Ignition Coil Plug Cap Spring Support Design
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Solution Overview
Problem
Existing ignition coil designs face issues with maintaining consistent electrical contact between the coil spring and sparkplug due to radial deformation of the intermediate coil spring portion, leading to potential electrical leaks to low-voltage components.
Innovation Solution
The design incorporates a rubber plug cap with a spring support portion that restricts radial deformation of the coil spring, ensuring stable electrical connection between the sparkplug and high voltage terminal, and includes an electrically insulative resin in the coil case to prevent voltage leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the coil spring is allowed to move freely in the fitting hole, then the ease of assembly is improved, but the intermediate portion of the coil spring may be radially deformed causing poor electrical contact and voltage leakage
Solution Approach 1:
The plug cap is made of rubber material that provides flexible support to the coil spring. The rubber material allows the coil spring to be easily assembled while simultaneously preventing radial deformation of the intermediate portion, maintaining both ease of assembly and electrical contact stability.
2Reliability
If the plug cap is made rigid to prevent coil spring deformation, then the electrical contact stability is improved, but the ease of assembly deteriorates
Solution Approach 1:
The plug cap is made of rubber material that provides flexible support to the coil spring. The rubber material allows the coil spring to be easily assembled while simultaneously preventing radial deformation of the intermediate portion, maintaining both ease of assembly and electrical contact stability.
3Device complexity
If no support structure is provided for the coil spring, then the device complexity is reduced, but the coil spring intermediate portion may deform radially causing harmful electrical leakage
Solution Approach 1:
The rubber plug cap acts as a flexible support structure that prevents radial deformation of the coil spring intermediate portion without adding complex mechanical components, thereby preventing voltage leakage to low-voltage components while keeping the structure simple.
4Reliability
If the coil spring is tightly constrained to prevent any deformation, then the electrical contact stability is improved, but the coil spring cannot accommodate thermal expansion and contraction
Solution Approach 1:
The rubber plug cap provides flexible support that prevents excessive radial deformation while allowing the coil spring to accommodate thermal expansion and contraction through controlled flexibility, maintaining both electrical contact stability and thermal stability.
Data Source
AI summary
An ignition coil includes primary and secondary coils accommodated in a coil case extending to define a cylindrical mount portion on a high voltage side. The mount portion includes a high voltage terminal electrically connected with the secondary coil. A coil spring electrically connects the high voltage terminal with a sparkplug. An electrically insulative plug cap is attached to the mount portion. The coil spring has a low voltage end electrically connected with the secondary coil via the high voltage terminal. The coil spring has a high voltage end in contact with a terminal of the sparkplug. The coil spring has an intermediate portion between the low voltage end and the high voltage end. The plug cap has a spring support portion, which is partially defining the fitting hole and restricting the intermediate portion of the coil spring from being radially deformed.