JP2006266912A - Gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor capable of preventing the first insulator and the second insulator from being damaged. <P>SOLUTION: This gas sensor 1 has a sensor element 2 for detecting a concentration of a specified gas in measured gas, the first insulator 11 for inserting and holding the sensor element 2, the second insulator 12 arranged on a base end face 110 of the first insulator 11 to oppose a tip face 120, and for coating a base end part 22 of the sensor element 2, and a housing 10 for intrusing holding the first insulator 11. The base end face 110 of the first insulator 11 and the tip face 120 of the second insulator 12 abut to a metal sheet 31 interposed between the both. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gas sensor for detecting a specific gas concentration in a gas to be measured.

  As shown in FIG. 11, as a gas sensor 9 used for combustion control of an internal combustion engine, a housing 90, a first insulator 91 that is inserted and disposed in the housing 90 and is configured so that the sensor element 8 can be inserted and disposed therein, It is known that a second insulator 92 is disposed in contact with the base end surface 910 of the first insulator 91.

  The first insulator 91 and the second insulator 92 are usually made of an insulating ceramic material. Due to variations in the molding density of the ceramic member, variations in the amount of heat received during firing, etc., variations in shrinkage of the ceramic occur during firing. Therefore, when viewed microscopically, a wavy undulation occurs on the base end surface 910 of the first insulator 91 and the distal end surface 920 of the second insulator 92.

  Due to this undulation, the contact portion 93 between the first insulator 91 and the second insulator 92 and the annular packing 94 which is the receiving surface of the first insulator 91 are the same in the axial direction of the gas sensor 9. It may not be located on the axis. As a result, bending stress (tensile stress) is generated in the first insulator 91, which may cause damage to the first insulator 91.

  Therefore, the projection range T in which the contact portion 93 projects the outer shape of the annular packing 94 disposed on the insulator receiving surface 900 of the housing 90 onto the base end surface 910 of the first insulator 91 in the axial direction of the gas sensor 9. A gas sensor 9 located inside is proposed (see Patent Document 1). According to the gas sensor 9, the contact portion 93 can be prevented from being displaced in the horizontal direction (the direction perpendicular to the axial direction of the gas sensor 9) with respect to the annular packing 94, so that the bending applied to the first insulator 91 is performed. The stress can be minimized. Therefore, the gas sensor 9 in which the first insulator 91 is not easily damaged can be obtained.

  However, when the contact portion 93 is viewed microscopically, the contact between the base end surface 910 and the distal end surface 120 is a contact between a curved surface and a curved surface between undulation peaks. Will receive a load. Thereby, in particular, the first insulator 91 or the second insulator 92 may be damaged due to the assembly load of the first insulator 91 and the second insulator 92 to the gas sensor 9. .

JP 2001-343355 A

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a gas sensor capable of preventing the occurrence of breakage of the first insulator and the second insulator.

According to a first aspect of the present invention, there is provided a sensor element for detecting a specific gas concentration in a gas to be measured, a first insulator for inserting and holding the sensor element, and a distal end surface opposed to a base end surface of the first insulator. A second insulator that is disposed and covers a base end portion of the sensor element; and a housing that fits and holds the first insulator.
The gas sensor is characterized in that the base end surface of the first insulator and the tip end surface of the second insulator are in contact with a metal plate interposed therebetween (claim 1).

Next, the effects of the present invention will be described.
Since the base end surface of the first insulator and the tip end surface of the second insulator are in contact with the metal plate interposed therebetween, the base end surface, the metal plate, and the tip end The contact between the surface and the metal plate can be made. That is, the metal plate that undergoes plastic deformation when a large stress is applied and the first insulator or the second insulator are brought into contact with each other.

  Therefore, when a load is applied between the first insulator, the metal plate, and the second insulator, even if undulation is generated on the base end surface and the distal end surface, the metal plate is formed on the undulation. Deform to fit. Thereby, the contact area between the said base end surface and the said metal plate, the said metal plate, and the said front end surface increases, and the stress concerning a contact part can be disperse | distributed. As a result, it is possible to prevent the first insulator and the second insulator from being damaged.

  As described above, according to the present invention, it is possible to provide a gas sensor that can prevent the first insulator and the second insulator from being damaged.

According to a second aspect of the present invention, there is provided a sensor element for detecting a specific gas concentration in a gas to be measured, a first insulator for inserting and holding the sensor element, and a distal end surface opposed to a base end face of the first insulator. A second insulator that is disposed and covers a base end portion of the sensor element; and a housing that fits and holds the first insulator.
In the gas sensor, the base end surface of the first insulator and the distal end surface of the second insulator are in contact with a powder layer made of insulating powder interposed therebetween. (Claim 4).

  The base end surface of the first insulator and the distal end surface of the second insulator are in contact with a powder layer made of insulating powder interposed therebetween. As a result, the insulating powder of the powder layer is brought into contact with the base end surface and the tip end surface by an assembly load when the first insulator and the second insulator are assembled to the gas sensor. You can get into the gap. Therefore, even if undulation occurs on the base end surface of the first insulator or the distal end surface of the second insulator, the valley portion of the undulation can be evenly filled with the powder layer.

  Therefore, it is possible to avoid the problem that the contact area between the base end surface of the first insulator and the tip end surface of the second insulator is minimized by the contact of the undulation peaks. For this reason, even when an assembly load is applied when the first insulator and the second insulator are assembled to the gas sensor, the gas sensor is locally excessively large between the first insulator and the second insulator. Concentration of various stresses can be avoided. Thereby, generation | occurrence | production of the failure | damage of the said 1st insulator and the said 2nd insulator can be prevented.

  As described above, according to the present invention, it is possible to provide a gas sensor that can prevent the first insulator and the second insulator from being damaged.

According to a third aspect of the present invention, there is provided a sensor element for detecting a specific gas concentration in a gas to be measured, a first insulator for inserting and holding the sensor element, and a distal end surface opposed to a base end face of the first insulator. A second insulator that is disposed and covers a base end portion of the sensor element; and a housing that fits and holds the first insulator.
The base end surface of the first insulator and the tip end surface of the second insulator are in contact with a glass layer fused to at least one of the base end surface and the tip end surface. (Claim 7).

  The proximal end surface of the first insulator and the distal end surface of the second insulator are in contact with the glass layer fused to at least one of the proximal end surface and the distal end surface. Therefore, even if waviness is formed on the base end face and the front end face, at least one of the base end face or the front end face on which the glass layer is fused by fusing the glass layer to cover the waviness. It can be planar. Thereby, it is possible to avoid contact between the curved surface and the curved surface between the undulation peaks on the base end surface and the distal end surface, and to make contact between the curved surface and the flat surface, or contact between the flat surfaces.

  Therefore, even if an assembly load is applied when the first insulator and the second insulator are assembled to the gas sensor, the gas sensor is locally disposed between the first insulator and the second insulator. Since it is possible to avoid excessive stress concentration, it is possible to prevent the first insulator and the second insulator from being damaged.

  As described above, according to the present invention, it is possible to provide a gas sensor that can prevent the first insulator and the second insulator from being damaged.

  In the first invention (Invention 1), the second invention (Invention 4), and the third invention (Invention 7), the gas sensor is installed in an exhaust system of the internal combustion engine. The present invention can be applied to many sensors such as an oxygen sensor, an air-fuel ratio sensor, and a NOx sensor that are used for combustion control.

In the present specification, in the gas sensor, the side to be inserted into the exhaust pipe or the like will be referred to as the distal end side, and the opposite side will be described as the proximal end side.
For the first insulator and the second insulator, for example, alumina or the like can be used as an insulating ceramic material.
The metal plate preferably has an annular shape along the base end face and the tip end face.
Moreover, if the thickness of the said metal plate is 0.05 mm or more, the effect of this invention can fully be acquired, but when production efficiency etc. are considered, it is preferable to set it as about 0.1-2 mm.

Further, alumina powder or the like can be used as the insulating powder. As the average particle diameter of the insulating powder, for example, a particle having a particle size of 2 to 100 μm can be used.
Moreover, the said powder layer can be made into thickness about 0.1-1 mm, for example.

The glass layer can be formed by adding, for example, soda-lime glass, lead glass, borosilicate glass, or a metal oxide such as alkaline earth metal based on silicate glass.
Moreover, the said glass layer can be made into the thickness of about 0.03-0.3 mm, for example.

The linear expansion coefficient α of the metal plate and the linear expansion coefficient β of the first insulator and the second insulator preferably have a relationship of α−β ≦ 4.1 × 10 ⁻⁶ / ° C. ( Claim 2).
In this case, it is sufficient that excessive stress such as thermal stress or thermal shock caused by the difference between the linear expansion coefficient α and the linear expansion coefficient β acts on the first insulator and the second insulator. Can be avoided. Therefore, it is possible to more reliably prevent the first insulator and the second insulator from being damaged.
On the other hand, when α−β> 4.1 × 10 ⁻⁶ / ° C., excessive stress such as thermal stress or thermal shock may act on the first insulator and the second insulator.

The metal plate is preferably made of a steel material, a ferritic stainless steel, a martensitic stainless steel, titanium, or a titanium alloy.
In this case, the difference between the linear expansion coefficient of the metal plate and the linear expansion coefficients of the first insulator and the second insulator can be made sufficiently small. Therefore, the first insulator and the first insulator 2 Occurrence of breakage of the insulator can be sufficiently prevented.

The powder layer is formed by applying a mixture of the insulating powder and water to at least one of the base end face of the first insulator and the tip end face of the second insulator and then drying. (Claim 5).
In this case, the powder layer made of the above-described insulating powder can be easily and reliably formed.
Moreover, when the said powder layer is formed in both the said base end surface and the said front end surface, generation | occurrence | production of a failure | damage of the said 1st insulator and the said 2nd insulator can be prevented more reliably.

The powder layer is a sheet-like body made of the insulating powder, and the sheet-like body is interposed between the base end face of the first insulator and the tip end face of the second insulator. It is preferable to form by installing (Claim 6).
In this case, the powder layer made of the above-described insulating powder can be easily and reliably formed.
Moreover, the said sheet-like body is producible with a doctor blade method, for example. And the said powder layer can be formed by punching out the produced said sheet-like body in a desired shape.

The linear expansion coefficient γ of the glass layer and the linear expansion coefficient β of the first and second insulators are in a relationship of 0.2 × 10 ⁻⁶ ≦ β−γ ≦ 3 × 10 ⁻⁶ / ° C. (Claim 8).
In this case, since sufficient compressive stress is applied to the glass layer, it is possible to sufficiently apply compressive stress to the base end surface of the first insulator or the distal end surface of the second insulator. Thereby, the tensile force to the radial direction outer direction which acts on the said 1st insulator and the said 2nd insulator can be suppressed. Therefore, it is possible to more reliably prevent the first insulator and the second insulator from being damaged.

On the other hand, when β−γ <0.2 × 10 ⁻⁶ / ° C., a compressive stress is sufficiently applied to the base end face of the first insulator or the tip end face of the second insulator by the glass layer formation. May be difficult. Therefore, it may be difficult to sufficiently suppress the tensile force in the radially outward direction that acts on the first insulator and the second insulator.
Further, when β−γ> 3 × 10 ⁻⁶ / ° C., cracks occurred in the glass layer or the glass layer was formed as the glass layer melted and cooled and solidified due to the difference in shrinkage. There is a possibility that peeling occurs between the first insulator or the second insulator and the glass layer.

The glass layer is preferably made of a glass material that does not contain a group I element in the periodic table.
In this case, the performance of the gas sensor can be ensured. That is, if the glass layer contains the group I element, the glass layer may be exposed to a high-temperature and high-humidity atmosphere for a long time, and the group I element may be eluted. Therefore, when the eluted group I element adheres between the electrode of the sensor element and the heater electrode, the insulation resistance of the sensor element is lowered, and the sensor performance may be lowered. Therefore, according to the ninth aspect of the present invention, it is possible to prevent such problems and ensure the performance of the gas sensor.

Example 1
A gas sensor 1 used for combustion control of an internal combustion engine according to an embodiment of the present invention will be described with reference to FIGS.
The gas sensor 1 of this example is an oxygen sensor that is installed in an exhaust system of an automobile engine and is used for engine combustion control.

  As shown in FIGS. 1 and 2, the gas sensor 1 includes a sensor element 2 for detecting a specific gas concentration under measurement, a first insulator 11 for inserting and holding the sensor element 2, and the first insulation. It has the 2nd insulator 12 which is arrange | positioned with the front end surface 120 facing the base end surface 110 of the insulator 11, and covers the base end part 22 of the sensor element 2, and the housing 10 which inserts and holds the 1st insulator 11. FIG.

As shown in FIGS. 1 to 3, the base end face 110 of the first insulator 11 and the tip end face 120 of the second insulator 12 are in contact with a metal plate 31 interposed therebetween.
Further, the linear expansion coefficient α of the metal plate 31 and the linear expansion coefficient β of the first insulator 11 and the second insulator 12 have a relationship of α−β ≦ 4.1 × 10 ⁻⁶ / ° C.
The metal plate 31 is made of ferritic stainless steel.
In FIG. 3, the undulation of the base end face 110 and the front end face 120 is greatly drawn for convenience of explanation.

As shown in FIGS. 4 and 5, the base end surface 110 of the first insulator 11 is formed with a recess 111 that is retracted toward the tip side, and the tip surface 120 of the second insulator 12 can be fitted into the recess 111. Convex part 121 is formed.
And the 1st insulator 11 and the 2nd insulator 12 are making the base end surface 110 and the front end surface 120 contact | abut in the state which fitted the said recessed part 111 and the said convex part 121. FIG. Here, the base end surface 110 and the front end surface 120 are in contact with each other at a portion where the concave portion 111 or the convex portion 121 is not formed (shaded portion in FIG. 4). Therefore, the metal plate 31 is in contact with the base end surface 110 and the front end surface 120 other than the portion where the concave portion 111 or the convex portion 121 is formed.

As shown in FIG. 1, the gas sensor 1 of this example includes an atmosphere-side cover 14 provided on the proximal end side of the housing 10 and a double measured gas-side cover 13 provided on the distal end side of the housing 10.
The base end 22 side of the sensor element 2 is located in the second insulator 12 in the atmosphere-side cover 14, and the distal end 21 side is located in the measured gas-side cover 13.

A cylindrical first insulator 11 is disposed inside the housing 10, and a central portion of the sensor element 2 is inserted and fixed therein. A space between the central portion and the first insulator 11 is sealed with a glass sealing material 5.
Further, the base end portion of the atmosphere-side cover 14 is closed by a rubber bush 16. The rubber bushing 16 is provided with four terminal storage holes 160, and four lead wires 15 are inserted into the terminal storage holes 160.

The second insulator 12 is disposed between the base end surface 110 of the first insulator 11 and the shoulder 140 of the atmosphere side cover 14. A disc spring 6 urged in a direction to widen the gap between the second insulator 12 and the shoulder 140 is disposed, and the second insulator 12 is urged by the urging force of the disc spring 6. Is pressed by the first insulator 11.
In addition, as shown in FIG. 1, the first insulator 11 is arranged via an annular packing 4 with respect to an insulator receiving surface 100 that is formed to protrude from the inner surface of the housing 10.

Further, the tip portion 21 of the sensor element 2 is exposed in the exhaust gas, and an electrochemical reaction due to the exhaust gas component occurs in the tip portion 21. The tip portion 21 is provided with an electrode. The electrode detects the electric signal generated by the electrochemical reaction, and detects the gas concentration by taking out the electric signal from the lead wire 15 to the outside. is doing.
The first insulator 11 and the second insulator 12 are made of an insulating ceramic material.
Moreover, the metal plate 31 can be 0.1-2 mm thick.

Next, the function and effect of this example will be described.
Since the base end face 110 of the first insulator 11 and the tip end face 120 of the second insulator 12 are in contact with the metal plate 31 interposed between them, as shown in FIGS. 110 and the metal plate 31, and the tip surface 120 and the metal plate 31 can be in contact with each other. That is, the metal plate 31 that is plastically deformed when a large stress is applied and the first insulator 11 or the second insulator 12 are brought into contact with each other.

  Therefore, when a load is applied between the first insulator 11, the metal plate 31, and the second insulator 12, even if undulation occurs on the base end surface 110 and the front end surface 120, as shown in FIG. It deform | transforms so that the metal plate 31 may adapt to a wave | undulation. Thereby, the contact area between the base end surface 110 and the metal plate 31, and between the metal plate 31 and the front end surface 120 increases, and the stress applied to the contact portion can be dispersed. As a result, it is possible to prevent the first insulator 11 and the second insulator 12 from being damaged.

Further, the linear expansion coefficient α of the metal plate 31 and the linear expansion coefficient β of the first insulator 11 and the second insulator 12 have a relationship of α−β ≦ 4.1 × 10 ⁻⁶ / ° C. Therefore, it is possible to sufficiently avoid that excessive stress such as thermal stress or thermal shock caused by the difference between the linear expansion coefficient α and the linear expansion coefficient β acts on the first insulator 11 and the second insulator 12. it can.

  The metal plate 31 is made of ferritic stainless steel. As a result, the difference between the linear expansion coefficient α of the metal plate 31 and the linear expansion coefficient β of the first insulator 11 and the second insulator 12 can be made sufficiently small. Therefore, the first insulator 11 and the second insulator Occurrence of breakage of the insulator 12 can be sufficiently prevented.

  As described above, according to this example, it is possible to provide a gas sensor that can prevent the first insulator and the second insulator from being damaged.

(Example 2)
In this example, as shown in FIGS. 6 and 7, the base end face 110 of the first insulator 11 and the tip end face 120 of the second insulator 12 are made of an insulating powder interposed therebetween. In contact with the layer 32.
The powder layer 32 is formed by applying a mixture of insulating powder and water to the base end face 110 of the first insulator 11 and then drying.

Moreover, alumina powder etc. can be used as insulating powder. Moreover, the average particle diameter of insulating powder can be 20-100 micrometers.
Moreover, the powder layer 32 can be 0.1-1 mm thick.
In FIG. 7, the undulation of the base end face 110 and the front end face 120 is greatly drawn for convenience of explanation.
Others are the same as in the first embodiment.

  In the case of this example, as shown in FIGS. 6 and 7, the base end face 110 of the first insulator 11 and the tip end face 120 of the second insulator 12 are made of insulating powder interposed between the two. It is in contact with the powder layer 32. As a result, the powder layer 32 is caused to enter the gap between the base end surface 110 and the front end surface 120 due to the assembly load when the first insulator 11 and the second insulator 12 are assembled to the gas sensor 1. Can do.

  Therefore, even if undulation occurs on the base end surface 110 of the first insulator 11 or the distal end surface 120 of the second insulator 12, the valley portions of the undulation are evenly filled with the powder layer 32 as shown in FIG. Can do. Thereby, the malfunction that the contact area of the base end surface 110 of the 1st insulator 11 and the front end surface 120 of the 2nd insulator 12 becomes the minimum by contact | abutting of the peak of a wave | undulation can be avoided.

  Therefore, even if an assembly load is applied to the gas sensor 1 when the first insulator 11 and the second insulator 12 are assembled, it is locally excessive between the first insulator 11 and the second insulator 12. Concentration of various stresses can be avoided. Thereby, generation | occurrence | production of the failure | damage of the 1st insulator 11 and the 2nd insulator 12 can be prevented.

The powder layer 32 is formed by applying a mixture of insulating powder and water to the base end face 12 of the first insulator 11 and then drying it. Thereby, since the powder layer 32 made of the above-described insulating powder can be easily and reliably formed, it is possible to more reliably prevent the first insulator 11 and the second insulator 12 from being damaged. it can.
In addition, the same effects as those of the first embodiment are obtained.

(Example 3)
In this example, as shown in FIGS. 8 and 9, the base end face 110 of the first insulator 11 and the tip end face 120 of the second insulator 12 are in contact with the glass layer 33 fused to the base end face 110. Yes.
The linear expansion coefficient γ of the glass layer 33 and the linear expansion coefficients β of the first insulator 11 and the second insulator 12 are 0.2 × 10 ⁻⁶ ≦ β−γ ≦ 3 × 10 ⁻⁶ / ° C. Have the relationship.
The glass layer 33 is made of a glass material that does not contain a group I element in the periodic table.

The glass layer 33 is fused to the base end face 110 of the first insulator 11, but is not fused to the tip face 120 of the second insulator 12.
Moreover, the glass layer 33 can be 0.03-0.3 mm thick.
In FIG. 9, the undulations of the base end face 110 and the front end face 120 are greatly drawn for convenience of explanation.
Others are the same as in the first embodiment.

  In the case of this example, as shown in FIGS. 8 and 9, the base end face 110 of the first insulator 11 and the tip end face 120 of the second insulator 12 are bonded to the glass layer 33 fused to the base end face 110. It is in contact. Therefore, even if undulations are formed on the base end face 110, the base end face 110 can be made flat by fusing the glass layer 32 to cover the undulations of the base end face 110 as shown in FIG. Thereby, it is possible to avoid the contact between the curved surface and the curved surface between the undulation peaks on the base end surface 110 and the distal end surface 120, and to make the contact between the curved surface and the flat surface, or the contact between the flat surfaces.

  Therefore, even when an assembly load is applied to the gas sensor 1 when assembling the first insulator 11 and the second insulator 12, locally between the first insulator 11 and the second insulator 12. Since it is possible to avoid excessive stress concentration, it is possible to prevent the first insulator 11 and the second insulator 12 from being damaged.

The linear expansion coefficient γ of the glass layer 33 and the linear expansion coefficients β of the first insulator 11 and the second insulator 12 are 0.2 × 10 ⁻⁶ ≦ β−γ ≦ 3 × 10 ⁻⁶ / ° C. Have the relationship. Therefore, since sufficient compressive stress is applied to the glass layer 33, it is possible to sufficiently apply compressive stress to the base end surface 110 of the first insulator 11 or the distal end surface 120 of the second insulator 12. Thereby, the tensile force to the radial direction outer direction which acts on the 1st insulator 11 and the 2nd insulator 12 can be suppressed.
The glass layer 33 is made of a glass material that does not contain a group I element in the periodic table. Therefore, the performance of the gas sensor 1 can be ensured.
The other functions and effects are the same as those of the first embodiment.

  In the third embodiment described above, the glass layer 33 is fused to the base end face 110 of the first insulator 11 and is not fused to the tip end face 120 of the second insulator 12. It is also possible to fuse the glass layer 33 to both surfaces 120. In this case, the occurrence of breakage of the first insulator 11 and the second insulator 12 can be prevented more reliably.

Example 4
In this example, as shown in Table 1 and FIG. 10, the loading test and the cooling test are performed on the gas sensor 1 shown in the first embodiment, and the first insulator 11 or the second insulator 12 is cracked or cracked. This is an example of investigating the situation.
First, a sample is prepared by assembling the second insulator 12 to the first insulator 11 with various metal plates 31 interposed therebetween, a load test is performed, and cracks in the first insulator 11 and the second insulator 12 are observed. Or the occurrence of cracks was investigated.

  In the above-described load test, as shown in FIG. 10, the second insulator 12 is placed on the support jig 72 with the base end side down, and the base end surface 110 is in contact with the front end surface 120. The first insulator 11 is combined with the second insulator 12. Then, the pressing jig 71 is covered from the front end side of the first insulator 11 and a load F of 10 KN is applied toward the supporting jig 72.

In addition, each sample was subjected to a 20-cycle cooling test by holding for 20 hours at 600 ° C., which is the maximum temperature during operation of the internal combustion engine, and then holding at room temperature for 4 hours, and the first insulator was tested. 11 and the state of occurrence of cracks in the second insulator 12 were investigated.
The cooling from 600 ° C. to room temperature is performed by taking the sample from the furnace at 600 ° C. into the atmosphere and naturally cooling, and the heating from room temperature to 600 ° C. is carried out from the atmosphere into the furnace at 600 ° C. It was done by throwing in.

In addition, as a comparative sample, a case where the first insulator 11 and the second insulator 12 were brought into contact without the metal plate 31 being interposed was also investigated in the same manner.
In the loading test, 20 samples were prepared for each sample. In the cooling test, four samples were prepared for each sample.
In addition, the first insulator 11 and the second insulator 12 were checked for cracks and cracks by color check by immersing them in a dyeing solution.
The survey results are shown in Table 1.

From Table 1, it can be seen that for the loading test, cracks or cracks occurred in the first insulator 11 or the second insulator 12 for three of the 20 comparative samples. On the other hand, for the sample with the metal plate 31 interposed, the first insulator 11 and the second insulator 12 are not cracked or cracked.
Moreover, about a thermal test, it turns out from Table 1 that the crack or the crack has generate | occur | produced in the 1st insulator 11 or the 2nd insulator 12 about the sample which interposed the metal plate 31 of Ni or SUS304.

Further, the difference in coefficient of linear expansion between Ni and the first insulator 11 and the second insulator 12 is 6.0 × 10 ⁻⁶ / ° C. On the other hand, mild steel that has obtained good results in both the above tests. The linear expansion coefficient difference between the first insulator 11 and the second insulator 12 is 4.1 × 10 ⁻⁶ / ° C.
That is, if the difference in linear expansion coefficient between the metal plate 31 and the first and second insulators 11 and 12 is within a range of 4.1 × 10 ⁻⁶ / ° C. or less, the first and second insulators 11 and 11 are used. Occurrence of breakage of the insulator 12 can be sufficiently prevented.

(Example 5)
In this example, as shown in Table 2, for the gas sensor 1 shown in Example 3 described above, various glasses were fused to the base end surface 110 to form a glass layer 33, and then a sample was prepared. 33, the occurrence of cracks or cracks in the first insulator 11 or the second insulator 12 was investigated.

Further, when the first insulator 11 and the second insulator 12 are assembled to the gas sensor 1, a loading test is performed on each sample, and the glass layer 33, the first insulator 11, or the second insulator 12 is cracked or cracked. We also investigated the situation of the occurrence.
The load test described above was performed in the same manner as the load test of Example 4.

Further, a comparative sample in which the glass layer 33 was not formed on either the base end face 110 or the front end face 120 was produced.
In addition, 20 samples were prepared for each sample.
The determination of cracks and cracks was performed in the same manner as in Example 4.
The survey results are shown in Table 2.

From Table 2, regarding the sample in which the glass layer 33 made of soda-lime glass or borosilicate glass was formed, the glass layer 33, the first insulator 11 or the second insulator 12 was cracked or cracked after the glass layer 33 was formed. You can see that it has occurred.
Furthermore, in the loading test, the glass layer 33, the first insulator 11, or the first layer is formed on a sample in which the glass layer 33 made of soda-lime glass or lead glass having a linear expansion coefficient of 7.5 × 10 ⁻⁶ / ° C. is formed. It can be seen that the two insulators 12 are cracked or cracked.

In addition, it can be seen that three out of 20 comparative samples are cracked or cracked in the glass layer 33, the first insulator 11, or the second insulator 12 in the loading test.
That is, from Table 2, when the difference in linear expansion coefficient between the first insulator 11 and the second insulator 12 and the glass layer 33 is 0.2 × 10 ⁻⁶ / ° C. or more and 3 × 10 ⁻⁶ / ° C. or less. It can be seen that the occurrence of breakage of the first insulator 11 and the second insulator 12 can be sufficiently prevented.

In the fifth embodiment, the glass layer 33 is formed on the proximal end surface 110 of the first insulator 11 and not formed on the distal end surface 120 of the second insulator 12, but the glass layer 33 is formed on the distal end surface 120. Even if it is formed and not formed on the base end face 110, it is considered that the same result can be obtained.
Furthermore, when the glass layer 33 is fused to both the base end face 110 of the first insulator 11 and the tip face 120 of the second insulator 12, the first insulator 11 and the second insulator 12 are damaged. Can be more reliably prevented.

FIG. 3 is a cross-sectional explanatory view of a gas sensor in the first embodiment. Sectional explanatory drawing of the contact part of the 1st insulator and the 2nd insulator in Example 1. FIG. Sectional explanatory drawing of the contact part of the base end surface of a 1st insulator and the front end surface of a 2nd insulator in Example 1. FIG. In Example 1, (a) Explanatory drawing of the base end surface of a 1st insulator, (b) Explanatory drawing of the front end surface of a 2nd insulator. Explanatory drawing which shows the 1st insulator and the 2nd insulator which inserted and hold | maintained the sensor element in Example 1. FIG. Sectional explanatory drawing of the contact part of the 1st insulator and the 2nd insulator in Example 2. FIG. Sectional explanatory drawing of the contact part of the base end surface of a 1st insulator and the front end surface of a 2nd insulator in Example 2. FIG. Sectional explanatory drawing of the contact part of the 1st insulator and the 2nd insulator in Example 3. FIG. Sectional explanatory drawing of the contact part of the base end surface of a 1st insulator and the front end surface of a 2nd insulator in Example 3. FIG. Explanatory drawing which shows the method of applying a load to the 1st insulator and the 2nd insulator in Example 4. FIG. Sectional explanatory drawing of the gas sensor in a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas sensor 10 Housing 11 1st insulator 110 Base end surface 12 2nd insulator 120 Front end surface 2 Sensor element 22 Base end part 31 Metal plate

Claims (9)

A sensor element for detecting a specific gas concentration in the gas to be measured, a first insulator for inserting and holding the sensor element, a distal end surface of the first insulator that faces the base end face of the first insulator, and the sensor A second insulator covering the base end of the element, and a housing for fitting and holding the first insulator;
The gas sensor according to claim 1, wherein the base end surface of the first insulator and the tip end surface of the second insulator are in contact with a metal plate interposed therebetween. In Claim 1, the linear expansion coefficient α of the metal plate and the linear expansion coefficient β of the first insulator and the second insulator have a relationship of α−β ≦ 4.1 × 10 ⁻⁶ / ° C. A gas sensor comprising:   3. The gas sensor according to claim 1, wherein the metal plate is made of steel, ferritic stainless steel, martensitic stainless steel, titanium, or a titanium alloy. A sensor element for detecting a specific gas concentration in the gas to be measured, a first insulator for inserting and holding the sensor element, a distal end surface of the first insulator that faces the base end face of the first insulator, and the sensor A second insulator covering the base end of the element, and a housing for fitting and holding the first insulator;
The gas sensor according to claim 1, wherein the base end face of the first insulator and the tip end face of the second insulator are in contact with a powder layer made of insulating powder interposed therebetween.   5. The powder layer according to claim 4, wherein the mixture of the insulating powder and water is applied to at least one of the base end face of the first insulator and the tip end face of the second insulator, A gas sensor formed by drying.   5. The powder layer according to claim 4, wherein the powder layer is a sheet-shaped body made of the insulating powder, and then the sheet-shaped body is divided into the base end surface of the first insulator and the distal end surface of the second insulator. A gas sensor formed by being interposed between the two. A sensor element for detecting a specific gas concentration in the gas to be measured, a first insulator for inserting and holding the sensor element, a distal end surface of the first insulator that faces the base end face of the first insulator, and the sensor A second insulator covering the base end of the element, and a housing for fitting and holding the first insulator;
The base end surface of the first insulator and the tip end surface of the second insulator are in contact with a glass layer fused to at least one of the base end surface and the tip end surface. . 8. The linear expansion coefficient γ of the glass layer and the linear expansion coefficient β of the first insulator and the second insulator are 0.2 × 10 ⁻⁶ / ° C. ≦ β−γ ≦ 3 ×. A gas sensor having a relationship of 10 ⁻⁶ / ° C.   9. The gas sensor according to claim 7, wherein the glass layer is made of a glass material that does not contain a group I element in the periodic table.

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