TSM 363 Fluid Power Systems

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TSM 363 Fluid Power Systems

• Hydrostatic Transmission

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Hydrostatic Transmission is popular in ORE
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Mechanical Drivetrain

• A mechanical drivetrain systemconsists of an
  engine, a clutch,a transmission, a universal
  drive-line, a differential, and the wheels.

• Transmission is used to increaseor decrease speed

• A differential is needed inmechanical
  drivetrain, becauseit allows the outside wheel
  torotate faster than in the insidewheel when
  the vehicle turns.

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Hydrostatic Transmission Drivetrain

• With a hydrostatic transmission, itconsists of
  an engine, a clutch,a hydrostatic transmission,
  a universal driveline, a differential, and the
  wheels.

• Change the displacement of thepump (or motor)
  can change the vehicle speed.

• HT improves maneuverability gt wide range of
  T/n ratio gt compacted, less mass inertia gt
  dynamic braking (inst. reverse) gt able to stall
  undamaged gt no interruption of power

• HT has lower efficiency

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Basic Concept of Hydrostatic Transmission
A hydrostatic transmission is simply a pump and
motor(s) connected in a circuit.
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Basic Types of HST
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Typical Closed-Circuit HST Configurations
(a) Fixed pump-fixed motor
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Typical Performance of VP-FM HST
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Typical Performance of FP-VM HST
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Typical Performance of VP-VM HST
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Typical HST Releasing Recharging
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Typical Controls of Closed-Circuit HSP
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Typical Open-Circuit HST Configurations
(a) Needle valve controlledfixed pump-fixed motor
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Typical E/H Controlled Open-Circuit HSP
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Typical HST Arrangement - 1
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Typical HST Arrangement - 2
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Typical HST Arrangement - 3
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Example Typical Calculations of HST
Suppose both the pump and the motor in a
hydrostatic transmission have disp. DM 1.925
in3/rev, and the volumetric efficiency are 0.90
for both the pump and motor. The pump is driven
by an engine at 2400 rpm, what is the motor speed?
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A Special HST Application
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Lecture Summary

• Discussed the basic concepts of HST
• Closed-circuit HST FP-FM VP-FM FP-VM VP-VM
• Open-circuit HST
• Applications of HST
• In-line design
• Sprit design
• V-controlled design
• Sprit-torque design