Steering system

Abstract

The invention relates to a steering system (1) for a vehicle, having: - at least one steered axle (2, 6); - a primary steering device (3) with a mechanical primary interface (3.1) for outputting a primary steering input to the at least one steered axle (2, 6), said primary steering device (3) having a primary steering input generating unit (3.2) which is designed to generate the primary steering input and to impress same onto the at least one steered axle (2, 6) via the mechanical primary interface (3.1); and - a secondary steering device (4) with a mechanical secondary interface (4.1) for outputting a secondary steering input to the at least one steered axle (2, 6), said secondary steering device (4) having a secondary steering input generating unit (4.2) which is designed to generate the secondary steering input and to impress same onto the at least one steered axle (2, 6) via the mechanical secondary interface (4.1). The steering system (1) is designed to actuate the primary steering device (3) and to control the secondary steering device (4) in order to generate the primary steering input and the secondary steering input according to a steering specification, and the secondary steering device (4) is designed to ensure that the vehicle in which the secondary steering device (4) is provided can be steered correctly when the primary steering device (3) has a fault, a redundancy case being characterized by a fault of the primary steering device (3). The invention also relates to a vehicle.

Description

[0001] DESCRIPTION

[0002] Steering system

[0003] The present invention relates to a steering system for a vehicle and a vehicle.

[0004] The electrification of steering systems in vehicles with at least one steered axle includes an electromechanically acting steering device with which a steering input can be applied to the steered axle(s) via a mechanical interface in order to steer or turn the wheels of the axle(s) accordingly. The present invention is based on this technical teaching.

[0005] This electromechanically acting steering device can have a steering input generation unit, which typically comprises an electrically acting machine and a mechanical transmission to generate the steering input from the force generated by the electrically acting machine or from the torque generated by the electrically acting machine. The electrically acting machine is typically a rotary or translational electric motor. The steering device is provided close to the axle or connected to the axle to minimize elasticities in the transmission path of the steering input via the mechanical interface.

[0006] This results in a conflict between the maximum force or torque that can be generated as steering input on the one hand, and the limited installation space on the other, because the greater the force or torque to be generated, the larger the electromechanical steering device, in particular its electrically acting machine and / or its mechanical transmission, must be.

[0007] Since electric vehicles, in particular, are generally heavier than conventionally powered vehicles, their axle loads are relatively high, which also requires significant steering inputs. Furthermore, vehicles with more than one steered axle are common, particularly in the commercial vehicle sector.

[0008] It is therefore an object of the present invention to provide possibilities to solve the above-mentioned problem and / or to demonstrate steering possibilities for vehicle configurations with multiple steered axles.

[0009] This problem is solved by the subject matter of the independent claims. Advantageous further developments are the subject matter of the dependent claims.

[0010] A primary steering device and a secondary steering device are described below, along with the use of associated terms (primary interface, primary steering input generating unit, primary control means, secondary interface, secondary steering input generating unit, secondary control means). This does not exclusively concern the case where items preceded by the term “primary” describe the main steering device and elements thereof, while items preceded by the term “secondary” identify an auxiliary or support steering device. This may represent a specific embodiment of the invention, but it does not necessarily have to be limited thereto. In general, the terms “primary” and “secondary” are used merely to distinguish between the described steering devices and the described components.used to assign the corresponding elements to these steering devices, without describing any prioritization or hierarchical assignment of the steering devices to one another.

[0011] Disclosed is a secondary steering device for a steering system having at least one steered axle and a primary steering device. The primary steering device is configured to impart a primary steering input to the at least one steered axle.

[0012] The secondary steering device has a mechanical secondary interface for outputting a secondary steering input to the at least one steered axle, wherein the secondary steering device has a secondary steering input generation unit which is designed to generate the secondary steering input and to apply it to the at least one steered axle via the mechanical secondary interface.

[0013] The secondary steering device disclosed here therefore serves to generate secondary steering inputs and to impose them on the at least one steered axle.

[0014] The secondary steering device can be designed to apply the secondary steering input to the at least one steered axle in addition to a primary steering input of the primary steering device, so that a steering input combined from the primary steering input and the secondary steering input is provided.

[0015] Alternatively or additionally, the secondary steering device can also be designed to apply the secondary steering input alone and without a primary steering input of the primary steering device to the at least one steered axle.

[0016] The secondary steering device thus represents a supplement to the primary steering device, with the primary steering device, in turn, representing an essential element of an electromechanical steering system according to the prior art described above. The disclosed secondary steering device can therefore be used to supplement an electromechanical steering system or a steering system with an electromechanically acting primary steering device.

[0017] Preferably, the primary steering input is a steering force or a steering torque.

[0018] Alternatively or additionally, the secondary steering input is a steering force or a steering torque.

[0019] Preferably, the primary steering device is designed to generate the primary steering input electromechanically or hydraulically, in particular electrohydraulically.

[0020] Preferably, the secondary steering input generating unit is designed to generate the secondary steering input electromechanically or hydraulically, in particular electrohydraulically. If the secondary steering input generating unit is designed to generate the secondary steering input electromechanically, the secondary steering device can preferably be designed identically to the primary steering device. In this way, a complex design of the steering system in which the secondary steering device is provided is avoided. If the secondary steering input generating unit is designed to generate the secondary steering input electromechanically, it can have an electric machine, which is optionally combined with a transmission. The transmission can comprise a ball screw drive, a spindle drive, or a combination of pinion and rack. The electric machine can be a rotary or translatory electric motor.

[0021] If the secondary steering input generating unit is designed to generate the secondary steering input hydraulically, this has the advantage that the secondary steering device can be positioned relatively freely within the steering system or within the vehicle, since pressure generators of the secondary steering input generating unit, such as pumps and other hydraulic elements of the secondary steering input generating unit, can be positioned relatively freely and do not necessarily have to be located close to the corresponding axle. Furthermore, by providing a hydraulic transmission, it is possible to dispense with mechanical transmissions or gears. Therefore, when the secondary steering input is generated hydraulically, the secondary steering input generating unit does not need to have a mechanical transmission or gear ratio. A secondary steering device with a secondary steering input generating unit that is designed to

[0022] Generating secondary steering input hydraulically thus represents an advantageous addition to a primary steering device which is designed to generate the primary steering input electromechanically.

[0023] Preferably, the primary steering device comprises a primary control means configured to control the primary steering input generation unit to generate the primary steering input based on a primary control signal. The primary control means may comprise an electrical or electronic means for controlling the primary steering input accordingly.

[0024] The secondary steering device preferably has a secondary control means configured to control the secondary steering input generating unit to generate the secondary steering input based on a secondary control signal. The secondary control means may comprise an electrical or electronic means, in particular a data processing means, to appropriately control the secondary steering input generating unit. The secondary control signal is preferably configured such that the secondary steering input generating unit or the secondary steering device generates the secondary steering input in such a way that the secondary steering input is generated to match the primary steering input. For example, if the primary steering device and the secondary steering device are in contact with the same steered axle via the respective mechanical interfaces, the secondary control signal can be generated such that the secondary steering input represents a support for the primary steering input.

[0025] For example, if the primary steering device and the secondary steering device are in contact with the respective mechanical interfaces with different steered axles, the secondary control signal can be generated such that the secondary steering device effects a steering of the vehicle in which the steering system is provided, which is kinematically coordinated with the steering by the primary steering input.

[0026] Both the primary control signal and the secondary control signal can be based on a steering command that is sent to the primary steering device and / or to the secondary steering device. The steering command can be designed as described below. The steering command can also be sent to a steering system in which the primary steering device and the secondary steering device are provided, for example, a steering system defined below. It can be provided that the primary control means is designed to generate the primary control signal and the secondary control signal from the steering command. However, it can also be provided that the primary control means is designed to generate the primary control signal from the steering command and the secondary control means is designed to generate the secondary control signal from the steering command.

[0027] Preferably, the secondary control means of the secondary steering device is configured to generate the secondary control signal itself. This option can be provided if the secondary steering device is configured such that only the steering command is sent to or received from the secondary steering device, in particular to the secondary control means.

[0028] The steering system in which the secondary steering device is provided can be designed such that the steering command is sent directly to the secondary steering device, in particular to the secondary control means, or is forwarded from the primary steering device, in particular from the primary control means, to the secondary steering device or to the secondary control means.

[0029] It can also be provided that the steering system in which the secondary steering device is provided is designed such that variables of the primary steering device, such as the primary steering input generated by the primary steering device, are sent to the secondary control means of the secondary steering device and are additionally taken into account when generating the secondary control signal by the secondary control means of the secondary steering device.

[0030] Preferably, the secondary control means of the secondary steering device is designed to generate the secondary control signal based on a load state of the steering system and / or based on a kinematic state of the steering system.

[0031] Preferably, the steering system in which the secondary steering device is provided and / or the secondary steering device itself has one or more detection means designed to detect one or more forces and / or one or more moments on the at least one steered axle and transmit them to the secondary control means of the secondary steering device. This can, for example, comprise force and / or moment detection at the primary interface and / or at the secondary interface. In particular, detection of the force on a push rod of the at least one steered axle can be provided.

[0032] Preferably, the steering system in which the secondary steering device is provided and / or the secondary steering device itself has one or more detection means configured to detect kinematic variables, such as steering angles or spring travels, on the at least one steered axle and transmit them to the secondary control means of the secondary steering device. This is advantageous because, in particular, a counterforce or countertorque that must be overcome at the primary interface and / or at the secondary interface by the applied primary steering input or secondary steering input depends on the kinematic state of the at least one steered axle.

[0033] The secondary control means of the secondary steering device is preferably designed to take into account the forces, moments and / or kinematic variables detected by the detection means when generating the secondary control signal.

[0034] Preferably, the secondary control means of the secondary steering device is designed to generate the secondary control signal on the basis of forces or moments acting on the at least one steered axle and in particular forces or moments acting on the mechanical secondary interface.

[0035] Preferably, the secondary steering device is configured to receive the secondary control signal from an external source. The external sources are further specified below in connection with the disclosed steering system. Therefore, reference is made to the following explanations. In particular, the primary steering device of the steering system in which the secondary steering device is provided, or a central control means, can act as the source. The secondary steering device can, in particular, be configured to provide a redundancy level to the primary steering device.

[0036] Preferably, the secondary steering device is designed to ensure the steerability of the vehicle in which the secondary steering device is provided if the primary steering device exhibits a fault. The secondary steering device therefore enables a redundant configuration of the steering system described below. If specific aspects of redundancy are addressed, this will be indicated below with the term "redundancy-fair" or "in the event of redundancy."

[0037] A steering system is disclosed below. Features of such a steering system that have already been explained in connection with the secondary steering device described above can also be considered features or embodiments of the steering system described below.

[0038] The secondary steering device described below as a component of the steering system can in particular be designed like the secondary steering device described above.

[0039] Disclosed is a steering system for a vehicle, comprising:

[0040] - at least one steered axle;

[0041] - a primary steering device with a mechanical primary interface for delivering a primary steering input to the at least one steered axle, wherein the primary steering device has a primary steering input generating unit which is designed to generate the primary steering input and to apply it to the at least one steered axle via the mechanical primary interface;

[0042] - a secondary steering device as described above, wherein the secondary steering device is designed to impart the generated secondary steering input via the mechanical secondary interface to the at least one steered axle.

[0043] According to one embodiment, the steering system comprises: - at least one steered axle;

[0044] - a primary steering device with a mechanical primary interface for delivering a primary steering input to the at least one steered axle, wherein the primary steering device has a primary steering input generating unit which is designed to generate the primary steering input and to apply it to the at least one steered axle via the mechanical primary interface;

[0045] - a secondary steering device with a mechanical secondary interface for outputting a secondary steering input to the at least one steered axle, wherein the secondary steering device has a secondary steering input generation unit which is designed to generate the secondary steering input and to apply it to the at least one steered axle via the mechanical secondary interface, wherein the steering system is designed to control the primary steering device and the secondary steering device to generate the primary steering input and the secondary steering input in accordance with a steering specification.

[0046] Preferred training options for steering systems are described below.

[0047] Preferably, the secondary steering device is designed to ensure steerability of the vehicle in which the secondary steering device is provided when the primary steering device has a fault, wherein a redundancy case is characterized by a fault in the primary steering device.

[0048] Since the secondary steering device, like the primary steering device, can apply a steering input to the at least one steered axle, it is possible in this way to design the steering system with diverse redundancy. This means that in the event of redundancy, steerability or use of the at least one steered axle is still possible and there is no need to switch to another system or method in order to steer the vehicle. Diverse redundancy can be achieved, for example, by the primary control means and the secondary control means being constructed differently or containing electronic components from different manufacturers. The steering system is preferably designed to control the primary steering device and the secondary steering device to generate the primary steering input and the secondary steering input in accordance with a steering specification.

[0049] The steering command can, for example, be a driver input via a driver interface, such as a steering wheel. In autonomous vehicles, the steering command can also be generated automatically by the vehicle and transmitted to the steering system. For example, a steering command can be a steering wheel angle or torque, or a target command for a steering angle, steering force, or steering torque.

[0050] The at least one steered axle may be a vehicle axle with wheels that are steered by turning or pivoting the wheels of these axles around a steering axis.

[0051] The primary mechanical interface may be in contact with a steered wheel of the at least one steered axle to apply the primary steering input to the at least one axle. In particular, this may be a steering lever on the wheel.

[0052] The primary mechanical interface may be in contact with a steering linkage of the at least one steered axle to apply the primary steering input to the at least one axle. In particular, this may be a push rod.

[0053] The mechanical secondary interface can be in contact with a steered wheel of the at least one steered axle in order to apply the secondary steering input to the at least one axle. In particular, this can be a steering lever on the wheel. The corresponding wheel can advantageously be a wheel of the steered axle that is not in direct contact with the mechanical primary interface and, in particular, is located transversely to the direction of travel and thus on the other side of the vehicle opposite the wheel that is in direct contact with the mechanical primary interface. This makes it possible to have a distributed arrangement of the primary steering device and the secondary steering device, which has an advantageous effect on the space required by the corresponding steered axle. The mechanical secondary interface can be in contact with a steering linkage of the at least one steered axle in order to apply the secondary steering input to the at least one axle.In particular, this can be a push rod. Particularly preferably, this can be the same steering linkage or push rod with which the primary mechanical interface is in contact. Thus, no additional coupling of the secondary mechanical interface or the secondary steering device is necessary, which has a beneficial effect on the space requirements of the corresponding steered axle.

[0054] Preferably, the secondary control means of the secondary steering device is configured to receive the secondary control signal based on the steering input for controlling the secondary steering input generation unit. In this case, the secondary control signal comes from an external source. This is described in more detail below.

[0055] The steering system preferably has a central control means designed to send the secondary control signal to the secondary control means of the secondary steering device. The central control means can comprise an electrical or electronic means, in particular a data processing means. The central control means is preferably designed to generate the secondary control signal from the steering input. The central control means can preferably also generate a primary control signal for the primary steering device. Thus, the primary steering device and the secondary steering device can be controlled centrally by a central control means, namely the central control means. The central control means can be designed to take into account information from the steering system, in particular the primary steering device and / or the secondary steering device, to generate the primary control signal and / or to generate the secondary control signal.The information can include information on the load state and / or kinematic state, as described further below in connection with the detection means. The central control means can preferably be freely positioned within the steering system or within the vehicle. The transmission of the secondary control signal to the secondary steering device or of the primary control signal to the primary steering device and the secondary control signal to the secondary steering device can be analog or digital. A bus connection is preferably used for this purpose.

[0056] Preferably, the secondary steering device, in particular the secondary control means, is designed to check the correctness of the received secondary control signal. This can be done, in particular, by using a checksum or other conventional testing methods.

[0057] The primary steering device preferably has a primary control means configured to send the secondary control signal to the secondary control means of the secondary steering device. The primary control means of the primary steering device is preferably configured to generate the secondary control signal to the secondary control means of the secondary steering device from the steering input. In particular, the primary control means of the primary steering device can be configured to generate a secondary control signal, on the basis of which the secondary steering device generates a secondary steering input that supports the primary steering input when the primary steering device and the secondary steering device act on the same steered axle.It can also be provided that the primary control signal and the secondary control signal are selected such that a primary steering input and a secondary steering input are generated in which neither the primary steering input generating unit nor the secondary steering input generating unit is overloaded or generates the maximum possible steering input. In this way, the load during steering can be distributed between the primary steering device and the secondary steering device.

[0058] The transmission of the secondary control signal from the primary steering device or from the primary control means to the secondary steering device can be analog or digital. A bus connection is preferably used for this purpose. The secondary steering device, in particular the secondary control means, is preferably designed to check the correctness of the received secondary control signal. This can be done, in particular, by using a checksum or other conventional testing methods.

[0059] If the primary steering device and the secondary steering device act on different steered axles, the primary control means of the primary steering device is preferably designed to generate the secondary control signal for the secondary steering device in such a way that the vehicle kinematics or

[0060] Chassis kinematics takes place.

[0061] However, it can also be provided that the secondary control signal for the secondary steering device is not generated by the primary control means of the primary steering device. Instead, it can be provided that the secondary control signal is generated by another external source or the central control means and sent to the primary control means of the primary steering device. This is then configured to send the secondary control signal to the secondary steering device or to the secondary control means of the secondary steering device.

[0062] The primary control means of the primary steering device may be identical to the primary control means described above, which is configured to control the primary steering input generation unit to generate the primary steering input based on a primary control signal. Alternatively, the two control means may be different from one another.

[0063] Preferably, the steering system has a detection means configured to detect the load state of the steering system or the kinematic state of the steering system. The detection means can be a separate part of the steering system, as described above, or can be provided as a component of the primary steering device and / or as a component of the secondary steering device.

[0064] Preferably, it can be provided that the primary steering device, in particular the primary control means, is designed to generate the secondary control signal based on the detected load state and / or based on the detected kinematic state. These can be determined in particular by detecting forces and / or moments acting at the primary interface or kinematic variables such as travel distance or steering angle. It can therefore be provided that only the load state and / or the kinematic state is detected at the primary interface or corresponding variables are detected only at the primary interface. The primary steering device, in particular the primary control means, is then preferably designed to generate the corresponding secondary control signal from this load state and / or kinematic state.

[0065] According to one embodiment, the primary mechanical interface and the secondary mechanical interface are connected to the same steered axle, so that the primary steering input and the secondary steering input can act individually or in combination to steer the axle. As described above, this allows the steering inputs to be distributed accordingly between the primary steering device and the secondary steering device, thus avoiding overloading the steering devices or generating a maximum steering input by either the primary steering device or the secondary steering device.

[0066] A connection of the mechanical primary interface and the mechanical secondary interface to the same steered axle does not exclude the possibility of a connection of the primary interface and / or the secondary interface to at least one further steered axle. In a steering system, it is possible for the primary interface to be connected to an axle and the secondary interface to be connected to the same axle. In addition, a mechanically and kinematically coordinated connection (e.g. a linkage) of the primary interface and / or the secondary interface to at least one further steered axle can be provided. Another possible configuration is characterized by a connection of the primary interface to a first steered axle and by a connection of the secondary interface to a second steered axle. Here, the primary interface can be connected via a mechanically and kinematically coordinated connection (e.g.A secondary interface can be connected to the second steered axle via a linkage (e.g., a linkage) to transmit the primary steering input to the second axle. Alternatively or additionally, the secondary interface can be connected to the first steered axle via a mechanically and kinematically coordinated connection (e.g., a linkage) to transmit the secondary steering input to the first axle. In this way, the primary and / or secondary steering input can be transmitted to multiple steered axles.

[0067] The secondary steering device is preferably designed as a support device for the primary steering device. If the mechanical primary interface and the mechanical secondary interface are connected to the same steered axle, the secondary steering device can be dimensioned such that its maximum possible secondary steering input does not exceed the maximum possible primary steering input of the primary steering device. In this case, the primary steering device preferably generates the majority of the required steering input, while the secondary steering device merely provides support. The support can be designed such that the secondary steering device generates a secondary steering input when the primary steering device generates the maximum possible primary steering input and thus cannot increase it any further. Both steering inputs then act in combination. The secondary steering input preferably does not exceed the primary steering input.However, this is not excluded. It can also be provided that, when a primary steering input is generated that corresponds to a predetermined limit value that is lower than the maximum possible primary steering input (e.g., 80% of it), a secondary steering input is generated by the secondary steering device in order to protect the primary steering device or to maintain sufficient adjustment potential of the primary steering device should further adjustment be necessary. The predetermined primary steering input can thus also determine the adjustment potential of the primary steering device. In the above example, the remaining 20% ​​of the primary steering input would function as adjustment potential until the maximum possible primary steering input is reached.

[0068] A primary steering device failure that triggers a redundancy event can be any failure that makes sufficient primary steering input at the primary interface impossible. For example, this can be a failure of the primary steering device as a whole or of parts thereof, such as the primary steering input generation unit or the primary control means. Another failure can be a failure of the primary steering device's power supply. Another failure can be a failure of a data connection of the primary steering device, via which the steering command is sent to the primary control means or via which other data, such as information from the secondary steering device, is sent to the primary control means.

[0069] The secondary steering device can be configured to ensure, in the case of redundancy, that a specified manual torque that a driver must apply to the steering wheel is not exceeded by means of the secondary steering input. In particular, it can be specified that this is done to ensure compliance with the ECE R79 standard.

[0070] To enable steering by the secondary steering device in the event of redundancy, it can be provided that the secondary steering device receives the steering command directly. This is advantageous when a steering command or a secondary control signal can no longer be sent from the primary steering device, and in particular from the primary control means, to the secondary steering device, and in particular to the secondary control means. In this case, it is further advantageous if the secondary steering device, and in particular the secondary control means, is designed to generate the secondary control signal itself.

[0071] A separate data connection can therefore exist between a detection means of the steering system designed to detect the steering input, for example, a torque and / or angle sensor on the steering wheel or steering column, and the secondary steering device. Alternatively, a branching data connection can be provided between this detection means and the primary steering device, on the one hand, and between this detection means and the secondary steering device, on the other hand. This can be implemented using a Y-cable.

[0072] Preferably, the primary steering device and in particular the primary control means are designed to transmit information to inform recipients of this information about an existing error and thus about the occurrence of the redundancy case. In particular, the central control means or the

[0073] The secondary steering device and, in particular, the secondary control means can be the recipients of this information. These can advantageously be configured to convert their operation to a mode intended for redundancy.

[0074] However, alternatively or additionally, in the case of redundancy, it may be possible to control the secondary steering device by an external source, such as the central control means.

[0075] The central control means can preferably be designed to control the entire steering system. In the case of redundancy, a steering command can be generated by the central control means into a secondary control signal for the secondary steering device. The central control means is preferably designed to take into account the presence of a redundancy, so that the secondary control signal is generated accordingly, in particular to ensure the steerability of the vehicle.

[0076] Alternatively, the secondary control means is configured to generate the secondary control signal itself in the event of redundancy. For this purpose, the secondary control means is preferably configured to take into account the presence of a redundancy situation, so that the secondary control signal is generated accordingly, in particular to ensure the steerability of the vehicle.

[0077] The secondary control means is preferably designed to ensure, in the case of redundancy, the steering of the steered axle to which the secondary interface is connected, by means of the secondary steering input. This can be the same steered axle to which the primary interface is connected. If the steering system has at least two steered axles, with the primary interface and the secondary interface being connected to different steered axles, steering of at least the axle connected to the secondary interface can still be ensured in the case of redundancy. However, the increased tire wear on the steered axle connected to the primary interface, which is to be expected when cornering, must be accepted; this is, however, acceptable in the case of redundancy.Preferably, in order to ensure the steering of the steered axle to which the secondary interface is connected, it can be provided that the secondary control signal in the case of redundancy is increased compared to normal operation, regardless of whether it is generated by an external source or by the secondary steering device or the secondary control means, in order to generate a larger secondary steering input and thus at least partially, preferably completely, compensate for the loss of the primary steering input.

[0078] Particularly preferably, the steered axles of the steering system are connected to one another, for example, as described above, by a mechanically and kinematically coordinated connection (e.g., a linkage). A primary steering input or a secondary steering input on one axle thus also causes a steering input on the other axle.

[0079] Preferably, the steering system comprises a secondary power supply unit that is provided independently of a primary power supply unit of the steering system. The secondary power supply unit is configured to supply the secondary steering device with power, while the primary power supply unit is configured to supply the primary steering device with power. A failure of the primary power supply unit can also be considered a fault in the primary steering device, triggering a redundancy case because the primary steering device can then no longer generate a primary steering input. The secondary power supply unit, provided independently of the primary power supply unit, ensures that the secondary steering device is not also affected by a failure.

[0080] It can be provided that the secondary energy supply unit continuously supplies the secondary steering device with energy. This means both when the primary energy supply unit is in operation and also when the primary energy supply unit has failed. According to an alternative embodiment, it can be provided that the primary energy supply unit is designed to supply both the primary steering device and the secondary steering device with energy. The secondary energy supply unit can then be designed to take over the energy supply of the secondary steering device in the case of redundancy in which the primary energy supply unit has failed. This can make it possible to design the secondary energy supply unit solely for this redundancy case and thus advantageously with a lower capacity or performance than the primary energy supply unit.This is particularly advantageous if, for this redundancy scenario, only limited steerability of the vehicle or steering system is desired, and in particular, one that is not designed for continuous operation. This can then be achieved, for example, by using the secondary steering device to maneuver the vehicle into a safe position, such as a parking position at the side of the road.

[0081] The primary energy supply unit is preferably an electrical energy storage device, such as a battery or a power source such as a generator-driven electrical machine.

[0082] The secondary energy supply unit is preferably an electrical energy storage device, such as a battery or a power source such as a generator-driven electric machine. If the secondary steering device is designed to generate the secondary steering input hydraulically, the secondary energy supply unit can also comprise a pressure generator, such as a pump, which is, for example, recuperatively driven. Such a secondary energy supply unit would provide energy as long as the vehicle is moving, i.e., until the vehicle is stationary and has preferably assumed a parked position.

[0083] According to one embodiment, the primary mechanical interface and the secondary mechanical interface are connected to different steered axles, so that the primary steering input can act on one axle and the secondary steering input on another. These can be two front axles. Alternatively, one or both axles can be configured as rear axles or trailing axles. It can also be provided that one axle is configured as the front axle and the other as the rear axle or trailing axle.

[0084] Preferably, the primary steering input generating unit is designed to generate the primary steering input electromechanically or hydraulically, in particular electrohydraulically.

[0085] Preferably, the primary steering input generating unit and the secondary steering input generating unit are configured such that the generated primary steering input and the generated secondary steering input, in combination, are sufficient even during parking and maneuvering operations. Since the highest forces in a vehicle's steering system must be overcome during parking and maneuvering operations, it can advantageously be provided that the primary steering input generating unit and the secondary steering input generating unit are configured such that they only generate steering inputs that together are sufficiently high to overcome the forces that occur. As soon as the vehicle is rolling or driving, the forces to be overcome are reduced to approximately 30 to 50%. Such a configuration has the advantage that both the primary steering input generating unit and the secondary steering input generating unit can be made smaller.In the case of redundancy when the vehicle is moving, the secondary steering device can still generate a sufficiently high secondary steering input, which is then sufficient to overcome the forces in the steering system and park the vehicle safely on the side of the road, as mentioned above. Conversely, it can also be provided that if the secondary steering device fails, a sufficiently high primary steering input is still generated by the primary steering device.

[0086] A vehicle, in particular a commercial vehicle, is disclosed, having a secondary steering device as described above or having a steering system as described above. The vehicle may be conventionally, hybridly, or electrically powered. The hybrid and electric drive may comprise a fuel cell drive or a battery-electric drive. Preferably, if the vehicle has a steering system in which the mechanical primary interface and the mechanical secondary interface are connected to the same steered axle, the vehicle is preferably designed such that the steered axle, in a possible loading condition for the vehicle, carries at least 20% of the sum of all axle loads of the vehicle or carries at least 11 t axle load.In this way, vehicle steering can be facilitated by the secondary steering system supporting the primary steering system, allowing the primary steering input and the secondary steering input to be combined and applied to the same axle. This can particularly address the problem of increased load on the steered axles, which is particularly prevalent in electric and hybrid-powered vehicles.

[0087] The invention is described below using preferred embodiments with reference to the accompanying drawings.

[0088] It shows

[0089] Fig. 1 a secondary steering device,

[0090] Fig. 2 shows a first embodiment of a steering system,

[0091] Fig. 3 shows a second embodiment of a steering system,

[0092] Fig. 4 shows a third embodiment of a steering system, and

[0093] Fig. 5 shows a fourth embodiment of a steering system.

[0094] Fig. 1 shows a secondary steering device.

[0095] The secondary steering device 4 shown is suitable for a steering system 1 having at least one steered axle 2, 6 and an electromechanically or hydraulically, in particular electrohydraulically, acting primary steering device 3, which is designed to impart a primary steering input to the at least one steered axle 2, 6. Examples that do not limit the disclosed invention, but merely show specific embodiments of such steering systems, are disclosed in Figures 2 to 5.

[0096] The secondary steering device 4 has a mechanical secondary interface 4.1 for outputting a secondary steering input to the at least one steered axle 2, 6, wherein the secondary steering device 4 has a secondary steering input generation unit 4.2 which is designed to generate the secondary steering input and to apply it to the at least one steered axle 2, 6 via the mechanical secondary interface 4.1.

[0097] The secondary steering input generation unit 4.2 is configured to generate the secondary steering input electromechanically. Alternatively, the secondary steering input generation unit 4.2 is configured to generate the secondary steering input hydraulically, in particular electrohydraulically.

[0098] If configured to generate the secondary steering input electromechanically, the secondary steering input generation unit 4.2 may comprise an electric machine, optionally combined with a transmission. The transmission may comprise a ball screw drive, a spindle drive, or a combination of a rack and pinion. The electric machine may be a rotary or translational electric motor.

[0099] If the secondary steering input generation unit 4.2 is designed to generate the secondary steering input hydraulically, this has the advantage that the secondary steering device 4 can be positioned relatively freely within the steering system or within the vehicle, since pressure generators of the secondary steering input generation unit 4.2, such as pumps and other hydraulic elements of the secondary steering input generation unit 4.2, can be positioned relatively freely and do not necessarily have to be located near the corresponding axle. Furthermore, by providing a hydraulic transmission, it is possible to dispense with mechanical transmissions or gears. Therefore, the secondary steering input generation unit 4.2 does not need to have a mechanical transmission or gear ratio when the secondary steering input is generated hydraulically.

[0100] The secondary steering device 4 has a secondary control means 4.3, which is designed to control the secondary steering input generation unit 4.2 to generate the secondary steering input based on a secondary control signal. The secondary control means has an electrical or electronic means, in particular a data processing means, for controlling the secondary steering input generation unit 4.2 accordingly.

[0101] The secondary control signal is preferably configured such that the secondary steering input generation unit 4.2 or the secondary steering device 4 generates the secondary steering input in such a way that the secondary steering input is generated in a manner that matches the primary steering input. For example, if the primary steering device and the secondary steering device are in contact with the same steered axle via the respective mechanical interfaces, the secondary control signal can be generated such that the secondary steering input supports the primary steering input.

[0102] For example, if the primary steering device and the secondary steering device are in contact with the respective mechanical interfaces with different steered axles, the secondary control signal can be generated such that the secondary steering device effects a steering of the vehicle in which the steering system is provided, which is kinematically coordinated with the steering by the primary steering input.

[0103] The secondary control means 4.3 can be configured to generate the secondary control signal itself, as explained above. Alternatively or additionally, the secondary steering device 4 or the secondary control means 4.3 can be configured to receive the secondary control signal from an external source, as explained above.

[0104] Such a secondary steering device 4 can be provided in a steering system.

[0105] Four exemplary embodiments of such steering systems are presented below, although this should not be construed as a limitation of the invention. Fig. 2 shows a first embodiment of a steering system.

[0106] Shown is a steering system 1 for a vehicle, comprising:

[0107] - one steered axle 2;

[0108] - a primary steering device 3 with a mechanical primary interface 3.1 for delivering a primary steering input to the steered axle 2, wherein the primary steering device 3 has a primary steering input generation unit 3.2 which is designed to generate the primary steering input electromechanically or hydraulically, in particular electrohydraulically, and to apply it to the steered axle 2 via the mechanical primary interface 3.1;

[0109] - a secondary steering device 4 as shown in Fig. 1, wherein the secondary steering device 4 is designed to generate the secondary steering input and to impart it to the steered axle 2 via the mechanical secondary interface 4.1.

[0110] The steering system 1 is designed to control the primary steering device 3 and the secondary steering device 4 to generate the primary steering input and the secondary steering input according to a steering command.

[0111] The steering command can, for example, be a driver input via a driver interface, such as a steering wheel. In autonomous vehicles, the steering command can also be generated automatically by the vehicle and transmitted to the steering system 1. For example, a steering command can be a steering wheel angle or a steering wheel torque, or a target command for a steering angle, a steering force, or a steering torque.

[0112] The mechanical primary interface 3.1 can be designed as described above. A detailed illustration of the mechanical primary interface 3.1 has been omitted here for the sake of simplicity. The mechanical secondary interface 4.1 can be designed as described above. A detailed illustration of the mechanical secondary interface 4.1 has been omitted here for the sake of simplicity.

[0113] The primary steering device 3 has a primary control means 3.3, which is designed to send the secondary control signal to the secondary control means 4.3 of the secondary steering device 4. For this purpose, a data connection 7 exists between the primary control means 3.3 and the secondary control means 4.3, which is indicated here by a dashed line. The data connection 7 can be designed as a direct connection between the primary control means 3.3 and the secondary control means 4.3 or as another suitable connection, such as a bus connection.

[0114] The data connection 7 can also be bidirectional. This means that information from the secondary steering device 4, in particular from the secondary control means 4.3, can also be sent to the primary control means 3.3 via the data connection 7. For example, information about the secondary steering input, which is applied to the steered axle 2 via the secondary interface 4.1, can be sent to the primary control means 3.3. The primary control means 3.3 is designed to control both the primary steering device 3 and the secondary steering device 4.

[0115] The primary control means 3.3 comprises an electrical or electronic means, in particular a data processing means, for transmitting the secondary control signal to the secondary steering input generation unit 4.2. In this way, the primary steering device 3 and the secondary steering device 4 can be controlled from the primary steering device 3.

[0116] Since both the primary steering device 3 and the secondary steering device 4 are connected to the same steered axle 2, the primary steering input of the primary steering device 3 and the secondary steering input of the secondary steering device 4 can be applied to the steered axle 2 in combination via the primary interface 3.1 or via the secondary interface 4.1, respectively. As explained above, the secondary steering device 4 can support the primary steering device 3 by applying both steering inputs to the steered axle 2 in combination. In particular, the secondary steering device 4 can be designed to support the primary steering device 3. This is advantageous, for example, if the steered axle 2, in a possible loading condition, carries at least 20% of the sum of all axle loads of the vehicle or carries at least 11 t of axle load.

[0117] Fig. 3 shows a second embodiment of a steering system.

[0118] Shown is a steering system 1 for a vehicle, comprising:

[0119] - a first steered axle 2 and a second steered axle 6;

[0120] - a primary steering device 3 with a mechanical primary interface 3.1 for outputting a primary steering input to a first steered axle 2, wherein the primary steering device 3 has a primary steering input generation unit 3.2 which is designed to generate the primary steering input electromechanically or hydraulically, in particular electrohydraulically, and to apply it to the first steered axle 2 via the mechanical primary interface 3.1;

[0121] - a secondary steering device 4 as shown in Fig. 1, wherein the secondary steering device 4 is designed to impart the generated secondary steering input to the second steered axle 6 via the mechanical secondary interface 4.1.

[0122] The steering system 1 is designed to control the primary steering device 3 and the secondary steering device 4 to generate the primary steering input and the secondary steering input according to a steering command.

[0123] The primary steering device 3 and the secondary steering device 4 essentially correspond to those shown in Fig. 2. Therefore, reference is made to the above explanations in this regard. In contrast to the embodiment shown in Fig. 2, the steering system 1 has two steered axles 2, 6 instead of one steered axle.

[0124] In this embodiment of the steering system 1, the secondary steering device 4 is designed to apply the secondary steering input to the second steered axle 6 via the secondary interface 4.1. Here, too, a data connection 7 is provided between the primary control means 3.3 and the secondary control means 4.3, via which control of the secondary steering device 4 and the secondary control means 4.3 by the primary control means 3.3 is possible.

[0125] The data connection 7 can also be bidirectional here. This means that information from the secondary steering device 4, in particular from the secondary control means 4.3, can also be sent to the primary control means 3.3 via the data connection 7. For example, information about the secondary steering input, which is applied to the second steered axle 6 via the secondary interface 4.1, can be sent to the primary control means 3.3. The primary control means 3.3 is designed to control both the primary steering device 3 and the secondary steering device 4.

[0126] This embodiment provides a steering system 1 that can control or steer two steered axles 2, 6. This is a particularly important application for commercial vehicles.

[0127] Fig. 4 shows a third embodiment of a steering system.

[0128] This steering system 1 corresponds to the steering system 1 shown in Fig. 2. In contrast, a central control means 5 is provided here, which is connected to the primary control means 3.3 via a data connection 7 and to the secondary control means 4.3 via a second data connection 8.

[0129] The central control means 5 has an electrical or electronic means, in particular a data processing means, in order to control the primary steering device 3 and the secondary steering device 4 in accordance with the steering specification.

[0130] The central control means 5 can thus be freely positioned in the steering system 1 or in the vehicle. The transmission of the secondary control signal to the secondary steering device 4 or the primary control signal to the primary steering device 3 and the secondary control signal to the secondary steering device 4 can be analog or digital. A bus connection is preferably used for this purpose.

[0131] Both the first data connection 7 and the second data connection 8 can be bidirectional. This means that information from the primary steering device 3 can be sent to the central control means 5 via the first data connection 7, and information from the secondary steering device 4 can be sent via the second data connection 8. For example, information about the secondary steering input, which is applied to the steered axle 2 via the secondary interface 4.1, can be sent to the central control means 5. The central control means 5 is designed to control both the primary steering device 3 and the secondary steering device 4 via the first data connection 7 and the second data connection 8, respectively.

[0132] Fig. 5 shows a fourth embodiment of a steering system.

[0133] This steering system 1 corresponds to the steering system shown in Fig. 3. In contrast, a central control means 5 is provided here, which is connected to the primary control means 3.3 via a first data connection 7 and to the secondary control means 4.3 via a second data connection 8.

[0134] The central control means 5 essentially corresponds to that shown in Fig. 4. Therefore, reference is made to the above explanations. Thus, central control of the primary steering device 3 and the secondary steering device 4 is possible even with two steered axles 2, 6.

[0135] All of the steering systems 1 shown here can be designed to achieve steering of the steered axle(s) 2, 6 in the case of redundancy solely by the secondary control means 4. LIST OF REFERENCE SYMBOLS

[0136] 1 steering system

[0137] 2 steered axle 3 primary steering device

[0138] 3.1 mechanical primary interface

[0139] 3.2 Primary steering input generation unit

[0140] 3.3 Primary tax resources

[0141] 4 Secondary steering device 4.1 Mechanical secondary interface

[0142] 4.2 Secondary steering input generation unit

[0143] 4.3 Secondary tax resources

[0144] 5 Central tax funds

[0145] 6 steered axle 7 data connection

[0146] 8 Data connection

Claims

PATENT CLAIMS 1 . Steering system (1 ) for a vehicle, comprising: - at least one steered axle (2, 6); - a primary steering device (3) with a mechanical primary interface (3.1) for outputting a primary steering input to the at least one steered axle (2, 6), wherein the primary steering device (3) has a primary steering input generation unit (3.2) which is designed to generate the primary steering input and to apply it to the at least one steered axle (2, 6) via the mechanical primary interface (3.1); - a secondary steering device (4) with a mechanical secondary interface (4.1) for outputting a secondary steering input to the at least one steered axle (2, 6), wherein the secondary steering device (4) has a secondary steering input generation unit (4.2) which is designed to generate the secondary steering input and to apply it to the at least one steered axle (2, 6) via the mechanical secondary interface (4.1), wherein the steering system (1) is designed to control the primary steering device (3) and the secondary steering device (4) to generate the primary steering input and the secondary steering input in accordance with a steering specification, wherein the secondary steering device (4) is designed to ensure steerability of the vehicle in which the secondary steering device (4) is provided if the primary steering device (3) has a fault, wherein a fault in the primary steering device (3) characterizes a redundancy case.

2. Steering system (1) according to claim 1, wherein the primary steering input generating unit (3.2) is designed to generate the primary steering input electromechanically or hydraulically, in particular electrohydraulically, and / or wherein the secondary steering input generating unit (4.2) is designed to generate the secondary steering input electromechanically or hydraulically, in particular electrohydraulically.

3. Steering system (1) according to one of the preceding claims, wherein the secondary steering device (4) has a secondary control means (4.3) which is designed to control the secondary steering input generation unit (4.2) to generate the secondary steering input based on a secondary control signal.

4. Steering system (1) according to claim 3, wherein the secondary control means (4.3) of the secondary steering device (4) is designed to generate the secondary control signal itself.

5. Steering system (1) according to claim 4, wherein the secondary control means (4.3) of the secondary steering device (4) is designed to generate the secondary control signal based on a load state of the steering system (1) or based on a kinematic state of the steering system (1).

6. Steering system (1) according to claim 4 or 5, wherein the secondary steering device (4) has detection means designed to detect one or more forces and / or one or more moments on the at least one steered axle, and / or wherein the secondary steering device (4) has detection means designed to detect kinematic variables of the at least one steered axle.

7. Steering system (1) according to one of claims 3 to 6, wherein the secondary steering device (4) is designed to receive the secondary control signal from an external source.

8. Steering system (1) according to claim 7, comprising a central control means (5) as an external source, which is designed to send the secondary control signal to the secondary control means (4.3) of the secondary steering device (4).

9. Steering system (1) according to one of claims 7 or 8, wherein the primary steering device (3) has a primary control means (3.3) which is designed to send the secondary control signal to the secondary control means (4.3) of the secondary steering device (4).

10. Steering system (1) according to one of claims 5 to 9, wherein the steering system (1) has a detection means which is designed to detect the load state of the steering system (1) or the kinematic state of the steering system (1).

11. Steering system (1) according to one of the preceding claims, wherein the mechanical primary interface (3.1) and the mechanical secondary interface (4.1) are connected to the same steered axle (2), so that the primary steering input and the secondary steering input can act individually or in combination to steer the axle (2).

12. Steering system (1) according to claim 11, wherein the secondary steering device (4) is designed as a support device for the primary steering device (3).

13. Steering system (1) according to one of the preceding claims, wherein the mechanical primary interface (3.1) and the mechanical secondary interface (4.1) are connected to different steered axles (2, 6) so that the primary steering input can act on one axle (2) and the secondary steering input on another axle (6).

14. Steering system (1) according to one of the preceding claims, wherein the fault of the primary steering device (3) is characterized by a failure of the primary steering device (3) as a whole or of parts thereof, by a failure of a power supply of the primary steering device (3) or by a failure of a data connection (7) of the primary steering device (3).

15. Steering system (1) according to one of the preceding claims, wherein the secondary steering device (4) is designed to ensure by means of the secondary steering input that a predetermined manual torque which a driver must apply to the steering wheel is not exceeded.

16. Steering system (1) according to one of the preceding claims, wherein the secondary steering device (4) is designed to receive the steering command directly.

17. Steering system (1) according to claim 16, wherein there is a direct data connection between a detection means of the steering system (1), which is designed to detect the steering input, and the secondary steering device (4).

18. Steering system (1) according to claim 16, wherein a branching data connection exists between a detection means of the steering system (1), which is designed to detect the steering input, and the primary steering device (3) on the one hand and, on the other hand, between this detection means and the secondary steering device (4).

19. Steering system (1) according to one of the preceding claims, wherein the primary steering device (3) and in particular the primary control means (3.3) is designed to send information in order to inform recipients of this information about an existing error and thus about the occurrence of the redundancy case.

20. Steering system (1) according to one of the preceding claims, wherein the primary steering input generating unit (3.2) and the secondary steering input generating unit (4.2) are designed such that the primary steering input that can be generated and the secondary steering input that can be generated in combination are sufficient even during parking and maneuvering operations.

21. Vehicle, in particular commercial vehicle, with a steering system (1) according to one of the preceding claims.

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