WO2011026703A1

WO2011026703A1 - Thrust bearing and suspension for vehicle

Info

Publication number: WO2011026703A1
Application number: PCT/EP2010/061338
Authority: WO
Inventors: Bruno Montboeuf; Richard Corbett; Jérôme DUBUS; Samuel Viault; Christophe Houdayer
Original assignee: SKF AB
Current assignee: SKF AB
Priority date: 2009-09-02
Filing date: 2010-08-04
Publication date: 2011-03-10
Anticipated expiration: 2012-03-02
Also published as: FR2949525A1; FR2949525B1

Abstract

Suspension thrust bearing device comprising a rolling-contact bearing (1) forming an axial thrust bearing, a lower cup (2) supporting the rolling-contact bearing (1) and forming a means against which a suspension spring can bear, and an upper cup (3) enclosing the rolling- contact bearing, the rolling-contact bearing comprising an upper ring (4) in contact with the upper cup (3), a lower ring (5) in contact with the lower cup (2) and a plurality of rolling elements (6) arranged between the rings, the lower cup (2) having a body (9)formed of a part (10) made of rigid material and of a part (11) made of flexible material defining at least one sealing lip in contact with the upper cup (3), catching means being provided to prevent the lower and upper cups from becoming disconnected axially. The flexible-material part (11) of the said body has a radially projecting annular rib (14) associated with a sealing lip (13), the said rib being capable of collaboration with at least one hook (3c) of the upper cup to prevent the lower and upper cups from becoming axially disconnected.

Description

THRUST BEARING AND SUSPENSION FOR VEHICLE

The present invention relates in general to suspension thrust bearing devices used in particular in motor vehicles in the suspension struts of the steered wheels.

A suspension thrust bearing device such as this in general comprises a ro lling bearing forming an axial thrust bearing and comprising an upper ring and a lower ring between which a plurality of rolling elements, for examp le balls or rollers, are arranged.

Preferably, use is made of an angular-contact rolling bearing that is able to absorb both the radial load and the axial load applied to the thrust bearing. The upper and lower rings of the rolling bearing, which may, for example, be produced by pressing a thin sheet, are generally mounted in contact with lower and upper bearing or support pieces such as retainers or cups . The upper and lower cups form a housing for the rings of the rolling bearing and provide the interface between the said rings and the surrounding elements.

A suspension thrust bearing device such as this may be mounted at the upper part of a suspension strut, between the bodyshell of a motor vehicle and a suspension spring. The spring is generally installed around a shock absorber piston rod, the end of which is connected to the vehicle bodyshell via an elastic mount that filters out vibrations. The suspension spring, generally a helical spring, bears axially, directly or indirectly, on the lower cup of the suspension thrust bearing device. The upper cup for its part is fixed to the bodyshell of the vehicle. A suspension thrust bearing device such as this allows axial load to be transmitted between the suspension spring and the bodyshell of the vehicle, while at the same time allowing a rotational movement between the lower cup and the filtering elastic mount, this movement resulting from a turning o f the steered wheels of the vehicle and/or from compression o f the suspension spring.

French Patent Application 1 901 737 (SKF) describes such a suspension thrust bearing device comprising a lower seating cup and a rolling bearing mounted to bear thereon. The lower cup is made of a synthetic material and is combined with a vibration filtering element that is provided with a stiffening reinforcement. Thus, it is possible to achieve good distribution of the load applied by the suspension spring and vibrations are appreciably reduced. In operation, such a suspension thrust bearing device is exposed to being splashed with water. The upper and lower seating cups are therefore shaped in such a way as to form a contactless seal using a labyrinth seal both on the inside and on the outside which is the side mo st exposed to being splashed with water. This earlier patent application also provides catching means between the upper cup and the lower cup to prevent the two cups from separating before the suspension thrust bearing is fitted.

French patent application 2 928 1 87 (SKF) describes another embodiment of a suspension thrust bearing in which the lower cup has a body formed o f a rigid material made of synthetic material for transmitting axial load between the spring and the rolling bearing and a flexible material, likewise synthetic, having sealing lips which can come into contact with axial cylindrical skirts that form part of the upper cup . In that document, the upper cup is caught on the lower cup as a result o f co llaboration between two hooks made on the upper cup and a flexible sealing lip which therefore performs two different technical functions . Such a dual-role can lead to disadvantages. Specifically, in order to seal appropriately, the sealing lip needs to be as flexible as possible. However, this flexibility may detract from good axial retention o f the upper cup with respect to the lower cup .

Patent application WO 2008/ 152241 (SNR) describes a suspension thrust bearing device in which the lower cup likewise has a body made o f relatively rigid material and a portion made o f a more flexible material and exhibiting a flexible sealing lip capable o f coming into contact with an axial skirt of the upper cup . In the embodiments illustrated in that earlier document, the function o f retaining the upper cup with respect to the lower cup is performed by the co llaboration o f hooks provided on the relatively rigid-material parts of the respective lower and upper cups. Such an embodiment presents practical difficulties because of the rigidity of these hook- shaped pieces or because of the risk of them breaking during fitting or removal.

It is an obj ect o f the present invention to eliminate the aforementioned disadvantages of the prior art.

Specifically, a subj ect of the present invention is a suspension thrust bearing device in which sealing is perfectly afforded and in which the lower and upper cups are secured to one another effectively and simply without adversely affecting the sealing function.

In one embodiment, a suspension thrust bearing device comprises a ro lling bearing forming an axial thrust bearing, a lower cup supporting the ro lling-contact bearing and forming a means against which a suspension spring can bear, and an upper cup enclosing the rolling bearing . The rolling bearing comprises an upper ring in contact with the upper cup, a lower ring in contact with the lower cup and a plurality o f rolling elements arranged between the rings. The lower cup has a body formed of a part made o f rigid material and of a part made of flexible material defining at least one sealing lip in contact with the upper cup . Catching means are provided to prevent the lower and upper cups from becoming disconnected axially. The flexible-material part of the said body has a radially proj ecting annular rib associated with a sealing lip, the said rib being capable of collaboration with at least one hook of the upper cup to prevent the lower and upper cups from becoming axially disconnected.

Thus, the lower and upper cups are held together dependably before the device is mounted in the vehicle suspension, by a flexible- material part the shape and thickness of which can be chosen in order to afford effective catching. Independently, sealing may be afforded under the best conditions, using a flexible sealing lip .

Preferably, the annular rib with the associated sealing lip are arranged on one side with respect to the rolling bearing, an additional sealing means being arranged on the opposite side.

When the annular rib with the associated sealing lip are arranged on the inside with respect to the rolling bearing, the flexible- material part of the said body may have an additional sealing lip arranged on the outside and in contact with a wall o f the upper cup .

When the annular rib with the associated sealing lip are arranged on the outside of the rolling-contact bearing, the body of the lower cup advantageously has, on the inside, a labyrinth seal form co llaborating with a complementary form of the upper cup . Because the ingress o f water is less o f a risk on the inside, it is thus possible to reduce friction while at the same time ensuring sufficient sealing.

In one embodiment, the annular rib and the associated sealing lip are arranged on one and the same side of the hooks of the upper cup, for examp le above the hooks of the upper cup .

In another embodiment, the annular rib and the associated sealing lip are arranged one on each side of the hooks of the upper cup .

In one embodiment, the flexible-material part of the said body has an additional sealing lip also associated with the annular rib , the two sealing lips being arranged one on each side of the said rib .

The rigid-material part and the flexible-material part of the said body are advantageously moulded on one another in synthetic materials o f different kinds.

For preference, the flexible-material part is arranged on the lower surface of the said body so that it can absorb vibrations transmitted by the suspension spring.

Another aspect of the invention proposes a strut comprising a shock absorber and a suspension thrust bearing device as described hereinabove.

The present invention will be better understood from studying a number o f embodiments which are described by way of entirely nonlimiting examples and illustrated by the attached drawings, in which:

- Figure 1 is a view in cross section o f a first embodiment of a suspension thrust bearing device;

- Figure 2 is an enlarged view o f part of Figure 1 ;

- Figure 3 is a view in cross section similar to that of Figure 1 ; but of a second embodiment of a suspension thrust bearing device; and - Figure 4 is a view in cross section similar to the previous ones, showing a third embodiment o f a suspension thrust bearing device; and

- Figure 5 is a view in cross section similar to Figures 3 and 4 , showing a suspension thrust bearing device that combines the features of the devices illustrated in Figures 3 and 4.

As illustrated in Figure 1 , a suspension thrust bearing device comprises, according to a first embodiment, a rolling bearing 1 forming an axial thrust bearing. The rolling bearing 1 is supported by a lower cup 2 which also constitutes a means against which a suspension helical spring, not depicted in the figures, can bear. The rolling bearing 1 is enclo sed between the lower cup 2 and an upper cup 3. The rolling bearing 1 comprises an upper ring 4 in contact with the upper cup 3 and a lower ring 5 in contact with the lower cup 2.

A plurality o f rolling elements 6 which, in the example illustrated are balls, are arranged in one row and held at a suitable spacing between the rings 4 and 5 by a cage 7. The balls 6 are arranged between raceways formed by the upper 4 and lower 5 rings. Advantageously, the rings 4 and 5 may be obtained from one and the same thin sheet metal blank by cutting and pressing by virtue of the fact that the outside diameter of the upper ring 4 is substantially equal to the inside diameter of the lower ring 5.

As can be seen more specifically in Figure 2, the upper ring 4 has a toroidal portion 4a in contact with a complementary surface of the upper cup 3. The said toroidal portion 4a is extended inwards by a cylindrical annular surface 4b . The interior surface of the toroidal portion 4a forms the raceway for the balls 6. The lower ring 5 also has a toroidal portion 5 a the concave exterior surface of which forms a raceway for the balls 6 and which comes into contact with a complementary surface of the lower cup 2. The toroidal portion 5 a is extended towards the upper cup 3 by a cylindrical annular portion 5b the end o f which has a radial rim 5 c .

The upper cup 3 may consist of a one-piece component made o f a synthetic material, for example of polyamide PA-6,6 which may or may not be glass fibre reinforced. The upper cup 3 comprises an upper surface 3 a (Figure 1 ) which, in the example illustrated, is directed at right angles to an axis X-X which makes an angle a with the axis Y-Y of the suspension spring that has not been illustrated in the figure. The axis X-X constitutes the axis of bearing on the bodywork of the vehicle, which bearing may invo lve an elastic mount, not illustrated, in contact with the surface 3 a o f the upper cup 3. The upper cup 3 also comprises an internal annular skirt 3b the thickness of which is not as great as that of the rest of the upper cup 3 and which on its lower peripheral edge has a plurality o f hooks 3 c, likewise distributed about its circumference and facing outwards, that is to say towards the rolling-contact bearing 1 . The hooks 3 c, which form outwardly directed radial projections, may, as an alternative, be replaced by a continuous rib produced circumferentially around the edge o f the axial skirt 3b . The upper cup 3 further has a support portion 3h which, on the inside, has a surface 3 d (Figure 2) which on the whole complements the toroidal surface 4a of the upper ring 4 of the rolling- contact bearing 1 . The upper cup 3 also has a surface 3 e of substantially frustoconical shape, facing towards the inside and capable of contributing towards the sealing of the device as will be seen later on. The surface 3 e continues in the form of an axial skirt 3 f directed towards the lower cup 2, leaving, with respect to the latter, a small-sized gap 8 capable o f preventing the ingress of loose chippings or dust into the device and the rolling-contact bearing 1 .

The lower cup 2 has a body 9 formed of a part 10 made of a rigid material and of a part 1 1 made of a flexible material. A reinforcing insert 12 gives the lower cup 2 satisfactory rigidity and good transmission o f axial and radial load between the suspension spring, not depicted in the figure, and the rolling bearing 1 . The part 1 0 of the body 9 may, for example, be made of a rigid synthetic material such as a polyamide PA-6,6, which may or may not be glass fibre reinforced. The rigid part 10 has a bearing surface 10a for the toroidal part 5 a of the lower ring 5 of the rolling bearing 1 . The rigid part 10 also has a part 10b (figure 1 ) in the form o f a radial plateau and a cylindrical annular skirt 10c arranged towards the inside and extending axially away from the upper cup 3. The reinforcing insert 12, which is advantageously made of metal, is arranged in the radial plateau portion 10b as in the annular skirt 10c . The synthetic material of which the rigid part 10 is made has advantageously been moulded over the reinforcing insert 12. It will be noted that the peripheral edge of the plateau 1 0b is situated a small distance away from the lower edge 3 f o f the upper cup 3 so as to define, as already mentioned, a small-sized gap 8 to form a labyrinth seal.

The flexible-material part 1 1 may be made of an elastomer, for example a synthetic rubber such as polyurethane. This material is overmoulded onto the reinforcing insert 12 and the rigid part 10, forming a surface 1 1 a, which may be continuous or discontinuous, which can come into direct contact with the suspension spring or with a mounting element o f the said spring not depicted in the figures, so as to absorb vibrations thanks to the flexible nature of the material o f which this part 1 1 is made . The overmoulding of the part 1 1 is achieved by virtue of the existence of open channels left in the rigid- material body 9 and in the insert, the moulding of the flexible-material part 1 1 thereby forming axial lugs l i b, 1 1 c which extend from the lower surface 1 1 a through the body 9 as far as the upper surface thereo f.

The part 1 1 has, radially on the inside of the rolling-contact bearing 1 , a sealing lip 13 in contact with the upper cup 3 and a radially proj ecting annular rib 14. The sealing lip 13 is in the form of an annular protrusion arranged on the uppermost edge of the flexible- material part 1 1 . The sealing lip 13 is slightly inclined inwards. In the example illustrated, it has a thickness that decreases towards its end so as to increase its flexibility at the point of contact with the upper cup 3. The sealing lip 13 comes into contact with a radial planar surface 3 g of the upper cup 3 . Of course, it would be equally possible to conceive contact with an inclined surface.

The rib 14 extends radially below the sealing lip 13 towards the internal skirt 3b of the upper cup 3. The projecting radial dimension o f the annular rib 14 is such that this rib can collaborate with the hooks 3 c in such a way as to prevent the upper cup 3 from becoming detached from the lower cup 2 before the device has been mounted in the suspension o f a motor vehicle. Specifically, what the annular rib 14 does is to prevent the hooks 3 c from moving in a direction that would allow the upper cup 3 to become detached from the lower cup 2. This effect of axially retaining the cups 2 and 3 the one relative to the other is thus obtained by means of a rib 14 which forms an integral part of the flexible-material portion 1 1 . The thickness of the radial rib 14 can be chosen so as to obtain this axial retention technical effect without there being any need to modify the structure of the sealing lip 13 which, on the other hand, can be designed to optimize sealing through contact with the surface 3 g. It will be noted that, in the example illustrated, the annular rib 14 has a radial lower surface 14a which is able to collaborate with a corresponding radial surface of the hooks 3 c. The rib 14 also has an upper radial surface 14b which faces the sealing lip 1 3. The rib 14 thus has a shape o f substantially rectangular cross section, while at the same time being connected to the flexible-material part 1 1 by fillets 14c and 14d. The sealing lip 13 is secured to an axial annular portion 13 a o f the part 1 1 so that the lip 13 can flex with respect to the said annular portion 13 a connected to the rib 14 by the fillet 14d without the presence of the rib 14 being able to reduce the ability o f the sealing lip 13 to flex. By thus combining a sealing lip such as the flexible-material lip 13 with a projecting annular rib such as the rib 14, that forms an integral part of the same flexible-material piece 1 1 , it is possible to optimize each of the respective technical functions o f the sealing lip 13 and of the rib 14, while at the same time simplifying manufacture, because these two associated elements form an integral part of one and the same piece.

Although in the examp le illustrated, the upper cup 3 comprises a plurality o f individual hooks 3 c associated with a continuous annular rib 14, it will be understood that it is equally possible to replace the multip le hooks 3 c with an outwardly projecting annular portion capable o f co llaborating with the annular rib 14. It would also be possible for the annular rib 14 to be replaced by several axial- retention segments.

On the outside o f the rolling-contact bearing 1 , the flexible- material part 1 1 also, in the example illustrated, has an outwardly proj ecting additional sealing lip 15 , inclined slightly upwards, and that comes into rubbing contact with the surface 3 e of the upper cup 3. Sealing on the outside is thus afforded by the combination o f a labyrinth seal formed by the narrow passage 8 and of the sealing lip 15.

Figure 3 illustrates a second embodiment in which elements that are similar bear the said references . In this embodiment, the structure of the lower 2 and upper 3 cups differs slightly. Nonetheless, the lower cup 2 still has a rigid-material body 10 onto which a flexible-material part 1 1 is overmoulded. The sealing lip 13 associated with the radial rib 14 are, in this embodiment, arranged on the outside of the rolling-contact bearing 1 . The sealing lip 13 , which projects outwards and is inclined upwards, comes into rubbing contact with a surface 3 f of a bell-shaped part 15 that faces downwards and forms an integral part of the upper cup 3. This bell-shaped part 15 also has an end in the form o f an axial skirt 16 with inwardly radially projecting hooks 17 capable o f co llaborating with the rib 14 to prevent unwanted separation o f the upper cup 3 with respect to the lower cup 2. Once again, the hooks 17 may be designed in the form o f individual hooks or of a continuous radial rib . A small gap 8 is maintained between the underside of the hooks 17 and the upper surface of the plateau-shaped part 10b of the body 9, in order to create a static seal in the form o f a labyrinth seal. In this way, sealing on the outside can be afforded by the combination o f this labyrinth seal and of the sealing lip 13.

It will be noted that, in this embodiment, the axial retention hooks 17 are arranged facing a portion of the flexible-material part 1 1 so that in the event of radial misalignment of the cup 3 with respect to the cup 2, no noise is generated. The radial clearance there is between the hooks 17 and the flexible-material piece 1 1 can therefore be reduced to no disadvantage, thus improving the static seal created by the formation of a labyrinth seal to supplement the sealing already created on account of the small gap 8.

On the inside of the rolling bearing 1 , sealing is afforded, in this embodiment, by a labyrinth seal 1 8 consisting o f an axial co llar 19 that forms part of the rigid part 10 of the body 9 and, on the other hand, a groove 20 made in a lower wall of the cup 3. The winding passage thus created by the co llar 19 and the groove 20 with no contact between the various parts, creates enough of a static seal on the inside of the device.

It will be noted that in this embodiment, the lower cup 2 has an axial skirt 10 of axis Y-Y that makes an angle a with respect to the axis X-X which is the axis o f symmetry o f the upper cup 3. This arrangement makes it possible to reduce the radial force exerted by the suspension spring, not depicted in the figure, while at the same time maintaining a good distribution of the axial load exerted by this spring on the axial thrust bearing that the rolling bearing 1 constitutes . The exterior surface o f the rigid-material skirt 10c also has annular ribs 21 , encouraging the attachment of the flexible synthetic material o f the part 1 1 when the latter is overmoulded on the rigid-material part 10. Specifically, in this embodiment, the surface 1 1 a of the flexible part 1 1 is continued in the form o f an axial annular portion l i d which covers the external surface of the rigid-material skirt 10c penetrating between the abovementioned ribs 21 . The rigid-material skirt 10c has, at its lower end, an outwardly directed radial bulge 22 defining a groove 23 for the retention of a protective shock absorber rod boot, not illustrated in the figure.

Figure 4 illustrates a third embo diment similar to the one illustrated in Figure 3. The references of components that are identical have been reused. The only difference compared with the second embodiment illustrated in Figure 3 relates to the layout of the sealing lip 1 3 and of the axial retention rib 14. Specifically, in the embodiment illustrated in Figure 4, the sealing lip 13 comes into contact with a planar radial surface 24 of a plateau-shaped part 25 that forms an integral part of the upper cup 3. The plateau 25 is arranged at the lower end o f the skirt 1 6 and has an external portion 25 a co llaborating, as has just been explained, with the sealing lip 13 , and an internal portion 25b which forms a retaining element capable o f co llaborating with the radially projecting annular rib 14 arranged above the portion 25b of the plateau 25. The sealing lip 13 and the rib 14 therefore find themselves arranged one on each side of the portion 25b . The said portion 25b may be continuous or may be in the form o f a plurality o f individual hooks. It will be noted that, in this embodiment, the part 25b or the individual hooks that replace it, face the flexible material 1 1 so that it is possible to reduce the radial clearance there is without the risk of generating noise, as in the embodiment of Figure 3. Sealing on the inside is afforded by a labyrinth seal 1 8 as in the embodiment o f Figure 3.

The embodiment of Figure 5 combines the embo diments illustrated in Figures 3 and 4. In this embodiment, the radially proj ecting annular retaining rib 14 is associated with a sealing lip 13 arranged in the same way as in the embo diment of Figure 3 , that is to say directed upwards and in contact with the surface 3 f of the upper cup 3. In addition, a second sealing lip 26 is identical to the sealing lip 13 illustrated in Figure 4 and comes into contact, like the former sealing lip, with the part 25 a of the plateau 25. In this embodiment, sealing on the outside is therefore improved because it is obtained using the two sealing lips 13 and 26. Axial retention o f the upper cup 3 with respect to the lower cup 2 is still afforded by the rib 14, under the same conditions as in the embodiments illustrated in Figures 3 and 4. These differences aside, the features of the embodiments illustrated in the preceding figures are repeated.

The various embodiments that have just been described make it possible to obtain a suspension thrust bearing device the sealing of which is afforded by one or more flexible sealing lips, while axial retention o f the upper cup with respect to the lower cup is obtained by an element that is independent but nonetheless forms an integral part of the flexible-material piece which defines the sealing lip . By thus separating the two technical functions : sealing on the one hand, and axial retention on the other, it is possible to improve the quality o f the sealing and of the axial retention considerably.

Claims

C L A I M S

1. Suspension thrust bearing device comprising a rolling bearing (1) forming an axial thrust bearing, a lower cup (2) supporting the rolling bearing (1) and forming a means against which a suspension spring can bear, and an upper cup (3) enclosing the rolling bearing, the rolling bearing comprising an upper ring (4) in contact with the upper cup (3), a lower ring (5) in contact with the lower cup (2) and a plurality of rolling elements (6) arranged between the rings, the lower cup (2) having a body (9) formed of a part (10) made of rigid material and of a part (11) made of flexible material defining at least one sealing lip in contact with the upper cup (3), catching means being provided to prevent the lower and upper cups from becoming disconnected axially, characterized in that the flexible-material part (11) °f the said body has a radially projecting annular rib (14) associated with a sealing lip (13), the said rib being capable of collaboration with at least one hook (3c) of the upper cup to prevent the lower and upper cups from becoming axially disconnected.

2. Device according to Claim 1, in which the annular rib with the associated sealing lip are arranged on one side with respect to the rolling bearing, an additional sealing means being arranged on the opposite side.

3. Device according to Claims 1 or 2, in which the annular rib (14) with the associated sealing lip (13) are arranged on the inside with respect to the rolling-contact bearing (1), the flexible-material part of the said body having an additional sealing lip (15) arranged on the outside and in contact with a wall (3e) of the upper cup (3).

4. Device according to Claims 1 or 2, in which the annular rib (14) with the associated sealing lip (13) are arranged on the outside of the rolling bearing (1), the body of the lower cup (2) having, on the inside, a labyrinth seal (18) form (19) collaborating with a complementary form (20) of the upper cup (3).

5. Device according to one of the preceding claims, in which the annular rib and the associated sealing lip are arranged on one and the same side o f the hooks of the upper cup .

6. Device according to Claim 5 , in which the annular rib and the associated sealing lip are arranged above the hooks of the upper cup .

7. Device according to one o f C laims 1 to 4 , in which the annular rib and the associated sealing lip are arranged one on each side o f the hooks of the upper cup .

8. Device according to Claim 7, in which the flexible-material part ( 1 1 ) of the said body has an additional sealing lip (26) also associated with the annular rib ( 14), the two sealing lips ( 13 , 26) being arranged one on each side of the said rib .

9. Device according to one of the preceding claims, in which the rigid-material part and the flexible-material part of the said body have been moulded on one another in synthetic materials o f different kinds.

10. Device according to one of the preceding claims, in which the flexible-material part is arranged on the lower surface of the said body so that it can absorb vibrations transmitted by the suspension spring.

1 1 . Strut comprising a shock absorber and a suspension thrust bearing device according to one of the preceding claims .