Yamaha YW125Y_ Utility Trailer User Manual

The O
sensor has been adopted to enable the catalyst to function at a high degree of efficiency by
maintaining the air-fuel mixture near the stoichiometric ratio (14.7:1). This sensor, which is a zirconia
type, utilizes the oxygen ion conductivity of the solid electrolyte for detecting the oxygen concentra-
tion levels. In actual operation, a zirconia tube made of solid electrolyte is exposed in the exhaust
gas, so that the exterior of the zirconia tube is in contact with the exhaust gas and the interior is in
contact with the atmosphere whose oxygen concentration level is known. When a difference in the
oxygen concentration level is created between the outside and the inside of the zirconia tube, the
oxygen ion passes through the zirconia element and generates an electromotive force. The electro-
motive force increases when the oxygen concentration level is low (rich air-fuel ratio) and the elec-
tromotive force decreases when the oxygen concentration level is high (lean air-fuel ratio). As elec-
tromotive force is generated in accordance with the concentration of the exhaust gas, the resultant
voltage is input into the ECU in order to correct the duration of the injection of fuel.
1 Inner cover
2 Outer cover
3 Zirconia tube
4 Exhaust gas
5 Atmosphere
A Atmosphere
B Inner electrode
C Zirconia element
D Outer electrode
E Porous ceramic layer
F Exhaust gas
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