Patent ID: 8376473

Claim:
A vehicular brake system comprising: a cylinder; an input piston supported freely movably in an axis direction in the cylinder; an operation part connected to the input piston; a pressurizing piston disposed coaxially with the input piston and supported freely movably in an axis direction in the cylinder, wherein the pressurizing piston is configured to be pushed by the input piston when a malfunction occurs; a control-hydraulic-pressure setting unit that sets a control hydraulic pressure that corresponds to an operation force applied to the input piston through the operation part; a hydraulic-pressure supply device that generates braking hydraulic pressure by supplying the control hydraulic pressure set by the control-hydraulic-pressure setting unit to the pressurizing piston; a pressure regulating device configured to regulate a braking hydraulic pressure for each of wheels individually, wherein the braking hydraulic pressure is generated by the hydraulic-pressure supply device; a hydraulic pressure source connected to the hydraulic-pressure supply device and the pressure regulating device; and an operation-force absorbing mechanism that absorbs the operation force applied to the input piston through the operation part, wherein the hydraulic-pressure supply device supplies the control hydraulic pressure to a first pressure chamber disposed on one side of the input piston with respect to a moving direction thereof, or to a second pressure chamber disposed on the other side of the input piston, the hydraulic pressure source is configured to supply hydraulic fluid to the first pressure chamber or the second pressure chamber and to the pressure regulating device, and part of a supply line from the hydraulic pressure source to the first pressure chamber or the second pressure chamber and part of a supply line from the hydraulic pressure source to the pressure regulating device are common, and the operation-force absorbing mechanism includes a communication passage provided to the input piston that is configured to supply and discharge hydraulic fluid between the first pressure chamber and the second pressure chamber when open, so that a pushing force of the input piston is not transmitted to the pressurizing piston when the communication passage is open.