Planetary gear transmission systems or components – Steering by driving – With infinitely variable drive
Patent
1990-04-06
1991-08-20
Herrmann, Allan D.
Planetary gear transmission systems or components
Steering by driving
With infinitely variable drive
475 18, 475 27, 475 28, F16H 4704
Patent
active
050410644
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a superimposed steering gear for tracklaying vehicles wherein the steering power required for turning is superimposed on the drive system via a neutral shaft and summarizing differentials and the neutral shaft is driven from a drive shaft of the steering gear via a hydrostatic-mechanical branching transmission which has a reversing transmission in its mechanical power branch and a hydrostatic unit of infinitely variable translation in its hydrostatic power branch. Both power branches being passed together into a summarizing transmission so that a desired steering radius can be adjusted within a mechanically shiftable radial range by changing the traverse angle of the hydrostatic unit.
In superimposed steering gears of the kind mentioned (German Patent No. 24 12 562), when using a hydrostatic-mechanical power branching steering, the radii both for left-hand and right-hand turns can be respectively adjusted within two mechanically shiftable radial ranges by infinite variation of the hydrostatic unit. Departing from the straight-ahead drive of the tracked vehicle, there is provided first in both steering directions a first radial range in which the whole steering power is conveyed via a hydrostatic unit and a stepdown gear rear-mounted on the neutral shaft. To this first radial range, which is delimited by the maximum negative and the maximum positive angle of the hydrostatic unit, there is attached at any given time an additional radial range which reaches down to the smallest steering radius and in which there takes place, by shifting two planetary transmissions, a summarization of the powers flowing in different directions of rotation over the hydrostatic and over the mechanical part.
Although only a small part of the steering power flows through the hydrostatic unit that works with poor efficiency, the required volume of construction of said unit and its power losses still are too great.
SUMMARY OF THE INVENTION
Therefore, the problem to be solved by the invention is to overcome said disadvantages and thus to accommodate in a given space an infinite hydrostatic-mechanical steering gear with the best possible efficiency.
This problem is solved by the fact that the summarizing transmission has at least two shiftable planetary-gear sets, one transmission component of each being connected with the drive shaft, via the reversing transmission, and one transmission component of each being connected with a hydrostatic shaft of the hydrostatic unit; the remaining transmission components can be coupled with the neutral shaft, by means of coupling shafts, for shifting at least two radial ranges according to the steering direction, the respective coupling shafts having equal speeds for infinite switching from one radial range to the next at a positive and negative maximum translation of the hydrostatic unit. Due to the fine distribution of the whole steering radius in individual radial ranges, on one hand, it is possible to minimize the power losses of the hydrostatic unit, which can also have a smaller volume due to the low flow of power over said hydrostatic unit and, on the other hand, a quicker change of the steering radii is possible, since a quick switch to another steering radii can take place in the mechanical part of the branching transmission.
When the summarizing transmission has two shiftable planetary-gear sets and, in order to produce a first radial range departing from the straight-ahead driving of the tracked vehicle, between the output shaft and the neutral shaft a stepdown transmission is shiftable in parallel, then in the maximum translation of the hydrostatic unit both coupling shafts must have equal speeds at the shift point of the separating clutches coordinated with them, while when the translation changes in the direction of an opposite maximum value, the second coupling shaft becomes infinitely quicker for smaller steering radii and the first coupling shaft becomes infinitely slower for larger steering radii up to a speed value resulting from the speed of the output
REFERENCES:
patent: 3426621 (1965-10-01), Mooney, Jr. et al.
patent: 3492891 (1970-02-01), Livezey
patent: 4327603 (1982-05-01), Zaunberger et al.
patent: 4557157 (1985-12-01), Oestmann
patent: 4569251 (1986-02-01), Greenwood
patent: 4614132 (1986-09-01), Hall, III
patent: 4682515 (1987-07-01), Reed
patent: 4860613 (1989-08-01), Hall, III et al.
patent: 4890508 (1990-01-01), Zaunberger
patent: 4960404 (1990-10-01), Reppert et al.
Eickhoff Hans-Jurgen
Tenberge Peter
Herrmann Allan D.
Massey Ryan W.
Zahnradfabrik Friedrichshafen AG
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