Abstract: A housing (10) has a planetary gear mechanism (20) composed of an inner gear (21), a planetary gear (22) and a sun gear (23), which mechanism is disposed within the housing (10) on its outer periphery side. The inner gear (21) is connected with a casing (31) arranged on a rotation axis (L). A spherical receiving portion (31a) is formed on the casing (31). This receiving portion (31a) is received in the sun gear (23). A pair of element gears (33, 33) and a pair of side gears (34, 34) of the planetary gear mechanism (30) are received in the receiving portion (31a).

Abstract: A carrier 2 is fixed to one end opening part of a circular cylindrical apparatus main body 1. A plurality of receiving holes 2d, which extend in parallel with a rotation axis L, are formed in the carrier 2 at the same interval in a peripheral direction. A planetary gear 4 is received in each receiving hole 2d such that the planetary gear 4 can rotate on its own axis. An inner gear 5 and a sun gear 9, which are arranged with their axes aligned with the rotation axis L of the apparatus main body 1, are disposed within the apparatus main body 1. The inner gear 5 is engaged with the planetary gears 4 at the outside thereof. The sun gear 9 is engaged with the planetary gears 4 at the inner side thereof. An engagement part between the inner gear 5 and the planetary gear 4 and an engagement part between the sun gear 9 and the planetary gear 4 are displaced from each other in a direction of the rotation axis L so that they are not overlapped with each other in a direction of the rotation axis L.

Abstract: A planetary gear 5 is contacted at its at least one tooth of all its teeth 51n with an end edge 23d facing an inner releasing part 23c of an inner peripheral surface of a receiving hole 23a irrespective of a rotational position of the planetary gear 5. By doing so, the planetary gear 5 is prevented from moving in the radial direction. As a result, the planetary gear 5 can be prevented from vibrating in the radial direction. Thus, vibrations of a planetary gear apparatus can be reduced, and the planetary gear and a carrier can be reduced in damage.

Abstract: A receiving portion 2e for rotatably receiving therein a planetary gear 3, is formed between a plurality of retaining protrusions 2d of a carrier. A connection portion 2f extending annularly about a rotation axis L is formed on an outer peripheral of a distal end portion of each retaining protrusion 2d. Through this connection portion 2f, the distal end portions of the respective retaining protrusions 2d are connected to each other. Owing to this arrangement, each retaining protrusion 2d is reinforced to minimize its deformation. As a result, deformation of the receiving portion 2e is greatly reduced and the planetary gear 3 receiving in the receiving portion 2e can rotate smoothly.

Abstract: A casing 23 of a second differential gear mechanism 2 is constituted by a carrier 19 and a sun gear 22 which are separately formed. Owing to this arrangement, the casing 23 is divided into two parts in a direction of its axis. The carrier 19 is movable in a direction of an axis L. By meshing engagement between a pinion gear 26 and a side gear 27A, the carrier 19, which forms a part of the casing 23, is press contacted with a housing 11 through a washer 29.

Abstract: A working oil receiving chamber 8 is provided with an expanding and contracting member 12. The expanding and contracting member 12 is comprised of an expansible and contractible bellows 2a made of metal, and a bottom portion 12b made of metal and for closing opposite open ends of the bellows portion 12a, so that the member 12 can expand as the pressure of the working oil in the working oil receiving chamber 8 is increased and can contract as the pressure is decreased. A slightly compressed gas is filled in the expanding and contracting member 12.

Abstract: In a differential gear system disclosed, a pair of sun gears and a plurality of pairs of planetary gears are received in a housing. The pair of sun gears are coaxial with a rotational axis of the housing. End portions of a pair of drive shafts extending through a pair of end walls of the housing are spline-engaged respectively with the pair of sun gears. The pair of sun gears have helical teeth, respectively. Each pair of intermeshing planetary gears are meshed respectively with the helical teeth of the pair of sun gears, respectively. A plurality of washers are interposed between the pair of sun gears. The plurality of washers have first washers and second washers, respectively, which first and second washers are alternately arranged. The first washers are engaged with end portions of reduced diameters of the sun gears such that the first washers are capable of moving axially but incapable of rotation.