CONTINUOUSLY VARIABLE TRANSMISSION

摘要

The invention concerns an arrangement for control of a continuously varia ble transmission. The transmission includes a variator (10) having a movable torque transfer part (rollers 18) whose position corresponds to a variator drive ratio. A hydraulic actuator (28) is arranged to exert an adjustable fo rce on the torque transfer part. The transmission further comprises a flow c ontrol arrangement which is arranged to receive as control inputs (a) the cu rrent position of the torque transfer part and (b) a demanded position for i t. The demanded position may for example be determined by driver input. The flow control arrangement is adapted to supply through a s upply o utlet w hi ch c omniunicates w ith t he h ydraulic actuator a flow of fluid which is mo dulated in accordance with an error between the two control inputs. The flow of fluid increases with increasing error. A relief passage (110) leads from the said outlet to a pressure sink and is constricted so that fluid flow th rough it results in a p ressure at the hydraulic a ctuator which is g reater than that of the sink by an amount which corresponds to the rate of flow th rough the relief passage. The result is a mode of control of the transmissio n which possesses some of the advantages of both torque and ratio control.