Chrysler Dodge Caravan 2002 Manual page 118

RS
BI-DIRECTIONAL OVERRUNNING CLUTCH (Continued)
STEADY STATE, HIGH SPEED, NO WHEEL SLIP
The roller cage positions the rollers on the input shaft
flats during low and high speed overrunning and during
initial BOC lockup. The roller cage is rotating at input
shaft (propeller shaft) speed at all times. At low speeds,
the friction shoes (Fig. 31) are pressed against the fric-
tion ground via the garter spring (Fig. 32), creating a
drag force on the roller cage. The drag force positions
the cage, which in turn positions the rollers to one side
of the flat. The direction of this drag force (position of
the roller) is dependent on the input (propeller shaft)
rotational direction. Since the rollers are always in con-
tact with the outer race, due to centrifugal forces, the
rollers want to follow the outer race due to drag. During
overrunning operation, the outer race is rotating faster
than the input; causing the rollers to want to traverse
the flat from one side to the other. During low speeds,
the brake shoes counteract this effect. To avoid exces-
sive wear, the ground shoes are designed to lift off from
the friction ground due to centrifugal forces at higher
rotational speeds.
Fig. 31 Front View of BOC
1 - GARTER SPRING
2 - FRICTION BRAKE SHOES
3 - FRICTION GROUND CONNECTED TO GROUND TAB
4 - INPUT SHAFT
To keep the rollers in the overrunning position and
avoid undesired high speed lockup , a high speed
latch (Fig. 33) positions the cage before the ground
shoes lift off. A further explanation of the high speed
effects follows as well. Utilizing only the friction
shoes approach means that at high speed the
required ground shoe drag torque would cause exces-
sive brake shoe wear or the roller will begin to
REAR DRIVELINE MODULE
Fig. 32 Location of the Grounding Element
1 - DIFFERENTIAL HOUSING
2 - GROUND TAB
3 - GARTER SPRING
migrate to the opposite side of the flat due to the
drag force of the outer race. This would result in sys-
tem lock-up. (Fig. 34) shows the BOC as it crosses
the speed where the brake shoe force is overcome by
the roller drag on the outer race. Notice that the
roller is locking up on the opposite side of the flat
and the cage supplies no force on the rollers.
Fig. 33 BOC High Speed Latch (Not Engaged)
1 - TOOTH (TWO PLACES)
2 - GARTER SPRING
3 - TABS AT BOTH ENDS FIT INTO SLOTS IN CAGE
4 - TWO PART DESIGN
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