Device for evaluating fretting of a bearing component

The present invention relates to a device for evaluating fretting of a bearing component according to claim 1 and to a method for evaluating fretting of a bearing component ac cording to claim 10.

Bearing components, for example outer rings of railway axle box bearings, may be affect ed by fretting damages in varying degrees. The fretting is usually irregular and forms map like formations. For a decision whether a bearing component can still be used when fret ting occurs, there applies geometrical limits and limits on range, depth or protrusion, and location of the fretting formations. Nowadays, the bearing component is removed from its installation position and is inspected visually by a worker, who decides subjectively on the extent, intensity, and location of fretting (for example, using musters of acceptable or un acceptable bearing components). In addition, the worker measures for example the external diameter with a traditional measurement tool, which takes a long time and does not provide reliable results about the state of the whole surface of the bearing component.

It is therefore object of the present invention to provide a reliable, automatic way of evalu ating fretting on bearing components.

This object is solved by a device for evaluating fretting of a bearing component according to claim 1 and by a method for evaluating fretting of a bearing component according to claim 10. The device for evaluating fretting of a bearing component comprises a sensor unit, a de termination unit, and an evaluation unit. The bearing component is dismounted from the bearing and then inspected in the device with respect to fretting.

The sensor unit is configured to sense distances between the sensor unit and a surface of the bearing component. Such sensed distances can be used as an indicator for fretting as fretting changes the surface of the bearing component and thus also changes of the distanc es between the surface of the bearing component and the sensor unit. As fretting typically occurs not in a uniform way on the surface but may vary over the surface, for example on varying locations on the surface of the bearing component, the distances vary during the sensing. Further, fretting may lead to indentations in the surface of the bearing component, and thus also to protrusions, which correspond to the remaining original surface of the bearing component before any fretting or wear occurred. Further, fretting may lead also to protrusions that rise above the original surface.

Thus, based on the sensed distances, or more specifically, based on different distance val ues across an inspected bearing component surface, the determination unit may determine a surface profile of the surface of the bearing component.

Such a surface profile may map the varying distances due to fretting damages occurring across the bearing component surface and illustrate the damages for example in a graph. For example, peaks of such a graph may correspond to the original surface and valleys of the graph may correspond to indentations or dimples of the surface, both being caused by fretting.

The evaluation unit is then configured to evaluate the surface profile and detect and evalu ate fretting of the bearing component based on the evaluated surface profile. This evalua tion may be used to decide whether the bearing component needs to be replaced or not, i.e., whether the fretting damages are still acceptable so that the bearing component can be fur ther used or whether the fretting damages are too great so that a replacement of the bearing component is necessary.

Using the described device, it is possible to scan a surface of a bearing component using a sensor unit and then to interpret the sensed distance values and to determine and evaluate an extent of the fretting. In contrast to existing solutions, the device provides an automatic way of determining and evaluating fretting and a potential replacement instead of a visual inspection by a worker.

According to an embodiment, the device further comprises an output unit for outputting a visual or acoustic warning signal based on a detection of the evaluation unit. Thus, when excessive fretting has been detected, in particular when changes in size or shape, which are caused by fretting, exceed predefined thresholds, the output unit may send a warning signal indicating the detected fretting. In one embodiment, the output unit may comprise a green and a red light and the warning signal may be a change from the green to the red light. In another embodiment, the output unit may comprise a display and the warning signal may be an alert being displayed on the display. In this case, the display may also show further information regarding the detected fretting, for example extent of the fretting, location of the fretting, or the like.

Preferably, a fixed distance between the sensor unit and a rotational axis of the bearing component is defined. This fixed distance may be used as a calibration distance for sensing changes of the distance between the sensor unit and the bearing component surface.

According to a further embodiment, the device further comprises a holding unit, for exam ple in the form of a pedestal, for holding the bearing component, wherein the holding unit is configured to rotate the bearing component passing the sensor unit. For example, the holding unit may comprise a rotating plate for rotating the bearing component. The sensor unit may be attached to the holding unit. Alternatively, the sensor unit may be configured to rotate around the bearing component.

According to a further embodiment, the holding unit is configured to define the fixed dis tance between the sensor unit and the rotational axis of the bearing component. Thus, the sensing distance from the sensor unit to the bearing component surface is a defined and constant distance provided by the relative arrangement of the sensor unit and the holding unit. Therefore, changes of the sensing distance due to fretting can be easily determined as changes of this defined distance. The bearing component may be for example an inner or outer ring of a rolling bearing, for example a cylindrical or tapered roller bearing. In such a bearing, fretting may occur on several surfaces of the bearing component, for example on an outer surface, an inner sur face or bore or a side face of the bearing component. Depending on the surface to be in spected, the sensor unit may be arranged at an outside of the bearing component, above the bearing component, or inside the bearing component.

In a preferred embodiment, the sensor unit comprises one or more laser sensors. Laser sen sors send a laser signal to the surface and receive a signal reflected from the surface. Based on a measurement of the time from sending the signal to receiving the signal, the distance may be calculated.

When only a single laser sensor is used, the laser sensor may be configured to scan the sur face of the bearing component in a line-per-line manner. Thus, the surface passes the laser sensor, which scans the surface line per line. Thereby, the laser may be moved or tilted in a vertical direction for example from up to down, until the whole surface is sensed. In this case, it is necessary to consider a difference in the run-time when the laser is tilted and scans different portions of the bearing component surface. Preferably, a plurality of laser sensors is used so that the surface can be scanned without, or at least with a reduced, verti cal movement of the sensor unit.

According to a further embodiment, the evaluation unit is configured to map the surface profile to a virtual landscape of the bearing component. Instead of only evaluating the sur face profile in the form of a graph, the evaluation unit may generate a virtual landscape representing the whole surface of the bearing component. Such a virtual landscape can for example be shown on a display.

In a further embodiment, the evaluation unit is configured to compare the virtual landscape with predetermined fretting thresholds. Instead of using the graph for determining fretting, the evaluation unit may also use the virtual landscape which includes all information from the graph, i.e., the surface profile.

The predetermined fretting thresholds may define for example thresholds for a range, depth, protrusion and/or location of fretting. Depending on the bearing component, differ- ent thresholds may apply. The evaluation unit may thus use different thresholds depending on the inspected bearing component.

According to a further aspect, a method for evaluating fretting of a bearing component is provided. The method comprises the following steps: sensing distances between a sensor unit and a surface of the bearing component, determining at least one surface profile of the surface of the bearing component based on the sensed distances, evaluating the surface profile and detecting and evaluating fretting of the bearing component based on the evalu ated surface profile.

The features described with reference to the proposed device also applies to the proposed method.

An even further aspect of the present invention relates to a computer program product comprising a computer program code which is adapted to prompt a control unit, e.g., a computer or a microchip, and/or a computer of the above discussed device to perform the above discussed steps.

The computer program product may be a provided as memory device, such as a memory card, USB stick, CD-ROM, DVD and/or may be a file which may be downloaded from a server, particularly a remote server, in a network. The network may be a wireless commu nication network for transferring the file with the computer program product.

Further preferred embodiments are defined in the dependent claims as well as in the de scription and the figures. Thereby, elements described or shown in combination with other elements may be present alone or in combination with other elements without departing from the scope of protection.

In the following, preferred embodiments of the invention are described in relation to the drawings, wherein the drawings are exemplarily only, and are not intended to limit the scope of protection. The scope of protection is defined by the accompanied claims, only.

The figures show: Fig. 1 : a schematic block diagram of a device for detecting fretting of a bearing compo nent;

Fig. 2: a perspective view of a first embodiment of the device of Fig. 1; and Fig. 3: a perspective view of a second embodiment of the device of Fig. It.

In the following same or similar functioning elements are indicated with the same refer ence numerals.

Fig. 1 shows a schematic block diagram of a device 1 for detecting fretting of a bearing component (not shown in Fig. 1). The device 1 comprises a sensor unit 2 for sensing dis tances from the sensor unit 2 to a surface of the bearing component. The bearing compo nent may be for example an outer ring (Fig. 2) or inner ring (Fig. 3) of a rolling bearing, for example a railway wheelset bearing

When fretting occurs on the surface of a bearing component, the surface characteristic changes, and indentations or protrusions caused by fretting occur on the surface, leading to an uneven surface having protrusions (being the original surface or being higher than the original surface) and dimples. This uneven surface may be sensed by the sensor unit 2 which detects changes in the distance between the sensor and the surface of the bearing component. The changes correspond to the fretting damages of the surface of the bearing component.

A determination unit 4 determines a surface profile 6 in the form of a graph based on the sensed distances. The peaks in the surface profile 6 correspond to the original surface or to the height of fretting formations and the valleys of the surface profile 6 correspond to dim ples in the surface. The surface profile 6 may consist of several graphs wherein the y-axis corresponds to a vertical axis of the bearing component and the x-axis corresponds to a horizontal axis of the bearing component. Preferably, the sensor unit 2 senses the distances about a 360° circumference of the bearing component so that the surface profile 6 shows also the 360° circumference of the bearing component.

The surface profile 6 may be used by an evaluation unit 8 for generating a virtual land scape 10 of the bearing component surface and for evaluating the surface profile 6 or the virtual landscape 10 and detecting and evaluating fretting of the bearing component. As described above, changes in the distances correspond to indentations of the bearing component surface, which in turn are caused by fretting and thus indicate locations of fret ting. Thus, based on the surface profile 6 and/or the virtual landscape 10, the evaluation unit 8 determines depth and extent of occurred fretting, but also the location of the fretting. Further, the evaluation unit 8 can compare the detected characteristics of fretting with pre defined thresholds regarding depth, protruded height, range or location. Based on this comparison, the evaluation unit 8 can decide whether the bearing component needs to be replaced or whether the fretting occurs at locations or within a range (regarding depth or extent) which is still acceptable, and the bearing component can be used further without replacement.

An output unit 12 can output a warning signal 14 indicating detected fretting, eventually in combination with further information like location, range etc. of the fretting of the bearing component.

Figs. 2 and 3 show two exemplary embodiments of the device 1 in a perspective view. The device 1 comprises a holding unit, for example in the form of a pedestal 16, on which a bearing component 26 may be placed. The bearing component 26 is shown as an outer ring in Fig. 2 and an inner ring in Fig. 3. However, it should be noted that also other kinds of bearing components and also different surfaces than the ones that are shown may be in spected.

The bearing component 26 is demounted from the installation point within a bearing and is placed on the pedestal 16. The pedestal 16 comprises a rotating plate for rotating the bear ing component 26 around a rotation axis X, passing the sensor unit 2. Alternatively, the sensor unit 2 may rotate around the pedestal 16 or the bearing component 26.

When switched on via the on/off switch 18, the rotation of the bearing component 26 starts, passing the bearing component 26 by the sensor unit 2. As can be seen in Fig. 2, the sensor unit 2 comprises a plurality of laser sensors 24 for scanning an outer surface of the bearing component 26. Alternatively, as shown in Fig. 3, the laser sensors 24 may be ar ranged to scan a side face of the bearing component 26. Other arrangements may be possi ble, for example for scanning an inner surface of a bearing component 26. When the evaluation unit 8 evaluates that the surface of the bearing component 26 does not show any signs of excessive fretting, i.e., only fretting below the predefined thresholds, as described above, the output unit 12 signals this using a green light 22. If the evaluation unit 8 detects fretting which exceeds the predefined thresholds, this will be signaled using a red light 20. An output unit 12 having a red and green light 20, 22 is a very simple way of in dicating fretting. Based on this information, it can be decided whether to replace the bear ing component 26 or to re-mount the bearing component 26.

In summary, the device described above provides a reliable and automatic way to detect and evaluate fretting of a bearing component.

Reference numerals

1 device

2 sensor unit

4 determination unit

6 surface profile

8 evaluation unit

10 virtual landscape

12 output unit

14 warning signal

16 holding unit/pedestal

18 on/off switch

20 red light

22 green light

24 laser sensor

26 bearing component

X rotational axis