| 摘要 |
Disclosed is a hydraulic system for construction machinery adapted to prevent the occurrence of off-course travel when performing a composite action on a working device such as a boom and vehicle travel. In the hydraulic system for construction machinery according to the present invention, provided is a system which comprises: a first and a second hydraulic pump; operating levers for a left and a right side travel operating device and a first and second working device; an actuator for a left-side travel motor and the first working device, the actuator being connected to the discharge flow pathway of the first hydraulic pump; an actuator for a right-side travel motor and the second working device, the actuator being connected to the discharge flow pathway of the second hydraulic pump; a first pressure compensating valve which is provided on one side, being either the upstream side or the downstream side, of a first control valve; a second pressure compensating valve which is provided on one side, being either the upstream side or the downstream side, of a second control valve; a third pressure compensating valve which is provided on one side, being either the upstream side or the downstream side, of a third control valve; a fourth pressure compensating valve which is provided on one side, being either the upstream side or the downstream side, of a fourth control valve; a first orifice which connects, to a hydraulic pressure tank, a first load sensing line connected to the first pressure compensating valve of the first control valve and the fourth pressure compensating valve of the fourth control valve; a second orifice which connects, to a hydraulic pressure tank, a second load sensing line connected to the second pressure compensating valve of the second control valve and the third pressure compensating valve of the third control valve; a flow combining valve which is provided in a flow combining flow pathway of the first and second hydraulic pumps; a travel link-through valve which is provided in a flow pathway connecting the downstream of the first pressure compensating valve and the downstream of the third pressure compensating valve; and a control unit for implementing control in such a way as to effect through linkage of the travel link-through valve during composite action involving operation of the working device and vehicle travel. |
