Electric pump

1. An electric pump using an inner-rotor type, brushless DC motor, wherein a casing of the electric pump is formed by a pump casing and a main casing; a sensor-stator assembly is disposed in a space between a side wall portion of the main casing and a can and is sealed with resin; a first elastic seal member is disposed, in a fluid-tight and compressed manner, between the can and the main casing; a second elastic seal member is disposed, in a fluid-tight and compressed manner, between the pump casing and the main casing; the pump casing and the main casing are fixed together; and wherein a shaft support portion is provided at a bottom plate portion of the main casing in such a manner that the shaft support portion projects toward the center of the interior of the main casing;

a support shaft portion of a shaft is fixed and cantilevered to a blind hole formed in the shaft support portion;

and a bearing is provided on a slide shaft portion of the shaft;

wherein impeller vanes are integrally provided on a rotor main body of the inner-rotor type, brushless DC motor and a vent hole is formed in the rotor main body, the vent hole penetrating the rotor main body in a direction parallel to the shaft to provide fluid communication from a space behind said rotor main body to a space in front of said rotor main body;

wherein an annular projection is provided on the interior side of the bottom plate portion;

wherein the can has a wall thickness and elasticity such that the can is configured to press the first and second elastic seal members for establishing fluid tightness, and to press and hold the sensor-stator assembly; and

wherein a press portion is formed at one end of the can, having three continuously formed surfaces including a first surface, a second surface and a third surface; the first surface being guided by means of the projection of the bottom plate portion, the second surface being pressed against a first the first elastic seal member for attaining fluid tightness, and the third surface abutting the inner surface of the bottom plate portion.

2. An electric pump according to claim 1 , wherein a bearing of the inner-rotor type, brushless DC motor is a submerged-type ceramic bearing which exhibits a lubrication effect when immersed in a coolant.

3. An electric pump according to claim 2 , wherein the submerged-type ceramic bearing is formed of silicon nitride, silicon carbide, alumina, or rice bran ceramic.

4. An electric pump according to claim 1 , wherein the shaft is formed of a material selected from the group consisting of nickel-chromium-molybdenum steel, DD material, ASK 8000, SUS3O3, SUJ2.

5. An electric pump according to claim 1 , wherein the surface of the shaft is treated with hard chrome plating, nitriding treatment, titanium carbide coating, titanium nitride coating, titanium aluminum nitride coating, or diamond-like carbon coating.

6. An electric pump according to claim 1 , wherein the impeller vanes are connected together by an impeller cover.

7. An electric pump according to claim 1 , wherein the pump casing guides fluid which is taken into through an inlet nozzle portion at the center of the pump casing, is rotated while being pushed radially outward by means of the impeller vanes, and is exited from an outlet via an outlet nozzle portion of the pump casing, and the vent hole suppresses generation of a negative pressure stemming from a difference between the flow velocity of fluid pushed out by means of the impeller vanes and the flow velocity of fluid stagnating in the space surrounded by the end of the rotor main body, the bottom plate portion of the main casing, and the shaft support portion.

8. An electric pump according to claim 1 , wherein a cylindrical yoke and a cylindrical magnet are integrally fitted onto an annular stepped portion of the rotor main body; and an end cover is fitted onto the yoke and the magnet so as to prevent the yoke and the magnet from separating from the rotor main body.

9. An electric pump accordingly to claim 1 , wherein the shaft fixed to the blind hole has a bearing stopper portion having a circular plate shape.

10. An electric pump accordingly to claim 9 , wherein the end of the shaft distal to the end of the shaft fixed to the blind hole is capped with a cap nut having a hemispherical shape.