Microelectromechanical coupling device

Abstract

A microelectromechanical coupling device (100) for coupling microelectromechanical components comprises a flexible ring structure (110) that forms a circle at rest, which can be deformed substantially parallel to the plane of the circle and which is suitable for coupling the microelectromechanical components, and a plurality of spring elements (120) that are suitable for connecting the ring structure (110) to a substrate (200). Each spring element (120) comprises at least one tangential spring (122) that can be deflected substantially tangentially to the ring structure (110), and at least one radial spring (124) that can be deflected substantially in the radial direction of the ring structure (110).The tangential spring (122) and the radial spring (124) of each spring element (120) are independent components and the ratio of spring stiffnesses of the tangential spring (122) and the radial spring (124) of each spring element (120) is designed such that a vibration deforming the ring structure (110) is energetically more favorable than a vibration displacing the ring structure (110) translationally and / or rotationally to the substrate (200) and / or that the natural frequency of the translational and / or rotational vibration and the nearest natural frequency of a deforming vibration have a difference that is greater than 5% of the natural frequency of this deforming vibration.

Description

The present invention relates to a microelectromechanical coupling device for coupling microelectromechanical components and to a ring gyroscope having such a coupling device.In micromechanical measuring devices such as rotational rate or acceleration sensors, various micromechanical components, such as vibration systems or masses, must frequently be connected to one another in order to couple the respective movements to one another.In this case, coupling by a freely floating, non-supported ring would often be desirable, since this ring reacts to a radial force effect with a deflection which, irrespective of the point in the circumferential direction at which the radial force effect takes place, has the same amplitude. It may likewise be advantageous to use a freely floating ring as a rotation rate sensor, in which a detection vibration is superimposed on an excitation vibration during rotation due to the Coriolis force.However, it is problematic here that without any connection to a substrate of the measuring device, translatory modes, rotation modes in which the ring rotates as a whole, or further parasitic modes form the first eigenmodes. However, these are not desirable. In addition, the production of a non-supported ring for coupling microelectromechanical components is associated with great outlay in terms of production technology.The use of systems with multiple rings, which are connected to one another by stiff, short connections (so-called Stokes), is known here, for example. The Stokes per se are indeed very space-saving. Due to the need to provide several rings in order to obtain a corresponding mounting, this saving in space is, however, partly compensated again. Moreover, owing to their stiffness, the Stokes do not have resonances in the range of a few kHz. Also, with this construction, a homogeneous behavior in the circumferential direction is difficult to achieve.Alternatively, extremely long springs are used which make up space, but also very soft springs. Although low resonant frequencies can thus be realized, here too the deviations from the ideal ring are very large, since no homogeneous behavior in the circumferential direction can be achieved.It is therefore an object of the present invention to specify a micromechanical coupling device or a ring gyroscope in which the excitation of translatory modes can be suppressed and at the same time installation space can be saved compared to the known solutions.This object is achieved by the subject matter of claim 1.A microelectromechanical coupling device for coupling microelectromechanical components comprises a flexible ring structure that at rest forms a circle that can be deformed substantially parallel to the plane of the circle and that is suitable for coupling the microelectromechanical components; and a plurality of spring elements suitable for connecting the ring structure to a substrate. Each spring element has at least one tangential spring, which can be deflected substantially tangentially to the ring structure, and at least one radial spring, which can be deflected substantially in the radial direction of the ring structure. The tangential spring and the radial spring of each spring element are independent components and the ratio of spring stiffnesses of the tangential spring and the radial spring of each spring element is configured such that a vibration deforming the ring structure is more favourable in terms of energy than a vibration displacing the ring structure translationally and / or rotationally with respect to the substrate and / or that the natural frequency of the translatory and / or rotational vibration and the closest natural frequency of a deforming vibration have a distance which is greater than 5% of the natural frequency of this deforming vibration. Preferably, the distance between the natural frequencies is in a range from 5% to 200%, more preferably from 5% to 100%, more preferably from 5% to 50% of the natural frequency of the deforming vibration.The coupling device thus has as a basic structure a ring which is mounted above a substrate and has, for example, the shape of a self-contained web, the height of which perpendicular to the substrate is many times its width parallel to the substrate. In the rest position, this ring forms a circle in the widest sense, i.e. a closed curve which lies parallel to the substrate. A deformation of the ring is then substantially only possible parallel to the substrate, i.e. deflections perpendicular to the substrate are negligible for operation.In order to suppress the translatory and / or rotatory mode or oscillation, the ring structure is connected to the substrate via spring elements which are composed of tangential springs and radial springs, i.e. springs which can be deflected substantially tangentially to the ring structure or perpendicularly to the ring structure. The spring stiffnesses of the tangential and radial springs can be adjusted independently of one another by appropriate dimensioning of the springs during the design and production of the coupling device. In this way, a ratio of the spring stiffnesses of the tangential and radial springs of each spring element can be adjusted, in which the translatory mode or other disturbing modes, such as rotational modes, is energetically impaired compared to at least one "genuine" vibration mode, i.e. a vibration mode deforming the ring structure, also referred to below as bending mode. This ensures that the ring structure deforms as desired upon excitation and does not execute a mere lateral movement.Additionally or alternatively, by adjusting the ratio of the spring stiffnesses of the tangential and radial springs, it can be achieved that the natural frequency of the translatory mode and / or of the rotational mode differs sufficiently from the closest natural frequency of the bending mode. This ensures that a force impact on the coupling device, e.g., exciting the translatory mode, does not couple into the actually desired vibration mode and interferes with it. In this way, disturbances of an operating vibration of the ring structure can thus be prevented.The possibility of achieving the above-mentioned effects by providing independently acting tangential and radial springs can be understood as follows.In the first non-translational vibration mode, the ring vibrates in the shape of an ellipse. At any time, two antinodes are formed, i.e. locations with maximum amplitude. This mode is therefore also called n=2 eigenmode. Further bending eigenmode with a plurality of vibration antinodes are accordingly designated as n=3, 4, 5,... Eigenmodes are designated.Due to the elliptical shape of the n=2 eigenmode, the deviation of the ring from the circular shape in cylindrical coordinates for each point can be parameterized as follows: Φ Fr,1= cos(2θ) for the radial direction and Φ F θ,1=-1⁄2 sin(2θ) for the tangential direction. The angle θ describes the circumferential angle.The points on the ring thus experience, in addition to a radial, also a tangential deflection. The tangential deflection is at most half as large as the radial deflection. In addition, the sum of the radial deflection of the points is greater than the sum of the tangential deflection. Thus, more radial deflection takes place than tangential deflection.There are points that undergo only a radial or tangential deflection and points that undergo a superimposed deflection in the radial and tangential directions.If spring elements are used for suspending a ring structure, which have radial and tangential springs that can be deflected independently of one another, the deflections in the radial and tangential directions can be controlled via the ratio of the spring stiffnesses of the tangential springs and the radial springs of each spring element. The greater the spring stiffness in the tangential direction compared to the spring stiffness in the radial direction, the less far the tangential spring is deflected with the same force exertion compared to the radial spring. Accordingly, the ring structure can also be deformed less easily in the tangential direction than in the radial direction if the spring stiffness of the tangential springs is high in comparison to the spring stiffness of the radial springs.In contrast to the n=2 eigenmode, a ring does not deform during a translatory movement, but rather behaves approximately like a rigid body with a mass. If the ring structure coupled to the substrate by means of the spring elements thus moves purely translationally over the substrate, only the spring elements are deformed, but not the ring structure. The deflection / deformation of the spring elements differs from the deflection of the spring elements in the n=2 eigenmode. Here, it is no longer true that the tangential deflection is at most half the radial deflection. In addition, the sum of the tangential deflection of the points is greater than in the case of the n=2 eigenmode. The sum of the radial deflections remains approximately unchanged.A ring behaves analogously in a rotation mode. Here, the ring rotates as a rigid body about the central axis and only the springs are deflected. In this case, the springs are deflected approximately exclusively in the tangential direction.Accordingly, the translatory mode and the rotational modes of the ring structure can be suppressed or shifted to higher frequencies by using independent radial and tangential springs in each of the spring elements, because these can suppress a deflection of the ring structure in the tangential direction by more than half the deflection in the radial direction due to their separately adjustable spring stiffnesses. The n=2 eigenmode can therefore be energetically favored compared to the translatory mode and / or rotational mode.The same also applies to the higher bending eigenmodes (n=3, 4, 5,... ). These modes can also be energetically promoted by a corresponding design of the radial and tangential springs of the spring elements in relation to the translation / rotation mode. Accordingly, by adjusting the spring stiffnesses, the natural frequencies of the natural vibration / bending modes can also be separated from the natural frequency of the translatory mode and / or rotational mode.The spring elements can be designed in such a way that the ratio of the spring stiffness of the tangential spring to the spring stiffness of the radial spring lies in a range from 1 to 3. This ensures that the translatory mode and / or rotational mode is not the mode that is most favourable in terms of energy or that its natural frequency is sufficiently far from the (or at least one) natural frequencies of the natural bending modes.The ring structure may be suitable for being excited to oscillations with an amplitude, preferably in the range between 0.1 μm and 10 μm, in which the spring stiffnesses of the tangential springs and of the radial springs remain constant. This means that both the tangential springs and the radial springs remain in the linear range in the case of the oscillations occurring through the ring structure during operation of the coupling device, in which the deflection is directly proportional to the deflecting force, i.e. in which the spring stiffness is constant. This can be achieved in particular by the separate configuration of the tangential and radial springs, which can deflect the movements in their corresponding preferred direction.The spring elements can have a radial extent of less than 25% of the radius of the ring structure in the idle state. This is also made possible by the separate design of tangential and radial springs. In particular, the radial springs can be narrow in the radial direction of the ring structure and can, for example, occupy only 10% or 5% of the radius of the ring structure. Since the tangential springs need / should only allow a smaller deflection than the radial springs, they can also be configured in a compact manner. This allows a compact suspension of the ring structure and thus a compact structure of the coupling device to be achieved.The spring elements can be connected to the ring structure from the outside. This makes it possible to keep the installation space free in the interior of the ring structure, for example for further components with additional functionality. Due to the small space requirement of the spring elements, no much space is required here even in the outer region of the ring structure. The coupling device can thereby be compact and nevertheless equipped with increased functionality.Each spring element can be designed in such a way that less than half of space is available for deflections of the tangential spring in the tangential direction than for deflections of the radial spring in the radial direction. As described above, oscillations of the ring structure are to be preferred in terms of energy, in which the tangential movement component of the ring structure is only a maximum of half as large as the radial movement component. Accordingly, the installation space to be kept free for the tangential movements can be reduced and the installation space which becomes free can be used for other components. As a result, the coupling device becomes more compact and can nevertheless be equipped with a multiplicity of components.In the circumferential direction of the ring structure, electrodes for exciting and / or reading out oscillations of the ring structure can be arranged between the spring elements. The ring structure is thereby designed to be particularly compact.Each of the electrodes can extend in the circumferential direction over an angle between 10° and 45° measured from the center of the ring structure, preferably over an angle between 15° and 30° and more preferably over an angle of 18°. As a result, the electrodes are in contact with large, contiguous sections of the ring structure. This reduces the voltage at the electrodes necessary for a force to be applied / read out. This makes the operation of the coupling device more efficient.The spring elements can be uniformly distributed in the circumferential direction of the ring structure. This facilitates the production of the coupling device.Each spring element can connect the ring structure to the substrate via exactly one anchor structure. This reduces the damping mechanism of the so-called "armature losses". Anchor losses occur when forces are introduced into the substrate via a plurality of points, which can then only be compensated at the level of the substrate. The "anchor losses" describe the energy which is introduced into the substrate by forces and moments at the anchor and dissipates via the substrate into the environment and is thus lost. This can be counteracted by compensating for forces and moments and by delivering these forces and moments to the substrate at as few and as central as possible points. Accordingly, the use of only one armature structure reduces the occurrence of such armature losses.In each spring element, the radial spring may include a double-folded bending beam spring extending in the tangential direction and being linked to the substrate and the tangential spring in the radial direction, and the tangential spring may be a more than double-folded bending beam spring or may include at least two double-folded bending beam springs extending in the radial direction and being linked to the radial spring and the ring structure in the radial direction. As a result, spring elements corresponding to those mentioned above can be produced in a simple manner.A ring gyroscope may include a micromechanical coupling device as described above. In this case, the ring structure may be suitable for carrying out an excitation oscillation on which a detection oscillation generated by the Coriolis force is superimposed during a rotation of the ring structure. The spring elements here represent the microelectromechanical components. In this way, a ring gyroscope can be realized in which the unwanted translational mode or its natural frequency can be sufficiently separated from the desired operating modes or its frequencies.In this case, the so-called "angular gain" of the second natural oscillation of the ring structure, which is formed from the ratio of Coriolis mass to double modal mass, can lie in a range between 0.3 and 0.4, preferably in a range between 0.35 and 0.4 and further preferably in a range between 0.38 and 0.4, wherein the end points are part of the ranges specified. The modal mass describes the proportional mass of the associated eigenwave, i.e. an effective mass of the corresponding eigenwave. It results from the eigenvector of the corresponding mode and the mass distribution. The Coriolis mass is composed of all mass points which move in the direction of the exciting oscillation during an excited oscillation and in the direction of the detection oscillation during the detection. The so-called "angular gain" can be determined from the ratio of Coriolis mass and modal mass. The theoretical maximum angular gain is 1 (Foucault pendulum). A large angular gain is advantageous and can be understood as the amplification factor of the rotation rate signal. Theoretically, the angular gain of a ring gyroscope in the n=2 eigenmode is 0.4.The invention will be further described below with reference to the figures. The figures and their description are purely exemplary. The present invention is defined solely by the subject matter of the claims. It shows: FIGS. 1A and 1B show a schematic illustration of a microelectromechanical coupling device; FIG. 2 shows a schematic illustration of a spring element formed from a combination of a tangential spring and a radial spring; FIGS. 3A and 3B are schematic representations of the deflections of the radial spring and the tangential spring of FIG. 2 ; FIG. 4 shows a schematic illustration of a further spring element; FIG. 5 shows a schematic illustration of a further spring element; FIG. 6 shows a schematic illustration of a further spring element; FIG. 7 shows a schematic illustration of a further spring element; FIG. 8 shows a schematic illustration of a further spring element; FIG. 9 is a schematic illustration of a ring gyroscope constructed of a microelectromechanical coupling device; FIG. 10 is a schematic illustration of another ring gyroscope; and FIG. 11 shows a schematic illustration of the arrangement of electrodes and spring elements in a coupling device.FIGS. 1A and 1B show a schematic illustration of a microelectromechanical coupling device 100 suitable for coupling microelectromechanical components, such as are used in microelectromechanical measurement devices, such as yaw rate and / or acceleration sensors, for example. Microelectromechanical coupling device 100 may also form the basic structure of an annular rotation rate sensor. FIG. 1B is a cross-sectional view of FIG. 1A along line I-I.The coupling device 100 has a flexible ring structure 110 and a plurality of spring elements 120. The ring structure forms a circle at rest as shown in FIG. 1A and can be deformed substantially parallel to the plane of the circle. As can be seen from FIG. 1B, the ring structure 110 has a substantially rectangular cross section perpendicular to the circular plane or perpendicular to a substrate 200 over which the ring structure 110 is mounted, with longitudinal sides perpendicular to the substrate 200, which are many times longer than the short sides parallel to the substrate 200. The ring structure 110 can thus be considered, for example, as a self-contained bending beam spring which can deform parallel to the substrate 200, wherein deformations perpendicular to the substrate 200 (in a first approximation) are negligible. The shown shape of the ring structure 110 is purely exemplary here. The ring structure 110 may have any shape that promotes deformation substantially only parallel to the substrate plane. The ring structure 110 can also have a degenerate circular shape in the rest position and can be designed, for example, as an ellipse or as a polygon with rounded corners. Such degenerate circular shapes should therefore also be covered by the reference to the circular ring structure 110.Coupling sites 112 are indicated on the ring structure 110, at which the microelectromechanical components to be coupled engage or at which these components are connected to the ring structure 110. By means of the coupling, movements between the microelectromechanical components can be transmitted or coordinated. In particular, the coupling device 100 can impart a force- and moment-free push-pull vibration between the components. The microelectromechanical components can be sensor masses or vibration systems, for example. In principle, however, the type, structure and size of the components 200 to be coupled are arbitrary. Likewise, the number of components 200 may be greater than two.The coupling can also take place via the spring elements 120. Then, the coupling points 112 are missing. In particular, if the coupling device 100 is part of an annular microelectromechanical rotation rate sensor, for example a ring gyroscope, the spring elements 120 may represent the microelectromechanical components. The ring structure is suitable here for carrying out an excitation oscillation on which a detection oscillation generated by the Coriolis force is superimposed during a rotation of the ring structure 110.The ring structure 110 is connected to the substrate 200 via a plurality of spring elements 120. The spring elements 120 engage at different points of the ring structure 110 and hold it over the substrate 200. As shown in FIGS. 1A and 1B, the spring elements 120 may be connected to anchoring structures 125 and thus directly connect the ring structure 110 to the substrate 200. The anchor structures 125 may have any shape as long as they allow a fixed connection to the substrate 200.As shown schematically in the enlargement of FIG. 1A, each spring element 120 has at least one tangential spring 122, which can be deflected substantially tangentially to the ring structure 110, and at least one radial spring 124, which can be deflected substantially in the radial direction of the ring structure 110.The tangential spring 122 and the radial spring 124 are represented completely schematically in FIG. 1A by spiral spring symbols. These springs can have any desired shape, as long as the tangential spring 122 and the radial spring 124 of each spring element 120 are independent components and the ratio of spring stiffnesses of the tangential spring 122 and the radial spring 124 of each spring element 120 is configured such that a vibration deforming the ring structure 110 is more favourable in terms of energy than a vibration displacing the ring structure 110 translationally to the substrate 200 and / or that the natural frequency of the translational vibration and the closest natural frequency of a deforming vibration have a distance which is greater than 5% of the natural frequency of this deforming vibration. Preferably, the distance between the natural frequencies is in a range from 5% to 200%, more preferably from 5% to 100%, more preferably from 5% to 50% of the natural frequency of the deforming vibration.The spring elements 120 thus consist of springs which are deformable substantially independently of one another and divide the total movement / deformation of the spring elements 120 into a radial component and a tangential component by the radial component being generated by the deformation of the radial spring 124 and the tangential component by a deformation of the tangential spring 122. The tangential spring 122 and the radial spring 124 are in this case in each case assemblies which are separated from one another and whose dimensions and properties can be adjusted separately during the production process of the coupling device 100. In particular, the masses and thicknesses of the tangential springs 122 and the radial springs 124 may be formed differently, e.g., in an etching process, to thereby achieve different spring stiffnesses.In this way, the ratios of the spring stiffnesses of the tangential springs 122 to the radial springs 124 can be adjusted such that a translatory or rotatory oscillation of the ring structure 110, i.e. an oscillation without deformation of the ring structure 110, becomes more disadvantageous in terms of energy than an oscillation which deforms the ring structure 110. Preferably, the second eigenmode of the freely floating ring structure 110, i.e. the n=2 eigenmode in which two antinodes form, should become more favourable in terms of energy than the translation or translation mode and / or rotation mode due to the connection to the spring elements 120. The ratio of the spring stiffnesses in the individual spring elements 120 can also be adjusted in such a way that the eigenmodes of the freely floating ring structure 110 are rearranged, i.e. for example the n=3 eigenmode of the freely floating ring structure 110 becomes more favourable in terms of energy than the n=2 eigenmode due to the coupling with the spring elements 120. For this purpose, the ratios of the spring stiffnesses in the individual spring elements 120 can also be designed differently.Instead of achieving a rearrangement of the excitation energies of the individual eigenmodes of the freely floating ring structure 110 (or in addition thereto), the ratio of the spring rigidities of tangential spring 122 and radial spring 124 can also be adjusted in such a way that the natural frequencies of the eigenmodes are sufficiently far apart. In particular, the natural frequency of the translation mode and / or rotation mode should be sufficiently far from the initially located natural frequency of a bending mode deforming the ring structure 110 in order to ensure that force shocks exciting the translation mode do not couple into this bending mode and disturb it. For this purpose, the natural frequencies can have a distance of more than 5%, for example, of the natural frequency of the bending mode. Preferably, the distance between the natural frequencies is in a range from 5% to 200%, more preferably from 5% to 100%, more preferably from 5% to 50% of the natural frequency of the deforming vibration.The spring elements 120 can be designed in particular such that the ratio of the spring stiffness of the tangential spring 122 to the spring stiffness of the radial spring 124 is in a range from 1 to 3. If the spring stiffness of the tangential spring 122 is selected to be greater than that of the radial spring 124, tangential movements are suppressed. This is preferred to have a motion pattern like that of the n=2 eigenmode, in which the maximum tangential deflection is smaller than the maximum radial deflection.For the same reason, each spring element 120 can also be designed in such a way that less than half of space is available for deflections of the tangential spring 122 in the tangential direction than for deflections of the radial spring 124 in the radial direction. This suppresses the translatory mode itself. On the other hand, the space in the tangential direction is not required given a corresponding setting of the spring elements 120 and can be used for the placement of other components, such as electrodes.In particular, the ring structure 110 should oscillate with such a low amplitude, preferably in the range between 0.1 μm and 10 μm, that the spring stiffnesses of the tangential springs 122 and of the radial springs 124 remain constant. The spring elements 120 therefore behave like linear springs in the deflection region of the ring structure 110. The linearity of the spring elements 120 is also attributable here to the separation of tangential springs 122 and radial springs 124. By this separation, the deflections in either direction parallel to the substrate 200 can be split into radial and tangential portions and accommodated by the corresponding spring. This prevents parts of the spring elements 120 from being deflected in their preferred directions, i.e. in directions in which they already leave the linearity range in the case of small deflections. As a result, the vibration of the ring structure 110 is more easily controllable.The above-described configuration of the coupling device makes it possible to effectively suppress excitations of the translational mode with respect to excitations of bending modes. The separation of the spring elements 120 into tangential springs 122 and radial springs 124 also allows a compact design of the spring elements 120, so that the suppression of the translatory mode can be achieved together with a compact design of the coupling device 100.The spring elements 120 can in particular have a radial extent of less than 25% of the radius of the ring structure 110 in the idle state, as a result of which the coupling device 100 becomes particularly compact. This allows further components to be placed in or around the ring structure 110.The spring elements 120 can be connected to the ring structure 110 from the inside, as shown in FIG. 1A. Due to its compact construction, a large part of the interior of the ring structure 110 remains free. However, they can also be connected to the ring structure 110 from the outside, since their small size nevertheless does not lead to an excessive enlargement of the coupling device. As a result, the interior of the ring structure 110 can be made completely free for the arrangement of further components, which is not possible, for example, in embodiments from the prior art in which the ring structure is held by long, centrally anchored springs or by large frame structures.The spring elements 120 may, as shown in FIG. 1A, in principle be distributed irregularly along the ring structure 110, if this is advantageous for the intended suppression of the translational mode. Preferably, however, the spring elements are uniformly distributed in the circumferential direction of the ring structure 110, since this facilitates production. In addition, the ring structure 110 can be excited homogeneously more easily as a result.As shown in FIGS. 1A and 1B, each spring element 120 connects the ring structure 110 to the substrate 200 via exactly one anchor structure 125. This prevents armature losses. These arise when forces are introduced into the substrate via a plurality of points, which can then only be compensated for at the level of the substrate. The anchor losses describe the energy which is introduced into the substrate by forces and moments at the anchor and dissipates via the substrate into the environment and is thus lost. This can be counteracted by compensating for forces and moments and by delivering these forces and moments to the substrate at as few and as central as possible points. Accordingly, the use of only one armature structure reduces the occurrence of such armature losses.As shown in FIG. 1A, the coupling device 110 may include a plurality of spring elements 120. The number of spring elements 120 can, however, also be different. For example, 4, 8, 16, 24, or 32 spring members 120 may be used.FIGS. 2 to 8 show different variants of spring elements 120. Common to these variants is that in the spring elements 120, the radial spring 124 has a double-folded bending beam spring which extends in the tangential direction and which is linked in the radial direction to the substrate 200 and the tangential spring 122, and the tangential spring 122 is a more than double-folded bending beam spring or has at least two double-folded bending beam springs which extend in the radial direction and which are linked in the radial direction to the radial spring 124 and the ring structure 110. In principle, other configurations are of course also possible, as long as the tangential spring 122 and the radial spring 124 can be made separately. For example, it is possible to attach the radial spring 124 to the ring structure and the tangential spring 122 to the substrate 200.FIG. 2 shows a spring element 120 in which the radial spring 124 is designed as a double-folded bending beam spring which establishes a connection between an anchor point 125 and the tangential spring 122. That is, a bending beam extending in the tangential direction is connected to the anchor structure 125, preferably at its center. At each end, the bending beam is folded through 360°, i.e. it returns in parallel and thus forms a second bending beam which runs parallel to the first bending beam. The two bending beams are connected at their ends. Such a structure can be produced in a manner known per se by an etching method.The tangential spring 122 consists of a bending beam spring which runs in the radial direction from a (preferably central) connection point with the radial spring 124 to the ring structure 110. At the end of this bending beam spring, a double-folded bending beam spring follows, which is folded into itself in such a way that it runs in a serpentine manner. The long sides of the serpentines run parallel to the centrally located bending beam spring, i.e. in the radial direction. In the example of FIG. 2, 3 serpentines are present, wherein the connection to the radial spring 124 and the ring structure 110 takes place at a central point. However, other numbers of serpentines are also possibleThe deflections of this spring element 120 are shown in greatly exaggerated form in FIGS. 3A and 3B. FIG. 3A shows the deflection in the radial direction r, in which essentially only the radial spring 124 is deformed. FIG. 3B shows the deflection in the tangential direction t, in which essentially only the tangential spring 122 is deformed.By suitably selecting the dimensions of the flexure springs forming the tangential spring 122 and the radial spring 124, e.g., by selecting the etch parameters during manufacture, the spring stiffness of the springs can be adjusted independently of each other. The spring element 120 shown in FIG. 2 is additionally extremely compact. Its use in a coupling device 100 as described above thus allows the translation mode to be suppressed without consuming excessive installation space.The spring element 120 shown in FIG. 4 corresponds to the configuration of FIG. 2, except for the use of two double-folded bending beam springs in the radial spring 124. As a result, the parameters of the radial spring 124 can be set even more flexibly.The spring element 120 shown in FIG. 5 uses as the tangential spring 122 fork-shaped pairs of bending beam springs, i.e. pairs of bending beam springs connected at one end, which are connected to one another at their other end. This embodiment also makes it possible to set the spring parameters of tangential spring 122 and radial spring 124 independently of one another.FIGS. 6 and 7 show two variants of a "two-tooth bending beam fork", which is connected to the radial spring 124 or the ring structure 110 via a single bending beam. These embodiments are particularly compact in the tangential direction.FIG. 8 shows a variant in which the tangential spring 122 consists of two double-folded bending beam springs which are connected by a frame to the radial spring 124 and a bending beam spring anchored to the ring structure 110. In addition, the radial spring 124, which is configured as a double-folded bending beam spring, is not continuous here, but rather merges into the frame.The examples of FIGS. 2 to 8 should illustrate that there are a multiplicity of different configurations for the spring elements 120 which allow the ratio of the spring stiffnesses of the tangential spring 122 and of the radial spring 124 to be freely adjusted within the scope of the production conditions, in order thereby to suppress the translatory mode.FIG. 9 shows a coupling device 100 in which the coupled microelectromechanical components are the spring elements 120. That is, the coupling device 100 corresponds to a deformable ring spring-mounted over the substrate 200. This can be used as the ring gyroscope 300 because the ring structure 110 is capable of performing an excitation vibration to which a detection vibration generated by the Coriolis force is superimposed upon rotation of the ring structure 110. If the ring structure 110 is therefore set into oscillation, for example by using excitation electrodes, a rotation of the ring structure 110 leads to a change in this oscillation, which can be read out, for example via detection electrodes, in order to determine the rotation rate of the rotation therefrom.Here, the suppression of the translational mode or the separation of the natural frequency of the translational mode from the operating frequency / excitation frequency of the ring gyroscope 300 is particularly advantageous, since this can reduce interferences in the measurement. This improves the measurement accuracy of the ring gyroscope 300.As shown in Fig. 10, a plurality of concentric rings connected to each other with short springs, e.g., short radial bending beams or ridges, may also be used as the ring structure 110 of a ring gyroscope 300, e.g., to increase the mass of the vibrating ring structure 110.As can be seen from FIGS. 9 and 10, the spring elements 120 are of compact design (less than 1 / 4 of the radius) in comparison with the dimensions of the ring structure 110 and therefore hardly increase the installation space for the ring gyroscope 300 in comparison with the ring structure 110 without spring elements 120.Electrodes 140 for exciting and / or reading out oscillations of the ring structure 110 can be arranged between the spring elements 120 both when used as a ring gyroscope 300 and generally in the circumferential direction of the ring structure 110. This is shown by way of example in FIG. 11. In this way, oscillations of the ring structure 110 can be excited or measured in a compact manner. In addition, the electrodes 140 can surround the ring structure 110 almost completely in the circumferential direction, whereby a homogeneous response behavior of the ring structure 110 can be achieved.As shown in FIG. 11, the electrodes 140 can be moved relatively close to the tangential springs 122, since these are deflected only comparatively little because of the suppressed translation mode. This improves the interaction between electrodes 140 and ring structure 110 and thus the response behavior of ring structure 110. In addition, the voltage at the electrodes required for a force to be applied / read out is reduced.Each of the electrodes 140 may extend circumferentially over an angle between 10° and 45° measured from the center of the ring structure 110, depending on the number of spring elements 120 used. An angle range between 15° and 30° has proven to be preferred here, when 10 to 20 spring elements 120 are used. For example, 16 spring elements 120 distributed uniformly along the ring structure 110 in the circumferential direction may be used, and the electrodes 140 may each assume an angle of 18°. In this way, 80% of the circumferential direction of the ring structure 110 may be provided with electrodes 140. Generally, an arrangement of electrodes 140 in a range on 70% to 90% of the circumferential direction of the ring structure 110 may be considered to be advantageous for the responsiveness of the ring structure 110.In the ring gyroscope 300, the angular gain (the ratio of Coriolis mass to twice modal mass) of the second eigenmode, i.e., the n=2 eigenmode, of the ring structure 110 may be in a range between 0.3 and 0.4, preferably in a range between 0.35 and 0.4, and more preferably in a range between 0.38 and 0.4 (endpoints included.The modal mass describes the proportional mass of the associated eigenwave, i.e. an effective mass of the corresponding eigenwave. It results from the eigenvector of the corresponding mode and the mass distribution. The Coriolis mass is composed of all mass points which move in the direction of the exciting oscillation during an excited oscillation and in the direction of the detection oscillation during the detection. The so-called "angular gain" can be determined from the ratio of Coriolis mass and modal mass. The theoretical maximum angular gain is 1 (Foucault pendulum). A large angular gain is advantageous and can be understood as the amplification factor of the rotation rate signal. Theoretically, the angular gain of a ring gyroscope in the n=2 eigenmode is 0.4. the above-described coupling device 100, operated as ring gyroscope 300, can achieve an angular which approximates this theoretical amount in an extremely close manner. This is due to the suppression of the translational mode.

Claims

Microelectromechanical coupling device (100) for coupling microelectromechanical components, comprising a flexible ring structure (110) that at rest forms a circle that can be deformed substantially parallel to the plane of the circle and that is suitable for coupling the microelectromechanical components; and a plurality of spring elements (120) that are suitable for connecting the ring structure (110) to a substrate (200); wherein each spring element (120) comprises at least one tangential spring (122) that can be deflected substantially tangentially to the ring structure (110) and at least one radial spring (124) that can be deflected substantially in the radial direction of the ring structure (110); the tangential spring (122) and the radial spring (124) of each spring element (120) are independent components; and the ratio of spring stiffnesses of the tangential spring (122) and of the radial spring (124) of each spring element (120) is configured such that a vibration deforming the ring structure (110) is more favourable in terms of energy than a vibration displacing the ring structure (110) translationally and / or rotationally with respect to the substrate (200) and / or that the natural frequency of the translational and / or rotational vibration and the closest natural frequency of a deforming vibration have a spacing which is greater than 5% of the natural frequency of this deforming vibration.Coupling device (100) according to claim 1, wherein the spring elements (120) are configured such that the ratio of the spring stiffness of the tangential spring (122) to the spring stiffness of the radial spring (124) is in a range from 1 to 3.Coupling device (100) according to one of the preceding claims, wherein the ring structure (110) is suitable for being excited to oscillations with an amplitude, preferably in the range between 0.1 μm and 10 μm, at which the spring stiffnesses of the tangential springs (122) and of the radial springs (124) remain constant.Coupling device (100) according to one of the preceding claims, wherein the spring elements (120) have a radial extent of less than 25% of the radius of the ring structure (110) in the idle state.Coupling device (100) according to one of the preceding claims, wherein the spring elements (120) are connected to the ring structure (110) from the outside.Coupling device (100) according to one of the preceding claims, wherein each spring element (120) is designed such that less than half of space is available for deflections of the tangential spring (122) in the tangential direction than for deflections of the radial spring (124) in the radial direction.Coupling device (100) according to one of the preceding claims, wherein electrodes (140) for exciting and / or reading out oscillations of the ring structure (110) are arranged between the spring elements (120) in the circumferential direction of the ring structure.The coupling device (100) according to claim 7, wherein each of the electrodes (140) extends circumferentially over an angle between 10° and 45° measured from the center of the ring structure (110), preferably over an angle between 15° and 30°, and more preferably over an angle of 18°.Coupling device (100) according to one of the preceding claims, wherein the spring elements (120) are uniformly distributed in the circumferential direction of the ring structure (110).Coupling device (100) according to one of the preceding claims, wherein each spring element (120) connects the ring structure (110) to the substrate (200) via exactly one anchor structure.The coupling device (100) according to any one of the preceding claims, wherein in each spring element (120), the radial spring (124) comprises a double-folded bending beam spring extending in the tangential direction and being radially linked to the substrate (200) and the tangential spring (122), and the tangential spring (122) is a more than double-folded bending beam spring or comprising at least two double-folded bending beam springs extending in the radial direction and being radially linked to the radial spring (124) and the ring structure (110).Ring gyroscope (300) with the micromechanical coupling device (100) according to one of the preceding claims; wherein the ring structure (110) is suitable for carrying out an excitation vibration on which a detection vibration generated by the Coriolis force is superimposed during a rotation of the ring structure (110); and the spring elements (120) represent the microelectromechanical components.The ring gyroscope (300) of claim 12, wherein the angular gain, i.e. the ratio of Coriolis mass to double modal mass, of the second eigenwave of the ring structure (110) is in a range between 0.3 and 0.4, preferably in a range between 0.35 and 0.4 and more preferably in a range between 0.38 and 0.4, wherein the end points are part of the indicated ranges.

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