A reduction gear configured to decelerate and output rotation of a motor includes two-stage planetary gear mechanisms that are provided side by side in an axial direction of the motor and are each configured of helical gears, and a case made of resin and formed into a cylindrical shape, the case incorporating the two-stage planetary gear mechanisms. At least one of an inner engagement ratio of a sun gear and a pinion gear of the planetary gear mechanism in a first stage and an outer engagement ratio of the pinion gear and a ring gear of the planetary gear mechanism in the first stage is 3.0 or more, and both the inner engagement ratio and the outer engagement ratio are larger than an engagement ratio of the planetary gear mechanism in a second stage.

Disclosed herein are actuator, planetary-gear apparatus, and structural-unit embodiments configured to reduce noise and vibration caused by operation of planetary gears. An embodiment may include a ring gear having an outer peripheral surface that extends in the axial direction. A first raised portion may be formed on said outer peripheral surface; and a housing having an inner peripheral surface that is provided facing, and with a gap from, the outer peripheral surface of the ring gear. A second raised portion may be formed on said inner peripheral surface. Movement of the ring gear in the circumferential direction is limited by linear contact or point contact between the first raised portion and the second raised portion, for example. The outer peripheral surface and/or the inner peripheral surface may be a surface of a crowned shape that is bowed in the outer radial direction, according to some further embodiments.

A hollow reducer for high precision control includes a pin wheel housing and two-stage reduction components disposed in the pin wheel housing. A first-stage reduction component includes a driving wheel on a servo motor, a dual gear, and a planet wheel; and a second-stage reduction component includes 2-3 eccentric shafts distributed uniformly, cycloidal gears, a pin, rigid disks, and bearings, wherein two eccentric sections of the eccentric shaft support the cycloidal gears by means of the bearings, shaft extensions on two sides of the eccentric section of the eccentric shaft are supported on the left and right rigid disks by the bearings, and the rigid disks are supported on two sides of the pin wheel housing by the bearings.

Disclosed is a gearing device for a seat including a first internally toothed gear, a second internally toothed gear, an externally toothed gear, and an eccentric member. The first internally toothed gear includes a rotation center axis. The second internally toothed gear has the rotation center axis in common with the first internally toothed gear and is rotatably supported by the first internally toothed gear. The externally toothed gear is arranged to an inner side of the first and the second internally toothed gear, to thereby mesh with the first and the second internally toothed gears. The eccentric member rotates the externally toothed gear such that a rotation center thereof follows a path around the rotation center axis, rotatably supports the externally toothed gear about the rotation center, and rotates about the rotation center axis in response to a rotational force being externally input thereto.

A circular wave drive system is provided. In one aspect, the circular wave drive includes a compliant input ring gear having an inner surface having internal input ring gear teeth; an input cycloidal disc having an outer surface having external input cycloidal disc gear teeth oriented on the outer surface, and wherein the external input cycloidal disc gear teeth at least partially engage the internal input ring gear teeth; a compliant primary drive gear having an outer surface having external primary drive gear teeth; an eccentric motion generator including an eccentric portion and a non-eccentric portion and wherein a centerline of the eccentric portion and the non-eccentric portion are offset from one another; and an output cycloidal disc having an inner surface with internal output cycloidal disc teeth, and wherein the internal output cycloidal disc teeth at least partially engage the external primary drive gear teeth.

An electric actuator includes a motor, a speed reduction mechanism, and a bearing fixed to a motor shaft having an eccentric axis portion. The speed reduction mechanism has: an externally toothed gear, an internally toothed gear, a facing member arranged facing the externally toothed gear, and column members arranged to protrude from one member of the facing member and the externally toothed gear toward the other member and surround the motor axis. The other member has hole portions arranged to surround the motor axis. The column members are inserted into the hole portions respectively, and support the externally toothed gear to be swingable around the motor axis via an inner side surface of each of the hole portions. At least one of the column members is attached to the one member in a manner of being rotatable around a central axis of the at least one column member.

A gear device includes an outer cylinder; an internal member at least partially housed in the outer cylinder and configured to rotate relative to the outer cylinder about a predetermined rotation axis; a first main bearing fitted into an annular space formed between the outer cylinder and the internal member; and a second main bearing fitted into the annular space and configured to define the rotation axis in cooperation with the first main bearing. A distance between a first intersection where a load action line of the first main bearing intersects with the rotation axis and a second intersection where a load action line of the second main bearing intersects with the rotation axis is set to fall within a range expressed by a predetermined inequality expression.

Proposed is a reducer including a reduction unit configured to reduce an input torque, and an output unit configured to be supplied with a preset reduction torque through the reduction unit and to transfer an output torque to the outside, wherein the reduction unit includes an input shaft configured to be supplied with the input torque, a cycloidal disc arranged on an outer circumferential surface of the input shaft in an eccentrically rotatable manner, a tooth-type protrusion being formed along a circumference of an edge of the cycloidal disc, a hollow housing configured to accommodate the cycloidal disc and including a plurality of inner pins arranged to be spaced a predetermined distance apart from each other along a circumference of an inner circumferential surface of the hollow housing in a manner that possibly comes into contact with the tooth-type protrusion on the cycloidal disc, and a plurality of rolling pins coupled to the cycloidal disc and having a concentrically shaped cylindrical structure, wherein the output unit includes an output rotor configured to accommodate the rolling pins and to transfer the reduction torque transferred from the rolling pins to the outside, and wherein the rolling pins are eccentrically moved relatively to the output rotor.

A speed reducer includes an input shaft, an input gear, a fixing gear and an output gear. The input shaft includes an eccentric structure. The input gear is disposed on the eccentric structure and includes first teeth of which each with a first contact portion and a second contact portion. The fixing gear and the output gear are disposed corresponding to the input gear, wherein the fixing gear includes second teeth, and the second teeth are in contact with the first contact portions, wherein the output gear includes third teeth, and the third teeth are in contact with the second contact portions. A first tooth number difference between the first teeth and the second teeth is different from a second tooth number difference between the first teeth and the third teeth.

The present disclosure provides a transmission device for a household electrical appliance, including a drive shaft and an output shaft assembly. The output shaft assembly includes a planetary carrier, a planetary gear train mounted on the planetary carrier, an output shaft and a follower shaft. The planetary gear train includes a sun gear and at least one planetary gear engaged with the sun gear. The planetary carrier is connected to the output shaft. The sun gear is connected to the follower shaft. The planetary carrier is provided with a first bearing and a second bearing that are disposed coaxially with the output shaft. One end of the follower shaft protrudes from the sun gear and is connected to the first bearing. One other end of the follower shaft passes through the second bearing, protrudes from the planetary carrier and is connected to the drive shaft in a clearance fit.