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

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Presentation on theme: "1 TSM363 Fluid Power Systems Pumps and Motors Tony Grift Dept. of Agricultural & Biological Engineering University of Illinois."— Presentation transcript:

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

2 2 Agenda Units, Pumps, Pressure Relief Valve Pressure, Flow, Torque and Power in pump/motors Volumetric and Torque efficiency of pump/motors Pump implementations

3 3 Hydraulic Units (SI) Pascal Newton Watt

4 4 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 5 Choice of pump depends on these factors Application Max and working Pressure and Flow rate requirements Constant rate / Variable rate Pump efficiency Leakage Noise level Contamination sensitivity Price

6 6 Pump ‘family tree’

7 7 Video 8: Power units (3:26) Power supply unit Converts Mechanical energy into hydraulic energy Hydraulic Fluid is conditioned (cooled, cleaned) Components Drive motor Safety valve Oil reservoir Pump External Gear pump function (constant delivery) Where teeth unmesh, volume increases, oil enters Where teeth mesh, volume decreases, oil leaves Pressure only builds when there is a resistance (load) Safety valve needed to prevent failure when cylinder stalls Pressure Relief Valve diverts flow back to tank when cylinders are stalled Reservoir Cools oil Cleans oil from suspended particles, water and air which takes time (Capacity) Filters trap impurities 70% of all malfunctions are due to impurities

8 8 In case of a motor shaft, the Work can be found by multiplying a force through a distance. Suppose we assume a force at a distance. The total work per radian of the shaft is now equal to Mechanical Torque in a pump/motor

9 9 Mechanical Power in a pump/motor The power is now equal to this value divided by the time per radian. If the shaft is turning at it takes seconds per radian. Since for Power we have to divide the Work by time, this leads to:

10 10 Hydraulic Power in pump/motor ( )

11 11 Pump/Motor flow is proportional to the speed of rotation and the displacement per revolution Pump displacement is a volume per angular displacement (radian). Assuming the volumetric efficiency is 1.0 (no leakage) More realistic, with Volumetric Efficiency (why in numerator?)

12 12 Torque Required to drive a pump is proportional to Pressure More realistic, with Torque Efficiency (why in the denominator?) (No losses here)

13 13 Power Efficiency of Pumps From before: And Power Efficiency: Without loss Efficiencies

14 14 Data sheet Data sheet Eaton MHT vane pump

15 15 Types of Pumps and Motors External Gear Internal Gear Vane Axial Piston Radial Piston

16 16 External Gear pump Poorly sealing Low flow rates Low pressures Fixed displacement Low cost

17 17 Internal Gear pump Poorly sealing Low flow rates Medium pressures Fixed displacement Medium cost

18 18 Vane pump Medium sealing Higher pressures Inexpensive Fixed or variable flow rate

19 19 Axial piston pump with swash plate. In this case the swash plate angle is variable, which results in a variable delivery pump Excellent sealing High pressures Relatively simple design Variable flow rate No need for valves Expensive

20 20 Axial piston pump with swash plate. In this case the swash plate angle is constant, which results in a constant delivery pump Here fixed flow rate

21 21 Radial piston pump with variable rate through changing eccentricity between shaft and ‘pintle’ Excellent sealing High pressures Relatively expensive Variable flow rate Valves are needed Complex design

22 22 Radial piston pump with variable rate through changing eccentricity between shaft and ‘pintle’ Excellent sealing High pressures Relatively expensive Variable flow rate

23 23 External Gear Fixed Displacement

24 24 Pump ‘family tree’

25 25 TSM363 Fluid Power Systems TSM363 Fluid Power Systems Pumps and Motors The End Dept. of Agricultural & Biological Engineering University of Illinois


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