| 摘要 |
PURPOSE:To make it possible to shift the steering mode of a vehicle into the two wheel steering mode while the steering characteristic of the vehicle is prevented from abruptly changing, by gradually communicating both pressure chambers in a power cylinder with each other when a control means fails to control the turn angle of rear wheels so that the latter is finally locked and held at zero angle. CONSTITUTION:In a power steering mechanism 16 in which a rear wheel steering mechanism 12 for turning rear wheels 2L, 2R is driven in association with the operation of an actuator 50 controlled by a control means 117, there is provided a communication passage 53 for communicating between both pressure chambers 17b, 17c of a power cylinder 17. The communication passage 53 is disposed therein with a valve means 54 for variably adjusting the passage area thereof. Further, a valve control means 118 controls the valve means 54 in such a way that the passage area of the communication passage 53 is gradually increased to its maximum area when the control means 110 malfunctions due to coupler disconnection and harness breakage. |
