Rotor for a radial flux machine

Abstract

The invention relates to a rotor (1) for a radial flux machine, wherein the rotor (1) has a plurality of rotor lamination stacks (4) comprising individual laminations in which a plurality of permanent magnets (3) are embedded, wherein the rotor (1) further comprises a cooling device with cooling channels (5) arranged in the rotor lamination stacks (4), wherein the cooling channels (5) have a respective enclosing lining (6) or casing made of a thin-walled plastic, which is introduced into a respective cavity in the rotor lamination stack (4) by means of an injection blow molding process, wherein an outer contour of the lining (6) is formed at least substantially corresponding to an inner contour of a respective cavity in the rotor lamination stack (4).

Description

[0001] The invention relates to a rotor for a radial flux machine according to the preamble of claim 1 and a method for sealing cooling channels in such a rotor according to the preamble of claim 6.

[0002] To increase the temperature resistance of permanent magnets in electric motors, the rare earth elements Dy, Tb, and Ho are alloyed. Without these elements, the magnets demagnetize at temperatures as low as approximately 80°C. To minimize the amount of rare earth alloying required, it is advantageous to reduce the maximum temperatures at the magnets. Direct cooling of the magnets allows for a significant temperature reduction. The existing flux barriers can be used as cooling channels on the magnets for this purpose. Since the rotor consists of thin individual laminations, bores such as those in the flux barriers act as leaky channels. This leads to the accumulation of coolant in the air gap between the rotor and stator, resulting in increased drag losses during rotation and consequently higher energy consumption of the electric motor.The described problem of the leaking channel in the electrical steel stack also results in a reduction of the effectively adjustable pressure and volume flow of the cooling medium.

[0003] The flux barriers, or other possible channels in the rotor, are shaped for optimal conduction of the magnetic flux. For this reason, they are generally not cylindrical bores with a fixed diameter.

[0004] It is known to glue the individual metal sheets together, for example using baking varnish. However, this method can lead to leaks due to the lack of guaranteed full-surface bonding. Furthermore, it typically involves several stacks of sheets that are mounted onto the rotor shaft one after the other.

[0005] This creates leaks between the individual packages. The use of baking varnish results in a greater adhesive thickness than with standard sheet metal insulating varnishes. Consequently, the sheet metal component at the rotor's height, and therefore its effective magnetic power, is reduced.

[0006] Therefore, the aim is to manufacture plastic cooling channels in the rotor's sheet metal stack, for example in the free space of the flux barriers, in order to seal them towards the air gap.

[0007] DE 10 2007 045 267 A1 describes a housingless dynamoelectric machine with a stator and a rotor, wherein the stator is constructed from axially layered electrical steel laminations which form slots and teeth facing the air gap, wherein a winding system is arranged in the slots which generates a magnetic flux and wherein the electrical steel laminations, viewed in the circumferential direction, have at least partially axially extending recesses in a yoke ridge which electromagnetically connects the teeth, wherein at least some recesses are provided with cooling tubes and at least these recesses are provided with magnetic flux barriers extending within the electrical steel lamination, so that no radial field components penetrate the cooling tube pitch circle surrounding the cooling tubes.

[0008] DE 10 2004 036 179 A1 describes a coolant line containing the following layers: I. an outer layer made of a polyamide molding compound and II. an inner layer containing polypropylene and at least 0.02 wt.% of a heat stabilizer.

[0009] The invention is based on the objective of providing a novel rotor for a radial flux machine and a novel method for sealing cooling channels in such a rotor.

[0010] The problem is solved according to the invention by a rotor for a radial flux machine with the features of claim 1 and a method for sealing cooling channels in such a rotor with the features of claim 6.

[0011] Advantageous embodiments of the invention are the subject of the dependent claims.

[0012] A rotor for a radial flux machine is proposed, wherein the rotor comprises a plurality of rotor lamination stacks containing individual laminations, in which a plurality of permanent magnets are embedded, and wherein the rotor further comprises a cooling device with cooling channels arranged in the rotor lamination stacks. According to the invention, the cooling channels have a respective enclosing lining or casing made of a thin-walled plastic, which is introduced into a respective cavity in the rotor lamination stack by means of an injection blow molding process, wherein an outer contour of the lining is formed at least substantially corresponding to an inner contour of a respective cavity in the rotor lamination stack.

[0013] The present invention proposes to realize thin-walled, in particular non-cylindrical, plastic cooling channels in existing rotor channels and flux barriers using an injection blow molding process. This makes it possible to ensure the best possible heat transfer from the magnet to the cooling medium without any risk of leakage.

[0014] The radial flux machine can be part of an electric powertrain (eATS) for propelling a predominantly or exclusively electrically powered vehicle. The rotor of the electric machine can be cooled with a coolant (preferably oil) via cooling channels in the laminated core. The electric machine can, for example, be a permanent magnet radial flux machine.

[0015] Exemplary embodiments of the invention are explained in more detail below with reference to drawings.

[0016] This shows: Fig. 1 A schematic view of a rotor and a stator for a radial flux machine, Fig. 2 a schematic view of the rotor, Fig. 3 A schematic view of a preform during a first process step of a process for sealing cooling channels in the rotor, Fig. 4 a schematic view of the rotor during a second process step, Fig. 5 a schematic view of the rotor during a third process step, Fig. 6 a schematic view of the rotor during a fourth process step, Fig. 7 a schematic view of the rotor during a fifth process step, and Fig. 8 a schematic view of the rotor during a sixth process step.

[0017] Corresponding parts are marked with the same reference symbols in all figures.

[0018] Fig. Figure 1 is a schematic view of a rotor 1 and a stator 2 for a radial flux machine, which can be used, for example, as a drive machine for an electrically powered vehicle, in particular a passenger car, a commercial vehicle or a bus. Fig. Figure 2 is another schematic view of the rotor 1. The rotor 1 has a plurality of permanent magnets 3 and is formed from a plurality of rotor lamination stacks 4 comprising individual laminations, in which the permanent magnets 3 can be embedded. The rotor 1 has a cooling device with cooling channels 5, wherein the cooling channels 5 each have an enclosing lining 6 or casing made of a thin-walled plastic, which is introduced into a respective cavity in the rotor lamination stack 4 by means of an injection blow molding process.

[0019] In this way, dense cooling channels 5 can be formed in cavities of rotor lamination stacks 4, in particular in non-cylindrical cavities such as flux barriers, which can be arranged, for example, at the ends of the permanent magnets 3.

[0020] The individual sheets can each have a coating, which may consist exclusively of a sheet metal insulating lacquer.

[0021] The lining 6 or sheathing eliminates the need to bond the individual sheets together with a baking varnish. Using a baking varnish results in a greater adhesive thickness than with standard sheet metal insulating varnishes. This reduces the sheet metal area in the axial direction of the rotor 1, thus reducing its effective magnetic power.

[0022] The linings 6 or casings can be made of PTFE and have a wall thickness of approximately 0.3 mm.

[0023] The stator 2 has a stator lamination stack 14 and a stator winding 15, within which the rotor 1 is arranged. An air gap 23 is located between the rotor 1 and the stator 2. The stator winding 15 has winding heads 16 at its axial ends.

[0024] A balancing disc 13 is arranged at each axial end of the rotor lamination stack 4. The cooling channels 5 each run axially through the rotor lamination stack 4 and open into one of the balancing discs 13 at both ends.

[0025] The rotor lamination stack 4 is arranged on a rotor shaft 18, which is designed as a hollow shaft to guide a cooling medium and is supported by rotor bearings 22. At least one oil inlet channel 19 extends from the rotor shaft 18 at least substantially radially into each balancing disk 13 and from there into at least one of the cooling channels 5. At the opposite end of each cooling channel 5, an oil outlet channel 20 extends radially or approximately radially out of the balancing disk 13, so that the cooling medium exits towards the winding head 16. In the axial direction, the cooling channels 5 at the end of the balancing disk 13 can be closed by a sealing plug 21, at least in the region of the oil inlet channel 19.

[0026] Fig. Figure 3 is a schematic view of a preform 10 during a first process step. The preform 10 is heated in a heating device 11, for example to approximately 130 °C. The preforms 10 have a length that is shorter, for example 1 mm shorter, than the length of the cooling channel 5 in the rotor 1. The wall thickness of the preforms 10 is, for example, approximately 0.3 mm. The preforms 10 are designed as tubes whose diameter results from the geometry of the cooling channel 5 in the rotor 1 to be sealed (flow barrier). In particular, after the preform 10 is inserted into the cooling channel 5 in the second process step, a minimum distance of 0.5 mm to the rotor lamination stack 4 should be maintained. One end of the preform 10 can be closed, while the other, open end can have a flange.

[0027] The preforms 10 are preferably made of PTFE.

[0028] Fig. Figure 4 is a schematic view of rotor 1 during a second process step.

[0029] In the second process step, the heated preforms 10 are inserted directly into the respective cooling channels 5 to insert and seal them. The preform 10 is then fixed to a sealing surface 12, which forms a balancing disc 13, using a nozzle 17. The contact pressure in the area of ​​the sealing surface 12 can be approximately 5 bar.

[0030] Fig. Figure 5 is a schematic view of rotor 1 during a third process step.

[0031] In the third process step, the lining 6 of the cooling channels 5 is formed by inflating the preforms 10. This involves two pressure stages. The first pressure stage ensures the preform 10 is precisely positioned within the cooling channel 5. The second pressure stage causes the lining 6 to burst in the area of ​​the oil outlet channels 20. This allows cold compressed air to be blown through the cooling channel 5 to rapidly cool the plastic. The air pressure for inflation in the first pressure stage is approximately 20 bar and is maintained for a defined time (preferably 10 seconds). The air pressure in the second pressure stage is approximately 30 bar. Subsequently, cold air at 20°C is blown through the cooling channels 5 at a volume flow rate of approximately 20 l / min.

[0032] Fig. Figure 6 is a schematic view of rotor 1 during a fourth process step.

[0033] In the fourth process step, nozzle 17 is removed again.

[0034] Fig. Figure 7 is a schematic view of rotor 1 during a fifth process step.

[0035] In the fifth process step, the rotor 1 is reworked. The oil outlet channels 20 of the balancing discs 13 are precisely drilled out, and the oil inlet channels 19 are exposed by drilling a hole in the balancing disc 13.

[0036] Fig. Figure 8 is a schematic view of rotor 1 during a sixth process step.

[0037] In the sixth process step, the lateral bores in the balancing discs 13 are provided with threads and closed by means of sealing plugs 21.

[0038] In a seventh process step, rotor 1 is balanced. Reference symbol list 1 Rotor 2 Stator 3 permanent magnets 4 Rotor lamination package 5 Cooling channel 6 Lining 10 preforms 11 Heating device 12 Sealing surface 13 Balancing disc 14 Stator lamination stack 15 Stator winding 16 winding head 17 nozzle 18 Rotor shaft 19 Oil inlet channel 20 Oil outlet channel 21 sealing plugs 22 rotor bearings 23 air gap QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] DE 10 2007 045 267 A1

[0007] DE 10 2004 036 179 A1

[0008]

Claims

[1] Rotor (1) for a radial flux machine, wherein the rotor (1) has a plurality of rotor lamination stacks (4) comprising individual laminations in which a plurality of permanent magnets (3) are embedded, wherein the rotor (1) further comprises a cooling device with cooling channels (5) arranged in the rotor lamination stacks (4), characterized by , that the cooling channels (5) have a respective enveloping lining (6) or casing made of a thin-walled plastic, which is introduced into a respective cavity in the rotor lamination stack (4) by means of an injection blow molding process, wherein an outer contour of the lining (6) is formed at least substantially corresponding to an inner contour of a respective cavity in the rotor lamination stack (4). [2] Rotor (1) according to claim 1, characterized by that the cavities are designed as a flow barrier and not cylindrical. [3] Rotor (1) according to claim 1 or 2, characterized bythat each individual sheet metal sheet has a coating consisting exclusively of a sheet metal insulating lacquer. [4] Rotor (1) according to one of claims 2 or 3, characterized by , that the respective lining (6) has an irregular contour. [5] Rotor (1) according to any one of the preceding claims, characterized by , that the lining (6) is made of PTFE and has a wall thickness of approximately 0.3 mm. [6] Method for sealing cooling channels (6) in a rotor (1) according to one of the preceding claims, characterized by , that the lining (6) is produced by means of an injection blow molding process, comprising the steps: - Heating preforms (10) of the linings (6), wherein the preforms (10) have a length that is slightly shorter than the length of the respective cooling channel (5) in the rotor (1), - Inserting the heated preforms (10) into the respective cooling channels (5) and fixing them by means of a nozzle (17) on a sealing surface (12), which forms a balancing disc (13), - Inflating the preforms (10) through the nozzle (17), wherein the preform (10) is applied in a first pressure stage to form the lining (6) in a defined manner against the contour of the cooling channel (5), wherein the lining (6) is subjected to higher pressure in a second pressure stage to burst in the area of ​​an oil outlet channel (20) which is arranged in a balancing disc (13), and - Cooling the lining (6) by passing cold air through it. [7] Method according to claim 6, characterized by the next steps: - Removing the nozzle (17), - Drilling out the oil outlet channels (20) in the balancing discs (13) and exposing oil inlet channels (19) by drilling in the balancing discs (13), - Providing lateral bores in the balancing discs (13) with threads and closing them by means of sealing plugs (21), and - Balancing the rotor (1).

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