ROTOR BEARING TEMPERATURE SENSOR

Abstract

A bearing assembly is provided with an improved mounting for a temperature sensor for monitoring a temperature of a race of the bearing. The assembly includes a temperature sensor assembly mounted to the race of the bearing and a thermal insulator arranged to thermally insulate the sensor from heat exchange with the surrounding environment and/or neighbouring components to which the bearing or assembly is mounted, in order to improve accuracy, reliability and speed of response of the temperature sensor readings.

Claims

1. A bearing assembly comprising: a bearing, having a first race and a second race; a temperature sensor assembly, comprising a temperature sensor, mounted to one of the first race and the second race; a first thermal insulator arranged to thermally insulate the temperature sensor from its surroundings; and a housing for the temperature sensor; wherein the temperature sensor and the first thermal insulator are located between the housing and the race of the bearing.

2. The bearing assembly according to claim 1, the temperature sensor assembly further comprising a thermal conductor element disposed between the temperature sensor and the race to which the sensor assembly is mounted.

3. The bearing assembly of claim 2, wherein the first thermal insulator is arranged to insulate the sensor and the thermal conductor element from their surroundings.

4. The bearing assembly of claim 1, wherein the bearing is mounted to a structure, the first thermal insulator being disposed between the sensor and the structure.

5. The bearing assembly of claim 1, wherein the temperature sensor, the first thermal insulator and a thermal conductor element are all located between the housing and the race of the bearing.

6. The bearing assembly of claim 1, wherein the first thermal insulator is disposed between the housing and the temperature sensor.

7. The bearing assembly of claim 1, wherein the temperature sensor is disposed between the first thermal insulator and the race of the bearing.

8. The bearing assembly of claim 1, wherein the first thermal insulator comprises a first portion, arranged substantially radially with respect to the bearing, and a second portion, arranged substantially axially with respect to the bearing.

9. The bearing assembly of claim 8, wherein the first portion is a substantially planar portion which is radially oriented with respect to the bearing and the second portion is a substantially part-cylindrical portion.

10. The bearing assembly of claim 1, comprising first and second thermal insulators, the second thermal insulator being arranged substantially opposite at least a part of the first thermal insulator, wherein the second thermal insulator is arranged between the temperature sensor and a structure to which the bearing is mounted.

11. (canceled)

12. The bearing assembly of claim 10, wherein one of the first and second thermal insulators is substantially disc shaped.

13. The bearing assembly of claim 1, further comprising a pre-loading mechanism for pre-loading at least the sensor against the race of the bearing.

14. The bearing assembly of claim 13, wherein the pre-loading mechanism is disposed in the housing.

15. The bearing assembly of claim 1, wherein the race comprises one or more flange portions for mounting the bearing to a structure or to a rotating component and wherein the temperature sensor is mounted substantially adjacent at least one of the flange portions.

16. The bearing assembly of claim 15, wherein plural flange portions are arranged in a substantially circular or arcuate array, and wherein the temperature sensor and/or the thermal conductor element are arranged substantially between an arc of the flange portions and an arc of the race.

17. The bearing assembly of claim 15, wherein the housing is attached to the race of the bearing at the one or more flange portions.

18. The bearing assembly of claim 17, wherein the bearing is attached to a structure or to a rotating component via fixing means at the flange portions and wherein the housing is attached to the flange portions by the same fixing means.

19. The bearing assembly of claim 15, wherein at least one of the sensor and/or the conductor element comprises a profile shape arranged to mate with at least one of the flange portions, to locate the temperature sensor circumferentially on the race of the bearing.

20. The bearing assembly of claim 10, wherein at least one of the first and second thermal insulators is disposed between at least a part of the bearing race and the component or structure to which the bearing is mounted.

21. The bearing assembly of claim 20, wherein the thermal insulator is disposed on a load path of fixing means for fixing the bearing to the component or structure to which the bearing is mounted.

22-26. (canceled)

27. The bearing assembly of claim 13, wherein the pre-loading mechanism comprises a threaded adjustor and/or a resilient biasing member.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Examples of the present invention are described below in detail with reference to the accompanying drawings, of which:

[0033] FIG. 1 illustrates an assembly of the present invention, showing an outside view of a housing containing a temperature sensor assembly of the present invention;

[0034] FIG. 2 shows a section through the assembly illustrated in FIG. 1;

[0035] FIG. 3 shows an alternative section through the assembly of FIGS. 1 and 2;

[0036] FIG. 4 shows a view of the assembly of FIG. 1 viewed from an opposite side to that shown in FIG. 1;

[0037] FIG. 5 shows an alternative section through the temperature sensor assembly of FIG. 1; and

[0038] FIG. 6 shows a view of a subassembly of the assembly shown in FIG. 1, viewed from an opposite side of the bearing to that shown in FIG. 1.

DETAILED DESCRIPTION OF EMBODIMENT(S)

[0039] FIG. 1 shows a bearing of assembly 1 of the present invention. In the illustrated embodiment, the bearing assembly of the invention is provided in a generator. The problems herein will be described with respect to such a generator, in particular an air or oil cooled generator, but the heating and temperature monitoring problems addressed by the invention apply equally to many other types of machines, as will become apparent on reading the following description.

[0040] The illustrated assembly comprises a bearing 10. The bearing 10 comprises an inner race 101 and an outer race 102. In the illustrated embodiment, the bearing 10 is mounted in a structure, which takes the form of a wall section 20. In the embodiment described, wall section 20 divides a chamber which contains a main stator (not shown) of a generator from a further chamber which is hermetically sealed and divided from the chamber containing the stator. The chamber containing the stator, in which the temperature sensor of the present invention is mounted, is a cooled chamber, since heat is generated by the stator as the generator carries out its usual function of generating electrical current from rotational motion. Such generators are conventional and are not described herein in any further detail. However, it will be appreciated that similar conditions rendering the present invention advantageous will be experienced in a range of other machines. These can include engines, motors, turbines, pumps and essentially any other type of machine with bearings which may generate heat. The fact that the chamber is cooled is not essential to the invention, but can in some situations, render the advantages of the present invention more pronounced. The chamber can be oil cooled or air cooled. Oil cooling can be used in higher power generators, while air cooling can be sufficient in generators operating at lower power levels.

[0041] In arrangements such as that illustrated in FIG. 1, known examples have mounted a temperature sensor within wall 20, at a location adjacent the bearing 10. However, in any such arrangement, the wall 20, due its thermally conductive materials, generally a metallic material, has the effect of dissipating heat generated within the bearing 10. Moreover, if the wall 20 is a wall of a cooled chamber, then that effect may be even more pronounced, since the cooling effect of the cooled chamber will dissipate heat more rapidly through and away from wall 20 and away from any temperature sensor mounted in wall 20. In such arrangements, there can therefore arise situations where a local temperature peak experienced in a race of the bearing 10 may not be detected by a temperature sensor seeking to monitor conditions of the bearing. This can result in an undetected bearing overheat condition, and can reduce the life of the bearing 10, or can ultimately result in failure of the bearing 10 before the end of its expected life.

[0042] The outer race 102 comprises relatively narrow portions 103, which have a radial dimension which is as determined by the mechanical strength required of the outer race. Outer race 102 further comprises relatively wide portions 104, which have a radial dimension greater than the relatively narrow portions 103. Relatively wide portion 104 can also be termed flange portions, since they act to form flange portions extending from the race 102, for attaching the race 102 to the wall 20 via fixing means 201.

[0043] The bearing assembly of the present invention seeks in particular to monitor the temperature of the relatively narrow portions 103 of the bearing outer race 102, since these can be especially susceptible to heat build-up. This is because they lack contact with any heat dissipating components, such as flange portions 104, or any part of wall 20 to which the outer race may be mounted and to which heat may be dissipated.

[0044] The illustrated temperature sensor assembly is therefore mounted in contact with a relatively narrow portion 103 of the outer race 102 and is located between adjacent flange portions 104.

[0045] Although the illustrated assembly shows the flange portions and the temperature sensor assembly mounted to the outer race, there may be instances where an inner race comprises either radially or axially projecting flange portions, to which a temperature sensor assembly of the present invention may be mounted in order to monitor temperature conditions of the inner race 101.

[0046] FIG. 1 further shows a view of the outside of a housing 30 which acts to hold the temperature sensor assembly of the present invention in place against the bearing outer race 102. Housing 30 has a first wall portion 30b, which is arranged in a substantially radial plane of the bearing, to maintain the temperature sensor assembly in a relatively fixed axial location relative to the bearing. The housing further comprises a second wall portion 30a, which is arranged radially around the temperature sensor, and having a substantially part-cylindrical form, to maintain the temperature sensor assembly in a fixed radial position relative to the bearing.

[0047] Housing 30 is provided with pre-loading means 310. In this instance, the illustrated pre-loading means is in the form of a threaded adjustor and so provides an adjustable mechanism for preloading the temperature sensor assembly against the outer race 102, but can also be a compression spring. Other forms of pre-loading means may be envisaged, such as biasing means in the form of a spring or other resilient member, which can be located between the housing 30 and the temperature sensor assembly, as will become apparent as further detail of the assembly is described in the following figures. The temperature sensor assembly is preferably provided between the bearing race and the preferably adjustable pre-loading means.

[0048] FIG. 2 shows a section through the assembly shown in FIG. 1. The main stator 200 of the generator of this embodiment is illustrated in this figure to illustrate its arrangement relative to the assembly of the present invention. The location of outer race 102 within wall 20 can be more clearly seen in this figure. The outer race is mounted with a clearance or interference fit with the wall 20. The cross-section of FIG. 2 through the temperature sensor assembly of FIG. 1, at the location of pre-loading means 310, gives a clearer illustration of the components inside the housing 30. Inside housing 30 there is located a temperature sensor 33. Surrounding the temperature sensor is an optional thermal conductor element 32. Located between temperature sensor 33 and housing 30 is a thermal insulator 31. The thermal conductor element 32 may surround the temperature sensor 33. As can be seen in the figure, pre-loading means 310 can be used to apply a force against any or all of the temperature sensor 33, the thermal conductor element 32 and the thermal insulator 31.

[0049] A further thermal insulator 34 is also located between the temperature sensor 33 and the structure 20, to prevent heat dissipation away from the temperature sensor to the structure before such heat has been properly sensed by the temperature sensor 33.

[0050] Thermal conductor element 32 may be formed from copper or aluminium or other thermally conductive materials, which have particularly good thermal conducting properties and so are well suited to the present invention. Although many materials are thermally conductive and very few are completely thermally insulative, suitable materials preferably have a thermal conductivity similar to or higher than that provided by copper alloys or aluminium alloys or other generally thermally conductive materials.

[0051] Thermal insulators 31 and 34 preferably have a low coefficient of thermal conductivity, this should be ideally lower than the thermal conductivity of copper or aluminium, preferably significantly lower, to substantially prevent or significantly reduce the conduction of heat away from the sensor. Any generally known thermally insulating material can be advantageous in this implementation.

[0052] Thermal insulator 31 has an axially extending portion 31a and a radially extending portion 31b. Since each of these portions extends circumferentially around a part of the bearing 10, each has a substantially plate-like form as can be seen from the figures. Radially extending portion 31b is substantially planar and is located in a plane substantially perpendicular to the axis of rotation of the bearing, being located axially displaced from the temperature sensor assembly, and located adjacent the temperature sensor assembly. Axially extending portion 31a has a part-cylindrical form and is radially displaced from the temperature sensor assembly, and located adjacent the temperature sensor assembly.

[0053] It can also be seen that further thermal insulator 34 is arranged substantially opposite the radially extending portion 31B of the thermal insulator 31 and the temperature sensor 33 is located between those two thermal insulators. The cylindrically formed axially extending portion 31A is arranged radially outside temperature sensor 33, and so a circumferentially extending enclosure is formed out of the thermal insulators 31 and 34, with the open face of the enclosure being directed toward the outer race 102 of the bearing. By virtue of this arrangement, the principle path for heat to be transmitted to and from the temperature sensor 33 is via the face of outer race 102 which is contacts, preferably via its thermal conductor element 32.

[0054] FIG. 3 illustrates a further section through the assembly shown in FIGS. 1 and 2, this section is through the fixing means 202 of FIG. 1. As can be seen in the figure, the preferred housing 30 contains a threaded portion 301, and a preferred bolt 202 comprises a corresponding threaded portion arranged to engage the threaded portion 301 of the housing 30. Bolt 202 also preferably further comprises a second threaded portion arranged to engage with flange portion 104 of the outer race 102, to fix the outer race 104 relative to the wall 20.

[0055] FIG. 4 illustrates a side of wall 20 opposite the side of wall 20 to which the temperature sensor assembly is mounted. Bolts 202 and 204 are lodged within the wall 20 and their heads can be lock wired together with a tie wire 40 to secure them in place to prevent them becoming loose or un-tightened during vibration conditions. FIG. 4 also illustrates an opening 42 which is provided in wall 20, which allows a signal wire 41 to pass through the wall 20. This wire 41 can bring signals out of the cooled chamber, from the temperature sensor 33 to a controller, and can provide power to the temperature sensor if necessary. Opening 42 will be sealed with a grommet. The opening 42 is provided with smooth radius to prevent excessive wear on temperature sensor wire 41. Use of the temperature sensor assembly of the present invention only requires a small opening to be provided in wall 20 for the passage of the wire 41. This is in contrast to previous implementations, where the whole temperature sensor itself would have to be incorporated into the structure of wall 20, which required more material and complex features to be provided in wall 20 to incorporate the sensor into an opening such as opening 43, for example. A temperature sensor would previously have been be incorporated by a direct threaded engagement in such an opening and, as is evident from the figure, it is necessary to build-up additional material around opening 43 or any opening provided in wall 20 to accommodate fixing means, sensors or components. Therefore, use of the temperature sensor assembly of the present invention reduces the need for the use of such additional features and materials in wall 20.

[0056] FIG. 5 illustrates a section cutting through the temperature sensor assembly 50 in the region of flanged portions 104 of the outer race 102 of the assembly of FIG. 1. The arrangement of thermal conductor element 32 around temperature sensor 33 can be more clearly seen in this figure. The temperature sensor 33 may therefore be a substantially elongate temperature sensor, or a preferably cylindrical wire temperature sensor, and it may be disposed in an elongate hole or opening in the thermal conductor element 32. Wire 41 for transporting power and/or signals to and from the temperature sensor 33 passes through the wall 20 and also through thermal isolator/insulator disc 51. As can be seen in the figures, thermal insulator disc 51, which is also the further thermal insulator 34 of FIG. 2, is located between flange portions 104 and wall 20. It will be appreciated that when fixing means 202 and 204 are engaged via threads with flange portions 104, they will, when tightened, create a compressive force or load which passes through flange portions 104, through thermal insulator disc 51 and on to wall 20. Therefore, when the fixing means 204 are tightened, a compressive force will be applied to thermal isolator/insulator disc 51. For this reason, its thickness must be catered for in the dimensioning of components for the assembly and it is preferable if it is made from a material which is highly resilient to compressive forces, so that it does not compress or deform over the life of the assembly and create unwanted slack or play in the fixing of the flange portions 104 to wall 20. The preferred material of the illustrated embodiment is a Kevlar™ sheet, which has a compressive strength similar to or better than the wall structure 20 and/or the bearing race 102. Any such material having the desired thermally insulating properties and the desired compressive strength can also be used.

[0057] It can further be seen that the temperature sensor assembly 50 comprises a profile portion 52, which is configured to mate with a corresponding profile of the outer race 102 to which it is mounted. This profile, preferably in combination with housing 30 (not shown in FIG. 5), acts to retain the temperature sensor assembly 50 from moving in a circumferential direction around the outer race 102 to which it is mounted.

[0058] FIG. 6 shows a view of the temperature sensor assembly 50, viewed from a direction of wall 20, with the wall 20 removed from the view, to illustrate internal components of the assembly 50. It can be seen that an upper or outer part of the insulator 31 has an arc shaped profile, substantially parallel with the profile of the race 102. This part also has an axial dimension, and it therefore has a part-cylindrical form.

[0059] The arrangement of the power/signal wire 41 for the sensor can also be seen, and it comprises a substantially right-angled bend in order to take signals from the temperature sensor 33, to carry them in a substantially axial direction relative to the axis of rotation of the bearing. The configuration of the wire 41 can also help to locate the sensor 33 circumferentially on the bearing race 102. The bearing 10 can also be seen to comprise roller elements 105, located between the inner 101 and outer 102 races. The invention could however also be applied to bearings which do not include such roller elements, since heat is generally generated in any kind of bearing. It should also be understood that, although the illustrated embodiment relates to a bearing having inner and outer races, arranged to journal a shaft and to react radial forces in the shaft, perpendicular the axis of rotation of the shaft, there are other implementations where bearings are arranged with axially opposed races, for journaling shafts which carry axial loads, generally known as thrust bearings. The present temperature sensor arrangement could also be applied to other such bearing arrangements.

[0060] Although the invention is described in relation to temperature sensors, the problems associated with signal attenuation due to location of a sensor remotely from the component to be monitored can be common to other types of sensor, such as vibration sensors, torque sensors, or strain sensors, for example. Any features of the invention, and in particular the features of the invention which allow its location in proximity to a component to be monitored, can therefore be advantageous in conjunction with any other type of sensor.

[0061] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.