Work machine

Patent metadata

Field	Value
Publication number	US-10655740-B2
Application number	US-201615577847-A
Country	US
Kind code	B2
Filing date	Feb 25, 2016
Priority date	Jun 3, 2015
Publication date	May 19, 2020
Grant date	May 19, 2020

Abstract

A work machine includes a closed circuit system in which there is provided a flushing valve. The flushing valve is equipped with: a valve main body; a spool which can select, in accordance with a position where the spool is arranged in the valve main body, connection between a first flow line and a third flow line, connection between a second flow line and the third flow line, or interruption of the connection between the first flow line, the second flow line, and the third flow line; a first liquid chamber that is provided inside the valve main body and into which a hydraulic working fluid from the first flow line flows; a first piston pressurizing the hydraulic working fluid having flowed into the first liquid chamber and moving the spool to a position where the second flow line and the third flow line are connected together, by the hydraulic pressure of the first liquid chamber; a second liquid chamber that is provided inside the valve main body and into which the hydraulic working fluid from the second flow line flows; and a second piston pressurizing the hydraulic working fluid having flowed into the second liquid chamber and moving the spool to a position where the first flow line and the third flow line are connected together, by the hydraulic pressure of the second liquid chamber.

First claim

The invention claimed is:

1. A work machine comprising:
one hydraulic pump having a regulator that controls a flow rate and direction of a hydraulic working fluid delivered;
a single rod hydraulic cylinder driven by the hydraulic working fluid and configured to drive a work device;
a hydraulic closed circuit that connects in a closed-circuit fashion, with the one hydraulic pump and the single rod hydraulic cylinder being connected by a flow line through which the hydraulic working fluid flows;
another hydraulic pump that delivers a hydraulic working fluid;
a relief valve connected to a delivery flow line of the other hydraulic pump;
a first flow line connected to a head side hydraulic fluid chamber of the single rod hydraulic cylinder of the hydraulic closed circuit;
a first check valve connected so as to be capable of supplying the hydraulic working fluid to the first flow line from the delivery flow line of the other hydraulic pump;
a second flow line connected to a rod side hydraulic fluid chamber of the single rod hydraulic cylinder of the hydraulic closed circuit;
a second check valve connected so as to be capable of supplying the hydraulic working fluid to the second flow line from the delivery flow line of the other hydraulic pump;
a third flow line connected to a tank via the relief valve; and
a flushing valve, wherein the flushing valve has:
a valve main body connected to the first flow line, the second flow line, and the third flow line;
a spool that can select, in accordance with a position where the spool is arranged in the valve main body, a connection between the first flow line and the third flow line, a connection between the second flow line and the third flow line, or an interruption of the connection between the first flow line, the second flow line, and the third flow line;
a first recess section formed on a first end surface of the spool in an axial direction of the spool;
a first piston slidably fit-engaged with the first recess section;
a first liquid chamber that is formed between the first piston and the first recess section inside the valve main body and into which the hydraulic working fluid from the first flow line flows;
a second recess section formed on a second end surface of the spool in an axial direction of the spool;
a second piston slidably fit-engaged with the second recess section; and
a second liquid chamber that is formed between the second piston and the second recess section inside the valve main body and into which the hydraulic working fluid from the second flow line flows, wherein
the first piston pressurizes the hydraulic working fluid having flowed into the first liquid chamber and moves the spool to a position where the second flow line and the third flow line are communicated together by hydraulic pressure of the first liquid chamber, and
the second piston pressurizes the hydraulic working fluid having flowed into the second liquid chamber and moves the spool to a position where the first flow line and the third flow line are communicated together, by a hydraulic pressure of the second liquid chamber.

2. The work machine according to claim 1 , wherein
an area of a pressure receiving section of the first piston is larger than an area of a pressure receiving section of the second piston.

3. The work machine according to claim 2 , wherein
a ratio between the area of the pressure receiving section of the first piston and the area of the pressure receiving section of the second piston is configured to be equal to a ratio between an area of a pressure receiving section of the head side hydraulic fluid chamber and an area of a pressure receiving section of the rod side hydraulic fluid chamber of the single rod hydraulic cylinder.

4. The work machine according to claim 3 , wherein
the flushing valve further has a spring generating a force maintaining the spool at a position where the first flow line, the second flow line, and the third flow line are interrupted from each other; and
a set load of the spring is equal to or larger than a value calculated by subtracting a second load generated in the second piston when a relief set pressure of the relief valve acts on the second liquid chamber from a first load generated in the first piston when a relief set pressure of the relief valve acts on the first liquid chamber.

5. The work machine according to claim 1 , wherein
areas of pressure receiving sections of the first piston and the second piston are the same;
the flushing valve further has a spring generating a force maintaining the spool at a position where the first flow line, the second flow line, and the third flow line are interrupted from each other; and
a set load of the spring is equal to or larger than a value calculated by multiplying a value obtained by subtracting 1 from a value obtained by dividing a pressure receiving area of a head side hydraulic fluid chamber of the single rod hydraulic cylinder by a pressure receiving area of a rod side hydraulic fluid chamber the single rod hydraulic cylinder by a load generated in the first piston when a relief set pressure of the relief valve acts on the first liquid chamber.

Assignees

• Hitachi Construction Mach Co

Inventors

• Shimizu Juri
• SAITOH Teppei
• Hiraku Kenji
• Akiyama Yuki
• Takahashi Hiromasa

Classifications

• F16K11/07 Primary

  with cylindrical slides · CPC title

• F16H61/4104

  Flushing, e.g. by using flushing valves or by connection to exhaust · CPC title

• F15B11/08

  with only one servomotor · CPC title

• E02F9/2289 Primary

  Closed circuit · CPC title