Eddy current retarder

An eddy current reduction gear comprising:

• a rotor (3) fixed to one end of a rotating shaft (1);
• a support ring (7) coaxial with said rotor (3) and axially slidably mounted on a fixed main body (5, 6, 11, 21) with a predetermined gap being secured between said rotor (3) and said support ring;
• a plurality of permanent magnets (10) mounted on an external circumferential surface of said support ring (7) in such a manner that magnetic poles of the magnets are aligned with a direction parallel to the axis of said support ring (7) and the polarities of any adjacent permanent magnets of said plurality of permanent magnets (10) become opposite to each other;
• and
• a shifting mechanism (13, 14, 16, 18, 19, 20) for axially shifting said support ring (7) between a first position where pole surfaces of all of said permanent magnets (10) confront an internal circumferential surface of said rotor (3) and a second position where said pole surfaces of all of said permanent magnets (10) substantially deviate from said internal circumferential surface of said rotor (3);
• a fan (30) having axial blades (35) and radial blades (36) formed, respectively, radially inwardly and radially outwardly of a support member (31) connecting a boss portion (22) of said rotor (3) and a cylindrical portion (32) of said rotor;
• stator blades (37) formed close to said axial blades (35) on a bearing member (4) supporting said rotating shaft (1) in such a manner as to extend along the circumference thereof;
• and
• cooling fins (28) radially disposed on an external circumferential surface of said bearing member (4).