| 摘要 |
PROBLEM TO BE SOLVED: To freely switch between one pump and two pumps for supplying operating oil to a service directional control valve. SOLUTION: The hydraulic circuit of a construction machine includes a first circuit (a) connected to a first pump 22 and having directional control valves 19, 20, 21 for a right travel device, a boom, and a basket, respectively, a second circuit (b) connected to a second pump 23 and having directional control valves 18, 17, 16 for a left travel device, an arm, and service, respectively, and a third circuit (c) connected to a third pump 24 and having directional control valves 13, 14, 15 for a boom swing, a blade, and turning, respectively. The hydraulic circuit further includes a junction valve 69 having a service single current circuit formation position 70a, a service junction circuit formation position 70b, and a travel position 70c. Accompanying the switching of the junction valve 69 from the service single current circuit formation position 70a to the service junction circuit formation position 70b, the operating oil passed through the third circuit (c) is supplied to the upstream side position of the service directional control valve 16 of the second circuit (b). COPYRIGHT: (C)2010,JPO&INPIT |
