EP1725836A1 - Magnetic sensor arrangement - Google Patents

Magnetic sensor arrangement

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Publication number
EP1725836A1
EP1725836A1 EP05707752A EP05707752A EP1725836A1 EP 1725836 A1 EP1725836 A1 EP 1725836A1 EP 05707752 A EP05707752 A EP 05707752A EP 05707752 A EP05707752 A EP 05707752A EP 1725836 A1 EP1725836 A1 EP 1725836A1
Authority
EP
European Patent Office
Prior art keywords
magnetic
sensor
magnetic sensor
sensor elements
sensor arrangement
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP05707752A
Other languages
German (de)
French (fr)
Inventor
Ingo Herrmann
Paul Farber
Ulrich May
Christian Bauer
Birgit Vogelgesang
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Bosch GmbH
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 EP1725836A1 publication Critical patent/EP1725836A1/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/022—Measuring gradient
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/142—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage using Hall-effect devices
    • G01D5/147—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage using Hall-effect devices influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/42—Devices characterised by the use of electric or magnetic means
    • G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
    • G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
    • G01P3/481—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals
    • G01P3/487—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals delivered by rotating magnets

Definitions

  • the invention relates to a magnetic sensor arrangement, in particular for sensing the movement of linearly or rotationally moved elements, according to the generic features of the main claim.
  • magnetic field-sensitive sensors are used in many areas in which contactless detection of a movement is desired. This can be both a rotational movement and a linear movement.
  • the movement can be determined directly by the time-changing magnetic field at the sensor location.
  • passive transmitter elements which consist of a soft magnetic material
  • the magnetic field is generated by a working magnet which is firmly connected to the sensor. The sensor measures the change in the magnetic field of the working magnet, which is caused by the movement of the encoder elements.
  • XMR sensors In addition to the Hall technology for magnetic field measurement which is known per se, so-called XMR technologies, ie magnetoresistive measuring principles, are also increasingly being used in the case of passive sensor elements in the motor vehicle sector. It should be noted that XMR sensors, in contrast to Hall sensors, detect the so-called "in-plane" component of the magnetic field in the sensor element. XMR sensors previously used use a working magnet for this purpose, the field of which must be adjusted so that the offset at the location of the sensitive element is zero, or a so-called back bias field is generated that defines the working point of the sensor.
  • DE 101 28 135 AI describes a concept in which a hard magnetic layer nearby, i.e. is deposited in particular on and / or under a magnetoresistive layer stack.
  • This hard magnetic layer then couples mainly to the magnetosensitive layers through its stray field and generates a so-called bias magnetic field, which acts as a magnetic field offset, so that even with only a slight variation of an external magnetic field superimposed on the internal magnetic field, a well measurable and a relatively large change in the actual measured value, which is detected as a change in resistance in the layer arrangement, can be achieved.
  • the sensors described above are often designed in a manner known per se for speed detection, for example in motor vehicle technology, in a so-called gradiometer arrangement.
  • the sensor thus only measures the signal of a magnetic pole wheel whose pole pair spacing corresponds approximately to the predefined gradiometer spacing.
  • the gradiometer principle in contrast to the absolutely measuring XMR elements, the sensitivity of the sensors to homogeneous interference fields can be reduced. A comparison of the magnets previously used so that the offset can be eliminated at both locations of the sensor elements of the gradiometer arrangement can no longer be carried out here; An electronic adjustment is possible in principle, but here there is a relatively small signal with a large offset.
  • the magnetic sensor arrangement according to the invention has two sensor elements in a gradiometer arrangement, each of which is assigned to one of two permanent magnets arranged at a predetermined distance.
  • the permanent magnets are advantageously arranged with respect to their dimensions, their distance and their positions from the sensor elements in such a way that the offset of the output signal of the sensor elements in the gradiometer arrangement is minimized.
  • the design of a magnetic circuit which has a working field for one on the gradiometer principle, ie with a detection of the Field gradient working sensor is generated, optimized and thus enables offset-free operation of the sensor with variation of the magnetic field by moving encoder elements, in particular gears.
  • the magnetic circuit was composed of two individual magnets, the fields of which overlap so that the so-called "in-plane" components of the resulting magnetic field at the gradiometer positions are reduced to such an extent that they vary around the zero position due to the influence of the passive transmitter elements. This means that very small signals can be detected without offset.
  • homogenizing plates are arranged between the sensor elements and the permanent magnets. This homogenizes the field in the plane of the sensor elements and reduces the necessary positioning accuracy of the sensor elements compared to the magnet pair for offset-free operation.
  • the magnetization of the permanent magnets is rotated by a predetermined angle ⁇ , deviating from its longitudinal direction facing the sensor elements.
  • This premagnetization which is caused by the oblique position of the field, ensures that the sensor elements are located in a magnetic field in which the sensitivity is maximum due to a so-called bias field.
  • an arrangement of the aforementioned homogenizing plates is advantageously possible.
  • the invention can be used particularly advantageously in a magnetic sensor arrangement for detecting the angle of rotation of a wheel as a transmitter element, the wheel, for example as a steel wheel, being provided with teeth on its periphery for influencing the magnetic field in the region of the magnetic sensor arrangement.
  • FIG. 1 shows a basic view of a magnetic sensor arrangement with two permanent magnets, each of which is opposite a magnetoresistive sensor element in a gradiometer arrangement
  • FIG. 2 shows an arrangement with homogenization plates that is expanded compared to FIG. 1,
  • FIG. 3 shows an exemplary embodiment of a magnetic sensor arrangement with two permanent magnets which, as a modification to FIG. 1, have an angled magnetic field
  • FIG. 4 shows an embodiment according to FIG. 3 with homogenizing plates corresponding to FIG. 2
  • Figure 5 is a view of a magnetic sensor arrangement for a sensor wheel provided with steel teeth
  • FIG. 6 shows a diagram of the course of the magnetic field as a function of the position of a tooth or a tooth gap of the sensor wheel according to FIG. 5.
  • FIG. 1 shows a basic view of a magnetic sensor arrangement 1 which has two permanent magnets 2 and 3, the respective magnetic field B of which is aligned with the field lines indicated here in the direction of a sensor 4.
  • the sensor 4 is designed here as an XMR sensor and has two magnetoresistive sensor elements 5 and 6.
  • the sensor elements 5 and 6 are shown in a gradiometer arrangement with the gradiometer distance GM and detect the changes in the respective field gradients, e.g. by a metallic donor element, e.g. a gear wheel shown in FIG. 5, which is guided past the magnetic sensor arrangement 1, is caused.
  • the optimal working point of the sensor 4 is set via the distance a between the magnets 2 and 3 and can be adapted to the gradiometer distance GM of the sensor elements 5 and 6. Furthermore, the field line profiles depend on the dimensions h, b and t of the permanent magnets 2 and 3. For a fixed gradiometer distance GM, for example 2.5 mm, the size, material and arrangement of the permanent magnets 2 and 3 can be determined here in such a way that the sensor 4 works without offset and can thus detect signals as small as possible again to achieve the greatest possible distance from a transmitter element.
  • the magnetic field lines of the magnetic sensor arrangement 1 run such that a small so-called “in-plane” component exists at the location of the sensor elements 5 and 6.
  • an external sensor element e.g. a gear wheel
  • the magnetic field lines of the magnetic sensor arrangement 1 run such that a small so-called “in-plane” component exists at the location of the sensor elements 5 and 6.
  • a moving gear wheel causes a variation of the magnetic field, the "in-plane" components being modulated around the zero position and thus generating an offset-free signal of the gradiometer arrangement.
  • FIG. 2 An exemplary embodiment can be seen in FIG. 2, in which, in a modification of the exemplary embodiment according to FIG. 1, an additional homogenizing plate 7 is attached between the surfaces of the permanent magnets 2 and 3 and the sensor 4.
  • the field in the plane of the sensor 4 is homogenized with the homogenizing plate 7, and the necessary positioning accuracy of the sensor 4 is reduced compared to the magnet pair 2, 3 for offset-free operation.
  • the sensor elements require constant bias. This premagnetization ensures that the sensor elements 5 and 6 are in a magnetic field in which the sensitivity is at a maximum. This so-called bias field is realized in each case with an embodiment shown in FIGS. 3 and 4.
  • this is realized by rotating the magnetization B in the permanent magnets 2 and 3 by the angle ⁇ . It can also here, as previously described, again implement two construction variants without ⁇ FIG. 3) and with an adjustment improvement by means of a homogenizing plate 7 (FIG. 4).
  • FIG. 5 shows a section of a model in which the magnetic sensor arrangement 1 according to the invention, for example according to FIG. 1, is used in connection with a sensor wheel 8 which is provided with teeth 9.
  • a measurement result is shown in a diagram according to FIG.
  • the so-called "in-plane" component of the magnetic field Bx is plotted here above the gradiometer position relative to the center of the sensor 4, in each case for a tooth 9 (course 10) and for a tooth gap (course 11).

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Transmission And Conversion Of Sensor Element Output (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

Abstract

The invention relates to a magnetic sensor arrangement (1) wherein sensor elements (5, 6) which are sensitive to magnetic fields (5, 6), and the electric properties thereof which can be modified according to a magnetic field, are influenced by a displaceable passive transmitter element. The magnetic sensor arrangement (1) comprises two sensor elements (5, 6) in a gradiometer arrangement. Said elements are respectively associated with one or two permanent magnets (2, 3) which are arranged at a predetermined distance. The dimensions, the distances and the positions of the permanent magnets (2, 3) in relation to the sensor elements (5, 6) are arranged such that the offset of the output signal of the sensor elements (5, 6) is minimised in the gradiometer arrangement.

Description

Magnetsensoranordnuncr Magnetsensoranordnuncr
Stand der TechnikState of the art
Die Erfindung betrifft eine Magnetsensoranordnung, insbesondere zur Sensierung der Bewegung von linear oder rota- torisch bewegten Elementen, nach den gattungsgemäßen Merkmalen des Hauptanspruchs .The invention relates to a magnetic sensor arrangement, in particular for sensing the movement of linearly or rotationally moved elements, according to the generic features of the main claim.
Es ist an sich bekannt, dass magnetfeldempfindliche Sensoren in vielen Bereichen Anwendung finden, bei denen eine berührungsfreie Detektierung einer Bewegung gewünscht ist. Dabei kann es sich sowohl um eine Rotationsbewegung als auch eine Linearbewegung handeln. Zu unterscheiden sind hier zwei grundlegend verschiedene Messprinzipien. Zum einen lässt sich durch Anbringen eines oder mehrerer magnetischer Dipole als aktive Elemente auf dem zu detek- tierenden Element die Bewegung direkt durch das sich zeitlich ändernde Magnetfeld am Sensorort bestimmen. Im Gegensatz dazu wird bei passiven Geberelementen, die aus einem weichmagnetischen Material bestehen, das magnetische Feld durch einen Arbeitsmagneten erzeugt, der fest mit dem Sensor verbunden ist. Der Sensor misst die Änderung des Magnetfeldes des Arbeitsmagneten, die durch die Bewegung der Geberelemente hervorgerufen wird. Neben der an sich bekannten Hall-Technologie zur Magnetfeldmessung werden vermehrt auch bei passiven Geberelementen im Kraftfahrzeugbereich alternativ sog. XMR- Technologien, d.h. magnetoresistive Messprinzipien, eingesetzt. Dabei ist zu beachten, dass XMR-Sensoren im Gegensatz zu Hall-Sensoren die sog. "in-plane"-Komponente des Magnetfeldes im Sensorelement detektieren. Bisher übliche XMR-Sensoren verwenden dazu einen Arbeitsmagneten, dessen Feld so abgeglichen werden muss, dass der Offset am Ort des sensitiven Elementes Null ist oder es wird ein sog. Backbias-Feld erzeugt, das den Arbeitspunkt des Sensors definiert.It is known per se that magnetic field-sensitive sensors are used in many areas in which contactless detection of a movement is desired. This can be both a rotational movement and a linear movement. There are two fundamentally different measuring principles. On the one hand, by attaching one or more magnetic dipoles as active elements on the element to be detected, the movement can be determined directly by the time-changing magnetic field at the sensor location. In contrast to this, in the case of passive transmitter elements, which consist of a soft magnetic material, the magnetic field is generated by a working magnet which is firmly connected to the sensor. The sensor measures the change in the magnetic field of the working magnet, which is caused by the movement of the encoder elements. In addition to the Hall technology for magnetic field measurement which is known per se, so-called XMR technologies, ie magnetoresistive measuring principles, are also increasingly being used in the case of passive sensor elements in the motor vehicle sector. It should be noted that XMR sensors, in contrast to Hall sensors, detect the so-called "in-plane" component of the magnetic field in the sensor element. XMR sensors previously used use a working magnet for this purpose, the field of which must be adjusted so that the offset at the location of the sensitive element is zero, or a so-called back bias field is generated that defines the working point of the sensor.
Beispielsweise ist in der DE 101 28 135 AI ein Konzept beschrieben, bei dem eine hartmagnetische Schicht in der Nähe, d.h. insbesondere auf und/oder unter einem magneto- resistiven SchichtStapel, deponiert wird. Diese hartmagnetische Schicht koppelt dann vorwiegend durch ihr Streufeld an die magnetosensitiven Schichten und erzeugt dabei ein,, sogenanntes Bias-Magnetfeld, das als Magnetfeld- Offset wirkt, so dass auch bei einer nur schwachen Variation eines dem internen Magnetfeld überlagerten externen Magnetfelds eine gut messbare und relativ große Veränderung des eigentlichen Messwertes, der als Widerstandsänderung in der Schichtanordnung detektiert wird, erreichbar ist.For example, DE 101 28 135 AI describes a concept in which a hard magnetic layer nearby, i.e. is deposited in particular on and / or under a magnetoresistive layer stack. This hard magnetic layer then couples mainly to the magnetosensitive layers through its stray field and generates a so-called bias magnetic field, which acts as a magnetic field offset, so that even with only a slight variation of an external magnetic field superimposed on the internal magnetic field, a well measurable and a relatively large change in the actual measured value, which is detected as a change in resistance in the layer arrangement, can be achieved.
Die zuvor beschriebenen Sensoren werden in an sich bekannter Weise zur Drehzahlerfassung, beispielsweise in der Kraftfahrzeugtechnik, oft in einer sogenannten Gradi- ometeranordnung ausgeführt. Das heißt je zwei Zweige einer Wheatstoneschen Messbrücke sind in vorgegebenem Abstand angeordnet, so dass ein homogenes Magnetfeld kein Brückensignal bewirkt. Eine Variation des Magnetfelds im Bereich des vorgegebenen Abstands hingegen erzeugt ein Brückensignal. Damit misst der Sensor nur das Signal eines magnetischen Polrads, dessen Polpaarabstand in etwa dem vorgegebenen Gradiometerabstand entspricht.The sensors described above are often designed in a manner known per se for speed detection, for example in motor vehicle technology, in a so-called gradiometer arrangement. This means that two branches of a Wheatstone measuring bridge are arranged at a predetermined distance, so that a homogeneous magnetic field does not cause a bridge signal. A variation of the magnetic field in the In contrast, the area of the predetermined distance generates a bridge signal. The sensor thus only measures the signal of a magnetic pole wheel whose pole pair spacing corresponds approximately to the predefined gradiometer spacing.
Durch den Einsatz des Gradiometerprinzips in einer magne- toresistiven XMR-Messbrücke lässt sich im Gegensatz zu den absolut messenden XMR-Elementen eine Reduzierung der Empfindlichkeit der Sensoren gegenüber homogenen Störfeldern erreichen. Ein Abgleich der bisher eingesetzten Magnete, so dass an beiden Orten der Sensorelemente der Gradiometeranordnung der Offset eliminiert werden kann, lässt sich hier jedoch nicht mehr durchführen; ein elektronischer Abgleich ist zwar prinzipiell möglich, aber hier ist ein relativ kleines Signal auf großem Offset vorhanden.By using the gradiometer principle in a magnetoresistive XMR measuring bridge, in contrast to the absolutely measuring XMR elements, the sensitivity of the sensors to homogeneous interference fields can be reduced. A comparison of the magnets previously used so that the offset can be eliminated at both locations of the sensor elements of the gradiometer arrangement can no longer be carried out here; An electronic adjustment is possible in principle, but here there is a relatively small signal with a large offset.
Vorteile der ErfindungAdvantages of the invention
Bei einer Weiterbildung einer Magnetsensoranordnung der eingangs angegebenen Art, weist die Magnetsensoranordnung erfindungsgemäß zwei Sensorelemente in einer Gradiomete- ranordnung auf, die jeweils einem von zwei in einem vorgegebenen Abstand angeordneten Permanentmagneten zugeordnet sind. Die Permanentmagnete sind in vorteilhafter Weise hinsichtlich ihrer Abmaße, ihres Abstandes und ihrer Positionen zu den Sensorelementen so angeordnet, dass der Offset des Ausgangssignals der Sensorelemente in der Gra- diometeranordung minimiert ist.In a development of a magnetic sensor arrangement of the type specified at the outset, the magnetic sensor arrangement according to the invention has two sensor elements in a gradiometer arrangement, each of which is assigned to one of two permanent magnets arranged at a predetermined distance. The permanent magnets are advantageously arranged with respect to their dimensions, their distance and their positions from the sensor elements in such a way that the offset of the output signal of the sensor elements in the gradiometer arrangement is minimized.
Mit der Erfindung wird somit erreicht, dass die Auslegung eines Magnetkreises, der ein Arbeitsfeld für einen auf dem Gradiometerprinzip, d.h. mit einer Erfassung des Feldgradienten arbeitenden Sensors erzeugt, optimiert ist und somit einen offsetfreien Betrieb des Sensors bei Variation des magnetischen Feldes durch sich bewegende Geberelemente, insbesondere Zahnräder, ermöglicht. Dazu wurde der Magnetkreis aus zwei Einzelmagneten zusammengesetzt, deren Felder sich so überlagern, dass die sog. "in-plane"-Komponenten des resultierenden magnetischen Feldes an den Gradiometerpositionen soweit reduziert werden, dass sie durch den Einfluss der passiven Geberelemente um die Nulllage variieren. Somit können sehr kleine Signale offsetfrei detektiert werden.It is thus achieved with the invention that the design of a magnetic circuit which has a working field for one on the gradiometer principle, ie with a detection of the Field gradient working sensor is generated, optimized and thus enables offset-free operation of the sensor with variation of the magnetic field by moving encoder elements, in particular gears. For this purpose, the magnetic circuit was composed of two individual magnets, the fields of which overlap so that the so-called "in-plane" components of the resulting magnetic field at the gradiometer positions are reduced to such an extent that they vary around the zero position due to the influence of the passive transmitter elements. This means that very small signals can be detected without offset.
Dies ist besonders bei sehr empfindlichen magnetoresisti- ven XMR-Sensoren von Vorteil, die möglichst ohne eine Offset-Korrektur einen großen Arbeitsbereich, d.h. sehr große bis sehr kleine Feldstärken, abdecken sollen.This is particularly advantageous in the case of very sensitive magnetoresistive XMR sensors, which have a large working area, i.e. very large to very small field strengths.
Bei einer vorteilhaften Ausführungsform sind zwischen den Sensorelementen und den Permanentmagneten Homogenisierungsplatten angeordnet . Damit wird das Feld in der Ebene der Sensorelemente homogenisiert und die notwendige Positioniergenauigkeit der Sensorelemente gegenüber dem Magnetpaar zum offsetfreien Betrieb reduziert.In an advantageous embodiment, homogenizing plates are arranged between the sensor elements and the permanent magnets. This homogenizes the field in the plane of the sensor elements and reduces the necessary positioning accuracy of the sensor elements compared to the magnet pair for offset-free operation.
Vorteilhaft ist es außerdem, wenn gemäß einer weiteren Ausführungsform die Magnetisierung der Permanentmagneten abweichend von ihrer den Sensorelementen zugewandten Längsrichtung jeweils um einen vorgegebenen Winkel α gedreht ist.It is also advantageous if, according to a further embodiment, the magnetization of the permanent magnets is rotated by a predetermined angle α, deviating from its longitudinal direction facing the sensor elements.
Durch diese, durch die Schräglage des Feldes bedingte Vormagnetisierung wird erreicht, dass sich die Sensorelemente in einem Magnetfeld befinden, bei dem die Sensiti- vität durch ein sog. Bias-Feld maximal ist. Auch hierbei ist eine Anordnung von den zuvor erwähnten Homogenisierungsplatten in vorteilhafter Weise möglich. Besonders vorteilhaft lässt sich die Erfindung bei einer Magnetsensoranordnung zur Erfassung des Drehwinkels eines Rades als Geberelement einsetzen, wobei das Rad, z.B. als Stahlrad, an seinem Umfang mit Zähnen zur Beeinflussung des Magnetfeldes im Bereich der Magnetsensoranordnung versehen ist. Insbesondere bei einer Anwendung in einem Kraftfahrzeug ergeben sich Einsatzgebiete als Drehzahlfühler am Rad oder an der Kurbelwelle, als Phasengeber an der Nockenwelle, als Drehzahlsensor im Getriebe oder als sonstige Linearweg-, Winkel- oder Näherungssensoren, bei denen die Magnetfeldänderungen durch bewegte metallische Elemente induziert werden.This premagnetization, which is caused by the oblique position of the field, ensures that the sensor elements are located in a magnetic field in which the sensitivity is maximum due to a so-called bias field. Here, too, an arrangement of the aforementioned homogenizing plates is advantageously possible. The invention can be used particularly advantageously in a magnetic sensor arrangement for detecting the angle of rotation of a wheel as a transmitter element, the wheel, for example as a steel wheel, being provided with teeth on its periphery for influencing the magnetic field in the region of the magnetic sensor arrangement. In particular in an application in a motor vehicle, there are areas of application as speed sensors on the wheel or on the crankshaft, as phase sensors on the camshaft, as speed sensors in the transmission or as other linear travel, angle or proximity sensors in which the magnetic field changes are induced by moving metallic elements ,
ZeichnuncrZeichnuncr
Ausführungsbeispiele der Erfindung werden anhand der Zeichnung erläutert. Es zeigen:Embodiments of the invention are explained with reference to the drawing. Show it:
Figur 1 eine Prinzipansicht einer Magnetsensoranordnung mit zwei Permanentmagneten, die jeweils einem magnetoresistiven Sensorelement in einer Gradiomete- ranordnung gegenüberliegen,FIG. 1 shows a basic view of a magnetic sensor arrangement with two permanent magnets, each of which is opposite a magnetoresistive sensor element in a gradiometer arrangement,
Figur 2 eine gegenüber der Figur 1 erweiterte Anordnung mit Homogenisierungsplatten,FIG. 2 shows an arrangement with homogenization plates that is expanded compared to FIG. 1,
Figur 3 ein Ausführungsbeispiel einer Magnetsensoranordnung mit zwei Permanentmagneten, die in Abwandlung zur Figur 1 ein abgewinkelt liegendes Magne t- feld aufweisen,FIG. 3 shows an exemplary embodiment of a magnetic sensor arrangement with two permanent magnets which, as a modification to FIG. 1, have an angled magnetic field,
Figur 4 ein Ausführungsbeispiel nach der Figur 3 mit Homogenisierungsplatten entsprechend der Figur 2, Figur 5 eine Ansicht einer Magnetsensoranordnung für ein mit Stahlzähnen versehenes Geberrad undFIG. 4 shows an embodiment according to FIG. 3 with homogenizing plates corresponding to FIG. 2, Figure 5 is a view of a magnetic sensor arrangement for a sensor wheel provided with steel teeth and
Figur 6 ein Diagramm des Verlaufs des Magnetfeldes in Abhängigkeit von der Position eines Zahnes bzw. einer Zahnlücke des Geberrades nach der Figur 5.FIG. 6 shows a diagram of the course of the magnetic field as a function of the position of a tooth or a tooth gap of the sensor wheel according to FIG. 5.
Beschreibung der AusführungsbeispieleDescription of the embodiments
In Figur 1 ist eine Prinzipansicht einer Magnetsensoranordnung 1 gezeigt, die zwei Permanentmagnete 2 und 3 aufweist, deren jeweiliges magnetisches Feld B mit hier angedeuteten Feldlinien in Richtung auf einen Sensor 4 ausgerichtet ist. Der Sensor 4 ist hier als XMR-Sensor ausgeführt und weist zwei magnetoresistive Sensorelemente 5 und 6 auf. Die Sensorelemente 5 und 6 sind in einer Gra- diometeranordnung mit dem Gradiometerabstand GM dargestellt und erfassen die Änderungen des jeweiligen Feldgradienten, die z.B. durch ein metallisches Geberelement, z.B. ein in Figur 5 gezeigtes Zahnrad, das an der Magnetsensoranordnung 1 vorbeigeführt wird, verursacht wird.FIG. 1 shows a basic view of a magnetic sensor arrangement 1 which has two permanent magnets 2 and 3, the respective magnetic field B of which is aligned with the field lines indicated here in the direction of a sensor 4. The sensor 4 is designed here as an XMR sensor and has two magnetoresistive sensor elements 5 and 6. The sensor elements 5 and 6 are shown in a gradiometer arrangement with the gradiometer distance GM and detect the changes in the respective field gradients, e.g. by a metallic donor element, e.g. a gear wheel shown in FIG. 5, which is guided past the magnetic sensor arrangement 1, is caused.
Die Einstellung des optimalen Arbeitspunktes des Sensors 4 erfolgt über den Abstand a der Magnete 2 und 3 zueinander und kann an den Gradiometerabstand GM der Sensorelemente 5 und 6 angepasst werden. Weiterhin hängen die Feldlinienverläufe von den Abmaßen h, b und t der Permanentmagnete 2 und 3 ab. Für einen festen Gradiometerabstand GM, z.B. 2,5 mm, kann hier beispielsweise Größe, Material und Anordnung der Permanentmagnete 2 und 3 so bestimmt werden, dass der Sensor 4 offsetfrei arbeitet und somit möglichst kleine Signale detektieren kann um wiederum einen möglichst großen Abstand zu einem Geberelement zu erreichen.The optimal working point of the sensor 4 is set via the distance a between the magnets 2 and 3 and can be adapted to the gradiometer distance GM of the sensor elements 5 and 6. Furthermore, the field line profiles depend on the dimensions h, b and t of the permanent magnets 2 and 3. For a fixed gradiometer distance GM, for example 2.5 mm, the size, material and arrangement of the permanent magnets 2 and 3 can be determined here in such a way that the sensor 4 works without offset and can thus detect signals as small as possible again to achieve the greatest possible distance from a transmitter element.
Ohne ein außen vorbeigeführtes Geberelement, z.B. ein Zahnrad, verlaufen die magnetischen Feldlinien der Magnetsensoranordnung 1 so, dass am Ort der Sensorelemente 5 und 6 eine kleine sog. "in-plane"-Komponente nach außen existiert. Durch den Einsatz z.B. eines sich bewegenden Zahnrads kommt es zu einer Variation des Magnetfeldes, wobei die "in-plane"-Komponenten um die Nulllage moduliert werden und damit ein offsetfreies Signal der Gradi- ometeranordnung erzeugen.Without an external sensor element, e.g. a gear wheel, the magnetic field lines of the magnetic sensor arrangement 1 run such that a small so-called "in-plane" component exists at the location of the sensor elements 5 and 6. By using e.g. A moving gear wheel causes a variation of the magnetic field, the "in-plane" components being modulated around the zero position and thus generating an offset-free signal of the gradiometer arrangement.
Aus Figur 2 ist ein Ausführungsbeispiel zu entnehmen, bei dem in Abwandlung zu dem Ausführungsbeispiel nach der Figur 1 eine zusätzliche Homogenisierungsplatte 7 zwischen den Oberflächen der Permanentmagnete 2 und 3 und dem Sensor 4 angebracht ist. Bei diesem Ausführungsbeispiel wird mit der Homogenisierungsplatte 7 das Feld in der Ebene des Sensors 4 homogenisiert und damit die notwendige Positioniergenauigkeit des Sensors 4 gegenüber dem Magnetpaar 2, 3 zum offsetfreien Betrieb reduziert.An exemplary embodiment can be seen in FIG. 2, in which, in a modification of the exemplary embodiment according to FIG. 1, an additional homogenizing plate 7 is attached between the surfaces of the permanent magnets 2 and 3 and the sensor 4. In this exemplary embodiment, the field in the plane of the sensor 4 is homogenized with the homogenizing plate 7, and the necessary positioning accuracy of the sensor 4 is reduced compared to the magnet pair 2, 3 for offset-free operation.
Bei einigen Anwendungsbeispielen mit den zuvor beschriebenen magnetoresistiven XMR-Sensorelementen 5 und 6 benötigen die Sensorelemente eine konstante Vormagnetisierung. Durch diese Vormagnetisierung wird erreicht, dass sich die Sensorelemente 5 und 6 in einem Magnetfeld befinden, bei dem die Sensitivität maximal ist. Realisiert wird dieses sog. Bias-Feld jeweils mit einem aus Figur 3 und 4 zu entnehmenden Ausführungsbeispiel.In some application examples with the magnetoresistive XMR sensor elements 5 and 6 described above, the sensor elements require constant bias. This premagnetization ensures that the sensor elements 5 and 6 are in a magnetic field in which the sensitivity is at a maximum. This so-called bias field is realized in each case with an embodiment shown in FIGS. 3 and 4.
Wie in den Figuren 3 und 4 gezeigt, wird dies durch eine Drehung der Magnetisierung B in den Permanentmagneten 2 und 3 um den Winkel α realisiert. Dabei lassen sich auch hier, wie zuvor beschrieben, wiederum zwei Aufbauvarianten ohne {Figur 3) und mit einer Justageverbesserung durch eine Homogenisierungsplatte 7 (Figur 4) realisieren.As shown in FIGS. 3 and 4, this is realized by rotating the magnetization B in the permanent magnets 2 and 3 by the angle α. It can also here, as previously described, again implement two construction variants without {FIG. 3) and with an adjustment improvement by means of a homogenizing plate 7 (FIG. 4).
In Figur 5 ist ein Ausschnitt eines Modells dargestellt, bei dem die erfindungsgemäße Magnetsensoranordnung 1, beispielsweise nach der Figur 1, im Zusammenhang mit einem Geberrad 8, das mit Zähnen 9 versehen ist, angewendet wird. Als Beispiel ist in einem Diagramm nach Figur 6 ein Messergebnis dargestellt. Aufgetragen ist hier die sog. "in-plane"-Komponente des magnetischen Feldes Bx über der Gradiometerposition relativ zur Mitte des Sensors 4, jeweils für einen Zahn 9 (Verlauf 10) und für eine Zahnlücke (Verlauf 11) .FIG. 5 shows a section of a model in which the magnetic sensor arrangement 1 according to the invention, for example according to FIG. 1, is used in connection with a sensor wheel 8 which is provided with teeth 9. As an example, a measurement result is shown in a diagram according to FIG. The so-called "in-plane" component of the magnetic field Bx is plotted here above the gradiometer position relative to the center of the sensor 4, in each case for a tooth 9 (course 10) and for a tooth gap (course 11).
Es ist hier bei einem vorgegeben konstruktiven Versuchsaufbau mit einem Gradiometerabstand GM von 2,5 mm zu erkennen, dass der Verlauf des Magnetfeldes Bx an der Sensorelementposition 1,25 mm für die zwei simulierten Positionen des Geberrades 8 (Zahn 9, Verlauf 10) und Lücke (Verlauf 11)) symmetrisch um die Nulllage erfolgt, das heißt, dass das Signal des jeweiligen Sensorelementes 5,6 offsetfrei ist. It can be seen here in a given constructive test setup with a gradiometer distance GM of 2.5 mm that the course of the magnetic field Bx at the sensor element position 1.25 mm for the two simulated positions of the encoder wheel 8 (tooth 9, course 10) and gap (Course 11)) takes place symmetrically around the zero position, that is to say that the signal of the respective sensor element 5, 6 is offset-free.

Claims

Patentansprücheclaims
1) Magnetsensoranordnung mit magnetfeldempfindlichen Sensorelementen (5,6) deren elektrische Eigenschaften in Abhängigkeit von einem Magnetfeld veränderbar sind, das durch ein bewegtes passives Geberelement (8) beeinflussbar ist, dadurch gekennzeichnet, dass die Magnetsensoranordnung (1) zwei Sensorelemente (5,6) in einer Gradiometeranordnung aufweist, die jeweils einem von zwei in einem vorgegebenen Abstand (a) angeordneten Permanentmagneten (2,3) zugeordnet sind, wobei die Permanentmagnete (2,3) hinsichtlich ihrer Abmaße, ihres Abstandes und ihrer Positionen zu den Sensorelementen (5,6) so angeordnet sind, dass der Offset des Ausgangssignals der Sensorelemente (5,6) in der Gradiometeranordung minimiert ist. 2) Magnetsensoranordnung nach Anspruch 1, dadurch gekennzeichnet, dass zwischen den Sensorelementen (5,6) und den Permanentmagneten (2,3) mindestens eine Homogenisierungsplatte (7) angeordnet ist.1) Magnetic sensor arrangement with magnetic field-sensitive sensor elements (5, 6) whose electrical properties can be changed as a function of a magnetic field that can be influenced by a moving passive transmitter element (8), characterized in that the magnetic sensor arrangement (1) has two sensor elements (5, 6) in a gradiometer arrangement, each of which is assigned to one of two permanent magnets (2, 3) arranged at a predetermined distance (a), the permanent magnets (2, 3) with respect to their dimensions, their distance and their positions from the sensor elements (5, 6) are arranged so that the offset of the output signal of the sensor elements (5, 6) is minimized in the gradiometer arrangement. 2) Magnetic sensor arrangement according to claim 1, characterized in that at least one homogenization plate (7) is arranged between the sensor elements (5,6) and the permanent magnets (2,3).
3) Magnetsensoranordnung nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die Magnetisierung der Permanentmagneten (2,3) abweichend von ihrer den Sensorelementen (5,6) zugewandten Längsrichtung jeweils um einen vorgegebenen Winkel ( ) gedreht ist.3) Magnetic sensor arrangement according to claim 1 or 2, characterized in that the magnetization of the permanent magnets (2, 3) is rotated differently from its longitudinal direction facing the sensor elements (5, 6) in each case by a predetermined angle ().
4) Magnetsensoranordnung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass die Magnetsensoranordnung (1) zur Erfassung des Drehwinkels eines Rades (8) als Geberelement eingesetzt ist, wobei das Rad (8) an seinem Umfang mit Zähnen (9) zur Beeinflussung des Magnetfeldes im Bereich der Magnetsensoranordnung (1) versehen ist.4) Magnetic sensor arrangement according to one of the preceding claims, characterized in that the magnetic sensor arrangement (1) for detecting the angle of rotation of a wheel (8) is used as a transmitter element, the wheel (8) on its circumference with teeth (9) for influencing the magnetic field is provided in the area of the magnetic sensor arrangement (1).
5) Magnetsensoranordnung nach Anspruch 4, dadurch gekennzeichnet, dass5) Magnetic sensor arrangement according to claim 4, characterized in that
- das Rad (8) ein Stahlrad ist.- The wheel (8) is a steel wheel.
6) Magnetsensoranordnung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass die Sensorelemente (5,6) magnetoresistive XMR-Sensoren sind. 6) Magnetic sensor arrangement according to one of the preceding claims, characterized in that the sensor elements (5, 6) are magnetoresistive XMR sensors.
EP05707752A 2004-03-11 2005-01-07 Magnetic sensor arrangement Withdrawn EP1725836A1 (en)

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