Hydraulic pressure assisting device provided for a hydraulic brake apparatus for a vehicle

A hydraulic pressure assisting device for a hydraulic brake apparatus of a vehicle, comprising:

• a power piston slidably accommodated in a housing and forming a power chamber in the housing;
• an input member movable relative to the power piston in response to operation of a brake operating member;
• an auxiliary hydraulic pressure source for increasing hydraulic pressure of brake fluid in a reservoir to a predetermined pressure level and for outputting power hydraulic pressure;
• a pressure modulating device connected to the auxiliary hydraulic pressure source and the reservoir for modulating the power hydraulic pressure outputted from the auxiliary hydraulic pressure source to a predetermined pressure level corresponding to movement of the input member relative to the power piston and for supplying the modulated power hydraulic pressure to the power chamber;
• and
• a cylindrical elastic member having two opening end portions, one opening end portion of being connected to the power piston and the other opening end portion being connected to the housing, with a space defined in the cylindrical elastic member communicating with the pressure modulating device and the reservoir.