JP2016012697A - Thermistor element and temperature sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermistor element which can suppress reductive reaction of a thermistor main body and deterioration of temperature detection accuracy as for the thermistor element, and a temperature sensor.SOLUTION: In a thermosensor 21 of a temperature sensor 1, oxygen is supplied from a joining brazing material 24 against an intruding gas that intrudes through a surface boundary between a leader line 25 and a coating part 71 into an element body part 22 so as to be capable of suppressing reductive reaction of the element body part 22 by the intruding gas. Even when a clearance gap exists in the surface boundary between the leader line 25 and the coating part 71, the joining brazing material 24 can suppress the element body part 22 from being exposed to strong reduction atmosphere so that reduction reaction of the element body part 22 can be suppressed and change of electrical characteristic as for the thermosensor can be suppressed. Therefore, the thermosensor 21 can suppress reductive reaction of the element body part 22 and deterioration of temperature detection accuracy as for the thermosensor 21.

Description

  The present invention relates to a thermistor element whose electrical characteristics change according to a temperature change, and a temperature sensor using the thermistor element.

  The thermistor element whose electrical characteristics change in response to temperature changes includes a thermistor body having a conductive oxide sintered body, a covering portion that covers the periphery of the thermistor body, and a covering portion that is connected to the thermistor body. What is known is provided with a set of leader lines that penetrate and extend toward the rear end side.

  Thus, by providing a coating | coated part, it can suppress that a reduction reaction arises in a thermistor main body, and can improve the reduction resistance of a thermistor element.

Japanese Patent No. 3806434 Japanese Patent No. 3650854

  However, in the above thermistor element, reducing gas may enter the thermistor body through the interface between the covering portion and the lead wire, and the temperature detection accuracy as the thermistor element may be reduced.

  That is, when the reducing gas reaches the thermistor body and a reduction reaction occurs in the thermistor body, the temperature detection characteristic of the thermistor element changes, and the temperature detection accuracy may be lowered.

  The present invention provides a thermistor element that can suppress a reduction reaction from occurring in the thermistor body, and can suppress a decrease in temperature detection accuracy as the thermistor element, and a temperature sensor including such a thermistor element. The purpose.

A thermistor element in one aspect of the present invention includes a thermistor body, a covering portion, and a set of lead wires.
The thermistor body has a conductive oxide sintered body. The covering portion covers the periphery of the thermistor body. The set of lead wires are connected to the thermistor body by a joining brazing material, and extend through the covering portion toward the rear end side.

The bonding brazing material contains a conductive metal and an oxygen supply oxide.
In the thermistor element having such a configuration, oxygen is supplied from the bonding brazing material to the intruding gas that enters the thermistor body through the interface between the lead wire and the covering portion. Can be suppressed.

  In other words, even when there is a gap at the interface between the lead wire and the covering portion, by providing the bonding brazing material containing the oxygen supply oxide, it is possible to suppress the thermistor body from being exposed to a strong reducing atmosphere, The reduction reaction of the thermistor body can be suppressed, and the change in electrical characteristics as the thermistor element can be suppressed.

  Here, the covering portion is formed so as to cover the periphery of the thermistor main body and the periphery of the bonding brazing material, so that oxygen contained in the bonding brazing material can be prevented from leaking to the outside, and the oxygen in the bonding brazing material Oxygen can be supplied for a longer period of time with respect to the intrusion gas in which the supply oxide enters the thermistor body through the interface between the lead wire and the covering portion.

Therefore, according to this thermistor element, it is possible to suppress a reduction reaction from occurring in the thermistor body, and it is possible to suppress a decrease in temperature detection accuracy as the thermistor element.
In the above thermistor element, the conductive metal contained in the bonding brazing material may mainly contain platinum.

In the above thermistor element, the bonding brazing material may be located on the rear end side of the center of the thermistor body.
The bonding brazing material is located near the interface between the lead wire and the covering portion, “on the rear end side from the center of the thermistor body”, so that the bonding brazing material can be more reliably protected against the intruding gas entering the thermistor body. Since oxygen is supplied, it is possible to suppress the reduction reaction of the thermistor body due to the intruding gas.

By adopting such a configuration, the conductivity of the bonding brazing material becomes good, and the electrical connection state between the thermistor body and the lead wire becomes good.
“Mainly containing platinum” means that platinum is the most among the conductive metals contained in the bonding brazing material.

  Next, in the above thermistor element, the oxygen supply oxide contained in the bonding brazing material may include at least one oxide of Cr, Mn, Fe, Co, Ni, Ce, and Pr. .

  Oxygen supply oxide containing such an oxide can supply oxygen to the intruding gas that enters the thermistor body through the interface between the lead wire and the covering portion, and the thermistor body is exposed to a strong reducing atmosphere. Can be suppressed.

Therefore, according to this thermistor element, it is possible to suppress a reduction reaction from occurring in the thermistor body, and it is possible to suppress a decrease in temperature detection accuracy as the thermistor element.
Next, in the above thermistor element, the content of the oxygen supply oxide in the bonding brazing material may be not less than 0.5 [vol%] and not more than 50.0 [vol%].

  That is, when the content of the oxygen supply oxide in the bonding brazing material is 0.5 [vol%] or more, oxygen can be supplied from the bonding brazing material to the intrusion gas, and the reduction reaction of the thermistor body by the intrusion gas can be performed. Can be suppressed.

  In addition, since the content of the oxygen supply oxide in the bonding brazing material is 50.0 [vol%] or less, the conductivity of the bonding brazing material can be secured, and the electrical connection state between the thermistor body and the lead wire can be ensured. It can be secured.

Next, in the above thermistor element, the covering portion may be formed of glass or a mixture of glass and metal oxide particles.
By providing such a covering portion, it is possible to suppress consumption of oxygen contained in the oxygen supply oxide of the bonding brazing material due to an oxidation reaction in a surrounding metal member or the like.

That is, it becomes possible to more reliably supply oxygen contained in the oxygen supply oxide of the bonding brazing material to the intruding gas that enters the thermistor body through the interface between the lead wire and the covering portion.
Therefore, in such a thermistor element, the reduction reaction can be further suppressed from occurring in the thermistor body, and the reduction resistance can be improved.

  In the above-described thermistor element, the second covering portion that surrounds the extension portion of the lead wire in the rear end region of the outer surface of the covering portion with respect to the center of the thermistor body, and mainly includes the oxygen supply. You may prepare.

  By providing such a second covering portion, oxygen is supplied from the second covering portion in addition to the bonding brazing material to the intruding gas that enters the element main body portion through the interface between the lead wire and the covering portion. Therefore, the reduction reaction of the element main body due to the intruding gas can be further suppressed.

A temperature sensor according to another aspect of the present invention includes any one of the thermistor elements described above.
Such a temperature sensor can suppress a reduction reaction from occurring in the thermistor body, and can suppress a decrease in temperature detection accuracy as a thermistor element, so that a decrease in temperature detection accuracy as a temperature sensor can be suppressed.

According to the thermistor element of this invention, it can suppress that a reductive reaction arises in a thermistor main body, and can suppress that the temperature detection precision as a thermistor element falls.
According to the temperature sensor of the present invention, since a decrease in temperature detection accuracy as a thermistor element can be suppressed, it is possible to suppress a decrease in temperature detection accuracy as a temperature sensor.

It is a fragmentary sectional view which shows the structure of a temperature sensor. It is explanatory drawing which fractures | ruptures and expands and shows the front end side of a temperature sensor. It is a perspective view of a temperature sensing element in the state where a covering part was omitted. It is a test result of the evaluation test in Examples 1-9. It is a test result of the evaluation test in Examples 10-15 and Comparative Examples 1-2. It is sectional drawing which shows the internal structure of a 2nd temperature sensing element provided with a 2nd coating | coated part. It is sectional drawing which shows the internal structure of a 3rd temperature sensing element provided with a 2nd coating | coated part and a 3rd stomach part. It is sectional drawing which shows the internal structure of the 4th temperature sensing element of the structure by which a 2nd coating | coated part is distributedly arranged.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
In addition, this invention is not limited to the following embodiment at all, and it cannot be overemphasized that various forms may be taken as long as it belongs to the technical scope of this invention.

[1. First Embodiment]
[1-1. overall structure]
As a first embodiment, a temperature sensor 1 used for detecting an exhaust gas temperature of an internal combustion engine such as an automobile will be described.

FIG. 1 is a partially broken cross-sectional view showing the structure of the temperature sensor 1. FIG. 2 is an explanatory diagram showing the tip side of the temperature sensor 1 in a broken and enlarged manner.
The temperature sensor 1 includes a sheath member 7 in which a pair of metal sheath core wires 3 (electrode wires 3) are insulated and held inside the cylindrical member 5, and a cylindrical metal tube 9 (in the axial direction with the distal end closed) ( A housing 9), a mounting member 11 that supports the metal tube 9, a nut member 17 having a hexagonal nut portion 13 and a screw portion 15, an outer cylinder 19 that fits in the rear end side of the mounting member 11, and a thermistor element. And the formed temperature sensing element 21.

  The axial direction is the longitudinal direction of the temperature sensor 1 and corresponds to the vertical direction in the figure in FIG. Moreover, the front end side in the temperature sensor 1 is a lower side in FIG. 1, and the rear end side in the temperature sensor 1 is an upper side in FIG. In FIG. 2, the rear end side is the right side in the figure, and the front end side is the left side in the figure.

  The temperature sensor 1 is attached to a flow pipe such as an exhaust pipe of an internal combustion engine, for example, and the temperature of the measurement target gas is detected by arranging the tip portion of the temperature sensor 1 in the flow pipe through which the measurement target gas (exhaust gas) flows. To do.

  The sheath core wire 3 is connected to the lead wire 25 (see FIG. 2) of the temperature sensing element 21 by laser welding, for example, and the rear end is connected to the crimp terminal 27, for example, by resistance welding. Thus, the sheath core wire 3 is connected at its rear end side to an external lead wire 29 for connecting an external circuit (for example, an electronic control unit (ECU) of a vehicle) via the crimping terminal 27.

  The pair of sheath core wires 3 and the pair of crimping terminals 27 are insulated from each other by an insulating tube 31, and the external lead wire 29 covers the inside of a grommet 33 made of heat-resistant rubber with a conductive wire covered with an insulating covering material. Arranged in a penetrating state.

  The sheath member 7 electrically insulates between the cylindrical member 5 made of metal, the pair of sheath cores 3 formed of a conductive metal, and the cylindrical member 5 and the two sheath cores 3. And an insulating powder 34 (see FIG. 2) such as silica for holding the core wire 3.

  The attachment member 11 includes a protruding portion 35 that protrudes radially outward, and a rear end-side sheath portion 37 that is positioned on the rear end side of the protruding portion 35 and extends in the axial direction. The attachment member 11 surrounds the outer peripheral surface on the rear end side of the metal tube 9 and supports the metal tube 9.

  The metal tube 9 is formed of a corrosion-resistant metal (for example, a stainless alloy such as SUS310S which is also a heat-resistant metal), and has a cylindrical shape extending in the axial direction in which the tube tip side is closed by deep drawing of a steel plate. It is comprised in the form which the shape tube rear end side opened.

  As shown in an enlarged view in FIG. 2, the metal tube 9 includes a small-diameter portion 41 on the front end side whose diameter is set small, and a large-diameter portion 43 on the rear end side whose diameter is set larger than the small-diameter portion 41. And a step 45 between the small-diameter portion 41 and the large-diameter portion 43.

The temperature sensor 1 includes a temperature-sensitive element 21 whose electrical characteristics change depending on the temperature inside the distal end side of the metal tube 9.
In addition to the temperature sensing element 21, cement 39 is housed inside the distal end side of the metal tube 9. The cement 39 is filled around the temperature sensing element 21, so It prevents rocking. The cement 39 is formed of an insulating material containing amorphous silica and amorphous aggregate.

  And the temperature sensor 1 of such a structure is measured, for example, by screwing and fixing the screw portion 15 to a sensor mounting portion provided in the exhaust pipe and arranging its tip inside the exhaust pipe. Detect the temperature of the target gas.

[1-2. Temperature sensitive element]
As shown in FIG. 2, the temperature sensitive element 21 includes an element main body part 22, two electrode parts 23, two lead wires 25, and a covering part 71.

The element body 22 is mainly formed of a conductive oxide sintered body whose electrical characteristics (electrical resistance value) change with temperature.
The two electrode portions 23 are formed on the upper surface and the lower surface of the element main body portion 22.

  The two lead wires 25 are conductive members formed of a platinum-rhodium alloy. The two lead wires 25 are respectively electrically connected to the two electrode portions 23 by the bonding brazing material 24 and are arranged to extend toward the rear end side.

The covering portion 71 is formed so as to cover the periphery of the element body portion 22 and is formed of a mixture of crystallized glass and metal oxide particles. The composition of the crystallized glass in the present embodiment is SiO ₂ —RO—Al ₂ O ₃ —ZrO ₂ (R is an alkaline earth metal), and the metal oxide particles are alumina (Al ₂ O ₃ ). .

The bonding brazing material 24 includes a conductive metal and an oxygen supply oxide. In this embodiment, the conductive metal contained in the bonding brazing material 24 is platinum (Pt), and the oxygen supply oxide contained in the bonding brazing material 24 is cerium oxide (CeO ₂ ). The content of the oxygen supply oxide in the bonding brazing material 24 is 5.0 [vol]. As described above, the joining brazing material 24 electrically connects the two lead wires 25 and the two electrode portions 23 together.

FIG. 3 is a perspective view of the temperature sensitive element 21 in a state where the covering portion 71 is omitted.
As shown in FIG. 3, the element main body 22 has a rectangular parallelepiped shape, and lead wires 25 are electrically connected to the respective electrode portions 23 on the upper surface and the lower surface thereof by a bonding brazing material 24.

[1-3. Method for manufacturing temperature-sensitive element]
Here, a manufacturing method of the temperature sensitive element 21 will be described.
First, in order to manufacture the element main body 22, in a large-sized ceramic plate having a conductive oxide sintered body, a platinum layer serving as the electrode portion 23 is formed on each of the front surface and the back surface, so that the front and back surfaces are formed. A ceramic plate having electrode portions formed on both sides is obtained. By cutting this ceramic plate into a rectangular parallelepiped shape (for example, a rectangular parallelepiped shape of 0.6 [mm] × 0.6 [mm] × 0.5 [mm]) by dicing, the element body 22 is obtained. It is done. At this time, the electrode part 23 is formed on each of the upper surface and the lower surface of the element body 22.

Thereafter, a bonding paste is prepared. Specifically, platinum powder as a conductive metal and cerium oxide (CeO ₂ ) as an oxygen supply oxide are prepared, and blended so that the content of cerium oxide is 5.0 [vol%]. To do. The obtained mixed powder is mixed with butyl carbitol as a solvent and a vehicle formed with ethyl cellulose as a binder to obtain a bonding paste.

  After applying the bonding paste containing platinum and cerium oxide to each of the electrode portion 23 and the lead wire 25, the electrode portion 23 and the lead wire 25 are bonded to each other by heat treatment. The bonding paste applied at this time is solidified to form the bonding brazing material 24.

Next, the element main body 22 to which the lead wire 25 is joined is crystallized glass powder and metal oxide particles (Al ₂ ) made of SiO ₂ —RO—Al ₂ O ₃ —ZrO ₂ (R is an alkaline earth metal). The covering portion 71 is formed by dipping into a paste containing O ₃ ) and heat-treating the paste (at 1100 ° C. for 1 hour).

Through such a manufacturing process, the temperature sensitive element 21 including the bonding brazing material 24 and the covering portion 71 is obtained.
[1-4. Evaluation test of reduction resistance in temperature sensitive element]
Here, the test results of the reduction resistance evaluation test in the temperature sensitive element 21 will be described.

In this evaluation test, the resistance value of the temperature sensing element was measured before and after placing the temperature sensing element in the reducing gas atmosphere for a certain period of time, and the amount of change in resistance value before and after placement (resistance value variation amount). ) Specifically, first, the resistance value of the temperature sensing element was measured in an atmospheric environment of 900 ° C. as the resistance value before the placement. Then, as the resistance value after placement, the 900 ° C. reducing gas atmosphere _{(Ar: H 2 = 95:} 5) after placing the temperature-sensitive element for 5 hours, to measure the resistance value of the temperature sensing element. The indicated temperature change amount ΔT was calculated based on the obtained resistance value change amount, and the reduction resistance of the temperature sensitive element was evaluated based on the magnitude of the absolute value of the indicated temperature change amount ΔT. In this case, as the absolute value of the indicated temperature change amount ΔT becomes smaller, it can be determined that the characteristic change of the temperature sensitive element due to the influence of the reducing gas can be suppressed, and it can be evaluated as a temperature sensitive element having excellent reduction resistance.

  In this evaluation test, the evaluation test was performed using 15 types of temperature-sensitive elements (Examples 1 to 15) having different materials for the covering portion and the bonding brazing material. Of these, Example 12 corresponds to the temperature sensitive element 21 of the first embodiment. The material of each temperature sensing element is as shown in FIG. 4 and FIG.

  Furthermore, in this evaluation test, as a comparative example, the temperature-sensitive element (Comparative Example 1) having a structure in which the bonding brazing material does not contain an oxygen supply oxide, and the content of the oxygen supply oxide in the bonding brazing material is 70 [vol. %] Of the temperature sensitive element (Comparative Example 2) was also subjected to an evaluation test.

  As shown in the test results of FIGS. 4 and 5, the absolute value of the indicated temperature change ΔT in Comparative Example 1 is 50 [° C.], whereas the absolute value of the indicated temperature change ΔT in Examples 1 to 15 is absolute. The value indicates 9 [° C.] or a value smaller than 9 [° C.]. That is, the temperature sensitive elements of Examples 1 to 15 have a smaller absolute value of the indicated temperature change ΔT than the temperature sensitive element of Comparative Example 1, and include a bonding brazing material containing an oxygen supply oxide. It can be seen that the reduction resistance is improved.

  That is, in Comparative Example 1 having a configuration in which the bonding brazing material does not include an oxygen supply oxide, the intruding gas having reducibility that has entered through the interface between the lead wire and the covering portion does not reduce the reducibility. It is thought that it acted on the element body 22. On the other hand, in Examples 1-15, by providing the joining brazing material containing an oxygen supply oxide, oxygen is supplied from the joining brazing material to the intrusion gas entering through the interface between the lead wire and the covering portion. Thus, it is considered that the reducing property of the intruding gas could be relaxed.

  On the other hand, in Comparative Example 2, since the content of the oxygen supply oxide is excessive, the electrical conductivity of the joining brazing material is lowered, and the electrical connection between the lead wire and the electrode portion becomes poor, and the pair of lead wires is not connected. The conduction was poor (conduction NG). For this reason, in Comparative Example 2, the resistance value of the temperature sensitive element could not be measured, and it was impossible to measure the indicated temperature change amount ΔT. In Example 11, the content of the oxygen supply oxide in the bonding brazing material is 50.0 [vol%]. However, the conductivity of the bonding brazing material can be secured, and the electrical connection between the lead wire and the electrode portion is achieved. Can be ensured, and the indicated temperature change ΔT can be measured. In Example 11, the absolute value of the indicated temperature change amount ΔT is 1 [° C.], so that the temperature sensitive element is excellent in reduction resistance.

  For this reason, by making the content of the oxygen supply oxide in the bonding brazing material 50.0 [vol%] or less, it is possible to secure electrical connection between the lead wire and the electrode portion and to provide a feeling of excellent reduction resistance. A temperature element can be realized.

[1-5. effect]
As described above, the temperature sensitive element 21 provided in the temperature sensor 1 of the present embodiment includes the bonding brazing material 24 containing an oxygen supply oxide.

The bonding brazing material 24 includes platinum (Pt) as a conductive metal and cerium oxide (CeO ₂ ) as an oxygen supply oxide.
In the temperature sensitive element 21 having such a configuration, oxygen is supplied from the bonding brazing material 24 to the intruding gas that enters the element main body 22 through the interface between the lead wire 25 and the covering portion 71. The reduction reaction of the element main body portion 22 due to can be suppressed.

  That is, even when a gap exists at the interface between the lead wire 25 and the covering portion 71, the element main body portion 22 is exposed to a strong reducing atmosphere by including the bonding brazing material 24 containing the oxygen supply oxide. Can be suppressed, the reduction reaction of the element body 22 can be suppressed, and the change in the electrical characteristics of the temperature sensitive element 21 can be suppressed.

Therefore, according to this temperature sensitive element 21, it can suppress that a reduction reaction arises in the element main-body part 22, and it can suppress that the temperature detection accuracy as the temperature sensitive element 21 falls.
Next, in the temperature sensitive element 21, since the conductive metal contained in the bonding brazing material 24 is platinum, the bonding brazing material 24 has good conductivity, and the electrode portion 23 of the element main body 22 and the lead wire 25. The electrical connection state with is improved.

  Moreover, in the temperature sensitive element 21, the coating | coated part 71 is formed with the mixture of glass and a metal oxide particle. By providing such a covering portion 71, it is possible to suppress consumption of oxygen contained in the oxygen supply oxide of the bonding brazing material 24 by an oxidation reaction in a surrounding metal member or the like.

  That is, it becomes possible to more reliably supply oxygen contained in the oxygen supply oxide of the bonding brazing material 24 to the intruding gas that enters the element main body portion 22 through the interface between the lead wire 25 and the covering portion 71. .

Therefore, in the temperature sensitive element 21, it can suppress that a reduction reaction arises in the element main-body part 22 further, and can improve reduction resistance.
Moreover, since the temperature sensor 1 provided with such a temperature sensing element 21 can suppress a reduction reaction from occurring in the element body 22 and can suppress a decrease in temperature detection accuracy as the temperature sensing element 21, it can be used as a temperature sensor. It can suppress that temperature detection accuracy falls.

[1-6. Correspondence with Claims]
Here, the correspondence of the words in the claims and the present embodiment will be described.
The temperature sensitive element 21 corresponds to an example of a thermistor element, the element body 22 corresponds to an example of a thermistor body, and the lead wire 25 corresponds to an example of a lead wire.

[2. Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it is possible to implement in various aspects.

  For example, the covering portion is not limited to a configuration formed of a mixture of crystallized glass and metal oxide particles, and the covering portion may be formed of only glass. Specifically, in Examples 1 to 11 and 15 shown in FIGS. 4 and 5, the covering portion is formed only of crystallized glass.

Further, the metal oxide particles contained in the covering portion are not limited to alumina (Al ₂ O ₃ ), and are Y ₂ O ₃ and SiO ₂ as in Examples 13 and 14 shown in FIG. Also good.
Furthermore, the oxygen supply oxide contained in the bonding brazing material is not limited to cerium oxide (CeO ₂ ), and as in Examples 1 to 7 shown in FIG. 4, Cr, Mn, Fe, Co, Ni, At least one oxide of Ce and Pr may be used.

  Furthermore, the conductive metal contained in the bonding brazing material is not limited to a metal composed of only platinum (Pt), but platinum (Pt) and rhodium (Rh) as in Examples 8 and 9 shown in FIG. Or an alloy of platinum (Pt) and iridium (Ir).

  Next, the content of the oxygen supply oxide in the bonding brazing material is not limited to 5.0 [vol%], and is set within a range of 0.5 to 50.0 [vol%] The absolute value of the indicated temperature change amount ΔT can be limited to 9 [° C.] or less. A decrease in temperature detection accuracy can be suppressed, and an electrical connection state between the element body (thermistor body) and the lead wire can be secured.

  In other words, if the content of the oxygen supply oxide in the joining brazing material is 0.5 [vol%] or more, oxygen can be supplied from the joining brazing material to the intruding gas, and the reduction reaction of the thermistor body by the intruding gas is suppressed. This can suppress a decrease in temperature detection accuracy. Further, if the content of the oxygen supply oxide in the joining brazing material is 50.0 [vol%] or less, the electrical conductivity of the joining brazing material can be secured, and the electrical connection state between the thermistor body and the lead wire is secured. it can.

  Moreover, the electrical connection state of the thermistor body and the lead wire can be improved by setting the content of the oxygen supply oxide in the joining brazing material within the range of 0.5 to 10.0 [vol%]. . In other words, if the content of the oxygen supply oxide in the bonding brazing material is 10.0 [vol%] or less, the bonding brazing material has good conductivity and improves the electrical connection between the thermistor body and the lead wire. it can.

  Furthermore, the reduction resistance of the thermistor element (temperature-sensitive element) can be further improved by setting the content of the oxygen supply oxide in the bonding brazing material within a range of 1.0 to 10 [vol%]. That is, if the content of the oxygen supply oxide in the bonding brazing material is 1.0 [vol%] or more, the absolute value of the indicated temperature change ΔT can be limited to 7 [° C.] or less, and the thermistor element ( The reduction resistance of the temperature sensing element) can be further improved, and a decrease in temperature detection accuracy can be further suppressed.

Further, the thermistor element (temperature-sensitive element) may include a second covering portion as a member containing the oxygen supply oxide, in addition to the bonding brazing material. Specifically, the second temperature sensing element 81 shown in FIG. 6 includes a second covering portion 73 containing an oxygen supply oxide. The second covering portion 73 contains cerium oxide (CeO ₂ ) as an oxygen supply oxide. Further, the second covering portion 73 is formed so as to cover the extended portion of the lead wire 25 in the outer surface of the covering portion 71. In addition, about the structure similar to the temperature sensing element 21 of 1st Embodiment among the 2nd temperature sensing elements 81, the same code | symbol is attached | subjected and represented.

  In the second temperature sensing element 81, in addition to the bonding brazing material 24, oxygen is also introduced from the second covering portion 73 against the intruding gas that enters the element main body portion 22 through the interface between the lead wire 25 and the covering portion 71. Therefore, the reduction reaction of the element main body 22 due to the intruding gas can be further suppressed.

  That is, even when there is a gap at the interface between the lead wire 25 and the covering portion 71, the element main body portion 22 is exposed to a strong reducing atmosphere by including the bonding brazing material 24 and the second covering portion 73. It is possible to suppress the reduction reaction of the element body 22, and it is possible to suppress the change in electrical characteristics as the temperature sensitive element.

  Therefore, according to the 2nd temperature sensing element 81, by providing the 2nd coating | coated part 73 in addition to the joining brazing material 24, it can suppress further that a reductive reaction arises in the element main-body part 22, and can serve as a temperature sensing element. It can suppress that temperature detection accuracy falls.

Here, the correspondence of the words in the claims and the second temperature sensing element 81 will be described. The second covering portion 73 corresponds to an example of a second covering portion.
Furthermore, in the thermistor element (temperature sensing element) provided with the second stomach part, a third stomach part that covers the second stomach part may be provided. Specifically, a configuration including a third covering portion 75 formed so as to cover the second covering portion 73 as in the third temperature sensing element 82 shown in FIG. The 3rd coating | coated part 75 is formed with the amorphous glass. The amorphous _{glass, SiO 2 -RO-Al 2 O} 3 (R is an alkaline earth metal) is. In addition, about the structure similar to the temperature sensing element 21 of 1st Embodiment among the 3rd temperature sensing elements 82, the same code | symbol is attached | subjected and represented.

  By providing such a third covering portion 75, it is possible to suppress consumption of oxygen contained in the oxygen supply oxide of the second covering portion 73 due to an oxidation reaction in a surrounding metal member or the like. That is, it is possible to more reliably supply oxygen contained in the oxygen supply oxide of the second covering portion 73 to the intruding gas that enters the element main body portion 22 through the interface between the lead wire 25 and the covering portion 71. Become.

Therefore, in the 3rd temperature sensing element 82, by providing the 3rd coating | coated part 75, it can suppress that a reductive reaction arises in the element main-body part 22 further, and can reduce reduction resistance.
Furthermore, although the said embodiment demonstrated the structure with which the 2nd coating | coated part 73 is provided as one lump, a 2nd coating | coated part is not restricted to such a structure, It is the structure arrange | positioned in multiple parts. There may be.

  For example, like the 4th temperature sensing element 83 shown in FIG. 8, even if it distributes the 2nd coating | coated part 73 in each of two places which are the extension parts of the leader line 25 among the outer surfaces of the coating | coated part 71. FIG. good. In the fourth temperature sensing element 83, the third covering portions 75 are also arranged at two locations. In addition, about the structure similar to the temperature sensing element 21 of 1st Embodiment among the 4th temperature sensing elements 83, the same code | symbol is attached | subjected and represented.

  In the same manner as the second temperature sensing element 81, the fourth temperature sensing element 83 is a bonding brazing material containing an oxygen supply oxide even when there is a gap at the interface between the lead wire 25 and the covering portion 71. In addition to 24, by providing the second covering portion 73, it is possible to suppress the element body portion 22 from being exposed to a strong reducing atmosphere. Thereby, while being able to suppress the reduction reaction of the element main-body part 22, it can suppress that the electrical property as a temperature sensitive element changes. Therefore, according to the 4th temperature sensing element 83, it can suppress that reductive reaction arises in the element main-body part 22, and can suppress that the temperature detection precision as a temperature sensing element falls.

  DESCRIPTION OF SYMBOLS 1 ... Temperature sensor, 3 ... Sheath core wire (electrode wire), 5 ... Cylindrical member, 7 ... Sheath member, 9 ... Metal tube (housing), 11 ... Mounting member, 13 ... Hex nut part, 15 ... Screw part, 17 DESCRIPTION OF SYMBOLS ... Nut member, 19 ... Outer cylinder, 21 ... Temperature sensitive element, 22 ... Element main-body part, 23 ... Electrode part, 24 ... Joining brazing material, 25 ... Lead wire, 71 ... Cover part, 73 ... 2nd cover part, 75 ... 3rd coating | coated part, 81 ... 2nd temperature sensing element, 82 ... 3rd temperature sensing element, 83 ... 4th temperature sensing element.

Claims (8)

A thermistor body made of a conductive oxide sintered body;
A covering portion covering the periphery of the thermistor body;
A set of lead wires that are connected to the thermistor body by a bonding brazing material and extend toward the rear end side through the covering portion;
A thermistor element comprising:
The bonding brazing material includes a conductive metal and an oxygen supply oxide;
Thermistor element characterized by The thermistor element according to claim 1,
The bonding brazing material is located on the rear end side of the center of the thermistor body;
Thermistor element characterized by The thermistor element according to claim 1 or 2,
The conductive metal contained in the bonding brazing material mainly contains platinum;
Thermistor element characterized by The thermistor element according to any one of claims 1 to 3,
The oxygen supply oxide included in the bonding brazing material includes at least one oxide of Cr, Mn, Fe, Co, Ni, Ce, and Pr;
Thermistor element characterized by The thermistor element according to any one of claims 1 to 4,
The content of the oxygen supply oxide in the bonding brazing material is 0.5 [vol%] or more and 50.0 [vol%] or less,
Thermistor element characterized by The thermistor element according to any one of claims 1 to 5,
The covering portion is formed of glass or a mixture of glass and metal oxide particles;
Thermistor element characterized by The thermistor element according to any one of claims 1 to 6,
A second covering portion that surrounds the extension portion of the leader line in the rear end region of the outer surface of the covering portion relative to the center of the thermistor body, and mainly includes an oxygen supply;
Thermistor element characterized by Comprising the thermistor element according to any one of claims 1 to 7,
Temperature sensor.