TM 5-3805-280-24-1
Theory of Operation
also serves as the drive shaft for the pump drive
The front and rear hydraulic pumps (N) are variable
gearbox. The drive shafts drive the cylinder blocks (M)
displacement, bent-axis, piston type pump. Two
through the center shafts (I). The cylinder block is
identical pumps are used to generate oil flow in the
positioned at an angle to the drive shaft. As the
hydraulic system. The pump can vary from minimum
cylinder block and drive shaft rotate, the pistons (J)
displacement to maximum displacement depending on
move in and out of their bores because of the angle.
hydraulic demand of the system.
The pistons which are moving out of their bores draw
oil from the hydraulic oil tank through a pump inlet port
A regulator (G) is attached to the top of housing (H) for
and ports in the valve plate (L). The pistons which are
each pump. A pilot oil signal to the regulator moves a
moving back into their bores push oil through ports in
piston which then directs pilot oil to the servo piston
the valve plate out the front and rear discharge ports
(K) which moves the valve plate (L) and cylinder block
(A and C) and to the control valve.
(M) changing the pump displacement. The feedback
link (F), connected to the valve plate, also moves
The pump displacement, or flow rate, is varied by
providing a mechanical feedback to the remote control
changing the angle of the cylinder block with respect to
sleeve in the regulator. The remote control sleeve
the drive shaft. Increasing the angle increases the
blocks the flow of pilot oil to the servo piston and also
distance that each piston travels into and out of the
traps the oil at both ends of the servo piston stopping
bore which increases displacement. Decreasing the
its movement.
angle reduces the distance that each piston travels
into and out of the bore which decreases
The front and rear pumps and pilot pump are driven at
displacement.
engine speed through a pump drive gearbox. The rear
pump drive shaft (D) as well as driving the rear pump
9025
05
17
TX,05,GG2151
1929MAY982/2
6-16
