TM 5-3895-359-14&P
then trapped between the rotating vanes and is forced,
SUBSECTION 11 FRONT AXLE AND STEERING
through porting in the pressure plate, to the outlet and
into the system as the chamber size
POWER STEERING PUMP
DESCRIPTION
A. GENERAL
The assembly and construction of the VT16 series
pumps are illustrated in cutaway in Figure 1. The unit
consists principally of a body, cover, ring, rotor, vanes,
pressure plate, relief valve sub-assembly, driveshaft
and reservoir. The vanes are contained in the rotor
slots and follow the cam shaped contour of the ring as
the rotor is driven in rotation by the driveshaft. Fluid
flow is developed by the vanes carrying fluid around the
ring contour.
PRINCIPLES OF OPERATION
A. GENERAL
These units depend on the vehicle engine as a source of
rotary mechanical power to produce fluid flow. Inlet flow
is created by a decreased pressure set up by the action
of the pumping cartridge. Flow is directed through the
cartridge to the pressure port and monitored by the flow
control and relief valve.
FIGURE 1
decreases at the pressure quadrants (small diameter)
B. PUMPING CARTRIDGE
section of the ring. System pressure fed under the
The pump cartridge consists principally of a ring, rotor
vanes assures sealing contact of the vanes against the
and vanes (see Figure 2). The rotor is driven within the
ring during normal: operation.
ring by a driveshaft, coupled to the power source.
Radial movement of the vanes, and the rotation of the
C. HYDRAULIC BALANCE
rotor, cause the chamber area between vanes to
The ring is shaped so that two pumping chambers are
increase in size at the inlet (large diameter) section of
formed 180 apart. Thus, any hydraulic loads on the
the ring. This results in a low pressure, or vacuum in
bearings are cancelled.
the chamber. This pressure differential forces oil to flow
into the inlet chamber by atmospheric pressure. Oil is
FIGURE 2
11-1
