Hydraulic circuit for construction machine

Patent metadata

Field	Value
Publication number	US-10161109-B2
Application number	US-201515323335-A
Country	US
Kind code	B2
Filing date	May 26, 2015
Priority date	Jul 3, 2014
Publication date	Dec 25, 2018
Grant date	Dec 25, 2018

Abstract

A recycling passage 71 is configured to perform “pressure oil recycling,” in which the recycling passage 71 feeds boom discharge oil 35 Fo (recycling discharge oil) discharged from a boom cylinder 23 F (a recycling actuator), to the boom cylinder 23 F (an actuator actuated with feeding of discharge oil from a second pump 12 ). A first sensing pressure rising passage 81 feeds a part of boom discharge oil 35 Fo to a first unload passage 31 upstream of a first pressure sensing point 61 p when the pressure oil recycling is performed.

First claim

What is claimed is:

1. A hydraulic circuit for a construction machine, the hydraulic circuit being connected to a first pump, a second pump, a tank, and a plurality of actuators, the hydraulic circuit comprising:
a first unload passage connected to the first pump;
a second unload passage connected to the second pump;
a tank passage connected to the first unload passage, the second unload passage, and the tank;
a plurality of directional control valves connected to the plurality of actuators, respectively, and configured to feed an oil from the first pump or the second pump to the plurality of actuators and discharge to the tank the oil discharged from the plurality of actuators;
a negative control pressure sensing unit configured to output, as a negative control pressure, lower one of a pressure sensed at a first pressure sensing point in a most downstream portion of the first unload passage and a pressure sensed at a second pressure sensing point in a most downstream portion of the second unload passage;
a regulator configured to control discharge rates of the first pump and the second pump in association with each other in accordance with the negative control pressure output from the negative control pressure sensing unit;
a recycling passage connected to a recycling actuator included in the plurality of actuators; and
a sensing pressure rising passage connected to the recycling actuator,
wherein the plurality of directional control valves include a recycling directional control valve configured to feed discharge oil from the second pump to the recycling actuator,
the recycling passage is configured to perform pressure oil recycling, in which the recycling passage feeds recycling discharge oil discharged from the recycling actuator, to the actuator actuated with feeding of the discharge oil from the second pump, and
the sensing pressure rising passage is configured to feed a part of the recycling discharge oil to the first unload passage upstream of the first pressure sensing point or the second unload passage upstream of the second pressure sensing point when the pressure oil recycling is performed.

2. The hydraulic circuit for a construction machine according to claim 1 , wherein the sensing pressure rising passage includes a first sensing pressure rising passage configured to feed a part of the recycling discharge oil to the first unload passage upstream of the first pressure sensing point when the pressure oil recycling is performed.

3. The hydraulic circuit for a construction machine according to claim 2 , wherein the sensing pressure rising passage includes a second sensing pressure rising passage configured to feed a part of the recycling discharge oil to the second unload passage upstream of the second pressure sensing point when the pressure oil recycling is performed.

4. The hydraulic circuit for a construction machine according to claim 2 , wherein the first sensing pressure rising passage is disposed inside the recycling directional control valve.

5. The hydraulic circuit for a construction machine according to claim 2 , wherein the plurality of directional control valves include:
an arm-related directional control valve serving as the recycling directional control valve; and
a boom-related directional control valve disposed downstream of the arm-related directional control valve,
wherein the boom-related directional control valve has:
a boom-lowering position selected for lowering a boom, the boom-lowering position causing the first unload passage to be unblocked, and
a boom-raising position selected for raising the boom, the boom-raising position causing the first unload passage to be blocked or throttled.

6. The hydraulic circuit for a construction machine according to claim 1 , wherein the recycling directional control valve is a boom-related directional control valve or an arm-related directional control valve.

7. The hydraulic circuit for a construction machine according to claim 1 , wherein the sensing pressure rising passage is configured to feed a part of the recycling discharge oil to the second unload passage upstream of the second pressure sensing point when the pressure oil recycling is performed.

Assignees

• Nabtesco Corp

Inventors

• Iwasaki Hitoshi

Classifications

• F15B2211/3116

  the pump port being open in the centre position, e.g. so-called open centre · CPC title

• F15B11/165

  for adjusting the pump output or bypass in response to demand · CPC title

• F15B2211/6654

  Flow rate control · CPC title

• F15B2211/20576

  with multiple pumps · CPC title

• E02F3/425

  Drive systems for dipper-arms, backhoes or the like · CPC title