Enhancement of the Flat-Belt, Continuously-Variable Transmission Technology

Development continued on the Kumm flat belt continuously variable transmission (ref. SAE 850488). Two prototype transmissions were built and tested. A plastic bearing material end cap and a drop center design on the belt drive elements resulted in low sliding friction and wear at the belt drive element - guideway interface. A 635 newton-meter, 10:1 speed ratio industrial CVT design was successfully tested. Efficiency of 96% was obtained over a wide power and speed ratio range. A 1.8 liter automotive powertrain 5.5:1 CVT was also built and tested with similar results. The hydraulic actuators provided responsive control and noise was not excessive. The next technical issues to be addressed are automatic controls and reliability.