1. TSM363 Fluid Power Systems Cylinders Tony Grift
Dept. of Agricultural & Biological Engineering University of Illinois

2. Units, Pumps, Pressure Relief Valve Cylinders
Agenda
Units, Pumps, Pressure Relief Valve
Cylinders
Double acting/ Single acting
Single rod, Double rod
Cylinder construction
Pressure, Flow, Work and Power in cylinders
Cylinder implementations

3. Hydraulic Units (SI)
Pascal
Newton
Watt

4. Control can take place in various ways
Control can take place in various ways. Power is pressure times flow rate
Pressure control
Pressure relief valve
Pressure reducing valve (regulator)
Pressure compensation: Only provide the pressure needed to move the load(s). In idle reduce energy loss by providing a open center condition
Pressure compensated pump. Make the pressure independent of the flow required to move the load at a preset speed. Deal with multiple cylinders that need to move simultaneously
Flow control
Throttle (needle valve, very crude, Orifice equation applies)
Pressure compensated Flow Control Valve: Assure a preset flow rate independent of the pressure drop across the valve
Pressure and Flow control
Load sensing systems: combine pressure and flow control to reduce energy losses

5. Video 9: Hydraulic actuators (6:58)
Cylinders convert hydraulic energy into linear motion
Motors generate rotary motion
Single acting cylinder: One working port
Can do work in only one direction (extension)
External force retracts the cylinder
No perfect seal, over time oil passes on to unpressurized side: need for drain
Good for high load single lift (scissor platform)
Return stroke through gravity or spring return
Plunger (ram) cylinders: Cap end only, very powerful and stiff
Double acting cylinder: Two working ports
Pressure advances and retracts the cylinder: push and pull
Cylinder retracts faster than it extends due to different areas of cap end and rod end side

6. Video 9: Hydraulic actuators (6:58) cont.
Example: ratio of cap and rod end side area is 2:1.
Assume
During extension rod end pressure =0
During retraction cap end pressure =0

7. Video 9: Hydraulic actuators (6:58) cont.
Example: ratio of cap and rod end side area is 2:1.
Linear Power:

8. Hydraulic Cylinder

9. Cylinder construction

10. Tie rod ( keeps cylinder assembly together )
Rod end head ( mounting point )
Rod end port ( fluid entrance/exit point )
Piston seals ( dynamic, seals cap end from rod end pressure)
Cap end head ( mounting point)
Cap end port ( fluid entrance/exit point )
Rod bearing ( lateral support of the rod )
Rod wiper ( keeps dirt out )
Rod seal (dynamic, seals fluid from environment )
Barrel ( cylinder )
Piston rod ( mechanical force output )
Piston ( pressure to force converter )
Static seal ( seals fluid from environment )

11. Cylinders are perfect for linear motion
Single rod (most common)
Dual rod (power steering)

12. Telescopic cylinder

13. Basic Circuit with Double Acting Cylinder
Pressure
gage
Actuator
Overload
Protection
Electric Motor
Reservoir
Pump

14. Question: Can the cylinder be moved ?
Double acting, differential area
Fluid is incompressible
Rod and cap end connected
Check in FluidSim

15. Hydraulic Work (rod end pressure = 0)

16. Differential area cylinder: Flow and displacement

17. Differential area cylinder: Force equilibrium

18. Differential area cylinder: Work

19. Differential area cylinder: Power

20. Dual rod cylinder: Power

21. Power if (as in motors and pumps)

22. Question: Will the cylinder extend ?
Check in FluidSim

23. Video 5: Pressure transmission (0:53)
Pressure intensification in hydraulic systems:
Differential area cylinders cause this effect
Max pressure in the system is NOT PRV setting !
Check in FluidSim

24. Question in ‘Customary Units’
Given
PRV Setting 15 MPa
pump displacement of cm3/rev
the speed of the pump is 1800 rpm
Required
Torque needed to drive the pump
Power needed to drive the pump
Neglect friction

25. Answer in ‘Customary Units’

26. Question in ‘Customary Units’
Given
PRV Setting
pump displacement of
the speed of the pump
Required
Torque needed to drive the pump
Power needed to drive the pump .
Neglect friction

27. Answer in SI Units

28. TSM363 Fluid Power Systems Cylinders The End
Dept. of Agricultural & Biological Engineering University of Illinois