Steering wheel unit for detecting a steering movement of a steering wheel for an electromechanical steering system

Abstract

Steering wheel unit (1) for an electromechanical steering system of a motor vehicle (10), comprising: - a force generating means for applying a mechanical feedback force to a steering wheel (4) about a current steering and / or driving condition to the driver, characterized in that the force generating means comprises two steering shaft nuts (21a, 21b) arranged axially adjustably on an external threaded section of a steering wheel shaft (3), two flanges (22a, 22b), a first and a second elastic element (23a, 23b), wherein each of the steering shaft nuts (21a, 21b) engages with one of the flanges (22a, 22b), wherein the flanges (22a, 22b) are arranged axially adjustable around a first flange shaft (24a) and a second flange shaft (24b), and wherein the first elastic element (23a) is arranged on the first flange shaft (24a) and the second elastic element (23b) is arranged on the second flange shaft (24b), and the elastic elements (23a, 23b) are deformable by axial movement of the flanges (22a, 22b), and wherein the force generating means applies force to the steering wheel shaft (3) in such a way that with increasing adjustment of the steering wheel (4) deviating from straight-ahead travel, an increasing restoring force can be generated on the steering wheel (4) for feedback of a wheel angle-related steering state to the driver.

Description

[0001] The invention relates to a steering wheel unit for an electromechanical steering system of a motor vehicle. Furthermore, the invention also relates to an electromechanical steering system comprising such a steering wheel unit.

[0002] The field of application of the invention extends to so-called steer-by-wire steering systems for motor vehicles, in which there is no direct mechanical coupling between the steering wheel and the steered wheels of the motor vehicle. Instead, the steering angle and, if applicable, the rotational speed of the steering wheel and / or the torque applied to the steering wheel are detected via a suitable sensor system and transmitted in the form of an electrical control value to an electromechanical steering actuator unit, which converts the electrically specified steering signal into a mechanical adjustment of the steering angle of the wheels of a steerable vehicle axle.

[0003] These steering systems therefore do not provide direct mechanical feedback on the actual steering movement of the wheels, which in mechanically coupled systems is usually felt by the driver in the form of a speed-dependent restoring torque on the steering wheel and superimposed vibrations.

[0004] US 2017 / 0 320 515 A1 discloses an electromechanical steering system for a motor vehicle. A steering wheel unit includes special force-generating means for applying a mechanical feedback force to the steering wheel, providing the driver with feedback about the current steering and vehicle status. For this purpose, the steering wheel unit has an electric motor for generating the feedback force by applying a corresponding torque to the steering wheel shaft. By appropriately controlling the electric motor, the driver is provided with a realistic driving experience via the steering wheel, similar to that experienced with mechanically coupled steering systems.The force-generating means provided for this purpose also include a lockable clutch, which acts as a brake and is controlled by an electromagnetic actuator to prevent further rotation of the steering wheel shaft when the wheels have reached the predetermined end stop position in the respective direction of rotation. For this purpose, the clutch locks the steering wheel shaft in the aforementioned situation according to an electronic control system. In this state of the art, the electric motor for applying the mechanical feedback force is an active component, which therefore also requires electronic control.

[0005] US 2002 / 0 189 888 A1 discloses another electromechanical steering system for a motor vehicle, which is also equipped with an electric motor for generating a mechanical feedback force on the steering wheel. For this purpose, the electric motor is arranged axially parallel to the steering wheel shaft and acts on it via a belt drive. Compared to the prior art discussed above, this technical solution requires more installation space transverse to the steering wheel shaft.

[0006] It is therefore an object of the present invention to provide a steering wheel unit for an electromechanical steering system of a motor vehicle, which can be space-saving and / or energy-saving and can transmit a mechanical feedback force about the current steering state to the driver using simple technical means.

[0007] The object is achieved based on a steering wheel unit according to the preamble of claim 1 in conjunction with its characterizing features. With regard to an electromechanical steering system comprising such a steering wheel unit, reference is made to claim 10. The dependent claims reflect advantageous developments of the invention.

[0008] The invention includes the technical teaching of providing a steering wheel unit for an electromechanical steering system of a motor vehicle. The steering wheel unit has a force generating means for applying a mechanical feedback force to the steering wheel, indicating the current steering and / or driving state to the driver. The force generating means comprises two steering shaft nuts arranged axially adjustably on an externally threaded portion of a steering wheel shaft, two flanges, and a first and a second elastic element. Each of the steering shaft nuts engages one of the flanges, and the flanges are arranged axially adjustably around a first flange shaft and a second flange shaft. The first elastic element is arranged on the first flange shaft and the second elastic element is arranged on the second flange shaft, and the elastic elements are deformable by axial movement of the flanges.The force generating means applies force to the steering wheel shaft in such a way that, with increasing adjustment of the steering wheel deviating from straight-ahead driving, an increasing restoring force can be generated on the steering wheel to provide feedback to the driver on a steering condition related to the wheel angle.

[0009] The advantage of the inventive solution lies in the fact that passive components are used to implement the inventive solution, which do not require control via an electronic control unit. This allows the power consumption of the electromechanical steering system to be reduced. Furthermore, the passive components, in particular the steering shaft nuts and the flanges engaging with the respective steering shaft nuts, can be arranged coaxially around the steering wheel shaft to save space.

[0010] In other words, the solution according to the invention ensures that when the steering wheel rotates in one direction or the other, the elastic elements arranged on the flange shafts are compressed by the flanges, which engage with steering shaft nuts arranged on the steering wheel shaft. In particular, the steering shaft nuts and consequently the flanges can convert a rotational movement of the steering wheel into a linear (axial) movement of the elastic elements, thereby building up potential mechanical energy, which serves to generate the mechanical feedback force.

[0011] The external thread section on the steering wheel shaft can be part of a wide variety of gear arrangements, which convert the rotary motion of the steering wheel shaft into linear motion for compressing the elastic elements. The external thread section of the steering wheel shaft and a corresponding internal thread of the steering shaft nut can be a metric, trapezoidal, or round thread to convert the rotary motion into linear motion. Such an arrangement of intermeshing threads is easy to manufacture. However, to minimize sliding friction losses, the external thread section of the steering wheel shaft can be part of a ball or roller screw drive or a planetary screw drive to convert the rotary motion into linear motion.

[0012] Preferably, each steering shaft nut has at least one locking element for restricting the axial movement of the flanges. In this way, the axial movement of the respective flanges, particularly toward the inner portion of the steering shaft, can be blocked by the locking element, preventing any potential collision between the steering shaft nuts and the flanges. For example, an additionally applied safety ring or a projection integrated into the steering shaft nut can be used as the locking element.

[0013] According to one embodiment, the flanges each border on at least two spacers arranged on outer sections of the flange shafts, which spacers limit the axial movement. The axial movement can in particular be in the direction of the outer section of the flange shafts. The spacers are preferably arranged on the flange shafts and can provide an evenly distributed pressure on the flanges. However, it is also possible for the flanges themselves to each have or integrate the at least two spacers. In other words, the spacers can also be formed directly on the flanges, wherein the spacers can be located at the same distance from an axis through the diameter of the flange in order to provide an evenly distributed pressure on the flanges.

[0014] According to one embodiment, the force generating means further comprises at least two stop disks, one of which is arranged at one end of the outer sections of the flange shafts and the other of which is arranged at the other ends of the outer sections of the flange shafts, such that the spacers provide a gap for the steering shaft nuts between the respective flange and the stop disk. In other words, one stop disk sits at the two ends of both flange shafts on one side of the force generating means and the other stop disk sits at the two opposite ends of both flange shafts on the other side of the force generating means. Due to the gap, the steering shaft nuts can be adjusted further axially towards the outer section of the flange shafts, although the movement of the flanges is restricted by the spacers. The axial movement of the steering shaft nuts can be restricted by the stop disks.

[0015] Preferably, the flanges, the elastic elements, and the spacers are axially adjustable along the flange shafts. Thus, the elastic elements can be deformed according to the movement of the flanges.

[0016] According to a preferred embodiment, during the movement of the first flange, the second flange is stationary and presses against the spacer adjacent to the second flange. In other words, depending on the direction of rotation of the steering wheel, only one flange (here, for example, the first flange) can move and the elastic elements can only be compressed from one side. During this time, the second flange (here, for example), can be in a position in which the second steering shaft nut, the second flange, the spacers adjacent to the second flange and the stop washer are in engagement with one another. In this way, the elastic elements can only be deformed from one direction, whereby overextension or overcompression of the elastic elements can be avoided. Thus, reliable feedback of the wheel angle-related steering state can be provided.

[0017] The feedback force generated according to the invention preferably serves to provide feedback on the current steering state. In order to also simulate other feedback information, such as the end stop position of the wheels - which can be felt via a corresponding end stop on the steering wheel - or surface structures of the road - which are reported back via corresponding mechanical vibrations - a measure that further improves the invention proposes that the steering wheel unit also have an electric motor and a transmission element for adjusting the preload of the elastic elements. In the solution according to the invention, the feedback force applied by the electric motor is used to specifically and situationally reduce or increase the forces generated by the elastic effect of the elastic elements in order to create an authentic driving feel at the steering wheel.Therefore, the electrical power consumption of the steering wheel unit according to the invention is lower than that of fully actively controlled steering wheel units of the prior art described above. Furthermore, the size of the electric motor used can be reduced, thereby saving space and costs.

[0018] According to one embodiment, the transmission element connects the electric motor, the steering wheel shaft, and the flange shafts. The transmission element can be a transmission belt. This means that the electric motor can be connected to one of the flange shafts by means of a transmission belt, which in turn can be connected to another flange shaft by means of a further transmission belt. This can then be connected to the steering wheel shaft by means of yet another transmission belt. In this way, the electric motor can exert further feedback forces that are superimposed on the feedback force and / or the additional feedback force of the passive components of the elastic elements. Furthermore, a variable simulation of the feedback force via the transmission belts can be enabled.The use of transmission belts also ensures short-term overload capacity, low maintenance and low costs.

[0019] According to one embodiment, the elastic elements are disc spring assemblies. However, it is also possible to use other types of (linear) springs, which are also axially deformable upon axial movement of the flanges.

[0020] A further aspect of the invention relates to an electromechanical steering system with a steering wheel unit as described above and below. This electromechanical steering system further comprises an electromechanical steering actuator unit for mechanically adjusting a steerable vehicle axle and, if appropriate, an electronic control unit. The electromechanical steering system can receive a control value from a steering movement sensor, which is then converted by the electronic control unit into control commands for the steering actuator unit, for example, an electric motor. This steering actuator unit, in turn, influences the vehicle's wheels such that they rotate according to the control value specified by the steering movement sensor. This allows a steerable vehicle axle to be created.

[0021] Further measures improving the invention are described in more detail below, together with the description of a preferred embodiment of the invention, with reference to the figures. It shows: Fig. 1 a motor vehicle with the steering wheel unit of the steering system, Fig. 2 a schematic representation of an electromechanical steering system for a motor vehicle according to Fig. 1, Fig. 3 a schematic longitudinal section through the steering wheel unit of the steering system according to Fig. 1 or Fig. 2, Fig. 4 a schematic cross-sectional view of the steering wheel unit of the steering system according to Fig. 1 to 3, and Fig. 5 is a schematic diagram of a variable adjustment of an elastic force of the steering wheel unit of the steering system according to Fig. 1 to Fig. 4.

[0022] Fig. 1 shows a motor vehicle 10 with an electromechanical steering system, which includes the steering wheel unit 1 described below. Typically, the electromechanical steering system is arranged in a front region of the motor vehicle 10 and configured to turn or steer the front wheels of the motor vehicle 10 according to the driver's wishes. Alternatively or additionally, the electromechanical steering system can also act on the rear wheels, e.g., in the case of active rear-wheel steering or in the case of a forklift. The steering wheel unit 1 can, for example, be arranged in the area of the driver's seat under the dashboard, facing the engine compartment.

[0023] According to Fig. 2, the electromechanical steering system for the motor vehicle 10 essentially consists of a steering wheel unit 1, in whose cylindrical housing 2 a steering wheel shaft 3 is rotatably mounted. A steering wheel 4 for operation by the driver is attached to a distal end of the steering wheel shaft 3.

[0024] Via an electrical connection 5, the steering wheel unit 1 is connected by means of an electronic controller 6 to a steering actuator unit 7, which is, for example, electromechanical. The steering actuator unit 7 serves to convert a steering signal electrically predetermined by the steering wheel unit 1 by means of the controller 6 into a mechanical adjustment of the steering deflection of the wheels 8a and 8b of the thus steerable vehicle axle 9. Furthermore, the steering actuator unit 7 can also be electrohydraulic or similar.

[0025] After Fig. 3, in the steering wheel unit 1, the torque applied by the driver to the steering wheel 4 as a result of the steering movement is transmitted through the steering wheel shaft 3 into the interior of the housing. There, the steering wheel shaft 3 has an external thread section that interacts with a non-locking internal thread section (not shown here) of the steering shaft nuts 21a, 21b to convert the rotational movement of the steering wheel 4 into a linear movement of the steering shaft nuts 21a, 21b. The steering shaft nuts 21a, 21b each engage one of the flanges 22a, 22b, which in turn are arranged on the flange shafts 24a, 24b spaced apart from one another around the steering wheel shaft 3. Thus, the flanges 22a, 22b are axially adjustable together with the steering shaft nuts 21a, 21b. Each of the steering shaft nuts 21a, 21b has at least one locking element 25, which is, for example, a safety ring and limits the axial movement of the flanges 22a, 22b towards the interior of the housing.The axial movement of the flanges 22a, 22b toward the outer section of the housing is limited by the stop disks 27a, 27b attached to the flange shafts 24a, 24b, which are axially supported by the spacers 26 arranged between the flange 22a, 22b and the stop disk 27a, 27b. The two stop disks 27a, 27b can be placed in the front end regions of the preferably cylindrical housing 2 of the steering wheel unit 1 in order to maximize the axial flange distance. An elastic element 23a, 23b, which is, for example, a disc spring assembly, is arranged between the flanges 22a, 22b along the flange shafts 24a, 24b. In the steering wheel unit 1, the steering shaft nuts 21a, 21b are axially adjusted as a result of a rotation of the steering wheel 4 in one direction or the other to compress the elastic elements 23a, 23b by means of the flanges 22a, 22b in order to thereby store potential energy.One of the flanges 22b is stationary during the movement of the other flange 22a and presses against the adjacent spacer 26. The stored energy is used to generate part of the feedback force about the current steering state to the driver via the steering wheel 4. The steering wheel shaft 3 and the flange shafts 24a, 24b are connected in a serial sequence to an electric motor 11 via a transmission element 12, such as a transmission belt. The electric motor 11 can be arranged on the front side of the housing 2 to reduce the motor speed.

[0026] As in the Fig. As shown in Figure 4, the electric motor 11 is connected to one of the flange shafts 24a by means of a transmission belt, wherein the flange shaft 24a is in turn connected to another flange shaft 24b via a second transmission belt. The steering wheel shaft 3 is connected to the second flange shaft 24b via a third transmission belt. In this way, the electric motor can exert further feedback forces, which are superimposed on the feedback force and / or the additional feedback force of the passive components of the elastic elements. In particular, the position of the flanges 22a, 22b, which cause the deformation of the elastic elements, is controlled and adjusted by the electric motor 11 in order to obtain the desired values of the restoring force. Furthermore, the use of the transmission belts enables a variable simulation of the feedback force, as in the Fig.5. The x-axis shows a rotation of the steering wheel 4, the y-axis a feedback force or spring force for returning the steering wheel 4, a solid line a through the zero point shows a material property of the elastic element and the striped area b shows a force amplified by the electric motor.

[0027] The invention is not limited to the preferred embodiment described above. Rather, modifications are also conceivable, which are also encompassed by the scope of the following claims. List of reference symbols 1 steering wheel unit 2 housings 3 steering wheel shaft 4 steering wheel 5 electrical connection 6 electronic control 7 Steering actuator unit 8 wheel 9 vehicle axle 10 motor vehicle 11 electric motor 12 transmission element 21a, 21b Steering shaft nut 22a, 22b flange 23a, 23b elastic element 24a, 24b Flange shaft 25 locking element 26 spacers 27a, 27b stop disc

Claims

[1] Steering wheel unit (1) for an electromechanical steering system of a motor vehicle (10), comprising: - a force generating means for applying a mechanical feedback force to a steering wheel (4) about a current steering and / or driving condition to the driver, characterized by that the force generating means comprises two steering shaft nuts (21a, 21b) arranged axially adjustably on an external threaded section of a steering wheel shaft (3), two flanges (22a, 22b), a first and a second elastic element (23a, 23b), wherein each of the steering shaft nuts (21a, 21b) engages with one of the flanges (22a, 22b), wherein the flanges (22a, 22b) are arranged axially adjustable around a first flange shaft (24a) and a second flange shaft (24b), and wherein the first elastic element (23a) is arranged on the first flange shaft (24a) and the second elastic element (23b) is arranged on the second flange shaft (24b), and the elastic elements (23a, 23b) are deformable by axial movement of the flanges (22a, 22b), and wherein the force generating means applies force to the steering wheel shaft (3) in such a way that with increasing adjustment of the steering wheel (4) deviating from straight-ahead travel, an increasing restoring force can be generated on the steering wheel (4) for feedback of a wheel angle-related steering state to the driver. [2] Steering wheel unit (1) according to claim 1, characterized by that each steering shaft nut (21a, 21b) has at least one locking element (25) for restricting the axial movement of the flanges (22a, 22b). [3] Steering wheel unit (1) according to claim 1 or 2, characterized by that the flanges (22a, 22b) each adjoin at least two spacers (26) arranged on outer sections of the flange shafts (24a, 24b), which spacers restrict the axial movement of the flanges (22a, 22b). [4] Steering wheel unit (1) according to the preceding claim, characterized bythat the force generating means further comprises at least two stop discs (27a, 27b), one of which is arranged at one end of the outer sections of the flange shafts (24a, 24b) and the other of which is arranged at the other ends of the outer sections of the flange shafts (24a, 24b), so that the spacers (26) provide a space for the steering shaft nuts (21a, 21b) between the respective flange (22a, 22b) and the stop disc (27a, 27b). [5] Steering wheel unit (1) according to one of the two preceding claims, characterized by that the flanges (22a, 22b), the elastic elements (23a, 23b) and / or the spacers (26) are axially adjustable along the flange shafts (24a, 24b). [6] Steering wheel unit (1) according to one of claims 3 to 5, characterized by that during the movement of the first flange (22a) the second flange (22b) is stationary and presses against the spacer (26) adjacent to the second flange (22b). [7] Steering wheel unit (1) according to one of the preceding claims, characterized by that the steering wheel unit (1) further comprises an electric motor (11) and a transmission element (12) for adjusting a preload of the elastic elements (23a, 23b). [8] Steering wheel unit (1) according to the preceding claim, characterized by that the transmission element (12) connects the electric motor (11), the steering wheel shaft (3) and the flange shafts (24a, 24b) to one another. [9] Steering wheel unit (1) according to one of the preceding claims, characterized by that the elastic elements (23a, 23b) are disc spring assemblies. [10] Electromechanical steering system for a motor vehicle (10), comprising a steering wheel unit (1) according to one of the preceding claims, and an electromechanical steering actuator unit (7) for mechanically adjusting the steering deflection of the wheels (8a, 8b) of a steerable vehicle axle (9).

Images