PURPOSE: To enhance the operating performance by improving the working responsiveness of each actuator, and exhausting the exhaust gas early as desired after the command for changeover of operation is given.

CONSTITUTION: A negative pressure side duty control valve 5 and an atmosphere side duty control valve 6 are connected with an EGR valve 1, and negative pressure side ON/OFF solenoid valves 7, 9 and atmosphere side ON/OFF solenoid valves 8, 10 are connected with a suction throttle valve 2 and a variable swirl valve 3. Besides them, a forced atmosphere introducing valve 11 to put each actuator (EGR valve 1, suction throttle valve 2, variable swirl valve 3) in communication with forced atmosphere introducing paths 1A-3A and break them from the atmosphere. If the forced introducing valve 11 is turned on, the atmosphere is introduced immediately to the actuators from the valve 11. Accordingly the working responsiveness of each actuator can be enhanced to a great extent, compared with a conventional arrangement where the atmosphere is introduced by turning on the duty control valves 5, 6 and the On/Off solenoid valves 7-10, so that it is possible to suppress worsening of the exhausting performance or the driving characteristic in association with changing-over of the operations of the actuators.