JPH0817559A - Heater - Google Patents

Abstract

PURPOSE:To provide a heater capable of surely preventing deterioration of a positive temperature coefficient thermister and thermal runaway accompanied by the deterioration. CONSTITUTION:A case 1 has an internal space 13 constituted so as to contain heat radiation surfaces 11, 12. Insulating frame members 91, 92 have holes 911, 921 within the faces, and are arranged in the internal space 13 of the case 1 so that one sides 911, 921 are faced each other. Electrode. plates 21, 22 are stacked on the other sides 913, 923 of the insulating frame members 91, 92 and heat-bonded to the heat radiation surfaces 11, 12 of the case 1. A positive temperature coefficient thermister 3 is arranged within the holes 911, 921 of the insulating frame members 91, 92, and electrodes 32, 33 are brought into electrical contact with the electrode plates 21, 22. The positive temperature coefficient thermister 3 has such thickness that a gap is produced between facing surfaces 912-922 of the insulating frame members 91, 92 in the state that the electrodes 32, 33 come in contact with the electrode plates 21, 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heater using a positive temperature coefficient thermistor as a heating element.

[0002]

2. Description of the Related Art A heater having a PTC thermistor as a heat generating element is well known in the art. The positive temperature coefficient thermistor is
Since the constant temperature operation is performed by the self-temperature control function, a safe and highly reliable heater can be realized. This type of heater has a structure in which a positive temperature coefficient thermistor is sandwiched between a pair of electrode plates and driven via the electrode plates. The electrode plate is further indirectly or directly thermally coupled to the heat dissipation plate, and heat is taken out through the heat dissipation plate. When used for heating a liquid such as water or oil, the heat dissipation plate is composed of a case, and the basic elements such as the positive temperature coefficient thermistor and the electrode plate are housed in the case. When a large amount of heat is generated, a plurality of PTC thermistors are used, each PTC thermistor is sandwiched by a pair of common electrode plates, and a plurality of PTC thermistors are simultaneously driven through the electrode plates. An example of a related technical document regarding such an assembly structure is, for example, Japanese Utility Model Publication No. 4-36071.

[0003]

As described above, in this type of heater, the electrode plate is used not only as a power supply to the PTC thermistor but also as a heat conductor.
It is very important to make the electrical contact and thermal coupling of the electrode plates to the PTC thermistor tight. However, it is technically difficult to satisfy these conditions reliably while ensuring ease of assembly and simplification of the structure.

Furthermore, when the electrical contact and thermal coupling of the electrode plate to the PTC thermistor are made tight and the PTC thermistor is sealed completely, a porcelain element constituting the PTC thermistor, for example, barium titanate system. The semiconductor porcelain may deteriorate, the peak resistance value of the positive temperature coefficient thermistor may decrease, and thermal runaway or thermal destruction may occur.

An object of the present invention is to provide a constant temperature heating operation type heater based on a self temperature control function.

Another object of the present invention is to provide a heater which is easy to assemble.

Still another object of the present invention is to provide a heater capable of reliably positioning a positive temperature coefficient thermistor at a predetermined position.

Still another object of the present invention is to provide a heater which can surely prevent deterioration of a positive temperature coefficient thermistor and thermal runaway associated therewith.

[0009]

In order to solve the above-mentioned problems, the heater according to the present invention comprises one case, at least two insulating frame members, at least two electrode plates, and at least one positive temperature coefficient thermistor. including. The case has an internal space including a heat dissipation surface.
Each of the insulating frame members is plate-shaped, has holes in the surface, and the holes are provided in the number corresponding to the number of the positive temperature coefficient thermistors. It is arranged in the internal space. Each of the electrode plates is stacked on the other surface side of the insulating frame member and is thermally coupled to the heat radiation surface of the case. The positive temperature coefficient thermistor has electrodes on both sides in the thickness direction of the positive temperature coefficient thermistor body, is arranged in the hole of the insulating frame member, and each of the electrodes electrically contacts the electrode plate to conduct electricity. However, the electrode has a thickness that creates a gap between the facing surfaces of the insulating frame member in a state where the electrode is in contact with the electrode plate.

Preferably, the electrode plate has a protrusion at an electrode contact portion.

More preferably, it contains a heat conductive filler,
The thermally conductive filler is made of resin and is filled between the electrode of the PTC thermistor and the electrode plate so as to fill the gap created by the protrusion.

[0012]

The positive temperature coefficient thermistor has electrodes on both sides in the thickness direction of the positive temperature coefficient thermistor body, and each of the electrodes electrically contacts the electrode plate to conduct electricity. It is possible to obtain a heater that performs a heat generation operation by feeding power through the heater and a constant temperature heat generation operation by the self-temperature control function of the positive temperature coefficient thermistor.

Each of the insulating frame members is plate-shaped,
Since there are holes in the surface and the holes are provided in the number corresponding to the number of the PTC thermistors, and the PTC thermistors are arranged in the holes of the insulating frame member, the PTC thermistor is prevented from being displaced. . Therefore, it is possible to eliminate the non-uniformity of heat generation due to the displacement of the PTC thermistor, prevent the resin from adhering to the side surface of the PTC thermistor, and realize a highly reliable heater.

Since the positive temperature coefficient thermistor has a thickness that allows a gap to be formed between the facing surfaces of the insulating frame member in a state where the electrodes are in contact with the electrode plate, the gap forms a ventilation path for connecting the holes of the insulating frame member to each other. It is formed. Therefore, it is possible to prevent the deterioration of the porcelain body that constitutes the PTC thermistor, and reliably prevent the deterioration of the PTC thermistor and the accompanying thermal runaway and thermal destruction.

In a preferred example in which the electrode plate has a protrusion at the electrode contact portion, the electrode plate surely contacts the electrode of the positive temperature coefficient thermistor at the protrusion.

In the structure in which the electrode plate has a protrusion at the electrode contact portion, the thermally conductive filler is the electrode of the positive temperature coefficient thermistor,
In the preferable example in which the gap is formed between the electrode plate and the electrode plate so as to fill the gap, the heat generated in the positive temperature coefficient thermistor is reliably transmitted to the electrode plate through the heat conductive filler. Therefore, although the protrusions cause a gap between the electrode plate and the electrode of the PTC thermistor, a high thermal coupling is formed between them. As a result, it is possible to obtain a heater that secures electrical contact between the electrode plate and the PTC thermistor and improves the heat conduction efficiency from the PTC thermistor to the electrode plate.

Since the heat conductive filler is made of resin, a considerably large thermal strain is generated in the heat conductive filler during the heat generating operation of the positive temperature coefficient thermistor. Since the electrode plate has protrusions on the surface side that contacts the PTC thermistor, the heat conductive filler is filled more on the protrusion side of the electrode plate than on the heat coupling surface side with the case. Therefore, the thermal strain generated in the thermally conductive filling acts to push up the electrode plate. Since the electrode plate is mechanically fixed or in contact with the heat radiation surface side of the case, when it receives thermal strain due to thermal expansion of the heat conductive filler, with the case side fixing point or contact point as a fulcrum, In reaction, it is pressed in the direction of the PTC thermistor. Therefore, the projections provided on the electrode plate are pressed against the surface of the electrode of the positive temperature coefficient thermistor, and stable electrical contact can be obtained even during the heat generation operation.

Even when a plurality of PTC thermistors are used to increase the amount of heat generation, the above-described structure is formed between each PTC thermistor and the electrode plate, so that each PTC thermistor has the above-mentioned structure. The action can be obtained.

[0019]

1 is an exploded perspective view of a heater according to the present invention, FIG. 2 is an enlarged exploded perspective view of an electrode plate and an insulating frame member which constitute the heater shown in FIG. 1, and FIG. 3 is shown in FIG. FIG. 4 is an enlarged sectional view showing a part of the heater, and FIG. 4 is a sectional view partially showing an assembled state of the electrode plate and the insulating frame member shown in FIG. The heater according to the present invention includes a case 1 and insulating frame members 91 and 92.
, The electrode plates 21 and 22, and the positive temperature coefficient thermistor 3.

The case 1 has an internal space 13 including a pair of heat radiating surfaces 11 and 12 facing each other with a space therebetween. The internal space 13 has an opening 14 on one side which is a side with respect to the heat dissipation surfaces 11 and 12, and closes the entire circumference except the opening 14. The case 1 shown in the embodiment is made of, for example, a metal plate material such as a stainless steel plate, and its periphery is completely sealed by means of mechanical coupling with a coupling tool 15 such as a screw or welding or adhesion.

Each of the insulating frame members 91 and 92 is plate-shaped and has holes 911 and 921 in the surface. Hole 91
1, 921 are provided in the number corresponding to the number of the positive temperature coefficient thermistors 3. Each of the insulating frame members 91 and 92 is
Case 1 so that one surface 912 and 922 face each other
Is disposed inside the internal space 13. Insulating frame member 9
1 and 92 are formed of an electrically insulating material having excellent heat resistance, such as polyphenylene sulfide (PPS) or bake. The holes 911 and 921 may be circular or polygonal.

A pair of electrode plates 21 and 22 are provided, each of which is stacked on the other surface side of the insulating frame members 91 and 92 and electrically insulated and thermally coupled to the heat radiation surfaces 11 and 12 of the case 1. There is. Each of the illustrated electrode plates 21 and 22 has protrusions 211 and 221 on one surface 212 and 222, respectively.
12, 222 are overlapped with the other surfaces 913, 923 of the insulating frame member 91, and the surfaces 213, 223 are the heat dissipation surface 1 of the case 1.
It is thermally coupled to the first and the second cases and is housed in the inner space 13 of the case 1. Electrode plates 21, 22 and insulating frame members 91, 92
In between, use a suitable adhesive to bond. In the embodiment, three to four projections 211 and 221 are set as one set, and this set is arranged at an appropriate interval. Reference numerals 23 and 24 are lead wires connected to the electrode plates 21 and 22.

Heat dissipation surfaces 11 and 12 of case 1 and electrode plate 2
Electrically insulating layers 51 and 52 are provided between the electrical insulating layers 1 and 22. The electric insulating layers 51 and 52 can be made of an electric insulating material having high heat resistance and excellent heat conduction, such as alumina, alumina nitride, polyimide or mica.
It is desirable that the contact surfaces between the electric insulating layers 51 and 52 and the case 1 be bonded by heat resistant adhesives 61 and 62 having high thermal conductivity. As the heat resistant adhesives 61 and 62, a thermoplastic polyimide resin or a silicone resin can be used. When the electric insulating layers 51 and 52 are made of thermoplastic polyimide, they can also serve as the adhesive layer. The case 1 can be made of alumina or the like, and in such a case, the electric insulating layers 51 and 52 can be omitted.

The PTC thermistor 3 has electrodes 32 and 33 on both sides in the thickness direction of the PTC thermistor body 31, and is arranged in the holes 911 and 921 of the insulating frame members 91 and 92. Each of the electrodes 32 and 33 of the positive temperature coefficient thermistor 3 is in electrical contact with the electrode plates 21 and 22 to be in conduction. In the figure, a plurality of positive temperature coefficient thermistors 3 are provided, and are arranged inside the internal space 13 so that the protrusions 211 and 221 are in pressure contact with the electrodes 32 and 33, respectively.

In the positive temperature coefficient thermistor 3, the insulating frame members 91, 9 are provided with the electrodes 32, 33 in contact with the electrode plates 21, 22.
It has a thickness d0 that causes a gap G between the two facing surfaces.

The positive temperature coefficient thermistor 3 has electrodes 32 and 33 on both surfaces in the thickness direction of the positive temperature coefficient thermistor body 31, and the electrodes 32 and 33 are electrically contacted with the electrode plates 21 and 22 to be conductive. From the above, it is possible to obtain a heater that performs a heat generation operation by supplying power to the positive temperature coefficient thermistor 3 through the electrode plates 21 and 22, and performs a constant temperature heat generation operation by the self temperature control function of the positive temperature coefficient thermistor 3.

Each of the insulating frame members 91 and 92 has a plate shape and has holes 911 and 921 in the surface thereof.
As many 921 as the positive characteristic thermistors 3 are provided, and the positive characteristic thermistors 3 are arranged in the holes 911 and 921 of the insulating frame members 91 and 92, the positional deviation of the positive characteristic thermistors 3 is prevented. It Therefore, it is possible to eliminate the unevenness of heat generation due to the displacement of the PTC thermistor 3 and prevent the resin from adhering to the side surface of the PTC thermistor, thereby realizing a highly reliable heater.

The positive temperature coefficient thermistor 3 has the insulating frame members 91 and 9 with the electrodes 32 and 33 in contact with the electrode plates 21 and 22.
Since there is a thickness d0 that causes a gap G between the two opposing surfaces, the gap G allows the holes 911 of the insulating frame members 91 and 92 to be formed.
A ventilation path 93 that connects the 921 to each other is formed. Therefore, deterioration of the porcelain body 31, which constitutes the PTC thermistor 3, for example, barium titanate-based semiconductor porcelain is prevented,
Deterioration of the positive temperature coefficient thermistor 3 and accompanying thermal runaway and thermal destruction can be reliably prevented. When the above-mentioned ventilation passage 93 is not formed, the hole 91 containing the positive temperature coefficient thermistor 3 is formed.
It was found that 1, 921 became a sealed state, the peak resistance value of the positive temperature coefficient thermistor 3 decreased, and there was a risk of thermal runaway. The reason is that PTC thermistor 3
When the holes 911 and 921 each having a hole are closed, it is presumed that the porcelain element body 31 forming the positive temperature coefficient thermistor 3 is reduced by the air in the heated hole 91. According to the present invention, as described above, such a problem can be solved.

Each of the electrode plates 21 and 22 has a surface 21.
2, 222 has projections 211 and 221 and one surface 212,
According to the embodiment, the electrode plates 21 and 22 are accommodated in the internal space 13 of the case 1 so that the other surfaces 213 and 223 are supported by the heat radiating surfaces 11 and 12, and the other surfaces 222 and 223 face each other with a space. Reliably contacts the electrodes 32, 33 of the PTC thermistor 3 at the protrusions 211, 221.

In the case where the electrode plates 21 and 22 have the projections 211 and 221, the electrodes 32 and 3 of the positive temperature coefficient thermistor 3 are formed.
3 and the electrode plates 21 and 22 between the protrusions 211 and 221.
So as to fill the gap created by the heat conductive filler 4
It is desirable to fill 1, 42. The thermally conductive fillers 41 and 42 to be selected here are resins. The heat generated by the PTC thermistor 3 is surely transferred to the electrode plates 21, 22 via the heat conductive fillers 41, 42 by the heat conductive fillers 41, 42 described above. Therefore, the protrusion 21
Although there is a gap between the electrode plates 21 and 22 and the electrodes 32 and 33 of the positive temperature coefficient thermistor 3 by the elements 1 and 221, a high thermal coupling is formed between them. Therefore, it is possible to obtain a heater that secures electrical contact between the electrode plates 21 and 22 and the PTC thermistor 3 and improves the heat conduction efficiency from the PTC thermistor 3 to the electrode plates 21 and 22.

Moreover, since the thermally conductive fillers 41 and 42 are made of resin, a considerably large thermal strain F1 is applied to the thermally conductive fillers 41 and 42 during the heat generation operation of the positive temperature coefficient thermistor 3, as shown in FIG. appear. The electrode plates 21 and 22 have projections 211 and 2 on the surfaces 212 and 222 that contact the PTC thermistor 3.
21, the heat conductive fillers 41 and 42 are
A larger amount is filled on the side where the protrusions 211 and 221 are present than on the side of the heat coupling surface with the case 1. Therefore, the thermally conductive filler 4
The thermal strain F1 generated in Nos. 1 and 42 acts to push up the electrode plate. Since the surfaces 213 and 223 of the electrode plates 21 and 22 are mechanically fixed to or in contact with the case 1, when the thermal distortion F1 caused by the thermal expansion of the thermally conductive fillers 41 and 42 is received, the case sides are provided. The fixed point or the contact point is used as the fulcrum P0, and is pressed in the direction of the positive temperature coefficient thermistor 3 as shown by an arrow F2. Therefore, the protrusions 211 and 221 provided on the electrode plates 21 and 22 are pressed against the surfaces of the electrodes 32 and 33 of the positive temperature coefficient thermistor 3, and stable electrical contact can be obtained even during the heat generation operation. In addition, in order to easily understand the pressing action due to thermal strain, FIG.
The illustration is exaggerated.

Although not shown, a thermal fuse is provided in the internal space 13 of the case 1, and the thermal fuse supplies power to the positive temperature coefficient thermistor 3 when the positive temperature coefficient thermistor 3 is abnormally heated due to a failure or the like. Can also be operated to stop.

[0033]

As described above, according to the present invention, the following effects can be obtained. (A) It is possible to provide a constant temperature heating operation type heater based on the self-temperature control function. (B) A heater that can be easily assembled can be provided. (C) It is possible to provide a heater that can reliably position the positive temperature coefficient thermistor at a predetermined position. (D) It is possible to provide a heater that can reliably prevent deterioration of the PTC thermistor and thermal runaway associated therewith.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a heater according to the present invention.

FIG. 2 is an enlarged exploded perspective view of an electrode plate and an insulating frame member that form the heater shown in FIG.

FIG. 3 is an enlarged cross-sectional view showing a part of the heater shown in FIG.

FIG. 4 is a sectional view partially showing an assembled state of the electrode plate and the insulating frame member shown in FIG.

FIG. 5 is a diagram illustrating the operation of the heater according to the present invention.

[Explanation of symbols]

 1 Case 11, 12 Heat Dissipation Surface 13 Internal Space 21, 22 Electrode Plate 211, 221 Protrusion 3 Positive Characteristic Thermistor 31 Positive Characteristic Thermistor Element 32, 33 Electrode 41, 42 Thermal Conductive Filler 91, 92 Insulating Frame Member 911, 921 Hole

Claims (3)

[Claims] 1. A heater including one case, at least two insulating frame members, at least two electrode plates, and at least one positive temperature coefficient thermistor, wherein the case includes a heat dissipation surface. Each of the insulating frame members has a plate shape and has holes in the surface, and the holes are provided in the number corresponding to the number of the positive temperature coefficient thermistors, and one surface is The electrode plates are arranged in the internal space of the case so as to face each other, and each of the electrode plates is stacked on the other surface side of the insulating frame member and is thermally coupled to the heat dissipation surface of the case. The PTC thermistor has electrodes on both sides in the thickness direction of the PTC thermistor body, is arranged in the hole of the insulating frame member, and each of the electrodes is in electrical contact with the electrode plate. Conductive and the electrode In a state of being in contact with the electrode plate,
A heater having a thickness that creates a gap between opposed surfaces of the insulating frame member. 2. The heater according to claim 1, wherein the electrode plate has a protrusion at an electrode contact portion. 3. The heater according to claim 2, wherein the heater includes a thermally conductive filling, and the thermally conductive filling is made of resin, and the electrode of the PTC thermistor and the electrode plate are provided. A heater filled in between so as to fill the gap created by the protrusion.