Drive Clutch Operation; Driven Clutch Operation - Polaris A12MH46AX Service Manual

Drive Clutch Operation

Drive clutches primarily sense engine RPM. The two
major components which control its shifting function are
the shift weights and the coil spring. Whenever engine
RPM is increased, centrifugal force is created, causing
the shift weights to push against rollers on the moveable
sheave, which is held open by coil spring preload. When
this force becomes higher than the preload in the spring,
the outer sheave moves inward and contacts the drive
belt. This motion pinches the drive belt between the
spinning sheaves and causes it to rotate, which in turn
rotates the driven clutch. At lower RPM, the drive belt
rotates low in the drive clutch sheaves. As engine RPM
increases, centrifugal force causes the drive belt to be
forced upward on drive clutch sheaves.
9923412 - 2012 Sportsman 400/500 and EFI Tractor Service Manual
© Copyright 2011 Polaris Sales Inc.

Driven Clutch Operation

Driven clutches primarily sense torque, opening and
closing according to the forces applied to it from the drive
belt and the transmission input shaft. If the torque resis-
tance at the transmission input shaft is greater than the
load from the drive belt, the drive belt is kept at the outer
diameter of the driven clutch sheaves.
As engine RPM and horsepower increase, the load from
the drive belt increases, resulting in the belt rotating up
toward the outer diameter of the drive clutch sheaves and
downward into the sheaves of the driven clutch. This
action, which increases the driven clutch speed, is called
upshifting.
Should the throttle setting remain the same and the
vehicle is subjected to a heavier load, the drive belt rotates
back up toward the outer diameter of the driven clutch and
downward into the sheaves of the drive clutch. This
action, which decreases the driven clutch speed, is called
backshifting.
In situations where loads vary (such as uphill and downhill)
and throttle settings are constant, the drive and driven
clutches are continually shifting to maintain optimum
engine RPM. At full throttle a perfectly matched PVT
system should hold engine RPM at the peak of the power
curve. This RPM should be maintained during clutch
upshift and backshift. In this respect, the PVT system is
similar to a power governor. Rather than vary throttle
position, as a conventional governor does, the PVT
system changes engine load requirements by either
upshifting or backshifting.
CLUTCHING
6
6.3