An oxygen sensor and its probe subassembly

Abstract

The oxygen sensor and its probe subassembly, the probe subassembly includes a zirconium element, a shell, a ceramic part, a sealing material and a lower shield, the zirconium element is a rectangular strip; the shell is U-shaped, including an upper opening, a shell bottom, and a cylindrical hollow part, the outer surface along the central axis includes an upper opening edge, an upper fastening cylinder, a shoulder, a lower connecting threaded cylinder, and a lower shield connecting flange, the shell bottom has a shell bottom plane and a rectangular through hole located on the central axis; the upper fastening cylinder is connected to the upper shield of the oxygen sensor by a tight fit; the lower shield connecting flange is connected to the lower shield; the lower connecting threaded cylinder has a thread for connecting the interface thread of the vehicle exhaust pipe; the sealing material fills the lower part of the cylindrical hollow part; the sealing material includes 30% to 50% talcum powder, 30% to 50% glass powder and 10% to 15% magnesium stearate; the ceramic part is located at the upper part of the cylindrical hollow part, and the ceramic part is fixed by riveting the upper opening edge. The structure is simplified, and the internal leakage of the oxygen sensor can be effectively controlled, and the powder is not easy to fall off.

Description

Technical Field

[0001] The invention relates to the field of automobile parts production and manufacturing, in particular to an oxygen sensor. Background Art

[0002] Oxygen sensors are essential auto parts in the vehicle manufacturing industry. They are used to detect the oxygen content in the exhaust gas in the exhaust pipe of the automobile engine to determine the real-time air-fuel ratio of the engine. According to the different oxygen concentrations, the sensor will output different voltage signals to the engine electronic control module (ECM), which serves as an important basis for the closed-loop fuel correction and compensation control of the system. Due to the application of oxygen sensors, the engine can operate in an ideal air-fuel ratio state under most working conditions, thereby obtaining good emission characteristics and fuel economy.

[0003] The oxygen sensor uses a flat multilayer ceramic element as the basic element, in which the zirconium oxide layer is the core element. The working principle of the zirconium oxide element is equivalent to a simple solid primary battery. According to the principle of electrochemistry, there will be a potential difference between the electrodes on both sides due to the difference in oxygen ion concentration. Since the outer electrode is exposed to the exhaust gas, the oxygen ion concentration will change according to the actual working conditions, while the inner electrode is the reference air, and the oxygen ion concentration is constant. When the engine air-fuel ratio is lean, the oxygen ion concentration in the exhaust gas is relatively high, and the difference in oxygen ion concentration between the inner and outer electrodes is small, that is, the potential difference is small, and the output voltage signal of the oxygen sensor is close to 0V; conversely, when the air-fuel ratio is rich, the oxygen ion concentration in the exhaust gas is also relatively low, and the difference in oxygen ion concentration between the inner and outer electrodes is large, that is, the potential difference is large, and the output voltage of the sensor is close to 1V.

[0004] The oxygen sensors on the market, whether switch type or wide-range type, generally use talcum powder and ceramic insulators, which need to be sealed by one or more press-fitting. The quality of the seal determines the accuracy of the sensor signal. On the one hand, the internal leakage of existing oxygen sensors is extremely difficult to control, the sealing performance is poor, and powder is easy to fall off, causing pollution; on the other hand, the structure is complex and the cost is high, which is extremely unfavorable for product production and market promotion. Summary of the invention

[0005] The object of the present invention is to provide a probe subassembly and an oxygen sensor using the probe subassembly, so as to simplify the structure and enable the oxygen sensor to effectively control internal leakage.

[0006] To achieve the above-mentioned purpose, the present invention provides a probe subassembly for an oxygen sensor, characterized in that it includes a zirconium element, a shell, a ceramic part, a sealing material and a lower shield, wherein the zirconium element is a long strip with a rectangular cross section, and is arranged to pass through the shell and the ceramic part and the sealing material located in the shell along the central axis of the shell; the shell is a U-shaped cylindrical shell, including an upper opening, a shell bottom, and a cylindrical hollow portion extending from the upper opening to the shell bottom, and the outer surface of the shell includes an upper opening edge, an upper fastening cylinder, a shaft shoulder, a lower connecting threaded cylinder, and a lower shield connecting flange connected in sequence starting from the upper opening along the central axis, wherein the shell bottom has a through hole with a rectangular cross section, and the through hole is provided with a through hole having a rectangular cross section. The hole is located at the central axis of the shell for the zirconium element to pass through; the upper fastening cylinder is used to connect the upper shield of the oxygen sensor through a tight fit; the lower shield connecting flange is used to connect the lower shield; the outer surface of the lower connecting threaded cylinder has threads for connecting the interface threads of the vehicle exhaust pipe; the sealing material fills the lower part of the cylindrical hollow part and is in close contact with the surface of the zirconium element and the cylindrical hollow part; the sealing material includes 30% to 50% talcum powder, 30% to 50% glass powder and 10% to 15% magnesium stearate; the ceramic part is located at the upper part of the cylindrical hollow part, pressed onto the sealing material, and the ceramic part is fixed by riveting the upper opening edge.

[0007] As a preferred embodiment, a heating circuit is printed on the surface of the zirconium element, and the heating circuit includes a heating resistor for heating the zirconium element.

[0008] As a preferred embodiment, the height of the sealing material accounts for five-sixths of the height of the cylindrical hollow portion; the height of the ceramic component accounts for one-sixth of the height of the cylindrical hollow portion.

[0009] As a preferred embodiment, the maximum value of the gap between the surface of the rectangular through hole and the surface of the zirconium element is 0.1 mm.

[0010] As a preferred embodiment, the sealing material is sintered at the lower portion of the cylindrical hollow portion.

[0011] As a preferred embodiment, the lower shield has an outer tube and an inner tube, the outer tube has a flange, the lower shield connecting flange is riveted onto the flange of the outer tube, and when the lower shield connecting flange is riveted onto the flange, the top end of the inner tube rests on the bottom plane of the shell.

[0012] As a preferred method, the preparation of the sealing material includes the following process: weigh the components of the sealing material according to the ratio, put them into a stirrer, add appropriate amount of pure water to stir evenly, put them into an oven for drying, keep the moisture content at 5% after drying, and granulate them with an 80-mesh or 100-mesh sieve.

[0013] As a preferred method, the assembly process of the probe subassembly is: take the zirconium element; place the zirconium element into the shell; inject an appropriate amount of the granulated sealing material; press-fit the ceramic part: press-fit the ceramic part into a fixed position, and rivet the upper opening edge to encapsulate it; sinter and solidify: put the pressed probe subassembly into a high-temperature furnace, heat it to 650°C~700°C, keep it warm for 20-60 minutes, and cool it down with the furnace.

[0014] As a preferred embodiment, the heat preservation time during sintering and curing is 30 minutes.

[0015] On the other hand, the present invention further provides an oxygen sensor, which includes the aforementioned probe subassembly.

[0016] The oxygen sensor for detecting oxygen content in the automobile exhaust system of the present invention detects oxygen concentration and feeds back to the vehicle ECU for closed-loop control to correct the fuel injection amount to achieve optimal emissions. The oxygen sensors of the prior art, whether heated or non-heated, switch type or wide-range type, generally use talcum powder and ceramic insulators for sealing through one or more press-fitting. The quality of the seal determines the accuracy of the sensor signal. The current problem is that internal leakage is difficult to control, and the structure is complex and the cost is high. The focus of the present invention is to change the design, that is, to reduce costs and solve the sealing problem at the same time.

[0017] Compared with the prior art, the oxygen sensor of the present invention can effectively control the internal leakage of the oxygen sensor, has high sealing performance, is not easy to fall off powder, and avoids pollution; and its structure is simple and the cost is low, which is extremely beneficial to product production and market promotion.

[0018] The present invention has the following advantages:

[0019] 1. The structure of the product is greatly simplified compared with the existing technology, which reduces the material cost.

[0020] 2. Brand-new sealing materials and brand-new curing structure have greatly improved the stability of sealing control and effectively prolonged the service life of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic perspective structural diagram of a part of an embodiment of a probe subassembly of an oxygen sensor of the present invention, without showing a lower shield and a zirconium element.

[0022] Figure 2 It is a schematic cross-sectional view of the shell of the probe subassembly embodiment of the present invention.

[0023] Figure 3 It is a cross-sectional schematic diagram of an embodiment of a probe subassembly of an oxygen sensor of the present invention.

[0024] Figure 4 It is a cross-sectional schematic diagram of an oxygen sensor embodiment of the present invention. DETAILED DESCRIPTION

[0025] Hereinafter, embodiments of an oxygen sensor of the present invention will be described with reference to the accompanying drawings.

[0026] The embodiments described herein are specific embodiments of the present invention, which are used to illustrate the concept of the present invention, are illustrative and exemplary, and should not be interpreted as limiting the embodiments of the present invention and the scope of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the claims and the contents disclosed in the specification of this application, including any obvious replacement and modification of the embodiments described herein.

[0027] The drawings in this specification are schematic diagrams, which assist in explaining the concept of the present invention and schematically show the shapes of various parts and their mutual relationships.

[0028] Figure 1 It is a schematic perspective structural diagram of a part of an embodiment of a probe subassembly of an oxygen sensor of the present invention, without showing a lower shield and a zirconium element. Figure 2 It is a schematic cross-sectional view of the shell of the probe subassembly embodiment of the present invention. Figure 3 It is a cross-sectional schematic diagram of an embodiment of a probe subassembly of an oxygen sensor of the present invention. Figure 4 It is a cross-sectional schematic diagram of an oxygen sensor embodiment of the present invention.

[0029] like Figure 4 As shown, the oxygen sensor of the present invention includes a probe subassembly and a wiring harness structure.

[0030] like Figure 1 , 2 As shown in FIG. 3 , the probe subassembly embodiment of the oxygen sensor of the present invention includes a housing 1, a sealing material 2, a ceramic component 3, a zirconium element 4 and a lower shield 5. The probe subassembly is as shown in FIG. Figure 2 Shown with a central axis.

[0031] The zirconium element 4 is a long strip with a rectangular cross section, and is arranged to pass through the housing 1 and the ceramic member 3 and the sealing material 2 located in the housing 1 along the central axis of the housing 1. A heating circuit is printed on the surface of the zirconium element 4, and the heating circuit includes a heating resistor for heating the zirconium element 4.

[0032] The shell 1 is a U-shaped cylindrical shell, including an upper opening 16, a shell bottom, and a cylindrical hollow portion extending from the upper opening 16 to the shell bottom. The outer surface of the shell 1 includes an upper opening edge, an upper fastening cylinder, a shoulder 11, a lower connecting threaded cylinder, and a lower shield connecting flange 141 along the central axis starting from the upper opening 16. Please note that these parts of the outer surface of the shell 1 are connected in sequence without any gaps.

[0033] The shell bottom has a shell bottom plane 14, a lower shield connection flange 141 and a through hole 17. The lower shield connection flange 141 extends vertically along the edge of the shell bottom.

[0034] The through hole 17 is located at the central axis of the housing 1 and has a rectangular cross section for the zirconium element 4 to pass through. The maximum value of the gap between the four surfaces of the rectangular through hole 17 and the corresponding four surfaces of the zirconium element 4 is 0.1 mm.

[0035] See also Figure 3 The lower shield 5 has an outer tube 51 and an inner tube 52, and the outer tube 51 has a flange. The lower shield connection flange 141 is used to connect the lower shield 5. The lower shield 5 and the shell 1 are connected by riveting the lower shield connection flange 141 on the flange of the outer tube 51. When the lower shield connection flange 141 is riveted to the flange of the outer tube 51, the top of the inner tube 52 abuts against the shell bottom plane 14. It is preferred to rivet the entire lower shield connection flange 141 on the flange of the outer tube 51, so that firstly, it is ensured that the gas enters from the opening of the lower shield instead of leaking in from the gap; secondly, it makes the fixation more secure.

[0036] See also Figure 4 The upper fastening cylinder is used to connect the upper shield of the oxygen sensor through a tight fit.

[0037] The outer surface of the lower connecting threaded barrel has threads for connecting the interface threads of the vehicle exhaust pipe. In this embodiment, the outer surface threads of the lower connecting threaded barrel extend along the entire length of the lower connecting threaded barrel and have a back cutter groove.

[0038] The sealing material 2 fills up the lower part of the cylindrical hollow portion, and is in close contact with the zirconium element 4 and the surface of the cylindrical hollow portion.

[0039] The ceramic part 3 is located at the upper part of the cylindrical hollow part, and is pressed onto the sealing material 2. The ceramic part 3 is fixed by riveting the upper opening edge. It is preferred that the upper opening edge is riveted to the ceramic part 3 to secure the parts. If distributed riveting points are used, the parts may be easily loosened.

[0040] The cylindrical hollow part is filled with the ceramic part 3 and the sealing material 2, except for the margin of the upper opening edge for pressing the ceramic part 3. The sealing material 2 occupies most of the space of the cylindrical hollow part, and the ceramic part 3 only occupies a small part of the space of the cylindrical hollow part. The height of the sealing material 2 occupies, for example, five-sixths, four-fifths, etc. of the height of the cylindrical hollow part, and the height of the ceramic part 3 occupies, for example, one-sixth, one-fifth, etc. of the height of the cylindrical hollow part.

[0041] In this embodiment, the shoulder 11 is hexagonal. The shoulder 11 is used to install and rotate the probe sub-assembly, and can also be quadrilateral or pentagonal, or circular, or have a knurled surface.

[0042] The sealing material 2 is formed at the lower portion of the cylindrical hollow portion by sintering.

[0043] The proportion of sealing material 2 is as follows:

[0044] 1. 30% to 50% talcum powder, the main component of talcum powder is magnesium silicate, which is used as the main material of sealing material 2;

[0045] 2.30% to 50% glass powder, the softening temperature of glass powder is 600-700℃, and talcum powder is blended together to improve air tightness.

[0046] 3.10% to 15% magnesium stearate. Magnesium stearate is used as a lubricant to facilitate powder flow and granulation during the powder production process.

[0047] The preparation process of sealing material 2 is as follows:

[0048] Talc powder, glass powder and magnesium stearate are weighed according to the determined ratio, the powder mixture is put into a blender, and an appropriate amount of purified water is added and stirred evenly. After that, the evenly stirred mixture is put into an oven for drying. After drying, the sealing material 2 is kept to contain 5% of moisture, and granulated with an 80-mesh or 100-mesh screen.

[0049] The probe subassembly assembly of the present invention comprises the following steps:

[0050] First, take the zirconium element 4;

[0051] Secondly, the zirconium element 4 is placed into the housing 1;

[0052] Afterwards, inject an appropriate amount of granulated sealing material 2;

[0053] Next, press-fit the ceramic part 3: press-fit the ceramic part 3 to a fixed position and rivet and seal it, that is, rivet and press the edge of the opening 16 of the central cylindrical cavity of the housing 1 to fix the ceramic part 3;

[0054] Finally, sintering and curing: put the pressed oxygen sensor probe subassembly into a high-temperature furnace, heat it to 650℃~700℃, keep it warm for 20-60min, and cool it down with the furnace. Please note that the sintering and holding time can be preferably 20min, 30min, 40min, but should not be less than 20min, because production is generally batch production, and there is a heat radiation process during sintering. The minimum time is guaranteed to heat through a batch of sintered parts.

[0055] A leakage comparison test was conducted between the oxygen sensor of the present invention and the oxygen sensor of the prior art, and the steps are as follows:

[0056] 1. Take the oxygen sensor probe subassembly pressed by the existing talc block as a comparison part, measure the leakage value and record it;

[0057] 2. Take the prepared sealing material 2, install the zirconium element 4 into the housing 1, fill the sealing material 2 and compact it, install the ceramic part 3 into the housing 1, press and rivet, measure the leakage value and record it;

[0058] 3. Assemble the oxygen sensor of the existing technology, measure the leakage value and record it;

[0059] 4. Place the assembled comparison parts and test parts in a high-temperature furnace and keep them at 650℃ for 30 minutes (high temperature and insulation to simulate the high temperature of actual vehicle testing). After the furnace cools down to room temperature, test the leakage values ​​of the comparison parts and test parts respectively and record them.

[0060] The results of the comparative test are as follows:

[0061]

[0062]

[0063] It can be seen from the test results that the leakage value of the talc block of the oxygen sensor of the prior art increased by 0.07-0.08cc after high-temperature sintering, an increase of about 40%. However, the sealing structure and sealing material 2 of the oxygen sensor of the present invention reduced the leakage value by 0.05-0.06cc after high-temperature sintering, which is about 25% lower than that of the prior art; therefore, the oxygen sensor of the present invention has a positive effect on improving the leakage rate.

[0064] At the same time, the oxygen sensor of the present invention improves the sealing structure, effectively reduces the number of parts and components, and greatly reduces the production cost.

[0065] The oxygen sensor of the present invention can effectively control the internal leakage of the oxygen sensor, has high sealing performance, is not easy to fall off powder, and avoids pollution; and the oxygen sensor of the present invention has a simple structure and low cost, which is extremely beneficial to product production and market promotion.

[0066] The present invention has the following advantages over the prior art:

[0067] 1. The structure of the product is greatly simplified compared with the existing technology, which reduces the material cost.

[0068] 2. The new sealing material 2 and the new curing structure greatly improve the stability of sealing control and effectively extend the service life of the product.

[0069] The above description of the embodiments of the oxygen sensor of the present invention is intended to explain the spirit of the present invention. Please note that those skilled in the art can modify and combine the features of the above embodiments without departing from the spirit of the present invention. Therefore, the present invention is not limited to the above embodiments. The specific features of the oxygen sensor, such as shape, size and position, can be specifically designed based on the effects of the features disclosed above, and these designs can be implemented by those skilled in the art. Moreover, the technical features disclosed above are not limited to the combination with other features disclosed. Those skilled in the art can also make other combinations between the technical features according to the purpose of the invention, so as to achieve the purpose of the present invention.

Claims

1. A probe subassembly for an oxygen sensor, characterized in that: It includes a zirconium element, a shell, a ceramic part, a sealing material and a lower shield, wherein: The zirconium element is a long strip with a rectangular cross section, and is arranged to pass through the shell and the ceramic member and the sealing material located in the shell along the central axis of the shell; The shell is a U-shaped cylindrical shell, including an upper opening, a shell bottom, and a cylindrical hollow portion extending from the upper opening to the shell bottom. The outer surface of the shell includes an upper opening edge, an upper fastening cylinder, a shaft shoulder, a lower connecting threaded cylinder, and a lower shield connecting flange connected in sequence along the central axis from the upper opening, wherein: The shell bottom has a shell bottom plane, a lower shield connecting flange extending vertically along the edge of the shell bottom plane, and a through hole with a rectangular cross section, the through hole is located at the central axis of the shell and is used for the zirconium element to pass through; The upper fastening cylinder is used to connect the upper shield of the oxygen sensor through a tight fit; The lower shield connecting flange is used to connect the lower shield; The outer surface of the lower connecting threaded cylinder has threads for connecting to the interface threads of the vehicle exhaust pipe; The sealing material fills the lower part of the cylindrical hollow part and is in close contact with the zirconium element and the surface of the cylindrical hollow part; the sealing material comprises 30% to 50% talc powder, 30% to 50% glass powder and 10% to 15% magnesium stearate; The ceramic piece is located at the upper part of the cylindrical hollow part and is pressed onto the sealing material. The ceramic piece is fixed by riveting the upper opening edge.

2. The probe subassembly according to claim 1, characterized in that: A heating circuit is printed on the surface of the zirconium element. The heating circuit includes a heating resistor for heating the zirconium element.

3. The probe subassembly according to claim 1, characterized in that: The height of the sealing material accounts for five sixths of the height of the cylindrical hollow portion; The height of the ceramic member accounts for one sixth of the height of the cylindrical hollow portion.

4. The probe subassembly according to claim 1, characterized in that: The maximum value of the gap between the surface of the rectangular through hole and the surface of the zirconium element is 0.1 mm.

5. The probe subassembly according to claim 1, characterized in that: The sealing material is sintered at the lower portion of the cylindrical hollow portion.

6. The probe subassembly according to claim 1, characterized in that: The lower shield has an outer tube and an inner tube, the outer tube has a flange, the lower shield connection flange is riveted on the flange of the outer tube, and when the lower shield connection flange is riveted on the flange, the top end of the inner tube abuts against the shell bottom plane.

7. The probe subassembly according to claim 1, characterized in that: The preparation of the sealing material includes the following process: weigh the components of the sealing material according to the ratio, put them into a stirrer, add appropriate amount of pure water to stir them evenly, put them into an oven for drying, keep the moisture content at 5% after drying, and granulate them with an 80-mesh or 100-mesh screen.

8. The probe subassembly according to claim 1, characterized in that: The assembly process of the probe subassembly is as follows: Taking the zirconium element; placing the zirconium element into a housing; injecting an appropriate amount of the granulated sealing material; Press-fitting the ceramic piece: press-fitting the ceramic piece to a fixed position, and riveting the upper opening edge to seal it; Sintering and curing: Place the pressed probe subassembly into a high-temperature furnace, heat it to 650℃~700℃, keep it warm for 20-60min, and then cool it down with the furnace.

9. The probe subassembly according to claim 1, characterized in that: The heat preservation time during sintering and curing is 30 minutes.

10. An oxygen sensor, characterized in that: Comprising a probe subassembly as described in any one of claims 1-9.

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