Patent ID: 7070025

Claim:
A drum brake apparatus, comprising: a drum; first and second brake shoes provided in the drum; a wheel cylinder that presses the first and the second brake shoes; and an automatic clearance adjusting device that automatically adjusts positions of the first and second brake shoes in accordance with wear amounts of the first and second brake shoes, the automatic clearance adjusting device including; an adjuster gear rotatably supported at the first brake shoe, the adjuster gear having a ratchet teeth formed on an outer surface thereof; an adjuster restricting lever including; a tip end portion having a ratchet pawl which is capable of engaging with the ratchet teeth of the adjuster gear; an intermediate portion having a controlling force receiving portion which receives a controlling force of the wheel cylinder; and a proximal end portion rotatably supported on the first brake shoe at a position outer than the controlling force receiving portion; a strut having a first end abutting against the adjuster restricting lever and a second end abutting the second brake shoe in order to maintain a distance between the first and second brake shoes; a lever restricting spring biasing the adjuster restricting lever to a strut side in order to release the engagement between the ratchet teeth and the ratchet pawl of the adjuster restricting lever; and an adjuster spring biasing the adjuster gear in a predetermined rotational direction, wherein the outer surface of the adjuster gear is formed in such a manner that a shortest distance defined between a rotation center of the adjuster gear and the cam surface where the ratchet pawl abuts is increased as the adjuster gear rotates in a biased direction, and the wheel cylinder rotates the adjuster restricting lever against a biasing force of the lever restricting spring so as to engage the ratchet teeth with the ratchet pawl when the controlling force of the wheel cylinder becomes larger than a predetermined force.