| 摘要 |
PURPOSE:To feed a proper amount of oil pressure responding to a load by arranging a power steering mechanism, a plurality of working oil passages, and a short-circuit oil passage in parallel with each other and respectively controlling capacity of pressure oil fed from a variable capacity hydraulic pump and the feed of pressure oil to each oil passage. CONSTITUTION:When a command switch 15 is in an OFF-state and a control valve 7 is in a neutral state, an electromagnetic on-off valve 14 is in a shut-off state, a hydraulic motor 12 is in an inoperative state, an electromagnetic type flow rate switching valve 5 is in a low flow rate throttle state, and a variable capacity type pump 2 is in a lowermost capacity state. When a power steering mechanism S is worked through steering operation of a handle 10, a relief valve 16 is communicated to a first working oil passage l2 by means of an oil pressure exerted on a power cylinder 9. A main oil passage L is more easier to flow than a short-circuit oil passage l1 in which throttles k1 and k2 are located, and pressure oil flows mainly through the main oil passage L. The feed of pressure oil to the first working oil passage l2 is practicable and when the longitudinal differential pressure of the electromagnetic type flow rate switching valve 5 is reduced, feed capacity of the variable capacity type hydraulic pump 2. |
