GB2576167A

GB2576167A - Sensing assembly for bearing and mounting method

Info

Publication number: GB2576167A
Application number: GB1812795.1A
Authority: GB
Inventors: Zorz Angelis Georgo; Cornelis Maria van Genuchten Henricus; Van Amerongen Gertjan
Original assignee: S360 Group BV
Current assignee: S360 Group BV
Priority date: 2018-08-07
Filing date: 2018-08-07
Publication date: 2020-02-12
Also published as: GB201812795D0

Abstract

Disclosed is a method of mounting a bearing and a sensor sleeve assembly to a machine in a housing with a housing bore diameter Dbh on a shaft with diameter d. The sensor sleeve assembly includes one or more ring elements and an optical sensing fibre provided on a radially oriented surface of at least one ring element. The bearing comprises an inner ring and an outer ring, one of which is a rotating and the other non-rotating. The sensor sleeve assembly is mounted in connection with the non-rotating ring. The method include the steps of selecting and mounting a bearing with an outer diameter D less than housing bore diameter Dbh and an inner diameter db greater than the shaft diameter d, selecting and mounting a sensor sleeve assembly with a thickness Tsa equal to the difference in diameters on the non-rotating side, and selecting and mounting an adapter ring with a thickness Tar equal to the difference in diameters on the rotating side. The sensor sleeve assembly may also include one or more load transfer rings, which may form grooves or cavities for accommodating the sensing fibre, and a sensor ring substrate which the fibre is provided on.

Description

Fig. 18

Sensing assembly for bearing and mounting method

The present invention relates to the field of fibre-optic sensing assemblies for rolling element bearings and is more particularly directed to a method of mounting a fibreoptic sensing assembly and a bearing in the annular gap between a bearing housing and a shaft, which enables retrofitting and re-use of the sensing assembly.

Technical Background

The use of optical sensing fibres for measuring operating parameters of a bearing is becoming increasingly common. In one known solution, such as disclosed in LIS2010158434 and in LIS2013188897, the optical sensing fibre is integrated within the bearing, for example in an annular groove that is machined into an outer circumference of the bearing outer ring. A disadvantage of this solution is that the bearing must be modified, significantly increasing production costs.

A further solution is known from W02014108170, which describes a fibre-optic sensor clip comprising a clamping ring for clamping engagement of a shaft or bearing. The clip may be a prefabricated element in which the sensing fibre is embedded. This solution has the advantage that the clip (sensing assembly) may be re-used, but again has the disadvantage of requiring modification of the bearing or its housing. Bearings and bearing housings are typically manufactured in a range of standardized dimensions, such as those defined in e.g. ISO-15. Consequently, in order to mount the clip in a bearing application, it is necessary, for example, to reduce the outer diameter of the bearing outer ring by removing material prior to hardening, or to increase the bore diameter of the housing by removing material from its inner circumference.

Consequently, there is room for improvement.

Summary of invention

An object of the present invention is to define a fibreoptic sensing assembly which can be executed as a reusable and replaceable component and to define a method of mounting the assembly to an off-the-shelf bearing on a shaft in a housing, without modifying the shaft, housing, or bearing.

This object is achieved by means of a method as defined in claim 1.

The fibreoptic sensing assembly is executed as a sensor sleeve assembly comprising one or more ring elements, at least one of which is provided with an optical sensing fibre for sensing e.g. operating parameters of the bearing such as load, temperature and/or vibrations. The sensor sleeve assembly is mounted in connection with a nonrotating ring of the bearing, which in most applications is an outer ring of the bearing, whereby an inner ring of the bearing is mounted to a rotational shaft. In other applications, the outer ring is the rotating ring and the inner ring is the non-rotating ring.

When the outer ring of the bearing is the non-rotating ring, the method comprises a step of selecting a bearing which has a load rating suitable for the machine application and which has a smaller outer diameter D than a bore diameter Dbh of the housing and which has an equal or larger bore diameter db than a diameter d of the shaft. Suitably, the selected bearing has standardized dimensions, in accordance with ISO-15, BS292-1 or other national standard for bearing dimensions. The method comprises further steps of selecting a sensor sleeve assembly with a thickness T_sa essentially equal to (Dbh - D)/2 and selecting an adapter ring with a thickness Tar essentially equal to (db - d)/2.

When the inner ring of the bearing is the non-rotating ring, the method comprises a step of selecting a bearing which has a load rating suitable for the machine application and which has an equal or smaller outer diameter D than a bore diameter Dbh of the housing and which has a larger bore diameter db than a diameter d of the shaft. Suitably, the selected bearing has standardized dimensions. The method comprises further steps of selecting a sensor sleeve assembly with a thickness T_sa essentially equal to (db - d)/2 and selecting an adapter ring with a thickness T_ar essentially equal to (Dbh - D)/2.

In a final step, a concentric arrangement of the bearing, sensor sleeve assembly and adapter ring is mounted on the shaft in the housing, such that the adapter ring is mounted in connection with a cylindrical surface of the rotating ring.

Thus, by using ring elements of various thicknesses, which are suitably dimensioned to fit on bearings and within bearing housings having a range of standardized dimensions, an existing machine application can be retrofitted with a re-usable sensing sleeve assembly in a straightforward and cost-effective manner, which can be tailored to suit any bearing application.

The sensor sleeve assembly may be executed in a variety of ways. In embodiments where the sensor sleeve assembly is configured to transfer load from the shaft to the inner ring or from the outer ring to the housing, the assembly comprises one or more ring elements in the form of load transfer rings, which are made of a strong and stiff material such as steel.

The sensor sleeve assembly may additionally comprise one or more ring elements in the form of sensor rings, which comprise an optical sensing fibre provided on a substrate of the ring element. Each sensor ring may have a radial thickness that is smaller than the radial thickness of the load transfers rings. In some examples, the sensor sleeve assembly comprises one sensor ring axially located between two load transfer rings. The assembly may also comprise two or more sensor rings for detecting parameters at different axial location, whereby each sensor ring is axially located between a load transfer ring. An advantage of such an assembly is that the width of the load transfer rings can be varied to match the width of the bearing. Load transfer rings of different widths can also be used to position the sensor ring at a desired axial position.

The radial thickness of the load transfer rings can be equal to the thickness T_sa of the sensor sleeve assembly. Alternatively, the load transfer rings may have a smaller thickness and assembly may comprise one or more concentrically arranged filler rings for achieving the required thickness T_sa.

In some embodiments, the assembly comprises at least one ring element that serves as a load transfer ring and provides the substrate for attachment of the optical sensing fibre. In one example, the sensor sleeve assembly consists of a single ring of thickness Tsa, which is provided with a circumferential groove in which the fibre is accommodated.

In a further example, the assembly comprises two load transfer rings in axial abutment with each other, whereby the optical sensing fibre is arranged in a groove or cavity. The groove or cavity may be formed in an axially inner end face of one of the rings, whereby the axially inner end face of the other ring encloses the groove or cavity, protecting the fibre against the ingress of contamination. Alternatively, the axially inner end face of the abutting load transfer rings may be provided with oppositely oriented curved profiles, which together form a groove for accommodating the sensing fibre. This enhances ease of manufacturing and cost-effectiveness via the use of simple parts that can together form complex grooves or enclosures.

Suitably, the assembly comprises at least one ring element with an axially extending through passageway, for leading the sensing fibre to an axially outer side of the assembly. In an advantageous embodiment, an axially outer end face of the ring element comprising the passageway is provided with an annular recess, with which the passageway is in communication. The annular recess is dimensioned to accommodate a free length of the sensing fibre, consisting of one or more wound up coils, within the axial confines of the sensor sleeve assembly. Preferably, the assembly additionally comprises a removable cover lid for enclosing the annular recess, whereby the lid also has an opening to enable the fibre to be led to the outside world for connection to e.g. a remote measurement device which processes the signal from the optical sensing fibre.

An advantage of such a sensor sleeve assembly is that during transportation and mounting of the assembly, the optical sensing fibre, which is delicate, is not hanging loose and is protected from damage.

Preferably, the one or more ring elements of the sensor sleeve assembly are formed as continuous rings, for ease of manufacture and assembly. It is also possible, where required, for the sensor sleeve assembly to comprise one or more ring elements composed of two or more arcuate segments which are joined together to form a complete ring.

In some embodiments, the sensor sleeve assembly comprises a sensor ring and a ring element made of a compliant material, which has sufficient strength but has a significantly lower Youngs modulus’ (stiffness) than metals such as steel. Examples of suitable compliant materials include: glass- or carbon fibre reinforced polymers; polymers such as polyetheretherkeytone (PEEK) and epoxies or elastomers such as natural or synthetic rubbers.

A first radial side of the compliant ring element is arranged in contact with the optical sensing fibre provided on the sensor ring. An advantage of such an assembly is that the compliant ring element is configured to suppress vibrations emanating from a surface with which an opposite radial side of the compliant ring element is in contact, which makes the sensing assembly more sensitive to the measurement parameter of interest. In most applications, the sensor ring and optical sensing fibre are in stiff connection with the non-rotating bearing ring, for measuring bearing operating parameters, and the compliant ring element is arranged radially between the sensor ring and the housing or shaft. In other applications, the sensor sleeve assembly is adapted to detect operating parameters of the machine and the sensor ring is mounted in stiff connection with the bearing housing. The compliant ring element is then arranged between the sensor ring and the bearing outer ring, to reduce noise and vibrations emanating from the bearing.

In further embodiments, the sensor sleeve assembly comprises a layer of electrical insulation material. Such an assembly is advantageous when the machine is an electrical motor or generator, as the insulation layer helps to reduce electrical discharges causing stray currents through the bearing that could damage the bearing.

The ring element which provides the substrate for the optical sensing fibre may be stiff element formed from e.g. steel, which is optimized to transfer deformation from load into strain of the sensing elements in the optical fibre, whereby the optical sensing fibre is attached to the substrate using a cement material, via adhesive bonding, via brazing or any other conventional joining technique.

In other embodiments, the ring element which provides the substrate for the optical sensing fibre may be formed from a thin and flexible carrier material. In one example, the substrate is formed as sensor tape or sensor strip, which is wound around a cylindrical surface of the sensor sleeve assembly. An underside of the tape/strip may comprise an adhesive layer for attachment. The sensing fibre comprises a number of sensing elements such as fibre-bragg gratings. Preferably, the fibre is arranged to follow a path comprising a first straight section having a first set of sensing elements and at least a second straight section having a second set of sensing elements, whereby the first and second straight sections are arranged parallel to each other with an axial offset. The sensor tape or sensor strip is wound helically, such that the first and second sets of sensing elements are arranged circumferentially on the sensor sleeve assembly at respective first and second axial positions.

Advantageously, the sensor sleeve assembly may comprise a ring element on which markers are provided for indicating a desired position of sensing elements within the fibre, to enable the sensor sleeve to be assembled in situ. When the assembly comprises a sensor tape or sensor strip, the length of the straight sections and the magnitude of the axial offset can be adapted to the diameter of the ring element.

In other embodiments, the sensor sleeve assembly is a cylindrical unit which is mounted as one part to the non-rotating bearing ring. When the assembly comprises an arrangement of several ring elements, such as described above, the ring elements may be arranged between an inner sleeve and an outer sleeve. The sensor sleeve assembly may be mounted with a press fit on the shaft or in the housing, as required.

The sensor sleeve assembly may also comprise clamping element for exerting a clamping force on the substrate of the ring element on which the sensing fibre is provided. In one example, the clamping element comprises a retaining ring and a number of adjustable setscrews which bear against the substrate.

As mentioned, the sensor sleeve assembly and mounting method of the invention enables an existing bearing application to be sensorized in a convenient and cost effect manner, using an off-the-shelf bearing and without the need to modify the bearing, shaft or housing. Furthermore, the sensor sleeve assembly may be adapted with a number of different functionalities, depending on the application, and can be executed with a scalable radial height and axial width using straightforward components.

Other advantages of the invention will become apparent from the detailed description and accompanying drawings.

Brief description of drawings

The features and advantages of the invention will now be explained further with reference to the following figures, in which:

Fig.1 shows a partial cross-sectional view of an example of a sensor-sleeve assembly according to the invention, mounted to a bearing between a shaft and a bearing housing;

Fig. 2a shows a cross-sectional view of a bearing without sensor mounted between a shaft and a bearing housing;

Fig. 2b shows an exploded view of components of a sensor sleeve assembly according to the invention mounted between the shaft and housing of Fig. 2a;

Fig. 3 shows a flowchart of the method according to the invention for selecting and mounting a bearing and sensor sleeve assembly in an existing machine application;

Fig. 4 shows a cross-section of an embodiment of a sensor-sleeve assembly according to the invention mounted between a bearing outer ring and a housing, the assembly comprising an optical sensing fibre provided in a circumferential groove in a ring element adapted for load transfer;

Fig. 5 shows a cross-section of a further embodiment of a sensor-sleeve assembly according to the invention mounted between the bearing outer ring and the housing, the assembly comprising an axial arrangement of a sensor ring element and load transfer ring elements;

Fig. 6 shows a cross-section of a still further embodiment of a sensor-sleeve assembly according to the invention mounted between the bearing outer ring and the housing, the assembly comprising two axially spaced sensor rings;

Fig. 7 shows a cross-section of a still further embodiment of a sensor-sleeve assembly according to the invention mounted between the bearing outer ring and the housing, the assembly being executed as a self-contained cylindrical unit;

Fig 8 shows a cross-section of a still further embodiment of a sensor-sleeve assembly according to the invention mounted between the bearing outer ring and the housing, the assembly comprising two ring elements in axial abutment and a sensing fibre provided in a groove in an axially inner end face of one ring element;

Fig. 9 shows a cross-section of a still further embodiment of a sensor-sleeve assembly according to the invention mounted between the bearing outer ring and the housing, the assembly comprising two ring elements in axial abutment and a sensing fibre provided in a groove formed by a shaped edge profile of each ring element;

Fig. 10 shows a cross-section of a still further embodiment of a sensor-sleeve assembly according to the invention mounted between the bearing outer ring and the housing, the assembly comprising a ring element having a recess for storing a free length of the sensing fibre;

Fig. 11 shows a side view of the embodiment depicted in Fig. 10;

Fig. 12 shows a cross-section of a still further embodiment of a sensor-sleeve assembly according to the invention mounted between the bearing outer ring and the housing, comprising a layer of compliant material arranged between the housing and a sensor part of the assembly;

Fig. 13 shows a cross-section of a still further embodiment of a sensor-sleeve assembly according to the invention mounted between the bearing outer ring and the housing, comprising a layer of compliant material arranged between the sensor part of the assembly and the bearing outer ring;

Fig. 14 shows a cross-section of a still further embodiment of a sensor-sleeve assembly according to the invention mounted between the bearing outer ring and the housing, in which the sensor sleeve is provided with a layer of electrically insulating material for reducing stray currents through the bearing;

Fig. 15 shows a cross-section of a still further embodiment of a sensor-sleeve assembly according to the invention mounted between the bearing outer ring and the housing, comprising an optical sensing fibre provided on a thin flexible substrate;

Fig. 16 shows views of an example of a flexible substrate, executed as a sensor tape, comprising an optical sensing fibre arranged in a zig-zag pattern, prior to and after being helically wound around a shaft;

Fig. 17 shows a side view of a construction to clamp a sensor-ring or sensor tape on a shaft, by means of four setscrews and a setscrew retaining ring;

Fig. 18 shows a cross-section a still further embodiment of a sensor-sleeve assembly according to the invention, comprising a sensor ring clamped to the bearing outer ring via a setscrew clamping construction;

It should be noted that the figures are schematic and are not to scale. Typically, an optical sensing fibre has diameter of about 0.12 to 0.25mm, while the sensor-sleeve assembly typically has a radial thickness in the range of 1 to 10 millimetres.

Fig. 1 shows an axial cross-section through an arrangement comprising a sensorsleeve assembly 10 according to the invention, mounted to a bearing 3 between a housing 1 and a shaft 2. The bearing 3 comprises an inner ring 4, a row of rolling elements 6 and an outer ring 5. The arrangement includes an adapter ring 8 mounted between the shaft 2 and the bearing inner ring 4.

The sensor-sleeve assembly 10 is constructed as a concentric stack of a sensor-ring 16 arranged at a bearing side of the assembly and a filler ring 9 at a housing side of the assembly. The purpose of the filler ring 9 is to give predetermined dimensions to the assembly as a whole. The sensor ring 16 comprises a ring made from a stiff material such as steel, to which an optical sensing fibre 11 is attached. In this example, the sensor ring 16 of the assembly is mounted in direct connection with the bearing outer ring 5, whereby the sensing fibre 11 is arranged to detect deformations due to the passage of rolling elements during bearing operation, or to detect global deformations due to the application loads, or both. The optical sensing fibre 11 is connected to a remotely located external measuring device (not shown in Fig. 1) which may be programmed to calculate bearing load. The housing 1 is thus suitably provided with a passageway 7 via which the sensing fibre 11 is led.

An advantage of adding the sensor-sleeve assembly 10 is that load transferred between bearing 3 and housing 1 can be measured. Besides load, other parameters which can be derived from the detected signal, such as temperature and vibration, can also be measured. The advantage of using an adapter ring 8 and a sensor sleeve assembly of predetermined dimensions is that an existing machine comprising a shaft supported in a housing via a bearing can be fitted with a sensor arrangement, without modifying the shaft, the housing or the bearing. This will be explained further with regard to the Figs. 2a and 2b and the flowchart of Fig. 3.

Fig. 2a shows an existing machine application comprising a bearing 3 mounted between a rotational shaft 2 and a housing 1, whereby the bearing has specific ISO dimensions. The bearing has an outer diameter that is essentially equal to a bore diameter Dbh of the housing. The bearing has an inner bore diameter that is essentially equal to the shaft diameter d. In this application, the inner ring of the bearing is the rotating ring and the outer ring is the non-rotating ring. In other applications, the inner ring can be the non-rotating ring and the outer ring is the rotating ring. Suitably, the sensor sleeve assembly is mounted to the non-rotating ring of the bearing, the outer ring in this application.

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Fig. 2b shows an alternative implementation in which an alternative bearing 3a has been selected and mounted between the same shaft 2 and housing 1 via an arrangement including a sensor sleeve assembly according to the invention, the components of which are shown in exploded view prior to mounting.

The alternative bearing 3a is suitably an off-the-shelf bearing with ISO dimensions that is capable of handling the loads for the application in question, whereby the alternative bearing 3a has a smaller outside diameter D than the outer diameter Dbh of the original bearing 3 and has a larger bore diameter db than the inner bore diameter d of the original bearing.

An adapter ring 8 is mounted on the shaft 2, in connection with the bearing inner ring. The adapter ring is thus selected to have a bore diameter essentially equal to the shaft diameter d and a radial thickness T_ar= (db - d)/2. The sensor sleeve assembly 10 has a radial thickness T_sa, essentially equal to (Dbh -D)/2, and consists of a sensor ring 16 mounted in connection with the bearing outer ring and a filler ring 9 of radial thickness Tfr mounted to the housing 1. The sensor ring 16 thus has a bore diameter essentially equal to the outer diameter D of the alternative bearing 3a and has a certain radial thickness T_sr, whereby T_sa = Tsr + Tfr. The thickness of the filler ring Tfr is thus selected such that Tfr = (Dbh -D)/2 - T_sr.

As a result, the existing machine application can be retrofitted with a bearing and sensor assembly without modifying the shaft, housing or any other part close to the bearing, while making use of an unmodified, standard bearing. Furthermore, it is possible to replace either the bearing or the sensor assembly separately, enabling the other component to be reused.

Fig. 3 shows a flowchart, which summarizes the inventive method for selecting an alternative bearing to add load sensing functionality to an existing situation. The method comprises a step 100 of identifying the existing bearing parameters, i.e. outer diameter Dbh, bore diameter d, width B and the required load capacity for the application. The method further comprises a step 200 of determining whether the inner ring of the bearing or the outer ring of the bearing is the non-rotating ring and the required load capacity for the application.

When the outer ring is the non-rotating ring, an alternative bearing with different standard dimensions is selected in a step 300. The alternative bearing has an appropriate load rating and has an outer diameter D < Dbh and a bore diameter db < d. Suitably, the width B_a of the alternative bearing is selected to fit in the housing, whereby Ba < B.

In a next step 400, a sensor sleeve assembly and an adapter ring of appropriate thickness T_sa and T_ar respectively are selected, whereby T_sa = (Dbh - D)/2 and T_ar = (db

- d)/2. Finally, the alternative bearing and sensor sleeve assembly are mounted in the application, whereby the adapter ring 8 is mounted in connection with the shaft 2 and inner ring and the sensor sleeve assembly 10 is mounted in connection with the housing 1 and bearing outer ring. Preferably, the adapter ring and sensor sleeve assembly have the same axial width as the alternative bearing. If either has a smaller axial width, then a spacer ring may be mounted on the shaft or in the housing, as appropriate.

When the inner ring is the non-rotating ring, an alternative bearing with different standard dimensions is selected in a step 310. The alternative bearing has an appropriate load rating and has an outer diameter D < Dbh and a bore diameter db > d. Again, the width B_a of the alternative bearing is selected to fit in the housing, whereby B_a < B.

In a next step 410, a sensor sleeve assembly and an adapter ring of appropriate thickness T_sa and T_ar respectively are selected, whereby T_sa = (db - d)/2 and T_ar = (Dbh

- D)/2. Finally, the alternative bearing and sensor sleeve assembly are mounted in the application, whereby the adapter ring is mounted in connection with the housing and bearing outer ring and the sensor sleeve assembly is mounted in connection with the shaft and inner ring. Preferably, the adapter ring and sensor sleeve assembly have the same axial width as the alternative bearing. If either has a smaller axial width, then a spacer ring may be mounted on the shaft or in the housing, as appropriate.

Fig. 4 shows an axial cross-section through a sensor-sleeve assembly 10 mounted between a housing 1 and the outer ring 5 of a bearing according to a first embodiment. The sensor-sleeve assembly 10 is constructed as a concentric stack of a load transfer ring 15 and a filler ring 9. In this embodiment, the load transfer ring 15 serves to transmit load from the bearing outer ring to the housing, via the filler ring 9, and is made from a material with high stiffness, such as non-hardened steel. The load transfer ring also serves as the sensor ring and is provided with an optical sensing fibre 11 which is integrated in a groove 12 in an outer circumference of the load transfer ring 15. The filler ring 9 again serves the primary function of providing a standardized outer dimension of the sensor-sleeve assembly 10 equal to the standardized dimension of the bore of the housing 1, but also transfers the application load between the load transfer ring 5 and the housing 1. The filler ring 9 can be made out of a material with high stiffness, such as non-hardened steel.

In addition, the load transfer ring 15 is provided with a passageway 7 for the optical fibre 11 to allow the fibre 11 to be connected to an external measurement unit. The fibre 11 may be attached in the groove 12 of the load transfer ring 15 using commonly known methods, for example by cement, solder or by brazing. The filler ring 9 can be joined to the load transfer ring 15 using a commonly known method such as spot welding or via cement.

The advantages of constructing a sensor-sleeve assembly 10 in this way is that the sensor-sleeve assembly 10 forms a single item which is easy to handle and is a separate part, not being part of the bearing or the housing, and therefore can be reused if the bearing needs to be replaced. Furthermore, the same bearing can be reused if only the sensor sleeve assembly needs to be replaced, thereby enhancing cost-effectiveness.

In an alternative embodiment, the sensor sleeve assembly is constructed from a single load transfer ring provided with an optical sensing fibre, whereby the dimensions of the single ring are selected to fit on the non-rotating part of the bearing without modifying the application in question.

A further embodiment of a sensor-sleeve assembly 10 mounted between a housing 1 and the outer ring 5 of a bearing is depicted in Fig. 5. The sensor-sleeve assembly 10 is constructed as a concentric stack of a first layer consisting of two load transfer rings 15 and a sensor ring 16 and a second layer consisting of the filler ring 9. The sensor ring 16 is arranged axially between the two load transfer rings 15 and in this embodiment has a smaller radial thickness than the load transfer rings. The sensor ring 16 preferably has a thickness in the range of 0.05 - 1.0 mm, which is beneficial for optimizing sensitivity. The load transfer rings 15 and the sensor ring 16 can be made from a material with high stiffness, such as steel, which is optimized to transfer deformation from load into strain of the sensing elements in the optical fibre Here, the load transfer rings 15 are dedicated to transferring the application load between bearing outer ring 5 and filler ring 9 and the sensor ring 16 is dedicated to sensing load by means of sensing fibre 11.

Load transfer rings 15 of different axial width may be used, so that the width of the assembly is scalable to match any bearing width dimension, thereby reducing manufacturing cost by limiting the number of unique parts to be produced. Furthermore, the axial position of the sensing fibre 11 on the sensor ring 16 can be controlled as required, by selecting load transfer rings 15 with different widths, or by adding an unequal number of load transfer rings 15 on either side of the sensor ring 16, thereby enabling radial loads to be distinguished from axial loads.

The sensor sleeve assembly may also comprise an axial arrangement of two or more sensor rings and three or more load transfer rings, such as shown in Fig. 6. In this embodiment, the first layer of the sensor sleeve assembly 10 is formed from an axial arrangement of two separate sensor rings 16 and three load transfer rings 15, whereby each sensor ring is in axial abutment with a load transfer ring. The two axially outermost load transfer rings 15 are each provided with an axially extending passageway 7 for respectively leading each sensing fibre 11 to an opposite side of the bearing. Alternatively, the centre load transfer ring and one of the axially outermost load transfer rings may be provided with a passageway 7 for leading each sensing fibre to the same side of the bearing arrangement, such as the embodiment shown in Fig. 7.

In this embodiment, the assembly additionally comprises an inner sleeve 27 and an outer sleeve 28 between which the load transfer rings 15 and the sensor rings 16 are arranged. Empty space between the sensor rings and the outer sleeve 28 may be filled with a potting material such as epoxy or silicone. The advantages of a sensor assembly comprising inner and outer sleeves are that the assembly is fully enclosed to prevent the ingress of contamination, and the sensor-sleeve assembly can be handled as one part.

The advantage of an assembly comprising two separate sensor rings 16 is that load can be measured at two axial positions, which is particularly useful for determining load distribution in roller bearings (which have a line contact between the rollers and bearing raceways) and for measuring axial as well as radial load. Again, the width of the rings may be selected to match the width dimensions of the bearing and to position the sensing fibre 11 as required for the application in question.

A further embodiment of a sensor-sleeve assembly 10 mounted between a housing 1 and the outer ring 5 of a bearing is depicted in Fig. 8. The sensor-sleeve assembly 10 is constructed as a concentric stack of a first layer consisting of two load transfer rings 15 and a second layer consisting of the filler ring 9. The two load transfer rings are in axial abutment with each other and in this embodiment, an axial end face of one of the load transfer rings is provided with a groove 12 in which the optical sensing fibre 11 is provided and acts as the sensor ring. The grooved ring provides both the load transfer function as well as the sensing function and is provided with an axially extending passageway 7 enabling the fibre 11 to be led to the outside world.

The advantage of constructing a sensor-sleeve assembly 10 in this way is that the sensor groove 12 is fully enclosed by the abutting load transfer ring 15, thereby protecting the fibre 11 against the ingress of contamination, which is particularly important when no filler ring 9 is required. A further advantage is a reduction of manufacturing cost by limiting the number of unique parts to be produced.

A further embodiment of a sensor-sleeve assembly 10 mounted between a housing 1 and the outer ring 5 of a bearing is depicted in Fig. 9. Like the embodiment depicted in Fig. 8, the sensor-sleeve assembly 10 is constructed as a concentric stack of a first layer consisting of two axially arranged load transfer rings 15 and a second layer consisting of the filler ring 9. In this embodiment, the axially abutting side faces of the rings 15 are each provided with an oppositely oriented curved profile which together form a groove 12 for receiving the sensing fibre 11, whereby one of the rings 15 is provided with an axially extending passageway 7 for leading the fibre 11 to the outside world.

Advantageously, each axial side of each load transfer ring may be provided with a shaped profile which is a mirror-image of the other side, so that any axial arrangement of two such load transfer rings creates a groove 12 for the sensing fibre 11 at the abutting side faces.

A further embodiment of a sensor-sleeve assembly 10 mounted between a housing 1 and the outer ring 5 of a bearing is depicted in cross-section in Fig. 10 and in axial view in Fig. 11. In this embodiment, the sensor-sleeve assembly 10 is constructed from an axial arrangement of a load transfer ring 15 in axial abutment with a sensor ring 17 with an integrated pocket 19 preferably formed as an annular recess provided in an axially outer end face of the sensor ring 17. The sensor ring 17 has three functions: a) to transfer load between bearing outer ring 5 and housing 1; b) to sense load by means of sensing fibre 11 at the location of the groove 12, which is provided at an axially inner end face of the ring 17 and c) for storing a wound-up length of one or more coils of the optical sensing fibre 11. Preferably, the sensor sleeve assembly additionally comprises a cover lid 20 that fits over and encloses the pocket 19. For leading the sensing fibre 11 out of the assembly, the sensor ring 17 comprises an axial passageway 7 in connection with the pocket 19, and the cover lid 20 is provided with an opening 18.

The advantage of a sensor-sleeve assembly comprising such a pocket 19 is that a length of the optical sensing fibre 11, which is fragile, can be stored in the pocket as part of the manufacturing process of the sensor-sleeve. As a result, no part of the optical sensing fibre hangs loose and unprotected during transport and installation of the sensor sleeve assembly. After installation, the pocket can be opened by removing the cover lid 20 and the stored length of optical fibre can be taken out of the pocket and fed through the opening 18 in the cover lid 20, after which the cover lid is replaced to enclose the pocket/annular recess in the sensor ring 17. The end of the sensing fibre is then connected to the external measuring device or to an intermediate fibre connector.

In a further example of this embodiment, the sensor sleeve assembly is formed from two such sensor rings 17, each of which has a pocket/ annular recess 19 in the axially outer end face for storing a length of sensing fibre 11. Suitably, the dimensions of the pocket are adapted for storing one or more coils of the sensing fibre, depending on the free length of fibre that is required for connection to the external measuring device or to the intermediate fibre-connector. In the depicted example, the pocket is dimensioned for storing three coils of sensing fibre.

Fig. 12 shows an axial cross-section through a sensor-sleeve assembly 10 mounted between a housing 1 and the outer ring of a bearing 5 according to a further embodiment of the invention. Here the sensor-sleeve assembly 10 is constructed as a concentric stack of a first layer consisting of a carrier 13, in connection with the bearing outer ring 5, a second layer consisting of a sensor ring 16 mounted on the carrier 15 and enclosed by compliant material 14, and a third layer consisting of a filler ring 9. Suitably, the carrier 13 is made of a thin layer, with a thickness in range of 0.05 to 1.0 mm, of a material with high stiffness to maintain proper fitting with the bearing outer ring 5, which is preferably made of the same material as the sensor ring 16 on which the sensing fibre 11 is provided. The layer of compliant material 14 is made from a material of sufficient strength but significantly lower Youngs modulus (stiffness) which may be a factor of 3 to 10 lower than the stiffness of the material used for the sensor ring 16. An example of a suitable material for the compliant layer is a polymer such as PEEK. In other embodiments, no filler ring 9 is present and the sensor ring 16 and compliant layer 14 are in direct contact with the bearing outer ring.

The advantage of a sensor-sleeve assembly 10 comprising a sensor ring in stiff contact with the bearing outer ring and a compliant layer between the housing and the sensor ring 16 is that deformations of the bearing outer ring 5, induced by application loads, are effectively transferred to the sensor ring 16 while deformations from the housing 1, induced by application loads, are taken up by the compliant material with minimal transfer to the sensor ring, which improves the sensitivity for measuring bearing operational parameters by suppressing disturbing noise, for example vibrations, from the housing side.

In most applications of a sensor sleeve assembly according to the invention, the sensor ring is mounted in stiff connection with the non-rotating ring of the bearing and is configured for detecting operating parameters of the bearing. The sensor sleeve assembly may also be used for monitoring or measuring operating parameters of the machine application. For example, in compressor applications, the sensor sleeve assembly could be used to detect an imbalance due to e.g. failure of a compressor blade. An example of such a sensor sleeve assembly is shown in cross-section in Fig. 13, whereby the assembly is again mounted between a housing 1 and the outer ring 5 of a bearing.

Here the sensor-sleeve assembly 10 is constructed as a concentric stack of a first layer consisting of an optional carrier 13 arranged in connection with the housing bore, a second layer consisting of a sensor ring 16 mounted at a radially inner side of the carrier 13 and enclosed by compliant material 14, and an optional third layer consisting of a filler ring 9 mounted to the bearing outer ring 5. The advantage of a sensor sleeve assembly comprising a sensor ring in stiff connection with the bearing housing and comprising a compliant layer between the sensor ring and the bearing outer ring is that deformations of the housing 1, induced by application loads, are effectively transferred to the sensor ring 16 while deformations from the bearing outer ring 5, induced by application loads, are taken up by the compliant material with minimal transfer to the sensor ring, which improves the sensitivity for sensing housing operational parameters by suppressing disturbing noise, for example vibrations, from the bearing side.

A sensor sleeve assembly according to the invention may also be provided with a layer of electrically insulating material, for the purpose of reducing stray currents through the bearing due to electrical discharges when used, for example, in electric generator applications. Fig. 14 shows an example of such a sensor-sleeve assembly 10 mounted between a housing 1 and the outer ring of a bearing 5.

Like the embodiment depicted in Fig. 5, the sensor-sleeve assembly 10 is constructed as a concentric stack of a first layer consisting of two load transfer rings 15, between which a sensor ring 16 is arranged in stiff connection with the bearing outer ring 5, and a second layer consisting a filler ring 9 mounted to the housing 1. Between the first and second concentric layer, a further layer is provided which is made from an electrically insulating material. The electrical insulation layer 21 is constructed from a thin layer, preferably made of polyimide with a thickness between 0.05mm and 0.2mm depending on the required electrical isolation strength. Suitably, the electrical insulation layer 21 is also provided on the axially outer side faces of the sensor sleeve assembly, which has the effect of increasing the electrical clearance distance for sparks and further increasing the insulation strength.

In other examples, an inner and/or outer circumference of the filler ring 9 is provided with the electrical insulation layer, which may also be executed as a ceramic coating.

A further embodiment of a sensor sleeve assembly, mounted between a housing 1 and the outer ring 5 of a bearing, is shown in Fig. 15. The assembly comprises a filler ring 9 mounted to the housing 1 and two load transfer rings 15 mounted in contact with the inner circumference of the filler ring 9. The optical sensing fibre 11 in this embodiment is attached to a radially outer surface of a carrier 13, on which the load transfer rings 15 are also provided. The radially inner surface of the carrier 13 is provided with an adhesive layer and is bonded to the bearing outer ring 5. Other methods of attaching the carrier to the outer ring are also possible. The carrier 13 is suitably a thin layer of material with a thickness of approx. 0.2 - 0.5 mm. The advantage of a sensor-sleeve assembly comprising a sensing fibre provided on a thin carrier layer is that the carrier is flexible, making it easy to bend manually and to wrap around a bearing or a shaft.

The carrier may thus be executed as a sensor strip or sensor tape 25, such as shown in Fig. 16. In this example, the sensor tape is wrapped around a shaft 2. Depending on the application, the sensor sleeve assembly will further comprise one or more load transfer rings and/or a filler ring of suitable dimensions to which the bearing inner ring (non-rotating ring) will be mounted. In accordance with the invention, an adapter ring of suitable dimensions will be mounted between the bearing outer ring (rotating ring) and the housing, enabling the bearing application to be sensorized without modifying the shaft or bearing or housing.

The illustration at the left side of Fig. 16 shows the sensor tape 25 in straight form, before it is wrapped around the shaft 2. The upper right illustration shows a top view of the sensor tape 25 wrapped around the shaft 2. The lower right illustration shows a bottom view of the sensor tape 25 wrapped round the shaft 2. The sensing fibre 11 comprises a number of sensing elements 26 in the form of fibre-Bragg gratings (FBGs), which in use of the assembly are preferably arranged around the shaft circumference at the same axial position.

The sensing fibre 11 is attached to the tape substrate and follows a zig-zag path comprising a number of straight sections of predefined length which are axially offset from each other by an amount b. The predefined length of each straight section is essential equal to the shaft circumference (shaft diameter d* pi), such that each straight section can encircle the shaft at a particular axial location. When the strip or tape is wound several times around the shaft 2 under a wrapping angle a, the wrapping results in a helical shape where the sensing fibre 11 lines up on multiple axial positions, with axial spacing b on the shaft, perpendicular to the shaft axis.

The advantage of a sensor-sleeve assembly comprising a sensor tape/ sensor strip that can be wrapped around a shaft or bearing outer ring is that the tape/strip can be pre-manufactured in different shapes and spooled like a tape which can be applied on a bearing or shaft in the field. The sensor tape can be held on stock, thereby reducing delivery times, and can be fitted to a range of shaft/bearing diameters and widths by the angle of wrapping and adding more or less winding.

Ideally, the sensing fibre would follow a sawtooth pattern on the substrate of the sensor tape, whereby between the straight sections of the optical fibre 11 comprising the FBGs 26, the optical fibre is arranged perpendicular to the straight sections and has a width essentially equal to the axial offset b. In practice, the bending radius of the optical sensing fibre 11 is restricted to a minimum value and it is therefore not be possible to make a right-angled bend. Preferably, in the region between the offset straight sections of the sensing fibre, the fibre follows a curving path, such that the length of the fibre between the straight sections is greater than the axial offset b. The curving path may comprise a number of sections, whereby each section has a radius of curvature greater than the minimum bending radius.

The sensor tape may have an adhesive underlayer or may be attached to the shaft or bearing outer ring via clamping.

An example of a sensor sleeve assembly comprising a clamping arrangement is shown in axial cross-section in Fig. 17. The sensor sleeve assembly is clamped on a shaft 2 by means of a setscrew clamping construction consisting of adjustable setscrews 24 in a retaining ring 23. The setscrews 24 push the sensor sleeve assembly 10 onto the surface of the shaft 2. The sensing fibre 11 which exits from the sensor sleeve is fed through a radially extending passageway 7 in the retaining ring

23. In the depicted example, the retaining ring comprises 4 setscrews arranged at even angular intervals. As will be understood, the number and angular position of the setscrews can be varied as required. The advantage of using a clamping arrangement is that the clamping force is adjustable by tightening the setscrews, meaning that the setscrews can also be used to apply a bias strain on the sensorsleeve to sense expansions and compressions.

An embodiment of a sensor sleeve assembly mounted between a housing 1 and the outer ring 5 of a bearing and comprising a clamping arrangement is shown in Fig. 18. The assembly 10 comprises a sensor ring 16 comprising the sensing fibre 11, which is arranged in contact with the bearing outer ring between two load transfer rings. The clamping construction includes a retaining ring 23 which is arranged around the sensor ring 16 and comprises a number of setscrews 24 which exert an adjustable clamping force on the sensor ring 16. The retaining ring 23 is kept in radial position by the load transfer rings 15, which comprise axially opposing annular grooves into which edges of the retaining ring extend.

The sensor sleeve assembly may also be retrofitted to an existing machine application or implemented on a new machine application by machining of the shaft, bearing or housing. For example, the sensor sleeve assembly could be mounted to the outer ring of a bearing which, before or after hardening, has been machined to obtain a smaller outside diameter that accommodates the radial thickness of the sensor sleeve assembly. This enables the sensor ring to be located closer to the raceway of the bearing, meaning that rolling element-induced deformations can be detected more easily. Also, in this case, the sensor sleeve assembly can be reused when the bearing needs to be replaced.

In each of the figures where a bearing or bearing ring has been depicted, the bearing is a deep-groove ball bearing. It is to be understood that the sensor sleeve assembly and method of mounting a bearing and sensor sleeve assembly may be applied for any kind of radial bearing, being a siding bearing or a rolling element bearing comprising one or more rows of balls or rollers. The invention is thus not restricted to the described embodiments, but may be varied with the scope of the claims.

List of reference numbers used in drawings

Housing

Shaft

Bearing

Inner ring of bearing

Outer ring of bearing

Rolling element of bearing

Feedthrough for optical fibre

Adapter ring mounted to non-rotating bearing ring

Filler ring forming part of sensor sleeve assembly

Sensor sleeve assembly

Optical sensing fibre

Cavity for optical sensing fibre

Carrier layer/substrate

Compliant layer

Load transfer ring

Sensor ring

Ring comprising pocket for storing a length of fibre

Opening towards pocket for feeding though the fibre

Pocket for fibre

Cover to close pocket

Layer for electrical isolation

Adhesive strain transfer layer

Retaining ring of clamping element

Setscrew of clamping element

Sensor tape

Sensing elements within optical fibre

Inner sleeve element of sensor sleeve assembly

Claims

1. A method of mounting a bearing (3) and a sensor sleeve assembly (10) to a machine in a housing (1) with a housing bore diameter Dbh on a shaft with a diameter d, whereby the sensor sleeve assembly comprises one or more ring elements (9, 14, 15, 16, 17) and an optical sensing fibre (11) provided on a radially oriented surface of at least one ring element, whereby the bearing comprises an inner ring (4) and an outer ring (5) one of which is a rotating ring and the other of which is a non-rotating ring in use of the bearing, whereby the sensor sleeve assembly (10) is mounted in connection with a cylindrical surface of the nonrotating ring, the method comprising steps of:

- selecting a bearing (3) with an outer diameter D, a bore diameter db, and load rating suitable for the machine application loads;

- selecting a sensor sleeve assembly with a thickness Tsa; and

- selecting an adapter ring (8) with a thickness Tar;

whereby when the outer ring (5) is the non-rotating ring of the bearing, the bearing, sensor sleeve assembly and adapter ring are selected such that: D < Dbh, db s d, Tsa is essentially equal to (Dbh - D)/2 and Tar is essentially equal to (d - db)/2;

and whereby when the inner ring (4) is the non-rotating ring of the bearing, the bearing, sensor sleeve assembly and adapter ring are selected such that:

D < Dbh, db > d, Tsa is essentially equal to (db - d)/2 and Tar essentially is equal to (Dbh - D)/2;

the method comprising a further step of

- mounting a concentric arrangement of the bearing (3), sensor sleeve assembly (10) and adapter ring (8) on the shaft (2) in the housing (1) such that the adapter ring is mounted in connection with a cylindrical surface of the rotating ring of the bearing.

2. The method of claim 1, wherein the sensor sleeve assembly comprises a ring element (17) with an axially extending passageway (7) through which the sensing fibre (11) is guided to an axially outer side face of the ring element.

3. The method of claim 2, wherein the ring element has an annular recess (19) in its axially outer side face in communication with the passageway (7), whereby the recess is dimensioned to accommodate a coiled-up length of the optical sensing fibre (11).

4. The method of claim 3, wherein the ring element (17) comprising the recess has a removable cover (20) for enclosing the recess (19).

5. The method of any preceding claim, wherein the sensor sleeve assembly (10) comprises a ring element in the form of load transfer ring (15), for transferring loads between the rotating bearing ring and the housing (1) or shaft (2).

6. The method of claim 5, wherein the sensor sleeve assembly has a single ring element in the form of a load transfer ring, in which an annular groove is provided for accommodating the sensing fibre (11).

7. The method of claim 5, wherein the sensor sleeve assembly comprises two load transfer rings (15) in axial abutment which each other, whereby one of the load transfer rings comprises an annular cavity (12) provided in an axial end face, for accommodating the sensing fibre (11), which cavity is enclosed via the axial abutment of the other load transfer ring, or whereby at the axial abutment of the two load transfer rings, each ring has a shaped edge which forms a groove or cavity for accommodating the sensing fibre (11).

8. The method of any preceding claim, wherein the sensor sleeve assembly comprises a ring element in the form of a sensor ring (16) having a substrate on which the sensing fibre (11) is provided, whereby the sensor ring has thickness Tsr smaller than Tsa.

9. The method of claim 8, wherein the sensor sleeve assembly (10) further comprises a ring element (14) made of a compliant material, whereby a first radial side of the compliant ring element (14) is in contact with the optical sensing fibre (11) provided on the sensor ring (16), whereby the compliant ring element (14) is configured suppress vibrations emanating from a surface with which an opposite radial side of the compliant ring element is in contact.

10. The method of claim 8, wherein the sensor sleeve assembly (10) comprises an axial arrangement of at least one sensor ring (16) and at least one load transfer ring (15).

11. The method of claim 1, wherein the optical sensing fibre (11) is provided on a substrate in the form of a sensor tape (25) or sensor strip and is arranged to follow path comprising a first straight section having a first set of sensing elements (26) and at least a second straight section having a second set of sensing elements, whereby the first and second straight sections are arranged parallel to each other with an axial offset (b), and wherein the sensor tape or sensor strip is wound helically around a cylindrical surface of the sensor sleeve assembly, such that the first and second sets of sensing elements (26) are arranged circumferentially on the sensor sleeve at respective first and second axial positions.

12. The method of claim 8 or claim 11, wherein the sensor sleeve assembly (10) further comprises a clamping element for exerting a clamping force on the substrate on which the sensing fibre (11) is provided.

13. The method of claim 12, wherein the clamping element comprises a retaining ring (24) and a number of adjustable setscrews (24) which bear against the substrate.

14. The method of any preceding claim, wherein the at least one ring element comprising the optical sensing fibre (11) is provided with markers for indicating a desired position of sensing elements (26) within the fibre.

15.The method of any preceding claim, wherein an inner or outer circumferential surface of the sensor sleeve assembly is provided with an electrical insulation 5 layer (21).