COLLECTION DEVICE FOR COLLECTING ELECTRICAL CURRENTS, AND MACHINE COMPRISING A COLLECTION DEVICE OF THIS KIND

Abstract

A discharge device for discharging electric currents from a rotor part of a machine, said rotor part having a shaft, the discharge device comprising an axially displaceable contact element, which is at least partly accommodated in a guide, for forming an electroconductive sliding contact between a sliding contact surface of the contact element and a shaft contact surface of the shaft, the sliding contact surface being provided for forming the sliding contact, the contact element being electroconductively connected to the guide and/or a retaining element of the machine, and the contact element being prestressed towards the shaft contact surface by means of a spring element, the contact element being at least partly wetted with an oily fluid, in particular at least in the area of its sliding contact surface.

Claims

1. A discharge device for discharging electric currents from a rotor part of a machine, said rotor part having a shaft, the discharge device comprising a displaceable contact element, which is at least partly accommodated in a guide, for forming an electroconductive sliding contact between a sliding contact surface of the contact element and a shaft contact surface of the shaft, the sliding contact surface being provided for forming the sliding contact, the contact element being electroconductively connected to the guide and/or a retaining element of the machine, and the contact element being prestressed towards the shaft contact surface by means of a spring element, wherein the contact element is at least partly wetted with an oily fluid, in particular at least in the area of its sliding contact surface.

2. The discharge device according to claim 1, wherein the oily fluid is motor oil and/or gear oil.

3. The discharge device according to claim 1, any one of the claim 1, characterized in that wherein the guide can be electroconductively connected to a stator part of the machine.

4. The discharge device according claim 1, wherein the contact element is electroconductively connected to the guide or a retaining element of the machine by means of a preferably low-resistance stranded wire, the stranded wire preferably being pressed or stamped into the contact element on one end and preferably welded or soldered or crimped to the guide on the other end.

5. The discharge device according to claim 1, wherein the guide is at least partly made of a low-resistance material, in particular metal, preferably aluminum, an aluminum alloy, copper and/or brass.

6. The discharge device according to claim 1, wherein the contact element is essentially made of a carbon-metal mixture, in particular a mixture of graphite and metal, the total volume fraction of the metal preferably being at least 30 percent by volume, silver preferably being provided as the metal at least in a front area of the contact element, said front area having the sliding contact surface, and copper preferably being provided as the metal in a rearward area of the contact element, the contact element preferably being free from copper in the area of the sliding contact surface.

7. The discharge device according to claim 1, wherein the contact element has a recess, in particular a hole or a slit, in the area of the sliding contact surface, the contact element preferably being open-pored in the area of the sliding contact surface.

8. The discharge device according to claim 1, wherein the contact element is a pin-shaped or bolt-shaped brush, the sliding contact surface preferably being rectangular or circular.

9. The discharge device according to claim 1, wherein the spring element is a helical compression spring which preferably abuts on the end face of the contact element opposite the sliding contact surface by means of one end.

10. A machine, in particular an electric drive motor or a transmission having a rotor part which has a shaft and having a discharge device claim 1, the contact element of the discharge device establishing an electric contact with the shaft by means of its sliding contact surface in order to form a sliding contact.

11. The machine according to claim 10, wherein oily fluid, in particular motor oil or gear oil, is provided at least in a space between the shaft and the guide which is bridged by the contact element.

12. The machine according to claim 10, wherein the discharge device (1) is disposed at least partly in a fluid guide (13, 15), the oily fluid (20) preferably initially flowing into the space (14) between the shaft (2) and the guide (6) and subsequently being discharged, in particular via the shaft (2).

13. The machine according to claim 10, wherein a line for the oily fluid, which preferably opens into the space between the shaft and the guide, is provided in the guide.

14. The machine according to claim 10, wherein the contact element is constantly pressed on the shaft with a force of at least 10 N/cm.sup.2 by means of the spring element.

15. The machine according to claim 10, wherein the shaft is essentially free from copper, at least in the area in which it is electrically connected with the contact element.

16. The machine according to claim 10, wherein the contact element establishes an electric contact with an end surface of the shaft, the contact element preferably being disposed essentially coaxially to the shaft.

17. The machine according to claim 10, wherein the contact element establishes an electric contact with the circumferential surface of the shaft.

Description

[0030] In the figures:

[0031] FIG. 1: shows a section of a machine according to the disclosure in the contact area between the contact element and the shaft in longitudinal section, the contact element being disposed coaxially to the shaft;

[0032] FIG. 2: shows a section of another embodiment of a machine according to the disclosure in the contact area between the contact element and the shaft in longitudinal section, the contact element being disposed radially to the shaft;

[0033] FIG. 3: shows an embodiment of a discharge device according to the disclosure;

[0034] FIG. 4: shows a longitudinal section through the discharge device of FIG. 3.

[0035] In the following, the same elements or elements having the same function are marked with the same reference numeral.

[0036] FIG. 1 shows a section of a machine 100 according to the disclosure in longitudinal section. In this case, machine 100 is an electric motor which has a rotor part having a shaft 2. A discharge device 1 for discharging electric currents is disposed on an end face 10 of shaft 2. The discharge device comprises a contact element in the form of a carbon brush 3 for forming an electroconductive sliding contact between sliding contact surface 4 of carbon brush 3 and a shaft contact surface 5 of shaft 2, sliding contact surface 4 being provided for forming the sliding contact. Carbon brush 3 is accommodated in a guide 6 so as to be axially displaceable. Guide 6 is a cylindrical housing and is located in a recess, which is also cylindrical, in a retaining element 7 of machine 100. Carbon brush 3 is electroconductively connected to retaining element 7 by means of a stranded wire 8.

[0037] Carbon brush 3 is prestressed towards shaft contact surface 5 by means of a helical compression spring 9. Thus, carbon brush 3 is subject to a contact force by means of spring 9 for forming an electroconductive sliding contact between sliding contact surface 4 of carbon brush 3 and axial shaft contact surface 5 of shaft 2, sliding contact surface 4 being provided for forming the sliding contact. On the side of guide 6 which faces shaft 2, carbon brush 3 somewhat protrudes out of guide 6 and establishes an electric contact with shaft 2 on its end face 10. In this case, carbon brush 3 is essentially positioned so as to be centered with respect to end face 10 of shaft 2 and is thus coaxially disposed to the shaft. As already described above, this setting is especially advantageous because it allows the smallest possible amount of wear on carbon brush 3.

[0038] On the other end of guide 6, it has a lid 11 which has a centered recess 12 which is penetrated by stranded wire 8. Spring 9 is disposed between lid 11 and carbon brush 3 and prestresses carbon brush 3 towards shaft 2.

[0039] Two oil-conducting channels 13 are provided in retaining element 7 of machine 100. These oil-conducting channels 13 are disposed above and below shaft 2, respectively, and initially run towards it at an angle. According to the arrows illustrated in FIG. 1, motor oil flows towards shaft 2 and enters space 14 between shaft 2 and guide 6 via oil-conducting channels 13, space 14 being bridged by front end area 16 of carbon brush 3. Thus, carbon brush 3 is wetted with oil in this area. In this process, oil also gets on sliding contact surface 4 and shaft contact surface 5. This oiling of carbon brush 3 and shaft 2 allows an ideal cooling in this area. From space 14, the heated oil flows on to two channels 15 which are disposed in shaft 2 and which are disposed parallel to the longitudinal axis of the shaft. Thus, the heat is basically transported away from carbon brush 3 via channels 15.

[0040] It is obvious that the wetting of carbon brush 3 could also be achieved in a different way. For example, it is possible that oil is drizzled on or oil vapor is applied to the carbon brush, especially in the contact area to the shaft. It is also conceivable that oil completely surrounds the entire machine, in particular in the contact area between shaft 2 and carbon brush 3.

[0041] Guide 6 and retaining element 7 are made of an electroconductive metal, such that guide 6 and retaining element 7 are electroconductively connected. In the exemplary embodiment at hand, guide 6 is made of aluminum.

[0042] Stranded wire 8 is also made of a low-resistance material. Stranded wire 8 is pressed into carbon brush 3 on one end and connected to retaining element 7 on its other end by means of crimping.

[0043] Carbon brush 3 has a two-layered structure. In the area of sliding contact surface 4, carbon brush 3 is made of a mixture of graphite and silver. This applies in particular to section 16 of carbon brush 3 which bridges space 14. The silver content in this part is approx. 3 percent by volume. The remaining part of carbon brush 3 is made of a mixture of graphite and copper. However, section 16 of carbon brush 3 and shaft 2 are essentially free from copper in order to prevent undesired reactions with the oil.

[0044] Carbon brush 3 is a cylindrical pin. In the exemplary embodiment at hand, carbon brush 3 is pressed on shaft 2 with a force of approx. 10 N/cm.sup.2.

[0045] FIG. 2 shows a longitudinal section of another embodiment of a machine 100 according to the disclosure. The main difference to machine 100 of FIG. 1 is that in this case, discharge device 1 is disposed radially to shaft 2, such that carbon brush 3 establishes an electric contact to circumferential surface 17 of shaft 2. Additionally, stranded wire 8 is connected to guide 6, such that in this case, stranded wire 8 acts as an electric line between carbon brush 3 and guide 6. In this embodiment, discharge device 1 is also disposed in a retaining element 7 of machine 100. Here, discharge device 1 is disposed in a space 18 which is part of an oil guide. Thus, discharge device 1 is constantly in contact with oil. Therefore, the thermal stress on the individual components, such as shaft 2 and carbon brush 3, can be kept low in this embodiment, as well. Here, too, the resulting heat is transferred to the oil during the discharge process.

[0046] FIG. 3 shows another embodiment of a discharge device 1 according to the disclosure, FIG. 4 showing said discharge device 1 in another embodiment of a machine 100 according to the disclosure. Machine 100 and discharge device 1 differ from the embodiments illustrated in FIGS. 1 and 2 in particular in that an oil line 19 is provided in guide 6, said oil line 19 extending from lid 11 in an axial direction to space 14 between guide 6 and shaft 2 and being openly connected to said space 14. As can be seen in FIG. 4, oil 20 flows from the area of lid 11 towards space 14 and pours out into it. Thereby, bridging section 16 of carbon brush 3 is flushed with oil. In FIG. 4, the two-layered design of carbon brush 3 can be seen clearly. In a front area 21, the carbon brush is made of a mixture of graphite and silver. In a rearward area 22, the carbon brush is made of a mixture of graphite and copper. In this case, stranded wire 8 is electrically connected to rearward area 22 of carbon brush 3 and guide 6 and electroconductively connects these elements.