11 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”.
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