| 摘要 |
<p>A rear wheel steering system is disposed in a rear wheel steering mechanism (B) and has a power cylinder (13) for generating a power for steering the rear wheels (2L,2R) in response to a liquid pressure. The power cylinder (13) is connected to a pump (20) as a source of generating the liquid pressure through a high pressure passage (18) and further to a reservoir tank (17) through a low pressure passage (19). The high pressure passage is connected to the low pressure passage through a relief passage on the pump side and a relief passage on the power cylinder side, the relief passages being disposed in parallel to each other. The rear wheel steering system is provided with a passage shifting system (H) for closing the relief passages during stationary period of time while opening each of the relief passages during operation and dividing the high pressure passage between the relief passages into sections and with a narrowed passage portion disposed at the relief passage on the power cylinder side. Operation of the passage shifting system independently allows the high pressure passage on the pump side and the high pressure passage on the power cylinder side to be communicated with the low pressure passage. At this time, the liquid pressure from the power cylinder is gradually released by the action of the narrowed passage portion. The liquid pressure withdrawn from the pump is rapidly released to the low pressure passage without interference with the narrowed passage portion.</p> |
