Seal device for bearings of motor vehicle wheel hubs

Abstract: A seal device for wheel hub bearings consists of a centrifugating device (1) equipped with a seal (3) and of a screen (2) mounted onto the outer fixed race (11). The centrifugating device (1) is fixed to the inner rotating race (10) of the bearing, while the seal (3) is provided with lips (7,8) which slide respectively against the outer race (11) of the bearing and against the screen (2) mounted on this race. The centrifugating device (1) and the screen (2) are shaped and positioned between the two races so as to form a first chamber (21) open towards the outside of the bearing, a second closed intermediate chamber (22) and a third chamber (23) open towards the inner parts of the bearing.

Description: The present invention is referred to a sealing device for vehicle wheel hub bearings. Recent generations of bearings, that are assembled on wheel hubs, allow very good operating performance, but are quite expensive, so they need to he provided with seals that guarantee a seal as safe as possible against the infiltration of external polluting agents such as water, dust, mud, to which the members on which the bearings are mounted, are constantly subject. At the moment these seals, although they have two sealing lips, are designed in such a way that these lips wear out very quickly and/or do not ensure satisfying operating conditions at the inside of the bearing, as the lips are not always orientated correctly and pushing on the surface of the member on which they have to carry out the sealing action. The rubber lips slide on a rotating counterface and their sealing action becomes less effective with time. After a working phase, a depression due to the cooling takes place, and after a long time corrosion phenomena may occur on the rotating counterface, in the exact zone that is engaged by the sealing lips. It is an object of the invention to overcome the aforesaid drawbacks by disclosing a device that: improves the seal both of the static type on the bearing's outer race and of the dynamic type (on the inner races); reduces the noxious effect that is due to the thermical variations which the parts that are in contact are subject to; provides a much longer life for the seal and consequently of the bearing itself, even in very hard working conditions. FR-A-2570146 discloses a sealing device comprising a seal which is fitted to the outer race of a bearing. The seal forms three lips, of which two are kept in sliding contact on a centrifugal annular screen fixed to the inner race, while a third lip faces the race. The seal may be on the inner race. Another sealing device for ball bearings is known from DE-A-3838824. A sealing member is disclosed having a supporting part formed by the union of three circular surfaces, of which a first surface is cylindrical and disposed axially, a second intermediate surface is planar and disposed radially, and a third surface is tapered and converging towards the outer race of the bearing. The above and further objects are attained according to the present invention by providing a sealing device as claimed in Claim 1. The device according to this invention is now going to be described with reference to the enclosed drawing, that is a cross-section of the device mounted on a bearing. A vehicle wheel hub bearing comprises an inner rotating race 10, an outer fixed race 11 and two sets of balls 12 forming a ring and kept in position by special cages that are interposed between such races. Members 10, 11 and 12 of the rolling-contact bearing will not be described in details as they are not the object of this invention. They are shown in the drawing with exemplifying shapes and sizes as they can follow any further configuration in accordance with the different uses, without modifying the objects and the benefits of the device that is the object of the present invention. A centrifugation device 1, made of rigid material, is bound to the inner rotating race 10 by means of a rubber seal 3. The seal 3 comprises a lower main body 4, a cylindrical portion 5 that stretches towards the balls 12, and a sealing lip 6 that reaches the wall 9. This wall has a toroidal shape so as to exploit the centrifugal action of the inner revolving race 10 sending away the polluting agents from the inside of the bearing. A small groove 19 is obtained nearby the conjunction of the cylindrical portion 5 to the central body 4, so as to make the two zones of the compressed rubber independent. The centrifugal device 1 is formed by the union of three surfaces: a cylindrical surface 18 disposed axially, a flat surface 17 disposed radially and a tapered surface 16 diverging in the direction of the outer race 11. The seal 3 is wrapped externally around the flat surface 17 of the centrifugal device 1 and covers up completely its tapered portion 16. Referring to the drawing, the seal 3 is further provided with two sealing lips. A main lip 7 stretches towards the outside of the bearing reaching the counterface 13 of a screen 2 that is forcibly fitted on a special surface of the outer fixed race 11. A secondary lip 8 stretches towards the inside of the bearing touching a radially disposed plane surface 20 of the outer race 11. Screen 2 is made of anti-corrosive material (such as stainless steel) and it is formed by the union of three circular surfaces: an axially disposed cylindrical surface 15, a flat radial surface 14 and a tapered overhanging surface 13 diverging towards the outside of the bearing. Surface 14 and 15 are pressed against the outer race 11. The screen 2 and the seal 3 are reciprocally positioned so as to form three separate chambers. A first chamber 21 is open towards the outside of the bearing; a second intermediate chamber 22 is closed by lips 7 and 8, by counterface 13 and by the outer race 11; a third chamber 23 is the most internal one, and it is the one where it is intended to prevent the infiltration of external polluting agents. The only possible way of entrance for polluting elements is the opening 24. The tapered portion 13 of the screen 2 is meant to act as a dust-cover, and it stretches towards the toroidal surface 9 in such a way that it tightens the entrance for the polluting agents and subsequently facilitates the expulsion thereof due to the centrifugal effect. During operation, the centrifugal device 1 and the seal 3 rotate together with the inner race 10. The centrifugal force that is generated expels eventual polluting agents out of chamber 21, and presses the main lip 7 against counterface 13, increasing the contact force and guaranteeing the sealing action. The secondary lip 8 slides on the surface 20 of the outer race 11 preventing polluting agents, that might have passed lip 7 getting into chamber 22, from reaching chamber 23. The sealing lip 6 is designed for ensuring a further sealing action so as to prevent polluting agents from getting near central body 4 of seal 3. Intermediate chamber 22 is filled with grease that lubricates sealing lips 7 and 8. Moreover, in operation the centrifugal device 1 is heat insulated by means of seal 3, from the high temperatures generated by the brake disks, overcoming in this way the above-mentioned drawbacks. The device according to this invention has the further advantage that it needs no springs to ensure the sealing contact between the seal 3 and the race 10 of the bearing.

Claims: A sealing device for motor vehicle wheel hub bearings comprising: a centrifugal device (1) mounted on the inner rotating race (10) of the bearing, the centrifugal device (1) being formed by the union of three circular surfaces, of which one (18) is cylindrical and disposed axially, one (17) is plane and disposed radially, and one (16) is tapered and diverging towards the outer race (11) of the bearing; a screen (2) mounted on the outer fixed race (11), said screen (2) being composed by the union of three circular surfaces, of which a first surface (15) is cylindrical and disposed axially, a second intermediate surface (14) is plane and disposed radially, and a third tapered surface (13) diverges towards the outside of the bearing, said third surface (13) projecting towards a toroidally shaped wall (9) of the inner rotating race (10) so as to define a narrow opening (24) with said toroidally shaped wall (9); a seal (3) provided on the centrifugal device binding the inner rotating race (10) and the centrifugal device (1), the seal (3) having sealing lips (8, 7) sliding respectively against the outer race (11) of the bearing and against the screen (2) mounted onto such race; the centrifugal device (1) and the screen (2) being shaped and positioned so as to form together with the seal a first chamber (21) open (24) towards the outside of the bearing, a second closed intermediate chamber (22) and a third chamber (23) open towards the inner parts of the bearing. A sealing device according to claim 1 wherein the seal (3) on the centrifugal device (1) is bound to the inner race (10) in respect of its central body (4) and a cylindrical portion (5) stretching towards the inside of the bearing. A sealing device according to claims 1 and 2, characterized in that the rubber seal (3) has a groove (19) near the junction between its central body (4) and said cylindrical portion (5).

Inventors: VIGNOTTO ANGELO, VIGNOTTO, ANGELO
Applicants: SKF IND SPA, SKF INDUSTRIE S.P.A.
Application year: 1991
Main classification: F16C33
IPC codes: F16J15, F16C33, F16C19