STEERING SYSTEM FOR A MOTOR VEHICLE

Description

State of the art

[0001] The invention relates to a steering system for a motor vehicle with a steering shaft, a torsion bar and a rotation sensor having at least one sensor element, comprising a magnetic element attached to the steering shaft and rotatable therewith about an axis, and two flux conductors, and two stator elements which are arranged coaxially and fixed relative to the steering shaft, are axially spaced from one another and are operatively connected to the at least one sensor element via the two flux conductors, wherein a flux conductor each has a collecting section, a connecting section and a compensator section, wherein the collecting section is connected to a stator element and is connected to the compensator section via a connecting section, and wherein the sensor element is arranged between the two flux conductors, wherein the steering shaft comprises an upper steering shaft which is connected to a lower steering shaft via the torsion bar.

[0002] In a generic electromechanical power steering system or a steer-by-wire steering system of a motor vehicle, the rotation sensor is used to detect a manual steering command. The rotation sensor detects the rotation of a steering shaft caused by manual actuation of a steering handle, and additionally or alternatively, the manual steering torque applied to the steering shaft. This generates electrical control signals to actuate an electric steering drive, which causes the steered wheels to turn accordingly.

[0003] For detecting a rotational movement, rotation sensors with a magnetic sensor device are known, which can be designed as a torque sensor or rotation angle sensor, or as a combined torque and rotation angle sensor. One such rotation sensor is described, for example, in WO 2020 / 174170 A1. This comprises two stator elements and a magnet element, which is arranged to be rotatable relative to the stator elements and is designed such that it couples a magnetic flux into the stator elements that depends on the relative angular orientation. By measuring the magnetic flux coupled into the stator elements, the rotation of a component having the magnet relative to the stator elements can be determined. To implement a rotation angle sensor, it is possible to determine the angle of rotation of the steering shaft, which is rotatable relative to the stator elements and has a magnet, by non-rotatably fixing the stator elements.

[0004] A torque can be determined by the relative rotation of two steering shaft parts coupled via a torsionally elastic element, for example a torsion bar.

[0005] The two stator elements are ring-shaped and made of magnetically conductive material and surround the magnetic element coaxially to the axis of rotation. The stator elements have peripheral, circular disk-shaped connecting sections that are coupled to a magnetoelectric sensor element via magnetic flux conductors, thus creating a magnetic connection. The sensor element, for example, comprises a Hall or magnetoresistive (GMR) sensor element, in which the magnetic flux introduced via the flux conductors is converted into an electrical signal.

[0006] The flux guides each have a collecting section that extends over a collecting surface and is connected to the connection section of a stator element. The flux guides each have at least one coupling surface and are shaped and configured such that the coupling surfaces of the two flux guides face each other on either side of an air gap. At least one sensor element is arranged between the coupling surfaces. The angle-dependent magnetic field generated by the magnetic element, referred to below as the measuring field, couples magnetic flux, the measuring flux, into the stator elements and guides it via the flux guides to the sensor element.

[0007] The measurement can be impaired by external magnetic interference fields, which are also coupled into the stator element from the outside and generate a magnetic interference flux that superimposes the measuring flux. To counteract such interference, the prior art proposes that the flux guides have at least one compensator section that is magnetically connected to the collecting section via a connecting section and is spaced apart from the stator elements. As a result, essentially only the interference field is coupled into the compensator section. The interference flux generated therein is superimposed with the opposite sign on the measuring flux coupled into the collecting section and superimposed by the interference flux, for example by an axially swapped arrangement of the collecting and compensator sections, in which the compensator section of one flux guide is arranged axially in the region of the collecting section of the other flux guide, and vice versa.

[0008] A steering column with a similar design is also known from FR 3 093 181 A1.

[0009] Steering columns with the features mentioned above are known from EP 3 961 174 A1 and US 2018 / 118259 A1.

[0010] Although conventional rotary sensors generally allow the measurement of rotary movements even under interference, the required high reliability under specific operating conditions and the stringent safety requirements of motor vehicle steering systems cannot be guaranteed in some cases.

[0011] In view of the problems explained above, it is an object of the present invention to enable improved and more robust detection of steering inputs in a steering system for a motor vehicle. Description of the invention

[0012] This object is achieved according to the invention by the steering system having the features of claim 1. Advantageous further developments emerge from the subclaims.

[0013] In a steering system for a motor vehicle with a steering shaft, a torsion bar and a rotation sensor having at least one sensor element, comprising a magnetic element attached to the steering shaft and rotatable therewith about an axis, and two flux conductors, and two stator elements arranged coaxially relative to the steering shaft, axially spaced from one another, which are operatively connected to the at least one sensor element via the two flux conductors, wherein a flux conductor each has a collecting section, a connecting section and a compensator section, wherein the collecting section is connected to a stator element and via a connecting section to the compensator section, and wherein the sensor element is arranged between the two flux conductors, wherein the steering shaft comprises an upper steering shaft which is connected to a lower steering shaft via the torsion bar, the invention providesthat an anti-twist device arranged on the upper steering shaft is engaged with an anti-twist device arranged on the lower steering shaft to limit twisting of the torsion bar in itself, wherein the anti-twist device comprises a ferromagnetic material, and the compensator section has a compensator area that is smaller than a collecting area of ​​the collecting section, wherein the area ratio of the collecting area and the compensator area is between 1.5 and 2, or between 1.5 and 1.75, or 1.75.

[0014] The anti-rotation device according to the invention creates a local accumulation of ferromagnetic material in the steering system, which influences the magnetic interference flux resulting from external magnetic interference fields through flux deflection. Gears arranged to one side of the rotation sensor can also influence the magnetic interference flux resulting from external magnetic interference fields through flux deflection. However, the solutions proposed according to the invention make it possible to achieve a significant improvement in the detection of steering inputs for such steering systems.

[0015] The causal relationships of the area ratios underlying the invention have not been recognized or addressed in the prior art, and consequently, the resulting specific problems when using a magnetic rotation sensor in a motor vehicle steering system could not be solved. Accordingly, the size ratios proposed by the invention represent a favorable representation for installation in a motor vehicle steering system.

[0016] Furthermore, it can preferably be stated that in a steering system for a motor vehicle with a rotation sensor, comprising a magnet attached to a steering shaft and rotatable therewith about an axis, and two stator elements arranged coaxially relative to the steering shaft, axially spaced from one another, which are operatively connected to at least one sensor element via two flux conductors, wherein a flux conductor has a collecting section, a connecting section and a compensator section, wherein the collecting section is connected to a stator element and via a connecting section to the compensator section, and wherein the sensor element is arranged between the two flux conductors, it is provided according to the invention that the steering shaft comprises an upper steering shaft, which is connected to a lower steering shaft via a torsion bar,wherein an anti-rotation device arranged on the upper steering shaft is engaged with an anti-rotation device arranged on the lower steering shaft to limit twisting of the torsion bar in itself, and wherein the compensator section has a compensator area that is smaller than a collecting area of ​​the collecting section, a significant improvement in the accuracy of the robustness of the detection of the steering inputs can be achieved.

[0017] Furthermore, it can preferably be stated that in a steering system for a motor vehicle with a rotation sensor, comprising a magnet attached to a steering shaft and rotatable therewith about an axis, and two stator elements arranged coaxially relative to the steering shaft, axially spaced from one another, which are operatively connected to at least one sensor element via two flux conductors, wherein a flux conductor has a collecting section, a connecting section and a compensator section, wherein the collecting section is connected to a stator element and via a connecting section to the compensator section, and wherein the sensor element is arranged between the two flux conductors, it is provided according to the invention that the steering shaft comprises an upper steering shaft, which is connected to a lower steering shaft via a torsion bar,Wherein an anti-rotation device arranged on the upper steering shaft is engaged with an anti-rotation device arranged on the lower steering shaft to limit the twisting of the torsion bar within itself, and a gear is provided which is fixed to one of the two steering shafts and encloses the torsion bar rotationally symmetrically, wherein the compensator section has a compensator surface that is smaller than a collecting surface of the collecting section, a significant improvement in the accuracy and robustness of the detection of the steering inputs can be achieved. The gear is preferably coupled to an electric drive via a gear. The stator elements, which are annular in their basic shape, preferably have circular disk- or annular-shaped connecting sections extending flatly transversely to the axis.which are also synonymously referred to as connecting flanges. The connecting sections preferably have axial surfaces on their opposing inner sides and their mutually facing outer sides.

[0018] The preferably flat surface extension of a collecting section corresponds by definition to the collecting surface, and accordingly the preferably flat surface extension of a collecting section corresponds by definition to the compensator surface. Each collecting section is magnetically connected to one of these axial surfaces, wherein the collecting surface can make full or partial surface contact with an axial surface of a connecting section. The compensator sections are arranged radially outside the stator elements, and the compensator surfaces preferably extend outside the connecting sections. Preferably, the inner and outer sides of the connecting sections of the stator elements, the collecting surfaces and the compensator surfaces can be flat at least in sections and aligned transversely to the axis, i.e. have axial surfaces that are parallel to one another at least in some regions.

[0019] According to the invention, the surface area of ​​the compensator section is smaller relative to the surface area of ​​the collector section. This ensures that the portion of a magnetic interference field used to compensate for the measurement signal, which is detected by the compensator sections and is also referred to as the compensation flux, is kept at an optimal level. In particular, overcompensation, which could otherwise lead to a falsification of the measurement result, can be prevented. This results in the advantage of higher measurement accuracy for the angle of rotation measurement, which leads to greater operational reliability. This is particularly advantageous for a motor vehicle steering system, which is highly safety-relevant for its operation.

[0020] To calculate the area ratio, the magnitudes of the area projections in a given direction can be used, for example, the collector and compensator areas projected in the axial direction. This ensures that an external magnetic interference field penetrating the collector and interference areas can be better compensated.

[0021] According to the invention, the area ratio of the collecting area and the compensator area is between 1.5 and 2, or in a narrower range between 1.5 and 1.75.

[0022] It can be particularly advantageous if the area ratio of the collecting area to the compensator area is 1.75.

[0023] The optimized effect in the inventive ranges of the ratio, and in particular for the aforementioned concrete ratio, can be explained by the fact that external interference fields impinge unhindered on the externally exposed compensator surfaces, but the collecting surfaces are at least partially shielded against external interference fields by the stator elements or the connecting sections of the stator elements.

[0024] A further practical advantage is that the compensator sections protrude less far outwards beyond the stator elements, which means that less installation space is required within the steering column.

[0025] Preferably, the flux guides are formed as one-piece sheet metal parts. The sheet metal parts consist of a material with good magnetic conductivity, for example, an iron sheet with defined magnetic properties. Production can be carried out efficiently by pressing, punching, fine blanking, bending, embossing, or the like. The flux guide can thus have a substantially uniform material thickness throughout, which essentially corresponds to the sheet thickness. In a design with collector and compensator surfaces aligned transversely to the axis, the sheet thickness corresponds to the axial thickness of the collector and compensator sections.

[0026] A preferred value for the sheet thickness is between 0.6 mm and 1 mm, particularly preferably 0.8 mm.

[0027] An advantageous embodiment can be realized by having the flux guides between the compensator sections and the collecting sections cross in the region of the connecting sections, so that the compensator sections and the collecting sections are axially opposite one another. The axial positions are reversed. This means that the collecting section of one flux guide and the compensator section of the other flux guide are axially located on one side, and the collecting section of the other flux guide and the compensator section of one flux guide are axially opposite one another on the other side. This creates an arrangement that is mirror-symmetrical with respect to a mirror plane perpendicular to the axis. Viewed in the circumferential direction, the connecting lines between the collecting and compensating sections form an X-shaped configuration. This enables effective compensation of external magnetic interference.

[0028] It is advantageous that the compensator surfaces and the collecting surfaces of the flux guides are predominantly parallel to each other and to the connecting sections of the stator elements to which the collecting sections are connected. The connecting surfaces of the stator elements are preferably circular disk-shaped or annular with axial surfaces that are connected to corresponding axial sections of the collecting sections. "Predominantly" means that at least 75% of the compensator surfaces and the collecting surfaces are aligned parallel to each other.

[0029] Preferably, the collecting sections are mounted on axially opposite inner sides of the stator elements. This allows both flux conductors to be protected and accommodated axially between the connecting sections in a space-optimized manner, with the collecting sections contacting the inner axial end faces of the connecting sections.

[0030] An advantageous embodiment may be that the axial distance between the collecting sections is smaller than the axial distance between the compensator sections. The collecting sections are offset inward in the axial direction relative to the compensator sections. The fact that the collecting sections are connected to the inner sides of the connecting sections of the stator elements enables improved structural integration and a smaller installation space.

[0031] An optimized further development can provide for the compensator sections to be aligned flush with the connecting sections of the stator elements. This means that an axial plane extends through the compensator sections and the circular disk- or annular-shaped connecting sections; in other words, their cross-sections overlap in the radial direction. This can be achieved, for example, by connecting the collecting sections to the inner sides of the connecting sections and offsetting them axially inward relative to the compensator sections by the axial thickness of the connecting sections. This can result in advantages regarding a better compensation effect, particularly in the case of inhomogeneous interference fields.

[0032] To implement the aforementioned embodiment, the axial spacing of the collecting sections can be smaller than the axial spacing of the compensator sections. The axial spacing of the outer sides of the collecting sections corresponds to the spacing of the inner sides of the connecting sections of the stator elements.

[0033] It can be provided that the compensator sections are connected to coupling sections which have coupling surfaces facing the sensor element. These coupling sections can be designed as narrow, finger-like strips, which are therefore also referred to as flux fingers. The coupling sections protrude into the axial space between the flux guides so that the coupling surfaces, which are preferably aligned parallel to one another and to the compensator surfaces, lie axially opposite one another on either side of the sensor element. They can be in direct contact or magnetically coupled to the sensor element via a defined air gap. The coupling sections can be formed together with the connecting sections, with a connecting section having at least one coupling surface. Alternatively or additionally, flux fingers can be formed separately from the connecting sections.Preferably, at least one flux finger can extend from the compensator section, which is not directly connected to the collecting section and is spaced apart from the connecting section that connects this compensator section to the collecting section. In its projecting end region, a flux finger can have a coupling surface that faces a corresponding coupling surface on a flux finger or a connecting section of the other flux conductor. The arrangement and design of the coupling sections enables optimized superposition and compensation of interference fields.

[0034] It is possible to use one sensor element. It can also be advantageous to provide at least two sensor elements spaced apart from one another. Hall or magnetoresistive (GMR) sensors, for example, can be used as sensor elements. By duplicating or multiplying the sensors, the measured values ​​can be averaging and / or other metrological processing can be carried out. The reliability of the arrangement can also be increased in this way through redundancy. The sensor elements are preferably spatially spaced apart from one another and, for example, are spaced circumferentially with respect to the axis. This allows the interference fluxes coupled into the compensator sections to be measured with spatial resolution, enabling further improved compensation of interference fields.

[0035] An advantageous further development can provide for a compensator section to have an angled wing section. A wing section, also synonymously referred to as a winglet, forms a partial or edge section bent transversely to the flat, preferably axial compensator surface, which can, for example, extend essentially parallel to the axis and thus protrudes into the space between the connecting sections of the stator elements. A winglet can preferably be directed towards the other compensator section. The axial extent of a winglet is preferably smaller than the axial distance between the compensator sections. One advantage is that the area of ​​the compensator section active for detecting interference fields can be enlarged, even with regard to obliquely stray interference fields. This allows the compensation effect to be optimized.

[0036] It can advantageously be provided that the flux guides and the sensor element are arranged in a housing. A housing (sensor housing) can be made of plastic, for example, as an injection-molded part, and protects the components housed within it. In an advantageous development, it is possible for the housing to be filled with a potting compound. This can be poured as a liquid resin, which flows around the flux guides and the sensor element and hardens to form a solid block in which the flux guides and the sensor element are then firmly embedded in a material-locking and / or form-fitting manner. This permanently fixes a clear positioning, which is positive for long-term stable measurement accuracy.

[0037] It can be provided that a compensator section and / or a collecting section has a guide section. The guide section enables guidance and positioning in a housing or on another component of the rotary sensor, which has a corresponding guide element, for example a guide groove. A guide section can, for example, have a guide projection, a guide lug, guide rail, or the like projecting outward from the compensator section, which can be brought into positive guide engagement with a corresponding guide element, for example by being inserted into a guide groove. This allows for improved positioning and fixing of the flux guides, which is advantageous both for assembly and for operational reliability.

[0038] It can be provided that a compensator section and / or a collecting section and / or a stator element has a stop section. A stop section is designed and arranged such that it can be brought into mechanical stop with a corresponding counter-stop, so that simple and precise mechanical positioning relative to one another can take place. A stop section can, for example, have a projection or the like that can abut against a corresponding surface or edge. For example, a collecting section can have an axially projecting stop section that can abut against an outer edge of a connection section of a stator element in the radial direction during assembly. The collecting section is then already precisely positioned relative to the stator element, which simplifies production.

[0039] Preferably, a collecting section of one flux guide and a compensator section of the other can be radially spaced from one another, which has a ratio of between 0.5 and 2 to the radial width of the collecting section of the other flux guide. This allows for further optimization of the compensation effect. Preferably, the ratio can be between 0.75 and 1.5. More preferably, it can be between 0.75 and 1.25, and even more preferably between 0.8 and 1.2.

[0040] It may be particularly advantageous that the ratio of the aforementioned distance to the width is 1, so that the radial distance corresponds to the radial width of the collecting section.

[0041] It can be provided that the collecting section of one flux guide has an axial height difference to the compensator section of the other flux guide, which has a ratio of between 0.5 and 2 to the axial thickness of a collecting section. The axial thickness corresponds to the sheet thickness explained above. This simplifies the flush alignment of the compensator sections with the connecting sections of the stator elements described above. The ratio can preferably be 0.75 to 1.5, or more preferably between 0.75 to 1.25, or even more preferably between 0.8 to 1.2. This can enable improved flush alignment of the compensator section with the connecting section of the stator element.

[0042] It may be particularly advantageous for the aforementioned axial height difference to be equal to the axial thickness, which corresponds to a ratio of 1.

[0043] It is advantageously possible for the collecting section of one flux guide to have an axial height difference from the compensator section of the same flux guide, which has a ratio of between 0.75 and 2.2 to the axial height difference between the connecting sections of the two flux guides. The axial distance of the connecting sections is measured in the axial direction between the sides to which the collecting sections are attached, for example, the aforementioned inner sides. The ratio can preferably be between 0.85 and 1.2, or more preferably between 0.9 and 1.15.

[0044] It may be particularly advantageous if the aforementioned axial height difference has a value of 1.125.

[0045] Preferably, the two flux guides in the region in which the sensor element is arranged have an axial height distance in the range of 1.8 to 2.2 times the axial thickness of the flux guides. The height distance refers to the air gap between the flux guides, whose axial thickness corresponds to the sheet thickness explained above.

[0046] It is advantageous for the axial height distance between the flux guides and the sensor element to be smaller than the axial thickness of the flux guides. This height distance refers to the air gap that exists between the sensor element and the aforementioned coupling surfaces, and should be as small as possible to ensure efficient transmission of the magnetic flux. The sheet thickness is used as the axial thickness. It is advantageous for the height distance to correspond to 0.6 to 1 times the sheet thickness, particularly preferably to 1 times the sheet thickness.

[0047] The axial distance between the connecting sections of the stator elements can be between 10 and 30 times the axial thickness of the flux guides, which corresponds to the above-mentioned sheet thickness, which can be, for example, 0.8 mm. Preferably, the distance can be 12 to 25 times, particularly preferably 12 to 15 times.

[0048] It may be particularly advantageous if the aforementioned axial distance corresponds to 15 times the sheet thickness.

[0049] The aforementioned angled winglet section can preferably protrude from the compensation surface by 2 to 7 times the axial thickness (sheet thickness) of the compensation section. Preferably, the axial height of the winglets can correspond to between 2.5 and 5 times the sheet thickness, particularly preferably 2.7 to 3.3 times.

[0050] It can be particularly advantageous for a winglet to protrude from the compensator section by 3.3 times the sheet thickness. Description of the drawings

[0051] Advantageous embodiments of the invention are explained in more detail below with reference to the drawings. In detail: Figure 1 shows a motor vehicle steering system in a schematic perspective view, Figure 2 shows an enlarged detailed view of the rotation sensor (=the sensor device) of the steering system according to Figure 1 in a free-standing schematic view, Figure 3 an enlarged detailed view of the rotation sensor according to Figure 2 , Figure 4 the stator elements and the flux guides isolated in a schematic perspective view, Figure 5 the flux guides according to Figure 4 isolated and enlarged in a schematic perspective view, Figure 6 a partial radial section through a rotary sensor according to Figure 2 or 3 (in a circumferential view), Figure 7 the flux conductors according to Figure 5 in an axial view, Figure 8 a sectional view similar Figure 6in an enlarged view, Figure 9 the flux guides in an alternative design isolated and enlarged in a schematic perspective view analogous Figure 5 , Figure 10 a rotary sensor in a second embodiment comprising flux guides according to Figure 9 , in a view analogous Figure 6 , Figure 11 the stator elements and the flux conductors of a rotary sensor according to Figures 9 or 10 isolated in a schematic perspective view analogous to Figure 4 , Figure 12 the stator elements and the flux conductors of a rotary sensor in a third embodiment, isolated in a schematic perspective view analogous to Figure 4 , Figure 13 an enlarged radial view from the outside of the rotation sensor according to Figure 12, Figure 14 inner strand of a steering system according to the invention with rotation sensor in an exploded view; Figure 14a representation of a section of a steering shaft part from Figure 14with anti-twist device; Figure 15 inner strand of a steering system according to the invention with rotation sensor in an exploded view in a further embodiment; Figure 15a representation of a section of a steering shaft part from Figure 15 with anti-twist device; Figure 16Representation from Figure 6 with illustration of the river deflection. Embodiments of the invention

[0052] In the various figures, identical parts are always provided with the same reference symbols and are therefore usually named or mentioned only once.

[0053] In Figure 1 A motor vehicle steering system 1 designed as an electromechanical power steering system is schematically shown. This system has a steering column 2 with a support unit 21 that can be attached to a motor vehicle body (not shown).

[0054] In the steering column 2, a first, upper steering shaft part 10 of a steering shaft is rotatably mounted about a longitudinal axis L. At the rear end with respect to the direction of travel, a steering wheel 12 is non-rotatably attached to the steering shaft part 10, via which a driver can introduce a steering torque (manual torque) as a steering command into the upper steering shaft part 10.

[0055] The upper steering shaft part 10 is connected to a second, lower steering shaft part 11 via a torsionally elastic torsion bar (not shown here).

[0056] The steering torque is transmitted via the steering shaft parts 10 and 11 via intermediate universal joints 13 to a steering pinion 14, which engages a longitudinally displaceable rack 15. This converts a rotation of the steering shaft 10 during a steering intervention into a displacement of tie rods 16, as indicated by the double arrow, which transmit the specified steering intervention as a steering angle to the steerable wheels 17 of the motor vehicle.

[0057] An electric power assist system can comprise an auxiliary drive 3 mounted on the steering column 2 and coupled to the steering shaft 10, or an auxiliary drive 31 coupled to the pinion 14 with the steering shaft part 11, wherein the auxiliary drives 3 and 31 can be constructed in the same way. The auxiliary drive 3 or 31 can couple an auxiliary torque into the lower steering shaft 11 and / or the steering pinion 14 to assist the driver in steering.

[0058] An auxiliary power drive 32 may also be provided to introduce an auxiliary power into the rack 15 to assist the steering.

[0059] Typically, an auxiliary drive 3, 31, or 32 is only mounted at one of the three positions shown. The auxiliary torque or auxiliary force to be applied to assist the driver by means of the respective auxiliary drive 3, 31, or 32 is determined taking into account a steering torque manually applied by the driver, as determined by a rotation sensor 4. For this purpose, the rotation sensor 4 has a torque sensor that detects the relative rotation of the steering shaft parts 10 and 11, which depends on the magnitude of the manually applied steering torque. Furthermore, a rotation angle sensor is preferably provided for detecting the angular position of the steering shaft part 10 and / or 11.

[0060] In the Figure 14 is the inner strand of the steering system 1, as shown in Figure 1is shown. According to the Figure 14 The embodiment is illustrated in which the auxiliary drive is provided by the auxiliary drive 31 of the Figure 1 is shown. The upper steering shaft part 10 is connected to the lower steering shaft part 11 via a torsionally elastic torsion bar 1002 fixed with a pin 1003. When a torque is applied to the steering wheel 12, the upper steering shaft part 10 is rotated and transmits the torque via the torsion bar 1002 to the lower steering shaft part 11. Since the rotation is initially resisted, the torsion bar 1002 twists in on itself, so that the upper steering shaft part 10 has a twist angle relative to the lower steering shaft part, which angle can be determined by the rotation sensor 4, of which in the Figure 14 only individual elements are illustrated, is recorded accordingly.

[0061] In order to limit the twisting and avoid mechanical overloading of the torsion bar 1002, an anti-twist device is provided, consisting of a first anti-twist device 1001, which engages with a second anti-twist device 1101. The projections 10012 of the first anti-twist device engage with recesses 11011 of the second anti-twist device with a predefined angular play. Likewise, the projections 11012 of the second anti-twist device engage with recesses 10011 of the first anti-twist device with a predefined angular play. If the specified angular play is reached, the maximum twisting of the torsion bar 1002 is achieved. For better illustration, Figure 14a the second anti-rotation device 1101 is shown in a different view.

[0062] These anti-rotation devices 1001 and 1101 have a significant impact on the path of the interference fluxes S1 and S2. The magnetic flux of the interference flux S1 and the interference flux S2 are subjected to a flux deflection SX by these anti-rotation devices 1001 and 1101 and are thereby altered.

[0063] In the Figure 15 is the inner strand of the steering system 1, as shown in Figure 1 is shown. Figure 15a shows in another view the second anti-twist device 1101 according to the design of the Figure 15 . According to the Figure 15 The embodiment is illustrated in which the auxiliary drive is provided by the auxiliary drive 3 of the Figure 1This means in the exemplary embodiment that a gear 9 is arranged directly near the rotation sensor 4, which encloses the torsion bar rotationally symmetrically. The gear 9, in the example designed as a worm gear, is coupled in the steering system to an electric drive (not shown) via a gear arrangement (not shown), preferably a worm gear. Apart from that, the features are analogous to those in the embodiment according to the Figure 14 illustrated embodiment, so that a repeated reproduction of the description can be dispensed with.

[0064] However, gear 9 has an even stronger influence on the interference fluxes S1 and S2, especially if it has a ferromagnetic core for attachment to one of the two steering shafts. The interference fluxes S1 and S2 are subjected to an even stronger flux deflection SX and are thus altered.

[0065] The rotation sensor 4 is mounted between the upper steering shaft part 10 and the lower steering shaft part 11, as shown in the enlarged illustration of Figure 2 which is a schematic perspective view of the steering column 2 from Figure 1 enlarged.

[0066] A magnet 41 is coaxially mounted on the steering shaft part 10. The magnet can be designed as a ring magnet and is arranged within two ring-shaped stator elements 42a, b, which are coaxially mounted on the second steering shaft part 11. The stator elements 42a, b have connecting sections 43a, b that are circular disk-shaped and project radially outward. The connecting sections 43a, b have axial surfaces perpendicular to the axis L on their axially opposing inner sides and their axially displaceable outer sides.

[0067] The two stator elements 42a,b are magnetically coupled to two flux conductors 5a,b, which are located in the Figures 4 to 8 are shown in different views.

[0068] The flux guides 5a,b are formed as one-piece sheet metal parts and have a collecting section 51a,b and a compensator section 52a,b, which are connected to each other via a web-shaped connecting section 53a,b. The collecting sections 51a,b and the compensator sections 52a,b extend parallel to an axial surface perpendicular to the axis, with collecting sections 51a,b each extending over a collecting surface, and the compensator sections 52a,b each correspondingly extending over a compensator surface.

[0069] In the Figure 16The effect of the flux deflection SX on the interference flux S1 and S2 at the collecting sections 51a and 51b is illustrated. The accumulation of ferromagnetic components, such as the anti-rotation devices 1001, 1101 and possibly also a gear 9, in particular a worm gear with a metal core as shown in the example, changes the magnetic flux ratios in such a way that the sizes of the areas of the collecting sections 51a and 51b in relation to the areas of the compensator sections 52a and 52b must be adjusted accordingly.

[0070] According to the invention, the collecting area is larger than the compensator area in one of the area ratios according to the invention specified above.

[0071] Flux fingers 54a,b are attached to the compensator sections 52a,b, which protrude axially into the space between the connecting sections 43a,b and serve as coupling elements. Sensor elements 6 for magnetic flux measurement, for example, Hall or GMR sensors, are arranged in the axial air gap between the flux fingers 54a,b. As shown in Figure 5 As can be seen, for example, two sensor elements 6 can be provided, which are arranged at a distance between coupling sections in the end regions of the spaced-apart flow fingers 54a,b in the circumferential direction.

[0072] As in Figures 3, 4 , 6 and 8 As can be seen, the collecting sections 51a,b are attached to the inside of the connecting sections 43a,b.

[0073] The flux guides 5a,b are crossed between the compensator sections 52a,b and the collector sections 51a,b in the region of the connecting sections 53a,b, so that they are axially opposite one another. The axial positions are reversed, so that the collector section 51a of one flux guide 5a and the compensator section 52b of the other flux guide 5b are axially located on the side where the connecting section 43a of one stator element 42a is arranged, and the collector section 51b of the other flux guide 5b and the compensator section 52a of one flux guide 5a are axially opposite one another on the other side. This creates an arrangement that is mirror-symmetrical with respect to a mirror plane perpendicular to the axis L. Seen in the circumferential direction, an X-shaped configuration is formed by the connecting lines along the connecting sections 53a,b between the collecting sections 51a and compensator sections 52b, as shown in the Figures 6and 8 is clearly visible.

[0074] In the Figures 3, 4 , 6 , 10 and 11 The magnetic flux coupled by the magnet 41 into one stator element 42a is designated as measuring flux M1, and the magnetic flux coupled into the other stator element 42b is designated as measuring flux M2. The measuring fluxes M1 and M2 are indicated by filled arrows.

[0075] External interference fields are in Figures 1 , 3 , 4 , 6 , 10 and 11 drawn as unfilled arrows, these generate magnetic interference fluxes S1 and S2.

[0076] The measuring flux M1 coupled by the magnet 41 into the stator element 42a is guided via the connecting section 43a into the collecting section 51a of the flux conductor 5a, and via the connecting element 53a and the compensator element 51a through the flux finger 54a into the sensor element 6. Accordingly, the measuring flux M2 passes through the collecting section 51b of the flux conductor 5b, via the connecting element 53b and the compensator element 51b through the flux finger 54b to the axially opposite side of the sensor element 6. This is shown in Figures 3 and 4 shown.

[0077] The external magnetic interference fields are coupled as interference fluxes S1 and S2 at least partially into the stator elements 42a,b, the connecting sections 43a,b, and the collecting sections 51, and into the compensator sections 52a,b. As shown in the sectional view of Figure 6As shown schematically, in the coupling section of the flux finger 54a, which is axially coupled to the sensor element 6, the measuring flux M1 is superimposed by the interference fluxes S1 and S2. Analogously, in the coupling section of the other flux finger 54b, the other measuring flux M2 is also superimposed by the interference fluxes S1 and S2.

[0078] Via the flux fingers 54a, b, the interference fluxes S1 and S2 coming from the collecting sections 51a, b and from the compensator sections 52a, b are coupled with opposite signs into the sensor element 6. As a result, they are compensated and, ideally, cancel each other out, so that only the measuring fluxes M1 and M2 are measured by the sensor element 6.

[0079] The collecting sections 51a,b may have projecting stop sections 55a,b, which in the example extend axially inwards as in Figures 5 and 8shown, and additionally or alternatively outwardly and / or in the circumferential direction. These can be formed in one piece, for example by bending the sheet metal.

[0080] The compensator sections 52a,b may have guide sections 56a,b projecting laterally, in the example in the circumferential direction. These can be formed as integrally formed guide lugs.

[0081] According to the invention, the collecting area, ie, the axial area of ​​a collecting section 51a,b, is larger than the compensator area, ie, the axial area of ​​a compensator section 52a,b. The area ratio can preferably be within the ranges defined above in the description of the invention.

[0082] The stator elements 42a,b, including the connecting sections 43a,b, can be formed from sheet metal with a sheet thickness BS, which can be, for example, 0.8 mm.

[0083] The flux guides 5a,b can be formed in one piece as sheet metal parts made of sheet metal with a sheet thickness BF, which can be, for example, 0.8 mm.

[0084] The compensator sections 52a,b may have an axial height difference relative to the collecting sections 51a,b, which approximately corresponds to the sheet thickness BF or BS, so that the compensator sections 52a,b are substantially flush with the connecting sections 43a,b, as in Figure 8 is indicated schematically.

[0085] The collecting sections 51a,b may have an axial distance As that is smaller than the axial distance Ak of ​​the compensator sections 52a,b.

[0086] The compensator sections 52a,b may have a radial distance Ra relative to the collecting sections 51a,b which is related to the radial width Rs of the collecting sections 51a,b (measured in the direction of the distance Ra), as defined above in the description of the invention.

[0087] In the region of the sensor element 6, the flux fingers 54a,b have an axial distance Lu of the air gap from each other, which can preferably be in a ratio to the sheet thickness BF according to the ranges defined above in the description of the invention. It is advantageous that the axial height distance between the flux fingers 54a,b and the sensor element 6 is smaller than the sheet thickness BF.

[0088] The axial distance Ab of the connecting sections 43a,b can preferably be approximately 15 times the sheet thickness BS.

[0089] The Figures 9 and 10 show in the same views as Figures 5 and 6 an alternative arrangement of the flux guides 5a,b. The connecting sections 53a,b intersect closer to the compensator sections 52a,b, whereas in the previously described embodiment they intersect closer to the collecting sections 51a,b.

[0090] The Figures 11 to 13The further development of the invention shown has the functional elements of the first embodiment described above, and the same reference numerals are used accordingly.

[0091] As in the first embodiment, there are two sensor elements 6 which are mounted on a printed circuit board 61 (circuit board 61) and electrically connected.

[0092] In addition to the first embodiment, the compensator sections 52a,b each have an angled wing section 57a,b, also referred to as a winglet, which projects in the axial direction into the space between the compensator sections 52a,b, as shown in the radial view of Figure 13 can be seen. A wing section 57a,b can have dimensions in relation to the sheet thickness Bf, as defined above in the description of the invention.

[0093] The flux conductors 5a,b are guided in sections into the interior of a housing 8. The sensor elements 6 are also accommodated therein. List of reference symbols

[0094] 1Steering system 10Steering shaft part 1001First anti-twist device 10011Recess 10012Protrusion, tooth 1002Torsionally elastic torsion bar 1003Pin 11Steering shaft part 1101Second anti-twist device 11011Recess 11012Protrusion, tooth 12Steering wheel 13Universal joint 14Pinion 15Rack 16Tie rod 17Wheel 2Steering column 21Support unit 3,31Auxiliary power drive 4Rotation sensor 41Magnet (ring magnet) 42a,bStator element 43a,bConnecting section 5a,bFlux guide 51a,bCollecting section 52a,bCompensator section 53a,bConnecting section 54a,bFlux finger 55a,bStop section 56a,bGuide section 57a,bWinglet section 6Sensor element 61Printed circuit board 8Housing 9Gear LAxis M1Measuring flow M2Measuring flow S1Interference flow S2Interference flow SXFlux deflection BFBile thickness BSBile thickness Abaxial distance Asaxial distance Acaxial distance Raradial distance Rsradial width Luaxial distance (air gap)

Claims

1. Steering system (1) for a motor vehicle having a steering shaft (10, 11), a torsion bar (1002) and a rotary sensor (4) having at least one sensor element (6), comprising a magnet element (41) which is attached to the steering shaft (10, 11) and can rotate with the latter about an axis (L), and two flux conductors (5a, 5b), and two stator elements (42a, b) which are fixedly arranged coaxially relative to the steering shaft (10, 11) and axially spaced apart from one another and which are operatively connected to the at least one sensor element (6) via the two flux conductors (5a, b), wherein one flux conductor (5a,b) has a collecting section (51a,b), a connecting section (53a,b) and a compensator section (52a,b), wherein the collecting section (51a,b) is connected to a stator element (42a,b) and is connected to the compensator section via a connecting section (53a,b) to the compensator section (52a,b), and wherein the sensor element (6) is arranged between the two flux conductors (5a,b), wherein the steering shaft comprises an upper steering shaft (10) which is connected to a lower steering shaft (11) via the torsion bar (1002), characterized in in that an anti-rotation lock (1001) arranged on the upper steering shaft (10) is brought into engagement with an anti-rotation lock (1101) arranged on the lower steering shaft (1002) for limiting a twisting of the torsion bar (1002) in itself, the anti-rotation lock (1001, 1002) has a ferromagnetic material, and the compensator portion (52a,b) has a compensator area which is smaller than a collecting area of the collecting portion (51a,b), wherein the area ratio of the collecting area and the compensator area is between 1.5 and 2, or between 1.5 and 1.75, or 1.75.

2. Steering system according to claim 1, characterized in that the flux conductors (5a, b) are designed as one-piece sheet-metal parts.

3. Steering system according to one of the preceding claims, characterized in that the flux conductors (5a, b) between the compensator sections (52a, b) and the collector sections (51a, b) are crossed in the region of the connecting sections (53a, b), so that the compensator sections (52a, b) and the collector sections (51a, b) are located axially opposite one another.

4. Steering system according to one of the preceding claims, characterized in that the compensator surfaces and the collecting surfaces of the flux conductors (5a, b) are predominantly parallel to one another and to connection sections (43a, b) of the stator elements (42a, b) to which the collecting sections (51a, b) are connected.

5. Steering system according to one of the preceding claims, characterized in that the collecting sections (51a, b) are attached to axially opposite inner sides of the stator elements (42a, b).

6. Steering system according to one of the preceding claims, characterized in that the axial spacing (Ab) of the collector sections (51a, b) is smaller than the axial spacing (Ak) of the compensator sections (52a, b).

7. Steering system according to one of the preceding claims, characterized in that the compensator sections (52a, b) are aligned flush with connection sections (43a, b) of the stator elements (42a, b).

8. Steering system according to one of the preceding claims, characterized in that the compensator sections (52a, b) are connected to coupling sections which have coupling surfaces facing the sensor element (6).

9. Steering system according to one of the preceding claims, characterized in that at least two sensor elements (6) are provided at a distance from one another.

10. Steering system according to one of the preceding claims, characterized in that a compensator section (52a, b) has an angled wing section (57a, b).

11. Steering system according to one of the preceding claims, characterized in that the flux conductors (5a, b) and the sensor element (6) are arranged in a housing (8).

12. Steering system according to one of the preceding claims, characterized in that a compensator section (52a,b) and / or a collector section (51a,b) has a guide section (56a,b).

13. Steering system according to one of the preceding claims, characterized in that a collecting section (51a) of one flux conductor (5a) and a compensator section (52b) of the other flux conductor (5b) have a radial distance (Ra) from one another, which has a ratio of between 0.5 and 2, or between 0.75 and 1.5, or between 0.75 and 1.25, or between 0.8 and 1.2, or of 1 to a radial width (Rs) of the collecting section (51b) of the other flux conductor (5b).

14. Steering system according to one of the preceding claims, characterized in that the collecting section (51a) of one flux conductor (5a) has an axial height difference to the compensator section (52b) of the other flux conductor (5b), which has a ratio of between 0.5 to 2, or between 0.75 to 1.5, or between 0.75 to 1.25, or between 0.8 to 1.2, or of 1 to an axial thickness (BF) of a collecting section (51a).

15. Steering system according to one of the preceding claims, characterized in that the collecting section (51a) of one flux conductor (5a) has an axial height difference to the compensator section (52b) of the same flux conductor (5a) which has a ratio of between 0.75 and 2.2, or between 0.85 and 1.2, or between 0.9 and 1.15, or of 1.125 to an axial height difference between the compensator sections (52a, b) of the two flow guides (5a, b).

16. Steering system according to one of the preceding claims, characterized in that the two flux conductors (5a, b) in the region in which the sensor element (6) is arranged have an axial height spacing (Lu) in the range from 1.8 to 2.2 of an axial thickness (BF) of the flux conductors (5a, b).

17. Steering system according to one of the preceding claims, characterized in that an axial height distance between the flux conductors (5a, b) and the sensor element (b) is smaller than the axial thickness (BF) of the flux conductors (5a, b).