The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 27, 2001
Filed:
Jun. 01, 1998
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
A differential pressure &Dgr;PLS between a delivery pressure of a hydraulic pump,and a maximum load pressure among a plurality of actuators,is maintained at a target differential pressure &Dgr;PLSref by pump displacement control means,The target differential pressure &Dgr;PLSref is modified depending on an engine rotational speed by introducing a differential pressure &Dgr;Pp across a throttle,disposed in a delivery line of a fixed pump,An unloading valve,has first and second auxiliary control pressure chambers,to which the differential pressure p across the throttle,is introduced, and a target differential pressure &Dgr;Pun of the unloading valve is also modified in match with change in the target differential pressure &Dgr;PLSref modified by the operation driver,Stable load sensing control is thereby achieved without being affected by the engine rotational speed.