FR2812045A1 - Self-lubricated bearing bush for shaft which extends through hole in bush guide body which delimits concave cylindrical lubricated section, one end of hole comprises cavity for channeling lubricant leaks - Google Patents

Abstract

A rotating shaft (18) extends axially through a hole (14) of the bush guide body (13) which delimits a concave cylindrical section (15) of the shaft guide whose surface is lubricated. One of the two ends of the hole comprises an end cavity (60) which surrounds the shaft and forms a receptacle for the channeling of lubricant leaks and which reduces the length of the guide section.

Description

"Self-lubricated bearing ring" The invention relates to a bearing ring

  of the self-lubricating type. The invention relates more particularly to a self-lubricated bearing ring for guiding a shaft in rotation. Such a type of ring is used in particular for guiding in rotation a free end of an armature support shaft

  of a rotating electric machine.

  Bearing rings of the self-lubricated type generally comprise 1o an annular metal ring on the inner face of which is deposited a layer of material with a porous structure, by a process such as sintering. It can also be produced in a single piece by compression of a powder of material so as to create a porous structure. The porous structure must allow the absorption and storage of a lubricant. Thus during assembly, a lubricant such as oil is absorbed by the porous structure, in particular by the concave inner face of an axial hole into which is introduced.

the free end of the shaft.

  When the shaft is rotated, the lubricant contained in the layer of material with a porous structure is "sucked" towards the axial hole by the movement of the shaft by a pumping phenomenon and by friction at the interface, and it thus creates a film of lubricant between the concave internal cylindrical surfaces of the ring and the convex external of the shaft opposite. The film of lubricant makes it possible to reduce the friction forces, as well as

the wear of these two elements.

  However, the centrifugal force resulting from the rotation of the shaft causes axial leakage of lubricant, by spraying outward lubricant which is located on the convex outer surface of the shaft at the axial ends of the bearing ring . The lost lubricant no longer participates in the lubrication of the

contact between the ring and the shaft.

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  Thus, the quantity of lubricant which is stored in the material with a porous structure and which allows the lubrication of the bearing, gradually decreases until it reaches a limit quantity which no longer allows the correct lubrication of the interface between the ring and the 'tree. The wear of the bearing ring and facing shaft surfaces is then accelerated and can cause

  seizure of the free end of the shaft in the bearing ring.

  In order to remedy these drawbacks, the invention proposes a self-lubricated type bearing ring for guiding in rotation a shaft which extends axially through a hole in the guide body of the ring which delimits a cylindrical section. concave for guiding the shaft, the surface of which is lubricated, characterized in that at least one of the two axial ends of the hole has an end cavity which surrounds the shaft, which forms a receptacle for channeling leaks from

  lubricant and which reduces the length of the guide section.

  According to other characteristics of the invention: - at least one of the cavities comprises a cylindrical section of larger diameter than that of the hole of the guide body; - The cylindrical section of larger diameter is coaxial with the hole of the guide body; - At least one of the cavities is delimited axially towards the inside of the guide body by an annular radial bottom surface; - A connection chamfer is provided between the guide section and the annular radial face; the body of the ring has a cavity at each of the two axial free ends of the hole; - The body of the bearing ring is made of a material which allows the absorption of lubricant; - The body is made of a material of the type which includes open cells; - the body is made of a sintered material

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  - The material which allows the absorption of lubricant comprises at least two zones whose lubricant absorption capacity of each is different; a first zone of predetermined absorption capacity extends close to the external surface of the ring, and a second zone of absorption capacity higher than that of the first zone extends from the first zone to the inner surface of the hole of the longitudinal axis of the guide body; - The outer surface of the ring is substantially cylindrical, and the zones of different absorption capacity are substantially cylindrical; - The outer surface of the ring is spherical convex so as to form a ball joint with a complementary i5 housing; - the zones of different absorption capacity are substantially spherical; - At least one of the cavities is closed axially towards the outside of the ring by a protective and sealing joint; - at least one of the cavities is filled at least

  partially by a material allowing the absorption of lubricant.

  Other characteristics and advantages of the invention

  will appear on reading the following detailed description for the

  understanding of which reference will be made to the accompanying drawings in which: - Figure 1 is a schematic view in axial section and in perspective of a bearing ring according to the state of the art which is mounted relative to a structural element of an electric motor; - Figures 2 to 4 show schematically in cross section, a shaft which is guided in rotation by a bearing ring of the self-lubricated type; - Figure 5 shows schematically, in axial section, a bearing ring of the self-lubricated type according to the invention;

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  - Figures 6 and 7 are views similar to that shown in Figure 5, which show the bearing ring

  according to two variants of the invention.

  FIG. 1 represents a bearing ring 10 produced according to the state of the art, and which is mounted in a structural element, here a flange 12 of axial end of a body (not shown) of a rotary electric machine such as an electric motor or an alternator. The longitudinal axis of the machine

  rotating electric is shown in Figure 1 by the axis A1.

  The bearing ring 10 consists of a guide body 13 in which a central hole 14 is formed which delimits a concave cylindrical section of guide 15 of a free end 16 of a shaft 18, of axis A2, of the rotating electric machine. Here the shaft 18 carries an armature collector 20 whose radial periphery

  is in electrical contact with brushes or carbon brushes 21.

  The other free end, not shown, of the shaft 18 is

  received in another rotating guide bearing ring.

  Advantageously, the bearing ring 10 is spherical and it is mounted articulated in an interior cavity delimited by retaining means 22, forming a ball-type joint. The means 22 consist essentially of two metal cups 26 and 28, which cooperate with the surface

  outer 24 convex spherical of the guide body 13.

  The bearing ring 10 can also, as a variation, be

cylindrical.

  The articulated bearing ring 10 can be oriented angularly with respect to the longitudinal axis A1 of the rotary electric machine so as to be perfectly aligned with the axis A2 of the shaft 18, and it thus makes it possible to overcome d 'A possible misalignment between the bearing ring 10 and the other bearing. The bearing ring 10 is of the self-lubricated type, that is to say that it operates without adding lubricant. To do this, the body

2812045

  guide 13 is made of a material which allows absorption

and storing a lubricant.

  The operation of a bearing ring 10 is shown in Figures 2 to 4 which schematically represent cross sections, along the median transverse plane, of the ring

  bearing 10 and the free end 16 of the shaft 18.

  FIG. 2 represents the so-called "rest" position in which the free end 16 of the shaft 18 is stationary relative to the bearing ring 10. The guide body 13 is then loaded

1o of lubricant.

  According to Figure 3, the shaft 18 is rotated, for example in the direction of the arrow 46. The rotation of the free end 16 causes a suction effect of the lubricant located inside the guide body 13 , according to the arrows 50, so as to create a layer of lubricant in the interface or "air gap" zone 48 situated between the concave cylindrical guide section 15 of the bearing ring 10 and the convex cylindrical surface of the free end 16 of the shaft 18. Friction and wear on the surfaces of the guide sections 15 and of the end

  free 16 vis-à-vis are reduced.

  When the rotation of the shaft 18 is stopped, the free end 16 returns to its rest position, in accordance with FIG. 4, and the lubricant located in the interface zone 48 is again absorbed by capillary action by the body of guide 13 of

the bearing ring 10.

  However, such a bearing ring 10 has axial and radial leaks of lubricant which cause a reduction in the quantity of lubricant stored in the guide body 13, which reduces the service life of the bearing ring 10 and what can cause the free end 16 of the shaft 18 to seize in the guide section 15 of the bearing ring 10. The axial leaks are the consequence of the projection towards the outside of the bearing ring 10 by centrifugal force, B718

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  lubricant which is located on the shaft 18 to the right of the ends

of the bearing ring 10.

  The radial leaks result as for them from phenomena such as the evaporation or the seepage of the lubricant from the spherical external surface 24 due to the pressure of the bearing in

  operation which is greater than the external pressure.

  The invention proposes, in accordance with FIG. 5, a bearing ring 10, each axial end of the central hole 14 includes an end cavity 60 which surrounds the free end 16 0o of the shaft 18 and which forms a receptacle for channeling the leaks

axial of lubricant.

  Each cavity 60 has a concave cylindrical surface 64 of larger diameter than that of the cylindrical guide section 15, and is delimited axially towards the inside of the

  guide body 13 by a bottom annular radial surface 66.

  The guide body 13 is for example made in one piece by compacting a material such as copper, bronze or iron, and for example a metal powder such as copper powder, in a mold whose shape corresponds to the shape of the spherical outer surface 24 the bearing ring 10 and which comprises a central core whose outer shape corresponds to the guide section 15 and to the cavities 60. The structure of the material is porous with open cells so as to allow the circulation of the lubricant, in particular of the surfaces 64 and 66 delimiting the cavities 60 towards the section of

guide 15.

  When the shaft 18 is rotated, the lubricant is sucked from the guide body 13 towards the guide section 15. Lubricant located on areas of the free end 16 of the shaft 18 near the end axial of the bearing ring

  is projected transversely outwards.

  The lubricant thus sprayed is received, in the cavities 60, on the cylindrical surfaces 64 and / or the radial surfaces 66. It's B718

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  then absorbed by the guide body 13 and can be sucked in again by the rotational movement of the free end 16 of the axis 18 in the cylindrical guide section 15 of the bearing ring 10. This creates a circulation of lubricant inside the guide body 13 of the bearing ring 10. The bearing ring 10 according to the invention thus makes it possible to "recover" the axial leaks of lubricant caused by the rotation of the free end 16 of the 'shaft 18, increasing its lifespan and reducing the risk of seizure of the free end 16

  io in the cylindrical guide section 15.

  In addition, the production of the cavities 60 reduces the length of the guide section 15, and consequently the contact surface and the friction forces between the internal concave cylindrical surface of the hole 14 and the external convex cylindrical surface of the end 16 of tree 18. Machine performance

electric is thus increased.

  The cavities 60 may for example be cylindrical,

  in accordance with Figures 5 to 7 or frustoconical.

  A connection chamfer 68 is produced between the guide section 15 and each of the radial surfaces 66 of the cavities 60. It facilitates the introduction of the free end

  16 in the hole 14 of the bearing ring 10.

  According to a variant, represented in FIG. 6, the material which allows the absorption of the lubricant comprises a first zone 70 and a second zone 72 each of which has a capacity

  different absorption of the lubricant.

  The difference in absorption capacity can result from a difference in porosity, that is to say different dimensions of pores or cells of the material. Thus, when the bearing ring 10 is obtained by compression of a metallic powder, the difference in absorption capacity can be obtained by applying the compression pressure only to the area in front of which the lowest absorption capacity is presented. or by

  the use of two different materials.

  B718 Depending on the method used, it is possible to obtain a gradual variation in the absorption capacity between the guide section 15 and the spherical outer surface 24, or delimited areas which each have an absorption capacity determined in accordance with the bearing ring 10 shown in FIGS. 6 and 7. Here, the first zone 70 which is located at the periphery of the guide body 13 of the bearing ring 10 has a lower lubricant absorption capacity than that of the 1o second zone 72. That is to say that during the molding of the bearing ring 10, the compression pressure is applied to the

  spherical outer surface 24 of the bearing ring 10.

  The first zone 70 makes it possible on the one hand to reduce the radial leaks of the lubricant, and on the other hand to prevent the air from penetrating inside the guide body 13 and from mixing with the lubricant, which limits degradation of the lubricant and in particular its oxidation. The lubrication between the free end 16 of the shaft 18 and the guide section 15 is thus improved and the service life

  of the bearing ring 10 is increased.

  The cavities 60 can also be filled at least partially with a material, such as a plastic composite, allowing the absorption of lubricant. Thus, the material can form a reserve of lubricant and / or allow the recovery and recycling of the axial leaks of lubricant caused by the rotation of the free end 16 of the shaft 18. The lifetime of the bearing ring 10 is then increased and its risks of

seizure are decreased.

  In accordance with FIG. 7, the bearing ring 10 according to the invention may also include a seal 74 for protection and sealing which axially closes each cavity 60 towards the outside of the bearing ring 10, so as to limiting contamination of the lubricant by air or by polluting elements such as dust or water droplets and, on the other hand, eliminating axial losses of the lubricant which would persist

  despite the arrangement of the cavities 60.

  Advantageously, the spherical outer surface 24 can be covered with a sealed envelope, such as a layer of metallic material or plastic material so as to suppress radial leaks and the penetration of the interior air of the

  guide body 13 and its contact with the lubricant.

B718

Claims (16)

  1. Bearing ring (10) of the self-lubricated type for guiding in rotation a shaft (18) which extends axially through a hole (14) in the guide body (13) of the ring (10) which delimits a concave cylindrical section (15) for guiding the shaft (18), the surface of which is lubricated, characterized in that at least one of the two axial ends of the hole (14) has a 0o end cavity (60) which surrounds the shaft (18), which forms a receptacle for channeling the lubricant leaks and which reduces the   length of the guide section (15).   2. bearing ring (10) according to the preceding claim, characterized in that at least one of the cavities (60) has a cylindrical section of larger diameter than that of the hole (14) of the guide body (13).   3. bearing ring (10) according to one of claims 1 or   2, characterized in that the larger cylindrical section   diameter is coaxial with the hole (14) of the guide body (13).   4. Bearing ring (10) according to any one of   previous claims, characterized in that one at   less of the cavities (60) is delimited axially towards the inside of the guide body (13) by an annular radial bottom surface (66). 5. bearing ring (10) according to the preceding claim, characterized in that there is provided a chamfer (68) for connection between the guide section (15) and the surface (66) radial annular.   6. Bearing ring (10) according to any one of   previous claims, characterized in that the body (13)   of the ring (10) has a cavity (60) in each of the two   axial free ends of the hole (14).   7. bearing ring (10) according to any one of   previous claims, characterized in that its body   B718 (13) is made of a material which allows the absorption of lubricant. 8. bearing ring (10) according to the preceding claim, characterized in that the body is made of a material of the type which comprises open cells.   9. bearing ring (10) according to one of claims 6 or   7, characterized in that the body (13) is produced in a sintered material.   10. Bearing ring (10) according to any one of   1o claims 6 to 9, characterized in that the material which   allows the absorption of lubricant comprises at least two zones (70, 72) whose lubricant absorption capacity of each is different. 11. bearing ring (10) according to the preceding claim, characterized in that a first zone (70) of predetermined absorption capacity extends near the outer surface (24) of the ring (10), and in that a second zone (72) of higher absorption capacity than that of the first zone (70) extends from the first zone (70) to the interior surface of the hole (14) of axis longitudinal of the guide body (13).   12. bearing ring (10) according to one of claims 10   or 11 characterized in that the outer surface of the ring (10) is substantially cylindrical, and in that the zones of   Different absorption capacities are substantially cylindrical.   13 bearing ring (10) according to any one of   claims 1 to 11 characterized in that the outer surface   (24) of the ring (10) is spherical convex so as to form   a ball joint with a complementary housing.   14 bearing ring (10) according to claim 13 taken   combination with one of claims 10 or 11 characterized   in that the zones (70, 72) of different absorption capacity are substantially spherical.   B718 15. Bearing ring (10) according to any one of   previous claims, characterized in that one at   less of the cavities (60) is closed axially towards the outside of   the ring (10) by a seal (74) for protection and sealing.   16. Bearing ring according to any one of   previous claims, characterized in that one at   less of the cavities (60) is filled at least partially by a   material allowing the absorption of lubricant.