| 摘要 |
<p>The purpose of the present invention is to provide a construction machine capable of improving boom raising performance. The construction machine comprises: a lower traveling body (1); an upper turning body (2); an operation attachment (9) which includes a boom (3), arm (4), and bucket (5), and also includes cylinders (6, 7, 8) for driving the boom (3), arm (4), and bucket (5); traveling motors (10, 11); a turning motor (12); a hydraulic actuator circuit; and first to third pumps (13-15). The hydraulic actuator circuit includes: a first circuit (A) connected to one of the traveling motors (10, 11) and the boom cylinder (6); a second circuit (B) connected to the other traveling motor and the arm cylinder (7); and a third circuit (C) connected to the turning motor (12), and the hydraulic actuator circuit has a control valve (16-20) for each hydraulic actuator. The first to third pumps (13-15) discharge hydraulic oil toward the first to third circuits (A-C), respectively. The traveling motors are arranged furthest upstream in the first and second circuits (A, B). The hydraulic actuator circuit includes a merging valve (22A). The merging valve (22A) has: a first position (P1) where the hydraulic oil discharged by the third pump (15) is unloaded through the second circuit (B) when any hydraulic actuator other than the two traveling motors (10, 11) is operating; a second position (P2) where the hydraulic oil discharged by the third pump (15) is merged into the first and second circuits (A, B) when simultaneous operation of the two traveling motors (10, 11) is conducted and an operation other than a boom raising operation for raising the boom is conducted for a hydraulic actuator other than the two traveling motors (10, 11); and a third position where the hydraulic oil discharged by the third pump (15) is merged into the first circuit (A) and is blocked with respect to the second circuit (B) when the boom raising operation is conducted.</p> |
