Steering system having a magnetorheological brake and permanent magnet assistance

Abstract

The present invention relates to a steering system (1) for controlling a vehicle by means of a steer-by-wire concept, comprising an operating element, a steering shaft (3), a rotor (9), a stator (8), and a continuously adjustable magnetorheological brake (5) which influences the rotation of the steering shaft (3) and has two components which can be rotated relative to one another about an axis of rotation, the stator (8) with the associated coil (14) and, at a distance therefrom, the rotor (9) connected to the steering shaft (3), wherein: at least one circumferential shear gap (16), (17) which is at least partially filled with a magnetorheological medium is provided between the rotor (9) and the stator (8); the stator (8) receives, in a receptacle (18), a permanent magnet (27) for building up a basic braking torque; the receptacle (18) has a radial boundary (29) against which the permanent magnet (27) is seated; the stator (8) has a radial thickness D in the region of the receptacle (18); the coil (14) is arranged directly on the second side (21) which faces the rotor (9); the receptacle (18) axially overlaps with the coil (14); the radial boundary (29) is at a distance T from the first side (20) of the stator (8) which radially faces away from the rotor (9), with T < D, such that a web (22) remains between the second side (21) and the receptacle (18) or the radial boundary (29); the web (22) has a web thickness d = D - T; and the web thickness is between 1 mm and 2.5 mm, preferably between 1.5 mm and 2.0 mm.

Description

[0001] P241525

[0002] - 1 -

[0003] Steering system with mechanical brake and permanent magnet support

[0004] The present invention relates to a steering system according to the preamble of claim 1.

[0005] A steer-by-wire steering system for a motor vehicle with an electric motor and a magnetorheological brake is known from DE 10 221 241 A1.

[0006] To achieve the most realistic steering feel possible in such steer-by-wire systems, it is also known to incorporate a magnetorheological brake into the torque flow of a steering device to increase the resistance torque. In combination, this allows for a higher total torque to be achieved with lower energy consumption in the same installation space. Such a braking system is also referred to as a force feedback actuator (FFA) or at least as a component of such an actuator.

[0007] Various magnetorheological brakes are known from the prior art, in which, for example, a second rotating component is decelerated relative to a first component by activating the device. The coupling is achieved via a magnetorheological medium located between the two components, which is activated by a magnetic field.

[0008] Magnetorheological brakes can be found, for example, in WO 2022 / 170 050 A1 or EP 3268262 B1. WO 2022 / 170 050 A1 shows a steering FFA of a steering system which demonstrates a magnetorheological fluid brake (MRF brake) in conjunction with an electric motor.

[0009] Such magnetorheological brakes consist of a rotor and a stator, e.g., a shaft as the stator and a rotor rotatable relative to the shaft, or a shaft as the rotor and a stator arranged relative to the rotatable shaft. The rotor and stator can be axially and radially nested. The rotational movement of the rotor can be stopped by means of the magnetorheological brake, which includes a coil. P241525

[0010] - 2 - is intended to be braked. For this purpose, a magnetorheological medium is introduced into a sealed receptacle formed between the stator, for example, the axle unit, and the rotor. In conjunction with a magnetic field from the electrical coil, the magnetorheological medium can generate a braking torque that selectively slows the rotation of the rotor. In particular, a powder brake consists of a stator with an integrated coil and an opposing rotor. A magnetorheological medium, especially powder, is located in an air gap between the two non-contacting components. When current flows through the coil, this powder forms chain-like structures in the resulting magnetic field. A friction-generating connection is created via these structures, which now touch both components. The resulting braking effect increases with the current flowing through the coil.

[0011] CN 218 761 045 U discloses a powder brake whose rotor is rigidly connected to the shaft of a steering device.

[0012] From DE 10 2018 200 590 A1, it is known to provide a permanent magnet in addition to a coil that activates the magnetorheological medium in order to increase or represent a basic friction of the magnetorheological medium. If necessary, the braking effect of the permanent magnet must be canceled by an opposing magnetic field of the coil.

[0013] It has been found that with the known designs of a steering system, the simultaneous provision

[0014] 1. of sufficient basic torque, i.e. a braking effect, without requiring a coil current,

[0015] 2. compensation of the fundamental torque at a low coil current and

[0016] 3. A necessary high maximum torque, which can serve as a stop against twisting a handlebar, cannot be achieved. P241525

[0017] - 3 - To generate a sufficient basic torque, i.e., a base braking torque that is available to activate the magnetorheological fluid even in the event of coil failure, the use of a stronger permanent magnet and fewer magnetic short circuits through the iron circuit would seem logical. However, this impedes the coil's magnetic circuit and increases the coil current required to achieve a high maximum braking torque. Likewise, this directly leads to significantly increased compensation currents needed to counteract the base braking torque. In other words, the currents required for the coil to enable virtually force-free steering movement increase considerably.

[0018] Since soft iron is preferably used as the stator material, compensating for the magnetic field would significantly push the soft iron into saturation. For example, on highways, steering movements with virtually no braking force are practically a constant condition. This requires the cancellation of at least the majority of the base torque. Due to the increased current input during this time, the heat input into the system would rise above a tolerable level, and / or the energy required to maintain this constant state would increase considerably with the use of such a stronger permanent magnet, which would, for example, affect the efficiency of the entire vehicle.

[0019] The object of the present invention is therefore to further develop a steering system of the generic type in such a way that the problems arising from the prior art, as described above, are at least reduced.

[0020] The object of the invention is achieved by a steering system of the generic type with the characterizing features of claim 1.

[0021] The system envisaged is a steering system for controlling a vehicle, using a steer-by-wire concept, comprising a control element, a steering shaft, a rotor, a stator, and a continuously adjustable magnetorheological brake influencing the rotation of the steering shaft, which includes two components rotatable relative to each other about a rotational axis: the stator with its associated coil and, spaced apart from this, the rotor connected to the steering shaft, with P241525 between the rotor and stator.

[0022] - 4 - at least one circumferential shear gap, at least partially filled with a magnetorheological medium, is provided. By energizing the coil, the magnetorheological medium can be activated, thereby increasing the friction between the rotor and stator. This can be used to simulate various driving situations. For example, when cornering, increased torque may be required from the driver to overcome the torque and angle the tires more sharply. Simultaneously, a stop with a maximum torque to be overcome, e.g., 10 Nm to 20 Nm, can also be implemented. A steering wheel or a joystick, for example, can be used as a control element. The steering shaft is connected to the rotor, which, relative to the stator, can be either an internal or an external rotor. The operating principle described below is reversible with respect to internal and external rotors.For the sake of simplicity, the case of an internally rotating rotor is described in each instance, although the arrangement for an externally rotating rotor can be easily inferred by those skilled in the art. Likewise, the arrangement can be integrated at various installation locations on a steering column, e.g., close to the steering wheel (without an intermediate shaft), concealed in the dashboard (connected to a telescopic steering shaft), or integrated into a outer tube.

[0023] Furthermore, the stator is designed to house a permanent magnet in a recess to generate a basic braking torque. This permanent magnet ensures that even in the event of a power failure or when the coil is not energized, the driver must exert a torque to control the vehicle. Mounting the permanent magnet on the outside of the stator allows for an assembly sequence in which the brake can be filled with powder without interference from the magnetic field, and only then is the magnet inserted. The permanent magnet should preferably be magnetized in the axial direction of the rotor.

[0024] The receptacle is designed to have a radial boundary, or, in the case of an internal rotor, a radially inner boundary, against which the permanent magnet rests. The stator, in the area of ​​the receptacle, has a radial thickness D between a first side facing away from the rotor and a second side facing the rotor; in the case of an internal rotor, this results in a radial outer and a radial inner surface. The coil P241525 is directly attached to the second side of the stator.

[0025] - 5 - arranged. In the axial direction, the coil is arranged on the stator such that the receptacle overlaps axially with the coil; radially, they lie one behind the other, and axially, the receptacle, and thus the permanent magnet, lies within the region of the coil. Or, in other words, the coil has an axial front and an axial back. The axial position of the permanent magnet is then described by a position axially between these front and back faces, in particular essentially midway between them.

[0026] The stator can, in particular, encompass the coil in a radial direction, so that the stator has portions both radially outside and radially inside the coil.

[0027] The receptacle can be equipped with an opening towards the first side, i.e., radially outwards in the case of an inner rotor, so that a receptacled permanent magnet is not covered in the direction of the first side radially outwards, or it can completely enclose a permanent magnet in all directions.

[0028] The radial boundary of the receptacle has a distance T to the first side of the stator in the area of ​​the receptacle, where T <D gilt. Auf diese Weise bleibt ein Steg zwischen der zweiten Seite und der Aufnahme stehen, der eine Stegdicke d=D-T misst. Im Falle eines Innenläufers bleibt der Steg zwischen radialen Innenseite des Stators und der radial innen liegenden Begrenzung der Aufnahme stehen. Die Stegdicke beträgt zwischen 1 mm und 2,5mm bevorzugt zwischen 1 ,5mm und 2mm.

[0029] It has been found that the thickness of the friction material is a crucial factor for a steering system that meets the requirements of sufficient basic braking torque, the required maximum braking torque, and an acceptable compensation current. Smaller friction material thicknesses obstruct the magnetic field lines, thus reducing the maximum torque and potentially making compensation of the basic braking torque difficult or even impossible.

[0030] A bridge thickness above 2.5 mm results in an insufficient base braking torque due to magnetic short circuits. Therefore, a standard permanent magnet cannot provide redundancy in the event of a coil malfunction, which would still result in residual friction / braking torque for the rider. P241525

[0031] - 6 -

[0032] It can further be provided that the receptacle has a ring-shaped structure in the circumferential direction of the stator and a width of between 2 and 6 mm, preferably between 2 and 4 mm, in the axial direction. The receptacle and the permanent magnet located therein then enclose the coil circumferentially, while the other dimensions are suitable for the use of robust permanent magnets that are not easily damaged during handling. Likewise, the aforementioned width makes the receptacle easy to manufacture using conventional methods (milling, turning).

[0033] To further simplify handling and allow the use of standard permanent magnets, the stator can be designed with 2 to 19 circumferential pockets for receiving permanent magnets. This facilitates easier insertion of the permanent magnets, as they can be inserted into the pockets from the radial outside. For example, two semi-circular permanent magnets can be inserted into corresponding semi-circular slots in the stator, separated by an axial rib.

[0034] Preferably, 11 to 19 pockets are provided around the circumference of the stator to accommodate permanent magnets. The permanent magnets used here are preferably cuboid in shape and without curvature, which makes them less susceptible to damage and easier to manufacture.

[0035] The orientation of the permanent magnetization is axial (parallel to the axis of rotation) and several magnets are installed in the same orientation.

[0036] A favorable magnetic field line pattern is achieved when the pockets are evenly distributed around the circumference of the stator and have a length of 20-60 mm. While the spaces between the pockets then represent an area that facilitates the passage of the magnetic field lines and thus undesirably increases the effective area of ​​the bridge in the radial direction, this has a positive effect on the availability of simpler or more commercially available magnets. Therefore, this disadvantage is accepted, which may need to be compensated for by a (further) reduction in the bridge width. In a further development, however, holes can also be drilled in these pockets. P241525

[0037] - 7 - Initial gaps are provided to further reduce the magnetically active area. Some of these holes are axial holes that can then be used to attach the stator.

[0038] To facilitate the insertion of permanent magnets, particularly a single ring-shaped permanent magnet, the stator can be constructed in multiple parts, preferably two parts in the axial direction, with a joining surface between the two stator parts in the area of ​​the receptacle or pockets, so that the receptacle or pockets are formed by and during the assembly of the stator parts. In a further development, axial holes in the circumferential direction between the pockets can be used to join the stator parts, while simultaneously reducing the magnetically active area. Stainless steel screws are preferred here due to their low magnetizability.

[0039] In a further development, for the simpler manufacture of the stator, including the permanent magnets, it can be provided that the receptacle or pockets in which the permanent magnet(s) are received are milled into the first side of the stator, in the case of an internal rotor, the radial outer side, or that two stator parts are provided and the receptacle or pockets represent completely closed cavities within the stator, in which the permanent magnet(s) are inserted before the two stator parts are joined together.

[0040] By incorporating one or more permanent magnets into the receptacle or pockets, which are completely filled, and / or the permanent magnet(s) being made of one of the magnet types "sintered neodymium" N20 to N60, a basic braking torque on the order of 5% to 10% of the maximum braking torque to be overcome, preferably a torque of 10 Nm to 20 Nm, can be achieved if the bridge, as intended, has a thickness of 1 mm to 2.5 mm, preferably between 1.5 mm and 2 mm. Thus, a balance between the magnetic field density in the bridge area, and therefore in the magnetorheological medium, can be achieved with a low compensation current and a maximum braking torque of 10 Nm to 20 Nm. P241525

[0041] - 8 -

[0042] The permanent magnet(s) may be coated with nickel to protect against corrosion and breakage.

[0043] In particular, it may be provided that the magnetorheological medium is a powder such as pure low-carbon carbonyl iron or ferntic steels such as FeCr13 in air or protective gas, and that the brake is therefore a magnetorheological powder brake.

[0044] An embodiment of the invention, from which further features of the invention may be derived and to which the invention is not limited, is shown in the following figures. They show:

[0045] Fig. 1 : a section of a steering system with magnetorheological powder brake and electric motor in a perspective view;

[0046] Fig. 2: a section of a magnetorheological powder brake according to the invention,

[0047] Fig. 3: a cross-section through the magnetorheological powder brake according to

[0048] Fig. 2,

[0049] Fig. 4a-c: magnetic flux density at different current intensities,

[0050] Fig. 5: a graph showing the braking torque characteristics for 4 different web thicknesses, and

[0051] Fig. 6a, b: illustration of the necessary bridge width depending on the magnet used.

[0052] Figure 1 shows a section of a steer-by-wire steering system 1 of a vehicle, in which there is no direct connection between a control element, in particular a steering wheel (not shown), and the steered vehicle wheels (not shown). The steering angle of the control element is determined by means of an angle sensor 2 and transmitted via wire to an associated actuator and / or steering mechanism for adjusting the steering wheels. The control P241525

[0053] - 9 - The element is connected at its end to a telescopic steering shaft 3 (possibly also a gearbox), which is adjustable in both length and angle in a known design. The control element can be, for example, a steering wheel or a joystick. The steering shaft 3 is operatively connected to an electric motor 4, also called a feedback motor, and a magnetorheological powder brake 5, also called a force feedback brake (MRP). The electric motor 4 is rotatably mounted on the steering shaft 3 by means of two motor bearings 6, 7 arranged on either side of the electric motor 4.

[0054] The magnetorheological powder brake 5 comprises a potted stator 8, which surrounds a rotor 9 at a distance from each other. These components are rotatable relative to each other and continuously about an axis of rotation. The rotor 9 is mounted on an axially projecting hub 11 within an annular cavity 12 of the stator 8 via a powder brake bearing 10. Furthermore, the rotor 9 is connected to the steering shaft 3 by means of an elastic coupling element 13. A coil 14 associated with the stator 8 engages with play in a receptacle 15 of the rotor 9, forming shear gaps 16, 17 offset in two planes between the stator 8 and the rotor 9.

[0055] The steering shaft 3 can be rotated or pivoted about an axis 28. Axial, radial and circumferential directions are referenced to this axis 28.

[0056] Figure 1, shown and described here, is intended to illustrate only an example of a steering system in which a permanent magnet 27 is mounted within the stator 8 while retaining a web 22. Such a mounting of permanent magnets 27 is then shown in more detail in Figures 2 and 3 and described below with reference to these drawings.

[0057] Fig. 2 shows a section of a steering system 1 as in Fig. 1, but with a magnetorheological powder brake 5, which now accommodates several permanent magnets 27 in pockets 23 of a receptacle 18. The pockets 23 are accessible through openings 19 on the first side 20, i.e., the radial outer side of the stator 8. Permanent magnets 27 can then be inserted into these openings 19. The permanent magnets 27 have an axial width of 2–5 mm, while the stator 8 has an axial width of approximately 30–60 mm. The permanent magnets 27 rest radially inside against a limit 29 and essentially fill the pocket 22.

[0058] - 10 - completely. These are rectangular permanent magnets 27, which are easy to handle and more stable than ring-shaped ones, but cannot be completely filled due to the ring-shaped structure of the pockets 22. The first side 20 of the stator 8 is radially spaced approximately 45 mm to 50 mm from the axis 28. The stator 8 has a radially inner region 30, which radially supports the coil 14 in the receptacle 15 of the rotor 9. The outer region 31 of the stator 8 has a thickness D, as shown in Fig. 3, so that after subtracting the radial depth T of the pockets 23, a web 22 with a radial width d remains, where d is in a range between 1 mm and 2.5 mm, preferably between 1.5 mm and 2 mm. That is, the distance d between the boundary 29 and the second side 21, i.e., the radial inside of the stator 8, lies in this area.

[0059] Axial webs 34 are located circumferentially between the pockets 23, which adversely increase the effective magnetic area of ​​the web 22. To reduce this area again, axial holes 32 are provided in the region of the axial webs 34. In the case of a split stator 8, or for attaching a side cover 35 to the stator 8, some of these axial holes 32 can serve for screwing in screws 33. The rotor 9 is soft magnetic and connected to the steering shaft 3 via a rotor carrier 36. Powder chambers 37 are filled with magnetorheological powder on both axial sides of the rotor carrier 36. A filling screw 38 is provided in the side cover 35 for introducing the powder.

[0060] Figure 3 shows a cross-section of a section of the magnetic powder brake 5 from Figure 2. Identical reference numerals denote identical elements. An optional joining surface 26 is also shown, extending radially within the axial area of ​​the pockets 23 and axially dividing them and the stator 8. In this optional embodiment, the pockets 23 are located in the first and second stator sections 24 and 25.

[0061] The permanent magnet 27 in the pocket 23 is made of N30 as a magnetic material with a field strength of 836,000 A / m. Its permanent magnetization is oriented horizontally (e.g., to the left), i.e., parallel to the axis of rotation 28. P241525

[0062] - 11 -

[0063] The braking torques or magnetic flux density generated in this way for a bridge with a bridge thickness of 1.5 mm are shown symbolically for different current strengths through the coil 14 in Fig. 4a (l=-2A), 4b (l=0A) and 4c (l=+1A).

[0064] Figure 4a shows that at a current of -2 A, a large number of field lines, i.e., a high flux density B, pass through or predominate in the shear gaps 16, 17. With a bridge thickness d = 1.5 mm, we have a flux density of approximately 1.5 T and a maximum braking torque of approximately 10 Nm for an N30 magnet, caused by the magnetorheological powder in the shear gaps 16, 17.

[0065] Figure 4b shows the situation with coil 14 switched off, i.e., I=OA. The permanent magnet, with a field strength of 836,000 A / m, still achieves a flux density of 0.4 T, which corresponds to a braking torque of more than 0.8 Nm, i.e., within the required 10% of the maximum braking torque. Part of the permanent magnet's field lines are short-circuited by the bridge 22 without generating a braking torque in the shear gaps 16, 17. This illustrates the conflicting objectives (the bridge 22 must not be too thick).

[0066] The situation with a coil current of +1 A is shown in Fig. 4c. The magnetic field lines B1 are compressed in the region of the gap 22 and generate a flux density in the region of 2T, i.e., in the saturation range of the soft iron, which is used as the stator material, at least in this region. In the region of the shear gaps 16, 17, a flux density of approximately 0.2T results, which corresponds to a braking torque of 0.2 Nm. To reduce the flux density to 0T, a coil current of +2 A would be necessary. However, this can be dispensed with in most cases. Even half the coil current for the maximum braking torque provides sufficient compensation for the flux density of the permanent magnet 27 in the region of the shear gaps 16, 17, so that practically no braking torque (approximately 0.2 Nm) is present. Increasing the current to +2 A would significantly reduce the efficiency of the magnetorheological brake 5 and is therefore not preferred.

[0067] Figure 5 shows four curves 39-42 for the same magnet material N30, where the bridge thickness d has been varied from 1.5 mm for curve 39, to 1 mm for curve 40, 2 mm for curve 41, and 3 mm for curve 42. The braking torque characteristic of the magnetorheological brake 5 is plotted against the coil current I of the coil 14. Curve 39, represented by circles, corresponds to the braking torque characteristic of the magnetorheological brake 5 as described in Figures 2 to 4. P241525

[0068] - 12 -

[0069] This results in a maximum braking torque of approximately 10 Nm at a current of l = -2 A. This maximum braking torque is essentially achievable for all curves 39-42.

[0070] The curve 39 approaches ONm at +1 A, and this value is actually reached at +2 A. At OA, the permanent magnet 27 still achieves a basic braking torque of approximately 0.8 Nm, which can be considered high enough to simulate a resistance at a control element even in the event of the failure of coil 14. This is the currentless braking resistance.

[0071] Curve 40, the lowest curve at -2A, corresponds to the braking torque characteristic of the magnetorheological brake 5, with a bridge thickness d=1mm, i.e., a thinner bridge 22 than in curve 39. This results in a maximum braking torque of approximately 10 Nm at a current l=-2A. Up to +2A, the curve 40 does not sufficiently approach a braking torque ONm, meaning that the flux density B of the permanent magnet 27 in the shear gaps 16, 17 cannot be adequately compensated for driving, e.g., on the motorway. At OA, the permanent magnet 27 still achieves a basic braking torque of over 1 Nm, which can be considered high enough to simulate a resistance at a control element, even in the event of a coil 14 failure. The lack of compensation possibility for the permanent magnet 27 at acceptable current strengths makes this bridge width unusable in conjunction with this magnet material N30.

[0072] Curve 41, the second highest curve at -2A, corresponds to the braking torque characteristic of the magnetorheological brake 5, with a bridge thickness d=2mm, i.e., a bridge 22 twice as thick as that in curve 39. This results in a maximum braking torque of over 10Nm at a current l=-2A. At negative currents of the coil 14, the shape of curve 41 approaches a braking torque of ONm. Therefore, at OA, a sufficiently high basic braking torque above ONm is not reached, which could be considered high enough to simulate a resistance at a control element even in the event of a coil 14 failure. The practically non-existent basic braking torque renders this bridge width unusable in conjunction with this magnet material N30.

[0073] Curve 42, the uppermost curve at -2A, corresponds to the braking torque characteristic of the magnetorheological brake 5, with a web thickness d=3mm, i.e., a web 22 three times thicker than that in curve 39. This results in a maximum braking torque of over 11 Nm at a current l=-2A. The shape of curve 42 compensates for the flux P241525

[0074] - 13 - The density B of the permanent magnet 27 in the shear gaps 16, 17 is already in the range of OA; thereafter, the flux density and thus the braking torque increase again. Therefore, at OA, no meaningful basic braking torque results. Simulating a resistance at a control element, even for the failure of the coil 14, cannot be achieved, which renders this bridge width unusable in conjunction with the magnet material N30.

[0075] In the described configurations, there are therefore only limited possibilities for variation around a bridge thickness d = 1.5 mm. The preferred bridge thickness of 1.5 mm can be described as sweet spot 43 for a magnet material N30.

[0076] This sweet spot 43 depends on the magnet material used, whereby the possible range of variation for the bridge thickness d does not change significantly, but is shifted towards different bridge thicknesses d with this sweet spot 43.

[0077] This shift of the sweet spot 43 is shown in Figs. 6a and 6b for the magnet materials N30 and N50, with the possible variance of the web thicknesses represented as a box 44 around the sweet spot 43.

[0078] In Fig. 6a, the sweet spot 43 for a magnet material N30 is located at a web thickness of approximately d = 1.5 mm for the web 22, with thicknesses between 1.4 mm and 1.75 mm still yielding acceptable results. The respective compensation currents achieved are shown as curves 45 running from bottom left to top right, and the corresponding basic braking torques as curves 46 running from top left to bottom right. Compensation currents in the range of 50% of the currents for the maximum braking torque are acceptable, i.e., here at approximately 1 A, with simultaneous basic braking torques in the range of around 1 Nm.

[0079] In Fig. 6b, the sweet spot 43 shifts towards approximately d=2mm, as a stronger magnet material (N50 with over 950 kA / m) was used here.

[0080] To achieve greater bridge thicknesses d, it is necessary to use stronger magnetic materials with field strengths exceeding 500 kA / m, which are achievable with sintered NdFeB. Thinner bridge thicknesses compromise the stability of the stator 8, or rather, the support of the coil 14 within the stator 8. P241525

[0081] - 14 -

[0082] Instead of a single coil 14, double coils or windings in series-parallel circuits can also be provided, thus enabling additional redundancy.

[0083] The permanent magnets 27 can be inserted directly into the receptacle 18 or the pockets 23, or via special magnetic holders with snap hooks or spring elements.

[0084] The holder is inserted into the receptacle 18 or the pockets 23. The receptacle 18 may be screwed in. The pockets 23 may have chamfered edges to facilitate the insertion of the permanent magnets 27.

[0085] P241525

[0086] - 15 -

[0087] List of reference signs

[0088] 1 Steering system

[0089] 2 Angle sensors

[0090] 3 Steering shaft

[0091] 4 electric motor

[0092] 5 Powder brake

[0093] 6 engine mounts

[0094] 7 engine mounts

[0095] 8 Stator

[0096] 9 Rotor

[0097] 10 powder brake bearings

[0098] 11 Hub

[0099] 12 Cavity

[0100] 13 coupling element

[0101] 14 coil

[0102] 15 recording

[0103] 16 Shear gap

[0104] 17 Shear gap

[0105] 18 recording

[0106] 19 Opening

[0107] 20 First page

[0108] 21 Second page

[0109] 22 Bridge

[0110] 23 bags

[0111] 24 First stator part

[0112] 25 Second stator part

[0113] 26 joining surface

[0114] 27 Permanent magnet

[0115] 28 Rotary axis

[0116] 29 Limitation

[0117] 30 Inner area

[0118] 31 Outer area

[0119] 32 Axial hole P241525

[0120] - 16 -

[0121] 33 screw

[0122] 34 Axial web

[0123] 35 side covers

[0124] 36 rotor carriers

[0125] 37 Powder room

[0126] 38 Filling screw

[0127] Curve 39

[0128] 40 Curve

[0129] 41 Curve

[0130] 42 Curve

[0131] 43 sweet spot

[0132] 44 boxes

[0133] 45 Curve

[0134] 46 Curve

[0135] B, B1 flux density d web thickness

[0136] T distance

[0137] D radial thickness

Claims

P241525 - 17 - Patent claims 1. Steering system (1) for steering a vehicle, using a steer-by-wire concept, comprising a control element, a steering shaft (3), a rotor (9), a stator (8), and a continuously adjustable magnetorheological brake (5) influencing the rotation of the steering shaft (3), the stator (8) comprising two components rotatable relative to each other about an axis of rotation, the stator (8) with associated coil (14), and, spaced apart therefrom, the rotor (9) connected to the steering shaft (3), wherein at least one rotating shear gap (16, 17) at least partially filled with a magnetorheological medium is provided between the rotor (9) and the stator (8), and wherein the stator (8) accommodates a permanent magnet (27) for generating a basic braking torque in a receptacle (18), characterized in that the receptacle (18) has a radial limit (29) against which the permanent magnet (27) rests, and the stator (8) in the region of the receptacle (18) has a radial thickness D,the coil (14) is arranged directly on the second side (21) facing the rotor (9), the receptacle (18) overlaps axially with the coil (14), the radial limit (29) is a distance T to the first side (20) of the stator (8) facing radially away from the rotor (9) with T <D aufweist, so dass ein Steg (22) zwischen der zweiten Seite (21 ) und der Aufnahme (18), bzw. der radialen Begrenzung (29) stehen bleibt, wobei der Steg (22) eine Stegdicke d=D-T misst, und wobei die Stegdicke zwischen 1 mm und 2,5mm, vorzugsweise zwischen 1 ,5mm und 2,0mm beträgt., 2. Steering system (1 ) according to claim 1 , characterized in that the receptacle (18) has a ring-shaped structure in the circumferential direction of the stator (8) and has a width between 2 and 6mm, preferably between 2 and 4mm in the axial direction. P241525 - 18 - 3. Steering system (1 ) according to claim 2, characterized in that the receptacle (18) is formed in the circumferential direction from pockets (23) 2 to 19, preferably 11 to 19 around the circumference of the stator (8) for receiving permanent magnets (27).

4. Steering system (1 ) according to claim 3, characterized in that the pockets (23) are arranged evenly distributed over the circumference of the stator (8) and the pockets (23) have a length of 20-60mm.

5. Steering system (1) according to one of the preceding claims, characterized in that the stator (8) is constructed in multiple parts, preferably in two parts in the axial direction, and a joining surface is provided between two stator parts (24, 25) in the area of ​​the receptacle (18) or the pockets (23), so that the receptacle (18) or the pockets (23) are formed by and during the joining of the two stator parts (24, 25).

6. Steering system (1) according to one of the preceding claims, characterized in that the receptacle (18) or the pockets (23) in which the permanent magnet(s) (27) are received are milled into the first side (20) of the stator (8), or that two stator parts (24, 25) are provided and the receptacle (18) or the pockets (23) represent completely closed cavities within the stator (8) in which the permanent magnet(s) (27) are inserted before the joining of the two stator parts (24, 25).

7. Steering system (1) according to one of the preceding claims, characterized in that the permanent magnet(s) (27) have a magnetic field strength greater than 500kA / m, preferably greater than 700kA / m.

8. Steering system (1) according to one of the preceding claims, characterized in that the permanent magnet(s) (27) hold the receptacle (18) or the pockets (23) P241525 - 19 - each completely filled and consisting of one of the following magnet types: sintered neodymium (NdFeB) N20 to N60.

9. Steering system according to claim 1, characterized in that the magnetorheological brake is a magnetorheological powder brake (5).

Images