Abstract: Coriolis motion gears can be produced in a mass-production manner and in low cost as follows: A ceiling surface of a body 8 is formed into a rotary table 9 and a drive shaft 11 is projected from a center of the rotary table. A slant portion 11a is formed at its end, and a turntable 12 on which a workpiece 13 is mounted is supported rotatably to the slant portion. The turntable 12 is rotated by the tooth number difference between the Coriolis motion gear pair A.sub.1 ' and A.sub.2 ' per one turn of the drive shaft 11 to determine a working position of the workpiece. Also, the workpiece 13 is maintained on the turntable 12 so that a swivel center P.sub.1 of the Coriolis motion gear pair is identical with a swivel center when the workpiece is installed into a gear device to take a Coriolis motion. As a result, the work surface of the workpiece takes a moving locus of the Coriolis motion gears integral with the turntable 12.

Abstract: A cross roller that may rotate at a high speed with high precision is provided. A first conical roller 7 for receiving loads in a first axial direction B and a radial direction and a second conical roller 8 for receiving loads in a second axial direction A and the radial direction are alternatively held by an inner race 3 and an outer race 4. Also, a predetermined space 9 is provided between large end faces 7b and 8b of the first and second conical rollers 7 and 8 and orbital surfaces 4a and 4b of the outer race 4. Then, a seat ring 10 that is elastically deformable is provided in the space 9. By using the conical rollers 7 and 8, a slippage between the orbital surfaces 3a, 3b, 4a and 4b and the rollers 7 and 8 is prevented. Also, the seat ring 10 is elastically deformed so that a suitable pre-pressure is applied to the first and second conical rollers 7 and 8 by its restoring force.

Abstract: In order to miniaturize a speed change gear assembly, the respective gears are arranged in the order of the first gear A.sub.1, the second gear A.sub.2, the fourth gear A.sub.4 and the third gear A.sub.3 in an axial direction (X-axis direction). A center of the common spherical surface passing through each pitch circle of the first and second gears is made in accordance with the center of the common spherical surface passing through each pitch circle of the fourth and third gears. The center is used as the origin O. An XY coordinate is provided on the origin O. An axis line of an input shaft is arranged on the X-axis of the XY coordinate. An engagement point between the first and second gears A.sub.1 and A.sub.2 and an engagement point of the fourth and third gears A.sub.3 and A.sub.4 are arranged in the same quadrant of the XY coordinate. The first to fourth gears are arranged on the same axial direction surface of a rotary member 3.