Centrifugal fan with waterproof structure

A centrifugal fan comprising:

• an electric motor including a stator having a stator-side magnetic pole and a rotor rotated about a revolving shaft outside said stator;
• said rotor including a cup-like member including a bottom wall fixed on said revolving shaft and a peripheral wall arranged so as to extend in an axial direction of said revolving shaft from an outer edge of said bottom wall, and a rotor-side magnetic pole fixed inside said peripheral wall of said cup-like member and arranged opposite to said stator-side magnetic pole of the said stator;
• an impeller including a fixed section fixed outside said cup-like member of said rotor of said electric motor, a blade support fixed on said fixed section and arranged so as to extend in a radial direction of said revolving shaft, and a plurality of blades fixed on said blade support so as to suck in air on one axial side of said revolving shaft and discharge the air in the radial direction of said revolving shaft;
• a casing including a first side wall provided with a suction port which is open to said one axial side of said revolving shaft, a second side wall positioned on the other axial side of said revolving shaft with respect to said first side wall and arranged so as to be spaced from said first side wall at a predetermined interval, and a peripheral wall arranged so as to connect said first side wall and second side wall to each other and form an air passage between said first side wall and said second side wall for guiding air discharged from said impeller to a discharge port which is open in a direction tangential to a direction of rotation of said impeller;
• said casing receiving said electric motor and impeller therein;
• said electric motor being arranged in said casing so that said stator is fixed on said second side wall and said cup-like member of said rotor permits said bottom wall to face said suction port of said first side wall;
• said second side wall of said casing and a wall of said blade support of said impeller having opposite surface portions arranged so as to be opposite to each other in said axial direction of said revolving shaft, respectively;
• said opposite surface portion of said second side wall of said casing and said opposite surface portion of said wall of said blade support of said impeller each being formed into a configuration which permits said opposite surface portions to cooperate with each other to provide a labyrinth structure which prevents water from intruding into a space defined between said cup-like member and said second wall from an outside in the radial direction of said revolving shaft;
• said blades being mounted on a surface portion of said blade support opposite to said opposite surface portion of said blade support.