Constant velocity universal joint

Details Constant velocity universal joint Constant velocity universal joint

1999-11-01

2001-11-27

Browne, Lynne H. (Department: 3629)

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

Coupling accommodates drive between members having...

Tripod coupling

C464S124000, C464S132000, C464S905000

Reexamination Certificate

active

06322453

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a constant velocity universal joint for use in a power transmission of automobiles or various types of industrial machines and, more particularly, to a tripod type constant velocity universal joint.
As a tripod type constant velocity universal joint, for example, known is the one with a configuration shown in
FIGS. 6 and 7
. The constant velocity universal joint comprises an outer joint member
21
having three axial track grooves
22
formed in the inner circumference portion thereof and having respective axial roller guideways
22
a
on both sides of each of the track grooves
22
, and a tripod member
24
having three radially protruding trunnions
25
, said tripod member
24
rotatably mounting a roller
20
to a cylindrical outer circumference surface of each of the trunnions
25
via needle rollers
26
respectively. Each roller
20
is accommodated in and mated with the roller guideways
22
a
of each of the track grooves
22
of the outer joint member
21
respectively. Each of the rollers
20
rolls on the roller guideways
22
a
while rotating about the center of axis of each of the trunnions
25
, thereby smoothly guiding relative axial displacement and angular displacement between the outer joint member
21
and the tripod member
24
. Simultaneously, smoothly guided is an axial displacement of each of trunnions
25
, with respect to the roller guideways
22
a,
accompanying a change in the rotational phase during the transmission of rotational torque between the outer joint member
21
and the tripod member
24
at a predetermined operating angle.
In practice, however, as shown in
FIGS. 8 and 9
, when the outer joint member
21
and the tripod member
24
transmit rotational torque while taking at an operating angle &thgr;, as the trunnions
25
being inclined, each of the rollers
20
and the roller guideways
22
a
are angularly disposed. Consequently, this prevents smooth rolling of each of the rollers
20
. That is, the roller
20
is to rotate in the direction shown with the arrow a (about the axis of the trunnion
25
) in FIG.
8
. On the other hand, since the roller guideway
22
a
has an arcuate cross section and extends in parallel to the axis of the outer joint member
21
, the roller
20
is to roll to move axially on the roller guideway
22
a
in such a manner as to gauge the same. Accordingly, sliding occurs at the contact portion between the outer circumference surface of the roller
20
and the roller guideway
22
a
to cause frictional resistance (sliding resistance) to increase, contributing to an increase in the induced thrust. The induced thrust contributes to inducing vibration at the joint portion. For example, in the power transmission of an automobile, there is such a problem that a large amount of induced thrust at the joint portion provides discomfort to passengers. This is because the thrust is transmitted to the automobile body via the power transmission path and is amplified, and produces resonance with the vibration of the automobile body, thus resulting in increased noise.
In view of the foregoing circumstances, in order to eliminate the angular disposition between a roller and a roller guideway and hereby reduce the induced thrust, a constant velocity universal joint with a configuration shown in
FIGS. 10 and 11
has been proposed (Japanese Patent Publication No.Hei 3 (1991) -1529, etc.). This has contributed to reducing vibration and noise. This constant velocity universal joint has a roller which is mounted to the trunnion
25
of the tripod member
24
, said roller comprising two types of rollers of an outer roller
23
and an inner roller
27
. This allows an inclination between the outer roller
23
and the trunnion
25
(and also inner roller
27
) (an inclination mechanism). The outer roller
23
is in contact with and rolls on the roller guideways
22
a.
The inner roller
27
has a spherical outer circumference surface
27
b
to engage the cylindrical inner circumference surface
23
a
of the outer roller
23
. The inner circumference surface of the inner roller
27
engages the cylindrical outer circumference surface of the trunnion
25
via the needle rollers
26
.
As shown in
FIG. 12
, when the outer joint member
21
and the tripod member
24
transmit rotational torque while taking an operating angle &thgr;, the inner roller
27
is inclined with respect to the roller guideways
22
a
as the trunnion
25
inclines. However, the outer roller
23
is allowed an inclination with respect to the trunnion
25
and the inner roller
27
, thereby allowed for maintaining parallel attitude with respect to and rolling on the roller guideways
22
a.
Consequently, smooth rolling of the outer roller
23
is ensured, the sliding resistance with the roller guideways
22
a
is reduced, thus the induced thrust is suppressed.
As described in the foregoing, the constant velocity universal joint shown in
FIGS. 10 and 11
has reduced induced thrust compared with conventional joints, however, there was a limit in further reducing the induced thrust. As the reason for this, the attitude of the outer roller is believed to be unstable with respect to the roller guideway although the constant velocity universal joint shown in
FIGS. 10 and 11
can maintain the parallel attitude of the outer roller to some extent by the inclination mechanism. This instability may be caused by a slight inclination of the outer roller in the longitudinal sectional direction of the outer joint member (the sectional direction including the axis of the outer joint member). Alternatively, a slight inclination of the outer roller in the cross sectional direction of the outer joint member (the sectional direction perpendicular to the axis of the outer joint member) may cause the instability. The inclinations may be resulted from the effect of the frictional force at the contact portion of the outer and inner roller or the imbalance of joint loading acting on the contact portions of the outer and inner roller, and on those of the outer roller and the roller guideways.
Based on the foregoing circumstances, the applicant had already filed a patent application for a constant velocity universal joint with a configuration exemplified in
FIG. 5
in order to further reduce the induced thrust (Japanese Patent Laid-Open Publication No.Hei 9 (1997) -14280). In the drawing, an inner roller
3
′ fits rotatably over the outer circumference of a trunnion
2
a
′ of a tripod member
2
′ via a plurality of needle rollers
7
′. Movement of the inner roller
3
′ in the direction of axis Z of the trunnion
2
a
′ is limited by means of a retainer ring
8
′ (and a snap ring
9
′) attached to the distal end of the trunnion
2
a
′ and a washer
10
′ attached to the proximal end of the trunnion
2
a
′. In fact, there is a slight axial clearance &dgr;′ between the needle roller
7
′ and the inner roller
3
′, and between the retainer ring
8
′ and washer
10
′ (the clearance &dgr;′ is made far larger than actually is for purposes of illustration). The inner circumference surface
3
a
′ of the inner roller
3
′ is a cylindrically shaped one and the outer circumference surface
3
b
′ is a spherically shaped convex one. The generating line of the outer circumference surface
3
b
′ is a circular arc of a radius of R
1
with the center thereof at point O
1
′ which is shifted outward by a predetermined amount from the center of radius O
2
′ of the inner roller
3
′.
The outer roller
4
′ fits rotatably over the outer circumference surface
3
b
′ of the inner roller
3
′. In the example shown in the figure, the inner circumference surface
4
a
′ of the outer roller
4
′ has a conical shape whose diameter decreases toward the distal end of the trunnion
2
a
′. The angle of inclination &agr;′ of the inner circumference surface
4
a
′ (see
FIG. 4
) ta

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