Spark Plug Projecting Portions Direct Air-Fuel Mixture Flow
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Solution Overview
Problem
In direct injection engines, accurately controlling the ignition timing of a combustible air-fuel mixture is challenging due to varying fuel injection conditions, leading to poor versatility and increased fuel consumption, and multiple spark discharges result in electrode erosion and reduced spark plug lifespan, while existing structural modifications are prone to deviations that hinder mixture flow to the firing portion.
Innovation Solution
A spark plug design featuring a metal shell with multiple projecting portions at the front end, evenly spaced in the circumferential direction, which redirects the combustible air-fuel mixture layer to the firing portion, ensuring consistent flow regardless of mounting orientation, and a ground electrode configuration that prevents hindrance of the mixture flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ignition timing is accurately controlled to match the combustible air-fuel mixture layer, then reliable ignition is achieved, but the cost for development increases and versatility is poor due to varying fuel injection conditions
Solution Approach 1:
The ground electrode is divided into multiple segments (first ground electrode and second ground electrode) separated by a groove. This segmentation allows the spark plug to effectively ignite different regions of the air-fuel mixture (central high-concentration region and peripheral low-concentration region) without requiring precise timing control, thereby maintaining reliability while improving adaptability to varying injection conditions.
Solution Approach 2:
The groove between the first and second ground electrodes acts as an intermediary structure that guides and concentrates the air-fuel mixture flow toward the firing portion. This intermediary structure ensures that the mixture is properly positioned for ignition regardless of timing variations, resolving the contradiction between reliable ignition and adaptability.
2Reliability
If the amount of fuel injection is increased to extend the combustible air-fuel mixture layer duration, then ignition can be conducted with slightly shifted timing, but fuel consumption deteriorates
Solution Approach 1:
The segmented ground electrode structure creates multiple ignition zones that can simultaneously ignite different portions of the air-fuel mixture. This allows the engine to maintain reliable ignition with standard fuel injection amounts and timing, eliminating the need to increase fuel injection to compensate for timing shifts, thereby preventing fuel consumption deterioration.
3Reliability
If the spark discharge is conducted two or more times to overlap with the combustible air-fuel mixture layer, then ignition reliability is improved, but electrode erosion progresses and service life is shortened
Solution Approach 1:
The segmented ground electrode structure enables a single spark discharge to effectively ignite multiple regions of the air-fuel mixture simultaneously. This eliminates the need for multiple spark discharges, thereby maintaining ignition reliability while preventing accelerated electrode erosion and extending spark plug service life.
4Reliability
If a wall surface with slits is used to introduce the combustible air-fuel mixture layer to the firing portion, then the mixture flow is improved, but manufacturing precision is compromised due to deviations in mounting orientation
Solution Approach 1:
The asymmetric arrangement of the first and second ground electrodes relative to the groove creates a directional flow guidance effect that is inherently tolerant of mounting orientation deviations. The groove structure naturally channels the air-fuel mixture toward the firing portion regardless of slight variations in mounting angle, maintaining reliable mixture flow without requiring high manufacturing precision.
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 design ensures reliable ignition of the air-fuel mixture by maintaining a sufficient amount of the mixture around the firing portion, reducing electrode erosion, and improving the spark plug's service life by accommodating manufacturing tolerances and varying engine conditions.
Implementation Method 1
the metal shell includes an add member of at least three or more projecting portions at a front end face thereof which are formed intermittently in a circumferential direction so as to protrude towards the combustion chamber... redirects the combustible air-fuel mixture layer to the firing portion
Implementation Method 2
the ground electrode in which one end thereof forms a firing portion with a front end of the center electrode so as to produce a spark discharge therebetween at the time of use
Data Source
Figure 1
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AI summary
Projecting portions (61-65) extended in an axis (○) direction and projecting forward are formed on a front end face (57) of a cylindrical portion (60) provided on a front end side of a metal shell (50). The projecting portions (61-65) are disposed at an equal interval therebetween in a circumferential direction revolving around a center S of a firing portion (70). No matter what the mounting state of a spark plug (100) on an engine head (shifted in the circumferential direction that is caused by a difference in tightening an fitting screw) may be, a side face or an end face of any one of projecting portions faces at an upstream side of a fuel (combustible air-fuel mixture layer) flow direction which flows with an air current in a combustion chamber. Therefore, the combustible air-fuel mixture layer colliding with the projecting portion includes the flow direction directed to the firing portion (70) as its reflective direction and is adrift around the firing portion (70).