Abstract: A cross flow having a volute is disclosed which is less noisy during its operation. A volute-portion starting radius which is the length of a segment O-F.sub.1 at a volute-portion starting point F.sub.1 is R.sub.1 ; a maximum volute radius which is the length of a segment O-F.sub.2 at the outlet portion starting point F.sub.2 is R.sub.M ; a maximum volute angle which is an angle formed by the segment O-F.sub.2 and O-F.sub.1 is .varies.M; a point on the volute portion having a distance to the center O of the rotating shaft is R.sub.J =(R.sub.1 +R.sub.M)/2; an angle .varies..sub.J is formed by a segment connecting that point and the center 0 of the rotating shaft; the segment O-F.sub.1 is .varies..sub.M /2 (=F.sub.1 -O-F.sub.J); a volute portion of a scroll casing is formed into a circular arc such that R.sub.1 <R.sub.J <R.sub.M, and the circular arc passes through the points F.sub.1, F.sub.J, and F.sub.2.

Abstract: An air conditioner indoor unit comprising: a housing; an impeller arranged in the housing and forming a cross flow fan; a rear side plate arranged downstream the impeller and forming a rear side of a diffused air path; a front side plate forming a front side of the diffused air path and including a first air outlet surface, a second air outlet surface and a third air outlet surface; the first air outlet surface arranged near to the impeller and having a portion on a side of an air outlet of the diffused air path slanted in a direction away from a reference surface defined by the rear side plate; the second air outlet surface arranged next to the first air outlet surface on the side of the air outlet and having a portion on the side of the air outlet slanted in a direction away from the reference surface; and the third air outlet surface arranged next to the second air outlet surface on the side of the air outlet end and having a portion on the side of the air outlet slanted at 20.degree.-30.degree.