Pump motor having fluid cooling system

A brushless electric motor comprising:

• a stator assembly having laminations and windings, and an interior portion defining a rotor chamber,
• a rotor assembly in said rotor chamber,
• partition structure between said rotor assembly and said stator assembly for isolating said stator assembly from said rotor chamber, said partition structure having a wall in communication with said rotor chamber,
• a shaft on which said rotor assembly is mounted, said shaft including a hollow portion in open communication with said rotor chamber, and
• bearing structure operatively associated with the hollow portion of said shaft for supporting said shaft for rotational movement,
• an electronic control unit coupled to said stator assembly and having an upper surface in communication with said rotor chamber,
• fluid flow path structure constructed and arranged to permit cooling fluid to pass from an inlet to said rotor chamber so that said rotor assembly being submergible in the fluid such that fluid contacts said upper surface of said electronic control unit to cool the electronic control unit, and fluid contacts said wall of the partition structure so that said wall is in heat exchange relation with said fluid to cool said laminations and said windings, and fluid enters said hollow portion of said shaft to cool said bearing structure, and
• fluid return structure for permitting fluid in said rotor chamber to pass to an outlet defined in the motor.

A method of cooling a pump motor, the pump motor including a pump housing having an impeller chamber with an impeller in said impeller chamber, a motor assembly coupled to said pump housing;

• said motor assembly being brushless and including:
• a stator assembly having laminations and windings, said stator assembly having an interior portion defining a rotor chamber, a rotor assembly in said rotor chamber, partition structure between said rotor assembly and said stator assembly for isolating said stator assembly from said rotor chamber, said partition structure including a wall in communication with said rotor chamber, a shaft on which said rotor assembly and impeller are mounted, said shaft including a hollow portion in open communication with said rotor chamber, and bearing structure operatively associated with the hollow portion of said shaft for supporting said shaft for rotational movement, the pump motor further including an electronic control unit coupled to said motor assembly and having an upper surface in communication with said rotor chamber;
• fluid flow path structure constructed and arranged to permit fluid to communicate between said impeller chamber and rotor chamber, and fluid return structure providing fluid communication between said rotor chamber and said impeller chamber,
• the method including:
• permitting fluid from a high pressure portion of said impeller chamber to move through said flow path structure to said rotor chamber such that said rotor assembly is submerged in the fluid and fluid contacts said wall of the partition structure such that said wall is in heat exchange relation with the fluid to cool said laminations and said windings, the fluid contacting said upper surface of the electronic control unit to cool the same,
• permitting fluid to pass to said hollow portion of said shaft to cool said bearing structure, and
• permitting fluid to pass through said fluid return structure to return fluid in said rotor chamber to a low pressure portion of said impeller chamber.