Spark Plug Thermal Resistance via Localized Shell Geometry
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Solution Overview
Problem
The reduction in ignition plug diameter for internal combustion engines leads to defects such as deterioration in thermal resistance and fouling resistance, affecting the engine's performance and durability.
Innovation Solution
The ignition plug design incorporates specific geometric and material configurations, including a metallic shell with an inside-diameter-reducing portion and an insulator with an outside-diameter-reducing portion, along with a packing system that satisfies certain relational expressions to enhance thermal and fouling resistance, and a control system for coolant flow management to regulate temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the ignition plug diameter is reduced to improve design freedom, then the ignition plug size decreases, but thermal resistance deteriorates
Solution Approach 1:
The patent applies local quality by creating an inside-diameter-reducing portion in the metallic shell and an outside-diameter-reducing portion in the insulator. These localized structural modifications concentrate thermal management resources at critical areas (the contact portion with combustion gas) rather than uniformly increasing the entire plug diameter, thus improving thermal resistance locally while maintaining overall compact dimensions.
Solution Approach 2:
The patent transitions from managing thermal resistance through a single dimensional parameter (overall diameter) to utilizing multiple dimensional aspects. By creating tapered portions with varying diameters along the axial direction and optimizing the contact area between the metallic shell and insulator, the solution addresses thermal management in both radial and axial dimensions simultaneously.
2Volume of moving object
If the ignition plug diameter is reduced, then the ignition plug size decreases, but fouling resistance deteriorates
Solution Approach 1:
The patent applies local quality by creating an inside-diameter-reducing portion in the metallic shell and an outside-diameter-reducing portion in the insulator. These localized structural modifications concentrate thermal management resources at critical areas (the contact portion with combustion gas) rather than uniformly increasing the entire plug diameter, thus improving thermal resistance locally while maintaining overall compact dimensions.
Solution Approach 2:
The patent transitions from managing thermal resistance through a single dimensional parameter (overall diameter) to utilizing multiple dimensional aspects. By creating tapered portions with varying diameters along the axial direction and optimizing the contact area between the metallic shell and insulator, the solution addresses thermal management in both radial and axial dimensions simultaneously.
3Duration of action of stationary object
If the contact portion temperature changes are restrained through increased contact area, then durability improves, but the device complexity increases
Solution Approach 1:
The patent applies parameter changes by modifying the geometric parameters of the metallic shell and insulator. Specifically, it creates tapered portions with controlled diameter variations along the axial direction, optimizing the contact area between components. This geometric parameter optimization improves thermal management and durability without fundamentally changing the device architecture or adding complex subsystems.
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 improves durability and thermal resistance, reducing the occurrence of defects like preignition and fouling, while the coolant control system further enhances thermal management, maintaining optimal engine performance.
Implementation Method 1
a contact portion between the outer circumferential surface of the insulator and the inside-diameter-reducing portion or the packing; since a change in temperature is restrained at a contact portion of the outer circumferential surface of the insulator with the inside-diameter-reducing portion or with the packing, durability can be improved
Implementation Method 2
a control system for controlling an internal combustion engine having an ignition plug and a coolant passage for cooling the ignition plug
Data Source
Figure 1
Figure 2(A)~3
Figure 4
AI summary
An ignition plug includes a tubular insulator having an axial hole extending in the direction of an axial line, a metallic shell disposed around the outer circumference of the insulator, a center electrode disposed in the axial hole of the insulator, and a ground electrode connected to the forward end of the metallic shell and facing the center electrode. The metallic shell has a threaded portion to be engaged with a thread ridge of a mounting hole of an internal combustion engine. The relational expression Ss/(Sa + Sb) ≥ 2.6 is satisfied, where Ss is the surface area of an outer circumferential surface of the metallic shell extending from the rear end of the threaded portion to the forward end of the threaded portion, Sa is the surface area of that portion of the metallic shell which is to be exposed to combustion gas of the internal combustion engine, and Sb is the surface area of that portion of the insulator which is to be exposed to the combustion gas.