A rotary actuator is used in a shift-by-wire system for a vehicle. A speed reducer includes a ring gear and a sun gear and reduces a rotational speed of the motor. An output shaft outputs rotation of the motor at a reduced rotational speed by the speed reducer. A regulating pin is disposed in a fixing member and allows the sun gear to revolve around a rotational axis of the motor and to rotate about an eccentric axis. The regulating pin is a separate member from the fixing member. The regulating pin has a strength equal to or greater than a maximum torque reaction force received from the sun gear. A first difference in hardness between an engaging portion and the sun gear is set to be less than a second difference in hardness between the fixing member and the sun gear.

The present invention provides a transmission mechanism which is suited to miniaturization and can reduce motion transmission errors. This transmission mechanism includes: a cam; a plurality of pins arrayed along a side surface of the cam; guide plates provided with a plurality of guide holes; and a pair of gears disposed so as to sandwich the cam. Each pin contacts only one of the pair of gears, and is guided to the corresponding guide hole in conjunction with the rotation of the cam and moves along the cam and the corresponding gear, thereby causing the guide plates or the pair of gears to rotate with respect to the cam.

A cycloid speed reducer includes an input shaft, a rolling assembly, first and second cycloid discs, a crankshaft and an output disc. The first and second cycloid discs are disposed around the input shaft and driven by the input shaft. The first and second cycloid discs are located at two opposite sides of the rolling assembly, respectively. The crankshaft includes first and second eccentric ends and first and second concentric ends integrally formed as a one-piece structure and arranged sequentially. The first and second eccentric ends are linked with the first and second cycloid discs respectively. An eccentricity value is between any neighboring two of the concentric and eccentric ends. The diameters of all the concentric and eccentric ends are equal. The output disc is linked with the first or second concentric end. The output disc is a power output end of the cycloid speed reducer.

A speed reducer includes an outer tubular member, internal tooth pins, oscillating gears and a carrier block. The outer tubular member has pin grooves on an inner circumferential surface thereof. The internal tooth pins are rotatably placed in the pin grooves. The oscillating gears have external teeth smaller in number than the pin grooves, and the oscillating gears are oscillatorily rotatable with the external teeth engaging with the internal tooth pins. The carrier block is cooperatively connected to the oscillating gears such that the oscillating gears are allowed to oscillatorily rotate relative to the carrier block and restricted from rotating on own axis relative to the carrier block. A displacement restricting member configured to restrict the internal tooth pins from being displaced inwardly in a radial direction of the outer tubular member is disposed between the outer peripheries of the oscillating gears adjacent to each other.

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.

A speed reducer casing of the present invention has inner teeth on an inner periphery thereof. The speed reducer casing includes an inner tooth portion and a casing body portion, the inner tooth portion including the inner teeth, the casing body portion supporting the inner tooth portion. The inner tooth portion is formed of a material having a higher slidability than the casing body portion. The casing body portion is formed of a material having a higher hardness than the inner tooth portion.

In one form there is disclosed an internally balanced involute-type speed reducer; the reducer comprising a stator stage, an input stage, an output stage, and a plurality of gear sets in mesh. In a further form there is disclosed an actuator assembly for a robot; said actuator assembly comprising a stator core located within an outer housing and subtended by inner and outer mounting hubs; said hub supporting a drive train and bearings within the actuator assembly. In a further form there is disclosed a transducer system operable in conjunction with the reducer or actuator assembly.

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 cycloidal transmission for a drive includes a housing, a drive shaft, an eccentric, a cam plate, a pin plate, an output shaft, and a torque detection mechanism. The housing includes a first bearing, a second bearing, and a rolling ring. The drive shaft is rotatably mounted in the first bearing. The eccentric is fixedly connected to the drive shaft. The cam plate is driven by the eccentric. The cam plate is configured to roll in the rolling ring. Pins of the pin plate are configured to engage holes of the cam plate, so that the pin plate is driven by the cam plate. The output shaft is fixedly connected to the pin plate. The output shaft is rotatably mounted in the second bearing. The torque detection mechanism is between the first bearing and the second bearing and configured to detect the torque of the output shaft.