Page 310 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

292 Methods for Monitoring and Diagnosing the Eficiency of Catalytic Converters

4) cumulatively adding the degree of performance of the catalytic converter in the
predetermined period to obtain an accumulative value
5) evaluating the deterioration of the catalytic converter on the basis of the accumulative value

The degree of performance of step 3 in the predetermined period is calculated based on a rate
of performance deterioration K of the converter. K is calculated from one of the following
methods:
1) from the equation:

1
InK=k, -k2.-++ln[0,]
T

where:
k,, kz, a: constants
T: temperature of the exhaust gases
[Oz]: concentration of oxygen in the exhaust gases
2) is expressed by a rate of change of a purification ratio y of the exhaust gases shown by the
equation:

where:
yo: a purification ratio of the exhaust gas at the time of start of use of the converter
A. H, a: constants
71 temperature of the exhaust gases
[02]: concentration of oxygen in the exhaust gases
t: an operating time
a
m: positive value of not more than I .O
3) is expressed by a rate of change of a degree of decrease ln(1Iy) of a purification ratio y of
the exhaust gas shown by the equation:

where:
k: constant
t: an operating time
m: a positive number

Next, an explanation will be made of the method of evaluating the deterioration of the three-
way catalytic converter based on the strictly found purification ratio w of the exhaust gas. As