Spark Plug Cap Resin Protrusion Vibration Resistance
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Solution Overview
Problem
Existing plug cap designs for internal combustion engines suffer from insufficient vibration resistance due to the lack of rigidity in rubber protrusions, leading to instability and potential current leakage caused by engine vibrations.
Innovation Solution
A plug cap design featuring a resin molded member with a protruding portion for engagement with the engine's cap mounting portion, covered by an elastic rubber material that provides enhanced rigidity and vibration resistance while maintaining ease of mounting through a combination of high-rigidity resin and heat-resistant rubber components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rubber protrusion with an engagement hole is formed on the outer circumferential surface of the plug cap to attach it to the cap supporting protrusion of the engine, then the mounted state is stabilized and the influence of engine vibrations is limited, but the rigidity of the rubber protrusion is insufficient leading to inadequate vibration resistance
Solution Approach 1:
The engagement protrusion is formed as a composite structure combining a resin molded member with a rubber cover member. The resin molded member provides the necessary rigidity and structural support, while the rubber cover member provides elasticity and vibration absorption. This composite structure resolves the contradiction by integrating materials with complementary properties - the rigid resin ensures structural integrity and vibration resistance, while the elastic rubber maintains ease of mounting and absorbs dimensional errors.
2Stability of the object's composition
If a flanged portion is formed on the cap body to insert the plug cap in a plug hole of the internal combustion engine, then the mounted state is stabilized by holding the plug cap with the connection terminal and the inner circumferential surface of the plug hole, but the plug hole cannot be formed in the engine due to design restrictions
Solution Approach 1:
The engagement protrusion with rubber cover acts as an intermediary mounting structure that eliminates the need for direct engine modification (plug hole formation). Instead of requiring the engine to have a plug hole, the invention creates a self-contained engagement mechanism where the protrusion on the plug cap itself provides the mounting interface, adapting to various engine designs without requiring structural changes to the engine block.
3Reliability
If the clearance between the engagement hole of the plug cap and the cap supporting protrusion of the engine is minimized to stabilize the mounted state, then the influence of engine vibrations is limited more effectively, but the ease of mounting is deteriorated
Solution Approach 1:
The rubber cover member's material properties and geometric parameters are optimized to provide the ideal balance between clearance and stability. The rubber's elasticity allows for sufficient clearance that facilitates easy mounting, while the engagement protrusion's rigid resin core maintains minimal effective clearance for vibration resistance. The parameter optimization of the rubber material (hardness, elasticity) enables both easy installation and stable mounted state.
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 achieves a stable mounted state and improved vibration resistance by engaging the high-rigidity resin protrusion with the engine via a rubber cover, absorbing dimensional errors and protecting the electrical components from heat and voltage stress.
Implementation Method 1
a cover member formed of an elastic rubber material softer than a resin material of the resin molded member and covering at least an outer circumferential surface of the resin molded member
Data Source
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AI summary
There is provided a plug cap for electrically connecting a high-tension cord to a spark plug fixed to an internal combustion engine. The plug cap includes an electrical connection member capable of making an electrical connection between the spark plug and the high-tension cord, a resin molded member covering at least part of an outer circumferential surface of the electrical connection member and a cover member covering at least an outer circumferential surface of the resin molded member and formed of an elastic rubber material softer than a resin material of the resin molded member. The resin molded member has a protruding portion radially outwardly extending in at least one direction. The cover member covers the protruding portion of the resin molded member in such a manner that at least part of the protruding portion is engaged with a cap mounting portion of the engine via the cover member.