Electric machine having surface-structured rotor and / or stator

Abstract

The invention relates to an electric machine (1), comprising a stator (2), which is accommodated in a manner fixed to a housing, and a rotor (4), which is rotatably mounted relative to the stator and which is spaced apart from the stator (2) by a radial gap (3). The rotor (4) and / or the stator (2) each comprise a lamination stack (5, 6) consisting of a plurality of laminations (7) stacked one on top of the other in the axial direction. A surface structure (9) that reduces aerodynamic resistance is formed on a surface (8) of the rotor (4) and / or the stator (2) facing the radial gap (3). In this case, the surface structure (9) is formed by stacking the laminations (7) on one another, said laminations having a circumferential structure (10), which forms the circumferential side on at least some of the laminations (7).

Description

Technical Field

[0001] This invention relates to an electric motor having a fixed stator and a rotor rotatably supported relative to the stator, the rotor being spaced apart from the stator by a radial clearance. The rotor and / or stator each comprise a lamination group consisting of a plurality of laminations stacked axially. Surface structures for reducing aerodynamic drag are constructed on the surfaces of the rotor and / or stator facing the radial clearance. Background Technology

[0002] In electric motors, frictional losses play a decisive role in the machine's efficiency and performance. Especially at high speeds, frictional losses caused by airflow around the rotor increase significantly. These aerodynamic losses arise from friction between the rotor's rotating surfaces and the surrounding air, leading to higher energy consumption and reduced efficiency. Therefore, understanding the causes and effects of these frictional losses is crucial in order to develop appropriate measures to minimize them and optimize the overall performance of the motor.

[0003] One possible solution to reduce frictional losses at the rotor is to reduce the rotor's circumferential speed. This can be achieved by using a rotor with a smaller diameter, thereby significantly reducing the effects of air friction. To still ensure the required power and torque transmission, this approach is typically combined with a higher transmission ratio. In this way, the speed can be matched to the operating range.

[0004] Furthermore, another solution is known from DE 10 2019 114 958 A1, which describes an electric motor for driving motor vehicles (such as passenger cars, trucks, or buses), having a stator and a rotor. Here, aerodynamic drag between the rotor and stator is reduced by special surface structures at the rotor and / or stator. These surface structures (implemented as recesses or protrusions, similar to the surface of a golf ball) reduce air friction and thereby reduce losses during motor operation. The surface structures can be implemented in the form of grooves, ribs, or pits to reduce aerodynamic drag by approximately 5% to 8%. The surface structures are manufactured here, in particular, by embossing, pressing, laser structuring, or chemical etching into the rotor surface. Alternatively, the surface structures can also be applied to the rotor or stator as a coating (e.g., by thin film or paint) to at least reduce manufacturing costs. However, compared to the motor according to the prior art, the manufacturing cost is still significantly higher due to the additional manufacturing steps. Summary of the Invention

[0005] In this context, the present invention is based on the objective of implementing a motor of the type mentioned at the beginning in such a way that the steps required to manufacture the motor and thereby minimize its cost.

[0006] The task is accomplished by means of a motor according to the invention. This document also relates to particularly suitable improvements to the invention.

[0007] According to the invention, an electric motor, preferably an electric motor, is provided, particularly for driving motor vehicles, having a stator fixedly received in a housing and a rotor rotatably supported relative to the stator (preferably about a rotation axis included by a rotor shaft) and spaced apart from the stator by a radial clearance.

[0008] Here, the rotor and / or stator each comprise a lamination group consisting of multiple laminations (especially plate laminations) stacked axially on top of each other. A surface structure is also constructed on the radial clearance-facing surfaces of the rotor and / or stator to reduce aerodynamic drag and thus form part of the surface. By specifically designing this surface structure on the radial clearance-facing surfaces of the rotor and / or stator, flow losses can be minimized. This results in improved motor efficiency because, especially at high speeds, less energy is lost due to air friction.

[0009] Furthermore, at least a portion (or subset, i.e., Teilmenge) of the laminations in the rotor and / or stator lamination assembly have circumferential structures formed (or removed, i.e., ausgenommen) on the circumferential side (i.e., on the outer circumference of the rotor lamination or the inner circumference of the stator lamination) and / or on the circumference of the corresponding lamination facing the radial gap. Here, the surface structure is constructed, particularly assembled, by stacking laminations with circumferential structures onto each other. Thus, the laminations with circumferential structures have a shape similar to a sprocket or chain link. Since the surface structure is also constructed by circumferential structures (which are formed and / or separated from the laminations during lamination manufacturing), no additional manufacturing steps (e.g., drilling, stamping, pressing, or laser structuring) are required to introduce the surface structure after the laminations are assembled into a rotor assembly. Therefore, the required manufacturing steps for the rotor can be reduced or kept to the same extent as for a rotor without additional surface structures. Therefore, when separating the laminates from the semi-finished products (especially sheet metal), a circumferential structure is simultaneously created, thus eliminating the need for additional manufacturing steps. Separation is preferably performed by cutting, and particularly preferably by stamping. However, other separation methods can also be used, such as laser cutting, waterjet cutting, or plasma cutting, as well as etching or milling.

[0010] In a particularly advantageous improvement of the invention, the corresponding circumferential structure includes a plurality of structural voids spaced angularly from each other in the circumferential direction of the lamination group and / or laminations. These structural voids here have at least partially different cross-sections, particularly different cross-sections in area and / or shape. By using the different cross-sections of the structural voids, the circumferential structure can be specifically adapted to different requirements, such as motor speed, efficiency, or cooling. Furthermore, by using laminations constructed with circumferential structures (which have structural voids with at least partially different cross-sections), a variety of possibilities for surface structure design are obtained. These structural voids, which are at least partially different in cross-section, enable the targeted modification and adaptation of the surface structure shaping. In particular, the differences in the cross-sections of the structural voids can influence specific aerodynamic characteristics of the surface structure, which can contribute to improved machine efficiency. Moreover, this approach provides high flexibility in the design of lamination groups, because customized surface structures optimally adapted to the requirements of motor applications can be achieved by combining different structural voids.

[0011] Therefore, an advantageous embodiment of the invention can also be seen below: recesses are formed by corresponding axially aligned structural gaps with at least partially different cross-sections in the stacked laminations, the recesses forming at least segmentally the surface structure. The recesses advantageously provide a surface structure that reduces aerodynamic drag on the rotor and / or stator, similar to that in a golf ball. Due to the at least partially different cross-sections of the structural gaps in the circumferential structure of the laminations, the recesses can also be variably designed in their axial shape, so that the recesses are not merely implemented as axially extending slots or gaps with consistently identical cross-sections. The portion of the rotor and / or stator surface formed by the corresponding recesses can thus approach a free-form surface, or be presented as a free-form surface through an envelope surface. However, due to the axial steps caused by the constant thickness of the laminations, the actual portion of the surface therefore has a discontinuous stepped orientation.

[0012] An advantageous improvement of the invention further lies in that the cross-sectional area of ​​the corresponding axially aligned structural recesses forming the recesses increases axially—especially in a stepped manner—from a minimum area to a maximum area, and then decreases again axially—especially in a stepped manner—from said maximum area to a minimum area. This ensures an advantageously simple design for the recesses and / or surface structure, as well as the circumferential structure.

[0013] It should be noted that, in principle, it is possible for at least a portion of the laminations constructing the surface structure to consist of a large number of laminations of various types, with different shapes, particularly in terms of circumferential structure and / or other lamination elements. However, from a manufacturing technology perspective, this is a less preferred feasible solution. Especially during lamination stamping, a large number of different stamping tools need to be prepared. This not only increases the cost of tool procurement but also the expenses associated with storing and managing these tools. Furthermore, using different stamping tools requires additional manufacturing steps and / or stamping machinery.

[0014] Therefore, it is preferable to construct lamination groups with only a few types of laminations (which have different shapes, especially in terms of circumferential structure and / or other lamination elements). It is conceivable that a portion of the laminations constituting the surface structure may contain at most eight, at most four, or at most two different types of laminations. Furthermore, it is possible that the number of lamination types depends on the number of poles of the motor. A portion of the laminations constituting the surface structure may here contain a number of different types of laminations equal to twice the number of poles of the motor, equal to the number of poles of the motor, or equal to half the number of poles of the motor. For example, both possibilities can be constructed when the motor is implemented as a synchronous machine, especially a permanent magnet excited or separately excited synchronous machine.

[0015] Especially in the context of needing as few different types of laminates as possible, but also generally advantageous in principle, in one embodiment of the invention, the laminates forming at least the recesses are at least partially stacked relative to each other—particularly about the longitudinal and / or radial axes—so that structural openings with at least partially different cross-sections are aligned with each other when the recesses are formed. Here, for each laminate, the structural openings of the circumferential structure should correspondingly have the same angular spacing. By stacking the laminates and their circumferential structures, especially by stacking them with an angular offset (where structural openings with at least partially different cross-sections are aligned to form the recesses of the surface structure), the surface structure and / or recesses can be achieved with a small number of types of laminates with different shapes.

[0016] Therefore, in another embodiment of the invention, it is even configured such that at least a portion, preferably, or even all, of the stacked sheets in at least one stacked group are constructed as a single, identical type of stacked sheet, each having the same shape. This significantly simplifies manufacturing, as only one stamping tool or one die is required, which also significantly reduces the required manufacturing steps and production costs.

[0017] The stacked sheets, which form at least a portion of the recesses and are correspondingly abutting each other, i.e., successively stacked, can be arranged, for example, in relation to the design of the target shape and / or circumferential structure of the recesses, and in principle—especially in the axial direction and / or about its longitudinal axis—rotate relative to each other by half a turn and / or and / or by 180°, a quarter turn and / or by 90°, or by integer divisions of 360° and / or by 360° divided by an integer. In particular, the integer can correspond to the number of structural gaps in at least one type of stacked sheet, such that the angular offset is equal to 360° divided by the number of structural gaps. Thus, the stacked sheets successively stacked can each rotate relative to each other by a structural gap. Furthermore, it is also possible to rotate 180° about the radial axis, i.e., essentially flip the stacked sheets. The rotation about the longitudinal axis and / or the radial axis also has a beneficial homogenizing effect on the magnetic and mechanical properties of the stacked sheet assembly.

[0018] Furthermore, one design aspect of the invention is advantageous: the structural voids are constructed at least partially rounded, particularly at least partially circular and / or arc-shaped, wherein structural voids having different radii, particularly in terms of area and / or shape, are structurally different. This results in an advantageously simple design for the circumferential structure, which still achieves the construction of effective recesses and / or effective surface structures that reduce the aerodynamic drag of the rotor and / or stator. Thus, the recesses are formed, in particular, close to a truncated spherical shape.

[0019] Here, in particular, the corresponding cross-section of the structural void, especially the corresponding cross-sectional portion, can be at least partially formed by a circular arc, preferably by two intersecting circular arcs, wherein one of the circular arcs or one of the circular arcs of different cross-sections or cross-sectional portions has a different radius. The other circular arc (where the center point of this arc is located at the center of the lamination) will here have the radius of the lamination itself, and therefore is always the same.

[0020] Furthermore, advantageously, in one embodiment of the invention, the corresponding radius of the structural void of a stacked sheet increases at least once in the circumferential direction—especially in a stepped manner—from the minimum radius to the maximum radius, and then decreases again in the circumferential direction at least once more—especially in a stepped manner—from said maximum radius to the minimum radius. Thus, by rotating a structural void in a stack of single, i.e., same-type stacked sheets with the same shape, a truncated spherical shape of recess can be advantageously produced.

[0021] Furthermore, the following improvement of the invention has proven advantageous: at least one lamination group has at least one, preferably multiple, pouch-like portions that extend at least segmentally through the lamination group along the axial direction, particularly radially open or radially closed, for arranging the functional elements of the motor. These pouch-like portions are formed by axially aligned, at least segmentally aligned, empty portions of elements in the stacked laminations. In this way, the possibility of realizing motors of different structural types is advantageously opened up. The functional elements can here be designed, for example, as permanent magnets, at least one coil segment, or shorting bars. Thus, the motor can be implemented as a synchronous machine, especially a permanent magnet-excited or separately excited synchronous machine, or as an asynchronous machine.

[0022] Another advantageous embodiment of the invention is designed such that at least a portion of the stacked sheets have the same number of element gaps and structural gaps, and / or at least one element gap and one structural gap in each portion of the stacked sheets are arranged radially aligned with each other. Thus, especially when directly adjacent stacked sheets (preferably with a structural gap) are rotatably stacked together, it is ensured that not only are the structural gaps, which at least partially have different cross-sections and construct recesses, arranged relatively aligned with each other, but the element gaps of the stacked sheets are also arranged aligned with each other, thereby forming a pouch-like portion for receiving functional elements. Attached Figure Description

[0023] This invention allows for various implementations. To further clarify its basic principles, some of these implementations are illustrated in the accompanying drawings and described below. The drawings show: Figure 1 , Figure 2 A schematic cross-section of an electric motor with a structural open section is shown; Figure 3 A schematic cross-section of a motor with structural and component clearances is shown. Figures 4 to 6 This shows the overlapping of the stacked pieces in rotation. Figure 7 , Figure 8 A longitudinal cross-sectional view shows a stack of sheets with different thicknesses. Detailed Implementation

[0024] from Figures 1 to 3 The schematic cross-sections of the motor 1 (here, an electric motor) are shown in either a quarter view or a full view. The motor 1 has a stator 2 fixedly received in a housing and a rotor 4 rotatably supported relative to the stator 2 and spaced apart from the stator 2 by a radial gap 3 forming an air gap. The rotor 4 and the stator 2 here respectively include lamination groups 5 and 6 consisting of multiple laminations 7 stacked axially.

[0025] A surface structure 9 for reducing the aerodynamic drag of the rotor 3 is also constructed on the surface 8 of the rotor 4 facing the radial clearance 3. This surface structure 9 is constructed by stacking laminations 7 with circumferential structures 10 on top of each other, the circumferential structure being formed with a circumferential gap for each lamination 7 at least a portion of the laminations 7 in the lamination group 6 of the rotor 3. Specifically, the circumferential structure 10 is formed with a gap on the outer circumference or at the periphery of the corresponding lamination 7 facing the radial clearance 4. The corresponding circumferential structure 10 has a plurality of structural gaps 11 spaced apart from each other, particularly uniformly at an angle, in the circumferential direction 21, the structural gaps having at least partially different cross-sections 16.

[0026] The structural voids 11 differ in at least part from each other in that they are at least partially rounded, and in particular at least partially circular and / or arc-shaped, having different radii. The corresponding radii of the structural voids 11 of the corresponding laminations 7 increase at least once (once per half circumference, i.e., twice in total) in the circumferential direction 21 from a minimum radius 19 to a maximum radius 20, and then decrease again at least once (once per half circumference, i.e., twice in total) in the circumferential direction from the maximum radius 20 to a minimum radius 19. Thus, two structural voids 11 with a minimum radius 19 and two structural voids 11 with a maximum radius 20 are formed. Furthermore, the four structural voids 11 each have a cross-section 16 with the same radius.

[0027] Figures 1 to 3 Furthermore, in an embodiment of the motor 1, at least a portion of the laminations 7 in the surface structure 9, preferably the lamination group 6, or even all of the laminations 7, are constructed as a single lamination of the same type, each having the same shape.

[0028] Here, in addition from Figure 3 As can be seen from this, one embodiment of the motor 1 is described, in which the lamination group 6 of the rotor 4 has a plurality of pouch-like portions 14 that pass through the lamination group 6 at least segmentally along the axial direction for arranging the functional elements 15 of the motor 1. These pouch-like portions are constructed by axially spaced gaps 13 in the laminations 7 that are at least segmentally aligned with each other along the axial direction. In this embodiment, the functional elements 15 are designed as short-circuit bars, thus the motor is an asynchronous machine. Here, from... Figure 3 It can also be concluded that the number of element blanking portions 13 and structural blanking portions 11 of the laminate 7 are the same, and each element blanking portion 13 and each structural blanking portion 11 of the laminate 7 are arranged radially aligned with each other.

[0029] exist Figures 1 to 3In the implementation method, the surface structure 9 already specified above is designed from now on in at least segmental form in the following manner, i.e., as Figure 7 and Figure 8 As shown in detail again, the recess 12 is formed by corresponding axially aligned structural gaps 11 of stacked sheets 7 (especially stacked sheets directly stacked on top of each other) having at least partially different cross-sections 16. This is achieved here by stacking the sheets 7 that form the recess 12 at least partially so as to rotate relative to each other such that the structural gaps 11 having at least partially different cross-sections 16 are aligned with each other axially.

[0030] exist Figures 1 to 3 In the implementation method, stacked sheets 7 of the same type are stacked one after another, such as Figures 4 to 6 As shown in detail, each is provided with a structural blanking portion 11 and / or each is provided again in Figure 3 The angular offset 22 shown is arranged to rotate relative to each other about the longitudinal axis 23 of the rotor 3 and / or lamination group 6. The laminations rotating relative to each other at the angular offset 22 are shown here... Figures 4 to 6 The arrow indicates this. The angular offset 22 here is equal to 360° divided by the number of structural empty spaces 11. Because, according to... Figure 3 In the embodiment of the motor 1, the number of element gaps 13 and structural gaps 11 of the lamination 7 are the same, and the element gaps 13 and structural gaps 11 of the lamination 7 are aligned with each other radially. Therefore, when the laminations are implemented in a way that the structural gaps 11 are stacked relative to each other, the element gaps 13 are also stacked with each other in an axial alignment, thereby forming an axially extended bag-shaped portion 14.

[0031] To create a surface structure 9 that reduces the aerodynamic drag of the rotor 3, the shape of the recess 12 is close to that of a truncated sphere, which is particularly useful for reducing the aerodynamic drag of the rotor 3. Figure 7 and Figure 8 As can be seen from this. For this purpose, the stacked pieces 7 are rotated relative to each other such that a structural void 11 is stacked on top of each other, so that the cross-sectional area 16 of the structural voids 11 that form the corresponding recesses 12 and are respectively aligned with each other along the axial direction increases along the axial direction from the minimum area 17 to the maximum area 18, and then decreases along the axial direction from the maximum area 18 back to the minimum area 17.

[0032] The portion of the surface 8 of the rotor 3 and / or lamination 6 formed by the corresponding recesses 12 has a discontinuous stepped orientation caused by axial steps based on the given thickness 24 of the laminations 7. Depending on the thickness 24 of the laminations 7 and the radial steps of the structural openings 11 of the circumferential structure 10 of the rotor 3 (which can be particularly influenced by the number of structural openings 11 in each lamination 7), the shape of the recesses 12 can be made to more closely or smaller fit their target shape (here, a truncated spherical shape). Figure 8 The thickness of the laminate 7 in the implementation scheme of laminate group 6 is 24, which is less than Figure 7 The thickness of the stacked sheet 7 in the embodiment of the stacked sheet group 6 is 24, so that it can more accurately approach the target shape of the truncated sphere.

[0033] List of reference numerals 1 motor 2 stators 3 Radial clearance 4 rotors 5-layer stack 6-layer stack 7-layer stack 8 surfaces 9 Surface Structure 10-circumferential structure 11 Structural Open Space 12 Recesses 13 components with empty space 14 sac-like parts 15 components 16 cross sections 17 Minimum Area 18 Maximum Area 19 minimum radius 20 Maximum radius 21-week direction 22-degree offset 23 Longitudinal axis 24mm thickness.

Claims

1. An electric motor (1) comprising a stator (2) fixedly received in a housing and a rotor (4) rotatably supported relative to the stator (2) and spaced apart from the stator (2) by a radial clearance (3), wherein, The rotor (4) and / or the stator (2) each comprise lamination groups (5, 6) consisting of a plurality of laminations (7) stacked together along the axial direction, and a surface structure (9) for reducing aerodynamic drag is provided on the surface (8) of the rotor (4) and / or the stator (2) facing the radial clearance (3), characterized in that, at least a portion of the laminations (7) in at least one lamination group (5, 6) are provided with a circumferential structure (10) formed for each lamination with a circumferential gap, wherein the surface structure (9) is constructed by stacking the laminations (7) provided with the circumferential structure (10) together.

2. The motor (1) according to claim 1, characterized in that, The corresponding circumferential structure (10) includes a plurality of structural voids (11) that are angularly spaced from each other in the circumferential direction, and these structural voids have at least partially different cross sections (16).

3. The motor (1) according to claim 1 or 2, characterized in that, Recesses (12) are formed by corresponding axially aligned structural gaps (11) of stacked sheets (7) with at least partially different cross sections (16), the recesses forming at least segmentally the surface structure (9).

4. The motor (1) according to at least one of the preceding claims, characterized in that, The area of ​​the cross section (16) of the corresponding axially aligned structural gap (11) that forms the recess (12) increases axially from the minimum area (17) to the maximum area (18) and then decreases axially from the maximum area (18) to the minimum area (17).

5. The motor (1) according to at least one of the preceding claims, characterized in that, The laminations (7) that form at least the recess (12) are stacked on top of each other at least partially so that the structural gaps (11) having at least partially different cross sections (16) are aligned with each other.

6. The motor (1) according to at least one of the preceding claims, characterized in that, At least a portion of the stacked sheets (7) of at least one stacked sheet group (5, 6), preferably even all of the stacked sheets (7), have the same shape.

7. The motor (1) according to at least one of the preceding claims, characterized in that, The structural void (11) is at least partially rounded, especially at least partially circular and / or arc-shaped, wherein the structural void (11) with different cross sections (16) has different radii.

8. The motor (1) according to at least one of the preceding claims, characterized in that, The radius of the corresponding empty portion (11) of a stack (7) increases at least once in the circumferential direction from the minimum radius (19) to the maximum radius (20) and decreases again at least once in the circumferential direction from the maximum radius (20) to the minimum radius (19).

9. The motor (1) according to at least one of the preceding claims, characterized in that, At least one lamination group (5, 6) has at least one pouch-shaped portion (14) that passes through the lamination group (5, 6) at least in sections along the axial direction for arranging the functional elements (15) of the motor (1), the pouch-shaped portion being constructed by element gaps (13) that are aligned with each other at least in sections along the axial direction in the laminations (7) stacked together.

10. The motor (1) according to at least one of the preceding claims, characterized in that, The number of element gaps (13) and structural gaps (11) of at least this portion of the stack (7) is the same, and / or at least one element gap (13) and one structural gap (11) of each portion of the stack (7) are arranged radially aligned with each other.

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