An Analytical Study Of Piston Impact And Scraping Force Induced By The Piston Secondary Motion

The impact between piston and cylinder wall is one of the major sources of noise and vibration in an internal combustion engine. The gap between piston and cylinder wall of an internal combustion engine is small, however it may induce the piston secondary motion (lateral and rotational motion) periodically and generate unwanted sound and vibration.A method to calculate piston secondary motion is presented in this paper, the motion model including the piston, the connect-rod and the crank shaft by the Newtonian second law and the impact model by the Lagrangian equation are established. By substituting the relations between the variables, the matrix function with the acceleration, velocity and scraping or impact force are obtained. The numerical simulation of this model was processed by FORTRAN code. So the lateral displacement, lateral velocity of the piston and the angle of piston rotation from vertical, the velocity of piston rotation in various angles of crank shaft can be calculated, and the scraping force and the impact force acted between the piston and the bore can also be calculated at the same time.The oil influence between the piston and the bore is analyzed, by writing difference equations of the Reynolds Equation within the lubricant film, and a difference approach for solving this equation is provided for the symmetric boundary condition.