| 摘要 |
Rotational control apparatus in the preferred forms of fan clutches (A) are shown including an eddy current drive (224). Specifically, the eddy current drive (224) includes a plurality of permanent magnets (226) mounted circumferentially spaced and with alternating polarity by a holder (228) to a radially extending surface (232) of a housing (62) rotatably mounted by a bearing (58) to the hub portion (24) of a friction disc (28). A magnetically conductive ring (242) is mounted on the opposite axial side of the friction disc (28) than the surface (34) engaged by a friction ring (86, 252) which is rotatably fixed but axially displaceable relative to the housing (62). In the embodiments shown, the friction ring (86, 252) is biased in a disengaged condition from the friction disc (28) by springs (138, 256) and is moved to an engaged condition by a fluid actuated piston (80). In one of the preferred forms, the friction ring (252) includes peripheral gear teeth (256) in slideable gearing relation with gear teeth (250) formed in the housing (62) and is formed of fiber brake material to act as a dampener between the friction disc (28) and the housing (62) to absorb torsional vibration. Thus, the housing (62) and the fan blades mounted thereto are driven with the friction disc (28) in its engaged condition and are driven at a rotational speed less than the speed of the friction disc (28) in its disengaged condition by the eddy current drive (224) and without separate controls for the eddy current drive (224).
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