Power plants – Pressure fluid source and motor – Having condition responsive control in a system of distinct...
Patent
1996-02-13
1997-10-07
Nguyen, Hoang
Power plants
Pressure fluid source and motor
Having condition responsive control in a system of distinct...
60428, 91388, 91403, 91448, F16D 3102
Patent
active
056735588
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a hydraulic circuit system for a hydraulic excavator, and more particularly to a hydraulic circuit system for a hydraulic excavator by which motions of three working elements, i.e., a boom, an arm and a bucket, in the combined operation thereof are improved.
BACKGROUND ART
JP,A, 58-146632 describes one known hydraulic circuit system which is mounted on a hydraulic excavator having at least three kinds of working elements, i.e., a boom, an arm and a bucket, and comprises a plurality of actuators including a boom cylinder for driving the boom, an arm cylinder for driving the arm and a bucket cylinder for driving the bucket. This known hydraulic circuit system also comprises at least two first and second hydraulic pumps, and a hydraulic valve apparatus for supplying hydraulic fluids from the first and second hydraulic pumps to at least the boom cylinder, the arm cylinder and the bucket cylinder therethrough. The hydraulic valve apparatus comprises a first boom directional control valve for controlling a flow of the hydraulic fluid supplied from the first hydraulic pump to the boom cylinder, a bucket directional control valve for controlling a flow of the hydraulic fluid supplied from the first hydraulic pump to the bucket cylinder, a second boom directional control valve for controlling a flow of the hydraulic fluid supplied from the second hydraulic pump to the boom cylinder, and an arm directional control valve for controlling a flow of the hydraulic fluid supplied from the second hydraulic pump to the arm cylinder, a first parallel passage for connecting feeder passages of the first boom directional control valve and the bucket directional control valve in parallel with respect to the first hydraulic pump so that the hydraulic fluid from the first hydraulic pump is supplied to these directional control valves in parallel, and a second parallel passage for connecting feeder passages of the second boom directional control valve and the arm directional control valve in parallel with respect to the second hydraulic pump so that the hydraulic fluid from the second hydraulic pump is supplied to these directional control valves in parallel.
DISCLOSURE OF THE INVENTION
In the prior art hydraulic circuit apparatus described above, the boom, the arm and the bucket can simultaneously be operated in various modes with the arrangement that the boom cylinder, the arm cylinder and the bucket cylinder are connected to the two hydraulic pumps through the directional control valves and the first and second parallel passages as explained above. For example, in the double combined operation of the boom and the arm, the hydraulic fluid from at least the first hydraulic pump is supplied to the boom cylinder through the first boom directional control valve, and the hydraulic fluid from the second hydraulic pump is supplied to the arm cylinder through the arm directional control valve, enabling the boom and the arm to be moved at the same time. In the double combined operation of the boom and the bucket, the hydraulic fluid from at least the second hydraulic pump is supplied to the boom cylinder through the second boom directional control valve, and the hydraulic fluid from the first hydraulic pump is supplied to the bucket cylinder through the bucket directional control valve, enabling the boom and the bucket to be moved at the same time. In the double combined operation of the bucket and the arm, the hydraulic fluid from the first hydraulic pump is supplied to the bucket cylinder through the bucket directional control valve, and the hydraulic fluid from the second hydraulic pump is supplied to the arm cylinder through the arm directional control valve, enabling the bucket and the arm to be moved at the same time. Further, in the triple combined operation of the boom, the arm and the bucket, when load pressures of the arm cylinder and the bucket cylinder are sufficiently high as developed during digging work, parts of the hydraulic fluids from the first and second hydraulic
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Hirata Toichi
Ishikawa Koji
Nakamura Tsuyoshi
Sugiyama Genroku
Toyooka Tsukasa
Hitachi Construction Machinery Co. Ltd.
Nguyen Hoang
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