HYDRAULIC CONTROLLER FOR AUTOMATIC TRANSMISSION

摘要

PROBLEM TO BE SOLVED: To accurately control the oil pressure in a friction engaging device during its transient speed changing in an automatic transmission and prevent damage to a control solenoid valve. SOLUTION: A hydraulic controller for an automatic transmission controls the oil pressures in friction engaging devices C2 and B1 by pressure regulating valves 24 and 45 respectively which relieve oil pressure in accordance with signal pressure inputted thereto. The hydraulic controller is provided with first solenoid valves 31 and 53 for producing signal pressure which varies in accordance with their electric signals, and second solenoid valves 28 and 50 with a coil of a larger resistance value than that of the first solenoid valves 28 and 50 for pressing signal pressure on the respective valves 24 and 45 in the same direction as the signal pressure from the first solenoid valves through electrification thereof.