WO2005116465A1

WO2005116465A1 - Wear detector for ball bearing

Info

Publication number: WO2005116465A1
Application number: PCT/NO2005/000173
Authority: WO
Inventors: Sven BJØRKGÅRD; Inge André H. JOHANSEN
Original assignee: Kongsberg Automotive As
Priority date: 2004-05-25
Filing date: 2005-05-25
Publication date: 2005-12-08
Also published as: SE0401352D0; DE112005001191B4; DE112005001191T5

Abstract

A device (30) for detecting and indicating wear of the anti-friction coating (31) between a first and a second bearing surface (12 and 14, respectively) of a bearing, wherein the device (30) comprises a pin (32) having a first end (33) facing the first bearing surface (12) and which at least partly is arranged to follow the displacement of the first surface (12) towards the second surface (14), and an indicator which on displacement of the pin (32) over a certain distance provides an indication of coating wear.

Description

Wear detector for ball bearing

The present invention relates to a device for detecting and/or indicating wear of the anti-friction coating between a first and a second bearing surface of a ball bearing in connection of a vehicles frame and wheel shaft. The device is intended, ter alia, for use in connection with maintenance-free sliding bearings. The way a maintenance-free sliding bearing works is that the anti-friction coating deposits PTFE which acts as a lubricant film. After being used for some time the coating will become thinner due to wear, and if there is complete break-through of the film, the wear will increase dramatically because there is steel-to-steel contact. Thus, in the case of a ball bearing, there may be a danger of the inner ball of the bearing jumping out of the outer ring.

Sliding bearings of this type are used, e.g., in the mounting of V-struts in large vehicles. On a V-strut, the anti-friction coating is worn after the vehicle has been driven for some time. This is a non tolerable situsion in a connection between a vehicles frame and wheel shaft. Measurement of the internal bearing clearance or play in the bearing, is used to detect wear of the anti-friction coating. According to the prior art, the play is measured using a measuring gauge and a lever which moves the bearing back and forth in the clearance between the bearing surfaces. Such a method is very bothersome, both in relation to time consumption, accessibility, manual labour and security of the results of the measurement.

To obtain a relative reliable measurement by moving the bearing in the clearance with a lever, the bearing must be unloaded so that the full play can be obtained with the force that is available. The force must also be sufficient to realise the internal bearing clearance. To be certain that the bearing is unloaded, the brakes must not be on and the V-strut must be in a position in which the rubber bushings at the other ends of the strut are not pre-loaded. In addition, the force used on the lever and the positioning of the lever will vary from person to person and also from one time to a second time and will thus also possibly affect the measuring result. As said the procedure is also awkward and particularly difficult if there is little space available.

However, if the play is not checked, a dangerous situation may arise in that the ball could fall out and control of the axle of the vehicle would be lost. This is particulary relavant in the cases with a single point fastening of ball bearings, for example a so called "standing" ball bearing, which has a centre axis not parallel with a surface for the vehicle, and which often is used in the connection between a vehicles frame and a wheel shaft. There are different methods for detecting the wear in other kinds of bearings and uses of these, for instance as described in SU 1167367 and DE 19915348.

The object of the invention is to overcome the said problems associated with the prior art by providing a device for detecting and indicating wear of the anti-friction coating between a first and a second bearing surface in a ball bearing in connection of a vehicles frame and wheel shaft. Another object is to provide a device for detecting wear in a ball bearing, which device is simple to use, easy to replace during repair or maintenance of the ball bearing, and which is simple to read when there is limited space available. An additional object will also be to provide a device which replaces the use of a lever and measuring tools, which thereby is independent of the person that performs the reading, the positioning of the vehicle and which may be read with a larger degree of certainty.

It is also an object to provide a device which only in a tiny degree affects the function of the ball bearing in relation to service life, integrity and strength.

According to the invention there is provided a device for a ball bearing in a connection between a vehicles frame and wheel shaft, for detecting and indicating wear of the anti-friction coating between a outer bearing surface arranged in a bearing house and an inner bearing surface arranged around an internal bearing element. The device comprises a receiving part and a indication element having a first end faced against the inner bearing surface and which at least partly is arranged to follow the movement of the inner bearing surface toward the outer bearing surface and an indicator device, which as a response to a given movement of the indication element, provides a read of the wear of the anti-friction coating. The receiving part is further arranged in a through going bore in the bearing housing.

According to the invention, one internal end of the through going bore may be arranged in or at the outer bearing surface. By at, it is meant in the bearing housing surrounding the bearing, but outside the outer bearing surface, but in the vicinity of this. Preferably the through going bore is arranged at the outer bearing surface opposite a fastening point for the internal bearing element. This is on the other side of a centre plane of a ball bearing mainly parallel with a base surface for the vehicle, preferably in the case where a ball bearing is a single point fastened ball bearing. It is also possible that the internal end of the through going bore is arranged at the side in relation to the anti-friction coating between the internal and outer bearing surface, however, in or at the outer bearing surface. The through going hole may have a relative to the ball bearing, radial centre axis or another angled centre axis for easy access for reading of the indicator element. The element in the device according to the invention may, for example, be a pin, a ball, an oviform element, a cube or an element of another shape as long as it comprises two ends or end surfaces which are spaced apart and connected so that displacement of one of the surfaces causes a change in the properties of the element. Such a change may be a displacement of the other surface and also that the element is compressed.

The element may comprise a rotating part capable of rotating across the first surface. The element may also comprise a part connected to the rotating part but which only moves in the longitudinal direction. In this way, the element will be able to follow the rotational movement of the first surface.

The first end of the element may be arranged at a distance from the first bearing surface or in contact with the first bearing surface. The difference between these two alternatives is the level of wear of the coating which will lead to an indication of coating wear, or in other words the threshold for triggering the device. A triggering threshold may also be set at the second end or the sides of the element. In the case where the first end of the element is arranged at a distance from the first bearing surface, the device could comprise means for setting the distance between the first end of the element and the first bearing surface. Advantageously, these means could be a threaded connection between the indicator and/or the element and a part fixedly arranged relative to the second bearing surface.

The indicator may be designed to provide a visual and/or tangible indication of displacement of the second end and/or sides of the element.

In one embodiment, the indicator comprises a sensor for detection of displacement of the second end of the element or its sides or their position relative to a part fixedly arranged in relation to the second bearing surface. The sensor may in turn be connected to an alarm or warning lamp.

In a preferred embodiment, the indicator comprises a part which is ruptured by the second end or sides of the element when the element is moved. The activation threshold is thus related to the mechanical strength of the part that is to be ruptured and also to the rigidity of the element.

In one embodiment, the indicator comprises a receiving part with a recess for receiving the element. The receiving part may be a part of the device according to the invention or it may be a recess in a part at a fixed distance relative to the second surface. This is because the object of the invention is to detect displacement of the first surface towards the second surface. In a variant of this embodiment, the recess has a bottom surface facing the second end of the element. The bottom surface is ruptured by the second end of the element upon displacement of the element. An indication of the fact that the bottom surface has been ruptured may, for example, be that the second end of the element becomes visible or that it projects slightly from the recess so that it can be felt with the hand or with a suitable tool. In another variant, the recess has attachments against the sides of the element and the attachments are broken upon displacement of the element. In this case, the recess may, for example, be through-going and thus designed to provide a visual or tangible indication of the second end of the element upon displacement over a certain distance (for example, in that the second end of the element becomes visible).

In one embodiment of the invention, the receiving part consists of a recess in the bearing housing or in material fixedly arranged relative to the second surface. One possibility in connection with this embodiment is that the bottom of the recess is designed to rupture when a certain wear threshold (and thus displacement) has been reached. Another possibility is that attachments against the pin and the recess sense the movement of the pin and thus the wear. In another embodiment, the receiving part is designed for positioning in a recess in the bearing housing or in material fixedly arranged relative to the second surface.

In connection with the embodiments that comprise a receiving part, the device may comprise a plug for temporarily closing the recess.

In addition, and in order to obtain an accurate and tolerance absorbing setting of the device, the receiving part may be provided with external threads and a wrench grip. On mounting, the receiving part will be screwed into a recess in material until the pin stops against the first surface, and then it can be unscrewed the number of revolutions that corresponds to the desired play. By using locking adhesive, the receiving part could be locked in this position.

The device according to the invention will indicate when the wear limit has been reached by detecting the play in the bearing, that is to say, the distance between two bearing surfaces. The device provides a quick and reliable warning of the operational state of the bearing.

In its simplest form, the device could provide a binary response, i.e., it will be possible to detect whether a limit has been reached or not. It is also possible to design the device so as to enable it to provide an indication of the degree of wear at any given time. The invention eliminates the need to measure the play between two bearing surfaces using a measuring gauge. The device may, as mentioned, also comprise a sensor which in turn triggers the provision of a warning signal, for example, the lighting of a lamp on the dashboard of a vehicle in which the device is in use.

The invention could be used in a simple version in a V-strut for accurate detection of wear level.

Advantageously, the element and a part of or the whole of the indicator will provide a unit that can easily be replaced. In this way, it will be possible to replace a used device with a new one. The indicator element and the through going bore may also be formed with such a small extent that they do not influence the bearings integrity, service life or strength.

In what follows the invention will be described in more detail with reference to the attached drawings, wherein:

Figure 1 is a view of a sliding bearing and a V-strut.

Figure 2 is a sectional view of a V-strut. Figure 3 illustrates the prior art.

Figure 4 is a sectional view of a first embodiment of the invention.

Figure 5 is a top view of the first embodiment of the invention.

Figure 6 shows an example of the first embodiment of the invention.

Figure 7 shows a second embodiment of the invention. In the embodiments of the invention shown in the figures, the element is a pin, but as mentioned it is quite possible to replace this with elements of other shapes.

Figure 1 is a view of a sliding bearing 1 and a v-strut 2. The recess in which the sliding bearing 1 is to be placed is indicated by the reference numeral 3. The sliding bearing 1 and the v-strut 2 as shown in the figure are, for example, used in large motor vehicles in connection with wheel suspension.

Figure 2 shows a section of the sliding bearing 1 in place in the recess 3. The sliding bearing 1 provides a connection between the v-strut 2 and the axle 10. The sliding bearing 1 comprises, inter alia, a bearing ball 11 and an outer ring 13. Disposed between the bearing ball 11, having a first bearing surface 12, and the outer ring 13, which forms the second bearing surface 14, is an anti-friction coating (not visible) which allows movement of the outer ring 13 relative to the ball 11. The purpose of the invention is to monitor the thickness of the anti-friction coating by following the movement of the first bearing surface 12 relative to the second bearing surface 14.

Figure 3 illustrates the prior art for measuring wear of anti-friction coatings. The figure shows the sliding bearing 1 in place in the V-strut 1, and a lever (where the point at which the lever is to be inserted is indicated by the reference numeral 20) which will be moved up and down whilst the play between the surfaces is measured using a measuring gauge (not shown).

Figures 4A and 4B are sectional views of a first embodiment of the invention. The figures show the device 30 for detecting and indicating wear of the anti-friction coating 31 between a first bearing surface 12 and a second bearing surface 14. The device 30 comprises an element, in this case a pin 32, having a first end 33 facing the first bearing surface 12. The pin 32 is positioned so that it will follow the displacement of the first surface 12 towards the second surface 14 (the direction of displacement is indicated by an arrow in Figure 4A). The device 30 also comprises an indicator which will provide an indication of coating wear when the first surface 12 has moved a certain distance relative to the second surface 14. In this case, the indicator comprises a receiving part 34 with a recess 35 for receiving the pin 34, and a bottom 36.

Figure 4 A shows a first state of the device 30, where the anti-friction coating 31 has an acceptable thickness. The figure shows the first end 33 of the pin 32 placed at a distance from the first surface 12 and in contact with the bottom 36 of the recess 35, but it is also possible to provide an embodiment in which the pin 32 rests on the surface 12 and at a distance from the bottom 35, or in contact with both surfaces at the same time from the start. As mentioned above, because of wear, the first bearing surface 12 will move towards the second bearing surface 14, and thus push the pin in the direction of the arrow. Since the pin 32 is rigid, the other end 37 of the pin will press against the bottom 36 of the recess, and when a certain threshold has been reached, rupture the bottom 36.

Figure 4B shows the second state of the device 30, where the second end 37 of the pin 32 has passed through the bottom 36. The second end 37 of the pin is thus visible from a point 38 away from the bearing surfaces 12, 14. It is possible to arrange the pin 32 so that it projects from the receiving part 34 and provides a tangible indication of movement of the pin 32.

A device according to this embodiment could easily be replaced when changing the bearing.

Figure 5 is a top view of the first embodiment of the invention. Figure 5 A illustrates the first state, where the bottom 36 of the receiving part 34 is whole. Figure 5B shows the second state where the bottom 36 has been ruptured, and the second end of the pin 37 is visible.

Figure 6 shows an example of the first embodiment of the invention. The figure shows a bearing ball 11 having a first bearing surface 12, an outer ring 13 having a second bearing surface 14, and an anti-friction coating 31 between the first and the second bearing surface (12 and 14 respectively). In this embodiment of the invention, the receiving part 34 is designed to be placed in a recess 38 in material 41 fixedly arranged relative to the second surface 14. The recess 38 in the material 41 is closed by a plug 42 which is designed to be screwed in place in the recess 38. On inspection, the plug 42 will be removed and it will be easy to see if there has been a rupture in the bottom of the receiving part 36 or not.

Figure 7 shows a second embodiment of the invention. In this embodiment, the recess 35 is through-going and it is equipped with attachments 50 against the sides of the pin 32 . Figure 7A shows a first state of the device 30, in which the anti- friction coating 31 has an acceptable thickness. The first end 33 of the pin 32 is at a distance from the first surface 12 and flush with the bottom 36 of the receiving part 34, but it is also possible to provide an embodiment in which the pin 32 projects into or out of the bottom 36. As mentioned above, because of wear the first bearing surface 12 will move towards the second bearing surface 14, and thus push the pin 32 in the direction of the arrow. A shear force will occur on the sides of the pin, and when this force is great enough the attachments 50 will break. A visual or tangible indication of wear of the anti-friction coating will be provided in this way.

Although two variants of the invention have been illustrated, it will be possible to implement the invention in a number of different ways. For example, spring elements may be used in the attachments to reinforce the shear force, or in the bottom of the receiving part to press the element against the first surface. The element may be placed in the anti-friction coating or outside it, i.e., in an area where the anti-friction coating is not present. The element may comprise an indicator on the inside, for example, a pressure sensor that detects compression of the element and which gives a signal that represents the stress condition of the element.

Although the described variants of the invention show a binary indication of wear, i.e., that there is an indication of whether the wear coating is below an acceptable level or not, it will be possible to adjust the device to provide a disclosure of the degree of wear, i.e., an indication of the different stages of the wear process. A continuous indication is also possible. In connection with the embodiment of the invention in which the recess of the receiving part has a bottom, it will be possible to arrange a sensor (for example, an optical sensor or a pressure sensor in the bottom of the recess) to provide the indication. The receiving part can also have a recess with a hole in the bottom, where the diameter of the hole is smaller than the diameter of the element. The element will then be elastic (for example, made of rubber) so that a displacement of the first end of the element will press the element though the hole in order to provide the desired indication. Lastly, it is possible to implement in the invention in connection with plastic parts, where the anti-friction coating is incorporated in the first or second bearing surface. Usually, the outer ring will be of plastic, so that the anti-friction coating will be an integral part of the second bearing surface. The anti-friction coating may also be provided by the lubricating grease between the bearing surfaces.

Claims

PATENT CLAIMS

1. A device for a ball bearing in a connection between a vehicles frame and a wheel shaft, for detecting and indicating wear of an anti-friction coating between an outer bearing surface (14) arranged in a bearing housing, and an inner bearing surface (12) arranged around an internal bearing element, which device comprises a receiving part (34) and a indicator element (32) having a first end (33) facing the inner bearing surface (12) and which at least partly is arranged to follow the displacement of the inner bearing surface (12) towards the outer bearing surface (14), and an indicator device which on displacement of the indicator element (32) over a certain distance provides an indication of coating wear, where the receiving part (34) is arranged in one in a bearing housing, through going bore.

2. A device according to claim 1, characterised in that an internal end of the through going bore is arranged in or at the outer bearing surface.

3. A device according to claim 1, characteri sed in that an internal end of the through going bore is arranged at the outer bearing surface opposite of a fastening point for the internal bearing element.

4. A device according to claim 1, characterised in that an internal end of the through going bore is arranged at the side of the antifriction coating between the inner and outer bearing surfaces.

5. A device according to claim 1, characterised in that the indicator element (32) is a pin, a ball, an oviform element or a cube.

6. A device according to one of the preceding claims, characterise d i n that the first end (33) of the indicator element is arranged at a distance from the first bearing surface (12).

7. A device according to claim 6, characterised in that it comprises means for setting the distance between the first end of the element and the first bearing surface.

8. A device according to one of the preceding claims, characteri se d i n that the indicator is designed to provide a visual and/or tangible indication of displacement of the second end (37) of the element and/or its sides.

9. A device according to one of the preceding claims, characterise d i n that it comprises a sensor for detection of displacement of the second end (37) of the element or its sides or their position relative to a part fixedly arranged relative to the second bearing surface (14).

10. A device according to one of the preceding claims, characteri sed i n that the indicator comprises a part that is ruptured by the second end (37) of the element or its sides on displacement of the element (32).

11. A device according to one of the preceding claims, characteri sed i n that the indicator comprises a receiving part (34) with a recess (35) for receiving the element (32).

12. A device according to claim 11, characterised in that the recess (35) has a bottom surface (36) facing the second end (37) of the element, and the bottom surface (36) is ruptured by the second end (37) of the element on displacement of the element (32).

13. A device according to claim 11, characterised in that the recess (35) has attachments (50) against the sides of the element, and the attachments (50) are broken on movement of the element (32).

14. A device according to claim 11, characterised in that the recess (35) is through-going and it is designed to provide a visual or tangible indication of the second end (37) of the element on displacement over a certain distance.

15. A device according to one of the preceding claims, characteri sed i n that it comprises a plug (42) for temporarily closing the recess (38).