JPH10206380A - Oxygen concentration detecting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen concentration detecting element which is excellent in quick heating performance and is excellent in responsiveness. SOLUTION: This detecting element is composed of solid electrolyte 10, an outside electrode 15 which is arranged on an outside surface of the solid electrolyte 10 and contacts with measuring object gas and an inside electrode arranged on its inside surface. A first insulating layer 11 which is composed of a gas permeable porous material and has electric insulating performance, is arranged on a surface offered to detect at least the oxygen concentration of the outside electrode 15, and a second insulating layer 12 having electric insulating performance is also arranged on the outside of the first insulating layer 11. A heater layer 13 is arranged between the first insulating layer 11 and the second insulating layer 12, and a gas impermeable layer 139 is arranged at least on an outside surface of the heater layer 13 having a thickness of 1 to 100μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an oxygen concentration detector installed in an exhaust system of an automobile internal combustion engine or the like.

[0002]

2. Description of the Related Art Conventionally, a gas detector capable of detecting an air-fuel ratio is installed in an exhaust system of an automobile internal combustion engine or the like. Based on the air-fuel ratio detected by the above gas detector,
The combustion state of the automobile internal combustion engine is controlled. As a result, the purification efficiency of the exhaust gas discharged from the internal combustion engine can be increased. As the gas detector, an oxygen concentration detector including an oxygen concentration detection element having a ZrO ₂ solid electrolyte and a housing holding the oxygen concentration detection element is used. The oxygen concentration detecting element includes a limiting current type or an oxygen concentration electromotive force type.

[0003] In the limiting current type oxygen concentration detecting element, an oxygen concentration detecting element having a bottomed cylindrical solid electrolyte is, for example, the one shown in FIGS. 10 and 11. The oxygen concentration detecting element 9 includes a bottomed cylindrical solid electrolyte 90, an outer electrode 95 provided on the outer surface of the solid electrolyte 90, and an inner electrode 96 provided on the inner surface thereof. An insulating layer 91 is provided on the surface of the substrate 95.

[0004] Further, inside the oxygen concentration detecting element 9 is provided an inner chamber 92 into which a reference gas is introduced.
2, a rod-shaped heater 99 is inserted and arranged. In addition,
The insulating layer 91 also has a role as a protective layer for the outer electrode 95, and is formed of a ceramic coating layer. Alternatively, the insulating layer 91 is formed of a composite layer in which, for example, a γ-Al ₂ O ₃ layer is formed on a ceramic coating layer.

[0005] Incidentally, in order to respond to the stricter exhaust gas regulations year by year, the automobile internal combustion engine is required to perform combustion control with a more precise air-fuel ratio.
Therefore, development of a highly accurate oxygen concentration detecting element is required. An example of the highly accurate oxygen concentration detecting element is an oxygen concentration detecting element which can detect the oxygen concentration in a short time after the start of the automobile internal combustion engine, that is, is excellent in quick heat property.

This is because the oxygen concentration detecting element has a property that accurate oxygen concentration detection cannot be performed unless the element is heated above the element activation temperature. Therefore, immediately after the start of the internal combustion engine, when the temperature of the exhaust system and its surroundings is not so high, the oxygen concentration detecting element is heated by the heater inserted into the inner chamber, and quickly becomes the element activation temperature. There is a need.

[0007] Therefore, when heating the oxygen concentration detecting element, in consideration of thermal efficiency, it is preferable to provide an integrated heater for the oxygen concentration detecting element rather than providing a separate heater. As such an oxygen concentration detecting element, the following oxygen concentration detecting element can be considered.

As shown in FIG. 12, the oxygen concentration detecting element comprises a bottomed cylindrical solid electrolyte 90 and a solid electrolyte 9.
Outer electrode 95 provided on the outer surface of the outer electrode 95 and in contact with the gas to be measured
And the solid electrolyte 9 provided on the inner surface thereof.
The inner electrode 96 is provided at a position opposed to the outer electrode 95 with the “0” interposed therebetween.

At least a surface of the outer electrode 95 to be used for oxygen concentration detection is provided with a first insulating layer 81 made of a gas-permeable porous material and having an electrically insulating property. An electrically insulating second insulating layer 82 is provided outside the insulating layer 81, and a heater layer 83 is provided between the first insulating layer 81 and the second insulating layer 82. Provided.

In the oxygen concentration detecting element, the distance between the heater layer 83 and the outer electrode 95 is equal to the thickness of the first insulating layer 81, that is, at most about 200 μm. For this reason,
The oxygen concentration detecting element is excellent in quick heat property. In the oxygen concentration detecting element, the heater layer 83 is usually made of a noble metal such as platinum in consideration of heat resistance.

[0011]

However, the oxygen concentration detecting element has the following problems. That is, in the oxygen concentration detecting element, the gas to be measured reaches the outer electrode 95 from the second insulating layer 82 via the first insulating layer 81. The heater layer 83 includes the first insulating layer 81 and the second insulating layer 8.
2, the gas to be measured may reach the outer electrode 95 via the vicinity of the heater layer 83. Since the heater layer 83 is made of a noble metal such as platinum as described above,
It has oxygen adsorption power.

As described above, when passing through the vicinity of the heater layer 83, oxygen in the gas to be measured is removed by the heater layer 8.
3 may be adsorbed. In this case, the response time of the oxygen concentration detecting element is deteriorated because the arrival time of oxygen to the outer electrode 95 is delayed. And this phenomenon is
In particular, the responsiveness of the oxygen concentration detecting element when the stoichiometry is interposed is deteriorated.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an oxygen concentration detecting element which is excellent in quick heat property and excellent in response.

[0014]

A first aspect of the present invention provides a solid electrolyte having a cylindrical shape with a bottom, an outer electrode provided on an outer surface of the solid electrolyte, the electrode being in contact with a gas to be measured, and an inner electrode provided on the inner surface thereof. In an oxygen concentration detecting element comprising an inner electrode provided at a position facing the outer electrode via a solid electrolyte, at least a surface of the outer electrode provided for oxygen concentration detection is made of a gas-permeable porous material. An electrically insulating first insulating layer is provided, and further, an electrically insulating second insulating layer is provided outside the first insulating layer. A heater layer is provided between the insulating layer and the second insulating layer, and a gas non-permeable layer having lower gas permeability than the first insulating layer is provided on at least the surface of the heater layer. In the oxygen concentration detecting element.

The operation of the present invention will be described below. In the oxygen concentration detecting element according to the present invention, a heater layer is provided between the first insulating layer and the second insulating layer. A gas-impermeable layer having a lower gas permeability than the first insulating layer is provided on at least the outer surface of the heater layer. This makes it difficult for the gas to be measured introduced from the second insulating layer to come into contact with the heater layer, thereby reducing the adsorption of oxygen in the gas to be measured to the heater layer. It can reach the electrodes. For this reason, the oxygen concentration detecting element can detect the fluctuation of the oxygen concentration of the gas to be measured more quickly than the element having no gas non-permeable layer.

Further, the distance between the heater layer and the solid electrolyte is at most several hundred μm. Therefore, much of the heat generated in the heater layer can be quickly conducted to the outer electrode side. Therefore, it is possible to obtain an oxygen concentration detecting element having excellent rapid heat property. Further, the heater layer is not exposed on the surface of the oxygen concentration detecting element, and is covered by the second insulating layer. Therefore, the heat generated in the heater layer can be suppressed from being released to the outside.

As described above, according to the present invention, it is possible to provide an oxygen concentration detecting element which is excellent in quick heat property and excellent in response.

In the oxygen concentration detecting element, the solid electrolyte may be provided with a heater terminal for supplying electricity to the heater layer and a heater lead connected to the heater terminal. In this case, it is preferable that the gas impermeable layer is provided together with the heater lead portion.

In providing the first insulating layer, the second insulating layer, the gas impermeable layer, and the heater layer, ordinary screen printing, pad printing, and roll transfer can be performed. However, variations in the thickness of the first insulating layer, the second insulating layer, and the heater layer affect the characteristics and durability of the oxygen concentration detection element. It is preferable to print the transfer layer, the heater layer, and the second insulating layer on a transfer paper and stick the transfer paper to a solid electrolyte. This makes it possible to obtain an oxygen concentration detecting element having a small variation in the thickness of the first insulating layer and the like.

Next, it is preferable that the gas impermeable layer is coated on the entire surface of the heater layer. This makes it possible to more reliably prevent the measured gas from contacting the heater layer.

Next, it is preferable that the gas impermeable layer is made of a heat-resistant inorganic oxide having a porosity of 5% or less. This makes it possible to more reliably prevent the measured gas from contacting the heater layer. Further, a gas impermeable layer having excellent heat resistance can be obtained. When the porosity exceeds 5%, there is a possibility that a problem may occur that it is difficult to reliably suppress gas permeation. The lower the porosity, the more preferable.

Next, it is preferable that the heat-resistant inorganic oxide is glass or ceramic. As a result, the platinum in the heater layer can be protected from poisons (adhering substances) in the exhaust gas. As the glass, borosilicate glass, lead glass, or the like can be used. In addition, as the ceramic, A
l ₂ O ₃ , Al ₂ O ₃ —SiO ₂ or the like can be used.

When glass is selected as the heat-resistant inorganic oxide, it is preferable to contain a divalent element having a large ionic radius, such as Ba, Pb, Sr, Ca, and Cd. Thereby, the gas impermeable layer (heater coating layer)
Can be prevented from lowering in conductivity. When glass is selected as the heat-resistant inorganic oxide, it is preferable to use crystallized glass. Thereby, the heat resistance of the heater layer can be increased.

Next, the thickness of the gas impermeable layer is preferably 1 to 100 μm. Accordingly, it is possible to prevent the gas to be measured from contacting the heater layer and to obtain a proper diffusibility of the gas to be measured in the insulating layer. If the thickness is less than 1 μm, a uniform layer cannot be formed, and the gas to be measured may not be prevented from contacting the heater layer. On the other hand, when the thickness is larger than 100 μm, the diffusivity of the gas to be measured is hindered, and the output current of the oxygen concentration detecting element may decrease.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 Regarding an oxygen concentration detecting element according to an embodiment of the present invention,
This will be described with reference to FIGS. Note that the oxygen concentration detecting element of this example is of a limiting current type. As shown in FIG. 1, the oxygen concentration detecting element 1 of the present embodiment has a bottomed cylindrical solid electrolyte 10.
And an outer electrode 15 provided on the outer surface of the solid electrolyte 10 for contacting the gas to be measured, and an inner electrode provided on the inner surface thereof and provided at a position facing the outer electrode 15 via the solid electrolyte 10. It consists of an electrode 16.

At least a surface of the outer electrode 15 to be used for oxygen concentration detection is provided with a first insulating layer 11 made of a gas-permeable porous material and having an electrically insulating property. Outside the insulating layer 11, an electrically insulating second insulating layer 12 is provided, and between the first insulating layer 11 and the second insulating layer 12 as shown in FIG. As shown, a heater layer 13 is provided.

The entire surface of the heater layer 13 has a gas-impermeable layer 13 having a lower gas permeability than the first insulating layer 11.
9 is provided. The gas impermeable layer 139 has a thickness of 20 μm and a porosity of 1% or less. Furthermore, it is composed of borosilicate glass.

The oxygen concentration detecting element 1 will be described in detail. As shown in FIG. 1, the solid electrolyte 10 includes a front end portion 101 provided with the outer electrode 15 in a strip shape, and a body portion 102 having a diameter larger than the front end portion 101. Further, a flange portion 19 is formed at the center of the body portion 102 so as to protrude outward in the radial direction. In addition, the solid electrolyte 10
Are provided with an outer electrode lead portion 150 and an outer electrode terminal portion 151 extending from the outer electrode 15.

The heater layer 13 is, as shown in FIG.
The first insulating layer 11 is provided on the outer electrode 15. Also, as shown in FIGS. 1 and 3, heater terminals 131 and 132 connected to the heater layer 13 via heater leads 130 are provided on the body 102 of the solid electrolyte 10. As shown in FIGS. 1 and 2, the gas impermeable layer 139 is provided on the entire surface of the heater layer 13 and also on the entire surface of the heater lead portion 130.

As shown in FIGS. 1 and 3, the widths of the heater lead portion 130 and the heater terminal portions 131 and 132 are formed wider than the heater layer 13. Further, the heater terminal portions 131 and 132 are terminal portions forming one heater layer 13, and one of the heater terminal portions 13 and 132.
A positive potential is applied to 1 and a negative potential is applied to the other heater terminal 132. The first insulating layer 21 and the second insulating layer 2
2 is provided up to above the flange 19 in the solid electrolyte 10.

Next, an oxygen concentration detector 2 including the oxygen concentration detection element 1 according to this embodiment will be described. As shown in FIG. 4, the oxygen concentration detector 2 includes a housing 20 for holding and fixing the oxygen concentration detection element 1 and the housing 20.
And element protection covers 231 and 232 provided at the lower end of the housing 20 to protect the lower portion of the oxygen concentration detecting element 1 and an atmosphere-side cover 241 provided at the upper end of the housing 20.
242 and 243.

The measured gas chamber 23 is surrounded around the oxygen concentration detecting element 1 by the element protecting covers 231 and 232.
9 are formed, and a plurality of measured gas inlets 230 and 233 are provided on the side surface thereof. The atmosphere side cover 24
1 is caulked and fixed to the housing 20 via a metal ring 215. In addition, the atmosphere side cover 24
2 is caulked and fixed to the atmosphere side cover 241, and the atmosphere side cover 243 is caulked and fixed to the atmosphere side cover 242.

The oxygen concentration detecting element 1 is provided with a flange 19
, Is supported via a washer 211 on a tapered portion provided inside the housing 20. A talc 212, a pad 213, and an insulator 214 are provided between the upper surface of the flange portion 19 and the housing 20, and hermetically sealed. The above-mentioned atmosphere side cover 2
The lower end of 41 is in contact with the insulator 214.

The output extraction path of the oxygen concentration detecting element 1 will be described. As shown in FIG.
In the above, the outer electrode 15 has an outer electrode lead 1
An outer electrode terminal portion 151 is provided via 50. The output of the oxygen concentration detecting element 1 is taken out to the outside by an output taking out part 163 attached to the outer electrode terminal part 151. The output extraction section 163 is connected to the outer electrode terminal section 15.
1 and a terminal piece which is electrically connected to the contact piece.

On the other hand, in the solid electrolyte 10, the inner electrode 16 is also provided with an inner electrode terminal via an inner electrode lead. The inner electrode lead and the inner electrode terminal are formed on the inner surface of the solid electrolyte 10.
The inner electrode terminal is provided separately from the outer electrode terminal 151 of the outer electrode, and the output extraction portion 164 is connected to the oxygen concentration detecting element 1 so as to contact the inner electrode terminal.
Installed for The output extraction portion 164 is a component separate from the output extraction portion 163 attached so as to be in contact with the outer electrode terminal portion 151 of the outer electrode 15.

Next, an energization path for the heater layer 13 will be described. As shown in FIG.
0, the heater layer 13 has a heater lead 130
And heater terminal portions 131 and 132 connected through the terminals. The energization of the heater layer 13 is performed by applying positive and negative energization terminals 161 and 16 to the heater terminal portions 131 and 132.
2 is carried out. The energizing terminals 161 and 162 are connected to the heater terminals 131 and 1 respectively.
32, and lead portions 166 and 167 which are electrically connected to the contact piece.

The output wires 163 and 164 and the current-carrying terminals 161 and 162 are connected to the lead wires 171 respectively.
To 174 are connected. The respective lead wires 171 to 174 are connected to the atmosphere side cover 2 of the oxygen concentration detector 2.
Via the inside of 41-243, it is connected to the connector 29 provided outside. The oxygen concentration detector 2 is attached to an exhaust system in an automobile internal combustion engine by a screw 201 provided on the housing 20.

Next, a method of manufacturing the oxygen concentration detecting element 1 will be described. First, a raw material powder such as ZrO _{2 is} subjected to pressure molding, and then fired at a temperature of 1400 to 1600 ° C. to obtain a bottomed cylindrical solid electrolyte 10. An inner electrode 16, an inner electrode lead, an inner electrode terminal, an outer electrode 15, an outer electrode lead 150, and an outer electrode are formed on the inner and outer surfaces of the solid electrolyte 10 by sputtering or plating of a noble metal such as Pt. The terminal part 151 is formed. Thereafter, a powder of magnesia-alumina spinel, which is a heat-resistant metal oxide, is plasma-sprayed on the outer surface above the flange portion 19 of the solid electrolyte 10 and the surface of the outer electrode 15, thereby forming the first insulating layer 11 by plasma spraying. Form.

Next, a paste a containing platinum for forming the heater layer 13 and the like is prepared. At the same time, a paste b containing borosilicate glass for forming the gas impermeable layer 139 is prepared. Thereafter, paste b is applied to the side surface of the solid electrolyte 10 so as to have the shape shown in FIG. 3 when developed on a plane. This time, paste a is applied to the surface of paste b. Further, paste b is applied to the surface of paste a,
As a whole, the sectional shape shown in FIG.

Thereafter, heat treatment is performed at a temperature of 900 to 1100 ° C. to form the heater layer 13, the heater lead 130, the heater terminal 131, and the gas impermeable layer 139. Next, the same heat-resistant metal oxide powder as used when forming the first insulating layer 11 is plasma-sprayed on the surfaces of the gas non-permeable layer 139 and the first insulating layer 11. Thereby, the second insulating layer 12 is formed. Thus, the oxygen concentration detecting element 1 according to the present example is obtained.

Next, the performance of the oxygen concentration detecting element 1 according to this embodiment will be described with reference to Table 1. Sample 1 shown in Table 1
Reference numerals 4 and 7 denote oxygen concentration detecting elements 1 according to this embodiment. However, the thickness and porosity of the gas impermeable layer 139 are different from each other. The sample 5 is the oxygen concentration detecting element 1 according to the present embodiment.
The heater layer 13 is sandwiched between the first insulating layer 11 and the second insulating layer 12. However, the gas non-permeable layer 139 is not provided for the heater layer 13. The sample 9 is the oxygen concentration detecting element 9 having the rod-shaped heater shown in the prior art (see FIGS. 10 and 11). The heater 99 is made of silicon nitride.

Next, the performance evaluation will be described in detail. The above performance evaluation was performed from three points of “RL responsiveness”, “LR responsiveness”, and “output current”. In the evaluation of the above "RL responsiveness" and "LR responsiveness", the oxygen concentration detecting elements according to the samples 1 to 9 were mounted on the oxygen concentration detector shown in FIG. Attach to exhaust system. And the above engine is 1100rpm
A / F is changed to 14 by changing the injector injection at m
To 15 ("RL responsiveness") or 15 to 14
("LR response"). At this time, the response time of the oxygen concentration detector was measured. Table 1 shows that the response time was 200 ms or less, and the case where the response time was longer than 200 ms was X.

The above-mentioned response time is defined as a change in the output current value of the oxygen concentration detector (limit current type), assuming that the change width is 100. The above A / F until reaching 63% change
It is the time required after switching.

The output current of the oxygen concentration detecting element was measured when the A / F was 18, and the output current was 6 to 8
○ if within the range of mA, × otherwise
Are shown in Table 1.

According to the table, the oxygen concentration detecting elements according to the samples 1 to 4 and 7 are “RL responsiveness” and “LR responsiveness”.
All of the "output currents" became "O", indicating that the oxygen concentration detecting element was excellent in response and detection accuracy. However, it has been found that the sample 6 having a thick gas non-permeable layer has a problem that the output current is small irrespective of the response and the detection accuracy is deteriorated.

In sample 3, the gas impermeable layer is thin,
The adsorption of oxygen in the gas to be measured to the heater layer could not be prevented, and only an oxygen concentration detecting element with poor response could be obtained. Sample 9 was an oxygen concentration detecting element in which a rod-shaped heater was inserted, and it was found that the response and the output current were excellent. However, as described in the prior art, the oxygen concentration detecting element has poor quick heat at the time of starting the engine.

FIG. 5 shows the oxygen concentration detecting element 1 (sample 1 in Table 1) according to the present embodiment and the oxygen concentration detecting element 9 (sample 8 in Table 1) in which a conventional rod-shaped heater 99 is inserted. The relationship established between the limit current and the air-fuel ratio was shown. According to the figure, it was found that there was almost no difference in characteristics between the present example and the conventional example.

FIG. 7A shows the oxygen concentration detecting element 1 (sample 1 in Table 1) and the gas impermeable layer 1 according to this example.
FIG. 7B shows the output waveform of the oxygen concentration detecting element having no 39 (sample 5 in Table 1) with respect to the timing of A / F switching. According to the figure, it was found that the device using the oxygen concentration detecting element 1 according to the present example suppressed the adsorption of oxygen by the platinum of the heater layer, and there was no delay in response when a stoichiometric condition was sandwiched. .

Next, the operation and effect of this embodiment will be described. In the oxygen concentration detecting element 1, the first insulating layer 1
A heater layer 13 is provided between the first and second insulating layers 12. A gas impermeable layer 139 is provided on the entire surface of the heater layer 13. Thereby, the second insulating layer 1
The gas to be measured introduced from 2 can be prevented from contacting the heater layer 13. Therefore, oxygen in the gas to be measured can reach the outer electrode 15 without being adsorbed by the heater layer 13. For this reason, the oxygen concentration detecting element 1 can quickly detect a change in the oxygen concentration of the gas to be measured.

The distance between the heater layer 13 and the solid electrolyte 10 is at most several hundred μm. Therefore, much of the heat generated in the heater layer 13 can be quickly conducted to the outer electrode 15. Therefore, it is possible to obtain the oxygen concentration detecting element 1 which is excellent in quick heat property. Further, the heater layer 13 is not exposed on the surface of the oxygen concentration detecting element 1 and is covered by the second insulating layer 12. Therefore, it is possible to suppress the heat generated in the heater layer 13 from being released to the outside.

As described above, according to the present embodiment, it is possible to provide an oxygen concentration detecting element which is excellent in quick heat property and excellent in responsiveness.

The oxygen concentration detecting element of this embodiment described above is a limiting current type oxygen concentration detecting element. As shown in FIG. 6, even in an oxygen concentration electromotive force type oxygen concentration detecting element having a characteristic that changes stepwise with a stoichiometric air-fuel ratio as a boundary,
A heater layer as in this example can be provided. This oxygen concentration detecting element also has the same function and effect as described above.

Further, in the oxygen concentration detecting element 1 of this embodiment, the gas non-permeable layer 139 is provided on the entire surface of the heater layer 13. However, as shown in FIG.
8B, the gas non-permeable layer 139 may be provided only in a portion in contact with the second insulating layer 12 into which the gas to be measured is introduced, as shown in FIG.
Further, as shown in FIG. 9, a gas non-permeable layer 139 may be provided so as to sandwich the heater layer 13.

[0054]

[Table 1]

[Brief description of the drawings]

FIG. 1A is a left side view and FIG. 1B is a right side view of an oxygen concentration detecting element according to a first embodiment.

FIG. 2 is a cross-sectional view of a main part of the oxygen concentration detecting element according to the first embodiment.

FIG. 3 is a planar development explanatory view showing the shapes of a heater layer and a gas non-permeable layer in the first embodiment.

FIG. 4 is an explanatory sectional view of an oxygen concentration detector according to the first embodiment.

FIG. 5 is a diagram showing a relationship between an air-fuel ratio and a limit current of the oxygen concentration detecting element according to the present embodiment and the conventional example in the first embodiment.

FIG. 6 is a diagram showing a relationship between an air-fuel ratio and an electromotive force of an oxygen concentration electromotive force type oxygen concentration detection element according to the first embodiment.

FIGS. 7A and 7B are diagrams showing (a) an output waveform of an oxygen concentration detection element and (b) a diagram showing A / F switching timing in the first embodiment.

FIG. 8 is a cross-sectional view of a main part of another oxygen concentration detecting element according to the first embodiment.

FIG. 9 is a cross-sectional view of a main part of another oxygen concentration detecting element according to the first embodiment.

FIG. 10 is a side view of an oxygen concentration detecting element in a conventional example.

FIG. 11 is a sectional view of a main part of an oxygen concentration detecting element in a conventional example.

FIG. 12 is a sectional view of a main part of an oxygen concentration detecting element.

[Explanation of symbols]

 1,9. . . 9. oxygen concentration detecting element, . . Solid electrolyte, 11. . . 11. first insulating layer; . . 12. second insulating layer; . . 139. heater layer . . 14. gas impermeable layer; . . Outer electrode, 16. . . Inner electrode,

Claims (5)

[Claims] 1. A solid electrolyte having a bottomed cylindrical shape, an outer electrode provided on an outer surface of the solid electrolyte and in contact with a gas to be measured,
An oxygen concentration detecting element provided on the inner surface thereof and comprising an inner electrode provided at a position facing the outer electrode via the solid electrolyte, wherein at least a surface of the outer electrode provided for oxygen concentration detection is provided. A first insulating layer made of gas-permeable porous material and having an electrically insulating property, and a second insulating layer having an electrically insulating property is provided outside the first insulating layer. A heater layer is provided between the first insulating layer and the second insulating layer, and at least a surface of the heater layer has a gas permeability lower than that of the first insulating layer. An oxygen concentration detecting element comprising a transmission layer. 2. The oxygen concentration detecting element according to claim 1, wherein the gas non-permeable layer covers the entire surface of the heater layer. 3. The oxygen concentration detecting element according to claim 1, wherein the gas impermeable layer is made of a heat-resistant inorganic oxide having a porosity of 5% or less. 4. The oxygen concentration detecting element according to claim 3, wherein the heat-resistant inorganic oxide is glass or ceramic. 5. The method according to claim 1, wherein:
An oxygen concentration detecting element, wherein the thickness of the gas impermeable layer is 1 to 100 μm.