Interlocking Powdered Metal Piston Assembly for Stronger Retention

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing piston assemblies in automotive shock absorbers formed from compacted powdered metal suffer from a weak and inconsistent locking system, with a high risk of damage during sintering and inadequate retention force due to the use of short cylindrical projections and shallow holes.

Innovation Solution

A piston assembly design featuring a pair of piston members with a central hub, outer rim, vent apertures, and a set of locking features including projections and recesses that extend radially from the axial end surface, allowing for secure frictional engagement between the members, enabling sintering without damaging external surfaces and providing a stronger, more consistent retention force.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If short cylindrical projections and shallow holes are used for locking, then the piston members can be assembled, but the retention force is relatively small and inconsistent

Engineering Contradiction:

Improveretention forceVSAvoidconsistency of retention force

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The locking features transition from simple cylindrical projections to complex three-dimensional interlocking structures with multiple surfaces and geometries, adding dimensional complexity to increase retention force and consistency

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The locking features have varying geometries at different locations, with projections and recesses designed with specific shapes, sizes, and distributions to optimize retention force at each engagement point

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If piston members are sintered while resting on short cylindrical projections, then the projections provide support, but the projections have a propensity to break off

Engineering Contradiction:

Improvesintering supportVSAvoidprojection integrity

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The piston members are designed with flat axial end surfaces that are prepared in advance to serve as stable support surfaces during the sintering process, preventing projection breakage before assembly

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The design provides a stable, flat support surface on the axial end that cushions and distributes the sintering load, preventing stress concentration on the projections during manufacturing

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Strength

If piston members are sintered while resting on axial end surface, then projection damage is avoided, but the axial end surface could become damaged

Engineering Contradiction:

Improveprojection integrityVSAvoidaxial end surface damage

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The axial end surface is designed with specific material properties, surface hardness, and geometric parameters that enable it to withstand sintering loads without damage, allowing it to serve as a durable support surface

Inventive Principle:

Principle #35Parameter changes

4Strength

If multiple locking features are added to increase retention force, then the locking becomes stronger, but the device complexity increases

Engineering Contradiction:

Improveretention forceVSAvoidlocking system complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The locking system is segmented into multiple discrete projections and recesses that are distributed around the piston member, allowing the retention force to be distributed across multiple engagement points rather than concentrated in a single location

Inventive Principle:

Principle #1Segmentation

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 new locking features allow for robust assembly and sintering without damaging the external surfaces, significantly increasing the retention force and reducing scrap rates due to improved orientation and assembly ease, with the retention force being approximately three times that of previous designs.

Implementation Method 1

The projections on each piston member are received into and are frictionally engaged with a corresponding one of the recesses that is formed on the other piston member to thereby secure the piston members to one another

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

Each of the piston members is formed of compacted powdered metal

Methodology Applied

Scientific EffectSintering: Sintering

Data Source

PatentUS11788621B2Piston assembly formed of interlocking piston members

Publication Date: 2023.10.17 AMERICAN AXLE & MANUFACTURING INC

AI summary

A piston assembly that includes a pair of piston members that are formed of compacted powdered metal. The piston members have sets of locking features that include alternating projections and recesses that are spaced circumferentially about and intersect a rod aperture that extends through the piston member. Each projection is formed along a projection axis, which extends radially from a center axis along which the rod aperture is formed, and has a pair of opposite side walls and an end wall that connects the side walls to one another on a side of the projection that is opposite the rod aperture. The recesses on each piston member are configured to matingly and frictionally receive the projections on the other piston member.