An industrial machinery, such as a forklift or a wheel loader, includes: a steering actuator configured to change a direction of the industrial machinery; and a loading-line actuator configured to move a fork, a bucket, and the like. A hydraulic driving system is connected to the steering actuator and the loading-line actuator and supplies operating oil to the steering actuator and the loading-line actuator to drive the steering actuator and the loading-line actuator. Known as one example of the hydraulic driving system is a hydraulic circuit device of PTL 1. The hydraulic circuit device includes two fixed displacement hydraulic pumps. One of the hydraulic pumps is connected to a steering cylinder through a steering-side passage, and a switching valve configured to control the flow rate of the operating oil flowing to the steering cylinder is interposed on the steering-side passage. The other of the hydraulic pumps is connected to a loading-line actuator through a loading-side passage, and a loading operating valve configured to control the flow rate of the operating oil flowing to the loading-line actuator is interposed on the loading-side passage. Further, a priority flow control valve is interposed on the steering-side passage so as to be located upstream of the switching valve. The priority flow control valve is configured to supply, to the loading-side passage, excess operating oil generated when the discharge amount of the pump exceeds the flow rate of the operating oil to be supplied to the steering actuator.
USPTO Backgrounds
USPTO Backgrounds