Directional control valves (DCVs) in hydraulics
Directional control valves (DCVs) in hydraulics control the direction of the oil flow and thus, for example, the direction of movement and the start/stop of an actuator, such as a cylinder or hydraulic motor. The function and connections of the valve can be seen from the circuit symbol. Here you see a complete hydraulic symbol showing a closed-center, 4-way, 3-position, spring-centered solenoid valve with manual override:
In hydraulics, there are far more center positions for directional control valves than in pneumatics. In the circuit example shown here, the pump is switched on. How does the cylinder or the circuit behave with a different directional control valve or with a different center?
The directional valves are shown in accordance with ISO 1219. The following is an overview of the most frequently used center-positions using a 4/3-way valve as an example. These center positions of course can also be adapted for 3/3-way valves (e.g. for single-acting cylinders).