Hub bearing arrangement and hub bearing seal

TECHNICAL FIELD

The invention relates to a hub bearing arrangement comprising a hub housing, a shaft end, a hub bearing between the hub housing and the shaft end for supporting the hub housing for rotation at the shaft end, a cavity between the hub housing and the shaft end at an inside of the hub bearing, and a seal at the shaft end between the hub bearing and the cavity to prevent transfer of bearing grease between them. The invention also relates to such a seal.

BACKGROUND

Particularly in vehicle wheel hubs, the cavity described above between the hub housing and the shaft end is usually partly full of wheel bearing grease. This bearing grease serves as a reserve stock for ensuring that even in difficult operating conditions the hub bearing and an opposite hub bearing situated at a distance receive sufficient lubrication during their service life. The stock of bearing grease forms an annular mass in the cavity within the hub housing and may, upon the development of heat during operation, "bleed" bearing grease to the hub bearings to prevent their possibly running dry and seizing when their local grease stock is used up. Examination of wheel hubs which have completed their service life shows, however, that the reserve stock is most often substantially intact, i.e. not used up. This means not only unnecessary extra costs for the bearing grease itself but also environmental pollution when hubs are scrapped. Such a grease stock in a scrapped hub housing of a truck wheel may comprise approximately a kilogram of bearing grease. As well as the original filling, this large amount of residual grease may also be due to bearing grease being pushed past the bearing and into the cavity, partly by centrifugal force during operation and partly by extra input during servicing and maintenance. A certain amount of bearing grease may well also bleed in a wrong direction, i.e. into the cavity. A seal of the kind according to the state of the art indicated in the introduction is referred to in US 5 391 004 A. It comprises a sleeve which has, applied at its ends, funnel-shaped sealing elements made of polymer material which abut sealingly against a rotating outer ring of the respective opposite hub bearing. Such a seal protects the

hub bearing from foreign particles in the cavity and prevents the bearing grease from reaching the cavity. The bearing grease then spreads instead to a space within the sleeve from which it can be moved back to the hub bearings by centrifugal force from a rotating drive shaft. This solution may, however, prevent superfluous grease from bleeding out to the cavity in the hub housing.

SUMMARY OF THE INVENTION

An object of the invention is to provide, relative to the state of the art, an alternative seal solution to the problem of overfilling of bearing grease in the hub housing.

According to a version of the invention, the seal comprises a shield at an axial distance from the hub bearing and with radial clearance with respect to an adjacent surface of the hub housing.

If the clearance is suitably dimensioned, it is possible thereby effectively to prevent excessive amounts of bearing grease from being pushed past the bearing and lying inactively in the cavity, while at the same time small amounts of bearing grease are allowed, where necessary, to continue to bleed in both axial directions. The clearance also reduces the risk of overfilling and consequent overheating. Maintaining the bearing grease better at the bearing makes it possible in principle to dispense with the reserve stock. Where applicable, however, a small bleeding reserve of bearing grease may still be allowed to remain in the cavity, to cater for difficult operating conditions and prevent corrosion in the hub housing.

According to an embodiment of the invention, the shield has axial wall portions adapted to at least partly maintaining wheel bearing grease between them. In other words, these wall portions divide the shield into compartments which may prevent a significant proportion of the bearing grease from being set in motion by the rotation of the bearing and thereby being driven or bleeding out into the cavity. The wall portions may also stiffen the shield so that it can withstand more pressure from the bearing grease. The shield may further be connected to the shaft end via a bearing spacing sleeve.

The shield may then also be arranged on a shield retainer which is releasably connected to the bearing spacing sleeve. It will then also be possible to fit the retainer subsequently on an existing hub bearing arrangement.

In addition, the retainer may be axially located on the bearing spacing sleeve by locking teeth which engage in a recess in the bearing spacing sleeve.

Other features and advantages of the invention are indicated by the claims and the description of embodiment examples set out below.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 depicts partly in longitudinal section, with portions cut away, a hub bearing arrangement according to the invention; and

FIG. 2 depicts separately a pair of shield retainers fitted on a spacing sleeve of the arrangement in FIG. 1.

DETAILED DESCRIPTION OF EMBODIMENT EXAMPLES

The hub bearing arrangement in FIG. 1 designated generally by ref. 10 has in a conventional manner a vehicle wheel hub housing 20 which is supported by a pair of taper rolling bearings 40 for rotation on a rotationally fixed hollow shaft end 30. In the example depicted, a drive shaft 32 extends through the shaft end 30. The drive shaft 32 engages drivingly with a conical drive shaft flange 80 which is itself in driving engagement, in a manner not depicted in more detail, with the hub housing 20 in order drivingly to rotate the hub housing 20 about the shaft end 30.

Each of the two rolling bearings 40, 40 has in a conventional manner an outer ring 42 and an inner ring 44 between which there are rollers 46. The inner rings 44, 44 are kept at a mutual axial distance by a bearing spacing sleeve 60 on the shaft end 30. A cavity 22 is delineated between, on the one hand, the bearings 40, 40 and, on the other hand, the spacing sleeve 60 and the inside of the hub housing 20.

As depicted at the bottom of the left bearing in FIG. 1, a region in and about each bearing 40 is filled with an annular mass of wheel bearing grease 70 at the time of delivery of the bearing arrangement. Conventionally there is also a reserve stock in the form of an annular mass of wheel bearing grease in the cavity 22, as indicated by chain-dotted lines at 70'. There is also within the drive shaft flange 80 an annular

mass of wheel bearing grease 70" which, by centrifugal force when the drive shaft flange 80 rotates during operation, may be pressed against the outer (in FIG. 1 the left) bearing 40.

At the side of the inner bearing 40 which faces away from the cavity 22 there is a hub seal 34. FIG. 1 also depicts a holder 36 for an undepicted angle sensor.

According to the invention there is at an axial distance from each hub bearing 40, with radial clearance s with respect to an adjacent surface of the hub housing 20, a shield 52 for preventing transfer of bearing grease between the respective bearing 40 and the cavity 22. During operation, large or excessive amounts of bearing grease 70 are thus prevented from being pressed into the cavity 22, while at the same time small amounts are still allowed to bleed in both axial directions between the respective bearings 40 and the cavity 22. The reserve stock 70' can thus be dispensed with or at least be greatly reduced. The magnitude of the clearance s is dimensioned with advantage to allow the possibility of insignificant pushing of grease through from the outsides of the bearings 40 by great pressure of the bearing grease 70, so that the function of the bearings is not disturbed, but primarily substantially to only allow bleeding of the grease 70 in both directions past the shields 52, 52.

Although other forms of construction are possible, each shield 52 in the example depicted takes the form of a radial circular flange connected to the shaft end 30 via the spacing sleeve 60. Although the shields 52 may be firmly connected to or formed on the spacing sleeve 60, in the example depicted they are each formed on their respective shield retainer 50 made of, for example, plastic.

As illustrated in FIG. 2, each shield retainer 50 takes the form of a short circular sleeve 54 which can be drawn onto the spacing sleeve 60 and supports the shields 52. A plurality of wall portions 56 distributed round the circular sleeve 54 and directed radially and axially stiffen the shields 52 at the circular sleeve 54 and advantageously divide the shields 52 into divisions or compartments in the circumferential direction. The compartments which face towards the relating bearing 40 enhance the ability of the shields 52 to maintain a local reserve of wheel bearing grease between the shields 52 and the bearings 40 as a result of the grease between the wall portions 52 tending not to be entrained by the rotation of the hub housing 20 and the bearing outer ring 42, and hence also tending not to be pressed out through the gap

s by centrifugal force. This grease reserve may instead bleed locally to the respective bearing 40. To still better maintain this local grease reserve, it is also possible within the scope of the invention for the compartments alternatively or additionally to be completely or partly enclosed by wall portions 53 directed tangentially and axially, as illustrated in the lower enlargement in FIG. 2. The compartments are thus only open in an axial direction towards the respective bearings 40.

The circular sleeve 54 of each shield retainer 50 has also extending from it a plurality of arms 58 distributed round its circumference and directed axially. At its free end, each arm 58 has a locking tooth 59 which engages with, by snapping into, a recess in the form of a circumferential groove 62 on the spacing sleeve 60 in order to locate the shield retainer 50 axially on the spacing sleeve 60.

The description set out above is primarily intended to facilitate comprehension and no unnecessary limitations of the invention are to be inferred therefrom. The modifications which will be obvious to one skilled in the art from perusing the description may be implemented without departing from the concept of the invention or the scope of the claims set out below.