Abstract: A fan includes a cylindrical impeller, and a casing including a first side plate, a second side plate and an outer plate. In each of the first side plate and the second side plate, parts respectively corresponding to starting end and terminal end sides of the spiral ventilation passage, and a section corresponding to a connecting ventilation passage extending from a terminal end portion of the spiral ventilation passage in a rotating direction of the impeller and connected to a starting end portion of the spiral ventilation passage form a smooth surface by: connecting flat planes having a certain height; connecting inclined planes having a height gradually changed; or connecting a flat plane and an inclined plane; and a dimension of the spiral ventilation passage in the rotation axis direction of the impeller gradually decreases from the starting end portion and the terminal end portion to a predetermined position.

Abstract: There is provided a centrifugal air blower capable of effectively suppressing noise caused by the shapes of a tongue part and a bell mouth formed in a scroll casing, and including: a fan 3 composed of a bottom plate 6 fixed to a rotating shaft, multiple blades 8, and an annular rim 9 provided concentrically with the bottom plate; a scroll casing 4 for housing the fan; a spiral flow passage 19 formed around the fan; and a tongue part 16 for suppressing an inflow of air from the end of winding to the beginning of winding of the spiral flow passage. A portion of the tongue part on the other end side in the axial direction of the rotating shaft is inclined to increase a dimension of overhanging in a counter-rotating direction of the fan toward the other end side in the axial direction of the rotating shaft.

Abstract: There is provided a centrifugal air blower capable of effectively suppressing noise caused by the shapes of a tongue part and a bell mouth formed in a scroll casing. The centrifugal air blower includes: a fan 3 composed of a bottom plate 6 fixed to a rotating shaft, multiple blades 8 whose bases are fixed to the outer circumference of the bottom plate, and an annular rim 9 provided concentrically with the bottom plate to couple distal ends of the blades; a scroll casing 4 for housing the fan and having a suction port 11 on one end side in an axial direction of the rotating shaft; a spiral flow passage 19 formed around the fan in the scroll casing; and a tongue part 16 for suppressing an inflow of air from the end of winding to the beginning of winding of the spiral flow passage.

Abstract: An airflow filter device is employed, for example, in an air-conditioning system for a vehicle and an air-conditioning system for a construction machine. The filter device has a filter for purifying an airflow, an ammeter for detecting clogging in the filter, a filter cleaning warning light that provides a warning to clean the filter when the number of times of clogging in the filter, which is detected by the ammeter, is equal to or less than a threshold value, and a filter replacement warning light that provides a warning to replace the filter when the number of times of clogging exceeds the threshold value.

Abstract: An air-conditioning system for a vehicle includes a clogging detection device for detecting clogging of a filter. The clogging detection device detects clogging of the filter only when a face damper for opening and closing a face air duct provided with movable louvers is in the closed position.