pushed downward by the spring 19 and the valve 20 closes the secondary air supply pipe 24 to suspend the air injection since the two negative pressure chambers 14 and 31 of vcv13 are connected to each other through the orifice 40 the pressure of said chambers will become the same after a certain period of time thereby causig the diaphragm 30 to return to the original position when the diaphragm 30 is drawn in downward when the diaphragm 30 is returned to the original position the valve 37 opens the second negative pressure pipe 16 and close the valve supporter 35 thus the pressure near the atmospheric pressure is transmitted to the second negative pressure chamber 17 of asv10 whereby the valve 20 opens the secondary air supply pipe 24 to start the air injection again in other words when decelerating suddenly the air injection will be suspended for a certain period of time after such decelerating operation referring to fig9 when tvsv7 is open and the throttle valve 3 is widely open i e when accelerating or having a very high load the two negative pressure ports 5 and 6 receive pressure near the atmospheric pressure and the.