Hydraulic system for work machine

Patent metadata

Field	Value
Publication number	US-10253479-B2
Application number	US-201514915311-A
Country	US
Kind code	B2
Filing date	Jan 9, 2015
Priority date	Mar 24, 2014
Publication date	Apr 9, 2019
Grant date	Apr 9, 2019

Abstract

When option attachment has not been attached, a reserve flow/direction control valve 8 is made to operate as a center bypass cut valve. When an option attachment has been attached, switching control is performed. In the switching control, when the option attachment is not used, the reserve flow/direction control valve 8 is made to operate as a center bypass cut valve for adjusting composite opening area of a center bypass and thereby controlling the flow rate of hydraulic fluid flowing into an actuator. When the option attachment is used, the reserve flow/direction control valve 8 is made to operate so as to supply the hydraulic fluid to an option hydraulic actuator 14.

First claim

The invention claimed is:

1. A hydraulic system for a work machine comprising:
a hydraulic pump;
a hydraulic actuator driven by hydraulic fluid delivered from the hydraulic pump;
a flow/direction control valve of center bypass type that controls a flow of the hydraulic fluid supplied from the hydraulic pump to the hydraulic actuator;
a reserve flow/direction control valve of the center bypass type arranged at a position in a center bypass line extending through the flow/direction control valve and on a downstream side of the flow/direction control valve, the reserve flow/direction control valve controlling the flow of the hydraulic fluid supplied from the hydraulic pump to an option hydraulic actuator when the option hydraulic actuator is used; and
a switching control device that makes the reserve flow/direction control valve operate as a valve for controlling the flow of the hydraulic fluid supplied to the option hydraulic actuator when the option hydraulic actuator is operated, while making the reserve flow/direction control valve operate as a center bypass cut valve when the option hydraulic actuator is not operated,
wherein:
the switching control device further comprises a sensor configured to detect that the hydraulic system is in a state not for making the reserve flow/direction control valve operate as a flow/direction control valve for the option hydraulic actuator, and
the switching control device performs control configured to switch the operation of the reserve flow/direction control valve based on a detection signal outputted from the sensor.

2. The hydraulic system for a work machine according to claim 1 , further comprising a switching valve arranged in an actuator hydraulic line for supplying the hydraulic fluid from the reserve flow/direction control valve to the option hydraulic actuator,
wherein the switching control device performs the control so as to close the switching valve and thereby block the hydraulic line when the reserve flow/direction control valve is made to operate as the center bypass cut valve.

Assignees

• Hitachi Construction Mach Co
• Satake Takako

Inventors

• KANETA Tomoaki
• Ishikawa Kouji
• Satake Hidetoshi
• Imura Shinya

Classifications

• E02F9/2292

  Systems with two or more pumps · CPC title

• E02F9/2225

  using pressure-compensating valves · CPC title

• F15B11/08

  with only one servomotor · CPC title

• E02F3/963 Primary

  Arrangements on backhoes for alternate use of different tools (backhoes per se E02F3/30; quick-acting devices to connect tools to arms E02F3/3609, for arms to tractors or the like E02F3/627) · CPC title

• E02F9/2296

  Systems with a variable displacement pump · CPC title