Motor

Abstract

The invention relates to an electric machine (10) having 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 engage with each other at a connection (46), a cavity (20) being formed in the rotor shaft (18). According to the invention, a molded insert (30) made of a plastic material is embedded in the cavity (20) of the rotor shaft (18) in a rotationally fixed manner, through which a cooling medium flows. The invention further relates to the use of an electric motor (10) in an electric axle module of an electrically driven vehicle.

Description

Technical Field

[0001] The invention relates to an electric machine having a rotor which is received on a rotor shaft which comprises a first rotor shaft part and a second rotor shaft part which are joined to one another at a connection, wherein a cavity is formed in the rotor shaft. A shaped insert made of plastic material is inserted in a rotationally fixed manner into the cavity of the rotor shaft and through which a cooling medium flows. The invention also relates to the use of the electric machine in an electric axle module of an electrically driven vehicle. Background Art

[0002] DE 10 2020 207 000 A1 is concerned with a device for an electric machine, which comprises a rotor, an exciter device and an integrated energy transmission system. In a preferred embodiment, the energy transmission system comprises an exciter stator and an exciter rotor. The exciter stator is preferably made of a plastic material, extends into the exciter rotor and can have holes designed as longitudinal holes or channels in order to cool the exciter stator from the inside, in particular with air, water and / or oil as a coolant. Such cooling can avoid overheating of the energy transmission device in the cavity of the motor rotor shaft and increase efficiency.

[0003] DE 10 2021 105 084 A1 discloses oil cooling by direct injection cooling at an electric motor. In one embodiment, the system can have: a shaft with an oil line extending axially therein; and a plurality of openings as fluid couplings relative 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. The oil can then be supplied to the oil line, for example, by an oil cooling system, which is coupled to the electric motor via at least one rotor and at least one valve. Thus, the temperature of the electric motor during operation can be reduced without the need to add a cooling jacket or a fan and therefore without increasing the weight or complexity of the motor.

[0004] DE 10 2015 218 620 A1 is about a housing for an electric machine, which mainly comprises an outer housing, an inner housing and a jacket intermediate space with cooling ribs, which are used to form a cooling channel extending in a spiral shape. The cooling ribs are constructed as independent plastic parts and are inserted into the intermediate space. According to the disclosure, the cooling ribs extend in the axial direction and also extend into the bottom intermediate space for cooling the bearings for the rotor shaft, where the cooling ribs extend further in the radial direction. Preferably, the outer housing and the cooling ribs constructed on the outer housing are made of aluminum or plastic material, especially polyamide or polypropylene, at low cost.

[0005] In electric machines, there is a need to cool the stator, its winding heads and the rotor. This is usually achieved by means of a cooling medium. The cooling medium, for example, enters the inner region of the electric machine through radially and axially extending holes via the rotor shaft and cools the winding heads there. However, since the holes in the rotor shaft usually have a large diameter, the flow of the cooling medium, in particular oil, in the rotor shaft depends strongly on the rotational speed of the electric machine in order to enter close to the rotor lamination stack and cool it better there. In the case of a small diameter of the rotor hole in the rotor shaft, the cooling medium cannot enter sufficiently close to the lamination stack, whereby the cooling performance is significantly reduced. Summary of the invention

[0006] According to the invention, an electric machine is proposed, which has a rotor, which is received on a rotor shaft, which comprises a first rotor shaft part and a second rotor shaft part which are joined to each other at a connection, wherein a cavity is formed in the rotor shaft. A molded insert made of plastic material is inserted into the cavity of the rotor shaft in a rotationally fixed manner, through which a cooling medium flows.

[0007] The solution proposed according to the invention provides an easily and cost-effective way to achieve a uniform distribution of the cooling medium in the electric machine. The insert made of plastic material is particularly fixedly mounted in the rotor shaft, which represents a significantly more cost-effective solution.

[0008] In an advantageous further embodiment of the electric machine according to the invention, the insert has an inlet and an outlet through which a coolant flows, or the formed insert has an inlet for a coolant which flows from the rotor shaft into the electric machine through radial holes and / or outlet nozzles.

[0009] In an advantageous further embodiment of the electric machine according to the invention, the connection between the first rotor shaft part and the second rotor shaft part of the rotor shaft is designed as a material-locked connection, in particular as a weld seam, or as a friction-locking connection, in particular as a press fit. Due to the at least two-part design of the rotor shaft, the insert can be very easily pushed axially into one of the rotor shaft parts and mounted there before the complete rotor shaft is produced by the connection to the other, second rotor shaft part.

[0010] In an advantageous further embodiment of the electric machine proposed according to the invention, the cavity in the rotor shaft or in one of the rotor shaft parts is delimited by an inner circumferential surface, on which the formed insert abuts against the abutment in a double-walled embodiment, in a meandering shape or in a complementary shape to the cavity of the rotor shaft. This solution makes it possible to achieve an improved heat transfer between the rotor core and the coolant, since a heat-conducting, closed and larger contact surface is achieved, which facilitates the heat transfer from the winding or the winding head of the rotor core to the coolant.

[0011] In an advantageous embodiment of the electric machine according to the invention, the molded insert in a double-walled embodiment is provided with an outer wall and an inner wall which delimit the annular chamber. In addition, in this embodiment variant, it is provided in the electric machine according to the invention that the outflow opening in the outer wall of the molded insert in a double-walled embodiment is aligned with the radial hole on the circumference of the rotor shaft. A cooling medium, for example oil, enters the interior of the electric machine through the outflow opening. Preferably, the winding heads of the stator of the electric machine are injected in this process so that the waste heat generated there can be discharged.

[0012] In a further advantageous embodiment variant of the electric machine proposed according to the invention, the shaped insert is designed in the shape of a spiral and comprises individual turns which are arranged at a distance from one another. In this embodiment, the individual turns of the shaped insert having a spiral shape can contact the inner circumference of the rotor shaft in order to enable heat conduction. In addition, the shaped insert having a spiral shape is self-centering when installed in the cavity of the rotor shaft.

[0013] In a further advantageous embodiment variant of the electric machine according to the invention, the formed insert is designed in a meandering shape, comprising individual meandering sections which extend in the axial direction in the cavity of the rotor shaft. The individual meandering sections achieve continuous contact when viewed in the axial orientation, so that in this embodiment variant, good heat dissipation or good heat transfer from the components in the form of winding heads and winding laminations received on the rotor shaft to the cooling medium is also possible.

[0014] In a further advantageous embodiment variant of the electric machine proposed according to the invention, the shaped insert is embodied in the form of a tube, wherein the outflow nozzles extend from the insert in radial direction towards a radial bore formed in the circumference of the rotor shaft.

[0015] Advantageously, outflow nozzles extending radially from the tubular, formed insert are aligned with radial holes on the circumference of the rotor shaft.

[0016] In a further advantageous embodiment of the electric machine according to the invention, the formed insert can also be embodied in a complementary shape to the inner contour of the cavity of the rotor shaft and likewise comprise an outflow nozzle which is aligned with a radial hole embodied in the circumference of the rotor shaft.

[0017] In an embodiment variant of the electrical machine, in which the formed insert is designed in the shape of a tube or the formed insert is designed in a complementary shape, a sealing system is produced by a sealing ring arranged in the first rotor shaft part.

[0018] The invention further relates to the use of an electric machine in an electric axle module of an electrically driven vehicle.

[0019] Advantages of the present invention.

[0020] The solution proposed according to the invention makes it possible to realize a rotor shaft in a manufacturing-friendly and cost-effective manner, which can be manufactured as a standard component. In particular, a conical bore in the interior of one of the rotor shaft parts, which is particularly complex in terms of manufacturing and would therefore have a very negative impact on manufacturing costs, can be avoided.

[0021] The solution proposed according to the invention makes it possible to provide a shaped insert for homogenizing the coolant distribution and thus the temperature level in the rotor assembly of an electric machine. By means of the briefly described embodiment variants of the shaped insert in the form of a double-walled embodiment, in a spiral shape, in a meandering shape, in a tubular shape or in a complementary shape to the cavity of the rotor shaft, different installation requirements can be taken into account and different temperature distribution gradients can be achieved. The fact that the shaped insert is made of a plastic material is advantageous in terms of the weight of the shaped insert and in terms of the geometric design, since a variety of geometries can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

[0023] in:

[0024] Figure 1 shows a longitudinal section through a one-piece rotor shaft of an electric machine according to the prior art,

[0025] Figure 2 A first embodiment variant is shown in longitudinal section through an electric machine according to the invention with a shaped insert.

[0026] Figure 3 A second embodiment variant shows a longitudinal section through an electric machine according to the invention with a shaped insert.

[0027] Figure 4 A further third embodiment variant of a formed insert received in a multi-part rotor shaft is shown.

[0028] Figure 5 A fourth embodiment variant of a shaped insert is shown, which is inserted into a rotor shaft part of an electric machine according to the invention, and

[0029] Figure 6 A fifth embodiment variant of a shaped insert is shown which is shaped complementarily to a cavity of one of the rotor shaft parts of a multi-part rotor shaft. DETAILED DESCRIPTION

[0030] By following Figure 1 The illustration of FIG. 1 shows an electric motor 10 having a rotor 12 that rotates relative to a stator 14 that is accommodated in the housing of the electric motor 10. A laminated core 13 is accommodated on the rotor 12, while the stator 14 comprises windings that each include a protruding winding head 15 at their ends. A running tooth system 16 is implemented on a rotor shaft 18 that is constructed in one piece here. According to FIG. Figure 1 , the rotor shaft 18 comprises a cavity 20 , from which a coolant distribution can be achieved via radial holes 22 provided in the shaft circumference 24 .

[0031] In the following description of embodiments of the invention, identical or similar elements are denoted by the same reference numerals, wherein a repeated description of these elements is omitted in individual cases. The figures merely schematically illustrate the subject matter of the invention.

[0032] Figure 2 A first embodiment variant of a shaped insert 30 is shown, which is inserted into a multi-part rotor shaft 18 of an electric machine 10 according to the invention.

[0033] By following Figure 2 The illustration shows that the insert 30 in the double-walled embodiment 32 is inserted in a rotationally fixed manner into the cavity 20 of the first rotor shaft part 42. In the double-walled embodiment 32 of the molded insert 30, the insert comprises an outer wall 34 and an inner wall 36. The outer wall 34 and the inner wall 36 delimit an annular chamber 38, through which flows a cooling medium, for example oil, which enters the molded insert 30 laterally via a sleeve at the end face of the first rotor shaft part 42. Sealing is achieved by a sealing ring 76.

[0034] The outflow opening 40 is located in the outer wall 34 of the double-walled embodiment 32 of the molded insert 30. In the molded insert 30 of the double-walled embodiment 32, which is mounted in a rotationally fixed manner in the cavity 20, the outflow opening 40 is aligned with the radial hole 22 located in the axial circumference 24 of the rotor shaft 18. By means of the molded insert 30, which is preferably manufactured as a molded part made of plastic material, a targeted and efficient cooling of the component in the form of a winding part received at the circumference of the rotor shaft 18 is achieved. In addition, the solution proposed according to the invention makes it possible to achieve efficient cooling of the winding heads 15 of the stator 14. A cooling medium, in particular oil for cooling, is preferably injected into the winding heads 15 extending laterally on the stator 14 in order to cool the winding heads and thereby discharge the waste heat generated.

[0035] In accordance with Figure 2 The formed insert 30 of the double-walled embodiment 32 is installed, for example, in the axial direction into the cavity 20 of the first rotor shaft component 42. After the formed insert 30 is fixedly secured in the cavity 20 of the first rotor shaft component 42 in a rotationally fixed manner, the first rotor shaft component 42 and the second rotor shaft component 44 are joined to each other at the connection 46. The connection 46 can be produced as a material-locked connection 48, in particular in the form of a weld seam, or as a friction-locking connection 50, for example as a press fit. As described above, the possible configurations of the connection 46 as a material-locked connection 48 and a friction-locking connection 50 involve the following: Figures 3 to 6 The present invention relates to all embodiment variants of the formed insert 30 .

[0036] In order to improve the heat transfer to the cooling medium, the insert 30 is formed in accordance with Figure 2 In the embodiment variant of , it is arranged as close as possible to the inner circumference 54 of the axial circumference 24 of the first rotor shaft part 42. The position 52 represents a rolling bearing in which the second rotor shaft part 44 of the rotor shaft 18, which is designed in multiple parts here, is rotatably received in the housing of the electric machine 10.

[0037] In accordance with Figure 3 The illustration of shows a second embodiment variant of a shaped insert 30 proposed according to the invention, which is embedded in the rotor shaft 18 of the electric machine 10 .

[0038] By following Figure 3 The illustration shows that in this embodiment variant of the shaped insert 30, the insert has a helical shape 60. The helical shape 60 of the shaped insert 30 according to the second embodiment variant comprises a plurality of individual turns 62, which can be arranged at regular or irregular intervals 64 within the axial length of the shaped insert 30. Figure 3The individual turns 62 of the molded insert 30 of the second embodiment variant are located in abutment 66 with respect to the inner circumference 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 molded insert 30. Figure 3 In the second embodiment variant shown in , the cooling medium enters the first rotor shaft part 42 via an inlet 56 and leaves it at an increased temperature at an outlet 58, which is also arranged in a lateral, axially oriented sleeve of the first rotor shaft part 42 of the rotor shaft 18. Figure 3 In the second embodiment variant, a coolant flows through the shaped insert 30 .

[0039] according to Figure 4 A further third embodiment variant of the shaped insert 30 proposed according to the invention, which is embedded in the first rotor shaft part 42 of the rotor shaft 18 , can be seen in the illustration of .

[0040] In this embodiment variant, the formed insert 30 essentially has a meander shape 68. The meander shape 68 is characterized by the fact that individual meander sections 69 extend essentially in the axial orientation 70 in the cavity 20 of the first rotor shaft part 42 of the rotor shaft 18. In the third embodiment variant of the formed insert 30, abutment 66 is also obtained between the meander section 69 of the formed insert 30 having the meander shape 68 on the one hand and the inner circumference 54 of the cavity 20 of the first rotor shaft part 42 on the other hand. As a result, a contact surface that is as large as possible and extends evenly with respect to the axial circumference 24 of the first rotor shaft part 42 of the rotor shaft 18 is obtained, which makes it possible to achieve a significantly improved heat transfer from the components mounted on the circumference of the rotor shaft 18 to the cooling medium flowing through the formed insert 30. In the third embodiment variant of the insert in meandering shape 68 , the coolant flows from the inlet 56 through the shaped insert 30 and leaves the shaped insert 30 in meandering shape 68 at the outlet 58 at an increased temperature, which is caused by the heat dissipation.

[0041] By following Figure 4 The illustration shows that the inserted part 30 formed in the meander shape 68 according to the third embodiment variant occupies almost the entire cavity 20 of the first rotor shaft part 42 and thus fills it, so that a large contact surface is obtained between the inner circumference 54 and the first rotor shaft part 42 of the rotor shaft 18 and the meander section 69, which is beneficial for heat removal.

[0042] By following Figure 5 A further fourth embodiment variant of the formed insert 30 is shown in the diagram of FIG. Figure 5 The fourth embodiment variant shown in FIG. 1 shows a shaped insert 30 which has essentially a tubular shape 72. A tubular body passes through the first rotor shaft part 42 essentially symmetrically to the axis of rotation of the first rotor shaft part 42, from which individual outflow nozzles 74 branch off in an essentially radially oriented manner and are connected, for example, to radial holes 22 embodied in the axial circumference 24 of the first rotor shaft part 42. Thus, in the shaped insert 30, the Figure 5 In the fourth embodiment variant shown in , the cooling medium flows out into the electric machine 10 through the outflow nozzle 74 or the radial holes 22 in the axial circumference 24. In the present case, the electric machine 10 is, for example, an ASM electric motor, which can be cooled with oil. In addition, such an electric machine 10 can also be cooled by means of other cooling media, for example water.

[0043] The formed insert 30 is Figure 5 In the fourth embodiment variant shown in FIG. 5 , the cooling medium flows to the insert via the inlet 56 . With the aid of the sealing ring 76 , the insert 30 formed with respect to the Figures 2 to 6 In the embodiment variant of , the first rotor shaft part 42 of the rotor shaft 18 which is designed in multiple parts is sealed. Instead of the four outflow nozzles 74 shown here branching off essentially radially from the tubular body of the formed insert 30 in the form of a tube 72, further outflow nozzles 74 can also be provided which are aligned with radial holes 22 respectively provided in the axial circumference 24 of the first rotor shaft part 42.

[0044] In accordance with Figure 5 In a variant embodiment, the rotor shaft 18 is also designed separately. The first rotor shaft part 42 and the second rotor shaft part 44 are connected to each other at a connection 46. The connection 46 can be designed as a material-locked connection 48, for example as a weld seam, or as a force-locking connection 50, for example as a press fit, as already mentioned above. Apart from the roller bearing 52 shown schematically, the bearing of the rotor shaft 18, which is designed separately here, is not shown in more detail.

[0045] From following Figure 6 A fifth embodiment variant of a shaped insert 30 made of plastic material is shown in the illustration of FIG. Figure 6 In the fifth embodiment variant shown in FIG. 7 , the insert has a complementary shape 78. In this context, it is understood that the shaped insert 30 is designed to be complementary to the geometry of the cavity 20 in the first rotor shaft part 42. The shaped insert 30 is formed in accordance with the geometry of the cavity 20 in the first rotor shaft part 42. Figure 6In the fifth embodiment variant of the present invention, the outlet nozzles 74 are cylindrical and are located with their circumferential side faces in the abutment 66 against the inner circumference 54 of the first rotor shaft part 42 of the rotor shaft 18 of the electric machine 10. The individual outlet nozzles 74 on the insert 30 formed according to the complementary shape 78 in the fifth embodiment variant are aligned with the radial holes 22, which are separately implemented in the axial circumferential side 24 of the first rotor shaft part 42 of the rotor shaft 18. As a result, the cooling medium flows out from the axial circumferential side 24 in the direction of the electric machine 10 through the outlet nozzles 74 or radial holes 22.

[0046] In accordance with Figure 6 In the fifth embodiment variant of the molded insert 30, the cooling medium also enters the molded insert 30 through the inlet 56 of the sleeve at the first rotor shaft part 42 and flows radially outward from the inside. Figure 6 In the fifth embodiment variant of , the first rotor shaft part 42 of the rotor shaft 18 , which is designed here in two parts, is sealed.

[0047] The insert 30 formed in a complementary shape 78 to the cavity 20 of the first rotor shaft part 42 is formed in Figure 6 In the fifth embodiment variant shown in , after the formed insert 30 with the complementary shape 78 has been inserted into the cavity 20 of the first rotor shaft part 42, the second rotor shaft part 44 is also 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-locked connection 48 in the form of a weld seam or as a friction-locking connection 50 in the form of a press fit and is sealed by means of a sealing ring 76.

[0048] according to Figures 2 to 6 All embodiments 1 to 5 of the shaped insert 30 have in common that the insert can be produced very cost-effectively and in a lightweight manner as a preformed component made of plastic material. By using the shaped insert 30, it is possible in particular to avoid a conical bore in the first rotor shaft part 42, which would be very cost-intensive to produce. The solution proposed according to the invention makes it possible to take into account various heat dissipation requirements and installation situations by means of a corresponding configuration and shape of the shaped insert 30.

[0049] The invention is not limited to the embodiments described here and the aspects emphasized therein. Rather, numerous variations are possible within the scope defined by the claims within the framework of practice of a person skilled in the art.

Claims

1. An electric machine (10) having a rotor (12) received on a rotor shaft (18), the rotor shaft having a first rotor shaft part (42) and a second rotor shaft part (44) engaged with each other at a connection (46), wherein: A cavity (20) is formed in the rotor shaft (18), characterized in that a shaped insert (30) made of plastic material is inserted in the cavity (20) of the rotor shaft (18) in a rotationally fixed manner and through which a coolant flows.

2. The electric machine (10) according to claim 1, characterized in that The formed insert (30) has an inlet (56) and an outlet (58) through which a coolant flows, or the formed insert (30) has an inlet (56) for the coolant, which flows out of the rotor shaft (18) into the electric machine (10) through radial holes (22) and / or outlet nozzles (74).

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

4. The electric 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), on which the formed insert (30) abuts against abutment (66) in a double-walled embodiment (32), in a spiral shape (60), in a meandering shape (68) and in a complementary shape (78) with respect to the cavity (20) of the rotor shaft (18).

5. The electric machine (10) according to claims 1 to 4, characterized in that The formed insert (30) in a double-walled embodiment (32) has an outer wall (34) and an inner wall (36) which delimit an annular chamber (38).

6. The electric machine (10) according to claim 5, characterized in that Outflow openings (40) in the outer wall (34) are aligned with radial holes (22) on the circumferential side (24) of the rotor shaft (18) and enable the cooling medium to flow out into the electric machine (10).

7. The electric machine (10) according to claims 1 to 4, characterized in that The insert (30) formed in the shape of a spiral (60) comprises individual turns (62) which are arranged at a distance (64) from one another.

8. The electric machine (10) according to claims 1 to 4, characterized in that The insert (30) formed in a meandering shape (68) comprises individual meandering sections (69) which extend in an axial orientation (70) within a cavity (20) of the rotor shaft (18).

9. The electric machine (10) according to claims 1 to 4, characterized in that The formed insert (30) is designed in a tubular shape (72), and an outflow nozzle (74) extends in the direction of a radial hole (22) on the circumference (24) of the rotor shaft (18).

10. The electric machine (10) according to claims 1 to 4, characterized in that A formed insert (30) of complementary shape (78) fills a cavity (20) of the rotor shaft (18) and comprises an outflow nozzle (74) aligned with a radial bore (22) in a circumferential side (24) of the rotor shaft (18).

11. The electric machine (10) according to claims 1 to 4, characterized in that The insert (30) in the shape of a tube (72) and the insert (30) in the shape of a complementary shape (78) are sealed by means of a sealing ring (76) in the first rotor shaft part (42). 12 . Use of an electric machine ( 10 ) according to claim 1 in an electric axle module of an electrically driven vehicle.

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