WO2012072110A1

WO2012072110A1 - Comb cage for ball bearing and ball bearing with such a cage

Info

Publication number: WO2012072110A1
Application number: PCT/EP2010/068507
Authority: WO
Inventors: Benoit Arnault
Original assignee: SKF AB
Current assignee: SKF AB
Priority date: 2010-11-30
Filing date: 2010-11-30
Publication date: 2012-06-07
Anticipated expiration: 2013-05-30
Also published as: DE112010006035T5

Abstract

Cage (5) for a ball bearing (1) comprising a body (7) of generally annular shape and clamps (8a, 8b), the body (7) comprising a heel (9) of substantially annular shape and a substantially axial portion (10) being connected to the heel (9) and wherein recesses (11) are arranged for the balls (4), the substantially axial portion (10) supporting said clamps (8a, 8b) on the side axially opposite to the heel (9). The cage (5) comprises protrusions (13a, 13b) extending radially outward.

Description

COMB CAGE FOR BALL BEARING AND BALL BEARING WITH SUCH A CAGE

The present invention relates to the field of ball bearings with a cage for ensuring an appropriate circumferential spacing between the balls . The invention also relates to ball bearing cages for high-speed operation.

Such types of cages have a generally annular shape with spherical recesses in which the balls are partially housed. The balls are retained in the recesses by clamps placed in pairs opposite to the heel of the cage. The spherical recesses have a diameter that is slightly greater than that of the balls, so that a certain functional clearance subsists between the balls and the recesses .

Document JP 2003 -035 3 17 (NSK) or patent application US 2002/ 1 14550 disclose a cage provided, between two recesses, with a deep groove extending from a radial face opposite to the clamps to the vicinity o f the clamps. Notches are provided from the groove to the cage bore.

Patent US 4 938 61 3 and patent application JP 2005 -5 142259 describe cages of constant thickness .

When the bearing rotates at high speed, under the effect of centrifugal force, the cage is subj ected to stresses which tend to deform said cage, mainly in the radial direction, and shape it like an umbrella, that is to say give the cage a conical shape by increasing the diameter on the side of the clamps. Such deformations have consequences that are harmful to the correct operation of the bearing. Specifically, the edges of the recesses tighten against the balls, causing an increase in the friction torque and a scraping effect of the lubricant, rapidly leading to an accelerated degradation of the lubrication conditions o f the bearing. There is also a risk that the ends of the clamps come into contact with the bore of the outer race of the bearing, risking to cause excessive wear of the cage.

Moreover, because o f the high rotation speeds to which the bearing is subj ected, the grease tends to be centrifuged outward into zones where it tends to stagnate or where the grease contributes only very little to the effective lubrication o f the rolling contacts.

French patent application FR 2 91 1 934 (SKF), which aims at so lving these problems, disclo ses a cage for a ball bearing comprising a body o f general annular shape and clamps. The body comprises a heel and a substantially axial portion being connected to the heel and wherein recesses are arranged for the balls . The substantially axial portion supports the clamps on the side axially opposite to the heel. The cage comprises an axial portion placed between the recesses and extending axially from the end of the heel to the clamps while radially determining external and internal free spaces. This thus lightens the cage and creates reservoirs of lubricant and circulation channels .

Such a cage ho lds the balls axially and circumferentially but not radially. The distribution of radial stresses may thus be insufficient in some cases and lead to the deformation o f the cage. Moreover, a high-quality circulation and distribution o f the lubricant during the rotation of the cage is essential to provide a good operation of the rolling bearing.

An obj ect of the present invention is to provide an improved cage for rolling bearing, with axial, circumferential and radial ho lding of the balls into the cage.

A further obj ect of the invention is to reduce the radial deformation o f the cage while providing a good circulation and distribution of the lubricant inside the bearing.

In one embodiment, the invention provides a cage for a ball bearing comprising a body of generally annular shape and clamps, the body comprising a heel of substantially annular shape and a substantially axial portion being connected to the heel and wherein recesses are arranged for the balls, the substantially axial portion supporting said clamps on the side axially opposite to the heel.

The cage comprises protrusions extending radially outward. These protrusions allow the radially holding of the balls into the cage and a self centering of the cage. During the rotation of the cage, these protrusions permit good stresses distribution, which prevents the deformation of the cage.

The substantially axial portion may be adapted to support said protrusions and may comprise a rib connecting clamps associated with two adjacent recesses .

Preferably, the protrusions associated with two adj acent recesses are connected with a concave portion.

In a preferred embodiment, each protrusion comprises claws extending around the ball. The claws allow a good distribution o f lubricant inside the bearing.

Advantageously, the axial portion comprises a through-ho le lo cated circumferentially between two adj acent recesses arranged for the balls through the thickness of the axial portion. This lightens the cage while creating lubricant reservoirs.

The external diameter of said substantially axial portion may be less than the external diameter of the heel.

The internal diameter of said substantially axial portion may be greater than the internal diameter of the heel.

Preferably, the heel comprises free spaces having the shape o f an arched slot fo llowing the general curvature of the heel.

It is another obj ect of the invention to provide a ball bearing comprising balls mounted in recesses of a cage as described above and placed between two raceways o f the bearing.

Advantageously, the ball bearing comprises a lubricant placed in each through-ho le. The ball bearing may be a Deep Groove Ball Bearing or an Angular Contact Ball Bearing.

The ball bearing may also be a Clutch Release Bearing Unit for actuating the clutch diaphragm o f a motor vehicle clutch mechanism.

By virtue of the invention, each ball is held circumferentially, axially and radially thanks to the protrusions radially extending around the associated recess.

In addition, since the structure of the cage is a connexion o f spherical arches by three cylinders, the centrifugal forces due to the rotation o f the cage have thus a limited effect and cause only minor deformations or local stresses on the cage at high rotation speeds.

Furthermore, thanks to the claws located at the end o f each protrusion, so as to extend around the associated ball, the external shape o f the cage is o f a pseudo-sinusoidal shape, thus improving the circulation of a lubricant around the balls.

In addition, the through-ho les lo cated between two adj acent recesses act as lubricant reservoirs, thereby allowing the lubricant to circulate around the balls .

The general structure of the cage is lightened by its through- ho les; hence a saving in material and a reduction in weight o f the cage, which causes to reduce the centrifugal effect at high rotation speeds.

For a given speed, the cage can thus be used at operating temperatures higher than in the case of a conventional cage, thanks to the reduction in deformation and o f the weight. In addition, the reduction in the quantity o f material forming the cage has a significant reduction effect on the cost of raw material.

The present invention will be better understood with the aid o f the detailed description o f a number of embo diments given by way o f non-limiting examp le and illustrated by the attached drawings, in which: Figure 1 is a perspective view o f a ball bearing according to the invention;

Figure 2 is a perspective view of a cage of the ball bearing of Figure 1 ;

- Figure 3 is a view along line III-III of Figure 2;

Figure 4 is a view along line IV-IV of Figure 3 ;

Figure 5 is a view along line V-V o f Figure 4.

Referring first to Figure 1 , which illustrates an embodiment o f a ball bearing 1 according to the invention; said ball bearing 1 comprises an inner ring 2 and an outer ring 3 with a row of balls 4 held by a cage 5 located between the inner ring 2 and the outer ring 3 . The cage 5 maintains the circumferential spacing of the balls 4. Sealing flanges or seals 6 may be attached to the outer ring 3 and form a friction seal or narrow passage seal with a bearing surface 2a o f the inner ring 2.

The inner ring 2 and outer ring 3 are o f the deep groove race type, for example obtained by machining a tube portion or a forged or rolled annular blank. The inner ring 2 comprises a cylindrical bore 2b, two opposite radial transverse surfaces 2c and an external surface from which a raceway 2d is formed for the balls 4. The outer ring 3 comprises a cylindrical axial external surface 3 a, two opposite radial transverse surfaces 3b and 3 c, and a bore from which a raceway 3 d is formed for the balls 4. The outer ring 3 is furnished with two symmetrical grooves 3 e in which the sealing flanges 6 can be fitted on the side o f each radial surface 3b and 3 c.

The cage 5 is more clearly visible in Figures 2 and 3 and comprises a body 7 o f generally annular shape and clamps 8a, 8b. The cage 5 may be a single-piece part, for example made of inj ection- moulded polyamide such as PA 6,6. The body 7 comprises a heel 9 o f generally annular shape and an axial portion 1 0 defining a plurality o f recesses 1 1 for the balls 4. The recesses 1 1 are of spherical shape. In addition, the clamps 8a, 8b further delimit the recesses 1 1 . Reference is hereby made to patent application FR 2 91 1 934 , which description is incorporated in the present description.

The heel 9 has an external diameter that is greater than the external diameter of the axial portion 10 and an internal diameter that is less than that of the axial portion 1 0. However, as a variant, it would be possible to provide a heel 9 having an internal diameter substantially equal to that of the axial portion 1 0. The axial portion 1 0 has an axial length at least equal to half the diameter of the recesses 1 1 , so that the balls elements 4 can be properly held in the recesses 1 1 .

Between two adj acent recesses 1 1 , the axial portion 1 0 forms an axial protrusion comprising two branches 10a, 10b in arc of circle each ending in a clamp 8a, 8b opposite to the heel 9. The axial portion 10 also comprises a rib 12 connecting the ends of the branches 10a, 10b associated with two adj acent recesses 1 1 . The clamps 8a, 8b extend beyond the rib 12 and around the balls 4. The branches 10a, 10b, the clamps 8a, 8b and the rib 12 may have substantially equal radial thickness. Thanks to the clamps 8a, 8b, balls 4 are held axially and circumferentially inside the cage 5.

Each branch 10a, 10b comprises a radial protrusion 13 a, 13 b extending radially outward. The axial portion 10 comprises a concave portion 13 connecting the end of two protrusions 13 a, 13b associated with two adj acent recesses 1 1 . The concave portion 13 is lo cated between the heel 9 and the rib 12. Each protrusion 13 a, 13b ends with a claw 14a, 14b extending around the balls 4, so as to maintain the balls 4 radially inside the cage 5.

The axial portion 10 also comprises a through-ho le 15 between the concave portion 13 and the heel 9. The through-ho le 15 has a substantially triangular shape. The through-ho le 15 extends radially through the thickness o f the axial portion 1 0 and is delimited in the circumferential direction by the branches 10a, 10b of two adj acent recesses 1 1 . Such through-ho le 15 may act as a lubricant reservoir. The lubricant used, may be, for example, grease.

The cage 5 can be made o f synthetic or metallic material.

The balls 4 come mainly into contact with a zone 16 o f the recesses 1 1 that is relatively limited in surface area and located axially at the level o f the ribs 12 and the concave portion 13. The forces exerted by a ball 4 on the contact zone 16 of a cage 5 are therefore bear, not only by the corresponding branch 10a, but also by the rib 12 , the concave portion 13 and the branch 1 0b o f the next recess 1 1 . The cage 5 therefore has excellent rigidity to circumferential, radial and axial forces exerted by the rolling elements 4 on said cage 5.

Furthermore, the hollowed structure of the cage 5 , thanks to the through-ho les 15 , allows the weight of the cage 5 to be lightened by reducing the quantity o f material used, hence a reduction in centrifugal forces during high-speed rotation. The axial and radial rigidity is fully satisfactory thanks to the ribs 12 and concave portions 13 , which prevents deformation o f the cage 5.

The presence of the through-ho les 1 5 makes it possible to have a significant reserve of lubricant close to the recesses 1 1 and the rolling elements 4. The lubricant merging from the through-ho le 1 5 may move outward by centrifugal force and reach the raceway 3 d o f the outer ring 3.

The claws 14a, 14b surrounding the balls 4 may then scrap the lubricant located on the balls 4. Thanks to the concave portion 1 3 connecting two adj acent claws 14a, 14b, the lubricant circulates easily from a rolling element 4 towards another ball 4 in the circumferential direction.

The circulation and distribution of the lubricant is also improved thanks to the clamps 8 a, 8b and the rib 12 connecting two adj acent clamps 8a, 8b. The cage 5 has also the advantage of making the bearing easier to clean, for instance during the assembly process of the bearing, during a cleaning step which takes place after the cage 5 has been installed. Indeed, the cleaning liquid inserted into the bearing 1 can circulate more easily between the inner ring 2 and the outer ring 3 and thereby more effectively carry out the contaminating particles which could otherwise remain in the bearing 1 and be harmful to its correct operation.

As illustrated in Figure 4, which represents a view along line IV-IV of figure 3 and in which identical elements bear the same reference, free spaces 17 may be arranged in the heel 9. The free spaces 17 have the shape of an arched slot fo llowing the general curvature of the heel 9 emerging on an end surface 9a o f the heel 9 in an opening o f oblong shape and emerging from the opposite side in the through-ho le 15 in an opening that is also of oblong shape.

Such free spaces 17 may also act as a lubricant reservoir. The lubricant emerging from the opening of the free space 17 may either move outward by centrifugal effect and reach the raceway 3 d of the outer race 3 , or move angularly and join the balls 4 placed in the recesses 1 1 .

The lubricant, for example grease, is thus placed in each through-ho les 15 and free spaces 17.

As illustrated in Figure 5 , which represents a detailed view of a part of a cage along lines V-V of Figure 4, the through-ho le 15 is delimited between two axial portions 10, the heel 9 and the rib 12. The concave portion 13 connecting claws 14a, 14b located radially on the concave rib 12 improve the stiffness o f the axial portions 10. The through-ho le 15 has a triangular shape having rounded edges.

The specific structure of the ball bearing 1 o f the invention is particularly stiffened, since the axial portions 1 0 o f the cage are stiffened radially by the concave portions 13 connecting the claws 14a, 14b which have a greater radial thickness. Deformation o f the cage 5 is thus avoided.

Moreover, circulation and distribution of lubricant inside the bearing is improved thanks to said claws 14a, 14b and concave portions 13 and thanks to the through-ho les 15.

Furthermore, the ho llowed structure of the cage 5 , notably thanks to the through-ho les 15 and the free spaces 17, allows the weight of the cage 5 to be lightened by reducing the quantity o f material used, hence a reduction in the centrifugal forces during a high-speed rotation.

The presence of the through-ho les makes it possible to have a considerable reserve of lubricant close to the recesses 1 1 and the balls 4. The lubricant emerging from the through-ho les is moved outward by centrifugal effect and reaches the raceway 3 d o f the outer ring 3 , and is then scraped by the claws 14a, 14b . The concave portion 1 3 allows the lubricant scraped by one of the claws 14a, 14b to move to an adj acent ball 4.

Claims

1. Cage (5) for a ball bearing (1) comprising a body (7) of generally annular shape and clamps (8a, 8b), the body (7) comprising a heel (9) of substantially annular shape and a substantially axial portion (10) being connected to the heel (9) and wherein recesses (11) are arranged for the balls (4), the substantially axial portion (10) supporting said clamps (8a, 8b) on the side axially opposite to the heel (9), characterized in that the cage (5) comprises protrusions (13a, 13b) extending radially outward.

2. Cage according to claim 1, wherein the substantially axial portion (10) is adapted to support said protrusions (13a, 13b).

3. Cage according to claims 1 or 2, wherein the substantially axial portion (10) comprises a rib (12) connecting clamps (8a, 8b) associated with two adjacent recesses (11).

4. Cage according to any of the preceding claims, wherein the protrusions (13a, 13b) associated with two adjacent recesses (11) are connected with a concave portion (13).

5. Cage according to any of the preceding claims, wherein each protrusion (13a, 13b) comprises claws (14a, 14b) extending around the ball (4).

6. Cage according to any of the preceding claims, wherein the axial portion (10) comprises a through-hole (15) located circumferentially between two adjacent recesses (11) arranged for the balls (4) through the thickness of the axial portion (10).

7. Cage according to any of the preceding claims, wherein the external diameter of said substantially axial portion (10) is smaller than the external diameter of the heel (9).

8. Cage according to any of the preceding claims, wherein the internal diameter of said substantially axial portion (10) is greater than the internal diameter of the heel (9).

9. Cage according to any of the preceding claims, wherein the heel 9 comprises free spaces 17 having the shape of an arched slot following the general curvature of the heel 9.

10. Ball bearing comprising balls (4) mounted in recesses (11) of a cage (5) as claimed in any preceding claims and placed between two raceways (2d, 3d) of the bearing.

11. Ball bearing according to claim 10, comprising a lubricant placed in each through-hole (15).

12. Ball bearing according to claim 10 or 11, whereby it is a Deep Groove Ball Bearing.

13. Ball bearing according to claim 10 or 11, whereby it is an Angular Contact Ball Bearing.

14. Ball bearing according to claim 13, whereby it is a Clutch Release Bearing Unit for actuating the clutch diaphragm of a motor vehicle clutch mechanism.