Constant velocity universal joint

Details Constant velocity universal joint Constant velocity universal joint

2001-05-10

2003-01-14

Browne, Lynne H. (Department: 3679)

Rotary shafts, gudgeons, housings, and flexible couplings for ro

Coupling accommodates drive between members having...

Coupling transmits torque via radially spaced ball

C464S906000

Reexamination Certificate

active

06506122

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a constant velocity universal joint capable of transmitting rotary torqe at a constant velocity whatever angles of the driving shaft and driven shaft may take. The constant velocity universal joints are roughly classified into the fixed type constant velocity universal joint that allows only an angular displacement between two axes and the plunging type constant velocity universal joint that allows an angular displacement and an axial displacement between two axes, and the present invention relates to the former fixed type constant velocity universal joint. The constant velocity universal joint of the present invention is suitable for use in connecting the drive shatt of an automobile, for example.
The connection structure of the drive shaft of an automobile varies with the suspension method of the vehicle. For example, in case of an automobile adapting the independent suspension method, the differential is provided to the car body, and the both ends of the drive shaft are connected to the differential and the axle through the universal joints, respectively. In order to permit the drive shaft to make a suspension-associated displacement, it is arranged such that the angular displacement of the drive shaft is allowed at the connection on the wheel-associated side, and the angular displacement and axial displacement of the drive shaft are allowed at the connection on-the differential-associated side.
As the above universal joint, the constant velocity universal joint is used most popularly, and the fixed type constant velocity universal joint, such as the Zepper type, that allows only the angular displacement between two axes is used at the connection on the wheel-associated side, and the plunging type constant velocity universal joint, such as the double offset type, tripod type, and cross groove type, that allows the angular displacement and axial displacement between two axes is used at the connection on the differential-associated side.
FIGS.
10
(
a
) and
10
(
b
) are views showing a fixed type constant velocity universal joint (RZEPPA type constant velocity universal joint: ball fixed joint) that has been used as connecting joint of the drive shaft of an automobile or the like. This constant velocity universal joint includes an outer joint member
11
having a spherical inner surface
11
a
axially formed with six curved guide grooves
11
b
, an inner joint member
12
having a spherical outer surface
12
a
axially formed with six curved guide grooves
12
b
and an inner surface formed with a fitting portion
12
c
having a tooth profile (serrations or splines), six torque transmitting balls
13
disposed in six ball tracks defined between the guide grooves
11
b
in the outer joint member
11
and the guide grooves
12
b
in the inner joint member
12
corresponding thereto, and a cage
14
having window-like pockets
14
c
for retaining the torque transmitting balls
13
.
The centers A and B of the guide grooves
11
b
and
12
b
of the outer and inner joint members
11
and
12
, respectively, are offset axially with respect to the spherical centers of the inner and outer surfaces
11
a
and
12
a
, respectively, by an equal distance in opposite directions (in case of the example shown in the same drawing, the center A is offset toward the open side of the joint, and the center B toward the inner side of the joint). As a result, the ball track defined between the guide groove
11
b
and the guide groove
12
b
corresponding thereto is wedge-wise enlarged in one sense of the axial direction (in case of the example shown in the same drawing, toward the open side of the joint). The spherical centers of the inner and outer surfaces
11
a
and
12
a
of the outer and inner joint members
11
and
12
, respectively, are located in the joint center plane O including the centers of the torque transmitting balls
13
.
When the outer and inner joint members
11
and
12
make an angular displacement of angle &thgr;, the torque transmitting balls
13
guided by the cage
14
are maintained in the bisector plane (&thgr;/2) bisecting the angle &thgr; at any operating angle &thgr; so that the uniformity of velocity for the joint is secured.
With the ball fixed type constant velocity universal joint of this type, it is important how an axial clearance between the pockets of the cage and the torque transmitting balls should be determined. In other words, if the interference (negative clearance) between the pockets of the cage and the torque transmitting balls is too large, so is a force of constrain on the torque transmitting balls, thereby inhibiting the smooth roiling movement of the torque transmitting balls. This causes sliding at a contact portion between the torque transmitting balls and ball tracks during the joint-associated rolling movement of the torque transmitting balls, and the sliding causes a temperature inside the joint to rise, which results in one of the factors to shorten the service life. On the contrary, when the play (positive clearance) between the pockets of the cage and the torque transmitting balls is too large, hammering occurs between the pockets and torque transmitting balls or the vibrations of the joint increase as undesirable influence from the functional viewpoint of the joint. Also, the axial wall surfaces of the pockets wear out by physical contact with the torque transmitting balls. Hence, the positive clearance that was adequate at the beginning of the use may become too large during the use. Further, the dimension of each component has inevitable dimensional variation within the manufacturing tolerance. Thus, in view of the foregoing, with the above-discussed conventional constant velocity universal joint (6-ball fixed type constant velocity universal joint), the axial initial clearance between the pockets of the cage and the torque transmitting balls is set within a range −50 to −10 &mgr;M.
FIGS.
11
(
a
) and
11
(
b
) are views showing the cage
14
in the above-discussed constant velocity universal joint. The cage
14
is provided with six circumferentially equispaced window-like pockets
14
c
for retaining the torque transmitting balls
13
. Both of the circumferential sides of each pocket
14
c
form column portions
14
d.
Conventionally, the pockets
14
c
of the cage
14
are formed by means of punching press and finished with shaving (broaching) on a pair of axial wall surfaces
14
c
1
(see FIG.
11
(
b
)) opposing each other along the axial line. In this case, the axial initial clearance between the pockets
14
c
and torque transmitting balls
13
is set within a range −50 to −10 &mgr;m by applying the treatment on the axial wall surfaces
14
c
1
. However, if the treatment margin on the axial wall surfaces
14
c
1
has variance, the center position of the pockets
14
c
varies with each of the circumferentially aligned pockets
14
c
, that is, a so-called pockets staggering state occurs, which reduces the strength and durability of the cage
14
. In order to prevent the occurrence of the so-called pockets staggering state, a small radius of curvature R is given to each radius (rounded corner)
14
c
3
of the pockets
14
c
to secure linear portions
14
c
4
, so that an axial dimension &dgr; between the axial wall surfaces
14
c
1
and linear portions
14
c
4
can be controlled. Thus, because the radius of curvature R of the radii
14
c
3
is lessened, a space of the pockets is expanded comparably and occupies an unnecessary portion from the functional viewpoint.
On the other hand, the applicant of the present invention has already proposed a ball fixed type constant velocity universal joint having eight ball tracks and eight torque transmitting balls disposed therein to realize a more compact and lightweight constant velocity universal joint while securing the strength, load capacity, and durability which are at least as high as those of the conventional constant velocity universal joint (6-ball fixed type constant velocity universal joint) shown

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