Method for producing at least one sleeve for encasing permanent magnets of a rotor of an electrical machine, sleeve for encasing permanent magnets of a rotor of an electrical machine and a winding core for producing a sleeve

Abstract

The invention relates to a method for producing at least one sleeve (1) for encasing permanent magnets of a rotor (2) of an electrical machine (10) with an axis of rotation (D), characterized in that a) a sleeve (1) with or made of a thermoplastic fiber composite material (8) is wound directly onto the rotor (2) in the circumferential direction under a defined prestress (S) or b) a plurality of sleeves (1a, 1b, 1c) with or made of a thermoplastic fiber composite material (8) are wound axially spaced from one another on a winding core (3), so that the sleeve (1) or the plurality of sleeves (1a, 1b, 1c) have a final shape at their respective axial edges (3) and • the thermoplastic fiber composite material (8) has a breaking elongation of the matrix of at least 5% and / or • the fiber of the thermoplastic fiber composite material (8) has a modulus of elasticity between 210 MPa and 600 MPa and / or • the fiber of the thermoplastic fiber composite material (8) has a tensile strength between 4500. The invention further relates to a sleeve and a winding core.

Description

[0001] The present disclosure relates to a method for producing at least one sleeve for enclosing permanent magnets of a rotor of an electrical machine having the features of claim 1, a sleeve for enclosing permanent magnets of a rotor of an electrical machine having the features of claim 14 and a winding core for producing a sleeve having the features of claim 16.

[0002] Electrical machines in the form of generators or motors are increasingly being used today, particularly in aircraft propulsion systems. Such applications are described, for example, in US 2022 / 0271588 A1, US 2022 / 0271601 A1, or US 2022 / 0278584 A1. In particular, electrical machines that use a sleeve to fix permanent magnets to the rotor are known from the prior art. The so-called rotor sleeves form a wound tube that is then cut. The sleeve is made of fiber composite material. The sleeves can also be referred to as a sheath (or fixation) or a fastening means for the permanent magnets. The production of sleeves of a similar type is also described in CN 2904393, CN 2669431, and CN112564351.

[0003] For use in aircraft, it is important that these sleeves for mechanically fixing the permanent magnets, especially when rotating, can be manufactured efficiently. A disadvantage, particularly in the so-called press-fitted design, is that once manufactured, fiber composite sleeves have to be mechanically reworked, for example by trimming edges. These additional work steps are not only complex, but they also always damage the fiber structure of the fiber composite materials. In so-called directly wound rotors (winding with Towpreg or wet winding), high preload losses occur due to flow effects of the matrix during winding. For this reason, direct windings can only be produced for thin sleeves using state-of-the-art technology. Press fitting here refers not only to purely mechanical pressing, but also to pressing in combination with a freeze fitting.

[0004] According to a first aspect, a method is provided having the features of claim 1. Accordingly, a sleeve of two types can be manufactured.

[0005] First, a sleeve made of or made of a thermoplastic fiber composite material can be wound directly onto a rotor under a defined circumferential prestress. This consolidates the sleeve on the rotor in situ (melts it and shapes it), e.g., with the aid of a laser or other heat source. This eliminates the need for any further processing. This is an example of net-shape manufacturing.

[0006] Secondly, a plurality of sleeves made of or made of a thermoplastic fiber composite material are wound axially spaced from one another on a winding core. The spacing allows individual sleeves to be produced in a single step, eliminating the need to separate the wound article. The sleeves are mechanically pressed onto the rotor in a subsequent step. This also constitutes a net-shape production of sleeves of the type in question here, and is intended particularly for press-fitted rotor sleeves.

[0007] Thus, the sleeve or the plurality of sleeves already have their final shape at their respective axial edges after winding.

[0008] For this net-shape production, one of the following conditions must be met alone or in combination: • the thermoplastic fiber composite material has a matrix elongation at break of more than 5% and / or • the fiber of the thermoplastic fiber composite material has a modulus of elasticity between 210 GPa and 600 GPa and / or • the fiber of the thermoplastic fiber composite material has a tensile strength of at least 4500 MPa.

[0009] This allows a net shape to be realized. The primary goal is to avoid a nested layer structure. According to the state of the art, a nested layer structure is required, especially for thicker laminates (> 1 mm), to prevent radial cracking and damage progression in the laminate. The desired net shape design can be achieved by using a ductile matrix, since a ductile matrix can significantly reduce the risk of interfiber fracture. This eliminates the nested layer structure.

[0010] For net-shape production, i.e., production without rework, the thermoplastic fiber composite material can be wound onto a winding core at an angle of between 88 and 90°, particularly between 89 and 90°, to the rotation axis. This means that the thermoplastic fiber composite material is wound exactly along the circumference, with a deviation of 2° still being tolerable.

[0011] In a further embodiment, the at least one sleeve has a final wall thickness between 0.5 and 15 mm. This is the wall thickness after winding is complete.

[0012] It is also possible that the plurality of cores wound on the winding core each have an axial width of at least 1.5 cm.

[0013] The simultaneous winding of a plurality of sleeves on a winding core for press-fitted rotor sleeves can be carried out efficiently if at least one component is provided for forming at least one winding groove running in the circumferential direction of the winding core, wherein the winding groove serves to accommodate the thermoplastic fiber composite material. This winding groove allows, for example, a forming winding, so that no post-processing is necessary. The components for forming the at least one winding groove can be designed as ring elements that can be arranged axially on the winding core, so that a winding groove for the thermoplastic fiber composite material is formed between the at least two ring elements.Alternatively, it is also possible for the winding core to have or be formed from at least two winding core modules, which are configured such that a winding groove for the thermoplastic fiber composite material is formed between the at least two winding core modules. This means that the winding core itself is divided into modules that, when assembled, create the winding grooves.

[0014] Spacers can be used between the ring elements (e.g. in the form of metal sleeves) if two-part ring elements are not used.

[0015] For efficient winding, it is useful if the winding core has a stop at one axial end so that the ring elements do not slip axially.

[0016] After winding onto the winding core or rotor, the thermoplastic fiber composite material can consolidate in situ. The consolidated cores can then be removed, for example, from the winding core.

[0017] Especially for the direct winding of the thermoplastic fiber composite material onto the rotor, it is possible and sensible to work with a prestress of at least 350 MPa.

[0018] In one embodiment, the matrix of the thermoplastic fiber composite material comprises PEEK, PPS or PAEK.

[0019] It may also be useful for the fiber of the thermoplastic fiber composite material to be only one uniform fiber, in particular a carbon fiber.

[0020] If, in one embodiment, the thermoplastic fiber composite material is used as a tape, efficient winding is possible. Tape widths between 1 / 16 inch (0.16 cm) and 2 inches (5.08 cm) can be used.

[0021] A second aspect relates to a sleeve for encasing permanent magnets of a rotor of an electrical machine, which sleeve can be produced using one of the described methods. Such a sleeve can be used, for example, in a motor or a generator, in particular for an aircraft.

[0022] A third aspect relates to a winding core having the features of claim 16.

[0023] Embodiments will now be described by way of example with reference to the figures, in which: Fig. 1 is a perspective sectional view of an embodiment of an electric machine with a rotor whose permanent magnets are surrounded by a sleeve; Fig. 2 a sectional view through an embodiment of a rotor with a sleeve; Fig. 3A shows a winding core for thermoplastic fiber composite material for use in an embodiment of the method; Fig. 3B the winding core Fig. 3A with axially separately wound thermoplastic fiber composite material; Fig. 3C isolated cores on the winding core after Fig. 3A and Fig. 3B; Fig. 4 an alternative winding core for an embodiment of the method; Fig. 5 a representation of a direct winding of a sleeve onto a rotor of an electrical machine.

[0024] It is well known that electric motors are used, especially in aircraft. Fiber composite materials are used primarily for reasons of weight savings and high mechanical loads.

[0025] Before discussing the design and use of fiber composite materials, the context of electrical machines is described.

[0026] A propulsion system for an aircraft may comprise one or more electrical machines 10, such as a motor as shown in Fig. 1 is shown.

[0027] The motor 10 may be a conventional electric motor, such as a turbo generator system (TGS) for generating electrical power. In other applications, a motor 10 may also be designed as a magneto-electric machine, which is used to drive a fan of an aircraft engine. The motor 10 may, for example, be mounted on a low-pressure shaft (in Fig. 1 not shown) that drives the fan. Thus, the motor 10 would be a "core shaft mounted" type, in which a rotor 2 of the motor 10 is mounted directly on a surface of the low-pressure shaft and is radially surrounded by a stator 11.

[0028] The motor 10 may, for example, be coupled to an energy storage device in the form of one or more chemical batteries, a fuel cell, or a capacitor, which supply the motor 10 with electrical energy during operation.

[0029] However, the drive system may alternatively or additionally comprise one or more electrical machines 10, such as a generator, coupled to the motor 10 and the energy storage device or to both.

[0030] The motor comprises a rotor 2 and a stator 11, wherein the rotor 2 is coupled to a shaft that rotates about the rotational axis D. The shaft is typically made of steel, aluminum, or titanium.

[0031] Radially outside the shaft, for example in the case of a so-called back yoke, there are a large number of steel layers, which are usually thin in order to minimize electrical losses due to eddy currents.

[0032] Radially outside these layers there are a multitude of permanent magnets 9 (see Fig. 2), also referred to as surface magnets. These permanent magnets 9 are typically bonded to the radially inner layers via an adhesive. This is intended to ensure that the permanent magnets 9 are secured during joining, while also filling gaps between the permanent magnets 9.

[0033] To support this positioning of the permanent magnets 9, it is generally known to use a sleeve 1 which at least partially surrounds the permanent magnets 9 radially outward.

[0034] In high-speed electric machines, the self-loading of a metallic sleeve can become significant, resulting in either an excessively thick rotor or no solution. Minimizing the electromagnetic air gap in the electric machine is critical to delivering compact and efficient machines. A thick sleeve moves the magnets away from the stator, thus reducing torque.

[0035] In the illustrated embodiment, an air gap 12 is located radially outside the sleeve 1, allowing relative rotation between the rotor 2 and the stator 11. The stator 11 comprises a plurality of stator coils which, when energized, cause the rotor 2 to rotate through interaction between the magnetic fields of the stator coils and the permanent magnets 9.

[0036] In this construction of the electrical machine 10, the design of the sleeve 1 is of particular importance because it must be particularly stable.

[0037] In connection with the Fig. 3A, Fig. 3B and Fig. 3C describes an embodiment of a method, wherein Fig. 3A shows a winding core 3. The winding core 3 is intended for winding a fiber composite material 8, in this case a tape. This winding core 3 has a stop 7 in the form of a ring element at one end, which is detachably connected to the winding core 3.

[0038] Seven winding grooves 4 are shown spaced axially from the terminal stop 7, each formed by two adjacent components, here eight ring elements 5, including the stop 7. The ring elements 5 are pushed axially onto the winding core 3, with a certain axial distance being maintained between each ring element 5. To maintain the distance between the ring elements 5, (metal) sleeves can also be used, for example, which are threaded onto the core together with the ring elements 5.

[0039] The wall of the winding core 3 and the two opposite walls of the ring elements 5 form the circumferentially extending winding grooves 4 into which thermoplastic fiber composite material 8 is wound. If, for example, (metal) sleeves are used to maintain spacing between the ring elements 5, these form the wall, together with the discs.

[0040] This winding is a subsequent process step, the end result of which is Fig. 3B. Thermoplastic fiber composite material 8 - here in the form of a tape - is wound into each of the eight winding grooves 4. The winding direction is perpendicular or almost perpendicular to the later rotational axis D of the rotor 2, ie, the winding angle is 88 to 90° perpendicular to the winding axis A. The winding groove 4 is in particular completely filled with thermoplastic fiber composite material 8, which later forms the sleeves 1a, 1b, 1c (see Fig. 3C).

[0041] After winding the thermoplastic fiber composite material 8, it is consolidated so that solid rings form on the winding core 3. These are the sleeves 1a, 1b, 1c.

[0042] If the ring elements 5 are removed from the winding core 3, e.g. if they are designed as disposable parts, the situation is that Fig. 3C, i.e., seven sleeves 1a, 1b, 1c are arranged axially spaced on the winding core 3. Depending on the tool concept, the ring elements 5 can also be pulled axially off the winding core (mandrel) together with the spacers and the composite sleeves 1a, 1b, 1c.

[0043] The individual sleeves 1a, 1b, 1c have a distance A between them in the axial direction, which corresponds to the axial width of the ring elements 5.

[0044] The sleeves 1a, 1b, 1c can now be removed from the winding core 3 in the axial direction.

[0045] By introducing the winding grooves 3 and the spacing A, the axial edges of the cores 1a, 1b, 1c are in their final state, so that the final shape of the cores 1a, 1b, 1c is already present without further processing. This is also referred to as net-shape manufacturing. Thus, the fibers are present as a whole, especially at the axial edges.

[0046] Unlike the prior art, the cores 1a, 1b, 1c in this embodiment are manufactured individually and not separated from a long core by cutting. Cutting results in the fibers being severed, particularly at the edges, which leads to an interruption of the fiber flow and damage to the cut edges.

[0047] It is also possible that the ring elements 5 are not disposable parts, for example the right-hand ring element 5 is removed so that the rightmost sleeve 1a can then be removed axially from the winding core 3. Then, starting from the right, a spacer (in Fig. 3C not shown) and the nearest ring element 5 is removed so that the next sleeve 1b can be removed. This process is repeated until all sleeves 1a, 1b, 1c have been removed from the winding core 3.

[0048] The width of the winding grooves 3—and thus the width of the resulting sleeves 1a, 1b, 1c—is more than 1.5 cm. The sleeves 1a, 1b, 1c have a wall thickness in the range between 0.5 and 15 mm.

[0049] The Fig. 3A, Fig. 3B and Fig. The number of winding slots 4 and sleeves 1a, 1b, 1c shown in Figure 3C is intended as an example. Fewer or more than seven sleeves can also be produced.

[0050] In the Fig. 4 shows a variant of a winding core 3 which is arranged in the same way as in the embodiment according to Fig. 3A, Fig. 3B, Fig. 3C. Therefore, reference can be made to the above description.

[0051] Here, the winding core 3 as a whole is constructed from individual winding core modules 6. Each of the winding core modules 6 has shoulders with two different diameters. When the winding core modules 6 are assembled, the larger diameters form the walls of the winding grooves 3, and the smaller diameters form the bottom surface of the winding grooves 3. The winding core modules 6 can be wound onto a mandrel or otherwise connected to one another. This is another exemplary embodiment for forming winding grooves 4.

[0052] Another alternative for producing a sleeve 1 that does not require winding grooves 4 is that thermoplastic fiber composite material 8 is wound under a prestress S in the circumferential direction onto the rotor 2 of the electrical machine 10. This is shown schematically in Fig.5. Thus, the sleeve 1 is manufactured in situ on the rotor 2, eliminating the need for a separate winding core 3. It is important that the preload S during direct winding is more than 350 MPa.

[0053] As with the variant using the winding slots 4, the sleeve 1 is already in its final shape in this method of direct winding onto the rotor 2. This embodiment is thus another net-shape variant.

[0054] Independently of the variants described above, the thermoplastic fiber composite material 8 has a number of properties which, individually or in combination, ensure manufacturability as a net-shape.

[0055] The thermoplastic fiber composite material 8 has a matrix elongation at break of more than 5% and / or the fiber of the thermoplastic fiber composite material 8 has a modulus of elasticity between 210 GPa and 600 GPa and / or the fiber of the thermoplastic fiber composite material 8 has a tensile strength of at least 3500 MPa.

[0056] The matrix of the thermoplastic fiber composite material 8 can consist, for example, of PEEK (polyether ether ketone), PPS (polyphenylene sulfide) or PAEK (polyaryletherketone) material.

[0057] In the exemplary embodiments, only one carbon fiber is used as the fiber in the thermoplastic fiber composite material 8. This means that only one type of fiber is deliberately used.

[0058] It should be understood that the invention is not limited to the embodiments described above, and various modifications and improvements may be made without departing from the concepts described herein. Any of the features may be employed separately or in combination with any other features, provided they are not mutually exclusive, and the disclosure extends to and encompasses all combinations and subcombinations of one or more of the features described herein. List of reference symbols 1 sleeve 2 Rotor of an electrical machine, rotor of a motor 3 winding core for core 4 winding groove 5 ring element 6 winding core module 7 Stop of the winding core 8 Fiber composite material 9 Permanent magnet 10 electrical machine, motor 11 Stator of an electrical machine, stator of a motor 12 Air gap A axis of the winding core D Rotor rotation axis QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] US 2022 / 0271588 A1

[0002] US 2022 / 0271601 A1

[0002] US 2022 / 0278584 A1

[0002] CN 2904393

[0002] CN 2669431

[0002] CN 112564351

[0002]

Claims

[1] Method for producing at least one sleeve (1) for encasing permanent magnets of a rotor (2) of an electrical machine (10) with an axis of rotation (D), characterized by , that a) a sleeve (1) with or made of a thermoplastic fiber composite material (8) is wound directly onto the rotor (2) in the circumferential direction under a defined prestress (S) or b) a plurality of sleeves (1a, 1b, 1c) with or made of a thermoplastic fiber composite material (8) are wound axially spaced from one another on a winding core (3), so that the sleeve (1) or the plurality of sleeves (1a, 1b, 1c) have a final shape at their respective axial edges (3) and • the thermoplastic fiber composite material (8) has a breaking elongation of the matrix of at least 5% and / or • the fiber of the thermoplastic fiber composite material (8) has a modulus of elasticity between 210 MPa and 600 MPa and / or • the fiber of the thermoplastic fiber composite material (8) has a tensile strength between 4500. [2] Method according to claim 1, characterized by that the thermoplastic fiber composite material (8) is wound at an angle between 88 and 90°, in particular between 89° and 90°, to the axis of rotation (D). [3] Method according to at least one of the preceding claims, characterized by that the at least one sleeve (1, 1a, 1b, 1c) has an end wall thickness between 0.5 and 15 mm. [4] Method according to at least one of the preceding claims, characterized by that the plurality of sleeves (1a, 1b, 1c) wound on the winding core (3) each have an axial width of at least 1.5 cm. [5] Method according to at least one of the preceding claims, characterized bythat the winding core (3) has at least one component (5, 6) for forming at least one winding groove (4) for the thermoplastic fiber composite material (8) running in the circumferential direction of the winding core (3). [6] Method according to claim 5, characterized by that at least two components (5) are designed as ring elements which can be arranged axially on the winding core (3), so that a winding groove (4) for the thermoplastic fiber composite material (8) is formed between the at least two ring elements (5). [7] Method according to claim 5, characterized by that the winding core (3) has or is formed from at least two winding core modules (6) which are designed such that a winding groove (4) for the thermoplastic fiber composite material (8) is formed between the at least two winding core modules (6). [8] Method according to at least one of the preceding claims, characterized bythat the winding core (3) has a stop (7) at one axial end. [9] Method according to at least one of the preceding claims, characterized by that the thermoplastic fiber composite material (8) is consolidated in-situ after winding. [10] Method according to at least one of the preceding claims, characterized by that the direct winding of the thermoplastic fiber composite material (8) is carried out with a prestress (S) of at least 350 MPa. [11] Method according to at least one of the preceding claims, characterized by that the matrix of the thermoplastic fiber composite material (8) comprises PEEK, PPS or PAEK or consists of these materials. [12] Method according to at least one of the preceding claims, characterized by that only one uniform fiber, in particular a carbon fiber, is used as the fiber of the thermoplastic fiber composite material (8). [13] Method according to at least one of the preceding claims, characterized by that the thermoplastic fiber composite material (8) is designed as a tape, in particular in tape widths between 1 / 16 inch and 2 inches. [14] Sleeve for encasing permanent magnets of a rotor (2) of an electrical machine (10), producible by one of the methods according to at least one of claims 1 to 13. [15] Sleeve according to claim 14, characterized by that the electrical machine (10) is designed as a motor or generator, in particular for an aircraft. [16] Winding core (3) for producing at least one sleeve (1) for encasing permanent magnets of a rotor (2) of an electrical machine (10) with an axis of rotation (D), characterized bya winding core (3) for a thermoplastic fiber composite material (9), wherein the winding core (3) has at least one component (5, 6) for forming a winding groove (4) running in the circumferential direction of the winding core (3), wherein at least two components (5) are designed as ring elements which are arranged axially on the winding core (3) so that a winding groove (4) for the thermoplastic fiber composite material (8) is arranged between the at least two ring elements (5), or that the winding core (3) has or is formed from at least two winding core modules (6) which are designed such that a winding groove (4) for the thermoplastic fiber composite material (8) is formed between the at least two winding core modules (6).

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