Table of Contents
Advertisement
Ig,.,ition port
of
plug
is up to
be
dirty by
carbon
generated
by
combustion gas
during
engine
revolution or by ail penetrated into the combustion chamber.
This
deposit
is electric
conductible itself.
and
makes short circuit of
high voltage
electricity.
Accordingly weaken
spark to decrease
engine power misfiring
and
in
worst
case will
stop
engine revolution.
To
prevent such
phenomenon
surface of
insulator should be heated enough to
cut
off
carbon
deposited. and
this is called
"self cleaning
temperature".
labout 450°
~
600°C
according
to
engine statel.
On the other
hand. it burned sparking
port of plug
at
higher
temperatur
e.
spark-
ing part will become over heated
point which invites harmful knocking
to
burn
mixture
gas
before hand than sparking the plug.
which
affect decreasing
of engine
power.
Therefore
it
is requested tnat temperature
of whole body of
spark plug
should
be
maintained
less
than
that
of
premature
sparking.
Iless
than
800°C
according
to engine
statel.
As
a
result it can
be said
"sparking part of plug
is no good
if too
cooled
also if too hot".
bl
Escaping of heat
Heat
received
f
rom
combustion gas escapes as shown
in the figure and
sparking
port maintains a certain
tem-
perature baloncing heat
quantity
escaping and receiving.
cI
Necessity
of
different types
of
plug having
each
dif-
ferent heat value.-Difference of heat quantity recieved
by each
plug.
Heat
quantity of
plug
received
from
engine
depend
on
kinds
of
engine
lair cooled o
r
water
cooled.
2 cyle or 4 cylel. design Icompression ratio.
shape
of combustion chamber.
plug
positionl
and
run-
ning
state Ispeed.
loading
.
different
fuel.
flat
ground
or
climbing
slopel greatly.
Fig
.
11
-
19.
Way of escaping
heat
Therefore it is necessary to furnish different types
of
plug to
function satisfactorily
under each
different
operating
condition.
This rate
of escaping of heat is called
"h
eat
vave
of
plug". and
it
is determined
by
its construction.
form.
dimension
and
material.
It is
called
"cold type"
Ifor
high
temperature
usel
which
disci
pates
heat
eaSily and is
hard to
be over
heated
.
and on the
contrary such
types as
hard to discipate heat and
easy
to be heated is
called
"Hot
type"
lIow
tem-
perature
usel.
In Fig.
11
-20.
difference between types functionally ore shown.
148
".
MEMO
•
ill
Low temperature
use
Iha
t
type}
®
Medium temperatu re
Im edium
type}
®
High temperature
Icald
type}
use
use
Fig
.
11
-
20
.
Different plug for heat
condition
II.
®
W~
<D
Dirty
•
®
Smooth
running
A
B
@
Ignition too
ea~
l
y
...
®
g
A;
Low
power
B;
Hi
gh power
Fig
.
11
-
21.
H
a
t
type plug
\for low
temperature usel
149
"
Hide quick links:
Advertisement
Chapters
Table of Contents
