Rotor assembly and electric machine

Abstract

The invention relates to a rotor assembly (30) comprising a rotor shaft (32), first laminated core segments (40), second laminated core segments (50), permanent magnets (60), and a bandage (70), wherein: the rotor shaft (32) is made of a fibre-reinforced plastic material at least in a specified first axial portion (A1); the permanent magnets (60) are situated between the first laminated core segments (40) and the second laminated core segments (50) and form rotor poles (61-66); the first laminated core segments (40) adjoin the rotor shaft (32) and at least two of the permanent magnets (60); and the bandage (70) is situated on the radially outer face of the second laminated core segments (50).

Description

[0001] Rotor arrangement and electric machine

[0002] The invention relates to a rotor arrangement and an electrical machine.

[0003] DE 10 2022 203 126 A1 shows a rotor with a rotor carrier rotatable about a rotor axis and a rotor laminated core comprising a sheet metal strip wound helically around the rotor carrier, wherein the sheet metal strip has magnetic pocket recesses arranged one behind the other in the longitudinal direction for forming magnetic pockets in the rotor laminated core.

[0004] DE 10 2022 203 125 A1 shows a rotor with a rotor shaft rotatable about a rotor axis, a fiber composite sleeve and a rotor body arranged between the rotor shaft and the fiber composite sleeve, which rotor body comprises a plurality of rotor poles and at least one magnet pocket per rotor pole for receiving permanent magnets.

[0005] DE 10 2021 105 499 A1 shows a rotor for an axial flux machine, which has several rotor plates made of a fiber composite material, several permanent magnets and a rotor shaft.

[0006] DE 10 2015 110 652 A1 shows a rotor-stator arrangement for a hybrid-excited synchronous machine, in which the rotor has an inner part which has alternating pole supports and recesses along its circumference, wherein at least one excitation winding is inserted into each recess.

[0007] WO 2021 / 225 902 A1 shows an inner rotor with a shaft, a central laminated core, V-shaped permanent magnets and pole pieces.

[0008] It is therefore an object of the invention to provide a new rotor arrangement and a new electric machine.

[0009] This problem is solved by the main claim and the subordinate claims. A rotor arrangement comprises a rotor shaft, first laminated core segments, second laminated core segments, permanent magnets, and a bandage, in which the rotor shaft is formed from a fiber-reinforced plastic at least in a predetermined first axial section, in which the permanent magnets are arranged between the first laminated core segments and the second laminated core segments and form rotor poles, in which the first laminated core segments border the rotor shaft and at least two of the permanent magnets, and in which the bandage is arranged on the radially outer side of the second laminated core segments.

[0010] Studies have shown that this design has a beneficial effect on the mechanical stress distribution, both radially and tangentially. Temperature changes have a smaller impact on the mechanical stress than in rotor arrangements with a rotor shaft made of iron or steel.

[0011] According to a preferred embodiment, the bandage is designed as a fiber composite bandage, wherein the bandage preferably comprises a carbon fiber reinforced plastic.

[0012] Such a bandage can absorb high forces and can therefore be made thin. This allows for a small magnetic air gap.

[0013] According to a preferred embodiment, the rotor shaft is formed from a carbon fiber-reinforced plastic, at least in the predetermined first axial section. This is advantageous both in terms of stability and density.

[0014] According to a preferred embodiment, the rotor poles each have two permanent magnets arranged in a V-shape. This results in a high flux density in the pole center.

[0015] According to a preferred embodiment, a first space is formed between the two V-shaped permanent magnets, wherein the first space is bounded at least in sections by the two V-shaped permanent magnets and the rotor shaft. This is advantageous as a flux barrier.

[0016] According to a preferred embodiment, the first space is delimited at least in sections by the first laminated core segments. The first laminated core segments can advantageously be used as spacers and for magnetic flux guidance.

[0017] According to a preferred embodiment, the permanent magnets are spaced apart from the rotor shaft, with an associated first laminated core segment preferably being arranged at least partially between the permanent magnets and the rotor shaft. This is mechanically advantageous because vibrations of the permanent magnets are not directly transmitted to the rotor shaft.

[0018] According to a preferred embodiment, at least one feature is fulfilled from a group of features consisting of:

[0019] - The first laminated core segments are each spaced apart from the other first laminated core segments,

[0020] - the second laminated core segments are each spaced apart from the other second laminated core segments,

[0021] - the first laminated core segments are each spaced apart from the second laminated core segments.

[0022] Magnetic stray fluxes between the laminated core segments can thereby be prevented or reduced.

[0023] According to a preferred embodiment, the rotor shaft has recesses in at least a second axial section, and the first laminated core segments extend into the recesses. This results in toothing, and the sheet metal available for the magnetic flux is advantageously increased. According to a preferred embodiment, the recesses in the cross-section of the rotor shaft have a concave profile, at least in sections. A shape with a concave curvature reduces stresses.

[0024] According to a preferred embodiment, the first laminated core segments on the side facing the rotor shaft are designed to be at least partially or completely complementary to the associated recess. This enables large-area force transmission and reduces occurring mechanical stresses.

[0025] According to a preferred embodiment, the rotor shaft has exactly one recess for each of the first laminated core segments. Such a recess can be comparatively large and allows a high magnetic flux through the first laminated core segments.

[0026] According to a preferred embodiment, the number of first laminated core segments corresponds to the number of rotor poles. This enables a high flux density on the radially inner side of the permanent magnets.

[0027] According to a preferred embodiment, the number of second laminated core segments corresponds to the number of rotor poles. This enables a high magnetic flux density on the radially outer side of the permanent magnets.

[0028] According to a preferred embodiment, the first laminated core segments extend to the bandage. This allows the bandage to exert a radial force on the first laminated core segments, resulting in a stable rotor arrangement.

[0029] An electrical machine comprises such a rotor arrangement and a stator arrangement. Such an electrical machine has advantageous properties due to the rotor arrangement. Further details and advantageous developments of the invention emerge from the details described below and illustrated in the drawings, which are in no way to be understood as limiting the invention.

[0030] Embodiments and the dependent claims. It is understood that the features mentioned above and those to be explained below can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the present invention. It shows:

[0031] Fig. 1 shows a schematic cross-section of an electrical machine with a rotor arrangement,

[0032] Fig. 2 shows a schematic side view of the rotor arrangement of Fig. 1,

[0033] Fig. 3 in a schematic representation of a non-inventive

[0034] Rotor arrangement,

[0035] Fig. 4 is a diagram showing the radial mechanical stress distribution of the rotor arrangement of Fig. 3,

[0036] Fig. 5 is a diagram showing the radial mechanical stress distribution of the rotor arrangement of Fig. 1,

[0037] Fig. 6 is a diagram showing the axial mechanical stress distribution of the rotor arrangement of Fig. 3, and

[0038] Fig. 7 is a diagram showing the axial mechanical stress distribution of the rotor arrangement of Fig. 1.

[0039] In the following, identical or equivalent parts are provided with the same reference numerals and are usually described only once. The description builds on each figure to avoid unnecessary repetition. Fig. 1 shows a schematic representation of an electric machine 20 with a rotor assembly 30 and a stator assembly 22. Fig. 2 shows a side view of the rotor assembly 30.

[0040] The stator arrangement 22 is shown only schematically; in particular, the stator slots and the inserted windings are missing.

[0041] The rotor assembly 30 has a rotor shaft 32, first laminated core segments 40, second laminated core segments 50, permanent magnets 60 and a bandage 70.

[0042] The rotor shaft 32 is formed from a fiber-reinforced plastic at least in a predetermined first axial section A1 (see Fig. 2).

[0043] The fiber-reinforced plastic of the rotor shaft 32 is preferably a carbon fiber-reinforced plastic.

[0044] The permanent magnets 60 are arranged between the first laminated core segments 40 and the second laminated core segments 50 and form rotor poles 61, 62, 63, 64, 65, 66. In the exemplary embodiment, the rotor assembly 30 has six rotor poles 61-66, but it can also have four rotor poles or eight rotor poles, or a higher number of rotor poles.

[0045] The first laminated core segments 40 are adjacent to the rotor shaft 32 and to at least two of the permanent magnets 60.

[0046] The bandage 70 is arranged on the radially outer side of the second laminated core segments 50.

[0047] The bandage 70 is preferably designed as a fiber composite bandage, more preferably comprising a carbon fiber-reinforced plastic. The rotor poles 61-66 each have two permanent magnets 60 arranged in a V-shape.

[0048] A first space 80 is formed between the two V-shaped permanent magnets 60 of one of the poles 61 - 66, wherein the first space 80 is delimited at least in sections by the two V-shaped permanent magnets 60 and the rotor shaft 32.

[0049] Preferably, the first space 80 is delimited at least in sections by the first laminated core segments 40.

[0050] The first space 80 can remain empty or be filled, for example, with a magnetically non-conductive plastic.

[0051] The permanent magnets 60 are preferably spaced apart from the rotor shaft 32, wherein an associated first laminated core segment 40 is preferably arranged at least in sections between the permanent magnets 60 and the rotor shaft 32.

[0052] Preferably, the first laminated core segments 40 are each spaced apart from the other first laminated core segments 40.

[0053] Preferably, the second laminated core segments 50 are each spaced apart from the other second laminated core segments 50.

[0054] Preferably, the first laminated core segments 40 are each spaced apart from the second laminated core segments 50.

[0055] The rotor shaft 32 has recesses 34 at least in a second axial section A2, and the first laminated core segments 40 extend into the recesses 34. This results in a toothing or a positive-locking arrangement in which high forces can be transmitted between the first laminated core segments 40 and the rotor shaft 32. The recesses 34 have a concave profile, at least in sections, in the cross-section of the rotor shaft 32.

[0056] The first laminated core segments 40 are formed on the side facing the rotor shaft 32 at least in sections complementary to the associated recess 34.

[0057] The rotor shaft 32 has exactly one recess 34 for each of the first laminated core segments 40.

[0058] In the embodiment, the number of first laminated core segments 40 corresponds to the number of rotor poles 61 - 66.

[0059] In the exemplary embodiment, the number of second laminated core segments 50 corresponds to the number of rotor poles 61 - 66.

[0060] The first laminated core segments 40 extend to the fiber composite bandage 70.

[0061] Lines 101 schematically show the magnetic flux density in the area of ​​pole 65, which acts as the north pole due to the arrangement of the V-shaped permanent magnets 60. In the exemplary embodiment, no excitation field generated by the stator poles of the stator arrangement 22 is taken into account.

[0062] The magnetic flux generated by pole 65 passes through the associated second laminated core segment 50 and the magnetic air gap 23 into the region of the stator arrangement, where it is conducted to the neighboring poles 64, 66 via the magnetic yoke. At the neighboring poles 64, 66, the magnetic flux passes through the magnetic air gap 23 back to the neighboring second laminated core segments 50 of the neighboring poles 64, 66 and to the associated south pole of the permanent magnets 60 of the neighboring poles 64, 66. Inside the rotor arrangement 30, the magnetic flux from the neighboring poles 64, 66 can pass through the associated first laminated core segment 40 back to the permanent magnets 60 of the rotor pole 65.In this case, the convex design of the surface of the first laminated core segment 40 assigned to the rotor shaft 32 is advantageous because the magnetic flux is not restricted and thus the risk of performance-reducing saturation in the area of ​​the first laminated core segment 40 is reduced.

[0063] In the side view shown in Fig. 2, rotor shaft end pieces 321 and 322 are provided at the axial ends of the rotor shaft 32. These are made of metal, for example, and enable good, stable support, for example, through rolling bearings (not shown). The first axial region A1 and the second axial region A2 can also be selected identically. The second axial region does not have to extend over the entire axial length of the laminated core segments 40, 50, but it can also extend beyond them.

[0064] Fig. 3 shows a schematic cross section through a rotor arrangement 130 not according to the invention.

[0065] The rotor assembly 130 has a rotor shaft 132, an annular laminated core 140, and laminated core segments 150. Permanent magnets 160 are formed between the laminated core segments 150 and the annular laminated core 140.

[0066] A bandage 170 is provided around the rotor assembly 130.

[0067] The rotor assembly 130 was chosen for comparison, and the rotor shaft 132 is conventionally made of iron with a mass density of 7.63 10' 9 kg / mm 3 .

[0068] The outer diameter of the rotor arrangement 130 was chosen to be 154 mm, as with the rotor arrangement 30.

[0069] Fig. 4 and Fig. 5 show diagrams which show on the ordinate the mechanical stress curve in radial direction in MPa at a speed of 23,575 min -1 The abscissa indicates the radius relative to the rotor arrangement in mm. The mechanical stress curve varies with the distance from the axis of rotation.

[0070] Line 111 shows the mechanical stress curve for the non-inventive rotor assembly 130 of Fig. 3 at a temperature of -25 °C, and line 112 shows the mechanical stress curve for the rotor assembly 130 of Fig. 3 at a temperature of 130 °C.

[0071] Line 113 shows the mechanical stress curve for the rotor assembly 30 of Fig. 1 at a temperature of -25 °C, and line 114 shows the mechanical stress curve for the rotor assembly 30 of Fig. 1 at a temperature of 130 °C.

[0072] Fig. 6 and Fig. 7 show diagrams which show on the ordinate the mechanical stress curve in tangential direction in MPa at a speed of 23,575 min' 1 and the abscissa indicates the radius relative to the rotor arrangement in mm.

[0073] Line 121 shows the mechanical stress curve for the non-inventive rotor assembly 130 of Fig. 3 at a temperature of -25 °C, and line 122 shows the mechanical stress curve for the rotor assembly 130 of Fig. 3 at a temperature of 130 °C.

[0074] Line 123 shows the mechanical stress curve for the rotor assembly 30 of Fig. 1 at a temperature of -25 °C, and line 124 shows the mechanical stress curve for the rotor assembly 30 of Fig. 1 at a temperature of 130 °C.

[0075] In rotor arrangements with buried permanent magnets, the centrifugal forces are absorbed either by rotor iron bars or by a tangentially or circumferentially wound bandage 70 or 170. The bandages 70 and 170 are prestressed, and the strength values ​​of the carbon fibers in the fiber direction are in the order of magnitude of up to 3,500 MPa. When designing the bandages 70 and 170, the mechanical stresses due to the undersize, the centrifugal force load, and the thermal expansion must be taken into account.

[0076] The drum height and the undersize between the drum (70, 170) and the rotor outer diameter must be selected so that the tangential tension in the drum does not exceed a specified limit at maximum operating temperature and spin speed. Furthermore, it must be ensured that at minimum operating temperature and spin speed, a minimum compressive stress between the permanent magnets and the rotor yoke is not exceeded, as this would otherwise lead to lift-off.

[0077] Due to the very different thermal expansion coefficients of electrical steel (a = 12.03 10' 6 K' 1 ) and permanent magnet (a = 3.03 10' 6 K' 1 ) to carbon fibers («radial = 34.3 10' 6 K' 1 , «tangential = 0.139 10' 6 K' 1), a high additional mechanical stress occurs in the tangential direction of the drum. In addition, the centrifugal force load leads to tensile stress, thus reducing the compressive stress primarily generated by the undersize, which prevents lift-off.

[0078] As can be seen in Fig. 6, in the rotor arrangement 130 of Fig. 3, a temperature increase from -25 °C to 130 °C leads to a stress increase from 1,523 MPa to 1,896 MPa, i.e. by +24.5%.

[0079] In comparison, Fig. 7 shows that in the rotor arrangement 30 of Fig. 1 with the segments, a stress increase from 1,558 MPa to 1,770 MPa occurs at the same temperature increase, i.e. by +13.6%. This results in a mechanical stress reserve compared to the rotor arrangement 30 of Fig. 3. This can be used to further increase the limiting speed of the rotor arrangement 30 with the fiber-reinforced rotor shaft 32. Alternatively, the bandage height, i.e. the thickness of the bandage 70, can be reduced in order to enable a smaller magnetic air gap 23 and thus a higher torque due to a higher air gap flux density at the same limiting speed. Which of these measures is selected depends heavily on the machine design and the requirements of the electrical machine 10.

[0080] As can be seen from Fig. 4 and Fig. 5, the mechanical stress profile in the radial direction in the rotor arrangement 30 of Fig. 1 is significantly lower in absolute terms and in terms of amount than in the rotor arrangement 130 of Fig. 3. In addition, the temperature-dependent change in the mechanical stress profile in the rotor arrangement 30 of Fig. 1 is smaller than in the rotor arrangement 130 of Fig. 3.

[0081] A further advantage of the solution in Fig. 1 results from the lower density of the carbon fiber reinforced plastic (CFRP) of the rotor shaft 32 (PCFRP ~ 1.54 kg / m 3 ) compared to steel or iron (pFe « 7.63 kg / m 3 ). This reduces the mass and thus also the rotational inertia of the rotor assembly 30. Compared to the rotor assembly 130, the rotor assembly 30 exhibits a mass reduction of -24.9% and a mass inertia reduction of -7.7%, with the same external dimensions.

[0082] A further advantage of the multiple segmentation of the rotor lamination with the laminated core segments 40, 50 arises during production, as these can be produced with less waste than with large central laminated cores as in Fig. 3. This increases the sustainability of the solution in Fig. 1

[0083] The rotor shaft 32 comprises carbon fibers and a plastic matrix, for example, made of epoxy resin. This makes the rotor shaft 32 electrically insulating. This reduces bearing currents, and previously necessary remedial measures such as a diverter ring can be eliminated. This reduces the number of required components and thus the assembly effort and costs.

[0084] Naturally, numerous variations and modifications are possible within the scope of the present invention. Instead of or in addition to carbon fibers, glass fibers can also be used for the fiber-reinforced plastics.

Claims

Patent claims 1. A rotor arrangement (30) comprising a rotor shaft (32), first laminated core segments (40), second laminated core segments (50), permanent magnets (60), and a bandage (70), in which the rotor shaft (32) is formed from a fiber-reinforced plastic at least in a predetermined first axial section (A1), in which the permanent magnets (60) are arranged between the first laminated core segments (40) and the second laminated core segments (50) and form rotor poles (61-66), in which the first laminated core segments (40) adjoin the rotor shaft (32) and at least two of the permanent magnets (60), and in which the bandage (70) is arranged on the radially outer side of the second laminated core segments (50).

2. Rotor arrangement (30) according to claim 1, wherein the bandage (70) is designed as a fiber composite bandage, wherein the bandage (70) preferably comprises a carbon fiber reinforced plastic.

3. Rotor arrangement (30) according to claim 1 or 2, wherein the rotor shaft (32) is formed from a carbon fiber reinforced plastic at least in the predetermined first axial section (A1).

4. Rotor arrangement (30) according to one of the preceding claims, in which the rotor poles (61 - 66) each have two permanent magnets (60) arranged in a V-shape.

5. Rotor arrangement (30) according to claim 4, wherein a first space (80) is formed between the two V-shaped permanent magnets (60), wherein the first space (80) is delimited at least in sections by the two V-shaped permanent magnets (60) and the rotor shaft (32).

6. Rotor arrangement (30) according to claim 5, wherein the first space (80) is delimited at least in sections by the first laminated core segments (40).

7. Rotor arrangement (30) according to one of the preceding claims, in which the permanent magnets (60) are spaced from the rotor shaft (32), wherein an associated first laminated core segment (40) is preferably arranged at least in sections between the permanent magnets (60) and the rotor shaft (32).

8. Rotor arrangement (30) according to one of the preceding claims, in which at least one feature is fulfilled from a group of features consisting of: - The first laminated core segments (40) are each spaced apart from the other first laminated core segments (40), - the second laminated core segments (50) are each spaced apart from the other second laminated core segments (50), - the first laminated core segments (40) are each spaced apart from the second laminated core segments (50).

9. Rotor arrangement (30) according to one of the preceding claims, in which the rotor shaft (32) has recesses (34) at least in a second axial section (A2), and in which the first laminated core segments (40) extend into the recesses (34).

10. Rotor arrangement (30) according to claim 9, wherein the recesses (34) in the cross section of the rotor shaft (32) have a concave profile at least in sections.

11. Rotor arrangement (30) according to claim 9 or 10, wherein the first laminated core segments (40) on the side facing the rotor shaft (32) are formed at least in sections complementary to the associated recess (34).

12. Rotor arrangement (30) according to one of claims 9 to 11, wherein the rotor shaft (32) has exactly one recess (34) for each of the first laminated core segments (40).

13. Rotor arrangement (30) according to one of the preceding claims, wherein the number of first laminated core segments (40) corresponds to the number of rotor poles (61 - 66).

14. Rotor arrangement (30) according to one of the preceding claims, wherein the number of second laminated core segments (50) corresponds to the number of rotor poles (61 - 66).

15. Rotor arrangement (30) according to one of the preceding claims, in which the first laminated core segments (40) extend to the bandage (70).

16. An electrical machine (20) comprising a rotor arrangement (30) according to any one of the preceding claims and a stator arrangement (22).

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