| 摘要 |
PURPOSE:To minimize the reduction in the quantity of ventilation air when a differential pressure is marked between indoors and outdoors or when a ventilation fan is subjected to the effect of open air, by installing an opening angle detection device designed to detect an opening angle of a wind pressure type shutter provided in a ventilation port and a control circuit designated to control a rotary speed based on the opening angle thus detected. CONSTITUTION:When electric power is supplied to a motor 3, a ventilation fan 2 rotates and starts air blow. When subjected to this wind pressure, a wind-pressure type shutter 4 opens and starts ventilation. When a differential pressure between indoors and outdoors is small or when the ventilation fan 2 is not subjected to an open air, the wind-pressure type shutter 4 maintains its open status without any reduction in the quantity of ventilation air. However, when the differential pressure is marked between indoors and outdoors or when the ventilation fan 4 is subjected to the open air, the quantity of ventilation air is reduced so that the opening angle of the wind-pressure type shutter 4 is reduced. Since this opening angle is detected by an opening angle detection device 5, a voltage control circuit 6 increases the application voltage to the motor 3, thereby accelerating the rotary speed of the ventilation fan 2 and increasing the quantity of ventilation air as well. |
