High-protection external rotor axial flow fan

An axial flow fan, comprising an external rotor motor and an impeller, wherein,

• the external rotor motor comprises a base, an external rotor assembly, a rotating shaft, and a stator assembly;
• the base comprises a base plate and a sleeve protruding upward from a middle of a top surface of the base plate;
• bearing chambers are respectively disposed at both ends of the sleeve, and bearings are disposed within the bearing chambers;
• the rotating shaft is rotatably supported by the bearings, and a top end of the rotating shaft is connected to the external rotor assembly;
• the stator assembly is disposed around the sleeve and is disposed within an inner cavity of the external rotor assembly;
• an annular protrusion is disposed at an edge of the base plate;
• a labyrinth seal structure is formed by a complementary engagement of convex and concave structures between the annular protrusion and an end of the external rotor assembly;
• the impeller comprises a plurality of blades and a hub;
• the plurality of blades is mounted on an outer side of the hub, and the hub is mounted to an outer end of the external rotor assembly via an installation bracket;
• an external water baffle ring is disposed around the base;
• the installation bracket is equipped with an internal water baffle ring;
• and
• the external water baffle ring cooperates with the internal water baffle ring to form a water blocking device around a periphery of the labyrinth seal structure.