Cub Cadet ISeries User Manual

Page 36

DRIVE SYSTEM-IVT

NOTE: The RPM numbers used in figures 5B.2,
5B.3 and 5B.4 are not the actual measurements
of the disc speeds. They are just an example to
demonstrate the speed differences.

When the rollers rides near the outer edge of the

input discs, they are pressing against the center of the
output discs. In this position, the output disc will be
turning at a much faster rate than the input discs.
See Figure 5B.4

When the rollers are in the neutral position or in the

center of the disc valley, all of the discs are rotating at
the same speed. See Figure 5B.5

The key to making this work is a special traction

fluid that was developed for this transmission. A Trac-
tion fluid is a synthetic transmission fluid designed with
properties specifically for transmitting torque between
the discs and rollers.

Under normal load conditions this fluid acts like a

conventional lubricating fluid. When the fluid is sub-
jected to extreme pressure, such as in the contact area
between the discs and rollers, the fluid changes to
exhibit its ElastoHydrodynamic Lubricant (EHL) proper-
ties. The EHL property of the traction fluid causes the
molecules in the fluid to become almost solid. This
increases the shear force transmitting properties of the
fluid.

The traction fluid in the contact area between the

rollers and discs turns into a semi-solid. This allows the
fluid to act like a gear tooth, transferring the torque
from the disc to the roller or vise versa. It also prevents
metal to metal contact extending the life of the moving
parts.

NOTE: Putting motor oil or hydraulic fluid in an
IVT transmission will destroy it.

Each of the variators are attached to a epicyclic,

also know as planetary, gear set. See Figure 5B.6

Figure 5B.4

500 rpm

1,000 rpm

Figure 5B.5

500 rpm

Figure 5B.6

Epicyclic gear sets