FR2812046A1 - Self-lubricated bearing bush for shaft which extends through hole in bush guide body which delimits concave cylindrical lubricated section, guide body has two lubricant storage zones - Google Patents

Abstract

A rotating shaft (18) extends axially through a hole of the bush guide body (13) which delimits a concave cylindrical section (15) of the shaft guide whose surface is lubricated. The body comprises at least two zones amongst which is a first zone (60) for lubricant storage with an absorption capacity greater than the lubricant absorption capacity of a second zone.

Description

"Self-lubricated bearing ring for guiding a shaft in rotation"

  The invention relates to a bearing ring of the self-lubricated type. The invention relates more particularly to a ring

  self-lubricated bearing 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.

  o0 Bearing rings of the self-lubricated type generally comprise a metallic annular 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 material i5 so as to create a porous structure. In both cases, the porous structure allows 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 tree.

  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 face of the shaft. 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.

  There is also radial leakage of lubricant, in particular by evaporation or seepage of lubricant from the outer surface of the ring. 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.

  It is therefore important to increase the quantity of lubricant stored by the bearing ring and to limit the axial and radial leaks of lubricant so as to maximize the life of 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 defines a cylindrical section. concave for guiding the shaft, the surface of which is lubricated, characterized in that the body comprises at least two zones among which a first lubricant storage zone has an absorption capacity greater than the absorption capacity

lubricant from a second area.

  The bearing ring therefore makes it possible to increase the quantity of lubricant absorbed by the porous structure so as to maximize

its lifespan.

  According to other characteristics of the invention - the second zone is adjacent to the surface to be lubricated of the guide section of the shaft, and in that the first storage zone extends from the second zone towards the external surface of the ring - the first storage zone is constituted at least partially by a cavity produced in the second zone of the guide body of the ring; - The first storage area is constituted at least partially in a cavity defined between a radial annular wall of the second area of the guide body and an envelope of the ring; - that the cavity is at least partially filled with lubricant; - the lubricant is a gel - the first storage zone comprises an absorbent material - the second zone extends near the outside face of the ring, and in that the first storage zone extends from the second zone up to 'to the surface to be lubricated of the shaft guide section; - the absorbent material is impregnated felt - the first storage area is made at least partially in a material with a cellular structure which comprises open cells; - The first storage area is made at least partially in a material of the sintered type; - The outer surface of the bearing ring is substantially cylindrical; - The outer surface of the bearing ring is spherical convex so as to form a ball joint with a complementary housing; - At least one of the two axial ends of the hole in the guide body 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.

  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 self-lubricated type bearing ring having first and second zones, according to a first embodiment of the invention; - Figure 6 shows schematically, in axial section, a bearing ring whose first zone is constituted by a cavity; - Figure 7 shows schematically, in axial section, a bearing ring whose cavity is delimited by the second zone and by an envelope of the ring; - Figure 8 shows schematically, in axial section, a bearing ring of the self-lubricated type, according to a second embodiment of the invention; - Figure 9 shows schematically, in axial section, a self-lubricated type bearing ring according to a

variant of the invention.

  In the description, identical or similar elements

  will be designated by the same reference numbers.

  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 variant, be cylindrical. The articulated bearing ring 10 can be oriented angularly with respect to the longitudinal axis A1 of the rotary electrical 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 guide body 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

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

  io free 16 opposite 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, of the lubricant which is located on the shaft 18 in line with the ends

of the bearing ring 10.

  The radial leaks result from phenomena such as the evaporation or the seepage of the lubricant from the spherical outer surface 24 due to the pressure of the bearing towards

external pressure.

  The invention proposes a bearing ring 10, the body 13 of which comprises at least two zones, among which there is a first lubricating storage zone 60 which has an absorption and storage capacity greater than the capacity of a

second zone 62.

  The absorption capacity of a material is defined as the quantity of lubricant stored in a determined volume of the material. According to a first embodiment, in accordance with FIG. 5, the second zone 62 is adjacent to the surface to be lubricated of the guide section 15 of the shaft 18, and the first storage zone 60 extends radially outwards from the ring 10 o10 from the second zone 62 to the outer surface 24 of the

ring 10.

  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 substantially to that of the guide section 15. The structure of the material is cellular and includes open cells. Thus the porosity of the material allows the circulation of the lubricant, in particular of surfaces 64 and 66

  delimiting the cavities 60 towards the guide section 15.

  The difference in absorption capacity can result from a difference in porosity, that is to say different dimensions and / or the number 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 using two different materials. The difference in absorption capacity can also be obtained by applying pressures of different values to

  different areas of the bearing ring 10.

  Depending on the method used, it is possible to obtain a progressive variation in the absorption capacity between the guide section 15 and the spherical outer surface 24, or to obtain delimited zones which each have an absorption capacity determined in accordance with to the bearing ring 10 shown in

Figure 5.

  Here, the second zone 62 which is situated at the inner periphery of the guide body 13 of the bearing ring 10 has a lower absorption capacity for the lubricant than that of the first zone 60. That is to say that during the molding of the bearing ring 10, the compression pressure is applied

  on the inner cylindrical surface of the bearing ring 10.

  The guide body 13 can be composed of two different materials each corresponding to a zone. Thus, the first zone 60 can for example be molded onto the second

zone 62.

  The first storage area 60 may comprise an absorbent material, in particular impregnated felt. Such a material tool has a high absorption capacity of

lubricant.

  The ring 10 according to the invention generally comprises a greater quantity of lubricant than a ring produced according to the state of the art. The lubricant contained in the first storage zone passes through the second zone 62 to ensure effective lubrication of the interface between the bearing ring 10 and

tree 18.

  The first storage area 60 can be constituted by a cavity 64 which is formed in the second area 62 of the body 13 for guiding the bearing ring 10, in accordance with FIG. 6. Thus, the cavity 64 can be filled with lubricant. The

  absorption capacity of the cavity 64 is therefore maximum.

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  The lubricant can be in liquid form, in the form of gel or be contained in an absorbent material such as

  felt or a material with a cellular structure.

  In order to form the cavity 64, the second storage zone 62 can be produced in two parts 66 and 68, in accordance with FIGS. 6. Here, the cavity 64 is delimited by the shape of the external and internal walls of the parts 66 and 68 respectively. The two parts 66 and 68 are assembled by an assembly

i0 greenhouse.

  The cavity 64 can be filled before the parts 66 and 68 are assembled. In this case, when the lubricant is liquid, it is advantageous for it to be contained in an envelope, not shown, of permeable material, of annular shape, the external dimensions correspond to the dimensions of the cavity 64. Thus, the casing makes it easier to assemble the bearing ring 10, retaining the lubricant, and it allows the transfer of the lubricant from the cavity 64 constituting the first storage area , towards the interface to be lubricated between the ring 10 and

  The shaft 18, during the rotation of the shaft 18.

  The second zone 62 can also be molded around the first storage zone 60. It may also include means connecting the first storage area 60 outside the bearing ring 10, so as to allow the filling of the

cavity 64.

  According to a variant, in accordance with FIG. 7, the bearing ring 10 consists of the body 13 and a peripheral envelope 70. The cavity 64 constituting the first storage area 60 is then defined between the outer annular radial wall of the second zone 62 of the guide body 13 and

envelope 70.

  The casing 70 is made of a material which is preferably impervious to the lubricant, that is to say that it has a

zero absorption capacity.

1O 2812046

  According to this configuration, the body 13 ensures optimal lubrication of the interface between the bearing ring 10 and the shaft 18. The materials constituting the first zone 60 and / or the second zone 62 are chosen so that, d on the one hand the first storage zone 60 allows the body 13 to have a high overall absorption capacity and so that, on the other hand, the second zone 62 allows to ensure a good distribution of the

  lubricant at the interface between the ring 10 and the shaft 18.

  In addition, the sealed envelope 70 makes it possible to eliminate the 1o radial leaks of lubricant. The envelope 70 also makes it possible to prevent the air from penetrating inside the guide body 13 and from mixing with the lubricant, which limits the degradation.

  lubricant and in particular its oxidation.

  The material constituting the envelope 70 is chosen so as to minimize the coefficient of friction with the metal cups 26 and 28 of the retaining means 22 to optimize the

ring performance 10.

  The envelope 70 and the body 13 are advantageously fixed

  to each other by a tight assembly.

  By way of example, a bearing ring produced according to the state of the art in absorbent material with a volume equal to 2091 mm 3 contains 456 mm 3 of lubricant. A bearing ring 10 of the same size, comprising a first zone 60 for storage with a volume of 326 mm3, and a second zone 62 with a volume of 692 mm3 which is made of the same absorbent material as that of the bearing ring performed according to the state of

  the technique contains 477 mm3 of lubricant.

  Thus, the bearing ring 10 according to the invention makes it possible to store a quantity of lubricant greater than that stored by a ring produced according to the prior art for a smaller volume of absorbent material. The invention makes it possible to increase the life of the bearing and to reduce its cost price,

  including the cost of absorbent material.

  According to a second embodiment, in accordance with FIG. 8, the second zone 62 extends near the outer surface 24 of the ring 10, and the first storage zone 60 extends from the second zone 62 towards the inside of the ring 10 up to the surface to be lubricated of the guide section 15 of the shaft 18. The production of the ring 10 according to the second embodiment as well as the materials used are similar to those described above for the first mode of realization of

io the invention.

  The second zone 62 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 i5 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.

  According to a variant which can be applied both to the first and to the second embodiment, the axial ends of the hole in the guide body 13 comprise an axial end cavity 72 which surrounds the free end 16 of the shaft 18 and who forms

  a receptacle for channeling axial lubricant leaks.

  FIG. 9 illustrates a bearing ring 10 according to the second embodiment of the invention comprising two cavities

end 72.

  Each end cavity 72 has a concave cylindrical surface 74 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 radial surface 76

bottom ring.

  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

12 2812046

  the shaft 18 near the axial end of the bearing ring

  is projected transversely outwards.

  The lubricant thus sprayed is received, in the cavities 72, on the cylindrical surfaces 74 and / or the radial surfaces 76. It is then absorbed by the first zone 60 and / or the second zone 62 of the guide body 13 and it 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 the lubricant inside the body of

  o10 guide 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 service life and reducing the risks of seizure of the free end 16

  in the cylindrical guide section 15.

  In addition, the production of the cavities 72 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 72 can for example be cylindrical,

  according to figure 9, or frustoconical.

  A connection chamfer 78 is produced between the guide section 15 and each of the radial surfaces 76 of the cavities 72. It facilitates the introduction of the free end

  16 in the hole 14 of the bearing ring 10.

  The cavities 72 can 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 life of the

13 2812046

  bearing ring 10 is then further increased and its risks of seizure are reduced. Advantageously, the spherical outer surface 24 may of the bearing ring 10 be covered with a sealed envelope, such as a layer of a metallic material or of plastic material so as to eliminate the radial leaks, the

  air penetration inside the guide body 13 as well as its contact with the lubricant.

14 2812046

Claims (14)

  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 which delimits a section ( 15) concave cylindrical shaft guide (18) whose surface is lubricated, characterized in that the body (13) comprises at least two zones among which a first zone (60) for storing the lubricant has a capacity of absorption greater than the lubricant absorption capacity of one second I0 zone (60).   2. bearing ring (10) according to the preceding claim, characterized in that the second zone (60) is adjacent to the surface to be lubricated of the section (15) for guiding the shaft (18), and   in that the first storage area (60) extends from the se-   conde zone (60) towards the external surface (24) of the ring (10).   3. bearing ring (10) according to the preceding claim, characterized in that the first storage area (60) is constituted at least partially by a cavity (64) formed in the second area (60) of the guide body (13 ) of the ring (10).   4. Bearing ring (10) according to any one of   previous claims, characterized in that the first   storage zone (60) is constituted at least partially in a cavity (64) defined between a radial annular wall of the second zone (60) of the guide body (13) and an envelope (70) of the ring (10).   5. bearing ring (10) according to one of claims 3 or   4, characterized in that the cavity (64) is filled at least partially lubricant.   6. bearing ring (10) according to the preceding claim,   characterized in that the lubricant is a gel.   7. bearing ring (10) according to any one of   previous claims, characterized in that the first   storage area (60) comprises an absorbent material. 2812046   8. bearing ring (10) according to the preceding claim, characterized in that the second zone (60) extends near the outer face of the ring (10), and in that the first zone (60) of storage extends from the second zone (60) to the surface to be lubricated of the section (15) for guiding the shaft (18). 9. Bearing ring (10) according to the preceding claim, characterized in that the absorbent material is impregnated felt. 10. Bearing ring (10) according to any one of   Claims 1 to 8, characterized in that the first zone   (60) storage is carried out at least partially in a   cell structure material that has open cells.   11. Bearing ring (10) according to any one of   Claims 1 to 8, characterized in that the first zone   (60) storage is carried out at least partially in a sintered material.   12. Bearing ring (10) according to any one of   previous claims, characterized in that the surface   outside (24) of the bearing ring (10) is substantially cylindrical. 13. Bearing ring (10) according to any one of   previous claims, characterized in that the surface   outer (24) of the bearing ring (10) is spherical convex so as to form a ball joint (22) with a complementary housing. 14. Bearing ring (10) according to any one of   previous claims, characterized in that one at   less than the two axial ends of the hole (14) of the guide body (13) has an end cavity (72) which surrounds the shaft (18), which forms a receptacle for channeling leaks from   lubricant and which reduces the length of the guide section (15).