BI-MATERIAL CAGE COMPRISING BEARINGS, FOR A BALL JOINT

Abstract

A method for producing a cage for a ball joint of a vehicle that includes a step of injecting a first material via a first injection point so as to form a shell that encloses at least one housing, on a substantially spherical inner surface and a step of injecting a second material via a second injection point so as to form a contact zone in the housing of the shell.

Claims

1. A method for manufacturing a cage for a ball joint of a vehicle, comprising: a step of injecting a first material through a first injection point, so as to form a shell comprising at least one housing on a substantially spherical inner surface; a step of injecting a second material through a second injection point, so as to form a contact zone in the housing of the shell.

2. The method for manufacturing a cage for a ball joint according to claim 1, wherein the second material circulates in at least one channel between the second injection point and the at least one housing.

3. The method for manufacturing a cage for a ball joint according to claim 1, comprising after the step of injecting a first material, a step of ejecting the shell from a first mold and a step of positioning the shell in a second mold.

4. The method for manufacturing a cage for a ball joint according to claim 1, comprising after the step of injecting a first material, a step of extracting a first core from a shell mold and a step of inserting a second core into the shell.

5. A cage for a ball joint of a vehicle manufactured by the method of claim 1, including a shell made of a first material and at least one contact zone made of a second material positioned integrally on a substantially spherical inner surface of the shell.

6. The cage for a ball joint according to claim 5, wherein the at least one contact zone is surrounded by the inner surface of the shell.

7. The cage for a ball joint according to claim 5, wherein the at least one contact zone forms a relief relative to the inner surface.

8. The cage for a ball joint according to claim 5, wherein the at least one contact zone is connected to a second injection point (34) by at least one channel.

9. The cage for a ball joint according to claim 8, wherein the at least one channel is in the same plane as the inner surface.

10. The cage for a ball joint according to claim 5, wherein the first material is a material whose Young's modulus is greater than 10,000 MPa.

11. The cage for a ball joint according to claim 5, wherein the second material is a material whose Young's modulus is in the range of 3,000 MPa.

Description

[0052] The invention will be better understood, thanks to the following description, which relates to an embodiment according to the present invention, given by way of non-limiting examples and explained with reference to the appended schematic drawings, in which:

[0053] FIG. 1 is a sectional view of a shell for a ball joint according to the invention;

[0054] FIG. 2 is a retaining tab of a shell for a ball joint according to the invention.

[0055] A shell 1 for a ball joint, as represented in FIG. 1, is manufactured using a method comprising a step of injecting a first material.

[0056] The first material constituting the shell 1 has mechanical properties allowing resistance of the shell 1 to mechanical forces and temperatures undergone in a vehicle power steering system. The Young modulus of the first material is greater than 10,000 MPa such as polyetheretherketone (PEEK) or a mixture of polymers from the group of polyphthalamides (PPA) loaded with glass or carbon fibers for example.

[0057] The first material is injected through a first injection point 22 in liquid to viscous form into a mold. The mold comprises a female portion cooperating with a first core. The female portion comprises a spherical cavity and the first injection point 22. The first core comprises a spherical element, cooperating with the spherical cavity of the female portion, on which shoulders extend.

[0058] The shell 1 produced during the step of injecting a first material comprises a substantially spherical cavity with a defined radius R1 having a substantially circular opening. The cavity is formed by 5 identical retaining tabs 43, as can be seen in FIG. 2, extending in a homogeneous manner from a bottom 23 opposite the opening. The bottom 23 comprises the first injection point 22.

[0059] An axis of rotation YY of the cavity is defined, as an axis perpendicular to the bottom 23.

[0060] An equator XX of the cavity is defined as an axis XX perpendicularly crossing the axis of rotation YY at a distance equal to the radius R1 of the cavity from the bottom 23.

[0061] A retaining tab 43 has a lateral edge 44 separated from a lateral edge 44 of an adjacent retaining tab 43 by a notch 42.

[0062] A portion of the retaining tab 43 comprised between the bottom 23 and the equator XX of the cavity will be called a lower zone and, a portion of the retaining tab 43 comprised between the equator XX of the cavity and the opening will be called an upper zone.

[0063] Each lower zone of a retaining tab 43 includes a housing 33 with a depth of 0.28 mm, extending 4 mm from the equator of the cavity XX, 2 mm from the bottom 23 and 2 mm from each of the lateral edges 44 of the retaining tab 43.

[0064] Each upper zone of the retaining tab 43 includes two elongations 4 separated by a notch 41 extending along the axis of rotation YY. Each elongation 4 includes a housing 31 with a depth of 0.28 mm, extending 1.5 mm from the equator of the cavity XX, 1.5 mm from the opening and 1.5 mm from each of the lateral edges 44 of the elongation.

[0065] Each housing 31 of each elongation 4 of a retaining tab is connected by a channel 32 to a housing of the lower zone of the retaining tab 43, itself connected to a second injection point 34 formed in a thickness of the shell 1 on the axis of rotation YY by another channel 32.

[0066] The housings 33, 31 and the channels 32 are formed by the shoulders of the first core.

[0067] When the shell 1 is solidified, the manufacturing method performs a step of extracting the first core from the mold and then a step of inserting a second core into the shell 1.

[0068] The second core comprises a spherical element with a diameter substantially similar to that of the spherical element of the first core allow cooperating with the spherical cavity of the shell 1. The spherical element of the second core comprises recesses facing the housings 31, 33 of the shell 1.

[0069] Then, the manufacturing method performs a step of injecting a second material.

[0070] The second material has sliding properties better than the first material but has a Young modulus in the range of 3,000 MPa such as polyoxymethylene (POM).

[0071] Thus, the second material flows when it is subjected to mechanical and temperature stresses such as those of a vehicle steering.

[0072] The second material is injected through the second injection point 34 in liquid to viscous form into the mold. The second material flows from the second injection point 34 into the channels 32 of the shell 1 so as to fill the housings 33, 31 of the shell 1 and the recesses of the second core. Thus, the second material present in the housings 31, 33, hereinafter called contact zones, forms a relief with a thickness of 0.02 mm relative to an inner surface 21 of the retaining tabs 43. The second material present in the channels 32 is flush with the inner surface 21.

[0073] A shell 1 whose housings 31, 33 are filled with the second material will be called a cage thereafter.

[0074] When the second material is solidified, the cage is ejected from the mold.

[0075] Finally, a step of assembling the ball joint consists of inserting a head for a ball joint in the cage so as to create, for example, a vehicle steering ball joint or a suspension ball joint.

[0076] During assembly, the head for a ball joint comes into contact and partially crushes the contact zones. Thus, the head is perfectly adjusted in the cage.

[0077] When the ball joint is under compressive stress, the head is designed to come into contact with the contact zones of the lower zones of the retaining tabs 43.

[0078] When the ball joint is under tensile stress, the head is designed to come into contact with the contact zones of the upper zones of the retaining tabs 43.

[0079] Of course, the invention is not limited to the embodiments described and represented in the appended figures. Modifications remain possible, in particular from the point of view of the constitution of the various elements or by substitution of technical equivalents, without thereby departing from the scope of protection of the invention.