油圧用2段絞りのキャビテーションに関する研究

第4報 : スプール弁の下流に絞りを設けた場合

抄録

In hydraulic systems, it is difficult to prevent cavitation in a single-stage spool valve, and a restrictor placed on the downstream of a spool valve is effective for the avoidance of cavitation and the reduction of its noise.
This paper deals with the cavitation in a two-stage restrictor which consists of an upstream spool valve and a downstream round edged choke. As a result, the following conclusions are obtained.
(1) The occurring pattern of cavitation is different according to the opening area of upstream spool valve, the diameter of downstream round edged choke and the outlet pressure.
(2) The critical conditions for cavitation of the spool valve with and without the downstream restrictor are identical.
(3) When the cavitation does not occur on the upstream spool valve, the critical condition for cavitation of the downstream restrictor is identical with that measured on the downstream restrictor only. But the cavitation on the downstream restrictor becomes more easy to occur when the cavitation is occurring at the upstream spool valve.
(4) The cavitation noise of the spool valve with downstream restrictor is much smaller than that measured on the spool valve only.
(5) When the distance between the upstream spool valve and the downstream restrictor becomes shorter, the inlet pressure of the downstream restrictor becomes higher and the flow rate becomes smaller.
(6) As the reduction of distance between the two restrictors, the noise becomes smaller in the region where the cavitation is occurring on the upstream spool valve, but it becomes larger in the region where the cavitation is occurring on the downstream restrictor.