Torque ratio control device for a V-belt type continuously variable transmission for vehicles

Claim 1

A torque ratio control device in a V-belt type continuously variable transmission for vehicles having input and output pulleys mounted respectively on an input and an output shaft and having variable effective diameters wherein the torque ratio between the input and output shafts is continuously controlled by adjusting said effective diameter of each pulley by hydraulic servo means, comprising: an electric control circuit which inputs accelerator and vehicle running condition signals such as the input pulley revolution speed, and outputs signals controlling said effective diameter of the input side pulley, and a torque ratio control device comprising: a primary hydraulic servo means arranged on said input side pulley, a second output side hydraulic servo arranged on said output side pulley, a spool, at least one spring means giving power to said spool in one direction, a primary hydraulic passage connecting to the one edge of said spool, a secondary hydraulic passage connecting to the other edge of said spool, a tertiary hydraulic passage connecting a hydraulic pressure source with said spool, an exhaust port discharging a hydraulic pressure of said primary hydraulic servo means, a primary orifice means arranged in said primary hydraulic passage, a primary solenoid valve means arranged in the spool side of said primary hydraulic passage through said primary orifice means and controlled by said electric control circuit, and a secondary solenoid valve means arranged in the spool side of a secondary hydraulic passage through a secondary orifice means and controlled by said electric control circuit, wherein the torque ratio pressure control device discharges a hydraulic pressure from said secondary hydraulic passage when said spool is given power in one direction by said spring means, wherein said spool is controlled in a primary position connecting said primary hydraulic servo with said tertiary hydraulic passage in connection with hydraulic pressure, a secondary position connecting said primary hydraulic servo with an exhaust port, and a tertiary position closing the connection between the primary hydraulic servo and the tertiery hydraulic passage and closing the connection between the primary hydraulic servo and the exhaust port, said primary and secondary hydraulic passages controlled by said two solenoid valve means, said secondary hydraulic servo means always being connected to a hydraulic pressure source and controlling the torque ratio continuously by adjusting the hydraulic pressure supplied to said primary hydraulic servo means, depending on vehicle running conditions.