Adjustable Steering Column Preload Structure for Low-Wear Precision
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Solution Overview
Problem
Existing electrically adjustable steering columns face challenges in precise and sensitive adjustment due to frictional forces acting in the circumferential direction, leading to increased wear and difficulty in setting the preload force accurately.
Innovation Solution
A clamping body interacts with slot edges via a deflection device that converts a reduction in slot width into a radial clamping movement, allowing for precise preload control by decoupling radial and circumferential force components, with the preload device being permanently fixed during assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a preloading device is used to apply clamping force to reduce slot width and preload the bearing surface, then the rigidity of the steering column is improved, but frictional forces in the circumferential direction increase making precise adjustment difficult and wear increases
Solution Approach 1:
The invention separates the circumferential clamping function and radial preloading function into distinct components: the slot edges provide circumferential clamping while the clamping body with bearing surfaces provides radial preloading. This segmentation eliminates the coupling of frictional forces between the bearing surface and cylindrical surface during clamping, allowing independent optimization of both rigidity and adjustment sensitivity.
Solution Approach 2:
The clamping body acts as an intermediary element between the slot edges and the cylindrical surface. It converts the circumferential clamping force into radial preloading force through its geometric design, mediating the force transmission to achieve decoupling of the force components and eliminate harmful frictional effects.
2Strength
If a higher preload force is set to ensure sufficient stiffness, then the rigidity is improved, but wear between the bearing surface and cylindrical surface increases
Solution Approach 1:
By segmenting the clamping and preloading functions, the invention eliminates the frictional wear mechanism that occurred when bearing surfaces slid against each other during clamping. The new design allows high preload forces to be applied without the accompanying circumferential friction that caused wear, thereby extending service life while maintaining stiffness.
3Force
If the slot width is reduced to apply clamping force, then the preload force is improved, but frictional forces superimpose on the radial preload making precise force specification difficult
Solution Approach 1:
The invention segments the force components so that circumferential clamping force and radial preload force are generated by different mechanisms. The slot width reduction produces circumferential clamping that is transmitted through the clamping body geometry to generate radial preload, eliminating the superposition of frictional forces and enabling precise specification of preload force independent of clamping adjustments.
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
This solution enables precise adjustment with reduced wear and increased service life by allowing for more accurate preload force specification and decoupling of force components, optimizing the sliding friction and required drive power.
Implementation Method 1
a deflection device, which converts a reduction in the slot width into a radial clamping movement of the clamping body
Implementation Method 2
an inner bearing surface formed inside the longitudinal passage surrounds an outer surface of the outer tube from the outside, thereby guiding the outer tube in a sliding manner in the longitudinal direction
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention relates to an electrically adjustable steering column (1) for a motor vehicle, comprising: a casing tube (33), in which a steering shaft (31) is rotatably mounted about its longitudinal axis (L), and which is, in the direction of the longitudinal axis (L), telescopically adjustably accommodated in a guide unit (34) that can be connected to a body of a motor vehicle; and an electric-motor adjustment drive (7) which is arranged between the casing tube (33) and the guide unit (34), wherein an inner bearing surface (36) of the guide unit (34) surrounds an outer casing surface of the casing tube (33), and has a slit (4) which extends in the direction of the longitudinal axis (L) and has a slit width between its opposing slit edges (41), on which slit a pretensioning device (5) engages, by which a tensioning force (S) acting to reduce the slit width can be applied in order to pretension the bearing surface (36) together with the casing surface. In order to be able to better and more precisely specify the pretensioning force, and to reduce wear during the adjustment, according to the invention a clamping body (6) interacts with the slit edges (41) via a deflection device (42, 62) which converts a reduction of the slit width into a radial clamping movement of the clamping body (6) in order to radially pretension against the outer casing surface of the casing tube (33).