EGR CONTROL METHOD AND EGR DEVICE

PROBLEM TO BE SOLVED: To enable a reduction in flow rate of recirculation exhaust gas associated with secular change to be positively detected, and at the same time to enable compensation for reduction in flow rate to be attained.SOLUTION: Whether or not a flowability of exhaust gas at an EGR valve for controlling a recirculation amount of exhaust gas to an intake side of an engine is lower than a prescribed reference is determined in reference to whether or not a clogged rate attained as a ratio of a flow rate of exhaust gas at the starting time of use of the EGR valve with respect to a flow rate of exhaust gas at the EGR valve at the time of determination of flowability exceeds a determination threshold. When the clogged rate exceeds the determination threshold, an alert is produced saying that the flowability of the exhaust gas decreases down the prescribed reference and at the same time the flow rate of the recirculation exhaust gas is corrected in response to a degree of reduction in flowability.SELECTED DRAWING: Figure 3 【課題】経年変化に伴う還流排気ガスの流量低下を確実に検出可能とすると共に、流量低下に対する補償を可能とする。【解決手段】エンジンの吸気側への排気ガスの還流量を制御するＥＧＲバルブにおける排気ガスの流通性が所定の基準を下回ったか否かを、流通性の判断時におけるＥＧＲバルブにおける排気ガスの流量に対する、ＥＧＲバルブの使用開始時における排気ガスの流量の比として求められるつまり率が判定用閾値を越えるか否かによって判断し、つまり率が判定用閾値を越える場合に、排気ガスの流通性が所定の基準を下回ったとして、警報を行うと共に、流通性の低下の程度に応じて、還流排気ガスの流量が補正されるものとなっている。【選択図】図３