Line pressure control apparatus and method for vehicle

A line pressure control method for a vehicle, comprising:

• providing a mechanical oil pump pumping actuated by a drive through a traveling drive source;
• and
• providing an electrically driven oil pump disposed in parallel to the mechanical oil pump on a hydraulic pressure circuit and pumping actuated by the drive through an electrically operated motor;
• and
• outputting a line pressure command through a line controller to produce a line pressure which is a basic pressure of a controlled hydraulic pressure for a predetermined hydraulic pressure engagement frictional element arranged in a drive train, with either or each of the mechanical oil pump and the electrically driven oil pump as a hydraulic pressure source,
• wherein the line pressure control method further comprises outputting the line pressure command through the line pressure controller to reduce an indicated pressure toward a required indicated pressure by which a required pressure can be secured and which is lower than an initial stage indicated pressure from the initial stage indicated pressure preset to be higher than the required pressure, while a state of each of the electrically driven oil pump and the mechanical oil pump enters a first region in which only the electrically driven oil pump is the hydraulic pressure source and a discharge pressure of the mechanical oil pump can be confirmed, and outputting the line pressure command through the line pressure controller to hold the indicated pressure at a time point at which the first region is ended, while the state of each of the electrically driven oil pump and the mechanical oil pump enters a second region in which both of the electrically driven oil pump and the mechanical oil pump are the hydraulic pressure sources, when the hydraulic pressure source is transitioned from the electrically driven oil pump to the mechanical oil pump.