Steering unit for vehicle

Abstract

The invention relates to a steering unit (1), in particular a steer-by-wire steering unit, for a vehicle, comprising: a steering rod (2) which is designed to be coupled at its axial ends to a wheel of the vehicle, a control actuator (3) which is coupled to the steering rod (2) via a conversion gear unit (4) such that a rotational movement of the control actuator (3) causes a translational movement of the steering rod (2), wherein the conversion gear unit (4) comprises a belt transmission (7) and a linear transmission (8), wherein the belt transmission (7) has a first drive wheel (9) with a first diameter, a second drive wheel (10) with a second diameter and a belt means (11), wherein the first drive wheel (9) is coupled to the control actuator (3) in a torque-transmitting manner and the second drive wheel (10) is coupled to the linear transmission (8) in a load-transmitting manner,and the belt means (11) is arranged on a circumferential surface of the first drive wheel (9) and the second drive wheel (10) and is configured to transmit a rotational movement of the first drive wheel (9) to the second drive wheel (10), and a sensor unit (5) for determining the position of the handlebar (2), comprising: a sensor device (12) for determining the position of the belt means (11), which comprises a plurality of markings (13) and a sensor (14), wherein the markings (13) are arranged on a circumferential surface of the belt means (11), and wherein the sensor (14) is configured to detect the plurality of markings (13), and a position sensor for detecting a rotational position of the actuator (3).,

Description

Prior ArtNowadays, both mechanical steering systems or steering units and so-called steer-by-wire steering systems or steering units are known. In this case, the steering systems can be divided into two subsystems, the system of the steering shaft with a steering element, such as a steering wheel, which is also referred to as a "hand wheel actuator" (HWA) system, and the system of the steering actuator for steering the wheels, which is also referred to as a "road wheel actuator" (RWA) system. In the case of the mechanical steering systems, these two subsystems are mechanically connected to one another via the steering column and, if appropriate, a steering gear. Thus, the two subsystems in the mechanical steering systems are connected to one another directly, i.e. physically. In these mechanical steering systems, a position of the steering element is thus always linked one-to-one to a position of the steering actuator, in particular of a steering rod. This means that a specific position of the steering element is assigned one-to-one to a specific position of the steering rod, so that each position of the steering rod is assigned a specific position of the steering element.In the steer-by-wire steering systems, the mechanical connection between the two subsystems via the steering column is dispensed with, and the steering of the wheels in accordance with a movement of the steering element is controlled by transmitting corresponding signals between the two subsystems HWA and RWA. In other words, with steer-by-wire steering systems, the physical steering column, which transmits the steering movement or driver's wishes from the steering wheel directly via the steering gear and tie rod and wheel carrier to the wheel, is replaced electrically redundantly by "by wire", i.e. signal transmission by means of cable. As a result, a position of the steering element is no longer physically coupled to a position of the steering rod, and such one-to-one coupling of the position of the steering element to the position of the steering rod is usually released with a sensor system which is arranged in the RWA system and serves to determine the position of the steering rod. Various sensor system arrangements are known, as for example from WO 2018 / 073267 A1, DE 11 2020 002 949 T5, DE 10 2021 212 470 A1.It has now been found that there is a further need to improve a known steering unit, in particular a steer-by-wire steering unit, for a vehicle. In particular, there is a further need to provide a steering unit which makes it possible to determine the position of the steering rod in an absolute manner, and further in particular also after the vehicle has been in a switched-off or non-powered state.Against this background, it is an object of the present invention to provide an improved steering unit, in particular a steer-by-wire steering unit, for a vehicle, which in particular enables an absolute, further in particular continuous, determination of the steering rod position.Disclosure of the InventionThese and other objects, which will be mentioned in the reading of the following description or which can be recognized by the person skilled in the art, are achieved by the subject matter of the independent claim. Advantageous embodiments and developments can be taken from the dependent claims and the following description.The steering unit according to the invention, in particular steer-by-wire steering unit, for a vehicle has a steering rod, a control actuator, and a sensor unit for determining the position of the steering rod. The steering rod is configured to be coupled at each of its axial ends to a wheel of the vehicle. The actuator is coupled via at least one conversion gear unit in such a way that a rotational movement of the actuator causes a translatory movement of the steering rod along its longitudinal axis. The conversion gear unit includes a continuously variable transmission and a linear transmission. The belt transmission has a first drive wheel with a first diameter, a second drive wheel with a second diameter, and a belt means. The first drive wheel is coupled to the actuator in a torque-transmitting manner and the second drive wheel is coupled to the linear transmission in a load-transmitting manner. The wrapping means is arranged on a circumferential surface of the first drive wheel and of the second drive wheel and is configured to transmit a rotational movement of the first drive wheel to the second drive wheel. The sensor unit for determining the position of the steering rod has a sensor device for determining the position of the wrapping means and a position sensor for detecting a rotational position of the actuator. The sensor device for determining the position of the wrapping means comprises a plurality of markings and a sensor, wherein the markings are arranged on a circumferential surface of the wrapping means, and the sensor is configured to detect the plurality of markings.The linear gear is in particular designed as a ball screw, wherein the steering rod has a spindle section at least in sections. Alternatively, other linear gears, such as a trapezoidal screw drive or a planetary roller screw drive, etc., can also be used.The first diameter of the first drive wheel and the second diameter of the second drive wheel may be the same as or different from each other. In particular, the second diameter of the second drive wheel is greater than the first diameter of the first drive wheel. Additionally, or alternatively, the two drive wheels are designed in particular as toothed wheels and the wrapping means is designed in particular as a toothed wrapping means, such as a toothed belt or a chain, etc. In this case, a gear ratio of the pulley transmission may also be indicated as a ratio of a number of teeth of the first drive gear and a number of teeth of the second drive gear. Furthermore, in particular, the wrapping means engages positively in the drive wheels, for example the wrapping means as a toothed belt or chain combined with the drive wheels as pulleys or sprockets. In addition, the largest common divisor of a number of teeth of the drive wheels and a number of teeth of the wrapping means is in particular a prime number, and further in particular greater than 23.The actuator is in particular designed as an electric motor, and the position sensor is configured to detect a rotational position of the rotor of the electric motor. This means that the position sensor is designed in particular as a rotor position sensor. The markings are in particular arranged at predetermined distances from one another. The term "markings" is to be understood in particular as meaning those features which substantially withstand the alternating bending loads and / or centrifugal forces occurring during operation of the wrapping means. In other words, it can be said that the markings do not tend to become detached from the wrapping means during operation on account of the operating conditions. For example, the markings can be printed, woven in, bonded in, vulcanized in, etc.The advantage of the solution according to the invention lies in particular in the fact that the position determination of the wrapping means does not have to be detected over the entire wrapping circumference, but rather a detection distributed in sections, in particular periodic, is sufficient over the wrapping means, since the position, in particular the absolute position of the steering rod, can be determined, in particular calculated, on the basis of the combination of the sensor unit and the position sensor for detecting a rotational position of the actuator, in particular according to the Nonius / Vernier principle. It can thus be said that the present invention makes it possible to determine the position, in particular the absolute position of the steering rod, without determining the position of the wrapping means in absolute terms. This makes it possible to use a less complex and / or more cost-effective sensor in the sensor unit without reducing an accuracy in the position determination of the steering rod.In this case, the rotor position sensor generally delivers a highly precise signal corresponding to an electrical or mechanical angle of the rotor, which signal is required for actuating the actuator, in particular in the form of an electric motor. The angle of the rotor behaves in a highly redundant manner in proportion to the position of the steering rod, in particular usually about 2-5 mm / U, but cannot be used-considered alone-to determine the absolute position of the steering rod, since the angle of the rotor performs a plurality of complete revolutions, for example of the order of magnitude of about 20-100 revolutions, over the entire travel path of the steering rod, which can also be referred to as steering rod travel path. In combination with the above-described sensor device, an accurate position determination of the steering rod, in particular the absolute position of the steering rod, is now possible, wherein the sensor device in this case only has to have a low resolution or accuracy, since the sensor device only has to perform a rough determination of the position determination of the wrapping means, while the rotor position sensor supplies the high resolution or accuracy, so to speak the fractional positions, in order to achieve an accurate position determination of the steering rod. Such a combination enables a cost-effective sensor device to be used in order to be able to realize a position determination of the steering rod in the steering unit with sufficiently high resolution and accuracy.Thus, the costs for the sensor unit for determining the position of the steering rod can be reduced, since the requirements placed on the sensor device are lower than in a case in which the sensor device alone, i.e. independently, would have to deliver the high accuracy or resolution. Even in a case where the rotor position sensor fails during operation, it is possible to regulate the actuator temporarily based on the signal of the sensor device even if the resolution or accuracy of the device with respect to the angle of the rotor of the actuator is rather low. Conversely, it is also possible to compensate for a failure of the device for determining the position of the steering rod during operation by incrementally "counting" the signal of the rotor position sensor, in particular at least as long as an energization of the rotor position sensor and, if appropriate, an associated control device is ensured.In addition, a continuous monitoring of the signal of the rotor position sensor and of the signal of the sensor device for determining the position of the wrapping means can make it possible to detect implausible discrepancies in the signals, which can indicate, for example, a jump in the wrapping means and / or wear on the wrapping means. Thus, an beginning failure of the mechanism can be detected early.In other words, it can be said that the steering unit can generally determine a position determination of the steering rod, in particular the absolute position of the steering rod, substantially independently and with sufficiently high accuracy, resolution and reliability and output as an output signal.In particular, the steering unit can further comprise a tensioning element, for example a tensioning wheel, which is configured to pretension the wrapping means. Thereby, meshing between the toothed wrap and the toothed drive wheels can be improved, and a risk of skip can be reduced.According to one embodiment, the plurality of markings is designed as optically detectable markings and the sensor is designed as an optical sensor. As a result, the markings can be detected in particular contactless by the sensor, whereby wear of the wrapping means due to contact with the sensor can be avoided.The circumferential surface is in particular a back surface which is opposite the surface or the region of the wrapping means on which / the elements of the form-locking wrapping means forming a form fit, e.g. a toothed belt or a chain, are arranged or formed. The markings can be formed or arranged on the wrapping means, e.g. as colored markings, or on the wrapping means, e.g. as geometric, in particular raised, markings, or in the wrapping means, e.g. as vulcanized-in or woven-in markings. In particular, the markings on or on the wrapping means can be bonded or printed on or on the wrapping means.According to one embodiment, the markings are arranged on an outer circumferential surface of the wrapping means facing away from the circumferential surface of the drive wheels and / or the markings are arranged on an inner circumferential surface of the wrapping means facing the circumferential surface of the drive wheels. In particular with the markings on the outer circumferential surface of the wrapping means, it is possible to arrange the sensor of the sensor device outside the wrapping means. As a result, the positioning of the sensor relative to the wrapping means can be selected more freely than within the wrapping means. For markings arranged on the inner circumferential surface, it is in particular conceivable to use the toothing geometry as geometric markings. In addition, it is conceivable to provide the toothing geometry, additionally or alternatively, with colored markings.According to one embodiment, the sensor of the sensor device is configured to detect the markings in a region of the wrapping means between the first drive wheel and the second drive wheel, in particular in a region of an empty and / or pull strand. Since the wrapping means extends substantially straight in this region, the detection of the markings by the sensor in this region is simplified.According to one specific embodiment, the sensor of the sensor device is configured to detect the markings in the region of the first drive wheel or of the second drive wheel. In the region of the drive wheels, due to the toothed engagement between the wrapping means and the drive wheels, a vibration of the wrapping means is significantly reduced compared to the region in the free / tension strand. In addition, sagging of the wrapping means can be avoided in the area of the drive wheels. Measurement errors due to oscillations and / or sagging of the wrapping means can thus be reduced or prevented. In particular, the sensor can be arranged in the region of the second drive wheel, since the second drive wheel is generally larger than the first drive wheel and thus a larger wrap angle is present here and more teeth are engaged, as a result of which the risk of the wrap means jumping over on the second drive wheel is lower.According to one embodiment, the markings are designed as colored markings or as geometric markings. In particular, the markings can be formed from a diffusely reflecting material. Furthermore, in particular, the markings can have a color which is high in contrast to the wrapping means, for example white, if the wrapping means is dark, for example black.According to one embodiment, the plurality of markings are of different sizes and / or distances between mutually adjacent markings are of different design, in particular different from one another. In particular in the case where a plurality of measurement tracks are present which are arranged next to one another, the markings can be embodied as binary coding or the like. In addition, it is also conceivable to provide further information in one or more measurement tracks via a barcode-like coding of the markings, e.g. define a zero point as a special marking etc.According to one embodiment, the plurality of markings is arranged on the winding means forming a measurement track or forming a plurality of measurement tracks, wherein the plurality of measurement tracks have markings which are different from one another and / or the markings which respectively form a measurement track are arranged on the same circumferential surface of the winding means. In particular with a plurality of measurement tracks, it is sufficient here, by the combination of the sensor unit with the position sensor, to determine the rotational position of the actuator to determine the position of the winding means exactly to, for example, 50 mm. Digital / discrete / binary sensors can also be used for this purpose. For example, for a wrapping means about 400 mm long, it is sufficient to use four binary-coded measurement tracks in order to achieve the required accuracy.According to one embodiment, the sensor device comprises an optical sensor which has at least one light source and one light sensor. The light source can be a visible light source or an infrared light source, or an ultraviolet light source, and the light sensor is configured-corresponding to the light source-to detect visible light or infrared light or ultraviolet light. In particular, the optical sensor is at least partially designed as a light barrier, for example a reflected light barrier.According to one embodiment, the sensor unit for determining the position of the steering rod is configured to determine the position of the steering rod on the basis of the position of the wrapping means detected by the sensor device and the rotational position of the actuator detected by the position sensor. It can thus be said that the determination of the position of the steering rod, in particular the absolute position of the steering rod, takes place with the aid of the Nonius / Vernier principle. This means that the sensor device for determining the position of the wrapping means is not designed for determining the absolute position of the wrapping means, but rather such that it covers only a small, in particular high-resolution, measurement range on the wrapping means, which periodically repeats over an entire wrapping path which is coupled to the entire travel path of the steering rod. The period length is to be selected in particular such that it differs only slightly from that of the rotor position sensor and the difference or phase shift between the signals allows a clear determination of the position, in particular the absolute position, of the steering rod at any time. As a result, the requirements with respect to the detection accuracy of the sensor unit, in particular of the sensor device, can be reduced, since a significantly smaller measurement range has to be covered, but instead it is arranged in a row several times.Detailed Description with DrawingsFurther measures which improve the invention are described in more detail below together with the description of preferred exemplary embodiments of the invention on the basis of the figures. It shows: FIG. 1 shows schematic representations of a steering unit according to an embodiment of the invention in a side view (a) and a top view (b), and FIG. 2 shows schematic representations of a steering unit according to an embodiment of the invention in a side view (a) and a top view (b).The figures are merely schematic in nature and serve only to understand the invention. The same elements are provided with the same reference numerals.FIGS. 1 and 2 show a detail, schematic and exemplary of a steering unit 1 for a vehicle according to various embodiments of the invention. The steering unit 1 according to both exemplary embodiments shown is designed in particular as a steer-by-wire steering unit and has a steering rod 2, a control actuator 3, a conversion transmission unit 4, a sensor unit 5 for determining the position of the steering rod 2. The conversion transmission unit 4 couples the actuating actuator 3 and the steering rod 2 in such a way that a rotational movement of the actuating actuator 3 brings about a translatory movement of the steering rod 2 along its longitudinal axis L.The actuator 3 is designed as an electric motor 6. The transmission unit 4 comprises a belt transmission 7 and a linear transmission 8, the belt transmission 7 has a first drive wheel 9 with a first diameter, a second drive wheel 10 with a second diameter and a belt means 11, wherein the second diameter of the second drive wheel 10 is greater than the first diameter of the first drive wheel 9, the first drive wheel 9 is coupled in a torque-transmitting manner to the actuator 3 and the second drive wheel 10 is coupled in a load-transmitting manner to the linear transmission 8, which is arranged on the steering rod 2. The winding means 11 is arranged in each case on a circumferential surface of the first drive wheel 9 and of the second drive wheel 10 and is configured to transmit a rotational movement of the first drive wheel 9 to the second drive wheel 10 or to transmit or translate a torque of the first drive wheel 9 to the second drive wheel 10. The wrapping means 11 is designed in particular as a toothed belt, as a chain, etc., which is positively engaged with a corresponding counter toothing on the drive wheels 9, 10. The tooth arrangements of the wrapping means 11 and of the drive wheels 9, 10 are not shown because of the simple schematic representations.The sensor unit 5 for determining the position of the steering rod 2 has a sensor device 12 for determining the position of the wrapping means 11 and a position sensor (not shown) for detecting a rotational position of the actuator 3. The position sensor (not shown) is in particular designed as a rotor position sensor for detecting a rotation angle of the rotor of the electric motor 6. The sensor unit 5 is configured to combine a signal of the sensor device 12 which corresponds to the position of the wrapping means 11 detected by the sensor device 12 and a signal of the position sensor which corresponds to the rotational position of the actuator 3 detected by the position sensor, in order to determine the position, in particular the absolute position of the steering rod 2.FIGS. 1 and 2 each show embodiments of the steering unit 1, in which the sensor device 12 for determining the position of the wrapping means 11 comprises a plurality of markings 13 (see view (b) in each case) and a sensor 14, wherein the markings 13 are arranged on an outer circumferential surface of the wrapping means 11, here at regular, predetermined distances from one another. The sensor 14 is configured to detect the plurality of markings 13 and is configured as an optical sensor. Thus, the embodiments shown in FIGS. 1 and 2 allow contactless detection of the markings 13 and thus contactless position determination of the wrapping means 11, whereby wear on the wrapping means 11 can be reduced.The embodiment shown in FIG. 1 differs from the embodiment shown in FIG. 2 only in the position of the sensor 14 of the sensor device 12, wherein the sensor 14 according to the embodiment shown in FIG. 1 is arranged in a region between the first drive wheel 9 and the second drive wheel 10, i.e. in a region of a so-called empty or pull strand (depending on the direction of rotation of the actuating actuator 3) of the wrapping means 11. In the embodiment shown in FIG. 2, the sensor 14 is arranged in the region of the second drive wheel 10.The embodiment shown in FIG. 1 makes it possible to also arrange the sensor 14 within the wrapping means 11 and to provide the markings 13 on an inner circumferential surface of the wrapping means 11.In the embodiment shown in FIG. 2, measurement inaccuracies or measurement errors due to oscillations and / or sagging of the wrapping means 11, as can occur in the region of the empty / pull strand, are avoided, since the wrapping means 11 is positively engaged with the second drive wheel 10 here. Alternatively, it is also conceivable to arrange the sensor 14 in the region of the first drive wheel 9, since here too hardly any oscillations and / or sagging of the wrapping means 11 occur. However, as also shown here by way of example, the second drive wheel 10 is generally larger than the first drive wheel 9, as a result of which a larger wrap angle is present here and more teeth are engaged. As a result, a risk of the wrapping means 11 jumping over on the second drive wheel 10 is significantly lower than on the first drive wheel 9.List of reference characters1 Steering unit 2 Steering rod 3 Actuator 4 Conversion transmission unit 5 Sensor unit for determining the position of the steering rod 6 Electric motor 7 Belt transmission 8 Linear transmission 9 First drive wheel 10 Second drive wheel 11 Belt means 12 Sensor device for determining the position of the belt means 13 Markings 14 Sensor L Longitudinal axis P 1 Arrow P 2 ArrowReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedWO 2018 / 073267 A1

[0002] DE 11 2020 002 949 T5

[0002] DE 10 2021 212 470 A1

[0002]

Claims

Steering unit (1), in particular a steer-by-wire steering unit, for a vehicle, having: a steering rod (2) which is configured to be coupled at each of its axial ends to a wheel of the vehicle, an actuating actuator (3) which is coupled to the steering rod (2) via a conversion transmission unit (4) in such a way that a rotational movement of the actuating actuator (3) brings about a translational movement of the steering rod (2), wherein the conversion transmission unit (4) comprises a belt transmission (7) and a linear transmission (8), wherein the belt transmission (7) has a first drive wheel (9) having a first diameter, a second drive wheel (10) having a second diameter and a belt transmission means (11), wherein the first drive wheel (9) is coupled to the actuator (3) in a torque-transmitting manner and the second drive wheel (10) is coupled to the linear transmission (8) in a load-transmitting manner, and the belt means (11) is arranged in each case on a circumferential surface of the first drive wheel (9) and of the second drive wheel (10), and is configured to transmit a rotational movement of the first drive wheel (9) to the second drive wheel (10), and a sensor unit (5) for determining the position of the steering rod (2), having: a sensor device (12) for determining the position of the belt means (11), which sensor device comprises a plurality of markings (13) and a sensor (14), wherein the markings (13) are arranged on a circumferential surface of the belt means (11), and wherein the sensor (14) is configured to detect the plurality of markings (13), and a position sensor for detecting a rotational position of the actuator (3).Steering unit (1) according to Claim 1, wherein the plurality of markings (13) are designed as optically detectable markings, and the sensor (14) is designed as an optical sensor.Steering unit (1) according to Claim 1 or 2, wherein the sensor (14) of the sensor device (12) is configured to detect the markings (13) in a region of the wrapping means (11) between the first drive wheel (9) and the second drive wheel (10).Steering unit (1) according to Claim 1 or 2, wherein the sensor (14) of the sensor device (12) is configured to detect the markings (13) in a region of the first drive wheel (9) or of the second drive wheel (10).Steering unit (1) according to one of Claims 1 to 4, wherein the plurality of markings (13) are of different sizes and / or distances between adjacent markings (13) are of different sizes.Steering unit (1) according to one of Claims 1 to 5, wherein the plurality of markings (13) are arranged on the winding means (11) forming a measurement track or forming a plurality of measurement tracks, and / or wherein the plurality of measurement tracks have markings (13) which are different from one another and / or the markings (13) which respectively form a measurement track are arranged on the same circumferential surface of the winding means (11).The steering unit (1) according to any one of claims 1 to 6, wherein the plurality of marks (13) are disposed on an outer circumferential surface of the winding means (11).The steering unit (1) according to any one of claims 1 to 6, wherein the plurality of marks (13) are disposed on an inner circumferential surface of the winding means (11).Steering unit (1) according to one of Claims 2 to 8, wherein the optical sensor has at least one light source and one light sensor.Steering unit (1) according to one of Claims 1 to 9, wherein the sensor unit (5) for determining the position of the steering rod (2) is configured to determine the position of the steering rod (2) on the basis of the position of the belt means (11) detected by the sensor device (12) and the rotational position of the actuator (3) detected by the position sensor.

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