Hydraulic system of construction machine

Patent metadata

Field	Value
Publication number	US-9546468-B2
Application number	US-201214360504-A
Country	US
Kind code	B2
Filing date	Dec 24, 2012
Priority date	Dec 27, 2011
Publication date	Jan 17, 2017
Grant date	Jan 17, 2017

Abstract

The present disclosure relates to a hydraulic system of a construction machine. The hydraulic system of the construction machine includes: an electronic proportional pressure reducing valve configured to control a flow rate, to which a maximum pressure is input as a control current value, and which is set to a minimum flow rate; a gear pump configured to provide pilot operation oil to the EPPRV; a shuttle valve configured to compare a pressure of first pilot operation oil passing through the EPPRV and a pressure of a flow rate control signal, and output second pilot operation oil having the greater pressure; a hydraulic pump of which a swash plate angle is controlled by the second pilot operation oil; and a pump control device configured to control a pressure of the EPPRV to be decreased from a maximum pressure by a predetermined inclination when the flow rate control signal is generated.

First claim

The invention claimed is:

1. A hydraulic system of a construction machine, comprising:
an electronic proportional pressure reducing valve (EPPRV) configured to control a flow rate, to which a maximum pressure is input as a control current value, and which is set to a minimum flow rate;
a gear pump configured to provide pilot operation oil to the EPPRV;
a shuttle valve configured to compare a pressure of first pilot operation oil passing through the EPPRV and a pressure of a flow rate control signal, and output second pilot operation oil having the greater pressure;
a hydraulic pump of which a swash plate angle is controlled by the second pilot operation oil; and
a pump control device configured to control the pressure of first pilot operation oil to be decreased from a maximum pressure by a predetermined inclination when the flow rate control signal is generated.

2. The hydraulic system of claim 1 , wherein a plurality of pressures of the flow rate control signal is input by first and second flow rate control signal lines,
the shuttle valve includes a first shuttle valve configured to compare a first pressure of the first flow rate control signal line and the first pilot operation oil pressure and output the greater pressure as third pilot operation oil, and a second shuttle valve configured to compare a second pressure of the second flow rate control signal line and the first pilot operation oil pressure, and output the greater pressure as fourth pilot operation oil and
the hydraulic pump includes a first hydraulic pump of which a swash plate angle is controlled by the third pilot operation oil, and a second hydraulic pump of which a swash plate angle is controlled by the fourth pilot operation oil.

3. The hydraulic system of claim 1 , wherein when the flow rate control signal is not generated, the pump control device controls the maximum pressure to be input as the control current value, and setting of the minimum flow rate to be returned.

Assignees

• Doosan Infracore Co Ltd

Inventors

• Bang Jai Seok

Classifications

• F15B2211/6652

  Control of the pressure source, e.g. control of the swash plate angle · CPC title

• F15B2211/20523

  Internal combustion engine · CPC title

• E02F9/2292

  Systems with two or more pumps · CPC title

• F15B2211/3052

  Shuttle valves · CPC title

• F15B11/167

  using pilot pressure to sense the demand · CPC title