Patent ID: 6679805
Filing Date: 2004-01-20
Classification: F16H,Y10T

Abstract:
Control system for a continuously variable transmission that is provide with a first pulley (1) having two pulley discs (5, 7), with a second pulley (2) having two pulley discs (6, 8) and with a drive belt (10) wound around said pulleys (1, 2) for transmitting torque there between, at least one disc (7) of the first pulley (1) being axially movable with respect to the other disc (5) of said pulley (1) under the influence of an axial force provided on said movable disc (7) by a line pressure (PLP) in a cylinder (13) of a piston/cylinder assembly (11, 13) associated with the first pulley (1) and at least one disc (6) of the second pulley (2) being axially movable with respect to the other disc (8) of said pulley (2) under the influence of an axial force provided on said movable disc (8) by a second cylinder pressure (P2CP) in a cylinder (14) of a piston/cylinder assembly (12, 4) associated with the second pulley (2), which control system is arranged to control the second cylinder pressure (P2CP) between two pressure levels (PLP; PR) by means of a second valve (40) that allows either a flow of medium from a first hydraulic line (20) where the line pressure prevails (PLP) to the cylinder (14) of the piston/cylinder assembly (12, 14) associated with the second pulley (2), a flow of hydraulic medium from this latter cylinder (14) to a reservoir for hydraulic medium (23) where the prevailing pressure is relatively low or no flow of hydraulic medium at all under the influence of a control pressure (P2C), characterised an that the second valve (40) may be further influenced by the level of the second cylinder pressure (P2CP).