Current transfer device for a rotor of an electric machine
The current transmission device addresses the challenges of complex connections and wear-related contact loss by using angled or curved spring elements to generate transverse forces, ensuring permanent contact and cost-effective, wire-free operation.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SCHAEFFLER TECHNOLOGIES AG & CO KG
- Filing Date
- 2026-01-08
- Publication Date
- 2026-07-23
Smart Images
Figure DE2026100010_23072026_PF_FP_ABST
Abstract
Description
[0001] Power transmission device for a rotor of an electric machine
[0002] The invention relates to a power transmission device for a rotor of an electric machine according to the type defined in more detail in the preamble of claim 1.
[0003] From DE 102006035441 A1, a brush holder with a carbon brush holder is known, which forms a guide for a carbon brush. A retaining spring presses the carbon brush against a first guide side of the guide with a holding force. It has two sections pre-tensioned against each other, between which both the carbon brush holder and the carbon brush are arranged in sections.
[0004] In DE 10241 382 A1, a brush arranged in a brush guide for a mechanically commutated dynamo-electric machine with a commutator with lamellae is disclosed, wherein an elastic element presses the brush against the lamellae and exerts a force on the brush at an angle deviating from the perpendicular to the end face of the brush facing the commutator.
[0005] A current transmission device for a rotor of an electric machine is known from DE 10 2023 103 005 A1, wherein the current transmission device has an annular disk that circumferentially, at least partially, surrounds a rotor shaft of the rotor, so that the rotor shaft rotates relative to the annular disk. At least one electrical contacting means is arranged on the annular disk, which is in electrically conductive contact with at least one circumferentially extending conductor track of the rotor shaft, wherein the guide means(s) is / are formed monolithically with the annular disk.
[0006] EP 1 763 123 A1 discloses a brush system for an electric motor, comprising a base body, two current guides, two interference suppression chokes, and a pressure spring for each pair of brushes, wherein the interference suppression chokes and the pressure springs each form a common helical and / or spiral component. The invention is therefore based on the objective of proposing a current transmission device of the aforementioned type, which improves electrical current transmission in a structurally simple and cost-effective manner.
[0007] The problem is solved by the features of claim 1. Further advantageous and claimed embodiments are described in the respective dependent claims, the description, and the drawings.
[0008] Thus, a current transmission device for the rotor of an electric machine is proposed, comprising at least one plate-shaped contact carrier on which several brushes are arranged for transmitting electric current to a sliding contact of the electric machine, which is coaxial to the rotor axis and associated with the contact carrier. The brushes are each guided in a brush holder and biased against the sliding contact with a normal force.The design provides that, for the application of spring elements to pre-tension the brushes, a contact surface is formed that runs obliquely or curved relative to the direction of the normal force. This allows the spring elements acting on the contact surface to generate, in addition to the normal force, a force acting transversely to it, pressing the respective brush against the electrically conductive contact carrier or brush holder. This ensures that a permanent, defined electrical current is transmitted or introduced to the brushes only through the contact carrier or brush holder. The spring elements are guided on the respective contact surface to compensate for brush wear and to ensure a largely constant normal force exerted by the spring elements against the sliding contact.
[0009] In this way, the spring element that generates the normal force for pressing the brush against the sliding contact simultaneously creates a lateral force for pressing the respective brush against the contact carrier or brush holder, thus ensuring a permanently defined contact of the brushes. This prevents any potential loss of contact between the contact carrier and brush holder during operation and eliminates the need for additional components, particularly the installation of further spring elements. Since the contact carrier and the brush holder are electrically conductive, a permanently defined current transmission or introduction to the brushes can be ensured, and additional electrical connections to the brushes, especially an additional wire for current transmission, can be avoided, thus realizing a wire-free current transmission device in a structurally simple manner.This also eliminates additional manufacturing and assembly costs, particularly for ensuring adequate electrical insulation of the connections from the adjacent components. Furthermore, it avoids any potential limitation of the brush travel for wear adjustment due to the wire length.
[0010] In a preferred embodiment of the invention, the contact surface is designed as a slope extending transversely to the direction of the normal force and rising axially towards the contact carrier. This allows a force to be generated acting transversely to the normal force in the axial direction, specifically directed towards the contact carrier, to press the respective brush against it.
[0011] It is also conceivable that the contact surface is designed as a slope running perpendicular to the direction of the normal force and descending axially towards the contact carrier, so that it rises axially away from it. This allows for the generation of a force acting perpendicular to the normal force in the axial direction, specifically directed towards the brush holder, to press the respective brush against it.
[0012] In a further preferred embodiment of the invention, the contact surface is designed as a slope extending transversely to the direction of the normal force and transversely to the axial direction. In this way, a force can be generated that is specifically directed towards the brush holder for pressing the respective brush against it.
[0013] In a further embodiment of the invention, the contact surface is designed as a bulge. Preferably, the contact surface is designed as a concave bulge. This allows a force acting transversely to the normal force to press the respective brush against the contact carrier or the respective brush holder.
[0014] It is also conceivable to design the contact surface as a convex curve. Furthermore, it is advantageous if the contact surface is preferably formed at the bottom of a groove, the side walls of which each secure a spring end of the spring element, which rests against the bottom of the groove or against the contact surface to pre-tension the respective brush, against axial migration.
[0015] In a further particularly preferred embodiment, the brushes are made of metal, which improves wear resistance and current flow, and simplifies the manufacturing process, especially of the contact surface. This applies particularly to a design as a solid metal brush.
[0016] In a further embodiment of the invention, the spring elements are designed as torsion springs, with the end of one spring leg applied to the contact surface of the respective brush to create a preload. The torsion spring generates a largely constant force through its deflection, pressing the respective brush against the associated sliding contact. Thus, the wear of the brush ensures both a largely constant normal force for pressing against the sliding contact and a largely constant force, generated at the contact surface and acting perpendicular to the normal force, for pressing against the contact carrier or the brush holder.
[0017] Manufacturing can be further simplified and the number of components reduced if the brush holder is made of electrically conductive metal as a single unit with the contact carrier.
[0018] A particularly simple design of the brush holder can be achieved if it has two opposing retaining brackets that encompass the respective brush laterally on the outer circumference and at least partially on the upper side facing away from the contact carrier.
[0019] Furthermore, it is advantageous if the contact carrier is made of sheet metal, thus saving weight and being easy and inexpensive to manufacture. Preferably, the retaining clips are punched out of the contact carrier in a particularly simple manner and bent into their holding position to accommodate the respective brush.
[0020] The proposed wireless power transmission device is particularly advantageous for use in an electric machine of an electrically powered vehicle, especially an electrically powered passenger car.
[0021] Further claimed features of the invention will become apparent from the following description and from the drawings, which further explain the present invention. The drawings show:
[0022] Figure 1 shows a current transmission device according to the invention for a rotor of an electric machine in a perspective view,
[0023] Figure 2 shows an enlarged section of Figure 1 with a brush of the power transmission device in a first embodiment,
[0024] Figure 3 is a perspective close-up view of the brush from Figure 2.
[0025] Figure 4 shows the brush from Figure 3 in a longitudinal section along the cutting plane A-A,
[0026] Figure 5 shows a sectional view of the brush from Figure 4 with the brush holder, the contact carrier and the spring means of the current transmission device.
[0027] Figure 6 shows an enlarged section of Figure 1 with a brush of the current transmission device in a second embodiment,
[0028] Figure 7 is a perspective close-up view of the brush from Figure 6; Figure 8 shows the brush from Figure 7 in a cutaway top view along the section plane AA.
[0029] Figure 9 shows a sectional view of the brush from Figure 8 with the brush holder, the contact carrier and the spring means of the current transmission device.
[0030] Figure 10 shows the brush from Figure 2 in a longitudinal section in a third embodiment,
[0031] Figure 11 shows a sectional view of the brush from Figure 10 with the brush holder, the contact carrier and the spring means of the current transmission device.
[0032] Figure 12 shows the brush from Figure 2 in a cutaway top view in a fourth embodiment,
[0033] Figure 13 shows a sectional view of the brush from Figure 12 with the brush holder, the contact carrier and the spring means of the current transmission device.
[0034] The figures show various views and embodiments of a current transmission device according to the invention for a rotor of an electric machine by way of example.
[0035] The current transmission device shown in Figure 1 has two identical, plate-shaped contact carriers 1, 2, each with three brushes 3, 4, 5 assigned to an electrical pole for transmitting electrical current to a corresponding sliding contact 6, 7 of the electric machine. Only one of each of the contact carriers 1, 2 and sliding contacts 6, 7 is shown. The contact carriers 1, 2 are preferably attached to opposite sides of a plate-shaped base 8 by means of screw connections. They are made of electrically conductive metal and are each connected to an electrical power source, while the base 8 also serves as an insulator and is preferably made of plastic. The current transmission device can be attached to a stationary component, for example, a housing of the electric machine, preferably by means of screw connections, via the base 8.
[0036] The base support 8 and the contact carriers 1, 2 are each arranged radially inside, coaxially along an imaginary rotor axis 9 (the axis of rotation and central axis of the rotor, not shown), with a central through-hole. In this way, they form a central through-hole 10 in the power transmission device, through which a shaft 11, in particular the rotor shaft of the electric machine, is axially guided. A slip ring 6, 7 is fixedly mounted on the shaft 11 as a sliding contact. The slip rings 6, 7 are integrated into a slip ring module 12 arranged on the shaft 11 and electrically connected to the rotor via this module.
[0037] The brushes 3, 4, 5 are arranged evenly distributed around the circumference of the through-hole 10. They are solid metal brushes, preferably made of brass or bronze, with a rectangular, elongated shape, and are each arranged in a brush holder 13, 14, 15 on the axial outer sides of the contact carriers 1, 2. To compensate for wear on the sliding contact 6, 7, they are spring-loaded and slidably guided in the brush holders 13, 14, 15. The brushes 3, 4, 5 each have a sliding contact surface 16, 17, 18 formed at one end facing the through-hole 10, which is in electrical sliding contact with the respective slip ring 6, 7.
[0038] According to Figures 1, 2, and 6, each brush 3, 4, 5 rests on the contact carrier 1 with its flat, wide underside 25. It is held at its narrow side surfaces and at its flat, wide upper surface 26, facing away from the underside, by two opposing retaining brackets forming the respective brush holders 13, 14, 15. To press the brushes 3, 4, 5 against the respective sliding contact or slip ring 6, 7, spring elements 19, 20, 21 are provided on the axial outer sides of the contact carriers 1, 2. These are preferably designed as torsion springs and each spring end 22, 23, 24 of a spring leg engages the end face of the contact surface 30, 31, 32, 33 formed away from the sliding contact surface 16, 17, 18, with a preload.The spring force transmitted at the contact surface 30, 31, 32, 33 of the respective brush 3, 4, 5 from the adjacent spring end 22, 23, 24 presses the respective brush 3, 4, 5 against the slip ring 6 with a normal force FN.
[0039] For the engagement of the spring elements 19, 20, 21, a groove 27 is formed on the end face of the end of each brush 3, 4, 5 facing away from the grinding contact surface 16, 17, 18. This groove runs continuously along the entire length of the end face, parallel to the flat underside 25 and the flat upper surface 26 of each brush 3, 4, 5. The respective spring end 22, 23, 24 engages in the groove 27. To engage the respective spring end 22, 23, 24, a contact surface 30, 31, 32, 33 is formed at the bottom of the groove 27. This contact surface is inclined or curved in the direction of the normal force FN and is formed in various configurations as shown in Figures 3 to 5, Figures 7 to 9, Figures 10 and 11, and Figures 12 and 13.The side walls 28, 29 of the groove 27 each secure the spring end 22, 23, 24, which rests against the contact surface 30, 31, 32, 33 formed on the bottom of the same for pre-tensioning the respective brush 3, 4, 5, against migrating in an axial direction towards the top or bottom 25, 26 of the respective brush 3, 4, 5.
[0040] The contact surfaces 30, 31, 32, 33 each extend along the groove 27, so that the displacement of the respective brush 3, 4, 5 caused by wear on the sliding contact 6, 7 does not break the contact of the respective spring end 22, 23, 24 with the respective contact surface 30, 31, 32, 33. The latter can also extend over the entire length of the groove 27.
[0041] The contact surfaces 30, 31, 32, 33 are designed such that, in addition to the normal force FN pressing the respective brush 3, 4, 5 against the slip ring 6, the spring force of the adjacent spring elements 19, 20, 21 generates a transverse force FQ acting perpendicular to the normal force FN, pressing the respective brush 3, 4, 5 against the contact carrier 1 or the respective brush holder 13, 14, 15 (Figures 5, 9, 11 and 13). This ensures permanent electrical contact between the respective brush 3, 4, 5 and the contact carrier 1 or the respective brush holder 13, 14, 15 during operation. Consequently, current transmission via the electrically conductive contact carrier 1 and / or the respective brush holder 13, 14, 15 to the respective brush 3, 4, 5 can be guaranteed. Therefore, the need for complex additional electrical connections to brushes 3, 4, 5, for example by means of a wire each, can be avoided.The power transmission device shown in Figure 1 is therefore designed without wires.
[0042] Figures 2 to 5 and Figures 6 to 9 show a first and a second embodiment of a current transmission device according to the invention with a contact surface 31 or 32 designed as an incline on the brushes 3, 4, 5. The incline 30, 31 runs along the bottom of the groove 27 (Figures 3 and 4 or 7 and 8).
[0043] In the first embodiment according to Figures 2 to 5, the inclined plane 30 runs in the axial direction indicated by the double arrow 9, the latter being defined by the imaginary rotor axis 9 in Figure 1. It thus runs transversely to the longitudinal direction of the groove 27 between the side walls 28, 29 thereof and is preferably inclined towards the side wall 29 facing the underside 25 of the respective brush 3, 4, 5 or towards the contact carrier 1. As a result, the spring force transmitted by the respective spring end 22, 23, 24 generates, in addition to the normal force FN, a force FQ directed transversely to the normal force FN in the axial direction towards the contact carrier 1 (Figure 5). Consequently, the force FQ presses the respective brush 3, 4, 5, particularly with its flat underside 25, against the flat axial outer surface of the contact carrier 1, thus ensuring permanent contact between them for current transmission.
[0044] In contrast, in the second embodiment according to Figures 6 to 9, the inclined plane 31 on the brushes 3, 4, 5 is designed to run transversely to the direction of the normal force FN and transversely to the axial direction 9. It thus extends in the longitudinal direction of the groove 27 (Figures 6 to 8). Accordingly, the spring force transmitted by the respective spring end 22, 23, 24 generates, in addition to the normal force FN, a force FQ directed transversely to the normal force FN in the longitudinal direction of the groove 27 (Figure 9). Consequently, the respective brush 3, 4, 5 is pressed particularly against one of the opposing retaining brackets of the respective brush holder 13, 14, 15 by the force FQ, and permanent contact for current transmission is ensured between them. The force FQ is directed against the retaining bracket 13, 14, 15 which lies in the rising direction of the inclined plane 31 (Figure 9).
[0045] A third and a fourth embodiment according to Figures 10 and 11 and Figures 12 and 13 respectively show a current transmission device according to the invention with a contact surface 32 or 33 designed as a concave curvature on the brushes 3, 4, 5. The curvature 32, 33 is in each case formed on the bottom of the groove 27 (Figures 3 and 4 and 7 and 8 respectively).
[0046] The concave curvature 32 in the third embodiment according to Figures 10 and 11 extends in the axial direction indicated by the double arrow 9. It thus runs between the side walls 28, 29 of the groove 27 and is preferably designed to rise towards the side wall 29 facing the underside 25 of the respective brush 3, 4, 5, or towards the contact carrier 1. Accordingly, the spring force transmitted by the respective spring end 22, 23, 24 generates, in addition to the normal force FN, a force FQ directed transversely to the normal force FN in the axial direction towards the contact carrier 1 (Figure 11). Consequently, the force FQ presses the respective brush 3, 4, 5, particularly with its flat underside 25, against the flat axial outer surface of the contact carrier 1, thus ensuring permanent contact between them for current transmission.
[0047] In the second embodiment according to Figures 12 and 13, a concave curvature 33 is formed on the brushes 3, 4, 5, extending transversely to the direction of the normal force FN and transversely to the axial direction 9. It thus extends in the longitudinal direction of the groove 27 (Figure 12). Accordingly, the spring force transmitted by the respective spring end 22, 23, 24 generates, in addition to the normal force FN, a force FQ directed transversely to the normal force FN in the longitudinal direction of the groove 27 (Figure 13). Consequently, the force FQ presses the respective brush 3, 4, 5 particularly against one of the opposing retaining brackets of the respective brush holder 13, 14, 15, ensuring permanent contact between them for current transmission. The force FQ is directed against the retaining bracket 13, 14, 15 located in the rising direction of the curvature 33 (Figure 13).According to Figures 1, 2 and 6, the brush holders 13, 14, 15 are each integrally formed with the contact carrier 1 and are electrically conductive, preferably made of sheet metal. The retaining brackets of the brush holders 13, 14, 15 are punched out of the contact carrier 1 and bent into their holding position to accommodate the respective brush 3, 4, 5.
[0048] Spring holders 37, 38, 39, connected to the base carrier 8, are guided axially through the punched-out through-holes 34, 35, 36, projecting through the contact carrier 1. The spring holders 37, 38, 39 are preferably formed integrally with the base carrier 8. The torsion springs 19, 20, 21 are each fitted with their helical spring body onto the projecting spring holders 37, 38, 39 and are pre-tensioned with one leg 22, 23, 24 against the contact surface 30, 31, 32, 33 of the respective brush 3, 4, 5, while the other leg is supported on the base carrier 8.
[0049] The contact carriers 1, 2, each attached to the base carrier 8, with the brushes 3, 4, 5 and the spring means 19, 20, 21 arranged on them, form a pre-assemblable modular unit with the base carrier 8, which can be easily mounted on the electric machine.
[0050] Due to the design of the base carrier 8, especially in plastic, the proposed power transmission device can be adapted particularly easily to the installation conditions, especially to the rotor shaft of the electric machine.
[0051] In this way, the power transmission device can be manufactured as a prefabricated module with flexible design and construction, as a standardized, cost-saving version with identical or largely identical and few components, and thus in particularly cost-effective series production. This applies especially to the contact carriers 1, 2 with the brushes 3, 4, 5 attached to them for sliding contact with the slip rings 6, 7 of the slip ring module 12. (List of reference symbols for contact carriers)
[0052] Contact carrier
[0053] brush
[0054] brush
[0055] brush
[0056] Slip contact, slip ring
[0057] Slip contact, slip ring
[0058] basic support
[0059] Rotor axis, rotation and central axis through hole
[0060] shaft, rotor shaft
[0061] Slip ring module
[0062] Brush holder, retaining bracket brush holder, retaining bracket brush holder, retaining bracket grinding contact surface
[0063] Grinding contact surface
[0064] Grinding contact surface
[0065] Spring elements
[0066] Spring elements
[0067] Spring elements
[0068] spring end, spring leg
[0069] spring end, spring leg
[0070] spring end, spring leg
[0071] bottom
[0072] Top
[0073] Nut
[0074] side wall
[0075] side wall
[0076] Contact surface, slope
[0077] Contact surface, slope
[0078] Contact surface, curvature 33 Contact surface, curvature 34 Through opening 35 Through opening 36 Through opening 37 Spring holder
[0079] 38 spring holders
[0080] 39 spring holders
[0081] FN Normal force
[0082] FQ Kraft
Claims
Patent claims 1. Current transmission device for a rotor of an electric machine, comprising at least one plate-shaped contact carrier (1) on which several brushes (3, 4, 5) are arranged for the transmission of electric current to a sliding contact (6, 7) of the electric machine, which is coaxial to the rotor axis (9) and associated with the contact carrier (1), wherein the brushes (3, 4, 5) are each guided in a brush holder (13, 14, 15) and biased against the sliding contact (16, 17, 18) with a normal force (FN), characterized in that a contact surface (30, 31, 32, 33) extending obliquely or curved relative to the direction of the normal force (FN) is formed for the application of spring means (19, 20, 21) for biasing the brushes (3, 4, 5), such that the acting spring means (19, 20, 21) exert, in addition to the normal force (FN), a force corresponding to this transverse force (FQ) for pressing down the respective brush (3, 4,5) can be generated on the electrically conductive contact carrier (1) or the respective electrically conductive brush holder (13, 14, 15) in such a way that a permanent, defined electrical current transmission or introduction to the brushes (3, 4, 5) is provided only through the contact carrier (1) or the respective brush holder (13, 14, 15), wherein the spring means (19, 20, 21) are guided on the respective contact surface (30, 31, 32, 33) in such a way that compensation for the displacement of the respective brush (3, 4, 5) caused by wear of the brush and a largely constant normal force (FN) of the spring means (19, 20, 21) for pressing against the sliding contact (16, 17, 18) is ensured.
2. Current transmission device according to claim 1, characterized in that, for pressing the respective brush onto the contact carrier (1), the contact surface (30) is designed as a slope extending transversely to the direction of the normal force (FN) and in the axial direction towards the contact carrier (1).
3. Current transmission device according to claim 1, characterized in that, for pressing the respective brush against the respective brush holder (13, 14, 15), the contact surface (31) is designed as a slope extending transversely to the direction of the normal force (FN) and transversely to the axial direction.
4. Power transmission device according to claim 1, characterized in that the contact surface (32, 33) is designed as a concave curvature.
5. Power transmission device according to one of claims 1 to 4, characterized in that the contact surface (30, 31, 32, 33) is formed on the bottom of a groove (27), the side walls (28, 29) of which each secure a spring end (22, 23, 24) of the spring means (19, 20, 21) against migration in the axial direction, which rests on the bottom to pretension the respective brush (3, 4, 5).
6. Power transmission device according to one of claims 1 to 5, characterized in that metal is provided as the material for the brushes (3, 4, 5).
7. Power transmission device according to one of claims 1 to 6, characterized in that the spring means (19, 20, 21) are each designed as a torsion spring which is applied to the contact surface (30, 31, 32, 33) of the respective brush (3, 4, 5) for preloading with the spring end (22, 23, 24) of a spring leg.
8. Power transmission device according to one of claims 1 to 7, characterized in that the brush holder (13, 14, 15) is made in one piece with the contact carrier (1) made of metal.
9. Power transmission device according to one of claims 1 to 8, characterized in that the brush holders (13, 14, 15) each have two oppositely arranged retaining brackets which encompass the respective brush (3, 4, 5) laterally and at least partially on the upper side (26) facing away from the contact carrier (1) on the outer circumference.
10. Power transmission device according to claim 9, characterized in that the contact carrier (1) is made of sheet metal and the retaining brackets of the brush holders (13, 14, 15) are punched out of the contact carrier (1) and bent into their holding position to receive the respective brush (3, 4, 5).