JPH1032081A - Surface heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently cope with an abrupt increase in temperature, and furthermore easily set a surface heater in a limited set-up space by letting the surface heater be applied to service requiring temperatures to be increased to a range of high temperatures in a short time. SOLUTION: The resistor 1 of a surface heater is made out of ferrite stainless steel, and it can be obtained as a fine resistor pattern by an etching process. Insulating bodies 3 and 5 made out of fluocopite mica material are disposed over the front and back sides of the resistor 1, the resistor 1 is held by the insulating bodies 3 and 5, and furthermore it is heated so as to be integrally contacted with pressure. Besides, both the ends of the resistor 1 are turned out to be electrodes 1a and 1b. The reason why ferrite stainless steel is used as the resistor 1, is that its coefficient of thermal expansion is comparatively low from the stand point of thermal expansion, and furthermore that it is identical or close to the coefficient of thermal expansion of the phlogopite mica material as the insulating bodies 3 and 5. Another reason is that a material provided with strong magnetism is fovorable from the stand point of manufacture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar heating element, and more particularly to an application for increasing a temperature to a high temperature range in a short time, for example, as a heating element for an image fixing unit of an image forming apparatus such as an electrophotographic apparatus. The present invention relates to a device devised so as to be suitable for the purpose of use.

[0002]

2. Description of the Related Art For example, in an image forming apparatus such as an electrophotographic apparatus, an image fixing section is provided, and a sheet passing through the image fixing section is pressed by a pressure roller while being heated by a heating element. Then, the toner image is surely fixed on the paper. FIG. 6 shows this state. First, there is a pressure roller 101.
01 is a cylindrical member 1 made of, for example, a heat-resistant film.
03 are opposed and arranged. At a predetermined position of the cylindrical member 103, a heating element 107 for heating the sheet 105 passing therethrough is arranged.

The heating element 107 has a configuration as shown in FIG. First, there is a substrate 109.
09 is made of, for example, alumina ceramics. On the substrate 109, a metal resistor 111 is mounted. The left and right ends of the resistor 111 in FIG. 7 are electrodes 111a and 111b.

According to the above configuration, for example, the paper 105 to which the toner adheres in a predetermined state (a state based on predetermined image information) passes through an image fixing unit, that is, between the pressure roller 101 and the cylindrical member 103. . At that time, the heating element 107
The paper 105 passing therethrough is heated, and pressed by the pressure roller 101 toward the cylindrical member 103. In this way, by applying heat and pressure, the adhered toner is fixed on the paper 105.

[0005]

According to the above-mentioned conventional configuration, there are the following problems. That is, in the image fixing section as described above, for example, in order to shorten the time required for fixing, a predetermined high temperature (about 250
(° C.). However, in the conventional heating element, the substrate 1 of the heating element 107 is not used.
09 may not be able to cope with such a rapid change in thermal environment and may be damaged. On the other hand, there are heating elements that respond to such rapid changes in the thermal environment,
Each of them is large in size and has a problem that it cannot be installed in a limited space like an image fixing section of an image forming apparatus such as an electrophotographic apparatus. Therefore, in the conventional case, the heating element 107 as shown in FIG. 7 is used, and at this time, in order to prevent the substrate 109 from being damaged, the temperature is gradually increased while avoiding a sudden change in the thermal environment. As a result, there has been a problem that the time required for fixing is prolonged and the operating rate of the apparatus is reduced.

The present invention has been made based on such a point, and an object of the present invention is to be able to sufficiently cope with a rapid temperature rise, and to provide a small installation space. Another object of the present invention is to provide a sheet heating element which can be easily installed.

[0007]

Means for Solving the Problems To achieve the above object, a planar heating element according to the present invention is a planar heating element formed by sandwiching and integrating a resistor made of metal foil with an insulator made of mica material. The thermal expansion coefficient of the resistor is relatively low or the same as the thermal expansion coefficient of the mica material, and is characterized in that it is used for increasing the temperature to a high temperature range in a short time. is there. At this time, it is conceivable to use a resistor having ferromagnetism as the resistor. It is also conceivable to use ferritic stainless steel as the resistor. Further, as a use for raising the temperature to a high temperature range in a short time, for example, a use as a heating element in an image fixing unit of an image forming apparatus such as an electrophotographic apparatus can be considered.

[0008]

In other words, in the case of the sheet heating element according to the present invention, a mica material having excellent heat resistance and thermal shock resistance is used as an insulator, and a relatively low coefficient of thermal expansion is used as a resistor. A material having the same or close thermal expansion coefficient as that of the mica material is used. Then, it is configured to be used for a high wattage application requiring a rapid temperature rise. Further, it is conceivable to use a resistor having ferromagnetism from the viewpoint of a manufacturing method. And
As such, for example, it is conceivable to use ferritic stainless steel. In the case of this ferritic stainless steel, its coefficient of thermal expansion is 13 × 10 ⁻⁶ / ° C.
The coefficient of thermal expansion is relatively low, and is close to the coefficient of thermal expansion of the flocopite-based mica material of 14 × 10 ⁻⁶ / ° C. It also has strong magnetism.
Further, as an application at a high wattage requiring a rapid temperature rise, for example, an application as a heating element in an image fixing unit of an image forming apparatus such as an electrophotographic apparatus can be considered, and in this case, further limited. In such a case, the resistor can be effectively applied in such a case, for example, by setting the resistance density of the resistor to 2Ω to 10Ω / cm ² .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS.
A first embodiment of the present invention will be described. First, the configuration of the sheet heating element according to the present embodiment will be described with reference to FIG. First, there is a resistor 1, which is made of ferritic stainless steel and obtained as a fine resistor pattern by etching.
On both front and back sides of the resistor 1, insulators 3 and 5 made of flocopite-based mica material are arranged.
Is sandwiched by the insulators 3 and 5, and
The structure is integrated by crimping. Note that both ends of the resistor 1 are electrode portions 1a and 1b.

Here, the background of using ferritic stainless steel as the material of the resistor 1 will be described. First, from the viewpoint of thermal expansion, the coefficient of thermal expansion is relatively low, and
It is conceivable to use a material having a thermal expansion coefficient equal to or close to that of the flocopite-based mica material as the insulators 3 and 5. For example, a nickel-chromium alloy (coefficient of thermal expansion: 14 ×
10 ^-6 / cm ² ) and ferritic stainless steel (coefficient of thermal expansion: 13 × 10 ^-6 / cm ² ). Incidentally, the thermal expansion coefficient of the flocopite-based mica material is 14 × 10 ⁻⁶ / cm ² .

Next, a problem in the manufacturing method for manufacturing the sheet heating element is taken into consideration. That is, in the sheet heating element according to the present embodiment shown in FIG. 1, the resistor 1 obtained by etching needs to be fixed on the insulator 3 (or 5), and the fixing is performed by a magnet. ing. Therefore, it is preferable that the resistor 1 has strong magnetism (because it is necessary to be attracted and attracted by a magnetic force via the insulator 3 or 5). From such a viewpoint, the nickel-chromium alloy (coefficient of thermal expansion: 14 × 10 ⁻⁶ /
cm ² ), ferritic stainless steel (coefficient of thermal expansion: 13 ×
10 ^-6 / cm ² ), nickel-chromium alloy (coefficient of thermal expansion: 14 × 10 ^-6 / cm ² ) has low magnetism, whereas ferritic stainless steel (coefficient of thermal expansion: 13 ×) 10
⁻⁶ / cm ² ) has strong magnetism. In the present embodiment, ferrite stainless steel (coefficient of thermal expansion: 13 × 10 ⁻⁶ / cm ² ) is used as the material of the resistor 1 for the above two reasons.

Next, the three types of sheet heating elements actually produced will be described in order as Example 1, Example 2, and Example 3.

[0013]

Embodiment 1 FIG. 2 shows a sheet heating element according to Embodiment 1. First, a resistor foil (thickness: 50 μm) made of ferritic stainless steel was etched to form a resistor portion dimension of 68 mm × 45 mm in a pattern width of 0.7 mm.
A resistor 1 having a pattern interval of 0.8 mm and a resistance value of 90Ω was obtained. The resistance density in this case is 2.9 Ω / cm ² . Such a resistor 1 is sandwiched between insulators 3 and 5 made of flocopite-based mica material (thickness 0.5 mm), heated and pressure-bonded to be integrated, and combined with a 80 mm × 55 mm × 1 mm sheet heating element. It was done.

Then, 100 is applied to the electrode portion of the planar heating element.
A voltage of V was applied. As a result, 110 W of power was obtained and reached 250 ° C. in about 15 seconds, after which the surface temperature was reduced to about 4
The temperature rose to 00 ° C. Thereafter, the resistance value, insulation resistance, withstand voltage, and the like were evaluated, but no deterioration in performance as a heater was observed. Next, the surface temperature was raised to 250 ° C.
The intermittent energization of OFF was performed for 100 cycles, and then the same evaluation was performed. However, the performance of the heater did not decrease.

[0015]

Second Embodiment FIG. 3 shows a planar heating element according to a second embodiment. First, a resistor foil (thickness: 50 μm) made of ferritic stainless steel was etched into a resistor portion having a dimension of 210 mm × 10 mm and a pattern width of 0.4 m.
m, the pattern interval was 0.6 mm, and a resistor 1 having a resistance value of 100Ω was obtained. The resistance density in this case is 4.8 Ω / cm ² . Such a resistor 1 is sandwiched between insulators 3 and 5 made of flocopite-based mica material (having a thickness of 0.5 mm), and is heated and pressed to be integrated to form a 215 mm × 15 mm × 1
This is a mm-shaped sheet heating element.

Then, 100 is applied to the electrode portion of the planar heating element.
A voltage of V was applied. As a result, 100 W of power was obtained and reached 250 ° C. in about 12 seconds, after which the surface temperature was reduced to about 4
The temperature rose to 00 ° C. Thereafter, the resistance value, insulation resistance, withstand voltage, and the like were evaluated, but no deterioration in performance as a heater was observed. Next, the surface temperature was raised to 250 ° C.
The intermittent energization of OFF was performed for 100 cycles, and then the same evaluation was performed. However, the performance of the heater did not decrease.

[0017]

Third Embodiment FIG. 4 shows a planar heating element according to a third embodiment. First, a resistor foil (thickness: 50 μm) made of ferritic stainless steel was etched to form a resistor portion dimension of 68 mm × 48 mm and a pattern width of 0.4 mm.
Resistor 1 having a pattern interval of 0.4 mm and a resistance value of 265Ω
I got In this case, the resistance density is 8.1 Ω / cm ² .
Such a resistor 1 is sandwiched between insulators 3 and 5 made of flocopite-based mica material (having a thickness of 0.5 mm),
It is heated and pressed to be integrated to form a planar heating element of 80 mm × 60 mm × 1 mm.

Further, 100 is applied to the electrode portion of the planar heating element.
A voltage of V was applied. As a result, 37.5 W of power was obtained and the surface temperature rose to about 250 ° C. Thereafter, the resistance value, insulation resistance, withstand voltage, and the like were evaluated, but no deterioration in performance as a heater was observed. Then, the surface temperature was set to 2
At 50 ° C., 100 cycles of on / off intermittent energization were performed, and then the same evaluation was performed, but no deterioration in the performance as a heater was observed. In this embodiment, such a planar heating element is used in a place where the temperature is rapidly increased, for example, an image fixing unit in an image forming apparatus such as an electrophotographic apparatus. In that case, a stable heating function can be provided for a long period of time even if the temperature rises sharply without deteriorating its soundness, and downsizing is possible. Can also be easily attached.

Next, a second embodiment of the present invention will be described with reference to FIG. In the first embodiment, the configuration is such that electrodes are provided at both ends of the resistor 1. In this embodiment, however, the resistors 1 are arranged in two rows, and both electrodes are provided on one side. Is arranged. Even in the case of the resistor 1 having such a pattern, the present invention can be applied similarly to the first embodiment, and an equivalent effect can be obtained.

The present invention is not limited to the first and second embodiments. First, the material of the resistor 1 is not limited to ferritic stainless steel. If strong magnetism is not required in the production method, it is conceivable to use a nickel-chromium alloy (thermal expansion coefficient: 14 × 10 ⁻⁶ / cm ² ). Further, the configuration of the planar heating element, for example, the pattern shape of the resistor may be arbitrarily set. Various applications other than the image fixing unit described in each of the above embodiments can be considered as applications for raising the temperature to a high temperature range in a short time.

[0021]

As described above in detail, according to the sheet heating element of the present invention, first, mica material having excellent heat resistance and thermal shock resistance is used as an insulator, and thermal expansion is used as a resistor. Since the coefficient of thermal expansion is relatively low and the same or close to the coefficient of thermal expansion of the mica material as the insulator,
Even if the resistor is formed in a dense pattern (for example, the resistance density is about ² Ω to 10 Ω / cm ² ), it is not affected by the thermal expansion, and the short circuit and the like can be eliminated. Therefore,
It is possible to provide a sheet heating element which is small and is suitable for use in a high temperature range or for use in a high wattage requiring a rapid temperature rise. Therefore,
For example, when used in an image fixing unit of an image forming apparatus such as an electrophotographic apparatus, it is possible to provide a stable function for a long period of time even without a loss of soundness even if the temperature rises sharply. As a result, the time required for image fixing can be shortened, and this greatly contributes to an improvement in the operation rate of the apparatus. In particular, when the resistor is made of a material having strong magnetism, the manufacturing method is advantageous. or,
Among them, particularly when ferritic stainless steel is used, good results can be obtained.

[Brief description of the drawings]

FIG. 1 is a view showing a first embodiment of the present invention, and is a perspective view showing a planar heating element with a part thereof being cut away.

FIG. 2 is a view showing Example 1 of the first embodiment of the present invention, and is a perspective view showing a planar heating element with a part thereof being cut away.

FIG. 3 is a diagram showing Example 2 of the first embodiment of the present invention, and is a perspective view showing the planar heating element with a part thereof being cut away.

FIG. 4 is a diagram showing Example 3 of the first embodiment of the present invention, and is a perspective view showing a planar heating element with a part thereof being cut away.

FIG. 5 is a view showing a second embodiment of the present invention, and is a perspective view showing a planar heating element with a part thereof being cut away.

FIG. 6 is a diagram used for describing a conventional example, and is a diagram schematically illustrating a configuration of a fixing unit of an image forming apparatus in an electrophotographic apparatus.

FIG. 7 is a diagram illustrating a conventional example, and is a perspective view illustrating a configuration of a heating element used in a fixing unit of an image forming apparatus in an electrophotographic apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Resistor 1a, 1b Electrode part 3 Insulator 5 Insulator

Claims (4)

[Claims] In a planar heating element in which a resistor made of metal foil is sandwiched and integrated by an insulator made of mica material, the coefficient of thermal expansion of the resistor is relatively low and the coefficient of thermal expansion of the mica material is relatively low. A planar heating element which is the same as or similar to that described above, and is used for raising the temperature to a high temperature range in a short time. 2. A sheet heating element according to claim 1, wherein said resistor has ferromagnetism. 3. The sheet heating element according to claim 2, wherein said resistor is a ferritic stainless steel. 4. The sheet heating element according to claim 1, wherein the sheet heating element is used as a heating element in an image fixing section of an image forming apparatus.