Slot wedge with reduced stiffness for the rotor of an electric machine

Abstract

The invention relates to a slot wedge for covering a rotor slot in a rotor body of a rotor of an electric machine, wherein the rotor slot is delimited by a first salient pole and a second salient pole of the rotor body. The slot wedge comprises a covering region that is designed to cover an opening between the two salient poles of the rotor body. The first salient pole has a first pole shoe having a first limb facing the opening in the rotor slot. The covering region, on the first edge facing the first limb, has a first profile complementary to a corresponding first mating profile of the first limb. The first profile has a covering lip that is designed to cover the first limb from the outside in the region of the first mating profile.

Description

[0001] 24-1914

[0002] - 1 -

[0003] Slotted locking wedge with reduced stiffness for the rotor of an electric machine

[0004] The invention relates to an electric machine, such as a synchronous machine. In particular, the invention relates to a slot sealing wedge for sealing a rotor slot of a rotor of an electric machine.

[0005] A vehicle that is at least partially electrically powered includes an electric machine for propelling the vehicle. The electric machine comprises a stator that surrounds a rotor of the electric machine.

[0006] The rotor slots of the (current-excited) rotor of an electric machine are typically each covered with a slot closure wedge to form a closed cavity in each rotor slot, which can each be filled with a potting compound to protect the windings. 24-1914

[0007] - 2 - to fix locally within the cavities of the individual rotomutes and / or to electrically insulate them from the rotor body.

[0008] The individual slot locking wedges can each be inserted axially, i.e., along the longitudinal axis of the slot locking wedge, between the legs of the pole shoes of two directly adjacent salient poles to cover the rotor slot formed by the salient poles. Installing the individual slot locking wedges may require relatively high assembly forces, thus increasing the manufacturing costs of the rotor.

[0009] This document addresses the technical task of providing a slot closure wedge that enables the efficient manufacture of an electrically excited rotor of an electric machine and a reliable sealing of a rotor slot of the rotor.

[0010] The problem is solved by the independent claim. Advantageous embodiments are described, inter alia, in the dependent claims. It should be noted that additional features of a claim dependent on an independent claim, without the features of the independent claim itself or only in combination with a subset of the features of the independent claim, can constitute a separate invention independent of the combination of all features of the independent claim, which can be made the subject of an independent claim, a divisional application, or a subsequent application. This applies equally to technical teachings described in the description, which can constitute an invention independent of the features of the independent claims.

[0011] According to one aspect, a slot closure wedge for covering a rotor slot of a rotor body of an electric machine rotor is described. The rotor slot is defined by a first salient pole and a second salient pole of the 24-1914

[0012] - 3 -

[0013] The rotor body is limited. Each salient pole can have a pole shoe with legs, the legs extending circumferentially around the rotor body. An opening in the rotor slot is typically formed between the salient poles, particularly between the opposing legs of the pole shoes. This opening can extend along the longitudinal axis of the rotor body from the first end face to the opposite second end face. Furthermore, the opening can extend circumferentially around the rotor body's surface from the first salient pole (particularly from the first leg of the pole shoe of the first salient pole) to the second salient pole (particularly to the second leg of the pole shoe of the second salient pole). The opening can have the form of a (missing) segment of the rotor body's surface.

[0014] The slot closure wedge includes a covering area designed to cover the opening between the two salient poles (in particular the opening between the two legs of the pole shoes of the two salient poles) of the rotor body.

[0015] The cover area can (at the first edge) have a first (sectional) profile extending along the longitudinal axis, which is complementary to a corresponding first (sectional) counter-profile of the first leg. Furthermore, the cover area can (on the opposite longitudinal side, i.e., at the second edge) have a second (sectional) profile extending along the longitudinal axis, which is complementary to a corresponding second (sectional) counter-profile of the second leg. A profile of the cover area can, for example, have a notch, recess, or groove (along the longitudinal axis) into which a complementary tongue of the respective leg can be arranged as a counter-profile. Alternatively or additionally, a profile of the cover area can have a tongue that fits into a notch, recess, or groove (along the 24-1914).

[0016] - 4 -

[0017] The longitudinal axis of the respective leg can be arranged as a counter-profile. A notch, depression, or groove can be formed (with respect to the respective cross-sectional profile) as a trough between two crests. Conversely, a spring can be formed (with respect to the respective cross-sectional profile) as a crest.

[0018] The covering area can have the shape of a segment of the rotor body's outer surface. In particular, the covering area of ​​the slot closure wedge can be designed such that it completes the outer surface of the rotor body at the location of the rotor slot opening when the slot closure wedge covers the opening of the rotor slot.

[0019] The cover area can be arranged above the opening of the rotor slot, so that the slot closure wedge is fixed locally by the opposing legs of the pole shoes, and so that the slot closure wedge is held in the rotor slot by the legs of the pole shoes even when centrifugal forces (acting in a radial direction) are present (up to reaching a certain limit centrifugal force).

[0020] As previously explained, the cover area of ​​the groove closure wedge has a first profile on its first longitudinal edge facing the first leg, which is complementary to a corresponding first counter-profile of the first leg. The aspects described in this document regarding the first profile and the first counter-profile are also applicable, mutatis mutandis, to the second profile and the second counter-profile located on the second longitudinal edge of the cover area of ​​the groove closure wedge. Preferably, the first and second profiles are identical. Furthermore, preferably, the first and second counter-profiles are also identical.

[0021] The cover area of ​​the groove closure wedge has a relief groove running along the longitudinal axis, which is designed to increase the stiffness of the 24-1914

[0022] - 5 -

[0023] The stiffness of the cover area (at the first edge) is reduced in a transverse direction (especially in the radial and / or circumferential direction) extending across the longitudinal axis. The relief groove can be designed such that the stiffness of the cover area (at the first edge) in the transverse direction is lower, in particular by at least 5% or at least 10%, than if the cover area did not have the relief groove.

[0024] The cover area of ​​the groove closure wedge can have at least one first relief groove facing the first edge of the cover area. Furthermore, the cover area of ​​the groove closure wedge can have at least one second relief groove facing the second edge of the cover area. The following discussion focuses on the one or more (first) relief edges facing the first edge of the cover area. It should be noted that the described features, individually or in combination, are also applicable to the one or more second relief edges facing the second edge of the cover area.

[0025] By locally reducing the stiffness of the cover area of ​​the groove closure wedge (at the first edge and / or at the second edge) by means of at least one relief groove, the installation force to be applied when installing the groove closure wedge can be reduced without impairing the sealing effect of the groove closure wedge.

[0026] As already explained, the covering area of ​​the groove closure wedge typically extends along the longitudinal axis and along the circumferential direction arranged transversely (in particular perpendicularly) to the longitudinal axis. The at least one relief groove can be designed to reduce the stiffness of the covering area (at the first edge) in the radial direction, which runs transversely (in particular perpendicularly) to the longitudinal axis and transversely (in particular perpendicularly) to the circumferential direction. Alternatively or additionally, the relief groove 24-1914

[0027] - 6 - be designed to reduce the stiffness of the cover area in the circumferential direction. This allows the assembly force for installing the groove closure wedge to be reduced in a particularly reliable manner.

[0028] The first profile of the groove-locking wedge can have a spring (e.g., a wave crest) designed to engage in a corresponding groove (e.g., a wave trough) of the first mating profile of the first leg. The groove-locking wedge can have a relief groove located within the spring of the first profile. The relief groove can be arranged within the spring of the first profile of the groove-locking wedge such that the relief groove divides the spring of the first profile into a first partial spring and a second partial spring, arranged radially one behind the other or one above the other.The first and second partial springs formed by the relief groove can be designed in such a way that the first and second partial springs can be bent towards each other by a force acting in a radial direction, thereby reducing in particular the gap width of the relief groove (in the radial direction).

[0029] By providing a relief groove within the first profile, the assembly force can be reduced in a particularly reliable manner without impairing the sealing effect of the groove closure wedge.

[0030] Alternatively or additionally, the groove closure wedge can have a relief groove arranged between the first profile of the cover area and a central section of the cover area, such that the relief groove forms a bending point along the longitudinal axis at which the first profile of the cover area can be bent towards the central section of the cover area under the influence of a circumferential force, thereby reducing, in particular, the gap width of the relief groove (in the circumferential direction). 24-1914

[0031] - 7 -

[0032] The relief groove can be arranged such that, in the installed state of the groove closure wedge, the relief groove does not contact the first mating profile of the first leg. Alternatively or additionally, the relief groove can be arranged on the surface of the cover area of ​​the groove closure wedge facing the rotor groove (i.e., on the inside). This allows for a particularly reliable bending or compression of the cover area of ​​the groove closure wedge to reduce the installation force without impairing the sealing effect of the groove closure wedge.

[0033] The groove closure wedge can have an elastic sealing element arranged in the relief groove. The sealing element can be designed such that

[0034] • the sealing element is arranged between the first profile and the first counter-profile; and / or

[0035] • the sealing element seals the gap between the first profile and the second counter-profile, at least in some areas.

[0036] The relief groove can extend from the surface of the cover area of ​​the groove closure wedge into the cover area, in particular by 1 mm or more. The sealing element can project above the surface of the cover area of ​​the groove closure wedge (out of the relief groove), in particular by 0.5 mm or more.

[0037] The sealing effect of the groove closure wedge can be further increased by providing a sealing element arranged in the relief groove.

[0038] The slot closure wedge typically includes an immersion area configured such that, when the cover area covers the opening of the rotor slot, the immersion area extends radially from the cover area into the rotor slot (towards the rotor axis). The immersion area may have side walls, each arranged substantially in one plane. 24-1914

[0039] - 8 - are, which is spanned by the longitudinal axis (i.e. the axis of rotation) and by a radial axis extending in a radial direction.

[0040] The immersion zone can extend along the longitudinal axis at least from the first to the second end face of the rotor body. Furthermore, the immersion zone can have a specific immersion depth along the radial direction (starting from the cover area towards the rotor axis of the rotor body).

[0041] The slot locking wedge, in particular the insertion area of ​​the slot locking wedge, can (at least in an area intended to be arranged between the first and second end faces of the rotor body) essentially have the shape of a (right) prism with a specific base area. The base area can, for example, be triangular or T-shaped.

[0042] The insertion area of ​​the slot locking wedge can be configured to divide the rotor slot, in or on which the slot locking wedge is arranged, into a first half and a second half along a dividing plane defined by the longitudinal and radial axes, with the first half facing the first salient pole and the second half facing the second salient pole. In the first half of the rotor slot, first windings can be arranged around the first salient pole, and in the second half of the rotor slot, second windings can be arranged around the second salient pole.

[0043] The rotomut can have a specific total depth in the radial direction with respect to the rotor axis. The immersion area can have an immersion depth along the radial direction that is 50% or more, in particular 70% or more, of the total depth. 24-1914

[0044] - 9 -

[0045] According to another aspect, a rotor for an electric machine is described. The rotor comprises a rotor body with a first salient pole and a second salient pole, which define a rotor slot that has an opening between the two salient poles. Furthermore, the rotor includes a slot closure wedge (designed as described in this document) that covers the opening. Typically, the rotor includes a plurality of rotor slots (e.g., 4 or more, or 6 or more) and a corresponding plurality of slot closure wedges.

[0046] According to another aspect, an electrical machine, in particular a (current-excited) synchronous machine, is described, which includes the rotor described in this document.

[0047] According to another aspect, a (road) motor vehicle (in particular a passenger car or a truck or a bus or a motorcycle) is described that includes the electric machine described in this document for propelling the vehicle.

[0048] It should be noted that the devices, methods, and systems described in this document can be used both alone and in combination with other devices and systems described in this document. Furthermore, any aspect of the devices and systems described in this document can be combined with one another in a variety of ways. In particular, the features of the claims can be combined with one another in a variety of ways. Features listed in parentheses are to be understood as optional features.

[0049] The invention will now be described in more detail using exemplary embodiments.

[0050] Figure a is an exemplary electrical machine;

[0051] Figure 1b a perspective view of an exemplary rotor body; 24-1914

[0052] - 10 -

[0053] Figure 1c shows a perspective view of an exemplary slot locking wedge; Figure Id shows a sectional view of a slot locking wedge arranged in a rotor slot;

[0054] Figures 2a and 2b each show a sectional view of an exemplary groove locking wedge with a relief groove; and

[0055] Figures 3a and 3b each show a sectional view of an exemplary groove closure wedge with an elastic seal.

[0056] As stated at the outset, this document deals with the efficient and reliable sealing of the individual rotor slots of the rotor of an electric machine, in particular to enable the efficient and reliable manufacture of an electric machine. In this context, Fig. 1a shows an exemplary electric machine 100 in a view perpendicular to the shaft 101 of the electric machine 100. The shaft 101 of the electric machine 100 can correspond to the longitudinal axis of the stator 110 and / or the rotation or rotor axis of the rotor 120 of the electric machine 100. Furthermore, the shaft 101 can run along the z-axis of the Cartesian coordinate system shown.

[0057] The electric machine 100 comprises a stator 110 with several stator windings 111 arranged at different angular positions around the rotational axis of the rotor 120, and configured to generate a rotating electromagnetic field. The stator 110 is enclosed by a housing 135 of the electric machine 100.

[0058] Furthermore, the electric machine 100 comprises the rotor 120, which is driven by the rotating magnetic field produced by the stator 110. The rotor 120 is rigidly connected to the shaft 101 driven by the electric machine 100 (which may be connected to the rotor shaft of the rotor 120 or may be identical to the rotor shaft of the rotor 120). The rotor 120 comprises a rotor body 122. 24-1914

[0059] - 11 -

[0060] The rotor 120 of an electric machine 100 can have a laminated iron core (e.g., composed of mutually insulating sheets) as its rotor body 122. Fig. 1b shows an exemplary rotor body 122 of a rotor 120 in a perspective view. The rotor body 122 extends along the axis of rotation or the longitudinal axis of the rotor 120 from a first end face 128 to an opposite second end face 129. In the illustrated example, the rotor body 122 has different salient poles 124 arranged at different angular positions around the axis of rotation of the rotor 120. The salient poles 124 can be evenly distributed around the axis of rotation. A rotor coil (i.e., windings) can be arranged around each salient pole 124, through which a magnetic field is generated. The individual salient poles 124 can thus form magnetic poles of the rotor 120.

[0061] The rotor body 122 has a central opening 123, in particular a bore, into which the rotor shaft 101 of the rotor 120 can be inserted. The rotor shaft 101 can be rotatably mounted on the end faces of the rotor body 122 via respective bearing surfaces to enable rotation of the rotor 120.

[0062] Between each pair of directly adjacent salient poles 124 of the rotor body 122, a rotor slot 125 is formed, in which the windings of the adjacent salient poles 124 are arranged. A rotor slot 125 extends along the longitudinal and / or rotational axis from the first end face 128 to the opposite second end face 129 of the rotor body 122. The rotor body 122 and the individual rotor slots 125 can each have a specific overall length 127 from the first end face 128 to the second end face 129. 24-1914

[0063] - 12 -

[0064] The rotomut 125 between two directly adjacent (circumferentially) salient poles 124 has an opening 126 on the outer surface of the rotor body 122 facing away from the rotor shaft, the opening 126 extending along the longitudinal axis from the first end face 128 to the second end face 129 of the rotor body 122. In the direction opposite the longitudinal axis, the opening 126 is bounded by (mutually facing) legs 131 of the pole shoes 130 of the two directly adjacent salient poles 124.

[0065] To manufacture a rotor 120, electrically conductive windings can be wound around the salient poles 124, such that windings of the two directly adjacent salient poles 124 are arranged in each rotor slot 125. After arranging the windings, the openings 126 of the individual rotor slots 125 can each be covered with a slot closure wedge. A slot closure wedge can be inserted from an end face 128 between the legs 131 of the pole shoes 130 of the two directly adjacent salient poles 124 to cover the opening 126.

[0066] Fig. 1c shows an exemplary slot closure wedge 180, which has a cover area 186 that covers the opening 126 of a rotor slot 125. The cover area 186 can have an outer surface designed to complete the outer surface of the rotor body 122 at the opening 126 to be covered. The cover area 186 can extend (along the longitudinal axis) from a first end face 181 to an opposite second end face 182. The first end face 181 of the cover area 186 can be arranged on the first end face 128 of the rotor body 122. The second end face 182 of the cover area 186 can be arranged on the second end face 129 of the rotor body 122. The length 184 of the cover area 186 of the groove locking wedge 180 can correspond to the overall length 127 of the rotor body 122. 24-1914

[0067] - 13 -

[0068] The cover area 186 can have lateral profiles 183, each extending along the longitudinal axis from the first end face 181 to the second end face 182 of the cover area 186. For the insertion of the groove-locking wedge 180 between two legs 131 of the pole shoes 130 of two directly adjacent leg poles 124, a first profile 183 can face a corresponding (complementary) counter-profile 193 of the first leg 131, and the opposite second profile 183 can face a corresponding (complementary) counter-profile 193 of the second leg 131 (see Fig. Id). The counter-profiles 193 of the legs 131 and the corresponding profiles 183 of the groove-locking wedge 180 can be slid into one another, so that the inserted groove-locking wedge 180 is held between the two legs 131. A profile 183 can, for example, have a spring that runs from the first end face 181 to the second end face 182.The complementary profile 193 can have a complementary groove for this spring. Alternatively, the profile 193 can have a spring and the profile 183 can have the complementary groove.

[0069] The slot closure wedge 180 can further have an immersion area 185 that extends from the cover area 186 into the rotor slot 125 when the slot closure wedge 180 covers the opening 126 of the rotor slot 125. The immersion area 185 can extend along the longitudinal axis from the first end face 181 to the second end face 182 of the cover area 186. Furthermore, the immersion area 185 can extend further along the longitudinal axis at the first end face 181 and / or at the second end face 182 (so that, in the pushed-in state of the slot closure wedge 180, the immersion area 185 projects beyond the first end face 128 and / or the second end face 129 of the rotor body 120). The protruding part of the immersion area 185 can be used, for example, to guide the windings 190 on the respective end face 128, 129 of the rotor body 122 (i.e., on the respective winding head).The immersion area 185 can extend radially (i.e., essentially perpendicular to the covering surface of the covering area 186) from the covering area 186 towards the axis of rotation of the rotor body 122. The immersion area 185 can thus penetrate radially into the respective rotor groove 125 when the groove closure wedge 180 covers the rotor groove 125. The immersion area 185 can have a specific immersion depth in the radial direction. The rotor groove 125 can, for example, have a total depth measured from the outer surface of the rotor body 122 (i.e., from the outer diameter of the rotor body 122). The immersion depth of the immersion area 185 can be, for example, 20% or more, or 50% or more, or 70% or more of the total depth.

[0070] As already explained above, in a rotor slot 125, which is bounded by a first salient pole 124 and by a directly adjacent second salient pole 124, first windings 190 around the first salient pole 124 and second windings 190 around the second salient pole 124 can be arranged. The insertion area 185 of the slot closure wedge 180 can be configured to form, at least in part, a partition between the first and second windings 190.

[0071] Following the arrangement of the slot closure wedge 180 at the openings 126 of the corresponding rotor slots 125 of the rotor body 122, the remaining cavities 192 of the covered rotor slots 125 can each be filled with a potting compound in order to locally fix the windings 190 in the individual rotor slots 125.

[0072] Stop elements 187 can be arranged on the end faces 181, 182 of the cover area 186 of the groove locking wedge 180, with which the groove locking wedge 180 can be fixed along its longitudinal axis (e.g., by abutting a stop element 187 against a bearing or against a slip ring module of the electric machine 100). - 15 -

[0073] The potting compound is introduced in a liquid state into the cavities 192 of the individual rotor slots 125. Cup-shaped covers with holes can be arranged on the end faces 128, 129 of the rotor body 122, through which the liquid potting compound can be introduced into the cavities 192. The potting compound can be introduced under a specific pressure to ensure that the cavities 192 are completely filled with potting compound.

[0074] As previously explained, during the manufacture of a rotor 120, a slotted locking wedge 180 can be inserted axially from an end face 128, 129 of the rotor body 122 between the legs 131 of the pole shoes 130 of two directly adjacent salient poles 124 to cover the rotomut 125 formed by the salient poles 124. The profile 183 on the longitudinal edges of the covering area 186 of the slotted locking wedge can have an interference with respect to the mating profile 193 of the legs 130 to ensure a reliable seal of the cavity 192. However, such a positive overlap typically leads to a relatively high assembly force when inserting the groove locking wedge 180. On the other hand, a negative overlap of the profile 183 of the groove locking wedge 180 with respect to the profile 193 of the corresponding leg 130 would lead to a leak in the cavity 192.If there is a relatively precise match between the two profiles 183, 193, manufacturing tolerances may occasionally lead to a positive or negative overlap, which would in each case result in the disadvantages described.

[0075] This document describes a groove closure wedge 180 which has at least one relief groove 203 extending along the longitudinal axis at the longitudinal edges and / or near the longitudinal edges of the cover area 186, as illustrated by way of example in Figures 2a and 2b. In the example shown in Fig. 2a, the profile 183 of the groove closure wedge 180 has a 24-1914

[0076] - 16 -

[0077] The spring (in particular a wave crest) and the counter-profile 193 of the leg 193 have a corresponding groove (or a corresponding wave trough) so that the spring of the profile 183 of the groove-closing wedge 180 can be pushed along the longitudinal axis into the corresponding groove of the profile 193 of the leg 130. The relief groove 203 runs within the spring of the profile 183 of the groove-closing wedge 180, so that the spring is divided into a first partial spring 201 and a second partial spring 202, which are arranged one behind the other or one above the other in the radial direction. The spring of the profile 183 of the groove-closing wedge 180 can thus, starting from the interior of the cavity 192, first have a first partial spring 201, followed in the radial direction by the relief groove 203, and then in the radial direction by the second partial spring 202.

[0078] The relief groove 203 between the two partial springs 201, 202 allows the two partial springs 201, 202 to be compressed together radially during assembly, thus reducing the width of the relief groove 203 along the radial direction. This reduces the assembly forces required when inserting the locking wedge 180 without (significantly) impairing the seal between the two profiles 183, 193.

[0079] In the example shown in Fig. 2b, the relief groove 203 is arranged between the spring 211 of the profile 183 (which is arranged in the corresponding groove of the counter-profile 193) and the central section 212 of the cover area 183, which is arranged between the two longitudinal edges of the cover area 183, in particular such that the relief groove 203 forms a bending point through which the cover area 183 can be compressed circumferentially during insertion, thereby reducing the assembly forces to be applied without (significantly) impairing the seal between the two profiles 183, 193. 24-1914

[0080] - 17 -

[0081] The relief groove 203 is preferably arranged on the inside of the cover area 183 facing the cavity 192.

[0082] An elastic sealing element 303 can be arranged in the relief groove 203, as shown by way of example in Figures 3a and 3b. The sealing element 303 can be arranged on the groove closure wedge 180 by a multi-component manufacturing process. By providing a sealing element 303 (extending along the longitudinal axis) in the relief groove 203, the sealing effect of the functional closure wedge 180 can be further increased.

[0083] Thus, an additional longitudinal groove 203 (i.e., a relief groove) can be provided in a groove locking wedge 180, which reduces the stiffness of the groove locking wedge 180, in particular of an edge of the cover area 186 of the groove locking wedge 180, in at least one transverse direction (perpendicular to the longitudinal axis). In this way, a groove locking wedge 180 with a profile 183 can be used that always has a positive overlap with respect to the mating profile 193 of the respective leg 130, without (significantly) increasing the assembly force required.

[0084] Alternatively or additionally, a sealing element 303 can be provided longitudinally to reliably seal the complementary profiles 183, 193. This makes it possible, if necessary, to use a profile 183 with negative overlap with respect to the mating profile 193 (to enable the lowest possible assembly force) without (significantly) impairing the seal. Furthermore, especially when using a 2K technology (e.g., injection molding the elastomer of the sealing element 303 directly onto the hard base body of the groove closure wedge 180), a sealing element can be attached axially to seal the bandage and / or the sealing cap on the respective end face of the rotor 120. 24-1914

[0085] - 18 -

[0086] The present invention is not limited to the embodiments shown. In particular, it should be noted that the description and the figures are intended only to illustrate the principle of the proposed devices and systems by way of example.

Claims

Claims 1) Slot closure wedge (180) for covering a rotor slot (125) of a rotor body (122) of a rotor (120) of an electric machine (100), wherein the rotor slot (125) is bounded by a first salient pole (124) and a second salient pole (124) of the rotor body (122); wherein - the slot closure wedge (180) comprises a cover area (186) designed to cover an opening (126) between the two leg poles (124) of the rotor body (122); - the first salient pole (124) has a first pole shoe (130) with a first leg (131) facing the opening (126) of the rotor slot (125); - the cover area (186) on a first edge facing the first leg (131), which runs along a longitudinal axis of the groove closure wedge (180), has a first profile (183) which is complementary to a corresponding first counter-profile (193) of the first leg (131); and - the cover area (186) has a relief groove (203) extending along the longitudinal axis, which is designed to reduce the stiffness of the cover area (186) at the first edge in a direction transverse to the longitudinal axis. 2) Groove locking wedge (180) according to claim 1, wherein the relief groove (203) is designed such that the stiffness of the cover area (186) at the first edge in the outward direction is lower, in particular by at least 5% or at least 10% lower, than if the cover area (186) did not have the relief groove (203). 3) Groove locking wedge (180) according to one of the preceding claims, wherein 24-1914 - 20 - - the covering area (186) of the groove closure wedge (180) extends along the longitudinal axis and along a circumferential direction arranged transversely to the longitudinal axis; - the relief groove (203) is designed to reduce the stiffness of the cover area (186) in a radial direction that runs transversely to the longitudinal axis and transversely to the circumferential direction; and / or - the relief groove (203) is formed to reduce the stiffness of the cover area (186) in the circumferential direction. 4) Groove locking wedge (180) according to one of the preceding claims, wherein - the first profile (183) of the groove locking wedge (180) has a spring (211) which is designed to be arranged in a corresponding groove of the first counter-profile (193) of the first leg (130); - the groove locking wedge (180) has a relief groove (203) which is arranged within the spring (211) of the first profile (183) of the groove locking wedge (180). 5) Groove locking wedge (180) according to claim 4, wherein the relief groove (203) is arranged within the spring (211) of the first profile (183) of the groove locking wedge (180) such that the relief groove (203) divides the spring (211) of the first profile (183) into a first partial spring (201) and a second partial spring (202), which are arranged one above the other in a radial direction. 6) Groove locking wedge (180) according to claim 5, wherein the first partial spring (201) and second partial spring (202) formed by the relief groove (203) are designed such that the first partial spring (201) and the second partial spring (202) can be bent towards each other by a force acting in a radial direction, thereby creating a gap width of the relief groove (203) 24-1914 - 21 - is reduced. 7) Groove locking wedge (180) according to one of the preceding claims, wherein the groove locking wedge (180) has a relief groove (203) arranged between the first profile (183) of the cover area (183) and a central section (212) of the cover area (183), such that the relief groove (203) forms a bending point extending along the longitudinal axis at which the first profile (183) of the cover area (183) can be bent towards the central section (212) of the cover area (183) under the influence of a circumferentially acting force, thereby reducing the gap width of the relief groove (203). 8) Groove locking wedge (180) according to claim 7, wherein - the relief groove (203) is arranged such that, in the installed state of the groove closure wedge (180), the relief groove (203) does not contact the first counter profile (193) of the first leg (131); and / or - the relief groove (203) is arranged on a surface of the cover area (183) of the groove closure wedge (180) facing the rotor groove (125). 9) Groove locking wedge (180) according to one of the preceding claims, wherein the groove locking wedge (180) has an elastic sealing element (303) arranged in the relief groove (203). 10) Groove locking wedge (180) according to claim 9, wherein - the relief groove (203) extends from a surface of the cover area (183) of the groove closure wedge (180) into the cover area (183), in particular by 1 mm or more; and 24-1914 - 22 - - the sealing element (303) protrudes above the surface of the cover area (183) of the groove locking wedge (180), in particular by 0.5 mm or more. 11) Rotor (120) for an electric machine (100); wherein the rotor (120) comprises, - a rotor body (122) with a first salient pole (124) and a second salient pole (124) by which a rotomut (125) is bounded, which has an opening (126) between the two salient poles (124); and - a groove closure wedge (180) according to one of the preceding claims, by which the opening (126) is covered.

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