PURPOSE: To provide a drum brake being easy in air bleeding by actuating a control piston and a shut-off valve to reflect the accompanied rotating force of a brake shoe on braking force.
CONSTITUTION: While master cylinder hydraulic pressure is low, and the accompanied rotating force of a leading shoe 22 and a trailing shoe 24 acting on a control piston 56 is little, the control piston 56 takes an advance position, and the master cylinder hydraulic pressure is transmitted to a wheel cylinder. When the accompanied rotating force of the shoes 22, 24 enlarge, and the control piston 56 thereby moves back, a shut-off valve 122 closes to cut off the transmission of the hydraulic pressure to the wheel cylinder. When the coefficient of friction of a lining enlarges, the accomanied rotating force of the shoes 22, 24 enlarges acceleratedly, but in such case, the shut-off valve 122 closes in the state of the low wheel cylinder hydraulic pressure, and the occurrence of excessive braking force can be avoided for controlling the dispersion of braking force to be a small quantity.
NAKAMURA AKIRA
OHORI HARUMI
TOBA FUJIO
SAKAI AKIRA
