Steering device for steer-by-wire steering system

Abstract

Steering device (10) for a steer-by-wire steering system of a motor vehicle, comprising a drive unit (12) for initiating a rotational movement about an axis of rotation AR, a first steering rod (14) and a second steering rod (16) and a rotation-translation transmission (18) arranged between the drive unit (12) and the two steering rods (14, 16) for translating the rotational movement into a steering movement transmitted via the steering rods (14, 16) to each axle body of the motor vehicle, characterized in that the rotation-translation transmission (18) indirectly couples the two steering rods (14, 16) to each other diametrically opposite each other on a circular path about the axis of rotation AR.

Description

The invention relates to a steering device for a steer-by-wire steering system of a motor vehicle, having a drive unit for initiating a rotational movement about an axis of rotation A R, of at least one first steering rod, and a rotational-translation transmission arranged between the drive unit and the steering rod, for translating the rotational movement into a steering movement transmitted via the steering rod to axle bodies of the motor vehicle.Steer-by-wire steering systems for motor vehicles, like conventional mechanical steering systems, receive manual steering commands from the driver through an input unit. This can be effected, for example, by a rotation of a steering wheel. The steering wheel is connected in a rotationally fixed manner to a steering rod unit via a steering shaft. However, the steering shaft is not necessarily mechanically connected to the wheels to be steered via a conventional steering gear and a steering rod, but can cooperate with rotational angle or torque sensors of the steering rod unit. These sensors detect the steering command introduced or an applied steering torque and transmit an electrical control signal determined therefrom to a steering device, which adjusts a corresponding steering angle of the wheel or of a wheel module by means of an electrical actuator. The steering device can also comprise a transmission and a steering rod which transmits the desired steering movement to the wheels to be steered.When using steer-by-wire steering systems, there are, in addition to technical requirements, also legal requirements which must be complied with. Purely by way of example, reference is made here to the ECE standard R79 which also applies to conventional steering systems and which requires in the core that a continuous mechanical connection must exist on the path from the steering force introduction and the transmission of the steering movement to the road-vehicle wheels. In this case, the mechanical connection must be realized by components made of metallic materials; for example, belts or components made of corresponding materials are not permissible.In a practical structural embodiment, conventional mechanical steering systems, consisting of a steering column, a spindle drive connecting the steering column to a steering rod and an electric ball screw drive supporting the steering rod in the intended steering movement, have been structurally supplemented by a further actuator to form a steer-by-wire steering system. The further actuator contains two redundant electric motors and bridges a mechanical interruption of the steering column which is now present. The disadvantage here is the enormous installation space requirement of the further actuator, even in this respect, since it is necessary to arrange this in an area below the instrument panel which is critical in any installation space.As generic prior art, WO 88 / 07953 A1 can be considered, from which a steering axle with power steering is known, in which a rotary drive mounted directly on the axle housing is provided for hydrostatic actuation of two steering levers mounted opposite each other outer wheel joint units by means of steering rods pivotably articulated thereto.DE 10 2016 201 227 A1 discloses a steering arrangement, comprising an input for actuation by a steering gear output and at least one output for actuation of a steering rotational axis to be steered. The steering assembly includes at least one transmission assembly. The transmission assembly is connected between the input, and thus the steering gear output, and one of the outputs, and thus the corresponding steering rotation axis. The steering rotation axis changes the steering angle of a single wheel.There is a constant need for a steer-by-wire steering system to provide an actuator system which can be more structurally integrated and which meets the legal requirements overall.It is the object of the invention to show measures which make it possible to provide such an actuator system.The object is achieved by a steering device having the features of claim 1. preferred embodiments of the invention are specified in the dependent claims and the following description, which can each represent an aspect of the invention individually or in combination.One embodiment relates to a steering device for a steer-by-wire steering system of a motor vehicle, having a drive unit for initiating a rotational movement about an axis of rotation A R, a first steering rod and a second steering rod, and a rotational-translation transmission arranged between the drive unit and the two steering rods, for translating the rotational movement into a steering movement transmitted via the steering rods to a respective axle body of the motor vehicle, wherein the rotational-translation transmission indirectly couples the two steering rods to one another on a circular path around the axis of rotation A R diametrically opposite one another.The axis of rotation A R is preferably located in a vertical longitudinal plane of the motor vehicle. In this case, the orientation of the rotational axis A can be arranged in R according to requirements in the vertical longitudinal plane.The first and the second steering rod can be designed identically in terms of their structure and geometry. If the two steering rods are embodied identically, it is expedient if the rotation-translation transmission, via which both steering rods are coupled, is likewise arranged in the vertical longitudinal plane. The rotation-translation gear preferably couples the two inner ends of the two steering rods facing each other to each other. The steering movement introduced into the steering rods is essentially an axial movement or a translatory movement transversely to a longitudinal direction of the vehicle.With the steering device for a steer-by-wire steering system, it is possible to meet the legally placed requirements. In addition, the requirements for functional safety--FuSi--are complied with. The steering device requires only a small installation space and allows I to adapt to different vehicle classes.In a preferred embodiment of the steering device, the drive unit comprises two electric motors that can be driven independently of one another or an at least double-wound electric motor and a transmission, wherein each of the electric motors can be coupled to the transmission as required in order to effect the rotational movement about the rotational axis A R. This prevents the steering device from failing. If a fault or fault occurs in a motor or one of the dual windings, the vehicle can continue to be steered with the remaining functional motor or the second of the dual windings.In a preferred embodiment of the steering device, it is provided that each of the steering rods has two steering rod sections that can be pivoted to one another. As a result, it is kinematically possible for a combined longitudinal and rotational movement to be imposed on the inner ends of the steering rods via the rotation-translation transmission and for the rotational component to be absorbed via the pivoting of the two steering rod sections relative to one another, with the result that an axial movement is substantially imposed on the outer steering rod section with respect to the longitudinal axis of the vehicle. In order to ensure this substantially axial movement, the steering rod section arranged R away from the axis of rotation A is preferably guided in an axial guide in each case.In a preferred embodiment of the steering device, the transmission is designed as a planetary transmission.In a preferred specific embodiment, the rotation-translation transmission comprises a transmission element which is driven pivotably about the axis of rotation A R and on which the mutually facing ends of the two steering rods are held pivotably with respect to the transmission element.Preferably, both steering rods are connected with their outer ends via a track lever to the respective axle body of the motor vehicle that can be pivoted about a vertical axis.In a preferred specific embodiment, the drive unit comprises an output shaft driven R about the axis of rotation A, which is connected via a positive connection to a drive pin of the rotation-translation transmission. Preferably, the drive pin carries the transmission element and is pivotably mounted in a housing element of the steering device. In this case, the drive pin and the transmission element can be connected to one another in a form-fitting manner.The invention is explained below by way of example with reference to the attached drawings on the basis of preferred exemplary embodiments, wherein the features illustrated below can represent an aspect of the invention both individually and in combination. The following are shown: FIG. 1 shows a conventional steering device, and FIGS. 2a) to 2c) show various representations of a steering device for a steer-by-wire steering system.FIG. 1 first shows a conventional steering device 1 with a continuous mechanical connection from a steering wheel 2 to to track levers 32 arranged on both sides, by means of which the respectively connected axle carrier with wheel-not shown-can be set to a toe angle. The mechanical path consists of a steering shaft 4 which is set in a rotational movement by an operator from the steering wheel 2 and which merges into a rack and pinion gear 6 which converts the rotational movement into a translatory movement of a spindle acting as a steering rod 14. The steering rod 14 is connected at each of its ends to the track levers 32. Furthermore, an electromechanical steering force amplification 50 is provided, which can apply a supporting axial adjusting force to the steering rod 14 via a ball-and-thread drive. The electromechanical steering force amplification 50 takes place as a function of a sensor signal which represents a sensed angle of the steering shaft 4 or a torque exerted on the steering shaft 4. A further detailed description of the conventional steering device is not required here.FIGS. 2 a), 2 b) and 2 c ) show a steering device 10 for a steer-by-wire steering system of a motor vehicle 52. FIG. 2 a ) shows a plan view of a purely schematically illustrated motor vehicle 52. The motor vehicle 52 includes a steer-by-wire steering system. On the vehicle axle 54 side, the steer-by-wire steering system is implemented via a steering device 10, as will be described below. FIG. 2 a) furthermore shows a steering wheel 2 and a steering shaft 4, wherein the steering shaft 4, unlike in the case of the steering device 1 of FIG. 1, is not mechanically connected to the vehicle axle 54, but instead only here a sensor signal is detected which represents an angle of the steering shaft 4 or a torque exerted on the steering shaft 4.FIGS. 2 a), 2 b) and 2 c) are described below essentially with common reference, wherein for the sake of clarity individual reference numerals are not shown in some figures. The steering device 10 consists structurally of a drive unit 12, a first and a second steering rod 14 and 16 and a rotation-translation transmission 18. Via the drive unit 12, a rotational movement about an axis of rotation A R can be introduced into the rotation-translation transmission 18, which is arranged between the drive unit 12 and the two steering rods 14, 16 and transmits the rotational movement via the steering rods 14, 16 as a steering movement to the respective axle body 56 of the motor vehicle 52.The drive unit 12 comprises a double-wound electric motor 22 and a transmission 24 designed as a planetary transmission. The drive unit 12 can be connected on the drive side to the planet carrier of the at least one planetary stage. On the output side of the planetary gear, a sun gear shaft can drive a drive pin 36 of the rotation-translation gear 18 via a positive connection. The drive pin 36 is rotatably mounted in a housing element 38, wherein a sliding or rolling bearing arrangement can be provided as the mounting 40. The axis of rotation of the drive pin 36 in the present case extends coaxially to the axis of rotation A R.Seated in a form-fitting manner on the drive pin 36 is a transmission element 30, which is illustrated in the present case in the form of a disk, as can be seen in particular in FIG. 2 c ). Both steering rods 14, 16 are rotatably connected to the transmission element 30 with their inner ends facing each other. It is provided here that the respective connection point 58 on the transmission element 30 lies diametrically opposite one another with respect to the axis of rotation A. By means of this connection of the steering rods 14, 16 to the transmission element 30, which connection is off-center with respect to the rotational axis A R and thus indirectly to the rotation-translation transmission 18, the rotational movement of the drive unit 12 can be translated into a translatory movement of the steering rods 14, 16 during a driving operation and the wheels can be set under a steering angle. The attachment points 58 can be designed differently, wherein the variant is shown in the present case, in which the steering rods 14, 16 engage around the transmission element 30 on both sides from the lateral direction in order to ensure a connection which applies as uniform a load as possible to the transmission element 30. In another variant, however, it can be provided that the steering rod 14, 16 is connected to the transmission element 30 on one side thereof.Each of the steering rods 14, 16 has two steering rod sections 14 1, 142, 161, 162 which can be pivoted to one another. The steering rod section 14 2, 162 arranged in each case at a distance from the transmission element 30 is guided in an axial guide 20. The respective sections 14 1, 142 and 16 1, 162 of the steering rods 14, 16 are pivotably connected to one another via a respective articulated connection 60.List of reference characters1 Steering device 2 Steering wheel 4 Steering shaft 6 Rack and pinion gear 10 Steering device 12 Drive unit 14 First steering rod 16 Second steering rod 18 Rotation-translation gear 20 Axial guide 22 Electric motor 24 Gear 30 Transmission element 32 Track lever 34 Output shaft 36 Drive pin 38 Housing element 40 Bearing 50 Steering force amplification 52 Motor vehicle 54 Vehicle axle 56 Axle body 58 Connection point 60 Articulated connection

Claims

Steering device (10) for a steer-by-wire steering system of a motor vehicle, having a drive unit (12) for initiating a rotational movement about an axis of rotation A R, a first steering rod (14) and a second steering rod (16), and having a rotational translation transmission (18) arranged between the drive unit (12) and the two steering rods (14, 16), for translating the rotational movement into a steering movement transmitted via the steering rods (14, 16) to a respective axle body of the motor vehicle, characterized in that the rotational translation transmission (18) indirectly couples the two steering rods (14, 16) to one another on a circular path about the axis of rotation A R diametrically opposite one another.Steering device (10) according to Claim 1, characterized in that each of the steering rods (14, 16) has two steering rod sections (14 1, 142, 161, 162) which can be pivoted with respect to one another.Steering device (10) according to Claim 1 or 2, characterized in that the steering rod section (14 2, 162) arranged at a distance from the axis of rotation A R is in each case guided in an axial guide (20).Steering device (10) according to one of Claims 1 to 3, characterized in that the drive unit (12) comprises two electric motors which can be driven independently of one another or an at least double-wound electric motor (22) and a transmission (24), wherein each of the electric motors (22) can be coupled to the transmission (24) as required in order to bring about the rotational movement about the rotational axis A R.Steering device (10) according to Claim 4, characterized in that the transmission (24) is designed as a planetary transmission.Steering device (10) according to one of Claims 1 to 5, characterized in that the rotation-translation transmission (18) comprises a transmission element (30) which is driven pivotably about the axis of rotation A R and the mutually facing ends of the two steering rods (14, 16) are held pivotably with respect to the transmission element (30).Steering device (10) according to one of Claims 1 to 6, characterized in that the two steering rods (14, 16) are each connected to the respective axle body of the motor vehicle via a track lever (32).Steering device (10) according to one of Claims 1 to 7, characterized in that the drive unit (12) comprises an output shaft (34) which is driven about the axis of rotation A R and is connected via a positive connection to a drive pin (36) of the rotation-translation transmission (18).Steering device (10) according to Claim 8, characterized in that the drive pin (36) carries the transmission element (30) and is mounted pivotably in a housing element (38) of the steering device (10).Steering device (10) according to Claim 8 or 9, characterized in that the drive pin (36) and the transmission element (30) are connected to one another in a positive-locking manner.

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