Excavating – Ditcher – Condition responsive
Patent
1997-04-09
1998-05-19
Carone, Michael J.
Excavating
Ditcher
Condition responsive
172 2, 36442407, F02F 343
Patent
active
057523339
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an area limiting excavation control system for construction machines, and more particularly to an area limiting excavation control system which is equipped in a construction machine such as a hydraulic excavator having a multi-articulated front device and can perform excavation while limiting an area where the front device is movable.
BACKGROUND ART
There is known a hydraulic excavator as typical one of construction machines. A hydraulic excavator is made up of a front device comprising a boom, an arm and a bucket which are each pivotable in the vertical direction, and a body comprising an upper structure and an undercarriage. The boom of the front device is supported at its base end to a front portion of the upper structure. In such a hydraulic excavator, front members including a boom are operated by respective manual control levers. However, because the front members are coupled to each other through articulations for pivoting motion, it is very difficult to carry out excavation work over a predetermined area. In view of the above, JP-A-4-136324 proposes an area limiting excavation control system for facilitating such excavation work. The proposed area limiting excavation control system comprises means for detecting a posture of a front device, means for calculating a position of the front device based on a signal from the detecting means, means for teaching an entrance forbidden area where the front device is inhibited from entering, lever gain calculating means for determining a distance d between the position of the front device and a boundary of the taught entrance forbidden area, and then outputting the product of a lever operation signal multiplied by a function depending on the distance d that takes a value 1 when the distance d is greater than a certain value, and a value between 0 and 1 when it is smaller than the certain value, and actuator control means for controlling motion of an actuator in accordance with a signal from the lever gain calculating means. With the construction of the proposed system, since the lever operation signal is restricted depending on the distance to the boundary of the entrance forbidden area, even when the operator attempts to move a tip of the bucket into the entrance forbidden area by mistake, the bucket tip is smoothly stopped at the boundary automatically, or on the way of movement of the bucket tip toward the boundary, the operator can notice approaching to the entrance forbidden area, judging from a reduction in the speed of the front device, and return the bucket tip.
DISCLOSURE OF THE INVENTION
However, the foregoing related art has problems as follows.
With the related art disclosed in JP-A-4-136324, since the lever gain calculating means outputs, to the actuator control means, the product of the lever operation signal directly multiplied by the function depending on the distance d, the bucket tip is gradually slowed down as it approaches the boundary of the entrance forbidden area, and is stopped at the boundary of the entrance forbidden area. Therefore, a shock that would otherwise be generated when the operator attempts to move the bucket tip into the entrance forbidden area can be avoided. But, this related art is designed to reduce the speed of the bucket tip such that the speed is always reduced regardless of the direction in which the bucket tip is moving. Accordingly, when excavation is performed along the boundary of the entrance forbidden area, the digging speed in the direction along the boundary of the entrance forbidden area is also reduced as the bucket tip approaches the entrance forbidden area with operation of the arm. This requires the operator to manipulate a boom lever to move the bucket tip away from the entrance forbidden area each time the digging speed is reduced, in order to prevent a drop of the digging speed. As a result, the working efficiency is extremely deteriorated when excavation is performed along the entrance forbidden area. On the other hand, to increase the working
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Egawa Eiji
Fujishima Kazuo
Haga Masakazu
Nakagawa Takashi
Watanabe Hiroshi
Carone Michael J.
Hitachi Construction Machinery Co. Ltd.
Pezzuto Robert
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