| 摘要 |
An electromagnetic servo unit (100) including a first shaft (12), a second shaft (7), an elastic member (21) interposed between the first and second shafts (12, 7) to interconnect them in a torque transmittable manner, a torque detection mechanism (5) for detecting input torque acting on either of the first and second shafts (12, 7), an electric motor (2) for developing assistant torque in accordance with a detection signal from the torque detection mechanism (5), and a torque transmission mechanism (3, 4) for transmitting the assistant torque to the second shaft (7). The servo unit (100) further comprises a direct coupling mechanism (39, 40, 23, 22, 12b-2) for directly coupling the first shaft (12) and the second shaft (7) to each other under a predetermined condition, to thereby effect direct torque transmission therebetween. The servo unit (100) is employed in a power steering system of a vehicle, and the direct coupling mechanism (39, 40, 23, 22, 12b-2) is adapted to directly couple the first and second shafts (12, 7) to each other in relation to the travelling speed of the vehicle. The direct coupling mechanism (39, 30, 23, 22, 12b-2) is adapted to directly couple the first and second shafts (12, 7) to each other when the vehicle is put in a high-speed travelling state.
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