Spindle Nut Variable Tooth Depth for Crash Stability
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Solution Overview
Problem
Existing adjustable mechanisms in motor vehicles face challenges in achieving a compact, stable, and lightweight design while preventing spindle nut slippage during crashes, which can lead to breakage due to notch tension effects and increased mechanical strain.
Innovation Solution
The spindle nut features radially inward recesses forming a globoid external toothing with a continuous transition to tooth-free end sections, and an internal toothing with increased tooth thickness, made from lightweight materials like plastics, and a gearbox housing with push-fit connections and reinforcement rings for enhanced stability and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the spindle nut is made from lightweight materials like plastics, then the overall weight of the adjustable mechanism is reduced, but the stability and resistance to crash forces may be compromised
Solution Approach 1:
The spindle nut features variable tooth depth along its axial length, with greater tooth depth in regions subjected to higher mechanical strain during crashes. This localized variation in structural properties allows the plastic spindle nut to maintain strength where needed while keeping overall weight low.
Solution Approach 2:
The invention uses plastic material with strategically designed geometric features (variable tooth depth, reinforcement structures) to achieve the performance previously requiring heavier materials. The composite approach combines material selection with structural optimization to resolve the weight-strength trade-off.
2Reliability
If the external toothing of the spindle nut extends over its entire outer surface, then the engagement with the spindle is maximized, but notch tension effects increase which can lead to breakage in crash situations
Solution Approach 1:
The external toothing is designed with variable tooth depth along the axial direction, with tooth depths diminishing towards axial ends. This creates regions of different structural properties - deeper toothing in the center for maximum engagement, and shallower or absent toothing at ends to reduce notch tension effects and prevent breakage.
3Reliability
If the spindle nut design is optimized for crash stability with reinforced structures, then reliability improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The spindle nut geometry is optimized by varying tooth depth as a parameter along the axial direction, creating a gradient structure that provides crash stability without requiring complex reinforcement elements. This parametric variation achieves reliability through geometric optimization rather than added structural complexity.
Data Source
AI summary
An adjustable mechanism for a motor vehicle is used to adjust an adjustable element in a motor vehicle, especially a seating part. Said mechanism comprises a spindle nut comprising an axis, said spindle nut co-operating with a thread spindle and comprising external toothing on the external surface thereof which is in contact with an additional drive element. The external toothing of the spindle nut is formed by recesses in the external surface of the spindle nut which are inwardly turned in a radial manner, the teeth depths thereof diminishing in the direction of at least one axial end of the spindle nut.