the Jeep to climb the rock like this. The following document is about the Jeep four-wheel drive system Quadra Drive II (Pump and Clutch-Pack Speed Sensitive LSD).
Hummer H3T
Four-Wheel and Four-Wheel Drive vehicle are popular for their enhanced capabilities in
inclement weather and off-highway conditions as compared with two-wheel drive vehicles.
In order to further boost these capabilities, modern four-wheel and all-wheel drive vehicles
frequently employ a Limited Slip Differential (LSD) between two respective rear axle-shaft
in place of a more common open type differential.
Some high performance four-wheel and all-wheel drive vehicles a limited slip differential in the
front axle, as well, when other go a step further in utilizing a centrally located limited slip
differential, between the axles.
By limiting the the velocity difference between a pair of wheel driven by their respective
axle half-shafts, an LSD can transmit useful torque as long as there is some friction available
at the interface between the ground and at least the one of the driven wheels.
Mercedes-Benz G Class
Limited slip differentials couple, operationally lock, the respective axle half-shafts when the
difference in the axle shafts' rotational velocity rises about a certain preset value. Two main
types of limited slip differentials are used on motor vehicles.
One type is torque sensitive, which is usually either geared or clutch-pack based, and the other
type is speed sensitive, which is mainly viscous or pump and clutch-pack based. Speed
sensitive limited slip differentials generally have been more popular than the torque sensitive
types, because they are mechanically less complex and tend to require less maintenance.
Pump and clutch-pack speed sensitive LSDs generally utilizes a pump, typically a gerotor,
for hydraulically compressing the clutch pack. When driving conditions produce a difference
in wheel rotation, the pump pressurizes its working fluid into the clutch-pack area, which
provides a clamp load for frictional resistance to couple the two respective axle half-shafts
and thereby transfer torque to the wheel with higher traction.
Land Rover Range Rover
However, additional pump and clutch-pack related components collectively resulted in large
LSD assembly which can cause packing issue as well as fuel efficiency.
Hydraulically Locking Limited Slip Differential
An improved hydraulically locking limited slip differential assembly for a drivetrain of a motor
vehicle having a fluid pump external to a differential carrier and arranged for preventing slip
between the wheels by selectively
The LSD assembly incluial clutch internal to the carrier, and
a controller arranged for selectively activating the fluid pump.
The limited slip differential comprises :
1. a housing
2. a carrier positioned inside the housing for supporting components of the differential,
3. a gear-set arranged for rotation inside the carrier to drive the wheels of a motor vehicle,
4. a clutch positioned between the gear-set and the wheels for preventing slip between driven wheels.
5. a pressure chamber arranged inside the carrier for selectively engaging the clutch.
Therefore, may be reducedes a fluid pump located externally from the carrier, and stationary
relative to the housing. The pump is in fluid communication with the pressure chamber via a
fluid pathway and is arranged for selectively engaging the clutch via fluid pressure applied in
response to signals received from an externally located controller.
A high-pressure dynamic seal may be required at the interface between the rotating
differential carrier and the stationary pump. Typically, high-pressure dynamic seals generate
considerable rotating friction which resulted in parasitic losses and reduced vehicle fuel
efficiency. By moving the pump outside the rotating differential carrier, the carrier to pump
interface diameter, ue which it transfers tod.
Jeep Grand Cherokee
Wheel speed may be detected in the vehicle real-time by sensors positioned at the individual
wheels. The sensors communicate with a processor which operates to compare sensed
wheel speed against a predetermined minimum wheel speed difference.
Drive wheels 20 are connected via axle half-shafts 30 to the front differential 60A and rear
differential 60B mounted inside transfer case 50.
Engine 58 generates torque which it transfers to transmission 55. Transfer case 50 receives
torque from transmission 55 and distributes it in the drivetrain. Each of differentials, 60A, 60B,
and 60C may be configured either as limited slip or open type.
Jeep Wrangler
Jeep Grand Cherokee. The chassis is based on the Mercedes-Benz ML Class.
Basically, the differential clutch pack is like motorcycle basket clutch. These clutches are usually made up of a stack of alternating plain steel and friction plates. Some of the plates have lugs on their inner diameters locking them to
the axle half-shaft, while the other plates have lugs on their outer
diameters that lock them to the differential carrier.
This figure denotes a typical limited slip differential with " Gerotor Fluid Pump " 70 internal
to the differential according to the prior art. Gerotor pump 70 is positioned inside the
differential adjacent piston 135 to transfer torque from a slipping drive wheel to one with more
grip by locking differential carrier 110 to gear-set 120.
Fluid inlet structure 80 delivers a working fluid to gerotor pump 70. Gerotor pump 70 is driven
by either driveshaft 40 or axle half-shafts 30 to apply pressurized working fluid against
piston 135. Piston 135, in turn, applies a clamping force to clutch assembly 130.
Two critical dimensional characteristics of a differential are span between support bearings
140A and 140B, labeled X, and diameter of high-pressure dynamic seal 75, which is
positioned at the rotational interface between fluid inlet 80 and differential carrier 110, labeled
Y1.
Jeep Grand Cherokee WK Electronic Limited Slip Differential (ELSD)
A gerotor pump (1) creates oil flow through the filter (4) whenever left or right wheels spin at
different speeds the the solenoid valve is activated. The oil flow is restricted by a
Pressure Regulating Valve (PRV) to build pressure. Pressurized oil is then fed to a piston (2)
chamber. The piston compresses the clutch pack (3pressurizing a differentorque to the lower
speed wheel.
when the anti-lock brakes are activated the differential solenoid is switched off and pressure is
bleed off the clutch pack.
This figure denotes a diagram of a four-wheel drive motor vehicle drivetrain with a hydraulically
locking limited slip differential assembly, where differential 60C is shown as a limited slip
differential mounted inside transfer case 50. Differential 60C is fluid communication with
external fluid pump 90. Pump 90 is in electrical communication with controller 95, which
activates the pump in response to threshold traction loss detected at wheel 20.
Lamborghini Gallardo
differential mounted for rotation inside housing 60. Fluid pump 90 and controller 95 are
mounted on the vehicle external to differential carrier 110.
Gear-set 120 and clutch pack 130 adjacent to the gear-set are mounted driveably inside
carrier 110. Clutch pack 130 has generally annular individual friction plates which are arranged
as a plurality complementary plate pairs, where in each adjoining pair one friction plate is
slidably engaged with carrier 110 and the other is slidably engaged with gear-set 120
(not shown). Annular piston 135 is mounted slidably inside carrier 110 adjacent to
clutch pack 130.
Pump 90 is activated in response to a signal generated by controller 95 to compress
clutch pack and couple gear-set 120 to differential carrier 110. Pump 90 delivers a
high-pressure fluid to carrier 110 via connector 160.
Connector 160, which may be made from an engineering plastic or a similarly heat and oil
resistant materials, has an internal fluid passage 170 and includes a heat and oil resistant
o-ring seal 180.
Connector 160 is inserted into plenum 190, which is stationary relative to housing 60, and is
hermetically sealed against the plenum with seal 180. Thus inserted, connector 160 is in
fluid communication with fluid pathway 155 running inside bearing trunion 150, which is part of
carrier 110, and under support bearing 140A. The high-pressure fluid is delivered to fluid
pathway 155 via channel 200 located on inner diameter of plenum 190. Channel 200 is
hermetically sealed against bearing trunion 150 via a pair of high-pressure dynamic seals
210 at diameter Y3. As such, rotating interface diameter Y3 is measurably smaller than
functionally comparable interface diameter Y1.
The invention concurrently minimizes span X between support bearings 140A and 140B,
and high-pressure dynamic seal diameter Y3 at stationary pump fluid inlet and rotating
differential carrier 110 interface.
Reference :
1. Hydraulically locking limited slip differential. US Patent.
2. Jeep Grand Cherokee WK Service Manual. Differential Diagnosis.
3. Basket Clutch. Wikipedia.
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