Math-based Torque Converter Modelling to Evaluate Damping
Characteristics and Reverse Flow Mode Operation
This paper presents math-based torque converter modelling and simulation in both forward flow mode and reverse flow mode operations. Since, a torque converter plays an
important role in transferring power from an engine shaft to the transmission shaft and
vice versa and affects the fuel consumption and vehicle longitudinal dynamics, simulating
the dynamic behaviour of this component in different operating modes is of great
importance. Our torque converter model is validated with the experimental results of the
Honda CRV during the forward flow mode operation.
The main focus of this research is on reverse flow mode simulation, and the application
of the proposed math-based torque converter model to evaluate damping characteristics of
a torque converter due to undesired disturbances generated either from engine pulsations
or from road bumps and potholes. The simulation results show that a torque converter
efficiently damps high frequency disturbances introduced from engine shaft to the
transmission side and vice versa.
Keywords: torque converter; powertrain damping; reverse flow mode;
In an automobile with an automatic transmission, instead of a mechanical clutch, a torque converter (a type of fluid coupling) can be utilized to transmit the engine‟s power. The major roles of a torque converter are multiplying torque generated by the engine, absorbing torsional vibration of the engine and
powertrain, and smoothing out the engine rotation .
The torque converter includes three rotating elements: the pump (impeller), the turbine, and the
stator (Figure 1). The pump is attached to the engine shaft, which is called the prime mover, and the
turbine is connected to the transmission shaft. The stator, which is placed between the pump and the
turbine, redirects the returning fluid from the turbine to the pump. A one-way clutch is used along with
the stator to either lock or unlock the stator depending on the fluid direction (whether it hits the front or
back of the stator‟s vanes). In modern automatic transmissions, a lock-up clutch is also implemented in the torque converter
to lock the engine and the transmission shafts at higher gear ratios. The torque converter‟s pump and turbine shafts are mechanically connected via the lock-up clutch at higher gear ratios (e.g. gear ratios = 3
and 4) to improve the fuel economy and enhance the efficiency.
Figure 1: Cross section of a torque converter
The torque converter‟s operating modes (during forward operation) can be explained by using the "coupling point", which is defined based on the stator‟s torque. In the torque multiplication range, below the coupling point, the stator is fixed by the one-way clutch and its rotational speed is zero. In the
coupling range, which happens after the coupling point, the stator freely rotates and the...