Mitsubishi Lancer Evolution 7. Manual — part 14
POWER TRAIN - Manual Transmission
2-9
POWER TRAIN
Helical Gear LSD
The helical gear LSD is composed of four long pinions, four short pinions, three thrust washers, side
gears A and B, and cases A and B.
The long pinions are in contact with the side gear B and short pinions, while the short pinions are in
contact with the side gear A and long pinions.
Case B
Case A
Side gear B
Side gear A
Long pinion
Short pinion
Thrust washer
Power Flow
Operations in forward driving
During forward driving, as the differential case and and drive shaft rotate at the same speed, they
rotate at the assembly without the inside of the differential moving.
The driving force at this time will be transmitted as follows.
Differential case
→
Long and short pinions
→
Side gears A and B
→
Drive shaft
Side gear B
Side gear A
Long pinion
Short pinion
Differential case
Driving power
POWER TRAIN - Manual Transmission
2-10
Operations during differential (when there is rotational difference between the left and right
wheels)
When the frictional coefficient of the left and right wheels are more or less equal, and a slight rotational
difference occurs at the left and right wheels (normal turning), rotational difference will also occur
between side gears A and B. In this case, while the long pinions and short pinions mutually rotate
in the reverse direction, the vicinity of side gears A and B revolves and absorbs the speed difference.
In this way, like normal differential, the high speed side accelerates for the revolved amount in respect
to the revolution speed of the differential case,while the low speed side rotates in the decelerated
state and performs differential.
Side gear B
Side gear A
Long pinion
Short pinion
Differential case
Driving power
Revolution
Autorotation
High speed side
Autorotation
Low speed
side
Operations during Limited Slip Differential
When the loads of the left and right wheels become unbalanced due to changes in road surface
conditions and sudden turning, the driving torque of side gears A and B will differ.
As mentioned earlier, because side gears A and B are in contact via the respective long and short
pinions, the gears influence each other, resulting in contact reaction force (F and f) between the
long pinion and side gear B, and the short pinion and side gear A.
The separating force (Ft and ft) in the axial direction of the contact reaction force causes side gears
A and B to be pushed and extended. From this force, side gears A and B are pushed against the
thrust washer (case) and friction occurs.
The separating force (Fr and fr) in the radial direction of the contact reaction force causes the long
pinion and short pinion to be pushed against the differential case (cases A and B). This force generates
a large friction between the long pinion, short pinion, and differential case (cases A and B).
Friction also occurs on the gear with the generation of contact reaction force (F and f) of the four
gears (pinions).
These frictional forces cause the generation of frictional torque at each section according to the
size of the driving torque input to the differential case, and the generation of limited slip differential
torque proportionate to the input torque.
POWER TRAIN - Manual Transmission
2-11
Long pinion
Short pinion
Differential case
Driving power
High speed
side
Low speed
side
Torque
Side gear B
Side gear A
Thrust washer
Thrust washer
Forward direction
F
Fr
Ft
f
fr
ft
TRANSMISSION CONTROL
D
The shift lever construction adopted the
spherical rotary shaft fulcrum type to assure
a non-rickety.
D
The base bracket material adopted a synthetic
resin for the weight reduction.
D
The shift and select cable securing portions
have been elastically supported to reduce
contained sound.
D
A mass-filled shift knob has been adopted to
minimize the binding touch at the time of a
shift.
CONSTRUCTION DIAGRAM
Select cable
Shift lever assembly
Base bracket
Shift cable
POWER TRAIN - ACD and AYC
2-12
ACTIVE CENTER DIFFERENTIAL (ACD) AND ACTIVE YAW
CONTROL (AYC)
The LANCER EVOLUTION-VII adopts the newly developed active center differential (ACD).
The driving performance of the ACD has been improved by varying the center differential drive by electronic
control.
The yaw moment is directly controlled by the active yaw control (AYC) adopted from EVOLUTION-V
onwards to improve the turning performance.
By combining and integratedly controlling these two systems, the driving performance has been further
improved.
RS, RS II
ACD
Option
ACD and AYC
Option
OUTLINE OF CONTROL
The following effects are obtained by equipping the ACD or ACD and AYC.
State of vehicle
ACD
AYC
Integrated control effects
1. During de-
celeration
(Before
corners)
Similar to the direct engagement
4WD by increasing the center
differential during sharp decelera-
tion to improve stability in decelera-
tion.
[When decelerated during
turning]
The driving power is moved to
the inside turning wheel to
reduce the tack in.
Stability against various
external influences such as
poor road conditions and
driver operations have been
improved.
2. First half of
turning
(Corner en-
trance)
The center differential restriction is
reduced according to the steering
angle and operation speed to set
the center differential as close as
possible to the free state and
improve turning performance.
The driving power is moved to
the outside turning wheel
according to the steering
angle and operation speed to
improve the turning perfor-
mance.
The response to steering
operations (brisk move-
ment) is improved as much
as possible.
3. Latter half
of turning
(Corner
exit)
The center differential restriction is
enhanced according to the amount
the acceleration is stepped to set
similar effects as the direct engage-
ment 4WD and improve the accel-
eration performance.
The driving power is moved to
the outside turning wheel
according to the amount the
acceleration is stepped to
decrease the acceleration
understeer and improve turn-
ing performance.
Two elements (acceleration
and turning) have been
improved simultaneously.
ACD: Free
AYC: Turning
1. During deceleration
2. First half of turning
ACD: Direct
engagement
AYC: Tack in deceleration
(During deceleration when turning)
3. Latter half of turning
AYC: Under steer deceleration
ACD: Direct engagement
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