Locking Differentials
-
Upload
satria-spa -
Category
Documents
-
view
226 -
download
0
Transcript of Locking Differentials
-
7/28/2019 Locking Differentials
1/22
AGM 240
Power Frames
Mr. Conrado
Locking Differentials
-
7/28/2019 Locking Differentials
2/22
Introduction
This lesson discusses methods
employed to override undesirable
differential action.
When the differential is locked up,
both of the axles will be driven at the
same speed regardless of wheelconditions.
-
7/28/2019 Locking Differentials
3/22
Locking Differentials
This differential can be locked or
unlocked with the differential switch
in the cab.
The operator should lock the
differential anytime the machine is
being operated in a straight line. This transfers all of the torque to all
wheels under all traction conditions.
The differential can be unlocked for
turns in order to reduce the turning
radius and tire wear.
-
7/28/2019 Locking Differentials
4/22
Locking Differentials
The differential has a clutch between
the left side gear and the differential
housing.
When the differential is locked, a
solenoid will allow oil flow behind the
clutch piston to engage the clutch.
The clutch will be engaged and left sidegear will rotate at the speed of the
rotating housing.
The differential pinion gears will not
rotate on their axes because the spider
and the side gear rotate at the same
speed.
The differential pinion gears will hold
the other side gear.
Both of the axle shafts will turn at the
speed of the rotating housing.
-
7/28/2019 Locking Differentials
5/22
Locking Differentials
When the differential is unlocked, the
solenoid will block the flow to the
clutch pack and both of the side
gears can turn freely.
Locking differentials force one of the
side gears to rotate with thedifferential housing.
This causes the differential to act like
a solid axle and transmit all of the
torque to both of the wheels.
This causes both wheels to rotate at
the same speed, regardless of
traction.
-
7/28/2019 Locking Differentials
6/22
Jaw Clutch
Some locking differentials use jaw
clutches.
The operator engages the jaw clutch
when a wheel is slipping.
By using a pedal or a switch to lock
the differential.
The operator determines when the
differential lock is needed.
Jaw Clutch
-
7/28/2019 Locking Differentials
7/22
Jaw Clutch
The operator should lower the
engine speed and not spin the wheel
while engaging the differential lock.
Engaging the jaw clutch at high
speeds can cause damage to the
differential. The operator should not attempt to
turn while the jaw clutch is engaged.
Sometimes the operator will hear
the jaw clutches hitting each other.
If that happens, the operator shouldlower the engine speed to let the jaw
clutches engage.
-
7/28/2019 Locking Differentials
8/22
Jaw Clutch
The jaw clutch connects one of the
side gears to the differential housing.
The differential pinion gears will not
rotate on their axes because the
spider and the side gear rotate at the
same speed. The differential pinion gears will hold
the other side gear.
Both of the axle shafts will turn at the
speed of the rotating housing.
When the differential is unlocked,springs will push the jaw clutch apart
and both of the side gears can turn
freely.
-
7/28/2019 Locking Differentials
9/22
Backhoe Loaders
In Backhoe Loaders, the jaw clutch is
engaged by pushing down on a foot
pedal.
This motion is transmitted through a
mechanical linkage and results in a
constant torque on a lock lever. The lock lever causes a fork to push
the coupling on the side gear into the
adapter on the differential housing.
When the two halves of the jaw
clutch are pushed together, one side
gear will be locked to the differential
housing.
-
7/28/2019 Locking Differentials
10/22
Backhoe Loaders
After full engagement has occurred,
the differential lock pedal should be
released.
The power that is transferred from
one wheel to the other wheel results
in a side force. This side force will keep the jaw
clutch engaged.
When the power becomes more
equally distributed, the side force will
reduce. The jaw clutch will disengage
automatically due to the reduced
side force.
-
7/28/2019 Locking Differentials
11/22
Wheel Tractor Scrapers
In Wheel Tractor Scrapers, air is used
to engage the jaw clutch.
One half of the jaw clutch is splined
to the differential housing. The other
half of the jaw clutch is fastened to
the left axle shaft. In older Wheel Tractor Scrapers, the
operator can engage the jaw clutch
by pushing down on a foot pedal.
In newer Wheel Tractor Scrapers, the
operator engages the jaw clutch by
pushing a switch.
When the pedal or switch is released,
the jaw clutch will release.
-
7/28/2019 Locking Differentials
12/22
Wheel Tractor Scrapers
When the pedal is depressed or theswitch is pushed, a differential lockvalve will allow air to flow behind apiston.
The piston will push the jaw that isconnected to the axle shaft so that it
contacts the jaw that is connected tothe differential housing.
When the two halves of the jawclutch are pushed together, one axleshaft will be locked to the differentialhousing.
When the pedal is released or whenthe switch is released, the pressureair will not flow behind the piston.
The spring will push the two halves ofthe jaw clutch apart.
-
7/28/2019 Locking Differentials
13/22
Limited Slip Differential
A limited slip differential is designedto provide equal power to bothwheels until the ground conditionscause a variance in traction betweenthe left and right wheel.
It contains two multidisc clutches.
Each clutch connects a side gear tothe rotating housing.
A small clearance is specified duringthe assembly of the limited slipdifferential to ensure proper clutchengagement.
Both wheels will be driven at equaltorque and speed during straightoperation if good traction is availablebeneath both wheels.
-
7/28/2019 Locking Differentials
14/22
Limited Slip Differential
In a standard differential, if the machine
is jacked up and one wheel is held or
braked, the other wheel turnscorrespondingly faster.
With a limited slip differential, the
clutches make this more difficult by a
factor that increases proportionally tothe input torque.
The locking effect happens due tointernal friction of the differential.
When a speed difference at the axles
occurs, the separating forces inside the
differential will cause the compression
of the clutch packs.
This causes torque in the faster wheel
to be redirected to the wheel with
better traction.
-
7/28/2019 Locking Differentials
15/22
Limited Slip Differential
When a turn is needed, the forces
from the wheels are sufficient to
overcome the clutch packs.
This design is used due to space
limitations.
In this design, the gear toothseparating forces are used to apply
the clutches.
-
7/28/2019 Locking Differentials
16/22
Spider
The spider shown consists of three
shafts.
The long shaft holds two differential
pinion gears.
Two half length shafts each hold one
differential pinion gear.
-
7/28/2019 Locking Differentials
17/22
Connector
The ends of the three shafts meet at
a connector.
Internal slack is present because this
type of connection is used instead of
a direct connection, and allows gear
tooth separating forces to be felt.
-
7/28/2019 Locking Differentials
18/22
Spider
Each spider shaft is inserted into the
connector through the rotating
housing and through the differential
pinion gears.
Three dowels are used to fasten the
shafts to the rotating housing.
-
7/28/2019 Locking Differentials
19/22
Side Gear
One side gear sits on top of the
connector and differential pinion
gears.
The other sits below the connector
and differential pinion gears.
The differential pinion gears meshwith the side gears.
The face of the side gear shown is the
contact surface for the clutch pack.
When a speed difference is present,
gear tooth separating forces push theside gears axially toward the clutch
packs.
The axial forces compress the clutch
packs.
-
7/28/2019 Locking Differentials
20/22
Discs and Plates
The discs are splined to the side gears.
The plates are connected to the
rotating housing.
The amount of torque used to
compress the clutch packs is called the
braking torque.
The braking torque is load dependentand is proportional to the amount ofinput torque.
When the clutch is engaged on the
faster axle, the total input torque will
increase.
All torque above the braking torque istransferred to the slower wheel.
Therefore, the limited slip differential
provides a torque split when the
clutches are engaged.
-
7/28/2019 Locking Differentials
21/22
Shims
Shims are used to set clearance when
necessary.
-
7/28/2019 Locking Differentials
22/22
Lab
Homework