Roller bearing with air passage in a bore provided with flutes

A roller bearing for the rotational guidance of a motor vehicle wheel, the bearing comprising a rotating inner member, a fixed outer member and rolling bodies allowing their relative rotation about an axis. The inner member includes a bore on the periphery of which flutes are provided so as to allow the rotational coupling of a fluted shaft with the internal member. The bearing has a path forming an air passage having an outer channel and an inner channel designed to pass right through respectively each of the members, in which, in combination, the path has a groove formed by the omission of at least the front part of at least one flute, from an intermediate zone of the bore as far as its front face. The downstream end of the inner channel opens out in the groove.

The invention concerns a roller bearing for the rotational guidance of a motor vehicle wheel. Such a bearing typically comprises a rotating inner member on which the said wheel is intended to be associated, a fixed outer member intended to be fixed to the chassis of the said vehicle, and rolling bodies disposed between the said members so as to allow the relative rotation of the members about an axis.

The invention typically applies to a bearing intended to be used in combination with a system for checking and regulating the pressure of the tyre mounted on the wheel.

To do this, it is known how to provide a path forming an air passage between the fixed member and the rotating member of the bearing, so as to be able to supply air to the tyre from the chassis by means of the bearing.

In particular, the document U.S. Pat. No. 4,932,451 describes such a bearing in which the inner member comprises a bore on the periphery of which axially extending flutes are provided so as to allow the rotational coupling of a fluted shaft with the inner member by fitting the said shaft in the said bore.

This document provides for an annular space at the fitting together to enable air to circulate in the bore when the shaft is fitted in.

However, this solution is not fully satisfactory. This is because the geometry of the annular space depends on the position of the shaft in the bore, a position which may vary in manufacture or during the service life of the bearing because of the forces to which it is subjected. In addition, the annular space is formed partly by an annular clearance at the coupling, which is not satisfactory because of the forces that are transmitted between the shaft and the rotating member.

Thus the solution proposed by the document mentioned above poses in particular a problem of reliability of the bearing, both with regard to the air passage function since the geometry of the annular space cannot be controlled precisely, and with regard to the force transmission function.

The invention aims in particular to resolve this problem by proposing a roller bearing in which the path forming an air passage is produced locally at the bore in a particularly simple and limited way, and this with a known reproducible geometry.

To this end, the invention proposes a roller bearing for the rotational guidance of a motor vehicle wheel, the said bearing comprising a rotating inner member on which the said wheel is intended to be associated, a fixed outer member intended to be fixed to the chassis of the said vehicle, and rolling bodies disposed between the said members so as to allow the relative rotation of the said members about an axis, the inner member comprising a bore on the periphery of which axially extending flutes are provided so as to allow the rotational coupling of a fluted shaft with the inner member by the fitting of the said shaft in the said bore, the said bearing comprising a path forming an air passage between the outside of the fixed member and the front face of the rotating member, the said path comprising at least one outer channel and at least one inner channel designed to pass respectively right through each of the members, in which, in combination, the path also comprises a groove formed by the omission of at least the front part of at least one flute, from an intermediate zone of the bore as far as its front face, and the downstream end of the inner channel opens out in the said groove.

In relation to the figures, a roller bearing for the rotational guidance of a motor vehicle wheel is described.

The bearing comprises a rotating member1intended to transmit the rotation movement of a rotating shaft to the vehicle wheel and a fixed member2intended to be fixed to the vehicle chassis. The rotating member1is mounted for rotation about an axis A inside the fixed member2.

In the remainder of the description, the terms “axial” or “longitudinal” and “radial” or “transverse” make reference to planes respectively parallel and perpendicular to the axis A. The terms “inner” and “outer” refer to longitudinal planes situated respectively close to and at a distance from the axis A. In addition, the terms “front” and “rear” refer to transverse planes situated respectively on the wheel side, namely the left hand side inFIG. 1, and on the drive shaft side, namely the right hand side inFIG. 1.

The rotating inner member1comprises a generally cylindrical hub3of axis A which comprises a front part4allowing the association of the vehicle wheel and a rear part5allowing the association of the drive shaft. The diameter of the front part4is greater than that of the rear part5so that the hub3has a shoulder6.

To enable the wheel to be fixed to the hub3, the front part4comprises a fixing flange which is in the general form of an annular ring7extending radially from the outer surface of the front part4. InFIGS. 1 and 2, axial fixing holes8are arranged on the ring7in order to be able to cooperate with members, such as bolts, for fixing the wheel to the hub3. The ring7can also have a centring orifice9for the brake discs.

The rear part5of the hub3comprises an axial bore10centred on the axis A and on the periphery of which axially extending flutes11are provided. The flutes11are intended to allow the rotational coupling of the drive shaft having a fluted end with the hub3by fitting the fluted end in the bore10.

The fixed outer member2is a generally cylindrical part whose axis is disposed coaxially with the axis A. The fixed member2also comprises a flange for fixing to the chassis formed by a radial ring20projecting from the outer surface of the fixed member2and provided with fixing holes21. The fixed member2also has an axial bore12centred on the axis A in which the rear part5of the hub3is rotationally mounted.

In the embodiment depicted, the relative rotation of the hub3and fixed member2about the axis A is provided by two rows of rolling bodies, such as balls13, spaced apart axially and disposed in a space between the hub3and the fixed member2. The balls13are held at equal distances by a cage14and disposed between the inner15and outer16rolling tracks.

InFIG. 1, a front row of balls13is disposed between a front rolling track15produced on the outer surface of the rear part5of the hub3opposite a front rolling track16produced on the bore12. In addition, a rear row of balls13is disposed between a rear rolling track15produced on an inner race18immobilised by fitting on the outer surface of the rear part5of the hub3, the rear rolling track15being opposite a rear rolling track16produced on the bore12.

To improve the positioning and immobilisation of the inner race18on the rear part5, it is possible to provide machining of the outer surface of this part5so as to form a rear shoulder19forming a stop for the inner race18. In addition, in other embodiments, not shown, the inner race18can comprise the two inner rolling tracks15, the inner race18then being fitted on the outer surface of the rear part5and coming into abutment against the shoulder6.

The balls13are arranged in an O-shaped mounting. In such a mounting, the distance between the surfaces of contact of the balls13with the outer rolling track16is less than the distance between the surfaces of contact of the balls13with the inner rolling tracks15. This makes it possible in particular to move the point of application of the loads away outside the bearings, thus producing a rigid compact mounting.

The impermeability of the bearing at the front is produced by a seal22for example made from elastomer associated with the bore12and comprising lips23in contact with the rear part5of the hub3and the shoulder6. At the rear, the impermeability is provided by a dynamic seal24disposed between the fixed member2and the inner race18.

To allow the control and regulation of the pressure of the tyre mounted on the wheel, the bearing according to the invention comprises a path forming an air passage between the outside of the fixed member2and the front face of the hub3.

In particular, the path comprises an outer channel25which extends substantially radially in the vicinity of a median transverse plane of the fixed outer member2. In the embodiment depicted, the outer channel25is formed in the outer member2and comprises an upstream end opening out in the outer face of the outer member2. The upstream end is intended to be connected to a system, not shown, for checking and regulating the pressure of the tyre mounted on the wheel. Such a system comprises in particular a compressor, solenoid valves, control devices for actuating and controlling the solenoid valve and the compressor so as to allow the inflation or deflation of the tyre. The outer channel25also comprises a downstream end opening out at the space between the rolling tracks15,16in which the balls13are provided.

The air path also comprises two assemblies disposed symmetrically with respect to the rotation axis A and each comprising an inner channel26and a groove27in which the channel26opens out. Each inner channel26is formed in the hub3and extends substantially radially between an upstream end opening out in the space and a downstream end opening out at the rear end of the groove27. Each groove27is arranged axially in the bore10and has an opening on the front face of the bore10so as to allow the supply of air to the tyre by means of a system that is not shown.

Thus the air path makes it possible to put the checking and regulation system and the tyre valve in sealed communication so as to be able to supply air to the said tyre.

For other embodiments in which the rotating1and fixed2members comprise several assembled elements, the inner26and outer25channels are designed to pass right through respectively each of the members1,2, and in particular the elements which make them up, in order to be able to provide the air passage function between the outside of the fixed member2and the front face of the moving member1.

Moreover, in order to put in air communication the downstream and upstream ends of respectively the outer25and inner26channels, the air path comprises a sealed annular chamber28provided between the rows of balls13.

InFIG. 1, the chamber28is formed between two adjacent seals29disposed on each side of the downstream and upstream ends of respectively the outer25and inner26channels. The seals29comprise a rigid frame30associated with the outer member2, for example by fitting in, and an elastomeric sealing lip31which is moulded onto the frame30in order to come into rubbing contact on the hub3. The elastomeric lip31is held in rubbing contact on the hub3by an elastic means of the spring type formed for example by a ring32.

According to the invention, each groove27is formed by the omission of at least the front part of at least one flute11, from an intermediate zone of the bore10as far as its front face.

According to one embodiment, this intermediate zone has a length adapted to satisfy the requirements relating to the combination of the two functions fulfilled by the bearing, namely the function of transmitting a rotation force from the rotating shaft to the wheel and the air passage function, whilst complying with the constraints related to the available space and mechanical strength. To do this, provision is in particular made for the intermediate zone to be situated substantially at a distance from the front face that is between 30% and 70% of the axial dimension of the bore10. In particular, inFIG. 1, the intermediate zone is situated substantially at a distance from the front face that is greater than half the axial dimension of the bore10.

In addition, in order to be able to achieve in combination the transmission of the rotation forces and the passage of air in a reduced size and without reducing the mechanical strength, the rear part33of the flutes11in which the groove27is formed has a geometry in transverse section, displayed inFIG. 2, which is similar to that of the other flutes11.

FIG. 4depicts a mounting comprising a drive shaft40fitted in the bore10and immobilised axially therein by means of a clamping nut41. The shaft40comprises flutes arranged to cooperate with the flutes11in the bore10so as to transmit the rotation forces. In this embodiment, the air path of the bore10is formed in the space formed between the periphery of the shaft10and the groove27. In addition, a rear sealing means, in the form of an O-ring seal42, is provided between the hub3and the shaft40, so as to prevent leaks of air from the groove27to the rear face of the bore10.

According to another embodiment shown inFIG. 5, it is possible to make provision for omitting at least one flute11over its entire length, the groove27then being produced over the entire axial dimension of the said flute. In this embodiment, the force transmission function is then provided at the other flutes11.