Steering Column Guide Bush Varying Cross Section
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Solution Overview
Problem
Existing steering column assemblies with uniform guide bush cross sections experience inconsistent clamp resistance during reach adjustment, leading to inadequate resistance at the Reach-Out position, potentially causing the column to slip when leaned on by the driver, especially in versions without positive locking mechanisms.
Innovation Solution
A guide bush with a varying cross section along its length, achieved through tapered wall thickness, provides a more uniform resistance to clamping across the adjustment range, ensuring consistent clamp force and preventing slippage by varying the outer or inner diameter from one end to the other.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform cross section guide bush is provided, then the structure is simple and easy to manufacture, but the clamp resistance is inconsistent across the adjustment range
Solution Approach 1:
The guide bush is designed with varying wall thickness along its length, creating different local properties. The wall thickness is greater at the first end than at the second end, providing higher resistance to crushing at the first end and lower resistance at the second end. This local variation in quality ensures consistent clamp resistance across the entire adjustment range, resolving the contradiction between reliability and structural simplicity.
2Reliability
If the guide bush wall thickness is increased, then the resistance to crushing is higher and clamp force is more consistent, but the manufacturing complexity increases
Solution Approach 1:
The guide bush geometry is modified by varying the wall thickness parameter along its length. The wall thickness transitions from a greater thickness at the first end to a lesser thickness at the second end, creating a tapered profile. This parameter change allows the guide bush to provide consistent clamp resistance across different adjustment positions while remaining manufacturable through standard tapering processes.
3Reliability
If the clamp mechanism applies sufficient force to prevent slippage at Reach-In position, then the clamp force is adequate, but the clamp lever locking effort becomes excessively high at Reach-Out position
Solution Approach 1:
The guide bush provides different local resistance properties at different positions along its length. By having greater wall thickness at the first end and lesser wall thickness at the second end, the guide bush creates position-dependent clamp resistance that compensates for the varying mechanical advantage throughout the adjustment range, maintaining consistent operation characteristics.
Solution Approach 2:
The varying wall thickness of the guide bush pre-compensates for the insufficient clamp resistance that would occur at the Reach-Out position with a uniform guide bush. The greater wall thickness at the first end provides the necessary resistance in advance, preventing the clamp force from becoming too weak during the adjustment range.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The varying cross section of the guide bush ensures a more consistent and controllable clamp force, enhancing driver feedback and preventing column slippage across the range of adjustment, thereby improving the overall stability and reliability of the steering column assembly.
Implementation Method 1
a guide bush which comprises a sleeve that is located between an outward facing wall of the end portion of the first member and an inward facing wall of the second member, the guide bush being fixed relative to one of the members and providing a surface over which the other member can slide
Data Source
Figure 1~2
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AI summary
A steering column assembly having a shroud comprises a first member 1 having an end portion which is received within a second member 2 having at least one slit through its wall extending partially along its length, a guide bush 20 located between the first member and the second member and fixed relative to one of the members and providing a surface over which the other member can slide to alter the overall length of the shroud and a clamp mechanism 7 which squeezes the second member 2 onto the guide bush 20 which is in turn squeezed onto the first member 1. The cross section of the guide bush 20 varies along its length to vary the resistance it provides to crushing by the action of the clamp mechanism when the shroud is at its greatest length and the resistance it provides when the shroud is clamped at its shortest length.