Dual hydraulic brake system

摘要

A proportioning valve is interposed between a master cylinder and rear wheel cylinders and includes a housing within which are accommodated a piston with a valve head, an opposed valve seat thereby and a spring urging the piston to thereby remove the valve head from the valve seat. The valve head and the valve seat cooperate to open and close the fluid circuit between the master cylinder and the rear wheel cylinder to reduce the hydraulic pressure when the hydraulic pressure delivered from the master cylinder exceeds a set value. In order to supply hydraulic pressure from the master cylinder to the rear wheel cylinders when fluid leakage or the like occurs at the front wheel side, a sleeve enclosing the spring in the housing is brought into engagement with the piston to prevent engagement of the valve head and the valve seat.