Patent ID: 7300383

Claim:
A hydraulic control apparatus for controlling a vehicular automatic transmission including (a) a plurality of hydraulically operated frictional coupling devices which are selectively engaged and released to selectively establish a plurality of gear positions having respective different speed ratios, and (b) a plurality of linear solenoid valves operable to regulate fluid pressures of the respective frictional coupling devices, each of said linear solenoid valves including a spool and a solenoid, and being operable between a pressure-regulating state in which the spool is movable to a position of equilibrium of forces for regulating an output fluid pressure according to an electromagnetic force produced by said solenoid, and a non-pressure-regulating state in which the spool is held at a stroke end thereof at which no output fluid pressure is generated from the linear solenoid valve, said each linear solenoid valve placed in the pressure-regulating state being operable to regulate a fluid pressure of the corresponding frictional coupling device according to said electromagnetic force, said hydraulic control apparatus comprising: a pressure-regulation switching portion operable to effect a determination on the basis of a present state of a vehicle provided with said automatic transmission, as to whether each non-used linear solenoid valve, which is one of said plurality of linear solenoid valves that is not presently used to engage the corresponding hydraulically operated frictional coupling device, should be placed in said pressure-regulating state or in said non-pressure-regulating state, said pressure-regulation switching portion placing said each non-used linear solenoid valve selectively in one of said pressure-regulating and non-pressure-regulating states, according to a result of said determination.