KR100431442B1 - Water proof thermister for automobile applications - Google Patents

Abstract

The present invention relates to a thermistor having a characteristic that its no-load resistance value changes with temperature change, and the manufacturing process is reduced by injection molding with a thermally conductive polyphenylene sulfide resin having a thermal diffusion coefficient of 0.3 x ㎡ / s or more. It provides thermistors for automotive air conditioners with improved temperature sensitivity while preventing the penetration of moisture.

Description

WATER PROOF THERMISTER FOR AUTOMOBILE APPLICATIONS}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermistor having the characteristic that its no-load resistance value changes with temperature change, and more particularly, to a waterproof thermistor for an automobile air conditioner.

Thermally Sensitive Resister is a semiconductor device called a thermister in the sense of "temperature sensitive resistor." The material is made of a sintered body of metal oxides such as manganese, nickel, cobalt, iron, and copper, and senses the temperature by using a characteristic that the resistance decreases as the temperature rises, called a negative temperature coefficient thermistor (NTC).

Conventional thermistors are generally applied by epoxy coating or molding, which requires a skilled worker due to the characteristics of the epoxy coating process, requires a drying process after epoxy coating, and takes a long time to manufacture, depending on the production lot. Since the ratio of the main ingredient and the curing agent becomes inconsistent, it causes another quality problem (Korean Utility Model Publication No. 97-59418). In addition, since the plasticizer component of the wire coating is volatilized during the epoxy drying process, a failure in breaking the wire coating may occur. In particular, the steam cracking test for use as a waterproof thermistor for an automobile air conditioner may cause the epoxy to be broken.

In view of the problems of the prior art, an object of the present invention is to provide a waterproof thermistor for an automotive air conditioner having excellent waterproofing and electrical properties and excellent temperature response time even after steam pressure test for use as a waterproof thermistor for an automobile air conditioner. .

1 is a schematic view showing a waterproof thermistor including a molding part of a conventional epoxy resin.

2 is a schematic view showing a waterproof thermistor including a molding part of the polyphenylene sulfide-based thermal conductive resin of the present invention.

The present invention, in order to achieve the above object, in the thermistor for automobile air conditioner,

a) 10 to 95% by weight of polyphenylene sulfide resin; And

b) 90 to 5% by weight of ceramic solids

A molded part of the polyphenylene sulfide-based thermal conductive resin containing a resin having a thermal diffusion coefficient of at least 0.3 × 10 ⁻⁶ m 2 / s

It provides a thermistor for a car air conditioner comprising a.

Hereinafter, the present invention will be described in detail.

In the present invention, the thermal conductivity is improved so that the thermal diffusion coefficient (α = k / ρCp, where α is the thermal diffusion coefficient, k is the thermal conductivity (W / mK), ρ is the density, and Cp is the heat capacity) of 0.3 x 10- ^{. The} thermistor manufactured by molding a thermally conductive polyphenylene sulfide-based resin of ⁶ m 2 / s or more into the temperature sensor part of the thermistor is designed to maintain waterproof and electrical properties and excellent temperature response time even after steam pressure test. Therefore, it is desirable as a waterproof thermistor for automobile air conditioners.

In the case of a material having a low thermal diffusion coefficient, molding at a thin thickness can give a quick temperature response time. However, since the thickness is limited, it is preferable to use a material having a thermal diffusion coefficient of 0.3 x 10 ^-6 m 2 / s or more. .

In case of molding with a general polyphenylene sulfide resin, waterproof performance is maintained, but temperature sensitivity is inferior when the thermal diffusion coefficient is 0.1 x 10 ^-6 m 2 / s or less. In addition, when molding with a resin having small or no crystals such as polyvinyl chloride or polycarbonate, the waterproof performance cannot be maintained. In the case of molding with polybutylene terephthalate, there is a waterproof performance, but after the vapor pressure test, the material is decomposed and the waterproof performance is deteriorated.

Therefore, it is a semi-crystalline thermoplastics, which has heat resistance, has crystals, and is thermally conductive polyphenylene sulfide-based resin with excellent thermal conductivity. Good waterproof waterproof thermistors can be manufactured. 1 shows a thermistor of the present invention.

The present invention for this purpose, the polyphenylene sulfide-based thermal conductive resin

It is preferably prepared by a process comprising the steps of a) 10 to 95% by weight of polyphenylene sulfide resin, and b) 90 to 5% by weight of a ceramic solid in a twin screw extruder at a barrel temperature of 250 to 340 ° C.

In particular, the ceramic solid of b) has silicon carbide, boron nitride, diamond, beryllium oxide, boron phosphide, aluminum nitride, beryllium sulfide, boron azenide, silicon having a thermal conductivity of at least 300 W / m · K at room temperature. It is preferable to select at least 1 type from the group which consists of gallium nitride, aluminum phosphide, and gallium phosphide.

In addition, the polyphenylene sulfide-based thermal conductive resin

c) 5 to 15% by weight of a filler selected from the group consisting of iii) flakes, ii) glass fibers or carbon fibers, and iii) halogen or non-halogen-based flame retardants.

In particular, the halogen or non-halogen flame retardant of iii) bromine carbonate oligomer, Sb ₂ O ₃ , phosphorus and phosphate flame retardant, melamine cyanurate, melamine, triphenyl isocyanurate, melamine phosphate, melamine pyrophosphate, It is preferable to select at least one member from the group consisting of ammonium polyphosphate, alkyl amine phosphate, melamine resin and zinc borate.

Therefore, the present invention is an injection molding of thermally conductive polyphenylene sulfide-based resin having a thermal diffusion coefficient of 0.3 x 10 ^-6 m 2 / s or more when manufacturing the thermistor. Can provide.

The present invention will be described in more detail with reference to the following examples and comparative examples. However, an Example is for illustrating this invention and is not limited only to these.

EXAMPLE

Thermistors for automotive air conditioners must pass the tests of 1) to 6) below.

1) Thermal time constant

After leaving the temperature sensor in the water bath at 12 ℃ for the first time for more than 1 hour, immerse it in the water bath at the final temperature of 2 ℃ and measure the time until the temperature reaches the resistance value corresponding to 5.68 ℃.

2) Steam pressure test

This test is required to satisfy the electrical characteristics after 96 hours at 121 ℃, 2 atm, 100% relative humidity.

3) Temperature test

The electrical characteristics should be satisfied after 48 hours in the condition of voltage DC 13.5 V, temperature 40 ℃, relative humidity 90-95%.

4) Heat Cycle Test

The electrical characteristics shall be satisfied after 20 cycles of repetition with a voltage of DC 13.5 V, temperature of -80 ° C (2 hours) and 80 ° C (2 hours) as one cycle.

5) High temperature leaving experiment

After 96 hours at 80 ℃ temperature, the electrical characteristics should be satisfied.

6) Low temperature leaving experiment

The electrical characteristics should be satisfied after 72 hours at the temperature of -30 ℃.

Example 1

Thermistor was molded as shown in Figure 2 with a polyphenylene sulfide-based resin (thermal conductivity resin PPS made by LG Chemical, 40% by weight of polyphenylenesulfide and 60% by weight of silicon carbide solid) having a thermal diffusion coefficient of 0.5 x 10 ^-6 m 2 / s. Was prepared. This product passed the test 2) ~ 6), and the molding had a thickness of 1 mm and a thermal time constant of 5 seconds or less, which was suitable for use as a waterproof thermistor for automobiles.

Comparative Example 1

Polybutylene terephthalate resin having a thermal diffusion coefficient of 0.5 x 10 ^-6 m 2 / s instead of polyphenylene sulfide resin (40% by weight of thermal conductivity resin manufactured by LG Chemical, 40% by weight of polybutylene terephthalate and 60% by weight of silicon carbide solid) Thermistor was manufactured in the same manner as in Example 1 except for changing to). This product passed the test 3) ~ 6) and the thermal time constant was 5 seconds at the thickness of the molding of 1 mm but did not pass the steam pressure test of 2).

Comparative Example 2

Example 1, except that instead of polyphenylene sulfide-based resin molded with a thermoplastic resin of polyvinyl chloride, polyphenylene sulfide, polycarbonate, and polypropylene having a thermal diffusion coefficient of 0.2 x 10 ^-6 m 2 / s Thermistors were prepared in the same manner as in the following. These products have a poor performance as a temperature sensor with a molding thickness of 1 mm and a thermal time constant of more than 14 seconds.

Comparative Example 3

Thermistors were manufactured in the same manner as in Example 1, except that the resin was coated with an epoxy resin instead of the polyphenylene sulfide-based resin. This product had a thermal time constant of 5 seconds when the coating thickness was 0.5 mm or less, the same as in Example 1, but did not pass the steam pressurization test.

Comparative Example 4

Thermistors were manufactured in the same manner as in Example 1, except that the polyphenylene sulfide-based resin was molded with an epoxy resin. This product has a thermal time constant of more than 14 seconds when the thickness is more than 1 mm, which degrades its performance as a temperature sensor.

The thermistor according to the present invention can be used as a waterproof thermistor for automotive air conditioners that require waterproofing by molding with thermally conductive polyphenylene sulfide and having excellent waterproof performance and temperature response time. It can be molded in various shapes.

Claims (5)

In the thermistor for automobile air conditioner consisting of a thermistor and a molding part surrounding the same, The molding part a) 10 to 95% by weight of polyphenylene sulfide resin; And b) Silicon carbide, boron nitride, diamond, beryllium oxide, boron phosphide, aluminum nitride, beryllium sulfide, boron azenide, silicon, gallium nitride, aluminum having a thermal conductivity of at least 300 W / mK Molding with a polyphenylene sulfide-based thermally conductive resin composition having a thermal diffusion coefficient of at least 0.3 × 10 ⁻⁶ m 2 / s, comprising 90 to 5% by weight of at least one ceramic solid selected from the group consisting of phosphides and gallium phosphides Thermistors for automobile air conditioners, characterized in that. delete The method of claim 1, The polyphenylene sulfide-based thermal conductive resin c) iii) flakes, ii) glass fibers or carbon fibers, and iii) 5 to 15% by weight of a filler selected from the group consisting of halogen or non-halogen-based flame retardants. . The method of claim 1, The polyphenylene sulfide-based thermally conductive resin is 10 to 95% by weight of a polyphenylene sulfide resin, and 90 to 5% by weight of a ceramic solid having a thermal conductivity of 300 W / m · K or more at room temperature is biaxially formed at a barrel temperature of 250 to 340 ° C. Thermistor for an automotive air conditioner manufactured by the method comprising the step of mixed extrusion in the extruder. The method of claim 1, The molding unit for automobile air conditioner thermistor injection.