Patent ID: 7625309

Claim:
A continuously variable transmission comprising: a transmission input, a transmission output, a variator which provides a continuously variable variator ratio, and gearing constructed and arranged to couple the variator between the transmission input and the transmission output in either of a low regime and a high regime, so that the transmission output is drivable from the transmission input at a transmission ratio which is related to the variator ratio, the relationship between the variator ratio and the transmission ratio being different in the two regimes, the gearing incorporating a first hydraulically actuated clutch to engage and disengage the low regime and a second hydraulically actuated clutch to engage and disengage the high regime and being such as to provide a synchronous ratio at which a change between low and high regimes at constant variator ratio produces no change in transmission ratio, and the transmission being provided with hydraulics incorporating a shift valve which controls application of hydraulic pressures to the first and second clutches, so that a change in state of the shift valve causes one clutch to change from engaged to disengaged and the other clutch to change from disengaged to engaged, and causing the transmission to change from one regime to the other, the transmission further comprising a hydraulic actuator, wherein the hydraulic actuator's force determines variator reaction torque, a valve arrangement for providing first and second variator control pressures, and a switching valve having a first state in which it applies the first variator control pressure to a first side of the hydraulic actuator, and a second state, in which it applies the second variator control pressure to a second side of the hydraulic actuator, so that a change in state of the switching valve produces a change in magnitude and direction of the actuator's force, the state of the switching valve being controlled by the shift valve.