Exhaust gas purifying apparatus for internal combustion engine and control method thereof

摘要

An exhaust gas purifying apparatus for an internal combustion engine includes plural catalysts provided in parallel. In a case where temperatures of the catalysts need to be raised, a catalyst is selected from among the catalysts and the exhaust gas is allowed to flow in the selected catalyst. In addition, the temperature of the selected catalyst is raised without using a reducing agent when the temperatures of the catalysts are lower than a temperature range in which the reducing agent can be purified. Alternatively, the reducing agent is supplied to the selected catalyst so as to raise the temperature thereof when the temperatures of the catalysts are equal to or higher than the temperature at which the reducing agent can be purified.