Electric machine with integrated eddy current brake

Abstract

The invention relates to an electric machine (24) with at least one disc-shaped designed rotor (58, 60) received on a shaft (52). The at least one disc-shaped designed rotor (58, 60) is provided on one side with a brake disk (54) of an eddy current brake (22). Furthermore, the invention relates to the use of an electric machine (24) with at least one integrated eddy current brake (22) as a central brake on the front axle (12) and / or the rear axle (38) of an electric vehicle (10).

Description

[Technical field]

[0001] The present invention relates to an electric machine with at least one rotor received on a shaft.Furthermore, the present invention relates to the use of an electric machine with at least one integrated eddy current brake as a central brake on the front and / or rear axle of an electric vehicle. [Background technology]

[0002] DE 212014000218 relates to a coupling mechanism and a motor vehicle drive train. The drive train comprises an internal combustion engine, an electric machine with a stator and a rotor, and a transmission mechanism. The coupling mechanism is arranged in the drive train between the internal combustion engine on the one hand and the electric machine and the transmission mechanism on the other hand. The actuation mechanism comprises an electric eddy current brake with a brake stator and a brake rotor, the brake stator having an inner stator with a central coil.

[0003] DE 10 2018 201689 A1 relates to a method for operating a brake system for a motor vehicle and a corresponding brake system. The brake system comprises an eddy current brake mechanically coupled to at least one wheel of the motor vehicle for providing a braking force acting on the wheel. An electric machine is mechanically coupled or coupleable to the wheel and electrically connected to the eddy current brake. Here, it is provided that in an emergency braking operating mode for braking the wheel, the energy provided by the electric machine operated as a generator and the electric energy drawn by the energy storage device are applied in parallel to the eddy current brake.

[0004] DE 102012210130 A1 relates to a wheel drive unit for wheels of an electric vehicle. The wheel drive unit comprises an electric machine with a stator and a rotor rotatably mounted on the stator, an electronic control for controlling the electric machine, and an eddy current brake with which the rotor can be decelerated. The eddy current brake makes an additional mechanical brake unnecessary. It is also supplied and controlled via the existing power electronics of the electric machine. In one variant, the eddy current brake comprises a disk made of a metallic material, which is connected non-rotatably to the rotor and extends radially perpendicular to the axis of rotation of the rotor, in which eddy currents for braking the rotor are generated.

[0005] DE 10 2004 007 434 A1 relates to an electric motor with a rotor, a stator and a shaft arranged coaxially with the axis of rotation and an eddy current brake with at least one brake magnet. The integration of the eddy current brake into the electric machine instead of a conventional external brake for slowing down the motor is realized at least partially by using components already present in the electric machine. The magnets of the eddy current brake are preferably coupled to the rotor in a non-rotatable manner and in particular comprise a magnetic ring, which is arranged coaxially with the axis of rotation and attached to the rotor via a support part. The conductors of the eddy current brake are preferably formed by stationary metal disks or flanges.

[0006] DE 10 2009 006 196 A1 is directed to a vehicle axle which in one embodiment is coupled to an electric machine and which is provided with an eddy current brake as braking mechanism. Electric vehicles are primarily braked regeneratively by the electric machine operated in generator mode. However, today's electric vehicles are equipped with the same hydraulically actuated friction brakes as vehicles with internal combustion engines. This is due to the fact that when braking at high rotational speeds of the electric machine, the electric machine is operated in the field weakening region. This means that at high vehicle speeds, the braking torque of an electric machine operated in generator mode is typically not sufficient for emergency braking. With regard to usability, with an electric machine operated in generator mode, in contrast to hydraulic braking systems, it cannot be assumed that the electric machine is always able to provide the required braking torque. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] German Utility Model No. 212014000218 [Patent Document 2] DE 102018201689 [Patent Document 3] DE 102012210130 [Patent Document 4] DE 102004007434 A1 [Patent Document 5] DE 102009006196 Summary of the Invention [Means for solving the problem]

[0008] According to the invention, an electric machine is proposed with at least one rotor designed in the shape of a disk, which is received on a shaft. The at least one rotor designed in the shape of a disk is provided on one side with a brake disk of an eddy current brake. With the solution proposed according to the invention, it can be achieved in particular that, on the one hand, an eddy current brake can be integrated into the electric machine, i.e., the eddy current brake is assigned to the electric machine as a central brake, and, on the other hand, with the solution proposed according to the invention, at least one rotor can be used in a dual role, for example in an electric machine configured as an axial flux machine. This means that, on the one hand, the rotor serves as a brake disk for at least one eddy current brake and, on the other hand, serves as a support for permanent magnets, which are provided, for example, in an axial flux machine.

[0009] In an advantageous development of the solution proposed according to the invention, in the electric machine proposed according to the invention, the eddy current brake is integrated into the housing of the electric machine, which makes it possible to save installation space and results in a particularly compact construction unit consisting of the electric machine and the eddy current brake.

[0010] In a development of the electric machine proposed according to the invention, the electric machine is designed in such a way that an eddy current brake is arranged in the housing on at least one rotor of the electric machine, directly opposite a brake disc.

[0011] One possible advantageous development of the electric machine proposed according to the invention consists in that the eddy current brake comprises a number of coils arranged distributed around its circumference, each of which comprises a winding and an iron core. Depending on the number of coils arranged around the circumference of the eddy current brake, the possible braking torque can be adjusted or predetermined.

[0012] In an advantageous configuration of the electric machine proposed according to the invention, the electric machine comprises a coil and at least one return element assigned to the coil. In the electric machine proposed according to the invention, the brake disc on the rear side of at least one rotor is designed with a disc thickness between 5 mm and 25 mm, preferably between 10 mm and 20 mm. The brake disc is made from an electrically and magnetically conductive material, for example grey cast iron. Depending on the disc thickness, the thermal properties of the brake disc can be adjusted, i.e. the amount of energy it can absorb can be determined.

[0013] In a particularly advantageous development of the electric machine proposed according to the invention, the electric machine, for example designed as an axial flux machine, is provided with a first rotor and a second rotor, both of which are configured in disk form and each of which is assigned an eddy current brake, whereby in this variant a particularly compact design of the electric machine, for example configured as an axial flux machine, is obtained, in which the rear faces of the two substantially disk-shaped rotors serve as brake disks for the eddy current brake.

[0014] In an advantageous development of the electric machine proposed according to the invention, the electric machine is provided with first and second rotors which, in the case of an axial flux machine, are provided with magnets, in particular permanent magnets, on the sides facing each other.

[0015] In an advantageous development of the electric machine proposed according to the invention, the coils of the electric machine are arranged on said sides of the first and second rotors which are designed in the shape of a disk. In the electric machine proposed according to the invention, the coils of the electric machine each include a winding and an iron core, and the shaft of the electric machine is connected via a transmission or directly to at least one front wheel and / or at least one rear wheel of the electric vehicle.

[0016] Furthermore, the invention relates to the use of an electric machine with at least one integrated eddy current brake as a central brake on the front and / or rear axle of an electrically powered vehicle. Advantages of the Invention The electric machine proposed according to the invention and the eddy current brake integrated therein make it possible to provide a particularly compactly designed central brake. The electric machine comprises at least one rotor configured substantially in the shape of a disk and a number of magnets, which can be, for example, permanent magnets. The advantages of an electric machine designed, for example, as an axial flux machine, lie in its short design, which saves on installation space, and in its high torque density. In the solution proposed according to the invention, the rear surface of at least one rotor of the electric machine is used as a brake disk, so that this component can be used in a dual role, whereby significant savings can be achieved in the material that would otherwise be used and the resulting weight that would otherwise be used, as well as in the costs that would otherwise be spent.

[0017] In an advantageous variant, a very short electric machine can be accommodated in a housing, the end faces of which accommodate, for example, an eddy current brake in each case, which interacts with a brake disk arranged on the rear faces of the two rotors of the electric machine, the rotors being connected to the shaft of the electric machine in a non-rotatable manner relative to each other.

[0018] Thus, two eddy current brakes can be integrated in one housing of the electric machine without a significant increase in the length of the housing, thus giving a more compact design.In the electric machine proposed according to the invention, the shaft of the electric machine can be connected to at least one front wheel or one rear wheel of the electric vehicle via a transmission, or the electric machine, for example configured as an axial flux machine, can be directly connected to at least one wheel located on the front and / or rear axle of the electric vehicle.

[0019] The electric machine with the integrated eddy current brake proposed according to the invention can be designed, as already mentioned above, for example as an axial flux machine with a number of magnets, in particular permanent magnets. It is of course also possible to design the electric machine as an electric machine without magnets, for example as an asynchronous machine, a reluctance machine or an electrically excited synchronous machine. At least one eddy current brake can be integrated into such types of electric machines as well.

[0020] Embodiments of the invention will now be explained in more detail with reference to the drawings and the following description. [Brief description of the drawings]

[0021] [Figure 1] 1 is a schematic diagram of an electric vehicle with a transmission and an electric machine assigned to an eddy current brake; [Diagram 2] 1 is a schematic cross-sectional view of an electric machine, here designed as an axial flux machine by way of example, in whose housing an eddy current brake is integrated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] In the following description of embodiments of the invention, identical or similar elements are designated with the same reference numerals, and in individual cases repeated description of these elements is omitted. The figures only diagrammatically represent the subject matter of the invention.

[0023] 1 shows an electric vehicle 10 including a front axle 12 and a rear axle 38. The front axle 12 receives a left front wheel 14 and a right front wheel 16, to which a left wheel brake 18 and a right wheel brake 20, respectively, are assigned. The wheel brakes 18, 20 are conventional hydraulically actuated service brakes. The electric vehicle 10 further includes an eddy current brake 22 assigned to an electric machine 24. The electric machine 24 further includes a transmission 26, which includes an output 28. The transmission 26 drives a differential gear 32 of a differential 30 via its output 28.

[0024] A first output shaft 34 runs to the left rear wheel 40 and a second output shaft 36 runs to the right rear wheel 42 on the side of the differential 30. The two output shafts 34, 36 form a rear axle 38 of the electric vehicle. According to the illustration in FIG. 1, the rear axle 38 of the electric vehicle 10 is not provided with a service brake, unlike the front axle 12. The central brake function for the rear axle 38 is taken over by an eddy current brake 22 assigned to the electric machine 24. The electric machine 24 of the electric vehicle 10 according to the schematic diagram in FIG. 1 is operated in motor mode by power electronics (not shown in detail here). Furthermore, the operation of the electric machine 24 in generator mode generates a brake torque in the regenerative operation of the electric machine 24. A transmission 26 driving the differential 30 is not necessarily required.

[0025] The electric vehicle 10 shown in Fig. 1 is, for example, one in which the electric machine 24 is configured in the form of an axial flux machine 48. The axial flux machine 48 is characterized by a short construction form and a very high torque density. The electric machine 24 may alternatively be an electric machine configured without magnets, for example an asynchronous machine or a reluctance machine, or an electrically excited synchronous machine. The solution proposed according to the invention is therefore applicable to many machine types.

[0026] The electric machine 24 proposed according to the invention will now be described in more detail with reference to figure 2. According to figure 2, the electric machine 24 is designed as an axial flux machine. From the illustration according to FIG. 2 it can be seen that the electric machine 24 comprises a housing 50. In the housing 50 of the electric machine 24, here configured as an axial flux machine 48, the eddy current brake 22 is integrated. At least a first rotor 58 is received on a shaft 52 of the electric machine 24, here configured as an axial flux machine 48. On one side of the first rotor 58 of the axial flux machine 48, magnets, in particular permanent magnets 70, are arranged. On the rear side of the first rotor 58, which is designed substantially in the shape of a disk, there is a brake disk 54 of the eddy current brake 22, which is integrated in the housing 50 of the axial flux machine 48. From the illustration according to FIG. 2 it can be seen that the brake disk 54 is designed with a disk thickness 56. The thickness of the brake disk 54 is in the range between 5 mm and 25 mm, preferably between 10 mm and 20 mm. The thickness of the brake disk 54 is of particular importance for the thermal properties of the brake disk 54, since it can determine the thermal mass and therefore the amount of energy that can be absorbed. In one possible embodiment, the brake disc 54 has a disc thickness of 15 mm. The material from which the brake disc 54 is made is a material that is both electrically and magnetically conductive. The electrical conductivity adjusts the rotational speed range. For example, grey cast iron provides optimal electrical conductivity.

[0027] 2 further shows that the eddy current brake 22 integrated in the housing 50 of the axial flux machine 48 shown here by way of example comprises a number of coils 62. The coils 62 are arranged around the circumference of the eddy current brake 22 and each comprise one winding 64, which runs around an iron core 66 receiving the winding 64. The coils 62 are assigned a return element 68. An end face of the eddy current brake 22 is located at a short distance relative to an end face of the brake disc 54, which is received on the rear side of the first rotor 58.

[0028] The axial flux machine 48 shown here by way of example according to the cross-sectional view in Fig. 2 also shows that a second rotor 60 is received on the shaft 52 of the axial flux machine 48. On the side of the second rotor 60 facing the permanent magnets 70 of the first rotor 58, the permanent magnets 70 are likewise arranged distributed around its circumference, the number of which corresponds to the number of permanent magnets 70 received on the corresponding side of the first rotor 58. Between the respective permanent magnets 70 on the mutually facing sides of the first rotor 58 and the second rotor 60, the coils 72 of the electric machine 24 configured here by way of example as an axial flux machine 48 extend. Each coil 72 of the electric machine 24 configured as an axial flux machine 48 includes a winding 74, which is received on a corresponding core 76. The number of coils 72 in the electric machine 24, configured in this example as an axial flux machine 48, corresponds to the pairs of opposing permanent magnets 70 on opposite sides of the first rotor 58 and the second rotor 60.

[0029] The second shaft 52 of the axial flux machine 48, shown broken away in FIG. 2, is connected to at least one front wheel 14, 16 of the electric vehicle 10 via the transmission 26 shown diagrammatically in FIG. 1, or is directly connected to at least one front wheel 14, 16 of the front axle 12 and / or at least one rear wheel 40, 42 of the rear axle 38 (formed by the first output shaft 34 and the second output shaft 36).

[0030] In the representation according to Fig. 2, the eddy current brake 22 is integrated into the housing 50 and is in particular assigned to an end face of the housing 50. As an alternative to the variant shown in Fig. 2, it is also possible to attach a brake disk 54 to the rear side of the second rotor 60 and, opposed to this, to provide a further eddy current brake 22 integrated into the housing 50 in a part of the housing 50 not shown. This does not significantly increase the axial length of the axial flux machine 48, which avoids disadvantages in terms of installation space requirements and offers the advantages of a high power density and a high brake torque setting.

[0031] The solution proposed according to the invention allows one and the same component, i.e. the first rotor 58 and possibly also the second rotor 60, which are non-rotatably assigned to the shaft 52, to be used in two roles, according to the illustration in Fig. 2: on the one hand, the mutually facing sides of the first rotor 58 and the second rotor 60 are used to receive the permanent magnets 70, between which run the coils 72 of the electric machine 24 configured as an axial flux machine 48. On the other hand, the brake disks 54 of the eddy current brake 22 assigned to the first rotor 58 and possibly also the second rotor 60 can be arranged on the rear side thereof. This allows considerable savings in material by using the rotors 58, 60 in two roles, which leads to a considerable reduction in costs and weight.

[0032] Furthermore, the invention relates to the use of an electric machine 24, here designed by way of example as an axial flux machine 48, in an electric vehicle 10. The electric machine 24, here designed as an axial flux machine 48, is characterized by a high power density and a short axial design. Furthermore, the solution proposed according to the invention results in a compact structural unit, if at least one eddy current brake 22 is integrated into the housing 50 of the axial flux machine 48, which, in addition to a high torque density and therefore high performance, can also apply high torques as a central brake, for example, on the rear axle 38 of the electric vehicle 10, as shown diagrammatically in FIG.

[0033] The present invention is not limited to the exemplary embodiments and aspects highlighted herein, but rather many modifications are possible within the scope of the invention as understood by those skilled in the art within the scope of the claims.

Claims

1. An electric machine (24) comprising at least one disc-shaped designed rotor (58, 60) received on a shaft (52), characterized in that said at least one disc-shaped designed rotor (58, 60) is provided on one side with a brake disc (54) of an eddy current brake (22).

2. 2. The electric machine (24) of claim 1, wherein the eddy current brake (22) is integrated into a housing (50) of the electric machine (24).

3. 3. The electric machine (24) of claim 1 or 2, characterized in that the eddy current brake (22) faces the brake disc (54) at the at least one rotor (58, 60) within the housing (50).

4. 4. An electric machine (24) according to claim 1, characterized in that the eddy current brake (22) comprises a plurality of coils (62) distributed around its circumference, each of the coils (62) including a winding (64) and an iron core (66).

5. 5. The electric machine (24) according to claim 4, characterized in that each of said coils (62) is assigned a return element (68).

6. 6. An electric machine (24) according to any one of the preceding claims, characterized in that the brake disc (54) is configured with a disc thickness (56) between 5 mm and 25 mm, preferably between 10 mm and 20 mm, and is made from an electrically and magnetically conductive material.

7. The electric machine (24) according to any one of claims 1 to 6, characterized in that the electric machine (24) comprises a first rotor (58) and a second rotor (60), each of which is designed in a disk shape and each of which is assigned one eddy current brake (22).

8. 7. An electric machine (24) according to any one of claims 1 to 6, characterized in that the electric machine (24) comprises first and second rotors (58, 60), the rotors (58, 60) being provided with magnets, in particular permanent magnets (70), on their sides facing each other.

9. 10. An electric machine (24) according to claim 8, characterized in that on the sides of the first rotor (58) and the second rotor (60) designed in the shape of a disk, the coils (72) of the electric machine (24), in particular designed as an axial flux machine (48), are arranged between magnets, in particular permanent magnets (70), which face each other.

10. The electric machine (24) of any one of claims 1 to 9, wherein the coil (72) of the electric machine (24) comprises a winding (74) and an iron core (76).

11. The electric machine (24) according to any one of claims 1 to 10, characterized in that the shaft (52) of the electric machine (24) is connected to at least one front wheel (14, 16) and / or at least one rear wheel (40, 42) of an electric vehicle (10) via a transmission (26) or directly.

12. Use of an electric machine (24) according to any one of claims 1 to 11, comprising at least one integrated eddy current brake (22) as a central brake on a front axle (12) and / or a rear axle (38) of an electric vehicle (10).

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