Method and tool for reducing imbalance of a rotor of an electric machine

Abstract

In order to provide a method for reducing the imbalance of a rotor of an electric machine, by which the dynamic imbalance of the rotor and the number of processes required for balancing can be reduced, a method (100) for reducing the imbalance of a rotor (10) of an electric machine is proposed, wherein the rotor (10) has a plurality of recesses (11) arranged along a circumferential direction (23), wherein a dynamic imbalance of the rotor (10) is determined, wherein a casting material (19) is introduced into the recesses (11) of the rotor (10) during a casting process, wherein a mass distribution of the casting material (19) is designed in such a way that the dynamic imbalance is compensated.

Description

Technical Field

[0001] This invention relates to a method for reducing rotor imbalance in an electric motor, wherein the rotor has a plurality of open sections arranged in a circumferential direction. Furthermore, this invention relates to a tool for implementing the method for reducing rotor imbalance in an electric motor. Background Technology

[0002] The motor rotor must be balanced to a high quality level to achieve stable and virtually vibration-free operation. This typically requires multiple balancing runs, increasing the number of balancing machines needed, which directly impacts the production cost of both the rotor and the motor. Furthermore, the maximum compensable imbalance is more or less limited depending on the balancing design. This results in undesirable scrap in production.

[0003] Various solutions for reducing imbalance in synchronous motors with permanent magnet excitation are known in the prior art. For example, attempts are made to reduce imbalance by aligning magnets in a magnet bag or magnet cavity, or by tilting and pressing the laminations together. Other methods known in the prior art reduce imbalance by adding or subtracting balancing elements. These designs require additional balancing elements, such as balancing discs.

[0004] Patent document US 2016 / 0013709 A1 discloses a method for balancing a laminated rotor core of an electric motor. The rotor core, with a permanent magnet embedded in a magnet cavity provided for this purpose, is clamped in a tool. A casting material, such as resin, is injected into the still-empty area of ​​the magnet cavity through a tool plate. Furthermore, pins are provided in the tool plate that can be moved into the empty areas of the magnet cavity. The amount of casting material introduced into the magnet cavity can be adjusted according to the depth to which the pins are moved into the magnet cavity.

[0005] Known methods for reducing rotor imbalance can reduce static rotor imbalance by selecting the amount of casting material. However, dynamic rotor imbalance is not compensated for in casting material-based processes. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for reducing rotor imbalance of an electric motor, which can reduce the dynamic imbalance of the rotor and the number of processes required for balancing.

[0007] To address this technical problem, a method for reducing the imbalance of a motor rotor is proposed, wherein the rotor has a plurality of empty portions arranged in a circumferential direction, wherein the dynamic imbalance of the rotor is determined, wherein casting material is introduced into the empty portions of the rotor during the casting process, and wherein the mass distribution of the casting material is designed in a manner that compensates for the dynamic imbalance.

[0008] The rotor can be designed as a rotor lamination assembly with a large number of slices or sheets stacked together in the axial direction. The rotor has circumferential openings. These openings can extend inside or outside the rotor or rotor lamination assembly. Furthermore, the openings can extend substantially parallel to the axial direction, or if necessary, slightly inclined relative to the axial direction, on or within the rotor from a first end side to an opposing second end side, and can preferably be designed to be open towards the end side. The openings can also be referred to as cavities or recesses. Moreover, these openings, or portions thereof, particularly on the first or second end side of the rotor, can also be designed as openings surrounding the rotor shaft in the circumferential direction. For example, the openings can be designed in the form of circular slots arranged on the respective end sides.

[0009] The rotor can be a rotor for a synchronous motor, especially a separately excited synchronous motor or a permanent magnet excited synchronous motor, or a rotor for an asynchronous motor. In the case of a rotor for a permanent magnet excited synchronous motor, the magnets, especially permanent magnets, can be arranged in a recess or cavity.

[0010] In a top view taken along the axial direction of the rotor, the open space can be arranged at constant or different angular distances along the circumferential direction.

[0011] According to the invention, the dynamic imbalance of the rotor is first determined. Then, during the casting process, casting material is introduced into the voids of the rotor. The total amount of casting material introduced into the voids of the rotor and remaining in the rotor and / or on the rotor and / or its end sides forms a mass distribution designed to compensate for the dynamic imbalance.

[0012] Since the dynamic imbalance has been largely compensated for by the overall casting material, additional balancing processes, such as those using balancing elements or balancing discs, can be omitted if necessary. However, additional balancing processes and / or fine balancing can be implemented through casting material removal or other balancing processes.

[0013] Preferably, the rotor has two end sides, wherein the void is open toward the end sides, and wherein the casting material is introduced into the void through at least one of the end sides, preferably through both end sides.

[0014] The open end portion preferably extends from the first end to the opposite second end on or within the rotor, substantially parallel to the axial direction, and if necessary slightly inclined relative to the axial direction. In the case of a synchronous motor, the open portion is preferably constructed inside the rotor and designed to accommodate magnets, especially permanent magnets.

[0015] Furthermore, the rotor can also be designed as a rotor for an asynchronous motor, in which case the void passes through the rotor at a slight inclination relative to the axial direction if necessary. In this case, the void can be formed as a groove or slot on the outer side of the rotor from one end to the other. The rotor's cage, including the rotor bars, is formed by introducing casting material into the void. In other words, the casting material introduced into the void forms the rotor bars.

[0016] Furthermore, in the case of an asynchronous motor rotor, a void in the form of a surrounding slot or the like can be provided on the end side. The casting material introduced into these surrounding voids or slots can then form a short-circuit ring for the rotor cage on the end side. Alternatively, the short-circuit ring for the cage can also be constructed by forming additional casting material onto the casting material introduced into the voids used to form the rotor bars. In this case, the surrounding slots on the end sides can be omitted if necessary. Even in this case, the rotor bars and the short-circuit ring are formed of casting material. In the case of an asynchronous motor rotor, the mass distribution used to compensate for dynamic imbalance of the rotor can be designed, for example, by changing the axial thickness of the short-circuit ring formed of casting material along the circumferential direction.

[0017] It is further advantageous to specify that the casting material introduced into the void is arranged in the void as a protrusion or retraction relative to the end side.

[0018] The protrusion can be designed as a partial or complete protrusion. The retractable portion can also be designed as a partial or complete retractable portion.

[0019] The casting material introduced into the void can thus protrude axially beyond the rotor's end. In the case of a rotor used in an asynchronous motor, the protruding or extended casting material can form a short-circuit ring.

[0020] Alternatively, the casting material may not reach all the ends of the rotor, and thus may be arranged at least partially inwardly offset within the rotor in the void.

[0021] The amount of casting material in the void region can be adjusted by the casting material extending beyond the end side from the void, or by the casting material that at least partially does not reach the end side. By changing the amount of casting material, a mass distribution of the casting material that can compensate for the dynamic imbalance of the rotor can be achieved.

[0022] A suitable tool can be provided to introduce casting material into the void. This tool may have two tool plates arranged on opposite ends of the rotor. Each tool plate may have a chamber with adjustable volume. For introducing the casting material into the void, the chamber is positioned above the void, which opens towards the end. The casting material can be introduced into the void by means of an introduction device aligned with the chamber. Furthermore, the size of any protrusion or extension of the casting material extending beyond the end of the void can be adjusted by adjusting the volume of the chamber. Alternatively or additionally, the tool plate may also have pins or core pullers that can be inserted into the void of the rotor through the end. The depth to which the pin or core puller penetrates into the corresponding void can reduce the amount of casting material in the void, such that the pin or core puller at least partially forms a retracted portion within the void. Furthermore, the tool may have a metering device designed to introduce a predetermined amount or volume of casting material into the void or form it on the rotor.

[0023] Furthermore, it is preferably specified that the dynamic imbalance is determined by preferred dynamic imbalance measurement and / or geometric measurement.

[0024] It can be further advantageously specified that the void extends substantially axially on or in the rotor, and / or that the void extends circumferentially.

[0025] As explained above, the empty portion can also be slightly inclined in the axial direction and preferably extend from the first end to the second end on or within the rotor. This design of the empty portion is particularly advantageous when the rotor is for an asynchronous motor.

[0026] Furthermore, as mentioned above, the void can be constructed, more preferably, in the form of a slot, particularly on the end side, surrounding the opening for the rotor shaft. This design of the void is particularly advantageous for the rotor of an asynchronous motor. The casting material introduced into the void constructed around the end side forms a short-circuit ring for the rotor. Here, it can be specified that the casting material forming the short-circuit ring constitutes a protrusion and / or a retraction relative to the end side. In this case, it is preferable to change the thickness of the casting material or the short-circuit ring formed by the casting material as viewed axially, thereby providing a mass distribution for compensating for dynamic imbalances.

[0027] However, in principle, the short-circuit ring may not be formed in the slots or empty spaces of the rotor body. The short-circuit ring may be made of castable material that is the same as or conforms to the shape of the rotor bar material of the cage. For this purpose, the castable material is introduced into the empty spaces for the rotor bars. The portion of the castable material protruding or extending from the empty spaces constitutes the short-circuit ring formed on the end side.

[0028] It can be further advantageously specified that the mass distribution is designed by selecting the amount and / or weight and / or volume and / or density and / or dosage of the casting material introduced into the corresponding void.

[0029] By selecting the amount and / or volume of casting material introduced into the corresponding void, the protrusion or retraction of the casting material relative to the end side in the void can be adjusted. Furthermore, the density of the casting material introduced into the void can also be changed. This change in density can be achieved, for example, by designing the casting material to consist of two components, each with a different density.

[0030] Further advantageously, it can be specified that the casting material is introduced into the void in multiple consecutive casting stages, wherein preferably, the amount and / or weight and / or volume and / or density and / or dosage of the casting material are changed, more preferably for the respective void, during the casting stages.

[0031] Therefore, multiple pours can be performed. In multiple pours, the pouring material can be successively introduced into the voids, so that these voids are successively filled.

[0032] If the casting material is introduced into the void in multiple consecutive casting stages, it is particularly suitable that the tool has a metering device for this purpose, which enables the precise introduction of a predetermined amount or volume of casting material.

[0033] Alternatively, the casting material can be introduced into the void simultaneously, wherein preferably, the amount and / or weight and / or volume and / or density and / or dosage of the casting material introduced into each individual void is varied.

[0034] More preferably, the mass distribution of the casting material may be designed differently in at least two equilibrium planes oriented substantially perpendicular to the rotor's axis of rotation or axial direction, observed in the circumferential and / or radial directions.

[0035] The balancing plane is an imaginary balancing plane or an imaginary layer or section passing through the rotor body, extending perpendicularly to the axial direction through the rotor. Here, two balancing planes arranged at different positions along the axial direction have different mass distributions in the circumferential and / or radial directions. The dynamic imbalance of the rotor can be compensated for by this different design of the mass distribution in at least two balancing planes, which are also arranged at different positions along the axial direction.

[0036] It can be further advantageously specified that the rotor's axis of rotation is inclined relative to the stable principal axis of inertia of the mass distribution of the casting material.

[0037] Furthermore, it can be specified that the void is a cavity, wherein, preferably, the magnet, especially a permanent magnet, is arranged in the void before the casting material is introduced, wherein the magnet does not completely fill the void.

[0038] Here, the size of the empty space is specifically designed so that the magnet, especially the permanent magnet, does not completely fill the empty space, thereby reserving additional volume in the empty space, which can be filled with casting material.

[0039] It can be further advantageously specified that the casting process can be a low-pressure casting process, a transfer molding process, a transfer molding process preferably using multi-plunger technology, an injection molding process, or a metal die casting process.

[0040] Furthermore, it can be advantageous to specify that the casting material is or includes plastic materials, particularly polymer materials, or metals, preferably copper or aluminum.

[0041] Especially in the case of permanently excited or separately excited rotors, the use of plastic materials, particularly polymer materials, is suitable. These rotors either have magnets or permanent magnets, or current coils or current loops, which can be fixed in corresponding open spaces or cavities by casting material. Therefore, by selecting the amount and distribution of the casting material, the dynamic mass balance of the rotor can be ensured while fixing the magnets or current loops in the open spaces.

[0042] Especially when the rotor is for an asynchronous motor, it is advantageous to use metal, preferably copper or aluminum, as the casting material. The casting material made of metal, especially copper or aluminum, introduced into the void, and the casting material that protrudes or extends relative to the end side if necessary, constitutes the rotor's cage. The particularly annular protrusions or extensions relative to the end side of the rotor, or the portion of the casting material arranged in the annular, preferably groove-shaped void, constitute the rotor's short-circuit ring.

[0043] Further advantageously, the rotor may be specified to include a rotor shaft and / or a balance disc and / or cover plates or end plates.

[0044] Therefore, it is preferably specified that the rotor shaft is inserted into the rotor and / or the balance disc is mounted on the rotor, and / or the rotor includes cover plates and end plates before the casting material is introduced into the void. Especially when the method is implemented with the rotor shaft already inserted into the rotor, the dynamic imbalance caused by the rotor shaft can also be compensated by this method.

[0045] Furthermore, it is preferable to specify that the rotor is a rotor for an asynchronous motor, particularly a short-circuit rotor or a squirrel-cage rotor, wherein the rotor includes rotor bars and / or short-circuit rings, wherein the rotor bars and / or short-circuit rings are formed from the casting material and / or manufactured by introducing the casting material into the empty space of the rotor, particularly into the slot.

[0046] In addition, the rotor can be a rotor used in separately excited synchronous motors.

[0047] Another solution to the technical problem upon which this invention is based is a tool for implementing the above-described method, wherein the tool has at least two tool plates, wherein at least one tool plate can be arranged on the end side of the rotor, wherein at least one, preferably each tool plate has an introduction device for introducing casting material into the empty portion of the rotor through the end side of the rotor, wherein at least one, preferably each tool plate has a variable volume chamber and / or a core extractor and / or a metering device for the casting material.

[0048] Here, variable-volume chambers are arranged in the tool plate such that, when the tool plate is positioned on the end side of the rotor, these chambers cover the voids, particularly those open towards the end side. Casting material is introduced into the chambers and flows from the chambers into the voids in the rotor. The amount of casting material protruding or extending relative to the end side can be adjusted by changing the volume of the chambers. A core puller or pin may be optionally or additionally provided. The core puller or pin can be inserted into the voids through the end side of the rotor, thereby reducing the amount of casting material introduced into the voids.

[0049] The tool can be designed to introduce casting material into the void via one or both ends. If the casting material is specified to be introduced via both ends, preferably both tool plates have variable-volume chambers and / or core pullers and / or metering devices for the casting material.

[0050] In addition, the tool may additionally or alternatively have a metering device by which the accurate amount or volume of casting material introduced into the void can be adjusted.

[0051] Another solution to the technical problem on which this invention is based is a rotor for an electric motor, which is manufactured by the method described above. Attached Figure Description

[0052] The invention is described in detail below with reference to the accompanying drawings. In the drawings:

[0053] Figure 1 A cross-sectional view of a rotor having cast material including protrusions is shown.

[0054] Figure 2A top view of the rotor is shown;

[0055] Figure 3 A cross-sectional view of a rotor having cast material including a retraction section is shown.

[0056] Figure 4 The tool used to reduce rotor imbalance is shown along with the rotor; and

[0057] Figure 5 The rotor used for an asynchronous motor is shown. Detailed Implementation

[0058] These figures illustrate a method 100 for reducing the imbalance of the rotor 10 of the motor.

[0059] Figure 1 The image shows a cross-sectional view obtained by cutting through the rotor 10 of the motor, which is not shown in detail. Figure 2 A top view of rotor 10 is shown.

[0060] The rotor 10 has cavities 11 in the form of chambers 12, which extend substantially along the axial direction 13 from a first end side 14 to a second end side 15 through the rotor 10. Magnets 16 are arranged in the cavities 11. Furthermore, the rotor 10 has a central opening 17 together with a rotor shaft 18 arranged in this central opening. Figure 2 As can be seen, these empty portions 11 are arranged in the rotor 10 along the circumferential direction 23 at a constant angular distance.

[0061] According to this method, casting material 19 is introduced into the remaining area of ​​the void 11. Here, the amount or volume of casting material 19 is selected such that it protrudes beyond the end sides 14, 15 of the rotor 10. The casting material 19 is thus constructed with protrusions 20 relative to the end sides 14, 15 of the rotor 10. By selecting the size of the protrusions 20, the first balance plane 21 and the second balance plane 22, which is offset relative to the first balance plane 21 along the axial direction 13, have different mass distributions, so that the overall casting material 19 forms a mass distribution that can compensate for the dynamic imbalance of the rotor 10.

[0062] The second design scheme of rotor 10 obtainable through method 100 is in Figure 3 The basic structure of the rotor 10 is shown in the figure. Figure 1 The same reference numerals denote corresponding parts of rotor 10.

[0063] But with Figure 1Compared to the rotor 10, the casting material 19 has been introduced into the void 11 in such a way that the casting material forms a retraction portion 24 relative to the end sides 14, 15. Through the retraction portions 24 of different sizes, different mass distributions are formed in the two balance planes 21, 22, and these different mass distributions ensure the dynamic balance of the rotor 10.

[0064] Figure 4 A rotor 10 is shown arranged between two tool heads 25, 26 of tool 27. Tool heads 25, 26 rest against the end sides 14, 15 of the rotor. Each of tool heads 25, 26 has an introduction device 28 for introducing casting material 19 into the void 11. In a first design of tool 27 shown in the left half of the figure, tool heads 25, 26 have a chamber 29 arranged above the void 11 open towards the end sides 14, 15. The volume of chamber 29 can be adjusted by plunger 30. By adjusting the volume of chamber 29, the protrusion 20 ( Figure 1 The amount of casting material is prominently displayed on the end sides 14, 15 of the rotor 10. In another design variant of the tool 27 shown in the right half of the figure, the tool heads 25, 26 have a core puller 31 that can be moved into the recess 11 that opens toward the end sides 14, 15. By adjusting the depth of the core puller 31 into the recess 11, the amount of casting material 19 can be reduced accordingly, so that the casting material forms a retraction portion 24 in the recess 11 relative to the end sides 14, 15. Figure 2 ).

[0065] according to Figure 4 The two design schemes of the left and right halves of the tool can also be combined.

[0066] at last, Figure 5 A rotor 10 for an asynchronous motor, manufactured according to this method, is shown. The rotor 10 has a rotor core 32 and a cage 33 comprising rotor bars 34 and short-circuit rings 35. The rotor bars 34 are manufactured by introducing a casting material 19 into a recess 11 extending on the outer side 36 of the rotor core 32; the recess is designed as a slot 37. The casting material 19 is aluminum or copper. The end-side short-circuit rings 35 protrude in the form of protrusions 20 relative to the end sides 14, 15 of the rotor 10. By selecting the amount or volume of the casting material 19 for the short-circuit rings 35, this results in a variable thickness 38 of the short-circuit rings 35 in the circumferential direction 23, forming a mass distribution suitable for compensating for dynamic imbalances in the rotor 10.

[0067] List of reference numerals

[0068] 100 methods

[0069] 10 rotors

[0070] 11. Empty space

[0071] 12 cavities

[0072] 13 Axial direction

[0073] 14 First end side

[0074] 15 Second end side

[0075] 16 Magnets

[0076] 17 Opening

[0077] 18 Rotor shaft

[0078] 19. Casting Material

[0079] 20. Protrusion

[0080] 21 First equilibrium plane

[0081] 22 Second Equilibrium Plane

[0082] 23. Circumferential direction

[0083] 24 Retraction section

[0084] 25 Toolboard

[0085] 26 Toolboard

[0086] 27 Tools

[0087] 28. Introduction device

[0088] 29 chambers

[0089] 30 plungers

[0090] 31 Core Puller

[0091] 32 Rotor core

[0092] 33. Cage

[0093] 34 rotor bars

[0094] 35 short circuit ring

[0095] 36 Outer side

[0096] 37 slots

[0097] 38mm thickness

Claims

1. A method (100) for reducing the imbalance of a rotor (10) of an electric motor, wherein, The rotor (10) has a plurality of open sections (11) arranged in the circumferential direction (23), wherein the dynamic imbalance of the rotor (10) is determined, wherein casting material (19) is introduced into the open sections (11) of the rotor (10) during the casting process, wherein the mass distribution of the casting material (19) is designed in a manner to compensate for the dynamic imbalance, wherein the rotor (10) has two end sides (14, 15), wherein the open sections (11) are open toward the end sides (14, 15), and wherein the casting material (19) The casting material (19) is introduced into the void (11) through at least one of the end sides (14, 15), preferably through both end sides, wherein the casting material (19) introduced into the void (11) is arranged in the void (11) with a protrusion (20) or a retraction (24) relative to the end side (14, 15), wherein the casting material (19) is successively introduced into the plurality of voids (11) in a plurality of casting stages, wherein the corresponding protrusion and / or retraction is adjusted for the corresponding void (11) in the plurality of casting stages. The dimensions of the part allow the overall mass distribution of the casting material to be formed, which can be used to compensate for the dynamic imbalance of the rotor. The rotor (10) is a short-circuit rotor or squirrel-cage rotor for an asynchronous motor. The rotor (10) has a rotor core (32) and a cage (33). The cage (33) includes rotor bars (34) and short-circuit rings (35). The casting material (19) is aluminum or copper. The rotor bars (34) are formed by introducing the casting material (19) into the rotor core (32). It is manufactured in a recess (11) extending on the outer side (36), wherein the recess (11) is designed as a groove (37), and wherein the casting material introduced into the recess, which is constructed around the end side, forms a short-circuit ring of the rotor, wherein the casting material forming the short-circuit ring constitutes a protrusion and / or a retraction relative to the end side, wherein by selecting the amount or volume of the casting material (19) for the short-circuit ring (35), the axial thickness of the short-circuit ring (35) is variable in the circumferential direction in order to provide a mass distribution for compensating for the dynamic imbalance of the rotor.

2. The method (100) according to claim 1, wherein, The empty portion (11) extends substantially along the axial direction (13) on or in the rotor (10), and / or wherein the empty portion (11) extends along the circumferential direction (23).

3. The method (100) according to any one of the preceding claims, wherein, The mass distribution is designed by selecting the amount and / or weight and / or volume and / or density and / or dosage of the casting material (19) introduced into the corresponding void (11), and / or wherein, In a series of successive pouring stages, pouring material (19) is introduced into the void (11), wherein preferably, the amount and / or weight and / or volume and / or density and / or dosage of pouring material (19) is changed, more preferably, for the corresponding void (11) during the pouring stages.

4. The method (100) according to any one of the preceding claims, wherein, The mass distribution of the casting material (19) is designed differently in at least two equilibrium planes (21, 22) oriented substantially perpendicular to the axial direction (13) and viewed in the circumferential direction (23) and / or radial direction, and / or wherein, The axis of rotation of the rotor (10) is tilted relative to the stable principal axis of inertia of the mass distribution of the casting material (19).

5. The method (100) according to any one of the preceding claims, wherein, The rotor (10) includes a rotor shaft (18) and / or a balance disc and / or a cover plate or end plate.

6. A tool (27) for carrying out the method (100) according to any one of the preceding claims, wherein, The tool (27) has at least two tool plates (25, 26), wherein at least one tool plate (25, 26) can be arranged on the end side (14, 15) of the rotor (10), wherein at least one, preferably each tool plate (25, 26) has an introduction device (28) for introducing casting material (19) through the end side (14, 15) of the rotor into the empty portion (11) of the rotor (10), wherein at least one, preferably each tool plate (25, 26) has a variable volume chamber (29) and / or a core extractor (31). And / or a metering device for casting material (19), wherein the chamber covers an open-end portion and is designed such that the size of the protrusion of the casting material relative to the end side can be adjusted by adjusting the volume of the chamber, the core puller is designed to be able to be inserted into the open end portion by the end side and the size of the retracted portion of the casting material relative to the end side can be adjusted according to the depth of the core puller entering the corresponding open end portion, and the metering device is designed to introduce a predetermined amount or volume of casting material into the corresponding open end portion so as to adjust the size of the corresponding protrusion and / or retracted portion.

7. A rotor (10) for an electric motor, said rotor (10) being manufactured by the method (100) according to any one of claims 1 to 5.

8. The rotor (10) according to claim 7, wherein, The rotor (10) is a short-circuit rotor or a squirrel-cage rotor for an asynchronous motor.

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