Lever synchronizers can be classified into two types, “high-performance” type and
“reverse” type. High-performance type takes advantage of the principle of
leverage where sleeve pushes synchronizer ring with magnified force through a
lever inside the synchronizer. The reverse type prevents gear noise when it is
shifted into reverse, by lever’s reverse effect.
Viewed from the front, each lever is shaped like an arc with apex at its center,
which is pushed by slanted surface formed inside the sleeve.
Using lever apex as a “point of force”, the slanted surface of the sleeve pushes the
apex in the direction of the shaft. This causes the synchronizer ring to be pushed
at “point of application” between apex and both ends of the lever, based on
principle of leverage using both ends of the lever as “fulcrum”.
Unlike conventional Warner-type synchronizers, this allows the synchronizer ring to
be pushed with a force greater than that applied by the sleeve, which enables
enhanced frictional contact in synchronization, thus obtaining an increased
frictional force. As a result, improved synchronization performance may be
obtained, enabling quick synchronization with less operating force.
Synchronizers have another important function which is to balk the movement of a
sleeve until synchronization is successfully completed.
Each synchronizer, thus, has two lugs in the direction of the shaft to push two
levers outward by using the friction torque applied to the synchronizer ring.
As described above, since the sleeve pushes the apex of levers with its slanted
surface, it cannot move unless the levers are pushed inward.
That is, the synchronizer is designed so that the movement of the sleeve is
prevented (balked) until synchronization is successfully completed since the lugs of
the synchronizer ring apply a large force to the levers to push them outwards by
using a torque accompanying the synchronization.
When synchronization has been achieved, the sleeve would allow the levers to
move inward and, at the same time, it moves forward while slightly turning its
mating cone connected to the synchronizer ring. The speed can be changed only
when the sleeve and its mating gear have reached the same rpm, and are smoothly
engaged with each other. Maximum leverage available for pushing the synchronizer ring is 2.
When fifth gear and reverse gear are in-line on the shift pattern
of a transmission, the lever synchronizer may be applied to the
fifth gear to make use of the reverse effect.?
In this case, a groove is provided inside the sleeve and both sides
of the groove have slanted surface. Since the lever top is fitted
into this groove, it is pushed toward the shaft where the sleeve
shifts either into the fifth gear or reverse.
When the lever is pushed toward the 5th gear, the lever
synchronizer operates as the fifth gear synchronizer , just like in
the high performance type.
The leverage in this case ranges approximately from 1.2 to 1.5.
The characteristics of the reverse type can be shown when the
sleeve is shifted not into the fifth but into reverse. That is, when
the sleeve shifts into reverse while a vehicle is not moving, the
slanted surface of the sleeve pushes the lever apex in the
direction opposite to fifth. When the lever apex moves in the
direction opposite to the fifth, both ends of the lever push the
synchronizer ring against the fifth gear by using a fulcrum
between the lever apex and its ends. This allows the clutch disc
and the input shaft to stop spinning, synchronizing their speeds
with the fifth gear that is stationary.
When the spinning of the input shaft has stopped, the sleeve
becomes movable and allows the engagement of the reverse
gear located in the another position.
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