摘要:
A first group (G1) is supplied with hydraulic power from a first hydraulic pump (7). In the first group (G1), an arm control valve (12) is disposed at the most downstream position. A throttle (20) is provided at the entrance of the arm control valve. Thus, a circuit is configured to give priority to boom raising or bucket excavation. During a combined operation, according to the operation amount of boom pulling or bucket excavation, a controller (35) decreases the upper limit of the discharge amount of the first hydraulic pump (7) determined by the operation amount of arm pulling and increases the recycling rate of oil to the expansion side of an arm cylinder (4).
摘要:
With respect to a method of controlling a pump flow rate of a hydraulic pump, a method having a small flow rate command value is selected between a pressure feedback control for controlling the pump flow rate based on a set pressure (a cutoff pressure) and a pump pressure, and, an ordinary control for controlling the pump flow rate based on operation information, and in a case that the pressure feedback control is selected, a flow rate increasing control for increasing the flow rate command value after the case with the passage of time is performed.
摘要:
A hydraulic control system comprising a boom control valve (7) in a first oil path (LCB) providing oil from a first hydraulic pump (2) to a boom cylinder (13), an arm control valve (10) in a second oil path (RCB) for providing oil from a second hydraulic pump (3) to an arm cylinder (16), a confluence switching valve (17) having a position (b) for joining the paths and a position (a) for stopping the confluence, a flow control valve (18) for returning pressure oil in the first oil path to a tank (28), and a control means (24,34) for switching the confluence switching valve to the confluence position and closing the flow control valve when the arm operating means (25) is operated independently and for switching the confluence switching valve to the confluence stop position and opening the flow control valve when the arm and boom operating means (25,22) are operated simultaneously.
摘要:
A hydraulic control device for a working machine includes hydraulic actuators (1,2,3), a hydraulic pump (10) which functions as a hydraulic power source, control valves (7,8,9) which control the actuators on the basis of operations by an operating unit, a common bleed-off valve (15) which returns excess oil to a tank via an unload passage on the basis of the operations by the operating unit, and a control unit (17) which controls the common bleed-off valve. The common bleed-off valve (15) is capable of setting a position for closing the unload passage when the common bleed-off valve is in a non-operating state. The control valves (7,8,9) have center bypass passages which function as individual bleed-off passages which open when the control valves are in neutral states. Opening characteristics of the control valves are set such that the center bypass passages are closed in initial stroke periods in which the control valves move toward operating positions.
摘要:
A hydraulic control system for a working machine according to the present invention includes a regulator control valve for controlling an operation of a pump regulator and a controller for sending a control signal for changing a discharge quantity of the pump to the regulator control valve in accordance with an operation amount of an operating means. On the basis of the control signal, a secondary pressure in the regulator control valve is fed to the pump regulator. This system further includes a fail-safe valve disposed in a control line joining the pump regulator and the regulator control valve. The fail-safe valve has an ordinary position for sending the secondary pressure to the pump regulator and a fail-safe position for sending an oil pressure from a path other than the regulator control valve to the pump regulator in such a manner that a predetermined discharge amount is ensured. The fail-safe valve is configured so as to switch from the ordinary position to the fail-safe position in accordance with a failure signal indicative of failure in the regulator control valve. According to this, while adopting an electronic control system for the pump, it is possible to continue a work even in the failed condition of the system.
摘要:
A first group (G1) is supplied with hydraulic power from a first hydraulic pump (7). In the first group (G1), an arm control valve (12) is disposed at the most downstream position. A throttle (20) is provided at the entrance of the arm control valve. Thus, a circuit is configured to give priority to boom raising or bucket excavation. During a combined operation, according to the operation amount of boom pulling or bucket excavation, a controller (35) decreases the upper limit of the discharge amount of the first hydraulic pump (7) determined by the operation amount of arm pulling and increases the recycling rate of oil to the expansion side of an arm cylinder (4).