Continuously variable transmission unit

Details Continuously variable transmission unit Continuously variable transmission unit

1999-10-18

2001-06-26

Marmor, Charles A (Department: 3681)

Planetary gear transmission systems or components

Nonplanetary variable speed or direction transmission...

Nonplanetary transmission is friction gearing

Reexamination Certificate

active

06251038

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a continuously variable transmission unit incorporating a toroidal-type continuously variable transmission that is utilized for a power transmission system of an automobile, for example, and more particularly, to a continuously variable transmission unit reduced in size and improved to secure the durability of the toroidal-type continuously variable transmission.
A study is made of use of a toroidal-type continuously variable transmission schematically shown in
FIGS. 4 and 5
as an automotive transmission. In this continuously variable transmission, an input disc
2
is supported coaxially on an input shaft
1
. An output disc
4
is fixed to an end portion of an output shaft
3
that is coaxial with the input shaft
1
. Pivots
5
and trunnions
6
are arranged in a casing (not shown) that contains the transmission therein. The pivots
5
are situated in torsional positions with respect to the input and output shafts
1
and
3
. The trunnions
6
are rockable around their corresponding pivots
5
.
Each pivot
5
is attached to each side face of each corresponding trunnion
6
in a coaxial manner. A displacement shaft
7
is provided in the center of each trunnion
6
. When each trunnion
6
rocks around its corresponding pivot
5
, the angle of inclination of its corresponding displacement shaft
7
changes. The displacement shaft
7
on each trunnion
6
supports a power roller
8
. The roller
8
can rotate around the shaft
7
. Each power roller
8
is interposed between opposite inner side faces
2
a
and
4
a
of the input and output discs
2
and
4
. The inner side faces
2
a
and
4
a
are concave surfaces that can be obtained if an arc of a circle around each pivot
5
is rotated around the shafts
1
and
3
. An outer peripheral surface
8
a
of each power roller
8
is a spherical convex surface that mates with the concave surfaces. The outer peripheral surface
8
a
is in contact with the inner side faces
2
a
and
4
a
of the discs
2
and
4
.
A loading cam device
9
for use as pressure means is interposed between the input shaft
1
and the input disc
2
. The cam device
9
elastically presses the input disc
2
toward the output disc
4
. The rotation of the input shaft
1
is transmitted to the input disc
2
via the device
9
. The loading cam device
9
includes a loading cam (cam plate)
10
, which can rotate integrally with the input shaft
1
, and a plurality of rollers
12
(e.g., four in number) that are held for rolling motion by means of a ring-shaped retainer
11
. A cam face
13
that undulates in the circumferential direction is formed on one surface (right-hand surface in
FIG. 4
) of the loading cam
10
. A cam face
14
, which resembles the cam face
13
in shape, is formed on the outer side face (left-hand surface in
FIG. 4
) of the input disc
2
. The rollers
12
are rotatably supported by shafts that extend radially from the center of the input shaft
1
.
In the toroidal-type continuously variable transmission constructed in this manner, the loading cam
10
rotates as the input shaft
1
rotates. When the cam
10
rotates, its cam face
13
presses the rollers
12
toward the cam face
14
of the input disc
2
. In consequence, the input disc
2
is pressed against the power rollers
8
, and at the same time, the cam faces
13
and
14
push each other with the rollers
12
between them, whereupon the input disc
2
rotates. As the input disc
2
rotates, the power rollers
8
rotate around their corresponding shafts
7
. The rotation of each roller
8
is transmitted to the output disc
4
. As the output disc
4
rotates, the output shaft
3
that is fixed to the disc
4
rotates.
The following is a description of the way of changing the ratio (i.e., gear ratio) of the rotating speed of the output shaft
3
to that of the input shaft
1
. In decelerating the rotation of the input shaft
1
and transmitting it to the output shaft
3
, the trunnions
6
are tilted around their corresponding pivots
5
, as shown in FIG.
4
. Thus, each displacement shaft
7
is inclined so that the outer peripheral surface
8
a
of each power roller
8
is in contact with the central portion of the inner side face
2
a
of the input disc
2
and the outer peripheral portion of the inner side face
4
a
of the output disc
4
. In accelerating the rotation of the input shaft
1
and transmitting it to the output shaft
3
, in contrast with this, the trunnions
6
are tilted in the opposite direction around their corresponding pivots
5
, as shown in FIG.
5
. Thus, each displacement shaft
7
is inclined so that the outer peripheral surface
8
a
of each power roller
8
is in contact with the outer peripheral portion of the inner side face
2
a
of the input disc
2
and the central portion of the inner side face
4
a
of the output disc
4
. If each displacement shaft
7
is inclined at an angle intermediate between the ones shown in
FIGS. 4 and 5
, an intermediate gear ratio can be obtained between the input and output shafts
1
and
3
.
FIGS. 6 and 7
show a more specific example of the toroidal-type continuously variable transmission. In this example, the input disc
2
and the output disc
4
are rotatably supported around a cylindrical input shaft
15
by means of needle bearings
16
, individually. A through hole
17
having a circular cross section is formed in the central portion of each of the discs
2
and
4
. The holes
17
are formed extending in the axial direction of the input shaft
15
through the respective inner side faces
2
a
and
4
a
and outer side faces of the discs
2
and
4
. Each needle bearing
16
is provided between the inner peripheral surface of its corresponding through hole
17
and the outer peripheral surface of an intermediate portion of the input shaft
15
. A retaining groove
18
is formed on the inner peripheral surface of an end portion of each hole
17
. A snap ring
19
is fitted in each retaining groove
18
. The rings
19
in the grooves
18
prevent the needle bearings
16
from slipping out of through holes
17
toward the inner side faces
2
a
and
4
a
of the discs
2
and
4
. The loading cam
10
is mounted on an end portion
15
c
(left-hand end portion in
FIG. 6
) of the input shaft
15
by spline fitting. A flange portion
20
prevents the cam
10
from moving away from the input disc
2
. The loading cam
10
and the rollers
12
constitute the loading cam device
9
, which rotates the input disc
2
while pressing it toward the output disc
4
as the input shaft
15
rotates. An output gear
21
is coupled to the output disc
4
by means of a key
22
. Thus, the disc
4
and the gear
21
can rotate in synchronism with each other.
As shown in
FIG. 7
, the opposite end portions of the trunnions
6
are supported by means of a pair of support plates
23
. The trunnions
6
are rockable around their corresponding pivots
5
and movable in the axial direction (horizontal direction in
FIG. 7
) of the pivots
5
. Each displacement shaft
7
is inserted in a circular hole
24
that is formed in the central portion of each trunnion
6
. Each shaft
7
includes a support shaft portion
25
and a pivot portion
26
that extend parallel and eccentrically to each other. The support shaft portion
25
is rotatably supported in each trunnion
6
by means of a radial needle bearing
27
that is fitted in the hole
24
. Each power roller
8
is rotatably supported on its corresponding pivot portion
26
by means of a radial needle bearing
28
.
The paired displacement shafts
7
are located diametrically opposite to each other with respect to the input shaft
15
. The pivot portions
26
are eccentric to their corresponding support shaft portions
25
in the same direction with respect to the rotating direction of the discs
2
and
4
. The direction of their eccentricity is substantially perpendicular to the axial direction of the input shaft
15
. Accordingly, each power roller
8
can move for a certain distance in the axial direction of th

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