Sensor

Abstract

A sensor is disclosed. In an embodiment, the sensor includes a fixed structure, a movable structure movable relative to the fixed structure, a magnet configured to generate a magnetic field and a first magnetically sensitive element configured to determine the magnetic field at a position of the first magnetically sensitive element. The magnet is fastened to the fixed structure and the first magnetically sensitive element is fastened to the movable structure. Alternatively, the magnet is fastened to the movable structure and the first magnetically sensitive element is fastened to the fixed structure.

Claims

1-15. (canceled)

16. A sensor comprising: a fixed structure; a movable structure movable relative to the fixed structure; a magnet configured to generate a magnetic field; and a first magnetically sensitive element configured to determine the magnetic field at a position of the first magnetically sensitive element, wherein the magnet is fastened to the fixed structure and the first magnetically sensitive element is fastened to the movable structure, or wherein the magnet is fastened to the movable structure and the first magnetically sensitive element is fastened to the fixed structure.

17. The sensor according to claim 16, wherein the sensor is configured to ascertain a relative position of the movable structure in relation to the fixed structure by determining the magnetic field at the position of the first magnetically sensitive element.

18. The sensor according to claim 16, further comprising a second magnetically sensitive element configured to determine the magnetic field at a position of the second magnetically sensitive element.

19. The sensor according to claim 18, wherein the first and second magnetically sensitive elements are arranged in one plane.

20. The sensor according to claim 19, wherein the magnet is arranged outside the plane when the movable structure is in an undeflected state.

21. The sensor according to claim 19, wherein the sensor has a stop which limits movement options of the movable structure in such a way that the magnet is always located on a first side of the plane or in the plane.

22. The sensor according to claim 19, wherein the sensor has a third magnetically sensitive element configured to determine the magnetic field at a position of the third magnetically sensitive element, wherein the third magnetically sensitive element is arranged outside the plane.

23. The sensor according to claim 16, wherein the movable structure is a diaphragm or a seismic mass.

24. The sensor according to claim 16, wherein the sensor is configured to excite the movable structure to oscillate.

25. The sensor according to claim 16, wherein the magnet is a structured thin-film permanent magnet.

26. The sensor according to claim 16, wherein the magnet has a length and a width, and wherein a ratio of the length to the width is not equal to 1.

27. The sensor according to claim 16, wherein the magnet comprises a coil through which current flows.

28. The sensor according to claim 16, further comprising a second movable structure movable relative to the fixed structure, a further magnet configured to generates a further magnetic field, and a second magnetically sensitive element configured to determine the further magnetic field at a position of the second magnetically sensitive element, wherein the further magnet is fastened to the fixed structure and the second magnetically sensitive element is fastened to the second movable structure, or wherein the further magnet is fastened to the second movable structure and the second magnetically sensitive element is fastened to the fixed structure.

29. The sensor according to claim 28, further comprising an electrode structure located on the fixed structure and on the second movable structure, the electrode structure being configured to excite the second movable structure to oscillate.

30. The sensor according to claim 16, further comprising structures for measuring a direction of the Earth's magnetic field and/or structures for measuring a pressure.

31. The sensor according to claim 16, wherein the sensor is configured to determine ten degrees of freedom, wherein all of the ten degrees of freedom are ascertainable by a relative position of one or more magnets in relation to one or more magnetically sensitive elements, and wherein either the one or more magnets or the one or more magnetically sensitive elements are arranged on the fixed structure and the respective other elements selected from the group consisting of the one or more magnets and the one or more magnetically sensitive elements are arranged on the movable structure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be described more precisely below with reference to figures.

[0045] FIG. 1 shows a first exemplary embodiment of a sensor;

[0046] FIG. 2 shows a second exemplary embodiment of a sensor;

[0047] FIG. 3 shows a third exemplary embodiment of a sensor;

[0048] FIG. 4 shows a fourth exemplary embodiment of a sensor;

[0049] FIG. 5 shows a fifth exemplary embodiment of a sensor;

[0050] FIG. 6 shows a sixth exemplary embodiment of a sensor; and

[0051] FIG. 7 shows a seventh exemplary embodiment of a sensor.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0052] FIG. 1 shows a sensor 1. The sensor 1 has a fixed structure 2 and a movable structure 3 which can move relative to the fixed structure 2.

[0053] The sensor 1 is configured to measure a movement of the movable structure 3 relative to the fixed structure 2. This sensor concept is used, for example, in pressure sensors in which the deflection of a diaphragm relative to a frame is measured. Accordingly, the movable structure 3 may be the diaphragm, and the fixed structure 2 may be the frame. Other sensors, for example, sensors for measuring accelerations or sensors for measuring rates of rotation, are also based on the measurement of the deflection of a movable structure 3 relative to a fixed structure 2. The movable structure 3 may be a seismic mass.

[0054] In the exemplary embodiment illustrated in FIG. 1, the movable structure 3 is a diaphragm. Furthermore, the fixed structure 2 is a frame.

[0055] The sensor 1 shown in FIG. 1 is an inertial sensor for measuring accelerations. The movable structure 3 is fastened to the fixed structure 2 in such a way that said movable structure can move relative to the fixed structure 2 in every direction in space. To this end, the movable structure 3 is suspended from the fixed structure 2 by way of spring elements (not shown).

[0056] Furthermore, the sensor 1 shown in FIG. 1 has a first magnetically sensitive element 4 and a magnet 5. The magnet 5 is configured to generate a magnetic field. The magnet 5 may be a permanent magnet which always generates a magnetic field. In particular, the magnet 5 may be a structured thin-film permanent magnet. The magnet 5 has an aspect ratio which is not equal to one. The aspect ratio is defined is as the ratio of the length of the magnet 5 to the width of said magnet. The magnet 5 can accordingly be designed in a rod-like or ellipsoidal manner, for example.

[0057] As an alternative, the magnet 5 may be a solenoid which generates a magnetic field only when it is switched on. The magnet 5 can accordingly have a coil through which current flows.

[0058] The first magnetically sensitive element 4 is configured to determine the magnetic field at the position of said first magnetically sensitive element. The magnetically sensitive element 4 may be, for example, a Hall element which determines the field strength of the magnetic field on the basis of the Hall effect. As an alternative or in addition, the magnetically sensitive element 4 can determine the magnetic field with the aid of the magnetoresistive effect.

[0059] The relative position of the magnetically sensitive element 4 in relation to the magnet 5 can be determined on the basis of this information.

[0060] In the exemplary embodiment shown in FIG. 1, the magnet 5 is fastened directly on the movable structure 3 and the magnetically sensitive element 4 is fastened directly on the fixed structure 2. In particular, the magnet 5 cannot move relative to the movable structure 3 and the magnetically sensitive element 4 cannot move relative to the fixed structure 2.

[0061] FIG. 1 shows, in the image on the left-hand side, a cross section through the sensor 1 in the xz plane. The image 1 on the right-hand side shows a cross section through the sensor 1 in the xy plane. The z direction is defined as the direction of the surface normal of the movable structure 3. The x and the y direction are arranged respectively perpendicular to the z direction and perpendicular to one another.

[0062] FIG. 1 shows the sensor 1 in a state in which the movable structure 3 is in an undeflected state. In this state, no external force acts on the movable structure 3. If a pressure is exerted on the movable structure 3, for example, due to sound waves, the movable structure 3 is deflected relative to the fixed structure 2.

[0063] Furthermore, the sensor 1 has a second, a third and a fourth magnetically sensitive element 104, 204, 304 in addition to the first magnetically sensitive element 4. The four magnetically sensitive elements 4, 104, 204, 304 are fastened to the fixed structure 2. The four magnetically sensitive elements 4, 104, 204, 304 are arranged in one plane. Furthermore, the magnet 5 is also arranged in the plane in the undeflected state of the movable structure 3. The sensor 1 allows the position of the movable structure 3 within the plane, which is also called the xy plane, to be unambiguously determined.

[0064] If the movable structure 3 moves in a direction perpendicular to the xy plane, the sensor 1 does not allow the z position of the movable structure 3 to be unambiguously determined. In particular, it is not possible to distinguish between whether the movable structure 3 is moving in the positive z direction or in the negative z direction. Here, the positive z direction is the direction from the bottom side of the movable structure 3 to the top side of the movable structure 3, wherein the magnet 5 is arranged on the top side of the movable structure 3 and the bottom side of the movable structure 3 is free of the magnet 5. The negative z direction is directed opposite to the positive z direction.

[0065] Furthermore, a comb structure 9 is formed between the movable structure 3 and the fixed structure 2. Electrodes can respectively form on the movable structure 3 and on the fixed structure 2 in the region of this comb structure 9. In particular, the movable structure 3 and the fixed structure 2 can each be composed of a conductive material, so that a voltage can be applied to each of said structures. The movable structure 3 can be electrostatically excited to oscillate by means of said electrodes. As an alternative, it is also possible to provide the movable structure 3 with an electrode structure and a piezoelectric film and to excite said movable structure to oscillate by means of the piezoelectric film. In the case of rate of rotation sensors, the movable structure 3 is made to oscillate in order to determine the rates of rotation.

[0066] Furthermore, it is feasible for the movable structure 3 and the fixed structure 2 to in each case form electrodes in the region of the comb structure 9 and for the sensor 1 to be operated in an electrostatic closed-loop process. In this case, a movement of the movable structure 3 is first detected and then an opposing field is applied to the electrodes, said opposing field holding the movable structure 3 still. This closed-loop measurement allows the dynamic behavior of the sensor 1 to be further improved. The comb structure 9 and the embodiments cited in this context are optional configurations which are not necessarily required for functioning of the sensor 1 but which may be advantageous in certain applications.

[0067] The sensor 1 shown in FIG. 1 has four magnetically sensitive elements 4, 104, 204, 304 which are interconnected by means of a Wheatstone measuring bridge and therefore are used to measure the position of the movable structure 3. Interconnection by means of the Wheatstone measuring bridge provides the advantages that unambiguous measurement is possible with simple circuitry, and that furthermore a high degree of measurement accuracy is achieved. The Wheatstone measuring bridge is a standard reading method which can be combined with numerous evaluation circuits.

[0068] The xy position of the movable structure 3 can already be unambiguously determined using two magnetically sensitive elements 4, 104. Accordingly, in an alternative configuration, the sensor 1 could have only the first and the second magnetically sensitive element 4 and 104.

[0069] FIG. 2 shows a second exemplary embodiment of the sensor 1. The image on the left-hand side shows a cross section through the sensor 1 in the xz plane, and the image on the right-hand side shows a cross section through the sensor 1 in the xy plane.

[0070] The sensor 1 shown in FIG. 2 differs from the sensor 1 shown in FIG. 1 in that, in an undeflected state of the movable structure 3, the magnet 5 is arranged outside the plane in which the four magnetically sensitive elements 4, 104, 204, 304 are arranged. As a result, the sensor 1 shown in FIG. 2 can unambiguously measure the x, y and z coordinates of the position of the movable structure 3. In particular, the movable structure 3 has a raised portion 10, on which the magnet 5 is arranged, on the top side of said movable structure. The sensor 1 allows the position of the movable structure 3 relative to the fixed structure 2 in the z direction to be unambiguously determined, provided that the magnet 5 does not move in the negative z direction to such an extent that it is located beneath the plane which is spanned by the magnetically sensitive elements 4, 104, 204, 304. In this case, there would be an ambiguous measurement result.

[0071] The sensor 1 shown in FIG. 2 has the same number of magnetically sensitive elements 4, 104, 204, 304 and magnets 5 as the sensor 1 shown in FIG. 1 and furthermore additionally allows the z coordinate of the position of the movable structure 3 to be determined.

[0072] FIG. 3 shows a third exemplary embodiment of the sensor 1. The image on the left-hand side shows a cross section through the xz plane, and the image on the right-hand side shows a cross section through the xy plane.

[0073] In comparison to the first exemplary embodiment shown in FIG. 1, the magnetically sensitive elements 4, 104, 204, 304 have been replaced by magnets 5, 105, 205, 305. Furthermore, the magnet 5 has been replaced by two magnetically sensitive elements 4, 104. Accordingly, magnets 5, 105, 205, 305 are now arranged on the fixed structure 2. In particular, the sensor 1 has four magnets 5, 105, 205, 305 which are each arranged on the fixed structure 2 and cannot move relative to the fixed structure 2. Furthermore, two magnetically sensitive elements 4, 104 are arranged on the movable structure 3. The two magnetically sensitive elements 4, 104 cannot move relative to the movable structure 3.

[0074] The sensor 1 is configured to determine a relative position of the movable structure 3 in relation to the fixed structure 2 in the xy plane.

[0075] FIG. 4 shows a fourth exemplary embodiment of the sensor 1, wherein the image on the left-hand side shows a cross section through the xz plane, and the image on the right-hand side shows a cross section through the xy plane.

[0076] The sensor 1 shown in FIG. 4 differs from the sensor 1 shown in FIG. 3 in that, in an undeflected state of the movable structure 3, the magnetically sensitive elements 4, 104 are arranged outside the plane which is spanned by the four magnets 5, 105, 205, 305. The movable structure 3 has a raised portion 10 on which the two magnetically sensitive elements 4, 104 are arranged. The sensor 1 allows the x, y and z coordinates of the position of the movable structure 3 relative to the fixed structure 2 to be determined. It is possible to unambiguously determine the z coordinate provided that the movable structure 3 does not move in the negative z direction to such an extent that the two magnetically sensitive elements 4, 104 are arranged beneath the plane which is spanned by the four magnets 5, 105, 205, 305.

[0077] FIG. 5 shows a fifth exemplary embodiment of the sensor 1. The fifth exemplary embodiment differs from the first exemplary embodiment shown in FIG. 1 in that a further magnetically sensitive element 404 is arranged above the magnet 5. The further magnetically sensitive element 404 is accordingly arranged outside the plane in which the first to fourth magnetically sensitive element 4, 104, 204, 304 are arranged. Accordingly, the sensor 1 allows the x, y and z coordinates of the position of the movable structure 3 to be unambiguously determined. In particular, it is possible to unambiguously determine the z coordinate without restrictions. The fixed structure 2 is designed as an open frame which surrounds the movable structure 3 at the sides and the top side and which has an opening 11 on its bottom side.

[0078] FIG. 6 shows a sixth exemplary embodiment of the sensor 1. In the sixth exemplary embodiment, four magnetically sensitive elements 4, 104, 204, 304 are arranged in one plane, and furthermore a magnet 5 is fastened on the movable structure 3 outside the plane, wherein the magnet 5 is located outside the plane when the movable structure 3 is in an undeflected state. Furthermore, the sensor 1 has a stop 12 which is configured to limit the movement options of the magnet 5 in such a way that the magnet 5 is always located on a top side of the plane or in the plane.

[0079] The fixed structure 2 is designed as a frame which surrounds the movable structure 3 on all sides. The fixed structure 2 is therefore a closed three-dimensional frame which includes a cavity, wherein the movable structure 3 is arranged within the cavity.

[0080] Further embodiments of the sensor 1 are feasible. For example, in the fifth and sixth exemplary embodiments as well, the magnetically sensitive elements 4, 104, 204, 304, 404 can be arranged on the movable structure 3 and the magnets 5, 105 can be arranged on the fixed structure 2.

[0081] In the exemplary embodiments shown in the figures, the movable structure 3 is always a diaphragm. However, the movable structure 3 can also be designed as a seismic mass.

[0082] FIG. 7 shows a seventh exemplary embodiment of a sensor 1. The sensor 1 is a sensor for measuring a pressure. The movable structure 3 is also a diaphragm in this sensor 1. Furthermore, the fixed structure 2 is a frame. The edge regions of the movable structure 3 are fastened to the fixed structure 2 in such a way that said edge regions cannot move in the z direction, wherein the z direction is defined as the direction of the surface normal of the movable structure 3. An inner region of the movable structure 3, which inner region adjoins the edge region, can move in the x direction relative to the fixed structure 2.

LIST OF REFERENCE SYMBOLS

[0083] 1 Sensor [0084] 2 Fixed structure [0085] 3 Movable structure [0086] 4 First magnetically sensitive elements [0087] 5 Magnet [0088] 9 Comb structure [0089] 10 Raised portion [0090] 11 Opening [0091] 12 Stop [0092] 104 Second magnetically sensitive elements [0093] 105 Magnet [0094] 204 Third magnetically sensitive elements [0095] 205 Magnet [0096] 304 Fourth magnetically sensitive elements [0097] 305 Magnet [0098] 404 Further magnetically sensitive elements