Hydraulikvorrichtung für ein stufenlos einstellbares Getriebe

摘要

An electronically controlled hydraulic apparatus for a belt drive type continuously variable transmission comprises a belt wound around a primary pulley and a secondary pulley, a line pressure control valve for controlling a line pressure of a secondary cylinder, a shift control valve for controlling a primary pressure of a primary cylinder. The shift control valve includes a pilot valve for generating a pilot pressure according to a solenoid current, a spool with a step and a valve body. The pilot pressure is applied to one end of the spool and the primary pressure feedbacked and a spring force are applied to the other end so as to control the primary pressure on the balance of the spool in the valve body. The step ratio of the spool is designed so as to be 1.11 to 1.5 and further the shift control valve is constituted such that the pilot pressure becomes near zero when the primary pressure is zero.