Nested Coil Spring Assembly Torsional Vibration Attenuation

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Solution Overview

Problem

Existing spring assemblies using nested coil springs face issues with the inner coil spring getting stuck between windings of the outer coil spring, leading to abrasion and formation of flashes due to friction, which compromises their effectiveness in absorbing and attenuating torsional vibration.

Innovation Solution

The spring assembly design includes an inner coil spring with chamfered end surfaces and a smaller outer diameter at the endmost windings, and optionally lower surface hardness than the outer coil spring, preventing the inner coil spring from getting stuck and reducing abrasion on the outer coil spring.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the inner coil spring is movable in the outer coil spring during compression, then the spring assembly can absorb and attenuate torsional vibration effectively, but the inner coil spring slides against the inner peripheral surface of the outer coil spring causing abrasion and flash formation

Engineering Contradiction:

Improvetorsional vibration attenuationVSAvoidabrasion and flash formation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The endmost windings of the inner coil spring are given a different local quality by reducing their outer diameter compared to other windings. This local modification prevents the endmost windings from getting stuck between outer coil spring windings, eliminating the sliding contact that causes abrasion and flash formation, while the rest of the spring maintains its vibration attenuation function

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The chamfered end surfaces and reduced outer diameter at endmost windings are designed in advance to prevent the inner coil spring from getting stuck before sliding and flash formation can occur. This preliminary geometric modification eliminates the harmful sliding contact during the compression cycle

Inventive Principle:

Principle #10Preliminary action

2Ease of manufacture

If the inner coil spring has the same outer diameter throughout, then manufacturing is simpler, but the endmost windings get stuck between outer coil spring windings causing flashes and abrasion

Engineering Contradiction:

Improvespring manufacturing simplicityVSAvoidflash prevention

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

Instead of making the entire spring with varying diameter (which would complicate manufacturing), only the endmost windings have a reduced outer diameter while the majority of the spring maintains a uniform diameter. This localized modification maintains manufacturing simplicity while preventing the sticking and flash formation problem

Inventive Principle:

Principle #3Local quality

3Strength

If the inner coil spring has high surface hardness, then the spring structure is stronger, but the outer coil spring inner peripheral surface gets abraded during sliding

Engineering Contradiction:

Improveinner coil spring strengthVSAvoidouter coil spring abrasion

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The inner coil spring is designed with different surface hardness at different locations: the body maintains high hardness for structural strength, while the endmost windings have lower surface hardness to reduce abrasion of the outer coil spring during any residual sliding contact

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The lower surface hardness of the endmost windings, which might seem to reduce spring strength, actually converts potential harm (severe abrasion of outer spring) into a beneficial outcome by reducing friction and wear during operation, while the overall spring strength is maintained by the harder body portion

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

This design effectively inhibits the inner coil spring from getting stuck between windings and reduces abrasion on the outer coil spring, enhancing the spring assembly's ability to absorb and attenuate torsional vibration without flash formation.

Implementation Method 1

When compressed by torsional vibration, the inner coil spring is moved to the outer peripheral side by a centrifugal force, and slides against the inner peripheral surface of the outer coil spring

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Implementation Method 2

The spring assemblies are configured to be compressed therebetween in a rotational direction. Additionally, torsional vibration inputted into the input-side rotary member is absorbed and attenuated by using the spring assemblies

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 3

a friction resistance portion configured to generate friction resistance in the relative rotation

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS10274068B2Spring assembly and lock-up device for torque converter including same

Publication Date: 2019.04.30 EXEDY CORP

AI summary

A spring assembly for absorbing and attenuating a torsional vibration includes an outer coil spring and an inner coil spring. The inner coil spring is disposed in an interior of the outer coil spring. The inner coil spring has a shorter free length than the outer coil spring. The inner coil spring is chamfered on end surfaces of both ends thereof. The inner coil spring has an outer diameter set to be smaller at least at an endmost winding on each of the ends thereof than at other windings thereof.