Planetary gear transmission systems or components – Nonplanetary variable speed or direction transmission... – Nonplanetary transmission is friction gearing
Reexamination Certificate
2001-08-09
2003-07-01
Wright, Dirk (Department: 3681)
Planetary gear transmission systems or components
Nonplanetary variable speed or direction transmission...
Nonplanetary transmission is friction gearing
Reexamination Certificate
active
06585619
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a transmission arrangement, in which a continuously variable toroidal drive mechanism, an intermediate planetary gear train and a final planetary gear train are arranged in the power path between an input shaft and an output shaft.
In a known transmission arrangement of this type (U.S. Pat. No. 6,059,685) a central intermediate shaft is connected to the input shaft, to a central toroidal drive disc of the toroidal drive mechanism and to the two-armed planet carrier of the intermediate gear train supporting double planet wheels. A concentric intermediate shaft, through which the central intermediate shaft extends with radial clearance, connects a central toroidal driven disc of the toroidal drive mechanism to a sun gear of the intermediate gear train, which has a drive connection containing a clutch with a first mechanism link in the form of a sun gear of the final gear train. The two concentric intermediate shafts create two central torque paths for the passage through the toroidal drive mechanism, thereby permitting a fundamentally coaxial arrangement of input and output shafts and also of the three gear trains, were the toroidal drive mechanism to be equipped with only one toroidal drive disc and one toroidal driven disc.
In order to also achieve the parallel connection of two central toroidal drive discs and two central toroidal driven discs, otherwise common in toroidal drive mechanisms, with a fundamentally coaxial arrangement of all the said transmission components, in the known transmission arrangement the concentric intermediate shaft is also connected in parallel with the second driven disc, and the one arm of the planet carrier of the intermediate gear train carrying the secondary planet wheels is also connected in parallel to the second drive disc of the toroidal drive mechanism. Furthermore, in the known transmission arrangement, in order to be able to bring the sun gear of the intermediate gear train connected to the concentric shaft into drive connection with the sun gear forming the first mechanism link of the final gear train, the other arm of the planet carrier, carrying the main planet wheels meshing with the secondary planet wheels, is connected by a radial drive arm to the central intermediate shaft, and two inner central gears meshing with the main planet wheels are arranged on both sides of the radial drive arm, one of the sun gears being connected to the concentric intermediate shaft and the other sun gear having the drive connection, containing an engageable and disengageable clutch, to the sun gear forming the first mechanism link of the final gear train.
The secondary planet wheels of the intermediate gear train in turn mesh with an ring gear, which has a drive connection, including an engageable and disengageable clutch, to a second mechanism link in the form of a planet carrier of the final gear train carrying double planet wheels, the carrier in turn also being connected to the output shaft.
Whilst in the final gear train of the known transmission arrangement one of each of the two intermeshing single planet wheels that form a double planet wheel meshes with the sun gear provided as the first mechanism link of the final gear train, the ring gear meshing with each of the other single planet wheels is fixed so that it cannot rotate in relation to a non-rotating part of the housing, as a third mechanism link of the final gear train.
In the known transmission arrangement the clutch connecting the outer ring gear of the intermediate gear train to the planet carrier of the final gear train is engaged in the bottom low-speed range and in reverse gear, whilst the clutch connecting the second sun gear of the intermediate gear train to the sun gear of the final gear train is engaged in the adjoining upper higher-speed range.
An inherent feature of a toroidal drive system is the reversal in the direction of rotation between input and output, because it is in principle a planetary gear train with firmly braked planet carrier, in which the planet wheels, here known as “rollers”, each in frictional contract with a toroidal central drive and driven disc, are mounted so that they can swivel about a swivel axis perpendicular to their axis of rotation but are otherwise immovably fixed in their position relative to the central axis. Since in the known transmission arrangement in the upper drive range the final gear train is driven directly by the output of the toroidal drive mechanism, the final gear train in this drive range must have a negative transmission ratio in forward drive, which is achieved by the double planet wheels, which at high road speeds, however, have high rotational speeds in relation to their planet carrier. In the lower drive range, too, the efficiency of the known transmission arrangement is low, because the output shaft is driven directly by the outer central gear of the intermediate gear train, thereby obviating the need for a final gear train, the latter nevertheless also giving rise to power losses in this drive range owing to its braked outer ring gear, and its sun gear thereby being geared up in relation to the output shaft.
The object of the invention is essentially to create a transmission arrangement with a high efficiency, in which a toroidal drive mechanism, an intermediate planetary gear train and a final planetary gear train are arranged in the power path between an input shaft and an output shaft with a fundamentally coaxial alignment of the transmission components.
SUMMARY OF THE INVENTION
In a transmission arrangement including a continuously variable toroidal drive mechanism, an intermediate planetary gear train and a final planetary gear train which are arranged in the power path between an input shaft and an output shaft, a central intermediate shaft is connected to the input shaft and to a central drive disc of the toroidal drive mechanism, and to a planet carrier of the intermediate gear train. A concentric intermediate shaft, through which the central intermediate shaft extends, is connected to a central driven disc of the toroidal drive mechanism and to a sun gear of the intermediate gear train. The concentric intermediate shaft has a drive connection to a first mechanism link of the final gear train in the form of a sun gear. An outer ring gear of the intermediate gear train has a drive connection to a second mechanism link of the final gear train. A third mechanism link of the final gear train is mounted on a housing part. A fourth mechanism link of the final gear train has a drive connection to the output shaft, this arrangement providing for high efficiency with a coaxial arrangement of the transmission components.
In the transmission arrangement according to the invention, the final gear train has a fourth mechanism link for driving the output shaft, it being possible to integrate the link into the transmission mechanism by way of a second toothed rim of the planet wheels or by means of an additional final planetary gear train with a common planet carrier for both final gear trains.
In the transmission arrangement according to the invention, the number of teeth situated in the power flow of the upper drive range is reduced to a minimum in order to achieve the same directions of rotation of input shaft and output shaft in forward drive and a fundamentally coaxial design for the arrangement.
In the transmission arrangement according to the invention, the rotationally fixed planet carrier achieves the function of an ordinary gear train without clutch power flows for the final gear train(s), thereby increasing the efficiency in the upper drive range affecting consumption, and thus obtaining a reduction in the fuel consumption.
In the transmission arrangement according to the invention, the use of a planet wheel with two toothed rims having an equal or unequal number of teeth in the final gear train means, on the one hand, that the rotational speeds of the planet wheel in relation to the planet carrier can be kept low and, on the other, that identical planet wheels can
Bach Klaus J.
Daimler Chrysler AG
Wright Dirk
LandOfFree
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