High clamping force levels reduce the efficiency of the Continuously Variable Transmission (CVT). However, high clamping force level are necessary to prevent slip between the belt and the pulleys. If a small amount of slip is allowed, the clamping force level can be reduced. To achieve this, slip in a CVT is investigated. From measurements on an experimental setup, Traction curve data and efficiency measurements are derived. A model describing slip in a CVT is verified using measurements with a belt with increased play. It is found that small amounts of slip can be controlled in a stable way on the setup. The traction curve was mostly dependent on the CVT ratio. Efficiency is found to be highest for 1 to 2% slip depending on the ratio. The model is in reasonable agreement with the measurements.
Combining both launch and reverse drive functions with the ratio change function in a geared neutral continuously variable transmission (GN-CVT), thus making a launch device like a torque converter and a drive-neutral-reverse (DNR) set obsolete, is attracting considerable attention. This paper covers the modelling and simulation of a V-belt geared neutral transmission in and around the geared neutral point. Owing to the specific nature of the geared neutral state, conventional driveline simulation models are shown to be inadequate. Experimental results are presented, allowing a more detailed description of the functional properties of the V-belt variator, especially those related to small amounts of slip between the belt and the pulleys. The measured data will be analysed to obtain grey model fitting parameters, which allow the data to be used in a simulation program based on a dynamic driveline model. It will be shown that, with a GN-CVT, stall and launch performance can be considerably better than that achieved with a driveline with a torque converter (TC).system level of a GN-CVT over a conventional D03004
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