Measuring transducer for end-face magnetostrictive measurement of loads, load measuring device and measuring arrangement equipped therewith, load measuring method and manufacturing method

Abstract

Sensor (16) for a load measuring device (14) for measuring a load on a test object (12), wherein the sensor (16) has several planar coils (36.1-36.4) to detect a magnetic field parameter on the test object (12) that changes due to the load, wherein the planar coils (36.1-36.4) are at least partially arranged in a ring around a center and each has a coil conductor (38.1-38.4) extending substantially in a radial plane, comprising inclined sections (40.1-40.4) and connecting sections (42.1-42.4), wherein the inclined sections (40.1-40.4) each extend obliquely in an inclination direction to a radial direction, wherein the connecting sections (42.1-42.4) each connect inclined sections (40.1-40.4) to each other and extend substantially in a radial direction, wherein the Planar coils (36.1-36.4) are connected in such a way that the connecting sections (42.1-42.4) Subtract the currents flowing in the circumferential or radial direction of the planar coils.

Description

[0001] The invention relates to a sensor for a load measuring device for measuring a load on a test object, wherein the sensor comprises a first and second planar coil to detect a magnetic field parameter on the test object that changes due to the load by means of signals at the outputs of the first and second planar coils. The invention further relates to a load measuring device for measuring a load on a test object, comprising a magnet generation device for generating a magnetic field in the test object and such a sensor. The invention further relates to a measuring arrangement comprising such a sensor or such a load measuring device and the test object, as well as a corresponding load measurement method. Finally, the invention relates to a manufacturing method for the sensor.

[0002] The invention lies in the field of magnetostrictive measurement of loads, such as stresses, forces, or—especially preferably—torques in a test object, such as a shaft. It is known that magnetic measurement methods can be used to determine the physical quantities of torque, force, and position on ferromagnetic objects. Magnetoelastic (or inverse magnetostrictive) sensors or eddy current sensors are most commonly used. The ferromagnetic materials used change their permeability under the influence of tensile or compressive stresses (also known as the Vilari effect).

[0003] Magnetostrictive load measurements and the devices used for them are well known; reference is made in particular to the following literature: [1] WO 2019 / 197500 A1 [2] WO 2019 / 207166 A1 [3] WO 2019 / 243448 A1 [4] WO 2018 / 229016 A1 [5] HINZ, Gerhard; VOIGT, Heinz; BOLL, R.; OBERSHOTT, K. J. (Hrsg.): Chapter 4 - Magnetoelastic sensors. In: Sensors: Magnetic sensors. Weinheim [u. a.]: VCH-Verl.-Ges., 1989 (Sensors: A comprehensive survey; 5). S. 97-152. - ISBN 3-527-26771-9 [6] US 3 311 818 A [7] EP 0 384 042 A2 [8] DE 30 31 997 A1 [9] US 3 011 340 A

[10] US 4 135 391 A

[11] DE 10 2009 008 074 A1

[12] WO 2012 / 152515 A1

[13] DE 85 11 143 U1

[14] DE 10 2021 123 392 A1

[15] WO 2018 / 185018 A1

[16] WO 2020 / 157278 A1

[17] US 2006 / 0179959 A1

[18] US 2020 / 0265995 A1

[19] DE 10 2019 214 219 A1

[0004] In some known measurement methods, a measuring area on the test object is permanently magnetized, and changes in the magnetic field caused by loading are detected by means of magnetic field detection devices, in particular measuring coils. In other measurement methods, active magnetization is carried out by means of a magnetic field generation device, in particular a measuring coil. From [1] to [4], the use and manufacture of planar coils for the measuring coils and the generator coil are known. In particular, three or five planar coil arrangements, which are formed from several stacked planar coils, are arranged in an X-arrangement or V-arrangement in a sensor head. From

[17] and

[18] , coil windings for sensor coils wound from single wire are known, which run around the shaft and have inclined measuring sections extending at 45° to the axis of rotation. Manufacturing methods for producing such coils are also described.In most known torque measurement methods, the measuring coils are arranged around the shaft, requiring a large amount of radial installation space. This is not always possible or desirable.

[0005] The invention aims to create a cost-effectively manufactured sensor for magnetostrictive load measurement that requires little radial installation space.

[0006] To solve this problem, the invention provides a measuring sensor according to claim 1 or 2.

[0007] Advantageous embodiments are the subject of the dependent claims.

[0008] Advantageous uses and a manufacturing method for the sensor are specified in the subsidiary claims.

[0009] According to a first aspect of the invention, a sensor for a load measuring device for measuring a load on a test object is provided, wherein the sensor has several planar coils to detect a magnetic field parameter on the test object that changes due to the load, wherein the planar coils are at least partially arranged in a ring around a center and each has a coil conductor extending in a substantially radial plane, comprising inclined sections and connecting sections, wherein the inclined sections extend – in particular in a straight line – obliquely to a radial direction, wherein the connecting sections each connect inclined sections to one another and extend (preferably in a straight line) in a radial direction or (preferably curved) in a circumferential direction, wherein the planar coils are interconnected in such a manner.that currents flowing through the connecting sections of the planar coils in the circumferential or radial direction subtract from each other.

[0010] According to a second aspect of the invention, a sensor for a load measuring device for measuring a load on a test object is provided, wherein the sensor has several planar coils to detect a magnetic field parameter on the test object that changes due to the load, wherein the planar coils are at least partially arranged in a ring around a center and each has a coil conductor extending in a substantially radial plane, comprising inclined sections and connecting sections, wherein the inclined sections extend – in particular in a straight line – obliquely to a radial direction in an inclination direction, wherein the connecting sections each connect inclined sections to one another and extend (preferably curved) in a circumferential direction, wherein the planar coils are interconnected in such a manner.that currents flowing through the connecting sections of the planar coils in the circumferential or radial direction subtract from each other. According to the second aspect, it is intended that the planar coils superimpose in the axial direction.

[0011] Preferably, the connecting sections of one of the planar coils run in the opposite direction to the connecting sections of another of the planar coils. Preferably, connecting sections with the same orientation are connected in pairs with opposite orientations. Preferably, inclined sections with the same orientation are connected in pairs with the same current direction.

[0012] In the first aspect as well, it is preferred that the planar coils overlap axially. However, the planar coils can also be arranged offset from each other circumferentially. Partial axial overlap and partial circumferential offset from each other is also possible.

[0013] According to the first aspect, it is intended that at least some or all of the connecting sections of at least one of the planar coils extend in a radial direction.

[0014] It is preferred that at least some or all of the connecting sections of at least one of the planar coils comprise an inner connecting section extending circumferentially with a smaller radius and at least one outer connecting section extending circumferentially with a larger radius.

[0015] It is preferred that the planar coils each have intersecting inclined sections directed obliquely to a radial direction at different inclinations.

[0016] It is preferred that the planar coils each have at least pairs of slant sections oriented in the same direction and are interconnected in such a way that the currents flowing obliquely to the radial direction through the at least pairs of slant sections oriented in the same direction add up.

[0017] It is preferred that the planar coils comprise at least one first and at least one second planar coil, wherein the at least one first planar coil and the at least one second planar coil are arranged at least partially in a ring shape around the center. wherein the at least one first planar coil has a first coil conductor extending substantially in a first radial plane, the first inclined sections extending obliquely to a radial direction in a first inclination direction, and first connecting sections connecting the first inclined sections together, wherein the at least one second planar coil has a second coil conductor extending substantially in a second radial plane, the second inclined section having inclined sections which each extend in the same direction to a first inclined section in the first inclination direction oblique to the radial direction, and second connecting sections which each extend antiparallel or opposite to a first connecting section in the circumferential or radial direction and connect the second inclined sections to each other, such that currents flowing through the first and second inclined sections in the first inclination direction add up and currents flowing through the first and second connecting sections in the circumferential or radial direction subtract.

[0018] It is preferred that the planar coils further comprise at least a third and at least a fourth planar coil, which are arranged at least partially in a ring shape around the center, wherein the at least one third planar coil has a third coil conductor extending substantially in a third radial plane, the third inclined sections extending obliquely to a radial direction in a second inclination direction with an inclination opposite to the first inclination direction, and third connecting sections connecting the third inclined sections together, wherein the at least one fourth planar coil has a fourth coil conductor extending substantially in a fourth radial plane, the fourth inclined sections extending in the same direction to a third inclined section in the second inclination direction oblique to the radial direction, and fourth connecting sections extending antiparallel or opposite to a third connecting section in the circumferential or radial direction and connecting the fourth inclined sections to each other, such that currents flowing through the third and fourth inclined sections in the second inclination direction add up and currents flowing through the third and fourth connecting sections in the circumferential or radial direction subtract.

[0019] In embodiments of the invention, the inclined sections are straight sections of the coil conductor that extend obliquely to the radial direction.

[0020] In embodiments of the invention, some inclined sections extend essentially parallel to the tensile stress, others essentially parallel to the compressive stress, each with reference to stresses that form in an area of ​​the test object near an end face surface on which the measuring sensor is to be arranged.

[0021] It is preferred that the first and second inclined sections lie on top of each other or parallel to each other or rotated parallel to each other, and that the first and second connecting sections lie oppositely on top of each other or antiparallel to each other or rotated antiparallel to each other, and that the third and fourth inclined sections lie on top of each other or run parallel to each other or run parallel to each other with a rotational offset, and that the third and fourth connecting sections lie oppositely on top of each other or run antiparallel to each other or run antiparallel to each other with a rotational offset.

[0022] It is preferred that inclined sections each extend at an angle of 30° to 60°, preferably 40° to 50°, in particular 44° to 46°, to a radial line passing through the center of the inclined section, or at an angle of -30° to -60°, preferably -40° to -50°, in particular -44° to -46°, to a radial line passing through the center of the inclined section.

[0023] For example, the first and second inclined sections can each run at an angle of 30° to 60°, preferably 40° to 50°, in particular 44° to 46°, to a radial line passing through the center of the first inclined section, and the third and fourth inclined sections can each run at an angle of -30° to -60°, preferably -40° to -50°, in particular -44° to -46°, to a radial line passing through the center of the second inclined section.

[0024] It is preferred that the coil conductors are designed as conductor tracks on printed circuit boards.

[0025] It is preferred that the measuring sensor is designed in a disc-shaped, ring-shaped or as part of a flange or flange segment lying in force-fit or secondary force-fit connection of a test object to be measured.

[0026] In some embodiments, the planar coils, or at least one of the planar coils, are configured as an annularly rotating planar coil with a zigzag and / or sawtooth-shaped coil conductor. In some embodiments, the planar coils, or at least one of the planar coils, are configured as a planar coil extending over a ring segment and covering only a sector of the circumference. In some embodiments, the planar coils, or at least one of the planar coils, are configured as a positive planar coil whose coil conductor runs counterclockwise over a radially outward inclined section, a radially outer connecting section, a radially inward inclined section, and a radially inner connecting section. It is irrelevant at which of these sections the conductor begins and ends.In some embodiments, the planar coils, or at least one of the planar coils, are configured as a negative planar coil whose coil conductor runs clockwise over an inclined section radially inward, a radially inner connecting section, an inclined section radially outward, and a radially outer connecting section. Here, too, it is irrelevant at which section the winding begins and ends. In some embodiments, the planar coils, or at least one of the planar coils, are configured as a positive spiral coil whose coil conductor runs spirally counterclockwise over several inclined sections and inner and outer connecting sections. In some embodiments, the planar coils, or at least one of the planar coils, are configured as a negative spiral coil whose coil conductor runs spirally clockwise over several inclined sections and inner and outer connecting sections.Several of these planar coils can be interconnected, particularly in series. Multiple ring-segment planar coils, extending only over a single circumferential sector, can be evenly distributed around the circumference and interconnected. For example, positive and negative coils, designed with only one loop or as spiral coils, can be arranged alternately around the circumference.

[0027] The sensor can, for example, be used on a permanently magnetized test object. However, in preferred designs, active magnetization takes place, so that the test object does not need to be magnetized beforehand.

[0028] According to another aspect, the invention therefore provides a load measuring device for measuring a load on a test object, comprising a magnet generating device for generating a magnetic field in the test object and a measuring sensor according to one of the preceding embodiments.

[0029] According to a further aspect, the invention provides a load measurement arrangement comprising a test object rotatable about a rotational axis and a measuring sensor according to one of the embodiments. The test object can be magnetizable, or the load measurement arrangement may additionally include a magnet generation device for generating a magnetic field in the test object, so that the load measurement arrangement operates with active magnetization.

[0030] It is preferred that the sensor is arranged with its center concentric to the axis of rotation and is configured to measure a load on a surface of the test object that is substantially perpendicular to the axis of rotation, or on a facet or flange of a shaft forming the test object. In particular, this achieves an end-face load measurement.

[0031] The sensor can be very flat and occupies little axial installation space and no additional radial installation space.

[0032] According to another aspect, the invention provides a load measurement method for measuring a load on a test object rotatable about a rotational axis, comprising: Providing a magnetic field at the test object, Arranging a measuring sensor according to one of the preceding configurations concentrically to the axis of rotation of the test object and Measuring the load on a surface of the test object that is essentially perpendicular to the axis of rotation using the measuring sensor.

[0033] Preferably, a torque is measured as the load.

[0034] According to another aspect, the invention provides a manufacturing method for producing a sensor according to one of the preceding embodiments, comprising manufacturing the planar coils using printed circuit board technology or by additive manufacturing.

[0035] Preferred embodiments deal with axial torque measurement using measuring coils, in which measuring sections of a coil conductor of at least one of the coils extend in the tensile direction, measuring sections of a coil conductor of at least one further coil extend in the compressive direction, and the remaining areas of the coil conductors are arranged such that currents in directions other than the tensile and compressive directions are subtracted from each other.

[0036] For measurements around a shaft, a measuring arrangement with coils elaborately wound around the shaft in a specific pattern is known from

[17] and

[18] , in which the measuring sections of one coil conductor extend in the tensile direction on the circumferential side of the shaft, the measuring sections of another coil conductor extend in the compressive direction on the circumferential side of the shaft, and connecting sections extending in the axial direction are connected in opposite directions to compensate for axially flowing currents. A similar principle is applied in embodiments of the invention to an arrangement of radially extending planar coils. Preferred embodiments deal in particular with axial torque measurement using coils with a coil conductor winding configuration according to

[17] and

[18] , but for end-face or facet measurement.

[0037] In preferred embodiments, a coil formed according to the technology of

[17] and

[18] is produced, for example, by winding, but preferably as a coil PCB (printed circuit board) or by additive manufacturing. The flat coil thus formed can be axially applied to the end facet or to a flange and can detect the stress or torque as a change in inductance.

[0038] In gearboxes and robotics, installation space is often very limited, especially in the axial direction, while an (electric) motor offers more radial space. Products available on the market, such as those from Sensodrive or Schaeffler, use strain gauge-based sensors (usually DMS) in gearboxes. These sensors are mounted on the facet or flange connecting an inner to an outer shaft. This solution allows for sensors that are only a few millimeters long in the axial direction. However, these strain gauge-based solutions are expensive, and the solution presented here can significantly reduce costs.

[0039] In

[17] and

[18] a complicated coil winding technique is proposed for measuring the torque in a shaft, which is even more costly than strain gauge-based solutions due to the complicated winding.

[0040] The measurement is based on the fact that the conductors are wound in such a way that currents flow along the tension axes, which are tilted at 45° to the rod axis. These currents generate a magnetic field perpendicular to the current axis, which is amplified by the permeability of the shaft. This permeability can be measured via the inductance of the coils wound in this manner. If a torque is now applied, the permeability changes along the tension axes, and consequently, so does the inductance.

[0041] In one facet of a shaft, the stress axis is tilted by 45° from the radial axis. Analogous to the approach in

[17] and

[18] , such a coil design can be used. As an example, a first to a fourth different winding are wound and connected such that the currents add in the tensile direction and the circulating currents subtract. By comparing the inductance of the coils sensitive in the tensile direction with the coils sensitive in the compressive direction, the stress in the material and thus the torque can be determined via the magnetoelastic change in permeability.

[0042] A major advantage of this geometry is that PCB coils (coils manufactured using printed circuit board technology, formed from planar coils – one or more layers) can be used, eliminating the need to develop complex winding machines. This makes it possible to manufacture these coils on a PCB, including the evaluation electronics. The PCB can be attached directly to a facet either without contact or via an insulating layer (screwed, glued, etc.).

[0043] Examples of implementation are explained in more detail below with reference to the accompanying drawings. These show: Fig. 1 a schematic perspective view of a first embodiment of a measuring arrangement comprising a test object and a load measuring device for measuring a load on the test object, wherein the load measuring device is provided with a sensor and an evaluation device; Fig. 2 a schematic perspective view of a second embodiment of the measuring arrangement with a further test object and the measuring sensor; Fig. 3 a schematic top view in axial direction with respect to an axis of rotation of one of the test objects, showing loads when a torque is applied; Fig. 4 an axial top view of a first layer of a first embodiment of the sensor with a first measuring coil designed as a first planar coil; Fig. 5 an axial top view of a second layer of the first embodiment of the sensor with a second measuring coil designed as a second planar coil; Fig. 6 an axial representation of the superimposed first and second layers of Fig. 4 and Fig. 5, to illustrate the course of the planar coils and their interconnection; Fig. 7 an axial top view of a first layer of a second embodiment of the sensor with a further embodiment of a first measuring coil, which is designed as a first planar coil; Fig. 8 an axial top view of a second layer of the second embodiment of the sensor with a further embodiment of a second measuring coil, which is designed as a second planar coil; Fig. 9 an axial top view of a third layer of the second embodiment of the sensor with a third measuring coil designed as a third planar coil; Fig. 10 an axial top view of a fourth layer of the second embodiment of the sensor with a fourth measuring coil designed as a fourth planar coil; Fig. 11 a schematic perspective representation of the second embodiment of the sensor with the first to fourth layers superimposed on top of each other of Fig. 4, Fig. 5, Fig. 6, Fig. 7 to Fig. 8, to illustrate the course of the planar coils and their interconnection in the second embodiment of the sensor; Fig. 12 a schematic representation of part of a planar coil arrangement of a fourth embodiment of the sensor; Fig. 13 a schematic representation of part of a planar coil arrangement of a fifth embodiment of the sensor; and Fig. 14 a schematic representation of part of a planar coil arrangement of a sixth embodiment of the sensor.

[0044] In the Fig. 1 and Fig. Figure 2 shows different embodiments of a measuring arrangement 10. The measuring arrangement 10 comprises a test object 12 and a load measuring device 14 for magnetoelastically measuring a load on the test object 12. The load measuring device 14 comprises a sensor 16 with several measuring coils 18.1-18.4 (in Fig. 1 and Fig. 2 (not shown, explained in more detail later) and an evaluation unit 20. The load measuring device 14 operates according to the measuring principles as explained in detail in references [1] to

[18] , which is why the measuring principle and the more precise construction of the evaluation unit 20 will not be discussed in detail here. In some embodiments, a region of the test object 12, on which the measuring coils 18.1-18.4 are arranged, is magnetized. In more preferred embodiments, the load measuring device 14 has a magnetic field generation device (not shown, well known from references [1] to

[18] ), in particular with at least one generator coil on the sensor 16, in order to actively generate a magnetic field in the test object 12. With the measuring coils 18.1-18.4. Changes in magnetic field parameters occurring due to loads in the test object 12 will be recorded in order to generate a signal indicating the load and, in particular, a signal indicating a torque M applied to the test object 12.

[0045] The test object 12 is designed to be rotatable about a central axis of rotation 22. The test object 12 is, for example, as in the embodiment of the measuring arrangement 10 of Fig. 1 shown, a rotating part of a gearbox, e.g. a flange 24 used for torque transmission, or, as in the embodiment of the measuring arrangement of Fig. Figure 2 shows a shaft 26. The test object has a front surface 28 that extends radially with at least one directional component. The sensor 16 is arranged axially next to the front surface 28 and detects loads on the test object 12 at the front surface 28.

[0046] Fig. Figure 3 shows the stresses on the test object 12 at the end face 28 when a torque M is applied to the test object 12. A compressive stress 30 and a tensile stress 32 are established, directed at 45° to the radial 34 and at 90° to each other. The tensile stress 32 is thus inclined at 45° to the radial direction in one direction of inclination (first inclination direction), while the compressive stress 30 is inclined at 45° to the radial direction in the other direction of inclination (second inclination direction). The sensor 16 is configured to detect the compressive stress 30 and / or the tensile stress 32 in order to thereby detect the torque M.

[0047] The following will be based on the representations of the Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11, Fig. 12, Fig. 13 to Fig. 14 different embodiments of the measuring sensor 16 are explained in more detail.

[0048] The sensor 16 has several planar coils 36.1-36.4 as measuring coils 18.1-18.4. The planar coils 36.1-36.4 are arranged at least partially in a ring shape around the center of the sensor 16, which is arranged concentrically with the axis of rotation 22.

[0049] The planar coils 36.1-36.4 each have at least one coil conductor 38.1-38.4, which runs substantially in a radial plane. Preferably, the coil conductor 38.1-38.4 of the respective planar coil 36.1-36.4 runs in a radial plane; small sections, such as vias or other connections, may also run axially. A route along a conical surface inclined slightly to the radial is also possible – for example, for measurements on an obliquely inclined end face.

[0050] The coil conductor 38 has inclined sections 40.1-40.4, whose principal directional component is oriented parallel to the tensile stress 32 and / or the compressive stress 30 (and thus inclined to the radial 34). A current flowing through these inclined sections 40.1-40.4 generates a magnetic field perpendicular to the current axis – i.e., to the path of the inclined sections 40.1-40.4 – which is amplified by the permeability of the test object 12. If the permeability of the test object 12 changes due to the tensile stress 32 or the compressive stress 30, the portion of the inductance of the planar coil 36.1-36.4 generated by the inclined sections 40.1-40.4 changes. These inclined sections 40.1-40.4 thus serve as measuring sections for detecting the tensile stress 32 or the compressive stress 30.

[0051] The connecting sections 42.1-42.4 of the planar coils 36.1-36.4 of the sensor 16 are arranged such that, with appropriate interconnection of the planar coils 36.1-36.4, the currents flowing through the connecting sections 42.1-42.4 cancel each other out as much as possible during operation.

[0052] The inclined sections 40.1-40.4 each extend obliquely in a direction of inclination relative to a radial direction, with the connecting sections 42.1-42.4, which connect inclined sections 40.1-40.4 to one another, extending in a radial or circumferential direction. The planar coils 36.1-36.4 are connected such that connecting sections 40.1-40.4 of one of the planar coils 36.1-36.4 run in the opposite direction to connecting sections 42.1-42.4 of another of the planar coils 36.1-36.4, and currents flowing through the connecting sections 42.1-42.4 of the planar coils 36.1-36.4 in the circumferential or radial direction are subtracted.

[0053] The design and arrangement of the planar coils 36.1-36.4 can vary. In the cases described in the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10 to Fig. In the embodiments of the sensor 16 shown in Figure 11, each planar coil 36.1-36.4 extends around the entire circumference of the center, and the planar coils 36.1-36.4 are axially offset from one another in superimposed layers 44.1-44.4. However, the planar coils 36.1-36.4 can also be arranged side by side in the circumferential direction essentially on the same layer, as shown in Figure 11. Fig. 11, Fig. 12, Fig. 13 to Fig. As indicated in point 14. In particular, combinations of these training programs are also possible.

[0054] Fig. Figure 4 shows an axial top view of a first layer 44.1 of a first embodiment of the sensor 16 with a first planar coil 36.1 as the first measuring coil 18.1. Fig. Figure 5 shows a second layer 44.2 of the first embodiment of the sensor 16 with a second planar coil 36.2 as the second measuring coil 18.2. Fig. Figure 6 shows an axial top view of the first embodiment of the sensor 16, which is designed to be transparent for illustrative purposes, where the first and second layers 44.1, 44.2 are superimposed.

[0055] How to get the Fig. 4, Fig. 5 to Fig. As can be seen from Figure 6, the first and second connecting sections 42.1 and 42.2 are radially aligned. During operation, the currents flowing in them are in opposite directions, thus canceling out the induced magnetic fields. The first inclined sections 42.1 are inclined at an angle of 45° to the radial in the first direction, and the second inclined sections 42.2 are inclined at an angle of -45° to the radial in the second direction. Therefore, when a torque is applied in one direction of rotation, the first inclined sections 42.1 run in the direction of the tensile stress 32, and the second inclined sections 42.2 run in the direction of the compressive stress 30.

[0056] In Fig. Figure 7 shows a first layer 44.1 of a second embodiment of the sensor 16 with a first planar coil 36.1. Fig. Figure 8 shows a second layer 44.2 of the second embodiment of the sensor 16 with a second planar coil 36.2. Fig. Figure 9 shows a third layer 44.3 of the second embodiment of the sensor 16 with a third planar coil 36.3. Fig. Figure 10 shows a fourth layer 44.3 of the second embodiment of the sensor 16 with a fourth planar coil 36.2. Fig. Figure 11 shows a schematic, transparent perspective view of the second embodiment of the measuring sensor 16, glued onto the test object 12, with the superposition of the first to fourth planar coil 36.1-36.4.

[0057] In the second embodiment, the connecting sections 42.1-42.4 extend circumferentially, with inner connecting sections 42i and outer connecting sections 42a being provided. The first inclined sections 40.1 on the first planar coil 36.1 and the second inclined sections 40.2 on the second planar coil 36.2 extend obliquely to the radial direction in the first inclination direction and are, in particular, parallel to the direction of tensile stress 32. The third inclined sections 40.3 on the third planar coil 36.3 and the fourth inclined sections 40.4 on the fourth planar coil 36.2 extend obliquely to the radial direction in the second inclination direction and are, in particular, directed towards compressive stress 30. The planar coils 36.1-36.4 are connected in such a way that the currents running through the inclined sections 40.1-40.4 add up and the currents running through the connecting sections 42.1-42.4, 42i, 42a subtract.

[0058] Fig. Figure 12 shows a circumferential segment of a planar coil arrangement 46 of a third embodiment of the sensor 16. A series of first planar coils 36.1 and second planar coils 36.2 are arranged alternately around the circumference. The planar coils 36.1, 36.2 are each "parallelogram-shaped" with circularly curved inner and outer connecting sections 42.1, 42.2, 42i, 42a and inclined sections 40.1, 40.2 inclined only in one direction. The current direction of the first planar coils 36.1 is counterclockwise to form positive coils. The current direction of the second planar coils 36.2 is clockwise to form negative coils.

[0059] The in Fig. The planar coil arrangement 46 of a fourth embodiment of the sensor 16, shown in Figure 13, is constructed similarly to the planar coil arrangement of the third embodiment, except that the coil conductors 38.1, 38.2 of the positive and negative coils – first and second planar coils 36.1-36.2 – do not just rotate once, but spirally several times. Thus, an arrangement of spiral positive and negative coils is provided, distributed alternately around the circumference.

[0060] At the in Fig. In the planar coil arrangement 46 of a fifth embodiment of the sensor 16 shown in Figure 14, the respective planar coils 36.1 are designed in a sawtooth shape.

[0061] It is in the Fig. 12, Fig. 13 and Fig. 14 each only shows a part of the planar coil arrangement 46; for example, the one in Fig. 14 shows the coil conductor path mirrored radially outside of it; and several of the in Fig. The 14 training courses shown are distributed across the scope.

[0062] In further embodiments, several of the elements described in the Fig. 12, Fig. 13 to Fig. The 14 layers shown are arranged one above the other. For example, in the embodiment of Fig. 12. A further layer may be provided with third and fourth planar coils 36.3, 36.4, alternately configured as positive / negative coils, the inclined sections 42.3, 42.4 of which run in the opposite direction of inclination to the inclined sections 42.1, 42.2 of the first and second planar coils 36.1, 36.2 shown. Several layers of the arrangement of first and second planar coils 36.1, 36.2 and several layers of the arrangement of third and fourth planar coils 36.3, 36.4 may be provided.

[0063] In preferred versions, the following are also included: Fig. The planar coils 36-36.4 shown in Figures 4, 5, and 7 to 10 are arranged in multiples, one above the other. This results in multiple first layers 48.1 with multiple first planar coils 36.1 stacked on top of each other, multiple second layers 48.2 with multiple second planar coils 36.2 stacked on top of each other, multiple third layers 48.3 with multiple third planar coils 36.3 stacked on top of each other, and multiple fourth layers 48.4 with multiple first planar coils 36.4 stacked on top of each other, the axial order being arbitrary.

[0064] A robust signal can be achieved by a circumferential arrangement of the sensor 16 or its arrangement of measuring coils 18.1-18.4, in which effects caused by inhomogeneities in the material of the test object 12 at the end face 28 are compensated. Instead of the circumferential configuration shown, for some applications it is sufficient if the planar coil arrangement 46 of the different embodiments of the sensor 16 extends only over a circumferential segment, e.g. over an angular range of 180° or even just 60°.

[0065] All embodiments of the measuring sensors 16 can be manufactured using PCB technology, wherein the coil conductors 38, 38.1-38.4 are formed as conductor tracks on a printed circuit board (PCB) and several such PCBs are stacked on top of each other with an insulating layer in between. Other manufacturing methods, such as additive manufacturing, are also possible.

[0066] The following explains the use of the measuring sensors 16 and the execution of the measurement procedure.

[0067] As in Fig. As shown in Figure 3, in a facet of a shaft 26 or a flange 24, the stress axes are tilted by 45° to the radial axis. Taking this into account, a coil design can be used in which currents parallel to these stress axes 30, 32 add up and currents directed in other directions subtract. Exemplary windings are shown in Figure 3. Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11, Fig. 12, Fig. 13 to Fig. 14 are shown. For example, in the Fig. 9, Fig. 10 to Fig.The coil design shown in Figure 11 incorporates at least four different windings – the first to fourth measuring coils 18.1–18.4 – connected in such a way that the currents in the direction of tension (first and second measuring coils 18.1, 18.2) and compression (third and fourth measuring coils 18.3, 18.4) add up and circulating currents subtract. By comparing the inductances of the measuring coils 18.1, 18.2, which are sensitive in the direction of tensile stress, with those of the measuring coils 18.3, 18.4, which are sensitive in the direction of compressive stress, the stress in the material and thus the torque M can be determined via the magnetoelastic change in permeability.

[0068] A major advantage of this geometry is that PCB coils can be used, eliminating the need to develop complex winding machines. Therefore, in some embodiments, these coils 18.1-18.4 are designed to be manufactured on a PCB including evaluation electronics 50.

[0069] The PCB 50 can be attached directly to a facet either without contact or using an insulating layer (screwed, glued, etc.).

[0070] The invention relates to magnetostrictive or magnetoelastic measurements of loads on a test object (12). In order to realize a particularly compact yet cost-effective measuring arrangement (14), the invention provides a sensor (16) for a load measuring device (14) for measuring a load on a test object (12), wherein the sensor (16) has several planar coils (36.1-36.4) to detect a magnetic field parameter on the test object (12) that changes due to the load, wherein the planar coils (36.1-36.4) are at least partially arranged in a ring around a center and each has a coil conductor (38.1-38.4) extending substantially in a radial plane, which includes inclined sections (40.1-40.4) and connecting sections (42.1-42.4), wherein the inclined sections (40.1-40.4) each extend obliquely in an inclination direction to a radial direction, wherein the connecting sections (42.1-42.4) each connecting inclined sections (40.1-40.4) to each other and extending substantially in a radial direction or substantially in a circumferential direction, wherein the planar coils (36.1-36.4) are interconnected such that currents flowing through the connecting sections (42.1-42.4) of the planar coils in the circumferential or radial direction are subtracted. Reference symbol list: 10 Measuring setup 12 test objects 14 Load measuring device 16 sensors 18.1 first measuring coil 18.2 second measuring coil 18.3 third measuring coil 18.4 fourth measuring coil 20 Evaluation unit 22 axis of rotation 24 flange 26 wave 28 front surface 30 Compressive stress 32 Tension 34 Radials (radial direction) 36.1 first planar coil 36.2 second planar coil 36.3 third planar coil 36.4 fourth planar coil 38 coil conductors 38.1 first coil conductor 38.2 second coil conductor 38.3 third coil conductor 38.4 fourth coil conductor 40.1 first inclined section 40.2 second inclined section 40.3 third inclined section 40.4 fourth inclined section 42.1 first connecting section 42.2 second connecting section 42.3 third connecting section 42.4 fourth connecting section 42i inner connecting section 42a outer connecting section 44.1 first shift 44.2 second layer 44.3 third layer 44.4 fourth layer 46 Planar coil arrangement 48 PCB 50 evaluation electronics

Claims

[1] Sensor (16) for a load measuring device (14) for measuring a load on a test object (12), wherein the sensor (16) comprises several planar coils (36.1-36.4) to detect a magnetic field parameter on the test object (12) that changes due to the load, wherein the planar coils (36.1-36.4) are at least partially arranged in a ring around a center and each has a coil conductor (38.1-38.4) extending substantially in a radial plane, comprising inclined sections (40.1-40.4) and connecting sections (42.1-42.4), wherein the inclined sections (40.1-40.4) each extend obliquely in an inclination direction to a radial direction, wherein the connecting sections (42.1-42.4) each connect inclined sections (40.1-40.4) to each other and extend substantially in a radial direction extend, wherein the planar coils (36.1-36.4) are interconnected in such a way that the connecting sections (42.1-42.4) Subtract the currents flowing in the circumferential or radial direction of the planar coils. [2] Sensor (16) for a load measuring device (14) for measuring a load on a test object (12), wherein the sensor (16) has several planar coils (36.1-36.4) to detect a magnetic field parameter on the test object (12) that changes due to the load, wherein the planar coils (36.1-36.4) are at least partially arranged in a ring around a center, overlap in an axial direction and each has a coil conductor (38.1-38.4) extending substantially in a radial plane, comprising inclined sections (40.1-40.4) and connecting sections (42.1-42.4), wherein the inclined sections (40.1-40.4) each extend obliquely in an inclination direction to a radial direction, wherein the connecting sections (42.1-42.4) each connect inclined sections (40.1-40.4) to each other and essentially extend in a circumferential direction, with the planar coils (36.1-36.4) are connected in such a way that currents flowing through the connecting sections (42.1-42.4) of the planar coils in the circumferential or radial direction are subtracted. [3] Sensor (16) according to any one of the preceding claims, characterized by , that the planar coils (36.1-36.4) comprise at least one first (36.1) and at least one second planar coil (36.2), wherein the at least one first planar coil (36.1) and the at least one second planar coil (36.3) are at least partially arranged in a ring shape around the center, wherein the at least one first planar coil (36.1) has a first coil conductor (38.1) extending substantially in a first radial plane, the first inclined sections (40.1) extending obliquely to a radial direction in a first inclination direction, and first connecting sections (42.1) connecting the first inclined sections (40.1) to each other, wherein the at least one second planar coil (36.2) has a second coil conductor (38.2) extending substantially in a second radial plane, the second inclined section (40.2) extending in the first inclination direction obliquely to the radial direction in the same direction as a first inclined section (40.1), and second connecting sections (42.2) extending antiparallel or opposite to a first connecting section (42.1) in the circumferential or radial direction and connecting the second inclined sections (40.2) to each other, such that currents flowing through the first and second inclined sections (40.1, 40.2) in the first inclination direction add up and currents flowing through the first and second connecting sections (42.1-42.2) in the circumferential or radial direction subtract. [4] Sensor (16) according to claim 3, characterized by , that the planar coils (36.1-36.4) further comprise at least a third and at least a fourth planar coil (36.3, 36.4) which are at least partially arranged in a ring shape around the center, wherein the at least one third planar coil (36.3) has a third coil conductor (38.3) extending substantially in a third radial plane, the third inclined sections (40.3) extending obliquely to a radial direction in a second inclination direction with an inclination opposite to the first inclination direction, and third connecting sections (42.3) connecting the third inclined sections (40.3) to each other, wherein the at least one fourth planar coil (36.4) has a fourth coil conductor (38.4) extending substantially in a fourth radial plane, the fourth inclined sections (40.4) extending in the same direction to a third inclined section (40.3) in the second inclination direction obliquely to the radial direction, and fourth connecting sections (42.4) extending in the same direction or opposite direction to a third connecting section (42.3) in the circumferential or radial direction and connecting the fourth inclined sections (40.4) to each other, such that currents flowing through the third and fourth inclined sections (40.3, 40.4) in the second inclination direction add up and currents flowing through the third and fourth connecting sections (42.3, 42.4) in the circumferential or radial direction subtract. [5] Sensor (16) according to claim 4, characterized by , that the first and second inclined sections (40.1, 40.2) lie on top of each other or run parallel to each other or run parallel to each other with a rotational offset, and that the first and second connecting sections (42.1, 42.2) lie on top of each other in opposite directions or run antiparallel to each other or run antiparallel to each other with a rotational offset, and that the third and fourth inclined sections (40.3, 40.4) lie on top of each other or run parallel to each other or rotated parallel to each other and that the third and fourth connecting sections (42.3, 42.4) lie oppositely on top of each other or run antiparallel to each other or rotated antiparallel to each other. [6] Sensor (16) according to any one of the preceding claims, characterized by , that the inclined sections (40.1-40.4) each extend at an angle of 30° to 60°, preferably 40° to 50°, in particular 44° to 46°, to a radial line passing through the center of the inclined section (40.1-40.4) or extend at an angle of -30° to -60°, preferably -40° to -50°, in particular -44° to -46°, to a radial line passing through the center of the inclined section (40.1-40.4). [7] Sensor (16) according to any one of the preceding claims, characterized by , 7.1 that the coil conductors (38.1-38.4) are designed as conductor tracks on printed circuit boards and / or 7.2 that the sensor (16) is designed in a disc-shaped, ring-shaped or as part of a flange or flange segment lying in force-fit or secondary force-fit connection of a test object to be measured. [8] Sensor (16) according to any one of the preceding claims, characterized by, that the planar coils (36.1-36.4) are selected from a group of planar coils comprising an annular planar coil with a zigzag and / or sawtooth-shaped coil conductor, a planar coil extending over a ring segment only over a sector of the circumference, a positive planar coil whose coil conductor runs counterclockwise over a radially outward slant, a radially outer connecting section, a radially inward slant, and a radially inner connecting section, a negative planar coil whose coil conductor runs clockwise over a radially inward slant, a radially inner connecting section, a radially outward slant, and a radially outer connecting section, a positive spiral coil whose coil conductor runs spirally counterclockwise over several slant sections and inner and outer connecting sections, and a negative spiral coil,whose coil conductor runs spirally in a clockwise direction over several inclined sections and inner and outer connecting sections. [9] Load measuring device (14) for measuring a load on a test object (12), comprising a magnetic field generation device for generating a magnetic field in the test object (12) and a measuring sensor (16) according to one of the preceding claims. [10] Load measuring device (14) according to claim 9, further comprising an evaluation device (20) which has evaluation electronics mounted on a printed circuit board element on which the planar coils (36.1-36.4) of the sensor (16) are also arranged. [11] Measuring arrangement (10) comprising a test object (12) rotatable about an axis of rotation (22) and a sensor (16) according to one of claims 1 to 8 or a load measuring device (14) according to one of claims 9 or 10, wherein the sensor (16) is arranged with its center concentric to the axis of rotation (22) and is configured to measure a load on a surface (28) of the test object (12) extending substantially perpendicular to the axis of rotation (22) or on a facet or flange of a shaft (26) used as a test object (12). [12] Load measurement method for measuring a load on a test object (12) rotatable about an axis of rotation (22), comprising: Providing a magnetic field at the test object (12), Arranging a measuring sensor (16) according to one of claims 1 to 8 concentrically to the axis of rotation (22) of the test object (12) and Measuring the load on a surface (28) of the test object (12) which is essentially perpendicular to the axis of rotation (22) using the measuring sensor (16). [13] Manufacturing method for manufacturing a sensor (16) according to any one of claims 1 to 8, comprising manufacturing the planar coils (36.1-36.4) using printed circuit board technology or additive manufacturing.

Images