Steering Yoke Groove Layout for EPAS Rattle Noise Reduction
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Solution Overview
Problem
Steering rattle noise persists in electric power assisted steering (EPAS) systems, particularly when traversing rough surfaces, despite the use of O-ring assemblies to reduce noise.
Innovation Solution
A yoke design with a first circumscribing groove and a first lateral groove is implemented to house O-rings, which inhibit noise generation from contact between the yoke and the gear housing, and between the yoke's tip portion and the gear housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a single circumscribing O-ring assembly is used to reduce noise from yoke-gear housing contact, then noise from general contact is inhibited, but noise from the tip portion contact on rough terrain persists
Solution Approach 1:
The patent divides the noise inhibition function into two separate O-ring assemblies: a first circumscribing O-ring assembly for general contact noise and a second lateral O-ring assembly for tip portion contact noise. This segmentation allows each assembly to target specific noise sources independently, resolving the contradiction by ensuring comprehensive noise inhibition across different contact points without interference between the two functions.
Solution Approach 2:
The patent introduces a second lateral O-ring assembly as an additional intermediary element between the yoke tip portion and the gear housing. This mediator specifically addresses the tip portion contact issue that the first circumscribing O-ring assembly cannot fully resolve, thereby enhancing overall noise inhibition effectiveness while maintaining the original circumscribing O-ring's function.
2Object-affected harmful factors
If O-ring assemblies are added to inhibit noise, then noise generation is reduced, but the complexity of the steering assembly increases
Solution Approach 1:
The patent uses O-rings, which are flexible elastic elements, to inhibit noise. These thin film-like components effectively reduce noise generation through their cushioning properties while adding minimal structural complexity. The flexible nature of O-rings allows them to conform to the yoke and gear housing surfaces without requiring complex mounting structures.
Solution Approach 2:
By dividing the noise inhibition function into two separate O-ring assemblies with distinct grooves, the patent manages complexity through functional segmentation. Each O-ring assembly is simple in design but together they provide comprehensive noise inhibition. The segmentation allows for independent installation and maintenance of each assembly, reducing overall system complexity management.
3Reliability
If the yoke maintains positive engagement with the rack shaft and pinion gear, then steering function is ensured, but contact noise occurs on rough surfaces
Solution Approach 1:
The patent introduces O-ring assemblies as intermediary elements between the yoke and the gear housing. These intermediaries maintain the necessary engagement for steering function while providing a cushioning layer that prevents direct hard contact noise on rough surfaces. The O-rings allow the steering function to proceed while absorbing the harmful contact noises.
Solution Approach 2:
The O-ring assemblies are pre-installed in grooves on the yoke to provide beforehand cushioning. This prior cushioning ensures that when contact occurs on rough terrain, the noise is already mitigated by the elastic O-rings, allowing the steering function to maintain positive engagement without generating contact noise.
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 yoke design effectively reduces steering rattle noise across various terrains by minimizing contact between the yoke and the gear housing, while maintaining proper lash between the rack shaft and the pinion gear.
Implementation Method 1
a first circumscribing groove extending around an outer diameter of the yoke to receive a first circumscribing O-ring to inhibit noise generation from contact between the yoke and the gear housing
Implementation Method 2
a first lateral groove disposed at a tip portion of the yoke between the pinion gear and the first O-ring assembly to receive a first lateral O-ring
Data Source
AI summary
A yoke for a steering assembly that includes a rack shaft and a pinion gear disposed at a gear housing may include a first circumscribing groove extending around an outer diameter of the yoke to receive a first circumscribing O-ring to inhibit noise generation from contact between the yoke and the gear housing, and a first lateral groove disposed at a tip portion of the yoke between the pinion gear and the first O-ring assembly to receive a first lateral O-ring. The first circumscribing groove lies in a first plane substantially perpendicular to an axis of the yoke, and the first lateral groove lies in a second plane substantially perpendicular to the first plane on a first lateral side of the yoke.