Spark Plug Ground Electrode Asymmetry for Mixture Flow

Solution Overview

Problem

The existing spark plugs with bent ground electrodes often obstruct the inflow of the mixture into the spark discharge gap due to widened portions caused by bending, leading to reduced ignitability, especially when the ground electrode is formed with a circular section.

Innovation Solution

A spark plug design with a ground electrode having a bulging curved face on the back opposite to the center electrode, where the maximum width within ±1 mm from the center point of the spark discharge gap is 105% or less of the ordinary portion's width, to minimize obstruction and maintain ignitability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If the ground electrode is bent at its longitudinally intermediate portion toward the center, then the leading end portion can be positioned opposite to the center electrode to form a spark discharge gap, but the bent portion is pulled on the outer side and collected on the inner side to form widened portions that obstruct the inflow of mixture to the spark discharge gap

Engineering Contradiction:

Improvepositioning of ground electrodeVSAvoidwidened portions obstructing mixture flow

Core Design Contradiction:

ShapeVSObject-generated harmful factors

Solution Approach 1:

The patent applies parameter changes by precisely controlling the width of the ground electrode at the bent portion. The maximum width at the bent portion is limited to 105% or less of the width of the ordinary portion within the range of ±1 mm from the center point of the spark discharge gap. This parameter control prevents excessive widening while maintaining the necessary positioning for spark discharge gap formation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces asymmetry in the ground electrode design by forming a bulging curved face on the back of the ground electrode opposite to the center electrode side. This asymmetric shape allows the bent portion to be positioned correctly while the bulging face directs mixture flow toward the spark discharge gap, compensating for the widening effect.

Inventive Principle:

Principle #4Asymmetry

2Ease of operation

If the ground electrode is formed with a circular section, then the mixture can go around to the inner side of the ground electrode to reach the spark discharge gap, but the bent portion forms widened portions that are especially serious in obstructing mixture flow

Engineering Contradiction:

Improvemixture flow around ground electrodeVSAvoidwidened portions obstructing mixture flow

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The patent applies parameter changes by precisely controlling the width of the ground electrode at the bent portion. The maximum width at the bent portion is limited to 105% or less of the width of the ordinary portion within the range of ±1 mm from the center point of the spark discharge gap. This parameter control prevents excessive widening while maintaining the necessary positioning for spark discharge gap formation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces asymmetry in the ground electrode design by forming a bulging curved face on the back of the ground electrode opposite to the center electrode side. This asymmetric shape allows the bent portion to be positioned correctly while the bulging face directs mixture flow toward the spark discharge gap, compensating for the widening effect.

Inventive Principle:

Principle #4Asymmetry

3Object-generated harmful factors

If the radius of curvature of the bent portion is enlarged to reduce widening, then the spacing between the center position of the spark discharge gap and the bent portion is narrowed, reducing combustion space

Engineering Contradiction:

Improvewidening of bent portionVSAvoidcombustion space

Core Design Contradiction:

Object-generated harmful factorsVSVolume of moving object

Solution Approach 1:

The patent applies parameter changes by precisely controlling the width of the ground electrode at the bent portion. The maximum width at the bent portion is limited to 105% or less of the width of the ordinary portion within the range of ±1 mm from the center point of the spark discharge gap. This parameter control prevents excessive widening while maintaining the necessary positioning for spark discharge gap formation.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7839064B2Spark plug for internal combustion engine

Publication Date: 2010.11.23 NITERRA CO LTD

AI summary

A spark plug including: a center electrode as defined herein; a substantially cylindrical insulator as defined herein; a cylindrical metal shell as defined herein; and a ground electrode as defined herein, wherein a spark discharge gap is provided between the leading end portion of the center electrode and the leading end portion of the ground electrode, and the ground electrode has a bulging curved face on a side opposite to a side in which the center electrode is provided, and a maximum of width of the ground electrode within a range of ±1 mm from a center point of the spark discharge gap in the axial direction, as viewed in a direction where the center electrode and the ground electrode overlap, is 105% or less of a width of an ordinary portion having a substantially constant width.