WO1998011443A1 - Sensor for capacitively recording an acceleration - Google Patents

Sensor for capacitively recording an acceleration Download PDF

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Publication number
WO1998011443A1
WO1998011443A1 PCT/DE1997/001898 DE9701898W WO9811443A1 WO 1998011443 A1 WO1998011443 A1 WO 1998011443A1 DE 9701898 W DE9701898 W DE 9701898W WO 9811443 A1 WO9811443 A1 WO 9811443A1
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WO
WIPO (PCT)
Prior art keywords
electrodes
sensor according
fingers
acceleration
electrode
Prior art date
Application number
PCT/DE1997/001898
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German (de)
French (fr)
Inventor
Karsten Funk
Bernd Maihöfer
Franz LÄRMER
Bernhard Elsner
Wilhelm Frey
Original Assignee
Robert Bosch Gmbh
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Application filed by Robert Bosch Gmbh filed Critical Robert Bosch Gmbh
Publication of WO1998011443A1 publication Critical patent/WO1998011443A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
    • G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
    • G01P15/125—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by capacitive pick-up
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
    • G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
    • G01P2015/0805—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration
    • G01P2015/0808—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining in-plane movement of the mass, i.e. movement of the mass in the plane of the substrate
    • G01P2015/0811—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining in-plane movement of the mass, i.e. movement of the mass in the plane of the substrate for one single degree of freedom of movement of the mass
    • G01P2015/0814—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining in-plane movement of the mass, i.e. movement of the mass in the plane of the substrate for one single degree of freedom of movement of the mass for translational movement of the mass, e.g. shuttle type

Definitions

  • the invention relates to a sensor for capacitively recording an acceleration with an interdigital capacitor which comprises two electrodes having a plurality of elongated fingers, the fingers of the two electrodes at least partially intermeshing and one of the two electrodes being displaceable with a deflectable one seismic mass is coupled.
  • Acceleration sensors are known from the prior art, which perform a capacitive recording of an acceleration with the aid of interdigital capacitors.
  • An interdigital capacitor is a capacitor which comprises two electrodes, each of which has a large number of fingers. At least the fingers grip partially into one another and thus form partial capacitances with the adjacent fingers of the counter electrode. The sum of these partial capacities then corresponds to the total capacitance of the interdigital capacitor.
  • the partial capacitance in these capacitors depends on the degree of interlocking of the fingers and the distance to the neighboring fingers.
  • This arrangement of the electrodes has the disadvantage that the change in capacitance is not proportional to the deflection and thus to the acceleration present.
  • the sensor with the features of claim 1 has the advantage that the change in capacitance of the capacitors is directly proportional to the deflection and thus to the acceleration. In addition, the occurrence of sticking of two fingers decrease significantly. Characterized in that the fingers of the displaceable electrode move parallel to the fingers of the other electrode, their distance transverse to the deflection direction remains essentially constant and the overlap (1) changes, the displaceable electrode can be amplified so that a movement perpendicular to it is no longer possible. This means that no more sticking occurs because the fingers are always at a defined distance from neighboring fingers.
  • the seismic mass coupled to the displaceable electrode is preferably suspended from four spring bars. This allows a high degree of stiffness to be achieved with respect to movements that are transverse to the direction of detection.
  • the seismic mass is divided into two parts, one part being assigned to one electrode, but the two mass parts remaining connected to one another. This makes it possible to compensate for material stresses that occur.
  • FIG. 1 shows a first exemplary embodiment of a broom acceleration sensor
  • FIG. 2 shows a second exemplary embodiment of an acceleration sensor
  • FIG. 3 shows a third exemplary embodiment of an acceleration sensor
  • Figure 4 shows a fourth exemplary embodiment of an acceleration sensor.
  • an acceleration sensor 1 is shown, which is suitable for capacitive recording of the acceleration. It is designed in a surface micromechanical technology and is increasingly used in automotive engineering in active and passive restraint systems and in vehicle dynamics control.
  • the acceleration sensor 1 comprises two capacitor units 3, 5, each of which is designed as an interdigital capacitor.
  • the two interdigital capacitors 3, 5 each comprise two electrodes 7, 9, on each of which a plurality of elongated fingers 11 are provided.
  • the electrodes 7, 9 thus have a comb structure.
  • FIG. 1 clearly shows that the individual fingers 11 of electrodes 7, 9 located opposite one another at least partially mesh. Thus, one finger of the electrodes 9 is immersed in a space between two fingers 11 of an electrode 7.
  • a capacitor is formed between a finger of the electrode 9 and an adjacent finger of the electrode 7.
  • the capacitance of this capacitor depends on the one hand on the height of the structure and on the distance c between the two fingers and on the other hand on a finger length 1 which the finger 11 dips into the space.
  • the two electrodes 9 are coupled to a seismic mass 13 which has stiffening extensions 15 running at both ends parallel to the fingers 11, on the ends of which spring rods 17 are in turn attached.
  • Two spring bars 17.1, 17.2 and 17.3, 17.4 are attached to an anchor 19, which is provided in the center of the electrode 9 and the opposite extensions 15.1, 15.2.
  • the unit consisting of electrodes 9, seismic mass 13 and extensions 15 is thus resiliently mounted on the spring bars 17 and can be deflected in the x direction.
  • the electrodes 7 are fixed in their position by means of anchoring means 21 which are likewise arranged in the center. If an acceleration directed in the x direction now acts on the sensor 1, the seismic mass 13 together with the electrodes 9 is deflected in the x direction due to its inertia.
  • the immersion depth 1 decreases in the exemplary embodiment shown Condenser unit 3, while the immersion depth e 1 in the condenser unit 5 increases.
  • the distance d between the fingers remains constant. This results in an overall change in capacitance that is proportional to the acceleration, since there is only a linear dependence on the immersion depth 1.
  • the extensions 15 are dimensioned and designed such that they cause stiffening.
  • the sensitivity to "out of plane” accelerations can be set by a factor of 100 smaller than that of the acceleration to be evaluated by an aspect ratio of the spring rod height to the spring rod width of approximately 5: 1. Such "out of plane” accelerations therefore have no negative influence on the measurement result.
  • fixed stops can be provided which are electrically at the same potential with the seismic mass and the electrodes 9.
  • FIG. 1 also shows that the spring bars 17 and the electrodes 7 on the anchors 19 and 21 are not directly connected to one another, but rather via narrow connecting pieces 23. These connecting pieces 23 and 25 serve to decouple mechanical ones Tensions. In addition, the positioning of the anchors is optimized with regard to the stresses caused by different thermal expansion coefficients of the materials used.
  • FIG. 2 shows a second exemplary embodiment of an acceleration sensor 1, the mode of operation of which corresponds to that of the first sensor according to FIG. 1. A repeated description of the parts identified by the same reference numerals is therefore omitted.
  • the difference from the first embodiment is, among other things, that the unit consisting of seismic mass 13 and electrode 9 has been separated.
  • the two fixed electrodes 7 are now inside, while the displaceable electrodes 9 are arranged outside.
  • the two external electrodes 9 and the seismic masses 13 are coupled via corresponding connection extensions 15.
  • FIG. 3 A modification of the embodiment shown in FIG. 2 can be seen in FIG. 3.
  • the spring bars 17 are no longer attached to the two ends of the electrodes, but to a fastening part 27 provided in the center.
  • the other ends of the spring bars 17 are fastened to a fastening web 29 which is coupled to centrally located anchors 19.
  • FIG. 3 Another embodiment of the acceleration sensor 1 is shown in FIG.
  • the two seismic masses 13 with the electrodes 9 are arranged between the two fixed electrodes 7.
  • the four spring rods 17 run between the two seismic masses 13 and are attached at one end to a common anchor 21 and at the other ends to connecting webs 15 which connect the two seismic masses 13.

Abstract

A sensor for capacitively recording an acceleration has at least two interdigital capacitors (3, 5), each pair of capacitors having electrodes (7, 9) with a plurality of elongated fingers (11) which at least partially mesh with each other. One of the electrodes (9) can be shifted and is coupled to a deflectable seismic mass (13). The invention is characterised in that the electrodes (7, 9) are arranged in such a way that when one electrode (9) is deflected the fingers (11) move in parallel towards each other, their spacing (d) transversely to the direction of deflection remaining substantially constant while their overlapping (1) changes. The two interdigital capacitors are arranged relative to each other in such a way that during acceleration the capacity value of one capacitor increases and that of the other decreases.

Description

Sensor zur kapazitiven Aufnahme einer Beschleunigung Capacitive sensor for acceleration
Stand der TechnikState of the art
Die Erfindung betrifft einen Sensor zur kapazitiven Aufnahme einer Beschleunigung mit einem Interdigi- tal-Kondensator, der zwei eine Vielzahl von länglichen Fingern aufweisende Elektroden umfaßt, wobei die Finger der beiden Elektroden zumindest teilweise ineinandergreifen und eine der beiden Elektroden verlagerbar ist, die mit einer auslenkbaren seismischen Masse gekoppelt ist.The invention relates to a sensor for capacitively recording an acceleration with an interdigital capacitor which comprises two electrodes having a plurality of elongated fingers, the fingers of the two electrodes at least partially intermeshing and one of the two electrodes being displaceable with a deflectable one seismic mass is coupled.
Aus dem Stand der Technik sind Beschleunigungssen- soren bekannt, die mit Hilfe von Interdigital-Kondensatoren eine kapazitive Aufnahme einer Beschleunigung durchführen. Als Interdigital-Kondensator wird dabei ein Kondensator bezeichnet, der zwei Elektroden umfaßt, die jeweils eine Vielzahl von Fingern aufweisen. Die Finger greifen zumindest teilweise ineinander und bilden somit mit den jeweils benachbarten Fingern der Gegenelektrode Teilkapazitäten aus. Die Summe dieser Teilkapazitaten entspricht dann der Gesamtkapazitat des Interdigi- tal-Kondensatorε .Acceleration sensors are known from the prior art, which perform a capacitive recording of an acceleration with the aid of interdigital capacitors. An interdigital capacitor is a capacitor which comprises two electrodes, each of which has a large number of fingers. At least the fingers grip partially into one another and thus form partial capacitances with the adjacent fingers of the counter electrode. The sum of these partial capacities then corresponds to the total capacitance of the interdigital capacitor.
Die Teilkapazitat ist bei diesen Kondensatoren abhangig von dem Grad des Ineinandergrei ens der Finger und dem Abstand zu den benachbarten Fingern.The partial capacitance in these capacitors depends on the degree of interlocking of the fingers and the distance to the neighboring fingers.
Zur Messung der Beschleunigung wird bei den bekannter. Losungen eine Elektrode beweglich gelagert, derart, daß die Abstände zwischen den Fingern der einen Elektrode und den benachbarten Fingern sicn ver ndern. Die Längsrichtung der Finσer liegt somit senkrecht zu der zu detektierenden Beschleunigungs- richtung.To measure the acceleration is known in the. Solutions an electrode movably mounted, such that the distances between the fingers of one electrode and the adjacent fingers sicn change. The longitudinal direction of the fin is therefore perpendicular to the direction of acceleration to be detected.
Diese Anordnung der Elektroden hat den Nachteil, daß die Kapazitatsanderung nicht proportional zur Auslenkung und damit zur anliegenden Beschleunigung ist. Darüber hinaus tritt häufig das Problem auf, daß benachbarte Finger der beiden Elektroden eines Kondensators zusammenkleben, wenn beispielsweise eine Uberbelastung vorliegt.This arrangement of the electrodes has the disadvantage that the change in capacitance is not proportional to the deflection and thus to the acceleration present. In addition, there is often the problem that adjacent fingers of the two electrodes of a capacitor stick together if, for example, there is an overload.
Vorteile der ErfindungAdvantages of the invention
Der Sensor mit den Merkmalen des Anspruchs 1 hat den Vorteil, daß die Kapazitätsänderung der Kondensatoren direkt proportional zur Auslenkung und damit zur Beschleunigung ist. Darüber hinaus läßt sich das Auftreten von Verklebungen zweier Finger deutlich verringern. Dadurch, daß sich die Finger der verlagerbaren Elektrode parallel zu den Fingern der anderen Elektrode bewegen, wobei deren Abstand quer zur Auslenkrichtung im wesentlichen konstant bleibt und sich die Überlappung (1) verändert, läßt sich die verlagerbare Elektrode so verstarken, daß eine Bewegung senkrecht dazu nicht mehr möglich ist. Damit treten keine Verklebungen mehr auf, da die Finger immer einen definierten Abstand zu benachbarten Fingern besitzen.The sensor with the features of claim 1 has the advantage that the change in capacitance of the capacitors is directly proportional to the deflection and thus to the acceleration. In addition, the occurrence of sticking of two fingers decrease significantly. Characterized in that the fingers of the displaceable electrode move parallel to the fingers of the other electrode, their distance transverse to the deflection direction remains essentially constant and the overlap (1) changes, the displaceable electrode can be amplified so that a movement perpendicular to it is no longer possible. This means that no more sticking occurs because the fingers are always at a defined distance from neighboring fingers.
Vorzugsweise ist die mit der verlagerbaren Elektrode gekoppelte seismische Masse an vier Federsta- ben aufgehängt. Damit laßt sich eine hohe Steifiσ- keit gegenüber Bewegungen erreichen, die quer zur Detektionsrichtung liegen.The seismic mass coupled to the displaceable electrode is preferably suspended from four spring bars. This allows a high degree of stiffness to be achieved with respect to movements that are transverse to the direction of detection.
In einer bevorzugten Weiterbildung der Erfindung ist die seismische Masse zweigeteilt, wobei jeweils ein Teil einer Elektrode zugeordnet ist, die beiden Masseteile jedoch miteinander verbunden bleiben. Hiermit läßt sich eine Kompensation von auftretenden Materialspannungen durchführen.In a preferred development of the invention, the seismic mass is divided into two parts, one part being assigned to one electrode, but the two mass parts remaining connected to one another. This makes it possible to compensate for material stresses that occur.
Weitere vorteilhafte Ausgestaltungen der Erfindung ergeben sich aus den übrigen Unteransprüchen.Further advantageous embodiments of the invention result from the remaining subclaims.
Zeichnungendrawings
Die Erfindung wird nun anhand von Ausführungsbei- spielen mit Bezug auf die Zeichnungen näher erläutert. Dabei zeigen: Figur 1 ein erstes Aus hrungsbeispiel eines Besenleunigungssensors,The invention will now be explained in more detail on the basis of exemplary embodiments with reference to the drawings. Show: FIG. 1 shows a first exemplary embodiment of a broom acceleration sensor,
Figur 2 ein zweites Ausfuhrungsbeispiel eines Be- schleunigungssensors,FIG. 2 shows a second exemplary embodiment of an acceleration sensor,
Figur 3 ein drittes Ausfuhrungsbeispiel eines Be- schleunigungssensors, undFIG. 3 shows a third exemplary embodiment of an acceleration sensor, and
Figur 4 ein viertes Ausfuhrungsbeispiel eines Beschleunigungssensors.Figure 4 shows a fourth exemplary embodiment of an acceleration sensor.
AusfuhrungsbeispielePractical examples
In Figur 1 ist ein Beschleunigungssensor 1 dargestellt, der zur kapazitiven Aufnahme der Beschleunigung geeignet ist. Er ist in einer Oberflachenmi- kromechnik-Technik konzipiert und findet in zunehmendem Maße im Automobilbau in aktiven und passiven Ruckhaltesystemen und in der Fahrdynamikregelung Verwendung.In Figure 1, an acceleration sensor 1 is shown, which is suitable for capacitive recording of the acceleration. It is designed in a surface micromechanical technology and is increasingly used in automotive engineering in active and passive restraint systems and in vehicle dynamics control.
Der Beschleunigungssensor 1 umfaßt zwei Kondensator-Einheiten 3,5, die jeweils als Interdigital- Kondensator ausgebildet sind.The acceleration sensor 1 comprises two capacitor units 3, 5, each of which is designed as an interdigital capacitor.
Die beiden Interdigital-Kondensatoren 3,5 umfassen jeweils zwei Elektroden 7,9, an denen jeweils eine Vielzahl von länglichen Fingern 11 vorgesehen sind. Damit weisen die Elektroden 7,9 eine Kammstruktur auf.The two interdigital capacitors 3, 5 each comprise two electrodes 7, 9, on each of which a plurality of elongated fingers 11 are provided. The electrodes 7, 9 thus have a comb structure.
Figur 1 laßt deutlich erkennen, daß die einzelnen Finger 11 gegenüberliegender Elektroden 7,9 zumin- dest teilweise ineinandergreifen. So taucht jeweils ein Finger der Elektroden 9 in einen Raum zwischen zwei Fingern 11 einer Elektrode 7.FIG. 1 clearly shows that the individual fingers 11 of electrodes 7, 9 located opposite one another at least partially mesh. Thus, one finger of the electrodes 9 is immersed in a space between two fingers 11 of an electrode 7.
Bei dieser Kammstruktur wird jeweils ein Kondensator zwischen einem Finger der Elektrode 9 und einem benachbarten Finger der Elektrode 7 ausgebildet. Die Kapazität dieses Kondensators hängt dabei einerseits von der Hohe der Struktur und von dem Abstand c zwischen den beiden Fingern ab und andererseits einer Fingerlange 1, die der Finger 11 in den Zwischenraum eintaucht.In this comb structure, a capacitor is formed between a finger of the electrode 9 and an adjacent finger of the electrode 7. The capacitance of this capacitor depends on the one hand on the height of the structure and on the distance c between the two fingers and on the other hand on a finger length 1 which the finger 11 dips into the space.
Die beiden Elektroden 9 sind mit einer seismischen Masse 13 gekoppelt, die an ihren beiden Enden parallel zu den Fingern 11 verlaufende Verεteifungs- fortsatze 15 besitzt, an deren Enden wiederum Federstäbe 17 angebracht sind. Jeweils zwei Feder- εtabe 17.1, 17.2 beziehungsweise 17.3, 17.4 sind an einer Verankerung 19 angebracht, die mittig zu der Elektrode 9 und den sich gegenüberliegenden Fortsätzen 15.1,15.2 vorgesehen ist.The two electrodes 9 are coupled to a seismic mass 13 which has stiffening extensions 15 running at both ends parallel to the fingers 11, on the ends of which spring rods 17 are in turn attached. Two spring bars 17.1, 17.2 and 17.3, 17.4 are attached to an anchor 19, which is provided in the center of the electrode 9 and the opposite extensions 15.1, 15.2.
Somit ist die Einheit aus Elektroden 9, seismischer Masse 13 und Fortsätzen 15 an den Federstäben 17 federnd gelagert und in x-Richtung auslenkbar.The unit consisting of electrodes 9, seismic mass 13 and extensions 15 is thus resiliently mounted on the spring bars 17 and can be deflected in the x direction.
Im Gegensatz dazu sind die Elektroden 7 in ihrer Lage über ebenfalls mittig angeordnete Verankerungen 21 fixiert. Wirkt nun eine in x-Richtung gerichtete Beschleunigung auf den Sensor 1 ein, wird die seismische Masse 13 zusammen mit den Elektroden 9 aufgrund ihrer Trägheit in x-Richtung ausgelenkt. Dabei verringert sich beispielsweise in dem gezeigten Ausfuhrungsbeispiel die Eintauchtiefe 1 in der Kondensator-Einheit 3, wahrend die Eintauchtie e 1 in der Kondensator-Einheit 5 zunimmt. Der Abstand d zwischen den Fingern bleibt jedoch konstant. Damit ergibt sich insgesamt eine Kapazitatsanderung, die proportional zu der Beschleunigung ist, da lediglich eine lineare Abhängigkeit von der Eintauchtiefe 1 vorliegt.In contrast to this, the electrodes 7 are fixed in their position by means of anchoring means 21 which are likewise arranged in the center. If an acceleration directed in the x direction now acts on the sensor 1, the seismic mass 13 together with the electrodes 9 is deflected in the x direction due to its inertia. Here, for example, the immersion depth 1 decreases in the exemplary embodiment shown Condenser unit 3, while the immersion depth e 1 in the condenser unit 5 increases. However, the distance d between the fingers remains constant. This results in an overall change in capacitance that is proportional to the acceleration, since there is only a linear dependence on the immersion depth 1.
Um zu verhindern, daß eine Auslenkung der seismischen Masse mit den Elektroden 9 in y-Richtung auftritt, sind die Fortsätze 15 so dimensioniert und ausgelegt, daß sie eine Versteifung bewirken.In order to prevent deflection of the seismic mass with the electrodes 9 in the y direction, the extensions 15 are dimensioned and designed such that they cause stiffening.
Mit Kilfe einer entsprechenden Dimensionierung der Federεtabe 17, beispielsweise eine Verbreiterung eines Teils des Stabes, können bestimmte die Empfindlichkeit des Sensors beeinflussende Parameter eingestellt werden. Die Empfindlichkeit gegenüber "out of plane"-Beschleunigungen läßt sich durch ein Aspektverhaltnis der Federεtabhohe zur Federstabbreite von ca. 5:1 um etwa den Faktor 100 kleiner einstellen als gegenüber der auszuwertenden Beschleunigung. Damit haben solche "out of plane"-Be- εchleunigungen keinen negativen Einfluß auf das Meßergebnis. Zur Begrenzung der Auslenkung in x- Richtung können feststehende Anschläge vorgesehen sein, die elektrisch auf gleichem Potential mit der seismischen Masse und den Elektroden 9 liegen.With the help of a corresponding dimensioning of the spring rod 17, for example a widening of part of the rod, certain parameters influencing the sensitivity of the sensor can be set. The sensitivity to "out of plane" accelerations can be set by a factor of 100 smaller than that of the acceleration to be evaluated by an aspect ratio of the spring rod height to the spring rod width of approximately 5: 1. Such "out of plane" accelerations therefore have no negative influence on the measurement result. To limit the deflection in the x direction, fixed stops can be provided which are electrically at the same potential with the seismic mass and the electrodes 9.
Figur 1 läßt noch erkennen, daß die Federstäbe 17 beziehungsweise die Elektroden 7 an den Verankerungen 19 beziehungsweise 21 nicht direkt, sondern über schmale Verbindungsstücke 23 miteinander verbunden sind. Diese Verbindungstücke 23 beziehungsweise 25 dienen zur Entkopplung von mechanischen Spannungen. Darüber hinaus ist die Positionierung der Verankerungen im Hinblick auf die durch unterschiedliche thermische Ausdehnungskoeffizienten der verwendeten Materialien hervorgerufenen Verspannungen optimiert.FIG. 1 also shows that the spring bars 17 and the electrodes 7 on the anchors 19 and 21 are not directly connected to one another, but rather via narrow connecting pieces 23. These connecting pieces 23 and 25 serve to decouple mechanical ones Tensions. In addition, the positioning of the anchors is optimized with regard to the stresses caused by different thermal expansion coefficients of the materials used.
Figur 2 zeigt ein zweites Ausfuhrungsbeispiel eines Beschleunigungssensors 1, dessen Funktionsweise derjenigen des ersten Sensors gemäß Figur 1 entspricht. Auf eine nochmalige Beschreibung der mit gleichen Bezugszeichen gekennzeichneten Teile wird deshalb verzichtet.FIG. 2 shows a second exemplary embodiment of an acceleration sensor 1, the mode of operation of which corresponds to that of the first sensor according to FIG. 1. A repeated description of the parts identified by the same reference numerals is therefore omitted.
Der Unterschied zu der ersten Ausfuhrungsform besteht unter anderem darin, daß die Einheit aus seismischer Masse 13 und Elektrode 9 aufgetrennt wurde. Die beiden festen Elektroden 7 liegen nun in der gezeigten Anordnung innen, während die verlagerbaren Elektroden 9 außen angeordnet sind. Gekoppelt sind die beiden außenliegenden Elektroden 9 und die seismischen Massen 13 über entsprechende Verbindungsforts tze 15.The difference from the first embodiment is, among other things, that the unit consisting of seismic mass 13 and electrode 9 has been separated. In the arrangement shown, the two fixed electrodes 7 are now inside, while the displaceable electrodes 9 are arranged outside. The two external electrodes 9 and the seismic masses 13 are coupled via corresponding connection extensions 15.
Eine Abwandlung der in Figur 2 gezeigten Ausführungsform ist in Figur 3 zu sehen. Hierbei wurde lediglich die Aufhängung der beiden seismischen Massen 13 und den Elektroden 9 verändert. Die Fe- derεtäbe 17 sind nicht mehr an den beiden Enden der Elektroden angebracht, sondern an einem mittig vorgesehenen Befestigungsteil 27. Die anderen Enden der Federstäbe 17 sind an einem Befeεtigungεsteg 29 befestigt, der mit mittig angeordneten Verankerungen 19 gekoppelt ist. Eine weitere Ausfuhrungsform des Beschleunigungs- sensorε 1 ist in Figur 4 dargestellt. Hierbei sind wiederum die beiden seismischen Massen 13 mit den Elektroden 9 zwischen den beiden festen Elektroden 7 angeordnet. Die vier Federεtäbe 17 verlaufen zwischen den beiden seismischen Massen 13 und sind an einem Ende an einer gemeinsamen Verankerung 21 befestigt und an den anderen Enden an Verbi dungsste- gen 15, die die beiden seismischen Massen 13 verbinden .A modification of the embodiment shown in FIG. 2 can be seen in FIG. 3. Here, only the suspension of the two seismic masses 13 and the electrodes 9 was changed. The spring bars 17 are no longer attached to the two ends of the electrodes, but to a fastening part 27 provided in the center. The other ends of the spring bars 17 are fastened to a fastening web 29 which is coupled to centrally located anchors 19. Another embodiment of the acceleration sensor 1 is shown in FIG. Here again the two seismic masses 13 with the electrodes 9 are arranged between the two fixed electrodes 7. The four spring rods 17 run between the two seismic masses 13 and are attached at one end to a common anchor 21 and at the other ends to connecting webs 15 which connect the two seismic masses 13.
Diese Ausfuhrungsforπ bietet die beste Kcrcensation vor. Verspannungen durch thermiscne Auεder.nung, da die seismische Masse nur in einem Punkt Kontakt zum Untergrund hat.This embodiment offers the best compensation. Tension due to thermal change, since the seismic mass is only in contact with the subsurface at one point.
Selbstverständlich sind auch andere nicht dargestellte Ausfuhrungsformen der Erfindung denkbar. Of course, other embodiments of the invention, not shown, are also conceivable.

Claims

Ansprüche Expectations
1. Sensor zur kapazitiven Aufnahme einer Beschleunigung mit zumindest zwei Interdigital-Kondensatoren (3,5), deren jeder zwei eine Vielzahl von länglichen Fingern (11) aufweisende Elektroden (7,9) umfaßt, wobei die Finger (11) zumindest teilweise ineinandergreifen und eine der Elektroden (9) verlagerbar ist, und mit einer auslenkbaren seismischen Masse (13), die mit der verlagerbaren Elektrode (9) gekoppelt ist, dadurch gekennzeichnet, daß die Elektroden (7,9) so angeordnet sind, daß sich die Finger (11) bei einer Auslenkung einer Elektrode (9) parallel zueinander bewegen, wobei deren Abstand (d) quer zur Auslenkungsrichtung im wesentlichen konstant bleibt und sich die Überlappung (1) verändert, und daß die beiden Interdigital-Kondensatoren so zueinander angeordnet sind, daß sich bei einer Beschleunigung der Kapazitätswert des einen Kondensators erhöht und der des anderen verringert. 1. Sensor for capacitive recording of an acceleration with at least two interdigital capacitors (3, 5), each of which comprises two electrodes (7, 9) having a plurality of elongated fingers (11), the fingers (11) at least partially interlocking and one of the electrodes (9) is displaceable, and with a deflectable seismic mass (13) which is coupled to the displaceable electrode (9), characterized in that the electrodes (7, 9) are arranged such that the fingers ( 11) move parallel to each other when deflecting an electrode (9), the distance (d) of which remains essentially constant transversely to the deflection direction and the overlap (1) changes, and that the two interdigital capacitors are arranged in such a way that one another upon acceleration, the capacitance of one capacitor increases and that of the other decreases.
2. Sensor nach Anspruch 1, dadurch gekennzeichnet, daß die seismische Masse (13) an vier Federstaben (17) gelagert ist.2. Sensor according to claim 1, characterized in that the seismic mass (13) is mounted on four spring bars (17).
3. Sensor nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß jeder verlagerbaren Elektrode (9) eine seismische Masse (13) zugeordnet ist, wobei die beiden Massen miteinander gekoppelt sind.3. Sensor according to claim 1 or 2, characterized in that each movable electrode (9) is assigned a seismic mass (13), the two masses being coupled to one another.
4. Sensor nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die beiden verlagerba- rεn Elektroden (9) zusammen mit der seismischen Masse (13) zwischen den festen Elektroden (7) angeordnet sind.4. Sensor according to one of the preceding claims, characterized in that the two relocatable electrodes (9) are arranged together with the seismic mass (13) between the fixed electrodes (7).
5. Sensor nach Anspruch 3, dadurch gekennzeichnet, daß die festen Elektroden (7) zwischen den verlagerbaren Elektroden (9) und den εeiεmiεchen Maεsen (13) angeordnet sind.5. Sensor according to claim 3, characterized in that the fixed electrodes (7) between the displaceable electrodes (9) and the εeiεmiεchen Maεsen (13) are arranged.
6. Sensor nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Federstabe (17) an den Enden der seismischen Massen (13) angebracht sind.6. Sensor according to one of the preceding claims, characterized in that the spring bar (17) are attached to the ends of the seismic masses (13).
7. Sensor nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß die Federstäbe (17) an den seismischen Massen (13) mittig angebracht sind.7. Sensor according to one of claims 1 to 5, characterized in that the spring bars (17) on the seismic masses (13) are attached centrally.
8. Sensor nach Anspruch 4, dadurch gekennzeichnet, daß die beiden verlagerbaren Elektroden (9) mit den seismischen Massen (13) parallel und beabstandet zueinander angeordnet sind und daß die Federstäbe (17) zwischen den beiden Elektroden (9) verlaufen und an einem gemeinsamen Verankerungspunkt (21) angebracht sind.8. Sensor according to claim 4, characterized in that the two displaceable electrodes (9) with the seismic masses (13) are arranged parallel and spaced apart and that the spring bars (17) run between the two electrodes (9) and are attached to a common anchoring point (21).
9. Sensor nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die festen Elektroden (7) mittig an einer Verankerung (19) angebracht sind.9. Sensor according to one of the preceding claims, characterized in that the fixed electrodes (7) are attached centrally to an anchor (19).
10. Sensor nach Anspruch 9, dadurch gekennzeichnet, daß die Verbindung zwischen Elektrode und Verankerung (19) über Verbindungsstege erfolgt, die der Entkopplung dienen.10. Sensor according to claim 9, characterized in that the connection between the electrode and anchoring (19) takes place via connecting webs which serve the decoupling.
11. Sensor nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß Anschläge vorgesehen sind, die den Auslenkungsbereich der seismischen Masse (13) begrenzen und auf dem gleichen Potential wie die Elektroden (9) liegen. 11. Sensor according to one of the preceding claims, characterized in that stops are provided which limit the deflection range of the seismic mass (13) and are at the same potential as the electrodes (9).
PCT/DE1997/001898 1996-09-13 1997-08-30 Sensor for capacitively recording an acceleration WO1998011443A1 (en)

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DE19637265.8 1996-09-13
DE1996137265 DE19637265A1 (en) 1996-09-13 1996-09-13 Capacitive sensor for acceleration

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