Oxygen Sensor; Function Introduction; Working Principle - Segway VILLIAN SSV Series Service Manual

ELECTRICAL SYSTEM

OXYGEN SENSOR

Function introduction

It is used in the feedback system of the electronic control fuel injection device to achieve closed-loop
control and improve the control accuracy of the air-fuel ratio of the electronic control unit. It is installed
on the exhaust pipe (see【A】in the fi gure below) close to the engine end. It determines whether the
gasoline is completely burned by measuring the oxygen content in the exhaust gas to ensure that the
three-way catalytic converter has the maximum of HC, CO and NOx in the exhaust gas.

Working principle

This is achieved by converting the diff erence in oxygen concentration inside and outside the sensing
ceramic tube into a voltage signal output. When the temperature of the ceramic tube of the sensor
reaches 350℃, the ceramic solid electrolyte has conductive properties. The oxygen molecules on
both sides of the ceramic are catalyzed into oxygen ions by the platinum electrode of the sensor, and
the oxygen ions can move inside the ceramic, therefore, the oxygen on both sides of the ceramic can
diff use through the ceramic itself.
It is this feature that converts the diff erence in oxygen concentration between the inner and outer sides of the
ceramic into a potential diff erence, thereby forming an electrical signal output. If the mixed gas is thicker and
the oxygen concentration in the exhaust gas produced by combustion is low, the oxygen ion concentration
difference between the inside and outside of the ceramic tube is higher, the potential difference is higher,
a large amount of oxygen ions move from the inside to the outside, and the output voltage is higher (about
800mv --1000mv) if the mixed gas is lean and the oxygen concentration in the exhaust gas produced by
combustion is high, the diff erence in oxygen ion concentration between the inside and outside of the ceramic
tube is low, the potential diff erence is low, the output voltage is low (about 100mv), and the signal voltage is A
sudden change occurs near the theoretical equivalent air-fuel ratio (λ=1).
The oxygen sensor electrical connector has 4 pins:
【A】connect to the negative signal of the signal (gray)
【B】connect to the positive pole of the heating
power supply (white)
【C】connect to the positive signal of the signal (black)
【D】connect to the negative pole of the heating
power supply (white)
A
A
C
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B
D