Differential device

A differential device comprising:

• a differential case that has first and second hubs arranged on a first axis on opposite side parts, is disposed within a transmission case, and rotates around the first axis upon being subjected to rotational power,
• a first transmission member that can rotate around the first axis together with the differential case,
• an eccentric rotating member that has integrally linked a hollow first output boss and an eccentric shaft portion, the first output boss being capable of rotating around the first axis, and the eccentric shaft portion having as a central axis a second axis that is eccentric from the first axis,
• a second transmission member that is disposed so as to oppose the first transmission member and is rotatably supported on the eccentric shaft portion,
• a third transmission member that has a hollow second output boss and is disposed so as to oppose the second transmission member, the second output boss being capable of rotating around the first axis,
• a first speed change mechanism that can transmit torque between the first and second transmission members while changing a speed, and
• a second speed change mechanism that can transmit torque between the second and third transmission members while changing a speed,
• the first and second speed change mechanisms driving the third transmission member with a speed increase ratio of twice a speed of the first transmission member when the eccentric rotating member is fixed,
• wherein the first output boss is spline fitted via a hollow part of the first output boss onto a first drive shaft rotatably fitted into and supported on the first hub and the second output boss is spline fitted via a hollow part of the second output boss onto a second drive shaft rotatably fitted into and supported on the second hub,
• the first output boss is integrally and connectedly provided with a first tubular shaft rotatably fitted into and supported on the first hub,
• one of mating faces of the first hub and the first tubular shaft is provided with a first helical groove that can draw in lubricating oil within the transmission case by means of relative rotation between the first tubular shaft and the first hub from an outer end side of the first hub to an inner end side, and an oil passage is provided between the differential case and the eccentric rotating member, the oil passage providing communication between an outlet of the first helical groove and an inner peripheral side of the first speed change mechanism.