Insulating Rolling Bearing Bushing for Electrolytic Corrosion Control

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Solution Overview

Problem

Existing insulating rolling bearings in refrigerant compressors face issues such as wear between the insulating sleeve and the crank shaft, leakage of conductive grease, and distortion of raceway surfaces due to high shaft voltage, leading to electrolytic corrosion, vibration, and abnormal noise.

Innovation Solution

An insulating rolling bearing design featuring a metal base with a resin layer on its surface, fitted to the inner or outer ring, preventing direct contact and rotation, thereby preventing electrolytic corrosion and maintaining dimensional accuracy while reducing the risk of wear and vibration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an insulating sleeve is fitted into the inner ring to prevent electrolytic corrosion, then electrolytic corrosion is prevented, but wear occurs on the insulating sleeve due to relative rotation between the sleeve and crank shaft

Engineering Contradiction:

Improveelectrolytic corrosion preventionVSAvoidinsulating sleeve service life

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The insulating bushing is divided into two functional parts: a metal base that contacts the crank shaft and inner ring (providing mechanical strength and rotational compatibility), and a resin layer that provides electrical insulation. This segmentation allows each material to perform its optimal function while working together as an integrated component.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The insulating bushing uses a composite structure combining metal and resin materials. The metal base (e.g., aluminum or steel) provides mechanical strength and durability for rotational contact, while the resin layer (e.g., epoxy or polyimide) provides electrical insulation. This composite approach resolves the contradiction by combining the advantages of both materials.

Inventive Principle:

Principle #40Composite materials

2Reliability

If a resin layer is formed on the metal base by injection molding, then electrical insulation is provided, but the high-pressure injection and cooling contraction deteriorate the shape accuracy of the raceway surface

Engineering Contradiction:

Improveelectrical insulationVSAvoidraceway surface accuracy

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The metal base acts as an intermediary between the injection molding process and the raceway surface. The resin layer is molded onto the metal base rather than directly onto the raceway surface, so any dimensional changes from cooling and contraction occur in the resin layer without affecting the precision of the raceway surface formed on the metal base.

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 prevents electrolytic corrosion, maintains the integrity of the raceway surfaces, and allows for downsizing of the device without the need for conductive grease, enhancing the reliability and efficiency of the refrigerant compressor.

Implementation Method 1

a resin layer formed on an inner peripheral surface or an outer peripheral surface of the metal base

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Data Source

PatentUS11873863B2Insulating rolling bearing

Publication Date: 2024.01.16 NTN CORP

AI summary

To provide an insulating rolling bearing that is capable of preventing electrolytic corrosion and preventing a gap from being undesirably formed between a shaft and a raceway ring. A sub bearing 21 includes an inner ring 22, an outer ring 23, balls 24 interposed between the inner ring and the outer ring, and an insulating bushing 28 fitted to an inner peripheral portion of the inner ring 22. The insulating bushing 28 includes a generally cylindrical metal base 28a, and a resin layer 28b formed on an inner peripheral surface of the metal base 28a. The insulating bushing 28 is fitted to the inner peripheral portion of the inner ring 22 such that the metal base 28a abuts on the inner peripheral portion of the inner ring 22.