Constant velocity universal joint

Details Constant velocity universal joint Constant velocity universal joint

2000-12-04

2002-11-05

Binda, Greg (Department: 3679)

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

Coupling accommodates drive between members having...

Tripod coupling

C464S124000

Reexamination Certificate

active

06475092

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sliding type, tripod type constant velocity universal joint.
Generally, a constant velocity universal joint is a kind of universal joint that establishes connection between a driving shaft and a driven shaft to allow torque transfer with constant velocity regardless of the angle between the two shafts. In a sliding type, joint plunging permits relative axial displacements between the two shafts. In a tripod type, a tripod member having three radially-projecting trunnions is linked to one of the shafts, and a hollow, cylindrical outer joint member having three axially-extending track grooves is linked to the other, so that the track grooves in the outer joint member accommodate the trunnions of the tripod member for torque transfer.
2. Description of the Related Art
Now, referring to FIGS.
10
(A) to
10
(C), description will be given of a sliding type, tripod type constant velocity universal joint. In this universal joint, an outer joint member
1
has three cylindrical track grooves
2
axially formed in its inner periphery. A tripod member
4
inserted into the outer joint member
1
has three radially-projecting trunnions
5
. Each of the trunnions
5
has a cylindrical outer periphery on which an annular roller
7
is rotatably fitted via a plurality of needle rollers
6
. The rollers
7
are inserted into the track grooves
2
. Each track groove
2
has a pair of circumferentially-opposed roller guideways
3
which are concave surfaces axially parallel to each other. Each of the rollers
7
on the three trunnions
5
has an outer periphery of convex surface conforming to the roller guideways
3
. Each roller
7
can move along the corresponding track groove
2
while engaging with the roller guideways
3
of the track groove
2
to rotate about the trunnion
5
.
When the joint transfers torque with an operating angle of &thgr; as shown in FIG.
10
(B), the rollers
7
and the roller guideways
3
are put in an oblique relationship as shown in FIG.
10
(C). In this case, the roller
7
tries to roll in the direction shown by the arrow t in FIG.
10
(B). However, since the track groove
2
is part of a cylindrical surface parallel to the axis of the outer joint member, the roller
7
is confined to move along the track groove
2
. As a result, the roller guideway
3
and the roller
7
cause a slide therebetween, producing a slide resistance. This slide also leads to an inductive thrust in the axial direction. Such slide resistances and inductive thrusts contribute to the production of vibrations and noises from a car body, affecting the noise vibration harshness (NVH) performances of motor vehicles and decreasing the flexibility in automotive suspension design. Thus, the resistances and thrusts are desirably reduced as much as possible.
Sliding type, tripod type constant velocity universal joints known as contemplated to reduce such slide resistances and inductive thrusts include the one having the structure shown in FIGS.
11
(A) to
11
(C). Specifically, as shown in the figures, each trunnion
5
of the tripod member
4
has an outer periphery of perfect spherical surface. To the perfect spherical surface is slidably fitted on the cylindrical inner periphery of a cylindrical ring
8
. Each ring
8
and roller
7
constitutes a roller assembly capable of relative rotations therebetween through the medium of rolling elements. Needle rollers
6
, the rolling elements, are arranged between the cylindrical outer periphery of the ring
8
and the cylindrical inner periphery of the roller
7
to provide a so-called full complement type bearing. The needle rollers
6
are stopped by annular washers
9
. The rollers
7
are accommodated in the track grooves
2
of the outer joint member
1
so as to move along the axial directions of the outer joint member
1
while rolling on the roller guideways
3
in the track grooves
2
.
The outer periphery of each trunnion
5
is a perfect spherical surface having the center of curvature on the axis of the trunnion
5
. The roller assembly (
7
,
8
) nutates about the center of curvature. Due to the roller assembly's capability of nutation, when the outer joint member
1
and the tripod member
4
perform torque transfer with an operating angle, the rollers
7
are guided by the roller guideways
3
of the outer joint member
1
so as to remain parallel to the axis of the outer joint member
1
while properly rolling on the roller guideways
3
in the same orientations. This reduces slides during the operation with angles, thereby suppressing the production of slide resistances and inductive thrusts.
Sliding type, tripod type constant velocity universal joints are known as being used for constant-velocity torque transfer from the engine to wheels of a motor vehicle. In a sliding type, tripod type constant velocity universal joint, spherical rollers are mounted on the trunnions of its tripod member. Between the outer peripheries of the trunnions and the inner peripheries of the spherical rollers are arranged needle rollers as rolling elements. The needle rollers are used as full complement type bearings without retainers. In transferring torque with an operating angle, internal components of the joint cause mutual frictions to generate inductive thrusts during rotations. Even at rest, forced extension or contraction of the joint produces slide resistances. Automotive NVH phenomena typically associated with such inductive thrusts and slide resistances include the rolling of a moving car and the vibrations of a car idling with its automatic transmission in a drive or D range, respectively.
The essence of the solution to the automotive NVH problems consists in reducing inductive thrusts and slide resistances a joint can produce. In general, inductive thrusts and slide resistances from a joint tend to depend upon the operating angle of the joint. In applications to automotive drive shafts, this tendency leads to a design limitation of prohibiting greater operating angles. Accordingly, the challenge to an improvement in flexibility of automotive suspension design is to reduce and stabilize the inductive thrusts and slide resistances.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to further reduce and stabilize such inductive thrusts and slide resistances.
According to an embodiment of the invention, a constant velocity universal joint comprises: an outer joint member having three track grooves each having circumferentially-opposed roller guideways; a tripod member having three radially-projecting trunnions; a roller inserted in each of the track grooves; and a ring fitted on each of the trunnions to support the roller rotatably, the roller being movable in axial directions of the outer joint member along the roller guideways. Here, the inner periphery of the ring is shaped arcuate and convex insection. The outer periphery of each of the trunnions is shaped straight in longitudinal section, as well as formed in cross section so as to make a contact with the inner periphery of the ring along a direction perpendicular to the axis of the joint and create a clearance with the inner periphery of the ring in an axial direction of the joint.
The cross-sectional configuration of the trunnions so as to make a contact with the inner periphery of the ring along a direction perpendicular to the axis of the joint and create a clearance with the inner periphery of the ring in an axial direction of the joint may otherwise be put in the following words. That is, the faces opposed to each other in the axial direction of the tripod member have made a retreat toward each other, i.e., to smaller diameters than the diameter of the imaginary cylindrical surface. A concrete example of such configuration is an ellipse.
Due to the alteration in cross section from the conventional circular shape to the configuration described above, the trunnions can tilt with respect to the outer joint member without changing the orientations of the

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