Rotary shafts – gudgeons – housings – and flexible couplings for ro – Coupling accommodates drive between members having... – Tripod coupling
Reexamination Certificate
1999-06-30
2001-03-13
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Coupling accommodates drive between members having...
Tripod coupling
C464S112000, C464S122000
Reexamination Certificate
active
06200224
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a constant velocity universal joint which is used in the power transmission systems of automobiles and various industrial machines, and more particularly it relates to a slidable constant velocity universal joint which is capable of transmitting rotary motion at constant velocity even when driving and driven shafts to be joined together form an angle (operating angle) and which allows a relative axial movement between the driving and driven shafts.
As for slidable constant velocity universal joints used in the transmission systems of automobiles, for example, there are some known forms of the so-called tripod type. One form, as shown in
FIGS. 9 and 10
, comprises an outer joint member
21
having three track grooves
22
formed in its inner peripheral surface and extending axially of the outer joint member, and a tripod member
24
having three radially extending leg shafts
25
with rollers
20
rotatably fitted on the cylindrical outer peripheral surfaces thereof through rolling elements
26
, said tripod member
24
being inserted in the outer joint member
21
with said rollers
20
fitted in the track grooves
22
. Each roller
20
is received in the associated track groove
22
such that it is engaged with the roller guide surfaces
22
a
of the associated track groove
22
opposed to each other circumferentially of the outer joint member, said roller
20
being capable of moving axially of the outer joint member while rotating around the axis of the leg shaft
25
.
When the outer joint member
21
and the tripod member
24
form a operating angle &thgr; as shown in
FIG. 11
during torque transmission, the roller
20
and the roller guide surface
22
a
of the track groove
22
are in mutually slanting relation as shown in FIG.
12
. In this case, the roller
20
tends to move by rolling in the direction of arrow a in
FIG. 11
, and since the track groove
22
has a cylindrical form extending parallel to the axis of the outer joint member, the roller
20
moves while being constrained by the track groove
22
. As a result, slippage occurs between the roller guide surface
22
a
of the track groove
22
and the roller
20
to produce heat, and such slippage induces an axial thrust force. Such induced thrust causes vibrations of the car body and noise and therefore should desirably be minimized.
There is known a tripod type constant velocity universal joint designed to reduce induced thrust and having rollers each constructed of a combination of inner and outer rings to make the joint oscillatable (Japanese Patent Publication 1991-1529). This joint, for example, as shown in
FIGS. 13 and 14
, includes inner rings
27
rotatably fitted on the cylindrical outer peripheral surfaces of the leg shafts
25
of the tripod member
24
through rolling elements
26
, and outer rings
23
rotatably fitted on said inner rings
27
. Each inner ring
27
has a truly spherical outer peripheral surface
27
b
around the axis of the leg shaft
25
, and the cylindrical inner peripheral surface
23
a
of the outer ring
23
is rotatably fitted on said spherical outer peripheral surface
27
b
, whereby the outer ring
23
is made swingable with respect to the axis of the leg shaft
25
. The outer rings
23
are received in the track grooves
22
of the outer joint member
21
and are capable of moving axially of the outer joint member while rolling on the roller guide surfaces
22
a.
In this oscillating or swing type, when the outer joint member
21
and the tripod member
24
form a operating angle during torque transmission as shown in
FIG. 15
, the outer ring
23
is inclined with respect to the axis of the leg shaft
25
, when the spherical outer peripheral surface
27
b
of the inner ring
27
relatively slides on the cylindrical inner peripheral surface
23
a
of the outer ring
23
. This relative movement between the inner and outer rings
27
and
23
causes the outer ring
23
to be guided parallel to the axis of the outer joint member
21
by the roller guide surfaces
22
a
of the outer joint member
21
, so that the outer ring
23
correctly rolls on the roller guide surfaces
22
a
; thus, the sliding resistance on the roller guide surfaces
22
a
is reduced and the generation of the induced thrust force is suppressed.
In this connection, in said oscillating constant velocity universal joint, during torque transmission at a operating angle, the relative sliding movement between the outer and inner rings
23
and
27
results in a sliding friction component in the direction of the axis of the leg shaft
25
acting on the outer ring
23
. This frictional force changes its direction of action through 180° at the ends of the stroke of said relative movement (when the phase angle is 0° and 180°, respectively). That is, immediately before the outer ring
23
reaches the stroke end shown in
FIG. 16
(the direction of rotation of the tripod member
24
being taken as clockwise), said frictional force F acts radially inward. Immediately after it has reached the stroke end shown in
FIG. 17
, however, the frictional force F is reversed to act radially outward. In the conventional article, since the center of curvature O of the spherical outer peripheral surface
23
b
of the outer ring
23
is located more inward than the cylindrical inner peripheral surface
23
a
, a clockwise moment M
F
around the sphere center O due to said frictional force F acts on the outer ring
23
immediately before the latter reaches the stroke end (see FIG.
16
), while a counterclockwise moment M
F
around the center of curvature O acts on the outer ring
23
immediately after the latter has reached the stroke end (see FIG.
17
).
Further, not only does the frictional force F act on the outer ring
23
but also a turning force P attending the torque transmission acts perpendicular to the cylindrical inner peripheral surface
23
a
. This turning force P acts always in a fixed direction, without changing the direction as does said frictional force F, with the result that a counterclockwise moment M
P
around the sphere center O always acts on the outer ring
23
.
As is apparent from the foregoing description, the two moments M
F
and M
P
acting on the outer ring
23
act in opposite directions to cancel out each other immediately before the outer ring
23
reaches the stroke end (
FIG. 16
) but in the same direction immediately after it has passed by the stroke end (FIG.
17
). Thus, the combined moment acting on the outer ring
23
suddenly changes before and after the stroke end, so that immediately after passing by the stroke end, the outer ring
23
inclines as shown in broken line in
FIG. 17
, a situation which could form a cause of generating an induced thrust or a sliding resistance.
There are various forms of said oscillating constant velocity universal joint as shown in
FIGS. 18 through 21
, and in each form, the center of curvature O of the spherical outer peripheral surface
23
b
of the outer ring
23
is deviated from the region S where a sliding movement in the direction of the leg shaft occurs; therefore, as in
FIGS. 16 and 17
, the outer ring
23
tends to exhibit unstable behavior at the stroke ends.
Accordingly, an object of the present invention is to prevent the outer ring from exhibiting such unstable behavior in specific phases.
SUMMARY OF THE INVENTION
To achieve the above object, the invention provide a slidable constant velocity universal joint comprising an outer joint member having a plurality of axial track grooves formed in the inner periphery thereof, a tripod member having a plurality of radially extending leg shafts and torque transmitting members which are rotatable about said leg shafts and whose outer peripheries are spherical, said tripod member being received in the inner periphery of said outer joint member, with the torque transmitting members of the tripod member being fitted in the track grooves of the outer joint member for sliding movement axially of the outer joint member, a sliding contact region de
Ishiguro Shigeyoshi
Kura Hisaaki
Sugiyama Tatsurou
Arent Fox Kintner & Plotkin & Kahn, PLLC
Browne Lynne H.
Dunwoody Aaron
NTN Corporation
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