Center Position Cap for Steering Input Shaft Sealing
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Solution Overview
Problem
The existing motor vehicle steering systems with input shaft torsion bar assemblies face challenges in cost-effectiveness and durability due to the need for O-ring grooves, which are expensive and prone to breaking, and the complexity of balancing caused by O-ring friction.
Innovation Solution
A motor vehicle steering system with an input shaft torsion bar assembly and a center position cap that eliminates the need for O-ring grooves by using a center position cap to seal and align the input shaft, allowing for cost-effective production and improved durability, where the center position cap surrounds the input shaft and provides additional sealing and positioning aids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an O-ring groove is provided in the torsion bar to accommodate the sealing ring, then the input shaft hollow bore is sealed, but the manufacturing cost increases and the torsion bar durability decreases
Solution Approach 1:
The sealing function is extracted from the torsion bar by removing the O-ring groove, and the sealing responsibility is transferred to the center position cap which seals the input shaft hollow bore from the steering column side, eliminating the need for grooves in the torsion bar
Solution Approach 2:
The center position cap acts as an intermediary sealing element between the steering column and the input shaft hollow bore, providing the sealing function without requiring modifications to the torsion bar structure
2Reliability
If an O-ring groove is provided in the torsion bar, then the input shaft hollow bore is sealed, but the torsion bar becomes more prone to breaking
Solution Approach 1:
The O-ring groove is completely removed from the torsion bar structure, eliminating the stress concentration point that would lead to cracking and breaking, while the sealing function is maintained by the center position cap
3Reliability
If an O-ring is used for sealing between the torsion bar and input shaft, then the hollow bore is sealed, but the balancing process becomes more difficult
Solution Approach 1:
The O-ring and its groove are removed from the torsion bar-input shaft interface, eliminating the friction source that complicates balancing, while sealing is provided by the center position cap at a different location
4Reliability
If the torsion bar is made longer to accommodate the O-ring groove, then the sealing is possible, but the material usage and cost increase
Solution Approach 1:
The O-ring groove and associated extended torsion bar length are removed, reducing material consumption, while the sealing function is transferred to the center position cap which seals from the steering column side
Data Source
Figure 1
AI summary
The invention relates to a motor vehicle steering system with an input shaft/torsion bar assembly, having a torsion bar (2) arranged in an axial hollow bore (5) in an input shaft (1), wherein the torsion bar is connected in a first end region to the input shaft for rotation therewith, and a central position cap (6) which at least partially surrounds the input shaft (1) and has an extension (13) which extends in the axial direction and is provided for aligning the input shaft (1) relative to a steering column, wherein the central position cap (6) engages in the hollow bore (5) in the input shaft (1) at an end (3') in the vicinity of the steering column.