Wrap Spring Clutch Overrun Locking Member Design

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Solution Overview

Problem

Existing decouplers are susceptible to rotational locking issues during mode transitions, particularly at high rotational speeds and abrupt torque changes, which can lead to separation of the wrap spring clutch from the output member, resulting in potential fatigue and reduced operational life.

Innovation Solution

Incorporation of an overrun locking member on the wrap spring clutch that engages with an overrun locking feature on the output member, ensuring the first helical end of the wrap spring clutch remains rotationally fixed with the output member even during overrun conditions, utilizing an interference fit and radial expansion to maintain engagement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the wrap spring clutch is allowed to rotate freely during overrun conditions, then the device can operate in overrun mode, but the wrap spring clutch may separate from the output member causing rotational locking and reduced operational life

Engineering Contradiction:

Improveoverrun capabilityVSAvoidengagement stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The overrun locking mechanism is segmented into distinct components: the overrun locking member with drive surfaces, the overrun locking aperture with engagement surfaces, and the face at the helical end. This segmentation allows independent optimization of each component's function while maintaining overall system reliability during mode transitions

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The overrun locking member acts as an intermediary element between the wrap spring clutch and the output member. During overrun conditions, this intermediary maintains the rotational connection through engagement of drive surfaces, preventing direct separation while still allowing the clutch to rotate independently when needed

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If the wrap spring clutch maintains firm engagement with the output member, then torque transfer efficiency is improved, but stress and fatigue on the clutch increase during mode transitions

Engineering Contradiction:

Improvetorque transfer efficiencyVSAvoidclutch durability

Core Design Contradiction:

PowerVSStrength

Solution Approach 1:

The engagement mechanism transitions dynamically between different states: fully engaged during torque transfer mode, partially engaged during mode transition, and disengaged during overrun mode. The overrun locking member enables this dynamic adjustment, maintaining optimal engagement level for each operational phase to balance torque transfer efficiency with stress reduction

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The overrun locking mechanism provides protective engagement before complete separation occurs during mode transitions. The gradual disengagement through controlled interaction of drive surfaces cushions the transition, preventing sudden impacts and reducing fatigue stress on the wrap spring clutch

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Speed

If the wrap spring clutch is designed for high-speed operation, then operational speed is improved, but rotational locking issues and separation risks increase

Engineering Contradiction:

Improverotational speedVSAvoidengagement stability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The overrun locking mechanism employs composite design principles combining rigid locking surfaces for stability with controlled compliance in the engagement interfaces. This composite approach maintains reliable engagement at high speeds while accommodating dynamic loads and preventing rotational locking through balanced structural properties

Inventive Principle:

Principle #40Composite materials

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 overrun locking mechanism effectively prevents rotational separation of the wrap spring clutch from the output member, reducing stress on the clutch and extending its operational life by maintaining engagement and torque transfer efficiency across mode transitions.

Implementation Method 1

utilizing an interference fit and radial expansion to maintain engagement

Methodology Applied

Scientific EffectInterference fit:

Implementation Method 2

utilizing an interference fit and radial expansion to maintain engagement

Methodology Applied

Scientific EffectRadial expansion:

Implementation Method 3

a wrap spring clutch having a first helical end and a plurality of coils

Methodology Applied

Scientific EffectHelical spring: Spring

Data Source

PatentUS9651099B2Clutched device with wrap spring clutch with overrun locking member

Publication Date: 2017.05.16 LITENS AUTOMOTIVE INC

AI summary

In an aspect, the invention is directed to a clutched device (such as, for example, a decoupler) that includes a clutch input member, a clutch output member, a wrap spring clutch. The wrap spring clutch has an overrun locking member thereon that is engageable with an overrun locking aperture in the output member so as to maintain a face at the helical end of the wrap spring clutch in engagement with a output member clutch drive face on the clutch output member.