This module demonstrates how shock can be generated in a system due to acceleration forces in a cylinder circuit and how this can be eliminated using direct operating and pilot operated proportional type directional valves.
Operate this hydraulic proportional valve simulation
Suggested exercises and observations
1. Select drop-down menu 1 the 'Direct acting open/close spool'. Click the question mark (?) and sound button for additional advice.
♦ Observe how the valve switches instantly from open to shut.
♦ Observe how the cylinder shudders as the direction instantly changes from extend to retract etc.
2. Select drop-down menu 2 the 'Pilot operated directional valve'. Or press the forward arrow. This is the same valve but with an instant pilot operation rather than a direct solenoid.
♦ Observe how the valve still switches instantly from open to shut.
♦ Observe how the cylinder still shudders as the direction instantly changes from extend to retract etc.
3. Select drop-down menu 3 the 'Ramp start with orifice + prop. spool'. Or press the forward arrow. This valve now has a small orifice in the pilot line to slow the valve movement and proportional notches in spool so that it opens gradually, not instantly.
♦ Observe how the valve moves slowly from open to shut.
♦ Observe how the cylinder accelerates slowly and smoothly with no judder.
4. Select drop-down menu 4 'Direct-acting proportional solenoid'. Or press the forward arrow. This valve has a proportional spool and its position is controlled by the voltage on the solenoid.
♦ Operate the solenoid voltage slidebar through positive to negative values.
♦ Observe how the spool moves proportionally to the solenoid voltage.
♦ Observe how the cylinder moves proportionally to the spool position.
5. Select drop-down menu 5 'Pilot pressure operated prop. valve'. Or press the forward arrow. The pilot valve is now switched by load limit switches but the valve position and cylinder speed is still controlled by the slidebar.
♦ Observe how cylinder speed changes in the graph.
♦ Adjust the load mass and observe how the speeds and stopping position change.
♦ Adjust the pilot pressure setting and observe how the speeds and stopping position change.
Experiment 1: Proportional valves are used to provide both smooth operation and speed control.
Question 1: How does a proportional directional valve differ from a standard directional valve?
Experiment 2: Proportional valves can be partially opened to control the flow restriction area size.
Question 2: Does part opening area control the speed or acceleration of the cylinder?
Experiment 3: Proportional valves can control the speed at which they open.
Question 3: Does opening speed control the speed or acceleration of the cylinder?