The flow control valve controls the flow by changing the opening area of the orifice, thereby controlling the movement speed of the actuator. The editor of Dalan Hydraulics in this article briefly introduces the classification and performance requirements of the flow valve in the hydraulic system.
1. Classification of flow control valves
Flow valves include throttle valve, one-way throttle valve, stroke throttle valve, speed control valve, stroke speed control valve, one-way speed control valve, overflow throttle valve, delay valve, diverter valve, collector valve, etc. There are many varieties, among which the throttle valve is the most basic flow valve, and most of the others are developed to overcome the shortcomings of a certain aspect of the throttle valve.
2. The basic performance requirements of the flow valve
1) Flow adjustment range Under the specified inlet and outlet pressure difference, the adjustment valve opening can change the range between the minimum stable flow and the maximum flow. The ratio of the maximum flow to the minimum stable flow is generally above 50.
2) The stiffness of the flow-pressure characteristic, that is, the output flow of the flow valve can be kept stable, and is not affected by external load changes. Expressed by speed rigidity T, the larger the speed rigidity T, the better, the speed rigidity of the speed control valve is better, and the speed rigidity of the throttle valve is poor.
3) Pressure loss The flow control valve is a throttling type resistance element, and there must be a certain pressure loss during operation. In order to avoid excessive power loss, the pressure loss when passing the rated flow is specified, which is generally below 0.4MPa and can be as high as 0.8MPa at high pressure.
4) The linearity of adjustment. When the handwheel is used for adjustment, the movement is light and the adjustment force is small. The rotation angle of the handwheel and the rate of change of the flow should be as uniform as possible, and the adjustment linearity should be good.
5) Internal leakage The leakage from the oil inlet cavity to the oil outlet cavity when the flow valve is closed will affect the minimum stable flow of the valve, so the internal leakage should be as small as possible.
6) The change of oil temperature during other work will affect the viscosity and change the flow rate. Therefore, thin-walled orifices that are not sensitive to oil temperature are often used.