Driving device for work machine and work machine equipped therewith

Patent metadata

Field	Value
Publication number	US-9845813-B2
Application number	US-201314413779-A
Country	US
Kind code	B2
Filing date	Jul 3, 2013
Priority date	Sep 20, 2012
Publication date	Dec 19, 2017
Grant date	Dec 19, 2017

Abstract

There is provided a driving device for a work machine, having a closed hydraulic circuit system for driving cylinders with hydraulic pumps, the driving device making the speed of operation substantially the same in both directions of piston rod extension and contraction. The driving device includes: a first hydraulic pump that has flow rate control device for controlling the flow rate and direction of hydraulic fluid to be delivered; a single rod hydraulic cylinder that is driven with the hydraulic fluid to drive one of work members of a work device on the work machine; a closed hydraulic circuit that connects the first hydraulic pump with the single rod hydraulic cylinder to form a closed circuit using flow lines through which the hydraulic fluid flows; a branch line that branches from the flow line between the first hydraulic pump and the single rod hydraulic cylinder; a first flow line of which one end is connected to the branch line; a tank to which the other end of the first flow line is connected; and a hydraulic fluid flow rate control device attached to the first flow line to control the flow rate of the hydraulic fluid flowing from the branch line to the tank or from the tank to the branch line.

First claim

The invention claimed is:

1. A driving device for a work machine, comprising:
a first hydraulic pump that has flow rate control device for controlling the flow rate and direction of hydraulic fluid to be delivered;
a first single rod hydraulic cylinder that is driven with the hydraulic fluid to drive one of work members of a work device on the work machine;
a closed hydraulic circuit that connects the first hydraulic pump with the first single rod hydraulic cylinder to form a closed circuit using a first flow line through which the hydraulic fluid flows;
a communication line that branches from the first flow line;
a second flow line of which one end is connected to the communication line;
a third flow line of which one end is connected to a tank;
a second hydraulic pump that has a first port and a second port, the first port being connected to the other end of the second flow line and the second port being connected to the other end of the third flow line, and is capable of controlling both a flow rate from the communication line to the tank and a flow rate from the tank to the communication line;
a second single rod hydraulic cylinder that drives a work member different from the one of work members;
a flow rate control valve that changes the flow rate and direction of the hydraulic fluid delivered by the second hydraulic pump, the flow rate control valve further supplying the delivered hydraulic fluid to the second single rod hydraulic cylinder;
an open hydraulic circuit that has a fourth flow line that connects the first port of the second hydraulic pump with the flow rate control valve, a fifth flow line that connects the flow rate control valve with the second single rod hydraulic cylinder, and a sixth flow line that connects the flow rate control valve with the tank; and
a selector valve attached to the second flow line, the selector valve selecting either communication or cut-off of the hydraulic fluid flowing through the second flow line.

2. The driving device for the work machine according to claim 1 , further comprising:
a plurality of the open hydraulic circuits;
a distribution circuit that connects the second hydraulic pump in one open hydraulic circuit with the flow rate control valve in another open hydraulic circuit using a seventh flow line; and
a selector valve attached to the seventh flow line of the distribution circuit, the selector valve selecting either communication or cut-off of the hydraulic fluid in the seventh flow line.

3. The driving device for the work machine according to claim 1 ,
wherein the second hydraulic pump includes a variable displacement device that is capable of changing the flow rate and delivery direction of the hydraulic fluid.

Assignees

• Hitachi Construction Mach Co

Inventors

• Shimizu Juri
• Hiraku Kenji
• SAITOH Teppei
• Mizuochi Mariko
• Ishii Akinori

Classifications

• F15B2211/20576

  with multiple pumps · CPC title

• F15B2211/41518

  being connected to multiple pressure sources · CPC title

• E02F9/2217

  with energy recovery arrangements, e.g. using accumulators, flywheels · CPC title

• F15B2211/20561

  reversible · CPC title

• F15B2211/20546

  variable capacity · CPC title