Hydraulic control system of an automatic transmission used in a vehicle

A hydraulic control system of an automatic transmission used in a vehicle, comprising:

• a torque converter for transferring an engine power to an input shaft of the transmission;
• an oil pump for pumping oil by means of the engine power;
• a pressure regulation means for regulating a line pressure produced by said oil pump according to a running condition of the vehicle;
• a damper clutch working control means for changing a direction of the pressure delivered to said torque converter in order to increase a power transfer rate of said torque converter;
• a manual valve operatively linked with a shift lever for performing a port change to supply the transmission with a hydraulic pressure suitable to each shifting mode;
• an N-D control valve for supplying a torque pressure and a drive pressure to a first friction element to reduce shifting shocks during range changing from a neutral mode to a running mode;
• a torque control regulator valve for converting the drive pressure to a torque control valve according to a duty control;
• a control switch valve for alternately supplying the torque pressure of said torque control regulator valve to a first and a second torque pressure line according to an on/off operation of a solenoid valve;
• a first to second shift valve, a second to third shift valve, a third to fourth shift valve and a third to second shift valve for making a port change with a control port receiving/discharging a hydraulic pressure according to the on/off operation of the solenoid valve so as to selectively supply the torque pressure of the first and the second torque pressure line and the drive pressure of a manual valve to the friction element;
• and
• a low/reverse clutch valve, a third clutch valve, and a second to fourth brake valve for receiving or supplying the torque pressure or drive pressure from or to the shift valves.