Planetary gear

Details Planetary gear Planetary gear

1997-08-22

1999-06-08

Wright, Dirk

Planetary gear transmission systems or components

Planetary gearing or element

Axis of planet pinion at angle intersecting rotational axis...

475338, 475331, F16H 136

Patent

active

059100664

DESCRIPTION:

BRIEF SUMMARY
The invention concerns a planetary gear having one driven sun gear and two internally toothed ring gears, one of which is mounted stationarily and the other rotatably forming the output. There have been several planetary gears devised which are supported upon planetary axles in a planetary carrier. The planetary gears are in constant tooth meshing contact with the sun gear and the ring gears.
Many problem scenarios in the driving technology require the realization of extreme ratios. Planetary gears are especially well suited for combining high ratios with a compact design. The Wolfrom coupling gear, which has a high ratio, still has good efficiency and constitutes such a planetary gear. The Wolfrom gear is designated a special simple coupling gear. The input is connected with a sun gear which interacts with a planetary gear block. The planetary gear supports itself on the internally toothed ring gear which is firmly attached to the housing. The web rotates along idly as a planetary carrier. The movement is passed on via the planetary carrier and the planetary gear(s) (step planet). The planetary gear meshes with an internally toothed ring gear which forms the output. The arrangement described is adequate for a compact design which in a narrow space allows high transmission densities (see Klein: Theoretische Grundlagen zum Auslegen von Wolfrom-Koppel-getrieben, in Maschinenmarkt 1982, pages 341 to 344).
Particularly, in the handling technology, high gear reduction transmissions are needed for power transmission in high-speed engines. Said transmissions must have a small amount of rotary play during a change in load direction. They must also have an anti-torsional, light and compact design.
In planetary gears of the kind in question, the total efficiency is another decisive criterion for determining their usefulness. Internal stresses, for example, have a negative influence on the total efficiency due to the elevated inner rubbing power that results.
U.S. Pat. No. 4,106,366 has disclosed a planetary gear wherein an internally toothed ring gear is pressed by coil compression springs upon the conically formed planetary gears. On account of the high tooth rubbing power due to inner stresses, the total efficiency is here inadmissibly reduced.
A planetary transmission with planet gears, which have piercing straight-cut teeth, has also been disclosed in U.S. Pat. No. 5,242,336. Said transmission has the disadvantage that a relatively large, contact-free, axial intermediate space is needed between both ring gears in order to compensate for the relatively great difference in the numbers of teeth of both ring gears without extreme distortions of the contact ratios. Said axial intermediate space naturally increases the axial length of the transmission and reduces the rigidity thereof. Of considerable disadvantage is the increase in drag torque, since the planets and the planet carrier become heavier due to said intermediate space. The dynamic properties of this drive are impaired by this configuration, especially when the planet gears and the planet carrier rotate at high speeds. When it is desired to omit said axial intermediate space, then considerable distortions of the contact ratios would be inevitable. Extreme values in the addendum modification coefficient of the ring gears result in sharp tooth gaps in the ring gears, which also act unfavorably upon the tooth-cutting tools. Extreme values in the pressure angles would lead to problems in noise, friction, torque and wear.
From European patent application 0 627 575 a Wolfrom planetary gear is defined wherein the planet gears are disposed axially in two differently toothed regions. The pitch diameters of both toothed regions can be equal or unequal. The axial forces appearing in both regions must be substantially removed head-on by opposing helical-cut teeth. Examining the tooth forces that appear, it is found that the occurring axial forces do not reciprocally cancel each other, but add up to a resultant.
In the planetary gear, according to international patent a

REFERENCES:
patent: 1499763 (1924-07-01), Davis
patent: 4043226 (1977-08-01), Buuck
patent: 4106366 (1978-08-01), Altenbokum et al.
patent: 4280376 (1981-07-01), Rosen
patent: 5242336 (1993-09-01), Hori
patent: 5295922 (1994-03-01), Amborn et al.
patent: 5385514 (1995-01-01), Dawe
patent: 5409430 (1995-04-01), Hashimoto et al.
patent: 5472387 (1995-12-01), Kamlukin

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