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 configured to be coupled at its axial ends to a wheel of a vehicle, a control actuator which is coupled to the steering rod (2) such that a rotational movement of the control actuator causes a translational movement of the steering rod (2), and at least one first sensor unit (3) for determining the position of the steering rod (2), comprising a measuring body (6) arranged on the steering rod (2), and a sensor device (5) comprising a cavity which extends in the axial direction (A) of the sensor device (5) along an entire axial length of the sensor device (5), wherein the sensor device (5) is configured to be attachable to a body-mounted component (4),wherein the measuring body (6) is arranged at least partially within the cavity of the sensor device (5) such that the measuring body (6) is displaceable in the axial direction (A) relative to the sensor device (5) by the translational movement of the handlebar (2), and wherein the sensor device (5) is configured to detect a position of the measuring body (6) relative to the sensor device (5).

Description

The present invention relates to a steering unit, in particular a steer-by-wire steering unit, for a vehicle.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 at least one first sensor unit. The steering rod is configured to be coupled at its axial ends to a wheel of a vehicle, respectively. The actuator is coupled to the steering rod in such a way that a rotational movement of the actuator causes a translatory movement of the steering rod along its longitudinal axis. The first sensor unit for determining the position of the steering rod has a measuring body and a sensor device. The measuring body is arranged on the steering rod. The sensor device has a cavity which extends through the sensor device in the axial direction of the sensor device along the entire axial length of the sensor device. The sensor device is configured to be attachable to a body-mounted component, e.g. housing of the steering rod. The measuring body is arranged at least partially within the cavity of the sensor device in such a way that the measuring body is displaceable in the axial direction relative to the sensor device by the translation movement of the steering rod. The sensor device is configured to detect an axial position of the measuring body relative to the sensor device.The advantage of the solution according to the invention lies in particular in the fact that the position determination is based on a direct detection or measurement of the steering rod movement along its longitudinal axis, a so-called linear movement. Direct means that the transformations of the linear path are avoided, whereby measurement inaccuracies due to tolerances, in particular a stringing together of several tolerances, can be avoided. Further, the steering unit may determine a position of the steering rod absolutely. This means that the determination of the position of the steering rod, in particular the absolute position of the steering rod, is possible at any point in time from the measurement signal.Since the sensing body is disposed on the handlebar, the sensing body contributes to each movement of the handlebar, and the sensor device detects the movement of the handlebar by detecting the sensing body moving in the axial direction relative to the sensor device. It can thus be said that the sensor unit uses an axis-parallel acting sensor, such as a linear-variable differential transformer (LVDT). The measuring body can be designed in particular cylindrically or conically. A conical measuring body makes it possible to make the sensor device shorter than the actual measuring path, because the cavity filling within the sensor device changes over the measuring path due to the measuring body moving relative thereto within the sensor device.Thus, the sensor unit for determining the position of the steering rod, in particular the absolute position of the steering rod, generally operates independently and can determine the position of the steering rod substantially alone with sufficiently high accuracy, resolution and reliability and output it as an output signal.In addition, however, it is also possible to combine the output signal of the sensor unit for determining the position of the steering rod with a further signal, in particular the signal of a rotor position sensor from the actuator. The rotor position sensor generally supplies 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 sensor unit described above, an accurate position determination of the steering rod, in particular the absolute position of the steering rod, is now possible, wherein the sensor unit in this case only has to have a low resolution or accuracy, since the sensor unit only has to perform a rough determination of the position determination of the steering rod, while the rotor position sensor supplies the high resolution or accuracy, so to speak the decimal point points. Such a combination may make it possible to further improve the resolution and the accuracy.Thus, the costs for the sensor unit for determining the position of the steering rod, and thus for the steering unit, can be reduced, since the requirements placed on the sensor unit are lower than in a case in which the sensor unit alone, i.e. independently, must provide 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 unit 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 sensor unit 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 unit for determining the position of the steering rod can make it possible to detect implausible discrepancies in the signals, which can indicate, for example, a belt jump and / or wear on the belt. Thus, an beginning failure of the mechanism can be detected early.It is also conceivable to determine the position of the steering rod, in particular the absolute position of the steering rod, with the aid of the Nonius / Vernier principle. In this case, it is conceivable not to configure the sensor unit for position determination for determining the absolute position of the steering rod, but rather such that it covers only a small, in particular high-resolution, measurement range on the steering rod, which measurement range is repeated periodically over 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. Inductive sensor devices are particularly suitable for this purpose.In particular, the sensor unit can be used to initially determine an absolute position, for example when the vehicle is started. During vehicle operation, the rotor position sensor could serve to determine the position of the steering rod and the sensor unit could serve here as a fall-back plane.According to one embodiment, the sensor device of the first sensor unit is configured to detect the relative axial movement of the measuring body of the first sensor unit electrically, inductively or magnetically. In particular inductive measuring methods make it possible for the measuring body to extend only over a partial region of the entire travel path of the steering rod, and for the position, in particular the absolute position, of the steering rod to be determined over the entire travel path of the steering rod.According to one embodiment, the sensor device of the first sensor unit is arranged in a housing of the steering rod. For this purpose, the housing can have, for example, a bulge which hardly influences, or does not adversely affect, a rigidity of the housing.According to one embodiment, the sensor device of the first sensor unit is designed as a hollow cylinder and the measuring body of the first sensor unit is designed as a plunger rod, wherein the plunger rod is guided in the hollow cylinder so as to slide in the axial direction. The sensor unit embodied in this way is suitable in particular for arrangement between a pressure piece and a pressure roller, which together form a bearing unit for the radial bearing of the steering rod. Here, the plunger rod can, as it were, penetrate between the pressure piece and the pressure roller during a movement of the steering rod, so that the measuring body does not require any additional installation space. In addition, the plunger rod can also penetrate together with the steering rod into a bellows space which is usually configured to enclose a region of the coupling points at the axial ends of the steering rod. In addition, in such an embodiment, it is also possible to mount two sensor units which are independent of one another on both sides of the pressure piece in order to create redundancy and thus improve reliability.Alternatively, it is also possible to arrange the sensor unit in the region of the pressure piece or the pressure roller. In such a case, the pressure piece or the pressure roller must have a recess in order to allow the measurement body to penetrate.According to one embodiment, the plunger rod is fastened or arranged on the steering rod by means of an elastic connection. As a result, it is possible to avoid stress and corruption of the measurement signal in the event of non-axial displacement of the steering rod. In particular, the plunger rod is arranged fixedly in the axial direction, elastically on the steering rod in other directions, in particular in the radial direction.According to one embodiment, the sensor device of the first sensor unit has a coil with inductance, wherein the plunger rod contains a ferromagnetic material for changing the inductance of the coil. The inductance of the coil changes by the change in the material located in the coil, in particular the plunger rod. The higher the proportion of ferromagnetic material arranged within the coil, the higher the inductance. Therefore, the plunger rod has in particular a mass of ferromagnetic material that varies over its length, so that the inductance of the coil is dependent on the position of the plunger rod, and thus on the position of the steering rod. The installation space for such a sensor unit can be reduced in particular in the axial direction. In other words, it can be said that the sensor device of the first sensor unit has a coil, in particular a coil arrangement, with magnetic coupling, wherein the plunger rod contains a ferromagnetic material for changing the magnetic coupling of the coil, in particular of the coil arrangement.According to one embodiment, the sensor device of the first sensor unit is of ring-like design and arranged coaxially around the steering rod, wherein the sensor device has at least one coil. In addition, the sensor device of the first sensor unit, in particular the at least one coil, can be introduced directly into the housing of the steering rod, as a result of which an installation space required for the sensor device can be reduced.According to one embodiment, the measuring body of the first sensor unit has a variable cross section. This makes it possible to make the sensor unit required for detecting the position of the steering rod shorter, in particular shorter than the measurement distance usually required for the entire travel path of the steering rod.According to one embodiment, the measuring body of the first sensor unit is integrally formed integrally with the handlebar. In other words, it can be said that the steering rod itself is the measuring body. This makes it possible to dispense with the provision of a separate measurement body.According to one embodiment, the measuring body is designed as a conical bore which is designed or arranged substantially concentrically with respect to the steering rod, penetrating the steering rod at least in sections. Alternatively, the steering rod is formed at least in sections as hollow cylindrical, and the measuring body is formed as a cone or wedge which is arranged within the hollow cylindrical steering rod, substantially concentrically thereto. As a result, the steering rod has a cross section that is non-constant over its length or a non-constant mass of ferromagnetic material, wherein the steering rod itself has the ferromagnetic material and / or the measuring body shaped as a cone or wedge has the ferromagnetic material. This makes it possible to arrange a short sensor coil as a sensor device concentrically around the steering rod, in particular as close as possible to the pressure piece. Due to the non-constant mass of ferromagnetic material, a different inductance can be measured at the sensor coil depending on the position of the steering rod.The short-circuit coil requires only a small additional installation space. In particular, the sensor device, combined with such a measuring body, does not have to extend over the entire length of the travel path, which further simplifies the assembly of the sensor device and further reduces the installation space.According to one specific embodiment, the first sensor unit is configured to determine an absolute position of the steering rod relative to the sensor device on the basis of the position of the measuring body, in particular the axial position, detected by the sensor device. This is particularly required in situations where the vehicle is started after it has been previously turned off.According to one specific embodiment, the steering unit also has a position sensor device for detecting a rotational position of the actuator. The position determination of the steering rod based on a combination of the measurement signals of the sensor unit and the position sensor device enables a more inaccurate measurement by the sensor unit, whereby simpler, i.e. less complex, and thus more cost-effective sensors can be used without having a loss of accuracy in the position determination of the steering rod.According to one embodiment, the steering unit further comprises a second sensor unit for determining the position of the steering rod. The second sensor unit has a measuring body which is arranged on the steering rod, and a sensor device having a cavity which extends through the sensor device in the axial direction of the sensor device along the entire axial length of the sensor device. The sensor device is configured to be attachable to a body-mounted component, e.g. housing of the steering rod. The measuring body is arranged at least partially within the cavity of the sensor device in such a way that the measuring body is displaceable in the axial direction relative to the sensor device by the translation movement of the steering rod, and wherein the sensor device is configured to detect the relative axial movement of the measuring body.In particular, the second sensor unit may have all the features described above with respect to the first sensor unit.The use of two of the more sensor units makes it possible to consider the respective measurement signals in a combined manner and to carry out the position determination of the steering rod, for example on the basis of averaging of the individual measurement signals. In particular, geometric averaging can serve to filter, for example, unwanted movements of the steering rod, e.g. torsion and / or bending. Depending on where and how the sensor devices are arranged, other processing of the signals may be meaningful.In addition, a plurality of sensors can be used to subdivide the entire linear measurement path into segments. In this case, in particular a plurality of secondary coils can be used to reduce a resolution of A / D converters. As a result, more cost-effective A / D converters can be used.According to one embodiment, the measuring body of the first sensor unit and the measuring body of the second sensor unit are integrally formed in one piece.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 a schematic illustration of a section of a steering unit according to one embodiment of the invention in a side view, FIG. 2 shows a schematic illustration of a steering unit according to an embodiment of the invention in a front view, FIG. 3 shows a schematic illustration of a steering unit according to an embodiment of the invention in a front view, FIG. 4 shows a schematic illustration of a detail of the steering unit according to an embodiment of the invention in a side view, and FIG. 5 shows a schematic illustration of a section of a steering unit according to an embodiment of the invention in a side view.The figures are merely schematic in nature and serve only to understand the invention. The same elements are provided with the same reference numerals.FIG. 1 shows schematically and by way of example a subsection of a steering unit 1 according to an embodiment of the invention in a longitudinal sectional view. The steering unit 1 has a steering rod 2, an actuator (not shown here) and a sensor unit 3. The steering rod 2 is accommodated in a housing 4 so as to be displaceable in the axial direction A along its longitudinal axis L. The sensor unit 3 comprises a sensor device 5, which is arranged fixed to the body, and a measuring body 6, which is arranged on the steering rod 2 and together with the steering rod 2 so as to be displaceable in the axial direction relative to the sensor device 5.The sensor device 5 is here designed, for example, as a hollow cylinder 7, which is fixedly arranged on the housing 4. The measuring body 6 is here exemplarily designed as a plunger rod 8 which is accommodated and guided in the hollow cylinder 7 so as to be axially movable. The plunger rod 8 comprises a ferromagnetic material, for example. Iron or steel, for example, contains:. The hollow cylinder 7 here has, by way of example, in particular at least one primary coil (not visible) and two secondary coils (not visible), the magnetic coupling of which changes in accordance with the position of the plunger rod 8 in the axial direction A relative to the hollow cylinder 7. Since the position of the plunger rod 8 in the axial direction A is directly related to the position of the steering rod 2 in the axial direction A, the position of the steering rod 2 can be determined based on the position of the plunger rod 8. The plunger rod 8 is connected to the steering rod 2 in an axially fixed manner via at least one coupling element 9, but elastically in all other directions, in particular in the radial direction R.The steering unit 1 further comprises a bearing unit 10 for radially bearing the steering rod 2. The bearing unit 10 is accommodated in the housing and here comprises, for example, a pressure piece 11 and a pressure roller 12 which are arranged opposite one another, guiding the steering rod 2 between them movably in the axial direction A. Here, the pressure piece 11 and the pressure roller 12 are arranged on the steering rod 2 in such a way that a free intermediate space is formed on both sides between the pressure piece 11 and the pressure roller 12, in which space either one sensor unit 3 (see FIG. 2 ) or two sensor units 3 (see FIG. 3 ) can be arranged. The intermediate space is sufficiently large that the plunger rod 8 can submerge between the pressure piece 11 and the pressure roller 12 during a movement of the steering rod along its longitudinal axis L. In order to accommodate the hollow cylinder or cylinders 7 in the housing 4, a bulge must (in each case) be provided in the housing 4, which bulge requires a little additional installation space, but does not adversely affect the rigidity of the housing 4.FIGS. 4 and 5 each schematically and exemplarily show an embodiment in which the measuring body 6 is provided in the handlebar 2.In the exemplary embodiment shown in FIG. 4, the steering rod 2 is also simultaneously the measuring body 6. The steering rod 2, which here is also configured simultaneously as a measuring body 6, is made of a ferromagnetic material, such as, for example. Iron or steel, and, as a result of the conical hollow bore 13, viewed over the axial length of the steering rod 2, has an unstable mass of ferromagnetic material or an unstable cross section. The sensor device 4 is designed as a short sensor coil 14 and is arranged concentrically around the steering rod 2 and as close as possible to the pressure piece 11 in the axial direction A. The non-constant cross section or the resulting non-constant mass of ferromagnetic material causes a position-dependent inductance at the sensor coil 14.In FIG. 5, the steering rod 2 has, at least in sections, a cylindrical bore 15, into which a conical or wedge-shaped measuring body 6, which is manufactured from a ferromagnetic material, e.g. iron or steel, is inserted. Due to the cone or wedge shape of the measuring body 6, the measuring body 6 has an unharmonic cross section and thus an unharmonic mass of ferromagnetic material as viewed over its axial length. As already shown in FIG. 4, the sensor device 4 is designed as a short-circuiting sensor coil 14 and is arranged concentrically around the steering rod 2 and as close as possible to the pressure piece 11 in the axial direction A. Analogously to the embodiment described in FIG. 4, the non-constant cross section or the resulting non-constant mass of ferromagnetic material of the measuring body 6 accommodated in the steering rod 2 brings about a position-dependent inductance at the sensor coil 14.List of reference characters1 Steering unit 2 steering rod 3 sensor unit 4 housing 5 sensor device 6 measuring body 7 hollow cylinder 8 plunger rod 9 coupling element 10 bearing unit 11 pressure piece 12 pressure roller 13 conical hollow bore 14 sensor coil 15 cylindrical bore A axial direction R radial direction L longitudinal axisReferences 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

[0003] DE 11 2020 002 949 T5

[0003] DE 10 2021 212 470 A1

[0003]

Claims

Steering unit (1), in particular steer-by-wire steering unit, for a vehicle, having: a steering rod (2) which is configured to be coupled at its axial ends in each case to a wheel of a vehicle, an actuating actuator which is coupled to the steering rod (2) in such a way that a rotational movement of the actuating actuator brings about a translatory movement of the steering rod (2), and at least one first sensor unit (3) for determining the position of the steering rod (2), having a measurement body (6) which is arranged on the steering rod (2), and a sensor device (5) having a cavity which extends through the sensor device (5) in the axial direction (A) of the sensor device (5) along an entire axial length of the sensor device (5), wherein the sensor device (5) is configured to be able to be fastened to a component (4) which is fixed to the body, wherein the measuring body (6) is arranged at least partially within the cavity of the sensor device (5) such that the measuring body (6) is displaceable relative to the sensor device (5) in the axial direction (A) by the translation movement of the steering rod (2), and wherein the sensor device (5) is configured to detect a position of the measuring body (6) relative to the sensor device (5).Steering unit (1) according to Claim 1, wherein the sensor device (5) of the first sensor unit (3) is configured to record the relative axial movement of the measurement body (6) of the first sensor unit (3) electrically, inductively or magnetically.Steering unit (1) according to claim 1 or 2, wherein the sensor device (5) of the first sensor unit (3) is arranged in a housing (4) of the steering rod (2).Steering unit (1) according to one of Claims 1 to 3, wherein the sensor device (5) of the first sensor unit (3) is designed as a hollow cylinder (7) and the measuring body (6) of the first sensor unit (3) is designed as a plunger rod (8), wherein the plunger rod (8) is guided in the hollow cylinder (7) such that it slides in the axial direction (A).Steering unit (1) according to claim 4, wherein the plunger rod (8) is arranged on the steering rod (2) by means of an elastic connection (9).Steering unit (1) according to claim 4 or 5, wherein the sensor device (5) of the first sensor unit (3) has a coil with inductance, and wherein the plunger rod (8) contains a ferromagnetic material for changing the inductance of the coil.Steering unit (1) according to Claim 1 or 2, wherein the sensor device (5) of the first sensor unit (3) is of annular design and is arranged concentrically around the steering rod (2), and wherein the sensor unit (5) has a coil (14).Steering unit (1) according to claim 7, wherein the measuring body (6) of the first sensor unit (3) is integrally formed integrally with the steering rod (2) or is accommodated in the steering rod (2).Steering unit (1) according to Claim 8, wherein the measuring body (6) is formed as a conical bore (13) which is formed so as to penetrate the steering rod (2) at least in sections, substantially concentrically with respect to the steering rod (2), or wherein the steering rod (2) is formed so as to penetrate the steering rod at least in sections, in a hollow-cylindrical manner, and the measuring body (6) is formed as a cone or wedge which is arranged substantially concentrically within the hollow-cylindrical steering rod (2).Steering unit (1) according to one of Claims 1 to 9, further having a second sensor unit (3) for determining the position of the steering rod, having a measuring body (6) which is arranged on the steering rod (2), and a sensor device (5) having a cavity which extends through the sensor device (5) along an entire axial length of the sensor device (5) in the axial direction (A), wherein the sensor device (5) is configured to be able to be fastened to a component (4) fixed to the body, wherein the measuring body (6) is arranged at least partially within the cavity of the sensor device (5) in such a way that the measuring body (6) is guided displaceably relative to the sensor device (5) in the axial direction (A) by the translation movement of the steering rod (2), and wherein the sensor device (5) is configured to detect the relative axial movement of the measuring body (6).

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