Spark Plug Heat Insulating Member for Combustion Chamber

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Solution Overview

Problem

The increasing temperatures in combustion chambers due to supercharging or higher compression ratios in internal combustion engines lead to heat deterioration of the rubber plug cap in spark plugs, as excessive heat is transferred from the center electrode to the stem, causing the insulator head portion to overheat.

Innovation Solution

A heat insulating member is interposed between the stem and the center electrode within the insulator, with a conductive member passing through the heat insulating member to maintain electrical connection, and the heat insulating member is positioned closer to the proximal side of the insulator to reduce heat transfer and prevent excessive temperature increase.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If supercharging or higher compression ratio is employed to increase fuel economy, then engine power and fuel efficiency are improved, but combustion chamber temperature increases causing heat deterioration of the rubber plug cap

Engineering Contradiction:

Improvefuel economyVSAvoidcombustion chamber temperature

Core Design Contradiction:

ProductivityVSTemperature

Solution Approach 1:

A heat insulating member is introduced as an intermediary between the center electrode and the stem to block heat transfer. This mediator prevents the thermal energy from reaching the rubber plug cap, allowing the engine to operate at higher compression ratios without causing heat deterioration of the plug cap.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Temperature

If heat insulating member is interposed between stem and center electrode, then heat transfer to insulator head portion is reduced, but electrical connection between stem and center electrode must be maintained

Engineering Contradiction:

Improveinsulator head portion temperatureVSAvoidelectrical connection

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The internal structure of the insulator is segmented into distinct functional zones: a heat insulating member to block thermal energy and a conductive member to transmit electrical energy. This segmentation allows simultaneous achievement of thermal insulation and electrical conductivity by assigning different material properties to different segments.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The insulator employs composite material construction with a heat insulating member made of thermally insulating material and a conductive member made of electrically conductive material. This composite structure enables the insulator to perform both thermal insulation and electrical conduction functions simultaneously.

Inventive Principle:

Principle #40Composite materials

3Temperature

If heat insulating member is positioned closer to proximal side of insulator, then heat transfer path is shortened and heat deterioration is prevented, but electrical connection path must be maintained

Engineering Contradiction:

Improveheat transferVSAvoidelectrical connection

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent resolves the spatial conflict by transitioning to a multi-dimensional arrangement where the heat insulating member and conductive member are positioned differently along the axial dimension. The heat insulating member is placed closer to the proximal side to shorten the heat transfer path, while the conductive member extends from the distal side to maintain the electrical connection path, utilizing different spatial dimensions for different functional requirements.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 configuration effectively reduces heat transfer from the center electrode to the stem, preventing excessive temperature increase in the insulator head portion and maintaining efficient electrical connection, thereby enhancing the durability of the spark plug.

Implementation Method 1

a heat insulating member is interposed between the stem and the center electrode within the insulator

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Implementation Method 2

a conductive member is disposed inside the insulator so as to pass through the heat insulating member for making electrical connection between the stem and the center electrode

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS20150123535A1Spark plug for internal combustion engine

Publication Date: 2015.05.07 DENSO CORP

AI summary

A spark plug for an internal combustion engine includes a center electrode, an insulator holding the center electrode inserted therein, a housing holding the insulator inserted therein, a ground electrode joined to the housing so as to form a spark discharge gap with the center electrode, and a stem electrically connected to the center electrode. The stem includes a stem body inserted and held inside the insulator and a terminal exposed from a proximal end of the insulator. The insulator includes a supported portion axially supported by the housing. A heat insulating member is interposed between the stem and the center electrode. A conductive member is disposed inside the insulator so as to pass through the heat insulating member for making electrical connection between the stem and the center electrode. The heat insulating member is located closer to a proximal side of the insulator than the supported portion is.