Power transmission device

A power transmission device comprising:

• a drive motor including a motor housing having a front surface, a rear cover coupled to a rear surface of the motor housing, a stator fixed in the motor housing and configured to generate a magnetic field, a rotor disposed radially inside the stator with a preset gap from the stator and configured to be rotated by the magnetic field generated by the stator, a motor shaft coupled to the rotor to rotate together with the rotor, the motor shaft extending in a longitudinal direction and penetrating the front surface and the rear cover, and a driving gear provided at one end of the motor shaft penetrating the front surface and protruding to the outside of the motor housing;
• a drum configured to surround the drive motor and including a drum circular plate portion provided on one surface in a wheel axis direction, and a cylindrical portion extending in the wheel axis direction from an outer diameter end of the drum circular plate portion;
• a drum cover coupled to the other surface of the drum based in the wheel axis direction and having an outer-diameter portion on which a driven gear engaging with the driving gear is provided;
• and
• a wheel hub on which a tire is mounted, the wheel hub being coupled to the drum to rotate together with the drum,
• wherein the drive motor is disposed to be directed downward so that a front surface of the drive motor is closer to the ground surface than a rear surface of the drive motor, and the drive motor further comprises a motor arm extending from the motor housing to the other side in the wheel axis direction,
• wherein the motor arm has a supply passageway for supplying oil into the drive motor, and a discharge passageway for discharging the oil in the drum to the outside, and
• wherein an oil gallery is disposed at an upper end portion of the motor housing, and an oil supply hole is formed in the motor housing and communicates the supply passageway and the oil gallery such that the oil supplied through the supply passageway is supplied to the drive motor through the oil gallery.