Servo valves have ten important functions, as follows:
1. Servo valve and proportional valve are by adjusting the input electrical signal analog quantity, so as to infinitely adjust the output of hydraulic valve, such as pressure, flow, direction.
2. (The servo valve also has a pulse width modulation input method).
3. But the structure of these two valves is completely different.
4. The servo valve relies on adjusting the electrical signal to control the action of the torque motor, deflect the armature, drive the front valve action, and the control oil of the front valve enters the main valve and pushes the valve core action.
5. The proportional valve is to adjust the electrical signal, so that the armature produces displacement, drives the pilot valve core to operate, and the control oil generated then pushes the main valve core.
6. The structure of the servo valve is very complex, the front valve has a nozzle baffle type, a jet pipe type, and the main spool also has displacement feedback.
7. The structure of the proportional valve is much simpler, and the pilot valve is a throttling type spool, which can also be equipped with spool displacement feedback, but it is not accurate.
8. The servo valve is too fine, sensitive to the pollution of hydraulic oil, the size of the main valve core is small, not suitable for high-pressure and large-flow systems, but the control is more accurate, and can do redundancy control.
9. The proportional valve is relatively simple, the pilot valve can produce 2 liters / minute of high-pressure oil, the flow of the main spool can reach more than 500 liters, but the hydraulic inertia is large, not suitable for high frequency, and the output flow is not so accurate.
10. The price of servo valve is very high, which is about 7-10 times of the proportional valve with the same pressure and flow.
The difference between servo valves and proportional valves:
generally speaking, it seems that servo systems are closed-loop control, and proportionality is mostly used for open-loop control; Secondly, there are many types of proportional valves, including proportional pressure, flow control valves, etc., and the control is more flexible than servo drugs. From their internal structure, servo valves are mostly zero-covering, proportional valves have a certain dead zone, and the control accuracy is low.