| 摘要 |
PURPOSE:To prevent a false decision due to a change of cooling water temperature by deciding that EGR gets out of order when the temperature in an EGR passage is less than a designated value determined according to cooling water temperature under condition that it is in an operating state where EGR is to be conducted. 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 valve device 20 through a temperature sensing valve 32 adapted to open when water temperature is more than a designated value and a negative pressure control valve 30 operated in response to exhaust pressure. A micro-computer 50 to which detection values of an engine speed sensor 56, a water temperature sensor 57, a temperature sensor 59 disposed in an EGR passage 13 and a negative pressure switch 58 which is turned on when the negative pressure at an intake tube negative pressure take-out port 62 is more than a designated value are input is adapted to decide the operation of EGR to be such a condition that it can be conducted according to whether the detection value of the temperature sensor 59 is higher than a value obtained by adding a designated value to cooling water temperature or not, under a condition that when the negative pressure switch is on and engine speed is within a designated range. |
