Switchable clutch for a steer-by-wire steering system, steer-by-wire steering system, steering gear, steering input device and method for operating a steer-by-wire steering system and vehicle

Abstract

Switchable clutch (10) for a steer-by-wire steering system (100) with a mechanical fallback level for a vehicle, wherein the clutch (10) has: - a first coupling part (11) which is rotatably coupled to a first, driver-side steering shaft (40) of a steer-by-wire system (100) which is rotatable about an axis of rotation (R), - a second coupling part (12) which can be coupled in a rotationally fixed manner to a second, wheel-side steering shaft (50) of the steer-by-wire system (100) which is rotatable about an axis of rotation (R), and - an actuator unit (70), wherein the first coupling part (11) and the second coupling part (12) can be engaged and / or disengaged from each other by means of the actuator device (70), wherein the clutch (10) is designed such that in a first, closed switching state of the clutch (10) the first clutch part (11) and the second clutch part (12) are positively engaged with each other in the circumferential direction, so that a torque can be transmitted between the first clutch part (11) and the second clutch part (12) and in a second, open switching state of the clutch (10) the first clutch part (11) and the second clutch part (12) are disengaged such that the first clutch part (11) is freely rotatable relative to the second clutch part (12), wherein the first coupling part (11) and the second coupling part (12) each have an end face (15A, 15B) facing the other coupling part (12, 11) with several projections (16A, 16B) and depressions (17A, 17B) extending at least in the axial and circumferential directions, wherein the protrusions (16A) of the first coupling part (11) can be engaged with the recesses (17B) of the second coupling part (12) and vice versa, and wherein the end faces (15) of the first coupling part (11) and the second coupling part (12) are designed such that when the coupling (10) is closed, in the event of an angular displacement (Δα) between the first coupling part (11) and the second coupling part (12), the closing of the coupling (10) causes the projections (16A, 16B) of the first coupling part (11) and the second coupling part (12) to slide against each other in the circumferential direction, and consequently a relative rotation occurs between the first coupling part (11) and the second coupling part (12), wherein the relative rotation leads to a compensation of at least part of the angular displacement (Δα) until the first coupling part (11) and the second coupling part (12) are positively engaged with each other in the circumferential direction, so that a torque can be transmitted between the first coupling part (11) and the second coupling part (12). is, characterized in that the coupling (10) is designed such that a rotational angle offset (Δα) of a maximum of 90° in the circumferential direction can be compensated, wherein each of the end faces (15; 16) has two or more protrusions (17; 18) and two or more recesses (19; 22) for this purpose.

Description

[0001] The present invention relates to a switchable clutch for a steer-by-wire steering system with a mechanical fallback level for a vehicle according to the preamble of claim 1.

[0002] Furthermore, the present invention relates to a steer-by-wire steering system with such a clutch according to the preamble of claim 9, as well as a steering gear with such a clutch and a steering input device with such a clutch.

[0003] Furthermore, the present invention relates to a method for operating a previously described steer-by-wire steering system according to the preamble of claim 15.

[0004] Furthermore, the present invention relates to a vehicle with a aforementioned clutch and / or a steer-by-wire steering system.

[0005] Steer-by-wire steering systems, in particular with a mechanical fallback level with at least one switchable clutch, are generally known from the prior art, for example from DE 10 2015 225 522 A1 or DE 199 26 534 A1.

[0006] In a steer-by-wire steering system, under normal operating conditions (i.e., when no fault is present), a steering input from the driver is typically detected by a steering input device, such as a steering wheel, which is mechanically separate from the steerable wheels. This input is then translated into a steering movement by a steering actuator, which is mechanically separate from the steering input device, and a steering assembly mechanically connected to the vehicle's steerable wheels. This fundamental mechanical separation of the steering input device from the steering assembly and the steerable wheels offers several advantages in terms of function, installation space, packaging, and crash safety.

[0007] Various concepts are known for the design of the fallback mechanism and for corresponding couplings for establishing and / or disconnecting the mechanical connection in the steering system between the steering input device and the steerable wheels of a vehicle. In particular, it is known, for example from the aforementioned DE 199 26 534 A1, to use a friction-fit single- or multi-disc coupling or a positive-locking jaw coupling. EP 2 330 012 A1 also teaches a steer-by-wire steering system with an alternative coupling design.

[0008] Furthermore, a steer-by-wire steering system is known, for example from US 6 580 989 B1, in which a mechanical coupling between a steering input device and the steerable wheels of the vehicle is not only provided for in the event of a fault, but can also be effected at the request of the driver, so that the steering system enables a manual driving mode, in particular with power steering, without being in a fault state, wherein, depending on the driver's request, the mechanical connection between the steering input device and the steerable wheels can be established or disconnected by means of a switchable clutch.

[0009] Furthermore, steer-by-wire steering systems are known which, in addition to a steer-by-wire mode in which a driver's steering request is detected by a steering input device mechanically separate from the steerable wheels and subsequently translated into a steering movement of the steerable wheels by the steering actuator and steering assembly, enable automatic or autonomous driving. This means that steering systems in which a steering request is not determined by a steering request transmitted and detected by a driver via a steering input device, but rather the steering request is generated automatically in another way, for example, based on route and / or environmental information.

[0010] In this case, it has proven advantageous if an existing steering input device is not moved to follow the steered wheels, but remains unchanged in its position, in particular if it is fixed. This means that every time the vehicle switches to steer-by-wire mode, a resynchronization between the position of the steering input device and the wheel position is required.

[0011] If the clutch is engaged without aligning the steering input device and the wheel position relative to each other so that both the wheels and the steering wheel are in a defined neutral position, particularly straight ahead or in a center position, this can lead to driver confusion, especially when switching to manual mode, if the wheels are straight ahead but the steering input device is rotated. This can occur particularly when the wheels are in the straight-ahead position but the steering input device is rotated.The steering input device is not in the expected straight-ahead position, but rather "tilted," for example, because the flattened side of the steering wheel is not at the bottom or a logo or inscription on the steering input device is crooked. This can be very confusing for the driver, as they can no longer tell from the position of the steering input device whether the wheels are straight-ahead or not. Moreover, the position of the steering input device in which the wheels are straight-ahead would constantly change.

[0012] Against this background, the object of the present invention is to provide an alternative clutch, in particular a clutch which enables simpler synchronization of the wheels with the steering input device of a steer-by-wire system, in particular simpler synchronization of the driver-side steering shaft with the wheel-side steering shaft, as well as an alternative, in particular improved, steer-by-wire system, an alternative steering gear, an alternative steering input device, an alternative, in particular improved, method for operating a steer-by-wire system and a corresponding vehicle.

[0013] This problem is solved by a clutch having the features of claim 1, by a steer-by-wire steering system having the features of claim 9, by a steering gear having the features of claim 13, by a steering input device having the features of claim 14, by a method having the features of claim 15 and by a vehicle having the features of claim 17.

[0014] Advantageous and preferred embodiments of the present invention are the subject of further claims and are explained in more detail below. The wording of the claims is made explicit by reference to the content of the description.

[0015] A switchable clutch according to the invention for a steer-by-wire steering system with a mechanical fallback level for a vehicle comprises a first clutch part which can be coupled in a rotationally fixed manner to a first driver-side steering shaft rotatable about an axis of rotation, in particular a rotationally fixed connection, a second clutch part which can be coupled in a rotationally fixed manner to a second wheel-side steering shaft rotatable about an axis of rotation, in particular a rotationally fixed connection, and an actuator device, in particular a controllable actuator device.

[0016] The first clutch part and the second clutch part can be engaged and / or disengaged from each other by means of the actuator device, the clutch being designed such that in a first, closed switching state of the clutch the first clutch part and the second clutch part are positively engaged with each other in the circumferential direction, so that a torque can be transmitted between the first clutch part and the second clutch part, in particular a steering torque applied by a driver.

[0017] A switchable clutch according to the invention is further designed such that in a second, open switching state of the clutch, the first clutch part and the second clutch part are disengaged in such a way that the first clutch part is freely rotatable relative to the second clutch part.

[0018] The first coupling part and the second coupling part each have an end face facing the other coupling part with several projections and depressions extending at least in the axial and circumferential directions, wherein the projections of the first coupling part can be brought into engagement with the depressions of the second coupling part and vice versa.

[0019] The end faces of the first coupling part and the second coupling part of a coupling designed according to the invention are designed such that, when the coupling is closed, in the event of an angular misalignment between the first coupling part and the second coupling part, the closing of the coupling causes the projections of the first coupling part and the second coupling part to slide against each other in the circumferential direction, resulting in a relative rotation between the first coupling part and the second coupling part, the relative rotation compensating for at least part of the angular misalignment until the first coupling part and the second coupling part are positively engaged with each other in the circumferential direction, so that a torque can be transmitted between the first coupling part and the second coupling part.

[0020] The inventive design of the opposing end faces of the coupling parts with several axial protrusions and recesses that can slide against each other allows for at least partial compensation of a rotational angle offset between the two coupling parts without further measures, in particular without further control or regulation measures, and purely mechanically. This improves synchronization in a steer-by-wire system, especially between a driver-side steering shaft and a wheel-side steering shaft or the wheels and a steering input device, and, depending on the coupling design, even achieves complete synchronization for a rotational angle offset up to a certain size.

[0021] The axis of rotation of the first steering shaft, particularly the driver's side, and the axis of rotation of the second steering shaft, particularly the wheel side, are preferably arranged coaxially. However, this is not strictly necessary. In some embodiments, it may be advantageous if the axes of rotation of the first and second steering shafts are not arranged coaxially. In this case, however, it may be necessary to provide suitable intermediate components, such as universal joints or the like.

[0022] In the context of the present invention, the term "coupleable" generally refers to a mechanical coupling of two components, i.e., a mechanical connection between these components. The coupled components in question do not necessarily have to be directly connected to each other, but they can be. That is, further components can be arranged between the two coupled components in the functional chain. However, this is not essential.

[0023] “Connected” in the sense of the present invention is preferably understood to mean that two corresponding components are connected to each other, in particular directly, i.e. preferably without any further components in between.

[0024] In the context of this connection, the term "rotationally rigid" refers in particular to a connection that is suitable for transmitting torque.

[0025] In an advantageous embodiment of a coupling according to the invention, one of the two coupling parts is preferably axially fixed or axially fixable, but rotatable in order to be able to rotate with a steering shaft coupled to this coupling part in the closed state of the coupling, for example in the event of a fault or in a manual operating mode.

[0026] The other of the two coupling parts is preferably not only rotatably mounted, but also axially displaceably mounted, in particular axially displaceable relative to the other coupling part, to allow the engagement and disengagement of the two coupling parts in the axial direction. However, both coupling parts can also be mounted axially displaceably. This is generally more complex to implement, as in this case an associated axial misalignment on both sides of the steering shaft must be compensated for.

[0027] It has proven particularly advantageous if the wheel-side coupling part is designed for fixed installation in the vehicle and the driver-side coupling part is mounted to be axially displaceable along its axis of rotation, with both coupling parts being rotatable in principle.

[0028] The actuator device of a coupling according to the invention is preferably designed to be controllable and in particular controllable by means of at least one signal, in particular by at least one control unit, in particular by at least one control unit of a steer-by-wire steering system, in particular depending on one or more corresponding signals.

[0029] In accordance with the present invention, the coupling according to the invention is closed when the first and second coupling parts are in such a way that when a further axial force is applied to one of the two coupling parts, essentially only an increase in an axial clamping force is caused, but no further significant relative axial displacement of the two coupling parts to each other occurs.

[0030] In the context of the present invention, a coupling is described as open when its two coupling parts are completely disengaged, i.e., entirely, so that the two coupling parts are freely rotatable relative to each other.

[0031] For the purposes of the present invention, the term "freely rotatable" means a state in which the two coupling parts can be rotated relative to each other by at least 360° without any mechanical limitation, whereby in particular a limitation by electrical components, such as cables or a coil spring or the like, is not considered a mechanical limitation.

[0032] The coupling is designed in such a way that a rotational angle offset of a maximum of 90° in the circumferential direction can be compensated, wherein each of the end faces has at least two protrusions and two depressions, in particular exactly two protrusions and two depressions, which are preferably arranged alternately in the circumferential direction and are in particular evenly distributed in the circumferential direction.

[0033] This allows for a good positive connection between the two coupling parts, in particular a connection which, compared to a design with only one raised section and corresponding recess, enables a better positive fit and has a higher connection strength, in particular allowing a larger torque to be transmitted, as well as compensating for a sufficiently large rotational angle offset of up to 90°.

[0034] In principle, a coupling according to the invention can also have coupling parts with end faces, each of which has more than two protrusions and depressions. However, this reduces the maximum compensation of an angle of rotation that can be achieved purely mechanically by the sliding of the protrusions of the end faces of the coupling parts against each other, where the achievable angle of rotation is 180° / n and n is the number of protrusions or depressions on the respective end faces.

[0035] In a further, particularly advantageous embodiment of a coupling according to the present invention, especially in a further development, at least one projection in the circumferential direction can have, in particular, a rounded contour, wherein preferably all projections are rounded. Preferably, one or more projections have a Gaussian, semicircular, or sinusoidal or cosine contour, wherein at least one recess has, in particular, a complementary contour, preferably all recesses.

[0036] This makes it easy to ensure that the two end faces, especially their raised sections, slide against each other when the coupling is closed in the event of a rotation angle misalignment.

[0037] Alternatively, the elevations can also be pointed and, for example, roof- or pyramid-shaped, with the depressions preferably being correspondingly pointed.

[0038] For further improved sliding, one or both coupling parts, in particular their end faces, especially in the area of ​​the protrusions and / or depressions, can each, in particular additionally, have a friction-reducing surface, wherein the surface can preferably have a defined surface quality and is in particular polished, finished or otherwise surface-treated accordingly and / or is designed as a sliding surface and / or has a friction-reducing coating.

[0039] In a further, particularly advantageous embodiment of a coupling according to the present invention, especially in a further development, each end face is preferably designed such that the path of a groove running circumferentially and through the highest points of the projections has a wave-like contour, in particular a Gaussian wave, semicircular wave, or sinusoidal or cosine wave contour. This allows the end faces of the two coupling parts to slide particularly smoothly against each other, so that only a small axial force is required to close the coupling. Furthermore, such a design of the end faces reduces the risk of self-locking and thus axial blocking of the coupling during closure.

[0040] In a further advantageous embodiment of a coupling according to the present invention, particularly in a further development, the highest points of the protrusions and the lowest points of the recesses of at least one end face are arranged, in particular along a path with a constant radius in the circumferential direction, i.e., along a circular path or lie on a circular path. This enables a particularly simple design and manufacture of the individual coupling parts, as well as simple assembly of a coupling according to the invention, since the two coupling parts can thus be installed in a steer-by-wire system in more than one relative position about the axis of rotation. It is particularly advantageous if the end faces of the two coupling parts are also rotationally symmetrical.

[0041] In a particularly preferred embodiment of a coupling according to the present invention, especially in a further development, at least one projection is symmetrically formed from its highest point at least in the circumferential direction, preferably all projections. This enables symmetrical compensation of an angular misalignment in both directions.

[0042] Preferably, one or more raised areas can be designed, in particular rib-like, whereby they slope laterally from their highest point only in the circumferential direction, while preferably having a constant height in the radial direction. This allows for good torque transmission around the axis of rotation due to the relatively large contact or support surfaces between the two end faces of the two coupling parts.

[0043] In a further possible and in some cases advantageous embodiment of a coupling according to the present invention, particularly in a further development, at least one projection is formed symmetrically in the radial direction from its highest point, preferably in addition to a symmetrical design in the circumferential direction, wherein all projections are particularly preferably formed symmetrically in the radial direction. Provided that the coupling parts are appropriately designed and mounted, this allows not only for at least partial compensation of an angular misalignment during closing, but also at least partial compensation of a radial misalignment between the two coupling parts, i.e., a misalignment between the axes of rotation or center axes of the two coupling parts, if these are not aligned or coaxial with each other, but slightly parallel but coaxial, i.e.,They should run in a straight line when the clutch is closed.

[0044] In a particularly preferred embodiment, one or more elevations are each shaped in a mountain- or dome-like form and, in particular, each slope down in all directions from their highest point. This allows for the simple realization of functional elevations that are symmetrical in both the circumferential and radial directions.

[0045] In a preferred embodiment of a coupling according to the present invention, particularly in a further development, at least one recess is symmetrically formed at least in the circumferential direction from its deepest point, particularly if at least one raised section is symmetrically formed in the circumferential direction, preferably all recesses, wherein one or more recesses are preferably valley-shaped and, in particular, rise only in the circumferential direction from their deepest point, but preferably have a constant depth in the radial direction. This allows symmetrically formed recesses to be provided corresponding to circumferentially symmetrical raised sections, which facilitate advantageous engagement of the two coupling parts and thus advantageous closure of the coupling.

[0046] In a further possible and in some cases advantageous embodiment of a coupling according to the present invention, particularly in a further development, at least one recess is symmetrically formed radially from its deepest point, in particular in addition to a symmetrical circumferential design, preferably all recesses, wherein one or more recesses are preferably bowl-shaped, valley-shaped, or plate-shaped and, in particular, rise on all sides from their deepest point. This allows symmetrically formed recesses to be provided corresponding to circumferentially symmetrical protrusions, which facilitate advantageous engagement of the two coupling parts and thus advantageous closure of the coupling.

[0047] Preferably, the first coupling part and the second coupling part of a coupling according to the invention interact in the closed state and are in particular positively connected to each other in the circumferential direction in such a way that the two coupling parts can no longer be rotated relative to each other about the axis of rotation, in particular almost without play.

[0048] In some cases, it can be advantageous to also have a centering pin arranged concentrically to the axis of rotation, which extends axially from the end face of one coupling part and is designed to engage in a corresponding recess in the other coupling part. This can, in some cases, enable more precise closure of the coupling.

[0049] A steer-by-wire steering system according to the invention, with a mechanical fallback mechanism for a vehicle, in particular a motor vehicle, for steering, in particular pivoting, at least one steerable wheel of the vehicle connected to the steering system in a functional installation state in a vehicle, comprises a steering input device, in particular a steering wheel, for steering input by a driver, a driver-side steering shaft rotatable about an axis of rotation and rotatable about an axis of rotation, a wheel-side steering shaft rotatable about an axis of rotation, a steering assembly rotatably coupled to the wheel-side steering shaft and connectable to at least one steerable wheel of a vehicle, at least one steering actuator, and a control device configured to actuate the steering actuator accordingly depending on a steering request.and a switchable clutch for establishing and disengaging a rotary connection between the driver's side steering shaft and the wheel-side steering shaft.

[0050] The coupling is designed such that, in the closed state of the coupling, a steering movement applied by a driver to the driver-side steering shaft via the steering input device can be transmitted to the wheel-side steering shaft by means of the coupling, and in the open state the driver-side steering shaft is freely rotatable relative to the wheel-side steering shaft, wherein the steering system is designed such that, in a functional installation state of the steering system in a vehicle, a steering movement of at least one steerable wheel coupled to the steering arrangement can be effected by means of a steering input applied to the wheel-side steering shaft and / or by means of the steering actuator.

[0051] A steer-by-wire steering system according to the invention comprises a clutch according to the invention, wherein the first clutch part of the clutch is rotationally fixed to the driver-side steering shaft, in particular connected, and the second clutch part is rotationally fixed to the wheel-side steering shaft, in particular connected.

[0052] A steer-by-wire steering system according to the invention can, in principle, be designed for both single-track and two-track motor vehicles. Depending on the type of vehicle for which the steering system is intended, a suitably appropriate steering arrangement must be selected.

[0053] The steering input device can be designed in various ways, for example as a steering wheel, or it can include one or more steering horns or similar components. It should simply be suitable for steering input by a driver.

[0054] Preferably, a coupling according to the invention of a steer-by-wire steering system according to the invention is designed as a so-called "normally closed" coupling, i.e. a coupling which closes in the event of a fault, in particular in the event of an interruption of the power supply.

[0055] The steering arrangement of a steer-by-wire steering system according to the invention can in particular comprise a steering gear and / or tie rods and optionally further transmission elements, such as further control arms, transmission components or the like.

[0056] In a preferred embodiment of a steer-by-wire steering system according to the present invention, the coupling according to the invention is arranged in the steering linkage between the steering input device and the steering assembly.

[0057] In an alternative, and in some cases advantageous, embodiment, the coupling of a steer-by-wire steering system according to the invention can also be part of the steering assembly, in particular part of a steering gear or, alternatively, part of the steering input device. This can result in space and / or cost advantages in some cases. In particular, existing components and parts, such as connectors and cables, can be used for connecting the actuator unit in some cases, thus eliminating the need to stock additional components.

[0058] Preferably, the control unit of a steer-by-wire steering system according to the invention is itself configured to determine a steering request. However, the steering request can also be received from another control unit.

[0059] A steer-by-wire steering system according to the invention is preferably designed to determine a corresponding steering requirement depending on a steering input from a driver.

[0060] In a particularly advantageous embodiment of a steer-by-wire steering system according to the invention, the steering system is, in particular, additionally designed to automatically determine a steering request, and preferably designed to enable autonomous driving.

[0061] Preferably, the control device of a steering system according to the invention is designed to detect a driver request regarding a driving mode and / or to detect a fault condition, wherein the driver can in particular choose between a steer-by-wire operating mode, an automatic mode and preferably also a manual operating mode, wherein the control device is in particular designed and configured to control the actuator device of the clutch accordingly, depending on the detected driver request, in particular to open or close the clutch accordingly depending on the selected operating mode.

[0062] In a particularly preferred embodiment of a steer-by-wire system according to the invention, the steering system is particularly designed to retract a steering input device in an automatic operating mode, preferably to lower it into an instrument panel or the like in the dashboard, and, preferably, when a steer-by-wire operating mode or a manual operating mode has been selected or an error condition has been detected, to extend the steering input device into a steering position.

[0063] In a steer-by-wire steering system according to the invention, the first coupling part can, for example, have a telescopic rod, or form part of a telescopic rod, or have a connecting section formed by a telescopic rod, particularly on the driver's side. This allows for a particularly simple extension and / or retraction of a steering input device.

[0064] Alternatively or additionally, the steering input device can also be coupled to the driver's side steering shaft via an additional telescopic rod for extending and / or retracting the steering input device.

[0065] In addition to the at least one steering actuator, a steer-by-wire steering system according to the invention can have one or more further steering actuators, for example for steering force assistance and / or for generating haptic feedback and / or for steering wheel return.

[0066] To prevent the steering input device from moving, and in particular rotating, in automatic mode, a steer-by-wire steering system according to the invention allows the steering input device to be locked when the clutch is disengaged, preferably by locking both the steering input device and / or the driver's side steering shaft. This provides a particularly user-friendly steer-by-wire steering system.

[0067] A steering gear according to the invention is characterized in that it has a clutch according to the invention.

[0068] A steering input device according to the invention is characterized in that it has a coupling according to the invention.

[0069] A method according to the invention for operating a steer-by-wire steering system with a mechanical fallback for steering, in particular pivoting, at least one steerable wheel of the vehicle connected to the steering system in a functional installation state in a vehicle, wherein the steering system comprises a steering input device, in particular a steering wheel, for steering input by a driver, a driver-side steering shaft rotatable about an axis of rotation and rotatable about an axis of rotation, a wheel-side steering shaft rotatable about an axis of rotation, a steering assembly rotatably coupled to the wheel-side steering shaft and connectable to at least one steerable wheel of a vehicle, at least one steering actuator, and a control device configured to actuate the steering actuator accordingly depending on a steering request.and a switchable clutch for establishing and releasing a rotary connection between the driver-side steering shaft and the wheel-side steering shaft, wherein the clutch is designed such that, in the closed state of the clutch, a steering movement applied by a driver to the driver-side steering shaft via the steering input device can be transmitted to the wheel-side steering shaft by means of the clutch, and in the open state, the driver-side steering shaft is freely rotatable relative to the wheel-side steering shaft, and wherein the steering system is designed such that, in a functional installation state of the steering system in a vehicle, a steering movement of at least one steerable wheel coupled to the steering arrangement can be effected by means of a steering input applied to the wheel-side steering shaft and / or by means of the steering actuator, comprises the steps: , - Detecting the state of the steering system, - Determining an operating mode of the steering system depending on the detected state of the steering system, and - Controlling the switchable clutch depending on the specified operating mode, wherein, if the operating mode that has been specified is a steer-by-wire mode or an automatic mode, the clutch is opened in a further step, or, if the operating mode that has been specified is a manual mode or a fault mode, the clutch is closed in a further step.

[0070] According to the invention, a coupling or a steer-by-wire steering system according to the invention is used in the implementation of a method according to the invention. This improves synchronization. Depending on the design of the coupling, a rotational angle offset up to a certain value can even be completely compensated.

[0071] In steer-by-wire mode, the clutch is always open, so that a mechanical connection between the first and second clutch parts is broken, and torque applied to the driver-side steering shaft via the steering input device cannot be transmitted to the wheel-side steering shaft. However, the steering movement applied by the driver can preferably be detected, and a corresponding steering request can be generated from it, which can then be implemented by the steering actuator and the steering assembly.

[0072] In automatic mode, which enables autonomous driving (i.e., the driver no longer needs to steer manually, but rather the steering requirements are determined automatically), the mechanical coupling between the driver-side steering shaft and the wheel-side steering shaft is also interrupted, as in steer-by-wire mode. This is also achieved by opening the coupling according to the invention. In this case, however, the steering requirement by which the steering actuator is controlled and / or regulated is not determined based on a steering input from the driver, but preferably based on other parameters, for example, based on a navigation route and / or environmental sensor data.

[0073] Additionally, particularly in a preferred embodiment of a steer-by-wire steering system according to the invention, the steering input device can be retracted and / or locked in automatic operating mode. This prevents unintentional steering inputs by the driver. Alternatively or additionally, in a further preferred embodiment of a steer-by-wire steering system according to the invention, the steering system is designed and configured such that, particularly unintentional, steering inputs by the driver in automatic mode are not used to control the steering movement, i.e., in particular, are not fed into a corresponding control loop or not taken into account by a corresponding control loop, but can be ignored.

[0074] In manual operating mode, the clutch is closed, with the first and second clutch parts engaging positively in the circumferential direction. This allows a steering torque, and thus a steering input, applied by the driver to the driver-side steering shaft via the steering input device, to be transmitted to the wheel-side steering shaft and thus, via the steering assembly, to the steerable wheels, resulting in the desired steering movement. In this mode, the steering actuator can preferably serve advantageously as a steering assist, applying an additional steering torque to the steering assembly and / or, particularly depending on the configuration of a steer-by-wire steering system according to the invention, to the wheel-side steering shaft.

[0075] In fault mode, i.e., in fail-safe operating mode, the clutch is also closed, thus creating a mechanical coupling between the driver's side steering shaft and the wheel-side steering shaft, so that a steering movement applied via the steering input device can be transmitted purely mechanically to the steering assembly and thus to the steerable wheels.

[0076] If the operating mode that has been determined is an error mode, the clutch will be closed.

[0077] In a particularly advantageous embodiment of a method according to the present invention, a further step, in particular before actuating the clutch, involves determining an angular misalignment between the driver-side steering shaft and the wheel-side steering shaft, wherein the clutch is preferably only engaged in manual mode if the determined angular misalignment between the driver-side steering shaft and the wheel-side steering shaft is less than a defined maximum permissible angular misalignment for engaging the clutch in manual mode, wherein the defined maximum permissible angular misalignment for engaging the clutch in manual mode is in particular 180° / n, where n is the number of respective protrusions in an end face of a clutch component.The coupling, for example, has a first coupling part with two protrusions and, in particular, two recesses, and a correspondingly complementary second coupling part which can be engaged with the first coupling part according to the invention. The number of coupling parts is n = 2, and the maximum permissible rotational angle offset is 90°. This allows the steering input device to be rotated relative to the wheels when the coupling closes, assuming a 1:1 gear ratio between the steering input device and the coupling. That is, a rotational angle offset of up to 90° can be compensated for.

[0078] This ensures that complete synchronization is always achieved when switching to manual mode. This results in particularly easy operation, high user comfort, and consequently, good driving safety.

[0079] If the operating mode that has been determined is an error mode, the clutch will be closed with particular preference in every case, regardless of whether a current rotation angle offset exceeds the defined maximum permissible rotation angle offset in manual mode between the two clutch parts or between the driver's side steering shaft and the wheel's side steering shaft or between the wheels and the steering input device, because in this case establishing a mechanical connection between the steering input device and the wheels takes precedence over a possible steering wheel misalignment.

[0080] A vehicle according to the invention, in particular a motor vehicle, has a steer-by-wire steering system with a mechanical fallback level and is characterized in that the steer-by-wire steering system has a clutch according to the invention and / or a steer-by-wire steering system according to the invention and / or is designed to carry out a method according to the invention.

[0081] The advantageous embodiments and their advantages presented with reference to a clutch according to the invention also apply accordingly to a steer-by-wire steering system according to the invention, as well as to a steering gear, a steering input device, a method and a vehicle according to the invention, and vice versa.

[0082] The invention is further explained below with reference to several preferred embodiments, wherein the invention is shown schematically and partly in a highly simplified manner in the accompanying figures, and functionally identical components or assemblies are provided with the same reference numerals. Fig. Figure 1 shows an embodiment of a steer-by-wire steering system according to the invention with a coupling according to the invention. Fig. Figure 2a shows a first embodiment of a coupling according to the invention for the steer-by-wire system made of Fig. 1 in a simplified, highly schematic representation in side view in an open state without rotation angle offset, Fig. 2b with rotation angle offset. The Fig. 3a and Fig. Figure 3b shows one end face of the first coupling part of the coupling. Fig. 2a in top view, while the Fig. 4a and Fig. 4b each end face of the second coupling part of the coupling made of Fig. 2a shows a top view. Fig. Figure 5 shows a top view of an end face of a further embodiment of a first coupling part of a coupling according to the invention. Fig. 6a a further embodiment of a first coupling part in top view and Fig. 6b an embodiment of a coupling part to the first coupling part made of Fig. 6a compatible second coupling part. Fig. Figure 7a shows the unfolded contours in the circumferential direction of the two coupling parts of a further, particularly preferred embodiment of a coupling according to the invention. Fig. 5 shaped end faces of the coupling parts in an open state of the coupling without rotation angle offset before closing the coupling. Fig. 7b illustrates one to Fig. 7a associated state of a vehicle according to the invention with a steer-by-wire system according to the invention with a coupling according to the invention. Fig. Figure 8a shows the unfolded contours in the circumferential direction of the two coupling parts. Fig. 7a in a closed state of the clutch. Fig. 8b illustrates the Fig. 8a associated state of the vehicle according to the invention Fig. 7b. Fig. Figure 9a shows the unfolded contours in the circumferential direction of the two coupling parts of a further, particularly preferred embodiment of a coupling according to the invention in an open state of the coupling with a rotational angle offset between the two coupling parts before the coupling is closed. Fig. 9b illustrates the Fig. 9a associated state of the vehicle according to the invention from the Fig. 7b and Fig. 8b. Fig. Figure 10 illustrates the sliding of the two coupling parts, in particular their raised sections, against each other when the coupling is closed. Fig. Figure 11a shows the unfolded contours in the circumferential direction of the two coupling parts. Fig. 9a in a closed state of the clutch and Fig. 11b illustrates the Fig. 11a associated state of the vehicle according to the invention from the Fig. 7b, Fig. 8b and Fig. 9b and Fig. 11a. Fig. Figure 12 shows a flowchart with the individual process steps of an embodiment of a particularly preferred method according to the invention for operating a steer-by-wire steering system according to the invention. All features described in more detail can be essential to the invention.

[0083] Fig. Figure 1 shows an exemplary schematic diagram of a possible embodiment of a steer-by-wire steering system 100 according to the invention. This exemplary steer-by-wire steering system 100 has a steering input device 20 in the form of a steering wheel 20, which is non-rotatably connected to a driver-side steering shaft 40, wherein the driver-side steering shaft 14 is rotatably mounted on the vehicle body and is non-rotatably coupled at its end away from the steering wheel 20 to a first coupling part 11 of a coupling 10 designed according to the invention, in particular via a first connecting section of the coupling 10 which is not shown here.

[0084] In the area of ​​the driver's side steering shaft 40, particularly near the steering wheel 20, there is a sensor device 21 by means of which a steering torque applied by the driver to the driver's side steering shaft 40 as well as a rotation angle of the steering wheel 20 about a rotational axis R, about which both the steering wheel 20 and the driver's side steering shaft 40 can be rotated, can be detected.

[0085] Furthermore, a feedback actuator 30 is provided in the area of ​​the driver's side steering shaft 40, by means of which a restoring torque can be applied to the driver's side steering shaft 40 and thus haptic feedback, in particular haptic feedback, can be generated for the driver, which can particularly influence the steering feel, which is especially advantageous.

[0086] This embodiment of a steer-by-wire steering system 100 according to the invention further comprises a wheel-side steering shaft 50, which at one end, in particular at the end facing the steering input device 20, is non-rotatably coupled to a second coupling part 12 of the coupling 10 according to the invention, in particular via a second connecting section of the coupling 10 which is not shown here. At its other end, in this case the wheel-side end, the wheel-side steering shaft 50 is non-rotatably connected to a steering assembly 80, which comprises a steering gear with a rack 81 as well as a left tie rod 82 and a right tie rod 82, via which steerable wheels 83 of a vehicle can be connected to the steering assembly 80, as shown in Fig. 1 shown as an example.

[0087] The steer-by-wire steering system 100 further comprises a steering actuator 70 by means of which a steering movement of the steerable wheels 83, in particular a pivoting of the steerable wheels 83, can be effected, in particular on its own, i.e. without active steering by the driver, in particular without a steering torque applied by a driver to the driver-side steering shaft 50, as well as in a supporting manner, i.e. in addition to a steering torque applied by a driver to the wheel-side steering shaft 50, as in a conventional, mechanical steering system known under the term "power steering".

[0088] In the area of ​​the wheel-side steering shaft 50, a further sensor device 60 is provided, with which a rotation angle of the wheel-side steering shaft 50 about an associated rotation axis R is detectable. In this steer-by-wire steering system 100, this axis coincides with the rotation axis R of the driver-side steering shaft 40 and the rotation axis R of the steering wheel 20, i.e., it is coaxial with them. Furthermore, the sensor device 60 can detect a torque applied to the wheel-side steering shaft 50, in particular a torque applied by a driver and transmitted from the driver-side steering shaft 40 to the wheel-side steering shaft 50.

[0089] Furthermore, the steer-by-wire steering system 100 has a control device 90 which is designed and configured to evaluate the sensor signals generated by the sensor devices 21 and 60 and to control, at least depending on these, the steering actuator 70, the feedback actuator 30 and the clutch 10 according to the invention, in particular an actuator device of the clutch 10 which is not shown here.

[0090] By means of the actuator device, the clutch 10 according to the invention can be opened or closed accordingly, in particular depending on the desired operating mode, wherein the clutch 10 according to the invention is designed and integrated into the steering system 100 in such a way that in a closed state of the clutch 10 the driver-side steering shaft 40 and the wheel-side steering shaft 50 are rotationally fixedly coupled to each other, so that a steering torque applied by the driver via the steering wheel 20 to the driver-side steering shaft 40 and thus a steering input or steering request can be transmitted to the wheel-side steering shaft 50 by means of the clutch 10.

[0091] In the open state of the clutch 10, however, a rotary connection between the driver's side steering shaft 40 and the wheel-side steering shaft 50 is mechanically separated, i.e. interrupted, and the driver's side steering shaft 40 and the steering wheel 20 which is non-rotatably connected to it are in principle free to rotate relative to the wheel-side steering shaft 50, the steering assembly 80 and the steerable wheels 83.

[0092] The control unit 90 is further equipped to receive a driver request signal W, which characterizes the operating mode in which the driver wishes to operate, and / or a corresponding signal from a higher-level vehicle controller, in order, for example, to permit only certain operating modes in specific situations or to specify a particular operating mode in the manner of a veto. Furthermore, the control unit 90 and the sensor units 21 and 60 can be used to detect a rotation angle offset Δα (see, e.g., Fig. 4b) between the driver's side steering shaft 40 and the wheel side steering shaft 50.

[0093] The driver request signal is in Fig. 1 For the sake of simplicity, symbolically represented as a signal W detected by the steering wheel 20, which can be detected, for example, by means of a corresponding input device integrated into the steering wheel 20, such as a driving mode selector switch.

[0094] In this embodiment, the steer-by-wire steering system 100 according to the invention is designed to operate in at least four different operating modes: a steer-by-wire mode, an automatic mode which enables autonomous driving, a manual mode, and a fault mode (hereinafter also referred to as "fail-safe mode"), wherein the driver can select between the steer-by-wire mode, the automatic mode, and the manual mode. The steering system 100 switches to the fail-safe mode only if a fault has been detected. The fail-safe mode cannot be selected by the driver.

[0095] An alternative steer-by-wire steering system, also designed according to the present invention, can be operated in only two of the four operating modes, namely the steer-by-wire mode and the fail-safe mode, or in three of the four operating modes. Preferably, however, a steer-by-wire steering system according to the invention is operable in at least the aforementioned two operating modes, "steer-by-wire" and "fail-safe".

[0096] In steer-by-wire mode, the clutch 10 is open, so that a mechanical connection between the first clutch part 11 and the second clutch part 12 is disconnected, and a torque applied to the steering shaft 40 via the steering wheel 20 cannot be transmitted to the wheel-side steering shaft 50. However, in order to steer the wheels 83 according to the steering request made by the driver on the steering wheel 20 and thus on the driver-side steering shaft 40, the driver's steering request can be detected in steer-by-wire mode by means of the sensor device 21, and a corresponding steering request can be determined by the control device 90 depending on the detected steering movement of the driver. The steering actuator 70 is then controlled based on this determined steering request such that a steering movement of the wheels 83 corresponding to the driver's steering request is effected by means of the steering arrangement 80.The sensor device 60 can detect whether the steering movement applied by the steering actuator 70 to the steering arrangement 80 actually corresponds to the desired steering requirement or not, and if necessary, it can be corrected accordingly using the control device 90.

[0097] In automatic mode, which enables autonomous driving (i.e., the driver no longer needs to steer, but the steering requirements are determined automatically), the mechanical coupling between the driver-side steering shaft 40 and the wheel-side steering shaft 50 is also interrupted, as in steer-by-wire mode, which is also achieved by opening the coupling 10 according to the invention.

[0098] The automatic mode enables autonomous driving, whereby in this case the control unit 90 is controlled from a different location than the sensor unit 21, for example as in Fig. 1 exemplified by another control device 91, receives a corresponding steering request or steering demand and, depending on this steering demand, controls the steering actuator 70 accordingly, as is the case in steer-by-wire operating mode for the conversion of the steering demand into a steering movement of the steerable wheels 83.

[0099] Additionally, particularly in a preferred embodiment of a steer-by-wire steering system 100 according to the invention, the steering wheel 20 can be retracted and / or locked in automatic operating mode, whereby the steering wheel 20 can be retracted, in particular, towards the instrument panel. This provides the driver with more space in the interior during this operating mode, which has a beneficial effect on travel comfort. Retracting and / or locking the steering wheel prevents unintentional steering inputs by the driver that could potentially lead to an undesirable steering reaction or vehicle reaction.

[0100] In manual operating mode, however, the clutch 10 is closed, with the first clutch part 11 and the second clutch part 12 engaging positively in the circumferential direction, so that a steering torque applied by the driver via the steering wheel 20 to the driver-side steering shaft 40, and thus a steering input, can be transmitted to the wheel-side steering shaft 50 and thus, via the steering arrangement 80, further to the steerable wheels 83 and a desired steering movement of the wheels 83 can be effected.

[0101] In this mode, the steering actuator 70 can serve to assist the steering force and apply an additional steering torque to the steering arrangement 80 and / or, in particular depending on the design of a steer-by-wire steering system 100 according to the invention, to the wheel-side steering shaft 50.

[0102] In the fourth possible operating mode of this embodiment of a steer-by-wire steering system 100 according to the invention, the fail-safe operating mode, the clutch 10 is also closed and thereby a mechanical coupling of the driver-side steering shaft 40 with the wheel-side steering shaft 50 is also established, so that a steering movement applied via the steering wheel 20 can be transmitted purely mechanically to the steering arrangement 80 and thus to the steerable wheels 83.

[0103] However, in this state, i.e., in this operating mode, both the feedback actuator 30 and the steering actuator 70 are out of service, i.e., deactivated, so that only purely mechanical steering is possible, i.e., without power assistance. Depending on the cause of the fault, it is also conceivable to leave some functionality of the manual mode active, e.g., power steering, and, for example, only deactivate the feedback actuator 30.

[0104] To ensure that the coupling 10 always closes in the event of a fault, especially in the event of a power failure or the like, the coupling 10 according to the invention, particularly in this embodiment and preferably generally, is advantageously designed as a so-called "normally-closed" coupling 10, i.e. as a coupling 10 which can only be kept open when energy is supplied and which always closes when the energy supply is interrupted due to an existing reset mechanism, which can be implemented, for example, by one or more reset springs.

[0105] Fig. Figure 2a shows a first embodiment of a coupling 10 according to the invention for the steer-by-wire system 100 made of Fig. 1 in a simplified, highly schematic representation in side view in an open state without a rotation angle offset Δα (cf. Fig. 4b), in which the first coupling part 11 with its end face 15 and its projections 17 extending in the axial direction, in the radial direction and in the circumferential direction with respect to the axis of rotation R and the recesses located between them, which are not specified in more detail here, are clearly recognizable, as is the second coupling part 12 with its end face 16 facing the first coupling part 11 and projections 18 extending from it in the axial direction, in the circumferential direction and in the radial direction and the recesses located between them, which are also not specified in more detail.

[0106] For the rotationally fixed connection of the first coupling part 11 to the driver-side steering shaft 40 of the steer-by-wire system 100, the first coupling part 11 has a first connecting section 13. The second coupling part 12 accordingly has a second connecting section 14 for connecting the second coupling part 12 to the wheel-side steering shaft 50.

[0107] In this embodiment of coupling parts 11 and 12 of a coupling 10 according to the invention, the elevations 17 and 18 are each mountain-shaped and dome-shaped, respectively, and are symmetrical both in the circumferential direction and in the radial direction, and are rounded, in particular with a semicircular contour.

[0108] Preferably, corresponding recesses border the projections 17 and 18, although this is not explicitly shown in detail here, wherein the recesses are also rounded and in particular designed to be complementary or corresponding to the individual projections 17 and 18, so that a complete positive locking can be achieved when closing the clutch 10 between the two clutch parts 11 and 12, in particular such that a torque can be transmitted between the two clutch parts 11 and 12, in particular a steering torque applied by the driver.

[0109] As mentioned at the beginning, the very schematically drawn elevations 17 and 18 serve to illustrate the compensation of a possible rotational angle offset present at the start of a closing process. This is shown in particular by the Fig. 2b as well as 3a and 3b in conjunction with the Fig. 4a and Fig. 4b below.

[0110] Fig. Figure 2b shows an embodiment of the coupling 10. Fig. 2a with a rotation angle offset Δα at the beginning of a closing process of the coupling 10 and the Fig. 3a and Fig. Figure 3b shows one end face 15 of the first coupling part 11 of the coupling 10. Fig. 2a in top view, while the Fig. 4a and Fig. 4b each end face 16 of the second coupling part 12 of the coupling 10 from Fig. 2a shows a top view.

[0111] Are the two coupling parts 11 and 12 as shown in Fig. 2a shown, in an open state aligned relative to each other such that the elevations 17 of the first coupling part 11 (cf. Fig. 2a and Fig. 3a) to the elevations 18 of the second coupling part 12 (cf. Fig. 4a) are aligned so that the protrusions 17 are arranged opposite each other in the axial direction to the corresponding recesses 22 and the protrusions 18 to the corresponding recesses 19, the coupling can be closed in a conventional manner, in particular by simply axially bringing together the two coupling parts 11 and 12.

[0112] The protrusions 17 engage in the recesses 22 and the protrusions 18 in the recesses 19, whereby in a closed state of the coupling 10 a positive locking is achieved which enables a torque transmission between the first coupling part 11 and the second coupling part 12.

[0113] However, if the first coupling part 11 and the second coupling part 12 are at the beginning of a closing process of the coupling 10, as in Fig. 2b shown to represent a rotation angle offset Δα (see below). Fig. 4b) If the couplings are oriented offset from each other, in particular such that the protrusions 17 of the first coupling part 11 are opposite the protrusions 18 of the second coupling part 12, then without compensation of this rotational angle offset Δα it is not possible to fully close the coupling 10.

[0114] The inventive projections 17 and 18 of the two coupling parts 11 and 12, wherein the projections 17 and 18 are in particular dome-shaped and especially rounded, as well as the recesses 19 and 22 provided between the projections 17 and 18 (cf. Fig. 3b and Fig. 4b), which are designed accordingly to the elevations 17, 18, the elevations 17 and 18 can slide against each other when the coupling 10 is closed until they reach the recesses 22, 19, whereby, due to the free rotation of the two coupling parts 11 and 12 relative to each other, a compensation of the rotation angle offset Δα can be achieved.

[0115] If the two coupling parts 11 and 12 each have exactly two protrusions 17 and 18 respectively, and two correspondingly alternately arranged recesses 19 and 22 distributed circumferentially with these, in particular uniformly distributed recesses, as schematically indicated in this embodiment, a rotation angle offset Δα of up to 90° when closing the coupling 10 can be compensated purely mechanically without further measures in a particularly advantageous embodiment as shown here.

[0116] For a particularly simple compensation of a rotational angle offset Δα, the surfaces of the protrusions 17 and 18 or the surfaces of the recesses 19 and 22 can be designed to reduce friction and, for example, have a friction-reducing coating or the like, such as a coating commonly used in sliding bearings or the like.

[0117] It is also particularly advantageous if the two coupling parts 11 and 12 have a defined surface quality in the corresponding sliding areas, in particular a surface quality which requires low roughness and which can be achieved in particular by surface treatment such as polishing, finishing or the like.

[0118] It is explicitly pointed out that in all of the embodiments shown here, the protrusions 17 and 18 and the recesses 19 and 22 are not shown to scale or with real geometries, but only in principle to illustrate the functional principle of coupling parts 11, 12 designed according to the invention with protrusions 17, 18 and recesses 19, 22.

[0119] Particularly preferably, the projections 17 transition uniformly and continuously into the immediately adjacent recesses 19, as do the projections 18 into the recesses 22. Furthermore, each projection 17 extends circumferentially over the same circumferential length as an adjacent recess 19, and thus, with two projections 17 or 18 per end face 15 or 16 and two recesses 19 or 22, preferably over a circumferential angle range of 90°, whereby a rotational angle offset Δα of up to 90° can be compensated for.

[0120] Fig. Figure 5 shows a top view of an end face 15 of a further embodiment of a first coupling part 11 of a coupling according to the invention, wherein in this embodiment the projections 17 are not mountain- or dome-shaped, but rather rib-shaped. The ribs extend outwards, particularly in the radial direction, and especially with a constant height, with the highest points P each running along the dashed line P. The projections 17 are also symmetrical in the circumferential direction and slope downwards to the sides to the right and left of the highest points P in the circumferential direction. However, they are not symmetrical in the radial direction.

[0121] The same applies to the intermediate, valley-shaped depressions 19, which are also symmetrical in the circumferential direction, with the depressions 19 also having a constant depth and their deepest points running along the dashed line Q and also extending radially. In this embodiment, the depressions 19 are also not symmetrical in the radial direction.

[0122] If one unwraps the contour in the circumferential direction from the raised areas 17 and the recesses 19 Fig. From 5 onwards, a wavy contour results, as exemplified in the Fig. 7a, Fig. 8a, Fig. 9a and Fig. 11a shown.

[0123] The Fig. 6a and Fig. Figure 6b shows a further embodiment of coupling parts 11, 12 of a coupling 10 according to the invention, wherein Fig. Figure 6a shows a further embodiment of a first coupling part 11 in top view and Fig. 6b an embodiment of a coupling part 11 to the first coupling part Fig. 6a compatible second coupling part 12.

[0124] In this case, each coupling part 11 or 12 has four projections 17 or 18, respectively, and four recesses 19 or 22 arranged circumferentially between them, alternating with the projections 17 or 18. The projections are also shaped like mountains or domes, and the recesses 19 and 22 are bowl-shaped, corresponding to the projections 17 and 18. The four projections 17 and 18 and the four recesses 19 and 22 can only compensate for a rotational angular misalignment Δα of 45° (=180° / n with n=4).

[0125] The elevations 17 and 18 and the depressions 19 and 22 are designed and arranged on the end faces 15 and 16 of the two coupling parts 11 and 12 in such a way that their highest points P and their lowest points Q each run along a circular path with a constant radius.

[0126] In contrast to the previous embodiments, a recess 23 for a centering pin is provided in the first coupling part 11 concentric to the axis of rotation R, i.e. to the axis of rotation of an associated steering shaft 40 or 50 or of the two coupling parts 11, 12, and a corresponding centering pin 24 extends axially from the end face 16 of the second coupling part 12.

[0127] The centering pin 24 is designed to interact with the recess 23, in particular to engage within it. The recess 23 and the centering pin 24 enable improved assembly and closing of the coupling 10.

[0128] Radially rounded elevations 17, 18, in particular mountain- or dome-shaped, or correspondingly shaped recesses 19, 22, have the advantage over recesses 19, 22 and elevations 17, 18 that are only rounded in the circumferential direction that, in addition to compensating for a rotational angle offset Δα, a radial offset can also be compensated, provided a corresponding design is in place, i.e., an offset of the center or rotation axes of the two coupling parts 11 and 12 to each other.

[0129] Based on the Fig. Sections 7a to 11b below will now explain, by way of example, the operating principle of the rotation angle offset compensation of a coupling 10 according to the invention, wherein Fig. 7a the developed contours in circumferential direction of the two coupling parts 11, 12 with according to Fig. 5 designed end faces 15, 16 of the coupling parts 11, 12 in an open state of the coupling 10 without a rotation angle offset before closing. Fig. 7b illustrates one to Fig. 7a associated state of a vehicle 200 according to the invention with a steer-by-wire system according to the invention with a coupling 10 according to the invention.

[0130] Are the wheels 83 of a vehicle 200 according to the invention, equipped with a steer-by-wire steering system 100 according to the invention, aligned synchronously with the position of the steering input device 20, as shown in Fig. As shown in Figure 7b, the protrusions 17 of the first coupling part 11 are located opposite corresponding recesses 22 of the second coupling part 12, and the protrusions 18 of the second coupling part 12 are located opposite the recesses 19 of the first coupling part 11. In this state, the coupling 10 can be closed without difficulty, which in Fig. 8a, which shows the unfolded contours of the two coupling parts 11 and 12 in the circumferential direction Fig. 7a shows the coupling 10 in a closed state. Fig. 8b illustrates the Fig. 8a associated condition of the vehicle 200 according to the invention Fig. 7b.

[0131] However, if the situation at the beginning of a closing process is, for example, as in Fig. 9a and Fig. Figure 9b shows the steering input device 20 in the straight-ahead position, as it was last locked in the straight-ahead position for an automatic mode, while the vehicle 200 is being driven autonomously, whereby the wheels 83 of the vehicle are currently not in the straight-ahead position, but offset by a wheel steering angle relative to these, and if, for example, a driver now expresses a wish to switch to manual mode, there is a rotation angle offset Δα between the wheel-side steering shaft 50 and the driver-side steering shaft 40, which must be compensated for before the clutch 10 is closed in order to avoid a steering wheel misalignment, where a rotation angle offset of Δα = 90° is shown here as an example.

[0132] Fig. Figure 9a shows the unfolded contours in the circumferential direction of the two coupling parts 11, 12. Fig. 7a in an open state of the coupling 10 with a rotation angle offset before the coupling 10 is closed between the two coupling parts 11, 12 and Fig. 9b the to Fig. 9a associated state of the vehicle 200 according to the invention from the Fig. 7b and Fig. 8b illustrates.

[0133] In this state, the projections 17 and 18 are opposite each other, as are the recesses 19 and 22, which means that the coupling 10 cannot be fully closed without compensating for the rotational angular misalignment Δα. However, due to the inventive design of the projections 17 and 18 and the recesses 19 and 22, a rotational angular misalignment Δα of up to 90° can be compensated for when closing the coupling 10, and thus, in this case, the entire rotational angular misalignment Δα can be compensated.

[0134] The compensation of the rotational angle offset Δα is effected in particular by the closing action, especially by an axial force applied during closing in conjunction with the geometry of the end faces 15, 16 of the two coupling parts 11 and 12 and a sliding of the projections 17 and 18 against each other, which can be seen from Fig. Figure 10 illustrates the sliding of the two coupling parts 11, 12, in particular their projections 17, 18, against each other caused by the closing of the coupling 10.

[0135] As a result of this sliding against each other, the two coupling parts 11 and 12, which are freely rotatable relative to each other, particularly about the axis of rotation R, when the coupling is open, result in a compensation of the angle of rotation Δα, especially up to the point shown in Fig. Figure 11a shows the developed contours in the circumferential direction of the two coupling parts 11, 12. Fig. Figure 9a shows the coupling 10 in a closed state. In this closed state, the projections 17, 18 engage in the corresponding recesses 22 and 19 of the other coupling part 12, 11.

[0136] Fig. 11b illustrates the Fig. 11a associated state of the vehicle 200 according to the invention from the Fig. 7b, Fig. 8b and Fig. 9b and Fig. 11a. With the two elevations 17 and two depressions 19 shown here, as well as two elevations 18 and two depressions 22, it is possible, as in Fig. As shown in Figure 11b, a rotation angle offset Δα of up to 90° can be compensated.

[0137] Fig. Figure 12 shows, by way of example, a flowchart with the individual process steps of a particularly preferred embodiment of a method according to the invention for operating a steer-by-wire steering system 100 according to the invention, wherein in a first step S1 a state of the steer-by-wire steering system 100 is detected, in a second step S2 an operating mode of the steer-by-wire steering system is determined depending on the detected state of the steer-by-wire steering system 100, wherein in particular it is checked whether a fault condition exists and thus it is mandatory to switch to the fail-safe mode, or whether no fault condition exists and thus it can switch to an operating mode selected by a driver, wherein in a third step S3 in this preferred embodiment of a method according to the invention a rotation angle offset Δα between the driver-side steering shaft 40 and the wheel-side steering shaft 50 is determined (cf. Fig.9a to 11b), and wherein in a fourth step S4 the switchable clutch 10 is actuated according to the determined operating mode (fail-safe mode, steer-by-wire operating mode, manual operating mode, or automatic mode), wherein if the operating mode that has been determined is a steer-by-wire mode or an automatic mode, in a further step S5a the clutch is opened, or if the operating mode that has been determined is the manual mode or the fault mode, in a further step S5b the clutch is closed, wherein in this preferred embodiment of a method according to the invention the clutch 10 is closed in manual mode only if the detected rotation angle offset Δα between the driver-side steering shaft 40 and the wheel-side steering shaft 50 is less than a defined rotation angle offset Δα maximum permissible for closing the clutch 10 in manual mode, in this case <90°.

[0138] If a coupling 10 according to the invention and / or a steer-by-wire steering system 100 according to the invention is used with a coupling 10 according to the invention which has two protrusions 17, 18 or recesses 19, 22 each end face 15, 16, the defined, maximum permissible rotation angle offset Δα is in particular 90°, since 180° / n applies, where n is the number of the respective protrusions in an end face of a coupling part.

[0139] Naturally, a large number of modifications, especially constructive modifications, to the described embodiment are possible without departing from the content of the patent claims. Reference symbol list: 200 vehicle according to the invention 100 Steer-by-Wire steering system according to the invention 10 coupling according to the invention 11 first clutch part 12 second clutch part 13 first connecting section 14 second connecting section 15 Front side of the first coupling part 16 Front side of the second coupling part 17 elevations of the first coupling part 18 elevations of the second coupling part 19 recesses of the first coupling part 20 Steering input device 21 Sensor device 22 recesses of the second coupling part 23 Recess for centering pin 24 Centering pin 30 Feedback actuator 40 driver's side steering shaft 50 wheel-side steering shaft 60 Sensor device 70 Steering actuator 80 Steering arrangement 81 Rack and pinion 82 Tie rod 83 steerable wheel 90 Control unit 91 additional control devices Δα Rotation angle offset P highest point of the elevation Q deepest point of the depression R Rotation axis of the steering shaft S1-S5b Procedure steps W Driver request signal

Claims

Switchable clutch (10) for a steer-by-wire steering system (100) with a mechanical fallback for a vehicle, wherein the clutch (10) comprises: - a first clutch part (11) that is rotationally fixed to a first, driver-side steering shaft (40) of a steer-by-wire system (100) rotatable about an axis of rotation (R), - a second clutch part (12) that is rotationally fixed to a second, wheel-side steering shaft (50) of the steer-by-wire system (100) rotatable about an axis of rotation (R), and - an actuator device (70), wherein the first clutch part (11) and the second clutch part (12) can be engaged and / or disengaged from each other by means of the actuator device (70), wherein the clutch (10) is designed such that in a first, closed switching state of the clutch (10) the first coupling part (11) and the second coupling part (12) are positively engaged with each other in the circumferential direction,such that a torque can be transmitted between the first clutch part (11) and the second clutch part (12), and in a second, open switching state of the clutch (10), the first clutch part (11) and the second clutch part (12) are disengaged in such a way that the first clutch part (11) is freely rotatable relative to the second clutch part (12), wherein the first clutch part (11) and the second clutch part (12) each have an end face (15A, 15B) facing the other clutch part (12, 11) with several projections (16A, 16B) and recesses (17A, 17B) extending at least in the axial and circumferential directions, wherein the projections (16A) of the first clutch part (11) can be brought into engagement with the recesses (17B) of the second clutch part (12) and vice versa, and wherein the end faces (15) of the first coupling part (11) and the second coupling part (12) are designed in such a way,that when the coupling (10) is closed, in the event of an angular displacement (Δα) between the first coupling part (11) and the second coupling part (12), the closing of the coupling (10) causes the projections (16A, 16B) of the first coupling part (11) and the second coupling part (12) to slide against each other in the circumferential direction, and consequently a relative rotation occurs between the first coupling part (11) and the second coupling part (12), wherein the relative rotation leads to a compensation of at least part of the angular displacement (Δα) until the first coupling part (11) and the second coupling part (12) are positively engaged with each other in the circumferential direction, so that a torque can be transmitted between the first coupling part (11) and the second coupling part (12), characterized in that the coupling (10) is designed such that an angular displacement (Δα) of a maximum 90° in the circumferential direction is compensable,wherein each of the end faces (15; 16) has two or more raised areas (17; 18) and two or more depressions (19; 22). Coupling (10) according to claim 1, characterized in that at least one projection (17; 18) has a rounded contour, a Gaussian, semicircular or sinusoidal or cosine contour in the circumferential direction, wherein at least one recess (19; 22) has a complementary contour. Coupling (10) according to one of the preceding claims, characterized in that each end face (15; 16) is designed such that a path of a track which runs in the circumferential direction and through the highest points (P) of the elevations (17; 18) has a wave-shaped contour, a Gaussian wave-shaped, semicircular wave-shaped or sinusoidal or cosine wave-shaped contour. Coupling (10) according to one of the preceding claims, characterized in that the highest points (P) of the elevations (17; 18) and the lowest points (Q) of the depressions (19; 22) of at least one end face (15; 16) are arranged along a path with a constant radius in the circumferential direction. Coupling (10) according to one of the preceding claims, characterized in that at least one elevation (17; 18) is symmetrical at least in the circumferential direction from its highest point (P). Coupling (10) according to one of the preceding claims, characterized in that at least one elevation (17; 18) is symmetrical in the radial direction from its highest point (P). Coupling (10) according to one of the preceding claims, characterized in that at least one recess (19; 22) is formed symmetrically at least in the circumferential direction from its lowest point (Q). Coupling (10) according to one of the preceding claims, characterized in that at least one recess (19; 22) is formed symmetrically in the radial direction from its lowest point (Q). A steer-by-wire steering system (100) with a mechanical fallback for a vehicle, in particular for a motor vehicle, for steering at least one steerable wheel (83) of the vehicle connected to the steering system (100) in a functional installation state in a vehicle, wherein the steering system (100) comprises: - a steering input device (20) for steering input by a driver, - a driver-side steering shaft (40) rotatable about an axis of rotation (R) and rotatable about a rotational axis (R) and rotatable about a wheel-side steering shaft (50) rotatable about an axis of rotation (R), - a steering assembly (80) rotatably coupled to the wheel-side steering shaft (50) and connectable to at least one steerable wheel (83) of a vehicle, - at least one steering actuator (70), - a control device (90) configured to actuate the steering actuator depending on a steering request. (70) to target accordingly,and a switchable clutch (10) for establishing and releasing a rotary connection between the driver-side steering shaft (40) and the wheel-side steering shaft (50), wherein the clutch (10) is designed such that, in the closed state of the clutch (10), a steering movement applied by a driver to the driver-side steering shaft (40) via the steering input device (20) can be transmitted to the wheel-side steering shaft (50) by means of the clutch (10), and in the open state, the driver-side steering shaft (40) is freely rotatable relative to the wheel-side steering shaft (50), wherein the steering system (100) is designed such that, in a functional installation state of the steering system (100) in a vehicle (200), a steering movement of at least one steerable wheel coupled to the steering arrangement (80) can be transmitted by means of a steering input applied to the wheel-side steering shaft (50) and / or by means of the steering actuator (70). (83) is effectable, characterized by,that the coupling (10) is designed according to one of claims 1 to 8, wherein the first coupling part (11) of the coupling (10) is rotationally fixed to the driver's side steering shaft (40), and the second coupling part (12) is rotationally fixed to the wheel's side steering shaft (50). Steer-by-wire steering system (100) according to claim 9, characterized in that the clutch (10) is part of the steering arrangement (80). Steer-by-wire steering system (100) according to claim 9, characterized in that the clutch (10) is part of the steering input device (20). Steer-by-wire steering system (100) according to one of claims 9 to 11, characterized in that when the clutch (10) is open, the steering input device (20) can be locked, wherein the steering input device (10) and / or the driver-side steering shaft (40) can be locked when the clutch (10) is open. Steering gear, characterized in that the steering gear has a clutch which is designed according to one of claims 1 to 8. Steering input device (20), characterized in that the steering input device (20) has a clutch which is designed according to one of claims 1 to 8. Method for operating a steer-by-wire steering system (100) with a mechanical fallback for a vehicle for steering at least one steerable wheel (83) of the vehicle connected to the steering system (100) in a functional installation state in a vehicle, wherein the steering system (100) comprises: - a steering input device (20) for steering input by a driver, - a driver-side steering shaft (40) rotatable about an axis of rotation (R) and non-rotatably connected to or connected with the steering input device (20), - a wheel-side steering shaft (50) rotatable about an axis of rotation (R), - a steering assembly (80) non-rotatably coupled to the wheel-side steering shaft (50) and connectable to at least one steerable wheel (83) of a vehicle, - at least one steering actuator (70), - a control device (91) configured to actuate the steering actuator (70) depending on a steering request. to target accordingly,and a switchable clutch (10) for establishing and releasing a rotary connection between the driver-side steering shaft (40) and the wheel-side steering shaft (50), wherein the clutch (10) is designed such that, in the closed state of the clutch (10), a steering movement applied by a driver to the driver-side steering shaft (40) via the steering input device (20) can be transmitted to the wheel-side steering shaft (50) by means of the clutch (10), and in the open state of the clutch (10), the driver-side steering shaft (40) is freely rotatable relative to the wheel-side steering shaft (50), wherein the steering system (100) is designed such that, in a functional installation state of the steering system (100) in a vehicle (200), a steering movement of at least one of the components coupled to the steering arrangement (80) can be transmitted by means of a steering input applied to the wheel-side steering shaft (50) and / or by means of the steering actuator (70). steerable wheel (83) is effectable,comprising the steps of: - detecting (S1) a state of the steering system (100), - determining (S2) an operating mode of the steering system (100) depending on the detected state of the steering system (100), and - actuating (S4) the switchable clutch (10) depending on the determined operating mode, wherein, if the operating mode that has been determined is a steer-by-wire mode or an automatic mode, the clutch (10) is opened in a further step (S5a), or, if the operating mode that has been determined is a manual mode or a fault mode, the clutch (10) is closed in a further step (S5b), characterized in that, in carrying out the method, a clutch (10) designed according to one of claims 1 to 8 and / or a steer-by-wire steering system (100) designed according to one of claims 9 to 12 is used. Method according to claim 15, characterized in that in a further step (S3) a rotational angle offset (Δα) between the driver-side steering shaft (40) and the wheel-side steering shaft (50) is determined, wherein the clutch (10) is only closed in manual mode if the determined rotational angle offset (Δα) between the driver-side steering shaft (40) and the wheel-side steering shaft (50) is less than a defined maximum permissible rotational angle offset (Δα) for closing the clutch (10) in manual mode, wherein the defined maximum permissible rotational angle offset (Δα) for closing the clutch (10) in manual mode is 180° / n, where n is the number of respective protrusions in an end face (15; 16) of a clutch part (11; 12). Vehicle (200), in particular motor vehicle, with a steer-by-wire steering system (100) with a mechanical fallback level, characterized in that the steer-by-wire steering system (100) has a clutch (10) according to one of claims 1 to 8 and / or is designed according to one of claims 9 to 12 and / or is designed for carrying out a method according to claim 15 or 16.

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