Subaru SVX 1992 Manual page 400

AUTOMATIC TRANSMISSION AND DIFFERENTIAL [M5BOI 3- 2
5. Planetary Gear
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A: CONSTRUCTION
The planetary gear train uses two sets of simple plane-
tary gears (front planetary gear and rear planetary gear),
four sets of multi-plate clutches (reverse clutch, high
clutch, forward clutch, and overrunning clutch), one
brake band, one set of multi-plate brake, and two sets of
one-way clutches (one-way clutch 1-2 and one-way
clutch 3-4) in order to allow shifting of four forward
speeds and one reverse speed .
Fig. 8
Two sets of simple planetary gears are used to allow
gear shifting from 1st speed to 4th speed or to reverse .
Both the front and rear planetary gear carriers are made
from pressed steel which is electron-beam welded to
other structural members . The front planetary gear has
three pinions while the rear planetary gear has four
pinions . Both are part of an integral unit, and disassem-
bling is not allowed.
B : FUNCTION
Internal gear
Pinion MR ^^!'!+'" ::. :. .
. i ;
.~i ..
Planetary
Sun gear
~°°~;Y
carrier
101
B3-454
Fig. 9
The automatic transmission uses a planetary gear sys-
tem instead of the parallel shaft (two shafts) gear sys-
tem adopted in the manual transmission .
The advantage of the planetary gear system is that it is
compact because it has only one center shaft. The gear
ratio can be changed by simply locking or releasing or
rotating certain portions, unlike the manual transmis-
sion that requires changing gear engagement .
The construction of the planetary gear is shown above.
The sun gear is located at the center, and each of the
pinion gears revolves around the sun gear while rotat-
ing on its axis . These gears are all enclosed in a large
ring, called the internal gear . Each pinion gear is sup-
ported by a planetary carrier, so that the pinion gears
revolve an equal amount in the same direction . As
mentioned above, the planetary gear consists of four
elements : the sun gear, pinion gears, internal gear, and
planetary carrier. The gears are shifted by imposing
certain conditions on two of the following three ele-
ments : sun gear, internal gear, and planetary carrier .
The clutches and brakes are used to impose the condi-
tions on the planetary gear set.
9