Current transfer device for a rotor of an electric machine
The power transmission device for electric machine rotors uses spring-integrated base carriers to pre-tension brushes, addressing inefficiencies and costs by ensuring continuous contact and eliminating complex connections, enhancing electrical insulation and wear resistance.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SCHAEFFLER TECHNOLOGIES AG & CO KG
- Filing Date
- 2025-12-08
- Publication Date
- 2026-07-23
Smart Images
Figure DE2025101163_23072026_PF_FP_ABST
Abstract
Description
[0001] P241729 DE
[0002] - 1 - Power transmission device for a rotor of an electric machine
[0003] 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.
[0004] 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.
[0005] The invention is therefore based on the objective of proposing a power transmission device of the aforementioned type, which improves the transmission of electrical current in a structurally simple and cost-effective manner.
[0006] 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.
[0007] Thus, a current transmission device for a rotor of an electric machine is proposed, comprising a plate-shaped base carrier to which at least one plate-shaped contact carrier is attached. One or more brushes for transmitting electric current to a sliding contact of the electric machine associated with the contact carrier are arranged on this contact carrier and each brush is guided in a brush holder. The device provides for the brush(es) to be pre-tensioned by at least one spring element connected to the base carrier, which passes through a through-opening in the contact carrier and exerts a force to press the respective brush against its electrically conductive brush holder.
[0008] Accordingly, a defined force can be generated in a structurally simple and cost-effective manner to press the respective brush against the respective brush holder, thus ensuring a permanently defined contact of the brushes. This is achieved in P241729 DE
[0009] -2 - Operation ensures that any potential loss of contact between the contact carrier and the brush holder is reliably avoided.
[0010] Since the brush holder is electrically conductive, a permanent and defined current transmission or supply to the brushes can be ensured. Additional electrical connections to the brushes, especially an extra wire for current transmission, can be avoided, and a wireless current transmission device can be implemented in a structurally simple manner. This also eliminates additional manufacturing and assembly effort, particularly for ensuring sufficient electrical insulation of the connections from the adjacent components. Furthermore, the potential limitation of the brush travel for wear adjustment due to the wire length is avoided.
[0011] Depending on the installation and operating conditions, the spring elements vary in design, especially in their size and number.
[0012] In a preferred embodiment of the invention, the spring elements are each formed integrally with the base support. This makes them particularly easy and cost-effective to manufacture. Additional components are avoided.
[0013] This is especially true if plastic is the preferred material for the base carrier. In this case, the spring elements and the base carrier can each be manufactured in a single step and in any desired shape, particularly by injection molding.
[0014] In a further particularly preferred embodiment that is easy to manufacture, the spring elements are each designed as a spring tongue and with the free end of the spring projecting outwards on the base carrier through the respective through-opening of the contact carrier and pre-tensioned on the underside of the respective brush facing the contact carrier.
[0015] A further embodiment of the invention provides that the brush or brushes are made of metal, which in particular improves wear resistance and the P241729 DE
[0016] - 3 - Current flow can be improved. This is especially true for a design using all-metal brushes.
[0017] In a further simplified embodiment of the invention, the spring elements preferably have an elongated, narrow rectangular shape in plan view. Preferably, they are slightly rounded at the free end.
[0018] Preferably, the through-holes on the contact carrier are each designed as an elongated hole with the longitudinal sides parallel to the longitudinal sides of the respective spring element.
[0019] It is also advantageous if the spring elements, preferably those passing through the through-openings, extend longitudinally in the direction of the wear path of the respective brush and are arranged with their free end pointing towards the respective sliding contact surface. In this way, the brushes, which are pre-tensioned against the sliding contact for wear adjustment, can slide along the length of the respective spring element during operation.
[0020] In a further preferred embodiment of the invention, the spring elements extend obliquely from the contact carrier at a slightly acute angle to the contact carrier and the underside of the respective brush. This allows for a particularly space-saving arrangement. Furthermore, the resistance at the contact with the respective brush during wear adjustment can be minimized.
[0021] In a further preferred embodiment of the invention, the spring elements are each arranged in a region of the base carrier that is at least partially encompassed by a web projecting from the base carrier and connected to it. The contact carrier, with its respective through-opening corresponding to the respective spring element, is placed against and supported by this web. In this way, a defined contact of the contact carrier against the base carrier and, at the same time, a defined contact of the respective spring element against the respective brush can be achieved in a simple manner. Preferably, the web is formed integrally with the base carrier. P241729 DE
[0022] - 4 - A particularly simple design of the brush holders can be achieved if they are each formed in one piece with the contact carrier.
[0023] Preferably, the brush holders each consist of two opposing retaining brackets that encompass the respective brush laterally and at least partially on the upper side facing away from the contact carrier on the outer circumference.
[0024] Preferably, a spring element integrated into the base carrier is provided for pressing the respective brush against the respective brush holder. This spring element passes through a through-opening located at least partially in a central area of the contact carrier between the retaining brackets. In this way, the spring element can be arranged particularly easily in a central area to make contact with the brush, which is slidably guided in the respective brush holder for wear adjustment.
[0025] Furthermore, it is advantageous if the contact carrier is made of sheet metal in a weight-saving, simple and cost-effective manner.
[0026] The brush holders are particularly easy to manufacture if, preferably, the retaining clips are punched out of the contact carrier and bent into their holding position to accommodate the respective brush.
[0027] Preferably, the spring elements on the upper side facing the respective brush are at least partially flat. This ensures, in particular, effective contact with the respective brush.
[0028] In a further particularly preferred embodiment of the invention, the current transmission device has two plate-shaped identical contact carriers which are attached to the opposite sides of the plate-shaped base carrier.
[0029] Preferably, three brushes, each assigned to an electrical pole, are arranged on the contact carriers for electrical current transmission to a corresponding sliding contact of the electric machine. P241729 DE
[0030] - 5 -
[0031] Preferably, three spring elements integrated into the base carrier are passed through three axial through-openings on each contact carrier to press the three brushes against the respective brush holder.
[0032] 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.
[0033] 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:
[0034] Figure 1 shows a current transmission device according to the invention for a rotor of an electric machine in a perspective view, Figure 2 shows a detailed view of a contact carrier of the current transmission device in a top view,
[0035] Figure 3 shows an enlarged section of Figure 1.
[0036] Figure 4 shows a sectional view of the power transmission device along the section line AA from Figure 4.
[0037] Figure 5 is a perspective partial top view of the power transmission device, Figure 6 is a perspective partial top view of the base support from Figure 2, Figure 7 is a cut partial view of the base support along the section line B-B from Figure 7.
[0038] The figures show various views of a current transmission device according to the invention for a rotor of an electric machine by way of example.
[0039] The current transmission device shown in Figure 1 has two plate-shaped identical contact carriers 1, 2, each preferably with three brushes 3, 4, 5 assigned to an electrical pole for transmitting electrical current to a respective P241729 DE
[0040] - 6 -associated sliding contact 6, 7 of the electric machine. Of the contact carriers 1, 2 and the sliding contacts 6, 7, only one contact carrier 1 is shown in each case, which is shown in a detail view in Figure 2 without the brushes 3, 4, 5. The contact carriers 1, 2 are preferably attached to the opposite sides of a plate-shaped base carrier 8 by means of screw connections.
[0041] The power 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 carrier 8. The contact carriers 1, 2 are electrically conductive and made of metal and can each be connected to an electrical power source, while the base carrier 8 also serves as an insulator and is preferably made of plastic.
[0042] The base carrier 8 and the contact carriers 1, 2 are each arranged radially inside with a central through-hole coaxially along an imaginary rotor axis 9, which serves as the axis of rotation and central axis of the rotor (not shown). 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 to prevent rotation. 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. It is also conceivable to arrange only one or two brushes, or even more than three brushes, on each contact carrier 1.
[0043] The brushes 3, 4, 5 are arranged evenly distributed around the circumference of the through-hole 10. They are preferably solid metal brushes, in particular made of brass or bronze, elongated and cuboid in shape, and each is arranged in a brush holder 13, 14, 15 on the axial outer sides of the contact carrier 1. 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.
[0044] - 7 - To press the brushes 3, 4, 5 against the respective slip ring 6, 7, preferably three torsion springs 19, 20, 21 are provided, which are arranged on the axial outer sides of the contact carriers 1, 2 (Figures 1 and 3). The torsion springs 19, 20, 21 each engage with one spring end of a spring leg 42, 43, 44 to apply preload to the end face 22, 23, 24 of the spring-side end of the respective brush 3, 4, 5 facing away from the sliding contact surface 16, 17, 18. The spring force transmitted from the adjacent spring end 42, 43, 44 presses the respective brush 3, 4, 5 with the respective sliding contact surface 16, 17, 18 against the slip ring 12 with a normal force FN or preloads it against the slip ring (Figure 4).
[0045] According to Figures 1, 3, 4, the brushes 3, 4, 5 are arranged with their flat, wide underside 25 facing the contact carrier 1. They are each held on their narrow side surfaces and on their flat, wide upper surface 26 facing away from the underside 25 by two opposing retaining brackets forming the respective brush holders 13, 14, 15.
[0046] As shown in Figures 2 and 4, an axial through-opening 27, 28, 29 is provided on the contact carrier 1 in the area of the brush holders 13, 14, 15 and the brushes 3, 4, 5. A spring element 30, 31, 32, each integrally formed with the base carrier 8 and spaced apart from the contact carrier 1 by a small air gap, passes through each of these openings. The respective brush 3, 4, 5 is pressed against the respective electrically conductive brush holder 13, 14, 15 by these spring elements. Thus, three spring elements 30, 31, 32, each integrally connected to the base carrier 8, pass through the contact carrier 1 at three axial through-openings 27, 28, 29 to press the three brushes 3, 4, 5 against the brush holders 13, 14, 15. The spring elements 30, 31, 32 each protrude into the respective brush holder 13, 14, 15.
[0047] The spring elements 30, 31, 32 are each, as shown in Figures 4 to 7, formed as a spring tongue on the flat outer surface of the base carrier 8 and are manufactured in one piece with it, for example by injection molding in a single operation. They each protrude with their free spring end 33, 34, 35 through the respective through-opening 27, 28, 29 of the contact carrier 1 and are slightly recessed on its axial outer surface.
[0048] - 8 -pre-tensioned on the flat underside 25 of the respective brush 3, 4, 5 facing the contact carrier 1.
[0049] The spring elements 30, 31, 32 each extend from the base carrier 8 with a projection 48 obliquely into the respective through-opening 27, 28, 29 and are angled obliquely at their respective free spring ends 33, 34, 35 and pre-tensioned at a small acute angle α to the contact carrier 1 and to the flat underside of the respective brush 3, 4, 5 (Figure 5). Each spring element 33, 34, 35 has a flat top and bottom surface and flat side surfaces (Figures 5 to 7).
[0050] The spring force of the respective spring element 30, 31, 32 generates a defined force FQ, which acts in the axial direction transversely to the normal force FN generated by the torsion springs 19, 20, 21, the latter being indicated in Figure 5 by the double arrow 9 and defined by the imaginary rotor axis 9 in Figure 1. The force FQ causes the respective brush 3, 4, 5 to be pressed against the respective electrically conductive brush holder 13, 14, 15, which is integrally formed with the contact carrier 1, in particular against the respective free end of the retaining bracket 13, 14, 15 (Figures 1, 3 and 4), which encompasses the upper surface 26 of the respective brush 3, 4, 5.
[0051] Accordingly, the spring elements 30, 31, 32 ensure a permanent electrical contact between each brush 3, 4, 5 and the respective brush holder 13, 14, 15 or contact carrier 1 for current transmission. This allows for continuous current transmission via the contact carrier 1 or the respective brush holder 13, 14, 15 to the respective brush 3, 4, 5 during operation. Consequently, complex additional electrical connections to the brushes 3, 4, 5, for example by means of an additional wire, are unnecessary. The current transmission device shown in Figure 1 is therefore wireless.
[0052] The spring elements 30, 31, 32 each have a narrow rectangular shape in the top view shown in Figures 5 and 6, with rounded edges at the free end of the spring. They each have a wall thickness D that is preferably smaller than the wall thickness of the base support 8, as shown in Figure 4. P241729 DE
[0053] - 9 - As indicated in Figure 6 in a section of the base support 8, the three spring elements 30, 31, 32 are each arranged in the same way on the base support 8 in a region encompassed by a web 49, 50, 51 projecting axially from the base support 8 and preferably formed integrally with it. This web forms an axial contact surface 52, 53, 54 at the end face of its free end, against which the contact carrier 1 with the respective through-opening 27, 28, 29 is placed and supported corresponding to the respective spring element 30, 31, 32.
[0054] The through-holes 27, 28, 29 are each designed as an elongated hole with parallel longitudinal sides, which are closed off at the narrow sides by semicircles whose diameter corresponds to the width of the elongated hole.
[0055] The through-holes 27, 28, 29 are each arranged in a central area of the contact carrier 1 located between the opposing retaining brackets of the respective brush holder 13, 14, 15 (Figure 5).
[0056] The spring elements 30, 31, 32 and the through-holes 27, 28, 29 each extend longitudinally in the direction of the wear path or in the direction of displacement of the respective brush 3, 4, 5, with the free spring end 33, 34, 35 aligned with the respective grinding contact surface 16, 17, 18 of the brush 3, 4, 5 or with the through-hole 10 (Figures 3 to 7). The direction of the wear path or the direction of displacement is indicated by a dashed arrow in Figure 5.
[0057] According to Figures 1, 3, 4 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.
[0058] The punched-out retaining clips of the brush holder 13, 14, 15 leave continuous recesses in the contact carrier 1 which are used as through holes 36, 37, 38 through which the torsion springs 19, 20, 21 with their respective coil-shaped spring bodies are guided (Figures 1 and 3). P241729 DE
[0059] - 10 - Spring holders 39, 40, 41, preferably integrally formed with the base carrier 8, project axially through the through-holes 36, 37, 38 in the contact carrier 1 with their free ends. The torsion springs 19, 20, 21 are coaxially mounted on the free ends of the spring holders 39, 40, 41 with their helical spring bodies. One spring leg 42, 43, 44 of each spring is pre-tensioned against the spring-side end face 22, 23, 24 of the respective brush 3, 4, 5 with the normal force FN, while the other spring leg is attached to the base carrier 8.
[0060] For the engagement of the torsion springs 19, 20, 21, a groove 45 is formed on the spring-side end face 22, 23, 24 of each brush 3, 4, 5 (Figures 2 and 3). This groove runs continuously along the entire length of the end face, parallel to the flat underside 25 and the flat upper surface 25 of each brush 3, 4, 5. The respective spring leg 42, 43, 44 of the torsion springs 19, 20, 21 engages in the groove 45 with its end. The side walls 46, 47 of the groove 45 secure the spring leg 42, 43, 44, which rests against the bottom of the groove to pre-tension the respective brush 3, 4, 5, against shifting axially towards the underside or upper surface 25, 26 of the respective brush 3, 4, 5.
[0061] The contact carriers 1, 2, each attached to the base carrier 8, with the brushes 3, 4, 5 arranged on them, form a pre-assemblable modular unit with the base carrier 8, which can be easily mounted on the electric machine.
[0062] Due to the design of the base carrier 8, especially in plastic, the power transmission device can be adapted particularly easily to the installation conditions, especially to the rotor shaft of the electric machine.
[0063] In this way, the proposed 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.P241729 DE
[0064] - 11 - List of reference symbols 1 Contact carrier
[0065] 2 contact carriers
[0066] 3 brushes
[0067] 4 brushes
[0068] 5 brush
[0069] 6. Slip contact, slip ring
[0070] 7. Slip contact, slip ring
[0071] 8 basic supports
[0072] 9 Rotor axis, rotation and central axis
[0073] 10 central through hole
[0074] 11 Shaft, rotor shaft
[0075] 12 Slip ring module
[0076] 13 Brush holder, retaining bracket
[0077] 14 Brush holder, retaining bracket
[0078] 15 brush holders, retaining brackets
[0079] 16 sliding contact surfaces
[0080] 17 Sliding contact surface
[0081] 18 sliding contact surfaces
[0082] 19 Torsion spring
[0083] 20 Torsion spring
[0084] 21 Torsion spring
[0085] 22 Front side, end
[0086] 23 Front side, end
[0087] 24 Front side, end
[0088] 25 Underside
[0089] 26 Top
[0090] 27 Through opening, elongated hole
[0091] 28 Through opening, elongated hole
[0092] 29 Through opening, slotted hole
[0093] 30 Spring element, spring tongue
[0094] 31 Spring element, spring tongue
[0095] 32 Spring element, spring tongue P241729 DE
[0096] - 12 - 33 Spring end
[0097] 34 Spring end
[0098] 35 Spring end
[0099] 36 Through hole, recess
[0100] 37 Through hole, recess
[0101] 38 Through hole, recess
[0102] 39 spring holders
[0103] 40 spring holders
[0104] 41 spring holders
[0105] 42 spring legs
[0106] 43 spring legs
[0107] 44 spring legs
[0108] 45 Nut
[0109] 46 side wall
[0110] 47 Side wall
[0111] 48 Approach
[0112] 49 Bridge
[0113] 50 jetty
[0114] 51 Bridge
[0115] 52 site area
[0116] 53 Plant area
[0117] 54 site area
[0118] FN Normal force
[0119] FQ Force
[0120] a angle of attack
[0121] D wall thickness
Claims
P241729 DE - 13 - Patent claims 1. Current transmission device for a rotor of an electric machine, comprising a plate-shaped base carrier (8) to which at least one plate-shaped contact carrier (1) is attached, on which one or more brushes (3, 4, 5) are arranged for electrical current transmission to a sliding contact (6, 7) of the electric machine associated with the contact carrier (1) and are each guided in a brush holder (13, 14, 15), characterized in that the respective brush (3, 4, 5) is biased by at least one spring element (30, 31, 32) integrated into the base carrier (8) and passed through a through-opening (27, 28, 29) on the contact carrier (1) with a force (FQ) to press the respective brush (3, 4, 5) against the respective electrically conductive brush holder (13, 14, 15).
2. Power transmission device according to claim 1, characterized in that the spring element (30, 31, 32) is formed integrally with the base carrier (8).
3. Current transmission device according to one of claims 1 or 2, characterized in that the spring elements (30, 31, 32) are each designed as a spring tongue and are projecting with the free spring end (33, 34, 35) through the respective through-opening (27, 28, 29) of the contact carrier (1) and are pre-tensioned on the contact carrier (1) on the underside (25) of the respective brush (3, 4, 5) facing the contact carrier (1).
4. Power transmission device according to one of claims 1 to 3, characterized in that plastic is provided as the material for the base carrier (8).
5. Power transmission device according to one of claims 1 to 4, characterized in that metal is provided as the material for the brushes (3, 4, 5). P241729 DE - 14 - 6. Power transmission device according to one of claims 1 to 5, characterized in that the spring elements (30, 31, 32) each have an elongated narrow rectangular shape in plan view with rounded edges at the free spring end (33, 34, 35).
7. Current transmission device according to one of claims 1 to 6, characterized in that the through-openings (27, 28, 29) on the contact carrier (1) are each designed as an elongated hole with the longitudinal sides parallel to the longitudinal sides of the respective spring element (30, 31, 32).
8. Power transmission device according to one of claims 1 to 7, characterized in that the spring elements (30, 31, 32) passing through the through-openings (27, 28, 29) extend along the wear path of the respective brush (3, 4, 5) and are arranged with the free spring end (33, 34, 35) aligned towards the sliding contact surface (16, 17, 18) of the respective brush (3, 4, 5).
9. Current transmission device according to one of claims 1 to 8, characterized in that the spring elements (30, 31, 32) are each arranged on the base carrier (8) in an area which is at least partially encompassed by a web (49, 50, 51) projecting from the base carrier (8) and connected to it, on which the contact carrier (1) with the respective through-opening (27, 28, 29) is placed and supported corresponding to the respective spring element (30, 31, 32).
10. Power transmission device according to one of claims 1 to 9, characterized in that the brush holders (13, 14, 15) are integrally formed with the contact carrier (1) and each have two opposing retaining brackets which encompass the respective brush (3, 4, 5) laterally and at least partially on the upper surface (26) facing away from the contact carrier (1) on the outer circumference, wherein a spring element (30, 31, 32) is provided in a space at least partially located between the opposing retaining brackets of the respective brush holder (13, 14, 15) to press the respective brush (3, 4, 5) against the respective brush holder (13, 14, 15). P241729 DE - 15 -located central area of the contact carrier (1) through the through-opening (27, 28, 29) for contact with the respective brush (3, 4, 5).