Electrical machine multi-stack transfer molding - multipart end bell

Abstract

The invention relates to a rotor body for an electrical machine, comprising a plurality of axial recesses which are designed to accommodate magnets and which extend in an axial direction from a first axial side to a second axial side opposite the first axial side, wherein: the axial recesses are each completely filled with a molding material; the molding material forms a first end bell at the first axial side, which first end bell is connected to the molding material from at least two of the axial recesses; the molding material forms a second end bell at the second axial side; and the second end bell is connected only to the molding material from one of the axial recesses. The invention also relates to an electrical machine.

Description

[0001] E-Machine Multistack Transfer Molding - Multi-part end cap

[0002] The invention relates to a rotor body for an electrical machine. Furthermore, the invention relates to an electrical machine comprising a corresponding rotor body.

[0003] Electric machines are used in a wide variety of applications. Electric machines are increasingly being used in the automotive industry to drive motor vehicles. An example of an electric machine that can be used within the drivetrain of a hybrid or fully electric vehicle is the so-called permanent magnet synchronous machine. Due to its high power density compared to other machine types, it is particularly popular in the field of electromobility, where the available installation space is often a limiting factor. The excitation field of the machine is usually generated by permanent magnets arranged in the rotor of the machine.

[0004] Particularly with regard to applications of electric machines in the automotive industry in vehicles with electric or hybrid drives, these machines are continuously being developed not only in terms of their efficiency and / or power and / or maximum torque, but also in terms of efficient production methods. Therefore, there is a need to be able to manufacture electric machines cost-effectively, with high quality, and in large quantities, even on a large industrial scale.

[0005] With a view to manufacturing the rotor of the electric machine, this requires the rotor magnets to be positioned, aligned, and joined as precisely as possible in the magnetic pockets of the rotor laminated core. Due to the high degree of integration, the installation space for all components and design solutions is very limited, which regularly also requires correspondingly space-efficient solutions for the arrangement and fixing of the rotor magnets. Various methods for attaching magnets to laminated cores to form a rotor are already known from the prior art. In addition to the option of pressing magnets into the corresponding cavities or caulking them, it is also known to fix the rotor magnets in the magnetic pockets of the rotor laminated core by means of transfer molding or by gluing. In particular, the use of plastics, in particular injection-moldable plastics in the form of thermoplastics and / or thermosetting plastics, is known.

[0006] For example, DE102015203018 A1 shows an electric machine comprising a rotor body having axial recesses for accommodating magnets. The axial recesses are filled with a potting material, wherein the potting material forms a ring on each axial side, which is connected to the potting material of each of the axial recesses.

[0007] The object of the present invention is to reduce or completely avoid the problems known from the prior art and to provide a rotor body for an electrical machine that can be manufactured with high quality and in large quantities. Furthermore, the object of the invention is to provide an improved electrical machine.

[0008] This object is achieved by the features described in the independent claims. Advantageous embodiments can be found in the dependent patent claims.

[0009] According to one aspect, a rotor body for an electric machine has a plurality of axial recesses designed to accommodate magnets. The axial recesses extend in the axial direction from a first axial side to a second axial side opposite the first axial side. The axial recesses are each completely filled with a potting material, wherein the potting material forms a first end cap on the first axial side, which is connected to the potting material of at least two of the axial recesses. Furthermore, the potting material forms a second end cap on the second axial side, wherein the second end cap is only connected to the potting material of one of the axial recesses.

[0010] The design of the end cap on the first axial side, via which the potting material is introduced into several recesses, and the design of the second end cap on the second axial side, via which excess potting material is removed from the one recess corresponding to the second end cap, ensure that no air pockets remain in the corresponding recess. Particularly for recesses that have smaller cross-sections than other recesses or that have narrow spots within the recess, for example, in the case of interlaced laminated cores, the previously described designs prevent air pockets from occurring in one recess due to lower flow velocities of the potting compound in one recess.In other words, the described embodiments prevent potting material from flowing into a recess from both the first axial side and the second axial side, thereby forming an air pocket. Particularly advantageously, the second end cap formed on the rotor body thus serves as an indicator that one recess, or the recess corresponding to the second end cap, is completely filled with potting material. Completely filled with potting material, as defined in the application, means that the recesses are filled with the potting material to at least 90% by volume.

[0011] For the purposes of the invention, a rotor body is understood to mean the rotor without the rotor shaft. The rotor body is therefore particularly preferably composed of a rotor core and the magnetic elements inserted into the recesses of the rotor core and / or fixed circumferentially to the rotor core, as well as any axial cover parts for closing the pockets.

[0012] The term "magnetic element," "rotor magnet," or simply "magnet," refers to the permanent magnets that are inserted into the pockets of the rotor core. Each pocket can contain a single, larger rotor magnet designed as a bar magnet, or several smaller permanent magnet elements.

[0013] According to one embodiment, a plurality of the axial recesses are designed to form a magnetic pole of the rotor body, wherein the first end cap is connected to the potting material of all axial recesses forming the magnetic pole.

[0014] The described design advantageously reduces the use of potting material.

[0015] According to a further embodiment, the potting compound of each of the axial recesses forming the magnetic pole is connected to a second end cap.

[0016] Advantageously, this provides a visual indicator for each recess that each of the recesses is completely filled with potting material.

[0017] According to a further embodiment, the second end cap is only connected to the potting material of one of the axial recesses forming the magnetic pole, wherein a third end cap on the second axial side is connected to the potting material of several of the other axial recesses forming the magnetic pole.

[0018] Advantageously, the second end cap can thus provide a visual indicator for a recess, which, without a corresponding second end cap, would lead to the formation of air pockets, particularly since, with an end cap connecting all the recesses, potting material flows into one recess from both the first axial side and the second axial side, forming an air pocket. According to a preferred embodiment, the rotor body is formed from a plurality of interlaced axial sections.

[0019] Advantageously, the interlaced arrangement of the rotor bodies can smooth the torque characteristics of the electric machine in such a way that so-called torque ripple is reduced or suppressed.

[0020] According to one embodiment, each axial section comprises axial recesses for receiving magnets, wherein the axial sections of adjacent recesses are arranged relative to one another in such a way that a substantially axial recess is produced with respect to the rotor body.

[0021] Advantageously, the recesses in the individual axial sections of the rotor body are designed such that they form communicating volumes. This ensures that the potting material can be filled from the first axial side to the second axial side. A substantially axial recess within the meaning of the present invention exists when an imaginary line between the respective centers of gravity of communicating recesses of two adjacent axial sections has a deviation of up to 15° relative to the rotational axis of the rotor body.

[0022] According to one embodiment, the rotor body has a lamination pack with sheet metal laminations stacked one above the other in the axial direction.

[0023] A rotor lamination stack is a collection of laminated individual laminations, usually made of electrical steel, that are stacked and packaged together to form a so-called rotor lamination stack. The individual laminations can then be held together in the lamination stack, for example, by stamping, bonding, welding, or screwing.

[0024] A rotor lamination may have one or more recesses, which may also be referred to as a cutout or opening. The individual recesses of the individual rotor laminations, taken together in a rotor lamination stack, form an axially oriented pocket for accommodating magnetic elements. This pocket is also referred to as a recess.

[0025] According to one embodiment, the potting compound is an injection-moldable plastic.

[0026] In the sense of the present application, injection-moldable plastic refers to a plastic that can be in a highly flowable state during the production step of filling the channels, so that the channels can be completely filled in a plastic injection molding process, such as a transfer molding process.

[0027] Furthermore, the injection-moldable plastic can be characterized by its ability to cure relatively quickly and its high mechanical stability when cured. The injection-moldable plastic can be a thermoplastic or a thermosetting plastic, for example.

[0028] According to a preferred embodiment, the injection-moldable plastic is a thermoset.

[0029] Thermosets are advantageously characterized by their hardness and rigidity. Their low coefficient of expansion results in high dimensional stability. Furthermore, thermosets have no softening range; the material retains its strength even at high temperatures and has high heat resistance.

[0030] According to a further aspect, an electric machine comprises a rotor body according to the previously described aspect and configurations.

[0031] Electrical machines are used to convert electrical energy into mechanical energy and / or vice versa. They typically comprise a stationary part known as a stator, stator, or armature, and a part known as a rotor or runner, which is arranged so as to be movable relative to the stationary part. The rotor preferably comprises a rotor shaft and one or more rotor bodies arranged in rotation on the rotor shaft. The rotor shaft can be hollow, which not only reduces weight but also allows the supply of lubricant or coolant to the rotor body.

[0032] The electric machine is designed, in particular, as a rotary machine. In the context of this invention, it is particularly preferred for the electric machine to be configured as a radial flux machine. A radial flux machine is characterized by the fact that the magnetic field lines in the air gap formed between the rotor and stator extend in the radial direction.

[0033] The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

[0034] It shows:

[0035] Figure 1 shows a rotor body in section, with a first axial side visible. Figure 2 shows the rotor body according to Figure 1 with a view of a second axial side. Figure 3 shows the rotor body according to Figure 2 with adapted end caps.

[0036] Figure 1 shows a rotor body 1 in section, with a first axial side 2 visible. The rotor body 1 comprises a plurality of axial sections 11, here designed as lamination packs 4, which in turn have a plurality of laminated laminations. Within the lamination packs 4, a plurality of recesses 5 extend from the first axial side 2 to a wide axial side 3, wherein the axial sections 11 or lamination packs 4 of axially adjacent recesses 5 are arranged relative to one another in such a way that a substantially axial recess results with respect to the rotor body 1. A plurality of magnets 6 segmented in the axial direction are arranged in each of the recesses 5. The magnets 6 are fixed in the recesses 5 by means of a potting material 7. The potting material 7 forms a plurality of first end caps 8 on the first axial side 2.The potting material 7 is introduced into the rotor body 1 from the first axial side 2, which is why a corresponding sprue section is visible centrally on the first end caps 8. The potting material 7 of the first end cap 8 is connected to the potting material 7 of all recesses 5 of a magnetic pole of the rotor body 1, which recesses 5 contain magnets 6, and completely covers them. The first end caps 8 thus cover the recesses 5 containing magnets 6 both in the radial and circumferential directions. In other words, the cross-section of the first end cap, viewed in the axial direction, is larger than an area formed by an imaginary circumferential line spanning all recesses 5 of a magnetic pole containing magnets 6.

[0037] Figure 2 shows the rotor body 1 according to Figure 1 with a view of a second axial side 3, according to the prior art. The second axial side 3 is opposite the first axial side 2 of the rotor body 1. Figure 2a shows the rotor body 1, wherein all recesses 5 of a magnetic pole, comprising magnets 6, are covered by a first end cap 8. Thus, the potting material 7 of each of the recesses 5 of a magnetic pole, comprising magnets 6, is connected to the potting compound of the first end cap 2, which is arranged on the second axial side 3 of the rotor body. Figure 2b shows, by way of example, a recess 5 of a magnetic pole, comprising all magnets 6. The arrangement of the magnets 6 shown, a so-called delta arrangement, is to be understood as an example. Also possible are arrangements such as V-arrangement, V-arrangement with a third magnet 6 aligned in the circumferential direction, so-called T-magnet, etc.

[0038] The recesses 5 have a larger cross-section in the axial direction than the magnets 6. The resulting volumes in the recesses 5 adjacent to the magnets 6 are completely filled with the potting compound 7. In particular, in the case of interlaced axial sections of the rotor body, in this case interlaced lamination packs, the recesses form a substantially axial recess relative to the rotor body, in which the volumes adjacent to the magnets 6 are connected to one another in such a way that the potting compound can be introduced from the first axial side 2 to the second axial side 3 into the rotor body 1 over the entire axial extent of the rotor body, so that the remaining volumes of the recesses 5 containing all the magnets 6 are completely filled with the potting compound.

[0039] Figure 3 shows the rotor body 1 according to Figure 2 with adapted end caps 9, 10. In this case, the recesses 5 of the magnetic pole from Figure 2b, which contain the potting compound 7 - the left-hand recess in the view, the right-hand recess, and the lower recess - are each connected to the potting compound 7 of a third end cap 10. The third end cap 10 completely covers the three recesses when viewed from the axial direction. A second end cap 9 completely covers only the fourth recess 5 of the magnetic pole from Figure 2b, which contains the fourth magnet 6 and is located at the top in the view. Thus, the potting compound 7 of the second end cap 9 is only connected on the second axial side 3 to the potting compound 7 of a recess 5. The potting compound 7 of the second end cap is not connected to the potting compound of the third end cap 10 on the second axial side.

[0040] List of reference symbols Rotor body First axial side Second axial side Disc pack Recess Magnet Potting material First end cap Second end cap Third end cap Axial section

Claims

Patent claims 1. Rotor body (1) for an electrical machine, comprising a plurality of axial recesses (5) which are designed to receive magnets (6) and which extend in the axial direction from a first axial side (2) to a second axial side (3) which is opposite the first axial side (2), wherein the axial recesses (5) are each completely filled with a potting material (7), the potting material (7) on the first axial side (2) forms a first end cap (8) which is connected to the potting material (7) of at least two of the axial recesses (5), the potting material on the second axial side (3) forms a second end cap (9), wherein the second end cap (9) is only connected to the potting material (7) of one of the axial recesses (5).

2. Rotor body (1) according to claim 1, wherein a plurality of the axial recesses (5) are designed to form a magnetic pole of the rotor body, wherein the first end cap (8) on the first axial side (2) is connected to the potting material (7) of all the axial recesses (5) forming the magnetic pole.

3. Rotor body (1) according to claim 2, wherein the potting material (7) of each of the axial recesses (5) forming the magnetic pole is connected to a second end cap (9) on the second axial side (3).

4. Rotor body (1) according to claim 2, wherein the second end cap (9) on the second axial side (3) is connected only to the potting material (7) of one of the axial recesses (5) forming the magnetic pole, wherein a third end cap (10) on the second axial side (3) is connected to the potting material (7) of several of the other axial recesses (5) forming the magnetic pole.

5. Rotor body (1) according to claim 1, wherein the rotor body (1) is formed from a plurality of axial sections (11) interlaced with one another.

6. Rotor body (1) according to claim 5, wherein each axial section (11) comprises axial recesses (5) for receiving magnets (6), wherein the axial sections (11) of axially adjacent recesses (5) are arranged relative to one another in such a way that a substantially axial recess (5) is produced with respect to the rotor body (1).

7. Rotor body (1) according to one of the preceding claims, wherein the rotor body (1) has a lamination pack (4) with sheet metal laminations stacked one above the other in the axial direction.

8. Rotor body (1) according to one of the preceding claims, wherein the potting compound (7) is an injection-moldable plastic.

9. Rotor body according to (7) claim 8, wherein the injection-moldable plastic is a thermoset.

10. Electrical machine comprising a rotor body (1) according to one of the preceding claims.

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