DE102008043753B4 - Sensor arrangement and method for operating a sensor arrangement - Google Patents

Abstract

Sensor arrangement (1) with a substrate (2) and a seismic mass (3), the seismic mass (3) being attached to the substrate (2) by means of suspension springs (4), the seismic mass (3) having a torsion axis (30) in the region of the suspension springs (4) and is provided to be elastically movable in the direction of a substrate element (2'), the seismic mass (3) having a main element (3') and a secondary element (3"), the main element (3' ) is connected to the secondary element (3") by means of a spring element (5), the spring element (5) being deflected from an equilibrium position when there is mechanical contact between the secondary element (3") and the substrate element (2'), characterized in that that-- the mass distribution of the seismic mass (3) is asymmetrical in relation to the torsion axis (30) and the spring element (5), the main element (3') and/or the secondary element (3'') on that side of the torsion axis (30 ) are arranged, which have a larger mass (3 ) or-- the maximum extent of the seismic mass (3) perpendicular to the torsion axis (30) is asymmetrical and the spring element (5), the main element (3') and/or the secondary element (3'') on that side the torsion axis (30) are arranged, which has a larger maximum extent.

Description

State of the art

The invention is based on a sensor arrangement according to the preamble of claim 1.

Such sensor arrangements are generally known. For example, from the reference DE 10 2006 026 880 A1 a micromechanical acceleration sensor with a flywheel in the form of a seesaw that can be deflected in the z-direction relative to a substrate, the micromechanical acceleration sensor having a stop device on the substrate to limit a maximum possible mechanical deflection of the flywheel. The centrifugal mass is suspended from the substrate by means of an anchoring device in such a way that the rocker has a geometry that is asymmetrical with respect to a torsion axis formed by the anchoring device. This asymmetrical geometry also causes a mass distribution that is asymmetrical with respect to the torsion axis, so that an acceleration of the micromechanical acceleration sensor in the z-direction produces a deflection of the centrifugal mass relative to the substrate due to inertial forces. This deflection can be measured capacitively by means of electrodes on one or both sides of the torsion axis and corresponding counter-electrodes on the substrate. Devices for preventing such moving elements from sticking to fixed elements in the event of contact between the moving elements and the fixed element due to excessive acceleration forces acting on the centrifugal mass are not provided.

Generic is from the DE 699 28 061 T2 an acceleration sensor is known, the movable mass of which has different, elastically coupled contact sections at different distances from a stop surface, so that only one contact section strikes during weak acceleration, while the other contact sections only strike during strong acceleration.

Disclosure of Invention

The sensor arrangement according to the invention and the method according to the invention for operating a sensor arrangement according to the independent claims have the advantage over the prior art that the risk of a sensor defect due to permanent adhesion (hereinafter also referred to as "sticking") between the seismic mass and the substrate element is significantly reduced. This is achieved in that the seismic mass is divided into a main element and a secondary element, with the main element and the secondary element being connected to one another via a spring element, so that mechanical contact between the secondary element and the substrate element causes the spring element to be deflected from its equilibrium position causes. The introduction of force for the deflection of the spring element comes from the substrate element. The deflection results in a spring force of the spring element acting on the main element in such a way that the main element is pressed in a direction away from the substrate element, so that a movement of the main element in the direction of the substrate element is braked and/or stopped. The spring element is supported by the substrate element via the secondary element. Contact between the main element and the substrate element is thus prevented in a particularly advantageous manner. However, in the event that the deceleration is not sufficient to prevent contact, the spring force continues to act increasingly on the main element during contact and thus generates a force effect which counteracts a possible adhesive connection between the main element and the substrate element. Particularly advantageously, the spring element is preferably arranged spatially closer to the contact than the suspension springs, so that the force to detach the main element from the substrate element, starting from the spring element, is considerably greater than the restoring force of the suspension springs, since the force of the suspension springs has a significantly less favorable effect, in particular longer lever arm is transmitted. The spring element is preferably designed to be significantly more rigid than the suspension springs, so that in "normal operation" (i.e. no movements of the seismic mass such that the main element comes close to the substrate element) there is no deflection of the spring element and the vibration behavior of the seismic mass is controlled by the spring element or is not influenced at all or only insignificantly by the subdivision of the seismic mass into a main element and a secondary element. The substrate element within the meaning of the invention comprises in particular an area of the substrate, an area of a micromechanical functional layer, an electrode, a stop, a capping element and the like. It goes without saying for a person skilled in the art that the substrate element does not necessarily have to be arranged on the substrate side of the seismic mass. A mechanical contact within the meaning of the present invention, such as between the secondary element and the substrate element, includes in particular a direct mechanical contact with a mechanical force transmission between the corresponding elements. In the context of the present invention, the spring element is to be arranged both on the "short" side of the seesaw and on the "long" side.

Advantageous configurations and developments of the invention can be found in the subclaims and the description with reference to the drawings.

According to a preferred development, it is provided that in a maximum deflection position of the spring element, mechanical contact is provided both between the main element and the substrate element and between the secondary element and the substrate element. In this case, particularly preferably, both a tensioning force of the spring element, which is supported on the substrate element, and a restoring tensioning force of the suspension element, which is supported on the substrate, act on the main element, pushing the main element away from the substrate element and thus increasing the risk of permanent adhesion between between the main element and the substrate element.

According to a further preferred development, it is provided that the spring element comprises a bending spring and/or a torsion spring, so that a plurality of different geometries can advantageously be realized when the seismic mass is formed. In particular, the integration of the spring element in various configurations of the seismic mass thus becomes possible in a simple manner, so that existing sensor arrangements can be expanded to include the spring element to prevent “sticking” in a particularly cost-effective manner.

According to a further preferred development, it is provided that the spring element comprises a leaf spring, the leaf spring preferably being aligned essentially parallel to a main plane of extension of the main element in the equilibrium position and being at least partially deflected out of the main plane of extension in the event of deflection. A leaf spring can be particularly advantageously integrated into the seismic mass in a particularly compact manner and at low cost.

According to a further preferred development, it is provided that the spring element and/or the secondary element comprises a contact element in the form of a projection, the projection being provided essentially protruding in the direction of the substrate element and mechanical contact being provided between the contact element and the substrate element in the event of deflection is. The contact element is particularly preferably arranged on the secondary element, with the contact element particularly advantageously preventing the secondary element from “sticking” to the substrate element. The contact element particularly preferably tapers in the direction of the substrate element, so that the contact area between the substrate element and the contact element is comparatively small in the case of mechanical contact, and “sticking” is thus suppressed.

According to a further preferred development, it is provided that the spring element and the secondary element comprise the same material and/or that the spring element, the secondary element and/or the contact element at least partially comprise an anti-adhesive material. In terms of the present invention, a seismic mass with a main element, a spring element and a secondary element also includes a seismic mass formed from one piece, which has a certain flexibility at least in partial areas. For example, the spring element and the secondary element are designed as a joint formation in the main element, for example in the form of a bar, web or tongue, and are therefore particularly advantageous to produce in a comparatively inexpensive manner. The spring element is produced, for example, by weakening the material of the main and/or secondary element. The weakening preferably comprises a cutout or a tapering of the material in the spring area.

The invention provides that the seismic mass has a torsion axis in the region of the suspension springs, with the mass distribution of the seismic mass being asymmetric relative to the torsion axis or the maximum extension of the seismic mass perpendicular to the torsion axis being asymmetric. In the case of an asymmetrical mass distribution, it is provided that the spring element, the main element and/or the secondary element are arranged on that side of the torsion axis which has a greater mass. The side with the greater mass is deflected more strongly than the other side by a high acceleration force, so that it is sufficient to arrange the spring element on this one side and manufacturing costs can thus advantageously be saved. If the seismic mass extends asymmetrically, it is provided that the spring element, the main element and/or the secondary element are arranged on that side of the torsion axis which has a larger maximum extension. In the event of excessive movement of the seismic mass out of the equilibrium position, it is particularly advantageous that the side of the seismic mass that is longer in relation to the torsion axis first touches the substrate element, so that it is particularly advantageous for the seismic mass to "stick" simply by integrating the spring element on the longer side can be prevented on the substrate element.

Another object of the present invention is a method for operating a sensor Sensor arrangement, wherein in the event of mechanical contact between the secondary element and the substrate element, the spring element is deflected from an equilibrium position, wherein according to a further preferred development it is provided that in the event of deflection, the spring element generates a force on the main element in the direction of an initial position of the seismic mass becomes. As already explained in detail above, the spring element is only deflected in the case of mechanical contact between the secondary element and the substrate element. The spring element is therefore particularly advantageously deflected only when necessary, ie when there is a risk that the main element will also touch the substrate element and there is a risk of the main element “sticking” to the substrate element. In this case, the deflection of the spring element generates a tensioning force that drives the main element away from the substrate element in the contact area and thus releases and/or prevents it from “sticking”. In the "normal" operating mode, no deflection of the spring element is aimed at, so that the vibration behavior of the seismic mass is not influenced by the spring element, or only insignificantly. The risk of a failure or defect in the sensor arrangement, caused by excessive acceleration of the sensor arrangement, is thus eliminated or significantly reduced.

Embodiments of the invention are shown in the drawings and explained in more detail in the following description.

character list

• 1a und 1b eine schematische Draufsicht und eine schematische Seitenansicht einer Sensoranordnung gemäß dem Stand der Technik,
• 2a, 2b und 2c eine schematische Draufsicht und zwei schematische Seitenansichten einer Sensoranordnung gemäß einer ersten Ausführungsform der vorliegenden Erfindung,
• 3a und 3b eine schematische Draufsicht und eine schematische Seitenansicht einer Sensoranordnung gemäß einer zweiten Ausführungsform der vorliegenden Erfindung,
• 4a und 4b eine schematische Draufsicht und eine schematische Seitenansicht einer Sensoranordnung gemäß einer dritten Ausführungsform der vorliegenden Erfindung und
• 5a, 5b und 5c eine schematische Draufsicht und zwei schematische Seitenansichten einer Sensoranordnung gemäß einer vierten Ausführungsform der vorliegenden Erfindung.

Show it

• 1a and 1b a schematic top view and a schematic side view of a sensor arrangement according to the prior art,
• 2a , 2 B and 2c a schematic top view and two schematic side views of a sensor arrangement according to a first embodiment of the present invention,
• 3a and 3b a schematic top view and a schematic side view of a sensor arrangement according to a second embodiment of the present invention,
• 4a and 4b a schematic plan view and a schematic side view of a sensor arrangement according to a third embodiment of the present invention and
• 5a , 5b and 5c a schematic top view and two schematic side views of a sensor arrangement according to a fourth embodiment of the present invention.

Embodiments of the invention

In the figures, the same elements are always provided with the same reference symbols and are therefore usually named or mentioned only once.

In the 1a and 1b a schematic top view and a schematic side view of a sensor arrangement 1 according to the prior art are shown, the sensor arrangement 1 having a substrate 2 and a seismic mass 3 . The seismic mass 3 is designed as a z-sensitive seesaw structure, ie the seismic mass 3 is elastically attached to the substrate 2 by means of suspension springs 4 in such a way that the seismic mass 3 can be tilted relative to the substrate 2 about a torsion axis 30, the seismic mass 3 having a first side 50 on a first side of the torsion axis 30 and a second side 51 opposite the first side 50, the second side 51 having a significantly greater maximum extension 52 perpendicular to the torsion axis 30 and parallel to the substrate 2. The material of the seismic mass 3 is essentially identical on both sides of the torsion axis 30 , so that the seismic mass 3 has an asymmetric mass distribution with respect to the torsion axis 30 due to the greater maximum extent 52 of the second side 51 . As a result, when the sensor arrangement 1 is accelerated perpendicularly to the substrate 2, ie parallel to the z-direction, the seismic mass 3 experiences a torque about the torsion axis 3 due to its mass inertia, so that the distance between the first side 50 and the substrate 2 and the second side 51 and the substrate 2 changed. This change in distance is preferably measured capacitively by means of electrodes not shown on first side 50 and/or second side 51 and corresponding counter-electrodes on substrate 2, not shown, and is therefore a measure of the acceleration of sensor arrangement 1 in the z-direction. If the acceleration is too strong, there is a risk that the second side 51 of the seismic mass 3 will touch the substrate 2 or a substrate element 2' and will stick to the substrate 2 or the substrate element 2'. This “sticking” disadvantageously leads to a total failure of the sensor arrangement 1 since the seismic mass 3 can no longer be moved in this case.

In the 2a , 2 B and 2c 1 are a schematic top view and two schematic side views of a sensor arrangement 1 according to a first embodiment of the present invention Invention shown, wherein the sensor arrangement 1 similar to that in 1a and 1b illustrated sensor arrangements, wherein the seismic mass 3 on the second side 51 comprises a main element 3', a secondary element 3" and a spring element 5. The spring element 5 is designed, for example, as a torsion spring 5' and the secondary element 3" as a U-shaped bracket , whereby the bracket is attached at its leg ends to the main element 3' via the torsion spring 5' in such a way that a deflection of the bracket or the secondary element 3" about an axis of rotation 50 formed by the torsion spring 5' (parallel to the torsion axis 30) relative to the main element 3' is made possible. In the equilibrium position of the torsion spring 5', the bracket is essentially parallel to a main extension plane of the main element 3', while in the case of deflection the main extension of the bracket deviates from the main extension plane of the main element 3'. This deflection of the secondary element 3" from the main extension plane of the main element 3 'is in 2c illustrated and takes place with a large deflection of the seismic mass 3 from the initial position, which in 2 B is shown, by a mechanical contact between the secondary element 3 "and the substrate 2 or the substrate element 2 ', wherein in the present case the substrate element 2' purely by way of example is a part of the substrate 2. The in 2c Illustrated deflection of the seismic mass 3 is so great that the main element 3 'touches the substrate element 2'. However, the deflected spring element 5 or the deflected torsion spring 5′ exerts a tensioning force on the main element 3′, which forces the main element 3′ away from the substrate element 2′. This clamping force is preferably significantly greater than the restoring force of the suspension spring 4. This is achieved, for example, in that the lever arm of the spring element 4' for generating a restoring clamping force on the main element 3' is significantly more favorable than the lever arm of the suspension springs 4, since the secondary element 3" parallel to the main plane of extension of the main element 3' is significantly shorter than the main element 3' (about half as long). The sum of the restoring forces originating from the spring element 5 and the suspension springs 4 is so great that the risk of "sticking "of the main element 3' on the substrate element 2' is eliminated or at least significantly reduced. In the contact area between the secondary element 3" and the substrate element 2' in the event of deflection, a contact element 6 is also arranged, which reduces the risk of the secondary element 3 "Suppressed on the substrate element 2 ', wherein the contact element 6 to has a taper in the direction of the substrate element 2'.

In the 3a and 3b a schematic top view and a schematic side view of a sensor arrangement 1 according to a second embodiment of the present invention are shown, the second embodiment essentially illustrating the first embodiment in FIGS 2a , 2 B and 2c is identical, the spring elements 5 not being designed as torsion springs 5', but together with two secondary elements 3" as leaf springs 5". The axis of rotation 50 of the spring element 5 is in turn parallel to the torsion axis 30 and in each case connects the secondary element 3" from the main element 3', with the leaf spring 5' in the form of a long spring functioning like a bending beam. The spring element 5 and the secondary element 3" are preferably made of made in one piece and/or consist of the same material. The main element 3', the secondary element 3'' and the spring element 5 are particularly preferably made from one piece and/or from one material, with the spring element 5 being formed by a weakening in the material of the seismic mass 3.

In the 4a and 4b a schematic top view and a schematic side view of a sensor arrangement 1 according to a third embodiment of the present invention are shown, the third embodiment being illustrated essentially identically to the second embodiment in FIGS 3a and 3b is, wherein the spring element 5 is designed meandering. Particularly preferably, the spring stiffness of the spring element 5 is reduced by the meandering design of the spring element 5 implemented in the form of a spiral spring 5".

In the 5a , 5b and 5c a schematic top view and two schematic side views of a sensor arrangement 1 according to a fourth embodiment of the present invention are shown, the fourth embodiment being illustrated essentially identically to the first embodiment in FIGS 2a , 2 B and 2c wherein the spring element 5 comprises a single torsion spring 5''' in a recess of the main element 3', the secondary element 3'' being constructed in the shape of a bar, the bar being attached at one end centrally to the torsion spring 5'''. In addition, the secondary element 3" is designed to be essentially rigid.

Claims (8)

Sensor arrangement (1) with a substrate (2) and a seismic mass (3), the seismic mass (3) being attached to the substrate (2) by means of suspension springs (4), the seismic mass (3) having a torsion axis (30) in the region of the suspension springs (4) and is provided to be elastically movable in the direction of a substrate element (2'), the seismic mass (3) having a main element (3') and a secondary element (3") points, the main element (3') being connected to the secondary element (3") by means of a spring element (5), the spring element (5) being in mechanical contact between the secondary element (3'') and the substrate element (2') is deflected from an equilibrium position, characterized in that -- the mass distribution of the seismic mass (3) is asymmetrical in relation to the torsion axis (30) and the spring element (5), the main element (3') and/or the secondary element (3'' ) are arranged on that side of the torsion axis (30) which has a greater mass (3), or -- the maximum extension of the seismic mass (3) perpendicular to the torsion axis (30) is asymmetrical and the spring element (5), the The main element (3') and/or the secondary element (3'') are arranged on that side of the torsion axis (30) which has a greater maximum extent. Sensor arrangement (1) after claim 1 , characterized in that in a maximum deflection position of the spring element (5) there is simultaneous mechanical contact both between the main element (3') and the substrate element (2') and between the secondary element (3") and the substrate element (2'). is provided. Sensor arrangement (1) after claim 1 , characterized in that the spring element (5) comprises a bending spring and / or a torsion spring. Sensor arrangement (1) according to one of the preceding claims, characterized in that the spring element (5) comprises a leaf spring, wherein the leaf spring is preferably aligned essentially parallel to a main extension plane of the main element (3') in the equilibrium position and is at least partially aligned in the event of deflection the main extension plane is deflected. Sensor arrangement (1) according to one of the preceding claims, characterized in that the spring element (5) and/or the secondary element (3") comprises a contact element (6) in the form of a projection, the projection essentially pointing in the direction of the substrate element (2nd ') is provided above and wherein a mechanical contact between the contact element (6) and the substrate element (2') is provided in the event of deflection. Sensor arrangement (1) according to one of the preceding claims, characterized in that the spring element (5) and the secondary element (3") comprise the same material and/or that the spring element (5), the secondary element (3") and/or the Contact element (6) at least partially comprise a non-stick material. Method for operating a sensor arrangement (1) according to one of the preceding claims, characterized in that in the event of mechanical contact between the secondary element (3") and the substrate element (2'), the spring element (5) is deflected from an equilibrium position. procedure after claim 7 , characterized in that in the case of deflection by means of the spring element (5) a force is generated on the main element (3) in the direction of an initial position of the seismic mass (3).

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