Patent attributes
In a lubrication groove, which is formed in an insertion hole into which is inserted an output shaft, and which winds around the circumference of the insertion hole while advancing in the axial direction of the insertion hole, there is a portion that is farther to the outside than a perpendicular plane that is perpendicular to a center plane of a differential case on which lie the axial centers of the insertion hole and a pinion gear shaft, the perpendicular plane including a line of intersection of the center plane and the insertion hole. That portion is a perpendicular groove portion which is parallel to a plane that is perpendicular to the axial center of the insertion hole. Accordingly, when extracting a core for forming the insertion hole and the lubrication groove from a die, projections formed on the core for forming the lubrication groove will not interfere with the die. As a result, it is possible to form the lubrication groove during casting of the differential case using that core.
