Brake system

Abstract

When an electrical fluid pressure generator fails and a wheel cylinder is operated by brake fluid pressure generated by a master cylinder, if a first fluid pressure system leading to a rear fluid chamber of the electrical fluid pressure generator fails and is opened to the atmosphere, braking is performed by brake fluid pressure of a second fluid pressure system transmitted from the master cylinder through a front fluid chamber of the electrical fluid pressure generator to a wheel cylinder. At this time, a front supply port, which communicates through a front second cup seal facing rearward with the rear fluid chamber opened to the atmosphere due to the failure, does not communicate with the master cylinder but with a reservoir. Therefore, it is possible to prevent leakage of the brake fluid pressure generated by the master cylinder through the front supply port, the front second cup seal and the rear fluid chamber, thereby ensuring braking by the second fluid pressure system leading to the front fluid chamber of the electrical fluid pressure generator.

1 . A brake system comprising:
 a master cylinder for generating brake fluid pressure based on braking operation of a driver;   an electrical fluid pressure generator communicating with the master cylinder, and having a rear fluid chamber and a front fluid chamber generating brake fluid pressure by an electrically controllable actuator; and   a plurality of wheel cylinders communicating with the rear fluid chamber and the front fluid chamber, respectively, and generating a braking force for braking wheels so that when the electrical fluid pressure generator fails, the wheel cylinders are operated by the brake fluid pressure generated by the master cylinder;   the electrical fluid pressure generator including:   a rear piston and a front piston which are advanced by the actuator to generate brake fluid pressure in the rear fluid chamber and the front fluid chamber, respectively;   a rear inlet port and a rear outlet port which are formed in the rear fluid chamber and connected to the master cylinder and the wheel cylinder, respectively;   a front inlet port and a front outlet port which are formed in the front fluid chamber and connected to the master cylinder and the wheel cylinder, respectively;   a rear first cup seal arranged at a front end of the rear piston so as to face forward;   a rear second cup seal arranged at a rear end of the rear piston so as to face forward;   a front first cup seal arranged at a front end of the front piston so as to face forward;   a front second cup seal arranged at a rear end of the front piston so as to face rearward; and   a rear supply port formed adjacent to and in the rear of the rear inlet port, and a front supply port formed adjacent to and in the rear of the front inlet port, the rear and front supply ports being connected to a reservoir.   
   
   
       2 . The brake system according to  claim 1 , further comprising an anti-lock braking system (“ABS”) provided between the electrical fluid pressure generator and the wheel cylinder, the ABS decreasing, maintaining and increasing brake fluid pressure transmitted to the wheel cylinder in order to suppress locking of a wheel upon braking. 
   
   
       3 . The brake system according to  claim 2 , further comprising a shutoff valve provided between the master cylinder and the electrical fluid pressure generator, the shutoff valve being closed at least during operation of the ABS. 
   
   
       4 . A brake system comprising:
 a master cylinder for generating brake fluid pressure based on braking operation of a driver;   an electrical fluid pressure generator communicating with the master cylinder, and having a rear fluid chamber and a front fluid chamber generating brake fluid pressure by an electrically controllable actuator; and   a plurality of wheel cylinders communicating with the rear fluid chamber and the front fluid chamber, respectively, and generating a braking force for braking wheels so that when the electrical fluid pressure generator fails, the wheel cylinders are operated by the brake fluid pressure generated by the master cylinder;   the electrical fluid pressure generator including:   a rear piston and a front piston which are advanced by the actuator to generate brake fluid pressure in the rear fluid chamber and the front fluid chamber, respectively;   a rear inlet port and a rear outlet port which are formed in the rear fluid chamber and connected to the master cylinder and the wheel cylinder, respectively;   a rear supply port formed adjacent to and in the rear of the rear inlet port and connected to the master cylinder;   a front inlet port and a front outlet port which are formed in the front fluid chamber and connected to the master cylinder and the wheel cylinder, respectively;   a front supply port formed adjacent to and in the rear of the front inlet port and connected to the master cylinder;   a rear first cup seal arranged at a front end of the rear piston so as to face forward;   a rear second cup seal arranged at a rear end of the rear piston so as to face forward;   a front first cup seal arranged at a front end of the front piston so as to face forward;   a front second cup seal arranged at a rear end of the front piston so as to face rearward; and   a front third cup seal arranged adjacent to and in front of the front second cup seal of the front piston so as to face forward.   
   
   
       5 . The brake system according to  claim 4 , further comprising an anti-lock braking system (“ABS”) provided between the electrical fluid pressure generator and the wheel cylinder, the ABS decreasing, maintaining and increasing brake fluid pressure transmitted to the wheel cylinder in order to suppress locking of a wheel upon braking. 
   
   
       6 . The brake system according to  claim 5 , further comprising a shutoff valve provided between the master cylinder and the electrical fluid pressure generator, the shutoff valve being closed at least during operation of the ABS. 
   
   
       7 . A brake system comprising:
 a master cylinder for generating brake fluid pressure based on braking operation of a driver;   an electrical fluid pressure generator communicating with the master cylinder, and having a rear fluid chamber and a front fluid chamber generating brake fluid pressure by an electrically controllable actuator; and   a plurality of wheel cylinders communicating with the rear fluid chamber and the front fluid chamber, respectively, and generating a braking force for braking wheels so that when the electrical fluid pressure generator fails, the wheel cylinders are operated by the brake fluid pressure generated by the master cylinder;   the electrical fluid pressure generator including:   a rear piston and a front piston which are advanced by the actuator to generate brake fluid pressure in the rear fluid chamber and the front fluid chamber, respectively;   a rear inlet port and a rear outlet port which are formed in the rear fluid chamber and connected to the master cylinder and the wheel cylinder, respectively;   a front inlet port and a front outlet port which are formed in the front fluid chamber and connected to the master cylinder and the wheel cylinder, respectively;   a rear first cup seal arranged at a front end of the rear piston so as to face forward;   a rear second cup seal arranged at a rear end of the rear piston so as to face forward;   a front first cup seal arranged at a front end of the front piston so as to face forward;   a front second cup seal arranged at a rear end of the front piston so as to face rearward; and   a means for preventing leakage of the brake fluid of the front fluid chamber through the rear fluid chamber.   
   
   
       8 . The brake system according to  claim 7 , wherein the means for preventing leakage of the brake fluid of the front fluid chamber through the rear fluid chamber comprises a rear supply port formed adjacent to and in the rear of the rear inlet port, and a front supply port formed adjacent to and in the rear of the front inlet port, the rear and front supply ports being connected to a reservoir. 
   
   
       9 . The brake system according to  claim 7 , wherein the means for preventing leakage of the brake fluid of the front fluid chamber through the rear fluid chamber comprises a front third cup seal arranged adjacent to and in front of the front second cup seal of the front piston so as to face forward. 
   
   
       10 . The brake system according to  claim 7 , further comprising an anti-lock braking system (“ABS”) provided between the electrical fluid pressure generator and the wheel cylinder, the ABS decreasing, maintaining and increasing brake fluid pressure transmitted to the wheel cylinder in order to suppress locking of a wheel upon braking. 
   
   
       11 . The brake system according to  claim 10 , further comprising a shutoff valve provided between the master cylinder and the electrical fluid pressure generator, the shutoff valve being closed at least during operation of the ABS.