With a pushbelt continuously variable transmission (CVT), the whole drivetrain including the engine of a passenger car can operate in an optimal state at any time. For further improvements with respect to fuel consumption, dynamic simulations of the system have been investigated by Bosch Transmission Technology B.V. and the Institute of Applied Mechanics of the Technische Universität München in recent years. The underlying mathematical models are characterised by numerous contacts and a large degree of freedom. In order to avoid high numerical stiffnesses due to springs and to encourage an efficient as well as a stable and robust numerical treatment, a nonsmooth contact description is chosen. Timestepping schemes are used to integrate the resulting measure differential inclusions. This work deals with a spatial transient mathematical model of pushbelt continuously variable transmissions to consider also out-of-plane effects, for instance pushbelt misalignment. The equations of motion result from using methods of multibody theory and nonlinear mechanics. The bodies themselves are described using rigid and large deflection elastic mechanical models. In-between the bodies, all possible flexible or rigid contact descriptions namely frictionless unilateral contacts, bilateral contacts with planar friction and even unilateral contacts with spatial friction occur. In comparison with the planar case, the calculation time increases significantly mainly because of the large degree of freedom and the number of contact possibilities. Stationary initial value problems are solved and parallelisation techniques are tested to reduce the computational effort. The validation with measurements of global values like thrust ratio, spiral running of the pushbelt in the pulleys and alignment as well as of local internal contact forces correlates very well. This completely proves the applicability of the simulation model. Altogether, a new level of detail in CVT modelling has been achieved giving the possibility to further analyse this complex physical system.
Spatial dynamics of pushbelt CVTs
2010
100 Seiten, 45 Bilder, 9 Tabellen, 91 Quellen
Hochschulschrift
Englisch
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