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

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

Hydraulic Units (SI) Pascal Newton Watt

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

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

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

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

Hydraulic Cylinder

Cylinder construction

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 )

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

Telescopic cylinder

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

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

Hydraulic Work (rod end pressure = 0)

Differential area cylinder: Flow and displacement

Differential area cylinder: Force equilibrium

Differential area cylinder: Work

Differential area cylinder: Power

Dual rod cylinder: Power

Power if (as in motors and pumps)

Question: Will the cylinder extend ? Check in FluidSim

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

Question in ‘Customary Units’ Given PRV Setting 15 MPa pump displacement of 10.54 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

Answer in ‘Customary Units’

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

Answer in SI Units

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