Construction machine

Patent metadata

Field	Value
Publication number	US-10041228-B2
Application number	US-201314442814-A
Country	US
Kind code	B2
Filing date	Nov 19, 2013
Priority date	Dec 13, 2012
Publication date	Aug 7, 2018
Grant date	Aug 7, 2018

Abstract

A construction machine includes: a lower traveling body; an upper slewing body; a front attachment; a plurality of hydraulic actuators including traveling motors; hydraulic pumps; a plurality of control valves for the hydraulic actuators; a plurality of operation units for the control valves; traveling operation detectors that detect operations for the operation units for the traveling motors of the operation units; a back-pressure compensation valve generating back pressure in a return pipe line connecting each of the control valves and a tank and having a setting pressure switchable between low and high pressure setting values; and a back-pressure control section performing a back-pressure lowering control of making the setting pressure of the back-pressure compensation valve be the low pressure setting value when traveling operation amounts in the traveling operation units are large.

First claim

The invention claimed is:

1. A construction machine, comprising:
a lower traveling body including left and right traveling units and adapted to travel by driving the left and right traveling units;
an upper slewing body disposed on the lower traveling body so as to be able to be slewed;
a front attachment attached to the upper slewing body;
a plurality of hydraulic actuators including a traveling motor which is a drive source of each of the left and right traveling units;
a hydraulic pump as a hydraulic pressure source supplying hydraulic oil to the hydraulic actuators;
a plurality of control valves adapted to operate supply of hydraulic oil from the hydraulic pump to the respective hydraulic actuators to thereby control respective operations of the hydraulic actuators individually;
a plurality of operation units provided for the respective control valves, the operation units including respective operation members each being adapted to receive an operation for moving the control valve corresponding to the operation unit;
a traveling operation detector that detects an operation applied to an operation member of a traveling operation unit, the traveling operation unit being one of the operation units and provided for operating the control valve corresponding to the traveling motor;
a plurality of operation detectors that detect respective operations of the operation units other than said traveling operation unit;
a back-pressure compensation valve that generates back pressure in a return pipe line connecting each of the control valves to a tank, the back-pressure compensation valve having a setting pressure switchable between a lower pressure setting value and a higher pressure setting value; and
a back-pressure control section configured to perform a back-pressure lowering control of making the setting pressure of the back-pressure compensation valve be the low pressure setting value in response to a traveling operation amount being equal to or greater than a preset value and no operation being applied to each of the operation units other than the traveling operation unit, and configured to make the setting pressure of the back-pressure compensation valve be the high pressure setting value not only in response to the traveling operation amount being less than the preset value but also in response to a combined operation of simultaneously making both of the traveling operation and an operation applied to at least one of the operation units other than the traveling operation unit be performed, the traveling operation amount being an amount of the operation applied to the operation member of the traveling operation unit.

2. The construction machine according to claim 1 , wherein: said back-pressure compensation valve is a pilot-controlled selector valve whose setting pressure of the pilot-controlled selector valve is shifted from said low pressure setting value to said high pressure setting value when pilot pressure is supplied from a pilot pressure source; and said back-pressure control section includes a back-pressure selector valve disposed between said back-pressure compensation valve and said pilot pressure source and having a pilot pressure supply position for allowing the pilot pressure to be supplied from said pilot pressure source to said back-pressure compensation valve and a pilot pressure shut-off position for shutting off the supply of the pilot pressure, and a back-pressure-selector-valve operation section configured to perform the back-pressure lowering control by shifting said back-pressure selector valve to said pilot pressure shut-off position.

3. The construction machine according to claim 2 , wherein said back-pressure selector valve is configured to be set at said pilot pressure supply position when no command signal is input from said back-pressure selector valve operation section and configured to be shifted to the pilot pressure shut-off position when the command signal is input.

4. The construction machine according to claim 2 , wherein: each of the control valves is a pilot-controlled selector valve configured to be operated by pilot pressure; each of the operation units is a remote control valve configured to output the pilot pressure from the pilot pressure source in accordance with the operation applied to the operation member; and the construction machine further includes a cabin disposed on the upper slewing body as an operation room, a gate lever manipulated so as to open and close an entrance of the cabin, and a hydraulic control valve configured to shut off all of the remote control valves from the pilot pressure source when the gate lever is opened, the hydraulic lock valve having an outlet pressure which is led to the back-pressure compensation valve via the back-pressure selector valve.

5. The construction machine according to claim 1 , further comprising a plurality of actuator operation detectors that detect respective operations of the operation units except said traveling operation units, wherein said back-pressure control section performs said back-pressure lowering control also when no operation is applied to all the operation units including said traveling operation unit.

6. The construction machine according to claim 1 , further comprising a slewing stop detector that detects that said upper slewing body is stopped, wherein said hydraulic actuator includes a slewing motor that slews said upper slewing body, and said back-pressure control section performs said back-pressure lowering control on condition that the stop of said upper slewing body is detected.

7. The construction machine according to claim 6 , wherein said slewing stop detector includes a slewing speed detector that detects a slewing speed of said upper slewing body, and said back-pressure control section is configured to judge that said upper slewing body is stopped when the slewing speed of the upper slewing body is 0.

8. The construction machine according to claim 6 , wherein said slewing stop detector includes a slewing operation detector that detects an operation applied to a slewing operation unit that is one of the operation unit and provided for said slewing motor, and said back-pressure control section is configured to judge that said upper slewing body is stopped when an operation amount of said slewing operation unit is kept less than a preset value for a predetermined period of time.

Assignees

• Kobelco Constr Mach Co Ltd

Inventors

• Ueda Koji

Classifications

• E02F9/2292

  Systems with two or more pumps · CPC title

• F15B2211/6653

  Pressure control · CPC title

• E02F9/2282

  Systems using center bypass type changeover valves · CPC title

• E02F3/32

  working downwardly and towards the machine, e.g. with backhoes · CPC title

• F15B2211/6346

  representing a state of input means, e.g. joystick position · CPC title