Abstract: A series of transmission gears use an internally meshing planetary gear structure. The structure has a first shaft, eccentric bodies provided on the first shaft, and external gears mounted on the eccentric bodies through bearings. An internal gear internally meshes with the external gears, and a second shaft is connected to the external gears through means for transmitting only the rotational component of the external gears. The series includes a group of sub-series of the transmission gears, including transmission gears which are different from each other in a speed change ratio within a range from a low speed change ratio to a high speed change ratio, and which are the same in the mating dimension for installation to a mating machine. The transmission gears in the same sub-series include a type of transmission gears of a low angular backlash type which do not reduce the angular backlash. Each type of transmission gear has a same speed change ratio, a same mating dimension, and a same transmission capacity.

Abstract: An inscribed meshing speed increasing and reduction gear construction in which external teeth (for example, a1 and a2, b1 and b2, and c1 and c2) cut at the same position during processing are not simultaneously meshed with (outer pins 111 of) internal-tooth gear during operation in order to improve the accuracy after completion of assembling even if the gear is cut by a machine of similar processing accuracy. Thereby, (although it seems to be contrary to a conventional idea that said external teeth cut at the same position should be simultaneously meshed with the internal-tooth gear), the actual accuracy after completion of assembling can be improved. In this case, when both the number of teeth (24 in FIG. 1) of external-tooth gears 105a and 105b, and a difference in the number of teeth (4 in FIG. 4) between the external-tooth gear and (outer pins 111) internal-tooth gear, are set to integer times of the number (2 in FIG.

Abstract: A rotary driving apparatus including internally-meshing planetary reduction gear to which the output rotation of a motor is inputted, a drive shaft to which the output rotation of the planetary reduction gear is transmitted, an output rotary shaft to which the rotation of the drive shaft is transmitted, and a rotary flange provided on the output rotary shaft with a wheel mounted on the flange. The speed of the output rotation of the motor is reduced and then transmitted to the wheel so as to cause a vehicle to run on the wheel.

Abstract: A gear is provided with a trochoidal curved disk comprising a tooth profile modified by rotatably shifting a theoretical trochoidal tooth profile about the center of the gear by a phase angle of .DELTA. .phi. to provide a backlash.