Abstract
A method for measuring a state of wear of a consumable friction element, a measuring device and a friction element, in particular a brush or the like. The measuring device includes a sensing device having a sensor. A magnetic field can be produced by means of the sensor, and the friction element can be moved in the magnetic field relative to the sensor. The measuring device comprises an indicator that can be attached to the friction element. The indicator comprises a ferromagnetic, antiferromagnetic and/or ferrimagnetic substance, and a change in the magnetic field can be detected by means of the sensing device as a result of a change in the position of the indicator relative to the sensor.
Claims
1. A measuring device for measuring a state of wear of a consumable friction element wherein the measuring device comprises a sensing device having a sensor wherein a magnetic field can be produced by the sensor, wherein the friction element can be moved in the magnetic field relative to the sensor, wherein the measuring device comprises an indicator, wherein the indicator can be attached to the friction element, wherein the indicator comprises a ferromagnetic, antiferromagnetic and/or ferrimagnetic substance, wherein a change in the magnetic field can be detected by means of the sensing device as a result of a change in a position of the indicator relative to the sensor.
2. The measuring device according to claim 1, wherein the sensor is a coil, wherein an impedance of the coil can be measured by a detection circuit of the sensing device.
3. The measuring device according to claim 1, wherein the measuring device comprises a brush holder for housing a friction element and disposing it in a moveable manner, wherein the sensor is fixedly disposed on the brush holder.
4. The measuring device according to claim 1, wherein the sensing device comprises an additional sensor that can produce an additional magnetic field, wherein the friction element or an additional friction element can be moved in the additional magnetic field relative to the sensor.
5. The measuring device according to claim 4, wherein the sensor and the additional sensor are connected to a detection circuit of the sensing device in series or in parallel.
6. A friction element for transmitting currents, realized for measuring a wear length of the friction element by a measuring device according to claim 1.
7. The friction element according to claim 6, wherein the material of the friction element is predominantly made of graphite.
8. The friction element according to claim 6, wherein the indicator is disposed in sections on the friction element, relative in reference to a length (L) of the friction element.
9. The friction element according claim 6, wherein an additional indicator is disposed on the friction element.
10. The friction element according to claim 6, wherein the indicator is a coiled strip spring disposed on the friction element.
11. The friction element according to claim 6, wherein the indicator is a coating disposed on the friction element.
12. The friction element according to claim 6, wherein the friction element realizes the indicator wherein the ferromagnetic, antiferromagnetic and/or ferrimagnetic substance is added to a material of the friction element.
13. The friction element according to claim 11, wherein the indicator is realized on its own in a consumable contact portion of the length of the friction element, relative in reference to a length (L) of the friction element.
14. The friction element according to claim 11, wherein the indicator is realized on its own in a coupling portion of the length of the friction element, relative in reference to a length (L) of the friction element.
15. The friction element according to claim 11, wherein the indicator is realized on its own in an indicator portion the length of the friction element in between a coupling portion and a consumable contact portion, relative in reference to a length (L) of the friction element.
16. The friction element according to claim 11, wherein the substance is made of iron, cobalt, nickel, their alloys, alloys of iron-silicon, iron-boron, iron-aluminum, aluminum-nickel-cobalt, manganese-antimony, or manganese-bismuth.
17. The friction element according to claim 6, wherein the substance comprises oxides of the elements iron (Fe.sub.2O.sub.3, Fe.sub.3O.sub.4), nickel (NiO), chromium (CrO.sub.2) and/or spinels of type AB.sub.2O.sub.3 on their own or in combination, said spinels of type AB.sub.2O.sub.3 having divalent metal cations (Mg, Mn, fe, CO, Ni, Cu) for the letter A and trivalent metal cations (Fe) for the letter B.
18. A method for measuring a state of wear of a consumable friction element wherein a magnetic field is produced by a sensor of a sensing device of a measuring device, wherein the friction element in the magnetic field is disposed relative to the sensor, wherein an indicator of the measuring device is disposed on the friction element, said indicator comprising a ferromagnetic, antiferromagnetic and/or ferrimagnetic substance, wherein a change in the magnetic field is detected by the sensing device as a result of a change a position of the indicator relative to the sensor.
19. The method according to claim 18, wherein an impedance of the sensor is measured by the sensing device and is compared to a reference impedance which is stored in the sensing device, wherein a partial length of a consumable contact portion of a length (L) of the friction element is determined by a difference of the measured impedance and the reference impedance.
20. The method according to claim 18, wherein a change in the position of the indicator relative to the sensor (59*is continuously measured by the sensing device.
21. The use of an indicator made of a ferromagnetic, antiferromagnetic and/or ferrimagnetic substance having a consumable friction element, for measuring a state of wear of the friction element.
Description
[0036] The disclosure is described in more detail with the aid of the attached drawings in the following.
[0037] In the figures:
[0038] FIG. 1 shows a perspective view of a first embodiment of a friction element;
[0039] FIG. 2 shows a perspective view of a second embodiment of a friction element;
[0040] FIG. 3 shows a perspective view of a third embodiment of a friction element;
[0041] FIG. 4 shows a perspective view of a fourth embodiment of a friction element;
[0042] FIG. 5 shows a perspective view of a fifth embodiment of a friction element;
[0043] FIG. 6 shows a perspective view of a sixth embodiment of a friction element;
[0044] FIG. 7 shows a perspective view of a seventh embodiment of a friction element;
[0045] FIG. 8 shows a perspective view of an eighth embodiment of a friction element;
[0046] FIG. 9 shows a perspective view of a ninth embodiment of a friction element;
[0047] FIG. 10 shows a perspective view of a tenth embodiment of a friction element;
[0048] FIG. 11 shows a schematic sectional view of brush holder having an unconsumed friction element;
[0049] FIG. 12 shows a schematic sectional view of brush holder from
[0050] FIG. 11 having a consumed friction element.
[0051] FIG. 1 shows a simplified perspective view of a friction element 10 which realizes a brush 11. A brush body 12 is substantially made of graphite and comprises a contact surface 14 on a forward end 13, said contact surface 14 serving to come in contact with a slip ring of an electric machine (not shown), and a stranded wire 16 on a rearward end 15, said stranded wire 16 being housed in brush body 12 and serving to connect brush 11 in an electrically conductive manner. An indicator 18 is attached to brush 11 or its surface 17 by means of a coating 19. Coating 19 is several micrometers thick and is substantially made of a ferromagnetic substance, wherein coating 19 can alternatively also comprise an antiferromagnetic and/or ferrimagnetic substance. The substance can be iron, cobalt or nickel and alloys of iron-nickel, iron-cobalt, nickel-cobalt, iron-silicon, iron-boron, iron-aluminum, aluminum-nickel-cobalt, nickel-iron-cobalt, manganese-antimony, or manganese-bismuth, for example. Coating 19 is fully applied on surface 17 on rearward end 15 relative to a longitudinal axis 20. Surface 17, on the other hand, does not have a coating and therefore realizes a consumable contact portion 21 having a partial length LK and a length L of brush body 12. As a result, coating 19 is realized in a coupling portion 22 having a length LV of length L of brush body 12. Brush 11 can be used together with a measuring device (not shown) and a brush holder, wherein a magnetic field is produced by means of a sensor of a sensing device of the measuring device and the brush is disposed relative to the sensor in the magnetic field, wherein indicator 18 causes a change in the magnetic field as a result of a change in a position of indicator 18 relative to the sensor due to a consumption of consumable contact portion 21. The measuring device can then use the change in the position of indicator 18 relative to the sensor for determining length LK of consumable contact portion 21.
[0052] FIG. 2 shows a friction element 23 which, in contrast to the friction element of FIG. 1, comprises a coating 24, which is only applied on a lateral surface 25 of surface 17 in coupling portion 22. It is important to note that friction element 23 must always be housed in a manner that allows coating 24 to reach a detection area of a sensor. Coating 24 can be applied by means of an adhesive layer (not shown) on lateral surface 25, for example.
[0053] FIG. 3 shows a friction element 26 which, in contrast to the friction element of FIG. 1, comprises a coating 27, which is only applied in consumable contact portion 21 on surface 17 of brush holder 12. Coating 27 is worn over the service life of friction element 26 due to an abrasive removal and is substantially completely removed at the end of the service life.
[0054] FIG. 4 shows a friction element 28 which, in contrast to the friction element of FIG. 1, comprises a coating 29, which is applied in a transition area of consumable contact portion 21 to coupling portion 22 on surface 17. Coating 29 realizes an indicator portion 30 in this way. If coating 29 passes a sensor due to an abrasive removal of consumable contact portion 21, an impedance of a magnetic field of the sensor can, for example, change from an initial value to a modified value and back to the initial value. It is then possible to detect at least two positions of friction element 28 without precisely calculating a length of friction element 28.
[0055] In contrast to the friction element of FIG. 4, friction element 31 shown in FIG. 5 comprises an additional coating 32 in indicator portion 30.
[0056] FIG. 6 shows a friction element 33 which, in contrast to the friction element of FIG. 1, comprises an indicator 34 in coupling portion 22 instead of a coating, said indicator being realized as a material of brush body 12 due to an addition of a ferromagnetic, antiferromagnetic and/or ferrimagnetic substance. The substance can be added to the material in the form of particles 35 if brush body 12 is sintered. Particles 35 are substantially distributed in a homogeneous manner in coupling portion 22, wherein no particles of the substance are added to consumable contact portion 21. A principle of a detection corresponds to the friction element shown in FIG. 1.
[0057] FIG. 7 shows a friction element 36 which, in contrast to the friction element of FIG. 6, comprises particles 35 only in a section 27 on a lateral surface 38 of coupling portion 22 or surface 17.
[0058] FIG. 8 shows a friction element 39 in which, in contrast to the friction element of FIG. 6, particles 35 of the substance are only added to the material of brush body 12 in consumable contact portion 21. Coupling portion 22 does not comprise any particles of the substance.
[0059] FIG. 9 shows a friction element 40 in which, in contrast to the friction element of FIG. 6, particles 35 of the substance are only added to the material in an indicator portion 41 between consumable contact portion 21 and coupling portion 22.
[0060] FIG. 10 shows a friction element 42 in which, in contrast to the friction element of FIG. 9, additional particles 43 are added to a material of brush body 12 in coupling portion 22, whereby an additional indicator 44 is realized in coupling portion 22.
[0061] A combined view of FIGS. 11 and 12 shows a schematic sectional view of a slip ring 45 of an electric machine (not shown in more detail) having a brush holder 46 and a friction element 47, which realizes a brush 48. Brush 48 is moveable along a longitudinal axis 40 within a shaft 50 of brush holder 46. A contact pressure is caused on a contact surface 52 of brush 48 via a spring 51. Electrical energy can then be transmitted to slip ring 45 via contact surface 52 via a stranded wire 53, which is attached to brush 48. Brush 48 is substantially made of graphite, wherein a ferromagnetic, antiferromagnetic and/or ferrimagnetic substance is added to the graphite in a section 54 of a coupling portion 55 of a brush body 56 of brush 48, such that an indicator 57 is realized. A sensor 59 which is substantially realized by a coil (not shown in more detail) is disposed in a cavity 58 on brush holder 46. Sensor 59 and indicator 57 are part of a measuring device 60 (not fully shown). A consumable contact portion 61 of brush body 56 is initially relatively long and is then reduced by an abrasive removal of the material of contact portion 61 so as to cause a position of indicator 57 relative to sensor 59, as can be seen from FIGS. 11 and 12. A magnetic field generated by sensor 59 is also changed by a changed relative positioning of indicator 57, a corresponding change in the length of consumable contact portion 61 being derived from the change in the relative position of indicator 57 of measuring device 60 or of a detection circuit (not shown) on measuring device 60 and the reaching of a wear limit being detected thereby.
