The open center system means that when the valve core of the reversing valve is in the middle position, the oil discharge of the hydraulic pump is directly returned to the tank through the middle position of the reversing valve.
When the valve core is reversed, the median oil path is gradually closed, and the pressure of the working oil path increases gradually until the load pressure is overcome and the actuator action is made. It overcomes the load pressure by the pressure generated by the return throttle, so the speed regulation characteristic is affected by the load pressure and the hydraulic pump flow rate.
When the load is light, the operation performance is better and the speed regulation range is large. However, with the increase of load, the speed regulation range becomes smaller and the speed regulation characteristic curve becomes steeper, which leads to a slight change in the opening of the control valve, the change of flow rate is very large, and the speed regulation stability of the valve becomes worse. When a hydraulic pump supplies oil to multiple actuators, the flow rate always flows to the light load actuators, which affects the stability of the composite action.