EP2222987A2

EP2222987A2 - Sealing device with built-in magnetic encoder including at least one frictional radial contact lip

Info

Publication number: EP2222987A2
Application number: EP08872531A
Authority: EP
Inventors: Siegfried Ruhland
Original assignee: Societe Nouvelle de Roulements SNR SA
Current assignee: NTN SNR Roulements SA
Priority date: 2007-12-21
Filing date: 2008-12-08
Publication date: 2010-09-01
Also published as: WO2009103870A2; FR2925643B1; FR2925643A1; WO2009103870A3

Abstract

The invention relates to a sealing device with a built-in magnetic encoder for a bearing, wherein said device includes an inner frame (5) to be combined with a rotary member (3) of the bearing and an outer frame (6) to be combined with a fixed member (2) of said bearing, said frames defining therebetween an annular gap (7) in which the magnetic encoder (1) is combined with the inner frame (5), the outer frame (6) being made of a non-magnetic material so that the magnetic signals provided by the encoder (1) can be read therethrough, said device further including a sealing member (8) associated with the inner frame in order to seal a side of the annular gap (7), the outer frame (6) having a free axial bearing surface (6a) and the sealing member (8) including at least one lip (9a, 9b) provided in radial, frictional contact on said bearing surface.

Description

Sealing device with integrated magnetic encoder comprising at least one radial contacting radial lip

The invention relates to an integrated magnetic encoder sealing device for a bearing, and a rolling bearing assembly equipped with such a device and an information sensor system.

In particular, the invention is applicable for sealing at least one side of the running space of rolling bearings of a motor vehicle, while benefiting from a coding of the angular position of the rotating member of the bearing.

Such bearings, when equipped with a speed sensor, angular position and / or direction of rotation system, may in particular be used for mounting a motor vehicle wheel which is provided with a embedded system of global control of the chassis. Indeed, the information can then be used by a computer of such a system as well as by all embedded systems using the measurement of wheel speed as input data.

One of the problems that arises with such assemblies is that of the protection of the encoder vis-à-vis the pollutants, in combination with the protection of the running space.

To solve this problem, it has been proposed an integrated magnetic encoder sealing device having an annular space formed between two rigid armatures which are respectively associated with the fixed member and the rotating member of the bearing. The tightness of the annular space is then achieved by means of a flexible element comprising at least one lip ensuring an axial frictional contact sealing during the rotation of the bearing. Thus, by arranging the encoder in the annular space, the protection of the encoder and the running space with respect to the pollutants is achieved.

However, the quality of the axial frictional sealing contact depends on the relative position of the reinforcements whereas this position can not be guaranteed. precise way in the assembly. Consequently, the control of the deflection of the lip under contact is not sufficient to guarantee the linear contact necessary for the reliability of the sealing function. In addition, the axial contact friction sealing is very dependent on the wear of the lip as well as the beat of it under rotation.

Furthermore, the encoder being disposed in the annular space, the reading of the signals it delivers must be performed through a frame. This embodiment can then lead to an increase in the size of the encoder in order to adjust the amplitude of the signals delivered to a value sufficient for their detection.

In addition, the amplitude of the signals must be all the more important in the case where the sensor is mechanically dissociated from the bearing, since it is then disposed at a greater distance from the encoder.

As a result, the solution proposed by the prior art for sealing requires a footprint which, in the case of reading the signals through the armature, is not always available in the assembly to be performed. Therefore, the satisfaction of the constraint on the amplitude of the signals can be achieved only to the detriment of the protection function, particularly the encoder.

However, in the envisaged applications, the sealing stresses are severe, especially with respect to the rotational speed, the desired service life and the environments to which the sealing devices are subjected.

The invention aims to solve the problems of the prior art by proposing in particular an integrated magnetic encoder sealing device in which the constraints of protection of the encoder and amplitude of the signals it delivers can be satisfied jointly, particularly in small space available in the assembly, even in case of dispersion in the relative positioning of the reinforcement. For this purpose, and according to a first aspect, the invention proposes an integrated magnetic encoder sealing device for a bearing, said device comprising an internal reinforcement intended to be associated with a rotating member of the bearing and an external reinforcement intended to be associated with a fixed member of said bearing, said armatures forming between them an annular space in which the magnetic encoder is associated with the inner armature, the outer armature being made of non-magnetic material so as to allow reading through it magnetic signals delivered by the encoder, said device further comprising a sealing element which is associated with the inner armature to be able to seal one side of the annular space, the outer armature having a free axial span and the sealing element comprising at least one lip which is disposed in radial contact rubbing on said surface.

According to a second aspect, the invention proposes a rolling bearing assembly comprising a fixed member, a rotating member and rolling bodies arranged in a running space formed between said members to allow their relative rotation, said bearing being equipped with least one such integrated magnetic encoder sealing device, the inner armature being associated with the rotating member and the outer armature being associated with the fixed member, said assembly further comprising an information sensor system comprising the encoder which delivers magnetic pulses and a sensor provided with at least two sensitive elements able to detect these pulses, said sensor being arranged opposite the encoder, in front of the external armature so that said pulses are detected through said armature.

Other objects and advantages of the invention will appear in the description which follows, made with reference to the appended figure which is a partial view in longitudinal section of an integrated magnetic encoder sealing device according to an embodiment of the invention. 'invention. In connection with this figure, there is described a sealing device with magnetic encoder 1 integrated for a bearing, in particular for a rolling bearing or a wheel bearing of a motor vehicle.

The bearing comprises a fixed member 2, a rotating member 3 and rolling bodies 4 arranged in a running space formed between said members to allow their relative rotation. In the embodiments described, the rotating member 3 is internal with respect to the fixed member 2, without this limiting the invention to this particular embodiment.

In the description, the terms of positioning in space are taken with reference to the axis of rotation of the bearing (horizontal in the figure which shows one side of the section, the other side being symmetrical with respect to said axis). In particular, the term "inside" relates to a disposition close to this axis and the term "outside" relates to a remote layout of this axis. Moreover, the terms "external" and "internal" are relative to the arrangement in the running space, namely on the left in the figure for internal and on the right for external.

To seal one side of the running space, the bearing is equipped with a sealing device which comprises an annular internal reinforcement 5 intended to be associated with the rotating member 3 and an annular external reinforcement 6 intended to be associated with the fixed member 2. In particular, the frames 5, 6 may be rigid by being made of metal material, in particular stamped sheet metal. According to one embodiment, each side of the running space can be sealed by a sealing device respectively.

The sealing device also incorporates a magnetic encoder 1. To do this, the armatures 5, 6 are arranged to form between them an annular space 7 in which the magnetic encoder 1 is associated with the inner armature 5, in particular by overmolding. The internal armature 5 shown comprises a free radial bearing surface 5a on the outer face of which the encoder 1 is associated for axial reading of the signals. In addition, the inner armature 5 has an inner axial bearing 5b whose inner face is fitted on the rotary member 3. The radial bearing 5a and axial 5b are connected by a radial connecting surface 5c which, by providing an axial portion 5d between them is axially offset inward with respect to the free radial bearing surface 5a.

Furthermore, since the encoder 1 is disposed inside the annular space 7, the reading of the magnetic signals delivered by said encoder must be performed through the external armature 6. To do this, it is intended that the external frame 6 is made of non-magnetic material. Moreover, as shown in the figure, the encoder 1 has in particular a large thickness in order to increase the amplitude of the signals to be detected through the outer armature 6. Thus, the encoder 1 substantially fills the entire space 7 available between the frames 5, 6, which leaves a limited space for sealing.

According to one embodiment, the encoder 1 forms a multipolar magnet comprising 2N pairs of poles, said magnet being made of elastomeric material loaded with magnetic particles.

By way of example, the coder 1 may be made of a nitrile-acrylic butadiene copolymer (NBR), optionally mechanically reinforced with fillers such as carbon black, the magnetic particles being able to be based on ferrite. Thus, by magnetization of the encoder 1, it is possible to obtain a plurality of contiguous domains which have a regular alternation of North and South poles forming a pair of poles.

To protect the encoder 1 against pollutants, the device also comprises a sealing element 8 which is associated, in particular by overmoulding, with the internal armature 5. In particular, the combination of the coder 1 and the sealing element 8 on the same armature 5 has the advantage of only have to prepare this frame for overmolding. In particular, the sealing element 8 may be made of elastomeric material, for example of the same nature as that of the coder 1, in particular nitrile butadiene copolymer (NBR), optionally mechanically reinforced with fillers such as carbon black, hydrogenated NBR (HNBR), fluoropolymer or polyacrylate.

The sealing element 8 comprises at least one sealing lip 9, said lip being disposed on a free axial bearing surface 6a of the outer armature 6 so as to ensure a radial frictional sealing contact during the rotation of the bearing . Thus, the control of the deflection of the lip 9 under contact can be satisfactorily guaranteed so as to form the linear contact necessary for the reliability of the sealing function.

In relation with FIG. 1, the sealing element 8 comprises two axially spaced lips 9a, 9b, said lips being in radial contact rubbing on the free axial bearing surface 6a. To do this, the sealing element 8 comprises an annular base associated with the inner armature 5, the lips 9a, 9b extending axi-radially from said base. In addition, to facilitate the axial release of the sealing member 8, the base of the inner lip 9a has a diameter greater than that of the base of the outer lip 9b.

The outer armature 6 shown comprises an axial bearing surface 6b on the outer member 2, a radial bearing surface 6c which is connected to the friction surface 6a by a connecting fillet 6d oriented towards the inner frame 5. In addition the signals delivered by the encoder 1 are read axially through the radial span 6c.

In connection with the figure, an outer baffle 16 of diameter greater than that of the sealing element 8 is formed radially between the free end of the radial bearing surface 5a and the inner face of the axial bearing surface 6b. This baffle 16 limits the introduction into the space 7 of the lubricant contained in the running space. Indeed, under the effect of the centrifugation induced during the rotation, the lubricant is trapped at this baffle, without ease to go down to the encoder 1 and the sealing element 8.

The inner axial bearing surface 5b is disposed facing radially of the friction surface 6a, the lips 9a, 9b being formed on the outer face of the inner axial bearing surface 5b to come into radial contact rubbing against the inner face of the friction surface 6a. . Moreover, the free end of the friction surface 6a has a chamfer 6aa oriented towards the lips 9a, 9b. When the armatures 5, 6 are disposed by axial displacement, the chamfer 6aa makes it possible to prevent the lips 9a, 9b from turning inside the free end of the friction surface in order to facilitate their arrangement in radial contact with friction such that shown in the figure.

In addition, the friction surface 6a is disposed opposite the radial bearing surface 5c, a baffle 10 being formed between said bearing surfaces. Thus, the lips 9a, 9b are disposed in an interior space 11 which is separated from the encoder 1 by the friction surface 6a, so as to limit the leakage of the lubricant contained in said space to the outer space 7 containing the encoder 1.

Furthermore, the inner face 1a of the encoder 1 is disposed facing the zone of the outer face of the friction surface 6a which is opposite to the friction zone. In other words, the inner spaces 11 containing the sealing element 8 and outer 7 containing the encoder 1 are superimposed radially. Thus, a sealing device is obtained that is particularly compact axially, while making the sealing more reliable because of the radial frictional contact.

According to another advantageous characteristic of the embodiment shown, the connecting fillet 6d has an annular groove 12 intersecting its outer radius, said groove can be made by plastic deformation or overmolding. In particular, the groove 12 has a section at right angles between an axial portion and a radial portion. Thus, it avoids the flow of pollutants, including water, along the radial scope 6c while it is particularly exposed since it is disposed in the outer plane of the bearing.

In addition, the embodiment of the groove 12 makes it possible to increase the axial dimension of the friction zone, since the cutting of the outer radius makes it possible to benefit from an extended flat contact surface. The increase of the plane contact surface is also conferred by the internal offset of the radial bearing surface 5c opposite which the friction surface 6a is disposed.

The sealing element 8 shown also comprises a deflector 13 which is disposed on the free end of the inner axial bearing surface 5b. The deflector 13 extends radially in the extension of the radial span 6c of the outer armature 6, more precisely by being in the extension of the groove 12 with a reduced clearance between said groove and said deflector.

Thus, in combination with the groove 12, the deflector 13 protects the sealing lips 9a, 9b vis-à-vis the introduction of pollutants. In addition, an annular chamber 14 is formed between the baffle 13 and the outer lip 9b, said chamber being arranged to be able to empty under the effect of centrifugal force induced by rotation. To do this, the thickness of the deflector 13 is reduced to allow axial deflection thereof. In addition, the axial release of the sealing member 8 is facilitated.

The sealing element 8 shown also comprises a static sealing bead 15 which is arranged, opposite the baffle 13, under the free end of the inner axial bearing surface 5b. The bead 15 is intended to be interposed between the axial bearing surface 5b and the zone of fitting with the member 3 so as to confer the static sealing function. Alternatively, the bead may be placed in abutment on the member 3 without interposition in the fitting zone. The bead 15 and the deflector 13 are made in one piece, in particular by molding, with the lips 9a, 9b being connected to them by an axial isthmus 16.

An assembly comprising a rolling bearing according to the invention and an information sensor system comprising the encoder 1 forming a magnet with 2N pairs of poles is described below so as to deliver magnetic pulses. In addition, the system comprises a sensor provided with at least two sensitive elements able to detect these pulses, said sensor being arranged, facing the encoder 1, in front of the outer armature 6 so that said pulses are detected through said frame. In particular, the sensor can be mechanically dissociated from the fixed member 2 and the external armature 6.

In combination with the size of the encoder 1, the increase of the amplitude of the delivered signals can be obtained with a multipolar magnet comprising a reduced number of pairs of poles, for example 2N pairs of poles with N strictly less than 24. In particular , N may be equal to 12 or 6 so as to have a multipole magnet with 24 or 12 pairs of poles. Thus, the number of pairs of poles being reduced, their dimension is greater so that each pole delivers a signal of greater amplitude. It follows therefore that the gap distance, that is to say the distance at which the sensitive elements can detect the signal delivered, is greater than with a conventional magnet 48 pairs of poles for example.

However, the resolution of the signal delivered by such a magnet is less important, since the number of pulses delivered by the sensor per encoder revolution 1 depends directly on the number of pairs of poles.

To overcome this drop in resolution, the sensor comprises a signal processing device detected by the sensitive elements which is arranged to increase the resolution of the output signal relative to that of the detected signals. To do this, the treatment device comprises triggering means and means for applying the XOR function (exclusive OR) on the triggered signals.

The processing of two sinusoidal analog signals S1, S2 which are delivered by the sensing elements is described. In this embodiment, the sensing elements may include Hall effect probes or magnetoresistors. In particular, two sensitive elements can be used to each deliver a sinusoidal signal S1, S2, or two groups of sensitive elements can be used for, by summation of each of the signals of a group, to deliver the two sinusoidal signals S1, S2 from a group respectively. In the description, the term "sensitive element" is used to designate indifferently a sensitive element or a group of sensitive elements.

The two sinusoidal signals S1, S2 are in quadrature and have a resolution equal to that of the signal delivered by the magnet. In one embodiment, this quadrature can be obtained by arranging the two sensitive elements at a distance equal to half a polar length of the magnet.

According to another embodiment, when the distance between the sensitive elements is not perfectly adapted to the polar length of the magnet, the processing device further comprises means for combining the two sinusoidal signals coming respectively from a sensitive element, from so as to deliver two signals S1, S2 in quadrature. In particular, the combining means can form the sum and the difference of the signals so as to respectively deliver the signals S1, S2 in quadrature.

Then, the signals S1, S2 in quadrature are processed by the triggering means to form the digital signals S'1 and S'2. For this purpose, the signals S1, S2 can be triggered around zero in a trigger circuit in which the amplitude of the output signal has a sudden and significant amplitude change for a small increase of the input signal from 'a zero value, so as to form S'1 signals, S'2 squares. The digital signals S'1, S'2 are phase shifted by 90 ° electrical and have a resolution equal to that of the multipolar magnet.

In the embodiment shown, the resolution of the signals S'1, S'2 is then multiplied by two by application of the function XOR. Thus, in the case of a 24 pole pair encoder, the resolution of the output signal is equivalent to that of a 48 pole pair encoder.

Claims

1. Sealing device with integrated magnetic encoder for a bearing, said device comprising an internal armature (5) intended to be associated with a rotating member (3) of the bearing and an outer armature (6) intended to be associated with an organ fixed (2) of said bearing, said armatures forming between them an annular space (7) in which the magnetic encoder (1) is associated with the internal armature (5), the external armature (6) being made of a non-magnetic material of so as to enable the magnetic signals delivered by the encoder (1) to be read therethrough, said device further comprising a sealing element (8) which is associated with the internal armature so as to be able to seal one side of the annular space (7), said device being characterized in that the outer armature (6) has a free axial span (6a) and in that the sealing element (8) comprises at least one lip (9a, 9b) which is arranged in contact ra dial rubbing on said scope.

2. Sealing device with integrated magnetic encoder according to the claim

1, characterized in that the sealing element (8) comprises two lips (9a, 9b) spaced axially, said lips being in radial contact rubbing on the free axial span (6a).

3. Sealing device with integrated magnetic encoder according to the claim

2, characterized in that the sealing element (8) comprises an annular base associated with the inner armature (5), the lips (9a, 9b) extending axi-radially from said base.

4. Sealing device with integrated magnetic encoder according to the claim

3, characterized in that the base of the inner lip (9a) has a diameter greater than that of the base of the outer lip (9b).

5. Sealing device with integrated magnetic encoder according to any one of claims 1 to 4, characterized in that the internal frame (5) has an inner axial bearing (5b) which is disposed facing radially of the friction surface (6a), the lips (9a, 9b) being formed on the outer face of the inner axial bearing (5b) to come into radial contact rubbing on the inner face of the friction surface (6a).

6. Sealing device with integrated magnetic encoder according to the claim

5, characterized in that the outer armature (6) comprises a radial bearing (6c) which is connected to the friction surface (6a) by a connecting fillet (6d) oriented towards the inner armature (5).

7. Sealing device with integrated magnetic encoder according to the claim

6, characterized in that the connecting fillet (6d) has a groove

(12) cutting off its outer radius.

8. Sealing device with integrated magnetic encoder according to claim 6 or 7, characterized in that the sealing element (8) comprises a deflector

(13) which is arranged on the free end of the inner axial seat (5b), to extend radially in the extension of the radial bearing surface (6c) of the outer frame (6).

An integrated magnetic encoder sealing device according to claim 8, characterized in that the sealing element (8) further comprises a static sealing bead (15) which is arranged opposite the baffle (13), on the free end of the inner axial bearing (5b).

10. Sealing device with integrated magnetic encoder according to any one of claims 5 to 9, characterized in that the encoder (1) is associated on the outer face of a free radial surface (5a) of the inner frame (5), said radial bearing being connected to the inner axial bearing (5b) by a connecting surface (5c) opposite which the friction surface (6a) is arranged.

Integral magnetic encoder sealing device according to claim 10, characterized in that a baffle (10) is formed between the connecting surface (5c) and the friction surface (6a).

12. Sealing device with integrated magnetic encoder according to claim 10 or 11, characterized in that the inner face (1a) of the encoder (1) is disposed facing the zone of the outer face of the friction surface (5b ) which is opposite to the friction zone.

Roller bearing assembly comprising a fixed member (2), a rotating member (3) and rolling bodies (4) arranged in a running space formed between said members to allow their relative rotation, said bearing being equipped with at least one integrated magnetic encoder sealing device according to any one of claims 1 to 12, the inner armature (5) being associated with the rotating member (3) and the outer armature (6) being associated with the fixed member (2), said assembly further comprising an information sensor system comprising the encoder (1) which delivers magnetic pulses and a sensor provided with at least two sensitive elements able to detect these pulses, said sensor being disposed opposite the encoder (1), in front of the outer armature (6) so that said pulses are detected through said armature.