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
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University of Illinois at Urbana-Champaign
ARG©2002
4/18/2002 1/34
Hydraulic Components: An
Introduction
Hydraulic Components: An
IntroductionDon Carter
Team Partner: Rong ZhangAdvisor: Prof. Andrew AlleyneProject Sponsor: Caterpillar
Don CarterTeam Partner: Rong Zhang
Advisor: Prof. Andrew AlleyneProject Sponsor: Caterpillar
University of Illinois at Urbana-Champaign
ARG©2002
4/18/2002 2/34
IntroductionIntroduction
ApplicationsWhy hydraulics?PumpsValvesActuatorsHoses and Hydraulic OilEVPSConclusion
ApplicationsWhy hydraulics?PumpsValvesActuatorsHoses and Hydraulic OilEVPSConclusion
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ApplicationsApplications
Hydraulic pressesAutomobile applicationsMotion control of airplanesCivil engineering applicationsAgricultural machineryIndustrial roboticsEarthmoving machinery!
Hydraulic pressesAutomobile applicationsMotion control of airplanesCivil engineering applicationsAgricultural machineryIndustrial roboticsEarthmoving machinery!
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Advantages of HydraulicsAdvantages of Hydraulics
Versatility in designNot constrained by mechanical linkagesSimply 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
Versatility in designNot constrained by mechanical linkagesSimply 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
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Advantages of HydraulicsAdvantages of Hydraulics
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DisadvantagesDisadvantages
Can be ‘messy’; LEAKAGENot 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?
Can be ‘messy’; LEAKAGENot 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?
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Hydraulic ComponentsHydraulic Components
PumpsFixed Displacement Variable Displacement
ValvesFlow control Pressure relief
ActuatorsCylindersMotors
PumpsFixed Displacement Variable Displacement
ValvesFlow control Pressure relief
ActuatorsCylindersMotors
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Hydraulic ComponentsHydraulic Components
HosesOther
ReservoirsFiltersHeat ExchangersAccumulators
• Stores hydraulic pressure• Absorb shock, maintain pressure, develop
system flow
HosesOther
ReservoirsFiltersHeat ExchangersAccumulators
• Stores hydraulic pressure• Absorb shock, maintain pressure, develop
system flow
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Hydraulic SymbolsHydraulic Symbols
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Pumps Pumps
Fixed DisplacementVaneLobedAdvantages: cheap and simple!No control over amount of flow output for
given rotational speed Variable Displacement
Piston-typeAdvantages include ability to adjust flow
output by varying swash plate angleExpensive and mechanically complex
Fixed DisplacementVaneLobedAdvantages: cheap and simple!No control over amount of flow output for
given rotational speed Variable Displacement
Piston-typeAdvantages include ability to adjust flow
output by varying swash plate angleExpensive and mechanically complex
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Vane PumpVane Pump
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Lobed PumpLobed Pump
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Variable Displacement Axial Piston Pump
Variable Displacement Axial Piston Pump
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Hydraulic ValvesHydraulic Valves
Responsible for controlling and directing flowDirectional 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)
Responsible for controlling and directing flowDirectional 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)
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Directional Control ValvesDirectional Control Valves
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Proportional Flow Control Valves
Proportional Flow Control Valves
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Pressure Relief ValvesPressure Relief Valves
Found in all hydraulic circuitsNormally closedCan 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
Found in all hydraulic circuitsNormally closedCan 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
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Pressure Relief ValvesPressure Relief Valves
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Check ValvesCheck Valves
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Hydraulic CylindersHydraulic Cylinders
Provides linear actuationSingle vs. Double actingSingle vs. Double endedComplexity varies, but basic
operation and principles the sameBasic design terminology
Stroke lengthPiston diameterPiston rod diameter
Provides linear actuationSingle vs. Double actingSingle vs. Double endedComplexity varies, but basic
operation and principles the sameBasic design terminology
Stroke lengthPiston diameterPiston rod diameter
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Hydraulic CylindersHydraulic Cylinders
Can generate very large forcesContamination of hydraulic oil and
proper maintenance directly affect the life of a hydraulic cylinder
Can generate very large forcesContamination of hydraulic oil and
proper maintenance directly affect the life of a hydraulic cylinder
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Hydraulic CylindersHydraulic Cylinders
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Hydraulic MotorsHydraulic Motors
Provides rotary actuation/torqueCan be thought of as a pump
working in reverseMotor ratings
DisplacementTorque capacitySpeedMax pressure
Provides rotary actuation/torqueCan be thought of as a pump
working in reverseMotor ratings
DisplacementTorque capacitySpeedMax pressure
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Hydraulic MotorsHydraulic Motors
Constant displacementVane (can be variable)GearPiston
Variable displacementAxial piston
High Speed, Low Torque (HSLT)Low Speed, High Torque (LSHT)
Constant displacementVane (can be variable)GearPiston
Variable displacementAxial piston
High Speed, Low Torque (HSLT)Low Speed, High Torque (LSHT)
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Hydraulic MotorsHydraulic Motors
Advantages over electric motorsInstant reversal of rotation of motor’s
shaftCan be stalled without damage Torque control through operating speedDynamic braking is easily accomplishedWeight to horsepower ratio of .5 lb/hp
compared to 10lb/hp for electric motors
Advantages over electric motorsInstant reversal of rotation of motor’s
shaftCan be stalled without damage Torque control through operating speedDynamic braking is easily accomplishedWeight to horsepower ratio of .5 lb/hp
compared to 10lb/hp for electric motors
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Gear MotorsGear Motors
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Radial Piston MotorRadial Piston Motor
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HosesHoses
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
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
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Hydraulic OilHydraulic Oil
Responsible for transmitting hydraulic power from source to actuator
Dissipates heat!Lubricates partsSeals clearancesBulk modulus, viscosity, and density
are the most important propertiesPetroleum based most common
Responsible for transmitting hydraulic power from source to actuator
Dissipates heat!Lubricates partsSeals clearancesBulk modulus, viscosity, and density
are the most important propertiesPetroleum based most common
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EVPS HydraulicsEVPS Hydraulics
DriveDrive
Hydr.PumpHydr.Pump
SteeringSteering
Implement
Implement EngineEngine54
3
2 1
ControlControl
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EVPS HydraulicsEVPS 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
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ReferencesReferences
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
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
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ConclusionsConclusions
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
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
University of Illinois at Urbana-Champaign
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4/18/2002 34/34
University of Illinois at Urbana-Champaign
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Bent Axis Piston PumpBent Axis Piston Pump
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