Cover device for a rotor with double steel sheeting

Abstract

The invention relates to a covering device (5) for a rotor (1) of a separately excited electric machine for covering winding heads of rotor windings of the rotor (1) arranged on an end face of a rotor body (2) of the rotor (1), comprising: - a first cover element (6) with a first metallic, profiled, deep-drawn cover plate (7) for covering the winding heads, which has several sheet bulges (8) arranged in the circumferential direction, wherein the sheet bulges (8) form shell-like indentations on a lower side of the first cover plate (7) facing the winding heads for partially receiving the winding heads and form bulges (10) on a upper side (9) of the first cover plate (7), - a second cover element (12) with a second metallic, rotationally symmetrical cover plate (13) through which a disk-like cover is formed axially overlapping to the top (9) of the first cover plate (7), wherein the cover plates (7, 13) are mechanically connected and a cavity is formed between the top (9) of the first cover plate (7) and the second cover plate (13).

Description

[0001] The invention relates to a covering device for a rotor of a separately excited electric machine for covering the winding heads of rotor windings arranged on an end face of a rotor body. The invention also relates to a rotor.

[0002] 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 that is 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. Winding sections of the rotor windings that extend over the end faces of the rotor body form axially projecting winding heads at the end faces. The rotor also typically has covering devices that axially cover the rotor body, enclosing the winding heads.These covering devices can also be used to cool the winding heads. To optimize cooling efficiency, the distance between the winding heads and the covering device should be as small as possible to reduce thermal resistance.

[0003] DE 10 2022 111 413 A1 proposes equipping the rotor with at least one end-face component, which is arranged on the end face of the rotor body, axially overlaps the rotor windings, and whose geometry on the side facing the rotor body corresponds to an outer contour of the rotor windings. For stability reasons, the end-face component is designed as a die-cast part, in particular an aluminum die-cast part. However, such die-cast parts are complex and expensive to manufacture.

[0004] The object of the present invention is to provide a cost-effective, stable and highly efficient cooling cover device for a rotor of a separately excited electric machine.

[0005] This problem is solved according to the invention by a covering device and a rotor 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.

[0006] A cover device according to the invention for a rotor of a separately excited electric machine serves to cover the winding heads of rotor windings arranged on an end face of a rotor body. The cover device comprises a first cover element with a first metallic, profiled, deep-drawn cover plate for covering the winding heads, which has several sheet bulges arranged circumferentially. The sheet bulges form shell-like indentations on an underside of the cover plate facing the winding heads for at least partially receiving the winding heads, and bulges on an upper side of the first cover plate. The cover device also comprises a second cover element with a second metallic, rotationally symmetrical cover plate, through which a disk-like lid is formed, axially overlapping the upper side of the first cover plate.The cover plates are mechanically connected, and a cavity is formed between the top of the first cover plate and the second cover plate.

[0007] A rotor according to the invention for a separately excited electric machine comprises a rotor body, rotor windings which are held by the rotor body and form winding heads on opposite end faces of the rotor body, and at least one covering device according to the invention, which is arranged overlapping with one of the end faces of the rotor body, covering the associated winding heads, and is mechanically connected to the rotor body. In particular, the rotor body comprises two covering devices according to the invention, which are arranged axially on both sides of the rotor body. The rotor body is in particular designed as a laminated core of axially stacked laminations. The rotor body is in particular manufactured in a salient-pole configuration and has an annular rotor yoke through which, in particular, a rotor shaft is passed. The rotor shaft is rotationally fixed to the rotor body.Around the circumference of the rotor yoke, salient poles are arranged, each featuring a pole tooth projecting radially from the rotor yoke and having parallel flanks, and a pole shoe that is radially adjacent to the pole tooth and projects 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.

[0008] Axial winding sections of the rotor windings are arranged in the slots. End-face winding sections of the rotor windings are arranged at the end faces, forming the winding heads. The rotor windings feature, in particular, a wire-like winding conductor, which is wound around the pole teeth in several layers and turns. Since the winding heads are subjected to high mechanical loads during operation of the electric machine due to rotation, a star disk is arranged against each end face and thus between the rotor body and the respective winding heads to support them. The star disk also serves as electrical insulation between the winding conductors and the rotor body.

[0009] The winding heads are also covered or enclosed by the cover devices. Each cover device is multi-part and has two cover elements arranged axially overlapping each other. Each cover element has a cover plate, which is preferably made of sheet steel. Furthermore, each cover element can have a through-hole in the respective cover plate for a rotor shaft that is non-rotatably connected to the rotor body. The through-hole can be a hole located centrally in the respective cover plate, which is formed, for example, by punching it out of the sheet steel.

[0010] The first cover plate is positioned adjacent to the winding heads. This cover plate has a profile formed by cost-effective deep drawing, which follows the surface contour of the rotor body's end face, where the winding heads are mounted. During the deep drawing process, the sheet metal curves are incorporated, forming the shell-like indentations or recesses on the underside. These indentations are cavities open at least towards the end face, with each indentation accommodating a winding head. The indentations ensure that the distance between a winding head surface and the underside of the cover plate remains essentially constant and can be particularly small to reduce thermal resistance between the winding heads and the cover assembly. The sheet metal curves form the bulges or recesses on the upper surface of the first cover plate, which is axially opposite the underside.There are protrusions that cause the surface of the first cover plate to be non-rotationally symmetrical. Therefore, the top surface of the first cover plate is not a surface of revolution.

[0011] To prevent this rotationally asymmetrical surface from causing end-face turbulence on the rotating rotor during operation of the electric machine, which would reduce the machine's efficiency, the upper surface of the first cover plate is covered by the second cover element, forming the cavity. The second cover plate is designed as a rotationally symmetrical, plate-shaped lid. For example, the first cover plate can have an axially extending collar area that projects axially beyond the protrusions, and the lid rests on the circular edge of this collar, enclosing the cavity. The resulting cavity is thus bounded axially by the upper surface of the first cover plate (i.e., the underside of the lid) and radially outwardly by the collar area of ​​the first cover plate. The covering assembly therefore functions as a double-walled end plate.

[0012] The cover elements are mechanically connected, resulting in a cover assembly with exceptionally high mechanical stability, comparable to that of a die-cast component. For example, the cover elements can have connection areas for mechanically joining them, designed as aligned screw holes in the cover plates. Screws can be inserted through these holes to mechanically connect the cover plates. The second cover plate can also be deep-drawn. For instance, a circumferential groove or annular groove can be formed in the top surface of the cover plate, containing the screw holes. This ensures that the screw heads are countersunk when the cover elements are screwed together and therefore do not protrude from the cover plate.The cover device can also be screwed to the associated star disk for mechanical connection to the rotor body via the screws.

[0013] The covering device preferably has an annular outer shell element extending from an edge of the cover towards the end faces and radially surrounding the first covering element. In the installed state of the outer shell element, the first covering plate thus forms an inner covering plate, and the second covering plate forms an outer covering plate. The outer shell element can, for example, be designed as a cylindrical steel band. For example, the outer shell element can close off the indentations, which are also open radially outwards. The outer shell element can also radially surround the respective star disk and stabilize the star disks by providing support for axially projecting, radially outwardly arranged star disk roofs against an inner surface of the outer shell element.

[0014] It proves advantageous if the cavity is designed as a cooling channel for conveying a coolant intended for winding head cooling. The coolant, which can be, for example, a cooling fluid in the form of oil, can be guided close to the winding heads by the first cover plate, which is positioned at a small distance from them, thus absorbing and dissipating the heat generated by the winding heads. For example, the cover can have an inlet area, aligned with coolant outlet openings in the rotor shaft carrying the coolant, and an outlet area for the radial discharge of the coolant conveyed within the cavity. The outlet openings can, for example, be designed as slots in the cover.The rotor shaft can be designed as a hollow shaft to guide the coolant and has coolant outlet openings in one wall for releasing the coolant into the cavity of at least one cover. The coolant can be transported purely by centrifugal force from the radially inner inlet area to the radially outer outlet area by the rotation of the rotor. Due to the radial discharge of the coolant, it can be flung onto the winding heads of the stator surrounding the rotor and thus advantageously used to cool the stator winding heads as well.

[0015] Furthermore, the first cover element can have collection areas for the coolant, which are formed as beads in the upper surface of the first cover plate. These beads can collect the coolant at overheating-prone areas of the winding heads before it is released through the outlet openings due to centrifugal force. The beads can be arranged circumferentially on the upper surface. For example, a bead can be positioned between two adjacent protrusions. This ensures particularly reliable cooling of the rotor winding heads.

[0016] The embodiments and advantages presented with reference to the covering device according to the invention apply accordingly to the rotor according to the invention.

[0017] 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 the features and combinations of features mentioned below in the description of the figures and / or shown in the figures alone, are not only usable in the combinations specified, but also in other combinations or on their own.

[0018] The invention will now be explained in more detail with reference to a preferred embodiment and the drawings. The drawings show: Fig. 1. A schematic perspective view of a rotor with a cover device; and Fig. 2 a schematic perspective view of the rotor with a first cover element of the cover device.

[0019] In the figures, identical and functionally equivalent elements are provided with the same reference symbols.

[0020] Fig. Figure 1 shows a rotor 1 for a separately excited electric machine, which can be used, for example, as a drive motor for an electric vehicle. The rotor 1 is designed as an internal rotor and can be rotatably mounted within a hollow cylindrical stator of the electric machine. The rotor 1 has a rotor body 2. The rotor body 2 has slots for receiving rotor windings of the rotor 1 (not shown here), the slots being closed by slot closure elements 3 or cover slides. A rotor shaft 4, designed here as a hollow shaft, passes through the rotor body 2 and is designed to guide a coolant axially through the rotor body 2. The rotor 1 also has two cover devices 5, which are arranged overlapping with the rotor body 2 at the end faces and are designed to enclose the winding heads of the rotor windings.

[0021] Each cover device 5 shows, as in Fig. Figure 2 shows a first cover element 6 with a three-dimensionally deep-drawn first cover plate 7. The cover plate 7 is made of sheet steel and has sheet plate bulges 8 formed by deep drawing. These sheet plate bulges 8 form indentations on an underside of the first cover plate 7 (not visible here) for receiving the winding heads. On an upper surface 9 of the first cover plate 7, the sheet plate bulges 8 form protrusions 10. Between two protrusions 10, beads 11 are also formed on the upper surface 9. A collar area 21 with an annular edge 22 of the first cover plate 7 projects axially beyond the protrusions 10.

[0022] Overlapping with the upper surface 9 of the first cover plate 7 is a second cover element 12, which has a second cover plate 13, also made of sheet steel, forming a rotationally symmetrical, plate-like lid. The lid 13 can, for example, rest on the edge 22. A casing element 14, which here is formed by a steel band, surrounds the winding heads radially and extends axially from the end face of the rotor body 2 to the second cover plate 13. Because the cover plates 7 and 13 are made of sheet steel, they achieve the necessary strength even with minimal material requirements and are significantly cheaper to manufacture. Furthermore, the expected cooling performance is comparable to that of a conventional die-cast aluminum lid.

[0023] The cover elements 6, 12 are mechanically connected by screws 15, which also allow the cover assembly 5 to be additionally fastened to the rotor body 2. For this purpose, the cover elements 6, 12 have fastening areas formed by aligned screw holes in the corresponding cover plates 7, 13. A top surface 16 of the cover 13 has a groove 17, formed, for example, by deep drawing, in which the screw holes for countersunk mounting of the screws 15 are located. Furthermore, both cover plates 7, 13 have filling openings 18 for a potting compound for encapsulating the rotor 1, which are aligned with each other. The cover assembly 5 also has a passage 19 for the rotor shaft 4, which is formed by aligned through-openings 20 in the cover plates 7, 13.

[0024] The mechanically connected cover elements 6, 12 form a cover assembly 5 with a substantially rotationally symmetrical, turbulence-reducing surface. Furthermore, the cover elements 6, 12 enclose a cavity that forms a cooling channel for a coolant used to cool the winding heads. The coolant supplied by the hollow rotor shaft 4 can thus be collected between the cover plates 7, 13 to fully utilize the cooling potential of the cover assembly 5. The coolant is thereby prevented from being blown off the end face by the ambient air in the electric motor compartment when the rotor 1 rotates and can instead spread evenly onto the upper surface 9 of the first cover plate 7, thus more effectively drawing heat from it.Furthermore, the coolant can be collected through the grooves 11 in the first cover plate 7 to further maximize the cooling performance before it is flung off through outlet openings, which are arranged, for example, in the second cover plate 13. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2022 111 413 A1

[0003]

Claims

[1] Covering device (5) for a rotor (1) of a separately excited electrical machine for covering winding heads of rotor windings of the rotor (1) arranged on an end face of a rotor body (2) of the rotor (1), comprising: - a first cover element (6) with a first metallic, profiled, deep-drawn cover plate (7) for covering the winding heads, which has several sheet bulges (8) arranged in the circumferential direction, wherein the sheet bulges (8) form shell-like indentations on a lower side of the first cover plate (7) facing the winding heads for partially receiving the winding heads and form bulges (10) on a upper side (9) of the first cover plate (7), - a second cover element (12) with a second metallic, rotationally symmetrical cover plate (13) through which a disk-like cover is formed axially overlapping to the top (9) of the first cover plate (7), wherein the cover plates (7, 13) are mechanically connected and a cavity is formed between the top (9) of the first cover plate (7) and the second cover plate (13). [2] Covering device (5) according to claim 1, characterized by , that the cover plates (7, 13) are made of sheet steel. [3] Covering device (5) according to claim 1 or 2, characterized by , that the covering device (5) has an annular mantle element (14) which extends from an edge of the cover (13) in the direction of the respective end face and which radially surrounds the first covering element (6). [4] Covering device (5) according to any one of the preceding claims, characterized by, that the first cover plate (7) has an axially extending collar area (21) that projects axially beyond the protrusions (10), on which the cover (13) rests, including the cavity. [5] Covering device (5) according to one of the preceding claims, characterized by that the cavity is designed as a cooling channel for guiding a coolant designed for winding head cooling. [6] Covering device (5) according to claim 5, characterized by , that the cover device (5) has an inlet area which is aligned with coolant outlet openings in a coolant-carrying rotor shaft (4) of the rotor (1) and an outlet area for radially discharging the coolant guided in the cavity. [7] Covering device (5) according to claim 5 or 6, characterized by, that the first cover element (6) has collection areas for collecting the coolant, which are formed as grooves (11) in the top surface (9) of the first cover plate (7). [8] Covering device (5) according to any one of the preceding claims, characterized by , that the cover elements have connection areas for mechanically connecting the cover elements, which are designed as screw holes arranged in alignment with each other in the cover plates. [9] Rotor (1) for a separately excited electric machine, comprising: - a rotor body (2), - Rotor windings which are held by the rotor body (2) and form winding heads on opposite end faces of the rotor body (2), and - at least one covering device (5) according to one of the preceding claims, which is arranged overlapping with one of the end faces of the rotor body (2) under covering the associated winding heads and is mechanically connected to the rotor body (2). [10] Rotor (1) according to claim 8, characterized by , that the rotor (1) has a rotor shaft (4) which is axially passed through the rotor body (2) and the at least one cover device (5) and is non-rotatably connected to the rotor body (2), wherein the rotor shaft (4) is designed as a hollow shaft for guiding a coolant and has outlet openings for releasing the coolant into the cavity of the at least one cover device (5).

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