Resin Overlay Sliding Surface for Cavitation Damage Reduction

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Solution Overview

Problem

Conventional sliding members with resin overlay layers suffer from cavitation damage due to bursting bubbles in lubricating oil, as the existing countermeasures are insufficient to reduce the impact force effectively, especially as device performance improves.

Innovation Solution

A sliding member with a resin overlay layer having a surface roughness parameter Rk of 0.4≤Rk≤1.2 and a surface area ratio S of 2.5≤S≤4.5 is designed to control bubble sizes, reducing cavitation damage by guiding bubble formation towards larger, fewer bubbles rather than smaller, numerous ones.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a resin overlay layer is used to reduce cavitation damage, then the sliding member's durability is improved, but the resin overlay layer still suffers impact force from bursting bubbles causing exfoliation

Engineering Contradiction:

ImprovedurabilityVSAvoidimpact force from bursting bubbles

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the surface parameters of the resin overlay layer by controlling the roughness parameter Rk (0.4≤Rk≤1.2) and surface area ratio S (2.5≤S≤4.5). These parameter changes modify how bubbles form and burst on the surface, reducing the impact force from cavitation while maintaining the protective function of the resin overlay layer.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If device performance is improved, then productivity and efficiency are enhanced, but bubbles in lubricating oil are more likely to be generated increasing cavitation damage

Engineering Contradiction:

Improvedevice performanceVSAvoidcavitation damage

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful effect of bubbles into a beneficial outcome by designing the resin overlay layer surface to promote the formation of fewer, larger bubbles instead of many fine bubbles. When these larger bubbles burst, they generate less impact force, thus transforming the inevitable cavitation phenomenon into a less damaging process that allows high-performance operation.

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

The controlled roughness and surface area ratio of the resin overlay layer result in larger bubbles, reducing the impact force on the resin overlay layer and subsequently minimizing cavitation damage, as demonstrated by increased durability under severe testing conditions.

Implementation Method 1

If bubbles are generated in lubricating oil when such a resin overlay layer comes into sliding contact with a mating member, the resin overlay layer suffers an impact force when the bubbles burst. This impact force causes so-called cavitation damage such as exfoliation of the resin overlay layer from the bearing alloy layer.

Methodology Applied

Scientific EffectCavitation: Cavitation

Data Source

PatentUS11629755B2Sliding member

Publication Date: 2023.04.18 DAIDO METAL CO LTD

AI summary

A sliding member includes a resin overlay layer on a sliding surface side coming into sliding contact with a mating member. The resin overlay layer has a surface roughness parameter Rk satisfying 0.4≤Rk≤1.2, and a surface area ratio S=S2/S1 calculated when an area of an arbitrary measurement field of view is designated by S1 and a surface area of the measurement field of view is designated by S2 satisfies 2.5≤S≤4.5.