| 摘要 |
PROBLEM TO BE SOLVED: To reduce the flow of operating oil fed to a power steering gear at the time of low load so as to attain energy saving by providing a load pressure sensing spool with a restriction control part for changing the opening of a variable restriction by relative displacement to a flow control spool. SOLUTION: The pressure of operating oil before passing a variable restriction 40 acts upon one end of a flow control spool 20, and the pressure after passing acts upon the other end. The opening of a by-pass passage 18 is therefore controlled to maintain this differential pressure constant, and excess operating oil is by-passed to the low pressure side of a pump 10 to control the quantity of flow to be supplied to a power steering gear 12 to the specified quantity. In a non-steering state, load pressure is low, so that the difference of oil pressure acting upon both ends of a load sensing spool 33 determined by a restriction rod 38 is small, and the restriction opening of the variable throttle 40 is also small. As a result, the quantity of flow supplied through the variable restriction 40 is reduced. Loss of energy required for pump power can therefore be reduced. |
