Glazed Ceramic Spark Plug Insulator for Dielectric Strength

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Solution Overview

Problem

Long, slim spark plugs with reduced ceramic insulator wall thicknesses in motor vehicles face issues with electrical strength and short service life due to high field strengths, especially in areas with reduced cross-sections, leading to problems with electrical breakdown and mechanical stability.

Innovation Solution

A ceramic spark plug insulator with a glaze applied to specific surface areas, particularly at the transition between the combustion chamber and outside areas, enhances dielectric strength and mechanical stability by reducing roughness, closing pores, and forming a protective layer, allowing for slimmer dimensions without compromising electrical or mechanical integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the wall thickness of the ceramic insulator is reduced to achieve long, slim spark plugs, then the installation space is reduced, but the electrical strength deteriorates due to high field strengths in areas with reduced cross-sections

Engineering Contradiction:
Improveinstallation spaceVSAvoidelectrical strength
Core Design Contradiction:
Volume of moving objectVSReliability

Solution Approach 1:

The patent applies a glaze coating specifically to the base fillet area and other critical regions of the ceramic insulator where the cross-section is reduced. This localized treatment enhances the dielectric strength and mechanical properties precisely where the field strength is highest and the insulator is most vulnerable, without requiring a complete redesign of the entire insulator geometry.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent combines the ceramic insulator material with a glaze coating to create a composite structure. The glaze layer, applied to specific surface areas, provides enhanced electrical insulation and mechanical strength, allowing the base ceramic to be made thinner while maintaining overall performance through the synergistic combination of materials.

Inventive Principle:
Principle #40Composite materials

2Volume of moving object

If the cross-section of the insulator is reduced to achieve slimmer dimensions, then the installation space is reduced, but the mechanical stability deteriorates due to high stress in thin-walled areas

Engineering Contradiction:
Improveinstallation spaceVSAvoidmechanical stability
Core Design Contradiction:
Volume of moving objectVSStrength

Solution Approach 1:

The glaze coating is selectively applied to the base fillet and other high-stress regions where the cross-section is reduced. This localized reinforcement provides enhanced mechanical strength and stress distribution precisely where the thin-walled structure is most vulnerable, without adding unnecessary weight or complexity to the entire insulator.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The glaze coating is applied during the manufacturing process to pre-reinforce the critical areas of the insulator before the spark plug enters service. This preliminary strengthening prevents mechanical failure under operating conditions by ensuring that the high-stress regions are already protected and reinforced before encountering bending loads or thermal cycling.

Inventive Principle:
Principle #10Preliminary action

3Volume of moving object

If the wall thickness of the ceramic insulator is reduced, then the installation space is reduced, but the service life deteriorates due to electrical breakdown in high field strength areas

Engineering Contradiction:
Improveinstallation spaceVSAvoidservice life
Core Design Contradiction:
Volume of moving objectVSDuration of action of stationary object

Solution Approach 1:

The glaze coating is applied specifically to the base fillet area and other regions where the electric field strength is highest. This localized dielectric reinforcement prevents electrical breakdown and arcing in the most vulnerable areas, thereby extending the service life of the spark plug without requiring a complete increase in insulator dimensions.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The combination of ceramic insulator and glaze coating creates a composite structure with superior electrical insulation properties. The glaze layer provides an additional dielectric barrier that prevents electrical breakdown, allowing the base ceramic to be thinner while maintaining long-term electrical stability and extending the spark plug's operational life.

Inventive Principle:
Principle #40Composite materials

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 solution significantly improves dielectric strength and mechanical stability, delaying electrical breakdown and enhancing the spark plug's ability to withstand mechanical stress, resulting in a longer service life and higher flexural strength.

Implementation Method 1

The application of the glaze reduces the roughness of the first surface area A of the spark plug insulator

Methodology Applied
Scientific EffectSurface smoothing:

Implementation Method 2

The glaze forms a kind of protective layer that increases the strength of the spark plug insulator in areas that are subject to high mechanical stress

Methodology Applied
Scientific EffectProtective coating: Coatings

Implementation Method 3

by applying the glaze after the glaze has melted, a mechanical compressive stress can be built up on the surface of the insulator, which leads to a partial pre-compensation of a tensile stress when bending loads act on the insulator surface

Methodology Applied
Scientific EffectCompressive stress: Compression

Data Source

PatentEP3192138B1Ceramic spark plug insulator, spark plug, and use of a glaze on a spark plug insulator
Publication Date: 2020.04.08 ROBERT BOSCH GMBH
  • EP3192138B1 patent drawingFigure 1
  • EP3192138B1 patent drawingFigure 2
  • EP3192138B1 patent drawingFigure 3~4

AI summary

The present invention relates to a ceramic spark plug insulator with improved electrical and mechanical strength.