sets of planetary gears. A compound planetary gearset
is used to provide more forward gear ratios than a
simple planetary gearset.
CLUTCHES AND BANDS
Automatic transmission clutches and bands are
friction devices that drive or lock planetary gearsets
members. They are used to cause the gearset to transfer
The multiple-disc clutch is used to transmit
torque by locking elements of the planetary gearsets to
rotating members within the transmission. In some
cases, the multiple-disc clutch is also used to lock a
planetary gearset element to the transmission case so it
can act as a reactionary member. The multiple-disc
clutch is made up of the following components (fig.
DISCS AND PLATES.The active components
of the multiple-disc clutch are the discs and the plates.
The discs are made of steel and are faced with a friction
material. They have teeth cut into their inner
circumference to key them positively to the clutch hub.
The plates are made of steel with no lining. They have
teeth cut into their outer circumference to key them
positively with the inside of a clutch drum or to the
inside of the transmission case. By alternately stacking
the discs and plates, they are locked together or
released by simply squeezing them.
CLUTCH DRUM AND HUB.The clutch drum
holds the stack of discs and plates and is attached to the
planetary gearset element that is being driven. The
clutch hub attaches to the driving member and fits
inside the clutch discs and plates.
Figure 4-31.Multiple-disc clutch.