Patent ID: 8069961

Claim:
A disk brake apparatus, comprising: a piston accommodated on a leading end opening side of a cylinder hole formed in a caliper body; a thrust conversion mechanism disposed on a bottom side of the cylinder hole; an adjuster which comprises an adjust nut and an adjust bolt and is interposed between the thrust conversion mechanism and the piston and a parking brake which pushes the piston from the thrust conversion mechanism through the adjuster, wherein the thrust conversion mechanism comprises: a fixed side cam plate mounted on a bottom wall of the cylinder hole; a cam shaft which penetrates through the cylinder hole so as to be rotatable with respect to the bottom wall of the cylinder hole and the fixed side cam plate and also to be movable in an axial direction of the cylinder hole; a drive side cam plate provided on the cylinder hole opening side of the cam shaft; ramp grooves formed at mutually opposed positions of the drive side cam plate and the fixed side cam plate, respectively and cam bearings accommodated into their associated ramp grooves, respectively, the adjuster comprises a thrust transmission plate provided on an end portion of the adjust nut or the adjust bolt at in the bottom side of the cylinder hole, the thrust transmission plate facing the drive side cam plate, a substantially cylinder housing accommodates the fixed side cam plate, the drive side cam plate, the thrust transmission plate, a cam spring which energizes the thrust transmission plate toward the drive side cam plate, engaging grooves, extending in the cylinder hole axial direction, are formed on the bottom side of the cylinder hole and a circumferential groove is formed to connect the engaging grooves at middle portions thereof in the cylinder hole axial direction, the housing comprises: at least one engaging rib which is entered into the circumferential groove and to be engaged with a corresponding one of the engaging grooves; and, at least one communication hole which is formed in the housing at the bottom side of the cylinder hole with respect to the engaging rib, the circumferential groove is formed to be deeper than the engaging grooves in a radial direction of the cylinder hole; and a liquid passage hole is formed on the caliper body to be connected to the corresponding one of the engaging grooves and the circumferential groove.