A cylindrical NOx gas sensor

Abstract

The present application relates to a cylindrical NOx gas sensor, which comprises, from inside to outside, a ceramic column base, a surface of which is printed with a test electrode and a counter electrode; a ceramic layer, a surface of which is printed with insulating material and which forms a channel and a cavity at the end; a heating electrode layer, which comprises a spiral heating zone, a power supply lead and a power supply electrode, the heating electrode being spirally distributed in the detection zone and connected to the power supply electrode through the power supply lead; and a protective layer, which is located outside the heating layer and used to protect the heating electrode and the overall structure. In the present application, the test electrode is made of NOx sensitive material and the counter electrode is made of noble metal electrode. During detection, the sensor is heated by the noble metal heating electrode, the test electrode and the counter electrode are pressurized, and the signal change between the test electrode and the counter electrode is detected to determine the content of NOx gas, thereby achieving the purpose of gas detection. The present application adopts a four-wire structure, which is simple in structure and easy to operate.

Description

Technical Field

[0001] This invention relates to a cylindrical NOx gas sensor, belonging to the field of gas sensors. Background Technology

[0002] Currently widely used solid-state electrolyte NOx gas sensors for automobiles have a multi-layer chip structure and include various electrode materials. This results in complex sensor structures, a large number of electrodes, severe signal interference, and cumbersome operation. Considering the advantages of electrochemical gas sensors—high detection accuracy and fast detection—allowing for rapid gas detection, optimizing the NOx gas sensor structure and designing a sensor that is easy to operate and has low interference is of great significance. Summary of the Invention

[0003] The purpose of this invention is to provide a cylindrical NOx gas sensor. The sensor provided by this invention has a simple structure, is easy to manufacture, and exhibits certain detection performance for NOx.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A cylindrical NOx gas sensor is characterized in that the sensor comprises, from the inside out, a ceramic column substrate (1), a ceramic layer (2), a heating electrode layer (3), and a protective layer (4). The ceramic column substrate (1) has a test electrode (13) and a counter electrode (11) printed on its surface, and is powered by a counter electrode power supply electrode (12) and a test electrode power supply electrode (14), respectively. An insulating material (21) is printed on the outer side of the ceramic layer (2), and a gas channel (22) and a gas mixing region (23) are formed on the top of the ceramic layer (2) near the test electrode (13). The heating electrode layer (3) is located outside the ceramic layer (2) and includes a spiral heating region located outside the gas mixing region (23). The heating electrode layer (3) is connected to a heating electrode positive electrode (31) and a heating electrode negative electrode (32) through lead electrodes. The protective layer (4) covers the outer side of the heating electrode layer (3).

[0006] Furthermore, the composition of the counter electrode (11), the lead wire and the power supply electrode is Pt, and the composition of the test electrode (13) is Pt 20-40%, Rh 60-80%, WO3 0-30%.

[0007] Furthermore, the diameter of the gas channel (22) is smaller than the diameter of the gas mixing zone (23).

[0008] Furthermore, the diameter of the gas channel (22) is 100 to 500 micrometers, and the diameter of the gas mixing zone (23) is 1 to 3 millimeters.

[0009] The beneficial effects of this invention are:

[0010] 1. The gas sensor of the present invention has a cylindrical structure. Compared with the traditional multilayer chip sensor fabrication, it avoids the problem of electrode misalignment caused by different shrinkage rates between layers, ensuring effective signal extraction. At the same time, the cylindrical structure is subjected to uniform stress, which can avoid the problem of easy breakage during later sensor encapsulation and fixation.

[0011] 2. The present invention adopts a spiral heating electrode structure, which, compared with the traditional sheet structure where the bottom of the serpentine heating electrode is heated, results in faster and more uniform heating of the core detection part of the sensor.

[0012] 3. In this invention, the outer protective layer forms gas channel regions and gas mixing regions with different apertures. During detection, the airflow flows from the small aperture into the large aperture, resulting in the formation of vortices, which can increase gas mixing and turbulence, and is beneficial to enhancing the gas mass transfer process.

[0013] 4. In this invention, the test electrode is made of a NOx-sensitive material, and the counter electrode is made of a precious metal. During operation, the electrode current conducts through the solid electrolyte between the electrodes. During the test, the reaction between the test electrode and NOx changes the magnitude of the electrode current. The NOx content can be determined by recording the changes in the current between the electrodes, thus achieving the purpose of NOx detection. This invention has a simple structure and is easy to operate. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the cross-section of the structure of the present invention.

[0015] In the diagram, 1-ceramic pillar substrate, 2-ceramic layer, 3-heating electrode layer, 4-protective layer, 11-counter electrode, 12-counter electrode power supply electrode, 13-test electrode, 14-test electrode power supply electrode, 21-insulating material, 22-gas channel region, 23-gas mixing region, 31-positive heating electrode, 32-negative heating electrode Detailed Implementation

[0016] The present invention will now be further described with reference to the embodiments.

[0017] like Figure 1 As shown, this invention discloses a cylindrical NOx gas sensor. The main structure of the sensor is composed of a ceramic column substrate 1, on which a test electrode 13 and a counter electrode 11 are printed. These electrodes are connected to the counter electrode power supply electrode 12 and the test electrode power supply electrode 14, respectively, to provide power. The test electrode 13 and the counter electrode 11 do not contact each other; during operation, they conduct electricity through an electrolyte between the electrodes. Preferably, the test electrode 13 is composed of 20-40% Pt, 60-80% Rh, and 0-30% WO3, while the counter electrode 11, its power supply electrode, and the leads are made of pure Pt material.

[0018] A ceramic layer 2 is attached to the outer side of the ceramic pillar substrate 1. An insulating material 21 is printed on the outer side of this layer to reduce electrical signal crosstalk. On the top of the ceramic layer 2, near the test electrode 13, a gas channel 22 and a gas mixing region 23 are formed. The gas channel 22, with a small diameter of 100–500 micrometers, is designed for rapid gas introduction; while the gas mixing region 23, with a larger diameter of 1–3 millimeters, is used for effective gas mixing to facilitate sufficient reaction between the gas and the test electrode 13.

[0019] The heating electrode layer 3 is located outside the ceramic layer 2 and has a spiral heating zone. This heating zone is located outside the gas mixing zone 23 and can be heated by electricity through the positive electrode 31 and the negative electrode 32. The heating effect of the heating electrode layer 3 can enable the test area of ​​the sensor to reach the operating temperature range of 500-800°C, thereby activating the sensitive material on the test electrode 13.

[0020] The outermost protective layer 4 is used to cover and protect the heating electrode layer 3, as well as the internal structure of the sensor.

[0021] Brief description of the testing principle: The test area is heated to 500-800℃ by heating electrode 3, thereby raising the temperature of the test electrode 13 and counter electrode 12. A voltage of 5-15V is applied to the test electrode 13 and counter electrode 12, and the change in the working circuit current is recorded. NOx is introduced; as NOx reacts with the sensitive material of the test electrode, the electrode resistance changes, and the working circuit current changes. The circuit control system can detect the change in the gas signal, thereby establishing the relationship between NOx concentration and current signal.

[0022] This cylindrical NOx gas sensor is designed to effectively enhance the contact efficiency between the gas and the electrode, accelerating gas transport and mixing, thereby providing rapid response and high-sensitivity measurement results. It is ideally suited for real-time monitoring of NOx gas concentrations in the environment. Through optimized electrode materials and structural design, this sensor ensures high accuracy and long-term stability, making it suitable for various industrial and environmental applications.

Claims

1. A cylindrical NOx gas sensor, characterized in that, The sensor comprises, from the inside out, a ceramic column substrate (1), a ceramic layer (2), a heating electrode layer (3), and a protective layer (4). The surface of the ceramic column substrate (1) is printed with a test electrode (13) and a counter electrode (11), which are connected to power supply via a counter electrode power supply electrode (12) and a test electrode power supply electrode (14), respectively. An insulating material (21) is printed on the outer side of the ceramic layer (2), and a gas channel (22) and a gas mixing region (23) are formed on the top side of the ceramic layer (2) near the test electrode (13). The heating electrode layer (3) is located outside the ceramic layer (2) and includes a spiral heating region located outside the gas mixing region (23). The heating electrode layer (3) is connected to the positive electrode (31) and the negative electrode (32) of the heating electrode via lead electrodes. The protective layer (4) covers the outer side of the heating electrode layer (3). The diameter of the gas channel (22) is smaller than the diameter of the gas mixing region (23).

2. The cylindrical NOx gas sensor according to claim 1, characterized in that, The composition of the counter electrode (11), lead wire and power supply electrode is Pt, and the composition of the test electrode (13) is Pt 20-40%, Rh 60-80%, WO 30-30%.

3. The cylindrical NOx gas sensor according to claim 1, characterized in that, The diameter of the gas channel (22) is 100 to 500 micrometers, and the diameter of the gas mixing zone (23) is 1 to 3 millimeters.

Images