GB2080490A

GB2080490A - Homokinetic joint of the tripod type

Info

Publication number: GB2080490A
Application number: GB8122012A
Authority: GB
Original assignee: Glaenzer Spicer SA
Current assignee: Glaenzer Spicer SA
Priority date: 1980-07-18
Filing date: 1981-07-15
Publication date: 1982-02-03
Also published as: IT8167996A0; GB2080490B; DE3128389A1; JPH0118295B2; FR2487022A1; FR2487022B1; ES268145Y; ES268145U; IT8153456V0; JPS5751020A; DE3128389C2; IT1144400B

Abstract

The homokinetic joint is of the tripod type in which the tripod is axially retained by an elastically yieldable attachment. In the free state of the joint, each branch (15) of the attachment (12) has a curved shape and extends alongside the corresponding petal portion (11) of the tulip element (4) of the joint with a radial clearance in substantially all of its length. In this way, the attachment can itself ensure a precise prestressing of the tripod element against the inner end of the tulip element while it is capable of resisting abnormally high axial forces. Application in the driving of front wheel drive vehicles. <IMAGE>

Description

SPECIFICATION Homokinetic joint of the tripod type The present invention relates to homokinetic joints of the tripod type comprising a tulip element and a tripod element whose centre portion is mounted to swivel with a radial freedom of movement against the inner end of the tulip element and is maintained pre-stressed against said inner end by an elastically yieldable attachment, the latter comprising branches whose free end portions are anchored on the petals of the tulip element. These homokinetic joints are usually employed for driving the steering and driving wheels of front wheel drive vehicles.

It is known that, in order to avoid the axial movements of the yoke or tulip element relative to the tripod element, which movements may result from alternating forces produced by the drive unit, the state of the road and various frictions, and also by the very operation of the joint which operates under torque and at an angle, the retaining attachment or clip must be capable of taking up the axial clearance or play of the assembly and establishing moreover a permanent axial prestress of given value which applies the centre portion of the tripod element against the inner end of the tulip element, notwithstanding machining tolerances of the component parts and wear which may occur after a long period of utilization of the joint, and without creating axial elasticity between the tripod element and the tulip element.

Further, the obtainment of this pre-stress must not have for consequence the creation of a substantial resistance to the correct operation of the joint which would have a harmful effect on the smoothness of the articulation. The elastically yieldable attachment must also be capable of withstanding abnormally high axial forces without deterioration.

ln order to satisfy all these requirements, it has been proposed to complete the clip with various clearance taking up devices. However, the known arrangements, for example that described in French patent NO 77 26873, have very considerable drawbacks for mass-production, namely: increase in the number of component parts to be assembled within the homokinetic joint; necessity of particular adjustment and checking in respect of each component part: increased assembly and checking time and cost and risks of errors; necessity to complicate and alter one of the main component parts of the joint, namely the tripod element, for the purpose of placing the clearance taking up devices which reduces the strength and increases the cost of this tripod element.

An object of the invention is to provide a joint having an axial retention in which the elastically yieldable attachment itself ensures, in a simple and cheap manner, and under satisfactory conditions, the function of the clearance taking up device and the axial pre stressing of the centre portion of the tripod element against the inner end of the tulip element with no interposition of an additional elastically yieldable element between these two main component elements of the joint.

Accordingly, the invention provides a homokinetic joint of the aforementioned type, wherein, in the free state of the joint, each branch of the attachment has a curved shape and is disposed alongside the corresponding petal portion of the tulip element with a radial clearance over a length which is sufficient to possess high axial flexibility for axial forces within a low range of values and, a much lower axial flexibility in the case of axial forces above said range, in respect of which the branch is applied against the petal portion.

Preferably, in order to render the assembly of the joint particularly convenient, each anchoring point is located in the region of the inner ends of the runways of the tulip element. In this case, it is very advantageous, when assembling the joint, to employ a tool comprising a lever whose terminal end portion comprises, on one hand, two projections for bearing against the end of the runways of the tulip element and, on the other hand, means for seizing the free end portion of the or each corresponding branch of the elastically yieldable attachment.

Further features and advantages of the invention will be apparent from the ensuing description which is given merely by way of example with reference to the accompanying drawings in which: Fig. 1 is a longitudinal sectional view of a homokinetic joint according to the invention; Fig. 2 shows the variations in the axial force as a function of the axial deflection of the elastically yieldable attachment; Figs. 3 and 4 are elevational views, in two directions perpendicular to each other, of the tulip element of said joint, these views illustrating the assembly of the elastically yieldable attachment; Fig. 5 is a view similar to Fig. 1 of a modification of the homokinetic joint according to the invention; Figs. 6 and 7 show respectively in end elevation and side elevation the elastically yieldable attachment of the homokinetic joint of Fig. 5;; Figs. 8 to 10 are partial longitudinal sectional views of three other modifications of the homokinetic joint according to the invention.

The homokinetic joint 1 shown in Fig. 1 connects a suspended transmission shaft 2 to the stub-axle 3 of a front driving wheel of a front-drive vehicle. It comprises a tulip element or yoke 4 which is rigid with the shaft 2 and a bowl element 5 rigid with the stub-axle 3. The tripod element 6 of the joint is a spider having three coplanar radial arms whose centre is formed by a spherical ball 7 rigid with the arms, the ends of the latter being fixed to the entrance portion of the bowl element 5. Each arm 8 carries an externally part-spherical roller 9 which is rotatable and slidable on the arm.

The roller 9 is received in a runway 10 having a part-circular section provided in the tulip element and extending parallel to the axis of the latter.

Each runway comprises two confronting tracks machined on the edges of two of the three petal portions 11 of the tulip element, said petal portions having a general orientation parallel to the axis X-X.of the shaft 2 and extending in a direction away from said shaft.

The joint further comprises an elastically yieldable attachment or clip 1 2 for axially retaining the tripod element fixed to the tulip element, and a gaiter 13 fixed in a sealed manner, on one hand, to the entrance peripheral portion of the bowl element 5 and, on the other hand, to the shaft 2.

The elastically yieldable attachment 12 is made in a single piece from an elastically yieldable metal sheet, for example of spring steel. It has, as the whole of the joint, a ternary symmetry about the longitudinal axis X-X of the joint which is assumed to be in perfect alignment. It has a pressed-out centre region 14 in the shape of a cup from the periphery of which extend three elastically yieldable very elongated branches.

The cup 14 has a planar inner end 1 6 in contact with the ball 7 and urging the latter against the planar inner end 1 7 of the tulip element, the inner ends 1 6 and 1 7 being both perpendicular to the axis X-X. The lateral wall of this cup comprises three very divergent portions 1 8 which connect the inner end portion 1 6 to the root of the branches 14 and, between said portions 18, three portions 1 9 which extend roughly axially.

Each branch 1 5 has a convex longitudinal profile. Its root is guided in the circumferential direction by the edges of a recess 20 formed in the outer surface of the free end portion of a petal portion 11 without however touching the inner end of said recess. Then the branch 1 5 extends alongside the outer surface of the petal portion with a small radial clearance to a cavity 21 in which its free enlarged end portion 22 is elastically disposed. This end portion 22 constitutes the point of anchorage of the branch.

The cavities 21 are located with respect to the axis X-X in the region of the inner ends of the runways 22, i.e. close to the root of the petal portions 11 where the latter are reduced in thickness and have surfaces 23 having an axial component facing the shaft 2 (Figs. 3 and 4).

The axial flexibility of the attachment 12 is shown in Fig. 4. When the axial force F increases, the curvature of the branches 1 5 decreases until these branches come in contact with the outer surface of the petal portions 11. Beyond this, the branches 1 5 are practically only subjected to tensile stress and the force is transmitted thereto through the axial portions 1 9 of the cap 14 so that the attachment becomes very rigid and is capable of withstanding considerable forces.

Owing to these properties, it is very easy to satisfy the following two conditions: the maintenance of the aforementioned radial clearance between the branches 1 5 and the petal portions 11 in the free state of the joint, which ensures a low variation in the pre-stressing from one joint to another, notwithstanding the manufacturing tolerances, and capacity of the attachment to withstand high axial forces without breaking or becoming separated from the tulip element.

This is achieved with an overall size which is small enough to enable the joint to operate under the required large angles and with no cost, great ease of manufacture and high reliability.

By way of a numerical example, in respect of a joint having average dimensions, the attachment 12 has an axial flexibility of about 1.5 mm for a force of about 1 50 kg, whereas the axial pre stressing is of the order of 60 to 1 50 kg. The branches 1 5 come in contact with the outer surface of the tulip element for a force exceeding about 200 kg and the attachment can withstand forces of the order of 1 500 kg which enables it to withstand without risk of fracture abnormal axial forces which might occur.

The assembly of the joint is rendered particularly easy because the end portions 22 of the branches 1 5 extend out of the bowl element 5 when the protective gaiter 13 is withdrawn. In particular, the tool shown In Figs. 3 and 4 may be employed. This tool comprises a lever 25 whose terminal end portion 26, which is slightly upwardly bent and enlarged, carries three roughly transversely aligned cylindrical pins 27 on its lower surface.

In order to assemble the joint, the attachment 12 is disposed ready within the bowl element 5 and the tulip element 4 is inserted into the latter.

In doing this, the branches'5, which are guided by the recesses 20, reach the vicinity of the cavities 21 and an axial force of 60 150 - 20 kg to ---- = 50 kg 3 3 must be exerted on each one thereof in order to achieve the desired pre-stressing.

For this purpose, the two end pins 27 of the tool 25 are placed against the two surfaces 23 of a petal portion 11 and the centre pin 27 Is hooked in an aperture 28 provided In the enlarged portion 22 of the corresponding branch 1 5. By means of a simple rotation of the lever 25 toward the shaft 2, in the direction of arrow fof Fig. 3, this enlarged portion 22 is then brought into the cavity 21 provided therefor. The operation is then repeated for the other two branches 15.

By way of a modification, the three branches 1 5 may be mounted more rapidly and simultaneously by means of more elaborate tooling (not shown), for example actuated hydraulically, which is preferable for an automatic assembly in massproduction of the joint.

Similar branches 1 5 may be employed with other types of elastically yieldable attachments for the axial retention with pre-stressing of a tripod element with the same advantages. Figs. 5 to 10 show several of these attachments.

The joints lea to 1 d of Fig* 6 to 10 are of the meniscus type. The centre portion of the spider of the tripod element 6a has two opposed planar surfaces perpendicular to the axis X-X, each of which is in contact with the planar surface of a part-spherical or meniscus dome 7a. The inner meniscus engages an adjacent part-spherical surface 1 7a provided in the inner end of the tulip element so as to swivel on this surface 1 7a and the other meniscus is engaged to swivel on a partspherical surface 1 6a on the elastically yieldable attachment.

In the joint 1 a shown in Fig. 5, the surface 1 6a is formed by the whole of the edge of part-circular profile of three axial webs 29 of the elastically yieldable attachment 1 2a (Figs. 6 and 7) which is made from a single piece by a press operation on a steel sheet which is very cheap. Each web 29 connects the adjacent edges of two branches 1 5 by passing through an edge of a planar and triangular centre zone 30 of the attachment. The outer edges of the webs 29 are rectilinear and centre the centre portion of the elastically yieldable attachment with respect to the inner bore 4a of the tulip element.

In the joints 1 b to 1 d shown in Figs. 8 to 10, the elastically yieldable attachment is made in two parts, namely: an elastically yieldable part of folded and hardened sheet metal comprising the three branches 1 5 and a centre region, and a centre pivotal bearing member which is separate and has a concave part-spherical surface and is self-centered by its outer edge inside the petal portions 11, i.e. in the bore 4a.

In Fig. 8, the centre portion 31 b of the elastically yieldable member 32b is planar and the centre pivotal bearing member 33b is a block of hardened steel or of another material which results in a good sliding of the adjacent meniscus 7a, this block bearing against the centre portion 31 b by a planar surface.

In Fig. 9, the centre pivotal bearing member 33c comprises a part-spherical web 34 and six axial webs 35, each of which axial webs bears against the centre region 31 c of the elastically yieldable member 32c only by its radially outer end in order to achieve stability.

In the joint 1 d shown in Fig. 10, each branch 1 5 of the elastically yieldable member 32d is extended inside the corresponding petal portion 11 by an axial extension 36 and the centre portion 31 d is hollowed out in a similar manner. The centre pivotal bearing member 33d is a partspherical web which has on its edge an outer shoulder 37 which bears axially against the ends of the extensions 36.

In each embodiment, the branches of the attachment may be shorter than illustrated, provided that the condition of double flexibility mentioned hereinbefore is respected.

Claims

1. A homokinetic joint of the tripod type comprising a tulip element and a tripod element whose centre portion bears against the inner end of the tulip element so as to swivel relative to said inner end with freedom of radial movement and is maintained pre-stressed against said inner end by an elastically yieldable attachment, said attachment comprising branches whose free end portions are anchored on the petal portions of the tulip element, wherein in the free state of the joint, each branch of the attachment has a curved shape and extends alongside the corresponding petal portion of the tulip element with a radial clearance over a length which is sufficient to impart thereto high axial flexibility in respect of axial forces within a low range of values and a much lower axial flexibility in the case of axial forces above said range, in respect of which the branch bears against the petal portion.

2. A homokinetic joint according to claim 1, wherein, in the free state of the joint, each branch has a convex shape and is in contact with the corresponding petal portion solely at its point of anchorage to said petal portion.

3. A homokinetic joint according to claim 1 or 2, wherein the elastically yieldable attachment has a roughly axial portion which transmits the axial forces of the centre of the tripod element to the branches.

4. A homokinetic joint according to claim 1, 2 or 3, wherein the elastically yieldable attachment is made in one piece and comprises a centre region in the shape of a cup which has an inner end which bears against the centre portion of the tripod element.

5. A homokinetic joint according to claim 1, 2 or 3, wherein the elastically yieldable attachment is made in a single piece and comprises in its centre region axial webs which bear against the centre portion of the tripod element.

6. A homokinetic joint according to claim 1, 2 or 3, wherein the elastically yieldable attachment bears against the centre portion of the tripod element through an attached member.

7. A homokinetic joint according to any one of the claims 1 to 6, wherein each anchoring point is located in the region of the inner ends of the runways of the tulip element.

8. A tool for assembling a joint according to claim 7, said tool comprising a lever having a terminal end portion which has, on one hand, two projecting portions for bearing against the end portions of the runways of the tulip element and, on the other hand, means for seizing the free end portions of the or each corresponding branch of the elastically yieldable attachment.

9. A tool according to claim 8, wherein said projections and said seizing means are pins which are roughly aligned with each other in a direction perpendicular to the general axis of the lever, the free end of each branch of the elastically yieldable attachment being provided with an aperture.

1 0. A homokinetic joint of the tripod type comprising a tulip element and a tripod element, substantially as hereinbefore described with reference to and as shown in Figs. 1 and 2, or Figs.

3 and Fig. 4, or Fig. 5, or Fig. 6, or Fig. 7 of the accompanying drawings.

11. A tool for assembling a homokinetic joint of the tripod type comprising a tulip element and a tripod element, substantially as hereinbefore described with reference to and as shown in Figs.

3 and 4 of the accompanying drawings.