Positive Center-Feel Torsion Bar

Positive Center-Feel Torsion Bar
The positive center-feel torsion bar improves the straight ahead feel of the steering in the region where very small amounts of hydraulic pressure, and hence reaction pressure, are generated.

The torsion bar assembly forms part of the hydraulic control valve assembly, and includes an axially pre-loaded metal bellows spring, which is arranged co-axially with the torsion bar. The torsion bar is positively connected between the end piece and the input shaft. One end of the bellows spring is attached to the input shaft, while the other end is attached to a centering device. The centering device has two prism-shaped recesses with caged, guided, ball bearings arranged between the recesses, and determines the zero-torsion position of the bellows spring.

On turning the steering wheel from the straight ahead position, the spring forces of the torsion bar assembly must be overcome. Initially, the bellows spring produces substantial additional torsional resistance. However, after an angular movement of approximately 0.2 degrees the torsional rigidity decreases and becomes similar to a conventional torsion bar.