Steering Shaft Sleeve Fixation for Thermal Expansion Stability
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Solution Overview
Problem
Existing steering shaft designs face issues with the secure fixation of profiled sleeves due to differing thermal expansion coefficients of materials, leading to stress and instability during temperature changes.
Innovation Solution
A steering shaft design that incorporates a profiled sleeve with an aperture on the inner shaft, where a projection from the inner shaft engages with the aperture to securely fix the sleeve, allowing axial movement while minimizing thermal expansion-induced stress, and is produced using materials like steel or fiber-reinforced plastics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the profiled sleeve is fixed on the inner shaft using latching lugs, then the sleeve is secured in the axial direction, but stress occurs in the sleeve due to different thermal coefficients of expansion of the materials during temperature changes
Solution Approach 1:
The connection between the profiled sleeve and inner shaft is segmented into multiple interaction points: the aperture provides axial positioning while the profiling provides radial engagement and torque transmission. This segmentation allows each feature to handle specific loads independently, reducing stress concentration.
Solution Approach 2:
The aperture is nested within the profiling structure of the inner shaft. The projection through the aperture creates a nested engagement system where the aperture provides axial constraint while the profiling provides radial constraint, allowing thermal expansion without stress.
2Power
If the profiled sleeve is fixed rigidly on the inner shaft, then torque transmission is improved, but the sleeve cannot accommodate thermal expansion differences, leading to forced states
Solution Approach 1:
The connection system transitions from a static rigid connection to a dynamic system that adapts to thermal conditions. The aperture allows controlled movement and adjustment, enabling the connection to remain reliable under varying thermal conditions while maintaining torque transmission capability.
Solution Approach 2:
The system changes its mechanical parameters based on temperature. At operating temperatures, the aperture allows slight movements that accommodate thermal expansion differences, while the profiling maintains torque transmission. This parameter adaptation prevents forced states while preserving power transmission.
3Adaptability or versatility
If the profiled sleeve is made from a material with different thermal expansion coefficient than the inner shaft, then design flexibility is improved, but thermal stress occurs during temperature changes
Solution Approach 1:
The aperture acts as an intermediary element between the profiled sleeve and inner shaft. It mediates the thermal expansion differences by allowing controlled movement, enabling the use of materials with different thermal properties without transmitting stress between components.
4Stability of the object's composition
If the aperture is positioned centrally in the profiled sleeve, then thermal expansion is accommodated symmetrically, but the positioning precision must be high
Solution Approach 1:
The aperture positioning is designed with asymmetric tolerances that compensate for thermal expansion patterns. The aperture may be positioned slightly offset or with asymmetric clearance zones that accommodate thermal growth in the most critical directions, reducing the stringency of manufacturing precision requirements.
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 solution provides a secure, play-free fixation of the profiled sleeve, allowing for torque transmission and adjustable length with minimal thermal expansion impact, ensuring rigidity and stability across temperature variations.
Implementation Method 1
a projection which is arranged on an outer face of the inner shaft engages in the aperture in a manner which secures the profiled sleeve in its position on the inner shaft at least in the axial direction
Implementation Method 2
the inner shaft and the outer shaft being coupled in a torque-transmitting manner with the profiled sleeve connected in between
Implementation Method 3
different thermal coefficients of expansion of the materials which are used for the inner shaft and the profiled sleeve. Stressing of the profiled sleeve occurs in the case of temperature changes
Data Source
AI summary
A steering shaft for a motor vehicle may have an inner shaft, an outer shaft, and a profiled sleeve that is fixed on the inner shaft such that the inner shaft is movable together with the profiled sleeve in an axial direction relative to the outer shaft. The inner shaft and the outer shaft may be coupled in a torque-transmitting manner with the profiled sleeve connected therebetween. The profiled sleeve may comprise an aperture into which a projection on an outer face of the inner shaft engages in a manner that secures the profiled sleeve in position on the inner shaft at least in the axial direction.