Analysis of Flow in the Lock-up Clutch of an Automotive Torque Converter

The flow through the single-plate lock-up clutch in an automotive torque converter with a 250-mm nominal diameter was numerically investigated using a CFD code. The flow was computed under various clearances between the lock-up piston and the torque converter cover. The stable location of the lock-up piston was determined so that the thrust acting on it became zero. The computation results showed that the fluid flowed outwards in the narrow channel between the lock-up clutch facing and the converter cover, whereas the flow reversed inwards near the lock-up piston surface upstream and downstream of the narrow channel in most cases. Along the outer surface of the axial flow channel near the exit, the flow also reversed far upstream of the channel. The computation results well predicted the stable position of the lock-up piston. It is noteworthy that the sharp increase in clearance in the coupling range can be clearly captured with this method.