JPH07176367A - Heater - Google Patents

Abstract

PURPOSE:To provide a thin, flat heater having a thinned metallic plate located on the upper side of heating elements by providing the heating elements each comprising a positive temperature coefficient thermistor, and tapering the heating elements from below. CONSTITUTION:A heater is provided with heating elements 1... each comprising a positive temperature coefficient thermistor and metallic plates 4, 5 sandwiching the elements 1... from above and below, all of which are sealed inside a package 6 made from an electrically insulating resin. Each of the elements 1... is made from a PTC material (e.g. a ceramic semiconductor made chiefly of barium titanate, etc.) and has a tapered heating member in the form of a sliced sphere or a truncated cone, etc., and electrodes 1a, 1c are formed respectively on the upper and bottom surfaces of the heating member. The heating temperature of the heater can thus be held constant without providing a temperature control circuit. Therefore, the possibility of the plate 4 on the upper side of the elements 1... being broken by the edges of the elements 1... is reduced, enabling thinning of the plate 4.

Description

Detailed Description of the Invention

[0001]

The present invention has a positive temperature coefficient (Positiv
e Temperature Coefficient) A 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 surface and the back surface of the heating element, and lead wires are soldered to these electrodes to connect to an external power source, so that the heat generated by the heating element is heated. 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.

[0005]

However, in the above conventional structure, when the heating element is covered with the insulating sheet, it is necessary to fix the heating element to the insulating sheet so that the heating element does not move in the insulating sheet. Therefore, there is a problem that an adhesive or the like must be used.

Further, when the heating element is covered with a case made of a ceramics molded article, it is necessary to separately prepare this case, the thickness of the planar heater becomes thicker, and the number of parts and steps for manufacturing the planar heater are increased. There is a problem that the number increases and the cost increases.

Further, since the above case is made of a ceramic molded product, it is poor in workability. Since it takes time to form unevenness in its shape, the case where the heating element has a low operating temperature and has heat resistance is not required. In this case, the above problem becomes more serious.

Therefore, 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.

However, in this planar heater, since the metal plate is easily broken by the pressure during molding, a thick and rigid metal plate is required. For example, in the case of an aluminum plate, unless the thickness is at least 0.2 mm or more, the aluminum plate breaks at the edge of the heating element.
Therefore, there is a problem that the planar heater cannot be thinned.

[0010]

In order to solve the above-mentioned problems, a heater according to the present invention comprises a plurality of heating elements composed of a positive temperature coefficient thermistor having electrodes on the upper and lower surfaces, and a plurality of these heating elements. And two metal plates that electrically connect the electrodes on the upper surface and the electrodes on the lower surface of the heating element, and an electrically insulating package that seals the two metal plates. The heating element is characterized by tapering from the lower surface to the upper surface.

[0011]

According to the above construction, since the heating element composed of the positive temperature coefficient thermistor is provided, the heating temperature of the heater can be kept constant without providing the temperature control circuit.
Moreover, since the heating element is tapered from the bottom to the top, the metal plate on the upper surface side of the heating element is less likely to be broken by the edge of the heating element. Therefore, the metal plate on the upper surface side of the heating element can be thinned, so that a thin planar heater can be realized.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

As shown in FIG. 1, the heater of the present embodiment comprises a heating element 1 made of a positive temperature coefficient thermistor, and metal plates 4 and 5 sandwiching the heating element 1 from above and below,
The structure is such that these are sealed in a package 6 made of an electrically insulating resin.

As shown in FIG. 2, the heating element 1 is made of a PTC material (for example, a ceramic semiconductor whose main raw material is barium titanate or the like), and has a shape in which a sphere is sliced or a tapered shape such as a truncated cone. The heat generating member 1b is provided, and the electrodes 1a.
c is formed.

The heat generating member 1b is obtained by forming a raw material powder with a die having an upper punch having a tapered shape and a die and a lower punch having a cylindrical shape, and firing the formed body.

The upper metal plate 4 is a thin plate or foil made of aluminum, gold, platinum, nickel, copper, silver or the like, and is electrically connected to the electrode 1a on the upper surface of the heating element 1 and the upper side surface. Is provided. Lower metal plate 5
Is made of a material similar to that of the metal plate 4 and is thicker than the metal plate 4, and is provided so as to be electrically connected to the electrode 1c on the lower surface of the heating element 1. The metal plates 4 and 5 may have holes or may have a wire mesh shape.

A part of the metal plates 4 and 5 is formed in a strip shape and protrudes from the package 6, and the strip portion serves as connection terminals 4a and 5a for connecting to a power source.

In the above structure, the power source is connected to the connection terminal 4a.
・ Connect 5a.

The heating elements 1 ... Are from room temperature to the Curie temperature Tc.
It is a positive temperature coefficient thermistor as a heat-sensitive element having a characteristic that it has a low resistance up to (rapid temperature change), but its resistance value sharply increases when it exceeds the Curie temperature Tc. 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 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.

The package 6 is integrally formed of a synthetic resin mixed with a filler containing long fibers, and the heating element 1
... and the metal plates 4 and 5 are covered and hermetically sealed, that is, sealed. In addition, the package 6 includes a lead wire and a connection terminal 4.
The metal plate 4 of the connection terminals 4a and 5a is arranged so that a mechanical load is not applied to the soldered portion with the a and 5a and the disconnection or the like does not occur.
・ It is designed to cover the 5 side as well.

The glass fibers are generally classified into long fibers and short fibers by the manufacturing method. The above long fibers are used in this sense, and do not mean long fibers.

The above-mentioned synthetic resin has a small heat shrinkage ratio, is excellent in electrical insulation and mechanical strength, is heat resistant to withstand the heat generation temperature of the heating elements 1, and is waterproof so that moisture such as water vapor does not pass inside. , It is necessary to have airtightness that does not allow air to pass inside, and it is necessary that the adhesion to the coating material of the lead wire is good, for example, unsaturated polyester resin, vinyl ester resin, epoxy resin, Thermosetting resin such as phenol resin, or polypropylene resin,
Thermoplastic resins such as polyamide resin and polyethylene terephthalate resin are used. The synthetic resin is, for example,
It may be appropriately selected according to 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.
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 (hereinafter referred to as "filler")
Must have excellent thermal conductivity, electrical insulation, and mechanical strength, must have heat resistance to withstand the heat generation temperature of the heating elements 1 ..., and must have good affinity with synthetic resin. 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.

Further, 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 diameters of the above-mentioned organic powder and inorganic powder are not particularly limited. The forms of the organic powder and the inorganic powder are not particularly limited.

The above-mentioned filler is, for example, according to the price, the affinity with the synthetic resin 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. It may be selected appropriately. Moreover, the compounding amount of the filler with respect to the synthetic resin is not particularly limited. Each of the above fillers may be mixed alone with the synthetic resin, but it is necessary to include long fibers. Further, two or more kinds may be mixed and blended with the synthetic resin, if necessary. Furthermore, the method of mixing the synthetic resin and the filler is not particularly limited.

The package 6 is, for example, SMC (S
heet Molding Compound), BMC (Bulk Molding Compou
For thermosetting resins such as nd), they are molded and manufactured by the heat compression molding method. Further, a thermoplastic resin (stampable sheet) such as long-fiber-reinforced polypropylene resin or polyamide resin is molded and manufactured by a compression molding method in which a heated resin is cooled and compressed.

Molding / manufacturing of the heater by the above SMC is performed by the following procedure. That is, first, a synthetic resin containing a filler (hereinafter referred to as a composite)
Is molded into three sheets of a predetermined shape and size, two of which are used as the top sheet and the bottom sheet, while the remaining one sheet has a size capable of accommodating the heating elements 1 ... The perforated sheet is opened to form a perforated sheet. The thickness and forming method of these sheets are not particularly limited.

Next, the metal plate 5, the perforated sheet in which the heating elements 1 are fitted in the holes, and the other metal plate 4 are placed on the lower sheet in this order at predetermined positions, and the metal plate 4 is further placed. Place the top sheet on top. Then, this laminate is placed in a mold (not shown) on a press molding machine, and pressed under predetermined conditions, that is, predetermined temperature, pressure, time, etc., to heat-harden the composite, and to form three sheets. Are integrated to form the package 6. As a result, the heating elements 1 ... And the metal plates 4 and 5 are sealed and fixed inside the package 6, and the heater is molded and manufactured.

The molding and manufacturing of the heater by the above BMC is performed by the following procedure. That is, first, after the composite is made into a paste, the paste-like composite is expanded by a predetermined amount. Next, the metal plate 4, the heating element 1 ..., the paste composite, and the other metal plate 5 are arranged on the above-mentioned paste composite at a predetermined position in this order, and the paste composite is further formed on the metal plate 5. Expand a predetermined amount. Then, this composite is pressed under predetermined conditions to heat-harden the composite to form the package 6, which is used as a heater.

Further, the molding and manufacturing of the heater made of the above thermoplastic resin is carried out by the following procedure. That is,
First, the composite is molded into three sheets of a predetermined shape and size, two of which are used as the top sheet and the bottom sheet, while the remaining one sheet is perforated to form a perforated sheet. . The thickness and forming method of these sheets are
It is not particularly limited.

Next, the above three sheets are heated to a predetermined temperature and sufficiently melted, and a metal sheet 4, a heat generating element 1 ... The metal plate 5 is placed at a predetermined position in this order, and the top sheet is further placed on the metal plate 5. Alternatively, the sheets may be sufficiently melted by heating in the order described above and then heating. After that, this laminate is placed in a die on a press molding machine and pressed under predetermined conditions to fuse and cool the composite, and the three sheets are integrated to form the package 6, which serves as a heater. .

The procedure for molding and manufacturing the heater using SMC, BMC, and thermoplastic resin (stampable sheet) reinforced with long fibers is not limited to the above procedure, and the package 6 generates heat. It is sufficient that the heater is molded and manufactured by covering and sealing the body 1 and the metal plates 4 and 5. Further, in compression molding, the perforated sheet may be omitted if there is no risk of the metal plates 4 and 5 coming into contact with each other during pressing. In this case, the heating element 1
The space between the metal plates 4 and 5 is filled with the synthetic resin that has passed through the holes of the metal plates 4 and 5.

However, the fiber length of the filler was
・ If the size of the hole is smaller than that of 5, the composites are placed on the upper and lower sides of the metal plates 4 and 5 and pressed, and most of the synthetic resin and filler are pressed by the pressure. It passes through the holes and enters between the metal plates 4 and 5, so that almost no composite remains above and below the metal plates 4 and 5. Therefore, only extremely thin packages 6 are formed above and below the metal plates 4 and 5, respectively.
Is exposed on the surface of the package 6. That is, the electric insulation of the heating elements 1 ... and the metal plates 4 and 5 is not ensured, and it becomes impossible to use them as a planar heater.

Further, in the above metal plates 4 and 5, by connecting the lead wires to the end surface side or the inner surface side of the metal plates 4 and 5, respectively, the lead wires are connected to the outer surface side of the metal plates 4 and 5. There is no unevenness due to the connection. Therefore, it is not necessary to provide the package 6 with a thickness for absorbing the unevenness, and the package 6, that is, the heater can be formed thin. As a result, the heater can be made smaller, lighter and thinner, and the heat generated by the heating elements 1 ... Can be efficiently transferred to the object to be heated. further,
Since the surface of the package 6 (heat generating surface) is smooth and can be brought into close contact with the object to be heated, the heat transfer efficiency can be further improved.

The above-mentioned lead wire is connected to a power cord (not shown), and is electrically connected to an external power source through this power cord. The heating elements 1 are connected in parallel with each other. The lengths of the lead wire and the power cord are not particularly limited.

Since the heater having the above-mentioned structure uses the heating elements 1 made of a positive temperature coefficient thermistor as a heating means, the temperature rises rapidly after energization, and when the temperature reaches a predetermined temperature, the temperature is maintained. Therefore, the surface of the package 6 quickly rises to a predetermined temperature, and the object to be heated can be quickly heated.

Further, since the heating element 1 is tapered from the bottom to the top, the edge of the heating element 1 is less likely to break the metal plate 4 on the upper surface side of the heating element 1. For this reason, the metal plate 4 on the upper surface side of the heating element 1 can be thinned, so that a thin planar heater can be realized.

Next, a method for manufacturing the heater having the above-mentioned structure will be described in detail with reference to specific examples, 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: C8010-N, composition: polypropylene resin 60w
t%, glass fiber 40 wt%, thickness 0.85 mm) 1
The sheet was cut into 50 mm squares to obtain two sheets, an upper sheet and a lower sheet. In addition, the company's stampable sheet (product number: C8040-N, composition: same as above, thickness 3.
3 mm) was cut into 150 mm squares, and then 5 holes with a diameter of 15 mm were opened at predetermined positions to form a perforated sheet.

The lower surface has a diameter of 15 mm and a thickness of 2.5 m.
m heating element 1 is used, an aluminum foil (thickness 0.02 mm) is used as the metal plate 4 on the upper surface of the heating element 1, and 1 is used on the lower surface.
30mm square aluminum plate (thickness 0.2
mm) was used as the metal plate 5.

Next, the above-mentioned top sheet and bottom sheet were heated with an infrared heater for 2 minutes and 30 seconds 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 being fitted, the aluminum foil as the metal plate 4 and the top sheet were placed in this order (see FIG. 3).

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 heater corresponding to the present invention has a plurality of heating elements 1 ... Composed of positive temperature coefficient thermistors having electrodes 1a and 1c on the upper and lower surfaces, and the heating elements 1 ... Two metal plates 4, 5 for electrically connecting the upper electrodes 1a ... And the lower electrodes 1c.
And an electrically insulating package 6 that seals the two metal plates 4 and 5, and the heating elements 1 ... are tapered from bottom to top.

According to this, since the heating elements 1 made of the positive temperature coefficient thermistor are provided, the heating temperature of the heater can be made constant without providing the temperature control circuit. Moreover, since the above-mentioned heating elements 1 ... Are tapered from the lower surface toward the upper surface, the edges of the heating elements 1 ... Are unlikely to break the metal plate 4 on the upper surface side of the heating elements 1. For this reason, the metal plate 4 on the upper surface side of the heating elements 1 ... Can be thinned, so that a thin planar heater can be realized.

[0048]

As described above, the heater according to the present invention has a plurality of heating elements composed of a positive temperature coefficient thermistor having electrodes on the upper and lower surfaces, and these heating elements sandwiched from above and below,
The heating element includes two metal plates that electrically connect electrodes on the upper surface of the heating element and electrodes on the lower surface of the heating element, and an electrically insulating package that seals the two metal plates. Has a taper shape from the lower surface toward the upper surface, the heat generation temperature of the heater can be made constant without providing a temperature control circuit. Depending on the edge of the heating element,
The metal plate on the upper surface side of the heating element is less likely to break. For this reason, the metal plate on the upper surface side of the heating element can be thinned, so that a thin planar heater can be realized.

[Brief description of drawings]

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

FIG. 2 is a vertical cross-sectional view showing a schematic configuration of a heating element used in the heater of FIG.

FIG. 3 is a plan view showing a specific example of the heater of FIG. 1 and showing a schematic configuration of the heater.

[Explanation of symbols]

 1 Heating Element 1a Electrode 1b Heating Member 1c Electrode 4 Metal Plate 5 Metal Plate

Claims (1)

[Claims] 1. A plurality of heating elements composed of positive temperature coefficient thermistors having electrodes on the upper and lower surfaces, and these heating elements sandwiched from above and below, and the electrodes on the upper surface and the electrodes on the lower surface of the heating element are electrically connected. Two metal plates and an electrically insulating package for sealing the two metal plates are provided, and the heating element is tapered from the lower surface to the upper surface. Heater