Current transmission device for energizing rotor winding of electric machine, and electric machine

Abstract

The invention relates to a current transmission device (10) for energizing a winding on a rotor of an electric machine, comprising: a slip ring unit (11) to which at least one slip ring (12) is fastened in a rotationally fixed manner, said slip ring being electrically connectable to the winding; a brush unit (13) on which at least two brushes (14) are held for energizing the slip ring (12) in parallel, the slip ring unit (11) being mounted so as to be rotatable about an axis of rotation (105) on the brush unit (13), the brushes (14) being held on the brush unit (13) in such a way that the brushes make contact with the slip ring (12) via a contact surface (15) in order to establish an electrical contact, the contact surface sweeps over a running surface (16) on the slip ring (12) during rotation of the slip ring unit (11), and wherein the brushes (14) are designed and arranged in such a way that the running surfaces (16) of the brushes on the slip ring (12) do not overlap one another; the invention also relates to an electric machine having a current transmission device (10) of this type.

Description

Technical Field

[0001] The invention relates to a current transmission device for energizing a winding on a motor rotor. The invention also relates to a motor of this type. Background Art

[0002] A separately excited motor has a rotor rotatably supported in a stator, the rotor being configured with a winding that can be energized via a current transmission system (also referred to herein as a current transmission device). For this purpose, the current transmission system typically has a slip ring unit and a brush unit. The slip ring unit has at least one slip ring. The brush unit typically has a plurality of brushes. During operation, the brushes slide in contact with the rotating slip rings along a so-called working surface (also referred to as a working track or trace) via a contact surface, wherein a plurality of the brushes use the same slip ring working surface.

[0003] Mechanical friction and current load between the brushes and the slip rings cause wear (material removal) of the slip rings, which limits the service life. Since a plurality of brushes use the same working surface, the wear of the slip rings is exacerbated.

[0004] To monitor wear, for example, DE 10 2014 007 690 A1 discloses a slip ring unit having a plurality of slip rings and associated brushes, wherein the working current between a position-fixed connection part and a rotating unit is always guided via a single brush and the associated slip ring. Wear monitoring of the slip ring unit provides two additional slip rings conductively connected to each other via an electrical connection to selectively guide a detection current via a brush in another slip ring to yet another additional slip ring, and to form a detection current loop via the brush assigned to the yet another additional slip ring and between the two brushes. In one embodiment, the two additional slip rings assigned to the detection current loop can also form a solid unit and be designed as a single slip ring without an additional electrical connection, the single slip ring contacting the two brushes of the detection current loop on two axially spaced-apart tracks.

[0005] Furthermore, from EP 3 021 428 A1, a structure of a slip ring module is known which, in a compact structural form, also increases the creepage distance between adjacent slip rings.

[0006] US2017 / 0214202 A1 discloses a wear indicator for monitoring the state of a slip ring system. Summary of the Invention

[0007] Against this background, an object of the present invention is to provide a current transmission device for energizing a rotor winding of a motor and a motor having the current transmission device, the current transmission device having low wear and high durability or a long service life.

[0008] This object is achieved by a current transmission device having the features described in claim 1 and an electric machine having the features described in claim 8. The corresponding dependent claims disclose particularly advantageous embodiments of the invention.

[0009] It should be noted that the features separately set forth in the claims can be combined with one another in any technically reasonable manner (even across category boundaries, for example, the boundary between a method and a device) and can represent other embodiments of the invention. The description characterizes and details the invention in particular in conjunction with the drawings.

[0010] It should also be noted that the conjunction “and / or” used here, which exists between two features and connects the features to each other, should always be interpreted such that in a first embodiment of the subject matter according to the invention, only the first feature can be present, in a second embodiment only the second feature can be present, and in a third embodiment both the first feature and the second feature can be present.

[0011] The subject matter of the invention is a current transmission device for energizing a winding on an electric machine rotor (also referred to here as the rotor winding). The current transmission device has a slip ring unit and a brush unit. At least one slip ring is non-rotatably fastened to the slip ring unit and can be electrically connected to the rotor winding or is electrically connected to the rotor winding in the state of being installed in the electric machine. For this purpose, the slip ring unit can provide, for example, an electrical connection part (such as a terminal, a tab, etc.) that is conductively connected to the slip ring on the one hand and can be electrically connected to the rotor winding on the other hand.

[0012] At least two brushes are held on the brush unit for energizing the slip rings in parallel. That is, during energization, currents in the same current direction are fed to the slip rings or extracted from the slip rings in parallel via the at least two brushes. At least two brushes are assigned to the same slip ring.

[0013] Furthermore, the slip ring unit is supported on the brush unit in a rotatable manner about a rotation axis, and the brushes are held on the brush unit such that the brushes establish electrical contact with the slip rings via contact surfaces that sweep over the working surfaces / active surfaces on the slip rings when the slip ring unit rotates (i.e., rotates relative to the brush unit). (Also referred to as the working track or locus). Preferably, the brushes are held in a manner that is elastic in the direction of the contact surfaces and exert an elastic pressure on the contact surfaces. According to the invention, at least two brushes are designed and arranged such that the corresponding working surfaces of the brushes on the slip rings do not overlap each other.

[0014] It is understood that the slip ring unit is mechanically connected to the rotor of the electric machine in a non-rotatable relative manner in the state of being installed in the electric machine according to the operating mode, so that the slip ring unit rotates relative to the brush unit together with the rotor.

[0015] In order to energize the rotor winding, at least one electrical connection part is preferably provided on the brush unit, and this electrical connection part is in conductive connection with the brush. Via this electrical connection part, the brush unit can be connected to an external energy source (such as in the motor operating mode) or an energy sink / energy absorber (such as in the generator operating mode). Accordingly, current can flow between the electrical connection part of the brush unit and the rotor winding electrically connected to the slip ring via the brush and the correspondingly contacted slip ring.

[0016] As described above, the brushes are arranged to energize the same slip ring in parallel, that is, the current directions of the currents flowing between at least two brushes and the assigned slip ring are the same. For example, in this way, a greater electric power can be transmitted between the brush and the slip ring and ultimately to the rotor winding. In any case, in the sense of the present invention, the current transmission between the brush and the assigned slip ring can provide sufficient electric power for the normal operation of the electric machine to energize the rotor winding. In addition, by energizing the slip ring in parallel via a plurality of brushes, redundancy in energization is provided, which significantly improves the reliability of the current transmission device or the electric machine.

[0017] Since each of at least two brushes in the current transmission device according to the present invention sweeps across its own, independent working surface on the slip ring, and this working surface does not overlap with the other working surfaces on the same slip ring, compared with the conventional configuration (in which multiple brushes share the same working surface on the slip ring), the wear of the slip ring working surface is significantly reduced. The present invention enables the total wear of the current transmission device to be distributed over a plurality of slip ring working surfaces, thereby significantly improving the durability or service life of the current transmission device.

[0018] In a preferred embodiment that achieves a particularly compact structure, at least three brushes are held on the brush unit, wherein the working surfaces of two of the three brushes on the slip ring at least partially overlap. Although the material removal in the overlapping area of the working surfaces is aggravated, in specific application cases, the more compact arrangement of the brushes has greater advantages compared with bearing higher wear. The current transmission device can be flexibly adapted to the corresponding application occasions in a structurally simple manner.

[0019] In an alternative preferred design, more than two brushes are held on the brush unit, and all these brushes sweep over non-overlapping working surfaces on the slip ring. In this way, the maximum durability of the current transmission device can be ensured, and at the same time, the power transmission capacity and / or reliability (redundancy) of the current transmission device can be improved.

[0020] In other embodiments, at least one of the working surfaces of the brush is located on the radially outer peripheral surface of the slip ring, that is, on the circumferential surface of the slip ring. This enables a radial arrangement of the brush relative to the slip ring, that is, the brush can be elastically preloaded relative to the circumferential surface of the slip ring in the radial direction. Thereby, a compact structure of the brush unit in the axial direction (that is, in the direction of the rotation axis of the slip ring unit) can be achieved. In a further embodiment, all the working surfaces of the brush are located on the radially outer peripheral surface (that is, the side surface) of the slip ring.

[0021] In another advantageous embodiment, at least one of the working surfaces of the brush is located on the axial end face of the slip ring. This allows an axial arrangement of the brush relative to the slip ring, that is, the brush can be elastically preloaded relative to the end face of the slip ring in the axial direction. This enables a compact structure of the brush unit in the radial direction (that is, in the direction perpendicular to the rotation axis of the slip ring unit). In different other embodiments, all the working surfaces of the brush are located on the axial end faces of the slip ring.

[0022] In yet another different embodiment, the working surfaces of the brush can be located on two axially opposite end faces of the slip ring.

[0023] It is conceivable that in further different embodiments, the above-described axial and radial arrangements of the brush are combined, that is, not only at least one of the brushes is arranged radially relative to the slip ring, but also at least another one of the brushes is arranged axially relative to the slip ring.

[0024] According to other preferred embodiments, at least two slip rings are fastened to the slip ring unit in a non-rotatable relative manner, wherein one slip ring can be electrically connected to the first pole (e.g., positive pole) of the winding or is electrically connected to the first pole of the winding in the state where it is already installed in the motor, and the other slip ring can be electrically connected to the second pole (e.g., negative pole) of the winding or is electrically connected to the second pole of the winding in the state where it is already installed in the motor. At least two brushes assigned to one slip ring and at least two brushes assigned to the other slip ring are held on the brush unit such that the brushes assigned to each slip ring establish electrical contact with the slip ring via corresponding contact surfaces, which sweep over the working surfaces on the corresponding slip ring when the slip ring unit rotates. The brushes assigned to the corresponding slip rings are designed and arranged such that the respective working surfaces of the brushes on the corresponding slip rings do not overlap each other. In other words, each slip ring of the slip ring unit supplies one pole of the rotor winding. The brushes assigned to a single slip ring ensure that the poles of the winding are energized in parallel. For each pole, the brushes are arranged and designed relative to the correspondingly assigned slip ring such that the working surfaces swept by the brushes on the same slip ring are separated and do not overlap.

[0025] Furthermore, the subject matter of the present invention is an electric motor having: a stator; a rotor rotatably supported in the stator, the rotor having at least one electrical winding; and a current transmission device for energizing the winding, wherein the current transmission device is designed according to one of the embodiments disclosed herein. The slip ring unit is connected to the rotor in a non-rotatable relative manner, such that the slip ring unit rotates together with the rotor. The rotor winding is electrically connected to at least one slip ring.

[0026] In a preferred embodiment, the electric motor is designed as a separately excited synchronous motor (FSM).

[0027] It can be understood that for the definitions of terms related to the electric motor and the effects and advantages of the features related to the electric motor, reference can be made entirely to the disclosure of the similar definitions, effects, and advantages of the current transmission device according to the present invention, and vice versa. Thus, for the sake of more concise description, repeated explanations of the same features, their effects, and advantages can be omitted, and such omission should not be construed as a limitation of one of the disclosed subject matters of the present invention. Description of the Drawings

[0028] Other features and advantages of the present invention result from the following description of embodiments of the present invention, which should not be understood as restrictive, and these embodiments are explained in more detail below with reference to the drawings. In the figures:

[0029] FIG. 1 schematically shows a perspective view of a current transmission device according to the prior art;

[0030] FIG. 2 schematically shows a partial side view of the current transmission device according to the prior art in FIG. 1;

[0031] Figure 3 A perspective view schematically showing a current transmission device according to an embodiment of the present invention; and

[0032] Figure 4 Schematically showing Figure 3 a side view of a part of the current transmission device in Detailed implementation manner

[0033] In different drawings, components that are the same in terms of function are always provided with the same reference numerals, and thus are generally only described once.

[0034] FIG. 1 shows a perspective view of a current transmission device 100 according to the prior art. The current transmission device 100 has a slip ring unit 101, and here, two slip rings 102 are fastened to the slip ring unit (see FIG. 2). In addition, the current transmission device 100 has a brush unit 103, and here, three brushes 104 for the slip rings 102 visible in FIG. 1 are held on the brush unit. The slip ring unit 101 is supported on the brush unit 103 in a rotatable manner about a rotation axis 105. The brushes 104 establish electrical contact with the corresponding slip rings 102. When the slip ring unit 101 rotates relative to the brush unit 103, the brushes 104 sweep across the working surface 106 on the slip rings 102, as shown in FIG. 2.

[0035] FIG. 2 shows a side view of a part of the current transmission device 100 according to the prior art in FIG. 1. This part is the part of the slip ring unit 101 where two slip rings 102 are arranged. It can be seen from FIG. 2 that all the brushes 104 assigned to the corresponding slip rings 102 use the same working surface 106. The mechanical friction and current load between the brushes 104 and the corresponding slip rings 102 cause increased wear (material removal) of the slip rings 102 because multiple brushes 104 use the same working surface for each slip ring 102.

[0036] Figure 3 A perspective view of a current transmission device 10 according to an embodiment of the present invention is shown. The current transmission device 10 is used to energize an electric winding (also not shown) on a rotor (also not shown) of a (not shown) motor, and has a slip ring unit 11, on which at least one slip ring 12 (here two slip rings 12) is fastened in a non-rotatable relative manner. The at least one slip ring or here the two slip rings 12 can be electrically connected to the winding, or can be electrically connected to the winding in a state where the current transmission device 10 is installed in the motor.

[0037] In addition, the current transmission device 10 has a brush unit 13, and this brush unit is in Figure 3is shown semi-transparently so that the two slip rings 12 of the slip ring unit 11 are visible. At least two brushes 14 are held on the brush unit 13 for energizing each slip ring 12 in parallel. In the embodiment shown here, three brushes 14 are provided for each slip ring 12 for parallel energization, but this number is not necessarily fixed. More than three brushes 14 or just two brushes 14 can also be provided for each slip ring 12.

[0038] The slip ring unit 11 is supported on the brush unit 13 in a rotatable manner about the axis of rotation 105. In combination with an electric motor not shown here, for example a separately excited synchronous motor, the slip ring unit 11 is connected to the rotor in a non-rotatable manner, so that these two components rotate together about the axis of rotation 105 relative to the brush unit 13 during motor operation.

[0039] Furthermore, the brushes 14 are held on the brush unit 13 such that the brushes establish electrical contact by contacting the respective slip rings 12 via contact surfaces 15, wherein the contact surfaces 15 sweep over working surfaces 16 on the respective slip rings 12 when the slip ring unit 11 rotates relative to the brush unit 13, as Figure 4 shown.

[0040] Figure 4 is shown Figure 3 a partial side view of the current transmission device 10 in. The part shown is the part of the slip ring unit 11 where two slip rings 12 are correspondingly arranged. From Figure 4 it is known that the brushes 14 assigned to the respective slip rings 12 (in Figure 4 two of the contact surfaces 15 can be seen for each slip ring 12 respectively) use separate working surfaces 16 (also called working tracks or traces). That is to say, the working surfaces 16 of the brushes 14 assigned to the same slip ring 12 and energizing the slip ring in parallel do not overlap each other. The wear of each working surface 16 is reduced, and the total wear of the slip ring 12 is distributed over a plurality of working surfaces 16. The durability or service life of the slip ring 12 is significantly improved.

[0041] In order to form non-overlapping working surfaces 16 for each slip ring 12, in the present case, the brushes 14 can be held on the brush unit 13 in a manner that they are correspondingly offset from each other in the axial direction, that is, in the direction of the axis of rotation 105.

[0042] In Figure 3 and Figure 4In the embodiment of the current transmission device 10 shown, the brush 14 is elastically held relative to the respective slip ring 12 in the radial direction, that is, perpendicular to the axis of rotation 15. Thereby, the working surface 16 of the brush 14 lies on the radial outer peripheral surface (i.e., the side surface) of the respective slip ring 12. However, the present invention is not limited to the radial arrangement of the brush 14 and the working surface 16. At least one or all of the brushes 14 can also be arranged on the brush unit 13 such that the working surface 16 of the brush 14 lies on the axial end face 17 of the respective one or more slip rings 12 (i.e., on the same end face or on opposite end faces 17).

[0043] It is understandable that in the case where the (multiple) brushes are arranged axially, instead of the shown slip rings 12, a sliding disk (not shown) can be provided, which provides the same function as the slip ring 12, but can have a larger radial extension length compared to the slip ring 12. Conversely, in terms of axial extension, the sliding disk can be configured to be shorter than the slip ring 12. Thereby, on the one hand, the material for the slip ring or the sliding disk can be saved, and on the other hand, a larger total area can be provided for arranging a plurality of non-overlapping working surfaces (i.e., the working surface 16) on one / more axial end faces 17.

[0044] In Figure 3 In the exemplary current transmission device 10 shown, one of the two slip rings 12 is electrically connected or can be electrically connected to the first pole (e.g., the positive pole) of a winding (not shown), and the other of the two slip rings 12 is electrically connected or can be electrically connected to the second pole (e.g., the negative pole) of the winding. That is, all the brushes 14 assigned to one of the slip rings 12 supply power to the corresponding pole of the winding in parallel. The corresponding pole of the winding can be electrically connected to the respective slip ring 12 via an electrical connection portion 18 (e.g., a terminal) provided on the slip ring unit 11.

[0045] List of reference numerals:

[0046] 10 Current transmission device

[0047] 11 Slip ring unit

[0048] 12 Slip ring

[0049] 13 Brush unit

[0050] 14 Brush

[0051] 15 Contact surface

[0052] 16 Working surface

[0053] 17 End face

[0054] 18 Connection portion

[0055] 100 Current transmission device according to the prior art

[0056] 101 Slip Ring Unit

[0057] 102 Slip Ring

[0058] 103 Brush Unit

[0059] 104 Brush

[0060] 105 Axis of Rotation

[0061] 106 Working Surface

Claims

1. A current transmission device (10) for energizing a winding on a rotor of an electric motor, the current transmission device comprising: a slip ring unit (11), on which at least one slip ring (12) is fixed in a relatively rotationally fixed manner, and the slip ring can be electrically connected to the winding; a brush unit (13), on which at least two brushes (14) are held for energizing the slip ring (12) in parallel, wherein: The slip ring unit (11) is supported on the brush unit (13) in a manner that it can rotate about a rotation axis (105), and the brushes (14) are held on the brush unit (13) in such a way that the brushes contact the slip ring (12) via contact surfaces (15) to establish electrical contact, and the contact surfaces sweep over the working surfaces (16) on the slip ring (12) when the slip ring unit (11) rotates, wherein the brushes (14) are designed and arranged so that the corresponding working surfaces (16) of the brushes on the slip ring (12) do not overlap each other.

2. The current transmission device according to claim 1, characterized in that: At least three brushes (14) are held on a brush unit (13), wherein the running surfaces (16) of two of the three brushes (14) on the slip ring (12) at least partially overlap.

3. The current transmission device according to claim 1, characterized in that: More than two brushes (14) are held on the brush unit (13), all of which sweep over non-overlapping running surfaces (16) on the slip ring (12).

4. A current transmission device according to any one of the preceding claims, characterized in that At least one of the working surfaces (16) of the brush (14) is located on the radial outer peripheral surface of the slip ring (12).

5. A current transmission device according to any one of the preceding claims, characterized in that At least one of the working surfaces (16) of the brush (14) is located on the axial end surface (17) of the slip ring (12).

6. The current transmission device according to claim 5, characterized in that: At least two of the working surfaces (16) of the brush (14) are located on two opposite axial end surfaces (17) of the slip ring (12).

7. A current transmission device according to any one of the preceding claims, characterized in that At least two slip rings (12) are fixed on a slip ring unit (11) in a non-rotatable manner, one of the slip rings being electrically connected to a first pole of a winding and the other slip ring being electrically connected to a second pole of the winding, and at least two brushes (14) assigned to one slip ring (12) and at least two brushes (14) assigned to another slip ring (12) are held on a brush unit (13) in such a manner that the brushes (14) assigned to the respective slip rings (12) contact the slip rings (12) via respective contact surfaces (15) to establish electrical contact, the contact surfaces sweeping over working surfaces (16) on the respective slip rings (12) when the slip ring unit (11) rotates, wherein the brushes (14) assigned to the respective slip rings (12) are designed and arranged so that the respective working surfaces (16) of the brushes on the respective slip rings (12) do not overlap with each other.

8. An electric machine comprising: a stator; a rotor rotatably supported in the stator, the rotor having at least one electrical winding; and a current transmission device (10) for energizing the winding, wherein: The current transmission device (10) is designed according to any of the preceding claims, wherein the slip ring unit (11) is connected to the rotor in a rotationally fixed manner and the winding is electrically connected to at least one slip ring (12). 9 . The electric machine according to claim 8 , which is designed as a separately excited synchronous machine.

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