JP6787691B2 - Temperature sensor - Google Patents

Description

The present invention relates to a temperature sensor including a temperature sensitive element.

Conventionally, a temperature sensor including a temperature sensitive element having an element core wire through which a temperature detection signal flows is known (Patent Documents 1 and 2).
In this temperature sensor, the element core wire of the temperature sensitive element is welded to the sheath core wire of the sheath member at the welded portion. The temperature sensitive element and the welded portion are accommodated in the element accommodating space of the element accommodating portion. An element holding member is arranged between the temperature-sensitive element and the inner wall of the element accommodating portion in the element accommodating space.

Such a temperature sensor can be used, for example, in the exhaust system of an internal combustion engine (for example, an automobile engine).

JP-A-2006-234632

However, in the above temperature sensor, the bonding interface between the element core wire and the welded portion and the bonding interface between the sheath core wire and the welded portion may be deteriorated by oxidation.
That is, if the bonding interface deteriorates due to oxidation, the electrical connection between the element core wire and the sheath core wire via the welded portion becomes poor, and there is a risk that the temperature detection signal cannot be output to the outside.

Therefore, an object of the present invention is to provide a temperature sensor capable of suppressing deterioration due to oxidation of the joint interface between the element core wire and the welded portion and the joint interface between the sheath core wire and the welded portion.

The temperature sensor in one aspect of the present invention is a temperature sensor including a temperature sensitive element, a sheath member, a welded portion, an element accommodating portion, and an element holding member, and includes a covering member.
The temperature-sensitive element has an element core wire that serves as a signal path for a detection signal according to the detection temperature. The sheath member has a sheath core wire extending in the longitudinal direction. The welded portion is a member that welds the element core wire and the sheath core wire. The element accommodating portion has an element accommodating space for accommodating the temperature sensitive element and the welded portion. The element holding member is arranged between the temperature-sensitive element and the inner wall of the element accommodating portion in the element accommodating space.

The covering member covers the joint interface between the element core wire and the welded portion and the joint interface between the sheath core wire and the welded portion, respectively. The covering member is made of a material having a lower porosity than the element holding member.
By providing the covering member as described above, this temperature sensor makes it difficult for oxygen to reach the joint interface between the element core wire and the welded portion and the joint interface between the sheath core wire and the welded portion, and the joint interface is oxidized. It is possible to suppress deterioration due to.

Therefore, according to this temperature sensor, deterioration due to oxidation of the bonding interface between the element core wire and the welded portion and the bonding interface between the sheath core wire and the welded portion can be suppressed.
Next, in the above-mentioned temperature sensor, the linear thermal expansion coefficient of the covering member may be included in the numerical range sandwiched between the linear thermal expansion coefficient of the element core wire and the linear thermal expansion coefficient of the sheath core wire.

In such a covering member, stress generated between the covering member and the welded portion, between the covering member and the element core wire, and between the covering member and the sheath core wire due to the difference in the coefficient of linear thermal expansion due to the temperature change, respectively. Can be suppressed from becoming large. As a result, it is possible to prevent cracks from occurring at the joint interface between the element core wire and the welded portion and the joint interface between the sheath core wire and the welded portion due to the stress generated due to the temperature change.

Next, in the above-mentioned temperature sensor, the coefficient of linear thermal expansion of the covering member is such that the difference value from the coefficient of linear thermal expansion of the element core wire is smaller than the difference value from the coefficient of linear thermal expansion of the sheath core wire. May be good.

As a result, it is possible to suppress the occurrence of cracks at the joint interface between the sheath core wire and the welded portion due to the stress generated due to the temperature change.
Next, in the above-mentioned temperature sensor, the covering member may be formed so as to cover the entire welded portion.

By providing such a covering member, oxidation of the welded portion can be further suppressed, and the connection state between the element core wire and the sheath core wire can be assisted by the covering member. As a result, the electrical connection state between the element core wire and the sheath core wire can be maintained in a good state.

Next, in the above-mentioned temperature sensor, a plurality of element core wires and a plurality of sheath core wires may be provided, and the covering member may be individually provided for each of the plurality of element core wires and the plurality of sheath core wires.

With such a configuration, it is possible to suppress the occurrence of electrical short circuits between different element core wires and electrical short circuits between different sheath core wires due to a decrease in insulation of the covering member at a high temperature. As a result, it is possible to prevent the signal path of the detection signal from becoming an inappropriate state due to an electrical short circuit.

Next, in the above-mentioned temperature sensor, a plurality of element core wires and sheath core wires may be provided, respectively, and one covering member includes all the joint interfaces between the element core wire and the welded portion, and the sheath core wire and the welded portion. It may be formed so as to cover all of the bonding interfaces of the above.

With such a configuration, the covering member can be formed all at once at the time of manufacturing the temperature sensor, and the covering member forming step can be simplified.

According to the temperature sensor of the present invention, deterioration due to oxidation of the joint interface between the element core wire and the welded portion and the joint interface between the sheath core wire and the welded portion can be suppressed.

It is a partial cross-sectional explanatory view which shows the whole structure of the temperature sensor of 1st Embodiment. It is sectional drawing which shows the tip side part of the temperature sensor which includes a covering member enlarged. It is sectional drawing explanatory drawing which enlarges and shows the tip end side part of the temperature sensor which includes the 2nd covering member. It is sectional drawing explanatory drawing which enlarges and shows the tip side part of the temperature sensor which includes the 3rd covering member. It is sectional drawing which shows the tip side part of the temperature sensor including the electrode side covering member and the sheath side covering member enlarged. It is sectional drawing explanatory drawing which enlarges and shows the tip end side part of the temperature sensor which includes the 4th covering member.

Hereinafter, embodiments to which the present invention has been applied will be described with reference to the drawings.
It should be noted that the present invention is not limited to the following embodiments, and it goes without saying that various forms can be adopted as long as it belongs to the technical scope of the present invention.

[1. First Embodiment]
[1-1. overall structure]
The structure of the temperature sensor according to this embodiment will be described.

FIG. 1 is an explanatory view showing an internal structure by breaking a part of the temperature sensor 1.
The temperature sensor 1 is mounted on a flow pipe such as an exhaust pipe of an internal combustion engine, is arranged in the flow pipe through which the fluid to be measured flows, and is used for temperature detection of the fluid to be measured (exhaust gas). As the temperature of the exhaust gas suddenly changes from a low temperature range of about 0 ° C. to a high temperature range of about 1000 ° C., the temperature sensor 1 also undergoes a thermal cycle of rising-cooling within the above temperature range.

Here, the longitudinal direction of the temperature sensor 1 is the axial direction, which is the vertical direction of FIG. The front end side of the temperature sensor 1 is the lower side of FIG. 1, and the rear end side is the upper side of FIG.
The temperature sensor 1 includes a temperature sensing element 3, a sheath portion 7, a metal tube 9 (also referred to as an inner cylinder 9), a mounting member 11, and a nut portion 13.

The temperature sensitive element 3 is a temperature measuring element arranged in a flow tube through which a gas to be measured flows, and is arranged inside a metal tube 9. The details of the temperature sensitive element 3 will be described later.
The sheath portion 7 insulates and holds a pair of metal core wires 15 (hereinafter, also referred to as sheath core wires 15) inside the outer cylinder 17. The sheath portion 7 electrically insulates between a metal outer cylinder 17, a pair of sheath core wires 15 formed by using a conductive metal, and the outer cylinder 17 and two sheath core wires 15 to form a sheath. It includes an insulating powder (not shown) that holds the core wire 15.

The temperature sensitive element 3 includes a pair of electrode wires 5. The pair of electrode wires 5 are formed by using a wire rod made of an expensive material (for example, a Pt wire, a Pt-Rh alloy wire, a wire rod containing Sr in Pt or a Pt alloy, etc.), but the temperature is sensitive. The sheath core wire 15 for transmitting the detection signal generated by the element 3 is formed of an inexpensive material (for example, SUS or the like) to reduce the cost.

The electrode wire 5 and the sheath core wire 15 are joined via a welded portion 61. The welded portion 61 is covered with a covering member 71. The temperature sensor 1 includes a pair of welded portions 61 and a pair of covering members 71. Details of the covering member 71 will be described later.

The metal tube 9 is a bottomed tubular member formed by closing the tip end side of a tubular member extending in the axial direction, and is made of a corrosion-resistant metal (for example, a stainless alloy such as SUS310S which is also a heat-resistant metal). It was formed using.

The metal tube 9 is formed in a tubular shape in which the tip (bottom) of the tube is closed and extends in the axial direction by deep drawing of a steel plate, and the rear end of the tubular tube is open. Further, the metal tube 9 is set in the axial direction so that the rear end side of the tube abuts on the inner surface of the mounting member 11.

The metal tube 9 includes a small diameter portion 25 formed at the tip portion, a large diameter portion 27 formed on the rear end side of the small diameter portion 25 and having a diameter larger than that of the small diameter portion 25, and a small diameter portion 25 and a large diameter portion 27. It has a stepped portion 29 formed between the two. The diameter of the step portion 29 gradually increases from the small diameter portion 25 to the large diameter portion 27.

A temperature sensitive element 3 and a cement 23 (element holding member 23) are arranged inside the metal tube 9. The cement 23 is filled around the temperature sensitive element 3 and holds the temperature sensitive element 3 to prevent its rocking. The cement 23 is made of a material having high thermal conductivity, high heat resistance, and high insulation.

As the cement 23, for example, an oxide mainly composed of oxides such as Al ₂ O ₃ and MgO, nitrides such as Al N, TiN, Si ₃ N ₄ and BN, and carbides such as SiC, TiC and ZrC are used. May be good. The cement 23 is mainly composed of oxides such as Al ₂ O ₃ and Mg O, nitrides such as Al N, TiN, Si ₃ N ₄ and BN, and carbides such as SiC, TiC and Zr C, and Al ₂ O. Cement mixed with an inorganic binder such as ₃ or SiO ₂ or MgO may be used.

The mounting member 11 is a member that supports the metal tube 9 by surrounding the outer peripheral surface on the rear end side of the metal tube 9 with at least the tip end side of the metal tube 9 exposed to the outside. The mounting member 11 is provided with a protruding portion 31 protruding outward in the radial direction, and a rear end side sheath portion 33 located on the rear end side of the protruding portion 31 and extending in the axial direction.

The protruding portion 31 is an annular member provided with a mounting seat 35 on the tip end side. The mounting seat 35 is a taper-shaped member whose diameter decreases toward the tip side, and corresponds to the shape of the sensor mounting position of the exhaust pipe (not shown). The sensor mounting position of the exhaust pipe is formed to include a taper portion whose diameter increases toward the rear end side of the temperature sensor 1 as a portion that abuts on the mounting seat 35.

When the mounting member 11 is arranged at the sensor mounting position of the exhaust pipe, the mounting seat 35 comes into close contact with the tapered portion of the sensor mounting position and suppresses the leakage of exhaust gas from the exhaust pipe to the outside.

The rear end side sheath portion 33 is formed in a tubular shape. The rear end side sheath portion 33 has a large outer diameter on the front end side and a large outer diameter on the rear end side. The rear end side sheath portion 33 has a constant inner diameter dimension on both the front end side and the rear end side.

After the mounting member 11 is press-fitted into the rear end portion of the metal tube 9, the rear end side sheath portion 33 and the metal tube 9 are joined by laser welding, so that the mounting member 11 and the metal tube 9 are fixed to each other. ..

The nut portion 13 is a tubular member having a hexagon nut portion 39 and a screw portion 41. The nut portion 13 is rotatably arranged on the outer circumference of the mounting member 11 in a state where the tip surface of the screw portion 41 is in contact with the rear end surface of the protruding portion 31 of the mounting member 11. The temperature sensor 1 is attached to the sensor mounting position of the exhaust pipe by screwing the screw portion 41 of the nut portion 13 with the screw hole provided in the exhaust pipe.

The tip of the sheath core wire 15 is electrically connected to the temperature sensitive element 3. The rear end of the sheath core wire 15 is connected to the crimping terminal 43 by resistance welding. That is, the rear end of the sheath core wire 15 is connected to the lead wire 45 for connecting an external circuit (for example, an electronic control device (ECU) of a vehicle) via a crimping terminal 43.

The rear end portions of the pair of sheath core wires 15 are insulated from each other by an insulating tube 47, and the pair of crimping terminals 43 are also insulated from each other by an insulating tube 47. The lead wire 45 is obtained by coating the lead wire with an insulating coating material, and the lead wire 45 is arranged so as to penetrate the inside of the auxiliary ring 49 made of heat-resistant rubber.

[1-2. Temperature sensitive element]
Next, the configuration of the temperature sensitive element 3 will be described.
As shown in FIG. 2, the temperature sensitive element 3 includes a temperature sensitive portion 4 whose electrical characteristics change according to temperature, and a pair of electrode wires 5 connected to the temperature sensitive portion 4.

The temperature-sensitive portion 4 has a ceramic substrate 54, a metal resistor 55, a bonding layer 56, a ceramic coating layer 57, and a pair of electrode pads 58.
The ceramic substrate 54 is made of alumina having a purity of 99.5 to 99.9%, and is a fired sheet obtained by firing a ceramic green sheet in advance.

The metal resistor 55 is a resistance temperature detector that is mainly composed of platinum (Pt) and whose electrical characteristics (electrical resistance value) change according to the temperature. The metal resistor 55 is formed on the surface of the ceramic substrate 54 in a predetermined pattern shape meandering a plurality of times.

The ceramic coating layer 57 is made of alumina having a purity of 99.5 to 99.9%, and is a fired sheet obtained by firing a ceramic green sheet in advance. The ceramic coating layer 57 covers the tip end side of the metal resistor 55 on the surface of the metal resistor 55 opposite to the surface in contact with the ceramic substrate 54.

The bonding layer 56 is made of alumina having a purity of 99.5 to 99.9%. The bonding layer 56 is a paste containing alumina powder before bonding, and the fired ceramic substrate 54 and the ceramic coating layer 57 are bonded to each other with the above paste and then heat-treated to finally form the bonding layer 56. Become.

On the rear end side (right side of FIG. 2) of the metal resistor 55, a pair of electrode wires 5 are electrically connected via a pair of electrode pads 58 formed wider than a conductor pattern coated by the ceramic coating layer 57. Connected to. The pair of electrode pads 58 and the pair of electrode wires 5 are joined at the welding point 60 by welding such as resistance welding and laser welding.

The joint portion between the pair of electrode pads 58 and the pair of electrode wires 5 is covered with a covering member 59. The covering member 59 is made of a glass material mainly composed of aluminosilicate glass. This glass material may contain a ceramic material (alumina or the like) as a subcomponent.

The pair of electrode wires 5 are arranged so as to extend from the rear end side of the metal resistor 55 toward the sheath portion 7. The rear ends of the pair of electrode wires 5 are arranged so as to abut against the tips of the pair of sheath core wires 15. The rear ends of the pair of electrode wires 5 and the tips of the pair of sheath core wires 15 are joined via a welded portion 61 by welding such as resistance welding and laser welding. The cross-sectional area of the electrode wire 5 is set to be smaller than the cross-sectional area of the sheath core wire 15. The cross-sectional area of the electrode wire 5 and the sheath core wire 15 is the area of the cross section orthogonal to the axial direction.

Then, in the present embodiment, the electrode wire 5 is configured by using a platinum wire.
On the other hand, the sheath core wire 15 connected to the electrode wire 5 is made of a material different from that of the electrode wire 5. Specifically, the sheath core wire 15 is made of an alloy containing any one of Fe, Ni, Co and Cr as a main component. In this embodiment, SUS310S was used as the Fe alloy. The sheath core wire 15 is not limited to the Fe alloy, and a Ni alloy may be used. As the Ni alloy, NCF600, NCF601, or the like can be used.

[1-3. Covering member]
Next, the covering member 71 will be described.
As shown in FIG. 2, the covering member 71 is formed so as to cover the joining interface between the electrode wire 5 and the welded portion 61 and the joining interface between the sheath core wire 15 and the welded portion 61, respectively. In particular, in the present embodiment, the covering member 71 is formed so as to cover the entire welded portion 61.

Further, a pair of electrode wires 5, a sheath core wire 15, and a welded portion 61 are provided, and a pair of covering members 71 are also provided. That is, the pair of covering members 71 are provided so as to individually cover the pair of electrode wires 5, the sheath core wire 15, and the welded portion 61.

The pair of covering members 71 are made of a material containing each component (element) shown in [Table 1]. The content ratio of each component is as shown in [Table 1], and the unit is atm%.

被覆部材７１が備えられることで、電極線５と溶接部６１との接合界面、およびシース芯線１５と溶接部６１との接合界面は、それぞれ、セメント２３と直接接触することがない。

By providing the covering member 71, the joining interface between the electrode wire 5 and the welded portion 61 and the joining interface between the sheath core wire 15 and the welded portion 61 do not come into direct contact with the cement 23, respectively.

Further, the covering member 71 does not have open pores (holes leading to the outside), and the cement 23 has open pores. That is, the covering member 71 has a smaller air permeability than the cement 23 (element holding member). In the present embodiment, the covering member 71 does not have open pores, but the present invention may have a slight open pore in the covering member 71 as long as the air permeability is smaller than that of the cement 23. Is acceptable.

Next, the coefficient of linear thermal expansion of the covering member 71 is 11.2 × 10 ^-6 / ° C, and the coefficient of linear thermal expansion of the electrode wire 5 (Pt wire) is 9.5 × 10 ^-6 / ° C. , The coefficient of linear thermal expansion of the sheath core wire 15 (manufactured by SUS310S) is 16.9 × 10 ^-6 / ° C. That is, the coefficient of linear thermal expansion of the covering member 71 is included in the numerical range sandwiched between the coefficient of linear thermal expansion of the electrode wire 5 and the coefficient of linear thermal expansion of the sheath core wire 15. In this specification, the numerical value of the coefficient of linear thermal expansion is the coefficient of linear expansion at 20 to 300 ° C.

Further, in the present embodiment, the difference value of the linear thermal expansion coefficient of the covering member 71 from the linear thermal expansion coefficient of the electrode wire 5 is smaller than the difference value from the linear thermal expansion coefficient of the sheath core wire 15.
[1-4. effect]
As described above, the temperature sensor 1 of the present embodiment includes the covering member 71, and the covering member 71 has a smaller air permeability than the cement 23. By providing the coating member 71, the temperature sensor 1 makes it difficult for oxygen to reach the bonding interface between the electrode wire 5 and the welded portion 61 and the bonding interface between the sheath core wire 15 and the welded portion 61.

Therefore, according to the temperature sensor 1, deterioration due to oxidation of the bonding interface between the electrode wire 5 and the welded portion 61 and the bonding interface between the sheath core wire 15 and the welded portion 61 can be suppressed.
Next, the coefficient of linear thermal expansion of the covering member 71 is included in the numerical range sandwiched between the coefficient of linear thermal expansion of the electrode wire 5 and the coefficient of linear thermal expansion of the sheath core wire 15.

In such a covering member 71, due to the difference in the coefficient of linear thermal expansion due to the temperature change, the covering member 71 and the welded portion 61, the covering member 71 and the electrode wire 5, and the covering member 71 and the sheath core wire 15 It is possible to suppress an increase in the stress generated between the two. As a result, it is possible to prevent cracks from occurring at the joint interface between the electrode wire 5 and the welded portion 61 and the joint interface between the sheath core wire 15 and the welded portion 61 due to the stress generated due to the temperature change.

Next, in the linear thermal expansion coefficient of the covering member 71, the difference value from the linear thermal expansion coefficient of the electrode wire 5 is smaller than the difference value from the linear thermal expansion coefficient of the sheath core wire 15.
In such a covering member 71, the stress generated between the covering member 71 and the sheath core wire 15 due to the temperature change is smaller (larger) than the stress generated between the covering member 71 and the electrode wire 5 due to the temperature change. can do. As a result, it is possible to further suppress the occurrence of cracks at the joint interface between the sheath core wire 15 and the welded portion 61 due to the stress generated due to the temperature change.

Next, one covering member 71 is formed so as to cover the entire one welded portion 61.
By providing such a covering member 71, oxidation of the welded portion 61 can be suppressed, and the connection state between the electrode wire 5 and the sheath core wire 15 can be assisted by the covering member 71. As a result, the temperature sensor 1 can maintain a good electrical connection state between the electrode wire 5 and the sheath core wire 15 by providing the covering member 71.

Next, in the temperature sensor 1, a plurality of electrode wires 5 and a plurality of sheath core wires 15 are provided, and a covering member 71 is individually provided for each of the plurality of electrode wires 5 and the plurality of sheath core wires 15. That is, the pair of covering members 71 are provided so as to individually cover the pair of electrode wires 5, the sheath core wire 15, and the welded portion 61.

With such a configuration, it is possible to suppress the occurrence of an electrical short circuit between different electrode wires 5 and an electrical short circuit between different sheath core wires 15 due to a decrease in insulation of the covering member at a high temperature. As a result, the temperature sensor 1 can prevent the signal path of the detection signal from becoming an inappropriate state due to an electrical short circuit.

[1-5. Correspondence of wording]
Here, the correspondence between words will be described.
The temperature sensor 1 corresponds to an example of a temperature sensor, the temperature sensitive element 3 corresponds to an example of a temperature sensitive element, the electrode wire 5 corresponds to an example of an element core wire, and the sheath portion 7 corresponds to an example of a sheath member. The metal core wire 15 (sheath core wire 15) corresponds to an example of the sheath core wire, the welded portion 61 corresponds to an example of the welded portion, the metal tube 9 corresponds to an example of the element accommodating portion, and the cement 23 corresponds to an example of the element holding member. The covering member 71 corresponds to an example of the covering member.

[2. Second Embodiment]
[2-1. overall structure]
Next, the second embodiment will be described. The same components as those in the first embodiment will be omitted, and different parts will be mainly described.

As shown in FIG. 3, the temperature sensor of the second embodiment is an example in which the configuration of the welded portion between the electrode wire 5 and the sheath core wire 15 in the temperature sensor 1 of the first embodiment is changed. The description of the same configuration and operation / effect as in the first embodiment will be omitted.

In the second embodiment, the rear end portion of the pair of electrode wires 5 is overlapped with the tip end portion of the pair of sheath core wires 15 drawn from the tip end of the sheath portion 7 (see FIG. 1). The pair of electrode wires 5 and the pair of sheath core wires 15 are joined at the second welded portion 62 by welding such as resistance welding and laser welding. The cross-sectional area of the electrode wire 5 is set to be smaller than the cross-sectional area of the sheath core wire 15. Further, in the second embodiment, NCF600, which is a Ni alloy, was used as the pair of sheath core wires 15.

In the temperature sensor 1 of the second embodiment, a part of the overlapping portion of the electrode wire 5 and the sheath core wire 15 and the second welded portion 62 are covered with the second covering member 73. That is, the temperature sensor 1 of the second embodiment includes a pair of second welded portions 62 and a pair of second covering members 73.

As shown in FIG. 3, the second covering member 73 is formed so as to cover the joining interface between the electrode wire 5 and the second welded portion 62 and the joining interface between the sheath core wire 15 and the second welded portion 62, respectively. There is. In particular, in the second embodiment, the second covering member 73 is formed so as to cover the entire second welded portion 62.

Further, a pair of the electrode wire 5, the sheath core wire 15, and the second welded portion 62 are provided, and a pair of the second covering member 73 is also provided. That is, the pair of second covering members 73 are provided so as to individually cover the pair of electrode wires 5, the sheath core wire 15, and the second welded portion 62, respectively.

The pair of second covering members 73 are made of a material containing each component (element) shown in the above [Table 1].
By providing the second covering member 73, the bonding interface between the electrode wire 5 and the second welded portion 62 and the bonding interface between the sheath core wire 15 and the second welded portion 62 are in direct contact with the cement 23, respectively. There is no.

Further, the second covering member 73 has a smaller air permeability than the cement 23. That is, the cement 23 has many open pores, but the cement 23 has substantially no open pores.

Next, the coefficient of linear thermal expansion of the second covering member 73 is 11.2 × 10 ^-6 / ° C, and the coefficient of linear thermal expansion of the electrode wire 5 (Pt wire) is 9.5 × 10 ^-6 / ° C. The coefficient of linear thermal expansion of the sheath core wire 15 (manufactured by NCF600) is 14.2 × 10 ^-6 / ° C. That is, the coefficient of linear thermal expansion of the second covering member 73 is included in the numerical range sandwiched between the coefficient of linear thermal expansion of the electrode wire 5 and the coefficient of linear thermal expansion of the sheath core wire 15.

Further, in the second embodiment, the difference value of the linear thermal expansion coefficient of the second covering member 73 from the linear thermal expansion coefficient of the electrode wire 5 is smaller than the difference value from the linear thermal expansion coefficient of the sheath core wire 15.
[2-2. effect]
As described above, the temperature sensor 1 of the second embodiment includes the second covering member 73, and similarly to the first embodiment, the joint interface between the electrode wire 5 and the second welded portion 62 and the sheath. Deterioration due to oxidation of the bonding interface between the core wire 15 and the second welded portion 62 can be suppressed.

[2-3. Correspondence of wording]
Here, the correspondence between words will be described.
The second welded portion 62 corresponds to an example of the welded portion, and the second covering member 73 corresponds to an example of the covering member.

[3. Other embodiments]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and can be implemented in various embodiments without departing from the gist of the present invention.

For example, in the above-described embodiment, the temperature sensitive portion 4 is configured by using the metal resistor 55 whose electrical characteristics change according to the temperature. For example, thermistor sintering whose electrical characteristics change according to the temperature. It may be constructed using the body. As the thermistor sintered body, for example, a perovskite-type oxide having a base composition of (Sr, Y) (Al, Mn, Fe) O ₃ or the like can be used.

FIG. 4 shows a temperature sensor 1 including a temperature sensing element 3 having a temperature sensing portion 4 composed of a thermistor sintered body and a pair of electrode wires 5 connected to the temperature sensing portion 4. The rear ends of the pair of electrode wires 5 are overlapped with the tip ends of the pair of sheath core wires 15 drawn from the tips of the sheath portions 7 (see FIG. 1). The pair of electrode wires 5 and the pair of sheath core wires 15 are joined at the third welded portion 63 by welding such as resistance welding and laser welding. The cross-sectional area of the electrode wire 5 is set to be smaller than the cross-sectional area of the sheath core wire 15.

The temperature sensor 1 includes a third covering member 75. Similar to the second embodiment, the temperature sensor 1 is configured such that a part of the overlapping portion of the electrode wire 5 and the sheath core wire 15 and the third welded portion 63 are covered with the third covering member 75. ing. That is, the temperature sensor 1 includes a pair of third welded portions 63 and a pair of third covering members 75.

Therefore, the temperature sensor 1 shown in FIG. 4 includes a third covering member 75, and similarly to the second embodiment, the bonding interface between the electrode wire 5 and the third welded portion 63, and the sheath core wire 15 and the third Deterioration due to oxidation of the joint interface with the welded portion 63 can be suppressed.

Next, in the above-described embodiment, the configuration in which the bonding interface between the electrode wire 5 and the welded portion 61 and the bonding interface between the sheath core wire 15 and the welded portion 61 are each covered with one covering member has been described. Is not limited to such a configuration. For example, as shown in FIG. 5, the covering member 71 in the first embodiment may be replaced with two covering members (electrode side covering member 77, sheath side covering member 79). The temperature sensor 1 shown in FIG. 5 includes an electrode-side coating member 77 that covers the bonding interface between the electrode wire 5 and the welded portion 61, and a sheath-side coating member 79 that covers the bonding interface between the sheath core wire 15 and the welded portion 61. Be prepared.

Similar to the first embodiment, the temperature sensor 1 can suppress deterioration due to oxidation of the bonding interface between the electrode wire 5 and the welded portion 61 and the bonding interface between the sheath core wire 15 and the welded portion 61.
Next, in the above-described first embodiment, a configuration in which a pair of covering members 71 is provided in a temperature sensor in which a pair of electrode wires 5, a sheath core wire 15, and a welded portion 61 are provided is described. It is not limited to such a configuration. For example, as in the fourth covering member 81 shown in FIG. 6, one covering member in a form in which the two covering members 71 of the first embodiment are connected may be provided. In other words, one fourth covering member 81 is formed so as to cover all of the joining interface between the electrode wire 5 and the welded portion 61 and all of the joining interface between the sheath core wire 15 and the welded portion 61. There may be.

If the temperature sensor 1 includes such a fourth covering member 81, the formation of the fourth covering member 81 can be executed at one time at the time of manufacturing the temperature sensor 1, and the forming step of the fourth covering member 81 can be performed. Can be simplified.

Next, the coefficient of linear thermal expansion of each of the covering member, the element core wire (electrode wire 5), and the sheath core wire is not limited to each numerical value in the above embodiment, and as long as it belongs to the technical scope of the present invention. Any numerical value can be taken.

Further, the material of each member (for example, temperature sensitive element, sheath portion, metal tube, mounting member, nut portion, etc.) constituting the temperature sensor is not limited to the material described in the above embodiment, and is not limited to the material described in the above embodiment. Any material can be used as long as it is within the technical scope.

Further, the configuration of the temperature sensor accommodating the temperature sensing element is not limited to the above configuration, and various known configurations can be adopted.

1 ... Temperature sensor, 3 ... Temperature sensitive element, 4 ... Temperature sensitive part, 5 ... Electrode wire, 7 ... Sheath part, 9 ... Metal tube (inner cylinder), 11 ... Mounting member, 15 ... Metal core wire (sheath core wire), 17 ... outer cylinder, 23 ... cement (element holding member), 61 ... welded part, 62 ... second welded part, 63 ... third welded part, 71 ... covering member, 73 ... second covering member, 75 ... third coating Member, 77 ... Electrode side covering member, 79 ... Sheath side covering member.

Claims (5)

A temperature-sensitive element having an element core wire that serves as a signal path for a detection signal according to the detection temperature,
A sheath member having a sheath core wire extending in the longitudinal direction,
A welded portion for welding the element core wire and the sheath core wire,
An element accommodating portion having an element accommodating space for accommodating at least the temperature sensitive element and the welded portion, and an element accommodating portion.
An element holding member arranged between the temperature-sensitive element and the inner wall of the element accommodating portion in the element accommodating space,
It is a temperature sensor equipped with
A covering member that covers the bonding interface between the element core wire and the welded portion and the bonding interface between the sheath core wire and the welded portion is provided.
The covering member has a smaller air permeability than the element holding member ,
The coefficient of linear thermal expansion of the covering member is included in a numerical range sandwiched between the coefficient of linear thermal expansion of the element core wire and the coefficient of linear thermal expansion of the sheath core wire.
Temperature sensor. Regarding the linear thermal expansion coefficient of the covering member, the difference value from the linear thermal expansion coefficient of the element core wire is smaller than the difference value from the linear thermal expansion coefficient of the sheath core wire.
The temperature sensor according to claim 1. The covering member is formed so as to cover the entire welded portion.
The temperature sensor according to claim 1 or 2. A plurality of the element core wire and the sheath core wire are provided, respectively.
The covering member is individually provided for each of the plurality of element core wires and the plurality of sheath core wires.
The temperature sensor according to any one of claims 1 to 3. A plurality of the element core wire and the sheath core wire are provided, respectively.
One covering member is formed so as to cover all of the joining interface between the element core wire and the welded portion and all of the joining interface between the sheath core wire and the welded portion.
The temperature sensor according to any one of claims 1 to 3.

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