Exhaust-gas-purifying system of internal combustion engine, method of using exhaust-gas-purifying catalyst and method of controlling air-fuel ratio

A method of using an exhaust-gas-purifying catalyst in which at least one of Rh, Pd, and Pt is supported on a CeO2-containing support, and an electronic control unit, wherein the electronic control unit includes:

• a flag ON setting unit, a reduction treatment performing unit, and a flag OFF setting unit, the method comprising:
• a process of setting a reduction treatment necessity flag to ON, using the flag ON setting unit, when an input gas temperature which is a temperature of an exhaust gas introduced into the exhaust-gas-purifying catalyst is higher than a reference temperature;
• a process of performing a reduction treatment, using the reduction treatment performing unit, in which an air-fuel ratio of an intake gas supplied to an internal combustion engine is adjusted to be richer than a stoichiometric air-fuel ratio when the reduction treatment necessity flag is set to ON and the input gas temperature decreases and falls within a preset temperature range up to the reference temperature or lower;
• and
• a process of setting the reduction treatment necessity flag to OFF, using the flag OFF setting unit, after the reduction treatment is performed.

An exhaust-gas-purifying system of an internal combustion engine, the system comprising;

• an exhaust-gas-purifying catalyst having a configuration in which at least one of Rh, Pd, and Pt is supported on a CeO2-containing support;
• and
• an electronic control unit programmed to:
• set a reduction treatment necessity flag to ON when an input gas temperature which is a temperature of an exhaust gas introduced into the exhaust-gas-purifying catalyst is higher than a reference temperature;
• determine whether reduction treatment execution conditions in which the reduction treatment necessity flag has been set to ON and the input gas temperature has decreased and falls within a preset temperature range up to the reference temperature or lower are satisfied;
• perform a reduction treatment in which an air-fuel ratio of an intake gas supplied to the internal combustion engine is adjusted to be richer than a stoichiometric air-fuel ratio when it is determined that the reduction treatment execution conditions are satisfied;
• and
• set the reduction treatment necessity flag to OFF when the reduction treatment is performed.

A method of controlling an air-fuel ratio in an exhaust-gas-purifying system of an internal combustion engine including an exhaust-gas-purifying catalyst in which at least one of Rh, Pd, and Pt is supported on a CeO2-containing support, and an electronic control unit, wherein the electronic control unit includes:

• a flag ON setting unit, a reduction treatment performing unit, and a flag OFF setting unit, the method comprising:
• setting a reduction treatment necessity flag to ON, using the flag ON setting unit, when an input gas temperature which is a temperature of an exhaust gas introduced into the exhaust-gas-purifying catalyst is higher than a reference temperature;
• performing a reduction treatment, using the reduction treatment performing unit, in which an air-fuel ratio of an intake gas supplied to an internal combustion engine is adjusted to be richer than a stoichiometric air-fuel ratio when the reduction treatment necessity flag is set to ON and the input gas temperature decreases and falls within a preset temperature range up to the reference temperature or lower;
• and
• setting the reduction treatment necessity flag to OFF, using the flag OFF setting unit, after the reduction treatment is performed.