CVT Control System

A method of operating a control system for a multi-regime continually-variable transmission including variator rollers and first and second regime clutches (37, 43), said transmission being driven by a prime mover and providing an output drive, first control means controlling a clutch apply pressure supplied to the clutches so as to initiate engagement and disengagement thereof during regime change, and

• second control means controlling the position of the variator rollers, characterized in that, said first and second control means are operable independently of each other in such a way that the settings of the variator rollers are unaffected by the variations in the clutch apply pressures, the method comprising the steps of:
• firstly, during regime change, initiating engagement of the of the otherwise unengaged clutch before the variator reaches synchronous ratio such that the engine load created by the transmission varies and thereby induces a change of regime;
• secondly, completing a regime change by disengaging the clutch associated with the regime from which the transmission has been changed and completing engagement of the clutch under engagement.

A hydraulic control system for a multi-regime continually variable transmission driven by a prime mover and providing an output drive, the transmission having hydraulically actuated first and second regime change clutches and variator having ratio varying rollers each associated with a respective hydraulic ram, the system having, at any particular moment in time, a higher and lower source of hydraulic pressure, supply means for causing the supply of hydraulic fluid to each clutch to vary between the fluid at the higher pressure and the fluid at the lower pressure and the supply of hydraulic fluid to the hydraulic ram to be such that the rollers respond to the differential pressure.