FAILURE DIAGNOSIS DEVICE OF EXHAUST EMISSION RECIRCULATION SYSTEM

To provide a failure diagnosis device of an exhaust emission recirculation system which can diagnose a failure in detail while securing the safety of an engine operation.SOLUTION: A failure diagnosis device for diagnosing the presence or absence of a failure of an EGR system 50 of an engine 2 in a plug-in hybrid vehicle comprises: an EGR temperature sensor 56 for detecting a temperature of an EGR gas; and an EGR failure determination part 60 for determining the presence or absence of the failure of the EGR system 50 on the basis of a change in temperature of the EGR gas when opening and closing an EGR valve 54. The EGR failure determination part 60 determines an open failure of the EGR valve 54 on the basis of the temperature change of the EGR gas by closing the EGR valve 54 at a warmup operation after start of the engine 2 at a transition to a series mode from an EV-mode, and determines a closed failure of the EGR valve 54 on the basis of the temperature change of the EGR gas by opening the EGR valve 54 from a closing operation state after the open failure determination.SELECTED DRAWING: Figure 2 【課題】エンジン運転の安定性を確保しつつ、詳細に故障判定可能な排気還流システムの故障診断装置を提供する。【解決手段】プラグインハイブリッド車におけるエンジン２のＥＧＲシステム５０の故障の有無を診断する故障診断装置であって、ＥＧＲガスの温度を検出するＥＧＲ温度センサ５６と、ＥＧＲバルブ５４を開閉作動させた際のＥＧＲガスの温度の変化に基づいて、ＥＧＲシステム５０の故障の有無を判定するＥＧＲ故障判定部６０と、を備え、ＥＧＲ故障判定部６０は、ＥＶモードからシリーズモードへの移行の際のエンジン２の始動後のウォームアップ運転時にＥＧＲバルブ５４を閉作動させてＥＧＲガスの温度変化に基づいてＥＧＲバルブ５４の開故障判定を行い、当該開故障判定後にＥＧＲバルブ５４を閉作動状態から開作動させてＥＧＲガスの温度変化に基づいてＥＧＲバルブ５４の閉故障判定を行う。【選択図】図２