Vibrations and Torque Losses of Synchronizers in Transmissions 2021-24-0068
Synchronizers are shifting elements in transmissions with power interruption, such as manual transmissions (MT) and automated manual transmissions (AMT). Synchronizers are also used in dual clutch transmissions (DCT) for shifting the preselected idler gear in the load-free branch of the transmission. Electric drive units (EDU) mainly consist of a two-stage transmission combined with a high-speed electric motor. Synchronizers realize the power flow from an idler gear to a gear shaft of the transmission.
Automotive transmissions are usually operated with lubricating oils in order to minimize friction and wear of the mechanical components. Lubricating oil has a major influence on torque losses and on vibration behavior of transmission components.
Torsional vibrations of mechanical components in transmissions lead to natural vibrations with high impact forces and thus to high radiated airborne sound levels. This occurs in particular when hard surfaces impact and the components have a high level of spring stiffness in addition to low damping properties. A drive torque that has a rotational irregularity leads to torsional vibrations of the components outside the power flow and is the starting point for transmission noises. Synchronizers have a function-related circumferential backlash in order to be able to shift the gear in a synchronized manner and therefore contribute to undesirable transmission noises.
The aim of this work is to measure the vibrations of a synchronizer ring due to torsional vibration excitation while varying various parameters and to show the influences of the parameters. In particular, the lubricating oil has an influence on the torque losses and on the vibration behavior of a synchronizer. Lubricating oil with a low coefficient of friction due to its chemical structure leads to lower torque losses of the synchronizer and reduces the vibrations, which leads to a 1-2 dB(A) lower noise level of the transmission.
