SAFARI

POWER STEERING

through the forward and return edges, and from

there the oil flows up through the corresponding

holes into an opening of the piston.The oil is then

drained for return motion. By operating the valve,

the side of the piston which is under pressure is

separated from the return and the opposite side

of the piston which is connected to the return flow.

The spool valve is equipped with two feed-back

pistons which have the task of making the

movement of the valve, from the neutral position

more difficult, depending on the oil pressure. The

activating force on the steering wheel increases

proportional to the forces which are applied to the

wheels.

Steering units which only require a proportional

increase of the steering force only up to a

predetermined oil pressure, are equipped with

Hydraulic reaction components (feedback piston).

The valve which is into the feedback piston

ensures that after reaching the cut-off pressure

the force on the steering wheel only increase

insignificantly.

Function of the feedback pistons :

(Hydraulic Reaction)

They are floating pistons mounted in the bore hole

of the valve spool.They are, however, held axially

and secured by connecting them with retaining

plates. The outer front areas of the two pistons

are continually under pressure while only one of

the internal front surfaces is under pressure in

the working position of the valve.The same applies

for the front surface in the bore holes of the valve

spool. In this way, no force occurs which tries to

push the valve spool into the neutral position.This

property is described as “hydraulic reaction”.