A review on belt and chain continuously variable transmissions (CVT): Dynamics and control

A study on the torque capacity of a metal pushing v-belt for cvts

The steel pushing V-belt continuously variable transmission (CVT) is now commercially available in the automobiles of a number of manufacturers but to date it has not led to a significant reduction...

Modelling of the Steel Pushing V-Belt Continuously Variable Transmission

Continuously variable transmissions (CVTs) are applied in an increasing number of vehicles. Large ratio coverage allows for reduced engine speeds, which adds to both highway driving comfort and reduced fuel consumption. It becomes increasingly important to further improve the performance in terms of efficiency, robustness and torque capacity of the CVT. This paper describes the possibilities of improving the CVT by minimising variator clamping forces. This is accomplished by using slip control technology. This technique allows for the best possible transmission efficiency, combined with improved robustness for slip damage. This paper first describes the relation between variator slip and functional transmission properties. The conditions for optimum performance regarding efficiency and robustness are identified. This leads to the development of a variator slip controller. The remaining sections describe experimental results on two test rigs and in a production vehicle. The paper concludes with an outlook into further developments.

http://www.mate.tue.nl/mate/pdfs/5359.pdf

Performance optimisation of the push-belt CVT by variator slip control

Transient dynamics of metal V-belt CVT : Effects of band pack slip and friction characteristic

To achieve the potential advantages to be gained by the use of a high ratio range, continuously variable transmission (CVT) in an automobile it is important that the system has a high efficiency and that any inherent loss mechanisms are fully understood.This paper investigates the belt-related torque loss in a steel V-belt CVT. Measurements show that the loss is dependent on the secondary pulley clamping force and on the belt configuration and these results are presented in the paper. A semi-empirical model is proposed to explain the loss. The agreement between the measured results and the values calculated from the model is shown to be good.It is also shown that when the system is in an overdrive ratio and a high efficiency is particularly important the torque loss is large and the efficiency is severely limited, probably to less than 90 per cent.

Belt Torque Loss in a Steel V-Belt Continuously Variable Transmission:

This paper investigates the reasons why in current passenger vehicles the steel pushing V-belt continuously variable transmission (CVT) has failed to achieve an improvement in fuel economy even though the CVT is correctly controlled and allows the engine to operate near to its region of maximum efficiency. It is shown that the overall efficiency of the transmission is low, especially at the lower vehicle speeds.The main losses are due to the belt torque loss, the hydraulic pump loss and the loss due to slip in the belt-pulley system. It is shown that a considerable improvement in vehicle economy is obtainable by controlling the transmission so that the sum of these losses is minimized as well as seeking to optimize the engine efficiency. This improved overall efficiency is achieved by operating the CVT with much lower pulley clamping pressures than have previously been considered desirable.

J D Micklem

Papers

Modelling of the Steel Pushing V-Belt Continuously Variable Transmission

Belt Torque Loss in a Steel V-Belt Continuously Variable Transmission:

The Magnitude of The Losses in the Steel Pushing V-Belt Continuously Variable Transmission: