Sealing device for a hub bearing assembly

Abstract

A sealing device for a hub bearing assembly, equipped with a rolling bearing unit, a circular metal shield, a radially extending end wall and a double cylindrical lateral wall fixed to and practically orthogonal to the end wall, formed by a first cylindrical lateral wall and a second cylindrical lateral wall. The metal shield is angularly coupled to a radially outer ring of the bearing. The second cylindrical lateral wall is connected in a fixed manner to a radially outer edge adapted to cover an axially inner surface of the terminal edge that is potentially subject to oxidation phenomena with the consequent formation of a layer of rust.

Claims

1. A sealing device for a hub bearing assembly equipped with a rolling bearing unit, the sealing device comprising: a circular metal shield keyed on to a radially outer ring of the rolling bearing unit and axially interposed between a phonic wheel and a revolution sensor of the hub bearing assembly; a radially extending end wall; a double cylindrical lateral wall fixed to and orthogonal to the radially extending end wall, the double cylindrical lateral wall being formed by a first cylindrical lateral wall and a second cylindrical lateral wall, the circular metal shield being angularly coupled to the radially outer ring of the rolling bearing unit by means of a stable contact between a radially inner lateral surface of an axially inner terminal edge of the radially outer ring and a lateral surface of the second cylindrical lateral wall, wherein the second cylindrical lateral wall is connected in a fixed manner to a radially outer edge adapted to cover an axially inner surface of the axially inner terminal edge that is subject to oxidation phenomena and a consequent formation of a layer of rust; and a sealant fluid adapted to be applied to one of the axially inner surface of the axially inner terminal edge of the outer ring and the radially outer edge of the shield.

2. The sealing device according to claim 1, wherein the first cylindrical lateral wall and the second cylindrical lateral wall are fixed to one another and bent back fully on to one another through an angle substantially equal to 180.

3. The sealing device according to claim 2, wherein the first cylindrical lateral wall and the second cylindrical lateral wall have thicknesses that are substantially equal to one another.

4. The sealing device according to claim 1, wherein the sealant fluid is a liquid adhesive, a varnish or another liquid or semi-liquid sealant substance.

5. The sealing device according to claim 4, wherein the liquid adhesive is an adhesive that cures in the absence of oxygen.

6. A hub bearing assembly comprising: a rotatable hub, and a rolling bearing unit, having a stationary radially outer ring, a rotatable radially inner ring, and a double ring of rolling bodies, interposed between the stationary radially outer ring and the rotatable hub, and between the stationary radially outer ring and the rotatable radially inner ring, respectively, and a detection unit for detecting an angular velocity of a wheel of a motor vehicle, having a phonic wheel and a sensor, and an axially inner sealing device comprising: a circular metal shield keyed on to the stationary radially outer ring of the rolling bearing unit and axially interposed between the phonic wheel and the sensor; a radially extending end wall; a double cylindrical lateral wall fixed to and orthogonal to the radially extending end wall, the double cylindrical lateral wall being formed by a first cylindrical lateral wall and a second cylindrical lateral wall, the circular metal shield being angularly coupled to the stationary radially outer ring of the rolling bearing unit by means of a stable contact between a radially inner lateral surface of an axially inner terminal edge of the stationary radially outer ring and a lateral surface of the second cylindrical lateral wall, wherein the second cylindrical lateral wall is connected in a fixed manner to a radially outer edge adapted to cover an axially inner surface of the axially inner terminal edge that is subject to oxidation phenomena and a consequent formation of a layer of rust; and a sealant fluid adapted to be applied to one of the axially inner surface of the axially inner terminal edge of the outer ring and the radially outer edge of the shield, and wherein the axially inner sealing device is angularly coupled to the stationary radially outer ring.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) The invention will now be described with reference to the attached drawings, showing some non-limiting exemplary embodiments of the invention, in which:

(2) FIG. 1 is an axially symmetric cross section of a hub bearing assembly equipped with a sealing device according to the prior art,

(3) FIG. 2 is a detail on an enlarged scale of the axially symmetric cross section of the hub bearing assembly of FIG. 1, equipped with a sealing device according to a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) With reference to FIG. 1, a hub bearing assembly is indicated as a whole by the number 10.

(5) The assembly 10 provides a hub 20, rotatable and acting as a radially inner ring of the bearing, a bearing unit 30, a detection unit 40 for detecting the angular velocity of a wheel of a motor vehicle, and a sealing device 50 in an axially inner position. Throughout the present description and claims, any terms and expressions indicating positions and orientations such as radial and axial are to be interpreted as relating to the central axis of rotation X of the bearing unit 30. However, expressions such as axially outer and axially inner refer to the assembled condition, and in the present case preferably refer to a wheel side and to a side opposite the wheel side, respectively.

(6) The bearing unit 30 provides a stationary radially outer ring 31, a rotatable radially inner ring 32, and a double ring of rolling bodies 33, 34, in this example balls, interposed between the outer ring 31 and the hub 20, and between the outer race 31 and the inner ring 32, respectively. To simplify the graphic representation, the references 33 and 34 can relate either to individual balls or to rings of balls; in particular, 33 indicates the axially outer ring of balls or individual ball, and 34 indicates the axially inner ring of balls or individual ball. Also for the sake of simplicity, the term ball is frequently used by way of example in the present description and in the appended drawings, rather than the more generic term rolling bodies (and the same reference numerals are also used). However, it should be understood that any other rolling bodies (such as rollers, tapered rollers, needle rollers, etc.) can be used in place of the balls.

(7) The stationary outer ring 31 has an axially extending tubular main portion 31a, which defines in its interior the races 35 and 36 for the rings of rolling elements 33 and 34 respectively. The outer ring 31 also has an axially inner terminal edge 31b, on the radially inner lateral surface 31b of which (see FIG. 2) the sealing device 50 is fitted, as described more fully below.

(8) The rolling elements 33, 34 also rotate, respectively, on the hub 20 and on the radially inner ring 32, which is fitted on the hub 20. The hub 20 and the inner ring 32 form the races 37 and 38 for the rings of rolling elements 33 and 34 respectively.

(9) The hub 20 has a central tubular portion 21 to which an axially inner rolled edge 22 is stably connected, this edge acting as an axial shoulder for the inner ring 32 and providing its axial pre-loading. Preferably, the rolled edge 22 is formed, after the inner ring 32 has been fitted, by cold plastic deformation, particularly by swaging or another similar operation.

(10) The detection unit 40 for detecting the angular velocity of a wheel of a motor vehicle provides a phonic wheel 41 angularly coupled to the rotating ring of the bearing, in this case the radially inner ring 32, and a sensor 42, in this case a revolution sensor capable of acquiring a signal generated by the phonic wheel which can be used to monitor the kinematic operating parameters of the bearing, hub and wheel assembly. In particular, the phonic wheel 41 has a first cylindrical metal shield 41a, coupled to the inner ring 32, connected in a fixed way to a second shield 41b extending in a radial direction. An annular disc 41c of magnetized plastic or rubber is attached to this second shield 41b, by a suitable adhesive medium for example. The annular disc 41c is therefore also angularly fixed to the rotating ring of the bearing. An example of material used for the annular disc 41c is ferro-plastic, a versatile material composed of 90% barium or strontium ferrite, the remaining 10% being thermoplastic binders. Ferro-plastic is an inert material which may be isotropic or anisotropic and, depending on the end use, may be magnetized. It is also has a high degree of resistance to atmospheric agents because of its thermoplastic component. Plasto-ferrite is magnetized in various modes, including the multipolar mode.

(11) With reference to FIG. 2, the sealing device 50, according to the present invention, provides a shield 51 which is keyed on to the outer ring 31 of the bearing 30 and is axially interposed between the phonic wheel 41 and the revolution sensor 42 (FIG. 1). The shield 51 is substantially cup-shaped and provides a circular, substantially radially extending end wall 52, and a double cylindrical lateral wall 53 which is fixed to and practically orthogonal to the end wall 52. The double cylindrical lateral wall 53 is formed by a pair of lateral walls 54, 55 which are fixed to one another and bent back fully on to one another through an angle substantially equal to 180, and which are of substantially equal thickness. The first cylindrical lateral wall 54 is connected in a fixed way to the end wall 52 and is placed at an angle of substantially 90 to the end wall. The second cylindrical lateral wall 55 has a radially outer lateral surface 55a. This surface is the surface affected by the force-fitting of the shield on to the radially inner lateral surface 31b of the axially inner terminal edge 31b of the outer ring 31. The second cylindrical lateral wall 55 is connected in a fixed way to a radially outer edge 56 and is placed at an angle of substantially 90 to this edge. The radially outer edge is the portion of the shield 51 adapted to cover an axially inner surface 31b of the terminal edge 31b, in other words the surface of the outer ring 31 that may be subjected to oxidation phenomena and the consequent formation of a layer of rust.

(12) Other things being equal, the particular configuration with a double cylindrical lateral wall 53 makes it possible to practically double the thickness of the wall of the shield subjected to force-fitting, thereby providing a more robust and reliable solution.

(13) The sealing device further provides a sealant fluid 57, which is applied to the axially inner annular surface 31b of the terminal edge 31b of the outer ring 31, or alternatively to the radially outer edge 56 of the shield 51. The main function of the adhesive is to contribute to the metal-to-metal seal between the radially outer edge 56 and the axially inner annular surface 31b, preventing the infiltration of water and contaminants and thereby reducing the risk of oxidation and rust formation along all the inner surfaces of the bearing rings.

(14) The sealant fluid that is used may be a liquid adhesive characterized in that it cures in the absence of oxygen, or a varnish or other liquid or semi-liquid sealing substance, produced, purely by way of example, by one of the following technologies:

(15) acrylic adhesives, for example cyanoacrylate-based adhesives, also known as instant adhesives. These adhesives may optionally be formed by UV curing. Thus they combine the advantages of UV curing technology with the characteristics of instant adhesives;

(16) polymer varnishes, for example an acrylic varnish containing a pigment in suspension in an acrylic polymer emulsion;

(17) aerobic adhesive, which may optionally be filled with elastomers;

(18) anaerobic adhesive.

(19) The sealing device 50 is fitted on to the outer race 31 of the bearing in the following manner:

(20) the sealant 57 is applied to the axially inner annular surface 31b of the terminal edge 31b of the outer ring 31, or alternatively to the radially outer edge 56 of the shield 51;

(21) force-fitting with radial interference (press-fitting) is performed between the diameters of the coupled surfaces, that is to say the radially inner lateral surface 31b of the terminal edge 31b of the outer ring 31 and the lateral surface 55a of the second cylindrical lateral wall 55 of the shield 51.

(22) The chosen solution is easily applied, and is financially advantageous because the sealant fluid has a low purchase price, but above all it is highly competitive in terms of performance: for example, a mere 0.1 g of sealant fluid substantially improves the seal, by comparison with the seal obtained by metal-to-metal contact, and makes it equivalent to that obtained by using the elastomeric element.

(23) Furthermore, because of the different embodiments described above, the process of assembling the device is not only faster because it does not require the operation of co-moulding the elastomeric element on to the metal shield, but is also simplified further by the flexibility offered by the adhesive fixing operation. This is because, depending on the configuration requirements of the device and the ease of application of the adhesive, this application may be carried out equally well on the terminal edge 31b of the outer ring 31, rather than on the radially outer edge 56 of the shield 51.

(24) It is to be understood that the liquid adhesive may be replaced with any other suitable sealant fluid which contributes to the realization of the same inventive concept.

(25) In addition to the embodiments of the invention as described above, it is to be understood that there are numerous other variants. For example, in the described configuration the outer ring of the bearing and the sealing device are both stationary, but the invention is also applicable to the case of an outer ring and sealing device which are both rotatable. It is also to be understood that the embodiments are solely exemplary and do not limit the scope of the invention, its applications, or its possible configurations. On the contrary, although the above description enables those skilled in the art to apply the present invention in at least one exemplary configuration, it is to be understood that numerous variations of the described components may be devised, without thereby departing from the scope of the invention as defined in the appended claims, whether interpreted literally and/or according to their legal equivalents.