Page 163 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey
P. 163
Chapter 1.7
Hitachi Ltd.
The methods proposed by Hitachi have been applied, except where otherwise mentioned, for
an engine layout similar to that of fig. 67.
Fig. 67 shows a catalytic converter, an upstream oxygen sensor 1 and a downstream oxygen
sensor 2 which are mounted upstream and downstream of the catalytic converter, respectively,
and a fuel injection control means for feedback controlling the aidfuel ratio based upon the
outputs of the oxygen sensors.
The upstream and downstream oxygen sensors which include zirconium, titania, etc. are used
as aidfuel ratio sensors. Hydrocarbon sensors may be used as the aidfuel ratio sensors. Some
hydrocarbon sensors that may be used measure the absorption factor of infra-red rays. Signals
derived from the upstream and downstream oxygen sensors I and 2 will be hereinafter
represented by characters x and y, respectively.
The fuel injection control means comprises fuel injection quantity calculating means, output
means and aidfuel ratio feedback calculating means. The fuel injection quantity calculating
means determines the fuel-injection quantity from a value detected by a sensor for detecting the
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