Super Ignition Spark Plug with Fine Center & Ground Electrodes 2003-01-0404
Spark plugs with higher ignitability are continuously in great demand to realize high fuel efficiency and low emissions. To meet this demand, DENSO launched the Iridium Spark Plug in 1997, which realized the two characteristics that had been conventionally difficult to achieve concurrently-high ignitability and long life. The development of this product was enabled by miniaturizing the center electrode, produced using DENSO's original, highly wear-resistant iridium alloy (featuring a high melting point and excellent oxidation resistance).
While spark plugs are now required to have a longer service life, they are also required to be higher in ignitability, as exhaust gas regulations have been tightened recently. However, the effort to miniaturize the center electrode is reaching a limit. While ignitability improvement is important, another critical point in the development of spark plugs is to reduce required voltage to accommodate a higher engine compression ratio, to keep up with future engine design trends. The most effective approach to reducing required voltage is to narrow the spark gap; however, a narrower spark gap might lower ignitability and it is difficult for conventional spark plugs to realize high ignitability and lowered required voltage.
Under such restrictions, DENSO proceeded with research paying attention to the miniaturization of the ground electrode in addition to the conventionally worked-on center electrode, and has succeeded in developing a spark plug that features excellent ignitability, lowered required voltage and long life.
This paper introduces the development of the new Super Ignition Spark Plug. It consists of three chapters:
Advantages of a fine ground electrode
Technical tasks concerned with a fine ground electrode
Development of Super Ignition Spark Plug
Requirements for the ground electrode to achieve high ignitability and low required voltage at the same time
Electrodes materials to achieve long life
Specification of Super Ignition Spark Plug
Contributions to the improvement of engine performance