Electric motor

1. An electric motor, comprising:

a stator;

a rotor axially supported to a rotational shaft in such a configuration as to rotate relative to the stator, the rotor being adapted to be cooled by a cooling medium;

a cooling medium storing portion disposed on the stator side and storing therein the cooling medium; and

a cooling medium channel for leading the cooling medium from the cooling medium storing portion to the rotor,

wherein

a discharge port for discharging the cooling medium of the cooling medium channel is disposed close to a rotational portion of the rotor,

the cooling medium storing portion is disposed lower than the discharge port, and

a negative pressure caused between the rotor and the discharge port sucks the cooling medium in the cooling medium storing portion.

2. The electric motor according to claim 1 , wherein

the cooling medium storing portion is disposed at a base portion in a case which is lower than the rotational shaft of the electric motor, the rotational shaft being positioned in a lateral direction, and

a surface of the cooling medium stored in the cooling medium storing portion is disposed lower than an air gap between the rotor and the stator.

3. The electric motor according to claim 1 , wherein the discharge port is formed into a protrusion opposed to the rotational portion of the rotor.

4. The electric motor according to claim 1 , wherein a flow channel forming portion having openings on both sides in a circumferential direction of the rotor and extending along the circumferential direction of the rotor is disposed at the discharge port.

5. The electric motor according to claim 4 , wherein, in the flow channel forming portion, a center portion in a rotational direction of the rotor is narrower than at least one of both end portions in the rotational direction of the rotor.

6. The electric motor according to claim 1 , wherein

the rotor includes a plurality of through holes disposed along a circumferential direction of the rotor and passing through a surface of the rotor and a backface of the rotor, and

the cooling medium passes through the through holes.

7. The electric motor according to claim 6 , wherein, on a face on the discharge port side of the rotor, the rotor has a receiving portion which serves as a receiving port for receiving the cooling medium discharged from the discharge port and which transmits the thus received cooling medium to a through hole of the through holes.

8. The electric motor according to claim 7 , wherein the flow channel forming portion is disposed higher than the receiving portion.

9. The electric motor according to claim 1 , further comprising:

a pressure adjusting valve for adjusting an internal pressure of the cooling medium channel.

10. The electric motor according to claim 9 , wherein

the pressure adjusting valve has a function to sense a temperature of the stator, and

according to the thus sensed temperature of the stator, the pressure adjusting valve adjusts the internal pressure of the cooling medium channel to equal to an internal pressure of the electric motor or into a negative pressure state caused during a rotation of the rotor.

11. The electric motor according to claim 1 , wherein

the rotor has a downward slanting face extending along a direction of the rotational shaft, and

absorbing a heat of the rotor by the cooling medium while moving the cooling medium, the slanting face allows the cooling medium to go off from the rotor by means of a centrifugal force caused in a rotation of the rotor.

12. The electric motor according to claim 1 , wherein

the cooling medium goes off from an end portion of the rotor, and

the rotor has a plate which blocks the air gap between the rotor and the stator to thereby prevent the thus going-off cooling medium from entering the air gap.

13. An axial gap electric motor, comprising:

a stator;

a rotor axially supported to a rotational shaft in such a configuration as to rotate relative to the stator, the rotor being adapted to be cooled by a cooling medium;

a cooling medium storing portion disposed on the stator side and storing therein the cooling medium;

a cooling medium channel for leading the cooling medium from the cooling medium storing portion to the rotor; and

a variable air gap mechanism for varying an air gap between the rotor and the stator by moving the rotor in such a configuration that the rotor approaches the stator and moves away from the stator,

wherein

a discharge port for discharging the cooling medium of the cooling medium channel is disposed close to a rotational portion of the rotor in such a configuration as to face a face opposite to the air gap between the rotor and the stator,

the cooling medium storing portion is disposed lower than the discharge port, and

a negative pressure caused between the rotor and the discharge port sucks the cooling medium in the cooling medium storing portion.