Hydraulic control system for automatic transmission of multiple clutch type

A hydraulic control system for an automatic transmission of multiple clutch type having at least two power transmission shafts each of which transmits power from a driving source to driving wheels, as well as clutches each of which connects or disconnects the corresponding power transmission shaft on the power transmission path, and being further furnished on said power transmission shafts with a plurality of speed change gears, as well as changeover elements which serve to select any of the plurality of speed change gears and to render the selected gear capable of transmitting the power, wherein said changeover elements are selectively brought into engagement by operating hydraulic actuators, thereby to attain a plurality of gear shift stages, comprising:

• a solenoid valve;
• a shift valve including a spool valvule whose position is switched-over by said solenoid valve so as to invert supply and cutoff of working oil for said hydraulic actuator, and thereby selectively cause at least one of said changeover elements to select one of the plurality of speed change gears and render the selected gear capable of transmitting the power;
• said shift valve being formed with a clutch-oil-pressure supply port which is supplied with a clutch oil pressure of said clutch, so as to hold the switchover position of said spool valvule by said clutch oil pressure even when said solenoid valve has failed.