Steering Column Slot and Clamp Mechanism for Free Play Control
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Solution Overview
Problem
Existing steering column assemblies face challenges in controlling the free play between inner and outer tubes, particularly due to inconsistent inner diameters of the outer tube during machining, leading to complex lock nut arrangements that require careful setup and can be easily disrupted over time.
Innovation Solution
A steering column assembly with an elongate slot and flanges, featuring a clamp mechanism and a catch that secures the flanges to control the inner diameter of the outer tube, ensuring predictable sliding friction and energy absorption during crashes, while allowing for reach and rake adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a clamp mechanism is used to hold the outer tube rigidly to the inner tube, then the bending stiffness of the column assembly is maximized, but the free play between the tubes becomes hard to control due to inconsistent inner diameters of the outer tube
Solution Approach 1:
The patent applies parameter changes by providing an elongate slot in the outer tube that can be partially closed by applying a load to cause a reduction in the internal diameter of the tube. This allows the inner diameter parameter to be dynamically adjusted from a larger relaxed state to a reduced clamped state, enabling the clamp mechanism to achieve consistent gripping force despite variations in the original tube dimensions.
Solution Approach 2:
The patent applies preliminary action by providing a catch that limits the movement of the clamp mechanism to prevent over-opening of the slot when unclamped. This preliminary constraint ensures that the flanges remain within optimal positioning bounds, maintaining consistent free play control while allowing the clamp mechanism to function effectively across different tube samples.
2Manufacturing precision
If lock nuts are added to control the free play between flanges, then the positioning precision is improved, but the device complexity increases and requires careful setup
Solution Approach 1:
The patent extracts the free play control function from the clamp mechanism itself and places it in a separate catch component. This separation allows the clamp mechanism to focus on providing clamping force while the catch independently manages the unclamped position limits, simplifying the overall design compared to using lock nuts integrated into the clamp mechanism.
Solution Approach 2:
The catch acts as an intermediary element between the flanges and the clamp mechanism. It mediates the positioning of the flanges by limiting their movement range, thereby controlling free play without requiring the clamp mechanism itself to be adjusted or modified with complex lock nut arrangements.
3Ease of operation
If the outer tube is allowed to open fully when unclamped, then the ease of operation is improved, but unwanted lateral play occurs between the tubes
Solution Approach 1:
The catch provides preliminary action by pre-establishing limits on flange movement before the clamp mechanism is engaged or disengaged. This ensures that even when unclamped, the slot cannot open beyond a predetermined amount, preventing excessive lateral play while still allowing sufficient movement for reach adjustment operations.
Data Source
AI summary
A steering column assembly comprises inner and outer tubes, an elongate slot in the outer tube closed by applying a load to either side of the slot to reduce the internal diameter of the tube, a pair of flanges fixed to the tube on opposing sides of the slot, and a clamp mechanism which connects one flange to the other, the clamp mechanism movable between a clamped position which applies a clamping force to the flanges to reduce the slot width and tighten the outer tube around the inner tube, and an unclamped position which permits the flanges to move away from one another, and a catch secured at one end to one of the flanges and catches a part of the other flange at its other end, to prevent movement of the flanges beyond a position wherein the inner diameter of the outer tube is equal to a predetermined maximum value.