Tripod sliding constant velocity joint

Details Tripod sliding constant velocity joint Tripod sliding constant velocity joint

1998-02-09

2001-01-16

Browne, Lynne H. (Department: 3629)

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

Coupling accommodates drive between members having...

Tripod coupling

C464S120000, C464S167000, C464S905000

Reexamination Certificate

active

06174239

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention concerns a tripod sliding constant velocity joint of the type comprising:
a male member having ternary symmetry about a first main axis and including a hub from which project three arms that each delimit a spherical bearing surface;
a female member defining three pairs of rolling tracks and having ternary symmetry about a second main axis; and
for each arm:
a one-piece intermediate shoe incorporating a cylindrical bore that cooperates with the spherical bearing surface and has two opposed rolling tracks, and
two series of rolling members each of which rolls on a rolling track of the female member and on a rolling track of the shoe.
The invention applies in particular to side drives of automobile vehicles.
When a tripod joint is operating at a break angle, the center of the tripod is known to describe a so-called “offset” orbital movement at a frequency three times the speed of rotation of the joint. Moreover, under the same conditions, each arm is displaced radially relative to the associated rolling tracks of the female member.
To obtain very free sliding of the joint whilst allowing for the above phenomena, FR-A-2 580 751, 2 628 803 and 2 703 416 propose providing each arm with a spherical bearing surface and disposing an intermediate bar and a series of rolling members between each side of the arm and the associated rolling track.
However, when the joint is operating out of alignment, the two phenomena referred to above cause geometrical play to appear in the mechanism and this play is proportional to the break angle of the joint. To mask this play as much as possible, an elastic spreader is used between the two bars associated with each journal in order to press the rolling members at all times against their respective rolling tracks. This spreader is bulky, however, and makes the structure of the joint more complex.
To eliminate the spreader and therefore to simplify the construction of the joint, DE-A-40 24 534 proposes a joint of the type indicated at the start of this description. In a joint of the kind concerned the two bars are replaced by a one-piece intermediate shoe. The radial displacement of the center of the spherical bearing surface associated with each of the arms of the tripod then requires a cylindrical circular bore in the shoe.
This design nevertheless has certain drawbacks. In particular, for each drive direction, only one series of rolling members is operative and there is play due to manufacturing tolerances on the opposite side. Consequently, noise is generated on reversing the rotation direction.
An object of the invention is to eliminate this latter disadvantage in a particularly simple and economic manner.
SUMMARY OF THE INVENTION
To this end, the invention provides a constant velocity joint of the above kind characterized in that the bearing distance between the center of the spherical bearing surface of each arm and the main axis of the male member is significantly different, for each rotation direction of the joint, from the rolling distance between the main axis of the mean plane of the rolling members associated with the same arm and transmitting torque in the direction concerned so that in operation the two series of rolling members are loaded regardless of the direction of the applied torque even when the joint is aligned.
It is particularly advantageous if the bearing distance is significantly greater than the rolling distance. The following important additional advantages are then obtained:
Firstly, the torque transmission lever arm being increased, the contact pressure between the spherical bearing surfaces and the cylindrical bores is reduced. This reduces the risks of indentation and even of binding.
The outward offsetting of the spherical bearing surfaces, exploiting the space made available by eliminating the spreader, frees up space towards the axis of the tripod. This significantly increases the mechanical strength of the area where the arms join to the hub of the tripod, generally subject to the provision of a clearance, such as a bevel, in the radially interior part of the bore in the intermediate shoe.


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