To detect abnormality of an opening/closing valve in its early stages by providing a non-hardening confirming means confirming the non-hardened state of the elastic material of an opening/closing valve, and letting the means to confirm the opening/closing operation of the opening/closing valve, when the open air temperature is lower than a fixed value and the elastic material is confirmed to be in the non-hardened state by the non-hardening confirming means.
An exhaust passage 3 and a surge tank 7 in an intake passage 2 are connected to each other through an exhaust reflux passage 17, and an exhaust reflux control valve 18 is arranged on the exhaust reflux passage 17. A C/U 47 is provided for adjusting the opening of the control valve 18 and controlling the reflux quantity of exhaust gas to the intake passage 2, but in this case, the C/U 47 is provided with a freeze judging means 48 and an operation confirming means 49. When the open air temperature is lower than a fixed value, a diaphragm is confirmed to be in a non-hardened state, and a pressure sensor 14 is judged to be in a non-frozen state by the freeze judging means 48, the opening/closing operation of the exhaust reflux control valve 18 is confirmed based on the change of the detected pressure by the pressure sensor 14.
HOSOGAI TETSUSHI
KAMAKURA TAMOTSU
SAKAMOTO KATSUHIKO
NISHIOKA FUTOSHI
KOUTOKU MASANOBU
NIIMOTO KAZUHIRO
