10 ^-6 /
Because of the low temperature of ℃, good matching with ceramic substrate with relatively low coefficient of thermal expansion is good, there is almost no risk of contact failure due to the same coefficient difference and heat transferability is impaired. It is uneconomical to use them in contact and close contact with each other. Usually, they are formed into a film on a substrate in a predetermined surface pattern and then joined.

However, in the case where a material compounded with another substance is used as a bypass as described above, a method that does not hinder thermal connection due to a difference in thermal expansion coefficient between both the bypass and the substrate is appropriately adopted. Choose. When the difference between the thermal expansion coefficients of the ceramic substrate and the bypass of the heater is large, that is, when the thermal stress generated in practical use when joining is large enough to peel off or damage the ceramic substrate (for example, the above-mentioned thermal expansion coefficient of the bypass body is large). When a large metal or resin is selected as a mating partner, the bypass is connected to the substrate surface by contact or close contact. When the difference between the two thermal expansion coefficients is relatively small (for example, when the above-mentioned metal / ceramic having a small thermal expansion coefficient is selected as a mating material for the bypass body), when the same thermal stress is not so large. Are connected by close contact or bonding.

When the bypass is thermally connected by contact, a part of the bypass may be extended to a space outside the substrate. In addition, if the bypass itself containing diamond can be made flexible by a matrix component other than diamond constituting it (for example, using an electrically insulating resin containing a thermally conductive material for the matrix, There are various methods for physically bringing the entire surface into close contact with or in contact with the substrate surface.
When a composite bypass containing diamond is used, in order to increase the amount of heat transfer, it is desirable to form the bulk as compact as possible.

The bypass made of a high thermal conductive material may be provided on any surface of the substrate, and may be provided not only on one surface but also on a plurality of surfaces. In this case, it is preferable to be provided over almost the entire surface. Since the heat accumulated in the non-sheet passing portion is transmitted to a wide portion of the ceramic substrate by being formed over almost the entire surface, not a part of the selected surface, the effect of lowering the temperature of the non-sheet passing portion is increased. It is. The arrangement pattern is
If you cover almost the entire surface when viewed from the top in one plane,
Any pattern may be used, and if it is desired to partially increase the cross-sectional area in the heat transfer direction due to the bypass shape,
The thickness of the bypass in that portion may be increased, or the cross-sectional shape of the bypass may be appropriately modified. For example, at a position corresponding to a portion that is always a paper passing portion when viewed from above, a slit portion or a thin portion where the substrate surface is exposed when viewed from above is provided, or the thickness of the cross section is reduced as a whole. Be creative. In order to increase the heat radiation area of the bypass portion corresponding to the non-sheet passing portion, it is also effective to make the surface uneven.

FIG. 5 schematically shows an example of the arrangement. In this example, a bypass is provided on almost the entire surface on the opposite side to the surface on which the heat generating portion is formed. In this case, the bypass may be formed on almost all of one or both of the side surfaces in the longitudinal direction of the substrate, or may be formed on the entire side surface of one or both ends in the longitudinal direction of the substrate. Alternatively, some of these positions may be arranged in combination. In this figure, a is a view as viewed from the upper surface of the heat-generating portion, b is a view as viewed from the back thereof, and c is a diagram showing a cross section taken along line AA ′ of a. In the figure, reference numeral 9 denotes a heat conduction bypass including a highly heat-conductive substance. Those with other instruction numbers are shown in FIG.
4 or FIG. This makes it possible to efficiently remove heat transmitted from the heat generating portion of the substrate in the thickness direction of the substrate.

The bypass may be provided at a position corresponding to the heat generating portion of the substrate. FIG. 6 schematically shows an example in which a bypass is provided at a position corresponding to a heat generating portion and on a glass layer covering the heat generating portion. In this case, the bypass is provided on the sliding contact surface of the substrate with the heat-resistant film. FIG. 7 schematically shows an arrangement in which a bypass having the same length as that of the heat generating portion is provided on the back surface of the heat generating portion. Note that the subdivisions a, b, and c in both figures and the designation numbers of the respective parts are the same as in FIG. In these cases, if the bypass is disposed at a position substantially corresponding to the heat generating portion, the bypass may be formed on one or both of the side surfaces in the longitudinal direction of the substrate, or may be formed on one or both sides in the longitudinal direction of the substrate. May be formed. Alternatively, some of these positions may be arranged in combination. Since a bypass having a higher thermal conductivity than a ceramic substrate is usually used, if a bypass is formed on the back surface as shown in FIG. 7, heat flows preferentially to the back surface when the temperature of the heater rises, and the bypass flows to the front surface. 6, the temperature rise on the fixing surface side for fixing tends to be slower than in the case of FIG. Therefore, from the viewpoint of quick start, the latter bypass arrangement is preferable. However, it has been confirmed by the present inventors that even the arrangement as shown in FIG. 7 does not significantly impair the quick start property of this method.

When a bypass is provided on the heat-generating portion side of the substrate, the heat-generating portion and the bypass must be electrically insulated, especially if the bypass is of the aforementioned composite type and is conductive. In FIG. 6, an electrically insulating glass layer is formed between them, but various measures are taken, such as leaving some space between them in consideration of the withstand voltage level of the substrate, or sandwiching another insulator between them. There is. In the case of FIG. 6, when the bypass is provided on the outermost surface, the heat-resistant film comes into direct sliding contact with the outermost surface. Therefore, if the diamond or the diamond composition portion in the bypass is exposed on the sliding contact surface, the sliding is performed. The wear caused by the material is not a problem, but if not, use ceramics with a low coefficient of friction as the mating material, or use the entire bypass or only its sliding contact surface with excellent sliding properties with the heat-resistant film. It is necessary to keep. Therefore, for example, in order from the substrate side,
It is also conceivable to laminate such as: / glass layer (or electric insulating layer) / bypass / glass layer (or good slidable electric insulating layer). In this case, if the electric insulating layer is also thermally conductive at the same time, nothing goes beyond that. The candidates are aluminum nitride (AlN), silicon nitride (Si
₃ N _4), there are so ceramics materials boron nitride (BN). However, in such a case, in the same plane from which the upper portion of the heat generating portion is removed, from the same plane to the adjacent plane, or FIG.
This problem does not occur if the bypass is provided in a plane where the heat generating portion is not formed as in the above. Of course, the bypass is made of an insulating and thermally conductive material such as aluminum nitride (Al
N), silicon nitride (Si ₃ N ₄ ), boron nitride (BN), and other ceramics do not require the above measures.

The same structure can be basically applied to the case of the back type in which the heat-generating portion shown in FIG. 6 is not provided on the heat-resistant film side. However, when the bypass is provided on the back surface of the heat-generating portion, that is, on the side in contact with the heat-resistant film. It is necessary to make the entire bypass or only the sliding contact surface thereof excellent in the slidability with the heat-resistant film as in the above. When the bypass is provided on the side of the heat-generating portion, there is no sliding with the heat-resistant film.

By eliminating the electrode portion for energizing the heat generating portion from the area where the heat generating portion is disposed as described above, the copper is disposed near the electrode and connects the electrode to an external power source without setting the entire surface of the bypass. Oxidation of the connector can be suppressed. If a bypass is also formed in a portion corresponding to the electrode portion, the thermal conductivity of the bypass portion is usually set to be higher than that of the substrate, so that heat flows selectively to the same portion, thereby causing the temperature near the electrode at the edge of the substrate to be lower. This is because the connector is easily oxidized since the connector easily rises. In particular, when a bypass is formed on the same surface as the connector arrangement surface as shown in FIG. 6, it is better to take this point into consideration, although there is a glass layer between them. In addition, as described above, when a conductive material other than diamond or a diamond composition is selected as a mating material for the bypass material, this point must be taken into consideration in order to ensure electrical insulation between the electrode and the bypass. Care is preferably taken. For the same reason, it is safe to set the distance between the end of the bypass and the end of the electrode portion near the heat generating portion as wide as not to impair the heat radiation effect of the bypass of the present invention.
As described above, the configuration of the bypass may be bulk or film. Depending on the type of the bypass material, a part of the bypass may be in contact with the substrate surface, Any connection method may be used, such as close contact or joining.

[0029]

EXAMPLES (Example 1) as an electrical insulating ceramic substrate, length 400 mm, width 10 mm, made of aluminum nitride having a thickness of 1 mm (AlN), silicon nitride (Si ₃ N ₄₎ made of alumina (Al ₂ O ₃₎ Was prepared. Their thermal conductivity is 150 W / m · K, 100 W / m · K, 20 W / m
· K, and thermal expansion coefficient in turn 4.2 × 10 ^{over 6} / ℃, 3.
0 was × 10 ^{over 6} /℃,7.0×10 ^{over 6} / ° C.. The ceramic heater shown in FIG. 3 was manufactured using these substrates. First, the Ag paste is screen-printed, the pattern of the current-carrying electrodes 13 is printed, and the Ag-Pd paste is screen-printed to form the patterns of the heat-generating portions 12, which are baked in the air at 880 ° C. and baked on the substrate 11. Was. Next, the glass paste is screen-printed at 750 ° C.
It was fired in the air and baked in the pattern shown in FIG. 3 to produce a ceramic heater having the structure shown in FIG.

Based on the connection structure shown in FIG. 5, FIG. 6, and FIG. 7, and according to the form of the heat generating portion of the finished ceramic heater substrate, a heat conductive material having a heat conductivity of 1
000 W / m · K diamond layer with hot filament C
It was formed with an average film thickness of 60 μm by the VD method. The pattern of the film forming section has a width of 8 mm, a length of 300 mm, and 38 mm.
Two shapes of 0 mm were formed. The film formation conditions were such that the gas composition was 2% methane and 98% hydrogen, and the pressure was 70 Torr. A pattern having a pattern length of 300 mm has a length equivalent to a heat generating portion, and is used for a sample having a connection structure corresponding to FIG. 6 or 7. A pattern having a pattern length of 380 mm has a length substantially corresponding to the entire length of the substrate. And used for a sample having a connection structure corresponding to FIG. Therefore, in Table 1, the "bypass" column is shown by the figure number. Thereafter, the heater was fixed to a resin support.

Further, the same connection structure, length and width pattern and a thickness of 2 μm with a 3 μm nickel plating on the outermost surface
mm electrolytic copper (thermal conductivity of 400W / m · K, the thermal expansion coefficient of 17 × 10 ^{over 6} / ° C.) of providing those using thin plate made of a bypass (samples 13 to 15 in Table 1) and heat the bypass Samples without samples (Samples 1, 5, and 9 in Table 1) were also prepared. In this state, a fixing test was performed by assembling the heat fixing device having the basic structure shown in FIG. In the case of using electrolytic copper as a bypass, one end of the thin plate was fixed to the resin support, and the thin plate was thermally connected to the corresponding surface on the substrate by its spring property.

At a fixing speed of 4 ppm, these set samples are first fixed continuously for a predetermined number of sheets of an envelope size having a sheet passing width of about 100 mm as shown in Table 1, and then A3 sheets having a sheet passing width of about 300 m at the same fixing speed. One sheet of large paper was fed, and the fixing state was observed. This was repeated, and the results were added together in Table 1.
Shown in It should be noted that the paper passing position of the envelope-sized paper was almost centered toward the paper passing surface as shown in FIG. In addition, the temperature of the non-paper passing part formed on the left and right of the paper passing part after the paper of the envelope size is passed is higher than the temperature of the paper passing part, and when confirmed with an infrared radiation thermometer from the front, The surface temperature difference of the heater between the paper passing portion and the non-paper passing portion at several stages of each paper passing was almost at the level described in the lower part of the “fixing status” column in Table 1. The evaluation (1) in the fixing status column in the table indicates the presence or absence of paper wrinkles, the evaluation (2) indicates the presence or absence of damage to the support, and the evaluation (3) indicates the fixing quality. In the evaluation (1), x indicates `` paper wrinkles occur in the non-sheet passing portion '', △ indicates `` paper wrinkles without practically hindering '', ○ indicates `` no paper wrinkles '', and x in evaluation (2) indicates `` The resin in the heater mounting part of the non-paper passing part is greatly damaged. "△" indicates that the resin in the heater mounting part of the non-paper passing part is partially damaged. "No change", x in evaluation (3), "high-temperature offset occurred in non-paper passing area", △: "slightly high-temperature offset occurred in non-paper passing area to the extent that practically no hindrance occurred", ●: "A"
A slight low-temperature offset occurs at the end of the non-sheet passing area of three large sheets
Corresponding to each level. The “non-sheet passing portion” in the above description of the evaluation level refers to the non-sheet passing portion of the large envelope.

Further, the same evaluation as described above was carried out by fixing the heater having the same basic bypass structure as that of the sample 4 to two support members of the front type and the back type. First, the same aluminum nitride substrate and the same bypass member as in Sample 4 were prepared.
The bypass was brought into close contact with the surface of the substrate on the side of the heat generating portion by the same procedure as in (1) (that is, the bypass was connected to the substrate surface in the same procedure as described above with the connection structure based on FIG. 7). In this case, as described above, the orientation of the heater on the side of the heat generating portion was of two types, a front type and a rear type. Fixing conditions are the same speed as above,
At the same fixing temperature, the same procedure as described above is performed. First, the envelope-sized paper is first pre-passed as shown in Table 2 and then the A3-sized paper is passed through one sheet. After passing A3 large sheets at each sheet passing number stage, the same items as described above were checked. Table 2 shows the results. Table 2 does not show the temperature difference of the substrate surface between the sheet passing portion and the non-sheet passing portion at each stage of the number of sheets of the envelope large sheet before passing the A3 large sheet. It was almost the same as Sample 4. “A3 paper fixing status” in the table means “A3 paper at each passing stage of large envelope paper”.
The number of sheets in the same column means the number of sheets of the large envelope paper at each passing stage. Hereinafter, the same display is performed in each table.

The same test and evaluation were performed on the set of sample numbers 2, 3, and 4 up to 1000 sheets under the same fixing conditions, and further, by increasing the fixing speed to 12 ppm and up to 1000 sheets. The evaluation result of the level described in 1 is obtained. By combining the thermal bypass of the present invention with an aluminum nitride ceramic substrate having a particularly high thermal conductivity, it can function stably even in a long-time and high-speed operation state. It turned out to be.

[0035]

[Table 1]

[0036]

[Table 2]

From the above results, the paper wrinkles of the A3 large paper at the non-paper passing portion of the envelope due to the abnormal temperature rise of the non-paper passing portion is due to the cumulative number of paper passing of the large envelope paper (that is, the number of paper passing in the above table). And the quality of the fixed image itself tends to decrease with the cumulative number of sheets passed, but it can be seen that the provision of the bypass improves the quality at least to a level at which there is no practical problem. In particular, as shown in FIG. 6, it can be seen that the arrangement structure of the sample 3 in which the bypass is provided on the side of the heat generating portion shows the most preferable result. This is probably because the bypass is provided close to the heat-radiating surface of the heat-generating portion, so that the heat moves faster. Note that no deterioration due to oxidation of the connector near the current-carrying electrode was confirmed within the test condition range of up to 10 sheets. From the data in Table 2 for both the front type and the back type arrangement, it can be seen that the back type has somewhat better long-term operation stability. This is considered to be due to the influence of the presence or absence of the heat insulation phenomenon of the nip portion due to the sliding contact with the heat-resistant film as in the front type in the back type.

(Example 2) As an electrically insulating ceramic substrate, aluminum nitride (Al) having the same shape as in Example 1 was used.
A heater having the basic structure shown in FIG. 3 using a ceramic substrate manufactured by N) was manufactured, and the basic structure shown in FIG.
A heat bypass containing a diamond or a diamond composition having an outer dimension of mm × 0.5 mm and containing the contents shown in Table 3 was arranged in the arrangement form shown in the same table, and a fixing test was performed under the same conditions as in Example 1. The same items as in Example 1 were evaluated. Table 4 shows the results.

For all the sample sets shown in Table 3, under the same fixing conditions, up to 1000 sheets and a fixing speed of 12
When the same test and evaluation were performed up to 1000 sheets at the same time, the evaluation results were obtained at the level substantially as described in Table 4 in each case. It turned out that it functions stably even in the state.

[0040]

[Table 3]

[0041]

[Table 4]

From the above results, by installing various composite materials containing diamond (diamond composition) as a thermal bypass on the ceramic substrate surface in various arrangements, the thermal conductivity of the bypass itself is not impaired, and the It can be seen that an excellent heat radiation effect for preventing the temperature rise of the paper portion was obtained, and no problems were caused by paper wrinkles, deterioration of image fixation, and overheating damage of the peripheral portion of the heater of the support. This stable state is
It has been found that the device can be stably maintained even in a high-speed operation or a long-time operation.

[0043]

According to the present invention, by disposing a thermal bypass made of a substance containing diamond having high thermal conductivity on the surface of the ceramic heater of the heating and fixing device which is heated by the ceramic heater, non-uniformity due to the size variation of the transfer material can be improved. It is possible to prevent the transfer material from being damaged in the paper passing portion and the thermal damage to peripheral members of the ceramic heater. Therefore, a highly stable heat fixing device can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a cross section of a fixing unit of a heat fixing device of the present invention.

FIG. 2 is a schematic view of a fixing unit of the heat fixing device of the present invention as viewed from the front.

FIG. 3 is a schematic view showing an example of a basic structure of the ceramic heater of the present invention.

FIG. 4 is a schematic diagram showing a heater arrangement type of a fixing unit of the heat fixing device of the present invention.

FIG. 5 is a schematic view showing one structural example of a heater of the heat fixing device of the present invention.

FIG. 6 is a schematic view showing one structural example of a heater of the heat fixing device of the present invention.

FIG. 7 is a schematic diagram showing one structural example of a heater of the heat fixing device of the present invention.

[Explanation of symbols]

 1, ceramic heater 2, support or heating roller 3, heat-resistant film 4, pressure roller 5, transfer material 6, paper passing unit 7, non-paper passing unit 8, non-paper passing unit 9, thermal bypass 10, toner image 11 , Ceramic substrate 12, heating section 13, conducting electrode 14, glass layer

Claims (6)

[Claims] 1. A ceramic heater provided on a heating roller and provided with a heat generating portion on a substrate made of an electrically insulating ceramic, a heat-resistant film rotating in sliding contact with the ceramic heater, and a pressure in sliding contact with the film. A pressure roller that rotates while applying pressure, and is moved between the heat-resistant film and the pressure roller by pressure by the pressure roller and heating by the ceramic heater via the heat-resistant film. A heat fixing device for fixing a toner image formed on a surface of a transfer material to be heated, wherein a heat bypass including diamond is provided on a surface of the ceramic heater. 2. The heat fixing device according to claim 1, wherein the heat generating portion is formed on a substrate on a side opposite to a sliding contact surface between the heat resistant film and the substrate. 3. The heat fixing device according to claim 1, wherein the thermal bypass is provided over at least one entire surface of the substrate. 4. The heat bypass according to claim 1, wherein the heat bypass is disposed on at least one surface of the substrate and is distributed at a position substantially corresponding to a heat generating portion. Heat fixing device. 5. The heat fixing device according to claim 1, wherein the heat bypass is provided on a surface of the substrate that is in sliding contact with the heat-resistant film. 6. The heat fixing device according to claim 1, wherein the electrically insulating ceramic is an aluminum nitride-based ceramic.