Lesson 2/Learning Event 1
The gearbox in an integral power steering system is basically a manual
gearbox adapted to include a power assist package. Integral power steering
gearboxes are of two types: offset and inline.
The offset type has a recirculatingball gearbox with a rack meshed to the
pitman sector gear above or on the opposite side of the ball nut. The power
steering force is developed in the power piston, which is offset from the
worm and nut and attached to the rack.
The inline design uses the recirculating ballnut assembly as a power
piston. In this design, the ball nut is sealed inside a cylindrical portion
of the steering gear housing. The power steering effect is produced by
alternately pressurizing either side of the power piston.
The hydraulic cylinder used on the semiintegral and integral power steering
systems is located on the steering linkage. The power assist is developed
in the cylinder through the action of the pressurized hydraulic fluid.
The cylinder may have single or doublewall construction. The hydraulic
hoses connect to the ports on each end of the singlewall cylinder. The
doublewall cylinder has connections on one end for both hoses and an
internal passageway between the walls to pressurize the other end of the
cylinder. Some linkage cylinders have shuttle valves built into the piston.
This valve opens at the end of the piston stroke. This feature helps
eliminate full hydraulic pressure from acting on the cylinder when the
piston is bottomed by opening and allowing fluid to flow through the piston.