Importance

Loading Importance Indicators...

Abstract

A hydraulic control apparatus for controlling a vehicular automatic transmission including hydraulically operated frictional coupling devices which are selectively engaged and released to selectively establish gear positions having respective different speed ratios, and linear solenoid valves operable to regulate fluid pressures of the respective frictional coupling devices, each linear solenoid valve 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 the 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, each linear solenoid valve in the pressure-regulating state being operable to regulate a fluid pressure of the corresponding frictional coupling device according to the electromagnetic force, the hydraulic control apparatus including a pressure-regulation switching portion operable to effect a determination on the basis of a present state of a vehicle provided with the automatic transmission, as to whether each non-used linear solenoid valve, which is one of the linear solenoid valves that is not presently used to engage the corresponding frictional coupling device, should be placed in the pressure-regulating state or in the non-pressure-regulating state, the pressure-regulation switching portion placing each non-used linear solenoid valve selectively in the pressure-regulating or non-pressure-regulating states, according to a result of the determination.

Loading the Abstract Image...

First Claim