PURPOSE: To prevent contaminated outside air from flowing backward from an internal air discharge outlet into a room by providing a frame structure including magnetic attraction means on a valve seat part, and a one-way valve including second electromagnet means magnetically attracting the magnetic attraction means at a contact part and it.
CONSTITUTION: A one-way valve 4 is mounted on the surface of a frame structure 2 outside a room, and is closed, securely sealing an internal air discharge outlet 24 by the aid of contact force acting on a valve seat part by the self weight thereof and of magnetic attraction force between magnetic attraction powder 3 and an electromagnet member 5 excepting the time when internal air R is discharged to the outside C of the room C. Accordingly, the internal air discharge outlet 24 is not opened because of the valve 4 springing up owing to vibration produced upon an automobile running, and hence contaminated outside air is prevented from flowing backward from the internal air discharge outlet 24 into the room B. When a sensor 73 of a control circuit 7 does not sense any contamination in the outside air, a current flowing through a coil 52 of the electromagnet member 5 is shut off and demagnetized. As the pressure difference between the inside B and outside C of the room exceeds the self weight of the valve 4, the valve 4 is separated off from the valve seat part 20 to discharge the internal air R to the outside C of the room.
MIYANO TETSUYA
MENJU YOSHIHIRO
