Hydraulic control means for an automatic transmission

Claim 1

A hydraulic control means for an automatic transmission comprising: an input shaft, an output shaft, a planetary gear mechanism installed between said input shaft and said output shaft, plural friction elements including a friction clutch or a friction brake, wherein a gear ratio of plural stages in a forward-running and a gear ratio in a reverse running are obtained by engaging or releasing suitably said friction elements with hydraulic (oil) pressure, a source of oil pressure, a pressure regulator valve means controlling the pressure generated by said source, a governor valve means which generates governor pressure expressed according to driving speed, a throttle valve means which generates throttle pressure expressed according to driving load, and a shift valve means which changes over low speed and high speed by providing said throttle pressure and governor pressure, wherein said shift valve means comprises: a primary valve means which acts between a position in low gear ratio and the position in high gear ratio, a secondary valve means which acts between the position disposed to said primary valve means in low gear ratio and the position disposed to said primary valve means in high gear, a spring means giving power to said secondary valve means in the direction to said primary valve means, a primary hydraulic pressure chamber, wherein said governor pressure pressing said primary valve means to the position of high gear ratio is input, a tertiary hydraulic pressure chamber, wherein said governor pressure is input when said valve means is in low gear ratio, wherein said primary valve means is pressed to the direction of low gear ratio, and said governor pressure is intercepted when said primary valve means is in high gear ratio, a fifth hydraulic pressure chamber, wherein said hydraulic pressure is input when said valve means is in low gear ratio, wherein said primary valve means is pressed to the direction of low gear ratio, and said hydraulic pressure is intercepted when said primary valve means is in high gear ratio, and said hydraulic pressure is connected to an exhaust port; and a secondary hydraulic pressure chamber, wherein said throttle pressure is input, said primary valve means is pressed to the position of low gear ratio, and said secondary valve means is pressed to the direction against spring means; and a fourth hydraulic pressure chamber, wherein said hydraulic pressure is input when said primary valve means is in low gear ratio, said secondary valve means is pressed to the direction against said spring means and said hydraulic pressure is connected to an exhaust port when said secondary valve means is in high gear ratio.