Telescopic Steering Shaft Sliding Coating With Coaxial Core Positioning
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Solution Overview
Problem
Existing methods for manufacturing telescopic steering shafts require high manufacturing effort and result in non-uniform sliding coatings due to the need for precise positioning of the shaft core in the injection mold, leading to dimensional deviations and misalignment.
Innovation Solution
The method involves using at least three positioning elements arranged evenly around the circumference within the gear teeth area to center and clamp the shaft core coaxially in the mold cavity, eliminating the need for additional machined mating surfaces and ensuring precise alignment for uniform sliding coating thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a steering column is constructed from multiple separate parts (housing, insert, airbag guide) that are pressed together, then assembly flexibility is improved, but the risk of foreign object contamination and assembly errors increases
Solution Approach 1:
The patent merges the housing, insert, and airbag guide into a single integrated steering column housing produced by injection molding. This eliminates the pressing assembly process and associated foreign object contamination risks while maintaining the functional separation of components through integrated design features.
Solution Approach 2:
The single steering column housing performs multiple functions that were previously distributed across separate parts: structural support, airbag guide formation, and insert integration. This multi-functional design reduces assembly steps while maintaining manufacturing flexibility through mold-based customization.
2Adaptability or versatility
If different materials with different shrinkage rates are pressed together to form a steering column, then material selection flexibility is improved, but warpage and assembly precision deteriorate
Solution Approach 1:
The patent changes the material parameter by using a single thermoplastic resin for the entire steering column housing, eliminating shrinkage rate mismatches between different materials. The design maintains flexibility by selecting from various thermoplastic materials and using insert molding to incorporate different material inserts where needed.
Solution Approach 2:
The patent introduces a molded-in insert as an intermediary element that connects different material regions. This insert, formed through insert molding, provides a transition zone that maintains dimensional stability and prevents warpage while allowing different materials to be used in different functional areas.
3Reliability
If a steering column is designed as a single integrated housing, then foreign object contamination is reduced, but the complexity of the molding process increases
Solution Approach 1:
The patent applies preliminary action by incorporating inserts and forming airbag guide features directly during the injection molding process itself. This eliminates subsequent assembly operations and reduces the overall process complexity despite the integrated design, as the complexity is front-loaded into a single molding operation.
Solution Approach 2:
The patent uses nesting by placing inserts within the main housing during a single molding cycle. The insert molding process allows one component to be formed within another, creating an integrated structure without requiring separate assembly steps, thereby reducing foreign object contamination risks.
4Ease of repair
If separate components are pressed together to form the steering column, then ease of repair and replacement is improved, but productivity and assembly time worsen
Solution Approach 1:
The patent maintains segmentation at the design level by incorporating distinct functional regions and molded-in inserts within the single housing. This allows certain features to be modified or replaced by retooling the mold rather than replacing the entire column, balancing repairability with manufacturing efficiency.
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 approach reduces manufacturing effort and achieves higher dimensional accuracy and quality of the sliding coating, ensuring consistent performance and operational reliability of the telescopic steering shaft.
Implementation Method 1
an injection molding apparatus for forming a steering column housing by molding a thermoplastic resin
Implementation Method 2
a plurality of heaters arranged along the barrel to heat and store thermal energy in the molten resin before injection into the mold cavity
Implementation Method 3
the mold is opened, the steering column housing is ejected from the mold, and the ejection is repeated to thereby mass-produce the steering column housing
Data Source
Figure 1~3
Figure 3a~5
Figure 6~6a
AI summary
The invention relates to a method for producing a variable-length steering shaft (2), comprising a hollow shaft (21) having an internal toothing, in which a positively engaging toothed shaft (22) is arranged telescopically in the axial direction, said toothed shaft having a toothing region (23) with teeth (24) extending in the axial direction arranged on the outer periphery, wherein in the injection molding process a shaft core (3) is overmolded in the toothing region (23) with a sliding coating (5) of thermoplastic plastic, comprising the steps of positioning the shaft core (3) inside a mold cavity (41) of an injection mold (4) coaxially with respect to a mold surface (411) which delimits the toothing region (23), injecting molten plastic into the mold cavity (41) between the shaft core (3) and the mold surface (411) of the mold cavity (41) through at least one injection nozzle (48), removing the toothed shaft (22) from the injection mold (4) after the solidification of the plastic, providing the hollow shaft (21) and introducing the toothing region axially into the internal toothing. The aim of the invention is to provide a method and a device which necessitates a lower manufacturing expenditure for producing a telescopic steering shaft. This aim is achieve, according to the invention, in that positioning elements (42a, 42b, 42c, 45a, 45b, 45c, 45d, 45e, 45f) are arranged at least partially in the region of the mold surface (411) of the toothing for positioning the shaft core (3), which positioning elements abut the shaft core (3) radially from the outside in the region of the toothing by means of positioning surfaces (44) and retain said shaft core coaxially in the mold cavity (41).