JPS59150966A - Ptc heater used for air suction system of engine - Google Patents

Abstract

PURPOSE:To improve a resistance against corrosion without spoiling an electric discharge effect by applying a protective film onto the surface of an electrode layer in the PTC heater controlling the heating of suction air. CONSTITUTION:The PTC heater is formed by ceramic semiconductor into a honeycomb type molded body 1 formed with a multitude of fine holes 2 into the direction of the thickness of a plate while the electrode layer 3 is formed by spraying or the like of an electro-conductive substance, such as aluminum or the like, to the surface of the internal walls of respective fine holes 2. The surfaces of respective electrode layers 3 are formed with the heat resistant resin protective films 4, including fine powdered body 5 of aluminum or the like, which has a good heat conductance, by the method of impregnation, coating or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a PT-C heater installed and used within an intake pipe of an engine to control the heating of intake air.

In recent years, safe and relatively inexpensive ceramic semiconductors have been made into molded bodies bK with a large number of pores a... as shown in Figure 5.
A heating element called a PTC heater, which is molded and has an electrode layer C in each of its pores a, to have positive resistance and humidity characteristics as shown in Fig. 6, has been disclosed in Japanese Patent Publication No. 1970
-36823 and JP-A No. 53-6739,
This has come to be used in place of the conventional nichrome heater to perform auxiliary thermal control of the intake air flowing into the intake pipe of the engine.

In this PTC heater, when a current is passed in the thickness direction of a molded body made of ceramic semiconductor, when the ambient temperature is low,
They lower their own electrical resistance to make it easier to conduct electricity and increase the amount of heat generated, but when the ambient temperature rises, they rapidly increase their own electrical resistance, making it difficult to conduct electricity and suppress the heat generation. By doing so, the generated heat is radiated to the intake air or mixed gas passing through the pores a, thereby performing heating control.

However, such PT4. When the heater is installed in the intake system, the electrode layer C... formed on the inner wall surface of the pore a... The problem was that it reacted with the metal and corroded.

Therefore, the present invention aims to eliminate such problems and to provide an excellent two-cutter C heater which often inhibits the heat dissipation effect. The gist is that a protective coating having thermal conductivity, corrosion resistance, and heat resistance is formed on the surface of the inner electrode layer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, one embodiment of a two-cutter C heater according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a schematic configuration of a two-cutter C heater according to this embodiment. In Fig. 1, the PTC heater is made by molding a ceramic semiconductor including barium titanate (BaTt03) into a honeycomb shape (4- The electrode layers 3 are formed by spraying a conductive material such as aluminum on the inner wall surface of each pore 2 . As seen in the schematic cross-sectional view in Figure 2, the surface contains fine powder (hereinafter referred to as "thermal conductive powder") 5... with good thermal conductivity such as aluminum, copper, and silver. The heat-resistant resin protective coating 4 is formed by dipping or coating.

Here, the heat-resistant resin forming the above-mentioned protective coating layer 4 is appropriately selected from thermosetting resins such as epoxy, ferro, and polyamide thread, all of which have heat resistance of 100°C or higher. In addition, it is necessary that the heat conductive fine powder 5 contained in this heat resistant resin...
It is preferable that the particles have a particle size of about 20 μm to 80 μm, and preferably that they are evenly dispersed within the heat-resistant resin.

Through the experimental results shown in Figs. 3 and 4, it has been found that it is desirable for the heat-resistant resin protective coating 4, which forms the main part of the above structure, to satisfy the following conditions. .

a. Content of thermally conductive fine powder The desirable range was confirmed from the viewpoint of the heat dissipation effect required for the 2-C heater and the adhesion to the electrode surface. As a result, 20 to 60% (parts by weight) was good, and the optimum range was 30 to 50%.

In other words, if the content of the thermally conductive fine powder is less than 20% (parts by weight), the thermal conductivity and therefore the heat dissipation effect will be poor, and heating of the mixture and vaporization of gasoline will be insufficient; In some cases, the adhesion to the electrode surface was insufficient.

b. Thickness of heat-resistant protective coating A desirable range was confirmed from the viewpoints of corrosion prevention effect against lead compounds, heat dissipation effect, and workability. As a result, the range of 5μ to 50μ was good, and the optimum range was 10 to 30μ.

In other words, if the film thickness is less than 5μ, it is difficult to uniformly coat the electrode surface, and if it is more than 50μ, the humidity difference between the electrode surface and the protective coating layer may exceed 10℃. As a result, the thermal conductivity decreases, and the heat dissipation effect also decreases.
TC heater and PT according to the present invention with a protective coating formed
C heater (film thickness 10μ, Ah content 40% (parts by weight),
As a result of conducting an experiment to compare and measure the depth of rust formed on a heat-resistant resin (using modified silicone), the graph shown in FIG. 4 was obtained, which confirmed the anti-corrosion properties of the present invention.

The conditions of use at this time were as shown in Table 1.

Table 1 As can be understood from the above explanation, according to the present invention, the problem of electrode corrosion of PTC heaters, which was considered unsolved in the past, can be solved advantageously without impeding the heat dissipation effect of the heater. The unique effect of being able to provide a P-type C heater with a long length is achieved.

[Brief explanation of the drawing]

FIG. 1 is a partially longitudinal perspective view showing a schematic configuration of a PTC heater according to an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view illustrating the structure of a heat-resistant resin protective coating in pores, 5 Figure 3 shows the experimental results showing the relationship between the content of thermally conductive fine powder in the heat-resistant resin protective coating and the film thickness with respect to the temperature difference between the electrode layer surface and the heat-resistant resin protective coating of the same P7C heater. FIG. 4 is a graph showing a comparative example of corrosion prevention effect between the conventional example and the present invention. FIG. 5 is a perspective view showing a conventionally known P″rCrC heater configuration. FIG. FIG. 3 is a temperature resistance characteristic diagram of a heater. (Explanation of symbols) 1... Molded body (ceramic heating element) 2... Pore 3... Electrode layer 4 - Heat-resistant resin protective coating 5... Fine powder with good thermal conductivity Fig. 3 Al 悄Ju ['/,] (! Collar) Figure 4 is shown: 40) t 1, ゛ Indication of the incident Patent Application No. 58-24476 2, Name of the invention I' used in the intake system of an engine TC heater 3, relationship with the case of the person making the amendment Patent applicant (3], :'5) Toyo Kogyo Co., Ltd. 4, agent 5, date of amendment order (1) Attachment to the scope of claims in the specification Correct as attached. (2) Part of the detailed description of the invention in the specification is amended as follows. ■ In the 17th line of the 4th edition of the specification, the statement ``120 to 60 parts by weight (parts by weight)'' should be corrected to ``20 to 60% by weight (hereinafter, ``sections'' indicate parts by weight). ■ On page 4, line 20 of the specification, "hereinafter (in parts by weight)," should be corrected to "hereinafter,". ■ tJ'] Slender Buttocks, page 5, line 2, replace ``60% or more (parts by weight)'' with ``60 section -hi.''
Correct. (2) In the specification, page 5, line 17 to page 18, line ``Al content 40 inches (parts by weight)'' is corrected to ``Al content 40 inches.'' What is claimed is a molded body made of a ceramic semiconductor in which a plurality of pores are bored in the thickness direction, and a thermally conductive material is provided on the surface of an electrode layer formed on the inner wall surface of each pore of the molded body. Good fine powder 2
4 that a heat-resistant resin protective coating containing 0 to 60 @ fi % and a layer thickness of 5 to 50 It was formed! PTC heat used in the engine's intake system.

Claims (1)

[Claims] It has a molded body made of ceramic semiconductor with multiple pores perforated in the thickness direction, and a fine powder with good thermal conductivity is applied to the surface of the electrode layer formed on the inner wall surface of each pore of this molded body. - A two-cutter C heater for use in an engine intake system, characterized by forming a heat-resistant resin protective coating with a layer thickness of 5 to 50 μm containing 20 to 60% (heavy part) of powder.