Spark Plug Insulator Sintering via High Oxygen Atmosphere
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Solution Overview
Problem
The existing methods for producing spark plug insulators require highly controlled formulation and manufacturing processes, and long sintering times, which limits the range of composition and particle size, resulting in decreased productivity and voltage resistance.
Innovation Solution
A method involving the use of an alumina molded body with a particle size of 2 μm to 5 μm, sintered in a continuous furnace with a heating zone at 700° C. to 1600° C. under a high oxygen atmosphere exceeding 20 mol % to accelerate sintering and achieve high voltage resistance without the need for sintering additives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sintering is carried out for a long time to progress sintering of the insulating material, then sintering density is improved, but productivity is decreased
Solution Approach 1:
The patent changes the sintering atmosphere parameter by introducing oxygen gas to create a high oxygen concentration atmosphere (exceeding 20 mol%). This parameter change enables rapid sintering at 1500°C for only 10 minutes, achieving high sintering density without requiring long sintering times, thus resolving the contradiction between sintering density improvement and productivity maintenance
Solution Approach 2:
The patent uses a composite raw material system consisting of alumina powder (2-5 μm), sintering aid powder (calcium carbonate, magnesium carbonate, or barium carbonate), and binder resin. This composite material formulation enables rapid sintering in a high oxygen atmosphere, achieving high sintering density in short time and resolving the contradiction between manufacturing precision and productivity
2Reliability
If formulation of raw material and manufacturing process is highly controlled to achieve desired properties, then voltage resistance is improved, but device complexity is increased
Solution Approach 1:
The patent simplifies the formulation control by specifying broad particle size ranges (alumina: 2-5 μm, sintering aid: 0.1-10 wt%) and using a high oxygen atmosphere sintering process. This parameter approach achieves high voltage resistance without requiring highly controlled formulation and manufacturing processes, resolving the contradiction between reliability improvement and device complexity reduction
Solution Approach 2:
The patent introduces sintering aid powders (calcium carbonate, magnesium carbonate, or barium carbonate) as intermediary substances that facilitate sintering in a high oxygen atmosphere. These intermediaries enable the formation of a stable microstructure with high voltage resistance without requiring highly controlled raw material formulation, thus resolving the contradiction between voltage resistance and formulation control complexity
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 allows for high productivity and improved voltage resistance of spark plug insulators by reducing the gaps between alumina particles through oxygen permeation, achieving high sintering density in a short time without the need for sintering additives or long sintering times.
Implementation Method 1
oxygen gas has been confirmed to permeate the alumina particles and is released at a high temperature of 1,200° or more
Implementation Method 2
a heating zone which is heated to 700° C. to 1600° C. by a heating means
Implementation Method 3
When adjacent alumina particles are bonded to one another while shrinking during the sintering step of an alumina sintered body
Data Source
AI summary
Provided are a molding step (A) of preparing an alumina molded body 11 from a molding raw material which contains an alumina raw material powder having an average particle size of 2 μm to 5 μm and a molding additive, and a sintering step (B) of preparing an alumina molded body 12, which becomes a spark plug insulator 1, by sintering the alumina molded body 11. At the sintering step (B), the alumina molded body 11 is conveyed to a continuous furnace 100 provided with a heating zone Z1 which is heated to 700° C. to 1600° C. by a heating means 401, followed by introducing oxygen gas to control the heating zone Z1 to have a high oxygen atmosphere with an oxygen concentration exceeding 20 mol %.