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:
May. 21, 2002
Filed:
Feb. 06, 2001
Takashi Niidome, Tsuchiura, JP;
Hitoshi Kagiwada, Tsuchiura, JP;
Takeshi Kobayashi, Chiyoda-machi, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
A volume control valve for controlling the volume of a variable displacement type hydraulic rotary machine includes a valve housing provided with a bore in which a spool slides axially to selectively establish and block communication of a pressure oil feed/discharge port with a high pressure port and a tank port. A first pressure receiving portion is formed in the spool to receive a load pressure as a pilot pressure introduced from a pilot port for displacing the spool axially within the bore. A bottomed axial bore is formed in the spool which has a slidable piston therein defining an oil chamber between the piston end and the bottom of the bore to receive a hydraulic reaction force induced within the oil chamber. A second pressure receiving portion is formed by the bottom of the bore to receive an internal pressure of the oil chamber, thereby changing a total pressure receiving area of the spool in conjunction with the first pressure receiving portion. An oil passage is formed in the spool at a position corresponding to the oil chamber.