Discharge unit of an electrical machine

Abstract

A conductive unit (1) for contacting a shaft (2) of an electric machine (10) having a housing (3), comprising an elongated base body (5) having a bore (7) and designed for insertion into a holder (4) of the housing (3), wherein the longitudinal axis (A5) of the base body (5) coincides with the central axis of the bore (7), and comprising a conductor strip (6) which is drawn through the bore (7) in such a way that contact sections (8, 9, 11) are formed by the conductor strip (6) on both sides of the bore (7), namely at least one housing-side contact section (8, 9) and one shaft-side contact section (11), which project beyond the base body (5) in its longitudinal direction.

Description

[0001] The invention relates to a discharge unit for establishing an electrically conductive connection between a shaft and a housing of an electrical machine. Furthermore, the invention relates to an electrical machine with such a discharge unit.

[0002] A discharge device for discharging electrostatic charges described in WO 2021 / 219159 A1 is designed to be flexible and has a closed ring shape. This ring-shaped discharge device performs a tangential movement between two machine elements rotating relative to each other.

[0003] A device for grounding a bearing is known from US 2011 / 0 149 459 A1. The known grounding device comprises an annular charge dissipation component and a preload element, designed, for example, as a helical spring, which applies an axial force to the charge dissipation component.

[0004] An arrangement for earthing a shaft of an electrical machine described in DE 10 2018 107 206 A1 comprises a sleeve and a ball which is movably guided in the sleeve and which partially protrudes from the sleeve and contacts the shaft.

[0005] Possibilities for establishing electrically conductive connections between bearing rings of a rolling bearing, in particular a ball bearing, are described, for example, in documents DE 10 2019 133 880 A1 and DE 10 2020 125 531 A1. A conceivable design of a grounding brush that contacts a shaft of a dynamoelectric machine is known, for example, from DE 10 2010 039 065 A1.

[0006] The documents WO 2022 / 258 106 A1 and WO 2022 / 258 107 A1 show different variants of rolling bearing devices with an electrically conductive bypass device which has loop-shaped embroidered fibers.

[0007] JP H02-24 579 A deals with securing an electrical connection on a rotating shaft. It proposes arranging a spring-loaded, grounded element on one end face of the shaft.

[0008] The invention is based on the object of providing possibilities for earthing a shaft of an electrical machine, i.e. a generator or an electric motor, which are further developed compared to the cited prior art and are characterized by a robust, production-friendly design.

[0009] This object is achieved according to the invention by a discharge unit having the features of claim 1. The discharge unit is suitable for installation in an electrical machine according to claim 9.

[0010] The discharge unit is provided for contacting a shaft of an electrical machine having a housing. The housing of the electrical machine has a holder into which the discharge unit is to be inserted. The discharge unit comprises an elongated base body in which there is a bore, wherein the longitudinal axis of the base body coincides with the central axis of the bore. A further element of the discharge unit is in the form of a conductor strip which is drawn through the bore of the base body in such a way that contact sections, namely a housing-side contact section and a shaft-side contact section, are formed by the conductor strip on both sides of the bore, which contact sections protrude beyond the base body in its longitudinal direction.

[0011] According to various possible embodiments, the shaft-side contact section is designed as an elastically deformable eyelet. The bore can terminate in a fork-like widening end piece of the base body toward the eyelet. This creates a defined shape for a section of the shaft-side eyelet. Optionally, the housing-side contact section is also designed as an eyelet.

[0012] On the side of the discharge unit facing the housing - more precisely: the holder - there can be two housing-side contact sections, each of which describes a U-shape, with the U-legs of both contact sections being tangent in the area of ​​the central axis of the bore.

[0013] Irrespective of the number and shape of the contact sections, a plurality of ribs can be formed by the base body in a manner which is advantageous for assembly purposes and which concentrically surround the central axis of the discharge unit, wherein a flange represents a closure of the ribbed section of the base body and is provided for contact with an inner surface of the housing.

[0014] A design of the discharge unit in which no eyelet is formed on the shaft side of the base body provides that the shaft-side contact section of the conductor strip rests on the shaft-side end of the base body and, starting from this adjacent section, continues on both sides in the form of flank sections, which each enclose an acute angle with the central axis and extend at a distance from the base body to the flange, penetrate it and, contacting the annular ribs, merge into the two U-shaped contact sections on the housing side.

[0015] In this design of the discharge unit, the bore can extend from the housing-side end of the base body to the flange, with the section of the base body protruding beyond the flange and the bore describing a strip shape with two adjacent embossed zones designed as mirrored sine curves. This form of embossing gives the base body good flexural rigidity, while at the same time providing at least slight elastic compliance in the longitudinal direction of the base body. In this design, the discharge unit can also be constructed from just two components, namely the base body and the conductor strip. The term "embossed zones" is used in this case regardless of the material and manufacturing technology. In addition to forming processes, primary forming processes such as injection molding can also be used to produce the embossed zones.In all cases, the base body of the discharge unit functions as an axial spring element through the embossed zones.

[0016] The base body of the arrester unit can generally be made of metallic or non-metallic materials. Regardless of the material chosen, the arrester unit can be aligned parallel to the shaft to be grounded, thereby contacting one end of the shaft. The mechanically prestressed sliding electrical contact between the conductor strip and the shaft can be established either centrically or eccentrically. An eccentric arrangement of the arrester unit is particularly suitable for grounding a hollow shaft.

[0017] Several embodiments of the invention are explained in more detail below with reference to a drawing. In the drawings: Fig. 1 a discharge unit which establishes an electrically conductive connection between a housing and a shaft of an electrical machine, in a sectional perspective view, Fig. 2 the discharge unit of the arrangement according to Fig. 1, Fig. 3 shows a section of a device installed in an electrical machine, which, compared to the embodiment according to Fig. 2 modified derivation unit in a representation analogous Fig. 1, Fig. 4 another design of a discharge unit in side view, Fig. 5 the discharge unit according to Fig. 4 in perspective view, Fig. 6 a discharge unit having a non-metallic base body and a shaft to be contacted in a schematic representation, Fig. 7 the discharge unit inserted into a housing and contacting the shaft according to Fig. 6, Fig. 8 shows a further arrangement comprising a discharge element for electrically connecting a shaft to a housing, Fig. 9 the discharge element of the arrangement according to Fig. 8 in enlarged view.

[0018] Unless otherwise stated, the following explanations refer to all embodiments. Corresponding or essentially equivalent parts are identified by the same reference numerals in all figures.

[0019] An electrical machine, designated overall by 10 and only partially illustrated in the figures, which may be a generator or an electric motor, comprises a discharge unit 1, which establishes electrical contact between a shaft 2 and a housing 3 of the electrical machine 10 and thus functions as a grounding element. The discharge unit 1 is fixed in a holder 4 of the housing 3, which in the present case is designed as a blind hole.

[0020] The discharge unit 1 is constructed in at least two parts, namely a base body 5 and a conductor strip 6. The base body 5 has an elongated shape aligned in the longitudinal direction of the shaft 2 and is traversed by a bore 7 designed as a through-hole, at least along part of its length. At least a section of the conductor strip 6 is located in the bore 7. Outside the bore 7, contact sections 8, 9, 11 are formed by the conductor strip, namely at least one housing-side contact section 8, 9 and one shaft-side contact section 11. The contact sections 8, 9, 11 protrude at least slightly beyond the base body 5 in its longitudinal direction. The center axis of the base body 5, which coincides with the center axis of the bore 7, is designated A5. A2 designates the center axis of the shaft 2.

[0021] In examples according to the Fig. 1 to 5, the base body 5 is a metal part. In each of these cases, the base body 5 has a flange 12, which is intended to be attached to the housing 3. Within the blind-hole-like holder 4, which is covered by the flange 12, several ribs 13 formed by the base body can be seen. These ribs concentrically surround the central axis A5 and ensure sufficiently stable fixation of the base body 5 in the holder 4. The at least one housing-side contact section 8, 9 contacts the housing 3 in the holder 4.

[0022] In the example according to the Fig. 1 and Fig. 2, the base body 5 extends towards the shaft 2 in the form of a fork-like widening end piece 14. The inner sides of the curved arms 15, 16 of the end piece 14 merge seamlessly into the inner circumferential surface of the bore 7. Within the bore 7, the conductor strip 6 is arranged in two layers. In the end piece 14, the two layers of the conductor strip 6 diverge approximately in a V-shape, with the spreading of the various sections of the conductor strip 6 being limited by the arms 15, 16. In the section projecting beyond the end piece 14, i.e. in the shaft-side contact section 11, the conductor strip 6 approximately describes a circular shape in the mechanically unloaded state, as can be seen from Fig. 2. The shaft-side contact section 11 thus represents an eyelet which is elastically deformable. The deformed state of the shaft-side contact section 11 is evident from Fig. 1. In Fig. 1 also shows a helical gear 17 on shaft 2, which is irrelevant to the function of the deflection unit 1. Shaft 2 is designed as a hollow shaft. The deflection unit 1 contacts the shaft 2 off-center at its end face.

[0023] The two ends of the conductor strip 6 emerge in the embodiment Fig. 1 and Fig. 2 on the housing side from the base body 5 of the discharge unit 1. The ends of the conductor strips 6 are bent outwards, rest against the ribs 13 and extend approximately to the flange 12. Thus, each of the two housing-side contact sections 8, 9 in this case describes a U-shape, as can be seen in particular from Fig. 2.

[0024] The discharge unit 1 according to Fig. 3 on the side of the shaft-side contact section 11 corresponds to the design according to the Fig. 1 and Fig. 2. In particular, the shaft-side contact section 11 is designed as an eyelet, which is forced into a predetermined shape towards the base body 5 by its fork-like widening end piece 14. In contrast to the embodiment according to Fig. 1 and Fig. 2, the ends of the conductor strip 6 are in the variant according to Fig. 3 inside the hole 7. From the outside, no ends of the conductor strip 6 are visible. Rather, in the case of Fig. 3, only a single contact section 8 is formed by the conductor strip 6 on the housing side, wherein the housing-side contact section 8, as well as the shaft-side contact section 11, is designed as an eyelet. Both in the embodiment according to Fig. 3 as well as in the embodiment according to the Fig. 1 and Fig. 2, the base of the holder 4, designated 18, has a conical shape. The at least one housing-side contact section 8, 9 is in particular electrically connected to the base 18.

[0025] The discharge unit 1 according to the Fig. 4 and Fig. 5 has housing-side contact sections 8, 9, the shape of which largely corresponds to the embodiment according to the Fig. 1 and Fig. 2. In contrast to the exemplary embodiments according to the Fig. 1 to 3 extends in the case of Fig. 4 and Fig. 5, the bore 7, starting from the housing-side end of the base body 5, does not extend beyond the flange 12. Rather, the base body 5 has a modified strip shape in its section projecting beyond the flange 12 and extending towards the shaft 2. Here, a tapering of the strip-shaped section, designated overall by 19, from the flange 12 to the shaft-side contact section 11 is provided. In comparison to the embodiments according to the Fig. 1 to 3, the shaft-side contact section 11 in the case of Fig. 4 and Fig. 5 takes up considerably less space, whereby it rests directly against a tip section 20 which is wider than the wall thickness of the adjacent area of ​​the strip-shaped section 19 without forming an opening, such as an eyelet. The tip section 20 extends in a strip-like manner, just like the shaft-side contact section 11, orthogonal to the central axis A5 and, in side view, has Fig. 4, has a concave curvature for stable support of the conductor strip 6 in the shaft-side contact section 11.

[0026] The case of Fig. 4 and Fig. 5 short shaft-side contact sections 11 merge on both sides into flank sections 21, 22 of the conductor strip 6. The flank sections 21, 22 each maintain a distance from the strip-shaped section 19 and extend to the flange 12. An acute angle is enclosed between the two flank sections 21, 22. At the end of the flank sections 21, 22, the conductor strip 6 is guided through an opening in the flange 12. The further, housing-side sections of the conductor strip 6 represent outer U-legs 23, 24 of the housing-side contact sections 8, 9. Each housing-side contact section 8, 9 has, in addition to its outer U-leg 23, 24, also an inner U-leg 25, 26. The two inner U-legs 25, 26 contact each other in the area of ​​the central axis A5 of the bore 7 and thus of the entire base body 5. In the embodiment according to the Fig. 4 and Fig. 5, the two ends of the conductor strip 6 are in the hole 7.

[0027] As can be seen from the Fig. 4 to 5, an embossed section 27 is formed within the strip-shaped section 19. Within the embossed section 27, the strip-shaped section 19 is split into two adjacent band-shaped embossed zones 28, 29. Each embossed zone 28, 29 describes a sine curve in side view. The two embossed zones 28, 29 represent curves mirrored on the axis A5. By embossing the section 27, several objectives are achieved: Firstly, the strip-shaped section 19 has increased flexural rigidity compared to an imaginary, continuously flat section. Secondly, the embossed section 27 ensures at least slight, but technically relevant, elastic compliance of the entire strip-shaped section 19 in the axial direction, i.e., in the longitudinal direction of the base body 5.

[0028] In the examples according to the Fig. 6 to 9, the base body 5 is a non-metallic element, namely a rubber plug. Alternatively, the base body 5 could be made of plastic. The base body 5 is provided with annular circumferential notches 30 on its essentially cylindrical circumferential surface. Optionally, an annular circumferential, possibly segmented flange 31 is provided, which Fig. 9 can be seen and further improves the fixation of the base body 5 in the housing 3.

[0029] In the example according to the Fig. 6 and Fig. 7, the electrical machine 10 including the discharge unit 1 has fundamental similarities with the embodiments according to the Fig. 1 to 5, as the central axis A5 of the base body 5 is spaced parallel from the rotational axis A2 of the shaft 2, so that the shaft-side contact section 11 rests eccentrically on an end face of the shaft 2. The ends of the conductor strip 6 are located both in the embodiment according to the Fig. 6 and Fig. 7 as well as in the embodiment according to the Fig. 8 and Fig. 9 within the bore 7 of the base body 5. The bottom 18 of the blind hole-like holder 4 is in the embodiment according to the Fig. 6 and Fig. 7 in contrast to all other embodiments.

[0030] In the embodiment according to Fig. 8 and Fig. 9, the base body 5 is completely recessed into the holder 4, with the outer surface of the base body 5 resting against a cylindrical inner circumferential surface 32 of the holder 4. The cylindrical inner circumferential surface 32 adjoins, on the one hand, the conical base 18 and, on the other hand, towards the opening of the holder 4, a conical opening section 33. The conicity angle of the opening section 33 is designated α. The extension of the conical opening section 33, measured in the longitudinal direction of the discharge unit 1, is designated T 33 . T4 denotes the depth of the entire support 4, measured in the same direction, but without taking into account the conical bottom 18.

[0031] In addition to the base body 5 and the conductor strip 6, the discharge unit 1 has, according to the Fig. 8 and Fig. 9 has two discs 34, 35, which are each attached to the front of the base body 5. The conductor strip 6 is pulled through openings in the discs 34, 35, whereby the discs 34, 35 make a significant contribution to the stable attachment of the conductor strip 6 to the base body 5. As can be seen from Fig. 8, the disc 35 is located within the conical opening section 33. Thus, none of the discs 34, 35 protrudes from the holder 4.

[0032] In the constellation after Fig. 8, the central axis A5 of the base body 5 and thus of the entire discharge unit 1 coincides with the rotational axis A2 of the shaft 2. The contact surface between the shaft-side contact section 11 and the end face of the shaft 2 is in Fig. 8 exaggeratedly large. Deviating from the schematic representation according to Fig.8, a significantly smaller, centric contact area between the discharge unit 1 and the shaft 2 is sufficient to establish potential equalization between the shaft 2 and the housing 3. List of reference symbols 1 discharge unit 2nd wave 3 housings 4 Bracket 5 basic bodies 6 conductor strips 7 Hole 8 first contact section, housing side 9 second contact section, housing side 10 electric machine 11 Contact section, shaft side 12 Flange 13 rib 14 End piece, fork-like 15 Arm of the end piece 16 Arm of the end piece 17 Helical gearing 18 Bottom of the bracket 19 strip-shaped section 20 top section 21 flank section 22 flank section 23 outer U-leg 24 outer U-leg 25 inner U-leg 26 inner U-leg 27 Embossing section 28 Embossing zone 29 Embossing zone 30 notch 31 flange 32 cylindrical inner peripheral surface 33 conical opening section 34 disc 35 disc α angle A2 Central axis of the shaft, rotation axis of the shaft A5 Longitudinal axis of the base body, central axis of the base body T4 Depth of the bracket T 33 Extension of the conical opening section

Claims

[1] Conductor unit (1) for contacting a shaft (2) of an electrical machine (10) having a housing (3), with an elongated base body (5) having a bore (7) and intended for insertion into a holder (4) of the housing (3), wherein the longitudinal axis (A5) of the base body (5) coincides with the central axis of the bore (7), and with a conductor strip (6) which is drawn through the bore (7) in such a way that contact sections (8, 9, 11), namely at least one housing-side contact section (8, 9) and one shaft-side contact section (11), are formed by the conductor strip (6) on both sides of the bore (7), which contact sections protrude beyond the base body (5) in its longitudinal direction. [2] Discharge unit (1) according to claim 1, characterized by that the shaft-side contact section (11) is designed as an elastically deformable eyelet. [3] Discharge unit (1) according to claim 2, characterized bythat the bore (7) ends towards the eyelet in a fork-like widening end piece (14) of the base body (5). [4] Discharge unit (1) according to claim 2 or 3, characterized by that the housing-side contact section (8, 9) is also designed as an eyelet. [5] Discharge unit (1) according to one of claims 1 to 4, characterized by that there are two housing-side contact sections (8, 9), each of which describes a U-shape, the inner U-legs (25, 26) of both housing-side contact sections (8, 9) being tangent in the region of the central axis of the bore (7). [6] Discharge unit (1) according to one of claims 1 to 5, characterized by a number of ribs (13) formed by the base body (5) which concentrically surround the longitudinal axis (A5), wherein a flange (12) represents a termination of the section of the base body (5) provided with ribs (13). [7] Discharge unit (1) according to claim 5 and 6, characterized bythat the shaft-side contact section (11) rests against the shaft-side end of the base body (5) and, starting from this adjacent section, continues on both sides in the form of flank sections (21, 22), which each enclose an acute angle with the longitudinal axis (A5) and extend at a distance from the base body (5) to the flange (12), penetrate the latter and, contacting the ribs (13), merge into the two U-shaped contact sections (8, 9). [8] Discharge unit (1) according to claim 7, characterized by that the bore (7) extends from the housing-side end of the base body (5) to the flange (12), wherein the section of the base body (5) projecting beyond the flange (12) and the bore (7) describes a strip shape with two embossed zones (28, 29) arranged next to one another and designed as mirrored sine curves. [9] Electrical machine (10), comprising a shaft (2) and a discharge unit (1) contacting the shaft (2) according to claim 1. [10] Electrical machine (10) according to claim 9, characterized by that the discharge unit (1) is aligned parallel to the shaft (2).

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