Wet-running brush slip ring system, electric motor with a brush slip ring system and vehicle with such an electric motor

Abstract

Disclosed is a brush-slip-ring system for an electric motor, in particular in the form of a separately excited synchronous machine, comprising at least one electrically conductive brush and at least one slip ring per polarity of at least one winding, wherein the at least one slip ring is arranged to be rotatably coupled to a rotor of the electric motor, wherein the at least one brush is arranged in a carrier subjected to spring tension by at least one spring element, which is arranged to be statically positioned in the area of ​​the slip ring, wherein in an assembled state of the system the at least one brush is pressed radially and / or axially against the at least one slip ring by a spring force of the spring element, wherein the at least one brush and / or the at least one slip ring are arranged to be supplied with at least one lubricant.wherein the at least one slip ring is made at least partially from an iron-based material in the form of Cf53 or 16MnCr5. Furthermore, an electric motor and a vehicle are disclosed.

Description

[0001] The invention relates to a brush-slip-ring system for an electric motor, in particular in the form of a separately excited synchronous machine, comprising at least one electrically conductive brush and at least one slip ring. The invention further relates to an electric motor and a vehicle with an electric motor.

[0002] Currently, electric motors in the form of separately excited synchronous machines are known, which use a dry-running slip ring transmission system or brush-slip ring system for electrical power transmission. This electrical power transmission method is well-established in the market, and readily available materials or material combinations are known for the brushes and slip rings. For example, brushes made of copper-particle-laden graphite and slip rings made of bronze are known. A problem with dry-running power transmission is the relatively high brush temperatures, for example, 160°C, which are transferred to the rotor shaft, rotor shaft seals, and bearings, potentially causing them to wear out more quickly.

[0003] Furthermore, separately excited synchronous motors with wet brush-slip-ring systems are known, which exhibit reduced friction between the brushes and slip rings, thereby reducing brush temperatures, for example to 75°C. This can lower the failure rate of the electric motor and optimize thermal management. However, a problem arises because the known materials, especially copper alloys, used for the brushes and slip rings are not permanently resistant to an oily atmosphere. Consequently, the desired electrical power transmission cannot be maintained over the long term. While silver-based material substitutes for the brushes are known, these are expensive.

[0004] US 2013 / 0210243A1 discloses a system with sliding contacts that may be partially made of a metal alloy, such as steel, bronze, or brass.

[0005] DE 12 84 017 A describes an arrangement of sliding contacts with brushes and a collector or slip ring, which can be made of copper and an iron alloy.

[0006] EP 4 123 847 A1 describes a slip ring which can consist at least partially of a composite material in the form of a contact surface.

[0007] DE 10 2019 120 802 A1 discloses an electric machine with a stator and a rotor, wherein energy transfer takes place through a contact element contacting a slip ring.

[0008] DE 10 2005 031 535 A1 describes a slip ring assembly for an electric machine.

[0009] In DE 10 2018 120 326 B3 a slip ring transmitter is disclosed.

[0010] The object of the present invention is to provide an electric motor with a brush slip ring system which can be operated wet in an oil bath with reduced friction.

[0011] According to the invention, this problem is solved by a brush-slip-ring system with the features of claim 1, by an electric motor with the features of claim 8, and by a vehicle with the features of claim 9. Advantageous embodiments and further developments are described in the dependent claims.

[0012] The brush-slip-ring system according to the invention is advantageously designed for use in an electric motor, particularly in the form of a separately excited synchronous machine. The system serves to transmit electrical power to the rotor windings of the electric motor's rotor. The system comprises at least one electrically conductive brush and at least one slip ring. For example, for each polarity of a rotor winding or a group of rotor windings, a current input brush and a current output brush with one or more corresponding slip rings can be provided in the rotor.

[0013] The at least one slip ring is designed to be rotatably coupled to a rotor of the electric motor. The at least one brush is spring-loaded by at least one spring element and arranged in a carrier, which is designed to be statically positioned in the area of ​​the slip ring, wherein, in a mounted state of the system, the at least one brush is pressed radially and / or axially against the at least one slip ring by a spring force of the spring element.

[0014] According to the invention, the at least one brush and / or the at least one slip ring are arranged to be supplied with at least one lubricant, wherein the at least one slip ring is made at least partially from an iron-based material in the form of Cf53 or 16MnCr5.

[0015] Iron-based materials such as Cf53 or 16MnCr5 are already used for various components and are also cost-effective for the production of brushes and / or slip rings. These iron-based materials exhibit long-term oil compatibility, thus enabling robust and efficient electromechanical power transmission.

[0016] The at least one slip ring can be made entirely of an iron-based material, be coated at least partially with an iron-based material, or consist of several sections made of different materials, one of which is made of an iron-based material.

[0017] For example, a lateral surface of the slip ring or an axial surface can consist of the iron-based material to implement direct contact with one or more brushes for electrical power transmission.

[0018] Such a combination of an iron-based material, at least for the slip ring, and lubrication of the electrical power transmission can be implemented cost-effectively and with an increased service life for the electric motor. The already established supply chains for iron-based materials, which offer improved mechanical properties, especially hardness, are particularly noteworthy, making a wet-running system for electrical power transmission technically simple and cost-efficient.

[0019] According to a further aspect of the invention, an electric motor is provided which has at least one brush-slip-ring system according to the invention. Advantageously, the brush-slip-ring system is configured to be fluid-conducting and coupled to an oil circuit. The brush-slip-ring system serves to transmit electrical power to the rotor-side windings of the electric motor.

[0020] According to a further aspect of the invention, a vehicle is provided which has at least one electric motor according to the invention. The vehicle can further have a traction battery which, by means of power electronics, can supply the electric motor with electrical energy in order to enable longitudinal guidance of the vehicle, in particular by accelerating or braking.

[0021] Substituting conventional materials for the slip ring allows for a particularly simple technical adaptation of the brush-slip ring system for lubrication, thereby reducing mechanical friction between the brush and the slip ring. In addition to lowering the operating temperature of the brush-slip ring system, this measure can also lead to increased installation space and / or improved performance. Furthermore, most iron-based materials are permanently resistant to oil, thus optimizing electrical power transmission and reducing mechanical and electrical losses, or at least achieving the performance levels of dry-running systems.

[0022] Furthermore, applying lubricant to the brushes and / or slip rings can be used for cooling in addition to reducing friction. For this purpose, the lubricant can be thermally conditioned using an external cooler to control the temperature development of the brush-slip ring system.

[0023] In one embodiment, the at least one slip ring is configured to be mounted directly on a rotor shaft or coupled to the rotor shaft indirectly, for example via a slip ring receptacle that extends the rotor shaft axially. A slip ring fitted directly onto the rotor shaft can be implemented in a particularly simple and robust manner. Indirect mounting of slip rings on the rotor shaft, on the other hand, allows for flexible arrangement and contact of the slip rings by means of brushes.

[0024] According to a further embodiment, the at least one brush and / or the at least one slip ring are configured to be at least partially immersed in a bath containing the lubricant. This allows the brush-slip ring system to be completely submerged in a lubricant bath. The lubricant can be, for example, an oil or an aqueous solution. Advantageously, the lubricant can be an oil used in a vehicle, specifically for lubricating the brush-slip ring system, or one used in conjunction with at least one other component, such as a transmission, differential, internal combustion engine, and the like. This also allows for the particularly advantageous use of additional components of a corresponding lubrication circuit, such as a radiator and filter.This allows any potential wear from the brush-slip ring system to be flushed away, and the brush-slip ring system can also be cooled or heated to set optimal operating conditions. According to another embodiment, the lubricant is thus designed as an oil, in particular a gear oil.

[0025] According to a further embodiment, the at least one brush and / or the at least one slip ring are designed to be at least partially surrounded or wetted with the lubricant. This can be achieved, for example, by a dispensing nozzle located in the area of ​​contact surfaces between the brushes and the slip rings. This ensures the continuous functioning of a brush-slip ring system, allowing the amount of lubricant to be precisely adjusted and deactivated as needed.

[0026] According to a further embodiment, the at least one slip ring is made of the iron-based material at least radially on the outer side and / or axially on the outer edge. This allows certain sections of the slip ring, which are in direct contact with the brushes, to be made of an iron-based material.

[0027] According to another embodiment, the at least one brush is made of a non-ferrous material or an iron-based material. For example, such brushes can consist of non-ferrous metals, such as brass, bronze, aluminum alloys, and the like, which are compatible with the lubricant used.

[0028] The invention is schematically illustrated with reference to embodiments in the drawings and is further described with reference to the drawings. It shows: Fig. 1 A schematic exploded view of an electric motor with a brush slip ring system according to an embodiment according to the invention.

[0029] Fig. Figure 1 shows an exploded view of an electric motor 100 with a brush-slip-ring system 10 according to an embodiment of the invention. The electric motor 100 is exemplary in the form of a separately excited synchronous machine. The electric motor 100 has a stator 110 and a rotor 120.

[0030] A plurality of stator windings 111 are provided on the stator 110 and a plurality of rotor windings 121 are provided on the rotor 120. The rotor 120 is rotatably mounted relative to the stator 110 with respect to the rotor windings 121. In the illustrated embodiment, the stator 110 surrounds the rotor 120 on its outer surface.

[0031] System 10 serves for electrical power transmission between a power electronics unit (not shown) and rotor windings 121 of the rotor 120 of the electric motor 100.

[0032] In the illustrated embodiment, system 10 comprises three pairs of electrically conductive brushes 11 and two slip rings 21. The slip rings 21 are designed to be rotatably coupled to the rotor 120 of the electric motor 100.

[0033] As an example, the slip rings 21 are indirectly rotatable via a slip ring receptacle 20 that extends axially along the rotor shaft 120 and are electrically coupled to the rotor shaft 120. Busbars 22 are also provided for transmitting electrical power from the slip rings 21 to the rotor windings 121. The slip ring receptacle 20 can be axially connected at its end to a rotor shaft of the rotor 120 by means of a fitting sleeve 23.

[0034] The brushes 11 are spring-loaded in a carrier 13 by spring elements 12, which is designed to be statically positioned in the area of ​​the slip rings 21. In a mounted state of the system 10, the brushes 11 are pressed radially against the slip rings 21 by a spring force of the spring elements 12. In the illustrated embodiment, three brushes 11 are pressed against each slip ring 21 by means of the spring elements 12, which are evenly distributed at an angle of 120° along a radial circumferential surface or a contact surface of the slip rings 21.

[0035] The brushes 11 and the slip rings 21 are supplied with at least one lubricant 30. The entire system 10 can be positioned in a flowing or stationary lubricant bath. The arrows illustrate a flow direction of the lubricant 30, which is exemplified as gear oil.

[0036] To ensure oil compatibility, the slip rings 21 are made of an iron-based material, such as Cf53 or 16MnCr5. The brushes 11 can be made of bronze or brass, for example. LIST OF REFERENCE SYMBOLS: 100 electric motor 110 Stator 111 stator windings 120 Rotor 121 rotor windings 10 brush slip ring system 11 brushes 12 spring elements 13 carriers 20 Slip ring holder 21 slip rings 22 busbars 23 Fitting sleeve 30 lubricants A axial direction R Radial direction

Claims

[1] Brush-slip ring system (10) for an electric motor (100), comprising at least one electrically conductive brush (11) and at least one slip ring (21), wherein at least one electrically conductive brush (11) and at least one slip ring (21) are provided for each polarity of at least one rotor winding (121) or group of rotor windings (121), wherein the at least one slip ring (21) is configured to be rotatably coupled to a rotor (120) of the electric motor (100), wherein the at least one brush (11) is arranged in a carrier (13) spring-loaded by at least one spring element (12), which is configured to be statically positioned in the region of the slip ring (21), wherein in an assembled state of the system (10), the at least one brush (11) is pressed radially and / or axially against the at least one slip ring (21) by a spring force of the spring element (12), characterized bythat the at least one brush (11) and / or the at least one slip ring (21) are designed to be acted upon by at least one lubricant (30), wherein the at least one slip ring (21) is made at least in regions from an iron-based material in the form of Cf53 or 16MnCr5. [2] Brush slip ring system according to claim 1, wherein the at least one slip ring (21) is designed to be attached directly to a rotor shaft of the rotor (120) or to be coupled to the rotor shaft indirectly, for example via a slip ring holder (20) axially extending the rotor shaft. [3] Brush-slip ring system according to claim 1 or 2, wherein the at least one brush (11) and / or the at least one slip ring (21) are designed to be immersed at least in regions in a bath containing the lubricant (30). [4] Brush-slip ring system according to one of claims 1 to 3, wherein the at least one brush (11) and / or the at least one slip ring (21) are designed to be at least partially surrounded or wetted with the lubricant (30). [5] Brush slip ring system according to one of claims 1 to 4, wherein the at least one slip ring (21) is made of the iron-based material at least radially on the outside and / or axially on the edge. [6] Brush slip ring system according to one of claims 1 to 5, wherein the at least one brush (11) is made of a non-ferrous material or of an iron-based material. [7] Brush slip ring system according to one of claims 1 to 6, wherein the lubricant (30) is designed as an oil, in particular a gear oil. [8] Electric motor (100) comprising a brush-slip ring system (10) according to one of the preceding claims, wherein at least the brush-slip ring system (10) is configured to be fluidly coupled to an oil circuit. [9] Vehicle comprising at least one electric motor (100) according to claim 8.

Images