The micro-speed difference dual-rotor system composed of a hydraulic torque converter and a crankshaft affects the idle twitch of an Automatic Transmission (AT) vehicle. Through the Hilbert transform of the dynamic unbalanced coupling excitation force of the dual-rotor system, it is revealed that the beat vibration of the component is the root cause of the regular idle twitch. The maximum twitch amplitude is the sum of the excitation forces, and the twitch time interval is the difference between the excitation force frequencies. The Automatic Dynamic Analysis of Mechanical Systems (ADAMS) model including engine, transmission and mounting system is established and simulated. The results show that the closer the vertical rigid body mode of the powertrain is to the excitation frequency, the greater the vertical first-order dynamic stiffness of the hydraulic mount and the greater the vibration amplitude. Therefore, the idle twitch can be improved by the frequency avoidance design of the Z-direction mode of the powertrain and the dynamic unbalance excitation frequency of the crankshaft, reducing the vertical dynamic stiffness of the hydraulic mount, and improving the vibration isolation performance of the mount system.

Dual-rotor system with micro-speed difference  /  Automatic Transmission (AT)  /  Idle  /  Twitch  /  Torque Converter  /  Engine