Rotor for an axial flux machine, in particular of a motor vehicle, method of such a rotor and axial flux machine

Abstract

The invention relates to a rotor (10) for an axial flux machine, with permanent magnets (14) and intermediate webs (16) which are arranged in the circumferential direction of the rotor (10) such that the permanent magnets (14) and the intermediate webs (16) are arranged alternately in succession in the circumferential direction of the rotor (10), wherein the intermediate webs (16) are bonded to the permanent magnets (14).

Description

[0001] The invention relates to a rotor for an axial flux machine, in particular for a motor vehicle. Furthermore, the invention relates to a method for manufacturing such a rotor. The invention also relates to an axial flux machine for a motor vehicle.

[0002] DE 69100180 B1 discloses a device for balancing rotors. DE 19645181 B4 discloses a manufacturing unit for turning, milling, and balancing. DE 10 2017 125 889 A1 discloses a method and a device for balancing. DE 50015924 B1 discloses a method and a device for compensating for imbalance by material removal. DE 2638876 C3 discloses a device for balancing rotors. DE 69726816 B1 discloses a device for balancing rotors by material removal. DE 3005423 A1 discloses a device for balancing rotors. DE 60122621 B1 discloses a method and a device for balancing rotating bodies. DE 1800946 U discloses a milling device for balancing machines for disc-shaped rotors for the purpose of mass balancing. DE 2908272 C2 discloses a method and a device for balancing rotors.DE 10 2004 016 431 A1 discloses a method for manufacturing a rotationally symmetrical component. DE 4229521 B4 discloses a method for balancing the imbalance of a rotor.

[0003] The object of the present invention is to provide a rotor for an axial flux machine, in particular for a motor vehicle, a method for manufacturing such a rotor and an axial flux machine, so that a particularly advantageous operation of the axial flux machine can be realized.

[0004] This problem is solved by a rotor with the features of claim 1, by a method with the features of claim 9, and by an axial flux machine with the features of claim 10. Advantageous embodiments with expedient further developments of the invention are specified in the remaining claims.

[0005] A first aspect of the invention relates to a rotor for an axial flux machine, in particular for a motor vehicle. This means that the motor vehicle, preferably designed as a motor vehicle, especially a passenger car, and simply referred to as a vehicle, in its fully manufactured state, comprises the axial flux machine and can be driven electrically by means of the axial flux machine, in particular purely electrically. This axial flux machine is also referred to as an axial flux motor (AFM). The axial flux machine is an electric machine and is therefore also referred to as an electric machine. In its fully manufactured state, the axial flux machine comprises the rotor and, for example, a stator by means of which the rotor can be driven and thus rotated about a machine axis of rotation relative to the stator. The rotor, whose axial direction coincides with the machine axis of rotation, has permanent magnets, which are also simply referred to as magnets.The rotor, whose radial direction is perpendicular to the axial direction of the rotor and thus perpendicular to the machine's axis of rotation, also has intermediate webs, which are simply referred to as webs. For example, each permanent magnet is made of a first material, which is also referred to as the magnet material. The respective intermediate web is made of an intermediate material different from the first material, which is also referred to as the web material. These intermediate webs are arranged between the permanent magnets in the circumferential direction of the rotor, which runs around the axial direction of the rotor and thus around the machine's axis of rotation, such that the permanent magnets and the intermediate webs alternate along the rotor's circumference. The intermediate webs are bonded to the permanent magnets, in particular directly.

[0006] Preferably, the respective permanent magnet is segmented, comprising separately formed and radially arranged magnetic segments arranged one after the other in the direction of the rotor, which are bonded together by means of an adhesive. In particular, the respective magnetic segment is made of the aforementioned magnetic material, which is, for example, a metallic material.

[0007] Preferably, the intermediate webs are glued to the permanent magnets using the same adhesive by which the magnet segments of the permanent magnets are glued together.

[0008] Preferably, the adhesive is electrically non-conductive, i.e., a non-conductor.

[0009] For the purposes of this disclosure, a non-conductor is a material whose electrical conductivity is less than 10-8 S * cm -1 exhibits.

[0010] Preferably, the intermediate webs are made of a fiber-reinforced plastic, which is also referred to as the first fiber-reinforced plastic, fiber composite, or first fiber composite material. When the fiber-reinforced plastic is mentioned before and below, unless otherwise specified, this refers to the first fiber-reinforced plastic from which the intermediate webs are formed.

[0011] Preferably, the fiber-reinforced plastic is formed, in particular entirely and / or exclusively, from a matrix, also referred to as the first matrix, and reinforcing fibers, also referred to as the first reinforcing fibers, embedded in the matrix. Where the term "matrix" is used before and below, it refers to the first matrix unless otherwise specified. Where the term "reinforcing fibers" is used before and below, it refers to the first reinforcing fibers unless otherwise specified. Preferably, the reinforcing fibers, and in particular all of them, are made of an electrically non-conductive material and are thus non-conductors.

[0012] Preferably, the electrically non-conductive material from which the reinforcing fibers are formed is a ceramic. Thus, the reinforcing fibers are or form a ceramic system that is electrically non-conductive.

[0013] Preferably, the material from which the reinforcing fibers are formed is magnetically non-conductive.

[0014] Preferably, the matrix is ​​formed, in particular completely and / or exclusively, from an electrically non-conductive material, in particular plastic.

[0015] For example, the intermediate webs and the permanent magnets form a component, also referred to as a unit or assembly. Preferably, the rotor has a ring, also referred to as an outer ring, which is formed separately from the component and completely surrounds the component in the circumferential direction of the rotor, thus covering 360 degrees. Preferably, the component is supported at least indirectly, and in particular directly, by the ring in the radial direction of the rotor. Preferably, the ring rests directly against the component in the radial direction of the rotor. Preferably, the ring is formed, in particular completely and / or exclusively, from a fiber-reinforced plastic, also referred to as a second fiber-reinforced plastic.Preferably, the second fiber-reinforced plastic from which the ring is formed is formed, in particular entirely and / or exclusively, from a matrix also referred to as a second matrix and reinforcing fibers, also referred to as second reinforcing fibers, embedded in the matrix, wherein the second reinforcing fibers, in particular all second reinforcing fibers, are formed from an electrically non-conductive material. Preferably, the electrically non-conductive material from which the second reinforcing fibers of the second fiber-reinforced plastic from which the ring is formed are formed is a ceramic, in particular the same ceramic from which the first reinforcing fibers are formed.

[0016] Preferably, the second matrix of the second fiber-reinforced plastic from which the ring is formed is made, in particular completely and / or exclusively, of an electrically non-conductive material, in particular plastic, and in particular of the same material, in particular plastic, as the first matrix. Preferably, the ring and the intermediate webs are made of the same fiber-reinforced plastic. Preferably, the rotor, in particular the assembly, has a through-opening, in particular a central and / or cylindrical one, which is completely surrounded in the circumferential direction of the rotor by an inner circumferential surface of the rotor, in particular of the assembly, and is thereby bounded in the radial direction of the rotor outwards, in particular directly, by the inner circumferential surface.Preferably, the inner circumferential surface is formed, in particular exclusively and / or completely, by first surface segments and second surface segments. Preferably, the first surface segments are formed by the permanent magnets. Preferably, the second surface segments are formed by the intermediate webs. Preferably, the first surface segments and the second surface segments are arranged alternately in the circumferential direction of the rotor.

[0017] Preferably, the inner circumferential surface is machined, in particular by cutting. Specifically, the inner circumferential surface is machined by grinding, cutting, and / or milling. Preferably, the rotor, and in particular the assembly, has a cylindrical outer circumferential surface. For example, the aforementioned ring rests against the cylindrical outer circumferential surface in the radial direction of the rotor, in particular directly. Preferably, the outer circumferential surface is machined, in particular by cutting. Preferably, the outer circumferential surface is machined by grinding, cutting, and / or milling. Preferably, the machining of the outer circumferential surface and the machining of the inner circumferential surface are carried out simultaneously.

[0018] A second aspect of the invention relates to a method for manufacturing a rotor, particularly according to the first aspect of the invention, for an axial flux machine. In this method, intermediate webs of the rotor are arranged circumferentially between permanent magnets of the rotor such that the permanent magnets and the intermediate webs are arranged alternately in succession. In this method, the intermediate webs are bonded, particularly directly, to the permanent magnets. Advantages and advantageous embodiments of the first aspect of the invention are to be considered as advantages and advantageous embodiments of the second aspect of the invention, and vice versa.

[0019] A third aspect of the invention relates to an axial flux machine for a motor vehicle, in particular for a motor car and especially for a passenger car. The axial flux machine according to the third aspect of the invention has at least one rotor according to the first aspect of the invention. Advantages and advantageous embodiments of the first and second aspects of the invention are to be regarded as advantages and advantageous embodiments of the third aspect of the invention, and vice versa.

[0020] The outer surface of the casing is also referred to as the outside. The inner surface of the casing is also referred to as the inside. Preferably, the outer surface, and especially the entire inner surface, are machined, particularly mechanically, and thus reworked, thereby bringing the outer surface and the inside to the required dimensions. This simplifies manufacturing, for example, by requiring only a rough fit in terms of dimensions and shapes, particularly of the permanent magnets (also simply referred to as magnets), since protrusions are removed by machining. Machining the inside and outside allows, for example, the removal, particularly of external contact points, by grinding them down.By removing, in particular grinding off, the contact points and by using electrically and preferably also magnetically non-conductive materials, an efficient rotor with only low eddy current losses across the magnets can be realized in a simpler way compared to conventional solutions.

[0021] The invention is based in particular on the following findings and considerations: A disc-shaped design of axial flux motors (AFMs) enables novel axle drive concepts for motor vehicles. Due to installation space limitations, the outer diameter of the axial flux machine is relatively limited, especially for coaxial applications in passenger cars. Therefore, and for efficiency reasons, an increase in efficiency is sought for their future applications. In axial flux motors, laminated permanent magnets are currently pressed into a magnet cassette made of SMC (Sheet Molding Compound). The lamination of the magnets reduces the eddy current losses occurring in the magnets. Carbon fibers in this composite are electrically conductive, which can lead to eddy currents within the axial flux motor, which is used as an electric traction machine, as a result of the alternating magnetic field. These eddy currents occur, on the one hand, within the carbon in the SMC composite.Furthermore, the electrical connection of the individual magnet segments via carbon fibers also induces eddy current paths in the magnets (contact resistance). This leads to a significant increase in rotor losses, which is detrimental both in terms of efficiency and magnetic performance (higher magnet temperature leads to derating due to low remanence and opposing field stability). Derating, also known as power reduction, means that the maximum power output of the axial flux machine is deliberately limited and reduced compared to a state in which derating is not performed.

[0022] The electrical contact between the carbon fibers, acting as the noble cathode, and the magnetic material, acting as the less noble anode, can also promote contact corrosion between these two components. Furthermore, individual magnets are currently joined together using an SMC pressing process. Due to the tolerance chain, consisting of magnet tolerances, batch and processing variations in the SMC, and tool tolerances, this process necessitates a post-processing chain. Post-processing can include grinding, brushing, laser cleaning, and blasting.

[0023] For example, the outside and / or the inside is treated by grinding, brushing, laser cleaning and / or blasting processes.

[0024] Axial flux machines can have a disc-shaped design, conventionally employing a double-rotor or double-stator arrangement. For traction machines with high torque and power density, double-rotor concepts are predominantly used, which incorporate rotor discs consisting of the main components: rotor carrier, electrical steel laminations, and magnet cassette. The permanent magnets are either components of a magnet cassette or form such a cassette, which is also simply referred to as the cassette. Furthermore, it is conceivable that the magnet cassette includes intermediate webs, so that, for example, the magnet cassette is formed by the permanent magnets and the intermediate webs. Preferably, to reduce eddy current losses within the respective magnets during operation of the axial flux machine, the permanent magnets are segmented by an electrically non-conductive adhesive layer.To withstand the high centrifugal forces acting on the magnets at high rotor speeds during operation of the axial flux machine, a ring, particularly one made of carbon, can be used. This ring is mounted on the magnets or magnet cassette with an interference fit or preload. To absorb compressive forces resulting from the ring, especially when the axial flux machine is stationary, a magnet cassette is used that incorporates the magnets and, for example, carbon fiber-reinforced SMC, specifically such that the intermediate webs are formed from the same carbon fiber-reinforced SMC. A disadvantage here can be higher rotor losses due to the electrically conductive carbon content. This induces eddy currents within the webs. Furthermore, the individual magnet segments can be short-circuited, which can also lead to eddy currents.Furthermore, due to its characteristic properties, SMC exhibits uneven electrical conductivity. This leads, on the one hand, to inhomogeneous contact resistances between the magnet and the SMC, and on the other hand, within the SMC itself. As a result, eddy current paths can increase significantly due to potential differences at the magnet cassette level. This also applies to any type of electrically conductive fiber composite material.

[0025] Therefore, it is preferably provided that the matrix of the fiber-reinforced plastic from which the intermediate webs are formed, and / or the, in particular all, reinforcing fibers of the fiber-reinforced plastic from which the intermediate webs are formed, are made of an electrically non-conductive material.

[0026] In order to prevent eddy current paths within the bridges and between isolated magnetic segments or magnets, a magnetic cassette is used which, for example, comprises the segmented magnets and a reinforcing material made of an electrically and magnetically non-conductive material with a ceramic system, in particular such that, for example, the intermediate bridges have the reinforcing material, in particular such that the reinforcing material is the aforementioned reinforcing fibers of the fiber-reinforced plastic from which the intermediate bridges are formed.

[0027] Preferably, the magnetic cassette is manufactured in such a way that the intermediate webs between the individual permanent magnets are inserted and bonded to the permanent magnets using the adhesive directly in an adhesive bonding process in which or through which the magnet segments of the permanent magnets are bonded together using the aforementioned adhesive, in order to realize a streamlined and therefore time- and cost-effective process chain for manufacturing the rotor.

[0028] Preferably, the intermediate webs, also referred to as struts or magnetic cassette struts, are formed, in particular completely and / or exclusively, from a material that is electrically and preferably magnetically non-conductive and, for example, insensitive to compressive forces, and which preferably has a similar or the same coefficient of thermal expansion as the magnetic material. In particular, the material from which the struts are formed is a ceramic. This allows them to withstand high compressive forces, such as those exerted on the magnetic cassette by a ring, particularly one made of carbon. Furthermore, the material from which the struts, in particular all of them, are formed, especially exclusively and / or completely, is preferably electrically and preferably also magnetically non-conductive.Furthermore, the material from which the intermediate webs, in particular all of them, are formed, especially completely and / or exclusively, is preferably designed such that it has similar or identical mechanical properties analogous to the respective permanent magnet, i.e., the magnetic material, so that subsequent post-processing of the magnetic cassette, in particular in a grinding process, results in the same material removal. In other words, the intermediate webs and the permanent magnets can thus be processed simultaneously on their respective outer and / or inner sides, in particular mechanically, in particular by grinding, thereby achieving the same material removal.The low and homogeneous density of the material, also known as the web material, from which the intermediate webs, in particular all of them, are formed, especially completely and / or exclusively, also contributes to a reduction in inertial mass, whereby the balancing quality can be very low. The rotor is manufactured, for example, using a production technology that serves to create a geometry of the magnetic cassette and thus enable it to be machined as a complete component. In particular, the magnetic cassette is the aforementioned assembly, i.e., the aforementioned composite.

[0029] After the bonding process, in which, for example, the individual magnet segments of the permanent magnets are bonded together and, in particular, the intermediate webs are simultaneously bonded to the permanent magnets, the magnetic cassette, or assembly, can be finished as a component. This finishing process involves machining, in particular, the outer circumferential surface and / or the inner circumferential surface. This can be done, for example, by a wire-cutting process and at least one or more grinding processes (including external cylindrical grinding, internal cylindrical grinding, double-surface grinding, etc.).

[0030] The invention allows at least the following advantages to be realized: - By using it as a component, geometric tolerances can be significantly improved. This is particularly helpful in terms of the roundness and tolerance of the outer diameter (through external cylindrical grinding of the magnetic cassette). This allows for the use of bandings such as the ring, which introduce compressive forces into the rotor during the process and operation, to increase rotational speed. - Improvement of tolerances regarding geometry, tolerances, parallelism, roundness, flatness, diameter (always uniform with regard to the ring, joining point, homogeneous surface or subsequent coating process of the surface) - Integration of magnetic cassette manufacturing into magnet production, resulting in complexity reduction and economic advantages - component-oriented manufacturing of the magnetic cassette in magnet production - Streamlining the entire production chain (including manufacturing, logistics, handling) - Functional mechanics: homogeneous force distribution, material usage and improved tolerances regarding higher compressive forces are possible, more reproducible properties of the magnetic cassette, homogeneous surface with regard to bonding to LBIR, NVH advantageous with regard to surface, subsequent process chain improved (e.g. coating, cleaning, structuring etc.), higher tolerable vibrations through material process - Reduced effort in process chain and logistics - The production concept opens up the possibility of generating new / adapted / improved material selections (for example, pressure-resistant ceramics, glass fiber or aramid fiber composites, etc.) - Processing at ambient temperature reduces the influence of adhesives and magnetic properties, thus reducing residual stresses in the components during the production chain. - Corrosion protection can be improved (reduction of surface tolerances regarding coating), contact corrosion is prevented by eliminating the "galvanic cell". - Reduction of eddy current losses in the rotor due to the alternating magnetic field during operation of the electric traction machine - No or reduced eddy current paths within the magnetic cassette assembly, since the material, unlike carbon fibers, is not electrically conductive. - No induction of additional eddy currents in the magnet due to the electrical connection of the carbon fibers with the individual magnet segments - Inhomogeneous electrical conductivity is overcome, which also leads to reduced losses in the rotor. - Improved magnetic performance due to reduced heat generation resulting from decreased eddy current losses in the rotor, thus increasing the efficiency of the axial flux machine by reducing rotor losses. - Cost reduction due to the reduced proportion of rare earth elements in the permanent magnets through a reduction in coercive field strength resulting from the lower operating temperatures of the axial flux machine. - mechanical advantages resulting from the use of ceramics (pressure stress)

[0031] Further advantages, features, and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and combinations of features mentioned above in the description, as well as those mentioned below in the figure description and / or shown in the figures alone, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention.

[0032] The drawing shows in: Fig. 1. A schematic front view of a rotor for an axial flux machine, in particular of a motor vehicle; and Fig. 2. A schematic side view of the rotor (in part).

[0033] In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

[0034] Fig. Figure 1 shows a schematic front view of a rotor 10 for an axial flux machine, in particular for a motor vehicle. The rotor 10 has a magnet cassette 12, which is also referred to as a composite or assembly. The magnet cassette 12, and thus the rotor 10, has permanent magnets 14, which are also referred to as magnets. Furthermore, the magnet cassette 12, and thus the rotor 10, has intermediate webs 16, which are arranged between the permanent magnets 14 in the circumferential direction of the rotor 10, the circumferential direction of which is illustrated by a double arrow 18, such that the permanent magnets 14 and the intermediate webs 16, which are also simply referred to as webs, are arranged alternately in the circumferential direction of the rotor 10, and thus of the magnet cassette 12. The intermediate webs 16 are bonded to the permanent magnets 14, in particular directly.

[0035] The magnetic cassette 12 has an outer circumferential surface 20 and an inner circumferential surface 22. The outer circumferential surface 20 forms or defines an outer contour of the magnetic cassette 12, and the inner circumferential surface 22 forms or defines an inner contour of the magnetic cassette 12. A portion of the outer circumferential surface 20 that has already been machined, in particular mechanically, is designated T1, and a portion of the outer circumferential surface 20 that has not yet been machined, in particular mechanically, is designated T2. A portion of the outer circumferential surface 22 that has already been machined, in particular mechanically, is designated T3, and a portion of the outer circumferential surface 22 that has not yet been machined, in particular mechanically, is designated T4.

[0036] In a method for manufacturing the rotor 10, in particular the magnet cassette 12, the webs are bonded to the magnets, after which the outer surfaces 20 and 22 are machined, in particular simultaneously, especially mechanically machined. The outer surface 20 is also referred to as the outside, and the outer surface 22 is also referred to as the inside.

[0037] Especially schematically in Fig. Figure 1 shows a grinding wheel 24, which is used to machine the outer surface 20. Also shown, particularly schematically, is a grinding wheel 26, which is used to machine the inner surface (outer surface 22).

[0038] Recognizable from Fig. The magnetic cassette 12 has a central through-opening 28, wherein the outer surface 22 completely surrounds the through-opening 28 in the circumferential direction of the rotor 10 and thus of the magnetic cassette 12, i.e., over 360 degrees. This means that the through-opening 28 is directly bounded externally in the radial direction of the rotor 10 and thus of the magnetic cassette 12 by the outer surface 22. The through-opening 28 is cylindrical. In particular, the outer surface 22 is cylindrical. The through-opening 28 and thus the magnetic cassette 12 have an inner diameter D. innen which is defined or formed by machining the lateral surface 22. The lateral surface 20 and the magnetic cassette 12 have an outer diameter D außen on, which is defined, that is, produced, by the mechanical processing of the lateral surface 20.

[0039] Fig.Figure 2 shows a partial schematic side view of the magnetic cassette 12. The height of the magnetic cassette 12, extending radially towards the rotor 10, is denoted by H. Magnetkassette denoted by H Magnetkassette by subtracting the inner diameter D innen of the outer diameter D außen is calculated.

[0040] It is evident that by machining the inner and outer surfaces, protrusions can be removed, i.e., ground down, so that the intermediate webs 16 and the permanent magnets 14 are arranged flush with each other in the radial direction of the rotor 10, both outwards and inwards. It is also evident that the respective cylindrical surface 20, 22 is formed, in particular exclusively and / or completely, by respective first surface segments and by respective second surface segments. The first surface segments are formed by the permanent magnets 14, thus surface segments of the permanent magnets 14. The second surface segments are formed by the intermediate webs 16, thus surface segments of the intermediate webs 16. The respective first surface segments and the respective second surface segments of the respective cylindrical surface 20, 22 are arranged alternately in succession in the circumferential direction of the rotor 10.Through mechanical processing, the first surface segments and the second surface segments are arranged flush with each other in the radial direction outwards and in the radial direction inwards. This allows for the production of an advantageous geometry of the magnetic cassette 12 and the rotor 10 in a time-efficient and therefore cost-effective manner. Reference symbol list 10 Rotor 12 magnetic cassettes 14 permanent magnet 16 Intermediate walkway 18 Double Arrow 20 outer circumferential surface 22 inner circumferential surface 24 grinding wheel 26 grinding wheel 28 Passage opening Outer diameter Inner diameter H-magnetic cassette height 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 69100180 B1

[0002] DE 19645181 B4

[0002] DE 10 2017 125 889 A1

[0002] DE 50015924 B1

[0002] DE 2638876 C3

[0002] DE 69726816 B1

[0002] DE 3005423 A1

[0002] DE 60122621 B1

[0002] DE 1800946 U

[0002] DE 2908272 C2

[0002] DE 10 2004 016 431 A1

[0002] DE 4229521 B4

[0002]

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