EGR RATE CALCULATION METHOD AND EGR DEVICE FOR ENGINE

摘要

PROBLEM TO BE SOLVED: To accurately calculate an actual EGR rate in a wide operating condition.SOLUTION: An oxygen concentration sensor 26 for detecting an oxygen concentration is provided in an intake passage 13 downstream of a position where an EGR passage 21 is merged with the intake passage 13. An intake flow velocity at a position where the oxygen concentration sensor 26 is installed is estimated, and when the intake flow velocity exceeds a predetermined threshold value, an actual EGR rate is calculated in a first actual EGR rate calculation method on the basis of a detection value obtained by the oxygen concentration sensor 26. When the intake flow velocity is equal to or less than the predetermined threshold value, the actual EGR rate is calculated in a second actual EGR rate calculation method on the basis of an engine operating status.SELECTED DRAWING: Figure 1