Magnetic powder brake and steering system

Abstract

The invention relates to a magnetic powder brake and a steering device for a motor vehicle, for example for use in a steering column. The magnetic powder brake (1) comprises a stator (10) and a rotor (11) arranged rotatably about an axis of rotation (14) with respect to the stator (10) and a coil (12) arranged on the stator (10), wherein at least a first shear gap (21) for receiving ferromagnetic powder is formed between the stator (10) and the rotor (11) and the coil (12) is arranged radially inside with respect to the shear gap (21). The magnetic powder brake and the steering device enable optimal use of existing installation space in a simple and cost-effective design.

Description

[0001] The invention relates to a magnetic powder brake and a steering device for a motor vehicle, for example for use in a steering column.

[0002] In vehicles where steering commands are transmitted from the steering wheel to the steered wheels via a sensor and an electromechanical actuator, i.e., when using steer-by-wire technology, there is no mechanical connection between the steering wheel and the chassis. To provide the driver with accurate road feel, impacts from the wheels or steering resistance, for example, must be transmitted electrically to the steering wheel. Powder brakes, among other things, are used to generate steering resistance at the steering wheel. These are installed in the steering column and are mechanically connected to the steering wheel.

[0003] To generate the braking torque, a coil in a magnetic powder brake is energized, inducing an electromagnetic field. Between the shearing surfaces located on the stator and rotor of the powder brake, a ferromagnetic powder aligns itself along the field lines of the magnetic field, thus generating the braking torque of the powder brake. The achieved braking torque varies depending on the number of shearing surfaces on the stator and rotor, as well as their width and radial position.

[0004] CN218761045U discloses a magnetic powder brake comprising a front coil seat, a rear coil seat, a front end cover, a rear end cover, and a rotor, wherein the front coil seat and the rear coil seat together form a receiving space. An electric coil is arranged in the receiving space, and the front end cover is fixedly arranged on the front coil seat in a covering mode. A through hole is formed in the front end cover, and the rotor is arranged in the through hole. A placement space for the magnetic powder is formed between the rotor and the rear end cover, and a magnetic gap connected to the placement space is formed between the rotor and the front coil seat.

[0005] In WO22170050A1 the coil is arranged radially outside the shear surfaces.

[0006] EP3286449B1 discloses a magnetorheological fluid coupling device comprising a stator adapted to be connected to a structure, the stator having at least one annular wall. Furthermore, the magnetorheological fluid coupling device comprises a first rotor rotatably mounted on the stator, the first rotor having at least one first shear surface. Furthermore, a second rotor is rotatably mounted on the stator for rotating about a common axis with the first rotor, the second rotor having at least one second shear surface opposite the at least one first shear surface, and the shear surfaces are separated by at least one annular space. The coil is arranged axially offset from the shear surfaces.

[0007] WO2021092683 discloses a system for operating at least one magnetorheological fluid coupling device. The system allows, in a first operating mode, the extent of torque transmission between a driving element and a driven element in the magnetorheological fluid coupling device to be varied by actuating at least one coil in the magnetorheological fluid coupling device. In a second operating mode, the system can effect torque transmission between the driven element and the driving element by setting a desired level of remanent magnetization in a magnetic component of the magnetorheological fluid coupling device by actuating the coil in the magnetorheological fluid coupling device. Here, the coil is arranged axially offset from the shear surfaces.

[0008] Conventional powder brakes often have the disadvantage of requiring a relatively large installation space for a given braking torque. This is due, for example, to the fact that the coils used are positioned radially outward relative to the shear surfaces of the stator and rotor, resulting in a shorter lever arm between the shear surfaces and the rotational axis of the powder brake than the installation space allows. Furthermore, many powder brakes have relatively small shear surfaces and do not utilize the available radially outer installation space efficiently. This is particularly in need of improvement when used in vehicles equipped with "steer-by-wire" technology.

[0009] It is therefore the object of the present invention to provide a magnetic powder brake and a steering device which, in a simple and cost-effective design, enable optimal use of an available installation space.

[0010] This object is achieved by a magnetic powder brake according to claim 1 and a steering device according to claim 8.

[0011] Advantageous embodiments of the magnetic powder brake are specified in subclaims 2 to 7. Advantageous embodiments of the steering device are specified in subclaims 9 and 10.

[0012] According to a first aspect of the invention, a magnetic powder brake is provided. The magnetic powder brake comprises a stator and a rotor arranged so as to be rotatable relative to the stator about a rotational axis, with a coil arranged on the stator. At least one first shear gap for receiving ferromagnetic powder is formed between the stator and the rotor, and the coil is arranged radially inward relative to the shear gap.

[0013] In the context of the present invention, the terms “radial” and “axial” always refer to the rotation axis of the magnetic powder brake.

[0014] The coil is firmly connected to the rotationally fixed stator and is ring-shaped and coaxial with the axis of rotation. The coil generates a magnetic field when current flows through it. The field lines of the magnetic field run through the stator surrounding the coil and through the rotor in a direction of least magnetic resistance. Both components are ferromagnetic. Since the stator and rotor are rotatable relative to one another, they are not in direct contact but are spaced apart. This means that the magnetic field must overcome at least one gap along its field lines in order to be circularly closed in a plane spanned on one side by the axis of rotation. In this case, this at least one gap is designed as a first shear gap and is bounded on two radially opposite sides by the stator and the rotor.The at least one first shear gap can have a distance of between 0.25 mm and 0.5 mm between the shear surfaces that bound it, although a distance of less than 0.1 mm should not be ruled out. When the magnetic powder brake is switched on, current flows through the coil and the magnetic field is aligned between the opposing shear surfaces of the stator and the rotor in the first shear gap. As a result, a ferromagnetic powder located in the at least one first shear gap is aligned along the magnetic field, forming particle chains that magnetically adhere to the shear surface walls and create a frictional connection between stator and rotor, which causes a braking torque between stator and rotor. The current in the coil can be between 0.1 and 10 amperes and cause a braking torque of 5 to 30 Nm.To increase the frictional connection between the rotor and stator through the ferromagnetic powder, three-dimensional structures can be present on the rotor's shear surfaces. Because the coil is positioned radially further inward than the first shear gap, the lever arm between the first shear gap or the rotor's shear surface and the rotation axis is relatively large compared to conventional designs.

[0015] In one embodiment of the magnetic powder brake, the coil and the first shear gap are arranged, at least in sections, in the same longitudinal section of the magnetic powder brake. This means that the at least one first shear gap and the coil are arranged, at least in sections, in the same axial region, with the first shear gap being located radially further outward than the coil. This results in a smaller axial extension of the magnetic powder brake than if the coil were arranged axially offset from the first shear gap.

[0016] In one embodiment, the coil and the first shear gap are arranged entirely in the same longitudinal section of the magnetic powder brake. This means that the first shear gap completely radially covers the coil. This has the advantage that the shear surfaces of the stator and rotor are maximal in their axial extent in the first shear gap, given the axial space. Shear surfaces refer to the surfaces of the stator and rotor that are opposite each other at the first shear gap and between which the ferromagnetic powder is aligned along the magnetic field. The larger the shear surfaces, the greater the achievable braking torque of the magnetic powder brake.

[0017] In a further embodiment of the magnetic powder brake, a second shear gap is formed between the stator and the rotor to accommodate ferromagnetic powder, the second shear gap being arranged further radially outward with respect to the first shear gap. By arranging a second shear gap radially outside the first shear gap, further shear surfaces are provided by the stator and rotor. Furthermore, a larger lever arm is realized between the axis of rotation and the shear surface of the rotor in the second shear gap, which increases the achievable braking torque of the magnetic powder brake. The at least one second shear gap can have a distance of between 0.25 and 0.5 mm between the shear surfaces, although a distance of less than 0.1 mm should not be ruled out.

[0018] One embodiment of the magnetic powder brake provides that the rotor is partially designed as a hollow cylinder arranged between a radially inner element of the stator and a radially outer element of the stator, with the first shear gap being formed between the radially inner element of the stator and the rotor, and the second shear gap being formed between the radially outer element of the stator and the rotor. The radial stacking of the two shear gaps on both sides of the hollow cylinder achieves a high functional density, i.e. a high braking torque within a given installation space. This arrangement also results in the magnetic field penetrating the first shear gap, the second shear gap and the hollow cylinder almost radially perpendicularly, which shortens the paths that the magnetic field has to travel. By shortening the paths that have to travel, the magnetic resistance decreases and the braking torque of the magnetic powder brake increases.

[0019] The attachment of the rotor to the shaft can be designed such that the hollow cylinder has a pot-shaped configuration, i.e. it has at least one torque transmission element on one axial side which axially delimits the interior of the hollow cylinder at least in part. The torque transmission element transmits the torque between the rotor and the shaft and is firmly connected to both. The seat of the at least one torque transmission element on the shaft can be located axially further inward than the axial boundary of the hollow cylinder to which the torque transmission element is attached. This helps to reduce the axial installation space of the magnetic powder brake and to reduce the tendency of the rotor to wobble, as the seat is thus closer to the axial position of the braking torque acting via the shear surfaces.The rotor, the radially inner element of the stator, and the radially outer element of the stator can be made of one-piece deep-drawn sheets with a thickness of 3 mm to 5 mm, although thicknesses of up to 8 mm are also possible. Furthermore, additional radial stacking of stator sheets, shear gaps, and rotor sheets can be provided, or additional zones or components for axial, disc-shaped shear gaps.

[0020] According to one embodiment, the magnetic powder brake is designed to include a shaft for transmitting torque to the rotor, wherein the shaft is arranged radially further inward relative to the stator. In this case, the stator is rotationally fixed to an external rigid housing, which is arranged at least partially in the same axial region as the shaft, while being arranged radially further outward than the shaft. The rotor is fixedly mounted on an internal shaft that rotates about the rotational axis. This embodiment is referred to as an internal rotor.

[0021] According to a further embodiment, the magnetic powder brake is designed to include a shaft for transmitting torque to the rotor, wherein the shaft is arranged radially further outward relative to the stator. The stator is mounted in a rotationally fixed manner on a rigid axle that extends along the axis of rotation. The shaft arranged radially further outward can also be referred to as a hollow shaft or rotary pot and limits the magnetic powder brake radially outward, at least in some areas. The rotor can be arranged in a rotationally fixed manner on or in the shaft. This embodiment is referred to as an external rotor.

[0022] In both of the preceding embodiments, the shaft is connected to the rotor in a rotationally fixed manner, so that when the rotor is braked, the shaft is also braked and thus a device connected to the shaft, such as a steering wheel.

[0023] One embodiment provides for the magnetic powder brake to include an angle sensor capable of detecting a relative angular movement between the stator and the shaft. The purpose of this is to detect a deflection from a fully braked situation. This can be the case, for example, if a driver attempts to reverse a steering rotation from a stop position simulated by the magnetic powder brake, thus inducing a rotational movement into the shaft from a stationary rotor position. Alternatively, or in addition, a torque sensor can also be used.

[0024] In one embodiment of the magnetic powder brake, the shaft is arranged radially further inward with respect to the stator, and the rotor and / or a torque transmission element between the rotor and the shaft is designed to be torsionally soft such that, when the rotor is fixed relative to the stator and a torque is introduced into the shaft, a relative angular movement can be carried out between the shaft and the stator. It is also possible for a relative angular movement to be carried out between the fixed area of ​​the rotor, such as its hollow cylinder, and the shaft. This embodiment of the magnetic powder brake as an internal rotor with torsionally soft torque transmission elements includes an angle sensor with which this relative angular movement can be detected. The torsional stiffness of the rotor and / or the torque transmission element can be 2-20 Nm / °.

[0025] A further embodiment of the magnetic powder brake provides that the stator and rotor have powder passages along their entire extension away from the shearing surfaces present in the shear gaps so that the ferromagnetic powder can be distributed throughout the powder space.

[0026] According to a further aspect of the invention, a steering device for a motor vehicle is provided, which comprises at least one magnetic powder brake as described. This steering device can be configured for "steer-by-wire," i.e., not for a mechanical steering device, but rather for a steering device with which an electrical signal for adjusting a steering angle on at least one wheel of a motor vehicle is generated simply by manually adjusting a rotation angle.

[0027] One embodiment of the steering device further comprises an electric rotary machine whose machine rotor is mechanically coupled or can be coupled to the rotor of the magnetic powder brake. "Couplable" means, for example, that a coupling is arranged between the machine rotor and the rotor of the magnetic powder brake, thus enabling the transmission of torque to be realized and interrupted. The drive torque of the electric rotary machine can be between 5 and 10 Nm.

[0028] A further embodiment of the steering device provides that the steering device comprises an electric rotary machine and a rotor position sensor, with which the position of the machine rotor relative to the machine stator of the electric rotary machine can be detected. If the rotor and / or a torque transmission element are designed to be sufficiently torsionally flexible, the rotor position sensor can detect when a rotational movement is initiated in the shaft from a fully braked or stopped rotor position. This can be the case, for example, if a driver attempts to steer back from a steering rotational movement limit simulated by the magnetic powder brake.

[0029] The magnetic powder brake can be arranged at the end of a steering device, for example, at an end section of the shaft that is axially opposite a connected device such as a steering wheel. The terminal arrangement of the magnetic powder brake in the steering device has the advantage that only one shaft seal needs to be installed to seal the powder chamber inside and outside the magnetic powder brake. This reduces frictional torque and costs. The mechanical torque transmission between the magnetic powder brake, the rotating machine, and the connected device, such as a steering wheel, can also be implemented entirely or partially via a gear system.

[0030] The invention described above will be explained in detail below against the relevant technical background with reference to the accompanying drawings, which show preferred embodiments. The invention is in no way limited by the purely schematic drawings, and it should be noted that the embodiments shown in the drawings are not limited to the dimensions shown. It is shown in Fig. 1: a sectional view of part of the magnetic powder brake; Fig. 2: in a perspective exploded view, an embodiment of the stator of the magnetic powder brake during its assembly; Fig. 3: the assembled stator in perspective view; Fig. 4: the assembled stator during assembly of the rotor in perspective view; Fig. 5: in a perspective sectional view of the magnetic powder brake with radially outer shaft before mounting on a shaft; Fig. 6: in a perspective sectional view of the magnetic powder brake with radially outer shaft after mounting on a shaft; Fig. 7: in a perspective sectional view, the magnetic powder brake with radially outer shaft after mounting on a shaft with a magnetic field; Fig. 8: in a sectional view a part of the steering device with the magnetic powder brake arranged at the shaft end; Fig. 9: in a perspective sectional view a detail of the mounted magnetic powder brake arranged at the shaft end; Fig. 10: in a perspective sectional view of the assembled rotor of the magnetic powder brake arranged at the shaft end; and Fig. 11: in a perspective view, the rotor of the magnetic powder brake for use on a shaft end;

[0031] In Fig. 1 shows part of the magnetic powder brake 1 for use with a radially outer shaft. The magnetic powder brake 1 has a stator 10 in which the coil 12 is arranged. The stator 10 further comprises a radially inner element of the stator 23 and a radially outer element of the stator 24, which are radially spaced from one another in the radially outer region of the magnetic powder brake 1 and between which the hollow cylinder 15 formed by the rotor 11 rotates contactlessly about the rotation axis 14. A first shear gap 21 exists between the radially inner element of the stator 23 and the rotor 11. A second shear gap 22 exists between the radially outer element of the stator 24 and the rotor 11.

[0032] When the magnetic powder brake 1 is actuated, a current flows via the power supply element 26 into the coil 12 and induces the magnetic field 28. This magnetic field 28 extends annularly along the stator 10, the first shear gap 21, the rotor 11 and the second shear gap 22, wherein the course of the magnetic field 28 is approximately radially perpendicular in the first shear gap 21, i.e. between the radially inner element of the stator 23 and the rotor 11, and in the second shear gap 22, i.e. between the rotor 11 and the radially outer element of the stator 24. The ferromagnetic powder present in the shear gaps 21, 22 in the ready-to-use state (not shown here for better clarity) aligns itself along the field lines of the magnetic field 28 and thus creates a force-locking connection between the stator 10 and the rotor 11. This force-locking connection causes a braking torque and brakes the rotor 11.For optimal distribution of the ferromagnetic powder within the magnetic powder brake 1, powder passages 27 are provided on the stator. The radially inner element of the stator 23, the radially outer element of the stator 24, and the power supply element 26 are connected to one another in a form-fitting and / or force-fitting manner via connecting elements 25, such as rivets. The coil 12 is also fixed within the stator 10 by means of this connection. The coil and the shear gaps 21, 22 are located in the same longitudinal section L.

[0033] In Fig. 2 shows a part of the magnetic powder brake 1 in a perspective exploded view during assembly. In Fig. 2, in a first step, the coil 12 is positioned in the annular recess of the radially inner element of the stator 24.

[0034] Fig. 3 shows the assembly of coil 12, the power supply element 26 arranged thereon and the radially inner element of the stator 23 with the radially outer element of the stator 24.

[0035] Fig. Figure 4 shows that the radially inner element of the stator 23 and the radially outer element of the stator 24 are positively and / or non-positively connected by connecting elements 25, which also fix the coil 12 and the power supply element 26. Furthermore, it is shown that the hollow cylinder 15 formed by the rotor 11 is axially inserted into the stator 10, which has a non-circular contour 39 for attachment to a shaft.

[0036] Fig. Figure 5 shows a composite assembly comprising a stator 10 and a coil 12 on a rigid shaft 34 extending along the rotational axis 14. Two shaft seals 30 are also arranged on the rigid shaft 34 to seal the powder chamber 35 from the outside. This chamber is filled with ferromagnetic powder before assembly.

[0037] In Fig. Figure 6 shows how a radially outwardly located shaft 13, together with the rotor 11 fixed to it, is mounted on bearings 31, here designed as ball bearings, on the rigid axle 34. The rotor 11 is designed as a hollow cylinder 15 and is caulked to the shaft 13. The shaft 13 is mounted on the rigid axle 34 via bearings 31 for rotation about the rotation axis 14. In the assembled state, the shaft 13 axially and radially delimits the powder chamber 35, which is also sealed by the shaft seals 30.

[0038] In Fig. Figure 7 shows a section of a portion of the magnetic powder brake 1 arranged at a shaft end. The magnetic powder brake 1 has a stator 10, in which the coil 12 is arranged and which is firmly connected to the housing 33. The stator 10 comprises a radially inner element of the stator 23 and a radially outer element of the stator 24, which are radially spaced from one another in the radially outer region of the magnetic powder brake 1 and between which the hollow cylinder 15 formed by the rotor 11 rotates contactlessly about the rotational axis 14. The hollow cylinder 15 is firmly connected via torque transmission elements 37 to the radially inner shaft 13, which is mounted for free rotation about the rotational axis 14 by means of the bearing 31. When the magnetic powder brake 1 is actuated, a current flows via the power supply element 26 into the coil 12 and induces the magnetic field 28.This magnetic field 28 extends in a ring shape along the stator 10, the first shear gap 21, the rotor 11, and the second shear gap 22, wherein the course of the magnetic field 28 is approximately radially perpendicular in the first shear gap 21, i.e., between the radially inner element of the stator 23 and the rotor 11, and in the second shear gap 22, i.e., between the rotor 11 and the radially outer element of the stator 24. The ferromagnetic powder present in the shear gaps 21, 22, but not shown, aligns itself along the field lines of the magnetic field 28, thus creating a force-locking connection between the stator 10 and the rotor 11. This force-locking connection causes a braking torque and thus decelerates a rotational movement of the rotor 11 and the shaft 13 about the rotation axis 14. The powder chamber 35, which comprises the first shear gap 21 and the second shear gap 22, is axially delimited by the housing cover 32 and sealed to the outside.The shaft seal 30 seals the powder chamber 35 to the housing 33.

[0039] In Fig. Figure 8 shows a sectional view of part of a steering device 40 with the magnetic powder brake 1 arranged at one end of the shaft 13. The steering device 40 comprises the magnetic powder brake 1, an electric rotary machine 41, and the shaft 13, which is rotatably mounted via the bearings 31 in the housing 33 and the housing receptacle 38. The magnetic powder brake 1 has torque transmission elements 37, which connect the rotor 11 to the shaft 13 and transmit the braking torque of the magnetic powder brake 1 into the shaft 13. The spoke-like design of the torque transmission elements 37 enables the distribution of the ferromagnetic powder located there, but not shown, in the powder chamber 35 and in the shear gaps of the magnetic powder brake associated with the powder chamber 35.The rotary machine 41, arranged axially next to the magnetic powder brake 1, has a machine stator 43 and a machine rotor 42, which is firmly connected to the shaft 13 and can introduce a torque into the shaft 13. The end of the shaft 13 (not shown) can be connected to a device for steering a vehicle, such as a steering wheel. By using the steering device 40, or by the braking and torques transmitted to the shaft 13 by the magnetic powder brake 1 and the electric rotary machine 41, torques on the steering device can be simulated for specific driving situations.

[0040] In Fig. Figure 9 shows a detail of the magnetic powder brake 1 arranged at one end of the shaft 13 in a perspective sectional view. The torque transmission elements 37 transmit the torque between the hollow cylinder 15 formed by the rotor 11 and the shaft 13 and are connected to both in a rotationally fixed manner. The seat of the torque transmission elements 37 on the shaft 13 is located axially further inward than the axial outer boundary of the hollow cylinder 15, which minimizes the axial offset of the braking torque and the shaft seat Va. This contributes to reducing the axial installation space of the magnetic powder brake 1 and to reducing the tendency of the rotor 11 to wobble, whose seat is thus closer to the axial position of the effective braking torque.

[0041] In Fig. Figure 10 shows a perspective sectional view of the rotor 11 arranged at one end of the shaft 13. The rotor is essentially designed as a hollow cylinder 15, which is connected to the shaft 13 via the torque transmission elements 37. Due to the three-dimensional structures on the radially inner and outer surfaces of the hollow cylinder 15, the ferromagnetic powder can adhere better to them when the magnetic powder brake 1 is actuated, thereby increasing the braking torque.

[0042] Fig. Figure 11 also shows these three-dimensional structures on the radially inner and outer surfaces of the hollow cylinder 15. Furthermore, the elastically designed torque transmission elements 37 are visible, which enable detection of a movement of the shaft from a braking position. On its radially inner surface, the rotor 11 has a non-circular contour 39 for rotationally fixed mounting on a shaft.

[0043] The magnetic powder brake and the steering device enable optimal use of available installation space in a simple and cost-effective design. List of reference symbols 1 magnetic powder brake 10 Stator 11 Rotor 12 coil 13 Wave 14 Rotation axis 15 hollow cylinders 21 first shear gap 22 second shear gap 23 radial inner element of the stator 24 radial outer element of the stator 25 connecting element 26 Power supply element 27 Powder passage 28 Magnetic field 30 shaft seal 31 warehouses 32 housing cover 33 housings 34 Rigid axle 35 Powder Room 37 Torque transmission element 38 Housing holder 39 Non-circular contour 40 Steering device 41 electric rotary machine 42 Machine rotor 43 Machine stator L Longitudinal section Va Axial misalignment of braking torque and shaft seat QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] CN 218761045U

[0004] WO 22170050A1

[0005] EP 3286449B1

[0006] WO 2021092683

[0007]

Claims

[1] Magnetic powder brake (1) with a stator (10) and a rotor (11) arranged so as to be rotatable about a rotation axis (14) with respect to the stator (10), and with a coil (12) arranged on the stator (10), wherein at least one first shear gap (21) for receiving ferromagnetic powder is formed between the stator (10) and the rotor (11), and the coil (12) is arranged radially inward with respect to the shear gap (21). [2] Magnetic powder brake (1) according to claim 1, characterized by that the coil (12) and the first shear gap (21) are arranged at least in sections in the same longitudinal section (L) of the magnetic powder brake (1). [3] Magnetic powder brake (1) according to one of the preceding claims, characterized bythat a second shear gap (22) for receiving ferromagnetic powder is formed between the stator (10) and the rotor (11), wherein the second shear gap (22) is arranged further radially outward with respect to the first shear gap (21). [4] Magnetic powder brake (1) according to claim 3, characterized by that the rotor (11) is designed in sections as a hollow cylinder (15) which is arranged between a radially inner element of the stator (23) and a radially outer element of the stator (24), wherein the first shear gap (21) is formed between the radially inner element of the stator (23) and the rotor (11), and the second shear gap (22) is formed between the radially outer element of the stator (24) and the rotor (11). [5] Magnetic powder brake (1) according to one of the preceding claims, characterized bythat the magnetic powder brake (1) comprises a shaft (13) for transmitting torque to the rotor (11), wherein the shaft (13) is arranged with respect to the stator (10) i) radially further outwards, or ii) is arranged radially further inwards. [6] Magnetic powder brake (1) according to claim 5, characterized by that the magnetic powder brake (1) comprises an angle sensor with which a relative angular movement between the stator (10) and the shaft (13) can be detected. [7] Magnetic powder brake (1) according to claim 6, characterized by that the shaft (13) is arranged radially further inward with respect to the stator (10) and the rotor (11) and / or at least one torque transmission element (37) between the rotor (11) and the shaft (13) is designed to be torsionally soft in such a way that when the rotor (11) is fixed relative to the stator (10) and a torque is introduced into the shaft (13), a relative angular movement between the shaft (13) and the stator (10) can be carried out. [8] Steering device (40) for a motor vehicle, comprising at least one magnetic powder brake (1) according to one of claims 1 to 7. [9] Steering device (40) according to claim 8, characterized in that the steering device (40) further comprises an electric rotary machine (41) whose machine rotor (42) is or can be mechanically coupled to the rotor (11) of the magnetic powder brake (1). [10] Steering device (1) according to claim 9, wherein the electric rotary machine (41) comprises a rotor position sensor with which the position of the machine rotor (42) in relation to the machine stator (43) of the electric rotary machine (41) can be detected.

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