Friction gear transmission systems or components – Friction gear includes idler engaging facing concave surfaces – Toroidal
Reexamination Certificate
2001-11-13
2004-06-08
Bucci, David A. (Department: 3682)
Friction gear transmission systems or components
Friction gear includes idler engaging facing concave surfaces
Toroidal
C384S492000, C384S625000, C148S326000
Reexamination Certificate
active
06746365
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a toroidal-type continuously variable transmission for use as an automatic transmission for a vehicle and, particularly, to a toroidal-type continuously variable transmission in which the durability of component parts thereof, that is, disks and power rollers is enhanced.
Conventionally, as a toroidal-type continuously variable transmission, there is known a transmission which has such a structure as shown in FIG.
1
.
Within a housing (not shown), an input side disk
1
and an output side disk
2
are disposed on an input shaft
3
which is rotatably supported in the interior of the housing, in such a manner that they are concentric with and opposed to each other. The input shaft
3
is penetrated through the axial core portion of a toroidal transmission part including the input side and output side disks
1
and
2
. A loading cam
4
is disposed on one end of the input shaft
3
. The loading cam
4
is structured such that it can transmit the power (rotational force) of the input shaft
3
to the input side disk
1
through a cam roller
5
. The input side and output side disks
1
and
2
are concentric with each other with their respective inner surfaces opposed to each other. The input side and output side disks
1
and
2
have substantially the same shape, while these opposed surfaces are formed as toroidal surfaces which cooperate together in forming a substantially semicircle.
Within a toroidal cavity defined by the toroidal surfaces of the input side and output side disks
1
and
2
, a pair of power roller bearings
6
and
7
are disposed in such a manner that they are contacted with the input side and output side disks
1
and
2
. By the way, the power roller bearing
6
is composed of a power roller
6
a
(which corresponds to an inner ring forming the power roller bearing
6
) which is allowed to roll on the toroidal surfaces of the input side and output side disks
1
and
2
, an outer ring
6
b
, and a plurality of rolling bodies (steel balls)
6
c
. On the other hand, the power roller bearing
7
is composed of a power roller
7
a
(which corresponds to an inner ring forming the power roller bearing
7
) which is allowed to roll on the toroidal surfaces of the input side and output side disks
1
and
2
, an outer ring
7
b
, and a plurality of rolling bodies (steel balls)
7
c.
That is, the power roller
6
a
serves also as an inner ring which is a component of the power roller bearing
6
, while the power roller
7
a
serves also as an inner ring which is a component of the power roller bearing
7
. In this structure, the power roller
6
a
is mounted pivotally and rotatably on a trunnion
10
through a pivot shaft
8
, the outer ring
6
b
and the plurality of rolling bodies
6
c
on the trunnion
10
swinging about a support shaft
20
disposed at a position which is perpendicular to an axial line of the input shaft
3
and does not intersect the axial line thereof (hereinafter, this physical relationship is referred as ″ a twisted position. The power roller
6
a
includes a peripheral surface which is formed as a spherical-shaped convex surface. The power roller
6
a
is supported in such a manner that it is able to inclinedly roll about shift shafts respectively supported on the trunnions and serving as the centers of the toroidal surfaces of the input side and output side disks
1
and
2
. On the other hand, the power roller
7
a
is mounted pivotally and rotatably on a trunnion
11
through a pivot shaft
9
, the outer ring
7
b
and the plurality of rolling bodies
7
c
, while the trunnion
11
can be oscillated about the pivot shaft
9
disposed at a twisted position with respect to the input shaft
3
. The power roller
7
a
includes a peripheral surface which is formed as a spherical-shaped convex surface. The power roller
7
a
is supported in such a manner that it is able to roll inclinedly about shift shafts
0
respectively supported on the trunnions and serving as the centers of the toroidal surfaces of the input side and output side disks
1
and
2
. And, to the contact surfaces of the input side and output side disks
1
and
2
with respect to the power rollers
6
a
and
7
a
, there is supplied lubricating oil which is large in viscous frictional resistance. Power input to the input side disk
1
can be transmitted to the output side disk
2
through the lubricating oil film, power roller
6
a
and power roller
7
a.
By the way, the input side and output side disks
1
and
2
are set independent of the input shaft
3
through a needle roller
12
(that is, they are not influenced directly by the power of the rotary shaft or input shaft
3
). On the output side disk
2
, there is disposed an output shaft
14
which is not only arranged parallel to the input shaft
3
but also rotatably supported by the housing (not shown) through angular bearings
13
. In this toroidal-type continuously variable transmission
20
, the power of the input shaft
3
is transmitted to the loading cam
4
. In case where the loading cam
4
is rotated due to such power transmission, the power of the loading cam
4
produced by the rotation thereof is transmitted through the cam roller
5
to the input side disk
1
, thereby causing the input side disk
1
to rotate. Further, the power of the input side disk
1
produced by the rotation thereof is then transmitted through the power rollers
6
a
and
7
a
to the output side disk
2
. As a result of this, the output side disk
2
is rotated integrally with the output shaft
14
.
In the case of transmission, the trunnions
10
and
11
are moved by a slight distance in the directions of the shift shafts
0
, respectively. That is, due to the movements of the trunnions
10
and
11
in the axial direction thereof, the intersection between the rotation axes of the power rollers
6
a
,
7
a
and the axes of the input side and output side disks
1
and
2
are shifted slightly from each other. As a result of this, the balance between the rotational peripheral speeds of the power rollers
6
a
,
7
a
and the rotational peripheral speed of the input side disk
1
is lost. In addition, due to the component of the rotation drive force of the input side disk
1
, the power rollers
6
a
,
7
a
are inclinedly rotated around the shift shafts
0
, respectively. Therefore, the power rollers
6
a
,
7
a
are inclinedly rotated on the curved surfaces of the input side and output side disks
1
and
2
, with the result that the speed ratio is changed, thereby accelerating or decelerating the speed of the vehicle.
As a toroidal-type continuously variable transmission having the above structure, for example, there is known a conventional transmission which is disclosed in Japanese Utility Model Examined Publication No. Hei. 2-49411U. Also, as the examples of the above-mentioned input side disk, output side disk and power roller bearings, there are conventionally known disks and bearings which, as set forth in [NASA Technical note NASA ATN D-8362], use AISI52100 (JIS SUJ
2
which corresponds to a high carbon chromium bearing). Further, disks and bearings which, as disclosed in Japanese Patent Unexamined Publication No. Hei. 9-79336, are produced by carbonitriding SCM420, that is, steel for machine-structural purposes containing Cr.
In the above-mentioned conventional toroidal-type continuously variable transmission, when it is driven, there are produced high contact pressures respectively between the input side disk and power roller bearings, between the output side disk and power roller bearings, and between the power roller inner and outer rings and rolling bodies. These high contact pressures give rise to the shortened rolling fatigue lives of the raceway surfaces. Also, an increase in the temperatures of the contact surfaces due to generation of heat in the lubricating oil (traction oil) flowing through between the input side and output side disks and power roller bearings as well as through between the power roller raceway surfaces and rolling b
Murakami Yasuo
Yoshikawa Tomonobu
Bucci David A.
McAnulty Timothy
NSK Ltd.
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