阅读说明：本技术 一种水温合理性诊断方法 (Water temperature rationality diagnosis method ) 是由 刘芳 于 2019-11-26 设计创作，主要内容包括：本发明公开了一种水温合理性诊断方法,获取整车状态数据,根据整车状态数据判断此时车辆所处工况；根据车辆所处工况选择对应的水温合理性故障诊断步骤；通过合理性诊断步骤对当前水温进行合理性判断。本发明的优点在于：可以对水温传感器的合理性进行判断,识别出高边故障、低边故障以及年至故障,有效的诊断出水温传感器的不合理故障。(The invention discloses a water temperature rationality diagnosis method, which comprises the steps of obtaining the state data of a whole vehicle, and judging the working condition of the vehicle at the moment according to the state data of the whole vehicle; selecting a corresponding water temperature rationality fault diagnosis step according to the working condition of the vehicle; and judging the rationality of the current water temperature through a rationality diagnosis step. The invention has the advantages that: the rationality of the water temperature sensor can be judged, high-side faults, low-side faults and year-to-year faults are identified, and unreasonable faults of the water temperature sensor are effectively diagnosed.)

1. A water temperature rationality diagnostic method characterized by:

acquiring the state data of the whole vehicle, and judging the working condition of the vehicle at the moment according to the state data of the whole vehicle;

selecting a corresponding water temperature rationality fault diagnosis step according to the working condition of the vehicle;

and judging the rationality of the current water temperature through a rationality diagnosis step.

2. A water temperature rationality diagnostic method according to claim 1, characterized by: the water temperature rationality fault diagnosis step comprises a high-side fault diagnosis step of the water temperature sensor, a low-side fault diagnosis step of the water temperature sensor and a viscous fault diagnosis step of the water temperature sensor.

3. A water temperature rationality diagnostic method according to claim 1 or 2, characterized by: when the water temperature sensor has no circuit fault, the rotating speed of the engine is greater than a set rotating speed value, and the air inflow is greater than a set value, entering a high-side fault diagnosis step of the water temperature sensor; or entering a high-side fault diagnosis step of the water temperature sensor when the engine of the hybrid vehicle is not operated and the vehicle speed is greater than the set vehicle speed value.

4. A water temperature rationality diagnostic method according to claim 3, characterized by: the high-side fault diagnosis step of the water temperature sensor comprises the following steps: calculating a theoretical reference value of the high-side water temperature through theory, wherein the theoretical reference value is the water temperature which can be reached to the maximum extent; and comparing the water temperature data output by the water temperature sensor with the theoretical reference water temperature of the high-side water temperature, and diagnosing the high-side fault of the water temperature sensor when the water temperature output by the water temperature sensor is greater than the theoretical reference water temperature plus the redundancy.

5. A water temperature rationality diagnostic method according to claim 4, characterized by: the calculation of the theoretical reference value of the high side water temperature comprises the following steps:

the initial value of water temperature is the water temperature value of the water temperature sensor, when the engine runs, the rising gradient of water temperature is obtained by looking up a table according to the air input and the current simulated water temperature simulated by the model, and the theoretical reference value of high-side water temperature is obtained by adding the initial value of water temperature and the rising gradient value of the table look-up corresponding to each scheduling time;

or for the hybrid vehicle, the water temperature decrease gradient is obtained by looking up a table according to the vehicle speed and the current simulated water temperature, and the theoretical reference value of the high-side water temperature is obtained by subtracting the water temperature decrease gradient from the water temperature sensor value.

6. A water temperature rationality diagnostic method according to any one of claims 1-5, characterized by: and entering a low fault diagnosis step of the water temperature sensor when no water temperature sensor circuit fails, no engine auxiliary heating module works and the engine has the rotating speed.

7. A water temperature rationality diagnostic method according to claim 6, characterized by: the fault diagnosis step at the bottom edge of the water temperature sensor comprises the following steps: and calculating a theoretical reference value of the water temperature at the bottom edge, and diagnosing that the low edge of the water temperature sensor has a fault if the water temperature output by the water temperature sensor is greater than the theoretical reference value of the low edge water temperature plus the redundancy and less than the theoretical reference value of the water temperature at the bottom edge minus the redundancy.

8. A water temperature rationality diagnostic method according to claim 6 or 7, characterized by: the calculation of the low-side water temperature theoretical reference value comprises the following steps: limiting the maximum value of the low-side reference water temperature according to the ambient temperature; when the engine is started, taking the smaller of the maximum values of the current simulated water temperature and the low-side reference water temperature as a calculation initial value; when the engine runs, the water temperature rising gradient is obtained by looking up a table according to the air inflow and the current simulated water temperature; if the vehicle is a hybrid vehicle: in the pure electric mode, the engine does not run, and the gradient of water temperature reduction is obtained by looking up a table according to the vehicle speed and the temperature difference between the water temperature and the ambient temperature; the low-side theoretical reference value of water temperature is equal to the initial value plus the gradient of water temperature change.

9. A water temperature rationality diagnostic method according to claim 1, characterized by: when no circuit fault of the water temperature sensor, no fault of the air inlet pressure sensor and no fault of the vehicle speed sensor exist, the step of viscous fault diagnosis of the water temperature sensor is carried out, and then after the engine is started, the maximum water temperature value and the minimum water temperature value of the output value of the current water temperature sensor are continuously calculated in real time until a high heat working condition and a low heat working condition are identified and the operation lasts for a certain time; and subtracting the minimum value output by the water temperature sensor from the maximum value of the temperature sensor calculated in real time at the moment to obtain temperature deviation, comparing the obtained temperature deviation with preset temperature difference redundancy, and diagnosing the viscous fault of the water temperature sensor when the temperature deviation is less than the temperature difference redundancy.

Technical Field

The invention relates to the field of automotive electronics, in particular to a water temperature rationality diagnosis method.

Background

The water temperature signal is an important input parameter to the engine control system. If the water temperature signal received by the ECU is low, the control deviation of the fuel injection quantity, the control deviation of the ignition angle, the control deviation of the idling speed and the like can be caused, and the emission exceeds the standard. If the water temperature is too high for a long time, the engine and related parts can be damaged. The national six regulations put forward specific requirements for rationality diagnosis on the comprehensive components: the rationality diagnostic should check whether the sensor output is unreasonably high or unreasonably low (i.e., a bilateral diagnosis). At present, most EMS systems only monitor voltage signals and physical value ranges of the water temperature sensors, and unreasonable signals caused by characteristic deviation of the water temperature sensors are rarely involved.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a water temperature rationality diagnosis method for diagnosing unreasonable faults of water temperature signals and giving out unreasonable fault types.

In order to achieve the purpose, the invention adopts the technical scheme that: a water temperature rationality diagnosis method comprises the steps of obtaining vehicle state data, and judging the working condition of a vehicle at the moment according to the vehicle state data;

selecting a corresponding water temperature rationality fault diagnosis step according to the working condition of the vehicle;

and judging the rationality of the current water temperature through a rationality diagnosis step.

The water temperature rationality fault diagnosis step comprises a high-side fault diagnosis step of the water temperature sensor, a low-side fault diagnosis step of the water temperature sensor and a viscous fault diagnosis step of the water temperature sensor.

When the water temperature sensor has no circuit fault, the rotating speed of the engine is greater than a set rotating speed value, and the air inflow is greater than a set value, entering a high-side fault diagnosis step of the water temperature sensor; or entering a high-side fault diagnosis step of the water temperature sensor when the engine of the hybrid vehicle is not operated and the vehicle speed is greater than the set vehicle speed value.

The high-side fault diagnosis step of the water temperature sensor comprises the following steps: calculating a theoretical reference value of the high-side water temperature through theory, wherein the theoretical reference value is the water temperature which can be reached to the maximum extent; and comparing the water temperature data output by the water temperature sensor with the theoretical reference water temperature of the high-side water temperature, and diagnosing the high-side fault of the water temperature sensor when the water temperature output by the water temperature sensor is greater than the theoretical reference water temperature plus the redundancy.

The calculation of the theoretical reference value of the high side water temperature comprises the following steps:

the initial value of water temperature is the water temperature value of the water temperature sensor, when the engine runs, the rising gradient of water temperature is obtained by looking up a table according to the air input and the current simulated water temperature simulated by the model, and the theoretical reference value of high-side water temperature is obtained by adding the initial value of water temperature and the rising gradient value of the table look-up corresponding to each scheduling time;

or for the hybrid vehicle, the water temperature decrease gradient is obtained by looking up a table according to the vehicle speed and the current simulated water temperature, and the theoretical reference value of the high-side water temperature is obtained by subtracting the water temperature decrease gradient from the water temperature sensor value.

And entering a low fault diagnosis step of the water temperature sensor when no water temperature sensor circuit fails, no engine auxiliary heating module works and the engine has the rotating speed.

The fault diagnosis step at the bottom edge of the water temperature sensor comprises the following steps: and calculating a theoretical reference value of the water temperature at the bottom edge, and diagnosing that the low edge of the water temperature sensor has a fault if the water temperature output by the water temperature sensor is greater than the theoretical reference value of the low edge water temperature plus the redundancy and less than the theoretical reference value of the water temperature at the bottom edge minus the redundancy.

The calculation of the low-side water temperature theoretical reference value comprises the following steps: limiting the maximum value of the low-side reference water temperature according to the ambient temperature; when the engine is started, taking the smaller of the maximum values of the current simulated water temperature and the low-side reference water temperature as a calculation initial value; when the engine runs, the water temperature rising gradient is obtained by looking up a table according to the air inflow and the current simulated water temperature; if the vehicle is a hybrid vehicle: in the pure electric mode, the engine does not run, and the gradient of water temperature reduction is obtained by looking up a table according to the vehicle speed and the temperature difference between the water temperature and the ambient temperature; the low-side theoretical reference value of water temperature is equal to the initial value plus the gradient of water temperature change.

When no circuit fault of the water temperature sensor, no fault of the air inlet pressure sensor and no fault of the vehicle speed sensor exist, the step of viscous fault diagnosis of the water temperature sensor is carried out, and then after the engine is started, the maximum water temperature value and the minimum water temperature value of the output value of the current water temperature sensor are continuously calculated in real time until a high heat working condition and a low heat working condition are identified and the operation lasts for a certain time; and subtracting the minimum value output by the water temperature sensor from the maximum value of the temperature sensor calculated in real time at the moment to obtain temperature deviation, comparing the obtained temperature deviation with preset temperature difference redundancy, and diagnosing the viscous fault of the water temperature sensor when the temperature deviation is less than the temperature difference redundancy.

The invention has the advantages that: the rationality of the water temperature sensor can be judged, high-side faults, low-side faults and year-to-year faults are identified, and unreasonable faults of the water temperature sensor are effectively diagnosed.

Drawings

The contents of the expressions in the various figures of the present specification and the labels in the figures are briefly described as follows:

FIG. 1 is a flow chart of the diagnostic method of the present invention.

Detailed Description

The following description of preferred embodiments of the invention will be made in further detail with reference to the accompanying drawings.

The invention provides a water temperature rationality diagnosis method meeting the requirements of national six regulations. The method can effectively identify the fault that the water temperature signal is unreasonable under the premise that no water temperature sensor circuit fault, air inlet pressure sensor fault, vehicle speed signal fault, high-speed fan fault, low-speed fan fault and the like exist (whether each fault is judged by self-checking during electrification).

The rationality diagnosis of the water temperature sensor includes three water temperature rationality faults:

(1) high-side fault: irrational failure of high water temperature areas

(2) Low-side fault: low water temperature region irrational failure in warm-up process

(3) Viscous failure: when the engine runs, the water temperature sensor value is not changed.

This patent mainly diagnoses the high limit of temperature, low limit and the viscous fault through engine cooling system's temperature rise characteristic. The method comprises the following specific steps:

high-side fault diagnosis of water temperature sensor

I. Selecting diagnosis conditions: no water temperature sensor circuit failure; and selecting a diagnosis interval with high engine speed (higher than 2500rpm/min, capable of being calibrated) and high air intake (higher than 1.8Kg/h, capable of being calibrated), and entering high-side fault diagnosis when detecting that the engine is in the working condition, wherein the two parameters of the high engine speed and the high air intake can be modified and calibrated according to actual requirements. When the water temperature sensor circuit fault is judged and diagnosed by ECU self-checking, the high-side fault diagnosis is carried out when no circuit fault of the water temperature sensor is diagnosed, and then the output rationality fault is judged.

Calculating a theoretical reference value of the high-side water temperature (the theoretical reference value is the maximum possible water temperature, and when the maximum possible water temperature is exceeded, the theoretical reference value is considered abnormal and belongs to the high-side fault). The initial value is the water temperature value of the water temperature sensor. When the engine runs, looking up a table (a map can be calibrated, wherein the map is a temperature rise gradient map corresponding to the air inflow and the current simulated water temperature) according to the air inflow and the current simulated water temperature (a model calculation value, and the current simulated water temperature is obtained according to the model calculation), and obtaining a high-edge theoretical reference water temperature by adding the rise gradient of the table at each scheduling time; if the vehicle is a hybrid vehicle: in the pure electric mode, when the engine is not operated but the vehicle speed is higher, the water temperature gradient (map can be calibrated) is obtained by looking up a table according to the vehicle speed and the current simulated water temperature (model calculation value), and the theoretical reference value of the water temperature on the high side is obtained by subtracting the water temperature gradient from the water temperature sensor value.

And III, when the condition I is met, if the output water temperature of the sensor is greater than (the high-side theoretical reference water temperature + the redundancy), reporting a high-side fault of the water temperature sensor.

Second, low-side fault diagnosis of water temperature sensor

I. Selecting diagnosis conditions: the circuit of the water temperature sensor has no fault, the heating module does not work, and the engine has rotating speed. The circuit fault of the water temperature sensor is confirmed by self-checking of the water temperature sensor chip after starting, and the condition that no heating module works means that no external heating unit is used for heating water temperature, an engine and the like; the engine has a rotating speed which means that the rotating speed of the engine is more than 25 rpm/min.

Calculating a theoretical reference value of the low side water temperature (the reference value is indicative of the water temperature of the slowest warming-up process). The maximum value of the low-side reference water temperature (below 45 ℃) is defined according to the ambient temperature. When the engine is started, the maximum value of the current simulated water temperature (model calculation value, water temperature data simulated by the model) and the maximum value of the low-side reference water temperature are taken, and the smaller value of the current simulated water temperature and the maximum value is taken as a calculation initial value. When the engine runs, looking up a table according to the air inflow and the current simulated water temperature (model calculation value) to obtain a water temperature increase gradient (a map can be calibrated, wherein the map is a comparison table of the current air inflow, the current simulated water temperature and the water temperature increase gradient); if the vehicle is a hybrid vehicle: in the pure electric mode, the engine is not operated, and the gradient of water temperature reduction (map can be calibrated) is obtained by looking up a table according to the vehicle speed and the temperature difference between the water temperature and the ambient temperature. The low-side theoretical reference value of water temperature is equal to the initial value plus the gradient of water temperature change. The water temperature rising gradient is positive, the water temperature falling gradient is negative, and the water temperature rising gradient taking positive or the water temperature falling gradient taking negative is added through the initial value during calculation.

And III, when the condition I is met, if the output water temperature of the sensor exceeds the range (the theoretical reference water temperature +/-redundancy), reporting a low-side fault of the water temperature sensor.

Third, viscous fault diagnosis of water temperature sensor

I. Selecting diagnosis conditions: the three sensors are considered to work normally because no circuit fault of the water temperature sensor, no fault of the air inlet pressure sensor and no fault of the vehicle speed sensor exist, namely, the three sensors all contend for production and have no abnormity in self-detection, and the control chip does not detect any fault signal of the sensor.

II, continuously calculating the maximum water temperature value and the minimum water temperature value of the output value of the current water temperature sensor in real time after the engine is started; (the output value of the water temperature sensor is circularly compared in real time to obtain the maximum value and the minimum value, the water temperature sensor is always circularly operated to detect the change of the water temperature data, and the maximum value and the minimum value of the water temperature are continuously updated according to the changed water temperature data)

And III, identifying a high-heat working condition (low vehicle speed of 0-50km/h and high air input) and a low-heat working condition (high vehicle speed of 50-200km/h and low air input) and operating for more than a certain time. (under the two working conditions, the water temperature can be obviously increased or decreased), and when the two working conditions are detected to respectively work, the maximum water temperature output value and the minimum value of the corresponding sensor from the beginning to the present time are calculated.

And IV, satisfying the conditions I and III, and reporting the viscous fault of the water temperature sensor if the deviation of the calculated maximum water temperature and the minimum water temperature is less than a redundancy quantity. That is, after the engine is started, the output value of the water temperature sensor is recorded in real time, and after the engine works under two working conditions, namely a high-heat working condition and a low-heat working condition, of the engine respectively, the maximum output temperature value and the minimum value of the water temperature sensor in the stage are immediately detected after the two working conditions are both worked for a period of time from the start to the detection, and when the difference between the maximum output temperature value and the minimum value is smaller than the temperature redundancy calibrated in advance, the water temperature sensor is judged to be a viscous fault.

The method for simulating the water temperature through the model comprises the following steps:

1. when the engine is stopped, the stop water temperature (the water temperature value at the stop time of the engine is equal to the output value of the water temperature sensor when no water temperature sensor circuit exists, and the water temperature value is equal to the simulated water temperature when the water temperature sensor fails) is recorded.

2. When the engine is not running, the simulated water temperature is equal to the shutdown water temperature minus the water temperature gradient. The water temperature drop gradient is equal to (difference between shutdown water temperature and intake air temperature) (water temperature drop coefficient determined from shutdown time, calibratable).

3. When the engine runs, the simulated water temperature is equal to the simulated water temperature plus the water temperature rising gradient at the previous moment. The water temperature rising gradient is obtained by simulating the water temperature and the air inflow at the previous moment and checking a calibration table.

The diagnosis method can be applied to gasoline engines, diesel engines and engine electric control systems with start-stop functions. The water temperature sensor can be subjected to non-rationality fault diagnosis for diagnosing unreasonable faults of water temperature signals, and an MIL lamp is lightened, so that a driver is prompted to maintain. Therefore, the content in the invention has practical application value and can solve the problems of oil consumption and emission caused by unreasonable water temperature signals.

It is clear that the specific implementation of the invention is not restricted to the above-described embodiments, but that various insubstantial modifications of the inventive process concept and technical solutions are within the scope of protection of the invention.