JPH07176370A - Heater - Google Patents

Abstract

PURPOSE:To efficiently heat a subject for heating and to decrease the amount of waste heat radiated from that surface of a package from which a smaller amount of heat is radiated by bringing the subject for heating into close contact with this surface of the package from which a greater amount of heat is radiated, the package comprising heat conductive layers and a heat insulating layer. CONSTITUTION:An electrically insulating package 6 sealing a heating element 1 and two metallic plates 4, 5 therein comprises a heat insulating layer 6a located on the plate 4, a heat conductive layer 6b located between the plates 4, 5, and a heat conductive layer 6c on the plate 5. When a power supply is connected to the plates 4, 5, the element 1 is heated, and the heat from the element 1 is transferred to the plate 5 and the layer 6c and radiated from the plate 5 side surface of the package 6. The heat from the element 1 is transferred also to the plate 4 but is blocked by the layer 6a and thus not radiated much from the plate 4 side surface of the package 6. Therefore, a subject for heating can be heated efficiently by bringing it into close contact with the plate 5 side surface of the package 6, and the amount of waste heat radiated from the opposite side of the package 6 can be reduced.

Description

Detailed Description of the Invention

[0001]

The present invention has a positive temperature coefficient (Positiv
e Temperature Coefficient) The present invention relates to a planar heater using a thermistor as a heating element.

[0002]

2. Description of the Related Art Heretofore, a planar heater using a plate-shaped heating element made of barium titanate-based porcelain semiconductor, which is a positive temperature coefficient thermistor having a self-temperature control function, has been considered. This planar heater does not require a temperature control circuit for maintaining a constant heat generation temperature or an overheat prevention circuit for preventing overheating, and has extremely high safety.

In the above-mentioned sheet heater, electrodes are provided on the front and back surfaces of the heating element, and lead wires are soldered to these electrodes to connect to an external power source. In order to transfer the heat evenly to the case, a case made of a molded article of ceramics such as alumina having excellent electrical insulation, heat resistance, mechanical strength and thermal conductivity, or an insulating sheet made of a thermoplastic resin, etc. The body is covered.

Since the lead wire is directly soldered to the electrodes provided on the front surface and the back surface of the heating element, there is a convex portion at that portion. If a space (gap) is formed between the case or the insulating sheet and the heating element, the thermal conductivity between the heating element and the object to be heated is reduced. Therefore, when covering the above heating element with a case, The case is provided with a concave portion in conformity with the soldering convex portion, and attention is paid to the adhesion between the case and the heating element.

Further, there has been considered a planar heater in which a heating element is sandwiched between metal plates which also serve as a heat dissipation plate and an electrode plate, and an insulator is provided so as to cover them. In order to improve heat conduction, the metal plate and the insulator are integrally formed by compression molding.

[0006]

However, in the above-mentioned conventional configuration, both sides of the sheet heater generate heat, so that, for example, when the mirror is heated by being closely attached to the back surface of the mirror to prevent fog of the mirror, There is a problem that the heat from the surface that is not in close contact with the mirror is wasted.

Further, a heater using a heating element composed of a PTC thermistor has a problem that power consumption increases because useless heat generation increases the supply current to the heating element.

[0008]

In order to solve the above-mentioned problems, a heater according to the present invention has a plurality of heating elements having electrodes on the upper and lower surfaces and an upper surface of the heating element sandwiching these heating elements from above and below. The two metal plates that electrically connect the electrodes of and the electrodes of the lower surface, and an electrically insulating package that seals the heating element and the two metal plates are provided.
The part of the package on one metal plate is characterized by higher heat insulation than the other parts of the package.

[0009]

According to the above construction, heat is radiated from the surface of the package on one metal plate less than that from the surface of the package on the other metal plate. Therefore, the object to be heated can be efficiently heated by bringing the object to be heated into close contact with the surface of the package on the side where the heat is released, and the wasteful release of heat from the surface on the opposite side of the package is reduced.

[0010]

EXAMPLE An example of the present invention will be described below with reference to FIG.

As shown in FIG. 1, the heater of the present embodiment includes a plurality of heating elements 1 having electrodes 2 and 3 on the upper and lower surfaces,
Two metal plates 4,5 for sandwiching these heating elements 1 ... From above and below and electrically connecting the electrodes 2 ... on the upper surface and the electrodes 3 ... on the lower surface of the heating elements 1 ,. An electrically insulating package 6 for sealing the two metal plates 4 and 5 is provided.

The package 6 has a heat insulating layer 3a on the metal plate 4, a heat conducting layer 3b between the metal plate 4 and the metal plate 5,
It is composed of a heat conduction layer 3c on the metal plate 5 (that is, on the lower side of the figure).

A porous material is preferable for the heat insulating layer 3a,
When the electric insulating property of the heat insulating layer 3a decreases due to moisture absorption, a waterproof layer may be provided on the surface of the heat insulating layer 3a.

In the above construction, when the power source is connected to the metal plates 4 and 5, the heating elements 1 ... Generate heat. The heat from the heating elements 1 ... Is transmitted to the metal plate 5 and the heat conduction layer 3c, and is radiated from the surface of the package 6 on the metal plate 5 side. On the other hand, heating element 1
The heat from ... Is transmitted to the metal plate 4, but is blocked by the heat insulating layer 3a and is not radiated so much from the surface of the package 6 on the metal plate 4 side.

Therefore, the object to be heated can be efficiently heated by adhering the object to be heated to the surface of the package 6 on the side of the metal plate 5, and moreover, unnecessary heat from the surface on the opposite side of the package 6 can be eliminated. The emission is small.

For the heater, for example, a disc-shaped heating element 1 made of a positive temperature coefficient thermistor is used.

The heating elements 1 have a low resistance from room temperature to the Curie temperature Tc (rapid temperature change resistance), but have a characteristic that the resistance value sharply increases when the Curie temperature Tc is exceeded. It is a thermistor. Due to this characteristic, when a voltage is applied from the power source, the heating elements 1 ... Initially have a low resistance value and a large current flows due to a low temperature. As a result, the temperature rises rapidly while the temperature rises. When the temperature exceeds the Curie temperature Tc, the resistance value sharply increases, so that the temperature does not rise above a certain temperature and the certain temperature is kept stable.

That is, the heating elements 1 ... Have a self-temperature control function. Therefore, the planar heater consumes less power, can omit the temperature control circuit and the overheat prevention circuit, and can be downsized. Further, there is no fear of ignition due to local overheating. Since the Curie temperature Tc of this heating element 1 can be arbitrarily set within the range of about 30 to 250 ° C. depending on the material composition, the heating element 1 in this embodiment has a package 6 effective for heating an object to be heated. The Curie temperature Tc may be set in consideration of safety and power saving.

As the metal plates 4 and 5, iron plates, stainless plates, copper plates, phosphor bronze plates, aluminum plates and the like are used. The metal plates 4 and 5 may be provided with holes. Further, it is not always necessary to use the same metal plates 4 and 5, but a metal plate with holes may be used for one and a metal plate without holes may be used for the other.

The electrical connection between the heating element 1 and the metal plates 4 and 5 is made by pressing them against each other. Alternatively, the heating element 1 and the metal plates 4 and 5 may be electrically connected to each other by, for example, adhering them with a conductive adhesive of epoxy resin / silver mixture.

The package 6 is integrally formed of a synthetic resin mixed with a filler containing long fibers, and the metal plate 4
The heating element 1 and the metal plates 4 and 5 are hermetically sealed except for the end portions 4a and 5a of 5.

The synthetic resin used for the package 6 has a small heat shrinkage ratio, is excellent in electrical insulation and mechanical strength, and has heat resistance capable of withstanding the heat generation temperature of the heating elements 1 ... It is necessary to have waterproofness that does not let air pass through and airtightness that does not let air pass inside. For example, thermosetting resin such as unsaturated polyester resin, vinyl ester resin, epoxy resin, phenol resin, or polypropylene resin. Thermoplastic resins such as polyamide resin and polyethylene terephthalate resin are used. The synthetic resin is appropriately selected according to, for example, the price, the affinity with the filler to be used, the molding method of the package 6, the use and size of the heater, the shape, the strength and various physical properties required for the heater, and the like. do it. Further, the synthetic resin may contain a curing agent, a release agent, a low-shrinking agent, a coloring agent, a thickening agent and the like.

The above-mentioned filler has excellent thermal conductivity, electrical insulation and mechanical strength, and also has heat resistance capable of withstanding the heat generation temperature of the heating elements 1 ... And has an affinity with synthetic resins. Is required, and for example, organic fiber, inorganic fiber, organic powder, inorganic powder or the like is used.

Examples of the organic fiber include cotton, wool,
Natural fibers such as hemp, chemical fibers such as rayon,
Synthetic fibers made of polyvinyl chloride resin, polyamide resin, wholly aromatic polyamide resin, saturated polyester resin or the like are used. As the inorganic fiber, for example, glass fiber, potassium titanate, boron, silicon carbide, alumina, polytitanocarbosilane and the like are used.

As the organic powder, for example, rubber such as styrene-butadiene rubber is used. As the inorganic powder, for example, calcium carbonate, kaolin, clay, alumina, aluminum hydroxide, barium sulfate, lithopone, glass powder in the form of cut fibers or milled fibers, glass flakes, glass beads, glass microballoons, aluminosilicate microballoons. , Silica microballoons, wollastonite, boron nitride, fine particle silicon, ultra fine particle anhydrous silica,
Quartz powder, talc, mica, antimony trioxide, etc. are used.

The particle size of the above-mentioned organic powder and inorganic powder is not particularly limited. The forms of the organic powder and the inorganic powder are not particularly limited.

The above-mentioned filler may be appropriately selected depending on, for example, price, affinity with synthetic resin, molding method of package 6, size and strength of planar heater, and various physical properties.

The sheet heater formed by the package 6 is, for example, SMC (Sheet Molding Compound), B
Thermosetting resins such as MC (Bulk Molding Compound) are molded and manufactured by a heat compression molding method. Also,
The thermoplastic resin is molded and manufactured by compression molding in which the heated resin is cooled and compressed.

If a sheet having a glass content of synthetic resin of 40% or more is used, the wraparound of the resin is reduced and the sheet becomes porous. Therefore, the heat insulating property becomes high.
When the package 6 is made of synthetic resin containing glass fiber, it is preferable to form a waterproof film on the surface of the package 6 in order to maintain electric insulation.

Even if the upper and lower parts of the package 6 are made of synthetic resin sheets having the same glass compounding amount, the synthetic resin of one side portion may be made to contain a foaming agent, or the foaming agent may be provided on one side of the sheet. By applying and heat-foaming, bubbles are formed and become porous, and the heat insulating property is improved.

As the foaming agent, hydrocellulose, hydrocellulose compound, azodicarbon acid, D
PT (Dinitrosopentamethylenetetramine), AZC
(Azodicarbonamide), TSH (p-Toluenesulfonyl
hydrazide), OBSH (4,4′-Oxybis), gas-filled organic beads, gas-filled organic powder, colloidal silica, silica gel, sodium silicate, lithium silicate and the like.

In the case of a thermoplastic resin, a sheet having a structure containing a gas or air layer is used as a sheet used for the surface to be made porous, and only that surface is not heated or is heated at a low temperature. Alternatively, by performing compression molding while shortening the heating time, it becomes possible to produce a planar heater having only one surface made porous.

The method for manufacturing the above heater will be described in detail below, but the present invention is not limited thereto. In addition, in the following specific examples, the shape of the planar heater is a flat rectangular shape.

A planar heater was molded and manufactured from a long fiber reinforced thermoplastic resin (stampable sheet). First, a stampable sheet manufactured by Cape La Sheet (product number: C6010-N, composition: polypropylene resin 70w
t%, glass fiber 30 wt%, thickness 0.85 mm) 1
It was cut into a 50 mm square to obtain a top sheet.

Further, a stampable sheet manufactured by the same company (product number: C6040-N, composition: same as above, thickness 3.3 mm) was cut into a 150 mm square, and then a diameter of 15 m was obtained at a predetermined position.
5 holes of m were opened to obtain a perforated sheet.

A composite product of polypropylene resin and glass fiber (custom-made product, composition: polypropylene resin 50 wt.
%, Glass fiber 50 wt%) was cut into a 150 mm square to obtain a lower surface sheet.

Further, a heating element 1 having a diameter of 15 mm and a thickness of 2.5 mm is used, an aluminum plate (having a thickness of 0.2 mm) is used as a metal plate 4 on the upper surface of the heating element 1, and a lower surface is 130 mm.
An aluminum plate (thickness: 0.2 mm) cut in all directions was used as the metal plate 5.

Next, the above-mentioned top sheet and bottom sheet were heated for 2 minutes and 30 seconds using an infrared heater, while the perforated sheet was heated for 4 minutes and 30 seconds to 200 ° C. A sheet is installed, an aluminum plate as a metal plate 5 and a perforated sheet are placed on the lower sheet in this order, and the heating element 1 is placed in the hole of the perforated sheet.
After fitting ..., The aluminum plate as the metal plate 4 and the top sheet were placed in this order.

Thereafter, this laminate was heated at a temperature of 50 ° C. and a pressure of 1
Pressed at 0 kg / cm ^{2 for} 40 seconds, fused polypropylene resin, and integrated 3 sheets into 150 mm
A heater of × 150 mm × 4 mm was obtained. It was confirmed that the electric insulation of this heater was extremely good. The temperature of each surface was 48 ° C. on the upper surface side and 62 ° C. on the lower surface side.

Another sheet heater was molded and manufactured using a long fiber reinforced thermoplastic resin (stampable sheet). Stampable sheet manufactured by Cape La Sheet (Part number:
C8010-N, Composition: Polypropylene resin 60 wt
%, Glass fiber 40 wt%, thickness 0.85 mm) 15
It was cut into 0 mm square to obtain a lower surface sheet.

A stampable sheet manufactured by the same company (product number: C8040-N, composition: same as above, thickness 0.85 mm)
Was cut into a 150 mm square, and one side thereof was coated with an OBSH foaming agent (trade name: Celmic S) manufactured by Sankyo Kasei Co., Ltd. to obtain a bottom sheet.

Further, a stampable sheet manufactured by the same company (product number: C8040-N, composition: same as above, thickness 3.3 mm) was cut into a 150 mm square, and then a diameter of 15 m was obtained at a predetermined position.
5 holes of m were opened to obtain a perforated sheet.

Further, a heating element 1 having a diameter of 15 mm and a thickness of 2.5 mm is used, an aluminum plate (thickness 0.2 mm) is used as a metal plate 4 on the upper surface of the heating element 1, and a lower surface is 130 mm.
An aluminum plate (thickness: 0.2 mm) cut in all directions was used as the metal plate 5.

Next, the lower surface sheet was heated for 2 minutes and 30 seconds using an infrared heater, while the perforated sheet was heated for 4 minutes and 30 seconds to 200 ° C., respectively, and then the lower surface sheet was installed. Then, the aluminum plate as the metal plate 5 and the perforated sheet are placed on the lower sheet in this order, and the heating elements 1 ... Are fitted into the holes of the perforated sheet.
Further, an aluminum plate as the metal plate 4 was placed in this order.

On the other hand, the top sheet was heated at 150 ° C. for 2 minutes, and thereafter, the surface of the top sheet on which the foaming agent was adhered was placed toward the metal plate 4 side.

Thereafter, this laminate was heated at a temperature of 50 ° C. and a pressure of 1
Pressed at 0 kg / cm ^{2 for} 40 seconds, fused polypropylene resin, and integrated 3 sheets into 150 mm
A heater of × 150 mm × 4 mm was obtained. It was confirmed that the electric insulation of this heater was extremely good. The temperature of each surface was 40 ° C. on the upper surface side and 62 ° C. on the lower surface side.

The heater corresponding to the present invention has a plurality of heating elements 1 having electrodes 2 and 3 on the upper and lower surfaces, and the electrodes 2 on the upper surface of the heating elements 1 ... And two electrodes 3 and 5 for electrically connecting the electrodes 3 on the lower surface to each other, and an electrically insulating package 6 for sealing the heating element 1 and the two metal plates 4 and 5. Therefore, the part of the package 6 on the metal plate 4 (or the metal plate 5) has a higher heat insulating property than the other parts of the package 6.

According to this, the heat release from the surface of the package 6 on the metal plate 4 (or the metal plate 5) is the heat release from the surface of the package 6 on the metal plate 5 (or the metal plate 4). Less than emission. Therefore, package 6
The object to be heated can be efficiently heated by bringing the object to be heated into close contact with the surface on the side where the heat is released, and useless heat is released from the surface on the opposite side of the package 6.

[0049]

As described above, the heater according to the present invention has a plurality of heating elements having electrodes on the upper and lower surfaces, and a plurality of heating elements sandwiching the heating elements from above and below, and electrodes on the upper surface and electrodes on the lower surface of the heating element. Is provided with an electrically insulating package that seals the heating element and the two metal plates.A part of the package on one metal plate is Due to its higher thermal insulation than the other parts, the heat dissipation from the surface of the package on one metal plate is less than the heat dissipation from the surface of the package on the other metal plate. Therefore, the object to be heated can be efficiently heated by adhering the object to be heated to the surface of the package on the side where the heat is released largely, and moreover, the wasteful release of heat from the surface on the opposite side of the package is reduced. Produce an effect.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a schematic configuration of a heater according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating element 2 Electrode 3 Electrode 4 Metal plate 5 Metal plate 6 Package 6a Heat insulation layer 6b Heat conduction layer 6c Heat conduction layer

Claims (1)

[Claims] 1. A plurality of heating elements having electrodes on the upper and lower surfaces, and two metal plates sandwiching the heating elements from above and below and electrically connecting electrodes on the upper surface and electrodes on the lower surface of the heating element. , A heating element and an electrically insulative package for sealing the two metal plates are provided, and the part of the package on one metal plate has a higher heat insulating property than the other part of the package. And heater.