| 摘要 |
PCT No. PCT/JP90/01062 Sec. 371 Date Jan. 7, 1991 Sec. 102(e) Date Jan. 7, 1991 PCT Filed Aug. 21, 1990 PCT Pub. No. WO91/02905 PCT Pub. Date Mar. 7, 1991.A delivery rate of a main hydraulic pump is controlled so that a load sensing differential pressure is held at a preset target value. In order to maintain the delivery rate of the pump substantially constant even in the case of external loads, inertial loads, and compressibility or leakage problems with the hydraulic fluid, there is provided a dead zone for permitting a deviation between the load sensing differential pressure and the preset target value.
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