EXHAUST EMISSION CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To enable suitable use of purifying capacity of three-way catalysts arranged in the downstream side while using existing equipment, in an exhaust emission control system for an internal combustion engine having the two three-way catalysts arranged on an exhaust passage of the internal combustion engine.

SOLUTION: This exhaust emission control system for the internal combustion engine is provided with a first three-way catalyst arranged on the exhaust passage of the internal combustion engine, a second three-way catalyst arranged in the downstream side from the first three-way catalyst and a secondary air supply device for supplying secondary air to the exhaust passage in the upstream side from the second three-way catalyst. A maximum value of oxygen amount storable by the second three-way catalyst is obtained, and secondary air including the same amount of oxygen as the maximum value is supplied to the second three-way catalyst every predetermined period.

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