Friction gear transmission systems or components – Friction gear includes idler engaging facing concave surfaces – Toroidal
Reexamination Certificate
2000-04-25
2001-12-25
Herrmann, Allan D. (Department: 3682)
Friction gear transmission systems or components
Friction gear includes idler engaging facing concave surfaces
Toroidal
C476S008000, C476S040000, C476S042000, C384S612000
Reexamination Certificate
active
06332858
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to support of power rollers of a toroidal continuously variable transmission for vehicles.
BACKGROUND OF THE INVENTION
Tokkai Hei 6-129509 published by the Japanese Patent Office in 1994 discloses a toroidal continuously variable transmission of a dual cavity-half toroidal type for vehicles.
This transmission comprises a pair of toroidal units disposed on the same input shaft. In each unit, a pair of power rollers are gripped between an input disk and an output disk disposed facing each other on the input shaft. The input disk rotates together with the input shaft, and the power rollers gripped between the input disk and output disk transfer a torque to the output disk by friction. Each power roller is supported by trunnions via a pivot shaft. The trunnions comprise a trunnion shaft which makes a right angle with the input shaft.
If the trunnion is displaced in the direction of the trunnion shaft, the contact point of the power roller with each disk will change, and the direction of the force exerted by each disk on the power roller will vary. Due to the variation of this force, the power roller undergoes a rotational displacement together with the trunnion shaft, and as a result, the contact radius of either the input disk or output disk increases, and that of the other disk decreases.
The variation of these contact radii causes the speed ratio of the input disk and output disk, i.e., the speed ratio of the transmission, to vary.
Thus, the speed ratio of the transmission can be continuously varied by displacing a trunnion in the direction of the trunnion shaft. The rotation angle of the power roller supported on the trunnion shaft as fulcrum is referred to for example as the gyration angle of the power roller, and directly corresponds to the speed ratio of the continuously variable transmission.
SUMMARY OF THE INVENTION
The input disk is supported by the input shaft so that it can displace in an axial directions, and the power roller is pushed against the output disk by a powerful thrust generated by loading cams which are in contact with a rear surface of the input disk.
Due to this powerful thrust, the input disk and output disk undergo a deformation in an axial direction of the input shaft.
If the power roller is to follow the deformation to maintain contact with both disks, it must displace in the direction of the input shaft according to the deformation of the disks.
The reason why the power roller is supported by a pivot shaft joined to the trunnion so that it is free to oscillate, is to satisfy the above requirement. That is, displacement of the power roller in the direction of the input shaft is permitted by having the pivot shaft oscillate according to the deformation of the input disk and output disk in the axial direction. However, when the pivot shaft oscillates, the power roller displaces not only in a horizontal direction but also in a vertical direction.
Due to this displacement, the force which the input disk and output disk exert on the power roller varies in a complex manner, and is a factor which reduces the response of gyration angle variation of the power roller. Moreover, machining of the pivot shaft is difficult, and due to the complex support mechanism wherein the power roller is supported via the pivot shaft, the trunnions become larger and heavier.
Tokkai Hei 7-198014 which the Japanese Patent Office published in 1995 discloses a mechanism wherein the power roller is supported on a pedestal by ball bearings so as to be free to rotate, and a groove is formed in the trunnions in the direction of the input shaft, the pedestal being supported in this groove via roller bearings. The pedestal displaces only in the direction of the input shaft according to the external force applied to the power roller.
When torque is transmitted to the trunnion, a load acts on the trunnion in a direction perpendicular to the input shaft, and this load is supported by the wall surface of the groove in contact with the pedestal However, due to this force, a large frictional force acts between the wall surface of the groove and the pedestal when a pedestal displaces in the direction of the input shaft. This frictional force prevents the smooth displacement of the pedestal.
It is therefore an object of this invention to reduce the frictional resistance between the pedestal of a power roller which displaces along an input shaft and a trunnion.
In order to achieve the above object, this invention provides a toroidal continuously variable transmission comprising an input shaft, an input disk supported on the input shaft, an output disk supported relative to the input disk on the input shaft, a power roller gripped by the input disk and the output disk, a pedestal which supports the power roller such that the power roller is free to rotate, a trunnion, a first roller bearing which supports the pedestal on the trunnion relative to a horizontal load which forms a right angle to the input shaft, and permits the pedestal to undergo a displacement parallel to the input shaft, and a second roller bearing which supports the pedestal on the trunnion relative to a vertical load which forms a right angle to the input shaft, and permits the pedestal to undergo a displacement parallel to the input shaft.
This invention also provides a toroidal continuously variable transmission comprising an input shaft, an input disk supported on the input shaft, an output disk supported relative to the input disk on the input shaft, a power roller gripped by the input disk and the output disk, a pedestal which supports the power roller such that the power roller is free to rotate, a trunnion, and a roller bearing which supports the pedestal on the trunnion relative to a horizontal load which forms a right angle to the input shaft, and a vertical load which forms a right angle to the input shaft, and permits the pedestal to undergo a displacement parallel to the input shaft.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.
REFERENCES:
patent: 3486391 (1969-12-01), Kraus
patent: 4275610 (1981-06-01), Kraus
patent: 5299987 (1994-04-01), Dawe
patent: 5536091 (1996-07-01), Takata et al.
patent: 5720689 (1998-02-01), Imanishi et al.
patent: 5823911 (1998-10-01), Hibi
patent: 5830103 (1998-11-01), Itoh et al.
patent: 6238318 (2001-05-01), Itoh et al.
patent: 6-129509 (1994-05-01), None
patent: 7-198014 (1995-08-01), None
Kumura Haruyoshi
Mori Haruhito
Oshidari Toshikazu
Sugihara Jun
Watanabe Jun
Foley & Lardner
Herrmann Allan D.
Nissan Motor Co,. Ltd.
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