Redundant Rotor Coupling Assembly for Lash-Free Power Steering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current rotor coupling assemblies in power steering assist mechanisms suffer from single-point failure modes and packaging constraints due to transitional fits that lead to product wear, lash development, and torsional loss, affecting durability and torsional strength.
Innovation Solution
A rotor coupling assembly with identical rotor coupling adapters and a substrate-overmold structure, featuring crush ribs and ultrasonic welding, provides a redundant and flexible connection between the motor output shaft and worm, ensuring a lash-free interface and improved durability through geometrically identical adapters and localized radial expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a transitional fit is used between spline teeth to achieve low lash, then initial lash is reduced, but product wear over time causes development of lash and torsional loss
Solution Approach 1:
The rotor coupling is segmented into multiple independent load paths through the inclusion of multiple reinforcing ribs (at least three radially extending ribs) that distribute mechanical loads across multiple contact points between the rotor coupling adapter and rotor coupling. This segmentation prevents single-point failure and reduces wear concentration, thereby maintaining reliability over time while preserving the low-lash transitional fit.
Solution Approach 2:
The reinforcing ribs are designed with predetermined geometric configurations and material properties that provide inherent compliance and load distribution capabilities before wear occurs. The ribs act as pre-engineered cushioning elements that accommodate dimensional variations and wear accumulation, preventing the development of excessive lash and torsional loss over the product lifecycle.
2Reliability
If greater interference is used to mitigate wear loss, then lash and torsional loss are reduced, but hoop stresses and part strength are negatively affected
Solution Approach 1:
The load transmission is segmented into multiple parallel paths through the reinforcing ribs, where each rib carries a portion of the total load. This distribution reduces the hoop stress concentration that would occur in a single-point interference fit, while collectively maintaining or improving torsional strength through the combined load-bearing capacity of multiple ribs.
Solution Approach 2:
The rotor coupling assembly utilizes composite construction with a rotor coupling adapter and rotor coupling made from different materials optimized for their specific functions. The reinforcing ribs are integrated into this composite structure, allowing the selection of material combinations that provide both the necessary interference fit for load transmission and the appropriate stress distribution characteristics to avoid excessive hoop stresses.
3Device complexity
If a single-point failure mode is accepted in the coupling system, then device complexity is reduced, but robustness to overall stresses is compromised
Solution Approach 1:
The coupling system is segmented into multiple load-bearing ribs that create redundant load paths. This segmentation transforms a potential single-point failure mode into a distributed failure mode, where the system can continue to function even if one rib experiences wear or damage, thereby improving robustness without significantly increasing overall device complexity.
Solution Approach 2:
The reinforcing ribs are designed with built-in redundancy and compliance characteristics that provide beforehand cushioning against failure. The geometric configuration and material selection of the ribs ensure that stress is distributed across multiple elements, preventing any single point from bearing excessive loads that would lead to premature failure.
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 solution enhances durability and reduces failure modes by providing a redundant, flexible connection with improved lash-free interface and increased contact area, resulting in enhanced torsional strength and reduced backlash over the assembly's life.
Implementation Method 1
ultrasonic welding the shaft and the rotor coupling adapter to each other
Data Source
AI summary
A rotor coupling assembly for a power steering assist mechanism includes a rotor coupling having a first axial side and a second axial side. The rotor coupling assembly also includes a first rotor coupling adapter having a plurality of teeth extending into a corresponding plurality of windows defined by the rotor coupling on the first axial side of the rotor coupling. The rotor coupling assembly further includes a second rotor coupling adapter having a plurality of teeth extending into a corresponding plurality of windows defined by the rotor coupling on the second axial side of the rotor coupling.