Spark Plug Core Material Segmentation for Heat Dissipation

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Solution Overview

Problem

Existing spark plugs for internal combustion engines face the issue of core material exposure due to discharge exhaustion from the outer circumferential side, which can lead to degraded heat dissipation properties and preignition.

Innovation Solution

The spark plug design includes a central electrode with a core material having a large diameter portion and a small diameter portion continuously formed on the tip side, where the small diameter portion is disposed further on the tip side than the insulating glass, and the distance between the discharge gap and the axial injection hole is shorter than the distance between the discharge gap and the tip of the insulating glass, preventing core material exposure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the core material is disposed in the central electrode protruding beyond the insulating glass to improve heat dissipation, then heat dissipation performance is improved, but the core material is exposed and exhausted by discharge leading to preignition

Engineering Contradiction:

Improveheat dissipation performanceVSAvoidcore material exposure prevention

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The core material is divided into two distinct portions: a large diameter portion disposed within the insulating glass and a small diameter portion disposed in the tip protruding portion. This segmentation allows the core material to extend beyond the insulating glass for heat dissipation while the larger diameter portion within the glass protects against discharge exhaustion and core material exposure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the core material have different diameters to serve different functions. The large diameter portion in the insulating glass provides protection against discharge exhaustion, while the small diameter portion in the tip protruding portion enables effective heat dissipation. This local quality variation resolves the contradiction between heat dissipation performance and core material exposure prevention

Inventive Principle:

Principle #3Local quality

2Loss of energy

If the core material extends beyond the insulating glass to promote heat dissipation, then thermal conductivity is improved, but discharge exhaustion from the outer circumferential side exposes the core material

Engineering Contradiction:

Improveheat dissipation efficiencyVSAvoidspark plug service life

Core Design Contradiction:

Loss of energyVSDuration of action of stationary object

Solution Approach 1:

The core material is segmented into a large diameter portion and a small diameter portion. The large diameter portion within the insulating glass resists discharge exhaustion to extend service life, while the small diameter portion extending beyond the insulating glass promotes heat dissipation efficiency

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The large diameter portion of the core material is preliminarily positioned within the insulating glass to provide protective coverage against discharge exhaustion before the spark plug operates. This preliminary protective arrangement prevents core material exposure and extends the spark plug's service life while maintaining heat dissipation capability

Inventive Principle:

Principle #10Preliminary action

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 design effectively prevents core material exposure while maintaining optimal heat dissipation properties, thereby extending the life of the spark plug and reducing the risk of preignition.

Implementation Method 1

the core material has a higher thermal conductivity than the base material

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS11695256B2Spark plug for internal combustion engine

Publication Date: 2023.07.04 DENSO CORP

AI summary

A spark plug for an internal combustion engine includes insulating glass having a tubular shape, a central electrode including a tip protruding portion, a housing having a tubular shape, and a plug cover provided over an auxiliary combustion chamber. The plug cover is provided with injection holes through which the auxiliary combustion chamber communicates with the exterior. The central electrode includes a base material and a core material disposed inside the base material and having a higher thermal conductivity than the base material. The core material includes a large diameter portion and a small diameter portion continuously formed on a tip side of the large diameter portion. The small diameter portion has a smaller diameter than the large diameter portion, and includes, in a part of the small diameter portion in an axial direction, a small-diameter columnar portion having a constant diameter. At least a part of the small-diameter columnar portion is disposed further on the tip side of the spark plug than a tip of the insulating glass.