WEAR DETECTION SYSTEM AND METHOD

Description

[0001] The invention relates to a wear detection system and a method for wear detection, in particular for friction elements such as brushes, friction linings, brake linings, lubricant pieces or the like, with at least one consumable friction element, and a transponder unit, wherein the transponder unit can communicate wirelessly with a transmitter-receiver unit.

[0002] Friction elements, such as carbon brushes for electric motors, friction linings for power transmission, brake pads, and solid lubricant components, are always subject to wear through the abrasion of the friction element material. It is often desirable to replace the friction element before it reaches a wear limit that impairs its function. Wear detection systems are therefore regularly used to monitor the wear condition of friction elements. These systems typically employ electrical contacts on the friction elements or switches that can signal when a wear limit has been reached. However, such wear detection systems require wiring the contacts or switches to a control unit. Such wiring is relatively expensive to manufacture, especially when a large number of friction elements need to be monitored simultaneously.For example, the wiring for generator brushes can be configured in series to reduce wiring complexity. However, the wear detection system can then no longer identify which brush triggered the signal.

[0003] It is also known to equip friction elements with a transponder unit that can communicate wirelessly with a transmitter-receiver unit, thus eliminating the need for complex wiring of the friction elements. DE 10 2007 009 423 A1 discloses such a wear detection system in which a carbon brush is equipped with a transponder unit. When the carbon brush reaches a wear limit, the transponder unit is destroyed by contact with a friction surface against which the carbon brush rests. The carbon brush can then no longer be detected by a transmitter-receiver unit, which then recognizes the carbon brush as worn. It is also possible for the transponder unit to have sensors for determining the temperature of the carbon brush, with this data being transmitted from the transponder unit to the transmitter-receiver unit.

[0004] The well-known wear detection system has the disadvantage that the transponder unit must be destroyed when the wear limit is reached. The transponder unit must therefore be designed or attached to the carbon brush in such a way that it is reliably destroyed when the wear limit or the friction surface is reached. Inexpensive transponder units, such as those available in label form, cannot be used here, as the labels can detach due to heat exposure in the immediate vicinity of the friction surface or cannot be mechanically destroyed due to poor adhesion to the carbon brush.

[0005] Further information about the wear condition of a friction element before reaching a wear limit can only be obtained if a transponder unit is additionally equipped with sensors. The transponder unit can be attached to a friction element at any suitable mounting position, connected, for example, via cables to a sensor or a simple contact located near the friction element's wear limit. Transponder units that require destruction are therefore difficult to mount, while those equipped with sensors and connecting cables are comparatively expensive.

[0006] Other wear detection systems are known from DE19840081 A1 and DE3247330 A1.

[0007] The present invention therefore aims to propose a wear detection system and a method for wear detection which enables cost-effective and simple wear monitoring of friction elements.

[0008] This problem is solved by a wear detection system having the features of claim 1 and a method for wear detection having the features of claim 6.

[0009] The wear detection system according to the invention, in particular for friction elements such as brushes, friction linings, brake linings, lubricants or the like, comprises at least one consumable friction element and a transponder unit, wherein the transponder unit can communicate wirelessly with a transmitter-receiver unit, wherein the wear detection system has a shielding device, wherein the shielding device is designed such that the transponder unit can be at least partially shielded by means of the shielding device depending on a wear state of the friction element, in such a way that communication between the transponder unit and the transmitter-receiver unit can be influenced, wherein the wear detection system comprises a holding device which serves for the movable positioning of the friction element relative to a friction surface, wherein the transponder unit is fixedly connected to the holding device.wherein the shielding device is designed as a shielding element arranged on the holding device, which can cover or uncover the transponder unit in a shielding manner when a movement of the friction element occurs relative to the holding device.

[0010] By influencing the transponder unit with an independently designed shielding device, it is possible to modify, block, or even establish a communication link between the transponder unit and the transmitter-receiver unit. Since the signal received by the transmitter-receiver unit is essentially only affected by the shielding device, virtually any transponder unit, especially an inexpensive one, can be used. Furthermore, communication between the transponder unit and the transmitter-receiver unit is significantly simplified because the content of the transmitted data is essentially irrelevant. The only requirement is that the transponder unit is detected or recognized by the transmitter-receiver unit.Furthermore, the integration of a new component or assembly is not necessarily required to create the shielding device. Instead, the components already present in the vicinity of the friction element can be used to form the shielding device, thus incurring no additional costs. It is also no longer necessary to attach the transponder unit directly to the friction element or to attach it in such a way as to guarantee its destruction. The transceiver unit can detect when the friction element reaches its wear limit by a change in the transponder unit's response signal, or alternatively, by the absence of a transponder signal after previous reception, or by reception after a previous absence of the transponder signal.

[0011] According to the invention, the wear detection system comprises a holding device that serves to movably position the friction element relative to a friction surface and to make contact between the friction element and the friction surface. The friction element can thus be held or received by the holding device and, for example, pressed against a friction surface with a contact force by means of a spring device or an actuator. For example, the friction element can be monolithic with a cuboid shape or rod-shaped and be received by the holding device in such a way that it is movable within the holding device essentially orthogonally to the friction surface. The reduction in length and longitudinal movement of the friction element relative to the holding device caused by wear of the friction element can then affect the communication between the transponder unit and the transmit-receive unit via the shielding device.

[0012] According to the invention, the transponder unit is fixedly connected to the holding device, with the shielding device being designed as a shielding element arranged on the holding device, which covers or releases the transponder unit when the friction element moves relative to the holding device. Thus, the transponder unit can, for example, be attached directly to a surface of the holding device without the transponder unit being in contact with the friction element. The shielding device is formed by a shielding element which, depending on a change in the length of the friction element, covers the transponder unit or releases it for communication with the transceiver unit. The shielding element can, for example, be designed as a simple metal sheet which is moved relative to the transponder unit after one end of the friction element passes through it.Such a shielding device is also cost-effective to design and enables particularly secure transmission and communication between the transponder unit and the transmitter-receiver unit, because the transponder unit is not exposed to high temperatures or vibrations due to the separation from the friction element. In particular, if the mounting device is made of a plastic material, the resonant frequency of, for example, an RFID transponder unit is hardly affected by surrounding materials, with the exception of the shielding element.

[0013] In one embodiment, the transponder unit can have a code that is receivable by the transceiver unit. This code can be used as a switching signal, for example, to start a machine. If a friction element is installed in the machine that does not have a predefined code, a corresponding switching signal cannot be generated, and consequently, the machine cannot be started. This ensures that only friction elements approved for the machine can be used. Furthermore, if a large number of friction elements are used, it becomes possible to determine which friction element has failed or is worn out, provided each friction element has an individual code via the transponder unit. The wear detection system can be connected to a control unit or machine control system for such control purposes.

[0014] An RFID transponder unit can be advantageous. While the use of a transponder unit based on optical transmission technology is also conceivable, RFID transponder units are comparatively inexpensive and also available in the form of an adhesive label. Passive RFID transponder units are preferable, as they do not require an external power supply. Furthermore, the radio signal between the RFID transponder unit and the transmitter-receiver unit can be easily influenced by means of a shielding device. For example, the resonant frequency of an antenna of the RFID transponder unit can be easily influenced by covering the antenna or by placing an electrical conductor near it, so that the radio signal is significantly attenuated or completely shielded.

[0015] The friction element can be, for example, a contact piece for transmitting electrical energy, such as a carbon brush for an electric motor or generator. The wear detection system can be particularly effective when an electric motor has a large number of carbon brushes that need to be replaced regularly due to wear or damage. Such a wear detection system is especially advantageous when the carbon brushes cannot be easily maintained, as is the case, for example, in a wind turbine. However, the wear detection system can also be used for other types of friction elements, such as all types of friction linings, brake linings, or dry lubricants.

[0016] Controlled shielding of the transponder unit can be achieved by positioning the shielding device directly adjacent to it. If the transponder unit has an antenna, it can be directly shielded by a material that interacts with electromagnetic radiation, such as a metal. The material, or the shielding device formed from it, always completely covers the transponder unit. The permittivity of the shielding device is then uneven relative to the transponder unit, so that communication with the transceiver unit is possible at least in one position relative to the shielding device, or when the shielding device is completely or partially removed.Overall, by placing the shielding device directly near the transponder unit, a change in the position of the friction element relative to the shielding device and / or the transponder unit can be detected through communication between the transponder unit and the transmitter-receiver unit.

[0017] In the inventive method for wear detection, in particular for friction elements such as brushes, friction linings, brake linings, lubricating elements or the like, with at least one consumable friction element and a transponder unit, the transponder unit can communicate wirelessly with a transmitter-receiver unit, wherein the transponder unit is at least partially shielded by means of a shielding device depending on the wear state of the friction element, such that communication between the transponder unit and the transmitter-receiver unit is affected, wherein the wear detection system comprises a holding device by means of which a movable positioning of the friction element relative to a friction surface is effected, wherein the transponder unit is fixedly connected to the holding device, and wherein the shielding device is designed as a shielding element arranged on the holding device.The transponder unit is either shielded or uncovered by means of a shielding device when the friction element moves relative to the holding device. A change in the length of the friction element due to wear can thus cause a change in the position of the transponder unit relative to the shielding device. For the advantages of the method for wear detection, reference is made to the more detailed description of the wear detection system according to the invention.

[0018] The method can be implemented particularly simply if the shielding device alters the permittivity of a spatial transmission area of ​​the transponder unit. For example, the shielding device can be located in the space between the transponder unit and the transceiver unit used for transmitting or receiving signals, and can influence these signals by changing the permittivity of that space. In electromagnetic transmission methods, this can be achieved, for instance, by introducing or removing electrically conductive materials from the space. If this is done in relation to the wear state of the friction element, a change in permittivity can indicate a state of wear.

[0019] This can also be caused by a wear-related change in the dimensions of the friction element, which can either shield or remove shielding of the transponder unit. Abrasion-related wear of the friction element is accompanied by a change in its dimensions. This change, such as a change in length or surface abrasion, can result in the transponder unit being shielded or, alternatively, its shielding being removed. Thus, wear of the friction element is associated with a change in the received signal of the transponder unit, which can be detected by the transmit-receive unit, and from which conclusions can be drawn about the wear condition of the friction element.

[0020] Thus, depending on the position of the transponder unit relative to a friction surface contacted by the friction element, shielding or removal of shielding of the transponder unit can occur.

[0021] Further advantageous embodiments of the method result from the feature descriptions of the dependent claims relating back to device claim 1.

[0022] A preferred embodiment of the invention is explained in more detail below with reference to the accompanying drawings.

[0023] They show: Fig. 1 a first embodiment of a wear detection system that does not conform to the invention, shown in a schematic representation; Fig. 2 the wear detection system according to the first embodiment with a feature opposite to the Fig. 1 altered wear condition; Fig. 3 a second embodiment of a wear detection system in a schematic representation; Fig. 4 the wear detection system according to the second embodiment with a feature opposite to the Fig. 3 altered wear condition.

[0024] Fig. 1 Figure 1 shows a schematic representation of a wear detection system 10 with a transponder unit 11, a transmitter-receiver unit 12, and a carbon brush 13. The carbon brush 13 is inserted into a holder 14 for longitudinally movable mounting and is pressed against a friction surface 16 of a slip ring 17 (shown here in section) by means of a spring 15. The transponder unit 11 is bonded to a side surface 19 at a rear end 18 of the carbon brush 13. Openings 20, 21, and 22 are formed in the holder 14, which is made of a metallic material, allowing the transponder unit 11 to be positioned within the holder depending on the length L of the carbon brush 13.

[0025] As from Fig. 1 As can be seen, when the carbon brush 13 has a length L1, the transponder unit 11 enters the area of ​​the opening 20 in such a way that the transmitter-receiver unit 12 can send a signal 23 to the transponder unit 11, which is received by the latter. The transponder unit 11 in turn sends a signal 24 back to the transmitter-receiver unit 12, thus informing the transmitter-receiver unit 12 that the transponder unit 11 has reached the area of ​​the opening 20 and that the carbon brush 13 must therefore have a length L1.

[0026] When a front end 25 of the carbon brush 13 wears down, the length L1 is reduced to the value shown here. Fig. 2 Length L2 is shown as an example. At length L2, the transponder unit 11 overlaps a shielding device 26 formed by the holder 14. In this case, the shielding device 26 is formed by a metal sheet wall 27 of the holder 14. If, as in Fig. 2 Since the transponder unit 11 is directly covered by a wall section 28, the transponder unit 11 is shielded from the transmitter-receiver unit 12 and the signal 23 emitted by the transmitter-receiver unit, and is therefore unreachable for the transmitter-receiver unit 12. This information can now be processed in a higher-level machine control system or by the transmitter-receiver unit 12 itself, whereby the interrupted communication between the transmitter-receiver unit 12 and the transponder unit 11 allows a conclusion to be drawn about the length L2 of the carbon brush 13.

[0027] The Fig. 3 und 4 Figure 29 shows a wear detection system with a transponder unit 30 and a transmitter-receiver unit 31 as well as a carbon brush 32. In contrast to the wear detection system from the Fig. 1 und 2 The carbon brush 32 is inserted in a holder 33, to the outer surface 34 of which the transponder unit 30 is firmly fixed. A shielding device 35 is formed from a metal cover element 36, which is pivotably mounted on a wall 38 of the holder 33 about an axis 37. The cover element 36 is designed in the form of a rocker, with an outer end 39 for shielding the transponder unit 30 and an inner end 40 for bearing against a side surface 41 of the carbon brush 32.

[0028] As from Fig. 3As can be seen, when the carbon brush 32 has a length of 11, the inner end 40 of the cover element 36 rests against the side surface 41 of the carbon brush 32 in such a way that the outer end 39 of the cover element 36 shields the transponder unit 30 from electromagnetic radiation or a signal 42 from the transmitter-receiver unit 31. If the carbon brush 32's length falls below 13, the inner end 40 can no longer rest against the side surface 41, so that the cover element 36 is suddenly released due to a force (not shown here, for example, from a spring or weight), causing it to pivot about the axis 37, and the outer end 39 no longer shields the transponder unit 30. The signal 42 can now be received by the transponder unit 30, whereby the transponder unit 30 sends a signal 43 back to the transmit-receive unit 31.The transmitter-receiver unit 31 can now register an exceedance of a length l3 of the carbon brush 32 and, if necessary, forward this information to a higher-level machine control system.

Claims

1. A wear detection system (29), in particular for friction elements, such as brushes, friction linings, brake linings, lubrication pieces or the like, comprising at least one consumable friction element and a transponder unit (30), wherein the transponder unit can communicate wirelessly with a transmitter-receiver unit (31), wherein the wear detection system comprises a shielding device (35), said shielding device being configured in such a manner that by means of the shielding device, the transponder unit can be at least partially shielded as a function of a wear condition of the friction element, such that communication between the transponder unit and the transmitter-receiver unit can be influenced, characterized in that the wear detection system comprises a support structure (33) which serves to movably position the friction element relative to a friction surface, the transponder unit being immovably connected to the support structure, the shielding device being formed as a shielding element (36), which is arranged at the support structure and which can cover the transponder unit in a shielding manner or uncover it when a motion of the friction element relative to the support structure occurs.

2. The wear detection system according to claim 1, characterized in that the transponder unit (30) has a coding that can be received by the transmitter-receiver unit (31).

3. The wear detection system according to claim 1 or 2, characterized in that the transponder unit (30) is an RFID transponder unit.

4. The wear detection system according to any of the preceding claims, characterized in that the friction element is a contact piece (32) for transmitting electric energy.

5. The wear detection system according to any of the preceding claims, characterized in that the shielding device (35) is arranged directly adjacent to the transponder unit (30).

6. A method for detecting wear, in particular for friction elements, such as brushes, friction linings, brake linings, lubrication pieces or the like, comprising at least one consumable friction element, and comprising a transponder unit (30), wherein the transponder unit can communicate wirelessly with a transmitter-receiver unit (31), characterized in that by means of a shielding device (35), the transponder unit is at least partially shielded as a function of a wear condition of the friction element, such that communication between the transponder unit and the transmitter-receiver unit is influenced, the wear detection system comprising a support structure (33) which serves to movably position the friction element relative to a friction surface (16), the transponder unit being immovably connected to the support structure, the shielding device being formed as a shielding element (36), which is arranged at the support structure and by means of which the transponder unit is covered in a shielding manner or uncovered when a motion of the friction element relative to the support structure occurs.

7. The method according to claim 6, characterized in that the shielding device (35) changes a permittivity of a spatial transmission range of the transponder unit (30).

8. The method according to claim 6 or 7, characterized in that by means of a wear-related dimensional change of the friction element, a shielding or an elimination of a shielding of the transponder unit (30) takes place.

9. The method according to any of the claims 6 to 8, characterized in that as a function of a position of the transponder unit (30) relative to a friction surface contacted by the friction element, a shielding or an elimination of a shielding of the transponder unit takes place.