Plastic Steering Column Spline with Tapered Teeth
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Solution Overview
Problem
Existing steering control shafts and shafts in motor vehicles lack a design that balances light weight, torsional rigidity, and the ability to be easily shifted along the main axis while maintaining structural integrity and safety during crashes.
Innovation Solution
A shaft design featuring a tube-shaped part and a pushed-in part connected by a spline, where the pushed-in part has elongated teeth that taper and engage a plastically deformable counter profile, allowing for sliding movement and compressibility during impacts, with optional reinforcement and lubrication to enhance stability and reduce crash energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a steering column is designed as a rigid integral structure, then structural integrity and strength are improved, but the ability to compress and deform during crashes is reduced
Solution Approach 1:
The steering column is divided into multiple segments (first part and second part) that can move relative to each other along the longitudinal axis. The spline connection allows these segments to slide past one another during impact, enabling controlled deformation and energy absorption while maintaining overall structural integrity through the engaged spline teeth.
2Adaptability or versatility
If a steering column uses a telescopic multi-part design, then compressibility and safety during crashes are improved, but structural rigidity and torsional stiffness are reduced
Solution Approach 1:
The spline connection extracts only the necessary degree of freedom (longitudinal movement) while constraining other movements (radial and rotational). This allows the steering column to compress during crashes through axial sliding of segments, while the engaged spline teeth maintain torsional rigidity by preventing relative rotation between segments.
3Manufacturing precision
If teeth of the spline are hardened and made as cutting edges, then manufacturing precision and connection strength are improved, but the ease of assembly and ability to accommodate plastic deformation is reduced
Solution Approach 1:
Only the critical load-bearing surfaces of the spline teeth (flank faces) are hardened to ensure precise engagement and high connection strength. The root and tip regions of the teeth remain softer and more ductile, allowing them to undergo plastic deformation during assembly without cracking, thus facilitating easier assembly while maintaining precision where needed.
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 design provides a lightweight, torsionally rigid shaft that can compress during crashes, reducing the risk of buckling and enhancing safety by allowing the parts to move relative to each other, while maintaining structural integrity and reducing crash energy through controlled deformation.
Implementation Method 1
The second part, at its circumference facing the first part, is made of plastically deformable plastic material, and the counter profile is pressed in the plastic material of the second part by intrusion of the teeth of the first part into the plastic material during assembly of the first and second parts.
Implementation Method 2
The first part and the second part are fixed to each other for rotation about the main axis and connected to each other in a gliding way in the direction of the main axis by a spline provided between the first and the second parts
Implementation Method 3
In case of a crash of a motor vehicle in which they are mounted, they may be deformed or telescopically pushed together and thus occupy a reduced space so that they do not put the driver at risk during the crash
Data Source
AI summary
A shaft comprises two parts. One of these two parts is tube-shaped, and the other is pushed into the tube-shaped part along a main axis. The two parts are fixed to each other for rotation about the main axis and connected to each other in a gliding way along the main axis, by a spline provided between the two parts. One of the two parts comprises a plurality of elongated teeth which are parallel to the main axis and whose cross-sections decrease from the first part towards the second part. Intermediate spaces between neighboring teeth are at least as broad as the teeth. The other of the two parts, at its circumference facing the first part, is made of plastically deformable plastic material, and a counter-profile into which the teeth engage is pressed in the plastic material by intrusion of the teeth during assembly of the two parts.