Spark Plug Ground Electrode Geometry for Pre-Ignition Control
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Solution Overview
Problem
Existing spark plugs with a ground electrode connected to a metal shell suffer from overheating, leading to pre-ignition issues due to inadequate cooling by the fuel or intake charge mixture.
Innovation Solution
A spark plug design where the ground electrode is rod-like and connected to the metal shell, with a specific configuration of the distal end portion having a hole for the ground electrode, ensuring a surface area ratio of less than or equal to 13.1 to effectively transfer heat from the ground electrode to the metal shell, preventing overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ground electrode is surrounded by the distal end portion of the metal shell, then the ground electrode is protected and electrically connected to the metal shell, but the ground electrode is hardly cooled by fuel or intake charge mixture, leading to overheating and pre-ignition
Solution Approach 1:
The invention applies local quality by creating a specific geometric configuration where only a portion of the ground electrode is surrounded by the distal end portion of the metal shell, while another portion extends through a hole to be exposed to cooling fuel or intake charge mixture. This local differentiation allows different parts of the ground electrode to have different thermal characteristics - the surrounded portion is protected and electrically connected, while the exposed portion receives cooling, thereby preventing overheating and pre-ignition without compromising the electrical connection integrity
2Use of energy by moving object
If the ground electrode is exposed to combustion gas, then it receives heat for ignition function, but excessive heat causes overheating and pre-ignition
Solution Approach 1:
The invention applies parameter changes by controlling the geometric parameters of the ground electrode and its interaction with the metal shell. Specifically, by defining the surface area S of the ground electrode portion surrounded by the distal end portion and the side surface area E of the portion inside the hole, and establishing that S/E ≤ 13.1, the invention optimizes the balance between heat reception (for ignition function) and heat dissipation (through cooling by fuel or intake charge mixture), thereby preventing overheating while maintaining effective ignition capability
3Loss of energy
If the surface area ratio S/E is high, then more heat is transferred to the metal shell, but the ground electrode overheats due to insufficient cooling surface area
Solution Approach 1:
The invention applies parameter changes by establishing a specific constraint on the ratio S/E ≤ 13.1, where S is the surface area of the ground electrode portion surrounded by the distal end portion and E is the side surface area of the portion inside the hole. This parameter constraint ensures optimal balance between heat transfer to the metal shell (which provides structural support and electrical connection) and heat dissipation through the cooling medium (fuel or intake charge mixture), thereby preventing ground electrode overheating while maintaining effective heat management
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 effectively reduces the occurrence of pre-ignition by balancing heat reception and transfer, ensuring the ground electrode remains cool and preventing premature ignition.
Implementation Method 1
a value obtained by dividing a surface area of a portion of the ground electrode, the portion being located on an inner circumferential side of the distal end portion, by a side surface area of a portion of the ground electrode, the portion being located inside the hole, is less than or equal to 13.1
Data Source
AI summary
A spark plug includes: a center electrode; a metal shell that holds the center electrode in an insulated manner; and a rod-like ground electrode electrically connected to the metal shell and having one end opposed to the center electrode. The metal shell includes a tubular distal end portion inside which the one end of the ground electrode is located. The distal end portion has a hole into which the other end of the ground electrode is inserted. A value obtained by dividing a surface area of a portion of the ground electrode, the portion being located on an inner circumferential side of the distal end portion, by a side surface area of a portion of the ground electrode, the portion being located inside the hole, is less than or equal to 13.1.