JP2846244B2 - heater - Google Patents

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 using a PTC thermistor as a heating element has been well known. Positive characteristic thermistors
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 PTC 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 sink, and heat is extracted through the heat sink. When used for heating liquid such as water or oil, the radiator plate is constituted by a case, and the case accommodates basic elements such as a positive temperature coefficient thermistor and an electrode plate. When a large amount of heat is to be obtained, a plurality of PTC thermistors are used, each of the PTC thermistors is sandwiched between a pair of common electrode plates, and the plurality of PTC thermistors are simultaneously driven via the electrode plates. As a related technical document example of such an assembly structure, there 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 for supplying power to the positive temperature coefficient thermistor but also as a heat conductor.
Tighter electrical contact and thermal coupling of the electrode plate to the positive temperature coefficient thermistor is extremely important. However, it is technically difficult to reliably satisfy these conditions while ensuring ease of assembly and simplification of the structure.

Furthermore, when the electrical contact and thermal coupling of the electrode plate to the positive temperature coefficient thermistor are made high and the positive temperature coefficient thermistor is completely sealed, a porcelain body constituting the positive temperature coefficient thermistor, for example, a barium titanate-based material The semiconductor porcelain deteriorates, the peak resistance of the positive temperature coefficient thermistor decreases, and thermal runaway and thermal destruction may occur.

[0005] It is an object of the present invention to provide a constant temperature heating operation type heater based on a self temperature control function.

It is another object of the present invention 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 capable of reliably preventing deterioration of the positive temperature coefficient thermistor and accompanying thermal runaway.

[0009]

In order to solve the above-mentioned problems, a heater according to the present invention comprises a 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 radiation surface.
Each of the insulating frame members is plate-shaped, has holes in a plane, and the holes are provided in a number corresponding to the number of the positive temperature coefficient thermistors, and the surfaces of the case are arranged so that one surface faces each other. 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 dissipation surface of the case. The positive temperature coefficient thermistor has electrodes on both surfaces in the thickness direction of the positive temperature coefficient thermistor body, is disposed in the hole of the insulating frame member, and each of the electrodes is electrically contacted with the electrode plate to conduct. In addition, the electrode has a thickness such that a gap is formed between the opposing surfaces of the insulating frame member when the electrode is in contact with the electrode plate.

[0010] Preferably, the electrode plate has a projection at an electrode contact portion.

More preferably, it comprises a thermally conductive filler,
The heat conductive filler is made of resin, and is filled between the electrode of the positive temperature coefficient thermistor and the electrode plate so as to fill a 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 is in electrical contact with the electrode plate to conduct electricity. , The heater operates to generate heat, and the self-temperature control function of the positive temperature coefficient thermistor provides a heater that generates heat at a constant temperature.

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

Since the positive temperature coefficient thermistor has a thickness that creates a gap between the opposing surfaces of the insulating frame member when the electrode is in contact with the electrode plate, the gap forms an air passage connecting the holes of the insulating frame member with each other. It is formed. For this reason, the deterioration of the porcelain body constituting the positive temperature coefficient thermistor is prevented, and the deterioration of the positive temperature coefficient thermistor and the resulting thermal runaway and thermal destruction are reliably prevented.

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

In a structure in which the electrode plate has a projection at an electrode contact portion, the thermally conductive filler is provided with an electrode of a positive temperature coefficient thermistor,
In a preferred example, the space between the electrode plate and the electrode plate is filled so as to fill the gap created by the protrusion, the heat generated in the positive temperature coefficient thermistor is reliably transmitted to the electrode plate via the thermally conductive filler. For this reason, high thermal coupling is formed between the electrode plate and the electrode of the positive temperature coefficient thermistor, despite the separation between the two. As a result, a heater can be obtained in which electrical contact between the electrode plate and the positive temperature coefficient thermistor is ensured and the efficiency of heat conduction from the positive temperature coefficient thermistor to the electrode plate is improved.

Since the thermally conductive filler is made of a resin, a considerably large thermal strain is generated in the thermally conductive filler when the positive temperature coefficient thermistor generates heat. Since the electrode plate has a protrusion on the surface contacting the positive temperature coefficient thermistor, the thermally conductive filler is filled more on the side of the electrode plate with the protrusion than on the side of the heat coupling surface with the case. Therefore, the thermal strain generated in the thermally conductive filler acts to push up the electrode plate. Since the electrode plate is mechanically fixed or in contact with the heat dissipation surface side of the case, when subjected to thermal strain caused by thermal expansion of the thermally conductive filler, the case side fixed point or contact point is used as a fulcrum, In reaction, it is pressed in the direction of the positive temperature coefficient thermistor. For this reason, the projection provided on the electrode plate is pressed against the surface of the electrode of the positive temperature coefficient thermistor, and stable electrical contact can be obtained even during the heating operation.

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

[0019]

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 constituting the heater shown in FIG. 1, and 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.
And 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 at an interval. The internal space 13 has an opening 14 on one side that is a side portion with respect to the heat radiation surfaces 11 and 12, and the entire periphery except the opening 14 is closed. The case 1 shown in the embodiment is made of, for example, a metal plate such as a stainless steel plate, and its periphery is completely sealed by means of mechanical coupling with a coupling 15 such as a screw or welding or bonding.

Each of the insulating frame members 91 and 92 is plate-shaped and has holes 911 and 921 in the plane. Hole 91
1 and 921 are provided in a number corresponding to the number of the PTC thermistors 3. Each of the insulating frame members 91 and 92 is
Case 1 so that the surfaces 912 and 922 face each other.
Is arranged inside the internal space 13. Insulating frame member 9
Reference numerals 1 and 92 are formed of an electric insulating material having excellent heat resistance, for example, 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 superimposed on the other surface of the insulating frame members 91 and 92, and is electrically insulated and thermally coupled to the heat radiation surfaces 11 and 12 of the case 1. I have. Each of the illustrated electrode plates 21 and 22 has protrusions 211 and 221 on one surface 212 and 222, respectively.
12 and 222 are overlapped on the other surfaces 913 and 923 of the insulating frame member 91, and the surfaces 213 and 223
1 and 12 are housed in the internal space 13 of the case 1. Electrode plates 21, 22 and insulating frame members 91, 92
Adhesion is performed using an appropriate adhesive. In the embodiment, three to four projections 211 and 221 are set as one set, and the sets are arranged at appropriate intervals. Reference numerals 23 and 24 are lead wires connected to the electrode plates 21 and 22.

Heat radiation surfaces 11 and 12 of case 1 and electrode plate 2
Electrical insulating layers 51 and 52 are provided between the first and second layers. The electric insulating layers 51 and 52 can be made of an electric insulating material having high heat resistance and excellent heat conductivity, for example, 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 with heat-resistant adhesives 61 and 62 having high thermal conductivity. As the heat-resistant adhesives 61 and 62, a thermoplastic polyimide resin or a silicon-based resin can be used. When the electric insulating layers 51 and 52 are made of thermoplastic polyimide, they can also be used as adhesive layers. 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 positive temperature coefficient thermistor 3 has electrodes 32, 33 on both sides in the thickness direction of the positive temperature coefficient thermistor body 31, and is disposed in holes 911, 921 of insulating frame members 91, 92. Each of the electrodes 32 and 33 of the positive temperature coefficient thermistor 3 is electrically connected to the electrode plates 21 and 22 so as to conduct. In the figure, a plurality of PTC thermistors 3 are provided, and are arranged inside the internal space 13 such that the protrusions 211 and 221 are pressed against the electrodes 32 and 33, respectively.

The PTC thermistor 3 holds the insulating frame members 91 and 9 in a state where the electrodes 32 and 33 are in contact with the electrode plates 21 and 22.
2 has a thickness d0 that creates a gap G between the opposing surfaces.

The positive temperature coefficient thermistor 3 has electrodes 32 and 33 on both sides in the thickness direction of the positive temperature coefficient thermistor body 31, and the electrodes 32 and 33 are electrically connected to the electrode plates 21 and 22, respectively, to conduct electricity. Thus, the heater is operated by supplying power to the positive temperature coefficient thermistor 3 through the electrode plates 21 and 22, and the constant temperature heat generation operation is performed 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 plane.
921 are provided in a number corresponding to the number of the PTC thermistors 3, and the PTC thermistors 3 are arranged in the holes 911 and 921 of the insulating frame members 91 and 92, so that the displacement of the PTC thermistor 3 is prevented. You. For this reason, the uniformity of heat generation due to the displacement of the positive temperature coefficient thermistor 3 is eliminated, and the adhesion of resin to the side surface of the positive temperature coefficient thermistor is prevented, so that a highly reliable heater can be realized.

The PTC thermistor 3 is configured such that the electrodes 32 and 33 are in contact with the electrode plates 21 and 22 while the insulating frame members 91 and 9 are in contact with each other.
2 has a thickness d0 for forming a gap G between the opposing surfaces, the gap G allows the holes 911 of the insulating frame members 91 and 92 to be formed.
An air passage 93 connecting the 921 to each other is formed. For this reason, the deterioration of the porcelain body 31 constituting the positive temperature coefficient thermistor 3, for example, the barium titanate-based semiconductor porcelain is prevented,
Deterioration of the positive temperature coefficient thermistor 3 and accompanying thermal runaway and thermal destruction are reliably prevented. When the above-described ventilation path 93 is not formed, the hole 91 containing the PTC thermistor 3 is formed.
1 and 921 were sealed, and it was found that the peak resistance value of the positive temperature coefficient thermistor 3 was reduced and there was a risk of causing thermal runaway. The reason is that the positive characteristic thermistor 3
When the holes 911 and 921 containing the holes are closed, it is presumed that the porcelain body 31 constituting the positive temperature coefficient thermistor 3 is subjected to a reducing action 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 is
2, 222 have protrusions 211, 221 and one surface 212,
According to the embodiment in which the electrode plates 21 and 22 are accommodated in the internal space 13 of the case 1 so that the opposite surfaces 222 and 223 and 223 are supported by the heat dissipation surfaces 11 and 12 at intervals. Are in reliable contact with the electrodes 32 and 33 of the positive temperature coefficient thermistor 3 at the projections 211 and 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 used.
3 and the electrode plates 21, 22 between the projections 211, 221.
To fill the gap created by the heat conductive filler 4
It is desirable to fill 1,42. The heat conductive fillers 41 and 42 to be selected here are resins. The heat generated in the positive temperature coefficient thermistor 3 is reliably transmitted to the electrode plates 21 and 22 via the heat conductive fillers 41 and 42 by the above-described heat conductive fillers 41 and 42. For this reason, the protrusion 21
Due to 1,221, high thermal coupling is formed between the electrode plates 21 and 22 and the electrodes 32 and 33 of the positive temperature coefficient thermistor 3 irrespective of the occurrence of a gap therebetween. Therefore, a heater can be obtained in which electrical contact between the electrode plates 21 and 22 and the PTC thermistor 3 is ensured and the efficiency of heat conduction from the PTC thermistor 3 to the electrode plates 21 and 22 is improved.

Further, since the heat conductive fillers 41 and 42 are made of resin, as shown in FIG. 5, when the positive temperature coefficient thermistor 3 generates heat, a considerably large thermal strain F1 is applied to the heat conductive fillers 41 and 42. Occur. The electrode plates 21 and 22 have protrusions 211 and 2 on surfaces 212 and 222 that are in contact with the thermistor 3.
21 so that the thermally conductive fillers 41 and 42
It is more filled on the side where the protrusions 211 and 221 are located than on the side of the thermal coupling surface with the case 1. Therefore, the heat conductive filler 4
The thermal strain F1 generated in the first and second elements acts to push up the electrode plate. Since the electrode plates 21 and 22 have the surfaces 213 and 223 mechanically fixed or in contact with the case 1, when the electrode plates 21 and 22 receive the thermal strain F1 due to the thermal expansion of the thermally conductive fillers 41 and 42, The fixed point or the contact point is set as a fulcrum P0 and is pushed in the direction of the positive temperature coefficient thermistor 3 as shown by an arrow F2. For this reason, the projections 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 heating operation. FIG. 5 shows the pressing action due to thermal strain in an easily understood manner.
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 characteristic thermistor 3 when the positive temperature characteristic thermistor 3 performs an abnormal heating operation 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 capable of reliably preventing deterioration of the positive temperature coefficient thermistor and accompanying thermal runaway.

[Brief description of the 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 constituting the heater shown in FIG.

FIG. 3 is an enlarged 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. 2;

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Case 11, 12 Heat dissipation surface 13 Internal space 21, 22 Electrode plate 211, 221 Projection 3 Positive temperature coefficient thermistor 31 Positive temperature coefficient thermistor body 32, 33 Electrode 41, 42 Thermal conductive filler 91, 92 Insulating frame member 911, 921 Hole

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H05B 3/02-3/18 H05B 3/40-3/82

Claims (3)

(57) [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 radiation surface. Each of the insulating frame members is plate-shaped, has holes in the surface, and the holes are provided in a number corresponding to the number of the positive temperature coefficient thermistors, and one surface is provided. 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 positive temperature coefficient thermistor has electrodes on both sides in the thickness direction of the positive temperature coefficient thermistor body, is disposed in the hole of the insulating frame member, and each of the electrodes is in electrical contact with the electrode plate. Conducts and the electrode is In a state of being in contact with the electrode plate,
A heater having a thickness that creates a gap between the opposing 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, further comprising a thermally conductive filler, wherein the thermally conductive filler is made of a resin, and wherein the electrode of the positive temperature coefficient thermistor and the electrode plate are connected to each other. The heater is filled so as to fill a gap created by the protrusion.