Brush module of an electric machine, electric motor and method for supplying lubricant to a brush module

Abstract

The invention relates to a brush module (10) of an electric machine (1), in particular of an electric motor, comprising a module plate (12) that has a central opening (26) for the passage of a shaft (4) of the electric machine (1), and contact brushes (15) that are arranged on both sides of the module plate (12) and intended to make contact with slip rings (16, 17) connected to the shaft (4), wherein the module plate (12) is designed as a lubricant-channelling element by virtue of the inner edge, surrounding said opening (26), of the module plate (12) having an at least partially roof-shaped ramp structure (25) that divides the lubricant flow over both sides of the module plate (12).

Description

[0001] Brush module of an electric machine, electric motor and method for supplying lubricant to a brush module

[0002] The invention relates to a brush module of an electric machine and to an electric motor with a brush module. Furthermore, the invention relates to a method for supplying lubricant to a brush module of an electric machine.

[0003] A brush holder disclosed in DE 10 2021 122 065 B3 is designed to hold at least two brushes for a sliding contact arrangement. The brush holder comprises a flat intermediate element and two contact elements arranged on opposite sides of the intermediate element. The brushes are guided on the contact elements and are spring-loaded in the radial direction of the brush holder. Channels for a coolant are formed within the brush holder according to DE 10 2021 122 065 B3.

[0004] German patent DE 374573 A discloses an oil-cooled electric machine in which a cooling fluid is pumped through a hollow machine shaft. The cooling fluid surrounds the stator components of the electric machine and circulates back to the hollow machine shaft without touching any external rotor components. The electric machine according to DE 374573 A is specifically a three-phase AC machine.

[0005] DE 10 2019 111 907 A1 relates to an electric drive with a shaft arrangement. Particular attention is paid to cooling and lubrication management. An oil channel is connected to an annular channel containing an oil guide ring. To influence the oil flow, the oil guide ring has at least one impact section. The shaft arrangement according to DE 10 2019 111 907 A1 can be part of an electric drive for a vehicle. The invention is based on the objective of further developing electric machines in which electric currents are transmitted between rotating and non-rotating parts, especially with regard to lubrication and cooling, compared to the prior art.

[0006] This problem is solved according to the invention by a brush module of an electric machine having the features of claim 1. The brush module can, in particular according to claim 8, be considered an electric motor. Likewise, the problem is solved by a method designed according to claim 9 for supplying lubricant to a brush module of an electric machine, i.e., an electric motor or a generator. The lubricant also functions as a cooling agent or, more generally, as a temperature control agent. For the sake of simplicity, the term "lubricant" is used throughout this text. The embodiments and advantages of the invention explained below in connection with the lubricant supply method also apply mutatis mutandis to the devices, i.e., the brush module and the electric machine equipped with the brush module, and vice versa.

[0007] The brush module, intended for use in an electric machine, in particular an electric motor, comprises a module plate having a central opening for the passage of a shaft of the electric machine. Grinding brushes are arranged on both sides of the module plate, which contact slip rings connected to the shaft. The module plate is designed as a lubricant-conducting element, with the inner edge of the module plate surrounding the opening having a ramp structure that is at least partially roof-like and divides the lubricant flow to both sides of the module plate.

[0008] The lubricant flow for the two groups of grinding brushes and associated slip rings, arranged on both sides of the module plate, is largely guided together before being divided shortly before the sliding contacts by a contour of the module plate, which is already present in some form as the edge of a central opening in the module plate. The division of the lubricant flow is thus achieved by reliable, passive means that require practically no additional space.

[0009] According to various possible configurations, a strip-shaped guide surface, running essentially tangentially to the shaft, adjoins the roof-like ramp structure on both sides. The oil supplied to the sliding contacts can thus flow mainly in the circumferential direction of the electric machine's shaft in this area.

[0010] The essentially strip-shaped guide surfaces can have a decreasing distance from the shaft's central axis in the circumferential direction, i.e., in the direction of oil flow determined by the shaft's rotation. Simultaneously, these same guide surfaces can have an increasing width, measured in the axial direction of the shaft, with decreasing distance from the central axis. Each guide surface can taper at its end—considered in the circumferential direction and thus in the direction of lubricant flow—which is closest to the axis of rotation, in the form of a terminal section that forms a larger angle relative to the tangential direction compared to the rest of the guide surface. In this way, a radial drip edge is formed at this end of the guide surface.

[0011] Regardless of the precise design of the guide surfaces, impact segments uniformly distributed around the circumference can be positioned in front of the ramp structure of the module plate in both axial directions. These impact segments extend further inwards in the radial direction than the ramp structure formed by the module plate. In this configuration, axial drip edges can be formed at the inner edge of the impact segments, which have the shape of upright tabs. On each side of the module plate, the drip edges can lie in a common plane that intersects the slip ring located on the same side of the module plate. The impact segments can be formed by pole plates on which the brushes of the brush module are slidably guided. The brushes are arranged in a circumferential section between two impact segments.The patented method for supplying lubricant to a brush module of an electric machine with a rotating shaft assumes that a lubricant flow is directed through the shaft in the axial direction. Furthermore, the lubricant is discharged from the shaft in its radial direction. The lubricant discharged from the shaft is supplied by a ramp structure, at least partially roof-like and formed by a module plate of the brush module, to several sliding contacts located on both sides of the module plate, i.e., each axially spaced from a central plane normal to the shaft and defined by the module plate.

[0012] According to one possible embodiment, the lubricant flow, which is divided into both axial directions by means of the ramp structure, is conveyed with motion components in the tangential direction, i.e. in the rotational direction of the shaft, as well as in the radial direction, namely in the direction towards the central axis of the shaft, whereby axial motion components of the lubricant flow are stopped by two pole plates parallel to the module plate, on which grinding brushes of the brush module are guided so as to be at least slightly displaceable.

[0013] The patented brush module is suitable not only for use in a separately excited electric motor, but also for use in a generator. Generally, the electric machine in which the brush module is used can be a machine in a vehicle or a stationary machine.

[0014] An embodiment of the invention is explained in more detail below with reference to a drawing. The drawing shows:

[0015] Fig. 1 shows a section of an electric motor in a cutaway perspective view, Fig. 2 shows a detail of the electric motor according to Figure 1 ,

[0016] Fig. 3 shows a shaft attachment of the electric motor according to Figure 1 ,

[0017] Fig. 4 shows a brush module of the electric motor surrounding the shaft attachment.

[0018] Fig. 5 shows a detail of the arrangement according to Figure 4 in a cutaway perspective view,

[0019] Fig. 6 shows the arrangement according to Figure 5 in a further sectional view,

[0020] Fig. 7 Components of the arrangement according to Figures 5 and 6 in front view,

[0021] Fig. 8 shows a further illustration of the brush module including several grinding brushes which contact a slip ring,

[0022] Fig. 9 shows a module plate of the brush module,

[0023] Fig. 10 shows a detail of the module plate.

[0024] An electric machine 1, shown incompletely in Figure 1, is designed as a separately excited electric motor, suitable, for example, for use as a traction motor in a motor vehicle. The rotor 2 of the electric motor 1 comprises current-carrying windings 3 and a shaft 4. Oil channels 5 for a lubricant are formed in the rotor 2. The oil channels 5 extend, among other things, through a rotor disk 6, which closes off the end face of the rotor 2. From the rotor disk 6, the lubricant flows into a shaft extension 7, which is also part of the rotor 2. The shaft extension 7 is firmly connected to the shaft 4 by means of a screw 8, which is screwed into a mounting washer 9 located in the shaft 4. The shaft extension 7, like the shaft 4, is hollow.

[0025] The rotor 2 is mounted, among other things, by means of a rolling bearing 11, in this case a ball bearing, which is mounted on the shaft end piece 7, in a housing of the electric machine 1 (not shown). The rolling bearing 11 is located, in the axial direction of the shaft 4 and thus of the entire electric machine 1, between the rotor disk 6 and a brush module 10. A module plate 12, made of plastic, is associated with the housing of the brush module 10 (which is shown only partially). The entire brush module 10 is essentially mirror-symmetrical about a plane passing centrally through the module plate 12. Electrical leads connected to the brush module 10, through which the windings 3 can be energized, are designated 13. On each side of the module plate 12 is a pole plate 14, on which three sliding brushes 15 are slidably guided.In the exemplary embodiment, the grinding brushes 15 are metal brushes.

[0026] The shaft extension 7, shown in isolation in Figure 3, comprises slip rings 16, 17, which are contacted by the grinding brushes 15 in the presence of lubricant. For conducting electrical current to the windings 3, the shaft extension 7 has electrical terminals 18 extending radially along the shaft 4, including the shaft extension 7. Axially offset in front of the electrical terminals 18, i.e., in the direction of the brush module 10, two parallel, spaced-apart annular grooves 19 are formed on the outer circumferential surface of the shaft extension 7. O-rings are inserted into these grooves as seals within the fully assembled electric machine 1.

[0027] Between the two annular grooves 19, a section of the shaft extension 7 is visible, in which several radial bores 20 are located. In the exemplary embodiment, the radial bores 20 are aligned with the oil channels 5, which are located in the rotor disk 6. An annular oil channel can also be formed between the oil channels 5 and the radial bores 20. In any case, the lubricant enters the interior of the shaft extension 7 via the radial bores 20. Approximately midway between the two end faces of the shaft extension 7, an intermediate disk 21 is formed integrally with the rest of the shaft extension 7. This disk has a shape similar to the rotor disk 6 but has a through-hole instead of a threaded bore. The head of the screw 8 rests on the intermediate disk 21.The intermediate washer 21 has several bores 22 located radially outside the head of the screw 8, which allow a flow of lubricant through the intermediate washer 21.

[0028] The lubricant that has escaped from the intermediate disk 21 flows into an annular space formed between the outer surface of the head of the screw 8 and an inner circumferential surface of the shaft attachment 7 designated 23, initially continuing in the axial direction of the rotor 2. From the annular space, the lubricant reaches several radial bores 24 that penetrate the inner circumferential surface 23.

[0029] The lubricant exiting the radial bores 24 of the shaft attachment 7 encounters a roof-like ramp structure 25, which is located at the inner edge of the module plate 12, i.e., at the edge of the opening of the module plate 12 designated 26 and of the entire brush module 10. Due to its roof-like shape, which can be seen, among other things, in Figures 5 and 6, the ramp structure 25 divides the lubricant flow, which impinges on the module plate 12 in a radial direction from the inside out, evenly into both axial directions, i.e., in the direction towards the two pole plates 14.

[0030] Details of the ramp structure 25 are shown, among other sources, in Figures 9 and 10. A strip-shaped guide surface 28, extending essentially in the tangential direction of the shaft 4, adjoins a so-called roof surface 27 of the ramp structure 25. The flow direction of the lubricant, which in this area essentially coincides with the tangential direction, is designated SR. The guide surface 28 has an increasing width in the flow direction SR, measured in the axial direction of the shaft 4. Simultaneously, the distance of the guide surface 28 from the central axis of the shaft end piece 7, designated MA, and thus from the entire shaft 4 and the electric machine 1, decreases in the flow direction SR. The guide surface 28 terminates in the flow direction SR with an end section 29, which is inclined at a larger angle to the tangential direction than all other sections of the guide surface 28.In the exemplary embodiment, the end section 29 connects to the remaining guide surface 28 with a bend 30. A radial drip edge 31 for the lubricant is formed in the end section 29. A step 32 adjoins the end section 29 in the circumferential direction, marking the beginning of the next roof surface 27 in the circumferential direction. In the exemplary embodiment, three roof surfaces 27 extend over an angle of 120° on each side of the module plate 12. The guide surfaces 28 each cover only a portion of the 120° angle.

[0031] The three grinding brushes 15, arranged on each side of the module plate 12, are located, viewed circumferentially, between three impact segments 33, which are formed directly by the pole plate 14 and project from it in the axial direction of the brush module 10. Flowing lubricant leaving the module plate 12 in either axial direction is thus stopped by the impact segments 33. The axial drip edges formed by the impact segments 33 are designated 34. From the axial drip edges 34, the lubricant reaches the surface of the slip rings 16, 17 and from there the sliding contacts formed by the grinding brushes 15. Lubricant exiting the brush module 10 can be pumped back into the rotor 2 by means of an oil pump (not shown).

[0032] List of reference symbols for electric machine, electric motor

[0033] rotor

[0034] winding

[0035] Wave

[0036] oil channel

[0037] rotor disk

[0038] shaft attachment

[0039] screw

[0040] Mounting washer

[0041] Brush module

[0042] rolling bearings

[0043] Module plate electrical line

[0044] Polar plate

[0045] Grinding brush

[0046] slip ring

[0047] slip ring

[0048] connector

[0049] Ring groove

[0050] radial bore

[0051] Intermediate disc

[0052] Drilling

[0053] Inner perimeter area

[0054] radial bore

[0055] Ramp structure

[0056] opening

[0057] Roof area

[0058] Guide surface

[0059] Final section

[0060] Bend 31 drip edge

[0061] Level 32

[0062] 33 Impact segment

[0063] 34 T drip edge

[0064] MA Central Axis

[0065] SR Flow direction

Claims

Patent claims 1. Brush module (10) of an electric machine (1), comprising a module plate (12) which has a central opening (26) for the passage of a shaft (4) of the electric machine (1), and grinding brushes (15) arranged on both sides of the module plate (12) which are provided for contacting slip rings (16, 17) connected to the shaft (4), wherein the module plate (12) is designed as a lubricant-conducting element in that the inner edge of the module plate (12) surrounding the said opening (26) has a ramp structure (25) that is at least partially roof-like and divides the lubricant flow to both sides of the module plate (12).

2. Brush module (10) according to claim 1 , characterized in that a strip-shaped guide surface (28) extending substantially in the tangential direction of the shaft (4) adjoins the roof-like ramp structure (25) on both sides.

3. Brush module (10) according to claim 2, characterized in that the guide surfaces (28) have a circumferentially decreasing distance from the central axis (MA) of the shaft (4).

4. Brush module (10) according to claim 3, characterized in that the guide surfaces (28) have a width that increases with decreasing distance from the central axis (MA), which can be measured in the axial direction.

5. Brush module (10) according to claim 3 or 4, characterized in that each guide surface (28) terminates at its end - to be considered in the circumferential direction - which has the smallest distance to the central axis (MA) in the form of an end section (29) which encloses a larger angle with respect to the tangential direction compared to the rest of the guide surface (28).

6. Brush module (10) according to one of claims 1 to 5, characterized in that impact segments (33) distributed uniformly around the circumference are positioned in front of the ramp structure (25) of the module plate (12) in both axial directions, wherein the impact segments (33) extend further inwards in the radial direction than the ramp structure (25) formed by the module plate (12).

7. Brush module (10) according to claim 6, characterized in that the impact segments (33) are formed by pole plates (14) on which grinding brushes (15) of the brush module (10) are slidably guided, wherein the Grinding brushes (15) are each arranged in a circumferential section between two impact segments (33).

8. Electric motor (1) comprising a brush module (10) according to claim 1.

9. Method for supplying lubricant to a brush module (10) of an electric machine (1) having a rotating shaft (4), wherein a lubricant flow is guided through the shaft (4) in the axial direction and is discharged from the shaft (4) in the radial direction, and wherein the lubricant discharged from the shaft (4) is supplied to several sliding contacts located on both sides of the module plate (12) by means of a ramp structure (25) formed by a module plate of the brush module (10) that is at least partially roof-like.

10. Method according to claim 9, characterized in that the lubricant flow, which is divided into both axial directions, is conveyed with motion components in the tangential direction, i.e. in the direction of rotation of the shaft (4), as well as in the radial direction, namely in the direction to the central axis (MA) of the shaft (4), wherein axial motion components of the lubricant flow are stopped by pole plates (14) on which grinding brushes (15) of the brush module (10) are slidably guided.

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