Device for measuring deformation, stress, force and / or torque in a plurality of shafts

Abstract

The invention preferably relates to a device for measuring deformations, stresses, forces and / or torques of an object, comprising a spring body and a sensor chip comprising one or more sensor elements for measuring deformations, stresses, forces and / or torques and an electronic circuit on a substrate. The spring body comprises a base plate on the front side of which a force conductor, preferably in the form of a pin, is mounted, the sensor chip being positioned on the back side of the base plate and below the force conductor. The invention also relates to a system comprising the described device and a data processing unit, wherein the data processing unit is configured to read the measurement data determined by the sensor chip and, preferably, based on this determined data, to detect the force and / or torque acting on the force conductor.

Description

Technical Field

[0001] The present invention preferably relates to an apparatus for measuring multiaxial loads on an object, the apparatus comprising a spring body and a sensor chip having one or more sensor elements and electronic circuitry on a substrate for measuring deformation, stress, force, and / or torque. The spring body includes a base plate on which a force transmitter is mounted, preferably in the form of a pin, on the front side. The sensor chip is positioned on the back side of the base plate and below the force transmitter. The present invention also relates to a system including such an apparatus and a data processing unit, wherein the data processing unit is configured to read measurement data detected by the sensor chip, and preferably, to calculate the force and / or torque acting on the object based on the measurement data. Background Technology

[0002] This invention relates to the field of sensors for measuring deformation, stress, force and / or torque.

[0003] For example, force measurements are performed on an object to determine the dimensions and inspect mechanically stressed components. When determining the dimensions of a mechanically stressed component based on its function, it is necessary to understand the nature of the load. The decisive variable for the design is the maximum stress that occurs, which ultimately limits the dimensions. These stresses must be identified in advance and then experimentally verified in testing. Therefore, experimental stress analysis can be seen as a link between theoretical calculations and verification in testing.

[0004] Force and / or deformation measurements are also required to monitor the machine's condition in order to identify and record variable loads. These may occur, for example, due to temporary changes in boundary conditions, operating conditions, and material properties.

[0005] To eliminate the influence of the machine or component being monitored, a particularly compact force sensor size is required. Furthermore, a compact force sensor size is also needed to address localized (potentially multiaxial) deformation or stress / strain conditions. Due to the localized distribution of deformation or stress gradients, large-area, non-compact transducers are disadvantageously limited to only coarsely identifying average local conditions.

[0006] The dimensions of a known force sensor are typically determined by the dimensions of the spring body or load cell and the minimum size of the sensor.

[0007] A spring body, or load cell, is typically a suitably shaped metal component used to transmit force, and its geometry changes slightly under the influence of force or torque. The resulting deformation is detected by a transmitter such as a strain gauge or other resistance or capacitance measuring unit.

[0008] The overall dimensions of the device are specifically determined by the minimum dimensions of the transmitter. When determining multi-axis loads, multiple sensors are typically required—at least one sensor per axis—with these sensors spatially distributed at appropriate locations.

[0009] Placing multiple transmitters (such as strain gauge-type transmitters) requires additional space.

[0010] Due to the geometry of the component and the applied load, the load state is a function of position. On the surface, the magnitudes of the principal stresses vary, and their principal directions also change. If no additional normal load (such as pressure) is applied, a biaxial stress state typically occurs on the surface of the object under test when multiaxial loads are present. However, in most cases, its principal directions are unknown.

[0011] Strain gauge rosettes, with multiple strain gauges in various directions, perform the crucial task of fully determining the biaxial stress / strain state in experimental stress analysis because it has been demonstrated that the principal strains can be detected by three independent strain measurements in different directions. Even when the principal directions are known, two independent strain measurements are still required to detect them. Known arrangements in the prior art are 45° right-angled rosettes and 60° triangular rosettes.

[0012] Common spring bodies are designed with multiple regions for their respective uniaxial loads, and can be specifically measured using multiple transmitters.

[0013] Typical spring body shapes used in load cells include, for example, double-bending beams for small loads, shear bars for larger loads, columnar spring bodies (compression bars or hollow cylinders), annular torsion spring bodies for high loads, multi-bending beam spring bodies for high-value scales, or small and highly rigid diaphragm spring bodies.

[0014] The stress state is measured by deformation or strain measurements. Even under high component loads (stress shortly before the fracture point), only very small deformations or strains (approximately 1-2° / oo) are present in most common metallic materials.

[0015] For particularly rigid systems, such as machine tools or linear measuring devices, the available strain is much smaller. Typically, only semiconductor strain gauges suitable for this purpose can be applied with great effort.

[0016] Strain gauges are essentially based on the change in resistance caused by changes in length and cross-section. If a strain gauge is subjected to strain, its resistance increases. If the strain gauge is compressed (negative strain), its resistance R decreases. Here, dR / R = k ε, where ε corresponds to the relative change in length.

[0017] Problem areas for metal strain gauges include a low k-factor, leading to low sensitivity, and a large strain gauge, resulting in poor spatial resolution, especially when using a zonal strain gauge. Due to the size of the strain gauge at different positions on different axes, poor spatial resolution and erroneous results may occur.

[0018] In contrast, semiconductor strain gauges can perform more sensitive measurements. However, these strain gauges are also highly mechanically sensitive, making assembly complex and prone to breakage. Furthermore, these semiconductor strain gauges are typically firmly adhered to the entire surface of the object being measured, usually to increase their stability. In this case, the mechanical properties of the adhesive can often affect and tamper with the strain measurement.

[0019] In addition, known strain gauge measurement methods often have problems, especially with the commonly used bridge circuit, which has only one or two active, relatively large strain gauges at different locations on the component and passive resistors added to the bridge circuit; these problems include poor temperature compensation and low sensitivity.

[0020] In the prior art, silicon chip-based sensors are also known, which have multiple sensor elements to measure stress distribution.

[0021] In 2000, Jaeger et al. disclosed stress measurements of piezoresistive behavior based on a CMOS integrated field-effect sensor. This circuit provides temperature-compensated measurements, which are correlated with the differential normal stress (σ) on the plane. xx - σ yy ) and shear stress (σ xy The ratio is proportional. Using silicon field-effect transistors (SFETs) as stress sensors has many advantages over traditional resistive elements because SFETs are small in size, highly sensitive, and can be integrated into active circuits. Furthermore, SFETs allow for good localized stress state measurements.

[0022] In 2009, Gieschke et al. proposed a CMOS integrated sensor using piezoresistive sensor bridges with both analog and digital circuitry. Thirty-two piezoresistive sensor bridges were distributed as sensor elements on the sensor chip, allowing for the measurement of shear stress (σ) within a plane. xy or normal differential stress (σ) xx - σ yyThe measurement is performed using four transistors arranged in a square, such as a Wheatstone bridge. The n-channel transistors detect shear stress, with the sensor bridge rotated 45° relative to the (x, y) coordinate system, while the p-channel transistors are arranged parallel to the coordinate system and measure the normal differential stress.

[0023] Kuhl et al. (2013) described a sensor chip based on the technology of Gieschke et al. (2009). The piezoresistive sensor bridge is configured as a square field-effect transistor (FET, preferably MOSFET) (piezoelectric FET) with four source / drain contacts, utilizing the piezoresistive shearing effect in an n-type (NMOS) or p-type (PMOS) inversion layer. Preferably, the NMOS sensor element is used for shear stress σ. xy Measurements are performed, and the PMOS sensor element is used to measure the normal differential stress (σ). xx - σ yy The measurement is performed using piezoresistive sensor bridges, which are distributed across the sensor chip as sensor elements. Ten NMOS sensor elements measure shear stress, and fourteen PMOS sensor elements measure normal differential stress.

[0024] However, improvements are needed in their application for measuring and / or monitoring multiaxial loads on components or objects.

[0025] Purpose of the invention The object of this invention is to provide a device that does not suffer from the disadvantages of the prior art. Specifically, one object of this invention is to provide a device that can detect multiaxial stress on an object with high precision, and is characterized by a compact and robust structure with low susceptibility to errors. Summary of the Invention

[0026] This objective is achieved through the technical solutions of the embodiments of this application. Advantageous embodiments of the present invention are described below.

[0027] In one aspect, the invention preferably relates to an apparatus for measuring multiaxial loads on an object, the apparatus comprising: - Spring body; and - A sensor chip comprising one or more sensor elements and electronic circuitry on a substrate, the sensor elements being used to measure deformation, stress, force, and / or torque. The spring body is characterized by having a base plate, a force conductor mounted on the front side of the base plate, and a sensor chip located on the back side of the base plate and below the force conductor.

[0028] The spring body advantageously allows stress, force, or strain from multiaxial loads or external loads to be concentrated in a small spatial region within the base plate. For example, the force transmitter can be an elongated elliptical force pointer or pin, which is locally connected to the base plate at a fixed point.

[0029] The load applied to the force transmitter at the end away from the base plate results in a localized stress distribution at the fixed point, and, given a proper configuration of the spring body, also results in a localized stress distribution on the back side of the base plate, which is advantageously clearly related to the magnitude (height) and direction of the load applied to the force transmitter.

[0030] Preferably, the maximum load at the measurement point is of the same order of magnitude as the maximum load at the front fixing point of the force transmitter or pin, thereby reducing the undesirable high notch stress at the pin fixing point. Preferably, the stress distribution on the back side is adapted to and increased in area with respect to the sensor chip. Advantageously, the external load or force to be measured can therefore be measured very sensitively, thus eliminating the limitations caused by rigidity issues at the fixing point.

[0031] Advantageously, the sensor chip attached to the back side of the substrate allows for precise, spatially resolved measurement of deformation, stress, force, and / or torque in a relevant area of ​​the substrate at the location of the chip. Preferably, the deformation, stress, or force and torque acting on the substrate is transmitted to the substrate of the sensor chip, whereby one or more sensor elements detect the deformation or stress of the substrate. With proper calibration, extremely accurate conclusions about the force or torque acting on the force transmitter can be drawn using the deformation or stress of the substrate (attached to the back side of the substrate).

[0032] For this purpose, the device can remain extremely rigid, because even slight deflection or translation of the force transmitter can be reliably measured in the form of characteristic deformation or stress distribution in the base plate.

[0033] The force transmitter itself can be mounted in an object (e.g., a component, operating element, or machine) via a forward connection and / or a friction connection, so that multiaxial loads on the object are directly transferred to the force transmitter.

[0034] Load refers to mechanical load, and for the purposes of this invention, it preferably means deformation, stress, force and / or torque acting on a corresponding component (such as an object, force transmitter or base plate).

[0035] The load can include, for example, deflection relative to the force transmitter, such as due to lateral force (F). x F yThe deflection caused by the lateral force is preferably applied at the end of the force transmitter away from the base plate, which is preferably a pin. The (mechanical) stress is preferably indicated by the ratio of forces (e.g., lateral forces) on the selected cross-sectional area. The mechanical normal stress σ exerted by the object on the selected cross-sectional area A is the component F of the external force F acting perpendicularly on area A. n Therefore, the normal stress σ xx Preferably, it indicates the force (F) acting along the x-axis in a selected x, y coordinate system on a cross-sectional region A (yz plane) perpendicular to the x-axis of the sensor chip or substrate. x ).

[0036] The deflection of the force transmitter causes deformation of the base plate, particularly in the area where the force transmitter is fixed, i.e., in the area where the force transmitter is positively connected and / or frictionally connected to the base plate, preferably, the force transmitter is a pin.

[0037] For example, in the area of ​​the base plate, strain or compression will occur, which is a function of the direction and magnitude of deflection, and conclusions can be drawn from strain or compression.

[0038] Strain (usually denoted by the formula ε) indicates the relative change in the length of an object, which can be either elongation or shortening. An increase in the size of an object is called positive strain or expansion, otherwise it is called negative strain or compression. Strain is preferably defined as ε = Δl / l0, where Δl represents the change in length and l0 represents the initial length.

[0039] Within the scope of this invention, particularly the detection of local expansion or contraction of the base plate using a sensor chip, enables precise determination of the deflection of the force transmitter across multiple axes. The plane (xy plane) preferably corresponds to the plane on which the sensor chip with sensor elements is arranged, and, for example, preferably measures shear stress or normal differential stress.

[0040] If the force transmitter is mounted in the forward orientation into an object such as a joystick or shaft, deformation or stress in the object can be detected directly by measuring the minimum deflection.

[0041] The load can also be the axial force (F) acting on the force transmitter along the axial direction (or along its longitudinal direction if the force transmitter is a pin) of the force transmitter. z Related to this. When there is axial tensile or compressive force on the force transmitter, unique deformation or stress will also occur in the fixed area of ​​the base plate. Preferably, the force transmitter is in the form of a pin. For example, in the case of a rounded pin, the base plate may experience bending due to axial tensile or shear force on the force transmitter, and exhibit characteristic expansion or compression patterns.

[0042] In addition, the torque (M) acting on the force transmitterz It can also advantageously induce specific deformations or stresses in areas of the base plate, for example, in the form of torsional modes. By appropriately integrating the device, particularly the force transmitter, into the component (e.g., the tool spindle), the torque or torsional mode within the component or spindle can be measured.

[0043] The possible applications of the device according to the invention are diverse, and the advantages of the proposed device are particularly evident in the measurement or monitoring of multiaxial loads.

[0044] In addition, the device is characterized by its compact structure, as it preferably uses only a single sensor chip to measure the load on the force transmitter in a localized area of ​​the base plate.

[0045] Due to the separation of media, this device is also particularly robust in handling. The force transmitter of the spring body is connected to the front of the object or component, while the sensor chip is mounted separately on the back of the spring body. For example, due to its compact structure, accurate measurement precision, and media separation, this device can be used as a miniaturized flow sensor, preferably based on the baffle or eddy current principle or a combination thereof.

[0046] Furthermore, the device according to the invention is particularly suitable for tactile control in human-machine interface (HMI) applications. The high rigidity of the spring body is advantageous in this regard, as it allows for precise, displacement-free control using preferably low forces (e.g., 5 N to 10 N).

[0047] When integrated into a joystick, this device can be used, for example, to operate machines, vehicles, or wheelchairs. It can also be used to provide a keyboard panel. Due to its highly sensitive measurement of Z-axis axial force and torque around the X or Y axes, the location and magnitude of forces applied to a panel connected to a force sensor can be measured with extreme sensitivity. This device is also particularly well-suited as a "sensing probe" in 3D coordinate metrology, thus providing a significantly smaller, more compact, and more cost-effective solution compared to existing technologies.

[0048] Furthermore, the compact and robust design of the device allows for particularly advantageous use as a force sensor in soft / sensitive robots. Here, force-based control can supplement or replace pure path control. This allows for much more sensitive control, such as in the positioning of clamping movements or automated guiding elements (e.g., tools) upon the occurrence of reaction forces. Advantageously, the device according to the invention can therefore also be used, for example, in complex human-machine collaborative work or precision machining, such as metal cutting.

[0049] Pure path-control robotic systems typically lack the sensitivity required for such applications. Although path control can be extremely precise, without accurate measurement of the forces applied, it is easy to cause unintended damage to the object being processed.

[0050] In a preferred embodiment, the spring body is configured such that the force and / or torque acting on the force transmitter is concentrated in a localized area of ​​the base plate, such that a sensor chip mounted on the back side and below said area allows conclusions about the force and / or torque acting on the force transmitter to be drawn based on measurements of deformation, stress, force and / or torque of the substrate of the sensor chip connected to said area of ​​the base plate.

[0051] Particularly preferably, the force transmitter is a pin (or also a rod or pointer), and preferably, the pin is arranged in a manner that is powerless (unloaded) and substantially perpendicular to the surface of the base plate.

[0052] Force conductors, particularly pin-shaped force conductors, are preferably elongated elliptical in shape, with a cross-sectional dimension relatively small compared to their length or height. The ratio of the cross-sectional dimension to the length or height is preferably referred to as the aspect ratio. The cross-sectional dimension preferably represents the maximum extension in the cross-section of the force conductor. In the case of a circular cross-section, the cross-sectional dimension preferably corresponds to the diameter. In the case of a square cross-section, the cross-sectional dimension preferably corresponds to the side length.

[0053] Terms such as substantially, approximately, about, etc., preferably describe tolerance ranges of less than ±20%, more preferably less than ±10%, even more preferably less than ±5%, and particularly less than ±1%. Indications such as substantially, approximately, about, etc., are also always disclosed and include the precise values ​​mentioned.

[0054] In a preferred embodiment, the force transmitter has a diameter of 0.5 mm to 5 mm, particularly preferably, a diameter of 1 mm to 3 mm, and / or a length of 5 mm to 500 mm, preferably, a length of 10 mm to 100 mm, and is preferably in the form of a pin.

[0055] In a preferred embodiment, the aspect ratio of the pin's diameter to its length is 1:3 to 1:100, and more preferably, the aspect ratio is 1:5 to 1:20.

[0056] In a preferred embodiment, the pin has a central hole, wherein, preferably, the wall thickness of the pin with the central hole is between 0.2 mm and 5 mm, and particularly preferably, the wall thickness of the pin with the central hole is between 0.5 mm and 2 mm. In this embodiment, preferably, the force transmitter has the shape of a hollow cylinder, wherein the hole exists along the central axis and the wall thickness preferably corresponds to the difference between the outer radius (of the pin) and the inner radius (of the hole).

[0057] Providing holes in the pins that act as force transmitters requires a special deformation of the base plate, which allows for particularly precise measurement of the force or torque acting on the force transmitter.

[0058] For the purposes of this invention, the base plate preferably refers to a substantially flat component having a front side and a back side, wherein the maximum extension (length, width) of the front or back side is relatively large compared to the thickness of the base plate. For example, in the case of a circular shape, the maximum extension of the front or back side of the base plate may correspond to the diameter. Preferably, the thickness of the base plate may be 5 times, 10 times, 20 times, or more smaller than the maximum extension of the front or back side (e.g., the diameter or edge length of the front or back side).

[0059] The shape of the front or back side of the base plate can have a variety of characteristics and can be, for example, circular, rectangular, trapezoidal, triangular, or elliptical, but is not limited to these examples.

[0060] Within the meaning of this invention, positioning the sensor chip below the force transmitter preferably means that the sensor chip is positioned in a localized area on the back side of the base plate opposite to the force transmitter or fixing point. Preferably, the sensor chip thus at least partially overlaps with the projection of the front fixing point of the force transmitter. In a preferred embodiment, the force transmitter and the sensor chip can be axially aligned with each other.

[0061] In a preferred embodiment, the base plate can be formed of a substantially homogeneous planar body. Similarly, it is preferred that the base plate is not a homogeneous body, but may have interruptions, such as slots, openings, or other forms of topological interruptions. The base plate can also be formed, for example, of a lattice structure that deforms in a characteristic (measurable) manner when a load is applied to the force conductor. Therefore, the term "basic structure" can preferably be used synonymously with the term base plate.

[0062] In a preferred embodiment, the base plate has a thickness between 0.1 mm and 2 mm, and preferably, the base plate has a thickness between 0.3 mm and 0.7 mm.

[0063] In a preferred embodiment, the base plate and / or force transmitter are made of metal, preferably selected from iron, steel, stainless steel, spring steel, brass, copper, titanium, aluminum, lead, magnesium, beryllium copper and / or other alloys of the foregoing.

[0064] In another preferred embodiment, the base plate and / or force transmitter may be provided not only by metal, but also by other materials of microsystems technology, such as semiconductors, ceramics, or plastics.

[0065] Ceramic materials are characterized, in particular, by their high tolerance to high-temperature applications or harsh environmental conditions, especially for providing base plates and / or force transmitters. For example, the device is also suitable for media separation because the sensor chip is attached to the back side of the base plate. Therefore, for applications in flow sensors, the force transmitter can be located in the flowing fluid (liquid or gas), while the sensor chip is mounted on the opposite side of the base plate.

[0066] In a preferred embodiment, the base plate and / or force conductor can be formed from a substrate, preferably selected from monocrystalline silicon, polycrystalline silicon, silicon dioxide, silicon carbide, silicon germanium, silicon nitride, nitride, germanium, carbon, gallium arsenide, gallium nitride, indium phosphide, and glass.

[0067] These materials are easy and inexpensive to process in semiconductor and / or microsystem manufacturing, and are suitable for mass production. Furthermore, this allows for the provision of devices that preferably employ integrated (semiconductor) processes, including a spring body and a sensor chip. This simplifies manufacturing, enabling the provision of particularly compact multiaxial force sensors at low cost.

[0068] The aforementioned dimensions and materials of the force transmitter and base plate have proven advantageous in providing a particularly sensitive measuring device.

[0069] In a preferred embodiment, the base plate and / or force transmitter has an unloading groove, preferably in the form of a boundary surrounding the area where the force transmitter is fixed to the base plate. The unloading groove particularly refers to a recess, cavity, or notch present in the form of a boundary on the base plate and / or force transmitter.

[0070] In this respect, it is particularly advantageous to provide a center hole and / or an unloading groove within the pin, preferably in the form of a groove surrounding the boundary of the area where the force transmitter is fixed to the base plate.

[0071] These two features are independent of each other, but together they are particularly pronounced, resulting in characteristic deformation of the base plate in the fixed area, thus allowing for particularly sensitive measurement of multiaxial loads on the force transmitter.

[0072] In a preferred embodiment, the spring body can be integral. That is, the force transmitter and the base plate are formed from a single material, preferably, the force transmitter is a pin. However, the spring body can also be formed as a composite, in which case the force transmitter is fixed to the base plate, preferably, the force transmitter is a pin.

[0073] Within the meaning of this invention, a sensor chip preferably refers to a semiconductor component comprising at least one substrate having one or more sensor elements and preferably electronic circuitry.

[0074] In a preferred embodiment, one or more sensor elements are configured to perform resistive, optical, magnetic, inductive, and / or capacitive measurements of the deformation, stress, force, and / or torque of the substrate, preferably, the resistive measurement being a piezoresistive measurement.

[0075] Resistive and piezoresistive sensor elements are typically based on the change in resistance caused by variations in the length of the substrate on which they are mounted. The piezoresistive change in resistance due to strain on the sensor element is significantly stronger (k-factor), especially in the case of (doped) semiconductors, and preferably allows for more sensitive and accurate strain measurements. Preferably, the change in resistance can be measured by the change in stress applied to the sensor element in a Wheatstone bridge.

[0076] Preferably, the piezoelectric sensor element is based on the inherent voltage of the material generated by the compressive and / or tensile forces acting on the device.

[0077] Preferably, the inductive measuring device is based on the intensity of the current induced by the changing magnetic field.

[0078] Preferably, the optical sensor element can measure the strain between different regions via distance measurement (e.g., interferometry), wherein the superposition of coherent optical signals provides information about their phase difference, which is readable. Preferably, this phase difference, in turn, contains information about the distance between the regions.

[0079] Magnetic sensor elements can be, for example, based on Hall sensors, which generate different voltages depending on the position within a magnetic field and thus on the magnetic flux density experienced. Therefore, preferably, in the case of a fixed reference magnetic field, the relative position of the Hall sensor to that magnetic field can be detected using the measured voltage. This measurement principle can be particularly used to achieve distance measurement (and thus stress or strain measurement) between different areas on a substrate.

[0080] Preferably, the capacitive sensor element is based on the principle that the capacitance of a capacitor changes measurably with the distance between capacitor plates (electrodes). Various different implementations are conceivable, such as in the form of capacitor plates on a substrate, as a (MEMS) comb structure, wherein the comb-shaped coverage and / or comb-shaped spacing can vary depending on the implementation.

[0081] Those skilled in the art know of various sensor elements and materials that can be preferably used to achieve resistive, optical, magnetic, inductive, and / or capacitive measurements of deformation, stress, force, and / or torque, preferably, the resistive measurement being a piezoresistive measurement.

[0082] Preferably, a MEMS sensor, i.e., a component based on MEMS technology, is used. MEMS stands for "microelectromechanical system," meaning a microsystem, which enables compact designs (in the micrometer range) while offering excellent functionality and lower manufacturing costs. In particular, the entire sensor chip, including the sensor elements and electronics, is preferably fully integrated into CMOS technology.

[0083] Preferably, the sensor element is arranged on the substrate together with electronic circuitry for evaluating and / or controlling the sensor element, and the sensor element is in contact with the circuitry via an electrical connection, which is made, for example, by wire bonding and / or laid in the substrate, for example, by conductor tracks. The substrate is particularly used as a mechanical carrier, but it can also realize electrical functions, such as providing electrical connections for various components.

[0084] Preferred electronic circuits include, but are not limited to, integrated circuits (ICs), application-specific integrated circuits (ASICs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), microprocessors, microcomputers, programmable logic controllers, and / or other electronic circuits, preferably programmable circuits.

[0085] With the aid of electronic circuitry on the sensor chip and / or additional electronic components, it is preferably possible to read and / or pre-process the measurement data of the sensor elements. For this purpose, a multiplexer (MUX, for reading signals from multiple sensor elements), an operational amplifier (e.g., a differential amplifier (DDA) with variable gain), or an analog-to-digital converter (ADC) may be present on the sensor chip or on a circuit carrier for converting the signals into digital data.

[0086] In a particularly preferred embodiment, one or more sensor elements include a piezoresistive structure; preferably, one or more sensor elements include a piezoresistive sensor bridge.

[0087] Preferably, the piezoresistive sensor bridge can be designed as a Wheatstone bridge, and more preferably, it can be designed as a full bridge. Advantageously, the four piezoresistive structures forming the full bridge can be positioned very close to each other. Because temperature drift preferably affects all piezoresistive structures equally, compensation is provided for interference sources such as temperature drift.

[0088] Particularly preferably, the sensor chip includes more than 3, more than 5, more than 10, more than 15, more than 20 or more sensor elements, wherein the sensor elements are distributed at various locations on the substrate.

[0089] Due to the large number of sensor elements, the two-dimensional distribution of deformation, stress, force, and / or torque on the substrate can be measured with exceptional precision. For example, unlike semiconductor strain gauge sensors, sensor chips do not integrate local loads on the entire surface of the substrate. Instead, by means of a large number of sensors on the substrate, spatially resolved measurements of stress or strain in relevant regions below the basic surface can be achieved.

[0090] In a preferred embodiment, one or more sensing elements are used to measure the differential stress σ on the substrate. xx –σ yy Perform measurements. Stress σ xx and σ yy This corresponds to the orthogonal normal stress in the xy plane.

[0091] In a preferred embodiment, one or more sensor elements respond to shear stress σ xy Measurements are performed to detect the shear force acting on the substrate.

[0092] In a preferred embodiment, the sensor element is designed as a piezoresistive sensor bridge, which is arranged in a square like a Wheatstone bridge, thereby detecting shear stress by means of an n-channel based transistor, and thus the sensor bridge is rotated 45° relative to the (x, y) coordinate system, while the p-channel based transistor is arranged parallel to the coordinate system of the sensor bridge and measures the normal differential stress by means of the p-channel based transistor.

[0093] Particularly preferably, the piezoresistive sensor bridge is designed as a square field-effect transistor (FET, preferably MOSFET) (piezoelectric FET) with four source / drain contacts, utilizing the piezoresistive shearing effect in an n-type (NMOS) or p-type (PMOS) inversion layer. Preferably, the NMOS sensor element is used to detect shear stress σ. xy Measurements are performed, and PMOS sensor elements are used to measure the normal differential stress (σ). xx –σ yy Measurements are performed using this method. Examples of preferred sensor chips with a piezoresistive sensor bridge as the sensor element were disclosed by Gieschke et al. (2009) and Kuhl et al. (2013). Advantageously, particularly compact sensor elements with dimensions of 10 μm × 10 μm or smaller can be realized.

[0094] Particularly preferably, the sensor may have a differential stress σ relative to the normal stress. xx –σ yy Multiple sensor elements for detection and the shear stress σ xyMultiple sensor elements are used for detection. This provides a particularly accurate image of the two-dimensional stress distribution in the substrate, and thus indirectly provides an image of the area of ​​the substrate on which the force conductor is fixed.

[0095] In a preferred embodiment, the substrate of the sensor chip comprises a semiconductor material, preferably silicon, monocrystalline silicon, polycrystalline silicon, silicon dioxide, silicon carbide, silicon germanium, silicon nitride, nitride, germanium, carbon, gallium arsenide, gallium nitride, and / or indium phosphide. These materials are easy to process and inexpensive in semiconductor and / or microsystem manufacturing, and are also well-suited for mass production. Similarly, these materials are particularly suitable for doping and / or coating to achieve desired electrical, mechanical, thermal, and / or optical properties in specific areas.

[0096] Sensor elements for measuring mechanical deformation and / or stress acting on a sensor chip are integrated onto or within a substrate. Materials and / or manufacturing techniques known in the semiconductor industry can be used here, characterized by their high efficiency, simplicity, low production cost, and suitability for mass production.

[0097] For example, masking (preferably photolithography) on a substrate can be used to define areas for forming sensor elements and / or electronic circuitry, on which further semiconductor processes, such as etching, doping, and / or deposition, can be performed. The substrate can also be a multilayer substrate comprising two or more layers that are individually processed and bonded together (adhesive).

[0098] Preferably, etching and / or patterning can be selected from dry etching, wet chemical etching and / or plasma etching, especially reactive ion etching and deep reactive ion etching (Bosch process).

[0099] Preferably, the application or deposition can be selected from physical vapor deposition (PVD), particularly thermal evaporation, laser beam evaporation, arc evaporation, molecular beam epitaxy, sputtering, chemical vapor deposition (CVD) and / or atomic layer deposition (ALD).

[0100] For example, doping can be performed using known processes such as alloying, diffusion, and / or ion implantation.

[0101] In a preferred embodiment, the substrate of the sensor chip has a thickness between 100 μm and 600 μm, and more preferably, the substrate of the sensor chip has a thickness between 200 μm and 400 μm. The substrate size is particularly suitable for ensuring good transmission of stress deformation or deformation of the base plate area to the sensor element.

[0102] Preferably, the sensor chip is attached to the back of the substrate from one side of the substrate. For this purpose, an adhesive can be used, for example, to create a direct connection between the substrate and the substrate.

[0103] In addition to using adhesives for bonding, various techniques in integrated circuit packaging (ICP) can be used to mechanically couple sensor chips to the substrate. These include, but are not limited to, the use of adhesive films, soldering, brazing (welding), reactive bonding (preferably using thermally reactive films, especially nanomultilayer or reactive multilayer systems RMS bonding), or bonding, such as anodic bonding, direct bonding, bonding processes with intermediate layers (e.g., eutectic bonding), glass frit bonding, adhesive bonding, and / or selective bonding.

[0104] Preferably, mechanical deformation is directly transferred to the thin film substrate via mechanical coupling using ICP technology (e.g., adhesive bonding, welding, reactive bonding, adhesion, etc.), wherein sensor elements on opposite sides of the substrate pick up two-dimensional stress or deformation images.

[0105] Therefore, preferably, the sensor element is used to detect deformation or stress of the sensor chip itself or the substrate. Due to the mechanical coupling with the force transmitter, the measured data provides direct conclusions about the stress, force, deformation, or torque acting on or in an object in which the force transmitter is integrated.

[0106] Through various calibrations, not only relative information about changes in mechanical loads within a force transmitter or object can be obtained, but also absolute information about stresses, forces, deformations, or torques acting on a component. For example, the mechanical properties of sensor chips or substrates, as well as force transmitters, can be included in the calibration.

[0107] Due to the finite thickness of the substrate, the two-dimensional stress or deformation image generated by the sensor element on the free side of the substrate may differ from the actual stress or deformation distribution on the substrate. However, for a given sensor chip and substrate, the difference is constant, and therefore these differences are included in the calibration.

[0108] In another preferred embodiment, the device includes one or more sensing interfaces, preferably coils, for transmitting measurements and / or for supplying energy.

[0109] This telemetry interface allows for particularly flexible use of energy-autonomous devices.

[0110] The power required for operation can be coupled in from an external reader via a sensing interface. The integrated sensor element can then measure stress or deformation distribution and wirelessly transmit the measured data to the reader. For data transmission via a telemetry interface, such as using NFC... Near Field Communication Standards may also be preferred.

[0111] Advantageously, the device can also be used, for example, to monitor rotating objects, such as tool spindles, which would otherwise be difficult to achieve through cable-based contact.

[0112] The sensing interface or (responder) coil can be mounted on the sensor chip itself, or separately on, for example, a printed circuit board.

[0113] In a preferred embodiment, the sensor chip is in contact with a circuit carrier. Preferably, the circuit carrier is a component comprising an electrically insulating material on which conductive connections (conductor tracks) and / or electronic components or assemblies are present.

[0114] In a preferred embodiment, the circuit carrier is a printed circuit board, wherein both conventional (rigid) printed circuit boards and flexible printed circuit boards can be used.

[0115] In a preferred embodiment, the sensor chip can also contact the circuit carrier via an on-board chip method, wherein, preferably, the electrical contact is achieved through flip-chip assembly or chip and lead technology, and preferably, the electrical contact is achieved through wire bonding.

[0116] In chip and wire bonding technology, preferably, the sensor chip is directly bonded to a circuit carrier (e.g., a printed circuit board) and electrically connected to the circuit carrier via wire bonding (a bridge made of fine wires).

[0117] Preferably, for example, the sensor chip can be attached to the back of the substrate using ICP technology (e.g., adhesive bonding, soldering, reactive bonding, etc.) and connected to a printed circuit board (PCB) via electrical connections (e.g., wire bonding), the PCB also being connected to the substrate. Alternatively, preferably, a flip-chip assembly can also be used, in which case the sensor chip is preferably attached to a circuit carrier (e.g., a PCB) having an active contact side on which sensor technology (sensor elements) and / or electronics are positioned. Preferably, contact is made via contact bumps, for example, via anisotropic conductive films. In flip-chip assemblies, it is preferable to attach the sensor chip directly to the base surface using adhesive to achieve optimal force transfer with the substrate, wherein the PCB is located on an accessible side away from the substrate.

[0118] Contact can be established between the sensor chip and the external data processing unit in a wired or wireless manner. Preferably, contact is established between the sensor chip and the external data processing unit via an interface on the circuit carrier.

[0119] Contact can be established between the sensor chip and the external data processing unit via wired or wireless means. Preferably, contact is established between the sensor chip and the external data processing unit via an interface on a circuit carrier (e.g., a printed circuit board).

[0120] For sensor chips, different shapes are preferred, such as circular, rectangular or other polygonal shapes, with rectangular shapes being particularly preferred, especially square shapes.

[0121] In a preferred embodiment, the sensor chip has a width and / or length of 0.5 mm to 10 mm, preferably 1 mm to 5 mm, and more preferably 1 mm to 3 mm. Preferably, the sensor chip has a thickness of less than 1 mm, more preferably less than 700 μm, or less than 500 μm.

[0122] Therefore, in a preferred embodiment, the sensor chip is substantially flat, i.e., the sensor chip is characterized by having a larger width and / or length in a plane (xy plane) compared to a dimension (z-axis, thickness) orthogonal to said plane. This factor can be, for example, 2, 3, 5, or greater.

[0123] In a preferred embodiment, the sensor chip has a diameter of 0.25 mm. 2 Up to 100 mm 2 The area, preferably, the sensor chip has 1 mm 2 Up to 25 mm 2 More preferably, the sensor chip has an area of ​​1 mm. 2 Up to 9 mm 2 The area.

[0124] In another aspect, the present invention preferably relates to a system comprising: a) the described apparatus; and b) Data processing unit, The data processing unit is configured to read the measurement data detected by the sensor chip.

[0125] Those skilled in the art will recognize that the technical features, definitions, and advantages disclosed for the preferred embodiments of the apparatus according to the invention are equally applicable to systems including such apparatus, and vice versa.

[0126] Preferably, the data processing unit is configured to detect the force and / or torque acting on the force transmitter by means of measurement data relating to the deformation, stress, force and / or torque of the substrate detected by the sensor chip.

[0127] Therefore, preferably, the data processing unit allows for the evaluation of measurement data from the sensor chip in order to detect the actual load on the force transmitter or the object connected to the force transmitter.

[0128] The electronic circuitry on the sensor chip itself can also perform (pre)evaluation of the measurement data. However, it is also preferable that the unprocessed measurement data is forwarded from the electronic circuit board to an (external) data processing unit for further processing and / or evaluation.

[0129] The (external) data processing unit is preferably a unit suitable for and configured to receive, transmit, store, and / or process data, preferably measurement data. Preferably, the data processing unit includes an integrated circuit, processor, processor chip, microprocessor, or microcontroller for processing the data, and a data storage device for storing the data, such as a hard disk, random access memory (RAM), read-only memory (ROM), or flash memory.

[0130] To detect the force and / or torque acting on the force transmitter based on measurement data related to the deformation, stress, force, and / or torque of the substrate detected by the sensor chip, preferably, a computer program including commands for performing corresponding calculation steps can be stored in a data memory. Preferably, for this purpose, reference data obtained through appropriate calibration can also be available on the data processing unit.

[0131] Particularly preferably, the data processing unit is a personal computer (PC), laptop computer, tablet computer, etc., which, in addition to including means for receiving, sending, storing and / or processing data, also includes a data display and input means such as a keyboard, mouse, touch screen, etc. Furthermore, preferably, the data processing unit can also be used to control the device, i.e., for example, to preset parameters used to perform measurements. Attached Figure Description

[0132] Figure 1A and Figure 1B A schematic diagram of a preferred embodiment of the spring body 1 according to the present invention is shown. Figure 1A A top view of the spring body 1 is shown, making the front side of the base plate 5 visible. Figure 1B The back side of the base plate 5 is shown. Figure 2A , Figure 2B , Figure 3A , Figure 3B and Figure 3C Measurements of stress or deformation generated in the area of ​​the base plate 5 and below the force transmitter 3 are shown.

[0133] Figure 4A , Figure 4Band Figure 4C A preferred embodiment of the sensor chip 2 is shown, illustrating sensor technology or electronics located on a substrate.

[0134] Figure 5A , Figure 5B and Figure 5C An example application of the preferred device is shown. Detailed Implementation

[0135] The present invention will now be described in more detail through embodiments, but the present invention is not limited to these embodiments.

[0136] Figure 1A and Figure 1B A schematic diagram of a preferred embodiment of the spring body 1 according to the present invention is shown.

[0137] The spring body 1 includes a force transmitter 3, which has a pin shape and is mechanically connected to the base plate 5 in a fixed area. When no force is applied, the force transmitter 3 is substantially perpendicular to the base plate 5. A force or torque acting on the force transmitter 3 causes deflection or deformation, which is transmitted directly to the fixed area of ​​the base plate 3.

[0138] Figure 1A A top view of the spring body 1 is shown, making the front side of the base plate 5 visible. Figure 1B The back side of the base plate 5 is shown.

[0139] Figure 1A The deflection of force transmitter 3 in the spatial direction is shown. For example... Figure 1B As shown, this deflection causes characteristic deformation on the back side of the base plate 5 and below the pin 3. The red area indicates extension, while the blue area indicates compression. The arrangement or alignment of the compressed and extended areas allows for highly accurate resolution of the deflection direction of the force transmitter 3. The magnitude of the deformation or stress in the base plate 5 is also very precisely correlated with the magnitude of the deflection of the force transmitter 3.

[0140] The spring body 1 shown allows the force and / or torque acting on the force transmitter 3 to be concentrated in a local area of ​​the base plate 5, such that the sensor chip on the back side and located below said area ( Figure 1A and Figure 1B (Not shown in the image) allows for the determination of the force and / or torque acting on the force transmitter 3 based on measurements of the deformation, stress, force, and / or torque of the substrate of the sensor chip connected to the base plate 5.

[0141] For this purpose, the shape of the circular pin 3 has proven advantageous, as the circular pin 3 is substantially perpendicular to the base plate 5 without any force. Particularly good results can also be obtained if the pin 3 has a central hole 6 and a relief groove 7 in the form of a boundary exists in the base plate 5 and / or the force transmitter 3.

[0142] Figures 2A to 3C Measurements of stress or deformation generated in the area of ​​the base plate 5 and below the force transmitter 3 are shown.

[0143] like Figure 2A and Figure 2B As shown, the sensor chip 2 or its substrate undergoes similar deformation or stress distribution due to its direct coupling to the base plate 5, which can be recorded on the sensor chip 2 by means of a sensor element (not shown).

[0144] Figures 3A to 3C It shows that due to, as Figure 1A and Figure 1B The two-dimensional stress distribution at the base plate 5 caused by the deflection of the force transmitter 3 is shown.

[0145] Figure 3A and Figure 3B The normal stress Sx (or σ) is shown respectively. xx ) and Sy (or σ) yy The two-dimensional distribution of ).

[0146] Preferably, the difference in normal stress Sx-Sy (or σ) between the sensor chip 2 or the sensor element mounted thereon and the sensor chip 2 is... xx -σ yy ) to conduct testing.

[0147] This difference can be found in Figure 3C As can be seen from this, the stress distribution is advantageously characterized by a series of characteristic peaks, which allows for highly accurate measurement of the deflection of the force transmitter 3.

[0148] Figures 4A to 4C A preferred embodiment of sensor chip 2 is shown. Figures 4A to 4C The illustration shows sensor technology or electronic devices located on a substrate.

[0149] The sensor chip 2 comprises a total of 32 sensor elements 9, which are located at different positions on the substrate to ensure two-dimensional resolution of stress distribution. The sensor chip 2 itself has a length and width of approximately 2 mm x 2.5 mm and a thickness of approximately 300 μm.

[0150] Sensor chip 2 is fully integrated using CMOS technology. Sensor element 9 is a piezoresistive sensor bridge; preferably, sensor element 9 is a Wheatstone bridge (see [link]). Figure 4B and Figure 4C ).

[0151] Figure 4B Sensor element 9 is shown, which is a PMOS type piezoresistive sensor bridge, arranged parallel to the coordinate system (x, y), and specifically for the difference in normal stress σ. xx -σ yy It is sensitive.

[0152] Figure 4C Sensor element 9 is shown, which is an NMOS type piezoresistive sensor bridge oriented at 45° with the coordinate system (x, y) and is particularly sensitive to shear stress σ. xy It is sensitive.

[0153] In addition to sensor element 9, the sensor chip also has additional electronic components. Specifically, sensor chip 2 includes control logic, which serves as electronic circuit 11 or an analog-to-digital converter (ADC) and operational amplifier (differential amplifier) ​​(DDA). In a preferred embodiment, a sensing interface (telemetry interface) is also present for wirelessly reading measurement data or for power supply.

[0154] Figures 5A to 5C An example application of the preferred device is shown. Here, the device with force transmitter 3 is located within the joystick. Movement of the joystick causes deflection of the force transmitter 3, which can be detected based on measurements of stress or deformation distribution by a sensor chip (not shown).

[0155] To supply power to the sensor chip and read measurement data, the device includes an inductive interface in the form of a secondary coil. The power required for operation can be coupled in via an external base unit or reader, which includes a primary coil for this purpose. The integrated sensor element can then measure voltage or deformation distribution and wirelessly transmit the measurement data to the base unit or reader.

[0156] The basic unit or reader can already perform (pre)evaluation of the data via an electronic reading process as a data processing unit. Preferably, the measurement data is also transferred to another external data processing unit, such as a PC, laptop, or mobile device, for evaluation, visualization, and / or storage.

[0157] Reference tag list 1. Spring body 2 sensor chips 3. Force transmitter, preferably a pin 5 base plates 6 center holes 7 Unloading groove 9 sensor elements 11 Electronic circuits, such as ASICs 13. Sensor interface.

[0158] References Gieschke P. , Y. Nurcahyo, M. Herrmann, M. Kuhl, P. Ruther and O.Paul, "CMOS Integrated Stress Mapping Chips with 32 N-Type or P-Type Piezoresistive Field Effect Transistors," 2009 IEEE 22nd International Conference on Micro Electro Mechanical Systems, Sorrento, Italy, 2009, pp.769-772, doi: 10.1109 / MEMSYS.2009.4805496. Jaeger Richard.C., Suhling, Jeffrey C., Ramani, Ramanathan, Bradley, Arthur T. and Xu, Jianping, CMOS Stress Sensors on (100) Silicon, IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 35, NO. 1, JANUARY 2000. Kuhl M., Gieschke, P., Rossbach, D., Hilzensauer, S., Panchaphongsaphak, T., Ruther, P., Lapatki, B., Paul, O., Manoli, Yi, "A Wireless Stress Mapping System for Orthodontic Brackets Using CMOS Integrated Sensors," in IEEE Journal of Solid-State Circuits, vol. 48, no. 9, pp. 2191-2202, Sept. 2013, doi: 10.1109 / JSSC.2013.2264619.

Claims

1. An apparatus for measuring multiaxial loads on an object, the apparatus comprising: -Spring body (1); as well as - Sensor chip (2), the sensor chip (2) includes one or more sensor elements (9) and electronic circuitry (11) on a substrate, the sensor elements (9) being used to measure deformation, stress, force and / or torque, wherein the substrate of the sensor chip (2) comprises semiconductor material, Its features are, The spring body (1) includes a base plate (5), on the front side of which a force transmitter (3) is mounted. The sensor chip (2) is located on the back side of the base plate (5) and below the force transmitter (3), and is attached to the back side of the base plate (5). The spring body (1) is configured such that the force and / or torque acting on the force transmitter (3) is concentrated in a local area of ​​the base plate (5), the substrate of the sensor chip (2) is connected to the local area, and the force and / or torque acting on the force transmitter (3) is converted into deformation or stress of the substrate of the sensor chip (2), and wherein the one or more sensor elements (9) are configured to measure the deformation or stress of the substrate of the sensor chip (2) to be able to draw conclusions about the force and / or torque acting on the force transmitter (3).

2. The apparatus according to claim 1, Its features are, The spring body (1), including the base plate (5) and the force transmitter (3), is formed as a single unit.

3. The apparatus according to claim 1, Its features are, The force transmitter (3) is formed by a pin that is substantially perpendicular to the base plate (5) when no force is applied to it.

4. The apparatus according to claim 3, Its features are, The pin (3) has a diameter of 0.5 mm to 5 mm, a length of 5 mm to 500 mm, and / or, the pin (3) has a diameter-to-length ratio of 1:3 to 1:

100.

5. The apparatus according to claim 3, Its features are, The pin (3) has a central hole, wherein the wall thickness of the pin with the central hole is between 0.2 mm and 5 mm.

6. The apparatus according to claim 1, Its features are, The base plate (5) has a thickness between 0.1 mm and 2 mm.

7. The apparatus according to claim 1, Its features are, The base plate (5) and / or the force transmitter (3) have unloading grooves (7) that are in the form of the boundary of the area where the force transmitter (3) contacts the base plate (5).

8. The apparatus according to claim 1, Its features are, The base plate (5) and / or the force transmitter (3) are made of metal selected from iron, steel, stainless steel, spring steel, brass, copper, titanium, aluminum, lead, magnesium, and beryllium copper.

9. The apparatus according to claim 1, Its features are, One or more of the sensor elements (9) are configured to perform resistive, optical, magnetic, inductive and / or capacitive measurements of the deformation, stress, force and / or torque of the substrate, wherein the resistive measurement is a piezoresistive measurement.

10. The apparatus according to claim 1, Its features are, One or more of the sensor elements (9) include a piezoresistive structure, and / or The sensor chip (2) has more than 5, more than 10, more than 15, more than 20 or more sensor elements (9), which have different sensitivities for measuring deformation, stress, force and / or torque of the substrate.

11. The apparatus according to claim 1, Its features are, The sensor chip (2) is configured to measure deformation, stress, force and / or torque in multiple axes.

12. The apparatus according to claim 1, Its features are, The sensor chip (2) includes 10 or more sensor elements (9) configured to measure the two-dimensional distribution of deformation or stress on the substrate.

13. The apparatus according to claim 1, Its features are, The semiconductor material of the substrate of the sensor chip (2) includes silicon, monocrystalline silicon, polycrystalline silicon, silicon dioxide, silicon carbide, silicon germanium, silicon nitride, nitride, germanium, carbon, gallium arsenide, gallium nitride and / or indium phosphide.

14. The apparatus according to claim 1, Its features are, The substrate of the sensor chip (2) has a thickness between 100 μm and 600 μm.

15. A system for measuring multiaxial loads on an object, the system comprising: a) The apparatus according to any one of claims 1-14; b) Data processing unit, Its features are, The data processing unit is configured to read the measurement data detected by the sensor chip.

16. The system according to claim 15, Its features are, The data processing unit is configured to detect the force and / or torque acting on the force transmitter based on measurement data related to the deformation, stress, force and / or torque of the substrate detected by the sensor chip.

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