Device for detecting a rotational property of an object rotating around an axis of rotation
A device with four equidistant sensor elements and an evaluation circuit for detecting rotational properties reduces interference field influence by calculating difference values, enhancing accuracy in automotive applications.
Patent Information
- Application Number
- DE102024205233
- Authority / Receiving Office
- DE · DE
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-06-07
- Publication Date
- 2025-12-11
AI Technical Summary
Existing devices for detecting rotational properties are affected by electromagnetic interference fields, which can lead to incorrect detection and malfunction of the entire device. This is particularly important for the automotive industry and the detection of the rotational properties of an object rotating about an axis of rotation, which is increasingly prevalent in automotive engineering, and is difficult to solve for devices with radial reading directions.
A device with four sensor elements arranged equidistant from the axis of rotation and in a radial direction, detecting radial and tangential magnetic field components, and an evaluation circuit calculating difference values to eliminate the influence of stray or interference fields.
The device effectively reduces the impact of stray or interference fields by calculating difference values from detected magnetic field components, ensuring accurate detection of rotational properties.
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Abstract
Description
State of the art
[0001] Numerous devices for detecting the rotational property of an object rotating about an axis of rotation are known in the prior art. These devices are particularly important for the automotive industry and serve, for example, to detect the rotational speed of a rotating object such as the output shaft of an electric machine. Some of the known devices comprise a magnet rotatably mounted about the axis of rotation and coupled to the rotating object, a magnetic field-sensitive sensor device that detects the magnetic field of the magnet during rotation, and an evaluation circuit that calculates the rotational property from the detected magnetic field.The magnets can, in particular, have a disc-shaped or ring-shaped geometry with a cylindrical circumferential wall surrounding the axis of rotation, wherein a magnetic north pole and a magnetic south pole of the magnet are diametrically opposite each other with respect to the axis of rotation. The magnets are then diametrically and not axially polarized. Such devices are known, for example, from: "Sensors in Motor Vehicles", 2nd edition April 2007, Technical Knowledge for Motor Vehicle Technology, p. 133, ISBN-13 978-3-86522-021-9. A magnetic field-sensitive sensor device can, in principle, be arranged either on the axis of rotation and in the axial direction in front of the rotating magnet (axial reading direction) or arranged in a radial direction perpendicular to the axis of rotation opposite the circumferential wall (radial reading direction).
[0002] A growing technical challenge lies in the immunity of such devices to magnetic stray or interference fields, which are increasingly prevalent in automotive engineering. In the worst-case scenario, such stray or interference fields can lead to an incorrect detection of the rotational quantity and thus to a malfunction of the entire device. Immunizing the sensor system against magnetic stray or interference fields is therefore of considerable importance. In the case of axial reading directions, this is less problematic, as immunity to stray or interference fields can be achieved directly through the sensor ASIC. In contrast, it is significantly more difficult to solve the problem for devices with radial reading directions using a simple measure.Nevertheless, devices with radial reading direction are interesting because they require less axial installation space and can therefore be integrated into an electric drive unit, especially an e-axis, in a more space-saving manner in many applications. Disclosure of the invention
[0003] The invention relates to a device for detecting a rotational property of an object rotating about an axis of rotation, comprising: a magnet rotatably mounted about the axis of rotation with a cylindrical circumferential wall surrounding the axis of rotation, wherein a magnetic north pole and a magnetic south pole of the magnet are diametrically opposite each other with respect to the axis of rotation, - a magnetic field-sensitive sensor device designed to detect the magnetic field of the magnet when the magnet rotates and - an evaluation circuit which calculates the rotational property from the detected magnetic field. According to the invention, the magnetic field-sensitive sensor device has four sensor elements, wherein the four sensor elements are arranged at equal distances from the axis of rotation and in a plane parallel to the axis of rotation, the plane being opposite the circumferential wall of the magnet in a radial direction perpendicular to both the axis of rotation and the plane, wherein a first sensor element and a second sensor element of the four sensor elements are arranged at a first distance from each other and are configured to detect a radial magnetic field component on a first circumferential track of the magnet, wherein a third sensor element and a fourth sensor element of the four sensor elements are arranged at a second distance from each other corresponding to the first distance and are configured toto detect a tangential magnetic field component on a second circumferential track of the magnet, which is parallel to the first circumferential track, wherein the evaluation circuit is configured to calculate a first difference value from the radial magnetic field components detected by the first sensor element and the second sensor element, and a second difference value from the tangential magnetic field components detected by the third sensor element and the fourth sensor element.
[0004] In the context of the present application, magnetic stray or interference field influence is considered to be any magnetic field strength that does not originate in the magnet of the device but in an external magnetic field source.
[0005] A sensor element is a single sensor element that enables the detection of magnetic fields in a predefined spatial direction at its location. Such sensor elements can be designed, for example, as Hall sensors or magnetoresistive sensors. In the case of Hall sensors, these are also referred to as "1D Hall sensors".
[0006] There are various ways to couple a magnet rotating around a rotational axis of the device with the rotating object whose rotational magnitude is to be measured. In a simple case, the object can be a rotating shaft and the magnet mounted directly on the shaft, so that the rotational axis of the magnet coincides with the rotational axis of the shaft.
[0007] The magnetic field-sensitive sensor device is arranged opposite the circumferential wall in a radial direction perpendicular to the axis of rotation, according to the orientation of the four sensor elements, so that, according to the invention, the radial reading direction is present, in which an axis perpendicular to the axis of rotation runs through the sensor device. Advantages of the invention
[0008] The invention advantageously makes it possible to provide a device for detecting a rotational property of an object rotating about an axis of rotation with a magnet and a sensor device arranged relative to the magnet in a radial reading direction, which largely eliminates magnetic stray or interference field influence.
[0009] To achieve this, four sensor elements are provided, each equidistant from the axis of rotation and arranged in a plane parallel to the axis of rotation. This plane is radially perpendicular to both the axis of rotation and the plane, opposite the magnet's circumferential wall. The magnitude and orientation of the magnet's magnetic field depend on the magnetic flux density, which is a vector quantity. Starting from a point on the magnet's circumferential wall, each magnetic flux density vector B has a radial component B. r , a tangential component B t and an axial component B aThe system works by arranging a first and second sensor element of the four sensor elements at a first distance from each other and designing them to detect a radial magnetic field component on a first circumferential track of the magnet at the location of each sensor element, while a third and fourth sensor element of the four sensor elements are arranged at a second distance from each other corresponding to the first distance and designing them to detect a tangential magnetic field component on a second circumferential track of the magnet parallel to the first circumferential track at the location of each sensor element. As a result, two values are recorded for both the radial and the tangential magnetic field components perpendicular to it. Since the four sensor elements are located close to each other, a stray or interfering magnetic field affects all four sensor elements to the same extent.Even with slight variations in size, the invention proposed here is still advantageously able to significantly reduce the influence of stray or interfering magnetic fields to a large extent. For this purpose, the evaluation circuit calculates a first difference value from the radial magnetic field components detected by the first and second sensor elements, and a second difference value from the tangential magnetic field components detected by the third and fourth sensor elements, respectively. By calculating the difference, the influence of stray or interfering magnetic fields is advantageously eliminated or at least reduced in both the radial and tangential directions.
[0010] Advantageous embodiments and further developments of the invention enable the features contained in the dependent claims.
[0011] A particularly advantageous embodiment is one in which the evaluation circuit calculates the rotation property from a quotient of the first difference value and the second difference value. If, for example, the rotation property is the rotation angle of an object rotating about the axis of rotation, the evaluation circuit can calculate the rotation angle from the quotient of the first difference value and the second difference value by a simple calculation of the arctangent (atan or arctan) or an extended arctangent relation (atan2 or arctan2).
[0012] The extended arctangent function, atan2 or arctan2, defines an extension of the inverse trigonometric function arctangent and, like it, is an inverse function of the tangent function, taking two real numbers as arguments, unlike the standard arctangent function, which takes only one real number as an argument. The atan2 or arctan2 function can return a value in a range of 360° and is therefore not limited to the angle range of -90° to 90° like the standard arctangent function.
[0013] The four sensor elements can be configured as one-dimensional Hall effect sensors or magnetoresistive sensors. In a particularly advantageous embodiment, the four sensor elements are each configured as ASIC components arranged in a rectangular configuration on a common printed circuit board. It is advantageous to mount the four components close together on the circuit board. However, the distances between them should be large enough to allow for a sufficient difference in the amplitude of the respective detected radial or tangential magnetic field components for differential measurement. The first distance between the first sensor element and the second sensor element, and the equally large second distance between the third sensor element and the fourth sensor element, can, for example, be between 3 and 15 millimeters.
[0014] Furthermore, the sensor device can include a microcontroller containing the evaluation circuit, which is mounted on the circuit board and is electrically connected to the four sensor elements, for example via conductor tracks on the circuit board.
[0015] The magnet has a cylindrical outer wall. For example, the magnet can be disc-shaped, in which case it has two circular surfaces facing away from each other and the cylindrical outer wall. Alternatively, the magnet can be annular and have an internal cylindrical opening into which, for example, a shaft can be inserted. The magnet preferably has exactly one north pole and exactly one south pole, which are diametrically opposed to each other with respect to the axis of rotation. Brief description of the drawings
[0016] Possible embodiments of the invention are explained below with reference to the accompanying figures. The drawing shows: Fig. 1 a first embodiment of a construction of a device according to the invention, Fig. 2 a second embodiment of a construction of a device according to the invention Fig. 3 a perspective view of a further embodiment of the invention, Fig. 4 A top view of a circuit board with the sensor device. Embodiments of the invention
[0017] Fig. Figure 1 shows a first embodiment of a device according to the invention for detecting a rotational property of an object rotating about an axis of rotation, which is, for example, the output shaft 110 of an electric machine 100 rotating about an axis of rotation 10. A magnet 1 is non-rotatably connected to the shaft 110, so that the magnet 1 rotates together with the shaft 110 about the axis of rotation 10. The magnet 1 has a cylindrical circumferential wall 11 that surrounds the axis of rotation 10. The device further comprises a sensor device 2, which is arranged opposite the circumferential wall 11 in a direction perpendicular to the axis of rotation 10 and therefore radially, so that a radial reading direction is present. The sensor device 2 can be arranged on a printed circuit board 5, which in the embodiment of the Fig. 1 is arranged parallel to the circuit board 5.
[0018] Fig. Figure 2 shows a second embodiment of a device according to the invention. In contrast to the embodiment of the Fig. 1 is in the Fig. 2 the circuit board 5 is arranged perpendicular to the axis of rotation 10. In this embodiment as well, the sensor device 2 is arranged opposite the circumferential wall 11 in a radial direction perpendicular to the axis of rotation 10, so that a radial reading device is present.
[0019] Fig. Figure 3 shows a more detailed embodiment of a device according to the invention. The device comprises a cylindrical magnet 1 which can rotate about a rotation axis 10. It can be seen in Fig. 1, that the outer contour of the magnet 1 has two opposing circular outer surfaces 13, 14 at its end faces, as well as a circumferential cylindrical outer wall 11. The magnet 1 is divided along a dividing plane 15, which runs through the axis of rotation 10, into exactly one north pole N and one south pole S. The north pole N is therefore diametrically opposite the south pole S with respect to the axis of rotation 10.
[0020] Furthermore, a magnetic field-sensitive sensor device 2 is provided, which is based on the Fig. 4 will be examined in more detail. As in Fig. As can be seen in Figure 3, the sensor device 2 has four sensor elements 21, 22, 23, 24, which are arranged at equal distances from the axis of rotation 10. The four sensor elements are arranged in a plane 30 parallel to the axis of rotation 10, with the plane 30 being opposite the circumferential wall 11 of the magnet 1 in a radial direction r0 perpendicular to both the axis of rotation 10 and the plane 30. The plane 30 is Fig. 3 spanned by the drawn x-direction and y-direction.
[0021] As further in Fig. As can be seen in Figure 3, a first sensor element 21 and a second sensor element 22 are arranged in the x-direction at a first distance d1 from each other. A third sensor element 23 and a fourth sensor element 24 are arranged in the x-direction at a second distance d2, which is equal to the first distance d1.
[0022] Starting from an arbitrary point on the circumferential wall 11 of the magnet 1, each vector of the magnetic flux density B has a radial component B. r , a tangential component B t and an axial component B a The first sensor element 21 and the second sensor element are designed to each detect a radial magnetic field component B on a first circumferential track U1 of the magnet 1 r to detect at the location of the sensor element. The first sensor element 21 thus detects a radial magnetic field component B. r1 and the second sensor element 22 a magnetic field component B r2 The third sensor element 23 and the fourth sensor element 24 are configured to each detect a tangential magnetic field component B on a second circumferential track U2 of the magnet 1, which is parallel to the first circumferential track U1. t to detect at the location of the sensor element. The third sensor element 23 thus detects a tangential magnetic field component B.t1 and the fourth sensor element 24 a tangential magnetic field component B t2 The sensor elements therefore only detect the magnetic field component of the magnetic flux density vector acting in one direction at the location of the respective sensor element, with the first and second sensor elements detecting a radial magnetic field component and the third and fourth sensor elements detecting a tangential magnetic field component.
[0023] Fig. Figure 3 shows that the four sensor elements 21, 22, 23, and 24 are arranged in a rectangular configuration. In this configuration, the sensor elements of the sensor device 2 can be mounted on a circuit board 5, as shown in Figure 3. Fig. 4 is shown. Fig. Figure 4 shows a view perpendicular to the surface of the circuit board 5 with the four sensor elements 21, 22, 23, 24. The surface of the circuit board 5 is thus arranged in the plane 30 spanned by the x-direction and y-direction, which corresponds to the plane of the figure. Fig. 4 corresponds to.
[0024] The four sensor elements 21, 22, 23 and 24 are mounted close together on the circuit board 5. The distance d1 of the first from the second sensor element, as well as the distance d2 of the third from the fourth sensor element, can be, for example, between 15 and 3 millimeters, as can the distance between the first sensor element 21 and the third sensor element 23, and between the second sensor element 22 and the fourth sensor element 24.
[0025] Furthermore, a microcontroller 4 is mounted on the circuit board 5, which is connected to the four sensor elements 21, 22, 23, 24 and includes an evaluation circuit 3, which is designed to calculate a first differential value ΔB r from the radial magnetic field components B detected by the first sensor element 21 and the second sensor element 22 respectively r1 , B r2 and a second difference value ΔB t from the tangential magnetic field components B detected by the third sensor element 23 and the fourth sensor element 24 respectively t1 , B t2 to calculate.
[0026] Therefore: ΔBr=Br1−Br2 and ΔBt=Bt1−Bt2.
[0027] This approach advantageously eliminates the influence of a magnetic stray or interference field, because in the case of the presence of a stray or interference field acting, for example, in a radial direction B S The equation above changes to: ΔBr=(Br1+Br2)−(Br2+BS)=Br1−Br2, And the situation therefore remains unchanged. The same applies to the tangential direction: ΔBr=(Bt1+BS)−(Bt2+BS)=Bt1−Bt2.
[0028] Since the scattering or interference field has a similar effect on the sensor elements 21, 22, 23, 24 due to their spatial proximity, the calculation of the difference allows the influence of the scattering or interference field to be factored out.
[0029] If the rotational property to be detected by the device is the rotation angle φ or the rotation angle of the magnet 1, then the evaluation circuit 3 can easily calculate the rotation angle φ from the quotient of the first difference value ΔB. r and the second difference value ΔB t in particular, calculate from an arctangent relationship or an extended arctangent relationship, for example according to the formula: φ=atan2(ΔBrΔBt) QUOTES INCLUDED IN THE DESCRIPTION
[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature
[0000] Sensors in motor vehicles”, 2nd edition April 2007, Technical knowledge of motor vehicle technology, p. 133, IDBN-13 978-3-86522-021-9
[0001]
Claims
[1] Device for detecting a rotational property of an object rotating about an axis of rotation, comprising: - a magnet (1) rotatably mounted about the axis of rotation (10) with a cylindrical circumferential wall (11) rotating around the axis of rotation (10), wherein a magnetic north pole (N) and a magnetic south pole (S) of the magnet (1) are diametrically opposite each other with respect to the axis of rotation (10), - a magnetic field-sensitive sensor device (2) which is designed to detect the magnetic field of the magnet (1) when the magnet is rotated and - an evaluation circuit (3) which calculates the rotational property from the detected magnetic field, characterized by, that the magnetic field-sensitive sensor device (2) has four sensor elements (21, 22, 23, 24), wherein the four sensor elements (21, 22, 23, 24) are arranged at equal distances from the axis of rotation (10) and in a plane (30) parallel to the axis of rotation (10), wherein the plane (30) is opposite the circumferential wall (11) of the magnet (1) in a radial direction (r0) perpendicular to both the axis of rotation (10) and the plane (30), wherein a first sensor element (21) and a second sensor element (22) of the four sensor elements (21, 22, 23, 24) are arranged at a first distance (d1) from each other and are configured to each detect a radial magnetic field component (B) on a first circumferential track (U1) of the magnet (1). r1 ; B r2) to detect, wherein a third sensor element (23) and a fourth sensor element (24) of the four sensor elements (21, 22, 23, 24) are arranged at a second distance (d2) to each other corresponding to the first distance (d1) and are configured to each detect a tangential magnetic field component (B) on a second circumferential track (U2) of the magnet (1) parallel to the first circumferential track. t1 , B t2 ) to detect, wherein the evaluation circuit (3) is configured to determine a first difference value (ΔB r ) from the radial magnetic field components (B) detected by the first sensor element (21) and the second sensor element (22) respectively r1 , B r2 ) and a second difference value (ΔB t ) from the tangential magnetic field components (B) detected by the third sensor element (23) and the fourth sensor element (24) respectively t1 , B t2 to calculate. [2] Device according to claim 1, characterized by, that the evaluation circuit (3) determines the rotation property from a quotient of the first difference value (ΔB) r ) and the second difference value (ΔBt). [3] Device according to claim 2, characterized by , that the rotation property is the rotation angle (φ) and that the evaluation circuit calculates the rotation angle (φ) from the quotient of the first difference value (ΔBr) r ) and the second difference value (ΔBt) is calculated in particular by means of an arctangent relation or an extended arctangent relation. [4] Device according to any one of claims 1 to 3, characterized by , that the four sensor elements (21, 22, 23, 24) are designed as one-dimensional Hall sensor elements or magnetoresistive sensor elements. [5] Device according to any one of the preceding claims, characterized by, that the four sensor elements (21, 22, 23, 24) are each designed as ASIC components, which are arranged on a common circuit board (5) in a rectangular configuration. [6] Device according to claim 5, characterized by , that a microcontroller (4) containing the evaluation circuit (3) is arranged on the circuit board (5), wherein the microcontroller (4) is electrically connected to the four sensor elements (21, 22, 23, 24). [7] Device according to any of the preceding claims, characterized by , that the magnet (1) is disk-shaped or ring-shaped with exactly one north pole (N) and exactly one south pole (S).