basic hydrostatic (closed circuit)
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© Blue Graphics Concept Sauer-Danfoss© Blue Graphics Concept Sauer-Danfoss
Basic Hydrostatic (closed circuit)
Introduction, July 2012
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What do you know about a closed circuit?
Components?Applications?
Advantage?
Only one fact per participant
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Main Menu
Basic Hydrostatic (closed circuit)
Exposition closed circuit
Definition Pump and
MotorDiesel Engine Advantages Comparison to
torque converter
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Main Menu
Basic Hydrostatic (closed circuit)
Exposition closed circuit
Definition Pump and
MotorDiesel Engine Advantages Comparison to
torque converter
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Exposition of the closed circuit
Production
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Pump and motor form a „Hydrostatic Transmission“
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Main Menu
Basic Hydrostatic (closed circuit)
Exposition closed circuit
Definition Pump and
MotorDiesel Engine Advantages Comparison to
torque converter
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Definition: Pump/Motor
Production
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• PumpTransport of fluids and gases. At the same time transforming mechanical power into hydraulic power.
• MotorPerforms mechanical work by transforming hydraulic power into mechanical power.
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Main Menu
Basic Hydrostatic (closed circuit)
Exposition closed circuit
Definition Pump and
Motor
Diesel Engine
Advantages Comparison to torque
converter
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Diesel Engine in Mobile Work Machines
Production
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Attributes:• Steady engine speed at partial load condition• Maximum engine power at maximum load condition• Increasing engine speed increases power due to roughly
constant engine torque • Direct drive vehicles (w/o transmission) have low
acceleration • It‘s recommended to use a transmission between the
engine and final drive • In this case it is recommended to use:
„Hydrostatic Transmission“
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Main Menu
Basic Hydrostatic (closed circuit)
Exposition closed circuit
Definition Pump and
MotorDiesel Engine Advantages Comparison to
torque converter
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Advantages of Hydrostatic Transmission MENU
Flexibility
High power density
Hydrostatic Braking
Continues variable
transmission
Hydrostatic Transmission
Variable and constant speed
of engine
Adjustable/ Programmable
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Advantages of Hydrostatic Transmission Flexibility
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Flexibility
High power density
Hydrostatic Braking
Continues variable
transmission
Hydrostatic Transmission
Variable and constant speed
of engine
Adjustable/ Programmable
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Advantages of Hydrostatic Transmission Flexibility
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• Independent arrangement of pump(s) and motor(s)
• Power transfer via hoses from pump to motor
• Independent arrangement of the Engine
• Pump arrangement as stacks or assembled to splitter box
• Wide transmission ratio
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Advantages of Hydrostatic Transmission Continues Variable Transmission
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High power density
Hydrostatic Braking Hydrostatic
Transmission
Variable and constant speed
of engine
Continues variable
transmission
Flexibility
Adjustable/ Programmable
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Advantages of Hydrostatic Transmission Continues Variable Transmission
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• Continuously variable speed w/o loss of traction • No clutch is required to change the vehicle direction from
forward to reverse
Mechanical transmission Hydrostatic transmission
AB
Speed [km/h]
Trac
t ive
Forc
e [N
]
Pump Ratio Motor Ratio
Installed Engine Power
- source 1 - - source 1 -
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Advantages of Hydrostatic Transmission Hydrostatic Braking
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High power density
Continues variable
transmission
Hydrostatic Transmission
Variable and constant speed
of engineHydrostatic
Braking
Flexibility
Adjustable/ Programmable
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Advantages of Hydrostatic Transmission Hydrostatic Braking
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• The engine braking power is the capability of the engine to absorb the braking power of the hydrostatic transmission
• Vehicle braking capability depends on engine braking power• Lower level of engine braking capability for new tier IV diesel
engines
pumpmotor
acceleration
principle of operation:
pump motor
deceleration/braking
principle of operation:
- source 2 -
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Advantages of Hydrostatic Transmission Hydrostatic Braking
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• If the vehicle braking power requirement exceeds the engine braking power capability the engine can overspeed and could be damaged
motorpump
deceleration/braking
principle of operation:
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Advantages of Hydrostatic Transmission High Power Density
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Adjustable/ Programmable
Hydrostatic Braking
Continues variable
transmission
Hydrostatic Transmission
Variable and constant speed
of engineFlexibility
High power density
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Advantages of Hydrostatic Transmission High Power Density
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• Power density is the relationship between power and package size
• Engine (here 90 kW) has lower power density than the hydrostatic pump (here H1P089)
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Advantages of Hydrostatic Transmission Further Details
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Hydrostatic Braking
Continues variable
transmission
Hydrostatic Transmission
Flexibility
Adjustable/ Programmable
High power density
Variable and constant speed
of engine
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Main Menu
Basic Hydrostatic (closed circuit)
Exposition closed circuit
Definition Pump and
MotorDiesel Engine Advantages Comparison
to torque converter
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Comparison HST vs. Torque ConverterTorque Converter construction
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- source 2 - - source 2 -
Turbine Impeller Turbine Stator Impeller
Stator
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Comparison HST vs. Torque ConverterOverview
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Description Hydrostatic Torque Converter
Drive Train Design / Layout Flexible Fixed, in line Programmability of Drive Behavior Programmable Fixed Traction Control Yes Suboptimal Shifting Drive Direction Without wear With wear Blocked Drive Train No Problem Overheating Variation of Transmission Ratio Without wear With wear Braking Capability Yes No Power Out Distribution Programmable Fixed Drop of Engine Speed (lug, stall) 100% traction force 70% traction force Hill-Hold-Function w/ engine off 100% traction force NONE Fast driving capability With additional gear included
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Comparison HST vs. Torque ConverterMENU
HST & AC Torque ConverterDrive Train Design flexible (+) fixed, in-line
package (-)
Hoses allow flexible arrangement of pump and motor
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Comparison HST vs. Torque ConverterMENU
HST & AC Torque ConverterDriving Behavior programmable (+) fixed (-)
• Adjustable drive curve for Control for example the ACII Control for the Pump with different programmable driving curves
Swas
hpl
ate
angl
e
01
3 45
6
2
7
Engine rpm
Curr
ent
mA
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Comparison HST vs. Torque ConverterMENU
HST & AC Torque ConverterTraction Control yes (+) limited (-)
• Tractive force of Torque Converter is depending on differential speed
• Tractive force of HST is controllable
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Comparison HST vs. Torque ConverterMENU
HST & AC Torque ConverterShifting Drive Direction
w/o clutch (+) w/ clutch (-)
• Shift of the Drive Direction with HST is possible by shift stroke of pump to opposite side
• Shift of the Drive Direction with Torque Converter only by shift a gear and use a clutch
• Clutch is a component with wear
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Comparison HST vs. Torque ConverterMENU
HST & AC Torque ConverterBlocked Drive Train no problem (+) overheating (-)
• Blocked Drive Train is similar to drive against a wall, drive train speed at working engine
• HST will destroke the pump to zero degree*• Torque Converter will be overheated by a large differential
speed
*with Pressure Limiter
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Comparison HST vs. Torque ConverterMENU
HST & AC Torque ConverterTransmission Ratio continues (+) mech. shifting gears (-)
• Torque Converter requires a mechanical gear shift transmission to reach the required transmission ratio
• HST has a large transmission ratio
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Comparison HST vs. Torque ConverterMENU
HST & AC Torque ConverterBraking capability yes (+) limited (-)Power output Distribution forpropel and auxiliary
programmable (+) fixed (-)
• HST is programmable to react on drop in diesel engine speed by drive of auxiliary machines
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Comparison HST vs. Torque ConverterMENU
HST & AC Torque ConverterDrop of Engine Speed
100% traction force (+)
70% traction force (-)
• Torque Converter is direct depending by drop of engine speed
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Comparison HST vs. Torque ConverterMENU
HST & AC Torque ConverterFast driving capability
With additional gear (+)
Included (+)
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The EndMENU
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Overview Literature SourcesMENU
- Source 1 - Ölhydraulik – Handbuch für die hydrostatisch Leistungsübertragung in der Fluidtechnik; Findeisen,
D.; Springer - Source 2 - Hydrodynamische Antriebskomponenten in
Forstschleppern; Jörg Hittenbeck; IFA- Source 3 - http://de.wikipedia.org/wiki/Drehmomentwandler- Source 4 - http://de.luk.de
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