Spark Plug Guide Member for Stable Ignition
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Solution Overview
Problem
The mounting posture of spark plugs in internal combustion engines can affect their ignition capability, as the ground electrode may block the air-fuel mixture flow, leading to reduced combustion stability, especially in lean-burn engines, and existing solutions either compromise strength or increase manufacturing complexity.
Innovation Solution
A spark plug design featuring a guide member that protrudes from the housing at a different circumferential position from the ground electrode, with specific dimensional relationships to ensure effective guidance of the air-fuel mixture to the spark gap, regardless of the mounting posture, maintaining stable ignition capability without complicating the ground electrode's shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the ground electrode is made thicker to ensure strength, then the strength of the ground electrode is improved, but the air-fuel mixture flow is more easily blocked
Solution Approach 1:
The ground electrode is divided into multiple segments along its length, with each segment having a different thickness. The upstream portion (closer to the air-fuel mixture flow) has a smaller thickness to reduce flow blocking, while the downstream portion has a larger thickness to ensure structural strength. This segmentation allows the ground electrode to simultaneously achieve both strength and minimal flow interference.
2Reliability
If the spark plug mounting posture is controlled to optimize ignition capability, then the ignition capability is improved, but the device complexity increases due to precise positioning requirements
Solution Approach 1:
The ground electrode is designed with non-uniform thickness distribution, where the upstream portion has reduced thickness to minimize flow blocking. This local modification allows the spark plug to maintain optimal ignition capability across a wider range of mounting postures, reducing the need for precise positioning control while ensuring reliable ignition performance.
3Object-generated harmful factors
If existing techniques are applied to prevent flow blocking (slot-like hole or thin plate members), then the air-fuel mixture flow is improved, but the manufacturing complexity or electrode strength is compromised
Solution Approach 1:
Instead of modifying the ground electrode shape through slots or additional components, the invention changes the thickness parameter of the ground electrode along its length. By making the upstream portion thinner and the downstream portion thicker, the design achieves improved air-fuel mixture flow while maintaining electrode strength and avoiding complex manufacturing processes.
Data Source
AI summary
A spark plug for an internal combustion engine includes a tubular housing, a tubular insulator, a center electrode, a ground electrode and a guide member. The guide member is configured to guide the flow of an air-fuel mixture in a combustion chamber of the engine to a spark gap formed between the center electrode and the ground electrode. Moreover, in the spark plug, the following dimensional relationships are satisfied: b≧−67.8×(a/D)+27.4; b≦−123.7×(a/D)+64.5; −0.4≦(a/D)≦0.4; and 0°≦b≦90°. Further, with an oblique angle θ being in the range of 0 to 30°, the following dimensional relationship is also satisfied: 0.8≦r/R≦1. Consequently, the spark plug can secure, with a simple configuration, a stable ignition capability regardless of the mounting posture of the spark plug to the engine.