A high-precision nitrogen and oxygen sensor ceramic chip

Abstract

A high-precision nitrogen and oxygen sensor ceramic chip comprises a first layer of zirconia substrate to a sixth layer of zirconia substrate, a first aluminum oxide diaphragm is arranged on the lower surface of the third layer of zirconia substrate, an external electrode is arranged on the first layer of zirconia substrate, grooves are arranged on the upper and lower surfaces of the second layer of zirconia substrate to form an upper slit a and a lower slit b with the first layer of zirconia substrate and the third layer of zirconia substrate, a gas buffer cavity k connected to the upper slit a and the lower slit b connected to the outside air is processed on the second layer of zirconia substrate between the upper slit a and the lower slit b, a first reaction cavity j with a first inner electrode, a second reaction cavity h with a second inner electrode, and a transition cavity c, a measuring channel g is arranged on the third layer of zirconia substrate and the first aluminum oxide diaphragm, a measuring cavity f with a measuring electrode is arranged on the fourth layer of zirconia substrate, a reference electrode and a reference channel d are arranged on the fourth layer of zirconia substrate, and a heating electrode insulating layer with a heating electrode is arranged between the fifth layer of zirconia substrate and the sixth layer of zirconia substrate.

Description

Technical Field

[0001] The invention belongs to a device for testing or measuring gas, and in particular relates to a high-precision nitrogen and oxygen sensor. Background Art

[0002] As national exhaust emission standards become increasingly stringent, the requirements for the development and application of diesel engines and their exhaust after-treatment technologies have increased accordingly. Selective catalytic reduction technology (SCR) has become indispensable in exhaust emission control, and the nitrogen oxide sensor is the core component of the SCR system.

[0003] The ceramic chip is the core component of the nitrogen oxide sensor. It utilizes the ionic conductivity of YSZ at high temperature, combined with sensitive electrode materials with special catalytic activity for NOx, with YSZ diaphragm as the substrate, and is prepared through processes such as screen printing, lamination, warm isostatic pressing, chip slitting, and co-sintering.

[0004] With the implementation of the National VI regulations for diesel vehicles and the T4 regulations for non-road mobile machinery, the SCR system has increasingly higher requirements for the measurement accuracy of NOx sensors and their stability under different operating conditions. Currently, NOx sensors on the market generally have poor low-concentration measurement accuracy and large measurement value deviations when the exhaust temperature is high under special operating conditions.

[0005] The measuring chamber f of the nitrogen oxide sensor ceramic chip disclosed in Chinese patent number ZL2018106225276 and titled "A Nitrogen Oxygen Sensor Ceramic Chip" is located in the same plane as the second gas reaction chamber. When the oxygen content in the exhaust gas suddenly changes, part of the gas has diffused to the measuring chamber f, resulting in a phenomenon in which the nitrogen oxide measurement value is too high; and the first inner electrode, the second inner electrode and the measuring electrode of the existing nitrogen oxide sensor ceramic chip all form a loop with the reference electrode and the outer electrode, and the pump oxygen current can flow through the two loops, but the control detection loop is composed of the outer electrode and the first inner electrode, the second inner electrode, and the measuring electrode, resulting in the loop current composed of the reference electrode and the first inner electrode, the second inner electrode, and the measuring electrode not being detected, resulting in a measurement error, thereby resulting in low measurement accuracy. Summary of the invention

[0006] The technology to be solved by the present invention is to overcome the shortcomings of the existing nitrogen oxide sensor ceramic chip and provide a high-precision nitrogen oxide sensor ceramic chip with reasonable design, simple production and high yield.

[0007] The technical solution adopted to solve the above technical problems is: a high-precision nitrogen oxygen sensor ceramic chip, including a first layer of zirconia substrate, a second layer of zirconia substrate, a third layer of zirconia substrate, a fourth layer of zirconia substrate, a fifth layer of zirconia substrate, and a sixth layer of zirconia substrate stacked in sequence from top to bottom, a first aluminum oxide diaphragm is stacked between the third layer of zirconia substrate and the fourth layer of zirconia substrate, an outer electrode with a protective layer is arranged on the upper surface of the first layer of zirconia substrate, a groove 1 is processed on the upper surface of the second layer of zirconia substrate directly below the outer electrode to form an upper slit a with the first layer of zirconia substrate, and a groove 2 is processed on the lower surface to form a lower slit b with the third layer of zirconia substrate, the upper slit a and the lower slit b are connected to the outside air, and a gas buffer cavity k, a first reaction cavity j, and a gas buffer cavity j connected to the upper slit a and the lower slit b are processed on the second layer of zirconia substrate between the upper slit a and the lower slit b. The second reaction chamber h and the transition chamber c, the first reaction chamber j is provided with a first inner electrode, the second reaction chamber h is provided with a second inner electrode, the third layer of zirconia substrate and the first aluminum oxide diaphragm directly below the transition chamber c are processed with a measuring channel g, the fourth layer of zirconia substrate is processed with a measuring chamber f, the transition chamber c is connected with the measuring chamber f through the measuring channel g, a measuring electrode is provided on the upper surface of the fifth layer of zirconia substrate in the measuring chamber f, a reference electrode is sealed on the fourth layer of zirconia substrate on one side of the measuring electrode, the reference electrode is attached to the upper surface of the fifth layer of zirconia substrate and an insulating layer is provided between the reference electrode and the fourth layer of zirconia substrate, a reference channel d connected to the outside air is processed on the fourth layer of zirconia substrate on one side of the reference electrode, a heating electrode insulating layer is provided between the fifth layer of zirconia substrate and the sixth layer of zirconia substrate, and a heating electrode is provided in the heating electrode insulating layer.

[0008] As a preferred technical solution, the heating electrode insulating layer is two layers of second aluminum oxide film, and the two layers of second aluminum oxide film are stacked between the fifth layer of zirconium oxide substrate and the sixth layer of zirconium oxide substrate.

[0009] As a preferred technical solution, the thickness of the second aluminum oxide membrane is 30-50 um.

[0010] As a preferred technical solution, a stress release channel e connected to the reference channel d is processed on the fifth layer of zirconia substrate.

[0011] As a preferred technical solution, the insulating layer is a porous aluminum oxide layer.

[0012] As a preferred technical solution, the thickness of the first aluminum oxide membrane is 15 to 30 um.

[0013] As a preferred technical solution, the protective layer of the external electrode is a porous aluminum oxide layer.

[0014] As a preferred technical solution, the width of the upper slit a is 8 to 15 um, and the width of the lower slit b is 10 to 20 um.

[0015] The beneficial effects of the present invention are as follows:

[0016] 1. The present invention sets a measuring channel g, places the measuring electrode and the first inner electrode and the second inner electrode in different planes, increases the distance from the atmosphere to the measuring electrode, avoids the influence of sudden changes in oxygen concentration in the exhaust gas on the measuring electrode, and avoids the contamination of the measuring electrode caused by the volatilization of the precious metal gold in the second inner electrode, so as to achieve higher measurement accuracy.

[0017] 2. In the present invention, a first aluminum oxide film is laminated between the third zirconium oxide substrate and the fourth zirconium oxide substrate for insulation, so that two separate current loops are formed inside the chip, that is, the outer electrode and the first inner electrode and the second inner electrode form a current loop, and the reference electrode and the measuring electrode form a current loop. The measuring current is the current between the reference electrode and the measuring electrode, which ensures the measurement accuracy.

[0018] 3. The first alumina diaphragm of the present invention is arranged between the third zirconia substrate and the fourth zirconia substrate in a stacking manner, thereby avoiding the sintering shrinkage mismatch and delamination cracking caused by the co-firing of the alumina diaphragm and zirconia in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the present invention.

[0020] Figure 2 It is a comparison chart of test data of the ceramic chip of nitrogen and oxygen sensor of the present invention and the existing one in air.

[0021] Figure 3 This is a comparison chart of test data of the ceramic chip of the nitrogen oxygen sensor of the present invention and the existing nitrogen oxygen sensor in an atmosphere with a nitrogen oxygen concentration of 315 ppm.

[0022] Wherein: outer electrode 1; first inner electrode 2; second inner electrode 3; measuring electrode 4; reference electrode 5; fourth zirconia substrate 6; first zirconia substrate 7; second zirconia substrate 8; third zirconia substrate 9; first aluminum oxide diaphragm 10; fifth zirconia substrate 11; heating electrode insulating layer 12; heating electrode 13; sixth zirconia substrate 14; upper slit a; lower slit b; transition chamber c; reference channel d; stress release channel e; measuring chamber f; measuring channel g; second reaction chamber h; gas buffer chamber k; first reaction chamber j. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below in conjunction with the accompanying drawings and examples, but the present invention is not limited to the following embodiments.

[0024] exist Figure 1In the embodiment, the high-precision nitrogen oxygen sensor ceramic chip includes a first layer of zirconium oxide substrate 7, a second layer of zirconium oxide substrate 8, a third layer of zirconium oxide substrate 9, a fourth layer of zirconium oxide substrate 6, a fifth layer of zirconium oxide substrate 11, and a sixth layer of zirconium oxide substrate 14 stacked in sequence from top to bottom. A first aluminum oxide diaphragm 10 is stacked between the third layer of zirconium oxide substrate 9 and the fourth layer of zirconium oxide substrate 6. The thickness of the first aluminum oxide diaphragm 10 is 15um, or 20um, or 30um. The first aluminum oxide diaphragm 10 controls the migration direction of oxygen ions to avoid current measurement errors. The upper surface of the first layer of zirconium oxide substrate 7 is provided with an outer electrode 1 with a protective layer. The upper surface of the second layer of zirconium oxide substrate 8 directly below the outer electrode 1 is processed with a groove that is aligned with the first layer of zirconium oxide substrate 8. The zirconium substrate 7 forms an upper slit a, and the lower surface is processed with a groove 2 to form a lower slit b with the third zirconia substrate 9. The upper slit a and the lower slit b are connected to the outside air. The width of the upper slit a is 10um, or 8um, or 15um, and the width of the lower slit b is 15um, or 10um, or 20um. The width of the upper slit a and the lower slit b will directly affect the gas content entering the first reaction chamber j and the measurement chamber f. A too small slit width will cause the gas flow rate to be too slow, resulting in a slow change in the measured value of the ceramic chip. A too large slit width will cause the measured value of the ceramic chip to be greatly affected by the airflow, and the gas concentration cannot be accurately measured. The second zirconia substrate 8 between the upper slit a and the lower slit b is processed with a groove 2 to form a lower slit b. a comprises a gas buffer chamber k connected to the lower slit b, a first reaction chamber j, a second reaction chamber h, and a transition chamber c. A first inner electrode 2 is arranged on the lower surface of the first zirconia substrate 7 and the upper surface of the third zirconia substrate 9 in the first reaction chamber j. A second inner electrode 3 is arranged on the lower surface of the first zirconia substrate 7 and the upper surface of the third zirconia substrate 9 in the second reaction chamber h. A measuring channel g is machined on the third zirconia substrate 9 and the first alumina diaphragm 10 directly below the transition chamber c, and a measuring chamber f is machined on the fourth zirconia substrate 6. The transition chamber c is connected to the measuring chamber f through the measuring channel g. A measuring electrode 4 is arranged on the fifth zirconia substrate 11 in the measuring chamber f. The measuring channel g is used to increase the distance from the atmosphere to the measuring electrode 4. At the same time, the position of the measuring electrode 4 in the vertical plane is not changed to ensure the thermal field distribution of the chip and avoid the influence of temperature on the activity of the measuring electrode 4. A reference electrode 5 is sealed on the fourth layer of zirconia substrate 6 on one side of the measuring electrode 4. The reference electrode 5 is attached to the upper surface of the fifth layer of zirconia substrate 11 and an insulating layer is provided between the fourth layer of zirconia substrate 6. The insulating layer is a porous aluminum oxide layer. A reference channel d connected to the outside air is processed on the fourth layer of zirconia substrate 6 on one side of the reference electrode 5. A stress release channel e connected to the reference channel d is processed on the fifth layer of zirconia substrate 11. A heating electrode insulating layer 12 is provided between the fifth layer of zirconia substrate 11 and the sixth layer of zirconia substrate 14, and a heating electrode 13 is provided in the heating electrode insulating layer 12.

[0025] The heating electrode insulating layer 12 of the present embodiment is two layers of second aluminum oxide diaphragms, which are stacked between the fifth zirconium oxide substrate 11 and the sixth zirconium oxide substrate 14. The thickness of the second aluminum oxide diaphragm is 30um, or 40um, or 50um. The heating electrode 13 is wrapped by two layers of second aluminum oxide diaphragms, which improves the compactness of the heating electrode insulating layer 12, avoids the influence of the heating signal on the measurement signal, and improves the measurement accuracy.

[0026] The protective layer of the external electrode 1 of this embodiment is a porous aluminum oxide layer.

[0027] The working principle of the present invention is as follows:

[0028] The tail gas enters the gas buffer chamber k through the upper slit a and the lower slit b. The tail gas is buffered to a certain extent in the gas buffer chamber k, and then enters the first gas reaction chamber through the upper slit a and the lower slit b. The oxygen in the tail gas is decomposed into oxygen ions on the first inner electrode 2 in the first gas reaction chamber. Zirconium oxide has the effect of ion migration at high temperature. The migration of oxygen ions forms a current. The electronic control unit measures the current value between the outer electrode 1 and the first inner electrode 2. As the oxygen ions migrate to the outside of the chip, the oxygen concentration in the first gas reaction chamber drops to 1ppm. The remaining gas enters the second gas reaction chamber through the upper slit a and the lower slit b. The oxygen in the tail gas is further decomposed on the second inner electrode 3 in the second gas reaction chamber. The oxygen concentration in the second gas reaction chamber drops to 10 -3 ppm, the remaining gas enters the measuring chamber f through the upper slit a, the lower slit b, the transition chamber c and the measuring channel g, and the NOx in the exhaust gas is decomposed into N 2 and O 2 , O 2 Decomposed into oxygen ions, the NOx concentration is accurately measured by measuring the current value generated between the measuring electrode 4 and the reference electrode 5 due to the migration of oxygen ions.

[0029] The present invention uses a first aluminum oxide diaphragm 10 to separate the third layer from the fourth layer of zirconium oxide substrate, and controls the migration direction of oxygen ions, that is, the migration direction of oxygen ions in the first gas reaction chamber and the second gas reaction chamber is from the first inner electrode 2 and the second inner electrode 3 to the outer electrode 1, and the migration direction of oxygen ions in the measuring chamber f is from the measuring electrode 4 to the reference electrode 5, so that the chip forms two separate current loops, that is, the outer electrode 1 and the first inner electrode 2 and the second inner electrode 3 form current loop one, and the reference electrode 5 and the measuring electrode 4 form current loop two, and the measuring current is the current between the reference electrode 5 and the measuring electrode 4, thereby ensuring the measurement accuracy.

[0030] experiment

[0031] In order to verify the beneficial effects of the present invention, the applicant used Chinese patent number ZL2018106225276, titled "A Nitrogen Oxygen Sensor Ceramic Chip" (in Figure 2 , 3 Structure A) and the high-precision nitrogen oxygen sensor ceramic chip of the present invention (in Figure 2 , 3 Structure B) was tested in air and in an atmosphere with a nitrogen and oxygen concentration of 315ppm. The test results are as follows Figure 2 , 3 .

[0032] It can be seen from the test results that the high-precision nitrogen oxygen sensor ceramic chip of the present invention has smaller measurement fluctuation and higher accuracy than the chip structure currently on the market.

Claims

1. A high-precision nitrogen and oxygen sensor ceramic chip, comprising a first layer of zirconia substrate, a second layer of zirconia substrate, a third layer of zirconia substrate, a fourth layer of zirconia substrate, a fifth layer of zirconia substrate, and a sixth layer of zirconia substrate stacked in sequence from top to bottom, characterized in that: A first aluminum oxide diaphragm is stacked between the third zirconium oxide substrate and the fourth zirconium oxide substrate, an outer electrode with a protective layer is arranged on the upper surface of the first zirconium oxide substrate, a groove one is processed on the upper surface of the second zirconium oxide substrate directly below the outer electrode to form an upper slit a with the first zirconium oxide substrate, and a groove two is processed on the lower surface to form a lower slit b with the third zirconium oxide substrate, the upper slit a and the lower slit b are connected to the outside air, a gas buffer chamber k connected to the upper slit a and the lower slit b, a first reaction chamber j, a second reaction chamber h, and a transition chamber c are processed on the second zirconium oxide substrate between the upper slit a and the lower slit b, a first reaction chamber j, a second reaction chamber h, and a transition chamber c, a first inner electrode is arranged in the first reaction chamber j, a second inner electrode is arranged in the second reaction chamber h, and a gas buffer chamber k connected to the upper slit a and the lower slit b is formed on the second zirconium oxide substrate between the upper slit a and the lower slit b. A measuring channel g is processed on the third zirconia substrate and the first alumina diaphragm directly below c, and a measuring chamber f is processed on the fourth zirconia substrate. The transition chamber c is connected with the measuring chamber f through the measuring channel g. A measuring electrode is arranged on the upper surface of the fifth zirconia substrate in the measuring chamber f. A reference electrode is sealed and arranged on the fourth zirconia substrate on one side of the measuring electrode. The reference electrode is attached to the upper surface of the fifth zirconia substrate and an insulating layer is arranged between the reference electrode and the fourth zirconia substrate. A reference channel d connected with the outside air is processed on the fourth zirconia substrate on one side of the reference electrode. A heating electrode insulating layer is arranged between the fifth zirconia substrate and the sixth zirconia substrate, and a heating electrode is arranged in the heating electrode insulating layer.

2. According to claim 1, the high-precision nitrogen oxygen sensor ceramic chip is characterized in that: The heating electrode insulating layer is two layers of second aluminum oxide film, and the two layers of second aluminum oxide film are stacked between the fifth layer of zirconium oxide substrate and the sixth layer of zirconium oxide substrate.

3. The high-precision nitrogen oxygen sensor ceramic chip according to claim 2 is characterized in that: The thickness of the second aluminum oxide film is 30-50 um.

4. The high-precision nitrogen oxygen sensor ceramic chip according to claim 1 is characterized in that: The fifth layer of zirconia substrate is processed with a stress release channel e connected to the reference channel d.

5. The high-precision nitrogen oxygen sensor ceramic chip according to claim 1 is characterized in that: The insulating layer is a porous aluminum oxide layer.

6. The high-precision nitrogen oxygen sensor ceramic chip according to claim 1 is characterized in that: The thickness of the first aluminum oxide film is 15-30 um.

7. The high-precision nitrogen and oxygen sensor ceramic chip according to claim 1 is characterized in that: The protective layer of the outer electrode is a porous aluminum oxide layer.

8. The high-precision nitrogen and oxygen sensor ceramic chip according to claim 1 is characterized in that: The width of the upper slit a is 8 to 15 um, and the width of the lower slit b is 10 to 20 um.

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