Patent ID: 8192165

Claim:
A multiblade fan comprising: an impeller having a discoid main plate configured to rotate about a rotational axis, a plurality of blades disposed annularly about the rotational axis on one side or both sides of the main plate, with one end of each of the blades being fixed to an outer peripheral portion of the main plate, and one or two side plates including an annular side plate body portion that joins outer peripheral edges of the other ends of the blades to each other, an axially extending portion that extends from an opposite-main plate side end of the side plate body portion in the rotational axis direction further than opposite-main plate side ends of the blades, and a radially extending portion that extends from an outer peripheral end of the side plate body portion further than a radial-direction outer peripheral end of the axially extending portion, the one or two side plates being attached to radially outermost surfaces of the blades which form the outer peripheral edges of the other ends of the blades such that the one or two side plates are disposed radially outward of the radially outermost edges of the blades; a drive mechanism configured to drive the main plate to rotate; and a casing including one or two suction openings formed facing the side plate such that the suction opening can suck in gas from the rotational axis direction and a blowout opening that blows out gas in a direction intersecting the rotational axis, an inner surface of the casing around the suction opening including a first annular concave section facing the main plate and facing radially outwardly and a second annular concave section facing the main plate and facing radially inwardly such that the second annular concave section is radially opposed to the first annular concave section, the axially extending portion of the side plate being disposed radially closer to the second annular concave section than the first annular concave section, with the opposite-main plate side end of the axially extending portion being disposed radially between the first and second annular concave sections, and a radial direction outer peripheral end of the radially extending portion being disposed so as not to protrude radially outwardly beyond a radial direction outer peripheral end of the second annular concave section toward an outer peripheral side when seen from the rotational axis direction.