| 摘要 |
A power steering mechanism includes a control valve which acts both to control the flow of pressurized fluid to and from a pair of working chambers of the mechanism and as a pressure relief valve to limit the maximum pressure which may be communicated to the working chambers. The valve includes a stack of plane annular discs which are relatively rotatable and arranged coaxially with the control shaft of the steering mechanism. The discs are resiliently biased together and define valve ports and compartments which cooperate to control the flow of pressure fluid dependent upon the relative rotational positions of the discs. Rotation of the control shaft causes rotation of one of the discs relative to the others to correlate the ports and chambers so as to supply pressure fluid to one chamber and to vent fluid from the other chamber. If the fluid pressure within the compartments of the control valve should exceed a predetermined value, the resilient bias holding the discs together is overcome and the discs separate slightly to open communication between the fluid supply ports and the vent ports. Another embodiment of the mechanism includes a linkage arranged to separate the discs and an abutment which cooperates with the linkage when the mechanism reaches either end of its range of travel. The working chambers are incapacitated when the linkage separates the discs so as to prevent damage to the mechanism from a too-high fluid pressure.
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