Steering Device Boss Asymmetric Geometry for Smooth Telescopic Adjustment
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Solution Overview
Problem
Existing steering devices face issues with smooth telescopic adjustment due to friction-induced rotation of the boss cam, which can cause it to get caught in the telescopic-adjust long groove, requiring excessive force and leading to operational difficulties during extension.
Innovation Solution
The steering device incorporates a boss with specific corner configurations forming an obtuse and acute angle pair, ensuring these corners are narrower than the groove width, preventing catching on the groove edges, and allowing smooth telescopic adjustment by maintaining consistent radii during rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the boss of the second cam has a rhombic or rectangular cross-section, then the fastening mechanism can achieve lock during tilt and telescopic adjustment, but the boss may rotate due to friction with the groove edge during telescopic adjustment and get caught like a wedge, requiring larger operating force
Solution Approach 1:
The boss is designed with an asymmetric cross-section where two opposite corners form obtuse angles and the other two corners form acute angles. This asymmetric geometry prevents the boss from rotating and getting caught in the groove during telescopic adjustment, while still maintaining the locking function when engaged with the cam mechanism.
Solution Approach 2:
Specific corners of the boss are designed with different angle characteristics (obtuse vs acute) to address different functional requirements. The obtuse-angled corners prevent catching on the groove edges during telescopic movement, while the overall rhombic shape maintains engagement with the cam for locking functionality.
2Reliability
If the boss width matches the groove width for secure engagement, then the fastening mechanism achieves reliable locking, but the boss catches on the groove edges during telescopic adjustment requiring excessive force
Solution Approach 1:
The asymmetric corner design creates clearance between the boss and groove edges during telescopic adjustment. The obtuse-angled corners are positioned such that they do not contact the groove edges, eliminating the wedge effect and reducing the force required for telescopic movement while maintaining secure engagement through the cam mechanism.
3Stability of the object's composition
If the boss has flat surfaces for stable engagement, then the fastening mechanism maintains stability, but the boss rotates and catches on groove edges during telescopic adjustment causing noise
Solution Approach 1:
The asymmetric corner configuration prevents rotational movement of the boss during telescopic adjustment. By designing two opposite corners with obtuse angles that face away from the groove edges, the boss is constrained to move linearly without rotating, thereby eliminating the rattling and jingling noise while maintaining stable engagement.
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A fastening mechanism fastens a first side plate to a second side plate by a first fastening member 32. A boss 50 with a rhombic cross-section of the first fastening member 32 is inserted into a telescopic-adjust long groove 23 of the second side plate. An outer periphery 50a of the boss 50 includes a first corner part 61 and a third corner part 63 each forming an obtuse angle and facing each other. The first corner part 61 is disposed on an upper side XU in an axial direction X, on a lower side YL in a tilt direction Y, while the third corner part 63 is disposed on a lower side XL in the axial direction X, on an upper side YU in the tilt direction Y. A width DT across the first corner part 61 and the third corner part 63 is shorter than a groove width W of the telescopic-adjust long groove 23.