Spark Plug Insulator Non-Contact Runout Inspection

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Solution Overview

Problem

Existing methods for measuring the circular runout of spark plug insulators can damage or dirty the insulator, particularly the leg portion, leading to issues like through discharge and creep discharge, and are inadequate for the precise control required with smaller spark plug diameters.

Innovation Solution

A non-contact measurement method using a light projector and receiver to determine the circular runout by measuring the radial distance between the leg portion and another portion of the insulator, with no direct contact to the leg portion, allowing for precise assessment without causing damage or dirt accumulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If contact measurement methods (dial gauge and chuck) are used to measure circular runout, then measurement can be performed, but the insulator leg portion may sustain damage or dirt

Engineering Contradiction:

Improvecircular runout measurementVSAvoiddamage and dirt on insulator

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the mechanical contact measurement system (dial gauge and chuck) with an optical measurement system using a laser displacement sensor. The laser sensor measures the position of the insulator leg portion non-contactly by detecting light reflection, thereby eliminating mechanical contact that causes damage and dirt while maintaining measurement precision for circular runout inspection

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces light as an intermediary medium between the measurement system and the insulator. The laser displacement sensor uses light reflection from the insulator surface to obtain measurement data without direct contact, serving as a mediator that transfers measurement information without causing harmful contact effects

Inventive Principle:

Principle #24Intermediary (Mediator)

2Volume of moving object

If spark plug diameter is reduced, then smaller spark plugs are achieved, but precise control of circular runout becomes more difficult

Engineering Contradiction:

Improvespark plug diameterVSAvoidcircular runout control

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The patent employs non-contact optical measurement with a laser displacement sensor to achieve high-precision circular runout measurement on reduced-diameter spark plugs. The optical system provides sufficient measurement resolution and accuracy even for smaller dimensions, enabling precise control of circular runout despite the reduced spark plug size

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the measurement approach from mechanical contact to optical non-contact measurement, which provides different measurement parameters and resolution characteristics suitable for smaller spark plug diameters. This parameter change enables accurate circular runout control even when the spark plug dimensions are reduced

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If contact measurement is performed on the leg portion, then circular runout can be measured, but through discharge and creep discharge may occur

Engineering Contradiction:

Improvecircular runout measurementVSAvoidinsulator discharge prevention

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces mechanical contact measurement with optical measurement using a laser displacement sensor. This substitution eliminates the risk of creating conductive paths through mechanical contact that could lead to through discharge or creep discharge, while maintaining the ability to accurately measure circular runout and ensure insulator reliability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 method effectively protects the insulator from damage and dirt during measurement, enabling precise control of circular runout, especially for smaller spark plug diameters, and ensures accurate clearance between the insulator and electrodes.

Implementation Method 1

a light projector and receiver to determine the circular runout by measuring the radial distance

Methodology Applied

Scientific EffectLight reflection: Reflection

Data Source

PatentEP3182532B1Inspection method and apparatus of spark plug insulator

Publication Date: 2020.07.08 NITERRA CO LTD

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AI summary

There is provided an inspection method of a spark plug insulator. The spark plug insulator includes a collar portion, a rear body portion located in rear of the collar portion and a leg portion located in front of the collar portion. The inspection method includes: performing measurement of a distance in a radial direction of the insulator between an outer circumferential surface of the leg portion at a first measurement point and an outer circumferential surface of a portion of the insulator other than the leg portion at a second measurement point, wherein the measurement is performed at a plurality of positions in a circumferential direction of the insulator with no contact to the measurement target; determining, as a circular runout, a difference between maximum and minimum values among measurement results of the distance; and making pass/fail judgment of the insulator based on the determined circular runout.