Planetary gear transmission systems or components – Planetary gearing or element – Particular gear tooth feature
Reexamination Certificate
1999-12-20
2002-03-26
Marmor, Charles A (Department: 3681)
Planetary gear transmission systems or components
Planetary gearing or element
Particular gear tooth feature
Reexamination Certificate
active
06361468
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to an automatic transmission and, more particularly, to a technology for supporting a thrust force generated at a change gear element by a power transmission in the gear train.
2. Description of Related Art
In addition to ensuring drivability of a vehicle, there is a demand for multi-staging of an automatic transmission for a vehicle in order to improve the consumption in fuel indispensable to energy saving. To respond to such a request, a change gear mechanism is changed from a conventional forward four-stage transmission to a five-stage transmission. Smaller elements of a gear train per gear change stage and simplification of the mechanism are required to realize further multi-staging in a limited vehicle loading space, requiring tremendous efforts to ensure the proper gear train structure. To accomplish this, there has been proposed a gear train for achieving forward six-stage and reverse one-stage transmission using a planetary gear set consisting of minimum change gear elements in U.S. Pat. No. 5,106,352 which shows a generic automatic transmission. The gear train according to the patent is characterized in that multi-stage gear change is achieved in combination with a reduction planetary gear and a planetary gear set for outputting a change gear rotation by defining the reduction rotation from the reduction planetary gear as an input.
A gear train structure according to the above proposal is principally reasonable in the number of change gear elements per gear change stage required and the required number of clutches and brakes; and, however, there is a practical problem to be addressed and corrected. In particular, in an automatic transmission for a vehicle, generally a helical gear is used for a sun gear, a pinion, and a ring gear that constitute a planetary gear in order to reduce gear noises. An advantage of such a structure is that the gear rates of the respective gears are increased by the helical gear, making it possible to reduce gear noises. In contrast, there is a problem that a thrust force contrary to the ring gear and sun gear, respectively, is generated.
The above patent does not address the problem in the thrust force or its solution. When the concepts, known to those of general skill, as employed in a conventional automatic transmission, are extended and applied to the above proposed gear train, the result is a method for disposing a center support between a reduction planetary gear (a single planetary gear set) and a planetary gear set (complex planetary gear set), thereby subjecting the center support and a case to the thrust force generated at the respective planetary gear sets by the power transmission so as not to interfere with each other. If such a structure is adopted, the axial dimensions of a transmission are increased by the arrangement of the center support. Thus, in particular, there is a problem that the ability to mount the gear on a vehicle is degraded because a large-scaled mechanism due to the multi-staging is unavoidable in a multi-stage transmission.
SUMMARY OF THE INVENTION
The present has been achieved to solve the above mentioned problem. It is one object of the invention to provide an automatic transmission capable of supporting a thrust force acting on a reduction planetary gear and a planetary gear set, respectively, without increasing axial dimensions of the transmission.
To achieve the above mentioned object, according to the invention, there is provided an automatic transmission for achieving a multi-stage gear change by a reduction planetary gear coupled to an input shaft and a fixed reaction force element so as to output a reduction rotation to an output element and a planetary gear set that outputs a rotation with a variable speed depending on the shift position upon input of the reduction rotation from the reduction planetary gear, in which a torsion direction of the helical teeth of the respective elements is set such that that a direction of the thrust force of the one element of the reduction planetary gear and a direction of the thrust force of the one element of the planetary gear set are different from each other during driving at one of a plurality of gear speeds.
In the above described structure, it is effective that the torsion direction is set such that a thrust force generated at one element of the reduction planetary gear and a thrust force generated at one element of the planetary gear set face each other during driving at the first gear speed; a bearing subjected to thrust forces generated at the respective elements in common is provided in the common force transmission route; and the bearing is subjected to a differential thrust force between a thrust force acting on one element of the planetary gear set and a thrust force acting on one element of the reduction planetary gear.
In addition, in the above mentioned structure, the foregoing torsion direction is a direction in which the thrust force generated at the one element of the reduction planetary gear and the thrust force generated at the one element of the planetary gear set depart from each other during first gear driving; a bearing subjected to a thrust force generated at the respective elements is provided; and the bearing is subjected to the thrust force acting on the one element of the planetary gear set and the thrust force acting on the one element of the reduction planetary gear independently.
In any of the above described structures, it is effective that a reaction force element of the reduction planetary gear is fixed to a case, and a thrust force to be transmitted to the common force transmission route is transmitted to the case via the bearing.
In addition, in any of the above described structures, it is effective that a carrier of the planetary gear set is supported axially on the common force transmission route.
Further, in any of the above described structures, it is effective that the planetary gear set includes a first sun gear as one element thereof and a second sun gear independent of the first gear; and a bearing subjected to a thrust force acting on the second sun gear is disposed on a passage different from the common force transmission route.
Furthermore, in any of the above described structures, it is effective that the planetary gear set includes a first sun gear and a second sun gear independent of the first sun gear; and a bearing is disposed between the first and second sun gears.
Still further, in any of the above described structures, it is effective that the foregoing one element of the reduction planetary gear is a ring gear.
Furthermore, in any of the above described structures, it is effective that a reaction force element of the reduction planetary gear is fixed to an oil pump case; and
a thrust force generated at the foregoing one element of the reduction planetary gear is transmitted to the oil pump case via the bearing.
Moreover, it is effective that the reduction planetary gear consists of a sun gear formed as the reaction force element; a carrier coupled with the foregoing one element of the planetary gear set for supporting a pinion geared with the sun gear; and a ring gear geared with a pinion supported by the carrier as the foregoing one element of the reduction planetary gear coupled with the input shaft via a coupling member, in which the bearing is disposed between the sun gear and the coupling member.
It is effective that the foregoing one element of the planetary gear set is a sun gear, the coupling member is disposed between the reduction planetary gear and the planetary gear set; and a second bearing is disposed between the coupling member and the sun gear.
Moreover, it is effective that the planetary gear set is formed as a planetary gear set of Ravigneaux type consisting of long and short pinions supported by a carrier and geared with each other; a first sun gear geared with the long pinion; a second sun gear geared with the short pinion; and a ring gear geared with any one of the long and short pinions.
Further it is effective tha
Hayabuchi Masahiro
Kasuya Satoru
Kato Akitoshi
Kato Hiroshi
Nishida Masaaki
Aisin Aw Co. Ltd.
Marmor Charles A
Parekh Ankur
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