GB2204647A

GB2204647A - A seal screen for a rolling element bearing, and a system for detecting the speed of a rotating member making use of this seal screen

Info

Publication number: GB2204647A
Application number: GB08810274A
Authority: GB
Inventors: Franco Colanzi
Original assignee: RIV SKF Officine di Villar Perosa SpA; RIV Officine di Villar Perosa SpA
Current assignee: SKF Industrie SpA
Priority date: 1987-05-08
Filing date: 1988-04-29
Publication date: 1988-11-16
Also published as: FR2614966A1; DE3814921A1; IT8767396A0; FR2614966B1; IT1208885B; ES2007828A6; GB2204647B; GB8810274D0

Abstract

A sealing screen (1) is described, in particular for rolling element bearings, and a system for detecting the angular velocity of a rotating member, in particular a vehicle wheel, usable in an ABS type anti-lock braking system; their principal characteristic is the presence, on an outer face of the sealing screen (1), which is mounted for rotation with the rotating member the speed of which it is desired to detect, with zones (10) of surface discontinuity such as cavities or protuberances disposed circumferentially in succession and spaced with a constant pitch around a circular ring; the said zones of surface discontinuity cooperate with a sensor (28, 29), for example an electromagnetic sensor.

Description

1 0 2. 204647 1 AN IMPROVED SEAL SCREEN IN PARTICULAR FOR A ROLLING

ELEMENT BEARING, AND A SYSTEM FOR DETECTING THE SPEED OF A ROTATING MEMBER MAKING USE OF THIS SEAL SCREEN The present invention relates to an improved type of seal screen which can be mounted for rotation w--t'--- a ---o±at-ing member to seal between this and another member in relative movement with respect to the rotating member, for example between the rings of a rolling element bearing, and operable simultaneously to allow thp speed of rotation of the rotating member to which it is fixedly mounted to be detected by means of a sensor, for example an electromagnetic sensor, cooperating with this seal screen; the invention further relates to a system for detecting the speed of rotation of a rotating member comprising this seal screen.

It is known that currently, especially on sporting motor vehicles or the so-called "grand touring" vehicles there are installed special control circuits of the type known as ABS, the purpose of which is to prevent the wheels of the vehicle from locking,during braking; these circuits comprise, as is known, an hydraulic operative part, acting by means of valves on the braking circuit, and an electronic control part able to make the operative part 2 intervene when "a differential variation in the speed of rotation of the wheels of each axle of the vehicle 1 E greater than a predetermined threshold is detected; these variations in speed are detected by an appropriate known circuit making, use of electromagnetic sensors, one for each wheel of the vehicle, each of which emits a pulse signal proportional to the speed of rotation of the wheel controlled by it; this pulse signal is obtained, in the majority of cases, by mounting, usually on the bearing which supports the wheel, a toothed element known in the art as a "sonic wheel" or "impulse ring"; this element essentially comprises a flange of ferromagnetic material mounted for rotation with the wheel and provided with a toothed ring in correspondence with which the sensor is mounted; during rotation of the wheel, therefore, the alternation in front of the sensor of the solid parts constituted b the teeth and the voids constituted by the spaces between the teeth causes a periodic variation in the air gap between the flange and the sensor and, i therefore, a periodic variation in the magnetic field with a consequent generation by the sensor of an oscillating periodic signal the frequency of which is proportional to the speed of rotation of the wheel.

A disadvantage of the above-described detection system lies in the large di mensions of the sonic wheel and in % 1.11 1 11 its cost, which is also rather high, due to the fact that in order to obtain the necessary constructional precision this must be worked by the removal of shavings. Above all, however, the described system involves the disadvantage of becoming unreliable after a relatively short period of use in that the ferromagnetic dust produced by wear of the braking seal screens becomes mixed with mud from the road, which comes into contact with the vehicle suspension during use, which enters the cavities between the teeth of the sonic wheel and therefore causes a fall or attenuation in the signal produced by the.sensor so that it is necessary periodically to renew the efficiency of the system by frequently washing the wheel-suspension unit.

1 r, The object of the invention is that of providing a system for detectingthe angular velocity of a rotating member, in particular a vehicle wheel, which will be free from the described disadvantages, as well as a seal screen which can be fixed to a rotating memivber and which is able simultaneously to exert a sealing action arid to allow the detection of the angular veloqity of the rgtating member to which it is fixed, for use in this system.

The said objects are achieved by the invention in that it relates to a seal screen, in. particular for roller 1 '.1, 1 4 element bearings, of the type which can be mounted for rotation with a rotating member to seal between this and a member in relative motion with respect to the said rotating member, characterised by the fact that it includes a substantially annular rigid element provided 1 with an outer face extending radially with respect to the axis of symmetry of the said rigid annular element, on which are formed a plurality of substantially identical zones of surface discontinuity in a circular ring circumferentially spaced from one another with a substantially constant pitch.

The invention further relates to a system for the detection of the speed of a rotating member, in particular a vehicle wheel, characterised by the fact that it comprises a seal screen fixed for rotation with the said rotating member and including, frontally an its outer surface and in succession around a circular ring, a plurality of zones of substantially identical surface discontinuity spaced circumferentially from one another with substantially constant pitch, and at feast one sensor disposed opposite the said seal screen, which can be activated by the transit past it of the said zones of surface discontinuity in such a way as to generate a periodic pulse signal having a frequency proportional to the number of the said zones of surface discontinuity . '. 1.

1 which pass in front of it in unit time.

For a better understanding of the invention a non-limitative description of several embodiments is now 5 given with reflerence to the attached drawings, in which:

Figure 1 is a front elevation view of a seal screen formed according to the invention, illustrated cnly in part for convenience; Figure 2 is a section taken on the line I!-II of the seal sgreen of Figure 1; Figure 3 is a sectional side view on a 'Long4tudinal plane of a sealing device making use of a possible variant of the seal screen of the invention; Figure 4 is a front view seen in the direction of the arrow A, of the screen of Figure 3, only partly illustrated f(r convenience; Figure 5 is a side elevation view of a possible variant of the screen of Figure 1; and Figure 6 illustrates two possible applications of the seal screen of the invention in a system for measuring the speed of rot,ation of a wheel.of a vehicle, not illustrated for simplicity.

Making reference to Figures 1 and 2, the reference numeral 1 indicates a seal screen of generally known 6 type, formed by a substantially rigid metal reinforcement element 2 constituted by a flat annular circular washer made of steel or other ferromagnetic material and a possible elastomeric annular element 3 illustrated in broken outlinein Figure 2, defining a deformable sealing lip 4 or, in a varicqnt not illustrated for simplicity, several sealing lips disposed in various possible configurations all well known in the art of sealing assemblies; the rigid reinforcement element 2 is provided with an outer peripheral rim 5 by means of which the screen 1 c,_:;n be fitted to a mechanical member, for example to the outer ring of a rolling element bearing, to sea! between this and another mechanical member in relative movement with respect thereto, for example the inner ring of a rolling element bearing; the rigid reinforcement element 2 is further provided Wi4th an inner -ionally, a possible peripheral rim 6 able to carry, opt projecting sealing lip (or lips) 4 and is delimited by a pair of parallel flat faces 7 and 8 extending radially with respect to the axis of symmetry of the element 2 itself; according to the invention the rigid reinforcing element 2 is provided, on jtsiouter front turface defined by the face 7 and which in use remains accessible from the exterior of the members between which the seal screen 1 is mounted, with a lurality of substantially identical zones 10 of surface discontinuity spaced 7 circumferentially from one another with a substantially constant pitch, which are formed in succession, around a circular ring, one adjacent the other; here and hereinbelow the term "zones of surface discontinuity" will be unders-tood to define portions c.' a surface at which there is a physical change (for example composition of material) or a geometric change (for example variation in curvature or interruption of the surface) of the surface characteristic thereof or of the immediately underlying zone; in the present case the zones 10 of surface discontinuity are formed by means of respective cavities formed on the surface or frontal face 7 a-rid -angular defined by respective radial substantially rect through slots 11 formed in the element 2 by cutting; the cavities or slots 11 are further totally filled with rubber, in particular with plugs 12 disposed flush with the surfaces efined by the faces 7 and 8; if the elastomeric element 3 is also present this is preferably formed integrally with the plugs 12 so that the reinforcement 2 is completely incorporated within the element 3 which also covers one or both of the faces 7 and 8.

In Figure 6 are i-llustrated two possible, examples of use of the screen 1 just described; in particular Figure 6 illustrates the essential parts of a drive axle of a 8 vehicle, not illustrated, comprising a central differential 15, respective half shafts 16, a hub 18 connected for rotation with one of the half shafts 16 and carrying a wheel 19 of the vehicle, and a strut 20 partially illustrated in section for convenience and forming part of a known suspension, not illustrated for simplicity, of the said vehicle, which supports the hub 18 freely rotatably by means of a rolling element bearing 21 having an outer ring 22 connected fixedly to the strut 20 and an inner ring 23 fixedly connected for rctation with the hub 18, and, consequently, with the whetal 19; the half shafts 16 are driven via sleeves 24 in turn carried freely rotatably by the differential casing 15 by means of respective rolling element bearings 25. In such a structure the screen 1 can be mounted directly on inner ring 23 of the bearing 21 carried for rotation this arid in such a way as to seal the rings 22 and 23 against external contaminants so as to preserve the rolling element bearings of the bearing 21 itself, in place of a normal sealing screen of known type, or else fixed for rotation with the half shaft 16, for example on the sleeve 24 or within the bigaring 25;forthe protection of the bearing 25 itself,. again in substitution for the normal sealing screen which, however, is necessary in this position as also in the preceding position, on the bearing 21; in the case of assembly in place of the the with Al 9 necessary sealing screen on the bearing 25, the screen is immersed in an oil bath; in both cases, however, the screen 1 is driven to rotate at the same speed as the wheel 19 and, by coupling with a respective sensor 28 or 29 of known type, can be activated by the transit in front of it of the zones 10 of discontinuity, in the illustrated example both constituted substantially by a_ simple electromagnetic connected in a known way, not illustrated for simplicity, to an oscillating electronic control circuit of known type and therefore also not illustrated for simplicity; this permits -1,11.1e rea-lisation of a simple and effective rotational speed detection system for a mechanical member, in the present case the wheel 19; during rotation of the wheel 19 the zones 10 of discontinuity transit successively in front of the sensors 28 or 29, which are disposed, according to the invention, facing the respective. screen 1, alternating with the portions of the element 2 from which they are separated and, being constituted substantially by non-ferromagnetic zones (in that they are defined by cavities possibly filled with rubber) cause a periodic variation in the magnetic-fluXI and, therefore, the generation by the sensors 28 or 29 of a periodic pulse signal having a frequency proportional to the number of slots 11 which transit in unit time in front of them, or rather, in short, to the speed of rotation of the wheel 19; this signal, in the present case, can be utilised in an ABS braking system of known type, not illustrated for simplicity, by comparing it with similar signals coming from like sensors cooperating with other sealing screens identical witIT the screen 1 and disposed similarly to this for the protection of corresponding members connected to the other wheels of the vehicle to determine the onset of anomalous differential variations in the speed of these and, consequently, to control in a known way, and therefore not described for simplicity, for example appropriate valves of the bra't'-.-4ng of vehicle. It is obvious that for each wheel tq- it is sufficient to install a single sensor 28 or 219, each ir correspondence with a respective single screen 1 utilised on its own or even in combination with other sealing members to forip a more complex sealing system, as long as each screen 1 rotates together wth the respective wheel 19 at the same speed or at a speed proportional to it in a known ratio; thus the configuration illustrated in Figure 6, where two different screens 1 with respective different sensors 28 and 29 are used for a single wheel 19, must be considered purtlylas exemplary. which is why both the sensors 28 and 29 are illustrated in broken outline; in practice, therefore, only the sensor 28 or, alternatively, only the sensor 29 will be installed for each wheel of the vehicle, whilst at the limit it is possible to utilise all the screens 1 in place of the normal sealing screens, which are free from slots 11, these latter not in any way altering the sealing efficiency of the screen 1 according to the invention with respect to that of known screens so as to leave the vehicle manufacturer or the installer of a possible subsequently installed ABS installation on the vehicle itself the maximum freedom of choice in the most suitable position in which to install the sensors of the installation itself.

possible In Figures 3 and 4 there is illustrated a first variant of the above- described screen 1, generally indicated 30 and illustrated for the purpose of example already installed within the interior of a rolling element bearing 31 of known type, between respective outer rings 32 and inner rings 3 thereof for the protection of an internal cavity 34 defined between them and housing respective rolling bodies 35; the screen 30 forms part of a sealing assembly 36 of known type composed of two elements and the screen 30, which includes a sleeve portion-36 which canbe fitted onto the ring 33 and an annular flange portion 37 projecting radially from'th6 portion 36 with respect to the axis of symmetry of the screen 30, and by a supplementary screen 38 of known type, provided with respective elastomeric 12 deformable annular sealing lips 39 and 40 which act to slide with low friction under pressure on respective inner surfaces of the screen 30 facing towards the screen 38, and fitted internally on the ring 32. According to the invention a front outer surface 41 of the flange portion 37, facing away from the screen 38 and forming the boundary of the screen 30 and the entire sealing complex 36 towards the exterior of the bearing 31, is provided peripherally on the outside with a plurality of zones of surface discontinuity of the type 10, ccristituted by respective cavities 42 disposed in a ring one alongside the other at a constant pitch; these cavities 42 are defined, in this embodiment of the invention, by respective radial indentations 43 formed on the rigid element defined by the flange portion 371 in such a way as to present respective concavities facing towards the oiter face 41; the indentations 43 are preferably shaped as illustrated in Figure 4 in such a way as to have an arcuate form curved in a sense i corresponding to the sense of rotation, in use, of the member on which the screen 30 is mounted arid such as to ensure that these define a substantially aznular array of blades 45 operable to centrifuge possible external contaminants away from the flange portion 37; in use the screen 30, which is made of ferromagnetic material, acts like the screen 1 described above if it is coupled to an 13 electromagnetic sensor of the same type as the sensors 28 or 29; the passage of the cavities 42 in front of this sensor in fact causes a variation in the magnetic field sufficient to cause the sensor to emit a periodic pulse signal havinga frequency proportional to the number of cavities 42 which tansit in front of it in unit time and, therefore, proportional to the speed of rotation of the ring 33 and of the member to which this is fitted. This result could be obtained, in this case, with an optical sensor in that the cavities 42 are empty so that they are able to reflect light incident on the surface 41 in a manner different from the rest of the surface 41 itself and therefore generate a periodic optical pulse signal.

r the screen 1 is illustrated A further possible variant cl. in Figure 5 wAich is generally indicated with the reference numeral 50; the screen 50 is constituted by an annular washer corrugated in a circumferential sense and delimited by a pair of opposite faces 51 and 52 parallel to one another and constituted by a regular succession of peaks 53 and troughs 54 which; by representing continuous periodic variations in the curvature of the surfaces 52 and 53, define alternate zones of surface discontinuity like the surface discontinuities 10; in practice, according to this variant, the whole of the surface which 14 remains in use facing towards the outside of the member between which the screen 50 is mounted results in a continuous succession of discontinuities; in substance, however, the result does not change in that, by making the screen 50,in ferromagnetic material, the rotation of this in front of an electromagnetic sensor is able to generate a periodic variation in the magnetic field sufficient to activate the sensor itself; obviously the washer constituting the screen 50 can also be embedded in a rubber cladding and/or can he provided with one or more sealing lips of the same type as the lip 4.

From what has been described the advantages connected with the sealing screen formed according to the invention are evident; thus, without losing any part of its normal 'ace the sealing functionality, it lends itself to rep. sonic wheels urrently in use, with a great advantage in terms of reduction in overall weight of the oscillating masses of the suspension of the vehicle and reduction in costs of production and assembly; screens formed according to the invention are in fact very economical to produce in that, thanks to their particular structure they can be produced with sufficient precision for use in combination with..sensors directly by pressing; moreover, they can replace normal sealing elements which would be necessary in any event and therefore do not represent 1 additional elements as are sonic wheels; finally, they make it possible to obtain systems for detecting the speed of rotation of the wheels of a vehicle with high reliability,.practically unaffected by soiling. In the first place, in fact, considering them as sealing members, they are already in themselves less exposed to the deposition of external contaminants such as the dust from wear of the brake seals, if mounted close to the wheels, or not at all exposed to these if mounted in positions inside the differential casing where they are absolutely preserved in an oil bath; the rubber filling of the cavities-which generate the physical discontinuities necessary for the actuation of the sensor, without altering the functionality Obviously further preserves these cavities from being filled by external contaminants; finally detection systems cf reduced dimensions are obtained.

i ..M 1.

A 16

Claims

1. A sealing screen, in particular for rolling element bearings, of the type which can be mounted for rotation with a rotatiig member to seal between this and a member in relative motion with respect to the said rotating member, characterised by the fact that it comprises a rigid substantially annular element provided with an outer face extending radially with respect to the axis of symmetry of the said rigid annular element, on which are formed a plurality jof substantially identical zones of surface discontinuity in a circular ring spaced circumferentially from one another with a substantially constant pitch.

is 2. A screen according tc Claim 1, characterised by the fact that the'Said zones of surface discontinuity are defined by respective cavities formed on the said outer face.

i 3. A screen according to Claim 2, characterised by the fact that the said rigid annular element is constituted by a metal reinforcement made of a ferromagnetic material, and by.the fact that the said cavities are 25 filled with rubber 1 1 4. A screen according to Claim 2 or Claim 3, characterised by the fact that the said cavities are defined by.respective radial through slots of substantially rectangular form passing through the said 5 rigid annular element.

1 5. A screen according to"Claim 2, characterised by the fact that the said cavities are defined by respective radial indentations formed on the said rigid element-in such a way as to present respective concavities in the said outer face; the said indentations being shaped in such a way as to present an arcuate form in the radial direction curved in the sense of rotation of the said rotating member and such as substantially to define an array of blades operable to centrifuge possible external contaminants away from the said rigid element.

6. A screen according to Claim 1, characterised by the fact that it is constituted by an annular washer corrugated in a circumferential sensOe and delimited by a pair of opposite faces parallel to one another and constituted by a regular succqssion of peaks and troughs alternately defining the said zones of surface discontinuity.

7. A system for detecting the speed of a rotating 18 member, in particular a vehicle wheel, characterised by the fact that it comprises a sealing screen fixed for rotation with the said rotating member and including.. on its outer face and in succession around a circular ring, 5 a plurality of substantially identical zones of surface 1 discontinuity spaced circumferentially from one another with a substantially constant pitch, and at least one sensor disposed opposite the said sealing screen and operable to be activated by the transit past it of the said zones of surface discontinuity in such a way as to generate a periodic pulse signal having a frequency proportional to-the number ef the said zones of surface discontinuity which transit past it in unit time.

8. A sealing screen substantially as hereinbefore described with reference to, and as illustrated in, Figures 1 and 2, or Figures 3 and 4, or Figure 5, of the accompanying drawings.

9. A system for detecting the speErd of a rotating member, substantially as hereinbefore described with reference to Figure 6 of the qccompanying rawings.

j Published 1988 at The Patent Office, State House, 66.71 High Holborn. London W01R 4TP. Further copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BRS 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent. Con. 1/87.

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