CN106401771B - A method of OBD torque limit when preventing engine from climbing - Google Patents

Abstract

The invention discloses a method for preventing OBD torque limitation when an engine is climbing a slope. A liquid level sensor is arranged on one side of a urea tank, and the liquid level change in the urea tank is collected. If the change is greater than a calibration value, it is determined that the engine is climbing. The engine is prohibited from OBD torque limiting. The invention only needs to change the installation position of the urea temperature and liquid level sensor on the basis of not adding additional hardware and sensors, and recognizes whether the engine is climbing through the control strategy. The invention judges that the engine is going up and down by using the liquid surface inclination characteristics of various liquids such as urea level, fuel oil, oil and the like when the engine climbs and descends, thereby releasing the engine torque limit.

Description

A Method to Prevent OBD Torque Limiting During Engine Climbing

technical field

The present invention relates to a method for preventing OBD torque limitation when an engine is climbing a slope.

Background technique

With the vigorous development of the automobile industry, engine exhaust emissions have become a factor that cannot be ignored in environmental pollution and human health. With the release of national engine emission regulations and on-board diagnostic system regulations, it is required that when the NOx in engine exhaust emissions exceeds 7g/Wk.h, the engine should be torque limited.

For safety reasons, regulations expressly require that engine torque be limited in the following two situations:

(1) When the engine is started next time;

(2) When the vehicle speed is very low.

Due to the large variety of vehicles and the complexity of engine operating conditions, the following situations may occur: in the same driving cycle, the engine exhaust emission exceeds the regulatory limit (7g/Wk.h due to urea injection system failure or SCR crystallization). ), but the vehicle travels at a fast speed, so the engine torque has not been limited. When the vehicle needs to climb a hill, the vehicle speed will be significantly reduced. If the engine torque is limited at this time, the consequences will be very serious.

Therefore, it is necessary to recognize the vehicle climbing to prevent engine torque limitation.

SUMMARY OF THE INVENTION

In order to solve the above problems, the present invention proposes a method for preventing OBD torque limitation when the engine is climbing. To judge whether the engine is going up or downhill, so as to release the engine torque limit.

In order to achieve the above object, the present invention adopts the following technical solutions:

A method to prevent the OBD torque limit when the engine is climbing. The liquid level sensor is set on the side of the urea tank, and the liquid level change in the urea tank is collected. If the change is greater than the calibration value, it is determined that the engine is climbing, and the engine is prohibited from performing OBD. Torque limit.

The liquid level sensor is arranged between the edge of the tank body of the urea tank and a position that is one third of the length of the tank body from the edge.

Filter the liquid level change, limit the filter output to the set range, and filter out small fluctuations or short-term fluctuations.

The urea tank is replaced with a fuel tank.

The urea tank is replaced with an oil tank.

When the liquid level sensor is arranged on the side of the tank close to the front end of the vehicle, the amount of liquid level change is replaced by the remaining amount of liquid.

When the liquid level sensor is set at the position of the tank away from the front end of the vehicle, the amount of liquid level change is replaced by the liquid level value.

The filtering time needs to be calibrated during filtering. The specific method is: simulating the acceleration and deceleration of the vehicle to collect the function of the urea level change, and gradually changing the filtering time until the appropriate filtering time can remove the liquid level fluctuation caused by the acceleration and deceleration of the vehicle.

The beneficial effects of the present invention are:

(1) the control logic of the present invention is simple, the calculation amount is small, the response is rapid, and the judgment is accurate;

(2) The present invention has little modification to the vehicle body structure and low cost investment;

(3) The present invention judges that the engine is going up and down by using the liquid level inclination characteristics of various liquids such as urea level, fuel oil, and oil when the engine climbs and descends, thereby releasing the engine torque limit.

Description of drawings

Fig. 1 is the schematic diagram of the urea tank during normal running of the engine of the present invention;

Fig. 2 is the schematic diagram of the urea tank when the engine of the present invention is climbing;

Fig. 3 is the urea liquid level PT filtering schematic diagram of the present invention;

FIG. 4 is a schematic diagram of the process flow of judging whether the engine is climbing a hill according to the present invention.

Among them: 1. Sensor; 2. Urea tank; 3. Urea solution.

Detailed ways:

The present invention will be further described below with reference to the accompanying drawings and embodiments.

Take the urea tank as an example to illustrate.

The present invention only needs to change the installation position of the urea temperature liquid level sensor 1 without adding additional hardware and sensors, and identify whether the engine climbs a slope through a control strategy.

The specific method is as follows: the installation position of the urea liquid level temperature sensor 1 is moved from the position A to the position B in FIG. 1 . When the engine climbs the slope, the urea tank 2 has a certain inclination with the slope shape, but the liquid level of the urea solution 3 is always parallel to the horizontal plane, so the liquid level of the urea solution 3 and the wall of the urea tank 2 form a non-right angle angle, resulting in the urea liquid level The urea level measured by the temperature sensor rises, thus judging that the engine is climbing a hill at this time.

Moving the position of the urea liquid level temperature sensor 1 from A to B can ensure that the liquid level of the tank changes significantly when climbing a slope.

When the engine accelerates and decelerates, it will also cause fluctuations in the urea level, but this temporary and small fluctuation can be handled by filtering the urea level. The control strategy is shown in Figure 3.

The measurement of the urea level (or the remaining amount) is done by the urea level temperature sensor. When the engine is running smoothly on a level road, the urea level does not change. But when the engine suddenly accelerates and decelerates or goes up and down the slope, the urea level will change. The liquid level fluctuation caused by sudden acceleration and deceleration is short-lived and small, and the liquid level fluctuation can be effectively removed by using a filter function (such as PT). The specific method for calibrating the filtering time is as follows: simulating the acceleration and deceleration of the vehicle to collect the function of the urea level change Y1, and simulating the vehicle uphill and downhill to collect the function of the urea level change Y2. Compared with the acceleration and deceleration of the car, the influence of the uphill and downhill on the urea level is longer in the time factor (up and downhill, the liquid level change time is slightly longer; acceleration and deceleration, the liquid level change time is short), so the filter time T_PT is more sensitive to Y1 , and gradually increase the filter time until the appropriate filter time can remove the fluctuation of the liquid level caused by the acceleration and deceleration of the vehicle, and has less influence on the change of the liquid level caused by the vehicle going up and down the slope.

The specific method of setting the calibration value in Figure 4 is: when the vehicle is running at a constant speed on a level road, the change value of the urea level (urea remaining amount) is 0; when the vehicle is set to climb a slope of 20°, we The OBD torque limit of the vehicle due to exhaust emissions is not allowed to occur when climbing a hill. When the vehicle climbs the slope, observe the change value of the filtered urea level (or the filtered residual urea) and record the value. The set value is only slightly smaller than the recorded value.

When the filtered urea level or the urea remaining amount is greater than the calibration value, it can be judged that the engine is climbing, and the output signal prohibits the engine from performing OBD torque limit; the control strategy is shown in Figure 4, otherwise, the vehicle is not climbing.

Although the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, they do not limit the scope of protection of the present invention. Those skilled in the art should understand that on the basis of the technical solutions of the present invention, those skilled in the art do not need to pay creative efforts. Various modifications or deformations that can be made are still within the protection scope of the present invention.

Claims (8)

1. a method for OBD torque limitation when preventing the engine from climbing, it is characterized in that: the liquid level sensor is arranged on one side of the urea tank, the liquid level variation in the urea tank when collecting the climbing, if the variation is greater than the calibration value, it is determined that The engine is climbing a hill and the engine is disabled for OBD torque limiting. 2. The method for preventing the OBD torque limit when the engine climbs a slope as claimed in claim 1, wherein the liquid level sensor is arranged at the edge of the tank of the urea tank to a distance of one third of the length of the tank from the edge. between locations. 3. The method for preventing OBD torque limitation when the engine climbs a slope as claimed in claim 1, wherein the liquid level variation is filtered, the filtering output is limited to a set range, and tiny fluctuations or short-term fluctuations are filtered out. . 4. The method for preventing the OBD torque limitation when the engine climbs a hill as claimed in claim 1, wherein when the liquid level sensor is arranged on the side of the box body close to the front end of the vehicle, the liquid level change is replaced by the remaining liquid quantity. 5. The method for preventing the OBD torque limit when the engine climbs a hill as claimed in claim 1, wherein when the liquid level sensor is arranged at a position where the tank body is far from the front end of the vehicle, the liquid level variation is replaced by a liquid level value . 6. The method for preventing OBD torque limitation when the engine climbs a slope according to any one of claims 1-5, wherein the urea tank is replaced with a fuel tank. 7 . The method for preventing OBD torque limitation when the engine climbs a slope according to claim 1 , wherein the urea tank is replaced with an oil tank. 8 . 8. the method for OBD torque limitation during a kind of preventing engine climbing as claimed in claim 3, it is characterized in that: need to demarcate filter time during filtering, concrete method is: simulate the function of vehicle acceleration and deceleration to collect urea liquid level change, gradually. Change the filter time until the appropriate filter time can remove the liquid level fluctuation caused by the acceleration and deceleration of the vehicle.