Rolling bearing with integrated optical fiber sensor

The rolling bearing provides a first ring, a second ring and at least one row of rolling elements arranged therebetween. Each of the first and second rings include an inner bore having an outer surface and at least one raceway for the row of rolling elements formed on one of the inner bore and outer surface. The first ring provides at least one part ring delimiting the raceway, and at least one sleeve secured to the part ring and delimiting at least partly the other of the inner bore and outer surface of the first ring. The rolling bearing further provides at least one optical fiber sensor mounted inside at least one circumferential groove formed on the first ring and passing through at least one optical fiber sensor passage opening into the circumferential groove.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention relates to condition monitoring of rolling bearings, notably the load sensing.

TECHNICAL FIELD OF THE INVENTION

More precisely, the present invention relates to a rolling bearing with integrated optical fiber sensor.

BACKGROUND OF THE INVENTION

In order to estimate bearing loads acting on a rolling bearing, it is known to integrate strain sensors onto the fixed stationary ring of the bearing.

In order to be able to measure different parameters and to monitor the condition of a rolling bearing in a reliable manner without any electrical power locally at the bearing, it is also known to use optical fiber sensors. For example, it is possible to refer to the patent EP2507603B1 (SKF).

Such optical fiber sensors may be disposed in circumferential grooves formed on the outer surface of the non-rotating outer ring. The outer ring is also provided with passages for entry/exit of the optical fiber sensors. Generally, such passages have complex shapes, for example like curves.

Classically, the grooves and the optical fiber sensor passages are machined on the heat-treated outer ring.

The main drawback of this solution is the cost of the operations, due to the very long machining time needed for very small milling tool. For example, the machining of the optical fiber sensor passages alone takes several hours.

One aim of the present invention is to overcome this drawback.

SUMMARY OF THE INVENTION

In one embodiment, the rolling bearing comprises a first ring, a second ring, and at least one row of rolling elements arranged therebetween.

Each of the first and second rings is provided with an inner bore, with an outer surface and with at least one raceway for the row of rolling elements formed on one of the inner bore and outer surface.

According to a general feature, the first ring comprises at least one part ring delimiting the raceway formed on one of the inner bore and outer surface. The first ring also comprises at least one sleeve secured to the part ring and delimiting at least partly the other of the inner bore and outer surface of the first ring. The sleeve is made from a softer material than that of the part ring.

According to another general feature, the rolling bearing further comprises at least one optical fiber sensor mounted inside at least one circumferential groove formed on the first ring and passing through at least one optical fiber sensor passage opening into the circumferential groove. At least the optical fiber sensor passage is formed on the sleeve of the first ring.

With such an arrangement, the complex machining of the optical fiber sensor passage, for example with curves, is made on the soft sleeve. If the soft sleeve is made by molding, for example from plastic material, the optical fiber sensor passage may also be obtained during molding. Additive manufacturing can also be used for obtaining the sleeve.

Otherwise, there is no change in the bearing behavior with respect to a conventional bearing since the part ring made of hard material delimits the raceway of the first ring.

Advantageously, the sleeve and the part ring of the first ring are mounted radially in contact one against the other.

The optical fiber sensor may be located radially between the sleeve and the part ring of the first ring. Accordingly, the optical fiber sensor is disposed inside the first ring.

In one embodiment the circumferential groove may be formed on the inner bore, or outer surface, of the sleeve mounted radially in contact with the part ring.

In another embodiment, the circumferential groove may be formed on the inner bore, or outer surface, of the sleeve which is not mounted radially in contact with the part ring. In such embodiment, the circumferential groove may be filled with potting resin.

In these two embodiments, the optical fiber sensor passage as well as the circumferential groove are provided on the sleeve. This facilitates again the fabrication operations. The optical fiber sensor passage may extend from a frontal face of the sleeve.

Alternatively, the circumferential groove may be formed on the inner bore, or outer surface, of the part ring mounted radially in contact with the sleeve.

Accordingly, the optical fiber sensor may be placed deeper in the rolling bearing, in an area with higher strains. This leads to higher sensitivity of the measurements.

Advantageously, the circumferential groove is axially disposed on the sleeve, or on the part ring, in order to be located, considering a radial plane of the bearing, on the line joining the points of contact of the rolling element of the row and the raceways of the first and second rings.

Therefore, the optical fiber sensor may be placed on the line along which the combined load is transmitted from one raceway to another.

In one specific embodiment, the first ring comprises at least two part rings mounted axially in contact one against the other. In this case, the part ring is split into stacked ring segments.

Advantageously, in such embodiment, the sleeve maintains together the part rings of the first ring. Accordingly, the sleeve is used to lock the part rings. No extra drillings and pins are needed.

The rolling bearing may comprise at least two rows of rolling elements arranged between the first and second rings, the part rings of the first ring each delimiting one raceway for one of the two rows of rolling elements.

In one embodiment, the sleeve of the first ring is provided with at least one protrusion extending radially towards the second ring, the circumferential groove being formed on the protrusion. Accordingly, the optical fiber sensor may also be placed deeper in the rolling bearing, in an area with higher strains.

The first ring of the rolling bearing is the outer ring when the inner ring is the rotating ring. Alternatively, the first ring of the rolling bearing is the inner ring when the outer ring is the rotating ring.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

The rolling bearing10as illustrated onFIGS.1and2comprises an inner ring12and an outer ring14. The inner and outer rings12,14are concentric and extend axially along the bearing rotation axis X-X′ (FIG.3) which runs in an axial direction.

As shown more clearly onFIG.3, the rolling bearing10also comprises two rows of rolling elements16,18, which are provided here in the form of balls, interposed between the inner and outer rings12,14. The rolling bearing10also comprises two cages20,22for maintaining the regular circumferential spacing of the rolling elements16,18of each row.

As will be described later, the rolling bearing10further comprises two optical fiber sensors24,26provided on the outer ring14.

In the disclosed example, the inner ring12is formed as a split-ring. The inner ring12is formed by the assembling of two annular part rings28,30which are mounted axially in contact one against the other. In other words, the inner ring12is subdivided in the axial direction by the two part rings28,30. The two part rings28,30are identical one to another, and symmetric with respect to the transverse radial plane passing through the centre of the rolling bearing10.

The inner ring12comprises a cylindrical inner bore12aand an opposite cylindrical outer surface12bfrom which two toroidal circular raceways32,34for the rolling elements16,18are formed, the raceway being directed radially outwards. The inner ring12further comprises two opposite radial frontal lateral faces12c,12dwhich axially delimit the bore12aand the outer surface12bof the ring.

In the disclosed example, the outer ring14comprises also two annular part rings36,38which are mounted axially in contact one against the other. The two part rings36,38are identical. The two part rings36,38are also symmetric with respect to the transverse radial plane passing through the centre of the rolling bearing10. The part rings28,30and36,38of the inner and outer rings are made of metal, for example a hardened steel. Alternatively, only the raceways provided on these part rings may be hardened.

The outer ring14further comprises an annular sleeve40made separately from the part rings36,38and secured thereto. The sleeve40may be secured to the part rings36,38by any appropriate means, for example by gluing, fretting, welding, etc.

The sleeve40is mounted radially around the part rings36,38. The sleeve40is mounted radially in contact with the part rings36,38. The sleeve40radially recovers the part rings36,38. The sleeve40is mounted on the outer surfaces of the part rings36,38.

The outer ring14comprises a cylindrical inner bore14afrom which two toroidal circular raceways42,44for the rolling elements16,18are formed, the raceway being directed radially inwards. The outer ring14further comprises a cylindrical outer surface14bwhich is opposite to the inner bore with regard to the radial direction.

The outer ring14further comprises two opposite radial frontal lateral faces14c,14dwhich axially delimit the bore14aand the outer surface14bof the ring. The lateral face14dof the outer ring is coplanar with the lateral face12dof the inner ring. The lateral face14cof the outer ring is coplanar with the lateral face12cof the inner ring.

The bore14aand the raceways42,44of the outer ring are formed by the part rings36,38. The outer surface14bof the outer ring is formed by the sleeve40. The lateral face14cof the outer ring is formed both by the part ring36and the sleeve40. Similarly, the lateral face14dof the outer ring is formed by the part ring38and the sleeve40.

The sleeve40comprises a cylindrical inner bore mounted radially in contact with the outer surfaces of the part rings36and38, and an opposite cylindrical outer surface forming the outer surface14bof the outer ring. The sleeve40also comprises two opposite radial frontal lateral faces which axially delimit the bore and the outer surface of the sleeve. Each lateral faces14c,14dof the outer ring is partly formed by one of these lateral faces of the sleeve.

As previously mentioned, the outer ring14is provided with two optical fiber sensors24,26. As shown more clearly onFIG.4, two circumferential grooves46,48are formed on the bore of the sleeve40inside which are respectively mounted the optical fiber sensors24,26.

In the disclosed example, the circumferential grooves46,48have an annular form. Alternatively, the circumferential grooves46,48may be not annular. For example, the circumferential grooves46,48may extend over an angular sector less than equal to 340°.

The groove46radially surrounds the part ring36. The groove48radially surrounds the part ring38. The grooves46,48are closed by the part rings36,38. The groove46is axially disposed on the bore of the sleeve40in order to be located on the line (not shown) joining the points of contact of the rolling element16and the inner and outer raceways32,42in the radial plane, along which the load may be transmitted from one raceway to another.

Similarly, the groove48is axially disposed on the bore of the sleeve40in order to be located on the line (not shown) joining the points of contact of the rolling element18and the inner and outer raceways34,44in the radial plane.

The thickness of the sleeve40is defined to position the optical fiber sensors24,26at the desired depth to optimize the measurement performance. For example, the thickness of the sleeve40may be comprised within a range of 20% to 50% of the global thickness of the outer ring14.

Referring once again toFIG.1, the sleeve40is also provided with passages50,52for entry/exit of the optical fiber sensors. In the disclosed example, each passage50,52extends axially from one of the frontal faces of the sleeve40into the thickness of the sleeve, and open on the outer surface of the sleeve. This is also shown onFIG.5for the passage50.

On the outer surface of the sleeve40, each passage50,52comprises an axial portion which is extended by a curved portion itself extended by a circumferential portion. The end of the circumferential portion of each passage50,52extends radially into the thickness of the sleeve, and opens into the associated grove46,48.

The sleeve40is made from a softer material than that of the part rings36,38. For example, the sleeve40may have a hardness lower than 38 Vickers. The part rings36,38may have at least a hardness of 58 Vickers.

The sleeve40may be made from metal, for example steel or metal alloy. Since the sleeve40is made from a softer material than that of the part rings36,38, the machining of the passages50,52with curved portions is easier. This also leads to a reduction of the machining time for the grooves46,48. Alternatively, the sleeve40may be made from plastic material. In this case, the passages50,52and the grooves46,48are formed on the sleeve during molding.

As previously mentioned, each optical fiber sensor24,26is mounted inside the associated groove46,48formed on the bore of the sleeve40. Each optical fiber sensor24,26is also mounted inside the passage50,52which is formed on the sleeve40and opens into the associated groove46,48.

Each passage50,52enables to manually guide the associated optical fiber sensor24,26when the sensor is axially introduced inside the thickness of the sleeve and then tangentially introduced into the groove48,50. After one turn inside the associated groove48,50, the associated optical fiber sensor24,26exits the groove and is secured inside the passage50,52.

Each optical fiber sensor24,26is provided with a plurality of light distorting structures which could be fiber Bragg gratings for example. For more detail concerning such optical fiber sensors, it is possible for example to refer to the patent EP-B1-2 802 796 (SKF). The optical fiber sensors24,26may be used to measure different parameters of the rolling bearing10, for example loads, temperatures, pressures, vibrations, etc.

The embodiment shown onFIGS.6and7, in which identical parts are given identical references, differs from the previous embodiment in that bore of the sleeve40is provided with an annular protrusion54extending radially inwards into recesses (not referenced) formed on the outer surface of the part rings36,38. The circumferential grooves46,48are formed on the bore of the protrusion54. With such arrangement, the optical fiber sensors24,26are placed deeper in the rolling bearing.

In the previous illustrated examples, the part rings28,36and30,38are disposed according to a back-to-back bearing arrangement. Alternatively, it could be possible to dispose the part rings28,36and30,38in a face-to-face bearing arrangement as illustrated in the embodiment shown onFIGS.8and9, or in a tandem arrangement.

With such face-to-face bearing arrangement, it is also possible to foresee a sleeve40provided with two protrusions extending radially inwards into recesses formed on the outer surface of the part rings36,38, and onto which are formed the circumferential grooves46,48.

In the previous illustrated examples, the outer ring14is provided with the sleeve40since the inner ring12is the ring which is intended to rotate.

Alternatively, when the outer ring14is the ring which is intended to rotate, the inner ring12may be provided with the sleeve40as illustrated for example in the embodiment shown onFIGS.10and11in which identical parts are given identical references.

In this embodiment, the sleeve40is mounted into the bore of the part rings36,38. The outer surface of the sleeve40is mounted radially in contact with the bore of the part rings28,30. The circumferential grooves46,48are formed on the outer surface of the sleeve40. The passages50,52for entry/exit of the optical fiber sensors extends axially from one of the frontal faces of the sleeve40into the thickness of the sleeve, and open on the bore of the sleeve. Each passage50,52extends axially and circumferentially along the bore of the sleeve40, and extends radially into the thickness of the sleeve and opens into the associated grove46,48.

In this embodiment, the part rings28,36and30,38are disposed according to a face-to-face bearing arrangement. Alternatively, it could be possible to dispose the part rings28,36and30,38in a back-to-back bearing arrangement or in a tandem arrangement. The outer surface of the sleeve40may also be provided with one or two protrusions extending radially outwards into recesses formed in the bore of the part rings28,30, and onto which are formed the circumferential grooves46,48.

In the illustrated examples, the sleeve40extends on the whole length of the associated part rings. Alternatively, the sleeve40may have a reduced length.

In the illustrated examples, the grooves46,48and the passages50,52are both provided on the sleeve40. Alternatively, only the passages50,52having curves may be provided on the sleeve40. In this case, the grooves46,48are formed on the part rings of the outer ring14or inner ring12. Accordingly, the optical fiber sensors24,26are placed deeper in the rolling bearing, in an area with higher strains.

The invention has been illustrated on the basis of a rolling bearing comprising inner and outer rings provided with two annular part rings mounted axially in contact one against the other. Alternatively, the inner ring and/or the outer ring may comprise only one part ring, or three part rings or more.

In the illustrated examples, the rolling bearing comprises two rows of rolling elements. Alternatively, the rolling bearing may comprise only one row of rolling elements, or three rows or more. In the illustrated examples, the rolling elements are balls. Alternatively, the rolling bearing may comprise other types of rolling elements, for example rollers. In the disclosed examples, the rolling bearing is adapted to accommodate both axial and radial loads. Alternatively, it may also be possible to have a rolling bearing adapted to accommodate axial loads or radial loads only.