automotive transmission - 14

8/6/2019 Automotive Transmission - 14

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AutomotiveTransmission

AUTOMATIC TRANSMISSION

Axles

PSG College of Tech Dept of Automobile Engg.. Asst. Prof. R. Karthikeyan

Axles were originally defined as rigid lateral connections between two wheelswhich could be steered together.

This type of axle helps ensure rolling stability and simplifies assembly by

providing a connection between the wheels and body.

the axle assembly includes the subframe, steering gear, stabilizer, anddifferential.


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Axles



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Axles types


Rigid axles (dependent wheel control)

Independent suspension systems (independent wheel

control)

A third axle concept can be defined which lies between

the two types listed above:

Semi-rigid axles (twist beam suspension systems)

Placed front orrearof the vehicle (front axles, and rear axles)


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Rigid Axles


A rigid axle is defined as a lateral axle body that rigidly connects twowheels to one another and makes the motion of one wheel dependent

on the motion of the other.

This solution is also known as a solid axle, live axle, or dependent

wheel control system

found on a small number of cars and SUVs built for maximum off-road

performance


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Live and Dead Axle


A live axle is one that supports part of the weight of a vehicle

and drives the wheels connected to it.

A dead axle is one that carries part of the weight of a vehicle but does

not drive the wheels.

The wheels rotate on the ends of the dead axle.

Usually, the front axle of a passenger car is a dead axle and the rear

axle is a live axle.


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Rear Drive Axles


The rear drive axle connects the differential side gears to the drive

wheels.

The axle may or may not support the weight of the vehicle.

Rear axles are normally induction hardened for increased strength.

semifloating, three-quarter floating, and full floating.

Most automobiles use the semifloating type, whereas four-wheel drive

vehicles and trucks use full floating axles.


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Rear Axle - Semifloating


The semifloating axle (fig. 13-21) used on mostpassenger cars and light trucks has its differential

case independently supported. The differential

carrier relieves the axle shafts from the weight of

the differential assembly and the stresses caused

by its operation. For this reason the inner ends of

the axle shafts are said to be floating. The wheelsare keyed to outer ends of axle shafts and the

outer bearings are between the shafts and the

housing. The axle shafts therefore must take the

stresses caused by turning, skidding, or wobbling

of the wheels. The axle shaft is a semifloating live

axle that can be removed after the wheel has beenpulled off


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Rear Axle - Semifloating


The semifloating axle (fig. 13-21) used on mostpassenger cars and light trucks has its differential

case independently supported. The differential

carrier relieves the axle shafts from the weight of

the differential assembly and the stresses caused

by its operation. For this reason the inner ends of

the axle shafts are said to be floating. The wheelsare keyed to outer ends of axle shafts and the

outer bearings are between the shafts and the

housing. The axle shafts therefore must take the

stresses caused by turning, skidding, or wobbling

of the wheels. The axle shaft is a semifloating live

axle that can be removed after the wheel has beenpulled off


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Rigid Axles

PSG College of Tech Dept of Automobile Engg.. Asst. Prof. R. KarthikeyanFour-wheel-drive off-road vehicle with rigidfront and rear axles


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Rigid Axles


Rigid driven rear axles are more common

and aregenerally used in heavier vehicles (SUVs,

vans, light

trucks) with reduced comfort expectations


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Rigid Axles


The properties of rigid axles are (Figure 4-3):

simplicity, economy, cost-effective integration of

the rear differential into the axle body (half-shafts

with no joints)

flat package shape wide loading surface for nondriven

axles

robustness, large load capacity

high roll center

identical orientation of both wheels during parallel

wheel travel (both wheels have the same toe and

camber)

large axle movements are possible (off-road use)

large unsprung mass (the entire axle moves withwheels), for driven axles up to twice as large as

that of an independent suspension system

the motion of one wheel affects the motion of the

other wheel during single-wheel compression

events (examples include tramping, wheel hop, and

a reduction in the wheels ability to compress) maneuver-de endant a lied wheel forces and


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Rigid Axles


The properties of rigid axles are (Figure 4-3):

simplicity, economy, cost-effective integration of

the rear differential into the axle body (half-shafts

with no joints)

flat package shape wide loading surface for nondriven

axles

robustness, large load capacity

high roll center

identical orientation of both wheels during parallel

wheel travel (both wheels have the same toe and

camber)

large axle movements are possible (off-road use)

large unsprung mass (the entire axle moves withwheels), for driven axles up to twice as large as

that of an independent suspension system

the motion of one wheel affects the motion of the

other wheel during single-wheel compression

events (examples include tramping, wheel hop, and

a reduction in the wheels ability to compress) maneuver-de endant a lied wheel forces and


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Rigid Axles


The differential on a driven rigid axle can either be

integrated into the axle housing or attached to the

vehicles body separate from the axle.

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