Rotor with extended active length for an electric machine

Abstract

A rotor for an electrically excited electric machine is described, wherein the rotor comprises a rotor body with N salient poles, with N > 1, and electrically conductive windings that form a winding head with N winding head regions at the corresponding N salient poles on each end face of the rotor body. The rotor further comprises an end-face component arranged on an end face of the rotor body, which has N recesses for receiving the corresponding N winding head regions of the winding head arranged on the end face, and which has at least N permanent magnets for the corresponding N salient poles.

Description

The invention relates to an electric machine, such as a (current-excited) synchronous machine. In particular, the invention relates to a rotor for an electric machine. A vehicle that is at least partially electrically powered comprises an electric machine for propelling the vehicle. The electric machine includes a stator that encloses a rotor of the electric machine, wherein a current-excited rotor has a rotor body with rotor slots in which electrically conductive windings for generating a magnetic field are arranged. The windings of the rotor form a winding head at each end face of the rotor, which extends axially beyond the rotor body. This document addresses the technical problem of increasing the power density of an electrical machine, in particular a current-excited synchronous machine, in a space-efficient manner. 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. According to one aspect, a rotor for a current-excited electric machine is described. The rotor comprises a rotor body with N salient poles, with N > 1, in particular N ≥ 3 (e.g., N ≥ 6). The rotor body can consist of a laminated core with a plurality of electrically insulated individual laminations. The salient poles form rotor slots in which electrically conductive windings are arranged. The rotor thus comprises electrically conductive windings, each forming a winding head with N winding head sections at the corresponding N salient poles on the end faces of the rotor body. The individual winding head sections of a winding head can each be connected to one salient pole. Furthermore, the rotor includes an end-face component arranged on one end face of the rotor body. Typically, the rotor includes an end-face component on each end face of the rotor body. The end-face component arranged on an end face of the rotor body can each comprise a laminated core with a plurality of electrically insulated individual laminations. The individual laminations of the end-face component can each have the same orientation as the individual laminations of the rotor body. The individual laminations can each be oriented perpendicular to the rotor shaft of the rotor. In particular, an end-face component can consist of a laminated core, wherein the laminated core can have N recesses for the winding head areas of the winding head and at least N receiving pockets for corresponding N permanent magnets. Furthermore, the end-face component, in particular the laminated core of the end-face component, can have a central bore for the rotor shaft of the rotor. The end face component may have one or more contours and / or structural elements designed to prevent and / or reduce magnetic short circuits between the different (permanent) magnets. The end-face component arranged on an end face of the rotor body thus has N recesses (in the laminated core) for receiving the corresponding N winding head areas of the winding head arranged on the end face. Furthermore, the end-face component has at least N permanent magnets for the corresponding N salient poles. The permanent magnets can each be arranged in a receiving pocket (of the laminated core) for receiving a permanent magnet. The one or more permanent magnets for a (salient) pole preferably have the same magnetic polarity as the (salient) pole to which the one or more permanent magnets are oriented (along the axial direction). By providing an end-face component with permanent magnets on at least one end face of the rotor body, the active length in the axial direction of the rotor can be increased in a space-efficient manner to provide an electric machine with a particularly high power density. An end-face component for a specific salient pole can each have at least one permanent magnet (arranged in a receiving pocket of the end-face component). The permanent magnet for the specific salient pole is preferably arranged on the outer side of the recess for the winding head area of ​​the winding head, facing away from the rotor shaft of the rotor. This allows for a particularly reliable increase in the active length of the rotor. The end-face component for a salient pole can have two or more permanent magnets. Using multiple permanent magnets per rotor pole can further increase the power density of the electric machine. The N recesses of the end-face component can each have an electrically insulating layer on an inner side facing the respective winding head area. This allows for a particularly reliable increase in the active length of the rotor. The individual salient poles of the rotor body typically each have a pole shoe, with the pole shoes of the salient poles typically forming the outer contour and / or the outer surface of the rotor. The one or more permanent magnets of the end-face component for a specific salient pole can each be arranged axially aligned with the pole shoe of that specific salient pole. This allows for a particularly effective increase in the active length of the rotor. The rotor may have an end disk located on an outer end face of the end face component. The end disk may be oriented perpendicular to the rotor shaft. The end disk may optionally be fastened to the rotor body (particularly to an end face of the rotor body) by one or more axially extending screws. The end disk may be designed to press the end face component axially against the end face of the rotor body against which the end face component rests. Alternatively or additionally, the end disk may be designed to block axial displacement of the permanent magnets. By providing end disks on the outer end faces of the rotor's end face components, the axial length of the rotor can be increased in a particularly effective and reliable manner. According to another aspect, an electrical machine, in particular a (current-excited) synchronous machine, is described, which includes the rotor described in this document. Furthermore, the electrical machine typically includes a stator. 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. It should be noted that the devices 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. The invention will now be described in more detail with reference to exemplary embodiments. Figure 1a shows an exemplary electric machine; Figure 1b shows a perspective view of an exemplary rotor body; Figure 1c shows a perspective view of an exemplary slot locking wedge; Figure 2a shows a perspective view of an exemplary rotor with rotor windings; Figure 2b shows an exemplary support ring; and Figures 3a to 3e show exemplary views of a rotor with an extended active length. As stated at the outset, this document deals with the efficient increase of the power density 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 rotational 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. 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. Furthermore, the electric machine 100 comprises the rotor 120, which is driven by the rotating magnetic field generated 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. 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 (i.e., in the axial direction) from a first end face 128 to an opposite second end face 129. In the example shown, 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. The rotor body 122 has a central opening 123, in particular a bore, into which the rotor shaft of the rotor 120 can be inserted. The rotor shaft can be rotatably mounted on the end faces of the rotor body 122 via respective bearing surfaces to enable rotation of the rotor 120. 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 groove 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 transverse direction to 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. 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 180 (see Fig. 1c). A slot closure wedge 180 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. Fig. 2a shows a perspective view of a rotor 120 with a rotor body 122, wherein a rotor shaft 202 is arranged in the central opening 123 of the rotor body 122. Furthermore, rotor windings 201 are arranged around each of the individual salient poles 124. The rotor windings 201 form a winding head 206 on each of the two end faces 128, 129 of the rotor body 122. The openings 126 of the individual rotor slots 125, which are to be covered, can be seen between the pole shoes 130 of the individual salient poles 124. During operation of the electric machine 100, centrifugal forces in a radial direction act on the rotor 120, in particular on the winding heads 206 on the two end faces 128, 129 of the rotor body 122. These forces could lead to damage to the electric machine 100, especially to the windings 201. To absorb the forces acting on the winding heads 206, a cup-shaped support ring 210 can be arranged as a cover on each end face of the rotor 120 (see Fig. 2b). The support ring 210 has a cover area 212 extending substantially parallel to the respective end face, which covers the respective end face in the axial direction. The cover area 212 has a central, circular recess 216 through which the shaft 202 of the rotor 120 passes. The support ring 210 further comprises an annular edge region 213, which extends axially from the outer edge of the cover region 212 towards the rotor body 122. The edge region 213 has an inner surface 214 which, when the support ring 210 is installed, can, for example, rest on bearing areas of the star disk 250 of the rotor 120 (in order to fix the support ring 210 to the rotor body 122). The star disk 250 can bear against the end face 128, 129 of the rotor body 122. The individual bearing areas can be formed by the outer surface of the star disk 250. During assembly, a support ring 210 can be pushed axially onto the support areas of the respective star disk 250 on both end faces of the rotor 120, so that the winding heads 206 on both end faces of the rotor 120 are each covered by a support ring 210 (each in the axial direction and in the radial direction). The fixation of a support ring 210 can be achieved by an interference fit between the support ring 210 and the star disk 250, in particular between the edge region 213 of the support ring 210 and the cylindrical surface of the star disk 250. To also ensure axial fixation, the support ring 210 can be screwed into the star disk 250. For this purpose, the support ring 210, in particular the cover region 212 of the support ring 210, can have one or more bores 217 through which a screw can be passed to fix the support ring 210 to the star disk 250. The star disk 250 itself can be fixed to the rotor body 112 via the respective winding head 206 and / or via an interference fit between the star disk 250 and the rotor shaft 202. Due to the winding heads 206 on the end faces 128, 129 of the rotor body 122, the rotor 120 of a current-excited synchronous machine (SSM) typically requires more installation space, particularly in the axial direction, than the corresponding rotor of a permanent magnet synchronous machine (PSM). A consequence of the larger axial installation space requirement of an SSM rotor 120 is that the power density of an SSM 120 is lower compared to a PSM (according to overall machine consideration), and consequently, more installation space must be provided. This document describes a current-excited rotor 120 in which the area of ​​the winding heads 206, which is normally not magnetically active, is made magnetically active, thereby extending the effective active length of the rotor 120. For this purpose, an end-face component (e.g., a laminated core structure) can be arranged on the individual end faces 128, 129 of the rotor body 122 (possibly in place of the star disk 250 and / or the support ring 210). This end face component has permanent magnets and is slid over the winding head 206 on the respective end face 128, 129. The winding head 206 on the respective end face 128, 129 is thereby electrically insulated from the end face component. The end face component can have receiving pockets for magnets in the areas radially outside of recesses for the respective winding head 206. Each receiving pocket can contain a permanent magnet.An end or balancing disc can be arranged on the outer face of the end-face component to axially clamp the end-face component and / or to protect the magnets from axial misalignment. This clamping reliably prevents a gap between the laminated core of the end-face component (for the PSM portion of rotor 120) and the laminated core of the rotor body 122 (for the SSM portion of rotor 120). Fig. 3a shows an exemplary rotor body 122 with a winding head 206 arranged on an end face 128, 129. The winding head 206 typically extends radially only to the base of the pole shoes 130 of the individual salient poles 124, so that windings 201 are typically not arranged in the area of ​​the pole shoes 130. This area can be used for arranging the end face component. In particular, an (electrically insulated) support surface 301 can be provided on the outside of the windings 201, on which the end face component can be arranged. Fig. 3b shows an exemplary end-face component 310, which has N recesses 311 for the winding head areas of the winding head 206 at the corresponding N leg poles 124 of the rotor body 122. The end-face component 310 is designed such that it can be arranged on an end face 128, 129 of the rotor body 120 (e.g., slid on in the axial direction), and that the winding head areas of the winding head 206 are arranged in the recesses 311 of the end-face component 310. The individual recesses 311 preferably have an electrically insulating insulating layer 313 on their inner surfaces facing the respective winding head area. The end-face component 310 further comprises receiving pockets 312 for permanent magnets. The individual receiving pockets 312 are arranged radially above the individual winding head recesses 311 (in the region of the pole shoes 130 of the salient poles 124). In the example shown in Fig. 3b, the end-face component 310 has two receiving pockets 312 for each winding head recess 311 (and thus for each pole of the rotor 120). A permanent magnet can be arranged in each of the individual receiving pockets 312. The permanent magnets arranged at the different poles of the rotor 120 have the magnetic polarity of the respective pole. Fig. 3c shows the end-face component 310 arranged on an end face 128, 129 of the rotor body 122. Fig. 3d additionally shows the rotor shaft 202 arranged in the recess 123 of the rotor body 122 and in the central bores 314 of the end-face components 310. Furthermore, Fig. 3e shows an end disk 320 arranged on the outer end face of an end-face component 310, which can be used to fasten the end-face component 310 to the rotor 120 in the axial direction. The measures described in this document make it possible to increase the active length of an SSM rotor 120 in the axial direction in a space-efficient manner in order to provide an electric machine 100 with a particularly high power density. 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

Rotor (120) for an electrically excited electric machine (100); wherein the rotor (120) comprises: - a rotor body (122) with N salient poles (124), with N>1, in particular N≥3; - electrically conductive windings (201) which form a winding head (206) with N winding head regions at the corresponding N salient poles (124) on end faces (128, 129) of the rotor body (122); and - an end face component (310) arranged on an end face (128, 129) of the rotor body (122), which has N recesses (311) for receiving the corresponding N winding head regions of the winding head (206) arranged on the end face (128, 129); and - which has at least N permanent magnets for the corresponding N salient poles (124). Rotor (120) according to claim 1, wherein the end face component (310) has at least N receiving pockets (312) for receiving the corresponding N permanent magnets. Rotor (120) according to one of the preceding claims, wherein the end-face component (310) for a specific salient pole (124) has at least one permanent magnet; and the permanent magnet for the specific salient pole (124) is arranged on an outer side of the recess (311) for the winding head area of ​​the winding head (206) located at the specific salient pole (124), facing away from a rotor shaft (202) of the rotor (122). Rotor (120) according to one of the preceding claims, wherein the end-face component (310) for a salient pole (124) has two or more permanent magnets. Rotor (120) according to one of the preceding claims, wherein the N recesses (311) of the end face component (310) each have an electrically insulating insulating layer (313) on an inner side facing the respective winding head area of ​​the winding head (206). Rotor (120) according to one of the preceding claims, wherein - the individual salient poles (124) of the rotor body (122) each have a pole shoe (130); and - the one or more permanent magnets of the end-face component (310) for a specific salient pole (124) are arranged in axial direction aligned with the pole shoe (130) of the specific salient pole (124). Rotor (120) according to one of the preceding claims, wherein the rotor (120) has an end disk (320) arranged on an outer end face of the end face component (310), and which is configured to: - press the end face component (310) in an axial direction against the end face (128, 129) of the rotor body (120) against which the end face component (310) abuts; and / or - block a displacement of the permanent magnets in an axial direction. Rotor (120) according to one of the preceding claims, wherein- the end-face component (310) comprises a laminated core with a plurality of electrically insulated individual laminations; and- the end-face component (310) in particular comprises a laminated core having N recesses (311) for the winding head areas of the winding head (206) and at least N receiving pockets (312) for the corresponding N permanent magnets. Rotor (120) according to one of the preceding claims, wherein the end face component (310) has a central bore (314) for a rotor shaft (202) of the rotor (120). Rotor (120) according to one of the preceding claims, wherein the rotor (120) has an end face component (310) on each of the two end faces (128, 129) of the rotor body (122).

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