Spark Plug Resistor Using Spherical Glass Powder
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Solution Overview
Problem
The existing spark plug resistor technology faces challenges in accurately imparting a predetermined resistance while minimizing variation, which affects the ignition performance and yield due to the use of crushed glass powder leading to irregular particle arrangements and conductive path variations.
Innovation Solution
The spark plug design incorporates a resistor composition with sintered glass powder where 50% or more of the particles have a circularity of 0.8 or greater, and the glass powder is predominantly spherical with an average size of 50 µm to 500 µm, ensuring consistent conductive path formation and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If crushed glass powder is used as the glass powder in the resistor composition, then the manufacturing cost is reduced, but the resistance variation among manufactured spark plugs increases greatly
Solution Approach 1:
The invention changes the shape parameter of glass powder from irregular (crushed) to spherical, while maintaining the same material composition. This parameter change leads to more uniform particle arrangement during sintering, resulting in consistent conductive path formation and reduced resistance variation among manufactured spark plugs.
Solution Approach 2:
The invention specifically employs spherical glass powder instead of irregularly shaped crushed glass powder. The spherical shape enables more uniform packing and arrangement of particles during the sintering process, leading to consistent conductive path geometry and reduced variation in resistance values across production batches.
2Object-affected harmful factors
If the resistance of the resistor is increased to enhance radio noise restraint, then the radio noise restraint effect is improved, but the energy required for spark discharge decreases potentially resulting in deterioration of ignition performance
Solution Approach 1:
The invention optimizes the resistance parameter within a specific range (100Ω to 1kΩ) to balance two opposing requirements: sufficient radio noise restraint and adequate spark discharge energy. This parameter optimization allows the resistor to simultaneously achieve electromagnetic interference suppression and maintain ignition performance.
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 approach significantly reduces variation in resistor resistance, allowing for more accurate resistance values and enhanced yield by stabilizing the conductive paths and improving workability and under-load life.
Implementation Method 1
a resistor formed in the axial hole through sintering of a resistor composition containing a conductive material, glass powder, and ceramic particles other than glass
Data Source
AI summary
Provided is a spark plug which allows a predetermined resistance to be imparted to a resistor with restraint of variation in resistance of the resistor and in turn, enables enhancement of yield. A spark plug 1 includes a ceramic insulator 2 having an axial hole extending in the direction of an axis CL1, a center electrode 5, and a terminal electrode 6. A resistor 7 is provided in the axial hole 4 through sintering of a resistor composition 56 which contains a conductive material such as carbon black 53, glass powder 51, and ceramic particles 54 other than glass. As viewed on a section of the resistor 7 taken along a direction orthogonal to the axis CL1, 50% or more of sintered glass powder 51 formed through sintering of the glass powder has a circularity of 0.8 or greater.