Study On The The Automotive Powertrain Mounting System With Semi-active Hydraulic Damping Strut

Rencently,the requirement for the automobile NVH performance is increasing,thus people have paid more attention to shock and vibration which come from the engine start-stop,auto start-stop and in situ shift for the traditional internal combustion engine.Some domestic and foreign automobile companies have started the related research about these transient vibrations.The vibration of the engine start-stop and in situ shift are transfered to the inside of the vehicle through the mount components.This paper designs and manufactures a semi-active hydraulic damping strut,which is installed in parallel with torque strut between engine and sub frame.The semi-active hydraulic damping strut will provide temporary large damping to attenuate vibraton and shock in these transient consitions to improve the vehicle NVH performance.The main research works in this paper include:1.The semi-active hydraulic damping strut is proposed to decrease the engine start and stop,auto start and stop and in situ shift shock and vibration in the original mount system.The semi-active hydraulic damping strut is described as the fourth mount in this paper,which is designed and manufactured.2.The physical parameter model and dynamic stiffness model are constructed for the semi-active hydraulic damping strut.The physical parameter models with the electromagnetic value closed or opened are constructed.The factors influencing the damping force of the semi-active hydraulic damping strut like the piston hole diameter,piston length,oil viscosity,nitrogen pressure and piston rod diameter are analyzed,which provides theoretical basis for the design.Put the semi-active hydraulic damping strut equivalent as two DOFs mass and spring model and build the dynamic stiffness expression.The dynamic stiffness of the semi-active hydraulic damping strut with the electromagnetic value closed and opened is calculated respectively,and the calculation values of the dynamic stiffness are verified by experiment.Different factors influencing the semi-active hydraulic damping strut dynamic stiffness and damping capacity such as equivalent spring stiffness,bushing hardness and damping conatant are analyzed.3.The semi-active hydraulic damping strut is described as fourth mount,and the installation location and idle state dynamic stiffness are optimized based on the powertrain mount system design method.The dynamic response evaluation indexes and calculation method based on powertrain and vehicle vibration are presented respectively.The vehicle 13 DOFs is build which cantains the semi-active hydraulic damping strut is described.The design method of the semi-active hydraulic damping strut under vehicle key on/off and vehicle in situ shift is proposed.4.The mount system active side acceleration and dynamic force are obtained through experiment when vehicle key on/off(engine start and stop)and engine auto start and stop,and the powertrain excitation forces are indentified.The piston hole diameter and number are calculated according to the semi-active hydraulic damping strut design method.The dynamic response evaluation indexes results with and without the semi-active HDS are compared according to vehicle 13 DOFs,which shows that the semi-active hydraulic damping strut can decrease the engine start and stop and auto start and stop vibration.The vehicle experiment is conducted to validate the design method of the semi-active hydraulic damping strut and the vehicle 13 DOFs are reasonable or not.5.The mount system active side acceleration and dynamic force are obtained through experiment when general rate in situ shift and quick in situ shift,and the powertrain excitation forces are indentified.The piston hole diameter and number are calculated according to the semi-active hydraulic damping strut design method.The dynamic response evaluation indexes results with and without the semi-active HDS are compared according to vehicle 13 DOFs,which shows that the semi-active hydraulic damping strut can decrease the general rate in situ shift and quick in situ shift vibration.The vehicle experiment is conducted to validate the design method of the semi-active hydraulic damping strut and the vehicle 13 DOFs are reasonable or not.