Nested Torsion Bar for EPS Redundancy and Stiffness Tuning

The patent applies the nesting principle by placing one torsion bar inside another torsion bar, forming a double torsion bar structure. The inner torsion bar is inserted through the hollow cross-section of the outer torsion bar, and both are fixed to the input and output shafts. This nested configuration provides redundancy - if one torsion bar fails, the other can still function to maintain steering operation, thereby improving reliability without requiring a completely separate backup system.

The patent segments the fastening function into separate components: a fastening portion with a through-hole in each torsion bar, and a separate fixing member (such as a pin or bolt) that passes through these holes to secure the torsion bars to the input and output shafts. This segmentation allows for easier assembly compared to conventional methods that may require complex pressing or welding operations, as the modular fastening structure enables simple insertion and fixation of the torsion bars.

The patent applies local quality by allowing different torsion bar configurations and materials to be selected for specific applications. The double torsion bar structure enables independent selection of bar diameters, lengths, and materials to achieve desired stiffness characteristics. Additionally, the fastening portions can be positioned at different locations along the torsion bars to locally adjust the effective stiffness, providing versatility in steering characteristic tuning without complicating the manufacturing process.