Radiaxial bearing having a cylindrical configuration centered on a central axis, the bearing having at least one harmonic wave-type reduction stage and including three or more rings and a first ring-shaped arrangement of rolling elements, each being centered on the central axis, the three or more rings enclosing the ring-shaped arrangement of rolling elements such that a) an innermost of the rings has a race in contact with the rolling elements from radially inward, an outermost of the rings has a race in contact with the rolling elements from radially outward, and a third ring, and possibly a fourth ring, has or have a race or races in contact with the rolling elements axially from both sides, or b) the three or more rings have four races contacting the rolling elements in a rectangular box formation, the box formation being oriented at an oblique angle with respect to the central axis of between 0? and 360?, wherein two opposed races have structures with different spatial frequencies that are designed to force the rolling elements into a harmonic-wave type oscillation between the structured races and translating a fast rotation of a ring with a structured race having a low spatial frequency into a slow rotation of a ring having a race with a high spatial frequency during operation of the bearing, wherein the ring or one of the rings that has or have the races that are oriented perpendicular to the structured races has separators separating adjacent rolling elements from one another, and to an electric motor. At least one of the structured races is structured such as to form an obstruction having at least one curve oscillating in a direction perpendicular to the direction of the rolling elements and contacting the rolling elements off-center such that the rolling elements partially protrude beyond the obstruction by varying amounts.

The retainer is provided so as to be prevented from being rotatable with respect to the rotary shaft, and rotation of the input-side rotary member is reduced in speed and transmitted to the output-side rotary member through intermediation of the balls which engage with both of the ball engagement grooves. A raceway center line of the second ball engagement groove is formed of a wave-shaped curve. When a speed reduction ratio of the speed reducer is represented by i, the wave-shaped curve has such a shape that the balls which engage with the first ball engagement groove engage with the second ball engagement groove at a given rotation angle () of the input-side rotary member in a state in which the output-side rotary member is at a rotation angle (i).

A transmission, including an outer shell (1), an inner shell (2), a drive disk (3), a plurality of T-shaped teeth (4), a gear (5), a tooth seat (6), an adjustable nut (7), balls (8), inner balls (9), outer balls (10), an inner protective frame (11), an outer protective frame (12), rollers (13), a first sealing ring (14), a second sealing ring (15) and a third sealing ring (16). Transmission clearance can be adjusted freely at any time, the meshing of the T-shaped tooth and the gear is a real surface meshing, and almost all the teeth participate in force transmission simultaneously. Therefore, the transmission has high precision, high mechanical properties, and long service life.

A harmonic drive assembly and fluid-powered linear motors with both axial pistons are rotary piston arrangements incorporating the harmonic drive assembly are disclosed. The motors may be used in downhole drilling applications, but the drive assembly and/or motors may be used in other applications. The assembly, motors and methods use advanced harmonic drives, advanced helical drives, and combinations thereof with 1) motors with axial pistons and reciprocating linear rings to convert reciprocative axial motion to continuous rotary motion, and 2) motors with rotary pistons and reciprocating linear rings to rectify reciprocative rotary motion to continual rotary motion to improve performance over prior configurations. Axial pistons provide a robust simple solution for generating rotation; Rotational pistons provide increased torque generation as the torque generated is proportional to motor length. Since downhole drills are long, a high-torque motor can be produced using this method.

A transmission device is provided in which a first speed change portion and a second speed change portion are formed. The first speed change portion includes an eccentric shaft having a main shaft portion on a first rotary axis and an eccentric shaft portion on a second rotary axis disposed eccentrically with respect to the first rotary axis; an eccentric unit that is rotatably supported on the eccentric shaft portion, and has external teeth formed on an outer peripheral portion thereof; and a housing having an axial center on the first rotary axis, and having internal teeth that mesh with the external teeth of the eccentric unit. The second speed change portion includes curved wave grooves respectively formed on the eccentric unit and a rotary unit; and rolling elements sandwiched between the curved wave grooves and moving along an orbit defined by the curved wave grooves.

A harmonic drive assembly and fluid-powered linear motors with both axial pistons are rotary piston arrangements incorporating the harmonic drive assembly are disclosed. The motors may be used in downhole drilling applications, but the drive assembly and/or motors may be used in other applications. The assembly, motors and methods use advanced harmonic drives, advanced helical drives, and combinations thereof with 1) motors with axial pistons and reciprocating linear rings to convert reciprocative axial motion to continuous rotary motion, and 2) motors with rotary pistons and reciprocating linear rings to rectify reciprocative rotary motion to continual rotary motion to improve performance over prior configurations. Axial pistons provide a robust simple solution for generating rotation; Rotational pistons provide increased torque generation as the torque generated is proportional to motor length. Since downhole drills are long (generally up to a maximum length of 30 ft.), a high-torque motor can be produced using this method. A pressurized fluid is used to drive the piston assemblies to produce bit shaft power. The axial piston motor converts the axial reciprocation produced by reciprocating pistons into continuous rotary motion. The rotary piston motor uses a mechanical rectifier to convert the rotational reciprocation produced by a reciprocating rotational piston into continuous rotary motion.

A transmission device includes one transmission member having a first axis, the other transmission member being capable of revolving around the first axis while rotating around a second axis eccentric from the first axis, and a transmission mechanism provided between the two transmission members, and that has one of transmission grooves provided in the one transmission member and having a wave-shaped annular form with the first axis, the other transmission groove provided in the other transmission member, having a wave-shaped annular form with the second axis, and a plurality of rolling bodies disposed in a plurality of intersecting parts between the two transmission grooves, wherein opposite side faces of a retainer are formed so as to be rotatably slidable with respect to the transmission members, and oil reservoir recesses are provided to one opposing face of the mutually opposing faces of the transmission members and the retainer.

A transmission device includes a first transmission member, an eccentric rotating member formed by integrally linking to each other a main shaft portion and an eccentric shaft portion, a second transmission member rotatably supported on the eccentric shaft portion, a third transmission member that opposes the second transmission member, a first transmission mechanism provided between the first and second transmission members, and a second transmission mechanism provided between the second and third transmission member. The second transmission member includes a first half body rotatably supported on the eccentric shaft portion, a second half body that opposes the first half body while sandwiching a housing space for the balance weight, and a linking member that links the two half bodies so as to surround the housing space, the linking member having a first access window that enables an operation of inserting the balance weight into the housing space.

A transmission device includes first and second rotation transmission members capable of relative rotation around a first rotary axis. A first eccentric unit is rotatably supported on an eccentric shaft portion on a second rotary axis eccentric to a main shaft portion of an eccentric shaft. A counterweight incapable of relative rotation with respect to the eccentric shaft is arranged between the first eccentric unit and a second rotation transmission member connected to the first eccentric unit. The orbit of the counterweight overlaps a portion of the orbits of multiple intermediate members, the orbits of which are defined by groove parts formed on the opposing surfaces of the first rotation transmission member and the first eccentric unit, and the opposing surfaces of the second rotation transmission member and the second eccentric unit, or, the orbit of the counterweight is outside of the orbits of the intermediate members.

A rolling-element bearing transmission includes a rotor configured to rotate a shaft relative to a stator and a rotatable output ring that includes a first rolled-on surface element. The shaft includes at least one second rolled-on surface element, and the stator includes a third rolled-on surface element. First and second pluralities of rolling elements are located between the shaft and the stator and between the shaft and the output ring. Also, a transmission mechanism transmits a rotary motion of the shaft to the output ring with a speed reduction such that the output ring rotates at a lower speed than the shaft.