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...

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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

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