Polaris 2014 Sportsman 570 EF, Руководство по обслуживанию

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6.4
9924871 R03 - 2014 Polaris Sportsman® 570 EFI Service Manual
© Copyright 2013 Polaris Sales Inc.
PVT SYSTEM OVERVIEW
General Operation
WARNING
All PVT maintenance or repairs should be performed
only by a certified Polaris Master Service Dealer (MSD)
technician who has received the proper training and
understands the procedures outlined in this manual.
Because of the critical nature and precision
balance incorporated into the PVT components, it is
absolutely essential that no disassembly or repair
be made without factory authorized special tools
and service procedures.
The Polaris Variable Transmission (PVT) consists of
three major assemblies:
1) The Drive Clutch
2) The Driven Clutch
3) The Drive Belt
The internal components of the drive clutch and driven
clutch control engagement (initial vehicle movement),
clutch upshift and backshift. During the development of a
Polaris ATV, the PVT system is matched first to the
engine power curve; then to average riding conditions
and
the vehicle’s intended usage. Therefore,
modifications or variations of components at random are
never recommended. Proper clutch setup and careful
inspection of existing components must be the primary
objective when troubleshooting and tuning.
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.
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
resistance 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