Hydraulic control system of 7-speed automatic transmission for vehicles

A hydraulic control system of a seven-speed automatic transmission for a vehicle, comprising:

• a line pressure control portion for controlling hydraulic pressure supplied from a hydraulic pump;
• a launch control portion for multiplying torque of a torque converter and controlling engagement and release of a damper clutch;
• a pressure reduction control portion for reducing a line pressure supplied from the line pressure control portion by a first reducing valve so as to supply a control pressure to pressure switches and first and second on/off solenoid valves used for each frictional element, and supplying a control pressure of a second reducing valve to proportional control solenoid valves as their control pressure;
• a manual shift control portion for controlling a hydraulic line in accordance with a manual shifting;
• a first clutch control portion for controlling a forward range pressure according to a control of a first proportional control solenoid valve so as to supply the forward range pressure to a first clutch at first, second, third, fourth, and fifth speeds and a low L range;
• a second clutch control portion for supplying the forward range pressure to a second clutch according to a control of a second proportional control solenoid valve at the third speed;
• a third clutch control portion for controlling the line pressure according to a control of a third proportional control solenoid valve so as to supply the line pressure to a third clutch at the fourth speed and a sixth speed;
• a fourth clutch and first brake control portion for controlling the forward range pressure according to a control of a fourth proportional control solenoid valve so as to supply the forward range pressure to a fourth clutch at the fifth speed, the sixth speed, and a seventh speed, and for supplying a control pressure of the fourth proportional control solenoid valve to a first brake at the low L range;
• and
• a second brake control portion for supplying the forward range pressure to a second brake according to a fifth proportional control solenoid valve at the second and seventh speeds.