Basic Hydrostatic (closed circuit)

© 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


Exposition closed circuit

Definition Pump and

MotorDiesel Engine Advantages Comparison to

torque converter

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Main Menu



Definition Pump and


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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Definition Pump and


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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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



Definition Pump and


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



of engine


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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


of engine

Continues variable

transmission

Flexibility


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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



of engineHydrostatic

Braking

Flexibility


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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


- source 2 -

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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


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Advantages of Hydrostatic Transmission High Power Density

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Hydrostatic Braking

Continues variable

transmission



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


Flexibility


High power density


of engine

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Main Menu



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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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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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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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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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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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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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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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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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

Documents

Basic Hydrostatic (closed circuit)