EP0014737B1 - Electromagnetic actuator - Google Patents

Electromagnetic actuator Download PDF

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Publication number
EP0014737B1
EP0014737B1 EP79104186A EP79104186A EP0014737B1 EP 0014737 B1 EP0014737 B1 EP 0014737B1 EP 79104186 A EP79104186 A EP 79104186A EP 79104186 A EP79104186 A EP 79104186A EP 0014737 B1 EP0014737 B1 EP 0014737B1
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EP
European Patent Office
Prior art keywords
permanent magnet
magnetic
pole pieces
magnetic flux
magnetic core
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Expired
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EP79104186A
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German (de)
French (fr)
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EP0014737A1 (en
Inventor
John Carl Tamulis
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International Business Machines Corp
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International Business Machines Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J9/00—Hammer-impression mechanisms
    • B41J9/26—Means for operating hammers to effect impression
    • B41J9/38—Electromagnetic means

Definitions

  • the invention relates to an electromagnetic actuating device, according to the preamble of claim 1, in which the actual actuating element or the armature is held tensioned against a biasing force and can be triggered selectively for a working stroke.
  • magnetic actuators are used to drive the print hammers and use compensation coils that counteract the excitation of the force attracting the hammer and thus release the hammer to stop.
  • the tripping current for the compensation coil is relatively high, so that additional components are required to control the driver circuits for the windings of the print hammer magnet. These components naturally cause additional effort in comparison to the production of the driver stages in integrated circuit technology, as is the case with most pressure control circuits today.
  • the object of the invention is therefore to provide an electromagnetic actuating device in which the tripping current for the compensation coil is further reduced.
  • the permanent magnet can either move back and forth or change to change the air gap and thus cyclically change the magnetic resistance between the permanent magnet and the core to generate a cyclically changing flux density on the pole faces of the pole pair that hold the actuating element.
  • the magnetic actuating device consists of a core 10, and an armature or actuating element 11, a reciprocating permanent magnet 12 and a compensation coil 13.
  • the core 10 is made of a magnetically permeable material and has a first pair of poles 14, 15 second pole pair 16, 17 and a middle leg 18.
  • the actuating element 11 is preferably made of magnetically permeable material and can consist, for example, of spring steel, although this is not absolutely necessary.
  • the actuating element must in any case have a magnetically permeable plate 20 which can be attracted by the pole faces of the pole pair 14, 15.
  • the actuating element 11 is clamped at its lower end and either shaped or arranged in such a way that it is biased relative to a rest position shown in broken lines.
  • the actuator 11 carries a print hammer 21 for use in a printer.
  • the permanent magnet 12 is U-shaped and has two pole faces 24, 25, which correspond to and oppose the pole pair 16, 17 of the magnetic core 10, and is slidably arranged on a pair of rails 26 for a reciprocating movement with respect to the magnetic core .
  • the permanent magnet 12 can be moved approximately in the manner shown by a push rod 27, which is articulated eccentrically on a rotating disc, which in turn is fastened on a shaft 29 which can be driven by a motor (not shown).
  • the shaft 29 also carries a disk 30 provided with slits 31, the slits 31 being sensed, for example, by a photodetector 32. This photodetector supplies a gate switching signal to a control circuit 33 which, in conjunction with a trigger command, causes the compensation coil 13 to be energized.
  • the rotation of the shaft 29 and the disk 28 mounted thereon cause the permanent magnet 12 to move back and forth with respect to the magnetic core 10.
  • the magnetic flux passing through the magnetic core provides the attractive force for the actuating element 11 on the pole faces of the pole pair 14, 15, thereby the actuator 11 is held in the position shown in solid lines.
  • the limit of the reciprocating movement or the greatest expansion of the air gap D between the permanent magnet and the magnetic core is determined by the flux density of the magnetic flux that is required to hold the actuator in the position shown.
  • the maximum allowable air gap width is that which is required to keep the actuator just in the position shown by solid lines.
  • the smallest air gap is again the one required to attract the actuator from a free-standing position.
  • the flux density changes cyclically both in the first pole pair 14, 15 and in the middle leg between a first high value 35 and a second low value 36 in FIG. 2a.
  • a trigger command is supplied to the control circuit 33 to excite the compensation coil 18.
  • This triggering command is controlled in such a way that it becomes effective at the same time that the magnetic flux at the pole faces of the pole pair 14, 15 opposite the actuating element 11 is at a low value.
  • This coincidence is determined by the position of the slots 31 of the clock disk and by the photodetector 32.
  • only a small current flowing through the compensation coil 13 is required so that the actuating element can be triggered. It is assumed that the direction of flow from the north pole of the permanent magnet runs through the middle leg 18 of the magnetic core and through the parallel flow path from pole 14, block 20 and pole 15 and from there to the south pole of the permanent magnet.
  • the compensation coil 13 When excited, the compensation coil 13 supplies an additional magnetic flux in the same direction as the flux generated by the permanent magnet in the middle leg. However, the newly generated magnetic flux is distributed over two flux paths, one running over the south and north poles of the permanent magnet and back, while the greater part of the additional magnetic flux is directed in the opposite direction and the original flux through the first pole pair 14, 15 is directed in the opposite direction on the actuating element. This creates a compensation flow in this leg, so that the holding flow is reduced so far at point 37 (FIG. 2a) that the actuating element 11 moves into the position shown in broken lines.
  • the magnetic actuation device can also be constructed as shown in FIG. 3.
  • a rotating permanent magnet is used, which causes a cyclical change in the magnetic flux flowing through the actuating element that is attracted.
  • the magnetic core 40 is shown here in a different plane than in FIG. 1, but also has a central leg 41, a first pair of poles 42, 43 and a second pair of poles 44, 45.
  • the compensation coil 46 is in turn mounted on the central leg 41.
  • the actuating element 47 has a magnetically permeable block 48 which is attracted by the magnetic flux occurring at the first pole pair 42, 43 against the bias of the spring 49.
  • the exciting magnetic flux is generated by a permanent magnet 50 which is arranged on a rotatable shaft 51 which also carries the clock disk, not shown.
  • the permanent magnet is provided with grooves 52 and, during its rotation, changes the density of the magnetic flux passing through the core, the pole faces and thus also the middle leg and the pole flux holding the actuating element.
  • the compensation winding can be excited in connection with the clock arrangement in FIG. 1 and releases the actuating element at the time of the lowest flux density. As a result, the compensation coil can be driven with a relatively low current.
  • the actuating device can be modified somewhat in terms of construction, and other arrangements for a relative movement between a permanent magnet and the magnetic core are conceivable, or additional reset windings could be provided.
  • the various pole faces may also be coated with a non-magnetic material to prevent the relatively moving parts from sticking.
  • a plurality of magnets can also be used.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Electromagnets (AREA)
  • Reciprocating, Oscillating Or Vibrating Motors (AREA)

Description

Die Erfindung betrifft eine elektromagnetische Betätigungsvorrichtung, gemäß dem Oberbegriff des Anspruchs 1, bei welcher das eigentliche Betätigungselement oder der Anker gegen eine Vorspannungskraft gespannt gehalten wird und selektiv für einen Arbeitshub ausgelöst werden kann. In manchen Anwendungsgebieten, wie z. B. bei Zeilendruckern, werden magnetische Betätigungsvorrichtungen zum Antreiben der Druckhämmer benutzt und verwenden Kompensationsspulen, die bei Erregung der den Hammer anziehenden Kraft entgegenwirken und damit den Hammer zum Anschlag freigeben. Bei bekannten Betätigungsvorrichtungen ist der Auslösestrom für die Kompensationsspule relativ hoch, so daß zusätzliche Bauelemente erforderlich sind, um die Treiberschaltungen für die Wicklungen des Druckhammermagneten anzusteuern. Diese Bauelemente verursachen natürlich zusätzlichen Aufwand im Vergleich mit der Herstellung der Treiberstufen in integrierter Schaltungstechnik, wie dies heute bei den meisten Drucksteuerschaltungen der Fall ist.The invention relates to an electromagnetic actuating device, according to the preamble of claim 1, in which the actual actuating element or the armature is held tensioned against a biasing force and can be triggered selectively for a working stroke. In some areas of application, such as. B. line printers, magnetic actuators are used to drive the print hammers and use compensation coils that counteract the excitation of the force attracting the hammer and thus release the hammer to stop. In known actuators, the tripping current for the compensation coil is relatively high, so that additional components are required to control the driver circuits for the windings of the print hammer magnet. These components naturally cause additional effort in comparison to the production of the driver stages in integrated circuit technology, as is the case with most pressure control circuits today.

Mit fortschreitender Entwicklung der Druckertechnik müssen solche Betätigungsvorrichtungen, nämlich die Druckhammermagnete, bei immer höheren Geschwindigkeiten arbeiten, woraus sich wiederum Schwierigkeiten bei der Ableitung der in der Druckhammermagnetspule auftretenden Wärme ergeben, weil die Einschaltzeit der Druckhammermagnete ständig zunimmt. Man hat schon versucht, diesen Schwierigkeiten dadurch zu begegnen, daß man die Masse der Druckhämmer verringerte, zusätzliche Wicklungen aufbrachte und Rückstellvorrichtungen für die Druckhämmer vorsah.With the advancing development of printer technology, such actuators, namely the print hammer magnets, have to operate at ever higher speeds, which in turn leads to difficulties in dissipating the heat occurring in the print hammer magnet coil because the on-time of the print hammer magnets increases continuously. Attempts have already been made to counteract these difficulties by reducing the mass of the pressure hammers, adding additional windings and providing return devices for the pressure hammers.

Aufgabe der Erfindung ist es also, eine elektromagnetische Betätigungsvorrichtung zu schaffen, bei der der Auslösestrom für die Kompensationsspule weiter verringert wird.The object of the invention is therefore to provide an electromagnetic actuating device in which the tripping current for the compensation coil is further reduced.

Die der Erfindung zugrunde liegende Aufgabe wird durch die Merkmale gemäß dem Anspruch 1 gelöst.The object on which the invention is based is achieved by the features according to claim 1.

Der Permanentmagnet kann dabei zur Änderung des Luftspaltes sich entweder hin- und herbewegen oder aber rotieren und damit den magnetischen Widerstand zwischen dem Permanentmagneten und dem Kern zur Erzeugung einer sich zyklisch ändernden Flußdichte an den Polflächen des Polpaares zyklisch verändern, die das Betätigungselement halten.The permanent magnet can either move back and forth or change to change the air gap and thus cyclically change the magnetic resistance between the permanent magnet and the core to generate a cyclically changing flux density on the pole faces of the pole pair that hold the actuating element.

Weitere Ausgestaltungen der Erfindung sind den Unteransprüchen zu entnehmen.Further embodiments of the invention can be found in the subclaims.

Die Erfindung wird nunmehr anhand von Ausführungsbeispielen in Verbindung mit den beigefügten Zeichnungen im einzelnen näher beschrieben.The invention will now be described in more detail with reference to exemplary embodiments in conjunction with the accompanying drawings.

In den Zeichnungen zeigt

  • Fig. 1 schematisch eine magnetische Betätigungsvorrichtung gemäß der Erfindung,
  • Fig. 2a, b und c den Verlauf der magnetischen Flußdichte, des Auslösestroms und des Arbeitshubs der Vorrichtung in Fig. 1 und
  • Fig. 3 schematisch eine weitere Ausführungsform der in Fig. 1 dargestellten Betätigungsvorrichtung, bei der ein rotierender Magnet zur Erzeugung der Änderungen in der Flußdichte verwendet wird.
In the drawings shows
  • 1 schematically shows a magnetic actuation device according to the invention,
  • 2a, b and c the course of the magnetic flux density, the tripping current and the working stroke of the device in Fig. 1 and
  • Fig. 3 schematically shows another embodiment of the actuator shown in Fig. 1, in which a rotating magnet is used to generate the changes in flux density.

Die magnetische Betätigungsvorrichtung gemäß der Erfindung besteht aus einem Kern 10, und einem Anker oder Betätigungseement 11, einem hin und her bewegbaren Permanentmagneten 12 und einer Kompensationsspule 13. Der Kern 10 ist aus einem magnetisch permeablen Material und weist ein erstes Polpaar 14, 15, ein zweites Polpaar 16, 17 und einen Mittelschenkel 18 auf. Das Betätigungselement 11 ist vorzugsweise aus magnetisch permeablem Material und kann beispielsweise aus Federstahl bestehen, obgleich dies nicht unbedingt erforderlich ist. Das Betätigungselement muß in jedem Fall eine magnetisch permeable Platte 20 aufweisen, die durch die Polflächen des Polpaars 14, 15 angezogen werden kann. Das Betätigungselement 11 ist an seinem unteren Ende eingespannt und entweder so geformt oder so angeordnet, daß es gegenüber einer gestrichelt eingezeichneten Ruhelage vorgespannt ist. In der Zeichnung trägt das Betätigungselement 11 einen Druckhammer 21 zum Einsatz in einen Drucker.The magnetic actuating device according to the invention consists of a core 10, and an armature or actuating element 11, a reciprocating permanent magnet 12 and a compensation coil 13. The core 10 is made of a magnetically permeable material and has a first pair of poles 14, 15 second pole pair 16, 17 and a middle leg 18. The actuating element 11 is preferably made of magnetically permeable material and can consist, for example, of spring steel, although this is not absolutely necessary. The actuating element must in any case have a magnetically permeable plate 20 which can be attracted by the pole faces of the pole pair 14, 15. The actuating element 11 is clamped at its lower end and either shaped or arranged in such a way that it is biased relative to a rest position shown in broken lines. In the drawing, the actuator 11 carries a print hammer 21 for use in a printer.

Der Permanentmagnet 12 ist U-förmig ausgestaltet und weist zwei Polflächen 24, 25 auf, die dem Polpaar 16, 17 des Magnetkerns 10 entsprechen und gegenüberliegen, und ist für eine hin und her gehende Bewegung in Bezug auf den Magnetkern auf einem Schienenpaar 26 gleitend angeordnet. Der Permanentmagnet 12 kann dabei etwa in der dargestellten Weise durch eine Schubstange 27 bewegt werden, die exzentrisch an einer rotierenden Scheibe angelenkt ist, die wiederum auf einer Welle 29 befestigt ist, die durch einen Motor (nicht gezeigt) angetrieben werden kann. Die Welle 29 trägt außerdem eine mit Schlitzen 31 versehene Scheibe 30, wobei die Schlitze 31 beispielsweise durch einen Photodetektor 32 abgefühlt werden. Dieser Photodetektor liefert ein Torschaltsignal an eine Steuerschaltung 33, die in Verbindung mit einem Auslösebefehl die Erregung der Kompensationsspule 13 bewirkt.The permanent magnet 12 is U-shaped and has two pole faces 24, 25, which correspond to and oppose the pole pair 16, 17 of the magnetic core 10, and is slidably arranged on a pair of rails 26 for a reciprocating movement with respect to the magnetic core . The permanent magnet 12 can be moved approximately in the manner shown by a push rod 27, which is articulated eccentrically on a rotating disc, which in turn is fastened on a shaft 29 which can be driven by a motor (not shown). The shaft 29 also carries a disk 30 provided with slits 31, the slits 31 being sensed, for example, by a photodetector 32. This photodetector supplies a gate switching signal to a control circuit 33 which, in conjunction with a trigger command, causes the compensation coil 13 to be energized.

Im Betrieb bewirken die Rotation der Welle 29 und der darauf befestigten Scheibe 28 eine hin und her gehende Bewegung des Permanentmagneten 12 gegenüber dem Magnetkern 10. Der den Magnetkern durchsetzende Magnetfluß liefert die Anziehungskraft für das Betätigungselement 11 an den Polflächen des Polpaares 14, 15, wodurch das Betätigungselement 11 in der mit ausgezogenen Linien dargestellten Position gehalten wird. Die Grenze der hin und her gehenden Bewegung oder die größte Ausdehnung des Luftspaltes D zwischen Permanentmagnet und Magnetkern wird durch diejenige Flußdichte des Magnetflusses bestimmt, der zum Halten des Betätigungselements in der dargestellten Position erforderlich ist. Die höchstzulässige Luftspaltbreite ist diejenige, die erforderlich ist, um das Betätigungselement gerade noch in der durch ausgezogene Linien dargestellte Position zu halten. Der kleinste Luftspalt ist wiederum derjenige, der erforderlich ist, um das Betätigungselement aus einer freistehenden Position anzuziehen. Wenn der Permanentmagnet hin und her bewegt wird, dann verändert sich die Flußdichte sowohl im ersten Polpaar 14, 15 als auch im Mittelschenkel zyklisch zwischen einem ersten hohen Wert 35 und einem zweiten niedrigen Wert 36 in Fig. 2a. Soll das Betätigungselement ausgelöst werden, dann wird ein Auslösebefehl der Steuerschaltung 33 zur Erregung der Kompensationsspule 18 zugeführt. Dieser Auslösebetehl ist dabei so gesteuert, daß er gleichzeitig mit dem Zeitpunkt wirksam wird, an dem der Magnetfluß an den dem Betätigungselement 11 gegenüberliegenden Polflächen des Polpaares 14, 15 auf einem niedrigen Wert ist. Diese Koinzidenz wird durch die Position der Schlitze 31 der Taktgeberscheibe und durch den Photodetektor 32 bestimmt. Zu diesem Zeitpunkt ist nur ein kleiner, die Kompensationsspule 13 durchfließender Strom erforderlich, damit das Betätigungselement ausgelöst werden kann. Es sei angenommen, daß die Flußrichtung von dem Nordpol des Permanentmagneten durch den Mittelschenkel 18 des Magnetkerns und durch den parallen Flußpfad vom Pol 14, Block 20 und Pol 15 und von dort zum Südpol des Permanentmagneten verläuft.In operation, the rotation of the shaft 29 and the disk 28 mounted thereon cause the permanent magnet 12 to move back and forth with respect to the magnetic core 10. The magnetic flux passing through the magnetic core provides the attractive force for the actuating element 11 on the pole faces of the pole pair 14, 15, thereby the actuator 11 is held in the position shown in solid lines. The limit of the reciprocating movement or the greatest expansion of the air gap D between the permanent magnet and the magnetic core is determined by the flux density of the magnetic flux that is required to hold the actuator in the position shown. The maximum allowable air gap width is that which is required to keep the actuator just in the position shown by solid lines. The smallest air gap is again the one required to attract the actuator from a free-standing position. When the permanent magnet is moved back and forth, the flux density changes cyclically both in the first pole pair 14, 15 and in the middle leg between a first high value 35 and a second low value 36 in FIG. 2a. If the actuating element is to be triggered, then a trigger command is supplied to the control circuit 33 to excite the compensation coil 18. This triggering command is controlled in such a way that it becomes effective at the same time that the magnetic flux at the pole faces of the pole pair 14, 15 opposite the actuating element 11 is at a low value. This coincidence is determined by the position of the slots 31 of the clock disk and by the photodetector 32. At this time, only a small current flowing through the compensation coil 13 is required so that the actuating element can be triggered. It is assumed that the direction of flow from the north pole of the permanent magnet runs through the middle leg 18 of the magnetic core and through the parallel flow path from pole 14, block 20 and pole 15 and from there to the south pole of the permanent magnet.

Die Kompensationsspule 13 liefert bei Erregung einen zusätzlichen Magnetfluß in der gleichen Richtung wie der durch den Permanentmagneten im Mittelschenkel erzeugte Fluß. Der neu erzeugte Magnetfluß verteilt sich jedoch über zwei Flußpfade, wobei der eine über den Süd- und Nordpol des Permanentmagneten und zurück verläuft, während der größere Teil des zusätzlichen magnetischen Flusses in der Gegenrichtung gerichtet ist und dem ursprünglichen Fluß durch das erste Polpaar 14, 15 am Betätigungselement entgegengerichtet ist. Das erzeugt einen Kompensationsfluß in diesem Schenkel, so daß am Punkt 37 (Fig.2a) der Haltefluß so weit verringert wird, daß das Betätigungselement 11 sich in die gestrichelt dargestellte Position bewegt.When excited, the compensation coil 13 supplies an additional magnetic flux in the same direction as the flux generated by the permanent magnet in the middle leg. However, the newly generated magnetic flux is distributed over two flux paths, one running over the south and north poles of the permanent magnet and back, while the greater part of the additional magnetic flux is directed in the opposite direction and the original flux through the first pole pair 14, 15 is directed in the opposite direction on the actuating element. This creates a compensation flow in this leg, so that the holding flow is reduced so far at point 37 (FIG. 2a) that the actuating element 11 moves into the position shown in broken lines.

Man sieht aus F i g. 2, daß der optimale Zeitpunkt für die Erregung der Kompensationsspule am Punkt 37 liegt, wo dann der Auslösestrom 38 mit dem niedrigsten Wert der Flußdichte durch die Polschuhe des Polpaares 14, 15 zusammenfällt. Diese Wirkung erfordert damit den kleinsten Kompensationsstrom für eine Betätigung des Betätigungselements. Die Bewegung des Betätigungselements aus seiner vorgespannten Position heraus ist bei 39 (Fig. 2c) gezeigt. Der Strom wird nur kurzzeitig an die Kompensationsspule angelegt, so daß der den Permanentmagneten durchsetzende Magnetfluß auf das nach dem Aufschlag zurückprallende Betätigungselement eine Anziehungskraft ausübt und es aus der Auslöseposition wieder zurückholt. Obgleich der Permanentmagnet zum Wiederanziehen des Betätigungselements verwendet werden kann, können auch andere Vorrichtungen, wie eine zusätzliche Spule oder eine mechanische Rückstellvorrichtung für die Rückstellung des Betätigungselements eingesetzt werden.One can see from F i g. 2, that the optimal time for the excitation of the compensation coil is at point 37, where then the tripping current 38 coincides with the lowest value of the flux density through the pole pieces of the pole pair 14, 15. This effect therefore requires the smallest compensation current for actuating the actuating element. The movement of the actuator from its biased position is shown at 39 (Fig. 2c). The current is only briefly applied to the compensation coil, so that the magnetic flux passing through the permanent magnet exerts an attractive force on the actuating element rebounding after the impact and brings it back again from the release position. Although the permanent magnet can be used to retighten the actuator, other devices such as an additional coil or a mechanical reset device can be used to reset the actuator.

Die magnetische Betätigungsvorrichtung kann auch so aufgebaut sein, wie dies Fig. 3 zeigt. Hier wird ein rotierender Permanentmagnet verwendet, der eine zyklische Veränderung des das angezogene Betätigungselement durchfließenden Magnetflusses bewirkt. Der Magnetkern 40 ist hier in einer anderen Ebene dargestellt als in Fig. 1, hat aber genauso einen Mittelschenkel41, ein erstes Polpaar 42, 43 und ein zweites Polpaar 44, 45. Die Kompensationsspule 46 ist wiederum auf dem Mittelschenkel41 angebracht.The magnetic actuation device can also be constructed as shown in FIG. 3. Here, a rotating permanent magnet is used, which causes a cyclical change in the magnetic flux flowing through the actuating element that is attracted. The magnetic core 40 is shown here in a different plane than in FIG. 1, but also has a central leg 41, a first pair of poles 42, 43 and a second pair of poles 44, 45. The compensation coil 46 is in turn mounted on the central leg 41.

Das Betätigungselement 47 weist einen magnetisch permeablen Block 48 auf, der durch den an dem ersten Polpaar 42, 43 auftretenden Magnetfluß gegen die Vorspannung der Feder 49 angezogen wird. Der erregende Magnetfluß wird durch einen Permanentmagneten 50 erzeugt, der auf einer drehbaren Welle 51 angeordnet ist, die außerdem die nicht gezeigte Taktgeberscheibe trägt. Der Permanentmagnet ist mit Nuten 52 versehen und verändert während seiner Drehung die Dichte des den Kern, die Polflächen und damit auch den Mittelschenkel und die das Betätigungselement festhaltenden Polflächen durchsetzenden magnetischen Flusses. Die Kompensationswicklung kann in Verbindung mit der Taktgeberanordnung in Fig. 1 erregt werden und gibt das Betätigungselement zum Zeitpunkt der geringsten Flußdichte frei. Dadurch läßt sich die Kompensationsspule mit einem relativ geringen Strom ansteuern.The actuating element 47 has a magnetically permeable block 48 which is attracted by the magnetic flux occurring at the first pole pair 42, 43 against the bias of the spring 49. The exciting magnetic flux is generated by a permanent magnet 50 which is arranged on a rotatable shaft 51 which also carries the clock disk, not shown. The permanent magnet is provided with grooves 52 and, during its rotation, changes the density of the magnetic flux passing through the core, the pole faces and thus also the middle leg and the pole flux holding the actuating element. The compensation winding can be excited in connection with the clock arrangement in FIG. 1 and releases the actuating element at the time of the lowest flux density. As a result, the compensation coil can be driven with a relatively low current.

Selbstverständlich läßt sich die Betätigungsvorrichtung konstruktiv durchaus noch etwas abändern, und es sind andere Anordnungen für eine Relativbewegung zwischen einem Permanentmagneten und dem Magnetkern denkbar, oder es könnten zusätzliche Rückstellwicklungen vorgesehen sein. Die verschiedenen Polflächen können außerdem zur Verhinderung des Anhaftens der relativ beweglichen Teile mit einem nichtmagnetischen Material überzogen sein. Bei der mit rotierendem Permanentmagneten arbeitenden Ausführungsform können ebenso mehrere Magnete benutzt werden.Of course, the actuating device can be modified somewhat in terms of construction, and other arrangements for a relative movement between a permanent magnet and the magnetic core are conceivable, or additional reset windings could be provided. The various pole faces may also be coated with a non-magnetic material to prevent the relatively moving parts from sticking. In the embodiment using a rotating permanent magnet, a plurality of magnets can also be used.

Claims (4)

1. Electro-mechanical actuator in which an armature, fixed at one end and acting as actuator element, is attracted against a resilient bias toward the pole pieces of a permanent magnetic circuit, and is releasable by controlling a bucking coil arranged on a leg of the magnetic core forming the permanent magnetic circuit, characterized in that the magnetic core (10) comprises a second pair of pole pieces (16, 17) which face the two pole pieces (24, 25) of the permanent magnet to form an air gap (D), the bucking coil (13; 46) being arranged on a transverse leg (18; 41) of the magnetic core (10), the leg being between the two pairs of pole pieces, that, for cyclically altering the size of the air gap and thus the magnetic resistance in this flux path, the permanent magnet (12; 50, 52) is cyclically movable relative to the magnetic core, so that the magnetic flux passing through the magnetic core (10) varies cyclically between first higher and second lower values which, however, are each sufficient to keep the actuator element (11; 47) attracted to the first pair of pole pieces (14, 15; 42, 43), and that for releasing the actuator element the bucking coil (13; 46) is controllable at the time of occurrence of the lower value of the magnetic flux, in such a manner that an additional magnetic flux is generated in the transverse leg (18; 41), which acts in the same direction as the magnetic flux generated by the permanent magnet.
2. Actuator according to claim 1, characterized in that the permanent magnet (12) is reciprocated cyclically by a drive (26, 27, 28).
3. Actuator according to claim 1, characterized in that the permanent magnet (50, 51) is rotatably arranged between the pole faces of the second pair of pole pieces (44,45).
4. Actuator according to claim 1, characterized in that a clock pulse circuit (30, 31, 32) is coupled to the drive, and that thereby (13, 46) and by the simultaneous presence of a release instruction, the bucking coil (13; 46) is controllable for a short period at the time of occurrence of the minimum of magnetic flux.
EP79104186A 1978-12-29 1979-10-29 Electromagnetic actuator Expired EP0014737B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US05/974,298 US4224589A (en) 1978-12-29 1978-12-29 Low energy magnetic actuator
US974298 1978-12-29

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EP0014737A1 EP0014737A1 (en) 1980-09-03
EP0014737B1 true EP0014737B1 (en) 1983-01-19

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AU (1) AU527732B2 (en)
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DE (1) DE2964555D1 (en)
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Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4392423A (en) * 1978-02-08 1983-07-12 Hitachi, Ltd. Printing hammer driving apparatus
US4461207A (en) * 1980-11-17 1984-07-24 International Business Machines Corporation Actuator mechanism for a printer or the like using dual magnets
JPS57191079A (en) * 1981-05-20 1982-11-24 Seikosha Co Ltd Printer head
US4423675A (en) 1982-03-08 1984-01-03 Hewlett-Packard Company Magnetic circuit and print hammer
US4441421A (en) * 1982-09-22 1984-04-10 Hossein Khorsand Print hammer apparatus
US5199804A (en) * 1991-05-31 1993-04-06 Smith Corona Corporation Quiet impact printer mechanism
JPH1042544A (en) * 1996-03-15 1998-02-13 Eastman Kodak Co Soft magnetic material core for magnetic actuator

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3146381A (en) * 1960-09-12 1964-08-25 Vente D Aimants Allevard Ugine Magnetic force control or switching system
CH395335A (en) * 1962-10-08 1965-07-15 Landis & Gyr Ag Electromagnetic relay
JPS5740522B2 (en) * 1974-01-18 1982-08-28

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ES486095A1 (en) 1980-09-01
DE2964555D1 (en) 1983-02-24
CA1124780A (en) 1982-06-01
IT1163744B (en) 1987-04-08
AU527732B2 (en) 1983-03-17
IT7928241A0 (en) 1979-12-20
AU5353579A (en) 1980-07-03
BR7908327A (en) 1980-09-16
EP0014737A1 (en) 1980-09-03
US4224589A (en) 1980-09-23

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