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:
Dec. 05, 2017
Filed:
Nov. 15, 2013
Hitachi Construction Machinery Tierra Co., Ltd., Koka-shi, Shiga, JP;
Kiwamu Takahashi, Koka, JP;
Shingo Kishimoto, Koka, JP;
Yoshifumi Takebayashi, Koka, JP;
Kazushige Mori, Koka, JP;
Natsuki Nakamura, Koka, JP;
Hitachi Construction Machinery Tierra Co., Ltd, Koka-shi, JP;
Abstract
An object of the invention is to achieve a travel speed known in the art during travelling operation, improve energy efficiency by reducing energy loss, and obtain favorable travel operability less susceptible to effects from variations in a travel load and changes in a pump delivery pressure when travelling operation is performed through operation of a travel lever over a half stroke range or less. A variable restrictor valveis disposed in parallel with a flow sensing valveof an engine speed sensing valve unitA travel pilot pressure is adapted to act in an opening direction of the variable restrictor valveThe variable restrictor valveis set to have a continuously increasing opening area from a full closure to a maximum with an increasing travel pilot pressure. Travel flow control valvesandhave an opening area that allows a predetermined flow rate QT required for traveling to be obtained even when a target LS differential pressure is decreased to a second specified value Pawhen the travel lever is fully operated. In a first half of a spool stroke, the travel flow control valvesandhave an opening area approximate to an opening area of comparative example 1.