Magnetic Field Differential Linear Torque Sensor

Abstract

The differential magnetic field torque sensor includes first and second magnetic field concentrators that direct magnetic flux from the first and second magnetic field directors to the magnetic field sensor, and a target such as a multi-pole magnet assembly configured as a ring magnet. The magnetic field concentrators have a pair of sections that are interdigitated and configured adjacent to the magnetic field sensing elements of the magnetic field sensor. The magnetic field directors can each have a number of teeth that can be interdigitated and adjacent or proximate to the target. The magnetic field directors can be configured to be mounted on a rotatable shaft together, while the target can be configured to be mounted on a different rotatable shaft. The magnetic field concentrators and the magnetic field sensor can be fixed, while the magnetic field directors and the target can rotate relative to each other about a torsion axis.

Description

[Background technology]

[0001]

[0001] Magnetic field sensors can be used in a variety of applications. In one application, magnetic field sensors can be used to detect the rotation angle of an object. In another application, magnetic field sensors can be used to sense the rotation (e.g., continuous or non-continuous rotation) of an object.

[0002]

[0002] Various magnetic field sensing elements may be used in magnetic field sensors. For example, planar Hall effect elements and vertical Hall effect elements are known types of magnetic field sensing elements. Planar Hall effect elements tend to be responsive to magnetic fields that are perpendicular to the surface of the substrate on which the planar Hall effect elements are formed. Vertical Hall effect elements tend to be responsive to magnetic fields that are parallel to the surface of the substrate on which the vertical Hall effect elements are formed. Magnetoresistance elements are also known types of magnetic field sensing elements used for magnetic field sensors. Some types of magnetoresistance elements tend to be responsive to magnetic fields that are parallel to the surface of the substrate on which the magnetoresistance elements are formed.

[0003]

[0003] Various parameters characterize the performance of magnetic field sensing elements and magnetic field sensors that use magnetic field sensing elements. These parameters include sensitivity, which is the change in the output signal of the magnetic field sensing element in response to a change in the magnetic field experienced by the magnetic field sensing element, and linearity, which is the degree to which the output signal of the magnetic field sensing element varies in direct proportion to the magnetic field. These parameters also include offset, which is characterized by an output signal from the magnetic field sensing element that is not representative of a zero magnetic field when the magnetic field sensing element is subjected to a zero magnetic field.

[0004]

[0004] Stray magnetic fields caused by magnetic components or other sources such as electric currents can interfere with the performance of magnetic field sensors and sensing elements. Such stray magnetic fields can pose serious problems in applications such as automobiles where electric motors, batteries, and other electromagnetic components are used. For example, electric motors that drive electric vehicles ("EVs") and hybrid electric vehicles ("HEVs") typically require significant amounts of current and therefore create strong magnetic fields around the cables that deliver current from the battery or alternator to the motor. Other common low current components can also generate significant stray magnetic fields in automotive applications such as electric power steering ("EPS") pumps, power windows or sunroofs, and any other electrically operated devices used in vehicles. Systems and signal processing that rely on such sensors can be adversely affected by stray magnetic fields as well, as stray magnetic fields can affect the accuracy of magnetic field sensors and cause significant output errors in such sensors. Summary of the Invention [Problem to be solved by the invention]

[0005]

[0005] Embodiments of the present disclosure provide systems, methods, and apparatus for differential angle and / or torque sensing with sensors that tend to eliminate and / or are resistant to stray magnetic fields. [Means for solving the problem]

[0006] An example differential magnetic field torque sensor may include a multi-pole magnet assembly configured for coupling to a first rotatable shaft. The sensor may include first and second magnetic field directors positioned adjacent the multi-pole magnet assembly and configured to affect magnetic flux from the multi-pole magnet assembly. The first and second magnetic field directors may be configured for coupling together to a second rotatable shaft. The first and second magnetic field concentrators are configured to concentrate magnetic flux from the multi-pole magnet assembly. Each magnetic field concentrator may have first and second sections offset from one another. The magnetic field sensor includes first and second magnetic field sensing elements each configured to measure magnetic flux and to generate an output signal based on a change in the measured magnetic flux due to relative angular motion between the multi-pole magnet assembly and the first and second magnetic field directors. The output signal may be indicative of a torque applied to the first or second rotatable shaft. Each section of each concentrator may be interdigitated with a section of the other concentrator to form two interdigitated section pairs. Each pair of interdigitated sections may be configured to receive a respective magnetic field sensing element. Either or both of the pairs of interdigitated sections may include a shield configured to shield the respective magnetic sensing element from stray magnetic fields.

[0007]

[0007] The first shaft may be coupled to the second shaft by a resilient member. The resilient member may include a torsion bar. The multi-pole magnet assembly may be configured as a ring magnet and may include a plurality of magnetic domains arranged in a cylindrical configuration, each of the plurality of magnetic domains having an opposite polarity relative to adjacent magnetic domains. The first and second magnetic field directors may each include a plurality of teeth. The multi-pole magnet assembly may be configured as a toroidal body. The first and second magnetic field directors may each be disposed about the periphery of the toroidal body. The teeth of the first magnetic field director may be spaced apart from and interdigitated with the teeth of the second magnetic field director. The magnetic sensor may be coupled to a housing that is stationary relative to the first and second rotatable shafts. The first and second magnetic field concentrators may be coupled to the housing.

[0008]

[0008] The sensor further comprises a summer configured to receive an output signal from each magnetic field sensing element and to subtract one magnetic field element output signal from the other, the summer configured to generate an output signal indicative of an angular displacement of the multi-pole magnet assembly relative to the first and second magnetic field directors, such that the effect of stray magnetic fields on the first and second magnetic field sensing elements is mitigated. The first and second rotatable shafts may include, be part of, or constitute a steering column. The magnetic field sensing elements may include Hall effect elements. The magnetic field sensing elements may include magnetoresistance elements.

[0009]

[0009] An exemplary embodiment of a differential magnetic field sensor may include a target configured for coupling to a first rotatable shaft, and first and second magnetic field directors positioned adjacent to the target and configured to affect magnetic flux from the target. The first and second magnetic field directors may be configured for coupling together to a second rotatable shaft. The sensor may include first and second magnetic field concentrators that may be configured to concentrate magnetic flux from the target. Each magnetic concentrator may have first and second sections offset from one another. The sensor may include a magnetic field sensor having first and second magnetic field sensing elements. Each magnetic field sensing element may be configured to measure magnetic flux and generate an output signal indicative of a change in the measured magnetic flux due to relative angular motion between the target and the first and second magnetic field directors. Each section of each concentrator may be interdigitated with a section of the other concentrator to form two interdigitated section pairs. Each interdigitated section pair may be configured to receive a respective magnetic field sensing element. Either or both of the interdigitated region pairs may include a shield configured to shield the respective magnetic sensing element from stray magnetic fields.

[0010] The target may include a multi-pole magnet assembly having a plurality of magnetic pole pairs. The multi-pole magnet assembly may include a plurality of magnetic domains arranged in a cylindrical configuration, each of the plurality of magnetic domains having an opposite polarity relative to adjacent magnetic domains. The multi-pole magnet assembly may include or be configured as a ring magnet. The sensor may include a summer configured to receive the output signal from each magnetic field element and to subtract one magnetic field element output signal from the other. The summer may be configured to generate an output signal indicative of motion of the target relative to the first and second magnetic field directors such that the effect of stray magnetic fields on the first and second magnetic field sensing elements is mitigated. The summer output signal may be indicative of a linear response to angular displacement of the multi-pole magnet assembly relative to the first and second magnetic field directors.

[0011] The multi-pole magnet assembly may be coupled to a first rotatable shaft, and the first and second magnetic field directors may be integrally coupled to a second rotatable shaft. The first rotatable shaft may be coupled to the second rotatable shaft by a torsion bar. The differential magnetic field sensor may be configured to measure torque applied to the first or second rotatable shaft. The first and second rotatable shafts may include, be part of, or constitute a steering column. The first and second magnetic field directors may each include a plurality of teeth. The multi-pole magnet assembly may be configured as a toroidal body. The first and second magnetic field directors may each be disposed about the periphery of the toroidal body. The teeth of the first magnetic field director may be spaced apart from and interdigitated with the teeth of the second magnetic field director. The first and second magnetic field sensors may be coupled to a housing that is stationary relative to the first and second rotatable shafts. The first and second magnetic field concentrators may be coupled to the housing. The magnetic field sensing element may be a Hall effect element.The magnetic field sensing element may include a magnetoresistive element.

[0012]

[0012] The features and advantages described herein are not all-inclusive, and many additional features and advantages will be apparent to those skilled in the art in view of the drawings, specification, and claims. Moreover, the language used within this specification has been selected primarily for ease of reading and guidance purposes, and does not in any way limit the scope of the present disclosure, which is open to many embodiments. The following is illustrative of the scope of the present disclosure, but is not exhaustive.

[0013]

[0013] The manner and process of making and using the disclosed embodiments may be understood by reference to the figures in the accompanying drawings. It should be understood that the components and structures illustrated in the figures are not necessarily to scale, emphasis instead being placed on illustrating the principles of the concepts described herein. Like reference numbers indicate corresponding parts throughout the different views. Moreover, the embodiments are illustrated in the figures by way of example and not by way of limitation. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 illustrates an example magnetic field differential torque sensor according to the present disclosure. [Figure 2A]

[0015] FIG. 2 is an enlarged view of a portion of the differential magnetic field torque sensor of FIG. [Figure 2B]

[0016] FIG. 2 is an enlarged view of the interdigitated area of ​​the magnetic field concentrator and the differential magnetic field torque sensor of FIG. 1. [Figure 2C]

[0017] 2 is a close-up view of an alternative embodiment of the magnetic field concentrator and interdigitated area of ​​the differential magnetic field torque sensor of FIG. 1, including shielding against stray magnetic fields. [Diagram 3]

[0018] 1 illustrates an exemplary embodiment of a magnetic field differential torque sensor in a side shaft configuration according to the present disclosure. [Figure 4]

[0019] FIG. 1 is a circuit diagram of an exemplary magnetic field differential linear torque sensor according to the present disclosure. [Diagram 5]

[0020] FIG. 1 is a block diagram of an example computer system operable to perform processing in accordance with the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015]

[0021] Before describing the exemplary embodiments of the present disclosure, some information is provided. As used herein, the term "magnetic field sensing element" refers to various electronic elements that can sense a magnetic field. The magnetic field sensing element may be, but is not limited to, a Hall effect element, a magnetoresistance element, or a magnetotransistor. As is known, there are different types of Hall effect elements, for example, planar Hall effect elements, and vertical Hall effect elements. As is further known, there are different types of magnetoresistance elements, for example, semiconductor magnetoresistance elements such as indium antimonide (InSb), giant magnetoresistance (GMR) elements, for example, spin valves, anisotropic magnetoresistance elements (AMR), tunnel magnetoresistance (TMR) elements, and magnetic tunnel junctions (MTJs). The magnetic field sensing element may be a single element, or alternatively, may include two or more magnetic field sensing elements arranged in various configurations, for example, a half bridge or a full (e.g., Wheatstone) bridge. Depending on the type of device and other application requirements, the magnetic field sensing element may be a device made of Group IV semiconductor materials such as silicon (Si) or germanium (Ge), or Group III-V semiconductor materials such as gallium arsenide (GaAs) or indium compounds, e.g., indium antimonide (InSb).

[0016]

[0022] As is known, some of the above-mentioned magnetic field sensing elements tend to have a maximum sensitivity axis parallel to the substrate supporting the magnetic field sensing element, while other of the above-mentioned magnetic field sensing elements tend to have a maximum sensitivity axis perpendicular to the substrate supporting the magnetic field sensing element. In particular, planar Hall effect elements tend to have a sensitivity axis perpendicular to the substrate, while metal-based or metallic magnetoresistance elements (e.g., GMR, TMR, AMR) and vertical Hall effect elements tend to have a sensitivity axis parallel to the substrate.

[0017]

[0023] As used herein, the term "magnetic field sensor" refers to an assembly that uses one or more magnetic field sensing elements in combination with electronic circuitry, typically all disposed on a common substrate, e.g., a semiconductor substrate. Magnetic field sensors are used in a variety of applications, including, but not limited to, angle sensors that sense the angle of a magnetic field direction, angle sensors that sense the angle of rotation of a target object, and rotation sensors that sense the rotation (e.g., speed and direction of rotation) of a rotating target object.

[0018]

[0024] Described herein is a magnetic field sensor in the form of an angle and / or rotation sensor capable of sensing the angle of rotation of a ferromagnetic object. As used herein, the term "magnetic field signal" is used to describe any circuit signal resulting from a magnetic field experienced by or sensed by a magnetic field sensing element.

[0019]

[0025] The terms "parallel" and "perpendicular" are used in various contexts within this specification. It should be understood that the terms parallel and perpendicular do not require exact perpendicularity or exact parallelism, but rather, normal manufacturing tolerances are intended to apply, which tolerances will depend on the context in which the terms are used. In some cases, the term "substantially" is used to modify the terms "parallel" or "perpendicular." In general, use of the term "substantially" reflects angles that are beyond manufacturing tolerances, for example, within + / - 10 degrees (plus or minus 10 degrees).

[0020]

[0026] As used herein, the term "processor" or "processing device" refers to an electronic circuit that performs a function, operation, or sequence of operations. The function, operation, or sequence of operations may be hard-coded into the electronic circuit or soft-coded with instructions held in a memory device. A "processor" or "processing device" may perform a function, operation, or sequence of operations using digital values ​​or using analog signals.

[0021]

[0027] In some embodiments, the "processor" or "processing unit" may be embodied in an application specific integrated circuit (ASIC), which may be an analog ASIC or a digital ASIC. In some embodiments, the "processor" or "processing unit" may be embodied in a microprocessor with associated program memory. In some embodiments, the "processor" or "processing unit" may be embodied in discrete electronic circuitry, which may be analog or digital.

[0022]

[0028] As used herein, the term "module" may describe a "processor." However, the term "module" may be used more generally to describe any circuit that can transform an input signal into an output signal that differs from the input signal.

[0023]

[0029] A processor may include an internal processor or internal module that performs a portion of a processor's function, operation, or sequence of operations. Similarly, a module may include an internal processor or internal module that performs a portion of a module's function, operation, or sequence of operations.

[0024]

[0030] Although the electronic circuits shown in the figures herein may be shown in the form of analog or digital blocks (e.g., processors or modules), it should be understood that the analog blocks may be replaced by digital blocks (e.g., processors or modules) performing the same or similar functions, and the digital blocks may be replaced by analog blocks performing the same or similar functions. Analog-to-digital or digital-to-analog conversion may not be explicitly shown in the figures, but should be understood to be present.

[0025]

[0031] In particular, it is understood that the so-called comparator may consist of an analog comparator having a two-state output signal indicating that an input signal is above or below a threshold level (or that one input signal is above or below another input signal). However, the comparator may also comprise, or alternatively consist of, a digital circuit (e.g., a processor or module) having an output signal or value with at least two states indicating that an input signal or value is above or below a threshold level (or that one input signal or value is above or below another input signal or value), respectively, or that a digital signal or value is above or below a digital threshold signal or value (or another digital signal or value), respectively.

[0026]

[0032] As used herein, the term "predetermined" when referring to a value or signal refers to a value or signal that is set or fixed in the factory at the time of manufacture or thereafter by external means, e.g., programming. As used herein, the term "determined" when referring to a value or signal refers to a value or signal that is recognized by the circuit after manufacture and during operation.

[0027]

[0033] As used herein, the term "amplifier" refers to a circuit element that has a gain greater than, less than, or equal to unity.

[0028]

[0034] As used herein, the terms "line" and "linear" are used to describe either a straight line or a curved line. A line may be described by a function having any degree, but is never infinite.

[0029]

[0035] FIG. 1 is a diagram of an example differential magnetic field torque sensor 100 configured to reject stray magnetic fields, according to an embodiment of the present disclosure. The sensor 100 includes first and second magnetic field concentrators 102, 104, one or more magnetic field sensors 106, first and second magnetic field directors 112, 116, and a target 120. The magnetic field sensor 106 may include or consist of a set or array of magnetic field sensing elements 106(1)-(2) positioned to detect magnetic field changes in a desired manner. In an exemplary embodiment, the target 120 may be a multi-pole magnet assembly having a plurality of magnetic domains 122(1)-(N), configured as a ring magnet with alternating magnetic field orientation, for example, as shown. The magnetic field directors 112, 116 may each have a plurality of teeth 114(1)-(N) and 118(1)-(N), respectively. The plurality of teeth 114(1)-(N) and 118(1)-(N) may be spaced apart and interdigitated in a circular configuration adjacent to the target 120. The magnetic field directors 112, 116 may be configured to be mounted together on a rotatable shaft (not shown), while the target 120 may be configured to be mounted on a different rotatable shaft (not shown). The magnetic field concentrators 102, 104 and the magnetic field sensor 106 may be fixed, for example, mounted or attached to a printed circuit board (PCB). The magnetic field directors 112, 116 and the target 120 may rotate relative to one another about a torsional axis shown as the Z-axis 124.

[0030]

[0036] The magnetic field concentrators 102, 104 have first and second sections (102a-b, 104a-b) that are offset from one another, e.g., such that they lie in parallel planes. Each section (e.g., 102a) of each concentrator 102, 104 is interdigitated with a section (e.g., 104a) of the other concentrator to form two interdigitated section pairs 105a-b (i.e., 102a-104a and 102b-104b). Each of the interdigitated section pairs 105a-b receives a magnetic sensing element 106(1)-106(2), respectively, and thus defines sections d, e.g., d, i.e., d, i, 1 , d 2 Each interdigitated section pair 105a-b may have a different configuration or orientation, as shown. For example, in interdigitated section pair 105a, section 102a from magnetic field concentrator 102 may be at a first location, e.g., along Z-axis 124, and section 104a from magnetic field concentrator 104 may be at a second location, e.g., along Z-axis 124. In contrast, in second interdigitated section pair 105b, the order of the sections may be swapped, such that section 102b from concentrator 102 is at a second location along Z-axis, while section 104b from concentrator 104 is at a first location along Z-axis, as shown. The swapping of section locations (i.e., the order of interdigitation) between interdigitated section pairs 105a-b may result in an increase in the number of air gaps d. 1 , d 2 The interdigitated configuration of the magnetic field concentrators 102, 104 reverses the magnetic field in the interdigitated region pair 105a and 105b. 1 , d 2 120 and the magnetic field directors 112, 116. Subtracting the signals generated by the magnetic sensing elements 106(1)-(2) provides a linear response to the angle (of twist) between the target 120 and the magnetic field directors 112, 116 while tending to reject the adverse effects of stray magnetic fields.

[0031]

[0037] In operation of the sensor 100, the magnetic field directors 112, 116 are rotated (together) about the torsion axis 124 relative to the target 120 due to, for example, torque applied to a shaft on which the magnetic field directors 112, 116 or the target 120 are mounted, respectively. As the magnetic field directors 112, 116 move relative to the target 120, magnetic flux variations are generated in adjacent teeth 114, 118 of the magnetic field directors 112, 116. The magnetic field directors 112, 116 affect (e.g., guide or direct) the magnetic flux from the target 120 while the target 120 and the magnetic field directors 112, 116 move relative to one another. The magnetic field concentrators 102, 104 collect and / or concentrate the magnetic flux from the magnetic field directors 112, 116 and provide the magnetic flux to the magnetic field sensor 106, completing the magnetic loop (magnetic circuit). The magnetic loop (formed by the target 120, the magnetic field directors 112, 116, the magnetic field concentrators 102, 104, and the magnetic field sensor 106) results in a linear magnetic field response at the magnetic sensing elements 106(1)-(2) to the angular difference between the target 120 and the magnetic field directors 112, 116. The linear magnetic field response can be detected by the magnetic field sensor 106, and the angle between the shafts can be calculated by a processor (not shown), for example, for determination of applied torque, as shown in more detail below.

[0032]

[0038] In an exemplary embodiment, the magnetic field directors 112, 116 and / or the target 120 may rotate more than 360 degrees, such as the range of rotation typical of a steering column with the rotation of a steering wheel in an automotive application. In an exemplary embodiment, the magnetic field sensor 106 may include two or more Hall effect elements configured such that the difference in the signals from the Hall effect elements may be used as a differential signal with stray magnetic field effects reduced and / or eliminated by differential processing. In some embodiments, the magnetic field sensor 106 may include two or more magnetic field sensors, each with two or more magnetic field sensing elements. In some embodiments, the magnetic field sensor 106 may include a magnetoresistive sensor. Although the target 120 is shown as having a plurality of magnetic domains 122(1)-(N), each having an opposite polarity to its neighbors, in some embodiments, the target 120 may include a plurality of magnetic domains separated by regions with no magnetic polarity, e.g., magnets spaced around a ferromagnetic yoke.

[0033]

[0039] Although the set of magnetic field concentrators 102, 104 is shown as providing a pair of interdigitated sections 105a-b for use with a single magnetic field sensor 106, it should be understood that in other embodiments, the concentrators 102, 104 may be configured with additional similar or replicated structures (e.g., 105a-b) each for use with a respective additional magnetic field sensor 106. Such additional structures may be used, for example, to provide redundancy. In an exemplary embodiment, the sensor 100 may be utilized as a torque measurement sensor for an electric power steering (APAS) system for automotive applications.

[0034]

[0040] 2A shows an enlarged view of a portion of the differential magnetic field sensor 100 of FIG. The magnetic field directors 112, 116 are shown configured for rotation relative to a target 120 configured as a ring magnet. The magnetic field directors 112, 116 include a plurality of teeth 114(1)-(N), 118(1)-(N), respectively, that are interdigitated (or meshed) in a circular arrangement about a radial surface of the target 120. The target 120 may include a plurality of magnetic domains 122(1)-(N) (NS orientation) arranged in a cylindrical configuration (shown with or without shading), each of the magnetic domains having an opposite polarity relative to an adjacent magnetic domain. The magnetic field directors 112, 116 are configured for coupling to a shaft or other element (not shown) that is rotatable together about a torsional axis, e.g., parallel to a Z-axis 124. Target 120 is configured for coupling to a different shaft or other element (not shown) that is rotatable about a torsion axis, e.g., parallel to Z-axis 124. Side portions of magnetic field concentrators 102, 104 (shown in FIG. 1 extending adjacent to portions of magnetic field directors 112, 116) are omitted for clarity and illustration.

[0035]

[0041] In some embodiments, for example, it may be desirable to minimize or prevent, to the extent possible, magnetic flux from flowing from one interdigitated pair of regions, e.g., 105a, to the other interdigitated pair of regions. Thus, the interdigitated pair of regions 105a-b may be spaced apart in a direction perpendicular to the Z-axis 124, as noted by the gap g, and / or the spacing between the regions of the interdigitated pair of regions 105a-b (e.g., d in FIG. 1 ). 1 and d 2) may be relatively small. Furthermore, magnetic field concentrators 102, 104 may be relatively thin to encourage magnetic flux to flow from one section, e.g., 102a, of an interdigitated section pair, e.g., 105a, to the other section, e.g., 104a, through an associated magnetic field sensing element, e.g., 106(1). In some embodiments, portions of magnetic field concentrators 102, 104 that are not included within interdigitated section pair 105a-b, e.g., portions that are not adjacent to magnetic field sensing elements 106(1)-(2) and do not overlap in the direction of Z-axis 124, may be spaced further apart (than for interdigitated section pair 105a-b) to reduce undesired magnetic flux flow outside interdigitated section pair 105a-b and / or to increase desirable magnetic flux flow through magnetic field sensing elements 106(1)-(2).

[0036]

[0042] FIG. 2B shows an expanded view of magnetic field concentrators 102, 104 and interdigitated section pair 105a-b as well as magnetic field sensor 106 of FIG. 1. As with FIG. 2A, side portions of magnetic field concentrators 102, 104 have been removed for clarity and illustration. Magnetic field sensor 106 includes magnetic field sensing elements 106(1)-106(2) disposed between or received by interdigitated section pair 105a-b, respectively. Magnetic field sensing element 106(1) senses the air gap (d 1 ) between the interdigitated areas 102b and 104b, while the magnetic field sensing element 106(2) is shown disposed within the air gap (denoted by d 2 In the exemplary embodiment, the gap d 1 and d 2 are the same or substantially the same. As noted above, the magnetic field sensor 106 may be mounted on a PCB (not shown). It should be understood that the interdigitated area pairs 105a-b and the magnetic field sensor 106 may be arranged in different configurations as desired depending on the particular application. In one example, the interdigitated area pairs may be rotated, for example, by 90 degrees from the configuration shown. In another example, the interdigitated area pairs 105a-b may be offset radially (instead of along the Z axis) to receive the magnetic field sensor 106 in a configuration that is generally parallel to the plane of the drawing.

[0037]

[0043] 2C shows a close-up view of an alternative embodiment of the magnetic field concentrators 102, 104 and the interdigitated areas 102a-104a, 102b-104 of the differential magnetic field torque sensor 100 of FIG. 1, including shielding against stray magnetic fields. As shown, in the example embodiment, the shields (shielding elements) 130a-b provide shielding against stray magnetic fields (B SF ) can be used to provide further mitigation or prevention of adverse effects caused by such stray magnetic fields (B SF ) may be generated, for example, by a conductive element close to the magnetic field sensing elements 106(1)-(2) of the differential magnetic field torque sensor 100. A representative conductive element (wire) 140 conducts a current (i) and generates a stray magnetic field (B SF ) to the sensor 100. The shields 130a-b are shown to generate a magnetic field that is presented to the sensor 100 as SF ) may be formed or positioned on the magnetic field concentrators 102, 104 to prevent or minimize magnetic field interference (MAI) from passing through the magnetic field sensing elements 106(1)-(2).

[0038]

[0044] In an example embodiment, a shield, e.g., 130a, may be used with the interdigitated section 104a of one interdigitated section pair 105a to sandwich the other interdigitated section 102a and corresponding magnetic field sensing element 106(1). When used for an interdigitated section pair, each shield may accordingly shield the respective magnetic sensing element from stray magnetic fields. For example, shield 130a is shown connected to magnetic field concentrator 104 at interdigitated section 104a, while shield 130b is shown connected to magnetic field concentrator 102 at interdigitated section 102b. In the illustrated embodiment, interdigitated section 102a and shield 130a are not in contact at planar section 150, although the perspective of the drawing may obscure that feature. By providing a conductive path on each of magnetic field concentrators 102, 104, shields 130a-b may shield the respective magnetic field concentrators 102, 104 from stray magnetic fields (B SF ) may be conducted around the magnetic field sensing elements 106(1)-(2) as opposed to through them.

[0039]

[0045] To facilitate sensing of magnetic flux from the target 120, the shields, e.g., 130a, may be configured to have a distance (d) from the shield 130a (as used with or mounted to one interdigitated section 104a) to the other interdigitated section 102a of the associated interdigitated section pair 105a. 3 , d 4 ) is the distance (d 1 , d 2 ) relative to the magnetic field concentrators 102, 104 and the shields 130a-b. Thus, the magnetic flux from the target 120 may be provided with a higher reluctance along the path between the magnetic field concentrators 102, 104 and the shields 130a-b than along the intended path between the interdigitated sections of the interdigitated section pairs 105a-b and through the magnetic field sensing elements 106(1)-(2). Of course, the shields 130a-b may have alternative configurations and / or shapes in other embodiments of the present disclosure, e.g., the shield 130a may be connected to the interdigitated section 102a while the shield 130b may be connected to the interdigitated section 104b, etc.

[0040]

[0046] Figure 3 shows an example differential magnetic field torque sensor 300 in a side-shaft configuration, according to an exemplary embodiment of the present disclosure. The sensor 300 is generally similar to the sensor 100 of Figure 1 and is mounted adjacent to a shaft assembly that includes two (first and second) rotatable shafts 312, 314 connected by an intermediate elastic element 316 (e.g., a torsion bar).

[0041]

[0047] The sensor 300 includes first and second magnetic field concentrators 102, 104, and a magnetic field sensor 106 mounted on a suitable support or substrate (not shown), e.g., a printed circuit board (PCB), adjacent the magnetic field directors 112, 116 and the target 120. In an exemplary embodiment, the target 120 may be a ring magnet having multiple alternating magnetic domains or poles formed, e.g., by separate joined magnets or by differently magnetized portions of a unitary ring structure. The magnetic field directors 112, 116 (together) and the target 120 may be coupled to the first and second shafts 312 and 314, e.g., by sheaths (sleeves or extensions) 322, 324, respectively. As noted above, the first and second shafts 312 and 314 may be connected by a resilient member 316, e.g., a torsion bar.

[0042]

[0048] The torsion bar 316 may be used to increase the angular signal strength and / or signal-to-noise ratio (S / N) for the angle measurement by creating a larger twist angle (easier to measure / detect) from a given applied torque on the first or second shafts 312, 314. The torsion bar 316 may be designed by appropriate geometry and / or material selection (e.g., use of a particular metal alloy) to twist by a particular angular range for a typical applied load. The sheaths 322, 324 allow the target 120 and the magnetic field directors 112, 116 to be mounted close to each other to facilitate measurement of the relative angle between the shafts 312, 314, even though the actual portions of the first and second shafts 312, 314 to which they are respectively attached are separated by a greater distance. Although not shown, other associated circuitry and components, e.g., one or more processors, may be included on or connected to the support.

[0043]

[0049] During operation of the sensor 300, when a torque is applied to either shaft 312 or 314, the torque is transferred to the other shaft through the elastic element 316 (e.g., a torsion bar). The torsion bar 316 undergoes an amount of twist (more extreme than would occur if it were not present), and the connected shafts (312, 314) are correspondingly rotated relative to one another about the torsion axis by an angle (e.g., theta). The target 120 and the magnetic field directors 112, 116 are adjacent to one another for angular measurement, while connected to separate shafts 312, 314, and correspondingly undergo the same angular misalignment (e.g., theta) relative to one another, as do the shafts 312, 314. The magnetic field sensor 106, including the magnetic field sensing elements 106(1)-(2), detects the angular misalignment between the magnetic field directors 112, 116 and the target 120 and generates an output signal corresponding to the angular misalignment, as described above with respect to FIG. 1. In an exemplary embodiment, system 300 may be utilized as a torque measurement sensor for an automotive electric power steering (APAS) application, with shafts 312, 314 and resilient element 316 comprising or being components of a steering column.

[0044]

[0050] 3, a processor (not shown) or other component may receive an output signal corresponding to the angular misalignment (angle). By multiplying the angle by a system-defined coefficient k, an applied torque may be obtained. The defined coefficient k may be related, for example, to the material's modulus of rigidity and / or the geometry (moment of inertia) of the elastic element 316 and / or shafts 312, 314.

[0045]

[0051] FIG. 4 illustrates an example block diagram of a magnetic field sensor 400 having a magnetic field sensing element positioned to detect a magnetic target (eg, 120 in FIG. 1), according to examples and embodiments of the present disclosure.

[0046]

[0052] The sensor 400 includes magnetic field sensing elements 402 (e.g., magnetic field sensing elements 106(1)-(2) of FIG. 1) to detect changes in a magnetic field caused by a moving target, such as a rotating multi-pole magnet assembly. In an example embodiment, the magnetic field sensing elements 402 include Hall effect elements configured such that the difference of their respective Hall effect signals can be sensed. An amplifier circuit 404 can amplify the differential voltage signals from the sensing elements for filtering by a low pass filter 406. Chopping techniques can be used to reduce or eliminate offsets. An angle calculation module 408 can determine an angle from the sensing element differential signal that is not affected by stray magnetic fields. A correction module 410 can provide various types of corrections to the angle output signal from the angle calculation module 408. An output interface module 414 can generate an output signal 416 having output information in one or more formats to meet the needs of a particular application.

[0047]

[0053] From the differential magnetic field signal, ARCTAN(tan -1 ) processing - such as by a processor included in the sensor or by a processor such as a DSP - may be performed to determine the rotation angle between the magnetic field director and the target. In some embodiments, ARCTAN processing may be performed by Coordinate-Rotation-Digital-Computer (CORDIC) processing. In an example embodiment, the sensor output signal 416 (including, for example, angle or torque measurements) may be provided in a Serial Peripheral Interface (SPI), Single Edge Nibble Transmission (SENT), Pulse Width Modulation (PWM), and / or analog output format.

[0048]

[0054] 5 is a block diagram of an example computer system 500 operable to perform processing according to the present disclosure. The computer system 500 may perform all or at least a portion of the processing, e.g., steps, in the algorithms, equations, and / or methods described herein. The computer system 500 includes a processor 502, a volatile memory 504, a non-volatile memory 506 (e.g., a hard disk), an output device 507, and a user input or interface (UI) 508, e.g., a graphic user interface (GUI), a mouse, a keyboard, a display, or any common user interface. The non-volatile memory (non-transient storage medium) 506 stores computer instructions 512 (also known as machine-readable instructions or computer-readable instructions), such as software (computer program products), an operating system 516, and data 518. In one example, the computer instructions 512 are executed by the processor 502 from outside (from) the volatile memory 504. In one embodiment, article 520 (e.g., a storage device or medium, such as a hard disk, optical disk, magnetic storage tape, optical storage tape, flash drive, etc.) includes or stores non-transitory computer-readable instructions.

[0049]

[0055] The processing may be implemented in hardware, software, or a combination of the two. The processing may be implemented in a computer program executed on a programmable computer / machine, each of which includes a processor, a storage medium or other article of manufacture (including volatile and non-volatile memory and / or storage elements) readable by the processor, and optionally at least one input device, and one or more output devices. The program code may be applied to data entered using an input device or input connection (e.g., a port or bus) to perform processing and to generate output information.

[0050]

[0056] The system 500 may implement processes at least in part through a computer program product (e.g., in a machine-readable storage device) for execution by or to control the operation of a data processing device (e.g., a programmable processor, a computer, or multiple computers). Each such program may be implemented in a high-level procedural or object-oriented programming language to communicate with a computer system. However, the programs may be implemented in assembly or machine language. The language may be a compiled or interpreted language, which may be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. The computer program may be deployed to run on one computer or on multiple computers at one location or distributed across multiple locations and interconnected by a communication network. The computer program may be stored on a storage medium or device (e.g., a CD-ROM, a hard disk, or a magnetic diskette), which is readable by a general-purpose or special-purpose programmable computer to configure and operate the computer when the storage medium or device is read by the computer. The process may also be implemented as a machine-readable storage medium configured with a computer program, the instructions in the computer program, when executed, causing a computer to operate.

[0051]

[0057] The processing may be performed by one or more programmable processors executing one or more computer programs to perform the functions of the system. All or part of the system may be implemented as special purpose logic circuitry, such as an FPGA (field programmable gate array) and / or an ASIC (application specific integrated circuit).

[0052]

[0058] Thus, examples and embodiments of the present disclosure may provide advantages over the prior art. Such advantages may include, but are not limited to, providing systems, sensors, and techniques that use non-contact angle measurement and / or torque sensing that are resistant to and / or tend to eliminate stray magnetic fields and the harmful effects of such stray magnetic fields. Such non-contact angle measurement and / or torque sensing may be implemented for various types of objects and in various applications. For example, such measurement and sensing may be accomplished in the case of shafts that are only rotating slowly or that rotate by small angles, including, for example, zero (0) rpm, and in the case of angles of, for example, 15 degrees, 10 degrees, 5 degrees, 2 degrees, less than 1 degree, etc. Examples and embodiments of the present disclosure may provide stray magnetic field robust angle and / or torque measurement using fewer and less expensive parts than conventional systems and techniques.

[0053]

[0059] Various examples and embodiments of the concepts, systems, devices, structures, and techniques sought to be protected are described above with reference to the associated drawings. Alternate embodiments may be modified without departing from the scope of the described concepts, systems, devices, structures, and techniques. It should be noted that various connections and relationships (e.g., above, below, adjacent, etc.) may be used to describe elements in the description and drawings. These connections and / or relationships may be direct or indirect unless otherwise stated, and the described concepts, systems, devices, structures, and techniques are not intended to be limiting in this respect. Thus, coupling of entities refers to either direct or indirect coupling, and relationships between entities may be either direct or indirect relationships.

[0054]

[0060] As an example of an indirect positional relationship, positioning element "A" above element "B" may include a situation where one or more intermediate elements (e.g., element "C") are between element "A" and element "B," so long as the relative features and functionality of elements "A" and "B" are not substantially altered by the intermediate elements.

[0055]

[0061] In addition, the following definitions and abbreviations shall be used for interpretation of the claims and the specification. The terms "comprise," "comprises," "comprising," "include," "includes," "including," "has," "having," "contains," or "containing," or any other variation, are intended to cover a non-exclusive inclusion. For example, a device, method, composition, mixture, or article that includes a list of elements is not necessarily limited to only those elements and may include other elements not expressly listed or inherent to such device, method, composition, mixture, or article.

[0056]

[0062] Additionally, the term "exemplary" means serving as an example, instance, or illustration. Any embodiment, example, or design described as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The terms "one or more" and "at least one" refer to any integer greater than or equal to one, i.e., 1, 2, 3, 4, etc. The term "multiple" refers to any integer greater than one. The term "connected" can include a direct "connected" and an indirect "connected."

[0057]

[0063] References herein to "an embodiment," "one embodiment," "one embodiment," "example embodiment," "example," "example," "aspect," and the like indicate that the embodiment being described may include a particular feature, structure, or feature, but all embodiments may or may not include the particular feature, structure, or feature. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or feature is described in connection with one embodiment, it may affect such feature, structure, or feature in other embodiments, whether or not explicitly described.

[0058]

[0064] Relational or positional terms, including but not limited to "above," "below," "right," "left," "vertical," "horizontal," "up," "below," and derivatives of these terms, refer to the described structures and methods as oriented in the drawings. The terms "overlying," "atop," "on top," "positioned on," and "positioned atop" mean that a first element, such as a first structure, is above a second element, such as a second structure, and that an intervening element, such as an interface structure, may be between the first and second elements. The term "direct contact" means that a first element, such as a first structure, and a second element, such as a second structure, are connected without any intermediate elements.

[0059]

[0065] The use of ordinal terms such as "first," "second," "third," etc. in the claims to modify claim elements does not, in itself, imply any priority, precedence, or ordering of one claim element over another, or the temporal order in which acts of a method are performed, but is merely used as a label to distinguish one claim element having a particular name from another element having the same name (through the use of ordinal terms) to distinguish the claim elements.

[0060]

[0066] The terms "approximately" and "about" may be used in some embodiments to mean within ±20% of a target value, in some embodiments within plus or minus (±) 10% of a target value, in some embodiments within ±5% of a target value, and even in some embodiments within ±2% of a target value. The terms "approximately" and "about" may include the target value. The term "substantially equal" may be used in some embodiments to refer to values ​​that are within ±20% of each other, in some embodiments within ±10% of each other, in some embodiments within ±5% of each other, and even in some embodiments within ±2% of each other.

[0061]

[0067] The term "substantially" may be used to refer to values ​​that are within ±20% of a comparative measurement in some embodiments, within ±10%, within ±5%, and even within ±2% in some embodiments. For example, a first direction that is "substantially" perpendicular to a second direction may refer to a first direction that is within ±20% of making a 90° angle with the second direction in some embodiments, within ±10% of making a 90° angle with the second direction in some embodiments, within ±5% of making a 90° angle with the second direction, and even within ±2% of making a 90° angle with the second direction in some embodiments.

[0062]

[0068] The disclosed subject matter is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings The disclosed subject matter is capable of other embodiments and of being practiced and carried out in various ways.

[0063]

[0069] Moreover, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. As such, the conception on which this disclosure is based may be readily utilized as a basis for the design of other structures, methods and systems for carrying out some of the purposes of the disclosed subject matter. It is therefore intended that the claims be deemed to include such equivalent constructions insofar as they do not depart from the spirit and scope of the disclosed subject matter.

[0064]

[0070] While the disclosed subject matter has been described and illustrated in the foregoing exemplary embodiments, the present disclosure is made by way of example only, and thus, numerous changes in the details of the implementation of the disclosed subject matter may be made without departing from the spirit and scope of the disclosed subject matter.

[0065]

[0071] Therefore, the scope of this patent should not be limited to the described implementations, but rather should be limited only by the spirit and scope of the appended claims.

[0066]

[0072] All publications and references cited in this patent are expressly incorporated by reference in their entirety.

Claims

1. 1. A differential magnetic field torque sensor comprising: a multi-pole magnet assembly configured for coupling to a first rotatable shaft; first and second magnetic field directors positioned adjacent to the multi-pole magnet assembly and configured to influence magnetic flux from the multi-pole magnet assembly, the first and second magnetic field directors being configured for coupling together to a second rotatable shaft; first and second magnetic field concentrators configured to concentrate the magnetic flux from the multi-pole magnet assembly, each magnetic field concentrator having first and second areas that are offset from one another; a magnetic field sensor having first and second magnetic field sensing elements each configured to measure magnetic flux and to generate an output signal based on changes in measured magnetic flux due to relative angular motion between the multi-pole magnet assembly and the first and second magnetic field directors, the output signal being indicative of a torque applied to the first or second rotatable shaft; Equipped with A differential magnetic field torque sensor, wherein each section of each magnetic field concentrator is interdigitated with a section of the other magnetic field concentrator to form two interdigitated section pairs, each interdigitated section pair configured to receive a respective magnetic field sensing element.

2. The sensor of claim 1 , wherein the first shaft is coupled to the second shaft by a resilient member.

3. The sensor of claim 2 , wherein the resilient member comprises a torsion bar.

4. 2. The sensor of claim 1, wherein the multi-pole magnet assembly is configured as a ring magnet and includes a plurality of magnetic domains arranged in a cylindrical configuration, each of the plurality of magnetic domains having an opposite polarity relative to adjacent magnetic domains.

5. The sensor of claim 1 , wherein the first and second magnetic field directors each include a plurality of teeth.

6. 6. The sensor of claim 5, wherein the multi-pole magnet assembly is configured as a toroidal body, the first and second magnetic field directors are each disposed about the toroidal body, and teeth of the first magnetic field director are spaced from and interdigitated with teeth of the second magnetic field director.

7. The sensor of claim 1 , wherein the magnetic field sensor is coupled to a housing that is stationary relative to the first and second rotatable shafts.

8. The sensor of claim 7 , wherein the first and second magnetic field concentrators are coupled to the housing.

9. 2. The sensor of claim 1, further comprising a summer configured to receive an output signal from each magnetic field sensing element and to subtract one magnetic field element output signal from the other, the summer configured to generate an output signal indicative of an angular displacement of the multi-pole magnet assembly relative to the first and second magnetic field directors, thereby reducing an effect of stray magnetic fields on the first and second magnetic field sensing elements.

10. The sensor of claim 1 , wherein the first and second rotatable shafts comprise a steering column.

11. The sensor of claim 1 , wherein the magnetic field sensing element comprises a Hall effect element.

12. The sensor of claim 1 , wherein the magnetic field sensing element comprises a magnetoresistive element.

13. The sensor of claim 1 , wherein each interdigitated area pair further comprises a shield configured to shield a respective magnetic sensing element from stray magnetic fields.

14. 1. A differential magnetic field sensor, comprising: a target configured for coupling to a first rotatable shaft; first and second magnetic field directors positioned adjacent to the target and configured to influence magnetic flux from the target, the first and second magnetic field directors being configured for coupling together to a second rotatable shaft; first and second magnetic field concentrators configured to concentrate the magnetic flux from the target, each magnetic field concentrator having first and second areas that are offset from one another; a magnetic field sensor having first and second magnetic field sensing elements each configured to measure magnetic flux and to generate an output signal indicative of changes in the measured magnetic flux due to relative angular motion between the target and the first and second magnetic field directors; Equipped with A differential magnetic field sensor, wherein each section of each magnetic field concentrator is interdigitated with a section of the other magnetic field concentrator to form two interdigitated section pairs, each interdigitated section pair configured to receive a respective magnetic field sensing element.

15. The sensor of claim 14 , wherein the target comprises a multi-pole magnet assembly having multiple pole pairs.

16. 16. The sensor of claim 15, wherein the multi-pole magnet assembly includes a plurality of magnetic domains arranged in a cylindrical configuration, each of the plurality of magnetic domains having an opposite polarity relative to adjacent magnetic domains.

17. The sensor of claim 15 , wherein the multi-pole magnet assembly comprises a ring magnet.

18. 15. The sensor of claim 14, further comprising a summer configured to receive an output signal from each magnetic field sensing element and to subtract one magnetic field element output signal from the other, the summer configured to generate an output signal indicative of an angle of the target relative to the first and second magnetic field directors, thereby mitigating the effect of stray magnetic fields on the first and second magnetic field sensing elements.

19. 20. The sensor of claim 18, wherein the output signal of the summer indicates a linear response to an angle of the multi-pole magnet assembly relative to the first and second magnetic field directors.

20. 16. The sensor of claim 15, wherein the multi-pole magnet assembly is coupled to the first rotatable shaft, the first and second magnetic field directors are coupled together to the second rotatable shaft, the first rotatable shaft is coupled to the second rotatable shaft by a torsion bar, and the differential magnetic field sensor is configured to measure torque applied to the first or second rotatable shaft.

21. The sensor of claim 20 , wherein the first and second rotatable shafts comprise a steering column.

22. The sensor of claim 15 , wherein the first and second magnetic field directors each include a plurality of teeth.

23. 23. The sensor of claim 22, wherein the multi-pole magnet assembly is configured as a toroidal body, the first and second magnetic field directors are each disposed about the toroidal body, and teeth of the first magnetic field director are spaced from and interdigitated with teeth of the second magnetic field director.

24. The sensor of claim 14 , wherein the first and second magnetic field sensors are coupled to a housing that is stationary relative to the first and second rotatable shafts.

25. The sensor of claim 24 , wherein the first and second magnetic field concentrators are coupled to the housing.

26. The sensor of claim 14 , wherein the magnetic field sensing element comprises a Hall effect element.

27. The sensor of claim 14 , wherein the magnetic field sensing element comprises a magnetoresistive element.

28. The sensor of claim 14 , wherein each interdigitated area pair further comprises a shield configured to shield the respective magnetic sensing element from stray magnetic fields.

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