46
What advantages does the U-groove in the
ground electrode have?
Ignitability can be improved without increasing
the required voltage.
(The U-groove is original DENSO
technology and a patent for it was acquired in 1975.)
Q
4
A
To improve ignitability, it is important to allow the good growth of the flame
nucleus (live coal) created in discharge.
The usual way of ensuring this is increasing the spark gap, but this also
increases the required voltage and thus places a great load on the ignition coil
and plug cords.
Spark gap
(small)
Spark gap
(small)
Ground electrode
with U-groove
Good
Spark gap
(small)
Spark gap
(large)
Flame
nucleus
Bad
Normal
electrode
The ground electrode, with its U-groove,
maintains a large volume of space
without altering the spark gap. Therefore, excellent firing ignitability is enabled
even though the sparking required is kept low.
