HYDRAULIC CIRCUIT FOR CONSTRUCTION MACHINE AND CONTROL DEVICE FOR SAME

• US 20150040552A1
• Filed: 10/28/2014
• Published: 02/12/2015
• Est. Priority Date: 07/02/2012
• Status: Active Grant

• Current Assignee: Sumitomo (S.H.I.) Construction Machinery Co., Ltd. (Sumitomo Heavy Industries Limited)
• Original Assignee: Sumitomo (S.H.I.) Construction Machinery Co., Ltd. (Sumitomo Heavy Industries Limited)
• Inventors: HASHIMOTO, Hirofumi
• Granted Patent: US 9,725,884 B2
• Time in Patent Office: Days
• US Class Current: 60/429
• CPC Class Codes: E02F 9/2242 including an electronic controller
• CPC Class Codes: E02F 9/2267 Valves or distributors position of valves arrangements on upper-structures E02F9/0875
• CPC Class Codes: E02F 9/2282 Systems using center bypass type changeover valves
• CPC Class Codes: E02F 9/2292 Systems with two or more pumps
• CPC Class Codes: F15B 11/16 with two or more servomotors
• CPC Class Codes: F15B 11/17 using two or more pumps
• CPC Class Codes: F15B 2211/20546 variable capacity
• CPC Class Codes: F15B 2211/20576 with multiple pumps
• CPC Class Codes: F15B 2211/30595 with additional valves between the groups of valves for multiple output members
• CPC Class Codes: F15B 2211/31517 having multiple pressure sources
• CPC Class Codes: F15B 2211/327 electrically or electronically
• CPC Class Codes: F15B 2211/41554 being connected to a return line and a directional control valve
• CPC Class Codes: F15B 2211/45 Control of bleed-off flow, e.g. control of bypass flow to the return line
• CPC Class Codes: F15B 2211/6346 representing a state of input means, e.g. joystick position
• CPC Class Codes: F15B 2211/6652 Control of the pressure source, e.g. control of the swash plate angle
• CPC Class Codes: F15B 2211/6654 Flow rate control
• CPC Class Codes: F15B 2211/7142 the output members being arranged in multiple groups

Abstract

A hydraulic circuit of a construction machine including center bypass passages, into which a pressurized oil from hydraulic pumps is supplied, includes a directional control valve group in tandem with the center bypass passages; a bleed-off valve on a downstream side of each center bypass passage; and a merging circuit that merges the pressurized oil supplied into one center bypass passage and that in another center bypass passage, wherein each directional control valve includes a first internal passage that flows the pressurized oil into the center bypass passages, and a second internal passage that supplies the pressurized oil to a hydraulic actuator, wherein the center bypass passages and the first internal passage form a parallel passage, wherein an opening area of the bleed-off valve is changed, wherein the merging circuit includes a merging directional control valve that controls an inflow direction of the pressurized oil to be merged.

Claims

1. A hydraulic circuit of a construction machine including a plurality of center bypass passages, into which a pressurized oil discharged from a plurality of hydraulic pumps is supplied, the hydraulic circuit comprising:

a directional control valve group including a plurality of directional control valves that are arranged in tandem with the center bypass passages;

a bleed-off valve arranged on a downstream side of each center bypass passage relative to the directional control valve group; and

a merging circuit that merges the pressurized oil supplied into one center bypass passage of the plurality of center bypass passages and the pressurized oil in another center bypass passage of the plurality of center bypass passages,

wherein each directional control valve includes

a first internal passage that flows the pressurized oil supplied into the directional control valve out into the center bypass passages, and

a second internal passage that supplies the pressurized oil supplied to the directional control valve to a hydraulic actuator of the construction machine,

wherein the center bypass passages and the first internal passage form a parallel passage where the first internal passage flows the pressurized oil discharged from the hydraulic pump out onto downstream sides of the center bypass passages relative to the directional control valve,

wherein the bleed-off valve performs a bleed-off control for the pressurized oil supplied through the parallel passage by changing an opening area of the bleed-off valve,

wherein the merging circuit includes a merging directional control valve that controls an inflow direction of the pressurized oil to be merged.

2. The hydraulic circuit of the construction machine according to claim 1,

wherein the first internal passage has substantially a same passage area regardless of a position of a spool included in each directional control valve and forms the parallel passage corresponding to the passage area,

wherein the directional control valve group is supplied with the pressurized oil from only the parallel passage.

3. The hydraulic circuit of the construction machine according to claim 1,

wherein a number of the plurality of hydraulic pumps is two,

wherein a number of the plurality of center bypass passages is two,

wherein the merging directional control valve switches over the inflow direction to supply one of pressurized oils respectively supplied to the two center bypass passages to the center bypass passage to which another of the pressurized oils is supplied.

4. The hydraulic circuit of the construction machine according to claim 1,

wherein the merging circuit further includes a check valve corresponding to the inflow direction, and prevents the pressurized oil from flowing in a direction inverse to the inflow direction.

5. A control device for controlling the hydraulic circuit of the construction machine according to claim 1.

6. The control device according to claim 5,

wherein the inflow direction is changed in response to operation information input into the construction machine.

7. The control device according to claim 5,

wherein the opening area of the bleed-off valve is decreased in a case where the pressurized oil is merged by the merging circuit.

8. The control device according to claim 5,

wherein the hydraulic actuator corresponding to the directional control valve, into which the pressurized oil that is merged is supplied, is preferentially operated.