Steering Column Actuator Helical Bushing Noise Reduction
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Solution Overview
Problem
Existing power actuator systems for adjustable steering columns suffer from noise issues due to over-constraint and binding caused by leadscrew rotational runout or misalignment, which compromises sound quality and axial load support.
Innovation Solution
A power actuator assembly incorporating an electric motor, leadscrew, gear arrangement, nut, leadscrew housing, and a helical bushing with radially exterior and interior features, along with a ball bearing set to allow radial compliance and reduce binding, enabling axial stiffness and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If thrust bearings are incorporated to support axial loads, then axial load support is improved, but the system becomes over-constrained and produces noise due to leadscrew runout or misalignment
Solution Approach 1:
The patent changes the compliance parameter of the bearing system by introducing elastomeric material elements between the thrust bearing and leadscrew housing. This allows the system to maintain axial stiffness for load support while introducing radial compliance to accommodate misalignment and runout, thereby reducing noise generation
Solution Approach 2:
The patent employs a composite bearing assembly combining rigid thrust bearings for axial load support with elastomeric compliance elements for radial flexibility. This composite structure enables simultaneous achievement of axial stiffness and radial compliance, resolving the noise issue caused by over-constraint
2Manufacturing precision
If a stiff and lash free system is designed, then motion precision is improved, but sound quality deteriorates due to binding from over-constraint
Solution Approach 1:
The patent modifies the stiffness parameter distribution in the system by maintaining high axial stiffness through thrust bearings while introducing radial compliance through elastomeric elements. This differential stiffness approach preserves motion precision in the axial direction while eliminating binding-induced noise through radial flexibility
3Force
If thrust bearings are used to support axial loads, then load capacity is improved, but adaptability to misalignment and runout deteriorates
Solution Approach 1:
The patent changes the compliance parameter by incorporating elastomeric material between the thrust bearing and housing, transforming the bearing assembly from a rigid over-constrained system to one with controlled radial compliance. This enables the system to adapt to misalignment and runout while maintaining axial load capacity
Solution Approach 2:
The elastomeric compliance elements act as intermediaries between the rigid thrust bearing and the leadscrew housing, absorbing misalignment and runout errors. This intermediary layer protects the precision components from the harmful effects of manufacturing tolerances and assembly variations
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 provides an axially stiff and low-lash bearing system that supports axial loads, absorbs energy, and allows for leadscrew eccentricity and misalignment without inducing noise, enhancing sound quality and motion precision.
Implementation Method 1
a helical bushing disposed between a radially inner surface of the leadscrew housing and a radially outer surface of the leadscrew
Implementation Method 2
a ball bearing set having an inner race in contact with the leadscrew and an outer race in contact with a leadscrew housing
Implementation Method 3
a nut threaded to the leadscrew, rotation of the leadscrew actuating linear motion of the nut relative to the leadscrew
Data Source
AI summary
A power actuator assembly for a steering column assembly is provided. The power actuator assembly include an electric motor. Also included is a leadscrew. Further included is a gear arrangement operatively coupled to the electric motor, the gear arrangement driving rotation of the leadscrew. Yet further included is a nut threaded to the leadscrew, rotation of the leadscrew actuating linear motion of the nut relative to the leadscrew, the nut operatively coupled to a moveable portion of the steering column assembly to actuate motion of the moveable portion. Also included is a leadscrew housing, the leadscrew extending axially through the leadscrew housing. Further included is a helical bushing disposed between a radially inner surface of the leadscrew housing and a radially outer surface of the leadscrew.