A discharge device for discharging an electric current and a machine equipped with this type of discharge device

Abstract

The present invention relates to a discharge device (1) for discharging an electric current from a rotor part of a machine (100) having a shaft (2), the discharge device (1) comprising an axially displaceable contact element (3) at least partially received within a guide unit (6), the contact element (3) serving to form a conductive sliding contact, the conductive sliding contact being the contact between the sliding contact surface (4) of the contact element (3) and the shaft contact surface of the shaft, the contact element (3) being conductively connected to the guide unit (6) and / or a holding element of the machine and being preloaded towards the shaft contact surface by a spring element, the contact element (3) being at least partially wetted by an oily fluid, in particular in the region of at least the sliding contact surface (4) of the contact element (3), at least one duct (19) being provided in a section of the guide unit (6) and / or the contact element (3) for at least the oily fluid, the duct (19) being formed by the guide unit (6) and the contact element (3).

Description

Technical Field

[0001] The present invention relates to a discharge device for discharging current from a rotor part of a machine having a shaft, the discharge device comprising a contact element that is at least partially received in a guide unit and is specifically axially displaceable, the contact element serving to form a conductive sliding contact, the conductive sliding contact being a contact between a sliding contact surface of the contact element provided to form the sliding contact and a shaft contact surface of the shaft, the contact element being conductively connected to a guide unit and / or a holding element of the machine and being preloaded towards the shaft contact surface by a spring element.

Background Art

[0002] Such discharge devices are known in various embodiments from the prior art. Specifically, it is known to use carbon brushes for discharging low-frequency current, these carbon brushes being distributed axially or radially around the shaft and connected to the stator via connecting wires. The carbon brushes received in the holding unit and / or brush holder can directly discharge current due to their low electrical resistance, thus avoiding unwanted current conduction via the bearing point of the shaft, which could lead to surface damage of the bearing body or bearing ring due to spot welding.

[0003] In this specification, the term "shaft" is used as a synonym for the term "rotor part" or "axle". Thus, the term "shaft" refers to all rotating machine parts that can discharge current to a fixed stator part and / or machine part of a machine.

[0004] Also, discharge devices are commonly used in railway technology where alternating current or even operating current may flow via the wheel axle. This type of discharge device is described, for example, in DE 10 2010 039 847 A1.

[0005] Means for discharging current are required for all electrical machines, such as automobiles for example. There is a risk that continuously varying alternating voltages and / or currents and high-frequency current pulses may occur in the motor drive shaft or in the connected transmission shaft and / or in other functional components, and furthermore there is a risk of damage to the bearing points of the rotor shaft or transmission shaft, so a discharge device is usually required here.

[0006] One problem with the aforementioned discharge devices and machines having such discharge devices is the generation of high heat caused by electrical losses and mechanical losses, which results in a high heat load on both the discharge device and the machine (such as a motor, transmission). To address this problem to some extent, ventilation systems have been used to dissipate the generated heat. However, such ventilation systems can only partially minimize the heat load on the components. A further drawback of such ventilation systems is that the installation space required to integrate the ventilation system into the machine increases dramatically.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] The object of the present invention is to overcome the drawbacks of the above-mentioned state of the art. Specifically, the object of the present invention is to minimize the heat load on the components when discharging parasitic current, and at the same time to minimize the required installation space.

Means for Solving the Problems

[0009] According to the present invention, this object is achieved by a discharge device of the type described above, characterized in that the contact element is at least partially wetted, especially in the area of the sliding contact surface of the contact element, using an oily fluid, and at least one duct is provided in at least a guide unit for the oily fluid and / or a section of the contact element, the duct being formed by the guide unit and the contact element.

[0010] By using the discharge device according to the present invention, it is ideally possible to discharge a capacitively coupled high-frequency voltage (so-called parasitic alternating voltage) formed by an electrical drive using power electronics (pulse width modulation) used, and at the same time to contain and / or release the heat resulting from the assistance of the oily fluid. In particular, the present invention does not require a special cooling device, such as a ventilation device, for example, to minimize the heat load. As a result, the design of a machine, such as an electric motor, for example, is simplified compared to previously known systems, and thus the cost can be kept lower and the cooling of the motor can be made more efficient. For example, the frictional losses caused especially by radial shaft seals are also eliminated. Furthermore, as described above, it is possible to make the overall dimensions of the machine smaller (the moment of inertia of the rotating parts is reduced).

[0011] Generally, the oily fluid is motor oil and / or transmission oil, and these are usually present in some way in the engine or transmission in which the discharge device according to the present invention is provided.

[0012] The duct can extend at least along the contact element. Thereby, it becomes possible to indirectly cool the contact element through the oily fluid flowing through the duct. Furthermore, the duct can also be formed in a narrow installation space. Preferably, the duct can extend along the entire length of the contact element.

[0013] The duct can be formed by a longitudinal recess in the guide wall portion of the guide unit and / or a longitudinal recess in the outer wall portion of the contact element. The longitudinal recesses in the contact element and the longitudinal recesses in the guide wall portion can be easily manufactured. These longitudinal recesses can form ducts for the oily fluid, either individually or in combination. Specifically, a plurality of longitudinal recesses can be formed in the guide wall portion and / or a plurality of longitudinal recesses can be further formed in the outer wall portion, that is, it is possible to realize that a corresponding number of ducts are available for the oily fluid.

[0014] The outer wall portion of the contact element can abut against the guide wall portion of the guide unit. It is possible to form a tolerance portion between the outer wall portion of the contact element and the guide wall portion of the guide unit so that the contact element can move easily. Similarly, this tolerance portion can be dimensioned so that the contact element does not become jammed or pinched within the guide unit. Therefore, at least some sections of the outer wall portion of the contact element abut against the guide wall portion of the guide unit.

[0015] At least some sections of the longitudinal recess can preferably have a semi-circular cross-section in the form of a groove. The cross-section of this longitudinal recess can generally have any suitable shape. A semi-circular cross-section is particularly easy to manufacture. The groove is understood to be a recess that is long compared to its width.

[0016] A passage can be formed in the guide unit, and the volumetric flow rate of the oily fluid passing through the duct can be limited by this passage. The passage can be a simple passage opening, such as a passage drill hole located on the side of the guide unit facing away from the shaft. The cross-sectional area of the passage can be smaller compared to the cross-sectional area of the duct and / or the total cross-sectional area of these ducts. This type of passage can be particularly easily and precisely manufactured for the duct, that is, it is possible to set the exact volumetric flow rate of the oily fluid passing through the duct using this passage.

[0017] This groove is preferably continuous. In the duct, since there may be a pressure loss with respect to the length of the duct, it is possible to further reduce the contact resistance by being able to apply an additional contact pressure to the contact elements on the shaft contact surface of the shaft.

[0018] This duct for the oily fluid can be open to the space between the shaft and the guide unit. In this embodiment, the heat generated in the contact area between the shaft and the contact element can be immediately dissipated by the oily fluid flow.

[0019] In a particularly preferred embodiment of the discharge device according to the invention, the guide unit can be conductively connected to the stator part of the machine. This stator part of the machine can, for example, serve as a holding device for the discharge device. When a current is discharged, this current is discharged from the associated shaft into the contact element and the guide unit of the discharge device. Then, in the described embodiment, this discharged current flows into the stator part of the machine.

[0020] Advantageously, the contact element is conductively connected to the guide unit, preferably by a low-impedance stranded wire, which is preferably pushed or pressed into the contact element at one end and preferably welded, soldered, or crimped to the guide unit at the other end. The guide unit is preferably at least partially made of a low-impedance material, in particular from a metal, preferably made of aluminum, an aluminum alloy, copper, and / or brass.

[0021] In a particularly preferred embodiment of the discharge device according to the invention, the contact element is made substantially from a carbon-metal mixture, in particular from a mixture of graphite and a highly conductive metal, preferably silver being the metal provided at least in the region of the sliding contact surface of the contact element, preferably copper being the metal provided in the rear region of the contact element, and the contact element preferably not containing copper in the region of the sliding contact surface. The proportion of metal in the contact element is preferably at least 30% by volume. Thus, in the region of the sliding contact surface, the contact element preferably does not contain copper. This is because this metal can cause catalytic changes in an oily fluid accompanied by the passage of an electric current, and as a result, it may negatively change the physical properties of this fluid. For this reason, the shaft of the machine according to the invention, which will be described in more detail hereinafter, also preferably does not contain copper at least in the region where this shaft contacts the contact element.

[0022] In order to maintain the system resistance as low as possible under all operating conditions, the resistance of the discharge device according to the invention should also be low. The overall resistance of the device can be kept low by using the above-described embodiment having a low-impedance material and a contact element made from a metal-carbon mixture. On the other hand, the system resistance is significantly affected by the voltage drop between the shaft surface and the sliding contact surface of the contact element. This accounts for the largest part of the entire system. Therefore, the system resistance should also be kept low. To ensure the condition of low system resistance under continuous lubrication, a high specific contact surface pressure of the contact element against the shaft is advantageous. This value should be at least 10 N / cm 2 . On the other hand, in combination with an oily fluid, no electrochemical reaction should occur in the contact element in the region of the sliding contact surface. This is specifically ensured by the silver-graphite material in the region of the contact element that undergoes wear over the entire service life.

[0023] Advantageously, the contact element has recesses, in particular drill holes or slots, in the region of the sliding contact surface. This prevents the contact part from floating on the oil film. Advantageously, the contact element has open holes in the region of the sliding contact surface. This contributes to suppressing the electrical contact loss between the shaft and the contact element and minimizes the floating of the contact element on the oil film.

[0024] The contact element is typically a pin-shaped brush or a bolt-shaped brush. The sliding contact surface is rectangular, polygonal, or circular. The brush is usually manufactured by compression molding and subsequent heat treatment.

[0025] Advantageously, the spring element is a coil spring, and one end of the spring element preferably abuts against the front surface of the contact element located on the opposite side of the sliding contact surface. By using this type of compression coil spring, it becomes easy to press the contact element against the shaft using a specific desired contact pressure at all times.

[0026] Furthermore, the present invention relates to a machine, in particular an electric drive motor or a transmission, having a rotor part with a shaft and the discharge device according to claims 1 to 12 of the present invention. The contact element of this discharge device forms a sliding contact part by contacting the shaft with the sliding contact surface of the contact element. The machine according to the present invention realizes the aforementioned advantage of a dramatic reduction in heat load due to its small installation size and non-complex design.

[0027] In the machine according to the present invention, the discharge device can be completely installed in an oily fluid, specifically in motor oil or transmission oil. Preferably, the oily fluid is supplied at least into the space between the shaft and the guide unit, and the contact element occupies this space. In this embodiment, the region where the maximum heat is generated, namely the region between the shaft and the contact element, is cooled by the oily fluid.

[0028] Advantageously, the contact element is at least 10 N / cm 2Using the force, it is constantly pressed against the shaft by the spring element. Thereby, the voltage drop between the shaft surface and the sliding contact surface of the contact element is minimized.

[0029] As described above, preferably, the shaft is substantially free of copper in at least the region covered by the contact with the contact element.

[0030] In a preferred embodiment of the machine according to the present invention, the contact element contacts the front surface of the shaft, and the contact element is preferably arranged substantially coaxially with the shaft. This type of shaft grounding is preferable for avoiding contact loss because the axial runout of the rotating shaft is usually low. By positioning the contact element near the rotation point of the shaft, the peripheral speed is minimized, and the actual running distance over the service life of the contact element is significantly shortened. This has a direct impact on the wear of the contact element and has a proportional correlation with the normal running distance. By minimizing the running distance, the wear of the contact element remains low, and as a result, the loss of the force of the spring element over the total wear length of the contact element is also minimized. This enables, for example, the use of a low-cost compression coil spring as described above. Furthermore, due to the low peripheral speed near the rotation axis of the shaft, the risk of forming a continuous electrically insulating lubricating film is reduced, that is, it is possible to maintain the contact pressure lower than the pressure required at a high peripheral speed. Another advantage of the front contact of the shaft near the rotation axis is that the frictional torque is minimized due to the short radial distance from the rotation point. Even when the frictional force is very high, the frictional torque as the product of the frictional force and the running radius remains small. As a result, this frictional force remains low in combination with the angular velocity (equivalent to the rotational speed), and the system loss also remains low.

[0031] In a further embodiment of the machine according to the invention, the contact element contacts the jacket surface of the surface. In this embodiment, preferably, the cross-section of the contact element is geometrically tapered in the preferred direction of rotation of the shaft to be contacted in order to achieve suppression of electrical contact loss due to floating between the shaft and the contact element.

[0032] Generally, the discharge device is positioned in a section of the machine where the main operating temperature exceeds 50°C.

[0033] Further features of the invention are shown in the following description of the figures in combination with the drawings and the dependent claims. The individual features can be realized alone or in combination with each other.

Brief Description of the Drawings

[0034]

Figure 1

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Figure 14

Embodiments for Carrying Out the Invention

[0035] The general outlines of FIGS. 1 to 3 show a section of a machine 100 according to the present invention having a discharge device 1. The machine 100 in this example is an electric motor having a rotor part with a shaft 2. The discharge device 1 for discharging an electric current is arranged on the front surface 10 of the shaft 2. The discharge device 1 comprises a contact element 3 in the form of a carbon brush for forming a conductive sliding contact portion, and this conductive sliding contact portion is a contact portion between the sliding contact surface 4 of the contact element 3 provided for forming the sliding contact portion and the shaft contact surface 5 of the shaft 2. The contact element 3 is received in a guide unit 6 in an axially displaceable manner. The guide unit 6 is designed as a cylindrical casing and is arranged in a recess (not shown) which is also cylindrical in the machine 100. The contact element 3 is conductively connected to the guide unit 6 by a stranded wire 8.

[0036] The contact element 3 is preloaded towards the shaft contact surface 5 by a compression coil spring 9. Accordingly, the contact element 3 receives a contact force by the spring 9 and forms a conductive sliding contact portion between the sliding contact surface 4 of the contact element 3 provided for forming the sliding contact portion and the axial shaft contact surface 5 of the shaft 2. On the side of the guide unit 6 facing the shaft 2, the carbon brush 3 projects slightly from the guide unit 6 and contacts the shaft 2 at its front surface 10. In this situation, the contact element 3 is substantially arranged at the center on the front surface 10 of the shaft 2 and is thus arranged coaxially with respect to the shaft. As described above, this position is particularly advantageous because the wear of the contact element 3 is minimized.

[0037] The guide unit 6 has a cover 11 with a stranded wire 8 attached to the other end. A spring 9 that preloads the contact element 3 towards the shaft 2 is disposed between the cover 11 and the contact element 3.

[0038] The guide unit 6 is made of a conductive metal, whereby a conductive connection is established between the guide unit 6 and a group of components (not shown) of the machine 100 that holds the guide unit 6. In this exemplary embodiment, the guide unit 6 is made of aluminum.

[0039] Furthermore, the stranded wire 8 is made of a low-impedance material. The stranded wire 8 is pushed into the contact element 3 at one end and connected to the cover 11 at the other end by crimping, resistance welding, or soldering. Furthermore, the stranded wire 8 can also be sent through the cover 11 and contacted in another manner.

[0040] The contact element 3 is a two-layer structure. In the region of the sliding contact surface 4, the contact element 3 is made of a graphite-silver mixture. This particularly affects the section 21 of the contact element 3. The silver content in this region is about 3% by volume. The other regions of the contact element 3 are made of a graphite-copper mixture. However, the section 21 of the contact element 3 and the shaft 2 are substantially copper-free to avoid an undesirable reaction with oil. The contact element 3 is designed as a cylindrical pin. In this exemplary embodiment, the contact element 3 is pressed against the shaft 2 using a force of about 10 N / cm 2 of force.

[0041] The duct 19 is formed within the guide unit 6 and extends axially from the cover 11 to the space 14 between the guide unit 6 and the shaft 2 and is in open communication with the space 14. As can be seen in FIG. 2, the oil 20 flows from the region of the cover 11 in the direction of the space 14 and is injected into this space 14. As a result, the section 21 of the contact element 3 is surrounded by the oil 20. In section 22, the contact element 3 is made of a graphite-copper mixture. In this example, the stranded wire 8 is connected to the section 22 of the contact element 3 and the guide unit 6 and / or the cover 11 and conductively connects these elements.

[0042] The section of the duct 19 formed within the guide unit 6 is also formed and / or defined by the contact element 3. Specifically, the duct 19 is formed by a longitudinal recess 23 in the guide wall portion 24 of the guide unit 6. Thus, the longitudinal recess 23 forms a groove 25 in the guide wall portion 24. This groove 25 is at least partially covered by the outer wall portion 26 of the contact element 13, and thus the cross-section 27 of the duct 19 through which the oil 20 flows is formed in this region between the outer wall portion 26 and the longitudinal recess 23.

[0043] When the oil 20 flows into the space 14, it reaches the sliding contact surface 4 and / or the shaft contact surface 5. This "oil supply" of the contact element 3 and the shaft 2 enables optimal cooling in this region. Then, this heated oil flows from the space 14 into a channel (not shown) of the machine 100. As a result, it is advantageous because thermal energy is dissipated from the contact element 3.

[0044] FIG. 4 shows a discharge device 30 in which a duct 31 is formed, in contrast to the discharge devices of FIGS. 1 to 3. This discharge device 30 is of a symmetric type.

[0045] FIG. 5 shows a discharge device 32 in which the contact element 33 is arranged asymmetrically with respect to the longitudinal axis 34 of the guide unit 35, in contrast to the discharge devices of FIGS. 1 to 3. Thus, it is possible to design a contact element 33 having a particularly large cross-sectional area.

[0046] FIG. 6 shows a discharge device 36 in which a duct 37 having a kidney-shaped cross section 38 that conforms to the outer edge 39 of the guide unit 40 is formed, in contrast to the discharge devices of FIGS. 1-3. Thus, this cross section 38 can be particularly large.

[0047] In the view of the discharge device 41 of FIG. 7, a plurality of ducts 37 are formed such that a particularly large amount of oil can be transported through the duct 37.

[0048] The discharge device 42 of FIG. 8 has two semi-circular ducts 43 that face the substantially flat outer wall portion 44 of the contact element 45.

[0049] FIG. 9 shows a discharge device 46 in which two ducts 47 are arranged laterally with respect to the outer wall portion 48 of the contact element 49.

[0050] FIG. 10 shows a discharge device 50 having a contact element 51 with a polygonal cross section 52. Ducts 54 are formed within the guide unit 55 of the discharge device 50 at each edge 53 of the contact element 51.

[0051] FIG. 11 shows a discharge device 56 having a contact element 57 in which a duct 58 is formed.

[0052] In the discharge device 59 shown in FIG. 12, a plurality of ducts 58 are formed within the contact element 60. The contact element 60 is symmetric.

[0053] In contrast to the discharge device of FIG. 12, in the discharge device 61 of FIG. 13, a part of the duct 63 is also formed within the guide unit 62. The discharge device 61 is symmetric.

[0054] FIG. 14 shows a discharge device 64 in which individual ducts 66 and / or sections thereof are formed within the guide unit 65, in contrast to the discharge device of FIG. 11.

Explanation of Reference Numerals

[0055] 1 Discharge device 2 Shaft 3 Contact element, carbon brush 4 Sliding contact surface 5 Shaft contact surface 6 Guide unit 8 Twisted wire 9 Compression coil spring, spring 10 Front surface 11 Cover 13 Contact element 14 Space 19 Duct 20 Oil 21 Section 22 Section 23 Longitudinal recess 24 Guide wall portion 25 Groove 26 Outer wall portion 27 Cross-section 30 Discharge device 31 Duct 32 Discharge device 33 Contact element 34 Longitudinal axis 35 Guide unit 36 Discharge device 37 Duct 38 Kidney-shaped cross-section, cross-section 39 Outer edge 40 Guide unit 41 Discharge device 42 Discharge device 43 Semi-circular duct 44 Outer wall portion 45 Contact element 46 Discharge device 47 Duct 48 Outer wall portion 49 Contact element 50 Discharge device 51 Contact element 52 Polygonal cross-section 53 Edge 54 Duct 55 Guide unit 56 Discharge device 57 Contact element 58 Duct 59 Discharge device 60 Contact element 61 Discharge device 62 Guide unit 63 Duct 64 Discharge device 65 Guide unit 66 Duct 100 Machine

Claims

1. A discharge device (1, 30, 32, 36, 41, 42, 46, 50, 56, 59, 61, 64) for discharging an electric current from a rotor part of a machine (100) having a shaft (2), wherein the discharge device comprises a displaceable contact element (3, 33, 45, 49, 51, 57, 60) at least partially received within a guide unit (6, 35, 40, 55, 62), the contact element (3, 33, 45, 49, 51, 57, 60) serving to form a conductive sliding contact, the conductive sliding contact being a contact between a sliding contact surface (4) of the contact element provided for forming the sliding contact and a shaft contact surface (5) of the shaft, the contact element being conductively connected to the guide unit and / or a holding element of the machine, and the contact element being preloaded towards the shaft contact surface by a spring element (9), in the discharge device (1, 30, 32, 36, 41, 42, 46, 50, 56, 59, 61, 64). The contact element is at least partially wetted using an oily fluid (20), in particular in the region of at least the sliding contact surface of the contact element, and at least one duct (19, 31, 37, 43, 47, 54, 58, 63) is provided in at least a section of the guide unit and / or the contact element for at least the oily fluid, the duct being formed by the guide unit and the contact element, characterized in the discharge device (1, 30, 32, 36, 41, 42, 46, 50, 56, 59, 61, 64).

2. The duct (19, 31, 37, 43, 47, 54, 58, 63) extends at least along the contact element (3, 33, 45, 49, 51, 57, 60), characterized in the discharge device according to claim 1.

3. The duct (19, 31, 37, 43, 47, 54, 58, 63) is formed by a longitudinal recess (23) in a guide wall part (24) of the guide unit (6, 35, 40, 55, 62) and / or a longitudinal recess in an outer wall part (26, 44, 48) of the contact element (3, 33, 45, 49, 51, 57, 60), characterized in the discharge device according to claim 1 or 2.

4. The outer wall portion (26) of the contact element (3, 33, 45, 49, 51, 57, 60) abuts against the guide wall portion (24) of the guide unit (6, 35, 40, 55, 62), the discharge device according to claim 3.

5. At least some sections of the longitudinal recess (23) have a semi-circular cross-section (27, 28, 52), preferably in the form of a groove (25), the discharge device according to claim 3 or 4.

6. The duct (19, 31, 37, 43, 47, 54, 58, 63) for the oily fluid (20) opens into the space (14) between the shaft (2) and the guide unit (6, 35, 40, 55, 62), the discharge device according to any one of claims 1 to 5.

7. A passage is formed in the guide unit (6, 35, 40, 55, 62), and the volume flow rate of the oily fluid (20) passing through the duct (19, 31, 37, 43, 47, 54, 58, 63) can be limited by the passage, the discharge device according to any one of claims 1 to 6.

8. The guide unit (6, 35, 40, 55, 62) is electrically conductively connectable to the stator parts of the machine (100), the discharge device according to any one of claims 1 to 7.

9. The contact element (3, 33, 45, 49, 51, 57, 60) is electrically conductively connected to the guide unit (6, 35, 40, 55, 62) or the holding element of the machine (100) preferably by a low-impedance stranded wire (8), and the stranded wire is preferably pushed into or pressed against the contact element at one end, and preferably welded, soldered or crimped to the guide unit at the other end, the discharge device according to any one of claims 1 to 8.

10. The contact elements (3, 33, 45, 49, 51, 57, 60) are made substantially from a carbon-metal mixture, in particular from a mixture of graphite and metal, the total volume fraction of the metal being preferably at least 30% by volume, preferably silver being the metal provided in at least the front region (16, 21) of the contact region having the sliding contact surface (4), preferably copper being the metal provided in the rear region (22) of the contact element, the contact element preferably being characterized by not containing copper in the region of the sliding contact surface, a discharge device according to any one of claims 1 to 9.

11. The contact elements (3, 33, 45, 49, 51, 57, 60) are pin-shaped brushes or bolt-shaped brushes, the sliding contact surface (4) preferably being rectangular, polygonal, or circular, a discharge device according to any one of claims 1 to 10.

12. The spring element (9) is a compression coil spring, one end of the spring element (9) preferably abutting against the front surface of the contact element (3, 33, 45, 49, 51, 57, 60) located on the opposite side of the sliding contact surface (4), a discharge device according to any one of claims 1 to 11.

13. A machine (100), in particular an electric drive motor or a transmission, having a rotor part with a shaft (2) and a discharge device (1, 30, 32, 36, 41, 42, 46, 50, 56, 59, 61, 64) according to any one of claims 1 to 12, wherein the contact element (3, 33, 45, 49, 51, 57, 60) of the discharge device (1, 30, 32, 36, 41, 42, 46, 50, 56, 59, 61, 64) forms a sliding contact portion by contacting the shaft by means of the sliding contact surface (4) of the contact element.

14. An oily fluid, in particular motor oil or transmission oil (20), is supplied into at least the space (14) between the shaft (2) and the guide unit (6, 35, 40, 55, 62), the contact element (3, 33, 45, 49, 51, 57, 60) occupying the space (14), a machine according to claim 13.

15. The machine according to claim 13 or 14, characterized in that the shaft (2) is substantially free of copper at least in the region covered by the contact with the contact elements (3, 33, 45, 49, 51, 57, 60).

16. The machine according to any one of claims 13 to 15, characterized in that the contact elements (3, 33, 45, 49, 51, 57, 60) contact the front face (10) of the shaft (2), and the contact elements are preferably arranged substantially coaxially with the shaft.

17. The machine according to any one of claims 13 to 15, characterized in that the contact elements contact the jacket surface of the shaft.

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