Steering Shaft Plastic Encapsulation for Torsional Rigidity
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Solution Overview
Problem
Telescoping steering shafts for motor vehicles face challenges in achieving high torsional rigidity with low displacement force while being easy to produce, and existing solutions often require complex tooth geometries or expensive production methods.
Innovation Solution
A steering shaft design featuring a first shaft part with a toothed area encapsulated in plastic, where the guide element is formed within the encapsulation, and transmission elements engage via a loose form fit, allowing for low friction and high torsional rigidity, reducing the stick-slip effect and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If complex tooth geometries are used to achieve high torsional rigidity with low displacement force, then the torsional performance is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The toothed area is segmented into two functional zones: guide elements for axial guidance and transmission elements for torque transmission. This segmentation allows each zone to be optimized independently, achieving high torsional rigidity through proper transmission element design while maintaining simple, standardized tooth geometries that are easy to manufacture.
Solution Approach 2:
Different properties are applied to different parts of the toothed area. The guide elements have geometry optimized for low-friction axial movement, while the transmission elements have geometry optimized for high-torsion rigidity. This local differentiation allows the system to achieve both low displacement force and high torsional rigidity without requiring complex overall tooth geometry.
2Ease of operation
If sliding sleeves are used to reduce friction during telescoping, then the smoothness of adjustment is improved, but the device complexity increases
Solution Approach 1:
The sliding sleeve component is completely removed from the design. Instead, the guide elements directly on the first shaft part provide the necessary low-friction guidance during telescoping. This extraction of the intermediate sliding sleeve component simplifies the overall structure while maintaining smooth adjustment through proper guide element geometry and material selection.
3Reliability
If elastic connecting elements are glued into grooves to transmit torque, then the torque transmission is improved, but the production cost increases
Solution Approach 1:
The transmission elements are designed to self-align and self-engage with the second shaft part through loose form fit. The elements automatically position themselves during assembly without requiring precise groove alignment or adhesive application. This self-service characteristic eliminates the need for costly glued connections while ensuring reliable torque transmission through the form-fit engagement.
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 achieves low displacement force for smooth adjustment, high torsional rigidity for torque transmission, and simplified production, reducing the stick-slip effect and noise, while maintaining structural integrity and ease of manufacturing.
Implementation Method 1
the toothed area is at least partially encapsulated with a plastic... serve to reduce the friction between the inner spindle and the outer spindle when telescoping
Implementation Method 2
at least one guide element that positively engages with the second shaft part for guiding the first shaft part opposite the second shaft part during telescoping
Implementation Method 3
at least one transmission element, which is in engagement with the second shaft part via a loose form fit, for transmitting a torque
Data Source
Figure 1~3
Figure 4~7
AI summary
The present invention relates to a steering shaft (1) for a motor vehicle, comprising a first shaft part (2) and a telescopable second shaft part (3) opposite the same, wherein the first shaft part (2) has at least one toothed region (20) comprising at least one guide element (6) engaged interlockingly with the second shaft part (3) for guiding the first shaft part (2) opposite the second shaft part (3) during telescoping, and comprising at least one transmission element (40) engaged with the second shaft part (3) via a loose interlocking for transmitting a torque, wherein the toothed region (20) is overmoulded at least partially with a plastic and the guide element (6) is formed by the overmoulding (4).