JP2002350238A - Temperature sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-reliability temperature sensor having excellent durability even if it is used in an environment with large temperature change and vibration such as the inside of an exhaust system of an automobile. SOLUTION: This temperature sensor 1 is provided with a metal tube 3 with a tip part closed and with an element 2 such as a thermistor having an electrical characteristic changing depending on temperature housed at the tip part, and a flange 4 jointed to the rear end part of the metal tube. The metal tube 3 is formed by deep drawing of a metal sheet such as a stainless steel sheet. In particular, the temperature sensor having relatively excellent responsiveness can be manufactured by setting the thickness of the tip part of the metal tube 3 smaller than other parts such as a part inserted into the flange.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature sensor having a thermistor made of a semiconductor such as a metal oxide as a temperature sensing element. More specifically, the present invention relates to a highly reliable temperature sensor in which a metal tube containing a temperature sensing element is formed by deep drawing of a metal plate. INDUSTRIAL APPLICABILITY The temperature sensor of the present invention can be used for various applications requiring temperature measurement, and detects temperature in an environment where both temperature change and vibration are severe, such as inside a catalytic converter and an exhaust pipe of an exhaust gas purifying device of an automobile. It has sufficient durability also when used for.

[0002]

2. Description of the Related Art Conventionally, there is known a temperature sensor having a structure in which a temperature-sensitive element such as a thermistor is sealed at a front end portion of a high-strength metal tube and a rear end portion of the metal tube is joined to a flange. . This metal tube is usually formed by curling one end of a metal tube and then welding. A temperature sensor having such a structure has sufficient strength and excellent heat resistance, and can be used for temperature detection in an environment where temperature changes and vibrations are severe, such as in a catalytic converter of an automobile or in an exhaust pipe. it can.

[0003]

However, in a metal tube formed by curling one end of a metal tube and then welding it, it is not easy to make the thickness of the tip portion uniform. In this method, after curling, one end of the metal pipe is closed by closing the hole remaining in the center by welding, but it is not easy to make the thickness of the weld uniform, and furthermore, Is inevitably thicker than other parts. When the thickness is non-uniform, the detection accuracy of the temperature sensor decreases. Also, after curling, the welded portion is easily oxidized, and when the oxygen concentration at the tip decreases due to oxidation, the surface of a temperature-sensitive element such as a thermistor is reduced, and its electrical characteristics change. May be reduced in reliability.

The present invention solves the above-mentioned conventional problems, and has high reliability, excellent responsiveness, and low oxygen concentration at the tip of a metal tube containing a temperature-sensitive element. It is an object of the present invention to provide a temperature sensor with stable performance in which changes in the electrical characteristics of the element are suppressed.

[0005]

The temperature sensor according to the present invention comprises:
In a temperature sensor comprising a metal tube in which a tip is closed and an element whose electrical characteristics change depending on temperature is housed in the tip, and a flange joined to a rear end of the metal tube, the metal tube is made of metal. It is characterized by being formed by deep drawing of a plate.

In this temperature sensor, a metal tube for containing a temperature-sensitive element such as a thermistor is formed by deep drawing a metal plate. Therefore, the thickness of the tip portion, especially the center portion thereof, becomes uniform, and furthermore, this portion does not become thicker than other portions, and the detection accuracy of the temperature sensor is improved. In addition, since there is no welded portion, even when the temperature sensor is used to detect the temperature of a high-temperature atmosphere such as the inside of a catalytic converter of an automobile or the inside of an exhaust pipe, the oxidation of the inner surface of the metal tube and the reduction of the oxygen concentration due to it are performed. The change in the electrical characteristics of the element due to the above is suppressed, and the reliability of the temperature sensor is further improved. The metal sheet used for deep drawing is not particularly limited as long as it has sufficient strength and heat resistance, and cold-rolled steel sheets and steel strips generally used for press forming can be used. . Further, it is preferable to use a stainless steel plate from the viewpoint of heat resistance, corrosion resistance and the like.

[0007] The reliability of the temperature sensor can be improved by making the thickness of the tip portion of the metal tube uniform, but the thickness of the metal tube in the vicinity of the element is reduced by the other portions such as the portion inserted into the flange. By setting the thickness to be smaller than the thickness, a temperature sensor having high responsiveness can be obtained.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to examples. Structures of Temperature Sensors of Examples and Comparative Examples Example 1 (Temperature sensor using metal tube formed by deep drawing a stainless steel plate) FIG. 1 is a cross-sectional view illustrating an example of a temperature sensor 1 of the present invention. It is. The temperature sensor 1 uses the thermistor element 2 as a temperature-sensitive element, is attached to an exhaust pipe of an automobile, and is used for detecting the temperature of exhaust gas.

The metal tube 3 is formed by deep drawing a SUS310S steel plate, and the thermistor element 2 is housed inside the distal end 31 thereof. The periphery of the thermistor element 2 is filled with the cement 10, thereby preventing the thermistor element 2 from swinging due to vibration or the like during use. The rear end side 32 of the metal tube 3 is open, this rear end side 32 is inserted into the flange 4, and the rear end face is brought into contact with a socket provided on the inner peripheral surface of the flange 4,
It is fixed by argon welding.

A hexagonal nut 5 is provided on the outer peripheral surface of the flange 4.
1 and a nut 5 having a screw portion 52 are rotatably fitted. In the temperature sensor 1, the distal end surface of the flange 4 abuts on a mounting portion provided at a predetermined position of the exhaust pipe, and is fixed by a nut 5. Also, the rear end side 42 of the flange 4
A small-diameter portion is formed on the outer peripheral surface of the end portion, and one end side of the joint 6 is fitted into the small-diameter portion and is argon-welded. The outer diameters of the joint 6 and the rear end side 42 of the flange 4 are substantially the same, and there is almost no step at the connection portion.

A sheath 8 containing a pair of sheath core wires 7 is disposed inside the metal tube 3, the flange 4, and the joint 6.
The thermistor element 2 is connected via a Pt / Rh alloy wire 9 to the sheath core wire 7 pulled out from the distal end 81 of the sheath. The Pt / Rh alloy wire 9 is formed by co-firing with the thermistor element 2.
The t / Rh alloy wire 9 is resistance-welded to the sheath core wire 7.

On the other hand, one end of a pair of lead wires 12 is connected by a caulking terminal 11 to the sheath core wire 7 pulled out from the rear end side 82 of the sheath 8 inside the joint 6. The lead wire 12 is contained in an auxiliary ring 14 made of heat-resistant rubber, and the other end is drawn out. The auxiliary ring 14 and the joint 6 are fixed to each other by caulking or hexagonally caulking the joint 6 from the outer peripheral surface side, and are sufficiently adhered to maintain airtightness. Thus, a sealed space is formed inside the metal tube 3, the flange 4, and the joint 6, and the thermistor element 2 is housed in the sealed space.

Since the temperature sensor 1 is used in a high-temperature environment as high as 1000 ° C., each component must have sufficient heat resistance. Therefore, the metal tube 3, the sheath core wire 7, and the sheath 8 are formed of SUS310S which is a heat-resistant alloy containing Fe as a main component and containing C, Si, Mn, P, S, Ni, and Cr.
The flange 4 is made of a heat-resistant alloy having the same composition except that the amount ratio of Cr is slightly lower than SUS310S.
309S. Further, the joint 6 is made of Cr
SUS304, which is a heat-resistant alloy having the same composition except that the amount ratio of SUS304 is lower.

The temperature sensor of the first embodiment uses a metal tube formed by deep drawing a stainless steel plate. Therefore, the wall thickness of the tube wall is substantially constant over the entire length of the metal tube as well as the tip portion in which the thermistor is housed, and a temperature sensor having high reliability and stable performance can be obtained.

Embodiment 2 (Oxygen sensor using a metal tube whose tip is thinner than the thickness of the portion inserted into the flange) In the temperature sensor of this embodiment 2, as shown in FIG. A metal tube is used in which the thickness of the distal end portion is smaller than the thickness of other portions such as the portion inserted into the flange.

Comparative Example 1 (Temperature Sensor Using Conventional Metal Tube) The temperature sensor of Comparative Example 1 uses a metal tube formed by curling one end of a metal tube made of SUS310S and then welding. Other than that, the structure is the same as that of the temperature sensor of the first embodiment. In this metal tube, as shown in FIG. 3, the central portion 331 of the distal end surface 33 is thicker than other portions by welding, and the thickness is not uniform at this portion.

The present invention is not limited to the above-described specific embodiments, but may be variously modified within the scope of the present invention depending on the purpose and application. For example, the inner peripheral surface of the distal end portion of the flange may be inclined from the distal end side to the proximal end side to have a tapered shape or the like. This facilitates the operation of press-fitting the flange to the rear end of the metal tube, and also suppresses the heat transfer from the heat-sensitive part to the flange, etc.
The reliability can be further improved. The heat transfer can be suppressed by increasing the length of the metal tube to the rear end of the flange and joining it to the flange by laser welding or the like on the rear end side, thereby suppressing the above-mentioned heat transfer and thereby improving reliability. It can also be done.

Further, the outer diameter of the metal tube is made larger in the vicinity of the front end of the flange than in the front end, the sheath is sheathed on the metal tube in the vicinity of the front end of the flange, or the front end of the flange is extended to the front end of the flange. By providing a sheath portion and covering the metal tube, the resonance frequency with respect to the acceleration in the direction perpendicular to the axis of the portion protruding from the flange of the metal tube to the distal end side can be shifted to the high frequency side. Accordingly, when the temperature sensor is used for detecting the temperature inside the catalytic converter and the inside of the exhaust pipe of the automobile, it is possible to prevent the occurrence of cracks and the like due to resonance, and it is possible to obtain a more durable temperature sensor. .

It is also possible to use a structure in which the sheath is not used, the metal tube has a length up to the rear end of the flange, and laser welding is performed at the rear end of the flange.
This suppresses heat transfer from the heat-sensitive part to the flange, etc.
A highly reliable temperature sensor can be provided.

[0020]

According to the present invention, excellent responsiveness, high reliability, and excellent durability when used in an environment in which temperature changes and vibrations are severe such as in a catalytic converter and an exhaust pipe of an automobile. Temperature sensor. Further, in the temperature sensor of the present invention, a metal tube is usually provided outside the sheath, instead of placing a cap on the distal end side of the sheath. Therefore, the strength is improved, and the metal tube can be easily pressed into the flange. And it can firmly fix by welding at a predetermined position, and thereby durability can be improved more.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a temperature sensor of Example 1 using a metal tube formed by deep drawing a stainless steel plate.

FIG. 2 is an enlarged cross-sectional view showing a distal end side of a metal tube used in Example 2 in which a distal end portion is formed thinner than other portions.

FIG. 3 is a cross-sectional view showing, on an enlarged scale, a distal end side of a metal tube formed by welding after curling one end of the metal tube.

[Description of Signs] 1; temperature sensor, 2; thermistor element, 3; metal tube, 31; tip side of metal tube, 32; rear end side of metal tube, 33; Part, 4; flange, 41; tip side of flange, 4
2; rear end side of flange; 5; nut; 51; hexagonal nut; 52; screw; 6; joint; 7;
8; sheath, 81; distal end of sheath, 82; rear end of sheath, 9; Pt / Rh alloy wire, 10; cement, 11;
Caulking terminal, 12; a pair of lead wires, 13; auxiliary ring.

 ──────────────────────────────────────────────────の Continued from the front page (72) Inventor Takaaki Nagasokabe 14-18 Takatsuji-cho, Mizuho-ku, Nagoya Japan Special Ceramics Co., Ltd.

Claims (2)

[Claims] 1. A temperature sensor comprising: a metal tube in which a tip is closed, an element whose electrical characteristics change depending on temperature is housed in the tip, and a flange joined to a rear end of the metal tube. A temperature sensor, wherein the metal tube is formed by deep drawing of a metal plate. 2. The temperature sensor according to claim 1, wherein a thickness of the metal tube in the vicinity of the element is smaller than a thickness of a portion inserted into the flange.