A vehicle hydraulic brake apparatus includes a brake member, a master cylinder generating brake hydraulic pressure, and a master piston movable in response to operation of the brake member. A closed chamber is defined by the master piston and a power piston is disposed behind the master piston. A power chamber is defined by the power piston rearwardly of the power piston. An auxiliary hydraulic pressure source generates power hydraulic pressure and a pressure regulating device regulates the output power hydraulic pressure and feeds it to the power chamber. A reaction force member is disposed in a front end portion of the power piston and is exposed towards the closed chamber. A retaining device maintains the reaction force member exposed towards the closed chamber, with the rearward reaction force of the master piston being transmitted to a front end portion of the power piston while bypassing the reaction force member.

A hydraulic pressure brake device for a vehicle includes a first piston outputting brake pressure generated in a first pressure chamber and a second piston having a larger diameter than that of the first piston and provided rearward of the first piston and forming a second pressure chamber having a larger diameter than that of the first pressure chamber. The hydraulic pressure brake device further includes a valve device closing the second pressure chamber hydraulically when actuation of the first piston and the second piston is assisted by the assisting device and establishing hydraulic communication between the second pressure chamber and the reservoir when the assisting is not carried out. The first pressure chamber is connected with wheel cylinders provided on front wheels through a first hydraulic pressure system and the second pressure chamber is connected with wheel cylinders provided on rear wheels through a second hydraulic pressure system.

A Hydraulic pressure control apparatus, includes a hydraulic pressure source device operable according to a control amount, to generate an output pressure thereof on the basis of a fluid pressure corresponding to an operating force of a manually operable operating member, and on the basis of a control pressure controlled by a pressure control actuator according to a control amount. The control apparatus further includes an actuator control device including a final-control-value determining portion operable to determine a final value of the control amount, which is used to control the pressure control actuator. A final control value is determined on the basis of at least two provisional control values.

A brake fluid pressure generating device includes a master cylinder piston slidably disposed in a cylinder body, a pressure chamber and a power chamber formed in the cylinder body, a master cylinder that generates a master cylinder fluid pressure in response to operation of a brake pedal, a supplemental fluid generator that generates a power fluid pressure, a fluid regulator that regulates the power fluid pressure to a regulator fluid pressure in response to operation of the brake pedal, a pressure increase valve that controls communication between the supplemental fluid generator and the power chamber, and a pressure release valve that controls communication between the power chamber and a reservoir tank. A valve operating force generating member controls the pressure increase valve and the pressure release valve, a first repulsion force generating member is controlled in response to the regulator fluid pressure and a second repulsion force generating member is controlled in response to the master cylinder fluid pressure. This invention generates a larger magnitude of regulator pressure under the condition that the master cylinder is in a disabled condition.

A vehicle hydraulic brake apparatus includes a brake member, a master cylinder generating a brake hydraulic pressure by increasing the pressure of brake fluid in a reservoir, a master piston moved forward in response to operation of the brake member, a closed chamber defined behind the master piston, a power piston disposed behind the master piston, and a power chamber defined behind the power piston. An auxiliary hydraulic pressure source generates power hydraulic pressure and a pressure regulating device connects the auxiliary hydraulic pressure source with the reservoir. The power hydraulic pressure is regulated to a predetermined hydraulic pressure and is fed to the power chamber. A normally-open type valve connects the closed chamber and the power chamber, and is closable upon operation of the brake member. The closed chamber is connected to the reservoir via the normally-open type valve, the power chamber and the pressure regulating device.