Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2002-10-03
2004-06-15
Footland, Lenard A (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C476S040000
Reexamination Certificate
active
06749343
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a power roller bearing for a toroidal-type continuously variable transmission for use, for example, in a power transmission system of a vehicle.
A half-toroidal-type continuously variable transmission, as shown partially in
FIGS. 9 and 10
, comprises a power roller
13
between an input disk
11
and an output disk
12
. The power roller
13
rotates about a displacement shaft
15
which is disposed on a trunnion
14
. The trunnion
14
is supported by a pair of trunnion shafts
16
so as to be swung with respect to a support body
17
. Between the trunnion
14
and power roller
13
, there is interposed a power roller bearing
18
.
The power roller bearing
18
comprises an inner ring
20
composed of a portion of the power roller
13
, an outer ring
21
disposed to be opposed to the inner ring
20
, a plurality of balls
22
respectively interposed between a raceway
21
a
formed in the outer ring
21
and a raceway
20
a
formed in the inner ring
20
, a ring-shaped retainer
24
for holding the respective balls
22
in a freely rotatable manner, and a thrust bearing
25
interposed between the outer ring
21
and trunnion
14
. The respective balls
22
are rotatably stored in their associated pockets
26
formed in the retainer
24
. These pockets
26
are disposed at an equal pitch, that is, at equally distant (equi-distant) positions in the peripheral direction of the retainer
24
.
When the toroidal-type continuously variable transmission is in operation, as shown in
FIG. 9
, the power roller bearing
18
and disks
11
,
12
are contacted with each other at two contact points C
1
, C
2
, thereby providing a so called two-point pressing state. In
FIG. 9
, &thgr; designates the contact angle. Therefore, the power roller bearing
18
receives the thrust component of a pressing force P at the contact points C
1
, C
2
and, at the same time, it generates the radial-direction component at the mutually 180° opposed position on the circumference of the power roller
13
. Thus, the circular-ring-shaped power roller bearing
18
is compressed in the radial direction and, due to this compression force, the inner ring
20
tends to deform into an elliptical shape.
As a result of this, the load distribution on the circumference of the power roller
13
is caused to vary. The balls
22
rotate at high speeds while they are receiving such variable loads and, therefore, the rolling portions of the balls
22
generate a lot of heat. That is, the power roller bearing
18
is used under the severer conditions than an ordinary bearing.
Also, when the toroidal-type continuously variable transmission is in operation, at the traction contact points C
1
, C
2
for transmission of power between the power roller
13
and the respective disks
11
,
12
, there are generated such tangential-direction forces Ft as shown in
FIGS. 10 and 11
. A force 2 Ft, which is the sum of two forces Ft respectively generated at the two contact points C
1
, C
2
, provides a force Fr (which is shown in
FIG. 10
) going in a direction to fall down the power roller bearing
18
, thereby causing the above-mentioned compression force to unbalance in magnitude.
The orbital speed of the balls
22
of the power roller bearing
18
used under the above conditions provide such distribution as shown by arrow marks in FIG.
12
. That is, in case where the rotation direction of the retainer
24
is shown by the arrow mark R, the orbital speeds R
1
of the respective balls
22
situated on the 2 Ft side are slower than the orbital speeds R
2
of the balls
22
situated on the anti-2 Ft side.
In this manner, when the power roller
13
rotates, since there are produced orbital speed differences between the respective balls
22
, as shown by the line L
1
in
FIG. 13
, the balls
22
are going to roll in such a manner that they are shifted from the above-mentioned their respective equi-distant positions. However, in fact, because the movements of the balls
22
are restricted by the retainer
24
, as shown in
FIG. 14
, the contact loads between the balls
22
and retainer
24
vary according to the positions of the balls
22
.
That is, the contact loads P
2
of the balls
22
situated on the anti-2 Ft side act on the balls
22
so as to push the retainer
24
in the rotation direction R. On the other hand, the contact loads P
1
of the balls
22
situated on the 2 Ft side act on the balls
22
so as to push the retainer
24
in the opposite direction to the rotation direction R. Due to this, the inner peripheral surfaces of the pockets
26
of the retainer
24
and balls
22
are contacted with each other, which results in the lowered durability of the retainer
24
.
Also, when the balls
22
are contacted with the retainer
24
, they receive a reactive force from the retainer
24
. Due to this, the actual shifting amounts of the balls
22
, as shown by the line L
2
in
FIG. 13
, become smaller by
M than their ideal shifting amounts (line L
1
). That is, the respective balls
22
are caused to slide on the rolling surface by the amount of
M, which reduces the efficiency of the toroidal-type continuously variable transmission.
In JP-A-2001-4003, there is disclosed a technique in which, in order to reduce phase differences to be generated between balls, pockets are made slightly longer in the peripheral direction of a retainer (that is, the pockets are respectively formed as elongated pockets) to thereby widen a clearance between the balls and the inner peripheral surfaces of the pockets. According to this conventional technique, in a high load area, the balls are able to shift in the longitudinal direction of the pockets and, therefore, the orbital speed differences of the balls can be absorbed. However, in a low load area, since the phase differences between the balls are small, the balls tend to stay in the vicinity of the centers of the pockets; and, because the above-mentioned clearance is relatively large, there is a possibility that the retainer can be vibrated in the peripheral direction thereof.
SUMMARY OF THE INVENTION
In view of the above circumstances of the related art, it is an object of the invention to provide a power roller bearing which can restrict the slippage between balls and rolling surfaces to thereby be able to prevent the efficiency of the power roller bearing from being lowered.
In attaining the above object, according to the invention, there is provided a power roller bearing for rotatably supporting a power roller of a toroidal-type continuously variable transmission, comprising: an inner ring; an outer ring; a plurality of balls interposed between the inner and outer rings; and, a retainer for holding the balls therein, wherein the retainer includes a plurality of pockets for storing the balls therein at equi-distant positions in the peripheral direction of the retainer, and the inner peripheral portions of the pockets are respectively formed of such elastic material that, when the power roller rotates, allows the balls to shift from the equi-distant positions.
According to the above construction of the invention, it is preferable that the inside diameter of each of the pockets is larger than the outside diameter of each of the balls, the inside diameter of the opening of the pocket is smaller than the outside diameter of the ball, and the opening has such elasticity that allows the opening to spread out to a size equal to or larger than the outside diameter of the ball.
Since, when the power roller rotates, for the above-mentioned reason, there are produced the orbital speed differences between the balls, the balls are going to roll shifted from their respective equi-distant positions. The retainer, which is used in the power roller bearing according to the invention, due to its elasticity, allows the balls to roll shifted from their respective equi-distant positions. Thus, the reactive forces, which are given to the balls from the retainer when they are contacted with each other, are small. Therefore, the shifting amounts of th
Kato Hiroshi
Machida Hisashi
Shimizuya Masayoshi
Footland Lenard A
NSK Ltd.
Sughrue & Mion, PLLC
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