Device for controlling limited-area excavation with construction machine

An area limiting excavation control system installed in a construction machine comprising a multi-articulated front device (1A) constituted by a plurality of front members (1a-1c) coupled to each other in a relatively vertically rotatable manner, including first and second front members (1b, 1a), a plurality of hydraulic actuators (3a-3f) including first and second hydraulic actuators (3b, 3a) to drive said first and second front members, a plurality of operating means (14a-14f;

• 4a-4f) including first and second operating means (14b, 14a;
• 4b, 4a) to instruct operation of said first and second front members, and a plurality of hydraulic control valves (15a-15f;
• 5a-5f) including first and second hydraulic control valves (15b, 15a;
• 5b, 5a) driven upon operation of said first and second operating means to control respective flow rates of a hydraulic fluid supplied to said first and second hydraulic actuators, said area limiting excavation control system comprising,
• first calculating means (9e;
• 90d) for calculating a moving speed (b;
• Vc) of said front device (1A) instructed by at least said first operating means (14b;
• 4b) among said plurality of operating means,
• second calculating means (9c;
• 90e) for calculating a limit value (a;
• hVcv;
• f(Ya)) of a moving speed component in the direction toward a boundary of a set area such that the limit value of the moving speed component is reduced as said front device comes closer to the boundary of said set area, and
• signal modifying means (9f-9j;
• 9f-9Bi, 12;
• 90e-90k, 12) for modifying an operation signal from at least said second operating means (14a;
• 4a) among said plurality of operating means by using the moving speed calculated by said first calculating means and the limit value of the moving speed component calculated by said second calculating means, so that the moving speed of said front device in the direction toward the boundary of said set area is reduced as said front device comes closer to the boundary, while said front device is allowed to move in the direction along the boundary,
• wherein said area limiting excavation control system for said construction machine further comprises:
• first detecting means (41a) for detecting a load acting on said front device (1A);
• and
• limit value modifying means (91;
• 9C1) for modifying said limit value (a;
• hVcv;
• f(Ya)) of the moving speed component calculated by said second calculating means in accordance with a magnitude of the load detected by said first detecting means;
• and
• wherein said limit value modifying means (91;
• 9C1) modifies said limit value (a;
• hVcv;
• f(Ya)) of the moving speed component such that the limit value becomes effective in a position closer to the boundary of said set area as the load acting on said front device (1A) detected by said first detecting means (41a) increases.