| 摘要 |
<p>PURPOSE:To use a motor driven power assisting mechanism in addition to a mechanism capable of changing the transmission ratio of the steering force by driving and controlling these mechanisms to required conditions according to the driving conditions of a vehicle. CONSTITUTION:A variable transmission reatio mechanism 10 which is driven with an electric motor 20 and changes the steered wheel angle relative to the steering wheel angle according to the vehicle speed is added to a steering gear mechanism 5. A power assist mechanism 30 is employed to transmit the torque of the electric motor to part of the steering gear mechanism. Controls 26 and 28 are employed to selectively drive and control both of the mechanisms according to the vehicle speed. The control is usually switched so that the variable steering force transmission mechanism is operated above a specified vehicle speed while the power assist mechanism is operated under the specified vehicle speed. This switching control is made only when the steering wheel is in the neutral position. If the vehicle speed incresese to a high speed during the operation of the power assist mechanism, however, the switch control is not made unless the vehicle speed lowers below the specified value.</p> |
