Contact device for transmitting electric current and machine having such a contact device

Abstract

The invention relates to the use of a contact device, a machine and a discharge device for transmitting current from a rotor part of a machine, the rotor part being formed by a shaft (11) and / or a slip ring, the discharge device comprising a contact element (10) for forming an electrically conducting slip contact (16) provided for forming said slip contact and located between a slip contact surface (13) of the contact element and a rotor contact surface (14) of the shaft or slip ring, a notch being formed in the slip contact surface and the contact element being at least partially, in particular at least in the region of its slip contact surface, wetted by an oil-like fluid.

Description

[Technical Field]

[0001] The present invention relates to a contact device for conducting electric current from a rotor part of a machine, formed of a shaft and / or slip rings, the contact device comprising contact elements for forming an electrically conducting slip contact between a slip contact surface of the contact element provided for forming said slip contact and a rotor contact surface of the shaft or slip ring. The invention also relates to a machine having such a contact device and its use. [Background technology]

[0002] Contact devices of this type are known in various embodiments from the prior art. In particular, carbon brushes are used to conduct low-frequency currents. These carbon brushes are distributed axially or radially around the shaft and are connected to the stator via pigtails. The carbon brushes, housed in a retaining device or brush holder, allow direct current conduction or transmission due to their low electrical resistance, thus avoiding undesirable current conduction through the shaft's bearing points, which could result in surface damage to the bearing body or bearing ring due to spot welding. Furthermore, carbon brushes can also be used to transmit current from the stator to the rotor, for example in electric motors. In this case, one or more slip rings on the shaft are regularly brought into contact with the contact elements. The slip rings can also be considered commutators.

[0003] The term "shaft" is used here as a synonym for the term "rotor part" or "shaft rod". The term "shaft" is therefore considered to be any rotating mechanical part for which a stationary stator part or mechanical parts of a machine can conduct or transmit electric current in or between them.

[0004] Contact devices are also regularly used in railway technology, where alternating current or working current can also be discharged through the axle. A contact device of this type is described, for example, in DE 10 200 04 11 522 A1.

[0005] In general, electrical machines, such as automobiles, also require measures to release or transmit current. Continuously fluctuating alternating voltages or currents and high-frequency current pulses can occur in the motor drive shaft or the transmission shaft connected thereto or other functional components, which can damage the bearing points of the rotor shaft or transmission shaft, and therefore regular contact devices are required here.

[0006] A problem with the described contact devices and machines that have such contact devices is the high heat generation due to electrical and mechanical losses, which leads to a high thermal load on the contact device and the machine (e.g., engine, transmission). To some extent, this problem has been addressed up to now, particularly by discharging the generated heat via ventilation systems. However, this type of ventilation system only partially reduces the thermal load on the components. Another disadvantage of such ventilation systems is the significantly increased installation space required to integrate such ventilation systems into the corresponding machines.

[0007] Furthermore, known contact devices or contact elements in contact with the shaft, when mounted adjacent to a bearing for example, can easily come into contact with engine or transmission oil due to the small mounting space. As has been shown, contact with oil, particularly in the case of radially arranged contact elements on the shaft, increases the electrical resistance of the slip contact, which impairs the function of the contact device. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] German Patent Application Publication No. 102010039847(A1) Summary of the Invention [Problem to be solved by the invention]

[0009] The object of the present invention is to overcome the above-mentioned drawbacks of the prior art, and in particular to ensure a reliable transmission of current. [Means for solving the problem]

[0010] This problem is solved by the use of a contact device with the features of claim 1, a machine with the features of claim 14 and a contact device with the features of claim 19.

[0011] The contact device according to the invention for transmitting current from a rotor part of a machine, formed of a shaft and / or slip ring, has contact elements for forming an electrically conducting slip contact, the slip contact being located between a slip contact surface of the contact element provided for forming this slip contact and a rotor contact surface of the shaft or slip ring, a notch being formed in the slip contact surface, and the contact element being at least partly, in particular at least in the region of the slip contact surface, wetted with an oil-like fluid.

[0012] The contact device according to the present invention makes it possible to reliably conduct capacitively coupled high-frequency voltages or so-called parasitic AC voltages (generated by the power electronics (pulse width modulation) used by the electric drive) or to transmit current to the rotor of the electric drive. The contact device can also be arranged in a relatively small installation space adjacent to the corresponding shaft or slip ring and can be wetted with an oil-like fluid. Wetting with an oil-like fluid also makes it possible to contain or dissipate heat generated by frictional contact with the shaft or slip ring by means of the oil-like fluid. In particular, in the present invention, special cooling devices, such as ventilation systems, are required to reduce the thermal load. This allows the construction of machines, such as electric motors, to be simpler and therefore more effective than in previously known systems, and the cooling of modules to be more efficient. Frictional effects, especially due to radial shaft sealing rings, are also eliminated. Furthermore, the overall machine dimensional design can be made smaller. The formation of recesses in the region of the slip contact surface of the contact element prevents the contact element from lifting off the shaft or slip ring in the event of, for example, an oil film forming on the shaft in a desired or undesired manner. The notches effectively prevent any hydrodynamic effects that may occur due to the formation of an oily fluid film between the contact element and the shaft or slip ring. The oily fluid can collect in the notches in the slip contact surface or be pushed out into the notches, so that any oily fluid film that may occur is interrupted or only formed very thinly. This makes it possible to achieve a particularly low electrical resistance in the slip contact or between the contact element and the shaft or slip ring. This prevents possible lifting of the contact element and avoids any possible electrical contact loss between the shaft or slip ring and the contact element. The contact element can contact the shaft or slip ring on its radial or axial side.

[0013] Typically, the oily fluid may be engine oil and / or transmission oil, which may generally be present originally in the engine or transmission in which the contact device according to the present invention is located.

[0014] The cutout can be formed by at least one hole or slit in the interior of the sliding contact surface. A hole in the contact element can be formed particularly simply. The hole can be a blind hole or a through hole. This hole ensures that the cutout is always present in the interior of the sliding contact surface, even if the contact element wears or the material of the contact element wears away.

[0015] Furthermore, two or more notches can be formed in the interior of the slip contact surface. Depending on the size of the slip contact surface, it may be advantageous to provide a number of smaller notches in the interior of the slip contact surface instead of just one relatively large notch.

[0016] The notch can be formed as at least one passageway, which penetrates the contact element and forms openings in the slip contact surface and in the jacket surface of the contact element opposite the slip contact surface. The passageway connects the slip contact surface with the corresponding outer surface. Unlike blind holes, the passageway also allows the oil-like fluid to be guided through the contact element. The fluid can collect in the passageway and then flow out again at the opening in the outer surface. This means that backflows in the notch can be prevented when the oil-like fluid is continuously transported or moved through the shaft.

[0017] The ratio of the cross-section or diameter of the passages in the slip contact surface to the cross-section or diameter of the passages in the outer surface, in particular the side or back surface, of the contact element can be ≧1.1. The cross-section of the passages in the slip contact surface is therefore at least 10% larger than the cross-section of the passages in the outer surface. The cross-sections in the slip contact surface and the outer surface can be formed, for example, as circles or diameters. Circles can be formed, in particular, simply by holes.

[0018] The passages may be formed with a diameter that decreases conically with respect to the contact element in longitudinal section and / or with passage sections that extend longitudinally and / or transversely relative to one another. The passages may therefore be formed as through holes extending from the slip contact surface to the rear surface, or as transverse holes from the side surfaces of the contact elements that intersect or communicate with holes in the slip contact elements.

[0019] The ratio of the area of ​​the recess inside the slip contact surface to the slip contact surface can be ≧0.08. This ratio ensures that the slip contact surface is still large enough to conduct current, while at the same time significantly reducing the potential film of oily fluid through the recess.

[0020] The contact element can be at least partially housed within a guide device of the contact device and can be slidable, the contact element can be connected to the guide device and / or a holding element of the machine so as to be electrically conductive, and the contact element can be biased towards the rotor contact surface by a spring member, and the guide device can be connected to the stator part of the machine so as to be electrically conductive.

[0021] The contact elements can be electrically connected to the guide device and / or the holding element of the machine by means of strands, preferably of low resistance, which can be pressed or embedded at one end into the contact element and preferably welded, soldered or crimped to the guide device at the other end. The guide device is preferably made at least in part from a low-resistivity material, in particular from metal, preferably aluminum, an aluminum alloy, copper and / or brass.

[0022] In a particularly preferred embodiment of the contact element according to the invention, the contact element is substantially formed from a carbon-metal mixture, in particular a mixture of graphite and a highly electrically conductive metal, with the metal preferably being silver at least in the region of the slip contact surface of the contact element and preferably copper in the rear region of the contact element, the contact element preferably being copper-free in the region of the slip contact surface. The proportion of metal in the contact element is preferably at least 30% by volume. Therefore, the contact element preferably is copper-free in the region of the slip contact surface, since this metal can combine with the current path and cause catalytic changes in the oily fluid, which can result in negative changes in the physical properties of this fluid. For this reason, the shaft or slip ring of the machine according to the invention, which will be described in more detail further below, is also copper-free or has only a small copper content, at least in the region where the shaft or slip ring contacts the contact element.

[0023] In order to keep the system resistance as low as possible under all operating conditions, the resistance of the contact device according to the invention must also be selected to be low. The above-described embodiment, which has low-resistivity materials and contact elements made of a metal-carbon mixture, allows the resistance of the entire device to be kept low. On the other hand, the system resistance is typically determined by the voltage drop between the shaft surface and the slip contact surface of the contact element. This accounts for the largest proportion of the overall system. Therefore, it must likewise be kept low. To ensure this under continuous lubrication, on the one hand, a high specific pressure of the contact element on the shaft is effective. This value should be at least 10 N / cm 2 On the other hand, no electrochemical reaction in the contact elements in the area of ​​the sliding contact surface with the oily fluid must occur. This is ensured by the silver-graphite material in the area of ​​the contact elements that wears over their entire lifespan.

[0024] The contact element may be a brush formed in the shape of a rod, and the slip contact surface may preferably be formed in a rectangular or square shape. The brushes described above may be formed by die pressing and subsequent heat treatment.

[0025] The cross section of the contact element can be at least partially conical, in particular arcuate. The conical or frustoconical cross section can extend in a direction opposite to the rotational direction or preferred direction of the shaft or slip ring. This prevents the formation of a run-up edge for the oily fluid on the contact element. The oily fluid can be expelled along the tapered outer surface of the contact element, making it difficult for a film of oily fluid to form on the slip contact surface.

[0026] The machine according to the invention, in particular an electric drive motor or transmission, comprises a rotor part having a shaft and / or slip rings and a contact device according to the invention, the contact elements of which bring the shaft or slip ring into contact with their slip contact surfaces to form a slip contact. This machine achieves the already-mentioned advantage of improved contact between the shaft or slip ring and the contact elements when an oily fluid is present in the area of ​​the slip contact surfaces. This allows the contact device to be supported completely in an oily fluid, in particular engine oil or transmission oil. Preferably, the oily fluid is provided in the space between the shaft or slip ring and the guide device, which space is bridged by the contact device. Therefore, it is also conceivable to apply the oily fluid to the contact device, in particular to the contact elements of the contact device, in the form of a spray, drips, or mist.

[0027] According to an embodiment of the machine, the contact elements can contact the circumferential surface of the shaft or slip ring, in which case the contact elements can be geometrically tapered in cross section, preferably against the preferred direction of rotation of the shaft or slip ring to be contacted, in order to suppress electrical contact losses due to lift between the shaft or slip ring and the contact elements.

[0028] Furthermore, the longitudinal axis of the contact element can be arranged to extend at a distance relative to the rotation axis of the shaft. Since the longitudinal axis of the contact element is not aligned with the rotation axis of the shaft, the contact element is positioned on the shaft or slip ring so that it extends obliquely or transversely to the rotation axis. The contact element can be arranged at an obtuse angle relative to the rotation direction or preferred direction of the shaft or slip ring, i.e., so that oily fluid present on the shaft or slip ring is scraped off the shaft or slip ring by the blades formed by the contact element. Scraping the fluid can also suppress the formation of a lubricant film on the slip contact surfaces.

[0029] According to another embodiment, the contact elements can contact the end faces of the shaft or slip ring, preferably arranged substantially coaxially with the shaft. This type of shaft grounding effectively prevents contact loss, since the axial eccentricity of a rotating shaft is generally small. By positioning the contact elements near the rotation point of the shaft, the peripheral speed is reduced, and thus the actual mileage over the life of the contact elements is also significantly reduced. This directly affects the wear of the contact elements, which is generally proportional to the mileage. Due to the reduced mileage, the wear of the contact elements remains small, and therefore the power loss of the spring element over the entire wear length of the contact elements is also minimized. This allows the use of the cost-effective compression coil springs already mentioned above. Furthermore, the low peripheral speed near the rotation axis of the shaft or slip ring reduces the risk of the formation of a continuous, electrically insulating lubricant film, thereby allowing the contact force to be lower than would be necessary at higher peripheral speeds. Another advantage of end-side contact of the shaft or slip ring near the axis of rotation is the reduction of the frictional moment due to the small radial distance from the point of rotation. Even when the frictional force is very large, the frictional moment as the product of the frictional force x and the running radius remains small. This further results in a low frictional power, and therefore a low system loss, even in combination with the shaft speed (equivalent to the rotational speed).

[0030] An oil-like fluid, in particular engine oil or transmission oil, can be provided at least in the space surrounding the slip contact between the shaft or slip ring and the contact element.

[0031] Further preferred embodiments of the machine follow from the characterizing recitations of the subclaims attributable to device claim 1.

[0032] The use according to the invention of a contact device for transmitting current from a rotor part of a machine, formed of a shaft and / or slip ring, comprises a contact element for forming an electrically conductive slip contact between the slip contact surface of the contact element and the rotor contact surface of the shaft or slip ring, the slip contact surface having a recess formed therein, and the contact element is at least partially, in particular in the region of the slip contact surface, wetted by an oil-like fluid. Regarding the advantages of this use, reference is made to the description of the advantages of the contact device according to the invention. Further preferred embodiments of the use can be obtained from the description of the features of the subclaims attributable to claim 1 of the device.

[0033] Other features will become apparent from the following description in combination with the drawings and the subclaims. The individual features can be realized alone or in combination with one another. [Brief explanation of the drawings]

[0034] [Figure 1] FIG. 1 shows a shaft with contact elements according to a first embodiment. [Figure 2] FIG. 2 shows a shaft with contact elements according to a second embodiment. [Figure 3] FIG. 3 shows a shaft with contact elements according to a third embodiment. [Figure 4] FIG. 4 shows a side view of the contact element. [Figure 5] FIG. 5 shows a plan view of a contact element according to the first embodiment. [Figure 6] FIG. 6 shows a longitudinal section of the contact element shown in FIG. [Figure 7] FIG. 7 shows a longitudinal section of a second embodiment of a contact element. [Figure 8] FIG. 8 shows a longitudinal section of a third embodiment of a contact element. [Figure 9] FIG. 9 shows a longitudinal section of a fourth embodiment of a contact element. [Figure 10]FIG. 10 shows a longitudinal section of a fifth embodiment of a contact element. [Figure 11] FIG. 11 shows a plan view of a sixth embodiment of a contact element. [Figure 12] FIG. 12 shows a plan view of a seventh embodiment of a contact element. DETAILED DESCRIPTION OF THE INVENTION

[0035] FIG. 1 shows a purely schematic representation of a contact element 10 of a contact device (not shown in detail) mounted on a machine shaft 11 (not shown in detail). The shaft 11 is wetted by an oil-like fluid (not shown in detail) and rotates in the direction of arrow 12. The contact element 10 forms a slip contact surface 13 and abuts against a rotor contact surface 14 formed by the circumferential surface 15 of the shaft 11. The slip contact surface 13 and the rotor contact surface 14 together form a slip contact 16 between the shaft 11 and the contact element 10, through which current can be conducted away from the shaft 11. A recess is formed in the interior of the slip contact surface 13, which is not visible here. In principle, in all of the described embodiments, the rotor contact surface can be formed by a slip ring.

[0036] 2 shows a contact element 17 which is arranged to rest against the shaft 11 and whose longitudinal axis 18 extends at a distance A from the axis of rotation 19 of the shaft 11. In particular, the contact element 17 is thus formed with a cutting edge 20 by means of which oily fluids can be scraped off from the peripheral surface 15.

[0037] 3 shows a contact element 21 in contact with a shaft 22, the contact element 21 contacting an axial end face 23 of the shaft 22. The contact element 21 has a notch in the slip contact face 24, which is again not shown in detail.

[0038] 4 shows a contact element 25, which consists essentially of a carbon-metal mixture, in particular a mixture of graphite and metal. In a front region 27 of the contact element 25, which has a slip contact surface 26, silver is provided as the metal, and in a rear region 28 of the contact element 25, copper is provided as the metal. At the rear surface 29 of the contact element 25, strands 30 are fixed. In the interior of the slip contact surface 26, a recess is formed, which is not shown in detail here.

[0039] 5 and 6 taken together show a contact element 31 having a slip contact surface 32 with a bore 33 formed therein that defines a passage 34 through the contact element 31. The bore 33 defines a diameter d1 in the slip contact surface 32 that corresponds to a diameter d2 at the back surface 35 of the contact element 31. The bore 33 therefore extends coaxially through the contact element 31.

[0040] 7 shows a contact element 36 in which the passage 37 is conically shaped. The diameter d1 in the slip contact surface 38 is larger than the diameter d2 in the rear surface 35 of the contact element 36.

[0041] 8 shows a contact element 40 having a passageway 41 formed from a first hole 42 and a second hole 43. The first hole 42 has a diameter d2 that is relatively smaller than the second hole 43, which has a diameter d1.

[0042] 9 shows a contact element 44 having a blind hole 45 in the sliding contact surface 46. Another blind hole 48 is formed in the side surface 47 of the contact element 44, which crosses the blind hole 45. Through the passage 49 thus formed, it is possible to conduct the oil-like fluid to the side surface 47. This is particularly advantageous when, for structural reasons, it is not possible to provide an opening in the rear surface 50 of the contact element 44.

[0043] 10 shows a contact element 51 having a through hole 52 connecting two side surfaces 53 of the contact element 51. Two blind holes 55 are formed in the slip contact surface 54 and both of them communicate with the through hole 52. Thus, two passages 56 are formed.

[0044] 11 shows a contact element 57 with holes 58 in the slip contact surface 59, in which the parallel side surfaces 60 are partially provided with bevels 61 and are formed conically with respect to the cross section 62 of the contact element 57. If an oily fluid flows onto the slip contact surface 59, this fluid can escape along the side surfaces 60 at least partially in the region of the bevels 61.

[0045] 12 shows a contact element 63 in which two holes 65 are formed in a slip contact surface 64. The two holes 65 are located on a transverse axis 66 of the slip contact surface 64 relative to the direction of movement of a shaft not shown here.

Claims

1. A contact device for transmitting current from a rotor part of a machine formed by a shaft (11, 22) and / or slip rings, comprising:

1. A contact device comprising contact elements (10, 17, 21, 25, 31, 36, 40, 44, 51, 57, 63) for forming an electrically conducting slip contact (16) between slip contact surfaces (13, 24, 26, 32, 38, 46, 54, 59, 64) of the contact elements provided for forming said slip contact and a rotor contact surface (14) of the shaft (11, 22), A notch is formed in the slip contact surface; the contact element is at least partially wetted by an oily fluid, in particular at least in the region of its sliding contact surface, the contact elements (10, 17, 21, 25, 31, 36, 40, 44, 51, 57, 63) are made substantially from a carbon-metal mixture, the total volume fraction of the metal being at least 30% by volume, and at least in the front region (27) of the contact elements having the slip contact surfaces (13, 24, 26, 32, 38, 46, 54, 59, 64) silver is provided as the metal and in the rear region (28) of the contact elements copper is provided as the metal, 10. A contact device, characterized in that the cutout in the slip contact surface (13, 24, 26, 32, 38, 46, 54, 59, 64) is formed by at least one hole (33, 42, 43, 45, 48, 52, 55, 58, 65) and / or slit.

2. 2. A contact device according to claim 1, characterized in that the oily fluid is engine oil and / or transmission oil.

3. 3. A contact device according to claim 1 or 2, characterized in that two or more notches are formed in the slip contact surface (13, 24, 26, 32, 38, 46, 54, 59, 64).

4. 4. A contact device according to claim 1, wherein the notch is formed as at least one passage (34, 37, 41, 49, 56) which passes through the contact element (10, 17, 21, 25, 31, 36, 40, 44, 51, 57, 63) and defines openings in the slip contact surface (13, 24, 26, 32, 38, 46, 54, 59, 64) and in an outer surface of the contact element opposite the slip contact surface, respectively.

5. 5. A contact device according to claim 4, characterized in that the ratio of the cross-sectional area of ​​the passages (34, 37, 41, 49, 56) in the slip contact surface (13, 24, 26, 32, 38, 46, 54, 59, 64) to the cross-sectional area of ​​the passages in the back surface (29, 35, 39, 50) of the contact element (10, 17, 21, 25, 31, 36, 40, 44, 51, 57, 63) is ≧1.

1.

6. 6. A contact device according to claim 5, characterized in that the passages (34, 37, 41, 49, 56) are formed in a conical shape in longitudinal section with a diameter (d1, d2) that decreases from the slip contact surface (13, 24, 26, 32, 38, 46, 54, 59, 64) towards the rear surface (29, 35, 39, 50).

7. 7. Contact device according to any one of claims 1 to 6, characterized in that the ratio of the area of ​​the notches in the slip contact surface to the area of ​​the slip contact surface (13, 24, 26, 32, 38, 46, 54, 59, 64) is ≧0.

08.

8. 8. A contact device according to claim 1, wherein the contact elements (10, 17, 21, 25, 31, 36, 40, 44, 51, 57, 63) are at least partially housed in a guide device of the contact device and are slidable, the contact elements are connected in electrical conduction with the guide device and / or a holding element of the machine, and the contact elements are biased in the direction of the rotor contact surface (14) by a spring element, and the guide device is connectable in electrical conduction with a stator part of the machine.

9. 9. A contact device according to claim 8, characterized in that the contact element (10, 17, 21, 25, 31, 36, 40, 44, 51, 57, 63) is electrically connected to the guide device or a holding element of the machine by means of a strand (30), preferably of low resistance, which is pressed or embedded into the contact element at one end and is preferably welded, soldered or crimped to the guide device at the other end.

10. 10. A contact device according to claim 1, characterized in that the contact element is copper-free in the area of ​​the slip contact surface, the contact element being formed substantially from a mixture of graphite and metal.

11. 11. A contact device according to claim 1, wherein the contact elements (10, 17, 21, 25, 31, 36, 40, 44, 51, 57, 63) are brushes formed in the shape of a rod, and the slip contact surfaces (13, 24, 26, 32, 38, 46, 54, 59, 64) are formed in the shape of a rectangle or a square.

12. 12. Contact device according to any one of the preceding claims, characterized in that the cross section (62) of the contact element (10, 17, 21, 25, 31, 36, 40, 44, 51, 57, 63) is at least partly conically, in particular arcuately, formed.

13. A machine, in particular a drive motor or transmission, having a rotor part with a shaft (11, 22) and / or slip rings and a contact device according to any one of claims 1 to 12, The contact elements (10, 17, 21, 25, 31, 36, 40, 44, 51, 57, 63) of the contact device bring slip contact surfaces (13, 24, 26, 32, 38, 46, 54, 59, 64) into contact with the shaft (11, 22) or the slip ring to form a slip contact (16).

14. 14. Machine according to claim 13, characterized in that the contact elements (10, 17, 21, 25, 31, 36, 40, 44, 51, 57, 63) contact the peripheral surface (15) of the shaft (11) or the peripheral surface of the slip ring.

15. 15. Machine according to claim 13 or 14, characterized in that the longitudinal axes (18) of the contact elements (10, 17, 21, 25, 31, 36, 40, 44, 51, 57, 63) are arranged to extend at a distance (A) relative to the rotation axis (19) of the shaft (11).

16. 14. Machine according to claim 13, characterized in that the contact element (21) is in contact with a shaft (22) or an end face (23) of a slip ring, the contact element being preferably arranged substantially coaxially with respect to the shaft.

17. 17. Machine according to any one of claims 13 to 16, characterized in that an oily fluid, in particular engine oil or transmission oil, is provided in contact with the shaft (11) or with the slip rings and contact elements (10, 17, 21, 25, 31, 36, 40, 44, 51, 57, 63) in the space surrounding at least the slip contact (16).

18. Use of a contact device for transmitting current from a rotor part of a machine, formed with a shaft (11, 22) and / or slip rings, comprising: the contact device comprises contact elements (10, 17, 21, 25, 31, 36, 40, 44, 51, 57, 63) for forming an electrically conducting slip contact (16) between slip contact surfaces (13, 24, 26, 32, 38, 46, 54, 59, 64) of the contact elements provided for forming the slip contact and the shaft (11, 22) or a rotor contact surface (14) of the slip ring; A notch is formed in the slip contact surface; the contact elements are at least partially wetted by an oily fluid, in particular at least in the region of the sliding contact surface, the contact elements (10, 17, 21, 25, 31, 36, 40, 44, 51, 57, 63) are made substantially from a carbon-metal mixture, the total volume fraction of the metal being at least 30% by volume, and at least in the front region (27) of the contact elements having the slip contact surfaces (13, 24, 26, 32, 38, 46, 54, 59, 64) silver is provided as the metal and in the rear region (28) of the contact elements copper is provided as the metal, Use of a contact device, wherein said cutout in said slip contact surface (13, 24, 26, 32, 38, 46, 54, 59, 64) is formed by at least one hole (33, 42, 43, 45, 48, 52, 55, 58, 65) and / or slit.

Images