ENGINE
WG972-E4, WSM
1-M22
[2] OXYGEN SENSOR
An Oxygen sensor is an essential element of a
feedback control of air-fuel ratio.
The sensor has a zirconia tube which is a solid
electrolyte.
The outside of zirconia tube contacts with the
exhaust gas and the inside of zirconia tube contacts with
the atmosphere to know each oxygen concentration.
The difference of oxygen concentration produced
between the outside and inside of the zirconia tube
causes electromotive force to be generated.
Oxygen sensor should be installed at the both of inlet
and outlet of catalyst.
[Pre-Catalyst Oxygen Sensor]
When the air-fuel ratio is rich, HC, CO, and H
2
etc.
react with the oxygen (O
2
) that remains in the exhaust
gas.
This causes a significant reduction of the
concentration of the remaining oxygen, which
considerably increases the ratio of it to the concentration
of oxygen contained in the atmosphere inside,
increasing the electromotive force.
When the air-fuel ratio is lean, the process is the
other way around, resulting in a significant drop in the
electromotive force near the stoichiometric ratio.
That is the feedback control functions as electronic
control that reduces the air-fuel ratio when it is judged to
be on the rich side based on the electromotive force and
increases the ratio when it is on the lean side.
Thus, pre-catalyst oxygen sensor is sensing the
density of oxygen in exhaust gas before passing of
catalyst, and adjusts the appropriate fuel injection
quantity.
[Post-Catalyst Oxygen Sensor]
A post-catalyst oxygen sensor is sensing the density
of oxygen in exhaust gas after passing of three-way
catalyst. Also the post-catalyst oxygen sensor senses
deterioration of catalyst, and also keeps and improves
the purification performance.
9Y1211108ENM0039US0
(1) Pre-Catalyst Oxygen Sensor
(2) Post-Catalyst Oxygen
Sensor
[A] CATALYTIC CONVERTER
[B] CATALYTIC MUFFLER
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