In-cylinder direction injection gasoline engine and control method thereof

Abstract

The invention provides an in-cylinder direction injection gasoline engine and a control method thereof so as to reduce the throttling loss, increase the combustion stability and reduce the oil consumption. As the in-cylinder direction injection gasoline engine of the invention is provided with two-stage type variable valve lift and variable valve timing, under a low load working condition, an electronic control unit controls an exhaust valve to be closed before a top dead center of an exhaust stroke and an intake valve to be closed in the first half of a suction stroke, therefore, a section of negative valve overlapping interval is formed nearby the top dead center of a compression stroke, a part of exhaust gas is remained in an air cylinder; the electronic control unit respectively controls a fuel injector to carry out the first injection in the minus 30-30 degree CA range of the top dead center of the air suction and the second injection in the compression stroke, therefore, the high remained waste gas in the cylinder can be used, the thermal efficiency is increased, and meanwhile the combustion stability is ensured; and under a high load working condition, the electronic control unit controls the intake valve and the exhaust valve to work under the big lift to carry out the normal fuel injection and phase control.

Description

technical field [0001] The invention belongs to the technical field of automobile engine manufacturing, and in particular relates to an in-cylinder direct-injection gasoline engine and a control method thereof. Background technique [0002] Compared with the traditional electronically controlled intake port injection method, the direct injection gasoline engine has more flexibility in the formation of the mixture. In-cylinder direct injection gasoline engine can realize the combustion of lean-burn mixture under partial load conditions, and can use a larger throttle opening to reduce pumping loss. Under heavy load conditions, the intake stroke is injected, Gasoline evaporation and heat absorption are used to reduce the temperature of the mixture in the cylinder, thereby reducing the knocking tendency of the gasoline engine in the cylinder, so the direct injection gasoline engine can adopt a higher compression ratio, and these advantages are beneficial to improve the fuel econ...

AI Technical Summary

Problems solved by technology

Due to the short injection time of direct injection in the cylinder, especially under partial load, the cylinder pressure is low, the intake air temperature is low, the fuel atomization is poor, and a part of the oil particles are sprayed onto the piston and the wall of the combustion chamber, resulting in unused fuel remaining on the wall. Evaporated droplets of fuel or a richer mixture, resulting in increased hydrocarbon and soot emissions

At the same time, the combustion of the heterogeneous mixture in the cylinder will lead to an increase in NOx emissions

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