Length-Adjustable Steering Shaft with Interlocking Sliding Layer

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Solution Overview

Problem

The existing length-adjustable steering shafts face issues with the sliding layer becoming uncontrolled during telescopic adjustment, potentially leading to compromised adjustment due to a lack of secure fastening, resulting in potential detachment from the toothed shaft.

Innovation Solution

The method involves configuring form-fitting elements on the toothed shaft or hollow shaft surfaces to create a substance-to-substance bonded and form-fitting connection with a thermoplastic sliding layer, which is either overmolded or inserted as a sliding sleeve, ensuring a reliable and load-bearing engagement that prevents uncontrolled movement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a sliding layer is attached between the inner toothing and the toothing to reduce friction and rotational play, then the steering precision and smoothness are improved, but the sliding layer may become uncontrolled and detach during telescopic adjustment

Engineering Contradiction:

Improvesteering precisionVSAvoidsliding layer retention

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The sliding layer is segmented with recesses and protrusions that interlock with corresponding features on the toothed shaft, dividing the continuous sliding surface into discrete engagement zones that prevent uncontrolled axial movement while maintaining smooth radial sliding capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The sliding layer is designed with locally differentiated properties: the radial surfaces maintain low friction for smooth telescopic adjustment, while the axial edges feature interlocking protrusions and recesses for secure retention, creating different functional zones within a single component

Inventive Principle:

Principle #3Local quality

2Reliability

If the sliding layer is firmly fastened to the toothing to prevent detachment, then the reliability is improved, but the frictional resistance and rotational play increase

Engineering Contradiction:

Improvesliding layer retentionVSAvoidfriction force

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The fastening function is segmented from the sliding function: interlocking protrusions and recesses provide retention in the axial direction, while the radial sliding surfaces remain smooth and low-friction for telescopic adjustment, allowing both functions to coexist without compromise

Inventive Principle:

Principle #1Segmentation

3Ease of operation

If the sliding layer is made softer and more elastic to reduce friction, then the ease of operation is improved, but the load-bearing capability and fastening strength decrease

Engineering Contradiction:

Improveadjustment smoothnessVSAvoidfastening strength

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The sliding layer's functionality is segmented into load-bearing interlocking zones with protrusions and recesses that engage mechanically, and low-friction sliding zones with softer elastic material, allowing the same component to provide both smooth operation and secure retention

Inventive Principle:

Principle #1Segmentation

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 provides a secure and durable attachment of the sliding layer, enhancing the load-bearing capability and preventing detachment during telescopic adjustments, ensuring precise and smooth steering operations while maintaining the play-free and comfortable steering experience.

Implementation Method 1

The sliding layer as a sliding coating by overmolding can be configured from thermoplastic plastics material, wherein the plastics material in the molten state is applied by an injection-molding method to the toothing so as to form a layer

Methodology Applied

Scientific EffectOvermolding:

Implementation Method 2

the plastics material in the molten state is applied by an injection-molding method to the toothing so as to form a layer

Methodology Applied

Scientific EffectInjection molding:

Implementation Method 3

The sliding layer is composed of plastics material which is softer and more elastic than the metallic material of the toothings and which in the sliding contact with the metallic surfaces of the toothings has a lower frictional resistance

Methodology Applied

Scientific EffectFriction reduction: Friction

Data Source

PatentUS10793180B2Method for producing a length-adjustable steering shaft, and length-adjustable steering shaft

Publication Date: 2020.10.06 THYSSENKRUPP PRESTA AG

AI summary

A method for producing a length-adjustable steering shaft having a hollow shaft in which a toothed shaft is received so as to be axially telescopic. The toothed shaft has a toothing with teeth on an external circumference that extend in the axial direction and which engages in a form-fitting manner in an inner toothing of the hollow shaft. A sliding layer of thermoplastic plastics material is at least in portions attached between the inner toothing and the toothing. In order to enable an improved fastening of the sliding layer to the toothing, prior to attaching the sliding layer, form-fitting elements which for forming a form-fitting connection that is effective in the axial direction are brought to engage with the sliding layer are configured in the region of the toothing of the toothed shaft or the inner toothing of the hollow shaft.