Noise Reduction of Chain-CVTs using Optimisation Techniques

Continuous variable chain drives have to satisfy high requirements to compete with common gears and therefore an improvement of certain properties of the CVT (= Continuously Variable Transmission) is desired. In this contribution the important goal to reduce the noise emission of the gear is realised by optimising the geometry of the rocker pin chain. This optimisation is carried out by applying numerical simulation techniques and an optimisation algorithm. For this purpose a detailed dynamical model of the CVT is introduced which includes an exact treatment of the rocker pin kinematics of the chain. The geometry of the rocker pin joints which shall be optimised is defined by the optimisation parameters. A good choice for a measure of the noise emission are the amplitudes of the forces in the bearings in a certain frequency domain. They are used to form the target function. A numerical simulation provides a connection between the optimisation parameters and the objective function, which is not given analytically and takes high simulation effort. Therefore the optimisation algorithm implicit filtering is applied to solve the optimisation problem. The presented approach is applied to minimise the noise emission of a CVT by finding optimal geometry parameters. A significant reduction of the noise emission is gained. The optimisation can be carried out on standard PCs.