Efficiency of Chain-CVTs at Constant and Variable Ratio - A new mathematical model for a very fast calculation of chain forces, clamping forces, clamping ratio, slip, and efficiency

The efficiency of chain-CVTs depends on friction forces and slip between the chain and the pulleys. The slip itself results from the elastic deformations of the pulleys, shafts, and the chain and from additional motions between chain and pulleys when changing the trans-mission ratio. The local friction forces depend on the local axial clamping forces and the local friction coefficients. A new mathematical model has been developed to calculate these relationships even in conditions with variable transmission ratio and furthermore with a very high calculation speed. Additional results are the relations between the clamping forces, which are necessary to transmit a certain torque at a certain ratio and a particular adjusting-speed, and the efficiency as well as the safety from gross slip. With this new tool it is much easier to improve the design of the CVT as well as the hydraulic system and the control strategies resulting in higher torque capacities and reduced power losses.