Device and system for monitoring oxygen concentration in automobile exhaust pipe

Abstract

The invention discloses a device and a system for monitoring oxygen concentration in an automobile exhaust pipe, and relates to the technical field of exhaust pipe oxygen monitoring, a central sampling pipe and a near-wall sampling pipe are correspondingly mounted on the inner walls of the two sides of the exhaust pipe, one end of the central sampling pipe extends to the center of the exhaust pipe, and the other end of the central sampling pipe extends to the other end of the near-wall sampling pipe; one end of the near-wall sampling pipe is communicated and connected with the inner wall of the exhaust pipe, the central sampling pipe and the near-wall sampling pipe are communicated and connected with each other and are jointly connected with a venturi tube, a zirconia ceramic oxygen sensor is arranged in the venturi tube, one end of the venturi tube is connected with an air pump, and the other end of the venturi tube is connected with an exhaust pipe. The other end of the venturi tube is connected with a filtering channel in a penetrating mode, oxygen selective membranes are correspondingly installed on the inner walls of the upper side and the lower side of the filtering channel, the oxygen selective membranes and the inner walls of the filtering channel form a closed cavity, and the two sides of the filtering channel are connected with the opening binding section of the venturi tube through pipelines in a penetrating mode respectively; the method has the characteristic of high detection precision.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas detection, in particular to an oxygen concentration monitoring device and system in an automobile exhaust pipe. BACKGROUND

[0002] The oxygen concentration sensor installed in the automobile exhaust pipe is used to detect the oxygen concentration in the exhaust gas and determine the combustion state of the engine. Most of them are based on the electrochemical principle of zirconia ceramic: by comparing the oxygen concentration difference between the exhaust gas and the reference air, an electric signal is generated, or the real oxygen concentration is reflected by the pump current.

[0003] The traditional oxygen concentration detection in the exhaust pipe adopts a single sampling point form for detection. Since the gas composition in the center of the exhaust pipe and near the wall is different, vortex and backflow are more likely to occur near the wall, and the oxygen in the backflow exhaust gas is less, and the oxygen proportion in the center mainstream is higher, so single-point measurement may be high or low. In order to overcome this problem, the prior art uses multiple probe arrangements to overcome the shortcomings of single-point detection, or tries to collect gas in different areas in a probe with a ring-shaped sampling head, or mixes and detects in a bypass chamber. The cost of multiple probes is high, the arrangement is complex, and the ECU calculation is large. The mixing of the ring-shaped sampling head is not complete and is easy to block. The bypass chamber needs to be fully mixed, and the response delay is large.

[0004] At the same time, the detection accuracy of the zirconia ceramic oxygen sensor is not uniform, but the accuracy is highest in a certain oxygen concentration range, and decreases significantly on both sides. With the uneven fluctuation of the exhaust gas, sometimes it may deviate from the optimal concentration range, resulting in that the detection data cannot be used many times. Therefore, it is necessary to design an automobile exhaust pipe oxygen concentration monitoring device and system with high detection accuracy. SUMMARY

[0005] The purpose of the present application is to provide an oxygen concentration monitoring device and system in an automobile exhaust pipe to solve the problems raised in the background art.

[0006] In order to solve the above technical problems, the present application provides the following technical scheme: an oxygen concentration monitoring device in an automobile exhaust pipe, comprising an exhaust pipe, the inner walls of both sides of the exhaust pipe are correspondingly provided with a center sampling pipe and a near-wall sampling pipe, one end of the center sampling pipe extends to the center of the exhaust pipe, one end of the near-wall sampling pipe is connected with the inner wall of the exhaust pipe, the center sampling pipe and the near-wall sampling pipe are connected with each other, and a Venturi tube is connected with both of them, the inside of the Venturi tube is provided with a zirconia ceramic oxygen sensor, and one end of the Venturi tube is connected with an air pump.

[0007] According to the technical scheme, the other end of the Venturi tube is connected with a filtering channel, the upper and lower inner walls of the filtering channel are correspondingly provided with oxygen selective membranes, the oxygen selective membranes and the inner walls of the filtering channel form a closed cavity, the two sides of the filtering channel are connected with the nozzle section of the Venturi tube through pipelines, the two sides of the filtering channel are respectively provided with a low threshold pressure transmitter and a high threshold pressure transmitter, the center sampling pipe is provided with an electric control throttle valve one, and the near wall sampling pipe is provided with an electric control throttle valve two.

[0008] According to the technical scheme, the oxygen concentration acquisition module is electrically connected with the zirconia ceramic oxygen sensor, the sampling ratio adjustment module is electrically connected with the throttle valve control unit, the low threshold pressure transmitter and the high threshold pressure transmitter, the throttle valve control unit is electrically connected with the electric control throttle valve one and the electric control throttle valve two, and the optimal concentration range setting module is electrically connected with the oxygen concentration correction module. The oxygen concentration acquisition module is used for processing a weak electric signal output by the zirconia ceramic oxygen sensor and acquiring an oxygen concentration value, the sampling ratio adjustment module is used for calculating a sampling ratio of gases in the center and the near wall of the exhaust pipe, the throttle valve control unit is used for controlling the flow of the electric control throttle valve one and the electric control throttle valve two, the optimal concentration range setting module is used for setting an optimal oxygen concentration range, and the oxygen concentration correction module is used for correcting the detection result of the zirconia ceramic oxygen sensor according to the sampling ratio of the gases, and calculating a real oxygen concentration in the exhaust pipe.

[0009] According to the technical scheme, S1, the gas pump is started, the zirconia ceramic oxygen sensor is used to detect the oxygen concentration under the condition that the center sampling pipe and the near wall sampling pipe are separately connected, the average oxygen concentration ratio of the center and the near wall of the exhaust pipe is calculated, and the opening ratio of the electric control throttle valve one and the electric control throttle valve two is calculated when the detection accuracy is the highest. S2, the oxygen concentration in the exhaust pipe is continuously detected at the opening ratio, the trigger pressures of the low threshold pressure transmitter and the high threshold pressure transmitter are set, and the oxygen in the middle part of the filtering channel is extracted to both sides by the negative pressure of the nozzle section as the gases flow in the Venturi tube. S3, when the oxygen concentration in the filtering channel is too high or too low, the low threshold pressure transmitter and the high threshold pressure transmitter act, the electric control throttle valve one and the electric control throttle valve two adjust the opening ratio, and the oxygen concentration in the filtering channel is adjusted to the vicinity of the optimal sampling range of the zirconia ceramic oxygen sensor. S4, according to the current opening ratio of the electric control throttle valve one and the electric control throttle valve two, the detection result of the zirconia ceramic oxygen sensor is corrected, and the real oxygen concentration in the exhaust pipe is calculated.

[0010] According to the above technical scheme, in S1, the calculation process of the average oxygen concentration ratio is specifically: S1-1, because the center and near-wall gas composition in the exhaust pipe changes with the engine working condition and the environment, the electric control throttle valve one and the electric control throttle valve two are opened respectively and independently for a set time every time the car is normally and stably driven , and the zirconia ceramic oxygen sensor is used to detect the oxygen concentration in the center of the exhaust pipe and the oxygen concentration near the wall of the exhaust pipe within ; S1-2, according to the oxygen concentration detection formula: , wherein is the sensor output voltage, is the gas constant, is the temperature, is the Faraday constant, is the oxygen partial pressure in the exhaust gas, is the oxygen partial pressure in the air, and the oxygen partial pressure is proportional to the oxygen concentration, and the conversion coefficient of the two is , is a known quantity, and it is verified by experiments that the detection accuracy is highest when , so the oxygen concentration when the detection accuracy is highest is calculated , and when selecting the type of zirconia ceramic oxygen sensor, it is necessary to ensure that , at this time the sampling gas oxygen concentration is , , and and are calculated, so that the opening ratio of the electric control throttle valve one and the electric control throttle valve two when the detection accuracy is highest is obtained.

[0011] According to the above technical scheme, in S2, the setting method of the trigger pressure is: S2-1, under the constant flow of the gas pump, the negative pressure of the Venturi tube will extract the oxygen in the filter channel to both sides, because the oxygen selective membrane can only permeate oxygen and block other gas molecules, the higher the oxygen concentration in the filter channel, the higher the pressure in the cavity between the oxygen selective membrane and the inner wall of the filter channel, until the trigger pressure of the high threshold pressure transmitter is reached, and vice versa. The lower the oxygen concentration in the filter channel, the lower the pressure in the cavity between the oxygen selective membrane and the inner wall of the filter channel, until the trigger pressure of the low threshold pressure transmitter is reached. S2-2, the best detection range is to The median value. The range of values, i.e., the minimum oxygen concentration within the optimal detection range, is... The highest oxygen concentration within the optimal detection range is ,in The constant is determined based on the actual situation. The oxygen supply ratio at the center of the exhaust pipe is gradually increased to adjust the oxygen concentration within the venturi tube. Elevation until detected At this point, record the pressure detected by the high threshold pressure transmitter. Slowly increase the proportion of oxygen supplied near the wall of the exhaust pipe to reduce the oxygen concentration in the venturi tube. Decrease until detected At this point, record the pressure detected by the low threshold pressure transmitter. , and These are the trigger pressures for the high-threshold pressure transmitter and the low-threshold pressure transmitter, respectively.

[0012] According to the above technical solution, in step S3, adjusting the opening ratio is subject to two triggering conditions: S3-1, When the trigger condition is a high threshold pressure transmitter, the detected pressure value is... If the oxygen concentration is too high, the opening of the electronically controlled throttle valve one is reduced and the opening of the electronically controlled throttle valve two is increased, while maintaining the total gas flow rate of the central sampling tube and the near-wall sampling tube equal. S3-2, When the trigger condition is a low threshold pressure transmitter, the detected pressure value is... If the oxygen concentration is too low, the opening of the electronically controlled throttle valve one is increased and the opening of the electronically controlled throttle valve two is decreased, while maintaining the total gas flow rate of the central sampling tube and the near-wall sampling tube equal. S3-3, Continue adjusting until the zirconia ceramic oxygen sensor detects that the oxygen concentration reaches [the specified value]. Stop adjusting the opening of the electronically controlled throttle valve one and electronically controlled throttle valve two.

[0013] According to the above technical solution, in step S4, calculating the actual oxygen concentration in the exhaust pipe specifically involves: when the adjustment stops, recording the opening degrees of the electronically controlled throttle valve one and the electronically controlled throttle valve two, and calculating their opening ratio to obtain the adjusted oxygen concentration. and Because the gas pumping ratio between the center and near the wall is artificially adjusted at this time, the actual oxygen concentration in the exhaust pipe is different from that in other parts of the exhaust pipe. There is a deviation. Comparing the opening ratios of the electronically controlled throttle valve one and two with the highest detection accuracy in S1-2, the oxygen concentration is calculated without adjusting the openings of electronically controlled throttle valve one and two. Let the oxygen concentration at the center of the exhaust pipe in S3 be... The oxygen concentration near the wall of the exhaust pipe is , the formula is , , wherein The sign of the positive and negative is defined according to the actual detected pressure in the filter channel, and the calculation is obtained And The real oxygen concentration in the exhaust pipe is calculated.

[0014] Compared with the prior art, the beneficial effects achieved by the present application are: the present application has a core sampling port and a near-wall sampling port in the exhaust pipe, and the center and near-wall of the exhaust pipe are sampled in a certain proportion, and the sampling gas passes through the filter channel with an oxygen selective microcavity film, when the oxygen concentration is too high or too low, the filter channel characteristics change suddenly, resulting in the change of the pressure transmitter display of the outlet, which controls the gas sampling ratio, when the oxygen concentration is too high, the near-wall gas sampling ratio of the exhaust pipe is increased, when the oxygen concentration is too low, the center gas sampling ratio of the exhaust pipe is increased, so that the oxygen concentration of the sampling gas is maintained near the optimal sampling range of the zirconia ceramic oxygen sensor, the effectiveness of the detection data is improved throughout the period, this method is more flexible than the sampling method of the annular sampling head, and only one sensor is needed for detection, the cost is low, and a special mixed response is not needed, which is faster. BRIEF DESCRIPTION OF DRAWINGS

[0015] The accompanying drawings are used to provide a further understanding of the present application, and constitute a part of the specification, together with the embodiments of the present application, to explain the present application, and do not constitute a limitation on the present application. In the drawings: Figure 1 is a schematic diagram of the principle of the present application; Figure 2 is a schematic diagram of the overall module structure of the present application; In the figure: 1, exhaust pipe; 21, center sampling pipe; 22, near-wall sampling pipe; 211, electric control throttle valve one; 221, electric control throttle valve two; 3, filter channel; 31, oxygen selective membrane; 32, low threshold pressure transmitter; 33, high threshold pressure transmitter; 4, venturi tube; 41, zirconia ceramic oxygen sensor; 5, air pump. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application, obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0017] Please refer to Figure 1 And Figure 2The application provides a technical scheme: an automobile exhaust pipe oxygen concentration monitoring device and system, which comprises an exhaust pipe 1, a center sampling pipe 21 and a near-wall sampling pipe 22 are correspondingly arranged on the inner walls of the two sides of the exhaust pipe 1, one end of the center sampling pipe 21 extends to the center of the exhaust pipe 1, one end of the near-wall sampling pipe 22 is connected with the inner wall of the exhaust pipe 1 in a penetrating mode, the center sampling pipe 21 and the near-wall sampling pipe 22 are connected with each other in a penetrating mode, and the two pipes are jointly connected with a Venturi tube 4, a zirconia ceramic oxygen sensor 41 is arranged in the Venturi tube 4, and one end of the Venturi tube 4 is connected with an air pump 5; The other end of the Venturi tube 4 is connected with a filtering channel 3 in a penetrating mode, oxygen selective membranes 31 are correspondingly arranged on the inner walls of the upper and lower sides of the filtering channel 3, the oxygen selective membranes 31 and the inner wall of the filtering channel 3 form a sealed cavity, the two sides of the filtering channel 3 are connected with the converging section of the Venturi tube 4 through pipelines in a penetrating mode, low threshold pressure transmitters 32 and high threshold pressure transmitters 33 are arranged on the two sides of the filtering channel 3, an electric control throttle valve one 211 is arranged on the center sampling pipe 21, and an electric control throttle valve two 221 is arranged on the near-wall sampling pipe 22; The system comprises an oxygen concentration collecting module, a sampling ratio adjusting module, a throttle valve control unit, an optimal concentration range setting module and an oxygen concentration correcting module, the oxygen concentration collecting module is electrically connected with the zirconia ceramic oxygen sensor 41, the sampling ratio adjusting module is electrically connected with the throttle valve control unit, the low threshold pressure transmitter 32 and the high threshold pressure transmitter 33, the throttle valve control unit is electrically connected with the electric control throttle valve one 211 and the electric control throttle valve two 221, and the optimal concentration range setting module is electrically connected with the oxygen concentration correcting module. The oxygen concentration collecting module is used for processing a weak electric signal output by the zirconia ceramic oxygen sensor and collecting the oxygen concentration of the weak electric signal, the sampling ratio adjusting module is used for calculating the ratio of gas sampling of the center of the exhaust pipe and the near wall, the throttle valve control unit is used for controlling the flow of the electric control throttle valve one 211 and the electric control throttle valve two 221, the optimal concentration range setting module is used for setting the optimal oxygen concentration range, and the oxygen concentration correcting module is used for correcting the detection result of the zirconia ceramic oxygen sensor 41 according to the ratio of gas sampling, so that the real oxygen concentration in the exhaust pipe is calculated. The working method of the system is as follows: S1, start the air pump 5, use the zirconia ceramic oxygen sensor 41 to detect the oxygen concentration under the condition that the center sampling pipe 21 and the near-wall sampling pipe 22 are separately connected, calculate the average oxygen concentration ratio of the center of the exhaust pipe 1 and the near wall, and calculate the opening ratio of the electric control throttle valve one 211 and the electric control throttle valve two 221 when the detection accuracy is the highest; S2, continue to detect the oxygen concentration in the exhaust pipe 1 with the opening ratio, set the trigger pressure of the low threshold pressure transmitter 32 and the high threshold pressure transmitter 33, and use the negative pressure of the beam section to extract the oxygen in the middle of the filter channel 3 to both sides as the gas flows in the Venturi tube 4; S3, when the oxygen concentration in the filter channel 3 is too high and too low, the low threshold pressure transmitter 32 and the high threshold pressure transmitter 33 act, and the electric control throttle valve one 211 and the electric control throttle valve two 221 adjust the opening ratio, so that the oxygen concentration in the filter channel 3 is adjusted to the vicinity of the best sampling range of the zirconia ceramic oxygen sensor; S4, according to the current opening ratio of the electric control throttle valve one 211 and the electric control throttle valve two 221, the detection result of the zirconia ceramic oxygen sensor 41 is corrected, and the real exhaust pipe oxygen concentration is calculated; In S1, the calculation process of the average oxygen concentration ratio is as follows: S1-1, because the center and near-wall gas composition in the exhaust pipe 1 changes with the engine working condition and the environment, each time the electric control throttle valve one 211 and the electric control throttle valve two 221 are opened separately for a set time when the car is normally and stably driven , the zirconia ceramic oxygen sensor 41 is used to detect the oxygen concentration of the center of the exhaust pipe 1 and the oxygen concentration near the wall of the exhaust pipe 1 ; S1-2, according to the oxygen concentration detection formula: , wherein is the sensor output voltage, is the gas constant, is the temperature, is the Faraday constant, is the oxygen partial pressure in the exhaust gas, is the oxygen partial pressure in the air, and the oxygen partial pressure is proportional to the oxygen concentration, and the conversion coefficient of the two is , is a known quantity, and it is verified by experiment that the detection accuracy is highest when , so the oxygen concentration when the detection accuracy is highest is calculated, and when the zirconia ceramic oxygen sensor 41 is selected, it needs to ensure that , at this time, the sampling gas oxygen concentration is , according to , , the and are calculated, so that the opening ratio of the electric control throttle valve one 211 and the electric control throttle valve two 221 when the detection accuracy is highest is obtained; In S2, the setting method of the trigger pressure is: S2-1, under the constant flow of gas pumping, the negative pressure of the Venturi tube 4 will extract the oxygen in the filter channel 3 to both sides, because the oxygen selective membrane 31 can only permeate oxygen and block other gas molecules, the higher the oxygen concentration in the filter channel 3, the higher the pressure in the cavity between the oxygen selective membrane 31 and the inner wall of the filter channel 3, until the trigger pressure of the high threshold pressure transmitter 33 is reached, otherwise the lower the oxygen concentration in the filter channel 3, the lower the pressure in the cavity between the oxygen selective membrane 31 and the inner wall of the filter channel 3, until the trigger pressure of the low threshold pressure transmitter 32 is reached; S2-2, the optimal detection range is as the intermediate value, as the range of the value interval, that is, the lowest value of the oxygen concentration in the optimal detection range is , and the highest value of the oxygen concentration in the optimal detection range is , wherein is a constant determined according to the actual situation, slowly increasing the supply ratio of oxygen at the center of the exhaust pipe 1 to increase the oxygen concentration in the Venturi tube 4 , until is detected, at which time the pressure detected by the high threshold pressure transmitter 33 is recorded , slowly increasing the supply ratio of oxygen near the wall of the exhaust pipe 1 to decrease the oxygen concentration in the Venturi tube 4 , until is detected, at which time the pressure detected by the low threshold pressure transmitter 32 is recorded , and are the trigger pressures of the high threshold pressure transmitter 33 and the low threshold pressure transmitter 32, respectively; In S3, when adjusting the opening ratio, there are two trigger conditions: S3-1, when the trigger condition is that the high threshold pressure transmitter 33 detects a pressure value of , it is determined that the oxygen concentration is too high, the opening degree of the electric control throttle valve one 211 is reduced and the opening degree of the electric control throttle valve two 221 is increased, and the total gas flow of the center sampling pipe 21 and the near-wall sampling pipe 22 is maintained equal; S3-2, when the trigger condition is that the low threshold pressure transmitter 32 detects a pressure value of , it is determined that the oxygen concentration is too low, the opening degree of the electric control throttle valve one 211 is increased and the opening degree of the electric control throttle valve two 221 is reduced, and the total gas flow of the center sampling pipe 21 and the near-wall sampling pipe 22 is maintained equal; S3-3, continuously adjust until the zirconia ceramic oxygen sensor 41 detects that the oxygen concentration reaches , stop adjusting the opening degrees of the electric control throttle valve one 211 and the electric control throttle valve two 221; In S4, the real oxygen concentration in the exhaust pipe is calculated, specifically: when the adjustment is stopped, the opening degrees of the electric control throttle valve one 211 and the electric control throttle valve two 221 are recorded, and the opening ratio of the two is calculated to obtain the adjusted And Since the gas pumping ratio of the center and the near wall is artificially adjusted at this time, the real oxygen concentration in the exhaust pipe deviates from Compared with the opening ratio of the electric control throttle valve one 211 and the electric control throttle valve two 221 when the detection accuracy is highest in S1-2, the oxygen concentration under the condition that the opening degrees of the electric control throttle valve one 211 and the electric control throttle valve two 221 are not adjusted is calculated, and the center oxygen concentration in the exhaust pipe 1 in S3 is And the near wall oxygen concentration in the exhaust pipe 1 is The formula is , Wherein The positive and negative signs are determined according to the actual detected pressure in the filter channel 3, and the And The real oxygen concentration in the exhaust pipe is calculated.

[0018] The oxygen-selective membrane is a special thin film material, which is particularly easy for oxygen molecules to pass through, and other gases (such as nitrogen, carbon dioxide, water vapor, hydrocarbons, etc.) are slower or almost impermeable. By adding an oxygen-selective membrane, oxygen molecules can be singled out and sent to the detection unit.

[0019] The present application sets core sampling ports and near wall sampling ports in the exhaust pipe, samples the center and near wall of the exhaust pipe in a certain proportion, and makes the sampling gas pass through the filter channel with an oxygen-selective microcavity membrane. When the oxygen concentration is too high or too low, the filter channel characteristics change suddenly, causing the outlet pressure transmitter to change the control gas sampling ratio, and when the oxygen concentration is too high, the exhaust pipe near wall gas sampling ratio is increased, and when the oxygen concentration is too low, the exhaust pipe center gas sampling ratio is increased. The oxygen concentration of the sampling gas is maintained near the best sampling range of the zirconia ceramic oxygen sensor, improving the effectiveness of the detection data throughout the period. Compared with the sampling method of the annular sampling head, this method is more flexible and only one sensor is needed for detection, which is low in cost and does not need a special mixed response.

[0020] It is to be noted that, in the present text, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0021] Finally, it should be noted that the above-mentioned only constitutes preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications, equivalent replacements, improvements and the like of the technical solutions described in the foregoing embodiments can still be made. Any modifications, equivalent replacements, improvements and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An oxygen concentration monitoring device for an automobile exhaust pipe, comprising an exhaust pipe (1), characterized in that: The inner walls on both sides of the exhaust pipe (1) are respectively equipped with a central sampling tube (21) and a near-wall sampling tube (22). One end of the central sampling tube (21) extends to the center of the exhaust pipe (1), and one end of the near-wall sampling tube (22) is connected to the inner wall of the exhaust pipe (1). The central sampling tube (21) and the near-wall sampling tube (22) are connected to each other and are connected to a Venturi tube (4). A zirconia ceramic oxygen sensor (41) is installed inside the Venturi tube (4), and one end of the Venturi tube (4) is connected to an air pump (5).

2. The oxygen concentration monitoring device in a car exhaust pipe according to claim 1, characterized in that: The other end of the Venturi tube (4) is connected to a filter channel (3). Oxygen selective membranes (31) are installed on the inner walls of the upper and lower sides of the filter channel (3). The oxygen selective membranes (31) and the inner walls of the filter channel (3) form a sealed cavity. The two sides of the filter channel (3) are connected to the constriction section of the Venturi tube (4) through pipes. A low threshold pressure transmitter (32) and a high threshold pressure transmitter (33) are respectively installed on the two sides of the filter channel (3). An electrically controlled throttle valve one (211) is installed on the central sampling tube (21), and an electrically controlled throttle valve two (221) is installed on the near-wall sampling tube (22).

3. An oxygen concentration monitoring system for an automobile exhaust pipe, characterized in that: It includes an oxygen concentration acquisition module, a sampling ratio adjustment module, a throttle valve control unit, an optimal concentration range setting module, and an oxygen concentration correction module. The oxygen concentration acquisition module is electrically connected to a zirconia ceramic oxygen sensor (41). The sampling ratio adjustment module is electrically connected to a throttle valve control unit, a low threshold pressure transmitter (32), and a high threshold pressure transmitter (33). The throttle valve control unit is electrically connected to an electrically controlled throttle valve one (211) and an electrically controlled throttle valve two (221). The optimal concentration range setting module is electrically connected to the oxygen concentration correction module. The oxygen concentration acquisition module is used to process the weak electrical signal output by the zirconia ceramic oxygen sensor and acquire its oxygen concentration reading. The sampling ratio adjustment module is used to calculate the ratio of gas sampling at the center and near the wall of the exhaust pipe. The throttle valve control unit is used to control the flow rate of the electronically controlled throttle valve one (211) and the electronically controlled throttle valve two (221). The optimal concentration range setting module is used to set the optimal oxygen concentration range. The oxygen concentration correction module is used to correct the detection result of the zirconia ceramic oxygen sensor (41) according to the gas sampling ratio and calculate the actual oxygen concentration in the exhaust pipe.

4. The oxygen concentration monitoring system in an automobile exhaust pipe according to claim 3, characterized in that: The system works as follows: S1. Start the air pump (5), use the zirconia ceramic oxygen sensor (41) to detect the oxygen concentration when the center sampling tube (21) and the near wall sampling tube (22) are connected separately, calculate the average oxygen concentration ratio of the center and near wall of the exhaust pipe (1), and calculate the opening ratio of the electronically controlled throttle valve one (211) and the electronically controlled throttle valve two (221) when the detection accuracy is the highest. S2. The oxygen concentration in the exhaust pipe (1) is continuously detected at this opening ratio. The trigger pressure of the low threshold pressure transmitter (32) and the high threshold pressure transmitter (33) is set. As the gas flows in the venturi tube (4), the oxygen in the middle of the filter channel (3) is extracted to both sides by using the negative pressure of the constriction section. S3. When the oxygen concentration in the filter channel (3) is too high or too low, the low threshold pressure transmitter (32) and the high threshold pressure transmitter (33) act to control the opening ratio of the electronically controlled throttle valve one (211) and the electronically controlled throttle valve two (221) so that the oxygen concentration in the filter channel (3) is adjusted to near the optimal sampling range of the zirconia ceramic oxygen sensor. S4. Based on the current opening ratio of the electronically controlled throttle valve one (211) and the electronically controlled throttle valve two (221), the detection result of the zirconia ceramic oxygen sensor (41) is corrected, and the actual oxygen concentration in the exhaust pipe is calculated.

5. The oxygen concentration monitoring system in an automobile exhaust pipe according to claim 4, characterized in that: The calculation process for the average oxygen concentration ratio in S1 is as follows: S1-1. Because the gas composition in the center and near the wall of the exhaust pipe (1) changes constantly with the engine operating conditions and environment, the electronically controlled throttle valve one (211) and electronically controlled throttle valve two (221) need to be opened separately for the set time each time the car is driving normally and stably. Using a zirconia ceramic oxygen sensor (41) to detect oxygen in Within a certain time period, the oxygen concentration at the center of the exhaust pipe (1) and the oxygen concentration near the wall of the exhaust pipe (1) ; S1-2. According to the oxygen concentration detection formula: ,in The sensor output voltage, The gas constant is For temperature, It is Faraday's constant. This refers to the partial pressure of oxygen in the exhaust gas. This represents the partial pressure of oxygen in the air. The partial pressure of oxygen is directly proportional to the oxygen concentration, and the conversion factor between the two is... , It is a known quantity, and its existence has been verified by experiments. The detection accuracy is highest at this time, therefore the oxygen concentration at which the detection accuracy is highest can be calculated. Furthermore, when selecting the zirconia ceramic oxygen sensor (41) model, it is necessary to ensure that... At this time, the oxygen concentration of the sampled gas is ,according to , Calculation and Thus, the opening ratio of the first (211) and the second (221) of the electrically controlled throttle valve is obtained when the detection accuracy is highest.

6. The oxygen concentration monitoring system in an automobile exhaust pipe according to claim 5, characterized in that: In S2, the method for setting the trigger pressure is as follows: S2-1. Under constant flow gas pumping, the negative pressure of the venturi tube (4) will draw oxygen in the filter channel (3) to both sides. Since the oxygen selective membrane (31) can only pass through oxygen and block other gas molecules, the higher the oxygen concentration in the filter channel (3), the higher the pressure in the cavity between the oxygen selective membrane (31) and the inner wall of the filter channel (3), until the trigger pressure of the high threshold pressure transmitter (33) is reached. Conversely, the lower the oxygen concentration in the filter channel (3), the lower the pressure in the cavity between the oxygen selective membrane (31) and the inner wall of the filter channel (3), until the trigger pressure of the low threshold pressure transmitter (32) is reached. S2-2, The optimal detection range is based on The median value. The range of values, i.e., the minimum oxygen concentration within the optimal detection range, is... The highest oxygen concentration within the optimal detection range is ,in The constant is determined based on the actual situation. The oxygen supply ratio in the center of the exhaust pipe (1) is slowly increased to reduce the oxygen concentration in the venturi tube (4). Elevation until detected At this point, the pressure detected by the high threshold pressure transmitter (33) is recorded. Slowly increase the oxygen supply ratio near the wall of the exhaust pipe (1) to reduce the oxygen concentration in the venturi tube (4). Decrease until detected At this point, the pressure detected by the low threshold pressure transmitter (32) is recorded. , and The trigger pressures are the high threshold pressure transmitter (33) and the low threshold pressure transmitter (32), respectively.

7. The oxygen concentration monitoring system in an automobile exhaust pipe according to claim 6, characterized in that: In S3, adjusting the opening ratio is subject to two triggering conditions: S3-1, When the trigger condition is a high threshold pressure transmitter (33) detects a pressure value of When the oxygen concentration is too high, the opening of the first electronically controlled throttle valve (211) is reduced and the opening of the second electronically controlled throttle valve (221) is increased, and the total gas flow rate of the central sampling tube (21) and the near-wall sampling tube (22) is kept equal. S3-2, When the trigger condition is low threshold, the pressure transmitter (32) detects a pressure value of When the oxygen concentration is too low, the opening of the first electronically controlled throttle valve (211) is increased and the opening of the second electronically controlled throttle valve (221) is decreased, and the total gas flow rate of the central sampling tube (21) and the near-wall sampling tube (22) is kept equal. S3-3, Continue adjusting until the zirconia ceramic oxygen sensor (41) detects that the oxygen concentration reaches [the specified value]. Stop adjusting the opening of the electronically controlled throttle valve one (211) and the electronically controlled throttle valve two (221).

8. The oxygen concentration monitoring system in an automobile exhaust pipe according to claim 7, characterized in that: In step S4, the calculation of the actual oxygen concentration in the exhaust pipe is specifically as follows: when the adjustment stops, record the opening degree of the electronically controlled throttle valve one (211) and the electronically controlled throttle valve two (221), and calculate the opening ratio of the two to obtain the adjusted oxygen concentration. and Because the gas pumping ratio between the center and near the wall is artificially adjusted at this time, the actual oxygen concentration in the exhaust pipe is different from that in other parts of the exhaust pipe. There is a deviation. Comparing the opening ratios of the electronically controlled throttle valve one (211) and electronically controlled throttle valve two (221) when the detection accuracy is highest in S1-2, the oxygen concentration is calculated without adjusting the opening degrees of electronically controlled throttle valve one (211) and electronically controlled throttle valve two (221). Let the oxygen concentration at the center of the exhaust pipe (1) in S3 be... The oxygen concentration near the wall of the exhaust pipe (1) is The formula is , ,in The sign is determined based on the actual pressure detected inside the filter channel (3), and is calculated accordingly. and This allows for the calculation of the actual oxygen concentration inside the exhaust pipe.

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