Patent ID: 7334573

Claim:
A NOx emission reduction apparatus of an engine, comprising: an EGR valve disposed in an EGR passage for communication between an intake passage and an exhaust passage so as to adjust an amount of an external EGR gas recirculated from the exhaust passage to the intake passage; a variable valve mechanism capable of varying either an intake valve open timing or an exhaust valve close timing of the engine so as to adjust an amount of an internal EGR gas returned from the cylinder to an intake port of the engine and resupplied into the cylinder; and a controller programmed to: detect an engine load of the engine; and when the detected engine load is in a very-low-load operation range, control the EGR valve to decrease an EGR rate of the external EGR gas as the engine load decreases and control the variable valve mechanism to adjust either the intake valve open timing or the exhaust valve close timing to increase an EGR rate of the internal EGR gas as the engine load decreases.