the vacuum control valve 19 includes a diaphragm 20 which defines a diaphragm chamber 21 on its lower side in the figure and a diaphragm chamber 22 on its upper side in the figure the diaphragm 20 is urged downwards in the diagram by the biasing action of a compression coil spring 23 the vacuum control valve 19 is provided with a valve port 24 opening to the inside of the diaphragm chamber 22 from the passage 17 at its part which is on the side of the exhaust gas recirculation control valve 7 from the throttling element 18 and this valve port 24 is opened and closed by a valve element 25 which is supported by the diaphragm 20 thus when the pressure in the diaphragm chamber 21 exceeds the pressure in the diaphragm chamber 22 by a specified value the resistance of the compression coil spring 23 is overcome and the diaphragm 20 is shifted upwards in the figure so that the valve port 24 is closed by the valve element 25 on the other hand when the pressure in the diaphragm chamber 21 does not exceed the pressure in the diaphragm chamber 22 by the specified amount the diaphragm 20 is moved downwards to the position shown in the diagram by the biasing force of the compression coil spring 23 and the valve element 25 is removed from the valve port 24 thus opening it the diaphragm chamber 21 is connected through.