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:
Aug. 06, 2002
Filed:
Mar. 27, 2001
Hiroshi Watanabe, Ushiku, JP;
Shuji Ohira, Tsukuba, JP;
Kazuo Fujishima, Ibaraki-ken, JP;
Hiroshi Ogura, Ryugasaki, JP;
Masakazu Haga, Ibaraki-ken, JP;
Sadahisa Tomita, Ibaraki-ken, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
Whether a previously computed valve command value Y−1 is within a neutral zone ±&agr; is determine. If the determination result is “Yes”, processing to compute a valve command value for a neutral dead zone is executed. If the determination result is “No”, processing to compute a valve command value for a driving zone is executed. In the latter case, by using a valve command value X and the previously computed valve command value Y−1, it is determined in which one of acceleration, deceleration/stop, and lever-reversed condition is the operating status, and a maximum setting rate in one of acceleration, deceleration/stop, and lever-reversed condition is computed from a corresponding function &Dgr;Y=fmax (X), etc. Then, a control signal is computed while restraining a change rate of the operational signal to be kept not more than the computed maximum change rate, and a flow control valve is controlled in accordance with the computed control signal. As a result, in a hydraulic drive system for controlling a flow control valve with an electrical operational signal to control the operation of an actuator, the flow control valve can be controlled at an optimum maximum change rate in any operating status of acceleration, deceleration/stop, and lever-reversed condition.