High Capacity Freewheels for Torque Converter Applications

The Mechanical Diode™ (MD) one-way clutch was the result of an engineering project to develop a C.A.R.T. (Indy Car) transmission based on the Epilogics Infinitely Variable Transmission technology. Because the available devices (of suitable torque capacity) were simply too heavy, an alternative to conventional one-way clutches had to be found in order to meet the weight requirement for this application. The solution was found in an innovative, planar, vemier ratchet design which incorporates low-mass, low-inertia “struts” to provide a fast-reacting, positive-engagement, lock-up mode as well as a non-contact freewheel mode to maximize overrunning performance.

This paper presents an evaluation of the MD used as a one-way clutch in high performance, drag racing torque converter reactors. In this application, the Mechanical Diode replaces conventional one-way clutches which are based on sprag and roller-rampdesign principles. Design rules, laboratory test results and in-car performance data are examined. Comparisons between the three different approaches are used extensively in the discussion., Dragstrip experience with several hundred MDs installed in a wide variety of race cars spanning a broad range of vehicle weight and engine power is used to corroborate the results of laboratory tests. The dragstrip proves to be an extremely harsh environment for automotive transmission one-way clutches in general and torque converter one-way clutches in particular due to the severe impact loads to which the one-way clutches are subjected. The results and conclusions presented in this study are clearly illustrated with case studies of actual race cars using MD-equipped, high performance torque converters.