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In a high gas velocity condition in cylinder, the ground electrode orientation of the spark plug causes the ignitability to fluctuate due to the change in gas flow around the spark gap. As one method to solve this issue we have focused on controlling the gas flow by plate like airfoils or turbine blades. We have developed gas flow control technology for the spark plug to achieve high ignitability under the worst case condition of ground electrode orientation. The adoption of current ground electrode welding technology has allowed us to locate a flow guide plate on the plug housing.

In recent years, from a viewpoint of global warming and energy issues, the need to improve vehicle fuel economy to reduce CO2 emission has become apparent. One of the ways to improve this is to enhance engine thermal efficiency, and for that, automakers have been developing the technologies of high compression ratio and dilute combustion such as exhaust gas recirculation (EGR), and lean combustion. Since excessive dilute combustion causes the failure of flame propagation, combustion promotion by intensifying in-cylinder turbulence has been indispensable. However, instability of flame kernel formation by gas flow fluctuation between combustion cycles is becoming an issue. Therefore, achieving stable flame kernel formation and propagation under a high dilute condition is important technology.