JPH10318850A - Temperature detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a temperature sensor whose durability with reference to a heat cycle is ensured and whose heat resistance can be maintained by a method wherein a coating film which is made of an inorganic oxide is executed to the circumferential surface of a temperature sensor. SOLUTION: A metal cap 1 is formed to be an NCH1 bottomed cylindrical shape which is prescribed in JIS C 2502, its tip side is closed, and its rear end side is opened. A cylindrical temperature sensor 2 whose surface is covered with a coating film 3 having a film thickness of 1 μm and made of an inorganic oxide is housed at the tip side of the metal cap 1. Two electrodes 4 which are composed of tubular platinum pipes and a cylindrical NTC thermistor 5, in a diameter of 2.35 mm, which is made of Al2 O3 , Cr2 O3 and Fe2 O3 components are constituted at the temperature sensor 2. In addition, the whole part excluding both ends of two metal wires 6 is fixed by an insulator 7 made of Al2 O3 , and its circumference is covered with a metal pipe 8 having a diameter of 3.15 mm and made of SUS 310 S. At this time, the two metal wires 6, the insulator 7 and the metal pipe 8 constitute a two-core pipe 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature detecting device used for detecting temperatures in various places, and more particularly to a system for purifying exhaust gas of an automobile which requires a heat resistance of 1000 ° C. or more, that is, a catalytic converter inside a catalytic converter. It provides something useful for temperature detection.

[0002]

2. Description of the Related Art In recent years, an exhaust gas purifying apparatus for an automobile, that is, a temperature detecting apparatus used for detecting the temperature inside a catalytic converter has been used at a high temperature due to an increase in the heat resistant temperature of the catalyst itself. In addition to heat resistance up to 900C and durability against heat cycles between 900C and room temperature, heat resistance of 1000C or more is desired.

[0003] A conventional temperature detecting device will be described below. FIG. 5 is a front view showing a half of a conventional temperature detecting device in cross section. In FIG. 5, 23 is two metal wires,
A metal tube 25 is arranged around the whole of the two metal wires 23 except for both ends thereof, and a metal tube 25 is provided between the metal wire 23 and the metal tube 25.
_{A two-} core tube 26 having a configuration filled with an insulator 24 made of ₂ O _3, a temperature detecting element 22 connected to each one end of the two-core tube 26, and one end for accommodating the temperature detecting element 22 Was provided with a closed-end cylindrical metal cap 21.

[0004]

However, in the above-mentioned conventional configuration, when the device is exposed to a high temperature of 1000 ° C. or more, the resistance of the temperature detecting element 22 is reduced due to the atmosphere inside the metal cap 21 where the temperature detecting element 22 is present. Rise significantly,
There was a problem that an accurate temperature could not be detected.

An object of the present invention is to provide a temperature detecting device having heat resistance of 1000 ° C. or more while ensuring durability against a heat cycle of 900 ° C.

[0006]

In order to achieve this object, a temperature detecting device according to the present invention has a metal tube disposed around the whole of two metal wires except for both ends thereof. A two-core tube fixed by filling with an insulator between the two core tubes, a temperature detecting element connected to one end of a metal wire forming the two-core tube, and the two-core tube so as to house the temperature detecting element. A bottomed tubular metal cap attached to one end of the core tube,
The temperature detecting element has a configuration in which a coating film of an inorganic oxide is provided on a peripheral surface.

According to this structure, since the temperature detecting element is coated with the coating film, the temperature detecting element is not directly exposed to the strong reducing atmosphere inside the metal cap due to oxidation of the internal surface of the metal cap, so that the resistance value characteristic is not deteriorated. Absent. Therefore,
A temperature detection device having heat resistance of 1000 ° C. or more and heat cycle resistance can be provided.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, a metal tube is disposed around the whole of two metal wires except for both ends, and an insulator is provided between the metal wires and the metal tube. A filled and fixed two-core tube, a temperature detecting element connected to one end of a metal wire constituting the two-core tube, a coating film covering the temperature detecting element, A bottomed cylindrical metal cap attached to one end of the two-core tube so as to house a membrane, even if the inside of the metal cap is in a strong reducing atmosphere,
By preventing the influence of the strong reducing atmosphere on the temperature detection element by the coating film, heat resistance of 1000 ° C. or more and heat resistance cycle resistance can be secured without impairing the resistance value characteristics of the temperature detection element.

According to a second aspect of the present invention, there is provided a temperature detecting device wherein the coating film has a thickness of 1 μm or more and 2 μm or less on the surface of the temperature detecting element, wherein the coating film prevents the influence of a strong reducing atmosphere, and , By making the element and the coating film a thickness that does not cause cracks,
Without impairing the resistance value characteristics of the temperature detecting element, 1000
Heat resistance of at least ℃ and heat cycle resistance can be secured.

According to a third aspect of the present invention, there is provided a temperature detecting device in which the coating film is formed on the surface of the temperature detecting element by a CVD method or a sputtering method. By generating
The influence of the strong reducing atmosphere can be prevented, and the heat resistance and heat cycle resistance of 1000 ° C. or more can be secured without impairing the resistance value characteristics of the temperature detecting element.

According to a fourth aspect of the present invention, there is provided a temperature detecting device in which the material of the coating film is alumina, wherein the material is stable at a high temperature in a strong reducing atmosphere.
Without impairing the resistance value characteristics of the temperature detecting element, 1000
Heat resistance of at least ℃ and heat cycle resistance can be secured.

According to a fifth aspect of the present invention, there is provided a temperature detecting device in which the temperature detecting element is a cylindrical or elliptical cylindrical thermistor element. Prevent the influence of the atmosphere,
Without impairing the resistance value characteristics of the temperature detecting element, 1000
Heat resistance of at least ℃ and heat cycle resistance can be secured.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a front view showing a half section of a temperature detecting device according to an embodiment of the present invention, and FIG. 2 is an enlarged sectional view thereof. FIGS. 3 and 4 are a top view and a front sectional view, respectively, of a temperature detecting element provided with a coating film used in the temperature detecting apparatus according to the present embodiment.

In FIG. 1, reference numeral 1 denotes JIS C 2502
NCH1 bottomed cylindrical metal cap 1 specified in
Its front end is closed and its rear end is open. As shown in FIG. 2, a cylindrical temperature detecting element 2 having a coating film 3 made of an inorganic oxide and having a thickness of 1 μm on its surface is housed inside the tip of the metal cap 1. Here, in this embodiment, alumina was used as the inorganic oxide, and the inorganic oxide was formed by a CVD method.

As shown in FIGS. 3 and 4, the temperature detecting element 2 has an electrode 4 composed of two tubular platinum pipes and an Al 4
2.35 mm diameter composed of ₂ O ₃ , Cr ₂ O ₃ and Fe ₂ O ₃ components
, And a cylindrical NTC thermistor 5. Electrode 4 composed of two tubular platinum pipes of temperature detecting element 2
Inside is a 0.3 mm diameter metal wire 6 made of Ni-Cr.
Are welded and electrically connected at the ends of the electrodes 4 as shown in FIG.

As shown in FIG. 1, the whole of the two metal wires 6 except for both ends is fixed by an insulator 7 made of Al ₂ O ₃ , and furthermore, a metal tube made of SUS310S having a diameter of 3.15 mm is formed. 8 covered. Here, the two metal wires 6, the insulator 7, the metal tube 8 and the like constitute a two-core tube 14.

Next, about 3 mm of the end of the metal tube 8 is inserted into the opening of the above-mentioned metal cap 1, and the metal cap 1 is inserted.
Of the metal cap 1 is temporarily fixed by caulking the periphery of the metal cap into a circular shape of about 3 mm from the opening end.
A seam welding process 9 is performed on the circumference by a laser welding machine at a position of about 5 mm to secure airtightness inside the metal cap 1.

A lead wire 10 is electrically connected to each of the other ends of the metal wires 6 of the two-core tube 14 so that an electric signal can be taken out.
It penetrates through a rubber material 11 made of cylindrical silicon having two through holes. Further, the rubber material 11
Is inserted into a pipe-shaped metal case 12, and the outer periphery of one end of the metal case 12 is plastically deformed inward to adhere to the inner rubber material 11, thereby ensuring airtightness in the temperature detecting device. I have. The other end of the metal case 12 is arranged on the outer peripheral portion of the metal tube 8 of the two-core tube 14,
It is fixed and sealed by laser welding 13.

Next, the results of the 1100 ° C. endurance test of the temperature detector manufactured as described above are shown in Table 1.
Regarding the performance in Table 1, the rate of change in the judgment resistance value was 3%.

[0020]

[Table 1]

According to Table 1, the present embodiment (film thickness 1 μm)
As a result, the rise in the resistance value of the temperature detecting element 2 can be reduced to half or less as compared with the related art.

Here, the coating film 3 applied to the surface of the temperature detecting element 2 was 1 μm, which is shown in Table 1.
From the result, it is preferable that the film thickness is 1 μm or more and 2 μm or less. If the thickness of the coating film 3 is less than 1 μm,
Since the temperature detecting element 2 was not completely covered, the resistance value was significantly increased when the temperature detecting element 2 was exposed to a reducing atmosphere, and there was no change from the conventional example. On the other hand, when the film thickness was larger than 2 μm, cracks occurred in the temperature detecting element 2 and the coating film 3, and the fluctuation of the resistance value became remarkably large. Therefore, by setting the thickness of the coating film 3 to 1 μm or more and 2 μm or less, it becomes possible to use the coating film 3 at a high temperature of 1100 ° C.

On the other hand, in the 900 ° C. heat cycle test, even if the alumina coating film 3 was formed by the CVD method, it was as good as the conventional example.

In this embodiment, the alumina coating film 3 is formed by the CVD method, but it has been confirmed that the same effect can be obtained by the sputtering method.

Although a cylindrical thermistor element was used as the temperature detecting element 2, similar results were obtained with an elliptical cylindrical thermistor element.

[0026]

As described above, according to the present invention, by providing an inorganic oxide coating film on the peripheral surface of the temperature detecting element, an excellent heat resistance of 1000 ° C. or more and a heat cycle resistance of 900 ° C. are obtained. A temperature detecting device can be realized.

[Brief description of the drawings]

FIG. 1 is a front view showing a half of a temperature detecting device according to an embodiment of the present invention in cross section.

FIG. 2 is an enlarged sectional view thereof.

FIG. 3 is a top view of a temperature detecting element provided with a coating film used in the temperature detecting device according to the embodiment of the present invention.

FIG. 4 is a front sectional view thereof.

FIG. 5 is a front view showing a half of a conventional temperature detecting device in cross section.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal cap 2 Temperature detection element 3 Coating film 6 Metal wire 8 Metal tube 14 Two-core tube

Continued on the front page (72) Inventor Tsuyoshi Tanaka 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Takashi Tamai 1006 Odaka Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Invention Person Hiroki Moribun 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Hideo Torii 1006 Kadoma Odoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. 1006 Oaza Kadoma Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A two-core tube in which a metal tube is disposed around the whole of two metal wires except for both ends, an insulator is filled between the metal wire and the metal tube and fixed, and the two-core tube is fixed. A temperature detecting element connected to one end of a metal wire constituting the tube, and a bottomed cylindrical metal cap attached to one end of the two-core tube so as to house the temperature detecting element. A temperature detecting device comprising a coating film made of an inorganic oxide on a peripheral surface of the temperature detecting element. 2. The temperature detecting device according to claim 1, wherein the coating film has a thickness of 1 μm or more and 2 μm or less. 3. The temperature detecting device according to claim 1, wherein the coating film is generated by a CVD method or a sputtering method. 4. The temperature detecting device according to claim 1, wherein the material of the coating film is alumina. 5. The temperature detecting device according to claim 1, wherein the temperature detecting element is a cylindrical or elliptic cylindrical thermistor element.