阅读说明：本技术 一种远程诊断柴油车scr系统尿素消耗量合理性的方法 (Method for remotely diagnosing reasonability of urea consumption of diesel vehicle SCR system ) 是由 王天田 于 2019-10-09 设计创作，主要内容包括：一种远程诊断柴油车SCR系统尿素消耗量合理性的方法,包括以下步骤：(1)通过OBD远程监管终端采集目标车辆的相关参数并上传至平台；(2)平台比对一段时间内的累计燃油消耗量或发动机累计功和累计尿素消耗量的相对关系来确认尿素消耗量的合理性；(3)确认尿素消耗量不合理后,诊断模块将通过尿素消耗量异常原因判别策略进一步确认具体原因；(4)依次确认车辆SCR系统是否存在故障、SCR上下游温度传感器信号是否合理、尿素起喷温度是否设定过高、尿素喷射状态下的NOx排放与喷射量的比例、累计喷射的尿素质量与实际尿素液位变化关系是否合理；(5)依据步骤(4)中各个环节的确认结果,确定出导致尿素消耗量不合理的根本原因。(A method of remotely diagnosing the rationality of urea consumption in a diesel vehicle SCR system comprising the steps of: (1) collecting relevant parameters of a target vehicle through an OBD remote monitoring terminal and uploading the relevant parameters to a platform; (2) comparing the accumulated fuel consumption or the relative relation between the accumulated work of the engine and the accumulated urea consumption in a period of time by the platform to confirm the reasonability of the urea consumption; (3) after the fact that the urea consumption is unreasonable is confirmed, the diagnosis module further confirms the specific reason through a urea consumption abnormity reason judgment strategy; (4) sequentially confirming whether a vehicle SCR system has faults or not, whether signals of temperature sensors on the upstream and downstream of the SCR are reasonable or not, whether the urea spraying starting temperature is set to be too high or not, the proportion of NOx emission and the spraying amount in the urea spraying state and whether the relation between the accumulated sprayed urea quality and the actual urea liquid level change is reasonable or not; (5) and (4) determining the root cause of unreasonable urea consumption according to the confirmation results of all links in the step (4).)

1. A method for remotely diagnosing the reasonability of urea consumption of an SCR system of a diesel vehicle is characterized in that the method collects dynamic running data and static data of an engine at a frequency of at least 1Hz through a terminal and uploads the dynamic running data and the static data to a platform; comparing the accumulated fuel consumption or the relative relation between the accumulated work of the engine and the accumulated urea consumption in a period of time by the platform to confirm the reasonability of the urea consumption; and further determining the root cause of unreasonable urea consumption by a urea consumption abnormity cause judgment strategy.

2. A method for remotely diagnosing the rationality of the urea consumption of a diesel vehicle SCR system according to claim 1, characterized by the following method steps:

(1) acquiring dynamic operation parameters and vehicle registration information static parameters related to reasonability diagnosis of the target vehicle and the urea consumption through an OBD remote monitoring terminal, and uploading the parameters to a platform;

(2) comprehensively confirming whether the urea consumption is too low through two methods;

(3) after the fact that the urea consumption is unreasonable is confirmed, the diagnosis module further confirms the reason causing the unreasonable urea consumption of the whole vehicle through a urea consumption abnormity reason distinguishing strategy;

(4) the diagnosis module needs to sequentially confirm whether a vehicle SCR system has faults or not, whether signals of temperature sensors on the upstream and downstream sides of the SCR are reasonable or not, whether the urea spraying starting temperature is set to be too high or not, the proportion of NOx emission and the spraying amount in the urea spraying state and whether the relation between the urea quality of accumulated spraying and the actual urea liquid level change is reasonable or not;

(5) and (4) determining the root cause causing the unreasonable urea consumption by the platform according to the confirmation results of all links in the step (4).

3. The method according to claim 1, characterized in that the platform is a motor vehicle emission remote supervision platform, and the platform can receive data uploaded by terminals installed on different vehicles, and perform a series of collection, processing, storage, calculation, display and management operations on the data uploaded by vehicle-mounted terminals to realize corresponding supervision service functions.

4. A method of remotely diagnosing reasonableness of urea consumption by a diesel vehicle SCR system according to claim 2, characterized in that said dynamic operating parameters comprise at least rotation speed, mass air intake flow, specific fuel consumption, net engine output torque, SCR inlet temperature, SCR outlet temperature, urea injection amount, urea level sensor signal, downstream NOx sensor measurement; the static parameters of the vehicle registration information at least comprise rated power, rated torque, rated rotating speed, engine displacement and urea tank volume of the engine.

5. The method for remotely diagnosing the reasonableness of the urea consumption of the SCR system of the diesel vehicle is characterized in that the target vehicle is required to be provided with an OBD remote supervision terminal, and the terminal can acquire all the dynamic operation parameters through an OBD interface and upload the parameters to a platform.

6. A method for remotely diagnosing reasonability of urea consumption of an SCR system of a diesel vehicle according to claim 2, wherein the step (2) comprises two methods: in the first method, when the ratio of the accumulated fuel consumption to the accumulated urea consumption exceeds a certain limit value, the urea consumption is considered to be too low; and secondly, when the ratio of the accumulated work of the engine to the accumulated urea consumption exceeds a certain limit value, the urea consumption is considered to be too low.

7. A method of remotely diagnosing the rationality of the urea consumption of a diesel vehicle SCR system according to claim 2, characterized in that the decision threshold of the method of confirming whether the urea consumption is too low is determined by means of the identification of the static parameter part of the target vehicle and the calibration of the platform existing engine and post-processing operating data.

8. A method for remotely diagnosing reasonableness of urea consumption of a diesel vehicle SCR system according to claim 7, characterized in that the calibration results of the existing engine and post-processing operation data of the platform are realized by one of two methods: calibrating the diagnosis module by obtaining corresponding data through real vehicle measurement in a normal state; the second step is as follows: and performing data screening and feature extraction through the existing similar vehicle data of the platform, and calibrating the diagnosis module.

Technical Field

The invention relates to a method for remotely diagnosing the reasonability of urea consumption of an SCR (selective catalytic reduction) system of a diesel vehicle, belonging to the technical field of motor vehicle emission control.

Background

The exhaust gas of the engine contains harmful substances (NOx for short) such as nitrogen oxides, and the main components of the harmful substances are NO and NO₂. NOx is N in the air drawn into the cylinder by the engine₂And O₂Reaction product at high temperatureA compound (I) is provided. National emission legislation limits the amount of NOx emissions and defines limits of varying degrees, requiring vehicles exceeding the respective limits to produce the necessary and differentiated reaction actions for the purpose of controlling NOx emissions.

SCR technology is a selective catalytic reduction technology, which is the main technology of engines to control NOx emissions, and the most common forms of this technology are: the ammonia gas is generated by decomposing the urea aqueous solution, and the ammonia gas and NOx are subjected to selective catalytic reduction reaction under the action of the SCR catalyst to generate nitrogen and water and then discharged into the atmosphere, and the emission of the NOx is effectively controlled by spraying different urea amounts into the exhaust of the diesel engine.

The most common SCR system currently on the market is the Urea-SCR system, as shown in fig. 1. The Urea-SCR system uses AdBlue as a reducing agent to reduce NOx in exhaust gas and mainly comprises an SCR catalyst, a Urea mixer, a Urea pump, a Urea nozzle, a Urea tank assembly, an SCR control unit (DCU), an SCR catalyst upstream temperature sensor, an SCR catalyst downstream temperature sensor, an SCR catalyst upstream NOx concentration sensor, an SCR catalyst downstream NOx concentration sensor, a Urea liquid level sensor, a Urea temperature sensor, a Urea quality sensor and the like. In the figure, long wide arrows indicate the reducing agent flow direction, short wide arrows indicate the exhaust gas flow direction, and thin solid arrows indicate the signal direction.

When the SCR system works, an SCR control unit (DCU) reads signals such as rotating speed, torque, fuel injection quantity, cooling water temperature, supercharging pressure, air inlet temperature, exhaust temperature, upstream NOx concentration measured by a NOx sensor (or upstream NOx concentration estimated through a NOx original discharge model) and the like from a CAN bus, the mass flow of exhaust gas obtained by calculation, the thermodynamic state of the SCR system and the like are used as input conditions of a control algorithm to calculate the mass of a reducing agent required by the system, and then the DCU controls actuating mechanisms such as a urea pump, a urea nozzle and the like to accurately inject the corresponding reducing agent. The exhaust gas temperature sensor measures as the most important switching signal for urea injection.

Since SCR systems require the consumption of urea solution to effectively perform catalytic conversion, which increases the cost of vehicle utilization, some of the current cheating methods in the vehicle market are developed around how to reduce or cut off the consumption of urea solution: if the temperature sensor is lifted or pulled out, the measured temperature is lower than the temperature required by the normal work of the SCR system in most of time, so that urea injection is avoided, and the aim of reducing the operation cost is fulfilled.

The OBD remote supervision terminal (hereinafter referred to as terminal) is usually installed on a vehicle OBD diagnosis interface, can acquire main operation parameters (such as rotating speed, air inlet mass flow, fuel consumption rate, net output torque of an engine, SCR inlet temperature, SCR outlet temperature, urea injection amount, urea liquid level sensor signals, downstream NOx sensor measurement values and the like) of a vehicle in the operation process, and sends data to a motor vehicle emission remote supervision platform (hereinafter referred to as platform) according to a specified format through a GPRS (general packet radio service) module (2G/4G) of the terminal.

The motor vehicle emission remote supervision platform can receive data uploaded by terminals installed on different vehicles, and carries out a series of operations such as collection, processing, storage, calculation, judgment, display and management on the data uploaded by the vehicle-mounted terminals so as to realize corresponding supervision service functions.

Disclosure of Invention

The invention aims to provide a method for remotely diagnosing the reasonability of the urea consumption of an SCR system of a diesel vehicle in order to remotely diagnose the unreasonable urea consumption possibly existing in the use process of the diesel vehicle.

The technical scheme of the invention is that the method for remotely diagnosing the reasonability of the urea consumption of the SCR system of the diesel vehicle acquires dynamic running data and static data of an engine at a frequency of at least 1Hz through a terminal and uploads the dynamic running data and the static data to a platform; the platform inputs the dynamic operation data uploaded by the vehicle into a corresponding diagnosis module to carry out signal diagnosis; and judging whether the urea injection quantity is reasonable or not by comparing the correlation between the engine emission data and the actual urea consumption data.

A method for remotely diagnosing the reasonability of the urea consumption of an SCR system of a diesel vehicle comprises the following steps:

(1) dynamic operation parameters (rotating speed, air inlet mass flow, fuel consumption rate, net output torque of an engine, SCR inlet temperature or SCR outlet temperature, urea injection quantity, urea liquid level sensor signals, downstream NOx sensor measured values and the like) related to the reasonability diagnosis of the urea consumption of the target vehicle and vehicle registration information static parameters are collected through an OBD remote supervision terminal and uploaded to a platform.

(2) After the platform receives the data uploaded by the terminal, whether the urea consumption is too low is comprehensively confirmed through two methods: in the first method, when the ratio of the accumulated fuel consumption to the accumulated urea consumption exceeds a certain threshold value, the urea consumption is considered to be too low; and secondly, when the ratio of the accumulated work of the engine to the accumulated urea consumption exceeds a certain threshold value, the urea consumption is considered to be too low.

(3) The proportion threshold value module characteristic parameters of the urea consumption reasonability diagnosis module are determined after the calibration of real vehicle test data or platform engine and postprocessing operation data of at least 5 normal vehicles, and the platform is required to identify static parameter parts of target vehicles to realize the accurate diagnosis of certain types of vehicles during diagnosis.

(4) After the fact that the urea consumption is unreasonable is confirmed, the diagnosis module further confirms the reason causing the unreasonable urea consumption of the whole vehicle through a urea consumption abnormity reason distinguishing strategy.

(5) Firstly, calculating the proportion of the working time of the SCR system to the total running time of the engine, if the proportion is too low, further confirming whether the SCR system has a fault by reading a fault code, if the SCR system has the fault, reporting a relevant fault, and if the SCR system has no fault, further confirming whether signals of temperature sensors at upstream and downstream of the SCR are reasonable;

(6) after the signal diagnosis of the temperature sensor is finished, if the diagnosis result is that the signal is unreasonable, a suspected cheating fault of the temperature sensor is reported, otherwise, whether the urea start-up temperature of the SCR system is too high needs to be further confirmed; and if the blowout starting temperature is too high, marking but not alarming (caused by OEM calibration).

(7) Finally, confirming whether the proportion of urea injected cumulatively in a period of time to NOx emitted by the engine in the urea injection state is too low again, and if the proportion is too low, carrying out identification but not alarming (caused by OEM calibration);

(8) if the urea consumption and the proportion of the original NOx of the engine in the injection state are in a reasonable range, but the NOx conversion amount calculated by the NOx discharged from a tail pipe and the original NOx of the engine is too low, the corresponding relation between the cumulative value of the urea injection amount and the urea liquid level change signal is further compared, if the urea injection amount is obviously higher than the liquid level change amount of the urea box in a period of time, the fact that the urea is not completely injected into the SCR catalyst or a false injection phenomenon exists is judged, and suspected cheating of an injection system is reported.

The platform is a motor vehicle emission remote supervision platform, can receive data uploaded by terminals installed on different vehicles, and carries out a series of collection, processing, storage, calculation, display and management operations on the data uploaded by the vehicle-mounted terminals, so as to realize corresponding supervision service functions.

The engine dynamic operating data includes net engine output torque, friction torque, accelerator pedal opening, specific fuel consumption, engine speed, vehicle speed, SCR upstream or downstream temperature sensor measurements, engine operating time, coolant temperature, etc.

The target vehicle must be equipped with an OBD remote supervisory terminal, and the data that the terminal can upload through the OBD interface includes at least rotational speed, intake mass flow, fuel consumption rate, engine net output torque, SCR inlet or outlet temperature, urea injection amount, urea level sensor signal, downstream NOx sensor measurement, etc.

The OBD remote monitoring terminal has to upload data to a unified platform, and the platform diagnoses the rationality of urea consumption through a calibrated diagnosis module and further confirms a fault.

The method has the advantages that the method can effectively finish the diagnosis of the reasonability of the urea consumption, can further identify a series of reasons which can cause the unreasonable phenomenon, can effectively identify the abnormal working state of the SCR system of the in-use vehicle, further improves the working effectiveness of the SCR system through the accurate supervision of an environmental protection department, and makes a substantial contribution to the reduction of the NOx emission of the in-use diesel vehicle.

Drawings

FIG. 1 is a schematic structural diagram of a conventional Urea-SCR system;

FIG. 2 is a schematic diagram of the operation of the OBD remote supervisory system of the present invention;

FIG. 3 is a flow chart of the invention for remotely diagnosing the urea consumption rationality of a diesel vehicle SCR system;

FIG. 4 is a schematic diagram of a urea consumption rationality diagnostic method;

FIG. 5 is a flowchart of a policy for determining the cause of an abnormal urea consumption;

FIG. 6 is a schematic diagram of a method for diagnosing suspected cheating in a urea injection system.

Detailed Description

The operating principle of the Urea-SCR system of the embodiment is shown in FIG. 1.

The Urea-SCR system is a main diagnostic object of the invention, uses Adblue (32.5% Urea solution, also called Urea for short in China) as a reducing agent to reduce NOx in exhaust gas, and mainly comprises an SCR catalyst, a Urea mixer, a Urea pump, a Urea nozzle, a Urea tank assembly, an SCR control unit (DCU), an SCR catalyst upstream temperature sensor or an SCR catalyst downstream temperature sensor, an SCR catalyst upstream NOx concentration sensor (common in diesel vehicles above the national V standard), an SCR catalyst downstream NOx concentration sensor, a Urea liquid level sensor, a Urea temperature sensor, a Urea quality sensor and the like. In the figure, long wide arrows indicate the reducing agent flow direction, short wide arrows indicate the exhaust gas flow direction, and thin solid arrows indicate the signal direction.

When the SCR system works, an SCR control unit (DCU) reads signals such as rotating speed, torque, fuel injection quantity, cooling water temperature, supercharging pressure, air inlet temperature, exhaust temperature, upstream NOx concentration measured by a NOx sensor (or upstream NOx concentration estimated through a NOx original discharge model) and the like from a CAN bus, the mass flow of exhaust gas obtained by calculation, the thermodynamic state of the SCR system and the like are used as input conditions of a control algorithm to calculate the mass of a reducing agent required by the system, and then the DCU controls actuating mechanisms such as a urea pump, a urea nozzle and the like to accurately inject the corresponding reducing agent, so that the aim of eliminating NOx emission in exhaust is fulfilled.

The working principle diagram of the OBD remote supervisory system of the present embodiment is shown in fig. 2.

The OBD remote supervision terminal is usually installed on an OBD diagnosis interface of a vehicle, CAN acquire main operation parameters (such as engine rotating speed, air inlet mass flow, fuel consumption rate, net engine output torque, SCR inlet temperature/SCR outlet temperature, urea injection amount, urea liquid level sensor signals, downstream NOx sensor measurement values and the like) of the vehicle in the operation process through a CAN bus, and sends data to a motor vehicle emission remote supervision platform according to a formulated format through a 4G module of the terminal. The platform can receive data uploaded by terminals installed on different vehicles, and perform a series of operations such as data preprocessing, storage, calculation and judgment to realize corresponding functions. The diagnosis method described in this embodiment is implemented by combining a platform with multiple vehicle big data.

The process for remotely diagnosing the reasonability of the urea consumption of the SCR system of the diesel vehicle is shown in the figure 3.

The embodiment provides a method for remotely diagnosing the reasonability of urea consumption of an SCR system of a diesel vehicle, which comprises the following steps:

(1) and acquiring relevant parameters of the target vehicle through the OBD remote monitoring terminal and uploading the relevant parameters to the platform.

(2) And comparing the accumulated fuel consumption or the relative relation between the accumulated work of the engine and the accumulated urea consumption in a period of time by the platform to confirm the reasonability of the urea consumption.

(3) After the fact that the urea consumption is not reasonable is confirmed, the diagnosis module further confirms the specific reason through a urea consumption abnormity reason judging strategy.

(4) Whether a vehicle SCR system has faults or not, whether signals of temperature sensors on the upstream and the downstream of the SCR are reasonable or not, whether the urea spraying starting temperature is set to be too high or not, the proportion of NOx emission and the spraying amount in the urea spraying state and whether the relation between the accumulated sprayed urea quality and the actual urea liquid level change is reasonable or not are sequentially confirmed.

(5) And (4) determining the root cause of unreasonable urea consumption according to the confirmation results of all links in the step (4).

The method for diagnosing the reasonableness of the urea consumption according to the present embodiment is schematically shown in fig. 4.

This example confirms whether the urea consumption is too low by two methods.

The first method is to compare the cumulative amount of urea consumed and the cumulative amount of fuel consumed in a long period of time (8 h of engine running time), and can be obtained by integrating the urea injection amount and the fuel consumption rate with time, or can be realized by monitoring the urea filling action/state and the fuel filling action/state for a long time through platform historical data. When the ratio of the accumulated fuel consumption to the accumulated urea consumption exceeds a certain limit value, the urea consumption is considered to be too low;

the second method is to determine the rationality of the urea consumption by statistically calculating the cumulative power of the engine and the cumulative urea consumption over a long period of time (8 hours of engine running time), and to consider that the urea consumption is too low when the ratio of the cumulative power of the engine and the cumulative urea consumption exceeds a certain limit. The proportional threshold of the second method needs to be realized by means of identification of the static parameter part of the target vehicle.

When the two methods both make the judgment result that the urea consumption is unreasonable, the urea consumption reasonability diagnosis module finally outputs the diagnosis result that the urea consumption is unreasonable, and the module characteristic parameters such as various thresholds in the diagnosis module are determined after the calibration of the engine and the post-processing operation data of at least 5 normal vehicles through real vehicle test data or a platform.

The policy for determining the cause of an abnormal urea consumption according to the present embodiment is shown in fig. 5.

In the embodiment, the specific reason causing the unreasonable urea injection amount is judged through a urea consumption abnormality judgment strategy, so as to determine whether the vehicle has man-made cheating behavior in the actual use process, wherein the specific identification strategy is as follows: firstly, after the fact that the urea consumption is unreasonable is confirmed, the diagnosis module further calculates the proportion of the working time of the SCR system in the total running time of the engine, if the proportion is too low, whether the SCR system has faults is further confirmed by reading fault codes, and if the SCR system has the faults, relevant faults are reported; if the SCR has no fault, further confirming whether the signals of the SCR upstream and downstream temperature sensors are reasonable; and then, after the signal diagnosis of the temperature sensor is finished, if the diagnosis result is that the signal is not reasonable, a suspected cheating fault of the temperature sensor is reported, otherwise, whether the urea spraying starting temperature of the SCR system is too high needs to be further confirmed, and if the urea spraying starting temperature is too high, identification is carried out but no alarm is given (caused by OEM calibration). Finally, confirming the proportional relation between urea injected accumulatively in a urea injection state and NOx emitted by the engine in a period of time again, and if the proportional relation is too low, identifying but not alarming (caused by OEM calibration); if the urea consumption and the proportion of the original NOx of the engine in the injection state are in a reasonable range, but the NOx conversion amount calculated by the NOx discharged from a tail pipe and the original NOx of the engine is too low, the corresponding relation between the accumulated value of the urea injection amount and the urea liquid level change signal is further compared, if the urea injection amount is obviously higher than the liquid level change amount of the urea box in a period of time, the fact that the urea is not completely injected into the SCR catalyst or a false injection phenomenon exists is judged, and a diagnosis result of 'suspected cheating of an injection system' is made.

Fig. 6 shows a method for diagnosing a suspected cheating in the urea injection system according to the present embodiment.

The method for diagnosing suspected cheating of the urea injection system in the embodiment comprises the following steps: under the condition that the engine normally works, the platform continuously integrates the time through urea injection quantity data uploaded by the vehicle, and calculates the urea mass which is injected in an accumulated mode when the vehicle works for 8 hours. And calculating the urea liquid level difference before and after 8h (filtering is carried out by a specific filtering method because the urea liquid level changes along with the posture of the vehicle), calculating the urea volume consumed in 8h according to the volume of the urea tank of the vehicle, and calculating the urea mass consumed in 8h according to the density of the urea solution.

If the cumulative mass of urea consumed (from the urea storage system information) is less than the cumulative mass of urea injected (from the urea injection system information) by more than 25%, the actual consumption is considered significantly lower than the injection amount, and a determination is made that "urea injection system is suspected of cheating", which may be caused by two reasons: 1. the injection amount is real, but urea is not completely injected into the SCR catalyst, and part of urea flows back to the urea box; 2. the urea injection quantity uploaded to the platform is not a true injection quantity, and there may be situations where the nozzle injection accuracy is insufficient or a false injection message is provided. The 2 cases all belong to emission cheating behaviors.