Patent ID: 8647081

Claim:
An electric water pump comprising: a stator generating a magnetic field according to a control signal; a rotor enclosed by the stator and rotated by the magnetic field generated at the stator; a pump cover having an inlet through which coolant flows in and an outlet through which pressurized coolant flows out; a body having: a front surface forming a volute chamber between the pump cover and the front surface; a stator chamber formed at an outer portion of the body in a radial direction and the stator being mounted in the stator chamber; and a rotor chamber formed at an inner portion of the body in a radial direction and the rotor being mounted in the rotor chamber; a shaft having a central axis, fixed to the rotor so as to rotate together with the rotor about the central axis, and mounted in the rotor chamber; and an impeller fixed to a front portion of the shaft so as to rotate together with the shaft, pressurizing the coolant having flowed in through the inlet, and mounted in the volute chamber, wherein the rotor chamber is fluidly connected to the volute chamber, and the stator chamber is fluidly closed and sealed from the rotor chamber; wherein the stator comprises: a stator core formed by stacking a plurality of pieces of a magnetic material; an insulator connecting pieces of the stator core to each other; a coil coiling the stator core so as to form a magnetic path; and a stator case disposed inside the stator chamber and wrapping and sealing the stator core, the insulator, and the coil; wherein the stator case is insert-molded with a bulk mold compound including a potassium family that has a low coefficient of contraction; and wherein the rotor comprises: a rotor core having a hollow cylindrical shape and made of a magnetic material; a permanent magnet mounted at an exterior circumference of the rotor core; a rotor cover mounted at both distal ends of the rotor core and the permanent magnet so as to fix the rotor core and the permanent magnet together; and a rotor case wrapping an exterior circumference of the rotor core and the permanent magnet so as to fix the rotor core and the permanent magnet in a state that the rotor core and the permanent magnet are mounted at the rotor cover.