Sensor device for determining the torsion angle of a torsion bar, steering system of a motor vehicle, motor vehicle, method for operating the sensor device

Abstract

The present invention relates to a sensor device (1) for determining the torsion angle of a torsion bar (2), in particular of a steering system for a motor vehicle, which comprises at least one first substrate (3), a second substrate (4) and a third substrate (5), each of which is plate-shaped or disk-shaped, the substrates (3, 4, 5) being arranged on the torsion bar (2) at a distance from one another and being connected to the torsion bar (2) so as not to be able to rotate relative to one another, and the third substrate (5) being located between the first substrate (3) and the second substrate (4) in the longitudinal direction of the torsion bar (2). and a sensor device (1) in which a first electrical receiving device (9) and a second electrical receiving device (10) are arranged on the first substrate (3) and the second substrate (4), and at least a part of an electrical transmitting device (11) is arranged on the third substrate (5), or in which at least a part of a first electrical transmitting device (9') and a second electrical transmitting device (10') are arranged on the first substrate (3) and the second substrate (4), and an electrical receiving device (11') is arranged on the third substrate (5). It is proposed that the first receiving device (9) and the second receiving device (10), or the first transmitting device (9') and the second transmitting device (10'), are differentially connected to each other.

Description

[Technical Field]

[0001] The present invention relates to a sensor device for determining the torsion angle of a torsion bar, in particular of a steering system of a motor vehicle, which comprises at least one plate- or disk-shaped first, second and third substrate, each of which is arranged on the torsion bar at a distance from one another and is connected to the torsion bar so that they cannot rotate relative to one another, and the third substrate is arranged between the first and second substrates in the longitudinal direction of the torsion bar, and a first electrical receiving device and a second electrical receiving device are arranged on the first and second substrates and at least a part of an electrical transmitting device is arranged on the third substrate, or at least a part of the first electrical transmitting device and the second electrical transmitting device are arranged on the first and second substrates and the third substrate is arranged.

[0002] Furthermore, the invention relates to a steering system equipped with such a sensor device, to a motor vehicle equipped with such a steering system, and to a method for operating such a sensor device. [Background technology]

[0003] Background technology Inductive torque or steering angle sensors (Torque Angle Sensors, TAS) are known that determine torque by the difference between two absolute angle measurements. For this purpose, the absolute angle at two axial positions of the torsion bar is determined. The torque acting on the torsion bar is, to a good approximation, proportional to the difference between the two angles. Such measurement methods are used, for example, in electromechanically assisted steering systems in motor vehicles.

[0004] In such sensors, two conductive eddy current targets are typically attached to the torsion bar and sensed by a measurement substrate that is isolated from the bar's rotation. The angle of the two targets relative to the measurement substrate (due to the periodicity of the design) is then electrically sensed (absolute angle). The difference between the two angles is proportional to the torque acting on the torsion bar, as discussed above. Therefore, any error in the absolute angle measurement directly affects the measured torque.

[0005] The prior art is known for sensor devices that improve the measurement accuracy of such angular difference formation. For example, German Patent Application No. 10 2008 006 865 A1 discloses an inductive torque sensor that includes an excitation coil, a stator substrate with first and second receiving means, and two rotors that are rotatable relative to each other and the stator substrate and that influence the strength of the inductive coupling between the excitation coil and the receiving means. The stator substrate is arranged between the two rotors. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] German Patent Application Publication No. 102008006865 Summary of the Invention [Means for solving the problem]

[0007] Disclosure of the Invention The sensor device according to the present invention, having the features of claim 1, is characterized in that the first receiving device and the second receiving device are differentially connected to each other, or the first transmitting device and the second transmitting device are differentially connected to each other. The differential connection, i.e., the electrically opposite connection, provides a particularly advantageous means for determining the torsion angle by directly measuring the differential angle of the mutual rotation of the receiving device or transmitting device, instead of determining the torsion angle from the difference in the absolute rotation angle of each receiving device relative to the transmitting device, as explained in the introduction, which involves high measurement uncertainty. This allows for accurate direct measurement of the differential angle by the differentially connected receiving device or transmitting device, without the need to take the detour of obtaining two separate absolute angles and then forming their difference again in a later step. The differential measurement method allows for the use of higher amplification factors compared to sensor devices known from the prior art, since the absolute angle signal is not superimposed on the differential signal. This improves signal quality, for example, by advantageously utilizing the dynamic range of an application-specific integrated circuit (ASIC) used for signal demodulation and thus increasing the signal-to-noise ratio (SNR). In this way, torque is resolved significantly more precisely, particularly advantageously, compared to sensor devices known from the prior art. The substrates on which the receiver and transmitter are arranged are preferably each fitted over the torsion bar. In particular, the substrates are configured as printed circuit boards. These printed circuit boards are non-rotatably connected to the torsion bar, i.e., they rotate together during rotation. Particularly preferably, at least one of the substrates, in particular the first and second substrates, is arranged by a retainer at a spacer attached to the torsion bar to increase the torsional leverage. To improve safety and monitorability in error cases, it is particularly preferred that the transmitter and receiver, in particular configured as coils, are individually measured and monitored at set time intervals by an electronic switch in the ASIC.Furthermore, the sensor device preferably comprises at least one magnetic angle sensor for measuring the absolute torsion angle, in order to achieve particularly advantageous validation of the sensor signal.In order to achieve advantageous redundancy of the sensor device, in particular, at least one of the transmitter and / or receiver devices is configured to be used by a second ASIC circuit.

[0008] According to a preferred embodiment of the present invention, the transmitter device has at least one transmitter coil, the first receiver device has at least one first receiver coil, and the second receiver device has at least one second receiver coil, or the first transmitter device has at least one first transmitter coil, the second transmitter device has at least one second transmitter coil, and the receiver device has at least one receiver coil. By using transmitter and receiver coils, the sensor device according to the present invention provides a particularly advantageous means for determining the torsion angle. For example, the transmitter coil (TX coil) is arranged on a third substrate, in particular configured as a printed circuit board (PCB). Preferably, the transmitter coil is configured such that it can generate or generates a harmonic magnetic field, in particular with a set frequency in the angular direction and in particular with a set periodicity in the angular direction. Furthermore, the transmitter coil is configured such that the magnetic field distribution or magnetic field strength is approximately rectangular as a function of angle and locally uniform in the radial direction. A time-varying magnetic field induces a voltage in a first receiving coil (RX coil) arranged on a first substrate and a second receiving coil (RX coil) arranged on a second substrate. The two coils are differentially connected, i.e., electrically oppositely connected, and are configured to be demodulated together. When torque acts on the shaft (torsion bar), the voltage difference between the two receiving coils changes, allowing the differential angle between fixed points on the corresponding substrates on the shaft to be estimated. Alternatively, instead of two receiving coils, a single receiving coil on a third substrate and a first transmitting coil on the first substrate and a second transmitting coil on the second substrate may be provided. Preferably, the voltage difference is directly proportional to the torque through appropriate selection of the coil geometry. The periodicity of the design, particularly the periodicity of the coil geometry, provides a uniqueness region for the measurement method. Particularly preferably, the periodicity of the design is selected so that the maximum differential angle occurring in the torsion bar optimally fills the uniqueness region.

[0009] It is particularly preferred that the first transmitter coil and the second transmitter coil each have the same number of windings, or that the first receiver coil and the second receiver coil each have the same number of windings, which particularly advantageously increases the robustness of the measurement method. As will be explained further below in this specification, if more than two transmitter coils or receiver coils are provided, it is particularly preferred that each transmitter coil or each receiver coil all have the same number of windings.

[0010] According to a preferred embodiment of the invention, the transmitter device includes a conductive active element, in particular a target, arranged on or configured as a third substrate, and a fixed excitation coil associated with the active element. This provides a particularly advantageous alternative for determining the torsion angle. Such an arrangement also generates an angle-dependent magnetic field. Instead of a specially shaped transmitter coil on the third substrate, a non-rotating, i.e., fixed, in particular rotationally symmetric transmitter coil is provided, associated with a conductive active element, in particular configured as a target to rotate together with the torsion bar. The active element is arranged on the third substrate, or the third substrate is electrically conductive and forms the active element itself. An electromagnetic field resulting from eddy currents in the target is superimposed on the generated magnetic field with a local angle dependence, which can be used to determine the torsion angle.

[0011] Particularly preferably, at least one of the transmitter coil or receiver coil or active element extends or is arranged geometrically periodic in the tangential direction along the respective substrate, such periodicity having the advantage that the coils and active elements are arranged geometrically differentially, in particular one period corresponding to a winding of a coil that is arranged in particular geometrically sinusoidally.

[0012] According to a preferred development of the invention, at least one of the transmitter coil, receiver coil or active element extends or is configured sinusoidally or at least approximately stepped, in particular rectangularly, in the tangential direction along the respective substrate, which provides a particularly geometrically easy means for achieving the periodicity described above.

[0013] Particularly preferably, the geometry is selected so that the output signal of the transmitter and / or receiver represents the torsion angle of the torsion bar. This relationship has the advantage that the torsion angle can be determined particularly easily and reliably by the sensor device according to the invention. For this purpose, in particular, several coils are provided as transmitters or receivers, electrically offset from one another by a set angle. For example, two coils electrically offset from one another by 90° or three coils electrically offset from one another by 120° are provided.

[0014] According to a preferred development of the invention, the voltage induced in the sensor device is configured to be proportional to the torsion angle of the torsion bar, which provides an advantageous and robust means for determining the torsion angle, in particular since the torsion angle is at least approximately proportional to the torsion torque acting on the torsion bar, the voltage induced in the sensor device is also proportional to the torsion torque.

[0015] Particularly preferably, at least two transmitters or at least two receivers are arranged on at least one of the substrates, each offset from one another by a set rotation angle. This provides redundancy and therefore particularly advantageously increases the robustness of the measurement method. Preferably, a duplicate transmitter and / or receiver is provided. For example, instead of providing only a single first receiver with one first receiver coil and a single second receiver with one second receiver coil, two first receiver coils and two second receiver coils are provided, where the two first receiver coils and the two second receiver coils are electrically offset from one another by a set angle, preferably 90°. Particularly preferably, the coils have a sinusoidal coil geometry. In such sinusoidal coils, the torque is proportional to the corrected arctangent of the ratio of the induced voltages in the two coil pairs. Alternatively, the coils may have a rectangular coil geometry. In the case where such rectangular coil pairs are used, the reference positions of the two coil pairs are preferably selected so that, in the absence of any torque acting, the differential voltage of the first coil pair is +50% of the full possible amplitude, and the differential voltage of the second coil pair is -50%. Particularly preferably, the coils have a large number of windings to increase the amplitude of the signal. Preferably, the two transmitter coils or the two receiver coils have the same number of windings.

[0016] According to a preferred embodiment of the invention, at least one other substrate with at least one other transmitter or at least one other receiver is arranged on the torsion bar so as to be non-rotatable relative to the torsion bar. This provides particularly advantageous redundancy in the event of a failure of one of the transmitters or receivers. Particularly preferably, each transmitter or receiver is arranged offset by a set rotation angle relative to at least one of the other transmitters or receivers, as described above. Alternatively, they are arranged with the same angular orientation, i.e., without any angular offset.

[0017] Particularly preferably, the torsion bar contains an electrically conductive material and is configured to form a ground connection for at least one of the transmitter or receiver devices, where forming the ground connection by means of the torsion bar has the advantage that a separate ground connection is omitted and, finally, due to the non-rotatable connection between the substrate and the torsion bar, the transmitter and receiver devices are in any case electrically conductively connected to the torsion bar.

[0018] According to a preferred development of the invention, the energy and / or signal transmission to at least one of the transmitter or receiver devices is provided via a flexible cable, a sliding contact or wirelessly. Such an electrical contact connection of the transmitter and / or receiver device provides a particularly advantageous means for efficient energy and / or signal transmission.

[0019] A steering device for a motor vehicle having the features of claim 13 is equipped with a sensor device according to the invention, which likewise provides the advantages mentioned above.

[0020] A motor vehicle having the features of claim 14 is equipped with a steering device according to the invention, which likewise provides the advantages mentioned above.

[0021] A method for operating a sensor device according to the invention is characterized in that the differential angle of rotation of the receiver or transmitter device relative to one another is determined as a function of the voltage difference between the induced voltages. Such a measuring method has a particularly advantageously high measurement accuracy due to the aforementioned advantages of the sensor device according to the invention.

[0022] Further preferred features and feature combinations will become apparent from the following description and claims.In the following, the invention will be explained in more detail on the basis of the drawings. [Brief explanation of the drawings]

[0023] [Figure 1] 1 illustrates an advantageous sensor device; [Figure 2] 1 shows a first embodiment of a transmitter or receiver device for a sensor device; [Figure 3] FIG. 2 shows a second embodiment of a transmitter or receiver device for a sensor device. [Figure 4] 1 is a circuit diagram of a transmitter or receiver for a sensor device; [Figure 5A] 10 is a magnetic field-angle graph when the sensor device is in use. [Figure 5B] 10 is a magnetic field-angle graph when the sensor device is in use. [Figure 6] 1 is a voltage-angle graph. DETAILED DESCRIPTION OF THE INVENTION

[0024] 1 shows a sensor device 1 for determining the torsion angle or twisting moment M of a torsion bar 2, indicated by a circular arrow. The torsion bar 2 is in particular part of a steering system (not shown) of a motor vehicle. The sensor device 1 has a first substrate 3, a second substrate 4 and a third substrate 5. Here, the substrates 3, 4 and 5 are configured, by way of example only, as disk-shaped printed circuit boards. The substrates 3, 4 and 5 are arranged at a distance from one another on the torsion bar 2 and are each connected to the torsion bar 2 so as not to be able to rotate relative to it.

[0025] Here, the first substrate 3 and the second substrate 4 are each connected to the torsion bar 2 by a holding device 6 having a holding part 7 and a spacer 8 attached to the torsion bar 2 so that they cannot rotate relative to each other. The holding device 6 (constructed in mirror symmetry) is used to increase the torsion leverage, i.e. the torsion angle that is detected.

[0026] The third substrate 5 is disposed between the first substrate 3 and the second substrate 4 in the longitudinal extension direction of the torsion bar 2. At least a part of an electrical receiving device or an electrical transmitting device is disposed on each of the substrates 3, 4, 5. These are not shown in detail in FIG. 1 for clarity.

[0027] There are various ways to arrange the receivers and transmitters on the substrates 3, 4, 5, such that the first electrical receiver and the second electrical receiver are arranged on the first substrate 3 and the second substrate 4, and at least a part of the electrical transmitter is arranged on the third substrate 5, or the first electrical transmitter and the second electrical transmitter are arranged on the first substrate 3 and the second substrate 4, and at least a part of the electrical receiver is arranged on the third substrate 5.

[0028] That is, at least two receiving devices and / or two transmitting devices are provided. The first receiving device and the second receiving device are differentially electrically connected to each other, or the first transmitting device and the second transmitting device are differentially electrically connected to each other. This will be further described with reference to FIG. 4.

[0029] The first specific means of arranging and configuring the transmitting device and receiving device is to arrange a first receiving device 9 having a first receiving coil on a first substrate 3, arrange a second receiving device 10 having a second receiving coil on a second substrate 4, and arrange a transmitting device 11 having a transmitting coil on a third substrate 5.

[0030] Alternatively, the roles of the transmitter and receiver can be exchanged according to a second solution, i.e. a first transmitter 9' with a first transmitter coil can be arranged on the first substrate 3, a second transmitter 10' with a second transmitter coil can be arranged on the second substrate 4, and a receiver 11' with a receiver coil can be arranged on the third substrate 5. For the sake of clarity, said solutions are not indicated by corresponding reference signs in the figures.

[0031] In a third solution, instead of the transmitter device 11 with the transmitter coil, a single electrically conductive active element, configured in particular as a target, is arranged on the third substrate 5 as part of the transmitter device 11 or is formed by the third substrate 5. In this case, a fixed excitation coil is associated with the active element.

[0032] These means will be explained below in the form of various examples with reference to FIGS.

[0033] 2 shows a first embodiment of a transmitter or receiver device 9, 10, 11 (or 9', 10', 11') for the sensor device 1. In this embodiment, the transmitter and receiver devices 9, 10, 11 each comprise at least one coil (first means and second means) as described above. Since corresponding arrangements are preferably configured in the same or at least similar manner, FIG. 2 shows an embodiment in which each of the substrates 3, 4, 5 comprises a transmitter and receiver device 9, 10, 11.

[0034] Here, the first receiving device 9 has a first receiving coil 12, the second receiving device 10 has a second receiving coil 13, and the transmitting device 11 has a transmitting coil 14. The coils 12, 13, 14 extend geometrically periodically in the tangential direction along the respective substrates 3, 4, 5. For this purpose, the coils are configured in a stepped, here rectangular, configuration in the tangential direction. Energy and / or signal transmission to or from the different coils 12, 13, 14 takes place via electrical contact connections 15, which are configured in particular as flexible cables or sliding contacts.

[0035] If a transmitter or receiver device 9', 10', 11' is used, corresponding coils 12', 13', 14' are provided, whereby the first transmitter device 9' comprises a first transmitter coil 12', the second transmitter device 10' comprises a second transmitter coil 13' and the receiver device 11' comprises a receiver coil 14'. For clarity, these means are not designated by corresponding reference signs in the figures.

[0036] 3 shows a second embodiment of such a transmitter or receiver device 9, 10, 11 for a sensor device 1. Instead of the transmitter coil 14, a conductive active element 16 configured as a target is arranged on the third substrate 5, to which a fixed excitation coil 17 with several windings is associated. The first and second receiver coils 12, 13 also extend geometrically periodically in the tangential direction along the respective substrates 3, 4, but, unlike the previous embodiment, are configured sinusoidally in the tangential direction and are therefore already configured differentially. In the sensor device 1 according to the invention, these differential coils are now connected differentially in series in pairs, as will be explained further with reference to FIG. 4.

[0037] Furthermore, in order to increase the robustness of the measurement method in each case, a further first receiver coil 18 and a further second receiver coil 19 are provided, the first receiver coils 12, 18 and the second receiver coils 13, 19 being arranged offset from one another. The corresponding substrates 3, 4, 5 are not shown or are shown transparent for clarity. Alternatively, the active element 16 can directly form the third substrate 5.

[0038] 4 shows an exemplary circuit diagram of two combinations of transmitter or receiver devices 9, 10, 11 for the sensor device 1. The connection state of two receiver coils 12, 13 on the first substrate 3 and on the second substrate 4 is shown by way of example. They are differentially connected to each other, i.e., the currents flow in opposite directions, via a circuit device 20 shown as a block, in particular configured as an ASIC. Similarly, a transmitter coil 14 is connected to the circuit device 20.

[0039] The circuit arrangement 20 is supplied with a voltage via a supply line 21 and is connected to an electrical reference potential via a ground line 22. An output signal of the sensor arrangement 1 is output via an output line 23.

[0040] 5A and 5B show magnetic field-angle graphs for use of the sensor device 1, i.e., here magnetic field-angle graphs showing the course of the magnetic field strength of the magnetic field B with respect to the torsion angle α, where Fig. 5A shows the values of the magnetic field B that occur when the torsion bar 2 is twisted in the case where the first and second receiving coils 12 and 13 have an electrical angular offset of 90° from each other.

[0041] In this arrangement, the regions of the coils 12, 13 with the maximum signal, as indicated by the corresponding hatched surfaces representing the strength of the magnetic field B, always alternate, so that the maximum possible overall signal is generated as the output signal of the sensor device 1.

[0042] 5B shows the value of the magnetic field B that results when the torsion bar 2 is twisted in the case where the coils 12, 13 have no angular offset from each other. Correspondingly, the areas with the maximum and minimum magnetic field strengths are aligned, which results in the smallest possible overall signal output.

[0043] 6 also shows a voltage-angle graph, which shows the course of the induced voltage U in the receiving coils 12, 13, here as a function of the difference angle φ. It can be seen that the voltage signal repeats with a periodicity P, which defines a region of uniqueness. In this case, the receiving coils 12, 13 are geometrically configured such that the induced voltage is proportional to the torsion angle and torsional moment in the torsion bar 2.

Claims

1. A sensor device (1) for determining the torsion angle of a torsion bar (2), in particular of a steering system of a motor vehicle, comprising: The device comprises at least one first substrate (3), a second substrate (4) and a third substrate (5), each of which is in the form of a plate or a disk, the substrates (3, 4, 5) being arranged on the torsion bar (2) at a distance from one another and being connected to the torsion bar (2) so as not to be able to rotate relative to one another; The third substrate (5) is disposed between the first substrate (3) and the second substrate (4) in the longitudinal extension direction of the torsion bar (2), - a first electrical receiving device (9) and a second electrical receiving device (10) are arranged on the first board (3) and the second board (4), and at least a part of an electrical transmitting device (11) is arranged on the third board (5), or At least a part of a first electrical transmitter (9') and a part of a second electrical transmitter (10') are arranged on the first board (3) and the second board (4), and an electrical receiver (11') is arranged on the third board (5). In the sensor device (1), The first receiving device (9) and the second receiving device (10) are differentially connected to each other, or the first transmitting device (9') and the second transmitting device (10') are differentially connected to each other. A sensor device (1) characterized in that

2. the transmitting device (11) has at least one transmitting coil (14), the first receiving device (9) has at least one first receiving coil (12), and the second receiving device (10) has at least one second receiving coil (13), or The first transmitting device (9') has at least one first transmitting coil (12'), the second transmitting device (10') has at least one second transmitting coil (13'), and the receiving device (11') has at least one receiving coil (14'). The sensor device according to claim 1 .

3. 3. The sensor device of claim 2, wherein the first transmitting coil (12) and the second transmitting coil (13) each have the same number of windings, or the first (12') and the second receiving coil (13') each have the same number of windings.

4. 2. The sensor device according to claim 1, wherein the transmitter device (11) comprises an electrically conductive active element (16), in particular a target, arranged on or configured as the third substrate (5), and a fixed excitation coil (17) associated with the active element (16).

5. 5. The sensor device according to claim 2, wherein at least one of the transmitting coil and the receiving coil (12, 13, 14) or the active element (16) extends or is configured geometrically periodically along each substrate (3, 4, 5) in the tangential direction.

6. 6. The sensor device according to claim 5, wherein at least one of the transmitting coil or the receiving coil (12, 13, 14) or the active element (16) extends or is configured sinusoidally or at least approximately stepped, in particular rectangularly, along the respective substrate (3, 4, 5) in the tangential direction.

7. 7. The sensor device according to claim 1, wherein the geometry is selected such that the output signal of the transmitter and / or receiver (9, 10, 11) represents the torsion angle of the torsion bar (2).

8. 8. The sensor device according to claim 7, wherein the voltage (U) induced in the sensor device (1) is proportional to the torsion angle of the torsion bar (2).

9. 8. The sensor device according to claim 7, wherein at least two transmitting devices or at least two receiving devices (9, 10, 11) are arranged on at least one of the substrates (3, 4, 5), each offset from one another by a set rotation angle.

10. 10. The sensor device according to claim 1, wherein at least one further substrate having at least one further transmitting device or at least one further receiving device is arranged on the torsion bar (2) in a non-rotatable manner relative to the torsion bar (2).

11. 11. The sensor device according to claim 1, wherein the torsion bar (2) contains an electrically conductive material and forms a ground connection for at least one of the transmitting device or the receiving device (9, 10, 11).

12. 12. The sensor device according to any one of claims 1 to 11, wherein energy and / or signal transmission to at least one of the transmitting or receiving devices (9, 10, 11) is performed via a flex cable, sliding contacts or wirelessly.

13. A steering system of a motor vehicle, characterized in that it is provided with a sensor device (1) according to any one of claims 1 to 12.

14. A motor vehicle provided with a steering device according to claim 13.

15. 13. A method for operating a sensor device (1) according to any one of claims 1 to 12, wherein the differential angle of rotation of the receiving or transmitting devices (9, 10, 11) relative to one another is determined as a function of the voltage difference of the induced voltages.

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