METHOD OF CONTROLLING EMISSION FROM GASOLINE ENGINE

摘要

A method of control emission from a fuel direct injection type gasoline engine uses an exhaust purifying catalyst (12), which contains one of precious metals such as platinum and transition metals, to purify exhaust which in response to a change in air-fuel ratio varies between a first exhaust state based on the air-fuel ratio near the theoretical air-fuel ratio and a second exhaust state of a more oxidizing atmosphere and a lower temperature than those of the first exhaust state, based on a greater air-fuel ratio than the theoretical air-fuel ratio. By the method, exhaust from a fuel direct injection type gasoline engine (1), whose air-fuel ratio varies between the theoretical air-fuel ratio and the air-fuel ratio in a lean burn region, can be purified by means of a single purification catalyst (12), so that purification of exhaust gas of which the composition and temperature vary widely due to frequent change of the air-fuel ratio can be simplified.