A magnetic sensor module configured to detect rotation of an object

Abstract

Various embodiments of the present disclosure relate to a zero-Gauss magnet for a differentially twist-insensitive magnetic velocity sensor. A magnetic sensor module includes an axially polarized reverse bias magnet having a body extending radially from an inner sidewall to an outer sidewall and a hole defining the inner sidewall. The magnet body generates a radially symmetric bias plane magnetic field about a central axis in a sensor plane. The magnetic field has a substantially zero magnetic flux density along an extension of the central axis and on a circumference of a zero field circle located in the sensor plane, wherein the circumference of the zero field circle vertically overlaps with the magnet body in a plan view. The magnetic sensor module includes a magnetic sensor, which includes at least three sensor elements, which are arranged at a position in the sensor plane where the magnetic field has a substantially zero magnetic flux density in a radially symmetric bias plane, including at least two sensor elements arranged on the circumference of the zero field circle.

Description

Technical Field

[0001] The present disclosure relates generally to sensing wheel speed, and more particularly to magnetic speed sensors. Background Art

[0002] To measure wheel speed (e.g. in automotive applications), a ferromagnetic wheel is usually used in combination with a magnetosensitive sensor and a magnet mounted to the sensor. The sensor generates output pulses. A control unit counts the pulses and is able to calculate the wheel speed and the actual angle of the rotating wheel, and optionally determine the direction of rotation of the wheel.

[0003] In camshaft sensing applications, a Hall cell configuration can be used that enables output switching at the tooth edge of a gear. When a ferrous target wheel rotates in front of the sensor, the z-magnetization back-biased sensor in combination with the Bz-sensitive cell sensor generates a sinusoidal signal. The maximum amplitude is achieved when the tooth passes the sensor, while the minimum signal is achieved when the sensor faces the groove of the gear. Therefore, the sensor device switches on the tooth edge.

[0004] The benefit of using a Hall cell sensor is that the sensor is insensitive to twisting, so that the sensor will work independently of the mounting position, regardless of its rotational orientation about its z-axis. Therefore, the air gap between the sensor module and the wheel can be adjusted during installation using a screw. That is, twisting the sensor module like a screw will adjust the air gap, and the rotational orientation of the sensor can be ignored. Therefore, due to the insensitivity to twisting, the assembly tolerance is relaxed during sensor installation.

[0005] On the downside, Hall cell sensors have disadvantages in terms of stray field robustness. Stray fields are magnetic fields introduced by external devices located in the sensor's proximal environment. For example, stray field interference can be caused by components located within the vehicle (e.g., for hybrid vehicles, due to current rails driving high currents close to the sensing device or due to inductive battery charging) or currents flowing through the rails of a train system that generates a magnetic field.

[0006] As an alternative to the Hall cell sensor, a differential Hall sensing element can be used to increase stray field robustness. In a differential Hall sensor, the two Hall plates are spaced apart. The output signal is calculated by subtracting the Bz signal of the first Hall plate from the Bz signal of the second Hall plate, and the uniform stray field in the z direction will be cancelled due to the differential calculation.

[0007] The differential Hall signal has its signal maximum at the rising edge of the gear tooth and its signal minimum at the falling edge of the gear tooth. Thus, compared to a single-cell Hall sensor, the output of the differential Hall sensor switches between the center of the tooth and the center of the notch.

[0008] However, due to the different switching points, the vehicle's electronic control unit (ECU) needs to be reconfigured to adjust the switching points. In addition, another disadvantage of the differential Hall sensor is that it is not sensitive to twisting. Twisting the sensor module around its z-axis will cause the signal to degrade. The worst case is a twist angle of 90°, when both Hall plates sense the same Bz field. In this case, there is no differential signal available, and the sensor cannot detect teeth or notches.

[0009] Therefore, there may be a need for an improved device that combines stray field robustness with twisting insensitivity (ie, twisting independence). Summary of the invention

[0010] Magnetic sensor modules, systems, and methods are provided that are configured to detect the rotation of an object, and more specifically, the rotational speed of an object.

[0011] One embodiment of the multiple embodiments provides a magnetic sensor module, which includes an axially polarized reverse bias magnet and a magnetic sensor. The axially polarized reverse bias magnet includes a magnet body extending from an inner side wall to an outer side wall in a radial direction and a hole defining the inner side wall, wherein the axially polarized reverse bias magnet generates a radially symmetric bias plane magnetic field about a central axis in a sensor plane orthogonal to an extension of a central axis of the axially polarized reverse bias magnet, wherein the hole is centered on the central axis and extends along the central axis in an axial direction of the axially polarized reverse bias magnet, wherein the radially symmetric bias plane magnetic field has a substantially zero magnetic flux density along the extension of the central axis and at the circumference of a zero field circle located in the sensor plane, wherein the circumference of the zero field circle is concentric with the extension of the central axis in a plan view and vertically overlaps with the magnet body. The magnetic sensor comprises at least three sensor elements, the at least three sensor elements being arranged in a sensor plane of the magnetic sensor at a position where a magnetic field in a radially symmetric bias plane has a substantially zero magnetic flux density, wherein the at least three sensor elements are configured to generate measurement values ​​in response to sensing the magnetic field in the radially symmetric bias plane, wherein at least two of the at least three sensor elements are arranged on the circumference of a zero field circle at substantially equidistant angles with respect to a central axis of an axially polarized reverse bias magnet.

[0012] One embodiment of the multiple embodiments provides a magnetic sensor module, which includes an axially polarized reverse bias magnet and a magnetic sensor. The axially polarized reverse bias magnet includes a magnet body extending from an inner side wall to an outer side wall in a radial direction and a hole defining the inner side wall, wherein the axially polarized reverse bias magnet generates a radially symmetric bias plane magnetic field about a central axis in a sensor plane orthogonal to an extension of a central axis of the axially polarized reverse bias magnet, wherein the hole is centered on the central axis and extends along the central axis in an axial direction of the axially polarized reverse bias magnet, wherein the radially symmetric bias plane magnetic field has zero magnetic flux density along the extension of the central axis and at the circumference of a zero field circle located in the sensor plane, wherein the circumference of the zero field circle is concentric with the extension of the central axis in a plan view and vertically overlaps with the magnet body. The magnetic sensor includes at least two sensor elements, which are arranged in a sensor plane of the magnetic sensor and further arranged on the circumference of the zero field circle at substantially equidistant angles about the central axis of the axially polarized reverse bias magnet.

[0013] One of the multiple embodiments provides a magnetic sensor module, which includes an axially polarized reverse bias magnet and a magnetic sensor. The axially polarized reverse bias magnet includes a magnet body extending from an inner side wall to an outer side wall in a radial direction and a hole defining the inner side wall, wherein the axially polarized reverse bias magnet generates a radially symmetric bias plane magnetic field about a central axis in a sensor plane orthogonal to an extension of a central axis of the axially polarized reverse bias magnet, wherein the hole is centered on the central axis and extends along the central axis in an axial direction of the axially polarized reverse bias magnet, wherein the radially symmetric bias plane magnetic field has zero magnetic flux density along the extension of the central axis and at the circumference of a zero field circle located in the sensor plane, wherein the circumference of the zero field circle is concentric with the extension of the central axis in a plan view and vertically overlaps with the magnet body. The magnetic sensor includes at least two sensor elements, the at least two sensor elements are arranged in a sensor plane of the magnetic sensor, and the magnetic sensor is arranged on the circumference of the zero field circle so that the at least two sensor elements are arranged at substantially equidistant angles about the central axis of the axially polarized reverse bias magnet. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Embodiments are described herein with reference to the accompanying drawings.

[0015] Figure 1A and 1B The magnetic field sensing principle of a gear according to one or more embodiments is shown;

[0016] Figure 2 A plan view (top view) of an axially polarized back bias magnet and its in-plane magnetic field distribution according to one or more embodiments is shown;

[0017] Figure 3 shows a graph plotting the in-plane magnetic field Bxy at different minimum distances taken in the z-direction versus the radial distance from the central axis of the back-bias magnet according to one or more embodiments;

[0018] Figure 4 shows a graph plotting the dependence of the in-plane magnetic field Bxy on the hole diameter according to one or more embodiments;

[0019] Figure 5 shows a plan view of a sensor module according to one or more embodiments, the sensor module comprising a sensor arrangement arranged above a back bias magnet;

[0020] Figure 6 A back bias magnet is shown according to one or more embodiments, the back bias magnet being an axially polarized cylinder and including a bore;

[0021] Figure 7 A speed sensing system including a sensor module according to one or more embodiments is shown;

[0022] Figure 8 shows a plan view of another sensor module including a sensor arrangement arranged above a back bias magnet according to one or more embodiments;

[0023] Fig. 9 shows a plan view of another sensor module including a sensor arrangement arranged above a back bias magnet according to one or more embodiments;

[0024] Figures 10A-10D According to one or more embodiments, Figure 5 A sensor signal of a sensor element of the sensor shown versus a rotation angle of a target wheel;

[0025] Fig.10E According to one or more embodiments, Figure 5 The output sensor signal of the sensor circuit of the sensor shown corresponds to the rotation angle of the target wheel;

[0026] Fig.10F According to one or more embodiments, Figure 5 Output sensor signals versus target wheel rotation angle for different twist insensitive mounting (TIM) angles of the sensor module shown; and

[0027] Fig.11 A flow chart illustrating a method of measuring a rotational speed of a rotating component by a magnetic sensor according to one or more embodiments. DETAILED DESCRIPTION

[0028] Hereinafter, the details are set forth to provide a more thorough explanation of the exemplary embodiments. However, it is clear to those skilled in the art that the embodiments can be practiced without these specific details. In other cases, well-known structures and devices are shown in block diagram form or schematic diagrams rather than in detail to avoid confusing the embodiments. In addition, unless otherwise specifically stated, the features of the different embodiments described below can be combined with each other. It should also be understood that other embodiments can be utilized and structural or logical changes can be made without departing from the scope defined by the claims. Therefore, the following detailed description should not be considered as limiting.

[0029] In addition, equivalent or similar elements or elements having equivalent or similar functions are indicated by equivalent or similar reference numerals in the following description. Since identical or functionally equivalent elements are given the same reference numerals in the figures, repeated descriptions of elements having the same reference numerals may be omitted. Therefore, descriptions provided for elements having the same or similar reference numerals are interchangeable.

[0030] Directional terms (e.g., "top," "bottom," "above," "below," "front," "rear," "back," "front," "trailing," "above," "below," etc.) may be used with reference to the orientation of the figures and / or elements being described. Because embodiments may be positioned in a variety of different orientations, the directional terms are used for illustrative purposes and are by no means limiting. In some cases, directional terms may be interchanged with equivalent directional terms based on the orientation of the embodiments, as long as the general directional relationship between elements and their general purpose is maintained.

[0031] In the present disclosure, expressions including ordinal numbers such as "first", "second", etc. can modify various elements. However, such elements are not limited by the above expressions. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only used for the purpose of distinguishing the elements from other elements. For example, the first box and the second box represent different boxes, although they are both boxes. For another example, without departing from the scope of the present disclosure, the first element can be called the second element, and similarly, the second element can also be called the first element.

[0032] It should be understood that when an element is referred to as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element or there may be intervening elements. Conversely, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.).

[0033] In the embodiments described herein or shown in the accompanying drawings, any direct electrical connection or coupling (i.e., any connection or coupling without additional intermediate elements) may also be achieved by an indirect connection or coupling, i.e., a connection or coupling with one or more additional intermediate elements, or vice versa, as long as the general purpose of the connection or coupling (e.g., transmitting a certain signal or transmitting certain information) is basically maintained. Features from different embodiments may be combined to form additional embodiments. For example, changes or modifications to the description of one embodiment in the embodiments may also apply to other embodiments, unless otherwise stated.

[0034] According to specific implementation requirements, the storage medium may include RAM, ROM, PROM, EPROM, EEPROM, FLASH memory, or any other medium having electronically readable control signals stored thereon, which cooperate (or can cooperate with) a programmable computer system to perform the corresponding method. Therefore, the storage medium can be considered as a computer-readable non-transitory storage medium.

[0035] In addition, the instructions can be executed by one or more processors, such as one or more central processing units (CPUs), digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuit systems. Therefore, the term "processor" used in this article refers to any of the aforementioned structures or any other structure suitable for implementing the technology described herein. In addition, in some aspects, the functions described herein can be provided in dedicated hardware and / or software modules. In addition, these technologies can be fully implemented in one or more circuits or logic elements. A "controller" including one or more processors can use electrical signals and digital algorithms to perform its reception, analysis and control functions, which can also include correction functions.

[0036] As used herein, signal conditioning refers to manipulating an analog signal so that the signal meets the requirements of the next stage for further processing. Signal conditioning can include conversion from analog to digital (e.g., via an analog-to-digital converter), amplification, filtering, conversion, bypassing, range matching, isolation, and any other process required to make the sensor output suitable for processing after conditioning.

[0037] Embodiments relate to sensors and sensor systems, and to obtaining information about sensors and sensor systems. A sensor may refer to a component that converts a physical quantity to be measured into an electrical signal (e.g., a current signal or a voltage signal). The physical quantity may include, for example, a magnetic field, an electric field, a pressure, a force, a current, or a voltage, but is not limited thereto. As described herein, a sensor device may be a speed sensor that measures the rotational speed of an object such as a gear.

[0038] For example, a magnetic field sensor includes one or more magnetic field sensor elements, which measure one or more characteristics of a magnetic field (e.g., the amount of magnetic field flux density, field strength, field angle, field direction, field orientation, etc.). The magnetic field can be generated by a magnet, a current-carrying conductor (e.g., a wire), the earth, or other magnetic field sources. Each magnetic field sensor element is configured to generate a sensor signal (e.g., a voltage signal) in response to one or more magnetic fields impinging on the sensor element. Therefore, the sensor signal represents the magnitude and / or orientation of the magnetic field impinging on the sensor element.

[0039] According to one or more embodiments, both the magnetic field sensor and the sensor circuit are housed (i.e., integrated) in the same chip package (e.g., a plastic package, such as a leaded package or a leadless package, or a surface mount device (SMD) package). Such a chip package is also referred to as a sensor package. The sensor package can be combined with a reverse bias magnet to form a sensor module, a sensor device, etc.

[0040] One or more magnetic field sensor elements (or simply magnetic field sensors) included in the sensor package are therefore exposed to the magnetic field, and the sensor signal (e.g., voltage signal) provided by each magnetic field sensor element is, for example, proportional to the magnitude of the magnetic field. In addition, it should be understood that the terms "sensor" and "sensing element" can be used interchangeably throughout the specification, and the terms "sensor signal" and "measurement value" can be used interchangeably throughout the specification.

[0041] The sensor circuit may be referred to as a signal processing circuit and / or a signal conditioning circuit that receives a signal from a magnetic field sensor element (i.e., a sensor signal) in the form of raw measurement data and derives a measurement signal representing the magnetic field from the sensor signal. The sensor circuit may include a digital converter (ADC) that converts analog signals from one or more sensor elements into digital signals. The sensor circuit may also include a digital signal processor (DSP) that performs some processing on the digital signal, which will be discussed below. Thus, the sensor package includes circuitry that conditions and amplifies the small signal of the magnetic field sensor through signal processing and / or conditioning.

[0042] As used herein, a sensor device may refer to a device including a sensor and a sensor circuit as described above. The sensor device may be integrated on a single semiconductor die (e.g., a silicon die or chip), but in other embodiments, a plurality of dies may be used to implement the sensor device. Therefore, the sensor and the sensor circuit are arranged on the same semiconductor die or on multiple dies in the same package. For example, the sensor may be on one die and the sensor circuit on another die so that they are electrically connected to each other within the package. In this case, the die may be composed of the same or different semiconductor materials, such as GaAs and Si, or the sensor may be sputtered onto a ceramic or glass sheet (which is not a semiconductor).

[0043] The magnetic field sensor element includes but is not limited to a vertical Hall effect device or a magnetoresistive sensor, commonly referred to as an XMR sensor, which is a general term for anisotropic magnetoresistive (AMR), giant magnetoresistive sensor (GMR), tunnel magnetoresistive (TMR), etc.

[0044] Figure 1A and 1B The magnetic field sensing principle of a gear 1 having alternating teeth 2 and notches 3 according to one or more embodiments is shown. In particular, the gear 1 can be made of a ferromagnetic material (e.g., iron) that attracts a magnetic field. In addition, a sensor arrangement 4 is configured to sense a magnetic field generated by an axially polarized (axially magnetized) reverse bias magnet 5, wherein the sensor arrangement 4 and the reverse bias magnet 5 include a sensor module 6. The reverse bias magnet 5 can be mounted to the reverse or back side of a sensor die (i.e., the sensor arrangement 4) relative to the gear 1, and the gear 1 is placed in front of the sensor die. The sensor arrangement 4 may generally be referred to as a sensor in this document and may be arranged in a sensor package. The axially polarized magnet 5 generates a radially symmetric bias magnetic field in the sensor package plane (i.e., the chip plane).

[0045] A cylinder with an axial hole or an axial cavity can be used as the axially polarized magnet 5. The in-plane magnetic field (ie, sqrt(Bx 2 +By 2)) is zero at the center of the magnet (i.e., at its central axis), increases in the radial direction from the central axis (e.g., the z-axis as shown), then, due to the axial hole or in the axial cavity, the in-plane magnetic field decreases back to zero at the zero field offset point, and then increases again in the radial direction from the zero field offset point. Therefore, the in-plane magnetic field is generated by the magnet 5, with zero magnetic flux density at the central axis and zero magnetic flux density at the zero field offset point. The zero field offset point is located at a radial (i.e., lateral) distance from the central axis and circumferentially around the central axis. In other words, the zero field offset point is located on the circumference of a zero field circle 12, which is concentric with the central axis (i.e., the z-axis) and is located on the sensor plane of the sensor element. The in-plane magnetic flux density of the magnetic field generated by the magnet 5 is zero along the circumference of the zero field circle 12 and along the central axis of the cylinder. Due to the hole, there will always be a zero transition for the radial field component, and this transition occurs at the zero field circle 12.

[0046] The radial distance at which the circumference of the zero field circle lies depends at least on the diameter of the hole or cavity and the minimum distance between the sensor arrangement 4 (ie the sensor plane) and the back-bias magnet 5 .

[0047] Here, the sensor plane(s) of the sensor elements within the sensor arrangement 4 are arranged parallel to the in-plane component of the magnetic field. Figure 1A and 1B The sensor planes shown are aligned in the x and y directions, perpendicular to each other, and represent the sensitivity axes of the sensor element, so that the sensor element is sensitive to the in-plane magnetic field component Bx (i.e. the magnetic field in the x plane) or the in-plane magnetic field component By (i.e. the magnetic field in the y plane) of the sensor arrangement 4. The sensor element is thus sensitive to the radially symmetric bias magnetic field generated by the magnet 5.

[0048] Figure 1A A tooth 2 of a wheel 1 is shown passing the sensor module 6. In this case, the magnetic lines of force of the radially symmetrical bias magnetic field generated by the back bias magnet 5 are pulled in the z direction towards the tooth 2. As a result, the magnetic lines of force are pulled away from the x-axis and y-axis (i.e., the sensor plane), and the magnetic field strength sensed in the x- and y-directions decreases, so that a minimum magnetic field strength is detected at the center of the tooth 2. This may be different in actual applications, where the minimum may not occur exactly at the center due to assembly tolerances, but the minimum field strength should be detected substantially at the center of the tooth 2.

[0049] on the contrary, Figure 1BThe notch 3 of the wheel 1 is shown passing the sensor module 6. In this case, the magnetic field lines of the radially symmetrical bias magnetic field generated by the back-bias magnet 5 are not (or less) pulled in the z-direction towards the notch 3. Therefore, the magnetic field lines remain concentrated with respect to the x and y axes (i.e., the sensor plane), and the magnetic field strength sensed in the x and y directions reaches a maximum at the center of the notch 3. This may be different in actual applications, in which the maximum value may not occur exactly at the center, but the maximum field strength should be detected substantially at the center of the notch 3.

[0050] As the wheel 1 rotates, the teeth 2 and the notches 3 alternately pass the sensor module 6, and the sensor elements within the sensor arrangement 4 sense the changes in the x-axis and y-axis magnetic field strengths, which vary as a sinusoidal waveform (i.e., as a signal modulation), whose frequency corresponds to the rotational speed of the wheel, which further corresponds to the rotational speed of the drive shaft (e.g., camshaft) that drives the wheel to rotate. Therefore, the sensor circuit of the sensor arrangement 4 receives a signal (i.e., a sensor signal) from the magnetic field sensor element, and derives a measurement signal representing the magnetic field as a signal modulation from the sensor signal. The measurement signal can then be output as an output signal to an external controller, control unit or processor (e.g., ECU). The external device counts the pulses of the output signal and is able to calculate the wheel speed and the actual angle of the rotating wheel.

[0051] Other embodiments relate to a torsion-insensitive differential sensor concept in combination with a zero-Gauss back-bias magnet 5. Specifically, the back-bias magnet 5 includes a central axis along which a hole or cavity extends axially. The hole may extend completely in the axial direction from one end face of the back-bias magnet 5 to the opposite end face of the back-bias magnet 5. Alternatively, the back-bias magnet 5 may have a closed end face with an inner cavity that extends in the axial direction partially between the two closed end faces (i.e., partially between the two end faces that are arranged opposite to each other in the axial direction). Alternatively, the hole may be open at one end face of the magnet 5 and closed at the opposite end face of the magnet 5.

[0052] In either case, the back bias magnet 5 is an axially polarized back bias magnet that generates a radially symmetric bias magnetic field in the sensor plane (e.g., in the xy plane) about the central axis of the axially polarized back bias magnet. The back bias magnet 5 may be an axially polarized annular magnet (i.e., a cylindrical magnet with an axial hole extending therethrough), an axially polarized conical magnet with an axial hole, an axially polarized cubic magnet with an axial hole, etc.

[0053] The sensor die (i.e., sensor arrangement 4) includes a minimum of two sensing elements, wherein at least two of the sensing elements are located at a zero field offset point, which is located on the circumference of a zero field circle, which is concentric with the central axis. In one case, all sensing elements (i.e., two or more) may be located at zero field offset points, which are located on the circumference of the zero field circle. In another case, one of the sensor elements may be located on the central axis, while the other sensor elements may be located at zero field offset points, which are located on the circumference of the zero field circle. For the sensing elements located on the circumference of the zero field circle, they are arranged at equidistant angles on a circle of radius r to provide radial symmetry.

[0054] The origin of the zero field circle is aligned with the central axis of the back bias magnet 5 (i.e., the center of the hole). In this way, all sensing elements are exposed to the same low magnetic offset. Ideally, the magnetic offset is 0 mT. Therefore, the back bias magnet 5 behaves like a zero Gauss magnet. It produces a magnetic field of essentially 0 mT in the sensor plane at the location of all sensing elements and in the sensitive field direction.

[0055] Low or zero magnetic field offset provides some key advantages. First, for sensors with saturation effect (limited linear range), such as XMR sensing elements, strong rare earth magnets can be used without saturating the sensing element. In particular, XMR sensing elements have a limited linear range. Outside of this linear range, the sensing element enters a saturated state and the sensor signal becomes unreliable (e.g., it is no longer proportional to the sensed magnetic field). Therefore, saturation should be avoided. When the XMR sensing element is placed away from the zero field circle, the probability of saturation increases when a strong rare earth magnet is used as the reverse bias magnet 5.

[0056] Low or zero magnetic field offset enables higher stray field robustness as the signal to stray field ratio increases. Secondly, low or zero magnetic field offset allows a reliable true power-on (TPO) feature to be achieved. In addition, with low or zero magnetic field offset, lifetime drift (aging effect of the magnet) and mismatch of the magnet temperature coefficient and the sensor temperature coefficient are less important. In addition, low or zero magnetic field offset enables the use of strong magnetic materials (e.g. rare earth materials such as NdFeB or SmCo) without the risk of saturating the sensor element. The use of strong magnetic materials enables high air gap capability between the sensor and the wheel and allows better manufacturing tolerances.

[0057] Furthermore, additional advantages of the overall system can be achieved, including enhanced stray field robustness due to the differential sensing principle, a twist-insensitive mount (TIM) in which the differential signal generated is independent of the twist about the z-axis, the shape of the soft magnetic pattern can be directly sensed (i.e., teeth -> high, notches -> low), and a small diameter module can be achieved (e.g., the back bias magnet diameter can be 5 mm or less).

[0058] Figure 2 A plan view (top view) of an axially polarized back bias magnet and its in-plane magnetic field distribution according to one or more embodiments is shown. The back bias magnet 5 includes an inner diameter 7 defined by a hole 10, and also includes an outer diameter 8. The back bias magnet 5 includes a central axis 9, which extends orthogonally to the xy sensor plane, and the inner diameter 7 and the outer diameter 8 are concentric with the central axis 9. The back bias magnet 5 generates a radially symmetric bias magnetic field Bxy about the central axis 9 in the xy sensor plane, also referred to as an in-plane magnetic field Bxy. The z-axis extends outside the sensor plane and is therefore referred to as out-of-plane.

[0059] It can be seen from the in-plane magnetic field distribution that the magnetic flux density of the magnetic field Bxy is zero at the center of the hole 10 at the central axis 9. The magnetic flux density of the magnetic field Bxy is also zero at the zero field offset point 11, which is located on the circumference of the zero field circle 12 concentric with the central axis 9. Because the magnetic field Bxy is radially symmetric about the central axis 9, each point at an equal radial distance from the central axis 9 has the same magnetic flux density. Therefore, each point on the zero field circle 12 experiences a zero magnetic field offset (i.e., 0 Tesla). The sensor elements will be placed or substantially placed at the zero field circle 12 (to allow for manufacturing and assembly tolerances) so that they are exposed to an in-plane magnetic flux density (i.e., magnetic field offset) that is zero or substantially zero (i.e., <15mT). In other words, due to manufacturing and assembly tolerance considerations, one or more sensor elements may be placed close to the zero field circle 12, where there is some (i.e., less than 15mT) residual offset field.

[0060] The zero field circle 12, and therefore the zero field offset point 11, is located at a radial distance between the inner diameter 7 and the outer diameter 8 of the back-bias magnet 5. In other words, when viewed from a top or plan view, the zero field circle 12 vertically overlaps the magnet body of the back-bias magnet 5, where the magnet body extends radially from the inner diameter 7 (i.e., the inner sidewall) to the outer diameter 8 (i.e., the outer sidewall).

[0061] The actual location of the zero field offset point 11 depends on the diameter of the aperture 10 and the minimum distance between the sensor arrangement 4 (i.e., the sensor plane) and the back bias magnet 5. The sensor can be placed at a location with a low magnetic offset defined as less than 15 mT, but ideally, is placed at a location where the magnetic field offset is zero (i.e., at the central axis 9 and at the zero field circle 12).

[0062] Figure 3 A graph of the in-plane magnetic field Bxy at different minimum distances taken in the z direction versus the radial distance from the central axis of the reverse bias magnet is shown according to one or more embodiments. Due to the hole 10, there will always be a zero transition for the radial field component, and the transition occurs at the zero field circle 12. In particular, the first curve is associated with the in-plane magnetic field Bxy at a first minimum distance of 0.7 mm from the reverse bias magnet 5, and the second curve is associated with the in-plane magnetic field Bxy at a second minimum distance of 0.3 mm from the reverse bias magnet 5. Each minimum distance is the z distance of the nearest end of the reverse bias magnet 5 relative to the sensor arrangement 4 defining the sensor plane. The diameter of the hole 10 of the two curves is the same.

[0063] It should be noted that the hole 10 extends axially from one end face of the back bias magnet 5 to an opposite second end face of the back bias magnet 5, with the end of the hole 10 exposed. However, in other cases, the hole 10 can be completely enclosed in the magnet body of the magnet 5 as long as a zero magnetic field offset (i.e., zero in-plane magnetic flux density) is generated at both the central axis 9 and the zero field circle 12.

[0064] Back to Figure 3 , the first curve shows that the zero magnetic field offset (i.e., magnetic flux density) exists at the central axis 9 (i.e., 0 mm) and at approximately 1.13 mm, wherein the inner diameter is located at a radial distance of 1 mm from the central axis 9 and the outer diameter is located at a radial distance of 2.5 mm from the central axis 9. In contrast, the second curve shows that the zero magnetic field offset exists at the central axis 9 (i.e., 0 mm) and at approximately 1.38 mm. Therefore, the minimum distance at which the sensor arrangement 4 is arranged can be configured according to the desired sensor spacing between the sensing elements. It should also be noted that the first curve has a much lower gradient of the field versus radial position than the second curve due to the increased minimum distance.

[0065] Figure 4 A diagram showing the dependence of the in-plane magnetic field Bxy on the hole diameter according to one or more embodiments is shown. In particular, several curves for the in-plane magnetic field Bxy are provided, where the diameter of the hole 10 varies from 1.6 mm to 2.8 mm in increments of 0.2 mm. It can be seen that there is a zero magnetic field offset at the central axis 9 (i.e., 0 mm) of all curves. However, the radial distance of the zero field circle 12 where the second zero magnetic field offset exists increases with the increase of the hole diameter.

[0066] For constant magnet outer dimensions and a constant minimum distance (in this case, the sensor is arranged at a z distance of 0.7 mm to the magnet 5), the position of the zero field offset can be adjusted by changing the hole diameter. A smaller diameter results in a smaller sensor spacing. Typically, the outer magnet diameter is limited due to limitations in module assembly. Therefore, for a fixed outer diameter, the position of the zero field offset can be adjusted with the hole diameter. Note that the sensor also implements a small diameter module because the outer diameter of the magnet 5 is only 5 mm because the sensing element is placed on or substantially on the zero field circle 12. The magnet size is reduced compared to other sensor modules that do not have such a configuration. However, it should be understood that the embodiments described herein are not limited to any particular size of the magnet 5.

[0067] Figure 5 A plan view of a sensor module according to one or more embodiments is shown, the sensor module including a sensor arrangement arranged above a reverse bias magnet. As used herein, the sensor arrangement 4 may also be referred to as a sensor chip layout, a single die sensor or a magnetic sensor, and includes at least two magnetic field sensor elements. In this case, four magnetic field sensor elements 20L, 20R, 20U and 20D (collectively referred to as sensor elements 20) are provided. The sensor die also includes a sensor circuit 21. The sensor elements 20 are arranged equidistant from each other on the circumference of the zero field circle 12. Therefore, the sensor elements 20 are uniformly distributed in space about the central axis 9 of the zero field circle 12, so that all sensor elements 20 are exposed to substantially the same or identical magnetic field operating points (due to a typical assembly tolerance of 3%). The diameter of the zero field circle 12 is D.

[0068] As described above, the magnetic flux density of the magnetic field varies symmetrically in the radial direction from a central axis (e.g., from the z-axis shown). For example, the magnetic flux density of the radially symmetric in-plane magnetic field generated by the axially polarized magnet 5 is zero at the center of the magnet (i.e., at its central axis) and is also zero at the zero field circle 12 due to the hole 10. Except for these two positions, the radially symmetric magnetic flux density is not zero according to the details described above. Therefore, the center point of the zero field circle 12 coincides with the central axis 9 of the magnet 5, so that each sensor element 20 (due to a typical assembly tolerance of 3%) is exposed to substantially the same or exactly the same in-plane magnetic field (i.e., magnetic offset).

[0069] Each point on the zero field circle 12 experiences zero magnetic flux density. In the preferred case, all sensor elements 20 are exposed to a zero in-plane magnetic field Bxy. Since they are arranged on or substantially close to the zero field circle 12 generated by the hole 10, all sensor elements always operate in a linear mode (i.e., a non-saturated mode) regardless of the overall magnetization of the magnet 5. Note that the out-of-plane magnetic field Bz is not a consideration because the sensor elements 20 are configured to measure the in-plane magnetic field component (i.e., the Bx magnetic field component or the By magnetic field component) via their respective sensing axes.

[0070] The sensor element 20 may be, for example, a single-axis or multi-axis XMR sensor element having a sensing axis for a velocity sensor which is aligned with one of the in-plane magnetic field components Bx or By. Figure 1A and 1B Similar to the description, for this example, it is assumed that the reverse bias magnet 5 generates a radially symmetric bias magnetic field. In addition, the transfer function of each sensor has a high linear range (minimum value is + / -25mT or greater) and is independent of the bias field in a wide range. That is, each sensor element 20 is sensitive to a first in-plane magnetic field component (e.g., Bx component), while it is independent of (or insensitive to) a different second in-plane magnetic field component (e.g., By component).

[0071] The arrow on each sensor element 20 indicates the direction of the reference layer of the sensor element 20 with the reference direction, so that the reference directions of the sensor elements 20L, 20R are the same and the reference directions of the sensor elements 20U, 20D are the same. Therefore, the sensor elements 20L and 20R share their same reference direction, and the sensor elements 20U and 20D share their own same reference direction. In addition, the signs of the paired reference directions are also reversible. This means that in another embodiment, the sensor elements 20L and 20R can also be sensitive to the -Bx direction, while the sensor elements 20U and 20D can be sensitive to the -By direction. Therefore, if the magnetic field points in the exact same direction as the reference direction, the resistance of the XMR sensor element is the largest, and if the magnetic field points in the exact opposite direction to the reference direction, the resistance of the XMR sensor element is the smallest.

[0072] According to this example, the oppositely arranged sensor elements 20L and 20R may have a sensing axis in the x-direction, which is configured to sense the in-plane magnetic field component Bx (i.e., sensitive to the magnetic field in the x-plane). Similarly, the oppositely arranged sensor elements 20U and 20D may have a sensing axis in the y-direction, which is configured to sense the in-plane magnetic field component By (i.e., sensitive to the magnetic field in the y-plane).

[0073] Two differential signals are obtained from the four sensors 20. Depending on the type or purpose of the sensor, the change in magnetic field is converted into a change in resistance, current or voltage. The first differential signal (e.g., speed signal) can be calculated as Δ1=left-right, or in magnetic field representation, Δ1=BxLeft-BxRight. The second differential signal (e.g., direction signal) that is 90° phase-shifted from the first differential signal can be calculated as Δ2=down-up, or in magnetic field representation, Δ2=ByDown-ByUp.

[0074] The sensor signal of each sensor element 20 is provided to the sensor circuit 21, which calculates two differential signals Δ1 and Δ2 and / or output signals using differential calculations that eliminate uniform stray fields in the x and y directions, and out-of-plane magnetic field components do not affect the output signal (i.e., sensor output). For example, the output signal R OUT or V OUT It can be calculated by the following equation:

[0075] R OUT =R LEFT -R RIGHT -(R UP -R DOWN ) (1), or

[0076] R OUT =R LEFT -R RIGHT +(R DOWN -R UP ) (2)

[0077] V OUT =V LEFT -V RIGHT -(V UP -V DOWN ) (3), or

[0078] V OUT =V LEFT -V RIGHT +(V DOWN -V UP ) (4)

[0079] Here, R LEFT Corresponding to the resistance value of the sensor element 20L, R RIGHT Corresponding to the resistance value of the sensor element 20R, R UP Corresponding to the resistance value of the sensor element 20U, R DOWN corresponds to the resistance value of the sensor element 20D. In addition, V LEFT Corresponding to the voltage value of the sensor element 20L, V RIGHT The voltage value corresponding to the sensor element 20R, V UPCorresponding to the voltage value of the sensor element 20U, V DOWN corresponds to the voltage value of sensor element 20D. Equations (1), (2), (3) and (4) can be summarized as follows:

[0080] SE OUT =(SE A -SE B )+(SE C -SE D ) (5), or

[0081] SE OUT =Δ1+Δ2 (6),

[0082] Where SE corresponds to the sensor element, SE A and SE B corresponds to the first pair of sensor elements arranged oppositely, and SE C and SE D Corresponding to a second pair of sensor elements arranged oppositely.

[0083] Since the sensor element 20 is an XMR sensor element, the resistance value varies according to the magnetic field strength in the direction of the sensing axis, and the resistance value of the XMR sensor element can be detected by the sensor circuit 21, or can be output from the sensor element as a voltage value representing the resistance value (that is, the voltage value varies as the resistance value changes). In the former case, the resistance value is output as a sensor signal, and in the latter case, the voltage value is output as a sensor signal, however, the sensor signal is not limited to this. Therefore, the external stray field in the sensor plane will be offset due to the differential calculation, and the out-of-plane magnetic field component will not affect the sensor output. When installed in front of the ferromagnetic target wheel 1, the sensor output is independent of the torsion of the sensor around the magnet axis 9. Therefore, the output signal SE OUT It does not change its phase, which means it has nothing to do with torsion.

[0084] Alternatively, the sensor element 10 may be, for example, a vertical Hall sensor element having a sensing axis for a speed sensor that is aligned with one of the in-plane magnetic field components Bx or By. In a vertical Hall sensor element, the voltage value output by the sensor element 10 varies according to the magnetic field strength in the direction of the sensing axis. Therefore, external stray fields in the sensor plane will be offset due to differential calculations, and out-of-plane magnetic field components will not affect the sensor output.

[0085] Thus, the oppositely arranged sensor elements 20L and 20R may have sensing axes aligned in the x-direction, which are configured to sense the in-plane magnetic field component Bx (i.e., sensitive to the magnetic field in the x-plane). Similarly, the oppositely arranged sensor elements 20U and 20D may have sensing axes aligned in the y-direction, which are configured to sense the in-plane magnetic field component By (i.e., sensitive to the magnetic field in the y-plane).

[0086] In addition, the sensor module 6 includes an axially polarized cylindrical magnet 5, wherein its central axis 9 points toward the wheel 1 and is concentric with the center of the inner diameter 7, the center of the zero field circle 12, and the center or outer diameter 8. Thus, the magnet produces a radially symmetric bias magnetic field in the sensor plane, so that each sensor element 20 is exposed to (due to a typical assembly tolerance of 3%) substantially the same or identical magnetic field operating points. The magnet can be any shape (e.g., cylindrical, cubic, etc.) that produces a radially symmetric magnetic field and also includes a hole (open end or closed end) that produces the zero field circle 12.

[0087] For example, Figure 6 A back-bias magnet 5 is shown which is an axially polarized cylinder and includes a bore 10 according to one or more embodiments. Figure 6 The in-plane magnetic field distribution in the sensor plane is also shown. The magnetic flux density is zero at the center of the plane and changes in the radial direction in the sensor plane so that it is also zero at the zero field circle 12. Therefore, due to the radially symmetric field distribution, all four sensor elements 20 are exposed to (due to the typical assembly tolerance of 3%) substantially the same or exactly the same magnetic field operating point.

[0088] Figure 7 A speed sensing system 400 including a sensor module 6 is shown according to one or more embodiments. In particular, a portion of a wheel 1 is shown with an air gap between the wheel 1 and the sensor module 6 and more particularly between the wheel 1 and the sensor arrangement 4. The sensor arrangement 4 is disposed on or coupled to a cylindrical back-bias magnet 5 such that a center point between the sensor elements 20 (e.g., the center of the circle 12) is aligned on a center axis 9 of the magnet 5. As described above, the sensor arrangement 4 (i.e., the sensor) includes a magnetic sensor element 20 and an IC for signal conditioning.

[0089] Figure 8A plan view of another sensor module according to one or more embodiments is shown, the other sensor module comprising a sensor arrangement arranged on a back bias magnet. In this case, three magnetic field sensor elements 20L, 20R and 20U are provided. The sensor elements 20 are arranged equidistant from each other on the circumference of the zero field circle 12. Therefore, the sensor elements 20 are spatially equally distributed about the center of the zero field circle 12, so that all sensor elements 20 are exposed to (due to a typical assembly tolerance of 3%) substantially the same or exactly the same magnetic field operating point.

[0090] As described above, every point on the zero field circle 12 experiences zero magnetic flux density. In the preferred case, all sensor elements 20 are exposed to a zero in-plane magnetic field Bxy, but may be exposed to a residual offset field if not accurately placed on the zero field circle 12. Since they are arranged on or substantially close to the zero field circle 12 generated by the aperture 10, all sensor elements always operate in a linear mode (i.e., a non-saturated mode) regardless of the overall magnetization strength of the magnet 5.

[0091] For each sensing element 20, the corresponding sensing axis is aligned in the radial or anti-radial direction of the in-plane field and is insensitive to other in-plane magnetic field components. The three sensing signals from the three sensing elements 20L, 20R and 20U can be combined by the sensing circuit 21 in any manner to generate an output signal.

[0092] From the three sensor elements 20, the sensor circuit 21 obtains three differential signals, including Δ1=BradialUP-BradialLEFT, Δ2=BradialLEFT-BradialRIGHT, Δ3=BradialRIGHT-BradialUP, where BradialUP is the sensor signal generated by the sensor element 20U, BradialLEFT is the sensor signal generated by the sensor element 20L, and BradialRIGHT is the sensor signal generated by the sensor element 20R. The three differential signals can then be added by the sensor circuit 21 to generate the sensor output signal SE OUT .

[0093] The sensor signal of each sensor element 20 is provided to the sensor circuit 21 which calculates three differential signals Δ1, Δ2 and Δ3 and / or output signals using differential calculation, and the out-of-plane magnetic field component does not affect the output signal (ie, sensor output).

[0094] Fig. 9A plan view of another sensor module according to one or more embodiments is shown, the sensor module including a sensor arrangement arranged above a reverse bias magnet. In this case, three magnetic field sensor elements 20L, 20R and 20C are provided. The sensor elements 20 are arranged linearly relative to each other, wherein two of the sensor elements 20L and 20R are arranged on the circumference of the zero field circle 12, equidistantly spaced from the central sensor element 20C. The central sensor element 20C is arranged on an extension of the central axis 9 of the hole 10, which also coincides with the center of the inner circumference 7, the center of the zero field circle 12 and the center of the outer circumference 8. In other words, each sensor element 20 is arranged at a position with a zero magnetic field offset, at which the magnetic flux density of the in-plane magnetic field generated by the magnet 5 is zero or substantially zero.

[0095] In this example, the sensor elements 20 are arranged linearly along the x-axis, and each sensor element has a sensing axis aligned with the x-direction to measure the magnetic field component Bx. Alternatively, the sensing axis can be aligned with the negative x-direction to measure the magnetic field component -Bx. Alternatively, the sensor elements 20 can be arranged linearly along the y-axis, and each sensor element has a sensing axis aligned with the positive direction of the y-axis or the negative direction of the y-axis. Alternatively, the sensor elements 20 can be arranged linearly along some other (i.e., arbitrary) in-plane axis, and their sensing axes point in the same direction. In each case, the central sensor element 20C is arranged on an extension of the central axis 9 (at the center of the zero field circle 12), and the other sensor elements are arranged equidistantly therefrom on the zero field circle 12.

[0096] The sensor signals generated from the two outer sensor elements 20 (i.e., sensor elements 20L and 20R) are received by the sensor circuit 21 and can thereby be used to generate a first differential measurement signal (e.g., Δ1=left-right, or in magnetic field representation, Δ1=BxLeft-BxRight). In addition, the sensor signal generated by the central sensor element 20C is received by the sensor circuit 21 and can thereby be used to generate a second differential measurement signal SE OUT The second measurement signal SE M (For example, SE OUT = center - (left + right) / 2). Signal Δ1 and SE OUT are 90° phase-shifted from each other and can be used to determine the speed and direction of rotation of a rotating target.

[0097] As described above, each point on the zero field circle 12 experiences zero in-plane magnetic flux density. In the preferred case, all sensor elements 20 are exposed to a zero in-plane magnetic field Bxy. Since they are arranged on or substantially close to the zero field circle 12 generated by the hole 10, all sensor elements always operate in a linear mode (i.e., a non-saturated mode) regardless of the overall magnetization intensity of the magnet 5. As described above, the transfer function of each sensor has a very high linear range (minimum of + / -25mT) and is within a wide range independent of the bias field. That is, each sensor element 20 is sensitive to a first in-plane magnetic field component (e.g., a Bx component or a By component), while it is independent of (or insensitive to) a different second in-plane magnetic field component (e.g., a Bx component or a By component).

[0098] In view of the above embodiments, at least two sensor elements 20 are provided in the sensor arrangement 4, wherein two or more sensor elements 20 are arranged on the zero field circle 12. In some cases, an additional sensor element 20C is arranged at the center point of the zero field circle 12 in the extension of the center axis 9 of the magnet 5. The central sensor element 20C may also be arranged at the center point of the zero field circle 12. Figure 5 and 8 The sensor arrangement shown is used in combination with . Alternatively, all sensor elements 20 of the sensor can be arranged on the zero field circle 12 .

[0099] Figures 10A-10D According to one or more embodiments, Figure 5 The sensor signal of the sensor element of the sensor is shown as a function of the rotation angle of the target wheel. Fig.10E According to one or more embodiments, Figure 5 The sensor circuit of the sensor shown outputs a sensor signal versus the rotation angle of the target wheel.

[0100] In other words, Fig. 10A The sensor signal shown represents the sensor signal SE according to different air gaps between the sensor arrangement 4 and the gear 1 A , Fig. 10B The sensor signal shown represents the sensor signal SE according to different air gaps between the sensor arrangement 4 and the gear 1 B , Fig. 10C The sensor signal shown represents the sensor signal SE according to different air gaps between the sensor arrangement 4 and the gear 1 C , Fig. 10D The sensor signal shown represents the sensor signal SE according to different air gaps between the sensor arrangement 4 and the gear 1 D , Fig.10E The output sensor signal shown represents the sensor output SE calculated according to equation (5) for different air gaps between the sensor arrangement 4 and the gear 1 OUTThe shape of the target wheel (teeth 2 and notches 3) is represented by a rectangular function in each figure.

[0101] also, Fig.10F According to one or more embodiments, Figure 5 Output sensor signal versus rotation angle of target wheel for different TIM angles of the sensor module are shown. Different twist angles (0°, 22.5° and 45°) of the sensor module 6 around its z-axis are superimposed for each air gap.

[0102] It can be seen that the distortion of the sensor module 6 about the z-axis has little effect on the output signal, and there is essentially no phase change caused by the TIM angle. In particular, the rotation of the target wheel modulates the magnetic field, and independent of the TIM angle of the sensor module 6, a clear signal change (modulation) as a function of the wheel rotation angle is generated by the sensor circuit 21. This phenomenon is due to Fig.10F Almost overlapping curves for different twist angles of each air gap are shown and observed.

[0103] Given that Figures 10A-10F , the output signal can be independent of the mounting angle (i.e., independent of the torsion angle about its z-axis). Due to the differential signal calculation that cancels out the uniform stray field in two in-plane directions (i.e., the x and y planes), the sensor arrangement 4 can be robust to stray fields, and the out-of-plane magnetic field components do not affect the output signal. The output signal of the sensor circuit 21 conforms to the output switching on the tooth edge. Therefore, there is no need to reconfigure the external control unit (e.g., ECU) during installation. In addition, a simple axially polarized cylindrical reverse bias magnet with a central hole or cavity is sufficient. Therefore, the described embodiment provides a torsion-insensitive sensing that is robust to stray fields of the wheel, and it comes with a low-cost magnetic reverse bias solution (e.g., a sintered ferrite cylindrical magnet). Alternatively, other types of magnets (e.g., rare earth magnets) may also be suitable as reverse bias magnets.

[0104] The low magnetic field offset that the sensor can see in the area of ​​the notch 3 of the gear 1 may also be useful for lifetime stability and true power-on characteristics. TPO indicates that the sensor circuit 21 is able to directly detect the correct position of the wheel 1 at start-up (e.g., it detects whether there is a tooth or notch in front of it). This is achieved via a threshold. If the sensed field exceeds the threshold, there is a tooth. If the sensed field is less than the threshold, there is a notch. If the magnet degrades during its service life (i.e., the magnet loses strength), the magnetic offset will still be zero or close to zero. Therefore, despite the degradation of the magnet, there is little impact on the performance of the sensor or its ability to detect a tooth or notch at start-up.

[0105] Fig.11A flow chart of a method 1100 for measuring the rotational speed of a rotating component by a magnetic sensor according to one or more embodiments is shown. As described above, the magnetic sensor includes a plurality of sensor elements arranged in a sensor plane of the magnetic sensor and exposed to substantially the same operating point of a radially symmetric bias magnetic field generated by an axially polarized reverse bias magnet having an aperture.

[0106] The method includes generating measurement values ​​by a plurality of sensor elements in response to sensing a radially symmetric bias magnetic field (operation 5). Changes in the measurement values ​​of the plurality of sensor elements are caused by rotation of the rotating member.

[0107] The method 1100 also includes generating a measurement signal using at least one differential calculation, the at least one differential calculation using the measurement value as an input to the differential calculation (operation 10). The differential calculation performed by the processor is configured to cancel stray fields along at least one sensitivity direction based on the measurement value. For example, the first pair of sensor elements is sensitive to a first in-plane magnetic field component of a radially symmetric bias magnetic field in the direction of a first sensitivity axis, and the second pair of sensor elements is sensitive to a second in-plane magnetic field component of a radially symmetric bias magnetic field in the direction of a second sensitivity axis. Therefore, the measurement signal oscillates between a maximum value and a minimum value based on the rotation speed of the rotating component.

[0108] Finally, method 1100 includes outputting the measurement signal to an external device (such as an ECU) for further processing (operation 15). The measurement signal may be output by transmission along a wired connection or a wireless connection.

[0109] In view of the above, assembly tolerances may be relaxed by implementing the above-described sensor module due to its distortion insensitivity and stray field robustness.

[0110] Although the above embodiments are described in the context of detecting wheel or camshaft speed, the sensor can be used to detect the rotational speed of any rotating member or object that produces sinusoidal changes in the magnetic field as it rotates and can be sensed by the sensor, including crankshaft and transmission speed sensing. For example, a combination of an iron wheel and a back-biased magnet can be used to generate a time-varying magnetic field.

[0111] In addition, although various embodiments have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the present invention. Accordingly, the present invention is not limited by the appended claims and their equivalents. With respect to the various functions performed by the above-described components or structures (components, devices, circuits, systems, etc.), the terms used to describe such components (including references to "devices") are intended to correspond (unless otherwise indicated) to any component or structure that performs the specified function of the described component (i.e., functionally equivalent), even if structurally not equivalent to the disclosed structure for performing the functions in the exemplary implementations of the invention shown herein.

[0112] Furthermore, the following claims are hereby incorporated into the detailed description, where each claim can stand on its own as a separate example embodiment. Although each claim can stand on its own as a separate example embodiment, it should be noted that although a dependent claim may refer to a specific combination with one or more other claims in a claim, other example embodiments may also include combinations of dependent claims with each other's dependent claims or the subject matter of independent claims. Unless it is stated that a specific combination is not intended, such a combination is suggested here. In addition, it is also intended to include features of one claim to any other independent claim, even if the claim is not directly dependent on the independent claim.

[0113] It should also be noted that the methods disclosed in the specification or claims may be implemented by a device having means for performing each of the corresponding acts of these methods.

[0114] In addition, it should be understood that the disclosure of multiple actions or functions disclosed in the specification or claims may not be interpreted as being in a specific order. Therefore, unless these actions or functions are not interchangeable due to technical reasons, the disclosure of multiple actions or functions does not limit these to a specific order. In addition, in some embodiments, a single action may include or may be decomposed into multiple sub-actions. Unless explicitly excluded, such sub-actions may be included and are part of the disclosure of the single action.

Claims

1. A magnetic sensor module configured to detect rotation of an object, comprising: an axially polarized back bias magnet comprising a magnet body extending in a radial direction from an inner side wall to an outer side wall and a hole defining the inner side wall, wherein the axially polarized back bias magnet generates a radially symmetric bias in-plane magnetic field about an extension of a central axis of the axially polarized back bias magnet in a sensor plane orthogonal to the extension of the central axis of the axially polarized back bias magnet, wherein the hole is centered on the central axis and extends along the central axis in an axial direction of the axially polarized back bias magnet, wherein the radially symmetric bias in-plane magnetic field has a substantially zero magnetic flux density along the extension of the central axis at a circumference of a zero field circle located in the sensor plane, wherein the circumference of the zero field circle is concentric with the extension of the central axis in a plan view and vertically overlaps the magnet body; and A magnetic sensor comprising at least three sensor elements, the at least three sensor elements being arranged in the sensor plane of the magnetic sensor at positions where the magnetic field in the radially symmetric bias plane has a substantially zero magnetic flux density, wherein the at least three sensor elements are configured to generate a measurement value in response to sensing the magnetic field in the radially symmetric bias plane, Wherein at least two of the at least three sensor elements are arranged on the circumference of the zero field circle at substantially equidistant angles with respect to the central axis of the axially polarized back bias magnet. 2 . The magnetic sensor module according to claim 1 , wherein one sensor element of the at least three sensor elements is arranged on the extension of the central axis. 3 . The magnetic sensor module according to claim 2 , wherein three of the at least three sensor elements are linearly arranged along an in-plane axis of the sensor plane, wherein the in-plane axis is orthogonal to the central axis. The magnetic sensor module of claim 3 , wherein the three sensor elements each have a sensitivity axis aligned with the in-plane axis. The magnetic sensor module of claim 1 , wherein the magnetic flux density being substantially zero means being less than 15 millitesla (mT). 6 . The magnetic sensor module according to claim 1 , wherein the at least three sensor elements are arranged in the sensor plane of the magnetic sensor at positions where a magnetic field has zero magnetic flux density within the radially symmetric bias plane. 7 . The magnetic sensor module of claim 1 , wherein the circumference of the zero field circle is defined as a region in the sensor plane where the magnetic flux density of the radially symmetric bias in-plane magnetic field is less than 15 millitesla (mT). 8 . The magnetic sensor module of claim 1 , wherein the circumference of the zero field circle is defined as a region in the sensor plane where the magnetic flux density of the radially symmetric bias-plane in-plane magnetic field is zero.

9. The magnetic sensor module of claim 1, wherein all of the at least three sensor elements are arranged on the circumference of the zero field circle at substantially equidistant angles with respect to the central axis of the axially polarized back bias magnet. 10 . The magnetic sensor module of claim 1 , wherein each of the at least three sensor elements has a respective sensitivity axis aligned in a different in-plane radial direction.

11. The magnetic sensor module according to claim 1, wherein: The at least three sensor elements include a plurality of pairs of sensor elements, a first sensor element of the first pair of sensor elements arranged opposite each other on the circumference of the zero field circle and having a first sensitivity axis sensitive to a first in-plane magnetic field component of the radially symmetric bias in-plane magnetic field, and The second sensor elements of the second pair of sensor elements are arranged opposite to each other on the circumference of the zero field circle and have a second sensitivity axis that is sensitive to a second in-plane magnetic field component of the radially symmetric bias in-plane magnetic field. 12 . The magnetic sensor module of claim 11 , wherein the first sensitivity axis is perpendicular to the second sensitivity axis. 13 . The magnetic sensor module of claim 11 , wherein the first sensitivity axis and the second sensitivity axis intersect and are perpendicular to the extension of the central axis of the axially polarized back-bias magnet. 14 . The magnetic sensor module of claim 11 , wherein each of the at least three sensor elements is exposed to substantially the same operating point of the magnetic field within the radially symmetric bias plane.

15. The magnetic sensor module according to claim 11, wherein: the measurement value generated by the first sensor element changes upon detecting a change in the magnetic field strength of the magnetic field within the radially symmetric bias plane in a first direction of the first sensitivity axis, and The measurement value generated by the second sensor element changes upon detecting a change in the magnetic field strength of the magnetic field within the radially symmetric bias plane in a second direction of the second sensitivity axis.

16. The magnetic sensor module according to claim 11, wherein: The axially polarized back bias magnet is configured such that the first in-plane magnetic field component and the second in-plane magnetic field component vary according to rotation of a rotating member having alternating first and second portions, and The first in-plane magnetic field component and the second in-plane magnetic field component are stronger when close to a first one of the first parts, and are weaker when close to a second one of the second parts. 17 . The magnetic sensor module of claim 16 , wherein the rotating member is a gear, and the first portion is a notch of the gear and the second portion is a tooth of the gear.

18. The magnetic sensor module of claim 1 , wherein the radially symmetric bias-plane in-field magnetic field is zero at the central axis and the extension of the central axis, the radially symmetric bias-plane in-field magnetic field increases from the central axis to a first radial distance in the radial direction in the sensor plane, the radially symmetric bias-plane in-field magnetic field decreases from the first radial distance to a second radial distance defining a radius of the zero-field circle in the radial direction in the sensor plane, and the radially symmetric bias-plane in-field magnetic field increases from the second radial distance to a third radial distance defining the outer side wall in the radial direction in the sensor plane. The magnetic sensor module of claim 18 , wherein the second radial distance is between the inner sidewall and the outer sidewall.

20. The magnetic sensor module according to claim 1, wherein The axially polarized back bias magnet comprises a first end and a second end disposed opposite the first end in the axial direction, and The bore extends from the first end to the second end.

21. The magnetic sensor module according to claim 1, wherein The axially polarized back bias magnet comprises a first end and a second end disposed opposite the first end in the axial direction, and The aperture extends partially from the first end toward the second end.

22. The magnetic sensor module according to claim 1, wherein: The axially polarized back bias magnet includes a first closed end and a second closed end disposed opposite the first closed end in the axial direction, and Wherein the aperture extends partially between the first closed end and the second closed end.

23. The magnetic sensor module of claim 1 , wherein the magnetic sensor further comprises a sensor circuit configured to receive the measurement values ​​from the at least three sensor elements and to generate a measurement signal using at least one differential calculation configured to cancel stray fields present along at least one sensitivity axis of the magnetic sensor based on the received measurement values.

24. The magnetic sensor module of claim 1, wherein the magnetic sensor module is torsionally insensitive about the central axis of the axially polarized back-bias magnet.

25. A magnetic sensor module configured to detect rotation of an object, comprising: an axially polarized back bias magnet comprising a magnet body extending in a radial direction from an inner side wall to an outer side wall and a hole defining the inner side wall, wherein the axially polarized back bias magnet generates a radially symmetric bias in-plane magnetic field about an extension of a central axis of the axially polarized back bias magnet in a sensor plane orthogonal to the extension of the central axis of the axially polarized back bias magnet, wherein the hole is centered on the central axis and extends along the central axis in an axial direction of the axially polarized back bias magnet, wherein the radially symmetric bias in-plane magnetic field has a zero magnetic flux density along the extension of the central axis at a circumference of a zero field circle located in the sensor plane, wherein the circumference of the zero field circle is concentric with the extension of the central axis in a plan view and vertically overlaps the magnet body; and A magnetic sensor comprising at least two sensor elements arranged in the sensor plane of the magnetic sensor and further arranged on the circumference of the zero field circle at substantially equidistant angles with respect to the central axis of the axially polarized back bias magnet.

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