Improved inductive torsion bar torque sensor

Abstract

The invention relates to an inductive torsion bar torque sensor (100) comprising at least: first and second stator arrangements (10, 10A) each having a receiving structure (11, 11A) comprising a periodic repeating structure with first and second cycles; first and second rotors (20, 20A) rotatably arranged relative to the first and second stator arrangements (10, 10A) so as to form two inductive position sensors (1, 1A) for measuring the angle of each end of the torsion bar (5) and generating respective signals; at least one excitation or transmitter coil (40); and an oscillator circuit for generating and coupling a periodic alternating voltage into the excitation coil (s) (40). The periodicity of the first receiving structure (11) is different from the periodicity of the second receiving structure (11A), the first and second receiving structures (11, 11A) comprising first and second coil structures (101, 101; the device comprises a first rotatable rotor (20) for the purpose of influencing the intensity of the inductive coupling between the excitation coil (s) (40) and the first receiving structure (11), and a second rotatable rotor (20A) for the purpose of influencing the intensity of the inductive coupling between the excitation coil (s) (40) and the second receiving structure (11A). The signals generated by the first and second pairs of receiving structures (11, 11A) and the rotor (20, 20A) are orthogonal.

Description

Technical Field

[0001] The invention relates to an inductive torsion bar torque sensor having the features of the first part of claim 1 . Background Art

[0002] For power-assisted steering of motor-driven vehicles, the requirements on control assistance are high. Steering assistance control is needed to allow the steering assistance to be calculated based on (among other things) the steering torque in the steering column. In order to sense the steering torque, it is known to use a steering torque sensor or a torsion bar torque sensor. Since the steering assistance control is safety-critical, the sensed torque value must be very accurate. The steering control concept must also be robust to interferences from electric and magnetic fields, which means that the sensor must be robust to any such interferences. It is also an indispensable requirement that the sensor has a long service life and is fail-safe.

[0003] In order to provide the sensor with a long service life, non-contact sensors have been used.In order to provide the sensor impedance to the electromagnetic field generated by the motor control, avoiding interference has become a problem.

[0004] Sensors for measuring the absolute angular position of two steering column sections relative to the vehicle for determining the torque from the calculation of the difference between the absolute angular positions are known. The inductive position sensing is based on at least one excitation coil, at least one oscillator circuit connected to the excitation coil and generating a periodic alternating voltage and coupling it into the excitation coil during operation, at least two stators each having a plurality of periodically repeating receiver structures, at least two rotors rotatable relative to the stators and influencing the inductive coupling strength between the excitation coil and the receiver part, and an evaluation device suitable for evaluating the signal induced in the receiver part.

[0005] Because the torsion bar torque sensing principle is based on two position sensors, there is a risk that one of the sensors also detects the other rotor position (so-called over-hearing) instead of just the one it is supposed to detect. This is especially evident when there is a torsion bar torque, so that the two rotors are changing their relative position due to the twisting of the torsion bar.

[0006] DE 19941464 discloses an inductive angle sensor comprising two receiver coils arranged in a plane and two rotors arranged on top of each other, wherein the angular periodicities are different and the ratio between the angular periodicities is a non-integer.

[0007] In WO 2009 / 095442 (US 8453518), it was found that the method disclosed in DE 19941464 with an inductive angle sensor comprising two receiver coils arranged in one plane is not satisfactory because the measurement of the angle is not precise enough and is unreliable, since the receiver coils influence each other, which is a source of error in the determination of the angle difference, and the measurement results generally contain large errors.

[0008] Therefore, in WO2009 / 095442, a sensor principle for solving the eavesdropping problem is proposed, which comprises a combination of two inductive position sensors, measuring the angle at each end of a torsion bar, the angle difference multiplied by the stiffness of the torsion bar being the torsion bar torque, wherein different numbers of rotors and receiver structures on different sides are such that the number N of said receiver structures of said first receiver and the number M of said receiver structures of said second receiver are in an integer ratio greater than 1 with respect to each other, which means that:

[0009]

[0010] However, the problem of eavesdropping is still not solved to a satisfactory degree by the solution discussed in WO2009 / 095442 and the sensor is susceptible to eavesdropping. Instead, the ratio condition seems to be only the result of exhaustive testing of an arbitrary solution, since it is stated: "It has been found that, surprisingly, due to an integer ratio of the number N of receiver structures of the first receiver part to the number M of receiver structures of the second receiver part (however, the number of receiver structures of the two receiver parts must not be the same), the measurement error in the angle measurement difference can be reduced".

[0011] Furthermore, as described in WO 2009 / 095442, there are considerable manufacturing constraints associated with the sensor, since the quotient between the number of receiver structures must be an integer greater than 1, ie differ by at least a factor of one.

[0012] WO20211250510A1 shows a torque sensor with an oscillator circuit that generates a periodic voltage signal and couples it to at least one excitation coil, a first channel having a first receiver having a periodically repeated receiver structure and a first rotor target, and a second channel having a second receiver having a periodically repeated receiver structure and a second rotor target. In order to reduce interference between the channel and one or more features, the electromagnetic coupling between the first and second channels is reduced. The number M of first receiver structures is determined based on the number N of second receiver structures, so that in some embodiments, M=2N+ / -1, and in some embodiments, M=2N. In order to reduce the electromagnetic coupling between the first channel and the second channel, a rotor target made of different types of materials is used, or a receiver period of different ratios relative to the rotor target is used to create a time-varying field in the rotor target.

[0013] In some embodiments where both channels of the torque sensor include rotor targets and receivers having the same configuration, the number M of first receiver structures is determined based on the number N of second receiver structures such that M=2N+ / -1, and the angular width of each target lobe of the first rotor target of the first channel is adjusted to be approximately equal to the angular width of a single period of a plurality of second receiver structures corresponding to the second receiver of the second channel. FIG. 6 shows, for example, a first rotor target 212 configured to be orthogonal to a second rotor target 214, i.e., the two rotors are geometrically positioned so that they are located only on a small portion of the circumference and are angled in different directions.

[0014] However, using a first number of receiver structures M=2N corresponds to the teaching of WO2009 / 095442 discussed above, and the torque sensor will suffer from the same disadvantages, and likewise the torque sensor will suffer from suboptimal resolution and noise on both angle sensors if a first number of receiver structures M=2N±1 is used, as if the optimal design had N periods, so clearly the M=2N±1 design is not optimal (given that N is greater than 1 - otherwise there would not be any reduction in electromagnetic coupling at all). Furthermore, due to the limited number of available receiver structures, the design freedom is also limited. Summary of the invention

[0015] It is therefore an object of the present invention to provide an improved inductive torque sensor by which one or more of the above-mentioned problems may be solved and by which one or more of the disadvantages may be overcome.

[0016] In particular, it is an object to provide an inductive torque sensor by means of which both inductive position sensings are substantially protected from eavesdropping.

[0017] A further object is to provide an inductive torque sensor which provides very accurate sensed torque values ​​and which is particularly useful for measuring steering torque values ​​for automotive steering assist control.

[0018] Furthermore, it is an object to provide an improved torque sensor having an increased resolution and a reduced noise reduction.

[0019] In particular, it is an object to provide an inductive torque sensor which is robust to disturbances from magnetic and electromagnetic fields and in particular from the motor control.

[0020] Another specific object is to provide an inductive torque sensor that is simple and inexpensive to manufacture.

[0021] Yet another object is to provide an inductive torque sensor which can be custom made and which allows a high degree of design freedom.

[0022] More specifically, an object is to provide an inductive torque sensor which is resistant to wear and has a long service life.

[0023] An inductive torque sensor as initially mentioned having the characterizing features of claim 1 is therefore provided.

[0024] Advantageous embodiments are given by the attached dependent claims and are described in the detailed description.

[0025] It will be appreciated that features of the invention are susceptible to being combined in any combination without departing from the scope of the invention as defined by the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will now be further described in a non-limiting manner with reference to the accompanying drawings, in which:

[0027] Figure 1 Schematically illustrates an inductive torque sensor according to an embodiment of the present invention,

[0028] Figure 2 Is has Figure 1 Schematic top view of a first stator arrangement of a receiving structure of an inductive torque sensor shown in,

[0029] Figure 3 yes Figure 1 Schematic top view of a first rotor of the inductive torque sensor shown in,

[0030] Figure 4 Yes Figure 1A schematic diagram of a receiving structure of an inductive torque sensor and a sensor element of a rotor shown in FIG. 1 , and

[0031] Figure 5 Is has Figure 1 Schematic diagram of a portion of a stator plate of a sensor chip of an inductive torque sensor shown in FIG.

[0032] For the purpose of describing the present invention, and to facilitate its understanding, the following definitions are given, some of which will be relied upon in the detailed description of advantageous embodiments:

[0033] Torsion bar torque is the torque measured using a sensor that is sensitive to the twisting of a specific torsion bar mounted somewhere in the steering column.

[0034] The excitation coil is typically a circular coil inducing one or several loops of an electromagnetic field which, for the applications described here, excites eddy currents in the surrounding conductive material.

[0035] Eddy currents (also called Foucault currents) are current loops induced in a conductor by a changing magnetic field in the conductor, according to Faraday's law of induction. Eddy currents flow in closed loops in the conductor, in a plane perpendicular to the magnetic field. They can be induced in a nearby stationary conductor by a time-varying magnetic field. By Lenz's law, eddy currents create a magnetic field that opposes the change in the magnetic field that created it, and therefore the eddy currents react against the source of the magnetic field.

[0036] An oscillator circuit is a circuit that varies the current in an excitation coil.

[0037] The stator is a fixed structure that holds one or several receiving structures.

[0038] The receiving structure is the coil structure on the stator.

[0039] The rotor is an electrically conductive rotating member having a shape such as to match the receiving structure in such a way that the rotor rotation can be detected in the current flow of the receiving structure.

[0040] Eavesdropping means the problem of inducing current in another receiving structure than the structure that should pick up the corresponding rotor magnetic field.

[0041] MCU is a microcontroller unit, a small computer on a single metal-oxide-semiconductor integrated circuit (IC) chip.

[0042] An ECU is an electronic control unit for the following functions: reading analog sensor signals and digital signals which can be transmitted via, for example, a signal bus, performing any type of calculations, such as, for example, performing control tasks and actuating actuators either via transmitted analog or digital signals or by directly controlling, for example, an electric motor from a motor control stage.

[0043] Orthogonal functions have the following definition: if the scalar product of functions f and g is zero, then they are orthogonal. Example of an orthogonal pair of .

[0044]

[0045] Here τ represents the interval of one revolution, 2π.

[0046] Fourier series are a set of orthogonal functions.

[0047]

[0048] where τ represents the interval of one revolution, 2π. This means that if M ≠ N, the functions from the Fourier series are always orthogonal.

[0049] Steering wheel torque measurement is the torque measured in the steering column or in the steering wheel. DETAILED DESCRIPTION

[0050] Figure 1 1 is a schematic diagram of an inductive torque sensor 100 according to a first embodiment of the present invention. The sensor principle mentioned above in the present application is based on a combination of two inductive position sensors 1, 1A, which are arranged to measure the angle of each end of the torsion bar 5 and obtain the torsion bar torque, which is the angle difference multiplied by the stiffness of the torsion bar 5. The inductive torque sensor 100 comprises: at least one excitation coil or transmitter coil 40 (see Figure 2 ); at least one oscillator circuit (not shown), which is connected to the excitation coil and which generates a periodic alternating voltage during operation and couples it into the excitation coil; at least two stator arrangements 10, 10A, each stator arrangement comprising a plurality of periodically repeated receiving structures 11, 11A (see Figure 2 ); two rotors 20, 20A, which can rotate relative to the stator arrangement 10, 10A and which influence the strength of the corresponding inductive coupling between the excitation coil and the receiving structure 11, 11A; and an evaluation component, such as an MCU (not shown) suitable for evaluating the signals induced in the receiving structure 11, 11A.

[0051] exist Figure 1In the embodiment shown in , the inductive torque sensor 100 is arranged to measure the torque in an axis including a first (e.g. upper) axis segment 6 and a second (e.g. lower) axis segment 6' (e.g. the steering torque of a steering column including a first steering column portion and a second column portion), between which a torsion bar 5 is arranged. As also mentioned above, the inductive torque sensor 100 comprises a first stator arrangement 10 and a second stator arrangement 10A, a first rotatable rotor 20 and a second rotatable rotor 20A. The first and second rotors 20, 20A are each connected to the axis, the first rotor 20 being connected to the upper axis segment 6, and the second rotor being connected to the second (here lower) axis segment 6'. The first rotor 20 is arranged at one end of the torsion bar 5, and the second rotor 20A is arranged at a second end opposite to the first end of the torsion bar 5, and the stator arrangement 10, 10A is arranged between the two rotors 20, 20A, each stator arrangement 10, 10A comprising a respective receiving structure 11, 11A facing the respective rotor 20, 20A.

[0052] The first rotatable rotor 20 is used for the purpose of influencing the strength of the inductive coupling between the excitation coil / excitation coil and the receiving structure 11 of the first stator arrangement 10 by rotation, and the second rotatable rotor 20A is used for the purpose of influencing the strength of the inductive coupling between the excitation coil / excitation coil and the second receiving structure 11A of the second stator arrangement 10A by rotation; the excitation coil generates eddy currents in the first rotor 20 by induction, and due to the eddy currents generated in the first rotor 10, the first receiving structure 11 will have an induced current, and correspondingly, the excitation coil generates eddy currents in the second rotor 20A by induction, and due to the eddy currents generated in the second rotor 20A, the second receiving structure 11A will have an induced current.

[0053] The shape of the rotor 20, 20A will be referred to below. Figure 3 Further described, and including a rotor structure period that matches the period of the receiving structure 11, 11A of the stator arrangement 10, 10A. Preferably, the first receiving structure 11 of the first stator arrangement 10 and the first rotor 20 have the same number of periods, and the second receiving structure 11A of the second stator arrangement 10A and the second rotor 20A have the same number of periods, but the period and number of rotor elements of the first rotor 20 and stator arrangement 10 structure (combination) should not be the same as the period and number of rotor elements of the second rotor 20A and stator arrangement 10A structure (combination). In an alternative embodiment, the first receiving structure 11 of the first stator arrangement 10 and the first rotor 20 are not the same number of periods, and the second receiving structure 11A of the second stator arrangement 10A and the second rotor 20A are not the same number of periods.

[0054] Figure 2A first stator arrangement 10 according to an embodiment of the invention is schematically illustrated. The first receiving structure 11 comprises a first coil structure 101, 101 and a second coil structure 102, 102. The coil structures 101, 101, 102, 102 are located here on a circuit or stator plate 12, and each coil structure 101, 102 has a sinusoidal shape. The first coil structure 101 comprises two cosine coils forming a cosine loop (solid line), and the second coil structure 102 comprises two sine coils forming a sine loop (dashed line). The first coil structure (cosine loop 101) and the second coil structure (sine loop 102) are connected so that a complete revolution of the first cosine coil is connected in series with the other cosine coil ( Figure 2 10 ). Different shapes are arranged in different layers on the circuit board. These cosine coils connected in series form the cosine part of the first receiving structure 10. The sine part of the first receiving structure 10 is made similarly. The excitation coil 40 can have one or several loops. Ideally, such a circular loop induces a uniform field through the plane of the circuit board 12.

[0055] The second stator arrangement 10A is similar to the first stator arrangement 10, but as mentioned above the number of periods of the first stator / rotor and the second stator / rotor structure (combination) differ, and thus the number of rotor elements of the first and second rotors 20, 20A also differ.

[0056] In a first embodiment, each stator arrangement comprises a circuit board 12, in an alternative embodiment (not shown) there is a common circuit board for the first and second receiving structures, which are then arranged in different layers of the circuit board, allowing cost savings and, in addition, a single excitation coil is then sufficient for the two angular sensing parts of the inductive torque sensor.

[0057] Figure 3 Schematically illustrated is a first rotor 20 having a plurality of rotor elements 21 which are arranged to form a square wave in a polar coordinate system during rotation, as will be explained further below.

[0058] Figure 4Schematically illustrated is a first sensor part 1 of an inductive torque sensor 100 comprising a first receiving structure 11 of a first stator arrangement 10 and a first rotor 20 (first rotor 20 and stator arrangement 10 structure). The solution according to the invention is based on orthogonal Fourier series and the first rotor 20 and stator arrangement 10 structure is orthogonal to the second rotor 20A and stator arrangement 10A structure and the first rotor 20 and stator arrangement 10 structure forms one function in an orthogonal system and the second rotor 20A and stator arrangement 10A structure forms another function in the same orthogonal system, which is the definition of orthogonality and the first rotor 20 and stator arrangement 10 structure will not see the second rotor 20A and stator arrangement 10A structure and vice versa. Therefore, when the two structures are orthogonalized in this way, there is no risk that one receiving structure will pick up the field of the other rotor and vice versa.

[0059] Since the stator arrangement and the rotor of each sensor 1, 1A of the inductive torque sensor 100 are located on the same axis, the excitation coil (not shown in the figure) will excite the first rotor 20, which in turn excites the first receiving coil structure 11. If the rotor 20 is just above one of the cosine "eyes" of the first (cosine) first coil structure 101 (cosine loop), the cosine current will have its maximum amplitude. Since the second coil structure 102 (sine loop) lags behind by 90 degrees, it will have zero amplitude at this position. Therefore, the first receiving structure 11 will receive sine and cosine currents reflecting the position of the rotor 20.

[0060] The first rotor 20 and stator arrangement 10 configuration will produce a pure sinusoidal signal with M complete periods for a complete revolution and the second rotor 20A and stator arrangement 10A configuration will produce a pure sinusoidal signal with N complete periods for a complete revolution, or vice versa. M and N are therefore integers.

[0061] Furthermore, in order to obtain the angle of one of the rotor and stator arrangements 11, 20; 11A, 20A, for each there should be two sinusoidal receiving arrangements with a phase difference of π / 2, namely one sine and one cosine. The resulting signal would then be:

[0062]

[0063] And therefore, the angle can be calculated as:

[0064]

[0065] where the result of the inverse tangent function is expanded so that the angle will be continuous. Note that when x is zero, y / x is singular. As is known to those skilled in the art, arctan(x / y) is used, and when beneficial, the correct angle can be calculated from this new angle, as is known.

[0066] In case two or more such rotor 20, 20A and stator arrangement 10, 10A structures produce pure sinusoidal signals with M or N periods for a complete revolution for two or more rotor and stator arrangements respectively, if M≠N, the resulting signals will belong to an orthogonal system of Fourier series. This is sufficient for the receiving structure 11, 11A of one rotor and stator arrangement structure to not eavesdrop or receive signals from the rotor of another rotor and stator arrangement structure; therefore

[0067]

[0068] In an alternative embodiment, each receiving structure is made of one or more sawtooth shapes. Since such a shape will result in a sawtooth current, it is possible to detect the position of the rotor. An advantage of the inductive torsion bar torque sensor according to the concept of the present invention is that the Fourier series relationship

[0069] M≠N

[0070] There are not many restrictions imposed on the design of the torsion bar torque sensor.The integers M and N can both be close to a desired integer, as defined by typical design aspects such as, for example, resolution, noise, etc.

[0071] For example, if the optimal integer for the sensor design is X, then X and X+1 (M and N, respectively) or X and X-1 may be used, both of which are still close to the optimal integer X; for example, in one embodiment, the optimal integer is 8, then M=7, N=8, or M=8 and N=9 may be used, or vice versa.

[0072] More generally, the number of periods (M, N) of the first and second receiving structures 10 ; 10A and the number of periods of the second receiving structure are at least greater than three, preferably greater than four, most particularly greater than five.

[0073] In an advantageous embodiment, the number of periods of the first receiving structure 10 is M=N+ / -S, N being the number of periods of the second receiving structure 10A, or vice versa, N=M+ / -S, where S is between 1 and 3. More particularly S≤2, most particularly S=1.

[0074] Being able to use close numbers has been shown to be very advantageous for several reasons.

[0075] First, the order M and N should be designed so that the sensor provides adequate resolution while it has low noise and high robustness. The larger the order, the greater the noise, and the greater the nonlinear effects that always occur (such as due to imperfect rotors, imperfect receiving and excitation coils, or the field shape produced by the excitation coils or the conductivity of the housing). Therefore, any design will have an optimal order, and it has been recognized that having an order that is both close to this optimal value is very advantageous.

[0076] Second, even if the ideal Fourier series is orthogonal, there are always imperfections. These imperfections can be seen as over-tones in the Fourier series, and according to the definition of orthogonality of the Fourier series, the over-tones may not be orthogonal. For example, as in the case of the torque sensor shown in WO2009 / 095442, the first overtone of order 8 will have order 16, which will not be orthogonal to order 16 and will therefore be overheard.

[0077] In the case of a relationship according to the invention, for example where M=8 and N=9, first there is a risk of eavesdropping for the first common overtone, which will then be the 9th overtone of order 8 (72) and the 8th overtone of order 9 (also 72), which are fairly high overtones, and the higher the overtone, the less energy, and therefore the risk of eavesdropping on the overtones will be very low.

[0078] It has been realised that in order to achieve a good resolution of the position sensor 1 , 1A, each of the structures N, M as defined above should have a high order, but in order to avoid high noise and limited accuracy the order should not be too high.

[0079] Preferably, the first common harmonic is high, or as high as possible taking into account also the above and also as discussed below.

[0080] Preferably, N, M are greater than or equal to 4, in particular between 4 and 10; even more in particular between 5 and 10. The resolution of the D / A converter will be about one period, and the resolution will therefore be proportional to 1 / N and 1 / M, respectively.

[0081] Most particularly, the relationship or quotient between the maximum number and the minimum number of repetitions of the shape of the first and second pairs of coil structures and the shape of the rotor is a non-integer between 1 and 3, and N and M are close.

[0082] The invention, with orthogonality by choosing M≠N, provides the possibility of having not only one single excitation coil and one oscillator circuit for the excitation of both rotors, but also one single board for the receiving structure, while avoiding eavesdropping. In simple terms, the receiving structure cannot then see the wrong rotor. As an example. An order 9 receiving structure cannot see an order 8 rotor, and vice versa.

[0083] Using a single board and a single excitation coil oscillator circuit is advantageous from a cost point of view and also from a packaging point of view, as there is only one circuit board and the rotor does not need to be separated to avoid eavesdropping.

[0084] However, it should be clear that the invention is not limited to the use of only one excitation coil oscillator circuit; two or more may be used in alternative embodiments. The invention is also not limited to the use of a single board.

[0085] It is possible to select any shape of the repetitive structure of both the rotor and the receiving structure. The only requirement is that the shape of the signal generated by the combination of the rotor shape and the receiving structure shape of the corresponding receiving structure and rotor pair is orthogonal. From the perspective of orthogonality, any signal shape is valid, where the Fourier terms of two different signals do not contain the same order. As an example, one signal can have a Fourier series [8 16 24 32 48 56 64], while another signal can have a Fourier series [9 18 27 36 45 54 63]. By the definition of orthogonality, the two angle signals are orthogonal and cannot see each other. So, again, all the benefits mentioned above can be achieved. Another benefit of selecting a higher order shape as in the present embodiment is that the resolution of the sinusoidal signal is best when it is close to zero, and very poor when it is close to the maximum amplitude (because at the maximum amplitude, there is no change in the signal for angle changes). Since two signals are used, see the embodiment with sine and cosine shapes, when one signal dominates the resolution, the signal can be chosen to have the largest possible slope (see arctan(y / x), where y dominates the resolution when x moves slowly, and vice versa). In this embodiment, the function arctan will be replaced by another function to implement the transfer function between the quotient between x and y and the angle (and as mentioned for the case of arctan, a transfer function between the quotient between y and x and the angle is also needed). Since all Fourier terms in the equations are known, such a function is always possible to calculate, at least numerically. By changing the shape from a single sinusoidal Fourier term shape to a more complex shape, the resolution or noise can be improved by nearly 50%.

[0086] If the rotor structure in the foregoing embodiment is a square wave in polar coordinates, as before, the generated signal corresponds to the shape of the Fourier term in the receiving structure.

[0087] Figure 5 is a schematic diagram of a portion of a first stator arrangement 10, showing a portion of a circuit board 12, and used to illustrate the connection to the sensor chip 7 (MCU). For simplicity, only (a portion of) the cosine loop structure 101 is illustrated, the operation and arrangement of the sine loop structure are similar. A cosine coil having a sine-cosine shape and a negative cosine shape is connected at 130. The cosine coil structure has ends 101', 101". connected to the sensor chip 7. The ends of the excitation coil 40 are connected in a similar manner (not shown).

[0088] According to the present invention, and as should be clear from the above, the orthogonality between the signals generated in two different angle sensors is crucial to achieving the benefit of essentially no or only very low risk of eavesdropping between the two angle sensors, the significantly increased design freedom allows making the two angle sensors optimal or very close to optimal in terms of resolution and noise suppression, for example by choosing the optimal orders of N and M.

[0089] Particular cost benefits can be achieved by using only one excitation coil and circuit, and / or one receiving structure circuit board.

[0090] Furthermore, by using both one circuit board and the closer proximity to, and therefore distance between, the rotors, particular packaging benefits may be achieved.

[0091] By choosing a common orthogonal function, it is possible to improve the resolution and / or noise level and make the resolution more uniform across all angles.

[0092] As also mentioned above, the present invention is also advantageous in that a very high degree of design freedom is allowed and the torque sensor is easy to manufacture, (among other things) because there is advantageously a relatively small number of rotor elements and because in advantageous embodiments an advantageously close or substantially similar number of rotor elements is used for the first and second rotors.

[0093] Several benefits are noted from embodiments of the present invention, and one particular benefit (i.e., optimization of resolution and reduction of noise) is to have the orders M and N of the repeating structures be similar. That is, the quotient between the maximum number and the minimum number of repeating shapes of the rotor 12, 12A and the first and second pairs of coil structures 11, 11A is a non-integer close to 1. To be fairly close to the optimal value, this number should preferably be between 1 and 3, or at least between 1 and 5.

[0094] An inductive torque sensor connected to an ECU as described above may for example be used in a power assisted steering system of a vehicle or the like, comprising connection to a steering shaft or axis of a steering arrangement for measuring torque in the steering shaft or axis.

[0095] Of course, it can also be used in many other applications where high accuracy, robustness against interference and eavesdropping, and long lifetime are important requirements.

[0096] It is clear that the invention is not limited to the specifically shown embodiments but can be varied in many ways within the scope of the appended claims.

Claims

1. An inductive torsion bar torque sensor (100), for example for use in a power assisted steering system, the inductive torsion bar torque sensor (100) comprising at least first and second stator arrangements (10, 10A) each having a receiving structure (11, 11A) having a periodically repeating shape or structure having first and second periods, respectively, and first and second rotors (20, 20A) rotatably arranged relative to the first and second stator arrangements (10, 10A) to form two inductive position sensors (1, 1A) arranged to measure the angle of each end of a torsion bar (5) and generate corresponding signals, wherein the product of the difference between the measured angle values ​​of the two inductive position sensors (1, 1A) and the stiffness of the torsion bar (5) is the torsion bar torque, the inductive torsion bar torque sensor (100) further comprising at least one excitation coil or transmitter coil (40) and at least one oscillator circuit for generating a periodic signal during operation. a first receiving structure (11) and a second receiving structure (11A) respectively comprising a first coil structure (101, 101) and a second coil structure (102, 102), each coil structure having a repeating shape; the first rotatable rotor (20) is used for the purpose of influencing the strength of the inductive coupling between the (one or more) excitation coils (40) and the receiving structure (11) of the first stator arrangement (10) by its position; and the second rotatable rotor (20A) is used for the purpose of influencing the strength of the inductive coupling between the (one or more) excitation coils (40) / the (one or more) excitation coils (40) and the second receiving structure (11A) of the second stator arrangement (10A) by its position, It is characterized in that The respective signals generated by the first and second pairs of receiving structures (11, 11A) and the rotor (20, 20A) are in quadrature.

2. The inductive torque sensor (100) according to claim 1, characterized in that The signals generated by the receiving structure (11, 11A) and the rotor (20, 20A) of the respective inductive position sensor (1, 1A) each have the shape of a respective repeating Fourier series, and wherein terms of the Fourier series of the signal generated by one receiving structure (11) and rotor include terms of the Fourier series of the signal generated by another receiving structure (11A) and rotor (20A) pair.

3. The inductive torque sensor (100) according to claim 1 or 2, characterized in that The relationship or quotient between the maximum number and the minimum number of repeating shapes of the first and second pairs of receiving structures (11, 11A) and the rotor (12, 12A) is a non-integer.

4. The inductive torque sensor (100) according to any one of claims 1 to 3, characterized in that: The relationship or quotient between the maximum number and the minimum number of repeated shapes of the first and second pairs of receiving structures (11, 11A) and the rotor (12, 12A) is a non-integer between 1 and 5, particularly between 1 and 3, and even more particularly between 1 and 2.

5. The inductive torque sensor (100) according to any one of the preceding claims, characterized in that The first stator arrangement (10) and the second stator arrangement (20) each comprise an electric circuit or a stator plate (12), on which a respective receiving structure (11, 11A) is arranged, and wherein each stator arrangement comprises a respective excitation coil.

6. The inductive torque sensor (100) according to any one of claims 1 to 5, characterized in that: The receiving structures (11, 11A) of the first stator arrangement (10) and the second stator arrangement (20) are arranged on a common circuit or stator plate, and wherein a common excitation coil (40) is used to excite the first and second receiving structures (11, 11A).

7. An inductive torque sensor (100) according to any one of the preceding claims, characterized in that Each rotor (20, 20A) comprises a number of rotor elements (21) or rotor structure periods, which is the same number as the number of periods of a corresponding receiving structure (11; 11A) of a corresponding, corresponding stator arrangement (10, 10A).

8. An inductive torque sensor (100) according to any one of the preceding claims, characterized in that Each rotor (20, 20A) comprises a plurality of rotor elements (21) or rotor structure periods, which match the number of periods of the corresponding receiving structure (11; 11A) of the corresponding stator arrangement (10, 10A), so that the first rotor (20) and stator arrangement (10) structure form one function in an orthogonal system, and the second rotor (20A) and stator arrangement (10A) structure form another function in the same orthogonal system.

9. The inductive torque sensor (100) according to any one of the preceding claims, characterized in that The first and second receiving structures (11, 11A) have a sinusoidal shape.

10. The inductive torque sensor (100) according to claim 9, characterized in that Each respective first coil structure (101) comprises a cosine loop having two first and second cosine coils connected such that a complete revolution of the first cosine coil is connected in series with the second cosine coil, wherein each second coil structure (102) comprises two sine coils, the first and second sine coils connected such that a complete revolution of the first sine coil is connected in series with the second sine coil.

11. The inductive torque sensor (100) according to any one of claims 1 to 8, characterized in that Each receiving structure comprises a corresponding first coil structure (101, 101) and a corresponding second coil structure (102, 102), each coil structure having a sawtooth shape.

12. The inductive torque sensor (100) according to any one of claims 1 to 11, characterized in that Each rotor (20, 20A) comprises a plurality of rotor elements (21) arranged to form a square wave in a polar coordinate system during rotation.

13. The inductive torque sensor (100) according to any one of the preceding claims, characterized in that The number of periods of the first and second receiving structures (10, 10A) is chosen so that the first common harmonic is high order with a low risk of overhearing of the harmonics.

14. The inductive torque sensor (100) according to any one of the preceding claims, characterized in that The period numbers of the first and second receiving structures (10, 10A) are selected so that at least the first harmonics are orthogonal.

15. The inductive torque sensor (100) according to any one of the preceding claims, characterized in that The number of periods (M, N) of the first and second receiving structures (10; 10A) and the number of periods of the second receiving structure are at least greater than 3, preferably greater than 4, most particularly greater than 5.

16. An inductive torque sensor (100) according to any one of the preceding claims, characterized in that The period number of the first receiving structure (10) is M=N+ / -S, N being the period number of the second receiving structure (10A), or vice versa, wherein S is between 1 and 3.

17. The inductive torque sensor (100) according to claim 16, characterized in that M=N+ / -2, or in particular M=N+ / -1, ie S=2, or more in particular S=1.

18. The inductive torque sensor (100) according to any one of claims 15 to 17, characterized in that The period M of the first receiving structure (10) is between 3 and 15, in particular between 6 and 12, in particular between 7 and 9.

19. An inductive torque sensor (100) according to any one of the preceding claims, characterized in that The evaluation component comprises a sensor chip (7), which comprises an MCU for evaluating the signal induced in the receiving structure (11; 11A), and wherein the ends of the first and second coil structures (101, 101, 102, 102) of the receiving structure (11; 11A) and the ends of the excitation coil (40) are connected to the sensor chip (7).

20. Use of an inductive torque sensor according to any one of claims 1-19 for sensing steering torque to calculate steering assist in a power assisted steering system of a vehicle, or for sensing torque in an axle in a machine or the like, the vehicle being, for example, a car, bus, truck, aircraft, boat or a remotely operable vehicle.

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