hydraulics

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hydraulics

  1. 1. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 1/34 Hydraulic Components: An Introduction Don Carter Team Partner: Rong Zhang Advisor: Prof. Andrew Alleyne Project Sponsor: Caterpillar
  2. 2. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 2/34 Introduction Applications Why hydraulics? Pumps Valves Actuators Hoses and Hydraulic Oil EVPS Conclusion
  3. 3. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 3/34 Applications Hydraulic presses Automobile applications Motion control of airplanes Civil engineering applications Agricultural machinery Industrial robotics Earthmoving machinery!
  4. 4. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 4/34 Advantages of Hydraulics Versatility in design Not constrained by mechanical linkages Simply route the hoses Actuator speed can be controlled via valves or pump displacement Reversibility of actuators without damage Overload protection High power density; High power/small size Actuators can be stalled
  5. 5. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 5/34 Advantages of Hydraulics
  6. 6. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 6/34 Disadvantages Can be ‘messy’; LEAKAGE Not as much of an issue as it used to be Hydraulic oil is not exactly environmentally friendly; must be replaced; can also be flammable Control of these inherently nonlinear systems can be challenging Noisy systems Others?
  7. 7. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 7/34 Hydraulic Components Pumps Fixed Displacement Variable Displacement Valves Flow control Pressure relief Actuators Cylinders Motors
  8. 8. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 8/34 Hydraulic Components Hoses Other Reservoirs Filters Heat Exchangers Accumulators • Stores hydraulic pressure • Absorb shock, maintain pressure, develop system flow
  9. 9. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 9/34 Hydraulic Symbols
  10. 10. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 10/34 Pumps Fixed Displacement Vane Lobed Advantages: cheap and simple! No control over amount of flow output for given rotational speed Variable Displacement Piston-type Advantages include ability to adjust flow output by varying swash plate angle Expensive and mechanically complex
  11. 11. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 11/34 Vane Pump
  12. 12. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 12/34 Lobed Pump
  13. 13. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 13/34 Variable Displacement Axial Piston Pump
  14. 14. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 14/34 Hydraulic Valves Responsible for controlling and directing flow Directional flow control valves • Spool and internal passages dictate flow paths Proportional flow control valves • Variable orifice • Gate, globe, and needle valves Check valves (similar to a diode in an electrical circuit)
  15. 15. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 15/34 Directional Control Valves
  16. 16. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 16/34 Proportional Flow Control Valves
  17. 17. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 17/34 Pressure Relief Valves Found in all hydraulic circuits Normally closed Can be pilot operated (i.e. Spool is biased by both spring and fluid pressure…less override) Provides protection against exceeding system pressure rating which can damage components
  18. 18. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 18/34 Pressure Relief Valves
  19. 19. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 19/34 Check Valves
  20. 20. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 20/34 Hydraulic Cylinders Provides linear actuation Single vs. Double acting Single vs. Double ended Complexity varies, but basic operation and principles the same Basic design terminology Stroke length Piston diameter Piston rod diameter
  21. 21. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 21/34 Hydraulic Cylinders Can generate very large forces Contamination of hydraulic oil and proper maintenance directly affect the life of a hydraulic cylinder
  22. 22. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 22/34 Hydraulic Cylinders
  23. 23. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 23/34 Hydraulic Motors Provides rotary actuation/torque Can be thought of as a pump working in reverse Motor ratings Displacement Torque capacity Speed Max pressure
  24. 24. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 24/34 Hydraulic Motors Constant displacement Vane (can be variable) Gear Piston Variable displacement Axial piston High Speed, Low Torque (HSLT) Low Speed, High Torque (LSHT)
  25. 25. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 25/34 Hydraulic Motors Advantages over electric motors Instant reversal of rotation of motor’s shaft Can be stalled without damage Torque control through operating speed Dynamic braking is easily accomplished Weight to horsepower ratio of .5 lb/hp compared to 10lb/hp for electric motors
  26. 26. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 26/34 Gear Motors
  27. 27. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 27/34 Radial Piston Motor
  28. 28. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 28/34 Hoses Used to connect the various components Analogous to wires in an electrical circuit Compliance of the hose can affect the effective bulk modulus Modeled as a fixed volume
  29. 29. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 29/34 Hydraulic Oil Responsible for transmitting hydraulic power from source to actuator Dissipates heat! Lubricates parts Seals clearances Bulk modulus, viscosity, and density are the most important properties Petroleum based most common
  30. 30. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 30/34 EVPS Hydraulics DriveDrive Hydr. Pump Hydr. Pump SteeringSteering Implement Implement EngineEngine5 4 3 2 1 ControlControl
  31. 31. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 31/34 EVPS Hydraulics MOTOR LEGEND high pressure oil low pressure oil control signal sensor signal LEGEND high pressure oil low pressure oil control signal sensor signal LOAD UNIT #1 ) ( LOAD UNIT #2 ) ( LOAD UNIT #3 ) ( Reservoir 1 Reservoir 2 Reservoir 3 3000psi Main Reservoir
  32. 32. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 32/34 References Merritt H.E. Hydraulic Control Systems. John Wiley & Sons, NY. 1967. Vickers. Industrial Hydraulics Manual. Copy in ARG! Watton. Fluid Power Systems. Prentice Hall. 1989
  33. 33. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 33/34 Conclusions Hydraulic systems offer versatility and high power density as compared to other types of power transmission Relatively small number of components; pumps, valves, actuators…that’s basically it! EVPS has relatively simple hydraulic setup similar to that of an actual piece of earthmoving machinery
  34. 34. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 34/34
  35. 35. University of Illinois at Urbana-Champaign ARG©2002 4/18/2002 35/34 Bent Axis Piston Pump

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