Electric machine

Abstract

The invention relates to an electric machine (10) comprising a rotor (12) which is accommodated on a rotor shaft (18) which has a first rotor shaft part (42) and a second rotor shaft part (44) which are joined to one another at a connection (46), wherein a cavity (20) is formed in the rotor shaft (18). A moulded insert (30), which is made of a plastic material and through which a cooling medium flows, is embedded in the cavity (20) of the rotor shaft (18) for conjoint rotation therewith. The invention also relates to the use of the electric machine (10) in an electric drive axle module of an electrically powered vehicle.

Description

[0001] Electric machine

[0002] Technical area

[0003] The invention relates to an electric machine with a rotor mounted on a rotor shaft comprising a first rotor shaft part and a second rotor shaft part joined together at a connection, wherein a cavity is formed in the rotor shaft. A molded insert made of a plastic material, through which a cooling medium flows, is rotationally fixedly embedded in the cavity of the rotor shaft. Furthermore, the invention relates to the use of the electric machine in an electric axle module of an electrically powered vehicle.

[0004] State of the art

[0005] DE 10 2020 207 000 A1 relates to an arrangement for an electrical machine, comprising a rotor, an excitation device, and an integrated energy transmission system. In a preferred embodiment, the energy transmission system comprises an excitation stator and an excitation rotor. The excitation stator is preferably made of a plastic material, projects into the excitation rotor, and can have a bore, configured as a longitudinal bore or channel, to cool the excitation stator from the inside, in particular with air, water, and / or oil as a coolant. Such cooling can prevent overheating of the energy transmission device in the cavity of the machine rotor shaft, and increase efficiency. DE 10 2021 105 084 A1 discloses oil cooling on an electric motor via direct spray cooling.In one embodiment, the system may include a shaft with an axially extending oil line and a plurality of openings for fluid coupling to the outside of the shaft, a rotor positioned coaxially with the shaft, and a gas-filled chamber between the inner surface of the rotor and the outer surface of the shaft. For example, oil may be supplied to the oil line via an oil cooling system coupled to the electric motor via at least one rotor and at least one valve. This allows the temperature of an electric motor to be reduced during operation without adding a cooling jacket or fan, thus without increasing the weight or complexity of the motor.

[0006] DE 10 2015 218 620 A1 relates to a housing for an electrical machine, comprising, among other things, an outer housing, an inner housing, and a shell intermediate space with cooling fins for forming a spiral cooling channel. The cooling fins are formed as a separate plastic part and inserted into the intermediate space. According to the disclosure, the cooling fins run in the axial direction and also extend into the base intermediate space for cooling the bearing for the rotor shaft, where they continue radially. Preferably, the outer housing and the cooling fins formed thereon are manufactured cost-effectively from aluminum or plastic material, in particular polyamide or polypropylene.

[0007] In electrical machines, it is necessary to cool the stator, its winding heads, and the rotor. This is usually achieved using a cooling medium. For example, the cooling medium flows via a rotor shaft through the radial and axial bores into the interior of the electrical machine, where it cools, among other things, the winding heads. However, the flow of the cooling medium, particularly oil, in the rotor shaft is highly dependent on the speed of the electrical machine, as the bore in the rotor shaft usually has a large diameter to reach the rotor lamination stack and provide better cooling there. If the rotor bore in the rotor shaft has a small diameter, the cooling medium cannot get close enough to the lamination stack, which significantly reduces the cooling performance. Disclosure of the Invention

[0008] According to the invention, an electric machine is proposed, comprising a rotor mounted on a rotor shaft comprising a first rotor shaft part and a second rotor shaft part joined together at a connection, wherein a cavity is formed in the rotor shaft. A molded insert made of a plastic material, through which a cooling medium flows, is rotationally fixedly embedded in the cavity of the rotor shaft.

[0009] The solution proposed by the invention provides a simple and cost-effective way to achieve a homogeneous distribution of the cooling medium within the electric machine. The plastic insert is installed in a rotationally fixed manner within the rotor shaft, which represents a significantly more cost-effective solution.

[0010] In an advantageous further embodiment of the electrical machine proposed according to the invention, the insert part has an inlet and an outlet through which the cooling medium flows through the insert part, or the shaped insert part has an inlet for the cooling medium, which exits from the rotor shaft into the electrical machine via radial bores and / or outlet nozzles.

[0011] In an advantageous further embodiment of the electric machine according to the invention, a connection between a first rotor shaft part and a second rotor shaft part of the rotor shaft is designed as a material connection, in particular as a weld seam, or as a force-fit connection, in particular as a press fit. Due to the at least two-part design of the rotor shaft, the insert part can be very easily inserted axially into one of the rotor shaft parts and mounted there before a complete rotor shaft is produced via the connection to the further, second rotor shaft part.

[0012] In an advantageous further embodiment of the electric machine proposed by the invention, the cavity within the rotor shaft or one of the rotor shaft parts is defined by an inner surface against which the molded insert, in a double-walled design, in a meander shape, or in a complementary shape with respect to the cavity of the rotor shaft, rests. This solution can create improved heat transfer between the rotor laminations and the cooling medium, as a closed and larger contact surface is created that facilitates heat conduction and promotes heat transfer from the windings or the winding heads of the rotor laminations to the cooling medium.

[0013] In an advantageous embodiment of the electrical machine proposed according to the invention, the molded insert is provided in a double-walled design with an outer wall and an inner wall that define an annular space. Furthermore, in this embodiment of the electrical machine according to the invention, outlet openings in the outer wall of the molded insert in a double-walled design are aligned with radial bores of a shaft casing of the rotor shaft. The cooling medium, for example oil, enters the interior of the electrical machine via the outlet openings. Preferably, the winding heads of the stator of the electrical machine are sprayed onto the windings so that waste heat generated there can be dissipated.

[0014] In a further advantageous embodiment of the electrical machine proposed according to the invention, the molded insert is spiral-shaped and comprises individual turns arranged at a distance from one another. In this embodiment, the individual turns of the spiral-shaped molded insert can contact the inner surface of the rotor shaft to facilitate heat conduction. Furthermore, the spiral-shaped molded insert is self-centering during installation in the cavity of the rotor shaft.

[0015] In a further advantageous embodiment of the electrical machine according to the invention, the shaped insert is designed in a meander shape and comprises individual meander sections that extend in the axial direction within the cavity of the rotor shaft. The individual meander sections achieve continuous contact, viewed in the axial direction, so that in this embodiment too, good heat dissipation or good heat transfer from the components mounted on the rotor shaft in the form of the winding overhangs and the winding laminations to the cooling medium can be achieved. In a further advantageous embodiment of the electrical machine proposed according to the invention, the shaped insert is designed in a tubular shape, with outlet nozzles extending radially from it in the direction of radial bores formed in the shaft casing of the rotor shaft.

[0016] Advantageously, the outlet nozzles extending radially from the shaped tubular insert are aligned with the radial bores of the shaft shell of the rotor shaft.

[0017] In a further advantageous embodiment of the electrical machine proposed according to the invention, the shaped insert part can also be designed in a complementary shape to the inner contour of the cavity of the rotor shaft and can also comprise outlet nozzles that are aligned with radial bores that are formed in the shaft casing of the rotor shaft.

[0018] In the design variants of the electric machine in which the shaped insert is designed in tubular form or the shaped insert is designed in a complementary form, a sealed system is created via a sealing ring provided within the first rotor shaft part.

[0019] The invention further relates to the use of the electric machine in an electric axle module of an electrically powered vehicle.

[0020] Advantages of the invention

[0021] The solution proposed by the invention makes it possible to create a rotor shaft that can be manufactured as a standard component in a more advantageous and cost-effective manner. In particular, a conical bore inside one of the rotor shaft parts can be avoided, which is particularly complex to manufacture and therefore has a significant negative impact on manufacturing costs.

[0022] The solution proposed by the invention makes it possible to provide a molded insert for evening the coolant distribution and thus for evening the temperature level within a rotor assembly of an electric machine. The outlined design variants of the molded insert—in a double-walled design, spiral shape, meander shape, tubular shape, or complementary shape with respect to the rotor shaft cavity—allow various installation requirements to be considered and various temperature distribution gradients to be achieved. The fact that the molded insert is made of a plastic material is advantageous in terms of weight and the geometric shape of the molded insert, as a wide variety of geometries can be realized.

[0023] Short description of the drawings

[0024] Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

[0025] They show:

[0026] Figure 1 shows a longitudinal section through a one-piece rotor shaft of an electrical machine according to the prior art,

[0027] Figure 2 shows a longitudinal section through an electrical machine proposed according to the invention with a shaped insert in a first embodiment,

[0028] Figure 3 shows a longitudinal section through an electrical machine proposed according to the invention with a shaped insert in a second embodiment,

[0029] Figure 4 shows a further, third embodiment of the shaped insert part accommodated in a multi-part rotor shaft,

[0030] Figure 5 shows a fourth embodiment of the shaped insert part, embedded in a rotor shaft part of the electrical machine proposed according to the invention and Figure 6 shows a fifth embodiment of the shaped insert part, shaped complementarily to the cavity of one of the rotor shaft parts of a multi-part rotor shaft.

[0031] The illustration in Figure 1 shows an electrical machine 10 having a rotor 12 that rotates relative to a stator 14 accommodated in the housing of the electrical machine 10. While lamination packs 13 are accommodated on the rotor 12, the stator 14 comprises windings, each of which has projecting winding heads 15 at its end. A rotor shaft 18, which is formed as a single piece here, has a running gear 16. The rotor shaft 18, as shown in Figure 1, comprises a cavity 20, from which cooling medium can be distributed through radial bores 22 provided in a shaft casing 24.

[0032] Embodiments of the invention

[0033] In the following description of the embodiments of the invention, identical or similar elements are designated by the same reference numerals, whereby a repeated description of these elements is omitted in individual cases. The figures only schematically illustrate the subject matter of the invention.

[0034] Figure 2 shows a first embodiment variant of the shaped insert 30, which is embedded in a multi-part rotor shaft 18 of an electrical machine 10 according to the invention.

[0035] From the illustration in Figure 2, it can be seen that an insert 30 in a double-walled design 32 is non-rotatably embedded in the cavity 20 of a first rotor shaft part 42. In the double-walled design 32 of the molded insert 30, this comprises an outer wall 34 and an inner wall 36. The outer wall 34 and the inner wall 36 define an annular space 38 through which a cooling medium, for example oil, flows, which enters the molded insert 30 laterally through a nozzle on the end face of the first rotor shaft part 42. Sealing is provided by a sealing ring 76. Outlet openings 40 are located in the outer wall 34 of the double-walled design 32 of the shaped insert 30. The outlet openings 40 are aligned in the shaped insert 30 in double-walled design 32, which is mounted in a rotationally fixed manner in the cavity 20, with radial bores 22 which are located in the shaft casing 24 of the rotor shaft 18.The molded insert 30, which is preferably manufactured as a molded part from a plastic material, achieves targeted and effective cooling of the components in the form of winding parts mounted on the circumference of the rotor shaft 18. Furthermore, the solution proposed by the invention can achieve effective cooling of the winding heads 15 of the stator 14. The cooling medium, in particular oil used for cooling, is preferably sprayed against the winding heads 15, which run along the sides of the stator 14, to cool them, thereby dissipating the resulting waste heat.

[0036] The assembly of the molded insert 30 in the double-walled design 32 according to Figure 2 takes place, for example, in the axial direction into the cavity 20 of the first rotor shaft part 42. After the rotationally fixed fastening of the molded insert 30 in the cavity 20 of the first rotor shaft part 42, the first rotor shaft part 42 and a second rotor shaft part 44 are joined together at a connection 46. The connection 46 can be produced either as a material-to-material connection 48, in particular in the form of a weld seam, or as a force-fit connection 50, for example as a press fit. The possible designs of the connection 46 as a material-to-material connection 48 and a force-fit connection 50, as described above, relate to all design variants of the molded insert 30 according to Figures 3 to 6.

[0037] To improve heat transfer to the cooling medium, the shaped insert 30 in the embodiment according to Figure 2 is arranged as close as possible to an inner surface 54 of the shaft shell 24 of the first rotor shaft part 42. Position 52 designates a rolling bearing in which the second rotor shaft part 44 of the rotor shaft 18, which is here constructed in several parts, is rotatably received in the housing of the electric machine 10.

[0038] The illustration in Figure 3 shows a second embodiment of the shaped insert 30 proposed according to the invention, embedded in the rotor shaft 18 of the electric machine 10. The illustration in Figure 3 shows that in this embodiment of the shaped insert 30, it takes on a spiral shape 60. The spiral shape 60 of the shaped insert 30 according to the second embodiment comprises a number of individual turns 62, which can be arranged at a regular or irregular spacing 64 over the axial length of the shaped insert 30. The individual turns 62 of the shaped insert 30 according to the second embodiment in Figure 3 lie in contact 66 with the inner circumferential surface 54, which delimits the cavity 20 of the first rotor shaft part 42 of the rotor shaft 18. This ensures heat transfer to the cooling medium flowing through the shaped insert 30.In the second embodiment of the molded insert 30 shown in Figure 3, the cooling medium enters the first rotor shaft part 42 via an inlet 56 and exits it at an elevated temperature at an outlet 58, which is also arranged in a lateral, axially oriented nozzle of the first rotor shaft part 42 of the rotor shaft 18. Thus, in the second embodiment shown in Figure 3, the cooling medium flows through the molded insert 30.

[0039] The illustration according to Figure 4 shows a further, third embodiment variant of the shaped insert part 30 proposed according to the invention, embedded in the first rotor shaft part 42 of the rotor shaft 18.

[0040] In this embodiment, the shaped insert 30 essentially has a meander shape 68. The meander shape 68 is characterized in that individual meander sections 69 extend essentially in an axial orientation 70 within the cavity 20 of the first rotor shaft part 42 of the rotor shaft 18. In the third embodiment of the shaped insert 30, a contact surface 66 is also formed between the meander sections 69 of the shaped insert 30 having the meander shape 68, on the one hand, and the inner surface 54 of the cavity 20 of the first rotor shaft part 42, on the other hand. This provides the largest possible, evenly extending contact surface with the shaft shell 24 of the first rotor shaft part 42 of the rotor shaft 18, which enables a significant improvement in heat transfer from the components mounted on the circumference of the rotor shaft 18 to the cooling medium flowing through the shaped insert 30.This flows through the shaped insert 30 in its third embodiment variant in meander shape 68, starting from the inlet 56 and leaves the shaped insert 30 in meander shape 68 at the outlet 58 with an increased temperature, which is caused by the heat dissipation.

[0041] From the illustration according to Figure 4 it can be seen that the shaped insert 30 according to the third embodiment variant in meander shape 68 occupies almost the entire cavity 20 of the first rotor shaft part 42, thus filling it, so that a large contact area is provided between the inner circumferential surface 54 and the first rotor shaft part 42 of the rotor shaft 18 and the meander sections 69, which promotes heat dissipation.

[0042] A further, fourth embodiment of the shaped insert 30 emerges from the illustration in Figure 5. The fourth embodiment shown in Figure 5 shows the shaped insert 30, which essentially has a tubular shape 72. Individual outlet nozzles 74, oriented essentially in the radial direction, branch off from the tubular body, which extends through the first rotor shaft part 42 essentially symmetrically to its axis of rotation, and are connected, for example, to the radial bores 22 formed in the shaft casing 24 of the first rotor shaft part 42. Thus, in the fourth embodiment of the shaped insert 30 shown in Figure 5, the cooling medium exits into the electrical machine 10 via the outlet nozzles 74 or the radial bores 22 in the shaft casing 24.In the present case, the electric machine 10 is, for example, an ASM-E motor that can be cooled with oil. Such electric machines 10 can also be cooled using other cooling media, such as water.

[0043] In the fourth embodiment of the shaped insert 30 shown in Figure 5, the cooling medium flows to it via the inlet 56. By means of a sealing ring 76, the shaped insert 30 is sealed with respect to the first rotor shaft part 42 of the rotor shaft 18, which is designed in multiple parts in the embodiments of Figures 2 to 6. Instead of the four outlet nozzles 74 shown here, which branch off essentially radially from the tubular body of the shaped insert 30 in tubular form 72, additional outlet nozzles 74 can also be provided, which are each aligned with radial bores 22 provided in the shaft casing 24 of the first rotor shaft part 42. In the embodiment according to Figure 5, the rotor shaft 18 is also split. The first rotor shaft part 42 and the second rotor shaft part 44 are connected to one another at the connection 46.As already mentioned above, the connection 46 can be designed either as a material connection 48, for example, as a weld seam, or as a force-fit connection 50, for example, as a press fit. The bearing of the rotor shaft 18, which is split here, is not shown in detail, except for the indicated rolling bearing 52.

[0044] The illustration in Figure 6 shows a fifth embodiment of the molded insert 30 made of plastic material. In the fifth embodiment of the molded insert 30 shown in Figure 6, the insert has a complementary shape 78. In the present context, this means that the molded insert 30 is designed to complement the geometry of the cavity 20 in the first rotor shaft part 42. The shaped insert part 30 in its fifth embodiment according to Figure 6 is cylindrical and lies with its outer surface in contact 66 with the inner surface 54 of the first rotor shaft part 42 of the rotor shaft 18 of the electric machine 10. Individual outlet nozzles 74 on the shaped insert part 30 according to the complementary shape 78 in the fifth embodiment are aligned with the radial bores 22 which are designed in the shaft shell 24 of the first rotor shaft part 42 of the rotor shaft 18 which is designed in a split manner here.As a result, the cooling medium exits the shaft casing 24 through the outlet nozzles 74 or the radial bores 22 in the direction of the electrical machine 10.

[0045] In the fifth embodiment of the molded insert 30 according to Figure 6, the cooling medium also enters the molded insert 30 via the inlet 56 of the nozzle on the first rotor shaft part 42 and flows radially outward from the inside. The molded insert 30 in its fifth embodiment according to Figure 6 is sealed against the first rotor shaft part 42 of the rotor shaft 18, which is here constructed in two parts, by the sealing ring 76.

[0046] Also in the fifth embodiment variant of the shaped insert part 30 in complementary shape 78 to the cavity 20 of the first rotor shaft part 42 shown in Figure 6, after the shaped insert part 30 in complementary shape 78 has been inserted into the cavity 20 of the first rotor shaft part 42, the second rotor shaft part 44 is joined to the first rotor shaft part 42 at the connection 46. As already mentioned, the connection 46 is formed, for example, by a material-to-material connection 48 in the form of a weld seam or as a force-to-friction connection 50 in the form of a press fit and is sealed by means of the sealing ring 76.

[0047] All embodiments 1 to 5 of the molded insert 30 shown in Figures 2 to 6 have in common that it can be manufactured as a preformed component made of plastic material, which is extremely cost-effective and lightweight. The use of the molded insert 30, in particular, avoids the need for a conical bore within the first rotor shaft part 42, the production of which would be very cost-intensive. The solution proposed by the invention allows for the appropriate configuration and design of the molded insert 30 to accommodate a wide variety of heat dissipation requirements and installation conditions.

[0048] The invention is not limited to the embodiments described here and the aspects highlighted therein. Rather, numerous modifications are possible within the scope of the claims, which are within the scope of one skilled in the art.

Claims

Claims 1. Electrical machine (10) with a rotor (12) which is received on a rotor shaft (18) which has a first rotor shaft part (42) and a second rotor shaft part (44) which are joined to one another at a connection (46), wherein a cavity (20) is formed in the rotor shaft (18), characterized in that a shaped insert part (30) made of a plastic material is inserted in a rotationally fixed manner into the cavity (20) of the rotor shaft (18), through which a cooling medium flows.

2. Electrical machine (10) according to claim 1, characterized in that the shaped insert part (30) has an inlet (56) and an outlet (58) through which the shaped insert part (30) is flowed through by cooling medium, or the shaped insert part (30) has an inlet (56) for the cooling medium, which exits from the rotor shaft (18) into the electrical machine (10) via radial bores (22) and / or outlet nozzles (74).

3. Electrical machine (10) according to claims 1 and 2, characterized in that the connection (46) between the first rotor shaft part (42) and the second rotor shaft part (44) is designed as a material-locking connection (48), in particular as a weld seam, or as a force-locking connection (50), in particular as a press fit.

4. Electrical machine (10) according to claims 1 to 3, characterized in that the cavity (20) in the rotor shaft (18) is delimited by an inner circumferential surface (54) against which the shaped insert (30) in double-walled design (32), in spiral form (60), in meander form (68) and in complementary form (78) bears in contact (66) with respect to the cavity (20) of the rotor shaft (18). Electrical machine (10) according to claims 1 to 4, characterized in that the shaped insert (30) in a double-walled design (32) has an outer wall (34) and an inner wall (36) that delimit an annular space (38). Electrical machine (10) according to claim 5, characterized in that outlet openings (40) in the outer wall (34) are aligned with radial bores (22) of a shaft casing (24) of the rotor shaft (18) and allow the cooling medium to escape into the electrical machine (10). Electrical machine (10) according to claims 1 to 4, characterized in that the shaped insert (30) in a spiral shape (60) comprises individual turns (62) that are arranged at a distance (64) from one another.Electrical machine (10) according to claims 1 to 4, characterized in that the shaped insert (30) in a meander shape (68) comprises individual meander sections (69) that extend in an axial orientation (70) within the cavity (20) of the rotor shaft (18). Electrical machine (10) according to claims 1 to 4, characterized in that the shaped insert (30) is designed in a tubular shape (72) and outlet nozzles (74) extend in the direction of the radial bore (22) of the shaft casing (24) of the rotor shaft (18). Electrical machine (10) according to claims 1 to 4, characterized in that the shaped insert (30) in complementary form (78) fills the cavity (20) of the rotor shaft (18) and comprises outlet nozzles (74) which are aligned with the radial bore (22) in the shaft casing (24) of the rotor shaft (18).Electrical machine (10) according to claims 1 to 4, characterized in that the insert part (30) in tubular form (72) and the insert part (30) in complementary form (78) are sealed by a sealing ring (76) in the first rotor shaft part (42). Use of the electric machine (10) according to one of claims 1 to 11 in an electric axle module of an electrically driven vehicle.

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