Spark Plugs
Chapter 2
Study Tips
The spark plugs are critical parts that dominate
the engine combustion and bear a major
responsibility for higher engine performance.
Spark Plugs
Chapter 2 Spark Plugs
13
2 Structure
Structure
A spark plug consists of three main parts, the housing, the
insulator, and the electrodes.
Let us take a look at the figure, which shows an spark plug as an example,
and look at the features of each part.
Insulator
Terminal
Ring
Center shaft (stem)
Housing
Glass seal
Gasket
Electrode with copper
Packing washer
0.4-mm iridium center electrode
U-groove ground electrode
Taper cut ground electrode
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Insulates the terminal, center shaft and
center electrode from the housing,
preventing escape of high voltage from the
electrodes.
Since the bottom of the insulator projects
into the combustion chamber, high purity
alumina with superior heat-proof
characteristic, mechanical strength,
excellent insulation and thermal conductivity
at high temperature, etc. is used.
Insulator
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1
The terminal is connected to a high-tension
cord through which high-voltage current
from the ignition system flows.
A terminal nut is installed so this type can
support almost any high-tension cord in the
world. For vehicles not requiring a terminal
nut, the terminal can be removed.
Terminal
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2
Makes the insulator and the housing fit
tightly to each other and maintains the
airtightness.
Ring, Packing washer
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