Hydraulic control system for automatic transmission

A hydraulic control system for an automatic transmission including a fluid coupling type torque converter and a gear system with a number of friction elements to establish two or more speed ratios, said hydraulic control system comprising:

• a hydraulic pressure source;
• a line pressure control valve receiving pressure from said hydraulic pressure source to generate a regulated line pressure;
• a throttle valve for generating a throttle pressure varying commensurate with the intake throttle opening;
• a governor valve for generating a governor pressure varying commensurate with the vehicle speed;
• a manual selector valve for manual switching the operating range of the transmission;
• a plurality of shift valves operable for switching paths of pressure to a servo mechanism for said friction elements under the influence of antagonistically acting force of said throttle and governor pressures wherein the shift valve operative to establish the highest speed ratio among said plurality of shift valves further comprises a first piston receiving the throttle pressure at the upper end thereof, a valve body receiving the governor pressure at the lower end thereof and a compression spring provided between said first piston and valve body;
• and
• a detent regulator valve for generating a detent pressure to be drawn to said shift valves at the time of kickdown;
• said detent pressure being drawn between the lower end of said first piston and the upper end of said valve body of the shift valve operative to establish the highest speed ratio in a manner to offset said throttle pressure and in a contrapositive relation with said governor pressure.