GB2345331A - Tripod joint - Google Patents

Abstract

In a tripod joint an inner sleeve 2 has radially extending journals 3, which carry rollers 4, each journal having a cavity 6. To save weight while retaining the same strength, at least one stiffening element is provided in the cavity 6, which reinforces the journal 3 in the peripheral direction of the tripod joint. The stiffening element may be at least one rib 5 and/or a resin (8, Fig 9) or the like substantially completely filling the space.

Description

TRIPOD JOINT The present invention relates to tripod joints. In particular the invention relates to joints of this type for use in high-performance applications in the automobile industry.

Tripod joints transmit torque via journals which protrude radially from an inner sleeve and on which rollers are mounted rotatably and displaceably in the longitudinal direction of the journals on longitudinal recesses of an outer casing, in which the rollers roll or slide without play, the inner sleeve being articulated with respect to the outer casing.

Because of the construction of a tripod joint of this type, load is applied to the journals only by the torque to be transmitted, i. e. substantially in the peripheral direction, since in all other directions forces act which are induced only by friction or inertia and which are negligibly small compared with the torque to be transmitted.

In the application sector mentioned in the introduction it is of great importance for each individual component used to be designed to be as light as possible and, therefore, the idea has already emerged of making the journals of the tripod joint hollow, thereby reducing their mass. However, because of the necessity to be able to bear the torques to be transmitted, a limit is imposed on the design of the hollow spaces which makes possible only a relatively small weight saving.

It is the object of the invention to increase this mass and therefore the weight saving, without likewise increasing the loss of strength.

According to the invention, this is achieved in that a stiffening element reinforcing the journal in the peripheral direction of the tripod joint is provided in the hollow space of the journal of the tripod joint.

This element may comprise an individual rib or a plurality of ribs or also a filler material of low density but of high mechanical durability, which substantially fills the hollow space.

The invention will be illustrated in more detail below with reference to the drawings, wherein: Figure 1 shows the inner spider of a tripod in a view along its axis; Figure 2 shows a section along the line II-II in Figure 1; Figure 3 shows an enlarged section through a part of the tripod spider along the line III-III in Figure 2; Figure 4 shows a graph of the improvement in load-bearing capacity to be achieved with the invention ; Figure 5 shows a section along the line V-V in Figure 3 through a conventional hollow journal of a tripod joint, and Figures 6 to 9 show purely schematic developments according to the invention of such a journal in a section similar to that in Figure 5.

As is evident from Figure 1, the inner part of a tripod joint, also termed the spider 1, substantially comprises an annular base member 2 and several radially projecting journals 3. Each journal carries a roller 4 which rolls or slides in recesses in the counterpart of the spider 1. This counterpart does not concern the invention and, therefore, is not illustrated.

The forces to be transmitted by a joint of this type are essentially the prevailing torques which occur at the journals 3 as forces which lie in the drawing plane of Figure 1 and which subject the journals substantially to bending loads and/or to shear loads at their base.

For reasons associated with weight saving, it is already known to make the journals hollow to a certain extent. A journal of this type with a hollow space 6 is illustrated in normal section in Figure 5.

To enable the mechanical load-carrying capacity of such a journal to be increased or the hollow space to be enlarged, without further reducing the mechanical load-carrying capacity, according to the invention it is proposed to provide a stiffening element 5 in the hollow space 6 of the journal 3.

Essentially this stiffening element only has to transmit forces which lie in the drawing plane of Figure 1 and, therefore, according to the invention is preferably in the form of a rib 5.

Figure 3 shows a section along the line III III in Figure 2 on an enlarged scale and illustrates only one journal 3. In this section to illustrate the stiffening provided, despite its small extension, the rib 5 is also illustrated in section transversely to the drawing plane. Additionally, the mounting of the rollers 4 on the journal 3 by means of needle-roller bearings 7 is indicated schematically.

Figure 6 shows a section along the line V-V in Figure 3, in which the applied peripheral force F, by which the torque is transmitted, is indicated so as to make clear the orientation of the rib 5 provided according to the invention.

Figure 7 shows a variant in which two ribs 5' are provided; in the embodiment according to Figure 8 two ribs are also provided but these ribs 5"are arranged in the manner of an arrowhead in relation to one another, whereby forces lying transversely to the force F can also be transmitted and the stability can be further increased.

Figure 9 illustrates an embodiment in which as a stiffening element a substance is used which at least substantially completely fills the hollow space 6 and because of its composition and density provides a satisfactory increase in the mechanical durability with a satisfactory weight saving.

Substances of this type may, for example, be those which are used as filling material in the construction of sandwich materials. These are resin mixtures which are interspersed with carbon fibres, thereby achieving outstanding mechanical stability with extremely low weight.

As an example of such a substance it is possible to indicate epoxy resin or phenol resin, to which carbon fibres are added. In the finished mixture the carbon fibres preferably assume 60% by volume of the mixture.

Such substances can be poured into the hollow space 6 either in the liquid or pasty state and allowed to solidify therein; they can also be prefabricated and glued in the hollow space 6 using appropriate adhesives. In both cases it is essential that there is sufficiently intimate contact between the inner surface of the hollow space 6 and the outer surface of the filler material in the finished condition so as to counteract, ab initio, deformation of the journal 3.

The increase in strength which can be achieved with the invention is illustrated in Figure 4, wherein for a given force the deformation is indicated (in mm) over the journal length (in mm, measured from the outer periphery of the base member 2). As is evident from the graph, this deformation is almost halved, which signifies an enormous increase in strength.

Both the hollow space and the ribs can be produced by electro-discharge machining and no significant problems arise in the use of this machining process. Of course, it is possible to prepare the hollow space 6 without ribs, as illustrated in Figure 5, and then glue the ribs or rib used in place or locate them or it by frictional grip; however, when providing one or more ribs the integral design is preferred.

Similarly, when providing a filling in accordance with Figure 9, which can also be effected by appropriate design of the surface (providing a minimum roughness for improved adhesion of the casting or filler material) and also, for example, by providing a constriction of the hollow space 6 outwards, at least in a small region of the hollow space, a form-locking securing feature is created for the filler material.

Of course, it is not necessary for the hollow space 6 to be given a circular cross-section. In particular, when using one or more ribs the wall region of the journal, which extends approximately parallel to the force F, can be chosen to be thinner since the rib or ribs are supporting in this direction.

It is also not necessary for the base portion of the hollow space to be of the form illustrated bu- it can be adapted to special requirements. Finally, even when using one or more ribs 5 it is possible to fill the remaining hollow space 6 with a filler substance.

Claims (9)

Claims

1. A tripod joint having an inner sleeve, journals which protrude radially therefrom, which carry rollers and which have a hollow space, and with an outer casing having recesses in which the rollers roll and/or slide, wherein the inner sleeve is articulated relative to the outer casing, wherein at least one stiffening element is provided in the hollow space, which reinforces the journal in the peripheral direction of the tripod joint.

2. A tripod joint according to Claim 1, wherein the stiffening element is at least one rib.

3. A tripod joint according to Claim 2, wherein the stiffening element is two mutually parallel ribs.

4. A tripod joint according to Claim 2, wherein the stiffening element is two ribs arranged Vshaped in relation to one another.

5. A tripod joint according to Claim 1, wherein the stiffening element comprises a filler material of low density but high mechanical durability, which substantially fills the hollow space.

6. A tripod joint according to Claim 5, wherein the filling materiai consists of a mixture of resin and carbon fibres.

7. A tripod joint according to Claim 6, wherein the resin is an epoxy resin or a phenol resin.

8. A tripod joint according to any one of the preceding Claims, wherein the hollow space is not of circular cross-section.

9. A tripod joint substantially as hereinbefore described with reference to and as illustrated in Figures 1-4 and 6-9.

9. A tripod joint substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Amendments to the claims have been filed as follows Claims

1. A tripod joint comprising an inner part, which is articulated relative to an outer part in use, and journals which protrude radially from the inner part, the journals carrying rollers for rolling and/or sliding in an outer part in use, each journal enclosing a chamber therein, wherein at least one stiffening element is provided in each chamber to reinforce the journal in the peripheral direction of the tripod joint.

2. A tripod joint according to Claim 1, wherein the stiffening element is at least one rib.

3. A tripod joint according to Claim 2, wherein the stiffening element is two mutually parallel ribs.

4. A tripod joint according to Claim 2, wherein the stiffening element is two ribs arranged Vshaped in relation to one another.

5. A tripod joint according to Claim 1, wherein the stiffening element comprises a filler material of low density but high mechanical durability, which substantially fills the chamber.

6. A tripod joint according to Claim 5, wherein the filling material consists of a mixture of resin and carbon fibres.

7. A tripod joint according to Claim 6, wherein the resin is an epoxy resin or a phenol resin.

8. A tripod joint according to any one of the preceding Claims, wherein the chamber is not of circular cross-section.