Patent ID: 7160226

Claim:
A continuously variable transmission comprising a transmission input, a transmission output, and a continuously variable ratio unit arranged to be coupled between the transmission input and output by means of at least one clutch thereby to enable transfer of drive between the input and the output at a continuously variable transmission ratio, wherein the variator is connected to a hydraulic control circuit and so subject to a hydraulic control pressure which is adjustable by the control circuit and is also influenced by changes in variator ratio, the variator being constructed and arranged such as to adjust its ratio to provide a variator reaction torque which corresponds to the control pressure, the transmission being characterised by provision of means for adjusting the torque capacity of the clutch while it is engaged, the transmission further comprising control electronics which establish a desired control pressure and set the control circuit in dependence thereupon, the control electronics also serving to adjust the torque capacity of the clutch while the clutch is engaged such that excursions of the control pressure from the desired level due to changes in variator loading are controlled by virtue of slipping of the clutch.