Driving device for work machine and work machine equipped therewith

• US 9,845,813 B2
• Filed: 07/03/2013
• Issued: 12/19/2017
• Est. Priority Date: 09/20/2012
• Status: Active Grant

• Current Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.)
• Inventors: Shimizu, Juri, Hiraku, Kenji, Saitoh, Teppei, Mizuochi, Mariko, Ishii, Akinori
• Primary Examiner(s): Kraft, Logan
• Application Number:
  US14/413,779
• Publication Number:
  US 20150135697A1
• Time in Patent Office: 1,630 Days
• CPC Class Codes: E02F 9/2217 with energy recovery arrangements, e.g. using accumulators, flywheels
• CPC Class Codes: E02F 9/2228 including an electronic controller
• CPC Class Codes: E02F 9/2235 including an electronic controller
• CPC Class Codes: E02F 9/2242 including an electronic controller
• CPC Class Codes: E02F 9/2289 Closed circuit
• CPC Class Codes: E02F 9/2292 Systems with two or more pumps
• CPC Class Codes: E02F 9/2296 Systems with a variable displacement pump
• CPC Class Codes: F15B 11/0423 by controlling pump output or bypass, other than to maintain constant speed
• CPC Class Codes: F15B 11/044 by means in the return line , i.e. "meter out"F15B11/046, F15B11/05 take precedence
• CPC Class Codes: F15B 11/17 using two or more pumps
• CPC Class Codes: F15B 2211/20546 variable capacity
• CPC Class Codes: F15B 2211/20561 reversible
• CPC Class Codes: F15B 2211/20576 with multiple pumps
• CPC Class Codes: F15B 2211/27 Directional control by means of the pressure source
• CPC Class Codes: F15B 2211/41518 being connected to multiple pressure sources
• CPC Class Codes: F15B 2211/41572 being connected to a pressure source and an output member
• CPC Class Codes: F15B 2211/665 Methods of control using electronic components
• CPC Class Codes: F15B 2211/6654 Flow rate control
• CPC Class Codes: F15B 2211/7053 Double-acting output members
• CPC Class Codes: F15B 2211/785 Compensation of the difference in flow rate in closed fluid circuits using differential actuators

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.

Claims

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.