JP2002350239A - 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 a temperature-sensitive element 2 such as a thermistor housed at the tip part, and a flange 4 for jointing the rear end side 32 of the metal tube 3. By increasing the diameter of the metal tube 3 at a position on the flange side, the resonant frequency of the metal tube to acceleration vertical to an axis of a part projecting to more tip side than the flange is set to 500 Hz or above. By armoring the metal tube 3 with a sheath 10 in a position on the flange side, or by covering the metal tube 3 with a sheath part 43 extended to the tip surface of the flange in the position on the flange side, the resonant frequency can similarly be set to 500 Hz or above.

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, it is a temperature sensor in which an element is sealed at the tip of a metal tube, and can be used for various applications requiring temperature measurement. The present invention also relates to a temperature sensor having sufficient durability for detecting a temperature in an environment where both temperature change and vibration are severe, such as in an exhaust pipe.

[0002]

2. Description of the Related Art Conventionally, a temperature-sensitive element such as a thermistor is sealed at the tip of a metal tube, and the rear end surface of the metal tube is brought into contact with a receptacle provided on the inner peripheral surface of a flange.
A temperature sensor having a structure joined by welding is known. This temperature sensor has sufficient mechanical strength and excellent heat resistance at high temperatures, and is suitable for temperature detection in environments where the temperature changes greatly from low to high and in which vibrations are severe, such as in the catalytic converter and exhaust pipe of automobiles. It is used.

[0003]

When the temperature inside the catalytic converter is detected by such a temperature sensor,
In order to improve the responsiveness, the diameter of the heat-sensitive portion on the distal end side of the metal tube may be reduced or reduced.
However, as a result, the resonance frequency of the metal tube on the tip side from the flange shifts to the low frequency side, and the resonance frequency range of the exhaust system of an internal combustion engine such as an automobile (generally, 500 to 700H).
z. ). This resonance frequency can be shifted to the high frequency side by shortening the metal tube on the tip side from the flange. However, since it is preferable that the heat-sensitive portion is as close as possible to the center of the catalytic converter or the exhaust pipe, it is not practical to shorten the metal tube.

The present invention solves the above-mentioned conventional problems, and has excellent durability even when used in an environment where both temperature change and vibration are severe, such as in a catalytic converter and an exhaust pipe of an automobile. And to provide a highly reliable temperature sensor.

[0005]

The temperature sensor according to the present invention comprises:
A metal tube in which a distal end is closed and an element whose electrical characteristics change depending on temperature is housed in the distal end, and a flange joined to a rear end of the metal tube; Since the rear end side of the metal tube has a large diameter at a portion protruding toward the distal end (hereinafter referred to as a protruding portion), the resonance frequency with respect to acceleration in a direction perpendicular to the axis of the protruding portion is 500 Hz or more. It is characterized by having been done.

[0006] In this temperature sensor, the rear end side of the metal tube has a portion inserted into the flange and a predetermined length from the front end surface of the flange, or only a predetermined length portion from the front end surface of the flange. The diameter is larger than the tip side. The large-diameter portion has an outer diameter and an inner diameter that are both larger than the distal end side, and may be approximately the same thickness as the distal end side,
Only the outer diameter is larger than the distal end side, the inner diameter is almost the same as the distal end side, and it may be thick at the large diameter part. As a result, the above-mentioned resonance frequency of the metal tube becomes 500 Hz or more, and when used for detecting the temperature inside the catalytic converter and the exhaust pipe of an automobile, the generation of cracks due to vibration is sufficiently suppressed, and the temperature is excellent in durability. It can be a sensor.

The resonance frequency varies depending on the ratio of the outer diameter of the large-diameter portion to the outer diameter of the distal end, and the length or thickness of the large-diameter portion.
If the length of the protruding portion is the same, the larger the diameter and the thicker the portion, the higher the frequency can be shifted. This resonance frequency is preferably 700 Hz or more, particularly 1000 Hz or more, and more preferably 1500 Hz or more. Depending on the outer diameter of the large diameter portion, or the length or thickness, it may be 2000 Hz.
The above can also be applied.

Further, in the present invention, the sheath is provided at the rear end side of the metal tube at least in a portion protruding from the flange to the front end side,
A temperature sensor having a resonance frequency of 500 Hz or more with respect to the acceleration in the direction perpendicular to the axis of the protruding portion may be used.

In this temperature sensor, the metal tube is provided only on the rear end side of the metal tube at a portion inserted into the flange and a predetermined length from the front end surface of the flange, or only at a predetermined length portion from the front end surface of the flange. Sheath made of steel. The inner diameter of the sheath is substantially the same as the outer diameter of the metal tube, that is, it is preferable that the sheath is in close contact with the metal tube, but the resonance frequency can be shifted to a higher frequency side even with some gaps.

[0010] The sheath can be fixed by welding its tip or the like to a metal tube by welding or the like. Also, if the rear end of the sheath is brought into contact with the socket provided on the inner peripheral surface of the flange and joined, or if it is joined to the front end of a joint connected to the rear end of the flange, it becomes more robust. It can be fixed, and the durability can be further improved. When the sheath is sheathed on the metal tube only at a predetermined length from the front end surface of the flange, it is preferable that the sheath is joined to the front end surface of the flange and fixed. As a result, even when used in a highly vibrating environment such as the inside of a catalytic converter of an automobile and the inside of an exhaust pipe, the generation of cracks due to the vibration is sufficiently suppressed, and a temperature sensor having excellent durability can be obtained.

The resonance frequency varies depending on the outer diameter of the sheath and the length from the tip end surface of the flange or the thickness thereof. If the length of the protruding portion is the same, the longer the sheath, the thicker the sheath, the higher the frequency. Can be shifted to Due to the sheath, the above-described resonance frequency of the metal tube can be set to 700 Hz or more, particularly 1000 Hz or more, and further to 1500 Hz or more. Further, depending on the outer diameter, length, and thickness of the sheath, the resonance frequency can be set to 2000 Hz or more.

Further, according to the present invention, the metal tube is covered by a sheath extending from the distal end of the flange at a portion protruding from the flange of the metal tube at the distal end, so that the metal tube is perpendicular to the axis of the projected portion. A temperature sensor having a resonance frequency with respect to acceleration of 500 Hz or more can also be used.

[0013] In this temperature sensor, a sheath is extended from the tip of the flange, and the sheath covers the metal tube. The inner diameter of the sheath is preferably substantially the same as the outer diameter of the metal tube, and the sheath and the metal tube are preferably in close contact with each other. However, the resonance frequency can be shifted to the higher frequency side. As a result, the above-mentioned resonance frequency of the metal tube shifts to a high frequency side, and even when the temperature sensor is used in a highly vibrating environment such as the inside of a catalytic converter and an exhaust pipe of an automobile, the generation of cracks due to the vibration is sufficiently suppressed. Thus, a temperature sensor having excellent durability can be obtained.

The resonance frequency varies depending on the outer diameter of the sheath portion and the length from the tip end surface of the flange or the wall thickness. The larger the outer diameter of the sheath portion, the longer the sheath portion, and the thicker the sheath portion, the higher the frequency side. Can be shifted to This resonance frequency is 7
00 Hz or more, especially 1000 Hz or more, and further 1500
Hz or higher. In addition, the resonance frequency can be set to 2000 Hz or more depending on the outer diameter, length, or thickness of the sheath.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to examples. (1) Structures of Temperature Sensors of Example and Comparative Example Example 1 (Temperature sensor in which metal tube is increased in diameter near the front end side of flange) FIG. 1 shows an example of a temperature sensor 1 of the present invention. It is sectional drawing. 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.

After curling, the distal end 31 of the metal tube 3 is closed by welding.
Thermistor element 2 is housed inside. The periphery of the thermistor element 2 is filled with the cement 11, 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, the rear end face is brought into contact with a socket provided on the inner peripheral surface of the flange 4, and is argon-welded. Fixed.

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 13 is connected by a caulking terminal 12 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 13 is included 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.

A feature of the temperature sensor of the first embodiment is that a large-diameter portion 321 having a larger outer diameter than the distal end 31 is formed at the rear end 32 of the metal tube 3. The outer diameter is large at the portion of the metal tube 3 inserted into the flange 4 and at a predetermined length from the distal end surface of the flange 4. , The resonance frequency of the metal tube protruding from the metal tube can be shifted to the high frequency side. The large-diameter portion 321 is larger in outer diameter and inner diameter than the distal end 31, and the thickness of the metal tube is substantially the same over the entire length.

Embodiment 2 (Temperature sensor in which a metal sheath is provided on a metal tube near the distal end side of the flange) The feature of the temperature sensor of this embodiment 2 is that, as shown in FIG. The point is that the metal sheath 10 is provided on the rear end side 32. The inner diameter of the sheath 10 is substantially the same as the outer diameter of the metal tube 3, and the inner peripheral surface of the sheath 10 and the outer peripheral surface of the metal tube are in close contact. In addition, sheath 1
Reference numeral 0 denotes a socket provided on a portion of the metal tube 3 inserted into the flange 4 and a predetermined length from the tip end surface of the flange 4, and a rear end surface provided on an inner peripheral surface of the flange 4. And is fixed by argon welding. The other structure is the same as that of the temperature sensor of the first embodiment. Since the sheath needs heat resistance like the metal tube, it is made of a heat-resistant alloy having the same composition.

Embodiment 3 (Temperature sensor in which a metal tube is covered by a sheath extending from the front end surface of the flange) A feature of the temperature sensor of Embodiment 3 is that, as shown in FIG. A sheath 4 having a predetermined length is provided on the end face of the distal end side 41.
3 is extended. The inner peripheral surface of the sheath 43 and the outer peripheral surface of the metal tube 3 are in close contact with each other, and are not joined by welding or the like. The other structure is the same as that of the temperature sensor of the first embodiment.

Comparative Example 1 (Temperature Sensor without Metal Tube) As shown in FIG. 4, the temperature sensor of Comparative Example 1 does not have a metal tube, and the thermistor element 2 has a sheath 8
Are housed in a metal cap 15 attached to the distal end of the head. A sheath 43 having a predetermined length and an inner diameter substantially equal to the outer diameter of the sheath 8 extends from an end surface of the distal end side 41 of the flange 4. The inner peripheral surface of the sheath 43 and the outer peripheral surface of the sheath 8 are in close contact, and are not joined by welding or the like. The other structure is the same as that of the temperature sensor of the first embodiment.

Comparative Example 2 (Temperature Sensor with No Sheath Extending at the Tip of Flange) As shown in FIG. 5, the temperature sensor of Comparative Example 2 has a sheath extending at the tip of the flange. Example 1 except for
This is the same structure as the temperature sensor of FIG.

(2) Measurement of Resonance Frequency of Temperature Sensors of Examples and Comparative Examples The resonance frequencies of the temperature sensors of Example 1 and Comparative Examples 1 and 2 were measured. FIG. 6 shows the results. As is clear from FIG. 6, the resonance frequency of the sensors of Comparative Examples 1 and 2 is 5
In contrast, the resonance frequency of the sensor according to the first embodiment is 600 Hz or higher, which is less than 00 Hz, which is outside the range of the vibration frequency of the internal combustion engine.

It should be noted that the present invention is not limited to the specific embodiments described above, but may be variously modified within the scope of the present invention according to the purpose and application. For example, a metal tube whose tip is closed by deep drawing of a steel sheet may be used instead of being closed by welding after curling the tip of the metal tube. This metal tube has a uniform thickness at the distal end, and can be used as a more reliable temperature sensor. In addition, the response of the temperature sensor can be improved by making the thickness of the tip portion thinner than other portions.

Further, the inner peripheral edge of the distal end portion of the flange can be inclined from the distal end side to the proximal end side to have a tapered shape, thereby facilitating the operation of press-fitting the flange into the rear end portion of the metal tube. Become. In addition, the length of the metal tube up to the rear end of the flange is joined to the flange by laser welding or the like on the rear end side and fixed, so that heat transfer from the heat-sensitive portion to the flange can be suppressed. Reliability can be further improved. In this case, the sheath is not always necessary.

[0029]

According to the present invention, a temperature sensor having excellent durability and high reliability even when used in an environment where temperature changes and vibrations are severe, such as inside a catalytic converter and an exhaust pipe of an automobile. Can be. Also, in the temperature sensor of the present invention, instead of placing a cap on the distal end side of the sheath,
Because a metal tube is further arranged outside the sheath,
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 the present invention in which a metal tube has a large diameter near a distal end side of a flange.

FIG. 2 is a partial cross-sectional view of the temperature sensor of the present invention in which a sheath is sheathed on a metal tube near the distal end side of a flange.

FIG. 3 is a partial cross-sectional view of the temperature sensor of the present invention in which a sheath is formed at the tip of a flange, and the sheath covers a metal tube.

FIG. 4 is a comparative example 1 in which a metal tube is not provided, a thermistor is housed in a cap mounted on a distal end of a sheath, and a sheath is formed on a distal end of a flange.
3 is a partial cross-sectional view of the temperature sensor of FIG.

FIG. 5 is a partial cross-sectional view of a temperature sensor of Comparative Example 2 having the same structure as that of Example 3 except that the flange has no sheath.

FIG. 6 is a graph illustrating a change in resonance frequency of the metal tubes of Example 3 and Comparative Examples 1 and 2.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1; Temperature sensor 2, 2; Thermistor element, 3; Metal tube, 31; Tip side of metal tube, 32; Rear end side of metal tube, 321; Large diameter part, 4; Flange, 41; 43; rear end side of the flange, 43;
5; nut, 51; hexagon nut part, 52; screw part, 6;
Joint, 7; a pair of sheath core wires, 8; sheath, 81; distal end side of sheath, 82; rear end side of sheath, 9; Pt / Rh alloy wire, 10; sheath, 11; cement, 12;
13; a pair of lead wires; 14; an auxiliary ring; 15;

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takaaki Nagasokabe 14-18 Takatsuji-cho, Mizuho-ku, Nagoya F-term (reference) in Japan Special Ceramics Co., Ltd. 2F056 QC01 QC04 QC05 QC06

Claims (3)

[Claims] 1. A metal tube having a front end closed and containing an element whose electrical characteristics change depending on temperature at the front end, and a flange joined to a rear end of the metal tube. At least a portion of the metal tube protruding forward from the flange (hereinafter referred to as a protruding portion) has a large diameter at the rear end side of the metal tube, so that resonance with respect to acceleration in a direction perpendicular to the axis of the protruding portion. A temperature sensor having a frequency of 500 Hz or more. 2. A metal tube having a front end closed and containing an element whose electrical characteristics change according to temperature at the front end, and a flange joined to a rear end of the metal tube. At least a portion of the metal tube protruding forward from the flange (hereinafter referred to as a protruding portion) is provided with a sheath on the rear end side of the metal tube, so that resonance against acceleration in a direction perpendicular to the axis of the protruding portion is achieved. A temperature sensor having a frequency of 500 Hz or more. 3. A metal tube having a distal end closed and containing an element whose electrical characteristics change depending on temperature at the distal end, and a flange joined to a rear end of the metal tube. The metal tube is covered by a sheath extending from the front end of the flange at a portion protruding from the front end of the flange (hereinafter referred to as a protruding portion), so that the metal tube extends in a direction perpendicular to the axis of the protruding portion. A resonance frequency with respect to acceleration of 500 Hz or more.