Brush module of an electric machine, separately excited electric motor and method for operating an electric machine

Abstract

A brush module (1) of an electric machine comprises several metallic, porous, oil-impregnated and oil-conducting grinding brushes (2), each of which is made of a single material and is constructed in one piece and is intended for contacting rotating current-carrying components of the electric machine.

Description

[0001] The invention relates to a brush module comprising several grinding brushes for an electric machine. Furthermore, the invention relates to a separately excited electric motor and a method for operating an electric machine.

[0002] EP 1 104 050 A1 discloses an electrically conductive contact element consisting of at least two materials. The first material is electrically conductive and has a porous structure. This porous, matrix-like structure is at least partially permeated with a second material, for example, a thermoplastic or a thermoset. The contact element according to EP 1 104 050 A1 can, for example, be configured as a current collector for a tram. Furthermore, EP 1 104 050 A1 mentions the possibility of designing the contact element as a brush for an electric machine, in which case it can have a cubic, cuboid, or cylindrical shape. The porous material can be, for example, copper, brass, or aluminum. The porous material can be in the form of a metal foam. Bronze spheres, which are pressed and sintered, are suitable for manufacturing the contact element from a copper-containing alloy.The pores formed in the workpiece in this way should be large enough to be filled with a filler that has good lubricating properties, for example a thermoset with added lubricant.

[0003] Various assemblies intended for use in electrical machines, which transmit electrical currents between rotating and non-rotating elements in the presence of oil, are described, for example, in documents DE 10 2023 102 684 A1 and DE 10 2011 113 964 A1. The device described in the latter document is intended to be particularly suitable for underground use, with operation in a pressure-compensated enclosure.

[0004] A power transmission unit for separately excited synchronous machines, disclosed in WO 2024 / 114848A1, comprises several support laminations as electrically conductive elements. An electrical contact between the support laminations and a rotor shaft of the synchronous machine, i.e., the electrical machine, is established via unspecified electrical contacting means.

[0005] The invention is based on the objective of providing more advanced possibilities for the transmission of electrical currents between rotating and non-rotating components of electrical machines compared to the prior art, with the aim of achieving high operational reliability and longevity, as independent as possible from the environmental conditions.

[0006] This problem is solved according to the invention by a brush module of an electric machine, i.e., an electric motor or generator, configured according to claim 1. According to claim 8, the brush module is, among other things, suitable for use in a separately excited electric motor. The problem is also solved by a method for operating an electric machine configured according to claim 9. The embodiments and advantages of the invention described below in connection with the operating method also apply mutatis mutandis to the devices, i.e., the brush module and the electric machine, in particular in the form of an electric motor, and vice versa.

[0007] The brush module according to the application comprises several metallic, porous, oil-impregnated and oil-conducting grinding brushes, each of which is constructed of a single material and in one piece and is intended for contacting rotating current-carrying components of the electrical machine.

[0008] In contrast to unstressed constructions in which grinding brushes are treated with a non-metallic substance, for example an oil, such that the substance adheres to the surface of the material from which the grinding brush is made, the solution according to the application thus provides for an oil flow through the metallic material of the grinding brushes.

[0009] In this way, the compact, manufacturable design of the brush module creates particularly good conditions for using the oil as both a lubricant and a coolant and supplying it to the sliding contacts. Apart from the structuring provided by the pores, the sliding brushes in numerous configurations have a compact form with smooth outer surfaces. This means that the surface of a brush in contact with a slip ring of the electric machine, in particular, exhibits no macroscopic structuring, such as grooves. Therefore, the abrasion of such structures during the operation of the electric machine is inherently impossible.Rather, the brush module exhibits consistent properties throughout the entire lifespan of the electric machine, with the overall flat contact of the grinding brush with the slip ring, combined with a constant supply of sufficient lubricant even at the start-up of the electric machine, resulting in a uniform wear pattern on the slip ring and overall very low wear.

[0010] In particular, the grinding brushes have an open-pore structure. Such a structure can, for example, be foam-like. In this context, it is also referred to as a dendritic structure. The open-pore structure of the grinding brushes can also be formed by a granular structure. The granular structure of the grinding brushes can be formed, in particular, by spherical particles that are bonded together. Likewise, particles that are not spherical, for example, approximately cubic, rod-shaped, or irregularly shaped particles, can be processed into grinding brushes, which are used in the brush module, particularly through the application of pressure and heat.

[0011] Regardless of the exact manufacturing process, the porosity of each grinding brush is, for example, at least 10% and at most 90%, and in particular at least 20% and at most 80%. Porosity is defined as the proportion of voids to the total volume of the grinding brush. The pores can be isotropic or anisotropic in shape and distributed within the grinding brush.

[0012] According to one possible embodiment of the brush module, several coolant channels are provided for supplying oil to the grinding brushes, which are formed on both sides of a carrier plate between this carrier plate and a pole plate, wherein a first subset of the grinding brushes is arranged on the first pole plate and a second subset of the grinding brushes is arranged on the second pole plate.

[0013] The operating method described in the application is based on an electric machine comprising a brush module including a plurality of porous metallic grinding brushes. Within the framework of the method, a lubricant, which lubricates the sliding contacts formed between each grinding brush and a slip ring, is circulated through the porous material of the grinding brushes, among other things, to cool the brush module. In this process, the lubricant is guided through the grinding brushes, particularly with a tangential motion component in the direction of movement of the brush module and thus of the entire electric machine.

[0014] Two exemplary embodiments of the invention are explained in more detail below with reference to a drawing. This drawing shows: Fig. 1. A brush module of an electric machine in perspective view, Fig. 2 and Fig. 3 Details of the brush module according to Fig. 1, Fig. 4 the structure of a grinding brush of the brush module according to Fig. 1, Fig. 5 the structure of another grinding brush for a brush module in an analogous representation Fig. 4.

[0015] Unless otherwise stated, the following explanations refer to both embodiments. Corresponding or essentially equivalent parts are marked with the same reference numerals in all figures.

[0016] A brush module, designated as a whole by reference numeral 1, is intended for use in an electric machine, in this case a traction motor of an electrically powered motor vehicle. The electric motor, i.e., the traction motor, which comprises the brush module 1, is designed as a separately excited synchronous motor. Alternatively, the brush module 1 can be used, for example, in an electric motor of a rail vehicle or a stationary electric machine.

[0017] In the present cases, the brush module 1 comprises a total of six sliding brushes 2, which are also referred to simply as brushes, and are designed to contact a slip ring 14, which is rigidly connected to a shaft of the rotor of the electric motor to which it is energized. The slip ring 14 comprises a current transmission section 15, which is also referred to as the slip ring in the narrower sense, and a mounting section 16 held on the shaft of the electric motor.

[0018] A first group of three grinding brushes 2 is arranged on one side of a carrier plate 3 of the brush module 1. The carrier plate 3 is part of a housing 7 of the brush module 1, which is made of plastic and is not fully shown in the figures. A second group of three brushes 2 is arranged on the opposite side of the carrier plate 3. The brushes 2 are each mounted in a linear guide 4 and are each spring-loaded by a torsion spring 5. In the present case, the brushes 2 are designed as metal brushes, the design of which will be discussed in more detail below.

[0019] All sliding contacts through which the rotor of the electric motor is energized are lubricated with oil. Accordingly, the brush module 1 represents a wet current transmission system. Oil channels 17 are provided to supply the oil, which also serves as a coolant, and to deliver the lubricant directly to the individual sliding contacts.

[0020] Each group of three brushes 2 is located on a pole plate 6. Sandwiched between the two pole plates 6 is a plate section 8 of the carrier plate 3. The pole plates 6 and the plate section 8 lie in planes to which the central axis of the electric motor rotor forms a surface normal. The oil channels 17 are formed between the plate section 8 and the pole plates 6.

[0021] The central axis of the rotor of the electric machine is, by definition, aligned in the longitudinal direction, i.e., the axial direction, of the brush module 1. At the edge of the plate section 8, an edge section 9, also belonging to the housing 7, is formed, which projects beyond the plate section 8 and also the two pole plates 6 in the axial direction of the brush module 1.

[0022] Overall, the brush module 1, viewed in the longitudinal direction of the electric motor shaft, has a modified triangular shape, with the three sides of the approximately triangular support plate 3 being defined by concave-convex-concave curved regions of the edge section 9. A mounting contour 10 is formed between each pair of these three curved regions, in which a screw 11 is located. An opening 12, designed to receive the slip ring 14, is located centrally in the support plate 3. The central axis of the electric motor shaft is identical to the central axis of the opening 12. The brushes 2 are slidably mounted radially around the shaft, and thus also around the brush module 1, by means of linear guides 4, and are arranged at angular intervals of 120° around the shaft. Electrical leads connected to the brushes 2 are generally designated 13.

[0023] The grinding brushes 2 are made of an open-pored metallic material, wherein the metal generally designated as 20 is in particular an iron-based alloy, as in the embodiment according to the Fig. 1 to 4, or a non-ferrous metal, as in the embodiment shown in Fig. 5, can act.

[0024] The following in the exemplary embodiment Fig. 1 to 4 grinding brushes used 2 show, as from Fig. 4 shows a foam-like porous structure 18. In contrast, in the embodiment according to Fig. 5 a granular porous structure 19 of the grinding brushes 2. Also the grinding brushes 2 after Fig. 5, which were manufactured by sintering spherical particles, in this case made of bronze, are in brush module 1 according to Fig. 1 usable. In the exemplary embodiment according to the Fig. 1 to 4 the porosity of the grinding brushes 2 is the same as in the exemplary embodiment according to Fig. 5 in the range of 10% to 90%. In none of the embodiments are cavities within the porous structures 18, 19 filled with fillers, such as a synthetic resin or graphite. Rather, the grinding brushes 2 are designed as single-piece components of the brush module 1, made of a single material.

[0025] In both embodiments, the porous structure 18, 19 is an open-pore structure. The grinding brushes 2 thus function as oil-conducting components of the brush module 1. Lubricant can flow through the grinding brushes 2 in all spatial directions. In particular, during operation of the brush module 1 within the electric machine, the lubricant experiences a tangential motion component of the brush module 1.

[0026] This means that not only is lubricant adhering to the slip ring 14 carried along by the rotation of the electric motor shaft, filling, among other things, narrow gaps on the surfaces of the grinding brushes 2, but an oil flow around the shaft is also initiated, which partially penetrates the porous structures 18, 19. This benefits both the lubrication and cooling effects of the oil. Wear occurring on the grinding brushes 2 during operation of the brush module 1 has practically no effect on their properties, particularly with regard to electrical contact and friction in the sliding contact.

[0027] Due to the elimination of macroscopic structures on the surfaces of the grinding brushes 2, such as grooves running in the tangential direction of the shaft of the electric motor, wear-related changes in operating relevant properties, such as those that can otherwise occur, for example, due to the decreasing depth of grooves or other geometrically defined structures during operation, are fundamentally excluded.

[0028] Brush module 1 is, both in its design according to the Fig. 1 to 4 as well as in the design according to Fig.5, also suitable for high-speed electric motors. In no application are so-called break-in aids, such as a wavy surface design of the grinding brushes 2, required. The porous, oil-impregnated structure 18, 19, which is also permeable to oil to a small, but technically relevant extent, helps, among other things, to prevent the formation of lubricating wedges, which would negatively affect current transmission. Finally, the constant sliding contact between brush 2 and slip ring 14 throughout its entire service life has a beneficial effect on the vibration behavior of the brush module 1 and the entire electric motor. Reference symbol list 1 brush module 2 grinding brushes, brush 3 Carrier plate 4 linear guides 5 springs 6 pole plate 7 cases 8 plate section 9. Marginal section 10 Mounting contour 11 screw 12 Opening 13 Management 14 Slip ring 15 Power transmission section 16 Fastening section 17 Oil channel 18 porous structure, foam-like 19 porous structure, granular 20 Metal, porous material QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 1 104 050 A1

[0002] DE 10 2023 102 684 A1

[0003] DE 10 2011 113 964 A1

[0003] WO 2024 / 114848A1

[0004]

Claims

[1] Brush module (1) of an electric machine, comprising several metallic, porous, oil-impregnated and oil-conducting grinding brushes (2), each of which is made of a single material and is constructed in one piece and is intended for contacting rotating current-carrying components of the electric machine. [2] Brush module (1) according to claim 1, characterized by , that the grinding brushes (2) have an open-pore structure. [3] Brush module (1) according to claim 2, characterized by , that the open-pore structure of the grinding brushes (2) is foam-like. [4] Brush module (1) according to claim 2, characterized by , that the open-pore structure of the grinding brushes (2) is formed by a granular structure. [5] Brush module (1) according to claim 4, characterized by , that the granular structure of the grinding brushes (2) is formed by spherical particles that are materially bonded together. [6] Brush module (1) according to any one of claims 2 to 5, characterized by , that the porosity of each grinding brush (2) is at least 10% and at most 90%. [7] Brush module (1) according to any one of claims 1 to 6, characterized by , that several coolant channels (17) are provided for supplying oil to the grinding brushes (2), which are formed on both sides of a carrier plate (3) between this carrier plate (3) and each pole plate (6), wherein a first subset of the grinding brushes (2) is arranged on the first pole plate (6) and a second subset of the grinding brushes (2) is arranged on the second pole plate (6). [8] Externally excited electric motor comprising a brush module (1) according to claim 1. [9] Method for operating an electric machine comprising a brush module (1) including a plurality of metallic porous grinding brushes (2), wherein a lubricant which lubricates grinding contacts formed between a grinding brush (2) and a slip ring (14) is passed, inter alia, through the porous material (20) of the grinding brushes (2) for cooling the brush module (1). [10] Method according to claim 9, characterized by , that the lubricant is guided through the grinding brushes (2) with a movement component in the tangential direction of the brush module (1).

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