| 摘要 |
PURPOSE:To prevent a false diagnosis due to a change of outside air temperature by deciding abnormality of EGR when a state where the temperature in an EGR passage is less than a designated value continues more than a designated period of time fixed according to outside air temperature on condition that it is in an operating range for conducting EGR. CONSTITUTION:Negative pressure from an intake tube negative pressure take-out port 34 is introduced into a diaphragm chamber 27 of a diaphragm device 25 for driving a valve element 24 of an EGR control valve 20 through a temperature sensing valve 32 adapted to open when water temperature is more than a designated value. A negative pressure control valve 30 operated in response to exhaust pressure is disposed in a conduit 29 connecting the diaphragm chamber 27 and the temperature sensing value 32 each other. A micro-computer 50 to which detection values of an air flow meter 3, an engine speed sensor 56, a water temperature sensor 57, a temperature sensor 59 disposed in an EGR passage 13 and an outside air temperature sensor 60 are input is adapted to decide abnormality when a state where the detected temperature of the temperature sensor 59 is less than a designated value continues more than a designated period of time which is decreased as the outside air temperature increases in spite of an operating state where EGR is to be conducted. |
