Friction gear transmission systems or components – Friction gear includes idler engaging facing concave surfaces – Toroidal
Reexamination Certificate
1999-06-22
2001-06-19
Bonck, Rodney H. (Department: 3681)
Friction gear transmission systems or components
Friction gear includes idler engaging facing concave surfaces
Toroidal
Reexamination Certificate
active
06248039
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a toroidal continuously variable transmission installed mainly in vehicles.
BACKGROUND OF THE INVENTION
Tokkai Hei 10-26201 published by the Japanese Patent Office in 1998 discloses a toroidal continuously variable transmission.
This toroidal continuously variable transmission comprises an input disk connected to a rotation shaft via a ball spline, an output disk facing the input disk, and plural power rollers gripped between these disks.
The power rollers transmit a rotation of the input disk to the output disk. By varying the contact points between the power rollers and the disks, a rotation speed ratio of the input disk and output disk, i.e., the speed ratio of the continuously variable transmission, is made to vary.
For this reason, the input disk and output disk must always be in contact with the power rollers with a predetermined frictional force.
A cam flange and cam rollers are provided for this purpose. The cam flange is supported free to rotate on the rotation shaft and, according to the relative rotational displacement of the cam flange and input disk, the cam rollers exerts a thrust load on the input disk.
SUMMARY OF THE INVENTION
When a rotational torque is transmitted from the input disk to the output disk, a large grip force acts on the power rollers due to the aforesaid thrust load. On the other hand a reaction in the reverse direction to the grip force acts on the input disk and output disk at the contact point with the power rollers, and due to this reaction force, the input disk and output disk deform in such a direction that their outer circumferences separate.
This deforming force causes a load to act both in radial and axial directions on the rotation shaft.
The ball spline which joins the rotation shaft to the input disk comprises a plural spline units. Each spline unit comprises a pair of spline grooves formed on both the input disk and rotation shaft, and plural balls held therein.
In an intermediate part between adjacent spline units, the inner circumference of the input disk and the outer circumference of the rotation shaft are in close proximity separated by a small gap, or are in direct contact under a weak contact pressure. Therefore, of the radial load supporting force of the spline units and the radial load supporting force of the intermediate part, the former is far larger. This difference causes a difference in the deformation state of the input disk. In other words, when there is a spline unit situated at the same rotation angle as the contact point of the disk and power roller, the deformation of the input disk is small, but when there is an intermediate part situated at the same rotation angle as the contact point of the disk and power roller, the deformation of the input disk is large.
Here, when the number of contact points of the disk and power rollers is equal to the number of power rollers, and when there is a spline unit at the same angle as one of the two contact points while there is an intermediate part at the same angle as another contact point, the deformation of the input disk varies irregularly depending on the rotation angle, and this irregular variation causes rotational vibration.
The same problem occurs regarding the deformation of the output disk when the output disk is connected to the rotation shaft by a ball spline.
It is therefore an object of this Invention to control the deformation of the disks of a toroidal continuously variable transmission which are connected to a rotation shaft via a ball spline, to a desirable state.
In order to achieve the above object, this invention provides a toroidal continuously transmission comprising a rotation shaft, an input disk disposed coaxially with the rotation shaft, an output disk disposed coaxially with the rotation shaft, power rollers disposed at a predetermined angular interval around the rotation shaft and gripped between the input disk and the output disk, a ball spline structure consisting of a group or groups of ball spline units for connecting the rotation shaft and either of the input disk and the output disk. Each ball spline unit comprises a pair of spline grooves and a ball gripped therein and each of the group or groups consists of ball spline units which are disposed at an angular interval equal to the predetermined angular interval.
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: 5027668 (1991-07-01), Nakano
patent: 5230670 (1993-07-01), Hibi
patent: 5299988 (1994-04-01), Fukushima et al.
patent: 5368529 (1994-11-01), Machida
patent: 5779591 (1998-07-01), Inoue
patent: 5971886 (1999-10-01), Yamamoto
patent: 6045481 (2000-04-01), Kumagai
patent: 6071210 (2000-06-01), Kato et al.
patent: 7-249423 (1995-09-01), None
patent: 10-26201 (1998-01-01), None
Bonck Rodney H.
Foley & Lardner
Nissan Motor Co,. Ltd.
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