Evaluating method for NOx eliminating catalyst, an evaluating apparatus therefor, and an efficiency controlling method therefor

An evaluating method for NOx eliminating catalyst installed in an exhaust gas system of an internal combustion engine, including

• NOx eliminating catalyst for reducing NOx in an oxidizing atmosphere, characterized in
• evaluating said NOx eliminating catalyst based on difference of
• oxygen concentration in exhaust gas at upstream side of said NOx eliminating catalyst and
• oxygen concentration in exhaust gas at downstream side of said NOx eliminating catalyst which is changed by effects of said NOx eliminating catalyst.

An evaluating apparatus for NOx eliminating catalyst comprising;

• (a) a base body composed of an ion conductive solid electrolyte,
• (b) platinum electrodes provided respectively at both surfaces of said base body holding said base body between,
• (c) diffused resistors covering said platinum electrodes,
• (d) an exhaust gas inlet path which flows exhaust gas at upstream side of the NOx eliminating catalyst to one of said diffused resistors, and flows exhaust gas at downstream side of the NOx eliminating catalyst to another one of said diffused resistors, and
• (e) an output portion for supplying electric signals generated between said platinum electrodes to a postfixed evaluating means.

An evaluating apparatus for NOx eliminating catalyst comprising;

• (a) a first base body composed of an ion conductive solid electrolyte,
• (b) platinum electrodes provided respectively at both surfaces of said first base body holding said first base body between,
• (c) a first diffused resistor covering one of said platinum electrodes at said first base body,
• (d) a first exhaust gas inlet path which flows exhaust gas at upstream side of the NOx eliminating catalyst to said first diffused resistors,
• (e) a second base body composed of an ion conductive solid electrolyte,
• (f) platinum electrodes provided respectively at both surfaces of said second base body holding said second base body between,
• (g) a second diffused resistor covering one of said platinum electrodes at said second base body,
• (h) a second exhaust gas inlet path which flows exhaust gas at downstream side of the NOx eliminating catalyst to said second diffused resistors, and
• (i) first and second output portions for supplying electric signals generated between said first platinum electrode at said first base body and said second platinum electrode at second base body to a postfixed evaluating means.

An efficiency controlling method for NOx eliminating catalyst installed in an exhaust gas system of an internal combustion engine, including

• NOx eliminating catalyst for eliminating NOx in exhaust gas, characterized in
• evaluating said NOx eliminating catalyst, and
• elevating temperature of said NOx eliminating catalyst or/and
• increasing an amount of hydrocarbon supplied to said NOx eliminating catalyst when said NOx eliminating catalyst is judged as deteriorated.