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