Bearing unit having at least two types of sensing elements mounted on a seat

Abstract

A bearing unit (10) comprises a seat (12) and at least one bearing (14, 16, 18) mounted in the seat (12). The bearing unit (10) comprises at least one load sensing element (30, 31, 32) and at least one vibration sensing element (33, 34) fixed to the seat (12).

Description

Technical Field

[0001] The present invention relates to the field of condition monitoring of bearings for control processes by actively sensing loads.

[0002] More particularly, the present invention relates to a rolling bearing equipped with a fiber optical sensing element (referred to as FOS) such as an optical fiber. Background Art

[0003] The optical fiber typically comprises a plurality of fiber Bragg gratings (FBGs) for sensing positions evenly distributed around the circumference of the ring of the bearing (eg for sensing at least one position outside the rolling elements).

[0004] Fiber optic sensing can be used to monitor machines such as, for example, pumps, compressors, wind turbines, ship propulsion systems, aircraft propulsion systems and other rotating machines used in applications such as oil and gas, mining, marine, papermaking (pulp and paper), aerospace, etc., as well as any equipment ( / facilities) (installations) that require long distance signals.

[0005] Reference may be made to documents US 2016 / 0305845-A1 and US 2013 / 188897-A1 and WO 2011 / 066926, which describe examples of bearings having circumferential grooves arranged on the outer surface of an outer ring of the bearing, each of the grooves accommodating an optical fiber sensing element for measuring the bearing load.

[0006] However, in this configuration, the optical fiber sensing element is subject to damage during transportation of the bearing.

[0007] In rotating machines, the loads of the rotating shaft are mainly supported by the bearings. Therefore, it is crucial to reduce maintenance time and assembly complexity to maximize the working time of the machine. With the help of condition monitoring systems, maintenance planning can be improved.

[0008] Since replacement operations of bearings used, for example, in cruise liners are often carried out in construction sites that are not best suited for bearing replacement, the rotating parts may be exposed to weather, moisture, contamination and uncontrolled temperature drifts resulting in insufficient measurement accuracy of the sensor system. This may lead to the risk of incorrect calibration of the sensor system.

[0009] Improved knowledge of bearing conditions, such as loads, is needed to improve bearing life prediction and fault detection. Summary of the invention

[0010] It is therefore an object of the present invention to provide a bearing unit which is easy to assemble, has a reduced risk of damage to the sensing element and has an improved measurement accuracy.

[0011] A particular object of the present invention is to provide a bearing unit comprising a seat and at least one bearing mounted inside the seat.

[0012] The bearing unit includes at least one load sensing element and at least one vibration sensing element fixed to the seat.

[0013] The at least one load sensing element is different from the at least one vibration sensing element. In other words, the bearing unit comprises a seat and two different types of sensing elements mounted on the seat.

[0014] The bearings are constructed to support the forces acting from the shaft to the bearing housing assembly. The bearings can be replaced without damaging the housing.

[0015] The mount acts as a load cell, amplifying the force and transferring the acceleration to the sensing element.

[0016] Force and vibration signals are used as input for bearing condition monitoring and life prediction to evaluate bearing performance.

[0017] Advantageously, at least one load-sensing element is mounted in a groove provided on a hole in the seat in which the bearing is mounted.

[0018] For example, the bearing is mounted axially between two axially opposite shoulders of the seat, the at least one load sensing element being mounted in a groove provided on at least one of the shoulders of the seat.

[0019] In an embodiment, the at least one vibration sensing element is mounted on a frontal surface of the seat.

[0020] In an embodiment, the at least one vibration sensing element is mounted on an outer peripheral surface of the seat.

[0021] For example, the bearing comprises at least two bearings mounted radially in a seat, for example, a toroidal roller bearing and a spherical roller thrust bearing.

[0022] In an embodiment, the bearing unit includes at least a first bearing (such as, for example, a toroidal roller bearing) configured to transmit radial loads and two adjacent second and third bearings (such as, for example, a spherical roller thrust bearing) configured to transmit axial loads and radial loads, wherein the first bearing, the second bearing and the third bearing are axially mounted between two axially opposite shoulders of the seat.

[0023] In another embodiment, the bearing unit comprises at least three load sensing elements, the at least three load sensing elements comprising:

[0024] - a first load sensing element located in a first groove provided in a first shoulder of the seat and in axial contact with the first bearing;

[0025] - a second load sensing element located in a second groove provided in the bore of the seat and in radial contact with the outer ring of the first bearing; and

[0026] - a third load-sensing element located in a third groove provided in a second shoulder of the seat axially opposite the first shoulder, said third load-sensing element being in axial contact with the third bearing.

[0027] In an embodiment, the bearing unit comprises at least two vibration sensing elements, the at least two vibration sensing elements comprising:

[0028] - a first vibration sensing element mounted on a first front surface of the seat; and

[0029] - A second vibration sensing element mounted on the outer cylindrical surface of the seat.

[0030] The number of load sensing elements is not limited to three. In practice, the bearing unit may include two or more than three load sensing elements.

[0031] The number of vibration sensing elements is not limited to two. In fact, the bearing unit may include more than two vibration sensing elements.

[0032] For example, the load sensing element is a fiber optic sensing element.

[0033] The optical fiber may include a plurality of fiber Bragg gratings (referred to as FBGs) for sensing positions uniformly distributed around the circumference of the first ring of the bearing. For example, the fiber Bragg gratings are used to measure local strain in a circumferential groove.

[0034] For example, the vibration sensing element is a piezoelectric sensing element.

[0035] The seat may be made as one piece, or may comprise a plurality of axially stacked seat assemblies. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A partial cross-sectional view of a bearing unit according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0037] The invention and its advantages will be better understood by studying the detailed description of a particular embodiment given by way of non-limiting example and illustrated by the accompanying drawing which shows a partial cross-sectional view of a bearing unit according to an embodiment of the invention.

[0038] The expressions "outer" and "inner" refer to the axis of rotation XX of the bearing, the inner part being closer to said axis of rotation than the outer part.

[0039] Reference Figure 1 , Figure 1 An embodiment of a bearing unit 10 is shown which comprises a housing 12 and three bearings 14 , 16 , 18 which are mounted radially inside the housing 12 and are designed to be mounted around the shaft 1 .

[0040] As another alternative, the bearing unit 10 may include a single bearing, or two bearings, or a number of bearings higher than three.

[0041] As shown, the seat 12 is radially bounded by an inner cylindrical surface 12a and an outer cylindrical surface 12b. The seat 12 also includes two radial frontal surfaces 12c, 12d that axially bound the inner cylindrical surface 12a and the outer cylindrical surface 12b. As shown, the seat 12 includes a first portion 13a and a second portion 13b stacked in the axial direction relative to the first portion 13a.

[0042] The bearings 14, 16, 18 are radially mounted on the inner surface of the seat 12 (especially the first part 13a) or inside the hole 12a, and are axially mounted between two axially opposite shoulders 12e, 12f of the seat 12. The first shoulder 12e is provided in the first part 13a of the seat 12, and the second shoulder 12f is provided in the second part 13b of the seat 12. The second part 13b of the seat 12 holds the bearings 14, 16, 18 axially inside the first part 13a of the seat 12.

[0043] As a non-limiting example, the bearing unit 10 includes a first bearing 14, such as, for example, an annular roller bearing configured to transmit radial loads. The first bearing 14 includes an inner ring 19, an outer ring 20, and a row of rolling elements 21 (such as, for example, rollers) arranged between the inner ring 19 and the outer ring 20. For example, the first bearing 14 includes a cage (not shown) configured to maintain the circumferential spacing of the rolling elements.

[0044] The inner ring 19 and the outer ring 20 of the first bearing 14 are in the form of concentric rings rotatable about the axis of rotation XX of the bearing unit 10 , the outer ring 20 surrounding the inner ring 19 in the radial direction.

[0045] As shown, the outer ring 20 of the first bearing 14 is solid and is radially bounded by an inner cylindrical surface 20a having a raceway for rolling elements 21 and an outer cylindrical surface 20b in radial contact with the inner surface 12a of the seat 12. The outer ring 20 also includes two opposite (opposite / ) radial front surfaces ( / front surfaces) 20c, 20d that axially bound the inner cylindrical surface 20a and the outer cylindrical surface 20b. The first front surface 20c is in axial contact with the first shoulder 12e of the seat ( / in axial contact), and the second front surface 20d is in axial contact with a shim 15 that is axially located between the first bearing 14 and the second bearing 16. The shim 15 is mounted in the hole 12a of the seat for mounting the bearings 14, 16, 18. As an option, the second front surface 20d of the outer ring 20 can directly contact the second bearing 16.

[0046] As shown, the inner ring 19 of the first bearing 14 is of solid type and is radially delimited by an inner cylindrical surface 19a and an outer cylindrical surface 19b, the inner cylindrical surface 19a being in radial contact with the shaft 1 and the outer cylindrical surface 19b having a raceway for rolling elements 21. The inner ring 19 also includes two opposite ( / back-to-back) radial front surfaces 19c, 19d delimiting the inner cylindrical surface 19a and the outer cylindrical surface 19b in the axial direction.

[0047] The bearing unit 10 includes two adjacent second bearings 16 and third bearings 18, such as, for example, spherical roller thrust bearings configured to transmit axial loads and radial loads. The second bearing 16 includes an inner ring 22, an outer ring 23, and a row of rolling elements 24 (such as, for example, rollers) arranged between the inner ring 22 and the outer ring 23, and the third bearing 18 includes an inner ring 26, an outer ring 25, and a row of rolling elements 27 (such as, for example, rollers) arranged between the inner ring 26 and the outer ring 25. For example, the second bearing 16 and the third bearing 18 each include a cage (not shown) configured to maintain the circumferential spacing of the rolling elements.

[0048] The bearing unit 10 further comprises two opposing sealing elements 28, 29, each of which is mounted in a hole (not shown) of a corresponding shoulder 12e, 12f of the seat 12 and extends radially inwardly towards the shaft 1. The sealing elements restrict the infiltration of liquids, particles and dust from the external environment between the rings of the bearing. The sealing elements are radial shaft seals with a garter shaft spring. As an alternative, the sealing elements can be of any other type.

[0049] As shown, the bearing unit 10 comprises three optical fiber sensing elements ( / fiber optic sensing elements) 30, 31, 32 configured to measure the bearing load. The loads acted by the rolling elements of the bearing are transmitted to the seat. Additional parameters may be measured, such as, for example, pressure, temperature, cage speed or direction of rotation.

[0050] The number of optical fiber sensing elements is not limited to three. In practice, the bearing unit may include one optical fiber sensing element, or two optical fiber sensing elements, or a number of optical fiber sensing elements higher than three. For example, the bearing unit may include an optical fiber sensing element corresponding to the number of outer ring raceways for rolling elements.

[0051] As shown, the first optical fiber sensing element 30 is located in the first groove 12g provided on the front surface (not shown) of the shoulder 12e of the seat. The first optical fiber sensing element 30 is in axial contact with the first front surface 20c of the outer ring 20 of the first bearing 14.

[0052] The bearing unit 10 further comprises a second optical sensing element 31 located in a second groove 12h provided on the inner surface 12a of the seat 12. The second optical fiber sensing element 31 is in radial contact with the outer surface 20b of the outer ring 20 of the first bearing 14.

[0053] The bearing unit 10 further comprises a third optical sensing element 32 located in a third groove 12i provided on a front surface (not shown) of the second shoulder 12f of the seat 12. The third optical fiber sensing element 32 is in axial contact with the third bearing 18.

[0054] As shown, the bearing unit 10 comprises two piezoelectric sensing elements 33, 34 configured to measure vibrations of the bearing. This allows any damage to be detected and maintenance to be planned prior to any further damage to other components.

[0055] The number of piezoelectric sensing elements is not limited to two. In fact, the bearing unit may include one piezoelectric sensing element, or more than two piezoelectric sensing elements.

[0056] As shown, the first piezoelectric sensing element 33 is mounted on the first front surface 12 c of the seat 12 , and the second piezoelectric sensing element 34 is mounted on the outer surface 12 b of the seat 12 .

[0057] The load and vibration signals transmitted by the optical fiber sensing element and the piezoelectric sensing element, respectively, can then be used as inputs for bearing condition monitoring and bearing life prediction.

[0058] The forces transmitted to the bearing cause elastic deformation of the outer ring of the bearing. If the bearing is damaged, vibrations will be transmitted from the damaged outer ring to the seat 12. The seat 12 thus acts as a load cell that absorbs the forces and transmits the acceleration to the sensing element.

[0059] The seat is designed in such a way that the bearing can be installed and removed without damaging the seat.

[0060] The bearing unit 10 can be assembled on the construction site under laboratory conditions and then transported to the assembly site together with the shaft. Thus, the sensing element is calibrated and preloaded, which improves the measurement accuracy and thus the life prediction of the bearing unit.

[0061] Thanks to the invention, it is easy to replace the entire bearing unit including the sensing element, which is used in time-critical applications such as, for example, marine cruise liners. It is also possible to reuse the seat as well as the sensing element and replace only the bearing when necessary.

Claims

1. A bearing unit (10) comprising a seat (12) and at least one bearing (14, 16, 18) mounted inside the seat (12), wherein: The bearing unit (10) comprises at least one load sensing element (30, 31, 32) and at least one vibration sensing element (33, 34) fixed on the seat (12); The bearing (14, 16, 20) is mounted in a hole of the seat (12), and the bearing unit (10) comprises at least two vibration sensing elements (33, 34), and the at least two vibration sensing elements (33, 34) include: a first vibration sensing element (33) mounted on a first front surface (12c) of the seat (12); and A second vibration sensing element (34) is mounted on the outer cylindrical surface (12b) of the seat (12).

2. The bearing unit (10) according to claim 1, characterized in that The at least one load sensing element (31) is mounted in a groove (12h) provided in a hole (12a) of the seat (12) for mounting the bearing.

3. The bearing unit (10) according to claim 1, characterized in that The bearing (14, 16, 18) is axially mounted between two axially opposite shoulders (12e, 12f) of the seat, and the at least one load sensing element (30, 32) is mounted in a groove (12g, 12i) provided in at least one of the shoulders (12e, 12f) of the seat (12).

4. The bearing unit (10) according to any one of claims 1 to 3, characterized in that The at least one vibration sensing element (33) is mounted on the front surface (12c) of the seat (12).

5. The bearing unit (10) according to any one of claims 1 to 3, characterized in that: The at least one vibration sensing element (34) is mounted on the outer peripheral surface (12b) of the seat (12).

6. The bearing unit (10) according to any one of claims 1 to 3, characterized in that The bearing unit (10) comprises at least a first bearing (14) configured to transmit radial loads and two adjacent second bearings (16) and a third bearing (18) configured to transmit axial loads and radial loads, wherein the first bearing (14), the second bearing (16) and the third bearing (18) are axially mounted between two axially opposite shoulders (12e, 12f) of the seat (12).

7. The bearing unit (10) according to claim 6, characterized in that The bearing unit (10) comprises at least three load sensing elements (30, 31, 32), wherein the at least three load sensing elements (30, 31, 32) comprise: A first load sensing element (30) is located in a first groove (12g) provided in a first shoulder (12e) of the seat (12) and is in axial contact with the first bearing (14); a second load sensing element (31) located in a second groove (12h) provided in the hole (12a) of the seat (12) and in radial contact with the outer ring (20) of the first bearing (14); and A third load sensing element (32) is located in a third groove (12i), wherein the third groove (12i) is arranged on a second shoulder (12f) of the seat (12) which is axially opposite to the first shoulder (12e), and the third load sensing element (32) is in axial contact with the third bearing (18).

8. The bearing unit (10) according to any one of claims 1 to 3, characterized in that The load sensing element is a fiber optic sensing element.

9. The bearing unit (10) according to any one of claims 1 to 3, characterized in that The vibration sensing elements (33, 34) are piezoelectric sensing elements.

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