Electric machine with integrated eddy current brake

Abstract

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

Description

Technical Field

[0001] The invention relates to an electric machine having at least one rotor which is received on a shaft. The invention also relates to the use of an electric machine having at least one integrated eddy current brake as a central brake at the front and / or rear axle of an electrically driven vehicle. Background Art

[0002] DE 212014000218 U1 relates to a clutch device and a motor vehicle drive train. An internal combustion engine and an electric machine with a stator and a rotor and a transmission device are accommodated in the drive train. The clutch device is arranged in the drive train between the internal combustion engine and the electric machine on the one hand and the transmission device on the other hand. The actuating device comprises an electric eddy current brake having a brake stator and a brake rotor, wherein the brake stator has an inner stator with a central coil.

[0003] DE 102018201689 A1 relates to a method for operating a brake system for a motor vehicle and a corresponding brake system. The brake system has an eddy current brake mechanically coupled to at least one wheel of the motor vehicle, which is used to provide a braking force acting on the wheel. The electric motor is mechanically coupled to the wheel or can be coupled thereto and is electrically connected to the eddy current brake. It is provided that the eddy current brake is loaded in parallel with energy provided by the electric motor operating as a generator and electrical energy obtained from an energy storage device in order to brake the wheel in an emergency braking operation mode.

[0004] DE 102012210130 relates to a wheel drive unit for a wheel of an electrically driven vehicle. The wheel drive unit comprises an electric motor having a stator and a rotor rotatably mounted on the stator, as well as an electronic control device for actuating the electric motor and an eddy current brake, by means of which the rotor is braked. The eddy current brake does not require an additional mechanical brake; the supply and control are also achieved by means of the existing power electronics of the electric motor. In a design variant, the eddy current brake has a disk formed of a metallic material, which is connected to the rotor in a rotationally fixed manner, extends in a radial direction perpendicular to the axis of rotation of the rotor, and in which eddy currents are generated for braking the rotor.

[0005] DE 102004007434 A1 relates to an electric motor having a rotor, a stator and a shaft arranged coaxially with respect to the axis of rotation, and having an eddy current brake with at least one braking magnet. The integration of the eddy current brake into the electric machine instead of a conventional external brake for braking the motor is achieved by utilizing components that are at least partially already present in the electric machine. Preferably, the magnet of the eddy current brake is coupled to the rotor in a rotationally fixed manner and comprises in particular a magnetic ring which is arranged coaxially with respect to the axis of rotation and is mounted on the rotor via a carrier component. The conductor of the eddy current brake is preferably formed by a fixed metal disk or a flange.

[0006] DE 10 2009 006 196 A1 has as its subject matter an axle which, in one embodiment, is coupled to an electric machine and has an eddy current brake as a braking device.

[0007] Electrically driven vehicles are braked in particular by means of recuperation by means of an electric motor which is operated in generator mode. Nevertheless, hydraulically actuated friction brakes are installed in today's electrically driven vehicles, as in vehicles with internal combustion engines. This is because the electric motor is operated in the field weakening region when braking at high rotational speeds of the electric motor. This means that the braking torque of the electric motor which is operated in generator mode is typically not sufficient for emergency braking at high vehicle speeds. In terms of availability, in contrast to hydraulic brake systems, it cannot be assumed that the electric motor which is operated in generator mode will always be able to provide the necessary braking torque. Summary of the invention

[0008] According to the invention, an electric machine is proposed, which has at least one rotor in the form of a disk, which is received on a shaft. At least one rotor in the form of a disk is provided with a brake disk of an eddy current brake on the side. The solution proposed according to the invention makes it possible, in particular, on the one hand, for the eddy current brake to be integrated into the electric machine, that is, it is in this sense associated with the central brake, and on the other hand, the solution proposed according to the invention makes it possible to use the at least one rotor doubly, for example, in an electric machine designed as an axial flux machine. This means that the rotor serves, on the one hand, as a brake disk for at least one eddy current brake and, on the other hand, as a carrier for permanent magnets, for example, which are installed 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, thereby saving installation space and achieving a particularly compact construction unit consisting of the electric machine and the eddy current brake.

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

[0011] An advantageous further development of the electric machine according to the invention is that the eddy current brake has a plurality of coils arranged distributed along its circumference, wherein the coils each include a winding and an iron core. The brake torque that can be generated can be set or predetermined according to the number of coils arranged at the circumference of the eddy current brake.

[0012] In an advantageous embodiment of the electric machine proposed according to the invention, the electric machine comprises a coil and at least one back-sealing element assigned to the coil.

[0013] In the electric machine proposed according to the invention, the brake disk is designed with a disk thickness of between 5 mm and 25 mm, preferably between 10 mm and 20 mm, on the back side of at least one rotor. The brake disk is made of an electrically and magnetically conductive material, such as, for example, gray cast iron. The thermal properties of the brake disk can be set by the disk thickness, that is, how much energy can be absorbed can be determined.

[0014] In a particularly advantageous development of the electric machine proposed according to the invention, such an electric machine, which is designed, for example, as an axial flux machine, can be provided with a first rotor and a second rotor, each of which is designed in the form of a disk and each of which is assigned an eddy current brake. This results in a particularly compact design of the electric machine, which is designed, for example, as an axial flux machine, in which case the back sides of the two essentially disk-shaped rotors serve as brake disks for the eddy current brakes.

[0015] In an advantageous development of the electric machine proposed according to the invention, the electric machine is provided with a first and a second rotor which, in the case of an axial flux machine, have magnets, in particular permanent magnets, on their sides facing one another.

[0016] In an advantageous development of the electric machine proposed according to the invention, the coils of the electric machine are arranged on the sides of the first and second rotors which are designed in the form of a disk.

[0017] In the motor according to the present invention, the coils of the motor each include a winding and an iron core. In the motor according to the present invention, the shaft of the motor is connected to at least one front wheel and / or at least one rear wheel of an electrically driven vehicle either through a transmission or directly.

[0018] The invention further relates to the use of an electric machine having at least one integrated eddy current brake as a central brake at the front axle and / or the rear axle of an electrically driven vehicle.

[0019] Advantages of the present invention.

[0020] The electric machine proposed according to the invention and the eddy current brake integrated into the electric machine make it possible to realize a central brake of particularly compact design. The electric machine comprises at least one rotor, which is essentially disc-shaped, and a plurality of magnets, which can be permanent magnets, for example. The advantages of an electric machine, which is designed, for example, as an axial flux machine, are the short construction, which saves installation space, and the high torque density. In the solution proposed according to the invention, the back side of at least one rotor of the electric machine is used as a brake disk, so that the component can be used in a dual manner, which can significantly save the material that would otherwise be used and the weight that would otherwise be generated and the costs that would otherwise be invested.

[0021] In an advantageous design variant, a very short electric motor can be accommodated in a housing, at the end sides of which, for example, eddy current brakes are respectively arranged, which interact with brake disks respectively arranged on the back sides of the two rotors of the electric motor, wherein the rotors are connected to the shaft of the electric motor in a rotationally fixed manner.

[0022] Thus, two eddy current brakes can be integrated into the housing of the electric machine without significantly increasing the housing length, so that a compact design is also achieved. In the electric machine proposed according to the invention, its shaft can either be connected to at least one front wheel or rear wheel of an electrically driven vehicle with an interposed transmission, or the electric machine, for example in the form of an axial flux machine, can be connected directly to at least one wheel mounted on the front and / or rear axle of the electrically driven vehicle.

[0023] As already mentioned above, the electric machine with an integrated eddy current brake according to the invention can be designed, for example, as an axial flux machine, which comprises a plurality of magnets, in particular permanent magnets. It goes without saying that there are also possibilities for the electric machine to be designed as a magnet-free machine, for example as an asynchronous machine, a reluctance machine or an electrically excited synchronous machine. At least one eddy current brake can also be integrated into these types of electric machines. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0025] in:

[0026] Figure 1 A schematic diagram of an electrically driven vehicle with an electric machine having an associated transmission and an eddy current brake is shown, and

[0027] Figure 2 A schematically illustrated section through an electric machine, which is designed here, for example, as an axial flux machine, is shown, in the housing of which an eddy current brake is integrated. DETAILED DESCRIPTION

[0028] 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.

[0029] Figure 1 An electrically driven vehicle 10 is shown, which comprises a front axle 12 and a rear axle 38. A left front wheel 14 and a right front wheel 16 are accommodated on the front axle 12, which are respectively assigned a left wheel brake 18 and a right wheel brake 20. The wheel brakes 18, 20 are conventional, hydraulically actuated service brakes. The electrically driven vehicle 10 also comprises an eddy current brake 22, which is assigned to an electric motor 24. The electric motor is also assigned a transmission 26, which comprises an output 28. The transmission 26 drives a differential wheel 32 of a differential 30 via its output 28.

[0030] A first output shaft 34 extends laterally from the differential 30 to a rear wheel 40 on the left, and a second output shaft 36 extends laterally from the differential 30 to a rear wheel 42 on the right. The two output shafts 34, 36 form a rear axle 38 of the electrically driven vehicle. Figure 1 In the illustration, in contrast to the front axle 12, no service brake is arranged at the rear axle 38 of the electrically driven vehicle 10. The function of the central brake with respect to the rear axle 38 is assumed by the eddy current brake 22 assigned to the electric motor 24. Figure 1 In the schematic diagram in FIG. 1 , the electric machine 24 of the electrically driven vehicle 10 is operated in motor mode by power electronics not shown in greater detail here; in addition, the braking torque in the recuperation operation of the electric machine 24 is generated by its operation in generator mode. The differential 30 is driven via a transmission 26, which is not absolutely necessary.

[0031] exist Figure 1 The electrically driven vehicle 10 shown in the figure is, for example, a vehicle in which the electric machine 24 is designed in the form of an axial flux machine 48. The axial flux machine 48 is distinguished by a short structural form and a very high torque density. The electric machine 24 can alternatively also be an electric machine designed without magnets, such as, for example, an asynchronous machine, a reluctance machine or an electrically excited synchronous machine. Therefore, a large number of electric machine types can be used for the solution proposed according to the invention.

[0032] according to Figure 2 The motor 24 according to the present invention is described in more detail. Figure 2 Implemented as an axial flux machine.

[0033] By following Figure 2As can be seen from the illustration, the electric machine 24 comprises a housing 50. The eddy current brake 22 is integrated into the housing 50 of the electric machine 24, which is designed here as an axial flux machine 48. At least one first rotor 58 is received on the shaft 52 of the electric machine 24, which is designed here as an axial flux machine 48. Magnets, in particular permanent magnets 70, are arranged on the sides of the first rotor 58 of the axial flux machine 48. The brake disk 54 of the eddy current brake 22 integrated into the housing 50 of the axial flux machine 48 is located on the back side of the first rotor 58, which is designed essentially in the form of a disk. By Figure 2 The diagram shows that the brake disc 54 is implemented with a disc thickness 56. The thickness of the brake disc 54 is in the range between 5 mm and 25 mm, preferably between 10 mm and 20 mm. The thickness of the brake disc 54 is particularly relevant for its thermal properties, because it determines the thermal mass and thus how much energy can be absorbed. In a possible embodiment, the disc thickness of the brake disc 54 is 15 mm. The material of which the brake disc 54 is made is a material that is both electrically conductive and magnetically conductive. The speed range is set by the electrical conductivity. For example, gray cast iron provides the best electrical conductivity.

[0034] In addition, Figure 2 It can be seen that the eddy current brake 22 integrated into the housing 50 of the axial flux motor 48 shown here by way of example comprises a plurality of coils 62. These coils 62 are arranged along the circumference of the eddy current brake 22 and each comprise a winding 64, which extends around a core 66 which receives the winding 64. The coil 62 is assigned a backing element 68. The end side of the eddy current brake 22 is at a small distance from the end side of the brake disk 54, which is received on the back side of the first rotor 58.

[0035] The axial flux motor 48 shown here by way of example is Figure 2 The cross-sectional view in FIG. 4 further shows that a second rotor 60 is received on the shaft 52 of the axial flux motor 48. On the side of the second rotor 60 facing the permanent magnets 70 of the first rotor 58, permanent magnets 70 are also arranged in a distributed manner on the circumference thereof, wherein the number of permanent magnets 70 corresponds to the number of permanent magnets 70 received on the corresponding side of the first rotor 58. The coils 72 of the motor 24, which is configured as an axial flux motor 48 here by way of example, extend between the corresponding permanent magnets 70 on the mutually facing sides of the first rotor 58 or the second rotor 60. Each of the coils 72 of the motor 24 configured as the axial flux motor 48 includes a winding 74 received on a corresponding iron core 76. In this embodiment, the number of coils 72 of the motor 24 configured as the axial flux motor 48 corresponds to the number of pairs of permanent magnets 70 facing each other on the mutually opposite sides of the first rotor 58 and the second rotor 60.

[0036] The axial flux motor 48 Figure 2 The second shaft 52 shown interrupted in the figure is either connected in the middle with Figure 1 In the case of the schematically indicated transmission 26 , it is connected to at least one front wheel 14 , 16 of the electrically driven vehicle 10 , or is connected in a direct path to at least one front wheel 14 , 16 of the front axle 12 and / or at least one rear wheel 40 , 42 at the rear axle 38 , which is formed by a first output shaft 34 and a second output shaft 36 .

[0037] In accordance with Figure 2 In the illustration of , the eddy current brake 22 is integrated into the housing 50, in particular assigned to its end side. Figure 2 As an alternative to the design variant shown in , there is the possibility of also attaching a brake disk 54 on the back side of the second rotor 60 and providing a further eddy current brake 22 integrated into the housing 50 opposite the second rotor in a part of the housing 50 that is not shown. As a result, the axial length of the axial flux motor 48 is not significantly increased, so that disadvantages with regard to the installation space requirement are avoided, but the advantages of a high power density and a high braking torque configuration are obtained.

[0038] By the solution proposed according to the present invention, according to Figure 2 , one and the same component, namely the first rotor 58 and optionally the second rotor 60, which is non-rotatably associated with the shaft 52, can be utilized in a dual manner: On the one hand, the sides of the first rotor 58 and the second rotor 60 facing each other are used to receive permanent magnets 70, between which the coils 72 of the electric machine 24, which is designed as an axial flux machine 48, extend. On the other hand, the brake disks 54 of the associated eddy current brakes 22 can be arranged on the back side of the first rotor 58 and optionally the second rotor 60. Therefore, the dual use of the rotors 58, 60 results in a significant saving of material and thus a significant reduction in costs and weight.

[0039] The invention further relates to the use of an electric machine 24, which is designed here by way of example as an axial flux machine 48, in an electrically driven vehicle 10. The electric machine 24, which is designed here as an axial flux machine 48, is distinguished by a high power density and a short axial design. If, according to the solution proposed according to the invention, at least one eddy current brake 22 is integrated into a housing 50 of the axial flux machine 48, a compact construction unit is obtained which, in addition to a high torque density and thus a high operating capacity, can also act as a central brake to apply high torques, for example to a motor. Figure 1 On a rear axle 38 of the electrically driven vehicle 10 shown schematically in FIG.

[0040] The invention is not limited to the embodiments described herein and the aspects highlighted therein. Rather, multiple variants are possible within the scope of the work of a person skilled in the art within the scope defined by the claims.

Claims

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

2. The electric machine (24) according to claim 1, characterized in that The eddy current brake (22) is integrated into a housing (50) of the electric machine (24).

3. The electric machine (24) according to claim 1 and 2, characterized in that An eddy current brake (22) of a brake disk (54) within the housing (50) is located opposite the at least one rotor (58, 60).

4. The electric machine (24) according to claim 1, characterized in that The eddy current brake (22) has a plurality of coils (62) distributed along its circumference, each of which includes a winding (64) and an iron core (66).

5. The electric machine (24) according to claim 4, characterized in that Each of the coils (62) is assigned a back-sealing element (68).

6. The electric machine (24) according to claim 1, characterized in that The brake disk (54) is designed with a disk thickness (56) of between 5 mm and 25 mm, preferably between 10 mm and 20 mm, and is produced from an electrically and magnetically conductive material.

7. The electric machine (24) according to claim 1, characterized in that The electric machine (24) has a first rotor (58) and a second rotor (60), each of which is disk-shaped and each of which is assigned an eddy current brake (22).

8. The electric machine (24) according to claim 1, characterized in that The electric machine (24) has a first rotor and a second rotor (58, 60), which have magnets, in particular permanent magnets (70), on their sides facing each other.

9. The electric machine (24) according to claim 8, characterized in that Coils (72) of an electric machine (24), in particular an axial flux machine (48), are arranged between mutually opposing magnets, in particular permanent magnets (70) on the sides of a first rotor (58) and a second rotor (60) which are embodied in the form of a disk.

10. The electric machine (24) according to claim 1, characterized in that The coil (72) of the motor (24) includes 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 motor (24) is connected to at least one front wheel (14, 16) and / or at least one rear wheel (40, 42) of the electrically driven vehicle (10) via a transmission (26) or directly.

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

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