| 摘要 |
A drum brake (1) includes a first brake shoe (3), a second brake shoe (4) and disposed opposite the first brake shoe (3) within a brake drum, a backing plate (7) supporting the first and second brake shoes (3,4), a wheel cylinder (5) disposed between the first brake shoe (3) and the second brake shoe (4), the wheel cylinder (5) including a drive piston (12) for pressing the first and the second brake shoes (3,4) against an inner surface of the brake drum, a control piston (17) for supplying hydraulic pressure in response to a braking reaction force from the second brake shoe (4), an anchor portion (9) for receiving an anchor reaction force from the second brake shoe (4), a control lever (25) for distributing the anchor reaction force to the anchor portion (9) and to the control piston (17) when the anchor reaction force reaches a predetermined braking force magnification, the drive piston (12) has a base end in the pressure chamber (10) and a leading end facing the first end of the second brake shoe (4) and is movable to and from the second brake shoe (4) by the hydraulic pressure supplied to the pressure chamber (10), and a control chamber (16) is pressurized by a hydraulic pressure from a master cylinder, wherein the control piston (17) is aligned with the drive piston (12), and the control piston (17) cuts off a supply of the hydraulic pressure to the pressure chamber (10) when the control piston (17) is displaced into the control chamber (16) by the anchor reaction force. <IMAGE> |
