Corona Igniter Sealing via Compressed Rubber Boot
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Solution Overview
Problem
Existing corona discharge ignition systems face challenges in controlling the electric field to prevent unwanted corona discharge between the ignition coil assembly and the firing end assembly, leading to inefficiencies in fuel-air mixture combustion.
Innovation Solution
A corona igniter assembly featuring a metal tube with holes to allow air exit and a compressed rubber boot providing a hermetic seal between the ignition coil and firing end assemblies, preventing unwanted corona discharge and directing energy effectively to the firing end.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the ignition coil assembly and firing end assembly are directly attached to one another, then the device structure is simple, but unwanted corona discharge occurs between the assemblies leading to energy loss
Solution Approach 1:
A rubber boot is introduced as an intermediary component between the ignition coil assembly and the firing end assembly. This rubber boot serves multiple functions: it provides electrical insulation to prevent unwanted corona discharge, creates a hermetic seal to maintain the combustion chamber integrity, and allows for thermal expansion differences between the two assemblies. The intermediary rubber boot eliminates energy loss from parasitic discharge while maintaining structural simplicity.
Solution Approach 2:
The rubber boot creates an inert electrical environment by providing high electrical insulation between the high-voltage ignition coil assembly and the grounded firing end assembly. This prevents the formation of conductive paths that would lead to corona discharge, effectively creating an 'inert' electrical zone that blocks unwanted energy transfer.
2Reliability
If the rubber boot is used to provide hermetic seal, then the sealing performance is improved, but the manufacturing process becomes more complex
Solution Approach 1:
A flexible rubber boot is used to provide the hermetic seal between assemblies. The flexible nature of the rubber boot allows it to conform to slight variations in assembly dimensions and tolerate thermal expansion/contraction cycles without compromising the seal. This flexible sealing approach is more reliable than rigid sealing methods while remaining relatively simple to manufacture and install.
Solution Approach 2:
The rubber boot is made from composite rubber materials that combine electrical insulation properties with sealing capabilities. These composite materials provide both the necessary electrical isolation to prevent corona discharge and the elastic properties required for effective sealing, eliminating the need for separate insulation and sealing components.
3Productivity
If the electric field is increased to improve combustion, then the combustion efficiency is improved, but unwanted corona discharge occurs along other portions of the assembly
Solution Approach 1:
The rubber boot acts as an intermediary that blocks the propagation of high-frequency electric fields along the assembly. By introducing this high-dielectric-strength material, the system can maintain high electric fields at the firing end for efficient combustion while preventing field propagation to other portions of the assembly where unwanted corona discharge would occur.
Solution Approach 2:
The rubber boot creates localized electrical insulation precisely where needed - at the interface between the ignition coil assembly and firing end assembly. This localized approach allows high electric fields to be maintained at the combustion chamber for efficient burning while preventing field propagation to other areas, achieving local quality control of the electric field distribution.
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 enhances the performance of the corona igniter assembly by ensuring that energy is directed to the intended discharge area, improving combustion efficiency by preventing unwanted corona discharge and maintaining dielectric properties of the fuel-air mixture.
Implementation Method 1
A rubber boot fills the tube volume and provides a hermetic seal between the ignition coil assembly and the firing end assembly
Implementation Method 2
compressing the rubber boot between the ignition coil assembly and the firing end assembly so that the rubber boot fills the tube volume
Implementation Method 3
The firing end assembly includes a corona igniter and distributes a radio frequency electric field... The electric field causes a portion of a mixture of fuel and air in the combustion chamber to ionize and begin dielectric breakdown, facilitating combustion
Data Source
Figure 1~1A
Figure 2
Figure 3
AI summary
A corona igniter assembly (20) comprises an ignition coil assembly (22), a firing end assembly (24), and a metal tube (26) connecting the ignition coil assembly (22) to the firing end assembly (24). A rubber boot (28) is disposed in the metal tube (26) and compressed symmetrically between a coil output member (30) of the ignition coil assembly (22) and an insulator (42) of the firing end assembly (24). Thus, the rubber boot (28) fills any air gaps and provides a hermetic seal between the ignition coil assembly (22) and the firing end assembly (24) to prevent unwanted corona discharge from forming from those air gaps.