Current transfer device for a rotor of an electric machine

Abstract

The invention relates to a current transfer device for a rotor of an electric machine, comprising a plate-like base carrier (8) to which is fastened at least one plate-like contact carrier (1) on which are arranged multiple brushes (3, 4, 5) for electrical current transfer to a sliding contact (6, 7) of the electric machine associated with the contact carrier (1), wherein the brushes (3, 4, 5) are each carried by a brush holder (13, 14, 15), characterized in that, in order to press the brushes (3, 4, 5) against the sliding contact (6), a torsion spring (19, 20, 21) generating a torque about the spring axis (30, 31, 32) is provided for each brush, and in each case the spring leg (33, 34, 35) supporting the torque of the torsion spring (19, 20, 21) against the base carrier (8) is axially secured by the contact carrier (1).

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 US patent 2004 245 886 A1, a brush holder for a dynamo-electric machine is known, comprising a base plate and at least one brush holder attached thereto, the brush holder being slidably mounted in the base plate towards a commutator of the dynamo-electric machine. A support pin and an anchoring portion protrude from the surface of the base plate. A torsion spring is attached to each support pin, pressing the associated brush against the commutator. One end of the spring is connected to the corresponding anchoring portion, while the other end of the spring presses against the rear end face of the respective brush.

[0004] The invention is therefore based on the objective of proposing a power transmission device of the aforementioned type, which is simplified in its manufacture in a structurally simple manner.

[0005] 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.

[0006] Thus, a current transmission device for the rotor of an electric machine is proposed, comprising a plate-shaped base carrier to which at least one plate-shaped contact carrier is attached. Several brushes are arranged on this contact carrier for transmitting electric current to a sliding contact of the electric machine associated with the contact carrier. Each brush is guided in a brush holder. A torsion spring, generating a torque about the spring axis, is arranged to press the brushes against the sliding contact. The spring leg that supports the torque of the torsion spring against the base carrier is axially secured by the contact carrier.The axial securing of the torsion spring by the contact carrier on the one hand, and the support of its torque on the base carrier on the other, avoids the need for axial securing of the spring leg to the base carrier and the associated undercut and additional design effort for its manufacture, particularly due to any openings in the base carrier, which would also increase the risk of leakage currents between the electrical poles of the electric machine. Consequently, the base carrier without an undercut can be manufactured particularly easily and cost-effectively, for example by casting, especially injection molding.

[0007] Such a design is particularly easy to achieve if, preferably, the torsion springs are each guided through a through-hole in the contact carrier. Preferably, the spring leg is positioned against an axial projection formed on the base carrier to support the torque, and the contact carrier rests on this projection with its inner side facing the base carrier. The contact carrier thus forms an axial stop on its inner side for the spring leg, against which the spring leg is axially secured.

[0008] The most uniform and safe force transmission possible to support the torque of the torsion springs is achieved if, preferably, the projection on the base carrier forms a flat contact surface for the respective spring leg.

[0009] The projection is particularly easy to produce if it is preferably designed as a cuboid wall section or cuboid web on the base support. In this case, the projection preferably forms a flat contact surface on one longitudinal side.

[0010] Manufacturing can be further simplified if the projection is formed as a single unit with the base carrier, thus avoiding additional components.

[0011] 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.

[0012] In a further embodiment of the invention, the torsion springs are each coaxially mounted and supported on a spring holder connected to the base carrier and projecting through the respective through-hole, with their coil-shaped spring body.

[0013] Preferably, the spring holder is formed as a single piece with the base carrier.

[0014] In a structurally simplified embodiment of the invention, it is provided that the respective through-hole on the contact carrier is formed by punching out a retaining bracket of the brush holders which are each integrally formed with the contact carrier.

[0015] Preferably, the brush holders each have 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.

[0016] The proposed power transmission device is particularly advantageous for use in an electric machine of an electrically powered vehicle, especially an electrically powered passenger car.

[0017] 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:

[0018] Figure 1 shows a current transmission device according to the invention for a rotor of an electric machine in a perspective view,

[0019] Figure 2 shows an enlarged section of Figure 1.

[0020] Figure 3 shows an enlarged section of Figure 1 without the brushes.

[0021] Power transmission device, Figure 4 a perspective partial view of the base support of the power transmission device with a torsion spring,

[0022] Figure 5 shows another perspective partial view of the base support of the power transmission device with a torsion spring.

[0023] The figures show various exemplary views of a current transmission device according to the invention for a rotor of an electric machine.

[0024] 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 contact carrier 1 of each of the contact carriers 1, 2 and sliding contacts 6, 7 is shown. The contact carriers 1, 2 are attached to opposite sides of a plate-shaped base 8, preferably by means of screw connections.

[0025] 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 each is connected to an electrical power source, while the base carrier 8 also serves as an insulator and is preferably made of plastic.

[0026] 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 as a sliding contact. The slip rings 6, 7 are integrated into a slip ring module 12 arranged on the shaft 11 and are electrically connected to the rotor via this module. 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, rectangular in shape and elongated, 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 contacts 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.

[0027] To press the brushes 3, 4, 5 against the respective slip ring 6, 7, torsion springs 19, 20, 21 are preferably provided, which are attached to the axial outer sides of the contact carriers 1, 2 (Figures 1, 3 and 5). The torsion springs 19, 20, 21 each engage with one spring end of the spring leg 27, 28, 29 facing the respective brush 3, 4, 5, applying a 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 27, 28, 29 presses the respective brush 3, 4, 5 with the respective sliding contact surface 16, 17, 18 against the slip ring 12 or preloads it (Figures 1 and 5).

[0028] According to Figures 1, 2 and 5, the brushes 3, 4, 5 each rest on the contact carrier 1 with their flat, wide underside 25. 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.

[0029] To press the brushes 3, 4, 5 against the sliding contact 6, the torsion springs 18, 19, 20 each generate a rotational or torsional moment about their respective imaginary spring axis 30, 31, 32. This axis is aligned parallel to the rotor axis 9. As shown in Figures 1, 3, and 5, the torsion springs 18, 19, 20 are each guided axially through a through-hole 39, 40, 41 of the contact carrier 1 with their coil-shaped spring body. The spring leg 33, 34, 35, facing away from the brushes 3, 4, 5, is each pressed against an axial projection 36, 37, 38 on the axial outer side of the base carrier 8 to support the torque of the torsion springs 19, 20, 21 (Figures 2 to 5). The projection 36, 37, 38 is preferably formed in one piece with the base carrier 8.

[0030] The projection 36, 37, 38 and the spring leg 33, 34 abutting it on the axial outer side of the base carrier 8 below the contact carrier 1 are positioned such that the spring leg 33, 34, 35 is axially secured by the flat inner surface of the contact carrier 1 facing the base carrier. The contact carrier 1 rests with its flat inner surface on the flat bearing surface 48, 49, 50 formed at the free end of the projection 36, 37, 38. In this way, it forms an axial stop 42, 43, 44 on its inner surface for the spring leg 33, 34, 35 abutting the projection 36, 37, 38.

[0031] The projection 36, 37, 38 is designed as a cuboid wall piece or cuboid web projecting axially from the base support 8 and forms a flat contact surface 45, 46, 47 on one longitudinal side, against which the spring leg 33, 34, 35 rests (Figures 2 to 5).

[0032] As shown in Figures 1 to 3 and 5, 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.

[0033] The punched-out retaining clips of the brush holders 13, 14, 15 leave through-holes in the contact carrier 1, which are used as through-holes 39, 40, 41. The torsion springs 19, 20, 21, with their respective coil-shaped spring elements, are guided through these holes. Spring holders 51, 52, 53, preferably integrally formed with the base carrier 8 and projecting axially, extend their free ends through the through-holes 39, 40, 41 in the contact carrier 1 (Figures 1 and 4). The torsion springs 19, 20, 21, with their coil-shaped spring elements, are coaxially mounted on the free ends of the spring holders 51, 52, 53. They are each attached with the spring leg 27, 28, 29 facing the brushes 3, 4, 5 to the spring-side end face 22, 23, 24 of the respective brush 3, 4, 5 with the spring force applied.

[0034] For the engagement of the torsion springs 19, 20, 21, a groove 54 is preferably formed on the spring-side end face 22, 23, 24 of each brush 3, 4, 5 (Figure 2), which runs continuously along the entire length of the end face parallel to the flat underside 25 and the flat top surface 25 of the respective brush 3, 4, 5. The respective spring leg 27, 28, 29 engages in the groove 54 with its end. The side walls of the groove 54 secure the spring leg 27, 28, 29, which rests against the bottom of the groove to pre-tension the respective brush 3, 4, 5, against shifting axially towards the top or bottom surface 25, 26 of the respective brush 3, 4, 5.

[0035] The contact carriers 1, 2, each attached to the base carrier 8, with the brushes 3, 4, 5 arranged on them, form a pre-assembled modular unit with the former, which can be easily mounted on the electric machine.

[0036] 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.

[0037] 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. (List of reference symbols for contact carriers)

[0038] Contact carrier

[0039] brush

[0040] brush

[0041] brush

[0042] Slip contact, slip ring

[0043] Slip contact, slip ring

[0044] basic support

[0045] Rotor axis, rotation and central axis, central through hole

[0046] shaft, rotor shaft

[0047] Slip ring module

[0048] Brush holder, retaining bracket brush holder, retaining bracket brush holder, retaining bracket grinding contact surface

[0049] Grinding contact surface

[0050] Grinding contact surface

[0051] Torsion spring

[0052] Torsion spring

[0053] Torsion spring

[0054] Front side, end

[0055] Front side, end

[0056] Front side, end

[0057] bottom

[0058] Top

[0059] Spring leg; spring end

[0060] Spring leg; spring end

[0061] Spring leg; spring end

[0062] Spring axle

[0063] Spring axle

[0064] Spring axle, spring leg, spring end, spring leg, spring end, spring leg, spring end, projection, wall piece, web, projection, wall piece, web, projection, wall piece, web, through hole, recess, through hole, recess, through hole, recess, stop

[0065] stop

[0066] stop

[0067] Site area

[0068] Site area

[0069] Mounting surface, bearing surface, bearing area, bearing surface

[0070] Spring holder

[0071] Spring holder

[0072] Spring holder

[0073] Nut

Claims

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 several 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), wherein the brushes (3, 4, 5) are each guided in a brush holder (13, 14, 15), characterized in that a torsion spring (19, 20, 21) generating a torque about the spring axis (30, 31, 32) is arranged to press the brushes (3, 4, 5) against the sliding contact (6) and the spring leg (33, 34, 35) supporting the torque of the torsion spring (19, 20, 21) on the base carrier (8) is axially secured by the contact carrier (1).

2. Current transmission device according to claim 1, characterized in that the torsion springs (19, 20, 21) are each guided through a through hole (39, 40, 41) of the contact carrier (1), wherein the spring leg (33, 34, 35) in each case rests against an axial projection (36, 37, 38) formed on the base carrier (8) to support the torque, on which the contact carrier (1) rests with its inner side facing the base carrier (8) and this forms an axial stop (42, 43, 44) for the spring leg (33, 34, 35).

3. Power transmission device according to claim 2, characterized in that the projection (36, 37, 38) on the base support (8) forms a contact surface (45, 46, 47) for the contact of the spring leg (33, 34, 35).

4. Power transmission device according to one of claims 2 or 3, characterized in that the projection (36, 37, 38) on the base support (8) is designed as a cuboid wall section or cuboid web and forms a flat contact surface (45, 46, 47).

5. Power transmission device according to one of claims 2 to 4, characterized in that the projection (36, 37, 38) on the base support (8) is formed integrally with the latter.

6. Power transmission device according to one of claims 1 to 5, characterized in that plastic is provided as the material for the base carrier (8).

7. Power transmission device according to one of claims 2 to 6, characterized in that the torsion springs (19, 20, 21) are each coaxially mounted and supported on a spring holder (51, 52, 53) connected to the base carrier (8) and projecting through the through hole (39, 40, 41) with their coil-shaped spring body.

8. Power transmission device according to one of claims 2 to 7, characterized in that the respective through-hole (39, 40, 41) on the contact carrier (1) is formed by punching out a retaining bracket of the brush holders (13, 14, 15) which are integrally formed with the contact carrier (1).

9. Power transmission device according to claim 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.

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