| 摘要 |
An electrically power-assisted four-wheel steering system (100) for vehicles with front wheels (32a, 32b) and rear wheels (48a, 48b) comprises a front-wheel steering device (35) including a rack (2) for the front wheels which transversely extends and has an end portion (2b) thereof formed with a first toothed part (2a) meshing with a first pinion (1, 1a) operatively connected to a steering wheel (27), a rear-wheel steering device (40), a linkage mechanism (50) including a second pinion (14) which meshes with a second toothed part (13) formed over a predetermined region at one side of a transversely substantially central portion of the rack to operatively transmit a transverse displacement of the rack to the rear-wheel steering device, and an electric motor (5) for operatively providing auxiliary torque to the front-wheel steering device and to the rear-wheel steering device. The motor is disposed near the rack, at a transversely substantially central location different in position from the second pinion, and has a rotating output shaft (7) disposed at another end portion (2c) of the rack. The steering system further comprises a ball and screw mechanism (10) disposed between the output shaft of the motor and the aforesaid another end portion of the rack to transmit auxiliary torque produced by the motor to the rack.
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