To prevent irregularities from being generated on the surface of an annular rotor section due to difference in heat capacities by arranging a plurality of second cooling ribs at positions different from the positions of other second cooling ribs in the radial direction of a disk rotor in vent holes at uniform intervals in the peripheral direction of the disk rotor.
Second cooling ribs 3 are arranged at prescribed positions in the peripheral direction in each of vent holes 6. Some among them are arranged on the outer peripheral side as outer peripheral side second cooling ribs 3B, and the others are arranged on the inner peripheral side as inner peripheral side cooling ribs 3A. The outer peripheral side cooling ribs 3B are arranged at uniform intervals in the peripheral direction of a disk rotor. Since combinations of the first cooling rib 2, vent hole 6 and second cooing rib 3 continue at uniform intervals, the heat capacity is made uniform at any portion, and irregularities can be suppressed from generating on the surface of an annular rotor section. Since mass becomes heterogeneous in the peripheral direction on the outer peripheral side, and the squeak of a brake can be negated.
TAKANO ATSUSHI
OKADA HIROKI
