| 摘要 |
<p>The present invention is directed to providing a construction machine capable of improving boom raising performance. The construction machine comprises: a lower propelling body (1); an upper slewing body (2); a working attachment (9) which includes a boom (3), an arm (4), a bucket (5), and three cylinders (6, 7, 8) for driving respective ones of the boom (3), arm (4) and bucket (5); two travel motors (10, 11); a slewing motor (12); a hydraulic actuator circuit; and first to third pumps (13 to 15). The hydraulic actuator circuit comprises: a first circuit (A) connected to one of the travel motors (10, 11) and the boom cylinder (6); a second circuit (B) connected to the other travel motor and the arm cylinder (7); and a third circuit (C) connected to the slewing motor (12), wherein the first to third circuits have a plurality of control valves (16 to 20) each associated with the hydraulic actuator. Each of the first to third pumps (13 to 15) discharges hydraulic fluid toward the respective first to third circuits (A to C). Each of the travel motors is disposed on an upstreammost side in the first and second circuits (A, B). The hydraulic actuator circuit includes a merging valve (22A), which has: a first position (P1) for unloading the hydraulic fluid discharged from the third pump (15) through the second circuit (B) when none of the hydraulic actuators other than the two travel motors (10, 11) is operated; a second position (P2) for merging hydraulic fluid discharged from the third pump (15) into each of the first and second circuits (A, B) when a simultaneous operation of the two travel motors (10, 11), and an operation of at least one of the remaining hydraulic actuators except for a boom raising operation which is an operation for raising the boom are performed; and a third position for merging hydraulic fluid discharged from the third pump (15) into the first circuit (A) while blocking the hydraulic fluid from the second circuit (B) when the boom raising operation is performed.</p> |
