ELECTRIC MOTOR

Abstract

Disclosed is an electric motor, in particular for a vehicle drive. In one example, the electric motor has a housing (12) and a rotor shaft (14) which is accommodated in the housing (12) such that it can rotate via bearings (16). The housing (12) and the rotor shaft (14) are electrically connected to one another via a singular electrically conductive contact ring (42) to ground the rotor shaft (14).

Claims

1-10. (canceled)

11. An electric motor for a vehicle drive, the electric motor comprising: a housing (12); a rotor shaft (14) accommodated in the housing (12) such that the rotor shaft can rotate via bearings (16); and an electrically conductive contact ring (42) electrically connecting the housing (12) to the rotor shaft (14), thereby grounding the rotor shaft (14).

12. The electric motor according to claim 11: wherein the rotor shaft (14) is a hollow and defines a fluid-conducting channel (26) in an interior of the rotor shaft, the fluid-conducting channel having an inlet opening (32); wherein the housing (12) comprises an inlet pipe (30) that projects into the inlet opening; and wherein the contact ring (42) is between the rotor shaft (14) and the inlet pipe (30).

13. The electric motor according to claim 12, wherein the contact ring (42) seals the fluid-conducting channel (26) on an axial end region of the rotor shaft (14).

14. The electric motor according to claim 12, wherein a receptacle for the contact ring (42) is configured in the rotor shaft (14) or in the inlet pipe (30).

15. The electric motor according to claim 14, wherein the contact ring (42) seals the fluid-conducting channel (26) on an axial end region of the rotor shaft (14).

17. The electric motor according to claim 11, wherein the contact ring (42) is made of steel or grey cast iron.

18. The electric motor according to claim 11, wherein the contact ring (42) is made of an electrically conductive polymer.

19. The electric motor according to claim 11, wherein the contact ring (42) has a square cross-section.

20. The electric motor according to claim 11, wherein the rotor shaft (14) or the housing (12) defines a groove and the contact ring (42) is held exclusively via the groove.

21. An electric motor comprising: a housing (12); a rotor shaft (14) accommodated in the housing (12) such that it can rotate via bearings (16); and electrically conductive contact rings (42) electrically connecting the housing (12) and the rotor shaft (14), wherein the electrically conductive contact rings (42) are arranged in a series connection.

22. The electric motor according to claim 21, further comprising: a planetary transmission (18) coupled to the rotor shaft (14), the planetary transmission including a planet carrier; wherein the electrically conductive contact rings (42) includes a first contact ring (42) between the rotor shaft (14) and the planet carrier (46) and a second contact ring (42) between the planet carrier (46) and the housing (12), so that current can flow from the rotor shaft (14) over the planet carrier (46) to the housing (12).

23. The electric motor according to claim 22, wherein individual contact rings (42) are made of material selected from steel, grey cast iron, and an electrically conductive polymer.

24. The electric motor according to claim 22, wherein a receptacle for at least one of the contact, rings (42) is configured in the rotor shaft (14) or in the inlet pipe (30).

25. The electric motor according to claim 24, wherein one or more of the contact rings (42) seals the fluid-conducting channel (26) on an axial end region of the rotor shaft (14).

26. The electric motor according to claim 21, wherein individual contact rings (42) are made of material selected from steel, grey cast iron, and an electrically conductive polymer.

27. The electric motor according to claim 21, wherein one or more of the contact rings (42) has a square cross-section.

28. The electric motor according to claim 21, wherein the rotor shaft (14) or the housing (12) defines a groove and one or more of the contact rings (42) is held exclusively via the groove.

29. An electric motor for a vehicle drive, the electric motor comprising: a housing (12); a rotor shaft (14) accommodated in the housing (12) such that the rotor shaft can rotate via bearings (16); and one or more electrically conductive contact rings (42) electrically connecting the housing (12) to the rotor shaft (14), thereby grounding the rotor shaft (14); wherein the rotor shaft (14) is a hollow and defines a fluid-conducting channel (26) in an interior of the rotor shaft, the fluid-conducting channel having an inlet opening (32); wherein the housing (12) comprises an inlet pipe (30) that projects into the inlet opening; and wherein one of the one or more contact rings (42) is between the rotor shaft (14) and the inlet pipe (30).

30. The electric motor of claim 29, further comprising a planetary transmission (18) coupled to the rotor shaft (14), the planetary transmission including a planet carrier, wherein the one or more electrically conductive contact rings (42) includes a first contact ring (42) between the rotor shaft (14) and the planet carrier (46) and a second contact ring (42) between the planet carrier (46) and the housing (12), so that current can flow from the rotor shaft (14) over the planet carrier (46) to the housing (12).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Further features and advantages of the invention will be apparent from the following description and from the accompanying drawings, to which reference is made. The figures show:

[0018] FIG. 1: a sectional view of an electric motor with a shaft grounding ring,

[0019] FIG. 2: the detail II from FIG. 1 with a shaft grounding ring according to the state of the art,

[0020] FIG. 3: an enlarged view of a first embodiment of an electric motor according to the invention with a contact ring in a rotor shaft,

[0021] FIG. 4: an enlarged view of a second embodiment of an electric motor according to the invention with a contact ring in an inlet pipe and

[0022] FIG. 5: an enlarged view of a third embodiment of an electric motor according to the invention with a series connection of contact rings.

DETAILED DESCRIPTION

[0023] FIG. 1 shows an electric motor 10 for a vehicle drive comprising a housing 12 in which a rotor shaft 14 is accommodated such that it can rotate via bearings 16, which are designed here as ball bearings.

[0024] A transmission 18 is coupled to one axial end region of the rotor shaft 14 and an impulse disc 20 for rotation speed determination is mounted to the other axial end region.

[0025] The electric motor 10 is designed here as an induction motor with a rotor and a stator and the transmission 18 is configured as a planetary transmission. However, it is also conceivable that other types of electric motors and transmissions are used.

[0026] The rotor and the stator of the electric motor 10 are disposed here in a separate engine compartment 24 that is sealed by shaft sealing rings 22. The rotor is coupled to the rotor shaft 14, which is configured here as a hollow shaft comprising an oil-conducting channel 26. The two axial end regions of the rotor shaft 14 project into oil chambers 28 which are configured on axially opposite sides of the housing 12, wherein the oil-conducting channel 26 fluidically connects the two oil chambers 28 to one another. The oil chambers 28 serve as oil reservoirs in their lower region.

[0027] On the side of the rotor shaft 14 facing away from the transmission 18, there is an oil inlet pipe 30 which projects into an oil inlet opening 32 of the rotor shaft 14, so that the oil inlet pipe 30 and the oil-conducting channel 26 of the rotor shaft are fluidly connected to one another. The oil inlet pipe 30 is configured on the housing 12 of the electric motor 10.

[0028] The arrangement for grounding the rotor shaft 14 according to the state of the art with a shaft grounding ring 34 is shown enlarged in FIG. 2. The shaft grounding ring 34 is disposed in the housing 12 and provides current paths from the rotor shaft 14 to the housing 12 via brush-like fibers 36. The brush-like fibers 36 are mounted between a plurality of annular discs 38 that are disposed in a base body 40. The shaft grounding ring 34 is disposed in a receptacle in the engine compartment 24.

[0029] FIG. 3 shows an enlarged view of the axial end region of the rotor shaft 14 facing away from the transmission 18, wherein the oil inlet pipe 30 projects into the oil inlet opening 32 of the rotor shaft 14. A singular electrically conductive contact ring 42 is disposed between the rotor shaft 14 and the oil inlet pipe 30 of the housing 12, so that a current path is provided from the rotor shaft 14 to the housing 12 without the use of a shaft grounding ring 34. There is consequently no need for a plurality of annular discs or for fibers. A singular ring assumes all of the functions of the many parts of the shaft grounding ring 34.

[0030] When the electric motor 10 is operated, currents, such as capacitive or circular currents, can arise, which flow from the rotor shaft 14 to the housing 12. The contact ring 42 provides a current path from the rotor shaft 14 to the housing 12 and grounds the rotor shaft 14.

[0031] The contact ring 42 is made of an electrically conductive material and the current path provided via the contact ring 42 has a lower electrical resistance than the current path via the bearings 16 or via the gears of the transmission 18, so that current that arises in the rotor shaft 14 during operation of the electric motor 10 flows from the rotor shaft 14 to the housing 12 via the contact ring 42 rather than via the bearings 16 or gears of the transmission 18. The contact ring 42 can be made of steel, grey cast iron or an electrically conductive polymer, for example.

[0032] The contact ring 42 here is accommodated in a groove in the rotor shaft 14. In an alternative embodiment, the contact ring 42 can be accommodated in a groove in the oil inlet pipe 30 (see FIG. 4). However, it is also conceivable that the contact ring 42 be disposed between the rotor shaft 14 and the housing 12 at another location in the electric motor 10. The placement between the oil inlet pipe 30 and the rotor shaft 14 has the advantage that the contact ring 42 can be designed with a particularly small diameter of the friction surface, which reduces friction during operation.

[0033] In the shown design examples, the contact ring 42 has a rectangular cross-section.

[0034] However, it is also conceivable that the contact ring 42 has another easy-to-produce cross-section, for example a trapezoidal or round cross-section.

[0035] In the shown design example, the contact ring 42 also seals the oil-conducting channel 26 on an axial end region.

[0036] FIG. 5 shows a further design variant of the electric motor 10 with a series connection of singular electrically conductive contact rings 42. Since the basic principle is the same as that of the embodiments of FIG. 3 and FIG. 4, only the differences are discussed in the following.

[0037] In the embodiment according to FIG. 5, two contact rings 42 are disposed in the electric motor 10.

[0038] A first contact ring 42 is disposed between the rotor shaft 14 and the transmission 18, and a second contact ring 42 is disposed between the transmission 18 and the housing 12. The first contact ring 42 is accommodated in a groove on the axial end region of the rotor shaft 14 to which the transmission 18 is coupled and forms an electrical connection from the rotor shaft 14 to a planet carrier 46 of the transmission 18. The contact ring 42 is positioned between the rotor shaft 14 and the transmission 18 in such a way that it has the smallest possible diameter on the friction surface.

[0039] The second contact ring 42 is mounted in a receptacle between the housing 12 and a mounting flange 48 of the planet carrier 46.

[0040] These two contact rings 42 form a series connection of contact rings 42, thereby providing a current path so that current can flow from the rotor shaft 14 via the planet carrier 46 to the housing 12.

LIST OF REFERENCE NUMERALS

[0041] 10 Electric motor [0042] 12 Housing [0043] 14 Rotor shaft [0044] 16 Bearing [0045] 18 Transmission [0046] 20 Impulse disc [0047] 22 Shaft sealing rings [0048] 24 Engine compartment [0049] 26 Channel [0050] 28 Oil chambers [0051] 30 Oil inlet pipe [0052] 32 Oil inlet opening [0053] 34 Shaft grounding ring [0054] 36 Fibers [0055] 38 Annular discs [0056] 40 Base body [0057] 42 Contact ring [0058] 44 Lubrication duct [0059] 46 Planet carrier [0060] 48 Mounting flange