Method and system for determining air-fuel ratio on basis of injection pulse width of fuel injector

Abstract

The invention discloses a method and system for determining the air-fuel ratio on the basis of the injection pulse width of a fuel injector. The method is used for an engine. The engine comprises a shell and the fuel injector. The fuel injector is arranged in the shell. The method includes the steps that when a vehicle is in the preset work condition, the total fuel injection pulse width of the fuel injector and the ignition angle of the engine are obtained; according to the ignition angle and the total fuel injection pulse width, the fuel injection mode of the fuel injector is determined; a first fuel injection pulse width of each time of injection of the fuel injector is determined; when the first fuel injection pulse width is not within the first preset range, according to the rail pressure of the fuel injector and the ignition angle of the engine, the first fuel injection pulse width is adjusted till the adjusted first fuel injection pulse width is within the first preset range, the adjusted first fuel injection pulse width is used as a second fuel injection pulse width, and the air-fuel ratio is determined on the basis of the second fuel injection pulse width. According to themethod and the system, the first fuel injection pulse width is accurately adjusted into the second fuel injection pulse width, the engine can accurately control the fuel injection amount of the fuelinjector, the air-fuel ratio is accurately determined, and therefore the emission of the engine is reduced.

Description

technical field [0001] The invention relates to the technical field of automobiles, in particular to a method and system for determining an air-fuel ratio based on an injection pulse width of an injector. Background technique [0002] With the improvement of living standards, the number of automobiles is increasing, and people pay more and more attention to the performance of automobile energy saving and emission reduction. Harmful emissions, according to engine combustion theory, if the engine can always be guaranteed to burn under the theoretical air-fuel ratio, then the emission of harmful substances can be effectively controlled. Therefore, the key way to realize engine emission control is to control the air-fuel ratio of the engine. [0003] In the prior art, the engine has open-loop control and closed-loop control. When the engine is under closed-loop control, the engine control system will use an oxygen sensor to detect the combustion situation of the engine. Accordi...

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Problems solved by technology

However, the work of the oxygen sensor requires its temperature to reach a certain limit before it can start working

It can be seen that under the condition that the oxygen sensor is not working normally, the air-fuel ratio of the engine cannot be controlled by the above method. However, according to the requirements of the National VI emission regulations, the vehicle emission detection is carried out from the moment the vehicle is started, so in the first few days Within minutes, the oxygen sensor cannot reach the operating temperature. At this time, the engine is under open-loop control, and the system cannot accurately control the air-fuel ratio through the oxygen sensor. Therefore, when the engine is under open-loop control, the The fuel ratio cannot be precisely controlled

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