Steering-by-wire system for motor vehicle

Abstract

The invention relates to a steer-by-wire system (2) for a motor vehicle, comprising a rack (4) for transmitting a steering movement to a wheel of the motor vehicle, a steering motor (6) for controlling the steering movement, a steering mechanism (12) having a steering angle pinion (14), a gear (8) for transmitting a steering movement of the steering motor (6) to the rack (4), the gear (8) being coupled to the steering angle pinion (14), and a gear (8) for determining the initial position of the rack (4) during the start-up of the motor vehicle, the gear (8) being designed and arranged in the steer-by-wire system (2) relative to the steering angle pinion (14) such that the gear (8) covers the complete steering travel of the gear (4) when the rack (4) is moved through the steering angle pinion (14).

Description

[0001] The invention relates to a steer-by-wire system for a motor vehicle, a method for determining the position of a steering rack of a steer-by-wire system, and a motor vehicle having such a steer-by-wire system.

[0002] Steer-by-wire systems, which are expected to be widely used in future vehicles, have no mechanical connection between the steering wheel and the steering gear. This means that the relationship between the steering wheel angle and the steering rack position is not fixed and may change during operation. Therefore, it is no longer possible to use the steering wheel angle to determine the current rack position. Therefore, in steer-by-wire systems, it is necessary to know the rack position at all times to ensure safe operation.

[0003] Conventional angle sensors, similar in structure to known torque sensors, are not suitable for determining the rack position in steer-by-wire systems because they cannot measure absolute values ​​and are expensive. Furthermore, these sensors do not measure "true power," meaning they lose their position as soon as the steering system loses power, necessitating retraining of the sensor in this situation.

[0004] Methods that attempt to at least partially address these issues are known from the prior art. Various angle encoders (as multi-turn sensors) are known to calculate the rack position or steering angle based on the relative motion between the steering angle pinion and the steering gear housing. However, this design disadvantageously requires at least two sensor transmitters and two sensor receivers, resulting in a large number of components and a large circuit board area. Consequently, such designs are both costly and prone to errors.

[0005] The object of the present invention is therefore to at least partially eliminate the above-mentioned disadvantages. In particular, the object of the present invention is to provide a steer-by-wire system for a motor vehicle which can be produced in a simple and cost-effective manner and which ensures a reliable and precise determination of the current rack position, thereby making it possible to increase the operational reliability of the steer-by-wire system. The above-mentioned task is solved by the patent claims. Therefore, the object is achieved by a steer-by-wire system having the features of independent claim 1, by a method having the features of independent claim 10 and by a motor vehicle according to claim 11. Further features and details of the invention emerge from the dependent claims, the description and the drawings. Features and details described in conjunction with the steer-by-wire system according to the invention naturally also apply to the method according to the invention or the motor vehicle according to the invention and vice versa, so that reference is always made to the disclosure concerning the various aspects of the invention.

[0006] According to the present invention, a steer-by-wire system for a motor vehicle is provided. The steer-by-wire system includes a rack for transmitting steering motion to wheels of the motor vehicle, a steering motor for controlling the steering motion, a steering mechanism having a steering angle pinion for transmitting the steering motion, the steering motion of the steering motor being transmitted to the rack, and a gear coupled to the steering angle pinion for determining an initial position of the rack during vehicle startup. The gear is designed and arranged relative to the steering angle pinion within the steer-by-wire system such that when the rack is moved by the steering angle pinion, the gear (which rotates less than one revolution about its axis of rotation) covers the complete steering travel of the rack.

[0007] According to the present invention, the steer-by-wire system in question is designed to enable reliable and precise determination of the current rack position in a simple and cost-effective manner, thereby ensuring increased operational safety, particularly by arranging a gearwheel, which is designed and arranged relative to the steering angle pinion within the steer-by-wire system such that the gearwheel covers the complete steering travel of the rack (rotation angle <360°) when the rack is moved by the steering angle pinion. The arrangement according to the present invention can, in particular, dispense with the use of different angle encoders as multi-turn sensors or multi-stage methods for determining the rack position.

[0008] The method according to the present invention can advantageously be performed in a motor vehicle, such as a car or truck. However, it goes without saying that the method can also be used in commercial vehicles, ships, trains, and even aircraft. The motor vehicle rack in question can be configured, in particular, to transmit steering movements to the vehicle's wheels. The initial position of the motor vehicle rack is preferably understood to mean the initial position of the rack determined before the start and / or steering process. Conversely, the current position of the motor vehicle rack is preferably understood to mean the current position of the rack determined after the start and / or steering process. A steering motor is preferably understood to mean an actuator or electric motor used to drive the steering movement. Covering the entire steering stroke, as provided by the present invention, can be understood to mean, in particular, that the gear coupled to the steering angle pinion rotates less than once about its axis due to the movement of the steering angle pinion, and that the rack is driven (rotation angle <360°) as the rack is driven by the steering angle pinion from one steering stop to the opposite steering stop. In particular, due to its diameter, the gear can have such a reduction that, during a complete steering stroke of the rack from one steering stop to the opposite steering stop, the gear rotates less than once about its axis. Preferably, the rotation angle can even be less than 340°, in order to provide a margin in each direction in the event of misuse (oversteering into the end stop), for example. The steer-by-wire system in question can preferably be designed as a "single-pinion steering system," with the gear and steering angle pinion preferably forming a gear by virtue of their coupling. The angle sensor encoder attached to the gear can thus provide a clear angle signal along the entire steering stroke of the rack, without requiring multiple signals from multiple angle encoders that must be evaluated against each other.

[0009] In order to easily detect the rotation angle and ensure a particularly safe design of the steer-by-wire system in question, the invention can advantageously provide for an angle sensor to detect the rotation angle of the gearwheel. The angle sensor is preferably designed to enable ASIL-D quality data acquisition. To ensure a correspondingly high level of reliability according to ASIL-D quality, for example, a redundant or dual-redundant power supply and / or a redundant or dual-redundant communication connection can be provided. The angle sensor can be designed, for example, in the form of a circuit board or the like.

[0010] Within the framework of a structurally easy-to-produce and robust design of the steer-by-wire system in question, it can be provided, for example, that the angle sensor is designed as a magnetic sensor, with a magnet being arranged on the gear for detecting the rotation angle, preferably between the angle sensor and the gear. The magnet can preferably be arranged on the shaft on which the gear is mounted, preferably on a shaft bearing. The magnet can also cover the entire travel of the rack or rotate through one revolution. For example, a two-pole magnet can be located on the driven gear as the sensor transmitter. However, any type of inductive or optical transmitter is also conceivable.

[0011] Within the framework of a stable and compact arrangement and ensuring particularly precise determination of the rack position, a cover can also be provided for accommodating the gear and / or angle sensor, with the gear preferably being arranged between the top side of the cover and the angle sensor. Alternatively, provision can also be made for the angle sensor to be arranged between the top side of the cover and the gear. The cover can preferably be designed in the form of a plastic cover. Furthermore, 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, thereby protecting the electronics from external influences such as dirt and moisture as much as possible during assembly and operation.

[0012] To ensure that the entire steering stroke of the rack provided according to the present invention is covered by the gear, it can be advantageous to design the transmission between the steering angle pinion and the gear so that the complete steering stroke of the rack can be achieved by rotating the gear about its axis of rotation through an angle of rotation of less than 360°, preferably less than 340°. A transmission ratio of >2, preferably >3, and in particular 3.25, can be present between the steering angle pinion and the gear. As part of a cost-effective, low-noise, and low-wear design, it can also be provided that the gear is made of plastic, for example. The gear can be connected to the bearing and arranged on the shaft, for example, by hot pressing or over-hot pressing.

[0013] Within the framework of determining the initial position of the gear rack during vehicle startup, a simple and energy-efficient determination of the current position of the gear rack after the initial position is determined during vehicle startup can advantageously include a motor position sensor for determining the initial position of the gear rack after the vehicle startup process, the motor position sensor being designed as a magnetic sensor. The angle sensor for detecting the angular position of the gear wheel is preferably not operated, which not only saves energy but also improves the electromagnetic compatibility of the electrical components involved, in particular the electromagnetic sensor system involved.

[0014] In order to ensure a durable, preferably wear-free arrangement of the transmission consisting of the gearwheel and the steering angle pinion, the invention can particularly provide that the gearwheel and / or the angle sensor can be displaced in the direction of the steering angle pinion, preferably by at least 3 mm. In this way, a material-friendly, play-free arrangement between the gearwheel and the steering angle pinion can be achieved.

[0015] To achieve a play-free arrangement between the gear and the steering angle pinion, it is alternatively possible to mount the gear eccentrically on the shaft. The gear with the rotational angle sensor can be mounted in the steering housing, for example, and radially adjusted relative to the steering angle pinion by means of an eccentric shaft, thereby adjusting the play of the teeth.

[0016] To ensure a play-free arrangement between the gear wheel and the steering angle pinion, it is also conceivable to provide a spring element for presetting the radial play between the gear wheel and the steering angle pinion, which spring element is preferably fixedly arranged on the steering device housing. The spring element can, for example, be attached to the shaft of the gear wheel and / or the bearing of the steering angle pinion and thus minimize the play between the gear wheel and the steering angle pinion.

[0017] The present invention also relates to a method for determining the position of a rack of a motor vehicle steer-by-wire system, preferably the aforementioned steer-by-wire system. The method includes the following steps: driving a steering angle pinion to move the rack between a first steering stop and an opposing second steering stop, simultaneously driving a gearwheel to determine an initial position of the rack; moving the rack between the first steering stop and the second opposing steering stop via the steering angle pinion, moving the gearwheel through a rotation angle of less than 360° about the axis of rotation; and determining the initial position of the rack based on the rotation angle of the gearwheel about the axis of rotation. The method thus offers the same advantages as those already described in detail with respect to the steer-by-wire system.

[0018] In the present case, it should also be understood that a single, several or all mandatory and / or optional steps of the method according to the present invention can be performed in the proposed order, but can also be performed in a manner deviating from the proposed order. Here, a single, several or all mandatory and / or optional steps of the method according to the present invention can in particular be performed repeatedly, for example in a cyclical manner. It should also be understood that a single, several or all mandatory and optional steps of the method according to the present invention can actually also be performed at least partially automatically or automatically and / or in a self-learning manner, in particular by a computer, preferably by a computer-implemented simulation method.

[0019] The invention also relates to a motor vehicle comprising a steer-by-wire system as described above.The motor vehicle according to the invention thus offers the same advantages as those already described in detail with respect to the steer-by-wire system according to the invention or the method according to the invention.

[0020] Further advantages, features and details of the invention emerge from the following description, in which exemplary embodiments of the invention are described in detail with reference to the accompanying drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination.

[0021] The accompanying drawings schematically show:

[0022] Figure 1 A steer-by-wire system for a motor vehicle according to the invention is shown in cross-section according to a first exemplary embodiment,

[0023] Figure 2 A section through a steer-by-wire system for a motor vehicle according to the invention is shown in accordance with a first exemplary embodiment.

[0024] Figure 3 showing first (top) and second (bottom) partial cross-sectional views of a steer-by-wire system according to the invention according to a first exemplary embodiment,

[0025] Figure 4 showing first (top) and second (bottom) partial cross-sectional views of a steer-by-wire system according to the invention according to a second exemplary embodiment,

[0026] Figure 5 showing first (top) and second (bottom) partial cross-sectional views of a steer-by-wire system according to the invention according to a third exemplary embodiment,

[0027] Figure 6 The individual steps of the method according to the invention for determining the position of a rack of a steer-by-wire system of a motor vehicle are shown.

[0028] Figure 1 A steer-by-wire system 2 for a motor vehicle according to the invention is shown in a sectional view according to a first exemplary embodiment.

[0029] like Figure 1As shown, the wire-controlled steer system 2 according to the present invention includes a rack 4 for transmitting steering motion to the wheels of a motor vehicle, a steering motor 6 for controlling the steering motion, a steering mechanism 12 with a steering angle pinion 14 for transmitting the steering motion of the steering motor 6 to the rack 4, a gear 8 connected to the steering angle pinion 14 for determining the initial position of the rack 4 during the starting process of the motor vehicle, and the gear 8 is designed and arranged in the wire-controlled steer system 2 relative to the steering angle pinion 14 so that when the rack 4 moves via the steering angle pinion 14, the gear 8 covers the entire steering stroke of the rack 4.

[0030] Figure 2 A slightly enlarged view shows the arrangement of Figure 1 The portion of the steer-by-wire system 2 according to the present invention is shown in the dashed box in FIG.

[0031] from Figure 2 As can be seen in FIG, the steering angle pinion 14 is driven by the worm gear 22 which is driven by the steering motor 6 .

[0032] Figure 3 The arrangement according to the first exemplary embodiment is shown in FIG. Figure 2 The first (top) and second (bottom) partial cross-sectional views of the portion of the steer-by-wire system 2 according to the present invention in the dashed box are shown, and the lower figure is a partial cross-sectional view along the section line AA of the upper figure.

[0033] from Figure 3 As can be seen in the figure, steer-by-wire system 2 also includes an angle sensor 10 for detecting the rotation angle α of gear 8 coupled to steering angle pinion 14. In this case, angle sensor 10 is designed for ASIL-D quality data acquisition. Gear 8 is rotatably mounted on shaft 20 via bearing 26. Angle sensor 10 is designed in the form of a magnetic sensor, with magnet 18 arranged on gear 8 to detect the rotation angle α between angle sensor 10 and gear 8.

[0034] Furthermore, a cover 16 is provided for accommodating the gear wheel 8 and the angle sensor 10 , in which case the gear wheel 8 is arranged between an upper side 16 a of the cover 16 and the angle sensor 10 .

[0035] The transmission between the steering angle pinion 14 and the gear wheel 8 is designed such that a complete steering stroke of the rack 4 is achieved by rotating the gear wheel 8 about its axis of rotation X by a rotation angle α<360°, preferably a rotation angle α<340°.

[0036] The gearwheel 8 and / or the angle sensor 10 can be moved 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 gearwheel 8 and the steering angle pinion 14 .

[0037] Figure 4The arrangement according to the second exemplary embodiment is shown in FIG. Figure 2 The first (top) and second (bottom) partial cross-sectional views of the portion of the steer-by-wire system 2 according to the present invention in the dashed box are shown, and the lower figure is a partial cross-sectional view along the section line AA of the upper figure.

[0038] like Figure 4 As shown, according to the second exemplary embodiment, the angle sensor 10 is arranged between the top 16 a of the cover 16 and the gear 8 , which in this case is eccentrically mounted on the shaft 20 , thereby ensuring or creating a play-free coupling with the steering angle pinion 14 . The steering angle pinion 14 is also provided with a magnet 18 .

[0039] Figure 5 The arrangement according to the third exemplary embodiment is shown in FIG. Figure 2 The first (top) and second (bottom) partial cross-sectional views of the portion of the steer-by-wire system 2 according to the present invention in the dashed box are shown, and the lower figure is a partial cross-sectional view along the section line AA of the upper figure.

[0040] like Figure 5 As shown, the third embodiment also has a spring element 24 for presetting the radial play between the gear 8 and the steering angle pinion 14, which in this case is arranged firmly on the housing of the steering device 12. Figure 6 The individual steps of the method according to the invention for determining the position of a rack 4 of a steer-by-wire system 2 of a motor vehicle are shown.

[0041] from Figure 6 As can be seen in the figure, the method according to the invention comprises the following steps: driving 100° the steering angle pinion 14 to move the rack 4 between a first steering stop and an opposite second steering stop, simultaneously driving the gear 8 to determine an initial position of the rack 4, moving the rack 4 200° between the first steering stop and the opposite second steering stop by means of the steering angle pinion 14, moving the gear 8 300° around the rotation axis X at a rotation angle α<360°, and determining 400° the initial position of the rack 4 by means of the rotation angle α of the gear 8 around the rotation axis X.

[0042] The above description of the embodiment only describes the present invention in an exemplary manner. Of course, if technically reasonable, the various features of the embodiment can be freely combined with each other without departing from the scope of the present invention.

[0043] Reference Signs List

[0044] 2-wire steering system

[0045] 4 racks

[0046] 6 Steering motor

[0047] 8 gears

[0048] 10 Angle Sensor

[0049] 12 Steering transmission mechanism

[0050] 14 Steering angle pinion

[0051] 16 covers

[0052] 16a upper side

[0053] 18 magnets

[0054] 20-axis

[0055] 22 worm gear

[0056] 24 spring elements

[0057] 26 bearings

[0058] X-axis rotation

[0059] α rotation angle

[0060] iGear Ratio

[0061] 100 drives the steering angle pinion to move the rack between the first steering stop and the opposite second steering stop

[0062] 200 moves the rack between the first steering stop and the second opposing steering stop

[0063] 300 gear moves around the rotation axis, the rotation angle is <360°

[0064] 400 determines the initial position of the rack by the rotation angle of the gear around the rotation axis.

Claims

1. A steer-by-wire system (2) for a motor vehicle, comprising: - a rack (4) for transmitting steering movements to the wheels of the motor vehicle, - a steering motor (6) for controlling the steering movement, - a steering mechanism (12) having 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), which serves to determine the initial position of the rack (4) during the starting process of the motor vehicle, -in, The gear wheel (8) is designed relative to the steering angle pinion (14) and is arranged in the steer-by-wire system (2) such that when the rack (4) is moved via the steering angle pinion (14), the gear wheel (8) covers the complete steering travel of the rack (4).

2. The steer-by-wire system (2) according to claim 1, It is characterized by: An angle sensor (10) is provided for detecting a rotation angle (α) of the gear (8), wherein the angle sensor (10) is preferably designed such that data detection can be performed with ASIL-D quality.

3. The steer-by-wire system (2) according to claim 2, It is characterized by: The angle sensor (10) is designed as a magnetic sensor, wherein a magnet (18) is arranged on the gear (8) for detecting the rotation angle (α), wherein the magnet (18) is preferably arranged between the angle sensor (10) and the gear (8).

4. Steer-by-wire system (2) according to any one of the preceding claims, It is characterized by: A cover (16) is provided for accommodating 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. A steer-by-wire system (2) according to any one of the preceding claims, characterized in that A transmission exists between the steering angle pinion (14) and the gear wheel (8), which is designed so that a complete steering stroke of the rack (4) can be implemented by rotating the gear wheel (8) about its axis of rotation (X) by a rotation angle (α) of <360°, preferably by a rotation angle (α) of <340°.

6. Steer-by-wire system (2) according to any one of the preceding claims, It is characterized by: A motor position sensor is provided for determining the current position of the toothed rack (4) based on the initial position of the toothed rack (4) after a starting process of the motor vehicle, wherein the motor position sensor is designed in the form of a magnetic sensor.

7. Steer-by-wire system (2) according to any one of the preceding claims, It is characterized by: The gear (8) and / or the angle sensor (10) can be moved in the direction of the steering angle pinion (14), preferably by at least 3 mm in the direction of the steering angle pinion (14).

8. Steer-by-wire system (2) according to any one of the preceding claims, It is characterized by: The gear (8) is eccentrically supported on the shaft (20).

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

10. A method for determining the position of a rack (4) of a steer-by-wire system (2) of a motor vehicle, preferably a steer-by-wire system (2) according to any one of claims 1 to 9, the method comprising the following steps: - driving (100) the steering angle pinion (14) to move the rack (4) between a first steering stop and an opposite second steering stop, while driving the gear (8) to determine the initial position of the rack (4), - moving (200) the rack (4) between a first steering stop and an opposite second steering stop via a steering angle pinion (14), - moving (300) the gear (8) around the axis of rotation (X) by an angle of rotation (α) <360°, - determining (400) the initial position of the rack (4) by the angle of rotation (α) of the gear wheel (8) about the axis of rotation (X).

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

Images