| 摘要 |
PURPOSE:To reduce NOx in the exhaust of the engine and improve the operation capacity thereof by a method wherein the openings and closings of an EGR control valve and a throttle valve in a suction air passage are controlled based on the detecting signal of at least one of an engine revolving speed, a load of the engine and a temperature of cooling water. CONSTITUTION:When an operation condition, wherein the engine revolving speed is less than a predetermined value at a high-speed running and the load for the engine is less than the predetermined value thereof, is detected by a speed sensor 15, a load sensor 16 and a water temperature sensor 17, after a warm-up operation, wherein the temperature of engine cooling water is arrived at a predetermined value or 50 deg.C, for example, a module 20 discriminates that it is a condition in which the EGR operation should be effected and excites and opens solenoid valves 9, 13. Then, a vacuum negative pressure and a suction negative pressure are supplied respectively into chambers 8b, 12b of respective actuators 8, 12 and a throttle valve 3 in the suction air passage 2 is closed while the EGR control valve 6 in an EGR passage 5 is opened. When the operation is in a condition except that of above- described, the solenoid valves 9, 13 are closed and the EGR is stopped. |
