Electromechanical Strut Bushing for Lateral Play Reduction

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Solution Overview

Problem

Existing electromechanical struts used in automotive closure systems, such as lift gates, face issues with contamination ingress, lateral play, and friction, leading to reduced lifespan and noise, which affect user convenience and perceived quality.

Innovation Solution

An electromechanical strut design featuring a housing with a tubular wall, a motor-driven power screw, an extensible member with a drive mechanism, and a bushing/seal assembly that reduces dynamic friction and lateral play, along with guide features and protrusions to maintain stability and prevent contamination, enhancing the strut's durability and performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a linear actuation assembly with lead screw and nut tube is used to reduce user effort, then the effort required to move the closure member is reduced, but contamination ingress and lateral play occur between linearly translatable components

Engineering Contradiction:

Improveuser effort to move closure memberVSAvoiddevice lifespan due to contamination and wear

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

A bushing is introduced as an intermediary component between the extensible member and housing. The bushing reduces dynamic sliding friction and maintains the annular gap, preventing direct contact and contamination ingress between the lead screw and nut tube, thereby extending device lifespan while maintaining ease of operation

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The bushing acts as a flexible protective shell that lines the annular gap between the extensible member and housing. This thin film structure reduces friction and prevents contamination from reaching critical moving parts, solving the reliability issue without compromising the mechanical advantage provided by the lead screw mechanism

Inventive Principle:

Principle #30Flexible shells and thin films

2Productivity

If linearly translatable components are used for actuation, then closure member movement is achieved, but lateral play and friction increase causing noise and wear

Engineering Contradiction:

Improveclosure member actuationVSAvoidnoise and wear from lateral play

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The bushing serves as a mediator between the extensible member and housing, eliminating lateral play by maintaining a precise annular gap. This intermediary component prevents metal-to-metal contact that causes noise and wear, while still allowing the necessary linear translation for closure member actuation

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The bushing replaces direct mechanical contact between the extensible member and housing with a low-friction interface. This substitution eliminates the harmful mechanical interactions that generate noise and wear, while maintaining the essential mechanical actuation function

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Stability of the object's composition

If the annular gap between housing and outer cover tube is maintained, then lateral play is reduced, but contamination may still ingress without additional protection

Engineering Contradiction:

Improvegap maintenance reducing lateral playVSAvoidcontamination ingress

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The bushing acts as an intermediary protective barrier within the annular gap. It maintains the gap to reduce lateral play while simultaneously serving as a shield that prevents contamination from reaching the critical moving parts, addressing both stability and contamination protection needs

Inventive Principle:

Principle #24Intermediary (Mediator)

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 effectively inhibits contamination ingress, reduces noise and friction, and extends the useful life of the electromechanical strut, providing improved user convenience and perceived quality by maintaining stability and reducing maintenance needs.

Implementation Method 1

An annular bushing is disposed within the annular gap, with the bushing reducing dynamic sliding friction, maintaining the gap and minimizing lateral play between the housing and the outer cover tube

Methodology Applied

Scientific EffectFriction reduction: Lubrication

Implementation Method 2

The extensible member has a drive mechanism for converting rotary motion of the power screw into linear motion of the extensible member to move the extensible member between retracted and extended positions relative to the housing

Methodology Applied

Scientific EffectScrew mechanism: Screw

Data Source

PatentUS10100568B2Electromechanical strut with lateral support feature

Publication Date: 2018.10.16 MAGNA CLOSURES INC

AI summary

An electromechanical strut for moving a closure member between open and closed positions relative to a vehicle body includes a housing having an inner surface bounding a cavity extending along a central axis between opposite first and second ends. A power screw is disposed in the cavity in operable communication with a motor, with a gear assembly operably connecting the motor to the power screw. An extensible member has an outer cover tube received in the housing cavity and a drive mechanism for converting rotary motion of the power screw into linear motion of the extensible member. An annular gap extends between the inner surface of the housing and an outer surface of the outer cover tube. An annular bushing is disposed within the annular gap to minimize laterally play between the housing and the outer cover tube.