Integrated sensor for ammonia and nitrogen oxides

Abstract

This invention relates to the field of gas sensor technology, and more particularly to an integrated sensor for ammonia and nitrogen oxides, comprising a probe assembly, a circuit package, and a lead tube connecting the two. The probe assembly includes a chip holder, in which a gas-sensitive chip is installed. A dust filter is located at the head end of the chip holder, and a slow-cooling cylinder is located at the tail end. A conditioning circuit board is located within the circuit package. The leads of the gas-sensitive chip are led out through the slow-cooling cylinder, pass through the lead tube, and then connect to the conditioning circuit board in the circuit package, thereby transmitting and analyzing the collected signals and converting gas composition information into digital signals. The above sensor adopts a detachable modular design, reliably packaging and protecting the mixed-potential gas-sensitive chip, thus accurately analyzing the gas composition information in diesel vehicle exhaust even under high-temperature and harsh operating conditions, meeting monitoring needs, and further optimizing the urea aqueous solution injection volume and reducing the risk of urea crystallization.

Description

Technical Field

[0001] This invention relates to the field of gas sensor technology, and more particularly to an integrated sensor for ammonia and nitrogen oxides. Background Technology

[0002] With the full implementation of the China VI emission standards for diesel vehicles, medium and heavy-duty diesel vehicles on the market are all using Selective Catalytic Reduction (SCR) after-treatment systems, and more and more after-treatment products are being launched on the market. However, the problem of urea crystallization in diesel engine catalytic mufflers is becoming increasingly prominent, directly affecting the daily operation of users and causing certain losses to users and enterprises.

[0003] Urea crystallization in SCR systems has been a key research focus for aftertreatment manufacturers, engine manufacturers, and vehicle manufacturers. Optimizing the urea solution injection rate can reduce the risk of urea crystallization while still meeting emission standards. Installing sensors at the rear of the SCR catalytic muffler to monitor for excess ammonia in real time can provide precise feedback on the urea solution injection rate, reducing urea consumption and avoiding crystallization risks.

[0004] Currently, the mainstream products used for diesel vehicle emission monitoring on the market are Delphi ammonia sensors from the United States and Continental nitrogen oxide sensors from Germany. Both of these sensors are electrochemical types based on solid electrolytes. Their working principle is to decompose gases through a chemical reaction, releasing oxygen, and measuring the amount of released oxygen to determine the ammonia or nitrogen oxide content. However, to decompose oxygen from ammonia or nitrogen oxides, at least two chambers are usually required for step-by-step decomposition, and a large number of electrodes are used, generally at least six or more, to ensure complete and accurate measurements, resulting in a relatively complex sensor structure.

[0005] Furthermore, for sensors installed in the exhaust pipe, reliable operation under high-temperature and harsh conditions is required, along with high detection accuracy and fast response. The main requirements are as follows: 1) The internal temperature of the engine is unstable and has a large temperature range. The sensor needs to maintain good test stability and consistency in operating temperatures from room temperature to 800℃; 2) The high temperature and pressure inside the engine place demands on the mechanical performance and heat resistance of the probe; 3) A large amount of particulate matter and other types of gases produced by combustion will interfere with the detection of nitrogen oxides. This requires the sensor to have good selectivity and response speed, as well as dustproof filtration design.

[0006] Therefore, further optimization of this type of sensor is needed. Summary of the Invention

[0007] Based on the above problems, the purpose of this invention is to provide an integrated sensor for ammonia and nitrogen oxides, which meets the requirement of simultaneously detecting the content of nitrogen oxides and ammonia in diesel vehicle exhaust, and can work reliably under high temperature and harsh conditions.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] An integrated ammonia and nitrogen oxide sensor includes a probe assembly, a circuit package, and a lead tube connecting the two. The probe assembly includes a chip holder, in which a gas-sensitive chip is installed. A dust filter is provided at the head end of the chip holder, and a slow-cooling cylinder is provided at the tail end. A conditioning circuit board is provided in the circuit package. The leads of the gas-sensitive chip are led out through the slow-cooling cylinder, pass through the lead tube, and are connected to the conditioning circuit board in the circuit package, thereby transmitting and analyzing the collected signals and converting the gas composition information into a digital signal.

[0010] Specifically, the gas-sensitive chip includes a substrate, on the front side of which intercalation electrodes are screen-printed, and a first insulating film is magnetron sputtered over the area outside the intercalation electrodes. A gas-sensitive film is screen-printed on the intercalation electrodes. A second insulating film is magnetron sputtered over the back side of the substrate, and a heating temperature sensing electrode is screen-printed on the second insulating film. A third insulating film is magnetron sputtered over the surface of the heating temperature sensing electrode.

[0011] Specifically, the substrate is made of zirconia ceramic material, the interdigitated electrodes and heating and temperature measuring electrodes are made of platinum metal material, the first insulating film, the second insulating film and the third insulating film are all made of alumina material, and the gas-sensitive film is a gas-sensitive material that can work normally at 800℃.

[0012] Specifically, the dust filter has a double-layer structure, including an inner cylinder and an outer cylinder. One end of the inner cylinder is threaded to the chip mounting base, and a vent hole is opened on the other end face of the inner cylinder. The outer cylinder is fitted around the inner cylinder with gaps, and one end of the outer cylinder is threaded to the chip mounting base. The other end of the outer cylinder is closed, and several perforated holes are evenly distributed on the side wall of the outer cylinder.

[0013] Specifically, the gas-sensitive chip is fitted with several zirconia rings. The outer edge size of the zirconia rings is adapted to the inner hole size of the chip holder. A boss is provided on the inner wall of one end of the chip holder to limit the zirconia rings. The inner cylinder extends into the inner hole of the other end of the chip holder to clamp and fix each zirconia ring.

[0014] Specifically, the slow cooling cylinder includes a main body cylinder, one end of which is threadedly connected to the chip mounting base, and the other end of the main body cylinder has a wire outlet hole. The side wall of the main body cylinder has a wiring port, and the main body cylinder is fitted with a sleeve that seals the wiring port.

[0015] Specifically, a wire support block is provided on the outer wall of the main body and on one side of the wire outlet. A wire clamping block is connected to the wire support block by bolts. The wire support block and the wire clamping block cooperate to clamp and fix the lead wire of the gas-sensitive chip.

[0016] Specifically, the assembly of the wire support block and the wire clamping block is cylindrical, with one end of the lead tube fitted onto the assembly and the other end of the lead tube having a quick-connect connector for insertion into the circuit package.

[0017] In particular, all components of the probe assembly are made of 310S stainless steel.

[0018] In summary, the beneficial effects of the present invention are as follows: compared with the prior art, the integrated ammonia and nitrogen oxide sensor adopts a detachable modular design, and reliably encapsulates and protects the mixed potential gas-sensitive chip, so as to accurately analyze the gas composition information in diesel vehicle exhaust gas even under high temperature and harsh working conditions, meet the monitoring needs, optimize the urea aqueous solution injection volume, reduce the risk of urea crystallization, and has a simple and reliable structure with low manufacturing and maintenance costs. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the integrated ammonia and nitrogen oxide sensor provided in an embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of the probe assembly in the integrated ammonia and nitrogen oxide sensor provided in an embodiment of the present invention;

[0021] Figure 3 This is an exploded view of the probe assembly in the integrated ammonia and nitrogen oxide sensor provided in this embodiment of the invention;

[0022] Figure 4 This is an exploded view of the gas-sensitive chip in the integrated ammonia and nitrogen oxide sensor provided in this embodiment of the invention;

[0023] Figure 5 This is a schematic diagram of the assembly of the gas-sensitive chip in the integrated ammonia and nitrogen oxide sensor provided in an embodiment of the present invention;

[0024] Figure 6 This is a process flow diagram of the gas-sensitive chip in the integrated ammonia and nitrogen oxide sensor provided in the embodiments of the present invention.

[0025] In the picture:

[0026] 1-Probe assembly; 11-Chip holder; 111-Boss; 12-Fum filter; 121-Inner cylinder; 122-Outer cylinder; 123-Ventilation hole; 124-Perforated hole; 13-Slow cooling cylinder; 131-Main body cylinder; 132-Cable outlet; 133-Connection port; 134-Sleeve; 135-Cable support block; 136-Cable clamping block;

[0027] 2-Circuit package;

[0028] 3-Lead tube;

[0029] 4-Gas-sensitive chip; 41-Substrate; 42-Intercalation electrode; 43-First insulating film; 44-Gas-sensitive film; 45-Second insulating film; 46-Heating and temperature-sensing electrode; 47-Third insulating film;

[0030] 5-Zirconium oxide ring. Detailed Implementation

[0031] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0032] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, a mechanical connection, an electrical connection, or an indirect connection via an intermediate medium. They can also refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0033] In the description of this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature. The technical solutions of this invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0034] Please see Figures 1 to 5 As shown, this preferred embodiment provides an integrated ammonia and nitrogen oxide sensor, which includes a probe assembly 1, a circuit package 2, and a lead tube 3 connecting the two. The probe assembly 1 encapsulates and protects the gas-sensitive chip 4, and the lead tube 3 transmits the signal to the conditioning circuit of the circuit package 2 for signal analysis, ultimately realizing the purpose of converting gas composition information into digital signals.

[0035] like Figure 2 As shown, the probe assembly 1 includes a chip holder 11, in which a gas-sensitive chip 4 is installed. A dust filter 12 is provided at the head end of the chip holder 11, and a slow cooling cylinder 13 is provided at the tail end. A conditioning circuit board is provided in the circuit package 2. The lead wire of the gas-sensitive chip 4 is led out through the slow cooling cylinder 13, passes through the lead tube 3, and is connected to the conditioning circuit board in the circuit package 2.

[0036] The probe assembly 1 is preferably designed as a detachable structure. To ensure its use, it should be made of a metal material that can work stably at a high temperature of 800℃, with low thermal stress, low thermal deformation and slight creep. Preferably, 310S stainless steel is used.

[0037] See details Figure 3 Specifically, the dust filter 12 is designed with a double-layer structure, including an inner cylinder 121 and an outer cylinder 122. One end of the inner cylinder 121 is threadedly connected to the chip holder 11, and a vent hole 123 is opened on the other end face of the inner cylinder 121. The outer cylinder 122 is fitted around the inner cylinder 121 with gaps, and one end of the outer cylinder 122 is threadedly connected to the chip holder 11. The other end of the outer cylinder 122 is closed. Several perforated holes 124 are evenly distributed on the side wall of the outer cylinder 122, thereby effectively filtering dust and avoiding interference with the detection of the gas-sensitive chip 4.

[0038] Considering the poor temperature resistance of the leads, the slow cooling tube, in addition to providing the operating space required for wiring, is more importantly designed to protect the subsequent wires from high temperatures. The slow cooling tube 13 here includes a main body tube 131, one end of which is threaded to the chip mounting base 11, and the other end of the main body tube 131 has a wire outlet hole 132. A wiring port 133 is provided on the side wall of the main body tube 131, and a sleeve 134 is provided on the main body tube 131 to seal the wiring port 133.

[0039] Furthermore, a wire support block 135 is provided on the outer wall of the main body cylinder 131 and on one side of the wire outlet hole 132. A wire clamping block 136 is connected to the wire support block 135 by bolts. The wire support block 135 and the wire clamping block 136 cooperate to clamp and fix the lead wire of the gas-sensitive chip 4.

[0040] Specifically, the assembly of the wire support block 135 and the wire clamp block 136 is cylindrical, one end of the lead tube 3 is sleeved on the assembly, and the other end of the lead tube 3 is provided with a quick-connect connector for insertion into the circuit package 2.

[0041] See details Figure 4The gas-sensitive chip 4 here adopts the form of an integrated hybrid potential gas-sensitive sensor, specifically including a substrate 41. The front side of the substrate 41 is screen-printed with interdigitated electrodes 42, and a first insulating film 43 is magnetron sputtered and covered in the area outside the interdigitated electrodes 42. A gas-sensitive film 44 is screen-printed on the interdigitated electrodes 42. A second insulating film 45 is magnetron sputtered and covered on the back side of the substrate 41. A heating temperature measuring electrode 46 is screen-printed on the second insulating film 45, and a third insulating film 47 is magnetron sputtered and covered on the surface of the heating temperature measuring electrode 46.

[0042] The substrate 41 should be made of a high-temperature resistant solid electrolyte ceramic material, preferably a zirconia ceramic material, and should have sufficient thickness to serve as a substrate to support the sensor structure and conduct oxygen ions, directly participating in the gas-sensitive reaction.

[0043] The materials of the interdigitated electrode 42 and the heating and temperature measuring electrode 46 should be metals with good electrical conductivity and temperature resistance characteristics, preferably platinum.

[0044] The first insulating film 43, the second insulating film 45, and the third insulating film 47 are all made of aluminum oxide, which serves to prevent short circuits between the heating and temperature measuring electrode 46 and the interdigitating electrode 42.

[0045] The gas-sensitive membrane 44 should be made of a gas-sensitive material with excellent gas-sensitive performance and capable of normal operation at a high temperature of 800℃. The gas-sensitive material can be a homogeneous single layer (such as a single phase or a mechanically mixed multiphase) or a heterogeneous multilayer (such as a stack or an island stack) or any combination thereof. The structure of the gas-sensitive membrane 44 can be nanorods, nanowires, nanoparticles, etc.

[0046] To ensure reliable fixation of the gas-sensitive chip 4, several zirconia rings 5 ​​are fitted around the gas-sensitive chip 4. The outer edge dimensions of the zirconia rings 5 ​​are adapted to the inner hole dimensions of the chip holder 11, as detailed in [link to details]. Figure 5 A boss 111 is provided on the inner wall of one end of the chip holder 11 to limit the zirconia ring 5. The inner cylinder 121 extends into the inner hole of the other end of the chip holder 11 to clamp and fix each zirconia ring 5. Furthermore, the end face of the chip holder 11 can be sealed with thermosetting adhesive to ensure the overall airtightness of the probe assembly 1.

[0047] For details, please see Figure 6 This embodiment also provides the manufacturing process flow of the gas-sensitive chip 4:

[0048] (1) The interdigitated electrode 42 is fabricated on the front side of the substrate 41 by screen printing;

[0049] (2) The first insulating film 43 is covered in the area excluding the interdigitated electrode 42 by magnetron sputtering;

[0050] (3) Screen printing a gas-sensitive film 44 on the interdigitated electrode 42;

[0051] (4) Perform magnetron sputtering on the entire reverse side of substrate 41 to process a second insulating film 45;

[0052] (5) Screen printing heating temperature measuring electrode 46 on the second insulating film 45;

[0053] (6) Magnetron sputtering is used to process the third insulating film 47.

[0054] In summary, the aforementioned integrated ammonia and nitrogen oxide sensor adopts a detachable modular design, reliably encapsulates and protects the hybrid potential gas-sensitive chip, and can accurately analyze the gas composition information in diesel vehicle exhaust even under high temperature and harsh working conditions, meeting monitoring needs, thereby optimizing the urea aqueous solution injection volume, reducing the risk of urea crystallization, and has a simple and reliable structure with low manufacturing and maintenance costs.

[0055] The above embodiments merely illustrate the basic principles and characteristics of the present invention. The present invention is not limited to the above embodiments. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. An integrated sensor for ammonia and nitrogen oxides, characterized in that, The device includes a probe assembly, a circuit package, and a lead tube connecting the two. The probe assembly includes a chip holder, in which a gas-sensitive chip is installed. A dust filter is provided at the head end of the chip holder, and a slow-cooling cylinder is provided at the tail end. A conditioning circuit board is provided in the circuit package. The lead wire of the gas-sensitive chip is led out through the slow-cooling cylinder, passes through the lead tube, and is connected to the conditioning circuit board in the circuit package, thereby transmitting and analyzing the collected signal and converting the gas composition information into a digital signal. The dust filter has a double-layer structure, including an inner cylinder and an outer cylinder. One end of the inner cylinder is threadedly connected to the chip mounting base, and a vent hole is opened on the other end face of the inner cylinder. The outer cylinder is intermittently sleeved outside the inner cylinder, and one end of the outer cylinder is threadedly connected to the chip mounting base. The other end of the outer cylinder is closed, and several perforated holes are evenly distributed on the side wall of the outer cylinder. The gas-sensitive chip is covered with several zirconia rings. The outer edge size of the zirconia rings is adapted to the inner hole size of the chip holder. A boss is provided on the inner wall of one end of the chip holder to limit the zirconia rings. The inner cylinder extends into the inner hole of the other end of the chip holder to clamp and fix each zirconia ring. The slow cooling cylinder includes a main cylinder, one end of which is threadedly connected to the chip mounting base, and the other end face of the main cylinder has a wire outlet hole. A wiring port is provided on the side wall of the main cylinder, and a sleeve covering the wiring port is provided on the main cylinder. The gas-sensitive chip includes a substrate. The front side of the substrate is screen-printed with interdigitated electrodes, and a first insulating film is magnetron sputtered over the area outside the interdigitated electrodes. A gas-sensitive film is screen-printed on the interdigitated electrodes. The back side of the substrate is magnetron sputtered over a second insulating film, on which a heating and temperature-sensing electrode is screen-printed. A third insulating film is magnetron sputtered over the surface of the heating and temperature-sensing electrode. The substrate is made of zirconia ceramic material, the interdigitated electrodes and the heating and temperature-sensing electrode are both made of platinum metal material, the first, second, and third insulating films are all made of alumina material, and the gas-sensitive film is a gas-sensitive material that operates normally at 800°C. A wire support block is provided on the outer wall of the main body cylinder and on one side of the wire outlet hole. A wire clamping block is connected to the wire support block by bolts. The wire support block and the wire clamping block cooperate to clamp and fix the lead wire of the gas-sensitive chip. The combination of the wire support block and the wire clamping block is cylindrical. One end of the lead tube is sleeved on the combination, and the other end of the lead tube is provided with a quick connector for insertion into the circuit package.

2. The integrated ammonia and nitrogen oxide sensor according to claim 1, characterized in that: Each component of the probe assembly is made of 310S stainless steel.

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