WO2000011448A1 - The use of magnetoresistive sensors for sorting particles - Google Patents

The use of magnetoresistive sensors for sorting particles Download PDF

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Publication number
WO2000011448A1
WO2000011448A1 PCT/EP1999/006167 EP9906167W WO0011448A1 WO 2000011448 A1 WO2000011448 A1 WO 2000011448A1 EP 9906167 W EP9906167 W EP 9906167W WO 0011448 A1 WO0011448 A1 WO 0011448A1
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WO
WIPO (PCT)
Prior art keywords
magnetic field
particles
metallic
sensors
magnetoresistive sensors
Prior art date
Application number
PCT/EP1999/006167
Other languages
German (de)
French (fr)
Inventor
Carsten Oldorf
Hans WÖRMCKE
Original Assignee
M.U.T. 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 M.U.T. Gmbh filed Critical M.U.T. Gmbh
Publication of WO2000011448A1 publication Critical patent/WO2000011448A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
    • B07C5/00—Sorting according to a characteristic or feature of the articles or material being sorted, e.g. by control effected by devices which detect or measure such characteristic or feature; Sorting by manually actuated devices, e.g. switches
    • B07C5/34—Sorting according to other particular properties
    • B07C5/344—Sorting according to other particular properties according to electric or electromagnetic properties

Definitions

  • the invention relates to the use of magnetoresistive sensors (MR, GMR) for sorting metallic and non-metallic particles.
  • MR magnetoresistive sensors
  • MR sensors magnetoresistive sensors or Hall sensors are suitable here. Hall sensors currently still require relatively strong fields and their bandwidth is restricted to relatively low frequencies, so that these are only suitable for the detection of larger particles. MR sensors have bandwidths of more than one megahertz, are very sensitive to the field and are therefore the most suitable sensors. New impulses from this area can be expected from the so-called giganto-magnetoresistive (GMR) sensors.
  • GMR giganto-magnetoresistive
  • the measuring principle has the potential to differentiate different metals of a mixed fraction (presorted by size if necessary) by their different electrical conductivities.
  • the invention is characterized by the use of sensors in which the metallic and non-metallic particles pass through an alternating magnetic field in the frequency range from 0.1 to 1.0 MHz and eddy currents are generated only in the metallic particles, which weaken the magnetic field and the changes of the magnetic field are detected by the magnetoresistive sensors and converted into electronic signals, which are rectified, filtered and increasingly evaluated as detection signals for the metallic particles.
  • the present invention is based on the finding that magnetoresistive sensors are suitable for detecting even relatively small changes in the magnetic field and for converting them into signals which can be evaluated electronically.
  • the practical application of this idea is in in the past, because on the one hand relatively large field changes only occurred if the parts to be detected had either moved very slowly or were relatively large or had to be magnetic. The use of higher frequencies alone would not have helped here, but rather relatively large magnetic field strengths would have had to be applied. On the other hand, sensors were not available that can be used for higher frequencies in the range of 1 MHz.
  • the block circuit diagram shows a frequency generator that operates in the range from 100 kHz to 1 MHz.
  • This frequency generator can be used to generate an alternating magnetic field of a corresponding frequency via a field coil.
  • the particles to be examined are sent in the transverse direction through the generated alternating field, these being those that are either metallic and consequently cause a magnetic field change or, on the other hand, those that are non-metallic and have no influence on the alternating field.
  • magnetic field sensor is to be understood as those elements which respond to changes in the magnetic field and react to this with a corresponding electronic output signal.
  • magneto-resistive sensors or the giganto-magneto-resistive sensors come into question.
  • the output signals of the sensors are conducted via sensor electronics, a rectifier and a low pass via an AC coupling, so that such a signal is used as the output is available that can somehow control the sorting process.
  • the invention is not restricted to the sorting out of metallic particles from a stream of metallic and non-metallic particles. It can also be used to find out which particles (different materials or conductivity differences) and / or what sizes are the particles that pass through the magnetic field.
  • the present invention is also suitable for measuring material flows, provided that they contain metallic particles - albeit in the smallest dimensions.
  • the present invention can also be used in the case of non-metallic particles if the particles to be detected generate eddy currents in the magnetic field and field changes occur as a result. If, for example, the fine dosing of active ingredients in small quantities compared to the carrier medium is concerned, these active ingredients could be made conductive and in this way the smallest quantities in a relatively large stream of matter could be precisely dosed.

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  • Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)

Abstract

The invention relates to the use of magnetoresistive sensors (MR, GMR) for sorting metallic and non-metallic particles. The particles pass through a magnetic alternating field in the frequency range of 0.1 to 1.0 MHz. Eddy currents are produced in the metallic particles and weaken the magnetic field. The changes in the magnetic field are detected by the magnetoresistive sensors and converted into electronic signals which are then evaluated.

Description

Anwendung von magnetoresistiven Sensoren zum Sortieren von Partikeln Use of magnetoresistive sensors for sorting particles
Die Erfindung bezieht sich auf die Anwendung von magnetoresistiven Sensoren (MR, GMR) zum Sortieren von metallischen und nichtmetallischen Partikeln.The invention relates to the use of magnetoresistive sensors (MR, GMR) for sorting metallic and non-metallic particles.
Durch neue Entwicklungen im Bereich der Halbleitersensoren stehen seit kurzen geeignete Magnetfeldsensoren zur Verfügung, die eine hohe Empfindlichkeit mit gleichzeitig hoher Frequenzbandbreite kombinieren. Prinzipiell geeignet sind hier magnetoresistive (MR-) Sensoren oder Hallsensoren. Hallsensoren benötigen zur Zeit noch relativ starke Felder und sind in ihrer Bandbreite auf relativ niedrige Frequenzen eingeschränkt, so dass diese nur für die Detektion größerer Partikel geeignet sind. MR-Sensoren besitzen Bandbreiten bis über ein Megahertz, sind sehr feldempflindlich und damit die am besten geeigneten Sensoren. Neue Impulse aus diesem Bereich sind von den sog. giganto-magnetoresistiven (GMR-) Sensoren zu erwarten. Die Eindringtiefe des Magnetfeldes in Aluminium beträgt etwa 0,3 mm bei 100 kHz und etwa 0,08 mm bei 1 MHz. Dadurch erzeugen in diesem Freuquenzband auch kleine oder sehr dünne Aluminium- Partikel eine messbare Abschwächung des Magnetfeldes . Die geringen Abmessungen der Halbleiter-Magnetfeldsensoren sowie die hohe Messfrequenz ermöglichen eine hohe räumliche Auflösung in einer Array-Anordnung bei gleichzeitig hoher Zeitauflösung. Damit ist dieses Messverfahren prädestiniert für den Einsatz in Sortieranlagen, in denen metallische und nichtmetallische Komponenten z.B. einer Schredderfraktion getrennt werden sollen. Auch die bisher sehr problematischen Beimengungen kleiner nichtmagnetischer Metallpartikel sind auch bei hoher Partikelgeschwindigkeit noch sicher zu erkennen.New developments in the field of semiconductor sensors have recently made available suitable magnetic field sensors that combine high sensitivity with a high frequency bandwidth. In principle, magnetoresistive (MR) sensors or Hall sensors are suitable here. Hall sensors currently still require relatively strong fields and their bandwidth is restricted to relatively low frequencies, so that these are only suitable for the detection of larger particles. MR sensors have bandwidths of more than one megahertz, are very sensitive to the field and are therefore the most suitable sensors. New impulses from this area can be expected from the so-called giganto-magnetoresistive (GMR) sensors. The penetration depth of the magnetic field in aluminum is approximately 0.3 mm at 100 kHz and approximately 0.08 mm at 1 MHz. As a result, even small or very thin aluminum particles produce a measurable weakening of the magnetic field in this frequency band. The small dimensions of the semiconductor magnetic field sensors and the high measurement frequency enable high spatial resolution in an array arrangement with high time resolution at the same time. This measurement method is therefore predestined for use in sorting systems in which metallic and non-metallic components, for example a shredder fraction, are to be separated. Even the previously very problematic admixtures of small non-magnetic metal particles can still be reliably recognized even at high particle speeds.
Mit diesen Eigenschaften ist ein äußerst wirtschaftlicher Betrieb einer Sortieranlage für Metall-Nichtmetallfraktionen möglich.With these properties, an extremely economical operation of a sorting plant for metal-non-metal fractions is possible.
Darüber hinaus besitzt das Messprinzip das Potential auch verschiedene Metalle einer Mischfraktion (ggf. vorsortiert nach Größe) über ihre unterschiedlichen elektrischen Leitfähigkeiten zu unterscheiden.In addition, the measuring principle has the potential to differentiate different metals of a mixed fraction (presorted by size if necessary) by their different electrical conductivities.
Die Erfindung ist durch die Anwendung von Sensoren charakterisiert, bei welcher die metallischen und nichtmetallischen Partikel ein magnetisches Wechselfeld im Frequenzbereich von 0,1 bis 1,0 MHz durchlaufen und nur in den metallischen Partikeln dabei Wirbelströme erzeugt werden, die das Magnetfeld abschwächen und die Änderungen des Magnetfeldes von den magnetoresistiven Sensoren erfasst und in elektronische Signale umgeformt werden, die gleichgerichtet, gefiltert und verstärkt als Nachweissignale für die metallischen Partikel ausgewertet werden.The invention is characterized by the use of sensors in which the metallic and non-metallic particles pass through an alternating magnetic field in the frequency range from 0.1 to 1.0 MHz and eddy currents are generated only in the metallic particles, which weaken the magnetic field and the changes of the magnetic field are detected by the magnetoresistive sensors and converted into electronic signals, which are rectified, filtered and increasingly evaluated as detection signals for the metallic particles.
Die vorliegende Erfindung beruht auf der Erkenntnis, dass magneto-resistive Sensoren geeignet sind, um auch relativ kleine Magnetfeldänderungen zu erfassen und in elektronisch auswertbare Signale umzuformen. Der praktische Einsatz dieser Idee ist in der Vergangenheit nicht realisiert worden, weil einerseits nur dann relativ große Feldänderungen auftraten, wenn die zu erfassenden Teile sich entweder sehr langsam bewegt hatten oder relativ groß waren oder magnetisch sein mussten. Der Einsatz höherer Frequenzen allein hätte hier auch noch nicht weiter geholfen, sondern es hätten dann auch noch relativ große Magnetfeldstärken aufgebracht werden müssen. Andererseits waren Sensoren nicht vorhanden, die für höhere Frequenzen im Bereich von 1 MHz einsetzbar sind.The present invention is based on the finding that magnetoresistive sensors are suitable for detecting even relatively small changes in the magnetic field and for converting them into signals which can be evaluated electronically. The practical application of this idea is in in the past, because on the one hand relatively large field changes only occurred if the parts to be detected had either moved very slowly or were relatively large or had to be magnetic. The use of higher frequencies alone would not have helped here, but rather relatively large magnetic field strengths would have had to be applied. On the other hand, sensors were not available that can be used for higher frequencies in the range of 1 MHz.
Die Erfindung wird nachstehend anhand des Blockschaltdiagramms erläutert, welches die Anwendung von magneto-resistiven Sensoren gemäß der Erfindung zeigt.The invention is explained below on the basis of the block circuit diagram which shows the use of magneto-resistive sensors according to the invention.
In dem Blockschaltdiagramm ist ein Frequenzgenerator, der im Bereich von 100 kHz bis 1 MHz arbeitet, gezeigt. Durch diesen Frequenzgenerator kann über eine Feldspule ein magnetisches Wechselfeld entsprechender Frequenz erzeugt werden. In Querrichtung werden durch das erzeugte Wechselfeld hindurch die zu untersuchenden Partikel geschickt, wobei es sich um solche handelt, die entweder metallisch sind und demzufolge eine Magnetfeldänderung bewirken oder andererseits solche, die nichtmetallisch sind und keinerlei Einfluss auf das Wechselfeld ausüben.The block circuit diagram shows a frequency generator that operates in the range from 100 kHz to 1 MHz. This frequency generator can be used to generate an alternating magnetic field of a corresponding frequency via a field coil. The particles to be examined are sent in the transverse direction through the generated alternating field, these being those that are either metallic and consequently cause a magnetic field change or, on the other hand, those that are non-metallic and have no influence on the alternating field.
Unter dem Begriff Magnetfeldsensor sind solche Elemente zu verstehen, die auf Magnetfeldänderungen ansprechen und hierauf mit einem entsprechenden elektronischen Ausgangssignal reagieren. Hier kommen die magneto-resistiven Sensoren oder die giganto-magneto-resistiven Sensoren in Frage.The term magnetic field sensor is to be understood as those elements which respond to changes in the magnetic field and react to this with a corresponding electronic output signal. Here the magneto-resistive sensors or the giganto-magneto-resistive sensors come into question.
Die Ausgangssignale der Sensoren werden über eine Sensorelektronik, einen Gleichrichter und einen Tiefpass über eine AC-Kopplung geführt, so dass als Ausgang ein solches Signal zur Verfügung steht, das auf irgendeine Weise den Aussortierungsvorgang steuern kann.The output signals of the sensors are conducted via sensor electronics, a rectifier and a low pass via an AC coupling, so that such a signal is used as the output is available that can somehow control the sorting process.
Die Erfindung ist nicht auf das Aussortieren von metallischen Partikeln aus einem Strom metallischer und nichtmetallischer Partikel beschränkt. Sie kann auch angewendet werden, um herauszufinden, welche Teilchen (unterschiedliche Materialien bzw. Leitfähigkeitsunterschiede) und/oder welche Größen die Teilchen haben, die das Magnetfeld passieren. Infrage kommt die vorliegende Erfindung auch zur Messung von Materialströmen, sofern diese metallische Partikel - wenn auch in kleinsten Abmessungen - enthalten. Es kommt auch für die vorliegende Erfindung bei nichtmetallischen Partikeln der Einsatz infrage, sofern die zu detektierenden Partikel im magnetischen Feld Wirbelströme erzeugen und dadurch Feldänderungen auftreten. Wenn es beispielsweise um die Feindosierung von Wirkstoffen in geringer Quantität im Vergleich zum Trägermedium geht, könnte man diese Wirkstoffe leitend machen und auf diesem Wege auch die kleinsten Quantitäten in einem relativ großen Materiestrom genauestens dosieren. The invention is not restricted to the sorting out of metallic particles from a stream of metallic and non-metallic particles. It can also be used to find out which particles (different materials or conductivity differences) and / or what sizes are the particles that pass through the magnetic field. The present invention is also suitable for measuring material flows, provided that they contain metallic particles - albeit in the smallest dimensions. The present invention can also be used in the case of non-metallic particles if the particles to be detected generate eddy currents in the magnetic field and field changes occur as a result. If, for example, the fine dosing of active ingredients in small quantities compared to the carrier medium is concerned, these active ingredients could be made conductive and in this way the smallest quantities in a relatively large stream of matter could be precisely dosed.

Claims

PatentanspruchClaim
Anwendung von magnetoresistiven Sensoren (MR, GMR) zum Sortieren von metallischen und nichtmetallischen Partikeln, bei welcher die Partikel ein magnetisches Wechselfeld im Frequenzbereich von 0,1 bis 1,0 Mhz durchlaufen und in den metallischen Partikeln dabei Wirbelströme erzeugt werden, die das Magnetfeld abschwächen und die Änderungen des Magnetfeldes von den magnetoresistiven Sensoren erfasst und in elektronische Signale umgeformt werden, die gleichgerichtet, gefiltert und verstärkt als Nachweissignale für die metallischen Partikel ausgewertet werden. Application of magnetoresistive sensors (MR, GMR) for sorting metallic and non-metallic particles, in which the particles pass through an alternating magnetic field in the frequency range from 0.1 to 1.0 Mhz and eddy currents are generated in the metallic particles that weaken the magnetic field and the changes in the magnetic field are detected by the magnetoresistive sensors and converted into electronic signals which are rectified, filtered and increasingly evaluated as detection signals for the metallic particles.
PCT/EP1999/006167 1998-08-22 1999-08-23 The use of magnetoresistive sensors for sorting particles WO2000011448A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE1998138249 DE19838249A1 (en) 1998-08-22 1998-08-22 Metallic and non-metallic particle sorting process comprises passing the particles through an alternating magnetic field to produce vortex streams which weaken the field and are detected by magneto-resistive sensors.
DE19838249.9 1998-08-22

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WO2000011448A1 true WO2000011448A1 (en) 2000-03-02

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ATE545047T1 (en) 2002-03-23 2012-02-15 Lorenz Roatzsch METHOD FOR DETECTING OBJECTS, IN PARTICULAR METAL OBJECTS
DE10213115A1 (en) * 2002-03-23 2003-10-16 Lorenz Roatzsch Detecting objects, especially metal objects, using individual pulse-induction probes to detect induction signals from objects and evaluating variations in induction signals emitted by object
AT504527B1 (en) * 2007-02-23 2008-06-15 Evk Di Kerschhaggl Gmbh Objects e.g. conductive and/or ferromagnetic objects, differentiating method for sorting system, involves calculating peak values from increase of sinusoidal current path and constant frequency of sinusoidal voltage of coil

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1548410A (en) * 1976-12-21 1979-07-11 Inst Fiz An Latvssr Method of and apparatus for sorting non-magnetic electrically conductive components
GB2029580A (en) * 1978-08-10 1980-03-19 Central Electr Generat Board Devices for detecting ferromagnetic particles in a liquid
GB2041532A (en) * 1979-01-31 1980-09-10 Plessey Co Ltd Metal detector
US4563644A (en) * 1982-04-01 1986-01-07 Asea Aktiebolag Device for detecting metallic objects in a flow of non-metallic material
EP0541403A2 (en) * 1991-11-08 1993-05-12 National Recovery Technologies Inc. Aluminum recovery system
US5315243A (en) * 1992-04-06 1994-05-24 Her Majesty The Queen In Right Of Canada, As Represented By The Minister Of National Defence Detection and discrimination between ferromagnetic and non-ferromagnetic conductive particles in a fluid
US5439117A (en) * 1993-12-22 1995-08-08 Particle Separation Technologies, L.C. System and method for separating electrically conductive particles

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1548410A (en) * 1976-12-21 1979-07-11 Inst Fiz An Latvssr Method of and apparatus for sorting non-magnetic electrically conductive components
GB2029580A (en) * 1978-08-10 1980-03-19 Central Electr Generat Board Devices for detecting ferromagnetic particles in a liquid
GB2041532A (en) * 1979-01-31 1980-09-10 Plessey Co Ltd Metal detector
US4563644A (en) * 1982-04-01 1986-01-07 Asea Aktiebolag Device for detecting metallic objects in a flow of non-metallic material
EP0541403A2 (en) * 1991-11-08 1993-05-12 National Recovery Technologies Inc. Aluminum recovery system
US5315243A (en) * 1992-04-06 1994-05-24 Her Majesty The Queen In Right Of Canada, As Represented By The Minister Of National Defence Detection and discrimination between ferromagnetic and non-ferromagnetic conductive particles in a fluid
US5439117A (en) * 1993-12-22 1995-08-08 Particle Separation Technologies, L.C. System and method for separating electrically conductive particles

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