Exhaust gas purifier for engines

An engine exhaust gas purifier comprising:

• a main catalytic converter for purifying exhaust gas;
• an auxiliary catalytic converter whose activation is accelerated;
• and
• catalyst diagnosis means for discriminating the deterioration of said auxiliary catalytic converter by comparing the rising characteristic of exhaust gas purification rate of said auxiliary catalytic converter in relation to the catalyst temperature with a reference rising characteristic.

An engine exhaust gas purifier comprising:

• a main catalytic converter;
• an auxiliary catalytic converter disposed upstream side of said main catalytic converter, said auxiliary catalytic converter including an early-activation catalytic converter whose activation is accelerated and a pre-catalytic converter for securing the purification after the activation;
• an exhaust gas sensor disposed at least downstream side between upstream and downstream sides of said auxiliary catalytic converter;
• means for detecting or estimating the temperature of said auxiliary catalytic converter;
• and
• catalyst diagnosis means for evaluating a rising characteristic of exhaust gas purifying rate of said auxiliary catalytic converter in relation to catalyst temperature and a steady state characteristic thereof after the rising, based on a temperature of said auxiliary catalytic converter and data from said exhaust gas sensor, and for comparing said rising characteristic with a reference rising characteristic and deciding that said early-activation catalytic converter is deteriorated if the resultant shift between these rising characteristics is beyond a predetermined value, and for comparing said steady state characteristic with a reference steady state characteristic and deciding that said pre-catalytic converter is deteriorated if the resultant shift between these steady state characteristics is beyond a predetermined value.