Research and Analysis on Knocking Noise of Mechanical Vacuum Pump of Turbocharged Direct Injection Engine

In the present paper, the knocking noise of a mechanical vacuum pump of turbocharged direct injection engine is researched. By noise, vibration, phase and air pressure signal during operation of engine, wavelet transform and angle domain analysis method are applied to identify the source of the knocking noise, determine the contribution of exhaust valve plate material, shape and stroke, etc. to the knocking noise. And the intensity of the knocking noise at idle speed is lowered by the methods of replacing material, changing shape and lowering stroke, etc. Based on this, the scheme of adding pressure stabilizing cavity on the back of the exhaust valve plate is finally determined by combining with reliability and cost to effective control the knocking noise of the mechanical vacuum pump. The present paper provides design suggestions and references for during design of engine mechanical vacuum pump, and it has certain guiding significance for avoiding knocking noise caused by design defects of mechanical vacuum pump.