An experimental study for effect factors of the roller tappet induced impact noise in high-pressure fuel system of GDi engine

Abstract

With the wide application of gasoline direct injection system, its noise problem is becoming increasingly prominent under serious competitive environment. As the primary noise source of the engine in idle condition, the significant noise generated by the low-to-high pressure transmission part of high-pressure fuel pump becomes more and more serious. This paper focuses on the driving component of high-pressure fuel pump, the roller tappet, and experimentally studies effect factors of impact noise induced by it at engine idle. Both the impact occurrence time and position are analyzed from the combined vibration acceleration and crankshaft/camshaft rotation angle signals in the time domain according to the structure and kinematic mechanism of the roller tappet. The influences of the axial clearance between roller and tappet shell, the engine rotation speed and the lubrication conditions are investigated by experiments. The experimental results show that the lubrication is the primary factor for the roller tappet induced impact noise reduction. A significant improvement about 83% can be achieved under pressure lubrication.