Modelling of loss mechanisms in a pushing metal V-belt continuously variable transmission. Part 1: Torque losses due to band friction

Abstract

The power transmission efficiency of continuously variable transmissions (CVTs) based on the pushing metal belt is acknowledged to be lower than that of discrete ratio alternatives. This tends to negate the potential fuel economy benefits that are obtained by improved engine/load matching with a CVT. This series of three papers details an investigation into the loss mechanisms that occur within the belt drive as a first step to obtaining improvements in efficiency. Experimental work has been undertaken to investigate the no-load and low-load torque losses associated with a pushing metal V-belt CVT. This first paper describes a new analysis of the principal torque losses occurring in the metal belt CVT due to relative motion occurring between the belt segments and bands. The work takes into account new findings in other research and changes in the design of the metal V-belt. The torque loss model proposed in this paper is supported by experimental data from several different test procedures. A number of additional torque loss mechanisms, due to pulley deflections, are described in Part 2 of the series. The findings from this current paper support an analysis of belt-slip losses, which is described in detail in Part 3.