Transmission device with oil discharging groove

A transmission device, comprising:

• a sun gear;
• a ring gear arranged concentrically with the sun gear;
• planetary gears meshing with the sun gear and with the ring gear;
• a differential case supporting the planetary gears in a rotatable manner;
• a differential mechanism arranged inside the differential case;
• a first output shaft and a second output shaft that are coupled to the differential mechanism;
• and
• a gear case supporting the differential case in a rotatable manner, wherein
• the differential mechanism includes:
• a first pinion gear and a second pinion gear that each have an axial center of rotation perpendicular to an axial center of rotation of the sun gear and that face each other;
• a first side gear and a second side gear that each have an axial center of rotation coincident with the axial center of rotation of the sun gear and that face each other,
• the first side gear meshes with the first pinion gear and with the second pinion gear, and is coupled to the first output shaft,
• the second side gear meshes with the first pinion gear and with the second pinion gear, and is coupled to the second output shaft,
• the differential case includes:
• a housing in which the first pinion gear, the second pinion gear, the first side gear, and the second side gear are housed;
• a first sleeve that is coupled to the housing and through which the first output shaft is inserted;
• a second sleeve that is coupled to the housing and through which the second output shaft is inserted;
• at least one oil discharging groove that is provided on an inner circumferential surface of the first sleeve and that extends from an outer end of the first sleeve to an interior of the housing;
• and
• at least one oil introducing groove that is provided on an inner circumferential surface of the second sleeve and that extends from an outer end of the second sleeve to the interior of the housing, and
• the at least one oil discharging groove reaches an internal space of the housing at a radial outside of the first side gear, and increases in width toward the outer end of the first sleeve, as viewed in an axial direction of the first side gear.