Control method of high-pressure common rail system pressure-limiting valve

Abstract

The invention discloses a control method of a high-pressure common rail system pressure-limiting valve. The control method comprises the steps that the state of the pressure-limiting valve is judged by motoring whether a rail pressure value is greater than a rail pressure upper limit threshold value or not and combining the rail pressure variable quantity calculated according to the monitored railpressure value and the rotating speed condition; when the pressure-limiting valve forced switching-off condition is met, the pressure-limiting valve is actively switched off for controlled start; when the pressure-limiting valve impact condition is met, the pressure-limiting valve is actively switched on for controlled start; when the response delay time alarm condition is met, corresponding alarm information is set; and when the pressure-limiting valve inhibition condition is met, the pressure-limiting valve is actively inhibited for controlled start, wherein the state of the pressure-limiting valve is divided into six types, namely initialization, switching-off, testing, switching-on, impact and inhibition. By means of the control method, the hazards of long-time insufficient power, engine combustion, emission deterioration and even engine stalling caused by switching-on of the pressure-limiting valve are avoided.

Description

technical field [0001] The invention relates to a control strategy and method for an electronically controlled high-pressure common-rail diesel engine, in particular to a control method for a pressure-limiting valve in a high-pressure common-rail fuel injection system. Background technique [0002] The aggravation of environmental pollution and the increasing exposure of the energy crisis, the increasingly stringent emission regulations have promoted the development of electronically controlled diesel engines. Due to the precise and flexible adjustment of fuel injection pressure and fuel injection law, the high-pressure common rail system has become the development direction of the diesel engine fuel system in the future. When the electric control or mechanical failure of the high-pressure common rail system occurs, the fuel pressure in the common rail pipe may exceed the maximum safe pressure that each component of the high-pressure common rail system can withstand, resulti...

AI Technical Summary

Problems solved by technology

The pressure limiting valve structure of different companies is quite different, such as using a two-stage piston structure pressure limiting valve or a variable cross-section single-stage piston structure pressure limiting valve, which leads to a large difference in the rail pressure change after the pressure limiting valve is opened, and the same During the opening process of the pressure limiting valve, the variation of rail pressure is also quite different in different periods

In order to ensure accuracy, it is necessary to use a smaller opening threshold of the pressure limiting valve and a larger threshold of the first counter, which will lead to a lag in opening judgment

[0005] 2) Since only the rail pressure drop rate is used as the condition for judging whether the pressure limiting valve is open, when a serious leakage occurs in the system or the injector is stuck, the rail pressure drop rate may reach the preset opening threshold of the pressure limiting valve, resulting in Misjudgment and failure to take control measures in time, resulting in energy loss

[0006] 3) Since only the rail pressure drop rate is used as the condition for judging whether the pressure limiting valve is open, when the fuel supply control of the high pressure fuel pump adopts the normally open fuel metering valve, if the electronic control unit fails and restarts when the engine is running at high speed, the injector will When the injection is stopped and the fuel metering valve is fully opened, the high-pressure oil pump will supply fuel at its maximum. When the engine is running at high speed, the fuel supply capacity is strong. The sudden increase in fuel supply and the sudden stop of fuel injection lead to the opening of the pressure limiting valve, and the ECU cannot monitor the rail during restart. pressure signal, and the abnormal restart time of the electronic control unit is relatively short. Although the stop of the injection causes the engine speed to drop, the rail pressure is still greater than the minimum limp pressure, that is, the pressure limiting valve is kept open. After the electronic control unit is restarted, the monitored rail pressure change may not be Reaching the preset opening threshold of the pressure limiting valve, resulting in misjudgment (such as resuming fuel injection, etc.) due to failure to correctly identify the opening of the pressure limiting valve, and failure to take control measures in time, resulting in poor vehicle power and economy

[0007] 4) Since only the rail pressure drop rate is used as the condition for judging whether the pressure limiting valve is open, when the rail pressure sensor fails, the rail pressure signal cannot be monitored normally, resulting in incorrect identification of the opening of the pressure limiting valve and misjudgment

[0008] 5) The pressure limiting valve only realizes passive opening monitoring, but does not realize active opening control. When the rail pressure sensor fails or the system mechanical failure causes the rail pressure to be too high, because no impact control is adopted, the high-pressure oil pump supplies oil normally at this time, and the fuel injector works normally. Fuel injection may cause the rail pressure to be higher than the rail pressure upper limit threshold and the duration of the pressure limiting valve not to open itself may be longer, resulting in poor system safety

[0009] 6) The opening times and cumulative opening time of the pressure limiting valve are not recorded and analyzed. After the opening times of the pressure limiting valve exceed a certain threshold or the accumulated opening time exceeds a certain period of time, the opening pressure of the pressure limiting valve will increase or decrease, increasing the total pressure of the high pressure. Risk of permanent failure of the rail system

[0010] 7) The response delay time of the pressure limiting valve is not recorded, analyzed and controlled

The response delay time is one of the key indicators of the safety performance of the pressure limiting valve. For example, when the pressure limiting valve is stuck, the response delay time will increase, increasing the risk of permanent failure of the high pressure common rail system

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