Anti-fouling Spark Plug Metal Oxide Coating

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Solution Overview

Problem

Existing spark plugs are susceptible to electrically conductive combustion deposit build-up, particularly during cold starts, leading to ignition failure due to incomplete combustion and electrical short circuits.

Innovation Solution

A spark plug with a substantially continuous metal oxide or noble metal coating on the insulative sleeve's shaped tip portion, which reduces combustion deposit accumulation by acting as a catalyst or oxygen absorber, applied through a slurry process and calcination to ensure adhesion and conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If silicone oil coatings or particulate vanadium oxide deposition are applied to the insulating sleeve, then combustion deposit build-up is reduced, but the coatings fail to provide adequate performance at elevated temperatures and insufficient reduction of combustion deposit build-up

Engineering Contradiction:

Improvecombustion deposit build-upVSAvoidperformance at elevated temperature

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent changes the chemical composition parameters of the coating material from silicone oil or simple vanadium oxide to a complex metal oxide composition containing vanadium, zinc, and zirconium in specific ratios. This compositional parameter change enables the coating to maintain both anti-fouling effectiveness and thermal stability at elevated temperatures, resolving the contradiction between deposit reduction and high-temperature performance.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite coating material combining multiple metal oxides (vanadium, zinc, zirconium) with specific weight percentages. This composite approach leverages the synergistic effects of different metal oxides to achieve both combustion deposit resistance and thermal stability, overcoming the limitations of single-material coatings.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If the insulative sleeve is left uncoated, then manufacturing is simpler, but combustion deposits build up electrically conductive layers causing electrical short circuits

Engineering Contradiction:

Improvecoating application complexityVSAvoidelectrical short circuit from combustion deposits

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The patent applies a relatively thin coating layer (0.5-5 micrometers) that provides sufficient protection against electrical short circuits without requiring thick, complex applications. This thin-film approach maintains manufacturing simplicity while effectively preventing harmful electrical shorts from combustion deposits.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Object-affected harmful factors

If a thick coating is applied to protect against combustion deposits, then deposit build-up is reduced, but the coating may interfere with spark formation and increase device complexity

Engineering Contradiction:

Improvecombustion deposit build-upVSAvoidcoating thickness and composition

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent optimizes the coating thickness parameter to a specific range (0.5-5 micrometers) and controls the metal oxide particle size (0.1-10 micrometers) to ensure the coating is thin enough to allow spark formation while thick enough to prevent combustion deposit build-up. This precise parameter control resolves the contradiction between protection effectiveness and device simplicity.

Inventive Principle:

Principle #35Parameter changes

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 coating significantly reduces combustion deposit build-up, preventing electrical shorts and ensuring reliable spark formation across the electrodes, even during cold starts, by facilitating more complete combustion.

Implementation Method 1

The coating comprises a metal oxide, a combination of metal oxides, a noble metal, a late transition metal, or a combination of two or more of the foregoing metals... which reduces combustion deposit accumulation by acting as a catalyst

Methodology Applied

Scientific EffectCatalysis: Catalysis

Implementation Method 2

acting as a catalyst or oxygen absorber

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Data Source

PatentUS8970096B2Anti-fouling spark plug and method of making

Publication Date: 2015.03.03 PGI NORTHSTAR LLC

AI summary

Disclosed herein is a spark plug comprising an insulative sleeve having a central axial bore and an exterior surface and a center electrode extending through the central axial bore of the insulative sleeve. The insulating sleeve is positioned within, and secured to, a metal shell that serves as a mounting platform and interface to an internal combustion engine. The metal sleeve also supports a ground electrode that is positioned in a spaced relationship relative to the center electrode so as to generate a spark gap. The insulating sleeve includes a shaped tip portion that resides in a recessed end portion of the metal shell. A coating is disposed on the exterior surface of the shaped tip portion of the insulative sleeve. The coating comprises a metal oxide, a noble metal, late transition metal, or a combination comprising two or more of the foregoing metals.