Planetary reduction gear

Details Planetary reduction gear Planetary reduction gear

1988-10-26

1990-02-06

Diehl, Dwight G.

Planetary gear transmission systems or components

Planet periphery surrounds axis of interacting gear

Circumferentially spaced connector pins

475178, 475162, F16H 128

Patent

active

048980650

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Industrial Field
The present invention relates to a planetary reduction gear having an inscribe type planetary gear mechanism.
2. Background Art
Reduction gears generally referred to as "harmonic drives" are broadly used as control reduction gears in driving systems of, for example, robots. This type of reduction gear has a flexible, thin-walled and externally-toothed ring, and a pair of opposing internally-toothed gears one of which is fixed while the other is rotatable. The ring is pressed onto the internally-toothed gears by means of a web generator so as to cause the rotatable gear to rotate by an amount which corresponds to the difference in the number of teeth between these internally-toothed gears. Unfortunately, the rigidity of this type of reduction gear is not so high because the speed reducing portion includes a flexible thin-walled part, though the size and weight are advantageously reduced. For these reasons, the harmonic drive reduction gears cannot be used satisfactorily as control reduction gears in driving systems which transmit large driving power and which are required to have large rigidity.
A planetary reduction gear, generally referred to as "cyclo reduction gear" (registered trademark) and having an inscribe type planetary gear mechanism is well known as having high level of rigidity and comparatively large reduction ratio. The cyclo reduction gear has an internally-toothed gear and at least one externally-toothed gear which is inscribed in the internally-toothed gear. The internally-toothed gear has teeth of an arcuate tooth form provided by pins or a combination pins and rollers, while the externally-toothed gear has epitrochoidal tooth shape following epitrochoidal parallel curve. The externally-toothed gear is provided with a plurality of pin-receiving holes which are spaced in the circumferential direction and which loosely receive respective inner pins. When at least one eccentric member fitting in the externally-toothed gear rotates, the externally-toothed gear is rotated in an orbiting manner so that the input torque is output at a reduced speed. This cyclo reduction gear can transmit a large torque and, in addition, provides a large reduction ratio, so that it is used in a variety of fields.
An example of the known "cyclo reduction gear" will be explained with reference to the drawings, particularly to FIGS. 1 and 2.
The reduction gear has an input shaft 1 onto which is keyed by a key 3 a hollow eccentric shaft 2 for rotation together with the input shaft 1. The eccentric shaft 2 has a pair of eccentric portions 4a and 4b which are arranged in a side-by-side fashion in the direction of axis of the shaft 2. Annular externally-toothed gears 6a and 6b are rotatably mounted on the respective eccentric portions 4a and 4b through rollers 5. The gears 6a and 6b are provided on the outer peripheral surfaces thereof with external teeth 7 having an epitrochoidal tooth form. An internally-toothed ring gear 8 is arranged such that the externally-toothed gears 6a, 6b are inscribed in this gear 8 has arcuate teeth provided with a plurality of outer pins 9 which are fixed to the inner peripheral surface thereof. These outer pins 9 mesh with the external teeth of the externally-toothed gears 6a and 6b. Outer rollers may be loosely fitted to the outer pins 9. Each of the externally-toothed gears 6a and 6b are provided with a plurality of, e.g., 8, pin-receiving bores 10. The pin-receiving bores 10 in the externally-toothed gear 6a and those 10 of the externally-toothed gear 6b are axially aligned. The axially aligned pin-receiving bores 10 loosely receive inner pins 11 each of which rotatably carries an inner roller 12. The inner pin 11 is held by an output flange 13 which is integrally connected to an output shaft 14.
The internally-toothed gear 8 is clamped at its both sides by stationary covers 15 and 16 and are fixed to these covers 15 and 16 by means of a plurality of bolt-and-nut assemblies 17. The output shaft 14 is rotatably supported by a pair of bearings 18 and 19 w

REFERENCES:
patent: 1673838 (1928-06-01), MacKenzie
patent: 3129611 (1964-04-01), Lee
patent: 3602070 (1971-08-01), Verge et al.
patent: 3874253 (1975-04-01), Waddington
patent: 4010653 (1977-03-01), Mekjian
patent: 4407170 (1983-10-01), Fukui
patent: 4656891 (1987-04-01), Durand
patent: 4690010 (1987-09-01), Matsumoto et al.

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