Exterior Mirror Pivot Joint With Nested Coil Spring Retention
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Solution Overview
Problem
Existing exterior rearview mirror assemblies face challenges with inconsistent biasing forces due to traditional coil springs, which are limited by packaging constraints and require higher forces for larger mirror heads, leading to potential stress on seals and reduced operational efficiency.
Innovation Solution
A dual/nested coil spring design with alternating and overlapping coil patterns provides consistent biasing forces, allowing for improved retention of the mirror head in detent positions and reduced stress on seals, suitable for both powerfold and breakaway mirror assemblies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a traditional coil spring is used in the pivot assembly, then the mirror head can be retained in detent positions, but the biasing force is inconsistent and packaging constraints limit the available force
Solution Approach 1:
The patent employs a nested spring configuration where an inner coil spring is positioned within an outer coil spring. Both springs are concentric and work together to provide biasing force. The inner spring has a smaller diameter and is contained within the outer spring's coil structure, creating a compact nested arrangement that maximizes force output while minimizing space requirements in the pivot assembly.
Solution Approach 2:
The patent combines multiple coil springs (inner and outer springs) into a single integrated biasing system. The springs are positioned to work together simultaneously, with their combined forces providing consistent and reliable biasing action on the pivot assembly. This merging of multiple spring elements creates a more robust force delivery system than a single spring could provide.
2Force
If higher biasing forces are used for larger mirror heads, then retention in detent positions is improved, but stress on seals increases
Solution Approach 1:
The nested spring configuration allows the system to generate higher biasing forces within a compact space. The inner and outer springs work together to provide increased force without requiring a larger overall spring diameter, thus maintaining space constraints while improving retention force for larger mirror heads.
Solution Approach 2:
The patent modifies the spring parameters by using two different coil springs with different characteristics (inner spring with smaller diameter, outer spring with larger diameter). This allows optimization of the force output to match the specific requirements of larger mirror heads while distributing the force application in a controlled manner that reduces harmful stress concentrations on seals.
3Force
If a larger coil spring is used to provide greater biasing force, then retention is improved, but the packaging space required increases
Solution Approach 1:
The inner coil spring is nested within the outer coil spring, creating a compact concentric arrangement. This nested configuration allows both springs to occupy overlapping spatial volumes, significantly reducing the overall package size compared to using two separate springs or a single larger spring. The inner spring fits within the coil structure of the outer spring, maximizing space efficiency.
Solution Approach 2:
The nested spring arrangement transitions from a single-dimensional (linear) spring configuration to a multi-dimensional concentric arrangement. By utilizing radial space in multiple dimensions simultaneously, the system accommodates greater biasing force capability within a smaller overall volume, effectively adding dimensional complexity to solve the space-force tradeoff.
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 dual/nested coil spring design enhances mirror performance by providing greater biasing force in a smaller package, ensuring secure retention of the mirror head in detent positions and reducing stress on seals, enabling efficient operation with larger mirror heads.
Implementation Method 1
The pivot assembly includes a dual/nested spring that biases the pivot assembly into the detent position
Data Source
AI summary
A vehicular exterior rearview mirror assembly includes a mirror head that includes a mirror reflective element and a mounting base configured for attachment at a side of a vehicle. The mirror head is movable relative to the mounting base between an extended position and a folded position. A pivot assembly includes (i) a pivot post fixed relative to the mounting base, (ii) a housing portion pivotable about the pivot post, and (iii) a biasing element disposed at the pivot post between the housing portion and an end of the pivot post, the biasing element urging a detent interface into engagement. The detent interface moves into engagement to secure the mirror head in the extended or folded position. The biasing element includes first and second coil portions having overlapping and alternating coil patterns.