Electric machine with integrated eddy current brake

Abstract

The invention relates to an electric machine (24) comprising at least one disc-type rotor (58, 60) received on a shaft (52). The at least one disc-type rotor (58, 60) is provided with a brake disc (54) of an eddy current brake (22) on one side. The invention also relates to the use of the electric machine (24) with 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 electrically operated vehicle (10).

Description

[0001] Electric machine with integrated eddy current brake

[0002] Technical area

[0003] The invention relates to an electric machine with at least one rotor mounted on a shaft. Furthermore, the invention relates to the use of the electric machine with at least one integrated eddy-current brake as a central brake on a front axle and / or a rear axle of an electrically powered vehicle.

[0004] State of the art

[0005] DE 21 2014000 218 U1 relates to a clutch device and a motor vehicle drivetrain. The drivetrain includes an internal combustion engine and an electric motor with a stator and a rotor, as well as a transmission device. A clutch device is arranged in the drivetrain between the internal combustion engine on the one hand and the electric motor and the transmission device on the other. An actuating device comprises an electric eddy-current brake with a brake stator and a brake rotor, wherein the brake stator has an internal stator with a central coil.

[0006] DE 10 2018 201 689 A1 relates to a method for operating a braking system for a motor vehicle and a corresponding braking system. The braking 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 to the wheel or can be coupled thereto and is electrically connected to the eddy-current brake. In an emergency braking mode, the eddy-current brake is supplied with energy provided by the electric machine operating as a generator and with electrical energy extracted from an energy storage device in parallel to brake the wheel.

[0007] DE 10 2012 210 130 relates to a wheel drive unit for a wheel of an electrically powered vehicle. The wheel drive unit comprises an electric machine having a stator and a rotor rotatably mounted on the stator, as well as an electronic control device for controlling the electric machine and an eddy current brake, via which the rotor can be braked. The eddy current brake eliminates the need for an additional mechanical brake; likewise, power supply and control are provided via the existing power electronics of the electric machine. In one embodiment, the eddy current brake has a disc made of a metallic material, which is connected to the rotor in a rotationally fixed manner, extends in a radial direction perpendicular to a rotational axis of the rotor, and in which eddy currents are generated to brake the rotor.

[0008] DE 10 2004 007 434 A1 relates to an electric motor with a rotor, a stator, and a shaft arranged coaxially to a rotational axis, and with an eddy-current brake having at least one brake magnet. The integration of an eddy-current brake into an electric machine instead of the usual external brake for braking a motor is achieved by at least partially utilizing components 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, in particular, comprises a magnetic ring arranged coaxially to the rotational axis and attached to the rotor via a support component. The conductor of the eddy-current brake is preferably formed by a fixed metal disc or a flange.

[0009] DE 10 2009 006 196 A1 relates to a vehicle axle which, in one embodiment, is coupled to an electric machine and has an eddy current brake as a braking device.

[0010] Electrically powered vehicles brake primarily in a recuperative manner through the electric motor, which operates in generator mode.

[0011] Nevertheless, today's electrically powered vehicles are equipped with the same hydraulically actuated friction brakes as those found in vehicles with combustion engines. This is because when braking at high speeds, the electric motor operates in the field-weakening range. This means that at high vehicle speeds, the braking torque of the electric motor operating in generator mode is typically insufficient for emergency braking. In terms of availability, unlike a hydraulic braking system, it cannot be assumed that the electric motor operating in generator mode will always be able to provide the required braking torque.

[0012] Description of the invention

[0013] According to the invention, an electrical machine is proposed which has at least one disc-shaped rotor which is received on a shaft. The at least one disc-shaped rotor is provided on one side with a brake disc of an eddy current brake. The solution proposed according to the invention makes it possible in particular to integrate an eddy current brake into the electrical machine, i.e. to assign it to it in the sense of a central brake, and secondly to use the at least one rotor twice, for example in an electrical machine designed as an axial flux machine. This means that the rotor serves on the one hand as a brake disc for the at least one eddy current brake and on the other hand as a carrier for permanent magnets installed, for example, in an axial flux machine.

[0014] In an advantageous development of the solution proposed according to the invention, the eddy-current brake is integrated into the housing of the electrical machine. This saves installation space and results in a particularly compact unit consisting of the electrical machine and eddy-current brake.

[0015] In a further development of the electrical machine proposed according to the invention, it is designed such that the eddy-current brake is located directly opposite the brake disc within the housing on the at least one rotor of the electrical machine. An advantageous further development of the electrical machine proposed according to the invention is that the eddy-current brake has several coils distributed along its circumference, each coil comprising a winding and an iron core. Depending on the number of coils arranged around the circumference of the eddy-current brake, the braking torque that can be generated can be adjusted or predetermined.

[0016] In an advantageous embodiment of the electrical machine proposed according to the invention, it comprises coils and at least one return element associated with them.

[0017] In the electric machine proposed by the invention, the brake disc on the rear side of at least one rotor is designed with a thickness between 5 mm and 25 mm, preferably between 10 mm and 20 mm. The brake disc is made of an electrically and magnetically conductive material, such as gray cast iron. The thermal properties of the brake disc can be adjusted via the thickness, i.e., the amount of energy that can be absorbed can be determined.

[0018] In a particularly advantageous development of the electrical machine proposed according to the invention, this electrical machine, embodied, for example, as an axial flux machine, can be provided with a first rotor and a second rotor, both of which are disk-shaped and each of which is assigned an eddy-current brake. This embodiment thus results in a particularly compact design of an electrical machine embodied, for example, as an axial flux machine, wherein in this case, the rear sides of the two essentially disk-shaped rotors serve as brake disks for eddy-current brakes.

[0019] In an advantageous development of the electrical machine proposed according to the invention, it 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 mutually facing sides. In an advantageous development of the electrical machine proposed according to the invention, coils of the electrical machine are arranged on the sides of the first and second rotor, which are designed in a disc shape.

[0020] In the electric machine proposed according to the invention, the coils of the electric machine each comprise a winding and an iron core. In the electric machine proposed according to the invention, the shaft of the electric machine is connected either via a transmission or directly to at least one front wheel and / or at least one rear wheel of an electrically powered vehicle.

[0021] Furthermore, the invention relates to the use of the electric machine with at least one integrated eddy current brake as a central brake on a front axle and / or a rear axle of an electrically driven vehicle.

[0022] Advantages of the invention

[0023] The electric machine proposed according to the invention and the eddy current brake integrated therein make it possible to create a particularly compact central brake. The electric machine comprises at least one rotor, essentially designed in the shape of a disk, and a number of magnets, which may be permanent magnets, for example. The advantages of an electric machine designed, for example, as an axial flux machine are its short design, which saves installation space, and its high torque density. In the solution proposed according to the invention, the rear side of at least one rotor of the electric machine is used as a brake disk, so that this component can be used twice, thereby achieving considerable savings in material that would otherwise be used and in the weight and costs that would otherwise be incurred.

[0024] In advantageous embodiments, the very short electrical machine can be accommodated in a housing, on the end faces of which, for example, an eddy current brake is accommodated, which interacts with a brake disc arranged on the back of two rotors of the electrical machine, wherein the rotors are rotationally connected to the shaft of the electrical machine.

[0025] Accordingly, two eddy-current brakes can be integrated into one housing of an electrical machine without significantly increasing the housing length, thus maintaining a compact design. In the electrical machine proposed according to the invention, its shaft can either be connected to at least one front wheel or one rear wheel of an electrically powered vehicle via a transmission, or the electrical machine, designed, for example, as an axial flux machine, can be connected directly to at least one wheel installed on the front axle and / or a rear axle of an electrically powered vehicle.

[0026] The electric machine with integrated eddy-current brake proposed according to the invention can, as already mentioned above, be designed, for example, as an axial flux machine comprising a number of magnets, in particular permanent magnets. Of course, it is also possible to design the electric machine as a magnet-free electric machine, for example, as an asynchronous machine, reluctance machine, or electrically excited synchronous machine. At least one eddy-current brake can also be integrated into such types of electric machines.

[0027] Short description of the drawings

[0028] Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

[0029] They show:

[0030] Figure 1 is a schematic representation of an electrically driven

[0031] Vehicle with an electric machine to which a gearbox and an eddy current brake are assigned, and Figure 2 shows a section through a schematically illustrated electric machine, designed here for example as an axial flux machine, in whose housing an eddy current brake is integrated.

[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 1 shows an electrically powered vehicle 10 comprising a front axle 12 and a rear axle 38. A left front wheel 14 and a right front wheel 16 are mounted on the front axle 12, each of which is 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 powered vehicle 10 further comprises an eddy current brake 22, which is assigned to an electric machine 24. This is further assigned a transmission 26, which includes an output 28. The transmission 26 drives a differential gear 32 of a differential 30 via its output 28.

[0035] Extending laterally from the differential 30 is a first output shaft 34 to a left rear wheel 40, and a second output shaft 36 to a right rear wheel 42. The two output shafts 34, 36 form the rear axle 38 of the electrically powered vehicle. Unlike the front axle 12, no service brakes are arranged on the rear axle 38 of the electrically powered vehicle 10, as shown in Figure 1. The function of a central brake with respect to the rear axle 38 is assumed by the eddy current brake 22 assigned to the electric motor 24. The electric motor 24 of the electrically powered vehicle 10, as shown schematically in Figure 1, is operated in motor mode via power electronics (not shown in detail here); furthermore, a braking torque is generated in recuperation mode of the electric motor 24 by operating it in generator mode.The transmission 26, via which the differential 30 is driven, is not absolutely necessary. The electrically powered vehicle 10 shown in Figure 1, for example, is one in which the electric machine 24 is designed in the form of an axial flux machine 48. An axial flux machine 48 is characterized by a short design and a very high torque density. The electric machine 24 can alternatively also be a magnet-free electric machine, such as an asynchronous machine, a reluctance machine, or an electrically excited synchronous machine. Thus, a large number of machine types are accessible to the solution proposed according to the invention.

[0036] The electrical machine 24 proposed according to the invention is described in more detail with reference to Figure 2. According to Figure 2, this machine is designed as an axial flux machine.

[0037] The illustration in Figure 2 shows that 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 a 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 one side of the first rotor 58 of the axial flux machine 48. On the rear side of the essentially disc-shaped first rotor 58 is a brake disk 54 of the eddy current brake 22 integrated into the housing 50 of the axial flux machine 48. The illustration in Figure 2 shows that the brake disk 54 has a disk thickness 56. The thickness of the brake disk 54 is in a 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, as it determines the thermal mass and therefore how much energy can be absorbed. In one possible design, the thickness of the brake disc 54 is 15 mm. The material from which the brake disc 54 is made is a material that is both electrically and magnetically conductive. The speed range is set via the electrical conductivity. Gray cast iron, for example, offers optimal electrical conductivity. Figure 2 also shows that the eddy current brake 22 integrated into the housing 50 of the axial flux machine 48 shown here as an example comprises a number of coils 62. The coils 62 are arranged along the circumference of the eddy current brake 22 and each comprise a winding 64 that extends around an iron core 66 that accommodates the winding 64. A return element 68 is assigned to the coils 62.The front side of the eddy current brake 22 is located at a short distance from the front side of the brake disc 54, which is accommodated on the back side of the first rotor 58.

[0038] The axial flux machine 48 shown here as an example according to the sectional view in Figure 2 further shows that a second rotor 60 is accommodated on the shaft 52 of the axial flux machine 48. On the side of the second rotor 60 facing the permanent magnet 70 of the first rotor 58, permanent magnets 70 are also arranged distributed around its circumference, the number of said permanent magnets corresponding to the number of permanent magnets 70 accommodated on the corresponding side of the first rotor 58. Coils 72 of the electrical machine 24, which is designed here as an axial flux machine 48, run between the respective permanent magnets 70 on the mutually facing sides of the first rotor 58 and the second rotor 60, respectively. Each of the coils 72 of the electrical machine 24, designed as an axial flux machine 48, comprises a winding 74, which is accommodated on a corresponding iron core 76.The number of coils 72 of the electrical machine 24, which in this example is designed as an axial flux machine 48, corresponds to the pairs of opposing permanent magnets 70 on the opposite sides of the first rotor 58 and the second rotor 60.

[0039] The second shaft 52 of the axial flux machine 48, shown broken away in Figure 2, is connected either with the interposition of the transmission 26 schematically indicated in Figure 1 to at least one front wheel 14, 16 of the electrically driven vehicle 10 or directly to at least one front wheel 14, 16 of the front axle 12 and / or at least one rear wheel 40, 42 on the rear axle 38, which is formed by the first output shaft 34 and the second output shaft 36.

[0040] In the illustration according to Figure 2, the eddy current brake 22 is integrated into the housing 50, in particular assigned to its front side. As an alternative to the embodiment shown in Figure 2, it is possible to also attach a brake disc 54 to the rear of the second rotor 60 and to provide a further eddy current brake 22 integrated into the housing 50 opposite this in the part of the housing 50 not shown. This does not significantly increase the axial length of the axial flux machine 48, so that disadvantages regarding the installation space requirement are eliminated, but the advantage of a high power density and a high braking torque setting is provided.

[0041] As shown in Figure 2, the solution proposed according to the invention allows one and the same component, i.e. the first rotor 58 and optionally also the second rotor 60, which are assigned to the shaft 52 in a rotationally fixed manner, to be used in a dual way: On the one hand, the mutually facing sides of the first rotor 58 and the second rotor 60 serve to accommodate the permanent magnets 70, between which the coils 72 of the electrical machine 24 designed as an axial flux machine 48 extend. On the other hand, brake disks 54 of the eddy current brakes 22 assigned to them can be arranged on the rear sides of the first rotor 58 and optionally of the second rotor 60. This results in considerable material savings through the dual use of the rotors 58, 60 and thus a significant reduction in costs and weight.

[0042] Furthermore, the invention relates to the use of the electric machine 24, embodied here by way of example as an axial flux machine 48, in the electrically powered vehicle 10. The electric machine 24, embodied here as an axial flux machine 48, is characterized by a high power density and a short axial design. Furthermore, if, following the solution proposed by the invention, at least one eddy current brake 22 is integrated into the housing 50 of the axial flux machine 48, a compact structural unit is obtained which, in addition to a high torque density and thus high performance, is also capable of applying a high torque as a central brake, for example, to the rear axle 38 of the electrically powered vehicle 10 shown schematically in Figure 1.

[0043] 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. Electric machine (24) with at least one disk-shaped rotor (58, 60) mounted on a shaft (52), characterized in that the at least one disk-shaped rotor (58, 60) is provided on one side with a brake disc (54) of an eddy current brake (22).

2. 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. Electric machine (24) according to claims 1 and 2, characterized in that the eddy current brake (22) of the brake disc (54) is located within the housing (50) opposite the at least one rotor (58, 60).

4. Electric machine (24) according to claims 1 to 3, characterized in that the eddy current brake (22) has several coils (62) arranged distributed along its circumference, each comprising a winding (64) and an iron core (66).

5. Electrical machine (24) according to claim 4, characterized in that each of the coils (62) is assigned a feedback element (68).

6. Electric machine (24) according to claims 1 to 5, characterized in that the brake disc (54) is formed in a disc thickness (56) between 5 mm and 25 mm, preferably between 10 mm and 20 mm and is made of an electrically and magnetically conductive material.

7. Electric machine (24) according to claims 1 to 6, characterized in that the electric machine (24) has a first rotor (58) and a second rotor (60), each of which is disc-shaped Electric machine (24) according to claims 1 to 6, characterized in that the electric machine (24) has a first and a second rotor (58, 60) which have magnets, in particular permanent magnets (70), on their opposing sides. Electric machine (24) according to claim 8, characterized in that coils (72) of the electric machine (24), in particular designed as an axial flux machine (48), are arranged on the disk-shaped sides of the first rotor (58) and the second rotor (60) between opposing magnets, in particular permanent magnets (70). Electric machine (24) according to claims 1 to 9, characterized in that the coils (72) of the electric machine (24) comprise a winding (74) and an iron core (76).An 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 via a transmission (26) or directly to at least one front wheel (14, 16) and / or at least one rear wheel (40, 42) of an electrically powered vehicle (10). Use of the electric machine (24) according to any one of claims 1 to 11 with 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 electrically powered vehicle (10).

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