Friction gear transmission systems or components – Friction transmission or element – Particular friction surface
Reexamination Certificate
2000-06-07
2002-10-15
Joyce, William C (Department: 3682)
Friction gear transmission systems or components
Friction transmission or element
Particular friction surface
C476S040000, C476S046000
Reexamination Certificate
active
06464616
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a toroidal-type continuously variable transmission which can be used as a transmission unit of a transmission for use in a car, or a transmission for use in various kinds of industrial machines.
2. Description of the Related Art
Conventionally, it has been studied that such a toroidal-type continuously variable transmission as schematically shown in
FIGS. 4 and 5
is used as a transmission for a car. In this toroidal-type continuously variable transmission, as disclosed, for example, in JP-A-62-71465U, an input side disk
2
is supported concentric with an input shaft
1
, while an output side disk
4
is fixed to the end portion of an output shaft
3
which is disposed concentric with the input shaft
1
. Also, at the lateral positions of the extensions of the input and output shafts
1
and
3
between the two disks
2
and
4
, there are disposed two trunnions
6
,
6
each of which is capable of swinging about a pair of pivot shafts
5
,
5
respectively situated at positions along an imaginary plane that is perpendicular to an imaginary line connecting the respective axes of the input and output shafts
1
and
3
, and distanced from the intersection of the imaginary plane and imaginary line. This physical relation is hereinafter referred to as “torsional relation”.
In other words, each of the trunnions
6
,
6
is formed with a pair of pivot shafts
5
on outer surfaces of the two end portions thereof in such a manner that the pair of pivot shafts
5
are concentric with each other. Therefore, the pair of pivot shafts
5
are disposed in such a manner that they do not cross the center axes of the two disks
2
,
4
but extend at right angles to the center axes of two disks
2
,
4
. Also, the base end portions of displacement shafts
7
,
7
are respectively supported on the center portions of their associated trunnions
6
,
6
such that the inclination angles of the respective displacement shafts
7
,
7
can be freely adjusted by swinging the trunnions
6
,
6
about their associated paired pivot shafts
5
,
5
. On the peripheries of the respective displacement shafts
7
,
7
thus supported on their associated trunnions
6
,
6
, there are rotatably supported power rollers
8
,
8
, respectively. These power rollers
8
,
8
are respectively held by and between the input side and output side disks
2
,
4
. Each of the mutually opposing inner surfaces
2
a,
4
a
of the input side and output side disks
2
,
4
has a cross section consisting of a concave surface which can be obtained when an arc having a center present on the extension of the center axis of the pivot shaft
6
is rotated about the input and output shafts
1
and
3
. And, the peripheral surfaces
8
a,
8
a
of the respective power rollers
8
,
8
, each of which is formed in a spherical-shaped convex surface, are respectively contacted with the inner surfaces
2
a,
4
a
of the input side and output side disks
2
,
4
.
Between the input shaft
1
and input side disk
2
, there is interposed a pressing device
9
such as a loading cam and, due to the pressing device
9
, the input side disk
2
can be elastically pressed toward the output side disk
4
. The pressing device
9
is composed of a cam plate
10
rotatable together with the input shaft
1
and a plurality of (for example, four) rollers
12
,
12
which are respectively held by a retainer
11
. On one side surface (in
FIGS. 4 and 5
, the left side surface) of the cam plate
10
, there is formed a cam surface
13
which is a curved surface extending over the circumferential direction of the cam plate
10
; and, on the outer surface (in
FIGS. 4 and 5
, the right side surface) of the input side disk
2
as well, there is formed a cam surface
14
which is similar to the cam surface
13
. And, the plurality of rollers
12
,
12
are supported in such a manner that they can be freely rotated about an axis extending in the radial direction with respect to the center of the input shaft
1
.
When the above-structured toroidal-type continuously variable transmission is in use, in case where the cam plate
10
is rotated with the rotation of the input shaft
1
, the cam surface
13
presses the plurality of rollers
12
,
12
against the cam surface
14
formed on the outer surface of the input side disk
2
. As a result of this, the input side disk
2
is pressed against the plurality of power rollers
8
,
8
and, at the same time, due to the mutual pressing contact between the pair of cam surfaces
13
,
14
and the plurality of rollers
12
,
12
, the input side disk
2
is caused to rotate. And, the rotation of the input side disk
2
is transmitted through the plurality of power rollers
8
,
8
to the output side disk
4
, so that the output shaft
3
fixed to the output side disk
4
can be rotated.
Now, description will be given below of a case where a rotation speed ratio (transmission ratio) between the input shaft
1
and output shaft
3
is changed. At first, when reducing the rotation speed ratio between the input shaft
1
and output shaft
3
, the trunnions
6
,
6
may be respectively swung about the pivot shafts
5
,
5
in a predetermined direction to thereby incline the displacement shafts
7
,
7
in such a manner that, as shown in
FIG. 4
, the peripheral surfaces
8
a,
8
a
of the respective power rollers
8
,
8
can be respectively contacted with the near-center portion of the inner surface
2
a
of the input side disk
2
and the near-outer-periphery portion of the inner surface
4
a
of the output side disk
4
. On the other hand, when increasing the rotation speed ratio between the input shaft
1
and output shaft
3
, the trunnions
6
,
6
may be respectively swung in the opposite direction about the pivot shafts
5
,
5
to thereby incline the displacement shafts
7
,
7
in such a manner that, as shown in
FIG. 5
, the peripheral surfaces
8
a,
8
a
of the respective power rollers
8
,
8
can be respectively contacted with the near-outer-periphery portion of the inner surface
2
a
of the input side disk
2
and the near-center portion of the inner surface
4
a
of the output side disk
4
. In case where the inclination angles of the displacement shafts
7
,
7
are set in the middle of the inclination angles respectively shown in
FIGS. 4 and 5
, there can be obtained a middle transmission ratio between the input shaft
1
and output shaft
3
.
Conventionally, the cross-sectional profile (hereinafter referred to as bus shape or shape of the bus) of the inner surface
2
a
of the input side disk
2
forming the toroidal-type continuously variable transmission which is structured and operates in the above-mentioned manner is generally formed in a single arc whose radius of curvature does not vary on the way as shown in FIG.
6
. Incidentally, the shape of the bus of the inner surface
4
a
of the output side disk
4
is the same as that of the inner surface
2
a
of the input side disk
2
, and the description thereof is omitted. That is, the bus shape is set as an arc surface having a single curvature which has not only a center of curvature O
2a
situated at a point nearer to the center axis of the input side disk than the outer peripheral edge of the input side disk
2
having an outside diameter D
2
but also a radius of curvature R
2a
. The diameter (the pitch circle diameter of the inside surface
2
a
) P.C.D of a circle formed by connecting together the centers of curvature O
2a
of the buses is smaller than the outside diameter D
2
of the input side disk
2
(that is, P.C.D<D
2
).
In an operation to grind the inner surface
2
a
of the input side disk
2
having the above-mentioned shape for finishing the same, as shown in
FIG. 7
, there is used a grinding wheel
15
in which the shape of the bus of the outer peripheral surface thereof is formed so as to be matched to the shape of the bus of the inner surface
2
a,
and thus, the inner surface
2
a
is ground on the grinding wheel
15
, while rotating the grindin
Kamamura Yuko
Matsumoto Yasutami
Joyce William C
NSK Ltd.
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