Gas sensing element and vehicle

Abstract

The utility model discloses a gas sensing element and a vehicle, the gas sensing element comprises a base body and a protective layer at least covering the base body, the protective layer comprises an internal protective layer, a middle protective layer and an external protective layer which are stacked in sequence; the internal protection layer is close to the base body, and the external protection layer is far away from the base body; the thermal expansion coefficient of the internal protection layer is alpha 1, the thermal expansion coefficient of the matrix is alpha, and alpha 1 is larger than alpha and smaller than 13 * 10 <-6 >. K <-1 >. The gas sensing element has higher stability.

Description

Technical Field

[0001] The utility model relates to the field of gas sensor elements, in particular to a gas sensor element and a vehicle. Background Art

[0002] The oxygen gas sensor element is an important component of the engine electronic fuel injection system and a key element for automobile exhaust emission control. This gas sensor element is made of a solid electrolyte stack with at least one pair of metal electrodes. Usually, the solid electrolyte is a zirconium oxide solid electrolyte, which needs to be above 350°C to have oxygen ion conductivity. Therefore, a pre-buried heater is required in the solid electrolyte to quickly heat up the oxygen sensor element. In the process of rapid heating of the gas sensor element, a large amount of heat is quickly transferred from the solid electrolyte matrix of the gas sensor element to the protective layer, and the protective layer is prone to fatigue cracks, which reduces the stability of the protective layer and gradually loses its original protective function. In addition, when the condensed water in the measured gas hits the surface of the gas sensor element with the high-speed jet of gas, a thermal shock caused by local extreme cold will occur, which will induce cracks in the gas sensor element. Utility Model Content

[0003] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a gas sensor element and a vehicle, which are used to solve the problem in the prior art that the protective layer of the gas sensor element is prone to fatigue cracks and reduced stability when subjected to thermal shock.

[0004] To achieve the above-mentioned object and other related objects, one aspect of the utility model is to provide a gas sensor element, the gas sensor element comprising a substrate and a protective layer at least partially covering the substrate, the protective layer comprising an inner protective layer, an intermediate protective layer and an outer protective layer stacked in sequence; the thermal expansion coefficient of the inner protective layer is α1, the thermal expansion coefficient of the substrate is α, and α<α1<13×10 -6 ·k -1 .

[0005] Preferably, the difference between the thermal expansion coefficient α1 of the inner protective layer and the thermal expansion coefficient α of the substrate is at most 3×10 -6 ·k -1 .

[0006] Preferably, the thermal expansion coefficients of the inner protective layer, the middle protective layer, and the outer protective layer are α1, α2, and α3, respectively, satisfying α3<α2<α1.

[0007] Preferably, the total thickness of the protective layer is less than 1 mm.

[0008] Preferably, the thickness of the inner protective layer and the outer protective layer are both less than 300 μm, and the thickness of the intermediate protective layer is less than 400 μm.

[0009] Preferably, the intermediate protective layer comprises at least two sub-layers.

[0010] Preferably, the intermediate protective layer includes a first intermediate protective layer and a second intermediate protective layer stacked in sequence; the first intermediate protective layer is close to the inner protective layer, and the second intermediate protective layer is far away from the inner protective layer.

[0011] Preferably, the protective layer includes an inner protective layer, a first intermediate protective layer, a second intermediate protective layer and an outer protective layer stacked in sequence.

[0012] Preferably, the thermal expansion coefficient of the first intermediate protective layer is α4, and the thermal expansion coefficient of the second intermediate protective layer is α5, where α4>α5.

[0013] Preferably, the thickness of the first intermediate protective layer and the second intermediate protective layer are both less than 200 μm.

[0014] Preferably, at least one of the protective layers has a porous structure.

[0015] Preferably, each layer in the protective layer has a porous structure, and the porosity of each layer decreases layer by layer in a direction away from the substrate.

[0016] Preferably, the porosity of the inner protective layer is 30-60%, the porosity of the first intermediate protective layer is 30-50%, the porosity of the second intermediate protective layer is 20-40%, and the porosity of the outer protective layer is 15-30%.

[0017] Preferably, the gas sensing element is an oxygen sensor.

[0018] A second aspect of the utility model provides a vehicle, wherein the vehicle comprises the gas sensor element according to the first aspect of the utility model.

[0019] As described above, the utility model has the following beneficial effects: the utility model limits the thermal expansion coefficient of the inner protective layer in the gas sensor element protective layer to be greater than the thermal expansion coefficient of the substrate and less than 13×10 -6 ·k -1 , thereby preventing the substrate from expanding outwards when heated by the protective layer, further avoiding fatigue cracks and ensuring that the protective layer has better stability during the heating stage of the gas sensor element.

[0020] Additional aspects and advantages of the present invention will be given in part in the following description, and in part will become apparent from the following description, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0022] Figure 1 Schematic diagram of a top view of a gas sensor element in one embodiment of the utility model.

[0023] Figure 2 for Figure 1 Cross-sectional view of the gas sensing element along the AA direction.

[0024] Figure 3 This is a partial enlarged view of the protective layer structure of the gas sensor element according to one embodiment of the utility model.

[0025] Reference numerals:

[0026] 100-gas sensing element, 1-first electrode, 2-gas detection channel, 3-first solid electrolyte layer, 4-second electrode, 5-pump battery cell, 6-detection chamber, 7-second solid electrolyte layer, 8-third electrode, 9-third solid electrolyte layer, 10-fourth electrode, 11-Nernst battery cell, 12-fifth solid electrolyte layer, 13-fifth electrode, 14-insulating layer, 15-sixth solid electrolyte layer, 16-heating unit, 17-diffusion barrier, 18-fourth solid electrolyte layer, 19-reference gas channel, 20-protective layer, 21-inner protective layer, 22-intermediate protective layer, 221-first intermediate protective layer, 222-second intermediate protective layer, 23-outer protective layer. DETAILED DESCRIPTION

[0027] The embodiments of the utility model will be described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the utility model, and cannot be understood as limiting the utility model. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0028] The term "first" or "second" in the specification and claims of this application may include one or more of the features explicitly or implicitly. In the description of this utility model, unless otherwise specified, "multiple" means two or more. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / " generally means that the objects connected before and after are in an "or" relationship.

[0029] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0030] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] Combine the following Figure 1-Figure 3 The gas sensing element described in the embodiment of the present utility model is described.

[0032] like Figure 1-Figure 2As shown, in one embodiment of the utility model, the gas sensor element 100 can be an oxygen sensor. The gas sensor element 100 includes a gas sensor element substrate and a protective layer at least partially covering the surface of the substrate. Specifically, the gas sensor element 100 is composed of a functional area consisting of a detection unit and a heating unit 16 having at least a pair of electrodes on a solid electrolyte substrate, and the surface of the part in contact with the gas detection channel 2 outside the functional area is covered with a protective layer 20. Among them, the functional area is formed by stacking and co-firing the detection unit and the heating unit 16, and the detection unit includes a pump battery unit 5 and a Nernst battery unit 11. The protective layer 20 can separate the functional area of ​​the gas sensor element 100 from the water in the detected gas, prevent moisture from contacting the functional area, thereby avoiding the occurrence of cracking of the solid electrolyte matrix or abnormal signal output caused by the local temperature reduction of the functional area of ​​the gas sensor element 100 due to water impact.

[0033] like Figure 2 As shown, in this embodiment, the functional area of ​​the gas sensor element 100 is composed of a pump battery unit 5, a Nernst battery unit 11 and a heating unit 16, and specifically includes: a first electrode 1, a first solid electrolyte layer 3, a second electrode 4, a second solid electrolyte layer 7, a third electrode 8, a third solid electrolyte layer 9, a fourth electrode 10, a fifth solid electrolyte layer 12, a fifth electrode 13, an insulating layer 14 and a sixth solid electrolyte layer 15. Among them, the first electrode 1, the first solid electrolyte layer 3 and the second electrode 4 constitute the pump battery unit 5; the third electrode 8, the third solid electrolyte layer 9 and the fourth electrode 10 constitute the Nernst battery unit 11; the fifth solid electrolyte layer 12, the fifth electrode 13, the insulating layer 14 and the sixth solid electrolyte layer 15 constitute the heating unit 16.

[0034] In this embodiment, the heating unit 16 is used to heat the gas sensor element 100, so that the gas sensor element 100 is heated rapidly, wherein the fifth electrode 13 is embedded in the insulating layer 14, and is connected to an external controller through a lead wire to realize heating control, so that the functional area of ​​the gas sensor element 100 is quickly heated to a normal working temperature. The material of the insulating layer 14 can be aluminum oxide.

[0035] In this embodiment, the first solid electrolyte layer 3, the second solid electrolyte layer 7, the third solid electrolyte layer 9, the fourth solid electrolyte layer 18, the fifth solid electrolyte layer 12 and the sixth solid electrolyte layer 15 can all be formed by yttrium-doped zirconium oxide or scandium-doped zirconium oxide, and are formed into a solid electrolyte matrix of the gas sensor element 100 by stacking and co-firing, wherein the molar fraction of yttrium or scandium can be optionally between 3 mol% and 10 mol%.

[0036] In this embodiment, the first electrode 1, the second electrode 4, the third electrode 8, the fourth electrode 10 and the fifth electrode 13 can all be formed of platinum electrodes made of metal platinum and connected to an external controller through leads. The first electrode 1 is in contact with the gas to be detected, while the fourth electrode 10 is in contact with the atmosphere or the reference gas. Since the third electrode 8, the third solid electrolyte layer 9 and the fourth electrode 10 form a Nernst battery unit 11, when the oxygen concentration difference on the third electrode 8 and the fourth electrode 10 is inconsistent, a potential difference, namely the Nernst potential difference, will be generated on the two electrodes. At this time, the pump battery unit 5 will adjust the pump current under the control of the vehicle electronic control system according to the size of the Nernst potential difference, thereby achieving real-time control of the air-fuel ratio of the engine.

[0037] In this embodiment, the protective layer 20 includes an inner protective layer 21, an intermediate protective layer 22 and an outer protective layer 23 stacked in sequence; the inner protective layer 21 is close to the substrate, and the outer protective layer 23 is far away from the substrate; the thermal expansion coefficient of the inner protective layer 21 is α1, and the thermal expansion coefficient of the substrate is α, satisfying α<α1<13×10 -6 ·k -1 If the thermal expansion coefficient of the internal protective layer 21 is smaller than the thermal expansion coefficient of the substrate, fatigue cracks are likely to occur in the internal protective layer 21 as the heating cycle inside the gas sensor element increases.

[0038] In this embodiment, the thermal expansion coefficients α1, α2 and α3 of the inner protective layer 21, the middle protective layer 22 and the outer protective layer 23 satisfy α3<α2<α1; at the same time, if the thermal expansion coefficient α2 of the middle protective layer 22 is greater than the thermal expansion coefficient α of the substrate, the middle protective layer 22 will expand greatly, thereby generating shear stress inside the middle protective layer 22. In order to avoid the above situation, the thermal expansion coefficients of the substrate, the inner protective layer 21, the middle protective layer 22 and the outer protective layer 23 satisfy α3<α2<α<α1<13×10 -6 ·k -1 This is because if the thermal expansion coefficient of the protective layer 20 is the same from the inside to the outside, when the temperature of the outer protective layer 23 located on the outside of the protective layer 20 drops suddenly when it encounters water impact, it will cause a large contraction; while the inner protective layer 21 located on the inside of the protective layer 20 contacts the substrate and absorbs the heat transferred from the substrate to the outside, which will cause a large degree of expansion. At this time, the difference in expansion and contraction between the inside and outside of the protective layer 20 is large, the stress is unbalanced, and cracks are easily generated inside the protective layer. Therefore, when the thermal expansion coefficients of the substrate, the inner protective layer 21, the middle protective layer 22 and the outer protective layer 23 satisfy α3<α2<α<α1<13×10 -6 ·k -1When the thermal expansion coefficient α1 of the inner protective layer 21 is greater than the thermal expansion coefficient α of the substrate, the protective layer 20 can expand synchronously with the substrate or maintain a similar expansion trend during the heating process of the gas sensor element, avoiding compressive stress on the protective layer 20 due to the expansion trend of the substrate being greater than the expansion trend of the protective layer 20; the thermal expansion coefficient α3 of the outer protective layer 23 should be less than the thermal expansion coefficient α of the substrate, so that the protective layer 20 only shrinks slightly when it is impacted by condensed water; the intermediate protective layer 22 is the buffer area of ​​the protective layer 20, and the thermal expansion coefficient α2 of the buffer area should be between the expansion coefficient α1 of the inner protective layer 21 and the expansion coefficient α3 of the outer protective layer 23, so that the expansion and contraction of the inner and outer sides of the protective layer 20 are buffered in the middle part, so that the protective layer 20 as a whole achieves temperature and thermal stress balance, and the protective layer 20 has good stability and protection.

[0039] In this embodiment, the thermal expansion coefficient α1 of the inner protective layer 21 is at most 3×10 -6 ·k -1 , that is, the difference α1-α between the thermal expansion coefficient α1 of the inner protective layer 21 and the thermal expansion coefficient α of the substrate is less than 3×10 -6 ·k -1 By controlling the difference in thermal expansion coefficients between the internal protective layer 21 and the substrate, the thermal expansion coefficient of the internal protective layer 21 is made slightly larger than that of the substrate, so that the expansion trends of the internal protective layer 21 and the substrate are kept consistent, and the internal protective layer 21 is not subjected to compressive stress generated by the expansion of the substrate. The thermal expansion coefficient of the internal protective layer 21 cannot be too large, otherwise the expansion trend of the internal protective layer 21 is significantly larger than that of the substrate and tensile stress is generated inside the internal protective layer 21, which may cause the internal protective layer 21 to rupture or peel off from the substrate.

[0040] In addition, the protective layer 20 should have a suitable thickness so that there is a certain buffering room for the expansion or contraction of the protective layer 20. Secondly, after the protective layer 20 is applied to the gas sensor element 100, it will increase the overall thermal mass of the gas sensor element 100, so the thickness of the protective layer 20 cannot be too thick, otherwise it will prolong the ignition time of the gas sensor element 100. In this embodiment, the total thickness of the protective layer 20 is less than 1mm, and the thickness of the inner protective layer 21 and the outer protective layer 23 are both less than 300μm, and the thickness of the intermediate protective layer 22 is less than 400μm. The thickness within this range is conducive to the gas sensor element having good performance.

[0041] The buffer zone inside the protective layer 20, that is, the middle protective layer 22, is to balance the expansion and contraction differences and temperature differences between the inside and outside of the protective layer 20, balance the thermal stress generated by the differences inside the protective layer 20, improve the stability of the protective layer 20, and make it have excellent protective characteristics. The buffer zone inside the protective layer 20 can be divided into several layers with different thermal expansion coefficients. The more layers there are, the more obvious the buffering effect will be. However, too many layers will make the manufacturing of the protective layer 20 more complicated and difficult. Therefore, in order to make the protective layer 20 have better performance, the middle protective layer of the protective layer 20 should be no less than two layers, that is, the number of layers of the protective layer 20 as a whole should be no less than 4 layers. In this way, it will not cause greater manufacturing difficulty, and the thermal stress inside and outside the protective layer 20 can be balanced in the middle protective layer 22, which improves the stability of the protective layer 20 and its protective performance.

[0042] In this embodiment, the intermediate protective layer 22 includes at least two sub-layers, that is, the protective layer 20 includes at least 4 layer structures. In some embodiments, the intermediate protective layer 22 includes two sub-layers, that is, the protective layer 20 includes an inner protective layer 21, a first intermediate protective layer 221, a second intermediate protective layer 222 and an outer protective layer 23. Moreover, the thermal expansion coefficient α4 of the first intermediate protective layer 221 should be greater than the thermal expansion coefficient α5 of the second intermediate protective layer 222. The thickness of the inner protective layer 21 and the outer protective layer 23 is less than 300 μm; the thickness of the first intermediate protective layer 221 and the second intermediate protective layer 222 is less than 200 μm. After the buffering of the first intermediate protective layer 221 and the second intermediate protective layer 222, the difference in expansion or contraction between the inner protective layer 21 and the outer protective layer 23 has become very small. In this case, the protective layer 20 will not produce cracks due to the inconsistent contraction or expansion between the inside and the outside, thereby improving the stability and protection of the protective layer 20.

[0043] In this embodiment, the protective layer 20 includes at least one layer with a porous structure. In some embodiments, the inner protective layer 21, the first intermediate protective layer 221, the second intermediate protective layer 222 and the outer protective layer 23 included in the protective layer 20 each have a porous structure, and the porosity of each layer decreases layer by layer along the direction away from the substrate. Specifically, the porosity of the inner protective layer 21 is 30-60%, the porosity of the first intermediate protective layer 221 is 30-50%, the porosity of the second intermediate protective layer 222 is 20-40%, and the porosity of the outer protective layer 23 is 15-30%. This structure can optimize the transmission of gas in the protective layer 20, so that the gas can pass through the protective layer 20 more effectively and participate in the electrochemical reaction; at the same time, this design can also improve the corrosion resistance of the protective layer 20 and extend the service life of the gas sensor element.

[0044] In addition, in this embodiment, the material of the inner protective layer 21 can be at least one of zirconium oxide, aluminum titanate or forsterite; the material of the intermediate protective layer 22 (i.e., the first inner protective layer 221 and the second inner protective layer 222) can be at least one of magnesium aluminum spinel, andalusite or alumina; the material of the outer protective layer 23 can be at least one of mullite, zircon or cordierite. Different materials have different thermal expansion coefficients. The present invention does not specifically limit the material of the protective layer 20, and it can be adjusted according to actual needs.

[0045] The utility model also provides a vehicle, comprising the gas sensor element in the above embodiment.

[0046] The technical solution of the present application is described in detail below in conjunction with specific embodiments.

[0047] Example 1

[0048] A gas sensor element comprises an inner protective layer 21, a first intermediate protective layer 221, a second intermediate protective layer 222 and an outer protective layer 23, wherein the thermal expansion coefficient of the solid electrolyte matrix is ​​9.6×10 -6 / ℃; the internal protective layer 21 is zirconium oxide, and the thermal expansion coefficient is 10.1×10 -6 / ℃, porosity of 50% and thickness of 150μm; the first intermediate protective layer 221 is alumina, with a porosity of 43% and a thickness of 50μm; the second intermediate protective layer 222 is magnesium aluminum spinel, with a porosity of 36% and a thickness of 50μm; the outer protective layer 23 is zircon, with a porosity of 28% and a thickness of 150μm.

[0049] Example 2

[0050] A gas sensor element, comprising an inner protective layer 21, a first intermediate protective layer 221 and an outer protective layer 23, wherein the thermal expansion coefficient of the solid electrolyte matrix is ​​9.6×10 -6 / ℃; the internal protective layer 21 is zirconium oxide, and the thermal expansion coefficient is 10×10 -6 / ℃, porosity of 55%, thickness of 200μm; the first intermediate protective layer 221 is alumina, porosity of 43%, thickness of 50μm; the outer protective layer 23 is zircon, porosity of 28%, thickness of 200μm.

[0051] Comparative Example 1

[0052] A gas sensing element without any protective layer applied.

[0053] Comparative Example 2

[0054] A gas sensor element, comprising an inner protective layer 21, a solid electrolyte matrix with a thermal expansion coefficient of 9.6×10 -6 / ℃; the internal protective layer 21 is zirconium oxide, and the thermal expansion coefficient is 10.3×10 -6 / ℃, porosity is 41% and thickness is 260μm.

[0055] Comparative Example 3

[0056] A gas sensor element, comprising an inner protective layer 21 and an outer protective layer 23, wherein the thermal expansion coefficient of the solid electrolyte matrix is ​​9.6×10 -6 / ℃; the internal protective layer 21 is zirconium oxide, and the thermal expansion coefficient is 10.3×10 -6 / ℃, porosity of 40%, thickness of 200μm; the outer protective layer 23 is zircon, with a porosity of 26% and a thickness of 100μm.

[0057] Comparative Example 4

[0058] A gas sensor element comprises an inner protective layer 21, a first intermediate protective layer 221, a second intermediate protective layer 222 and an outer protective layer 23, wherein the thermal expansion coefficient of the solid electrolyte matrix is ​​9.6×10 -6 / ℃; the internal protective layer 21 is zirconium oxide, and the thermal expansion coefficient is 9.8×10 -6 / ℃, porosity of 60% and thickness of 300μm; the first intermediate protective layer 221 is alumina, with a porosity of 50% and a thickness of 200μm; the second intermediate protective layer 222 is magnesium aluminum spinel, with a porosity of 40% and a thickness of 200μm; the outer protective layer 23 is zircon, with a porosity of 30% and a thickness of 300μm.

[0059] Comparative Example 5

[0060] A gas sensor element comprises an inner protective layer 21, a first intermediate protective layer 221, a second intermediate protective layer 222 and an outer protective layer 23, wherein the thermal expansion coefficient of the solid electrolyte matrix is ​​9.6×10 -6 / ℃; the internal protective layer 21 is zirconium oxide, and the thermal expansion coefficient is 10.3×10 -6 / ℃, porosity of 30% and thickness of 400μm; the first intermediate protective layer 221 is alumina, with a porosity of 30% and a thickness of 220μm; the second intermediate protective layer 222 is magnesium aluminum spinel, with a porosity of 20% and a thickness of 210μm; the outer protective layer 23 is zircon, with a porosity of 15% and a thickness of 400μm.

[0061] Comparative Example 6

[0062] A gas sensor element, comprising an inner protective layer 21, a solid electrolyte matrix with a thermal expansion coefficient of 10.3×10 -6 / ℃; the internal protective layer is zirconium oxide, and the thermal expansion coefficient is 9.7×10 -6 / ℃, porosity is 60% and thickness is 260μm.

[0063] In order to support the beneficial effects of the present application, the following performance tests were performed on the gas sensor elements of the above embodiments and comparative examples:

[0064] (1) Water shock test

[0065] The basis for judging the failure of the protective layer during the working stage of the oxygen sensor:

[0066] A 12V DC power is applied to the heating unit to heat the oxygen sensor. After 1 minute, the oxygen sensor is in a stable state. About 50μL of water is sprayed onto the protective layer of the oxygen sensor. The internal resistance of the oxygen sensor is then measured. If the internal resistance exceeds the variation range of 5%, it is determined that cracks have occurred in the solid electrolyte body of the oxygen sensor. The number of water spraying times when the cracks occur is recorded, which is the effective number of times the oxygen sensor resists water shock.

[0067] The test results are shown in Table 1, where √ represents that the sample has this layer, and × represents that the sample does not have this layer.

[0068] (2) Ignition time test

[0069] The ignition time refers to the time it takes for the oxygen sensor to reach a stable working state from the beginning of heating. Generally speaking, the thicker the protective layer of the oxygen sensor, the longer the ignition time.

[0070] The test results are shown in Table 1, where √ represents that the sample has this layer, and × represents that the sample does not have this layer.

[0071] (3) Protective layer peeling test

[0072] The oxygen sensor element is fixed on the test bench. Each thermal cycle is powered by 14V DC for 1 minute, and then powered off and air-cooled for 2 minutes. After 5000 thermal cycles, a drop test is performed. The drop height is 500mm, the drop ground is a cement floor, and the drop method is that the length direction of the oxygen sensor is parallel to the ground. The number of drops when the protective layer falls off is recorded.

[0073] The test results are shown in Table 2, where √ represents that the sample has this layer, and × represents that the sample does not have this layer.

[0074] Table 1

[0075]

[0076] Table 2

[0077]

[0078]

[0079] The above results show that the test results of each embodiment are good, the water shock resistance is strong, the ignition time is short, and the stability is obviously better than the comparative example. The gas sensor element of the utility model has good stability.

[0080] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0081] Although the embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A gas sensing element, It is characterized in that The gas sensor element comprises a substrate and a protective layer at least partially covering the substrate, wherein the protective layer comprises an inner protective layer, an intermediate protective layer and an outer protective layer stacked in sequence; the inner protective layer is close to the substrate, and the outer protective layer is far away from the substrate; the thermal expansion coefficient of the inner protective layer is α 1 , the thermal expansion coefficient of the substrate is α, satisfying α<α 1 <13×10 -6 ·k -1 .

2. The gas sensor element according to claim 1, It is characterized in that The thermal expansion coefficient of the inner protective layer is α 1 The difference in thermal expansion coefficient α from the substrate is at most 3×10 -6 ·k -1 .

3. The gas sensor element according to claim 1, It is characterized in that The thermal expansion coefficients of the inner protective layer, the middle protective layer and the outer protective layer are α 1 , α 2 and α 3 , satisfying α 3 <α 2 <α 1 .

4. The gas sensor element according to claim 1, It is characterized in that The total thickness of the protective layer is less than 1 mm.

5. The gas sensor element according to claim 1, It is characterized in that The thickness of the inner protective layer and the outer protective layer are both less than 300 μm, and the thickness of the intermediate protective layer is less than 400 μm.

6. The gas sensor element according to claim 1, It is characterized in that The intermediate protective layer includes at least two sub-layers.

7. The gas sensor element according to claim 6, It is characterized in that The intermediate protective layer includes a first intermediate protective layer and a second intermediate protective layer stacked in sequence; the first intermediate protective layer is close to the inner protective layer, and the second intermediate protective layer is far away from the inner protective layer.

8. The gas sensor element according to claim 7, It is characterized in that The protective layer includes an inner protective layer, a first intermediate protective layer, a second intermediate protective layer and an outer protective layer which are sequentially stacked.

9. The gas sensor element according to any one of claims 7 to 8, It is characterized in that The thermal expansion coefficient of the first intermediate protective layer is α 4 , the thermal expansion coefficient of the second intermediate protective layer is α 5 , α 4 ﹥α 5 .

10. The gas sensor element according to any one of claims 7 to 8, It is characterized in that The thickness of the first intermediate protective layer and the second intermediate protective layer are both less than 200 μm.

11. The gas sensor element according to any one of claims 1 or 8, It is characterized in that At least one of the protective layers has a porous structure.

12. The gas sensor element according to claim 11, It is characterized in that Each layer in the protective layer has a porous structure, and the porosity of each layer decreases layer by layer in a direction away from the substrate.

13. The gas sensor element according to claim 8, It is characterized in that The porosity of the inner protective layer is 30-60%, the porosity of the first intermediate protective layer is 30-50%, the porosity of the second intermediate protective layer is 20-40%, and the porosity of the outer protective layer is 15-30%.

14. The gas sensor element according to claim 1, It is characterized in that The gas sensing element is an oxygen sensor.

15. A vehicle, It is characterized in that The vehicle comprises the gas sensor element according to any one of claims 1-14.

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