POWER TRANSMISSION OF HALF-TOROIDAL TRACTION DRIVE CONTINUOUSLY VARIABLE TRANSMISSION (4-WHEEL-DRIVE CVT DESIGN AND ITS PERFORMANCE)

Four-wheel drive offers cruising stability and high road gripping forc e at the expence of the power weight ratio due to implementation of an additional mechanism of a center differential gearbox with a torque s plit clutch. We developed a dual-cavity half-toroidal traction-drive c ontinuously variable power transmission (CVT) for 3 L passenger cars i n 1990, which can be easily remodelled into a CVT with two output shaf ts since it has two independent CVT units. Since the CVT has a hydraul ic-control equal-force-transmitting mechanism for speed ratio control, it is easy to synchronize the force transmission of front and rear ax les without using a center differential gear box. In this paper we des cribe the mechanism, efficiency and control principle for the equivale nt function of a center differential gear box of the four-wheel-drive CVT with nominal input torque capacity of 250 N . m, rotational speed of 5500 rpm and maximum speed ratio range of 1: 8.7.