Musashi Seimitsu Industry Co., Ltd.

Musashi Selmitsu Industry Co., Ltd.

Akihiro Uchida

Akuto Sekiguchi

Tetsuya Okabe

Yoichi Yanase

In a power transmission device in which a hub portion of a ring gear is fixed by a weld portion to a flange portion on an outer periphery of a transmission member, a positioning outer peripheral part of an outer periphery of the flange portion has a radial direction positioning face that positions the hub portion in a radial direction with respect to the flange portion, and an axial direction positioning face that positions in an axial direction, a first annular recess part is provided in the positioning outer peripheral part, the first annular recess part alleviating stress caused by a pushing load via which the positioning projecting part pushes the radial direction positioning face due to the hub portion receiving a tensile force inward in the radial direction accompanying thermal shrinkage of the weld portion between a first outer peripheral part and the hub portion.

Power transmission device

A power transmission device has a hub portion of a ring gear is fixed by a weld portion to a flange portion on an outer periphery of a transmission member, an annular groove that is recessed in the inner side of the axial direction is formed in a side face of the hub portion for making axial positions of the annular groove and the cavity part partially coincide with each other, the hub portion is narrowed partway along a part sandwiched between the cavity part and weld portion and the annular groove when viewed in a cross section transecting the annular groove, and a narrowed portion is set to have a thickness that alleviates residual stress produced around the weld portion of the flange portion by the force with which the flange portion and the hub portion pull each other in response to thermal shrinkage of the weld portion.

A differential device includes a ring gear receiving a rotational driving force from a drive gear, a differential case rotating integrally with the ring gear around a predetermined axis, and a differential mechanism installed within a barrel part of the differential case. The ring gear includes a gear portion meshing with the drive gear, and a rim portion that is formed integrally with an inner periphery of the gear portion and is fitted, in a non-welded state, onto a maximum diameter outer peripheral portion of the barrel part or a predetermined outer peripheral portion having a smaller diameter than the maximum diameter outer peripheral portion. The rim portion has a to-be-fixed portion welded to the barrel part at a position spaced in an axial direction from a fitting part via which the rim portion and the barrel part are fitted, the position being further radially inward than the fitting part.

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Toyohashi, Japan

Akihiro Uchida