WO2010105664A1

WO2010105664A1 - Seal and rolling bearing comprising such a seal

Info

Publication number: WO2010105664A1
Application number: PCT/EP2009/053069
Authority: WO
Inventors: Thomas Perrotin; Fabio Picatto; Laurent Varnoux
Original assignee: SKF AB
Current assignee: SKF AB
Priority date: 2009-03-16
Filing date: 2009-03-16
Publication date: 2010-09-23
Anticipated expiration: 2011-09-16

Abstract

The seal is designed to be mounted between two elements (14, 16) rotatable relative to one another, notably rings of a rolling bearing. The seal comprises sealing portions (36, 38) respectively capable o f applying a dynamic sealing with one of the two elements (16) and a static sealing with the other element (14). The dynamic sealing portion (38) comprises at least first and second lips (42, 44) delimiting an annular chamber (50). The seal further comprises a deflector portion (52) axially offset relative to the first and second lips (42, 44) to orient foreign matter away from said lips.

Description

Seal and rolling bearing comprising such a seal.

The present invention relates to the field of seals and in particular the seals used in rolling bearings. In a rolling bearing, one or more seals are generally used to keep the lubricant, such as grease, inside the rolling bearing and to prevent ingress of foreign matter. Generally, the seals are attached to one of the rings of the rolling bearing and cooperate by friction contact with the other ring. A rolling bearing can be exposed to various kinds of pollution.

Pollution of the bearing by external or foreign matter may adversely affect its operation.

With the aim of limiting or delaying as much as possible the ingress of such foreign matter inside the bearing, the frictional force of a contact lip of the seal is generally increased.

A considerable contact pressure between the lip of the seal and the corresponding ring is particularly effective with respect to the sealing. This is however detrimental in terms of consuming energy and overheating. In fact, a rise in temperature can be harmful for the rolling bearing, or more generally for the associated machine.

One aim of the present invention is to overcome these drawbacks.

It is a particular object of the invention to provide a seal that limits the intrusion of water, dust and other foreign matter. The invention also seeks to provide a seal with good sealing properties while limiting in operation the dissipation and waste o f energy by friction.

Another object of the present invention is to provide a seal suitable for a rolling bearing. In one embodiment, a seal designed to be mounted between two elements rotatable relative to one another, notably rings of a rolling bearing, comprises sealing portions respectively capable of applying a dynamic sealing with one of the two elements and a static sealing with the other element. The dynamic sealing portion comprises at least first and second lips delimiting an annular chamber. The seal further comprises a deflector portion axially offset relative to the first and second lips to orient foreign matter away from said lips.

"Static sealing" means the sealing made between two parts that do not move relative to one another, and "dynamic sealing" means the sealing between two parts that move relative to one another.

The seal is adapted to protect an interior space between the two elements and to keep foreign particles out of said space. The deflector portion axially offset outwards relative to the interior and exterior lips makes it possible to interrupt flow present in the area surrounding the two elements in such a way as to limit the presence of a flow directed towards said lips.

In one embodiment, the dynamic sealing portion at least partly constitutes the deflector portion. The seal may comprise a stiffening insert onto which the dynamic sealing portion is provided. The stiffening insert can at least partly constitute the deflector portion.

Advantageously, the dynamic sealing portion comprises a concavity oriented towards the deflector portion. The deflector portion may be axially offset relative to the concavity.

In one embodiment, the dynamic sealing portion comprises an annular portion delimiting the concavity, the first and second lips being issued from said annular portion. Preferably, at least one of the lips is adapted to come into contact with the corresponding element. At least one of the lips may have in cross section a triangular shape.

The deflector portion may be distinct from the first and second lips.

The invention also relates to a rolling bearing comprising an inner ring, an outer ring, at least one row of rolling elements placed between the rings, and at least one seal attached to one of the rings and provided with sealing portions interacting respectively with one of the rings and the other ring in order to provide a dynamic sealing and a static sealing.

The dynamic sealing portion comprises at least inner and outer lips delimiting an annular chamber. The seal further comprises a deflector portion axially offset outwards relative to the inner and outer lips to orient foreign matter away from said lips and from the bearing.

In other words, the deflector portion extends axially beyond the inner and outer lips towards the outside.

"Inner lip" means the lip oriented towards the inside of the rolling bearing, i.e. situated axially on the side of the rolling elements, and "outer lip" means the lip oriented towards the outside of the rolling bearing.

The present invention and its advantages will be better understood by studying the detailed description of embodiments taken as non-limiting examples and illustrated by the appended drawings, in which:

- Figure 1 is a half-view in axial section of a rolling bearing according to a first embodiment of the invention,

- Figure 2 is a part section on a larger scale of Figure 1 , - Figure 3 is a half-view in axial section of a rolling bearing according to a second embodiment of the invention,

- Figure 4 is a half-view in axial section of a rolling bearing according to a third embodiment of the invention, - Figure 5 is a half-view in axial section of a rolling bearing according to a fourth embodiment of the invention, and

- Figure 6 is a half-view in axial section of a rolling bearing according to a fifth embodiment of the invention.

In Figure 1 , a rolling bearing 10, with an axis 12, comprises an outer ring 14, an inner ring 16, a plurality of rolling elements 18 , which in this case are balls, interposed between the rings 14 and 16, and a cage or retainer 19 for maintaining the rolling elements 18 circumferentially spaced apart. On each of the opposite sides of the rolling bearing 10 there is an annular seal 20, 22 to close the radial space that exists between the rings 14, 16. The seals 20, 22 are identical to one another and symmetrical relative to a transverse radial plane passing through the centre of the rolling bearing 10.

The inner and outer rings 14, 16 are concentric and symmetric with respect to the transverse radial plane passing through the centre of the rolling bearing 10. The outer ring 14 and inner ring 16 are o f the solid type. A "solid ring" is to be understood as a ring obtained by machining with removal of material (by turning, grinding) from tube stock, bar stock, rough forgings and/or rolled blanks.

The outer ring 14 comprises an axial outer surface 14a, a bore 14b, two opposing radial transverse faces or surfaces 14c and 14d delimiting axially the outer surface 14a and the bore 14b, and a toroidal circular raceway 14e formed onto the bore 14b and having in longitudinal cross section a concave internal profile adapted to the rolling elements 18, the said raceway being directed radially inwards. The outer ring 14 also comprises two annular recesses or grooves 24, 26 formed radially towards the outside from the bore 14b, respectively in the vicinity of the radial surfaces 14c, 14d. The grooves 24, 26 are symmetrical relative to the radial plane passing through the centre of the rolling bearing 10.

Similarly, the inner ring 16 comprises a bore 16a, an outer axial surface 16b, two opposing radial transverse faces or surfaces 16c and 16d delimiting axially the bore 16a and the outer surface 16b, and a toroidal circular raceway 16e formed onto the outer axial surface 16b and having in longitudinal cross section a concave internal profile adapted to the rolling elements 18, the said raceway being directed radially outwards. The radial surface 16c, 16d is respectively situated in a radial plane containing the transverse surface 14c, 14d.

As more clearly shown in Figure 2, the seal 20 comprises a stiffening framework or insert 32, in the form of a relatively rigid annular disc, onto which a sealing element 34 made of nitrile rubber or another elastomer is overmoulded or vulcanized. The sealing element 34 is made in one part. The insert 32 can be made from metal or from thermoplastic. The insert 32 comprises a radial portion or flange 32a which is axially extended inwards by an annular axial portion 32b.

The sealing element 34 covers the outer surface of the flange 32a and forms two radially opposed peripheral sealing portions 36, 38 applying respectively a static sealing with the outer ring 14 and a dynamic sealing with the inner ring 16. The outer sealing portion 36 is forced into the annular groove

24 of the outer ring 14 in order to attach the seal to the said ring. At the groove 24, the sealing portion 36 therefore matches the shape of the said groove to form a means for fixing or attaching the seal 20 to the outer ring 14. The sealing portion 36 axially surrounds the axial portion 32b of the insert 32 and radially surrounds the outer surface o f said portion so that only the sealing element 34 is in contact with the outer ring 14. This helps to hold the seal 20 in position inside the groove 24 by forced mounting and by friction. The inner sealing portion 38 comprises an annular portion 40 projecting radially inward from a radially inner edge of the flange 32a of the insert 32. The annular portion 40 has, in longitudinal cross section, a shape that is generally curved in a concave internal profile directed axially outwards. More precisely, the annular portion 40 has a shape that is curved in the form of a U oriented axially outwards. From the annular portion 40 issue an inner lip 42 situated axially on the side of the rolling elements 18 (Figure 1 ) and an outer lip 44 extending outwards.

The annular portion 40 comprises a first oblique portion 40a extending radially towards the rotational axis 12 of the rolling bearing in the direction of the rolling elements 18 and extended to a small- diameter edge towards the inside of the rolling bearing by a radial portion 40b. The radial portion 40b extends close to the radially inner edge of the flange 32a of the insert 32, while being radially offset towards the inside of the rolling bearing. The radial portion 40b is extended by a second oblique portion 40c extending radially towards the inside and axially in the direction opposite to the first oblique portion 40a, i.e. on the side opposite to the rolling elements 18. This gives the U shape. The first oblique portion 40a, the radial portion 40b and the second oblique portion 40c constitute an annular chamber or concavity 46 oriented axially towards the outside of the rolling bearing and adapted to capture solid foreign matter, as will be described in more detail below. The concavity 46 extends substantially obliquely towards the outside of the rolling bearing.

The annular inner lip 42 extends the annular portion 40, and more precisely the second oblique portion 40c, radially towards the inside in the direction of the outer axial surface 16b of the ring 16 to form a narrow annular passage 48 with said surface. In other words, the inner lip 42 is located slightly away from the inner ring 16 to form a labyrinth seal. The inner lip has in cross section a triangular shape.

The annular outer lip 44 extends obliquely outwards from the small-diameter free end of the annular portion 40, and more precisely from the second oblique portion 40c. The outer lip 44 extends radially inwards in the direction of the outer axial surface 16b of the inner ring 16 and comes into permanent friction radial contact with said surface. The lip 44 is axially offset towards the outside relative to the lip 42 and here axially situated in a radial plane containing the flange 32a of the insert 32.

The inner and outer lips 42, 44 form an upside-down V and delimit axially an annular chamber 50. The chamber 50 is delimited radially by the said lips and by the outer surface 16b of the inner ring 16. The chamber 50 forms a tank to storage foreign particles especially the very small ones which may pass between the friction lip 44 and the axial surface 16b of the inner ring 16. Further, the chamber 50 can advantageously be filled with a lubricant, such as grease, for instance a hydrophobic grease, to increase the overall sealing of the dynamic portion 38, said lubricant forming a sealed rim.

The dynamic sealing portion 38 further comprises an annular deflector lip 52 extending towards the outside of the rolling bearing. The lip 52 extends obliquely outwards from the external side of the sealing element 34 and radially inwards. The lip 52 is radially offset inwards relative to the radially inner edge of the flange 32a of the insert 32 while being radially spaced apart from the lips 42, 44. The deflector lip 52 is located axially on the opposite side of the radial portion 40b of the annular portion 40 relative to concavity 46. The lip 52 is axially offset towards the outside relative to the lips 42, 44 and to the annular concavity 46. The deflector lip 52 protrudes axially towards the outside relative to the annular concavity 46 and to the lips 42, 44. In other words, the lip 52 extends axially outwards beyond the lips 42, 44 and the concavity 46. The free end of the lip 52 is axially situated in a radial plane containing the radial surfaces 14c, 16c of the rings 14, 16 in order that said lip is always inside the bearing. The deflector lip 52 has an upper inclined surface 52a oriented towards the outside. The lip 52 is formed from the external side of the annular portion 40 in order to protrude axially relative to said side and thus enables to increase its deflector effect and reduce the amount of foreign matter directed towards the lips 42, 44.

As above-mentioned, the concavity 46 is adapted to capture solid foreign matter or particles. As a matter of fact, due to its position on the external side of the dynamic sealing 38 and to its orientation, the concavity 46 can be located in the path of a contamination flow thrown in the direction of the inside of the rolling bearing and oriented towards the outer ring 14. Said flow is schematically represented by arrow referenced 54. The concavity 46 forms a tank to store temporarily or permanently foreign matter contained into that flow contamination 54.

Besides, with the deflector lip 52, there is also a reduction o f foreign matter which tends to be directed towards the lips 44, 42. In fact, the lip 52 forms a flow deflector portion for diverting a contamination flow, illustrated by arrow 56, thrown in the direction of the inside of the rolling bearing and oriented towards the inner ring 16. Thus, it is less likely that foreign matter will reach the outer lip 44 and the inner lip 42. Hence, it is not necessary to make the interference or the pressing force between said inner lip 42 and the inner ring 16 substantially large. This is advantageous to avoid overheating.

The variant embodiment illustrated in Figure 3 in which identical elements have the same reference numbers only differs from the embodiment previously described in that the inner lip 42 also comes into permanent friction radial contact with the outer axial surface 16b of the inner ring 16. Such an embodiment is particularly useful when the rolling bearing 10 is operating in harsh environment with a high level of dirts and/or liquids by being sprayed with various contaminants. In fact, even if solid foreign matter does pass between the outer friction sealing lip 44 and the inner ring 16, it is blocked by the inner friction sealing lip 42 and thus prevented from intruding inwards.

With such an embodiment, the contact pressure applied by the seal 20 on the inner ring 16 increases. However, the tip of the inner lip 42 in contact with the inner ring 16 has in cross section a triangular shape in order to obtain an annular linear contact with the inner ring 16. With such a design, when wear appears, there is less friction than with a rounded portion for the tip of the inner lip 42. Besides, even if the pressing force of the inner lip 42 is low, the surface pressure o f that lip on the inner ring 16 increases. Hence, even with a small interference between the inner lip 42 and the inner ring 16, intrusion of solid foreign matter can be effectively prevented.

The variant embodiment illustrated in Figure 4 in which identical elements have the same reference numbers only differs from the first embodiment described in that the insert 32 of the seal 20 is disposed on the external side of the rolling bearing 10, i.e. oriented towards the outside. The sealing element 34 covers the inner surface o f the flange 32a. Such a disposition could also be applied to the seals o f the second embodiment illustrated in Figure 3.

The variant embodiment illustrated in Figure 5 in which identical elements have the same reference numbers differs from the third embodiment described in that the radial inner edge of the flange 32a of the insert 32 is extended towards the outside by an oblique portion 32c extending radially towards the inside, itself extended by a radial portion 32d extending radially towards the inner ring 16. The external surface of the radial portion 32d is situated in the radial plane containing the surfaces 14c, 16c of the rings 14, 16 in order that the seal 20 is always inside the bearing. In this embodiment, the external surfaces of the flange 32a and of the oblique and radial portion 32c,

32d are not covered by the sealing element 34. The sealing element 34 covers the internal side of the flange 32a and of the oblique and radial portion 32c, 32d.

The dynamic sealing portion 38 further comprises an annular axial projection 60 covering the radial inner edge of the radial portion

32d of the insert 32. The free end of the projection 60 is situated in the radial plane containing the surfaces 14c, 16c of the ring 14, 16. The projection 60 is located axially on the opposite side of the radial portion 40b of the annular portion 40 relative to concavity 46. The projection 60 and the oblique and radial portions 32c, 32d are axially offset towards the outside relative to the lips 42, 44 and to the annular concavity 46. The projection 60 and the oblique and radial portions 32c, 32d protrude axially towards the outside relative to the annular concavity 46 and to the lips 42, 44. The projection 60 and the oblique and radial portions 32c, 32d extend axially outwards beyond the lips 42, 44 and the concavity.

In this embodiment, the oblique portion 32c and the radial portion 32d of the insert 32 constitute with the projection 60 a deflector portion to orient foreign matter away from the inner and outer lips 42, 44 and from the inside of the bearing 10.

The variant embodiment illustrated in Figure 6 in which identical elements have the same reference numbers only differs from the embodiment previously described in that the inner lip 42 comes into permanent friction radial contact with the outer axial surface 16b of the inner ring 16.

In the previous described embodiments, the seal 22 is identical and symmetrical to the seal 20 relative to the radial plane passing through the centre of the rolling bearing 10. However, the seal 22 could have a different structure.

In the embodiments illustrated in Figures 1 , 4 and 5 , the seal 20 comprises an inner lip 42 forming a labyrinth seal with the inner ring 16 and an outer lip 44 coming into friction contact with said ring. However, it should be understood that the invention can also be applied to a seal having an inner friction sealing lip and an outer labyrinth sealing lip.

The embodiments previously described may naturally be used without distinction with one of the rings rotating while the other is fixed or also rotating. It should be noted that the embodiments illustrated and described were given merely by way of non-limiting indicative examples and that modifications and variations are possible within the scope of the invention. For example, although the present invention has been illustrated on the basis of ball bearings having a single row of rolling elements, it should be understood that the invention can be applied to a bearing using several rows of rolling elements.

The disclosed seals are particularly useful as seal for a rolling bearing, for instance for a rolling bearing adapted to a gearbox. In such application, the interference between the friction lip(s) and the corresponding ring can be adapted to allow that some lubricant oil o f the gearbox present in the area surrounding the rolling bearing intrudes inside the rolling bearing. The friction lip(s) and/or the labyrinth sealing lip prevent the ingress inside of the bearing of solid foreign particles contained into lubricant oil, as it is often the case with small metallic particles in a conventional gearbox such as a gearbox for a motor vehicle. However, the seals can be applied equally well to others applications.

Claims

1. Seal designed to be mounted between two elements (14, 16) rotatable relative to one another, notably rings of a rolling bearing, the seal comprising sealing portions (36, 38) respectively capable of applying a dynamic sealing with one of the two elements ( 16) and a static sealing with the other element ( 14), characterized in that the dynamic sealing portion (38) comprises at least first and second lips (42, 44) delimiting an annular chamber (50), the seal further comprising a deflector portion (52 ; 32d, 60) axially offset relative to the first and second lips (42, 44) to orient foreign matter away from said lips.

2. Seal according to claim 1 , wherein the dynamic sealing portion (38) at least partly constitutes the deflector portion (52; 32d, 60).

3. Seal according to claim 1 or 2, wherein the deflector portion (52 ; 32d, 60) comprises a lip.

4. Seal according to any of the preceding claims, comprising a stiffening insert (32) onto which the dynamic sealing portion (38) is provided.

5. Seal according to claim 4, wherein the stiffening insert (32) at least partly constitutes the deflector portion (32d, 60).

6. Seal according to any of the preceding claims, wherein the dynamic sealing portion (38) comprises a concavity (46) oriented towards the deflector portion (52 ; 32d, 60).

7. Seal according to claim 6, wherein the deflector portion

(52 ; 32d, 60) is axially offset relative to the concavity (46).

8. Seal according to claim 6 or 7, wherein the dynamic sealing portion (38) comprises an annular portion (40) delimiting the concavity (46), the first and second lips (42, 44) being issued from said annular portion.

9. Seal according to any of the preceding claims, wherein at least one of the lips (42, 44) has in cross section a triangular shape.

10. Rolling bearing comprising an inner ring ( 16), an outer ring ( 14), at least one row of rolling elements ( 18) placed between the rings, and at least one seal (20) according to any one of the preceding claims and attached to one of the rings.