Spark Plug Resistance Element With Fine Non-Conductive Particles

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Solution Overview

Problem

Current spark plugs have resistive elements with limited electrical stability, leading to premature breakdown under high current intensity, which affects their lifespan and performance.

Innovation Solution

The spark plug design features a material mixture with non-conductive particles of reduced diameter, enhancing the surface-to-volume ratio and conductive path thickness, allowing for a significantly higher current intensity before breakdown, with optimal results when at least 90% of non-conductive particles have a maximum diameter of 20 μm or less.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If non-conductive particles with larger diameter are used in the resistance element, then the manufacturing is easier and material distribution is simpler, but the conductive path thickness is reduced and electrical stability deteriorates

Engineering Contradiction:
Improveease of manufactureVSAvoidelectrical stability
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The invention changes the size parameter of non-conductive particles from larger diameter (prior art) to reduced diameter (maximum 20 μm, preferably maximum 10 μm). This parameter change increases the surface-to-volume ratio of non-conductive particles, which improves their coating by conductive particles and increases conductive path thickness, thereby enhancing electrical stability and maximum current intensity by a factor of 3 to 6.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If non-conductive particles with reduced diameter are used in the resistance element, then the conductive path thickness is increased and electrical stability is improved, but the manufacturing precision requirements increase

Engineering Contradiction:
Improveelectrical stabilityVSAvoidmanufacturing precision
Core Design Contradiction:
ReliabilityVSManufacturing precision

Solution Approach 1:

The invention specifies precise diameter parameters for non-conductive particles (maximum 20 μm, preferably maximum 10 μm) and conductive particles (less than 1 μm, typically 300 nm to 1300 nm with average diameter of 500 nm). These controlled parameter ranges ensure homogeneous distribution and adequate coating while maintaining manufacturing feasibility.

Inventive Principle:
Principle #35Parameter changes

3Quantity of substance

If the proportion of glass particles in the resistance element is increased, then the non-conductive particle content is increased, but the conductive path thickness is reduced and current density decreases

Engineering Contradiction:
Improveproportion of non-conductive particlesVSAvoidcurrent density
Core Design Contradiction:
Quantity of substanceVSReliability

Solution Approach 1:

The invention optimizes the proportion of glass particles (non-conductive particles) to be less than or equal to 30% by weight in the resistance element. This controlled proportion, combined with reduced particle diameter, ensures adequate spacing for conductive paths while maintaining electrical stability and high current density.

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

This configuration enhances the electrical stability of the resistive element, enabling a 3 to 6-fold improvement in the maximum current intensity before destruction, thereby extending the spark plug's lifespan and performance.

Implementation Method 1

The conductive particles form the pathways for the current through the resistive element

Methodology Applied
Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

This results in a larger surface-to-volume ratio for the non-conductive particles, which ensures better coating of the non-conductive particles by the conductive particles in the material mixture of the resistance panel, thereby enabling a more homogeneous distribution of conductive paths

Methodology Applied
Scientific EffectSurface-to-volume ratio effect:

Implementation Method 3

the specific electrical resistance in the resistance element... the resistive element has a maximum current that can flow through the resistive element before a breakdown of the current occurs in the resistive element

Methodology Applied
Scientific EffectElectrical resistance: Electrical Resistance

Data Source

PatentEP3688850B1Spark plug resistance element comprising fine non-conductive particles
Publication Date: 2022.11.16 ROBERT BOSCH GMBH
  • EP3688850B1 patent drawingFigure 1
  • EP3688850B1 patent drawingFigure 2~3
  • EP3688850B1 patent drawingFigure 4

AI summary

The invention relates to a spark plug comprising: a housing; an isolator arranged in the housing; a central electrode arranged in the isolator; a terminal stud arranged in the isolator; a resistance element which is arranged in the isolator and is spatially arranged between the central electrode and the terminal stud, connecting said central electrode to said terminal stud, said resistance element containing a resistance material containing conductive particles and non-conductive particles; and a ground electrode which is arranged on a front surface of the housing, on the combustion chamber side, and forms a spark gap together with the central electrode, at least 80% of the non-conductive particles having a maximum diameter of 20 µm.