FR3069294A1 - METHOD FOR MANUFACTURING A MONOBLOC MONOBLOC METAL RING OF SMOOTH OR BEARING BEARING, AND BEARING COMPRISING AT LEAST ONE RING OBTAINED BY THE PROCESS - Google Patents

Abstract

To manufacture a one-piece (12, 14, 14.1, 14.2) plain bearing or rolling bearing metal ring (10) having at least one open-pore structural metal foam zone (12B, 14B, 14.1B, 14.2B) and a peripheral solid area (12A, 14A, 14.1A, 14.2A) at least partially covering the metal foam area (12B, 14B, 14.1B, 14.2B), at least a portion of the peripheral solid area (12A, 14A, 14.1A, 14.2A) constituting an annular guide track (18, 18.1, 18.2, 20, 20.1, 20.2), a manufacturing step is carried out by casting of a blank comprising the metal foam zone with a regular structure (12B , 14B, 14.1B, 14.2B) and an unfinished peripheral full area, followed by a finishing step of the full peripheral area (12A, 14A, 14.1A, 14.2A), the finishing step of the solid area device having at least one finishing step of the annular guide track (18, 18.1, 18.2, 20, 20.1, 20.2). For the casting step, a destructible core (58) having open pores is inserted into a casting mold (52), a void volume (60) being preserved between the destructible core (58) and at least one wall of the mold and casting a molten metal material into the casting mold (52) so that the molten metal material fills the void volume (60) and the open pores of the destructible core (58), and destroys the destructible core. (58) after solidification of the metallic material.

Description

METHOD FOR MANUFACTURING A LIGHTWEIGHT MONOBLOCK SMALL OR ROLLING BEARING RING, AND BEARING COMPRISING AT LEAST ONE RING OBTAINED BY THE METHOD

TECHNICAL FIELD OF THE INVENTION The invention relates to the manufacture of a lightened guide ring for a plain or rolling bearing, this ring comprising an annular guide track, which can be a sliding track for a plain bearing or a raceway for a rolling bearing.

STATE OF THE PRIOR ART The bearings used to guide the rotation of the robot arms are generally very rigid, since they are subjected to strong accelerations and forces in variable directions, and must guarantee high performance in terms of precision. This results in massive steel constructions, which have a high mass and moment of inertia. However, there is a class of applications that are less demanding in terms of rigidity, and which would take advantage of less massive bearings. This application class includes, for example, personal assistance robots or collaborative robots.

In document US2002174545 is disclosed a lightened bearing module suitable for this class of applications, which comprises composite bearing rings, consisting of steel raceways welded by diffusion on the bodies of light alloy rings. The ring bodies provide the interface functions of the module to the external elements of the robot arm and are therefore provided with fixing holes. The steel raceways provide the guiding function in rotation. But the reduction is obtained at the price of a particularly complex and expensive manufacturing process.

In document FR3032017 there is provided a bearing module comprising: an outer steel bearing ring defining a reference axis and forming an annular outer raceway turned radially inward, a first inner steel bearing ring forming a first annular inner raceway facing radially outward facing the outer raceway, an outer interface ring of light alloy, integral with the outer race ring, an inner interface ring of light alloy, integral with the first inner race, and with the first rolling bodies circulating on the outer race and on the first inner race to guide a relative movement of rotation between the outer interface ring and the inner interface ring around the reference axis. Remarkably, the outer interface ring is a single piece forming a hooping surface turned radially inward and extending axially from a transverse bearing shoulder of the outer interface ring to a flap of material, the outer interface ring projecting radially inwards relative to the hooping surface of the outer interface ring, the outer bearing ring being hooped in the hooping surface of the outer interface ring, in direct or indirect support against the transverse bearing shoulder of the outer interface ring and against the material flap of the outer interface ring. Similarly, the inner interface ring is a single piece forming a hooping surface facing radially outward extending from a bearing shoulder of the inner interface ring to a flap of material of the inner interface ring projecting radially outward relative to the hooping surface of the inner interface ring, the first inner bearing ring being hooped on the hooping surface of the inner interface ring, in abutment direct or indirect against the transverse bearing shoulder of the inner interface ring and against the material flap of the inner interface ring. By light alloy is meant here in particular an alloy less dense than the steel of the bearing rings, in particular an aluminum or titanium alloy, having sufficient ductility for the formation of a flap of material. The light alloy may be different for the inner interface ring and the outer interface ring.

However, this solution requires taking into account the differential thermal expansion between the steel bearing rings and the light alloy interface rings, which induces stresses in the hooping. This thermal behavior can be accentuated in particular if the gearmotor which drives the robot arm has poor efficiency and causes overheating. In addition, the requirements for dimensional tolerances can be difficult to meet with a light alloy and a hooped assembly.

In document W02014166486 is described a guide ring for a plain or rolling bearing, this ring comprising a load zone, a fixing zone, and an intermediate damping zone between the load zone and the zone of fixation. The load area forms an annular guide track, which can be a sliding track for a plain bearing or a raceway for a rolling bearing. The attachment zone can form a hooping surface. The intermediate damping zone consists of one or more cavities, filled with a filling material which can be a metallic foam. It is envisaged to fabricate these three areas separately before assembling them, or to fabricate them in one piece. However, the filling material is in any case made up independently of the load, fixing and damping zones and is assembled so as to fill the cavities. The cavities of the intermediate damping zone are separated from each other by bridges of material which connect the fixing zone to the load zone, these bridges of material ensuring the structural rigidity of the ring. Thus, the filling material plays no role in the transmission of static charges and does not respond to a problem of lightening the ring. It essentially contributes to giving the guide ring the desired acoustic damping properties.

In document DE 10 2016 123 017 is described a bearing ring on which a guide track is formed, and which comprises one or more cavities, which can in particular form a honeycomb structure. This ring can be in one piece, if necessary made of metal. It is proposed to manufacture this ring by an additive manufacturing process or by sintering. However, such methods appear to be hardly compatible with a high production rate.

In document FR 2 921 281 is described a method of manufacturing a foundry piece combining solid areas and areas made of metal foam, using a preform made up of aggregated elements defining between them interstices. This preform is placed in a mold leaving an empty volume between the preform and a wall of the mold, and molten metal is poured into the mold, so that it infiltrates on the one hand into the interstices of the preform where it constitutes a metallic foam zone, and on the other hand fills the empty volume where it constitutes a solid zone of the part. After the metal has solidified, the preform is destroyed and removed. Document FR 2 927 269 specifies a possible structure of the preform, which facilitates its destruction and its evacuation by vibration and / or by dissolution.

PRESENTATION OF THE INVENTION The invention aims to remedy the drawbacks of the state of the art and to propose a lightened guide ring, compatible with a simple industrial manufacturing process.

To do this is proposed, according to a first aspect of the invention, a method of manufacturing a one-piece metal ring of plain or rolling bearing, the one-piece metal ring comprising at least one metal foam area with regular structure with open pores and a full peripheral zone at least partially covering the metal foam zone, at least part of the full peripheral zone constituting an annular guide track. This process includes a stage of foundry fabrication of a blank comprising the metal foam zone and an unfinished full peripheral zone, followed by a stage of finishing the full peripheral zone, the stage of finishing the full peripheral zone comprising at least one step of finishing the annular guide track.

By one-piece metal ring is meant here a metal ring in one piece, with structural continuity in particular between the solid peripheral zone and the metal foam zone. In particular, the different zones of the one-piece metal ring are made of the same metallic material, so that the thermal expansions of the ring are homogeneous and that there are, in particular, no stresses or clearances induced by expansion. differential.

By metallic foam is meant here a honeycomb structure of a metallic material (metal or alloy), having a high porosity rate, greater than 50%. The metal foam has a regular structure when the geometry of the pores is ordered and predetermined, in contrast to so-called stochastic metal foams.

The pores obtained by the foundry process are preferably open, which offers, when the ring is in service, a large heat exchange surface, which can be used to cool the ring and the bearing which incorporates it, by placing the ring in a natural or forced flow of a heat transfer fluid, which can be gaseous or liquid.

The annular guide track, where the load is concentrated, is formed by the solid peripheral zone, while the parts of the metal ring least exposed to stress peaks are formed by the metal foam zone, promoting lightening. of the ring and of the bearing which incorporates it, without affecting the mechanical strength. If necessary, more than one annular guide track can be formed on the solid peripheral zone. The ring can if necessary be constituted by the solid peripheral zone and the zone in metallic foam. Alternatively, the ring may include, in addition to the solid peripheral zone and the metal foam zone, one or more internal solid zones, surrounded by the metal foam zone.

The foundry process achieves higher industrial rates than other processes, including additive manufacturing.

According to one embodiment, it is provided that during the founding step, a destructible core having open pores is inserted into a casting mold, a peripheral empty volume being preserved between the destructible core and at least one wall of the mold, then a molten metallic material is poured inside the casting mold so that the molten metallic material fills on the one hand the peripheral void volume where it constitutes the unfinished peripheral full area and on the other hand the open pores of the destructible core where it constitutes the metallic foam zone, then the destructible core is destroyed and removed after solidification of the metallic material. By this process, the metal foam is open pore. The solidified metallic material constitutes, in its part filling the space between the core and the mold wall, the unfinished full peripheral zone, and, in its part filling the open pores of the destructible core, the metal foam. The destructible core may have no contact with the walls of the mold with the exception of a few point contact areas, so that the empty volume completely surrounds the destructible core. Alternatively, the destructible core can be in surface support on one or more of the walls of the mold. The destructible core can itself surround an empty interior volume which, after filling with the molten metallic material, constitutes a solid interior zone.

The cavity of the casting mold defines a reference axis which is also the axis of revolution of the annular guide track, and which can be an axis of symmetry of revolution of the mold cavity. The introduction of the molten metallic material inside the mold takes place through one or more tap holes in the walls of the mold. These tap holes may in particular include:

one or more tap holes oriented parallel to the reference axis and opening onto a transverse wall of the mold cavity; and / or one or more tap holes oriented radially with respect to the reference axis and opening onto an axisymmetric wall of the mold cavity.

According to one embodiment, all of the tap holes open into the empty volume.

According to another embodiment, only some of the tap holes open into the empty volume, others opening onto a wall of the mold in direct contact with the destructible core.

The core can in particular be destroyed by vibration and / or dissolution.

Preferably, the method comprises a step of manufacturing the destructible core comprising a step of aggregating elements using a binder, leaving between the aggregated elements interstices constituting the open pores.

Alternatively, the method comprises a step of manufacturing the destructible core comprising an outer shell containing elements, interstices constituting the open pores being preserved between the elements. The nucleus is then destroyed in two stages, first by destroying the shell, then by dissolving the elements it contained.

These techniques make it possible, if necessary, to produce pores having a shape of Kelvin truncated octahedron, which makes it possible to obtain a zone of metallic foam respecting the Plateau conditions. Reference may in particular be made to documents FR 2 921 281 or FR 2 927 269 for a description of the foundry molding step.

According to an alternative embodiment, it can be envisaged that the stage of manufacture by foundry comprises several successive sub-stages, namely a sub-stage of manufacture of a metal foam area with closed pores, then a remolding. of the metal foam zone in a mold, so as to define a peripheral void volume between the metal foam zone and at least one wall of the mold, then a filling of the mold so that the molten metal material fuses with the periphery adjacent to the metal foam area and defines the unfinished full peripheral area. The manufacturing of the closed-pore metal foam zone can be carried out by injecting a gas or mixing a foaming agent in a liquid metal.

The thickness of the full peripheral zone must be adapted to the envisaged application. Preferably, the finished full peripheral zone has, at the level of the annular guide track, a thickness greater than 1mm, preferably greater than 2mm. Preferably, the finished full peripheral zone has, at the level of the annular guide track, a thickness less than 5 mm, preferably less than 3 mm. These dimensions are particularly suitable for the application of the invention to guiding a robot arm, in particular a human assistance robot or collaborative robot.

Preferably, the finished full peripheral zone has, at the level of the annular guide track, a thickness of less than 20%, preferably less than 10% of the thickness of the ring. The lightening effect is then particularly noticeable.

In practice, the guide track is a rolling or sliding track, which must undergo finishing operations. Thus, according to one embodiment, the step of finishing the full peripheral zone comprises a rectification and / or a superfinishing at least of the annular guide track. According to one embodiment, the step of finishing the full peripheral zone includes a step of heat treatment.

According to one embodiment, the step of finishing the full peripheral zone includes a step of deformation, in particular of press-cutting, punching or crimping.

Preferably, the metal foam area is axisymmetric. The axis of revolution defined by the annular guide track being taken as the reference axis of the ring, the annular zone of metallic foam can be located radially outside the guide track, in the event that the track guidance is an external sliding or rolling track, turned radially inwards. Alternatively, the annular metal foam zone can be located radially inside the guide track, in the event that the guide track is an inner sliding or rolling track, facing radially outwards. According to another embodiment, the guide track can be turned in the axial direction and be positioned on a transverse face of the ring, at least part of the annular zone of metallic foam being positioned axially set back with respect to this transverse face. .

Preferably, the metal foam zone has a volume porosity rate greater than 60%, preferably greater than 70%, preferably greater than 75%, preferably greater than 80%, and preferably less than 90%. The relief obtained is particularly important. The porosity rate can be constant throughout the metal foam area, or variable. One can in particular consider a density varying monotonously with the distance to the reference axis, or with the distance to the full peripheral zone. It is also possible to envisage a zone made of metal foam, the porosity rate of which is lower in a restricted angular zone around the reference axis, corresponding to a main load zone under the operating conditions of the plain or rolling bearing, the ring is part.

In practice, the full peripheral zone can be unitary or subdivided into several sub-zones. The monobloc metal ring can also have a full internal zone, if necessary subdivided into several sub-zones. The metallic foam zone can also be subdivided into several sub-zones. Thus, for example, the solid peripheral zone can cover two opposite faces of the ring, and the latter can comprise a full internal zone constituted by veils or partitions which connect the two opposite faces, the zone in metallic foam being subdivided into subzones separated by from each other by the partitions. The opposite faces can for example be two transverse faces of the ring, perpendicular to the axis of revolution of the ring. Alternatively, the opposite faces may consist of a face facing radially inward and a face facing radially outward. The partitions preferably extend in planes passing through the axis of revolution of the ring.

If necessary, the full peripheral zone can completely cover the metal foam.

According to one embodiment, the finished full peripheral zone includes a hooping surface, preferably cylindrical, preferably facing away from the annular guide track, respectively. This hooping surface allows the fixing of the ring to a rotating member.

According to one embodiment, the finished full peripheral zone comprises an annular groove for fixing a seal.

Particularly advantageously, the one-piece metal ring has cylindrical fixing holes. These fixing holes can be threaded or not, blind or through. They can be oriented parallel to the axis of revolution of the metal ring, and distributed around the axis of revolution. Alternatively, they can be oriented in a direction perpendicular to a plane containing the axis of revolution. They can also be oriented radially, or at a solid angle, the apex of which passes through the axis of revolution of the bearing.

According to one embodiment, at least one of the cylindrical fixing holes is formed in the solid peripheral zone.

According to one embodiment, at least one of the cylindrical fixing holes is formed within the metal foam zone and constitutes a housing for a fixing insert, in particular a fixing sleeve. The insert may in particular take the form of a metal socket, threaded or not.

Preferably, the one-piece metal ring is made of steel, preferably in a grade of rolling steel, in particular a grade 100 Cr 6.

The guide track may in particular be a raceway. The shape of the raceway will be adapted to the type of rolling bodies used, which may be cylindrical or frustoconical rollers, barrels or balls, or more generally solid of revolution. If necessary, several coaxial raceways can be formed on the solid peripheral zone.

According to another aspect of the invention, it relates to a guide ring, in particular a rolling ring or plain bearing, obtained by the method described above.

According to another aspect of the invention, it relates to a rolling bearing, comprising at least a first rolling ring, a second rolling ring and rolling bodies capable of rolling on a first raceway of the first rolling ring and a second raceway of the second rolling ring when the first rolling ring rotates relative to the second rolling ring about an axis of revolution of the rolling bearing, characterized in that at least one of the first and second bearing rings is a one-piece metal ring obtained by the method described above.

BRIEF DESCRIPTION OF THE FIGURES Other characteristics and advantages of the invention will emerge on reading the description which follows, with reference to the appended figures, which illustrate:

Figure 1, an axial sectional view of a bearing comprising two bearing rings according to an embodiment of the invention;

Figure 2, a front view, with a detail in section, of a wheel bearing comprising three bearing rings according to a second embodiment of the invention;

Figure 3, an axial sectional view of the wheel bearing of Figure 2;

Figure 4, an axial sectional view of a rolling bearing having two bearing rings according to a third embodiment of the invention;

Figure 5, an axial sectional view of an angular contact bearing comprising two bearing rings according to a third embodiment of the invention;

Figure 6, an axial sectional view of a bearing with two rows of rolling bodies comprising three bearing rings according to a fourth embodiment of the invention;

Figure 7, an axial sectional view of a stage of manufacturing by foundry of a guide ring blank, according to a manufacturing process according to an embodiment of the invention.

For the sake of clarity, identical or similar elements are identified by identical reference signs in all of the figures.

DETAILED DESCRIPTION OF EMBODIMENTS In FIG. 1 is illustrated a bearing 10 of a robot arm, comprising an outer bearing ring 12 made of steel, an inner bearing ring 14 made of steel, and a row of rolling bodies 16.1, 16.2 running on annular raceways 18.1, 18.2, 20.1, 20.2 formed on the outer ring 12 and the inner ring 14 to guide in rotation relative to each other the outer ring 12 and the inner ring 14, around a common axis of revolution 100 defined by the raceways.

More specifically, each ring 12, respectively 14, has two raceways 18.1,18.2, respectively 20.1, 20.2 forming in axial section a right angle, and the rolling bodies 16.1,16.2 are rollers arranged to form a row of crossed rollers, alternately including first rollers 16.1 oriented so as to roll on a first race 18.1 of the outer ring 12 and a first race 20.1 of the inner ring 14, and second rollers 16.2 rolling on a second track bearing 18.2 of the outer ring 12 and a second race 20.2 of the inner ring 14.

The outer ring 12 further comprises a radial insertion well 22 passing radially closed by a plug 24 whose end facing the inner bearing ring 14 is shaped to be in continuity with the raceways 18.1,18.2 of the outer bearing ring 12. An axial pin 26 passing through a bore 28 formed in the outer ring 12 makes it possible to secure the positioning of the plug 24 in the well 22.

The outer ring 12 has threaded fixing holes 30 parallel to the reference axis. These fixing holes 30 are distributed over the circumference of the ring 12 and open onto a flat annular interface face 32 of the outer ring 12. They are intended to allow the fixing of the outer ring 12 to a robot arm member. .

The inner ring 14 also includes a circular row of threaded blind fixing holes 34 parallel to the reference axis 100 and opening onto a flat interfacing face 36. The inner ring 14 forms a hooping surface 38 to allow interfacing with the robot arm member.

The bearing 10 is optionally provided with a sealing device 40, in this case in this case a seal 42 made of elastomer molded onto a rigid frame 44, for example metallic. The seal 42 is mounted on a surface 46 of the outer ring 12 and by sliding support on a sliding track 48 constituted by a rectified surface of the inner ring 14. The support of the seal 42 on the sliding track 48 is provided by a spring 50.

Remarkably, each of the rings 12,14 is made in one piece and has a solid peripheral zone 12A, 14A, that is to say without porosity, also called "skin", and a zone in metallic foam 12B, 14B. In this embodiment, the solid peripheral zone 12A, 14A completely covers the metal foam zone 12B, 14B. It forms in particular the zones undergoing the load, in particular the raceways 18.1, 18.2, 20.1, 20.2, as well as the interfacing walls 32 and the walls of the fixing holes 30, 34, of the bore 28 and of the well of insertion 22, as well as the hooping surface 38. It also constitutes the fixing surface 46 of the seal and the opposite sliding track 48.

In known manner, the assembly of the bearing comprises a step of inserting the rolling bodies 16.1,16.2 between the bearing rings 12,14 by the well 22 after the raceways 18.1,18.2 of the outer ring 12 have been positioned opposite the raceways 20.1, 20.2 of the inner ring

14.

It should be noted that there is shown the rolling bodies 16.1,16.2 in the form of rollers 26.1 of a row of crossed rollers, but one can alternatively provide other types of rolling bodies, in particular balls, the raceways possibly being shaped as a warhead, so as to produce three or four contact points per ball.

Figures 2 and 3 is illustrated a wheel bearing 10 having an outer race 12, two inner race rings 14.1, 14.2 and rolling bodies 16.1, 16.2, in this case balls, arranged in two rows so as to run on tracks 18.1,

18.2, 20.1, 20.2 formed on the outer ring 12 and on the inner rings 14.1,

14.2. The outer ring 12 also has threaded bores 30 parallel to the axis of revolution 100 of the bearing 10, to fix the outer ring 12 to a suspension strut. Remarkably, each of the rings has a one-piece structure and is made up of an internal zone of metallic foam, and of a full peripheral zone which completely covers the internal zone.

In Figure 4 is illustrated a ball bearing 10, comprising two monobloc metal bearing rings 12,14 on which are formed raceways 18, 20 guiding the circulation of rolling bodies 16 constituted by balls. Remarkably, each ring 12, 14 consists of a solid peripheral zone 12A, 14A on which the raceway 18, 20 is formed, and of a zone of metallic foam 12B, 14B forming the part of the ring 12 , 14 furthest from the raceway 18, 20. Unlike the previous embodiments, the full peripheral zone 12A, 14A does not cover the faces of the ring furthest from the raceway 18, 20. The foam zone metallic 12B, 14B preferably has an open or semi-open porosity, which makes it possible to envisage cooling of the ring by natural or forced convection, by taking advantage of the large exchange surface of the zone of metallic foam 12B, 14B.

In Figure 5 is illustrated an angular contact rolling bearing 10, the rings 12, 14, as in the previous embodiment, each consist of a full peripheral area 12A, 14A on which is formed a raceway 18, 20, and a metal foam area 12B, 14B forming the part of the ring furthest from the raceway.

FIG. 6 shows a rolling bearing with two rows of rolling bodies, comprising an outer rolling ring 12, two inner rolling rings 14.1,14.2 and rolling bodies 16.1,16.2, in this case balls , arranged in two rows so as to run on raceways

18.1.18.2, 20.1, 20.2 formed on the outer ring 12 and on the inner rings

14.1, 14.2. Remarkably, each ring 12, 14.1, 14.2 consists of a solid peripheral zone 12A, 14.1A, 14.2A on which the race or tracks are formed, and a zone of metallic foam 12B, 14.IB , 14.2B forming the part of the ring 12,14.1,14.2 furthest from the raceways 18.1,18.2, 20.1,

20.2. Similarly to the embodiments of FIGS. 4 and 5, and unlike the embodiments of FIGS. 1 to 3, the solid peripheral zone 12A, 14.IA, 14.2A does not cover the most distant faces of the ring of the raceway

18.1.18.2.20.1.20.2.

In all the embodiments, the raceways 18, 18.1,

18.2, 20, 20.1, 20.2 are preferably rectified, and more optimally superfinished, and have where appropriate undergone a local heat treatment.

Naturally, the examples shown in the figures and discussed above are given only by way of illustration and not by way of limitation.

Illustrated in Figure 7 a step of manufacturing a guide ring according to the invention, in this case one of the inner rings 14.1 or 14.2 of Figure 6. The step illustrated in Figure 7 is a step of manufacturing a blank by foundry in a mold 52 comprising two annular parts 54, 56 defining a reference axis 200 of the mold 52, which is intended to be confused with an axis of symmetry of the blank and with the axis of revolution 100 of the finished inner ring. The parts 54, 56 of the mold are preferably metallic, the mold being permanent. However, a sand mold is also possible. At least one of the two parts of the mold, here the upper part 56, is movable in translation relative to the other part, here the lower part 54, parallel to the reference axis 200. Inside the mold was disposed a destructible core 58 consisting of elements aggregated to each other by a binder, which preserves between the elements interstices forming open pores. The destructible core 58 is formed according to the teaching of documents FR 2 921 281 or FR 2 927 269. The core does not occupy the entire cavity defined by the parts of the mold, and a volume 60 remains empty before the casting of the metallic material .

At least one of the two parts of the mold, here the fixed lower part 56, is provided with one or more tap holes 62, 64, for the introduction of a molten metallic material. More specifically, there is shown here a radial orientation tap hole 62 (that is to say opening onto a side wall of the cavity) and an axial orientation tap hole 64 (that is to say say leading to a wall of the cavity perpendicular to the reference axis). The radially oriented taphole 62 opens into the empty volume. The axially oriented taphole 64 opens onto a wall of the destructible core. It should be noted that this is only one of the possible arrangements. We can consider that no hole opens on a wall of the destructible core. It is also conceivable that the holes are all of radial orientation, or all of axial orientation. The mold also includes one or more vents 66.

After having carried out the molding operation, by positioning the destructible core 58 precisely in the lower part 54 of the mold, then by closing the upper part 60 of the mold, the actual casting is carried out, preferably under pressure, by tap holes 62, 64, simultaneously or sequenced. Where appropriate, the pouring may be accompanied by centrifugation around the reference axis 200, in particular if the tap hole or holes open onto a wall of the cavity turned radially outwards, or a wall perpendicular to the 'reference axis. The flow invades the empty volume 60 and the open pores of the core 58.

Once the metallic material has cooled in the mold, the metal blank obtained is ejected (or the mold is destroyed if it is made of sand). The blank can then be immersed in a solvent to dissolve the binder and remove the disaggregated elements from the core.

The cooled metallic material which occupied the pores of the destructible core 58 constitutes the metal foam zone 14.1B, 14.2B of the finished part. The metallic material which occupied the empty volume 60 of the cavity is intended to constitute the full peripheral zone 14.IA, 14.2A of the finished ring 14.1, 14.2. However, the work still needs to be completed, by carrying out various operations which may include cutting the feed system, grinding, deburring. The finishing also includes the finishing of the guide track 20.1, 20.2, here a raceway, by grinding or superfinishing. The finishing of the guide track can also include a heat treatment. Other forming operations, in particular by rolling, punching or crimping can be carried out.

Naturally, the foundry manufacturing process of Figure 7, described in connection with the inner rings of Figure 6, is immediately transferable to the inner and outer rings 12,14,14.1,14.2 of Figures 1 to 6.

For each of the rolling bearings of Figures 1 to 6, there is illustrated two rolling rings comprising a metal foam. However, it is also conceivable that only one of the bearing rings includes a metal foam, the other being of conventional solid structure. For a bearing for which a rolling ring is "fixed" in rotation in a Galilean frame of reference, one can for example choose to lighten only the rotating ring to minimize the moment of inertia of the rotating crew comprising this ring. For a bearing comprising an inner ring and an outer ring, it is for example possible to provide metal foam only on the outer ring, potentially more massive than the inner ring.

If the ring has interior zones subjected to high stresses under the conditions of use, it is possible to provide interior solid zones corresponding to these zones of high stresses.

The rolling bodies can be of any type. What has been illustrated for rolling bearings can be transposed to plain bearings.

It is explicitly provided that one can combine them the various embodiments illustrated to propose others.

It is pointed out that all the characteristics, as they emerge for a person skilled in the art from the present description, the drawings and the attached claims, even if concretely they have only been described in relation to other specified characteristics, both individually and in any combination, may be combined with other characteristics or groups of characteristics disclosed herein, provided that this has not been expressly excluded or that technical circumstances make such combinations impossible or meaningless.

Claims (19)

1. Method for manufacturing a one-piece metal ring (12, 14, 14.1, 14.2) of a plain or rolling bearing (10), the one-piece metal ring (12,14,14.1,14.2) comprising at least one foam zone metallic with regular structure with open pores (12B, 14B, 14.1B, 14.2B) and a solid peripheral zone (12A, 14A, 14.ΙΑ, 14.2A) covering at least partially the zone in metallic foam (12B, 14B, 14.1 B, 14.2B), at least part of the full peripheral zone (12A, 14A, 14.1A, 14.2A) constituting an annular guide track (18, 18.1, 18.2, 20, 20.1, 20.2), characterized in that '' it includes a stage of foundry fabrication of a blank comprising the metal foam zone (12B, 14B, 14.IB, 14.2B) and an unfinished peripheral full zone, followed by a stage of finishing the solid zone peripheral (12A, 14A, 14.IA, 14.2A), the step of finishing the full peripheral zone (12A, 14A, 14.IA, 14.2A) comprising at least one stage finishing example of the annular guide track (18,18.1,18.2, 20, 20.1,20.2). 2. Manufacturing method according to claim 1, characterized in that during the founding step, a destructible core (58) having open pores is inserted into a casting mold (52), a peripheral void volume (60) being preserved between the destructible core (58) and at least one wall of the mold, then a molten metallic material is poured inside the casting mold (52) so that the molten metallic material firstly fills the peripheral void volume (60) where it constitutes the unfinished peripheral full area and on the other hand the open pores of the destructible core (58) where it constitutes the metal foam area, then the destructible core (58) is destroyed and removed after solidification of the metallic material. 3. Manufacturing method according to claim 2, characterized in that it comprises a step of manufacturing the destructible core (58) comprising a step of aggregating elements using a binder, leaving between the elements aggregated interstices constituting the open pores. 4. The manufacturing method according to claim 2, characterized in that it comprises a step of manufacturing the destructible core (58) comprising an outer shell containing elements, interstices constituting the open pores being preserved between the elements. 5. Manufacturing method according to any one of the preceding claims, characterized in that the finished full peripheral zone (12A, 14A, 14.1A, 14.2A) has, at the level of the annular guide track, a thickness greater than 1mm , preferably greater than 2mm. 6. Manufacturing method according to any one of the preceding claims, characterized in that the finished full peripheral zone (12A, 14A, 14.1A, 14.2A) has, at the level of the annular guide track, a thickness less than 5 mm, preferably less than 3 mm. 7. Manufacturing method according to any one of the preceding claims, characterized in that the finished full peripheral zone (12A, 14A, 14.1A, 14.2A) has, at the level of the annular guide track, a thickness of less than 20 %, preferably less than 10% of the thickness of the ring. 8. Manufacturing method according to any one of the preceding claims, characterized in that the step of finishing the full peripheral zone (12A, 14A, 14.IA, 14.2A) comprises a rectification and / or a superfinishing at least of the annular guide track (18,18.1,18.2, 20, 20.1, 20.2). 9. The manufacturing method according to any one of the preceding claims, characterized in that the step of finishing the full peripheral zone (12A, 14A, 14.1A, 14.2A) comprises a step of heat treatment. 10. The manufacturing method according to any one of the preceding claims, characterized in that the step of finishing the full peripheral zone (12A, 14A, 14.ΙΑ, 14.2Α) comprises a deformation step, in particular of press-cutting, punching or crimping. 11. The manufacturing method according to any one of the preceding claims, characterized in that the metal foam zone (12B, 14B, 14.IB, 14.2B) is axisymmetric. 12. Manufacturing method according to any one of the preceding claims, characterized in that the metal foam zone (12B, 14B, 14.1B, 14.2B) has a volume-average porosity rate greater than 60%, preferably greater to 70%, preferably greater than 75%, preferably greater than 80%, and preferably less than 90%. 13. The manufacturing method according to any one of the preceding claims, characterized in that the finished full peripheral zone (12A, 14A, 14.1A, 14.2A) comprises a hooping surface (38, 46), preferably cylindrical, of preferably turned away from the annular guide track (20, 20.1, 20.2), respectively (18,18.1,18.2). 14. The manufacturing method according to any one of the preceding claims, characterized in that the one-piece metal ring (12,14,14.1,14.2) has cylindrical fixing holes (30, 34). 15. The manufacturing method according to claim 15, characterized in that at least one of the cylindrical fixing holes (30, 34) is formed in the solid peripheral zone (12A, 14A, 14.ΙΑ, 14.2A). 16. Manufacturing method according to any one of claims 14 to 15, characterized in that at least one of the cylindrical fixing holes is formed within the metal foam zone (12B, 14B, 14.IB, 14.2B ) and constitutes a housing for a fixing insert, in particular a fixing sleeve. 17. Manufacturing method according to any one of the preceding claims, characterized in that the one-piece metal ring (12, 14, 14.1, 14.2) is made of steel, preferably in a grade of bearing steel, in particular a grade 100 Cr 6. 18. Rolling bearing (10), comprising at least a first rolling ring (12), a second rolling ring (14,14.1,14.2) and rolling bodies (16, 16.1,16.2) able to roll on a first raceway (18,18.1,18.2) of the first raceway (12) and a second raceway (20, 20.1, 20.2) of the second rolling ring (14, 14.1, 14.2) when the first rolling ring (12) rotates relative to the second rolling ring (14, 14.1, 14.2) about an axis of revolution ( 100) of the rolling bearing (10), characterized in that at least one of the first and second rolling rings (12, 14, 14.1, 14.2) is a one-piece metal ring obtained by the manufacturing process according to any of the preceding claims.