Hydraulic circuit for construction machine

Patent metadata

Field	Value
Publication number	US-9903097-B2
Application number	US-201414536776-A
Country	US
Kind code	B2
Filing date	Nov 10, 2014
Priority date	Jun 15, 2012
Publication date	Feb 27, 2018
Grant date	Feb 27, 2018

Abstract

A hydraulic circuit for a construction machine including a direction control valve group including direction control valves provided in tandem to a center bypass passage, and a bleed-off valve provided to the center bypass passage downstream of the direction control valve group.

First claim

The invention claimed is:

1. A hydraulic circuit for a construction machine comprising:
a direction control valve group including a plurality of direction control valves that are provided in tandem to a center bypass passage of the construction machine; and
a bleed-off valve provided to the center bypass passage downstream of the direction control valve group;
wherein the direction control valve includes a first internal passage that flows out pressure oil supplied to the direction control valve to the center bypass passage, and a second internal passage that supplies the pressure oil to a hydraulic actuator of the construction machine,
wherein the first internal passage causes pressure oil discharged from a hydraulic pump to flow out to the center bypass passage downstream of the direction control valve, so that the center bypass passage and the first internal passage form a parallel passage, and
wherein the bleed-off valve performs bleed-off control on pressure oil supplied by way of the parallel passage by changing an opening area of the bleed-off valve.

2. The hydraulic circuit for the construction machine of claim 1 ,
wherein the first internal passage has substantially the same passage area regardless of spool position of the direction control valve and forms the parallel passage that corresponds to the passage area, and
wherein the plurality of direction control valves is supplied with pressure oil only from the parallel passage.

3. The hydraulic circuit for the construction machine as claimed in claim 1 , further comprising:
a plurality of the direction control valve groups and a plurality of the center bypass passages,
wherein the plurality of the direction control valve groups each provided to each of the plurality of center bypass passages, and
wherein the plurality of the center bypass passages and each first internal passage of the plurality of the direction control valves form a parallel passage.

4. The hydraulic circuit for the construction machine as claimed in claim 1 ,
wherein the direction control valve group is provided to the center bypass passage between a running direction control valve and the bleed-off valve.

5. The hydraulic circuit for the construction machine of claim 1 ,
wherein the bleed-off valve includes an unloading position at which the opening area becomes largest and a blocking position at which the opening area becomes zero, and
wherein the bleed-off control is performed by switching from the unloading position to the blocking position.

6. The hydraulic circuit for the construction machine as claimed in claim 1 ,
wherein the bleed-off valve changes the opening area in response to operation information input to the construction machine.

Assignees

• Sumitomo Shi Constr Mach Co

Inventors

• Hashimoto Hirofumi

Classifications

• F15B2211/781

  one or more output members having priority · CPC title

• E02F9/2267

  Valves or distributors (position of valves arrangements on upper-structures E02F9/0875) · CPC title

• E02F9/2228 Primary

  including an electronic controller · CPC title

• F15B2211/31582

  having multiple pressure sources and a single output member · CPC title

• F15B2211/78

  Control of multiple output members · CPC title