Rotor having star disks protruding axially into rotor slots

Abstract

The invention relates to a rotor (1) for a separately excited electric machine, having: - a rotor body (2) having a rotor yoke (3) and having salient poles (4), arranged on the rotor yoke (3) so as to be distributed in the circumferential direction, for holding rotor windings of the rotor (1), wherein each salient pole (4) has a pole tooth (5) protruding radially from the rotor yoke (3) and has a pole shoe (6) arranged radially on the outside of the pole tooth (5), and wherein one slot (7) for receiving axial winding portions of two adjacent rotor windings is formed between each pair of adjacent salient poles (4); and - two star disks (10) for arranging on axially opposite end faces (8) of the rotor body (2) and for supporting winding heads formed by end-face winding portions of the rotor windings, said star disks each having a star disk yoke (11) for arranging on the rotor yoke (3), star disk arms (12) for arranging on the pole teeth (6), and star disk roof portions, protruding axially from the star disk arms (12), for arranging on the pole shoes (6), wherein each star disk (10) has slot lining elements (16) which are formed by axial side wall portions (17a, 17b), protruding into the slots (7), of the star disk (10) and which cover slot walls (9a, 9b, 9c) in respective slot end portions (7a) of the slots (7), wherein outer surfaces of the slot lining elements (16) have an electrically insulating material (14, 15) and thus form, in the region of the slot end portions (7a), a slot insulation for insulating winding conductors of the rotor windings with respect to the rotor body (2).

Description

[0001] Rotor with star disks axially immersed in rotor grooves

[0002] The invention relates to a rotor for a separately excited electric machine. The rotor comprises a rotor body with a rotor yoke and salient poles arranged circumferentially on the rotor yoke for holding rotor windings of the rotor, each salient pole having a pole tooth projecting radially from the rotor yoke and a pole shoe arranged radially on the pole tooth, and a groove being formed between each pair of adjacent salient poles for receiving axial winding sections of two adjacent rotor windings. The rotor also comprises two star disks for mounting on axially opposite end faces of the rotor body and for supporting winding heads formed by end-face winding sections of the rotor windings. The star disks each have a star disk yoke for mounting on the rotor yoke, star disk arms for mounting on the pole teeth, and star disk roofs projecting axially from the star disk arms for mounting on the pole shoes.The invention also relates to an electric machine for a motor vehicle.

[0003] The focus here is on externally excited or electrically excited electric machines for electrified motor vehicles, such as electric or hybrid vehicles. Such machines typically have a stationary stator and a rotor rotatably mounted relative to the stator. The rotor has current-carrying rotor windings, which are held by a rotor body, for example, a lamination stack. In a salient-pole rotor body, the winding conductors of the rotor windings are wound around the salient poles and thereby arranged section by section in axial slots of the rotor body. Between the end faces of the rotor body and the end-face winding sections of the rotor windings, which form the winding heads of the rotor windings, at least one star disk is typically arranged to support the winding heads.The star discs typically have a metallic base body overmolded with an insulating material, thus forming an insulating layer. To ensure correct positioning of the star discs on the rotor body, each disc may have a pin on its underside. This pin is inserted into the star disc base body and pressed into a blind-like opening in the respective end face of the rotor body. This process, however, undesirably pulls a swarf from the pin.

[0004] Due to their geometry, the insulation layers of the star disks sometimes have a greater wall thickness than necessary. Particularly in a corner-side transition area between the slot-internal winding sections and the end-face winding sections, the star disks exhibit large wall thicknesses in the insulation layer due to a prescribed minimum length of the slot insulation provided by the star disk between the winding conductors and the rotor body. This negatively impacts heat transfer between the winding conductors and the base body of the star disks. Furthermore, increased insulation lengths are required for a potting-free rotor to prevent leakage currents between the winding conductors and the rotor body along the surfaces of the star disks.

[0005] The object of the present invention is to provide a rotor with easily positioned star disks, in which the slot insulation and the cooling potential of the rotor are also improved.

[0006] This problem is solved according to the invention by a rotor and an electric machine with the features according to the respective independent claims. Advantageous embodiments of the invention are the subject of the dependent claims, the description, and the figures.

[0007] A rotor according to the invention for a separately excited electric machine comprises a rotor body with a rotor yoke and salient poles arranged circumferentially on the rotor yoke for holding rotor windings of the rotor, wherein each salient pole has a pole tooth projecting radially from the rotor yoke and a pole shoe arranged radially on the pole tooth, and wherein a groove is formed between two adjacent salient poles for receiving two axial winding sections of two adjacent rotor windings. The rotor also comprises two star disks for arrangement on axially opposite end faces of the rotor body and for supporting winding heads formed by end-face winding sections of the rotor windings. Each star disk has a star disk yoke for arrangement on the rotor yoke, star disk arms for arrangement on the pole teeth, and star disk roofs projecting axially from the star disk arms for arrangement on the pole shoes.Furthermore, each star disk has a number of slot lining elements corresponding to the number of slots. These elements are formed by axial side wall sections of the star disk that extend into the slots and cover the slot walls in the respective slot end sections. The outer surfaces of the slot lining elements are made of an electrically insulating material and thus form slot insulation in the area of ​​the slot end sections to insulate the winding conductors of the rotor windings from the rotor body.

[0008] The invention further relates to a separately excited electric machine for a motor vehicle, comprising a stator and a rotor according to the invention, rotatably mounted relative to the stator. The electric machine is, in particular, a drive machine or traction machine for a motor vehicle designed as an electrified vehicle. The electric machine can, for example, be a current-excited synchronous machine (SSM). The electric machine is preferably an internal rotor machine in which the stator surrounds the rotor and the rotor is rotatably mounted within a hollow cylindrical stator body.

[0009] The rotor comprises the rotor body, which is designed in particular as a laminated core of axially stacked electrical steel laminations. The rotor body is manufactured in a salient-pole configuration and features an annular rotor yoke through which a rotor shaft passes. The rotor shaft is rotationally fixed to the rotor body. The salient poles are arranged circumferentially around the rotor yoke, each having a pole tooth projecting radially from the rotor yoke and having parallel flanks, and a pole shoe radially adjacent to the pole tooth and projecting tangentially or laterally beyond it. A groove is formed between two adjacent pole teeth, extending axially through the rotor body between the two end faces. A pole gap is formed between two adjacent pole shoes, the tangential width of which is smaller than the tangential width of the respective groove and which forms an access opening to the respective groove.Each groove has groove walls in the form of a groove base, which is formed by an outer surface area of ​​the rotor yoke, two groove flanks, which are formed by the tooth flanks of the pole teeth adjacent to the groove, and a groove front side interrupted by the pole gap, which is radially opposite the groove base and which is formed by inner surfaces of the pole shoe areas projecting tangentially from the pole teeth.

[0010] Furthermore, the rotor can comprise rotor windings for exciting a rotor magnetic field, the winding conductors of which are wound around the salient poles, forming axial and end-face winding sections, with one winding section of two adjacent rotor windings arranged in each slot, and the end-face winding sections projecting from the end faces of the rotor body and forming winding heads. The winding conductors are particularly well-designed as wires.

[0011] Before the rotor body is wound with the winding conductors, a star disk is arranged on each end face. This disk forms a bearing area for the winding conductors at the transition between the slots and the end faces, and on the end faces themselves. It also insulates the winding heads from the laminated core and supports them against rotational centrifugal forces. The underside of the star disk forms a contact area or surface for contact with the end face of the rotor body. The star disks preferably have a metallic base, for example, a steel base, the underside of which forms the contact surface for contact with the respective end face of the rotor body. Sides of the base, other than the underside, are at least partially covered with an insulating layer.In this process, at least those areas of the top and side of the base body that form the contact surfaces for the winding conductors are covered by the insulating material. For example, the base body of the star disk, which increases the mechanical strength of the star disk and is designed to absorb heat from the winding conductors, can be partially overmolded with an electrically insulating material, such as plastic, which forms the insulating layer.

[0012] One shape of the star disks corresponds to a shape of the rotor body's end face. Each star disk has a star disk yoke, which also has a through-opening for the rotor shaft. The star disk arms are arranged radially from the star disk yoke and distributed circumferentially around it. The star disk roofs are located radially outside the star disk arms, projecting axially from one upper surface of the star disk arms and tangentially from one side of the star disk arms.An outer surface of the star disk yoke, an inner surface of the star disk roofs, and the upper surface of the star disk arms each define a winding space for the end-face winding sections of the rotor windings. The upper surface of a star disk arm forms the winding base of the winding space, the inner surface of a star disk roof, and the radially aligned outer surface of the star disk yoke form the winding flanges of the winding space. The star disks are not only positioned against the end faces of the rotor body, and thus outside the slots, but also extend into the slots. The areas of the star disks that extend into the slots form the slot lining elements. Within the slot, the slot walls are therefore covered by a slot lining element in the slot end sections adjacent to the end faces.The end sections of the groove have a significantly smaller axial dimension than the central section of the groove extending between them. The side wall sections of the star disks, forming a groove lining element, are formed by the facing arm flanks of two adjacent star disk arms, an outer surface area of ​​the star disk yoke between the arm flanks, and inner surface areas of two adjacent star disk roofs projecting tangentially from the arm flanks. Because the side wall sections, particularly the arm flanks of the star disk arms, are extended axially, the star disk arms are fitted onto the pole teeth, thus providing a positive-locking connection along the circumferential direction between the star disk and the rotor body and advantageously preventing rotation of the star disk along the circumferential direction.

[0013] At least the outer surfaces of the slot lining elements consist of an electrically insulating material to insulate the winding conductors from the rotor body in the transition area between the axial winding sections within the slot and the end-face winding sections forming the winding heads. In particular, the slot lining elements themselves consist of this electrically insulating material. For example, the insulating material, which covers at least part of the base of the star disk (apart from the underside), can project axially from the underside of the base in the area of ​​the relevant side wall sections. The insulation length can be increased by the side wall sections extending into the slot. This allows the corner contact surfaces in the transition area of ​​the star disk to be better adapted to the base, as they can be pushed further towards the rotor body.This improves heat dissipation in the rotor, thus increasing the efficiency and continuous torque of the electric machine.

[0014] In an advantageous embodiment of the invention, the groove walls of each groove have two steps between the central groove section and the axially opposite end groove sections adjacent to the end faces. These steps enlarge the respective groove cross-section in the end groove sections and form an axial stop for the groove lining elements of the star disks, which compensate for the enlarged groove cross-section. Thus, a first step is formed between a first end groove section adjacent to the first end face and the central groove section, and a second step is formed between a second end groove section adjacent to the axially opposite end face and the central section. The steps are formed in all groove walls of the groove, i.e., in the groove base, the groove flanks, and the groove face, and therefore extend along the groove cross-section.The steps result in a narrower groove width and depth in the central section of the groove compared to the end sections. This creates a larger cross-sectional area in the central section and a larger cross-sectional area in the end sections. These larger cross-sectional areas are compensated for by the respective groove lining elements, ensuring that the groove lined with these elements has a substantially constant cross-section in the axial direction. Each step width corresponds approximately to the wall thickness of the groove lining elements. The steps also serve to position the star discs and provide an axial stop for them.

[0015] It is advantageous to arrange slot insulation elements, particularly slot insulation papers, in the slots, overlapping the slot lining elements in the slot end sections, thus creating double slot insulation in the slot end section. The slot insulation papers completely line the slots along their entire axial length, covering the slot walls in the slot center section and the slot lining elements in the slot end sections. In the slot center sections, the slots are insulated only by the slot insulation paper, resulting in single insulation. In the slot end sections, the slots are doubly insulated by the slot lining elements and the slot insulation papers. This reliably prevents leakage currents in the transition area between the slot-internal and end-face winding sections between the rotor windings and the rotor body, particularly in the case of an unencapsulated rotor.

[0016] It can be provided that the length of the slot insulation elements is greater than the length of the slots, so that the slot insulation elements protrude axially from the slots on both sides. Bulges are arranged on the areas of the slot lining elements that protrude from the slots, forming L-grooves for receiving the slot insulation elements protruding from the slots. These bulges are formed, in particular, on the outer surfaces of the slot lining elements in the area of ​​a transition between the side wall sections and the upper surface of the star disks. The slot insulation papers thus abut axially against the L-grooves, preventing axial slippage of the slot insulation papers within the slots.

[0017] In one embodiment of the invention, at least one groove lining element and at least one groove wall of the associated groove form a snap connection for the positive locking connection of the respective star disk and the rotor body in each star disk. For example, the at least one groove lining element can have a snap-hook profile at least partially on its inner surface facing the groove wall, and the groove wall can have an undercut, for example, a receiving opening, for the snap-hook profile. For example, the side wall sections of the star disk arms can have the snap-hook profile on their inner surface, and the opening, for example, groove-like, can be arranged in the groove flank.When the star disk is axially pushed onto the rotor body, the snap hook profile slides over the groove flank until it snaps into the undercut of the rotor body, thereby positively connecting the star disk to the rotor body in the axial direction as well.

[0018] This advantageously eliminates the need for additional positioning elements on the rotor body and on the star slides, for example pins on the star disks, which would cause a chip to be pulled when pressed into an opening in the front face of the rotor body.

[0019] The embodiments and advantages presented with reference to the rotor according to the invention apply accordingly to the electrical machine according to the invention.

[0020] Further features of the invention will become apparent from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as those subsequently mentioned in the description of the figures and / or shown in the figures alone, are usable not only in the combinations specified, but also in other combinations or individually. The invention will now be explained in more detail with reference to a preferred embodiment and the drawings.

[0021] Figure 1 shows a perspective view of a section of a first embodiment of a rotor;

[0022] Fig. 2 shows a perspective view of a section of a second embodiment of a rotor; and

[0023] Fig. 3 shows a perspective view of a section of a third embodiment of a rotor.

[0024] In the figures, identical and functionally equivalent elements are provided with the same reference symbols.

[0025] Figures 1, 2, and 3 show perspective views of a section of a rotor 1 for a separately excited electric machine. The rotor 1 has a rotor body 2, which serves to hold rotor windings of the rotor 1 (not shown here). A section of the rotor yoke 3 and one of several salient poles 4 projecting from the rotor yoke 3 are shown. Each salient pole 4 has a pole tooth 5, in particular one with parallel flanks, and a pole shoe 6. A groove 7 is formed between each pair of salient poles 4, extending axially through the two end faces 8 of the rotor body 2. The grooves 7 are designed to receive axial winding sections of the rotor windings. Each rotor winding has two axial winding sections arranged on slot walls in the form of tooth flanks 9a of the associated pole tooth 5 and two end-face winding sections arranged on the end faces 8 of the rotor body 2.Each of the 7 slots contains axial winding sections of two adjacent rotor windings.

[0026] A star disk 10 or a winding head carrier is also arranged on each end face 8 of the rotor body 2, which is shown here in section in the area of ​​a salient pole 4. Each star disk 10 has a star disk yoke 11 arranged on the rotor yoke 3 and a star disk arm 12 for each pole tooth 5. Radially adjacent to the respective star disk arm 12 is a star disk roof, not shown here due to the section, which is arranged on the respective pole shoe 6. The star disk 10 has a contact surface on its underside for bearing against the end face 8 of the rotor body 2. In the embodiments according to Fig. 1 and Fig. 2, the star disk 10 has a base body 13, for example a steel base body, the underside of which forms the contact surface. Sides of the base body 13 apart from the underside are at least partially covered by an insulating layer 14. In the embodiment according to Fig.3 the star disk 10 is formed entirely from an insulating material 15, for example a high-performance plastic.

[0027] The star disk 10 also has groove lining elements 16, which are formed by axially extended side wall sections 17a, 17b of the star disk 10 that project axially from the bearing surface of the star disk 10. The side wall sections 17a, 17b are, in this context, arm flanks 17a of the star disk arms 12, outer surface areas 17b of the star disk yoke 11, and, not shown, inner surface areas of the star disk roofs. The groove lining elements 16 are arranged on the groove walls 9a, 9b, 9c, specifically on the tooth flanks 9a, a groove base 9b formed by the rotor yoke 3, and an inner surface 9c of the pole shoes 6, in a groove end section 7a of the groove 7. The groove end section 7a extends from the end face 8 to a groove center section 7b. Between the end section of the groove 7a and the middle section of the groove 7b, a step 18 is also formed in the groove walls 9a, 9b, 9c, which forms an axial stop for the groove lining elements 16 and thus for the star disk 11.The slot lining elements 16 are made of an electrically insulating material, for example the material of the insulating layer 14 or the insulating material 15, and insulate the winding conductors of the rotor winding in the slot end section 7a and furthermore in the area of ​​the end face 8 from the rotor body 2.

[0028] Furthermore, the side wall sections 17a and 17b have a projection 19 in the form of an L-groove, which forms a stop for a groove insulation paper (not shown) that can be arranged in the groove 8. The groove insulation paper protrudes from the grooves 7, abuts the projection 19, and together with the associated groove lining element 16 provides double insulation in the groove end section 7a, thus enabling the rotor 1 to be manufactured without potting.

[0029] In the design of the rotor 1 according to Figs. 1 and 2, the groove lining element 16 forms a snap connection 20 with the rotor body 2, thus positively connecting the star disk 10 to the rotor body 2. For this purpose, the arm flank 17a has a snap hook profile 21 on its inner surface, which, with an undercut 22 in the associated groove wall 9a, forms the snap connection 20. The snap connection 20 eliminates the need for other positioning elements.

Claims

Patent claims 1. comprising a rotor (1) for a separately excited electrical machine: - a rotor body (2) with a rotor yoke (3) and salient poles (4) arranged circumferentially on the rotor yoke (3) for holding rotor windings of the rotor (1), wherein each salient pole (4) has a pole tooth (5) projecting radially from the rotor yoke (3) and a pole shoe (6) arranged radially outside the pole tooth (5), and wherein a groove (7) for receiving axial winding sections of two adjacent rotor windings is formed between two adjacent salient poles (4), - two star disks (10) for arrangement on axially opposite end faces (8) of the rotor body (2) and for supporting winding heads formed by end-face winding sections of the rotor windings, each with a star disk yoke (11) for arrangement on the rotor yoke (3), star disk arms (12) for arrangement on the pole teeth (6) and star disk roofs projecting axially from the star disk arms (12) for arrangement on the pole shoes (6), characterized in that each star disk (10) has groove lining elements (16) which are formed by axial side wall sections (17a, 17b) of the star disk (10) immersed in the grooves (7) and which cover groove walls (9a, 9b, 9c) in respective groove end sections (7a) of the grooves (7), wherein outer surfaces of the groove lining elements (16) have an electrically insulating material (14, 15) and thus form a groove insulation in the area of ​​the groove end sections (7a) for insulating winding conductors of the rotor windings from the rotor body (2).

2. Rotor (1) according to claim 1 , characterized in that the side wall sections (17a, 17b) of the star disks (10) forming a groove lining element (16) are formed by arm flanks (17a) of two adjacent star disk arms (12), an outer side area (17b) of the star disk yoke (11) between the arm flanks (12) and inner sides of two adjacent star disk roofs are formed.

3. Rotor (1) according to claim 1 or 2, characterized in that the star disks (10) each have a metallic base body (13) whose underside forms a contact surface for contacting the respective end face (8) of the rotor body (2), wherein sides of the base body (13) apart from the underside are at least partially covered by an insulating layer (14) and wherein the insulating layer (14) projects axially on the underside of the respective base body (13) to form the side wall sections (17a, 17b) forming the groove lining elements (16).

4. Rotor (1) according to one of the preceding claims, characterized in that the groove wall of each groove (7) has two steps (18) between a groove center section (7b) and the axially opposite groove end sections (7a) adjacent to the end faces (8), by which a respective groove cross-section in the groove end sections (7a) is enlarged and which form a respective axial stop for the groove lining elements (16) of the star disks (10) that at least partially compensate for the enlarged groove cross-section.

5. Rotor (1) according to one of the preceding claims, characterized in that slot insulation elements, in particular slot insulation papers, are arranged in the slots (7) which are arranged overlapping with the slot lining elements (16) in the slot end sections (7a), so that a double slot insulation is formed in the area of ​​the slot end sections (7a).

6. Rotor (1) according to claim 5, characterized in that the length of the slot insulation elements is greater than the length of the slots (7), so that the slot insulation elements project axially out of the slots (7) on both sides, wherein projections (19) are arranged on areas of the slot lining elements (16) projecting out of the slots (7), which form L-slots for receiving the slot insulation elements projecting out of the slots (7).

7. Rotor (1) according to claim 6, characterized in that the protrusions (19) on the outer surfaces of the groove lining elements (16) in The area of ​​a transition between the side wall sections (17a, 17b) and a top surface of the star disks (10) is formed.

8. Rotor (1) according to one of the preceding claims, characterized in that at least one groove lining element (16) and the groove wall (9a, 9b, 9c) of the associated groove (7) form a snap connection (20) for positive locking connection of the respective star disk (10) and the rotor body (2) in each star disk (10).

9. Rotor (1) according to claim 8, characterized in that the at least one groove lining element (16) has at least partially a snap hook profile (17) on its inner surface facing the groove wall (9a) and the groove wall (9a) has an undercut (22) for the snap hook profile (17).

10. Electric machine with a stator and a rotor (1) rotatably mounted with respect to the stator according to one of the preceding claims.

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