An electric actuator according to an aspect of the disclosure includes: a motor including a rotor having a motor shaft extending along a central axis and a stator facing the rotor in a radial direction; and a deceleration mechanism which is disposed on a side of the stator in an axial direction and connected to the motor shaft. The motor shaft includes an eccentric shaft part with an eccentric axis, which is eccentric with respect to the central axis, as a center, and the eccentric shaft part is connected with the deceleration mechanism. The eccentric shaft part includes a balance concave part disposed on an end part of the eccentric shaft part in a predetermined direction which is in a radial direction from the central axis toward the eccentric axis. The balance concave part is recessed from an outer surface of the eccentric shaft part.

A cycloid speed reducer includes a weight element, an input shaft and a cycloid disc. The weight element is disposed within an accommodation space of the cycloid disc. An eccentric part is disposed on the input shaft. Since the length of the input shaft is reduced, the overall length of the cycloid speed reducer is shortened. Moreover, the mass center of the weight element and the mass center of the eccentric part and the cycloid disc are arranged along the same axial direction. That is, the line passing through the mass center of the weight element and the mass center of the eccentric part and the cycloid disc is perpendicular to the input shaft. Consequently, the efficacy of the dynamic balance of the cycloid speed reducer is enhanced.

A transmission is described, comprising a hollow cylindrical base body (1) with a first internal gear (z1), a ring with a second internal gear (z2) arranged rotatably about the cylinder axis (14) of the base body (1), a central shaft (9) extending along and rotatable about the cylinder axis (14) and having an eccentric section (13), and a wheel (11) rotatably mounted on the eccentric portion and first external gear (zs1) via which it meshes with the first internal gear (z1) of the base body (1) and a second external gear (zs2) via which it meshes with the second internal gear (z2) of the hollow cylindrical ring.

The wheel (11) is designed as a double wheel. The double wheel comprises two individual wheels which are non-rotatably connected to each other in accordance with their axes and are each provided with one of the two external gears (zs1, zs2). The single wheels are connected to each other by bonded connecting means. The connecting means are bonded to both one and the other individual wheel.

To provide an inexpensive and thin motor with a speed reducer capable of elongating lifetime of bearings by reducing the effect of internal moments acting on an output member without using expensive bearings. A motor with a speed reducer performing output with a gear mechanism rotating to reduce speed around an electric motor M and an eccentric shaft driven to rotate by the electric motor M, in which a plurality of external gears are respectively assembled to the eccentric shaft at positions where moments obtained by multiplying distances in an axial direction from a position of a bearing provided in a speed reducer housing by magnitudes of loads acting on output pins at the positions are cancelled out with each other.

Examples are provided that describe a cycloid transmission with a chain link ring. An example cycloid transmission includes a motor shaft attached to a disc. The motor shaft may be used for rotating the disc. The cycloid transmission also comprises an outer chain link ring that surrounds the disc. The outer chain link ring includes rollers that are inserted at given interfaces between links of the outer chain link ring. The rollers contact the disc as the disc rotates. The cycloid transmission also comprises a housing. The links of the outer chain link are coupled at the given interfaces. The rollers are inserted at the given interfaces and into the housing.

Gear systems include a dual pinion and ring architecture. A gear system includes a housing with a shaft extending in the housing. The shaft includes an eccentric section and is rotatable about an axis. The eccentric section has a center that circles around the axis when the shaft rotates. A pinion gear unit is mounted on the eccentric section and has two sets of gear teeth. A ring gear is fixed to the housing and engages with one set of the gear teeth. Another ring gear engages with the other set of gear teeth and is fixed to a rotatable member. The gear system operates so that rotation of the shaft at a first speed effects rotation of the rotatable member at a second speed through the shaft, the pinion gear unit, and the ring gears.