Rotor lamination for electric machine, electric machine, vehicle, and method for producing rotor lamination

Abstract

The present disclosure relates to a rotor lamination (10) having a first region (11) and a second region (12), where the first region (11) is larger than the second region (12) and a first alloy is present in the first region (11) and a second alloy is present in the second region (12). According to the present disclosure, the second alloy is soft magnetic and has a higher magnetic permeability than the first alloy. The disclosure also relates to an electric machine (10) and an electric vehicle. The invention further relates to a method for producing the aforementioned rotor lamination (10). For this purpose, a corresponding green body (50) is printed in a stencil printing process and then sintered to form a rotor lamination.

Description

Technical Field

[0001] The present disclosure relates to a rotor for an electric motor, such an electric motor and a method of manufacturing the electric motor. An electric vehicle is also disclosed. Background Art

[0002] The performance or power density of the electric motor and its efficiency play a particularly important role in electric vehicles, but not only. Various methods can be used to optimize these parameters.

[0003] For example, by reducing the thickness of the laminations or selecting high-performance alloys, the torque and efficiency of the motor can be increased. However, these soft magnetic high-performance alloys are often extremely difficult to process. As a result, the manufacturing costs are correspondingly high.

[0004] Various solutions can be found in the prior art, and are discussed below as examples.

[0005] US 2021 / 0111613 A1 is concerned with changing the insulation density of electrical steel laminations for electric motors. The main effect is to minimize eddy currents, thereby improving efficiency.

[0006] US 2018 / 0233997 A1 relates to an additively manufactured iron core for electric motors, which improves efficiency by introducing air gaps between and within layers. The main purpose is to reduce iron losses.

[0007] US 11362552 B2 teaches the use of stamped and stacked laminations of different shapes. Some layers are produced in 3D. In certain areas, non-ferromagnetic materials are used to reduce magnetic leakage.

[0008] US 11025142 B2 discloses a method of combining stamped metal sheets with additional reinforcements made of laser-melted powder. The aim is to reduce magnetic flux leakage and increase the structural strength of the rotor. It is necessary to eliminate or at least reduce the disadvantages of the known systems without having to compromise to the extent that has been necessary so far. In particular, there is still a need to optimize the electric machine in terms of performance / power density and efficiency. Summary of the invention

[0009] The problem is solved by the subject matter of the independent claims. Advantageous embodiments are given in the dependent claims and in the following description, each of which can characterize an aspect of the disclosure alone or in a (sub)combination. Various aspects are explained with respect to the device, other aspects with respect to the method. However, these aspects will be transferred to each other accordingly.

[0010] According to one aspect, a rotor lamination is provided. The rotor lamination has a first region and a second region. The first region is larger than the second region. In addition, the rotor lamination includes a first alloy in the first region and a second alloy in the second region. The second alloy is soft magnetic and has a higher magnetic permeability than the first alloy.

[0011] A soft magnetic material is a material that is easily demagnetized or remagnetized in a magnetic field. In the context of the present disclosure, a soft magnetic alloy is an alloy having a coercive field strength of less than 1000 A / m.

[0012] Soft magnetic high performance alloys with lower coercive field strengths of less than 100 A / m are preferred. Examples of these soft magnetic high performance alloys include certain iron-cobalt alloys (FeCo) or ferrosilicon alloys (FeSi) with relatively high silicon contents of about 0.5 to 8 wt%.

[0013] Using soft magnetic alloys with increased magnetic permeability allows for higher magnetic flux, resulting in higher torque on the rotor. In addition, the magnetic flux is guided by strong soft magnetic materials on intentionally formed flux paths.

[0014] According to an advantageous aspect, the first alloy is also soft magnetic. Alternatively, the first alloy can also be a non-magnetic iron-based alloy. The subsequent magnetic flux in the rotor can be specifically guided by the choice of material. The area with the non-magnetic iron-based alloy can be used in particular for mechanical reinforcement of the rotor core.

[0015] This means that the combination of soft magnetic high-performance alloys with conventional soft magnetic or non-magnetic alloys makes targeted use of material properties that have a particularly positive effect on the efficiency and performance of the electric machine. In this way, the material usage of resource-intensive alloys can be significantly reduced.

[0016] The rotor laminations may have a plurality of cutouts. At least some of these cutouts then form pockets in the subsequent rotor stack for accommodating permanent magnets. These rotor laminations are particularly advantageous for use in reluctance torque assisted permanent magnet machines, in which the permanent magnet components can be reduced in this way.

[0017] At least a portion of the region of higher magnetic permeability may advantageously be located between the magnet pockets and the outer periphery of the rotor laminations.

[0018] For example, the recesses can be arranged in pairs in each case in a V-shape, so that magnetic islands are formed between them. The region with higher magnetic permeability (second region) preferably comprises the majority of these magnetic islands.

[0019] Preferably, the rotor lamination is designed so that every two pairs of recesses are arranged in a V shape, and are arranged up and down in a double V shape in the radial direction. The second region having the alloy with higher magnetic permeability specifically includes the region between the recesses arranged up and down.

[0020] The magnet pockets may also have lateral free areas acting as flux barriers. The first area with lower magnetic permeability preferably also extends around these flux barriers.

[0021] The above configuration has proven to be particularly suitable for the intended application.

[0022] A motor is also provided, which has a rotor made of the rotor laminations.

[0023] These motors are preferably reluctance torque assisted permanent magnet machines. These motors are particularly efficient with judicious use of materials and have very good speed-torque performance.

[0024] According to another aspect, there is also provided a vehicle comprising the electric machine as described above.

[0025] In this context, a vehicle is understood to be a device configured to transport objects, goods or people between different destinations. Examples of vehicles include land-based vehicles such as motor vehicles, electric vehicles, hybrid vehicles, rail vehicles, aircraft or ships. Preferably, in the present context, a vehicle can be regarded as a road-based vehicle such as a car, truck, bus, etc.

[0026] In advantageous embodiments, the above-described electric machine can be arranged in a vehicle, for example, as a front wheel drive, a central drive, an underfloor drive or a wheel hub drive.

[0027] A method for manufacturing the above rotor laminations is also disclosed. The method comprises the following steps: S1: Manufacturing green rotor laminations using a stencil printing process, and S2: Sintering the rotor lamination green body to form rotor laminations.

[0028] The production of the rotor lamination green body comprises the following sub-method steps: S1a: applying a first suspension in a first region of the rotor lamination green body defined by a first mask, and S1b: Applying a second suspension in a second region of the rotor lamination green body defined by a second mask.

[0029] Either the first suspension or the second suspension can be applied first.

[0030] A suspension is a heterogeneous mixture of matter consisting of a liquid and finely divided solids (particles), in this case metal powders.

[0031] Preferably, the suspension is a paste. A paste is a suspension with a high solids content. A paste is no longer free-flowing but spreadable.

[0032] Pastes are particularly suitable for this manufacturing method, because otherwise the edges would flow after printing and the component might appear "fuzzy". Pastes that exhibit shear-thinning behavior are used in particular. The viscosity of these pastes decreases at high shear rates (e.g. when in contact with a squeegee). However, if there is no shear, e.g. after a printing process, the viscosity is very high.

[0033] As described above, when manufacturing the rotor lamination green body, the first region is larger than the second region. The first suspension contains powder of the first alloy, and the second suspension contains powder of the second alloy. According to the present disclosure, the second alloy is soft magnetic and also has a higher magnetic permeability than the first alloy.

[0034] The printing process can be used to produce particularly thin electrical steel laminations with a thickness of less than 0.4 mm, in particular less than 0.3 mm, preferably less than 0.25 mm. The thinner the electrical steel laminations, the lower the eddy current losses that occur at high frequencies and the higher the efficiency of the motor. However, this does not apply indefinitely. As the insulating layer between the electrical steel laminations becomes thicker, the stacking factor decreases as the laminations become thinner. Therefore, the minimum thickness of the electrical steel laminations should be 0.05 mm, preferably at least 0.1 mm, more preferably at least 0.15 mm.

[0035] Preferably, the thermal expansion coefficients of the first alloy and the second alloy may differ by no more than 20%. For example, the thermal expansion coefficients of the two alloys are advantageously in the range of 8-14 ppm / K, preferably in the range of 10-12 ppm / K.

[0036] Additionally or alternatively, the elastic modulus of the first alloy and the second alloy may differ by no more than 20%. For example, the elastic modulus of the two alloys may be in the range of 160-200 GPa, preferably in the range of 170-190 GPa.

[0037] Preferably, the deviation between the sintering shrinkage of the rotor core in the first region and the sintering shrinkage in the second region should not exceed 20%.

[0038] Advantageously, the sintering temperatures of the first alloy and the second alloy do not differ by more than 250 K. For example, the sintering temperature may be in the range of 1200-1500°C, preferably in the range of 1300-1400°C.

[0039] Advantageous variants of the method minimize the defect rate, thereby increasing the efficient utilization of resources.

[0040] All features described in relation to each aspect may be combined alone or in (sub)combination with other aspects. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present disclosure and further advantageous embodiments and developments thereof are described and explained in more detail below with reference to the examples shown in the accompanying drawings, in which: Figure 1 A simplified schematic diagram of the rotor laminations and their details are shown. Figure 2 shows a simplified schematic diagram of a method for manufacturing rotor laminations, Figure 3 A simplified schematic diagram of the motor is shown, and Figure 4 A simplified schematic diagram of the vehicle is shown. DETAILED DESCRIPTION

[0042] The following detailed description in conjunction with the accompanying drawings is intended to describe various embodiments of the disclosed subject matter, rather than merely represent individual embodiments, and the same reference numerals in the accompanying drawings represent the same elements. Any embodiment described in the present disclosure is intended to be an example or illustration only and should not be construed as being superior to other embodiments. The illustrative examples contained herein are not exhaustive, nor do they limit the claimed subject matter to the precise form disclosed. Various modifications to the described embodiments will be apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the described embodiments. Therefore, the described embodiments are not limited to the embodiments shown, but have as wide a range of applications as possible consistent with the principles and features disclosed herein.

[0043] All features disclosed below with respect to the exemplary embodiments and / or figures may be combined alone or in any sub-combination with features of aspects of the present disclosure, including features of the preferred embodiments, provided that the resulting feature combination is beneficial to a person skilled in the art.

[0044] For purposes of the present disclosure, the phrase "at least one of A, B, and C" means, for example, (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C), including all other possible combinations when more than three elements are listed. In other words, the term "at least one of A and B" generally refers to "A and / or B", i.e., "A" alone, "B" alone, or "A and B".

[0045] Figure 1 A simplified plan view of a rotor lamination 10 is shown with an enlarged detail to the right.

[0046] The rotor lamination 10 is used for a motor which combines the functionality of a permanent magnet synchronous motor with an additional reluctance torque caused by buried magnets due to the arrangement of the magnets in the rotor. In principle, however, the technical teachings taught can also be used for pure reluctance synchronous motors or pure permanent magnet synchronous motors.

[0047] The rotor laminations are substantially circular and flat and have a large number of cutouts 20. Depending on the positioning and location of the cutouts 20, they have different functions.

[0048] Some of the cutouts 20 are intended as pockets 21 for receiving permanent magnets. They generally have an elongated shape, but may also have different shapes. The magnets are usually rectangular and are then held in a defined position by corresponding protrusions. Thus, the magnetic force exerted by the stator coil system is transmitted to the rotor and thus generates torque.

[0049] Other cutouts 20 are used to direct the magnetic flux into a predetermined path or for cooling the rotor, for example through coolant channels. Further cutouts may be provided to reduce the weight of the rotor.

[0050] The cutouts 20 forming pockets 21 for holding the magnets also have lateral free areas acting as flux barriers 25 .

[0051] The magnet pockets 21 are arranged in pairs in each case in a V-shape and together form the magnetic poles of the synchronous machine. In the variant shown, two pairs of magnet pockets 21a, 21b are arranged one above the other in the radial direction in each case. For machines with buried permanent magnets, this arrangement is also referred to as a double V-shape or "double V" configuration.

[0052] An additional triangular or triangle-shaped free area is formed between the poles and also acts as a flux barrier.

[0053] The other configurations considered here can be easily transferred to a configuration with a single pair of magnet pockets arranged in a V-shape ("single V-shape") or a so-called "triangular" configuration in which a third magnet pocket (radially) is located above the pair of magnet pockets arranged in the V-shape.

[0054] In order to increase the efficiency and / or torque of electric machines, in particular the range of electric vehicles, a particularly advantageous hybrid electrical steel lamination arrangement for a rotor is proposed.

[0055] The core idea is to combine high-performance soft magnetic alloys with traditional soft magnetic materials. The key is not to make the entire rotor core with this high-performance soft magnetic alloy, because this is very expensive.

[0056] Therefore, a layout is proposed to identify specific areas that benefit most from high-performance materials and areas where the benefit is negligible.

[0057] In other words, the rotor lamination 10 has a first alloy in the first region 11 and a second alloy in the second region 12. At least the second alloy is magnetically soft and has a higher magnetic permeability than the first alloy. The first alloy may also be magnetically soft or may be a non-magnetic iron-based alloy.

[0058] The first region 11 is larger than the second region 12. Particularly preferably, the second region 12 has only a small area ratio relative to the first region 11. For example, the second region can constitute a maximum of 25%, preferably a maximum of 20%, or even only 15% or less than 10% of the total area of ​​the rotor core 10 (without the cutouts).

[0059] It may be useful to provide further regions with different material properties in addition to the first region 11 and the second region 12. For example, as described above, the first region 11 and the second region 12 may be magnetically soft, while the rotor lamination 10 also has a non-magnetic iron-based alloy in defined regions.

[0060] At least a portion of the second region 12 is located between the magnet pockets 21 and the outer periphery Ra of the rotor lamination 10. Preferably, the entire second region 12 may be arranged as a ring radially defined outwardly by the outer periphery Ra and inwardly substantially defined by the location of the pockets 21.

[0061] The V-shaped pockets 21 define so-called magnetic islands between them. The second region 12 comprises at least a large part of the magnetic islands 23. The web between the magnet pockets 22 may comprise the first alloy.

[0062] In particular, the second region 12 includes a region 24 located between a pair of recesses 21a, 21b disposed one above the other.

[0063] Around the flux barrier 25 of the recess 21 extends the first region 11 or third region which comprises in particular a non-magnetic iron-based alloy.

[0064] Since the rotor laminations 10 cannot be manufactured using conventional rolling and stamping methods, a new manufacturing method is proposed.

[0065] As an alternative to the obvious manufacturing methods, for example the joining (e.g. laser welding) of separately manufactured sheet metal parts, which would however require particularly high material handling costs, or to generative layering processes such as selective laser sintering, which, however, are generally uneconomical in large-scale manufacturing, a manufacturing method is proposed in which the corresponding green bodies are firstly printed from a suitable paste using template printing and are then sintered to form the rotor laminations.

[0066] This method is simplified as Figure 2 It consists of the following steps: First, in a first method step S1 , a rotor lamination green body 50 is manufactured using a template printing process (eg screen printing).

[0067] In the manufacture of sintered workpieces, a green body or green compact is an unsintered blank that can be easily machined. For example, a green body or green compact is a powder bound with a binder. The dimensions of the green compact are designed to ensure that the final product reaches the planned dimensions by shrinking during the sintering process.

[0068] The manufacture of the green body comprises (in appropriate order) applying S1a a first suspension 61 in a first region 51 of the rotor lamination green body 50 defined by a first mask 71 and applying a second suspension 62 in a second region 52 of the rotor lamination green body 50 defined by a second mask 72. Preferably, the suspensions 61, 62 may be pastes.

[0069] Before the next processing step, the applied suspension should be dried. For example, infrared emitters can assist drying, which takes about 1-25 seconds, depending on the layer thickness.

[0070] The first suspension 61 contains powder of a first alloy, and the second suspension 62 contains powder of a second alloy.

[0071] The second alloy is magnetically soft and has a higher magnetic permeability than the first alloy.

[0072] Although the shape of the green body 50 already corresponds to the rotor lamination 10 later, the metal powder is only bound by a suitable binder as a matrix. The size is also different from the final product. However, the first area 51 of the green body 50 is already larger than the second area 52.

[0073] In a second method step S2 , the rotor stack green body 50 is then sintered to form the rotor stack 30 .

[0074] Preferably, the thermal expansion coefficients of the first alloy and the second alloy differ by no more than 20%, so that the rotor laminations 30 do not crack or wrinkle during sintering. In particular, the thermal expansion coefficient is in the range of 8-14 ppm / K, preferably in the range of 10-12 ppm / K.

[0075] The elastic modulus of the first alloy and the second alloy should also differ by no more than 20%. Particularly suitable materials have an elastic modulus in the range of 160-200 GPa, preferably in the range of 170-190 GPa.

[0076] In order to minimize inhomogeneities, the sintering shrinkage of the rotor lamination green body 50 in the first region should not deviate from the sintering shrinkage in the second region by more than 20%. The printing paste containing the alloy must be selected accordingly.

[0077] The sintering temperatures of the first alloy and the second alloy should also not differ by more than 250 K. In particular, the sintering temperature may be in the range of 1200-1500°C, preferably in the range of 1300-1400°C.

[0078] exist Figure 3 In the figure, an electric machine 30 is shown in a simplified perspective view. The electric machine 30 comprises a rotor 31 having a plurality of rotor laminations 10, as already shown and described. The electric machine is a reluctance synchronous machine with buried magnets. These types of electric machines are also known as IPM / IPSM ("Interior Permanent Magnet" or "Interior Permanent Magnet Synchronous Machine", i.e. permanent magnet machines with integrated magnets), PMa-SynRM ("Permanent Magnet Assisted Synchronous Reluctance Machine") or IPM-SynRM ("Interior Permanent Magnet Synchronous Reluctance Machine", i.e. synchronous reluctance machines with buried permanent magnets).

[0079] This combination is particularly suitable for electric vehicles because it combines the ideal properties of high efficiency at low and high speeds. In addition, the proportion of permanent magnets can be significantly reduced in this way.

[0080] Figure 4 A simplified schematic diagram of a vehicle 32 is shown in a side view. The vehicle 32 has at least one electric machine as described above. For example, the electric machine can be arranged in the vehicle 32 as a front wheel drive 41, a central drive 42, an underfloor drive 43 or a wheel hub drive 44.

[0081] Quantities and numbers are mentioned in this application. Unless explicitly stated, these quantities and numbers should not be considered as limitations, but should be considered as examples of possible quantities or numbers in the context of this application. In this case, the term "plurality" can also be used in this application to refer to quantities or numbers. In this case, the term "plurality" refers to any number greater than 1, such as 2, 3, 4, 5, etc. The terms "approximately", "approximately", "close to", etc. refer to plus or minus 5% of the value.

[0082] Although the disclosure has been shown and described with respect to one or more embodiments, equivalent changes and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings.

Claims

1. A rotor lamination (10) comprising a first region (11) and a second region (12), wherein the first region (11) is larger than the second region (12), wherein the rotor lamination (10) comprises a first alloy in the first region (11) and a second alloy in the second region (12), wherein at least the second alloy is soft magnetic, and wherein the magnetic permeability of the second alloy is higher than the magnetic permeability of the first alloy.

2. The rotor lamination (10) of claim 1, wherein the rotor lamination (10) has a plurality of cutouts (20), wherein at least some of the cutouts (20) form pockets (21) for receiving permanent magnets, and wherein at least a portion of the second region (12) is located between the pockets (21) and an outer periphery (Ra) of the rotor lamination (10).

3. The rotor stack (10) according to claim 3, wherein the pockets (21) are arranged in pairs in a V-shape in each case so as to define a magnetic island (23) between them, and wherein the second region (12) comprises a large part of the magnetic island (23).

4. The rotor lamination (10) according to claim 4, wherein the recesses (21) are arranged in each case in two pairs of recesses (21a, 21b) in a V-shaped arrangement and arranged one above the other in a double V-shaped arrangement in the radial direction, and further wherein the second region (12) includes a region (24) located between the recesses (21a, 21b) arranged one above the other.

5. The rotor lamination (10) according to any one of claims 3 or 4, wherein the pockets (21) have a lateral free area as a flux barrier (25), and wherein the first area (11) extends around the flux barrier (25).

6. An electric machine (30) comprising a rotor (31) having a rotor lamination (10) according to any one of claims 1 to 5, in particular, wherein the electric machine (30) is a reluctance torque assisted permanent magnet electric machine.

7. A vehicle (32) having at least one electric machine (30) according to claim 6, in particular wherein the electric machine (30) is arranged as a front wheel drive (41), a central drive (42), an underfloor drive (43) and / or a wheel hub drive (44) in the vehicle (32).

8. A method for manufacturing a rotor lamination (10) according to any one of claims 1 to 5, comprising the following steps: S1: Manufacturing a rotor lamination green body (50) in a template printing process, comprising: • S1a: applying a first suspension (61) in a first region (51) of the rotor lamination green body (50) defined by a first mask (71), and • S1b: applying a second suspension (62) in a second region (52) of the rotor lamination green body (50) defined by a second mask (72), The first area (51) is larger than the second area (52), The first suspension (61) contains a first alloy powder, the second suspension (62) contains a second alloy powder, and wherein at least the second alloy is soft magnetic and has a higher magnetic permeability than the first alloy, S2: Sintering the rotor lamination green body (50) to form a rotor lamination (30).

9. The method according to claim 8, wherein the thermal expansion coefficients of the first alloy and the second alloy differ by no more than 20%, in particular wherein the thermal expansion coefficients are in the range of 8-14 ppm / K, preferably in the range of 10-12 ppm / K, and / or Wherein the elastic modulus of the first alloy and the second alloy differ by no more than 20%, in particular wherein the elastic modulus is in the range of 160-200 GPa, preferably in the range of 170-190 GPa.

10. The method according to any one of claims 8 or 9, wherein a sintering shrinkage of the rotor laminate green body (50) in the first region and a sintering shrinkage in the second region deviate by no more than 20%.

11. The method according to any one of claims 8 to 10, wherein the sintering temperatures of the first alloy and the second alloy differ by no more than 250 K, in particular wherein the sintering temperature is in the range of 1200-1500°C, preferably in the range of 1300-1400°C.

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