Spark Plug Metallic Insulator Coating for High Capacity
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Solution Overview
Problem
Existing spark plugs with integrated capacitors fail to increase spark intensity effectively due to mechanical fragility, chemical oxidation, and high-temperature degradation, limiting their service life and durability during assembly operations.
Innovation Solution
A spark plug design featuring a tubular ceramic insulator with an outer and inner metallic film, surrounded by a metallic shell, which forms a dielectric to store electrical energy and sustain a capacitive electrical field for enhanced spark intensity, using noble metal coatings to prevent oxidation and migration into the ceramic matrix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a metallic silver coating is applied to the alumina ceramic insulator to increase capacitance, then the spark intensity increases, but the ceramic deteriorates due to silver migration into the alumina at high temperature causing dielectric failure
Solution Approach 1:
A nickel barrier layer is introduced as an intermediary between the silver coating and the alumina ceramic insulator. This barrier layer prevents silver migration into the alumina at high temperatures while allowing the silver to maintain its capacitive function, thus resolving the contradiction between increasing spark intensity and maintaining dielectric strength.
Solution Approach 2:
The insulator structure is transformed into a composite material system consisting of alumina ceramic, nickel barrier layer, and silver coating. This multi-layer composite structure combines the dielectric properties of alumina with the protective function of nickel and the capacitive function of silver, enabling both high spark intensity and long-term reliability.
2Power
If a capacitor is integrated into the spark plug to increase spark intensity, then ignition efficiency improves, but the component becomes mechanically fragile and susceptible to chemical oxidation during assembly operations
Solution Approach 1:
The capacitor is merged with the ceramic insulator structure itself, using the insulator as the dielectric medium between inner and outer conductive layers. This integration eliminates separate capacitor components that would be mechanically fragile, while the robust ceramic structure provides mechanical strength and resistance to oxidation during assembly operations.
Solution Approach 2:
Thin metallic films are applied to the inner and outer surfaces of the ceramic insulator to form the capacitor electrodes. These thin films are mechanically supported by the rigid ceramic structure, providing the necessary capacitance without compromising mechanical durability or susceptibility to oxidation during assembly.
3Duration of action of stationary object
If the service life of spark plugs with integrated capacitors is extended, then operational durability improves, but the capacitors succumb to chemical oxidation and mechanical destruction from assembly operations
Solution Approach 1:
The capacitor components (metallic films and ceramic insulator) are designed to withstand the harsh oxidative environment of engine operation and assembly. The ceramic insulator provides a chemically inert barrier that protects the metallic films from oxidation, while the integrated structure resists mechanical destruction during assembly operations, thereby extending service life.
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 design provides a spark plug with increased capacitance and durability, resisting chemical and mechanical degradation, ensuring a longer service life without deterioration, and effectively igniting air/fuel mixtures with intensified sparks.
Implementation Method 1
The ceramic insulator forms a dielectric between the inner and outer metallic films and is operative to sustain a capacitive electrical field therein
Implementation Method 2
The inner and outer metallic films are operative to store a charge of electrical energy therebetween in response to an electrical potential between the center electrode and the shell
Data Source
AI summary
A spark plug (24) of an internal combustion engine is provided with an integrated capacitor feature to increase the intensity of its spark. The capacitor feature is formed by applying metallic film (62, 64) to the inner (30) and outer surfaces of a tubular insulator (26). The insulator (26) forms a dielectric and sustains an electrical charge when an electrical differential is established between the inner (64) and outer (62) metallic films. The stored electrical charge is discharged with the firing of a spark. The metallic films can be applied as a paint or ink directly to the surfaces of the insulator (26), or can be mixed with a glazing compound to form conductive coatings simultaneous with the glazing operation. Ganged (62′) or serpentine (62″) micro-plates can be formed within either or both of the inner and outer metallic films to increase the charge-carrying surface area.