Planetary gear transmission systems or components – Nonplanetary variable speed or direction transmission... – Nonplanetary transmission is friction gearing
Reexamination Certificate
1999-10-22
2001-04-10
Marmor, Charles A (Department: 3681)
Planetary gear transmission systems or components
Nonplanetary variable speed or direction transmission...
Nonplanetary transmission is friction gearing
C475S217000, C475S219000
Reexamination Certificate
active
06213907
ABSTRACT:
TECHNICAL FIELD
This invention relates to continuously variable toric type traction transmissions and more particularly to such transmissions having a geared neutral.
BACKGROUND OF THE INVENTION
Toric or toroidal type traction drive continuously variable transmissions have an input disc, an output disc and a plurality of traction rollers that tractionally engage the input and output discs. Power is transferred through the transmission by the traction drive train between the input discs, output discs and the traction rollers. The transmission ratio between the input discs and the output discs is determined by the angle of operation of the traction rollers relative to the input and output discs. The input discs and output discs are preferably arranged in pairs with the input discs being opposite ends and the output discs being in the center. The input power is connected with the input discs by a toric input shaft and the output power is taken from the output discs by a toric output shaft. The toric output shaft passes through the center of at least one of the input discs.
To accommodate the positioning of the toric output shaft a dual axis design is common. These systems employ a countershaft to connect the two input discs to the power output. The counter shaft is located radially outward of the input and output discs which requires that the transmission have a larger barrel size than required by the radius of the discs.
In order to transmit the power tractionally, the input discs are urged toward each other by mechanical or hydraulic means to establish the proper normal force between the input discs, output discs and the traction rollers and the operating angle of the traction rollers. The most recent designs of these transmissions use electro-hydraulic control systems to apply the normal forces required. These systems permit a more accurate control of the forces needed to establish the correct normal force and the force which establishes the positioning of the traction rollers. In the prior art transmissions of the single cavity designs, the forces applied to the input discs are absorbed or reacted by the transmission housing through rotating bearings. While this is a very effective structurally, it does reduce the overall efficiency of the transmission due to the power loss in the relative rotation of the bearing surfaces.
In order to establish a geared neutral condition, a summing planetary is commonly used. The summing planetary has one member connected with the toric input, one member connected with the toric output and a third member connected with the transmission output. Two types of summing planetary gear sets have been used.
The most commonly used is a simple planetary gear set which has a sun gear, a ring gear and a planetary carrier assembly that includes a plurality of pinion gears meshing with both the sun and ring gears. The toric input is connected with the carrier assembly, the toric output is connected with the sun gear and the transmission output is connected with the ring gear. Depending on the tooth ratio between the sun gear and the ring gear, the transmission output can be stationary (in neutral), rotated in a forward direction or rotated in a reverse direction.
One co-axial arrangement that has been used is shown in U.S. Pat. No. 5,607,372. The co-axial arrangement shown therein includes two sun gears and a carrier assembly having a plurality or interconnected pinion gears which mesh with both the sun gears. The carrier assembly is connected with the toric input, one sun gear is connected with the toric output and the other sun gear is connected with the transmission output which happens to be a planetary gear arrangement and a summing differential. The toric arrangement shown in the above mentioned patent eliminates the need for a counter shaft to provide the input drive to the toric input.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved co-axial toric transmission. In one aspect of the present invention, a toric transmission provided with coaxial input and output shafts. In another aspect of the present invention a planetary gear set is positioned centrally of the output discs to transmit power therefrom. In yet another aspect of the present invention, the toric output is connected with a summing differential external to the toric drive.
In still another aspect of the present invention, the toric input is connected with the summing differential by a central shaft which passes through the centrally located planetary gear set. In a further aspect of the present invention, the normal force applied to the input discs is contained within the input drive members. In yet a further aspect of the present invention, the normal forces applied to the input discs are contained without the use relatively rotating thrust bearings.
The present invention is represented in a single mode, geared neutral, continuously variable transmission. The transmission has a continuously variable unit (CVU) with co-axial toric input and output shafts. The input shaft supplies power from a prime mover, such as an internal combustion engine, to the input discs of the CVU. The input shaft is directly connected with one input disc, through a ball spline, and to the other input disc through the planet carrier of a summing differential gear set. The thrust loads on the CVU input discs are contained within the input shaft.
The power at the input discs is transferred through a plurality of traction rollers to a pair of output discs which are interconnected through the carrier of a compound planetary gear set located between the output discs in concentric relation with the input shaft. The sun gear of the compound planetary gear set is connected through a sleeve shaft with the sun gear of the summing differential. The ring gear of the compound planetary gear set is grounded to the transmission housing. The ring gear of the summing differential is connected through a selectively engageable clutch to a transmission output shaft. The speed and direction of the ring gear of the summing differential, and therefore the transmission output, is determined by the ratio of the CVU. By controlling the angle of the traction rollers relative to the input and output discs, the ratio of the CVU is manipulated. The rotation of the output shaft of the transmission can be forward, reverse or neutral depending on the speed of the individual members of the summing differential.
REFERENCES:
patent: 2140012 (1938-12-01), Hayes
patent: 3410146 (1968-11-01), Nordeen
patent: 4355547 (1982-10-01), Poole et al.
patent: 5238460 (1993-08-01), Esaki et al.
patent: 5254056 (1993-10-01), Nakano
patent: 5607372 (1997-03-01), Lohr
patent: 5967931 (1999-10-01), Hoge et al.
patent: 6045477 (2000-04-01), Schmidt
patent: 6110070 (2000-08-01), Nagai et al.
patent: 404327055 (1992-11-01), None
General Motors Corporation
Hargitt Laura C.
Ho Ha
Marmor Charles A
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