JP6576766B2 - Temperature sensor - Google Patents

Description

  The present invention relates to a temperature sensor including a temperature sensitive element such as a thermistor element or a Pt resistor element.

As a temperature sensor for detecting the temperature of exhaust gas or the like of an automobile or the like, a sensor using a temperature change of resistance such as a thermistor or a Pt resistor is known.
As shown in FIG. 4, in such a temperature sensor, generally, the thermistor element 100A and the sheath member 200 are welded and accommodated in the metal tube 300A, and a cement such as alumina is placed in the gap in the metal tube 300A. 400 is configured (see Patent Document 1). The metal tube 300A is formed by integrally deep drawing a hemispherical (cross-section arc-shaped) tip 302A on the tip side of the cylindrical body 301A parallel to the axial direction.
In addition, as shown in FIG. 5, a temperature sensor is also known in which the front end side of the thermistor element 100B is planar, and the distal end portion 302B of the metal tube 300B is substantially planar according to this shape (see Patent Document 2). ). Further, as shown in FIG. 6, a metal tube 300C in which the distal end side of the cylindrical portion main body 301C is sharpened and a small-diameter hemispherical (section is arc-shaped) distal end portion 302C is provided at the distal end of the tapered portion 303C. The temperature sensor which has is also known (refer patent document 3).

JP 2008-286789 A (FIG. 2) JP 2008-256471 A (FIG. 2) JP 2006-30030 A (FIG. 2)

By the way, in the case of the temperature sensor described in Patent Documents 1 and 3 as shown in FIGS. 4 and 6, the thermistor elements 100A and 100C are round at the tip side (the cross section is arcuate). The tip shape of each thermistor element 100A, 100C is similar to the inner surface shape of 302C. For this reason, each thermistor element 100A, 100C can be stored close to the distance G1 in the axial direction on the inner surface of each metal tube, and the responsiveness of the sensor can be improved.
However, as shown by the broken line in FIG. 4, when a thermistor element 100B having a flat tip end is used instead of the thermistor element 100A, the inner shape of the tip 302A of the metal tube 300A and the tip shape of the thermistor element 100B are different. It is greatly different and when the thermistor element 100B is brought close to the inner surface of the metal tube 300A, they interfere with each other. For this reason, the metal tube 300A and the thermistor element 100B must be separated from each other, and there is a problem that the distance G2 in the axial direction of both is larger than the distance G1 and the responsiveness of the sensor is lowered.

  On the other hand, in the case of the temperature sensor described in Patent Document 2 shown in FIG. 5, the shape of the inner surface of the tip portion 302B of the metal tube 300B is similar to the shape of the tip of the thermistor element 100B. Can be stored close together. However, if the tip 302B of the metal tube 300B is planar, the strength is lower than when it is hemispherical, so the tip 302B is deformed and cracked when a thermal stress such as a thermal cycle is applied. There is a problem that it becomes easy.

  Accordingly, an object of the present invention is to provide a temperature sensor that improves both the responsiveness of the sensor and the strength of the cylindrical metal member that houses the temperature sensitive element.

In order to solve the above-described problem, a temperature sensor of the present invention includes a temperature-sensitive element having a temperature-sensitive part whose electrical characteristics change according to temperature, and a pair of element electrode wires extending from the temperature-sensitive part to the rear end side, A sheath member that is disposed on the rear end side of the thermosensitive element and has a sheath core wire connected to the element electrode wire and a sheath outer tube that encloses the sheath core wire between insulating materials; A temperature sensor comprising a metal member that accommodates at least the temperature-sensitive element and a joint portion between the element electrode wire and the sheath core wire in its own internal space. A straight portion that is parallel to the axial direction and accommodates the temperature sensing portion, a distal end portion that is located on the distal end side of the straight portion and has an arc-shaped cross section, and extends from the distal end portion to the rear end side. Connect to the straight section And a tip-facing surface of the temperature sensing portion has a planar shape, and is a virtual circle having the same diameter as the outer diameter of the straight portion in a cross section along the axial direction, When a virtual circle is touched to both outer edges or their extension lines and the center of itself is at the same position in the axial direction as the tip of the temperature sensing portion, the radius of curvature of the tip is the curvature of the virtual circle In addition to being smaller than the radius, the outer edge of the tip is disposed inside the first semicircle on the tip side of the virtual circle.

According to this temperature sensor, the tip of the metal member can be formed into a spherical shape having a relatively small radius of curvature (the cross section in the axial direction is an arc shape), so that the strength is higher than when the tip is flat. Therefore, it is possible to suppress the tip portion from being deformed and cracked when a thermal stress such as a cooling / heating cycle is applied.
Furthermore, since the outer edge of the tip portion is disposed inside the first semicircle, even if the tip-facing surface is a flat temperature-sensitive portion, the temperature-sensitive portion is axially aligned with the inner surface of the tip portion of the metal member. Can be stored close to the sensor, and the responsiveness of the sensor can be improved. Note that “arranged inside the first semicircle” includes the circumference of the first semicircle.

In the temperature sensor of the present invention, the outer edge of the tip portion may be disposed on the tip side from the center toward the tip side with respect to the length of ½ of the radius of the virtual circle.
When the outer edge of the tip portion is arranged on the rear end side with respect to the length of ½ of the radius of the virtual circle, the length in the axial direction of the connecting portion between the tip portion and the straight portion is shortened. For this reason, since a connection part becomes a shape close | similar to a plane, the intensity | strength of a connection part falls and when a thermal stress like a thermal cycle is added, a metal member may deform | transform from a connection part and it will become easy to break. On the other hand, according to this temperature sensor, the strength of the connecting portion can be improved and the metal member can be further prevented from cracking.

In the temperature sensor of the present invention, at least a part of the temperature sensing unit may be disposed inside a second semicircle on the rear end side of the center of the virtual circle.
When the temperature sensing part is arranged outside the rear end side of the second semicircle, the axial distance between the inner surface of the tip part of the metal member and the temperature sensing part is increased, and the response of the sensor is lowered. There is. On the other hand, according to this temperature sensor, the responsiveness of the sensor can be further improved, and damage to the temperature sensing part can be suppressed.

  According to this invention, the temperature sensor which improved both the responsiveness of the sensor and the intensity | strength of the cylindrical metal member which accommodates a temperature sensing element is obtained.

FIG. 3 is a cross-sectional structure diagram in which a part of the temperature sensor according to the first embodiment of the present invention is broken along the axial direction. It is the elements on larger scale of FIG. It is the cross-section figure which fractured | ruptured a part of temperature sensor which concerns on the 2nd Embodiment of this invention along the axial direction. It is the elements on larger scale of the cross section of the conventional temperature sensor. It is the elements on larger scale of the cross section of another conventional temperature sensor. It is the elements on larger scale of the cross section of another conventional temperature sensor.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 shows a cross-sectional structure in which a part of the temperature sensor 1 according to the first embodiment of the present invention is broken along the axis O direction. The temperature sensor 1 according to the first embodiment is a mode in which the sheath member 20 is housed from the rear end side of the metal member 30.
The temperature sensor 1 is attached by being inserted through an opening (not shown) on the side wall of the exhaust pipe of the internal combustion engine, and detects the temperature of the exhaust gas of the automobile. As the exhaust gas temperature rapidly changes from a low temperature range of around 0 ° C. to a high temperature range of around 1000 ° C., the temperature sensor 1 also undergoes a cooling cycle that rises and cools within the temperature range.

The temperature sensor 1 includes a Pt resistor element (temperature sensing element) 10, a sheath member 20 connected to the Pt resistor element 10, and a bottomed cylindrical metal member that houses the Pt resistor element 10 and the sheath member 20. (In the present embodiment, SUS310S is used) 30, a mounting portion 50 fitted to the outer periphery of the metal member 30, a nut portion 60 loosely fitted to the outer periphery of the mounting portion 50, and a rear end side of the mounting portion 50 A cylindrical metal outer cylinder 70 attached to the outer cylinder 70 and a heat-resistant rubber auxiliary ring 26 attached to the rear end of the outer cylinder 70 and leading the lead wire 24 to the outside.
In the temperature sensor 1 of the present invention, the metal member 30 extends in the direction of the axis O, and the bottom side of the metal member 30 is defined as the “front end” and the open end side of the metal member 30 is defined as the “rear end”.

The Pt resistor element (temperature sensing element) 10 includes a Pt resistor part (temperature sensing part) 11 for measuring temperature and a pair of element electrode wires 12 extending from one end (rear end side) of the Pt resistor part 11. And have.
The Pt resistor portion 11 has a configuration in which a film-like metal resistor is sandwiched between ceramic layers, and is generally plate-shaped as a whole, with the longitudinal direction parallel to the axis O direction of the temperature sensor 1 (metal member 30). Arranged in the metal member 30. The metal resistor has a composition mainly composed of platinum (Pt) (50 mass% or more), and a pair of element electrode wires 12 are connected to be separated from each other. Then, since the electrical resistance value of the metal resistor changes according to the temperature change, the change can be detected as a voltage change between the pair of element electrode lines 12. As the ceramic layer, a composition having an alumina purity of 99.9% by mass or more can be used. In addition to the resistor such as Pt, a thermistor can be used as the temperature sensing part.
The sheath member 20 includes a sheath core wire 21 connected to each of the pair of element electrode wires 12 of the Pt resistor element 10 and a metal sheath outer tube 22 that accommodates the sheath core wire 21, and the sheath core wire 21 and the sheath An insulating material made of SiO ₂ is filled between the inner surface of the outer tube 22.
Usually, since the element electrode wire 12 is an expensive Pt-Rh wire or the like, the cost is reduced by connecting to the inexpensive sheath core wire 21 made of SUS or the like.

The attachment portion 50 has a substantially cylindrical shape in which a central hole for inserting the metal member 30 is opened in the direction of the axis O, and has a large-diameter flange 51 and a smaller diameter than the flange 51 from the distal end side of the temperature sensor 1. The cylindrical sheath portion 52, the first step portion 54 constituting the front end side of the sheath portion 52, and the second step portion 55 constituting the rear end side of the sheath portion 52 and having a smaller diameter than the first step portion 54 are provided. It is formed in order. The front end surface of the flange portion 51 has a tapered seat surface 53. When a nut portion 60 described later is screwed into the exhaust pipe, the seat surface 53 is pressed against a corner (not shown) of the side wall of the exhaust pipe. The seal is done.
The attachment portion 50 is press-fitted into the outer periphery of the rear end portion of the metal member 30, and both the second step portion 55 and the metal member 30 are laser-welded around and fixed to each other.
Moreover, the outer cylinder 70 is press-fitted into the outer periphery of the first step portion 54, and both are fixed by full-circle laser welding. The outer cylinder 70 accommodates and holds the connection portion between the sheath core wire 21 drawn from the sheath member 20 and the lead wire 24.

The nut portion 60 has a center hole having a slightly larger diameter than the outer periphery of the outer cylinder 70 in the direction of the axis O, and a screw portion 62 and a hexagonal nut portion 61 having a larger diameter than the screw portion 62 are formed from the distal end side. Then, with the front surface of the screw portion 62 in contact with the rear surface of the flange portion 51 of the mounting portion 50, the nut portion 60 is loosely fitted to the outer periphery of the mounting portion 50 (outer cylinder 70) and rotates in the direction of the axis O. It is free.
And the temperature sensor 1 is attached to the side wall of an exhaust pipe by the screw part 62 screwing together with the predetermined | prescribed screw hole of an exhaust pipe.

Two sheath core wires 21 are drawn out from the rear end of the sheath outer tube 22 of the sheath member 20, the terminal ends of the sheath core wires 21 are connected to the crimp terminals 23, and the crimp terminals 23 are connected to the lead wires 24. Yes. Each sheath core wire 21 and the crimping terminal 23 are insulated by an insulating tube 25, respectively.
Each lead wire 24 is pulled out through the lead wire insertion hole of the auxiliary ring 26 fitted inside the rear end of the outer cylinder 70, and is connected to an external circuit via a connector (not shown).
Further, the gap between the inner surface of the metal member 30 and the Pt resistor element 10 and the sheath member 20 is filled with cement 40 such as alumina, and the Pt resistor element 10 and the sheath member 20 are held and vibrations thereof are held. Is suppressed. As the cement 40, a material having high thermal conductivity, high heat resistance, and high insulation may be used.

Next, the configuration of the metal member 30 that is a characteristic part of the present invention will be described with reference to FIG. 2 which is a partially enlarged view of FIG.
First, as described above, the Pt resistor portion 11 has a substantially plate shape and is disposed in the metal member 30 with the longitudinal direction parallel to the axis O direction. Therefore, the tip-facing surface (end surface) 11a of the Pt resistor part 11 has a planar shape perpendicular to the direction of the axis O. In the present invention, the tip-facing surface 11a of the Pt resistor part 11 has a planar shape as described above, and does not include the tip-facing surface that is not planar (for example, spherical).

On the other hand, the metal member 30 has a cylindrical body 31, a tapered portion 35, a straight portion 34, a connecting portion 33, and a tip portion 32 in order from the rear end side, and each of these components is a deep drawing of a metal plate. It is integrally formed by processing.
The tubular body 31 has a straight shape parallel to the direction of the axis O, and the tubular body 31 has an inner diameter that is larger than the outer diameter of the sheath member 20 so that the sheath member 20 can be accommodated therein. In addition, the outer diameter of the cylindrical portion main body 31 is set to a size that fits the inner surface of the second step portion 55. The tapered portion 35 is tapered from the cylindrical body 31 toward the distal end, and when the sheath member 20 and the Pt resistor element 10 are inserted from the rear end side of the metal member 30, the distal end of the sheath member 20 is inserted into the tapered portion 35. The side contacts to position the insertion depth. In addition, as a result, the distal end side of the sheath member 20 closes the opening of the metal member 30, and at least the Pt resistor element 10 and the joint portion J between the element electrode wire 12 and the sheath core wire 21 in the internal space of the metal member 30. Is stored. The interior space is filled with cement 40.
The straight portion 34 extends in parallel to the direction of the axis O from the tapered portion 35 toward the distal end side. The straight part 34 has an inner diameter larger than the maximum outer diameter of the Pt resistor part 11 and can accommodate the Pt resistor part 11 therein.
The distal end portion 32 has an arc shape in the cross section in the direction of the axis O, and the connecting portion 33 is connected to the distal end portion 32 by reducing the diameter from the straight portion 34 toward the distal end.

  Further, in FIG. 2, a virtual circle C having the same diameter as the outer diameter of the straight portion 34, is in contact with both outer edges 34 e and 34 e of the straight portion 34 or their extension lines, and its own center Ce is a Pt resistor portion. Draw a virtual circle C at the same position in the direction of the axis O with the 11th most leading edge 11f. At this time, the radius of curvature of the tip portion 32 is smaller than the radius of curvature of the virtual circle C, and the outer edge of the tip portion 32 is arranged inside the first semicircle C1 on the tip side of the virtual circle C from the center Ce. Yes.

If the metal member 30 is configured in this manner, the tip portion 32 can be formed into a spherical shape with a relatively small radius of curvature (the cross section in the direction of the axis O is an arc shape), so that the tip portion 32 is planar. The strength is increased, and it is possible to suppress the tip 32 from being deformed and cracked when a thermal stress such as a cooling / heating cycle is applied.
Furthermore, since the outer edge of the tip 32 is disposed inside the first semicircle C1, even if the tip-facing surface 11a is a planar Pt resistor 11, the Pt resistor 11 is used as the metal member 30. Can be accommodated close to the inner surface of the distal end portion 32 in the direction of the axis O, and the responsiveness of the sensor can be improved. The phrase “arranged inside the first semicircle C1” includes the circumference of the first semicircle C1.
Here, since the curvature radius of the tip portion 32 is smaller than the curvature radius of the virtual circle C, the tip portion 32 cannot be directly connected to the straight portion 34. Therefore, a connecting portion 33 is provided between the distal end portion 32 and the straight portion 34 to connect them. Although the shape of the connection part 33 is not specifically limited, The shape which diameter-reduces from the front-end | tip of the straight part 34 to a curved surface shape, and also the front-end | tip side is tapered is preferable.

Further, it is preferable that the tip-facing surface 11a of the Pt resistor part 11 is arranged perpendicular to the axis O direction. However, due to a blur at the time of manufacture, as shown in FIG. The surface 11a may be inclined with respect to a direction perpendicular to the axis O direction. Therefore, in consideration of such a case, when a line segment L perpendicular to the direction of the axis O is drawn through the leading edge 11f with reference to the leading edge 11f of the Pt resistor portion 11, the position on the line segment L is determined. The center Ce of the virtual circle C is defined. In FIG. 2, the right end of the tip-facing surface 11a is the leading edge 11f.
Further, as will be described later, it is preferable that the tip-facing surface 11a of the Pt resistor portion 11 is disposed on the rear end side with respect to the tip of the straight portion 34. However, due to manufacturing errors, the tip-facing surface of the Pt resistor portion 11 is disposed. In some cases, 11a is arranged on the tip side of the straight portion 34. In this case, since the virtual circle C drawn from the center Ce does not contact the both outer edges 34e, 34e of the straight portion 34, the virtual circle C only needs to contact the extension line (in the direction of the axis O) of both the outer edges 34e, 34e. It was stipulated.

  As shown in FIG. 2, the outer edge of the tip end portion 32 is at a position of r / 2, which is half the radius r of the virtual circle C from the center Ce of the first semicircle C1 toward the tip side. Alternatively, it is preferably disposed on the tip side of r / 2. When the outer edge of the distal end portion 32 is arranged on the rear end side with respect to the length r / 2, the length in the axis O direction of the connecting portion 33 between the distal end portion 32 and the straight portion 34 becomes shorter. For this reason, the connection part 33 becomes a shape close to a plane, and similarly to the case of FIG. 5 described above, when the strength of the connection part 33 is reduced and a thermal stress such as a cooling cycle is applied, the metal is removed from the connection part 33. The member 30 may be deformed and easily broken.

In addition, as shown in FIG. 2, it is preferable that at least a part of the Pt resistor portion 11 is disposed inside the second semicircle C2 on the rear end side of the center Ce in the virtual circle C. When the Pt resistor part 11 is disposed outside the rear end side of the second semicircle C2, the distance in the axis O direction between the inner surface of the tip part 32 of the metal member 30 and the Pt resistor part 11 is increased. Sensor responsiveness may decrease.
On the other hand, when the Pt resistor part 11 is arranged on the tip side with respect to the center Ce of the second semicircle C2, the Pt resistor part 11 is placed on the inner surface of the connection part 33 or the tip part 32 due to a shake at the time of manufacture. There is a risk of contact and damage.
Note that “arranged inside the second semicircle C2” includes the circumference of the second semicircle C2.

  Next, a temperature sensor 1B according to a second embodiment of the present invention will be described with reference to FIG. FIG. 3 shows a cross-sectional structure in which a part of the temperature sensor 1B is broken along the axis O direction. The temperature sensor 1B is an aspect in which the sheath member 20 is exposed to the rear end side of the metal member 30B, and is the same as the temperature sensor 1 according to the first embodiment except that the configuration of the metal member 30B is different. The same parts as those of the temperature sensor 1 are denoted by the same reference numerals and description thereof is omitted.

In the temperature sensor 1B, the metal member 30B is placed on the distal end portion of the sheath member 20, but the rear end side from the distal end portion of the sheath member 20 is exposed without being covered by the metal member 30B. And the attaching part 50 is crimped and fixed to the outer periphery of the rear end part of the sheath member 20 instead of the metal member 30B, and both the second step part 55 and the sheath member 20 are fixed by laser welding all around. .
On the other hand, the metal member 30B has a cylindrical part main body 31B, a taper part 35, a straight part 34, a connection part 33, and a tip part 32 in this order from the rear end side. It is integrally formed by processing.
The inner diameter of the cylindrical portion main body 31B is slightly larger than the outer diameter of the sheath member 20, and the sheath member 20 can be inserted into itself. The tapered portion 35 is tapered toward the tip from the cylindrical portion main body 31B, and when the sheath member 20 and the Pt resistor element 10 are inserted from the rear end side of the metal member 30B, as in the temperature sensor 1, the tapered portion 35 is inserted. The distal end side of the sheath member 20 is in contact with 35 to position the insertion depth.

Then, when the sheath member 20 and the Pt resistor element 10 are inserted from the rear end side of the metal member 30B, the distal end side of the sheath member 20 comes into contact with the tapered portion 35 and is positioned. In addition, as a result, the distal end side of the sheath member 20 closes the opening of the metal member 30B, and at least the Pt resistor element 10 and the joint portion J between the element electrode wire 12 and the sheath core wire 21 in the internal space of the metal member 30B. (See FIG. 2) is stored.
Furthermore, the metal member 30 is joined to the distal end side of the sheath member 20 by welding the entire rear end side of the metal member 30B to form the welded portion w.

It goes without saying that the present invention is not limited to the above-described embodiment, but extends to various modifications and equivalents included in the spirit and scope of the present invention. For example, a thermistor sintered body may be used as the temperature sensing part instead of the Pt resistor part 11 described above. As the thermistor sintered body, a perovskite oxide having a base composition of (Sr, Y) (Al, Mn, Fe) O ₃ can be used, but is not limited thereto.
As the thermistor sintered body, for example, one having a hexagonal column shape as a whole can be used. In this case, if the column axis direction of the hexagonal column is arranged in the metal member 30 so as to be perpendicular to the direction of the axis O, and one of the six surfaces forming the outer edge of the hexagon is the tip-facing surface, thermistor firing The leading end facing surface of the bonded body has a planar shape perpendicular to the axis O direction.
As long as the tip-facing surface has a planar shape, the overall shape of the temperature-sensitive portion is not particularly limited, and may be, for example, a rectangular column in addition to the plate shape and the hexagonal column described above. Further, the plane of the cylindrical temperature sensing part may be the tip-facing surface.
In the above embodiment, the insulating material made of SiO2 is filled between the sheath core wire 21 and the inner surface of the sheath outer tube 22, but the present invention is not limited to this, and an insulating material made of MgO or Al2O3 is filled. Good.

DESCRIPTION OF SYMBOLS 1, 1B Temperature sensor 10 Temperature sensing element 11 Temperature sensing part 11a The tip-facing surface of the temperature sensing part 11f The most advanced of the temperature sensing part 12 Element electrode wire 20 Sheath member 21 Sheath core wire 22 Sheath outer tube 30, 30B Metal member 32 Tip 33 Connecting portion 34 Straight portion 34e Both outer edges of straight portion J Joint portion O Axis C Virtual circle Ce Center of virtual circle C1 1st semicircle C2 2nd semicircle

Claims (3)

A temperature sensing element having a temperature sensing part whose electrical characteristics change with temperature and a pair of element electrode wires extending from the temperature sensing part to the rear end side;
A sheath member that is disposed on the rear end side of the temperature sensitive element and has a sheath core wire connected to the element electrode wire and a sheath outer tube that encloses the sheath core wire between insulating materials;
A metal member that has a cylindrical shape that is closed in the distal end side and extends in the axial direction, and that houses at least the temperature-sensitive element and a joint between the element electrode wire and the sheath core wire in its internal space;
In a temperature sensor comprising:
The metal member includes a straight portion that is parallel to the axial direction and accommodates the temperature sensing portion, a distal end portion that is located on the distal end side of the straight portion and has an arc-shaped cross section in the axial direction, and a rear portion from the distal end portion. A connection portion extending to the end side and connected to the straight portion,
The tip-facing surface of the temperature sensing part has a planar shape,
A virtual circle having the same diameter as the outer diameter of the straight portion in a cross section along the axial direction, and is in contact with both outer edges of the straight portion or their extension lines, and its center is the most advanced of the temperature-sensitive portion. And when drawing a virtual circle at the same position in the axial direction,
The radius of curvature of the tip portion is smaller than the radius of curvature of the virtual circle, and the outer edge of the tip portion is disposed inside the first semicircle on the tip side of the virtual circle from the center. Temperature sensor.   2. The temperature sensor according to claim 1, wherein an outer edge of the distal end portion is disposed on the distal end side from the center toward the distal end side with respect to a length that is ½ of a radius of the virtual circle.   3. The temperature sensor according to claim 1, wherein at least a part of the temperature sensing unit is arranged inside a second semicircle on the rear end side of the center of the virtual circle.

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