Direct drive rotor with metal coupler

A rotor for an outer rotor-type electric motor, said rotor being rotatable about an axis, said rotor comprising:

• a plurality of permanent magnets;
• a polymeric frame supporting the magnets;
• and
• a metallic coupler including—
• an inner axial surface configured to interface with a shaft to be driven by the rotor when the motor is energized,
• an outer axial surface that corresponds to a multiplicity of outer teeth, and
• a first generally radial surface,
• said polymeric frame including a hub molded over at least the outer axial surface of the metallic coupler,
• said hub engaging the first generally radial surface,
• said outer teeth engaging the hub such that torque is transmitted from the coupler to the frame,
• said coupler having a nominal outer diameter, ODcoupler, and a height, Hcoupler,
• each of said outer teeth having a generally arcuate tooth width, Wtooth, and a generally radial tooth depth, Dtooth,
• each tooth width Wtooth being between about 62% and about 63% of the corresponding tooth depth Dtooth,
• each tooth depth Dtooth being between about 4% and about 8% of ODcoupler, and between about 5% and about 8% of Hcoupler.