Patent ID: 7426922

Claim:
An exhaust gas purifier for an engine comprising: an injection controller allowing a fuel injection valve presented to a combustion chamber of the engine to inject a predetermined amount of fuel near the top dead center on each compression stroke; an EGR amount controller for controlling the amount of exhaust gas recirculated into the combustion chamber so that a high-temperature part of a combustion air-fuel mixture has a lower temperature than the temperature at which NOx is produced; an excess air ratio controller for controlling the excess air ratio in the combustion chamber so that the local equivalence ratio in a late combustion stage is lower than the equivalence ratio at which soot is produced; and an intake air temperature controller for controlling the temperature of intake air after being mixed with exhaust gas and before being supplied into the combustion chamber within a temperature range lower than an upper temperature limit below which a predetermined ignition delay time can be secured after fuel injection of the fuel injection valve and higher than a lower temperature limit above which the production of HC and CO can be avoided.