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:
Apr. 24, 2001
Filed:
Dec. 03, 1998
Kouji Ishikawa, Ibaraki-ken, JP;
Toichi Hirata, Ibaraki-ken, JP;
Genroku Sugiyama, Ibaraki-ken, JP;
Tsukasa Toyooka, Ibaraki-ken, JP;
Tsuyoshi Nakamura, Ibaraki-ken, JP;
Yasuharu Gotou, Ibaraki-ken, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
A hydraulic drive system is provided with a signal guide system for guiding a delivery pressure of a pump as a command pressure via a line and a port, another signal guide system for guiding a pilot pressure of a pilot pump as another command pressure via a line and a port, a tilting control unit for controlling the displacement of the pump by the command pressures guided to the ports, a controller having a command current-setting unit for setting a relationship between a target engine speed and a command current, a target engine speed-indicating unit for an engine, and a solenoid-operated proportional valve for allowing the pilot pressure of the line to pass as is while no drive signal is outputted from the controller but for being reduced in opening to change the pilot pressure to a smaller value when a drive signal is outputted from the controller.