JP2016012696A - 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 second coating layer 73 against an intruding gas that intrudes through a surface boundary between a leader line 25 and a first coating layer 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 first coating layer 71, the second coating layer 73 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 21 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 made of a conductive oxide sintered body, a coating layer covering the periphery of the thermistor body, and a coating layer 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.

  By providing the coating layer in this way, it is possible to suppress the reduction reaction from occurring in the thermistor body and to improve the reduction resistance of the thermistor element.

Japanese Patent No. 3806434

  However, in the above thermistor element, the reducing gas may enter the thermistor body through the interface between the coating layer 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 according to one aspect of the present invention includes a thermistor body, a first coating layer, and a set of lead wires, and further includes a second coating layer.
The thermistor body is formed of a conductive oxide sintered body. The first coating layer covers the periphery of the thermistor body. The set of lead wires is connected to the thermistor body and extends through the first coating layer toward the rear end side.

The first coating layer is made of glass or a mixture of glass and metal oxide particles.
A 2nd coating layer is formed in the state which surrounds the extension part of a leader line in the rear end side area | region rather than the center of a thermistor main body among the outer surfaces of a 1st coating layer. The second coating layer is formed mainly including an oxygen supply oxide.

  In the thermistor element having such a configuration, oxygen is supplied from the second coating layer to the intruding gas that enters the thermistor body through the interface between the lead wire and the first coating layer. Reduction reaction can be suppressed.

  That is, even if there is a gap at the interface between the lead wire and the first coating layer, the second coating layer can be provided to prevent the thermistor body from being exposed to a strong reducing atmosphere, and the thermistor body can be reduced. The reaction can be suppressed, and the change in electrical characteristics as the thermistor element 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.
Note that “formed mainly including an oxygen supply oxide” means that the oxygen supply oxide is the most among the components forming the second coating layer.

The above-described thermistor element may include a third coating layer that is formed so as to cover the second coating layer and is formed of glass or a mixture of glass and metal oxide particles.
By providing such a third coating layer, it is possible to suppress consumption of oxygen contained in the oxygen supply oxide of the second coating layer 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 second coating layer to the intruding gas that enters the thermistor body through the interface between the lead wire and the first coating layer.

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 thermistor element, the oxygen supply oxide of the second coating layer may include at least one oxide of Cr, Mn, Fe, Co, Ni, Ce, and Pr.

  The oxygen supply oxide containing such an oxide can supply oxygen to the intrusion gas that enters the thermistor body through the interface between the lead wire and the first coating layer, and the thermistor body has a strong reducing atmosphere. It can suppress exposure.

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.
A temperature sensor according to another aspect of the present invention includes the thermistor element 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 a state where a first covering layer, a second covering layer, and a third covering layer are omitted. It is a test result of the evaluation test in Examples 1-8. It is a test result of the evaluation test in Examples 9-13 and Comparative Examples 1-2. It is sectional drawing which shows the internal structure of a 2nd temperature sensing element which is not provided with a 3rd coating layer but is provided with a 1st coating layer and a 2nd coating layer. It is sectional drawing which shows the internal structure of the 3rd temperature sensing element of the structure by which a 2nd coating layer is dispersively 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, a first covering layer 71, a second covering layer 73, and a third covering layer 75. ing.

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 electrically connected to the two electrode portions 23, respectively, and are arranged to extend toward the rear end side.

The 1st coating layer 71 is formed in the state which coat | covers the circumference | surroundings of the element main-body part 22, and is formed with the mixture of crystallized glass and a metal oxide particle. 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 second coating layer 73 is formed mainly including an oxygen supply oxide. The oxygen supply oxide in this embodiment is cerium oxide (CeO ₂ ). The second coating layer 73 is formed in a rear end region of the outer surface of the first coating layer 71 from the center of the element body 22 (region in the rear end side from the virtual center line C in FIG. 2). Yes. Further, the second coating layer 73 is formed in a state of continuously surrounding the extended portion of the lead wire 25 in the outer surface of the first coating layer 71.

The third coating layer 75 is made of amorphous glass. The amorphous glass in the present embodiment is SiO ₂ —RO—Al ₂ O ₃ (R is an alkaline earth metal). The third covering layer 75 is formed so as to cover the second covering layer 73.

FIG. 3 is a perspective view of the thermosensitive element 21 in a state where the first covering layer 71, the second covering layer 73, and the third covering layer 75 are 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 electrode portions 23 on the upper surface and the lower surface thereof.

[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, a large-sized ceramic plate formed of a conductive oxide sintered body is formed by forming a platinum layer serving as the electrode portion 23 on each of the front and back surfaces. A ceramic plate having electrode portions formed on both the front and back surfaces 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.

After applying a paste containing platinum to each of the electrode portion 23 and the lead wire 25, the electrode portion 23 and the lead wire 25 are joined to each other by heat treatment.
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 first coating layer 71 is formed by dipping into a paste containing O ₃ ) and heat-treating the paste (at 1100 ° C. for 1 hour).

Subsequently, a paste containing cerium oxide (CeO ₂ ) powder is applied to the extended portion of the lead wire 25 of the first coating layer 71 using a known liquid dispensing device (dispenser). After the applied paste is dried, the second coating layer 73 is formed by heat-treating the paste (1000 ° C. for 1 hour).

Subsequently, an amorphous glass powder made of SiO ₂ —RO—Al ₂ O ₃ (R is an alkaline earth metal) is used by using a known liquid dispensing apparatus (dispenser) so as to cover the second coating layer 73. Apply paste containing. After the applied paste is dried, the third coating layer 75 is formed by heat-treating the paste (900 ° C. for 1 hour).

Through such a manufacturing process, the temperature sensitive element 21 including the first coating layer 71, the second coating layer 73, and the third coating layer 75 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 addition, in this evaluation test, the evaluation test was implemented using 13 types of thermosensitive elements (Examples 1-13) from which each material of a 1st coating layer, a 2nd coating layer, and a 3rd coating layer differs. Of these, Example 9 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.

  Of the 13 types of temperature sensitive elements, Example 1 is a temperature sensitive element that does not include the third coating layer but includes the first coating layer and the second coating layer. FIG. 6 is a cross-sectional view showing the internal configuration of the temperature sensing element of Example 1 (hereinafter also referred to as the second temperature sensing element 81).

  The second temperature sensitive element 81 includes an element main body part 22, two electrode parts 23, two lead wires 25, a first covering layer 71, and a second covering layer 73. Among the second temperature sensing elements 81, the same reference numerals are given to the same configurations as those of the temperature sensing element 21.

  Furthermore, in this evaluation test, as a comparative example, the second coating layer and the third coating layer are not provided, the temperature sensitive element including only the first coating layer (Comparative Example 1), and the second coating layer are not provided. An evaluation test was also conducted on the temperature sensitive element (Comparative Example 2) provided with the first coating layer and the third coating layer.

  As shown in the test results of FIGS. 4 and 5, the absolute values of the indicated temperature change ΔT in Comparative Example 1 and Comparative Example 2 are 50 ° C. and 18 ° C., respectively, whereas in Examples 1 to 13 The absolute value of the indicated temperature change amount ΔT is 9 ° C. or a value smaller than 9 ° C. That is, in the temperature sensitive elements of Examples 1 to 13, the absolute value of the indicated temperature change amount ΔT is smaller than that of the temperature sensitive elements of Comparative Example 1 and Comparative Example 2, and the second temperature containing the oxygen supply oxide is second. It can be seen that the reduction resistance is improved by providing the coating layer.

  That is, in Comparative Example 1 and Comparative Example 2 that do not include the second coating layer, the reducing gas that has entered through the interface between the lead wire and the first coating layer does not relax the reducing property. It is thought that it acted on the main body 22. On the other hand, in Examples 1-13, by providing the 2nd coating layer containing an oxygen supply oxide, it is the 2nd coating layer with respect to the intrusion gas which penetrates through the interface of a leader line and the 1st coating layer. It is thought that oxygen was supplied from the gas, and the reducibility of the intruding gas was alleviated.

  In addition, in Examples 2 to 13 including the third coating layer, the indicated temperature change amount ΔT is smaller than that in Example 1 including no third coating layer. Accordingly, by providing the third coating layer covering the second coating layer, oxygen of the oxygen supply oxide contained in the second coating layer is consumed for the oxidation reaction of the metal parts around the temperature sensitive element. It is thought that this can be suppressed. In other words, the oxygen of the oxygen supply oxide contained in the second coating layer effectively acts on the intrusion gas entering through the interface between the lead wire and the first coating layer, thereby effectively reducing the reduction property of the intrusion gas. It is thought that it has eased.

[1-5. effect]
As described above, the temperature sensitive element 21 provided in the temperature sensor 1 of the present embodiment includes the first coating layer 71, the second coating layer 73, and the third coating layer 75.

The first coating layer 71 is formed of a mixture of crystallized glass (SiO ₂ —RO—Al ₂ O ₃ —ZrO ₂ (R is an alkaline earth metal)) and metal oxide particles (Al ₂ O ₃ ). Yes.
The second coating layer 73 is formed in a rear end region of the outer surface of the first coating layer 71 from the center of the element body 22 (region in the rear end side from the virtual center line C in FIG. 2). Yes. Further, the second coating layer 73 is formed in a state of continuously surrounding the extended portion of the lead wire 25 in the outer surface of the first coating layer 71. Further, the second coating layer 73 is formed mainly including an oxygen supply oxide (cerium oxide (CeO ₂ )).

  In the temperature sensitive element 21 having such a configuration, oxygen is supplied from the second covering layer 73 to the intruding gas that enters the element body 22 through the interface between the lead wire 25 and the first covering layer 71. The reduction reaction of the element main body 22 due to the intruding gas can be suppressed.

  That is, even when there is a gap at the interface between the lead wire 25 and the first coating layer 71, the element body portion 22 can be prevented from being exposed to a strong reducing atmosphere by including the second coating layer 73. In addition, the reduction reaction of the element body 22 can be suppressed, and the change in electrical characteristics as 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.
The temperature sensitive element 21 includes a third coating layer 75, and the third coating layer 75 is formed of amorphous glass (SiO ₂ —RO—Al ₂ O ₃ (R is an alkaline earth metal)). In addition, the second covering layer 73 is formed so as to cover the second covering layer 73.

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

Therefore, in the temperature sensitive element 21, by providing the 3rd coating layer 75, it can suppress further that a reduction reaction arises in the element main-body part 22, and reduction resistance can be improved.
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 first coating layer is not limited to a configuration formed of a mixture of crystallized glass and metal oxide particles, and the first coating layer may be configured of only glass. Specifically, in Examples 1 to 8, 12, and 13 shown in FIGS. 4 and 5, the first coating layer is formed only of crystallized glass.

In addition, the metal oxide particles contained in the first coating layer are not limited to alumina (Al ₂ O ₃ ), and may be Y ₂ O ₃ or SiO ₂ as in Examples 10 and 11 shown in FIG. There may be.
Furthermore, the oxygen supply oxide contained in the second coating layer is not limited to cerium oxide (CeO ₂ ), and Cr, Mn, Fe, Co, Ni, as in Examples 2 to 8 shown in FIG. , Ce, Pr may be at least one oxide.

In addition, the third coating layer is not limited to a configuration formed only of amorphous glass, and is a mixture of crystallized glass and metal oxide particles as in Examples 12 and 13 shown in FIG. The structure formed may be sufficient. The metal oxide particles, as in Examples 12 and 13 shown in FIG. 5 include _{as Al} 2 _{O 3} and _Y 2 _{O 3.}

  Furthermore, although the said embodiment demonstrated the structure with which the 2nd coating layer 73 was provided as one lump, a 2nd coating layer is not restricted to such a structure, It is the structure arrange | positioned in multiple parts. There may be.

  For example, like the third temperature sensing element 83 shown in FIG. 7, the second coating layer 73 is dispersedly arranged in each of two locations on the outer surface of the first coating layer 71 that are the extended portions of the lead wires 25. May be. Further, in the third temperature sensing element 83, the third covering layer 75 is also arranged at two places.

  This third temperature sensing element 83 is provided with the second coating layer 73 even when there is a gap at the interface between the lead wire 25 and the first coating layer 71, similarly to the temperature sensing element 21. Exposure of the element body 22 to a strong reducing atmosphere can be suppressed, the reduction reaction of the element body 22 can be suppressed, and changes in electrical characteristics as the temperature-sensitive element 21 can be suppressed. Therefore, according to the 3rd 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 accuracy as the temperature sensing element 21 falls.

  In addition, the second coating layer includes not only the region on the rear end side (rear end side region) from the center of the thermistor body on the outer surface of the first coating layer but also the region on the front end side (front end) from the rear end side region For example, the second coating layer may be formed so as to cover the entire outer surface of the first coating layer.

  The second coating layer is formed only in the rear end region of the outer surface of the first coating layer, so that the volume of the second coating layer can be reduced and the heat capacity can be reduced, and the temperature as the thermistor element can be reduced. The influence on the responsiveness of changes can be reduced. Furthermore, since the second coating layer takes a form formed in a layer shape, the volume of the second coating layer can be reduced, the heat capacity can be reduced, and the influence on the responsiveness of the temperature change as the thermistor element can be reduced. Here, “layered” means that the thickness dimension of the second coating layer (the direction perpendicular to the outer surface of the first coating layer) is the width dimension of the second coating layer (the direction parallel to the outer surface of the first coating layer). ) Means a smaller shape.

  Moreover, in the said embodiment, although the joining brazing material obtained by heat-processing the paste containing platinum is used as a joining brazing material for joining the electrode part 23 and the leader line 25, This joining brazing material is used. An oxygen supply substance may be included. Specifically, the bonding brazing material containing the oxygen supply oxide can be obtained by heat-treating the paste containing the oxygen supply oxide.

  In the thermistor element having such a bonding brazing material, 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 first coating layer. The reduction reaction of the main body can be suppressed. In other words, even if there is a gap at the interface between the lead wire and the first coating layer, by providing a bonding brazing material containing an oxygen supply oxide, the thermistor body is prevented from being exposed to a strong reducing atmosphere. In addition, the reduction reaction of the thermistor body can be suppressed, and changes in electrical characteristics as the thermistor element can be suppressed.

  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, 25 ... Lead wire, 71 ... 1st coating layer, 73 ... 2nd coating layer, 75 ... 3rd coating Layer, 81 ... second temperature sensing element, 83 ... third temperature sensing element.

Claims (4)

A thermistor body made of a conductive oxide sintered body;
A first coating layer covering the periphery of the thermistor body;
A set of lead wires connected to the thermistor body and extending toward the rear end side through the first coating layer;
A thermistor element comprising:
The first coating layer is formed of glass or a mixture of glass and metal oxide particles,
A second coating layer is formed which surrounds the extension portion of the lead wire in the rear end region of the outer surface of the first coating layer from the center of the thermistor body and mainly contains oxygen-supplying oxide. about,
Thermistor element characterized by The thermistor element according to claim 1,
A third covering layer formed to cover the second covering layer and formed of glass or a mixture of glass and metal oxide particles;
Thermistor element characterized by The thermistor element according to claim 1 or 2,
The oxygen supply oxide of the second coating layer includes at least one oxide of Cr, Mn, Fe, Co, Ni, Ce, and Pr;
Thermistor element characterized by Comprising the thermistor element according to any one of claims 1 to 3,
Temperature sensor.