Magnetorheological brake with damping

Abstract

The invention relates to a magnetorheological brake (1) comprising a rotor (3) which is provided to be rotatable about an axis (18), a mechanical interface (6) which is rotatable about the axis (18), and a damping device (20) with a sliding surface pairing, wherein the damping device (20) has a damping element (20.1) which forms a surface of the sliding surface pairing. wherein the rotor (3) is designed to receive a braking effect, and the damping device (20) is designed to dampen the braking effect before transmission to the mechanical interface (6). The invention further relates to a force feedback actuator (50), a steering device (100), and a damping element (20.1).

Description

[0001] The present invention relates to a magnetorheological brake, a force feedback actuator, a steering device and a damping element.

[0002] Magnetorheological brakes are well-known today. These brakes feature a rotor that is rotatable around an axis and is designed to absorb a braking effect and transmit this braking effect to a mechanical interface, such as a rotatable shaft. The braking effect on the rotor is generated by the friction of a magnetorheological powder (hereinafter referred to as powder) located in a gap between the rotor and a stator. This powder is designed to change its shear or friction properties in the direction of rotation of the rotor when a suitable magnetic field is applied, thereby initiating the braking effect on the rotor. The shear or friction properties are essentially determined by chains of powder particles that form in response to the magnetic field, as the powder particles adhere to each other and to the rotor and stator.

[0003] These types of brakes can generate frictional vibrations, vibrations, and noise emissions. Consequently, they may exhibit poor noise, vibration, and harshness (NVH) characteristics. In haptic applications (human-machine interfaces such as steering, joysticks, or rotary knobs), this can be uncomfortable or irritating. The reason for poor NVH performance can be frictional vibrations caused by a stick-slip effect between the powder and the rotor.

[0004] Based on this, there is a need to improve such a magnetorheological brake.

[0005] Against this background, it is an object of the present invention to provide a magnetorheological brake which in particular has improved NVH behavior. Disclosure of the invention

[0006] These and other problems, which will be mentioned in the following description or which can be recognized by a person skilled in the art, are solved by the subject matter of the independent claims. Advantageous embodiments and further developments can be found in the dependent claims, the following description, and the drawings.

[0007] The magnetorheological brake according to the invention comprises a rotor rotatably mounted about an axis, a mechanical interface rotatably mounted about the axis, and a damping device. The damping device has a sliding surface pairing, wherein the damping device includes a damping element that forms one surface of the sliding surface pairing. The rotor is designed to receive a braking effect, and the damping device is designed to dampen the braking effect before it is transmitted to the mechanical interface. The damping by the damping device allows a reduction or elimination of vibrations, e.g., frictional vibrations, that can act on the mechanical interface. These vibrations can arise, in particular, during the generation of the braking effect as a result of stick-slip effects. The transmission of the braking effect to the mechanical interface can, for example,This is done via a mounting section between the rotor and the mechanical interface.

[0008] To achieve the damping effect, the surface pairing can be provided with a counter surface that is in contact with the surface of the damping element. The surface of the damping element and the counter surface can be designed to slide against each other when the rotor rotates around its axis. In this way, the damping device can be designed with the fewest possible moving parts.

[0009] The braking effect can be achieved through magnetorheological powder as a frictional action in response to a magnetic field that permeates both the powder and the rotor. Due to the magnetic field, the powder particles essentially bind together in the direction of the magnetic field relative to the axis, forming chains that adhere to the rotor and, if applicable, to the stator mentioned below. Shearing of these chains in the rotational or circumferential direction leads to a relative movement of the powder particles with respect to each other, thus resulting in a friction-induced braking effect on the rotor. This method of generating the braking effect allows for simple and rapid control of the braking force by appropriately adjusting the current of an electromagnet.

[0010] The mechanical interface can be a shaft. Other elements, such as a haptic input element (e.g., a steering element, especially a steering wheel, a rotary knob, or a joystick), can be connected to the mechanical interface. This allows a braking effect, particularly a braking torque, to be applied to the element connected to the mechanical interface. In this way, the haptic feedback during operation of the element can be influenced accordingly.

[0011] The damping element can be deformed by contact with the mating surface when the rotor rotates, with the damping effect being caused by the material damping of the damping element. This means that energy from the rotor's vibration to be damped is converted into heat through (vibratory) deformation of the damping element or through deformation of the damping element's material. This deformation can be elastic. By using a separate damping device, the damping effect can be optimally matched to the rotor and the brake in general.

[0012] The damping device can exert a braking effect on the mechanical interface of the brake and / or on the rotating rotor. This braking effect is achieved by designing the damping device in such a way as to reduce, dampen, or even eliminate vibrations, particularly friction-induced vibrations. The damping element, its material, and / or its design are crucial for this. Another factor influencing the damping effect is the design of the mating surface, its material, and / or surface finish, which can be, for example, smooth or textured. Thus, the braking effect achieved here differs from a conventional braking effect, which is not designed to reduce, dampen, or eliminate vibrations.

[0013] Alternatively or additionally, the damping effect is achieved through sliding motion, whereby the damping element is dissipated at the opposing surface, and the resulting friction dampens vibrations of the rotor. Similar to viscous fluid damping, the frictional effect can increase with increasing speed in the sliding surface pair compared to the material damping, or even constitute the main component of the damping effect.

[0014] According to one embodiment, the damping element can comprise or consist of polyethylene, a polymer, in particular polymer foam, rubber, hard rubber, PVC, and / or a natural material such as cork. With these materials, material damping can be achieved in the sliding surface pairing.

[0015] In general, for material damping, it is advantageous if the damping element has a material with a high loss factor, meaning that the material absorbs as much vibrational energy as possible, particularly through deformation. The loss factor corresponds to the energy loss per oscillation when a free vibration is coupled into the damping element. A loss factor of 0.1 to 1 has proven advantageous for haptic applications.

[0016] Alternatively or additionally, the damping element can be made of a highly flexible material, whereby a high degree of deformation allows for the absorption of a comparatively large amount of vibrational energy, which can then be released again with a low loss factor. The material can have a modulus of elasticity between 150 and 1500 N / mm². 2 exhibit characteristics in order to achieve a corresponding damping effect.

[0017] The material of the damping element must not be chosen to be too soft, as otherwise the damping element is at risk of being destroyed during the deformation processes that occur during operation.

[0018] According to one embodiment, the surfaces of the sliding surface pair can be oriented perpendicular to the axis about which the rotor is rotatable. This means that the surfaces are in axial contact with each other with respect to the axis about which the rotor is rotatable. Particularly when the damping element and / or the counter surface are disk- or ring-shaped, this allows for the largest possible sliding surface pair while simultaneously minimizing the axial extent of the damping unit.

[0019] The damping device can be designed to act directly on the rotor, either by having the damping element slide in contact with a surface of the rotor, or by having the damping element mounted on the rotor in a rotationally fixed position, with the damping element in contact with a fixed mating surface to form the surface pairing. Alternatively, the damping device can act on the mechanical interface, either by having the damping element in contact with the mechanical interface and forming the sliding surface pairing, or by having the damping element mounted on the mechanical interface in a rotationally fixed position and in contact with a fixed mating surface to form the surface pairing. The latter two embodiments are less direct, since the rotor is not in contact with the damping element or the damping element is not rotationally fixed to the rotor.However, they can represent alternative solutions if a more direct connection is not possible due to space constraints.

[0020] According to one embodiment, the damping element is fixed relative to the rotor and is in contact with a surface of the rotor, thus forming the sliding surface pairing. The corresponding surface of the rotor forms the mating surface of the sliding surface pairing. For example, the damping element can be in contact with a surface of a disk-shaped section of the rotor. This design allows the use of a rotor whose axial dimensions can correspond to those of a rotor according to the prior art. Only a suitable mating surface needs to be provided, which can be created, for example, by appropriate surface treatment of the rotor, such as grinding and / or polishing, or by roughening and / or profiling. In particular, this does not result in a significant increase in the rotational moment of inertia of the rotor.

[0021] According to one embodiment, the damping element is coupled to the rotor and is in contact with a stationary surface of the brake, thus forming the sliding surface pairing. The stationary surface forms the mating surface of the sliding surface pairing. This mating surface can be located on an inner surface of a brake housing. The damping element can be mounted directly on the rotor. This embodiment allows for particularly easy assembly of the brake, as the rotor and the sealing element can be pre-assembled and then inserted into the brake or connected via the mechanical interface.

[0022] According to one embodiment, the sliding surface pair is subjected to an elastic preload. This elastic preload ensures that the surfaces of the damping element and the mating surface of the sliding surface pair are always in contact, so that the damping effect is always present in every operating state of the brake. The preload can be initially set by appropriately designing the preload element. The preload element can, for example, be designed as a spring element, such as a disc spring. The preload can be adjusted, in particular, by the spring constant of the preload element and / or by a corresponding installation space for the spring element. The preload element can be identical to the damping element. If the preload element is made of an elastic material, an interference fit can be used to achieve preload and thus press the damping element against the mating surface.If the damping element is not elastic or not sufficiently elastic, the preload element can be designed separately to preload the damping element or the sliding surface pair accordingly. It can also be provided for preloading even if the damping element alone would be sufficiently elastic to apply the preload force. In this case, the preload element can provide support. The preload force can be 100–200 N to ensure sufficient preload while simultaneously preventing the static friction moment generated by the preload from becoming too large, thus avoiding any irritating static friction effects in the damping device when the mechanical interface begins to move or when the direction is reversed.

[0023] According to one embodiment, the damping element has a profile. The profile can be designed to increase the compliance of the damping element in the direction of movement in which the damping element moves against the counter surface. That is, the damping element becomes softer in this direction of movement. This can be achieved, for example, by segmenting the damping element, dividing the surface of the damping element that is in contact with the counter surface into segments. Recesses are provided between the segments so that the segments can shift as they slide against the counter surface due to friction.In particular, the damping element can be designed as a ring, with the side of the ring in contact with the counter surface being slotted transversely to the sliding motion between the damping element and the counter surface to create surface segmentation. If the damping element is a ring in axial contact with the counter surface, the ring can be provided with radially extending slots to create segmentation, separating the individual segments. Such segmentation of a ring reduces the torsional stiffness of the damping element. This allows for greater shear stress in the material of the damping element, thus enabling more vibrational energy to be absorbed within the material.

[0024] According to one embodiment, the brake has a stator that is fixed relative to the rotor. The rotor and the stator are spaced apart radially with respect to the axis about which the rotor is rotatable. A gap is provided between the rotor and the stator, in which a magnetorheological powder, as described above, is placed. The brake is designed to generate a magnetic field that penetrates the gap and the magnetorheological powder contained therein in order to produce the braking effect on the rotor. The generation of the magnetic field can be achieved by means of a magnetic field generator in the brake, such as an electrical coil. In this way, the magnetic field, and thus ultimately the generated braking effect, can be controlled by appropriately adjusting the electric current flowing through the magnetic field generator or by appropriately adjusting the electric voltage applied to the magnetic field generator.

[0025] The rotor can be located within the stator, i.e., radially with respect to the axis about which the rotor is rotatable. Alternatively, the stator can be arranged coaxially with respect to the rotor, also with respect to the axis about which the rotor is rotatable. In this way, the rotor and stator can define the gap radially through mutually facing surfaces. The rotor surface that defines the gap in this manner can be a circumferential surface. The rotor can have several such circumferential surfaces. Alternatively or additionally, the rotor can have other surface shapes that define the gap. The corresponding stator surface can be designed such that the gap always has the same width along its path. In this way, the rotor and stator can be adapted to achieve the desired guidance of the magnetic flux through the rotor and stator materials.

[0026] According to one embodiment, the sliding surface pair is arranged outside the interior space containing the magnetorheological powder. This prevents powder from entering the sliding surface pair and thus negatively affecting the damping behavior of the damping device. The powder particles could act as small rolling elements or abrasives, significantly altering the friction or wear in the surface pair. This would simultaneously reduce the damping effect of the damping device, a problem avoided by arranging the damping device outside the interior space.

[0027] The interior space containing the magnetorheological powder can be formed within a brake housing, with the rotor extending into this interior space. The interior space can therefore be located radially outside the axis about which the rotor is rotatable, while the sliding surface pair is arranged radially inside, i.e., radially closer to the axis about which the rotor is rotatable.

[0028] To prevent powder leakage from the interior, the interior is sealed by means of sealing elements that radially define the interior space with respect to the axis about which the rotor is rotatable. Such sealing elements can be designed as sliding, particularly axially extended, sealing elements that are in contact with the rotor, which extends radially into the interior space with respect to the axis about which the rotor is rotatable, thereby defining and sealing the interior space radially, e.g., internally. The damping device, in which either the mating surface or the damping element is located on the rotor, can then be positioned internally below such a sealing element and thus outside the interior space.By placing the damping device directly on the rotor, the most direct possible damping effect is achieved, without the need for further intermediate elements that would be required to transfer the damping effect to the rotor.

[0029] To increase the distance between the damping device and the axis about which the rotor is rotatable, and thus the lever arm for the damping device, the damping device can be positioned axially, with respect to the axis about which the rotor is rotatable, and also axially from the rotor and the interior, instead of the placement proposed above. In this way, the damping device can be arranged at a greater radial distance from the axis about which the rotor is rotatable, thereby achieving a longer lever arm for the damping device. This allows for improved damping effect to be applied to the rotor or directly to the mechanical interface.The connection between the damping device and the rotor or mechanical interface can be achieved via a separate element that is rotationally fixed to the rotor or mechanical interface to transmit the damping effect. This allows for a more flexible arrangement of the damping device in the axial and / or radial direction.

[0030] According to one embodiment, the brake is designed to apply an axial force to the sliding surface pair of the damping device. This axial force is generated by a magnetic field generator. This generator can be identical to or different from the aforementioned magnetic field generator, so that the brake has at least two magnetic field generators, e.g., two electrical coils.

[0031] The axial force can be generated by an attractive force between the rotor and stator, acting on a gap in the brake that extends essentially radially between the rotor and stator. The magnetic field of this gap acts on, or penetrates, this radially extended gap. If the sliding surface pair is oriented such that it consists of, or has, axially opposing surfaces, then the axial force generated in this way can be supported within the sliding surface pair, more precisely, within the axially opposing surfaces of the surface pair. This increases the frictional force in the sliding surface pair and thus the damping effect. The axial force is caused by an attractive force resulting from the magnetic field that penetrates the gap and acts between the rotor and stator surfaces that define the first gap in the axial direction.

[0032] To support the axial force in the sliding surface pairing, the rotor and / or the shaft on which the rotor is provided can be mounted in such a way that support of this axial force is not provided or is only partially provided by the mounting of the rotor and / or the shaft, so that at least a portion or the entire axial force can be supported in the sliding surface pairing.

[0033] Depending on the magnitude of the magnetic field strength and / or the magnetic flux of this magnetic field penetrating the radially extended gap, a different magnitude of axial force is established. Thus, by appropriately controlling and thereby generating this magnetic field, the axial force on the sliding surface pair can be adjusted. In particular, it can be provided that the corresponding magnetic field generator is controlled in such a way that the axial force acts on the sliding surface pair in such a way as to achieve a desired damping effect. By setting this damping effect, a braking effect is automatically generated through the interaction of the set magnetic field with the powder in the first gap and the creation of a corresponding friction point. If the brake has a second magnetic field generator, such as...The second magnetic field generator, which acts on an axially extended gap, can, for example, complement the first magnetic field generator and be controlled in such a way that a second braking effect is achieved, so that the first and second braking effects combined result in the desired target braking effect. In this way, the desired target braking effect is achieved with simultaneously optimized damping.

[0034] According to one aspect, a force feedback actuator is provided. The force feedback actuator comprises a drive unit, a magnetorheological brake as described above, and a mechanical interface. The force feedback actuator is designed to apply a force or torque to the mechanical interface in order to provide feedback to a user via the mechanical interface. The mechanical interface can be designed as a rotatable shaft, so that a rotary or pivoting movement can be subjected to the corresponding torque feedback by the force feedback actuator. The rotatable shaft can, in particular, be arranged coaxially to the axis about which the brake rotor is rotatable, in order to achieve a compact design for the force feedback actuator. The drive unit can be an electric motor with a rotary axis.The axis of rotation of the drive unit can be arranged, in particular, coaxially with the axis of the rotatable shaft of the force feedback actuator and preferably also coaxially with the axis about which the brake rotor is rotatable, in order to achieve a compact design for the force feedback actuator. Using an electric motor as the drive unit allows for a fast response time of the force feedback actuator. The mechanical interface of the force feedback actuator can be connected to an input element through which a user has haptic contact with the mechanical interface and can make manual inputs. The input element can be designed, in particular, as a steering element, such as a steering wheel, as a rotary knob, and / or as a pivoting element, such as a joystick. In this way, the force feedback actuator can be designed according to the specific application.The force feedback actuator is designed to imprint haptic feedback onto its mechanical interface, and thus onto the input element, via the brake and / or the drive unit. This allows for different types of haptic feedback to be provided to the rider. Specifically, supportive feedback can be generated when the drive unit actuates the mechanical interface of the force feedback actuator in response to the user's input. Conversely, braking feedback can be generated by controlling the brake and / or the drive unit in such a way that it decelerates the mechanical interface of the force feedback actuator in response to the user's input. Therefore, a variety of haptic feedback options can be presented to the rider.

[0035] According to one aspect of the invention, a steering system for a vehicle is provided. The steering system comprises an input element designed as a steering element, a force feedback actuator as described above, or a magnetorheological brake as described above. The input element is rotationally fixed to the mechanical interface of the force feedback actuator or to a mechanical interface of the brake. The steering element can, for example, be designed as a steering wheel or joystick, via which a driver, as the user, can input steering commands into the steering system. The steering system is designed to provide haptic feedback to the driver via the coupling of the steering element to the mechanical interface of the brake or the force feedback actuator.This is particularly advantageous when the steering system is a steer-by-wire system, which lacks a mechanical linkage to the steered wheels, thus preventing direct haptic feedback from the steered axle or wheels to the steering element. However, even with a steering system that does have a mechanical linkage, the desired steering feel can be generated using the brake and / or the force feedback actuator, which the driver can then experience haptically via the steering element.

[0036] The brake according to the invention is particularly advantageous during slow steering movements, because the damping device and the compliance of the damping element prevent operating conditions in which stick-slip effects have a strong impact.

[0037] According to a further aspect of the invention, a damping element is provided for a magnetorheological brake. The damping element can be designed as described above and, in particular, can be annular and / or segmented. Detailed description based on drawing

[0038] Further embodiments of the invention are described in more detail below, along with a description of exemplary embodiments of the invention, with reference to the figures. The figures show: Fig. 1 a schematic sectional view of a magnetorheological brake according to an embodiment of the invention, Fig. 2 a schematic sectional view of a brake according to a further embodiment of the invention, Fig. 3 a schematic perspective sectional view of a brake, Fig. 4 a schematic perspective sectional view of a housing section, Fig. 5 a perspective view of a damping element, Fig. 6. A comparison of moment diagrams, Fig. 7 a schematic representation of a force feedback actuator, Fig. 8 a schematic representation of a steering device for a vehicle, and Fig. 9 a schematic sectional view of a magnetorheological brake according to an embodiment of the invention.

[0039] The figures are purely schematic and serve only to illustrate the invention. The same elements are identified by the same reference symbols.

[0040] Fig. Figure 1 shows a schematic and exemplary sectional view of a magnetorheological brake according to an embodiment of the invention.

[0041] A magnetorheological brake 1 is shown, comprising a rotor 3 and a mechanical interface 6. The rotor 3 and the mechanical interface 6 are rotatably mounted about an axis 18. The mechanical interface 6 is designed here as a rotatable shaft extending horizontally. The rotor 3 and the mechanical interface 6 are arranged coaxially with the axis 18. The rotor 3 is non-rotatably connected to the mechanical interface 6 via a fastening section 7, whereby a fastening element 7.1, such as a screw, detachably connects the rotor 3 and the mechanical interface 6. In this way, a detachable connection between the rotor 3 and the mechanical interface 6 is created, which facilitates maintenance and assembly of the brake 1.

[0042] The rotor 3 is designed to receive a braking effect and is designed to transmit the braking effect via the mounting section 7 to the mechanical interface 6.

[0043] The brake 1 shown has an interior space 8 that extends annularly around the axis 18 and is axially bounded by the housing sections 9 and 10. Furthermore, the interior space 8 is internally bounded radially by the sliding sealing elements 11 and 12. The left sealing element 11 is located on the housing section 9, and the right sealing element 12 is located on the housing section 10. Both sealing elements 11 and 12 extend axially with respect to the axis 18 and contact the rotor 3 from both sides. Externally, the interior space 8 is bounded radially by a stator 2, with the interior space 8 sealed by a sealing element 13 located between the housing section 9 and the stator 2, and by a sealing element 14 located between the housing section 10 and the stator 2. A magnetorheological powder is provided in the interior space 8, which is thus sealed from the environment.Housing section 10 also serves to support the mechanical interface 6 by providing a bearing 15. Additionally, the mechanical interface 6 is supported in housing section 9 by a further bearing 19. From the left, housing section 9 is fitted with a screwed-on cover 22, which axially positions the housing section 9.

[0044] The rotor 3 and the stator 2 are spaced apart radially with respect to the axis 18, forming a gap 4 that is bounded radially on the inside by the rotor 3 and radially on the outside by the stator 2. The gap 4 extends rotationally symmetrically around the axis 18. The rotor 3 can therefore rotate within the stator 2 around the axis 18. In other words, the stator 2 surrounds the rotor 3 circumferentially with respect to the axis 18.

[0045] Within the gap 4, a magnetic field generator 5, similar to an electrical coil, is provided. The magnetic field generator 5 is designed to produce a magnetic field to generate the braking effect on the rotor 3. This field propagates through the gap 4 and the magnetorheological powder contained therein, and its field lines extend further through the rotor 3 and the stator 2, resulting in a closed field line pattern. This process creates chains within the powder that extend radially around axis 18 as a result of the magnetic field and consist of powder particles that adhere to one another due to the magnetic field.When the rotor 3 rotates around the axis 18, these chains, which ultimately also adhere at their ends to the surfaces of stator 2 and rotor 3 that define the gap 4 in the radial direction, are sheared off circumferentially. This creates a friction point in the circumferential direction between the sheared chains or between the powder and the corresponding surfaces of stator 2 or rotor 3. As a result, a braking effect is exerted on the rotor 3 due to the friction at this point. Because of this mechanism for forming the friction point or adjusting the braking effect, the friction point can shift radially within the powder or spontaneously form at a specific radial location within the powder. This can lead to stick-slip effects and frictional vibrations, which impair the NVH (noise, vibration, and harshness) performance of the brake and which may be affected by a user who, for example,via an input element that is in contact with the mechanical interface 6, can be experienced haptically, which can lead to irritation.

[0046] To dampen stick-slip effects and frictional vibrations, and thus improve NVH behavior, the brake has a damping device 20. This damping device includes a damping element 20.1, which is provided in housing section 9. The damping element 20.1 contacts the surface of the rotor 3 on the left side of the drawing in the axial direction, with the damping element 20.1 being fixed relative to the rotor 3. In this way, a sliding surface pairing is formed at the contact point between the rotor surface and the surface of the damping element 20.1 facing axially towards the rotor 3. This sliding surface pairing is designed to exert a damping effect on the rotor 3. In this sliding surface pairing, the surface of the rotor 3 with which the damping element 20.1 is in contact acts as the mating surface.

[0047] The damping effect is achieved by deformation of the damping element 20.1 in the direction of rotation of the rotor 3 about the axis 18. The damping element 20.1 is thereby twisted and absorbs vibrational energy, which is converted into heat by the material damping of the damping element 20.1. In addition, a frictional force arising in the sliding surface pair can further contribute to the damping.

[0048] The damping element can consist of an elastomer and have a loss factor of 0.1 and / or a modulus of elasticity of 150 - 1500 N / mm². 2 .

[0049] As can be seen in the drawing, the damping device 20 is arranged outside the interior 8. More precisely, the damping device 20 is arranged radially inside the interior 8, with the damping element 20.1 being axially positioned approximately in the same location as the sealing element 11. The illustration makes it clear that the damping device 20, which here has a ring-shaped damping element 20.1, can be positioned such that the brake 1 is not axially wider than a brake 1 without such a damping device 20. This becomes clear when considering the maximum axial extent of the rotor 3. The damping element 20.1 can still be arranged radially below the axially extending portion of the rotor 3, which ultimately defines the inner radial boundary of the gap 4. Thus, the damping element 20.1 radially placed at a constriction or narrowing of the rotor 3, which does not lead to any axial widening of the brake 1, because in the example shown this is largely determined by the axial extent of the rotor 3.

[0050] The contact force with which the damping element 20.1 is pressed against the rotor 3 can be adjusted by the design of the brake 1. In particular, the interaction of housing section 9 and cover 22, which is fastened by means of screws, allows for the adjustment of the axial position of the damping element 20.1 and thus the contact force on the rotor 3. The damping effect can therefore be influenced accordingly.

[0051] The placement of the damping device 20 outside the interior 8 also has the advantage that no powder particles can enter the sliding surface pairing, i.e., between the damping element 20.1 and the rotor 3. This prevents the friction conditions in the sliding surface pairing from changing, which would reduce the damping effect. Otherwise, the powder particles could act like small rolling elements or even as abrasives in the sliding surface pairing and reduce the vibration damping or service life. The sealing element 11 shields the damping device 20 in this respect.

[0052] Fig. Figure 2 shows a schematic sectional view of a brake according to a further embodiment of the invention.

[0053] The design and function of the magnetorheological brake 1 shown largely corresponds to the design and function of the one described in Fig. 1. Brake shown. Therefore, only the differences will be discussed below, and otherwise the preceding description applies. Fig. Referenced in 1. Identical elements are otherwise marked with the same reference symbol.

[0054] Compared to brake 1 in Fig. In this case, a preload element 21 is provided, which acts axially on the damping element 20.1 and presses it axially against the rotor 3 and thus against the mating surface of the sliding surface pair. In this way, permanent contact can be established in the sliding surface pair by the preload element 21 overcoming or compensating for tolerances and play as well as wear of the damping element 20.1, i.e., material loss due to friction in the sliding surface pair. Thus, the damping effect on the rotor 3 is ensured over the service life of the brake 1, provided the preload element 21 is appropriately designed.

[0055] Fig. Figure 3 shows a schematic perspective sectional view of a brake. Fig. Figure 4 shows a schematic perspective sectional view of a housing section. Fig. Figure 5 shows a perspective view of a damping element made of Fig. 3 and Fig. 4. This could also include the damping elements of the brakes 1, which are located in the Fig. 1 and Fig. 2 are shown. Identical elements are therefore marked with the same reference symbol.

[0056] The views shown here depict a further development of the damping element 20.1. The damping element 20.1 here has a segmented surface design, through which it comes into contact with the opposing surface in the sliding surface pairing.

[0057] As in Fig. As can be seen in Figure 5, the damping element 20.1 is ring-shaped and divided into segments 20.2 by means of slots that extend from the surface on the left in the drawing to approximately half the material thickness of the damping element 20.1. The slots can run radially. As shown in the Fig. 3 and Fig. As can be seen in section 4, the damping element 20.1 is positioned in the housing section 9 in such a way that its segmented side comes into contact with the rotor 3.

[0058] Compared to a damping element without segments 20.2, the damping element 20.1 shown here is torsionally flexible, since the segments 20.2 can deform more during relative movement in the sliding surface pairing. This, in turn, allows for better transmission of vibrational energy into the damping element 20.1 and the associated absorption of this energy. Reversal of direction is also easier, as a change in the direction of rotation can cause the segments 20.2 to become preloaded in the opposite direction before the damping element 20.1 adheres to the surface.

[0059] Fig. Figure 6 shows a comparison of torque curves at a mechanical interface of a magnetorheological brake over time. The dashed line shows a braking torque curve exhibiting a comparatively high oscillation. This corresponds to a frictional vibration of the rotor interacting with the powder without a damping device according to the invention, where the braking torque, plotted on the vertical axis, was measured at the mechanical interface of the brake. In comparison, the solid line shows the torque curve of an otherwise identical magnetorheological brake equipped with a damping device according to the invention. It is evident that the amplitude of the frictional vibration is more than halved. The NVH behavior of the brake was significantly improved by the damping device.

[0060] Fig. Figure 7 shows a schematic representation of a force feedback actuator, according to a further aspect of the invention.

[0061] The force feedback actuator 50 shown has a magnetorheological brake 1, which, like the brake 1 from the Fig. 1, Fig. 2 to Fig. 3. Furthermore, the force feedback actuator 50 has a drive unit 51. The drive unit 51 can be designed as an electric motor or include an electric motor.

[0062] The force feedback actuator 50 has a mechanical interface 52 that extends vertically in the drawing and is designed as a shaft. The shaft is rotatable about the vertically extending axis 53 and is oriented coaxially with the axis 53. The mechanical interface 52 is designed to be connected to an input element. This can be, for example, a joystick, a rotary knob, or a steering element such as a steering wheel. The input element can be connected to the mechanical interface 52, for example, at its upper free end.

[0063] Brake 1 and drive unit 51 are connected via the mechanical interface 52. For example, it may be provided that the mechanical interface 52 is connected to the mechanical interface 6 of one of the brakes 1 from the Fig. 1, Fig. 2 to Fig. 3 is connected so that the rotor 3 can apply a braking torque generated by the brake 1 to the mechanical interface 52. In this case, the mechanical interface 52 represents an extension of the shaft-shaped mechanical interface 6 from the Fig. 1, Fig. 2 to Fig. 3, wherein the mechanical interface 52 is, for example, connected to or identical with the mechanical interface 6. The drive unit 51 is configured to apply a drive torque to the mechanical interface 52. The drive unit 51 can preferably be configured to apply the drive torque to the mechanical interface 52 in both directions of rotation.

[0064] By appropriately controlling the brake 1 and the drive unit 51, e.g. by a control unit (not shown) of the force feedback actuator 50, haptic feedback can be generated which is perceptible to a user at the mechanical interface 52 or at an input element coupled to it in a torque-transmitting manner.

[0065] Fig. Figure 8 shows a schematic representation of a steering device for a vehicle, according to a further aspect of the invention.

[0066] As part of the steering system 100, the above-mentioned Fig. The force feedback actuator 50 shown here is outlined in section 7, surrounded by a dashed box. For its description, please refer to the description at Fig. 7 referred.

[0067] A torque-transmitting input element 101 is coupled to the mechanical interface 52. This input element is configured here as a steering element, for example, a steering wheel, steering lever, or joystick. A user can thus receive haptic feedback directly via the steering element. This feedback is applied to the mechanical interface 52 in the form of a braking torque from the brake 1 and / or a driving torque from the drive unit 51 of the force-feedback actuator 50. The geometric arrangement of the drive unit 51 and the brake 1 with respect to the interface 52 is arbitrary, as the torque is added without preference at the mechanical interface 52. Therefore, the mechanical interface 52 can also be located closer to the drive unit 51 (the drive unit 51 and the brake 1 can be interchanged).

[0068] The steering device 100 shown can be configured as a steer-by-wire steering device. In this configuration, the mechanical interface 52 is not connected to, or designed for, the steered wheels of a vehicle. Haptic feedback about the current driving state of the steered wheels, e.g., through a return torque at the input element 101, is not possible here due to the lack of a mechanical connection between the wheels and the steering element. This feedback can instead be provided by the integrated force-feedback actuator 50 by controlling the drive unit 51 and / or the brake 1 accordingly, e.g., by a control unit (not shown) of the force-feedback actuator 50 or the steering device 100. In this way, eliminating the mechanical connection to the wheels results in a space-saving advantage for the steering device 100 and / or the vehicle.

[0069] However, it is also conceivable that the steering device 100 is designed for mechanical coupling with the steered wheels of a vehicle. In this case, it is possible to supplement the haptic feedback, which is perceptible via the mechanical coupling with the steered wheels, by the drive torque of the drive unit 51 and / or by the braking torque of the brake 1, by controlling the drive unit 51 and / or the brake 1 accordingly, e.g. by a control unit (not shown) of the force feedback actuator 50 or the steering device 100, in order to set a desired steering feel.

[0070] Fig. Figure 9 shows a schematic sectional view of a magnetorheological brake according to an embodiment of the invention.

[0071] A magnetorheological brake 1 is shown. The brake 1 has a rotor 3 which is fixedly mounted on a mechanical interface 6, such as a shaft 6. In the drawing, the shaft 6 extends from left to right and is rotatable about the horizontal axis 18.

[0072] Information regarding the positioning or direction of some elements of brake 1 is given in the drawing with respect to axis 18. That is, in the drawing, a radial direction is a vertically upward direction, and an axial direction is a direction parallel to axis 18, which runs from left to right in the drawing.

[0073] The shaft 6 is supported in the housing of the brake 1 by means of a bearing 15. The housing has, in particular, housing sections 9 and 10, which axially define an interior space 8 of the brake, wherein the interior space 8 is externally and radially bounded by the stator 2, more precisely by a stator section 2.2. The stator 2 is fixed relative to the rotor 3, so that when the shaft 6 rotates, the rotor 3, to which it is attached via the mounting section 7 of the shaft 6 by means of a fastening element 7.1, such as a screw, rotates relative to the stator 2.

[0074] The interior space 8 is sealed radially inwards with respect to axis 18 by sealing elements 11 and 12. Sealing element 11 is located in the housing section 10, where it is in sliding contact with a surface of the rotor 3. Sealing element 12 is located on the shaft 6, where it is in sliding contact with a surface of the housing section 9.

[0075] A sealing element 13 is provided between housing section 9 and stator section 2.2 to seal the interior 8. A sealing element 14 is provided between housing section 10 and stator section 2.2 to seal the interior 8.

[0076] Within the interior 8, the brake 1 has a first gap 40 and a second gap 41. The first gap 40 extends essentially radially. Axially, it is bounded to the left by a corresponding surface of the rotor 3, while axially it is bounded to the right by a corresponding surface of a stator section 2.1. In the illustrated embodiment, the stator section 2.1 is fastened to the housing section 10 by means of a fastening element 2.4, such as a screw. The second gap 41 extends essentially axially and is bounded internally and radially by a corresponding surface of the rotor 3, while externally and radially by a corresponding surface of the stator section 2.2.

[0077] The brake 1 further comprises a first magnetic field generator 60 and a second magnetic field generator 61. Both magnetic field generators 60, 61 can be configured as electrical coils which, depending on their number of turns and their current, can generate a first magnetic field and a second magnetic field, respectively. The first magnetic field, generated by the first magnetic field generator 60, passes through the first gap 40. The second magnetic field, generated by the second magnetic field generator 61, passes through the second gap 41. A magnetorheological powder is located in the interior 8, particularly in the gaps 40, 41. In response to the first magnetic field and the second magnetic field, respectively, this powder forms chains between its particles, thus changing the shear and friction properties of the powder within the gaps 40, 41.Chains of powder particles then run essentially in the axial direction in the first gap 40, while they run essentially in the radial direction in the second gap 41. In this way, corresponding friction points are created in the gaps 40 and 41, resulting in a first braking effect, generated in the first gap 40, and a second braking effect, generated in the second gap 41, each acting on the rotor 3 and which can be combined to form a total braking effect.

[0078] It can also be seen that the stator 2 has several stator sections 2.1, 2.2. The stator sections 2.1, 2.2, as well as the housing sections 9 and 10, are connected to each other by means of the fastening elements 30, 31 and fastening element 2.4, or they are assembled accordingly during assembly, which facilitates the assembly of the brake 1. The fastening elements 2.4, 30, 31 can be screws.

[0079] To dampen stick-slip effects and frictional vibrations, and thus improve NVH behavior, the brake 1 has a damping device 20. The damping device 20 has a damping element 20.1, which is provided in the housing section 10. The damping element 20.1 contacts the surface of the rotor 3 on the right side of the drawing in the axial direction, with the damping element 20.1 being fixed relative to the rotor 3. In this way, a sliding surface pairing is formed at the contact point between the rotor surface and the surface of the damping element 20.1 facing axially towards the rotor 3, which is designed to exert a damping effect on the rotor 3. In the sliding surface pairing, the surface of the rotor 3 with which the damping element 20.1 is in contact acts as the mating surface.

[0080] The damping effect is achieved by deformation of the damping element 20.1 in the direction of rotation of the rotor 3 about the axis 18. The damping element 20.1 is thereby twisted and absorbs vibrational energy, which is converted into heat by the material damping of the damping element 20.1. In addition, a frictional force arising in the sliding surface pair can further contribute to the damping.

[0081] The damping element can consist of an elastomer and have a loss factor of 0.1 and / or a modulus of elasticity of 150 - 1500 N / mm². 2 .

[0082] As can be seen in the drawing, the damping device 20 is arranged outside the interior space 8. More precisely, the damping device 20 is arranged radially inside the interior space 8, i.e., it is located below the sealing element 11. The illustration makes it clear that the damping device 20, which here has a damping element 20.1 designed as a ring, can be positioned such that the brake 1 is not axially wider than a brake 1 without such a damping device 20. This becomes clear when considering the maximum axial extent of the rotor 3. The damping element 20.1 can be arranged radially below the axially extending area of ​​the rotor 3, which ultimately defines the gap 40 axially and the gap 41 radially inside. Thus, the damping element 20...1 radially placed at a constriction or narrowing of the rotor 3, which does not lead to any axial widening of the brake 1, because in the example shown this is largely determined by the axial extent of the rotor 3.

[0083] The contact force with which the damping element 20.1 is pressed against the rotor 3 can be determined by the design of the brake 1. In particular, the interaction of housing section 10 and damping element 20.1, when connecting the stator sections 2.1 and 2.2 by means of the fastening element 30, allows for the adjustment of the axial position or preload of the damping element 20.1 and thus the contact force on the rotor 3. The damping effect can therefore be influenced accordingly.

[0084] The placement of the damping device 20 outside the interior 8 also has the advantage that no powder particles can enter the sliding surface pairing, i.e., between the damping element 20.1 and the rotor 3. This prevents the friction conditions in the sliding surface pairing from changing, which would reduce the damping effect. Otherwise, the powder particles could act like small rolling elements or even as abrasives in the sliding surface pairing and reduce the vibration damping or service life. The sealing element 11 shields the damping device 20 in this respect.

[0085] Optionally, as shown here, a preload element 21 can be provided, which acts axially on the damping element 20.1 and presses it axially against the rotor 3 and thus against the mating surface of the sliding surface pair. In this way, permanent contact can be established in the sliding surface pair by the preload element 21 overcoming or compensating for tolerances and play as well as wear of the damping element 20.1, i.e., material loss due to friction in the sliding surface pair. Thus, the damping effect on the rotor 3 is ensured over the service life of the brake 1 with appropriate design of the preload element 21.

[0086] The radial extent of the first gap 40 results in an axial attractive force between the rotor 3 and the stator 2, more precisely, between the stator section 2.1 and the corresponding opposite rotor surface, which axially limits the first gap 40. The brake 1 can be designed such that the axial attractive force is used to adjust the damping of the damping device 20. For this purpose, the brake 1 can be designed such that the axial attractive force is supported at least partially, preferably completely, in the sliding surface pairing between the rotor 3 and the damping element 20.1. In this way, the driving force in the sliding surface pairing is increased accordingly, which leads to an increase in the damping effect.At the same time, this can also create a braking effect on the rotor 3, so that the first braking effect, which is generated by the first magnetic field generator 60 in the first gap 40, is supplemented by this braking effect.

[0087] Generating a second braking effect in the second gap 41, where the second magnetic field generator 61 permeates it with a second magnetic field, has no effect on the action of the damping device 20. Here, the attractive force between rotor 3 and stator section 2.2 acts in a radial direction. The rotor 3 is therefore not drawn axially towards the damping device 20, and consequently, no further force is introduced into the sliding surface pairing between rotor 3 and damping element 20.1. Thus, controlling the second magnetic field generator 61 allows the generation of a braking effect that is essentially produced by the friction point in the first gap 41.

[0088] The gap 41 and the second magnetic field generator 61 of the in Fig. The nine brakes shown can be understood as optional. A brake 1 that does not have these elements, but otherwise matches the one shown in Fig. The brake 1 shown in Figure 9 can also exert a braking effect on the rotor 3 in the form of the first braking effect generated in the gap 40. If the damping device 20 described above is present, the damping effect can also be adjusted according to the axial contact force resulting from the magnetic field of the first magnetic field generator 60, which penetrates the first gap 40.

[0089] Alternatively, the gap 41 of the in Fig. Brake 1 shown in 9 also from gap 4 Fig. 1 or Fig. 2 correspond to, while the second magnetic field generator 61 corresponds to the magnetic field generator 5 from Fig. 1 or Fig. 2 can correspond. In this case, the in Fig. Brake 1 shown in section 9 is a further development of brake 1 from the Fig. 1 or 2.

[0090] The embodiment of the in Fig. The brake shown in Figure 9, which has a first magnetic field generator 60 and a second magnetic field generator 61, allows different operating strategies for the brake 1.

[0091] The second magnetic field generator 61 can be used to supplement the first braking effect, i.e., the braking effect generated by the first magnetic field generator 60. This means that the braking effects of the first and second magnetic field generators 60, 61 are combined into a total braking effect that corresponds to a target braking effect, which can be higher than the maximum possible individual braking effects that can be produced by the first magnetic field generator 60 and the second magnetic field generator 61. The corresponding control of the first magnetic field generator 60 and the second magnetic field generator 61, which essentially consists of adjusting the respective coil current, in particular the current intensity and / or the current flow direction, can be implemented by a control device (not shown) of the brake 1, such as a control unit.

[0092] Alternatively or additionally, the first magnetic field generator 60 and the second magnetic field generator 61 can be configured redundantly with respect to each other, meaning that if one of the two magnetic field generators 60, 61 fails or malfunctions, a braking effect is generated by the other of the two magnetic field generators 60, 61 in the respective gap 40, 41 and / or in a further gap. In this way, the fail-safe operation of the brake 1 is ensured. It should be noted that a maximum braking effect on the rotor 3, which can be generated by both the first magnetic field generator 60 and the second magnetic field generator 61 simultaneously, is no longer possible, since in this case of redundancy only one magnetic field generator 60, 61 can be activated.

[0093] Alternatively or additionally, the two magnetic field generators 60, 61 can be controlled independently of each other, thereby achieving a basic braking effect. Setting a desired braking effect is not possible with this control method when both magnetic field generators 60, 61 are active. However, this eliminates the need for a complex control system for brake 1.

[0094] Alternatively or additionally, one of the magnetic field generators 60, 61 can be controlled to generate a basic braking effect on the rotor 3. The other magnetic field generator 60, 61 is then controlled to produce an overall braking effect, resulting from the combination of the first and second braking effects, thus achieving the desired braking effect on the rotor 3. This is particularly relevant in the case of the Fig.In the embodiment shown in Figure 9, which includes the damping device 20, such a control system can be implemented. The first magnetic field generator 60 can be controlled to produce the first braking effect as the basic braking effect. For example, a predetermined coil current can be set by the control unit of the brake 1, so that, in addition to the first braking effect generated in the first gap 40, a predetermined contact force is established in the sliding surface pairing of the damping device 20. The predetermined coil current and / or the predetermined contact force required to generate the desired first braking effect and the desired damping effect on the rotor 3 can, for example, be stored in a memory, particularly in the control unit, and assigned to an application case, which is characterized, for example, by the target braking effect to be set, and thus be retrievable.The second magnetic field generator 61 can then be controlled in a controlled manner to adjust the total braking effect on the rotor 3, which results from the first and second braking effect as well as any existing braking effect of the sliding surface pairing, according to a target braking effect.

[0095] The embodiments of the invention described here in connection with the figures and the embodiments described above in the general part of the description can be combined with each other as desired. Reference symbol list 1 magnetorheological brake 2 Stator 2.1 Stator section 2.2 Stator section 2.4 Fastening element 3 Rotor 4 columns 5 magnetic field generators 6 mechanical interface / shaft 7 Mounting section 7.1 Fastening element 8 Interior 9 Housing section 10 Housing section 11 Sealing element 12 Sealing element 13 Sealing element 14 Sealing element 15 warehouses 18 axle 19 warehouses 20 Damping device 20.1 Damping element 20.2 Segment 21 Preload element 22 Cover 30 Fastening element 31 Fastening element 40 first gap 41 second slit 50 Force feedback actuator 51 Drive unit 52 mechanical interface 53 axle 60 first magnetic field generator 61 second magnetic field generator 100 Steering device 101 Input element

Claims

Magnetorheological brake (1) comprising a rotor (3) rotatably about an axis (18), a mechanical interface (6) rotatably about the axis (18), and a damping device (20) with a sliding surface pairing, wherein the damping device (20) comprises a damping element (20.1) forming a surface of the sliding surface pairing, wherein the rotor (3) is designed to receive a braking effect, and the damping device (20) is designed to dampen the braking effect before transmission to the mechanical interface (6), characterized in that the damping element (20.1) comprises or consists of polyethylene. Brake (1) according to claim 1, wherein the damping element (20.1) is arranged in a fixed position relative to the rotor (3) and is in contact with a surface of the rotor (3), thereby forming the sliding surface pairing, or wherein the damping element (20.1) is coupled to the rotor (3) and is in contact with a fixed surface of the brake (1), thereby forming the sliding surface pairing. Brake (1) according to one of the preceding claims, wherein the sliding surface pairing is subjected to an elastic preload. Brake (1) according to one of the preceding claims, wherein the damping element (20.1) has a profile. Brake (1) according to one of the preceding claims, comprising a stator (2) which is fixed relative to the rotor (3), wherein the rotor (3) and the stator (2) are spaced apart from each other in the radial direction with respect to the axis (18) and a gap (4) is provided between the rotor (3) and the stator (2) in which a magnetorheological powder is provided, wherein the brake (1) is configured to generate a magnetic field which penetrates the gap (4) and the magnetorheological powder contained therein in order to generate the braking effect on the rotor (3). Brake (1) according to claim 5, wherein the sliding surface pairing is arranged outside an interior space (8) in which the magnetorheological powder is provided. Force feedback actuator (50) comprising: a drive unit (51), a magnetorheological brake (1) according to one of claims 1 to 6, and a mechanical interface (52). Steering device (100) for a vehicle, comprising: an input element (101) designed as a steering element, a force feedback actuator (50) according to claim 7 or a magnetorheological brake (1) according to one of claims 1 to 6, wherein the input element (101) is rotationally fixed to the mechanical interface (52) of the force feedback actuator (50) or rotationally fixed to a mechanical interface of the brake (1). Damping element (20.1) for a magnetorheological brake (1) according to one of claims 1 to 6 .

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