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:
Jul. 23, 2002
Filed:
Jan. 23, 2001
Yusaku Nozawa, Ibaraki-ken, JP;
Mitsuhisa Tougasaki, Ibaraki-ken, JP;
Yoshizumi Nishimura, Tsuchiura, JP;
Kinya Takahashi, Tsuchiura, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
A fixed throttle is provided in a delivery line of a fixed pump driven by an engine for rotation together with a hydraulic pump , and a differential pressure detecting valve is provided in association with the fixed throttle to detect a differential pressure across the fixed throttle and to output a pressure lower than the detected differential pressure by a predetermined value. The output of the differential pressure detecting valve is introduced, as a signal pressure, to a pressure bearing section of a load sensing valve , thereby setting a target differential pressure. With that arrangement, a pressure in link with an engine revolution speed can be directly employed as the set differential pressure of the load sensing valve, and the structure of the load sensing valve can be avoided from being complicated. Further, in the idling revolution range in which the work amount is relatively small, the displacement of the hydraulic pump can be reduced to improve fine operability and cut down fuel consumption.