Steering system comprising a shielded magnetic torque sensor device

Abstract

The invention relates to an electromechanical steering system comprising a steering shaft, a magnetic torque sensor device (3) for measuring the torque applied to the steering shaft, and a shielding element (4). The steering shaft comprises an input shaft (21) connectable to a steering handle for joint rotation and protruding through the shielding element (4), and an output shaft (22) connected to the input shaft (21) via a torsionable torsion bar (23). The torque sensor device (3) comprises a multipole magnetic ring (31) connected to the input shaft (21) for joint rotation, a stator ring element (32) connected to the output shaft (22) for joint rotation and encircling the magnetic ring (31), a magnetic flux collector (33), and a sensor (34) for detecting the magnetic flux density. The shielding element (4) is arranged downstream of the magnetic ring (31), said shielding element (4) covering the surface of the magnetic ring (31) and the stator ring element (32) relative to the steering handle (7).

Description

[0001] This invention relates to an electromagnetic steering system having a steering shaft, a magnetic torque sensor device for measuring the torque applied to the steering shaft, and a shielding element for reducing interfering magnetic fields acting on the torque sensor device. For this purpose, the steering shaft includes an input shaft rotatably fixed to a steering handle and an output shaft connected to the input shaft via a torsion bar. The torque sensor device of the steering system includes a multipole magnetic ring rotatably fixed to the input shaft, a stator ring element rotatably fixed to the output shaft and surrounding the magnetic ring, a flux collector, and a sensor for detecting magnetic flux density.

[0002] Torque sensors are used in motor vehicles, particularly to measure the torque applied to the steering wheel by the driver. Currently, commonly used torque sensor devices include magnetic sensors that are sensitive to external interfering magnetic fields, which can lead to erroneous measurement results. Due to the increasing electrification of motor vehicles, which are often now purely electric, there is an increased risk that the measurement results of magnetic torque sensor devices may be affected by flowing current. Therefore, current-carrying cables, for example, near the steering system, can be a cause of this measurement influence, as some current-carrying cables conduct high currents. However, the Earth's magnetic field may also have an interfering effect on magnetic torque sensor devices.

[0003] Prior art discloses magnetic torque sensor devices with magnetic shielding for reducing the influence of external interference. For example, DE 10 2019 105 234 A1 discloses an electromechanical steering system with a magnetic torque sensor unit. This torque sensor unit includes an annular magnet housed within a housing, several magnetic flux conductors, and a sensor unit having a magnetic sensor arranged within the sensor housing. Furthermore, the torque sensor unit includes a magnetic shield surrounding the sensor unit. The shield is sandwiched between the housing and a housing cover that encloses the housing. Therefore, in this design, the shield must conform to the housing to achieve a clamping effect. Consequently, the shield cannot be optimally designed in every aspect.

[0004] In this context, the object of the present invention is to provide an improved shielding for a magnetic torque sensor device in an electromechanical steering system. Specifically, an improved arrangement of the shielding elements is achieved, preferably with improved functionality.

[0005] To achieve this objective, an electromagnetic steering system according to the present invention has been proposed. Other advantageous embodiments of the invention are described in the specification and illustrated in the accompanying drawings.

[0006] The proposed solution provides an electromechanical steering system comprising a steering shaft, a magnetic torque sensor for measuring the torque applied to the steering shaft, and a shielding element for reducing interfering magnetic fields acting on the torque sensor. The steering shaft includes an input shaft rotatably fixed to the steering handle and passing through the shielding element, and an output shaft connected to the input shaft via a torsion bar. Furthermore, the torque sensor includes a multipole magnetic ring rotatably fixed to the input shaft, a stator ring element rotatably fixed to the output shaft and surrounding the magnetic ring, a flux collector, and a sensor for detecting magnetic flux density. Here, the shielding element is arranged after the magnetic ring, covering the surfaces of the magnetic ring and the stator ring element relative to the steering handle. Preferably, the shielding element comprises a metal plate, particularly formed of a metal plate. According to an advantageous embodiment, the shielding element is formed of multiple parts, particularly multiple circular portions. In particular, the shielding element forms a closed surface, preferably a flat surface. The surface advantageously has a larger size than the magnetic ring and stator ring, and advantageously also larger than the flux collector, such that the shielding element covers the surface of the magnetic ring and stator ring relative to the steering handle, and advantageously also covers the flux collector. Therefore, when the steering shaft is oriented in the direction of view starting from the steering handle, the shielding element particularly completely covers the torque sensor device. The shielding element here advantageously conducts external magnetic flux, particularly flux acting from the direction of the steering handle, around the torque sensor device. Advantageously, it has been found that in this way, the torque sensor device produces fewer measurement errors, and thus advantageously detects the torque applied to the steering shaft with higher accuracy. Because the shielding element is arranged behind the magnetic ring, and therefore advantageously adjacent to the magnetic ring directly or at a distance in the longitudinal direction of the steering shaft, it advantageously shields against external interference signals, particularly interfering magnetic fields. Therefore, advantageously, distortion of the torque sensor's output signal due to external influences is greatly reduced or even avoided.

[0007] Advantageously, the shielding element has a permeability μ r > 200, especially with a permeability of 200 < μ r The permeability is < 15000. Advantageously, with such permeability, the magnetic flux of the interfering magnetic field deflects better around the torque sensor device, and thus further improves the measurement accuracy. More advantageously, the shielding element comprises a material with soft magnetic properties. In particular, it is configured that the shielding element comprises at least partially iron as the material. Therefore, the shielding effect of the shielding element is advantageously further improved.

[0008] Specifically, the steering system is configured to include a receiver unit in which the input shaft is rotatably mounted. Advantageously, a shielding element extends between the receiver unit and a portion of the input shaft. Advantageously, this further improves the shielding effect. Particularly advantageously, this portion of the input shaft is a protrusion of the input shaft. Advantageously, the shielding element can rest on the foot of the protrusion. More advantageously, this portion is a projection from the input shaft. In particular, this portion can also be an increased diameter portion of the input shaft, in which the shielding element advantageously rests against. Advantageously, as another function of the shielding element, this restricts the degree of freedom of axial movement of the steering shaft, thereby advantageously ensuring that, in the event of torsion bar fracture, the two broken halves, as well as the input and output shafts, can thus move apart from each other to a very limited extent at most. Otherwise, such separation of the broken halves, particularly with inclined fracture edges, could occur, and then lead to further damage to the steering system. The shielding element is arranged such that one side faces the receiver unit and the other side faces the protrusion of the input shaft, and thus the advantageous arrangement of the shielding element between the receiver unit and the protrusion of the input shaft advantageously acts as a stop that largely or even completely prevents the movement of the input shaft in the direction of the steering handle.

[0009] The protrusion of the input shaft can be, in particular, a circumferentially enlarged portion of the input shaft, especially a shoulder of the input shaft. This protrusion can be formed by the input shaft itself, but alternatively, it can be formed by an element attached to the input shaft. The receiver unit is advantageously the inner tube of the telescoping steering column of the steering system. According to an advantageous embodiment, a shielding element extends between the inner tube and the protrusion of the input shaft, such that the shielding element covers, in particular, completely covers, the inner tube, especially the opening of the inner tube, thereby advantageously further improving the shielding effect. In particular, with this advantageous embodiment, the magnetic flux of the interfering magnetic field from the inner tube is conducted to the input shaft, thereby advantageously reducing the induced magnetic flux in the torque sensor device. Therefore, the torque applied to the steering shaft can be determined more accurately.

[0010] According to an advantageous improvement, the receiver unit is configured to serve as an end stop for the outer surface of the shielding element. The outer surface of the shielding element is, in particular, a portion of the side facing the receiver unit, which rotates towards the receiver unit. Specifically, a circular shielding element is provided, wherein the inner or outer ring of the shielding element rests against the outer surface of the receiver unit, which acts as the end stop. Advantageously, this better restricts the degree of freedom of axial movement of the steering shaft.

[0011] It is particularly advantageous that the shielding element is arranged on the receiver unit, especially fixedly arranged on the receiver unit. The shielding element can be arranged directly or indirectly via at least one other element. In particular, the shielding element can be arranged on the receiver unit via solder joints. However, other suitable possible arrangements can be used.

[0012] According to other advantageous embodiments of the invention, the shielding element is arranged to enclose the space between the receiver unit and the input shaft. In particular, in embodiments where the receiver unit is an inner tube, the space between the input shaft and the inner shell surface of the input tube is closed at the point where the shielding element is arranged. This further improves the magnetic shielding of the torque sensor device. Furthermore, such an embodiment is advantageously easy to implement structurally.

[0013] Another advantageous embodiment is that the input shaft penetrates the shielding element orthogonally. Specifically, the sides of the shielding element are each orthogonal to the input shaft. Advantageously, this further simplifies production and installation.

[0014] More advantageously, the shielding element is concentrically positioned around the input shaft. In addition to further installation advantages, this also advantageously enables further improved shielding of the torque sensor assembly.

[0015] According to other advantageous embodiments of the invention, the shielding element is arranged on the input shaft, particularly fixedly arranged on the input shaft. The shielding element can be arranged directly or indirectly via at least one other element. In particular, the shielding element can be arranged on the input shaft via a solder joint. However, other suitable possible arrangements can be used. Particularly advantageously, the shielding element is arranged on a stepped region of the input shaft. Advantageously, this arrangement achieves further improvement in restricting the degrees of freedom of axial movement.

[0016] Another advantageous arrangement is that the shielding element has a raised molded part that coaxially surrounds a portion of the input shaft. Specifically, the raised molded part is provided with a fluid transition portion starting from the side. The side surfaces preferably each form a closed, flat surface with a circular periphery. In an advantageous embodiment, the raised molded part is in the form of a sleeve. Specifically, the shielding element is arranged on the raised molded part on the input shaft, wherein a pressure seat for the input shaft can be particularly realized via the raised molded part. Advantageously, the raised molded part provides better restriction of axial movement freedom. Furthermore, advantageously, magnetic flux from the receiver unit, particularly from the receiver unit formed as an inner tube, can be conducted into the input shaft, and thus the interference effects in the magnetic torque sensor device can be further reduced.

[0017] More advantageously, the protrusion of the input shaft is configured as an end stop for the raised molded part used as a shielding element. In particular, according to an advantageous embodiment of the invention, the input shaft has an increased diameter portion serving as the end stop for the raised molded part used as a shielding element. Advantageously, especially in the event of torsion bar breakage, this further restricts the axial degree of freedom of the steering shaft, or makes the already implemented restriction of the steering shaft's degree of freedom more reliable in case of failure.

[0018] According to other advantageous embodiments, the shielding element is designed in the form of a rosette. This design advantageously achieves a good shielding effect. Furthermore, this shape is structurally advantageous and simple to manufacture.

[0019] Other advantageous aspects, features, and details of embodiments of the invention will now be explained in more detail with reference to the exemplary embodiments shown in the accompanying drawings (Figure = Figures). In the drawings:

[0020] Figure 1 A schematic perspective view of an exemplary embodiment of an electromechanical steering system for a motor vehicle constructed according to the present invention is shown;

[0021] Figure 2 A perspective view of an exemplary embodiment of a steering column for a steering system constructed according to the present invention is shown;

[0022] Figure 3 It shows that according to Figure 2 Another perspective view of the simplified diagram of the steering column;

[0023] Figure 4 It shows that according to Figure 2 The steering column and Figure 3 Another 3D diagram compared to a further simplified version;

[0024] Figure 5 It shows that according to Figure 2 A transverse cross-sectional view of a selected portion of the steering column; and

[0025] Figure 6 A perspective view of an exemplary embodiment of a shielding element constructed according to the present invention is shown.

[0026] In different accompanying drawings, the same parts often have the same reference numerals, and therefore sometimes only one of the accompanying drawings is used for interpretation.

[0027] Figure 1A simplified perspective view shows an electromechanical steering system 1 for a motor vehicle. The steering system 1 includes a steering column 10 with a steering shaft 2. The steering shaft 2 is mechanically connected to the steerable wheels 12 of the motor vehicle via a steering gear 11. In this exemplary embodiment, the steering gear 11 includes a pinion 5 and a toothed connecting rod 6, wherein the steering gear 11 is used to convert the rotational motion of the pinion 5 into a translational motion of the connecting rod 6 along its longitudinal axis. A steering handle 7, particularly a steering wheel, is rotatably fixed to the driver-facing end of the steering shaft 2 for inputting a steering request or steering command from the driver, wherein the driver can rotate the steering handle 7, configured as a steering wheel, in a known manner to input the driver's steering command. In this exemplary embodiment, the connecting rod 6, capable of linear movement along its longitudinal axis, is mechanically connected to tie rods 8 on both sides of the motor vehicle. Each tie rod 8 is sequentially mechanically connected to a wheel 12. The steering gear 11 is thus configured to convert a steering command, taking into account at least one input variable, into steering motion of the steerable wheels 12 of the motor vehicle.

[0028] In addition, the steering system 1 includes a magnetic torque sensor device 3 for measuring the torque applied to the steering shaft 3. Figure 1 (not explicitly shown in the text) and shielding elements for reducing the influence of external interference magnetic fields on the torque sensor device 3. Figure 1 (Not explicitly shown in the text). Here, steering shaft 2 includes an input shaft ( Figure 1 (not shown in the image) and output shaft ( Figure 1 (Not shown in the image) The input shaft is rotatably fixed to the steering handle 7 and passes through the shielding element, and the output shaft is connected via a torsion bar ( Figure 1 (Not shown in the image) is connected to the input shaft. The torque sensor device 3 includes a multipole magnetic ring (not shown in the image) that is rotatably fixedly connected to the input shaft. Figure 1 (Not shown in the image) Stator ring element that surrounds the magnetic ring and is rotatably fixed to the output shaft. Figure 1 (not shown in the image), flux collector ( Figure 1 (not shown in the image) and a sensor for detecting magnetic flux density ( Figure 1 (Not shown in the figure). The shielding element is arranged behind the magnetic ring, and the shielding element covers the surfaces of the magnetic ring and stator ring elements facing the steering handle 7. The advantageous embodiment of the steering shaft 2 having a torque sensor device 3 arranged thereon and having a shielding element is explained in more detail below with particular reference to the steering column 10 of the steering system 1 shown in the following figures.

[0029] to this end, Figure 2 An exemplary embodiment of a telescopic steering column 10 is shown, which has a steering shaft 2, a magnetic torque sensor device 3 arranged in a housing 38, and a... Figure 2The shielding element is invisible. The steering column 2 includes an input shaft 21, at which a steering handle is rotatably fixed. The input shaft 21 is connected via a torsion bar ( Figure 2 The output shaft 22 (not visible in the center) is connected to the steering shaft 2. The input shaft 21 is rotatably mounted in the receiver unit 27, which is configured as an inner tube. To adjust the length of the steering column, the inner tube 27 can be partially or completely received by the outer tube 28.

[0030] Figure 3 and Figure 4 It shows that according to Figure 2 The steering column 10, in which some components have been omitted to specifically show the torque sensor device 3 and the shielding element 4. Furthermore, Figure 5 A side view shows the passage according to Figure 2 The cross-section of the steering column 10, wherein, Figure 5 The diagram shows a region of the steering column 10 with a torque sensor device 3 and a portion of the inner tube 27 with an input shaft 21 mounted therein.

[0031] Figure 3 and Figure 4 Details of the shielding element 4 and the magnetic torque sensor device 3 arranged in the housing 38 having housing components 381, 382 are shown here; these details include a stator ring element 32, a flux collector 33, and a sensor 34, the stator ring element 32 being rotatably fixed to the output shaft 22 and surrounding a multipole magnetic ring being rotatably fixed to the input shaft 21. Figure 3 (Not visible in the image), sensor 34 is arranged in the sensor housing for detecting magnetic flux density. Sensor 34 may be, in particular, a Hall sensor. Input shaft 21 penetrates shielding element 4, which is arranged behind the magnetic ring such that the shielding element 4 is located between the receiver unit 27, which is constructed as an inner tube, and the protrusion of input shaft 21 (…). Figure 3 and Figure 4 The end of the steering handle, which is arranged towards the input shaft 21, extends between (not visible in the middle) and is covered on the surface with a magnetic ring and a stator ring element 32.

[0032] Here Figure 6 The perspective view shows an advantageous embodiment of the shielding element 4, in Figure 6 In this design, the shielding element 4 takes the form of a rosette. The shielding element 4 comprises a material with soft magnetic properties, preferably iron, and has a magnetic permeability μ. r > 200, especially μ r = 2000 permeability. For example, from Figure 6Of particular notable feature is the shielding element 4, which has a raised molded part 42. Furthermore, the shielding element 4 has a first side 43 pointing towards the torque sensor device 3 and a second side 44 pointing towards the end 26 of the steering handle or steering shaft 2. A fluid transition portion is formed between the raised molded part 42 and the sides 43 and 44. Each of the first side 43 and the second side 44 forms a closed, flat surface with a circular periphery. Accordingly, the torque sensor device 3 is covered by the shielding element 4 arranged on the input shaft 21 and is thus shielded from interfering magnetic fields.

[0033] exist Figures 2 to 5 In the embodiment shown, the protruding molded part 42 of the shielding element 4 is arranged on the input shaft 21, wherein the protruding molded part 42 is coaxially surrounding a portion 24 of the input shaft 21. The input shaft 21 orthogonally penetrates the shielding element 4 such that the sides 43, 44 of the shielding element 4 are orthogonally oriented to the input shaft 21, and the shielding element 4 is concentrically surrounding the input shaft 21.

[0034] As from Figure 5 Of particular notable is that the input shaft 21 is rotatably mounted within the receiver unit 27, which is constructed as an inner tube. A shielding element 4—a sleeve-shaped protruding molded part 42 of the shielding element 4 arranged on the input shaft 21—extends between the receiver unit 27 and a protrusion 25 of the input shaft 21, wherein the protrusion 25 is formed as a stepped shoulder by an increase in the diameter of the input shaft 21. The protruding molded part 42 of the shielding element 4 coaxially surrounds a portion 24 of the input shaft 21, wherein the protrusion 25 of the input shaft serves as an end stop for the protruding molded part 42. Furthermore, the shielding element 4 is arranged on the receiver unit 27 via a portion of a side surface 44, wherein the receiver unit 27 also serves as an end stop for the shielding element 4, and here the shielding element 4 extends between the receiver unit 27 and the protrusion 25 of the input shaft 21 such that the shielding element 4 completely covers the opening of the receiver unit 27. The outer surface 41 of the side surface 44 contacts the housing cover 39 of the housing 38.

[0035] because Figure 5In the design shown, the magnetic flux of the interfering magnetic field from the receiver unit 27 is conducted to the input shaft 21, thus reducing the magnetic flux induced in the torque sensor device 3 by the interfering magnetic field. Because the shielding element 4 rests on both the protrusion 25 of the input shaft 21 and the receiver unit 27, and both the protrusion 25 and the receiver unit 27 serve as end stops for the shielding element 4, the axial movement freedom of the input shaft 21 and the steering shaft 2 is restricted, which is particularly important in the case of a tilted breakage of the torsion bar 23. The shielding element 4 then prevents the broken edge of the torsion bar 23 from rotating relative to each other, and thus prevents the input shaft 21 from moving in the direction of arrow L. Therefore, in the case of a breakage of the torsion bar 23, the input shaft 21 and the output shaft 22 can only move apart from each other to a very limited extent.

[0036] The exemplary embodiments illustrated in and explained in conjunction with the accompanying drawings are used to explain the invention and not to limit it.

[0037] List of reference numerals

[0038] 1. Steering System

[0039] 2. Steering shaft

[0040] 21 Input axis

[0041] 22 Output shaft

[0042] 23 Torsion bar

[0043] 24 Input axis (21) part

[0044] 25. Protrusion of the input shaft (21)

[0045] 26. End of input shaft (21)

[0046] 27 Receiver Unit (Inner Tube)

[0047] 28 outer tubes

[0048] 3 Torque Sensor Device

[0049] 31 Magnetic Ring

[0050] 32 Stator ring elements

[0051] 33 Flux Collector

[0052] 34 sensors

[0053] 38 Housing of torque sensor device (3)

[0054] 381, 382 Housing components of housing (38)

[0055] 39 Housing cover

[0056] 4 Shielding components

[0057] 41. External surface of shielding element (4)

[0058] 42. Protruding molded part of shielding element (4)

[0059] 43, 44 Sides of shielding element (4)

[0060] 5 small gears

[0061] 6 Connecting rods

[0062] 7. Steering handle

[0063] 8 tie rods

[0064] 9. Magnetic ring

[0065] 10. Steering column

[0066] 11. Steering gear

[0067] 12 rounds

[0068] L (arrow direction) (direction of axial movement)

Claims

1. An electromechanical steering system (1), the electromechanical steering system (1) having a steering shaft (2), a magnetic torque sensor device (3) for measuring the torque applied to the steering shaft (2), and a shielding element (4), wherein, The steering shaft (2) includes an input shaft (21) and an output shaft (22). The input shaft (21) is rotatably and fixedly connected to the steering handle (7) and penetrates the shielding element (4). The output shaft (22) is connected to the input shaft (21) via a torsion bar (23). The torque sensor device (3) includes a multipole magnetic ring (31) rotatably and fixedly connected to the input shaft (21), and a multipole magnetic ring (31) rotatably and fixedly connected to the output shaft (22) and surrounding the magnetic ring (31). The stator ring element (32), the flux collector (33), and the sensor (34) for detecting the flux density are characterized in that the shielding element (4) is arranged after the magnetic ring (31), and the shielding element (4) covers the surfaces of the magnetic ring (31) and the stator ring element (32) relative to the steering handle (7); the input shaft (21) is rotatably mounted in the receiver unit (27), wherein the shielding element (4) extends between the receiver unit (27) and a portion (24) of the input shaft (21).

2. The steering system (1) according to claim 1, characterized in that, The receiver unit (27) serves as an end stop for the outer surface (41) of the shielding element (4).

3. The steering system (1) according to claim 1 or claim 2, characterized in that, The shielding element (4) is arranged on the receiver unit (27).

4. The steering system (1) according to any one of claims 1 to 2, characterized in that, The shielding element (4) is arranged to enclose the space between the receiver unit (27) and the input shaft (21).

5. The steering system (1) according to any one of claims 1-2, characterized in that, The input shaft (21) penetrates the shielding element (4) orthogonally.

6. The steering system (1) according to any one of claims 1-2, characterized in that, The shielding element (4) surrounds the input shaft (21) concentrically.

7. The steering system (1) according to any one of claims 1-2, characterized in that, The shielding element (4) is arranged on the input shaft (21).

8. The steering system (1) according to any one of claims 1-2, characterized in that, The shielding element (4) has a magnetic permeability µ r Permeability > 200.

9. The steering system (1) according to any one of claims 1-2, characterized in that, The shielding element (4) comprises a material with soft magnetic properties.

10. The steering system (1) according to any one of claims 1-2, characterized in that, The shielding element (4) has a raised molded part (42) that coaxially surrounds a portion (24) of the input shaft (21).

11. The steering system (1) according to claim 10, characterized in that, The input shaft (21) has a diameter increase portion, which serves as a stop for the protruding molded part (42) of the shielding element (4).

12. The steering system (1) according to any one of claims 1-2, characterized in that, The shielding element (4) is designed in the form of a rose knot.

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