Multi-blade centrifugal blower

A multi-blade centrifugal blower comprising:

• an impeller wheel which is rotatable with respect to a rotation shaft thereof,
• the impeller wheel having a plurality of blades which are arranged around the rotation shaft, a side plate which is connected with each of the blades at a side of one rotation-shaft-direction end of the blade, and a main plate which is connected with each of the blades at a side of other rotation-shaft-direction end of the blade,
• the main plate being integrated with the rotation shaft;
• and
• a casing for accommodating the impeller wheel, wherein:
• when the impeller wheel is rotated, air is sucked through a suction portion formed at the side of the one rotation-shaft-direction end and is blown toward a diameter-direction outer side of the impeller wheel;
• an inside periphery of the blade has a taper portion which is arranged at least at the side of the one rotation-shaft-direction end, the taper portion tapering from the side of the other rotation-shaft-direction end toward the side of the one rotation-shaft-direction end;
• the taper portion is positioned at a front side of a rotation direction R of the impeller wheel with respect to a back portion which is disposed at the side of the other rotation-shaft-direction end of the blade;
• and
• each of inlet angles throughout the taper portion has a value in a predetermined range, the inlet angles being respectively at cross sections of the blade which are perpendicular to the inside periphery of the blade in a meridional plane.