An oxygen sensor electrode with a gradient porosity protective layer
By setting a gradient porosity protective layer on the oxygen sensor electrode, the outer layer intercepts large particulate impurities, while the inner layer regulates gas diffusion. This solves the problems of insufficient sensor response speed and accuracy in the existing technology, achieves more efficient impurity filtration and gas diffusion, and extends the service life of the sensor.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SUZHOU BOCAI GUIJIN NEW MATERIAL CO LTD
- Filing Date
- 2025-08-08
- Publication Date
- 2026-07-07
AI Technical Summary
The protective layer of existing oxygen sensor electrodes mostly adopts a single uniform porosity structure, which cannot effectively block large particulate impurities and ensure gas diffusion efficiency at the same time. This results in insufficient sensor response speed and accuracy, especially with severe performance degradation in high particulate matter emission scenarios.
A gradient porosity protective layer is adopted. The outer layer with high porosity is used to intercept large particulate impurities, while the inner layer with low porosity is used to filter small impurities and regulate the gas diffusion rate, forming a multi- or three-layer structure to relieve structural stress and ensure uniform gas diffusion.
It improves the sensor's response speed and detection accuracy, extends its service life, avoids the problems of easy clogging in high porosity and response lag in low porosity, and maintains the stability and durability of the sensor in complex exhaust gas environments.
Smart Images
Figure CN224471614U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of oxygen sensor technology, and in particular to an oxygen sensor electrode with a gradient porosity protective layer. Background Technology
[0002] As a key component in the exhaust emission control system of automobile engines, the oxygen sensor is mainly used to detect the concentration of oxides in the exhaust in real time. Its detection accuracy and response speed directly affect the optimization of engine combustion control strategy and the efficient operation of exhaust after-treatment system. It is of great significance for reducing motor vehicle pollutant emissions and meeting increasingly stringent environmental regulations (such as China VI and Euro VII standards).
[0003] As the core sensitive element of the oxygen sensor, the electrode typically operates in harsh exhaust gas environments characterized by high temperature, high humidity, and high particulate matter. Its surface is susceptible to impact, coverage, or chemical corrosion from particulate matter, leading to failure of active sites and blockage of gas diffusion channels, ultimately resulting in sensor performance degradation and shortened lifespan. To address this issue, current technologies commonly employ a ceramic protective layer on the outer surface of the electrode detection end. This porous structure achieves both gas diffusion and particulate filtration functions, balancing the sensor's response speed and long-term stability.
[0004] However, the protective layers of existing oxygen sensor electrodes mostly employ porous ceramic structures with a single uniform porosity. While high-porosity protective layers can reduce gas diffusion resistance and accelerate the diffusion rate of gases such as NOx and O2 to the electrode surface, thereby improving the sensor's response speed, the large pore size makes them unable to effectively block large particles of ash, carbon deposits, and other impurities in exhaust gases. These impurities can easily directly impact and cover the electrode surface, even clogging the pore channels. This is especially true in high-particulate-emission scenarios such as diesel engines, significantly accelerating electrode performance degradation. On the other hand, low-porosity protective layers can intercept most particles through smaller pore sizes, reducing the erosion of the electrode surface by impurities and providing better physical protection. However, the extended gas diffusion path and increased resistance reduce the diffusion efficiency of gas molecules into the electrode interior, resulting in sensor response lag and decreased detection accuracy. Summary of the Invention
[0005] This invention overcomes the shortcomings of the prior art and provides an oxygen sensor electrode with a gradient porosity protective layer.
[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows: an oxygen sensor electrode with a gradient porosity protective layer, comprising: an electrode body, wherein a gradient porosity protective layer is provided on the outer surface of the detection end of the electrode body, and the porosity of the gradient porosity protective layer is distributed in a gradient decreasing manner from the outer layer to the inner layer along the gas diffusion direction.
[0007] The gradient porosity protective layer comprises at least two layers of porous ceramic structures with different average porosities stacked along the gas diffusion direction.
[0008] In a preferred embodiment of this utility model, the gradient porosity protective layer comprises an outer layer and an inner layer sequentially along the gas diffusion direction, and the outer layer and the inner layer are integrally formed porous ceramic structures.
[0009] In a preferred embodiment of this invention, the outer layer is a filter layer used to intercept large particulate impurities in the exhaust gas; the inner layer is a diffusion regulating layer used to further filter small impurities and control the gas diffusion rate.
[0010] In a preferred embodiment of this utility model, the outer layer has a thickness of 0.1-0.3 mm, an average porosity of 60-70%, and a pore size of 30-50 μm; the inner layer has a thickness of 0.05-0.15 mm, an average porosity of 10-20%, and a pore size of 1-5 μm.
[0011] In a preferred embodiment of this utility model, the gradient porosity protective layer comprises an outer layer, a middle layer, and an inner layer sequentially along the gas diffusion direction, and the outer layer, the middle layer, and the inner layer are integrally formed porous ceramic structures.
[0012] In a preferred embodiment of this invention, the outer layer is a filter layer used to intercept large particulate impurities in the exhaust gas; the middle layer is a porosity transition layer used to filter medium-sized particles and alleviate structural stress caused by the abrupt change in porosity between the outer and inner layers; and the inner layer is a diffusion regulation layer used to further filter small impurities and control the gas diffusion rate.
[0013] In a preferred embodiment of this invention, the outer layer has a thickness of 0.1-0.3 mm, an average porosity of 60-70%, and a pore size of 30-50 μm; the middle layer has a thickness of 0.2-0.4 mm, an average porosity of 30-50%, and a pore size of 5-20 μm; and the inner layer has a thickness of 0.05-0.15 mm, an average porosity of 10-20%, and a pore size of 1-5 μm.
[0014] In a preferred embodiment of this invention, the gradient porosity protective layer is a protective sleeve or protective cap structure that covers the outer periphery of the portion of the electrode body that needs to be exposed to the gas to be measured.
[0015] In a preferred embodiment of this utility model, the layers of the gradient porosity protective layer are fixedly connected into an integral structure by high-temperature co-sintering, high-temperature resistant inorganic adhesive, or mechanical pressing with a high-temperature resistant sealing ring.
[0016] In a preferred embodiment of this invention, the inner layer of the gradient porosity protective layer is fixedly connected to the outer surface of the electrode body by a high-temperature resistant solder or a snap / thread mechanical structure.
[0017] This utility model solves the defects existing in the background technology, and has the following beneficial effects:
[0018] (1) This utility model provides an oxygen sensor electrode with a gradient porosity protective layer. By coaxially setting a gradient porosity protective layer on the outer surface of the detection end of the oxygen sensor electrode, the layer is composed of at least two layers of porous ceramic structures with different average porosities. The outer layer with higher porosity can preferentially intercept large particulate impurities in the exhaust gas, while the inner layer with lower porosity can further filter small impurities and regulate the gas diffusion rate, thereby achieving graded filtration of impurities of different particle sizes. At the same time, it ensures that the gas diffuses to the electrode surface uniformly and efficiently. Compared with the defects of the uniform porosity protective layer in the prior art, which cannot take into account both particle filtration and gas diffusion efficiency, this invention can avoid the problems of easy clogging of high porosity and response lag of low porosity, thereby effectively improving the response speed and detection accuracy of the sensor and extending its service life in complex exhaust gas environments.
[0019] (2) In this utility model, the gradient porosity protective layer can be set as a double-layer structure of an outer filter layer and an inner diffusion regulation layer, or a triple-layer structure with an intermediate porosity transition layer. The double-layer structure balances the filtration and diffusion performance through the synergistic effect of the outer layer intercepting large particles and the inner layer regulating diffusion. The transition layer in the triple-layer structure can alleviate the structural stress caused by the sudden change in porosity between the outer and inner layers, improve the structural stability of the protective layer, and reduce the risk of cracking caused by thermal expansion and contraction or mechanical vibration. Compared with a single-layer uniform porosity structure, the multi-layer structure has more advantages in filtration efficiency, gas diffusion regulation and structural durability, thereby ensuring the structural integrity of the sensor under long-term high-temperature conditions and maintaining stable detection performance. Attached Figure Description
[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments;
[0021] Figure 1 This is a schematic diagram of the electrode body and gradient porosity protective layer structure of Embodiment 1 of this utility model;
[0022] Figure 2 This is a utility model Figure 1 Enlarged structural diagram at point A in the middle;
[0023] Figure 3 This is a schematic diagram of the electrode body and gradient porosity protective layer structure of Embodiment 2 of this utility model;
[0024] Figure 4 This is a utility model Figure 3Enlarged structural diagram at point B;
[0025] In the figure: 1. Electrode body; 2. Gradient porosity protective layer; 21. Outer layer; 22. Inner layer; 23. Intermediate layer. Detailed Implementation
[0026] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. These drawings are simplified schematic diagrams, which are only used to illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.
[0027] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "setup," and "connection" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.
[0028] Example 1:
[0029] like Figure 1 and Figure 2 As shown, an oxygen sensor electrode with a gradient porosity protective layer includes: an electrode body 1, and a gradient porosity protective layer 2 is disposed on the outer surface of the detection end of the electrode body 1. The porosity of the gradient porosity protective layer 2 decreases in a gradient manner from the outer layer 21 to the inner layer 22 along the gas diffusion direction. The gradient porosity protective layer 2 includes an outer layer 21 and an inner layer 22 in sequence along the gas diffusion direction. The outer layer 21 and the inner layer 22 are integrally formed porous ceramic structures.
[0030] It should be noted that the outer layer 21 is a filter layer used to intercept large particulate impurities in the exhaust gas; the inner layer 22 is a diffusion regulation layer used to further filter small impurities and control the gas diffusion rate; the outer layer 21 has a thickness of 0.1-0.3 mm, an average porosity of 60-70%, and a pore size of 30-50 μm; the inner layer 22 has a thickness of 0.05-0.15 mm, an average porosity of 10-20%, and a pore size of 1-5 μm; there is a 5-20 μm micro-gap between the inner layer 22 and the surface of the electrode body 1, which allows the gas to form a uniform flow field at the outlet of the diffusion regulation layer, eliminates local diffusion dead zones, and ensures the consistency of the reaction rate on the electrode surface.
[0031] Specifically, by setting a gradient porosity protective layer 2 on the outer surface of the detection end of the electrode body 1, the porosity of the protective layer decreases gradually from the outer layer 21 to the inner layer 22 along the gas diffusion direction. The outer layer 21 is a filter layer that intercepts large particulate impurities in the exhaust gas, while the inner layer 22 is a diffusion regulation layer that further filters small impurities and controls the gas diffusion rate. This achieves graded filtration of impurities of different particle sizes, while ensuring that the gas diffuses uniformly and efficiently to the electrode surface. Compared with the shortcomings of the uniform porosity protective layer in the prior art, which cannot take into account both particle filtration and gas diffusion efficiency, this method can avoid the problems of easy clogging with high porosity and response lag with low porosity. This effectively improves the response speed and detection accuracy of the sensor and extends its service life in complex exhaust gas environments.
[0032] For example, the electrode body 1 can be a platinum or platinum alloy porous electrode on a YSZ (yttrium-stabilized zirconium oxide) substrate, preferably applied in an oxygen sensor of model NP400. In this sensor, the electrode body 1 serves as the working electrode, responsible for sensing changes in oxygen concentration in the exhaust gas, the catalytic reduction reaction of NOx, and generating a current signal to convert the gas concentration into an electrochemical signal, which is then output to the engine control unit to adjust the air-fuel ratio of the engine, thereby achieving more efficient combustion and lower emissions.
[0033] In this embodiment, the gradient porosity protective layer 2 is a protective sleeve or protective cap structure, covering the outer periphery of the part of the electrode body 1 that needs to be exposed to the gas to be measured; the inner layer 22 of the gradient porosity protective layer 2 is fixedly connected to the outer surface of the electrode body 1 by high-temperature resistant solder or snap / thread mechanical structure.
[0034] It should be noted that the high-temperature resistant solder is preferably a silver-copper-titanium active solder with a melting temperature higher than 800℃, which can form a metallurgical bond with the ceramic and electrode metal layers during co-sintering. The snap-fit structure can adopt an interference fit, with matching snaps and slots set on the inner layer 22 and the electrode body 1 respectively. The inner layer 22 is pressed into the electrode body 1 by external force, so that the snaps are embedded in the slots to achieve a tight connection. The threaded mechanical structure can be achieved by machining threads of the corresponding specifications, such as M6 or M8, on the inner layer 22 and the electrode body 1. The inner layer 22 is tightened onto the electrode body 1 by rotation, and an appropriate amount of high-temperature resistant thread adhesive is applied to the threaded connection to enhance the sealing and reliability of the connection.
[0035] In this embodiment, the layers of the gradient porosity protective layer 2 are fixedly connected into an integral structure by high-temperature co-sintering, high-temperature resistant inorganic adhesive, or mechanical pressing with a high-temperature resistant sealing ring.
[0036] It should be noted that the high-temperature resistant inorganic adhesive is a phosphate-based high-temperature resistant inorganic adhesive, preferably an aluminum phosphate adhesive, which has good high-temperature resistance and can maintain bonding strength in high-temperature environments above 1000℃. It also has good chemical stability and good tolerance to various components in the exhaust gas, which can effectively ensure the reliability of the connection between the layers of the gradient porosity protective layer 2.
[0037] Example 2:
[0038] like Figure 3 and Figure 4 As shown, the implementation method of this embodiment is basically the same as that of embodiment 1, except that: the gradient porosity protective layer 2 includes an outer layer 21, a middle layer 23 and an inner layer 22 in sequence along the gas diffusion direction, and the outer layer 21, the middle layer 23 and the inner layer 22 are integrally formed porous ceramic structures.
[0039] It should be noted that the outer layer 21 is a filter layer used to intercept large particulate impurities in the exhaust gas; the middle layer 23 is a porosity transition layer used to filter medium-sized particles and alleviate the structural stress caused by the abrupt change in porosity between the outer layer 21 and the inner layer 22; the inner layer 22 is a diffusion regulation layer used to further filter small impurities and control the gas diffusion rate; the outer layer 21 has a thickness of 0.1-0.3 mm, an average porosity of 60-70%, and a pore size of 30-50 μm; the middle layer 23 has a thickness of 0.2-0.4 mm, an average porosity of 30-50%, and a pore size of 5-20 μm; the inner layer 22 has a thickness of 0.05-0.15 mm, an average porosity of 10-20%, and a pore size of 1-5 μm.
[0040] Specifically, this embodiment adds an intermediate layer 23 as a porosity transition layer to the double-layer structure. The three-layer gradient design alleviates the structural stress between the high porosity of the outer layer 21 and the low porosity of the inner layer 22. Due to the buffering effect of the intermediate layer 23, the risk of cracking of the protective layer caused by the difference in thermal expansion coefficients under high-temperature conditions is reduced. Compared with the double-layer structure of Embodiment 1, this further improves the structural reliability of the sensor under temperature cycling from -40℃ to 800℃. During operation, the intermediate layer 23 not only filters medium-sized particles but also alleviates the structural stress caused by the abrupt change in porosity between the outer layer 21 and the inner layer 22. Compared with a single-layer uniform porosity structure, the multi-layer structure has advantages in filtration efficiency, gas diffusion control, and structural durability, thereby ensuring the structural integrity of the sensor under long-term high-temperature conditions and maintaining stable detection performance.
[0041] Based on the above description and the preferred embodiments of this utility model, it will be apparent to those skilled in the art that this utility model is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this utility model. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of this utility model is defined by the appended claims rather than the foregoing description, and thus all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this utility model. No reference numerals in the claims should be construed as limiting the scope of the claims.
[0042] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. An oxygen sensor electrode with a gradient porosity protective layer, comprising an electrode body (1), characterized in that: The outer surface of the detection end of the electrode body (1) is provided with a gradient porosity protection layer (2), and the porosity of the gradient porosity protection layer (2) decreases in a gradient manner from the outer layer (21) to the inner layer (22) along the gas diffusion direction. The gradient porosity protective layer (2) comprises at least two layers of porous ceramic structures with different average porosities stacked along the gas diffusion direction.
2. The oxygen sensor electrode with a gradient porosity protective layer according to claim 1, characterized in that: The gradient porosity protective layer (2) includes an outer layer (21) and an inner layer (22) in sequence along the gas diffusion direction. The outer layer (21) and the inner layer (22) are integrally formed porous ceramic structures.
3. An oxygen sensor electrode with a gradient porosity protective layer according to claim 2, characterized in that: The outer layer (21) is a filter layer used to intercept large particulate impurities in the exhaust gas; the inner layer (22) is a diffusion regulation layer used to further filter small impurities and control the gas diffusion rate.
4. An oxygen sensor electrode with a gradient porosity protective layer according to claim 2, characterized in that: The outer layer (21) has a thickness of 0.1-0.3 mm, an average porosity of 60-70%, and a pore size of 30-50 μm; the inner layer (22) has a thickness of 0.05-0.15 mm, an average porosity of 10-20%, and a pore size of 1-5 μm.
5. An oxygen sensor electrode with a gradient porosity protective layer according to claim 1, characterized in that: The gradient porosity protective layer (2) includes an outer layer (21), a middle layer (23) and an inner layer (22) in sequence along the gas diffusion direction. The outer layer (21), the middle layer (23) and the inner layer (22) are integrally formed porous ceramic structures.
6. An oxygen sensor electrode with a gradient porosity protective layer according to claim 5, characterized in that: The outer layer (21) is a filter layer used to intercept large particulate impurities in the exhaust gas; the middle layer (23) is a porosity transition layer used to filter medium-sized particles and alleviate the structural stress caused by the abrupt change in porosity between the outer layer (21) and the inner layer (22); the inner layer (22) is a diffusion regulation layer used to further filter small impurities and control the gas diffusion rate.
7. An oxygen sensor electrode with a gradient porosity protective layer according to claim 5, characterized in that: The outer layer (21) has a thickness of 0.1-0.3 mm, an average porosity of 60-70%, and a pore size of 30-50 μm; the middle layer (23) has a thickness of 0.2-0.4 mm, an average porosity of 30-50%, and a pore size of 5-20 μm; the inner layer (22) has a thickness of 0.05-0.15 mm, an average porosity of 10-20%, and a pore size of 1-5 μm.
8. An oxygen sensor electrode with a gradient porosity protective layer according to claim 1, characterized in that: The gradient porosity protective layer (2) is a protective sleeve or protective cap structure that covers the outer periphery of the electrode body (1) that needs to be exposed to the gas to be tested.
9. An oxygen sensor electrode with a gradient porosity protective layer according to claim 1, characterized in that: The gradient porosity protective layer (2) is fixedly connected into an integral structure by high-temperature co-sintering, high-temperature resistant inorganic adhesive, or mechanical pressing with a high-temperature resistant sealing ring.
10. An oxygen sensor electrode with a gradient porosity protective layer according to claim 1, characterized in that: The inner layer (22) of the gradient porosity protective layer (2) is fixedly connected to the outer surface of the electrode body (1) by high-temperature resistant solder or snap / thread mechanical structure.