Magnetic angle position sensor

Abstract

A magnetic angle position sensor system (100) comprising: a shaft (104) rotatable about an axis of rotation, which has a soft magnetic shaft end piece; a sensor chip (110) which is spaced axially from the shaft end piece and defines a sensor plane which is essentially perpendicular to the axis of rotation; at least four magnetic field sensor elements (114a, 114b, 115a, 115b, 116a, 116b, 117a, 117b, 118a, 118b, 119a, 119b, 120a, 120b, 121a, 121b; 114b', 116a', 114a', 116b', 117b', 115a', 117a', 115a') integrated into the sensor chip (110), wherein two of the magnetic field sensor elements (114a, 114b, 116a, 116b, 118a, 118b, 120a, 120b; 114b', 116a', 114a') 116b') are spaced apart from each other and are sensitive only to magnetic field components in a first direction, and wherein two of the magnetic field sensor elements (115a, 115b, 117a, 117b, 119a, 119b, 121a, 121b; 117b', 115a', 117a', 115a') are spaced apart from each other and are sensitive only to magnetic field components in a second direction; the first and the second direction are mutually non-parallel and the first and the second direction are perpendicular to the axis of rotation; a magnetic field source (102, 102') which magnetizes the wave end piece, wherein the wave end piece is shaped such that a magnetic field in the sensor plane caused by the magnetic field source (102, 102') is symmetric with Nth order, where N is a finite integer ≥ 1; and a circuit arrangement coupled with at least four magnetic field sensor elements (114a, 114b, 115a, 115b, 116a, 116b, 117a, 117b, 118a, 118b, 119a, 119b, 120a, 120b, 121a, 121b; 114b', 116a', 114a', 116b', 117b', 115a', 117a', 115a') configured to calculate an angular position of the shaft by processing output signals from the at least four magnetic field sensor elements (114a, 114b, 115a, 115b, 116a, 116b, 117a, 117b, 118a, 118b, 119a, 119b, 120a, 120b, 121a, 121b; 114b', 116a', 114a', 116b', 117b', 115a', 117a', 115a') can be combined, wherein the shaft end piece has at least a groove (P) arranged in its end face (105) or at least a projection (150) arranged on the end face (105), wherein the groove (P) or the projection (150) is shaped such that the shaft end piece has a rotational symmetry of Nth order, where N is a finite integer ≥ 2.

Description

TECHNICAL AREA

[0001] The invention relates generally to angular position sensors which use magnetic field sensors to measure an angular value, in particular on-axis angular position sensors, systems and methods with a variety of applications, including brushless DC motors. BACKGROUND

[0002] Magnetic field sensors can be used to measure the angular position of a shaft or other object. For example, a permanent magnet can be mounted on the shaft, and a magnetic field sensor can be positioned near the magnet to measure the magnetic field generated by the magnet as it rotates with the shaft. When the magnetic field sensor is mounted next to the shaft at a certain distance from the shaft's axis of rotation, the sensor is often referred to as a magnetic off-axis angular position sensor. Magnetic off-axis angular position sensors are frequently implemented when the end face of the shaft is inaccessible (e.g., due to a specific application or assembly of the shaft) and, consequently, the sensor elements cannot be mounted on the axis of rotation.Conversely, a magnetic on-axis angular position sensor is mounted at or near one end of the shaft, facing its end face, and is generally in line with or symmetrical to the axis of rotation. In some embodiments, magnetic on-axis angular position sensors can be designed to measure a magnetic field gradient. For this purpose, the magnetic field can be measured at two different points located on opposite sides of the axis of rotation and symmetrical to it. The gradient can then be determined with sufficient accuracy for many applications by combining the two measured magnetic field values, for example, by subtraction.

[0003] In many applications, a general design goal for magnetic angular position sensors is to be inexpensive while remaining robust against external magnetic fields and other disturbances, as well as insensitive to assembly tolerances. A specific application for magnetic angular position sensors is the detection of the shaft's (angular) position during rotation in brushless DC motors (BLDC motors). BLDC motors present a challenging environment for magnetic field sensors because they typically feature strong, rotating magnets and copper windings carrying high currents; both generate time-varying magnetic fields that interfere with the magnetic field used for angular position measurement, causing measurement errors. These interfering magnetic fields are highly inhomogeneous, making it difficult to eliminate their effects on the angular position measurement.In light of these problems, there is a general need for improvements in magnetic angle position sensors. Publication DE 100 49 351 A1 discloses a position sensor with a rotating shaft having a magnetic irregularity on one end face and a sensor arrangement for detecting the rotational position of the shaft. The sensor arrangement comprises a plurality of pie-shaped magnetic resistance elements whose respective resistances change with changes in the magnetic field. DE 10 2014 116 842 A1 discloses a magnetic field angle sensor system with a shaft having a rotationally asymmetric end section and with three magnetic field sensor elements that are sensitive to the axial magnetic field component. Further angle sensors are known, for example, from publication DE 10 2014 116 826 A1. SUMMARY

[0004] A magnetic angular position sensor system is described here. According to an exemplary embodiment, the angular position sensor system comprises a shaft rotatable about an axis of rotation, the shaft having a soft magnetic end piece. The system further comprises a sensor chip axially spaced from the end piece and defining a sensor plane substantially perpendicular to the axis of rotation. At least four magnetic field sensor elements are integrated into the sensor chip, wherein two of the magnetic field sensor elements are spaced apart and are sensitive only to magnetic field components in a first direction, and wherein two of the magnetic field sensor elements are spaced apart and are sensitive only to magnetic field components in a second direction, the first and second directions being mutually non-parallel and perpendicular to the axis of rotation.Furthermore, the system comprises a magnetic field source that magnetizes the shaft end piece, wherein the shaft end piece is shaped such that a magnetic field in the sensor plane, generated by the magnetic field source, is N-th order symmetric, where N is a finite integer ≥ 1. The system also includes a circuit arrangement coupled to the at least four magnetic field sensor elements, configured to calculate an angular position of the shaft by combining output signals from the at least four magnetic field sensor elements. The shaft end piece has at least one groove or at least one projection arranged on its end face, wherein the groove or projection is shaped such that the shaft end piece exhibits N-th order rotational symmetry, where N is a finite integer ≥ 2.

[0005] According to another exemplary embodiment, the angular positioning system comprises a shaft rotatable about an axis of rotation, the shaft having a soft magnetic end piece. The system further comprises a sensor chip axially spaced from the end piece and defining a sensor plane substantially perpendicular to the axis of rotation. At least four magnetic field sensor elements are integrated into the sensor chip, wherein a first and a second magnetic field sensor element are spaced apart from each other and are sensitive only to magnetic field components in a first direction. A third and a fourth magnetic field sensor element are spaced apart from each other and are sensitive only to magnetic field components in a second direction, wherein the first and the second directions are mutually non-parallel and perpendicular to the axis of rotation.The system further comprises a magnetic field source that magnetizes the shaft end, the shaft end being shaped such that a magnetic field in the sensor plane, generated by the magnetic field source, is symmetrical to order N, where N is a finite integer ≥ 1. The system also includes a signal processing circuit coupled to the at least four magnetic field sensor elements, configured to: calculate a first signal representing the difference between the magnetic field components measured by the first and second magnetic field sensor elements; calculate a second signal representing the difference between the magnetic field components measured by the third and fourth magnetic field sensor elements; and calculate an angular position of the shaft by combining at least the first and second signals.The shaft end piece has at least one groove arranged in its end face or at least one projection arranged on the end face, wherein the groove or projection is shaped such that the shaft end piece has rotational symmetry of Nth order, where N is a finite integer ≥ 2.

[0006] Additionally, an electric motor arrangement is described here. According to an exemplary embodiment, the electric motor arrangement comprises a stator comprising at least one stator coil, a rotor comprising at least one shaft with an end face and a soft magnetic shaft end piece, and a printed circuit board (PCB) arranged such that it faces the end face of the shaft. At least one sensor chip is attached to the PCB and spaced apart from the shaft end piece.At least four magnetic field sensor elements are integrated into the sensor chip, wherein two of the magnetic field sensor elements are spaced apart and are sensitive only to magnetic field components in a first direction, and wherein two of the magnetic field sensor elements are spaced apart and are sensitive only to magnetic field components in a second direction, wherein the first and second directions are mutually non-parallel and perpendicular to the axis of rotation. A magnetic field source is provided that magnetizes the shaft end piece, wherein the shaft end piece is shaped such that the magnetic field components in the first and second directions are rotationally symmetric with Nth order, where N is a finite integer ≥ 1.An evaluation circuit is coupled to the at least four magnetic field sensor elements and is configured to calculate the angular position of the shaft by combining at least four output signals from the at least four magnetic field sensor elements. Furthermore, a power electronics circuit arrangement is mounted on the PCB, which is coupled to the stator coils and configured to supply operating current to the stator coils. The shaft end has at least one groove or projection arranged on its end face, wherein the groove or projection is shaped such that the shaft end has rotational symmetry of order N, where N is a finite integer ≥ 2.

[0007] Furthermore, a method for measuring the angular position of a shaft having a soft magnetic shaft end is described here. According to an exemplary embodiment, the method comprises magnetizing the shaft end, wherein the shaft end is shaped such that, in a sensor plane that is substantially perpendicular to the axis of rotation, the magnetic field components in a first and a second direction are rotationally symmetric to order N, where N is a finite integer ≥ 1. The method further comprises measuring the magnetic field components in the first direction at at least a first and a second position in the sensor plane, wherein the second position is different from the first position, as well as measuring the magnetic field components in the second direction at at least a third and a fourth position in the sensor plane, wherein the fourth position is different from the third position.Furthermore, the method includes calculating the angular position of the shaft with respect to its axis of rotation based on the difference of the magnetic field components at the first and second positions and on the difference of the magnetic field components at the third and fourth positions. The shaft end piece has at least one groove arranged in its end face or at least one projection arranged on the end face, wherein the groove or projection is shaped such that the shaft end piece has rotational symmetry of order N, where N is a finite integer ≥ 2. BRIEF DESCRIPTION OF THE IMAGES

[0008] The invention can certainly be better understood with reference to the following illustrations and descriptions. The components shown in the illustrations are not necessarily to scale; rather, the emphasis is on explaining the principle underlying the invention. Furthermore, identical reference symbols in the illustrations denote corresponding parts. Regarding the illustrations: Fig. Figure 1 is a sectional view illustrating a longitudinal section of an on-axis angular position sensor. Fig. Figure 2 illustrates magnetic interference fields due to high currents on the printed circuit board (PCB). Fig. Figure 3 illustrates a longitudinal section of an on-axis angular position sensor arrangement according to an embodiment and a cross-section through a shaft which rotates about the axis. Fig. Figure 4 illustrates three different examples of shaft end pieces for use in an on-axis angular position sensor. Fig. Figure 5 illustrates another example of a shaft end piece for use in an on-axis angular position sensor. Fig. Figure 6 illustrates a longitudinal section of an on-axis angular position sensor arrangement according to another example, wherein the groove in the shaft end piece is filled with a permanent magnet. Fig. Figure 7 illustrates an example of a wave end piece that has a 3rd order rotational symmetry. Fig. Figure 8 illustrates a longitudinal section through another embodiment of an angular position sensor arrangement with a flexible spring made of magnetic material. Fig. Figure 9 illustrates – in a top view of the circuit board carrying a magnetic field sensor – two exemplary implementations of the in Fig. 7 flexible springs shown. Fig. Figure 10 illustrates a longitudinal section through another embodiment of an angular position sensor arrangement with a flexible spring made of magnetic material. Fig. Figure 11 illustrates a longitudinal section through another embodiment of an angular position sensor arrangement with a flexible spring made of magnetic material. Fig. Figures 12-14 illustrate various exemplary arrangements of magnetic sensor elements for use in a magnetic angular position sensor. Fig. Figures 12-16 illustrate two different examples of how an on-axis angular position sensor can be used in a brushless DC motor (BLDC motor). DETAILED DESCRIPTION

[0009] The embodiments described here relate to magnetic field sensors used in magnetic angular position sensors with on-axis arrangements of the sensor elements relative to the axis of rotation of a magnet or a shaft. In one embodiment, a magnetic angular position sensor is mounted in an on-axis configuration relative to a rotatable shaft. The shaft includes an end piece, which may be made of a soft magnetic material or a permanent magnet. The end piece may have an end face that faces the sensor and may be rotationally asymmetric with respect to an axis of rotation of the shaft. The sensor comprises at least three magnetic field sensor elements arranged in a plane that is generally perpendicular to the axis of rotation.The circuit arrangement coupled to the magnetic field sensor elements is configured to estimate the angular position of the shaft by combining the signals from at least three magnetic field sensor elements. While there are numerous applications for various embodiments of the sensor, some embodiments, among others, may be particularly suitable for use in or with MLDC motors. Any specific reference to directions made herein (i.e., down, up, right, left, etc.) is used solely for reference to a particular illustration and is not limiting with respect to the claims.

[0010] An example of an on-axis angular position sensor system 100 is in Fig. Figure 1 shows the sensor system 100 comprising a magnetic field source, such as a permanent magnet 102, and a sensor housing 106, which is arranged on a printed circuit board (PCB) 108. The sensor housing 106 is arranged – at least partially – between the permanent magnet 102 and an end piece of a shaft 104, which is designed to rotate about an axis of rotation. Fig. 1. The axis of rotation is defined as the z-axis of a Cartesian coordinate system, and the xy-plane lies perpendicular to the axis of rotation.

[0011] In some embodiments, the permanent magnet 102 comprises a ferrite magnet. Ferrite magnets can be less expensive than other types of magnets (e.g., rare-earth magnets) and contribute to lower overall system costs. However, in other embodiments, rare-earth magnets or other types of magnets may be used. In some embodiments, the magnet 102 may even be omitted. In this case, the end of the shaft 104 has a significant remanent magnetization. For example, the magnet 102 may comprise an Sr ferrite, a Ba ferrite, or other ferrites, as well as AlNiCo, a rare-earth material such as NdFeB, or SmCo, or some other suitable materials. In general, the magnet 102 comprises a material with a remanent magnetization of at least 100 mT and sufficient coercivity to ensure the stability of the magnet 102.

[0012] In the Fig. In the example shown, magnet 102 is in an axial direction (see arrows in Fig. 1) magnetized. That is, the orientation of the magnetization of magnet 102 is generally parallel to the axis of rotation of shaft 104 (z-axis). In other embodiments, magnet 102 may be magnetized in the radial direction. However, magnet 102 is usually (but not necessarily) rotationally symmetric (i.e., it exhibits both geometric and magnetic symmetry, so that the geometry and magnetization do not depend on the angular position with respect to the axis of rotation). For example, magnet 102 may be, as in the example from Fig. Figure 1 shows a cylindrical shape. However, other shapes and magnetization directions can be used in other embodiments. In general, the magnet 102 is rotationally symmetric and provides a magnetic field during operation that is rotationally symmetric with respect to the axis of rotation. However, the non-rotationally symmetric geometry of the shaft end of the shaft 104 interrupts this rotational symmetry. Due to the resulting asymmetry, the angular position of the shaft 104 can be detected by the angular position sensor.

[0013] As in Fig. As shown in Figure 1, the shaft 104 comprises an end piece with a front face (surface 105) that is located opposite the sensor housing 106. As mentioned, the shaft 104 is generally rotationally symmetric, whereas the front face 105 of the shaft 104 can be asymmetric with respect to the axis of rotation. In the Fig. In the example shown, the end face 105 is inclined at an angle α with respect to the xy-plane. In one embodiment, the angle α is approximately 15 degrees, although it can be larger or smaller in other embodiments. Theoretically, the angle α can lie between 0 degrees and 90 degrees; in practical implementations, α can range from approximately 5 degrees to approximately 25 degrees. Due to the fact that α is greater than 0 degrees, the size of the air gap (in the z-direction) at a given position in the xy-plane generally depends on the angular position of the shaft 104.

[0014] In some embodiments, the shaft 104 comprises ferrous material such as a soft magnetic material like iron or mild steel with a relative permeability µ Rin the range of approximately 1600 (steel) to 4000 (iron). Generally, the shaft 104 can comprise ferrous material with a relative permeability of more than 100 or more than 1000. In some embodiments, only the end of the shaft comprises magnetic material, whereas the remainder of the shaft 104 consists mainly of non-magnetic material such as a non-ferrous alloy, non-magnetic or low-magnetic steel, or another material.

[0015] As in Fig. As shown in Figure 1, the sensor housing 106 is generally arranged between the permanent magnet 102 and the end face 105 of the shaft 104. The xy-plane is defined as the plane in which the magnetic field sensor elements 114a, 114b are arranged within the chip housing. Therefore, the axial distance between the xy-plane and the end face 105 of the shaft 104 is the effective air gap of the magnetic circuit. The sensor housing 106 can be arranged essentially in line with the axis of rotation and consequently forms an on-axis sensor arrangement. The sensor housing 106 comprises at least one semiconductor die 110 in which the magnetic field sensor elements 114a, 114b are integrated. The semiconductor wafer 110 is generally oriented perpendicular to the axis of rotation (z-axis) and comprises a main surface 112, which is the sensitive plane (i.e., the xy-plane) of the sensor elements 114a and 114. In the cross-sectional view according to Fig. In Figure 1, only two sensor elements, 114a and 114b, are visible. However, the angle position sensor comprises at least three sensor elements, and in some configurations, at least four. In both cases, the sensor elements are spaced alternately from each other, and each sensor element provides its own sensor signal, which represents the magnetic field component in the sensitive direction of the respective sensor element and at the location of the respective sensor element.

[0016] In some embodiments, the housing 106 is a surface-mounted device (SMD) in which the semiconductor wafer 110 is arranged on a leadframe 116. The leadframe 116 includes pins which are soldered onto the PCB 108. In the embodiment according to Fig. In Figure 1, the permanent magnet 102 is arranged at least partially within an opening 130 in the PCB 108, such that the permanent magnet 102 can contact a rear side of the housing 106. However, the opening is not required in other embodiments where the permanent magnet 102 can be mounted below the PCB 108. For example, in one embodiment, the permanent magnet 102 is mounted on the rear side of the PCB 108. In this context, the rear side of the housing is the side opposite the front side, and the front side of the housing 106 is any side facing the end face 105 of the shaft. It should be noted that in other embodiments, the construction of the angle position sensor differs from that described in Figure 1. Fig. The example shown in Figure 1 can be distinguished. For instance, a bare die semiconductor die can be mounted on the PCB instead of using a chip package. In other embodiments, the sensor elements 114a and 114b can be arranged in separate semiconductor dies within one or more chip packages. In some embodiments, the permanent magnet 102 can be attached to the underside of the PCB 108 or integrated into the sensor housing 106.

[0017] The sensor elements 114 (collectively referred to as 114a and 114b) can be sensitive to magnetic field components in either the axial direction or the radial direction. In various embodiments, the sensor elements 114 can include magnetoresistive (MR) sensor elements (e.g., AMR, GMR, TMR, CMR, and others), giant magneto-impedance (GMI) sensor elements, Hall-effect sensor elements (e.g., vertical Hall sensor element), MAGFETs, and other magnetic field sensor elements, as well as combinations thereof, suitable for measuring magnetic field components in a plane perpendicular to the axis of rotation of the shaft whose angular position is to be measured.In various embodiments, the sensor elements 114 are oriented such that they are sensitive either to a magnetic field component in the x-direction or in the y-direction, wherein the rotation axis of the shaft is defined as extending along the z-direction; the x-, y- and z-directions form a Cartesian coordinate system.

[0018] In general, the sensor setups described here can be used in brushless direct current (BLDC) motors. Such BLDC motors use a permanent magnet to magnetize the rotor (armature), while stator windings are used to form coils to magnetize the stator. Current pulses are applied to the stator coils, with the current patterns designed to achieve a desired torque and / or rotor rotation. To enable a compact BLDC motor design, on-axis angular position sensors are used. The printed circuit board (PCB) carrying the power electronics generates the aforementioned current pattern and typically also houses the angular position sensor components. Exemplary embodiments demonstrating the application of an on-axis angular position sensor in BLDC motors are described later in Fig. 15 and Fig. 16 shown.

[0019] Fig. Figure 2 illustrates how magnetic interference fields can affect the field measurement by the magnetic field sensor elements 114. Fig. Figure 2 shows only the sensor housing 106 together with a current-carrying element 201 (e.g., a stripline or a power semiconductor housing element) mounted on the PCB 108. The current i0 flows through the element 201 essentially parallel to the y-axis and consequently generates a magnetic field H0, which is defined by the magnetic field lines in Fig. Figure 1 shows that, as can be seen from the field lines, the magnetic field H0 includes a significant component H. 0,z in the z-direction at the location of the magnetic field sensor elements, which is highly inhomogeneous. This magnetic field component H 0,z can the magnetic field of the permanent magnet 102 (in Fig. (2 not shown) superimpose and cause a measurement error when determining the angular position from the sensor signals. In practice, the magnetic field components H that are perpendicular to the z-axis 0,x and H 0,y (in the xy-plane) a significantly smaller amount at the location of the magnetic field sensor elements. To minimize the effect of the magnetic interference fields generated by the currents produced by power semiconductor devices on PCB 108, magnetic field sensor elements 114 are used which are sensitive only to magnetic field components in the x and y directions and essentially insensitive to magnetic field components in the z direction (axial direction). Furthermore, pairs of sensor elements are used to implement differential measurement, which will be explained further below (see Fig. 11-13). Differential measurement is used to implement a type of gradiometer that measures the spatial gradient of the measured magnetic field components and consequently eliminates the effect of homogeneous magnetic interference fields (generated outside the PCB 108 or in the BLDC motor). Combining the use of magnetic field sensors that are essentially insensitive in the axial (i.e., z-) direction with a differential measurement principle enables angular position measurement that is robust against magnetic interference fields generated on the circuit board (i.e., by the power electronics on the PCB 108) and off the circuit board (i.e., essentially homogeneous external magnetic fields).

[0020] In the embodiments described here, the end piece of shaft 104 has a rotational symmetry of a certain order, where N-th order rotational symmetry (also called N-fold rotational symmetry) means that every rotation by an angle of 360° / N does not change the object. N is a finite (non-zero and non-infinite) integer greater than or equal to 1. It should be noted that first-order symmetry is actually not symmetry, since only a full rotation of the shaft by 360° yields an unchanged geometry. In contrast, second-order symmetry means that a rotation of the shaft by 180° yields an unchanged geometry. In the example from Fig. 3. The end piece of shaft 104 has a recess P (groove) in its end face. The recess P has the form of a slot that runs in a straight line (e.g., along the y-direction) through the axis of rotation, which results in the shaft end piece having second-order symmetry (see section AA' in Fig. 3) Apart from the end piece of shaft 104, the structure of the in Fig. The angle position sensor arrangement shown in section 3 is almost identical to the example from Fig. 1. However, the permanent magnet 102 is mounted on the back of the printed circuit board (PCB) 108 instead of, as shown in Fig. Figure 1 shows that the sensor housing 106 is located on the rear side of the PCB 108, through an opening in the PCB 108. The sensor housing 106 is mounted on the front side of the PCB 108 and comprises at least one semiconductor chip 110, in which several magnetic field sensor elements 114a, 114b are integrated. All magnetic field sensor elements are sensitive to a magnetic field component in the xy-plane and insensitive to a magnetic field component in the z-direction (i.e., axial direction).

[0021] In an alternative embodiment, represented by the curved dashed line in Fig. 3 is shown (and also in the one discussed below) Fig. 6), the groove P has the shape of a half-cylinder (semicircular cross-section) instead of a rectangular cross-section. Both embodiments were simulated. In both embodiments, the sensor chip 110 is arranged in the xy-plane at z=0, and the sensitive magnetic field sensor elements are located at z=0.1 mm. The axis of rotation is defined by x=y=0. In the first embodiment, the permanent magnet has a diameter of 10 mm, is arranged coaxially with the shaft 104, and has an axial length of 5 mm (from z=-6.5 mm to z=-1.5 mm). The remanent magnetization of the permanent magnet 102 is 1 tesla; its relative permeability µ R The relative permeability is 1.1. The diameter of shaft 104 is 6 mm, and the end face of shaft 104 is at z = 1 mm. The air gap between the shaft and the permanent magnet is therefore 2.5 mm. RThe value of shaft 204 is 1700. The width w of the groove is 2 mm and its depth is 3 mm (rectangular cross-section). With the above data, the magnetic field components H can be determined. X , H Y in the xy-plane (i.e., in the sensor plane in which the sensor elements extend) as Hx = a·x / µ0 with a=56.6 T / m and H Y= b·x / µ0 with b = 10 T / m (using linear regression on the simulated magnetic field data), where µ0 denotes the vacuum permeability. In the second embodiment, the diameter of the permanent magnet is 4 mm, its remanent magnetization is 1 Tesla (magnetized parallel to the z-axis), and its axial length is 4 mm (from v = -4.2 mm to -0.2 mm). The shaft has a diameter of 6 mm, and the groove P is a half-cylinder with a radius of 1.5 mm. The end face of the shaft is at z = 1.8 mm, so the air gap is 2 mm. Unlike the first embodiment, the groove P is filled with another permanent magnet 102' (as in the example from Fig. 6) with a magnetization of -1T (magnetized parallel to the z-axis). The magnetic field sensor elements are located at z = 0.5 mm. In this arrangement, the magnetic field components in the x and y directions of the two permanent magnets superimpose constructively. The simulation yields an approximation of HX = a·x / µ0 with a=175.4 T / m and H Y = b·x / µ0 with b = 102.2 T / m. Therefore, the second permanent magnet 102' makes the diametrical magnetic field component (x and y components) stronger and the axial magnetic field component (z component) weaker. In an ideal implementation, the two magnets should be symmetrically balanced to eliminate the axial magnetic field in the sensor elements, because then small tilts of the sensor plane (xy plane) with respect to the axis of rotation—which are unavoidable due to assembly tolerances—have the smallest possible impact on the accuracy of the angular position measurement.

[0022] As mentioned above, the groove P can be filled with a second permanent magnet 102'. Generally, one permanent magnet is attached to the shaft 104 (e.g., in the groove P) so that it rotates synchronously with the shaft 104, and the other permanent magnet (see permanent magnet 102 in Fig. 3) is on the sensor housing 106 (see Fig. 1) or on PCB 108 (see Fig. 3) is fixed so that it does not rotate. Both permanent magnets are magnetized in a direction parallel to the axis of rotation (z-direction), with one of the permanent magnets magnetized in the positive z-direction and the other in the negative z-direction. In this way, their magnetic field contribution H is added together. X , H Y in the xy-plane. One of the two permanent magnets can be omitted and the sensor arrangement would still function. Whether one or two magnets are used can depend on the available space, cost, stray field robustness of the surrounding electronic components, etc.

[0023] Different magnetic materials can be used for the two permanent magnets. The rotating permanent magnet, for example, can be made of an injection-molded magnetic material in which magnetic particles are embedded in a polymer matrix, whereas the non-rotating permanent magnet (permanent magnet 102) can be a sintered magnet, which is not easily manufactured in complex geometries. However, sintered magnets can exhibit very high remanent magnetizations (in the case of NdFeB material, the remanence can exceed 1 T). In contrast, polymer-bonded or injection-molded magnets have lower remanent magnetizations (in the case of polymer-bonded NdFeB magnets, the remanent magnetization can only reach up to 0.6 T).

[0024] In a specific embodiment, the sensor chip 110, in which the magnetic field sensor elements are integrated, has a size of approximately 0.5 mm to 4 mm, e.g., 1.5 mm, in the x-direction. Therefore, the distance between the magnetic field sensor elements is also within this range (see also Fig. 11-13). The width w (along the x-direction) of the groove P in the end piece of shaft 104 can be of a similar size to, or slightly wider than, the chip 110, e.g., 2 mm. The shaft diameter can range from approximately twice the width of the groove P (e.g., 4 mm) to – theoretically – infinitely large diameters. The depth d of the groove (i.e., the axial length along the z-direction) can exceed half the width of the groove (i.e., more than 1 mm) and, for example, be equal to its width. In this case, the cross-section (perpendicular to the y-axis in the example from Fig. 3) The groove is square. Deeper grooves are possible. However, deeper grooves do not result in magnetic behavior that differs significantly from the magnetic behavior of those grooves whose depth equals their width. Fig. Figure 4 shows three further examples of shaft end pieces, which have different grooves P. In all three examples ( Fig. 4a, Fig. 4b and Fig. 4c) The groove extends directly through the axis of rotation of the shaft end piece. The example in Fig. 4a has a groove P with a V-shaped cross-section, the example in Fig. 4b has a groove P with a trapezoidal cross-section, the cross-section becoming narrower with increasing depth, and the example in Fig. 4c has a groove P with a trapezoidal cross-section, the cross-section becoming wider with increasing depth.

[0025] Furthermore, the groove P does not necessarily have to have a constant depth d. The depth d of the groove P can increase towards the axis of rotation and decrease towards the circumference of the shaft. The end face (the surface of the end end) of the end piece is also not necessarily a flat surface. In the Fig. In the example shown in Figure 5, the end face has a curvature. For instance, the end face can be part of a spherical surface whose center of curvature lies on the axis of rotation. Alternatively, the end face can be part of a cylindrical surface whose cylinder axis intersects the axis of rotation at 90°. Such curvatures can help to "design" the magnetic field in such a way that the signal level of the output signals of the magnetic field sensor elements is maximized (or, in the case of a differential measurement, that the difference between two corresponding output signals of a pair of magnetic field sensor elements is maximized). Fig. Figure 5 illustrates two different longitudinal sections (section AA' and section B-B') and a bottom view of the same shaft end piece.

[0026] In general, a shaft end with N-fold rotational symmetry enables the measurement of an angular position in the interval [0, 360° / N]. The shaft 104 is the component of the sensor assembly that is generally manufactured with the highest precision compared to other components. In contrast, the permanent magnet 102 can be manufactured with significantly less precision than the shaft 104. Neither the shape of the permanent magnet 102, nor its material homogeneity, nor its magnetization (with respect to magnitude, direction, and homogeneity) and its stability over time and temperature are well-defined. In the embodiments described here, however, the permanent magnet 102 is used only to magnetize the shaft end and does not rotate. In other words, the permanent magnet 102 does not define the angular position of the magnetic field; it merely (magnetically) biases the shaft end, which defines the angular position of the magnetic field.Therefore, minor inaccuracies (in terms of geometry and magnetization) of the permanent magnet 102 have no significant effect on the angular position measurement. For the reasons explained above, there is no need for the permanent magnet 102 to have a precise and complex shape and magnetization, and a cost-effective sintered magnet can be used. Sintered rare-earth magnets can exhibit a high remanent magnetization of more than 1 T, resulting in comparatively strong magnetic fields through the sensor elements and consequently increasing robustness against noise and interference (i.e., the magnetic signal-to-noise ratio is high). Furthermore, since the permanent magnet 102 does not rotate, it does not produce large rotating magnetic fields that could interfere with other electronic components. The shaft end can be positioned very close to the sensor chip 110 and consequently to the magnetic field sensor elements (e.g.,(1 mm air gap or even less, depending on the axial tolerance of the shaft). The distance between relevant magnetized parts of the shaft end and the sensor elements can therefore be comparatively small, which also increases the magnitude of the measured magnetic field components.

[0027] In the embodiments described above, the shaft end has second-order rotational symmetry (double rotational symmetry), which enables unambiguous angular position measurement in the range between 0 and 180°. Due to this symmetry, the sensor arrangement cannot distinguish between an angle φ and an angle φ+180°. However, unambiguous angular position measurement across the full range from 0° to 360° is not necessary in many applications, such as brushless DC (BLDC) motors.

[0028] However, if an unambiguous angular position measurement over the full range between 0° and 360° is desired, the orientation of the remanent magnetization of the rotating permanent magnet 102' with respect to the axis of rotation (z-axis) can be as in the example in Fig. Figure 6 shows that the magnet should be inclined. This means that, in addition to its magnetization in the z-direction (i.e., parallel to the axis of rotation), the rotatable magnet should have a certain (preferably small) amount of magnetization normal to the z-direction (i.e., along the x-, y-, or another diametrically opposed direction). Fig. 6 The dashed arrow in the permanent magnet 102' indicates the previously explained remanent magnetization, which is antiparallel to the z-direction, whereas the solid arrow indicates the aforementioned oblique magnetization.

[0029] According to one embodiment, the permanent magnet has, for example, 80% of its magnetization along the z-direction and 20% along the x-direction (or another diametrical direction such as the y-direction), resulting in an inclination of 14° with respect to the axis of rotation and a small magnetic field H. X This contributes to a signal that essentially passes homogeneously through a sensor chip. The sensor system can therefore distinguish between an angle φ and an angle φ + 180° by calculating the sum and difference of the sensor signals from different magnetic field sensor elements (see Fig. 6, magnetic field sensor elements 114a, 114b) are evaluated, which are spaced apart from each other in the sensor plane (xy-plane), are sensitive to magnetic field components orthogonal to the rotation axis and insensitive to axial magnetic field components. The differential signal (e.g. H X (x=x1,y=0) - H XThe differential signal (x=-x1,y=0) obtained from a pair of magnetic field sensor elements can be used to determine an exact angular position, either in the range of 0 to 180° or in the range of 180° to 360°. This differential signal is a result of the magnetic effect of the groove and the axial magnetization of both magnets. The sum signal (e.g., H) X (x-x1,y=0) + H X The signal obtained from a pair of magnetic field sensor elements (x=-x1,y=0)) can be used to determine in which of the two regions the angle φ lies (i.e., whether 180° must be added to the previously determined angle φ or not). This sum signal is a consequence of the diametrical magnetization of the rotatable magnet. Apart from the shape of the groove P and the additional permanent magnet 102' arranged in the groove, the example in Fig. 6 identical to the example from Fig. 3.

[0030] In another embodiment, the remanent magnetization of the rotating permanent magnet 102' is oriented parallel to the x-axis (or any other diametrical direction, e.g., the y-direction), resulting in an inclination (which was 14° in the previous example) of 90°. The non-rotating permanent magnet 102, however, remains magnetized parallel to the z-axis (and consequently generates a rotationally symmetric magnetic field). The remanent magnetization of the permanent magnet 102' should be strong enough that the resulting homogeneous diametrical field component is stronger than any potential external magnetic field component in that direction. Since the diametrical field component is used only to distinguish the 0°–180° sector from the 180°–360° sector, there are no specific requirements regarding the precision of the magnetization.

[0031] In another example, the shaft end piece is shaped with rotational asymmetricity; that is, it is shaped such that it exhibits first-order rotational symmetry, allowing measurement across the full range from 0° to 360°, even if the permanent magnets are magnetized only along the z-direction. Using this approach, the groove P can be shifted from the center to the circumference of the shaft end piece. Alternatively, a shaft end piece could be used as in Fig. 1 shown. Furthermore, the depth of the groove P can vary in a rotationally asymmetric manner.

[0032] In the example according to Fig. 7. The shaft end is shaped such that it exhibits third-order rotational symmetry. This means that a unique angular position measurement is possible in the sector from 0° to 120° (360° / 3). As can be seen in the Fig. As can be seen in the view shown from below (Figure 7), the groove P at the center of the shaft splits into two branches, forming a Y-shape. Generally, the shaft 104 and the end piece, which has Nth-order symmetry, can be a single component. However, in some embodiments, the shaft end piece is a separate component that is attached to the shaft 104, e.g., by clamping, gluing, press fit, etc.

[0033] In the Fig. In the examples shown in Figures 8 to 11, the shaft end piece is a flexible (elastically deformable) part or has one, which is attached to the shaft 104 and consequently rotates synchronously with the shaft. The flexible part 151 of the shaft end piece can be designed to compensate for axial play or axial tolerances of the shaft 104. In the example shown in Fig. In the example shown in Figure 8, the flexible part 151 is a leaf spring which is attached to the shaft 104 by means of an anchor element 150. In a relaxed state, the leaf spring 151 is essentially flat, perpendicular to the axis of rotation and arranged in front of the end face of the shaft 104. The axis of rotation of the shaft 104 intersects a longitudinal axis of the leaf spring. In the Fig. 8 and Fig. In the nine examples shown, the longitudinal axis of the leaf spring is parallel to the x-axis, and in general, the longitudinal axis of the leaf spring extends radially and intersects the axis of rotation. In general, this illustrates Fig. 8 a longitudinal section along the z-axis and is essentially identical to those in Fig. 3 and Fig. 6 examples shown, apart from the fact that the shaft end piece is made up of the leaf spring 151, the mentioned anchor element 150 and a spacer 152 which is arranged between the sensor housing 106 and the leaf spring 152.

[0034] In one embodiment, the shaft exhibits an axial play of approximately ±1 mm, and the leaf spring 151 bends to a greater or lesser degree to maintain mechanical contact with the sensor housing 106 via the spacer 152. The armature element 150 can be configured to fix the leaf spring 151 to the rotating shaft 104, such that the leaf spring is flexible along an axial direction (z-direction) but comparatively rigid in lateral (i.e., x-, y-) directions. The leaf spring 151 can be made of or have a soft magnetic material (e.g., spring steel) so that it performs the magnetic function of the groove P shown in the previous embodiments (see Figure 1). Fig. 1 and Fig. 3) can assume this function. Alternatively, the leaf spring 151 can be constructed from a non-magnetic spring body (e.g., consisting of beryllium bronze or beryllium copper) and a soft magnetic element attached to the non-magnetic spring body. The purpose of the flexible element is to ensure that—regardless of small axial position changes of the shaft—a soft magnetic part, which is not rotationally symmetric, is held at a substantially constant axial distance from the sensor elements. This non-rotationally symmetric soft magnetic part can be the spring itself (as in the Fig. 8-11) or any other soft magnetic component attached to the flexible end of the spring (not shown). Since the axial distance between the soft magnetic component and the sensor elements is kept essentially constant, any axial play in the shaft can have only a minor effect on the angular position measurement and should result in smaller errors in the measured angular position value.

[0035] In the Fig. In the embodiment shown in Figure 8, a small spacer 152 is attached to the leaf spring 151 on the axis of rotation. Consequently, the spacer 152 can rotate synchronously with the shaft 104 about the axis of rotation, defining the mechanical contact point between the shaft end and the sensor housing 106 and the axial distance between the flexible shaft end and the sensor housing 106. The spacer 152 can be made, for example, of Teflon (polytetrafluoroethylene, PTFE) or another type of material that ensures low friction between the spacer 152 and the sensor housing 106. The sensor housing 106 generally has a cast component that includes an abrasive filler. Therefore, low friction can be a goal when selecting the material for the spacer.The spacer can be magnetic or not; due to its rotational symmetry, the spacer would not generate a magnetic field that varies depending on the angular position.

[0036] The flexible part of the shaft end (e.g., the leaf spring) can have various shapes. Two exemplary embodiments of the leaf spring 151 are shown in the Fig. 9a and Fig. 9b shown, both of which show a top view of the leaf spring, which is shown in the sectional view in Fig. 8 corresponds. In the in Fig. In the embodiment shown in 9a, the leaf spring 151 has the form of a small strip-shaped plate with a width w S , which is smaller in the xy-plane than the sensor chip 110 (width wc), so that the leaf spring 151 only covers part of the sensor chip 110 (see top view in Fig. 9a). In the alternative embodiment from Fig. 9b is the width w SThe leaf spring 151 is larger than the sensor chip 110 and consequently covers the entire chip. In the middle of the leaf spring 151, along its longitudinal axis (x-axis, see...) Fig. 9b) a slot is formed such that the axis of rotation passes through the slot. The width w SL The slot can be smaller than the width wc of the chip (as in the example in Fig. 9 is the case). In this embodiment, the effect of the slot on the resulting magnetic field “seen” by the magnetic field sensor elements in chip 110 is very similar to the effect of the groove P in the Fig. 3 and Fig. 6 examples shown. Consequently, in the present embodiment in Fig. 8 and Fig. 9. The shaft end piece has a second-order symmetry (N=2, double rotational symmetry) for angular position measurement in the range of 0° to 180°. In other embodiments, the leaf spring 151 has a tapered geometry (i.e., its width is smaller at one end compared to the other) to achieve first-order symmetry and enable angular position measurement in the range of 0° to 360°. Furthermore, the strip-shaped plate 151 (i.e., the spring) can be Fig. 9a wider and longer and shifted in the negative y-direction, so that the upper edge of the spring is at y=0 and the spring 151 covers that part of the chip for which y<0 (see dotted area in Fig. 9a) If this spring is ferromagnetic (i.e., soft magnetic) and magnetized by a permanent magnet 102 fixed to the sensor housing 106 or to the PCB 108, or by a permanent magnet 102' fixed to the shaft, and if these magnets are rotationally symmetric with a rotationally symmetric remanent magnetization, then the spring 151—at the location of the magnetic field sensor elements—generates a magnetic field with first-order symmetry (N=1), i.e., its magnetic field on the sensor elements enables an unambiguous measurement of angles in the range of 0° to 360°. The same applies to a wide strip in Fig. 9, if the width w SL the slot is wide enough (e.g. wider than wc / 2) and long enough (e.g. longer than the chip), and if the slot is shifted towards the negative y-direction, its upper edge is aligned with the x-axis.

[0037] In the embodiment from Fig. In section 10, the leaf spring 151 is bent by 90° and attached directly to the shaft 104, instead of a separate anchor element (such as the anchor element 150 in section 10). Fig. 8) to use. For example, the part of the leaf spring 151 that is attached to the shaft 104 can be inserted into a groove that extends axially in the outer surface of the shaft and screwed, welded, or otherwise fixed to the shaft. In general, it is also possible to machine the leaf spring 152 in relief on the axis of rotation instead of attaching a separate spacer. In this case, the spacer is implemented as an embossment 152' as in the examples from Fig. 10 and Fig. 11 is shown. In the example in Fig. In example 11, the leaf spring has an S-shape and is attached to the end face of the shaft 104 instead of to the outer surface as in the previous example. Fig. 10. In this case, an additional asymmetry (first-order symmetry) is achieved by an asymmetrical recess R in the end face of the shaft 104. The effect of the recess R on the resulting magnetic field "seen" by the magnetic field sensor elements is similar to the effect of an inclined end face of the shaft, as in the example from Fig. 1. As in the previous embodiments, a permanent magnet 102 can be attached to the PCB 108. Additionally or alternatively, another permanent magnet 102' can be attached to the shaft 104 (in Fig. 10 (shown as dotted lines).

[0038] In the embodiments shown here, the sensor chip 110 is closer to the spacer 152 or the bulge 152' than the leadframe 116, ensuring a small distance (air gap) between the shaft end and the magnetic field sensor elements integrated in the sensor chip 110. Such an arrangement can help to maximize the level of the magnetic field in the sensor elements and the signal output of the magnetic field sensor elements. In other embodiments, however, the sensor chip can be inverted so that an exposed metal surface (the paddle) is in contact with the spacer 152 or the bulge 152' instead of the plastic part (encapsulation) of the sensor housing. In this case, the metal surface protects the sensor housing 106 against wear caused by the rotating spacer or the rotating bulge. Even if the metal surface were not exposed (i.e.,It is covered with potting compound, and consequently the spacer 152 or the protrusion 152' is in contact with the abrasive potting compound; nevertheless, it would protect the chip from the spring 151. In alternative embodiments, the magnetic field sensor housing 106 can be mounted on the underside of the PCB, while the shaft faces the top side of the PCB, and the spacer 152 contacts the top side of the PCB or a metal plate or similar structure mounted on the top side of the PCB. In this embodiment, there is no friction between the rotating spacer and the abrasive potting compound of the sensor housing, and the sensor housing is protected from the rotating spacer 152 by the intervening PCB.

[0039] In general, the permanent magnets on the PCB 108 (see Fig. 10 and Fig. 11), the sensor housing 106 (see Fig. 1), wave 104 (see Fig. 6), the leaf spring 151 (e.g., at its flexible end), or between the shaft and the spring, or even on the armature element 150. The permanent magnet can have various shapes, such as a ring shape, a pill shape, a cylindrical shape, or a cuboid shape with different magnetization directions (purely axial or purely radial, or combinations of axial and diametrical or axial and radial). By combining different aspects of the embodiments described above, further embodiments can be created.

[0040] The following Fig. Figures 12 to 14 illustrate different arrangements (layouts) of the magnetic field sensor elements integrated in at least one sensor chip 110 (see e.g. Fig. 3, Fig. 6 and Fig. 8) In general, at least four magnetic field sensor elements are used in the embodiments described here, although in the embodiments described in Fig. In the embodiments shown in Figures 12 to 14, eight or sixteen magnetic field sensor elements are used (where, in the latter case, two related magnetic field sensor elements are arranged a short distance apart or adjacent to each other and their sensor output signals are averaged, see Figure 12 to 14). Fig. 12 and Fig. 13) The sensor chip 110 defines a sensor plane, which is essentially perpendicular to the axis of rotation (z-axis) and in which the magnetic field sensor elements are arranged. Generally, a first and a second magnetic field sensor element are spaced apart from each other and are sensitive only to magnetic field components in a first direction (e.g., x-direction), and a third and a fourth magnetic field sensor element are also spaced apart from each other and are sensitive only to magnetic field components in a second direction (e.g., y-direction). As mentioned above, the x-direction, the y-direction, and the z-direction (defined by the axis of rotation) form a Cartesian coordinate system. The first and second directions are not parallel and are perpendicular to the axis of rotation.As mentioned above, the sensor elements used in the embodiments described here are essentially insensitive to magnetic field components perpendicular to the sensor plane (and consequently parallel to the axis of rotation). In the embodiments described here, the individual magnetic field sensor elements can, for example, be arranged along a circle with radius r concentric to the axis of rotation. At (or near) the angular positions 0° (i.e., at P1=(r, 0)), 90° (i.e., at P2=(0, r)), 180° (i.e., at P3=(-r, 0)), and 270° (i.e., at P4=(0, -r)), magnetic field sensor elements are provided that are sensitive to magnetic field components in the x and y directions but insensitive in the z direction (Hx sensor elements and H). Y -Sensor elements).

[0041] In the embodiments described here, the sensor elements 114a, 114b, 116a, 116b, 118a, 118b, 120a, 120b are sensitive to magnetic field components in the y-direction and are therefore referred to as H Y -Sensor elements. Similarly, sensor elements 115a, 115b, 117a, 117b, 119a, 119b, 121a, 121b are sensitive to magnetic field components in the x-direction and are therefore designated as H X -Sensor elements. Theoretically, the magnetic field sensor elements (e.g., sensor elements 114a, 114b, 115a and 115b in) should Fig. 12) are provided at exactly the same point on the circle with radius r (at positions P1, P2, P3, P4), which is difficult to implement because the magnetic field elements would have to be stacked. The example from Fig. Figure 12 shows an implementation according to which two Hx sensor elements and two H Y-Sensor elements are arranged symmetrically to and close to the angular positions P1, P2, P3 and P4 on the circle with radius r. Fig. 12 are pairs of H Y -Sensor elements 114a, 114b, 116a, 116b, 118a, 118b, and 120a, 120b are aligned along the x-axis (sensor elements 114a, 114b, 118a, 118b) or have an axis parallel to the x-axis (sensor elements 116a, 116b, 120a, 120b), and each pair is arranged symmetrically with respect to the respective positions P1, P2, P3, and P4. The magnetic field components H X and H Y For a specific position P1, P2, P3, and P4, the output signals of the sensor elements of each pair can be obtained by averaging them. For example, the output signals of the H Y -Sensor elements 114a and 114b averaged to measure the y-component H Y to obtain the magnetic field at position P1. Accordingly, the output signals of the H X-Sensor elements 121a and 121b averaged to measure the x-component H X of the magnetic field at position P4. Essentially, the sensor elements 114a and 114b can be considered a single (albeit distributed) H Y -Sensor element at position P1. Accordingly, sensor elements 117a and 117b can be considered as a single H X -Sensor element at position P2, etc. According to another implementation, the sensor elements are not "split" into pairs, but the H X - and H Y Sensor elements are positioned so close to the desired positions P1, P2, P3, and P4 that the deviation between the actual sensor position and the target position (P1, P2, P3, and P4) is negligible. The example from Fig. 13 is essentially the same as the example from Fig. 12. However, in Fig. 13 the positions P1', P2', P3' and P4', where the magnetic field sensor components H X and H Y be measured in comparison to those in Fig. The 12 positions shown, P1, P2, P3, and P4, are shifted by 45°. In general, the distance between different measurement positions on the sensor plane is at least as large as (or at least twice as large as) the largest dimension of a single magnetic field sensor element.

[0042] In the example from Fig. In Figure 14, a magnetic field sensor element is provided on the circle with radius r at each of the following angular positions on the circle: 0°, 45°, 90°, 135°, 180°, 225°, 270°, 315°. A H Y -Sensor element is provided on the circle at angles of 0°, 135°, 180° and 315° (H Y -Sensor elements 114b', 116a', 114a' 116b'). A H X -The sensor element is provided on the circle at angles of 45°, 90°, 225° and 270° (H X-Sensor elements 117b', 115a', 117a', 115a'). Since only one magnetic field sensor element is provided at each position, the magnetic field sensor elements can be placed exactly at the desired positions. For all three in the Fig. An important aspect of the embodiments shown in 12 to 14 is that only H X - and H Y Sensor elements are used that have sensitivity in a direction perpendicular to the axis of rotation (z-direction), but are not affected by magnetic field components in the z-direction. Furthermore, the individual magnetic field sensor components are oriented such that they measure magnetic field components in the x- and y-directions and not in any arbitrary radial direction (e.g., along the 45° line through points P1' and P3' in [reference missing]). Fig. 13) In practice, it can be difficult to align a sensor element precisely in any radial direction, whereas it is easier to align it in the x and y directions because the x and y directions are parallel to the edges of the chip, and this is the usual grid according to which electronic components are oriented in common microelectronic technologies. However, it should be noted that the output signals of the diametrically arranged magnetic field sensor element pairs 114a', 114b', 115a', 115b', 116a', 116b', and 117a', 117b' are not averaged, whereas in the examples from the Fig. 12 and Fig. 13 the output signals of corresponding pairs of magnetic field sensor elements 114a, 114b, 115a, 115b, etc., are averaged to obtain an averaged output signal.

[0043] Furthermore, it should be clear that other orientations of the sensor elements, such as radial or azimuthal orientation, are also possible because, by means of a simple transformation of coordinate systems, a field in a first direction can be expressed as a combination of field components in at least two other non-parallel directions. It is also not necessary to place all sensor elements on a circle centered on the axis of rotation, as shown in the present embodiment (the center point can be defined as the projection of the axis of rotation onto the sensor plane). In principle, the sensor elements can be placed on a regular or even irregular grid in the xy-plane to represent the field components H. X (x,y) or H Y (x,y) or H R (x,y) (i.e. radial component) or H PSI (x,y) (i.e., azimuthal component) to sample and the functions H X (x,y) or H Y(x,y) or H R (x,y) or H PSI (x,y) to reconstruct by interpolation or approximation such as the least squares method or similar mathematical methods.

[0044] The following description deals with an algorithm that can be used to derive an angular position of the wave from the output signals of the magnetic field sensor elements, according to the in Fig. The layouts shown in Figures 12 to 14 are arranged as follows. There are numerous ways to determine the angular position, and only a few examples (for twofold symmetry, i.e., N=2) are discussed as a comprehensive class of algorithms. In general, the embodiments described here can include a circuit arrangement coupled to the (at least four) magnetic field sensor elements integrated in the sensor chip 110 and configured to calculate an angular position of the shaft by combining the output signals of the magnetic field sensor elements. A common aspect of these approaches is that two or more output signals from the magnetic field sensor elements are combined to obtain two signals which (1) have a defined amplitude relationship (e.g., equal amplitude), (2) have a defined phase shift (e.g., 90°), and (3) are insensitive to homogeneous magnetic interference fields.The last property can be achieved by using a differential measurement. That is, the output signals of an H. X -Sensor element pair (or one H Y The signal components of the sensor element pairs are subtracted to obtain a differential signal in which those signal components originating from a homogeneous disturbance field cancel each other out. In the example from Fig. 14 Differential signals can be obtained from a pair of sensor elements located at two diametrically opposed positions on the circle with radius r (i.e., 114a' and 114b', 115a' and 115b', 116a' and 116b', etc.). Instead of subtraction, a weighted sum of the output signals from different magnetic field sensor elements can be used (where negative weighting factors are possible). As mentioned, the magnetic field sensor elements do not necessarily have to be arranged on a circle. In general, magnetic field components in the first direction (e.g., x-direction) are measured at at least one first and one second position in the sensor plane (e.g., positions P1 and P3 in the example from Fig. 12). Furthermore, magnetic field components in the second direction (e.g., y-direction) are measured at at least a third and fourth second position in the sensor plane (e.g., positions P2 and P4 in the example from Fig. 12) The desired angular position of the shaft with respect to its axis of rotation can then be calculated based on the difference in magnetic field components at the first and second positions and on the difference in magnetic field components at the third and fourth positions. These differences are used to implement the differential measurement mentioned above. The angular position sensor system can therefore be considered a type of gradiometer.

[0045] Referring to Fig. 12 one obtains a signal S COS , which is proportional to the cosine of twice the angular position φ (S COS ~ cos(2φ)) is by (H X (0°)-H X (180°)) - (H Y (90°)-H Y (270°)) calculated. A signal S SIN , which is proportional to the sine of twice the angular position φ (S SlN ~ sin(2φ)) is obtained by (H Y (0°)-H Y (180°)) calculated. Another signal SSIN ', which is proportional to the sine of twice the angular position, is obtained by (H X (90°)-H X (270°)) is calculated. The cosine signal Scos and any one of the two sine signals S SIN , S SIN ' can be used to calculate the tangent function tan(2φ) (ratio S SIN / S COS or S SIN ' / S COS ) to calculate the angular position 2φ, from which the desired angular position can be calculated, as the arctangent of e.g. S SlN / S COS For example, the CORDIC algorithm can be used to implement the arctangent function. Using the layout from Fig. 12 one obtains the magnetic field component H Y (0°) by averaging the output signals of the magnetic field sensor elements 114 and 114b. The same is done for the H X-component and other positions of the magnetic field sensor elements. The factor 2 in the expressions cos(2φ), sin(2φ) and tan(2φ) arises as a consequence of the aforementioned double symmetry of the setup, and the angular position can only be uniquely determined in a range of 0° to 180°, which is sufficient when the on-axis angular position sensor is used to control certain types of BLDC motors.

[0046] When using the layout according to the example from Fig. 13 can use the signal S1 and S2 according to S1=(HX(45°)−HX(225°))+(HY(315°)−HY(135°)) and S2=(HX(135°)−HX(315°))+(HY(45°)−HY(225°)) The angle φ can be calculated where the sum of S1 and S2 is equal to A·sin(2φ) and the difference S1-S2 is equal to A·cos(2φ). Similar to the previous example, the angular position φ can be derived as 1 / 2·arctan((S1+S2) / (S1-S2)).

[0047] When using the layout according to the example from Fig. 14 can produce a sine signal SSIN and a cosine signal S COS according to SSIN=(HX(270°)−HX(90°))−(HY(0°)−HY(180°)) and SCOS=2⋅SC−SSIN, where SC=(H X (225°)-H X (45°)) - (H Y (315°)-H Y (135°)). As mentioned, the examples discussed above involve a twofold symmetry of the wave end. It should be noted that similar expressions can be found for signals suitable for measurement setups with first-order, third-order, or higher-order symmetry. In the equations above, the positions P1, P1', P2, P2', P3, P3', P4, and P4' are represented by corresponding angles (0° denotes P1, 45° denotes P1', 90° denotes P2, 135° denotes P2', 180° denotes P3, 225° denotes P3', 270° denotes P4, and 315° denotes P4'). Together with the radius r, the angles uniquely define the associated measurement points P1, P1', P2, P2', P3, P3', P4, and P4'.

[0048] As mentioned above, a double symmetry of the shaft end piece may be sufficient in at least some applications where the rotational movement of BLDC motors is to be controlled. Fig. 15 and Fig. Figure 16 illustrates two different examples of how an on-axis angular position sensor can be arranged in a brushless DC (BLDC) motor assembly. Fig. Figure 15 is a sectional view of a part of a BLDC motor, with the section plane passing through the axis of rotation of shaft 104. It should be noted, however, that Fig. Figure 15 is not to scale and should be considered a schematic sketch. Also in Fig. Figure 15 shows the permanent magnets (PM) 217 ​​and 218, which are attached directly or indirectly to the shaft 104 along its circumference. The shaft 104 can be supported by at least two bearings, with bearing 214 being a ball bearing in the example shown. However, depending on the actual implementation, other types of bearings can also be used. The shaft 104 and the PMs attached to the shaft form the rotor (armature) of the motor. The stator 201 of the motor has coils 211 and 212, which are supplied with current to control the rotational movement of the motor.

[0049] As in the examples described above, the shaft end piece has a recess P similar to yours in Fig. 3 and Fig. 4 examples shown, wherein a permanent magnet 102' is attached to the shaft 104 similarly to the one above with reference to Fig. 6 discussed examples. To achieve a compact design, the magnetic field sensors (in Fig. 15 represented by the sensor chip 106), which are used to build an on-axis angular position sensor, are arranged on the PCB 108 together with the power electronics, which are used to generate the operating current supplied to the stator coils 211, 212.

[0050] How to in Fig. As can be seen in Figure 15, the PCB faces directly towards the end face of the shaft 104 (i.e., the shaft end piece), and the magnetic field sensor elements are symmetrical to the axis of rotation on the PCB 108 in the present example, as shown in the Fig. The electrical contacts C (solder contacts, pins) of the stator coils 211, 212 protrude from the stator towards the PCB 108, enabling a direct electrical connection between the coils 211, 212 and the PCB 108. The PCB 108 can be mounted on an inner surface of a motor housing H facing the stator 210 of the motor.

[0051] The example from Fig. 16 essentially corresponds to the previous example from Fig. 15, apart from the fact that the permanent magnet 102' attached to the shaft end was omitted and instead, similar to the one in Fig. In the example shown in Figure 3, a permanent magnet 102 is arranged on the back of the PCB 108. It is understood that any other angular position sensor arrangement in a BLDC motor arrangement as shown in Figure 3 can be used. Fig. 15 and Fig. 16 shown can be used.

[0052] PCB 108 carries the sensor chip 106 as well as the power components 215, 216, which provide the (controlled) load current supplied to the stator coils 211, 212. The distance between the magnetic field sensor elements (in sensor chip 106) and the power components 215, 216, or between the magnetic field sensor elements and the load current lines on PCB 108, is often relatively small (e.g., less than 10 mm or 20 mm), so that the magnetic field generated by the power lines or the power components is highly inhomogeneous at the positions of the magnetic field sensor elements. Therefore, an ordinary gradiometer is insufficient to eliminate the effect of the magnetic interference fields caused by the load current lines and the power components. However, the load current lines and the power components are located (at least approximately) at the same z-position (i.e.,of the same axial position) as the magnetic field sensor elements (and consequently the magnetic field lines intersect the sensor elements as in . Fig. (2 shown almost vertically). The angular position measurement becomes very robust against these disturbances if the magnetic field sensor elements do not react to these magnetic field components in the z-direction. Therefore, the embodiments described here include gradiometer setups that are sensitive to magnetic field components in the x- or y-direction.

[0053] Although the invention has been described and illustrated with reference to one or more implementations, changes and / or modifications may be made to the illustrated examples without departing from the spirit and scope of the appended claims. In particular, with regard to the various functions performed by the components or structures (units, assemblies, devices, circuits, systems, etc.) described above, the designations (including reference to a "means") used to describe such components shall also apply to any other component or structure that performs the specified function of the described component (i.e., that is functionally equivalent), even if it is not structurally equivalent to the disclosed structure that performs the function in the exemplary implementations of the invention illustrated herein.

[0054] Furthermore, although a particular feature of the invention may be disclosed only in relation to one of several implementations, such features may be combined with one or more features of the other implementations if desirable or advantageous for any or a particular application. Moreover, insofar as terms such as "including," "encompassing," "having," "has," "with," or variations thereof are used either in the detailed description or in the claims, such terms shall be understood as inclusive, similar to the term "comprise."

Claims

[1] A magnetic angular position sensor system (100) comprising: a shaft (104) rotatable about a rotation axis, said shaft having a soft magnetic shaft end piece; a sensor chip (110) axially spaced from the shaft end piece and defining a sensor plane substantially perpendicular to the axis of rotation; at least four magnetic field sensor elements (114a, 114b, 115a, 115b, 116a, 116b, 117a, 117b, 118a, 118b, 119a, 119b, 120a, 120b, 121a, 121b; 114b', 116a', 114a', 116b', 117b', 115a', 117a', 115a' integrated in the sensor chip (110), wherein two of the magnetic field sensor elements (114a, 114b, 116a, 116b, 118a, 118b, 120a, 120b; 114b', 116a', 114a' 116b') are spaced apart from each other and are only sensitive to magnetic field components in a first direction, and wherein two of the magnetic field sensor elements (115a, 115b, 117a, 117b, 119a, 119b, 121a, 121b; 117b', 115a', 117a', 115a') are spaced apart from each other and are only sensitive to magnetic field components in a second direction; the first and second directions are mutually non-parallel and the first and second directions are perpendicular to the rotation axis; a magnetic field source (102, 102') which magnetizes the shaft end piece, wherein the shaft end piece is shaped such that a magnetic field in the sensor plane caused by the magnetic field source (102, 102') is symmetrical to the Nth order, where N is a finite integer ≥ 1; and a circuit arrangement coupled to the at least four magnetic field sensor elements (114a, 114b, 115a, 115b, 116a, 116b, 117a, 117b, 118a, 118b, 119a, 119b, 120a, 120b, 121a, 121b; 114b', 116a', 114a', 116b', 117b', 115a', 117a', 115a') which is designed to calculate an angular position of the shaft by output signals of the at least four magnetic field sensor elements (114a, 114b, 115a, 115b, 116a, 116b, 117a, 117b, 118a, 118b, 119a, 119b, 120a, 120b, 121a, 121b; 114b', 116a', 114a' 116b',117b', 115a', 117a', 115a') are combined, wherein the shaft end piece has at least one groove (P) arranged in its end face (105) or at least one projection (150) arranged on the end face (105), wherein the groove (P) or the projection (150) are shaped such that the shaft end piece has a rotational symmetry of the Nth order, where N is a finite integer ≥ 2. [2] The magnetic angular position sensor system (100) according to claim 1, wherein the at least four magnetic field sensor elements (114a, 114b, 115a, 115b, 116a, 116b, 117a, 117b, 118a, 118b, 119a, 119b, 120a, 120b, 121a, 121b; 114b', 116a', 114a', 116b', 117b', 115a', 117a', 115a') are arranged in the sensor plane around a center point defined by a projection of the rotation axis onto the sensor plane. [3] The magnetic angular position sensor system (100) according to claim 1 or 2, wherein the magnetic field source (102, 102') comprises at least one permanent magnet. [4] The magnetic angular position sensor system (100) according to claim 3, wherein the sensor chip (110) is arranged in a chip housing (106) which is attached to a printed circuit board (108), and wherein the at least one permanent magnet (102, 102') is attached to the chip housing (106) or to the circuit board (108) or to the shaft end piece. [5] The magnetic angular position sensor system (100) according to one of claims 1 to 4, wherein the magnetic field source (102, 102') comprises a first permanent magnet and at least one second permanent magnet; wherein the sensor chip (110) is arranged in a chip housing (106) which is attached to a printed circuit board (108), and wherein the first permanent magnet is attached to the chip housing (106) or to the circuit board (108) or to the shaft end piece. [6] The magnetic angular position sensor system (100) according to any one of claims 1 to 5, wherein the shaft end piece comprises a spring (151) rotating synchronously with the shaft (104), the spring (151) being substantially resilient in an axial direction of the rotation axis. [7] The magnetic angular position sensor system (100) according to claim 6, wherein the spring (151) is substantially non-compliant in directions perpendicular to the rotation axis. [8] The magnetic angular position sensor system (100) according to claim 6 or 7, wherein the spring (151) is arranged between the sensor chip (110) and an end face of the shaft end piece, and wherein the spring (151) is mounted on a chip housing (106) of the sensor chip (110) via a spacer (152). [9] The magnetic angular position sensor system (100) according to claim 8, wherein the spacer (152) is attached to the spring (151) or is formed by a bulge of the spring (151), and wherein the spring (151) is configured to exert an axial force on the chip housing (106). [10] The magnetic angular position sensor system (100) according to one of claims 1 to 9, wherein the at least four sensor elements (114a, 114b, 115a, 115b, 116a, 116b, 117a, 117b, 118a, 118b, 119a, 119b, 120a, 120b, 121a, 121b; 114b', 116a', 114a', 116b', 117b', 115a', 117a', 115a') are distributed symmetrically along a circle coaxial with the rotation axis. [11] A magnetic angular position sensor system (100) comprising: a shaft (104) rotatable about a rotation axis, said shaft having a soft magnetic shaft end piece; a sensor chip (110) axially spaced from the shaft end piece and defining a sensor plane substantially perpendicular to the axis of rotation; at least four magnetic field sensor elements (114a, 114b, 115a, 115b, 116a, 116b, 117a, 117b, 118a, 118b, 119a, 119b, 120a, 120b, 121a, 121b; 114b', 116a', 114a', 116b', 117b', 115a', 117a', 115a' integrated in the sensor chip (110), wherein a first and a second magnetic field sensor element (114a, 114b, 116a, 116b, 118a, 118b, 120a, 120b; 114b', 116a', 114a' 116b') of the at least four magnetic field sensor elements (114a, 114b, 115a, 115b, 116a, 116b, 117a, 117b, 118a, 118b, 119a, 119b, 120a, 120b, 121a, 121b; 114b', 116a', 114a' 116b', 117b', 115a', 117a', 115a') are spaced apart from one another and are only sensitive to magnetic field components in a first direction, and wherein a third and a fourth magnetic field sensor element (115a, 115b, 117a, 117b, 119a, 119b, 121a, 121b; 117b', 115a', 117a', 115a') of the at least four magnetic field sensor elements (114a, 114b, 115a, 115b, 116a, 116b, 117a, 117b, 118a, 118b, 119a, 119b, 120a, 120b, 121a, 121b;114b', 116a', 114a', 116b', 117b', 115a', 117a', 115a') are spaced apart from each other and are only sensitive to magnetic field components in a second direction, the first and second directions being mutually non-parallel and the first and second directions being perpendicular to the axis of rotation; a magnetic field source (102, 102') which magnetizes the shaft end piece, wherein the shaft end piece is shaped such that a magnetic field in the sensor plane caused by the magnetic field source (102, 102') is symmetrical to the Nth order, where N is a finite integer ≥ 1; and a signal processing circuit coupled to the at least four magnetic field sensor elements (114a, 114b, 115a, 115b, 116a, 116b, 117a, 117b, 118a, 118b, 119a, 119b, 120a, 120b, 121a, 121b; 114b', 116a', 114a', 116b', 117b', 115a', 117a', 115a'), which is designed to: to calculate a first signal representing the difference between the magnetic field components measured by the first and second magnetic field sensor elements (114a, 114b, 116a, 116b, 118a, 118b, 120a, 120b; 114b', 116a', 114a', 116b'); to calculate a second signal representing the difference between the magnetic field components measured by the third and fourth magnetic field sensor elements (115a, 115b, 117a, 117b, 119a, 119b, 121a, 121b; 117b', 115a', 117a', 115a'); to calculate an angular position of the shaft (104) by combining at least the first and second signals, wherein the shaft end piece has at least one groove (P) arranged in its end face (105) or at least one projection (150) arranged on the end face (105), wherein the groove (P) or the projection (150) are shaped such that the shaft end piece has a rotational symmetry of the Nth order, where N is a finite integer ≥ 2. [12] The magnetic angular position sensor system (100) according to claim 11, wherein the at least four sensor elements (114a, 114b, 115a, 115b, 116a, 116b, 117a, 117b, 118a, 118b, 119a, 119b, 120a, 120b, 121a, 121b; 114b', 116a', 114a', 116b', 117b', 115a', 117a', 115a') are distributed symmetrically along a circle coaxial with the rotation axis. [13] The magnetic angular position sensor system (100) according to claim 12, wherein a first part of the magnetic field sensor elements (115a, 115b, 116a, 116b, 119a, 119b, 121a, 121b) are arranged along a first circle, and wherein a second part of the magnetic field sensor elements (114b, 117b, 118, 121a; 114a, 117a, 118b, 121b) are arranged along a second circle, and where the first and second circles are coaxial to the axis of rotation and have different radii. [14] The magnetic angular position sensor system (100) according to any one of claims 11 to 13, wherein the first and second magnetic field sensor elements (114a', 114b'; 116a', 116b') are arranged diametrically with respect to the rotation axis; and / or wherein the third and fourth magnetic field sensor elements (115a', 115b'; 117a', 117b') are arranged diametrically with respect to the rotation axis. [15] The magnetic angular position sensor system (100) according to any one of claims 11 to 14, wherein a first edge of the sensor chip (110) in the first surface is arranged parallel to the first direction, and a second edge of the sensor chip (110) in the first surface is arranged parallel to the second direction. [16] An electric motor assembly comprising: a stator (201) comprising at least one stator coil (211, 212); a rotor comprising at least one shaft (104) with an end face and a soft magnetic shaft end piece; a printed circuit board (108) arranged to face the end face of the shaft (104), at least one sensor chip (110) attached to the circuit board (108) and spaced from the shaft end piece; at least four magnetic field sensor elements (114a, 114b, 115a, 115b, 116a, 116b, 117a, 117b, 118a, 118b, 119a, 119b, 120a, 120b, 121a, 121b; 114b', 116a', 114a', 116b', 117b', 115a', 117a', 115a' integrated in the sensor chip (110), wherein two of the magnetic field sensor elements (114a, 114b, 116a, 116b, 118a, 118b, 120a, 120b; 114b', 116a', 114a' 116b') are spaced apart from each other and are only sensitive to magnetic field components in a first direction, and wherein two of the magnetic field sensor elements (115a, 115b, 117a, 117b, 119a, 119b, 121a, 121b; 117b', 115a', 117a', 115a') are spaced apart from each other and are only sensitive to magnetic field components in a second direction; the first and second directions are mutually non-parallel and the first and second directions are perpendicular to the rotation axis; a magnetic field source (102, 102') which magnetizes the shaft end piece, wherein the shaft end piece is shaped such that the magnetic field components in the first and second directions are rotationally symmetric to the Nth order, where N is a finite integer ≥ 1; and an evaluation circuit coupled to the at least four magnetic field sensor elements (114a, 114b, 115a, 115b, 116a, 116b, 117a, 117b, 118a, 118b, 119a, 119b, 120a, 120b, 121a, 121b; 114b', 116a', 114a' 116b', 117b', 115a', 117a', 115a'), which is designed to determine an angular position of the shaft (104) by combining at least four output signals of the at least four magnetic field sensor elements (114a, 114b, 115a, 115b, 116a, 116b, 117a, 117b, 118a, 118b, 119a, 119b, 120a, 120b, 121a, 121b; 114b', 116a', 114a' 116b', 117b', 115a', 117a', 115a'); a power electronics circuit arrangement arranged on the circuit board (108), which is coupled to the stator coils (211, 212) and is designed to supply operating current to the stator coils (211, 212), wherein the shaft end piece has at least one groove (P) arranged in its end face (105) or at least one projection (150) arranged on the end face (105), wherein the groove (P) or the projection (150) are shaped such that the shaft end piece has a rotational symmetry of the Nth order, where N is a finite integer ≥ 2. [17] A method for measuring the angular position of a shaft (104) having a soft magnetic shaft end piece, the method comprising: Magnetizing the shaft end piece, wherein the shaft end piece is shaped such that in a sensor plane which is substantially perpendicular to the rotation axis, the magnetic field components in a first and a second direction are rotationally symmetric with Nth order, where N is a finite integer ≥ 1; Measuring the magnetic field components in the first direction at at least a first and a second position (P1, P3; P2', P4') in the sensor plane, the second position being different from the first position; Measuring the magnetic field components in the second direction at at least a third and a fourth position (P1', P3', P2, P4) in the sensor plane, the fourth position being different from the third position; Calculating the angular position of the shaft (104) with respect to its rotation axis based on the difference between the magnetic field components at the first and second positions (P1, P3; P2', P4') and on the difference between the magnetic field components at the third and fourth positions (P1', P3', P2, P4), wherein the shaft end piece has at least one groove (P) arranged in its end face (105) or at least one projection (150) arranged on the end face (105), wherein the groove (P) or the projection (150) are shaped such that the shaft end piece has a rotational symmetry of the Nth order, where N is a finite integer ≥ 2. [18] The method according to claim 17, wherein measuring the magnetic field components comprises: Providing a first sensor signal using at least one first magnetic field sensor element (114b') configured to measure magnetic field sensor components in the first direction at the first position (P1); Providing a second sensor signal using at least one second magnetic field sensor element (114a') configured to measure magnetic field sensor components in the first direction at the second position (P3); Providing a third sensor signal using at least one third magnetic field sensor element (115b') configured to measure magnetic field sensor components in the second direction at the third position (P2); and Providing a fourth sensor signal using at least one fourth magnetic field sensor element (115a') configured to measure magnetic field sensor components in the second direction at the fourth position (P4). [19] The method of claim 18, wherein calculating the angular position of the shaft (104) comprises: Calculating a fifth signal representing the difference between the first and second sensor signals; Calculating a sixth signal representing the difference between the third and fourth sensor signals; and Calculate the angular position based on the fifth and sixth signals.

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