Control unit and steer-by-wire steering system

Abstract

The invention relates to an operating unit (1), in particular for a steer-by-wire steering system (2) of a motor vehicle (3), comprising a steering shaft (4) which can be coupled to a steering device (5) for specifying a steering direction by a user, wherein a brake disc (6) is arranged non-rotatably on the steering shaft (4), the outer cylindrical surface (7) of which is at least partially enclosed by a brake band (8), the free ends (11) of which are connected to a tensioning device (9), by which the brake band (8) can be moved into a first tensioned operating state (9) for generating a braking torque and a second untensioned operating state (10), in which the steering shaft (4) rotates substantially without being subjected to a braking torque and / or the brake band (8) can be moved by the tensioning device (9) into a third tensioned operating state for generating a braking torque, wherein the third operating state generates a braking torque.which is smaller than the braking torque of the first operating state.

Description

[0001] The present invention relates to an operating unit, in particular for a steer-by-wire steering system of a motor vehicle, comprising a steering shaft that can be coupled to a steering means for specifying a steering direction by a user. The invention further relates to a steer-by-wire steering system.

[0002] Electric steering systems are used - among other things in motor vehicles - to receive a driver's directional command and translate it into corresponding movements of one or more wheels. In contrast to purely mechanical steering systems, electric steering systems are divided into electrically assisted steering systems and fully electric steering systems, so-called "steer-by-wire" steering systems. These steer-by-wire steering systems in particular have the advantage that the control unit can be positioned relatively freely within the vehicle, independent of mechanical connecting components. This not only saves costs when distinguishing between, for example, right- and left-hand drive vehicles, but also improves accident behavior due to the absence of a steering column. Furthermore, the control unit can be moved into a stowed position, which is also used, for example, in fully automatic steering.

[0003] A steer-by-wire steering system, as defined in the present invention, is a steering system that essentially consists of a so-called handwheel actuator (HWA), for example, the actuator system around the commanding vehicle steering wheel, and a roadwheel actuator (RWA), i.e., the actuator system acting on the steering mechanism connected to the vehicle wheels. The steering signal is transmitted from the HWA to the RWA via a cable ("by wire").

[0004] To create a realistic driving experience, it is also known in the prior art to record parameters such as vehicle speed, steering angle, lateral acceleration, tie rod force, and the like from an actual, current driving situation or to calculate them in a simulation, and to use these to generate a feedback signal that is fed into a force feedback actuator. The force feedback actuator is integrated into the input unit and has an actuator unit that includes an actuator that serves as a manual torque or steering wheel actuator and, depending on the feedback signal, couples a feedback torque (feedback torque) that at least partially corresponds to the actual reaction torque via the steering shaft into the steering wheel. A partial feedback torque is particularly suitable when other, possibly controllable, components such as springs or brakes provide supplementary feedback torque.Feedback torque refers to both directions of action, meaning that the feedback actuator can be rotated by the driver as an adjustable load. Such "force feedback" systems give the driver the impression of a real driving situation, similar to a conventional steering system, facilitating intuitive response.

[0005] DE 102008036730 A1 discloses a steer-by-wire steering system with an input unit that includes an actuator unit driven by an electric motor. The electric motor can be controlled by an electronic control unit, which adjusts the motor current depending on measured values ​​that characterize the respective driving situation. The motor shaft is directly coupled to the steering shaft, thus the motor torque is identical to the manual torque coupled to the steering shaft. The electric motor is flanged axially to the casing unit with respect to its longitudinal axis, and the motor shaft is connected via a coupling to the steering shaft mounted in the casing unit. An actuator unit of a similar design is described in EP 2414211 B1. In the embodiment described therein, the steering shaft itself forms the motor shaft of the electric motor, allowing for a more compact design.

[0006] In order to achieve the most realistic steering feel in such steer-by-wire systems, it is also known to arrange a magnetorheological brake in the torque flow of a steering device to increase the resistance moment. In combination, this makes it possible to achieve a higher total restoring torque with lower energy consumption in the same installation space. However, such combinations are still comparatively large and are also expensive to manufacture. Furthermore, the resulting braking torque depends on fluctuations in the coefficient of friction and external influences such as temperature. Also characteristic of such magnetorheological brakes is hysteresis behavior and a torque that is not zero when there is no field or current. The torque therefore decreases due to aging even with the same coil current.

[0007] The object of the invention is therefore to provide an operating unit, in particular for a steer-by-wire steering system of a motor vehicle, that can be manufactured cost-effectively and has a constant torque capacity over its service life with regard to the braking torque that can be applied to a steering shaft. Furthermore, the object of the invention is to implement an improved steer-by-wire steering system.

[0008] This object is achieved by an operating unit, in particular for a steer-by-wire steering system of a motor vehicle, comprising a steering shaft which can be coupled to a steering means for specifying a steering direction by a user, wherein a brake disc is arranged in a rotationally fixed manner on the steering shaft, which is at least partially wrapped on its outer circumferential surface by a brake band, the free ends of which are connected to a tensioning device by means of which the brake band can be placed in a first tensioned operating state for generating a braking torque and a second untensioned operating state by means of which the steering shaft rotates essentially without the application of a braking torque and / or the brake band can be placed by the tensioning device in a third tensioned operating state for generating a braking torque, wherein the third operating state generates a braking torque which is smaller than the braking torque of the first operating state.

[0009] This provides the advantage that the direct contact between the brake band and the brake disc allows for effective generation of a braking torque on the steering shaft. The friction between the brake band and the brake disc generates high braking forces, resulting in rapid, easily controllable, and efficient deceleration or stopping of the rotational movement of the steering shaft. The high braking forces achievable with the control unit according to the invention also allow for a steering stop or curb impact, with very limited installation space and energy consumption.

[0010] A key advantage of this arrangement is the constant friction coefficient, which allows for precise and simple control of the braking torque. It also eliminates the need for significantly more complex braking torque control.

[0011] The brake band, which is placed around the brake disc, also ensures an even distribution of the braking force over the entire circumferential braking surface of the brake disc, which can contribute to a stable and consistent braking effect and thus enables even braking and reliable control of the movement.

[0012] Furthermore, the assembly for generating the braking torque is low-maintenance and durable, as the brake band exhibits less wear than other braking systems and therefore needs to be replaced less frequently.

[0013] The tensioning device, which keeps the brake band taut when no braking force is applied, ensures reliable brake function. The brake band is firmly applied to the brake disc as soon as the tensioning device is actuated, ensuring quick response and safe deceleration or stopping of the steering shaft movement.

[0014] The brake band, brake disc, and tensioning device can be adapted to different braking torque requirements by, for example, varying the tensioning force of the tensioning device or the friction properties of the brake disc or brake band. This allows the braking performance to be adapted to the specific conditions at a given control unit.

[0015] Overall, the control unit according to the invention offers high braking performance, even distribution of braking force, durability, reliability and adaptability due to its design with brake disc, brake band and tensioning device.

[0016] The brake disc is firmly connected to the steering shaft and rotates with it. The brake disc can be connected to the steering shaft by a form-fitting, material-fitting and / or friction-fitting connection. In particular, it is also conceivable for the brake disc to be releasably fixed to the brake disc, for example via a spline connection or a welded connection. The brake disc can be made of various materials, such as cast iron, steel alloys or composite materials. It is also conceivable for the brake disc to be provided with a special coating to improve friction properties, reduce wear or prevent corrosion. It would also be possible for the brake disc to be provided with ventilation slots or cooling fins to improve heat dissipation and prevent overheating.

[0017] The smallest possible wrap angle of the brake band can be achieved by selecting a material pairing between the brake band and the brake disc with the highest possible friction coefficient. For example, it can be advantageous if the friction disc is made of plastic, particularly polyamide.

[0018] The brake band is advantageously designed as a steel band that is wrapped around the brake disc. The brake band may include an additional friction material, which can also be referred to as a brake pad.

[0019] The tensioning device is used to pull the brake band toward the brake disc and create the braking effect. It preferably includes a mechanism that keeps the brake band taut when no braking force is applied.

[0020] The brake disc, brake band, and tensioner function as follows: When at rest, the brake band is loosely wound around the brake disc. The tensioner holds the brake band in position without exerting pressure on the brake disc. When the tensioner is activated, the brake band is pulled against the brake disc. The friction between the brake band and the brake disc transmits torque, which slows or stops the movement of the steering shaft. When the tensioner is released, thereby releasing the brake band from the brake disc, the brake band is moved back to its original position, reducing or completely eliminating the braking force and allowing the steering shaft to move again.

[0021] The brake band is typically made of steel, which offers high tensile strength and durability. However, the band can also be coated or reinforced with other materials to improve friction properties or reduce wear. Preferably, the brake band can exhibit elasticity. Furthermore, it is conceivable for the brake band to have a flat or curved shape, depending on design preferences and application requirements. The brake band can also be designed as a rope with a round cross-section.

[0022] The brake band can either be attached directly to the tensioning device or fixed using special connecting elements such as screws or rivets.

[0023] Advantageous embodiments of the invention are specified in the dependent claims. The features listed individually in the dependent claims can be combined with one another in a technologically expedient manner and can define further embodiments of the invention. Furthermore, the features specified in the claims are further specified and explained in the description, where further preferred embodiments of the invention are presented.

[0024] The tensioning device, which keeps the brake band taut when no braking force is applied and pulls the brake band against the brake disc to generate the braking torque, can take various forms.

[0025] According to an advantageous embodiment of the invention, the tensioning device can comprise a rotatable control shaft to which the free ends of the brake band are connected. Preferably, the ends of the brake band can be connected directly to the control shaft, which facilitates a particularly compact design of the control unit in terms of installation space.

[0026] According to a further preferred development of the invention, it can also be provided that a first lever is connected to the control shaft in a rotationally fixed manner, with the free ends of the brake band being fixed at different positions on the first lever. This can, for example, also ensure that several brake bands are positioned side by side and do not tend toward one another. This can, in particular, prevent the brake bands from overlapping and interfering with one another.

[0027] Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that the first lever has a first leg and a second leg, which extend at an angle of between 45° and 135° to one another, and one of the free ends of the brake band is fastened to the first leg and one of the free ends of the brake band is fastened to the second leg. The angle is preferably approximately 90°. Because the band ends are fixed to the preferably rectangular lever, which can be subjected to a preload torque via the control shaft, the preload torque is adjustable, so that the resulting slip torque (resistance torque) on the steering shaft is controllable. In the unloaded state, the slip torque can be reduced to almost zero and can be controlled in both the pulling and pushing directions.

[0028] According to another particularly preferred embodiment of the invention, the first leg and the second leg can be of different lengths. This allows, in particular, an asymmetrical distribution of the braking torque in the pulling and pushing directions to be achieved by selecting different lengths for the two lever lengths. The lever is preferably designed so that the braking torque is the same regardless of the direction of rotation.

[0029] Furthermore, the invention can also be further developed in such a way that an electric motor is connected to the control shaft for the rotational drive of the control shaft. This allows for precise and, thanks to the use of standard components, cost-effective control of the control shaft and thus the brake using a comparatively small electric motor with a relatively low torque.

[0030] In a likewise preferred embodiment of the invention, a second lever connected to a linear actuator can also be arranged on the control shaft, so that a linear displacement by the linear actuator causes a rotation of the control shaft. This allows the control shaft to be actuated, which can be implemented somewhat more cost-effectively than using an electric motor. A linear actuator can be implemented, for example, as a linear motor or a solenoid. It is preferred that the linear displacement be between 2 and 15 mm.

[0031] It may also be advantageous to further develop the invention such that a spring element is arranged on the control shaft, which applies a preload to the control shaft in the direction of rotation of the control shaft, whereby the behavior of the operating device in an emergency running situation can be positively influenced in particular. The spring element provides a residual torque in the event of a power failure. The mechanical spring element is preferably designed as a rotation spring, in particular as a leg spring, and provides a torque that can be acted upon the control shaft. The torque mechanically generated by the spring element is advantageously between 5-20% of the electrically achievable control torque. The spring element therefore prevents the steering wheel from turning without resistance in emergency running, e.g. in the event of a power failure.Should a resistance-free situation nevertheless be required during operation, the electrical control can overpress the mechanical spring element in the opposite direction.

[0032] According to a further preferred embodiment of the subject matter of the invention, the brake band can be provided to completely wrap around the brake disc at least once, thereby achieving a particularly high braking torque. Multiple such wraps, depending on the base friction coefficient, also enable greater independence from fluctuations in the friction coefficient and thus a particularly constant friction coefficient.

[0033] Since the steering shaft is preferably in a static position, the control shaft can be connected to a mount that is fixed relative to the steering shaft.

[0034] Finally, the object of the invention can also be achieved by a steer-by-wire steering system comprising an operating unit according to one of claims 1-9.

[0035] The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

[0036] It shows: Fig. 1 a control unit in a perspective view, Fig. 2 an operating unit in a perspective axial section view, Fig. 3 a released operating unit comprising a steering shaft, a brake disc, a brake band, a control shaft and an electric motor in a perspective view, Fig. 4 a released operating unit comprising a brake disc, a brake band and a lever in a perspective view, Fig. 5 a released operating unit comprising a brake band and a lever in a perspective view, Fig. 6 a released operating unit comprising a steering shaft, a brake disc, a brake band and a control shaft in a perspective view, Fig. 7 a released operating unit comprising a steering shaft, a brake disc, a brake band and a first lever fixed to the control shaft in a perspective view, Fig. 8 shows a perspective view of an isolated operating unit comprising a steering shaft, a brake disc, a brake band and a first and second lever fixed to the control shaft, Fig. 9 a free-standing operating unit comprising a steering shaft, a brake disc, a brake band and a first lever fixed to the control shaft as well as a spring element in a perspective view, Fig. 10 a steer-by-wire steering system in a schematic representation.

[0037] The Fig. 1 shows an operating unit 1 for a steer-by-wire steering system 2 of a motor vehicle 3, as is also shown in the Fig. 10 is outlined.

[0038] The control unit 1, housed in a housing 21, comprises a steering shaft 4, which can be coupled to a steering means 5 for specifying a steering direction by a user. The control unit 1 also has a force feedback actuator 20, which is coupled to the steering shaft 4.

[0039] As can be seen from the Fig. 2-5, a brake disc 6 is arranged on the steering shaft 4 in a rotationally fixed manner, which is at least partially wrapped on its outer surface 7 by a brake band 8, the free ends 11 of which are connected to a tensioning device 9, by means of which the brake band 8 can be placed in a first tensioned operating state for generating a braking torque and a second untensioned operating state, by means of which the steering shaft 4 rotates essentially without the application of a braking torque and / or the brake band 8 can be placed by the tensioning device 9 in a third tensioned operating state for generating a braking torque, wherein the third operating state generates a braking torque which is smaller than the braking torque of the first operating state.

[0040] As from the Fig. As can be seen in Figure 2, the brake disc 6 is rotatably mounted in the housing 21 via a bearing 22.

[0041] From the overview of the Fig. 4-5 it can be seen particularly well that the brake band 8 completely wraps around the brake disc 6 at least once.

[0042] The tensioning device 9 comprises a control shaft 12 which is rotatable relative to the housing 21 via the bearing 23 and to which the free ends 11 of the brake band 8 are connected. This connection can be made directly by fixing the ends 11 directly to the control shaft 12, as shown in the Fig. 6 can be seen.

[0043] Alternatively, a first lever 13 can be connected to the control shaft 12 in a rotationally fixed manner, wherein the free ends 11 of the brake band 8 are fixed at different positions on the first lever 13. Such a lever 13 is shown in the Fig. 4-5 and the Fig. 7. Here, the first lever 13 has a first leg 18 and a second leg 19, which run at an angle of approximately 90° to one another, and one of the free ends 11 of the brake band 8 is fastened to the first leg 18 and one of the free ends 11 of the brake band 8 is fastened to the second leg 19. If the braking torque is to be different in the pushing and pulling directions, the first leg 18 and the second leg 19 can have different lengths. Extending from the first leg 18 in the axial direction to the control shaft 12 is a first bolt 24, to which a first of the ends 11 is fastened, and a second bolt 25, to which a second of the ends 11 of the brake band 8 is fixed, extends from the second leg 19. The control shaft 12 is connected to the first lever 13 via the opening 26 of the latter.

[0044] For the rotary drive of the control shaft 12, an electric motor 14 can be connected to it, as is also the case in the Fig. 7 is shown.

[0045] In the Fig. 8 shows a further embodiment variant in which a second lever 15 is arranged on the control shaft 12, which is connected to a linear actuator 16, so that a linear displacement by the linear actuator 16 causes a rotation of the control shaft 12.

[0046] Fig. 9 shows a spring element 17 arranged on the control shaft 12, which applies a preload to the control shaft 12 in the direction of rotation of the control shaft 12.

[0047] Finally, the Fig. 10 shows a steer-by-wire steering system 2 comprising an operating unit 1, as known from the previous figures. In addition to the operating unit 1, the steer-by-wire steering system 2 has an RWA 27 (road wheel actuator), which converts the steering commands from the operating unit 1 into a steering movement of the wheels of an axle.

[0048] The invention is not limited to the embodiments illustrated in the figures. The above description is therefore not to be considered restrictive, but rather explanatory. The following claims are to be understood in such a way that a stated feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. Where the claims and the above description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing a priority. List of reference symbols 1 control unit 2 Steer-by-wire steering system 3 Motor vehicle 4 Steering shaft 5 Steering devices 6 brake disc 7 Shell surface 8 brake band 9 Clamping device 11 endings 12 Control shaft 13 levers 14 Electric motor 15 levers 16 linear actuators 17 Spring element 18 legs 19 legs 20 force feedback actuators 21 housings 22 warehouses 23 camps 24 bolts 25 bolts 26 Opening 27 smoke and heat extraction systems QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 102008036730 A1

[0005] EP 2414211 B1

[0005]

Claims

[1] Operating unit (1), in particular for a steer-by-wire steering system (2) of a motor vehicle (3), comprising a steering shaft (4) which can be coupled to a steering means (5) for specifying a steering direction by a user, characterized byin that a brake disc (6) is arranged on the steering shaft (4) in a rotationally fixed manner, which brake disc is at least partially wrapped on its outer surface (7) by a brake band (8), the free ends (11) of which are connected to a tensioning device (9), by means of which the brake band (8) can be placed in a first tensioned operating state for generating a braking torque and a second untensioned operating state, by means of which the steering shaft (4) rotates essentially without the application of a braking torque and / or the brake band (8) can be placed by the tensioning device (9) in a third tensioned operating state for generating a braking torque, wherein the third operating state generates a braking torque which is smaller than the braking torque of the first operating state. [2] Control unit (1) according to claim 1, characterized by that the tensioning device (9) comprises a rotatable control shaft (12) to which the free ends (11) of the brake band (8) are connected. [3] Control unit (1) according to claim 1 or 2, characterized by that a first lever (13) is connected to the control shaft (12) in a rotationally fixed manner, wherein the free ends (11) of the brake band (8) are fixed at different positions on the first lever (13). [4] Control unit (1) according to claim 3, characterized by that the first lever (13) has a first leg (18) and a second leg (19) which extend at an angle of between 45°-135° to one another and one of the free ends (11) of the brake band (8) is fastened to the first leg (18) and one of the free ends (11) of the brake band (8) is fastened to the second leg (19). [5] Control unit (1) according to claim 4, characterized by that the first leg (18) and the second leg (19) have a different length from each other. [6] Control unit (1) according to one of the preceding claims, characterized bythat an electric motor (14) for the rotary drive of the control shaft (12) is connected to the latter. [7] Control unit (1) according to one of the preceding claims 1-5, characterized by that a second lever (15) is arranged on the control shaft (12) and is connected to a linear actuator (16), so that a linear displacement by the linear actuator (16) causes a rotation of the control shaft (12). [8] Control unit (1) according to one of the preceding claims, characterized by that a spring element (17) is arranged on the control shaft (12) which applies a preload to the control shaft (12) in the direction of rotation of the control shaft (12). [9] Control unit (1) according to one of the preceding claims, characterized by that the brake band (8) wraps completely around the brake disc (6) at least once. [10] Steer-by-wire steering system (2) comprising an operating unit (1) according to one of the preceding claims.

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