Torque Converter Dynamic Characterization Using Torque Transmissibility Frequency Response Functions: Open Clutch, Hydro-Mechanical Response

The torque transmissibility frequency response functions of four torque converters were measured over a range of operating conditions. In previous works, frequency response function measurements of torque converters contained test setup dynamics which dominated the measurements. Thus, a unique torque converter dynamometer was deployed to measure said frequency response functions and to quantify torsional vibration isolation performance. The frequency response of the hydro-mechanical torque converter was measured under simulated powertrain boundary conditions and separate from other powertrain dynamics. The tested hardware variations covered a range of K-factor, diameter, and lockup clutch damper architectures. The experimental results demonstrated the presence of a damper mode (only present in the turbine damper architectures), which showed that the open torque converter transmits enough torsional vibration to excite downstream damper springs. A lumped parameter model of the torque converter and test setup, containing a widely used hydrodynamic torque converter sub-model, was also validated with the test data. The hydrodynamic torque converter behaved like a low pass filter in the frequency domain, and its performance was characterized with a cutoff frequency. The best correlated model had an average percent error of 10% in the 0–10 Hz frequency range, showing that an accurate prediction of the frequency response could be obtained in the 0–10 Hz range from the hydrodynamic torque converter model. The lumped parameter model consistently overpredicted the natural frequency of the damper mode, and inertial coupling between the working fluid and mechanical torque converter elements or the sensitivity of friction parameters were presented as possible explanations for the natural frequency error.