GB2421769A

GB2421769A - A plain bearing providing a visual indication of wear

Info

Publication number: GB2421769A
Application number: GB0428534A
Authority: GB
Inventors: John Frederick Harrison; Ian Kerr
Original assignee: Daido Industrial Bearings Europe Ltd; Daido Metal Co Ltd
Current assignee: Daido Industrial Bearings Europe Ltd; Daido Metal Co Ltd
Priority date: 2004-12-30
Filing date: 2004-12-30
Publication date: 2006-07-05
Anticipated expiration: 2024-12-30
Also published as: GB0428534D0; GB2421769B

Abstract

A plain bearing 1 providing a visual indication of wear comprises one or more surface features in the edge of the running surface of the bearing 1. The surface features are sufficiently distanced from either side of the centreline of the bearing 1 so as not to, in use, affect the bearings 1 load bearing function. The surface features preferably include one or more circumferential grooves or one or more co-aligned recesses 2. When checking the bearing 1, visual assessment of the surfaces features can be made and compared with a standard chart or diagram to provide information on the condition of the bearing 1.

Description

1 2421769 Plain Bearing The present invention relates to bearings for use

in machinery, for example engines, compressors or any other equipment where it is customary to remove the bearings for inspection of wear.

As well as relating to a modified type of plain bearing, in particular, the present invention also relates to a method of determining the wear of such bearings, so that worn bearings can be visually identified and replaced as required.

For many types of bearings it is common practice to remove a bearing and after examination decide either to refit the same bearing or dispose of the old bearing and fit a new bearing. This is often done with reference to a visual chart provided by the equipment builder.

Recently, the present inventors have been trying to devise a way of demonstrating the wear of aluminium tin bearings. This has proved problematic compared to say overlay or rillenlager bearings, since there is no easy visual check on the bearings.

In bearings with thin surface layers, wear is easy to determine by the amount of lining material that can be seen through the original overlay.

Plain bearings, such as aluminium tin bearings however do not have such obvious changes in appearance in use. This means that such bearings may be refitted when the clearance is too big, and the oil pump cannot cope, or may be thrown away when perfectly acceptable for re-use.

Thus, the problem that faced the present inventors when developing the present invention was how to determine when a bearing has worn through by a fixed amount given that there is no other simple way of assessing wear of a bearing surface that is constructed from plain materials such as steel-backed aluminium-tin-silicon. Other conventional types of bearing, for example made from steel-backed leaded-bronze, have a thin electroplated surface layer which, when worn through, is apparent by a marked colour change and signifies replacement is necessary.

The present inventors have previously tried to overcome the problem by measurement of the bearing wall thickness to estimate the wear.

However, this is difficult in practice for the following reasons given below:- a) The amount of wear being measured may be small in relation to the measuring capability available at the point of use.

b) Service personnel may not be skilled at using measuring equipment and interpreting the results.

c) An unworn datum wall thickness reading would be required for each bearing and recorded by bearing number or marked indelibly on the part. This causes logistics and traceability problems at manufacturing and through the supply chain to the end user.

d) The region of bearing wear must be known in advance to produce a datum measurement in the correct position. In practise the wear may not occur where expected.

It is one aim of the present invention to overcome such prior methods' disadvantages.

In one aspect, therefore, the present invention provides a method of visually assessing the wear upon use of a plain bearing according to claim 1.

Compared to historical ways of addressing the problem, the present inventors' new approach offers a purely visual indication of bearing wear and can be used in conjunction with a simple visual chart to assess the amount of wear and whether the bearing can be refitted or whether bearing replacement is needed. In addition, it can give other information on whether the wear is abnormal, prompting further investigation of such geometric errors as misalignment between the bearing and the shaft. The method can be easily incorporated into conventional manufacturing routes and provides a robust wear indicator only removable by a pre-determined amount of bearing wear. It does not interfere in any significant way with the bearing operation.

The indication of wear operates by introducing a shallow groove or grooves into the bearing surface with closely controlled dimensions.

Alternatively small shallow recesses can be introduced into the bearing surface such that they are of closely controlled radial depth, axial width and circumferential length. The positioning of the grooves or recesses is important, they must be located in positions of low oil film pressure so as not to unduly influence the generation of a satisfactory oil film to separate the shaft and bearing surfaces during bearing operation. Thus in a journal bearing the grooves or recesses must be positioned close to the axial bearing ends. To cover the possible areas of wear recesses should also preferably be spaced uniformly around the circumference of the half bearing, e.g. 30 , 60 , 90 , 120 , 150 from the bearing joint in each half. As wear occurs the bearing surface will gradually be worn down until part of one or more of the bearing grooves, or one or more of the recesses in the surface are removed. The visual appearance of the worn grooves or pattern of recesses can then be compared to a chart which interprets the wear pattern and extent, gives a diagnosis and suggests the correct action to take, i.e. refit, replace or investigate further.

In a further aspect, the present invention provides a plain bearing according to claim 5.

In a further aspect, therefore, the present invention provides a kit according to claim 16.

The present invention can also be used for other purposes.

Within the plain bearing field there are other applications of this invention, such as but not limited to wear in other materials that are difficult to interpret visually such as white-metal or polymer-lined bearings. Also the present technology is applicable to other types of plain bearings such as thrust washers, tilt pad journal and tilt pad thrust bearings.

The present invention will now be described with reference to the following non-limiting example by way of the following drawings, in which: Figure 1A illustrates a plan view of a bearing according to one embodiment of the present invention; Figure lB shows a side view along section A-A of the embodiment depicted in Figure 1A; Figure 1C illustrates a cross-sectional view along section X-X of the embodiment shown in Figure 1A; and Figure 2 shows a perspective view of the same embodiment as illustrated in Figures 1 A-C.

Figure 1A shows a half bearing 1 that can be used in an engine or compressor or any other equipment, in which it is customary to remove the bearing for inspection and then replace the old bearings if necessary.

The method of this embodiment is better than other existing methods, because it does not rely upon any change in the appearance of the bearing due to the wearing of different functional layers, but instead relies on the change of appearance of specific features that have been introduced into the bearing surface. The later such features are designed so as to be non-detrimental to the bearing's function.

The indication of wear operates by introducing a shallow groove or grooves (not shown) into the bearing surface with closely controlled dimensions. Alternatively small shallow recesses 2 can be introduced into the bearing surface such that they are of closely controlled radial depth, axial width and circumferential length. The positioning of the grooves or recesses 2 is important in that they must be located in positions of low oil film pressure so as not to unduly influence the generation of a satisfactory oil film to separate the shaft and bearing surfaces during bearing operation.

Thus, in a journal bearing the grooves or recesses, they must be positioned close to the axial bearing ends. To cover the possible areas of wear recesses should also preferably be spaced uniformly around the circumference of the half bearing, e.g. 30 , 60 , 900, 120 , 150 from the bearing joint in each half (see Figure 1B). As wear occurs the bearing surface will gradually be worn down until part of one or more of the bearing grooves, or one or more of the recesses in the surface are removed.

The visual appearance of the worn grooves or pattern of recesses can then be compared to a chart which interprets the wear pattern and extent, gives a diagnosis and suggests the correct action to take, i.e. refit, replace or investigate further. Of course, a standard charts can be easily constructed using basic principles and comparing wear patterns for different degrees of wear for appropriate bearings.

One novel dimension of the features of the grooves and recesses 2 is their location close to the edge of the bearing 1, away from the highly loaded zone of the bearing in the middle of the running surface. Another novel dimension of these features is their manufacture into such a width and depth as to have no effect on the operation of the bearing.

Typically, a groove is envisaged to be 1-5mm in width and 5-50 pm in depth located 5-15 mm from the edge of the bearing. Similarly, a series of indents would be 1-5mm in width and 5-50 p.m in depth located 5-15 mm from the edge of the bearing at a frequency of every 5-45 mm, alternatively of every 5-45 p.m.

However, it is envisaged that the exact size and location of these features may vary from application to application.

It is also envisaged that grooves and recesses may be closer to the centre-line of the bearing, in cases where the particular application so allows.

Further, the depth of the grooves or indents can optionally be varied at different points of the circumference. And the grooves and indents can alternatively be manufactured to a given wall thickness (either variable or fixed) rather than to a given depth.

Figure 2 shows a perspective view of the half bearing depicted in Figures lA-C. In particular, in this view, it is easier to see oil sump 4 and oil groove 3.

The present invention provides a novel means for assessing wear of bearings for which previous methods are of limited value. Advantageously, the related bearings relatively are simple, and thus inexpensive, to manufacture and can be used in conjunction with simple visual charts.

Claims

CLAIMS: 1. A method of visually assessing the wear upon use of a plain

bearing, comprising: (i) imparting one or more surface features in the axial ends of the running surface of the bearing, said surface features being sufficiently distanced from either side of the centreline of the bearing so as not to effect said bearing's load bearing function in use, and (ii) making a visual assessment of wear after use.
2. A method as claimed in claim 1, wherein the surface features comprise one or more circumferential grooves, or one or more plurality of coaligned recesses.
3. A method as claimed in claim 1 or 2, wherein visual assessment is made with the aid of a standard chart or diagram.
4. A method as claimed in any preceding claim, wherein the positioning of the surface features is such that the positions are in the relatively low oil film pressure regions of the bearing.
5. A plain bearing arranged for use in any one of claims 1-4, comprising one or more surface features, in the edge of the running surface of the bearing, said surface features being sufficiently distanced from either side of the centreline of the bearing so as not to effect said bearing's load bearing function in use.
6. A bearing as claimed in claim 5, wherein the surface features comprise one or more one or more circumferential grooves, or one or more plurality of co-aligned recesses.
7. A bearing as claimed in claim 6, wherein the relative depth of the groove(s)/recess(es) is smaller than the depth of the wall of the bearing itself.
8. A bearing as claimed in either claim 6 or 7, wherein the recesses are shaped so as to be rectangular or square shaped.
9. A bearing as claimed in any one of claims 6-8 wherein the grooves, or rectangular or square shaped recesses, are replaced by a special shape such as a company logo.
10. A bearing as claimed in any one of claims 6-9, wherein the grooves/recesses are uniformly spaced around the circumference of the half-bearing.
11. A bearing as claimed in claim 10, wherein the grooves/recesses are spaced around the circumference of the half-bearing 300, 600, 900, 120 , or 150 from the bearing joint in each half.
12. A bearing as claimed in any one of claims 6-11, wherein each groove is 1-5mm in width, 5-50 p.m in depth and located 5-15 mm from the edge of the bearing.
13. A bearing as claimed in any one of claims 6-11, wherein each indent is 1-5mm in width, 5-50 p.m in depth and located 5-15 mm from the edge of the bearing at a frequency of every 5-45 mm.
14. A bearing as claimed in any one of claims 6-13, the depth of the grooves or indents being varied at different points of the circumference of the bearing.
15. A bearing as claimed in any one of claims 6-14, wherein said grooves and indents are manufactured to a given wall thickness (either variable or fixed) rather than to a given depth.
16. A bearing as claimed in any one of claims 6-15, wherein the bearing is a steel-backed bearing of aluminium-tin-silicon.
17. A plain bearing, or kit substantially as hereinbefore described with reference to, and/or as illustrated in, the accompanying drawings.

17. A kit comprising a plain bearing as claimed in any one of claims 6-16 and a standard chart or diagram for visually assessing the wear of said plain bearing upon use.

16. A method, plain bearing, or kit substantially as hereinbefore described with reference to, and/or as illustrated in, the accompanying drawings.

Amendments to the claims have been filed as follows 1. A plain bearing comprising a wear indicator, said bearing having one or more surface features, in the edge of the running surface of the bearing, said surface features being sufficiently distanced from either side of the centreline of the bearing so as not to effect said bearing's load bearing function in use.

2. A bearing as claimed in claim 1, wherein the surface features comprise one or more one or more circumferential grooves, or one or more plurality of co-aligned recesses.

3. A bearing as claimed in either claim 1 or claim 2, wherein the relative depth of the groove(s)/recess(es) is smaller than the depth of the wall of the bearing itself.

4. A plain bearing as claimed in any preceding claim, comprising: (i) one or more surface features in the axial ends of the running surface of the bearing, said surface features being sufficiently distanced from either side of the centreline of the bearing so as not to effect said bearing's load bearing function in use.

5. A plain bearing as claimed in any preceding claim, wherein the wear indicator is such that in use, visual assessment is made with the aid of a standard chart or diagram.

6. A plain bearing as claimed in any preceding claim, wherein the positioning of the surface features is such that the positions are in the relatively low oil film pressure regions of the bearing.

7. A bearing as claimed in any one of claims 2-6, wherein the recesses are shaped so as to be rectangular or square shaped.

I

8. A bearing as claimed in any one of claims 2-7 wherein the grooves, or rectangular or square shaped recesses, are replaced by a special shape such as a company logo.

9. A bearing as claimed in any one of claims 2-8, wherein the grooves/recesses are uniformly spaced around the circumference of the half-bearing.

10. A bearing as claimed in claim 9, wherein the grooves/recesses are spaced around the circumference of the half-bearing 300, 600, 90 , 120 , or 150 from the bearing joint in each half.

11. A bearing as claimed in any one of claims 2-10, wherein each groove is 1-5mm in width, 5-50 im in depth and located 5-15 mm from the edge of the bearing.

12. A bearing as claimed in any one of claims 2-10, wherein each indent is 1-5mm in width, 5-50 i.m in depth and located 5-15 mm from the edge of the bearing at a frequency of every 5-45 mm.

13. A bearing as claimed in any one of claims 2-12, the depth of the grooves or indents being varied at different points of the circumference of the bearing.

14. A bearing as claimed in any one of claims 2-13, wherein said grooves and indents are manufactured to a given wall thickness (either variable or fixed) rather than to a given depth.

15. A bearing as claimed in any one of claims 2-14, wherein the bearing is a steel-backed bearing of aluminium-tin-silicon.

16. A kit comprising a plain bearing as claimed in any one of claims 2and a standard chart or diagram for visually assessing the wear of said plain bearing upon use.