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Apart from performance, comfort, cost and fun to drive, the reduction of fuel consumption has become a primary driver in the world market of the automotive industry. As continuously variable transmissions based on the pushbelt principle can be operated in an optimal state at any time, they are very suitable to meet the mentioned requirements. However, the power transmission in the system is very complicated. Both detailed measurements and simulations are necessary to understand and to optimize the physical mechanisms, power density and shift characteristics. The current paper presents a spatial simulation model for transient analysis at different levels of detail. An initial model based on non-smooth multi-body theory is outlined. It consists of two rigid pulleys each with one tilting loose sheave. The pushbelt comprises two ring packages based on the co-rotational approach.

The efforts to further reduce fuel consumption of vehicles equipped with a pushbelt type Continuously Variable Transmission (CVT) focus on different sources of loss. In this paper the magnitude of these losses and their potential for reduction is described. Inside the CVT, the variator, its control strategy and the hydraulic actuation circuit can be distinguished as the main potentials. A major opportunity is offered by a new control strategy that takes the actual slip between belt and pulley as the control parameter. The resulting decrease of clamping forces on the pushbelt leads to a reduction of variator and actuation losses. Further potential is found in the hydraulic actuation circuit by an improved tuning of the power supply to the actual power requirement. Outside the CVT additional potential is found in start-stop functionality as supported by measures inside the transmission.