Brake system

Abstract

In a BBW type brake system, first ports of fluid pressure generators are closed to generate brake fluid pressure in respective wheel cylinders before a master cylinder generates brake fluid pressure, by initiating the operation of the fluid pressure generators based on the output of a pedal stroke sensor. Therefore, the brake fluid pressure generated by the master cylinder is prevented from being transmitted to wheel cylinders, even when a shutoff valve, which closes during normal operation of a conventional BBW type brake system, is not provided, thereby providing reliable operation of the BBW type brake system. Thus, since the master cylinder and the fluid pressure generators are kept in communication at a non-braking time, a reservoir of the master cylinder can be also used as the reservoir of the fluid pressure generators without providing the system with an atmosphere valve, which is conventionally required.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fluid pressure system diagram of a brake system for a vehicle according to the present invention during normal operation of the brake system.

FIG. 2 is a fluid pressure system diagram corresponding to FIG. 1 during abnormal operation of the brake system.

FIG. 3 is an enlarged view of a master cylinder and a fluid pressure generator.

FIG. 4A is an explanatory view of the configuration of the brake system of FIG. 1 during a period of non-operation.

FIG. 4B is an explanatory view of the configuration of the brake system of FIG. 1 during an initial period of operation.

FIG. 4C is an explanatory view of the configuration of the brake system of FIG. 1 during a period of ABS operation.

FIG. 5 is a prior art fluid pressure system diagram of a brake system for a vehicle during normal operation.

FIG. 6 is a prior art fluid pressure system diagram corresponding to the brake system of FIG. 5 during abnormal operation.

Claims

1. A brake system, comprising: a master cylinder which generates brake fluid pressure based on a brake operation of a driver;a reservoir which is connected to the master cylinder;a wheel cylinder which brakes a wheel;a brake operation detecting device which detects the brake operation of the driver; anda fluid pressure generator, the fluid pressure generator comprising: a generator cylinder;a first port which communicates with the master cylinder;a second port which communicates with the wheel cylinder; andan electrically operated piston disposed in the generator cylinder which generates brake fluid pressure;wherein an operation of the fluid pressure generator is started based on a brake operation detection signal of the brake operation detecting device.

2. The brake system according to claim 1, further comprising a shutoff valve between the master cylinder and the fluid pressure generator, wherein the shutoff valve is closed when the piston of the fluid pressure generator retreats to reduce the brake fluid pressure of the wheel cylinder.

3. The brake system according to claim 1, wherein the piston of the fluid pressure generator closes the first port before the piston of the master cylinder closes a refilling port connected to the reservoir.

4. The brake system according to claim 2, wherein the piston of the fluid pressure generator closes the first port before the piston of the master cylinder closes a refilling port connected to the reservoir.

5. The brake system according to claim 1, wherein the first port communicates with the master cylinder via a first communication passage, and a normally-open shutoff valve is disposed in the first communication passage, the shutoff valve provided in an open configuration during both normal and abnormal braking operations except during anti-lock braking operations.

6. A brake system, comprising: a master cylinder which generates brake fluid pressure based on a brake operation of a driver;a reservoir which is connected to the master cylinder;a wheel cylinder which brakes a wheel;a brake operation detecting device which detects the brake operation of the driver; anda fluid pressure generator, the fluid pressure generator comprising: a generator cylinder;a first port formed in the generator cylinder which communicates with the master cylinder;a second port formed in the generator cylinder which communicates with the wheel cylinder; anda piston disposed in the generator cylinder, the piston generating a brake fluid pressure;wherein operation of the fluid pressure generator is started based on a brake operation detection signal of the brake operation detecting device.

7. The brake system according to claim 6, wherein the generator cylinder further comprises a fluid chamber, the fluid chamber located between the piston and an end of the generator cylinder, and wherein the first port is disposed on the generator cylinder at a location spaced from the end of the generator cylinder, and the second port is disposed on the generator cylinder between the first port and the end of the generator cylinder.

8. The brake system according to claim 7, the brake system further comprising a shutoff valve between the master cylinder and the fluid pressure generator, and when no braking operation is provided, the shutoff valve is in an open position, and the piston is positioned at a first position within the generator cylinder adjacent to the first port such that both the first port and the second port communicate with the fluid chamber, andwhen a braking operation is detected, the shutoff valve remains in the open position, and the piston is positioned in an advanced position relative to the first position such that the first port is prevented from communicating with the fluid chamber and the second port communicates with the fluid chamber.

9. The braking system according to claim 8, wherein when an anti-lock braking operation is detected, the shutoff valve is in a closed position, and the piston is movable within the generator cylinder between the first position, the advanced position, and a retracted position, the retracted position located such that both the first port and the second port communicate with the fluid chamber, and such that a volume of the fluid chamber is increased relative to that of the first position.

10. The brake system according to claim 6, wherein the piston of the fluid pressure generator closes the first port before the piston of the master cylinder closes a refilling port connected to the reservoir.