Tripode constant velocity joint

Details Tripode constant velocity joint Tripode constant velocity joint

2002-10-16

2004-08-17

Binda, Greg (Department: 3679)

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

Coupling accommodates drive between members having...

Tripod coupling

C464S905000

Reexamination Certificate

active

06776720

ABSTRACT:

TECHNICAL FIELD
This invention relates to shudderless, tripode, plunging, constant-velocity, universal joints.
One type of such a constant-velocity, universal joint comprises a first rotary member having a rotary axis, three trunnions extending from the first member, a roller mounted directly or indirectly on a spherical surface on each trunnion, such surface being provided by the trunnion itself or by a member rotatably mounted on the trunnion, the roller including a cylindrical bore which engages the spherical surface so that each roller can rotate, tilt and slide relative to its supporting trunnion, the centers of the spherical surfaces on all the trunnions lying in a plane perpendicular to said rotary axis, a second rotary member having a rotary axis, three grooves formed in said second rotary member so as to extend parallel to the rotary axis of the second rotary member, each roller being engaged with one of the grooves, the engagement between each roller and its associated groove being such that the orientation of the roller with respect to the second member is determined solely by said engagement. In such a joint there is relative radial movement between the spherical surface of the trunnion and the roller.
BACKGROUND ART
One known form of shudderless, plunging, tripode joint is shown in cross section in FIG.
1
. Referring to this figure there is a spider or inner member
10
of the joint which has three trunnions, one of which is shown at
11
. The trunnion has a part-spherical surface
12
which receives an inner roller
13
having a cylindrical bore
14
. The inner roller
13
can slide and tilt relative to the trunnion and moves radially relative to the center of the trunnion when the joint is articulated and rotating. An outer roller
15
is mounted on the inner roller
13
to rotate relative thereto, there being a needle roller bearing
16
between the rollers
13
and
15
. The parts of the roller assembly are kept together by two rings
17
and
18
. The outer race of the joint is indicated at
19
and has three grooves, each groove being formed by a pair of opposed tracks one of which is shown at
20
. The cross-sectional shape of each track is formed by two circular arcs which give a “Gothic arch” form and angular contacts between the track and the roller. The centers
21
of the spherical surfaces of all of the trunnions lie in a plane perpendicular to the rotary axis
21
a
of the spider.
When torque is to be transmitted from the outer race
19
to the spider
10
in an anticlockwise direction in
FIG. 1
, there is a reaction force F
0
which acts from the trunnion to the inner roller
13
and thence to the outer roller
15
. The force F
0
is generally perpendicular to the rotary axis of the roller
13
, ignoring friction. There is two-point contact between the roller
15
and the right-hand track
20
and the reaction forces are shown at F
1
and F
2
. The roller
15
is able to rotate about the intersection of these forces at
22
and without further constraint would be unstable. Because the roller
15
is free to tilt about the intersection
22
, in order for the roller to be stable it will also engage the left-hand track so that there will be one or more reaction forces such as F
3
or F
4
on the circumference of the roller and/or a force F
5
on the upper surface of the roller which limits its tilting movement. These additional forces on the left-hand side of the roller are intermittent and are due to the fact that, as the trunnion
11
moves up and down through the roller bore
14
, the position of the roller
15
relative to the outer race
19
can, in general, only be defined by two points of contact (i.e. those of the forces F
1
and F
2
) instantaneously when the trunnion is in a certain position with respect to the roller so that other forces are generally required to determine the orientation of the roller. These intermittent other forces F
3
, F
4
and F
5
increase the resistance of the roller to rolling along the tracks and hence the plunge resistance of the joint, i.e the passive resistance. They may also cause the joint to generate a cyclic net axial force when it rotates with the rotary axes of the spider and outer race misaligned, this can give rise to shudder vibration in a vehicle in which the joint forms part of the driveline.
A similar arrangement is shown in
FIG. 2
except that in this case the trunnion
22
is cylindrical and an inner roller
23
provides the part-spherical outer surface
24
which engages a cylindrical bore
25
of the outer roller
26
. The inner roller
23
is mounted on the trunnion by a needle roller bearing
27
and can not tilt or slide relative to the trunnion. The outer roller
26
can rotate, tilt or slide relative to the trunnion and to the part-spherical outer surface
24
which moves up and down within the bore
25
. The forces on the roller
26
are similar to those described in relation to the joint shown in FIG.
1
and are shown by the same reference characters.
Because in each of the above examples the rollers
15
and
26
can tilt, slide and rotate relative to the trunnions and because the rollers are “shaped” to fit the grooves, the orientation of each roller with respect to its associated groove is determined solely by the engagement of the roller with the groove. There are other configurations of tripode joints in which the orientation of each roller relative to the outer race is determined by the engagement of the roller with the groove.
There is described in WO 97/25545 a further type of tripode shudderless joint and reference is made particularly to FIG. 17. In this joint, the tripode trunnions are cylindrical and mounted on each trunnion by needle roller bearings is an inner roller with a part-spherical outer surface. This engages an outer roller with an inner spherical-surface. The outer roller can tilt with respect to the inner roller but any sliding radial movement takes place between the trunnion and the inner roller. The outer spherical surface does not move radially with respect to the outer roller so that, unlike the joint of the current invention as will be described below, the force between the trunnion and the roller assembly acts at a fixed position relative to the roller assembly. Therefore there may be no tendency for the roller assembly to twist about an axis parallel to the axis of the second member.
In the prior joint the outer roller has a trapezoidal outer surface which engages a track surface of corresponding shape. It is suggested that contact may take place between three faces of the outer roller and the track but this would seem to require a very accurate fit between roller and track. This is acknowledged by the fact that the roller and track inclined surfaces are described as facing one another with “a gapless contact or a very small gap”. In practice the two trapezoids will generally only be in contact on one or two of their sides.
WO 97/25545 also describes how the rollers are only in contact with the track surface through which torque is being transmitted. This may be achieved by making the driving track (i.e. the track through which torque is transmitted) narrower than the other track. This results in asymmetric grooves and a requirement for different components to be used on the left and right hand sides of a vehicle.
SUMMARY OF THE INVENTION
An object of the present invention is to reduce the resistance of the rollers to rolling along the tracks and thus to reduce the plunge resistance whilst ensuring that the rollers are stable and that there is continuous three-point contact between the roller and the track, without requiring the profiles of the roller and the track to be matched with extreme accuracy.
Another object of the invention is to provide a shudderless, tripode joint in which the stability of each roller is determined solely by its engagement with the driving track and there are no intermittent contacts between the roller and the other track.
Another object of the invention is to reduce the NVH (noise, vibration, harshness) associated with cleara

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