Patent ID: 6756870
Filing Date: 2004-06-29
Classification: H01F,H02K

Abstract:
An eddy current retarder, comprising a rotary shaft, a brake drum coupled to the rotary shaft, and stationary magnet unit disposed on the inside of the brake drum in the radial direction, wherein the stationary magnet unit comprises:an annular base portion; a plurality of iron core portions extending outward in the radial direction from the outer peripheral edge of the base portion and spaced at intervals in the circumferential direction; a plurality of coils wound on the outer peripheral surfaces of respective pairs of the plurality of iron core portions; magnetic pole pieces arranged at the ends of the iron core portions so as to be opposed to the inner peripheral surface of the brake drum; the iron core portions and the coils forming a plurality of electromagnets; and at least one permanent magnet buried in the iron core portion of each of said electromagnets, with the magnetic pole surfaces being directed in the radial direction; wherein said eddy current retarder produces a braking force in the brake drum only when an electric current is supplied to the coils to cause an eddy current to be generated by a magnetic field due to the electromagnets and the corresponding permanent magnets.