To effectively incorporate a lubricant by the rotation of a differential gear by forming a pocket communicated with a through-hole by sealing an upper part of an outer edge of the through-hole, and comprising a lubricant passage forming means having the shape to open an recessed groove.
Four through-holes 104 are formed on an outer surface of a case 10 at equal intervals on a circumference of a rotary shaft of a differential gear 1, and the annular recessed grooves 106 are respectively extended in the circumferential direction from the outer edges of the through-holes 104. The differential gear 1 is rotated in a state that its lower part is dipped in the lubricant at all times. Accordingly, when the recessed groove 106 of the differential gear 1 is lcoated at a lower part of the lubricant surface 9, the lubricant flows into the recessed groove 6, and the lubricant is pressed into a pocket by the rotation of a vaned ring member 11 to be entered into the differential gear 1. On the other hand, when the recessed groove 106 is come out to an upper part of the lubricant surface 9, the lubricant in the through hole 104 does not come out by the centrifugal force because a left end of the recessed groove 106 has the shape of a pocket.
ITO YOSHITAKA