To prevent generation of chip, pitching, and the like on meanderingly continuing grooves and a cross part of opposing surfaces by carrying out chamfering on a cross part of opposing surfaces and the meanderingly continuing grooves arranged on surfaces opposed to a pair of disk plates which are coaxially arranged with an input side rotor and in which a plurality of balls are arranged between the opposing surfaces.
In a differential gear formed in such a constitution that a ball holder 5 in which a plurality of balls 6 are rotatably held is arranged between a pair of disk plates 3, 4 coaxially arranged opposing to each other meanderingly continuing grooves 31, 41 are formed, which is meandered so as to fluctuate a radial direction position on opposing surfaces of disk plates 3, 4 in a constant cycle, and which are continued in a circumferential direction, and the balls 6 are rotated along the meanderingly continuing grooves 31, 41. In this case, circular cone shaped chamfers 31e, 41e are preferably formed on both sides where the meanderingly continuing grooves 31, 41 are crossed with the opposing surfaces. It is thus possible to reduce abrasion caused by contact with the ball, and it is also possible to prevent generation of chip and pitching on the cross part of the meanderingly continuing grooves and the opposing surfaces.
OUCHI MAKOTO
ITO YOSHITAKA
