JP2000-120810 (See FIGS. 1 and 2) discloses a conventional motor-incorporated hypocycloid-type speed reducer, in which an eccentric portion (carrier), which rotates an external gear (a planetary gear) in an eccentric manner, is connected to a rotor, which is electrically rotated, in such a manner that a rotational force of the rotor can be transmitted. The rotor is fitted with, and is supported by, a bearing rod so as to freely rotate.
In the above-described motor-incorporated hypocycloid-type speed reducer, the external gear is supportedly mounted on a ball bearing, and an output shaft fixed with an internal gear is rotatably supported by a plain bearing formed at a central portion of a case. According to this type of structure, when the output shaft is subjected with a load applied in a radial direction, the external gear or the internal gear (the output shaft) may on occasions tilt or lean due to the ball bearing or a clearance between the plain bearing and the output shaft, which may lead to an occurrence of a noise. Such tilting or lean of the external gear, or, of the internal gear (the output shaft) can be prevented by increasing an axial length of the plain bearing axially supporting the output shaft. This, however, may result in an increase in an axial length of the hypocycloid-type speed reducer.
A need thus exists to provide to a motor-incorporated hypocycloid-type speed reducer, which can restrain an angle amount of tiling or lean of an output shaft.