Steer-by-wire steering system for a motor vehicle

Abstract

The invention relates to a steer-by-wire steering system (2) for a motor vehicle, comprising: a steering rack (4) for transmitting a steering movement to wheels of the motor vehicle, a steering motor (6) for driving a steering movement, a steering gear (12) having a steering angle pinion (14) for transmitting the steering movement of the steering motor (6) to the steering rack (4), a gear wheel (8) coupled to the steering angle pinion (14) for determining an initial position of the steering rack (4) when the motor vehicle is started, wherein the gear wheel (8) is configured relative to the steering angle pinion (14) and arranged inside the steer-by-wire steering system (2) in such a way that the gear wheel (8) covers a complete steering range of the steering rack (4) when the steering rack (4) is moved over the steering angle pinion (14).

Description

[0001] Description

[0002] Steer-by-wire steering system for a motor vehicle

[0003] The present invention relates to a steer-by-wire steering system for a motor vehicle, a method for determining a position of a rack of a steer-by-wire steering system and a motor vehicle with such a steer-by-wire steering system.

[0004] Steer-by-wire steering systems, which may be used in large-scale production in the automotive sector in the future, do not have a mechanical connection between the steering wheel and the steering gear. As a result, the relationship between the steering wheel angle and the rack position is not fixed and can change during operation. Determining the current rack position using the steering wheel angle is therefore no longer possible. Therefore, in steer-by-wire steering systems, it is necessary to know the rack position at all times to ensure operational reliability.

[0005] Conventional angle sensors, which are similar in design to conventional torque sensors, are not suitable for determining the rack position in a steer-by-wire steering system because the sensors do not provide absolute measurements and are also expensive. Furthermore, these sensors do not measure "true power-on." This means that they lose their position as soon as the steering system is de-energized, requiring the sensors to be re-trained in such a case.

[0006] Methods are known from the prior art that attempt to at least partially solve these problems. For example, it is known to calculate a rack position or a steering angle using various angle sensors – as a multi-turn sensor – from a relative movement between the steering angle pinion and the steering gear housing. However, such a design requires at least two sensor transmitters and two sensor receivers, which requires a large number of components as well as a larger circuit board area. Such a design is therefore both cost-intensive and error-prone.

[0007] It is therefore an object of the present invention to at least partially remedy the disadvantages described above. In particular, it is the object of the present invention to provide a steer-by-wire steering system for a motor vehicle which can be produced in a simple and cost-effective manner and guarantees reliable and precise determination of a current rack position, thus enabling increased operational reliability of the steer-by-wire steering system. The above object is achieved by the patent claims. Accordingly, the object is achieved by a steer-by-wire steering system having the features of independent claim 1, by a method having the features of the independent claim 10 and by a motor vehicle according to claim 11. Further features and details of the invention can be found in the subclaims, the description and the drawings.Features and details that are described in connection with the steer-by-wire steering system according to the invention naturally also apply in connection with the method according to the invention or the motor vehicle according to the invention and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is or can always be made to each other.

[0008] According to the invention, a steer-by-wire steering system for a motor vehicle is provided. The steer-by-wire steering system according to the invention comprises a rack for transmitting a steering movement to wheels of the motor vehicle, a steering motor for controlling a steering movement, a steering gear with a steering angle pinion for transmitting the steering movement of the steering motor to the rack, and a gear coupled to the steering angle pinion for determining an initial position of the rack during a start-up process of the motor vehicle. The gear is designed relative to the steering angle pinion and arranged within the steer-by-wire steering system in such a way that the gear covers a complete steering stroke of the rack (with less than one revolution around its axis of rotation) when the rack moves via the steering angle pinion.

[0009] According to the invention, the steer-by-wire steering system in question is designed, in particular by arranging a gearwheel that is configured relative to a steering angle pinion and arranged within the steer-by-wire steering system in such a way that the gearwheel covers a complete steering stroke of the rack (with a rotation angle of < 360°) when the rack moves via the steering angle pinion, to enable a reliable and precise determination of a current rack position in a simple and cost-effective manner, thus ensuring increased operational reliability. The arrangement according to the invention makes it possible, in particular, to dispense with the use of various angle sensors as multi-turn sensors or multi-stage methods for determining a rack position.

[0010] The method according to the invention can advantageously be carried out in motor vehicles, such as cars or trucks. However, it is understood that the method can also be applied to commercial vehicles, ships, trains or even aircraft. The specific steering rack of the motor vehicle can be provided in particular for transmitting a steering movement to the wheels of the motor vehicle. An initial position of a steering rack of a motor vehicle can preferably be understood as the initial position of a steering rack determined before a starting process and / or a steering process is carried out. In contrast, a current position of a steering rack of a motor vehicle can preferably be understood as the current position of a steering rack determined after a starting process and / or a steering process is carried out. A steering motor can preferably be understood as an actuator oran electric machine for driving a steering movement. Covering the entire steering stroke as provided according to the invention can in particular be understood to mean that the gear coupled to the steering angle pinion rotates less than once around its axis (angle of rotation < 360°) due to a movement of the steering angle pinion for driving the rack when the rack is moved from one steering stop to the opposite steering stop by the steering angle pinion. In particular, due to its diameter, the gear can have a reduction ratio such that it rotates less than once around its axis during a complete steering stroke of the rack from one steering stop to the opposite steering stop. Preferably, the angle of rotation can even be < 340° in order to be able to provide a reserve in every direction in case of misuse (oversteering the end stop), for example.The steer-by-wire steering system in question can preferably be designed as a single-pinion steering system. The gear and the steering angle pinion can preferably form a gearing system depending on their coupling. An angle sensor attached to the gear can thus provide a clear angle signal along the entire steering stroke of the rack, without the need for multiple signals from multiple angle sensors that would need to be offset against each other.

[0011] With a view to simple detection of a rotation angle and to ensure a particularly safe design of the steer-by-wire steering system in question, the invention can advantageously provide an angle sensor for detecting a rotation angle of the gearwheel, wherein the angle sensor is preferably designed such that data acquisition can be carried out in ASIL-D quality. To ensure a correspondingly high level of reliability in accordance with ASIL-D quality, a redundant or doubly redundant power supply and / or a redundant or doubly redundant communication connection can be provided, for example. The angle sensor can be designed, for example, in the form of a printed circuit board or the like.

[0012] Within the scope of a structurally simple and robust design of a steer-by-wire steering system in question, it can be provided, for example, that the angle sensor is designed in the form of a magnetic sensor, wherein a magnet is arranged on the gear to detect an angle of rotation, wherein the magnet is preferably arranged between the angle sensor and the gear. The magnet can preferably be arranged on a shaft on which the gear is mounted, preferably on a bearing of the shaft. The magnet can also cover the entire stroke of the rack or perform one rotation over the entire stroke of the rack. A two-pole magnet on the driven gear, for example, serves as a sensor transmitter. However, any form of inductive or optical transmitter is also conceivable.

[0013] In the context of a stable and compact arrangement and to ensure particularly precise determination of a rack position, it can further be provided that a cover is provided for receiving the gear and / or the angle sensor, wherein the gear is preferably arranged between an upper side of the cover and the angle sensor. Alternatively, it can also be provided that the angle sensor is arranged between an upper side of the cover and the gear. The cover can preferably be designed in the form of a plastic cover. In addition, the cover can have an integrated plug or an integrated cable tail. The electronics with the sensor receiver can advantageously be integrated into the sensor cover in such a way that it is optimally protected from external influences such as dirt and moisture during assembly and operation.

[0014] To ensure that the entire steering stroke of the rack is covered by the gearwheel as provided for in the invention, it can advantageously be provided that the transmission ratio between the steering angle pinion and the gearwheel is designed such that a complete steering stroke of the rack can be carried out by means of one rotation of the gearwheel about its axis of rotation with a rotation angle of < 360°, preferably with a rotation angle of < 340°. Between the steering angle pinion and the gearwheel, there can be a transmission ratio with a transmission ratio of > 2, preferably > 3, in particular 3.25. In the context of a cost-effective, low-noise, and low-abrasion design, it can further be provided that the gearwheel is made of a plastic, for example. The gearwheel can be connected to a bearing, for example by warm or hot caulking, and can be arranged on a shaft.

[0015] Within the scope of a simple and energy-saving determination of the current position of a rack after determining the initial position of a rack when starting a motor vehicle, it can advantageously be further provided that an engine position sensor is provided for determining the current position of a rack after starting the motor vehicle based on the initial position of the rack, wherein the engine position sensor is designed in the form of a magnetic sensor. In this case, the angle sensor for detecting the angular position of the gear is preferably not in operation, which not only saves energy but also promotes the electromagnetic compatibility of the electrical components involved, in particular the electromagnetic sensors involved.

[0016] To ensure a long-lasting, preferably wear-free arrangement of a transmission comprising a gear and a steering angle pinion, the invention can, in particular, provide for the gear and / or the angle sensor to be movable in the direction of the steering angle pinion, preferably by at least 3 mm in the direction of the steering angle pinion. In this way, a material-friendly, backlash-free arrangement between the gear and the steering angle pinion can be achieved.

[0017] To achieve a backlash-free arrangement between the gear and the steering angle pinion, the gear can alternatively be mounted eccentrically on a shaft. The gear with the angle sensor can be mounted in the steering gear housing, for example, and can be adjusted radially relative to the steering angle pinion using the eccentric shaft, allowing the backlash of the gearing to be adjusted.

[0018] To ensure a play-free arrangement between the gear and the steering angle pinion, it is alternatively conceivable to provide a spring element for presetting a radial play between the gear and the steering angle pinion, wherein the spring element is preferably fixedly mounted on a housing of the steering gear. The spring element can, for example, be attached to the gear shaft and / or a bearing of the steering angle pinion, thus minimizing play between the gear and the steering angle pinion.

[0019] The invention also further relates to a method for determining a position of a rack of a steer-by-wire steering system of a motor vehicle, preferably a steer-by-wire steering system as described above. The method according to the invention comprises the steps of driving a steering angle pinion for moving a rack between a first steering stop and an opposite second steering stop and, at the same time, a gear for determining an initial position of the rack, moving the rack between the first steering stop and the second opposite steering stop by means of the steering angle pinion, moving the gear about an axis of rotation with a rotation angle of < 360°, and determining an initial position of the rack via the rotation angle of the gear about the axis of rotation.The method according to the invention thus brings with it the same advantages as have already been described in detail with regard to the steer-by-wire steering system according to the invention.

[0020] It is also understood in the present case that individual, several or all of the mandatory and / or optional steps of the method according to the invention can be carried out in the proposed order, but also deviating from the proposed order. In this case, individual, several or all of the mandatory and / or optional steps of the method according to the invention can be carried out repeatedly, for example cyclically. It is further understood that individual, several or all of the mandatory and optional steps of the method according to the invention can also be carried out at least partially automatically or automated and / or in a self-learning manner, in particular can be implemented by a computer, preferably via computer-implemented simulation methods.

[0021] The invention also further relates to a motor vehicle comprising a steer-by-wire steering system as described above. Thus, the motor vehicle according to the invention offers the same advantages as those already described in detail with regard to the steer-by-wire steering system according to the invention and the method according to the invention.

[0022] Further advantages, features, and details of the invention will become apparent from the following description, which describes exemplary embodiments of the invention in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination.

[0023] They show schematically:

[0024] Figure 1 shows a steer-by-wire steering system according to the invention for a motor vehicle according to a first embodiment in a sectional view,

[0025] Figure 2 shows a part of the steer-by-wire steering system according to the invention for a motor vehicle according to the first embodiment in a sectional view,

[0026] Figure 3 shows a first (top) and second (bottom) partial sectional view of the steer-by-wire steering system according to the invention according to the first embodiment,

[0027] Figure 4 shows a first (top) and second (bottom) partial sectional view of the steer-by-wire steering system according to the invention according to a second embodiment, Figure 5 shows a first (top) and second (bottom) partial sectional view of the steer-by-wire steering system according to the invention according to a third embodiment,

[0028] Figure 6 shows the individual steps of a method according to the invention for determining the position of a rack of a steer-by-wire steering system of a motor vehicle.

[0029] Figure 1 shows a steer-by-wire steering system 2 according to the invention for a motor vehicle according to a first embodiment in a sectional view.

[0030] As can be seen from Figure 1, the steer-by-wire steering system 2 according to the invention comprises a rack 4 for transmitting a steering movement to wheels of the motor vehicle, a steering motor 6 for controlling a steering movement, a steering gear 12 with a steering angle pinion 14 for transmitting the steering movement of the steering motor 6 to the rack 4, a gear 8 coupled to the steering angle pinion 14 for determining an initial position of the rack 4 during a start-up process of the motor vehicle, wherein the gear 8 is designed relative to the steering angle pinion 14 and arranged within the steer-by-wire steering system 2 in such a way that the gear 8 covers a complete steering stroke of the rack 4 when the rack 4 moves via the steering angle pinion 14.

[0031] Figure 2 shows the part of the steer-by-wire steering system 2 according to the invention arranged in the dashed box in Figure 1 in a slightly enlarged view.

[0032] As can be seen from Figure 2, the steering angle pinion 14 is driven via the worm gear 22 driven by the steering motor 6.

[0033] Figure 3 shows a first (top) and second (bottom) partial sectional view of the part of the steer-by-wire steering system 2 according to the invention according to the first embodiment arranged in the dashed box of Figure 2, wherein the lower illustration represents a partial sectional view of the upper illustration along the section line AA.

[0034] As can be seen in Figure 3, the steer-by-wire steering system 2 additionally comprises an angle sensor 10 for detecting a rotational angle α of the gear 8 coupled to the steering angle pinion 14. The angle sensor 10 is designed in this case for data acquisition in ASIL-D quality. The gear 8 is rotatably mounted on the shaft 20 via the bearing 26. The angle sensor 10 is designed in the form of a magnetic sensor, with a magnet 18 arranged on the gear 8 for detecting a rotational angle α between the angle sensor 10 and the gear 8.

[0035] Furthermore, a cover 16 is provided for receiving the gear 8 and the angle sensor 10, wherein the gear 8 is arranged between an upper side 16a of the cover 16 and the angle sensor 10.

[0036] In the present case, the transmission between the steering angle pinion 14 and the gear 8 is designed such that a complete steering stroke of the rack 4 can be carried out by means of a rotation of the gear 8 about its axis of rotation X with a rotation angle a of < 360°, preferably with a rotation angle a of < 340°.

[0037] The gear 8 and / or the angle sensor 10 are movable in the direction of the steering angle pinion 14, preferably by at least 3 mm, in order to set a play-free coupling between the gear 8 and the steering angle pinion 14.

[0038] Figure 4 shows a first (top) and second (bottom) partial sectional view of the part of the steer-by-wire steering system 2 according to the invention arranged in the dashed box of Figure 2 according to a second embodiment, wherein the lower illustration represents a partial sectional view of the upper illustration along the section line AA.

[0039] As can be seen from Figure 4, according to the second embodiment, the angle sensor 10 is arranged between the upper side 16a of the cover 16 and the gear 8, wherein the gear 8 is mounted eccentrically on the shaft 20 in this case, thus ensuring or creating a backlash-free coupling to the steering angle pinion 14. Additionally, the steering angle pinion 14 is also provided with a magnet 18.

[0040] Figure 5 shows a first (top) and second (bottom) partial sectional view of the part of the steer-by-wire steering system 2 according to the invention arranged in the dashed box of Figure 2 according to a third embodiment, wherein the lower illustration represents a partial sectional view of the upper illustration along the section line AA.

[0041] As can be seen in Figure 5, the third embodiment additionally has a spring element 24 for presetting a radial play between the gear 8 and the steering angle pinion 14, which in this case is fixedly arranged on the housing of the steering gear 12. Figure 6 finally shows the individual steps of a method according to the invention for determining the position of a rack 4 of a steer-by-wire steering system 2 of a motor vehicle.

[0042] As can be seen from Figure 6, the method according to the invention comprises the steps of driving 100 a steering angle pinion 14 for moving a rack 4 between a first steering stop and an opposite second steering stop and, at the same time, a gear 8 for determining an initial position of the rack 4, moving 200 the rack 4 between the first steering stop and the second opposite steering stop by means of the steering angle pinion 14, moving 300 the gear 8 about an axis of rotation X with a rotation angle a of < 360° and determining 400 an initial position of the rack 4 via the rotation angle a of the gear 8 about the axis of rotation X.

[0043] The above explanation of the embodiments describes the present invention exclusively by way of examples. Of course, individual features of the embodiments can be freely combined with one another, provided they are technically feasible, without departing from the scope of the present invention.

[0044] List of reference symbols

[0045] 2 Steer-by-Wire steering system

[0046] 4 rack

[0047] 6 Steering motor

[0048] 8 gear

[0049] 10 Angle sensor

[0050] 12 steering gear

[0051] 14 steering angle pinion

[0052] 16 lids

[0053] 16a top

[0054] 18 Magnet

[0055] 20 Wave

[0056] 22 worm gears

[0057] 24 spring element

[0058] 26 warehouses

[0059] X axis of rotation a angle of rotation i gear ratio

[0060] 100 Driving a steering angle pinion to move a rack between a first steering stop and an opposite second steering stop

[0061] 200 Moving the rack between the first steering stop and the second opposite steering stop

[0062] 300 Moving the gear around a rotational axis with a rotation angle of < 360° 400 Determining an initial position of the rack via the rotation angle of the gear around the rotational axis

Claims

Patent claims 1. Steer-by-wire steering system (2) for a motor vehicle, comprising: a rack (4) for transmitting a steering movement to wheels of the motor vehicle, a steering motor (6) for controlling a steering movement, a steering gear (12) with a steering angle pinion (14) for transmitting the steering movement of the steering motor (6) to the rack (4), a gear (8) coupled to the steering angle pinion (14) for determining an initial position of the rack (4) during a starting process of the motor vehicle, wherein the gear (8) is designed relative to the steering angle pinion (14) and is arranged within the steer-by-wire steering system (2) in such a way that the gear (8) covers a complete steering stroke of the rack (4) when the rack (4) moves via the steering angle pinion (14).

2. Steer-by-wire steering system (2) according to claim 1, characterized in that an angle sensor (10) is provided for detecting a rotation angle (a) of the gear (8), wherein the angle sensor (10) is preferably designed such that data acquisition in ASIL-D quality can be carried out.

3. Steer-by-wire steering system (2) according to claim 2, characterized in that the angle sensor (10) is designed in the form of a magnetic sensor, wherein a magnet (18) is arranged on the gear (8) for detecting a rotation angle (a), wherein the magnet (18) is preferably arranged between the angle sensor (10) and the gear (8).

4. Steer-by-wire steering system (2) according to one of the preceding claims, characterized in that a cover (16) is provided for receiving the gear (8) and / or the angle sensor (10), wherein the gear (8) is preferably arranged between an upper side (16a) of the cover (16) and the angle sensor (10).

5. Steer-by-wire steering system (2) according to one of the preceding claims, characterized in that that between the steering angle pinion (14) and the gear (8) there is a transmission which is designed such that a complete steering stroke of the rack (4) can be carried out by means of a rotation of the gear (8) about its axis of rotation (X) with a rotation angle (a) of < 360°, preferably with a rotation angle (a) of < 340°.

6. Steer-by-wire steering system (2) according to one of the preceding claims, characterized in that an engine position sensor is provided for determining a current position of a rack (4) after a starting process of the motor vehicle on the basis of the initial position of the rack (4), wherein the engine position sensor is designed in the form of a magnetic sensor.

7. Steer-by-wire steering system (2) according to one of the preceding claims, characterized in that the gear (8) and / or the angle sensor (10) are movable in the direction of the steering angle pinion (14), preferably at least by 3 mm in the direction of the steering angle pinion (14).

8. Steer-by-wire steering system (2) according to one of the preceding claims, characterized in that the gear (8) is mounted eccentrically on a shaft (20).

9. Steer-by-wire steering system (2) according to one of the preceding claims, characterized in that a spring element (24) is provided for presetting a radial play between the gear (8) and the steering angle pinion (14), wherein the spring element (24) is preferably arranged fixedly on a housing of the steering gear (12).

10. A method for determining a position of a rack (4) of a steer-by-wire steering system (2) of a motor vehicle, preferably a steer-by-wire steering system (2) according to one of claims 1 to 9, comprising the steps: Driving (100) a steering angle pinion (14) for moving a rack (4) between a first steering stop and an opposite second steering stop and at the same time a gear (8) for determining an initial position of the rack (4), Moving (200) the rack (4) between the first steering stop and the second opposite steering stop by means of the steering angle pinion (14), Moving (300) the gear (8) around a rotation axis (X) with a rotation angle (a) of < 360°, Determining (400) an initial position of the rack (4) via the angle of rotation (a) of the gear (8) about the axis of rotation (X).

11. Motor vehicle comprising a steer-by-wire steering system (2) according to one of claims 1 to 9.

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