JPS634382Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a positive temperature coefficient thermistor heater used in a crankcase heater for heating oil in the crankcase of a compressor.

Generally, a closed type compressor used in an electric refrigerator or the like is provided with a crankcase heater for increasing the temperature of oil in the crankcase. For example, if the electric refrigerator is turned off and the ambient temperature is low, freon gas may liquefy and get mixed into the oil in the crankcase, and when the refrigerator is restarted, the pressure will be high and the piston will This is to prevent the so-called nekomi phenomenon, which causes the destruction of.

Conventionally, this type of crankcase heater uses a nichrome heater wound around the outer periphery of the compressor, or a terminal plate 2a, to which lead wires 1a and 1b are attached, as shown in FIG.
A heating unit 4, in which electrodes 3a and 3b formed on both sides of a plate-shaped positive temperature coefficient thermistor substrate 3 are electrically connected to each other, is placed in a potting material 5 such as cement.
It is generally known that the porcelain case 6 is potted in a porcelain case 6 with one end open.

Further, as shown in FIG. 2, a porcelain case 11 having an open end and a pair of terminal plates 15 and 16 each having a spring portion 16b on at least one end are connected to the spring portion 16b.
The electrode surface 14 of the positive temperature coefficient thermistor substrate 14 is
a, 14b and a heat generating unit 17 housed in the porcelain case 11, and an insulating lid member 19 that closes the opening 12 at one end of the porcelain case 11, and the lid member 19 and the porcelain case 11. A device is also known in which the heating unit 17 is sealed within the porcelain case 11 by the sealing material 21 and the lid member 19.

Incidentally, as shown in Fig. 3, the crankcase heater is used by being inserted into a well 32 made of a copper pipe welded to the crankcase 31. Case heaters use porcelain cases 6 and 11 as exterior cases, which are difficult to obtain with a certain level of dimensional accuracy.
A gap is created between the well 32 and the well 32.

Therefore, in order to efficiently transfer the heat generated by the crankcase heater to the oil (not shown) in the crankcase 31 through the well 32, silicone grease or the like is applied to the outer surfaces of the porcelain cases 6 and 11. It was necessary to apply a resin to fill the above-mentioned gap with silicone grease or resin.

On the other hand, in order to eliminate the above-mentioned drawbacks, as shown in FIG. It is proposed that the entire body be molded with an elastic material 36 such as silicone rubber mixed with particles (filler) having good thermal conductivity in order to improve the thermal conductivity, and lead wires 37, 37 are drawn out from the heat dissipation plates 34, 34, respectively. has been done.

In the above manner, the surface of the crankcase heater comes into close contact with the inner wall surface of the well 32 of the crankcase 31 due to the elasticity of the elastic material 36, but the surface of the crankcase heater is in close contact with the inner wall surface of the well 32 of the crankcase 31. This lack of consideration led to problems such as variations in power and differences in expansion rates during heat generation.

The present invention was devised to solve the above-mentioned problems in PTC thermistor heaters used in crankcase heaters, etc., and includes at least two different particle sizes in the heat-resistant resin used to mold the PTC thermistor substrate. By mixing particles with good thermal conductivity into the heat-resistant resin at a weight ratio of 100% or more, the heat-resistant resin's thermal conductivity is increased and the thermal conductivity of each part of the heat-resistant resin is made uniform, making it possible to extract the heat-resistant resin. It is an object of the present invention to provide a positive temperature coefficient thermistor heater which is easy to manufacture and has good dimensional stability, which increases the electric power and reduces the variation in electric power.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 5, 111 is a positive temperature coefficient thermistor substrate, and 112 and 112 are positive temperature coefficient thermistor substrates 11.
1 is in contact with a heat sink, 113, 113 are fixing rings, 114 is a silicone resin as a heat-resistant resin, and 115, 115 are lead wires.

As shown in FIG. 6, the positive temperature coefficient thermistor substrate 111 is produced by molding and firing a positive temperature coefficient thermistor material into a rectangular plate shape, and forming electrodes 11 on both main surfaces thereof.
6,116.

On the other hand, the heat sinks 112, 112 are both formed by extrusion molding or the like using a metal material with good thermal conductivity and electrical conductivity, such as aluminum, so that the cross-sectional shape has a roughly semicircular shape. and lead wires 115, 115 on each end face of one of them.
The core wires 115a, 115a of the lead wires 115, 115 are inserted into these holes 117, 117, respectively, and the heat sink 11 is installed.
By crushing 2,112, the lead wire 11
5,115 is installed.

A positive temperature coefficient thermistor substrate 111 is sandwiched between the heat sinks 112, 112, and these heat sinks 112,
112 and the electrode 11 of the positive temperature coefficient thermistor substrate 111
A fixing ring 1 made of silicone rubber or the like, which has semicircular protrusions 113a, 113a, .
13,113 are fitted externally. In this case, if the electrodes 116, 116 and the heat sink 112 are brought into contact with each other through, for example, a conductive adhesive, their adhesion becomes more reliable.

As mentioned above, the heat sinks 112, 112 from both sides
With the fixing rings 113, 113 fitted over the PTC thermistor substrate 11, the PTC thermistor substrate 11 is inserted into a substrate containing particles 18, 18, etc. of alumina (Al ₂ O ₃ ) having at least two different particle sizes. More preferably, it is potted in an addition reaction-curing silicone resin that produces less products during curing.

Note that the fixing rings 113, 113 are fixed even if the mold position of the positive temperature coefficient thermistor substrate 111 is shifted during the above-mentioned potting.
3 is in contact with the inner wall of the mold for molding the silicone resin 114 so that the heat sink plates 112, 112 are not exposed, that is, the silicone resin 114 is always applied to the entire outer periphery.

Furthermore, the particles contained in the silicone resin 114 are intended to increase the thermal conductivity of the silicone resin 114 and to reduce the amount of unnecessary gas generated.
As the material, the above-mentioned material such as alumina is used, and for the above-mentioned silicone resin 114,
It is mixed in at a weight ratio of 100% or more.

If the positive temperature coefficient thermistor heater has the above configuration,
The particles in the silicone resin 114 are mixed in such a way that particles with a small particle size are inserted between particles with a large particle size, so that the thermal conductivity of the silicone resin 114 increases, and a large amount of electric power is extracted from the PTC thermistor substrate 111. In addition, since the distribution of particles becomes uniform, variations in power are also reduced.

By the way, by mixing equal amounts of 100 mesh alumina and 500 mesh alumina, silicone resin 11
When the thermal conductivity λ (×10 ^-3 cal/℃seccm) of silicone resin 114 is measured by changing the mixing ratio of silicone resin 114 from 0% to 200% by weight, it is as shown in Figure 7, and the above result is obtained. It can be seen that when the mixing ratio exceeds 100%, the thermal conductivity λ of the silicone resin 114 increases rapidly.

Therefore, the power extracted from the positive temperature coefficient thermistor heater is as shown by curve _l1 in Figure 8,
When the particle mixing ratio is between 0 and 100%,
The power increases by only about 1.4 times, whereas between 100% and 200%, the power increases by about 2 times.

However, the data in Figure 8 shows that the dimensions of the PTC thermistor board 111 are 14 mm in width and 15 mm in length, and the dimensions of the heat sinks 112 are 15 mm in diameter and 15 mm in length.
mm, the electrode 11 of the positive temperature coefficient thermistor substrate 111
Apply voltage of AC230Vpp between 6 and 116, and reduce to 0℃.
This is data when power was measured underwater.

The viscosity of the silicone resin 114 before curing is
As shown by the curve _l2 in FIG. 8, the larger the particle mixing ratio, the larger the silicone resin 114.
Possible viscosity for inflow casting and pressure casting is 50000 cps
Therefore, it is preferable to select the mixing ratio of the particles so that the viscosity of the silicone resin 114 is 50,000 cps or less.

As mentioned above, the upper limit of the mixing ratio of particles is determined by the viscosity because the viscosity of the silicone resin 114 before curing depends on the viscosity of the base silicone resin, the particle size of the particles, and the state of their surface treatment. This is to change.

In the positive temperature coefficient thermistor heater shown in FIG. 5, in order to adjust the output power, in addition to the particle mixing ratio, as can be seen from FIG.
The length or dimensions of 12 may vary.

The data in FIG. 9 is based on the heat sink 112 of the positive temperature coefficient thermistor heater used to measure the data in FIG.
0℃ by changing the length of 113 from 10mm to 30mm
This is a measurement of the electric power underwater.

In addition, in the above embodiment, the heat dissipation plates 112,1
12, as shown in FIG. 10, if recesses 112a, .

As is clear from the above detailed explanation, the present invention improves the thermal conductivity of the heat-resistant resin by mixing particles of different particle sizes at a weight ratio of 100% or more into the heat-resistant resin for molding the PTC thermistor substrate. Since the value is uniform and high, the power extracted from the PTC thermistor board is large, and since it is a potting type using elastic heat-resistant resin, it is easy to manufacture and is resistant to shock. , the dimensional accuracy of the external shape is also improved.

In addition, when heat is generated, the thermal expansion of the heat-resistant resin can be reduced because the amount of particles mixed in the heat-resistant resin is large, and it is also possible to reduce the thermal expansion of the heat-resistant resin when it generates heat. Therefore, the variation in the power extracted is also reduced.

Furthermore, by changing the mixing ratio of particles mixed into the heat-resistant resin and the dimensions of the heat sink of the PTC thermistor substrate, the extracted power can be broadly controlled, making it possible to obtain a PTC thermistor heater with the power required. can.

In addition to the crankcase heater, this invention also applies to
It can also be applied to a heater that heats water or the like.

[Brief explanation of drawings]

Figures 1 and 2 are sectional views of a conventional crankcase heater, Figure 3 is a sectional view of a crankcase, Figure 4 is a sectional view of a conventional crankcase heater whose exterior is molded with an elastic material, and Figure 5 is a sectional view of a conventional crankcase heater. The figure is a cross-sectional view of the positive temperature coefficient thermistor heater according to the present invention.
The figure is an exploded perspective view of Figure 5, Figure 7 is an explanatory diagram showing the relationship between the mixture ratio of particles and the thermal conductivity of silicone resin, and Figure 8 is the mixture ratio of particles and the electric power extracted and the viscosity of silicone resin. An explanatory diagram showing the relationship between
FIG. 9 is an explanatory diagram showing the relationship between the length of the heat sink and the electric power taken out, and FIG. 10 is a perspective view of a modified example of the heat sink. 111... Positive temperature coefficient thermistor board, 112...
Heat sink, 113...fixing ring, 114...silicon resin, 115...lead wire, 116...electrode, 118...particle.

Claims (1)

[Claims for Utility Model Registration] (1) A heat dissipation plate is thermally adhered to the heat dissipation surface of a positive temperature coefficient thermistor board and the whole is sealed in a heat-resistant resin,
A positive temperature coefficient thermistor heater in which heat generated by a positive temperature coefficient thermistor substrate is dissipated through the heat-resistant resin, wherein the heat-resistant resin contains particles having good thermal conductivity having at least two different particle sizes. A positive temperature coefficient thermistor heater characterized by being mixed in a heat-resistant resin at a weight ratio of 100% or more. (2) A positive temperature coefficient thermistor heater according to claim 1 of the utility model registration claim, characterized in that particles are mixed into the heat resistant resin so that the viscosity of the heat resistant resin before curing is 50,000 cps or less. . (3) Utility Model Registration A positive temperature coefficient thermistor heater according to claim 1 or 2, characterized in that the generated power is adjusted by changing the dimensions of a heat sink.