Steering: Description and Operation

Fig. 1 Exploded View Of Ford Power Steering Gear:

DESCRIPTION
The power steering unit is a torsion bar type of hydraulic-assisted system. This system furnishes power to reduce the amount of turning effort required at the steering wheel. It also reduces road shock and vibrations.

The unit includes a worm and one piece rack-piston which is meshed to the gear teeth on the steering sector shaft. The unit also includes a hydraulic valve, valve actuator, input shaft and torsion bar assembly which are mounted on the end of the worm shaft and operated by a twisting action of the torsion bar.

The gear unit is designed with the one piece rack-piston, worm and sector shaft in the one housing and the valve spool in an attaching housing. This makes possible internal fluid passages between valve and cylinder, thus eliminating all external lines and hoses except the pressure and return hoses between pump and gear.

The power cylinder is an integral part of the gear housing. The piston is double acting in that fluid pressure may be applied to either side of the piston.

OPERATION
The operation of the hydraulic control valve spool is governed by the twisting of a torsion bar. All effort applied to the steering wheel is transmitted directly through the input shaft and torsion bar to the worm and piston. Any resistance to the turning of the front wheels results in twisting of the bar. The twisting of the bar increases as the front wheel turning effort increases. The control valve spool, actuated by the twisting of the torsion bar, directs fluid to the side of the piston where hydraulic assistance is required.

As the torsion bar twists, its radial motion is transferred into axial motion by three helical threads. Thus, the valve is moved off center, and fluid is directed to one side of the piston or the other.