Pre-Chamber Spark Plug Housing Layout for Insulator Fracture Resistance
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Solution Overview
Problem
Existing pre-chamber spark plugs face limitations in design freedom due to the formation of the ground electrode, which restricts the pre-chamber volume and increases the risk of insulator base fractures under high combustion pressures.
Innovation Solution
The ground electrode is positioned inside the housing, forming an ignition gap with the center electrode, and the housing surrounds the insulator and insulator base, providing protection against pressure peaks and allowing for a more flexible pre-chamber design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the ground electrode is formed through or against the wall of the pre-chamber, then the ignition gap can be formed, but the degree of freedom in designing the pre-chamber volume is severely limited
Solution Approach 1:
Instead of forming the ground electrode through or against the pre-chamber wall as in conventional designs, the invention inverts the approach by positioning the ground electrode on the inside surface of the housing. This reversal of the ground electrode formation location eliminates the constraint that previously limited pre-chamber volume design freedom, allowing the pre-chamber to be optimally sized and shaped without structural interference.
2Volume of stationary object
If the insulator base protrudes far into the pre-chamber, then the center electrode can be positioned, but the pre-chamber volume is restricted
Solution Approach 1:
The invention repositions the ground electrode from the pre-chamber wall to the housing interior, which indirectly allows the insulator base to be positioned optimally without restricting pre-chamber volume. The inverted ground electrode location creates spatial freedom that enables both adequate insulator support and sufficient pre-chamber volume.
3Reliability
If the ground electrode is positioned on the pre-chamber wall, then the ignition function is achieved, but insulator base fractures occur under high combustion pressures
Solution Approach 1:
The housing acts as an intermediary protective structure between the combustion pressure peaks and the insulator base. By positioning the ground electrode on the housing interior rather than the pre-chamber wall, the housing wall serves as a buffer that absorbs and distributes combustion pressure, preventing direct transmission of pressure peaks to the insulator base and thereby reducing fracture risk.
4Volume of stationary object
If the pre-chamber volume is increased for better ignition, then the housing structure must be modified, but manufacturing complexity increases
Solution Approach 1:
The inverted ground electrode positioning on the housing interior eliminates structural constraints that previously complicated manufacturing when increasing pre-chamber volume. This design inversion allows the housing to be manufactured as a simple extended structure without complex wall penetrations or attachments, making larger pre-chamber volumes easier rather than more difficult to manufacture.
Data Source
Figure 1
AI summary
Pre-chamber spark plug (1) comprising a housing (2) with a bore along its longitudinal axis (X), wherein the housing (2) has an outer surface (24) and an inner surface (23), a cap (80) arranged at the combustion chamber end of the housing on the housing (2) and which together with the housing (2) forms a pre-chamber (81), an insulator (3) arranged inside the housing (2), a center electrode (4) arranged inside the insulator (3), and a ground electrode (5), wherein the ground electrode (5) and the center electrode (4) are arranged such that the two electrodes form an ignition gap, the ground electrode (5) being arranged on the inner surface (23) of the housing (2).