Magnetoelastic torque sensor devices, systems, and methods

Abstract

1. A magnetoelastic torque sensor system comprising: a shaft having at least one circumferentially magnetized axial section; and a magnetic sensor device disposed proximate the shaft, the sensor device comprising: a first semiconductor substrate (109) having processing circuitry; a second semiconductor substrate (106a) having a first magnetic sensor (S1); and a third semiconductor substrate (106b) having a second magnetic sensor (S2), each magnetic sensor configured to measure a magnetic field component, the first, second, and third semiconductor substrates being integrated into a single packaged device, and the processing circuitry being configured to determine pairwise differences between the magnetic field components and to output a signal or value indicative of a torque applied to the shaft based on said pairwise differences.

Description

[Technical Field]

[0001] The present invention relates generally to the field of magnetic sensor devices, systems and methods, and more particularly to magnetoelastic torque sensors. [Background technology]

[0002] Magnetoelastic torque sensors are known in the art. They are based on the reversal of the physical effect of magnetostriction (the deformation of magnetic material by an applied magnetic field), where a torque acting on a magnetized shaft causes the shaft to twist and, as a result, causes a modification of the magnetic field outside the shaft. This modification is very sensitive to the degree of torque and can be measured with a magnetic field sensor.

[0003] Magnetoelastic torque sensors have been known in the art for over 20 years, for example from US Pat. No. 5,629,999.

[0004] There is always room for improvement or substitution. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 6,047,605 Summary of the Invention [Problem to be solved by the invention]

[0006] It is an object of an embodiment of the present invention to provide a magnetoelastic torque sensor system comprising a shaft and at least one magnetic sensor device.

[0007] It is an object of an embodiment of the present invention to provide a method for measuring torque on a shaft.

[0008] It is an object of embodiments of the present invention to provide such a system or method that uses a shaft having as little as one axial zone magnetized in a circumferential direction, or having two axial zones magnetized in a single circumferential direction (e.g., both clockwise), or having two axial zones magnetized in opposite circumferential directions (e.g., one clockwise and one counterclockwise), or having three axial zones magnetized in different circumferential directions.

[0009] It is an object of embodiments of the present invention to provide such a system or method that uses a shaft having two axial zones spaced apart by a distance greater than 3.0 mm, or greater than 5.0 mm.

[0010] It is an object of embodiments of the present invention to provide such a system or method that uses a shaft having three axial zones.

[0011] It is an object of embodiments of the present invention to provide such a system that has improved accuracy (e.g., has a better signal-to-noise ratio and / or is less sensitive to disturbance fields) and / or is less complex and / or is more compact than systems known in the art.

[0012] It is also an object of embodiments of the present invention to provide such a system in which the sensor device can be more easily customized for a particular shaft without requiring a complete redesign.

[0013] It is also an object of embodiments of the present invention to provide such a system in which the sensor device may be positioned differently relative to the shaft, resulting in different form factors and / or allowing for different mounting of the sensor device to, for example, the chassis.

[0014] It is also an object of embodiments of the present invention to provide a torque sensor system comprising a shaft and a sensor device having dimensions that can be more easily modified or customized for a particular application (e.g., for use with electric bicycles of various sizes) without a complete redesign.

[0015] It is also an object of embodiments of the present invention to provide a torque sensor system comprising a shaft and at least one sensor device, which is insensitive to mounting position offsets of the at least one sensor device, such as offsets in the axial direction of the shaft and / or offsets in the radial direction of the shaft, or in both cases, in other words, a torque sensor system with relaxed mounting requirements for the at least one sensor device.

[0016] The torque sensor system provided by the present invention can be used in electric bicycles, automotive applications, industrial applications, and robotic applications. [Means for solving the problem]

[0017] These and other objects are achieved by embodiments of the present invention.

[0018] According to a first aspect, the present invention provides a magnetoelastic torque sensor system comprising: a shaft comprising at least one (e.g., first) circumferentially magnetized (e.g., first) axial section; and three semiconductor substrates disposed proximate the shaft, the three semiconductor substrates including at least a first semiconductor substrate comprising a processing circuit, a second semiconductor substrate comprising a first magnetic sensor, and a third semiconductor substrate comprising a second magnetic sensor, each magnetic sensor configured to measure a magnetic field component of a magnetic field generated by said shaft when torque is applied to said shaft; the first magnetic sensor and the second magnetic sensor are spaced apart from each other by a predetermined distance; the first semiconductor substrate, the second semiconductor substrate, and the third semiconductor substrate are incorporated into a single packaged device having a plurality of terminals electrically connected to the first substrate; and the processing circuitry is configured to determine pairwise differences (e.g., ΔBx) between the measured magnetic field components and to output a signal or value indicative of torque applied to said shaft based on said pairwise differences.

[0019] Such magnetoelastic torque sensors are based on the reversal of the physical effect of magnetostriction (the deformation of magnetic materials by an applied magnetic field), where a torque acting on a magnetized shaft causes the shaft to twist and, as a result, causes a modification of the magnetic field outside the shaft. This modification is very sensitive to the degree of torque and can be measured with a magnetic field sensor.

[0020] The first substrate is also referred to herein as the "main substrate."

[0021] The second substrate is also referred to herein as the "first sensor substrate."

[0022] The third substrate is also referred to herein as the "second sensor substrate."

[0023] The output signal may be a torque value (eg, expressed in Nm), or a digital value proportional to the torque, or an analog signal (eg, a voltage or current signal) proportional to the torque.

[0024] The first substrate may be disposed between the second and third substrates. Alternatively, the second and third substrates may be attached to the top or bottom of the first substrate.

[0025] The first and second sensors may comprise, for example, one or more horizontal Hall elements (for measuring Bz), or an IMC disk having two horizontal Hall elements (e.g., for measuring Bx or By), or one or more vertical Hall elements (e.g., oriented in the same direction to measure Bx or By), or one or more magnetoresistive (MR) elements (e.g., AMR, XMR), (e.g., for measuring Bx or By), one or more GMI elements, etc.

[0026] The predefined direction can be X (parallel to the substrate and defined by the position of the sensor element), or Y (parallel to the substrate but orthogonal to X), or Z (perpendicular to the substrate).

[0027] In one embodiment, the output signal is proportional to said difference, for example using a constant K stored in the non-volatile memory of the sensor device.

[0028] There is an advantage to using the difference signal between the two parallel field components, as the resulting output signal is less sensitive to external disturbance fields.

[0029] The first and second magnetic sensors are spaced apart from one another by a predefined distance (e.g., dx), which may be related to one or more dimensions of at least one axial zone of the shaft.

[0030] In one embodiment, the first substrate has a size of at most 2.0 mm x 2.0 mm or at most 1.5 mm x 1.5 mm, and each of the sensor substrates has a size of at most 0.8 mm x 0.8 mm, at most 0.5 mm x 0.5 mm, at most 0.4 mm x 0.4 mm, at most 0.3 mm x 0.3 mm, or at most 0.25 mm x 0.25 mm. Because the contact zones of the sensor substrates may be smaller than contact zones connected by bond wires or wire bonds, it is a significant advantage that such contact zones are connected to contact zones of the main substrate by one or more RDL layers. As a result, the size of the sensor substrates can also be reduced compared to sensor substrates having the same magnetic sensors but contact zones connected using bond wires or wire bonds.

[0031] In one embodiment (of a wafer level packaged device or a device with a lead frame), the first substrate is spaced apart from each of the sensor substrates by at least 1.0 mm, or at least 1.5 mm, or at least 2.0 mm, or at least 2.5 mm.

[0032] In this embodiment, the sensor substrate is intentionally placed a relatively long distance from the first (or main) substrate, even though their size and technology would allow them to be placed closer. Typically, this is counterintuitive because packages are made "as small as possible," but this is not the case here.

[0033] Preferably, the magnetic sensor device has a plurality of external terminals (also referred to herein as "external contacts") electrically connected to the first substrate. The plurality of terminals may include at least three terminals, including one terminal (e.g., in the form of a contact pad) for receiving a supply voltage (e.g., VDD), one terminal for receiving a reference voltage (e.g., GND), and one output terminal for providing an output signal. These terminals are exposed to the outside world. However, of course, the present invention is not limited to magnetic sensor devices having only three terminals; sensor devices having more than four terminals may also be used, for example, having at least four terminals, or at least six terminals, or at least eight terminals.

[0034] In one embodiment, the processing circuitry may include a programmable processor having random access memory (e.g., RAM) and non-volatile memory (e.g., FLASH). The FLASH may include at least one constant value, e.g., a scaling factor K, for multiplying the at least one difference signal to obtain a torque value (e.g., expressed in Nm). However, the invention is not limited thereto and may also provide an analog signal, e.g., a voltage signal, as an indication of the torque value. The difference may be determined in the analog domain.

[0035] In a simple embodiment, the sensor device has two "1D magnetic sensors" configured to measure magnetic field components (e.g., Bz1, Bz2) oriented in a certain direction at two sensor positions spaced apart by a predefined distance (e.g., dx), and a processing circuit configured to determine the difference between the two measurements and to multiply said difference by a predefined constant stored in a non-volatile memory embedded in the main board, and to output the result as a torque value (e.g., expressed in Nm).

[0036] The sensor substrate may include a Hall element and four contact zones, two of which can be used to provide a voltage or current to the Hall element and two of which can be used for readout.

[0037] In one embodiment, the magnetic sensor device is configured to measure or estimate a first temperature of a first sensor and a second temperature of a second sensor, and to temperature compensate the signals obtained from the first and second sensors before calculating said difference.

[0038] In one embodiment, the first substrate further comprises a temperature sensor for measuring the temperature of the main substrate, and the processing circuitry is configured to temperature correct the sensor signal based on the measured temperature before determining the aforementioned difference.

[0039] Temperature compensation can be performed in the analog or digital domain.

[0040] In an embodiment in which the sensor includes a single horizontal Hall plate or multiple horizontal Hall plates connected in series or parallel, the electrical resistance of the Hall plate can be used to estimate the temperature of each individual Hall plate. The electrical resistance can be determined during a calibration test and stored in nonvolatile memory, or it can be calculated during actual use, for example, by applying a known bias voltage and measuring the current flowing through the Hall plate or by applying a known bias current and measuring the voltage on the Hall plate. By way of example, one or more pairs of Hall plates are typically used to perform pairwise differential measurements. An average temperature reading can then be used for temperature compensation of the differential measurements. This average temperature can be obtained from a temperature sensor on the CMOS substrate when the temperature sensor is located near the center of an imaginary circle that intersects the individual Hall plates.

[0041] In one embodiment, each of the sensor substrates further comprises a temperature sensor for measuring the temperature of said sensor substrate, and the processing circuitry is configured to temperature correct the sensor signals based on these temperature signals before determining said difference.

[0042] In some embodiments, the magnetic sensing element itself (e.g., a horizontal Hall plate) can be used as a temperature sensor, in which case no additional contacts and additional interconnects are required between the sensor substrate and the first substrate.

[0043] In other embodiments, a separate temperature sensor circuit is provided on the sensor substrate, for example, with components having a negative temperature coefficient (NTC), which may require additional contacts and additional interconnects between the sensor substrate and the first substrate.

[0044] In another or further embodiment, the processing circuitry is further configured to estimate a first amount of power consumed by the first sensor substrate and a second amount of power consumed by the second sensor substrate, to estimate a first temperature of the first sensor substrate based on the first amount of power, to estimate a second temperature of the second sensor substrate based on the second amount of power, and to temperature correct the sensor signals based on the respective temperature signals before determining the difference.

[0045] In one embodiment, a first semiconductor substrate comprises a plurality of first contact zones (e.g., first bond pads), a second semiconductor substrate comprises a plurality of second contact zones, and a third semiconductor substrate comprises a plurality of first contact zones, a first subset of the first contact zones being electrically connected (e.g., by bond wires or conductive tracks) to at least some of the second contact zones, and a second subset of the first contact zones being electrically connected to at least some of the third contact zones, the first semiconductor substrate being positioned near at least one contact zone from the first subset, and the second substrate (all The first semiconductor substrate further comprises a first temperature sensor (T1) configured to provide a first temperature signal indicative of the temperature of the third substrate (i.e., the first sensor substrate), the first semiconductor substrate being positioned near at least one contact zone from the second subset and further comprising a second temperature sensor (T2) configured to provide a second temperature signal indicative of the temperature of the third substrate (i.e., the second sensor substrate), the processing circuitry being further configured to temperature compensate the signal obtained from the first sensor (e.g., S1) using the first measured temperature and to temperature compensate the signal obtained from the second sensor (e.g., S2) using the second measured temperature.

[0046] Because the first and second magnetic sensors are not monolithically integrated, their temperatures may differ significantly from one another, especially if they are relatively far apart. Because the electrical connections are in fact also thermal connections (e.g., bond wires made of gold or copper wires in a redistribution layer), it is advantageous to estimate the temperatures of the first and second semiconductor substrates by measuring the temperatures of the first and second sensors on the main substrate at or near the contact zones that are electrically connected to the first or second sensors. Providing the thermal sensors on the first substrate is advantageous because in this way the surface area (and therefore cost) of the second and third substrates can be reduced, and the number of interconnections between the sensor substrate and the main substrate can also be reduced.

[0047] In one embodiment, the shaft comprises steel or a steel alloy, and one or two axial sections of the shaft are circumferentially magnetized.

[0048] In another or further embodiment, at least one axial section of the shaft comprises or consists of a magnetized ring attached or wound around the shaft. The ring is attached to the shaft so that torque applied to the shaft is transmitted to the ring. The ring can be made of the same material as the shaft or a different material. An advantage of this embodiment is that the ring can be selected from a different material than the rest of the shaft, allowing the magnetic field generated by the ring to be significantly larger. The outer diameter of the ring can be the same as or larger than the outer diameter of the shaft.

[0049] The first semiconductor substrate may be a CMOS substrate.

[0050] In one embodiment, the first semiconductor substrate comprises primarily silicon, and the second and third semiconductor substrates comprise primarily silicon.

[0051] In one embodiment, the first semiconductor substrate comprises primarily silicon, and the second and third semiconductor substrates are separate (eg, individual) silicon substrates.

[0052] This solution can be much more cost-effective than integrating Hall sensors into the CMOS chip, especially when the distance between sensors is relatively large (e.g., greater than 2.0 mm), because the price per unit area of ​​a fan-out reconfigured wafer is much lower than the price of wafer processing of signal-conditioning CMOS circuits.

[0053] The separate silicon substrate may include a Hall plate made with a proprietary manufacturing process that is not compatible with standard CMOS processing but offers better performance (e.g., higher sensitivity) than a CMOS Hall plate.

[0054] In one embodiment, both the main substrate and the sensor substrate are fabricated in CMOS technology, but using different technology nodes.

[0055] In one embodiment, the main substrate is a CMOS silicon substrate, while the sensor substrate is a bipolar silicon substrate.

[0056] In one embodiment, the main board may use a first type of sensor element (e.g., a horizontal Hall element or a vertical Hall element), while the sensor board may use another type of sensor element (e.g., a magnetoresistive element, e.g., an AMR or XMR element, or a GMI sensor).

[0057] In one embodiment, the first semiconductor substrate comprises primarily silicon, and the second and third semiconductor substrates comprise a compound semiconductor material selected from III-V, for example, Ga—As or In—As.

[0058] This embodiment offers a combination of advantages: (1) a highly sensitive magnetic sensor (e.g., approximately an order of magnitude greater than a horizontal Hall sensor implemented in standard CMOS), (2) an increased distance between the sensor elements and therefore an increased differential signal, and (3) a cost-effective package.

[0059] In one embodiment, the sensor device is a wafer-level packaged device, wherein the first semiconductor substrate is between a second semiconductor substrate and a third semiconductor substrate, and the first semiconductor substrate is electrically connected to the second semiconductor substrate and to the third semiconductor substrate by at least one redistribution layer (RDL).

[0060] In one embodiment, the main substrate is positioned relative to the sensor substrates such that the distance between the main semiconductor substrate and any of the sensor substrates is less than the distance between the two sensor substrates.

[0061] Preferably, the active surfaces of the first, second and third semiconductor substrates lie in a single imaginary plane, or in other words, preferably the active surfaces of the first, second and third semiconductor substrates are substantially coplanar.

[0062] By having the substrates adjacent to each other, the projections of the substrates in the direction perpendicular to the substrates do not overlap each other, which simplifies the routing of the interconnects.

[0063] An advantage of placing the three substrates next to each other is that doing so reduces or avoids the risk of one substrate putting mechanical stress on another, for example when the substrates are mounted on top of each other and one of the substrates expands, for example due to heat dissipation.

[0064] This embodiment offers a combination of advantages: (1) it allows for heterogeneous integration, (2) it allows for increasing the distance between sensor elements independent of the size of the main substrate, so that the distance between sensor elements can be optimized for a specific shaft, (3) a cost-effective package, (4) it allows for the development of "custom devices" for specific applications (e.g., a torque sensor for a specific shaft having one or more magnetized zones with specific dimensions without redesigning, testing, and creating the CMOS substrate that is part of the wafer-level package, and (5) in the event of chip shortages on the sensor substrate, other sensor substrates can be used). In other words, this wafer-level package offers great design flexibility, allowing existing substrates to be used and reused for various applications.

[0065] It is an advantage of using a good thermally conductive material (such as copper or aluminum) that at least one re-distribution layer (RDL) also functions as a heat spreader. In this way, the temperature difference between the main substrate and the sensor substrate is limited on the one hand, and on the other hand, it becomes possible to use the temperature measured on the main substrate (for example near the connection zone of this re-distribution layer) as an estimate or approximation of the temperature of the respective sensor substrate. If only one temperature sensor is provided on the main substrate, this temperature sensor is preferably located in a central location, for example in or near the center between the locations of the two sensors.

[0066] In one embodiment, the wafer level packaged device further comprises at least one passive SMD component, such as a resistor or a capacitor or a diode, for example, to suppress noise and / or stabilize the voltage supply and / or reduce the effects of EMI (electromagnetic interference).

[0067] This offers the important advantage that sensitive circuitry is better protected even when the sensor device is not mounted on a printed circuit board, and it also allows for more compact mounting of the package in difficult environments, such as close to the shaft of an electric bicycle.

[0068] The wafer-packaged device may further comprise a plurality of terminals (also referred to herein as "external contacts") electrically connected to the first substrate (e.g., to its contact zones or bond pads) by the aforementioned redistribution layer.

[0069] In other words, the electrical connections from the sensor substrate to the main substrate and from the main substrate to the external terminals are made in the aforementioned RDL layer.

[0070] The projection of the external terminals in a direction perpendicular to the active surface of the substrate may be on the main substrate (called "fan-in") or outside the perimeter of the main substrate ("fan-out").

[0071] Preferably, the (external) terminal protrusions are not located on the sensor substrate due to stress caused by soldering. Some of the terminals may be near the corners of the package. External devices can be connected to these terminals by wire bonding or soldering or the like.

[0072] It is an advantage that the external terminals are in direct contact with the RDL layer, which allows them to be created using photolithography processes, which is not the case when using lead frames.

[0073] It is advantageous that the active surfaces of the three substrates lie in the same (imaginary) plane (i.e., they are coplanar), even if the substrates have different thicknesses. This allows the three substrates to be mounted at the same distance from external objects, such as shafts, magnet surfaces, etc. This also allows many or all of the vias in the redistribution RDL layer to have substantially the same length (in the direction perpendicular to the substrates).

[0074] In one embodiment, the number of redistribution layers is no more than one or no more than two.

[0075] This offers the advantage of a cheaper and thinner package, and avoids the need for a complex three-dimensional redistribution layer stack.

[0076] In one embodiment, the magnetic sensor device further comprises a lead frame, the first substrate being between a second semiconductor substrate and a third semiconductor substrate on a single side of the lead frame, and the first semiconductor substrate being electrically connected to the second semiconductor substrate and to the third semiconductor substrate by bond wires (e.g., directly or indirectly via the lead frame).

[0077] An embodiment of such a sensor device is illustrated in FIG.

[0078] It is advantageous to arrange the three substrates next to each other, for example, to avoid the risk of mounting the substrates on top of each other and one of the substrates putting mechanical stress on another, for example when expanding due to heat dissipation.

[0079] Preferably, the electrical interconnections between the first semiconductor substrate and the sensor substrate are internal to the package, i.e., not exposed and therefore not accessible from outside the package. Some contact zones (or bond pads) of the first semiconductor substrate are electrically connected to external leads (e.g., for receiving a supply voltage signal VDD, a reference voltage signal GND, and for outputting a torque signal or a signal or value indicative of torque).

[0080] In one embodiment, the lead frame further comprises at least one passive SMD component such as a resistor or capacitor or diode, for example to suppress noise and / or to stabilize the voltage supply and / or to reduce the effects of EMI (electromagnetic interference).

[0081] This offers the important advantage that sensitive circuitry is better protected even when the sensor device is not mounted on a printed circuit board, and it also allows for more compact mounting of the package in difficult environments, such as close to the shaft of an electric bicycle.

[0082] In one embodiment, the magnetic sensor device further comprises a lead frame, wherein the first semiconductor substrate is attached to the lead frame, the second semiconductor substrate and the third semiconductor substrate are disposed above or below the first substrate, and the first semiconductor substrate is electrically connected to the second semiconductor substrate and to the third semiconductor substrate by bond wires (e.g., directly or indirectly via the lead frame).

[0083] An example of such a sensor device is illustrated in Figures 6A to 6C.

[0084] Preferably, the electrical interconnections between the first semiconductor substrate and the sensor substrate are internal to the package, i.e., not exposed and therefore not accessible from outside the package. Some contact zones (or bond pads) of the first semiconductor substrate are electrically connected to external leads (e.g., for receiving a supply voltage signal VDD, a reference voltage signal GND, and for outputting a signal indicative of torque, e.g., a torque signal).

[0085] In one embodiment, the shaft comprises at least a first axial section magnetized in a first circumferential direction and optionally also a second axial section magnetized in a second circumferential direction opposite to the first circumferential direction, the magnetic sensor device is oriented with respect to the shaft such that a first axis (e.g., X) defined by an imaginary line passing through the first sensor and the second sensor is parallel to the shaft, the first sensor and the second sensor are configured to measure first and second magnetic field components oriented parallel to the shaft, the first sensor is at a first axial position near a center of the first magnetized axial section, and the second sensor, if present, is near a center of the second magnetized axial section.

[0086] An example of this embodiment is illustrated in FIGS.

[0087] The sensor device may be configured, for example, to determine a torque based on a difference (eg, ΔBx) between the first and second magnetic field components, the difference being proportional to said difference.

[0088] The shaft preferably includes two axial sections magnetized in opposite circumferential directions, although this is not absolutely necessary and one of these axial sections may be omitted.

[0089] In one embodiment, the magnetic sensor device is oriented relative to the shaft such that a first axis (e.g., X) defined by an imaginary line passing through the first sensor and the second sensor is oriented radially relative to the shaft, the first sensor and the second sensor are configured to measure first and second magnetic field components oriented parallel to the shaft, the first sensor is at an axial position near the center of the magnetized axial section at a first radial distance (e.g., d1) from the shaft, and the second sensor is at the same axial position as the first sensor but at a second radial distance (e.g., d2) from the shaft that is greater than the first axial distance.

[0090] An example of this embodiment is illustrated in FIGS.

[0091] The sensor device may be configured, for example, to determine a torque based on a difference between the first and second magnetic field components (eg, ΔBax) that is proportional to said difference.

[0092] Depending on the orientation of the sensor device, the axial component Bax relative to the shaft corresponds to the component By (FIG. 13) or the component Bz (FIG. 15) of the sensor device.

[0093] In one embodiment, the magnetic sensor device is oriented with respect to the shaft such that a first axis (e.g., X) defined by an imaginary line passing through the first sensor and the second sensor is parallel to the shaft, the first sensor and the second sensor are configured to measure first and second magnetic field components oriented radially with respect to the shaft, the first sensor being at a first axial position near a first edge of the magnetized axial section, and the second sensor being at a second axial position near a second edge of the magnetized axial section.

[0094] An example of this embodiment is illustrated in FIG.

[0095] The sensor device may be configured, for example, to determine a torque based on a difference between the first and second magnetic field components (eg, ΔBz) that is proportional to said difference.

[0096] In one embodiment, the magnetic sensor device is oriented relative to the shaft such that a first axis (e.g., X) defined by an imaginary line passing through the first sensor and the second sensor is oriented radially relative to the shaft, the first sensor and the second sensor are configured to measure first and second magnetic field components oriented radially relative to the shaft, and the first and second sensors are at axial positions near a first edge of the magnetized axial section.

[0097] An example of this embodiment is illustrated in FIGS.

[0098] The sensor device may be configured, for example, to determine a torque based on a difference (eg, ΔBx) between the first and second magnetic field components, the difference being proportional to said difference.

[0099] In one embodiment, the shaft comprises at least a first axial section magnetized in a first circumferential direction and optionally also a second axial section magnetized in a second circumferential direction opposite to the first circumferential direction, the magnetic sensor device is oriented with respect to the shaft such that a first axis (e.g., X) defined by an imaginary line passing through the first sensor and the second sensor is parallel to the shaft, the first sensor and the second sensor are configured to measure first and second magnetic field components oriented radially with respect to the shaft, the first sensor being at a first axial position near an edge of the first magnetized axial section, and the second sensor, if present, being near an edge of the second magnetized axial section.

[0100] An example of this embodiment is illustrated in FIGS.

[0101] Depending on the orientation of the sensor device, the radial component Br relative to the shaft corresponds to the component Bz (FIG. 9) or the component By (FIG. 16) of the sensor device.

[0102] The shaft preferably includes two axial sections magnetized in opposite circumferential directions, although this is not absolutely necessary and one of these axial sections may be omitted.

[0103] In one embodiment, the shaft comprises a first axial section magnetized in a first circumferential direction and a second axial section also magnetized in the first circumferential direction, the magnetic sensor device is oriented with respect to the shaft such that a first axis (e.g., X) defined by an imaginary line passing through the first sensor and the second sensor is parallel to the shaft, the first sensor and the second sensor are configured to measure first and second magnetic field components oriented radially with respect to the shaft, and the first sensor and the second sensor are either both near an inner edge of the respective axial section or both near an outer edge of the respective axial section.

[0104] An example of this embodiment is illustrated in FIGS.

[0105] Depending on the orientation of the sensor device, the radial component Br relative to the shaft corresponds to the component Bz (FIG. 18) or the component By (FIG. 19) of the sensor device.

[0106] According to a second aspect, the present invention also provides a method of measuring torque on a shaft, comprising the steps of: a) providing a shaft comprising at least one (e.g., first) axial section that is (e.g., first) circumferentially magnetized; b) providing a magnetic sensor device in the form of a single packaged device comprising at least three semiconductor substrates, including a first semiconductor substrate (e.g., CMOS) comprising at least processing circuitry, a second semiconductor substrate (e.g., Ga-As) comprising a first magnetic sensor, and a third semiconductor substrate (e.g., Ga-As) comprising a second magnetic sensor; c) positioning the sensor device in the vicinity of the shaft; d) measuring a first magnetic field component (e.g., Bz1) using the first magnetic sensor and measuring a second magnetic field component (e.g., Bz2) using the second magnetic sensor; e) determining pairwise differences between the magnetic field components (e.g., ΔBz); and f) outputting a signal or value indicative of torque on said shaft based on said pairwise differences.

[0107] Step a) may include providing a shaft having no more than one axial section that is circumferentially magnetized.

[0108] Step a) may include providing a shaft having no more than two axial sections that are magnetized in opposite circumferential directions and having a non-magnetized section therebetween.

[0109] Step a) may include providing a shaft having three axial sections that are magnetized in opposite circumferential directions (i.e., not all magnetized in the same direction) and with two non-magnetized sections therebetween.

[0110] Step b) may include providing such a device in which the two magnetic sensors are spaced apart along a first direction (X) by a predefined distance (e.g., dx) in the range of 1.5 mm to 25.0 mm, or 2.5 to 25.0 mm, or 4.0 to 25.0 mm, or 6.0 mm to 25 mm, or 8.0 mm to 25 mm, or 10 mm to 25 mm, or 12 mm to 25 mm.

[0111] Step b) may comprise providing such a device, in which each of the two magnetic sensors is a 1D magnetic pixel, for example comprising only a horizontal Hall element.

[0112] Step c) may include positioning the sensor device such that the first sensor (eg, S1) is positioned at an axial position near the center of the first magnetized zone.

[0113] Step c) may include positioning the sensor device so that the first sensor (e.g., S1) is positioned at an axial position near the edge of the first magnetized zone (e.g., at an axial distance of up to 3.0 mm from said edge).

[0114] Step c) may include orienting the sensor device such that an imaginary axis (e.g., X) between the first sensor and the second sensor is oriented substantially parallel to the longitudinal axis of the shaft.

[0115] Step c) may include orienting the sensor device such that an imaginary axis (e.g., X) between the first and second sensors is oriented substantially perpendicular to the longitudinal axis of the shaft, e.g., radially.

[0116] Step f) may include outputting a voltage proportional to said pairwise difference, or outputting a digital value proportional to said pairwise difference.

[0117] Step f) may include calculating and outputting a torque value (eg, T) based on said pairwise differences.

[0118] If the shaft has two axial sections that are circumferentially magnetized, and if the imaginary axis (X) between the two sensors is substantially parallel to the longitudinal axis of the shaft, the second sensor may be positioned near the second axial section.

[0119] In one embodiment, the first substrate further comprises a temperature sensor (e.g., near a central position of the first substrate), and step d) further includes measuring the temperature of the first substrate and temperature compensating the measurements of the first and second sensors using the measured temperature of the first substrate as an estimate of the temperatures of the first and second sensor substrates.

[0120] In one embodiment, the first substrate further comprises two temperature sensors, for example a first temperature sensor near a contact zone connected to the contact zone of the first sensor substrate and a second temperature sensor near a contact zone connected to the contact zone of the second sensor substrate, and step d) further includes measuring a first temperature with the first temperature sensor and temperature compensating the measurement value of the first sensor using the first temperature, measuring a second temperature with the second temperature sensor and temperature compensating the measurement value of the second sensor using the second temperature.

[0121] According to a third aspect, the present invention also provides a magnetoelastic torque sensor system comprising: a shaft comprising a first axial section, a second axial section, and a third axial section magnetized in a first circumferential direction, a second circumferential direction, and a third circumferential direction, respectively, wherein the second axial section is located between the first axial section and the third axial section, and the third circumferential direction is equal to the first circumferential direction (e.g., clockwise) and the second circumferential direction is opposite to the first circumferential direction (e.g., counterclockwise); and at least one magnetic sensor device arranged in the vicinity of the shaft, wherein the magnetic sensor device comprises at least a first magnetic sensor device having a processing circuit. a semiconductor substrate including a first semiconductor substrate having a first magnetic sensor, a second semiconductor substrate including a first magnetic sensor, and a third semiconductor substrate including a second magnetic sensor, each magnetic sensor configured to measure a magnetic field component (e.g., Bz1, Bz2) of a magnetic field generated by the shaft when a torque is applied to the shaft, the first and second magnetic sensors being spaced apart from each other by a predefined distance (e.g., dx), and a processing circuit configured to determine pairwise differences (e.g., ΔBz) between the measured field components and to output a signal or value indicative of the pairwise differences and / or the torque applied to the shaft based on the pairwise differences.

[0122] In a variant, the torque sensor system according to the third aspect further comprises a processor (e.g. an electronic control unit) external to the magnetic sensor device, in which case the main board of the sensor device may be omitted or may be present and may be configured to bias, read out and output the sensor signal, optionally after temperature compensation, but the pair-wise differences may be calculated in the external processor.

[0123] In one embodiment, the first semiconductor substrate is a CMOS substrate, and the second and third semiconductor substrates comprise a compound semiconductor material selected from III-V, for example, Ga—As or In—As.

[0124] In one embodiment, the first and second sensors are configured to measure a magnetic field component oriented radially of the shaft.

[0125] In one embodiment, the first and second sensors are configured to measure a magnetic field component oriented axially of the shaft.

[0126] In one embodiment, the first and second sensors are configured to measure two orthogonal magnetic field components, one oriented radially of the shaft and one oriented axially of the shaft.

[0127] In one embodiment, the first sensor and the second sensor are in a space between a first imaginary plane (e.g., Ω1 in FIG. 22A ) and a second imaginary plane (e.g., Ω2), the first imaginary plane being oriented perpendicular to the axial direction of the shaft (e.g., X) and intersecting the shaft at a first axial position between the first and second magnetized sections, and the second imaginary plane being oriented perpendicular to the axial direction of the shaft and intersecting the shaft at a second axial position between the second and third magnetized sections.

[0128] In one embodiment, the first, second, and third semiconductor substrates are integrated into a single module or a single packaged device.

[0129] In one embodiment, the distance dA between the first and second axial zones is substantially equal to the distance dB between the second and third axial zones (e.g., within a tolerance margin of ±25%), the radial distance ds between the shaft and the first and second sensors is substantially equal to said distance dA (e.g., within a tolerance margin of ±25%), and the distance dx between the first and second sensors is a value in the range of (L2-2*dA) and (L2+dA), where L2 is the axial length of the second magnetized zone. Preferably, dx is a value in the range of (L2-2*dA) to (L2), or in the range of (L2-1.5*dA) to (L2-0.5*dA), or in the range of (L2-1.25*dA) to (L2-0.75*dA), e.g., dx is substantially equal to (L2-dA).

[0130] In one embodiment, the sensor system comprises two magnetic sensor devices mounted near the shaft, for example between the aforementioned first imaginary plane and the aforementioned second imaginary plane, and circumferentially spaced apart by an angle (e.g., θ) of at least 30°, or at least 45°, or at least 60°, or at least 70°, or at least 85°, or at least 95°, for example, an angle in the range of 165° to 180°. The signals from these two magnetic sensor devices may be combined by one of the magnetic sensor devices or by an external processor to determine the value of the torque on the shaft.

[0131] In one embodiment, the sensor system comprises three magnetic sensor devices mounted near the shaft, for example between the first and second imaginary planes, and circumferentially spaced apart by an angle (e.g., θ) of at least 30°, or at least 45°, or at least 60°, or at least 70°, or at least 85°, or at least 95°, for example, in the range of 105° to 135°. The signals from these three magnetic sensor devices may be combined by one of the magnetic sensor devices or by an external processor to determine the value of the torque on the shaft.

[0132] In one embodiment, the sensor system comprises four magnetic sensor devices mounted near the shaft, e.g., between the aforementioned first imaginary plane and the aforementioned second imaginary plane, and circumferentially spaced apart by an angle (e.g., θ) of at least 30°, or at least 45°, or at least 60°, or at least 70°, or at least 85°, or at least 95°, e.g., an angle in the range of 80° to 100°. The signals from these four magnetic sensor devices may be combined by one of the magnetic sensor devices or by an external processor to determine the value of the torque on the shaft.

[0133] According to a fourth aspect, the present invention also provides a shaft for use in a magnetoelastic torque sensor system (e.g. in electric bicycles, automotive applications, industrial applications, robotic applications), the shaft comprising at least one axial section that is circumferentially magnetized, at least an outer portion of said at least one axial section being made from maraging steel (e.g. containing 17-19 wt. % nickel) or made from (e.g. hardened) martensitic stainless steel (e.g. containing 12%-17 wt. % Cr).

[0134] The outer portion may be integrally formed with the inner portion of the shaft (forming a solid shaft) or may be a ring portion fixedly attached to the inner portion of the shaft or to the inner shaft.

[0135] In one embodiment, the axial length of the at least one axial zone is in the range of 5.0 mm to 15.0 mm, for example, equal to about 8.7 mm or equal to about 13.7 mm, and the outer diameter of the at least one axial zone is in the range of 10 mm to 30 mm or in the range of 15 mm to 25 mm, for example, equal to about 17 mm.

[0136] In one embodiment, the shaft comprises at least two axial sections magnetized in opposite circumferential directions, or at least three axial sections magnetized in alternating circumferential directions, and at least the outer portions of said at least two or at least three axial sections are made of maraging steel (preferably containing 17-19 wt. % nickel) or (e.g., hardened) martensitic stainless steel (preferably containing 12-17 wt. % Cr).

[0137] In one embodiment, the outer portion is / is made of so-called 18Ni maraging steel having a grade of 200 or 250 or 300 or 350, also known as maraging C200, C250, C300 or C350 steel alloy.

[0138] In one embodiment, the outer portion is / is made of a maraging T200 steel alloy, a maraging T250 steel alloy, a maraging T300 steel alloy, or a maraging T350 steel alloy.

[0139] In one embodiment, the outer portion is / is made of steel containing 17-19% by weight nickel and 8-12% by weight nickel.

[0140] In one embodiment, the outer portion is / is made of steel containing 17-19 wt% nickel and 8-12 wt% cobalt, and 3-5 wt% molybdenum.

[0141] In one embodiment, the outer portion is / is made of steel containing 17-19 wt% nickel and 8-12 wt% cobalt, as well as 3-5 wt% molybdenum and 0.2-1.6 wt% titanium.

[0142] In one embodiment, the outer portion is / is made of stainless steel containing 17-19 wt. % nickel and 8-12 wt. % cobalt, as well as 3-5 wt. % molybdenum, 0.2-1.6 wt. % titanium, and at least 0.1 wt. % chromium.

[0143] In one embodiment, the outer portion is / is made of martensitic stainless steel having a 410, 420 or 440 type, preferably a 410 or 420 or 440 type, also referred to as condition H (i.e., hardened).

[0144] In one embodiment, the outer portion is / is made of type 416 or type 440B martensitic stainless steel.

[0145] In one embodiment, the martensitic stainless steel contains 12% to 17% by weight of Cr.

[0146] In one embodiment, the martensitic stainless steel is hardened.

[0147] In one embodiment, the outer portion is / is made of a steel having a coercivity (Hc) of at least 35 Oersted, or at least 40 Oersted, or at least 45 Oersted, such as a maraging steel or a (e.g. hardened) martensitic stainless steel.

[0148] In one embodiment, the distance between two adjacent axial zones (e.g., dA, dB) is a value in the range of 0.5 mm to 1.5 mm, for example equal to about 1.0 mm, the axial lengths (e.g., L1, L2, L3) of said at least two or said at least three axial zones are a value in the range of 5.0 mm to 15.0 mm, for example equal to about 8.7 mm or equal to about 13.7 mm, and the outer diameters of said at least two or said at least three axial zones are a value in the range of 10 mm to 30 mm, or a value in the range of 15 mm to 25 mm, for example equal to about 17 mm.

[0149] In one embodiment, the shaft is a crankshaft (e.g., for an electric bicycle), the shaft having a first end and a second end opposite the first end, each of the first end and the second end having at least one flattened portion, or at least two flattened portions (e.g., opposite each other), or at least four flattened portions (e.g., having a generally square cross-section, optionally with rounded corners).

[0150] Optionally further, each of the first and second ends has an axially extending blind bore having an internal or external thread.

[0151] The flattened portion may be configured for attaching a first crank to a first end of the shaft and a second crank to a second end of the shaft.

[0152] According to a fifth aspect, the present invention also provides an electric bicycle comprising one or more of: i) a magnetoelastic torque sensor system according to the first aspect; ii) a magnetoelastic torque sensor system according to the third aspect; and iii) a shaft according to the fourth aspect.

[0153] In one embodiment, the electric bicycle further comprises a first crank attached to the first end and a second crank attached to the second end.

[0154] Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. [Brief explanation of the drawings]

[0155] [Figure 1A]Illustrative examples of magnetic sensor devices that can be used in embodiments of the present invention are shown in Figure 1A, which is a top view of the magnetic sensor device; [Figure 1B] 1B is a cross-sectional view of the magnetic sensor device of FIG. 1A along line AA. [Figure 2] FIG. 2 is a functional block diagram of the magnetic sensor device of FIGS. 1A and 1B. [Figure 3] 1A and 1B show a flowchart of a method for manufacturing a magnetic sensor device such as that shown in FIGS. [Figure 4A] Illustrated in more detail are various steps of a method that can be used to manufacture a magnetic sensor device such as that shown in FIGS. 1A and 1B. [Figure 4B] Illustrated in more detail are various steps of a method that can be used to manufacture a magnetic sensor device such as that shown in FIGS. 1A and 1B. [Figure 4C] Illustrated in more detail are various steps of a method that can be used to manufacture a magnetic sensor device such as that shown in FIGS. 1A and 1B. [Figure 5] 1B shows an example of a variation of the magnetic sensor device of FIG. 1A having only four terminals that can be used in embodiments of the present invention. [Figure 6A] Examples of other magnetic sensor devices that can be used in embodiments of the present invention are shown below, which include a lead frame, a first (main) semiconductor substrate mounted on the lead frame, and two sensor substrates mounted on top or bottom of the first semiconductor substrate. [Figure 6B] Examples of other magnetic sensor devices that can be used in embodiments of the present invention are shown below, which include a lead frame, a first (main) semiconductor substrate mounted on the lead frame, and two sensor substrates mounted on top or bottom of the first semiconductor substrate. [Figure 6C]Examples of other magnetic sensor devices that can be used in embodiments of the present invention are shown below, which include a lead frame, a first (main) semiconductor substrate mounted on the lead frame, and two sensor substrates mounted on top or bottom of the first semiconductor substrate. [Figure 7] 1 shows an example of another magnetic sensor device that can be used in embodiments of the present invention, the sensor device comprising a lead frame, a first semiconductor substrate attached to the lead frame, and two sensor substrates also attached directly to the lead frame such that the first semiconductor substrate is between the two sensor substrates. [Figure 8A] 8A is an abstract representation of a magnetic sensor device that can be used in the torque sensor system described in Figures 9-19, depicting a magnetic sensor device such as any of those shown in Figures 5-7 and variations thereof, showing its position and orientation relative to the shaft. [Figure 8B] FIG. 20 is a schematic top view of a magnetic sensor device that can be used in the torque sensor system described in FIGS. 9 to 19. [Figure 9] A single packaged sensor device comprising three semiconductor substrates is used to illustrate an illustrative embodiment of the magnetoelastic torque sensor system proposed by the present invention, for example as described in Figures 1 to 7 or variations thereof. [Figure 10] A single packaged sensor device comprising three semiconductor substrates is used to illustrate an illustrative embodiment of the magnetoelastic torque sensor system proposed by the present invention, for example as described in Figures 1 to 7 or variations thereof. [Figure 11] A single packaged sensor device comprising three semiconductor substrates is used to illustrate an illustrative embodiment of the magnetoelastic torque sensor system proposed by the present invention, for example as described in Figures 1 to 7 or variations thereof. [Figure 12]A single packaged sensor device comprising three semiconductor substrates is used to illustrate an illustrative embodiment of the magnetoelastic torque sensor system proposed by the present invention, for example as described in Figures 1 to 7 or variations thereof. [Figure 13] A single packaged sensor device comprising three semiconductor substrates is used to illustrate an illustrative embodiment of the magnetoelastic torque sensor system proposed by the present invention, for example as described in Figures 1 to 7 or variations thereof. [Figure 14] A single packaged sensor device comprising three semiconductor substrates is used to illustrate an illustrative embodiment of the magnetoelastic torque sensor system proposed by the present invention, for example as described in Figures 1 to 7 or variations thereof. [Figure 15] A single packaged sensor device comprising three semiconductor substrates is used to illustrate an illustrative embodiment of the magnetoelastic torque sensor system proposed by the present invention, for example as described in Figures 1 to 7 or variations thereof. [Figure 16] A single packaged sensor device comprising three semiconductor substrates is used to illustrate an illustrative embodiment of the magnetoelastic torque sensor system proposed by the present invention, for example as described in Figures 1 to 7 or variations thereof. [Figure 17] A single packaged sensor device comprising three semiconductor substrates is used to illustrate an illustrative embodiment of the magnetoelastic torque sensor system proposed by the present invention, for example as described in Figures 1 to 7 or variations thereof. [Figure 18] A single packaged sensor device comprising three semiconductor substrates is used to illustrate an illustrative embodiment of the magnetoelastic torque sensor system proposed by the present invention, for example as described in Figures 1 to 7 or variations thereof. [Figure 19] A single packaged sensor device comprising three semiconductor substrates is used to illustrate an illustrative embodiment of the magnetoelastic torque sensor system proposed by the present invention, for example as described in Figures 1 to 7 or variations thereof. [Figure 20]1 shows an illustrative embodiment of a magnetoelastic torque sensor system proposed by the present invention comprising a shaft with three magnetized zones and a magnetic sensor device comprising two sensor substrates and optionally also a processing circuit. [Figure 21] The simulation results of the torque sensor system shown in Fig. 20 are shown. [Figure 22A] A side view is shown. [Figure 22B] FIG. 21 is a front view of a torque sensor system as in FIG. 20 having two magnetic sensor devices circumferentially spaced apart by an angle of 180°. [Figure 23] 19 shows a flowchart of a method for determining torque on a shaft, such as may be used in an arrangement such as illustrated in FIGS. 9-19, according to one embodiment of the present invention. [Figure 24] 2 shows a flowchart of a method for determining torque on a shaft having three magnetized zones, such as may be used in an arrangement such as illustrated in FIGS. 20-22B, according to one embodiment of the present invention. [Figure 25] A graph showing the results of measurements of magnetic field strength measured at a distance of approximately 1 mm from a shaft made of maraging steel or made of (e.g., hardened) martensitic stainless steel, magnetized as illustrated in Figure 21 and having an outer diameter of 17 mm. [Figure 26] 1 shows a 3D view of an illustrative embodiment of a shaft for an electric bicycle.

[0156] The drawings are only schematic and non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes. Any reference signs in the claims should not be construed as limiting the scope. In different drawings, the same reference signs refer to the same or similar elements. DETAILED DESCRIPTION OF THE INVENTION

[0157] The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims.

[0158] Terms such as first, second, and the like in this specification and claims are used to distinguish between similar elements and not necessarily to describe an order, temporally, spatially, sequentially, or in any other manner. Terms so used are interchangeable under appropriate circumstances, and it is understood that embodiments of the invention described herein are capable of operating in orders other than those described or illustrated herein.

[0159] Terms such as top, bottom, and the like in this specification and claims are used for descriptive purposes and not necessarily to describe relative positions. The terms so used are interchangeable under appropriate circumstances, and it is understood that the embodiments of the invention described herein are capable of operation in orientations other than those described or illustrated herein.

[0160] It should be noted that the term "comprising" used in the claims should not be interpreted as being limited to the means listed thereafter, nor does it exclude other elements or steps. Thus, it is interpreted as specifying the presence of stated features, integers, steps or referenced components, but does not exclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to a device consisting of only components A and B. This means that, in the context of the present invention, the only relevant components of the device are A and B.

[0161] References throughout this specification to "an embodiment" or "one embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrase "in one embodiment" or "in one embodiment" in various places throughout this specification do not necessarily all refer to the same embodiment, although they may. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments, as would be apparent to one of ordinary skill in the art from this disclosure.

[0162] Similarly, in describing exemplary embodiments of the invention, it should be understood that various features of the invention may be grouped together in a single embodiment, drawing, or description for the purpose of streamlining the disclosure and facilitating understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

[0163] Furthermore, some embodiments described herein may include some features included in other embodiments but not other features, and as will be understood by those skilled in the art, combinations of features from different embodiments are meant to be within the scope of the present invention and form different embodiments. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0164] In the description provided herein, numerous specific details are set forth. However, it will be understood that embodiments of the present invention may be practiced without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail in order not to obscure an understanding of this description.

[0165] In this document, the abbreviation "RDL" stands for "Redistribution Layer."

[0166] In this document, the abbreviation "IMC" stands for "integrated magnetic concentrator."

[0167] In this document, the abbreviation "SNR" means "signal-to-noise ratio."

[0168] In this document, the abbreviation "MR element" means "magnetoresistive element."

[0169] In this document, the term "magnetic sensor device" or "sensor device" refers to a device comprising three semiconductor substrates integrated in a single package, for example, positioned next to each other or positioned on top of each other.

[0170] In this document, the expressions "axial section of a shaft" and "axial zone of a shaft" mean the same thing and are interchangeable.

[0171] Embodiments of the present invention may typically be described using a Cartesian coordinate system fixed to the sensor device and having three axes X, Y, and Z, with the X and Y axes parallel to the substrate and the Z axis perpendicular to the substrate. The X axis may be defined by the locations of the first and second sensors. Embodiments of the present invention may also be described using a polar coordinate system relative to the shaft, which defines axial, radial, and circumferential directions relative to the shaft. The correspondence between the coordinate systems depends on the relative orientation of the sensor device with respect to the shaft.

[0172] In this document, the expression "substrate primarily comprising silicon" means that at least 50% of the atoms of the substrate are Si atoms. Examples of such substrates are silicon substrates, silicon-on-insulator SoI substrates, bipolar Si substrates, and CMOS substrates.

[0173] In this document, the expressions "the sensor is located near the edge of the magnetized zone" or "the sensor is located in the vicinity of the edge" mean "the sensor is closer to said edge than an imaginary circle in the middle between two edges of said zone", unless it is clear from the context that something else is meant.

[0174] The present invention relates to the field of magnetoelastic torque sensors. Such magnetoelastic torque sensors are based on the reversal of the physical effect of magnetostriction (the deformation of a magnetic material by an applied magnetic field), where a torque acting on a magnetized shaft causes the shaft to twist and, as a result, causes a change in the magnetic field outside the shaft. This change is very sensitive to the degree of torque and can be measured with a magnetic field sensor device.

[0175] Such magnetoelastic torque sensors may be used, for example, in electric bicycles, automotive applications, industrial applications, robotics applications, etc. A typical requirement is that the torque sensor have good accuracy despite the fact that the shaft may only generate a relatively weak magnetic field (e.g., a magnetic field strength of less than 10 mT, or less than 3 mT, or less than 1 mT) even in the presence of a magnetic disturbance field. Due to the variety of applications in which torque sensors may be used, various geometric arrangements are proposed.

[0176] 9 to 19 illustrate various torque sensor systems proposed by the present invention, which comprise a magnetic sensor device including a shaft and two magnetic sensors.

[0177] A variety of shafts can be used. The shaft has at least one axial zone that is circumferentially magnetized. In some embodiments (e.g., as illustrated in Figures 11-15), the shaft has only one axial zone that is circumferentially magnetized. In other embodiments, the shaft has two axial zones that are magnetized in opposite circumferential directions. In still other embodiments (e.g., as illustrated in Figures 18 and 19), the shaft has two axial zones that are magnetized in the same circumferential direction. In still other embodiments (e.g., as illustrated in Figures 20-22B), the shaft has three axial zones that are magnetized in alternating circumferential directions.

[0178] Various magnetic sensor devices can be used, comprising two magnetic sensors S1, S2 spaced apart by a predefined distance dx, which may correspond to the dimensions of one or more axial zones of the shaft.

[0179] Magnetoelastic torque sensors comprising a shaft and a sensor device have been known for over 20 years. While the dimensions of the shaft (for a specific application) have remained largely unchanged over these two decades, the dimensions of the electronics, especially those implemented in CMOS technology, have changed dramatically. In particular, over the years, it has become possible to integrate the magnetic sensor and digital storage and processing circuits on a single semiconductor die, reducing the size of such dies to dimensions of less than approximately 2.0 mm x 2.0 mm. While such a high level of integration and miniaturization is highly desirable in certain technical fields, it does not automatically translate into a good solution in the field of magnetoelastic torque sensors. In fact, the magnetic field generated by the magnetoelastic effect is relatively weak (e.g., the magnetic field strength generated by such a shaft is typically less than 10 mT, or less than 3 mT, or even less than 1 mT).

[0180] The challenge is to provide a cost-effective solution that is highly insensitive to disturbance fields, can be easily attached to the shaft providing good accuracy, and preferably provides all of these (criteria that are very important for high volume, highly competitive markets such as the automotive and / or e-bike industry).

[0181] The solutions proposed by the present invention are novel because they use a novel sensor device, or a novel arrangement of the sensor device relative to the shaft, or both. Alternatively or additionally, the distance dx between the sensor elements may be selected such that the resulting accuracy of the measured torque signal is relatively high (e.g., has a good signal-to-noise ratio SNR), while the mounting requirements (e.g., axial and / or radial) are relatively low.

[0182] Figures 1 to 7 illustrate illustrative embodiments of a sensor device that can be used in the torque sensor system proposed by the present invention, Figures 8A and 8B are abstract representations of such a sensor device, and Figures 9 to 19 illustrate the magnetoelastic torque sensor system proposed by the present invention, where such a sensor device is arranged in a specific way relative to one or two magnetized zones of a shaft.

[0183] The present invention provides a magnetoelastic torque sensor system including a shaft and a magnetic sensor device disposed near the shaft. The shaft has at least one axial section that is circumferentially magnetized. The magnetic sensor device includes three semiconductor substrates, including a first semiconductor substrate (e.g., a CMOS substrate, referred to herein as "main") that includes at least a processing circuit, a second semiconductor substrate (e.g., a GaAs substrate) that includes at least a first magnetic sensor S1, and a third semiconductor substrate (e.g., a GaAs substrate) that includes at least a second magnetic sensor S2. Each magnetic sensor is configured to measure a magnetic field component (e.g., Bx1, Bx2) of a magnetic field generated by the shaft when torque is applied to the shaft. The first substrate, second substrate, and third substrate are integrated into a single packaged device. The first and second magnetic sensors are spaced apart from each other by a predetermined distance (e.g., about 1.5 mm to 25.0 mm). The processing circuitry is configured to determine pairwise differences between the measured field components and output a signal or value indicative of (eg, substantially proportional to) the torque applied to the shaft.

[0184] Providing this sensor device as a single package is advantageous because it ensures accurate distances between sensor locations and simplifies mounting of the packaged device to the shaft rather than mounting individual sensors.

[0185] The inclusion of at least three individual semiconductor substrates in a sensor device is a significant advantage, since they can be fabricated separately, e.g., using different materials and / or different technologies or processes and / or using different "technology scaling." This makes it possible, for example, to combine processing circuits implemented in one material and / or one technology node with sensors implemented in another material and / or another technology node. This also makes it possible, for example, to combine processing circuits implemented in CMOS technology with sensors implemented in GaAs or InAs, or other compound semiconductor materials selected from the III-V group. Such sensors typically have a much higher magnetic sensitivity than CMOS sensors.

[0186] A major advantage of this device is that it allows one substrate (e.g., the processing substrate) to be "shrunk" without necessarily changing the position and / or size of the sensor, which would be the case if the sensor were integrated on the same semiconductor substrate as the processing circuitry.

[0187] Various magnetic sensor devices, e.g. (a) a wafer-level packaged device, as described in more detail in FIGS. 1A-5; or (b) a magnetic sensor device in which a sensor substrate is stacked above or below a first substrate, and the first substrate is attached to a lead frame, as illustrated in, for example, Figures 6A-6C; or (c) a magnetic sensor device comprising a lead frame, wherein each of the first, second, and third substrates is directly attached to the lead frame, for example as illustrated in FIG. 7; Or variations of (a) or (b) or (c) can be used.

[0188] Various shafts and various arrangements of the sensor device relative to the shaft are proposed by the present invention, for example as illustrated in Figures 9-19.

[0189] Referring to the drawings:

[0190] Figures 1A and 1B show an illustrative embodiment of a magnetic sensor device 100. Figure 1A shows a plan view and Figure 1B shows a cross-sectional view of the magnetic sensor device of Figure 1A along line AA.

[0191] The device 100 includes three separate semiconductor substrates: a first substrate 109, also referred to herein as the "main substrate," and two sensor substrates 106a, 106b, each including a magnetic sensor (not explicitly shown).

[0192] The three substrates are surrounded and held in place by a molding compound 101, for example, epoxy, although the invention is not limited thereto.

[0193] For simplicity, each sensor is assumed to be a single horizontal Hall element. However, the present invention is not limited thereto and may include other magnetic sensors, such as two connected horizontal Hall elements, multiple Hall elements optionally connected in series or parallel with an IMC, one or more vertical Hall elements, or a Wheatstone bridge with at least one MR element. As is well known in the art, horizontal Hall elements typically have two "excitation nodes" to which a voltage or current is applied and two "output nodes" at which an output signal, e.g., an output voltage, can be measured, thus requiring a total of four contacts. Similarly, a Wheatstone bridge has two excitation nodes and two output nodes, thus requiring four contacts. Other magnetic sensors (e.g., IMCs with two horizontal Hall elements) may have more than four contacts, as is known in the art. In the example of FIG. 1A , sensor substrate 106a has four contacts, e.g., in the form of bond pads 107a, and sensor substrate 106b has four contacts, e.g., in the form of bond pads 107b. Of course, in other embodiments the number of contacts may be more than four or less than four, for example three.

[0194] The four contacts 107a of the first sensor substrate 106a are electrically connected to four contacts 110a of the main substrate 109 by four electrical interconnects 102a implemented in one or more redistribution layers (RDLs), also referred to herein as "RDL stacks." Similarly, the four contacts 107b of the second sensor substrate 106b are electrically connected to four contacts 110b of the main substrate 109 by four electrical interconnects 102b implemented in the aforementioned one or more RDL layers. In the case of a horizontal Hall element, the main substrate 109 may provide a bias voltage or bias current across two of these contacts and read the sensor signal across the other two contacts. However, of course, more complex biasing and readout schemes may also be used, for example, using so-called spin current techniques.

[0195] 1A, the main substrate 109 also includes a plurality of contacts (e.g., bond pads) 110c that connect via interconnects 102c formed in at least one RDL layer to a plurality of contact zones 103. The contact zones 103 can be used to form external terminals of the packaged device 100, for example, as further described in Figures 4(h) and 4(j) shown in Figure 4C.

[0196] The principles used in device 100 allow different trade-offs to be made between the following conflicting requirements: i) providing a (relatively) small CMOS chip (e.g., having a length "L1" that is smaller than the distance "dx" between the sensors); ii) measuring magnetic field differences or gradients having relatively large magnitudes (e.g., at least 10 mT) by increasing the distance "dx" between the sensors; iii) providing a single packaged device (thus avoiding external wires); In fact, the proposed solution also has the following (optional) advantages: iv) It allows the distance between sensors to be "customized" during the packaging stage without having to redesign any of the three substrates, allowing a much smaller set of solutions to be optimized. v) By using different sensor substrates (eg Ga-As or In-As), it is even possible to use sensors with higher sensitivity than CMOS sensors.

[0197] FIG. 1B shows three semiconductor substrates 109, 106a, and 106b arranged adjacent to each other. In a preferred embodiment, the substrates are arranged so that their "active surfaces" are coplanar, even if the first substrate 109 has a different thickness (in the Z direction) than the sensor substrate. Layers 108a, 111, and 108b are passivation layers on the top of the first sensor substrate 106a, the top of the first substrate 109, and the top of the second sensor substrate 106b, respectively. Layer 104 is the first passivation layer of the RDL stack, and layer 105 is the second passivation layer of the RDL stack. The tracks 102 are preferably copper or aluminum tracks. They provide good electrical and thermal contact between the contact areas (e.g., bond pads) 107a and 107b of the sensor substrates and the contact areas (e.g., bond pads) 110a and 110b of the main substrate 109. The packaged device 100 may have a primarily rectangular shape (as viewed perpendicular to the substrate).

[0198] In the embodiment shown in Figures 1A and 1B, the first substrate 109 is substantially centered between the two sensor substrates 106a, 106b, although this is not absolutely required for the invention to function.

[0199] Figure 2 is an illustrative functional block diagram of the magnetic sensor device of Figures 1A and 1B, which is not a primary aspect of the invention but is provided for completeness.

[0200] In the illustrated embodiment, the packaged device 200 comprises three substrates: a first substrate 209 comprising at least a processing circuit 201, a second substrate 206a comprising a first magnetic sensor S1, and a third substrate 206b comprising a second magnetic sensor S2.

[0201] 2, the first substrate 209 further includes bias and readout circuitry 210 configured to provide a first bias voltage Vbias1 or a first bias current to the first sensor substrate 206a and a second bias voltage Vbias2 or a second bias current to the second sensor substrate 206b. In response, the first sensor substrate 206a provides a first sensor signal s1 to the first substrate 209, and the second sensor substrate 206b provides a second sensor signal s2 to the first substrate 209 for further processing.

[0202] The first board may further comprise one or more of an analog multiplexer, an amplifier for amplifying the first and second signals s1, s2, an analog-to-digital converter ADC, and the like.

[0203] The first substrate 209 may also include a temperature sensor 211 for measuring the temperature of the first substrate 209. This temperature may be used as an indication of the temperature of the first and second sensors S1, S2 and may be used for temperature compensation of the sensor signals. Temperature compensation may be performed in the analog or digital domain.

[0204] In one particular embodiment, when the magnetic sensor is biased with a known current, the temperature of the sensor substrate can also be estimated by measuring the resulting voltage difference across the supply nodes and estimating the resulting power loss.

[0205] In certain embodiments, the first sensor substrate may further comprise a first temperature sensor, the second sensor substrate may further comprise a second temperature sensor, the first sensor substrate will further provide a first temperature signal to the main substrate, and the second sensor substrate will further provide a second temperature signal to the main substrate.

[0206] The bias source (e.g., a voltage source or a current source) may be an independent voltage source or current source, or may be a dependent voltage source or current source, for example, as described in more detail in EP 3 885 779 (A1), which is incorporated herein by reference in its entirety. For purposes of understanding the present disclosure, it is sufficient to say that the sensor signals are temperature compensated (in the analog or digital domain) before the difference between the sensor signals is calculated. As explained in EP 3 885 779 (A1), the difference may be calculated in the analog domain (i.e., before digitization) or in the digital domain (i.e., after digitization). Calculating the difference in the analog domain reduces the risk of saturating the ADC, especially in the presence of disturbance fields.

[0207] The processing circuit 201 may comprise a programmable processor, for example a programmable DSP (Digital Signal Processor).

[0208] The processing circuit 201 also includes a non-volatile memory 203, e.g., a flash memory, for storing programmable instructions for the programmable processor and, optionally, may store at least one constant K. The processing circuit may be further configured to provide an output value derived from the aforementioned difference signal, for example, calculated according to the following formula: Output = K(s1-s2), where s1 is the first sensor signal or a signal derived therefrom (e.g., after amplification, temperature compensation, and digitization), s2 is the second sensor signal or a signal derived therefrom (e.g., after amplification, temperature compensation, and digitization), and K is a predefined constant stored in the non-volatile memory.

[0209] In another or further embodiment, the non-volatile memory may store a predefined function f(), for example in the form of polynomial coefficients or in the form of a table, and the processing circuitry may be further configured to provide an output value as a function of said difference signal, for example calculated according to the formula: output = f(s1 - s2).

[0210] This provides the advantage that the power output can be a measured torque value (expressed in Nm, for example).

[0211] In certain embodiments, the sensor substrate is configured to receive a bias voltage and / or a bias current from the first substrate and provide an output of the sensor circuit (e.g., an output of a Hall plate or an output of a Wheatstone bridge) to the first substrate for further processing.

[0212] In the embodiment shown in FIG. 2, bias and readout circuitry 210 and optional temperature sensor 211 are implemented on the first substrate 209, although at least a portion of the bias and readout circuitry may be implemented on the sensor substrates 206a, 206b, although this is not absolutely required for the invention to function and is generally not preferred.

[0213] In the example shown in FIG. 2, the first substrate 209 has an optional temperature sensor 211, and the sensor substrate does not have a temperature sensor, although it is also possible to provide a temperature sensor on each of the sensor substrates as described above.

[0214] FIG. 3 shows a flow chart of a method 300 for manufacturing a magnetic sensor device such as that shown in FIGS. 1A and 1B. The method 300 includes: a) in step 301, providing a first semiconductor substrate 109 (e.g., a CMOS substrate) having an active surface comprising at least a processing circuit 201 configured to determine a difference between signals obtained from two magnetic sensors S1, S2; b) in step 302, providing a second semiconductor substrate (e.g., GaAs) having an active surface with a first magnetic sensor S1, and providing a third semiconductor substrate (e.g., GaAs) having an active surface with a second magnetic sensor S2; c) in step 303, positioning the first semiconductor substrate 109 at a position between the second semiconductor substrate 106a and the third semiconductor substrate 106b; d) in step 304, electrically connecting the first semiconductor substrate 109 to the second semiconductor substrate 106a and to the third semiconductor substrate 106b by at least one redistribution layer (RDL) or by an RDL stack.

[0215] 4(a)-4(j) in conjunction with FIGS. 4A-4C illustrate in more detail the various steps of a method for manufacturing a magnetic sensor device such as that shown in FIGS. 1A and 1B.

[0216] Before describing the various steps, please note the following. Figure 4(g) shows a plan view with a line AA passing through both sensor substrates 106a, 106b. Figures 4(a) to 4(f) show cross-sectional views along this line AA. - Figure 4(j) shows a plan view with a line BB passing through one sensor substrate 106a and through one terminal contact 103. Figures 4(h) and 4(i) show cross-sectional views along this line BB.

[0217] The various steps can now be described.

[0218] In FIG. 4(a), a carrier substrate 480, for example a glass substrate or a metal substrate, is provided.

[0219] In FIG. 4(b), three semiconductor substrates are provided, including a first semiconductor substrate 109 including at least a processing circuit, a second semiconductor substrate 106a (also referred to as a first sensor substrate) including at least a first sensor S1, and a third semiconductor substrate 106c (also referred to as a second sensor substrate) including at least a second sensor S2. The first substrate 109 is preferably a Si substrate processed using a CMOS-compatible process. The sensor substrates 106a and 106b may be Si substrates compatible with CMOS processes, or Si substrates that are not compatible with CMOS processes but provide magnetic sensor elements with higher sensitivity than CMOS processes, or may include compound semiconductor materials selected from III-V groups, such as Ga—As or In—As. The substrates are placed (e.g., clamped) with their active surfaces facing the carrier substrate 480 so that the first substrate 109 is positioned in the area between the sensor substrates 106a and 106b. A temporary bonding material may be used to temporarily bond the substrates to the carrier substrate. There may be passivation layers 108a, 108b on the active surfaces of the sensor substrates 106a, 106b (not shown here to avoid overloading the drawing, but see, e.g., FIG. 1B), and there may be a passivation layer 111 on the active surface of the first substrate 109 (e.g., shown in FIG. 1B).

[0220] FIG. 4(c) shows the structure of FIG. 4(b) after the substrate has been overmolded with epoxy molding material 101 and after curing.

[0221] Figure 4(d) shows the structure of Figure 4(c) after peeling off the carrier substrate 480 and cleaning off the bonding material. This result is called a "reconstituted wafer." The molding material provides structural strength.

[0222] It is advantageous that the active surfaces of the three substrates lie in the same (virtual) plane, even if the substrates have different thicknesses. This allows many or all of the vias in the redistribution RDL layer to have substantially the same length (in the direction perpendicular to the substrates), which is beneficial for their manufacture. Another advantage is that in some applications, this allows the three substrates to be mounted at the same distance from an external object.

[0223] Figure 4(e) shows the structure of Figure 4(d) after being rotated upside down and providing an electrical insulating layer 104, e.g., a polyimide layer, and then patterning the insulating layer 104 to create openings to provide access to the contact zones (e.g., bond pads) 107a on the first sensor substrate 106a, and openings to the contact zones (e.g., bond pads) 110a, 110c, 110b on the first substrate 109, and openings to the contact zones (e.g., bond pads) 107b on the second sensor substrate 106b.

[0224] FIG. 4(f) shows the structure of FIG. 4(e) after providing a patterned conductive layer (e.g., by patterning a resist and electroplating with copper) to provide electrical connection 102a between aforementioned contact zones 107a and 110a, to provide electrical connection 102b between aforementioned contact zones 107b and 110b, and to create electrical connection 102c, as will be further described.

[0225] Figure 4(h) shows a cross section of the same structure, but through line BB in Figure 4(j). The left side of Figure 4(h) is identical to Figure 4(f), but the right side is different.

[0226] Figure 4(i) shows the structure of Figure 4(h) after applying and patterning an upper passivation layer 105, e.g., a second polyimide layer, which forms openings to provide access to the contact zones 103 formed by the electrical interconnects 102c. A noble metal (e.g., silver or gold) may be provided over these contact zones 103, thereby forming the external terminals of the packaged device.

[0227] It should be noted that although Figures 4(a)-4(j) show just one sensor device, in practice this process is performed at the wafer level, meaning that a relatively large number of sensor devices are formed simultaneously when performing the steps shown in Figures 4(a)-4(j). The method typically also includes a singulation step, for example by sawing or by laser cutting the wafer into individual sensor devices.

[0228] Figure 5 shows another embodiment of a magnetic sensor device 500, which can be seen as a variation of the magnetic sensor device 100 shown in Figures 1A and 1B. The main difference between the sensor device 500 of Figure 5 and the sensor device 100 of Figures 1A and 1B is that the sensor device 500 has only four terminals 503. These terminals can be used, for example, to provide a supply voltage (e.g., VDD), a reference voltage (e.g., GND), and an output port or a communication interface (e.g., a serial communication interface).

[0229] In certain embodiments of the sensor device 500 of FIG. 5, the main board 509 may further include a temperature sensor configured to measure the temperature of the main board, and the processing circuitry may be configured to use this temperature as an estimate of the temperature of the sensor board and to perform temperature correction of the signal obtained from the sensor based on this single temperature.

[0230] In one particular embodiment of the sensor device 500 of FIG. 5 , the main substrate 509 may further include two temperature sensors: one temperature sensor T1 located near a contact zone (e.g., a bond pad) connected to the first sensor substrate 506 a, and one temperature sensor T2 located near a contact zone (e.g., a bond pad) connected to the second sensor substrate 506 b. By placing the temperature sensors near the contact zones connected to the respective sensor substrates, the measured temperatures can be used to estimate the temperature of the sensor substrates and the signals can be corrected accordingly. This technique allows for temperature differences between the two sensor substrates to be corrected. Having the temperature sensors implemented on the main substrate has the advantages, among others, of (i) keeping the area of ​​the (typically more expensive) sensor substrate small and (ii) keeping the number of interconnects between the main substrate and the sensor substrate small.

[0231] In one particular embodiment of the sensor device 500 of FIG. 5, each sensor substrate further comprises a temperature sensor (not shown), the sensor substrate is further configured to provide a temperature signal to the first substrate, and the processing circuitry is further configured to correct the signal obtained from the magnetic sensor using the measured temperature signal.

[0232] In one particular embodiment, when the magnetic sensor is biased with a known current, the temperature of the sensor substrate can also be estimated by measuring the resulting voltage difference across the supply nodes and estimating the resulting power loss.

[0233] The two sensor substrates 506a, 506b may each include a magnetic sensor (not explicitly shown) capable of measuring a magnetic field component in the Z direction, and the processing circuitry may be configured to further process the two sensor signals Bz1, Bz2. Such sensor devices may be used in torque sensor systems, for example, as illustrated in Figures 9, 11, 15, and 18.

[0234] The two sensor substrates 506a, 506b may each include a magnetic sensor (not explicitly shown) capable of measuring a magnetic field component in the X direction, and the processing circuitry may be configured to further process the two sensor signals Bx1, Bx2. Such sensor devices may be used in torque sensor systems, for example, as illustrated in Figures 10, 12, 14, and 17.

[0235] The two sensor substrates 506a, 506b may each include a magnetic sensor (not explicitly shown) capable of measuring a magnetic field component in the Y direction, and the processing circuitry may be configured to further process the two sensor signals By1, By2. Such sensor devices may be used in torque sensor systems, for example, as illustrated in Figures 13, 16, and 19.

[0236] While the sensor substrates are shown in Figure 5, the magnetic sensors themselves (e.g., horizontal Hall plate, vertical Hall plate, Wheatstone bridge with MR sensor elements) are not shown because Figure 5 is relevant not to the magnetic sensor elements or structure, but rather to show how the sensor substrates 506a, 506b are interconnected to the main substrate 509. Indeed, any suitable magnetic sensor could be used, for example, with only horizontal Hall elements, or with only vertical Hall elements, or with only MR elements (e.g., AMR or XMR elements), or with GMI sensors. However, because the magnetic field generated by the shaft is typically very weak, the sensor substrates 506a, 506b are preferably made with a semiconductor technology (not CMOS-compliant) that offers greater sensitivity than CMOS sensors.

[0237] It is also worth mentioning that the sensor substrates 506a, 506b are larger than the magnetic sensors themselves, as they need to provide several contact zones (e.g., bond pads) to allow, among other things, connection of the sensor substrates to the main substrate 509.

[0238] 6A-6C show examples of other magnetic sensor devices 600, 600', 600" that can be used in embodiments of the torque sensor system proposed by the present invention. These sensor devices comprise a lead frame, a first semiconductor substrate 609, 609', 609" mounted on the lead frame, and two sensor substrates 606a and 606b, 606a' and 606b', 606a" and 606b", with the top of the first semiconductor substrate 609, 609', 609" attached to the bottom and connected thereto by bond wires. The arrangement is then preferably overmolded with a molding compound 601, 601', 601" to form a single packaged device, using, for example, epoxy.

[0239] The sensor substrates illustrated in Figures 6A-6C may include various types of magnetic sensors, for example, as described above (with respect to Figure 5), including only horizontal Hall elements, or only vertical Hall elements, or only MR elements.

[0240] In another or further embodiment, the main board illustrated in Figures 6A-6C may be equipped with non-volatile memory and may include a look-up table having at least one constant value or values ​​that can be used (e.g., interpolated) to convert the magnetic difference signal to a torque value.

[0241] In another or further embodiment, the first substrate 609, 609′, 609″ illustrated in FIGS. 6A-6C may comprise one temperature sensor to measure the temperature of the main substrate and use this as an estimate of the temperature of the sensor substrate to correct the signal obtained from the sensor substrate for temperature variations by optionally further taking into account an estimate of the power dissipated by the sensor substrate. The latter can be determined by providing a known bias voltage Vbias and measuring the bias current Ibias, or vice versa.

[0242] In another or further embodiment, the main substrates 609, 609', 609" illustrated in Figures 6A-6C may include two temperature sensors (schematically designated T1, T2) each positioned near a contact zone (e.g., bond pad) connected to a respective sensor substrate for measuring a temperature indicative of the temperature of each sensor substrate, and the processing circuitry may be configured to use these two temperature signals to correct the signals obtained from the sensor substrates.

[0243] In another or further embodiment, each sensor board may include a temperature sensor, and the sensor board may be further configured to provide temperature signals to the first board, and the processing circuitry of the first board may be further configured to temperature compensate the signals obtained from the magnetic sensors taking these temperature signals into account.

[0244] 7 shows an example of another magnetic sensor device 700 that can be used in embodiments of the present invention. The sensor device 700 comprises a lead frame 720, a first semiconductor substrate 709 (also referred to as a "main substrate") mounted on the lead frame 720, and two sensor substrates 706a, 706b also mounted on top of the lead frame, such that the first semiconductor substrate 709 is between the two sensor substrates 706a, 706b on the same side of the lead frame. Preferably, the substrates and bond wires as well as a portion of the lead frame are then overmolded (not shown for purposes of illustration).

[0245] The first substrate 709 may be connected to the first and second sensor substrates 706a, 706b by bond wires either directly (as shown) or indirectly through certain leads of a lead frame (not shown) connected to the sensor substrates at one location and to the first substrate at another location, which is particularly useful for relatively large values ​​of the distance dx between sensors S1, S2.

[0246] The lead frame shown in FIG. 7 has only a very simple layout, but of course the invention is not limited to this and other lead frames can also be used.

[0247] In the example shown in Figure 7, the two sensor substrates 706a, 706b are positioned approximately halfway (in the Y direction) on the main substrate 709, although this is not necessary for the invention to function. In fact, in some embodiments it may be better to move the sensor substrates so that they are aligned with the edges of the main substrate 709, so that the sensors are closer to the shaft, as in Figures 16 and 17, for example.

[0248] The sensor substrate illustrated in FIG. 7 may comprise various types of magnetic sensors, for example, as described above (with respect to FIG. 5), comprising only horizontal Hall elements, or only vertical Hall elements, or only MR elements.

[0249] In another or further embodiment, the main board illustrated in Figures 6A-6C may be equipped with non-volatile memory and may include a look-up table having at least one constant value or values ​​that can be used (e.g., interpolated) to convert the magnetic difference signal to a torque value.

[0250] 6A-6C may include a temperature sensor to measure the temperature of the main board and use this as an estimate of the temperature of the sensor board to optionally correct the signal obtained from the sensor board by further taking into account an estimate of the power dissipated by the sensor board, which may be determined by providing a known bias voltage Vbias and measuring the bias current Ibias, or vice versa.

[0251] In another or further embodiment, the main substrate illustrated in Figures 6A-6C may be configured to include two temperature sensors each positioned near a contact zone (e.g., bond pad) connected to a respective sensor substrate, and to use these two temperature signals to measure a temperature indicative of the temperature of each sensor substrate, and to correct the signals obtained from the sensor substrates not only for temperature fluctuations, but also for temperature differences between the two sensor substrates.

[0252] In another or further embodiment, each sensor board may include a temperature sensor, and the sensor board may be further configured to provide temperature signals to the first board, and the processing circuitry of the first board may be further configured to temperature compensate the signals obtained from the magnetic sensors taking these temperature signals into account.

[0253] Of course, the embodiments shown in Figures 5-7 are merely examples, and variations of these examples may have other characteristics than those shown in Figures 5-7, such as a different number of external terminals, or package pins, or dimensions.

[0254] 8A and 8B are abstract representations of a magnetic sensor device that can be used in the torque sensor system proposed by the present invention and further described in FIGS. 9-19. As mentioned above, this abstract representation can cover various types of magnetic sensor devices comprising three individual semiconductor substrates in a single package, which substrates can be positioned adjacent to each other or on top of each other. At least the following embodiments are contemplated: (a) a wafer-level packaged device, for example, as illustrated in FIGS. 1A-5; (b) a magnetic sensor device in which a sensor substrate is stacked on top of or on top of a first substrate, the latter being attached to a lead frame, for example, as illustrated in FIGS. 6A-6C; and (c) a magnetic sensor device comprising a lead frame, with each of the first, second, and third substrates directly attached to the lead frame, for example, as illustrated in FIG. 7.

[0255] The main purpose of this abstract representation is to show that the device has a first magnetic sensor S1 and a second magnetic sensor S2 spaced apart along the X direction by a predetermined distance dx. The abstract representation of the side or top view makes it possible to clearly specify the position and orientation of the magnetic sensor devices relative to the shaft in the torque sensor system and its variants which will now be described in Figures 9 to 19.

[0256] 9-19 show illustrative examples of magnetoelastic torque sensor systems proposed by the present invention, such as those described in FIGS. 1-7, using a single packaged sensor device with three semiconductor substrates. As noted above, in these figures, the magnetic sensor device is represented by the abstract representations of FIGS. 8A and 8B, which, for illustrative purposes, may be any of the sensor devices described in FIGS. 1-7 or variations thereof. Thus, although the two magnetic sensors S1, S2 of the magnetic sensor device shown in FIGS. 9-19 are shown next to a first substrate labeled "main," the present invention is not limited thereto and also covers embodiments in which the two sensor substrates are attached to the top or bottom of the main substrate (e.g., as illustrated in FIGS. 6A-6C). Important to the present invention is that the magnetic sensor device is a single packaged device comprising three semiconductor substrates (i.e., not a single monolithic semiconductor substrate containing processing circuitry and the magnetic sensor), regardless of whether the first semiconductor substrate is mounted between the second and third semiconductor substrates (e.g., as illustrated in Figures 1-5 or 7), or whether the sensor substrate is mounted on top or bottom of the first substrate (e.g., as illustrated in Figures 6A-6C). In all of these embodiments, the active surfaces of the three substrates are oriented parallel.

[0257] 9 shows an illustrative embodiment of a magnetoelastic torque sensor system 970 comprising a shaft 973 having two axial zones 971, 972 magnetized in opposite circumferential directions, and a magnetic sensor device 900 having two magnetic sensors S1, S2 spaced a predefined distance dx along an X-axis parallel to the shaft 973. As noted above, such shafts are known in the art and therefore need not be described in further detail here. Suffice it to say that the shaft may comprise a material that is itself magnetized, for example a steel alloy, or the shaft may comprise one or more magnetic rings fixedly attached to the shaft such that torque is transmitted from the shaft to the rings.

[0258] The sensor device 900 is oriented such that the normal (Z) to the substrate is oriented radially relative to the shaft 973. Two sensors S1, S2 are located axially near the edges (or ends) 975, 977 of the magnetized zones 971, 972, and measure magnetic field components Br1, Br2 oriented radially of the shaft. These magnetic field components may also be referred to as Bz1, Bz2 in a Cartesian coordinate system connected to the sensor device 900, where the X axis is defined by an imaginary line passing through the two sensors S1, S2, the Z axis is perpendicular to the three substrates, and the Y axis is perpendicular to the X and Z axes.

[0259] Each of the sensors S1 and S2 may comprise one or more horizontal Hall elements (preferably without an integrated magnetic concentrator), for example, as few as one horizontal Hall element, or two horizontal Hall elements connected in series or in parallel, or four horizontal Hall elements, for example, two horizontal Hall elements biased orthogonally with respect to each other.

[0260] Assuming that the first axial zone 971 has an axial length L1, the second axial zone 972 has a second axial length L2, and the two axial zones are spaced apart by a distance L3, the distance dx between the centers of the two sensors S1 and S2 is preferably equal to (L1 + L3) with a tolerance margin of ±10%, ±5%, or ±2%. Preferably, the first sensor S1 and the second sensor S2 are slightly offset from the respective edges (or ends) 975 and 977 of the magnetized zones 971 and 972 by a distance ε having a value in the range of 0 to 20% of L1, or a value in the range of 3% to 15% of L1, e.g., a value equal to about 10% of L1, to reduce the effect of mounting position offsets (e.g., axial mounting offsets) and / or to enable easier mechanical assembly. In FIG. 9, the offset is inward (i.e., toward the center of the magnetized zones), but the invention is not limited thereto and outward offsets are also possible.

[0261] The processing circuitry of the magnetic sensor device 900 is adapted to determine a difference signal ΔBz between the magnetic field components Bz1, Bz2 according to the formula ΔBz=(Bz1-Bz2). and is configured to output a signal or value indicative of the torque applied to the shaft. The processing circuitry may be configured to determine a value of the torque T applied to the shaft as a predefined function of this difference signal, for example according to the following equation: T=f9(ΔBz), where f9 is a predefined function, for example a cubic, quadratic or first order polynomial function of (ΔBz). The function may be stored in a suitable manner in a non-volatile memory of the processing device, for example by coefficients of a polynomial function or in the form of a look-up table. By determining a signal indicative of the torque as a function of the magnetic field difference, the effect of external disturbance fields is greatly reduced or eliminated.

[0262] In a preferred embodiment, the torque T is calculated as a value proportional to the magnetic field difference ΔBz, for example, according to the following formula: T=K9*(ΔBz), where K9 is a predefined constant that may be determined, for example, by a calibration test performed during production, and that may be written to the aforementioned non-volatile memory in the sensor device 900. For example, for a sensor device manufactured using the method described in FIGS. 1A-4, the value of K9 may be written to the non-volatile memory at wafer level before cutting or sawing the wafer.

[0263] The sensor device 900 is preferably mounted to the shaft 973 such that the distance d1 between the outer surface of the shaft and the sensor elements S1, S2 is less than 10.0 mm, or less than 8 mm, or less than 5.0 mm. In preferred embodiments, the radial distance "g" between the shaft and the packaging device 900 is at least 0.1 mm, or at least 0.3 mm, or at least 0.5 mm. The radial distance d1 between the shaft and the active surface of the sensor may be at least 0.2 mm, or at least 0.4 mm, or at least 0.5 mm, or at least 0.8 mm, for example, equal to about 1.0 mm, or equal to about 2.0 mm, or equal to about 3.0 mm.

[0264] 9 (not shown), the device is mounted "upside down," i.e., device 900 is oriented so that the active surface of the sensor substrate is oriented toward the shaft. This may allow the distance "d1" to be reduced.

[0265] In a variation of FIG. 9 (not shown), the shaft has only one axial zone that is circumferentially magnetized, e.g., zone 971 is present and zone 972 is not. In this case, the first sensor S1 would still be positioned relative to axial zone 971 as illustrated in FIG. 9 and would measure a signal Bz1 indicative of the magnetic field induced by torque plus a disturbance field (if present), while the second sensor S2 would measure only the disturbance field (if present). This embodiment offers the advantage of making the shaft easier to manufacture, but the amplitude of the difference signal ΔBz is typically only half that of FIG. 9, and therefore the signal-to-noise ratio (SNR) of this signal will be slightly worse than that of FIG. 9. The formula T=K*(ΔBz) can also be used in this case, although the value of K may typically be twice the value of K9 in FIG. 9.

[0266] Figure 10 shows an illustrative embodiment of a magnetoelastic torque sensor system 1070, which can be seen as a variation of the system 900 shown in Figure 9. The system 1000 comprises a shaft 1073 identical to the shaft 973 of Figure 9, and a magnetic sensor device 1000 having two magnetic sensors S1, S2 spaced a predefined distance dx along an X-axis that is parallel to the shaft 1073.

[0267] The sensor device 1000 is oriented such that the normal (Z) to the substrate is oriented radially with respect to the shaft 1073. Two sensors S1, S2 are located axially near the middle of the magnetized zones 1071, 1072. The two sensors S1, S2 measure magnetic field components Ba1, Ba2 oriented in the axial direction of the shaft 1073. These magnetic field components may also be referred to as Bx1, Bx2 in a Cartesian coordinate system connected to the sensor device 1000.

[0268] Each of sensors S1 and S2 may comprise an integrated magnetic concentrator and two horizontal Hall elements positioned near the periphery of its IMC and located on the X-axis, or may comprise one or more vertical Hall elements oriented with their axes of greatest sensitivity aligned in the X-direction, or may comprise one or more magnetoresistive (MR) elements positioned to measure magnetic field components oriented in the X-direction.

[0269] Assuming that the first axial zone 1071 has an axial length L1, the second axial zone 1072 has a second axial length L2, and the two axial zones are spaced apart by a distance L3, preferably the distance dx between the centers of the two sensors S1, S2 is equal to [L3 + (L1 + L2) / 2] with a tolerance margin of ±10%, ±5%, or ±2%. Preferably, the first sensor S1 and the second sensor S2 are offset from the respective edges (or ends) of the magnetized zones 1071, 1072 by a distance μ having a value in the range of 40% to 60% of L1, or in the range of 45% to 55% of L1, for example equal to about 50% of L1.

[0270] The processing circuitry of the magnetic sensor device 1000 is adapted to determine a difference signal ΔBx between the magnetic field components Bx1, Bx2 according to the formula ΔBx=(Bx1-Bx2). and is configured to output a signal or value indicative of the torque applied to the shaft. The processing circuitry may be configured to determine a value of the torque T on the shaft as a predefined function of this difference signal, for example according to the following equation: T=f10(ΔBx), where f10 is a predefined function, for example a cubic, quadratic or first order polynomial function of (ΔBx). The function may be stored in a suitable manner in the non-volatile memory of the sensor device 1000, for example by coefficients of a polynomial function or in the form of a look-up table. By determining a signal indicative of the torque as a function of the magnetic field difference, the effect of external disturbance fields is greatly reduced or eliminated.

[0271] In a preferred embodiment, the torque T is calculated as a value proportional to the magnetic field difference ΔBx, for example according to the following formula: T=K10*(ΔBx), where K10 is a predefined constant that may be written into the aforementioned non-volatile memory in the sensor device 1000, for example during manufacturing or a calibration procedure.

[0272] Similar distances d1 and g may be used as described in FIG.

[0273] 10 (not shown), the device is mounted "upside down," i.e., the device 1000 is oriented so that the active surface of the sensor substrate is oriented toward the shaft. This may allow the distance "d1" to be reduced.

[0274] In a variation of FIG. 10 (not shown), the shaft has only one axial zone that is circumferentially magnetized, e.g., zone 1071 is present and zone 1072 is not. In this case, the first sensor S1 would still be positioned relative to axial zone 1071 as illustrated in FIG. 10 and would measure a signal Bx1 indicative of the magnetic field induced by torque plus a disturbance field (if present), while the second sensor S2 would measure only the disturbance field (if present). This embodiment offers the advantage of making the shaft easier to manufacture, but the amplitude of the difference signal ΔBx would typically be only half that of FIG. 10, and therefore the signal-to-noise ratio (SNR) of this signal would be slightly worse than that of FIG. 10. The formula T=K*(ΔBx) could also be used in this case, although the value of K would typically be twice the value of K10 in FIG. 10.

[0275] FIG. 11 shows an illustrative embodiment of a magnetoelastic torque sensor system 1170 comprising a shaft 1173 having only one axial zone 1171 that is circumferentially magnetized (or having two magnetized zones but only one is used) and a magnetic sensor device 1100 having two magnetic sensors S1, S2 spaced a predefined distance dx along an X-axis that is parallel to the shaft 1173.

[0276] The torque sensor system 1100 of FIG. 11 can be considered another variation of the torque sensor system of FIG. 9, and much of what was discussed above is also applicable here.

[0277] The sensor device 900 is oriented such that the normal (Z) to the substrate is oriented radially relative to the shaft 1173. The two sensors S1, S2 are axially positioned near the edges (or ends) 1175, 1176 of the magnetized zone 1171, and preferably between those edges.

[0278] The magnetic field components measured by sensors S1, S2 can be referred to as Br1, Br2 relative to the shaft 1173 or Bz1, Bz2 relative to the sensor device 1100.

[0279] The magnetized zone 1171 has an axial length L1. Preferably, the first sensor S1 and the second sensor S2 are slightly offset from the edge of the magnetized zone 1171 by a distance ε having a value in the range of 0-20% of L1, or a value in the range of 3%-15% of L1, for example, a value equal to approximately 10% of L1, to reduce the effect of mounting position offsets. Preferably, the distance dx between the centers of the two sensors S1, S2 is equal to (L1-2*ε) with a tolerance margin of ±10%, ±5%, or ±2%. Alternatively, the sensors are shifted outward by the aforementioned offset ε, in which case the distance dx between the centers of the two sensors S1, S2 is equal to approximately (L1+2*ε) with a tolerance margin of ±10%, ±5%, or ±2%.

[0280] The processing circuitry of the magnetic sensor device 1100 is adapted to determine a difference signal ΔBz between the magnetic field components Bz1, Bz2 according to the formula ΔBz=(Bz1-Bz2). and is configured to output a signal or value indicative of the torque applied to the shaft. The processing circuitry may be configured to determine a value T of the torque applied to the shaft as a predefined function of this difference signal, for example according to the following equation: T=f11(ΔBz), where f11 is a predetermined function of the magnetic field difference. In a preferred embodiment, the torque T is calculated as a value proportional to the magnetic field difference ΔBz, for example according to the following equation: T=K11*(ΔBz), where K11 is a predefined constant. The value of K11 may be hard-coded or may be stored in non-volatile memory within the sensor device 1100, for example during manufacturing or a calibration procedure.

[0281] As mentioned above, similar distances between the shaft and the sensor device are also applicable here. In a variation of Figure 11 (not shown), the device is mounted "upside down".

[0282] FIG. 12 shows an illustrative embodiment of a magnetoelastic torque sensor system 1270 comprising a shaft 1273 having only one axial zone 1271 that is circumferentially magnetized (or having two magnetized zones but only one is used) and a magnetic sensor device 1200 having two magnetic sensors S1, S2 spaced a predefined distance dx along an X-axis that is radially oriented relative to the shaft 1273.

[0283] The torque sensor system 1200 of FIG. 12 can be considered a variation of the torque sensor system 1000 of FIG. 10, in which the sensor device is rotated 90° about its Y axis and then 90° about its X axis, the shaft has only one magnetized zone, and the sensor device is shifted to an axial position near the end 1275 of the magnetized zone 1273.

[0284] The sensor device 1200 is preferably oriented such that the normal (Z) to the substrate is oriented circumferentially with respect to the shaft 1273. The two sensors S1, S2 are in an axial position between the two edges of the magnetized zone 1271 and relatively close to one of the edges 1275. In a variant (not shown), the axial position of the sensors is slightly outside the magnetized zone 1271.

[0285] The magnetic field components measured by sensors S1, S2 can be referred to as Br1, Br2 relative to shaft 1273 or Bx1, Bx2 relative to sensor device 1200.

[0286] The magnetized zone 1271 has an axial length L1. Preferably, the axial positions of the first sensor S1 and the second sensor S2 are slightly offset from one of the edges 1275 of the magnetized zone 1271 by a distance ε having a value in the range of 0-20% of L1, or a value in the range of 3%-15% of L1, for example a value equal to about 10% of L1, in order to reduce the effect of mounting position offsets and / or to allow easier mechanical assembly. In Fig. 11, the offset is inward (i.e., towards the center of the magnetized zone), but the invention is not limited thereto and an outward offset is also possible.

[0287] The distance dx between the centers of the two sensors S1, S2 can be selected substantially independently of the length L1, but may be selected depending on the distance "g" between the shaft 1273 and the packaging of the sensor device 1200, and hence the distances d1, d2 between the shaft and the first and second sensors S1, S2. The smaller the value of d1 and the larger the value of d2, the larger the value of ΔBx for a given torque on the shaft.

[0288] In preferred embodiments, the radial distance "g" between the shaft and packaging device 900 is at least 0.1 mm, or at least 0.3 mm, or at least 0.5 mm, and at most 5.0 mm. The radial distance d1 between the shaft and sensor device 1200 is preferably at most 5.0 mm, or at most 4.0 mm, or at most 3.0 mm, or at most 2.0 mm, or at most 1.0 mm. Preferably, the distance dx between sensors S1 and S2 is at least twice d1 (dx≧2*d1), or at least three times d1 (dx≧3*d1), or at least four times d1 (dx≧4*d1), or at least five times d1 (dx≧5*d1).

[0289] The processing circuitry of the magnetic sensor device 1200 is adapted to determine a difference signal ΔBx between the magnetic field components Bx1, Bx2 according to the equation ΔBx=(Bx1-Bx2): and is configured to output a signal or value indicative of the torque applied to the shaft. The processing circuitry may be configured to determine a value of the torque T applied to the shaft as a predefined function of this difference signal, for example according to the following equation: T=f12(ΔBx), where f12 is a predefined function of the magnetic field difference ΔBx. In a preferred embodiment, the torque T is calculated as a value proportional to the magnetic field difference ΔBx, for example according to the following equation: T=K12*(ΔBx), where K12 is a predefined constant. The value of K12 may be stored in non-volatile memory within the sensor device 1200, for example during manufacturing or during a calibration procedure.

[0290] FIG. 13 shows an illustrative embodiment of a magnetoelastic torque sensor system 1370 comprising a shaft 1373 having only one axial zone 1371 that is circumferentially magnetized (or having two magnetized zones but only one is used) and a magnetic sensor device 1300 having two magnetic sensors S1, S2 spaced a predefined distance dx along an X-axis that is radially oriented relative to the shaft 1373.

[0291] At first glance, the torque sensor system 1300 of FIG. 13 may appear to be a variation of the torque sensor system 1200 of FIG. 12, with the sensor device shifted in an axial position towards the center of the magnetization zone 1371, but in fact it is a different sensor device because the sensors S1, S2 of this sensor device 1300 are configured to measure the magnetic field components Ba1, Ba2 parallel to the shaft or the magnetic field components By1, By2 relative to the sensor device.

[0292] Each of sensors S1 and S2 may comprise an integrated magnetic concentrator and two horizontal Hall elements positioned near the periphery of its IMC and lying on an imaginary line parallel to the Y axis, or may comprise one or more vertical Hall elements oriented with their axes of greatest sensitivity aligned in the Y direction, or may comprise one or more magnetoresistive (MR) elements positioned to measure magnetic field components oriented in the Y direction.

[0293] The sensor device 1300 is preferably oriented such that the normal (Z) to the substrate is oriented circumferentially with respect to the shaft 1373. The two sensors S1, S2 are axially positioned between two edges 1375, 1376 of the magnetized zone 1371 near the center of the magnetized zone 1371. More specifically, if the magnetized zone 1371 has an axial length L1, the axial positions of the first sensor S1 and the second sensor S2 are preferably offset from one of the edges 1375 of the magnetized zone 1371 by a distance μ having a value in the range of 40% to 60% of L1, or having a value in the range of 45% to 55% of L1, for example a value equal to about 50% of L1.

[0294] The distance dx between the centers of the two sensors S1, S2 can be selected substantially independently of the length L1, but may be selected depending on the distance between the shaft and the packaging of the sensor device 1300, and thus depending on the distances d1, d2 between the shaft and the first and second sensors S1, S2. The smaller the value of d1 and the larger the value of d2, the larger the value of ΔBy for a given torque applied to the shaft. Similar distances "d1", "g", and "dx" may be used as described in FIG. 12.

[0295] The processing circuitry of the magnetic sensor device 1300 is adapted to determine a difference signal ΔBy between the magnetic field components By1, By2 according to the equation ΔBy=(By1-By2): and is configured to output a signal or value indicative of the torque applied to the shaft. The processing circuitry may be configured to determine a value of the torque T applied to the shaft as a predefined function of this difference signal, for example according to the following equation: T=f13(ΔBy), where f13 is a predefined function of the magnetic field difference. In a preferred embodiment, the torque T is calculated as a value proportional to the magnetic field difference ΔBy, for example according to the following equation: T=K13*(ΔBy), where K13 is a predefined constant. The value of K13 may be stored in non-volatile memory within the sensor device 1300, for example during manufacturing or during a calibration procedure.

[0296] FIG. 14 shows an illustrative embodiment of a magnetoelastic torque sensor system 1470 comprising a shaft 1473 having only one axial zone 1471 that is circumferentially magnetized (or having two magnetized zones but only one is used) and a magnetic sensor device 1400 having two magnetic sensors S1, S2 spaced a predefined distance dx along an X-axis that is radially oriented relative to the shaft 1473.

[0297] The torque sensor system 1400 of FIG. 14 can be considered a variation of the torque sensor system 1200 of FIG. 12 in which the sensor device is rotated 90° about its X-axis.

[0298] In Figure 14, the sensor device 1400 is oriented such that the normal (Z) to the substrate is oriented in the axial direction of the shaft 1473. Everything else described for the torque sensor system of Figure 12 and its variations is also applicable here.

[0299] 12 and 14, the sensor device 1400 rotates at any angle around the X-axis. In all of these embodiments, the same magnetic field components Br1, Br2 relative to the shaft or Bx1, Bx2 relative to the sensor device 1400 are measured. In all of these embodiments, the torque can be calculated according to the following formula: T=f14(ΔBx), e.g., T=K14*(ΔBx), where K14 is a predefined constant that can be stored in non-volatile memory.

[0300] FIG. 15 shows an illustrative embodiment of a magnetoelastic torque sensor system 1570 comprising a shaft 1573 having only one axial zone 1571 that is circumferentially magnetized (or having two magnetized zones but only one is used) and a magnetic sensor device 1500 having two magnetic sensors S1, S2 spaced a predefined distance dx along an X-axis that is radially oriented relative to the shaft 1573.

[0301] At first glance, the torque sensor system 1570 of FIG. 15 may appear to be a variation of the torque sensor system 1370 of FIG. 13 in which the sensor device is rotated 90° about the X-axis, but in fact it is a different sensor device because the sensors S1, S2 of this sensor device 1500 are configured to measure magnetic field components Ba1, Ba2 or Bz1, Bz2 that are parallel to the shaft in a direction perpendicular to the sensor device, i.e., the substrate.

[0302] The sensor device 1500 is preferably oriented such that the normal (Z) to the substrate is axially oriented relative to the shaft 1573. The two sensors S1, S2 are axially positioned between two edges 1575, 1576 of the magnetized zone 1571 near the center of the magnetized zone 1571. More specifically, if the magnetized zone 1571 has an axial length L1, the axial positions of the first sensor S1 and the second sensor S2 are preferably offset from one of the edges 1575 of the magnetized zone 1571 by a distance μ having a value in the range of 40% to 60% of L1, or having a value in the range of 45% to 55% of L1, for example a value equal to about 50% of L1.

[0303] The distance dx between the centers of the two sensors S1, S2 can be selected substantially independently of the length L1, but may also be selected depending on the distance "g" between the shaft and the packaging of the sensor device 1500, and hence the distances d1, d2 between the shaft and the first and second sensors S1, S2. The smaller the value of d1 and the larger the value of d2, the larger the value of ΔBz for a given torque on the shaft.

[0304] The values ​​for the radial distance "g", the radial distance "d1", and the ratio (dx / d1) described with reference to FIG. 12 are also applicable here.

[0305] The processing circuitry of the magnetic sensor device 1500 is adapted to determine a difference signal ΔBz between the magnetic field components Bz1, Bz2 according to the formula ΔBz=(Bz1-Bz2). and is configured to output a signal or value indicative of the torque on the shaft. The processing circuitry may be configured to determine a value T of the torque on the shaft as a predefined function of this difference signal, for example according to the following formula: T=f15(ΔBz), where f15 is a predefined function of the magnetic field difference. In a preferred embodiment, the torque T is calculated as a value proportional to the magnetic field difference ΔBz, for example according to the following formula: T=K15*(ΔBz), where K15 is a predefined constant. The value of K15 may be stored in non-volatile memory within the sensor device 1500.

[0306] FIG. 16 shows an illustrative embodiment of a magnetoelastic torque sensor system 1670 comprising a shaft 1673 having two axial zones 1671, 1672 that are magnetized in opposite circumferential directions, and a magnetic sensor device 1600 having two magnetic sensors S1, S2 spaced a predefined distance dx along an X-axis that is parallel to the shaft 1673.

[0307] While the torque sensor system 1600 of FIG. 16 may at first glance appear to be a variation of the torque sensor system 900 of FIG. 9 in which the sensor device is rotated 90° relative to the X-axis, it is in fact a different sensor device because the sensors S1, S2 of this sensor device 1600 are configured to measure magnetic field components Br1, Br2 oriented radially relative to the shaft, or magnetic field components By1, By2 oriented relative to the sensor device, i.e., parallel to the substrate and perpendicular to the X-axis defined by the two sensors S1, S2.

[0308] Each of sensors S1 and S2 may comprise an integrated magnetic concentrator and two horizontal Hall elements positioned near the periphery of its IMC and lying on an imaginary line parallel to the Y axis, or may comprise one or more vertical Hall elements oriented with their axes of greatest sensitivity aligned in the Y direction, or may comprise one or more magnetoresistive (MR) elements positioned to measure magnetic field components oriented in the Y direction.

[0309] The sensor device 1600 is oriented such that the normal (Z) to the substrate is oriented circumferentially with respect to the shaft 1673. The two sensors S1, S2 are in axial positions near the edges 1675, 1677 of the magnetized zones 1671, 1672.

[0310] More specifically, if the first axial zone 1671 has an axial length L1, the second axial zone 1672 has a second axial length L2, and the two axial zones are spaced apart by a distance L3, the distance dx between the centers of the two sensors S1 and S2 is preferably equal to (L1 + L3) with a tolerance margin of ±10%, ±5%, or ±2%. Preferably, the first sensor S1 and the second sensor S2 are slightly offset from the edges 1675 and 1677 of the magnetized zones 1671 and 1672, respectively, by a distance ε having a value in the range of 0 to 20% of L1, or a value in the range of 3 to 15% of L1, for example, a value equal to about 10% of L1, to reduce the effect of mounting position offset. In FIG. 16, the sensors are axially positioned slightly "inward" relative to the edges 1675 and 1677, i.e., toward the middle of the magnetized zones 1671 and 1672. In a variant, the two axial positions are shifted slightly "outward" by a distance ε relative to the edges 1675, 1677 (ie, away from the middle of the magnetized zones 1671, 1672).

[0311] The processing circuitry of the magnetic sensor device 1600 is configured to determine a difference signal ΔBy between the magnetic field components By1, By2 according to the equation ΔBy=(By1-By2): and is configured to output a signal or value indicative of the torque applied to the shaft. The processing circuitry may be configured to determine a value T of the torque applied to the shaft as a predefined function of this difference signal, for example according to the following equation: T=f16(ΔBy), where f16 is a predefined function of (ΔBy). In a preferred embodiment, the torque T is calculated as a value proportional to the magnetic field difference ΔBy, for example according to the following equation: T=K16*(ΔBy), where K16 is a predefined constant that may be stored in non-volatile memory within the sensor device 1600.

[0312] The sensor device 900 is preferably mounted such that the radial distance "g" between the shaft and the packaging device 900 is at least 0.1 mm, or at least 0.3 mm, or at least 0.5 mm, and at most 5.0 mm. The radial distance d1 between the shaft and the sensor device 1600 is preferably at most 5.0 mm, or at most 4.0 mm, or at most 3.0 mm, or at most 2.0 mm, or at most 1.0 mm.

[0313] In a variation of Figure 16 (not shown), the shaft has only one axial zone that is circumferentially magnetized, e.g., zone 1671 is present and zone 1672 is not. In this case, the first sensor S1 would still be positioned relative to axial zone 1671 as illustrated in Figure 16 (or at an axial distance to the left of edge 1675 in Figure 16) and would measure a signal By1 indicative of the magnetic field induced by torque plus a disturbance field (if present), while the second sensor S2 would measure only the disturbance field (if present). The advantage of this variation is that a shaft 1673 with only one axial magnetized zone is easier to manufacture, but the amplitude of the difference signal ΔBy will typically be smaller, e.g., only half the amplitude of Figure 16, and therefore the signal-to-noise ratio (SNR) of the signal ΔBy will be slightly worse than that of the torque sensor system of Figure 16. The formula T=K*(ΔBy) can also be used in this case, although the value of K may typically be twice the value of K16 in FIG.

[0314] 16, the sensor device 1600 is rotated at any angle around an axis parallel to the Y axis, passing through the first sensor S1. The formula T=K*(ΔBy) can also be used in this case.

[0315] FIG. 17 shows an illustrative embodiment of a magnetoelastic torque sensor system 1770 comprising a shaft 1773 having two axial zones 1771, 1772 that are magnetized in opposite circumferential directions, and a magnetic sensor device 1700 having two magnetic sensors S1, S2 spaced a predefined distance dx along an X-axis that is parallel to the shaft 1773.

[0316] The torque sensor system 1700 of Figure 17 can be considered a variation of the torque sensor system 1000 of Figure 10, in which the sensor device is rotated 90° about its X-axis. Preferably, however, the sensor substrates of the sensor device 1700 are slightly shifted relative to the main substrate so that they are located closer to the shaft 1773 (for a given distance between the packaged device and the shaft).

[0317] 17, the sensor device 1700 is oriented such that the normal (Z) to the substrate is oriented circumferentially about the shaft 1773, i.e., tangentially to an imaginary circle concentric with the axis of the shaft 1773. Everything else described for the torque sensor system of FIG. 10 is also applicable here. For example, the torque on the shaft can be calculated as a function of the difference ΔBx, for example, according to the following equation: T=f17(ΔBx), where f17 is a predefined function, for example, K17*ΔBx, and K17 is a predefined constant that can be stored in the non-volatile memory of the sensor device 1700.

[0318] In a variation of FIG. 17 (not shown), the shaft has only one axial zone that is circumferentially magnetized, e.g., zone 1771 and no zone 1772. In this case, the first sensor S1 would still be positioned relative to axial zone 1771 as illustrated in FIG. 17. The advantage of this variation is that a shaft with only one axially magnetized zone is easier to manufacture, but the amplitude of the difference signal ΔBx will typically be smaller, e.g., only half the amplitude of FIG. 17, and therefore the signal-to-noise ratio (SNR) of the signal ΔBx will be slightly worse than that of the torque sensor system 1700 of FIG. 17. The formula T=K*(ΔBx) can also be used in this case, although the value of K may typically be twice the value of K17 of FIG. 17.

[0319] FIG. 18 shows an illustrative embodiment of a magnetoelastic torque sensor system 1870 comprising a shaft 1873 having two axial zones 1871, 1872 magnetized in the same circumferential direction (e.g., both clockwise or both counterclockwise) and a magnetic sensor device 1800 having two magnetic sensors S1, S2 spaced a predefined distance dx along an X-axis parallel to the shaft 1873.

[0320] The torque sensor system 1800 of Figure 18 can be considered a variation of the torque sensor system 900 of Figure 9, in which a second axial zone 1872 of the shaft 1873 is magnetized in the same circumferential direction as the first axial zone 1871, and the first and second sensors S1, S2 are both positioned at two axial positions near the inner edges 1875, 1876 of the two axial zones 1871, 1872 (as shown), where the distance dx is preferably equal to about (L3±2*ε), depending on whether the offset is on the inner or outer side, or the first and second sensors S1, S2 are both positioned at two axial positions near the outer edges 1877, 1878 of the two axial zones 1871, 1872, where the distance dx is preferably equal to about (L1+L3+L2±2*ε). In both cases, the offset ε preferably has a value in the range of 0 to 20% of L1, or in the range of 3% to 15% of L1, for example equal to about 10% of L1.

[0321] 9 is also applicable here. For example, the torque on the shaft can be calculated as a function of the difference ΔBz, for example, according to the following formula: T=f18(ΔBz), where f18 is a predefined function, for example, K18*ΔBz, and K18 is a predefined constant that can be stored in the non-volatile memory of the sensor device 1800.

[0322] In a variation of Figure 18 (not shown), the shaft has only one axial zone that is circumferentially magnetized, e.g., zone 1871 is present and zone 1872 is not. In this case, the first sensor S1 would still be positioned relative to axial zone 1871 as illustrated in Figure 18 and would measure a signal Bz1 indicative of the magnetic field induced by torque plus a disturbance field (if present), and the second sensor S2 would measure only the disturbance field (if present). The formula T = K * (ΔBz) could also be used in this case, although the value of K would typically be twice the value of K18 in Figure 18.

[0323] FIG. 19 shows an illustrative embodiment of a magnetoelastic torque sensor system 1970 comprising a shaft 1973 having two axial zones 1971, 1972 magnetized in the same circumferential direction (e.g., both clockwise or both counterclockwise) and a magnetic sensor device 1900 having two magnetic sensors S1, S2 spaced a predefined distance dx along an X-axis parallel to the shaft 1973.

[0324] The torque sensor system 1900 of Figure 19 can be considered a variation of the torque sensor system 1600 of Figure 16, in which a second axial zone 1972 of the shaft 1973 is magnetized in the same circumferential direction as the first axial zone 1971, and the first and second sensors S1, S2 are both positioned at two axial positions near inner edges 1975, 1976 of the two axial zones 1971, 1972 (as shown), where the distance dx is preferably equal to about (L3±2*ε), or the first and second sensors S1, S2 are both positioned at two axial positions near outer edges 1977, 1978 of the two axial zones 1971, 1972, where the distance dx is preferably equal to about (L1+L3+L2±2*ε). In both cases, the offset ε preferably has a value in the range of 0 to 20% of L1, or in the range of 3% to 15% of L1, for example equal to about 10% of L1.

[0325] 16 is also applicable here. For example, the torque on the shaft can be calculated as a function of the difference ΔBy, for example, according to the following formula: T=f19(ΔBy), where f19 is a predefined function, for example, K19*ΔBy, and K19 is a predefined constant that can be stored in the non-volatile memory of the sensor device 1900.

[0326] In a variation of Figure 19 (not shown), the shaft has only one axial zone that is circumferentially magnetized, e.g., zone 1971 is present and zone 1972 is not. In this case, the first sensor S1 would still be positioned relative to axial zone 1971 as illustrated in Figure 19 and would measure a signal By1 indicative of the magnetic field induced by torque plus a disturbance field (if present), and the second sensor S2 would measure only the disturbance field (if present). The formula T = K * (ΔBy) could also be used in this case, although the value of K would typically be twice the value of K in Figure 19.

[0327] 9-19 show only one magnetic sensor device, the invention is not so limited, and embodiments of the invention may include multiple magnetic sensor devices, for example, two magnetic sensor devices mounted near the shaft and circumferentially spaced apart by an angle (e.g., θ) in the range of 165° to 180°. However, other angular positions may also work, for example, at least 30°, or at least 45°, or at least 60°, or at least 70°, or at least 85°, or at least 95°. Signals from these two magnetic sensor devices may be combined by one of the magnetic sensor devices or by an external processor (not explicitly shown) to determine the value of the torque applied to the shaft.

[0328] In a variant, the torque sensor system comprises three magnetic sensor devices mounted near the shaft and spaced circumferentially apart by an angle (e.g., θ) of at least 30°, or at least 45°, or at least 60°, or at least 70°, or at least 85°, or at least 95°, for example, an angle in the range of 105° to 135°. The signals from these three magnetic sensor devices may be combined by one of the magnetic sensor devices or by an external processor to determine the value of the torque applied to the shaft.

[0329] In another variation, the sensor system comprises four magnetic sensor devices mounted near the shaft and spaced circumferentially apart by an angle (e.g., θ) of at least 30°, or at least 45°, or at least 60°, or at least 70°, for example, an angle in the range of 80° to 100°. The signals from these four magnetic sensor devices may be combined by one of the magnetic sensor devices or by an external processor to determine the value of the torque on the shaft.

[0330] In any of these variations comprising multiple sensor devices angularly spaced from one another circumferentially around the shaft, the signal combination may use parameters determined during a calibration procedure and stored in the non-volatile memory of the magnetic sensor device. It is an advantage of using multiple sensor devices that mechanical offset or mechanical play, particularly in the radial direction of the shaft, may be reduced or at least partially compensated for by combining the signals from these multiple sensor devices.

[0331] 20-22B show a further proposed magnetoelastic torque sensor system comprising a shaft having three axial zones magnetized in alternating circumferential directions and one or more magnetic sensor devices disposed near the shaft, each having at least two axially spaced magnetic sensors and, optionally, a processing substrate. Sensor devices such as those illustrated in FIGS. 1-8 may be used, but are not required. For example, if a torque sensor system includes multiple magnetic sensor devices, one of the magnetic sensor devices may include a processing substrate and two sensor substrates, while the other magnetic sensor devices may require only two sensor substrates. As another example, if the torque sensor system includes an external processor, such as the display and computing device of an electric bicycle, the magnetic sensor device may include only a sensor substrate.

[0332] The process substrate, if present, may be a CMOS substrate. The sensor substrates may be compound semiconductor substrates including materials from the III-V group, e.g., Ga—As or In—As. Each of the sensor substrates may include one or more horizontal Hall elements configured to measure magnetic field components oriented radially relative to the shaft.

[0333] 20 shows an illustrative embodiment of a magnetoelastic torque sensor system 2070 comprising a shaft 2073 having three axial zones, including a first axial zone 2071a magnetized in a first circumferential direction (e.g., clockwise), a second axial zone 2071b magnetized in a second circumferential direction opposite the first circumferential direction, and a third axial zone 2071c magnetized in a third circumferential direction opposite the second circumferential direction. The system further comprises at least one magnetic sensor device 2000 having two magnetic sensors S1, S2 spaced a predefined distance dx apart along an X-axis that is parallel to the shaft 2073.

[0334] The torque sensor system 2000 of FIG. 20 can be considered a variation of the torque sensor system 1100 of FIG. 11 in which the shaft has two additional axial sections. Everything else described for the torque sensor system of FIG. 11 is also applicable here. For example, the torque on the shaft can be calculated as a function of the difference ΔBz, for example, according to the following equation: T=f20(ΔBz), where f20 is a predefined function, for example, K20*ΔBz, and K20 is a predefined constant that can be stored in the non-volatile memory of the sensor device 2000.

[0335] The first axial zone 2071a has a first axial length L1, the second axial zone 2071b has a second axial length L2, and the third axial zone 2071c has a third axial length L3. Preferably, L1=L2 and L2=L3.

[0336] The first axial zone 2071a is spaced apart from the second axial zone 2071b by a distance dA, and the third axial zone 2071c is spaced apart from the second axial zone 2071b by a distance dB. Preferably, dA is substantially equal to dB, for example, equal to dB. The value of dA can be a value in the range of 0.5 mm to 5.0 mm, for example, equal to about 1.0 mm. The region between the first axial zone 2071a and the second axial zone 2071b can be a code-free region having an axial length equal to dA. The region between the second axial zone 2071b and the third axial zone 2071c can be a code-free region having an axial length equal to dB.

[0337] The active surfaces of the sensors S1 and S2 are spaced apart from the shaft by a distance ds. The value of ds can be a value in the range of 0.5 mm to 2.5 mm, for example, equal to about 1.0 mm. Preferably, the value of ds is substantially equal to dA, for example, equal to dA.

[0338] The device 2000 can have an encapsulation portion spaced apart from the shaft by a distance g, also referred to as "clearance".

[0339] The center of the first sensor S1 is spaced apart from the center of the second sensor S2 by a distance dx. The value of dx can be less than or equal to L2 (i.e., dx ≦ L2). Preferably, the value of dx is less than L2 (i.e., dx < L2). More preferably, dx = L2 - (2*ε), where L2 is the length of the central axial zone 2071b and ε is the inner offset from the circular edges 2075, 2076 of the central zone.

[0340] In a preferred embodiment, one or more or all of the following descriptions apply. i) dx ≦ L2, or dx < L2, for example, dx = L2 - (2*ε) and ε > 0, ii) dA / dB is a value of 50% to 200%, or 80% to 125%, or 90% to 110%, iii) ds / dA is a value of 50% to 200%, or 80% to 125%, or 90% to 110%.

[0341] In one embodiment, i) dx≦L2, and ii) dA / dB is a value between 50% and 200%.

[0342] In one embodiment, i) dx≦L2, and iii) ds / dA is a value between 50% and 200%.

[0343] In one embodiment, i) dx≦L2, and ii) dA / dB is a value between 50% and 200%, and iii) ds / dA is a value between 50% and 200%.

[0344] Figure 21 shows simulation results for an arrangement such as that illustrated in Figure 20, where dA = dB = ds and L1 = L2 = L3, but the invention is not so limited. The graph shows the value of Bz (in arbitrary units) as a function of axial displacement along the X direction at radial distance ds from the shaft.

[0345] As can be seen from this graph, if the two sensors S1, S2 can be spaced apart in the X direction by positions corresponding to a triangle, i.e., when dx=L2+d, the value of (Bz1-Bz2) can be maximum, and the axial mounting position of the sensor device may need to be accurate, since a slight shift of the curve to the left or right may decrease (Bz1-Bz2).

[0346] If the two sensors S1, S2 can be spaced apart in the X direction by positions corresponding to a circle, i.e., dx is approximately equal to L2, the value of (Bz1-Bz2) can be close to the maximum value, but a shift to the left / right can increase / decrease the value of Bz1 (in absolute value) and decrease / increase the value of Bz2 (in absolute value), but the increase and decrease may not be the same, and therefore, although there is some compensation, the compensation is not ideal, so the axial mounting position of the sensor devices can be somewhat relaxed.

[0347] If the two sensors S1, S2 can be spaced apart in the X direction by positions corresponding to a square, i.e., if dx is approximately equal to (L2-dA), the value of (Bz1-Bz2) can have an amplitude of approximately 60% of the maximum value, i.e., the signal-to-noise ratio can lose approximately one bit, but the axial mounting position of the sensor devices can be strongly relaxed, since a shift to the left / right can increase / decrease the value of Bz1 (in absolute value) and decrease / increase the value of Bz2 (in absolute value) by approximately the same amount, and therefore the compensation becomes close to ideal.

[0348] The dotted curve in Figure 21 shows the value of ΔBz = (Bz1 - Bz2) as a function of the mounting position of the sensor device, where dx = (L2 - dA), corresponding to a square. As can be seen, the dotted curve has a substantially "flat top," meaning that the value of ΔBz is substantially constant (e.g., less than ±3% variation) for mounting offsets up to about 33% of L2. This value of dx is said to be optimal because it maximizes the ratio of axial offset (±33% of L2 for the intended position) and the variation of ΔBz (less than ±3%). However, of course, the present invention also works very well when dx is not exactly equal to (L2-dA), but has a value in the range of (L2-2*dA) to (L2+dA), or has a value in the range of (L2-2*dA) to (L2), or has a value in the range of (L2-1.5*dA) to (L2-0.5*dA), or has a value in the range of (L2-1.2*dA) to (L2-0.8*dA). Returning to Figure 20, this means that preferably ε has a value in the range of 0 to 2*dA, and more preferably in the range of 0.5*dA to 1.5*dA, or 0.8*dA to 1.2*dA.

[0349] In one embodiment, the values ​​of dA and dB may be in the range of 0.5 mm to 1.5 mm, e.g., equal to about 1.0 mm, the values ​​of L1=L2=L3 may be in the range of 5.0 mm to 15.0 mm, e.g., equal to about 8.7 mm, or equal to about 13.7 mm, and the shaft diameter may be in the range of 10 mm to 30 mm, or in the range of 15 mm to 25 mm, e.g., equal to about 17 mm.

[0350] Figure 22A shows a side view and Figure 22B shows a front view of a torque sensor system like Figure 20 or Figure 21, with two magnetic sensor devices 2200a, 2200b mounted near a shaft 2273 and spaced circumferentially apart by an angle of at least 30°, or at least 45°, or at least 60°, or at least 70°, or at least 85°, or at least 95°, or at least 120°, or at least 150°, for example about 180°. As can be seen, the first sensor S1 and the second sensor S2 are in the space between a first imaginary plane Ω1 and a second imaginary plane Ω2, the first imaginary plane Ω1 being oriented perpendicular to the axial direction of the shaft (e.g., X) and intersecting the shaft at a first axial position between the first magnetized section 2271a and the second magnetized section 2271b, and the second imaginary plane Ω2 being oriented perpendicular to the axial direction of the shaft and intersecting the shaft at a second axial position between the second magnetized section 2271b and the third magnetized section 2271c.

[0351] 22B, when a shaft is mounted in a housing between two sensor devices 2200a, 2200b, ideally, the first clearance c1 and the second clearance c2 would be substantially equal to each other, but in reality, there may be some radial position offset of the shaft, which may cause c1 to increase and c2 to decrease, or vice versa. By combining the differential signals obtained from both magnetic sensor devices, the effect of such radial offset can be reduced. When using sensor devices as described in FIG. 21, the system is very robust to both axial and radial offsets.

[0352] This effect can also be obtained by combining signals obtained from three magnetic sensor devices (not shown) circumferentially spaced by at least 30°, or at least 45°, or at least 60°, or at least 70°, or at least 85°, or at least 95°, e.g., multiples of about 120°±15°. Note that the angular offset between the sensor devices need not be constant. For example, the angular offset between the first and second devices may be equal to 90°, the angular offset between the second and third devices may be equal to 90°, and the angular offset between the first and third devices may be equal to 180°.

[0353] This effect can also be obtained by combining signals obtained from four magnetic sensor devices (not shown) circumferentially spaced at least 30°, or at least 45°, or at least 60°, or at least 70° apart, for example spaced at multiples of about 90°±15°.

[0354] The principle of using multiple magnetic sensor devices circumferentially spaced around a shaft can also be used in combination with the torque sensor systems illustrated in Figures 9-19, for example as illustrated in Figure 22B or its variations having three or four sensor devices. By combining the signals obtained from multiple sensor devices, the effect of radial play (or radial position offset) of the shaft relative to the housing can be reduced, or in other words, robustness to radial offset of the shaft can be improved.

[0355] 23 shows a flow chart of a method 2300 for determining torque on a shaft. The method comprises: a) in step 2301, providing a shaft comprising at least one axial section that is circumferentially magnetized; b) providing a magnetic sensor device integrated in a single package in step 2302, the magnetic sensor device comprising: a first semiconductor substrate (e.g., a CMOS substrate) comprising at least a processing circuit; a second semiconductor substrate or layer (e.g. Ga-As) comprising a first magnetic sensor (S1) mounted above, below or next to the first substrate; - providing a third semiconductor substrate or layer (e.g., Ga-As) comprising a second magnetic sensor (S2) mounted above, below or next to the first substrate at a predefined distance (dx) from the first sensor (S1), c) in step 2303, placing the sensor device proximate to the shaft; d) in step 2304, measuring a first magnetic field component (e.g., Bz1) using a first magnetic sensor (S1) and measuring a second magnetic field component (e.g., Bz2) parallel to the first magnetic field component (e.g., Bz1) using a second magnetic sensor (S2); e) determining a pairwise difference (e.g., ΔBz) between the first and second magnetic field components (e.g., Bz1, Bz2) in step 2305; f) In step 2306, outputting a signal or value indicative of the torque applied to the shaft based on the pairwise differences, for example as a predefined function of the pairwise differences, for example as a value proportional to the pairwise differences.

[0356] Step a) may include providing a shaft having only one axial section that is circumferentially magnetized (e.g., as illustrated in Figures 11-15), or providing a shaft having two axial sections that are magnetized in opposite circumferential directions (e.g., as illustrated in Figures 9, 10, 16, 17), or providing a shaft having two axial sections that are magnetized in the same circumferential direction (e.g., as illustrated in Figures 18, 19).

[0357] In the sensor device provided in step b), the first semiconductor substrate is electrically connected to the second and third semiconductor substrates, for example, by at least one RDL layer or by bond wires. The magnetic sensor of this sensor device can be a 1D magnetic sensor with one or more horizontal Hall elements connected in series or parallel (e.g., Figures 9, 11, 15, 18), or with one or more vertical Hall elements or magnetoresistive elements (e.g., Figures 10, 12-14, 16 and 17, 19).

[0358] Step c) may involve positioning the sensor device relative to the shaft as illustrated in any of Figures 9 to 19. In some cases, this means that the distance dx between sensor elements, the number and / or dimensions of axial zones, and / or the distance between axial zones must satisfy a predefined relationship.

[0359] The sensor device provided in step b) may comprise a non-volatile memory containing data of a predefined function, such as, for example, coefficients of a polynomial function, or a look-up table, or predefined constants, enabling the processing circuitry to calculate the torque applied to the shaft.

[0360] Figure 24 shows a flow chart of a method 2400 for determining torque on a shaft, which can be seen as a special case or variant of method 2300 of Figure 23. Method 2400 includes: a) in step 2401, providing a shaft comprising first, second, and third axial sections magnetized in first, second, and third circumferential directions, respectively, wherein the second section is located between the first and third sections, the third circumferential direction being equal to the first circumferential direction, and the second circumferential direction being opposite to the first and third circumferential directions; b) in step 2402, providing at least one magnetic sensor device, a first semiconductor substrate (e.g., a CMOS substrate) comprising at least a processing circuit, a second semiconductor substrate or layer (for example Ga-As) provided with a first magnetic sensor (S1), for example at least one horizontal Hall plate, - providing at least one magnetic sensor device comprising a third semiconductor substrate or layer (e.g. Ga-As) comprising a second magnetic sensor (S2), for example at least one horizontal Hall plate, the second sensor being at a predefined distance "dx" from the first sensor (S1); c) placing at least one sensor device in the vicinity of the shaft in step 2403, for example as illustrated in any of Figures 20-22B; d) in step 2404, measuring a first magnetic field component (e.g., Bz1) using a first magnetic sensor (S1) and measuring a second magnetic field component (e.g., Bz2) parallel to the first magnetic field component (e.g., Bz1) using a second magnetic sensor (S2) of the at least one magnetic sensor device; e) in step 2405, determining at least one pairwise difference (e.g., ΔBz) between the first magnetic field component and the second magnetic field component (e.g., Bz1, Bz2); f) in step 2406a, outputting a signal or value indicative of the torque applied to the shaft based on the at least one pairwise difference, for example as a predefined function of the pairwise difference, for example as a value proportional to the pairwise difference.

[0361] The shaft may have three axial zones with dimensions L1, L2, L3 spaced apart by distances dA, dB as illustrated in Figures 20-22B, and the dx between the sensor elements may be selected as described in Figure 21.

[0362] FIG. 25 is a graph showing the magnetic field strength measured at a distance "g" of about 1 mm from a shaft having an outer diameter D of about 17 mm, which was magnetized as described in FIG. 21 with L1=L2=L3 of about 8 mm and dA=dB of about 1 mm.

[0363] The curve indicated by the black circle shows the measured magnetic field strength (e.g., magnitude of the radial component) of a first shaft made of maraging steel grade C300, but the invention is not limited thereto and other suitable maraging steel types can be used, such as 18Ni maraging steel having a grade of 200, 250, 300, or 350, also known as maraging C200, C250, C300, or C350. Indeed, not only C-type maraging steels but also T-type maraging steels can be used, such as maraging T200, T250, T300, or T350.

[0364] The curve indicated by the black squares shows the measured magnetic field strength (e.g., magnitude of the radial component) of a second shaft made of martensitic steel, more specifically grade X20Cr13, type AISI 420 stainless steel, although the invention is not limited thereto and other suitable martensitic steel types may also be used, such as 410, 420, or 440, preferably martensitic stainless steels having condition H (i.e., hardened). Preferably, the martensitic stainless steel contains 12% to 17% Cr by weight.

[0365] In preferred embodiments, the entire shaft, or at least the outer portion of the shaft (e.g., a ring around the inner shaft), is made of a steel having a coercivity (Hc) of at least 35 Oersted, or at least 40 Oersted, or at least 45 Oersted, such as a maraging steel or martensitic stainless steel.

[0366] FIG. 26 shows a 3D perspective view of a shaft having an outer diameter D and first and second ends. In the illustrated embodiment, both ends have four flattened surfaces that together form a substantially square cross-section, with optional rounded corners. The shaft is preferably made of maraging steel or martensitic stainless steel, as described in FIG. 25 . Additionally, the shaft of FIG. 26 has two axial blind holes with internal threads. While such a shaft is ideally suited for electric bicycles, the present invention is not limited to shafts shaped and sized for electric bicycles, as the same principles can be used in other torque sensor systems, for example, in other automotive, industrial, or robotic applications.

Claims

1. 1. A magnetoelastic torque sensor system comprising: a shaft comprising at least one axial section that is circumferentially magnetized; a magnetic sensor device arranged in the vicinity of the shaft, the magnetic sensor device comprising three semiconductor substrates including a first semiconductor substrate (109) comprising at least a processing circuit, a second semiconductor substrate (106a) comprising a first magnetic sensor (S1), and a third semiconductor substrate (106b) comprising a second magnetic sensor (S2), each magnetic sensor being configured to measure a magnetic field component of a magnetic field generated by the shaft when a torque is applied to the shaft; the first, second, and third semiconductor substrates (109, 106a, 106b) are incorporated into a single packaged device having a plurality of terminals electrically connected to the first substrate (109); 10. A magnetoelastic torque sensor system, wherein the processing circuitry is configured to determine pairwise differences between the measured field components and to output a signal indicative of a torque applied to the shaft based on the pairwise differences.

2. 2. The magnetoelastic torque sensor system of claim 1, wherein the magnetic sensor device is configured to measure or estimate a first temperature of the first sensor (S1) and a second temperature of the second sensor (S2), and to temperature compensate the signals obtained from the first and second sensors before determining the difference.

3. 3. The magnetoelastic torque sensor system of claim 1, wherein the first substrate (109) further comprises a temperature sensor for measuring a temperature of a main substrate, and the processing circuitry is configured to temperature correct the sensor signal based on the measured temperature before determining the difference.

4. Each of the sensor substrates (106a, 106b) further comprises a temperature sensor for measuring the temperature of the sensor substrate; 4. The magnetoelastic torque sensor system of claim 1, wherein the processing circuitry is configured to temperature correct the sensor signals based on these temperature signals before determining the difference.

5. the first semiconductor substrate (109) comprises primarily silicon; The magnetoelastic torque sensor system according to any one of claims 1 to 4, wherein the second and third semiconductor substrates (106a, 106b) mainly comprise silicon and / or are separate silicon substrates.

6. the first semiconductor substrate (109) comprises primarily silicon; The magnetoelastic torque sensor system according to any one of claims 1 to 4, wherein the second and third semiconductor substrates (106a, 106b) comprise a compound semiconductor material selected from the III-V group.

7. the sensor device is a wafer-level packaged device; the first semiconductor substrate (109) is between the second semiconductor substrate (106a) and the third semiconductor substrate (106b); A magnetoelastic torque sensor system according to any one of claims 1 to 6, wherein the first semiconductor substrate (109) is electrically connected to the second semiconductor substrate (106a) and to the third semiconductor substrate (106b) by at least one redistribution layer (RDL).

8. the magnetic sensor device further comprising a lead frame; the first substrate (709) is between the second semiconductor substrate (706a) and the third semiconductor substrate (706b) on a single surface of the lead frame; A magnetoelastic torque sensor system according to any one of claims 1 to 6, wherein a first semiconductor substrate (709) is electrically connected to the second semiconductor substrate (706a) and to the third semiconductor substrate (706b) by bond wires.

9. the magnetic sensor device (600, 600', 600") further comprises a lead frame; the first semiconductor substrate is attached to the lead frame, and the second semiconductor substrate and the third semiconductor substrate are disposed above or below the first substrate; 7. The magnetoelastic torque sensor system of claim 1, wherein the first semiconductor substrate is electrically connected to the second semiconductor substrate and to the third semiconductor substrate by bond wires.

10. the shaft comprises at least a first axial section magnetized in a first circumferential direction and optionally also a second axial section magnetized in a second circumferential direction opposite the first circumferential direction; the magnetic sensor device is oriented with respect to the shaft such that a first axis (X) defined by an imaginary line passing through the first sensor (S1) and the second sensor (S2) is parallel to the shaft; the first sensor (S1) and the second sensor (S2) are configured to measure first and second magnetic field components (Bax1, Bax2) oriented parallel to the shaft, 10. A magnetoelastic torque sensor system (1070, 1770) according to any one of claims 1 to 9, wherein the first sensor (S1) is at a first axial position near the center of the first magnetized axial section, and the second sensor (S2), if present, is at a first axial position near the center of the second magnetized axial section.

11. the magnetic sensor device is oriented relative to the shaft such that a first axis (X) defined by an imaginary line passing through the first sensor (S1) and the second sensor (S2) is oriented radially relative to the shaft; the first sensor (S1) and the second sensor (S2) are configured to measure first and second magnetic field components (Bax1, Bax2) oriented parallel to the shaft, 10. A magnetoelastic torque sensor system (1370, 1570) according to any one of claims 1 to 9, wherein the first sensor (S1) is at an axial position near the center of the magnetized axial section at a first distance (d1) from the shaft, and the second sensor (S2) is at the same axial position as the first sensor (S1) but at a second distance (d2) from the shaft that is greater than the first axial distance (d1).

12. the magnetic sensor device is oriented with respect to the shaft such that a first axis (X) defined by an imaginary line passing through the first sensor (S1) and the second sensor (S2) is parallel to the shaft; the first sensor (S1) and the second sensor (S2) are configured to measure first and second magnetic field components (Br1, Br2) oriented radially with respect to the shaft; A magnetoelastic torque sensor system (1170) as described in any one of claims 1 to 9, wherein the first sensor (S1) is located at a first axial position near a first edge (1175) of the magnetized axial section (1171), and the second sensor (S2) is located at a second axial position near a second edge (1176) of the magnetized axial section (1171).

13. the magnetic sensor device is oriented relative to the shaft such that a first axis (X) defined by an imaginary line passing through the first sensor (S1) and the second sensor (S2) is oriented radially relative to the shaft; the first sensor (S1) and the second sensor (S2) are configured to measure first and second magnetic field components (Br1, Br2) oriented radially with respect to the shaft; 10. The magnetoelastic torque sensor system (1270, 1470) of claim 1, wherein the first sensor (S1) and the second sensor (S2) are at an axial position near a first edge (1275, 1475) of the magnetized axial section (1271, 1471).

14. said shaft comprising at least a first axial section (971, 1671) magnetized in a first circumferential direction and optionally also a second axial section (972, 1672) magnetized in a second circumferential direction opposite said first circumferential direction; the magnetic sensor device is oriented with respect to the shaft such that a first axis (X) defined by an imaginary line passing through the first sensor (S1) and the second sensor (S2) is parallel to the shaft; the first sensor (S1) and the second sensor (S2) are configured to measure first and second magnetic field components (Br1, Br2) oriented radially with respect to the shaft; A magnetoelastic torque sensor system (970, 1670) according to any one of claims 1 to 9, wherein the first sensor (S1) is at a first axial position near an edge (975, 1675) of the first magnetized axial section, and the second sensor (S2), if present, is near an edge (977, 1677) of the second magnetized axial section.

15. the shaft comprises a first circumferentially magnetized first axial section (1871, 1971) and a second circumferentially magnetized second axial section (1872, 1972), also magnetized in the first circumferential direction; the magnetic sensor device is oriented with respect to the shaft such that a first axis (X) defined by an imaginary line passing through the first sensor (S1) and the second sensor (S2) is parallel to the shaft; the first sensor (S1) and the second sensor (S2) are configured to measure first and second magnetic field components (Br1, Br2) oriented radially with respect to the shaft; A magnetoelastic torque sensor system (1870, 1970) as described in any one of claims 1 to 9, wherein the first sensor (S1) and the second sensor (S2) are either both located near the inner edge of the respective axial section or both located near the outer edge of the respective axial section.

16. A method (2000) for measuring torque on a shaft, comprising: a) providing a shaft comprising at least one axial section that is circumferentially magnetized (2001); b) providing a magnetic sensor device in the form of a single packaged device comprising at least three semiconductor substrates, including a first semiconductor substrate comprising at least a processing circuit, a second semiconductor substrate comprising a first magnetic sensor (S1), and a third semiconductor substrate comprising a second magnetic sensor (S2) (2002); c) placing the sensor device in the vicinity of the shaft (2003); d) measuring a first magnetic field component (2004) using said first magnetic sensor (S1) and measuring a second magnetic field component using said second magnetic sensor (S2); e) determining pairwise differences between said magnetic field components (2005); f) outputting a signal indicative of torque applied to said shaft based on said pairwise differences (2006).

17. 1. A shaft for use in a magnetoelastic torque sensor system, comprising: the shaft having at least one axial section that is circumferentially magnetized; A shaft, wherein at least an outer portion of said at least one axial section is made of maraging steel or made of martensitic stainless steel.

18. the axial length of the at least one axial zone is a value in the range of 5.0 mm to 15.0 mm; The shaft of claim 17, wherein the outer diameter of the at least one axial zone is a value in the range of 10 mm to 30 mm.

19. the shaft comprises at least two axial sections magnetized in opposite circumferential directions, or at least three axial sections magnetized in alternating circumferential directions; 19. The shaft according to claim 17 or 18, wherein at least the outer portions of the at least two or at least three axial sections are made of maraging steel or of martensitic stainless steel.

20. the distance (dA, dB) between two adjacent axial zones is a value in the range of 0.5 mm to 1.5 mm; The axial lengths (L1, L2, L3) of the at least two or at least three axial zones are in the range of 5.0 mm to 15.0 mm; 20. The shaft of claim 19, wherein the outer diameter of the at least two or the at least three axial zones is a value in the range of 10 mm to 30 mm.

21. the shaft is a crankshaft (e.g., for an electric bicycle), the shaft having a first end and a second end opposite the first end; each of the first and second ends having at least one flattened portion, or at least two flattened portions (e.g., opposite each other), or at least four flattened portions (e.g., having a square cross-section); 21. A shaft according to any one of claims 17 to 20, wherein optionally each of the first and second ends has an axially extending blind bore having an internal or external thread.

22. An electric bicycle, A magnetoelastic torque sensor system according to any one of claims 1 to 15, and / or an electric bicycle comprising the shaft according to any one of claims 17 to 21.

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