Abstract
The objective of this project was to significantly reduce fuel consumption of current ICE drivelines by designing a new transmission system which keeps the engine on its lowest consumption curve at all times while being very efficient in itself through elimination of power consuming components as e.g. slipping friction plates, synchronizers, torque converters and leaking piston rings. The system should be able to change ratios between high forward and reverse in one stepless movement without the need for a clutch. The result was the Reversible Variable Transmission, a new kind of transmission benefiting from being a continuous system while avoiding the drawbacks of current CVTs. All existing CVT systems except the RVT suffer from the known drill-slip which limits the effectiveness of traction by friction wheels and which creates heat and losses. The RVT is specially designed to eliminate this major drawback. Also, it solves the problem of geometrical inaccuracies by the mechanism to change the ratios. No power burning components were used, the hydraulics work at optimum efficiency thanks to the absence of leaking piston rings. The first RVT prototype demonstrates the perfectly smooth ratio changes even when changing driving direction between forward and reverse. The RVT ratios have an exceptionally large spread; for the current RVT prototype designed for a passenger car e.g. they vary between speed ratio 2.4 (torque ratio 0.417) in forward to 0.26 (torque ratio 3.846) in reverse. There is no reduction in efficiency nor in traction while changing the ratio. Driving under load at creeping speed or in geared neutral under varying loads are possible for an unlimited period of time without heat dissipation. This paper focuses on the physical principles leading to the design of the RVT. From these theories calculation programs were derived for faster design of new RVT models for different applications. These calculation programs are also the basis for ‘model based controls’.
KEYWORDS – variable transmission, RVT, CVT, clutch, creeping