(4) Driveshaft. (5) Swashplate. (6) Servo piston neutral adjustment screw. (7) Barrel assembly. (8) Charge oil inlet. (9) Passage (charge oil).
(10) Closed circuit loop line ports. (11) Pot plates. (12) Spring. (13) Pistons.
When the engine is running, driveshaft (4) and barrel assembly
(7) are rotating. There are nine pistons (13) in barrel assembly
(7). Spring (12) keeps a force on barrel assembly (7) to make
a high pressure seal between barrel assembly (7) and port
plate (11). When barrel assembly (7) is rotating, each piston
(13) follows the angle of swashplate (5). If swashplate (5)
angle is at zero, the pistons do not move in and out of barrel
assembly (7) and there is no oil flow. Charge oil from charge
filter maintains oil pressure in the hydraulic pump to keep
barrel assembly (7) full of oil, lubricate the pump components
and to make up for the normal, internal loss of oil due to
The position of swashplate (5) is controlled by the EDC, and
servo piston (6). When the EDC receives an electrical signal
from the vibratory control switch, it causes a servo valve inside
the EDC assembly to move. The servo valve routes charge oil
to activate and adjust servo piston (6). Servo piston (6)
controls the direction and amount of swashplate (5) angle.
Oil flows from the pump to the eccentric weight motor and back
to the pump through closed circuit loop line ports (10). The
position of swashplate (5) determines the direction and rate of