Hydraulic control system for automatic transmissions to improve shift quality

A hydraulic control system for automatic transmissions, comprising:

• a pressure regulating means for regulating hydraulic pressure produced when oil is pumped in an oil pump;
• a manual and automatic shift control means for forming a shift mode;
• a hydraulic pressure control means for regulating shift quality and responsiveness for smoothly forming shift modes during shifting;
• a damper clutch control means for operating a damper clutch of a torque converter;
• and
• a hydraulic pressure distribution means for supplying and distributing an appropriate amount of hydraulic pressure to a first, second, third, fourth, and fifth friction members, which operate as input and reaction members in each shift stage, the hydraulic pressure distribution means comprising:
• a 1-2 shift valve, controlled by the second speed pressure of a shift control valve of the manual and automatic shift control means, the 1-2 shift valve supplying hydraulic pressure, supplied from a first pressure control valve, to a control switch valve and a 2-3/4-3 shift valve;
• the control switch valve, having means for regulating the timing to which hydraulic pressure is supplied to the third friction member and a timing control line to control the second friction member, operating as a reaction member in second and fourth speeds, and when 4-2 downshifting, changes operational pressure of an operational side chamber of the second friction member to the second speed pressure, and uses operational pressure of the third friction member as control pressure of the first pressure control valve to control release pressure;
• a fail-safe valve, controlled by hydraulic pressure supplied to the first, second, third, and fourth friction members and which controls the hydraulic pressure supplied to the operational side chamber of the second friction member;
• a high-low pressure valve, controlled by receiving control pressure from a timing control line by the ON/OFF control of solenoid valves, and after third and fourth speed shifting is completed, supplies third speed pressure to a pressure regulator valve to allow change of line pressure;
• the 2-3/4-3 shift valve, controlled by third and fourth speed pressure in third and fourth speeds and which selectively supplies hydraulic pressure received from the 1-2 shift valve and from the 3-4 shift valve in a reverse R shift range to the fourth friction member and a release side chamber of the second friction member;
• and
• a 3-4 shift valve, controlled by fourth speed pressure of the shift control valve, which in first, second, and third speeds, supplies hydraulic pressure supplied from a second pressure control valve to the first friction member, and in the fourth speed, is controlled by the supply of fourth speed pressure to the 2-3/4-3 shift valve such that the hydraulic pressure supplied to the release side chamber of the second friction member and to the fourth friction member is interrupted and, at the same time, release pressure is able to be controlled.