Sensor Head For a Force or Torque Sensor

Abstract

In order to enable practical suitability of a force or torque sensor and usability for a variety of applications in conjunction with cost-effective production, the invention provides a sensor head (10) for a magnetoelastic force or torque sensor for measuring a force or a torque in a ferromagnetic body (9), comprising: a magnetic field generating unit (14) for generating a magnetic field in the ferromagnetic body (9) and a magnetic field measuring unit (16) for measuring a magnetic field change in the ferromagnetic body (9), wherein the magnetic field generating unit (14) has an excitation coils (18) and a soft-magnetic excitation flux amplifying element (20), wherein the magnetic field measuring unit (16) has a plurality of measurement coil (22) with a soft-magnetic measurement flux amplifying element (24), wherein at least the excitation coil (18) and the measurement coils (22, 22a-22d) are integrated in a common integrated component, such as, in particular, a printed circuit board element (26) and/or MEMS component (28).

Claims

1. A sensor head (10) for a magnetoelastic force or torque sensor for measuring a force or a torque in a ferromagnetic body (9), comprising: a magnetic field generating unit (14) for generating a magnetic field in the ferromagnetic body (9) and a magnetic field measuring unit (16) for measuring a magnetic field change in the ferromagnetic body (9), wherein the magnetic field generating unit (14) has an excitation coil (18) and a soft-magnetic excitation flux amplifying element (20), wherein the magnetic field measuring unit (16) has a plurality of measurement coils (22) with a soft-magnetic measurement flux amplifying element (24), and wherein at least the excitation coil (18) and the measurement coils (22, 22a-22d) are integrated in a common integrated component (26, 28).

2. The sensor head according to claim 1, characterized in that at least the excitation coil (18) and the measurement coils (22, 22a-22d) are integrated at a common printed circuit board element (26) and/or MEMS component (28).

3. The sensor head according to either of the preceding claims, characterized in that the soft-magnetic excitation flux amplifying element is a soft-magnetic excitation core (20), around which the excitation coil (18) is arranged, and in that the measurement coils (22) are provided with a soft-magnetic measurement core (24) as measurement flux amplifying element.

4. The sensor head (10) according to claim 3, characterized in that the measurement cores (24) of a first measurement coil (22a) and of a second measurement coil (22b) are connected in order to form a magnetic circuit by means of a yoke (34) composed of soft-magnetic material, wherein the yoke (34) is at least partly incorporated or integrated into the integrated component (26, 28), and in particular is incorporated in a printed circuit board (36) or is integrated in a MEMS component (28).

5. The sensor head (10) according to either of claims 3 and 4, characterized in that the excitation core (20) forms a flux concentrator (32), which is arranged as a central magnetic pole (30) between at least two measurement coils (22, 22a-22d).

6. The sensor head (10) according to claim 4 and according to claim 5, characterized in that the excitation core (20) is contact-connected to the yoke (34).

7. The sensor head (10) according to any of the preceding claims, characterized in that at least one ferritic film (42) is provided.

8. The sensor head (10) according to claim 7, characterized in that the ferritic film (42) has a thickness of 0.1 mm to 3 mm, in particular 0.1 mm to 0.5 mm or 1 mm to 2 mm.

9. The sensor head (10) according to claim 7 or 8, characterized in that the ferritic film (42) is embedded into the integrated component and/or is applied on the component and/or is fitted, in particular is adhesively bonded, onto a printed circuit board at which the coils are formed.

10. The sensor head (10) according to any of claims 7 to 9, characterized in that the at least one ferritic film (42) forms at least one part of one of the soft-magnetic flux amplifying elements.

11. The sensor head (10) according to any of claims 7 to 10 and according to any of claims 4 to 6, characterized in that the excitation core (20) and/or the measurement cores (24) and/or the yoke (34) are/is formed by the at least one ferritic film (42).

12. The sensor head (10) according to any of the preceding claims, characterized by a first integrated component, in particular a first printed circuit board element (26) or a first MEMS component (28), at which at least the excitation coil (18) and a plurality of measurement coils (22, 22a-22d) are provided in an integrated fashion in such a way that a plurality of magnetic poles (30, 30a-30e) are formed, and by a second integrated component, in particular a second printed circuit board element (26) or a second MEMS component (28), into which is incorporated or integrated at least one soft-magnetic material for connecting and/or forming soft-magnetic cores of the magnetic poles (30, 30a-30e), wherein the first and second integrated components are connected to one another.

13. The sensor head (10) according to any of the preceding claims, characterized by an integrated circuit, in particular an IC component, having a signal processing electronic unit (4), which is arranged at the integrated component, in particular the printed circuit board element (26) or the MEMS component (28), or is bonded or soldered thereto or is formed as an integrated part of the integrated component.

14. The sensor head (10) according to any of the preceding claims, characterized in that the coils (6) integrated in the integrated component (26, 28) have windings (40) formed by a spiral formed at a conductive layer (38) of the integrated component (26, 28).

15. The sensor head (10) according to any of the preceding claims, characterized in that at least one excitation coil (18), a first measurement coil (22a) and a second measurement coil (22b) have windings (40) formed by a common conductor layer (38) of the integrated component, in particular of the printed circuit board element (26) or of the MEMS component (28).

16. The sensor head (10) according to any of the preceding claims, characterized in that a polymer is injection-molded around the integrated component with the integrated coils (6) and the soft-magnetic flux amplifying elements (20, 24, 34, 42).

17. A method for producing a sensor head (10) for a magnetoelastic force or torque sensor for measuring a force or a torque in a ferromagnetic body (9), which sensor head (10) comprises a magnetic field generating unit (14) for generating a magnetic field in the ferromagnetic body (9) and a magnetic field measuring unit (16) for measuring a magnetic field change in the ferromagnetic body (9), wherein the magnetic field generating unit (14) has an excitation coil (18) and a soft-magnetic excitation flux amplifying element (20, 42) and the magnetic field measuring unit (16) has a measurement coil (22, 22a-22d) and a soft-magnetic measurement flux amplifying element (24, 42), comprising the following steps: a) providing at least one printed circuit board (36), patterning a conductive layer (38) of the printed circuit board (36) in order to form windings (40) of the excitation coil (18) and of the measurement coil (22, 22a-22d) or b) forming windings (40) of the excitation coil (18) and of the measurement coil (22, 22a-22d) in an integrated fashion by means of micromechanical manufacturing and/or patterning and/or additive manufacturing methods.

18. The method according to claim 17, characterized in that step a) contains: embedding a soft-magnetic material into the printed circuit board (36) in order to form the flux amplifying elements (20, 24) and/or in that step b) contains: forming windings (40) of the excitation coil (18) and of the measurement coil (22, 22a-22d) and of the soft-magnetic cores in an integrated fashion by means of micromechanical manufacturing and/or patterning and/or additive manufacturing methods.

19. The method according to claim 17 or 18, characterized in that step a) contains: applying, in particular adhesively bonding, at least one ferritic film (42) onto the printed circuit board (36) in order to form the flux amplifying elements (20, 24).

20. The method according to claim 19, characterized by at least one, a plurality or all of the following steps: 20.1 producing the at least one ferritic film (42) in a stamping process, 20.2 providing the at least one ferritic film with a thickness of 0.1 mm to 3 mm, in particular 0.1 mm to 2 mm or 0.1 mm to 0.5 mm and 1 mm to 2 mm, 20.3 providing a film (42) composed of or comprising an iron oxide.

21. The method according to one of the preceding claims, characterized by: providing a second printed circuit board (36) comprising an incorporated soft-magnetic material for forming a magnetic circuit with coil cores (20, 24) and connecting the first printed circuit board (36) to the windings (40) and the second printed circuit board (36) in such a way that at least three magnetically interconnected magnetic poles (30, 30a-30e) having magnetic pole cores and coils (18, 20) at least partly formed by the conductor layer (38) of the first printed circuit board (36) and surrounding the coil cores (20, 24) are formed.

22. The method according to one of the preceding claims, characterized by providing a chip having a signal processing electronic unit (4) and electrically connecting terminals of the chip to the coils (18, 22) in order to form a sensor package (12) in this way.

23. The method according to one of the preceding claims, characterized by injection molding (5) a polymer material around at least the printed circuit board (36) or the integral component (28) formed by micromechanical manufacturing with the coils (18, 22) and the flux amplifying elements (20, 24).

Description

[0061] Exemplary embodiments of the invention are explained in greater detail below with reference to the accompanying drawings, in which:

[0062] FIG. 1 shows a sectional illustration through a sensor head in accordance with a first embodiment;

[0063] FIG. 2 shows a sectional illustration through a sensor head in accordance with a second embodiment;

[0064] FIG. 3 shows a sectional illustration through a sensor head in accordance with a third embodiment;

[0065] FIG. 4 shows a section along the line IV-IV from FIG. 3 and

[0066] FIG. 5 shows a section through a further embodiment of a component for forming the sensor head; and

[0067] FIG. 6 shows a view as in FIG. 5 which shows the corresponding component from FIG. 5 in the configuration in accordance with the embodiments in FIGS. 1 to 4.

[0068] The figures show various embodiments of a sensor head 10 for a magnetoelastic force or torque sensor for measuring a force or a torque in a ferromagnetic body 9. The sensor head 10 is formed by a sensor package 12 constructed by means of packaging methods. The manufacturing is furthermore effected using micromechanical manufacturing methods (MEMS), additive manufacturing or printed circuit board technology. Combinations are also possible.

[0069] The sensor head 10 comprises a magnetic field generating unit 14 for generating a magnetic field in the ferromagnetic body 9 and a magnetic field measuring unit 16 for measuring a magnetic field change in the ferromagnetic body 9.

[0070] The magnetic field generating unit 14 has an excitation coil 18 and a flux amplifying element. In the configurations in FIGS. 1 to 4, the excitation coil 18 is provided around a soft-magnetic excitation core 20; at least one ferritic film 42 is provided in the configuration in FIG. 5 in order to form the flux amplifying element instead of the excitation core 20 or, in other embodiments (not illustrated), in addition to the excitation core 20.

[0071] The magnetic field measuring unit 16 has a plurality of measurement coils 22, each comprising a soft-magnetic flux amplifying element such as, in particular, a measurement core 24 or a region of at least one ferritic film 42.

[0072] The excitation coil 18 and the measurement coils 22 are constructed in an integrated fashion at a common printed circuit board element 26 and/or integrated component, in particular MEMS component 28.

[0073] The figures illustrate exemplary embodiments of the sensor head 10 having a total of five magnetic poles 30, wherein a central first magnetic pole 30a is part of the magnetic field generating unit 14 and has the excitation coil 18 and the excitation flux amplifying element such as the excitation core 20 or a region of the at least one ferritic film 42. The first magnetic pole 30a acts as a flux concentrator 32 for concentrating the magnetic flux generated by the excitation coil 18 in the surface of the measurement object 9 to be measured.

[0074] The further magnetic poles 30b to 30e are the poles of the magnetic field measuring unit 16. In the embodiments illustrated here, the magnetic field measuring unit 16 has in each case two magnetic pole pairs 30b-30c, 30d-30e for measuring the magnetic fields in different orientations. Another embodiment, not illustrated in more specific detail here, manages with only two magnetic poles of the magnetic field measuring unit 16; the fourth magnetic pole 30d and the fifth magnetic pole 30e are omitted here.

[0075] In the case of the embodiments illustrated in FIGS. 1 to 4, all the magnetic poles 30 are provided with cores, wherein the cores of the second to fifth magnetic poles form the measurement cores 24 and are surrounded by the respective measurement coils 22a to 22d. The core of the first magnetic pole 30a is the excitation core 20, which is surrounded by the measurement coil 22. All the cores 24, 20 are formed by soft-magnetic material. At least the cores of the magnetic pole pairs 30a-30b or 30c-30d of the magnetic field measuring unit 16 are connected to one another to form a yoke composed of soft-magnetic material. The soft-magnetic material is formed in particular by a ferrite core 3.

[0076] In the embodiments illustrated in FIGS. 1 to 4, all the magnetic poles 30a-30e are connected by the ferrite core 3; the latter can have a pot-shaped or star-shaped configuration, wherein the measurement cores 24 and respectively the excitation core 20 are formed by projections protruding in a corresponding fashion with respect to a direction, the respective coils 22, 22a-22d being provided around said projections.

[0077] The coils 22, 22a-22d are configured as coils 6 integrated in the integrated component, that is to say in particular in the printed circuit board element 26 or in the MEMS component 28.

[0078] In particular, the printed circuit board element 26 comprises at least one printed circuit board (PCB for short) comprising a carrier composed of insulating material and at least one conductor layer 38.

[0079] As evident from FIG. 4, the conductor layer 38 is patterned in such a way that windings 40 of the integrated coils 6 are formed. The windings 40 are formed in particular in a spiral fashion, wherein contact pads are formed at the ends, wherein one of the contact pads is led through a via through the insulation layer. By placing one on top of another and connecting in series a plurality of such printed circuit boards 36 having the correspondingly spirally formed windings 40, it is possible to form the integrated coils 6 having a multiplicity of windings 40.

[0080] The interior spaces centrally between the windings 40 can e.g. be drilled out and be filled with ferromagnetic material for forming the ferrite core 3.

[0081] The ferrite core can also be introduced into the sensor package 12 by means of additive manufacturing methods or by means of other packaging methods or micromechanical manufacturing methods. Overall, it is possible to construct the sensor head 10 comprising the integrated coils 6 and the ferromagnetic material for forming the yoke 34 and the cores 20, 24 by means of micromechanical manufacturing.

[0082] In all embodiments, the sensor package 12 furthermore comprises a signal processing electronic unit 4, in particular in the form of an integrated circuit, preferably in the form of an IC component, more particularly in the form of an ASIC, which is integrated into the sensor head 10. Packaging methods and/or micromechanical manufacturing methods are preferably used for this as well. Preferably, the signal processing electronic unit 4 is connected to the respective contacts of the integrated coils 6 by means of an array of solder balls 1.

[0083] The printed circuit board element 26 or the MEMS component 28 with the signal processing electronic unit 4 can be encapsulated by injection molding by means of a polymeric material, as is illustrated as injection-molding encapsulation 5 in the embodiments in FIGS. 1 and 2. FIG. 3 shows a piggyback arrangement of the printed circuit board element 26 or the MEMS component 28 with the integrated coils 6 and the integrated ferrite core 3 on the signal processing electronic unit 4.

[0084] The signal processing electronic unit 4 can be connected to an evaluation unit 8 by means of wire or cable 7 or some other conductive connection. Said evaluation unit (ECUElectrical Control Unit) can contain a memory and a processor.

[0085] In order to direct the magnetic field in magnetically inductive sensors, a ferritic material is provided. In FIGS. 1 to 4, the use of customary materials such as e.g. sintered ferrites for forming flux amplifying elements such as, in particular, cores and yokes can be provided for this purpose. Sintered ferrites of this type have the disadvantage that the ferrites are brittle and rigid, that is to say that they cannot be produced in any shape and can be destroyed by mechanical shocks. Therefore, at least one ferritic film 42 as ferritic material is provided in the configuration in FIG. 5.

[0086] Here, in particular, a ferritic film 42 is provided for forming flux amplifying elements instead of the cores 20, 24 and/or for forming the yoke or instead of the yoke 34.

[0087] A ferritic film 42 can be produced with any desired size and dimensioning by means of a stamping process and be attached by adhesive bonding. The use of the ferritic film 42 makes it possible to achieve significantly more flexible dimensions in the configuration of the sensor.

[0088] The ferritic film has a diameter of a few 1/10 mm (up to 1-2 mm in the case of higher powers) and is also used for shielding purposes, that is to say that the susceptibility to interference of the low signals (typically in the two-digit mV range) is significantly reduced. Materials are typically iron oxides (like magnetic tape, material for audio tape cassettes or the like).

[0089] Otherwise, the component shown in FIG. 5 can have all features and elements explained with reference to the embodiments in FIGS. 1 to 4 and can be used in the sensor head 10. As a comparison with respect to FIG. 5, FIG. 6 shows the same view for the corresponding component comprising sintered ferrite, as can be used in the previous embodiments. As evident, the component in FIG. 5 can replace the corresponding components in FIGS. 1 to 4.

[0090] A comparison of FIGS. 5 and 6 also shows that the ferritic film 42 can extend spatially beyond the locations of the cores of the coils.

LIST OF REFERENCE SIGNS

[0091] 1 BGA Ball Grid Array, solder balls [0092] 2 PCB with integrated coil [0093] 3 Ferrite core incorporated in PCB [0094] 4 Signal processing electronic unit (ASIC) [0095] 5 Molding compound (injection molding encapsulation) [0096] 6 Integrated coils [0097] 7 Wire or cable (conductive connection) [0098] 8 Evaluation unit ECU (electrical control unit), memory, processor [0099] 9 Measurement object (shaft, cylinder, ferromagnetic body) [0100] 10 Sensor head [0101] 12 Sensor package [0102] 14 Magnetic field generating unit [0103] 16 Magnetic field measuring unit [0104] 18 Excitation coil [0105] 20 Excitation core [0106] 22 Measurement coil [0107] 22a First measurement coil [0108] 22b Second measurement coil [0109] 22c Third measurement coil [0110] 22d Fourth measurement coil [0111] 24 Measurement core [0112] 26 Printed circuit board element [0113] 28 MEMS component [0114] 30 Magnetic pole [0115] 30a First magnetic pole [0116] 30b Second magnetic pole [0117] 30c Third magnetic pole [0118] 30d Fourth magnetic pole [0119] 30e Fifth magnetic pole [0120] 32 Flux concentrator [0121] 34 Yoke [0122] 36 Printed circuit board [0123] 38 Conductor layer [0124] 40 Windings [0125] 42 Ferritic film