8/10/2019 2.3 Differentials
http://slidepdf.com/reader/full/23-differentials 1/17
Analysis of Open and Torsen
DifferentialGroup Members:
Scott Anderson
Michael Bullard
Jason Yount
8/10/2019 2.3 Differentials
http://slidepdf.com/reader/full/23-differentials 2/17
Differential Overview
• When turning, the
inner and outer wheels
have arcs of differentturning radii
• Consequently, the
inner wheels travel
less distance than theouter wheels
8/10/2019 2.3 Differentials
http://slidepdf.com/reader/full/23-differentials 3/17
Differential Overview
• Because the turning paths
of the inner and outer
wheels are different, the
wheels on both axles need
to be able to spin
independently of each
other
• A differential is used toallow the wheels to spin at
different speeds
8/10/2019 2.3 Differentials
http://slidepdf.com/reader/full/23-differentials 4/17
Different Types of Differentials
• Open Differential
• Limited Slip
Differential (LSD) – Clutch LSD
– Viscous Coupling LSD
– Locking LSD
– Torsen LSD
8/10/2019 2.3 Differentials
http://slidepdf.com/reader/full/23-differentials 5/17
Schematic of an Open Differential
• The “Sun” gear and
“Ring” gear are
identical and supply power to the drive
axles.
• The planetary gears, or
spider gears allow theaxles to rotate at
different speeds.
8/10/2019 2.3 Differentials
http://slidepdf.com/reader/full/23-differentials 6/17
• The open Differential is a planetary gear
set. Therefore the following equation
applies
Open Differential
gear sunof velocityangular
gear ring of velocityangular
carrier planet of velocityangular
gear ring onteethof number N
gear sunonteethof number N
N
N
s
r
c
r
s
c s
cr
r
s
8/10/2019 2.3 Differentials
http://slidepdf.com/reader/full/23-differentials 7/17
Open Differential
• The number of teethon the ring gear andsun gear are equal andthe planetary gearformula is simplified
• The angular velocityof the differential isequal to the averageangular velocity of theaxles
2,1 sr
cr
s
c s
cr
r
s
therefore N
N
N
N
8/10/2019 2.3 Differentials
http://slidepdf.com/reader/full/23-differentials 8/17
Open Differential Problems
• As a result, if one
wheel has little
friction there is noresistance to its
rotation and slipping
occurs
• The slipping wheelwill spin twice as fast
as the differential Left rear tire
slipping on sandy
surface
8/10/2019 2.3 Differentials
http://slidepdf.com/reader/full/23-differentials 9/17
The Torsen Differential
• The Torsen
Differential is capable
of perfectdifferentiation
• The Torsen
Differential transfers
power to the wheelswith traction
Torque transferred to
wheel with traction
8/10/2019 2.3 Differentials
http://slidepdf.com/reader/full/23-differentials 10/17
How the Torsen Differential Works
• Power is transferred fromthe engine to thedifferential housingcausing the housing to
turn• Power flows from the
housing to the wormwheels attached to thehousing
• The worm wheels aremeshed with the wormgears attached to the axleswhich turns the axle with
the differential housing
8/10/2019 2.3 Differentials
http://slidepdf.com/reader/full/23-differentials 11/17
Differential Function
• When turning, the outer wheelturns at a high RPM withrespect to the differentialhousing
• Therefore, the outer wheel axleturns its worm gear and itsmating worm wheel
• The mating worm wheels aremeshed together by spur gears – Perfect Differentiation: as one
wheel increases speed theother wheel decreases speed proportionally
– Torque is maintained at bothwheels while cornering
8/10/2019 2.3 Differentials
http://slidepdf.com/reader/full/23-differentials 12/17
Traction Loss By One Wheel
• Spinning wheel turnsits worm gear whichturns its mating worm
wheel• Mating worm wheel
wants to turn oppositeworm wheel
• Opposite worm wheeltransfers power toopposite worm gear
8/10/2019 2.3 Differentials
http://slidepdf.com/reader/full/23-differentials 13/17
Traction Loss By One Wheel
• Opposite worm gear is
attached to the axle of
the wheel with traction – The slipping wheel
does not spin
– Torque is transferred to
the wheel with traction
8/10/2019 2.3 Differentials
http://slidepdf.com/reader/full/23-differentials 14/17
Torque Transfer
• The torque bias ratio
determines the amount
of torque transferred andis dependant on the gear
design
– 5:1 ratio transfers 5 times
the torque to the wheel
with traction
– If one wheel loses all
traction no torque is
transferred to the wheel
with traction Torque transferred to
wheel with traction
8/10/2019 2.3 Differentials
http://slidepdf.com/reader/full/23-differentials 15/17
Application of Torsen Differentials
• Torsen differentials
are used in off-road
and high performanceall-wheel drive
vehicles.
• Torsens can also be
handy on icy or dirtroads
8/10/2019 2.3 Differentials
http://slidepdf.com/reader/full/23-differentials 16/17
Automobile Companies Using the
Torsen Differential
– AM General
– Audi – BMW
– Ford
– GM
– More specific details athttp://www.torsen.com
/oem.htm
– Honda
– Lexus – Land Rover
– Mazda
– Toyota
– Volkswagen