WO1993020417A1 - Temperature compensation for a force or pressure sensor - Google Patents

Temperature compensation for a force or pressure sensor Download PDF

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Publication number
WO1993020417A1
WO1993020417A1 PCT/DE1992/000277 DE9200277W WO9320417A1 WO 1993020417 A1 WO1993020417 A1 WO 1993020417A1 DE 9200277 W DE9200277 W DE 9200277W WO 9320417 A1 WO9320417 A1 WO 9320417A1
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WO
WIPO (PCT)
Prior art keywords
conductor tracks
force
resistor
carrier
resistors
Prior art date
Application number
PCT/DE1992/000277
Other languages
German (de)
French (fr)
Inventor
Kurt Schmid
Rudolf Heinz
Jürgen Wendel
Ralf Haug
Original Assignee
Robert Bosch Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch Gmbh filed Critical Robert Bosch Gmbh
Publication of WO1993020417A1 publication Critical patent/WO1993020417A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
    • G01L9/0001—Transmitting or indicating the displacement of elastically deformable gauges by electric, electro-mechanical, magnetic or electro-magnetic means
    • G01L9/0002—Transmitting or indicating the displacement of elastically deformable gauges by electric, electro-mechanical, magnetic or electro-magnetic means using variations in ohmic resistance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/18—Measuring force or stress, in general using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
    • G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
    • G01L1/2268—Arrangements for correcting or for compensating unwanted effects
    • G01L1/2281—Arrangements for correcting or for compensating unwanted effects for temperature variations
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
    • G01L9/0041—Transmitting or indicating the displacement of flexible diaphragms
    • G01L9/0051—Transmitting or indicating the displacement of flexible diaphragms using variations in ohmic resistance
    • G01L9/0052—Transmitting or indicating the displacement of flexible diaphragms using variations in ohmic resistance of piezoresistive elements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
    • G01L9/0041—Transmitting or indicating the displacement of flexible diaphragms
    • G01L9/0051—Transmitting or indicating the displacement of flexible diaphragms using variations in ohmic resistance
    • G01L9/0058—Transmitting or indicating the displacement of flexible diaphragms using variations in ohmic resistance of pressure sensitive conductive solid or liquid material, e.g. carbon granules

Definitions

  • the invention is based on a sensor for determining a pressure or a force according to the preamble of the main claim.
  • a sensor is known in which a thick-film resistor is applied to a carrier and which is in operative connection with a force introduction part.
  • the temperature dependence of the oh's resistance of this thick-film resistor limits the areas of use of such a sensor. It can either be used only for dynamic measurements, that is to say the absolute pressure or the absolute force cannot be determined, or their determination requires a zero adjustment before each measurement process.
  • Piezoresistive pressure sensors are also known, in which an elastically deformable membrane interacts with piezoresistive resistors according to the principle of the strain gauges. Such membranes are expensive to manufacture and often have only a very short life (DE-OS 39 19 059, DE-OS 39 28 542).
  • a sensor is known from DE-OS 31 25 640, in which piezoresistive measuring elements are mounted on a carrier and are arranged as close as possible to the pressure chamber. Should by a bridge circuit of suitable resistors "a • Temperature compensation achieved become. For this purpose, only part of the elements of the bridge are exposed to pressure and the other part is pressure-shielded. This should be done by means of a ring or a cover plate with which the part of the bridge to be shielded in a pressure-tight manner is provided. Such an arrangement is very complex.
  • the measuring elements that is to say the resistors, since they are almost directly exposed to the pressure, are also the temperatures of approximately 2000 ° prevailing there C exposed. This can result in tension in the sensor housing, which can lead to a falsification of the pressure signal. In addition, the service life is very short at these high temperatures.
  • a pressure sensor is described in US Pat. No. 4,645,965, the measuring element of which consists of piezoelectric material.
  • Piezo-ceramic components for example, can be used as the piezoelectric elements, which are contacted with contact disks by complex welding of wires.
  • a charge and thus a voltage is generated in piezoelectric elements when pressure is applied to generate the measurement signal. This voltage is tapped and evaluated.
  • a voltage is applied to piezoresistive elements, and the electrical resistance in the piezoresistive element is changed by the pressure acting on it.
  • the electronic processing of the measurement signal is simpler in the case of purely ohmic sensors.
  • the sensor according to the invention with the characterizing features of the main claim has the advantage that a uniform, homogeneous and orthogonal load over the measuring resistor is possible during the measurement. This leads to a low hysteresis and linear characteristic curve in the beginning.
  • the sensor is small and compact and is characterized in particular by a very low thermal drift, that is to say the ambient temperature and in particular temperature fluctuations have little or no influence on the measurement signal.
  • this sensor can be produced simply and inexpensively, since resistors in layer technology, ie thin-film or thick-film technology, are used for the measuring elements.
  • FIG. 1 shows a side view of a first embodiment of a pressure sensor
  • FIG. 2 a top view of this pressure sensor
  • FIG. 3 shows a top view of a second embodiment of the pressure sensor
  • FIG. 4 shows a side view of a third embodiment
  • FIG. 5 shows a top view of this embodiment.
  • 10 denotes a sensor in which two resistors 11, 12 using thin or thick-film technology and corresponding conductor tracks 13 are attached to one end face of a cylindrical substrate serving as a carrier 14.
  • the carrier 14 can consist, for example, of ceramic, polymer material or steel.
  • an insulation layer (not shown here), which consists, for example, of thick-layer glass, thin-layer or polymer layer material, polymer film or adhesive.
  • the outer surface of the carrier 14 is flattened at two opposite sections 15, 16.
  • a metallic zone 17 is attached to section 15 and overlaps with a section of conductor tracks 13.
  • two further metallic zones 18, 19 are arranged, which are also connected to the conductor tracks 13.
  • Electrical connecting wires 20 are connected to these zones 17 to 19.
  • the conductor tracks 13 are designed such that the resistors 11, 12 and the connecting wires 20 are connected to one another in the form of a half bridge, the resistor 11 serving as a variable resistor (piezoresistive measuring element).
  • the two resistors 11, 12 are arranged so that they are close to each other and the resistor 11 is arranged approximately in the center on the end face of the carrier 14 and interacts there with a cylindrical force introduction part 21.
  • a force is introduced orthogonally into the resistor 11 or the carrier 14 by this force introduction part 21.
  • the diameter of the force introduction part 21 is selected such that almost the entire area 22 of the resistor 11 which is not covered by conductor tracks 13 is covered, but the resistor 12 is not covered.
  • the force introduction part 21 can be made of the same materials as the carrier 14, a corresponding insulation layer also being applied when using conductive materials. If the resistors 11 and 12 are provided with a glass cover, the insulation layer on the force introduction part 21 can be dispensed with.
  • Force application part 21, resistor 11 and the carrier 14 are firmly connected to one another, for example by gluing with glass or polymer material or when using thick film resistors themselves.
  • the force application part 21 is placed on the still soft paste of the resistor 11 during manufacture of the sensor and lightly pressed.
  • the insulation layer described above can also be used to firmly connect the force introduction part 21 to the resistor 11 or the carrier.
  • the previously described resistor arrangement in the form of a half-bridge and orthogonally loaded resistor (measuring element) achieves both a uniform force distribution and temperature compensation by arranging the second, unloaded resistor in the immediate vicinity of the measuring element. Due to the orthogonal loading of the measuring element, the specific resistance of the piezoresistive resistance is changed when force is applied, and a measuring signal is thus generated.
  • the exemplary embodiment shown in FIG. 3 differs from the one described above by the connection of the lead wires.
  • the sensor 10A has a carrier 14A which likewise consists of a cylindrical substrate and which has three incisions 23 on the outer circumference instead of the flat sections. These incisions 23 extend into the area of the conductor tracks 13A and are cut, for example, by means of a laser from the substrate of the carrier 14A " .
  • the lead wires 20A are guided, which protrude from below through the conductor tracks 13A and on the upper sides thereof This simplifies both the manufacture of the carrier 14A and the conductor tracks 13A and the connection of the lead wires 20 A.
  • the contact point or the connection of the lead wires 20A to the conductor tracks 13A when the Protect the sensor from damage, for example, in a housing, which also simplifies the shape of such a housing.
  • they can also run in bores on the edge of the carrier.
  • the sensor 10B shown in FIGS. 4 and 5 differs from that described above in the shape of the carrier, the switching of the resistors and the connection of the lead wires.
  • the carrier 14B is formed like a gaiter; on an approximately square end face it carries a thick or thin layer circuit in which four resistors 25 to 28 and corresponding conductor tracks 13B are arranged in the form of a full bridge.
  • the two variable resistors 25, 26, (piezoresistive measuring elements) have an approximately rectangular shape and are arranged relatively close to one another approximately in the middle of the end face of the carrier 14B.
  • Four electrical connecting wires 20B are connected to the conductor tracks 13B, so that - in a manner known per se - a bridge voltage is applied to a bridge diagonal and the measuring voltage is removed from the other bridge diagonal.
  • the conductor tracks 13B are designed such that the contacting parts with the lead wires 20B are each located approximately in the region of a corner of the end face.
  • the force introduction part 21B is approximately cylindrical and interacts with the two resistors 25, 26, that is to say they are almost completely covered by the force introduction part 21B. For this purpose, this can also have an approximately rectangular end face. Analogous to the previous embodiment, the two resistors 27, 28 are also unloaded and are used for temperature compensation.
  • the direct, orthogonal loading of the measuring elements enables a very small, compact sensor.
  • a membrane for introducing an expansion into the resistors is not necessary, since the measurement signal is generated by the piezoresistive resistors (measuring elements) being loaded orthogonally and changing their specific resistance under the influence of force.
  • an axially very rigid sensor is formed, which is due to the temperature compensation has only a small thermal drift due to the switching of the resistors in half or full bridge, and is therefore also suitable for static measurements.
  • the full bridge circuit can be applied to square or rectangular end faces of a support and can thus be printed and equipped in multiple uses. If the dimensions are sufficiently large, contacting of the connecting wires by bonding or soldering on the end face can also take place.
  • the contacting of the connecting wires can also be carried out on the flattened areas of a cylindrical carrier.
  • the contacting can also be carried out analogously to the exemplary embodiment according to FIG. 3.
  • the sensor or the carrier can then be printed and equipped in large-area multiple uses. For this purpose, it is advantageous to drill holes for the lead wires so that they lie on the separating step of the individual substrates, so that each substrate or carrier is assigned, after separation, borehole sections with an approximately semicircular cross section.

Abstract

The sensor proposed has film resistors (11, 12) on a substrate (14), at least one of the film resistors (11, 12) being directly and orthogonally acted on by a force-transfer element (21). A second resistor (12) not subjected to load is connected to the force-transfer element (21) to form a resistance bridge and provides temperature compensation.

Description

Temperaturkompensation eines Kraft- oder Drucksensors. Temperature compensation of a force or pressure sensor.
Stand der TechnikState of the art
Die Erfindung geht aus von einem Sensor zur Bestimmung eines Drucks oder einer Kraft nach der Gattung des Hauptanspruchs. Aus der DE-OS 38 18 191 ist ein Sensor bekannt, bei dem ein Dickschichtwi¬ derstand auf einen Träger aufgebracht ist und der mit einem Kraft¬ einleitungsteil in Wirkverbindung steht. Die Temperaturabhängigkeit des oh schen Widerstandes dieses Dickschichtwiderstandes begrenzt die Einsatzgebiete eines derartigen Sensors. Er kann entweder nur für dynamische Messungen eingesetzt werden, das heißt der absolute Druck oder die absolute Kraft sind nicht zu bestimmen oder deren Be¬ stimmung erfodert einen Nullabgleich vor jedem Meßvorgang.The invention is based on a sensor for determining a pressure or a force according to the preamble of the main claim. From DE-OS 38 18 191 a sensor is known in which a thick-film resistor is applied to a carrier and which is in operative connection with a force introduction part. The temperature dependence of the oh's resistance of this thick-film resistor limits the areas of use of such a sensor. It can either be used only for dynamic measurements, that is to say the absolute pressure or the absolute force cannot be determined, or their determination requires a zero adjustment before each measurement process.
Weiterhin sind piezoresistive Drucksensoren bekannt, bei denen eine elastisch verformbare Membran mit piezoresistiven Widerständen nach dem Prinzip der Dehnmeßstreifen zusammenwirkt. Derartige Membranen sind aufwendig herzustellen und haben oftmals nur eine sehr geringe Lebensdauer (DE-OS 39 19 059, DE-OS 39 28 542).Piezoresistive pressure sensors are also known, in which an elastically deformable membrane interacts with piezoresistive resistors according to the principle of the strain gauges. Such membranes are expensive to manufacture and often have only a very short life (DE-OS 39 19 059, DE-OS 39 28 542).
Aus der DE-OS 31 25 640 ist ein Sensor bekannt, bei dem piezoresi¬ stive Meßelemente auf einem Träger angebracht sind und möglichst na¬ he am Druckraum angeordnet werden. Durch eine Brückenschaltung von geeigneten Widerständen"soll eine •Temperaturkompensation erreicht werden. Dazu wird nur ein Teil der Elemente der Brücke dem Druck ausgesetzt und der andere Teil druckabgeschirmt. Das soll durch ei¬ nen Ring oder eine Abdeckplatte geschehen, mit denen der druckdicht abzuschirmende Teil der Brücke versehen ist. Eine derartige Anord¬ nung ist sehr aufwendig. Wird darüber hinaus ein derartiger Sensor zum Beispiel als Brennrau drucksensor in einem Kraftfahrzeug einge¬ setzt, sind die Meßelemente, das heißt die Widerstände, da sie nahe¬ zu direkt dem Druck ausgesetzt sind, auch den dort herrschenden Tem¬ peraturen von ca. 2000 °C ausgesetzt. Dadurch können sich Verspan- nungen im Gehäuse des Sensors ergeben, die zu einer Verfälschung des Drucksignals führen können. Darüber hinaus ist die Lebensdauer bei diesen hohen Temperaturen sehr kurz.A sensor is known from DE-OS 31 25 640, in which piezoresistive measuring elements are mounted on a carrier and are arranged as close as possible to the pressure chamber. Should by a bridge circuit of suitable resistors "a • Temperature compensation achieved become. For this purpose, only part of the elements of the bridge are exposed to pressure and the other part is pressure-shielded. This should be done by means of a ring or a cover plate with which the part of the bridge to be shielded in a pressure-tight manner is provided. Such an arrangement is very complex. If, in addition, such a sensor is used, for example, as a combustion pressure sensor in a motor vehicle, the measuring elements, that is to say the resistors, since they are almost directly exposed to the pressure, are also the temperatures of approximately 2000 ° prevailing there C exposed. This can result in tension in the sensor housing, which can lead to a falsification of the pressure signal. In addition, the service life is very short at these high temperatures.
Ferner wird in der US-PS 4645 965 ein Drucksensor beschrieben, des¬ sen Meßelement aus piezoelektrischem Material besteht. Als piezo¬ elektrische Elemente können zum Beispiel piezokeramische Bauteile verwendet werden, die durch eine aufwendige Verεchweißung von Dräh¬ ten mit Kontaktscheiben kontaktiert werden. Bei piezoelektrischen Elementen wird im Unterschied zu piezoresistiven Elementen bei Druckeinwirkung zur Meßsignalerzeugung eine Ladung und somit eine Spannung erzeugt. Diese Spannung wird abgegriffen und ausgewertet. Im Unterschied hierzu wird bei piezoresistiven Elementen eine Span¬ nung angelegt, und der elektrische Widerstand im piezoresistiven Element wird durch den einwirkenden Druck verändert. Die elektroni¬ sche Aufbereitung des Meßsignales ist bei rein ohmschen Sensoren einf cher.Furthermore, a pressure sensor is described in US Pat. No. 4,645,965, the measuring element of which consists of piezoelectric material. Piezo-ceramic components, for example, can be used as the piezoelectric elements, which are contacted with contact disks by complex welding of wires. In contrast to piezoresistive elements, a charge and thus a voltage is generated in piezoelectric elements when pressure is applied to generate the measurement signal. This voltage is tapped and evaluated. In contrast to this, a voltage is applied to piezoresistive elements, and the electrical resistance in the piezoresistive element is changed by the pressure acting on it. The electronic processing of the measurement signal is simpler in the case of purely ohmic sensors.
Vorteile der ErfindungAdvantages of the invention
Der erfindungsgemäße Sensor mit den kennzeichnenden Merkmalen des Hauptanspruchs hat demgegenüber den Vorteil, daß .eine gleichmäßige, homogene und orthogonale Belastung über dem Meßwiderstand während der Messung möglich ist. Das führt zu einer hysteresearmen und be- reits im Anf ngsbereich linearen Kennlinie. Die Kontaktierungsstel-The sensor according to the invention with the characterizing features of the main claim has the advantage that a uniform, homogeneous and orthogonal load over the measuring resistor is possible during the measurement. This leads to a low hysteresis and linear characteristic curve in the beginning. The contact points
__, _t __ len der Ableitdrahte und die Erganzungswiderstande liegen außerhalb des eigentlichen Meßbereichs und können somit die Wirkung des Meßwi- derstandes nicht störend beeinflussen.__, _ t __ len of the lead wires and the supplementary resistances lie outside the actual measuring range and can therefore not interfere with the effect of the measuring resistance.
Der Sensor baut klein und kompakt und zeichnet sich insbesondere durch eine sehr geringe thermische Drift aus, das heißt die Umge¬ bungstemperatur und insbesondere Temperaturschwankungen beeinflussen das Meßsignal nicht oder nur unerheblich. Darüber hinaus kann dieser Sensor einfach und kostengünstig erstellt werden, da für die Meßele¬ mente Widerstände in Schichttechnik, das heißt Dünnschicht- oder Dickschichttechnik, genutzt werden.The sensor is small and compact and is characterized in particular by a very low thermal drift, that is to say the ambient temperature and in particular temperature fluctuations have little or no influence on the measurement signal. In addition, this sensor can be produced simply and inexpensively, since resistors in layer technology, ie thin-film or thick-film technology, are used for the measuring elements.
Zeichnungdrawing
Drei Ausführungsbeispiele der Erfindung werden in der nachfolgenden Beschreibung und Zeichnung näher erläutert. Letztere zeigt in ver¬ einfachter Darstellung in Figur 1 eine Seitenansicht eines ersten Ausführungsbeispiels eines Drucksensors, in Figur 2 eine Draufsicht auf diesen Drucksensor. Figur 3 zeigt eine Draufsicht auf ein zwei¬ tes Ausführungsbeispiels des Drucksensors, Figur 4 eine Seitenan¬ sicht eines dritten Ausführungsbeispiels und Figur 5 eine Draufsicht auf dieses Ausführungsbeispiel.Three embodiments of the invention are explained in more detail in the following description and drawing. The latter shows a simplified representation in FIG. 1 a side view of a first embodiment of a pressure sensor, in FIG. 2 a top view of this pressure sensor. FIG. 3 shows a top view of a second embodiment of the pressure sensor, FIG. 4 shows a side view of a third embodiment and FIG. 5 shows a top view of this embodiment.
Beschreibung der AusführungsbeispieleDescription of the embodiments
In den Figuren 1 und 2 ist mit 10 ein Sensor bezeichnet, bei dem zwei Widerstände 11, 12 in Dünn- oder Dickschichttechnik und ent¬ sprechende Leiterbahnen 13 auf einer Stirnseite eines als Träger 14 dienenden, zylinderförmigen Substrats angebracht sind. Der Träger 14 kann zum Beispiel aus Keramik, Polymerwerkstoff oder Stahl bestehen. Bei der Verwendung von Stahl oder anderen elektrisch leitenden Ma¬ terialien ist zwischen den Widerständen 11, 12 und den Leiterbah- nen 13 einerseits und dem Träger 14 andererseits eine - hier nicht dargestellte - Isolationsschicht angeordnet, die beispielsweise aus Dickschichtglas, Dünnschicht- oder Polymerschichtwerkstoff, Polymerfolie oder Klebstoff besteht.In FIGS. 1 and 2, 10 denotes a sensor in which two resistors 11, 12 using thin or thick-film technology and corresponding conductor tracks 13 are attached to one end face of a cylindrical substrate serving as a carrier 14. The carrier 14 can consist, for example, of ceramic, polymer material or steel. When using steel or other electrically conductive materials, between the resistors 11, 12 and the conductor tracks NEN 13 on the one hand and the carrier 14 on the other hand arranged an insulation layer (not shown here), which consists, for example, of thick-layer glass, thin-layer or polymer layer material, polymer film or adhesive.
Die Mantelfläche des Trägers 14 ist an zwei sich gegenüberliegen¬ den Abschnitten 15, 16 abgeflacht. Am Abschnitt 15 ist eine metalli¬ sche Zone 17 angebracht, die mit einem Abschnitt der Leiterbahnen 13 überlappt. Am Abschnitt 16 sind zwei weitere metallische Zonen 18, 19 angeordnet, die ebenfalls mit den Leiterbahnen 13 verbunden sind. An diese Zonen 17 bis 19 sind elektrische Anschlußdrähte 20 ange¬ schlossen. Die Leiterbahnen 13 sind so ausgebildet, daß die Wider¬ stände 11, 12 und die Anschlußdrähte 20 in Form einer Halbbrücke miteinander verschaltet sind, wobei der Widerstand 11 als veränder¬ barer Widerstand (piezoresistives Meßelement) dient.The outer surface of the carrier 14 is flattened at two opposite sections 15, 16. A metallic zone 17 is attached to section 15 and overlaps with a section of conductor tracks 13. At section 16, two further metallic zones 18, 19 are arranged, which are also connected to the conductor tracks 13. Electrical connecting wires 20 are connected to these zones 17 to 19. The conductor tracks 13 are designed such that the resistors 11, 12 and the connecting wires 20 are connected to one another in the form of a half bridge, the resistor 11 serving as a variable resistor (piezoresistive measuring element).
Die beiden Widerstände 11, 12 sind so angeordnet, daß sie sich nah beieinander befinden und der Widerstand 11 etwa mittig auf der Stirnfläche des Trägers 14 angeordnet ist und dort mit einem zylindrischen Krafteinleitungsteil 21 zusammenwirkt. Durch dieses Krafteinleitungsteil 21 wird eine Kraft orthogonal in den Widerstand 11 bzw. den Träger 14 eingeleitet. Der Durchmesser des Kraftein¬ leitungsteils 21 ist so gewählt, daß nahezu der gesamte nicht von Leiterbahnen 13 abgedeckte Bereich 22 des Widerstandes 11 überdeckt ist, der Widerstand 12 jedoch nicht überdeckt wird. Das Krafteinlei¬ tungsteil 21 kann aus den gleichen Werkstoffen hergestellt sein wie der Träger 14, wobei bei der Verwendung von leitenden Materialien ebenfalls eine entsprechende Isolationsschicht aufgebracht ist. Sind die Widerstände 11 und 12 mit einer Glasabdeckung versehen, kann auf die Isolationsschicht am Krafteinleitungsteil 21 verzichtet werden. Krafteinleitungsteil 21, Widerstand 11 und der Träger 14 sind fest miteinander verbunden, zum Beispiel durch Klebung mit Glas oder Polymerwerkstoff oder bei Verwendung von Dickschichtwiderständen durch diesen selbst. Dazu wird das Krafteinleitungsteil 21 beim Herstellen des Sensors auf die noch weiche Paste des Widerstands 11 aufgesetzt und leicht angedrückt. Bei elektrisch leitendem Kraftein¬ leitungsteil 21 und/oder Träger 14 kann auch die zuvor beschriebene IsolationsSchicht zur festen Verbindung des Krafteinleitungsteils 21 mit dem Widerstand 11 bzw. dem Träger genutzt werden.The two resistors 11, 12 are arranged so that they are close to each other and the resistor 11 is arranged approximately in the center on the end face of the carrier 14 and interacts there with a cylindrical force introduction part 21. A force is introduced orthogonally into the resistor 11 or the carrier 14 by this force introduction part 21. The diameter of the force introduction part 21 is selected such that almost the entire area 22 of the resistor 11 which is not covered by conductor tracks 13 is covered, but the resistor 12 is not covered. The force introduction part 21 can be made of the same materials as the carrier 14, a corresponding insulation layer also being applied when using conductive materials. If the resistors 11 and 12 are provided with a glass cover, the insulation layer on the force introduction part 21 can be dispensed with. Force application part 21, resistor 11 and the carrier 14 are firmly connected to one another, for example by gluing with glass or polymer material or when using thick film resistors themselves. For this purpose, the force application part 21 is placed on the still soft paste of the resistor 11 during manufacture of the sensor and lightly pressed. In the case of an electrically conductive force introduction part 21 and / or carrier 14, the insulation layer described above can also be used to firmly connect the force introduction part 21 to the resistor 11 or the carrier.
Durch die zuvor beschriebene Widerstandsanordnung in Form einer Halbbrücke und orthogonal belastetem Widerstand (Meßelement) wird sowohl eine gleichmäßige Kraftverteilung erreicht als auch durch die Anordnung des zweiten, unbelasteten Widerstandes in unmittelbarer Nähe des Meßelementes eine Temperaturkompensation erreicht. Durch die orthogonale Belastung des Meßelementes wird bei Krafteinwirkung der spezifische Widerstand des piezoresistiven Widerstands verändert und somit ein Meßsignal erzeugt.The previously described resistor arrangement in the form of a half-bridge and orthogonally loaded resistor (measuring element) achieves both a uniform force distribution and temperature compensation by arranging the second, unloaded resistor in the immediate vicinity of the measuring element. Due to the orthogonal loading of the measuring element, the specific resistance of the piezoresistive resistance is changed when force is applied, and a measuring signal is thus generated.
Das in Figur 3 dargestellte Ausführungsbeispiel unterscheidet sich von dem zuvor beschriebenen durch die Anbindung der Ableitdrähte. Der Sensor 10A hat einen ebenfalls aus einem zylindrischen Substrat bestehenden Träger 14A, der statt der flachen Abschnitte drei Ein¬ schnitte 23 am Außenumfang aufweist. Diese Einschnitte 23 reichen bis in den Bereich der Leiterbahnen 13A und sind beispielsweise mittels eines Lasers aus dem Substrat des Trägers 14A "geschnitten. In den Einschnitten 23 sind die Ableitdrähte 20A geführt, die von unten durch die Leiterbahnen 13A ragen und auf deren Oberseiten mit diesen verlötet sind. Dadurch wird sowohl die Fertigung des Trä¬ gers 14A und der Leiterbahnen 13A als auch die Anbindung der Ableit¬ drähte 20A vereinfacht. Weiterhin wird dadurch auch die Kontakt¬ stelle bzw. die Anbindung der Ableitdrähte 20A an die Leiterbahnen 13A beim Einbau des Sensors beispielsweise in ein Gehäuse vor Beschädigung geschützt. Damit wird auch die Formgebung eines solchen Gehäuses vereinfacht. Alternativ zu der Führung der Anschlußdrähte in den Einschnitten können diese auch in Bohrungen am Rand des Trägers verlaufen.The exemplary embodiment shown in FIG. 3 differs from the one described above by the connection of the lead wires. The sensor 10A has a carrier 14A which likewise consists of a cylindrical substrate and which has three incisions 23 on the outer circumference instead of the flat sections. These incisions 23 extend into the area of the conductor tracks 13A and are cut, for example, by means of a laser from the substrate of the carrier 14A " . In the incisions 23, the lead wires 20A are guided, which protrude from below through the conductor tracks 13A and on the upper sides thereof This simplifies both the manufacture of the carrier 14A and the conductor tracks 13A and the connection of the lead wires 20 A. Furthermore, the contact point or the connection of the lead wires 20A to the conductor tracks 13A when the Protect the sensor from damage, for example, in a housing, which also simplifies the shape of such a housing. As an alternative to guiding the connecting wires in the incisions, they can also run in bores on the edge of the carrier.
Der in den Figuren 4 und 5 dargestellte Sensor 10B unterscheidet sich von dem zuvor beschriebenen durch die Form des Trägers, die Schaltung der Widerstände und die Anbindung der Ableitdrähte.The sensor 10B shown in FIGS. 4 and 5 differs from that described above in the shape of the carrier, the switching of the resistors and the connection of the lead wires.
Der Träger 14B ist guaderförmig ausgebildet; auf einer etwa quadra¬ tischen Stirnseite trägt er eine Dick- oder Dünnschichtschaltung, bei der vier Widerstände 25 bis 28 und entsprechende Leiterbahnen 13B in Form einer Vollbrücke angeordnet sind. Die beiden variablen Widerstände 25, 26, (piezoresistive Meßelemente) haben eine etwa rechtwinklige Form und sind relativ nah zueinander etwa in der Mitte der Stirnfläche des Trägers 14B angeordnet. Mit den Leiterbahnen 13B sind vier elektrische Anschlußdrähte 20B verbunden, so daß - in an sich bekannter Weise - an eine Brückendiagonale eine Brückenspan¬ nung angelegt wird und an der anderen Brückendiagonalen die Meßspan¬ nung abgenommen wird. Die Leiterbahnen 13B sind so ausgebildet, daß sich die Kontaktierungssteilen mit den Ableitdrähten 20B jeweils etwa im Bereich einer Ecke der Stirnfläche befinden.The carrier 14B is formed like a gaiter; on an approximately square end face it carries a thick or thin layer circuit in which four resistors 25 to 28 and corresponding conductor tracks 13B are arranged in the form of a full bridge. The two variable resistors 25, 26, (piezoresistive measuring elements) have an approximately rectangular shape and are arranged relatively close to one another approximately in the middle of the end face of the carrier 14B. Four electrical connecting wires 20B are connected to the conductor tracks 13B, so that - in a manner known per se - a bridge voltage is applied to a bridge diagonal and the measuring voltage is removed from the other bridge diagonal. The conductor tracks 13B are designed such that the contacting parts with the lead wires 20B are each located approximately in the region of a corner of the end face.
Das Krafteinleitungsteil 21B ist etwa zylinderförmig ausgebildet und wirkt mit den beiden Widerständen 25, 26 zusammen, das heißt diese werden nahezu vollständig vom Krafteinleitungsteil 21B überdeckt. Dieses kann dazu auch eine etwa rechteckige Stirnfläche aufweisen. Analog zum Ausführungsbeispiel zuvor sind auch hier die beiden Widerstände 27, 28 unbelastet und dienen zur Temperaturkompensation.The force introduction part 21B is approximately cylindrical and interacts with the two resistors 25, 26, that is to say they are almost completely covered by the force introduction part 21B. For this purpose, this can also have an approximately rectangular end face. Analogous to the previous embodiment, the two resistors 27, 28 are also unloaded and are used for temperature compensation.
Durch die direkte, orthogonale Belastung der Meßelemente wird ein sehr kleinbauender, kompakter Sensor ermöglicht. Eine Membran zur Einleitung einer Dehnung in die Widerstände ist nicht notwendig, da das Meßsignal erzeugt wird, indem die piezoresistiven Widerstände (Meßelemente) orthogonal belastet werden und ihren spezifischen Widerstand bei .Krafteinwirkung ändern. Dadurch wird ein axial sehr steifer Sensor ausgebildet, der aufgrund der Temperaturkompensation durch die Schaltung der Widerstände in Halb- oder Vollbrücke nur eine geringe thermische Drift aufweist, und sich somit auch für statische Messungen eignet. Die Vollbrückenschaltung kann auf qua¬ dratischen oder rechteckigen Stirnflächen eines Trägers aufgebracht werden und damit in Mehrfachnutzen gedruckt und bestückt werden. Bei ausreichend großen Abmessungen kann damit auch eine Kontaktierung der Anschlußdrähte durch Bonden oder Löten an der Stirnseite er¬ folgen. Bei geringen Abmessungen kann die Kontaktierung der An¬ schlußdrähte auch an den abgeflachten Bereichen eines zylinderförmi- gen Trägers vorgenommen werden. Die Kontaktierung kann auch analog zum Ausführungsbeispiel nach Figur 3 ausgeführt werden. Dadurch ent¬ fällt ein Abwinkein der Ableitdrähte, wie in Figur 4 dargestellt. Darüber hinaus kann der Sensor bzw. der Träger dann in großflächigen Vielfachnutzen bedruckt und bestückt werden. Dazu ist es vorteil¬ haft, Bohrungen für die Ableitdrähte so anzubringen, daß sie auf dem Trennschritt der einzelnen Substrate liegen, so daß jedem Substrat bzw. Träger nach dem Trennen Bohrungs bschnitte mit etwa halbkreis¬ förmigem Querschnitt zugeordnet sind. The direct, orthogonal loading of the measuring elements enables a very small, compact sensor. A membrane for introducing an expansion into the resistors is not necessary, since the measurement signal is generated by the piezoresistive resistors (measuring elements) being loaded orthogonally and changing their specific resistance under the influence of force. As a result, an axially very rigid sensor is formed, which is due to the temperature compensation has only a small thermal drift due to the switching of the resistors in half or full bridge, and is therefore also suitable for static measurements. The full bridge circuit can be applied to square or rectangular end faces of a support and can thus be printed and equipped in multiple uses. If the dimensions are sufficiently large, contacting of the connecting wires by bonding or soldering on the end face can also take place. With small dimensions, the contacting of the connecting wires can also be carried out on the flattened areas of a cylindrical carrier. The contacting can also be carried out analogously to the exemplary embodiment according to FIG. 3. This eliminates the need for the lead wires to bend, as shown in FIG. In addition, the sensor or the carrier can then be printed and equipped in large-area multiple uses. For this purpose, it is advantageous to drill holes for the lead wires so that they lie on the separating step of the individual substrates, so that each substrate or carrier is assigned, after separation, borehole sections with an approximately semicircular cross section.

Claims

Ansprüche Expectations
1. Sensor (10/ 10A,-" 10B) zur Bestimmung eines Drucks oder einer Kraft mit Hilfe mindestens eines auf einem Träger (14; 14A; 14B) aufgebrachten Schichtwiderstandes (11; 25, 26), der mit einem Kraft¬ einleitungsteil (21; 21A; 21B) in Wirkverbindung steht, und mit Lei¬ terbahnen (13; 13A; 13B), die den Widerstand (11; 25, 26) mit Ablei¬ tungen (20; 20A; 20B) verbinden, wobei Krafteinleitungs eil und Trä¬ ger gegenüber dem Widerstand und den Leiterbahnen elektrisch iso¬ liert sind, dadurch gekennzeichnet, daß auf dem Träger mindestens ein zusätzlicher Schichtwiderstand (12; 27, 28) angeordnet ist, der in unmittelbarer N he des mit dem Krafteinleitungsteil (21; 21A; 21B) zusammenwirkenden Widerstandes (11; 25, 26) und außerhalb des Kraftflusses zwischen diesem Krafteinleitungsteil und dem mit diesem zusammenwirkenden Widerstand angeordnet ist.1. Sensor (10 / 10A, - "10B) for determining a pressure or a force with the aid of at least one sheet resistance (11; 25, 26) applied to a carrier (14; 14A; 14B), which is connected to a force introduction part ( 21; 21A; 21B) is in operative connection, and with conductor tracks (13; 13A; 13B), which connect the resistor (11; 25, 26) to leads (20; 20A; 20B), force introduction and Carriers are electrically insulated from the resistor and the conductor tracks, characterized in that at least one additional sheet resistor (12; 27, 28) is arranged on the carrier, which is in the immediate vicinity of the one with the force introduction part (21; 21A; 21B) cooperating resistor (11; 25, 26) and outside the force flow between this force introduction part and the cooperating resistor is arranged.
2. Sensor nach Anspruch 1, dadurch gekennzeichnet, daß" die Schicht¬ widerstände (11, 12, 25 - 28) und die Leiterbahnen (13; 13A; 13B) in Dünnschichttechnik erstellt sind. 2. Sensor according to claim 1, characterized in that " the film resistors (11, 12, 25 - 28) and the conductor tracks (13; 13A; 13B) are created in thin-film technology.
3. Sensor nach Anspruch 1, dadurch gekennzeichnet, daß die Schichtwiderstände (11, 12, 25 - 28) und die Leiterbahnen (13; 13A; 13B) in Dickschichttechnik erstellt sind.3. Sensor according to claim 1, characterized in that the sheet resistors (11, 12, 25 - 28) and the conductor tracks (13; 13A; 13B) are created in thick-film technology.
4. Sensor nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß der mit dem Krafteinleitungsteil (21; 21A; 21B) zusammenwirkende Widerstand und der zusätzliche Widerstand durch die Leiterbahnen in Form einer Halbbrücke verschaltet sind.4. Sensor according to one of claims 1 to 3, characterized in that the with the force introduction part (21; 21A; 21B) cooperating resistance and the additional resistance are connected by the conductor tracks in the form of a half bridge.
5. Sensor nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß mit dem Krafteinleitungsteil (21B) zwei Widerstände zusammen¬ wirken, die mit zwei zusätzlichen Widerständen (27, 28) eine Voll¬ brücke bilden.5. Sensor according to one of claims 1 to 3, characterized in that with the force introduction part (21B) act two resistors together, which form a full bridge with two additional resistors (27, 28).
6. Sensor nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß die Ableitungen (20A, 20B) mit den Leiterbahnen (13A; 13B) im Bereich der Stirnfläche des Trägers (14A; 14B) verbunden sind, wobei sich diese Kontaktierungsstellen außerhalb des Bereiches des Kraft¬ einleitungsteils befinden.6. Sensor according to one of claims 1 to 5, characterized in that the leads (20A, 20B) with the conductor tracks (13A; 13B) in the region of the end face of the carrier (14A; 14B) are connected, these contact points outside the Area of the Kraft¬ introduction part are.
7. Sensor nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß die Ableitungen (20) im Bereich der Mantelfläche des Trägers (14) über leitende Zonen (17 - 19) mit den Leiterbahnen (13) verbun¬ den sind. 7. Sensor according to one of claims 1 to 5, characterized in that the derivatives (20) in the area of the lateral surface of the carrier (14) via conductive zones (17-19) with the conductor tracks (13) are the verbun.
PCT/DE1992/000277 1991-04-06 1992-04-07 Temperature compensation for a force or pressure sensor WO1993020417A1 (en)

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DE4300995C2 (en) * 1993-01-15 1994-10-27 Lucas Ind Plc Force sensor and method for its manufacture
US7441467B2 (en) * 2006-07-12 2008-10-28 Cts Corporation Compression strain sensor
JP5604035B2 (en) * 2008-07-18 2014-10-08 本田技研工業株式会社 Force sensor unit

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