67
More cooling
Flame kernel
Flame kernel
Normal spark plug
•
Rapid growth of flame kernel
•
Cylinder compression ratio
Effect of ultra-fine iridium electrode
TDC
Electric discharge
energy activates part of
mixed air and a small
flame is produced.
Sparks discharge on the
part of the electrode
where they can
discharge most easily.
The flame grows even
though energy is being
absorbed in the ground
electrode.
Growth of the flame
accelerates and finally,
the flame spreads as
explosive combustion.
Less cooling
1600cc 4cyl
1200rpm-60KPa
0.4MPa/DIV
Average waveform for 256 cycle
The electrode also has a quenching (cooling) effect (effect where the electrode takes
away the heat of the spark as soon as firing occurs). Therefore, in a thick electrode the
cooling effect is large and sometimes firing does not occur as shown in Figure 4. The
characteristics of this firing is called
ignitability
. To improve
ignitability
, the contact area
between the electrode and the flame kernel needs to be made reduced in size.
Accordingly, the electrode was made as fine as possible in the to
improve
ignitability
.
What makes the ignitability of
so good?
The quenching effect of the plug is reduced by
using the ultra-fine 0.4mm dia. center electrode.
Pattern from sparking to firing
1 Sparking
2 Generation of flame kernel
3 Growth of flame kernel
4 Firing
Normal spark plug
2.5
0.4